Summary Statement

Repetitive loading of degenerated human intervertebral discs in combined axial compression, flexion and axial rotation, typical of manual handling lifing activities, causes: an increase in intradiscal maximum shear strains, circumferential annular tears and nuclear seperation from the endplate.

Anterior lumbar inter-body fusion (ALIF) is a surgical procedure that is available to chronic lower back pain patients who fail to respond to conservative treatments. Failure to achieve fusion may result in persistence of pain. Fusion of the lumber vertebral segment is more accurately assessed using fine-cut helical Computed tomography (CT) scans (0.25 mm thickness slices). Unfortunately this technique exposes the body to high radiation dose with hazard of increase risk of late malignancy. An alternative imaging tool is radiostereometry (RSA) which developed as a means to determine the magnitude of relative motion between two rigid bodies. In this study we used RSA to detect movement at the fused lumbar segment (ALIF site) during flexion and extension and compare the results obtained with fine-cut helical CT scan using histopathology as final gold standard assessment tool.

ALIF of three levels of lumbar spine (L1-L2, L3-L4, and L5-L6) was done in 9 sheep. The sheep divided into three groups (3sheep each). The first group had RSA assessment immediately, 3, and 6 months after surgery. The second group had RSA immediately, 3, 6, 9 months after surgery. The third group had an RSA immediately, 3, 6, 9, 12 months after surgery All the animals were humanly killed immediately after having the last scheduled RSA (group1, group2, and group 3 sheep were killed 6 month, 9month and 12 months after surgery respectively). This followed by in vitro fine cut CT and histopathology after the animals are scarified. Micro CT scan has been also used to identify the area where histopathology slide should be made to pick up fusion. Fine cut CT scan assessment for all sheep were done. The CT scan has been reported by two independent radiologists. Histopathology has been started and will finish in 2 weeks

RSA showed there was significant increasing stiffness of the spine though the fused segments as the time pass on compare to immediate postoperative assessment. CT scan were done and showed variable fusion though out the spinal segments. Histopathology of all sheep has been started and the results will be available in 2 weeks which will be followed by statistical assessment to decide how accurate RSA compare to CT scan in assessment of fusion.

Long term, secondary implant fixation of Total Disc Replacements (TDR) can be enhanced by hydroxyapatite or similar osseo-conductive coatings. These coatings are routinely applied to metal substrates. The objective of this in vivo study was to investigate the early stability and subsequent bone response adjacent to an all polymer TDR implant over a period of six months in an animal model.

Six skeletally mature male baboons (Papio annubis) were followed for a period of 6 months. Using a transperitoneal exposure, a custom-sized Cadisc L device was implanted into the disc space one level above the lumbo-sacral junction in all subjects. Radiographs of the lumbar spine were acquired prior to surgery, and post-operatively at intervals up to 6 months to assess implant stability. Flourochrome markers (which contain molecules that bind to mineralization fronts) were injected at specified intervals in order to investigate bone remodeling with time.

Animals were humanely euthanized six months after index surgery. Test and control specimens were retrieved, fixed and subjected to histological processing to assess the bone-implant-bone interface. Fluorescence microscopy and confocal scanning laser microscopy were utilized with BioQuant image analysis to determine the bone mineral apposition rates and gross morphology.

Radiographic evaluation revealed no loss of disc height at the operative level or adjacent levels. No evidence of subsidence or significant migration of the implant up to 6 months. Heterotopic ossification was observed to varying degrees at the operated level.

Histology revealed the implant primary fixation features embedded within the adjacent vertebral endplates. Flourochrome distribution revealed active bone remodeling occurring adjacent to the polymeric end-plate with no evidence of adverse biological responses. Mineral apposition rates of between 0.7 and 1.7 microns / day are in keeping with literature values for hydroxyapatite coated implants in cancellous sites of various species.

Radiographic assessment demonstrates that the Cadisc L implant remains stable in vivo with no evidence of subsidence or significant migration. Histological analysis suggests the primary fixation features are engaged, and in close apposition with the adjacent vertebral bone. Flourochrome markers provide evidence of a positive bone remodelling response in the presence of the implant.

Introduction

Different subclinical neurological dysfunction has been reported in adolescent idiopathic scoliosis (AIS), including poor postural control and asymmetric otolith vestibulo-ocular responses when compared with normal controls. The objective of this pilot study is to establish whether abnormal MRI morphoanatomical changes arise in the CNS (brain and vestibular system), among left-thoracic versus right-thoracic AIS when compared with normal adolescent controls, with use of advanced computerised statistical morphometry techniques.

To evaluate the cost-effectiveness IDET relative to circumferential lumbar fusion with femoral ring allograft (FRA).

Cost-effectiveness analysis

Patient-level data were available for patients with discogenic low back pain treated with FRA (n=37) in a randomized trial of FRA vs. titanium cage, and for patients recruited to a separate study evaluating the use of IDET (n=85). Patients were followed-up for 24 months.

Oswestry Disability Index, visual analogue scale, quality of life (SF-36), radiographic evaluations, and NHS resource use. Cost-effectiveness was measured by the incremental cost per quality-adjusted life year (QALY) gained.

Both treatments produced statistically significant improvements in pain, disability and quality of life at the 24-month follow-up. Costs were significantly lower with IDET due to a shorter mean procedure time (377.4 minutes vs. 49.9 minutes) and length of stay (7 days vs. 1.2 days). The mean incremental cost of IDET was -£3,713 per patient; the mean incremental QALY gain was 0.03. At a threshold of £20,000 per QALY the probability that IDET is cost-effective is 1, and the net health benefit is 0.21 QALY per patient treated.

Both treatments led to significant improvements in patient outcomes which were sustained for at least 24 months. Costs were lower with IDET, and for appropriate patients IDET is an effective and cost-effective treatment alternative.

Ethics approval: Ethics committee COREC

This cost-effectiveness analysis was carried out by the York Health Economics Consortium at the University of York, and was funded by Smith & Nephew. Smith & Nephew had no financial or other involvement in the collection or analysis of the data on which the CEA is based.

The purpose of this cohort study is to determine the incidence of all congenital vertebral anomalies detected antenatally through ultrasound. We also reported on the early mortality rate for this patient cohort, as well as the frequency and type of associated congenital anomalies.

The East Midlands and South Yorkshire Anomalies Register consists of data on all voluntary reports of congenital anomalies, from an annual baseline birth rate of 67000 births. We analysed all registered congenital anomalies reported over a 10 year period.

Between January 1997 and January 2007, 108 vertebral anomalies were reported, excluding spinal dysraphism (incidence 0.01%). 61 of these were detected antenatally (56%), 17 were detected postnatally (16%) and in 30 patients, the precise time of diagnosis was unclear (28%).

At the time of analysis January 2007, 45 of 108 patients had died, either in utero or soon after delivery (42%). 12 fetuses remained in utero and 51 infants were alive. The mortality rate for antenatally diagnosed patients was 41% and the majority were electively terminated (72%). 2 fetuses electively terminated had vertebral anomalies in isolation.

There is a relatively high incidence of elective termination of pregnancy as a result of antenatal anomaly ultrasound screening. We have evidence to suggest that foetuses with potentially minor congenital anomalies are being electively terminated at approximately 18 weeks gestation. A structured and timely spinal counselling should be offered once antenatal vertebral anomalies have been identified.

The purpose of this study was to ascertain whether early diagnosis through antenatal ultrasound screening and intervention lead to a reduction in morbidity associated with congenital scoliosis.

Prospective cohort study

All fetuses with vertebral body anomalies detected over a thirteen years period were included. Maternal risk factors, accuracy of antenatal diagnosis, associated fetal anomalies and ultimate outcome are described.

Twenty-four fetuses with congenital hemivertebrae were identified from 39,000 antenatal scans (incidence 0.061%). The mothers' median age at conception was 26 years (range 18-40 years). The median fetal gestational age at diagnosis was 20 weeks (range 18-38 weeks). The median gestational age at delivery was 38 weeks (range 27-40).

Antenatal ultrasound identified eighteen fetuses with a single hemivertebra, six fetuses with multiple hemivertebrae. Eleven patients (50%) have undergone early surgical intervention with median post-natal follow up was 4 years (range 0-9 years). The median age at surgery was 12 months (range 1.2 - 47 months). The median pre-operative Cobb angle was 33 degrees and the median Cobb angle at final follow up was 25 degrees.

In this series 50% of patients required surgical intervention. We felt that pre-natal diagnosis of congenital vertebra abnormally has resulted in early surgical intervention using less complex surgical technique to halt progressive deformity. However, further studies are required to compare the results with the abnormally not detected antenatally.

Study design

Economic evaluation alongside a prospective, randomised, controlled trial from a two-year National Health Service (NHS) perspective.

Study Design

Prospective cohort study.

We report a prospective case-series study to evaluate the results of non-operative and operative treatment of symptomatic unilateral lumbar spondylolysis. Non-operative treatment results in healing in most patients with symptomatic unilateral spondylolysis. Surgery however is indicated when symptoms persist beyond a reasonable time affecting the quality of life in young patients particularly the athletic population.

We treated 41 patients [31 male, 10 female] with suspected unilateral lumbar spondylolysis. Thirty-one patients were actively involved in sports at various levels. Patients with a positive stress reaction on SPECT imaging underwent a strict protocol of activity restriction, bracing and physical therapy for 6 months. At the end of six months, patients who remained symptomatic underwent a Computed Tomography [CT] scan to confirm the persistence of a spondylolysis. Seven patients subsequently underwent a direct repair of the defect using the modified Buck's Technique. Baseline Oswestry disability index [ODI] and Short-Form-36 [SF-36] scores were compared to two year ODI and SF-36 scores for all patients.

In the non-operated group, the mean pre-treatment ODI was 36 [SD=10.5], improving to 6.2 [SD=8.2] at two years. In SF-36 scores, the physical component of health [PCS] improved from 30.7 [SD=3.2] to 53.5 [SD =6.5] [p<0.001], and the mean score for the mental component of health [MCS] improved from 39 [SD=4.1] to56.5 [SD=3.9] [p<0.001] at two years. 20/31 patients resumed their sporting career within 6 months of onset of treatment, a further 4/31 patients returned to sports within one year.

The seven patients who remained symptomatic at six months underwent a unilateral modified Buck's Repair. The most common level of repair was L5 (n=4). The mean pre-operative ODI was 39.4 (SD=3.6) improving to 4.4 (SD=4) at the latest follow-up. The mean score of PCS [SF-36] improved from 29.6 [SD=4.4] to 51.2 [SD=5.2] (SD=5.2) (p<0.001) and the mean score of MCS (SF-36) improved from 38.7 (SD=1.9) to 55.5 (SD=5.4) (p<0.001).

A specific protocol of conservative treatment for patients with a unilateral lumbar spondylolysis resulted in a high rate of success with 83% of patients avoiding surgery. If symptoms persist beyond a reasonable period (i.e. 6 months) and reverse gantry CT scan confirms a non-healing defect of the pars interarticularis one may consider a unilateral direct repair of the defect with good outcome ultimately.

Our prospective observational study of patients treated for Thoracolumbar Adolescent Idiopathic Scoliosis (AIS) by anterior instrumentation aimed at investigating the correlation between the radiographic outcome and the recently-developed scoliosis research society self-reported outcomes instrument (SRS-22) which has been validated as a tool for self-assessment in scoliosis patients. Previous patient based questionnaires demonstrated poor correlation with the radiological parameters.

Introduction: Capasso’s method(CM) has been described in orthopaedic textbooks to be the most sensitive tool for measuring Cobb angle in scoliosis. This method based on “bi-univocal principle” views the scoliosis curve to be an arc of circumference, to be a true reflection of angular values and hence geometrically more valid. However there is no comparative study between the established measurement tools i.e. Oxford cobbometer(OC) & Traditional protractor(TP) vs. CM. Our objectives were to to evaluate the sensitivity of CM against OC & TP in scoliosis and to determine intra & inter-observer reliability of the three methods.

Methods: Three independent blinded observers measured 24 digital AP radiographs of scoliosis on three separate occasions one week apart by CM, OC & TP. The three sets of readings obtained were statistically analysed for intra-observer (Cronbach’s alpha) & inter-observer [Inter-class correlation coefficient(ICC)] reliability.

Results: The mean Cobb angle measured by OC was 42.4(r13-91), by TP was 45.1(r16-89) and by CM was 70.4(r 20-148). The cronbach’s was 0.94 for OC, 0.91 for TP & 0.88 for CM. The ICC was 0.96 for OC, 0.90 for TP & 0.71 for CM. The measurements obtained by CM were higher than the other two methods for all magnitudes of the curves.

Conclusion: CM based on sound geometric principles is perceived to be superior to Cobb angle and has reasonable correlation(Pearson’s®=0.74) with it. However CM overestimates the magnitude of scoliosis as compared to other standard measurement tools. Management decisions based on CM would be inappropriate by current guidelines.

Ethics approval: Not applicable Interest Statement: None

Purpose: To review the existing practice of coding in spinal surgery and ascertain its accuracy for surgical procedures, co-morbidities and complications.

Methods: A retrospective review of 70 cervical and 100 lumbar consecutive spinal surgeries performed since April 2006 was conducted. The clinical coding data and hospital notes were reviewed.

Results: Coding data of 5 cervical spine surgeries were not available. Of the 165 cases, the accuracy of primary procedural codes was 93.9% (90.8% cervical & 96% lumbar). This reduced to 77.6% (75.4% cervical & 79% lumbar) when the accuracy for entire description of performed surgery was considered. Medical co-morbidities were coded appropriately in 64.2% of the patients (55% cervical & 70% lumbar). The procedural codes did not specifically reflect the surgery performed and lacked reproducibility. Surgical levels were coded incorrectly in 9% of the cases. Cervical surgeries were coded as lumbar in 4 and posterior surgery as anterior in 3 cases respectively. The commonly missed co-morbidities were drug allergies, hypercholesterolemia, smoking and alcoholism. Post-op adverse events were coded in 75% of the cases (16/20 cervical & 5/8 lumbar). The accuracy was better for lumbar as compared to cervical spinal surgeries.

Conclusion: Coding is a universal language of communication and its accuracy is important not just for PbR, but for data quality, audit and research purposes too. The financial implications regarding PbR governed by HRG codes (dictated by OPCS 4.4 & ICD–10 codes) are discussed. Following this study, a clinical coding facilitation form has been introduced to improve data quality.

Ethics approval: None

Interest statement: None

Introduction: Intra-operative localisation of small nidus in osteoid osteoma & osteoblastoma is difficult resulting in failed excision. Wide resection is fraught with prolonged operative time, increased bleeding and instability.

Methods: 8 patients (6M & 2F) with a diagnosis of osteoid osteoma(7) and osteoblastom(1) were operated at our centre between 1995–2005. The mean age at presentation was 20.9 years (9–31 yrs). The tumour was localised to cervical(2), thoracic(4) and lumbar(2) posterior elements respectively. All had back/neck pain of varying duration (mean 20 mo; range 6–48 mo). 2 patients presented with thoraco-lumbar scoliosis and 3 had failed treatments. All patients were worked-up with x-rays, CT/MRI and 99m technetium scan to localise lesion. 600 MBq Tech HMDP(hydroxy-methylene-di-phosphate) was administered intra-venously 3 hrs prior to surgery and fluoroscopy was used to confirm anatomical level. A 5 mm cadmium telluride (Cd Te) probe & rate meter were used to scan the area containing lesion and counts per second (cps) recorded. Background count from adjacent area was obtained for comparison purposes. The tumour nidus was then excised & cps from tumour bed and excised specimen recorded.

Results: The mean follow-up was 5.85 years (2–12.33). The mean cps for osteoid osteoma pre-excision was 203.8 (60–515) which fell to 72.5 (10–220) post-excision. The cps reduced from 373 to 40.5 postoperatively for osteoblastoma. Complete excision was recorded every time and all patients reported characteristic disappearance of pre-operative pain. All had discontinued analgesic medication, returned back to normal activities by 3 months and were followed-up at regular intervals for 2 yrs when they filled NDI, ODI & SF-36 questionnaire.

Discussion: Gamma probe guided surgical excision facilitates accurate localisation of lesion, is less invasive warranting minimal bone resection & resultant instability and perhaps most importantly confirmation of complete excision of the tumour nidus consistently every time (esp. failed surgeries).

Introduction: A prospective randomised controlled trial of circumferantial spinal fusion has shown superior clinical outcome when a femoral ring allograft (FRA) is used compared to when a titanium cage (TC) is used. The implant cost of the TC is nearly ten fold that of the FRA. However the additional costs of surgery and related costs also need to be considered to determine if there is a real cost advantage of FRA over TC. We can find no previously reported studies which economically evaluate the TC and the FRA in circumferential lumbar spinal fusion. The aim of this study was to investigate cost-effectiveness of TCs in comparison to FRAs for circumferential lumbar spinal fusion over a two year National Health Service (NHS) perspective using a cost-utility evaluation

Methods: This randomised study had the approval of the local ethical committee and the institutional research and development board (Reference OR059844) prior to its commencement. Eighty-three patients were randomly allocated to receive either the TC or FRA as part of a circumferential lumbar fusion between 1998 and 2002. NHS costs related to the surgery and revision surgery needed during the trial period were monitored and adjusted to the base year (2005/6 pounds sterling). The Short Form-6D (SF-6D) was administered preoperatively and at 6, 12 and 24 months in order to elicit patient utility and subsequently Quality-Adjusted Life Years (QALYs) for the trial period. Return to paid employment was also monitored. Bootstrapped mean differences in discounted costs and benefits were generated in order to explore cost-effectiveness.

Results: Baseline demographic data including age, sex, smoking history, previous surgery history and number of operated levels did not differ between the two groups. A significant cost difference of £1,942 (AUD4,255), (95% CI £849 (AUD1,860) to £3,145 (AUD6,891)) in favour of FRA was found. Mean QALYs per patient over the 24 month trial period were 0.0522 (SD 0.0326) in the TC group and 0.1914 (SD 0.0398) in the FRA group, producing a significant difference of −0.1392 (95% CI 0.2349 to 0.0436). With regard to employment, incremental productivity costs were estimated at £185,171 (AUD 405,745) in favour of FRA.

Discussion: From an NHS perspective, the trial data show that TC is not cost-effective in circumferential lumbar fusion. The use of FRA was found to dominate (generating greater QALY gains and less cost). In addition FRA patients reported a greater return to work rate and hence, productivity costs were also in favour of FRA.

Introduction: Historically segmental sublaminar wiring (SLW) fixation has been used for the correction of spinal deformity in neuromuscular scoliosis, however pedicle screw (PS) fixation is gaining popularity. We compared the results of both techniques in patients with Duchenne Muscular Dystrophy (DMD).

Methods: Two groups of patients with DMD were matched according to the age at surgery, magnitude of deformity and vital capacity. Indications for surgery included loss of sitting balance, rapid decline of vital capacity and curve progression. In Group 1 (22 patients) SLW fixation was used from T2 to S1 with the Galveston technique. In Group 2 (18 patients) PS fixation was used from T2 to L5. Minimum follow-up was 2 years (range 2–13 years). Radiographs, SRS-22 and lung function tests were performed at standardised intervals.

Results: Mean Cobb angle in Group 1 improved from 47° (range 26°–75°) to 23.5° (range10°–36°) and mean pelvic obliquity improved from 15° (range8°–25°) to 2.4° (range0°–8°). Mean Cobb angle in Group 2 improved from 46° (range28°–82°) to 8.5° (range 0°–18°) and mean pelvic obliquity improved from 15° (range7°–30°) to 1.1° (range 0°–6°) [p< 0.05]. Mean operating time and blood loss were less in Group 2 [p< 0.05]. In Group 1, the infection rate and instrumentation failure was higher, and SRS-22 outcomes showed no significant difference between the groups. Interestingly the mean Body Mass Index (BMI) in Group 2 was much higher than group 1.

Conclusions: PS fixation resulted in superior correction and controlled pelvic obliquity to a large extent without the need for pelvic fixation. Lower rates of infection and failure of instrumentation were noted with PS fixation, despite high BMI of patients presumably due to steroid therapy. We recommend the use of PS instrumentation for the correction of spinal deformity in DMD.

Observation of sub-clinical neurological abnormalities has led to the proposal of a neuro-developmental etiologic model for AIS. Our research group have demonstrated longer latency in somatosensory–evoked potential (SSEP) and impaired balance control in AIS subjects. A previous pilot study compared the regional brain volume between right thoracic AIS subjects and normal controls. Significant regional brain differences were found relating to corpus callosum, premotor cortex, proprioceptive and visual centers. Most of these regions involved the brain unilaterally, indicating there might be abnormal asymmetrical development in the brain in right thoracic AIS. In this pilot study, we investigated whether similar changes are present in left thoracic AIS patients who differ from matched control subjects. Nine AIS female patients with atypical left thoracic AIS (mean age 14.8, mean Cobb angle 19°) and 11 matched controls as well as 20 right thoracic AIS (mean Cobb angle 33.8°) and 17 matched controls, underwent three-dimensional isotropic magnetization prepared rapid acquisition gradient echo (3D_MPRAGE) magnetic resonance (MR) imaging of the brain. Fully automatic morphometric analysis was used to analyse the MR images; it included brain-tissue classification into grey matter (GM), white matter (WM) and cerebrospinal fluid (CSF). and non-linear registration to a template brain. Tissue densities were compared between AIS subjects and controls. There was no significant difference between AIS subjects and normal controls when comparing absolute and relative (i.e. brain-size adjusted) volumes of grey and white matter. Using voxel-based morphometry, significant group differences (controls > left AIS) were found in the density of WM in the genu of the corpus callosum, the left internal capsule (anterior arm) and WM underlying the orbitofrontal cortex of the left hemisphere. The above differences were not observed in the right AIS group. This first controlled study of regional tissue density showed that corpus callosum, which is the major commissural fiber tract, was different in the atypical left thoracic scoliosis while significant regional brain changes have not yet been found in those with typical right thoracic scoliosis. Further investigation is warranted to see whether the above discrepancy is related to laterality of the scoliotic curves and infratentorial neuroanatomical abnormalities. A larger sample and a longitudinal study is required to establish whether the brain abnormalities are predictive of curve progression.

Introduction: Ronald McRae’s textbook clinical orthopaedic examination mentions “Capasso’s method1 of evaluation of coronal plane deformity to be the most sensitive tool of measuring cobb angle. However there is no study to date evaluating/comparing this method against popular & widely used tools viz. cobbometer and traditional protractor.

Objectives: To evaluate Capasso’s method against commonly used measurement aids w.r.t measurement of cobb angle in scoliosis.

Summary of background data: Studies of Cobb method of measurement have multiple sources of error and intra & inter-observer variability. The Capasso’s method which is based on “bi-uni-vocal principle” views the scoliosis curve to be an arc of circumference and to be a true reflection of angular values and hence geometrically more valid.

Methods: 24 scoliosis curves were measured by three different examiners on three separate occasions one week apart by 1) Capasso’s method 2) Cobbometer and 3) Traditional protractor on same set of hard copies of digital x-rays. The three set of Cobb angle readings obtained were statistically analysed for intra & inter-observer reliability and assessed for agreement between the three methods of clinical measurement.

Results: The mean intra observer variability for protractor, cobbometer & Capasso’s methods were 8.50, 5.50 10.00 respectively. The cobb angle readings obtained by Capas-so’s method was higher than the other two methods for all magnitudes of the curves (< 300, 300–600 & > 600) and was more than two times the conventional readings for curves < 300. The disagreement between Capasso’s method with either of the other two methods (cobbometer & protractor) was statistically significant (p< 0.01).

Discussion: This study demonstrates that Capasso’s method significantly overestimates the magnitude of scoliotic deformity esp. for curves < 300 as compared to other existing popular measurement tools. Surgical decision making if were to be based on it would invite criticism and wrath. The present existing methods have their own limitations and the need of the day is a simple three dimensional measuring system to accurately define the magnitude of the deformity.

Introduction: Accurate and ethical coding is challenging and directly impacts on Payment by Results (PbR). The aims & objectives of this study were to review the existing pattern of coding for spinal surgery and ascertain its appropriateness & accuracy for surgical procedures, medical co-morbidities and post-op complications.

Methods: A retrospective review of 70 consecutive cervical and 100 consecutive lumbar spine patients who were operated from April 2006 onwards was conducted. The excel sheet provided by coding department, hospital notes – clinic letters, physicians’ entries, theatre notes and laboratory reports (biochemistry/microbiology/histology) – were reviewed. Of the 170 cases, 165 were available for analysis.

Results: Coding data of 5 patients who underwent cervical spine surgeries were not available. Of the 165 cases, the accuracy of primary procedural codes was 93.9% (90.8% cervical & 96% lumbar). However this reduced to 77.6% (75.4% cervical & 79% lumbar) when the accuracy for entire description of performed surgery was considered. The procedural codes did not specifically reflect the surgery performed and lacked reproducibility. Surgical levels were coded incorrectly in 9% of the cases. Cervical surgeries were coded as lumbar in 4 and posterior surgery as anterior in 3 cases respectively. Harvest of iliac crest bone graft was not coded in 5 cases. Medical comorbidities were coded appropriately in 64.2% of the patients (55% cervical & 70% lumbar). The commonly missed comorbidities were drug allergies, hypercholesterolemia, smoking and alcoholism. Post-op adverse events were coded in 75% of the cases (16/20 cervical & 5/8 lumbar). The accuracy was better for lumbar as compared to cervical spinal surgeries.

Conclusion: Coding is a universal language of communication amongst healthcare professionals. Its accuracy is important not just for PbR, but for data quality, audit and research purposes too. The financial implications regarding PbR governed by HRG codes (dictated by OPCS 4.4 & ICD–10 codes) are discussed. The awareness of clinical coding is low amongst junior doctors. Following this study, a clinical coding facilitation form has been introduced to improve data quality. Our plan is to close the audit loop and re-evaluate. Literature emphasises qualification of coders, legible documentation by physicians and interaction between coders and clinicians.

Introduction: Observation of sub-clinical neurological abnormalities has led to the proposal of a neuro-developmental etiologic model for adolescent idiopathic scoliosis (AIS). We have previously demonstrated prolonged latency in somatosensory evoked potentials (SSEP) and impaired balance control in subjects with AIS. Furthermore we have compared regional brain volumes in right thoracic AIS subjects and normal controls. Significant neuro-anatomic regional differences were observed in the corpus callosum, premotor cortex, proprioceptive and visual centers of the AIS subjects compared to control subjects. Most of these regional differences involved the brain unilaterally, indicating there may be abnormal asymmetrical development in the brain of subjects with right thoracic AIS.

Methods: Following ethical committee approval a total of 29 subjects with AIS were recruited. Patients with congenital, neuromuscular or syndromic scoliosis were excluded from the study. Twenty-eight age- and sex-matched controls were recruited from local schools. All recruits underwent three-dimensional isotropic magnetization prepared rapid acquisition gradient echo (3D_MPRAGE) magnetic resonance (MR) imaging of the brain. Modern morphometric analyses of the MR images were carried out including classification of tissue into grey matter (GM), white matter (WM) and cerebrospinal fluid (CSF). Tissue densities were compared between AIS subjects and controls. Comparisons were made between those subjects with left thoracic AIS (n=9) and age and sex-matched controls (n=11) and those subjects with right thoracic AIS (n=20) and age and sex-matched controls (n=17).

Results: For subjects with left thoracic curves the mean Cobb angle was 19 degrees. For subjects with right thoracic curves the mean Cobb angle was 33.8 degrees There was no significant differences observed between AIS subjects and normal controls when comparing both absolute and relative (i.e. adjusted for brain size) volumes of GM and WM. However voxel-based morphometric analysis identified significant differences in the density of WM in the genu of the corpus callosum, the left internal capsule and WM underlying the left orbitofrontal cortex when comparing those subjects with left thoracic scoliosis to controls. The above differences were not not observed when those subjects with right thoracic scoliosis were compared to controls..

Discussion: This controlled study of regional brain tissue density has demonstrated important differences in the corpus callosum, the left internal capsule and the left orbitofrontal cortex when the brain of those subjects with left thoracic scoliosis is compared to age and sex matched controls. In this study significant regional brain differences have not been identified in those subjects with right thoracic scoliosis. Further studies are warranted to ascertain whether these morphologial differences in the brain are linked with the etiopathogenisis of left sided thoracic scoliosis. A larger sample and a longitudinal study are required to establish whether brain abnormalities are predictive of curve progression.

The possibility that AIS aetiology involves undetected neuromuscular dysfunction is considered likely by several workers [1,2]. Yet in the extensive neuroscience research of idiopathic scoliosis certain neurodevelopmental concepts have been neglected. These include [3]:

a CNS body schema (“body in the brain”) for posture and movement control generated during development and growth by establishing a long-lasting memory, and

During normal development the CNS has to adapt to the rapidly growing skeleton of adolescence, and in AIS to developing spinal asymmetry from whatever cause. Examination of publications relating to the CNS body schema, parietal lobe and temporo-parietal junction [4,5] led us to a new concept: namely, that a delay in maturation of the CNS body schema during adolescence with an early AIS deformity at a time of rapid spinal growth results in the CNS attempting to balance the deformity in a trunk that is larger than the information on personal space (self) already established in the brain by that time of development. It is postulated that this CNS maturational delay allows scoliosis curve progression to occur – unless the delay is temporary when curve progression would cease. The maturational delay may be primary in the brain or secondary to impaired sensory input from end-organs [6], nerve fibre tracts [2,7,8] or central processing [9,10]. The motor component of the concept could be evaluated using transcranial magnetic stimulation [11].

Conclusion: Any maturational delay of the CNS body schema could impair postural mechanisms in girls and boys with or without early AIS deformity. The “body in the brain” concept adds a particular CNS mechanism (maturational delay) to the neuro-osseous timing of maturation (NOTOM) hypothesis for the pathogenesis of AIS [12,13]. The NOTOM hypothesis states that there are more girls than boys with progressive AIS because of different developmental timing of skeletal maturation and postural maturation between the sexes in adolescence [12,13].

In subjects with lumbar, thoracolumbar or pelvic tilt scoliosis no pattern of structural leg length inequality has been reported [1]. Forty-seven girls of 108 consecutive adolescent patients referred from routine scoliosis school screening during 1996–1999 had lower spinal scoliosis – lumbar (LS) 17, or thoracolumbar (TLS) 30 (mean Cobb angle 16 degrees, range 4–38 degrees, mean age 14.8 years, left curves 25). The controls were 280 normal girls (11–18 years, mean age 13.4 years). Anthropometric measurements were made of total leg lengths (LL), tibiae (TL) and feet (FL) by one observer (RGB) and asymmetries calculated for LL, TL and FL, as absolutes and percentage asymmetries of right/left lengths. There are no detectable changes of absolute asymmetries with age for LL, TL or FL in scoliotic or normal girls. Asymmetries are found in scoliotic girls compared with normals with relative lengthening on the right for each of LL (0.95%) and TL (0.99%) (each p< 0.001), but not FL (0.38%).

Conclusion: The relative lengthenings in the right leg are unrelated statistically to the severity or side of the lower spinal scoliosis; the cause is unknown and may be related to posture – free standing on the right leg [2] – to neuromuscular mechanisms, or to primary skeletal changes in growth plates of femur(s) and tibia(e).

Patterns of extra-spinal skeletal length asymmetry have been reported for upper limbs [1] and ribcage [2] of patients with upper spine adolescent idiopathic scoliosis. This paper reports a third pattern in the ilia. Seventy of 108 consecutive adolescent patients referred from routine scoliosis school screening during 1996–1999 had lower spine scoliosis – lumbar (LS), thoracolumbar (TLS), or pelvic tilt scoliosis (PTS). Radiologic bi-iliac and hip tilt angles were both measurable in 60 subjects: LS 18, TLS 31, and PTS 11 (girls 44, boys 16, mean age 14.6 years). Cobb angle (CA), apical vertebral rotation (AVR) and apical vertebral translation from the T1-S1 line (AVT) were measured on standing full spine radiographs (mean Cobb angle 14 degrees, range 4–38 degrees, 33 left, 27 right curves). Bi-iliac tilt angle (BITA) and hip tilt angle (HTA) were measured trigonometrically and iliac height asymmetry calculated as BITA minus HTA (corrected BITA=CBITA) and directly as iliac height asymmetry. Iliac height is relatively taller on the concavity of these curves (p< 0.001). CBITA is associated with Cobb angle, AVR and AVT (each p< 0.001).

Conclusion: The relatively taller concave ilium may be 1) real from primary skeletal changes or asymmetric muscle traction on iliac apophyses [3], or 2) apparent from rotation/torsion at the sacro-iliac joint(s).

In schoolchildren screened for scoliosis about 40% have minor, non-progressive, lumbar scolioses secondary to pelvic tilt with leg-length and/or sacral inequality [1] not reported with preoperative thoracic curves [2]. Forty-nine of 108 consecutive adolescent patients referred from routine scoliosis school screening during 1996–1999 had lower spinal scoliosis with measurable radiological sacral alar and hip tilt angles – lumbar scoliosis 18, thoracolumbar scoliosis 31 (girls 41, boys 8, mean Cobb angle 16 degrees, range 4–38 degrees). In standing full spine antero-posterior radiographs measurements were made of Cobb angle and pelvic asymmetries as sacral alar and iliac heights (left minus right). From anthropometric measurements derivatives were calculated as ilio-femoral length (total leg length minus tibial length) and several length asymmetries, namely: ilio-femoral length asymmetry, total leg length inequality and tibial length asymmetry (all left minus right). Ilio-femoral length asymmetry correlates significantly with sacral alar height asymmetry (girls negatively r= − 0.456, p=0.002, boys positively r=0.726 p=0.041) but not iliac height asymmetry (girls p=0.201) from which three types are identified. Total leg length inequality but not tibial length asymmetry in the girls is associated with sacral alar height asymmetry (r= − 0.367 p=0.017 & r=0.039 p=0.807 respectively). Interpretation is complicated by total leg lengths each including some ilium in which there is asymmetry [3]. But lack of association between ilio-femoral length asymmetry and iliac height asymmetry suggests that the femoral component is more important than iliac component in determining the associations between sacral alar height asymmetry and each of ilio-femoral length asymmetry and total leg length inequality.

Conclusions:

Sacral alar height asymmetry and leg length asymmetries. The evidence suggests that sacral alar height asymmetry is not secondary to the leg length inequalities at least in most girls (negative correlations) and is more likely to result from primary skeletal changes in femur(s) and sacrum.

Study Design: Long-term retrospective case review of function in children with early onset scoliosis managed by selective anterior epiphysiodesis and posterior ‘Luque trolley’ growing instrumentation

Method: spinal and clinical function was assessed utilising SRS-22 and SF-36 outcome measures. The rates of secondary surgical procedures and further definitive fusion were recorded. Pulmonary function was assessed by standardised and averaged spirometric data at follow up.

Results: 25 patients have been clinically reviewed and functionally assessed (age range 6–35 years) mean age 17.7 years at follow up. 16 patients have reached skeletal maturity (8males, 8females) with mean follow up 11.8 years, to a mean age of 22.4 years. clinically 80% of cases were well balanced. At maturity the average loss of axial spinal growth measured 10.25cm (arm span- standing height) (range +4 cm to −21cm). In the immature cohort still growing, median shortening was 0.75%, with average height loss 1.63% of predicted. SRS- 22 and SF-36 questionnaires indicated moderate – good functional outcomes in 80% of patients. Spirometric data, with one case incapable of test compliance, demonstrates 24 % of patients had normal spirometric functional parameters, 32% had mild restrictive deficits, 12% had moderate and 28% had severe restrictive deficits. Poor spirometric function did not correlate with poor outcome measures. Over 50% had required further surgery.

Conclusions: Poor functional outcomes occurred in patients requiring early and multiple surgical revision procedures associated with loss of control or fixation of primary and secondary spinal deformities.

The side distribution of single spinal curves in our school screening referrals for 1988–99 (n=218) suggests that the mechanism(s) determining curve laterality for the upper spine differs from those for the lower spine. We address here the laterality of right thoracic AIS. In the search to understand the aetiology of AIS some workers focus on mechanisms initiated in embryonic life including a disturbance of bilateral symmetry. The normal external bilateral symmetry of the body, highly conserved in vertebrates, results from a default process involving mesodermal somites. The normal internal asymmetry of the heart, major blood vessels, lungs and gut with its glands is also highly conserved among vertebrates. There is recent evidence that vertebrates retain an archaic asymmetric visceral organization in thoracic and abdominal organs (Cooke). In early embryonic life the visceral asymmetry develops from the breaking of the initial bilateral symmetry by a binary asymmetry switch producing asymmetric gene expression around the embryonic node and/or in the lateral plate mesoderm. In the mouse this switch occurs during gastrulation by cilia driving a leftward flow of fluid and morphogen(s) at the embryonic node (nodal flow) favouring precursors of heart, great vessels and viscera on the left. Based on the non-random laterality of thoracic AIS curves, we suggest that the binary asymmetry switch – through genetic/environmental factors extending to involve anomalously left-sided mesodermal precursors of vertebrae, ribs and/or muscles (positively or negatively), explains the distribution of right/left thoracic AIS. Some support for this hypothesis is the prevalence of scoliosis curve laterality associated with situs inversus.

Most workers consider that ribcage changes in AIS are secondary to spinal deformity. Others claim that ribs are pathogenic in curve initiation or aggravation. In 117 consecutive patients referred from school screening in 1996–99 and routinely scanned by ultrasound, 24 had thoracic and 33 thoracolumbar scolioses (right 37, left 20; mean age 14.9 years, range 12–18 years, girls 44 postmenarcheal 37, boys 13). On anteroposterior standing radiographs, Cobb angle (CA), apical vertebral rotation (AVR, Perdriolle) and apical vertebral translation (AVT from the T1-S1 line) were measured (mean & range: CA 19°, 6–42°; AVR 15°, 0–39°; AVT 17 mm, 0–38 mm). Real-time ultrasound in the prone position recorded laminal rotation (LR) and rib rotation (RR) segmentally and the spine-rib rotation difference (SRRD) as LR minus RR to estimate the combined rib deformity in the transverse plane using for thoracic curves apical LR and RR and for thoracolumbar curves T12 LR and T12 RR (mean LR 8.3°, RR 3.8°, SRRD 5.2° absolute). All deformity parameters, radiological and ultrasound, are unrelated to age. SRRD correlates significantly with each of AVR (r=0.753 p< 0.0001), Cobb angle (r=0.738 p< 0.0001), and AVT (r=0.725 p< 0.0001). Partial correlation analysis shows AVR rather than AVT is associated with the transverse plane rib deformity (SRRD/AVR controlling for AVT r=0.386 p=0.004; SRRD/AVT controlling for AVR r=0.257 p=0.058; SRRD/CA controlling for AVR r=0.260 p=0.055 and for AVT r=0.223 p=0.101). These and other findings suggest that rib rotation in thoracic curves is associated with AVR and AVT and in thoracolumbar curves more with AVR than AVT each within the 4^th column of the spine.

Introduction: Patient questionnaires permit a direct measure of the value of care as perceived by the recipient. The Scoliosis Research Society outcomes questionnaire (SRS-22) has been validated as a tool for self-assessment. We investigated the correlation between SRS-22 and a detailed radiological outcome two years following anterior correction of Thoraco-Lumbar Adolescent Idiopathic Scoliosis (TL-AIS).

Methods: The SRS-22 questionnaire was completed by 30 patients two years following anterior correction of TL-AIS. Pre-operative, post-operative and two year follow-up radiographs of all 30 patients were assessed. The following parameters were measured at each time point:

Primary Cobb angle,

The percentage improvements for each were noted. Correlation was sought between Total SRS score, each of the five individual domains and various radiographic parameters listed above by quantifying Pearson’s Correlation Coefficient (r).

Results: Percentage improvement in primary Cobb angle (r = 0.052), secondary Cobb angle (r = 0.165) and AVT of the primary curve (r = −0.353) showed little or no correlation with the SRS-22 total score or any of its five domains. Significant inverse correlation was found between the UIV tilt angle at two years and the SRS-22 (r = −0.516). Lateral radiographs however showed little or no correlation between thoracic kyphosis (r = 0.043) and SRS-22.

Conclusion: The SRS-22 outcomes questionnaire does not correlate with most of the radiographic parameters commonly used by clinicians to assess patient outcome.

Several workers consider that the aetiology of adolescent idiopathic scoliosis (AIS) involves undetected neu-romuscular dysfunction. During normal development the central nervous system (CNS) has to adapt to the rapidly growing skeleton of adolescence, and in AIS also to developing spinal asymmetry from whatever cause. A new etiologic concept is proposed after examining the following evidence:

anomalous extra-spinal left-right skeletal length asymmetries of upper arms, ribs, ilia and lower limbs suggesting that asymmetries may also involve vertebral body and costal growth plates;

The central of four requirements is maturational delay of the CNS body schema relative to skeletal maturation during the adolescent growth spurt that disturbs the normal neuro-osseous timing of maturation. With the development of an early AIS deformity at a time of rapid spinal growth the association of CNS maturational delay results in postural mechanisms failing to balance a lateral spinal deformity in an upright moving trunk that is larger than the information on personal space (self) established in the brain by that time of development. It is postulated that CNS maturational delay allows scoliosis curve progression to occur – unless the delay is temporary when curve progression would cease. The concept brings together many findings relating AIS to the nervous and musculoskeletal systems and suggests brain morphometric studies in subjects with progressive AIS.

In idiopathic scoliosis the detection of extra-spinal left-right skeletal length asymmetries in the upper limbs, ribs, ilia and lower limbs [1–7] begs the question: are these asymmetries unconnected with the pathogenesis, or are they an indicator of what may also be happening in immature vertebrae of the spine? The vertebrate body plan has mirror-image bilateral symmetries (mirror symmetrical, homologous morphologies) that are highly conserved culminating in the adult form [8]. The normal human body can be viewed as containing paired skeletal structures in the axial and appendicular skeleton as a) separate left and right paired forms (e.g. long limb bones, ribs, ilia), and b) united in paired forms (e.g. vertebrae, skull, mandible). Each of these separate and united pairs are mirror-image forms – enantiomorphs. In idiopathic scoliosis, genetic and epigenetic (environmental) mechanisms [9–11] may disturb the symmetry control of enantiomorphic immature bones [12–13] and, by creating left-right endochondral growth asymmetries, cause the extra-spinal bone length asymmetries, and within one or more vertebrae create growth conflict with distortion as deformities (= unsynchronised bone growth concept) [14].

Conclusion: This enantiomorphic disorder concept applied to the axial skeleton during infancy, juvenility and adolescence – through reductionism into the molecular mechanisms of growth plate responses to different hormones at successive phases of development – provides a new theoretical insight to explain the whole body deformity of AIS. The concept suggests preventive surgery on spine and ribs.

Study design: A retrospective review of patient records with recent clinical and radiographic assessment.

Objective: Long-term evaluation of the Luque trolley for posterior instrumentation in congenital scoliosis.

Summary of background data: From a group of 51 cases treated with the Luque trolley, we review 10 patients with progressive congenital scoliosis (5male, 5female) for a mean follow-up period of 14.8 years, to mean age of 19 years. The mean Cobb angle of the primary curve before surgery was 69.5 degrees. The mean Cobb angle of the secondary cervico-thoracic curve before surgery was 37.1 degrees and of the caudal secondary curve was 26.4 degrees. The mean age at surgery was 5.0 years. 8 patients had a selective epiphysiodesis procedure, 2 with hemi-vertebrectomy, and all underwent single- stage (7 patients) or dual-staged (3 patients) posterior instrumentation with a Luque trolley growing construct.

Method: Clinical evaluation and sequential measurements of Cobb angle were done, with recording of further surgical procedures, associated complications, and final coronal balance. The thoracolumbar longitudinal spinal growth (T1-S1) and growth in the instrumented segmented were also calculated.

Results: The mean preoperative primary curve Cobb angle of 69.5degrees, corrected to a mean postoperative angle of 30.6 degrees, with progression from here to curve magnitude of 38.8 degrees on latest follow up (approximate rate of progression of 0.55 degrees per year).

The mean pre-operative cephalic (cervico-thoracic) Cobb angle of 37.1degrees, corrected to 22 degrees, with progression to 26.6 degrees.

The mean pre-operative caudal (lumbar) Cobb angle of 26.4degrees, corrected to16.2 degrees, this later progressed to 20.6 degrees.

Coronal plane translation measured 1.68 cm at latest follow up [range 0.5–5.1cm].

The thoracolumbar longitudinal growth measured a mean of 8.81cm (approx0.8 cm/year) with a recorded lengthening of 2.54 cm (approx 0.23cm/year) in the instrumented segmented. Half the patients did not require further surgery.

Conclusion: Selective fusion does not always prevent further deformity in congenital scoliosis. The addition of posterior growing construct instrumentation did demonstrate capacity for good correction of primary and secondary curvatures and a limited capacity for further longitudinal growth.

Left-right skeletal length asymmetries in upper limbs related to curve side have been detected with adolescent thoracic idiopathic scoliosis (AIS). In school screening referrals with thoracic scoliosis we find apical vertebral rotation (AVR, Perdriolle) is associated significantly with upper arm length asymmetry. Sixty-nine of 218 consecutive adolescent patients referred routinely during 1988–1999 had idiopathic thoracic scoliosis of whom 61 had left and right upper arm lengths measured with a Holtain anthropometer (right curves 49, left curves 12, mean age 14.9 years, girls 38 postmenarcheal 34, boys 23). The controls are 278 normal girls and 281 boys (11–18 years, mean age 13.5 years). The mean value for Cobb angle is 18 degrees (range 4–42 degrees), AVR 13 (range 0–34 degrees), Cobb angle (CA) and AVR are each positively associated with upper arm length asymmetry (p=0.001 & p< 0.0001 respectively) and after correcting for each of Cobb side, apical level, sex and handedness, AVR and upper arm length asymmetry are still significantly associated (p=0.004 ANOVA). Partial correlation analysis shows AVR is associated with upper arm length asymmetry after controlling for CA (p=0.033); but not CA and upper arm length asymmetry after controlling for AVR (p=0.595). The reason why a larger AVR to the right is associated with a relatively longer right upper arm is unknown. Possibilities include neuromuscular and skeletal mechanisms, the latter relative concave overgrowth of neurocentral synchondrosis and/or of periapical ribs. We suggest consideration be given to combining convex vertebral body stapling (Betz) with concave periapical rib resection (Sevastik and Xiong) for right thoracic AIS in girls.

Introduction: Intra-Discal Electrothermal Therapy (IDET) has been used to treat chronic discogenic low back pain. Proposed mechanisms of action include denervation of the posterior annulus and collagen denaturation. Previous authors have reported on changes in internal disc mechanics following IDET including reduction in stress concentrations possibly leading to a more even distribution of load across the end-plate¹. A novel intradiscal decompression catheter has been developed to reduce local disc bulging in cases of contained prolapse. This new catheter is inserted percutaneously into a disc and advanced under radiographic control into a postero-lateral position targeting the herniation. The decompression catheter uses more focused heating and higher temperatures than previous devices and is intended to provide a local decompression of the disc through a thermally-mediated reduction in nuclear volume. The purpose of this study was to investigate changes in internal stress profiles following use of the new catheter.

Methods: Five cadaveric lumbar ‘motion segments’ were dissected from two spines (age 64–84 yrs). Each segment was compressed, normally to 1 kN, while a miniature pressure transducer was withdrawn from posterior to anterior across the mid-sagittal diameter of the disc producing a baseline stress profile. A decompression catheter was inserted into the disc and its position confirmed with plain radiography. The temperature of the catheter was increased to 90°c over a period of 14 minutes. Stress profiles were then repeated.

Results: Stress profiles in three of the five segments showed changes consistent with degenerative change. In these discs stress profiles following ‘treatment’ showed up to a 35% reduction in the magnitude of stress peaks in the posterior annulus. There was very little change in the distribution of stress in the two non-degenerate discs. Stress in the nucleus appeared unchanged in all discs.

Conclusions: Treatment of degenerate discs with the decompression catheter lead to a measurable alteration annular stress peaks that have been associated with degenerative disc disease, while non-degenerate discs were unaffected. These preliminary findings of an ongoing study suggest that the novel decompression catheter has a biomechanical effect in certain classes of disc.

Introduction: Intra-Discal Electrothermal Therapy (IDET) has been proposed as a treatment for chronic discogenic low back pain. Reports from prospective outcome studies demonstrate statistically significant improvements, but there are no published randomized controlled trials assessing efficacy against a placebo group.

Methods: Ethical committee approval was obtained prior to the study. Patients with chronic low back pain who failed conservative treatment were considered for the study. Inclusion criteria included one or two level symptomatic internal disc disruption as determined by provocative CT/discography. Patients were excluded if there was > 50% loss of disc height or had had previous back surgery. Fifty-seven patients were randomized with a 2:1 (IDET: Placebo) ratio, 38 to the active IDET arm and 19 to the sham (placebo). The IDET catheter was positioned under sedation to cover at least 75% of the annular tear as defined by the CT/discogram. An independent technician connected the catheter to the generator and either delivered electrothermal energy (active group) or did not (sham group). Surgeon, patient and independent outcome assessor were all blinded. All patients followed a standard rehabilitation programme.

Outcome Measures: Low Back Outcome Score (LBOS), Oswestry Disability Index (ODI), SF-36 questionnaire, Zung Depression Index (ZDI) and Modified Somatic Perceptions Questionnaire (MSPQ) were measured at baseline and 6 months. Successful outcome was defined as: No neurological deficit resulting from the procedure, improvement > 7 points in LBOS, improvements > 7 points in SF-36 subsets (pain / disability, physical functioning and bodily pain)

Results: Two subjects withdrew from the study (both IDET). Baseline demographic data, employment and worker’s compensation status, sitting tolerance, initial LBOS, ODI, SF-36, ZDI and MSPQ were similar for both groups. No neurological deficits occurred as a result of either procedure. No subject in either treatment arm showed improvement of > 7 points in LBOS or the specified domains of the SF-36. Mean ODI was 41.4 at baseline and 39.7 at 6 months for the IDET group compared to 40.7 at baseline and 41.5 at six months for the Placebo group. There was no significant change in ZDI or MSPQ scores for either group.

Discussion: No subject in either treatment arm met criteria for successful outcome. There was no significant change in outcome measures in either group at six months. This study demonstrates no significant benefit from IDET over placebo.

Introduction: Propionibacterium acnes (P. acnes), a common anaerobic skin commensal, has been implicated in biomaterial-related infections (BRI). Bacteria can adhere to biomaterial surfaces and grow as a bio-film held together by exopolymer, exhibiting increased antimicrobial resistance. To our knowledge, images of P. acnes biofilms have not previously been published. We have demonstrated the ability of P. acnes to adhere to surgical steel and to develop a biofilm on this material. However its ability to adhere to and develop a biofilm on titanium, a commonly used surgical implant material, has not been fully investigated.

Aims:

To determine the quantitative adherence and biofilm development of P. acnes on titanium compared to surgical steel.

Method: Six clinical isolates of P. acnes were assayed for adherence to materials with and without plasma glycoprotein conditioning film by chemiluminescence and culture. Biofilm development was assessed by chemiluminescence, fluorescence microscopy, environmental (ESEM) and scanning electron microscopy (SEM). Mature biofilms were exposed to plasma concentrations of penicillin and quantified by chemiluminescence and culture. Unpaired student’s t tests and univariate linear regression models were calculated using SPSS software (version 12).

Results: Univariate linear regression showed that P. acnes adherence to titanium was 18% (p=0.001) greater than to steel. Adherence was reduced by the presence of the conditioning film on titanium by 28% (p=0.001), but this made no significant difference to P. acnes adherence to steel. P. acnes biofilms were clearly demonstrated, along with bacterial expolymer, showing an interesting similarity to biofilms of S. epidermidis. P. acnes grows as a thick biofilm on both materials held together by exopolymer and our preliminary results suggest that biofilms on titanium might be less susceptible to antimicrobials after 24 hours of penicillin treatment; a reduction of 94% on steel and 81% on titanium (p=0.057, p=0.39 resp).

Conclusions: P. acnes adheres to steel and titanium, a crucial first step in BRI. Greater numbers of P. acnes adhere to titanium than to steel. The naked surface of titanium is microporous, assisting adhesion. A conditioning film reduces P. acnes adherence to titanium but not to steel. P. acnes develops as a biofilm on steel and titanium. Results indicate that pathogenesis of P. acnes infection on titanium is more successful than on steel. P. acnes biofilms on titanium may be harder to eradicate with antimicrobial agents.

Introduction: Dynesys is a novel, dynamic stabilization system designed for the treatment of degenerative conditions of the lumbar spine that present with unstable motion segments. This system uses pedicle screws with a modular spacer mounted on a stabilising cord, which controls movement of the instrumented segment in all planes. The purpose of this study was to investigate changes in the biomechanic response of the intervertebral disc (IVD) under normal, flexed and extended loading conditions before and after Dynesys is applied. The IVDs of both the instrumented (bridged) and the adjacent (floating) segment were studied.

Methods: Twelve L3-5 cadaveric segments were dissected and compressed to 1kN in 6° flexion, neutral and 4° extension. The test was done without spacers and with spacers measured to +2mm, neutral and −2mm, where neutral equates to the normal distance between the pedicle screws without an applied load. The stress distribution in the mid-sagittal and posterolateral diameters of both the bridged and floating discs was measured using a miniature pressure transducer. This resulted in greater than 300 stress profiles per specimen. Disc movement and segment motion during loading were recorded using ultrasound imaging and infra-red reflection respectively.

Results: Without stabilization, stress peaks observed in the anterior annulus increased by more than 85% as the specimen was loaded from 4° extension to 6°flexion. With the application of Dynesys, these anterior stress peaks were reduced across the bridged segment. This was most pronounced in 6° flexion where anterior stress peaks of greater than 1 MPa were reduced by 100% in the bridged segment in more than 90% of specimens.

Conclusions: The degree of flexion or extension of the specimen during loading influences the peak stresses generated in the annulus. Dynesys has the potential to relieve peak stresses in the anterior annulus which is most pronounced when the specimen is loaded in flexion.

Background: In lumbar scoliosis curves of school screening referrals were evaluated (1) for the possible relation of pathomechanisms to standard and non-standard vertebral rotation (NSVR) [1], and (2) the relation between apical lumbar axial vertebral rotation and the frontal plane spinal offset angle (FPTA) [2].

Methods: Consecutive patients referred to hospital during routine school screening using the Scoliometer were examined in 1996–9. None had surgery for their scoliosis. There are 40 subjects with either pelvic tilt scoliosis (11), idiopathic lumbar scoliosis (19), or double curves (10)(girls 31, postmenarcheal 25, boys 9, mean age 15.3 years). One observer (RGB) measured: 1) in AP spinal radiographs Cobb angles (CAs), apical vertebral rotations (Perdriolle AVRs), and trigonometrically sacral alar tilt angle (SATA), and FPTA as the tilt of the T1–S1 line to the vertical; and 2) total leg lengths (tape).

Results: Excluding the double curves there are 16 left and 14 right lumbar curves mean CA 11 degrees (range 4–24 degrees), mean AVR 9 degrees (concordant to CA in 18/30, discordant in 7/30), SATA 2.8 degrees (range 0.2–7.7 degrees associated with CA side and severity, p=0.0003), and leg-length inequality 0.7 cm (significantly shorter on left, p< 0.0001 and associated with SATA (p=0.02) but not CA). Neither CA nor AVR in each of the laterality concordant and discordant lumbar or thoracic curves is significantly different. Twenty-six subjects have thoracic curves (16 right) 22 with AVR (mean CA 11 degrees, range 4–17 degrees, AVR 9 degrees, n=22) the CA being associated with each of lumbar CA and SATA (respectively p< 0.0001, p=0.003, n=26). Thoracic curve laterality of CA and AVR is concordant in 12/26 curves and discordant in 10/26 and for concordance/discordance neither is significantly different; thoracic AVR sides with laterality of lumbar curve AVR shown by thoracic AVR (but not CA) being greater in lumbar discordant than in lumbar concordant curves (14 & 7 degrees respectively, p=0.03, n=18 & 7). Both for lumbar curves alone and for lumbar with double curves, AVR by side is significantly associated with FPTA by side (r= −0.568, p=0.001, n=30; r=−0.560, p=0.0002, n=40).

Conclusion: (1) It is hypothesized that different pathomechanisms may separately affect the frontal (CA) and transverse (AVR) planes: in discordant curves these mechanisms may neutralize each other and limit curve progression; concordant curves require these biplanar mechanisms to summate and facilitate curve progression. (2) The association of frontal plane spinal tilt angle and lumbar AVR may result from balance mechanisms affecting trunk muscles – mechanisms that may underlie the complication of post-operative frontal plane spinal imbalance or decompensation [2].

Background: To assess the treatment of Lenke Type 1 Curves with anterior USS Instrumentation.

Methods: A retrospective radiographic review of 29 cases. Twenty nine patients with Lenke type 1 curves were treated with anterior USS instrumentation. The average age was 14.8 years (range 12–25 years) with an average of 17.4 month follow up (range 6–61 months). 27 were right sided curves, with 2 left sided. Standard AP and Lateral Standing X-rays were taken preoperatively (together with bending films), post-operatively and at follow-up. Measurements recorded at each assessment were the mean Cobb angle, sagittal and coronal balance, kyphosis and lordisis. Complications we associated with the instrumentation were also recorded.

Results: 12 patients had double minithoracotomies, the rest (17), single thoracotomies, the average blood loss at operation was 1055mls, with no significant difference between the two groups. The mean number ofleve1s instrumented was 6 (range 4–8). The mean pre-operative Cobb angle of the major thoracic curve was 53° (range 37–74). This value corrected to 24° on fulcrum bending films. The compensatory lumbar curve averaged 36° bending down to 6.°. The mean correction of these two curves post-operatively and then at most recent follow-up was 21 and 26 degrees for the thoracic curve, and 21 and 20 degrees for the lumbar curve. The mean pre-operative kyphosis was 25 increasing to 34 post-operatively and 39 at follow-up. The mean lumbar lordosis readings were 46, 46 and 45 respectively. Sagittal balance, gradually improved from a mean of 12mm to 11 then 10 at follow -up. Coronal balance did not show the same trend and was 3mm pre-operatively then 7 and 7 at final follow up. Instrumentation complications in total occurred in 9 cases, which included 4 cases of vertebral body fracture requiring circlage wiring and 5 cases of partial screw pulling out of the vertebral body. Fractures requiring wiring occurred at T5, T7, one case of three levels T6,7,8 and one case of two levels T6,7, this complication always occurred at the highest level instrumented. Partial screw pull-out always occurred at T5, with two cases occurring at two levels i.e T5,6.

Conclusion: Good correction was obtained with an mean of 6 instrumented levels. There was however a significant instrumentation complication (31 %). Despite this the intra-operative fractures caused no significant complications and good correction was still achieved in these cases. There are some concerns over mild deterioration in the curves over long term follow up but this deterioration is not clinically significant.

Background: In preoperative thoracic (TC) and thoracolumbar (TLC) AIS curves to evaluate periapical rib-vertebra angle asymmetry [1] and rib-spinal angle asymmetry in relation to the spinal deformity and the 4th column support of the spine [2].

Methods: Consecutive preoperative AIS patients having spinal instrumentation and fusion were assessed using radiographs and ultrasonographs. Twenty-eight preoperative patients with AIS were studied (TC 19, apex T8-9 in 15, TLC 9, apex T12 in 2, L1 in 7, mean Cobb angle 51 degrees). In AP radiographs the following were measured by one observer (RGB): Cobb angle (CA), apical vertebral rotation (AVR) and apical vertebral translation (AVT) from the T1-S1 line; in TC at 6 levels about the apical vertebra (3 above, at and 2 below) for each of 1) rib-vertebral angles (RVAs) and difference (RVAD=concave minus convex RVA), 2) rib-spinal angles (RSAs) to the T1-S1 line and difference (RSAD), and 3) vertebral tilt; and in TLC the RVAs, RVADs, RSAs and RSADs of ribs 11 & 12. The ultrasound apical spine-rib rotation difference (SRRD) was obtained as a measure of transverse plane rib deformity. With the subject in a prone position and head supported, readings of laminal rotation (LR) and rib rotation (RR) were made on the back at 12 levels by one of two observers (RKA, ASK) using an Aloka SSD 500 portable ultrasound machine with a veterinary long (172mm) 3.5 MHz linear array transducer. The maximal difference between LR and RR about the curve apex was calculated as the apical spine-minus-rib rotation difference (SRRD).

Results: Thoracic curves. The RVADs (but not the RVAs, RSAs or RSADs) only at 2 & 3 levels above the apex correlate significantly with each of CA (p=0.054), AVR (p=0.047), AVT (p=0.014, after controlling for CA p=0.131) and vertebral tilt (p=0.032) but not SRRD (all two levels above apex). Thoracolumbar curves. The 11th RSAD (but not RVAD or RSAs) correlates significantly with each of AVR (r= −0.776, p=0.014, after controlling for CA p=0.022) and SRRD (r= −0.890, p=0.001, after controlling for CA p=0.003) that together correlate significantly (r=0.672, p=0.048).

Conclusion: In TC supra-apical rib asymmetry (RVAD) in sternally-stabilized [2] and longest levers of the sternal-rib complex is associated with spinal deformity; in TLC supra-apical rib asymmetry (11th RSAD) is associated with transverse plane deformity of each of the apical vertebra (mainly L1) and 12th ribs. These rib associations, probably secondary to the spinal deformity, may involve a primary rib component in the 4th spinal column. The prognostic value of supra-apical RVAD and RSAD for progressive AIS needs to be evaluated.

Objective: We evaluated retrospectively whether there is a role for selective posterior thoracic correction and fusion in double major curves with third generation instrumentation systems.

Methods: In a retrospective review the radiographs of 36 patients with Lenke 3C type curve patterns and having had a selective posterior thoracic correction and fusion with either the Cotrel-Dubousset instrumentation or the Universal Spine System, were evaluated in terms of coronal and sagittal plane balance, curve flexibility, and curve correction with a minimum follow up of two years. Postoperative coronal spinal decompensation was investigated with respect to preoperative radiographic parameters on standing AP, thoracic and lumbar supine side-bending as well as lateral standing radiographs. Coronal spinal decompensation was defined as plumbline deviation of C7 of more than 2 cm with respect to the center sacral vertical line within two years postoperatively. Two groups of patients were analyzed.

Results: 26 patients (72%) showed satisfactory frontal plane alignment by means of C7 plumb line deviation (group A, 1.2 cm to the left), whereas 10 patients (28%) showed coronal spinal decompensation (group B: 2.7 cm to the left; p=0.003). Group differences, could be revealed for lumbar apical vertebral rotation (Perdriolle) (p=0.02, A: 16°, B: 22°) and the percentage correction (derotation) of lumbar apical vertebrae in lumbar supine side-bending films in comparison to AP standing radiographs (p=0.002, A: 49%, B: 27%). Average thoracic curve correction was 51% in group A and 41% in group B (p=0.05). Average lumbar curve correction was 34% in group A and 23% in group B (p=0.09).

High correlation was revealed between postoperative decompensation and derotation of lumbar apical vertebrae (P=0.62, p< 0.001) with a critical value of 40%. A 2x2 table showed that in patients with lumbar apical vertebral derotation of less than 40% specificity was 90% with regard to postoperative decompensation.

Conclusion: Lumbar apical vertebral derotation of less than 40%, determined on lumbar supine side-bending films in comparison to AP standing radiographs, provided the radiographic prediction of postoperative coronal spinal imbalance. We advice close scrunity of the transverse plane in the lumbar supine side-bending film when planning surgical strategy.

Study Design: Prospective cohort study

Summary of Background data: A definite link between Modic end plate changes and discogenic low back pain has yet to be established. However, current prospective data indicates that Modic changes strongly correlate with the pain provocation of lumbar discography and improved clinical outcome following instrumented posterolateral fusion. Consequently, there is recent heightened awareness using this radiological entity in the selection of patients for interbody fusion or total disc replacement.

Objective: To prospectively evaluate whether Modic changes can predict improved clinical outcome following antero-posterior lumbar interbody fusion using femoral ring allograft.

Methods: A cohort of chronic low back pain patients were investigated with MRI and lumbar discography. Twenty-six patients with disco-graphically-proven concordant pain reproduction were prospectively entered into the study. Clinical results were collected using the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) and Short Form 36 Health Questionnaire (SF-36) at the pre-operative and two-year follow up. The minimal clinically important difference (MCID) was taken as 10 points for ODI, 2 points for VPAS, and 7 points for the physical function and bodily pain subset of the SF-36 questionnaire.

Results: MRI scans evaluated for the level fused revealed 13 patients with no end-plate changes (Type 0), whilst 2 patients had Modic Type I and 11 had Modic Type II changes. MCID in ODI were achieved in Type 0, Type 1 and Type 2, but improvement in VAS only was achieved in the Type 0 and Type 1. For SF-36, the MCID of 7 points was reached in most domains for all types of Modic change. There was no statistical difference in clinical outcome between those patients with Modic Type 0 and those with Modic type I or II.

Conclusion: This prospective study shows that Modic changes do not predict improved clinical outcome following antero-posterior interbody fusion using the femoral ring allograft.

Study Design: Retrospective chart review.

Objective: To assess the clinical and radiological outcome of surgery for both dystrophic and non-dystrophic curves resulting from neurofibromatosis Type I.:

Subjects: 10 patients (7 females, 3 males) underwent surgical correction for neurofibromatous kypho-scoliosis between 1997–2003. The mean age at surgery was 16 years (range 8–37 years). Average follow-up 20 months (range 9 months – 4.5 years). Seven patients had MRI proven dystrophic curves (group I). These underwent 2–3 level apical vertebrectomy, followed by 2–3 weeks in Halo traction, followed by instrumented posterior spinal fusion and anterior rib strut grafting. Three patients had non-dystrophic curves (group II). Two underwent posterior instrumented fusion and one (aged 8 years) underwent convex epiphyseodesis with posterior Luque trolley.

Outcome Measures: Cobb angle, thoracic kyphosis, lumbar lordosis, global apical vertebral translation (AVT), regional AVT, coronal and sagittal balance, complications and Modified SRS Outcomes Instrument completed at final follow.

Results: For the dystrophic curves the Cobb angle improved from a mean of 81.5 degrees (mean bending film to 76 degrees) to 26.6 degrees post-operatively (68% correction) and 35.8 degrees at final follow-up (56% correction) and the global AVT improved from 61.5 mm to 29 mm at final follow-up. The average score for the modified SRS outcome instrument was 91.6 (Good). For the non-dystrophic curves the Cobb angle improved from a mean of 57.5 degrees (mean bending film to 47 degrees) to 23.5 degrees post-operatively ( 60% correction) and 24.6 degrees at final follow-up (57% correction) and the global AVT improved from 56.8 mm to 27.8 mm at final follow-up. The average score for the modified SRS outcome instrument was 98.5 (Good). All complications occurred in the dystrophic group including superficial infection in 2, dural leaks in 3, temporary brachial plexus injury in 1, worsening of lower limb neurological deficit in 1 and one death (upper GI haemorrhage). There was no failure of metalwork or evidence of pseudarthrosis identified. Seven of eight patients stated that they would have the surgery done again.

Conclusions: Non-dystrophic curves maybe treated by posterior fusion alone achieving 60% Cobb correction and 55% AVT correction. Close observation should be maintained for the appearance of dystrophic features and deterioration of correction. Dystrophic curves should be treated early and aggressively by two/three stage apical vertebrectomy, grafting and posterior spinal fusion. In this series 68% coronal Cobb and 63% AVT correction was achieved post-operatively. Complications can be expected with scoliosis associated with more than 50 degrees of kyphosis.

Study Design: Retrospective chart review.

Summary of Background Data: Spinal osteotomy in ankylosing spondylitis is performed to restore forward gaze and sagittal balance. Closing wedge lumbar osteotomy and polysegmental thoracic osteotomy in the same patient has not been reported.

Objective: To study the factors affecting correction of sagittal balance.

Subjects: 27 patients (23 male, 4 female) operated between 1989–2002: average age 46 years: minimum follow-up: 18 months. 19 patients had lumbar osteotomy alone, 6 had both lumbar and thoracic osteotomies and 2 had thoracic osteotomy alone. Three groups were identified: A) patients with decreased lumbar-lordosis and normal thoracic-kyphosis B) Normal / increased lumbar-lordosis and increased thoracic-kyphosis C) Decreased lumbar-lordosis and increased thoracic-kyphosis.

Results: Preoperatively, mean sagittal balance was +103 mm, thoracic-kyphosis 61 degrees, and lumbar-lordosis 25 degrees. Three months postoperatively, sagittal balance was +36 mm, thoracic-kyphosis 55 degrees, and lumbar-lordosis 49 degrees. At final follow-up sagittal balance was +44 mm, thoracic-kyphosis 57 degrees and lumbar-lordosis 46 degrees. In patients who had thoracic osteotomies, thoracic-kyphosis of 78 degrees was corrected to 48 degrees. There were no spinal cord injuries or permanent nerve root palsies. Six patients had deterioration of sagittal balance (SB) (> 45 mm), 5 of them required cervical osteotomy. There was significant association between post-operative thoracic-kyphosis of > 60 degrees and SB deterioration (p-value < .001, sensitivity 100%, specificity 75%). Statistically there was no significant association between SB deterioration and post-operative sagittal balance, lumbar-lordosis, osteotomy-angle and extent of fixation.

Conclusions: Correction of thoracic-kyphosis affected final sagittal balance significantly. Consideration should be given to the simultaneous performance of lumbar osteotomy and polysegmental thoracic osteotomies in selected patients to obtain greater correction and restoration of near normal sagittal balance.

Study Design: A consecutive retrospective cohort including all patients treated by a single consultant spinal surgeon (BJCF) with targeted foraminal epidural steroid injection (FESI) for radicular pain.

Objective: To assess the efficacy of targeted foraminal epidural steroid injection (FESI) for radicular pain in preventing surgical intervention.

Summary of Background Data: 90% of sciatica resolves within 90 days. Beyond this period, decompresssive surgery for pain relief maybe considered. Open surgery however carries attendant risk including nerve root injury, dural laceration, cauda equina syndrome, deep infection, recurrent disc prolapse, epidural fibrosis and post-discectomy lumbar instability. Peri-radicular infiltration of local anaesthetic and steroid has been shown to reduce pain, at least in the short term. We were interested in whether FESI could obviate the need for surgery in refractory cases of nerve root pain.

Methods: 83 consecutive patients (45 female, 38 male) with a mean age of 51 years (range 24 to 87) presenting between November 2000 and February 2003 with radicular pain were treated with targeted FESI. 55 patients had a principal diagnosis of disc prolapse, 20 had lateral canal stenosis and 8 had degenerative spondylolisthesis. Fourteen had previous surgery and 38 had previous caudal or lumbar epidural injections.

Outcome Measures: Pain was assessed using the Visual Analogue Score and disability by the Oswestry Disability Index. The product-limit method of Kaplan Meier was used to assess the time to further procedure or the date of last review.

Results: 21 of 83 patients (25.3%) underwent an open procedure (discectomy/decompression) within the designated time period (median 20 months). Median time to open procedure was 6.5 months (mean 8.2 months). Repeat FESI was required in 16 patients (19.2%). The remaining 46 (55.4%) patients avoided any further procedure at a median of 20 months (range 13 to 36). No complications resulted from these procedures.

Conclusions: Targeted foraminal epidural steroid injection can resolve radicular pain caused by varying pathologies. Surgical procedures (decompression/discectomy) can be avoided in 74.7% of cases up to a median of 20 months thereby avoiding unnecessary surgical risk.

Objective: To investigate the effects of intra-discal electro-thermal therapy (IDET) on an experimentally induced posterolateral annular inter vertebral disclesion in sheep.

Summary of Background Data: IDET is being used increasingly as a minimally-invasive treatment for chronic discogenic low back pain, with success reported in up to 70% of cases. The mechanism of action however is poorly understood. Proposed mechanisms include the contraction of collagen and the coagulation of annular nociceptors. An ovine model was used to assess the innervation of peripheral posterolateral annular lesions and the potential for IDET to denervate this region.

Methods: Posterolateral annular incisions were made in 36 lumbar discs of 18 sheep. After twelve weeks the sheep underwent IDET at one level and a sham treatment at the other level. IDET was performed using a modified intradiscal catheter (SpineCATH™, Oratec Interventions Inc., Menlo Park, CA). Temperatures were recorded in the nucleus (T_N) and the posterior annulus (T_Pa). The spines were harvested at intervals up to eighteen months. Histological sections of the discs were stained with haematoxylin and eosin and an antibody to the general neuronal marker PGP 9.5.

Results: The target temperature of 90°C at the catheter was tip was reached in all cases. The mean maximum T_Pa was 63.6°C and the mean maximum T_N 67.8°C. Vascular granulation tissue consistent with a healing response was observed in the region of the posterior annulus tear of all incised discs from 12 weeks. PGP 9.5 positive nerve fibres were clearly identified in the adjacent periannular tissue, but were scarce within the outer few lamellae of the annulus. There were no fewer nerve fibres identified in those specimens that had undergone IDET. From six weeks after IDET there was evidence of thermal necrosis in the inner annulus, sparing the periphery of the disc.

Conclusions: IDET delivered at 90°C in the sheep consistently heats the posterior annulus and the nucleus to a temperature range associated with coagulation of nociceptors and collagen contraction. Thermal necrosis was observed within the inner annulus from six weeks after IDET. In this model IDET did not produce denervation of the experimentally induced posterior annular lesion.

Study Design. A reliability study of the Modic classification.

Objective. To determine the reliability and reproducibility of the Modic classification for lumbar vertebral marrow changes.

Summary of Background data. In 1988, Modic with colleagues described two degenerative stages of vertebral marrow and endplate morphology. These were Type I (inflammatory phase) and Type II (fatty phase). Later in 1988, he added a third variety; Type III where there was marked sclerosis adjacent to the endplates. No formal reliability or reproducibility studies had been performed on the Modic classification.

Methods. This study involved five independent observers of differing spinal experience using the Modic classification to grade fifty sagittal T1 and T2 weighted MRI scans. The observers repeated the assessment at three weeks. Intra- and inter-observer reliabilities were assessed using kappa statistics.

Results. There were 7 type I, 40 type II, 1 type III and 2 normal levels. The individual intra-observer agreement was substantial or excellent with kappa values ranging from 0.71 to 1.00. The overall inter-observer agreement was excellent with a kappa value of 0.85. There was complete agreement in 78% of the levels, a difference of one type in 14% and a difference of two or more in 8% of levels. The level of experience of the observer did not correlate with a better score.

Conclusions. We have shown that the Modic classification is both reliable and reproducible. It is simple and easy to apply for observers of varying clinical experience. We therefore recommend its use in clinical research and practice.

Study Design: Retrospective case series.

Objective: To evaluate the clinical outcome, radiographic results and complications associated with single rod anterior instrumentation in neuromuscular thoracolumbar scoliosis.

Methods: Retrospective study with mean follow up of 35 months.

Subjects: Nine patients (6F, 3M), mean age 15 years, were operated on between 1994–2000. This heterogeneous patient group consisted of five cases of spinal dysraphism, one prune belly syndrome, one arthrogryposis, one myotonic dystrophy and one congenital myopathic dystrophy (muscle-eye-brain-syndrome). All patients were ambulatory and had minimal pelvic obliquity (< 15degrees).

Outcome measures: Pre-operative, post-operative and final follow-up measurements of Cobb angles, apical vertebral translation (AVT), thoracic kyphosis, lumbar lordosis, sagittal and coronal balance were recorded along with operative complications, pseudarthrosis, metalwork failure and loss of correction.

Results: There was one rod breakage and one case of proximal thoracic curve progression requiring supplementary posterior surgery. For the remaining 7 patients, the average corrections for Cobb angle was 62% (52 to 20 degrees), AVT was 53% (5.7 to 2.7cms), and both thoracic kyphosis and lumbar lordosis remained unchanged. No pseudarthrosis, vascular or neurological complications were encountered. Subjectively results were excellent in six and good in one.

Conclusions: Selective anterior instrumentation for neuromuscular scoliosis using a single rod resulted in acceptable clinical and radiographic outcomes in this highly selected series. Advantages include preservation of distal lumbar motion segments whilst maintaining sagittal and coronal alignment. We believe that this method of scoliosis correction has a definite yet select role in patients who are ambulatory, have minimal pelvic obliquity (< 15degrees), non-progressive pathology and near normal mental function.

Study Design: Retrospective study.

Objective: To describe a modified cervico-thoracic extension osteotomy and evaluate clinical & radiographic outcomes.

Subjects: 10 patients with fixed cervico-thoracic kyphosis, average age 56 years, minimum 12 months follow-up. Three patients had psoriatic spondyloarthropathy, Three patients had previous lumbar osteotomies.

Technique: General anaesthesia and SSEP spinal cord monitoring was used. Complete laminectomy of C7, hemilaminectomy of C6 and T1, plus pedicle subtraction osteotomy and decancellisation of C7 was performed. Upon completion of the osteotomy, controlled halo manipulation allowed closure of the osteotomy: the pivot point being the anterior longitudinal ligament. Segmental fixation with lateral mass and pedicle screws plus bone graft was then added. All patients were immobilised for three months in halo-jacket.

Results: Restoration of normal forward gaze was achieved in all patients. Mean preoperative kyphosis of 17 degrees was corrected to lordosis of 36 degrees (mean total correction 53 degrees). No spinal cord injuries or permanent nerve root palsies occurred. Three patients had mild sensory radiculopathies lasting a few weeks. No loss of correction, no pseudarthrosis, one patient had 50% anterior subluxation that later united. Two deep infections were successfully treated with wound washout and antibiotics.

Conclusions: Cervico-thoracic osteotomy in ankylosing spondylitis continues to be challenging and hazardous. C7 decancellisation and extension osteotomy supplemented with segmental internal fixation provides immediate spinal stability, reduces sagittal spinal translation and associated high risk of neurological injury, whilst maintaining correction until bony union.

Study Design: Cadaveric study on the effects of Dynesys.

Summary of Background Data: Dynesys is a novel form of soft stabilization that utilises pedicle screws and modular spacers mounted on a stabilising cord to control movement of the instrumented segment in all planes. In this way it provides a biomechanical alternative with greater physiological function than spinal fusion and may prevent the penalties of “overworking” adjacent levels.

Objective: The biomechanical response of both the instrumented and adjacent intervertebral discs (IVD) is investigated under compressive loading in flexion and extension. The effects of varying spacer heights on intradiscal pressure distribution are also reported.

Methods: Twelve L3-5 cadaveric lumbar segments were compressed to 1 kN in 6° flexion, neutral and 4° extension. The stress distribution in the mid-sagittal and posterolateral diameters of both the bridged and adjacent discs was measured by withdrawing a miniature pressure transducer across the IVD. Dynesys was applied across a single level and +2mm, neutral and −2mm spacer configurations tested in each position of loading. Over 2500 stress profiles were collected and the data obtained from measurements with and without application of Dynesys was analysed.

Results: In the absence of instrumentation stress peaks in the anterior annulus increased with a greater degree of specimen flexion. In 0° to 6° flexion, Dynesys eliminated the anterior stress peaks observed in the instrumented disc in 80% of specimens tested. In the +2mm to −2mm spacer range tested, posterior stress peaks were generally seen to increase with decreasing spacer height. Little effect is seen with the application of Dynesys to a non-degenerate disc. Preliminary analysis of the data suggests that stress distribution through the adjacent disc appears largely unchanged with instrumentation of the inferior segment.

Conclusions: Dynesys has the potential to relieve peak stresses in the anterior annulus seen particularly in positions of flexion. Spacer size influences the generation of peak stresses seen within the posterior annulus. Initial observations indicate that the IVD of the adjacent motion segment is not biomechanically prejudiced following the application of Dynesys.

Introduction: Dynesys is a novel, dynamic stabilization system designed for the treatment of degenerative conditions of the lumbar spine that present with unstable motion segments. This system uses pedicle screws with a modular spacer mounted on a stabilising cord, which controls movement of the instrumented segment in all planes. The purpose of this study was to investigate changes in the biomechanic response of the intervertebral disc (IVD) under normal, flexed and extended loading conditions before and after Dynesys is applied. The IVDs of both the instrumented (bridged) and the adjacent (floating) segment were studied.

Methods: Eight L3–5 cadaveric segments were dissected and compressed to 1kN in 6° flexion, neutral and 4° extension. The test was done without spacers and with spacers measured to +2mm, neutral and −2mm, where neutral equates to the normal distance between the pedicle screws without an applied load. The stress distribution in the mid-sagittal and postero-lateral diameters of both the bridged and floating discs was measured using a miniature pressure transducer. This resulted in greater than 300 stress profiles per specimen. Disc movement and segment motion during loading were recorded using ultrasound imaging and infrared reflection respectively.

Results: Without stabilization, stress peaks observed in the anterior annulus increased by more than 85% as the specimen was loaded from 4° extension to 6°flexion. With the application of Dynesys, these anterior stress peaks were reduced across the bridged segment. This was most pronounced in 6° flexion where anterior stress peaks of greater than 1 MPa were reduced by 100% in the bridged segment in more than 90% of specimens.

Conclusions: The degree of flexion or extension of the specimen during loading influences the peak stresses generated in the annulus. Dynesys has the potential to relieve peak stresses in the anterior annulus which is most pronounced when the specimen is loaded in flexion.