Statement : A prospective review of the clinical outcome following reconstruction of isolated posterolateral corner (PLC) injuries to the knee.

Method : 10 patients underwent an isolated PLC reconstruction for symptomatic instability. All patients had preoperative and post operative clinical examination, and functional knee scores.

Results : There were 9 males and 1 female, mean age of 35, with 100% follow up. Median length of follow up was 46 months (range 2 – 69). At the latest follow up, the mean Lysholm scores were 89.9, with an average increase in Tegner scores of 3.3 (range 2–10). IKDC scores showed a median of 93 (66 – 100). All patients had < 3 mm mean side to side difference using the KT1000 arthrometer, and no increase in PLRI. There were no complications and no clinical failures requiring further surgery. All the patients said they would undergo the surgery again.

Conclusion : In this series of patients with symptomatic PLC injury, hamstring graft reconstruction has restored knee stability with good functional outcomes.

The visco-elastic behaviour of acrylic bone cement is a key feature of cement-implant performance. The ability of the cement to creep in conjunction with a force-closed design of stem (collarless polished taper) affords protection of the vital bone-cement interface. Most surgeons in the UK use antibiotic-laden PMMA in primary total joint arthroplasty. In revision surgery the use of bespoke antibiotic-cement combinations is common.

The aim of this study was to elicit the effect of antibiotics upon the physical properties of bone cement.

Methods: The static properties of the cements were assessed following protocols described in ISO 5833: 2002, while the viscoelastic properties of the cement were measured with in-house developed apparatus in quasi-static conditions. Creep tests were performed in four point bending configuration over a 72 hour period in physiological conditions. Porosity was measured on the mid cross section of the creep samples using a digital image technique.

The cements used were Palacos R40 and Palacos R with gentamicin. The antibiotics added included fucidin, erythromycin, teicoplanin and vancomycin in 500mg powder aliquots up to a maximum of 1g per 40 g mix.

All data were analysed using ANOVA with Bonfer-roni post-hoc test. Pearson’s correlation coefficient was used to investigate the association between physical factors (SPSS).

Results: The static and working properties did not vary significantly with antibiotic additions. The mean creep of the cement increased in line with the amount of antibiotic added. The specific antibiotic was not relevant. The differences were statistically significant. Mean porosity also increased with antibiotic mass. There was a linear relationship between cement porosity and creep!

Conclusions: Despite modern mixing techniques the porosity of bone cement increases with antibiotic additions. This increased porosity is related to the greater creep seen in the cement. Surgeons should apply these findings when planning revision hip surgery.

The visco-elastic behaviour of cement, is a key feature of cement-implant performance in total hip arthroplasty.

The aim of this study was to describe the creep behaviour of the leading plain bone cements under standardised physiological in-vitro conditions.

Methods: Cements were mixed under vacuum conditions as per manufacturers instructions. Moulds were used to to produce beams of standard dimensions. These were stored in saline at 37oC for 21 days to ensure thorough polymerisation. Under the same conditions, the beams were tested for 72 hours in a 12-station quasi-static creep rig, using a four-point bending configuration. The rig applied a constant stress of 8MPa to each beam and the deflection was recorded at 8-minute intervals by a data-logging device. The porosity was measured in the mid-cross section of each beam sample using a digital image technique.

The cements tested were Palacos R, CMW1 and Smartset GHV and Surgical Simplex P.

All data were analysed using ANOVA with Bonfer-roni post-hoc test (SPSS).

Results: Palacos R exhibited the highest mean deflection at 72 hours (0.86+/- 0.21mm) followed by Surgical Simplex P (0.85 +/- 0.18mm), CMW1 (0.72 +/- 0.09mm) and Smartset GHV (0.60 +/- 0.16mm). The difference between the two DePuy cements and Palacos R (p=0.03) and Surgical Simplex P (p=0.04) were statistically sig-nificant. None of the beams failed during the test. The creep behaviour correlated with the cross-sectional porosity measurements.

Conclusions: This study has shown that there are sig-nificant differences in the creep bahaviour of the leading medium and high viscosity bone cements. In particular Palacos R and Surgical Simplex P demonstrate ‘High’ creep and the DePuy cements ‘Low’ creep. Creep appears sensitive to subtle changes in the composition of the material. This may be reflected in the clinical behaviour of different bone cements and stresses the importance of the time-dependent properties of PMMA.

Introduction: Immediate postoperative stability of cementless hip stems is one of the key factors for the long-term success of total hip replacement. The ability to discriminate between stable and unstable stems in the laboratory constitutes a desirable tool for the industry, as it would allow the identification of unsuitable stem designs prior to clinical trials. The use of composite femora for stability investigations is wide spread [1,2] even though their use in this application is yet to be validated. This study is aimed at establishing whether Sawbones composite femora are suitable for the assessment of migration and micromotion of a cementless hip stem. The stability of two SL Plus stems (Precision Implants, CH) implanted into Sawbone was compared to that of two SL Plus stems implanted into cadaveric femora. Ethical approval was obtained for the harvest and use of cadaveric material.

Methods: Stability was assessed in terms of micromotion and migration. Micromotion was defined as the recoverable movement of the implant relative to the bone under cyclic loading. Migration was defined as the non-recoverable movement of the implant with respect to the surrounding bone. Movement of the implant with respect to the surrounding bone was monitored at two locations on the lateral side of the stem by means of two custom made transducers based on the concept described by Berzins et al [3]. Each femur was tested in two different sinusoidal loading configurations: single leg stance (SLS-11° of adduction and 7° of flexion) [4] loaded up to 400N and stair climbing (SC-11° of adduction and 32° of flexion) loaded up to 300N. The effect of the abductor muscles was included in the model [5]. Each test consisted of 200 loading cycles applied at 50 Hz. The captured data was post-processed by a MATLAB routine and converted into translations and rotations of the stem with respect to the bone.

Results: The proximal part of the implant was subject to the highest amplitudes of micromotion in both loading configurations independent of the host. During SLS the largest micromotion was measured in the direction of the axis of the femur, this amplitude was in the order of 20 μm for the stems implanted in sawbones and varied between 13 and 39 μm for the stems implanted in cadaveric femora. The migration of the implants was minimal both in SLS and SC for both hosts with values measured in the sawbones model nearly on order of magnitude smaller than the cadaveric. In the case of SLS the prevalent movement consisted of a translation along the axis of the bone, while during SC the rotations became prevalent.

Discussion: This study has demonstrated that Sawbones provide an effective model to establish micromotion with oscillation patterns and orders of magnitiude similar to cadaveric bone. However the migration is much more dependent on the quality of fit and the internal geometry of the femur and therefore more caution should be placed on interpreting migration data from Sawbones models.

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: The study evaluates the inter-relationships between Cobb angle (CA), apical vertebral rotation (AVR), apical vertebral translation (AVT) and maximal angle of trunk inclination (max ATI). The effects of sex, curve laterality, curve type and apical levels will be studied

Methods: This is a study of consecutive pre-operative AIS patients. There are 122 pre-operative AIS patients (106 thoracic, 16 thoracolumbar), with a mean age of 15.6 years. From the pre-operative AP radiograph, CA, AVR (Perdriolle) and AVT are measured. The max ATI is measured using the Scoliometer with the patient in a standing forward bending position. Ratios between the measurements are calculated to allow comparison between different curve types and curves at different apical levels.

Results: For a given Cobb angle, each of AVR, AVT and max ATI are largest in King type IV curves, less in King type III curves and smallest in King type II curves (p=0.001 to 0.015). For curves without a significant compensatory curve, for a given AVR, the max ATI reduces significantly as the curve apex passes caudally (p=0.002 to 0.019). Sex and curve laterality are not significant factors.

Conclusion: It is suggested that as a curve develops, the interaction between the measurements in different planes may be responsible for determining the curve type (presence or absence of a compensatory curve). The smaller surface hump as the curve apex passes caudally is probably due to the transition from fixed ribs to floating ribs to no ribs. These finding also have implications for surgery. In King type IV and III curves, the emphasis should be on correcting translation and derotation perhaps with a primary costoplasty whilst in King type II curves, the emphasis should be on the correct selection of fusion levels and achieving a balanced spine.

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.

The static properties of bone cements have been widely reported in the literature (Lewis, 1997, Khun, 2000, Armstrong 2002). Commercial bone cements are expected to perform above the minimum values in static tests specified by ISO 5833: 2002. It has been suggested that the viscoelastic properties of bone cement, such as creep and stress relaxation, might bear more relevance to the in-vivo behaviour of the cement-implant construct (Lee 2002). This study aimed to compare numerous properties of Simplex P, Simplex Antibiotic and Simplex Tobramycin and identify those properties most sensitive to subtle changes in cement composition. The three cements were chosen on the basis that they are characterised by the same liquid and powder compositions, the only difference being represented by the type and amount of added antibiotics. In Simplex Antibiotic the additives are 0.5g Erythromycin and 3 million I.U. Colistin, while in Antibiotic Simplex with Tobramycin the only additive is 0.5g of Tobramycin. The static properties of the cements were assessed following protocols described in ISO 5833: 2002, while the viscoelastic properties of the cement were measured with in-house developed apparatus in quasi-static conditions. Creep and stress relaxation tests were performed in four point bending configuration. Porosity was measured on the mid cross section of the creep samples using a digital image technique. All cements exhibited properties compatible with the ISO standard, but in plain Simplex the ISO minimum for bending and compressive strength was within the variation of the batches tested. Bending strength measurements were the least sensitive to differences in the cements. Plain Simplex displayed lower bending and compressive strength but higher bending modulus than the antibiotic laden options. The bending modulus could only discriminate between Simplex P and Simplex Antibiotic (p=0.02). Differences in the compressive strength of the three cements were significant, with the plain option being the weakest. Stress relaxation only discriminated between plain and Tobramycin loaded cement (p=0.028), while creep was more sensitive to differences and allowed distinction between plain and antibiotic loaded bone cements. The creep behaviour correlated with the cross sectional porosity measurements. This study demonstrated that the static tests specified by the current international standard are not as sensitive to subtle changes in the composition of the material as the time temperature dependent parameters characteristic of creep and stress relaxation. The authors advocate the evaluation of time and temperature dependent characteristics as a complement to the current standard.

Introduction Unicompartmental Knee Replacement (UKR) has now become an accepted and widely used treatment for unicompartmental arthritis. Our unit has performed over 1000 UKRs in the past 22 years. The optimal mechanical design of the implant has yet to be determined.

Methods After gaining ethical approval a prospective randomised trial was commenced in 1999 to compare the 2–5 year results of a fixed bearing with a mobile bearing prosthesis. 104 knees in 91 patients underwent a UKR, the mean age of the group was 65 years and a mean weight of 80kg. 57 had a St Georg Sled fixed bearing prosthesis and 47 an unconstrained mobile bearing Oxford UKR. All were prospectively reviewed using the Oxford and Bristol Knee Scores.

Results All 104 knees have been reviewed at 2 years, with none lost to follow-up. 3 patients in the Oxford group suffered a dislocated meniscus and a further 4 required revision, as well as 3 in the St Georg Sled group. The overall function of the 2 groups was the same, but the Oxford mobile bearing group had significantly more persistent pain (p=0.013).

Conclusion The results in both groups were less satisfactory than previous series from this unit probably due to the efforts being made to use minimal incision. However the early complication rate was higher with the mobile bearing devise. This must be balanced against the possible better long-term survival.

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: Retrospective review.

Objective: A prospective study to evaluate for the presence of occult spinal injuries using MRI following aircraft ejection.

Summary of Background Data: The use of an ejection seat in order to escape from a stricken aircraft is associated with the exposure of significant forces. These vertical accelerative forces on the body are in the order of 15 – 25G with rates of onset of up to 250G per second. Therefore, it is common to see vertical compression fractures, mainly in the thoraco-lumbar region. Although most vertebral fractures are evident on plain radiographs, other subtle spinal injuries elsewhere may not be immediately apparent.

Methods: Between 1996 and 2003, 22 ejectees from 18 aircrafts, mean age 32 years (range 24 to 48), were admitted to a regional spinal unit for comprehensive evaluation of their injuries that included whole spine radiographs and Magnetic Resonance Imaging (T1, T2 weighted and STIR sagittal sequences). All ejections occurred within the ejection envelope and were flying below 2000 ft (mean 460 feet) and below 500 knots airspeed (mean 275 knots).

Results: All 5 ejectees (23%) with vertebral compression fractures (one at T6 and 4 in thoraco-lumbar region) had pain and tenderness in the appropriate area of the spine that was evidently detected on plain radiographs. 3 of these patients with a thoraco-lumbar fracture (AO A3.3) had more than 50% canal compromise and more than 30 degrees angular kyphosis underwent surgery. Neurological compromise consisting of acute cauda equine syndrome occurred in one patient with a L2 AO A3.3 fracture. More importantly 10 ejectees (45%) had MRI evidence totalling 21 occult thoracic and lumbar vertebral fractures. 4 ejectees had a single occult fracture, 4 had double, 1 had 3 and 1 had 6 occult fractures.

Conclusion: This study confirms the high incidence of occult vertebral injuries following vertical acceleration insult to the spine consequent to emergency aircraft ejection. Once life-saving priority measures have taken place, MRI of the entire spine remains mandatory as part the comprehensive evaluation of the patient. Early use of MRI scanning in the management will significantly increase an ejectee’s safe return to flying duties.

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: 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.

Introduction: In-vivo elution studies on Antibiotic-loaded Bone Cement (ABC) have concentrated on the short to medium term. This unit has previously described gentamicin release from cement during revision surgery and its presence in the joint aspirates of THAs at up to 12 years. We elected to study the late elutional behaviour of gentamicin-loaded cement in THA.

Methods: 51 patients undergoing revision THA surgery, for aseptic failure, at our centre were studied. Details of the original operation and the subsequent clinical and radiographic course were noted. Pre-operative urine samples and intra-operative joint fluid aspirates (prior to cement disruption) were assayed for their gentamicin concentrations using a fluorescence polarisation immunoassay (Abbott TDX). Cement samples underwent a Bacillus subtilis agar plate inhibition bioassay to assess for antimicrobial activity.

Results: Urine samples were obtained in 43 (84%) of the cases. All were negative for gentamicin (sensitivity level of 0.06 mg/L). Cement samples were retrieved in 36 cases (71%) and all of these (100%) demonstrated significant antimicrobial activity when compared to a standard 10 mg gentamicin disc. In 25 cases (49%) the joints were aspirated and 8 (32%) of these had a gentamicin concentration > 0.1 mg/L. The concentrations however were all below the Minimum Inhibitory Concentration (MIC) for intermediate sensitivity organisms. The longest interval between the primary and revision operations, in these positive cases was 25 years!

Conclusions: This study uniquely demonstrates sequestration of gentamicin within cement for up to 27 years. In addition, one third of joint aspirates had detectable though subtherapeutic gentamicin concentrations at up to 25 years. There was no evidence of late systemic release. These low concentrations of antibiotics, released after many years, are probably a potent stimulus to the emergence of resistant organisms. The use of antibiotic-loaded bone cement in primary THA remains controversial and requires further scrutiny.

Objective: To report on the long-term follow-up (mean 14.2 years) of patients with early onset idiopathic scoliosis treated with convex epiphysiodesis (CE) and Luque trolley instrumentation (LTI) without fusion. To evaluate factors influencing curve progression during the adolescent growth spurt in such patients.

Methods: Thirty-one cases of early onset idiopathic scoliosis with documented progression were surgically treated with CE and LTI without fusion between 1984 and 1992. Twenty-three (14 male, 9 female) of 31 cases had reached a minimum of 16 years of age at follow-up. These 23 cases were reviewed. The overlapped ‘L’ configuration of Luque trolley was used for the first 14 cases (prior to 1988), the overlapped ‘U’ configuration was used subsequently in the following 9 cases.

Results: Mean age at operation was 4.3 years (range, 1.5 – 9 years). Mean pre-operative Cobb angle was 65° (range 30° – 95°), and immediate post-operative Cobb angle was 28° (range 10° – 60°). Mean follow-up was 14.2 years (range, 7–19 years). Four cases required insertion of longer Luque rods (mean age of 7.5 years).

Definitive spinal fusion was required in thirteen cases at a mean age of 14.5 years (range 12–23 years), due to progression of scoliosis in 9 cases (mean Cobb angle 55°), and the development of junctional kyphosis in 4 cases. In ten cases the correction obtained was maintained through skeletal maturity (mean Cobb angle at final follow-up 33°). These cases did not require definitive spinal fusion.

The mean growth within the instrumented segment was 3.2 cm (42% of the expected growth). Progression of scoliosis was predicted by pre-operative apical convex rib-vertebra angle (RVA) (p=0.002). Excessive growth within the instrumented segment was predictive of junctional kyphosis but not of scoliosis progression. Age at operation and initial curve magnitude were not found to be significant predictive factors. 72% of overlapped ‘L’ rod construct (10 cases), and 33% of overlapped ‘U’ rod construct (3 cases) had documented curve progression within the adolescent growth spurt and required definitive spinal fusion.

Conclusions: CE and LTI was effective in controlling early onset idiopathic scoliosis, whilst still allowing significant growth. Pre-operative convex RVA was predictive of curve progression. The overlapped ‘U’ rod construct was more effective than the overlapped ‘L’ rod construct in preventing curve progression.

Objective: To identify radiographic parameters which could predict postoperative spinal decompensation in the frontal plane in King type II adolescent idiopathic scoliosis after posterior thoracic correction and fusion with third generation instrumentation systems.

Design: Retrospective radiographic analysis.

Subjects: The radiographs of 36 patients with King type II adolescent idiopathic scoliosis (AIS) who had had posterior thoracic correction and fusion, either with the Cotrel-Dubousset instrumentation (CDI) or the Universal Spine System (USS), were evaluated in terms of frontal and sagittal plane balance, curve flexibility, and curve correction with a minimum follow up of two years. Postoperative spinal decompensation in the frontal plane was investigated with respect to preoperative radiolographic parameters on standing upright AP, thoracic and lumbar supine side-bending as well as lateral standing radiographs. Spinal decompensation in the frontal plane was defined as plumbline deviation of C7 of more than 2 cm with respect to the centre sacral line within two years postoperatively. Two groups of patients were analyzed.

Outcome measures: 26 patients (72%) showed satisfactory frontal plane alignement by means of C7 plumb line deviation (group A, 1.2 cm to the left), whereas 10 patients (28%) showed spinal decompensation (group B: 2.7 cm to the left). Group differences were significant (p=0003).

Results: The two groups were found statistically equivalent in terms of preoperative C7 plumbline deviation (p=0.112, group A: 0.8 cm, group B: 0.7 cm to the left), thoracic cobb angles (p=0.093, group A: 56°, group B: 62°), lumbar cobb angles (p=0.115, group A: 42°, group B: 47°), lumbar curve flexibility (p=0.153, group A: 78%, group B: 67%); thoracic kyphosis (p=0.153) and lumbar lordosis (p=0.534) and age at operation (p=0.195), Significant group differences, however could be revealed for thoracic curve flexibility (p=0.03, group A: 43%, groupB: 25%) and the percentage of derotation of lumbar apical vertebrae in lumbar supine side-bending films in comparison to AP upright standing radiographs (p=0.002, group A: 49%, group B: 27%). Average thoracic curve correction was 51% in group A and 41% in group B. Group differences were significant (p=0.05). Average lumbar curve correction was 34% in group A and 23% in group B (p=0.09). No group differences could be revealed for postoperative thoracic kyphosis and lumbar lordosis measurements. Logistic regression analysis with C7 plumbline deviation of more than 2 cm postoperatively as the dependent variable yielded the amount of lumbar apical vertebral derotation in lumbar supine side-bending films as the only risk-factor (p=0.007).

Conclusion: Fixed lumbar rotation, measured in terms of the percentage of derotation of lumbar apical vertebrae in lumbar supine side-bending films in comparison to AP upright standing radiographs, provided the radiographic prediction of spinal decompensation in the frontal plane after posterior thoracic correction and fusion of King II type curves.

Objective: To assess the intra- and inter-observer reproducibility of a number of commonly used radiological measurements in pre- and post-operative patients with thoracic adolescent idiopathic scoliosis (AIS). Reproducibility of measures other than Cobb angle and vertebral rotation have not been studied and particularly there are no reports of reproducibility in patients after instrumentation.

Design: Repeat measurement of radiographs before and after surgery by 2 observers.

Subjects: 30 patients with thoracic AIS were selected from a scoliosis database at random: 15 treated with posterior USS and 15 with anterior instrumentation (8 Zielke / 7 anterior USS).

Outcome measures: The pre-operative AP radiograph, supine lateral bending radiograph and the post-operative AP radiograph at 6 months were selected for each patient. Two observers (MM beginner, AAC experienced) obtained the following measurements from the radiographs: Cobb angle, apical vertebral rotation (AVR, Perdriolle), apical vertebral translation (AVT) to the T1-S1 line, and frontal plane imbalance (FPI). With all marks removed, the radiographs were re-measured by each observer at least one week later. Repeatability was calculated using the method described by Bland and Altman (BMJ 1996). This method is a widely accepted anthropometrical technique but has not previously been used for assessing scoliosis measurements. It was assessed as 95% reproducibility. The co-efficient of reliability (r) expresses the proportion of the observed variability that is not due to error, i.e. higher is better. This was calculated as a means of assessing the usefulness of our measurements and to enable us to compare them.

Results: Intra-observer repeatability (MM vs. AAC): Whether the instrumentation was anterior or posterior had no effect on Cobb angle, AVT or FPI repeatability. AVR however was worse for posterior instrumentation 19° vs. 12°. “r” was > 90% for Cobb angle, AVT and PFI. But, for AVR r measured pre-op 52-92% and post-op 38–69%.

There was no relationship between repeatability and the measurement size.

Conclusions: Measurement reproducibility / error is slightly worse than previously suspected. E.g. a 5–6° curve progression is thought to be significant. We suggest that this could be due to measurement error and the figure should be 6–8°. There is no learning curve for the technique used to measure Cobb angle, AVT and FPI. AVR (Perdriolle) however requires experience. Cobb angle measurement error post-op is similar to pre-op. The Perdriolle method has greater error post-op especially in posterior instrumentation.