Existing techniques of posterior multi-point C1/2 stabilisation are technically demanding and can be hazardous. The coauthors have recently reported successful atlantoaxial fusion using a novel C1/2 stabilisation technique employing C1 multi-axial posterior arch screws (MA-PAS) in a clinical series of three patients where anatomical anomalies precluded established techniques.

The technically less demanding nature of this new technique, and possible wider application in patients with normal anatomy, led the authors to investigate its biomechanical stability compared to other established techniques.

Twenty-four human fresh-frozen cadaveric spines were harvested C0-C5. Motion was restricted to between C0 and C4. Each spine was non-destructively tested in flexion/extension, lateral bending and axial rotation, firstly in the intact state and then after Type 2 odontoid fracture destabilisation and insertion of Magerl-Gallie, Unicortical Harms, Bicortical Harms or MA-PAS instrumentation. ROM between C1 and C2 was monitored using two digital cameras. Results for each technique were compared statistically compared using ANOVA.

The C1-C2 joint of the intact spines demonstrated high flexibility in flexion/extension (16.5deg). After instrumentation all specimens showed significantly reduced ROM in flexion/extension (Magerl-Gallie FE = 4.2deg, Unicort Harms FE = 7.2deg, Bicort Harms FE = 4.4deg). Lateral bend ROM of instrumented specimens (Magerl-Gallie LB =3.8deg, Unicort Harms LB = 3.8deg, Bicort Harms LB =2.3 deg) was, however, similar or slightly greater than intact (2.7 deg) . MA-PAS showed similar ROM in flexion/extension (4.2 deg) as the Magerl-Gallie and Harms techniques but was slightly higher in lateral bend (5.3 deg).

The MA-PAS technique was shown to have similar biomechanical stability to the Magerl-Gallie and Harms techniques. Given the demonstrated biomechanical stability of the MA-PAS technique, it may be a suitable alternative to the existing technically demanding, and possibly more hazardous, multi-point fixation techniques in patients with normal, as well as anomalous, C1/2 segmental anatomy.

Introduction: The complex anatomy and biomechanics of the atlantoaxial motion segment impose technical challenges in the achievement of safe and successful surgical stabilization and fusion. The coauthors have recently reported successful clinical results using a novel C1-C2 stabilization technique employing C1 multi-axial posterior arch screws (MA-PAS). This study compares biomechanical stability of MA-PAS with two established multi-point fixation techniques (Magerl-Gallie and Harms) using non-destructive and destructive testing.

Methods: 15 human fresh-frozen cadaveric occipital-C5 cervical spines (average age 77.4 [51–95], sourced from ScienceCare, USA) were randomly allocated to 3 equal groups. Screws were passed up through adjacent end vertebrae such that motion was limited to between C0 and C4. Each spinal column was non-destructively tested in flexion/extension (±1.5Nm), lateral bend (±1.5Nm) and axial rotation (±1.5Nm), firstly in their INTACT state and then after Type 2 odontoid fracture destabilization combined with MAGERL-GALLIE (n=5), HARMS (n=5) or MA-PAS (n=5) instrumentation. All 15 reconstructed spines were finally loaded to failure in forward flexion only.

Results: Non-destructive testing: The C1-C2 joint of the INTACT spines all demonstrated high flexibility in flexion/ extension (ave 16.5deg) and axial rotation (ave 52.6 deg) while lateral bending (ave 2.7deg) was less compliant (see Fig.3). After instrumentation all specimens showed significantly reduced ROM in flexion/extension (MAGERL-GALLIE=4.2deg, HARMS=4.4deg, MA-PAS=4.2deg) and axial rotation (MAGERL-GALLIE=4.05deg, HARMS=0.59deg, MA-PAS=3.7deg) while lateral bend ROM of all instrumented specimens was similar or slightly greater than INTACT (HARMS=2.3deg, MAGERL-GALLIE=3.8deg, MA-PAS=5.3deg). There was no significant difference between the instrumented groups in each loading direction.

Destructive testing: MAGERL-GALLIE was the strongest requiring an average of 13.5Nm to cause failure while HARMS was the weakest requiring 7.8Nm of torque. MA-PAS technique averaged 12.2Nm of torque to cause failure.

Conclusions: The MA-PAS technique was shown to have similar ultimate strength in flexion to the MAGERL-GALLIE and HARMS techniques and stability in flexion-extension, axial rotation and lateral bend. The MA-PAS failure load in flexion was greater than the HARMS technique, and nearly as high as the MAGERL-GALLIE. Given the biomechanical stability of the MA-PAS technique, it is proposed that this technique is an alternative to the technically demanding, and possibly more hazardous, conventional multi-point fixation techniques in patients with normal, as well as anomalous, C1/2 segmental anatomy.

Introduction: The role of spinal fusion in patients suffering degenerative spine disease may be scrutinized more as costs of surgical treatment rise. Health-related quality of life (HRQL) measurement instruments enable outcome comparisons following treatment of different medical conditions. Rampersaud et al (1) recently presented the results of a comparative study of HRQL outcomes after surgery for lumbar spinal stenosis and hip and knee total joint arthroplasty. The latter are now accepted benchmarks for improvement in patient health.

Methods: A retrospective, observational cohort study was undertaken of 12-item Short Form Health Survey (SF-12) outcome data of 105 consecutive patients of two surgeons (1st and 2nd authors) who underwent single level Posterior Lumbar Interbody Fusion (PLIF) for lumbar spinal stenosis associated with degenerative spondylolisthesis. Minimum 12-month (F/U) data was available for 98 patients (93%). Comparison was made with published SF-12 results of hip and knee total joint arthroplasty (THR and TKR) and with age-related Australian population norms. Analyses were performed using XLSTAT version 7.5.3. Non-parametric statistics were used for assessment of skewed continuous variables. Overlappng 95%CIs were interpreted as indicating lack of significant difference in outcomes between patient and population groups.

Results: Median follow-up was 24months (range: 12–60months). Median age was 65 (Interquartile range: 59–75) years. Male:female ratio 2.8:1

Mean (95%CI) pre-op Physical Component Summary score (PCS) was 28.1 (26.6–29.5). This increased at last F/U to 39.3 (36.9–41.7, P< 0.0001). Mean Mental Component Summary score (MCS) was 47.8 (45.5–50.1) pre-op and 52.3 (50.2–54.5) at last F/U (P=< 0.0001).

While there was no difference in patient demographics, a significant difference existed in the pre-op SF-12 scores between the patients of the two surgeons (mean PCS: 24.9 (22.7–27.0) vs. 29.6 (27.8–31.5) and MCS: 44.0 (39.3–48.6) vs. 49.5 (46.8–52.1)). No significant difference was found in the improvements in mean SF-12 scores between these two patient groups (PCS: 12.3 (7.6–17.1) vs. 10.8 (8.3–13.3) and MCS: 6.3 (1.8–10.8) vs. 3.0 (0.3–5.6)) or in the SF-12 scores at 12-months (PCS: 37.2 (32.8–41.6) vs. 40.2 (37.2–43.2) and MCS: 52 (48.3–55.7) vs. 52.3 (50.1–54.4)). No significant difference was found between post-op PCS of the less disabled patient group or MCS scores of either group and published SF-12 age-matched population norms (65–74 years: mean PCS of 44.4 (42.7–46.1) and MCS of 53.8 (52.7–55.0)).

Three published series (869 patients) were located providing SF-12 data for TKR surgery. Weighted mean age was 69 years and pre-op PCS was 30 (range:27–34). 12-month improvement in PCS was 7.0 (range:7–8.5). For THR, one paper (147 patients from 3 hospitals) containing SF-12 data was found. Mean age was 68 years (range:36–89). Mean pre-op PCS and MCS of 30.5 and 41.4, increased to 45.6 and 49.7 at one year.

Discussion: The current study shows that spinal fusion can return patients’ HRQL to that of age-matched population norms and yield outcomes comparable to those of total hip and knee arthroplasty. Strict comparison with the arthroplasty literature was problematic however owing to variations in the methodology of their data presentation. Prospective collaboration with surgical colleagues in other disciplines is required.

Introduction The management of severe pain associated with progressive adult scoliosis remains a challenging problem. Radicular symptoms are often caused by bony foraminal stenosis and significant global and segmental imbalance may exist in both the sagittal and coronal planes. The patients are often elderly and have intercurrent medical conditions. The use of disc space distraction, pedicle screw instrumentation and posterior lumbar interbody fusion (PLIF) with Insert and Rotate prostheses has been shown to be effective in the correction of sagittal plane deformity (1). The current study examines the safety, clinical and radiological efficacy of this technique in the management of adult multilevel scoliosis.

Methods A prospective single cohort observational study of 15 consecutive patients with a degenerative scoliosis of 20 degrees or greater managed using an Insert and Rotate PLIF technique between October 2000 and July 2003. The minimum follow-up was 2 years. Clinical outcome measures included VAS pain score, SF-12, LBOS and Patient Satisfaction survey. Pre- and post-operative measures of radiological sagittal and coronal deformity were manually obtained. Wilcoxon signed-ranks test and Spearman’s non parametric test for correlation were used with significance set at 0.05.

Results The median age was 72 years (range: 56–80). Male: female ratio was 6:9. PLIF was carried out at 2 levels in 7 patients, 3–5 levels in 8 patients. Median blood loss was 1100mls for 2 level patients and 2550mls for 3–5 level patients. Operating time was 345mins and 545mins in the 2 and 3–5 level cases respectively. Median pre-operative scoliosis was 31degrees (range: 20–65) and post-operatively measured 14degrees (range: 0–30, p=0.001). Median pre-op VAS of 53 reduced to 20 (p=0.003). LBOS improved from 24 to 37 (p=0.004). A correlation was found between the amount of pre-operative coronal plane deformity and the post-operative VAS (r=0.6, p=0.003). 13 of the 15 patients considered the procedure was worthwhile and that they would have it again under similar circumstances. Early post-operative complications included electrolyte/fluid disturbance in 2 patients, 2 cardiac arrhythmias, one DVT/PE and 2 returns to the O.R. for pain caused by a misplaced pedicle screw or bone graft. One patient developed a progressive scoliosis above the fusion and one a pathological wedge compression fracture. 4 patients required late surgery including 2 who had been fused down to L5 and required extension of their fusion to the sacrum for pain associated with an L5/S1 foraminal stenosis and one who developed a painful non-union.

Discussion PLIF with an Insert and Rotate technique following disc space distraction for severe and progressive adult scoliotic deformity is technically difficult and can be associated with significant peri-operative morbidity. Nevertheless, the reported satisfaction rates by the patients in this small series are encouraging and the procedure appears to have achieved substantial correction of global and segmental deformity in both the coronal and sagittal planes. Whether this will be beneficial in the long term requires further study.

Introduction Cervical disc replacement has been advocated as a technique for retaining segmental motion following discectomy. The in vivo kinematics of the prosthesis are predicted to influence outcome, but remain poorly understood. The aim of this study was to determine whether factors that might possibly influence outcome can be reliably measured.

Methods Anteroposterior and lateral xrays were performed pre-, inter- and post-operatively on 67 patients undergoing cervical prosthetic disc replacement. The xrays were reviewed by 3 observers. Measurements were performed manually by two observers and using digital image analysis software by a third observer.

The inter-rater reliability of categorical measurements such as overall cervical alignment, degree of disc degeneration and length of spinous processes was assessed using unweighted kappa scores. Intra-class correlation coefficients (ICCs) were calculated using a two-way random effects model to assess inter-rater agreement in the observation of continuous variables such as intra-operative disc angles, post-operative shell angles and change in focal lordosis. The intra-rater reliability of measurements of disc space angulation was calculated on a subset of 17 sets of xrays measured by three observers on two occassions, five months apart.

Kappa and ICC values were interpreted as recommended by Altman.

Results The inter-rater reliability of measuring the degree of disc degeneration (κ= 0.29 p< 0.0001) was fair and the spinous process length (κ = 0.79 p< 0.0001) and overall spinal alignment (κ = 0.69 p< 0.0001) good.

The inter-rater reliability of measuring pre-operative focal lordosis (ICC 0.88 (95%CI 0.82–0.92 p< 0.0001)), intra-operative disc angle (ICC 0.86 (95%CI 0.79–0.92) p< 0.0001) and post-operative shell angle (ICC 0.99 (95%CI 0.98–1.00) p< 0.0001) were excellent.

ICCs were higher when the average of the rater scores was considered. The ICCs were substantially reduced when agreement between the observers and values obtained using digital imaging was assessed.

The intra-rater reliability of measurements of focal lordosis however revealed good agreement when measured manually (ICC 0.68 (95%CI 0.06–0.89) p=0.02) but very good agreement when measured using digital imaging software (ICC 0.82 (95%CI 0.54–0.93) p< 0.0001). The inter-rater reliability of average disc space height when measured using digital imaging software was excellent (ICC 0.83 (95%CI 0.58–0.94) p< 0.0001).

Conclusions Whilst the reliability of determining the degree of disc degeneration in the cervical spine is fair, the measurement of focal lordosis, intra-operative disc angles and post-operative shell angle is good or excellent. As these radiological measures can be reliably assessed, they may be further evaluated as predictors of outcome following cervical disc replacement.

Introduction The early clinical results of cervical disc replacement surgery are encouraging but the in vivo kinematics of prostheses remains poorly understood. Two recent published reports suggest that use of a prosthesis with an unconstrained (over normal range of motion) biconvex nucleus (Bryan Cervical Disc® – Medtronic Sofamor Danek, Memphis, TN) can be associated with post-operative segmental kyphosis.

This study examines post-operative kyphosis and segmental imbalance following cervical disc replacement using the Bryan Cervical Disc prosthesis and factors which may influence this. In particular, the influence of change in disc space height as a result of surgery was studied.

Methods 67 patients underwent prosthetic disc replacement by one of three surgeons (19, 25 and 23 patients, respectively) using the Bryan prosthesis. 46 single, 20 double and 1 triple level were operated. Neutral pre- and post-op erect and intra-operative x-rays were examined manually and using digital image analysis software (Medical Metrics, Inc. Houston, TX). Possible contributing factors to segmental alignment were studied including: pre-op alignment, angle of prosthesis insertion, disc space degeneration and sacrifice of the posterior longitudinal ligament (PLL). Particular attention was given to changes in disc space height and factors which may influence this.

Inter- and intra-observer agreement was assessed. Non-parametric tests were used for assessment of categorical and skewed continuous variables. Multivariate linear regression was used to adjust significant correlation coefficients. Significance was set at p< 0.05.

Results The median pre-op focal lordosis of +0.5° (range: 21 to −14°, −ve = kyphotic) changed by −1° (+14 to −17°), to post-op: 0° (+11.5 to −16°).

There was a significant difference in the median change in focal lordosis for surgeon 1 (−3°) vs. surgeons 2 & 3 (−1°) (p< 0.005) and in the loss of disc space height. Median loss of disc space height for surgeon 1 was 22% vs. 8% for surgeons 2 & 3 (p< 0.002). Correlation co-efficient (Spearman) for change in disc space height vs. change in disc space angulation was 0.67 (p< 0.0001). No single pre- or intra-operative factor was found to clearly correlate with subsequent loss of disc space height apart from a trend towards a weak correlation with the angle of prosthesis insertion (r=0.24, p=0.06).

Discussion The median change (loss) in focal lordosis was −1.5° but there was considerable range: from +14° to −17°. Attempts to identify contributing factors suggest that a number may be involved but there did appear to be a highly significant correlation between loss of disc space height following surgery and subsequent focal kyphosis.

While the difference in outcomes between Surgeon 1 and Surgeons 2 & 3 is probably not clinically significant, it does suggest that intra-operative factors such as the angle of prosthesis insertion may be important. We are continuing to study these factors.

Introduction: While anterior cervical decompression and fusion has been shown to be clinically effective in cases of myelopathy or radiculopathy, several studies have suggested an increased risk of development of adjacent segment degeneration. The Bryan Cervical Disc Pros-thesis was developed to address this complication and was fi rst used clinically in Europe in January 2000. The author began to use the device in June of 2001 and since that time has implanted 30 prostheses in 22 patients. The present prospective study was commenced at the time (concurrently with an ASERNIPS study) with a view to examine the clinical efficacy and safety of this device. The results in the author’s first 14 patients are reported, all with a minimum follow-up of 12 months (mean 20 months).

Methods: An observational audit of 14 consecutive patients with cervical radiculopathy (6 patients), myelopathy (6 patients) or discogenic neck pain (2 patients) operated upon between July 2001 and November 2002. Average age was 48 years (range 27 – 61 years). 5 patients underwent two level procedures. Operative / post-op complications and clinical / radiological outcomes were recorded at 6 weeks, 3, 6, 12 months and January 2004.

Results: Follow-up data is available at > 12 months on 13 of the 14 patients at an average 23 months post op (Range: 14–30 months). The patient for whom data is not available is known to have had a poor clinical outcome. She developed an unusual symptom complex with complex regional pain syndrome and is very unhappy with the surgery. Of the other 13 patients, 12 consider their outcome to have been excellent and 1 fair. In the two patients who underwent surgery purely for discogenic neck pain, substantial relief was reported. In the 8 patients with pre-operative arm pain, 6 reported complete relief, 1 substantial relief and one partial relief. There were no intra-operative complications. Two patients developed dysphagia which resolved after several months, one has described a clicking sensation in his neck for which no cause has been identified and one experiences persistent ‘neural surges’. One patient required surgery for a disc herniation at an adjacent level, 9 months post-op while in another patient, on routine 12 month follow-up MRI scan, an asymptomatic disc herniation adjacent to the operated segment had resolved spontaneously. One patient underwent foraminotomy for recurrent arm pain, 19 months post-op. All prostheses appear mobile on dynamic x-rays but it is apparent that the Bryan device does not correct any pre-operative degenerative deformity using the current technique.

Discussion: The current study appears to indicate satisfactory clinical outcomes at an average of 23 months post surgery in this group of patients. Longer follow-up and larger patient numbers are required as well as comparative studies.

Introduction: Posterior interbody fusion (PLIF) can be performed for a variety of indications and by a variety of methods. This paper presents a prospective observational study of the outcome for PLIF using an insert and rotate lordotic implant with pedicle screws for the indication of neurological compression caused by segmental deformity.

Methods: Prospective data was collected preoperatively and at regular intervals during the post operative period. Self assessed outcome measures of visual analog pain score (VAS), Low Back Outcome Score (LBOS) and SF12 general health data was obtained at intervals after the surgery. This paper presents the results of a consecutive series who have a minimum of 6 months followup. All surgery was performed by the two authors. Implants used were a carbon fibre composite ramp (DePuy AcroMed), a titanium mesh lordotic cage (Medtronic Sofamor Danek) or a lordotic PEEK spacer (R90, Medtronic Sofamor Danek).

Results: One hundred and twenty eight cases were performed. The mean age was 61.5 yrs(sd 15.1), 63 (49% ) were female and 65(51%) were male. Thirteen cases (10%) were workers compensation. Eighty seven (69%) had a single level fused, thirty three (26%) had 2 levels fused. Six cases had three or more levels fused. Forty cases had had one or more previous decompressive procedures at the target level. All cases had leg pain due to neurological compression associated with some form of deformity. Fifty three percent had a spondylolisthesis, 20 % had degenerative scoliosis with collapse of the disc space being the most common other deformity. The mean pre operative VAS pain score dropped from 6.95 (sd 2.0) to 3.2 (sd 2.4). (p< 0.0001 paired t test). The mean percentage VAS improvement was 49.7% (95% ci 42.4% to 57.1%). Twenty seven percent achieved greater then 80% pain improvement with 47% achieving greater than 60% pain improvement. The mean LBOS score rose from 21.8 (95% ci 19.6 to 24.0) to 37.9 (95% ci 35.1 to 40.6) (p< 0.001 paired t test). The mean percentage improvement in LBOS was 120.7% (95% ci 94.6% to 146%).

Complications consisted of 3 cases of minor wound drainage that settled, a possible deep infection that settled with antibiotics. There were 4 cases of transient leg weakness that recovered and one case of postoperative extradural heamatoma requiring evacuation for partial cauda equina lesion (near full recovery). Unexplained persistence of leg pain or new leg pain was present 8 cases. Three cases resolved spontaneously , 2 cases were due to screw malposition and required revision and 3 cases required re-exploration for further foraminal decompression. Other medical problems included pulmonary embolus (1), chest infection/atelectasis (2), confusional state (2), paralytic ileus (3), Atrial fibrillation (2), myocardial infarction (1).

Discussion: Posterior lumbar interbody fusion with insert an rotate implants for neural compression gives reasonable pain relief and reduction in disability with a low complication rate for the target (elderly) population.

Introduction: Since Briggs and Milligan first described posterior lumbar interbody fusion (PLIF) in 1944, it has been a controversial technique. However, modern pedicle screw instrumentation and the use of intervertebral spreaders and implants have provided a powerful technique for the restoration of spinal balance in degenerative deformity.

This study assesses the functional outcomes and safety in a series of patients undergoing complete reduction and posterior interbody fusion (PLIF) of lumbosacral spondylolisthesis with interbody fusion spacers implanted using an Insert and Rotate technique.

Methods: A prospective, non-randomized, observational study of pre- and post-operative data, in a series of 35 patients with lumbosacral degenerative or isthmic spondylolisthesis, between April 2001and June 2002. All patients underwent decompressive laminectomy followed by complete reduction of the spondylolisthetic deformity with the aid of intervertebral disc space spreaders and pedicle screw instrumentation. Wedge shaped spacers made from Carbon Fiber, Titanium mesh or PEEK plastic were then inserted on their sides and rotated 90 degrees to support the vertebral end plates prior to placing bone graft beside them, within the disc space.

Outcomes were measured using the Low Back Outcome Score (LBOS), SF-12, visual analogue pain scores (VAS) and patient satisfaction survey.

Results: Of the 35 patients, 24 had degenerative spondylolisthesis and 11 were isthmic in type. 26 were Meyerding Grade I; seven were Grade II; one was Grade III and one was Grade IV. The indications for surgery included relief of foraminal stenosis in 26 and likely post operative instability in 24. Average time of last follow-up was 7.4 ± 3.0 months. Data is available on 34 of the 35 patients at 3 months and 29 at six to twelve months (83%). Mean pre-operative VAS and LBOS were 5.1 ± 2.5 and 26.5 ± 16.9, respectively. Mean scores at last follow up were 2.2 ± 2.4 and 45.6 ± 14.6 (p< 0.01 for both measures). At last follow-up, 30 of the 35 patients or 88.2% described their outcome as good or excellent. One patient considered himself worse. 91% said the procedure had been worthwhile but only 79% said they would have it again under similar circumstances.

There were no deaths. There were no interbody implant / PLIF related problems but five intraoperative problems related to pedicle screw placement with one screw loosening during slip reduction, requiring replacement. Post-operatively, 3 patients developed an ileus. One patient developed a probable wound infection with high fever which settled on antibiotics.

Discussion: This series represents a recent subset of a much larger total series managed with this technique for symptoms associated with spondylolisthetic deformity (187 patients to date). The author has previously reported to the society on the clinical results of the technique but without the benefit of prospective pre-operative data. This smaller series appears to confirm the results of the earlier studies and suggests that PLIF using an Insert and Rotate technique can yield satisfactory clinical outcomes with high patient satisfaction and low levels of complications.

INTRODUCTION: Posterior interbody fusion (PLIF) can be performed for a variety of indications and by a variety of methods. This paper presents a prospective observational study of the outcome for PLIF using an insert and rotate lordotic implant with pedicle screws for the indication of neurological compression caused by segmental deformity.

METHODS: Prospective data were collected pre-operatively and at regular intervals during the post-operative period. Self assessed outcome measures of visual analog pain score (VAS), Low Back Outcome Score (LBOS) and SF12 general health data were obtained at intervals after the surgery. This paper presents the results of a consecutive series who have a minimum of six months follow-up. All surgery was performed by the two authors. Implants used were a carbon fibre composite ramp (DePuy AcroMed), a titanium mesh lordotic cage (Medtronic Sofamor Danek) or a lordotic PEEK spacer (R90, Medtronic Sofamor Danek).

RESULTS: One hundred and twenty eight cases were performed. The mean age was 61.5 years (sd 15.1), 63 (49% ) were female and 65 (51%) were male. Thirteen cases (10%) were workers compensation. Eighty seven (69%) had a single level fused, thirty three (26%) had two levels fused. Six cases had three or more levels fused. Forty cases had had one or more previous decompressive procedures at the target level. All cases had leg pain due to neurological compression associated with some form of deformity. Fifty three percent had a spondylolisthesis, 20% had degenerative scoliosis with collapse of the disc space being the most common other deformity. The mean pre-operative VAS pain score dropped from 6.95 (sd 2.0) to 3.2 (sd 2.4). (p< 0.0001 paired t test). The mean percentage VAS improvement was 49.7% (95% ci 42.4% to 57.1%). Twenty seven percent achieved greater than 80% pain improvement with 47% achieving greater than 60% pain improvement. The mean LBOS score rose from 21.8 (95% ci 19.6 to 24.0) to 37.9 (95% ci 35.1 to 40.6) (p< 0.001 paired t test). The mean percentage improvement in LBOS was 120.7% (95% ci 94.6% to 146%).

Complications consisted of three cases of minor wound drainage that settled, a possible deep infection that settled with antibiotics. There were four cases of transient leg weakness that recovered and one case of post-operative extradural haematoma requiring evacuation for partial cauda equina lesion (near full recovery). Unexplained persistence of leg pain or new leg pain was present in eight cases. Three cases resolved spontaneously, two cases were due to screw malposition and required revision and three cases required re-exploration for further foraminal decompression. Other medical problems included pulmonary embolus (1), chest infection/atelectasis (2), confusional state (2), paralytic ileus (3), atrial fibrillation (2), myocardial infarction (1).

DISCUSSION: Posterior lumbar interbody fusion with insert and rotate implants for neural compression gives reasonable pain relief and reduction in disability with a low complication rate for the target (elderly) population.

INTRODUCTION: Since Briggs and Milligan first described posterior lumbar interbody fusion (PLIF) in 1944, it has been a controversial technique. However, modern pedicle screw instrumentation and the use of intervertebral spreaders and implants have provided a powerful technique for the restoration of spinal balance in degenerative deformity.

This study assesses the functional outcomes and safety in a series of patients undergoing complete reduction and posterior interbody fusion (PLIF) of lumbosacral spondylolisthesis with interbody fusion spacers implanted using an Insert and Rotate technique.

METHODS: A prospective, non-randomised, observational study of pre- and post-operative data, in a series of 35 patients with lumbosacral degenerative or isthmic spondylolisthesis, between April 2001 and June 2002.

All patients underwent decompressive laminectomy followed by complete reduction of the spondylolisthetic deformity with the aid of intervertebral disc space spreaders and pedicle screw instrumentation. Wedge shaped spacers made from Carbon Fiber, Titanium mesh or PEEK plastic were then inserted on their sides and rotated 90 degrees to support the vertebral end plates prior to placing bone graft beside them, within the disc space.

Outcomes were measured using the Low Back Outcome Score (LBOS), SF-12, visual analogue pain scores (VAS) and patient satisfaction survey.

RESULTS: Of the 35 patients, 24 had degenerative spondylolisthesis and 11 were isthmic in type. 26 were Meyerding Grade I; seven were Grade II; one was Grade III and one was Grade IV. The indications for surgery included relief of foraminal stenosis in 26 and likely post-operative instability in 24. Average time of last follow-up was 7.4 ± 3.0 months. Data are available on 34 of the 35 patients at three months and 29 at six to twelve months (83%). Mean pre-operative VAS and LBOS were 5.1 ± 2.5 and 26.5 ± 16.9, respectively. Mean scores at last follow-up were 2.2 ± 2.4 and 45.6 ± 14.6 (p< 0.01 for both measures). At last follow-up, 30 of the 35 patients or 88.2% described their outcome as good or excellent. One patient considered himself worse. 91% said the procedure had been worthwhile but only 79% said they would have it again under similar circumstances.

There were no deaths. There were no interbody implant/PLIF related problems but five intraoperative problems related to pedicle screw placement with one screw loosening during slip reduction, requiring replacement. Post-operatively, three patients developed an ileus. One patient developed a probable wound infection with high fever which settled on antibiotics.

DISCUSSION: This series represents a recent subset of a much larger total series managed with this technique for symptoms associated with spondylolisthetic deformity (187 patients to date). The author has previously reported to the society on the clinical results of the technique but without the benefit of prospective pre-operative data. This smaller series appears to confirm the results of the earlier studies and suggests that PLIF using an Insert and Rotate technique can yield satisfactory clinical outcomes with high patient satisfaction and low levels of complications.

Introduction: Since Briggs and Milligan¹ first described posterior lumbar interbody fusion (PLIF) in 1944, posterior lumbar interbody fusion has been a controversial fusion technique. Reports regarding the safety, efficacy and fusion rates have varied greatly over the years. Modern pedicle screw instrumentation and the use of intervertebral spreaders / implants have provided a powerful technique for the restoration of spinal balance in degenerative deformity.

Since 1993, the author has performed over 400 posterior interbody fusions for a wide variety of degenerative, traumatic and neoplastic conditions. A review was undertaken of 362 consecutive patients who were managed with this technique between October 1993 and July 2001. The purpose of this review was to determine the efficacy and safety of the technique and in particular, to attempt to identify those factors, which have contributed to patient outcomes.

Methods: The first 86 patients underwent wide posterior decompression with resection of facet joints and interbody grafting using morcellised posterior elements and pedicle screw stabilisation. From February 1995, the interbody graft was supplemented with Carbon wedge shaped spacers bearing serrated upper and lower surfaces (Ramps). From July of 1996 (patient 170), the interbody graft was supplemented with posterior grafting, and from December 2000 with Autologous Growth Factor (AGF) treated graft.

Patient pre-operative, operative and post-operative data and complications and follow-up Surgeon Subjective Outcome Assessments (SSOA’s) were acquired prospectively. Questionnaires were administered seeking patient generated follow-up data, including Patient Subjective Outcome Assessment (PSOA).

Results: Follow-up data (SSOA ± PSOA) was available on 327 or 91% of patients. The data was for periods greater than 6 months in 64% of patients. PSOA data was available on 31% – mean follow-up time for these patients was 27.7 months (± 25.8). Average age at surgery was 56 years (± 16). Average number of levels operated was 1.5 (± 0.9). Average number of previous surgeries was 0.7 (± 1.0). 286 patients were private and 76 were compensation. 88 patients had no deformity while the remainder had some form of deformity, the most common of which were spondylolisthesis – 156 and scoliosis – 94.

Overall, private patients did much better (very good or excellent outcomes) than compensation ones: 76% vs. 57% (p < 0.002). Patients who underwent surgery for conditions associated with deformity did significantly better than those without: 80% vs. 57% (p < 0.01). The outcomes since the introduction of interbody serrated spacers and additional posterior grafting have been significantly improved: for private patients, 86% now vs. 62% (p < 0.002).

The introduction of ramps improved the non-union rate from 16.3% in the first 86 patients to 8.3% in the next 84. The addition of posterior grafting improved the non-union rate to 1.0% in the next 198 patients. There have been no non-unions since the introduction of AGF.

Serious complications included three deaths, five deep infections, eight early returns to theatre for radiculopathy, four partial and one complete foot drop, four CSF leaks and one pulmonary embolus. Of the patients surveyed, 123/131 or 94% considered the surgery worthwhile and 88% said that they would have it again, if necessary.

Discussion: Refinements in technique and improved patient selection have resulted in a significant improvement in clinical outcomes over the last eight years. While technically demanding, this PLIF technique now yields a high fusion rate, the ability to fully correct sagittal and coronal deformity and a high rate of good or excellent clinical outcomes: 86% in private patients.

Introduction: The lordosis of the lumbar spine, flexion angle and body weight result in significant shear forces through the lumbar and lumbosacral disc spaces. These shear forces result in translational motion across the disc space, which is resisted but not completely abolished by pedicle screw stabilisation. Failure of lumbar interbody fusions through non-union may be related to translational micromotion at the vertebral endplate / bone graft interface. A porcine in vitro model was established to test whether variations in the design of inter-body implants and in particular, the presence of surface serrations would assist in resisting shear forces – especially those causing anterior translation.

Methods: Measurements of anterior vertebral translation were recorded on porcine cervical spine segments, subjected to 25 N antero-posterior shear load while under a 300 N compressive pre-load. Baseline testing was firstly performed on the intact specimens and following removal of the facet joints. The annulus, disc nucleus and cartilaginous endplates were then removed and the specimens were divided into two groups for testing using interbody implants. Four stainless steel blocks measuring 15 mm (length) × 5 mm (height) × 4 mm (width) were manufactured to act as intervertebral disc spacers. Two were made with smooth surfaces and two were made with 1 mm deep serrations on the upper and lower surfaces. One group was tested with two smooth and one with two serrated implants.

Results: Under 25 N shear load, the specimens tested with the serrated implants showed anterior vertebral translation of 0.046 ± 0.013 mm while those tested with the smooth surfaced implants measured 0.152 ± 0.075 mm (p < 0.01). A significant difference was also found between the stiffness of the specimens implanted with smooth surfaced (432.8 N/mm) and serrated (1088.4 N/mm) implants (p < 0.01). The value for peak load at failure for the specimens with smooth surfaced implants (150.43N) was less than those implanted with serrated implants (175.48 N), but not significantly different.

Discussion: The presence of surface serrations on the interbody implants significantly increased the resistance to shear forces in this model. In the clinical setting, we postulate that the degree of micromotion generated by anterior shear forces at interbody fusion sites should be substantially less when serrated implants are used and reduce the incidence of non-union. This may explain the improved fusion rates reported by contemporary authors when using some interbody implants. Further research is needed to clarify the combined effects of pedicle screw stabilisation and interbody implants upon shear displacement and variations in implant design.

Introduction: The management of patients with thoracolumbar burst fractures has evolved over the last 60 years from the days of conservative management through to the current era of anterior decompression combined with either anterior or posterior stabilisation. There is no doubt that surgical outcomes have improved markedly with the more modern techniques. Nevertheless, there are still technical and other difficulties, which the surgeon may encounter. Based upon his experience with posterior vertebrectomy and reconstruction for thoracolumbar tumours, the author has used this technique for the management of acute burst fractures in this region.

This paper presents a review of 10 patients with severe thoracolumbar burst fracture or fracture dislocation managed since 1997, using a single stage posterior decompression, realignment and stabilisation/interbody fusion.

Methods: Data were acquired prospectively on consecutive patients between June 1997 and October 2000. All patients underwent single stage posterior decompression via laminectomy and then a subtotal eggshell vertebrectomy with removal of any herniated bone fragment(s) or partial vertebrectomy/ pedicle subtraction osteotomy. Pedicle screw stabilisation was performed to include one or two vertebrae above and below the involved vertebra(e). The intervertebral discs adjacent to the fractured vertebra were removed prior to realigning the vertebral column and performing inter-body fusion using carbon fibre spacers and autograft (4 patients) or vertebral body reconstruction with Titanium mesh cages and autograft (6 patients).

Results: The mean age was 37 years (21–52 years). There were six males and four females. Three patients had no neurological deficit. Seven had incomplete paraplegia, three of which were severe with no or only a flicker of leg movement. The principal fracture involved L1 in 6 patients, L2 in 2, L4 in 1 and L5 in 1. Seven had herniated bone fragments occupying 90+% of the spinal canal. Of the seven patients with incomplete paraplegia, all recovered the ability to walk. Two with conus lesions still self catheterize. There were no serious early complications. A serious late complication was the development at three months of a severe deep wound infection, which required debridement and subsequent anterior/ posterior revision surgery. One patient with severe polytrauma and an L4 burst fracture/dislocation has developed a chronic pain syndrome.

Discussion: The decompression, realignment, interbody reconstruction and stabilisation of thoracolumbar burst fractures/dislocations using a single stage posterior technique is technically demanding but the neurological outcome and restoration of spinal balance in these 10 patients was gratifying. The procedure appears to have two advantages over an anterior decompression and reconstruction combined with anterior or posterior stabilisation: first, it appears to provide easier access and improved visualisation for lumbar burst fractures where the psoas muscle may be swollen and contused, and second, it allows for easier realignment of any coronal or sagittal deformity.