Purpose. To determine if clinical outcomes are correlated with center of rotation (COR) in patients implanted with a viscoelastic total disc replacement (VTDR). Methods. Fifty patients with single-level, symptomatic lumbar DDD between L4 and S1 were enrolled in a clinical trial of a VTDR across three surgical centres. A comprehensive, independent review and statistical analysis of both clinical and radiographic outcomes was performed and analyzed for correlations. Data from preoperative through 2 years were available. The COR was calculated for the index levels and compared to data for an asymptomatic population. Each COR coordinate was classified as abnormal if outside of the 95% confidence interval for an asymptomatic population. Results. At most recent follow-up, 69% of the patients had achieved at least a 15 point Oswestry Disability Index (ODI) improvement. 76% of the patients achieved at least a 10 point improvement. At most recent follow-up, 78% of cases had a normal COR-X and 92% had a normal COR-Y. Results from three statistical tests show the association between COR-X and outcomes. 1) Based on latest available time point for each patient, the improvement in ODI score was significantly better for patients with a normal anterior-posterior (AP) coordinate of the COR (P=0.03). 2) Anterior COR corresponded with anterior placement of the device in the disc space, and patients were almost 7 times less likely to achieve at least a 15 point improvement in the ODI score if the COR was positioned too anteriorly. 3) This effect was also seen in the average AP coordinate of the COR for patients who achieved a 15 point ODI improvement. Conclusions. A viscoelastic TDR can restore a normal COR. This is the first study to show that restoration of a normal COR correlates with a significant and clinically relevant improvement in patient disability

Introduction. Both intra- and post-operative radiographs are traditionally obtained after instrumented lumbar spinal surgery; however the clinical advantage of routine post operative images has not been demonstrated. Aim. To explore the usefulness of routine pre-discharge postoperative radiographs in patients undergoing instrumented spinal surgery. Methodology. Patients (n = 124) who underwent a lumbar spinal fusion were identified from a retrospective database, 58 patients were excluded. Unaltered intra-operative and pre-discharge post-operative PACS images for 66 patients were reviewed and were scored for: i) Quality (0 = non-diagnostic, 1 = suboptimal, 2 = diagnostic, 3 = good quality), ii) Focus (number of vertebra and disc seen), iii) Centering using a numbered (1–9) grid system, and iv) Rotation. Results. 66 radiographs were analysed for i) Quality: 60 AP and 56 lateral intra-operative images while 57 AP and 39 lateral postoperative images were diagnostic, ii) Focus: average number of unnecessary vertebra seen in intra-operative AP and lateral images were 0.89 and 1.09, while on post-operative AP and lateral images were 8.05 and 6.45 respectively, iii) Centering: 48 AP and 51 lateral intra-operative images, while 27 AP and 20 lateral post-operative images were adequately centered and iv) Rotation was adequate in both intra-operative and post-operative images. Conclusion. Intra-operative images scored higher in all parameters suggesting that routine post-operative pre-hospital discharge radiographs are unnecessary unless specifically indicated and this practice should be discontinued with benefits including reduction of radiation dose (and subsequent sequelae), fiscal burden and length of stay

We investigated the spinopelvic morphology and global sagittal balance of patients with a degenerative retrolisthesis or anterolisthesis. A total of 269 consecutive patients with a degenerative spondylolisthesis were included in this study. There were 95 men and 174 women with a mean age of 64.3 years (sd 10.5; 40 to 88). A total of 106 patients had a pure retrolisthesis (R group), 130 had a pure anterolisthesis (A group), and 33 had both (R+A group).

A backward slip was found in the upper lumbar levels (mostly L2 or L3) with an almost equal gender distribution in both the R and R+A groups. The pelvic incidence and sacral slope of the R group were significantly lower than those of the A (both p < 0.001) and R+A groups (both p < 0.001). The lumbar lordosis of the R+A group was significantly greater than that of the R (p = 0.025) and A groups (p = 0.014). The C7 plumb line of the R group was located more posteriorly than that of the A group (p = 0.023), but was no different from than that of the R+A group (p = 0.422). The location of C7 plumb line did not differ between the three groups (p = 0.068). The spinosacral angle of the R group was significantly smaller than that of the A group (p < 0.001) and R+A group (p < 0.001).

Our findings imply that there are two types of degenerative retrolisthesis: one occurs primarily as a result of degeneration in patients with low pelvic incidence, and the other occurs secondarily as a compensatory mechanism in patients with an anterolisthesis and high pelvic incidence.

Cite this article: Bone Joint J 2013;95-B:1244–9.

This prospective multicentre study was undertaken to determine segmental movement, disc height and sagittal alignment after total disc replacement (TDR) in the lumbosacral spine and to assess the correlation of biomechanical properties to clinical outcomes.

A total of 173 patients with degenerative disc disease and low back pain for more than one year were randomised to receive either TDR or multidisciplinary rehabilitation (MDR). Segmental movement in the sagittal plane and disc height were measured using distortion compensated roentgen analysis (DCRA) comparing radiographs in active flexion and extension. Correlation analysis between the range of movement or disc height and patient-reported outcomes was performed in both groups. After two years, no significant change in movement in the sagittal plane was found in segments with TDR or between the two treatment groups. It remained the same or increased slightly in untreated segments in the TDR group and in this group there was a significant increase in disc height in the operated segments. There was no correlation between segmental movement or disc height and patient-reported outcomes in either group.

In this study, insertion of an intervertebral disc prosthesis TDR did not increase movement in the sagittal plane and segmental movement did not correlate with patient-reported outcomes. This suggests that in the lumbar spine the movement preserving properties of TDR are not major determinants of clinical outcomes.

Cite this article: Bone Joint J 2013;95-B:81–9.