Purpose: A long spinal fusion across the thoracolumbar region is sometimes applied in scoliosis. Adjacent level degeneration below these constructs has been documented. Treatment with an artificial disc replacement below the fusion has been proposed to prevent degeneration there. There is currently little data detailing the expected biomechanics of this situation. The objective of this study was to evaluate range of motion (ROM) and helical axis of motion (HAM) changes due to one- and two-level Maverick total disc replacement adjacent to a long spinal fusion.

Method: A multidirectional flexibility testing protocol with compressive follower preload was used to test seven human cadaveric spine specimens (T8-S1). A continuous pure moment ±5.0 Nm was applied in flexion-extension (FE), lateral bending (LB) and axial rotation (AR), with a compressive follower preload of 400 N. The motion of each vertebra was monitored with an optoelectronic camera system. The test was completed for the intact condition and after each surgical technique:

T8-L4 fusion and facet capsulotomy at L4–L5 and L5-S1;

Maverick total disc replacement and fusion with the CD Horizon system was performed. Repeated measures ANOVA was used to analyze changes in ROM and HAM of the L4–L5 and L5-S1 segments.

Results: Following L4-L5 Maverick replacement, L4-L5 ROMs tended to decrease slightly (on average from 6.2°±2.8° to 5.1°±3.8° in FE, 1.1°±1.1° to 0.9°±0.5° in LB and 1.3°±0.9° to 1.0°±0.6° in AR). With two-level Maverick implantation, L5-S1 ROMs tended to increase slightly in FE (from 6.6°±2.6° to 7.1°±3.9°), and to decrease slightly in LB (from 1.5°±0.9° to 1.0°±0.3°) and AR (from 1.5°±1.5° to 1.1°±0.6°), compared to the fused condition. As a trend, HAM location shifted posteriorly in FE and AR, and inferiorly in LB following Maverick replacement. However, neither ROM nor HAM at these two segments showed any significant change due to the implantation of one-or two-level Maverick total disc replacement in any of the three directions.

Conclusion: The present results suggested that lower lumbar segments with Maverick disc replacement exhibited intact-like kinematics in both extent and quality of motion.

Background: To present the experience of three centres in the surgical management of scoliosis in patients with Prader-Willi syndrome¹, and to describe the associated complications. A retrospective case series reviewing treatment type, surgical outcomes and complications with a review of the literature

Methods: There were 15 patients treated surgically in the three centres over an eleven year period. The average age at initial surgery was 9.6 (5 to 16+8) yrs. Minimum follow-up from index procedure was 28 months. 5 underwent posterior spinal fusion, 2 had anterior fusion alone and 2 had combined anterior/ posterior fusions as their index procedure. 6 patients were initially managed with growing rod constructs. Outcome measures included fusion rate, curve progression and complication rate.

Results: 11 patients achieved a solid fusion. 2 patients were still undergoing the lengthening process and were thus unfused. 1 patient had broken instrumentation with pseudarthrosis, and one patient not fit for final fusion remained without implants. No curve progression was seen in the 11 fused spines. Progressive kyphosis and scoliosis were noted in the two ongoing lengthening patients. There were 17 revision procedures not including planned lengthenings, with a total of 59 surgical procedures. 5 rod breakages occurred in the growing-rod patients. There were 11 infections (4 deep) in 7 patients. There were 6 respiratory complications, 3 requiring ventilatory support. One patient had post-operative neurological deterioration requiring re-exploration and who had grade 3 paraparesis at final follow-up. In total there were 36 complications (240%)

Conclusion: The outcome of surgical management of scoliosis in Prader-Willi syndrome is adversely affected by the obesity and respiratory difficulties of the patients and complications abound². The use of growing constructs, whilst enabling the management of the growing child, greatly increases the risk of implant failures. Their use in Prader-Willi requires careful consideration.