OBJECTIVE: The aim was to determine in vivo whether pre-operative mobility of the lumbar spine (overall and segmental) is retained after surgical intervention. METHODS: Functional imaging of the lumbar spine was performed in flexion and extension, using a lateral projection under standardised conditions. This allowed assessment of the overall mobility, mobility of the instrumented mobile segments and the disc height of the adjacent cranial segment (intervertebral space; IVS) before and after surgical intervention. Images were evaluated independently by a radiologist and an orthopaedic surgeon. A comparative analysis of preoperative and postoperative functional images was carried out with the aid of a computer and appropriate software (ACES) for further assessment of the extent to which the range of movement was retained. The Oswestry Disability Index (ODI, quality of life assessment) and the visual analogue scale (VAS, pain assessment) were used as clinical criteria and compared pre-and postoperatively. The mean follow-up (FU) intervals were 13.5 days (FU 1) and 19 months (FU 2). RESULTS: Radiological results showed that the overall mobility of the lumbar spine (L1 to S1) decreased on average by one third of the flexion/extension range, from 25.0º preoperatively to 17.6º postoperatively. The segmental mobility of the monosegmental stabilisation decreased on average from 3.7º to 2.3º. The caudal segments of the bisegmental dynamic stabilisation retained their preoperative movement range of 2.6º, with a postoperative range of 2.4º. The IVS did not change. The ODI improved postoperatively from 59 (preoperative) to 39/41 (FU1/FU2) points, while the VAS (during movement) improved from 7.6 (pre-op) to 4.4/4.5 (FU1/FU2). Computer-assisted analysis showed that small and functionally insignificant micro-motion of 0.4º (error 0.12%) remained in the stabilised and unfused mobile segment. CONCLUSION: Comparison of preoperative and postoperative measurements showed that overall mobility and segmental micro-motion were retained after non-fusion stabilisation of the lumbar spine with monosegmental and bisegmental instrumentation. The adjacent cranial segment (IVS) did not collapse. Activity levels (ODI) and pain symptoms (VAS) of the patients showed significant improvement at follow-up, comparable to that reported in the literature for conventional rigid spinal fusions.
Radiography; Internal fixators; Spine; Bone screws
