Monosegmental Fusion Research Articles

Adjacent Segment Mobility After Rigid and Semirigid Instrumentation of the Lumbar Spine

Retrospective radiographic analysis of lumbar spine range of motion (ROM) after monosegmental fusion and posterior dynamic stabilization at the level L4-L5. Comparison of segmental ROM at the index level and the cranial and caudal adjacent levels and of global lumbar spine ROM after monosegmental fusion and posterior dynamic stabilization. The postulated advantage of nonfusion technology compared with fusion is based on the assumption that preservation of motion at the treated segment reduces the incidence of adjacent segment effects. Therefore, it is imperative to provide evidence that dynamic stabilization devices avoid hypermobility at the adjacent segments because this might substantiate a protective effect on the adjacent segments. Twenty-six patients with low back pain and claudication due to degenerative instability at the level L4-L5 with concomitant spinal stenosis were treated either with decompression and Dynesys (n = 11) or with decompression and fusion (n = 15). All patients underwent flexion/extension radiographs before surgery and at latest follow-up. ROM was assessed at the index level (L4-L5), the cranial/caudal adjacent levels (L3-L4/L5-S1), and at the lumbar spine from L2 to S1. There was a significant reduction of the global ROM of the lumbar spine (L2-S1) and the segmental ROM at the index level (L4-L5) in the fusion group, whereas adjacent level ROM did not change significantly. In the Dynesys group, no significant changes of global lumbar spine ROM (L2-S1) and segmental ROM (index level and cranial/caudal adjacent levels) were seen. This study shows that neither monosegmental instrumented fusion nor monosegmental posterior dynamic stabilization with Dynesys alter the ROM of the cranial and caudal adjacent levels. Consequently, monosegmental posterior dynamic stabilization with Dynesys has no effect with regard to adjacent segment mobility compared with monosegmental fusion.

Ergebnisse der operativen Behandlung bei Spondylolisthesen sowie bei lumbalen und sakralen Wirbelsäuleneingriffen

Presented are the results after the surgical treatment (CDI) of 25 patients suffering from spondylolisthesis and of 25 patients with a lumbar or a sacral spondylodesis. The mean follow up reaches from 8.4 (spondylolisthesis) to 16.6 months (lumbar and sacral spondylodesis). 15 (60%) of the patients with spondylolisthesis showed an excellent or good result, in 3 (12%) the result was unsatisfactory. Only 7 of the patients of the second group were without further complaints, in 6 an amelioration of pain relief could be reached. The complications demonstrate the fault of the instrumentation in the beginning. After the development of a new screw the monosegmental fusion with CDI can be achieved in spondylolisthesis with a slipping to 70%, in more severe spondylolisthesis bisegmental fusion is necessary. The results in lumbar and sacral spondylodesis demonstrate that the operation should be only performed when all other methods have been unsuccessful.

Outcomes nach ventraler Spondylodese der Halswirbelsäule - eine klinische Untersuchung von 368 Patienten

The object of this study was to identify those factors with a direct influence on the treatment outcome of anterior cervical fusion. The clinical relevance of intervertebral cage subsidence in the course of disease is discussed. In a prospective clinical study we followed up 368 patients with degenerative disease of the cervical spine one year after anterior fusion and cage implantation. We found a statistically significant association between a good outcome and young adults with monosegmental fusion of the lower cervical spine. Early treatment of moderate degenerative cervical disc diseases using an intervertebral cage and anterior fusion leads to a good outcome. Subsidence of the cage does not correlate with a poor outcome.

Anatomische Reposition und monosegmentale Fusion bei hochgradiger dysplastischer Spondylolisthese L5/S1

Developmental spondylolisthesis leads to lumbosacral kyphosis with retroversion of the sacrum and lumbar hyperlordosis. The overall sagittal profile of the spine is affected. The deformity is progressive during growth. This retrospective study describes a technique for complete reduction with clinical and radiological evaluation. Thirty-four patients (mean age 16 years 3 months, 10 males, 24 females) with severe developmental spondylolisthesis L5/S1 (Meyerding grades 3 to 5) were operated on between February 1997 and July 2002. Reduction was achieved by temporary transpedicular instrumentation of L4. These screws were removed at the end of the operation or 12 weeks later. Mean slippage was corrected from 76 % preoperatively to 10 % postoperatively. Segmental kyphosis L5/S1 improved from + 21 degrees preoperatively to - 7 degrees postoperatively. Sacral inclination was 34 degrees preoperatively, 43 degrees postoperatively, and 47 degrees at latest follow-up. 76 % of the patients were pain free at the latest follow-up. In 4 patients a fusion at L4/5 was performed due to subsequent decompensation. The technique described allows for a nearly anatomic reduction with correction of slippage as well as segmental kyphosis. Correction of the local deformity with monosegmental fusion L5/S1 improves dramatically the overall sagittal profile of the spine. Fusion of the primarily healthy segment L4/5 can be avoided.

Anatomic Reduction and Monosegmental Fusion in High-Grade Developmental Spondylolisthesis

A retrospective review of the clinical and radiographic outcomes of reduction by temporary instrumentation of L4 and monosegmental fusion of L5/S1 in patients with high-grade developmental spondylolisthesis. To assess the efficacy of this technique in the reduction of local deformity and correction of overall sagittal profile. In situ fusions as well as partial reduction with fusion L4-S1 via various approaches have been described previously. To date and to our knowledge, there have been no reports describing complete reduction and monosegmental fusion for high-grade developmental spondylolisthesis. A total of 27 consecutive patients with severe developmental spondylolisthesis of L5/S1 were treated with operative reduction via temporary instrumentation of L4 and monosegmental fusion of L5/S1. The clinical and radiographic outcomes were retrospectively reviewed for each case at a minimum of 2 years (mean follow-up of 45 months; range 24-80). Mean age at surgery was 16.7 years (range 9-29). At most recent follow-up, 23 patients were pain free. There were 4 patients who had moderate pain. All radiographic parameters improved. Mean slippage improved from 74.0% before surgery to 11.0% after surgery and 10.0% at latest follow-up. Slip angle improved from 36.6 degrees before surgery to 8.1 degrees after surgery and 7.6 degrees at latest follow-up. Sacral inclination improved from 34.6 degrees before surgery to 43.4 degrees after surgery and 47.2 degrees at latest follow-up. The overall sagittal profile improved dramatically. There was 1 superficial infection, 6 patients had L5 root symptoms (5 of these resolved, 1 patient had a persistent sensory deficit). Four patients had decompensation at L4/5 (2 reoperations). Reduction of L5/S1 with temporary instrumentation of L4 and monosegmental fusion of L5/S1 is an effective technique for the treatment of high-grade developmental spondylolisthesis. A complete reduction of local deformity and excellent correction of overall sagittal profile can be achieved. Fusion of the primarily healthy segment L4/5 can be avoided.

CT-basierter Auswertungsscore nach ventraler Spondylodese bei thorakolumbalen Wirbelfrakturen

Dorsoventral stabilization is a common procedure to treat thoracolumbar spine fractures. Especially in respect of the evaluation of alternative procedures to autogenous bone graft, a standardized evaluation score for ventral spondylodesis is necessary. In a group of 44 patients a follow-up CT scan was evaluated with a standardized scoring system by four different independent evaluators (a trauma surgeon, an orthopedic surgeon, and two radiologists). The score is based on the morphologic classification of the region between graft and vertebral body. It allows a classification of the spondylodesis as sufficient, partial, and not sufficient. The statistical evaluation of the classification of the different evaluators shows very good interobserver agreement in monosegmental fusion and good agreement in bisegmental fusion. The demonstrated score is easy to handle, does not need special equipment for CT scans, and shows good interobserver agreement in the classification of spinal fusion after ventral spondylodesis for thoracolumbar spine fracture.

Posterior reduction and anterior lumbar interbody fusion in symptomatic low-grade adult isthmic spondylolisthesis: short-term radiological and functional outcome.

The aim of this study was to evaluate the short-term radiological and functional outcome of surgical treatment for symptomatic, low-grade, adult isthmic spondylolisthesis. Twelve patients underwent a monosegmental fusion for symptomatic spondylolisthesis. Posterior reduction with pedicle screw instrumentation was followed by second-stage anterior interbody fusion with a cage. All patients underwent a decompressive laminectomy. At an average of 2.1 (range 1.4-3.0) years following surgery, all patients completed the Oswestry questionnaire, VAS back pain score and a questionnaire detailing their work status. Radiographs were evaluated for maintenance of reduction and fusion. The patients (nine male, three female; mean age 42, range 22-54 years) had experienced preoperative symptoms for an average of 38 (range 6-96) months. An average preoperative slip of 21% (range 11-36%) was reduced to 7% (range 0-17%). Reduction of slip was maintained at latest follow-up, at which time the average VAS score was 2.8 (range 0-8) and the average Oswestry score was 13 (range 0-32). All patients achieved a successful fusion. There were no postoperative nerve root deficits. All patients stated that they would be prepared to undergo the same procedure again if required. Seventy-five percent returned to their pre-symptom work status. Our findings suggest that posterior reduction and anterior fusion for low-grade adult isthmic spondylolisthesis may yield good functional short-term results. A high fusion rate and maintenance of reduction with a low complication rate may be expected. Further follow-up is necessary to evaluate long-term outcome.

Initial instability of different cages for fusion of the cervical spine

Purpose of the present investigation is to determine the biomechanical behaviour of different cages for monosegmental fusion of the cervical spine. Three commercially available cages (BAK, NOVUS, WING) representing the different principles of intercorporal implants and a combination of intercorporal bone graft together with anterior plating were tested for their resistance and sintering patterns under axial compression conditions. Therefore, FSU (functional spine-units) of 5-months old calfs were used. After preparation, the anterior fusion was performed by an orthopaedic surgeon. Specimen were mounted in a testing machine Zwick 1425 and axial load from 100 N up to 2000 N was applied. The compressed distance was measured and put into relation to the applied load. After that, the device was unloaded and the test was repeated another 2 times to determine the plastic deformation of implant and specimen. There was no significant difference to all of the constructs in the first compression. After repeated compression, the WING-cage, the NOVUS-cage and the plate-construct showed a constant compression pattern as expression of resting stable on the vertebral endplates, whereas the cylindrical BAK-cage had a decrease in compression distance, but increase in sintering into the vertebral body. Intercorporal implants that require the destruction of the vertebral endplates as described in the Cloward dowel-technique may have a higher risk of sintering into the vertebral body and therefore of developing progressive kyphosis. By attaching lateral supporting areas this risk can be reduced and the advantage of sponges contact for fusion is preserved.

Treatment of thoracolumbar burst fractures without neurologic deficit by indirect reduction and posterior instrumentation: bisegmental stabilization with monosegmental fusion.

This study retrospectively reviews 20 sequential patients with thoracolumbar burst fractures without neurologic deficit. All patients were treated by indirect reduction, bisegmental posterior transpedicular instrumentation and monosegmental fusion. Clinical and radiological outcome was analyzed after an average follow-up of 6.4 years. Re-kyphosis of the entire segment including the cephaled disc was significant with loss of the entire postoperative correction over time. This did not influence the generally benign clinical outcome. Compared to its normal height the fused cephalad disc was reduced by 70% and the temporarily spanned caudal disc by 40%. Motion at the temporarily spanned segment could be detected in 11 patients at follow-up, with no relation to the clinical result. Posterior instrumentation of thoracolumbar burst fractures can initially reduce the segmental kyphosis completely. The loss of correction within the fractured vertebral body is small. However, disc space collapse leads to eventual complete loss of segmental reduction. Therefore, posterolateral fusion alone does not prevent disc space collapse. Nevertheless, clinical long-term results are favorable. However, if disc space collapse has to prevented, an interbody disc clearance and fusion is recommended.