Does hormone replacement therapy prevent lateral rotatory spondylolisthesis in postmenopausal women?

PURPOSE: Degenerative scoliosis usually begins at menopause and lateral rotatory olisthesis (LRO) might be a triggering factor in the onset of degenerative scoliosis in postmenopausal women. We set out to evaluate the influence of hormone replacement therapy (HRT) on degenerative scoliosis and on LRO. METHODS: A cross-sectional study was conducted in 146 postmenopausal women: 75 women had received HRT for more than 1 year (HRT > 1) and 71 women had never received HRT or less than 1 year (HRT < 1). Scoliotic curve, LRO, sacral slope, lordosis, kyphosis were measured. The excess risk of LRO associated with age, BMI, isometric strength of brachial biceps, bone mineral density, lean mass and HRT was evaluated using a multiple logistic regression model. RESULTS: No difference was found in sacral slope, lumbar lordosis or thoracic kyphosis between both groups or in the presence of scoliosis. The prevalence of LRO was significantly lower in HRT >1 than HRT <1 (8 vs. 30%) while the risk was dependent on age, HRT and their interaction. LRO increased with age only in HRT <1 (11% when aged ≤66 years vs. 39% when aged >66 years, p = 0.013), whereas the prevalence of LRO remained stable in HRT >1. CONCLUSIONS: LRO was significantly lower in women who received HRT. The excess risk of LRO was dependent on both age and HRT status. These findings suggest that HRT might prevent the onset of LRO, and therefore might contribute to the prevention of low back pain.

The effect of bilateral laminotomy versus laminectomy on the motion and stiffness of the human lumbar spine: a biomechanical comparison.

STUDY DESIGN: A cadaveric simulation model of the lumbar spine was used to study the intervertebral motion characteristics of the lumbar spine after bilateral laminotomy and facet-sparing laminectomy. OBJECTIVE: To assess differences in motion patterns and lumbar spine stiffness after bilateral laminotomy versus laminectomy. SUMMARY OF BACKGROUND DATA: Spondylolisthesis after facet-sparing laminectomy has been reported with a frequency of 8% to 31%. Bilateral laminotomies have been shown to be effective in decompressing the spine, without resection of the posterior osteo-ligamentous complex. We hypothesize that bilateral laminotomies induce significantly less iatrogenic hypermobility and less stiffness reduction than a traditional facet-sparing laminectomy in the lumbar spine. METHODS: Six fresh frozen human cadaveric lumbar spines (L1-L5) were mounted into a spine motion simulator for testing. With physiologic follower preload, flexion/extension, lateral bending, and axial rotation moments were applied to the lumbar spine in 3 trials: (1) Intact lumbar spine-no surgery, (2) Lumbar spine after bilateral lumbar laminotomies at L2-L5, (3) Lumbar spine after full laminectomies at L2-L5. The lumbar spine kinematics were measured using a Vicon motion tracking system. Total and segmental range of motion and spine stiffness were recorded. RESULTS: In flexion/extension, bilateral laminotomies resulted in an average increase in L2-L5 range of flexion/extension motion of 14.3%, whereas a full laminectomy resulted in an increase of 32.0% (P<0.05). Analysis per level demonstrated roughly twofold increase in motion with laminectomy compared with bilateral laminotomies (P<0.05, at every treated level). Stiffness was decreased by an average of 11.8% after the 3-level-laminotomies and by 27.2% (P<0.05) after the 3-level-laminectomy. CONCLUSION: These data demonstrate that bilateral laminotomies induce significantly less hypermobility and less stiffness reduction compared with a full laminectomy. The preservation of the central posterior osteo-ligamentous structures may provide a stabilizing effect in preventing postdecompression spondylolisthesis.

Long-term follow-up results and radiographic findings of anterior surgery with Cloward trephination for cervical spondylotic myelopathy.

STUDY DESIGN: Serial retrospective long-term follow-up study. OBJECTIVE: To assess the long-term results of anterior surgery with Cloward trephination and iliac strut grafting for cervical spondylotic myelopathy. SUMMARY OF BACKGROUND DATA: Anterior surgery remains the most common surgical option and generally gives good results, although early and late deterioration after initial postoperative improvement has been noted. Although anterior decompression with trephination is a variant of the Cloward technique, little information is available concerning the long-term results after this procedure. METHODS: One hundred sixty-eight consecutive patients treated with this technique by the same author from the years 1978 to 1992 were followed serially. One hundred and seven patients were followed for over 10 years (mean: 14.1 y) (follow-up rate: 71.8%). Clinical results were evaluated according to the Japanese Orthopedic Association system and the results at different postoperative intervals were analyzed. Thirty-six patients returned for the final follow-up. Plain radiographs were taken in neutral and flexion-extension positions and computed tomography scans were taken at fused segments and unfused levels. RESULTS: The mean recovery rate was 56.8% at final follow-up. Deterioration of 2 Japanese Orthopedic Association points or more was experienced in 44 patients at various postoperative periods and was more frequent at over 10 years follow-up. Kyphosis of fused segments was noted frequently on the radiographies of the 36 patients with a mean of 7.8 degrees. A straight or misaligned cervical spine was found in 28 (77.8%) patients and these deformities were more serious in multilevel fusions. Stenosis of the canal at fused segments was found in 15 (41.7%) patients owing to osteogenesis resulting from inadequate decompression or pseudoarthrosis. At unfused levels, the incidence of spondylolisthesis, bony bridge, disc hernia, and thickening or bulging of the ligament flavum was 19.4%, 27.8%, 33.3%, 19.4%, respectively, and these abnormalities almost always occurred at levels adjacent to the fusion. Radiographic abnormalities were pejorative for long-term clinical results. CONCLUSIONS: Anterior surgery with Cloward trephination provides generally acceptable long-term results with considerable incidences of deterioration and radiographic abnormalities. This underlines the need for thorough decompression and preservation of the subchondral endplate bone for solid fusion and maintenance of the cervical lordotic curvature.

[Adjacent segment disease after spine fusion and instrumentation].

Spinal instrumentation is a common method for the treatment of spinal disorders, but it can lead to the changes of spine biomechanics. Because of the stress changes, accelerated degeneration of the adjacent segment may occur as time goes by, namely adjacent segment disease. The accelerated degeneration can lead to secondary spinal stenosis, articulated joint degeneration, acquired spondylolisthesis, and spine instability, and some patients may have to receive surgery again. In recent years, the researchers gradually recognized the importance of this disease, and began to investigate its pathogenesis and management.