Abstract
Purpose of the study: The surgical treatment of degenerative lumbar stenosis associated with degenerative lumbar spondylolithesis (DLSP) is generally treated by decompression of the neurological structures combined with fusion. Results have been superior compared with decompression alone. We opted for decompression combined with stabilization without fusion using the Dynesys® in order to limit the morbidity related to instrumented fusion in older patients and to avoid the progressive aggravation of the lithesis.
Material and methods: This was a prospective series of 25 patients with symptomatic DLSP. Inclusion criteria were: saccoradiculographic confirmed degenerative stenosis of the canal associated with static anteroposterior intervertebral translation measuring at least 3 cm in the upright position irrespective of the degree of displacement demonstrated on the stress images. Incomplete reduction of the anteroposterior translation in extension, osteoporosis, associated deformity in the frontal plane were not considered to be contraindications for Dynesys® instrumentation. Exclusion criteria were: complete uni- or bilateral arthrectomy, history of lumbar surgery involving the olisthesic level. The series included 19 women and 6 men, mean age 71 years (range 53–83). All 25 cases involved the L4–L5 level. Twelve single level (L4–L5) and 13 two level (L3–L5) instrumentations were performed. All patients had a CT scan and saccoradiculography and 12 had an MRI. Pre- and postoperative stress images were obtained using the Putto protocol. Whole spine weight-bearing images were also obtained to study pelvic and sagittal parameters before and after surgery. The Beaujon classification was determined at minimum 12 months follow-up (mean follow-up 22 months, range 12–48 months).
Results: Outcome was very good in 72% of patients (relative gain > 70%) and good in 28% (relative gain 40–70%). There were no fair or poor results (100% good or very good results). There were two complications: on patient whose preoperative crural paresia worsened before complete recovery and on neuroaggressive pedicular screw which had no later consequence. The radiologic study revealed four case with an antelisthesis reduction but generally the displacement persisted and did not worsen over time. The stress films confirmed the presence of residual mobility of the instrumented level when the disc height remained sufficient. A lucent line around a screw was found in two cases with no clinical expression. After instrumentation with the Dynesys®, sagittal tilt at T9 due to accentuated lordosis below the instrumentation was observed, even in cases with an spine unbalanced anteriorly.
Discussion: This prospective study can be validly compared with another prospective study we performed in 1999 in which we compared the outcome after isolated canal decompression for DLSP with that after decompression combined with fusion. Using the same evaluation criteria, the results after fusion in a comparable population (18 patients) were similar to those observed in the present study where good and very good outcome was achieved in 88% of patients. Stabilization with Dynesys® provides results at least as good as arthrodesis with lesser perioperative morbidity.
Conclusion: In our opinion, it would be rational to propose this method for DLSP patients aged less than 65 years with a self-reducible predominantly angular displacement and satisfactory disc height. This context (group 3)occurs for pelvi with a small sacral slope and incidence, and minimal lordosis adapted to the pelvic parameters. Dynesys® is a palliative alternative to fusion for more advanced DLSP with anterior imbalance when fusion would technically difficult to correct for the kyphosis or with in a patient with significant surgical risk. Longer follow-up would be needd to confirm these good results over time and to demonstrate that Dynesys® «protects» the adjacent levels against degeneration (stenosis, destabilization).
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