The influence of sagittal profile alteration and final lordosis on the clinical outcome of cervical spondylotic myelopathy. A Delta-Omega-analysis

PURPOSE Decompression and maintaining or restoring a cervical lordosis are major goals in the surgical treatment of cervical spondylotic myelopathy (CSM). Numerous studies support the assumption that cervical lordosis is a key factor for neurological recovery and pain reduction. However, even kyphotic patients can be asymptomatic. The balance of the spine is subject of an increasing number of publications. The main purpose of the study was to evaluate the validity of lordotic alignment on the course of CSM and to set this parameter in context with well-validated tools, namely the modified Japanese Orthopaedic Association scoring system (mJOAS) and the visual analogue scale (VAS), to predict and measure the clinical outcome after surgery. METHODS This is a retrospective study with prospectively collected data of a heterogeneous cohort. The authors analyzed the records of 102 patients suffering from CSM that underwent decompressive surgery and instrumentation. Clinical outcome was assessed by using the mJOAS, VAS and Odom's criteria. The radiological analysis involved comparison of pre- and postoperative radiographs. The patients were divided into subgroups to be able to compare the influence of various amounts of correction (3 Delta-groups: <0°, 1-7° and ≥8°) and final lordosis (4 Omega-groups: 0-7°, 8-14°, 15-21°, ≥22°). RESULTS 219 levels were fused in 102 patients. Surgery improved the clinical outcome of all groups significantly. A lordotic profile was achieved in all analyzed groups. Patients that showed small lordosis after surgery (<8°) did not have an inferior clinical outcome compared to patients with larger cervical lordosis (>14°). The comparison of Odom's criteria showed that preoperatively kyphotic patients benefitted more from surgery than lordotic patients (p = 0.029), but no differences could be seen comparing neck pain and neurological improvement. The improvement of pain and neurological impairment measured by VAS and mJOAS supports the statistical impact and validity of the data despite comparatively small numbers of patients. The lack of postoperative kyphosis is a major limitation of the study to encompass the impact of sagittal alignment on clinical outcome. CONCLUSIONS Decompression and stabilization appear to be key elements of surgical treatment of CSM. While the achievement of cervical lordosis remains a major goal of surgery, clinical improvement is not hindered in patients who show small lordosis. However, kyphosis should be eliminated in symptomatic patients. The terms "balance" and "physiologic lordosis" remain complex entities without clear definition. To check the results of our study controlled randomized trials to validate and determine the exact role of cervical balance on the course of CSM would be helpful.