Severity of degenerative lumbar spinal stenosis affects pelvic rigidity during walking.

Background Context: To understand the role of compensation mechanisms in the development and treatment of symptomatic degenerative lumbar spinal stenosis (DLSS), pelvic stability during walking should be objectively assessed in the context of clinical parameters.

Purpose: To determine the association among duration of symptoms, lumbar muscle atrophy, disease severity, pelvic stability during walking, and surgical outcome in patients with DLSS scheduled for decompression surgery.

Study Design/setting: Prospective observational study with intervention.

Patient Sample: Patients with symptomatic DLSS.

Outcome Measures: Oswestry Disability Index score; duration of symptoms; lumbar muscle atrophy; severity grade; pelvis rigidity during walking.

Methods: Patients with symptomatic DLSS were analyzed on the day before surgery and 10 weeks and 12 months postoperatively. Duration of symptoms was categorized as: <2years, <5years, and >5years. Muscle atrophy at the stenosis level was categorized according to Goutallier. Bilateral cross-sectional areas of the erector spinae and psoas muscles were quantified from magnetic resonance imaging. Stenosis grade was assessed using the Schizas classification. Pelvic tilt was measured in standing radiographs. Pelvic rigidity during walking was assessed as root mean square of the pelvic acceleration in each direction (anteroposterior, mediolateral, and vertical) normalized to walking speed measured using an inertial sensor attached to the skin between the posterior superior iliac spine.

Results: Body mass index but not duration of symptoms, lumbar muscle atrophy, pelvic rigidity, and stenosis grade explained changes in Oswestry Disability Index from before to after surgery. Patients with greater stenosis grade had greater pelvic rigidity during walking. Lumbar muscle atrophy did not correlate with pelvic rigidity during walking. Patients with lower stenosis grade had greater muscle atrophy and patients with smaller erector spinae and psoas muscle cross-sectional areas had a greater pelvis tilt.

Conclusions: Greater pelvic rigidity during walking may represent a compensatory mechanism of adopting a protective body position to keep the spinal canal more open during walking and hence reduce pain. Pelvic rigidity during walking may be a useful screening parameter for identifying early compensating mechanisms. Whether it can be used as a parameter for personalized treatment planning or outcome prognosis necessitates further evaluation.