Recovery of ankle dorsiflexion weakness following lumbar decompressive surgery.

This retrospective study evaluated the recovery of ankle dorsiflexion (ADF) weakness following decompressive surgery in order to identify factors indicative of a better outcome. Fifty-six consecutive patients with ADF weakness secondary to nerve root compression underwent lumbar decompressive surgery. The demographic features, duration and severity of preoperative ADF weakness, associated radicular pain, as well as the radiological and intraoperative findings were recorded. ADF weakness at the time of initial follow-up at 6 weeks following surgery, and the latest follow-up at a median of 24 months was recorded. The patients had a mean age of 50.5 years with equal numbers of men and women. Acute disc prolapse was the compressive pathology in 88%. Clinical foot drop, defined as an ADF power of <3 by manual testing according to the Medical Research Council classification, was present in 66% of patients on presentation. Grade 3 power was present in 27% of patients and 7% had grade 4 power on presentation. The mean ADF power on presentation was 1.8. This improved to a mean of 3.2 at 6 weeks following surgery (p < 0.0001). A further small improvement in ADF power occurred after 6 weeks following surgery to a power of 3.5 at the latest follow-up (p < 0.0001). The degree of ADF weakness at latest follow-up correlates with the deficit at presentation (p <0.001). Younger patients made a better recovery (p = 0.03). No other significant associations between the demographic or clinical features and the recovery of the weakness could be identified. Thus, decompressive surgery was associated with an early improvement in ADF weakness. Only small improvements take place beyond 6 weeks following surgery. The degree of deficit at presentation is predictive of the extent of recovery. Recovery in ADF strength is more evident in younger patients.