Hip Abduction Weakness as a Bedside Localization Sign: Lumbar Radiculopathy versus Common Peroneal Neuropathy

Objective: Distal lower-extremity weakness may arise from lumbar radiculopathy (LR) or common peroneal neuropathy (CPN).However, localization can be difficult because both conditions may produce overlapping ankle and/or great toe dorsiflexion weakness.This study evaluated hip abduction weakness as a bedside localization sign for LR.Methods: We retrospectively reviewed 68 surgically treated patients with preoperative ankle and/or great toe dorsiflexion weakness due to lumbar degenerative disease or peripheral nerve lesions.Patients were classified according to whether they had LR or CPN.Hip abduction weakness was defined as a Medical Research Council (MRC) grade <5.Diagnostic indices were calculated using LR as the target condition.Results: Among 68 patients, 59 had LR and 9 had CPN.Hip abduction weakness was present in 57 of 59 patients with LR and in no patients with CPN (p < 0.001).Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 96.6%, 100.0%(95% confidence interval [CI], 66.4-100.0%),100.0%, 81.8% (95% CI, 48.2-97.7%),and 97.1%, respectively.Results were similar among patients who underwent electrodiagnostic (EDX) studies and among those with mild-to-moderate distal weakness, defined as a lowest distal MRC grade of ≥3 and <5.Among 37 patients with conclusive EDX localization, hip abduction-based bedside localization agreed with EDX localization in 36 patients (97.3%;Cohen's κ, 0.92).Conclusion: In this selected surgical cohort, hip abduction weakness was strongly associated with LR and was absent in patients with CPN.Hip abduction testing may provide a simple complementary bedside localization sign in patients with ankle and/or great toe dorsiflexion weakness.