3D motion analysis after surgical treatment of elbow flexor spasticity: a proof-of-concept study

INTRODUCTION: Postoperative outcomes after hyperselective neurectomy of the elbow flexors are commonly assessed with the modified Ashworth Scale or the Tardieu Scale. A degree of subjectivity exists despite our best efforts. This proof-of-concept study evaluated the feasibility and added value of an instrumented protocol combining three-dimensional motion analysis and surface electromyography. METHODS: In this prospective, monocentric proof-of-concept study, 12 patients (aged 17-70 years) with upper motor neuron lesions underwent hyperselective neurectomy of the elbow flexors. Seven patients had concomitant musculotendinous lengthening of the elbow flexors. Assessments were performed preoperatively, and at 6 and 12 months postoperatively, including the Modified Ashworth and Tardieu scales. Instrumented assessment included three-dimensional kinematics with synchronized surface electromyography of the biceps during slow and fast passive elbow stretch and standardized functional tasks. Ten patients completed the 12 month follow-up. RESULTS: Postoperatively, elbow flexor spasticity significantly decreased on the Tardieu Scale. Instrumented kinematics detected a significant reduction in passive elbow extension deficit in the patients with additional musculotendinous lengthening, whereas clinical goniometry underestimated extension deficits. Preoperatively, clinical scores correlated with instrumented parameters, but these associations were not observed postoperatively. Active elbow kinematics during functional tasks showed no significant group-level change. Exploratory surface electromyography recordings indicated a consistent, non-significant reduction in velocity-dependent muscle activation. CONCLUSIONS: By providing objective, joint-specific information complementary to clinical scales, instrumented three-dimensional motion analysis with synchronized surface electromyography is a potentially feasible tool for evaluating outcomes after hyperselective neurectomy of the elbow flexors. However, its use warrants further research in larger cohorts. LEVEL OF EVIDENCE: IV.