Design and validation of a reaching-task system for quantifying wrist extension recovery after radial nerve repair in nonhuman primates.

BACKGROUND

Advances in peripheral nerve surgery remain suboptimal, underscoring the need for novel therapies typically tested in small-animal models, where functional assessment, a critical translational endpoint, is inherently limited. Non-human primates (NHPs) bridge this gap but lack standardized quantitative functional assessments. Here, we aimed to design and validate a standardized, reproducible, and quantitative reaching-task system for measuring maximum active wrist extension in NHPs, and to demonstrate its applicability for the longitudinal assessment of motor recovery following radial nerve repair. New method A custom-built reaching-task system was developed to isolate wrist extension in NHPs while minimizing upper-limb compensation. A standardized dual-camera configuration enabled frame-by-frame kinematic analysis via motion-tracking software. Reliability was tested in two healthy NHPs across three repeated sessions, and a proof-of-concept experiment assessed recovery in an NHP following nerve repair.

RESULTS

Maximum wrist extension angles showed high inter- and intra-subject reliability (ICC > 0.90), with a significant relationship between target height and extension angle (β = 3.92°, R² = 0.77). In the nerve repair model, maximum wrist extension improved from 20.1 ± 7.7° at 103 days post-repair to 39.5 ± 6.9° at 180 days (p < 0.001), consistent with electrophysiological evidence of reinnervation; kinematic profiles revealed gradual restoration of function. Comparison with existing methods This system standardizes limb positioning and target placement, enabling synchronized kinematics for consistent extraction of wrist angles.

CONCLUSIONS

This reaching-task system provides a standardized, quantitative assessment of wrist extension after radial nerve repair, supporting its translational relevance as a platform for preclinical therapeutic evaluation.