Background and Clinical Significance: Post-traumatic finger stiffness is frequently attributed to soft tissue adhesions; however, mechanical obstruction from occult osseous structures remains a rare but critical differential diagnosis in adults. Case Presentation: This report describes a 56-year-old female presenting with severe, refractory stiffness of the little finger eight months after a proximal phalanx fracture. Despite extensive conservative therapy, active and passive flexion at the proximal and distal interphalangeal joints remained locked in extension. While conventional radiographs demonstrated bony union, musculoskeletal ultrasonography (MSUS) revealed an occult protruding malunited fragment incarcerating the flexor tendons. Dynamic MSUS provided real-time evidence of mechanical impingement by demonstrating proximal muscle contraction without distal tendon excursion. Intraoperatively, initial soft tissue tenolysis failed to restore motion; further exploration guided by MSUS evidence successfully identified a sharp bone spike. Subsequent ostectomy resulted in immediate restoration of functional range of motion. This case underscores the limitations of static imaging in evaluating the dynamic gliding mechanism and highlights the valuable role of MSUS in identifying mechanical functional obstructions. Conclusions: Early sonographic evaluation should be considered for refractory post-traumatic stiffness to prevent prolonged, ineffective conservative care and to guide definitive surgical management.
Chang et al. (Thu,) studied this question.