Scaphoid nonunion in the presence of a Scapho-Lunate coalition: a rare case report

Carpal coalitions are rare congenital anomalies, with an estimated prevalence of 0.1% in Europeans. Scapholunate (SL) coalitions are particularly uncommon (~ 2% of coalitions). Altered carpal kinematics in this context are thought to predispose to fracture and nonunion. To date, no case of scaphoid pseudarthrosis in association with an SL coalition has been reported.

We describe a 25-year-old man presenting with chronic wrist pain and limited extension following multiple skeletal injuries. Examination revealed tenderness in the anatomical snuffbox. Imaging demonstrated a scaphoid waist pseudarthrosis associated with an incomplete osseous SL coalition (Minnaar type 2), combined with a complete capitotrapezoid and a fibrous capitate-hamate coalition. The contralateral wrist showed a trapezoid-capitate coalition. Reconstruction was performed with a non-vascularized corticocancellous iliac crest graft and fixation using a cannulated headless compression screw.

Union was confirmed by CT after 10 weeks of immobilization. At 6 months, the patient was nearly pain-free and exhibited good wrist motion (extension/flexion 60-0-70°, ulnar/radial deviation 30-0-20°, pronation/supination 85-0-80°). Grip strength was symmetric (32 kg bilaterally). Histology of resected fragments revealed non-physiological microarchitecture consistent with pseudarthrosis.

This is the first reported case of scaphoid pseudarthrosis associated with an SL coalition. The case highlights therapeutic dilemmas in coalition-related fractures: distal scaphoid resection risks midcarpal instability, whereas reconstruction faces an increased risk of nonunion due to altered biomechanics. Successful consolidation demonstrates that standard reconstructive techniques remain feasible and underscores the importance of recognizing coalitions as risk factors for nonunion in surgical planning.

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