This study was to assess the morphological changes of the pronator quadratus (PQ) muscle using an ultrasonography in the volar locking plate fixation group and in the percutaneous K-wire fixation group for distal radius fracture, and to evaluate the impact on clinical outcomes.

Fifty-four patients who received surgical treatment for distal radius fracture were enrolled in this study. They were divided into two groups according to treatment modality: Group 1 included 34 patients who underwent internal fixation with volar locking plate and Group 2 included 20 patients with percutaneous K-wire fixation. Thickness of the PQ muscle was measured using an ultrasonography at the final follow-up. We evaluated the outcomes using the Mayo wrist score, wrist range of motion, and grip strength at the final follow-up.

Compared with the uninjured side, thickness of the PQ muscle showed 31.9% of mean atrophy in Group 1 and 11.4% in Group 2. The atrophy of PQ muscle was severe in Group 1 (p=0.01). However, there was no significant difference in the mean Mayo wrist score between the two groups (83.1±10.9 in Group 1 and 80.2±8.9 in Group 2, p=0.28), except a mild limitation of pronation in Group 1.

The healed PQ muscle from fracture itself after distal radius fracture revealed a morphological atrophy. Moreover, the volar locking plate resulted in greater atrophy of the PQ muscle, but there was no specific impact on clinical outcomes.