Introduction: The flexor carpi radialis brevis (FCRB) is a rare anatomical variation, with a reported prevalence ranging from 0.9% to 8.7%. Our previous report showed three cases of FCRB in distal radius fracture (DRF) and found that hypoplastic pronator quadratus (PQ) adjacent to the FCRB muscle made it difficult to cover a volar locking plate (VLP). As we subsequently experienced additional six FCRBs, we report on new findings and surgical tips.
Case report: VLP fixation was performed on DRF with FCRB in nine limbs of eight patients. The prevalence was 2.9% (9 of 310 limbs). Of the seven patients that underwent unilateral surgery, six were muscle type and one was tendon type. One patient who underwent bilateral surgery had a muscle type on the left and a tendon type on the right. In three muscle types, as the FCRB muscle belly was widely attached to the radial side of the radius and the radial side of the PQ was hypoplastic, postoperative covering of the plate by repair of the PQ was impossible. Then, in two of those cases, the PQ and FCRB were sutured and the plate was covered. FCRB muscle could be retracted to the radial side in all cases. One patient with a tendon type had a ruptured tendon, which was left unrepaired. All patients had no postoperative problems.
Conclusion: In the muscle-type FCRB, the muscle should be retracted to the radial side for VLP fixation. The muscle belly might occupy the radial side of the radius, and the PQ might be hypoplastic and unrepairable. However, the plate can be covered by suturing the PQ and FCRB.
Keywords: Flexor carpi radialis brevis; distal radius fracture; hypoplastic pronator quadratus.
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