Appearance of the bare area of the proximal radius on magnetic resonance imaging: preliminary assessment on its potential usefulness in preoperative planning for distal biceps brachii tendon repair.

Abstract

Bare area of the proximal radius (BA) is a variable osseous component within the floor of the supinator canal, caused by a slip between the insertions of the two layers of the supinator muscle. As this variable structure potentially increases the likelihood of iatrogenic injury to the deep branch of the radial nerve (DBRN) during distal biceps brachii tendon repair, this study aimed to assess the appearance of the BA on MRI to evaluate its usefulness in preoperative planning for reinsertion procedures. A total of 103 elbow MRIs of adult patients were retrospectively included in the study. Each elbow was evaluated in transverse, sagittal, and coronal planes by two observers. Unclear cases were resolved by a consensus among all authors. In case of the presence of the BA, its width was measured, its extent was compared with the level of the radial tuberosity, and its relationship with the DBRN was noted. Inter- and intraobserver agreement was assessed with the use of Cohen's κ coefficient. The BA was detected in 49.5% of cases, with a mean width of 4.6 mm. Extent of the BA frequently overlapped with the level of radial tuberosity in 70.6% of cases. The DBRN was in direct contact with the periosteum due to the presence of the BA in 29.4% of cases. No statistically significant differences were found between sides and sexes. Inter- and intraobserver reliability reached almost perfect agreement (all κ > 0.845). Given the frequent presence of the BA, MRI appears to be suitable for preoperative detection of the BA and assessment of its relationship with the DBRN. Preoperative MRI in distal biceps brachii tendon ruptures seems to be beneficial for surgical planning of the fixation device choice and placement.