Glenoid defect size increases but the bone fragment rarely resorbs in shoulders with recurrent anterior instability

Shigeto Nakagawa; Takehito Hirose; Ryohei Uchida; Hiroyuki Nakamura; Tatsuo Mae; Kenji Hayashida; Minoru Yoneda

doi:10.1016/j.jseint.2022.12.010

Glenoid defect size increases but the bone fragment rarely resorbs in shoulders with recurrent anterior instability

JSES Int. 2022 Dec 21;7(2):218-224. doi: 10.1016/j.jseint.2022.12.010. eCollection 2023 Mar.

Authors

Shigeto Nakagawa¹, Takehito Hirose², Ryohei Uchida³, Hiroyuki Nakamura⁴, Tatsuo Mae⁵, Kenji Hayashida⁶, Minoru Yoneda⁷

Affiliations

¹ Department of Orthopaedic Sports Medicine, Yukioka Hospital, Osaka, Osaka, Japan.
² Department of Orthopaedic Surgery, Daini Osaka Police Hospital, Osaka, Osaka, Japan.
³ Department of Orthopaedic Sports Medicine, Kansai Rosai Hospital, Amagasaki, Hyogo, Japan.
⁴ Soai Orthopaedic Clinic, Takarazuka, Hyogo, Japan.
⁵ Osaka Yukioka Medical University, Ibaraki, Osaka, Japan.
⁶ Department of Orthopaedic Surgery, Osaka Central Hospital, Osaka, Osaka, Japan.
⁷ Department of Orthopaedic Surgery, Kashiwa Tanaka Hospital, Kashiwa, Chiba, Japan.

Abstract

Background: With recurrent anterior instability the bone fragment of a bony Bankart lesion is often small compared to the glenoid defect. The purpose of the present study was to clarify the changes to both the bone fragment and glenoid defect over time in a single subject.

Methods: Participants were patients who underwent computed tomography (CT) at least twice after an instability event between 2004 and 2021 and had a fragment-type glenoid at first CT. The glenoid rim width (A), glenoid defect width (B), and bone fragment width (C) were measured in millimeters. If B or C increased by 1 mm or more from the first to final CT, the change was judged as "enlarged," and if B or C decreased by 1 mm or more, it was judged as "reduced"; all other cases were judged as "similar." Then, glenoid defect size and bone fragment size were calculated as B/A×100% and C/A×100%, respectively, and the changes from the first to final CT were compared.

Results: From the first to final CT, the glenoid defect was enlarged in 30 shoulders, similar in 13 shoulders, and reduced in 4 shoulders, and the bone fragment was enlarged in 18 shoulders, similar in 24 shoulders, and reduced in 5 shoulders. The mean glenoid defect size significantly increased from 10.9% to 15.3% (P < .001), and the mean bone fragment size increased from 6.4% to 7.8%, respectively (P = .005). At the final CT, in 6 shoulders a new glenoid fracture was observed at a different site from the original fracture. When they were excluded from the analyses, the mean glenoid defect size still significantly increased (from 11.2% to 15.2%; P < .001), but the mean bone fragment size did not (6.5% vs. 7.3%, respectively; P = .088).

Conclusions: In shoulders with recurrent anterior instability, glenoid defect size appears to increase significantly over time, whereas the bone fragment size remains unchanged or increases only slightly. Bone fragment resorption is quite rare, and a bone fragment appears to be small because of an enlarged glenoid defect.

Keywords: Bone fragment resorption; Bone fragment size; Glenoid defect enlargement; Glenoid defect size; Glenoid fracture; Recurrent anterior shoulder instability.