The process of bone union after arthroscopic bony Bankart repair in younger athletes with a subcritical glenoid defect: An advantage of remained large bone fragment

Burkhart and De Beer reported that patients with a significant bony defect, such as an inverted pear glenoid, were not candidates for arthroscopic Bankart repair (ABR) [1]. A preoperative glenoid defect of 20%–25% was suggested to be the critical size at which ABR should generally be avoided [[2], [3], [4]]. Shaha et al. investigated clinical outcomes in active duty military personnel and reported that a preoperative glenoid defect of 13.5% was an appropriate threshold for ‘‘subcritical’’ bone loss, which led to a clinically significant worsening in Western Ontario Shoulder Instability Index scores consistent with an unacceptable outcome [5]. Recently, a glenoid defect of 13.5% or larger has become accepted as the definition of a large defect [[6], [7], [8], [9], [10]].

Regarding the management of large glenoid defects, Sugaya et al. reported that arthroscopic repair of bony Bankart lesions (arthroscopic bony Bankart repair, ABBR) was successful even in patients with a chronic glenoid defect because most of the bone fragments were preserved [11]. Kitayama et al. studied the morphologic characteristics of the glenoid rim after ABBR and reported that they had normalized in all patients after 5–8 years [12]. Nakagawa et al. also found that when postoperative union was achieved after ABBR, the postoperative recurrence rate was significantly lower and that the glenoid rim morphologic characteristics became closer to normal because the united bone fragment frequently enlarged by remodeling [13]. Despite these reports that favorable clinical outcome was obtained when bone union was achieved after ABBR, when deciding on the appropriate surgery, surgeons generally consider only the size of a glenoid defect and they do not include factors such as possible bone union from remaining bone fragments or increased size due to remodeling.

Recently, Nakagawa et al. reported that the postoperative recurrence rate after ABBR in male competitive rugby and American football players was lower in shoulders with a subcritical glenoid defect (≥13.5%) than in shoulders with a smaller glenoid defect (<13.5%) [14]. While a large bone fragment (≥7.5%) frequently remained in shoulders with a large glenoid defect (≥13.5%), complete union rate was significantly higher after repair of a large fragment (≥7.5%) than after repair of a small fragment (<7.5%). The postoperative recurrence rate was significantly lower in shoulders with complete union after ABBR, so they concluded that the presence of a large fragment might decrease the recurrence rate in the presence of a large glenoid defect. However, bone union process in shoulders with a subcritical glenoid defect was still unclarified.

In the present study, we investigated the process of bone union after ABBR in competitive athletes younger than 30 years with a subcritical glenoid defect (≥13.5%) who underwent computed tomography (CT) at least twice postoperatively. The change of bone union between first CT and final CT were investigated in detail, especially noticing the bone fragment size (≥7.5% versus <7.5%). We hypothesized that longer periods after ABBR would be advantageous for bone union, especially for shoulders with a large bone fragment.

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