The critical size of a defect in the glenoid causing anterior instability of the shoulder after a Bankart repair, under physiological joint loading

Abstract

Aims Patients with recurrent anterior dislocation of the shoulder commonly have an anterior osseous defect of the glenoid. Once the defect reaches a critical size, stability may be restored by bone grafting. The critical size of this defect under non-physiological loading conditions has previously been identified as 20% of the length of the glenoid. As the stability of the shoulder is load-dependent, with higher joint forces leading to a loss of stability, the aim of this study was to determine the critical size of an osseous defect that leads to further anterior instability of the shoulder under physiological loading despite a Bankart repair. Patients and Methods Two finite element (FE) models were used to determine the risk of dislocation of the shoulder during 30 activities of daily living (ADLs) for the intact glenoid and after creating anterior osseous defects of increasing magnitudes. A Bankart repair was simulated for each size of defect, and the shoulder was tested under loading conditions that replicate in vivo forces during these ADLs. The critical size of a defect was defined as the smallest osseous defect that leads to dislocation. Results The FE models showed a high risk of dislocation during ADLs after a Bankart repair for anterior defects corresponding to 16% of the length of the glenoid. Conclusion This computational study suggests that bone grafting should be undertaken for an anterior osseous defect in the glenoid of more than 16% of its length rather than a solely soft-tissue procedure, in order to optimize stability by restoring the concavity of the glenoid.

The Anatomy of Glenoid Concavity—Bony and Osteochondral Assessment of a Stability-Related Parameter

“…The most recent definition focusing on concavity derives from Moroder et al, who defined the bony shoulder stability ratio (BSSR) [ 11 ]. The BSSR is a mathematical approximation of the stability ratio (SR), which has been used as a measure of stability in many biomechanical and simulative studies [ 6 , 12 , 13 , 14 , 15 , 16 , 17 ]. The SR is derived from the maximum dislocating force relative to a joint compression force.…”

When to Abandon the Arthroscopic Bankart Repair: A Systematic Review

“…Su et al 56 reported similar high rates of postoperative instability correlated with increasing amounts of glenoid bone loss with the revision arthroscopic Bankart procedure. Klemt et al 31 utilized a finite element model for simulating the stability of the glenohumeral joint under varying conditions and stressors. Their results support the above, indicating a cutoff of 16% glenoid bone loss for arthroscopic Bankart repairs to maintain stability.…”

“…Their results support the above, indicating a cutoff of 16% glenoid bone loss for arthroscopic Bankart repairs to maintain stability. 31…”

Reporting of glenoid bone loss measurement in clinical studies and the need for standardization

“…Recent studies have suggested that this threshold should be lower, with Shaha et al 6 recommending 13.5% bone loss as an indication for bony reconstruction and Cavalier et al 7 suggested young patients (aged < 23 years) with > 10% bone loss should be considered for the Latarjet procedure. Klemt et al 8 used computer modelling with different activities of daily living (ADLs), and found a range of bone loss values associated with instability depending on activity. They found a quarterback throw was unstable at 16% bony deficiency, but shoulder flexion was stable at 24%.…”