Beyond guesswork: how accurate are surgeons at determining the degree of glenoid bone loss in instability surgery?

Abstract

BackgroundAccurate measurement of glenoid bone loss (GBL) is critical to preoperative planning in cases of recurrent shoulder instability. The concept of critical bone loss has been established with a value of GLB >13.5% being associated with higher failure rate following arthroscopic Bankart Repair. Advanced imaging, such as MRI scans, can be used to quantify GBL prior to surgery utilizing the best-fit circle technique. Surgeons have traditionally relied on visual inspection of the MRI scan preoperatively or on visual inspection of the glenoid at the time of arthroscopy to determine whether GBL is present. The purpose of this study is to determine if 3 fellowship-trained shoulder surgeons could adequately quantify GBL without utilizing best-fit circle measurements on MRI. MethodsA retrospective review was performed which included 122 patients over an 8-year period who had an arthroscopic Bankart repair performed by 3 fellowship-trained surgeons. In all patients, preoperative MRI scans were retrospectively measured utilizing best-fit circle technique to determine true GBL and compare that to the surgeons' pre- and intraoperative estimation of GBL. ResultsGBL was correctly identified in only 36% (18/50) of patients when the preoperative best-fit circle measurements were not made. Critical bone loss was missed in 9.8% (15/122) of patients in the study group. The estimated mean bone loss in that group by visual inspection was 11.3% compared to 16% true bone loss measured on MRI. Even in the 18 patients with some identified bone loss prior to surgery, critical bone loss was missed in 6 patients when utilizing visual inspection of the MRI or intraoperative inspection alone. ConclusionsSimple visual inspection of glenoid images on MRI scan as well as visual inspection of the glenoid at the time of surgery are inaccurate in determining the true extent of glenoid bone loss especially in cases of subtle bone deficiency. Preoperative planning is dependent on the exact degree of bone deficiency and measurement on the MRI scan utilizing the best-fit circle technique is recommended on all cases of instability surgery.