Restoration of the Posterior Glenoid in Recurrent Posterior Shoulder Instability Using an Arthroscopically Placed Iliac Crest Bone Graft: A Computed Tomography-Based Analysis

Abstract

Background: Posterior shoulder instability is uncommon, and its treatment is a challenging problem. An arthroscopically assisted technique for posterior iliac crest bone grafting (ICBG) has shown promising short- and long-term clinical results. Changes as shown on imaging scans after posterior ICBG for posterior shoulder instability have not been investigated in the recent literature.

Purpose: To evaluate changes on computed tomography (CT) after arthroscopically assisted posterior ICBG and to assess clinical outcomes.

Study design: Case series; Level of evidence, 4.

Methods: Patients with preoperative CT scans and at least 2 postoperative CT scans with a minimum follow-up of 2 years were included in the evaluation. Of 49 initial patients, 17 (follow-up rate, 35%) met the inclusion criteria and were available for follow-up. We measured the glenoid version angle and the glenohumeral and scapulohumeral indices on the preoperative CT scans and compared them with measurements on the postoperative CT scans. Postoperatively, graft surface, resorption, and defect coverage were measured and compared with those at early follow-up (within 16 months) and final follow-up (mean ± SD, 6.6 ± 2.8 years).

Results: The mean preoperative glenoid version was -17° ± 13.5°, which was corrected to -9.9° ± 11.9° at final follow-up (P < .001). The humeral head was able to be recentered and reached normal values as indicated by the glenohumeral index (51.8% ± 6%; P = .042) and scapulohumeral index (59.6% ± 10.2%; P < .001) at final follow-up. Graft surface area decreased over the follow-up period, from 24% ± 9% of the glenoid surface at early follow-up to 17% ± 10% at final follow-up (P < .001). All clinical outcome scores had improved significantly. Progression of osteoarthritis was observed in 47% of the shoulders.

Conclusion: Arthroscopically assisted posterior ICBG restored reliable parameters as shown on CT scans, especially glenoid version and the posterior subluxation indices. Graft resorption was common and could be observed in all shoulders. Patient-reported clinical outcome scores were improved. Osteoarthritis progression in almost 50% of patients is concerning for the long-term success of this procedure.

Keywords: arthroscopic; glenoid version; iliac crest bone graft; instability; posterior subluxation; recurrent posterior shoulder instability; shoulder.

Figure 1.

Flowchart of the study patients. CT, computed tomography; ICBG, iliac crest bond grafting.

Figure 2.

Intraoperative view. (A) Graft harvesting from iliac crest with the 2 “top hats” washers placed in the outer cortex, (B, C) iliac crest bone graft attached to the double-barrel cannula, and (D) arthroscopic view with posteriorly placed iliac crest bone grafting (*), humeral head (**), and posterior part of the glenoid (***).

Figure 3.

Method used to calculate (A) glenoid version angle α (white-shaded area), (B) humeral head subluxation according to scapulohumeral index (Pf/Df) and (C) glenohumeral index (Pg/Dg), (D) best-fit circle (yellow-shaded area), and (E) ICBG surface area (red-shaded area). The ICBG surface area (red-shaded area) and glenoid defect coverage (black-striped red shading area within the best-fit circle [yellow-shaded area]) are illustrated; the graft overhang is the dotted red-shaded area outside the yellow circle. Df, diameter of the humeral head perpendicular to Friedman's line; Dg, diameter of the humeral head; GL, line tangent to the anterior and posterior edges of the glenoid fossa; ICBG, iliac crest bond grafting; Mg, line bisecting the glenoid; Pf, relative part of the humeral head position posterior to Friedman's line; Pg, relative part of the humeral head position posterior to Mg.

Figure 4.

(A) Preoperative axial computed tomography scan and (C) 3-dimensional en face view of a 46-year-old male patient with a painful right shoulder (visual analog scale for pain, 6) and failed posterior Bankart procedure 4 years before arthroscopically assisted iliac crest bone grafting. This patient showed preoperative glenoid retroversion of 30° and humeral posterior subluxation with a scapulohumeral index of 80%. (B, D) Postoperatively, at 9-year follow-up, the patient showed decreased glenoid retroversion of 17° and a scapulohumeral index of 67%. This patient showed high-grade osteoarthritis preoperatively. Nevertheless, he had a good clinical outcome, with a Constant score of 95.