Arthroscopic Posterior Articular Coverage and Shift (PACS) Procedure for Treatment of Preosteoarthritic Constitutional Static Posterior Shoulder Instability (Type C1)

Abstract

Background: Different joint-preserving techniques for treatment of preosteoarthritic, constitutional static (type C1) posterior shoulder instability (PSI) have been proposed, including posterior glenoid open wedge osteotomy and bone graft augmentation. However, the techniques are demanding, the reported complication and reoperation rates are high, and posterior decentering cannot reliably be reversed. Purpose: To assess the clinical and radiological longitudinal outcomes of patients with type C1 PSI after arthroscopic posterior articular coverage and shift (PACS) surgery. Study Design: Case series; Level of evidence, 4. Methods: We performed a retrospective analysis of a prospective database with longitudinal follow-up including 14 shoulders in 13 patients who underwent an arthroscopic PACS procedure for symptomatic preosteoarthritic constitutional static posterior instability (type C1) with previous failed nonoperative treatment. Patients were clinically evaluated before surgery and at 3, 6, 12, and 24 months postoperatively in terms of satisfaction and pain levels as well as standardized physical examination, Subjective Shoulder Value (SSV), Western Ontario Shoulder Instability Index (WOSI) score, Constant score, and Rowe score. Preoperative, postoperative, and follow-up magnetic resonance imaging scans were obtained in all patients. A paired 2-sample t test was used to compare changes in continuous variable parameters over time. Correlation analyses were performed using the Pearson correlation coefficient. Results: All outcome scores and the pain level improved significantly from preoperatively to postoperatively, and the improvement was sustained over the follow-up period of 2 years (pain level, 6.4 preoperatively vs 3.3 at 2 years, P < .001; SSV, 40 vs 70, P = .001; WOSI, 33 vs 56, P = .001; Constant, 70 vs 79, P = .049; Rowe, 52 vs 76, P < .001). The mean glenohumeral and scapulohumeral subluxation indices were significantly lower in the early postoperative period compared with preoperative measurements (glenohumeral, 52% ± 6% vs 58% ± 10%, P = .02; scapulohumeral, 70% ± 8%; vs 77% ± 9%, P = .002, respectively); however, they returned to baseline values at follow-up (57% ± 7% vs 58% ± 10%, P = .7; 75% ± 6% vs 77% ± 9%, P = .4, respectively). A high scapulohumeral subluxation index, excessive glenoid retroversion, and increased posterior positioning of the humeral head in relation to scapular blade axis and older age were correlated with worse clinical outcomes. Conclusion: Over the follow-up period of 2 years, the PACS procedure significantly improved outcome scores in patients who had preosteoarthritic constitutional static posterior shoulder instability, especially in younger patients with less severe glenoid retroversion and posterior decentering of the humeral head. However, similar to other techniques, the PACS procedure needs to be considered a symptomatic therapy that does not reverse the underlying cause or stop the progressive pathology.

Diagnosis and treatment of posterior shoulder instability based on the ABC classification

“…The available surgical treatment options include arthroscopic posterior articular coverage and capsular shift (PACS) (Fig. 7), posterior open-wedge osteotomy, and posterior bone block procedures (61,62,63,64). While all mentioned surgical techniques have been reported to improve symptoms, at least temporarily, none of the techniques was able to recenter the joint reliably, which is why the treatment of this subgroup still remains a challenge.…”

“…While all mentioned surgical techniques have been reported to improve symptoms, at least temporarily, none of the techniques was able to recenter the joint reliably, which is why the treatment of this subgroup still remains a challenge. A stepwise treatment approach starting with non-operative management, followed by arthroscopic soft tissue procedures, and subsequently bone graft interventions have been suggested in an attempt to buy time in the typically rather young patients before arthroplasty might become necessary due to progressive eccentric wear (62).…”

Differences in Osseous Shoulder Morphology, Scapulothoracic Orientation, and Muscle Volume in Patients With Constitutional Static Posterior Shoulder Instability (Type C1) Compared With Healthy Controls

“… 21 C1 has been recognized as a pre–osteoarthritic deformity that may lead to early-onset posterior decentering osteoarthritis. 34 At this time, C1 instability seems to be an irreversible progressive pathology, as suggested surgical options including open-wedge osteotomy, 5 , 23 , 35 posterior bone grafting, 5 or arthroscopic posterior articular coverage and shift 19 have failed to permanently recenter the joint. Furthermore, patients are often affected at a young age.…”

Correction of Static Posterior Shoulder Subluxation by Restoring Normal Scapular Anatomy Using Acromion and Glenoid Osteotomies

“…Currently, correction of SPSL is attempted by arthroscopic soft-tissue procedures 14 , restoration of normal glenoid version using scapular neck osteotomies [15][16][17][18] , or posterior bone block procedures 15,19,20 . Most studies report some subjective improvement but neither consistent correction of posterior subluxation nor prevention of progression of OA [14][15][16][17][18][19][20] .…”

“…A multifactorial etiology is postulated 1,5,[8][9][10][11] : The focus has been on glenoid shape alterations 4,8,12,13 , but such changes are neither consistent, nor do they satisfactorily explain the condition. Currently, correction of SPSL is attempted by arthroscopic soft-tissue procedures 14 , restoration of normal glenoid version using scapular neck osteotomies [15][16][17][18] , or posterior bone block procedures 15,19,20 . Most studies report some subjective improvement but neither consistent correction of posterior subluxation nor prevention of progression of OA [14][15][16][17][18][19][20] .…”