Is posterior delamination in arthroscopic rotator cuff repair hidden to the posterior viewing portal?

PURPOSE The purposes of this study were (1) to examine whether posterior delamination is hidden to the most commonly used posterior viewing portal compared with differential rotator cuff portals and (2) to observe posterior delamination patterns so that a treatment-based classification system may be proposed. METHODS One-hundred thirty consecutive patients undergoing arthroscopic rotator cuff repair by 4 different surgeons were evaluated for the presence of posterior delamination viewable through the posterior, posterolateral, and lateral portals. Randomized arthroscopic pictures were viewed by 2 independent blinded observers, and the Fleiss κ was used to assess inter-reliability agreement. In addition, patterns of posterior delamination and surgical treatment were assessed. RESULTS The incidence of posterior delamination was 88%. Only 11% of cases were visualized through the posterior portal, whereas 70% and 100% were visualized through the posterolateral and lateral portals, respectively. The Fleiss κ was 0.78 (95% confidence interval, 0.73 to 0.83), indicating substantial agreement. Three general patterns of posterior delamination with specific surgical repair strategies were identified and subclassified into 5 types: type A1, full-thickness tears with extensive posterior delamination separating the rotator cuff into 2 layers and sometimes with dissociation of the rotator cable; type A2, bursal-sided partial-thickness tears with posterior delamination; type B1, delamination with an L-shaped bursal layer tear and crescent-shaped articular layer tear; type B2, a partial-thickness articular-sided tear with extensive posterior delamination; and type C, extensive degeneration with multiple longitudinal bursal-sided tears. CONCLUSIONS The incidence of posterior delamination is extremely high, and most of these lesions are missed if one is viewing from just the posterior portal. Differential rotator cuff portals are needed to appreciate and treat posterior delamination. Patterns of delamination can be classified according to surgical repair strategy. It is important to recognize that the rotator cable may delaminate from the cuff and not to mistake it for a "retracted" articular layer, as previously described. LEVEL OF EVIDENCE Level II, prospective comparative study.