Patellar tendon autografts outperform fascia lata in superior capsular reconstruction: a comparative histopathological and biomechanical study

Background: In the treatment of irreversible rotator cuff tears, surgeons reconstruct the superior capsule of the shoulder using tensor fascia lata (FL) or various allografts to halt progressive joint degeneration. This study evaluated the healing characteristics of patellar tendon (PT) autograft vs. tensor FL autograft in superior capsular reconstruction (SCR), examining both biomechanical and histological aspects. Methods: A total of 28 shoulders from 14 rabbits were used in this experimental study. Retracted tear models involving complete resection of both the supraspinatus and subscapularis tendons were created in all surgical groups. After an 8-week retraction period, superior capsular reconstruction (SCR) was performed using standardized techniques: FL autografts were implanted in the right shoulders and PT autografts in the left shoulders, while the control group received no intervention. All grafts were fixed identically with bone tunnels and prolene sutures at the glenoid superiorly and the greater tuberosity laterally. Rabbits were observed for 8 weeks postoperatively. Outcome measures included biomechanical testing (load-to-failure) and histopathological analysis (tendon maturation scoring, collagen type I-III ratio, and cluster of differentiation 31 (CD31) immunoreactivity). Results: Post hoc pairwise analysis revealed that the load-to-failure values were significantly lower in FL group compared to those in control group (P < .01), suggesting that FL group could not maintain biomechanical stability and tendon-bone integration. No significant difference was found between PT and control groups (P > .05). Cellularity, vascularity, collagen continuity, and tidemark development showed no significant differences between the PT and control groups (P > .05), while these parameters were significantly reduced in the FL group (P < .05). FL group's mean total modified Watkins score was much lower than that of the control group (P = .01), while the PT group nearly equaled the control group. Tendons of PT groups had significantly higher immunoreactivity for collagen type I and type III and CD31 compared to the control group (P = .019, P = .015, and P = .014, respectively). Conclusions: In this rabbit model, PT autografts showed superior biomechanical strength, vascularity, and collagen remodeling compared to FL autografts in SCR, suggesting improved graft integration. Further studies, including cadaver-based research and clinical trials, are required to validate these findings and establish the clinical relevance of graft choice for SCR in humans.