Microfracture Lateral to the Greater Tuberosity of the Humerus Enhances Tendon-to-Bone Healing in a Rat Rotator Cuff Model

Abstract

Background: Microfracture at the rotator cuff insertion is an established surgical marrow-stimulation technique for enhancing rotator cuff healing. However, the effect of lateralized or medialized microfracture on the insertion is unknown. Purpose: To compare the biomechanical and histologic effects of microfracture at 3 different regions for rotator cuff repair in a rat model. Study Design: Controlled laboratory study. Methods: A total of 72 Sprague-Dawley rats with bilateral supraspinatus tendon insertion detachment were allocated into 4 groups with 4 different interventions: no microfracture at the humeral head as a control group (Con), traditional microfracture at the footprint area (MFA), and medialized microfracture to the footprint area (MMFA) on the articular surface of the humerus or lateralized microfracture to the footprint area at the greater tuberosity (LMFA). All underwent immediate repair. Tendon-to-bone healing was assessed by biomechanical and histologic tests 4 and 8 weeks postoperation. Results: At 4 weeks, the LMFA group showed a significantly superior failure load compared with the other groups (all P < .05). The LMFA and MFA groups showed significantly superior stiffness compared with the Con and MMFA groups (all P < .01). At 8 weeks, superior failure load and stiffness were observed in the LMFA group compared with the control group (all P < .05). Histologic examination revealed that the LMFA group had superior collagen composition and tendon-to-bone maturation at the interface at 4 and 8 weeks compared with the Con group (all P < .05). Conclusion: Lateralized microfracture at the greater tuberosity improved the histologic quality of repair tissue and biomechanical strength at the tendon-to-bone insertion after rotator cuff repair in a rat model. Clinical Relevance: Microfracture lateral to the footprint area might be a better way to enhance rotator cuff healing clinically.