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Updated: Sep 2, 2026
Development of a Rabbit Chronic-Like Rotator Cuff Injury Model for Study of Fibrosis and Muscular Fatty Degeneration
Published on: March 31, 2023
A Repair-Tension Sweet Zone Maximizes Tendon-to-Bone Healing in a Rat Rotator Cuff Model
Qiaonan Liu1, Lang Bai1, Xiangyang Li1
1Department of Orthopaedics, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, P. R. China.
Purpose:
To define a sweet zone of repair tension that maximizes tendon-to-bone healing while maintaining early functional safety in a rat model of rotator cuff repair.
Methods:
Forty-eight rats were used to create a graded-tension supraspinatus repair model with four discrete repair tensions: minimal-tension (MinT), low-tension (LowT), medium-tension (MedT), and high-tension (HiT) at two postoperative time points (n = 6 per group per time point). Intraoperative peak tension was measured during supraspinatus tendon reattachment using a digital tension gauge and normalized to tendon cross-sectional area (N/mm2). Functional recovery was assessed by gait analysis at 2 and 4 weeks; magnetic resonance imaging evaluated edema and tendon continuity; biomechanical testing quantified failure load, stiffness, and stress; histology assessed enthesis organization, fibrocartilage formation, and collagen fiber alignment.
Results:
Measured repair stresses were 0.015, 0.060, 0.110, and 0.305 N/mm2 for MinT, LowT, MedT, and HiT groups, respectively. At 4 weeks, MedT showed superior biomechanical healing, achieving the highest LowT ultimate failure load (23.24 ± 2.08 N) versus MinT (14.78 ± 1.40 N, P = .001) and HiT (14.90 ± 0.94 N, P < .001) and the greatest stiffness (11.63 ± 0.46 N/mm) versus LowT (8.44 ± 0.13 N/mm, P < .001), MinT (6.35 ± 1.36 N/mm, P = .003), and HiT (3.05 ± 0.04 N/mm, P < .001). Histologic healing was also best in MedT and worst in HiT (MedT 14.00 ± 1.10 vs. MinT 10.17 ± 0.75, LowT 11.17 ± 0.98, and HiT 8.83 ± 0.75; overall P < .001). Overall, outcomes followed a bell-shaped relationship with repair stress, defining a sweet zone centered at 0.10 to 0.12 N/mm2.
Conclusions:
This study identifies a sweet zone of repair tension (0.10-0.12 N/mm2) that maintains early functional safety and achieves superior late structural and mechanical outcomes compared with under- or over-tensioned repairs.
Clinical Relevance:
Rotator cuff repairs should aim not only to avoid excessive tension but also to target the sweet zone to optimize enthesis regeneration.
