Seok Won Chung1, HaeBong Park2, Jieun Kwon3, Ghee Young Choe4, Sae Hoon Kim5, Joo Han Oh6. 1. Department of Orthopaedic Surgery, Konkuk University School of Medicine, Seoul, Korea. 2. CM Chungmu Hospital, Seoul, Korea. 3. Department of Orthopaedic Surgery, National Police Hospital, Seoul, Korea. 4. Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Korea Department of Pathology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam-si, Korea. 5. Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Korea. 6. Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Korea ohjh1@snu.ac.kr.
Abstract
BACKGROUND: The incidence of healing failure after rotator cuff repair is high, and fatty infiltration is a crucial factor in healing failure. PURPOSE: To verify the effect of hypercholesterolemia on fatty infiltration and the quality of tendon-to-bone healing and its reversibility by lowering the cholesterol level in a chronic tear model using the rabbit supraspinatus. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-eight rabbits were randomly allocated into 4 groups (n = 12 each). After 4 weeks of a high-cholesterol diet (groups A and B) and a regular diet (groups C and D), the supraspinatus tendon was detached and left alone for 6 weeks and then was repaired in a transosseous manner (groups A, B, and C). Group D served as a control. Group A continued to receive the high-cholesterol diet until the final evaluation (6 weeks after repair); however, at the time of repair, group B was changed to a general diet with administration of a cholesterol-lowering agent (simvastatin). Histological evaluation of the fat-to-muscle proportion was performed twice, at the time of repair and the final evaluation, and an electromyographic (EMG) test, mechanical test, and histological test of tendon-to-bone healing were performed at the final evaluation. RESULTS: For the EMG test, group A showed a significantly smaller area of compound muscle action potential compared with groups C and D (all P <.01), and group B showed a larger area than group A, almost up to the level of group C (P = .312). Similarly, group A showed significantly lower mechanical properties both in load-to-failure and stiffness compared with groups C and D (all P <.05). In addition, although not significantly different, the mechanical properties of group B were higher than those of group A (mean load-to-failure: group A = 42.01 N, group B = 58.23 N [P = .103]; mean stiffness: group A = 36.32 N/mm, group B = 47.22 N/mm [P = .153]). For the histological test, groups A and B showed a significantly higher fat-to-muscle proportion than did groups C and D at 6 weeks after detachment (all P <.05), but at the final evaluation, group B showed a decreased fat-to-muscle proportion (mean ± SD: from 64.02% ± 11.87% to 54.68% ± 10.47%; P = .146) compared with group A, which showed increased fat-to-muscle proportion (from 59.26% ± 17.80% to 78.23% ± 10.87%; P = .015). Groups B and C showed better tendon-to-bone interface structures than did group A, which showed coarse and poorly organized collagen fibers with fat interposition. CONCLUSION: Hypercholesterolemia had a deleterious effect on fatty infiltration and the quality of tendon-to-bone repair site, and lowering hypercholesterolemia seemed to halt or reverse these harmful effects in this experimental model. CLINICAL RELEVANCE: Systemic diseases such as hypercholesterolemia should be tightly controlled during the perioperative period of rotator cuff repair.
BACKGROUND: The incidence of healing failure after rotator cuff repair is high, and fatty infiltration is a crucial factor in healing failure. PURPOSE: To verify the effect of hypercholesterolemia on fatty infiltration and the quality of tendon-to-bone healing and its reversibility by lowering the cholesterol level in a chronic tear model using the rabbit supraspinatus. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-eight rabbits were randomly allocated into 4 groups (n = 12 each). After 4 weeks of a high-cholesterol diet (groups A and B) and a regular diet (groups C and D), the supraspinatus tendon was detached and left alone for 6 weeks and then was repaired in a transosseous manner (groups A, B, and C). Group D served as a control. Group A continued to receive the high-cholesterol diet until the final evaluation (6 weeks after repair); however, at the time of repair, group B was changed to a general diet with administration of a cholesterol-lowering agent (simvastatin). Histological evaluation of the fat-to-muscle proportion was performed twice, at the time of repair and the final evaluation, and an electromyographic (EMG) test, mechanical test, and histological test of tendon-to-bone healing were performed at the final evaluation. RESULTS: For the EMG test, group A showed a significantly smaller area of compound muscle action potential compared with groups C and D (all P <.01), and group B showed a larger area than group A, almost up to the level of group C (P = .312). Similarly, group A showed significantly lower mechanical properties both in load-to-failure and stiffness compared with groups C and D (all P <.05). In addition, although not significantly different, the mechanical properties of group B were higher than those of group A (mean load-to-failure: group A = 42.01 N, group B = 58.23 N [P = .103]; mean stiffness: group A = 36.32 N/mm, group B = 47.22 N/mm [P = .153]). For the histological test, groups A and B showed a significantly higher fat-to-muscle proportion than did groups C and D at 6 weeks after detachment (all P <.05), but at the final evaluation, group B showed a decreased fat-to-muscle proportion (mean ± SD: from 64.02% ± 11.87% to 54.68% ± 10.47%; P = .146) compared with group A, which showed increased fat-to-muscle proportion (from 59.26% ± 17.80% to 78.23% ± 10.87%; P = .015). Groups B and C showed better tendon-to-bone interface structures than did group A, which showed coarse and poorly organized collagen fibers with fat interposition. CONCLUSION:Hypercholesterolemia had a deleterious effect on fatty infiltration and the quality of tendon-to-bone repair site, and lowering hypercholesterolemia seemed to halt or reverse these harmful effects in this experimental model. CLINICAL RELEVANCE: Systemic diseases such as hypercholesterolemia should be tightly controlled during the perioperative period of rotator cuff repair.
Authors: Joseph B Newton; George W Fryhofer; Ashley B Rodriguez; Andrew F Kuntz; Louis J Soslowsky Journal: J Biomech Date: 2021-01-13 Impact factor: 2.712
Authors: Phillip E McClellan; Lekha Kesavan; Yujing Wen; Jason Ina; Derrick M Knapik; Robert J Gillespie; Ozan Akkus; Victoria A Webster-Wood Journal: Clin Orthop Relat Res Date: 2021-02-01 Impact factor: 4.755