Expression of Substance P and Nerve Growth Factor in Degenerative Long Head of Biceps Tendon in Patients with Painful Rotator Cuff Tear

Abstract

Masashi Izumi,1 Yohei Harada,2,3 Yukihiro Kajita,2 Yoshitaka Muramatsu,2,4 Toru Morimoto,1 Yutaka Morisawa,5 Yusuke Iwahori,2,6 Masahiko Ikeuchi1 1Department of Orthopaedic Surgery, Kochi Medical School, Kochi University, Nankoku-City, Japan; 2Department of Orthopaedic Surgery, Aichi Medical University, Nagakute, Japan; 3Department of Orthopaedic Surgery, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan; 4Department of Orthopaedic Surgery, Saiseikai Futsukaichi Hospital, Futsukaichi, Japan; 5Department of Orthopaedic Surgery, Aki General Hospital, Aki, Japan; 6Department of Orthopaedic Surgery, Sports Medicine and Joint Center, Asahi Hospital, Kasugai, JapanCorrespondence: Masashi IzumiDepartment of Orthopaedic Surgery, Kochi Medical School, Kochi University, 185-1 Kohasu, Oko-cho, Nankoku-City, Kochi Pref, 783-8505, JapanTel [phone]Fax [phone]Email [email protected]: Degenerative long head of biceps tendon (LHBT) has been recognized as a notable pain source in patients with rotator cuff tear (RCT). Tenotomy or tenodesis of LHBT is frequently indicated together with arthroscopic rotator cuff repair (ARCR) aiming for complete pain relief; however, it has not been fully investigated whether resected LHBT is really a source of pain. The purpose of this study was to investigate expression levels of pain-associated mediators in LHBT and its association with preoperative pain profiles.Methods: Twenty-seven RCT patients who underwent ARCR with LHBT resection were included. Each LHBT was resected due to its abnormal arthroscopic findings including tenosynovitis, hypertrophy, and partial tear. Worst macroscopic lesion of the LHBT was obtained, and expression levels of substance P (SP) and nerve growth factor (NGF) were evaluated using enzyme-linked immunosorbent assay (ELISA). Ten healthy knee flexor tendons were analyzed as non-degenerative samples. Preoperatively, subjective shoulder pain VAS and pain duration were investigated. Conventional LHBT pain provocation tests (Speed, Yergason, O’Brien) were performed. Pressure pain threshold (PPT) of bilateral LHBT on the groove was recorded.Results: Levels of SP and NGF expression were significantly higher compared with non-degenerative tendons (P< 0.01). Shoulder pain VAS and pain duration were not directly associated with SP and NGF expression level. Patients with positive O’Brien test expressed greater SP than negative patients (P=0.001). Significant negative correlation between the PPT ratio (ipsilateral/contralateral) and SP expression level was observed (r=− 0.453, P=0.034).Conclusion: Greater expression of SP and NGF in degenerative LHBT supported our hypothesis that it would be a pain source in RCT patients. SP was likely to be expressed highly in patients with localized pressure pain hypersensitivity and positive O’Brien test (ie, altered mechanistic pain profile of LHBT), which may help when considering simultaneous LHBT resection during ARCR.Clinical Registration: UMIN000023943.Keywords: long head of biceps tendon, pain, tendinopathy, substance P, nerve growth factor, pressure pain threshold

Keywords

• long head of biceps tendon
• pain
• tendinopathy: substance p
• nerve growth factor
• pressure pain threshold