Is there a Correlation between the Coaptation and Regeneration of Tendon Stumps in Endoscopic Assisted Achilles Tendon Rupture Repair?

Abstract

Background Direct stitch of the ruptured site is very difficult to perform due to the frayed tendon stumps when endoscopic Achilles tendon repair technique is utilized. There is little known about whether undesirable coaptation of the tendon stumps affect the regeneration of tendons. Methods A retrospective analysis of 46 patients who underwent a modified endoscopic Achilles tendon rupture repair from October 2018 to June 2020. Patients were divided into 2 groups according to the coaptation of tendon stumps on postoperative ultrasonography. 17 cases in group 1 with undesirable coaptation(<50%) and 29 cases in group 2 with appropriate coaptation(≥ 50%). Magnetic resonance imaging (MRI) was obtained at postoperative 3, 6 and 12 months to evaluate the tendon morphological construction. Clinical evaluations were performed using the American Orthopedic Foot and Ankle Society (AOFAS) ankle-hind foot score, Achilles Tendon Total Rupture Score (ATRS), muscle power, and Achilles tendon resting angle at the final follow-up. Complications were also encountered. Results The mean follow-up time was 37.5 ± 10.6 months in group 1 and 39.0 ± 11.6 months in group 2, respectively. The average age in group 1 is slightly older than that of group 2 (37.3 ± 6.1 vs 32.7 ± 6.3, P = 0.021). The tendon cross-section areas and thickness increased initially and decreased later on postoperative MRI evaluation. It also showed a significant higher signal/noise quotient (SNQ) in group 1 at postoperative 3 months. At postoperative 6 and 12 months, the SNQ between both groups was similar. The AOFAS score (95.9 ± 5.1 vs 96.2 ± 4.9, P = 0.832), ATRS score (97.0 ± 3.6 vs 97.7 ± 3.3, P = 0.527), and muscle power (21.38 vs 24.74, P = 0.287) were not significantly different between both groups. However, the resting angle of group 1 was significantly larger than that of group 2 (4.6 ± 2.4 vs 2.4 ± 2.3, P = 0.004). There was no difference in the complications (P = 0.628). Conclusions There is no obvious correlation between coaptation and regeneration of tendon stumps when endoscopic Achilles tendon repair technique is applied. However, older patients could possibly have a separation of tendon stumps, resulting in an elongation of the tendon.