Abstract
Category:
Ankle
Introduction/Purpose:
New techniques and anchors have been developed for the surgical treatment of insertional Achilles tendinopathy and rupture to allow for earlier return to postoperative weight bearing and accelerated rehabilitation. Two recently introduced soft tissue-to-bone anchor technology have purported advantages for insertional Achilles repairs. Knotless suture anchors allow suture tension to be precisely controlled with a ratcheting mechanism. The other is a suture bridge construct fastened with biotenodesis screws, increasing the soft tissue footprint and reducing the risk of suture pullout through the tendon. However, neither technology has been studied in a biomechanical model of Achilles tendon repair. We hypothesized that there would be no difference in the biomechanical characteristics of a single-row all-suture anchor repair to a double-row repair with knotless anchors and suture tape.
Methods:
Six matched-pairs of fresh-frozen lower leg cadaveric specimens (12 total) were obtained. All tendons were completely detached from their calcaneal insertions and tendon thickness was measured. Calcaneal exostectomies were performed (e.g., Haglunds removal) above the Achilles insertion. Group 1 was repaired with a single-row construct with two all-soft anchors.
Group 2 was repaired with a double-row suture bridge construct with two knotless anchors distally and two suture tape anchors proximally. The repaired specimens were cyclically loaded from 10N to 100N at 1 Hz for 2,000 cycles then to failure at 1mm/sec. A motion capture system measured Achilles-calcaneal displacement at the medial and lateral anchors. Paired t-tests and linear mixed models (LMMs) were used to analyze the following outcomes: clinical failure load, ultimate failure load, Achilles-calcaneal medial and lateral displacement, distance at ultimate failure load, tendon thickness, footprint, and mode of failure. A p-value of <0.05 was considered statistically significant.
Results:
Group 2 showed significantly less Achilles-calcaneal overall medial and lateral displacement, 19.5% and 36.9% respectively (Table 1). Group 2 showed a statistical trend toward greater clinical and ultimate failure load, 23.8% and 34.2%, respectively (Table1). LMM analyses showed that a suture bridge repair over all-soft anchor repair was independently associated with a 50.24N increase in the load to clinical failure (p=0.0011). Higher clinical failure loads were associated with higher BMI (p<0.0001), thinner tendons (p<0.0001), and smaller tendon footprints on the calcaneus (p=0.0013). Higher absolute failure loads were associated with older age (p<0.0001), higher BMI (p<0.0001), thinner tendons (p=0.0028), and larger footprints (p<0.0001).
Conclusion:
These data suggest a trend toward higher clinical and ultimate failure loads in a suture bridge construct compared to all-soft suture anchors for insertional Achilles repair. Loads to failure in both groups were higher than previously reported pull-out strengths for most suture anchors (150-300 N), but are lower than typical loads at the Achilles insertion during walking activities. The use of the suture bridge repair method may result in superior loads to failure compared to all-soft anchors. Patient age, BMI and tendon thickness impact failure loads. Adequate healing should be allowed followed repair of complete Achilles detachment.