Biomechanical comparison of patellar tendon repairs in a cadaver model: an evaluation of gap formation at the repair site with cyclic loading

Abstract

Background: Ruptures of the patellar tendon are rare injuries. Surgical treatment for this injury is mandatory.

Hypothesis: Gap formation does not differ between the three patellar tendon repair techniques.

Study design: Controlled laboratory study.

Methods: Twelve fresh-frozen cadaveric knees were used to compare three techniques of patellar tendon repairs. The standard suture repair used two Krackow sutures placed in the avulsed patellar tendon, passed through transpatellar drill holes, and secured with the knee in 30 degrees of flexion. In the second group, suture repair was augmented with a No. 5 Ethibond suture. In the third group, suture repair was augmented with a 2.0 Dall-Miles cable. Testing was performed with the specimens mounted to a custom knee jig with the tibia free, simulating the knee moment of a 70-kg person. Each knee was then cycled 250 times at 0.25 Hz.

Results: Gap formation across the standard suture repair averaged 7.3 mm; across the suture augmentation and cable augmentation groups it averaged 4.9 mm and 3.5 mm, respectively.

Conclusions: Augmentation of patellar tendon avulsions can decrease gap formation at the repair site, allowing early mobilization.

Clinical relevance: Gap formation seen in repair without augmentation could lead to clinical failure with resultant patella alta and extensor mechanism lag.