A pilot study testing an Achilles tendinopathy human cadaver model using intratendinous injection of collagenase

Background: Achilles tendinopathy is one of the most frequently occurring soft-tissue injuries. Despite decades of research, there is still much that is unknown about the progression of tendinopathy. Animal models, such as collagenase injection, allow researchers to gain insight into disease progression and investigate clinical interventions, yet are limited in their direct application to humans. Establishment of a cadaver model of tendinopathy would provide another method of investigating clinical interventions in human tissues. The purpose of this study is to develop such a model and evaluate biomechanical changes in cadaveric Achilles tendons using ultrasound elastography. Methods: Achilles tendons of five female foot/ankle cadavers were injected with two different concentrations (three with 10 mg/mL, two 20 mg/mL) of collagenase and incubated for 24 h. Ultrasound elastography images were collected at baseline, 16 and 24 h post-injection. Elasticity of tendons was calculated using a custom image analysis program. Findings: Elasticity decreased over time in both dosage groups. In the 10 mg/mL group, mean elasticity decreased from 642 +/- 246 kPa at baseline to 392 +/- 38.3 kPa at 16 h and 263 +/- 87.3 kPa at 24 h. In the 20 mg/mL group, mean elasticity decreased from 628 +/- 206 kPa at baseline to 176 +/- 152 kPa at 16 h and 188 +/- 120 kPa at 24 h. Interpretation: Injection of collagenase into cadaveric Achilles tendons resulted in decreases in elasticity. Decreases were observed in tendons that received injections with both 10 and 20 mg/mL collagenase dosages. Further biomechanical and histological testing is needed to evaluate this cadaveric tendinopathy.