Introduction

Up to 36% of athletes are found with significant cartilage defects (1). Symptomatic defects can be treated with multiple different reparative and restorative techniques including debridement, microfracture, MACI, and osteochondral autografts and allografts (2)(3). The Nanochon ChondrograftTM is an innovative, cost-effective synthetic cartilage repair implant for symptomatic focal defects. Larger defects may require multiple implants to restore the injured area. There is no consensus on the safe distance between implants.

Methods

To mimic ChondrograftTM in vivo, subchondral bone foam (PCF 40) was utilized for initial testing. The control group was a solitarily reamed 10 mm hole at a depth of 4-5mm, whereas the experimental group had two 10 mm holes reamed 3 mm apart at the same depth. A force gauge was used to determine the fixation strength by pulling on sutures applied to the implant. A T-test was used to compare the control and experimental groups. To validate the findings of the bone foam, three cadaveric specimens were tested using 10-, 15-, and 20-mm implants.

Results

Single implants (control) had an average pull out strength of 27.5 newtons (7.67). The multiple implants (3mm distance) had an average pull out strength of 31.8 newtons (6.71). The difference between the two groups is not statistically significant (p=0.28). In the cadaveric testing, the pull-out strength was similar to the in vitro testing with average pull out strength of 31.7 newtons (10.2).

Conclusions

A 3mm bridge between implants was found to be a safe distance to maintain ChondrograftTM fixation strength. Fixation strength did not differ in situations where single verses multiple plugs were utilized. This information is important as the ChondrograftTM moves to human safety studies.