ACL reconstruction using the Rigidfix femoral fixation device via the anteromedial portal: a cadaver study to evaluate chondral injuries

The aim of this anatomic descriptive cadaver study is to evaluate the entrance points of cross-pins and the possible chondral damages, using a two cross-pin femoral fixation device via anteromedial portal, during anterior cruciate ligament (ACL) reconstruction. Twenty fresh-frozen cadaver knees (12 cadavers) were tested. We employed the Rigidfix Cross Pin device (Mitek, Norwood, MA), designed to use two biodegradable pins (PLA, length 42 mm, diameter 2.7 mm). Instead of PLA pins, we used color coded metallic pins. Femoral tunnel drilling and cross-pin guide insertions were performed through the anteromedial portal. We gave three positions to the cross-pin guide: 0 degrees , 45 degrees and 90 degrees slope, referring to the horizontal plane. Per each position, we inserted two metallic pins. We recorded and subdivided the pin holes, in three different groups: Group A (0 degrees ); B (45 degrees ); C (90 degrees of slope). Then a wide dissection has been implemented. Group A: 6 knees (30%) had two pins inside the cartilage of the lateral femoral condyle; 10 knees (50%) had one pin inside the cartilage; and 4 knees (20%) had both pins out of the cartilage. Group B: 7 knees (35%) had two pins inside the cartilage; 12 knees (60%) had one pin inside the cartilage; and one knee (5%) had both pins out of the cartilage. Group C: 7 knees (35%) had two pins inside the cartilage; and 13 knees (65%) had one pin inside the cartilage. The risk of chondral injury, using this technique, is high: from 80% (group A) to 100% (Group C) to have at least one pin inside the cartilage. The use of Rigidfix via AM portal is not recommended for routine ACL reconstruction.