The Retropatellar Portal as an Alternative Site for Tibial Nail Insertion: A Cadaveric Study

Objective: To define spatial relationships between major intra-articular structures of the knee and the entry site of a tibial nail inserted using a retropatellar portal. Design: Cadaveric study using 16 fresh-frozen limbs. Setting: University-affiliated cadaver and anatomy laboratory. Results: The mean distance of the nail entry site and the medial and lateral menisci were 6.6 +/- 3.2 mm and 6.4 +/- 4.4 mm, respectively. The distance to the medial and lateral articular surfaces were 5.6 +/- 3.6 mm and 7.4 +/- 4.2 mm, respectively. The mean distance to the anterior cruciate ligament footprint was 7.5 +/- 3.5 mm. The lateral meniscus was never injured during the procedure. The anterior cruciate ligament was undisturbed in all specimens. The medial meniscus was injured 1 to 2 mm in 12.5% of specimens. The intermeniscal ligament was injured 1 to 2 mm in 81.2% of the specimens. Conclusion: The intermeniscal ligament and medial meniscus are at the most risk during intramedullary nailing of the tibia using the retropatellar technique. This may be corrected by avoiding an excessively medial start point. Damage to the intermeniscal ligament and medial meniscus occurs more commonly with the retropatellar portal, but this damage was never more than 1 to 2 mm. This risk, however, appears similar to the pattern and incidence of injury that occurred in prior studies investigating tibial nail insertion through a standard patellar tendon approach. The retropatellar technique demands clinical investigation to further define both its safety and its use.