Intra-articular proximal jig pin placement during tibial plateau leveling osteotomy

Background: During tibial plateau leveling osteotomy (TPLO), a TPLO jig is often used. For placement of the jig, one of the pins is placed slightly distal to the joint line. Erroneous pin placement may lead to intra-articular damage: however, the path of the pin tract has not been thoroughly investigated. Aim: To document the rate and identify potential risk factors of intra-articular jig pin placement in dogs undergoing TPLO with the use of a TPLO jig. Methods: Medical records and pre- and postoperative radiographs (2007-2017) of 696 dogs with TPLO performed with a jig were reviewed. Primary surgeon and tibial plateau angles (TPA) were recorded. Postoperative radiographs were evaluated and classified according to intra-articular jig pin placement. Medial tibial plateau jig pin placement was defined as a radiolucent tract on the osteochondral junction of the medial tibial plateau. Lateral tibial plateau placement was defined as a radiolucent tract within 3 mm of the medial tibial plateau with a pin trajectory penetrating the lateral tibial plateau. Rates of intra-articular jig pin placement were calculated, and associations between intra-articular jig pin placement and surgeon experience and TPA were assessed with a chi-squared test. Results: Thirty-seven (5.32%) dogs had intra-articular placement of the jig pin. Seven dogs had medial tibial plateau jig placement, and 30 had lateral tibial plateau placement. There was no relationship between the TPA or surgeon level of experience and intra-articular placement of the pin. Conclusion: This study serves as a reminder to be cautious when placing the proximal jig pin during TPLO to avoid intra-articular placement. In addition, guidelines for evaluating proximal jig pin placement on postoperative radiographs are provided.