Avoiding tibia physeal injury during double-bundle posterior cruciate ligament reconstruction

BackgroundAnatomic studies of the paediatric posterior cruciate ligament (PCL) demonstrate that the tibial attachment spans the epiphysis, physis and metaphysis. To better reproduce the anatomy of the PCL and avoid direct physeal injury, a double-bundle PCL reconstruction technique that includes both an all-epiphysial and an all-metaphyseal tibial tunnel has been proposed. The purpose of this study was to evaluate tibial tunnel placement in a paediatric double-bundle PCL reconstruction technique that avoids direct physeal injury using a 3-D computer model.MethodsTen skeletally immature cadaveric knee specimens (ages 5–11) were used to create 3-D model reconstructions from CT scans. All-metaphyseal and all-epiphysial tibial tunnels were simulated with the goal of maintaining adequate spacing (≥2 mm) between the tibial physis and tunnels to avoid injury. The all-metaphyseal tunnel, simulated at sizes of 5, 6 and 7 mm, entered anteriorly, below the tibial tubercle (apophysis) and exited posteriorly in the metaphyseal PCL footprint, distal to the proximal tibial physis. Four-millimetre all-epiphysial proximal tibial tunnels were simulated to enter the epiphysis anteromedially and exit posteriorly at the central epiphysial region of the PCL footprint, proximal to the physis. The distance was measured from the all-metaphyseal tunnels to the physis posteriorly and from the all-epiphysial tunnels to the physis, both anteriorly and posteriorly.ResultsIn all specimens, the 4 mm all-epiphysial tunnel and the 5, 6 and 7 mm all-metaphyseal tunnels maintained adequate spacing, ≥2 mm from the physis. In the specimens aged 5–7 years, the 5, 6 and 7 mm all-metaphyseal tunnels measured a mean distance of 3.5, 2.8 and 2.5 mm from the physis, respectively. In the specimens aged 8–11 years, the 5, 6 and 7 mm all-metaphyseal tunnels measured a mean distance of 3.4, 2.9 and 2.6 mm from the physis. In the specimens aged 5–7 years, the all-epiphysial tunnel measured a mean of 2.1 mm to the physis anteriorly and a mean of 2.8 mm posteriorly. In the specimens aged 8–11 years, the all-epiphysial tunnel measured a mean of 2.2 mm to the physis anteriorly and 2.4 mm posteriorly.ConclusionThese computer-aided 3-D models of paediatric knees illustrate that 5, 6 and 7 mm all-metaphyseal tunnels as well as 4 mm all-epiphysial tunnels can be placed without direct injury to the proximal tibial physis. The margin of error for direct physeal injury is small, especially for the all-epiphysial tunnel. Further, the all-epiphysial tunnel, while reproducing the anatomy of the PCL epiphysial attachment, may also produce a more extreme ‘killer turn’ of the graft. Modifications to the all-epiphysial tunnel may be considered to reduce the impact of the high ‘killer turn’ angle on the tibia.Level of evidenceIV.