Differences of Intra-Articular Graft Length between Sandwich-Style Reconstruction and Zhao-Style Non-Remnant-Preserving Double-Bundle Reconstruction of Posterior Cruciate Ligament

Appropriate graft length within the joint and inside the osseous tunnel is essential for achieving posterior stability and adequate anchorage strength. Because of the curving path and thickness of the graft in double-bundle posterior cruciate ligament (PCL) reconstruction, especially in double-bundle PCL augmentation (with remnant preservation), the actual intra-articular length of PCL grafts, which remains unknown, may be longer than previously published values. The main purpose of the current study is to measure the actual intra-articular graft length required in sandwich-style PCL reconstruction (remnant-preserving double-bundle PCL augmentation) and Zhao-style non-remnant-preserving double-bundle PCL reconstruction (semi-anatomic double-bundle PCL reconstruction using double-double tunnel with tibial medial and lateral arrangement). Nine matched pairs of intact cadaveric knees were randomized between two groups and respectively received sandwich-style PCL reconstruction (remnant-preserving group) and Zhao-style non-remnant-preserving double-bundle PCL reconstruction (non-remnant-preserving group). The tunnel positions were exactly the same in two groups. The anterolateral (AL) bundle was reconstructed with four-stranded semitendinosus tendon, and the posteromedial (PM) bundle was reconstructed with four-stranded gracilis tendon. For each bundle, the length of the graft portion within the joint was measured. The current study indicated that in remnant-preserving group, the average intra-articular exposed portion was 42.0 mm (SD, 1.3 mm; range, 40.0 mm to 43.4 mm) for the AL bundle and 32.5 mm (SD, 2.9 mm; range, 27.8 mm to 35.8 mm) for the PM bundle. In non-remnant-preserving group, the intra-articular exposed portion was 34.5 mm (SD, 1.0 mm; range, 32.7 mm to 36.0 mm) for the AL bundle and 29.1 mm (SD, 2.1 mm; range, 25.2 mm to 31.9 mm) for the PM bundle. For both the AL and PM bundles, significant differences were found in average intra-articular graft length between the two groups. The current study, whose methodology is more rigorous and accurate by measuring the actual intra-articular graft length, has direct applications to clinical practice. When considering the total graft lengths during reconstruction, it is necessary to recognize that remnant PCL has a space occupation effect on graft and that remnant preservation requires longer intra-articular graft lengths than non-remnant preservation.