PCL Inlay a Better Way?
Abstract & Commentary
Synopsis: PCL reconstruction with a tibial inlay technique resulted in significantly more stable knees with less graft damage upon cyclic loading as compared to the trans-tibial tunnel technique.
Source: Bergfeld JA, et al. A biomechanical comparison of posterior cruciate ligament reconstruction techniques. Am J Sports Med. 2001;29(2):129-136.
PCL reconstruction techniques are generally known to produce results that are less predictable than the results achieved with ACL reconstructions. In an effort to improve the clinical results, techniques have been developed to better reproduce the femoral attachment anatomy using a double-bundle graft. A trans-tibial tunnel, however, is not anatomic and can be difficult to reproducibly position with arthroscopic methods. A tibial inlay technique has recently been introduced that attaches the graft to a trough on the back of the tibia at the anatomic insertion. Proponents suggest that this avoids the "killer turn" the graft otherwise must make as it exits a posteriorly directed tibial tunnel and turns toward the femoral attachment. This inlay technique hasn’t really been tested in the lab the way the other PCL techniques have until this study by Bergfeld and colleagues at the Cleveland Clinic.
Six pairs of cadaver knees were tested for displacement in a custom device with a posteriorly directed load. Each knee was tested while intact, after PCL sectioning, and after reconstruction with either a trans-tibial or tibial-inlay method. Ipsilateral bone-tendon-bone grafts were used with interference fixation in tunnels and screw and washer fixation for the inlay. Measurements were performed at 0, 30, 60, and 90° of flexion and at neutral, internal, and external tibial rotation.
The tibial-inlay group had the most stable knees under all conditions. After 72 cycles of repetitive loading, both graft systems stretched, but the inlay group still approximated the laxity of the intact PCL knee. However, the tunnel group was significantly more lax than both the inlay group and the intact knee. Moreover, gross inspection of the retrieved grafts demonstrated significantly more thinning and damage to the tendon of the tunnel group where the graft makes the "killer turn."
Comment by David R. Diduch, MS, MD
This paper clearly provides excellent evidence in support of the tibial inlay technique for PCL reconstruction. For myself, and I am sure many of the readers, we just can’t get the PCL reconstructions to stay tight. Initially stable knees tend to stretch with time to a one plus or worse exam. Many factors could play a role, including loss of fixation, stretch of allograft, or nonanatomic fixation. Bergfeld et al provide sound evidence here that the "killer turn" is a major culprit. This is a problem that the new 2 bundle techniques don’t address. The tibial inlay technique prevents this problem, and this paper demonstrates that it results in a more stable knee. This is true initially and more importantly with repetitive loading.
Bergfeld et al are to be commended on a solid study with sound methods and statistics. The only shortcoming could have been the older age of cadaver specimens and that the same knee was not reconstructed both ways but rather compared to the contralateral knee. They compensated somewhat with cement augmentation of graft fixation to ensure that fixation slip was not the difference. Now we have biomechanical and anatomic evidence of an advantage of the inlay technique. Next we need clinical studies. Anecdotally, I have been impressed with tighter knees with the inlay technique and have made the switch. The surgical methods for this new approach need to be disseminated next as the back of the knee is not a place orthopaedic surgeons often go on purpose.
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