By Mark D. Miller, MD
Reconstruction of the posterior cruciate ligament (PCL) continues to be a subject of much debate within sports medicine. Despite the evolution of various surgical techniques, we are still not as successful in reconstructing the PCL as we are at reconstructing the ACL. This is probably due to a variety of factors that we are only beginning to understand. Perhaps the most basic reason is that PCL injuries are far less common. The average sports medicine surgeon may see only a handful of these injuries each year, and may see an equal number of ACL injuries in a month or even a week. The old adage "Practice makes Perfect" certainly applies.
Another major factor is the recognition of the importance of other structures that may be injured at the time of PCL injury. Perhaps the most important of these structures is the posterolateral corner (PLC). We now recognize that PCL injuries with more than 10-12 mm of posterior displacement commonly have associated PLC injuries. Reconstruction of the PCL should not be attempted without combined PLC reconstruction. A variety of techniques for PLC reconstruction have been described and primary repair of injured structures with augmentation when necessary is recommended.1
Another factor that continues to evolve is controversy regarding the best technique for PCL reconstruction. Recent biomechanical studies have suggested that the traditional arthroscopic trans-tibial technique may subject the graft to excessive bending, abrasion, and even failure.2 Because of these concerns, the tibial inlay technique has been developed. This technique avoids the so-called "killer turn" at the back of the knee. It does require a posterior approach, but the safety of this approach has been demonstrated in a recent cadaveric study.3
The tibial inlay technique is perhaps best carried out when the patient is positioned in the lateral decubitus position with the injured leg up. The leg is externally rotated at the hip for patella tendon graft harvest, arthroscopy, debridement of the PCL stump, and femoral tunnel placement. The guide wire for the femoral tunnel is placed in the anterolateral portion of the PCL origin, at approximately the 10:30 or 11:00 position, 8 mm from the articular surface. It is overdrilled with a 10- or 11-mm drill and the back edge is rasped. The leg is positioned on a Mayo stand and a posterior approach is made in the flexion crease overlying the popliteal fossa. The key to the approach is to incise the fascia and mobilize the medial head of the gastrocnemius. Retracting this muscle laterally protects the neurovascular structures and allows direct access to the back of the tibia. A trough is made in the PCL fossa, and the graft bone plug is fixed with spiked, soft tissue washer plus a low-profile, bicortical screw placed from posterior to anterior. This provides secure fixation of the graft. The graft is delivered into the knee through a posterior arthrotomy and retrieved with a bent wire that is placed from the femoral tunnel into the back of the knee. After the knee is cycled, the graft is fixed in the femoral tunnel with an interference screw and back-up screw and washer fixation.
Another controversial issue centers on whether 2 femoral tunnels should be used. This 2-bundle technique has been shown biomechanically to result in better graft stability in both extension (which would be expected) and also in flexion.4 The unknown factor is whether these biomechanical differences will affect clinical results.
There are extremely limited published reports of PCL reconstruction in the literature. Fanelli has published good results with trans-tibial PCL reconstruction.5 Unfortunately, like a lot of these studies, his population was mixed and included many cases of combined PLC reconstructions. Cooper has presented results using the tibial inlay technique with side-to-side differences on stress radiographs of approximately 3 mm (compared to 10-15 preoperatively).6 Jung and associates recently reported their 2-year follow-up results of PCL inlay reconstructions done in Korea. Average posterior displacement on stress radiography improved from 10.8 mm to 3.4 mm in this study with 90% of patients reporting a satisfactory outcome.7
Although we are encouraged by these reports, PCL reconstruction, even with the inlay technique, is not as successful as ACL reconstruction. The theoretical improvement offered by 2-bundle femoral reconstructions may not justify the additional technical difficulty and potential complications of this new technique. Better grafts, improved techniques, and long-term results may change the way that we perform PCL reconstruction in the future.
Dr. Miller, Co-Director, Sports Medicine, Associate Professor, UVA Health System, Department of Orthopaedic Surgery, Charlottesville, VA, is Associate Editor of Sports Medicine Reports.
References
1. Miller MD, et al. Posterior cruciate ligament: Current concepts. Instr Course Lect. Rosemont, IL: AAOS; 2002;51:347-351.
2. Markolf KL, et al. J Bone Joint Surg Am. 2002;84-A:518-524.
3. Miller MD, et al. J Knee Surg. In Press, Summer 2002.
4. Griffin JR, et al. J Knee Surg. 2002;15(2):114-120.
5. Fanelli GC, et al. Arthroscopy. 1996;12(5):521-530.
6. Cooper DE. Primary PCL reconstruction with the tibial inlay technique. AOSSM Proceedings, June 2001, Keystone, CO.
7. Jung Y-B, et al. Reconstruction of the posterior cruciate ligament by the modified tibial inlay method. Paper #9, Proceedings of the 2002 Annual Meeting of the AAOS, Feb. 2002, Dallas, TX, 3:602
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