PCL Deficiency is Bad to the Bone

Abstract & Commentary

Synopsis: PCL insufficiency is associated with early and continuous cartilage degeneration of the medial femoral condyle and patella.

Source: Strobel MJ, et al. Arthroscopic evaluation of articular cartilage lesions in posterior cruciate ligament-deficient knees. Arthroscopy. 2003;19(3):262-268.

The long-term effects of PCL (Posterior Cruciate Ligament) deficiency on the articular cartilage of the medial femoral condyle and patella are well recognized.1,2 The present paper, however, suggests that these changes occur much more rapidly than we have previously believed. In this retrospective study Strobel and associates reviewed almost 600 cases of patients with a PCL injury (documented with stress radiography) treated at their institution between 1993 and 1999. From this group, they selected 181 patients who underwent arthroscopy without PCL or ACL reconstruction. Most of these arthroscopies were performed immediately prior to PCL reconstruction. Groups were stratified based upon the duration of PCL deficiency, whether they had combined PCL-PLC (posterolateral corner) deficiency (characterized by posterior tibial displacement with more than 12-mm side-to-side difference on stress radiography), and based upon prior medial meniscal surgery.

The overall incidence of degenerative articular cartilage lesions (Outerbridge grade II-IV) in the study was 67.4%. Almost half of the study group had degenerative lesions on the medial femoral condyle and one-third had changes on the patella. These changes significantly increased with chronicity of PCL deficiency—especially on the medial femoral condyle. Degenerative changes were also more common in patients with combined PCL-PLC deficiency and those patients with prior partial medial meniscectomy.

Comment by Mark D. Miller, MD

This paper is retrospective and has some potential problems with conflicting variables that make proper statistical analysis difficult. As Strobel et al point out, there may also have been at least some selection bias because they performed arthroscopy only on patients who were symptomatic (about half of their entire group of PCL-deficient patients). Nevertheless, it provides another piece to the puzzle regarding the long-term effects of PCL deficiency. It is critical that Strobel et al have considered the degree of instability (based on stress radiography) in their results. It has only recently been recognized (at least in the United States) that increased posterior tibial displacement of greater than 12 mm on stress radiographs is associated with a combined PCL-PLC injury. In fact, combined PCL-PLC injuries have only been well characterized within the last decade. Of course, these patients will also have external rotation asymmetry at 30° and 90° of knee flexion, but stress radiographs allow critical objective evaluation of these injuries.

Natural history studies of PCL-deficient knees are extremely limited in the current literature. The few studies that have been done reported the results of radiographic degenerative changes and did not address combined injuries and prior partial meniscectomy.1,2 The present study, based on arthroscopic evaluation, suggests that chondral degeneration occurs much earlier (often within 5 years) than the prior studies have suggested (20 years or more). It is not surprising that prior medial meniscectomy and increased laxity are associated with more rapid progression of degenerative changes in the medial compartment. The effect of meniscectomy and PCL deficiency on contact pressures in vitro have been well characterized. Increased laxity and rotational instability associated with combined PCL-PLC injury markedly alters the contact areas of the medial femoral condyle and medial tibial plateau. The present in vivo study suggests that these alterations in contact result in chondral changes—and much earlier than previously thought. This has important implications regarding surgical indications for PCL reconstruction, especially in patients with combined PCL-PLC injuries. 

Dr. Miller is Associate Professor UVA Health System, Department of Orthopaedic Surgery, Charlottesville, VA.

References

1. Dejour H, et al. The natural history of rupture of the posterior cruciate ligament. Rev Chir Orthop Reparatrice Appar Mot. 1988;74:35-43.

2. Keller PM, et al. Nonoperatively treated isolated posterior cruciate ligament injuries. Am J Sports Med. 1993; 21:132-136.