The Management of Posterior Cruciate Ligament (PCL) Injuries of the Knee
Christopher D. Harner, M.D. is the Blue Cross of Western Pennsylvania Professor of Orthopaedic Surgery at the University of Pittsburgh School of Medicine. Dr. Harner is also Chief of the Division of Sports Medicine, Fellowship Director, and Medical Director at the UPMC Center for Sports Medicine.
Dr. Harner specializes in sports medicine, especially knee, ligament and cartilage injuries. His research focuses on healing such injuries, especially those of the anterior and posterior cruciate ligaments, through new surgical techniques.
Recent research has shed new light on the anatomy of the posterior cruciate ligament, showing that it is sub-divided into separate bundles. Could you explain this arrangement and its functional relevance?
"The posterior cruciate ligament (PCL) has three main components: the Antero-Lateral bundle, the Postero-Medial bundle and the Menisco-Femoral ligaments. These components have distinct anatomic and bio mechanical properties. The fibers of the stronger Antero-Lateral component are more taut when the knee is flexed, while the Postero-Medial component is taut when the knee is extended. The Menisco-Femoral ligaments are smaller in size but have significant mechanical strength and attach from the lateral meniscus to the femoral insertion of the PCL. Their importance is not well understood, but they are believed to help stabilize the lateral meniscus. [6][10]
Athletes are able to return to sports without surgery following 'isolated' PCL injuries. This is different from ACL injuries. Why is surgery not required for isolated PCL injuries?
"Unlike the ACL, the PCL suffers partial injuries more commonly (grades I-III). The PCL has various secondary structures and restraints attached to it. In an isolated PCL injury it is likely that the integrity of these structures and various portions of the PCL remain intact and provide some stability. Not all patients with an isolated grade III (completely ruptured) PCL do well and my eventually require surgical treatment. [3]
Conversely PCL injuries which also have damage to the 'posterolateral' corner usually require surgery. Could you explain why?
"The posterolateral corner is the primary restraint to external rotation at 90° and 30° of knee flexion. When the PCL is injured, along with the posterolateral corne,r the secondary structures remaining may be unable to restrain the knee enough to provide joint stability. This injury changes the 'neutral position' of the knee and in the long term patients can become symptomatic for pain and instability. [1][2][5][9][11]
The PCL is thicker than the ACL, so what do you prefer to use as a graft during reconstructive surgery?
"For single bundle PCL reconstruction I use an Achilles tendon allograft (tissue from a donor). For double bundle PCL reconstruction I use an Achilles tendon allograft plus a semi-tendinosis autograft (one of the patients hamstring tendons). For ACL reconstruction, I use three different grafts depending on different clinical situations. My approximate breakdown for each graft is patellar tendon autograft (portion of the patients patella tendon) 60%, hamstring tendon autograft (one of the patient's hamstring tendons) 30% and patellar tendon allograft (portion of a donor's patella tendon) 10%. I tend to use allograft in my older patients (>40 yrs). [4][8]
Conventionally, following surgical repair of the PCL, the knee is immobilized for up to a month. This is the opposite of the post-op regime for the ACL reconstruction. Why is this?
"Actually, following PCL surgery I now begin knee range of motion one week post-op, based on scientific work performed in our lab at the University of Pittsburgh Medical Center [3][7]. It is safe to move the knee in closed-chain exercises (where the foot is in contact with a firm surface), thus I lock the brace in full extension for one week and then begin motion with mini-squats, with patients remaining on crutches for 6 weeks. The reason that we have to protect the PCL patients more is because the forces of gravity on the graft as well as collateral ligament surgery may create problems before the grafts heal to bone. "
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