Anterior Cruciate Ligament Injury Combined with Medial Collateral Ligament, Posterior Cruciate Ligament, and/or Lateral Collateral Ligament Injury

Introduction

A knee dislocation injury is a rare but potentially devastating injury. The definition of knee dislocation includes the grossly unstable knee, with a minimum of two of the four major knee ligaments injured, regardless of a reduced joint line. Some authors suggest that any combined anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) injuries be considered a knee dislocation, although knee dislocations have been described without cruciate injury. The injury is commonly attributed to high-velocity motor vehicle accidents and low-velocity sports injuries, with the rate of knee dislocation reported to be 0.001%–0.013% of all knee injuries. This may represent an underestimation of this devastating injury because some knee dislocations spontaneously reduce before the patient receives a physical examination, and the patient may suffer other physical injuries that require medical attention.

Commonly, a knee dislocation involves injury to the ACL, PCL, and either the medial collateral ligament (MCL) or the lateral-side structures of the knee. Of knee dislocations, associated medial-side tears represent approximately 90% of all the injuries, whereas lateral-sided injuries represent approximately 10% of the knee dislocation injuries.

We see almost 10 times more knee dislocations involving the medial side than we do involving the lateral side. Nonoperative treatment of knee dislocations involving the lateral side usually results in a grossly unstable knee and causes severe functional disability for the patient. Because of these occurrences, acute reconstruction of all injured structures with all knee dislocations has been advocated; this recommendation has included knee dislocations involving the medial side. This approach has resulted in many stable but stiff knees after surgery.

The morbidity associated with acute surgery for knee dislocations caused us to alter our treatment approach for knee dislocations to consider the healing potential of each torn structure. Although a knee dislocation involving the lateral side is an injury that requires surgery at least semiacutely, a knee dislocation involving the medial side is not an injury that requires immediate surgery and may not require surgery at all.

We will review our treatment approach to dislocated knees involving the ACL, PCL, and either the MCL injury or lateral-side structures. This approach was derived from an understanding of the injuries to the individual ligaments and their potential to heal, the natural history of the injury, and the effects of the injury in combination.

Ligament Healing

Posterior Cruciate Ligament

In contrast to the ACL, PCL injuries have the potential for intrinsic healing ( Fig. 99.1 ). Evaluation with MRI of acute PCL injuries has been found to be 99%–100% sensitive and specific in documenting acute PCL tears. In contrast, MRI evaluation of chronic PCL laxity are less accurate than that of acute injury because the PCL appears healed even when the patient has laxity. Shelbourne et al. evaluated 40 patients who had acute PCL injuries with MRI at the time of the acute injury and again at a mean of 3.2 years after injury. Twenty-three patients had isolated PCL tears, and 17 patients had combined PCL and additional ligament injury. The healing of partial and complete tears was graded with MRI. The results showed that 37 of 40 PCLs healed with continuity. All partial tears and most complete (19 of 22) PCL tears regained continuity. Twelve of 12 combined PCL/MCL injuries healed. In two patients with acute ACL, PCL, and MCL injuries, the MCL and PCL healed without treatment. Location, severity, and associated ligament injuries did not affect healing. The healed PCL demonstrated abnormal morphology in 25 of the 37 cases on follow-up. In a recent follow-up study at a mean of 4.6 years after knee dislocations to the lateral side, the PCL in 16 of 16 patients appeared healed on the MRI and no patient had more than 1+ laxity upon examination (Shelbourne et al.). Tewes et al. evaluated follow-up MRIs on 13 patients with high-grade PCL injury an average of 20 months postinjury. Their results showed 10 of 13 patients (77%) had regained MRI continuity of the PCL, although with an abnormal appearance. They could not correlate functional or clinical status with degree of clinical laxity. The time to obtain healing after acute PCL injury is yet unknown. However, Shelbourne et al. described a firm endpoint, and a painless posterior drawer at follow-up examination of acute PCL injuries approximately 2 weeks postinjury.