Chapter 84

Injury to the posterolateral corner of the knee is a rare but often debilitating entity. Posterolateral corner injury is usually associated with additional ligament injury and can be missed on initial physical examination.1–4 If it is identified early (within 3 weeks), many authors recommend acute repair of the posterolateral corner. However, recent data suggest that the results of reconstruction may be better than those of acute repair.⁵ Reconstruction of the posterolateral corner is indicated for those who are seen 3 weeks after injury or who have inadequate soft tissue for successful repair. Biomechanical data have shown that reconstruction of the posterolateral corner must restore function of the lateral collateral ligament and popliteofibular ligament to resist posterior translation, varus opening, and external rotation of the tibia on the femur.^5–8

Preoperative Considerations

History

It is essential to obtain a complete history of the injury at the time of the initial evaluation. Injuries to the posterolateral corner of the knee are rarely isolated and are usually associated with significant trauma to the knee. A detailed account of previous treatments, as well as operative reports, if they are available, should be obtained before consideration of additional surgical intervention.

Typical History

• Acute, traumatic knee injury

• Activity-related instability

• Previous ligament reconstruction (anterior or posterior cruciate ligament) may have failed

Physical Examination

Examination of the cruciate and collateral ligaments as well as of the neurovascular status of the patient should be well documented. A significant percentage of posterolateral corner injuries occur in the setting of knee dislocation. Examination of the acute injury may be limited by pain.

Acute Injury

• Tenderness over posterolateral aspect of the knee with ecchymosis (Fig. 84-1)

Figure 84-1 Clinical appearance of the knee after posterolateral corner injury.

• Positive varus instability at 30 degrees (and 0 degrees with combined injury)

• Possible associated ligamentous instability (anterior cruciate ligament, posterior cruciate ligament)

• Positive result of posterolateral drawer test

• Positive result of external rotation (dial) test: increased only at 30 degrees, isolated posterolateral corner injury; increased at 30 degrees and 90 degrees, posterior cruciate ligament and posterolateral corner injuries

• Positive result of external rotation recurvatum test (with combined injury) (Fig. 84-2)

Figure 84-2 Positive result of external rotation recurvatum test.

• Positive result of reverse pivot shift test

• Examination findings possibly consistent with peroneal nerve injury

Chronic Injury

• Similar to acute injury, although a varus thrust during gait may develop

• Lateral joint line pain

Imaging

Radiography

• Weight-bearing anteroposterior radiograph in full extension

• Weight-bearing posteroanterior 45-degree flexion radiograph

• Non–weight-bearing 45-degree flexion lateral radiograph

• Patella Merchant radiograph

• Hip-to-ankle alignment film to evaluate position of weight-bearing axis in the knee

Other Modalities

Magnetic resonance imaging is performed to assess meniscus and ligamentous structures. Magnetic resonance arteriography may be considered, in conjunction with magnetic resonance imaging, for evaluation of acute or subacute posterolateral corner injuries in the setting of suspected knee dislocation.

Electromyelography is performed at 3 weeks if peroneal nerve injury is present.

Indications and Contraindications

Reconstruction of the posterolateral corner of the knee is generally indicated for complete disruptions (grade III) or grade II injuries with symptomatic instability. Associated ligamentous injuries may need to be addressed at the time of posterolateral corner reconstruction. A relative contraindication for posterolateral corner reconstruction is varus knee alignment. High tibial osteotomy, before or in conjunction with the posterolateral corner reconstruction, should be considered in chronic injury.

Surgical Planning

Concomitant Procedures

Significant limb malalignment, chondral injury, or associated ligament injuries may need to be addressed before or in conjunction with the posterolateral corner reconstruction in chronic injury. Our standard technique uses a single graft passed through the fibula head and fixed to the anatomic insertions of the popliteal tendon and lateral collateral ligament on the femur (Figs. 84-3 and 84-4).⁹ If there is extreme instability of the posterolateral corner, consideration can be given to adding a tibial tunnel to the construct.¹⁰

Figure 84-3 Posterolateral corner anatomy and tunnel landmarks. (Modified from McCarthy M, Camarda L, Wijdicks CA, et al. Anatomic posterolateral knee reconstructions require a popliteofibular ligament reconstruction through a tibial tunnel. Am J Sports Med. 2010;38:1674-1681.)

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