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Practical management of posterolateral instability of the knee

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Abstract

Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 2 (February, Suppl 1), 2002: pp 1–8

Section snippets

Anatomy of the posterolateral corner

The posterolateral corner (PLC) of the knee is comprised of a complex array of static and dynamic structures that act in conjunction to provide posterolateral knee stability. Static components of the PLC include the lateral collateral ligament (LCL), the popliteofibular ligament, the arcuate ligament complex, the fabellofibular ligament, and the posterolateral capsule. The dynamic contributions are provided by the biceps tendon, the iliotibial tract, and popliteus muscle tendon complex.1 Of

Biomechanics of the PLC

The structures of the lateral and PLC of the knee function primarily to resist varus rotation and posterolateral tibial rotation at all flexion angles. The PLC and posterior capsule of the knee joint are important secondary restraints to posterior tibial translation particularly with the knee near full extension. The posterolateral structures act in combination with the PCL to provide overall stability to the lateral knee. The complex structure of the knee does not allow for isolated rotation

Biomechanics of posterolateral reconstruction

The surgical reconstruction for posterolateral instability involves the creation of ligamentous substitutes positioned to resist varus rotation and posterolateral tibial rotation. These procedures all involve the creation of structural bands from either the fibular head or the PLC of the tibia to the region of the lateral femoral epicondyle. Structure bands are created from existing structures, autografts, or allografts. It is important in planning a surgical reconstruction to understand the

Isometry of the LCL and popliteofibular ligament

The isometry of the lateral side of the knee has been studied at the University of Washington.4 The study investigated length relationships between the fibular head and the lateral aspect of the femur. A summary of the findings is shown diagrammatically in Fig 2.

. The entire fibular head is nearly isometric in relation to the lateral femoral epicondyle. The posterior aspect of the fibular head shows slightly improved isometry with the anterior aspect of the epicondyle (cross-hatched areas). The

Evaluation of posterolateral instability

Patients presenting with acute posterolateral instability may have posterolateral knee pain, peroneal nerve symptoms (sensory and/or motor), and most likely associated ligament pathology. Patients with chronic posterolateral instability may present with hyperextension instability, posterolateral pain, peroneal nerve symptoms, varus thrust, functional instability, and medial or lateral joint line pain.7

Isolated LCL injury will demonstrate increased varus rotation maximum at 30° of knee flexion.

Classification of posterolateral instability

We have described three types of posterolateral instability: A, B, and C.12 Posterolateral instability includes at least 10° of increased tibial external rotation compared to the normal knee at 30° of knee flexion (positive dial test, and external rotation thigh foot angle test), and variable degrees of varus instability depending upon the injured anatomic structures.12 Posterolateral instability (PLI) type A has increased external rotation only, corresponding to injury to the popliteofibular

Surgical indications for posterolateral reconstruction

Isolated low-grade posterolateral complex injuries may do well with nonoperative treatment, however, in our experience, the low-grade isolated PLC injury is uncommon. PLC injuries are most commonly combined with posterior cruciate ligament injuries, and are part of a multiple ligament injured knee complex.7 These combined instability knees are best treated with surgical correction of all components of the instability. Chronic posterolateral injuries often present with functional instability,

Surgical treatment principles

  • Surgical treatment principles include:

  • Identifying and treating all injured ligaments, and other structural injuries.

  • Restoring bony alignment.

  • Correcting the abnormal motion.

  • Primary repair of injured structures when possible.

  • Establishing a posterolateral soft tissue post of strong allograft or autograft tissue for augmentation of a primary repair, and as the foundation of the reconstruction.

  • Assessing the proximal tibio-fibular joint. When the proximal tib-fib joint is intact the soft tissue

Surgical technique of LCL and popliteofibular ligament reconstruction using a free semitendinosus tendon graft

The use of an autogenous semintendinosus free graft to reconstruct the LCL and popliteofibular ligament has been very effective when used to augment primary repairs of acute damaged structures.13 The procedure can also be utilized alone for treating varus or posterolateral laxity of a moderate degree in both acute and chronic situations. It is most often done in combination with an ACL or PCL reconstruction where the injury has involved the lateral and posterolateral structures.

The procedure

Posterolateral reconstruction using the split biceps femoris tendon transfer procedure

The surgical technique for posterolateral reconstruction using the split biceps tendon transfer to the lateral femoral epicondyle has been well described.12 The requirements for this procedure include an intact proximal tibiofibular joint, the posterolateral capsular attachments to the common biceps tendon should be intact, and the biceps femoris tendon insertion into the fibular head must be intact. This technique recreates the function of the popliteofibular ligament and LCL, tightens the

Fanelli sports injury clinic results

Our results of surgical correction of posterolateral instability using the full biceps tendon transfer procedure have been previously reported.13, 14, 15, 16 The results of 10 consecutive ACL/PCL/posterolateral and 17 PCL/posterolateral reconstructions using the split biceps tendon technique described above for the posterolateral reconstruction are presented below. The ACL/PCL/posterolateral group consisted of 6 acute and 4 chronic injuries with follow-up of 1 to 5 years. The external rotation

Summary

Posterolateral instability is common with posterior cruciate ligament tears, is less common with anterior cruciate ligament tears, and isolated posterolateral instability is rare. There are varying degrees of posterolateral instability with respect to pathologic external tibial rotation, and varus instability. The external rotation thigh foot angle (dial) test is the most useful test for PLRI in our hands, however, the use of multiple tests helps confirm the diagnosis. Surgical treatment of

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