Posterolateral Corner Injuries of Knee

POSTEROLATERAL CORNER INJURIES OF KNEE

DR JOHN T JOHN¹ DR SHINAS B SALAM ² DR DIVYA G³

Abstract

Posterolateral corner injuries have seen an increasing trend in view of the increased high velocity injuries .Though isolated injuries are rare, it is usually associated with other ligament injuries. A meticulous clinical examination with a high index of suspicion and radiological assessment is needed for the diagnosis, failure of which may lead to chronic pain, chronic knee instability, cartilage damage, and failed cruciate ligament reconstruction. Surgical or nonsurgical intervention are based on the extend of the injuries.

Key words :posterolateral corner,knee,injuries,management

^{1 DR JOHN T JOHN MBBS MS (Orth) MCh Orth (UK). MRCS (Glasg) FRCS(Glasg) ,HEAD OF THE DEPARTMENT,DEPARTMENT OF ORTHOPAEDICS, LOURDES HOSPITAL, KOCHI}

^{2.DR SHINAS B SALAM MBBS D-ORTHO DNB ,JUNIOR CONSULTANT ,DEPARTMENT OF ORTHOPAEDICS ,LOURDES HOSPITAL ,KOCHI}

^{3. DR DIVYA G MBBS DNB ( ORTHO) ,JUNIOR CONSULTANT ,DEPARTMENT OF ORTHOPAEDICS ,LOURDES HOSPITAL ,KOCHI}

^{Address for correspondence: shinassalam@gmail.com}

Introduction

The posterolateral corner because of its complex structure and biomechanics was once considered the dark side of the knee. Newer research regarding the anatomy and biomechanics has improved the understanding of PLC injuries. PLC injuries are more commonly associated with ACL or PCL injuries and isolated injuries as such are less common.  Failure to address a PLC injury may compromise concurrent cruciate ligament reconstructions and alter the knee biomechanics leading to an early degenerative change of the joint^{1 2 3}. High index of suspicion is needed for diagnosis. Detailed physical examination and a comprehensive review of radiographic and magnetic resonance imaging (MRI) studies help in determining these injuries better. Management protocol for lower grade injury are conservative, but higher grade injuries require operative interventions.

Anatomy

The lateral side of the knee is divided into three anatomic layers as described by Seebacher et al^[1]. The most superficial layer or layer 1, consists of the lateral fascia, iliotibial (IT) band, and the superficial portion of the biceps femoris tendon. The peroneal nerve is located in the deepest aspect of layer 1. The intermediate layer consists of the retinaculum of the quadriceps and the proximal and distal patellofemoral ligaments. The deep layer or layer 3, includes the lateral part of the joint capsule, the fibular collateral ligament, the fabellofibular ligament, the coronary ligament, the popliteal tendon, and the arcuate ligament.

The 3 most important stabilizing structures providing static (passive) and dynamic (active) posterolateral knee stability are the popliteus tendon, popliteo fibular ligament, and fibular collateral ligament ^[2]

The FCL is the primary Varus stabilizer of the knee. The femoral attachment of the FCL is in a small bony depression slightly proximal and posterior to the lateral epicondyle. The distal insertion is mainly on the distal one-third of the lateral aspect of the fibular head, the remaining insertion blends with the peroneus longus fascia

The femoral insertion of the popliteus constitutes the most anterior femoral insertion of the PLC. After its femoral insertion in the proximal half of the popliteal sulcus, it courses posterodistally in an oblique fashion to insert into the posteromedial tibia

The popliteofibular ligament originates at the musculotendinous junction of the popliteus with its two divisions (anterior and posterior) embracing popliteus musculotendinous junction and inserting distally into the posteromedial aspect of the fibular head.

Figure 1 : ANATOMY OF POSTEROLATERAL CORNER- Fibular collateral ligament (FCL) popliteus tendon (PLT) and Popliteofibular Ligament.

Secondary structures help stabilize the knee in a static and dynamic manner. From deep to superficial these structures are:

• The lateral capsular thickening with meniscofemoral and meniscotibial ligaments
• The coronary ligament
• The lateral gastrocnemius tendon
• The fabellofibular ligament
• The long head and short head of biceps femoris
• The iliotibial band

Biomechanics

The PLC structures provide the primary restraint to varus forces of the knee. PLC also resists external tibial rotation, and posterior tibial translation. Additionally, the PLC structures affect the function and loads seen on the cruciate ligaments

Role of PLC Structures to Varus Motion

The FCL is the primary restraint to varus stress. Deficiency of FCL causes increases in varus motion in all degrees of knee flexion. Varus stress produces the greatest load on the FCL with the knee in 30 degrees of flexion, and the load subsequently decreases once the knee reaches 90 degrees of flexion. Once the FCL is torn, secondary structures assume the main restraint to varus motion, including the posterior cruciate ligament (PCL), popliteofibular ligament, posterior capsule, mid-third lateral capsule ligament, IT band, and popliteal tendon.

Role of the PLC Structures in Preventing External Rotation

The popliteus tendon and the popliteofibular ligament are the primary restraints to external rotation. FCL plays a primary role in external rotation restraint when the knee is closer to full extension, and the popliteus and popliteofibular ligament assume responsibility with increasing degrees of knee flexion. The PCL also affects external rotation resistance. The PLC and PCL work in concert to resist external rotation stresses. Isolated sectioning of the PCL does not affect external rotation motion of the knee if the PLC is intact. As noted, the PLC experiences greatest external rotation moments at 30 degrees of knee flexion. The PCL does not experience external rotation loads until 80 to 90 degrees of knee flexion, when it becomes a secondary stabilizer to external rotation.

Role of the PLC Structures in Preventing Anterior/Posterior Tibial Translation

Injured PLC structures have little effect on total anterior tibial translation if the anterior cruciate ligament (ACL) is intact , but if the ACL is also torn, the combined ACL/PLC injury leads to significantly increased anterior tibial translation. Combined sectioning of the PLC and ACL causes an additional anterior translation. Isolated PLC injuries can cause increased posterior tibial translation, even in the setting of an intact PCL. In the knee with a deficient PCL, the PLC assumes a major stabilizing role, with increases in force load of six to eight times that of the knee with an intact PCL, especially at higher degrees of knee flexion. The total posterior tibial translation increases significantly, when both the PCL and PLC are torn.

Mechanism of injury

Common causes of posterolateral corner knee injury are posterolateral force on the anteromedial portion of the tibia, varus angulating force on a flexed knee, any injury that may hyperextend, externally rotate, or force the tibia into a varus angle or a knee dislocation.

Physical Examination

Both the knees should be compared. Any gait abnormalities need to be screened out, like varus thrust of the knee usually seen with chronic posterolateral knee injury. Vascular compromise and neural symptoms need to be evaluated.

Several special are described which help confirm a diagnosis. Commonly used are the posterolateral drawer, Dial, external rotation recurvatum, varus stress, reverse pivot-shift, and standing apprehension tests.

The posterolateral drawer test : Patient in supine with the knee flexed to 80° to 90° and the foot externally rotated 15°,foot is stabilised and posterolateral drawer force is applied . A positive posterolateral drawer test, indicated by increased posterolateral rotation compared to the contralateral knee, may implicate injury to the popliteus tendon, popliteofibular ligament, and FCL.

The Dial test : Patient in prone the knee is flexed to 30° and then 90°.  The foot is externally rotated, comparing with the uninvolved side. An increase of greater than or equal to 15°, as compared to the contralateral side, is considered positive. A Dial test that is positive at 30° of knee flexion but normal at 90° of knee flexion is indicative of PLC injury. A positive test at both 30° and 90° of knee flexion indicates both a PCL and PLC injury.

The external rotation recurvatum test : Lifting off supine patient's great toe, and observing the relative amount of genu recurvatum present. The test is considered positive if the amount of genu recurvatum measured by either a goniometer or heel height off the examination table is greater than the contralateral knee.

The varus stress test : Patient is supine, with the proximal femur stabilized on the examination table. The tibia is stabilised from unwanted rotation and applies a varus stress is applied 30° of flexion and repeated with the knee extended to 0°. The test is considered positive if translation is more than the opposite knee.

Reverse pivot shift test : Patient supine with the knee flexed to 40° and the tibia in external rotation. As the knee is extended, the tibia is reduced with a clicking sound. The reduction indicate positive test.

Standing apprehension test: The patient stands with his/her weight on the injured (tested) knee and slightly flexes it, while the clinician applies a medially directed force on the anterolateral portion of the lateral femoral condyle. Rotation of the condyle relative to the tibia, in addition to the patient feeling a giving-way sensation, indicates a positive test.

Investigations

1) Plain radiography

Plain radiography with anteroposterior (AP), lateral, and axial views is taken to rule out other injuries such as fractures. AP view to assess limb alignment.^[3]

2) Stress radiography

Varus stress test to assess lateral opening.^[4]

3) Magnetic resonance imaging (MRI)

MRI test helps to identify PLC structures. T2-weighted coronal oblique view is more useful in the evaluation of the posterolateral structures than the traditional coronal or sagittal view. MRI is also helpful to evaluate acute or subacute PLC injuries .

Arthroscopy

Arthroscopy provides intraarticular information of posterolateral structures, such as the popliteus complex, coronary ligament of the lateral meniscus, and posterolateral capsule. It helps to decide the appropriate treatment and provides accurate anatomical information in surgical treatment.

A drive-through sign occurs when there is more than 1cm lateral joint opening under varus stress to the knee joint, which can be confirmed with arthroscopy . Also, popliteal hiatus widening during internal rotation of the tibia, tears of the inferior and superior popliteomeniscal fascicle, and abnormal popliteomeniscal motion during rotation may be observed in arthroscopy.

Figure 2 : Drive through sign in arthroscopy

PLC injuries can be classified according to the damage to the posterolateral structures or the degree of posterolateral instability. The following two classifications are most commonly used:

Bleday et al and Fanelli and Larsonn classified the PLC injuries into type A, B, and C based on damage to structures.^[5],[6]

Table 1: Classification of Damage in Posterolateral Structures

Note: PFL: popliteofibular ligament; LCL: lateral collateral ligament.

The Hughston classification, is based on the assessment of varus instability or rotational instability under varus stress force with the knee in full extension.^[7]

Table 2: Classification of Posterolateral Instability

This table details the grading system based on physical exam findings and the status of the posterior cruciate ligament (PCL).

Note: PCL -Posterior Cruciate Ligament

Treatment

Non-Operative Treatment

Grade I and grade II isolated PLC injuries can be treated with non-operative management. Appropriate rehabilitation and gait training may be helpful in treating grade I or grade II injuries. Non-operative treatment may offer good outcomes; however, care should be taken considering non-operative treatment of complete tears involving the PLC has shown poor functional results^.

Operative Treatment

For grade III and grade II PLC injuries accompanied by other structural injuries, surgical management is recommended . The approach to Posterolateral Corner (PLC) injuries is primarily dictated by the chronicity of the trauma and the underlying mechanical alignment of the limb.

Acute PLC Injuries (Within 3 Weeks)

For injuries sustained within three weeks of treatment, the gold standard involves a combination of direct anatomical repair and augmentation using the Larson method of reconstruction.

• Key Clinical Note: Isolated primary repair is generally discouraged, as it is associated with high failure rates; augmentation is essential to provide the necessary stability during the healing process.

Chronic PLC Injuries

Chronic cases require a more complex, reconstructive approach, typically utilizing the anatomic LaPrade technique to restore the three primary stabilizing structures of the PLC.

In chronic presentations, assessing lower extremity alignment and gait patterns is critical to the success of the surgery:

• Varus Malalignment: If there is a varus deviation exceeding 3°, or if the mechanical axis (hip-knee-ankle) passes through the medial 30% of the tibial plateau, the reconstruction is at high risk of failure due to excessive tensile stress. In these instances, a High Tibial Osteotomy (HTO) should be performed—either prior to or in conjunction with the reconstruction—to realign the weight-bearing axis and protect the new graft.

 Reconstruction 

There are various methods of reconstruction, which can be divided into anatomic reconstruction and non-anatomic reconstruction.

Non-anatomic reconstruction is to obtain posterolateral stability by applying tension on the uninjured posterolateral structures. Arcuate complex or bone block advancement, extracapsular ITB sling, augmentation technique, and bicep tenodesis are recommended for non-anatomic reconstruction.

Anatomic reconstruction is indicated in cases with significant hyperextension, external rotation recurvatum , proximal tibiofibular instability an concomitant PCL injury.

Anatomical and biomechanical research of posterolateral structures has been conducted recently and precise anatomic reconstruction of the injured LCL, popliteus tendon and PFL is recommended with use of the fibular-based technique and tibiofibular-based technique

LaPrade et al., in 2004, introduced the term anatomical reconstruction of the PLC of the knee, based on previous anatomic and biomechanical testing, surgically reproducing the three main structures of this complex: the fibular collateral, popliteofibular ligament and polpliteuss tendon.The technique was tibio-fibular based  anatomic reconstruction technique, which included :Tibial tunnel ,fibular tunnel ,2 femoral tunnels for the LCL & popliteus. The graft preferred was Achilles tendon graft.

For all chronic cases—defined as injuries persisting for more than three weeks—we employ a modified LaPrade technique, which is a tibio-fibular based anatomic reconstruction. Unlike the original technique described by LaPrade et al., which utilizes two femoral tunnels, our modification utilizes a single femoral tunnel alongside one tibial and one fibular tunnel to reconstruct the fibular collateral ligament (FCL), popliteus tendon, and popliteofibular ligament. The graft we used is the semitendinosus and gracilis graft.

Anatomic tunnel placement is guided by specific bony landmarks: the fibular tunnel is positioned at the FCL insertion by identifying the small sulcus distal and posterior to the fibular styloid, while the femoral tunnel is placed proximal and posterior to the lateral epicondyle. Finally, the tibial tunnel for the popliteus is drilled from the midpoint between the tibial tuberosity and Gerdy’s tubercle, exiting at the popliteus sulcus."

Figure 4: Modified LaPrade Technique

Figure 3: LaPrade technique

Figure5: Anatomical Reconstruction of the PLC: Single-Tunnel Modified LaPrade Technique

Yoon and Stannard described similar methods .Franciozi described similar method with hamstring grafts.

Larsen et al described a fibular sling procedure which made the popliteal complex and LCL balanced . This method is commonly used as it is a simple procedure that provides good results.

For acute injuries, we prefer the Larsen technique utilizing a semitendinosus autograft; however, a gracilis graft is often sufficient to provide adequate stability.

Figure 6: Posterolateral corner reconstruction using the Larsen technique with a semitendinosus autograft.

YANG ET AL focused on reconstruction of the lateral collateral ligament and the popliteofibular ligament using a single hamstring autograft tendon.

The varus and external rotation were reduced significantly in the anatomic reconstruction group compared to the non-anatomic reconstruction group. The tibiofibular-based technique seems to be advantageous since it allows for anatomic reconstruction of the three important structures. However, this method is somewhat difficult to perform and may excessively limit the posterolateral motion. Yoon et al. reported that there was no significant difference between the group that had all three structures reconstructed and the group where the popliteus tendon was not reconstructed.

Despite a majority of studies presenting similar results comparing non-anatomic to anatomic PLC reconstructions, it is important to note that some biomechanical and clinical studies present superior results favouring anatomical PLC reconstructions.

In cases of bicruciate reconstruction associated with PLC the PCL should be tensioned and fixed first maintaining step off manually followed by the ACL and finally the PLC (fixation of the FCL at 30° of knee flexion applying a valgus force, followed by the remaining PLC structures at 60° of flexion and neutral rotation).

Postoperative Rehabilitation

Postoperative rehabilitation emphasises on protection of the reconstructed or repaired ligament structures initially and then gradually leads to muscle strengthening, functional exercises, and daily activities so that the patient may eventually participate in sports activities. Training is focused on first developing a muscular endurance base and then progressing to muscular strength and power development. Return to sports or activity is allowed once strength, stability, and knee range of motion becomes comparable with opposite side. (usually between 6 to 9 months and based on concurrent cruciate ligament or other ligament surgery).

In short PLC reconstruction is preferred compared to direct repair in surgical treatment of PLC injuries especially for chronic cases. Anatomic reconstruction is better compared to non-anatomic reconstruction. Currently, fibular-based reconstruction are preferred.

1. Seebacher JR, Inglis AE, Marshall JL, Warren RF. The structure of the posterolateral aspect of the knee. J Bone Joint Surg Am. 1982;64(4):536-41 ↑

2. LaPrade RF, Ly TV, Wentorf FA, Engebretsen L. The posterolateral attachments of the knee: a qualitative and quantitative morphologic analysis of the fibular collateral ligament, popliteus tendon, popliteofibular ligament, and lateral gastrocnemius tendon. Am J Sports Med. 2003;31(6):854–60. ↑

3. Bae, WH, Ha, JK, and Kim, JG (2010). Treatment of posterolateral rotatory instability of the knee. J Korean Knee Soc. 22, 1-10. ↑

4. Jackman, T, LaPrade, RF, Pontinen, T, and Lender, PA (2008). Intraobserver and interobserver reliability of the kneeling technique of stress radiography for the evaluation of posterior knee laxity. Am J Sports Med. 36, 1571-6. ↑

5. Bleday RM, Fanelli GC, Giannotti BF, Edson CJ, Barrett TA. Instrumented measurement of the posterolateral corner. Arthroscopy. 1998;14:489–94. doi: 10.1016/S0749-8063(98)70077-5. ↑

6. Fanelli GC, Larson RV. Practical management of posterolateral instability of the knee. Arthroscopy. 2002;18(2 Suppl 1):1–8. doi: 10.1053/jars.2002.31779. ↑

7. Hughston JC, Andrews JR, Cross MJ, Moschi A. Classification of knee ligament instabilities: part II. The lateral compartment. J Bone Joint Surg Am. 1976;58:173–9. doi: 10.2106/00004623-197658020-00002. ↑