Posterolateral Corner Injury PLC/LCL
Posterolateral corner injury PLC/LCL
Posterolateral Corner (PLC) knee injuries usually are traumatic in origin that are associated with instability of lateral side of knee. These injuries are commonly associated with a concomitant ACL or PCL ligament injury, association with PCL is more common than ACL.
Posterolateral corner injury comprises nearly 7-16% knee ligament injuries. Isolated posterolateral corner injury are only 28% of all PLC injuries, usually combined with cruciate ligament injury (PCL > ACL).
Etiology and Mechanisms of injury:
- Direct blow to anteromedial aspect of knee
- Varus blow over a partially flexed knee
- Contact and noncontact hyperextension injuries
- External rotation twisting injuries
- Dislocation of knee joint
Associated injuries include common peroneal nerve palsy, vascular injury etc.
Anatomy of Posterolateral Corner injury:
There are three major static stabilizers over lateral side of the knee.
1) Lateral Collateral Ligament (LCL)
The LCL is the primary varus stabilizer at 0° and 30°, and it also provides stability against external rotation and internal rotation of tibia. The origin of the LCL is located 1.4 mm proximal and 3.1 mm posterior to the lateral femoral epicondyle and is attached to the lateral aspect of the fibular head.
2) Popliteus Tendon (PLT)
Popliteus is a small, flat, triangular shaped muscle of the proximal leg. The popliteus muscle with popliteofibular ligament forms a part of the posterolateral corner of the knee. It is one of the deeper muscles of the knee joint which forms the floor of the popliteal fossa.
3) Popliteofibular Ligament
It originates from the musculotendinous junction of the popliteus muscle and inserts distally at the tip of the fibular styloid process.
Function of PLC:
Popliteus has synergistic action with the PCL and prevents external rotation of tibia, varus, and posterior translation of tibia. Popliteus muscle and popliteofibular ligament works better with knee in flexion to resist external rotation.
LCL is primary restraint to varus stress at 5° and 25° of knee flexion.
Presentation and Symptoms of PLC Injury:
Patients have symptoms of instability particularly during knee in full extension, difficulty with using stairs, pivoting, and cutting activities etc.
On physical examination, patient walks with varus thrust or hyperextension thrust gait, stands with varus alignment.
On varus stress – varus laxity at 0° indicates both LCL and cruciate (ACL or PCL) injury and varus laxity at 30° indicates LCL injury.
Some patients may have common peroneal nerve injury and presents with altered sensation to dorsum of foot and weak ankle dorsiflexion.
Clinical tests for Posterolateral Corner injury:
A) External rotation recurvatum test
The clinician grasps the great toe and lifts the leg off the table. If PCL is torn, the tibia externally rotates and slides posteriorly, if it is associated with injury to the posterolateral corner, the result of the will be more conspicuous, because of posterolateral instability.
The great toes are held by the clinician and both legs are raised simultaneously. A positive test results in hyperextension, external rotation of the tibia and results in apparent tibia vara of the affected limb.
B) Posterolateral drawer test
With the knee in 90° of flexion, the foot is rotated externally by 15°. Posteriorly directed force is applied to the proximal tibia and degree of subluxation is compared to normal leg. A positive posterolateral drawer test usually indicates a popliteal tendon or PFL injury.
C) Dial test:
This test is performed at 30 and 90° of knee flexion. Positive test at 30° knee flexion suggests PLC injury, while at 90° knee flexion indicates combined PCL and PLC injury.
The medial border of the foot in its neutral position is used as a reference point for external rotation and it is measured by noting the foot-thigh angle.
In addition, the tibial plateaus are palpated to determine their relative positions compared with the femoral condyles. This determines whether the external rotation is caused by the lateral tibial plateau moving posteriorly (posterolateral instability) or by the medial plateau moving anteriorly (anteromedial instability).
More than a 10-degree increase in external rotation compared with that of the contralateral side at 30 degrees of knee flexion, but not at 90 degrees, indicates an isolated injury to the posterolateralcorner. An increase in external rotation of more than 10 degrees compared with that on the contralateral side at both 30 and 90 degrees of knee flexion indicates injury of both the posterior cruciate ligament and the posterolateral corner.
D) Reverse pivot shift test
With knee at 70–80° of flexion and foot externally rotated, posterior sag of tibia is noted due to posterior subluxation. The leg is then slowly brought into full extension as a valgus force is applied. With this maneuver performed slowly the knee is felt to reduce at about 20° of flexion.
This sign is present in patients with acute or chronic posterolateral instability of the knee. The lateral tibial plateau shifts from a position of posterior subluxation to a position of reduction as the flexed knee is extended under valgus stress and with the foot held in external rotation. The plateau subluxates again as the knee is flexed in the opposite manner.
Because it describes a shift of the lateral tibial plateau in the opposite direction from the true joint shift, it is called the reverse pivot shift. A significantly positive reverse pivot shift suggests that the posteriorcruciate ligament, the arcuate complex, and the LCL are all torn.
Posterolateral corner injury classification
Modified Hughston classification:
- 0-5 mm of lateral opening on varus stress
- 0°-5° rotational instability on dial test
- Sprain, no tensile failure of capsuloligamentous structures
- 6-10 mm of lateral opening on varus stress
- 6°-10° rotational instability on dial test
- Partial injuries with moderate ligament disruption
More than 10 mm of lateral opening on varus stress, no endpoint
more than 10° rotational instability on dial test, no endpoint
Radiographs may show avulsion fracture of the fibula (arcuate fracture) or femoral condyle.
Bilateral varus stress x ray in 20° flexion, if it shows side-to-side difference of 2.7-4 mm, it indicates isolated LCL tear. If side-to-side difference is more than 4 mm, it is indicative of PLC injury.
Long-leg standing radiographs are required in cases of chronic PLC injury to evaluate alignment. Secondary varus is seen in cases of LCL deficiency with increased lateral opening.
It is the best modality, surgeon always looks for injury to the LCL, popliteus, and biceps femoris tendon. In acute injuries impact lesions like, bone bruising of medial femoral condyle and medial tibial plateau may be seen. Coronal oblique views with thin-slice through the fibular head are best at visualizing the PLC structures.
- knee immobilization in full extension for 4 weeks followed by rehabilitation
- indicated in – grade I PLC injury, isolated mid-substance grade II injury
- initially hinged knee brace locked in extension for 4 weeks
- followed by progressive functional rehabilitation
- quadriceps strengthening
- return back to sports usually in 8 weeks.
A) PLC repair
Indicated in isolated acute grade II PLC avulsion injuries.
Techniques: repair of LCL, popliteus tendon and/or popliteofibular ligament should be performed if structures can be anatomically reduced to their attachment site.
If it is not reducible, PLC reconstruction has to be done.
If repair is tenuous, augmentation of PLC has to be done with free graft. We, the Cruciates team prefer to use Fiber Tape with graft for PLC augmentation.
Avulsion fracture of fibular head is repaired with screws or suture anchors.
B) PLC hybrid reconstruction and repair
- grade III midsubstance injuries
- avulsion injuries where repair is not possible or tissue is of poor quality.
- main goal is to reconstruct LCL and the popliteofibular ligament using a free tendon graft, we prefer hamstring tendon graft for PLC reconstruction.
C) Fibular-based reconstruction (Larson method):
It is done as mini open procedure, soft tissue graft is passed through bone tunnel in fibular head, limbs are then crossed to create figure-of-eight and fixed to lateral femur to a single tunnel.
D) trans-tibial double-bundle reconstruction
Split achilles tendon is fixed to isometric point of the femoral epicondyle, one tibia-based limb and one fibula-based limb. Fibular limb is fixed to the fibular head with a bone tunnel and transosseous sutures are used to reconstruct the LCL. Tibial limb is brought through the posterior tibia to reconstruct the popliteofibular ligament.
E) LaPrade anatomic reconstruction
Two soft tissue grafts are used
- graft #1 is used to reconstruct the LCL and PFL, proximal attachment site is at anatomic femoral insertion of LCL attachment, with graft passing through the fibular head lateral to medial docking into the tibial tunnel posterior to anterior with graft #2.
- graft #2 reconstructs the popliteus tendon, proximal attachment site is at the anatomic popliteus tendon attachment docking into the tibial tunnel posterior to anterior with graft #1.
F) PLC reconstruction with internal brace FiberTape
First minimally invasive incision is made and proper soft tissue dissection done, windows are created. The Fibular, Tibial, and Femoral Collateral Marking Hooks are used for anatomic precision and osseous measurements when drilling the appropriate reconstruction tunnels. Using the Femoral Collateral Marking Hook in conjunction with the Parallel Drill Guide will increase the efficiency of anatomic femoral drilling by significantly reducing convergent tunnels and allowing for accurate guide pin placement at multiple incremental distances. During tunnel creation the spooned ends of the Collateral Ligament Retractor are used to protect the neurovascular structures and the Collateral ligament rasp is used to chamfer the aperture of the completed reconstruction tunnels. The prepared grafts are then passed with the use of Fiber Wire and tensioned into the desire position prior to graft fixation.
Post operative rehabilitation
- Hinged knee brace, non-weight bearing for 6 weeks
- Range of motion protocols varies between surgeons, some advice for passive ROM immediately 0-90°, others immobilize for 2 weeks then starts passive mobilization.
- At 6 weeks, weight bearing and closed-chain strengthening exercises start.
- return to sports takes 6 to 9 months
Operative treatment has improved outcomes as compared to nonoperative treatment. PLC repair has higher failure rate than reconstruction, particularly for mid-substance injuries, but also for soft tissue avulsions. Outcomes are always better with early treatment. Reconstructions have less revision rates and better outcome scores than ligament repair
Some cases may also require High tibial osteotomy as additional procedure. It can be done in same sitting or as a second stage procedure.