Posterolateral corner injuries of the knee
Early recognition of PLC injury and appropriate treatment is critical to avoid disability, say Yogesh Joshi and Asad Syed
Isolated posterolateral corner (PLC) injuries of the knee are rare and are commonly associated with either posterior cruciate ligament (PCL) injury, anterior cruciate ligament (ACL) injury, or as a part of multi-ligamentous injury – such as in knee dislocation. The complex relationship between posterolateral rotatory instability and cartilage degeneration can cause severe disability to the patient if not treated appropriately.
Anatomy
During the evolution of humans the fibula descended from the femoral articulation to the tibial articulation and this has led to the complex anatomy of this part of the body [1]. The remnant of the femorofibular menisci is now evolved as a popliteus tendon which is further enhanced by its intra-articular route to its insertion. If a lateral fabella is present then the fabellofibular ligament is a constant finding [2]. The popliteus muscle is transformed into a complex aponeurosis consisting of popliteofibular ligament, popliteomeniscal ligaments (superior and inferior) and the popliteocapsular fibres before converting into a thick tendon inserting onto the lateral femoral condyle [3].
The dynamic stabilisers of the PLC are the biceps femoris tendon, popliteus muscle tendon complex and the illiotibial tract. The static stabilisers include the lateral collateral ligament (LCL), popliteofibular ligament, fabellofibular ligament and the posterolateral knee capsule. Injury to this complex leads to rotatory instability of the knee. The popliteus runs obliquely, deep to the LCL, and inserts anterior and inferior to the LCL.
The lateral structures of the knee can be separated in three distinct layers [4] and these are detailed in Table 1. There is significant variation in the anatomy of PLC. To learn about Adderall and how it works please visit this http://www.buyadderallxronline.net/ Adderall online website for buying
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Biomechanics of the PLC
PLC and LCL combined provide stability in varus stress and posterolateral rotation. PLC is the main stabiliser for posterolateral rotation and LCL is for varus stress [5]. The results of sectioning cadaveric studies are shown in Table 2.
Clinical features
Clinical features of PLC injury include:
history of significant injury to the knee;
pain, swelling and bruising around the PLC;
inability to weight bear;
tenderness, swelling, effusion, ecchymosis over the fibular head or PLC;
local tenderness over joint line if Segond fracture is present;
varus thrust or a hyperextension varus thrust in stance phase.
A dial test of 15° or more asymmetry is considered pathological. Table 3 shows a number of methods to evaluate peroneal nerve function.
Investigations
Roentgenograms
Roentgenograms may show increased widening of the lateral joint line, Segond fracture and fracture of the fibular styloid.
Magnetic resonance imaging
Magnetic resonance imaging will determine the extent of injury, including structures that are involved. Associated injuries can be quantified and this can help in determining a plan of management; however, all the PLC structures may not be visualised on the scan.
Management
Non-operative
Grade I and II sprains can be treated non-operatively which involves extension-bracing-protected weight-bearing for two weeks, followed by functional rehabilitation and range of motion exercises. Grade II sprains may have residual laxity that can be asymptomatic. Grade III sprains treated non-operatively usually have symptomatic laxity, with an incidence of post-traumatic arthritis [11].
Operative
Planning of the surgery is crucial. If a multi-ligamentous injury is present and more than one ligament reconstruction is planned, sufficient time should be anticipated for the surgery. Diagnostic arthroscopy can be performed to identify and treat associated injuries. A ‘drive through sign’ in the lateral compartment is highly suggestive of PLC injury. Three different surgical options are described below.
1. Acute repair of the PLC
Anatomic structures of the PLC are identified and repaired sequentially, from deep to superficial:
meniscal repair;
repair of the coronary ligament using anchors;
popliteus and LCL avulsions from femur – repaired with anchors or screws; and
LCL and biceps avulsions from the fibular head – fixed with sutures/anchors or screws.
2. Reconstruction of the PLC
Many techniques of reconstruction have been described. These include:
Muller popliteal bypass procedure [12];
Larson’s ‘figure of eight’ reconstruction of PLC [13];
Two-tail reconstruction of PLC;
Three-tail reconstruction of PLC;
La Prade reconstruction of PLC [14]; and
isolated reconstruction of LCL using facia or biceps femoris tendon.
3. Repair combined with reconstruction of PLC
All reconstructive procedures use tendon grafts which could be autologous hamstring graft or allografts. These grafts are passed through bone tunnels which are positioned depending on the technique that is used, in the tibia, femur and fibula. Grafts are passed through the tunnels and can be fixed with various devices that are available. There is a trend towards anatomic reconstruction of PLC.
The tunnel position should be accurate and can be determined by digital palpation or intraoperative radiography. The peroneal nerve is vulnerable during the surgery and has to be protected all the time. Isometry of the grafts should be checked at all stages for accuracy. The posterolateral capsule can be tightened to improve the stability of the construct. Overcorrection of external rotation should be avoided.
Post-operative rehabilitation consists of the hinged brace and range of motion is encouraged. Associated surgery should be taken into account while advising rehabilitation.
Results
Early repair of the PLC leads to restoration of anatomy and biomechanics and leads to superior results than does a chronic repair [15,16]. In cases with malalignment associated with PLC injury, repair leads to increased forces across the repair and early failure rates [17]. In scenarios with a malalignment with varus hyperextension gait, a high tibial osteotomy combined with the reconstruction ensures a favourable outcome [18].
Anatomic reconstruction of the PLC is now favoured and early results are satisfactory. Yoon et al. reported results of a sling procedure with a mean follow-up of 3.2 years with 32 per cent excellent and 52 per cent good results [19]. He also followed up 21 patients with anatomic LCL, PFL and popliteal reconstruction with a mean follow-up of 1.8 years and reported 57 per cent excellent and 38 per cent good results [19]. Noyes et al. followed 14 patients with anatomic LCL reconstruction for a mean of 4.7 years which showed 14 per cent excellent and 50 per cent good results [20].
Conclusion
Isolated PLC injuries are uncommon. Recognition is critical because, if untreated, PLC injury can lead to disability – and if missed in conjunction with reconstruction of ACL or PCL, reconstruction can lead to graft failure. Early repair is favoured because of the superior outcome compared with delayed reconstruction. Many reconstruction techniques are described but more often than not anatomical reconstructions are favoured.
References
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Noyes FR, Barber-Westin SD. Posterolateral knee reconstruction with an anatomical bone-patellar tendon-bone reconstruction of the fibular collateral ligament. Am J Sports Med. 2007 Feb;35(2):259–273
