- Short report
- Open Access
- Open Peer Review
A modified Larson’s method of posterolateral corner reconstruction of the knee reproducing the physiological tensioning pattern of the lateral collateral and popliteofibular ligaments
© Niki et al.; licensee BioMed Central Ltd. 2012
- Received: 9 July 2011
- Accepted: 13 June 2012
- Published: 13 June 2012
Consensus has been lacking as to how to reconstruct the posterolateral corner (PLC) of the knee in patients with posterolateral instability. We describe a new reconstructive technique for PLC based on Larson's method, which reflects the physiological load-sharing pattern of the lateral collateral ligament (LCL) and popliteofibular ligament (PFL).
Semitendinosus graft is harvested, and one limb of the graft comprises PFL and the other comprises LCL. Femoral bone tunnels for the LCL and popliteus tendon are made at their anatomical insertions. Fibular bone tunnel is prepared from the anatomical insertion of the LCL to the proximal posteromedial portion of the fibular head, which corresponds to the insertion of the PFL. The graft end for popliteus tendon is delivered into the femoral bone tunnel and secured on the medial femoral condyle. The other end for LCL is passed through the fibular tunnel from posterior to anterior. While the knee is held in 90 of flexion, the graft is secured in the fibular tunnel using a 5 mm interference screw. Then, the LCL end is passed into the femoral bone tunnel and secured at the knee in extension.
Differential tension patterns between LCL and PFL is critical when securing these graft limbs. Intrafibular fixation of the graft using a small interference screw allows us to secure these two graft limbs independently with intended tension at the intended flexion angle of the knee.
- Posterolateral corner
- Lateral collateral ligament
- Popliteofibular ligament
- Reconstructive technique
Generally, posterolateral corner (PLC) reconstruction is performed to treat chronic posterolateral instability in patients with PLC injury. However, consensus has been lacking as to how to reconstruct the PLC. Abundant surgical procedures for PLC have been accumulated, and can be broadly divided into two types: anatomical and non-anatomical. Non-anatomical reconstructions include biceps tenodesis [1, 2], arcuate complex , proximal bone block advancements , and extracapsular iliotibial band sling . However, current techniques have shifted to more anatomical reconstruction of the three major functional components of the PLC: the lateral collateral ligament (LCL), popliteofibular ligament (PFL), and popliteus tendon [6–9]. We have developed a new reconstructive technique for PLC based on Larson’s method , which reflects the physiological load-sharing pattern of the LCL and PFL. This technique is less invasive and less technically demanding than current anatomical reconstructive techniques.
The patient is positioned supine on the operating table with an arthroscopic leg holder, after precise diagnosis of posterolateral instability and concomitant injuries. Arthroscopy is performed to identify lateral drive-through sign as well as concomitant disruption of the anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL). If the decision has been made to reconstruct either of the cruciate ligaments, this should be performed first. After cruciate ligament reconstruction, PLC reconstruction is initiated. Semitendinosus (ST) tendon is normally harvested ipsilaterally using a smooth tendon stripper, but if ipsilateral ST tendon is planned for use as either PCL or ACL graft, the graft for PLC is harvested from the contralateral ST tendon. The appropriate length of ST graft for PLC is 16–19 cm, which typically reflects the distance between the femoral and fibular insertions of the PLC plus an additional 30 mm, as both ends of the graft require at least 15 mm each, corresponding to the insertion into bone tunnels. One limb of the graft comprises PFL and the other comprises LCL. A baseball glove suture using FiberWireTM (Arthrex, Naples, FL) is carried used at the both ends of the graft, and one end of the popliteus tendon is connected to an EndobuttonTM (Smith & Nephew, Memphis, TN), then placed within antibiotic-soaked gauzes and set aside for later use.
The postoperative program is normally dictated by the cruciate ligament reconstruction, particularly for PCL reconstruction. The affected knee joint is immobilized in a hinged knee brace locked in extension for 2 weeks postoperatively. Range of motion (ROM) exercises are initiated using a continuous passive motion (CPM) device and are permitted from 0° to 90° of flexion during weeks 3 and 4. From week 4 on, >90 ° of flexion is permitted. The knee is maintained at 0° except during ROM exercises. A hinged functional brace is used for 3 months postoperatively. Partial weight-bearing with the brace locked in extension is initiated at 2 weeks postoperatively, with gradual progression to full weight-bearing by 4 weeks postoperatively.
Written informed consent was obtained from the patient for publication of this report and any accompanying images.
Injuries to the PLC of the knee can result in severe disability due to both instability and articular cartilage degeneration. These injuries do not commonly occur in isolation, but are usually found in the setting of other injuries, such as ACL or PCL ruptures. Most authorities recommend surgical reconstruction of the PLC in combination with ACL or PCL reconstruction [11–13], since solitary reconstruction of these cruciate ligaments may results in high in situ force in the graft and concomitant PLC reconstruction potentially exerts protective effects on early failure of the cruciate ligament reconstruction.
Historically, numerous techniques for PLC reconstruction have been described, but which technique represents the best method for reconstructing physiologically functional PLC remains controversial. According to the distal insertion site of grafts for PLC, two surgical techniques are available: fibular-based techniques and combined tibial-fibular-based techniques. Larson’s procedure was one of the first fibular-based techniques, and reconstructs the LCL and PFL with distal insertion sites located at the fibula . Larson’s procedure is still widely accepted due to the virtues of being less technically demanding and offering promising clinical results. Our technique was developed based on Larson’s methods, and has been modified to reproduce a physiological tension pattern for LCL and PFL using a single ST autograft.
Tibial-fibular-based techniques have gained increasing attention due to their nature of more anatomical reconstruction capable of reconstructing all three major PLC components at each precise insertion site, but certain investigations have reported that these techniques potentiate overconstraint of posterolateral instability [14, 15]. We believe that force distribution between the popliteus complex (PFL and popliteus tendon) and LCL is critical and should be taken into careful consideration when securing these grafts intraoperatively. A previous biomechanical study has reported that the magnitude and distribution of in situ force between the LCL and popliteus complex are affected by knee flexion angle and magnitude of posterior tibial load . LCL represents a larger in situ force near full extension, decreasing with increasing flexion angle of the knee, which may explain the clinical observation that LCL is taut near full extension and relatively lax with the knee in flexion. In contrast, the popliteus complex represents a larger in situ force with the knee in flexion than with the knee in extension . This force distribution pattern was employed in our modified Larson’s procedure, which may thus mimic the physiological load-sharing pattern between LCL and the popliteus complex and avoid overconstraint of external and varus rotations of the tibia. Actually, LCL is secured at full extension with 10 N, whereas the PFL is secured at 90° of knee flexion with 10 N in our procedure. Particular emphasis in our technique is placed on intrafibular fixation of the ST graft using a small interference screw, which allows us to secure two graft limbs for LCL and PFL independently with intended tension at the intended flexion angle of the knee, achieving differential tension patterns for LCL and PFL.
Although favorable short-term results of tibial-fibular-based techniques have been reported [7, 8], further studies documenting long-term clinical results are warranted to determine whether tibial-fibular-based techniques represent a standard optimal procedure for PLC reconstruction. At present, controversy remains as to whether all three components of the PLC should be reconstructed. Recent studies have postulated several drawbacks for tibial-fibular-based techniques, including increased technical difficulty and potential overconstraint of external and varus rotations of the knee [14, 15]. Veltri and Warren have advocated reconstruction of PFL and LCL as sufficient to adequately control posterolateral instability such as posterior tibial translation and external and varus rotations [17, 18], which may support our modified Larson’s method. Moreover, as the popliteus constitutively possesses a muscle belly and acts as a dynamic ligament, it is disputable that popliteus is reconstructed as a static ligament using ST tendon. Our modified Larson’s method has advantages of technical simplicity and reproduction of a more physiological load-sharing pattern among grafts as compared with previously described reconstructive procedures and can offer an acceptable choice to treat chronic posterolateral instability. Further follow-up is needed to ensure that our reconstruction techniques of LCL and PFL are suitable to restore posterolateral instability of the knee.
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