Multiple ligament knee injuries: Clinical practice guidelines

Emergency room protocol

• All high-velocity knee injuries should be viewed with suspicion, as these may be spontaneously reduced knee dislocations with associated neurovascular complications

• Grossly deformed limbs should be gently repositioned. This may itself reduce the dislocated joint. Formal reduction of the joint should be avoided prior to confirming the radiographic status of the knee, unless the deformity is severely compromising the skin and soft tissues

• Vascularity and neurological status of the limb should be evaluated

• An immediate radiograph should be performed to confirm the diagnosis, understand the type of knee dislocation, and determine the presence of an associated fracture.

Immediate reduction

• A knee dislocation warrants reduction on an emergency basis preferably under anesthesia

• Traction followed by gentle extension is often all that is required to achieve reduction; however, this is dictated by the type and direction of dislocation

• Following reduction, a detailed examination under anesthesia of knee ligament stability should be performed. The Lachman’s test (ACL), posterior sag and posterior drawer test (PCL), valgus stress test (MCL), varus stress test (lateral collateral ligament [LCL]), and dial test (PLC) usually suffice in the acute setting. Tests which involve a greater degree of knee manipulation are unnecessary and best avoided

• If the knee is not grossly unstable and there is no indication for emergency intervention, the knee is immobilized in full extension in a long knee brace

• If the knee is extremely unstable, with a tendency to redislocate following reduction, then temporary external fixation may be warranted

• At times, the knee may require immobilization in flexion to avoid anterior tibial subluxation in anterior knee dislocations, or to avoid posterior tibial subluxation due to an incompetent posterior capsule.^[5]

Post-reduction protocol

• Post-reduction antero-posterior and lateral radiographs are mandatory to confirm joint reduction, identify avulsion fractures around the knee, and assess the need for associated fracture surgery

• MRI is the imaging investigation of choice in knee dislocations and helps determine the extent of injury to soft tissues, ligaments, and muscle-tendon units.^[6] MRI significantly aids in surgical planning and should be done early in the treatment process

• A CT scan may be useful for detailed characterization of fracture dislocations

• Stress radiography may be considered in select cases to document the extent of ligamentous laxity

• Regular monitoring of the distal pulsations and ankle brachial index (ABI) should be done in the acute setting for at least 72 h [Figure 2]. Although asymmetry of distal pulses, or fall of ABI below 0.9 is an absolute indication for angiography, many centers advocate routine vascular studies for any multiple ligament injured knee.

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Figure 2:

The ankle brachial index (ABI) is calculated by taking the ratio of (a) the systolic blood pressure in the injured limb at the ankle measured by a Doppler probe to (b) the systolic arterial brachial blood pressure in the uninjured upper limb. (ABI = systolic blood pressure in the injured limb/systolic blood pressure in the uninjured upper limb). Any fall of the ABI below 0.9 is an indication for angiography.

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Operative versus non-operative

Systematic reviews and meta-analyses^[22,23] reveal that surgical treatment results in better functional outcomes as compared to non-operative treatment with IKDC excellent and good results being 58% versus 20%, respectively. However, the mean range of motion (126° vs. 123°) and flexion loss (4° vs. 3°) is comparable in both the groups.

Early versus late surgery

Although the optimum time to perform MLKI surgery is a topic of debate, most surgeons prefer to perform this before 3 weeks to better identify anatomy before scarring and tissue necrosis affect outcomes. This is also essential for bony avulsion of ligaments. Patients undergoing surgery within 3 weeks of injury have been shown to have higher return to sports as compared to those who undergo surgery in the chronic stage (mean 51 weeks). However, the functional outcome scores reported are similar in both the groups.^[22]

Repair versus reconstruction

Although a systematic review found no difference between outcomes of repair and reconstruction for MLKI,^[22] PLC ligament repair is reported to have a higher failure rate than PLC reconstruction (37% vs. 9%), and return to sports is higher with reconstruction than repair (51% vs. 23%).^[24] Similarly, another study demonstrated that while the functional outcome scores were similar in ligament repair and reconstruction, patients who underwent repair had a greater flexion loss, posterior sag, and lower return to pre-injury activity level.^[25] However, en masse repair of lateral side structures in multi-ligament injuries has reported a 81% return to sports rate at a mean follow-up of 55 months with excellent functional outcomes.^[11] When allografts are available, it may be preferable to choose reconstruction over repair; however, when multiple autograft options are limited especially in acute KD 4 situations, it may be prudent to primarily repair the collateral ligaments and preserve autograft options for same stage or subsequent cruciate reconstruction.

Early simultaneous repair versus staged repair and reconstruction

While early surgery has been shown to give better results, there has been debate whether the procedure should be staged, or whether all ligaments should be repaired and reconstructed initially itself. Patients who undergo early simultaneous repair or reconstruction of three or more ligaments are at higher risk of knee stiffness after surgery. A systematic review has reported that staged repair gives better clinical outcomes (79.1%) than simultaneous ligament surgery in acute cases (58.4%) and chronic cases (45.5%), with no difference between KD3M and KD3L knees.^[26] In a study on staged reconstruction of multiligament injuries 70% patients had an IKDC score of A or B.^[27]

Staged surgery includes collateral ligament repair and/or reconstruction within 3 weeks of injury, followed by supervised rehabilitation for 4–6 weeks. Once knee range of motion is achieved beyond 120°, second stage arthroscopic bicruciate reconstruction is performed. The advantages of staged surgery include shorter operative time, decreased chances of infection, and decreased chances of arthrofibrosis.^[28,29] However, staging the reconstruction can potentially alter joint kinematics, and increase the risk of graft failure.^[30,31]

Tunnel placement and convergence

Tunnel placement in cruciate and collateral ligament reconstructive surgery is critical for anatomical restoration since this allows adequate stability and full range of motion. Tunnel malposition and graft impingement are the most common reason for failure in MLKI surgery. Surgeons should be aware of the exact anatomical insertion site for each ligament being reconstructed and plan tunnel orientation so as to avoid convergence or hardware. Vertical femoral tunnels in ACL reconstruction provide suboptimal rotational stability, whereas anterior tibial tunnels cause notch impingement and loss of extension. In PCL reconstruction, a high tunnel aperture on the posterior tibia will lead to suboptimal lever arm and potential graft failure.

Drilling multiple tunnels, especially in the distal femur, raises the potential risk of tunnel convergence which may result in graft damage, fixation impairment, and reconstruction failure. This is most often encountered in the lateral femoral condyle when performing ACL and PLC combined ligament reconstruction, in the medial femoral condyle when performing combined PCL and MCL ligament reconstruction, and in the tibia when performing combined bicruciate and collateral reconstruction. To prevent such complications, surgeons should be well versed with published data providing recommendations for reducing the risk of convergence in the multiple ligament reconstructed knee.^[35,36] In combined PCL-MCL reconstruction, the POL tunnel should be aimed to a point 15 mm medial to Gerdy’s tubercle to reduce risk of convergence with the PCL, and the sMCL tunnel should be aimed 30° distally to avoid convergence with the PCL. In combined ACL-PLC reconstructions, a 40° angulation in the axial plane and 0° in the coronal plane while performing the LCL and popliteus tunnels avoids tunnel convergence with the ACL tunnel. There are special aiming jigs available for extra-articular ligament reconstruction that can plan tunnel trajectories that avoid co-existing tunnels. In cases of doubt, and especially in revision situations, intraoperative fluoroscopy can be helpful for correct tunnel placement.

Graft tensioning sequence

The position of the knee and sequence in which each graft is tensioned and fixed is critical to achieve good stability and full range of motion in MLKI surgery. The tensioning sequence is a topic of debate, and different sequences have been reported in the literature. The sequence we normally follow in tensioning and fixing grafts for multiple ligaments reconstruction, and the rationale for the same is: (1) PCL double bundle graft passed, (2) ACL single-bundle graft passed with suspensory femoral fixation, (3) PCL double-bundle grafts fixed on femur and tibia, (4) PLC grafts passed and fixed, and (5) ACL tensioning and tibial fixation (6) sMCL and POL grafts passed and fixed.^[37] The PCL is tensioned and fixed first, since this is the central pillar of the knee, and fixing this reduces the knee, restores the central pivot with tibial step-off, and achieves the basis for anatomical reduction of subsequent ligaments. If a single-bundle graft is used, tension the graft at 90°, whereas if a double-bundle graft is used, tension the AL bundle at 90°, and the PM at 0°. With a very unstable knee, or especially with anterior knee dislocations, anatomical reduction should be confirmed with a C-arm image prior to PCL graft fixation. The PLC is fixed next, since integrity of PLC is a critical prerequisite for tibiofemoral rotational orientation when an ACL graft is tensioned. In a PLC deficient knee, tension during fixation of the ACL graft increases external tibial rotation of the tibia.^[38] We normally fix both the femoral LCL and femoral popliteus first, and the tibial tunnel last. The knee is kept in 30° of flexion with valgus force during tightening and fixation. The already passed ACL with femoral suspensory fixation is fixed on the tibia next. The graft is tensioned at 30° of knee flexion in neutral rotation. This achieves the 4-bar cruciate linkage system. The sMCL and POL are tensioned and fixed last. The sMCL is tensioned in 30° of flexion with varus corrective force to close knee joint of any possible medial opening. The POL is tensioned and fixed in full extension because this is when the POL is tightest in a normal knee. Although there is a lack of scientific data to back this exact sequence, to us, this is the most logical and scientific way to go about it.

Rehabilitation

MLKI are complex and challenging pathologies to rehabilitate due to the extensive soft tissue damage and the different injury patterns that can occur. An appropriate diagnosis and treatment of all the damaged structures is vital for a successful outcome. Reconstruction of all injured ligaments and repair of soft-tissue structures such as the meniscus or cartilage are recommended to aid in early mobilization and to avoid joint stiffness or graft failure. A well-crafted rehabilitation plan after a MLKI reconstruction should focus on graft protection and functional outcomes including regaining motion, strength and function. Post-operative recovery after MLKI surgery typically requires 9–12 months of rehabilitation before returning to full activities. This allows proper time for the grafts to incorporate and to heal in order to prevent reconstruction graft failure. Use of a dynamic PCL brace in the rehabilitation period and in the 1^st year of returning to activities is recommended to protect the reconstruction.