The first step in preoperative planning is recognition of the injury. Knee dislocations most frequently occur as a result of high-energy trauma such as motor vehicle or motorcycle collisions, with concomitant injuries that may draw attention away from the knee. Ipsilateral extremity fractures are very common and make performing a knee
examination in the trauma room very difficult. The key to making the diagnosis is to have a high index of suspicion. An effusion may or may not be present depending on the degree of damage to the joint capsule. However, any knee with an effusion should be examined thoroughly. Similarly, abrasions and contusions around the knee may indicate significant trauma to the joint. The condition of the soft-tissue envelope should be documented because it may influence the timing of surgical repair. Additionally, radiographs of the knee may demonstrate subtle clues such as avulsions of flecks of bone or asymmetry between compartments of the knee. Finally, an examination under anesthesia (EUA) is the “gold standard” test to diagnose a knee dislocation and to classify the torn structures.

Patients who present with the knee dislocated should have the joint reduced as quickly as possible. Normally, longitudinal traction on the lower leg produces a rapid and easy reduction. Occasionally, patients will present with an irreducible knee, most frequently as a result of the femoral condyle “button holing” through the capsule or muscle. This is frequently accompanied by puckering of the skin when a reduction is attempted. If the knee does not reduce easily, the patient should be taken to the operating room for a reduction under anesthesia expeditiously.

In a patient with a suspected ligamentous injury to the knee, a careful and gentle knee exam should be performed. The anterior cruciate ligament (ACL) is best examined with the Lachman’s test with the knee in approximately 30 degrees of flexion. The posterior cruciate ligament (PCL) should be examined with a posterior drawer test. It is important to make certain the knee is not posteriorly subluxed prior to the examination, as that can yield a false diagnosis of a torn ACL rather than a torn PCL. Varus and valgus laxity testing should be done with the knee in full extension and 30 degrees of flexion. Instability in extension implies both the PCL and one of the lateral collateral ligaments is torn. The dial test performed at both 30 and 90 degrees of flexion can identify a posterolateral corner (PLC) tear with damage to the popliteus muscle unit. Finally, an anterior drawer that is increased with the knee in external rotation can differentiate a torn posteromedial corner (PMC) from a simple medial collateral ligament (MCL) tear.

It is critical to perform a careful neurologic and vascular examination of the leg, in addition to the assessment knee stability. The vascular examination must include palpation of the distal pulses, which is the best marker of clinically significant vascular injury. Popliteal artery injuries occur in 5% to 15% of patients with knee dislocations and are limb-threatening injuries. There is strong support in the literature for a “selective arteriography” that uses a careful vascular examination as the trigger for obtaining vascular imaging studies. If the vascular examination is normal, the patient should be admitted for observation with serial clinical examinations. If the vascular status is abnormal, vascular surgery consultation and additional studies are warranted. If there is any doubt regarding the vascular status of the patient, a magnetic resonance angiogram (MRA) or classic contrast angiography should be obtained. MRA is usually adequate and is preferred in stable patients who can undergo this procedure in the acute setting. Otherwise, arteriography is utilized. If the imaging study documents an intimal tear, the patient should be evaluated by a vascular surgeon. The contemporary treatment of a non-flow limiting intimal tears is observation and careful serial vascular examinations. Additional physical examination tests such as ankle brachial index may be performed in equivocal cases, but are not necessary in most patients.

A detailed neurologic examination of the extremity should also be performed and documented. Peroneal nerve injuries due to traction at the fibular head occur in up to 20% of patients and are often a source of longterm disability. It is important to document neurological injuries prior to surgical reconstruction. It may be beneficial to perform a peroneal nerve neurolysis at the time of knee ligament reconstruction if there is a traction injury. While much less common, tibial nerve injuries do occur, and the status of that nerve should also be documented prior to surgical intervention.

In all patients with trauma around the knee, an anteroposterior (AP) and lateral radiograph should be obtained. These should be studied carefully as they frequently yield subtle signs of a ligament knee injury such as bony flecks or avulsions, asymmetry of the medial or lateral compartments, subtle subluxation, or rim fractures. If the physical examination documents ligamentous instability, an MRI scan should be obtained when the patient is stable as a supplement to the physical examination. The MRI scan helps identify the pathoanatomy,
the location, and pattern of injury, provides a good evaluation of the menisci, and can confirm the exact location of the neurovascular bundle relative to the knee joint.

The timing of surgical repair in patients with a knee dislocation is controversial. Open dislocations require urgent reduction, irrigation and débridement, and placement of a spanning external fixator. Similarly, patients with irreducible dislocations should be taken to the operating room as soon as an operating room becomes available. In patients with closed injuries without vascular embarrassment, the timing of definitive ligament repair is debatable. The condition of the soft-tissue envelope as well as other associated injuries is a key factor in determining the ideal timing for reconstruction. My preference is to treat associated fractures within 1 week of injury and reconstruct the ligaments in the 3rd or 4th week following injury. I place the vast majority of patients in a simple knee immobilizer prior to reconstructive surgery. The exceptions are open injuries and grossly unstable knees where a spanning external fixator is employed for 3 to 4 weeks prior to reconstruction.

Reconstruction of a dislocated knee is a complex procedure that requires careful preoperative planning in order to maximize results. It is important to understand which structures are torn prior to surgery so that appropriate equipment and allografts are available. An EUA is always performed at the beginning of the case to confirm the findings on physical examination and correlate it with the results of the MRI. The sequence of the reconstruction is important, particularly if a hinged external fixator will be used in conjunction with the reconstruction.

My surgical tactic includes a diagnostic arthroscopy at the outset of the case to document ligament injury and assess the knee for meniscal and articular cartilage injury. After addressing those injuries, the notch is débrided of torn ligament remnants, and the PCL reconstruction is performed when disrupted. Following repair of the PCL, a reference wire for a hinged external fixator (if necessary) and the femoral pins must be placed prior to further reconstruction. Next, the PMC and PLC are constructed. All tunnels are drilled and allografts placed prior to tightening any of the PMC or PLC reconstructions. Normally, the PCL is tensioned first, followed by the two corners. If a hinged external fixator is used, it is placed on the femoral pins after the skin is closed, and the three tibial pins are drilled and placed as the final step of the procedure. I prefer to delay reconstruction of the ACL for 6 weeks or longer in the majority of cases. This allows rehabilitation to be focused on the PCL initially, shortens an already long case, and allows the surgeon to “jump start” knee motion at the time of ACL reconstruction if the patient is having difficulty with motion.

The surgical procedures described later in this chapter are my preferred techniques. I use an inlay double-bundle PCL reconstruction in virtually all cases. If the patient has an adequate sized femur, I combine it with a doublebundle ACL reconstruction 6 weeks later. There is no compelling clinical evidence that double-bundle reconstructions are superior to their single-bundle counterparts. However, both seek to reconstruct the precise anatomy and both provide additional rotational stability. This may be more important in a patient who has a PCL injury as well as medial and lateral corner damage than in a patient with an isolated cruciate ligament injury. However, in patients with complex multiligament knee injuries, there is limited bone stock available for tunnel placement, and they must be placed perfectly when performing combined ACL and PCL reconstructions using double-bundle techniques. I routinely use drill guides that improve tunnel placement as “free-hand techniques” are often unreliable.

Another controversy is whether to repair the PMC and PLC primarily if adequate tissue is present. Recent studies have shown that reconstruction is superior to primary repair for tears of the PMC and PLC. As a result, I routinely reconstruct these areas. If the patient has reasonable tissue that might be amenable to repair, it is repaired and then reconstructed in a belt and suspenders technique. The time necessary to complete a complex multiligament knee injury is approximately 4 hours, and there is a long learning curve.

General, spinal, or regional anesthesia can be utilized for reconstruction of a knee dislocation. These are lengthy and painful procedures, and an indwelling epidural catheter or a femoral nerve block helps alleviate postoperative pain and is strongly encouraged. Because these cases frequently take 3 to 4 hours to complete, a Foley catheter is advisable. The need for arterial lines, central venous pressure (CVP) lines, or a Swan-Ganz catheter is determined by the age, physiologic status of the patient, and associated injuries. Patients are given 1 to 2 g of a first-generation cephalosporin and are given an additional 1 g if the surgery takes longer than 4 hours.

The PCL is the cornerstone of the knee and should be reconstructed and tightened prior to any of the other ligaments in most cases. Historical results of PCL reconstructions have been very disappointing, with many
patients having mild to moderate residual posterior laxity following reconstruction. There are two potential causes for the unsatisfactory results associated with PCL reconstructions. The first is that the PCL has two functional bundles: the anterolateral (AL) and the posteromedial (PM). They are named for their position on the femur and tibia, respectively, when the knee is in extension. The AL bundle is tight with the knee in 70 to 80 degrees of flexion, while the PM bundle is tight with the knee in approximately 15 degrees of flexion. Reconstructing both ligaments may improve stability throughout the entire range of motion of the knee. The second potential cause of postoperative instability following ACL reconstruction is the sharp angle the graft must turn around the back of the knee when a transtibial reconstruction technique is used. The angle has been called the “killer turn,” and may be responsible for graft stretching and/or failure. The anatomic PCL reconstruction I will detail below addresses both of these issues and yields a consistently stable reconstruction.

The patient is positioned supine on the operating table. After an EUA confirms the diagnosis, standard arthroscopy portals are created, and the knee is examined. Arthroscopic portions of the procedure are completed by dropping the leg off the side of the table or using a lateral post if necessary. Particular care should be taken to evaluate both menisci as well as both femoral condyles for articular cartilage injuries. Since many of these injuries result from impact between a flexed knee and the dashboard of a vehicle, the femoral condyles are at particular risk of articular cartilage damage. Once that assessment is complete and the articular cartilage and meniscus have been addressed, attention is turned to the PCL. The notch is débrided of the remnants of the torn ligament, while noting the femoral footprint of the native PCL.

The femoral tunnels are drilled using a guide that drills from the outside in through the medial femoral condyle. Advantages of using the “outside in” guide include precise placement of the tunnel with no constraints based on the patient’s anatomy and eliminating a “killer turn” at the femoral tunnel. The AL guidewire is drilled first and should be placed high in the notch 8 to 10 mm back from the articular cartilage. After marking the skin with the guide, a stab incision is made over the medial femoral condyle, and a drill tip-guide pin is drilled through the condyle and into the notch. After confirming the position in the notch, the process is repeated for the PM tunnel. The PM tunnel should be placed immediately inferior to the AL tunnel, with a minimum 4- to 5-mm bone bridge between the two tunnels. The diameter of the two tunnels is determined by the graft, but is usually either 8 or 9 mm for the AL tunnel and 6 or 7 mm for the PM tunnel. Both tunnels are drilled to match the measured diameter of the limbs on the graft (Fig. 26.1). Both tunnels are tapped if necessary for the interference screws used to stabilize the graft. The arthroscope is now removed from the knee.

A nonirradiated Achilles tendon allograft is selected for the anatomic PCL reconstruction. The tendon is split into a larger (about 60%) AL bundle and a smaller PM bundle. Locking stitches are placed into each of the limbs using a strong suture to allow the graft to be passed into the knee and the respective tunnels. The bone block is cut with an oscillating saw. The block should be trimmed to a size that is 15 to 20 mm long, 10 to 15 mm wide, and at least 10 mm thick (Fig. 26.2). It is very important to leave the bone block a minimum of 10 mm thick, as a thinner bone block can crack when the screw is tightened to secure it into the trough. Once the trimming has been completed, a 4.5-mm hole is drilled through the bone block in a slightly oblique PM to AL direction.