Introduction
Posterior cruciate ligament (PCL) injuries are most commonly encountered in the setting of multiligamentous knee injuries. Isolated injuries of the PCL are relatively less common by comparison. A prospective analysis by Fanelli found the rate of PCL injury among acute knee injuries in 222 patients to be 38%, with just 3.5% representing isolated injuries. The most common associated ligamentous injuries included PCL with posterolateral corner (PLC) injury (62%), anterior cruciate ligament (ACL) injury (46%), or medial collateral ligament injury (31%). Typical mechanisms of PCL injury include a posterior directed force against a flexed knee, hyperflexion injury with a plantar flexed foot, or hyperextension. An understanding of injury mechanism, associated injuries, and epidemiology, along with a thorough history and physical examination, is critical to accurate clinical diagnosis. This is the first step in limiting complications associated with these injuries.
Recent studies have further elucidated the relevant anatomy and biomechanical role of the PCL complex and meniscofemoral ligaments (MFLs). Despite our improved understanding of the basic science related to the PCL and its function, significant controversy remains over the appropriate management and specific operative techniques used to treat PCL injuries. Although more prospective studies are needed to address the lack of consensus on this front, an awareness of commonly encountered complications in the evaluation, nonoperative management, intraoperative management, postoperative management, and rehabilitation of PCL injury is integral to mitigating events that can lead to poor outcomes. This chapter will review the common pitfalls associated with PCL injury and management, along with strategies to prevent or address these complications ( Table 16.1 ).
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Preoperative Complications
Neurovascular Injury
Complications may occur with the initial injury. There are relatively high rates of neurvovascular injuries associated with multiligamentous knee injury and dislocation. Almost one-third of knee dislocations have an injury to the popliteal artery, ranging from a tear of the intima to a complete arterial transection. Minor injuries may not cause significant damage, but missed injuries affecting perfusion can have severe consequences including amputation. Evaluation and documentation of pulses is a critical step in the initial injury management. In the absence of abnormal physical examination findings, serial examination and ankle-brachial index assessment are important steps in patient observation in case of an evolving injury. Any abnormality in examination should investigated further using arteriography and imaging or immediate exploration as warranted by the severity of symptoms.
Neurological damage can also be associated with multiligamentous knee injury, and is most frequently encountered in the context of a dislocation. Rates of injury have been estimated between 16% and 40%. The common peroneal nerve is involved more often than the tibial nerve, and injury severity can range from neuropraxia to neurotmesis. Therefore careful neurologic assessment is necessary, and examination should be performed before and after any reduction maneuver if necessary. Patients with neurological injury should be counseled appropriately because there are low rates of recovery (31%), but young age has been shown to be a good prognostic factor.
Deep venous thrombosis (DVT) is a common complication in orthopedic surgery. Although there are relatively low rates of symptomatic DVT (0.3%) and pulmonary embolism ([PE], 0.18%) after ACL surgery, there is evidence of increased rates of DVT in asymptomatic patients who have suffered high-energy trauma even before undergoing surgery. , A series by Rong found a 10.9% preoperative incidence of proximal DVT on venography in patients with high-energy knee trauma, including injury to one or both of the cruciate ligaments. There was also evidence of increased risk for DVT in patients undergoing arthroscopic surgery for PCL injury alone (17.4%) and PCL with multiligamentous injuries (PCL + medial collateral ligament [MCL]/lateral collateral ligament [LCL], 23.5%; PCL + ACL, 25%) compared with ACL alone (7.2%). Although prospective studies tend to have higher rates owing to detection of asymptomatic DVT, it is important to consider this factor in the preoperative management of a patient with a PCL injury. Of course, traditional risk factors must always be accounted for when working up these patients. The senior author recommends routine evaluation for DVT with ultrasound preoperatively in patients with multiligamentous knee injury. If a clinically significant DVT is identified, and the patient is undergoing immediate surgery, then an inferior vena cava (IVC) filter can placed preoperatively to decrease the risk of PE. Once the patient is postoperatively stable and appropriately anticoagulated for treatment, the IVC filter can be retrieved to limit complications such as thrombosis or filter migration. If the patient’s knee ligament injury can be delayed, then the DVT can be treated without a filter, and the patient can undergo elective surgery at a later date. Postoperatively, appropriate DVT prophylaxis must be continued for prevention of recurrence.
Diagnosis
Beyond assessment of neurovascular status, a thorough physical examination for associated ligamentous injuries should be performed. However, in the acute setting this may be challenging. PCL injury can be evaluated in the office setting with the posterior sag test, quadriceps active test, posterior drawer test, and reverse pivot shift test. The amount of translation with posterior drawer should be noted in comparison with the contralateral limb. Lachman, pivot shift, and anterior drawer tests can all be used to assess the status of the ACL. Varus and valgus stress should be performed at 0 degrees and 30 degrees to examine the integrity of the LCL and MCL, respectively. The PLC (LCL, popliteus tendon, popliteofibular ligament) may be examined with the posterolateral drawer test and the dial test, which is performed at 30 degrees and 90 degrees (increased rotation at 30 degrees and 90 degrees is suggestive of PLC injury in addition to PCL).
Although an accurate history and physical examination are important, the final working diagnosis will require high-quality imaging studies. Radiographs must be carefully analyzed for both obvious and less obvious bony injuries ( Fig. 16.1 ). Subtle avulsion fractures, nondisplaced fractures, and subluxations must be recognized and, in most cases, treated surgically in the first 2 weeks ( Fig. 16.2 ). Postreduction radiographs are also critical to ensuring concentric reduction and reduction maintenance in the case of dislocation or subluxation. If reduction cannot be maintained, knee-spanning external-fixation may be necessary until the patient is ready for surgery. Magnetic resonance imaging (MRI) has high sensitivity and specificity for diagnosing PCL injury, and can identify other soft tissue pathology in the knee. In the setting of chronic injury, MRI imaging may not be sufficient to accurately diagnose the severity of injury. In this case stress radiographs may be required to assess true ligamentous involvement. Early detection of associated injuries to bone, soft tissue, and neurovascular structures will be critical to treatment decisions and successful outcomes with minimal complications.
Nonoperative Complications
A complete discussion of the complications of PCL injury management must include a discussion regarding the pitfalls of nonoperative treatment. Conservative management is a mainstay of treatment for partial PCL (grade I/II) injuries. In general, bracing in extension for 2 to 6 weeks (depending on grade), followed by well-supervised physical therapy, will give the patient the best chance for recovery. For partial PCL injuries, it has been shown that most patients have the same or slightly reduced laxity at follow-up. Despite the residual laxity, more than half of patients returned to the same or increased level of activity, and another third of patients return to a lower level of sport. An average of 14 years’ follow-up of the same patient cohort revealed favorable outcomes compared with results from studies investigating PCL reconstruction in cases of isolated PCL injury.
Despite studies showing good results in patients treated nonoperatively with chronic PCL injury, there is concern––especially for high-grade injuries managed nonoperatively––that outcomes can be unpredictable. Biomechanical studies have demonstrated increased contact pressures in the medial and patellofemoral compartments of PCL-deficient knees. , There is also evidence of an increase in medial-sided meniscal and chondral injuries of chronic PCL injuries compared with the rate of associated meniscal and chondral injuries that occur in the acute setting. A concern given these findings is the potential for instability and laxity to lead to the development of osteoarthritis. However, the rates of osteoarthritis in nonoperative (17%–88%) and operative (13%–67%) management of PCL injuries vary widely. Given the heterogeneity of results, the management of isolated high-grade PCL injuries remains controversial.
Intraoperative Complications
Arthroscopic surgery has been found to have an overall complication rate of 4.7%, whereas surgery involving the PCL is noted for an increased complication rate at 20% ( Fig. 16.3 ). The high complication rate in the operative management of PCL injury is because of a variety of factors, including less frequent occurrence of PCL injury and subsequent lack of experience in treating these injuries, technical difficulty of PCL reconstruction, and the proximity of neurovascular structures. This section will review the intraoperative diagnosis and management of complications that can occur with PCL reconstruction.
Intraoperative Planning and Evaluation
Appropriate planning can help limit complications postoperatively. The anesthesia team should be aware of the nature and extent of the procedure, and decisions regarding the type of anesthesia should be made after deliberation with the surgeon, anesthesiologist, and patient. Preoperative regional anesthesia with femoral, adductor canal, and/or sciatic nerve blocks can be performed to decrease the amount of anesthetic required intraoperatively and improve pain management postoperatively. , A Foley catheter should be considered to help monitor fluid status during these cases as the surgical time can often exceed 2 hours. Cases should be coordinated with a vascular surgeon who can be available in case of intraoperative vascular injury.
Although the importance of correct clinical diagnosis and identification of other injuries cannot be stressed enough, the office physical examination can be difficult or inaccurate. Imaging is a helpful adjunct, but can also be misleading. An accurate examination under anesthesia (EUA) is crucial to delineate the final ligament pathology. The EUA should be compared with the original preoperative diagnosis and plan, and adjustments should be made accordingly to the operative plan ( Fig. 16.4 ). Care should be taken to avoid an overly aggressive EUA, which could convert a partial ligamentous injury (grade I/II) into a complete (grade III) injury. Stress radiographs utilizing intraoperative fluoroscopy can be performed to get an accurate assessment of laxity in the anterior/posterior and varus/valgus planes. The patient should be meticulously positioned by the surgeon to prevent major complications. These cases can take well beyond 2 hours, which can put the patient at risk for neurovascular, skin, and other position-related complications. Compartment syndrome of the contralateral limb has been reported because of positioning during PCL surgery. , The senior author prefers supine positioning without the use of a leg holder to limit neurovascular complications associated with positioning ( Fig. 16.5 ). Tourniquet is not used routinely during the surgery to allow for immediate identification of any vascular injuries. If one is used, a sterile tourniquet is preferred with inflation time limited to less than 2 hours. Anatomic landmarks and anticipated surgical incisions can be marked to allow for appropriate spacing and preoperative local anesthetic injection. A thorough preoperative plan and set-up is important for patient stability and safety throughout the case, and maximizes efficiency during surgery.
