Soft tissue of the knee
Surgical reconstruction of the posterior cruciate ligament: current perspectives

https://doi.org/10.1016/j.mporth.2019.01.002Get rights and content

Abstract

After over a century of orthopaedic attention, injuries to the posterior cruciate ligament (PCL) continue to pose a significant management challenge. Isolated PCL tears constitute the minority of cases, with multiligament trauma (most commonly posterolateral corner injuries) predominating. Surgical reconstruction of the PCL remains technically demanding. Historical long-term outcomes have been associated with persisting knee instability and secondary degenerative arthrosis, irrespective of surgical intervention. The past two decades have witnessed a renewed focus on understanding the anatomy and biomechanics of the PCL, and its spectrum of injury. This, along with advancements in surgical technology and techniques, has heralded a renewed impetus for operative reconstruction. While there remains no clinically demonstrated difference in outcomes of double-bundle surgery over single-bundle reconstruction, many prefer a double bundle approach due to empirical data supporting its biomechanical superiority. Concomitant bony realignment in the coronal and sagittal plane should be considered where necessary. Graft reinforcement is an emerging concept that may aid in protecting the neoligament during the early healing phase. With modern approaches, there are increasing reports of more favourable short and mid-term post-operative outcomes. Despite this, most studies remain of a low level of evidence, with relatively small case series, and there is a paucity of well-designed controlled studies contrasting operative techniques.

Introduction

Surgical reconstruction of the posterior cruciate ligament (PCL) has been described since the early 20th century.1 However, in over a century of orthopaedic attention, injuries to the PCL continue to pose a management challenge. Historical long-term outcomes have been associated with persisting knee instability and secondary degenerative arthrosis, irrespective of surgical intervention.2 The past two decades have witnessed a renewed focus on understanding the anatomy and biomechanics of the PCL and its injury spectrum. This, along with advancements in surgical technology and techniques, has heralded a renewed impetus for operative reconstruction, and authors are increasingly reporting more favourable short and mid-term outcomes. Despite this, most studies remain of a low level of evidence, with relatively small case series, and there is a paucity of well-designed controlled studies comparing operative versus non-operative management or contrasting operative techniques.

PCL injuries are relatively uncommon, with an approximate incidence of only 3% of outpatient knee trauma. However, up to 40% of patients presenting with an acute haemarthrosis may have a PCL tear.3 Isolated PCL tears constitute the minority of cases, with multiligament trauma (most commonly associated posterolateral corner injuries) predominating. Surgical reconstruction of the PCL remains technically demanding, and managing patients with PCL injury requires the surgeon to be proficient with the management of all aspects of the ligamentously-injured knee, in both the acute and chronic setting. This also produces significant heterogeneity in patient groups, and hence reported outcome studies, as concomitant injuries may influence management approaches.

This article will briefly review the anatomy, biomechanics and diagnosis of PCL injuries, while focusing on surgical reconstruction strategies and outcomes. More recent developments in arthroscopic surgery using all-inside approaches and graft reinforcement will also be explored.

Section snippets

Anatomy

The PCL is a stout intra-articular but extra-synovial ligament, averaging 38 mm in length and 13 mm in width.4 It receives a blood supply from the middle geniculate artery. The ligament is functionally divided into two bundles; the major anterolateral (AL) bundle, and the more minor posteromedial (PM) bundle. These bundles can each be further subdivided into two fascicles, but this is not of significant surgical relevance. The AL and PM bundles are relatively easy to define on the lateral face

Biomechanics

In all angles of knee flexion, the PCL is the dominant restraint to posterior tibial translation, with its most significant contribution being at 90° of flexion. PCL injury is therefore best assessed with the knee at this angle. Generally, the PM bundle is thought to have a greater contribution in knee extension, and the AL bundle a more significant role in higher degrees of knee flexion, but this relationship has been questioned.7 There is also a developing understanding that the PM bundle may

Diagnosis and grading

The classic cause of an isolated PCL injury is a dashboard impact, where a posteriorly directed force is applied to the anterior aspect of the tibia with the femur relatively fixed. A similar mechanism is encountered with a fall onto a flexed knee in sporting situations. In addition, the PCL may be injured in hyperextension or with significant varus or valgus loading after failure of the primary varus/valgus restraints of the posterolateral corner or the medial collateral ligament (MCL).

Imaging

Plain radiographs and MRI scanning are the routine imaging modalities. Radiographs may show PCL or posterolateral corner avulsion fractures, which are best managed by early operative fixation. MRI scanning is nearly 100% accurate in the acute setting but may be misleading in the chronic setting, as the PCL does have a propensity to heal, albeit with residual laxity.16 In chronic cases, secondary degenerative changes may be identified, and limb alignment must be evaluated, including the use of

Non-operative management

Unlike the ACL, the PCL has been shown to have good intrinsic healing potential.19 Traditionally, with wilful neglect (either on behalf of the patient or the treating surgeon) the PCL will heal in an elongated manner with residual laxity. An MRI may show a serpentine nature to the PCL or a secondarily lax ACL. The importance of recognizing the capacity for healing of the PCL is such that appropriate early conservative management may have a significant impact on residual laxity. The availability

Surgical reconstruction

Almost every aspect of surgical reconstruction of the PCL and postoperative rehabilitation is still debated, as the optimal technique is yet to be established. PCL avulsion fractures from the posterior aspect of the tibia are a relatively clear indication for early operative intervention and may typically be accessed via a posteromedial approach with mobilization of the medial head of gastrocnemius. Simple screw and washer fixation constructs are often sufficient for such injuries.

Early forms

Conclusion

The management of PCL injury continues to challenge the orthopaedic community. Most diagnoses are associated with concomitant ligamentous disruption and possible neurovascular compromise, which must be attended to. Surgical reconstruction of the PCL remains a technically challenging operative procedure and should be undertaken by surgeons experienced in the management of the multiligament injured knee. Bony realignment in the coronal and sagittal plane should be considered where necessary.

Acknowledgement

The author would like to acknowledge Mr Adrian Wilson for his contribution to the some of the clinical photographs used in this article.

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