General Considerations and Complications for Pediatric Anterior Cruciate Ligament Reconstruction

Introduction

Although once considered rare among skeletally immature patients, anterior cruciate ligament (ACL) injuries have increased in frequency among children and adolescents over recent years. ^, The observed increase in the incidence of ACL injuries may be related to any combination of a rise in youth sports participation, single-sport specialization, increased training time and intensity, and enhanced recognition of ACL tears with improved diagnostic modalities. In fact, the rate of ACL reconstruction (ACLR) in children under 15 years of age increased by 924% between 1994 and 2006. With several studies reporting poor functional outcomes, higher rate of instability, new meniscal tears, and degenerative knee changes with nonoperative management, ^, ^, there has been an increasing trend toward earlier surgical management. The current literature describes a number of surgical techniques for pediatric ACLR. Early operative management has been recommended to restore knee stability and to prevent progressive chondral and meniscal damage, however, techniques vary among surgeons and there is not a consensus on a single operative technique. , ^, Although a number of complications described in adult patients apply to children and adolescents, the pediatric population is also uniquely at risk for additional issues before, during, and after surgery. Recognition and management of these issues is of paramount importance when caring for ACL injuries in children.

Preoperative Issues

Stiffness and Quadriceps Weakness

Patients with an acute ACL injury are often found to have knee stiffness at initial presentation due to inflammation and hemarthrosis. It is important to address this stiffness before surgery because poor preoperative motion is a major risk factor for postoperative motion deficits. To assess the effects of preoperative rehabilitation on postoperative functional outcomes, patients from the Delaware-Oslo ACL cohort were compared to those from the Multicenter Orthopaedic Outcomes Network registry. The authors reported that patients who were treated with extended preoperative rehabilitation had significantly higher functional outcomes and return-to-sports rates than those who did not receive preoperative rehabilitation. Similarly, others have advocated for the role of aggressive preoperative rehabilitation focusing on achieving full knee extension and quadriceps strength to reduce the chance for postoperative arthrofibrosis. The authors of this chapter recommend operative intervention only full range of motion (ROM) has been achieved, pain and effusion have subsided, and no extensor lag is present on physical examination.

Timing of Anterior Cruciate Ligament Reconstruction

The optimal timing of ACL reconstruction (ACLR) remains a controversial subject. It is generally recognized that the risk of postoperative arthrofibrosis is increased by poor preoperative ROM and quadriceps control, as well as reconstruction prior to resolution of the associated inflammation and effusion. ^, A classic study suggests this risk to be as high as 18% when ACLR is performed within 1 week following the injury, compared with 6% when it was delayed by more than 4 weeks. Subsequent investigations link early ACLR (within 3–4 weeks following the injury) to increased risk of postoperative stiffness and lack of full extension. ^,

Conversely, several studies report increased rates of meniscus tears, chondral damage, and sports-related disability with delayed surgery. ^, ^, ^, The rate of medial meniscus tears is reported to be as high as 36% when ACLR is delayed for more than 6 weeks. With a similar delay, the odds of developing a lateral meniscus tear are 1.45 times higher. These odds increase to 2.82 when reconstruction is delayed for more than 12 weeks after injury. In a recent metaanalysis, nonoperative or delayed ACLR (30.3 ± 25.7 months after injury) was associated with a 34-fold increase in the risk of knee instability compared with early ACLR (12.9 ± 14.2 months after injury). In light of the trends favoring early surgical stabilization, the authors recommend deferring reconstruction until full range of motion is achieved, but generally not for more than 3 months after injury because this can significantly increase the risk of meniscal and chondral damage. Of note, early ACLR is especially advisable in the setting of multiligament injury. Although ligament reconstructions can be staged, delayed ACLR heightens the risk of interim meniscal and chondral injury in these patients. ^,

Posterolateral Corner Injury

The posterolateral corner (PLC) of the knee primarily consists of the lateral collateral ligament (LCL), popliteus tendon, popliteofibular ligament, arcuate ligament, and joint capsule. In adults, a PLC injury is identified in up to 48% of all multiligamentous injuries of the knee, with only 28% of all PLC injuries occurring in isolation. ^, Conversely, the incidence of concomitant ACL and PLC injury was reported to be as high as 37.3% in a study of 102 children and adults. PLC injury often necessitates surgical management because nonoperative treatment in the setting of marked pathologic laxity may be associated with poor outcomes resulting from varus and rotational instability of the knee. ^, In patients undergoing ACLR, an unrecognized or untreated PLC injury results in significant strain on the ACL graft and high risk of graft failure. Additionally, instability resulting from an untreated grade III PLC injury can transfer excessive loads to the medial joint compartment, potentially resulting in degenerative changes in the long term. The PLC should be scrutinized in preoperative evaluation to avoid the potentially catastrophic consequences of a missed diagnosis. Physical examination maneuvers with proven utility in identifying PLC injuries include varus stress testing, the dial test, the reverse pivot shift test, and the external rotation recurvatum test. Table 12.1 describes these maneuvers. Magnetic resonance imaging (MRI) should be evaluated closely after a thorough physical examination.

Table 12.1

Physical Examination Maneuvers to Identify Posterolateral Corner Injuries

Varus stress test	The varus stress test is performed with patient in supine position with knees flexed between 20 and 30 degrees. The examiner’s fingers are placed over the joint line, stabilizing the distal femur. Then a varus stress is loaded on the knee. Varus gapping occurs in patients with compromised posterolateral structures.
Dial test	The dial test can be performed with the patient in either the supine or prone position with 30 and 90 degrees of knee flexion. It assesses the increased external rotation of the tibia compared to the contralateral uninjured knee. Increased external rotation at 30 degrees but not at 90 degrees indicates an isolated injury to posterolateral structures, whereas increased external rotation at both angles suggests injury to both posterolateral structures and the posterior cruciate ligament (PCL). ^,
Reverse pivot shift test	The reverse pivot shift test can be performed with the patient supine on the examination table with knee flexed to between 70 and 80 degrees and external rotation and valgus force applied to the tibia. The knee is then allowed to be straightened. The test is considered positive when the lateral tibial plateau shifts from a position of posterior subluxation to a position of reduction as the flexed knee is brought into extension, resulting in a characteristic clunk.
External rotation recurvatum test	The external rotation recurvatum test is performed with the patient supine by lifting the great toe and observing the relative amount of genu recurvatum present. The knee with a PLC injury will fall into relative hyperextension laterally, and the tibia will be externally rotated into relative varus.

If a PLC injury with marked pathologic laxity is diagnosed along with ACL rupture, both should be addressed surgically. Primary repair of the LCL and popliteofibular ligament is associated with a significantly higher failure rate compared to reconstruction (37% vs. 9%, respectively). Therefore the authors tend to perform reconstruction of the PLC in all cases of concomitant injury. Reconstructions of the ACL and PLC can be performed simultaneously or in a staged fashion, with maintenance of knee ROM and stability key factors to consider.

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