NATURAL HISTORY OF ANTERIOR CRUCIATE LIGAMENT INJURY IN CHILDREN

In adults, chronic ACL insufficiency leads to intra-articular damage. Meniscal tears and chondral damage occur in individuals who continue to participate in sports and recreational activities without the benefit of a stable knee.^11–13 What is the evidence? A number of Level II and III studies confirm the same dismal prognosis in children with open physes; namely, if the ACL is left untreated, the patient has a markedly increased risk for development of meniscal tears and chondral damage leading to eventual osteoarthritis.^4,5,14–18

Level III studies by Graf and colleagues,⁴ McCarroll and coworkers,⁵ and Angel and Hall¹ all report on the high incidence of meniscal tears and the inability to resume preinjury activity levels. Level II studies by Aichroth and investigators,¹⁴ Pressman and researchers,¹⁸ and Kannus and Jarvinen¹⁹ have confirmed the results of these earlier studies.

MAKING THE DIAGNOSIS

Since the early 1990s, the orthopedic literature has discussed in depth the possibility of an ACL disruption in the growing child. Before these detailed descriptions, it was generally believed that children did not tear the ACL with the exception of the pediatric equivalent, namely, the tibial eminence fracture.^20–23 With that background, it is important for the physician to have a high index of suspicion in a child presenting with a presumed hemarthrosis (swollen knee) after a knee injury.

In a number of series of knee injuries in the pediatric population, the incidence rate of ACL disruption has been reported to be as low as 10% and as high as 65% in series with the number of patients ranging from 35 to 138 patients.^24–28

A physical examination in this clinical setting should include a careful examination for ACL insufficiency. The examination should consist of a careful and gentle Lachman test for anteroposterior instability with the knee at 20 to 30 degrees of flexion, an anterior drawer test at 90 degrees if the patient’s pain and tense effusion will allow, and finally, a gentle examination for a positive pivot shift.

Again, a high index of suspicion is necessary. Except in the incidence of tibial or femoral bony avulsion, there is no need for urgent surgical reconstruction (Level of Evidence V). The patient can be instructed to ice the knee, start active range-of-motion exercises and strengthening, and be re-evaluated in 2 to 3 weeks when the physical examination will be more reliable and easier to perform because the patient will be more comfortable and the majority of the hemarthrosis will be resorbed.

DIAGNOSTIC IMAGING

All patients with a significant knee injury and presenting with an effusion (hemarthrosis) should have plain radiographs of the knee to rule out tibial eminence fracture or other bony avulsions and osteochondral fractures.

The decision to order magnetic resonance imaging still remains somewhat controversial. However, in 2007, it is recommended for patients with suspected ACL tears to be evaluated for meniscal tear and osteochondral lesions (such as a fracture or a “bone bruise”) (Fig. 31-1) (Level of Evidence V).

FIGURE 31-1 A, Magnetic resonance imaging (MRI) of a skeletally immature adolescent with disruption of anterior cruciate ligament (ACL) tear. Note disruption of anterior cruciate ligament (white arrows) and open physes. B, Same patient. Note peripheral separation of lateral meniscus, an injury commonly seen in patients with ACL disruption.

TREATMENT

Operative Treatment

Given the unique anatomic aspects of the growing child, nontraditional surgical methods have been used in an attempt to prevent knee instability whereas at the same time preventing or reducing the risk for growth disturbance.

These surgical methods can be divided into the following categories:

1. Extra-articular surgical reconstructions

2. Physis-sparing surgical reconstructions including graft fixation in the epiphysis

3. Partial physeal-sparing reconstructions

4. Transphyseal reconstructions

Extra-articular Surgical Reconstruction.

Extra-articular surgical reconstruction was popular in adults in the 1970s. Unfortunately, the location of the graft in a nonanatomic location was unsuccessful in controlling anterior translation of the tibia on the femur. Nevertheless, these extra-articular reconstructions have been proposed as a “temporizing” procedure in the skeletally immature patient^{2,4, 5} (Level of Evidence IV). No evidence suggests that they will act any more efficiently than reported previously.

Physis-Sparing Reconstructions.

In an attempt to avoid crossing the physis with the graft, a number of grafts have been used with variations on a theme. The graft avoids the proximal tibial physis by using a drill hole in the proximal epiphysis only.^35–37 In addition, the distal femoral physis is avoided by placing the graft in an “over-the-top” position through the posterior capsule^35,37 or by a drill hole into the epiphysis only³⁶ (Fig. 31-2). Only Level III and IV studies have documented the efficacy of these surgical treatments, with the longest follow-up being 5 years.^{35,36,38–43}

FIGURE 31-2 Physis-sparing technique of anterior cruciate ligament reconstruction utilizing autogenous patellar tendon as the graft. The graft remains attached distally to the tibia and is passed through a notch in the proximal tibial epiphysis beneath the intermeniscal ligament to an intra-articular position, and subsequently is passed through the posterior capsule to an “over-the-top” position on the distal femur above the distal femoral physis.

A variation of the combined intra-articular and extra-articular reconstruction popularized by McIntosh and Darby has been proposed by Kocher³⁷ in prepubescent skeletally immature children and adolescents to provide knee stability whereas at the same time avoiding the dreaded iatrogenic complication of growth disturbance seen with drill holes through either the proximal tibial or the distal femoral physis, or both (Level of Evidence IV) (Fig. 31-3).

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