Surgery for Anterior Cruciate Ligament Deficiency in Children and Young Adults.

Edited By: Gregory A. Schmale, M.D.
Last updated Wednesday, January 12, 2005

Considering surgery

Types of surgery recommended

Surgery for the unstable knee may be considered during the diagnostic as well as the therapeutic phases of treatment.

Exam under anesthesia with stress radiographs may help with diagnosis. Diagnostic arthroscopy may also be helpful in making the diagnosis as well as initiating treatment of the knee injury.

Reduction (re-alignment to a more natural position) of displaced tibial eminence fractures (fractures of the bony bump on the central tibial plateau that are moved from their natural position) should be performed via attempts at closed reduction with or without general anesthesia. Myers and McKeever type II fractures with anterior displacement and posterior hinging (tilting up of the front of the bony prominence where the ACL attaches to the tibia) may respond to casting in full extension, either by pressure of the condyles on the plateau based fragment or pressure of the notch on the displaced eminence (the thigh bone may actually push the piece fractured off the top of the tibia back into place when the knee is extended or straightened). Menisci ("C"-shaped cartilage rings that serve as bumper between the thigh and leg bones) may be entrapped under displaced fragments prohibiting reduction.

Fully displaced fragments, Myers and McKeever type III fractures, require anatomic reduction and internal fixation. Treatment of these injuries may proceed via arthroscopic exam. Fixation is performed via arthroscopically guided suture placement, potentially through drill holes placed with the ACL tibial guide, and tied over a narrow anterior tibial bone bridge just medial to the tibial eminence. Arthroscopically assisted open reduction and internal fixation, by suture(s), epiphyseal screws, or transphyseal screws may also be performed. Open reduction and fixation through a small incision on the front of the knee without the use of arthroscopy may also be performed, though it may miss concomitant meniscal injuries.

Because interstitial tearing of the anterior cruciate may accompany avulsion fractures, some laxity may persist despite fixation of fragments. Recessing fragments prior to fixation so as best restore prior tension to the ACL may decrease future laxity and decrease the risk of symptomatic giving-way (buckling or collapse from pain or weakness).

Acute reconstruction of anterior cruciate ligament deficient knees (i.e. within the first three weeks after injury) is not indicated unless significant meniscal injury is suspected. Meniscal repairs have a higher success rate when performed at the same time as an ACL reconstruction. Knees having undergone acute ACL reconstruction prior to restoration of normal motion are at risk for post-operative stiffness.

Skeletally immature youth deserve a trial of rehabilitation of the knee with strengthening of secondary stabilizers such as the hamstrings prior to embarking on reconstruction. High level sports should be attempted with brace support to prevent meniscal injury from subluxation events (giving-way episodes). Unlike adults, however, children and adolescents may be unlikely to apply a knee brace prior to unorganized play such as recess/playground time after school and prior to neighborhood pick-up games. It is during these activities that further knee injury may occur. Graf (1992) noted new meniscal injuries in ACL deficient knees in seven of twelve patients over an average period of 15 months. Because of this, reconstruction of the ACL is recommended in prepubescent skeletally immature patients with laxity greater than 11-12 mm, i.e. an amount necessary to produce a pivot shift, despite absence of giving-way events.

The method selected for ACL reconstruction should depend on the skeletal age of the child. Repair of torn anterior cruciate ligaments has historically been as unsuccessful in children as it has in adults, and thus is not recommended. For those children of skeletal age approaching closure of their femoral and tibial physes or growth plates, approximately bone age 14 1/2 years in girls and 16 years in boys, the method of ACL reconstruction selected is of less importance. For children with more than one to two years of growth remaining, however, ACL reconstruction may put open physes (still growing at the knee) at risk for injury and/or early closure. Reconstructions in this population should not employ the use of grafts with bone blocks placed into transphyseal tunnels (tunnels that cross the growth plates above and/or below the knee). Any method employing the use of transphyseal tunnels puts the physes at risk, though few reports of growth arrests or angular deformities after such procedures exist in the literature. Transphyseal tunnels enable isometric or ideal positioning of a graft, allowing for optimal function of a reconstructed knee. Non-isometric positioning, via over the top femoral or tibial graft placement may result in progressive laxity as range of motion is restored in the post-operative period.

A number of animal studies have helped identify the effects of drilling tunnels across open physes. Early work in rabbits showed that drill holes left open across the physes or growth plates of the femur and tibia lead to bone growth across the tunnels, effectively causing bony bars and local growth arrests. Drilling across open physes in canine knees where soft tissue graft filled the tunnels resulted in no growth arrests in a recent study. Another dog model followed the growth of the femora and tibia after transphyseal tibial and femoral tunnel drilling and ACL reconstruction via fascia latta autograft fixed with 80 newtons of tension (greater than typical tension used in fixation of ADULT ACL grafts). In this model, angular deformities developed over four months following reconstruction (valgus of the distal femora and varus of the proximal tibiae), leading the authors to caution against excessive tension with this form of fixation.

Long term follow-up of a group of young children who have undergone ACL reconstruction using fixation above and below a graft passed through transphyseal femoral and tibial tunnels has not been published. Andrews et al. (1994), reported on eight patients between age 10 and 15 years chronologically, bone age unknown, who underwent ACL reconstruction with transphyseal tibial tunnels and over the top allograft placement on the femoral side. No significant limb length differences were identified at skeletal maturity in any patient. The transphyseal tunnels were 7 mm in diameter, positioned centrally and oriented vertically in the proximal tibia. A similar procedure was employed by Lo et al. (1997) in five patients with a minimum anticipated growth remaining of 5 cm. One patient in this group at 4 1/2 years follow-up has developed no significant laxity, no angular deformities at the knee, and no leg length inequalities, with proximal migration of the femoral fixation suggesting growth and elongation of the new, reconstructed ligament. The risks of over the top fixation on the femoral side include exposure of the physis or growth plate and resulting formation of a bony bar which would arrest growth, and inadvertent stapling across the physis as performed in one patient in a series reported by Lipscomb (1988). Because of these risks, small, centrally and vertically oriented transphyseal tunnels on both the femoral and tibial sides in pre-pubescent patients with more than one to two years of growth remaining are recommended using hamstring autograft.

Who should consider anterior cruciate ligament deficiency surgery?

Children and adolescents with pathologic laxity (positive pivot shift or greater than 10-12 mm of anterior translation on Lachman’s test) would benefit most from reconstruction of their anterior cruciate ligament, so as to protect their knee from meniscal or chondral injury.

Those with ACL deficiency without pathologic laxity would probably do best to pursue an aggressive non-operative ACL rehabilitation program. They should participate in sports in a hinged knee brace designed to prevent against hyperflexion (bending beyond the normal amount of knee bending), hyperextension (straightening past the normal amount of knee straightening), varus and valgus deformity (bow-legged or knock-kneed deformities), and anterior translation of the tibia on the femur (increased forward slipping of the tibia at the knee) until such time as they approach within one-two years of skeletal maturity, or they are unsatisfied with this form of treatment.

For those who fail these tests for non-operative management, and who have more than one to two years of growth remaining at the knee, we recommend reconstruction procedures that provide the most anatomic reconstruction with the least risk of growth arrest or angular deformity of the knee. The graft should be autograft of semitendonosis and gracilis tendon. The tibial graft placement should be through a vertically oriented, centrally located transphyseal tunnel less than or equal to 7 mm in diameter, with the graft fixed at the tibial metaphysis. The femoral fixation may be either over the top, well proximal to the physis, or via a transphyseal femoral tunnel with proximal metaphyseal cortical fixation.

ACL reconstruction is most effective when the patient follows a simple exercise program after surgery. Thus, the patient's motivation and dedication are important elements of the partnership.

Effectiveness

Urgency

Risks

The most serious risks of anterior cruciate ligament surgery in children and adolescents would be of growth arrest or deformity about the knee resulting from injury to the growth plate of the tibia or femur. This complication is not commonly encountered but is potentially devastating enough to discourage many from pursuing reconstruction in children with much growth remaining about the knee, particularly those who are pre-pubescent.

Physeal or bony bars across a growth plate can be treated, however, with bar resection or osteotomy--bone cutting and realignment--above or below such a deformity, or with closure of the growth plate on the side of the knee opposite an increasing deformity. Thus this complication is treatable and is potentially without long-lasting sequelae (consequences).

On the other hand, injury to the menisci may lead to early arthritis, which is not reversible. The menisci help to distribute the load borne by the knee evenly across the tibial plateau. Injury to the menisci during youth as a result of an unstable knee with an untreated ACL deficiency may lead to cartilage injury and painful arthritis in the future.

Risks of surgery also include graft loosening and recurrence of instability, infection, nerve or blood vessel injury, and the need for additional surgeries. There is also an anesthesetic risk to this procedure, as a general anesthetic is usually employed.

Managing risk

Many of the risks of anterior ligament reconstruction surgery can be effectively managed if they are promptly identified and treated. Infections may require a wash-out in the operating room followed by a course of antibiotics. Rarely, the graft may have to be removed.

Growth arrest is determined by careful monitoring of the growth of the operative limb in comparison to the non-operative limb. As described above, such a complication can be effectively treated with further surgery.

Post-operative stiffness not responding to therapy may require manipulation or arthroscopy to debride (clear out) scar tissue which can grow in the notch region of the knee, preventing full flexion (bending) or extension (straightening).

If the patient has questions or concerns about the course after surgery, the surgeon should be informed as soon as possible.

Surgery for Anterior Cruciate Ligament Deficiency at the University of Washington

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