ACL Tears in Children: Physeal Sparing Reconstruction

Mark L. Burman M.D., FRCSC
Assistant Professor
Division of Orthopaedics, Department of Surgery
Sports Medicine Group
McGill University
Montreal, QC

ACL injury in children with significant skeletal growth remaining poses a unique surgical challenge to the orthopaedic surgeon. While adolescents nearing skeletal maturity can usually be treated as their adult counterparts, concern for damage to the physes around the knee makes this younger group of patients a challenge.

The distal femoral physis contributes 70% to femoral growth (approximately 1.2 cm / year), while the proximal tibial physis provides for 60% of tibial growth (average 0.9cm / year)1 (Figure 1).This growth increases around the time of the adolescent growth spurt.

Figure 1: Growth rates of growth plates around the knee

Animal studies have demonstrated that drilling tunnels involving greater than 7-9% of the cross-sectional area of the physis caused growth arrest2,3, and excessive tension across physes can result in angular deformity4.

Given the potential risk of physeal arrest and the resulting angular deformity or leg length inequality, many surgeons have been reluctant to drill across open physes, as done in traditional "Adult-type" surgery. Delaying surgical treatment can result in recurrent instability and risk articular and meniscal damage and ultimately long-term degenerative changes5,6. Extra-articular reconstructions, while used by some, are non-anatomic and therefore risk loosening and failing7. As a result, many surgeons advocate partial or complete physeal sparing techniques for patients with significant skeletal growth remaining who require surgical ACL reconstruction.

Partial physeal sparing techniques involve drilling through only one physis (usually the tibia) and avoiding the other (usually the femur).

Lipscomb and Anderson8 used a hamstring autograft with a transphyseal tibial tunnel and a femoral tunnel completely within the epiphysis. This was supplemented with an extra-articular procedure. Only one of 24 patients had a significant leg length discrepancy related to staples crossing both physes. There were 23 good to excellent functional results.

Other partial sparing techniques involve drilling a small 6-7 mm central transphyseal tibial tunnel and stapling the graft on the femur in an over-the-top position9,10. By keeping the tibial tunnel central and vertical, the damage to the physis can be minimized11.

Both Andrews et al.9, and Lo et al.10 reported on small series' of patients using this technique. No patient had evidence of clinically significant leg length discrepancy, and all had KT-1000 differences of < 5mm (10/13 < 3mm).One patient in Lo's study had a poor IKDC grade, resulting from a subsequent patellar dislocation and osteochondral fracture.

Recently, techniques completely sparing both physes have been described. These techniques have either been non-anatomic12,13,14 or anatomic, but technically demanding15,16.

Kocher et al.14 described a modification of the MacIntosh combined intra and extra-articular reconstruction using a strip of Iliotibial band. The graft is kept attached distally and the free proximal end is passed into the knee from over-the-top. It is then routed under the inter-meniscal ligament over the front of the tibia and sutured to the antero-medial tibial periosteum. Forty-four Tanner stage 1 and 2 patients were studied with a mean 5.3 year follow-up. There were no leg length discrepancies, nor angular deformities. Mean Lysholm score was 96.7, and all patients returned to cutting and pivoting sports except for those with congenital limb deficiencies (3/24). Two patients required revision for graft failure.

Anderson15 described an arthroscopic transepiphyseal technique that involved creating bone tunnels completely in the epiphysis of the femur and tibia under fluoroscopy (Figure 2). A hamstring autograft is fixed on the femur with an Endobutton (Acufex-Smith & Nephew) and tied over a screw and post on the tibia. This series of 12 patients had a mean follow-up of 4.1 years, with no clinically significant leg length discrepancies. Mean KT-1000 difference was 1.5 mm and all patients were graded normal or nearly normal on IKDC scoring. While the results of this preliminary report show the technique to be quite effective, the author cautions that it is "...a technically demanding procedure with a small margin of error, (and) should be attempted only by accomplished knee surgeons"15.

Figure 2a
Figure 2b














Figure 2: Complete phsyeal sparing technique

Kim et al.16 described another challenging technique avoiding all growth plates by using an Achilles allograft over-the-top on the femur and drilling a tibial socket (under fluoroscopy) from the joint down towards the physis without violating it. The graft is fixed with an interference screw on the tibia and stapled to the femur. While this study documented the safety and feasibility of this technique, no clinical outcome data was presented.

In conclusion, young athletes with ACL injuries near skeletal maturity can be treated with transphyseal techniques much like their adult counterparts. For the young growing patient in whom delaying surgery is not an option, physeal sparing reconstructions seem to present a safe and reliable option although a high level of technical expertise is required. Despite avoiding the physis with tunnels, the proximity to, and the tension across the physis still present theoretical concerns to limb growth and thus even these physeal sparing techniques must be considered with caution.


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