Anterior Cruciate Ligament Reconstruction in the Skeletally Immature An Anatomical Study Utilizing 3-Dimensional Magnetic Resonance Imaging Reconstructions

• Type of Material: Article
• Authors: Jim Kercher, Emory University; John Xerogeanes, Emory University; Allen Tannenbaum, Emory University; Ramsey Al-Hakim, University of California Los Angeles; James C. Black, Emory University; John Zhao, Georgia Institute of Technology; Allen Tannenbaum, Georgia Institute of Technology
• Language: English
• Date: 2009-03-01
• Publisher: Lippincott, Williams & Wilkins
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2009 by Lippincott Williams & Wilkins.
• Final Published Version (URL): http://dx.doi.org/10.1097/BPO.0b013e3181982228
• Title of Journal or Parent Work: Journal of Pediatric Orthopaedics
• ISSN: 0271-6798
• Volume: 29
• Issue: 2
• Start Page: 124
• End Page: 129
• Keywords: Pediatrics; physis; ACL; PATIENT; ADOLESCENTS; CONSERVATIVE TREATMENT; KNEE; MRI; COMPLETE TEARS; Orthopedics; GROWTH PLATES; reconstruction; Science & Technology; pediatrics; CHILDREN; PHYSEAL ARREST; 3-dimensional model; knee; Life Sciences & Biomedicine; anterior cruciate ligament; MANAGEMENT; ACL RECONSTRUCTION; magnetic resonance imaging
• Research Categories: Engineering, Biomedical

Abstract

INTRODUCTION: Anatomic anterior cruciate ligament (ACL) reconstruction has proven to be a reliable method to restore knee stability. However, the risk of physeal arrest with transphyseal tunnel placement in skeletally immature patients has raised concern regarding this technique. Conservative nonoperative management also has its limitations resulting in meniscal and chondral damage that may lead to degenerative joint disease and poor return to sport. Researchers have used animal models to study the threshold of physeal damage producing growth deformity. The purpose of this study was to examine the distal femoral and proximal tibial physes and determine the damage produced by drilling transphyseal tunnels. In addition, we attempted to find a reproducible angle at which to drill the tibial tunnel for safe interference screw placement. To do this, we used a custom software module. METHODS: A custom software package designed by our team was used: Module for Adolescent ACL Reconstructive Surgery (MAARS). This module created a 3-dimensional model of the distal femur and proximal tibia. The data required for MAARS were sagittal and coronal T1 magnetic resonance imagings of at least 1.5T. Thirty-one knee magnetic resonance imaging studies from patients aged 10 to 15 years old were used. The physes were segmented out to obtain volumetric measurements. Transphyseal tunnels were simulated based on the anatomic trajectory of the native ACL. The module calculated volume of physis was removed with the use of an 8-mm tunnel and the optimum angle for trajectory. RESULTS: Average volume of the tibial and femoral physis was 12,683.1 μL and 14,708.3 μL, respectively. The volume increased linearly with age. Average volume removed from the tibial and femoral physis was 318.4 μL and 306.29 μL, respectively. This represented 2.4% of the distal femoral physis and 2.5% of the proximal tibial physis. The volume percent removed decreased linearly with age.Manipulation of the variables demonstrates graft radius is the most critical parameter affecting the volume of physeal injury. Variation of graft diameter from 6 mm to 11 mm will increase volume percent removed from 2.3% to 7.8%, which averages 1.1% for every 1 mm increase. Increasing tunnel drill angle from 45 degrees to 70 degrees will decrease volume percent removed from 4.1% to 3.1% which averages 0.2% removed for each 5 degrees increase in drill angle. The average angle to maintain a distance of 20 mm from the proximal tibial physis was 65 degrees with a range of 40 degrees to 85 degrees. DISCUSSION: Less than 3% injury occurs when drilling an 8-mm tunnel across the physis. A vertical tunnel has minimal effect, but the tunnel diameter is critical. Interference screws can be placed safely to avoid the physis but requires careful planning. The MAARS module may be helpful in preoperative planning. LEVEL OF EVIDENCE: Diagnostic, level IV.