Study finds physeal-sparing method for ACL reconstruction of pediatric patients
SAN FRANCISCO — A combination of two techniques could spare the physis of skeletally-immature patients when drilling the femoral tunnel during anatomic ACL reconstruction, according to a study presented here.
Kyle E. Hammond, MD, shared his group’s findings at the 2011 Annual Meeting of the Arthroscopy Association of North America.
Hammond said his study aimed to develop a reliable and easily reproducible anatomic technique that used intra- and extra-articular landmarks to construct a femoral tunnel that avoided the physis.
“There is an increasing number of reported pediatric ACL injuries and reconstructions performed,” Hammond said. “Concern remains over injury to the physis. There is also an increasing interest in anatomic ACL reconstructions.”
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Landmarks in the knee
The investigators studied 188 MRIs from children aged 6 years to 17 years and examined multiple anatomic landmarks in the effort to locate optimal landmarks for ACL reconstruction. Hammond reported the femoral origin of the popliteus tendon and the lateral epicondyle were used as extra-articular landmarks, with the intra-articular landmark defined as the central portion of the femoral ACL origin.
Multi-plane computer software was used to plot points at the three landmarks in multiple planes, and lines were then drawn to depict potential femoral tunnels connecting the ACL origin to the popliteal insertion and the lateral epicondyle. The investigators then used these lines to calculate distances for tunnel lengths, the shortest distance from the physis to the tunnels, width of the femoral notch, and width and height of the femoral condyles.
Hammond said the group used 3-D MRI physeal reconstruction to confirm the physis was spared when these landmarks were used.
Safe and reliable
Hammond's group found significantly differing results across age groups and sexes for total femoral widths, notch widths, condylar heights, tunnel lengths from the ACL origin to the popliteus insertion and tunnel lengths from the ACL origin to the lateral epicondyle.
Hammond noted the average distance from the femoral physis to the tunnel that ran from the ACL origin to the popliteus was 12 mm — a finding that was independent of patient age or gender. The tunnel length averaged 30.1 mm in male subjects and 27.4 mm in female subjects. Hammond also reported an average tunnel length of 25.6 mm in 6-year-olds and 30.2 mm in 17-year-olds.
The tunnel leading from the ACL origin to the lateral epicondyle was 8.8 mm from the femoral physis in male patients and 8.9 mm from the femoral physis in female patients, with an average tunnel length of 34.3 mm in male patients and 31.6 mm in female patients.
“So even with the shortest distance we found to the femoral physis from the center of the popliteal femoral tunnel, which was 8 mm seen in one 6-year-old patient, you are still able to safely drill at least an 8 mm tunnel using this technique,” Hammond said. “Also, we found that the distance to the physis increased as the children matured — allowing even larger tunnels.”
The findings, Hammond said, show that drilling from the ACL origin to the popliteal insertion will produce an average tunnel length of 27 to 30 mm — allowing “at least” an 8 to 10 mm diameter tunnel in patients from 6 years to 17 years old. Use of the landmarks identified in the study, he noted, should allow for anatomic ACL reconstructions to be safely and reliably performed without intraoperative X-rays.
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