An anatomical study of the pediatric intercondylar notch.

Background: Anterior cruciate ligament reconstructions in skeletally immature patients are becoming more commonplace. Complications of growth disturbance remain a major concern, especially at the distal femoral physis, and are often attributed to technical errors. A review of the literature revealed limited anatomical data of the skeletally immature intercondylar notch to guide surgical technique.

Methods: We studied 103 preserved femora aged 3 to 20 years, with 33 of these aged 7 to 15 years. The distance between the "resident's ridge" (lateral intercondylar ridge) and the "over-the-top" position (OTP) was measured at the 11-, 10-, and 9-o'clock positions in the right femora, and the 1-, 2-, and 3-o'clock positions in the left femora. The angles between the femoral surface, distal femoral physis, and femoral shaft were measured in the coronal and sagittal planes using a goniometer.

Results: Femora in the 13- to 15-year-old subgroup tended to have a more clearly defined resident's ridge than femora in the younger subgroups. The space between resident's ridge and the OTP was on average greater than 8 mm at all 3 positions in the 13- to 15-year-old subgroup, and greater than 7 mm at all 3 positions in the 10- to 12-year-old subgroup, with more space available with a more peripheral starting point. The average angles between the femoral surface and physis in the sagittal and coronal planes were 47 degrees and 36 degrees in the 13- to 15-year-old subgroup, and 58 degrees and 28 degrees in the 10- to 12-year-old subgroup. The average angles between the distal femoral shaft and physis in the sagittal and coronal planes were -9 degrees and 7 degrees in the 13- to 15-year-old subgroup, and -6 degrees and 7 degrees in the 10- to 12-year-old subgroup. Analysis of females versus males demonstrated larger distances between resident's ridge and the OTP in males, but no differences in the angular measurements.

Conclusions: In younger patients, the resident's ridge is less commonly present and less clearly defined. The femoral tunnel can usually be drilled behind the resident's ridge at the 11-o'clock/1-o'clock position, although in females, the ridge is more likely to be included in the drill hole. In both males and females, the tunnel should be aimed posterior and medial with respect to the perpendicular of the femoral surface and anterior and medial with respect to the shaft to drill through the physis with less obliquity, and to provide a tunnel deep enough to avoid spanning the physis with bone or hardware.