Abstract
Introduction:
Peak external knee valgus moment can predict future ACL injury and is, often times, asymmetric following anatomic intra-articular ACL reconstruction. The purpose of this study is to evaluate the external knee valgus moment during a drop landing and a single limb squat 2 years following an iliotibial band (ITB) intra-articular and extra-articular physeal-sparing ACL reconstruction. Methods: Fourteen study subjects (mean age: 14.3 ± 2.6 yrs) who had previously undergone a physeal-sparing ACL reconstruction, as originally described by McIntosh using an ITB autograft, were enrolled in this IRB-approved study. All subjects were seen at a minimum of 24 months after surgery (mean follow-up: 55.0 ± 28.9 mos) and clinical, radiographic, and patient reported outcomes were collected. During functional testing, subjects underwent drop landing (DL) and unilateral squat (US) tasks. Isokinetic muscle strength of the hip and knee was collected using an isokinetic dynamometer at 60°/s. Paired student’s t-tests evaluated differences between affected (AFF) and unaffected (UNAFF) limbs.
Results:
During a drop landing, the AFF limb, compared to the UNAFF limb, did not demonstrate a difference in external knee valgus moment (0.50° vs. 0.51°, p=0.736). However, in the AFF limb, the mean knee peak knee valgus angle was 2.8 degrees less than the UNAFF limb during a drop landing (p=0.039). This difference was not considered within the range of a minimal clinical difference (MCD) of 5.1 degrees. Similar trends were found during a single limb squat with no significant difference seen in peak knee valgus moment between AFF and UNAFF (0.14° vs. 0.07°, p=0.150) with a statistical, yet not minimal clinical difference, in knee valgus angle at 45° squat position (-2.4° vs. 0.7°, p=0.033; MCD = 5.2). Thus, no asymmetry in peak knee valgus moment during a drop landing or a single limb squat following an ITB intra- and extra-articular ACL reconstruction was observed.
In this series at 2 years’ post-op, the Pedi-IKDC and HSS Pedi-FABS were 96.54 ± 5 and 22.6 ± 5, respectively. Subjects demonstrated return to pre-operative Tegner Activity scores (8.42 vs. 8.17, p=0.33). Normalized hip abduction strength was significantly stronger in AFF (1.05 Nm/kg) vs. UNAFF (0.93 Nm/kg, p=0.02).
Conclusion:
Overall, there were no clinically significant differences, or asymmetry, in functional knee valgus in subjects following combined intra- and extra-articular iliotibial band ACL reconstruction during a drop landing or single leg squat. Young athletes can be expected to return to pre-operative activity levels and demonstrate appropriate knee valgus control following this physeal-sparing ACL reconstruction.