Summary

Contralateral knee hyperextension of ≥ 5 degrees in patients under 18 was not associated with increased revision ACL reconstruction or postoperative anterior knee laxity, but was associated with worse subjective outcomes on KOOS subscales Sports/Function and Quality of Life.

Abstract

Objective

This study aimed to evaluate the association between contralateral knee hyperextension (KHE ≥ 5 degrees) and revision anterior cruciate ligament reconstruction (ACLR), postoperative anterior knee laxity and subjective knee function after primary ACLR in patients younger than 18 years.

Methods

Patients who underwent primary ACLR at our institution from January 2002 to March 2017 were identified. Patients with contralateral ACLR or missing preoperative contralateral range of motion (ROM) data were excluded. Patients with primary ACLR prior to 2005 were excluded from the revision ACLR analyses.
Depending on preoperative contralateral knee extension degree, the group was dichotomized into the hyperextension group (KHE ≥ 5 degrees) and the no hyperextension group (KHE < 5 degrees). Anterior knee laxity (KT-1000 arthrometer, 134N) was measured preoperatively and 6 months postoperatively. Patient-reported outcome measures (PROMs) included the Knee injury and Osteoarthritis Outcome Score (KOOS) and EuroQoL-5 Dimension Questionnaire (EQ5D) and were collected preoperatively and at 2 years postoperatively. Occurrence of revision ACLR within five years from primary ACLR was collected from the Swedish National Knee Ligament Registry (SNKLR), which started registration of ACLRs in 2005.

Results

A total of 1250 patients were included (hyperextension group [KHE ≥ 5 degrees]: 661 [52.9%]; no hyperextension group [KHE < 5 degrees]: 598 [47.8%]). The mean age was 15.5 ± 1.5 years. The total rate of ACLR revisions within five years following the primary ACLR was 11.2% (117/1048) patients. No significant association between revision rate and contralateral knee hyperextension was seen. There was no significant difference in the rate of surgical failures, defined as side-to-side difference (STS) > 5 mm when measured with KT1000, between the two groups. A significant difference between the groups was seen at 2-year follow up in KOOS Sports/Function Subscale (hyperextension group, 73.2±23.8; no hyperextension group, 78.6±22.0; P=0.03) and in the Quality of Life subscale (Hyperextension group, 64.8±25.0; no hyperextension group, 70.0±22.7). No difference was seen in the remaining KOOS subscales or in EQ5D.

Conclusion

Contralateral knee hyperextension was not associated with increased revision ACLR or postoperative anterior knee laxity in children and adolescents. However, patients with KHE reported worse subjective outcomes on KOOS subscales Sports/Function and Quality of Life at 2-year follow-up.

Level of Evidence
Retrospective cohort study, Level of evidence III

Keywords
Knee Hyperextension, ACL reconstruction, children, adolescents, revision, laxity