Knee hyperextension is not associated with anterior knee laxity, subjective knee function or revision surgery after anterior cruciate ligament reconstruction in children and adolescents.

purposeTo evaluate whether contralateral knee hyperextension (KHE) is associated with anterior knee laxity, subjective knee function or revision surgery after primary anterior cruciate ligament reconstruction (ACLR) in patients <18 years.

methodsPatients <18 years who underwent primary ACLR at Capio Artro Clinic, Stockholm, Sweden between January 2002 and March 2017 were identified. They were dichotomised into a 'hyperextension' group (≤-5°) and 'no hyperextension' group (>-5°) depending on preoperative contralateral passive knee extension degree. Anterior knee laxity (KT-1000 arthrometer) was measured preoperatively and 6 months post-operatively. The knee injury and osteoarthritis outcome score (KOOS) was collected preoperatively and after 2 years. Revision ACLR within 5 years after primary ACLR was captured in the Swedish National Knee Ligament Registry.

results1250 patients (63.6% female [n = 795]; mean age 15.5 ± 1.5 years) were included (hyperextension group: 52.9% [n = 661]). Mean extension was -6.1 ± 2.2° in the hyperextension group and 0 ± 0.7° in the no hyperextension group. Hamstring autograft was used in 93.3% (1166 out of 1250). No significant difference between the groups was seen in anterior knee laxity or in the rate of surgical failure at 6 months post-operatively (side-to-side difference: >5 mm) (hyperextension group, 6.6% [32 out of 484 patients] vs. no hyperextension group, 6.8% [29 out of 428 patients]; p = ns). Statistically significant but non-clinically relevant intergroup differences were seen in the KOOS Sport/Recreation and Quality of Life subscales after 2 years. The rate of revision ACLR within 5 years was 11.1% (119 out of 1073 patients). The hazard for revision ACLR in the hyperextension group was not significantly different from the no hyperextension group (hazard ratio, 0.91; 95% confidence interval, 0.63-1.31; p = ns).

conclusionsThere was no significant association between preoperative passive contralateral KHE and anterior knee laxity, subjective knee function or the risk of revision ACL surgery in paediatric patients. These findings suggest that KHE alone should not preclude the use of hamstring tendon grafts in children and adolescents undergoing ACL reconstruction. The study found a high rate of revision ACL surgery in this paediatric population. LEVEL OF EVIDENCE: Level III.