Summary

Paediatric male patients did demonstrate evidence of increased healthy-knee laxity compared to other sub-groups

Abstract

Introduction

Children and adolescents have a high incidence of anterior cruciate ligament (ACL) injury. Young female athletes are particularly strongly represented in this cohort. The reasons for the increase in injury rates is undoubtedly multifactorial. Collagen integrity and ligament laxity may play a plausible role in patients who sustain the ACL injury. Normative values for knee ligament laxity are not well reported.

GNRB arthrometer has been demonstrated to measure knee joint laxity in patients who sustain ACL rupture. GNRB arthrometer assessment of healthy non-injured knees in patients undergoing ACL reconstruction may provide some insight into the baseline characteristics of knee joint laxity. We aimed to define the normative values for healthy knee joint laxity in a paediatric cohort and to determine whether they are different from an adult population. Our primary hypothesis was that paediatric ACL patients would have more healthy-knee joint laxity than adults. Our secondary hypothesis was that female patients would demonstrate increased healthy-knee joint laxity compared to male patients.

Methods

GNRB arthrometer has been routinely used on all patients in our institution undergoing ACL reconstruction at 12 months post-surgery. The GNRB measures tibial displacement with anteriorly directed force delivered at 134 Newtons (N), 150 N and 200 N. Normally, the data is used to compare the healthy knee to the ACLR knee. In this study, we assessed only the laxity results from the healthy knees amongst a cohort of ACLR patients at 12 month post-surgery. We subdivided the cohort according to age and gender. Groups were compared using student t-test.

Results

660 (375 female; 285 male) patients underwent GNRB arthrometer testing at 12 months post ACLR. Mean age of the cohort was 27.3 years (SD 10.9) and range from 9 years to 64 years. Paediatric patients (n = 96; aged 16 years or below) adult patients (n = 564; aged above 16 years). Mean displacement was recorded at 134 N (5.34 mm; SD 1.88), 150 N (6.02 mm; SD 1.90) and 200 N (7.73 mm; SD 2.04). There were no differences between males and females at 134 N (p = 0.21), 150 N (p = 0.13) or 200 N (p = 0.11). There were no differences between children and adults at 134 N (p = 0.34), 150 N (p = 0.22) or 200 N (p = 0.31). Paediatric males did show increased laxity compared to adult males at 134 N (5.85 mm vs 5.21 mm; p = 0.03) and 150 N (6.54 mm vs 5.83 mm; p = 0.02), but not at 200 N (8.14 mm vs 7.55 mm; p = 0.06).

Conclusion

There was no evidence of female patients having any significant difference in healthy-knee joint laxity compared to males. There was no difference between paediatric patients and adult patients. However, paediatric male patients did demonstrate evidence of increased healthy-knee laxity compared to other groups. The relationship between healthy-knee laxity and ACL injury risk is not known.