Knee Anterior Laxity and Graft Maturation After Transphyseal Anterior Cruciate Ligament Reconstruction.

Background: The failure rate of anterior cruciate ligament (ACL) reconstruction in children and adolescents is a significant concern. Of the multitude of clinical factors that contribute to this risk, delayed maturation and graft laxity are potentially related and modifiable elements. The aim was to investigate knee anterior laxity and graft maturation in children and adolescents. The ligamentization of the graft may be correlated with the residual laxity.

Methods: A single-center prospective study included skeletally immature patients treated with transphyseal ACL reconstruction using semitendinosus tendon autograft from 2017 to 2019. Participants were evaluated on 4 occasions: preoperatively, then at 6, 12, and 24 months with instrumented laximetry and MRI to analyze graft maturation according to the Signal-to-noise Quotient (SNQ) and Howell classification.

Results: A total of 50 patients (33 boys and 17 girls), with a mean age of 13.2 years (range, 9 to 16) at the time of surgery, were included. Mean side-to-side knee anterior laxity decreased from 2.78 mm preoperatively to 1.59, 1.80, and 1.30 mm (at 6, 12, and 24 mo follow-up, respectively), P<0.05. No statistical difference was noted according to the follow-up or sex. SNQ was unchanged between 6 and 12 months, but a significant difference was demonstrated between 12 months and 24 months (P=0.008). There was no statistical correlation between laximetry and graft maturation.

Conclusions: ACL graft ligamentization is delayed in children and adolescents and only occurs between 12 and 24 months postoperatively. Residual laximetry and MRI signal of the graft may become one of the multiple elements upon which to base the decision to return to sport.