Developmental changes in ACLs and semitendinosus tendons dimensions according to age in children

Growth progression of anterior cruciate ligament bone grafts in a pediatric population: magnetic resonance imaging analysis

BACKGROUND

In children, the incidence of anterior cruciate ligament (ACL) ruptures and reconstructions has significantly risen. Unfortunately, re-rupture rates following surgery are substantially higher in children than adults. Previous research suggests that smaller graft diameters are predictive of re-rupture.

OBJECTIVE

This study aimed to investigate the growth progression of the ACL bone graft, specifically in terms of width and length, within the intra-articular portion and tunnels, using successive magnetic resonance imaging (MRI) scans. The hypothesis was that the ACL grafts would undergo thinning during growth.

MATERIALS AND METHODS

The cohort comprised 100 patients who underwent ACL reconstruction. Among them, 37 patients with significant residual growth were selected for analysis. Of these, 4 patients experienced graft rupture, 5 had "over-the-top" techniques, 12 had missing MRI scans and 5 were lost to follow-up. Each included patient underwent two MRI scans; the analyses of which were conducted in a double-masked manner.

RESULTS

A total of 13 knees (and patients) were analyzed, with a mean ± SD (range) delay of residual growth between the two MRI scans of 3.3 + / - 1.4 (1.2-5.2) years. The graft exhibited elongation, thinning and eventual integration with the surrounding bone in the tunnels. Within the intra-articular portion, the mean [95% CI] increase in graft size between the two MRI scans was 30.8% in length and 14.8% in width. The width/length ratio in the intra-articular part was 20.4% on the first MRI and 20.8% on the second MRI. Since this difference in the ratio (+ 0.4%) was not statistically significant (P=0.425), our results indicate that the grafts remained stable in terms of proportions without thinning or thickening. Therefore, the initial hypothesis was validated for the tunnel portion but not the intra-articular portion of the grafts.

CONCLUSION

In children with open physes, ACL grafts demonstrate smooth growth progression in all dimensions. However, this finding does not fully explain the high rate of re-rupture observed in children. Further research is needed to elucidate the underlying factors contributing to re-rupture in this population.

Height is a predictor of hamstring tendon length and ACL graft characteristics in adolescents

BACKGROUND

Knowing the potential hamstring tendon length is relevant for planning ligament reconstructions in children and adolescents, as it is not uncommon to encounter small hamstring tendons intraoperatively. The aim of this study is to predict semitendinosus and gracilis tendon length based on anthropometric values in children and adolescents. The secondary aim is to analyse hamstring tendon autograft characteristics in a closed socket anterior cruciate ligament reconstructions and to evaluate the relationship with anthropometric variables. The hypothesis of this study was that height is predictor of hamstring tendon length and thereby graft characteristics.

METHODS

This observational study included two cohorts of adolescents undergoing ligament reconstructions between 2007-2014 and 2017-2020. Age, sex, height and weight were recorded preoperatively. Semitendinosus and gracilis tendon length and graft characteristics were measured intraoperatively. Regression analysis was performed on tendon length and anthropometric values. Subgroup analyses of the closed socket ACL reconstruction were performed and the relation between anthropometric values and graft characteristics were analysed.

RESULTS

The population consisted of 171 adolescents from 13 to 17 years of age, with a median age of 16 years [IQR 16-17]. The median semitendinosus tendon length was 29 cm [IQR 26-30] and gracilis tendon length was 27 cm [IQR 25-29]. Height was a significant predictor of semitendinosus and gracilis tendon length. Subgroup analysis of the closed socket ACL reconstructions showed that in 75% of the procedure, the semitendinosus tendon alone was sufficient to create a graft with a minimum diameter of 8.0 mm.

CONCLUSIONS

Height is a significant predictor of semitendinosus and gracilis tendon length in adolescents between 13 and 17 years of age and outcomes are similar to data in adults. In 75% of the closed socket ACL reconstructions, the semitendinosus tendon alone is sufficient to create an adequate graft with a minimum diameter of 8 mm. Additional use of the gracilis tendon is more often necessary in females and shorter patients.

LEVEL OF EVIDENCE: 3

Intact PCL is a potential predictor of ACL graft size in the skeletally immature knee and other anatomic considerations for ACL reconstruction

PURPOSE

To develop a method for using an intact posterior cruciate ligament (PCL) as a predictor of anterior cruciate ligament (ACL) graft size and examine possible differences in tunnel length based on all-epiphyseal drilling method.

METHODS

One hundred one patients 5-18 years of age with magnetic resonance imaging (MRI) of the knee at an outpatient pediatric orthopaedic clinic from 2008 to 2020 were included. ACL and PCL coronal, sagittal, and length measurements were made in all patients. Tunnel length measurements were made in patients with open physes. Statistical analyses were performed to evaluate potential associations in patient bony or ligamentous measurements.

RESULTS

PCL sagittal width and PCL coronal width were statistically significant predictors of ACL sagittal width and ACL coronal width, respectively (p = 0.002, R = 0.304; p = 0.008, R = 0.264). The following equations were developed to calculate ACL coronal and sagittal width measurements from the corresponding measurement on an intact PCL; ACL Coronal Width (mm) = 6.23 + (0.16 x PCL Coronal Width); ACL Sagittal Width (mm) = 5.85 + (0.53 x PCL Sagittal Width). Mean tibial maximum oblique length (27.8 mm) was longer than mean tibial physeal sparing length (24.9 mm). Mean femoral maximum oblique length (36.9 mm) was comparable to mean femoral physeal sparing length (36.1 mm). Both were longer than mean femoral straight lateral length (32.7 mm).

CONCLUSION

An intact PCL is a predictor of native ACL size. Tunnel length differs based on chosen drilling method in all-epiphyseal technique.

LEVEL OF EVIDENCE

Diagnostic Level III.