Measuring Proximal Tibial Metaphyseal Width and Lateral Epiphyseal Height Improves Determination of Remaining Growth in Children

Abstract

Background: Accurate assessments of skeletal maturity is of critical importance to guide type and timing of orthopaedic surgical interventions. Several quantitative markers of the proximal tibia were recently developed using historical knee radiographs. The purpose of the present study was to determine which marker would be most effective in assessment of fulllength radiographs in a modern pediatric patient population. Methods: All full-length radiographs at our institutions between 2013 and 2018 were reviewed. Inclusion criteria for our study required that the child reached final height as defined by 2 consecutive unchanged heights, at least 6 months apart, after age 16 for boys and 14 for girls. Patients with metabolic bone disease, prior surgery such as epiphysiodesis, or previous infections around the knee were excluded. Summary statistics for each of the 3 proximal tibial ratios were calculated and multiple linear regression was performed with percent of growth remaining as a dependent variable. A recommended regression model is presented and evaluated. Results: A total of 692 full-length radiographs met inclusion criteria. Proximal tibial ratios were calculated and averaged values for each percent of growth remaining was presented. Multiple linear regression demonstrated that using all 3 variables led to overfitting of the model so tibial metaphyseal width/lateral tibial epiphyseal height was selected as the optimal ratio for use by clinicians. The optimal model for determining growth was found to have R 2 = 0.723 in the developmental set and R 2 = 0.762 in an excluded validation set.Conclusions: This study demonstrates that the proximal tibial metaphyseal width/lateral tibial epiphyseal height is the ideal measurement for clinicians seeking to determine growth remaining in children. It presents average values between 0% and 25% of growth remaining. This study also develops and validates a multivariable regression model for determining percentage of growth remaining in children that will allow for quantitative determination of growth using full-length radiographs. Level of Evidence: Level III.

Does Skeletal Maturity Predict the Pattern of Tibial Tubercle Avulsion Fracture?

“…We also utilized the first post-treatment radiographs performed within 2 weeks of surgery which provided more standardized imaging on which to perform our skeletal maturity assessments. Third, the Kahan formula utilized in this study to estimate GRP was derived from the Bolton Brush study, which was sourced in 1926 from predominantly white children from wealthy families 13,16 . As such, while prior studies have demonstrated the Brush cohort has matched well to a modern cohort, it is possible that this influences generalizability in our predominantly Black and more socioeconomically diverse cohort 11 .…”

“…Two maturity markers capable of being generated exclusively from knee radiographs were identified. Kahan and colleagues developed a system for predicting skeletal maturity based on measurements of the regional physes of the knee which was derived from a study cohort of primarily adolescents 13,16–19 . Their growth remaining percentage (GRP) was calculated using the following formula:…”

“…of the knee which was derived from a study cohort of primarily adolescents. 13,[16][17][18][19] Their growth remaining percentage (GRP) was calculated using the following formula:…”

“…Growth remaining = 0.038 × sex + 0.025 × age + 0.014 × Ra + 0.014 × Rb + 0.007 × Ro + 0.075 × central peak height-/physeal length + 0.009 × tibial metaphysis width/lateral height + 0.351 where, Ra, Rb, and Ro were variables to account for differences between patient race (each variable equals 0 except for the variable corresponding to the patient race). Central peak height, physeal length, tibial metaphysis width, and lateral height were measured on radiographs as per Kahan et al's 16 original technique. We secondarily categorized patients according to a radiographic classification of epiphyseal union based on the stages described by Mckern and Stewart, 20 and more recently by O'Connor et al 21 : nonunion, beginning union, active union, recent union, and complete union.…”

“…The purpose of this study was to evaluate the relationship between skeletal age and TTAF pattern using 2 established TTAF injury classifications. With consistently available imaging in a retrospective patient cohort limited largely to knee radiographs, we identified 2 radiographic markers of skeletal maturity derived only from this modality and assessed the maturity characteristics across both TTAF fracture classifications 13,16 . We hypothesized that unique TTAF injury patterns would occur at specific stages of skeletal maturity due to the organized closure of the proximal tibial apophysis and physis.…”