Predicting Growth Quantitatively Through Proximal Tibia Radiograph Markers

Abstract

Background: The creation of accurate markers for skeletal maturity has been of significant interest to orthopaedic surgeons. They guide the management of diverse disorders such as adolescent idiopathic scoliosis, leg length discrepancy, cruciate ligament injuries, and slipped capital femoral epiphysis. Multiple systems have been described to predict growth using radiographic skeletal markers; however, no such system has yet been developed for the proximal tibia. The purpose of this study was to establish quantitative radiographic parameters within the proximal tibia that can be used to assess degree of skeletal maturity. Methods: From the Bolton Brush collection, 94 children, consisting of 49 girls and 4 boys between the ages of 3 and 18 years old, were followed annually throughout growth with serial radiographs and physical examinations. Final height at maturity was used to calculate the growth remaining at each visit. Multiple measurements for each knee radiograph were performed and correlated with the percentage of growth remaining. Tibial epiphysis width, tibial metaphysis width, and height of the lateral tibial epiphysis were measured on each film and the composite ratios between each of these sets of variables along with their respective accuracy and reliability were calculated. Single and multiple linear regression models were constructed to determine accuracy of prediction. Interobserver and intraobserver studies were performed with 4 investigators ranging from medical student to senior attending and calculated using the intraclass correlation coefficient. All 4 examiners measured all of the subjects and the ratios created were averaged. Results: Tibial epiphysis width, tibial metaphysis width, and height of the lateral tibial epiphysis were all found to be strongly correlated with growth remaining with R 2 values ranging from 0.57 to 0.84. In addition, all 3 ratios were found to be reliable with intraobserver and interobserver intraclass correlation coefficients ranging from 0.92 to 0.94 and 0.80 to 0.94, respectively. A multiple linear regression model demonstrated that combining these 3 ratios allows for a predictive R 2 value of 0.917, showing that these ratios when combined were highly predictive of growth remaining. All findings were independent of sex (P=0.996). Conclusions: We describe 3 measurements that can easily be obtained on an anteroposterior radiograph of the knee. We demonstrate that ratios of these variables can be measured reliably and correlate closely with remaining growth, independent of sex. Together, we believe that these factors will improve the accuracy of determining growth from lower extremity radiographs that include the proximal tibia. Clinical Relevance: This study provides a new quantitative technique to evaluate growth in the lower extremity, which can inform a range of conditions including adolescent idiopathic scoliosis, leg length discrepancy, cruciate ligament injury, and slipped capital femoral epiphyses.

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:…”

“…While their findings were suggestive of increasing age among subsequent Pandya subtypes, the methodologic approach limited further conclusions regarding the relationship between physeal maturation and fracture pattern. Consideration toward skeletal maturity evidently plays a critical role in the management of a variety of pediatric orthopaedic injuries; however, because children enter their peak growth velocity periods at varying times, chronologic age is an unreliable predictor of skeletal maturity in the pediatric population 12,13 . Given this knowledge, orthopaedists have favored estimates of skeletal maturity, which have demonstrably better correlation with the percentage of adult height attainment 12 .…”

“…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.…”

“…Consideration toward skeletal maturity evidently plays a critical role in the management of a variety of pediatric orthopaedic injuries; however, because children enter their peak growth velocity periods at varying times, chronologic age is an unreliable predictor of skeletal maturity in the pediatric population. 12,13 Given this knowledge, orthopaedists have favored estimates of skeletal maturity, which have demonstrably better correlation with the percentage of adult height attainment. 12 A variety of methods to calculate this "skeletal age" have been proposed; however, most of these rely on supplementary imaging (eg, hand bone age).…”