Systematic Isolation of Key Parameters for Estimating Skeletal Maturity on Anteroposterior Wrist Radiographs

Optimizing calibration of modern skeletal maturity systems

Purpose

Greulich and Pyle is the most used system to estimate skeletal maturity but has significant drawbacks, prompting the development of newer skeletal maturity systems, such as the modified Fels skeletal maturity systems based on knee radiographs. To create a new skeletal maturity system, an outcome variable, termed a "skeletal maturity standard," must be selected for calibration of the system. Peak height velocity and 90% of final height are both considered reasonable skeletal maturity standards for skeletal maturity system development. We sought to answer two questions: (1) Does a skeletal maturity system developed using 90% of final height estimate skeletal age as well as it would if it was instead developed using peak height velocity? (2) Does a skeletal maturity system developed using 90% of final height perform as well in lower extremity length prediction as it would if it was instead developed using peak height velocity?

Methods

The modified Fels knee skeletal maturity system was recalibrated based on 90% of final height and peak height velocity skeletal maturity standards. These models were applied to 133 serially obtained, peripubertal antero-posterior knee radiographs collected from 38 subjects. Each model was used to estimate the skeletal age of each radiograph. Skeletal age estimates were also used to predict each patient's ultimate femoral and tibial length using the White-Menelaus method.

Results

The skeletal maturity system calibrated with 90% of final height produced more accurate skeletal age estimates than the same skeletal maturity system calibrated with peak height velocity (p < 0.05). The 90% of final height and peak height velocity models made similar femoral and tibial length predictions (p > 0.05).

Conclusion

Using the 90% of final height skeletal maturity standard allows for simpler skeletal maturity system development than peak height velocity with potentially more accuracy.

The Addition of Hand-specific Skeletal Maturity Parameters Does Not Improve Skeletal Maturity Estimation Accuracy of the Modified Fels Wrist System

BACKGROUND

The Modified Fels Wrist system is potentially the most accurate clinically accessible skeletal maturity system utilizing hand or wrist radiographs. During development, parameters distal to the metacarpals were excluded. We attempted to further optimize the Modified Fels wrist system through the inclusion of hand parameters distal to the metacarpals.

METHODS

Forty-three new anteroposterior (AP) hand radiographic parameters were identified from the Fels and Greulich and Pyle (GP) skeletal maturity systems. Twelve parameters were eliminated from further evaluation for poor correlation with skeletal maturity, poor reliability, and lack of relevance in the peripubertal years. In addition to the 8 previously described Modified Fels Wrist parameters, 31 hand radiographic parameters were evaluated on serial peripubertal AP hand radiographs to identify the ones most important for accurately estimating skeletal age. This process produced a "Modified Fels hand-wrist" model; its performance was compared with (1) GP only; (2) Sanders Hand (SH) only; (3) age, sex, and GP; (4) age, sex, and SH; and (5) Modified Fels Wrist system.

RESULTS

Three hundred seventy-two radiographs from 42 girls and 38 boys were included. Of the 39 radiographic parameters that underwent full evaluation, 9 remained in the combined Modified Fels Hand-Wrist system in addition to chronological age and sex. Four parameters are wrist specific, and the remaining 5 are hand specific. The Hand-Wrist system outperformed both GP and SH in estimating skeletal maturity ( P <0.001). When compared with the Modified Fels Wrist system, the Modified Fels Hand-Wrist system performed similarly regarding skeletal maturity estimation (0.36±0.32 vs. 0.34±0.26, P =0.59) but had an increased (worse) rate of outlier predictions >1 year discrepant from true skeletal maturity (4.9% vs. 1.9%, P =0.01).

CONCLUSIONS

The addition of hand parameters to the existing Modified Fels Wrist system did not improve skeletal maturity estimation accuracy and worsened the rate of outlier estimations. When an AP hand-wrist radiograph is available, the existing Modified Fels wrist system is best for skeletal maturity estimation.

LEVEL OF EVIDENCE

Level III.

An age-matched comparative study on intramedullary nailing and plate fixation of both-bone diaphyseal forearm fracture in adolescents

OBJECTIVE

This study aimed to compare radiological and functional outcomes and complication rates between intramedullary nailing (IMN) and plate fixation for diaphyseal forearm fractures in adolescents via an age-matched analysis.

METHODS

Data were collected from medical records at 11 hospitals from 2009 to 2019, and the age-matched study was conducted between IMN and plate fixation. Functional outcomes, radiographic outcomes, and postoperative complication rates were compared.

RESULTS

The IMN group (Group N) and plate fixation group (Group P) each comprised 26 patients after age matching. The mean age after matching was 13.42 years old. Bone maturities at the wrist of the radius and ulna were not significantly different between the two groups (p = 0.764 and p = 1). At the last follow-up period, functional outcomes using the Price criteria were over 90% in both groups, and the rotational range of motion was comparable to that of the healthy side. Over 70% of cases in Group N were performed by closed reduction, and operation time was half that of Group P. Postoperative neurological symptoms and refractures were more common in Group P than in Group N, although not statistically significantly so.

CONCLUSIONS

Treatment outcomes for age-matched adolescent diaphyseal forearm fractures were excellent with IMN, as well as with plate fixation in many cases despite fewer complications, better cosmesis, and shorter operative times with IMN. IMN for diaphyseal forearm fractures is a useful treatment option even in adolescents although the indications for the best procedure to perform should be considered depending on individual patient needs.

LEVEL OF EVIDENCE IV

Multicenter retrospective study.

Correlations Between Eight Comprehensive Skeletal Maturity Systems in a Modern Peripubertal Pediatric Population

BACKGROUND

Several skeletal maturity systems allow for accurate skeletal age assessment from a wide variety of joints. However, discrepancies in estimates have been noted when applying systems concurrently. The aims of our study were to (1) compare the agreement among 8 different skeletal maturity systems in modern pediatric patients and (2) compare these discrepancy trends qbetween modern and historic children.

METHODS

We performed a retrospective (January 2000 to May 2022) query of our picture archiving and communication systems and included peripubertal patients who had at least two radiographs of different anatomic regions obtained ≤3 months apart for 8 systems: (1) proximal humerus ossification system (PHOS), (2) olecranon apophysis ossification staging system (OAOSS), (3) lateral elbow system, (4) modified Fels wrist system, (5) Sanders Hand Classification, (6) optimized oxford hip system, (7) modified Fels knee system, and (8) calcaneal apophysis ossification staging system (CAOSS). Any abnormal (ie, evidence of fracture or congenital deformity) or low-quality radiographs were excluded. These were compared with a cohort from a historic longitudinal study. SEM skeletal age, representing the variance of skeletal age estimates, was calculated for each system and used to compare system precision.

RESULTS

A total of 700 radiographs from 350 modern patients and 954 radiographs from 66 historic patients were evaluated. In the modern cohort, the greatest variance was seen in PHOS (SEM: 0.28 y), Sanders Hand (0.26 y), and CAOSS (0.25 y). The modified Fels knee system demonstrated the smallest variance (0.20 y). For historic children, the PHOS, OAOSS, and CAOSS were the least precise (0.20 y for all). All other systems performed similarly in historic children with lower SEMs (range: 0.18 to 0.19 y). The lateral elbow system was more precise than the OAOSS in both cohorts.

CONCLUSIONS

The precision of skeletal maturity systems varies across anatomic regions. Staged, single-parameter systems (eg, PHOS, Sanders Hand, OAOSS, and CAOSS) may correlate less with other systems than those with more parameters.

LEVEL OF EVIDENCE

Level III-retrospective study.

An Automated TW3-RUS Bone Age Assessment Method with Ordinal Regression-Based Determination of Skeletal Maturity

The assessment of bone age is important for evaluating child development, optimizing the treatment for endocrine diseases, etc. And the well-known Tanner-Whitehouse (TW) clinical method improves the quantitative description of skeletal development based on setting up a series of distinguishable stages for each bone individually. However, the assessment is affected by rater variability, which makes the assessment result not reliable enough in clinical practice. The main goal of this work is to achieve a reliable and accurate skeletal maturity determination by proposing an automated bone age assessment method called PEARLS, which is based on the TW3-RUS system (analysis of the radius, ulna, phalanges, and metacarpal bones). The proposed method comprises the point estimation of anchor (PEA) module for accurately localizing specific bones, the ranking learning (RL) module for producing a continuous stage representation of each bone by encoding the ordinal relationship between stage labels into the learning process, and the scoring (S) module for outputting the bone age directly based on two standard transform curves. The development of each module in PEARLS is based on different datasets. Finally, corresponding results are presented to evaluate the system performance in localizing specific bones, determining the skeletal maturity stage, and assessing the bone age. The mean average precision of point estimation is 86.29%, the average stage determination precision is 97.33% overall bones, and the average bone age assessment accuracy is 96.8% within 1 year for the female and male cohorts.

Applicability of Shoulder, Olecranon, and Wrist-based Skeletal Maturity Estimation Systems to the Modern Pediatric Population

BACKGROUND

The proximal humerus ossification system (PHOS), olecranon apophyseal ossification system (OAOS), and modified Fels wrist skeletal maturity system (mFWS) were recently developed or updated using a historical, mostly White, pediatric population. These upper extremity skeletal maturity systems have demonstrated skeletal age estimation performance superior or equivalent to Greulich and Pyle in historical patients. Their applicability to modern pediatric populations has not yet been evaluated.

METHODS

We reviewed anteroposterior shoulder, lateral elbow, and anteroposterior hand and wrist x-rays of 4 pediatric cohorts: White males, Black males, White females, and Black females. Peripubertal x-rays were evaluated: males 9 to17 years and females 7 to 15 years. Five nonpathologic radiographs for each age and joint were randomly selected from each group. Skeletal age estimates made by each of the 3 skeletal maturity systems were plotted against the chronological age associated with each radiograph and compared between cohorts, and with the historical patients.

RESULTS

Five hundred forty modern radiographs were evaluated (180 shoulders, 180 elbows, and 180 wrists). All radiographic parameters had inter- and intra-rater reliability coefficients at or above 0.79, indicating very good reliability. For PHOS, White males had delayed skeletal age compared with Black males (Δ-0.12 y, P=0.02) and historical males (Δ-0.17 y, P<0.001). Black females were skeletally advanced compared with historical females (Δ0.11 y, P=0.01). For OAOS, White males (Δ-0.31 y, P<0.001) and Black males (Δ-0.24 y, P<0.001) had delayed skeletal age compared with historical males. For mFWS, White males (Δ0.29 y, P=0.024), Black males (Δ0.58 y, P<0.001), and Black females (Δ0.44 y, P<0.001) had advanced skeletal age compared with historical counterparts of the same sex. All other comparisons were not significant (P>0.05).

CONCLUSIONS

The PHOS, OAOS, and mFWS have mild discrepancies in skeletal age estimates when applied to modern pediatric populations depending on the race and sex of the patient.

LEVEL OF EVIDENCE

Level III - retrospective chart review.

The Systematic Isolation of Key Parameters for Estimating Skeletal Maturity on Lateral Elbow Radiographs

BACKGROUND

Skeletal maturity estimation is central in the management of scoliosis and lower-limb deformity. Utilizing demographic characteristics and modern computing, we sought to create a reliable, rapid, and accurate method for measuring skeletal maturity on an elbow radiograph.

METHODS

Utilizing the Bolton-Brush Collection, 4 parameters from the modified Sauvegrain method and 7 novel parameters were screened. Ten parameters were evaluated on serial peripubertal elbow radiographs, using Greulich and Pyle (GP) skeletal age from corresponding hand radiographs as a comparison. Stepwise linear regression and generalized estimating equations were used to identify radiographic and demographic parameters for estimating skeletal maturity based on 90% of final height. The elbow system was compared with GP only; olecranon apophysis only; age, sex, and GP; age, sex, and olecranon apophysis; age, sex, and elbow system with anteroposterior and lateral parameters; age, sex, and elbow system with anteroposterior parameters; and age, sex, and elbow system with lateral parameters.

RESULTS

In this study, 367 radiographs from 77 patients (40 girls and 37 boys) were included. Following stepwise linear regression, 4 radiographic parameters were included in the anteroposterior and lateral elbow system; 3 were included in the anteroposterior elbow system; and 4 were included in the lateral elbow system. The lateral elbow system predicted skeletal maturity with a mean discrepancy of 0.41 year and produced similar mean discrepancies to GP with age and sex (0.42; p = 0.93), and it trended toward better performance than the olecranon apophysis system with age and sex (0.43; p = 0.06). The lateral elbow system had the lowest percent of outlier predictions >1 year discrepant from the skeletal maturity reference (4.6%), although it was only significantly better than the GP-only group (29.4%) and the olecranon apophysis-only group (21.0%) (p < 0.001 for both).

CONCLUSIONS

We systematically developed a lateral elbow system that performed equivalently to GP using 4 simple parameters and trended toward outperforming the olecranon apophysis systems in skeletal maturity estimation. Future clinical validation will be necessary to understand the utility of this system.

CLINICAL RELEVANCE

The lateral elbow system may be a more accurate prediction of skeletal maturity compared with the previously described olecranon apophysis system and can be used to guide the management of many pediatric orthopaedic conditions.