Humeral Head Ossification Predicts Peak Height Velocity Timing and Percentage of Growth Remaining in Children

Abstract

Background: Understanding skeletal maturity is important in the management of idiopathic scoliosis. Iliac apophysis, triradiate cartilage, hand, and calcaneal ossification patterns have previously been described to assess both peak height velocity (PHV) and percent growth remaining; however, these markers may not be present on standard spine radiographs. The purpose of this study was to describe a novel maturity assessment method based on proximal humeral epiphyseal ossification patterns.

Methods: Ninety-four children were followed at least annually throughout growth with serial radiographs and physical examinations. The PHV of each child was determined by measuring the change in height observed at each visit and adjusting for the interval between visits. Percent growth remaining was determined by comparing current to final standing height. The humeral head periphyseal ossification was grouped into stages by 8 investigators ranging from medical student to attending surgeon.

Results: The morphologic changes involving the proximal humeral physis were categorized into 5 stages based on development of the humeral head epiphysis and fusion of the lateral margin of the physis. Our novel classification scheme was well distributed around the PHV and reliably correlated with age of peak growth and percent growth remaining with >70% nonoverlapping interquartile ranges. Furthermore, the scheme was extremely reliable with intraclass correlation coefficients of 0.96 and 0.95 for intraobserver and interobserver comparisons, respectively.

Conclusions: The humeral head classification system described here was strongly correlated with age of PHV as well as percentage growth remaining. Furthermore, the staging system was extremely reliable in both interobserver and intraobserver correlations suggesting that it can be easily generalized.

Clinical relevance: As a view of the humeral head is almost always present on standard scoliosis spine x-ray at our institution, our classification can be easily adapted by surgeons to gain additional insight into skeletal maturity of patients with scoliosis. We believe that our method will significantly improve the evaluation of the child with scoliosis without increasing radiation exposure, time, or cost.

FIGURE 1

Periphyseal changes around the proximal humerus: stage 1 demonstrates an incompletely ossified lateral epiphysis such that the lateral margin is oblique (short bold line). Stage 2 demonstrates increased ossification of the lateral epiphysis with a curvilinear lateral margin (bold curve). Note that in stages 1 and 2, the bold line parallel to the lateral metaphysis does not touch the epiphysis. Stages 3 through 5 all demonstrate colinearity between the lateral margin of the epiphysis and the metaphysis such that a single bold line touches both edges. In stage 3, the lateral half of the physis is open without obvious fusion. In stage 4, the lateral half of the physis thins and begins partial fusion. Finally, by stage 5 the lateral half of the physis demonstrates essentially complete fusion. Fusion is indicated by the hashes.

FIGURE 2

Representative images of the humeral stages. Stage 1 demonstrates an incompletely ossified lateral epiphysis leaving a triangular area of radiolucency on the lateral aspect of the epiphysis. Stage 2 demonstrates increased ossification of the lateral epiphysis leaving a crescent shaped area of radiolucency on the lateral side of the epiphysis. These shapes are highlighted below the annotations with representative images shown both unmodified and with the shapes superimposed. Note that in stages 1 and 2, the black line parallel to the lateral metaphysis does not touch the epiphysis. Stages 3 through 5 all demonstrate colinearity between the lateral margin of the epiphysis and the metaphysis. In Stage 3, the lateral half of the physis is open without obvious fusion. In stage 4, the lateral half of the physis thins and begins partial fusion. Finally, by stage 5 the lateral half of the physis demonstrates essentially complete fusion. The same annotations used on the schematic are superimposed upon the radiographic examples for ease of comparison.

FIGURE 3

Normalized distribution of staging with age to PHV (years) on the x-axis and proportion of observations on the y-axis. A vertical line is drawn at PHV occurring between stages 2 and 3. PHV indicates peak height velocity.

FIGURE 4

Humeral head ossification system placed in context of currently used standards for the determination of skeletal maturity including TRC, iliac apophysis ossification (Risser), hand scoring systems, and menarche. Boxes are indicated based on the stage containing the plurality of data at that time point. All ossification systems were measured on the same patients used to develop our humeral head staging system. Menarche for this dataset is likely unreliable for modern patients so a modern standard from our previous work has been used. Time relative to PGA was measured in years. PGA indicates peak growth age; TRC, triradiate cartilage closure.

FIGURE 5

Humeral head staging system with regard to percentage of growth remaining in patients as determined by current standing height versus final standing height. Note that PHV usually occurs around 90% of growth completed and is indicated by the horizontal line. PHV indicates peak height velocity.