Binary and analogue markers of skeletal maturity: clinical utility of the thenar and plantar sesamoids

PURPOSE: We investigate the thenar and plantar sesamoids as markers of skeletal maturity, and grade appearance using two scales, a binary system (absent or present), and an analogue system that relies upon judging regular changes in morphological appearance. METHODS: We studied 94 healthy children (49 female and 45 male patients) between ages three and 18 years who had approximately 700 serially acquired sets of radiographs and physical examinations. The children had at least annual radiographs taken of the left hand and left foot. Velocity of growth was calculated and curves were fit to a cubic spline model to determine age of maximum height velocity, or peak height velocity (PHV). Appearance of the plantar and thenar sesamoids was recorded using a binary system classifying the sesamoids as absent or present and an analogue system classifying the sesamoid as absent, present as a small ossification centre or larger than a small ossification centre. RESULTS: The plantar sesamoids appear 1.67 years before PHV and reach mature size 1.02 years after PHV. The thenar sesamoids appear 0.32 years before PHV and reach mature size 2.25 years after PHV. The plantar sesamoids are present and thenar sesamoids are absent at a mean 1.5 years prior to PHV. No patients had the thenar sesamoids present while the plantar sesamoids were absent. CONCLUSION: As binary markers, when the plantar and thenar sesamoids are considered together it is possible to localize maturity. As analogue markers, they offer more information. The sesamoids also allow clarification of the calcaneal and Sanders stages. LEVEL OF EVIDENCE: Not Applicable.