Modified Fels knee skeletal maturity system accurately predicts ultimate limb length
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The modified Fels knee skeletal maturity system accurately estimates ultimate limb length discrepancy and appropriate timing of epiphysiodesis in pediatric patients with lower limb discrepancy, according to a presenter.
At the Limb Lengthening and Reconstruction Society Annual Scientific Meeting, Ryan J. Furdock, MD, an orthopedic surgery resident at Case Western Reserve University in Cleveland, Ohio, presented results on the utility of the modified Fels knee skeletal maturity system.
“Our research group is developing skeletal maturity estimation systems for every major joint and including all of those systems in our free ‘What's the Skeletal Maturity?’ mobile application,” Furdock told Healio Orthopedics. “Our end goal is to provide orthopedic surgeons with a simple, quick and accurate means of obtaining a bone age on any child with any X-ray they have available.”
Furdock and colleagues analyzed 247 radiographs (109 prior to skeletal maturity) from 47 patients with unilateral lower extremity pathology. According to the abstract, the researchers defined skeletal maturity by closed distal femoral, proximal tibial and proximal fibular physes. They then applied the modified Fels knee skeletal maturity system to all radiographs taken prior to maturity and judged the system for accuracy of lower extremity length prediction in estimated skeletal age vs. chronological age inputs.
Furdock and colleagues found linear mixed effects modeling using skeletal age was “uniformly associated” with improved R2 values compared with the chronological age-based models. They also found the skeletal age models had lower Akaike information criterion values compared with the chronological age-based models, indicating “superior performance,” according to the abstract.
“Our work indicates that orthopedic surgeons may not need to obtain an additional hand radiograph for bone age when treating patients with limb length discrepancy. Instead, they can use the radiograph they already have and our free mobile application to accurately estimate skeletal maturity and ultimate limb length,” Furdock added. “While further study is necessary, we believe this system may allow for more appropriately timed epiphysiodesis procedures,” he concluded.
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Calculating the amount of growth remaining in a limb is limited by the accuracy of determining the patient’s skeletal age. The Greulich and Pyle method is currently the most commonly utilized method to calculate skeletal age but is known to have shortcomings that can create inaccurate calculations.
The modified Fels knee skeletal maturity system has been found to be more accurate than the Greulich and Pyle method. In addition, it avoids the need to obtain separate radiographs of the upper extremity (elbow or wrist) when calculating skeletal maturity for the lower extremity. While using the modified Fels knee skeletal maturity system is more time consuming than the shorthand bone age assessment technique, a free, well-designed smartphone application (What’s the Skeletal Maturity?) is available to help simplify the process.
I congratulate Furdock and his team for helping to advance the science of determining skeletal maturity and expect the modified Fels method to become more widely used among pediatric limb reconstruction surgeons in the future.
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Furdock RJ, et al. The utility of the modified Fels knee skeletal maturity system in limb length prediction. Presented at: Limb Lengthening and Reconstruction Society Annual Scientific Meeting; July 16-17, 2021; New York.
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