O3257: How Fast and How Far? Prospective Study on Femoral Overgrowth in Diaphyseal Femur Fractures

Background: Femoral shaft fractures account for 1-2% of all pediatric fractures. Stimulation of growth following this fracture is a well-recognized phenomenon. However, most literature on this topic does not differentiate between “catch up growth” and overgrowth.

Methods: Patients with diaphyseal femur fractures between the age of 6 months and 4 years were prospectively enrolled and randomized to treatment with either a spica cast or a functional brace. Radiographs at time of injury were compared to those with 1 year follow up and analyzed with regards to shortening and varus malalignment. Initial shortening was measured based on fracture overlap from the injury films and 1 yr shortening was measured in comparison to the contralateral femur. Patients who lacked a full-length hip to ankle film at 1 yr post injury were excluded.

Results: 45 patients met the inclusion criteria, mean age 2.2 ± 0.9years. 24 were treated in a functional brace and 21 were treated with a spica. Femoral shortening at the time of injury was a mean of 7.3±7.4 mm. At time of injury, 11 patients had > 10mm of shortening, of which all 11 had 10-20 mm.

At 1 yr follow up femoral shortening was a mean of 0.8±3.2 mm overall, for an increased growth of 0.5 mm/month. In the subset of 11 patients with >10mm of shortening, the mean shortening at 1 year was 2.2±3.9 mm for a rate of increased growth of 1.2±0.4mm/month. Rate of overgrowth was significantly higher in those that had more shortening (p < 0.01). At 1 year, 8 patients had overgrowth and had a longer femoral shaft on the affected side by mean 4.05±1.3 mm. One of these patients had greater than 5mm of length compared to the contralateral side.

There were no differences in fracture shortening between the spica and functional brace groups at time of injury (p=0.47). There was a slight decrease in femoral shortening in the brace group as compared to the spica at 1 year follow-up (p=0.046, Brace= -0.1mm, Spica=1.8mm), though likely not clinically significant.

Conclusion: Overall, the group experienced femoral overgrowth at a rate of 0.5mm/month following diaphyseal femur fracture in this prospective cohort. This rate was more than doubled in those with greater shortening. These numbers can be helpful to help guide parental and provider expectations following femur fractures in patients ages 6 months to 4 years.