PRECICE nail bending in femur lengthening

Intramedullary nails (ILNs) are commonly used in orthopedic surgery for the fixation of long bone fractures and limb lengthening. Understanding the structural mechanics (i.e. nail bend) of an ILN device is crucial in determining its performance under various loading conditions. Furthermore, nail diameter was found to play a key role in an ILN's susceptibility to plastic deformity. This study aims to investigate the degree of nail bending and incidence of plastic deformity in patients receiving antegrade femoral ILNs (PRECICE, NuVasive, Inc.).

Retrospectively evaluated 130 ILNs (PRECICE, NuVasive, Inc.) in 100 adult patients who underwent limb lengthening done in a single center. Patients who had concomitant osteotomies, tibial lengthening, malunion, non-union, mechanical failure, or revision surgery for any reason were excluded. All nails were inserted through the greater trochanter or piriformis. Patients' age, weight, height, and body mass index (BMI)were extracted. Radiologic assessments involved analyzing long lower limb standing X-rays before, during, and at consolidation for total distraction and nail bend. Naildiameter and patient characteristics were directly sourced from medical records.

Nail bend at consolidation averaged 2.4° (SD 2.4), ranging from 0 to 9. Additionally, total femoral lengthening was assessed, with a mean value of 5.3 cm (SD 2.1). A significant positive association was observed in the nail bend and weight (weight in kg/nail diameter in mm) coefficient (P < 00.01). Bilateral limb lengthening was also correlated to increase nail bend (P < 00.05).

Patient's weight to nail diameter ratio and bilateral limb lengthening were found to be significant factors affecting nail bend. These findings advance our understanding of the interrelation between the nail biomechanical profile and the patient's physical attributes, offering important implications for limb lengthening.

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