Entry point soft tissue damage in antegrade femoral nailing: A cadaver study

Introduction: Little attention is paid to insertion site morbidity associat ed with antegrade femoral nailing. However, residual peritrochanteric pain after nailing is not uncommon. Additionally, the end branches of the medial femoral circumflex artery (m.f.c.a.) supplying the femoral head are in clo se proximity to the insertion site of the nail, and the occurrence of avasc ular necrosis of the femoral epiphysis after nailing in adolescents is rath er frequent. Objective: The aim of this study was to assess iatrogenic soft tissue injur ies at the site of nail insertion. Materials and Methods: Nailing with a reamed AO universal femoral nail was performed on sixteen adult cadavers followed by dissection of the proximal part of the femur to assess possible damage to the soft tissues. Three entr y portals were defined. (A) entry portal lateral to the junction of the nec k and the greater trochanter; (B) entry portal at the base of the greater t rochanter anterior to a line along the longitudinal axis of the femoral nec k; and (C) entry portal at the base of the greater trochanter posterior to a line along the axis of the femoral neck (at the piriformis fossa). Results: In Group A, partial avulsion of the piriformis and the obturator i nternus tendon were present in four and in one of five specimens, respectiv ely. Group B showed injuries to the piriformis tendon in two and to the glu teus minimus tendon in one of four cases. In Group C, partial avulsion of t he piriformis, obturator internus, and obturator externus tendon were encou ntered in five, six, and two of seven specimens, respectively. Anterior bra nches of the ramus profundus of the m.f.c.a. within the synovial fold were damaged in all of these cases. Conclusion: To select the best nail entry portal, the ease of nail insertio n must be weighed against the resulting soft tissue damage at the site of i nsertion. The nail entry portal at the piriformis fossa, although geometric ally ideal and most recommended, causes the most significant damage to musc le and tendons as well as to the blood supply to the femoral head. Therefor e, even if reported only once, the occurrence of avascular necrosis of the femoral head after nailing in adults is a possible complication of this nai l entry portal. The authors therefore prefer to avoid this entry portal in every case. The nail entry portal anterior to the longitudinal axis of the femoral neck, as in group B, although better with respect to the soft tissu e damage, has the worst geometric and biomechanical disadvantages. The resu lts of the current study favor the nail entry portal lateral at the greater trochanter as in Group A, which is equal to the entry portal B with respec t to the soft tissue damage but allows introduction of the nail into the me dullar cavity without difficulties.