In this study, we introduced a novel RIA technique for distal femur nonunion. This technique reduces the complications and adverse effects associated with RIA. It removes the added pain and discomfort associated with a separate entry site. As the reamer is introduced into the medullary canal through the femoral nonunion site, and proximal harvest is limited to the subtrochanteric region, the technique also avoids the complications associated with eccentric reaming of the distal and proximal femur, which may contribute to secondary fracture.6,7,11,12Although the proposed technique is practical, it may present some technical difficulties. First, failed fixation hardware must be removed, and by necessity some stripping of soft tissues is required. These actions are unavoidable, as hardware revision is inherent in the treatment of nonunion. During the procedure, the focus should be on minimizing the insult to bony healing. The nonunion also needs to be completely mobilized to allow adequate angulation, guide wire passage, and sequential reaming. The dual vascular insult of intramedullary reaming combined with the soft-tissue débridement and detachment required for hardware removal and mobilization can be concerning for devascularization of the fracture fragment. However, animal studies have suggested reaming does not affect metaphyseal blood flow; it affects only diaphyseal bone.6,14 The metaphyseal/diaphyseal location of these distal femur nonunions is thought to provide at least partial sparing from the endosteal injury that the RIA may cause. Another difficulty is that the angle of passage of the wire requires a relatively steeper curve to be able to pass beyond the medial distal femoral wall and proceed more proximally. Strong manipulation of the segment is required, which in 1 case caused the reamer shaft to break. This complication had minimal sequelae; the shaft was easily retrieved by withdrawing the ball-tipped guide wire. In addition, strong manipulation of the segment can lead to asymmetric medial reaming or fracture—an outcome easily avoided with a small bend in the distal tip of the guide wire and frequent use of fluoroscopy. In all cases in this series, we achieved proximal passage of the wire and the reamer.
Most RIA bone graft is harvested by reaming the medullary canal at the midshaft of the femur. Passing from the distal femoral nonunion precludes obtaining only a small source of potential distal femoral bone graft, though this metaphyseal bone typically is not used for fear of eccentric reaming and secondary fracture.6,7,11,12 The amount of bone graft obtained from selected patients who undergo retrograde RIA passage through the nonunion site should be similar to the amount obtained with the traditional antegrade method. Our newly proposed technique provided an average bone graft volume of 33 mL, which compares favorably with that reported in the literature for the traditional RIA technique.1,5,6,13,15,16
Conclusion
In distal femoral cases, retrograde passage of the RIA through the nonunion site is technically feasible and has reproducible yields of intramedullary bone graft. Adequate mobilization of the nonunion is a prerequisite for reamer harvest. However, this technique obviates the need for an additional entry point. Furthermore, the technique may limit the perioperative fracture risk previously seen with eccentric reaming of the distal and proximal femur using traditional intramedullary harvest.
Am J Orthop. 2016;45(7):E493-E496. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.