Intraoperative diagnosis of rotational instability in femoral shaft fracture non‐union revision surgery

Femoral shaft fracture non-union is common and frequently associated with poor functional outcome and protracted or incomplete functional recovery of the patient. Non-union presents a difficult clinical challenge perioperatively.1, 2 Whilst limited available evidence exists, rotational instability is regarded by clinicians to be a potentially important contributing factor to non-union in the intramedullary nailed femur.3-5 Rotational instability in femoral shaft fracture non-union is theoretically an important factor but it has not been quantified in practice, although revision fixation methods (extra locking screws, larger diameter nail, supplemental plating), are frequently addressing this problem.4, 5 Additional methods include exchange for larger diameter reamed intra-medullary nail, utilization of locking screws in different planes, and locking screws with thread purchase in the nail with or without augmentation plating.2, 4, 5 However, no standard intraoperative technique is available to diagnose and assess rotational instability in femoral shaft fracture nonunion. The diagnosis of rotational instability is crucial in the selection of specific revision method. Hence, this manuscript presents a practical intraoperative technique with images to diagnose rotational instability and accurately measure its degree in femoral shaft fracture non-union. Pre-operative imaging is performed and an operative plan is established focusing on options of minimally invasive surgery. The patient is positioned lateral decubitus on a radiolucent table with anterior and posterior pelvic support. Prophylactic antibiotics are administered, intraoperative X-ray guidance is utilized, and routine sterile preparation and draping is completed. Minimally invasive approach is performed through previous incision sites to access proximal and distal locking screws either side of the non-union. Engage appropriate screw drivers to both proximal and distal locking screws simultaneously. Once appropriately engaged, opposing rotational forces are applied to each segment of the femur. Clockwise and anticlockwise rotation of each segment gives a measurable arc of rotation and thus the degree of rotational instability can be quantitatively determined in degrees (Fig. 1). When open technique is required to achieve femoral shaft fracture non-union revision the proximal and distal segments of the femur can be assessed for rotational instability with reduction clamps. Reduction clamps can be placed either side of the non-union ensuring they are aligned in the same plane. Rotation in opposite directions as shown in Fig. 2 can then similarly be applied as above to confirm macroscopic torsional instability. Once macroscopic rotational instability is quantified, tailored revision fixation can be performed. Exchange reamed intra-medullary nailing is the standard treatment for femur shaft fracture non-union with success rate of 70%–100%.6 If torsional stability cannot be achieved with intra-medullary nailing due to excessively wide medullary canal or lack of locking options outside of previously used screw trajectories, augmentation with percutaneous or open plating with or without bone graft is warranted. Figure 3 demonstrates post-op radiographs from the patients exhibited in Figs. 1 and 2 which highlight various revision options that can be performed in situations of rotational instability. This simple and safe technique does not require any additional steps or equipment during femoral shaft non-union revision surgery but quantifies rotational instability and aids in selection of the most appropriate extent of implant selection and revision configuration. Open access publishing facilitated by The University of Newcastle, as part of the Wiley - The University of Newcastle agreement via the Council of Australian University Librarians. Brent D. Whittaker: Data curation; writing – original draft; writing – review and editing. Zsolt J. Balogh: Conceptualization; data curation; formal analysis; methodology; project administration; supervision; writing – original draft; writing – review and editing. Video S1. The supplied video displays the technique described to diagnose inherent rotational instability in femoral shaft fracture non-union. Screwdrivers are engaged proximally and distally on the femur. Opposite forces are then applied to the two screwdrivers allowing a measurable arc of rotation. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.