Second-generation locked nails help avoid rotational malalignment in femur fractures
Locked intramedullary nailing is the gold standard for treating femoral shaft fractures. Union rates are reportedly as high as 99% and infection rates as low as 1%. The most common complication of this procedure is rotational malalignment. Studies report the incidence of malrotation in femoral intramedullary nailing to be between 19% and 56%. Comminuted or transverse femur fractures are particularly at risk of having this complication due to the absence of landmarks to assist with alignment during surgery.
A rotational difference greater than 15° between the operated and uninjured extremity is the point at which patients notice an effect on function. External malrotation is tolerated better than internal rotation.
The best way to measure rotational malalignment of the femur is with an axial CT scan. A CT scanogram is a CT scan in which the scout view is used to measure length, and axial cuts of the hip and knee are used to measure rotational alignment (Figure 1). These measurements have been shown to be more accurate than clinical evaluation or standard radiographs when evaluating for rotational deformity.
The rotational alignment of the femur is determined by an angle formed by the line along the long axis of the femoral neck and a line along the posterior condylar axis, which is referred to as the version of the femoral neck (Figure 2). The normal femoral version in adults is reported to be 8.84° ± 9.668° anteversion. Patients with excessive anteversion have feet that toe in and patients who have smaller amounts of anteversion or even retroversion toe out (Figure 3).
Second- or third-generation femoral nails — ones that allow locking into the neck and head of the femur — are designed to fit the average human femur with built-in anteversion of 9° to 11° depending on the manufacturer of the nail (Figure 3, page 4). Using a second- or third-generation nail to set the version of a broken femur has been described in a paper by Espinoza and colleagues that discusses a series of four cases.
In an attempt to validate these results, a prospective, IRB-approved study was performed at our institution that included 52 consecutive patients with comminuted femur fractures. The first 27 patients had the anteversion determined using the patellar shadow and lesser trochanter and formed the traditional group (TG). The next 25 patients were treated by the Espinoza technique (ET).
Standard technique is used for the starting point, reduction and insertion of the second-generational nail into the femur. The proximal locking screw or blade of the second- or third-generation nail is placed into the neck and head of the femur. A “look back” lateral fluoroscopic view is used (Figure 4) with superimposition of the drill and locking handle to bisect the femoral head. This must be performed accurately as each degree off the center axis of the femoral neck will lead to a degree of malrotation. Once the nail has been locked proximally with screws or a blade, we performed two steps: 1) we set-up freehand distal locking with perfect circles of the distal locking holes on fluoroscopy; and 2) we rotated the distal femur until it had the perfect lateral view with the condyles overlapping. We then locked the nail twice with a freehand technique (Figure 5). A CT scanogram can be performed postoperatively to determine the femoral version of both lower limbs and determine the leg lengths. By using this technique, we are essentially utilizing the nail to set the anteversion of the femur. Again, most second- and third-generation nails are designed to have 11° of anteversion.
The ET group exhibited anteversion differences from the unoperated leg that were more consistent (P < .0230) and had a clinically significant difference of less than 15° less often (one of 25) than patients in the TG (eight of 27) (P < .0068) (Table). In the one patient in the ET group with a greater than 15° variation, the unfractured femur had 17.9° retroversion, while the fractured limb was fixed at 11° anteversion, which was our goal. A difference of 28.9° occurred. This case illustrates the ET technique does not account for patients who have congenital anteversion outside the norm and we must find a way to account for this.
The inherent anteversion of a second-generation nail can be used to minimize malrotation of the femur after comminuted fractures during locked IM nailing in patients with normal anteversion. Some patients have a native version which is outside the norm and this technique does not account for that.
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- For more information:
- Rahul Vaidya, MD, FRCSC, FAOA, FAAOS, can be reached at 9C University Health Center Detroit Receiving Hospital, 4201 Saint Antoine, Detroit, MI 48201; email: firstname.lastname@example.org.
Disclosure: Vaidya reports no relevant financial disclosures.