Clinical outcomes of using contralateral-side laterally bent intramedullary nails in atypical femur fractures with femoral bowing

Surgical strategy of the treatment of atypical femoral fractures

The atypical femoral fracture (AFF) has been attracting significant attention because of its increasing incidence; additionally, its treatment is challenging from biological and mechanical aspects. Although surgery is often required to manage complete AFFs, clear guidelines for the surgical treatment of AFFs are currently sparse. We reviewed and described the surgical treatment of AFFs and the surveillance of the contralateral femur. For complete AFFs, cephalomedullary intramedullary nailing spanning the entire length of the femur can be used. Various surgical techniques to overcome the femoral bowing common in AFFs include a lateral entry point, external rotation of the nail, and the use of a nail with a small radius of curvature, or a contralateral nail. In the case of a narrow medullary canal, severe femoral bowing, or pre-existing implants, plate fixation may be considered as an alternative. For incomplete AFFs, prophylactic fixation depends on several risk factors, such as a subtrochanteric location, presence of a radiolucent line, functional pain, and condition of the contralateral femur; the same surgical principles as those in complete AFFs can be applied. Finally, once AFF is diagnosed, clinicians should recognize the increased risk of contralateral AFFs, and close surveillance of the contralateral femur is recommended.

Iatrogenic Vertebral Fracture During Intramedullary Nailing for Femoral Fracture: A Case Report

CASE

A 73-year-old woman with advanced ankylosing spondylitis (AS) underwent closed reduction and internal fixation using antegrade intramedullary nailing because of midshaft fracture of her right femur. After the surgery had been performed, a fracture and dislocation at T12-L1 was detected. Therefore, emergency spinal decompression and posterior instrumentation placement from T11 to L5 were then performed.

CONCLUSION

Patients with advanced AS have a high risk of vertebral fracture, so special care must be taken not to transmit excessive stress on the spine for surgical reduction and manipulation of the lower extremity.

Association of atypical femoral fracture location and lower limb mechanical axis: a computed tomography-based finite element analysis

Atypical femoral fractures (AFFs) are categorized as low-energy fractures of the femoral shaft or subtrochanteric region. The use of computed tomography-based finite element analysis demonstrated that the femoral weakest point against tensile stress coincided with AFF location, which was determined by the lower limb axis and femoral bowing.

INTRODUCTION

This study aimed to assess the relationship between the femoral weakest point against tensile stress and the lower limb axis and geometry, including femoral bowing, using a computed tomography (CT)-based finite element analysis (FEA) model.

METHODS

We retrospectively reviewed 19 patients with AFFs and analyzed their CT images of the contralateral intact femur. We performed FEA to find the maximum principal stress (MPS) and maximal tensile stress loading area (femoral weakest point, FWP) of each patient and matched the FWP with the real location of AFF. We applied mechanical axes differently, as neutral, varus, and valgus, in the FEA model, when we analyzed the change in MPS and FWP based on lower limb alignment. We compared the degree of agreement between the real fracture location and FWP before and after knee mechanical axis adjustment.

RESULTS

The average participant age was 75.9 (range, 61-87) years, and all participants were women. In the 19 patients included, we observed 20 and 7 shaft and subtrochanteric AFFs, respectively. The average mechanical axis at the knee joint level was 22.6 mm (range, 0-70 mm) of the varus. All the patients showed an increasing trend of MPS and a distal movement of FWP when the mechanical axis of the knee was applied from the valgus to varus alignment. The root mean square errors between the FWP and real fracture location were 14.58% and 10.87% before and after adjustment, respectively, implying that the degree of agreement was better in patients who underwent mechanical adjustment.

CONCLUSION

The use of CT/FEA demonstrated that the FWP against tensile stress coincided with AFF location, which was determined by the lower limb axis and femoral bowing.

Intramedullary Nailing for Atypical Femoral Fracture With Lateral Bowing: Does Medial Gap Matter?

When performing intramedullary nailing for atypical femoral fractures (AFF), especially in lateral bowing femurs, a medial opening wedge-shaped gap in the fracture site may occur after nailing. We intended to analyse and compare clinical outcomes according to the medial gap in AFF cases after intramedullary nailing. Materials and Methods: Of the 38 consecutive patients with complete AFF treated by intramedullary nailing, 22 patients (all female, mean age of 76.5 years [range, 62–87]) available for follow-up for more than 12 months were included. According to the size of the medial gap, the patients were divided into 2 groups: large and small medial gaps. Comparative analysis was performed between groups in terms of patient, fracture characteristics and post-operative clinical outcomes. Results: There was no significant difference in bone union time between the 2 groups (5.4 months vs 5.6 months, P = .628). When comparing the amount of change in the hip–knee–ankle angle after the surgery with reference to the contralateral side, there was a significant difference between the 2 groups (−4.4° [femoral straightening and relatively changed to a more valgus pattern, that is, in cases of varus alignment, towards neutral alignment] vs .5°, P = .002). There was no significant difference in leg length discrepancy between the 2 groups (4.1 mm vs 3.2 mm, P = .674). In terms of functional outcomes, there was no significant difference in the recovery of ambulatory ability (ΔKoval grade: post-operative Koval grade–pre-operative Koval grade, 0 vs .1, P = .771). Conclusion: Even if the medial gap occurs following intramedullary nailing in AFF, post-operative clinical outcomes seem to be acceptable. However, if previous total knee arthroplasty is performed and neutral alignment is maintained, care should be taken as the occurrence of the gap may result in lower limb malalignments.

Bilateral Incomplete Atypical Femur Fractures with Severe Bowing Treated Using Elastic Intramedullary Nails: A Case Report

CASE

A 77-year-old woman with bilateral symptomatic atypical femoral fractures (AFFs) and severe anterolateral bowing due to long-term bisphosphonate administration was treated using stainless elastic intramedullary nails. Weight-bearing pain disappeared immediately after surgery. Radiographs obtained 1 year postoperatively showed fracture healing.

CONCLUSION

Although intramedullary nail insertion has been recommended for symptomatic incomplete AFFs, in cases of severe bowing, rigid nail insertion was often challenging, and the complication rates were higher than those with mild bowing. The advantage of our method is easy insertion, suggesting effective treatment.

Straight nail insertion through a laterally shifted entry for diaphyseal atypical femoral fractures with bowing: good indications and limitations of this technique

PURPOSE

Inserting a straight (piriformis fossa entry) nail through the tip of the greater trochanter has been used for treating atypical femoral fractures (AFFs) with bowing. This study aimed to determine what degree of bowing can be successfully treated using a laterally shifted entry technique.

METHODS

Twenty-three complete and six incomplete diaphyseal AFFs treated using the shifted entry technique were retrospectively analysed. Radiologic parameters and complications were evaluated. The complete AFFs were divided into two groups based on the severity of preoperative bowing: grade 0-II bowing and < 20° lateral bowing (minimal/moderate) and grade III bowing or ≥ 20° lateral bowing (severe). Comparison according to postoperative malalignment, a change of lateral or anterior bowing ≥ 5° was also performed.

RESULTS

Three complete AFFs in the minimal/moderate group showed malalignment, as did all in the severe group (p < 0.001). The change of bowing was greater for the severe group in lateral and anterior bowing (p = 0.004 and 0.001, respectively). A greater fracture gap was found on AP and lateral radiographs in the severe group (p = 0.044 and 0.026, respectively). In the comparison according to postoperative malalignment, a significant difference was found for the percentage of severe deformity (p < 0.001). All incomplete AFFs were united without complication.

CONCLUSION

Diaphyseal AFFs with grade 0-II bowing and < 20° anterior bowing were treated successfully by the shifted entry technique. However, postoperative malalignment was found in all cases of AFFs with severe bowing. Therefore, other techniques should be considered for AFFs with grade III bowing or ≥ 20° anterior bowing.