Femoral offset loss and internal arch restoration defect are correlated with intramedullary nail cut-out complications after pertrochanteric fractures: a case-control study

How to get better TAD? Relationship between anteversion angle of nail and position of femoral neck guide pin during nailing of intertrochanteric fractures

Background

To demonstrate the correlation between guide pin-shaft angle (PSA) at the anteroposterior film and anteversion angle of guide pin at the lateral film and investigate whether excellent tip–apex distance (TAD) can be obtained by changing the entry point via axial rotation of the main intramedullary nail.

Methods

Fifty patients with intertrochanteric femoral fractures (IFFs) undergoing internal fixation with intramedullary nails under 2D fluoroscopy were retrospectively enrolled. Both of the PSA at the anteroposterior film and anteversion angle at the lateral film before and after adjustment of the guide pin were collected. Pearson correlation analysis was performed to investigate their correlation. Intraoperative and postoperative outcomes were recorded. Furthermore, the software of Mimics 10.0 and Pro/E were used to establish the 3D models of the proximal femur and main intramedullary nail/guide pin, respectively. Surgery was simulated on the Pro/E software platform and solid geometry analysis was conducted to calculate the correlation between the PSA and the anteversion angle.

Results

Pearson correlation analysis indicated there was a positive correlation between PSA and anteversion angle, with the correlation coefficient of 0.902 (p < 0.01). By altering the PSA and anteversion angle, TAD was adjusted to be less than 25 mm in all patients. The mean operative time, fluoroscopy time and length of hospital stay were 65.82 ± 11.16 min, 2.03 ± 0.79 min and 6.66 ± 2.49 d. Thirty-one patients received blood transfusions (3.55 ± 1.95 U). Fracture reduction was considered to be good or acceptable in all patients. Complications occurred only in 6 patients (12.00%). At a 3-month follow-up, the mean Timed Up and Go was 31.54 ± 20.95 s and Harris Hip Score was 72.88 ± 8.79. The 3D surgery model also showed when the main intramedullary nail was externally rotated or internally rotated of 20° at the standard location, the PSA of guide pin at the anteroposterior position and anteversion angle of the guide pin at the lateral position were simultaneously increased or decreased.

Conclusion

Our findings suggest altering the PSA and anteversion angle may be beneficial for obtaining excellent TAD and achieving superior outcomes.

Is rotation the mode of failure in pertrochanteric fractures fixed with nails? Theoretical approach and illustrative cases

PURPOSE

The present article reviews data from biomechanical and clinical studies which indicate that rotational instability can cause failure of fixation due to the particular characteristics of the fracture, the mechanical properties of the chosen implant or flaws in surgical technique.

METHODS

Although radiographs give a similar impression in failure of fractures fixed with cephalomedullary nails, different mechanisms involving rotation of the femoral head may play a key role.

RESULTS

The incidence of failure in pertrochanteric fracture fixation is decreasing as implants continue to evolve. It is possible that currently reported low failure rates do not apply equally to all subtypes of this diverse group of fractures. Since the introduction of sliding hip screws, "cut-out" due to varus collapse of the proximal fracture fragment has been the only reported mode of failure.

CONCLUSION

Excessive rotation leading to eventual "cut-out" has not been adequately studied, and thus, available evidence is not sufficient to definitely prove this theoretical approach. As nailing is gradually overtaking extramedullary fixation as the treatment of choice, especially for comminuted pertrochanteric fractures which can be rotationally unstable, further research is warranted to improve our understanding of the pathogenetic mechanisms of failure.