Anterior Malreduction is Associated With Lag Screw Cutout After Internal Fixation of Intertrochanteric Fractures

Abstract

Background: Lag screw cutout is a devastating complication after internal fixation of an intertrochanteric fracture. Although the tip-apex distance (TAD) is known to be associated with this complication, another factor we thought was potentially important-fracture reduction on an oblique lateral view-has not, to our knowledge, been explored.

Questions/purposes: (1) Is a well-reduced fracture position on an oblique lateral view after internal fixation of intertrochanteric fracture associated with a lower odds of postoperative cutout, independently of the TAD? (2) Is postoperative sliding of the lag screw after fixation associated with postoperative cutout?

Methods: Patients with intertrochanteric fractures who were at least 65 years old and who had been treated with internal fixation in one of six facilities between July 2011 and December 2017 were included. All patients in the study group had lag screw cutout, and controls were selected by risk-set sampling of age-matched and sex-matched patients using a ratio of 4:1 for patients from each hospital. Of the 2327 intertrochanteric fractures, there were 36 patients (0.02 per person-year), with a mean age of 85 years; 89% (32) were women. In the control group, there were 135 controls. There was no difference in age or sex between the two groups. Sagittal reduction was evaluated using an immediate postoperative oblique lateral radiograph (anterior malreduction versus anatomic reduction or posterior malreduction). The association between anterior malreduction and the odds of cutout was estimated by conditional logistic regression analysis with the TAD and interaction between the TAD and the reduced position as covariates. As a sensitivity analysis, we estimated whether sliding within 2 weeks postoperatively was associated with cutout.

Results: After controlling for the potentially confounding variables of age and sex, we found that anterior malreduction was independently associated with a higher odds of cutout compared with anatomic reduction or posterior malreduction (adjusted OR 4.2 [95% CI 1.5 to 12]; p = 0.006). There was also an independent association between cutout and larger TAD (≥ 20 mm) (adjusted OR 4.4 [95% CI 1.4 to 14]; p = 0.01). However, the association between cutout and reduction was not modified by the TAD (adjusted OR of interaction term 0.6 [95% CI 0.08 to 4]; p = 0.54). Postoperative sliding ≥ 6 mm within 2 weeks was associated with higher odds of cutout after adjusting for age and sex (adjusted OR 11 [95% CI 3 to 40]; p < 0.001).

Conclusion: In patients older than 65 years with intertrochanteric fractures, anterior malreduction on a lateral oblique view was associated with much greater odds of postoperative cutout than anatomic reduction or posterior malreduction. Because anterior malreduction is within the surgeon's control, our findings may help surgeons focus on intraoperative reduction on an oblique lateral view to prevent cutouts. Although this factor is a reliable indicator, the results should be applied to cephalomedullary nails, because there was only one patient with cutout among those with sliding hip screws. Because this study was conducted in a homogenous Japanese population, future studies should focus on the association between anterior malreduction and cutout in people of different ethnicities, adjusting for confounding factors such as implant type and surgeon level.

Level of evidence: Level III, therapeutic study.