Can't stop the slide: factors associated with lag screw slide following cephalomedullary nail fixation of intertrochanteric hip fractures.

OBJECTIVE

To examine factors associated with lag screw slide following fixation of intertrochanteric hip fractures with 1 type of cephalomedullary nail.

METHODS

Retrospective review of patients operatively treated for intertrochanteric hip fractures (OTA/AO 31A1 and 31A2) with a single cephalomedullary nail (CMN) at a single academic medical centre between November 2014 and November 2023. CMN lag screw was placed in "dynamic" mode to allow for controlled collapse, or screw "slide." Screw slide was defined as the difference in lateral prominence of the lag screw at latest follow up compared to its initial position. Patients were grouped based on the amount of screw slide (<5 mm, 5-15 mm, >15 mm) and correlation analysis was performed.

RESULTS

614 intertrochanteric hip fracture patients were identified (mean age 80.76 years; 72.3% female) with mean 6.2 months follow-up. Mean amount of slide was 3.77 ± 4.79 mm. 66.3% of patients had <5 mm of slide, while 31.3% had 5-15 mm and 2.4% had >15 mm. Univariate analysis demonstrated that slide >15 mm was associated with increased patient BMI (p = <0.001), use of some anti-osteoporotic medications (p = 0.021) and more than 5 mm of immediate postoperative prominence (p = 0.016). Although not statistically significant, patients with >15 mm of slide were only taking vitamin D and calcium whereas those with <15 mm slide more often took bisphosphonates, denosumab and teriparatide (p = 0.163). Multivariate regression demonstrated that only BMI (OR 1.14, 95% CI, 1.04-1.24; p = 0.002) was associated with >15 mm screw slide.

CONCLUSIONS

Excessive lag screw slide (>15 mm) was associated with higher patient BMI. Patients with higher BMIs should be monitored to identify excessive slide. Surgeons should attempt to keep the lag screw as close to the lateral cortex as possible. While the use of anti-osteoporotic therapy was associated with more slide, this was almost exclusively seen in patients only prescribed vitamin D and calcium.