Structures at risk with intrapelvic guide wire migration during cephalomedullary fixation of hip fractures: CT based analysis.

Objectives: To identify which intrapelvic structures may be injured in cases of intrapelvic migration of the guide wire used for head screw/blade placement during cephalomedullary nail fixation.

Methods: Design: Retrospective review.

Setting: Single academic, level 1 orthopaedic trauma subspeciality unit in university hospital.

Patient selection criteria: Patients with contrast-enhanced computed tomography treated with cephalomedullary nail fixation for AO/OTA type 31A1,31A2,31A3 fractures from December 2022 to July 2024.Outcome Measures and Comparisons: The primary outcome measure of this study was the quantification of pelvic structures that are at risk of iatrogenic injury related to mispositioned/over advanced guide wire. Six simulation scenarios were created with variations applied in the sagittal axis: neutral anteversion, 7.5° anteversion, and 7.5° retroversion. Each three scenario applied for penetration depths of 2 cm and 5 cm. Additionally, the safe distance was recorded. All simulations and measurements were analyzed both pooled and comparatively based on sex and laterality.

Results: 88 patients were included in the analysis, 47 (53.4%) were female and 41 (46.6%) were male. The median age was 77.5 years (IQR 65-85). In 48 (54.5%) patients, measurements were performed on the right hip. In neutral version trajectory, penetration of 2 cm resulted in contact with anatomical structures in 78% of cases, increasing to 98% at 5cm. With anteversion, the rates were 90% at 2 cm and 98% at 5 cm. With retroversion, the corresponding rates were 55% and 93%, respectively. The most frequently affected structures at 2 cm were the external iliac artery (EIA) and vein (EIV), whereas at 5 cm, the small intestine and colon were most involved structures in addition to EIA and EIV. Other at-risk structures included the uterus, bladder, internal iliac artery, and internal iliac vein at both penetration depths and uterine venous plexus at 5cm penetration. Notably, injury to external iliac vessels was significantly more common in males under the neutral sagittal projection(63% vs 34% at 2 cm and 63% vs 36% at 5 cm) (p < 0.05 for both depths). Safe distances were significantly greater in males across all simulations(12.6 cm vs 11.4 cm in neutral version, 12.4cm vs 11.0 cm in anteversion, 12.2 cm vs 10.9 cm in retroversion) (p < 0.05 for all).

Conclusion: Intrapelvic mispositioning of the guide wire used for head screw/blade placement during cephalomedullary nail fixation posed a substantial risk of iatrogenic injury to intrapelvic structures and this risk increased further with deeper penetration. However, the clinical implications of such injuries remain unclear.

Level of evidence: Diagnostic Level IV.