Effectiveness of the Dorr index in predicting implant failure before proximal femoral nail application

Abstract

Objectives: This study aimed to investigate the importance of the Dorr index in the preoperative evaluation of implant failure in patients who underwent proximal femoral nail (PFN).

Patients and methods: This retrospective study examined 312 patients who underwent PFN for intertrochanteric fractures between January 2016 and January 2020. Patients with unstable fractures according to the AO/OTA (AO Foundation/Orthopaedic Trauma Association) classification, those over 65 years of age, with at least one year of regular follow-up, a tip-apex distance <25 mm, and a caput-collum-diaphyseal angle between 125° and 135°, were included. Seventy patients (19 males, 51 females; mean age: 72±3.8 years; range, 65 to 88 years) who met the inclusion criteria were included in the study. According to the Dorr index, patients were type A if the ratio was <0.5, type B if the ratio was between 0.50 and 0.75, and type C if the ratio was >0.75.

Results: The mean follow-up period was 46.2±4.4 months. As indicated by the Dorr index, the failure rates were 0%, 17%, and 63% for Dorr types A, B, and C, respectively. The comparison of failure rates between Dorr types A and B (p=0.02), B and C (p=0.016), and A and C (p=0.001) yielded statistically significant results. Patients with Dorr types B and C exhibited significantly inferior outcomes compared to those with type A. The mean time to failure was 27±3 days after surgery.

Conclusion: Dorr index is an important parameter that can be easily checked and used on preoperative radiographs to predict implant failure. The high probability of failure in the early period should be taken into account, particularly if PFN is planned in Dorr type C.