Rotational problems and clinical reflections after locked intramedullary nailing in diaphyseal femur fractures: A minimum follow-up of 5 years

Abstract

Background: Rotational malalignment following intramedullary nailing (IMN) of femoral shaft fractures remains a clinically significant concern, with previous studies reporting variable incidence rates and inconsistent risk factors. This study aimed to determine the incidence of rotational malalignment after closed static-locked intramedullary nailing for adult diaphyseal femoral fractures, identify contributing etiological factors, and evaluate its clinical impact on functional capacity and quality-of-life metrics.

Methods: A retrospective cohort study was conducted involving 54 adults treated with closed static-locked IMN for diaphyseal femur fractures between 2014 and 2019. Rotational alignment was assessed using computed tomography (CT)-measured femoral anteversion (FAV) differences, with a threshold of ≥15° defined as malalignment. Multivariate logistic regression was employed to examine associations with fracture pattern, nail entry site, surgical timing (day vs. night), and coronal alignment. Functional outcomes were assessed using the WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) knee, Harris hip, Lower Extremity Functional Scale, and Kujala patellofemoral scores. Receiver operating characteristic (ROC) analysis was used to determine optimal FAV thresholds.

Results: Rotational malalignment (≥15° FAV difference) was observed in 33.3% of cases, with 94.4% involving internal rotation. Multivariate analysis identified no independent predictors among the following factors: fracture location (proximal 44.4% vs. middle 29.2%, p=0.625), AO classification (Type A 34.3% vs. Type C 33.3%, p=0.914), nail entry site (lateral trochanteric 40% vs. piriformis 16.6%, *p*=0.574), and surgical timing (night 26.1% vs. day 38.7%, p=0.228). Patients with malalignment demonstrated significantly poorer functional outcomes, as evidenced by higher WOMAC knee scores (12.7+-4.8 vs. 6.4+-4.8, p<0.001). ROC curve analysis identified 13.5° as the optimal FAV threshold (area under the curve, AUC: 0.78), although the 15° cutoff maintained strong clinical utility with a specificity of 83%.

Conclusion: Rotational malalignment following IMN occurs in one-third of cases and has a significant negative impact on functional outcomes. However, it appears to be independent of commonly considered surgical variables such as entry site and timing. These findings support technical flexibility in IMN procedures while highlighting the need for improved intraoperative techniques to assess rotational alignment.

Figure 1

Measurement of coronal plane deformity. To evaluate frontal plane deformity of the femur, a line was drawn from the fracture site to the proximal center of the medulla. A second line was drawn from the fracture site to the midpoint of the distal femoral joint surface. The angle between these two lines was calculated. A valgus deformity of 6.7° is observed in the operated right femur (a). Femur length was measured as the distance between the center of the femoral head and the most distal point of the medial femoral condyle. The difference in length between the operated and uninjured femurs was recorded (b).

Figure 2

Assessment of femoral malrotation using the method described by Jeanmart et al.[16] Femoral torsion is determined by measuring the angle between a line drawn along the posterior edge of the femoral condyles and another line passing through the femoral neck. Rotational malalignment is defined as the difference in this angle between the injured and uninjured sides. A decrease in the angle on the fractured side indicates increased external rotation of the distal fragment, while an increase indicates greater internal rotation of the distal femoral fragment. A 37° difference in femoral anteversion (FAV) angles was measured between the operated and uninjured left femurs (40–3=+37), indicating an internal rotation deformity.

Figure 3

Assessment of femoral malrotation using the method described by Jeanmart et al.[16] A difference of 13° in femoral anteversion (FAV) angles was measured between the operated and uninjured left femurs (0–13=-13), indicating an external rotation deformity.