Complete fracture of posterior cortex increases the risk of avascular necrosis after osteosynthesis for non-displaced femoral neck fractures in elderly patients.

To the Editor: Osteosynthesis is considered as a standard management for the non-displaced femoral neck fracture in elderly patients,[1] but some of the patients would be suffered from avascular necrosis or non-union after osteosynthesis. It has been demonstrated that the outcome of the salvage procedure after primary avascular necrosis is not reliable.[2] Therefore, the preoperative detection of the risk factors should be of great significance. The Garden classification system has been the most commonly used to distinguish the severity of femoral neck fracture, but it is mainly focused on the displacement in the coronal plane. Since the integrity of posterior cortex has been demonstrated as an important role in the outcomes of displaced femoral neck fractures,[3] it is reasonable to investigate the effect of posterior cortex on the non-displaced pattern. Recently, we compared the outcome after osteosynthesis for non-displaced femoral neck fractures with and without posterior cortex complete fracture. This study was approved by the Ethics Committee of Beijing Jishuitan Hospital (No. 202203-100). Written informed consent was obtained from all the subjects. Patients data including age, sex, affected side, body mass index (BMI), American Society of Anesthesiologists classification (ASA), Harris score, Pain Intensity-Numerical Rating Scale (PI-NRS), 3- Level Europe Quality of life Five Dimensions Questionnaire, and Visual Analogue Score (EQ-5D-3L and EQ-5D-VAS), 1-year mortality, local and systemic complication, and avascular necrosis, were collected. The inclusion and exclusion criteria, statistical analysis were shown in Supplementary Materials, https://links.lww.com/CM9/B710. A total of 157 consecutive patients aged ≥65 years old with non-displaced femoral neck who were admitted to our department between January 1, 2015 and October 1, 2019, were included in the present study. About 15 patients were lost to follow-up and 16 were excluded based on the exclusion criteria. Among ten patients who died by the last follow-up, two died of fatal pulmonary embolism and hepatic carcinoma within one year, respectively. The 1-year fatality was 1.59% (2/126). One hundred and sixteen patients with complete data were enrolled for the analysis [Supplementary Figure 1, https://links.lww.com/CM9/B710]. The average age of these 116 patients was 72.5 ± 6.3 years (range: 65.0–92.0). Ninety-eight (94/116, 84.5%) patients were female. Sixty-two (62/116, 53.4%) cases were left side. All of the patients suffered from low-energy injuries. The mean follow-up period was 4.6 ± 1.4 years (range: 2.0–6.7). Assessment of the integrity of the posterior cortex was based on the oblique axial views of computerized tomography (CT) scans, which were available for all patients. If there was no displacement or only angulation at the fracture site and both ends of posterior cortices at the fracture site were still shaped in a smooth curve, it was categorized as the incomplete fracture of the posterior cortex. Correspondingly, if there was an overlap or gap at the posterior cortex so that both ends of posterior cortices could not form a smooth curve at the fracture site, it was categorized as a complete fracture of posterior cortex. For the assessment of the integrity of the posterior cortex, the interclass agreement of Hangyu Gu (HG) and Minghui Yang (MY) showed substantial agreement with κ = 0.65 (95% confidence interval [CI]: 0.40–0.90); the intraclass agreement of HG and MY showed substantial agreement with κ = 0.72 (95% CI: 0.49–0.95) and κ = 0.75 (95% CI: 0.52–0.98), respectively. Based on the integrity of the posterior cortex, the patients were divided into group I (incomplete fracture of posterior cortex) and group II (complete fracture of posterior cortex). A significant difference was found in the incidence of avascular necrosis between the two groups (4.5% [4/88] in group I vs. 32.1% [9/28] in group II, odds ratio [OR]: 9.95, 95% CI [2.77–35.73], P <0.001). This result indicated that the complete fracture of the posterior cortex was a risk factor for avascular necrosis in patients with the non-displaced femoral neck fractures. Also, the scores of Harris and EQ-5D-3L questionnaires were significantly lower in group II due to the higher rate of avascular necrosis (91.00 [87.00, 97.00] vs. 84.00 [72.75, 91.00], Z =–3.068, P = 0.002; 1.00 [0.85, 1.00] vs. 0.85 [0.72, 1.00], Z =–2.263, P = 0.024, respectively). Other sets of data, such as average age, sex ratio, BMI, follow-up time, EQ-5D-VAS, and the ratio of ASA III-IV, did not significantly differ between groups I and II [Supplementary Table 1, https://links.lww.com/CM9/B710]. In conclusion, the complete fracture of posterior cortex was a risk factor for avascular necrosis in non-displaced femoral neck fractures. Given that avascular necrosis of the femoral head would lead to poor hip function and quality of life in elderly patients, a CT scan should be performed to help orthopedic surgeons evaluate the non-displaced femoral neck fractures in elderly patients. Funding This work was funded by grants from the National Natural Science Foundation of China (No. 82072445) and National Natural Science Foundation Cultivation Programme of Beijing Jishuitan Hospital (No. ZR-202309). Conflicts of interest None.