This study included 257 patients admitted to our hospital between 2.1.2014 and 29.12.2017, diagnosed with displaced femoral neck fractures and treated with hip hemiarthroplasty.

Patient medical records and relevant radiographs were reviewed. Data on age, sex, comorbidities (hypertension, ischemic heart disease and diabetes mellitus), ambulatory status prior to injury, duration of surgery, surgical approach, use of a Corail prosthesis or Austin-Moore, surgeon experience, and type of anesthesia were collected and analyzed.

Inclusion criteria included patients over the age of 65 with a displaced femoral neck fracture, who underwent hemiarthroplasty of the hip with a Corail or Austin-Moore prosthesis. Exclusion criteria included patients with a pathologic fracture, anterior ipsilateral hip fracture, or anterior ipsilateral hip fixation.

X-rays were reviewed and analyzed. Whereas Dorr’s channel type is an established risk factor for REIT11.12calcar/canal ratio (CCR) by Dossick and Dorr13, was used to classify femurs. In order to calculate the CCR, the diameter of the femoral canal 10 cm distal to the lesser trochanter was divided by the diameter of the canal at the middle part of the lesser trochanter13 (Fig. 1).

Figure 1

The calcar-to-canal ratio (CCR) is calculated by dividing the diameter of the femoral canal at a point 10 cm distal to the midline of the lesser trochanter (A) by the diameter of the femoral canal at the middle part of the lesser trochanter (B).

Lower values ​​indicate thicker cortices. Dorr A has a CCR of less than 0.5 and represents a femur with thick cortices beginning distal to the lesser trochanter which rapidly thicken creating a funnel-shaped proximal femur. Dorr B has a CCR between 0.5 and 0.75 and represents a wider femoral canal with some bone loss. Dorr C has a CCR greater than 0.75 and indicates considerable bone loss with thin cortices (Fig. 2).

Figure 2
Figure 2

Types of Dorr femur. Dorr (A) represents a femur with thick cortices and a narrow canal. Dorr (B) represents a femur with thinner cortices and a wider canal. Dorr (VS) represents a femur with thin cortices and a wide femoral canal.

The femurs were also graded using the canal to shaft ratio (CDR). The CDR was once established as a tool for assessing the risk of occurrence of intertrochanteric fractures14. The CDR was calculated by dividing the width of the femoral canal by the width of the diaphysis at a point 5 cm distal to the midline of the lesser trochanter (Fig. 3). The higher the ratio, the wider the channel and therefore the thinner the cortex. A CDR greater than 0.62 indicates that there is a high risk of hip fracture.

picture 3
picture 3

The canal to shaft ratio (CDR) is calculated by dividing the width of the femoral canal at a point 5 cm distal to the midline of the lesser trochanter (black arrows) by the width of the shaft at the same point (white arrows) .

Measurements were taken either on the contralateral femur or on the postoperative radiograph of the ipsilateral femur due to rotational deformities resulting from the fracture on the admission radiograph.

Ambulatory status prior to injury was divided into 4 categories: 1. Freely mobile without assistance 2. Mobile outdoors with assistance 3. Mobile primarily indoors 4. Not mobile.

The duration of surgery was recorded in minutes. The three surgical approaches used were the direct lateral (Hardinge), posterior (Moore or Southern) and anterior (Smith-Petersen). The surgical approach was determined primarily by surgeon preference.

Hemiarthroplasty surgery was performed using a cementless technique. The prosthesis used was either an Austin-Moore prosthesis (Treu Instrumente GmbH, Tuttlingen, Germany) or a collarless Corail femoral stem with a bipolar head (Depuy International, Leeds, England).

Our institute moved from Austin-Moore to the Corail prosthesis with a bipolar head for hip hemiarthroplasty in December 2015. This change allowed us to compare these two prostheses, comparing two different periods, two years before the era of the Coral prosthesis. , and two years later. Patients operated between 2.1.2014 and 20.12.2015 were treated with an Austin-Moore prosthesis, while patients operated between 26.12.2015 and 29.12.2017 were treated with a Corail prosthesis.

Surgeons have been divided into residents and seniors, while seniors are surgeons who have completed residency. The types of anesthesia are general, regional which includes spinal, epidural or peripheral nerve blocks, and combined anesthesia which includes intravenous anesthesia combined with regional anesthesia.

In the case of an IPF, the following information has been recorded if available; 1. The anatomical site of the fracture, including the greater trochanter, calcar, anterior femoral neck, and lateral femoral cortex. 2. Steps leading up to fracture, including: pinning and reaming of the femoral canal, insertion and reduction of the trial implant, and final insertion and reduction of the implant. 3. The IPF treatment used, including: cerclage wiring, conversion to a cemented stem, and conservative treatment.

Data entry was done using a spreadsheet (Excel 2016, Microsoft Corp., Redmond, WA). Frequency tables and descriptive statistics (mean, standard deviation, Min, Max) were presented for all variables. Categorical variables were presented as proportions and continuous variables were presented as mean. Pearson’s chi-square test and Fisher’s exact test were used for comparison between categorical variables, while Mann-Whitney U-test was used for continuous variables. Statistical significance was set at p≤ 0.05 and data analysis was performed using SPSS (SPSS Inc., Chicago, IL, Version 27).

For statistical analysis, IPF rates were compared between the Corail and Austin-Moore groups using Fisher’s exact test. Univariate analysis tests were used to assess the effects of patient characteristics and surgery on the likelihood of developing IPF. ROC analysis was performed for the CDR and CCR variables to determine the optimal cut-off value and the area under the curve (AUC) was calculated.

All procedures performed in this study complied with institutional research committee ethical standards and the 1964 Declaration of Helsinki and subsequent amendments or comparable ethical standards. The study was approved by the bioethics committee of the Rambam Healthcare Campus. Our Institutional Ethics Research Committee has determined that there is no need for informed consent, as this is a retrospective study.