1. Target population and study design

This study enrolled patients with age of 50 or above diagnosed with either stable or unstable, intertrochanteric or subtrochanteric femur fractures. Patients with poor preinjury walking ability, sustaining pathologic fractures or multiple fractures, and candidates for revision surgery were ineligible for participation. This study was approved by our Institutional Review Board of Jeju National University Hospital (2014-02-003).

Following study was conducted as prospective, noncomparative, post-market, clinical follow-up study of ZNN CM nail. Patients were enrolled consecutively into the study postoperatively. Written consent was obtained after informing each patient about the purpose of the study. Upon signing the informed consent form, relevant preoperative and operative data, radiographic assessment and discharge data were collected and analyzed. Each patient will return to the clinic for follow-up at 6 weeks, 3 months, 6 months, and 12 months postoperatively. Follow-up evaluation includes radiographic assessment, physical examination, quality-of-life questionnaire completion and reporting of adverse events.

Demographic characteristics such as gender, age, body mass index, and bone marrow density (BMD) collected from the baseline information of patients were analyzed. The lowest value of bone mineral density was assigned, excluding the Ward's portion measured in the hip joint. Trauma mechanism and fracture types using the AO classification were also analyzed.

2. Surgical techniques

Surgery was performed with the patient in supine position on a radiolucent traction table under fluoroscopic control. All procedures were performed under aseptic conditions in accordance with the established procedure specified in the appropriate surgical technique manual. A routine method of closed reduction was performed to achieve fracture alignment with optional assistance from percutaneous bone hooks or long forceps. The entry point of the nail is located at the tip of the greater trochanter, in antero-posterior (AP) view. In the lateral (LAT) view, the entry point should be at the midpoint of the greater trochanter. The specific lag screw was introduced into the center of the femoral head by drilling in both AP and LAT view. A set screw should also be used to prevent lag screw rotation. All procedures were performed by a single experienced surgeon.

3. Clinical outcomes measurement

One of the objectives of this study was to evaluate the clinical outcomes of the ZNN CM nail in the treatment of proximal femur fracture. Patient quality of life was determined by evaluation of the EuroQol-5 Dimension (EQ-5D) self-completed questionnaire. Patient clinical outcome was determined using the Harris hip score (HHS). HHS was categorized as excellent (90–100), good (80–89), fair (70–79), or poor (<70). Patients completed the two questionnaires at the time of discharge and at 6 weeks, 3 months, 6 months, and 1 year postoperatively. The surveys were administered by a trained research nurse blinded to clinical information and not involved in the study. Operation time, length of stay, weight bearing without pain, resumption of pre-injury activity level, and patient work status were also measured.

4. Radiographic outcomes measurement

Implant-specific complications, implant position, and fracture union were evaluated for all participating patients through plain radiographs at immediate postoperative, 6 weeks, 3 months, 6 months, and 1 year postoperatively. Tip-apex distance (TAD) was defined as the distance between the tip of the screw and the apex of the femoral head on both AP and LAT views with consideration of the radiographic magnification.8) Radiologic fracture union is defined as bridging of the fracture site by callus or bone at a minimum of three cortices. Cortical healing is assessed in four anatomic proximal femur regions (anterior, posterior, medial and LAT) using AP and LAT views of plain hip joint radiography (Fig. 1).9,10)

Fig. 1
(A) Hip antero-posterior (AP) view of left intertrochanteric fracture immediately postoperation. Medial and lateral (LAT) cortex fracture gap at the fracture site is depicted by white arrows. (B) Hip left LAT view of intertrochanteric fracture immediately postoperation. Anterior and posterior cortex fracture gap at the fracture site is depicted by white arrows. (C) Hip AP view of left intertrochanteric fracture 6 months postoperation. Medial cortex shows no fracture gap (white triangles) and callus formation is observed. (D) Hip left LAT view of femur intertrochanteric fracture 6 months postoperation. Anterior and posterior cortex shows no fracture gap (white triangles) and callus formation is observed.

• Download Figure

5. Statistical analysis

Statistical analyses were performed using IBM SPSS statistical software version 20 (IBM Corp., Armonk, NY, USA). Clinical scores, such as EQ-5D, HHS were compared at the time of discharge and 1 year postoperatively using a paired samples t-test. A p-value <0.05 was considered statistically significant.

1. Patient baseline characteristics information

The study was originally planned to enroll 50 patients at the Jeju National University Hospital. However, due to the slow recruitment rate, the study was conducted with 49 patients. Following the manufacturer' surgical technique, all enrolled patients received the CM Asia nail (short) or CM long nail for treatment of proximal femur fracture. The numbers of patients available for the postoperative follow-ups were 41, 30, 25, and 39 at 6 weeks, 3 months, 6 months, and 1 year, respectively. Five patients withdrew their consent and other 5 patients were not available for the final follow-up (Fig. 2). The mean follow-up period for patients involved in the study was 16.04±7.51 months.

Fig. 2
Patient enrollment and follow-up flow chart. This study involved intertrochanteric or subtrochanteric fractures in 39 patients requiring cephalomedullary nailing. FUP: follow-up percentage.

• Download Figure

Preoperative BMD was measured in all patients. Only 2.1% of the patients (n=1) had normal value of T-score −1.0 to +1.0, while 85.7% of the patients (n=42) showed osteoporosis with T-score of −2.5 or less and 12.2% (n=6) showed osteopenia with T-score of −1.0 to 2.5. There were 6.1% AO 31-A1 simple petrochanteric fractures (n=3), 77.6% AO 31-A2 multifragmentary petrochanteric fractures (n=38), 12.2% AO 31-A3 intertrochanteric fractures (n=6), and 4.1% AO 32-A3.1 subtrochanteric fractures (n=2). ZNN CM Asia nail (short) was used in 95.9% fractures (n=47) while the CM long nail was used in only 4.1% cases (n=2). The 2 cases in which the CM long nail was used were subtrochanteric fractures with fracture lines that were distal to the lesser trochanter. A summary of the demographic, injury, operative and device information are outlined in Table 1 and 2, respectively.

Table 1
Baseline Characteristics Included in This Study

• Download Table

Table 2
Intra- and Postoperative Variables

• Download Table

2. Clinical outcomes

The mean EQ-5D score increased after discharge: from 0.4±0.3 points at discharge (n=49) to 0.6±0.3 points at 1 year follow-up (n=39) (Fig. 3). The difference in EQ-5D score observed at discharge and at 1 year follow-up was statistical significant (p<0.001).

Fig. 3
Mean EuroQol-5 Dimension (EQ-5D) score. Mean value of EQ-5D score measured in outpatient clinic using questionnaires at each follow-up period. Scores tend to increase from the EQ-5D baseline over time.

• Download Figure

The mean health state score also increased from 61.2±15.0 points at discharge (n=49) to 80.7±11.6 points, at 1 year follow-up (n=39). There was a statistically significant difference between mean health state scores measured at discharge and at 1 year follow-up (p<0.001). At final follow-up, 41% of the cases achieved a good to excellent grade in the HHS. The mean HHS increased from 56.3±16.0 points, at discharge (n=49) to 72.1±16.9 points, at 1 year follow-up (n=12) (Fig. 4). There was a statistically significant difference between HHS scores at discharge and at 1 year follow-up (p<0.001). The mean operation time was 63.9±23.3 minutes, length of stay was 27.6±14.3 days. At 1 year follow-up, 77% of patients (n=13) achieved full weight bearing without pain compared to 56% (n=41) at postoperative 6 weeks (Fig. 5). At 1 year postoperative, 54% of the patients indicated that they were able to resume the activity level they had before the accident. At the same time, 8% of the patients were able to stay employed compared to 3% at 3 months follow-up.

Fig. 4
Mean Harris hip score (HHS). Mean value of HHS measured in outpatient clinic questionnaires at each follow-up period. Scores tend to increase from the HHS baseline over time.

• Download Figure

Fig. 5
Weight bearing without pain. Proportion of weight bearing without pain observed in outpatient clinic at each follow-up period. Proportion of weight bearing without pain increases over the follow-up period.

• Download Figure

3. Radiographic outcomes

The mean TAD of the implanted CM nail was 11.2–17.6 mm and anatomic nail fit was assessed to be good in all cases (Table 2). At postoperative 1 year, 95% of patients (n=37) who continued follow-up with X-rays achieved bone union without soft tissue complication (Fig. 6). The 5% (n=2) who did not achieve radiological union at 1 year postoperative showed callus in only 2 cortices. Bony union was confirmed on subsequent follow-up X-rays. Radiologic union was achieved at an average rate of 44.84±15.6 weeks postoperatively. No adverse events such as implant specific complication were reported.

Fig. 6
Radiologic fracture healing. Radiologic bone union rate confirmed on plain radiographs at each follow-up period. Radiologic bone union rate increases over the follow-up period.

• Download Figure