Femoral intertrochanteric fracture is a commonly observed fracture that occurs in 133 cases per 100,000 in Korea every year.1) Conservative treatment of femoral intertrochanteric fractures leads to a higher frequency of non-union and an increased mortality rate due to pneumonia or pressure ulcers from long-term bed rest compared to surgical treatment. Therefore, surgery is the gold standard treatment for femoral intertrochanteric fractures, and the surgical method of using an intramedullary nail is what is commonly used.2,3) The currently used intramedullary nails include the proximal femoral nail antirotation (PFNA; DePuy Synthes, Warsaw, IN, USA), Gamma3 nail (Stryker Trauma, Schönkirchen, Germany), and InterTAN (Smith & Nephew, Memphis, TN, USA); however, complications, such as cervical screw and blade cut-through as well as breakage of the nails, have also been reported.4,5) To reduce these complications, an antirotation helical blade, which allows for higher rotational stability of the femoral head and neck, is used in PFNA-II. Additionally, when the antirotation helical blade is inserted into the head, it can compress the surrounding bones, thereby increasing the fixation force and reducing the frequency of cut-out of the head. However, complications, including cut-out of the head and breakage of the intramedullary nail, are constantly observed in some patients.4,5,6) To reduce these complications, the trochanteric fixation nail-advanced (TFNA; DePuy Synthes, West Chester, PA, USA) was developed and approved for use in Korea in September 2018. TFNA was modified in general to reduce chronic pain and breakage of the intramedullary nail from cut-out of the head by the PFNA-II antirotation helical blade and lateral femoral stimulation by the protrusion of the antirotation helical blade. A set screw locking function was added, and the Lateral Relief Cut™ design of the intramedullary nail and the sloped surface design on the outer surface of the antirotation helical blade were used to reduce stimulation of the outer surface of the femur. Moreover, the Bump Cut™ design was newly added to the antirotation helical blade insertion hole to reduce the frequency of intramedullary nail breakage.7)

A titanium-molybdenum (Ti-Mo) alloy was used to increase the fatigue strength, and the curvature was increased for the overall shape of the intramedullary nail to be more anatomically suitable for Asians. In this study, we assessed and compared the functional and radiological outcomes of TFNA, which is an improved fracture fixation device compared to the previously used PFNA-II, in elderly patients with osteoporotic femoral intertrochanteric fracture.

There was no significant difference in the reduction of fractures as anatomical 14 cases, intramedullary 3 cases, extramedullary 21 cases in the TFNA group, and anatomical 12 cases, intramedullary 5 cases, and extramedullary 27 cases in the PFNA-II group (p=0.23). Femoral neck shortening was 1.35 mm (range, 0-12.2 mm) in the TFNA group and 1.47 mm (range, 0-16.9 mm) in the PFNA-II group, with no significant difference between the two groups (p=0.69). TAD was 29.0 mm in the TFNA group and 32.4 mm in the PFNA-II group, and it was not significantly different between the two groups (p=0.24).

Bone union on radiographic findings was observed rather quickly within 20.0 and 20.9 weeks on mean in the TFNA and PFNA-II groups, respectively. There was no significant difference between the two groups (p=0.77).

The postoperative Koval score level was 3.61 and 3.45 in the TFNA and PFNA-II groups, respectively, and the difference between the pre and postoperative Koval score was 1.34 in the TFNA group and 1.36 in the PFNA-II group. There was no difference in the pre and postoperative Koval score in both groups (p=0.36 and p=0.78, respectively).

Complications were observed in 3 patients in the PFNA-II group and 1 patient in the TFNA group; however, there was no significant difference between the two groups (p=0.37). All 4 cases with loss of fracture reduction were intramedullary reduction.

In the PFNA-II group, 2 cases of femoral head cut-out and 1 case of varus collapse were observed. Total hip arthroplasty was performed for the single case of varus collapse, and bipolar hemiarthroplasty was conducted in the 2 cases of femoral head cut-out (Fig. 1). In the TFNA group, 1 case of femoral head cut-out was observed. The patient was elderly, with a poor medical condition, and the family of the patient refused to undergo surgery. Hence, the patient was followed up regularly (Table 2,Fig. 2). No infection was observed in both groups.

Fig. 1
Postoperative complications of the PFNA-II system. (A) Preoperative radiography of a 76-year-old male patient with intertrochanteric fracture. (B) Postoperative radiography of the patient taken 24 months after surgery using PFNA-II. (C) Plain radiography showed the cut-out of the blade of the PFNA-II. (D) Conversion to total hip arthroplasty was performed.

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Fig. 2
Postoperative complication of the TFNA system. (A) Preoperative radiography of a 84-year-old male patient with intertrochanteric fracture. (B) Postoperative radiography of the patient taken 11 months after surgery using TFNA. (C) Plain radiography showed the cut-out of the blade.

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Table 2
Clinical and Functional Results

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For the intertrochanteric fractures, as enabling early movement through stable fixation of the fracture reduces the frequency of complications and promotes recovery, various devices have been developed for more stable fracture fixation.1) In particular, the proximal femoral nail helps to secure more stability in unstable fractures and stable intertrochanteric fractures.2,3,4) Even though it was impossible to minimize the shortening of the neck because the intramedullary nail such as PFNA-II does not have a mechanism that can effectively control the slide of the fractured area.12) Since it is possible to control the slide with the set screw function of the TFNA, it is expected that the shortening of the fracture will be prevented to some extent.

Kim and Shon14), who reported the treatment results of stable femoral intertrochanteric fractures using PFNA-II and Zimmer Natural Nail (ZNN), evaluated that the sliding distance tended to be small in ZNN with the set screw fixed. This supports the authors’ idea that set screw fixation will help prevent neck shortening.

Cut-out of the femoral head, which is a typical complication of using proximal femoral nails, is approximately 8%.15) In a computational study, the frequency of cut-out of the femoral head can be reduced by compressing the medullary bone inside the femoral head with an antirotation helical blade.16) Similar findings were observed in a biomechanical study.17) However, cut-out of the femoral head is still observed even when an antirotation helical blade is used,5) and two cases of femoral head cut-out requiring additional surgery were also observed in this study. In a study by Lenich et al.18), 120 cases were followed up for at least 6 months and femoral head cut-out was observed in 3 cases (2.3%). In a study of Korean participants using TFNA for intertrochanteric fractures, Yoon and Kim7) reported that femoral head cut-out was not observed in any of the 26 cases. Consistent with these results, this study shows that femoral head cut-out occurred in 1 in 38 cases when using TFNA. In all cases with cut-out observed in this study, the post-operative reduction was intramedullary position. As reported by Lee et al.19), varus reduction was achieved in 2 of 3 cases where cut-out occurred in the study using TFNA with helical blade. Therefore, reduction quality of fractures is considered to have an unyielding importance in the treatment of intertrochanteric fractures. In the TFNA group, there was no significant difference compared to what was observed in the PFNA-II group; however, the incidence of femoral head cut-out was low tendency.

Previous studies reported that excessive shortening of the femoral neck by 5 mm or more may impair gait function by reducing the gluteal muscle length and range of motion.20) The newly added set screw locking function to the TFNA system was expected to further preserve the length of the femoral neck; however, the difference in the postoperative length of the femoral neck between the two groups was not statistically significant.

To prevent breakage of the intramedullary nail, a Ti-Mo alloy (Ti-15Mo) was used for its greater fatigue strength than that of a titanium-6% aluminum-7% niobium alloy of PFNA. However, intramedullary nail breakage was not observed in both groups. Therefore, the effects of Ti-Mo alloy could not be further assessed.21) And Wallace et al.22) compared TFNA with other proximal femoral nails and confirmed that the proportion of nail breakages was equivalent.

The limitations of this study were as follows. First, a powerful statistical analysis was difficult due to the relatively small number of study subjects. And as a retrospective study, the follow-up period of the two groups was relatively short. In particular, the PFNA-II group had a significantly longer follow-up period than the TFNA group, which may have underestimated the frequency of complications and long-term prognosis in the TFNA group. Also, randomization of the study group was not performed.

Nevertheless, this study is considered meaningful in that it attempted to find out whether TFNA, developed by supplementing the shortcomings of PFNA-II, showed improved results by applying it to clinical practice.

PFNA-II and TFNA showed satisfactory clinical outcomes with no significant differences in elderly patients with femoral intertrochanteric fractures. In patients who underwent surgeries using TFNA, the recovery of gait ability, frequency of complications, and shortening of the femoral neck were not different significantly, suggesting that both TFNA and PFNA-II are considered to be suitable instrument choices for intertrochanteric fracture treatment. However, the clinical significance must be further assessed using a larger group of patients over a longer follow-up period in future studies.