Treatment of Proximal Femur Fracture with a Newly Designed Nail: Trochanteric Fixation Nail-Advanced (TFNA)

Hip fractures frequently occur in elderly patients with osteoporosis and are rapidly increasing in prevalence owing to an increase in the elderly population and social activities.1) Hip fractures are associated with high morbidity and mortality in patients and a high economic burden to society.2) The basic principle for treatment of intertrochanteric fractures and subtrochanteric fractures is osteosynthesis. Various surgical implants can be used according to fracture type, condition of the patient, and the surgeon's preference. Among the available implants, intramedullary devices have shown successful clinical outcome with better biomechanical stability because they have a short lever arm and require a relatively small skin incision compared with conventional extramedullary devices.3)

Trochanteric fixation nail-advanced (TFNA; DePuy Synthes, Warsaw, IN, USA) was first introduced in 2015 as the result of several design modifications from the existing Trochanteric Fixation Nail (TFN; DePuy Synthes) and was used first in South Korea in 2018.4) The design characteristics of the new device include decreased proximal nail diameter (from 17 to 15.66 mm) and decreased radius of curvature (ROC, from 1.5 to 1.0 m). The LATERAL RELIEF CUT™ design provides reduced impingement on the lateral cortex and the BUMP CUT™ design, which is a small tubercle at the mid-portion of the lateral proximal aperture, is said to allow improved fatigue strength compared to previous nails of similar size (Fig. 1).4, 5, 6)

Fig. 1
Photograph showing the design characteristics of the Trochanteric Fixation Nail-Advanced (TFNA). The LATERAL RELIEF CUT™ (dotted lines) and BUMP CUT™ (arrows) are marked in the pictures. (A) True lateral view of the proximal aperture of the TNFA. (B) Anterolateral view of the proximal aperture.

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Despite the many advantages of the new design characteristics of TFNA, Lamber et al.7) recently published a worrisome report of 16 cases of early implant breakage in the treatment of hip fracture patients. According to the data, implant failure mostly occurred in AO/OTA 31A3 fractures (reverse oblique type), and almost all implant fractures occurred at the proximal aperture.7) The purpose of this study is to report clinical outcomes and share our experiences regarding implant safety in hip fracture patients, with a minimum follow-up of six months.

A total of 26 patients with an mean age of 71.2 years (95% confidence interval [CI], 68.2–74.2) enrolled in this study. The mean follow-up duration was 6.5 months (95% CI, 6.1–6.9). The patients' demographic factors are presented in Table 1. BMD was performed in patients ≥50 years old. The mean T-score for patients who underwent the BMD test was −3.0, with 73.9% (17/23) of patients having a BMD score of less than −2.5. There were 19 intertrochanteric fractures (AO/OTA A31) and 7 subtrochanteric fractures (AO/OTA A32). Six out of 7 subtrochanteric fracture patients were diagnosed with an atypical femur fracture.

Table 1
Patients' Demographic Factors

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The mean time to start using a wheelchair and ambulation was 2.2 days and 2.7 days, respectively, with a mean hospital stay of 8.9 days. There were no early postoperative complications such as infection, deep vein thrombosis, pulmonary embolism, or in-hospital death. There was 1 case of pneumonia that improved within two weeks after surgery. Fourteen patients were discharged home, and the other 12 patients were transferred to another hospital for further rehabilitation and recovery. Perioperative patient variables are presented in Table 2.

Table 2
Perioperative Patient Variables

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The radiographically measured mean tip-apex distance (TAD) was 19.4 mm (95% CI, 18.4–20.4). Most cases, except for two cases of subtrochanteric atypical femoral fracture, satisfied the mean TAD of less than 25 mm. Bone union was observed in all cases, and the mean union time was 12.9 weeks (95% CI, 11.6–14.2) (Fig. 2, 3).

Fig. 2
(A) Total hip anteroposterior (AP) radiograph of 71-year-old female diagnosed with an intertrochanteric fracture of the right hip (AO/OTA 31A1.3). (B) Immediate postoperative total hip AP and cross-table lateral x-ray. The fractured segment was reduced in a slight valgus position (extramedullary). (C) Postoperative three months x-ray shows callus formation and bone bridging at the medial fracture gap. (D) Postoperative six months x-ray shows a complete union of the fracture.

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Fig. 3
(A) Total hip anteroposterior (AP) radiograph of 90-year-old female diagnosed with an intertrochanteric (reverse obliquity) fracture of the right hip (AO/OTA 31A3.1). (B) Immediate postoperative total hip AP and cross-table lateral x-ray. Cerclage wire before nailing was used to reduce the fragment in an anatomical position. (C) Fracture remained stable, and callus formation was visible around the medial calcar area in the postoperative three-month x-ray. (D) Complete bone union was achieved at the six-month follow-up.

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The mean Koval score at the postoperative six months follow-up was 2.8 (95% CI, 2.2–3.3). The mean HHS score improved from 64.9 (95% CI, 56.4–67.4) at discharge to 76.3 (95% CI, 70.2–82.4) at the six-month follow-up, and the improvement was statistically significant (p<0.001) (Fig. 4). The mean EQ-5D score increased from 0.25 (95% CI, 0.18–0.31) at discharge to 0.72 (95% CI, 0.63–0.83) at the six-month follow-up, and the increase in score was statistically significant as well (p<0.001) (Fig. 5).

Fig. 4
Change in the mean Harris hip score (HHS) following hip surgery. A serial survey of the patients was conducted at admission (before discharge) and in the out-patient clinic. The mean HHS score showed gradual improvement, and the increase was statistically significant (p<0.001). Postop.: postoperative.

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Fig. 5
Change in the Euro-Qol-5 Dimension (EQ-5D) score following hip surgery. A serial survey of the patients was conducted at admission (before discharge) and in the out-patient clinic. The EQ-5D score showed improvement, and the increase was statistically significant (p<0.001). Postop.: postoperative.

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TFNA for proximal femoral fractures showed a successful union rate (100%) with a mean union time of 12.9 weeks. Considering that all 6 atypical subtrochanteric fractures achieved bone union within six months, the outcome is satisfactory and is in line with the clinical results of previous studies using other implants.8, 9, 10, 11, 12, 13) Both patient functional outcome measures, HHS and EQ-5D score, also showed statistically significant improvement on serial follow-up (p<0.001) and had similar results compared to other previous studies using different implant systems in hip fracture patients.13, 14)

In the current study, there were no implant failures or implant fractures. Meanwhile, Lambers et al.7) reported on 16 cases (13 patients) of implant fractures that occurred between 2016 and 2018. Most of the implant fracture patients in their study had reverse oblique type fractures corresponding to AO/OTA classification 31A3 (75%), and the implant fracture occurred at the proximal aperture in almost all patients (94%). Either delayed union (69%) or nonunion (31%) were confirmed in all cases, and implant breakage was thought to be attributable to the new design of TFNA, which has a LATERAL RELIEF CUT™ and BUMP CUT™ design around the proximal aperture (Fig. 1). Both the nail width (17 mm in TFN vs 15.6 mm in TFNA) and wall thickness in the proximal area are reduced in the newly designed nail compared to its predecessor. Design characteristics of the implant, as well as abnormal stress concentration in specific fracture types, may have affected the vulnerability of the nail. Although the percentage of AO/OTA 31A3 (reverse oblique type) patients in our study (23.1%) was lower than that in the study by Lamber et al., all six cases showed successful bone union during follow-up, and no implant fracture occurred during or after the six-month radiological assessment.7)

In seven cases of long nail use, there was no iatrogenic fracture or perforation of the distal anterior cortex at the distal femur, which results from a mismatch between femur and nail. The ROC of the newly designed TFNA is 1.0 m, and the curvature is increased compared to the conventional TFN, which has a ROC with a radius of 1.5 m.4, 5) Asian patients usually have more femoral bowing than do Western patients.15, 16) In these patients, the distal tip of long straight nails can collide with the anterior cortex of the distal femur during implant insertion and cause implant breakthrough or iatrogenic fracture. For this reason, the new design of the TFNA can be a good alternative for patients with greater femoral bowing. By selecting an implant with the proper design, we were able to prevent implant-femur mismatch and the occurrence of iatrogenic fractures.

The free selectability of the cephalomedullary fixation system between a conventional screw and a helical blade is another advantage of this instrument. Although there is controversy in the clinical aspects, the helical blade has advantages in gaining firm bone compaction and additional bone purchase for fracture site compression in osteoporotic patients, preventing implant cut-out or -through.17, 18) The mean BMD of our enrolled patients was −3.0, showing a severe degree of osteoporosis in the majority of the patients. We, therefore, used the blade type in two-thirds of the patients (17 cases, 65.4%), and no cut-out or -through was observed in any patient.

There are several limitations to this study. First, this is a retrospective cohort study, and the level of evidence is relatively low. To compensate, we only included patients who were surgically treated by a single surgeon at a single institution. We also encouraged all patients to visit our out-patient clinic postoperatively to minimize loss to follow-up. Second, the number of enrolled patients is relatively small, which makes it difficult to derive meaningful conclusions. The purpose of our study was to briefly report on clinical outcomes and personal experiences of using TFNA in our patient group for the first time. We expect to carry out a prospective case-control study with more enrolled patients soon. Finally, the clinical observation period may be too short to evaluate the safety of the newly developed implant. In the data of Lamber et al.,7) however, the mean time to implant failure was 5.0±2.2 months, and our follow-up period is not shorter than that of the other study.

Our clinical outcome demonstrated that a new nail, TFNA, was safe and produced satisfactory outcomes. TFNA may be a useful option for fixation of simple intertrochanteric or subtrochanteric fractures with increased femoral bowing. However, we advise clinicians to be aware of the issues related to implant failure and pay careful attention to long-term outcomes and safety.