Japanese Proximal Femoral Nail (Antirotation) Study

The AOs First Completely Bilingual Study

AO Clinical Investigation (AOCID) has, in cooperation with Japanese colleagues, initiated the first multicenter study in orthopedic trauma in Japan. The proximal femoral nail antirotation Asia (PFNA study) will occupy Japanese researchers at 29 hospitals over the next 2 years. The first patients were already included. When the study is completed, more than 300 cases of patients over 65 years with proximal femoral fractures (more specifically isolated, unstable, closed trochanteric fractures) will have been examined. Among Japanese patients aged 65 years and older with proximal femoral fractures, the proportion of those aged 90 years and older has increased over the last decades from 3% in 1983 to nearly 20% in 2004. One reason for this is the increasing number of patients with osteoporosis in the older population. Compared to other ethnic groups, Asian people have the lowest bone mass.

Study background

The idea for the study came from the Asian Trauma Working Group (ASWG) because Asian people have different geometric proportions of the femoral bone compared to European or American populations. For example, studies have shown that Asian women have shorter femoral necks, smaller femoral neck angles, and a more anterior bowing of the shaft than white Americans. The new PFNA Asia has specially adapted sizes and geometry to better suit the local population. It boasts a flat lateral side, higher bending point of the nail resulting in a straighter tip point, a smaller medial-lateral bending of 5, and adapted surgical instruments. Japanese doctors were the driving force behind the development of the PFNA Asia and are pivotal to this study. In addition to the principal clinical investigator, Dr Takeshi Sawaguchi, Drs Tadashi Tanaka, Yasuhiro Nanri, and Atsushi Sakurai are also central to the studys success.

Although original PFNA have been in clinical use since 2005 in Japan, no data on the rate of mismatch are available yet. Therefore, one of the studys goals is to determine whether potential mismatch exists between the new PFNA Asia and Japanese patients, and whether both Japanese patients and surgeons needs will be met.

Objectives of the study

The primary objective of this prospective multicenter case series is to assess any fracture fixation complication and revision rates during the clinical use of the proximal femoral nail antirotation Asia (PFNA Asia) for the treatment of unstable, closed trochanteric fractures, classified according to the Mller AO Classification type 31-A2 or 31-A3. Fracture fixation complications include any bone/fracture- or implant/surgery-related event.

In addition to the assessment of potential mismatches of femoral medullary cavity and the PFNA Asia at the femoral great trochanter (lateral to blade insertion point), the middle medial portion and distal end of the nail are investigated: soft tissue, wound or general complications, prognostic factors for the occurrence of complications (eg, bone mineral density, dementia), length of hospital stay, walking ability, capacity to return to pre-injury status, quality of life, mortality, anatomical restoration (clinically and radiographically), length of surgery (skin to skin time) and operative handling of the implant and the instrumentation.

The follow-up schedule applying to this study includes initial hospitalization, as well as follow-up visits at 6 weeks, 12 weeks, 6 months and 12 months (these are the defined time intervals). The final evaluation of x-rays and complications will be performed by a study review board at the end of the study.

First completely bilingual study

Every document in the study is written in both Japanese and English. For example, every question on each case report form is asked in Japanese and English. The aim of this is to ease the filling out of the case report forms for Japanese colleagues. Additionally, for the first time, the OpVerdi database has been completely created in both languages. This naturally created a lot of work for the AOs team of computer specialists due to the different characters used in both languages. The key to success for the planning phase of this study was the close collaboration between the principle clinical investigator (PCI) in Japan and the responsible AOCID study manager, despite a distance of more than 10,000 kilometres between them.

Background information

Unstable trochanteric fractures, mainly due to osteoporosis, are a surgical challenge worldwide. However, significant regional variations are apparent in both the size and the characteristics of the problem. For example, it is known that East-Asians have different geometric proportions to Caucasians, resulting in complications due to a mismatch when using standard implants.

The Proximal Femoral Nail Antirotation (PFNA) Asia
To help cope with the differences described above, an Asian version of the existing Proximal Femoral Nail Antirotation (PFNA) was developed and introduced into the market. The PFNA Asia (also known as PFNA II) (Fig 1) has a proximal diameter of 16.5 mm, Caput Collum Diaphyseal (CCD) angles of 125 or 130, a range of lengths (short: 170 mm, 200 mm; long: 300 mm420 mm) and distal diameters (9 mm12 mm) with an adapted geometry, i.e., a flat lateral side, a straighter tip point, and medial-lateral bending of 5.

Study Rationale and Aims

While few previous studies have been conducted to compare the standard PFNA with other implants in the treatment of trochanteric fractures in Asians, no prospective study had focused on the effect of the PFNA Asia in the Asian population with respect to a detailed complication analysis.
The primary focus of the AOTrauma Japan multicenter case series
study was safety, examined by assessing the 1-year local bone/fracture and implant/surgery complication rates in patients treated with the PFNA Asia. In addition, secondary outcomes focused on assessing function and quality of life-related patient outcomes, operative handling by the surgeon, potential mismatches between the femur and implant, anatomical restoration, and prognostic factors associated with the occurrence of complications.

Study conduct
The clinical investigation was performed in 20 Japanese hospitals over a three year period. The study population was 176 patients aged 65 years and older with a radiologically-confirmed, unstable, closed trochanteric fracture, sustained seven days or less before primary fixation treatment with the PFNA Asia.

Preliminary results and conclusion

Patient functional outcomes and health-related quality of life were similar between the pre-injury and final follow-up evaluations, and surgeons were highly satisfied with the implant and its handling. There is also a large societal benefit to enabling patients of advanced age that have sustained an unstable trochanteric fracture to return to their preinjury residential status.

The preliminary results from this study highlight the importance of
having implants designed for older Asian patients available to surgeons in the region.

Features of the Proximal Femoral Nail Antirotation (PFNA ) Asia

The Proximal Femoral Nail Antirotation (PFNA), with its helical blade concept, is a state-of-the-art treatment method for proximal femoral fractures, providing rotational and angular stability with one single element. The intramedullary nail acts as an internal splint that controls but does not prevent micromovements of the bone fragments. The PFNA provides relative stability, leading to indirect healing through callus formation.

With the PFNA Asia, the proximal-lateral portion of the nail has been narrowed to prevent jamming with the lateral cortex, and to facilitate smooth insertion of the nail.

90-year-old male, injured by fall down.

Case provided by Toru Sato, Okayana, JP

77-year-old male.

Case provided by Takeshi Sawaguchi, Toyama, JP

78-year-old female.

Case provided by Takeshi Sawaguchi, Toyama, JP

Elderly patient with fall injury

Case provided by Takeshi Sawaguchi, Toyama, JP.

An 85-year-old Japanese woman fell down at her home. She sustained an AO 31-A2.1 fracture. The images indicate various stages of the operation, using the PFNA Asia.