Orthopedics

Feature Articles 

The New Proximal Femoral Nail Antirotation-Asia: Early Results

Chaoliang Lv, MD; Yue Fang, MS; Lei Liu, MD; Guanglin Wang, MD; Tianfu Yang, BS; Hui Zhang, MD; Yueming Song, MD

Abstract

The proximal femoral nail antirotation system was introduced by the Arbeitsgemeinschaft fur Osteosynthesfragen/Association for the Study of Internal Fixation (AO/ASIF) in 2003 and is suitable for treating unstable trochanteric fractures. However, proximal femoral nail antirotation was designed according to the geometric proportions of the White population, and it is known that important differences exist between Asians and Americans with regard to femoral geometry. Reports of serious postoperative complications also exist when used for the elderly Asian population. Therefore, geometrical mismatch between proximal femoral nail antirotation and the femora of Asians has led the AO/ASIF to design a new proximal femoral nail antirotation for Asia with adapted sizes and geometry. This article reports early clinical results of using proximal femoral nail antirotation for Asians in 84 consecutive patients to stabilize unstable trochanteric fractures (AO classification, 31.A2 and A3). Patients were followed up for an average 8 months (range, 4-11 months). Intraoperative and postoperative complications, surgical details, and outcome measurements were evaluated. Fractures were treated by closed reduction and intramedullary fixation. The proximal femoral nail antirotation Asia position was ideal in 80 cases (95%). No patients showed complication related to the mismatch between the nail and femora. The mean time to bone healing was 14 weeks. Functionally, 90% of the patients regained pretrauma mobility. According to the Harris hip scoring system, 63 patients (78%) had an excellent or good outcome. The new proximal femoral nail antirotation Asia yields better results in the treatment of unstable trochanteric fractures in elderly patients by closely matching Asian femoral anatomy and thereby reducing complications related to the implants.

Unstable trochanteric fractures are common in elderly patients and their treatment continues to be a challenge for orthopedic surgeons. The dynamic hip screw is an adequate implant that has been available for years for 31.A1 fractures (Arbeitsgemeinschaft fur Osteosynthesefragen/Association for the Study of Internal Fixation [AO/ASIF] classification).1,2 For the unstable A2 and A3 fractures, intramedullary stabilization including the Gamma nail, proximal femoral nail, and proximal femoral nail antirotation, has become a standard procedure over the past decade.3-5 The proximal femoral nail antirotation system was introduced by the AO/ASIF in 2003 and is the most suitable for treating unstable trochanteric fractures.5-8 However, proximal femoral nail antirotation was designed according to the geometric proportions of Caucasians, and it is known that there are important differences between Asians and Americans with regard to the femoral geometry.9,10 For example, Chinese women have shorter femoral necks, smaller femoral neck angles, and increased anterior bowing of the shaft than those in white Americans.11,12 A study reported that the proximal end of the nail did not match the specific anatomy of some patients of short stature when used for treating an elderly Chinese population.5 In addition, reports of postoperative complications have arisen.13,14 Therefore, further modifications of proximal femoral nail antirotation are necessary for the elderly Asian population.

According to geometric proportions of Asians, the AO/ASIF designed the proximal femoral nail antirotation Asia with adapted sizes and geometry. The current study was undertaken to evaluate the early clinical outcomes of unstable trochanteric fractures that were treated using this new design.

The study included patients older than 65 years of age who had a recent traumatic unstable trochanteric fracture that was treated using proximal femoral nail antirotation Asia within 7 days and were able to attend the planned follow-up. Patients with previous implants in the fractured hip or femur and those who were bedridden or wheelchair-bound before injury were excluded. Informed consent was obtained from the patients or their guardians.

The modified nail of the proximal femoral nail antirotation Asia (Synthes GmbH, Oberdorf, Switzerland) has a proximal…

Abstract

The proximal femoral nail antirotation system was introduced by the Arbeitsgemeinschaft fur Osteosynthesfragen/Association for the Study of Internal Fixation (AO/ASIF) in 2003 and is suitable for treating unstable trochanteric fractures. However, proximal femoral nail antirotation was designed according to the geometric proportions of the White population, and it is known that important differences exist between Asians and Americans with regard to femoral geometry. Reports of serious postoperative complications also exist when used for the elderly Asian population. Therefore, geometrical mismatch between proximal femoral nail antirotation and the femora of Asians has led the AO/ASIF to design a new proximal femoral nail antirotation for Asia with adapted sizes and geometry. This article reports early clinical results of using proximal femoral nail antirotation for Asians in 84 consecutive patients to stabilize unstable trochanteric fractures (AO classification, 31.A2 and A3). Patients were followed up for an average 8 months (range, 4-11 months). Intraoperative and postoperative complications, surgical details, and outcome measurements were evaluated. Fractures were treated by closed reduction and intramedullary fixation. The proximal femoral nail antirotation Asia position was ideal in 80 cases (95%). No patients showed complication related to the mismatch between the nail and femora. The mean time to bone healing was 14 weeks. Functionally, 90% of the patients regained pretrauma mobility. According to the Harris hip scoring system, 63 patients (78%) had an excellent or good outcome. The new proximal femoral nail antirotation Asia yields better results in the treatment of unstable trochanteric fractures in elderly patients by closely matching Asian femoral anatomy and thereby reducing complications related to the implants.

Unstable trochanteric fractures are common in elderly patients and their treatment continues to be a challenge for orthopedic surgeons. The dynamic hip screw is an adequate implant that has been available for years for 31.A1 fractures (Arbeitsgemeinschaft fur Osteosynthesefragen/Association for the Study of Internal Fixation [AO/ASIF] classification).1,2 For the unstable A2 and A3 fractures, intramedullary stabilization including the Gamma nail, proximal femoral nail, and proximal femoral nail antirotation, has become a standard procedure over the past decade.3-5 The proximal femoral nail antirotation system was introduced by the AO/ASIF in 2003 and is the most suitable for treating unstable trochanteric fractures.5-8 However, proximal femoral nail antirotation was designed according to the geometric proportions of Caucasians, and it is known that there are important differences between Asians and Americans with regard to the femoral geometry.9,10 For example, Chinese women have shorter femoral necks, smaller femoral neck angles, and increased anterior bowing of the shaft than those in white Americans.11,12 A study reported that the proximal end of the nail did not match the specific anatomy of some patients of short stature when used for treating an elderly Chinese population.5 In addition, reports of postoperative complications have arisen.13,14 Therefore, further modifications of proximal femoral nail antirotation are necessary for the elderly Asian population.

According to geometric proportions of Asians, the AO/ASIF designed the proximal femoral nail antirotation Asia with adapted sizes and geometry. The current study was undertaken to evaluate the early clinical outcomes of unstable trochanteric fractures that were treated using this new design.

Materials and Methods

The study included patients older than 65 years of age who had a recent traumatic unstable trochanteric fracture that was treated using proximal femoral nail antirotation Asia within 7 days and were able to attend the planned follow-up. Patients with previous implants in the fractured hip or femur and those who were bedridden or wheelchair-bound before injury were excluded. Informed consent was obtained from the patients or their guardians.

The modified nail of the proximal femoral nail antirotation Asia (Synthes GmbH, Oberdorf, Switzerland) has a proximal lateral flat surface, a mediolateral angle of 5°, and a proximal diameter of 16.5 mm to suit the anatomical characteristics of Asians. The blade is available in lengths of 75 to 120 mm in steps of 5 mm (Table 1, Figure 1). Additionally, the proximal femoral nail antirotation Asia, like the proximal femoral nail antirotation, is available in 4 sizes (standard, small, extra small, and long) with 4 different distal diameters ranging from 9 to 12 mm. The long proximal femoral nail antirotation Asia (300 and 340 mm) is available in 2 distal diameters of 9 and 10 mm.

Table 1


Figure 1: The proximal femoral nail antirotation Asia design.
Figure 1: The proximal femoral nail antirotation Asia design.

The AO classification system15 was adopted to classify the fractures and the American Society of Anesthesiologists (ASA) scale16 was used to evaluate comorbidity.

 All fractures were treated by closed reduction with proximal femoral nail antirotation Asia under C-arm fluoroscopy control. Using a fracture table, the fractured hip was placed in a slightly adducted position to facilitate the insertion of the nail. All operations were performed by the same group of experienced surgeons (C.L., Y.F., L.L.). The surgical procedure was the same as that used for the standard proximal femoral nail antirotation, in the manufacturer’s instructions. The operative time, blood loss during surgery, overall fluoroscopy time, amount of transfused blood, duration of hospitalization, surgical complications, and assessment of nail handling for proximal femoral nail antirotation Asia were compared with those of proximal femoral nail antirotation.

In all cases, antithrombotic prophylaxis was administered using low-molecular-weight heparin for 3-5 days, and antibiotic prophylaxis was administered within 1 day after the operation. Rehabilitation was important; patients were mobilized on the first postoperative day, and partial weight bearing was encouraged with the aid of a walker or crutches on the following day.

 Radiographs of the affected hip were obtained in the anteroposterior (AP) and medial-lateral planes to assess postoperative fracture reduction. The quality of fracture reduction was graded as good, acceptable (5-10° varus/valgus and/or anteversion/retroversion), or poor (>10° varus/valgus and/or anteversion/retroversion).17 The position of the proximal femoral nail antirotation was graded as good if the blade was placed into the lower half of the neck on the AP view and centrally on a lateral view and if the nail did not protrude outside the greater trochanter.

Follow-up evaluations, which included a clinical and radiographic assessment, were performed at 4, 12, 24, and 52 weeks. The clinical results were assessed using the Harris hip score.18 Harris hip scores were categorized as excellent (90-100 points), good (80-89 points), fair (70-79 points), or poor (<69 points). Radiographs of the affected hip were obtained in the AP and mediolateral planes at each follow-up visit, and any changes in the position of the implant and the extent of the fracture union were noted. Fractures were judged to be healed radiographically if the bridging callus was evident on 3 to 4 cortices, as noted on 2 views.19

Results

 From November 2009 to October 2010, eighty-four consecutive patients with unstable trochanteric fractures were included in this study. Preoperative patient data are shown in Table 2. There were 60 female and 24 male patients with a mean age of 79.5 years (range, 65-92 years). The majority of the fractures resulted from a fall at home. According to the AO classification,15 fifty-seven fractures were classified as 31.A2 and 27 fractures as 31.A3. In addition, 24 patients were classified as ASA 1, thirty-nine patients were classified as ASA 2, fifteen patients were classified as ASA 3, and 6 patients were classified as ASA 4, reflecting significant comorbidity ranging from malignancies to cardiac morbidity.

Table 2

 All fractures were successfully treated by closed reduction. The mean duration of surgery (skin to skin) was 48 minutes for A2 fractures and 61 min for A3 fractures. C-arm fluoroscopy control required a mean time of 113 seconds for fixing A2 fractures and 152 seconds for fixing A3 fractures. Mean blood loss was 50 mL in A2 fractures and 150 mL in A3 fractures. Twenty-four patients required blood transfusions with an average volume of 400 mL. The mean duration of hospital stay was 7 days. Ten patients did not require reaming, as shown in Table 3. Postoperative radiographs showed a good or acceptable fracture reduction in 78 cases (93%), an ideal implant position in 80 cases (95%), and a tip-apex distance of 10 to 20 mm in 50% of patients (Table 4).

Table 3


Table 4

 Of the proximal femoral nail antirotation Asia standard sizes, the 90-mm and 95-mm blade sizes and 170-mm nail length were the most frequently used. All distal locking procedures were performed using static or dynamic instruments by using one 4.9-mm screw. Insertion of the nail was perceived to be easy. The proximal end of the nail and proximal femur matched well in most patients (Figure 2).

Figure 2A: Preoperative AP radiograph Figure 2B: Postoperative radiograph Figure 2C: Follow-up AP radiograph of the left hip at 3 months
Figure 2: An 85-year-old woman sustained an isolated and closed Arbeitgemeinschaft Osteosynthesefragen classifi cation 31.A2 fracture at the left side after a fall at home. Preoperative AP radiograph showing the displaced intertrochanteric fracture (A). Postoperative radiograph after closed reduction and internal fixation using proximal femoral nail antirotation Asia (B). Follow-up AP radiograph of the left hip at 3 months postoperatively showing the united fracture with the proximal femoral nail antirotation in situ (C). Abbreviation: L, left.

 At most recent follow-up, 2 patients died within 4 months due to causes unrelated to the implant, and 4 patients could no longer be contacted or refused further participation. The remaining 78 patients were evaluated. Ninety-eight percent of the fractures united with a good component position, and the average time to bone healing was 14 weeks (range, 12-24 weeks). None of the patients had deep infection or failures or breakages due to implant fatigue. Mechanical failures such as bending or breaking of the implant or intraoperative or postoperative fractures were not noted; screw cut-outs were also not observed. None of the patients developed thigh pain or mismatch of the proximal end of the nail or required reoperation. Ninety percent of the patients regained their preinjury mobility and could take care of themselves. The Harris hip score results were as follows: 24, excellent; 37, good; 13, fair; and 4, poor. In all, 61 patients (78%) showed an excellent or good outcome. The mean Harris hip score was 85 points (range, 52-95 points).

Discussion

 A long debate has been ongoing concerning the preferred implant for stabilization of unstable trochanteric fractures. For operative treatment of this kind of fracture, 2 options exist: extramedullary or intramedullary stabilization. Because of the biomechanical advantage and minimal invasion, intramedullary devices such as the Gamma nail, proximal femoral nail, and proximal femoral nail antirotation are preferred in elderly patients.3,20,21 To improve the rotational and angular stability using a single element, the AO/ASIF group modified the proximal femoral nail to the proximal femoral nail antirotation in 2003. The compaction of cancellous bone is a unique property of the proximal femoral nail antirotation blade, and it has been biomechanically proven to have a better purchase in the osteoporotic bone.22 Unstable trochanteric fractures have been successfully treated using proximal femoral nail antirotation.5-7,13,14 However, when proximal femoral nail antirotation is used in the Asian population, suitable implants are not always available and geometric mismatch between the proximal end of the nail and proximal femur are generally encountered in elderly patients of short stature. To improve the design of the nail, the AO/ASIF designed the new proximal femoral nail antirotation Asia, on the basis of an anthropometric study.

 The standard proximal femoral nail antirotation nail has a mediolateral angle of 6° and a proximal diameter of 17 mm. To insert the nail, a much larger femoral canal needs to be prepared to accommodate the nail of the given diameter.23 This means that a considerable amount of cortical bone has to be reamed, thus weakening the osteoporotic bone in most patients. Friedl et al24 suggested that the necessary overreaming of the shaft weakens the entire shaft,25 and that reaming of the medulla can lead to increased blood loss. In addition, this geometric mismatch between the proximal end of the nail and proximal femur is the most probable cause of the intraoperative complications of jamming and fracturing of the lateral cortex. Based on the results of the anthropometric study, the modified nail was designed to have a mediolateral angle of 5° and a proximal diameter of 16.5 mm. Additionally, the proximal lateral surface was made flat to facilitate insertion and to lower the pressure on the lateral cortex. The modified nail, therefore, has a considerably better anatomic fit. In this study, nearly 70% of the fractures could be fixed using lesser degrees of reaming or with no reaming. The decrease in the mediolateral curvature and the proximal diameter together with a proximal lateral flat surface facilitated insertion and lowered the stress on the anterior and medial cortices. This effectively decreases the hoop stress inside the femoral shaft and may have contributed to a significant decrease in intraoperative and postoperative diaphyseal fractures.26 In our consecutive patients, no diaphyseal fractures related to the nail were found. All of the fractures healed within 4 months. Postoperative radiographs showed a good or acceptable reduction in 78 cases (93%) and an ideal implant position in 80 cases (95%).

With the new proximal femoral nail antirotation Asia, the operative technique could be improved to facilitate implantation. Operative time, blood loss, and fluoroscopy time were greatly reduced compared with those of the standard proximal femoral nail antirotation and other reported devices.5,27,28

Thigh pain and discomfort have been reported to occur occasionally when the standard proximal femoral nail antirotation is used; a study reported that 11 out of 87 patients who underwent treatment with proximal femoral nail antirotation experienced tenderness in the affected hip after the operation.5 The main reason for this tenderness is a mismatch between the femoral component and the geometry of the proximal femur, which affects the insertion of the nail and causes an excessive protrusion of the nail outside the greater trochanter, resulting in unnecessary irritation around the hip (Figure 3). Previously, the position of the blade was the only standard used to evaluate proximal femoral nail antirotation position.8,21 In this study, the position of the end of the nail was used as an additional standard besides the blade. As a result, in 95% of patients, the proximal femoral nail antirotation was in a good position, and thigh pain and discomfort were not observed.

Figure 3: Surgery using the smallest version of the standard proximal femoral nail
Figure 3: A 90-year-old man (height, 155 cm; weight, 58 kg) underwent surgery using the smallest version of the standard proximal femoral nail antirotation (length, 170 mm). The proximal end of the nail is prominent (arrow).

Conclusion

The early results of the proximal femoral nail antirotation Asia were satisfactory in most patients included in this study. The modification of the proximal femoral nail antirotation provides an anatomic fit in the proximal femur and contributes to decreased complications. However, the number of the patients included in our study was small and the time of the follow-up was short. A multicentric clinical study will be required for definitive assessment.

References

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Authors

Drs Lv, Liu, Wang, Zhang, and Song and Messrs Fang and Yang are from the Department of Orthopedic Surgery, West China Hospital, Sichuan University, Chengdu, China.

Drs Lv, Liu, Wang, Zhang, and Song and Messrs Fang and Yang have no relevant financial relationships to disclose.

Correspondence should be addressed to: Yue Fang, MS, Department of Orthopedic Surgery, West China Hospital, Sichuan University, 37 Guo Xue Xiang, Chengdu, Sichuan Province, 610041, China (fangyuegk3@163.com).

doi: 10.3928/01477447-20110317-26

10.3928/01477447-20110317-26

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