A Comparison of the Proximal Femoral Nail Antirotation Device and Dynamic Hip Screw in the Treatment of Unstable Pertrochanteric Fracture

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1 The Journal of International Medical Research 2010; 38: A Comparison of the Proximal Femoral Nail Antirotation Device and Dynamic Hip Screw in the Treatment of Unstable Pertrochanteric Fracture YZ XU*, DC GENG*, HQ MAO, XS ZHU AND HL YANG Department of Orthopaedic Surgery, First Affiliated Hospital of Soochow University, Suzhou, China This prospective randomized study compared the outcome of elderly patients with an unstable pertrochanteric fracture, treated with a proximal femoral nail antirotation device (PFNA; n = 51) or a dynamic hip screw (DHS; n = 55). All patients in the DHS group and nine in the PFNA group had open reductions. Incisions were significantly shorter for the PFNA than the DHS group. Blood loss and the number of patients requiring postoperative blood transfusions were significantly greater, but operation and fluoroscopy times were significantly shorter, for the DHS versus the PFNA group. Time to mobilization with a frame was significantly shorter in the PFNA group, and post-operative complications were more common in the DHS group. Poor fracture reduction led to three revisions. All fractures in both groups united during follow-up. The PFNA allowed earlier mobilization and faster recovery than the DHS. The PFNA is a highly acceptable, minimally invasive implant for unstable fractures. KEY WORDS: PROXIMAL FEMORAL NAIL ANTIROTATION DEVICE; DYNAMIC HELICAL SCREW; PERTROCHANTERIC FRACTURE; MOBILITY; COMPLICATIONS Introduction The incidence of proximal femoral fractures has increased considerably during recent years because of the worldwide increase in life expectancy. 1 Treatment of these fractures ideally requires an implant with a minimally invasive operation technique, full body weight-bearing after the operation and a low complication rate. The dynamic hip screw (DHS) has gained widespread *These authors contributed equally to this work. acceptance during the last decade and is currently considered the standard device for comparison of outcomes. 2,3 The DHS has been shown to produce good results but complications are frequent, particularly in unstable pertrochanteric fractures. 4,5 The proximal femoral nail (PFN) appears to have theoretical advantages over other devices in the treatment of trochanteric fractures because it is an intramedullary implant. 3,5 9 Data published so far confirm that the PFN is a reliable implant, producing 1266

2 results similar to those obtained with the DHS for unstable trochanteric fractures. 3,5 Various authors have, however, reported screw cut-out of the femoral head and a higher rate of intra-operative difficulties with the PFN. 5,6,9 There is, therefore, an urgent need to modify the intramedullary nail design in order to minimize complications. For this reason, the proximal femoral nail antirotation device (PFNA) was designed by the Arbeitsgemeinschaft für Osteo - synthesefragen/association for the Study of Internal Fixation (AO/ASIF). The PFNA has a small distal shaft diameter, resulting in a lower concentration of stress in the tip than in the PFN. The greatest change is the use of a helical neck blade in the PFNA: the PFNA blade prevents the bone loss that occurs during drilling and insertion of the standard sliding hip screw The PNFA provides improved purchase in the femoral head, by radial compaction of the cancellous bone around the blade during insertion Few data are available about the PFNA, however, because previous studies were often retrospective and lacked control groups. 13,14 The purpose of the present study was to compare outcome and complications between the PFNA and DHS in the treatment of elderly patients with an unstable pertrochanteric fracture. Patients and methods PATIENTS Between August 2006 and June 2008, patients with unstable pertrochanteric fracture were randomized to be treated with a PFNA or a DHS. No patient refused randomization, which was accomplished by using consecutive numbered and sealed envelopes based on a computer-generated list. Sealed envelopes were opened before the surgeon performed the operation. Patients who were admitted to the Department of Orthopaedic Surgery, First Affiliated Hospital of Soochow University, Suzhou, China during the study period, with an unstable proximal femoral fracture (AO category 31-A2), 15 were considered eligible for the study. Exclusion criteria were age < 65 years, pathological fractures, fractures associated with polytrauma, previous surgery on the ipsilateral hip or femur, inability to work before injury, and a severe concomitant medical condition (grade V on the American Society of Anesthesiologists [ASA] scale). 5 Background variables including age, sex, ASA risk score and walking ability, which was assessed with the mobility score (0 9 points) of Parker and Palmer, 16 were recorded for all patients. The Ethics Committee of the First Affiliated Hospital of Soochow University approved the study. Informed written consent was obtained from each patient or from their relative if the patient was incapable of providing consent. TREATMENTS Operations were performed according to standard protocols for either PFNA or DHS, as recommended by device manufacturers and described previously. 13,14 The PFNA used in the present study was a solid titanium nail 170 or 240 mm in length and 10 or 11 mm in diameter, which was inserted without reaming of the medullary canal. The helical blade was inserted into the femoral neck without drilling. The PFNA may be distally locked either dynamically or statically. The neck shaft angle of the implant was 130. The DHS used had three or four holes and a 135 plate with a screw of appropriate length. These procedures were performed through an open approach with direct exposure of the fracture. All operations were performed by surgeons who had performed at least three 1267

3 procedures with both the PFNA and the DHS. All patients received a pre-operative intravenous injection of the antibiotic ceftriaxone (2 g). General or spinal anaesthesia were used in both groups. The operation time, fluoroscopy time, blood loss and any intra-operative complications were recorded. After operation, all patients had suction drains put in place for h and received prophylactic antibiotics for 3 5 days. All patients were encouraged to move the hip, knee and ankle joints on the first postoperative day, under the surgeon s guidance. Continuous passive motion rehabilitation devices (Smith & Nephew, Shanghai, China) were used twice a day after the suction drain had been removed. FOLLOW-UP Plain anteroposterior and lateral radiographs were obtained on the first postoperative day, and analysed for reduction of the fracture and position of the implant. Reduction was classified as good if alignment was normal and if the displacement between the fragments did not exceed 2 mm in any projection. The ideal position for the screw or the blade in the femoral neck was defined as central on the lateral radiograph and central or inferior on the anteroposterior radiograph (Figs 1 and 2). Starting as soon as possible after the operation, all patients were encouraged to walk in a fully weight-bearing fashion, assisted by a surgeon. Follow-up reviews were performed 1, 3, 6 and 12 months after surgery (6-month data not reported). At each post-operative review the patient s mobility score was recorded and plain anteroposterior and lateral radiographs were obtained. All changes in the position of the fracture and implant, when compared with the radiograph taken on the first post-operative day, were recorded and considered as secondary measures of outcome. Shortening of the femur was measured on the last radiograph. STATISTICAL ANALYSIS Statistical analysis was performed using SPSS statistical package, version 10.0 (SPSS Inc., Chicago, IL, USA) for Windows. Quantitative variables were analysed using A B C FIGURE 1: Radiographs showing intramedullary fixation of a proximal femoral fracture treated with a proximal femoral nail antirotation device: (A) before surgery; (B) immediately after surgery (first post-operative day); and (C) 6 months after surgery 1268

4 A B C FIGURE 2: Anteroposterior radiographs demonstrating a left pertrochanteric fracture treated with a dynamic helical screw: (A) before surgery; (B) immediately after surgery (first post-operative day); and (C) 6 months after surgery the Student s t-test and categorical variables were analysed by the χ 2 test or Fisher s exact test where appropriate. The level of statistical significance was set at a two-sided P-value of Results Between August 2006 and June 2008, 106 patients with unstable pertrochanteric fractures were randomized to be treated with a PFNA (n = 51) or a DHS (n = 55). The PFNA and DHS groups were comparable with regard to all features assessed before the fracture occurred, and at 3 months and 1 year after surgery (Table 1). The numbers of patients receiving general or spinal anaesthesia did not differ significantly between the two study groups (Table 2). All 55 patients treated with a DHS, but only nine of the 51 patients treated with a PFNA, had an open reduction. Mean ± SD incision length was significantly shorter in the PFNA group compared with the DHS group (P < ). The mean operating and fluoroscopy times were significantly longer in the PFNA group than in the DHS group (P < ). Blood loss was significantly lower in the PFNA group than in the DHS group (P < ); 48 of the 55 patients in the DHS group received blood transfusions compared with 19 of the 51 patients in the PFNA group (P < ). Two femoral shaft fractures with minor splits in the cortex at the tip of the nail were observed intra-operatively in the PFNA group, but none was observed in the DHS group (Table 3). These fractures were treated successfully with conservative management, i.e. a delay of full weight-bearing for 6 8 weeks. All the fractures in both groups eventually united and did not affect the patients mobility. Complications were more common in the DHS group (38.2%) than in the PFNA group (29.4%). Three wound infections requiring antibiotics occurred in the DHS group but only one infection occurred in the PFNA group (difference not statistically significant). There were three cases of fixation failure (two in the PFNA and one in the DHS groups; difference not statistically significant); all three patients had revision operations. No patient had a pulmonary embolus, but seven (two in the PFNA and five in the DHS groups; difference not statistically significant) developed a postoperative chest infection that required 1269

5 TABLE 1: Baseline data on patients before surgery and 3 months and 1 year after implantation of a proximal femoral nail antirotation device (PFNA) or a dynamic hip screw (DHS) to treat an unstable pertrochanteric fracture Before surgery 3 months after surgery 1 year after surgery Statistical Statistical Statistical PFNA DHS significance PFNA DHS significance PFNA DHS significance Patients (n) Female (n) NS NS NS Age (years) 78.5 ± ± 7.82 NS 78.0 ± ± 7.97 NS ± ± 7.93 NS ASA risk score NS NS NS Mobility score 6.71 ± ± 1.83 NS 4.04 ± ± ± ± 1.39 P = Data are mean ± SD or n. Quantitative variables were analysed using the Student s t-test and categorical variables were analysed by the χ 2 test or Fisher s exact test where appropriate. ASA, American Society of Anesthesiologists; NS, not statistically significant (P > 0.05). 1270

6 TABLE 2: Intra-operative variables in patients treated with a proximal femoral nail antirotation device (PFNA) or a dynamic hip screw (DHS) for an unstable pertrochanteric fracture PFNA DHS Statistical Variable (n = 51) (n = 55) significance Type of anaesthesia General (n) NS Spinal (n) Length of incision (cm) 5.5 ± ± 2.4 P < Operating time (min) 68.5 ± ± 11.8 P < Open reduction (n) 9 55 Blood loss (ml) ± ± P < Blood transfusion (n) P < Fluoroscopy time (min) 2.99 ± ± 0.48 P < Data are mean ± SD or n. Quantitative variables were analysed using the Student s t-test and categorical variables were analysed by the χ 2 test or Fisher s exact test where appropriate. NS, not statistically significant (P > 0.05). TABLE 3: Intra-operative and post-operative complications in patients treated with a proximal femoral nail antirotation device (PFNA) or a dynamic hip screw (DHS) for an unstable pertrochanteric fracture PFNA DHS Variable (n = 51) (n = 55) Fixation failure 2 1 Femoral shaft fracture Intra-operative 2 0 Post-operative 1 0 Superficial wound infection 1 3 Chest infection 2 5 Decubital ulcer 2 3 Urinary tract infection 4 9 Cerebral infarction 1 0 Data are n of patients. No significant differences between the PFNA and DHS groups were found (P > 0.05). antibiotic treatment. In the PFNA group, one femoral shaft fracture appeared 1 month after surgery because of a fall; this patient received an osteosynthesis plate and the new fracture had united at the last follow-up. No cut-out of the femoral head or non-union was observed in either group during the follow-up period. The duration of hospital stay did not differ significantly between the two treatment groups. The mean time to mobilization with a frame was significantly shorter in the PFNA group than in the DHS group (P < ; Table 4). In the PFNA group, 39.6% of the patients had returned to their previous level of walking ability by 3 months postoperatively, compared with 16% in the DHS group (P = 0.009; Table 4). 1271

7 TABLE 4: Post-operative variables in patients treated with a proximal femoral nail antirotation device (PFNA) or a dynamic hip screw (DHS) for an unstable pertrochanteric fracture PFNA DHS Statistical Variable (n = 51) (n = 55) significance Hospital stay (days) 7.0 ± ± 1.7 NS Mean time to mobilization with a frame (days) 3.6 ± ± 1.3 P < Recovery of walking ability to pre-operative status 19/48 (39.6) 8/50 (16.0) P = months after surgery a Recovery of walking ability to pre-operative status 27/40 (67.5) 19/43 (44.2) P = year after surgery b Mean shortening of the femur (mm) 2.6 ± ± 4.0 P = Mobility score at the last follow-up 5.6 ± ± 1.8 P < Data are mean ± SD or n/n (%). a At 3 months, 98 (PFNA 48, DHS 50) of the initial 106 patients were followed up; b at 1 year, 83 patients (PFNA 40, DHS 43) of the initial 106 patients were followed up. Quantitative variables were analysed using the Student s t-test and categorical variables were analysed by the χ 2 test or Fisher s exact test where appropriate. NS, not statistically significant (P > 0.05). At 3 months, 98 (48 in the PFNA and 50 in the DHS groups) of the initial 106 patients were followed up. Of the eight patients unavailable for analysis, three had died, four had been lost to follow-up, and one was excluded because of femoral shaft fracture after surgery (Table 5). Throughout the study, deaths were attributable to concomitant medical problems and were unrelated to the method of fixation. The reasons for loss to follow-up were a move to an unknown location and refusal of further participation. At 1 year, another five patients had died, seven were lost to follow-up and three patients with revision surgery were excluded TABLE 5: Reasons for loss to follow-up for the 23 patients who withdrew from a study comparing use of a proximal femoral nail antirotation device (PFNA) or a dynamic hip screw (DHS) for unstable pertrochanteric fracture PFNA DHS Follow-up and end-point (n = 51) (n = 55) 3 months Died 1 (2.0) 2 (3.6) Lost 2 (3.9) 2 (3.6) Excluded 0 1 (1.8) 1 year Died 2 (3.9) 3 (5.5) Lost 4 (7.8) 3 (5.5) Excluded 2 (3.9) 1 (1.8) Data are n (%). The two groups of patients were treated with a proximal femoral nail antirotation device (PFNA, n = 51) or a dynamic hip screw (DHS, n = 55) for an unstable pertrochanteric fracture. Categorical variables were analysed by the χ 2 test or Fisher s exact test where appropriate. No significant differences between the PFNA and DHS groups were found (P > 0.05). 1272

8 (Table 5). In the remaining 83 patients (40 in the PFNA and 43 in the DHS groups), both functional tests and radiographs showed that every fracture had united. The mean shortening of the femoral shaft was significantly less in the PFNA group compared with the DHS group (P = ; Table 4). At the last follow-up (not necessarily at 1 year), patients who had a PFNA were significantly more mobile than those with a DHS (mobility score 5.6 ± 1.4 versus 4.4 ± 1.8; P < ), and were more likely to regain their pre-operative mobility score (Table 4). Discussion This trial was initiated in order to compare the outcomes of unstable pertrochanteric fracture treated with a PFNA and a DHS. Pilot studies had shown a good outcome with few complications after treatment with a PFNA, 13,14 although in those studies no comparison was made with a DHS. The PFNA was developed by the AO/ASIF group as an alternative to the PFN with a special helical blade. The helical blade allows improved purchase in the femoral head by radial compaction of the cancellous bone around the blade during insertion Its improved purchase in osteoporotic bone has been demonstrated biomechanically. Strauss et al. 11 reported that fixation of the femoral head with a helical blade was biomechanically superior to fixation with a standard sliding hip screw. A similar biomechanical study demonstrated that the helical blade provided the greatest resistance to cut-out compared with the lag screw design. 10 Thus, the helical neck blade has the advantages of fixation stability, antirotation and antivarus collapse. 12 The PFNA seems to be associated with a lower incidence of complications. At 3 months after the index operation, restoration of walking ability was more frequent in patients treated with PFNA than in those treated with DHS in the present study. All fractures in both groups had united at the 1-year follow-up. Patients who received a PFNA were, however, significantly more mobile than those with a DHS (P ). Moreover, 67.5% of patients in the PFNA group had returned to their previous level of walking activity 1 year after surgery compared with 44.2% in the DHS group. This finding agrees with the results of Mereddy et al. 13 and Simmermacher et al., 14 who observed the restoration of the pre-fracture activity level in approximately 56 80% of patients treated with a PFNA. In contrast, several studies showed that the use of a DHS led to about 40 50% restoration of the previous level of mobility. 5,17 19 Pajarinen et al. 5 suggested that impaction of the fracture in patients treated with a DHS leads to femoral neck shortening and that the substantial compression that occurs may prevent restoration of the ability to walk. These results demonstrated that the use of a PFNA may favour better restoration of function in trochanteric fractures compared with the use of a DHS. The present study showed that the time taken to regain mobility with a frame was shorter with the PFNA than with the DHS. Little et al. 20 reported that treatment of trochanteric fractures with a Holland nail and a DHS gave similar results. They suggested that post-operative complications, such as pain, muscle dysfunction and medical comorbidities, may affect restoration of mobility. Implantation of a PFNA is minimally invasive: 13,14 the entry point above the greater trochanter causes less damage to the gluteus medius muscle than entry points in the piriform fossa. 21 The DHS, however, requires a larger incision and probably damages more muscle. 20 The 1273

9 results from the present study showed that blood loss was significantly lower in the PFNA group than in the DHS group (P < ), and significantly more patients in DHS group than in the PFNA group needed a blood transfusion (P < ). The authors believe that these factors slowed mobilization in the DHS group. The operation and fluoroscopy times were significantly longer in the PFNA group (P < , both variables), which may be related to the investigators learning curves for this new method. There were also more chest infections in the DHS than in the PFNA group, but this difference did not reach statistical significance. Fracture of the femoral shaft at the tip of the nail is a known complication associated with the use of intramedullary nails in the treatment of proximal femoral fractures. 3,5,9 In the present study, there were three cases of femoral shaft fracture in the PFNA group: two intra-operative and one post-operative. The intra-operative femoral shaft fractures observed in the present study were related to an immature learning curve, and were treated successfully with the conservative method of delaying full weight-bearing for 6 8 weeks. The post-operative femoral shaft fracture resulted from a fall at home 1 month after the operation and was treated with an osteosynthesis plate. These new fractures healed within the follow-up period and did not affect patients mobilization. Three fixation failures occurred: two in the PFNA group and one in the DHS group. All were caused by poor fracture reduction, and all three patients had revision operations. Patients who had a second operation were excluded from the study. There were several limitations to the present study. The operations were performed by different surgeons, which may have affected the functional outcome, the study did not include a large number of patients, and larger sample sizes will be needed for further analysis. A common problem in this type of study 5,19,22 is the withdrawal of a large number of patients, which occurred in the present study and may be explained in part by the age of the patients. In the present series, the 23 patients who did not attend their final review had either died during the follow-up period, had been too weak to attend, or were excluded because of revision surgery. It was presumed that this high dropout rate did not bias the comparison between the two methods, as the drop-out rate was similar in both study groups. The purpose of the surgical treatment of unstable pertrochanteric fractures is the stabilization of the fracture and early mobilization, restoring limb function. This was achieved more satisfactorily with the use of a PFNA than with a DHS. At present, the authors consider that the PFNA is a highly acceptable, minimally invasive implant for unstable fractures. Conflicts of interest The authors had no conflicts of interest to declare in relation to this article. Received for publication 3 February 2010 Accepted subject to revision 8 February 2010 Revised accepted 26 May 2010 Copyright 2010 Field House Publishing LLP References 1 Kannus P, Parkkari J, Sievänen H, et al: Epidemiology of hip fracture. Bone 1996; 18(1 suppl): 57S 63S. 2 Parker MJ, Handoll HH: Gamma and other cephalocondylic intramedullary nails versus extramedullary implants for extracapsular hip fractures in adults. Cochrane Database Syst Rev 2008; 16: CD Saudan M, Lübbeke A, Sadowski C, et al: 1274

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