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Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail
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Guidelines for Treatment
Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail Kazuma Takashima a, Ichiro Nakahara b, Keisuke Uemura a, Hidetoshi Hamada c, Wataru Ando a, Masaki Takao c, Nobuhiko Sugano a,∗ a b c
Department of Orthopaedic Medical Engineering, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, Japan Department of Orthopaedic Surgery, Osaka National Hospital, 2-1-4 Hoenzaka, Chuo-ku, Osaka, Japan Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, Japan
a r t i c l e
i n f o
Article history: Accepted 5 January 2020 Available online xxx keywords: Carbon fiber-reinforced polyetheretherketone Intramedullary nail Proximal femoral fractures Clinical trial
a b s t r a c t Introduction: We developed a new carbon fiber-reinforced polyetheretherketone (CFR/PEEK) intramedullary nail for proximal femoral fractures. This study aimed to examine the efficacy and safety of the CFR/PEEK intramedullary nail for use in the treatment of patients with proximal femoral fractures. Methods: This multicentre single-arm clinical trial enrolled 20 patients (3 men, 17 women; mean age 85.0 years, range 72–95 years) with proximal femoral fractures treated with the CFR/PEEK intramedullary nail. The follow-up period was >4 months. Primary outcomes were union of the bone fracture, time to bone union, bone nonunion, complications, implant failure, and the reoperation rate. Secondary outcomes were fracture reduction success, and clinical scores using the Harris hip score, Barthel index, Vitality index, Mini-Mental State Examination, and Numerical Rating Scale. Results: Among the 20 patients with proximal femoral fractures treated with CFR/PEEK intramedullary nails, 19 (95%) were confirmed to display bone union within 3.7 months (range 2.8–10.0 months). One patient was diagnosed as having bone nonunion, although the patient did not complain any pain, and there was no radiological evidence of failure after a follow-up period of >18 months. There were no complications (e.g., cut out, infection, hardware failure), and reoperation was not required. Fracture reduction was good and acceptable in all cases, and the mean tip–apex distance was 13.5 mm (range 9.0–19.1 mm). The results indicated that preoperative activity was maintained (preoperative and postoperative Harris hip scores were 73.2 and 71.0 points, respectively; p = 0.61). Conclusion: There were no adverse reactions or failures related to the CFR/PEEK implant, and it provided satisfactory clinical results and a high union rate. Thus, use of the novel CFR/PEEK intramedullary nail is feasible. © 2020 Elsevier Ltd. All rights reserved.
Introduction Carbon fiber-reinforced polyetheretherketone (CFR/PEEK), which has excellent strength, wear resistance, and biocompatibility, has been expected to be available for clinical application as a new material for repairing bone fractures and joint prostheses [1,2]. CFR/PEEK does not have the fatigue phenomenon seen with metallic materials, and this high fatigue resistance could be advantageous for preventing implant failure [3]. Rigidity can be easily designed by the arrangement of its carbon fibers, so a wide range of rigidity adjustments is possible [4]. If the rigidity of a CFR/PEEK implant is properly designed, it can be expected to suppress bone
∗
Correspondence Author. E-mail address: [email protected] (N. Sugano).
atrophy by stress shielding, in contrast to metal implants, which have a higher elastic modulus than bone [5]. In addition, CFR/PEEK has X-ray permeability, which ensures that CFR/PEEK fracture fixation devices can be useful for confirming fracture reduction intraoperatively, new bone formation, and union of bone fractures [6]. The use of CFR/PEEK implants is also beneficial in the treatment of patients with musculoskeletal tumors [7]. The radiolucent characteristic of CFR/PEEK implants provide an option for obtaining artifact-free CT and MRI images, which is useful for evaluating local recurrence. Moreover, CFR/PEEK implants have minimal perturbation effects on the radiotherapy dose distribution, and may offer benefits for patients receiving postoperative external beam radiation treatment [8]. Based on preclinical mechanical studies and in vivo trials of CFR/PEEK implants in animals [9–12], we developed a new device for proximal femoral fractures using CFR/PEEK (Fig. 1). The
https://doi.org/10.1016/j.injury.2020.01.007 0020-1383/© 2020 Elsevier Ltd. All rights reserved.
Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007
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Fig. 2. (A, B) A 92-year-old woman with a right proximal femoral fracture (AO/OTA 31A1.2). (D, E) Early postoperative radiographs showed good reduction of the fracture.
Materials and Methods
Fig. 1. The newly developed CFR/PEEK intramedullary nail. The tapered portion of the proximal one-third of the nail was slimmed down so the nail could be inserted even in the narrowest medullary canal, based on CT images of 100 cases of proximal femoral fracture while having the same level of fatigue strength as standard metal nails. Four metal wire markers were placed parallel to the long axis of the nail with discontinuity at the lag and distal screw holes so the screws could be inserted safely under image intensifier guidance. The thread portion at the tip of the lag screw is composed of titanium alloy for insertability and radiographic visibility. In addition, four metal wire markers were placed parallel to the long axis of the lag screw.
CFR/PEEK intramedullary nail had several characteristics as follows. The tapered portion of the proximal one-third of the nail was slimmed down so the nail could be inserted even in the narrowest medullary canal, based on CT images of 100 cases of proximal femoral fracture while having the same level of fatigue strength as standard metal nails. Four metal wire markers were placed parallel to the long axis of the nail with discontinuity at the lag and distal screw holes so the screws could be inserted safely under image intensifier guidance. We conducted a preliminary clinical trial with this femoral intramedullary nail system to evaluate its safety and efficacy in patients with proximal femoral fractures. The purpose of the present study was to examine the efficacy and safety of this newly developed CFR/PEEK intramedullary nail to treat patients with proximal femoral fractures.
The study was designed as a multicentre, single-arm, clinical trial. The Pharmaceuticals and Medical Devices Agency of Japan approved the study, and all analyses were performed with the approval of the institutional review board of the authors’ institution. The inclusion criteria for the study were (1) presence of a trochanteric region fracture or a basicervical fracture of the femur (AO/OTA 31A1.2, 1.3, 2.2, 2.3, or 31B3) [13]; (2) age ≥20 years; (3) informed consent obtained and the consent form signed. The exclusion criteria were (1) pathological fracture due to a tumour or a tumour-like lesion; (2) hip disorders, previous surgery, or previous injury in the target hip joint; (3) serious preexisting medical disease(s) or active infection; (4) subtrochanteric fracture; (5) pregnancy; (6) refusal to give informed consent. Between March 2018 and November 2018, we enrolled 20 patients (3 men, 17 women; mean age 85.0 years, range 72–95 years; mean body mass index 21.3 kg/m2 , range 15.9–31.1 kg/m2 ) with a trochanteric fracture treated with the CFR/PEEK intramedullary nail. According to the AO/OTA classification of fractures, 11 patients had a 31A1.2 fracture, 3 had a 31A2.2 fracture, 5 had a 31A2.3 fracture, and 1 had a 31B3 fracture. The operative procedure was the same as when using a traditional femoral intramedullary metal nail system. All patients were positioned on a traction table under general anaesthesia. We attempted manual closed reduction under fluoroscopic guidance. If no acceptable reduction was achieved, we performed an open reduction using elevators and a Kirschner wire via skin incision for lag screw insertion. The CFR/PEEK intramedullary nail was inserted from the tip of the greater trochanter with a target device after pre-drilling the canal. The position of the nail was adjusted for a lag screw to the centre of a femoral head on both anteroposterior and lateral views. We selected the length of the lag screw so the tip of the lag screw reached within 5 mm from the subchondral bone plate. One distal titanium screw was then inserted with the target device (Fig. 2). We assessed the fracture reduction
Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007
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[14], and calculated the tip–apex distance on immediately obtained postoperative radiographs [15]. The reduction was evaluated based on the amount of displacement and the neck–shaft alignment on the obtained postoperative anteroposterior and lateral radiographs and was categorised as good, acceptable, or poor. “Good reduction” of the fracture was defined as displacement of <4 mm on both images, anatomical or slightly valgus neck–shaft alignment on the anteroposterior view, and <20° angulation on the lateral view. An “acceptable reduction” satisfied one of the requirements regarding displacement or alignment. “Poor reduction” was when it met neither the “good” nor “acceptable” criteria. Intraoperative adverse events were recorded. The postoperative protocol followed the following pattern: All patients were allowed full weight-bearing during the immediate postoperative period. All patients underwent clinical and radiographic examination with follow-up at 1 and 4 weeks postoperatively. We then saw the patients at monthly intervals until bone fracture union was confirmed. To mitigate bias, fracture union was assessed by two independent experienced orthopaedic surgeons who were not involved with this clinical trial. Bone union was defined by radiographic evidence of bridging callus across the fracture and solid contact of cortical bone on anteroposterior and lateral radiographs [16]. The appearance of complications, including cut out, infection, hardware failure, and reoperation rates, were monitored during the follow-up period. We also evaluated clinical outcomes using the Harris hip score [17], Barthel index [18], Vitality index [19], and Mini-Mental State Examination [20]. We asked patients about the presence of hip pain on the affected side, and quantified it with the Numerical Rating Scale [21]. Major complications of intramedullary nails for proximal femoral fractures (e.g., nonunion, cut out, hardware failure) reportedly occur in approximately 6.3% of cases [22–24]. Therefore, we set 93.7% as a reference value of bone union for traditional metal implants, 10% as the clinically acceptable non-inferiority margin, and 95% as an expected bone union rate in this clinical trial. With the significance level set at 0.05 and the power of the test at 0.55, a binominal test with power analysis suggested that 18 patients would be required to prove non-inferiority compared with the traditional metal implants. As we assumed a dropout of two patients, the number of clinical trials was set at 20. Continuous data were presented as means ± standard deviations with the minimum and maximum. The data were compared between preoperative and postoperative measurements using Student’s t-test or Wilcoxon’s rank sum test, as appropriate. Categorical data were presented as frequencies and percents. A value of p < 0.05 was considered to indicate a statistically significant difference. Statistical analysis was performed using JMP or SAS software (SAS Institute, Cary, NC, USA).
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Fig. 3. An 82-year-old woman with a right proximal femoral fracture was treated with a metal implant on one side and a CFR/PEEK implant on the other side. Visibility was better on the CFR/PEEK side, allowing us to assess bone healing with postoperative radiographs in more detail. Table 1 Comparison of measurement items between pre- and postOP. Variable HHS (points, mean ± SD) BI (points, mean ± SD) VI (points, mean ± SD) MMSE (points, mean ± SD) NRS (points, mean ± SD)
PreOP 73.2 ± 13.8 71.1 ± 26.9 7.7 ± 2.0 19.2 ± 8.3 –
PostOP 71.0 ± 13.3 57.1 ± 31.9 7.6 ± 2.8 18.8 ± 9.6 0.9 ± 1.3
p value 0.61 0.15 0.81 0.97 –
OP = operation; SD = standard deviations; HHS = Harris hip score; BI = Barthel index; VI = Vitality index; MMSE = Mini-Mental State Examination; NRS = Numerical Rating Scale
compared with their preoperative status. The average Numerical Rating Scale was very low (0.9 ± 1.3 points) at the final follow-up (Table 1). Radiographically, 19 of 20 patients (95%) were confirmed to have achieved bone union at an average duration of 3.7 months (range 3–10 months). One patient was judged not to have achieved bone union, although the patient did not complain any pain and had no radiological evidence of failure during the following 18month follow-up (Fig. 4). There were also no complications overall, such as cut out, infection, or hardware failure. There were no reoperations required in this cohort.
Results
Discussion
The mean operation time was 27.5 min (range 12.0–64.0 min). The mean intraoperative blood loss was 55 ml (range 10–120 ml). Eight cases required open reduction of the fracture. The postoperative qualities of fracture reduction were good or acceptable in all cases, and the tip–apex distance was <20 mm in all cases (mean 13.5 ± 2.4 mm; range 9.0–19.1 mm) (Fig. 3). No intraoperative adverse events or technical difficulties were encountered. Patients were followed-up for a minimum of 4 months (mean 8.4 months). The following values showed that preoperative activity was maintained postoperatively (preoperative vs postoperative values, respectively): Harris hip score 73.2 ± 13.8 vs 71.0 ± 13.3 points (p = 0.61); Barthel index 71.1 ± 26.9 vs 57.1 ± 31.9 points (p = 0.15); Vitality index 7.7 ± 2.0 vs 7.6 ± 2.8 points (p = 0.81); Mini-Mental State Examination 19.2 ± 8.3 vs 18.8 ± 9.6 points (p = 0.97). Nor were these parameters impaired postoperatively
Several studies have shown that CFR/PEEK implants display good stability and favourable mechanical properties for treating fractures. CFR/PEEK is suitable for use in orthopaedic implants and has excellent mechanical strength, potential for adjusting for optimal stiffness, in vitro biocompatibility with direct cellular contact, and lack of cytotoxicity [25]. Therefore, CFR/PEEK implants have been proposed for treating several fractures [26]. Mitchell et al evaluated 11 patients with distal femoral fractures treated with CFR/PEEK plates. They showed low nonunion and reoperation rates in patients in the CFR/PEEK group and concluded that CFR/PEEK might be an alternative to metal for treating several fractures [27]. However, proximal femoral fracture cohorts treated with CFR/PEEK intramedullary nails had not been reported to date. We believe that this clinical trial during which we treated proximal femoral fractures with CFR/PEEK intramedullary nails is the first such study
Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007
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cases showed complete union of the cortex. CFR/PEEK implants can be made rigid by arranging carbon fibers [5]. Previously, the concept of treating fractures was to fix the lesion firmly for safe, rapid healing. However, a good biological environment and semirigid fixation has proved important to fracture healing in recent studies [29,30]. Furthermore, trabecular bone loss might occur due to stress shielding by metal implants, which could be a risk factor for re-fracture at the bone loss area [9,31]. Although the degree of rigidity required that is ideal for treating bone fractures remains unclear, this characteristic of CFR/PEEK could be used in the future to determine the optimal rigidity. Furthermore, previously used metal implants present potential problems, such as fatigue failure, wear, and imaging artifact, whereas use of CFR/PEEK avoids these problems. This study had several limitations. Although it was a prospective clinical study of the newly developed CFR/PEEK implants, there was no control group. Further, the number of clinical cases is small. Nevertheless, this clinical trial showed the non-inferiority of efficacy compared with the historical control of traditional metal intramedullary nails even under statistical power assumed in advance. Moreover, no intraoperative adverse events or postoperative complications related to the implant were noted, indicating the safety of using the CFR/PEEK nail system. Based on this encouraging outcome, a larger population in a controlled study is warranted to confirm the benefits of the CFR/PEEK intramedullary nail. Fracture union could not be demonstrated as objective data. Some reports showed utility as a radiographic union score in tibial fractures [32], however, it was difficult to apply the score to trochanteric femoral fractures in this study. Therefore, fracture union was assessed by two independent experienced orthopaedic surgeons not involved with this study to mitigate bias. Conclusions
Fig. 4. (A, B). An 83-year-old woman with a right, complex, proximal femoral fracture (AO/OTA 31A2.3). (C, D) Reduction of the fracture was good, and the tip–apex distance was 14.3 mm). (E, F) Bridging callus formation was visible, and the postoperative radiograph at the final follow-up (18 months) showed no progressive subsidence of the lag screw or nail failure. This case, however, was judged as nonunion because a solid contact of cortical bone was not confirmed on the radiographs at 6 months.
to be reported. There were no adverse reactions or failures related to the CFR/PEEK implants, and bone union was confirmed in 95% of the cases. This novel CFR/PEEK intramedullary nail provided satisfactory clinical results. CFR/PEEK implants do not interrupt traditional radiographic views and cause no artifacts on CT or MRI [28]. CFR/PEEK may allow a more lucid intraoperative interpretation during reduction, osteosynthesis, postoperative callus formation, and bone union in fractures than with standard imaging modalities. It allows analysis of fracture and dislocation [6,11]. The radiolucency of CFR/PEKK, however, has an issue of difficulty recognising the position of the nail on fluoroscopy. Therefore, radiopaque metal wires were arranged in the nails and lag screws as markers. In the present study, the radiolucency of CFR/PEEK implants was helpful for surgeons to confirm the grade of fracture reduction during the operation, and there were no difficulties in positioning the nail or inserting the lag screw and distal titanium screw. It was also good for evaluating bone healing in detail on postoperative radiographs (Fig. 3). Radiographic union did not occur in one patient with a complicated fracture in our study, although the patient had good callus formation, and the fracture site was stable (Fig. 4). The other
There were no adverse reactions or failures related to the CFR/PEEK implant, and it provided satisfactory clinical results and a high union rate. Thus, use of the novel CFR/PEEK intramedullary nail is feasible. Declaration of Competing Interest The authors, Kazuma Takashima, Ichiro Nakahara, Keisuke Uemura, Hidetoshi Hamada, Wataru Ando, Masaki Takao, and Nobuhiko Sugano, declare no conflict of interest. Acknowledgments We thank Drs. Mitsuyoshi Yamamura, Hidenobu Miki, Takaaki Shibuya, Tatsuya Kitaura, and Nayuki Kitaura for their helpful support. This study was funded by the Development of Medical Devices through Collaboration between Medicine and Industry from Japan Agency for Medical Research and development, AMED. References [1] Kurtz SM, Devine JN. PEEK biomaterials in trauma, orthopedic, and spinal implants. Biomaterials 2007;28(32):4845–69. [2] Wenz LM, Merritt K, Brown SA, Moet A, Steffee AD. In vitro biocompatibility of polyetheretherketone and polysulfone composites. J Biomed Mater Res 1990;24(2):207–15. [1] Akay M, Aslan N. An estimation of fatigue life for a carbon fibre/poly ether ether ketone hip joint prosthesis. Proc Inst Mech Eng H 1995;209(2):93–103. [2] Scotchford CA, Garle MJ, Batchelor J, Bradley J, Grant DM. Use of a novel carbon fibre composite material for the femoral stem component of a THR system: in vitro biological assessment. Biomaterials 2003;24(26):4871–9. [3] Skinner HB. Composite technology for total hip arthroplasty. Clin Orthop Relat Res 1988(235):224–36. [4] Krüger T, Alter C, Reichel H, Birke A, Hein W, Spielmann RP. Possibilities of follow-up imaging after implantation of a carbon fiber-reinforced hip prosthesis. Aktuelle Radiol 1998;8(2):81–6.
Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007
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Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007
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[m5G;January 17, 2020;23:20]
Injury xxx (xxxx) xxx
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Guidelines for Treatment
Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail Kazuma Takashima a, Ichiro Nakahara b, Keisuke Uemura a, Hidetoshi Hamada c, Wataru Ando a, Masaki Takao c, Nobuhiko Sugano a,∗ a b c
Department of Orthopaedic Medical Engineering, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, Japan Department of Orthopaedic Surgery, Osaka National Hospital, 2-1-4 Hoenzaka, Chuo-ku, Osaka, Japan Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, Japan
a r t i c l e
i n f o
Article history: Accepted 5 January 2020 Available online xxx keywords: Carbon fiber-reinforced polyetheretherketone Intramedullary nail Proximal femoral fractures Clinical trial
a b s t r a c t Introduction: We developed a new carbon fiber-reinforced polyetheretherketone (CFR/PEEK) intramedullary nail for proximal femoral fractures. This study aimed to examine the efficacy and safety of the CFR/PEEK intramedullary nail for use in the treatment of patients with proximal femoral fractures. Methods: This multicentre single-arm clinical trial enrolled 20 patients (3 men, 17 women; mean age 85.0 years, range 72–95 years) with proximal femoral fractures treated with the CFR/PEEK intramedullary nail. The follow-up period was >4 months. Primary outcomes were union of the bone fracture, time to bone union, bone nonunion, complications, implant failure, and the reoperation rate. Secondary outcomes were fracture reduction success, and clinical scores using the Harris hip score, Barthel index, Vitality index, Mini-Mental State Examination, and Numerical Rating Scale. Results: Among the 20 patients with proximal femoral fractures treated with CFR/PEEK intramedullary nails, 19 (95%) were confirmed to display bone union within 3.7 months (range 2.8–10.0 months). One patient was diagnosed as having bone nonunion, although the patient did not complain any pain, and there was no radiological evidence of failure after a follow-up period of >18 months. There were no complications (e.g., cut out, infection, hardware failure), and reoperation was not required. Fracture reduction was good and acceptable in all cases, and the mean tip–apex distance was 13.5 mm (range 9.0–19.1 mm). The results indicated that preoperative activity was maintained (preoperative and postoperative Harris hip scores were 73.2 and 71.0 points, respectively; p = 0.61). Conclusion: There were no adverse reactions or failures related to the CFR/PEEK implant, and it provided satisfactory clinical results and a high union rate. Thus, use of the novel CFR/PEEK intramedullary nail is feasible. © 2020 Elsevier Ltd. All rights reserved.
Introduction Carbon fiber-reinforced polyetheretherketone (CFR/PEEK), which has excellent strength, wear resistance, and biocompatibility, has been expected to be available for clinical application as a new material for repairing bone fractures and joint prostheses [1,2]. CFR/PEEK does not have the fatigue phenomenon seen with metallic materials, and this high fatigue resistance could be advantageous for preventing implant failure [3]. Rigidity can be easily designed by the arrangement of its carbon fibers, so a wide range of rigidity adjustments is possible [4]. If the rigidity of a CFR/PEEK implant is properly designed, it can be expected to suppress bone
∗
Correspondence Author. E-mail address: [email protected] (N. Sugano).
atrophy by stress shielding, in contrast to metal implants, which have a higher elastic modulus than bone [5]. In addition, CFR/PEEK has X-ray permeability, which ensures that CFR/PEEK fracture fixation devices can be useful for confirming fracture reduction intraoperatively, new bone formation, and union of bone fractures [6]. The use of CFR/PEEK implants is also beneficial in the treatment of patients with musculoskeletal tumors [7]. The radiolucent characteristic of CFR/PEEK implants provide an option for obtaining artifact-free CT and MRI images, which is useful for evaluating local recurrence. Moreover, CFR/PEEK implants have minimal perturbation effects on the radiotherapy dose distribution, and may offer benefits for patients receiving postoperative external beam radiation treatment [8]. Based on preclinical mechanical studies and in vivo trials of CFR/PEEK implants in animals [9–12], we developed a new device for proximal femoral fractures using CFR/PEEK (Fig. 1). The
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Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007
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Fig. 2. (A, B) A 92-year-old woman with a right proximal femoral fracture (AO/OTA 31A1.2). (D, E) Early postoperative radiographs showed good reduction of the fracture.
Materials and Methods
Fig. 1. The newly developed CFR/PEEK intramedullary nail. The tapered portion of the proximal one-third of the nail was slimmed down so the nail could be inserted even in the narrowest medullary canal, based on CT images of 100 cases of proximal femoral fracture while having the same level of fatigue strength as standard metal nails. Four metal wire markers were placed parallel to the long axis of the nail with discontinuity at the lag and distal screw holes so the screws could be inserted safely under image intensifier guidance. The thread portion at the tip of the lag screw is composed of titanium alloy for insertability and radiographic visibility. In addition, four metal wire markers were placed parallel to the long axis of the lag screw.
CFR/PEEK intramedullary nail had several characteristics as follows. The tapered portion of the proximal one-third of the nail was slimmed down so the nail could be inserted even in the narrowest medullary canal, based on CT images of 100 cases of proximal femoral fracture while having the same level of fatigue strength as standard metal nails. Four metal wire markers were placed parallel to the long axis of the nail with discontinuity at the lag and distal screw holes so the screws could be inserted safely under image intensifier guidance. We conducted a preliminary clinical trial with this femoral intramedullary nail system to evaluate its safety and efficacy in patients with proximal femoral fractures. The purpose of the present study was to examine the efficacy and safety of this newly developed CFR/PEEK intramedullary nail to treat patients with proximal femoral fractures.
The study was designed as a multicentre, single-arm, clinical trial. The Pharmaceuticals and Medical Devices Agency of Japan approved the study, and all analyses were performed with the approval of the institutional review board of the authors’ institution. The inclusion criteria for the study were (1) presence of a trochanteric region fracture or a basicervical fracture of the femur (AO/OTA 31A1.2, 1.3, 2.2, 2.3, or 31B3) [13]; (2) age ≥20 years; (3) informed consent obtained and the consent form signed. The exclusion criteria were (1) pathological fracture due to a tumour or a tumour-like lesion; (2) hip disorders, previous surgery, or previous injury in the target hip joint; (3) serious preexisting medical disease(s) or active infection; (4) subtrochanteric fracture; (5) pregnancy; (6) refusal to give informed consent. Between March 2018 and November 2018, we enrolled 20 patients (3 men, 17 women; mean age 85.0 years, range 72–95 years; mean body mass index 21.3 kg/m2 , range 15.9–31.1 kg/m2 ) with a trochanteric fracture treated with the CFR/PEEK intramedullary nail. According to the AO/OTA classification of fractures, 11 patients had a 31A1.2 fracture, 3 had a 31A2.2 fracture, 5 had a 31A2.3 fracture, and 1 had a 31B3 fracture. The operative procedure was the same as when using a traditional femoral intramedullary metal nail system. All patients were positioned on a traction table under general anaesthesia. We attempted manual closed reduction under fluoroscopic guidance. If no acceptable reduction was achieved, we performed an open reduction using elevators and a Kirschner wire via skin incision for lag screw insertion. The CFR/PEEK intramedullary nail was inserted from the tip of the greater trochanter with a target device after pre-drilling the canal. The position of the nail was adjusted for a lag screw to the centre of a femoral head on both anteroposterior and lateral views. We selected the length of the lag screw so the tip of the lag screw reached within 5 mm from the subchondral bone plate. One distal titanium screw was then inserted with the target device (Fig. 2). We assessed the fracture reduction
Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007
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[14], and calculated the tip–apex distance on immediately obtained postoperative radiographs [15]. The reduction was evaluated based on the amount of displacement and the neck–shaft alignment on the obtained postoperative anteroposterior and lateral radiographs and was categorised as good, acceptable, or poor. “Good reduction” of the fracture was defined as displacement of <4 mm on both images, anatomical or slightly valgus neck–shaft alignment on the anteroposterior view, and <20° angulation on the lateral view. An “acceptable reduction” satisfied one of the requirements regarding displacement or alignment. “Poor reduction” was when it met neither the “good” nor “acceptable” criteria. Intraoperative adverse events were recorded. The postoperative protocol followed the following pattern: All patients were allowed full weight-bearing during the immediate postoperative period. All patients underwent clinical and radiographic examination with follow-up at 1 and 4 weeks postoperatively. We then saw the patients at monthly intervals until bone fracture union was confirmed. To mitigate bias, fracture union was assessed by two independent experienced orthopaedic surgeons who were not involved with this clinical trial. Bone union was defined by radiographic evidence of bridging callus across the fracture and solid contact of cortical bone on anteroposterior and lateral radiographs [16]. The appearance of complications, including cut out, infection, hardware failure, and reoperation rates, were monitored during the follow-up period. We also evaluated clinical outcomes using the Harris hip score [17], Barthel index [18], Vitality index [19], and Mini-Mental State Examination [20]. We asked patients about the presence of hip pain on the affected side, and quantified it with the Numerical Rating Scale [21]. Major complications of intramedullary nails for proximal femoral fractures (e.g., nonunion, cut out, hardware failure) reportedly occur in approximately 6.3% of cases [22–24]. Therefore, we set 93.7% as a reference value of bone union for traditional metal implants, 10% as the clinically acceptable non-inferiority margin, and 95% as an expected bone union rate in this clinical trial. With the significance level set at 0.05 and the power of the test at 0.55, a binominal test with power analysis suggested that 18 patients would be required to prove non-inferiority compared with the traditional metal implants. As we assumed a dropout of two patients, the number of clinical trials was set at 20. Continuous data were presented as means ± standard deviations with the minimum and maximum. The data were compared between preoperative and postoperative measurements using Student’s t-test or Wilcoxon’s rank sum test, as appropriate. Categorical data were presented as frequencies and percents. A value of p < 0.05 was considered to indicate a statistically significant difference. Statistical analysis was performed using JMP or SAS software (SAS Institute, Cary, NC, USA).
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Fig. 3. An 82-year-old woman with a right proximal femoral fracture was treated with a metal implant on one side and a CFR/PEEK implant on the other side. Visibility was better on the CFR/PEEK side, allowing us to assess bone healing with postoperative radiographs in more detail. Table 1 Comparison of measurement items between pre- and postOP. Variable HHS (points, mean ± SD) BI (points, mean ± SD) VI (points, mean ± SD) MMSE (points, mean ± SD) NRS (points, mean ± SD)
PreOP 73.2 ± 13.8 71.1 ± 26.9 7.7 ± 2.0 19.2 ± 8.3 –
PostOP 71.0 ± 13.3 57.1 ± 31.9 7.6 ± 2.8 18.8 ± 9.6 0.9 ± 1.3
p value 0.61 0.15 0.81 0.97 –
OP = operation; SD = standard deviations; HHS = Harris hip score; BI = Barthel index; VI = Vitality index; MMSE = Mini-Mental State Examination; NRS = Numerical Rating Scale
compared with their preoperative status. The average Numerical Rating Scale was very low (0.9 ± 1.3 points) at the final follow-up (Table 1). Radiographically, 19 of 20 patients (95%) were confirmed to have achieved bone union at an average duration of 3.7 months (range 3–10 months). One patient was judged not to have achieved bone union, although the patient did not complain any pain and had no radiological evidence of failure during the following 18month follow-up (Fig. 4). There were also no complications overall, such as cut out, infection, or hardware failure. There were no reoperations required in this cohort.
Results
Discussion
The mean operation time was 27.5 min (range 12.0–64.0 min). The mean intraoperative blood loss was 55 ml (range 10–120 ml). Eight cases required open reduction of the fracture. The postoperative qualities of fracture reduction were good or acceptable in all cases, and the tip–apex distance was <20 mm in all cases (mean 13.5 ± 2.4 mm; range 9.0–19.1 mm) (Fig. 3). No intraoperative adverse events or technical difficulties were encountered. Patients were followed-up for a minimum of 4 months (mean 8.4 months). The following values showed that preoperative activity was maintained postoperatively (preoperative vs postoperative values, respectively): Harris hip score 73.2 ± 13.8 vs 71.0 ± 13.3 points (p = 0.61); Barthel index 71.1 ± 26.9 vs 57.1 ± 31.9 points (p = 0.15); Vitality index 7.7 ± 2.0 vs 7.6 ± 2.8 points (p = 0.81); Mini-Mental State Examination 19.2 ± 8.3 vs 18.8 ± 9.6 points (p = 0.97). Nor were these parameters impaired postoperatively
Several studies have shown that CFR/PEEK implants display good stability and favourable mechanical properties for treating fractures. CFR/PEEK is suitable for use in orthopaedic implants and has excellent mechanical strength, potential for adjusting for optimal stiffness, in vitro biocompatibility with direct cellular contact, and lack of cytotoxicity [25]. Therefore, CFR/PEEK implants have been proposed for treating several fractures [26]. Mitchell et al evaluated 11 patients with distal femoral fractures treated with CFR/PEEK plates. They showed low nonunion and reoperation rates in patients in the CFR/PEEK group and concluded that CFR/PEEK might be an alternative to metal for treating several fractures [27]. However, proximal femoral fracture cohorts treated with CFR/PEEK intramedullary nails had not been reported to date. We believe that this clinical trial during which we treated proximal femoral fractures with CFR/PEEK intramedullary nails is the first such study
Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007
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cases showed complete union of the cortex. CFR/PEEK implants can be made rigid by arranging carbon fibers [5]. Previously, the concept of treating fractures was to fix the lesion firmly for safe, rapid healing. However, a good biological environment and semirigid fixation has proved important to fracture healing in recent studies [29,30]. Furthermore, trabecular bone loss might occur due to stress shielding by metal implants, which could be a risk factor for re-fracture at the bone loss area [9,31]. Although the degree of rigidity required that is ideal for treating bone fractures remains unclear, this characteristic of CFR/PEEK could be used in the future to determine the optimal rigidity. Furthermore, previously used metal implants present potential problems, such as fatigue failure, wear, and imaging artifact, whereas use of CFR/PEEK avoids these problems. This study had several limitations. Although it was a prospective clinical study of the newly developed CFR/PEEK implants, there was no control group. Further, the number of clinical cases is small. Nevertheless, this clinical trial showed the non-inferiority of efficacy compared with the historical control of traditional metal intramedullary nails even under statistical power assumed in advance. Moreover, no intraoperative adverse events or postoperative complications related to the implant were noted, indicating the safety of using the CFR/PEEK nail system. Based on this encouraging outcome, a larger population in a controlled study is warranted to confirm the benefits of the CFR/PEEK intramedullary nail. Fracture union could not be demonstrated as objective data. Some reports showed utility as a radiographic union score in tibial fractures [32], however, it was difficult to apply the score to trochanteric femoral fractures in this study. Therefore, fracture union was assessed by two independent experienced orthopaedic surgeons not involved with this study to mitigate bias. Conclusions
Fig. 4. (A, B). An 83-year-old woman with a right, complex, proximal femoral fracture (AO/OTA 31A2.3). (C, D) Reduction of the fracture was good, and the tip–apex distance was 14.3 mm). (E, F) Bridging callus formation was visible, and the postoperative radiograph at the final follow-up (18 months) showed no progressive subsidence of the lag screw or nail failure. This case, however, was judged as nonunion because a solid contact of cortical bone was not confirmed on the radiographs at 6 months.
to be reported. There were no adverse reactions or failures related to the CFR/PEEK implants, and bone union was confirmed in 95% of the cases. This novel CFR/PEEK intramedullary nail provided satisfactory clinical results. CFR/PEEK implants do not interrupt traditional radiographic views and cause no artifacts on CT or MRI [28]. CFR/PEEK may allow a more lucid intraoperative interpretation during reduction, osteosynthesis, postoperative callus formation, and bone union in fractures than with standard imaging modalities. It allows analysis of fracture and dislocation [6,11]. The radiolucency of CFR/PEKK, however, has an issue of difficulty recognising the position of the nail on fluoroscopy. Therefore, radiopaque metal wires were arranged in the nails and lag screws as markers. In the present study, the radiolucency of CFR/PEEK implants was helpful for surgeons to confirm the grade of fracture reduction during the operation, and there were no difficulties in positioning the nail or inserting the lag screw and distal titanium screw. It was also good for evaluating bone healing in detail on postoperative radiographs (Fig. 3). Radiographic union did not occur in one patient with a complicated fracture in our study, although the patient had good callus formation, and the fracture site was stable (Fig. 4). The other
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Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007
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Please cite this article as: K. Takashima, I. Nakahara and K. Uemura et al., Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail, Injury, https://doi.org/10.1016/j.injury.2020.01.007