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Clinical and radiological outcome of the Chimaera short nailing system in inter- and subtrochanteric fractures

Open AccessPublished:January 10, 2023DOI:https://doi.org/10.1016/j.injury.2023.01.027

      Highlights

      • The Chimaera short cephalomedullary device is a valuable implant for therapeutic nailing of intertrochanteric and subtrochanteric fractures of the femur.
      • The self-locking lag screw avoids fascia lata friction, and the insertion of a set screw is not needed.
      • Short- and mid-term good to excellent functional outcomes can be obtained with the Chimaera short cephalomedullary device.

      ABSTRACT

      Background

      cephalomedullary devices are popular treatment for femoral intertrochanteric or subtrochanteric fractures. Various complications include post-surgical lateral thigh pain and cut-out. To prevent those complications, a new concept cephalomedullary device system was designed (Chimaera, Orthofix®). This study aimed to evaluate the clinical and radiological outcomes in patients with femoral intertrochanteric or subtrochanteric fractures treated with the proximal femoral cephalomedullary device system.

      Methods

      A prospective cohort study involved consecutive patients with Arbeitsgemeinschaft für Osteosynthesefragen/ Orthopaedic Trauma Association type 31-A1, 2, 3 fractures treated with the Chimaera short cephalomedullary device system from October 2016 to September 2017 at our level 1 trauma center. The Parker and Palmer mobility score and Jensen social function scores and post-surgical lateral thigh pain were assessed at 3 months post-operatively and compared to before surgery. Radiologic assessment consisted of controlling the position of the cephalic screw by using the tip-apex distance (TAD) and Cleveland zone as well as union and cut-out rates.

      Results

      We included 99 patients (79 women; 100 hips; one bilateral fracture 3 months after a first trochanteric fracture) with a mean follow-up of 2 years. The Parker and Palmer mobility score decreased by 22% at 3 months post-operatively as compared with the pre-fracture score (42/99 patients showed a return to their pre-injury level). The Jensen social function score increased by 16.5% at 3 months post-operatively as compared with the pre-fracture score (68/99 patients showed a return to their pre-injury level). No major intra-operative complication was recorded. Nine TAD scores were > 25 mm. The mean TAD was 16.5 mm (range 5–36), and the lag screw position was well positioned in most (95%) hips according to Cleveland zones. Three patients required revision surgery (one for cut-out of the lag screw, one for hip osteoarthritis and one for gluteus medius insufficiency). All patients but the one with the cut-out showed fracture union.

      Conclusion

      The Chimaera short cephalomedullary device exhibited good mid-term functional and radiological outcomes.

      Keywords

      Introduction

      Cephalomedullary devices are a possible surgical treatment option for intertrochanteric and subtrochanteric femoral fractures and became the gold standard in recent years [
      • Rosa N.
      • Marta M.
      • Vaz M.
      • Tavares S.M.O.
      • Simoes R.
      • Magalhães F.D.
      • Marques A.T
      Intramedullary nailing biomechanics: evolution and challenges.
      ]. The age distribution of patients is usually bimodal, with high-velocity trauma responsible for fractures in young men and most of the fracture are mainly low energy fractures in the female geriatric population with osteoporotic bone [
      • Weiss R.J.
      • Montgomery S.M.
      • Al Dabbagh Z.
      • Jansson K.A
      National data of 6409 Swedish inpatients with femoral shaft fractures: stable incidence between 1998 and 2004.
      ]. During the last 2 decades, nail designs and materials have evolved, but the increase in indications for cephalomedullary devices was the major factor popularizing the technique [
      • Bong M.R.
      • Koval K.J.
      • Egol K.A.
      The history of intramedullary nailing.
      ]. Compared with other stabilization methods, cephalomedullary devices advantages include minimal disturbance to the fracture site, early patient ambulation, decrease blood loss, small operative scars and low infection rate [
      • Rosa N.
      • Marta M.
      • Vaz M.
      • Tavares S.M.O.
      • Simoes R.
      • Magalhães F.D.
      • Marques A.T
      Intramedullary nailing biomechanics: evolution and challenges.
      ].
      The post-operative lateralization of the lag screw after dynamization of the fracture can be a cause of post-surgical lateral thigh pain due to fascia lata friction and this makes it mandatory to remove or change the screw [
      • Rosa N.
      • Marta M.
      • Vaz M.
      • Tavares S.M.O.
      • Simoes R.
      • Magalhães F.D.
      • Marques A.T
      Intramedullary nailing biomechanics: evolution and challenges.
      ]. Femoral head rotation is a major risk factor for cut-out of the lag screw [
      • Rosa N.
      • Marta M.
      • Vaz M.
      • Tavares S.M.O.
      • Simoes R.
      • Magalhães F.D.
      • Marques A.T
      Intramedullary nailing biomechanics: evolution and challenges.
      ]. To counteract these complications, the Chimaera (Orthofix®, Lewisville, Texas, USA) short nail (CSN) has a self-retaining and sliding lag screw, and its design allows for inserting a second lag screw. Other complications of anterograde cephalomedullary device are non-union and mal-union (about 1%) and femoral shaft fracture [
      • Chinzei N.
      • Hiranaka T.
      • Niikura T.
      • Tsuji M.
      • Kuroda R.
      • Doita M.
      • Kurosaka M.
      Comparison of the Sliding and Femoral Head Rotation among Three Different Femoral Head Fixation Devices for Trochanteric Fractures.
      ,
      • Horner N.S.
      • Samuelsson K.
      • Solyom J.
      • Bjørgul K.
      • Ayeni O.R.
      • Östman B.
      Implant-related complications and mortality after use of short or long gamma nail for intertrochanteric and subtrochanteric fractures: a prospective study with minimum 13-Year Follow-up.
      ]. Only a few studies have described mobility and social function outcomes after femoral fractures treatment [
      • Rosa N.
      • Marta M.
      • Vaz M.
      • Tavares S.M.O.
      • Simoes R.
      • Magalhães F.D.
      • Marques A.T
      Intramedullary nailing biomechanics: evolution and challenges.
      ,
      • Sharma A.
      • Mahajan A.
      • John B.
      A comparison of the clinico-radiological outcomes with proximal femoral nail (PFN) and proximal femoral nail antirotation (PFNA) in fixation of unstable intertrochanteric fractures.
      ,
      • Yang Y.H.
      • Wang Y.R.
      • Jiang S.D.
      • Jiang L.S.
      Proximal femoral nail antirotation and third-generation Gamma nail: which is a better device for the treatment of intertrochanteric fractures?.
      ,
      • Huang B.Z.
      • Park Y.W.
      • Park J.S.
      • Noh K.C.
      • Kim S.Y.
      • Chung K.J.
      • Kim H.K.
      • Kim H.N.
      • Yoon Y.H.
      • Hwang J.H.
      Results of Asian Type Gamma 3 Nail in treatment of trochanteric fractures.
      ,
      • Park M.S.
      • Lim Y.J.
      • Kim Y.S.
      • Kim K.H.
      • Cho H.M.
      Treatment of the proximal femoral fractures with proximal femoral nail antirotation (PFNA).
      ] and mainly focused on muscle testing. Mid-term clinical and radiological results after fixation of intertrochanteric and subtrochanteric femoral fractures using the CSN have not been reported to any meaningful extent.
      The aim of this prospective study was to evaluate the clinical outcomes of the CSN for treating Arbeitsgemeinschaft für Osteosynthesefragen/ Orthopaedic Trauma Association (AO/OTA) fracture types 31-A1,2,3 by using the Parker and Palmer mobility score [
      • Parker M.J.
      • Palmer C.R.
      A new mobility score for predicting mortality after hip fracture.
      ] and the Jensen social function score [
      • Jensen J.S.
      Determining factors for the mortality following hip fractures.
      ]. We also evaluated the radiological outcomes and complication rates specific to this new device.

      Materials and methods

      Patients

      This was a prospective cohort study performed between October 2016 and September 2017 in our level-1 trauma center after local ethics committee approval (CER-VD 2016–02,228) in accordance with the Declaration of Helsinki. All patients were informed and agreed to participate. Inclusion criteria were AO/OTA type 31-A1, 2, 3 fractures caused by high- or low-energy trauma and treated with CSN. Exclusion criteria were inability to walk before the trauma, open fractures, bilateral fractures, major concomitant trauma, severe hip arthrosis, preexisting hip surgery or pathological fractures.

      Chimaera cephalomedullary device characteristics

      The Chimaera short nail is made of titanium alloy with anodized type II surface treatment. It is cannulated for guide-wire controlled insertion. The CSN length is 180 mm. The proximal diameter of the nail is 15.5 mm; distal diameter is 11 mm. There are two proximal cephalomedullary device angles available: 125° or 130° The lag screw is self-locking into the nail by the extension of the wings into the cephalomedullary device once it is fully tightened. Tts length goes from 70 mm to 130 mm with 5 mm increments. The screw is locked The supplementary lag screw is also self-locking and its length goes from 60 mm to 120 mm with 5 mm increments. The sliding mechanism of the two screws allows their telescoping. The dynamic distal locking hole can be used to allow fracture compression up to 6 mm in the diaphysis direction. All details are given according to the reference guide available online.

      Surgical technique

      All of the operations were performed by a senior surgeon or by a trained-resident under supervision of a senior surgeon. The patient is placed in a supine position on a fracture table and the fracture is reduced under fluoroscopic guidance (open reduction was performed if the surgeon deemed it useful). A single-shot prophylactic antibiotic therapy is given 30 min before surgery. The CSN is inserted through the tip of the greater trochanter [
      • Park M.S.
      • Lim Y.J.
      • Kim Y.S.
      • Kim K.H.
      • Cho H.M.
      Treatment of the proximal femoral fractures with proximal femoral nail antirotation (PFNA).
      ]. The lag screw positioning can be similar to that of other commonly used cephalomedullary device or can be preceded by insertion of a second wire through the supplementary lag screw hall to prevent head rotation. The supplementary lag screw can be inserted using the wire placed or the pin can be removed if the use of a single cervical screw is decided. Screws should be inserted till it locks itself into the nail. The distal locking screw is inserted similarly to that of other commonly used cephalomedullary device.

      Post-operative follow-up

      Early mobilization was initiated with full weight-bearing as tolerated and without limitation of the hip motion on the first post-operative day. All patients had the same rehabilitation protocol. Post-operative antero-posterior and lateral X-rays (Fig. 1) were performed three day after the surgery. Patients were followed up at 2 weeks, 6 weeks, 3 months, 6 months and 1 years after the surgery and then annually.
      Fig. 1
      Fig. 1Pre- and post-operative (3 days and 3 months) radiographs with AO/OTA type 31A2.2 type fracture treated with Chimaera short nail showing telescoping sliding movement of the lag screw (white arrows) without protrusion from the lateral cortex (blue arrows) AO/OTA, Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association.

      Per- and postoperative assessment

      Per-operative data, such as surgical time and fluoroscopy time were recorded. The TAD [
      • Baumgaertner M.R.
      • Curtin S.L.
      • Lindskog D.M.
      • Keggi J.M.
      The value of the tip-apex distance in predicting failure of fixation of peritrochanteric fractures of the hip.
      ] and the Cleveland zone [
      • Cleveland M.
      • Boswirth D.M.
      • Thompson F.R.
      • Wilson Jr, H.J.
      • Ishizuka T.
      A ten-year analysis of intertrochanteric fractures of the femur.
      ] were analyzed on the first post-operative AP pelvis X-ray and lateral hip X-ray. The primary outcome was the patients’ mobility and return to social life at 3 months. We used the mobility score of Parker and Palmer, a score from 0 to 9 based on the ability to mobilise inside the house, outside the home and tasks outside the home (0 = poor mobility; 9 = hightly mobile) [
      • Parker M.J.
      • Palmer C.R.
      A new mobility score for predicting mortality after hip fracture.
      ] and the social function score of Jensen, classification into one of 4 groups based on independence (1 = independent; 4 = totally dependent) [
      • Jensen J.S.
      Determining factors for the mortality following hip fractures.
      ] assessed at 3 months to evaluate early recovery. We stated that an excellent outcome was a same score before the trauma and after the surgery. A good outcome was the loss of one point maximum. Secondary outcomes were post-surgical lateral thigh pain, intraoperative complications, surgical time, fluoroscopy time, adverse events, material breakage, wound problems, length of hospital stay and readmission rate. Mal-union and non-union were analyzed respectively at 3, 6 and 12 months.

      Statistical analysis

      Descriptive statistics were used to characterize the population. Continuous variables were expressed as the median and interquartile range (IQR) [25th–75th percentiles]. Categorical variables were summarized as a percentage. All statistical analyses were performed with Miniwebtool.

      Results

      We included 99 patients, 79 females, (100 hips: one patient had a contralateral fracture 3 months after the first trochanteric fracture) (Table 1), the mean age was 83 years (range: 37–99). According to the AO/OTA fracture classification, 14 fractures were type 31-A1; 73 were type 31-A2 and 13 were type 31-A3. Four patients experienced high-energy trauma. All other patients experienced low-energy trauma (fall from the patient's height). The mean follow-up was 24 months (median 12 months [IQR 5–58]). Twenty one patients died before the 1-year follow-up. All remaining patients were followed at a minimum of 1 year after the surgery.
      Table 1Patient demographics (n = 99 patients; n = 100hips).
      Mean age (years)83 (37–99)
      Gender

      Women

      Men


      79 (80%)

      20 (20%)
      Hip side

      Right

      Left


      60 (60%)

      40 (40%)
      AO/OTA classification

      31 – A1

      31 – A2

      31 – A3


      14 (14%)

      73 (73%)

      13 (13%)
      Velocity

      Low

      High


      96 (96%)

      4 (4%)
      AO/OTA, Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association.
      Data are median (interquartile range) unless otherwise indicated.

      Clinical outcomes

      The Parker and Palmer [
      • Parker M.J.
      • Palmer C.R.
      A new mobility score for predicting mortality after hip fracture.
      ] mobility score was good to excellent at 3 months. It was equivalent or slightly modified in 57/99 patients (maximum loss of 1 in 9 points) with a median change of 1 point [IQR: 0–2] from pre- to post-operatively (Table 2). The Jensen social score [
      • Jensen J.S.
      Determining factors for the mortality following hip fractures.
      ] at 3 months was good to excellent for 86/99 patients (maximum gain of 1 point) with no median change in score [IQR: 0–1] (Table 2).
      Table 2Patients’ postoperative functional status at 3 months (n = 86 for mobility score and n = 57 for social score).
      Mobility score of Parker and Palmer10

      0–1     Point change

      ≤ 2     Point change

      ≤ 3     Point change


      57%

      79%

      91%
      Social function score of Jensen11
        • 1-%2
          Point change
      ≤ 2     Points change


      86%

      94%
      Median operative time was 52 min [IQR 40.5–60] (mean operative time was 54 min). The median fluoroscopy time was 57 s [IQR 42.5–82]. A second lag screw was inserted in 3 cases (3%) to increase rotational stability (Table 3).
      Table 3Patients’ peri‑operative data (n = 99 patients).
      Operation time (minutes)52 (40.5–60)
      Fluoroscopy time (s)57 (42.5–82)
      Secondary lag screw3 (3%)
      Tip apex distance, mm12

        ≤ 24.9

        ≥ 25.0


      91 (91%)

      9 (9%)
      Cleveland zone13

        3

        4

        5

        6

        8


      1 (1%)

      2 (2%)

      87 (87%)

      2 (2%)

      8 (8%)
      Data are median (interquartile range) unless otherwise indicated.

      Radiologic outcomes

      The median TAD was 16.78 mm (range 5–36); 9 TAD measurements were > 25 mm (Table 3). The lag screw position was center-center or inferior-center in 95% of patients according to the Cleveland zone [
      • Cleveland M.
      • Boswirth D.M.
      • Thompson F.R.
      • Wilson Jr, H.J.
      • Ishizuka T.
      A ten-year analysis of intertrochanteric fractures of the femur.
      ] (Cleveland zone 5 and 8) (Table 3). Other positions (5%) were zone 3 (1 patient), zone 4 (2 patients) and zone 6 (2 patients) (Table 3).

      Complications

      We did not find any perioperative fracture, cortical scraping or adverse events of the cephalomedullary device. We noted one minor intra-operative complication: The breakage of a cervical screw thread because the screw was turned too tight in the nail (Table 4). The damaged cervical screw was removed and a new screw was inserted, with no complications.
      Table 4Complications (n = 99 patients).
      Per-operative (breakage of a cervical screw thread)

      Post-operative

      Cephalic screw cut out

      Distal screw breakage

      Revision surgery
      1 (1%)

      1 (1%)

      0 (0%)

      3 (3%)
      We found no wound healing problems or infections, lateral pain of the thigh due to lag screw irritation, or bony mal-union/non-union during post-operative follow-up. One patient presenting a cut-out of the lag screw after 3 weeks (the TAD was > 25 mm, and according to the Cleveland zone, the cephalic screw was in position 3). This fixation failure was treated by revision cephalic hip arthroplasty and hook plate insertion (Fig. 2). A second patient had revision surgery for osteoarthritis (total hip arthroplasty) at 8 months after the initial surgery. A third patient had revision surgery for gluteus medius insufficiency (muscle shortening due to fracture dynamization) (total hip arthroplasty). Therefore, the reoperation rate was 3%.
      Fig. 2
      Fig. 2Cut-out of the lag screw and revision with open reduction with internal fixation and cemented hemi-arthrop lasty.

      Recovery

      In total, 92/99 patients were able to weight bear as tolerated within 7 days after the surgery. One patient died during the first post-operative week due to very poor general health. Those who did not walk at 1 week (8%) had dementia or general poor condition. The mean length of hospital stay was 11 days (range 3–32).

      Discussion

      Cephalomedullary device has become a standard treatment for intertrochanteric and subtrochanteric femoral fractures because of decreased risk of non-union and low rate of complications as compared will all other possible treatments [
      • Horner N.S.
      • Samuelsson K.
      • Solyom J.
      • Bjørgul K.
      • Ayeni O.R.
      • Östman B.
      Implant-related complications and mortality after use of short or long gamma nail for intertrochanteric and subtrochanteric fractures: a prospective study with minimum 13-Year Follow-up.
      ]. Ricci et al. [
      • Ricci W.M.
      • Devinney S.
      • Haidukewych G.
      • Herscovici D.
      • Sanders R.
      Trochanteric nail insertion for the treatment of femoral shaft fractures.
      ] found that hip range of motion was similar to that on the unaffected side when using a femoral nail specifically designed for trochanteric insertion, which is the case for the CSN.
      Our study provides new data regarding the use of CSN in treating intertrochanteric and subtrochanteric femoral fractures. Post-operative analysis and direct comparison of absolute figures within a margin of error show the results bellow. Analysis of the Parker and Palmer mobility score [
      • Parker M.J.
      • Palmer C.R.
      A new mobility score for predicting mortality after hip fracture.
      ] showed that the CSN provides good to excellent mid-term functional results at 3 months post-operatively with the same or slightly modified score for most patients as compared with the pre-operative score (Table 2). Sharma et al. [
      • Sharma A.
      • Mahajan A.
      • John B.
      A comparison of the clinico-radiological outcomes with proximal femoral nail (PFN) and proximal femoral nail antirotation (PFNA) in fixation of unstable intertrochanteric fractures.
      ] showed that 8/23 (35%) of their proximal femoral nail (PFN) group and 8/25 (32%) of their proximal femoral nail autorotation (PFNA) group were able to return to their pre-injury Parker and Palmer score. Our study showed better results, with 42% (28/68) of patients who were able to return to their pre-injury Parker and Palmer score. Post-operative analysis of the Jensen score [
      • Jensen J.S.
      Determining factors for the mortality following hip fractures.
      ] showed that the CSN provided good to excellent mid-term social results at 3 months post-operatively, with the same or slightly modified score for most patients as compared with the preoperative score (Table 2). Huang et al. [
      • Huang B.Z.
      • Park Y.W.
      • Park J.S.
      • Noh K.C.
      • Kim S.Y.
      • Chung K.J.
      • Kim H.K.
      • Kim H.N.
      • Yoon Y.H.
      • Hwang J.H.
      Results of Asian Type Gamma 3 Nail in treatment of trochanteric fractures.
      ] reported that the 1.3 mean pre-operative Jensen social score [
      • Jensen J.S.
      Determining factors for the mortality following hip fractures.
      ] increased to 1.8 post-operatively (increase of 38.5%), which is more than double than in our study, with a pre-operative mean score of 2.29 that increased to 2.67 (increase of 16.5%).
      One major advantage of the CSN is the self-retaining locking mechanism of the cephalic screw, which can slide on itself. In Soucanye de Landevoisin et al. [
      • Soucanye de Landevoisin E.
      • Bertani A.
      • Candoni P.
      • Charpail C.
      • Demortiere E.
      Proximal femoral nail antirotation (PFN-ATM) fixation of extra-capsular proximal femoral fractures in the elderly: retrospective study in 102 patients.
      ], 15.7% of patients had pain due to screw impingement on the fascia lata; 2% underwent reoperation. For the Talon Distalfix Proximal Femoral Nail, Yapici et al. [
      • Yapici F.
      • Ucpunar H.
      • Camurcu Y.
      • Emirhan N.
      • Tanoglu O.
      • Tardus I.
      Clinical and radiological outcomes of patients treated with the talon distalfix proximal femoral nail for intertrochanteric femur fractures.
      ] reported 3.6% of lateral migration of the cephalic screw. In our study, no cephalic screw back-out occurred because of intranail fixation of the screw, thus preventing irritation of the fascia lata. Compression of the fracture is still permitted by the self-telescoping effect of the screw. However one screw breakage occur during surgery. The screw has been tightened too much and one wing has broken. The screw and the wing was removed and a new screw has been inserted.
      Overall, 91 of our patients had a TAD < 25 mm according to the Baumgartner et al. [
      • Baumgaertner M.R.
      • Curtin S.L.
      • Lindskog D.M.
      • Keggi J.M.
      The value of the tip-apex distance in predicting failure of fixation of peritrochanteric fractures of the hip.
      ] principle of the lag screw positioning. Our mean TAD of 16.78 mm was less than that in Sharma et al. [
      • Sharma A.
      • Mahajan A.
      • John B.
      A comparison of the clinico-radiological outcomes with proximal femoral nail (PFN) and proximal femoral nail antirotation (PFNA) in fixation of unstable intertrochanteric fractures.
      ] 19.08 mm for the PFN group (range 8.42–27.37 mm) and 21.13 mm for the PFNA group. The cut-out recorded was probably due to excessive TAD (TAD 25 to 30). Our study showed a lower cut-out rate than with the Talon distalfix proximal femoral nail (3.6%) [
      • Yapici F.
      • Ucpunar H.
      • Camurcu Y.
      • Emirhan N.
      • Tanoglu O.
      • Tardus I.
      Clinical and radiological outcomes of patients treated with the talon distalfix proximal femoral nail for intertrochanteric femur fractures.
      ], the PFNA nail (8.3%) [
      • Zehir S.
      • Şahin E.
      • Zehir R.
      Comparison of clinical outcomes with three different intramedullary nailing devices in the treatment of unstable trochanteric fractures.
      ] and the Dyna Locking Trochanteric nail (25%) [
      • Gunay C.
      • Atalar H.
      • Altay M.
      • Yavuz O.Y.
      • Yildirim A.O.
      • Oken O.F.
      Does the wedge wing in the neck screw prevent cut-out failure in Ota/AO 31-A2 trochanteric fractures in elderly patients?.
      ] (Table 4).
      According to Cleveland et al. [
      • Cleveland M.
      • Boswirth D.M.
      • Thompson F.R.
      • Wilson Jr, H.J.
      • Ishizuka T.
      A ten-year analysis of intertrochanteric fractures of the femur.
      ], 5 lag screws (5%) were not positioned properly. Center-center or inferior-center placement of the lag screw in the femoral neck is recommended to prevent migration and cut-out because of the intersection of the compression and tensile trabeculae of the proximal femur leading to strong architecture at the inferior part of the neck [
      • Yapici F.
      • Ucpunar H.
      • Camurcu Y.
      • Emirhan N.
      • Tanoglu O.
      • Tardus I.
      Clinical and radiological outcomes of patients treated with the talon distalfix proximal femoral nail for intertrochanteric femur fractures.
      ]. These results show a lower rate of malposition of the femoral lag screw than Sharma et al. [
      • Sharma A.
      • Mahajan A.
      • John B.
      A comparison of the clinico-radiological outcomes with proximal femoral nail (PFN) and proximal femoral nail antirotation (PFNA) in fixation of unstable intertrochanteric fractures.
      ] who found a malposition of the lag screw in 4 of 23 (17%) patients in the PFN group and 8 of 25 patients (32%) in the PFNA group, and Yapici et al. [
      • Yapici F.
      • Ucpunar H.
      • Camurcu Y.
      • Emirhan N.
      • Tanoglu O.
      • Tardus I.
      Clinical and radiological outcomes of patients treated with the talon distalfix proximal femoral nail for intertrochanteric femur fractures.
      ], who found 15.5% malpositioning with their talon distalfix proximal femoral nail. The risk of cut-out of various proximal femoral intertrochanteric nails ranges from 4% to 20% [
      • Yapici F.
      • Ucpunar H.
      • Camurcu Y.
      • Emirhan N.
      • Tanoglu O.
      • Tardus I.
      Clinical and radiological outcomes of patients treated with the talon distalfix proximal femoral nail for intertrochanteric femur fractures.
      ] fracture type, reduction quality and position of the lag screw have a direct influence on the risk of cut-out [
      • Yapici F.
      • Ucpunar H.
      • Camurcu Y.
      • Emirhan N.
      • Tanoglu O.
      • Tardus I.
      Clinical and radiological outcomes of patients treated with the talon distalfix proximal femoral nail for intertrochanteric femur fractures.
      ]. In our study, the lag screw was in position 3 for the only cut-out recorded (no supplementary lag screw was added), which can explain the failure of the fixation in addition to the poor bone quality. This complication lead to nail removal and hemi-arthroplasty combined with open reduction and internal fixation of the trochanteric area (Fig. 2).
      Our surgical time indicates that insertion of the CSN is within the average of insertion of other proximal femoral nails (mean Talon distalfix proximal femoral nail insertion: 34.9 min; PFNA nail insertion: 44.4 min; InterTran nail insertion: 55.4 min) [
      • Yapici F.
      • Ucpunar H.
      • Camurcu Y.
      • Emirhan N.
      • Tanoglu O.
      • Tardus I.
      Clinical and radiological outcomes of patients treated with the talon distalfix proximal femoral nail for intertrochanteric femur fractures.
      ,
      • Zehir S.
      • Şahin E.
      • Zehir R.
      Comparison of clinical outcomes with three different intramedullary nailing devices in the treatment of unstable trochanteric fractures.
      ]. These results may be influenced by the technical novelty of the implant and hence its learning curve (Table 3). Our fluoroscopy time was lower than that in other studies for cephalomedullary device of intertrochanteric and subtrochanteric fractures. In Zehir et al. [
      • Zehir S.
      • Şahin E.
      • Zehir R.
      Comparison of clinical outcomes with three different intramedullary nailing devices in the treatment of unstable trochanteric fractures.
      ], the average time for a similar procedure of 100 s for the Talon distalfix proximal femoral nail, 110 s for the PFNA nail and 120 s for the InterTran nail (Table 3) which is longer than our average time.
      In comparison with other studies, our reoperation rate (3%) was lower than in Yapici et al. [
      • Yapici F.
      • Ucpunar H.
      • Camurcu Y.
      • Emirhan N.
      • Tanoglu O.
      • Tardus I.
      Clinical and radiological outcomes of patients treated with the talon distalfix proximal femoral nail for intertrochanteric femur fractures.
      ] for the Talon distalfix proximal femoral nail (5.5%) and Zehir et al. [
      • Zehir S.
      • Şahin E.
      • Zehir R.
      Comparison of clinical outcomes with three different intramedullary nailing devices in the treatment of unstable trochanteric fractures.
      ] for the Talon distalfix proximal femoral nail (3.8%), the PFNA nail (9.4%) and the InterTran nail (4.9%).
      The mean hospital stay was 11 days in our study which is longer than for Hoffmann et al. [
      • Hoffmann M.F.
      • Khoriaty J.D.
      • Sietsema D.L.
      • Jones C.B
      Outcome of intramedullary nailing treatment for intertrochanteric femoral fractures.
      ] in their review of cephalomedullary device treatment for intertrochanteric femoral. This long stay is probably due to different health systems and their functioning.
      The complication rate of treating intertrochanteric fracture with proximal cephalomedullary device ranges from 4% to 53%16. We did not find any wound complications. Our local complication rate was lower than Yapici et al. [
      • Yapici F.
      • Ucpunar H.
      • Camurcu Y.
      • Emirhan N.
      • Tanoglu O.
      • Tardus I.
      Clinical and radiological outcomes of patients treated with the talon distalfix proximal femoral nail for intertrochanteric femur fractures.
      ] for the Talon distalfix proximal femoral nail (1.8% superficial infection and 1.8% hematoma). It was also lower than Zehir et al. [
      • Zehir S.
      • Şahin E.
      • Zehir R.
      Comparison of clinical outcomes with three different intramedullary nailing devices in the treatment of unstable trochanteric fractures.
      ] for the Talon distalfix proximal femoral nail (3.8%), the PFNA nail (9.4%) and the InterTran nail (4.9%). We did not find any nail breakage. Our in-hospital mortality rate was 4% (n = 4), which is lower than that for Zehir et al. [
      • Zehir S.
      • Şahin E.
      • Zehir R.
      Comparison of clinical outcomes with three different intramedullary nailing devices in the treatment of unstable trochanteric fractures.
      ] for the InterTran nail (4.9%) but higher than the same authors for the Talon distalfix proximal femoral nail (2.6%) and PFNA nail (2.1%).

      Study limitations and strengths

      The first limitation of the study is the lack of a randomized control group, which implies lack of a control group and could lead to interpretation bias. Second, a number of patients withdrew before functional and social score recording due to concomitant illnesses affecting their general health and mortality rate, which could also lead to interpretation bias, although the follow-up of geriatric patients often implies a high loss of follow-up. Third, although our study is the first to analyze the CSN functional and radiological outcome, future studies should include a larger population for more formal conclusions. The major strength of our study is its design, as it is the first prospective cohort study analyzing the clinical and radiological outcomes of a new proximal femoral nail.

      Conclusions

      The new Chimaera short nail is a valid implant for nailing intertrochanteric and subtrochanteric fractures of the femur within the limitations of this study. The CSN can be easily inserted, it provides stable fixation and good to excellent functional outcomes, with few preoperative, postoperative and radiological complications.

      Funding

      No funding

      Competing interests

      The authors have nothing to disclose

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