Clinical and radiological outcomes of patients treated with the Orthofix Chimaera Long nailing system for proximal and diaphyseal femoral fracture

doi:10.21203/rs.3.rs-2946275/v1

Background

Intramedullary long nailing is a popular method to treat femoral shaft or sub-trochanteric fractures. Various complications have been described such as intraoperative anterior cortical perforation of the distal femoral shaft or post-surgical lateral thigh pain. In order to prevent those possible complications, a new intramedullary nailing system (Chimaera, Orthofix®) was designed. This study aims to evaluate the clinical and radiological results after antegrade intramedullary nailing of traumatic femoral shaft and inter-/subtrochantreric fractures.

Methods

A prospective cohort study was conducted on 20 consecutive patients with AO/OTA type 31A2.3-A3.3 and type 32A-C fractures treated with the Chimaera long nailing system from December 2017 to January 2021 at our level 1 trauma center. Parker & Palmer and Jenson scores were assessed at 3 months and compared to before the surgery. Radiologic assessment consisted in checking the position of the cephalic screw, using the tip-apex distance (TAD) and Cleveland zone. The mean follow-up was 12.5 (1–33) months.

Results

Parker and Palmer scores were equivalent to before the fracture for 4 patients (31%); minor changes were seen in 6 patients (46%). Jensen score was equivalent or with maximum gain of 1 point for 11 patients (87%) at 3 months. No intra-operative major complication was recorded. The median TAD was 16.4 mm (IQR 14.0-20.2) and lag screw position was in 85% of patients in the Cleveland central zone. Two patients needed revision surgery. Fracture union occurred in all patient.

Conclusion

The long Chimaera nailing device showed good functional and radiological outcomes.

proximal femoral fracture

diaphyseal femoral fracture

surgical treatment

intramedullary nailing

new nail

Orthofix® Chimaera

intertrochanteric fracture

subtrochanteric fracture

1. The Chimaera Orthofix® long nail is a valuable implant for therapeutic nailing of diaphyseal and sub-trochanteric fractures of the femur.

2. This new nail can easily be inserted, minimizing the risk of anterior distal cortical perforation with its bending of 1500mm and provides stable fixation.

3. The self-locking lag screw averts fascia lata friction and makes the insertion of a set screw superfluous.

4. Good to excellent functional outcomes can be obtained with the Chimaera long nailing device.

Intramedullary nailing is one possible surgical treatment option for intertrochanteric and subtrochanteric, as well as diaphyseal femoral fractures¹. A Swedish national data study showed the annual incidence of femoral shaft fractures (6409 fracture identified in a period of 7 years) to be 1 per 10 000 person per years². A bimodal age distribution is usually found, with high velocity trauma responsible for fractures in young men and mainly low energy fracture in the female geriatric population².

Küntscher introduced the concept of intramedullary nailing for stabilization of long bone fractures in the 1940’s. During the last two decades, nail designs and materials have evolved, but the increase of indications for intramedullary nailing was the major factor popularising the technique³.

The long nail design can be responsible for major perioperative complications⁴. Due to an insufficient anteroposterior curve of the long nail, intraoperative anterior cortical fractures of the distal femoral shaft have been reported. Additionally, the postoperative lateralization of the lag screw after dynamisation of the fracture can cause post-surgical lateral thigh pain due to fascia lata friction¹. In order to counteract those two complications, the Chimaera (Orthofix®, Texas, USA) long nail (CLN) has a bending curve of 1500 mm and a self-retaining and sliding lag screw. Other complications of anterograde nailing are nonunion and malunion (around 1%)⁵.

Mobility and social function outcomes after management of femoral fractures are described in only few studies¹, which mainly focus on muscle testing⁶. Short-term results after fixation of intertrochanteric fractures and diaphyseal femoral shaft fractures using the CLN have not been reported to any meaningful extent until now.

The aim of this prospective study was to evaluate the CLN for treatment of AO/OTA (Arbeitsgemeinschaft für Osteosynthesefragen/ Orthopaedic Trauma Association) fractures type 31-A2/3 and 32-A/C using the Mobility scores of Parker & Palmer⁷ and social function scores of Jensen⁸. We also evaluate the radiological outcomes and complication rate specific to this new device.

1. Patients

We conducted a prospective cohort study between December 2017 and January 2021 in our Trauma Center level-1 after local ethical committee approval in accordance with the Declaration of Helsinki. All patients included in the study were informed and consented. Inclusion criteria were the patients with AO/OTA type 31-A2/3 and 32-A/C fractures caused by high or low energy trauma (Fig. 1), treated with Chimaera long nail. Exclusion criteria were patients not able to walk before the trauma, open fracture, bilateral fractures, major concomitant trauma, severe hip osteoarthritis, preexisting hip surgery or pathological fracture. Of the 20 patients (Table 1), 12 females and 8 males were included in the study. The mean age was 80.2 years (range: 25–95 years old). According to the AO/OTA fracture classification, 14 patients had type 31A2.3-A3.3 / per-subtrochantreric (six 31A2.3 and eight 31A3.3); 6 patients had type 32A-C / diaphyseal (three 32A1a, one 32A1b, one 32A3a and one 32C3i) fractures. High energy trauma was found in 2 patients (one fall from a 2 meters wall and one fall during winter skiing). All other patients had low energy trauma (fall from patient’s height). At 6 months, seven patients were lost to follow up (5 had passed away). All patients alive were followed at a minimum of one year after the surgery. The median follow-up was 12.5 months (IQR 3–28). All included patient were classified as ASA 1 to 4 on ASA scale according to the American Society of Anesthesiologists

Table 1

Patients demographics.

Number of Patients

20

Mean age (years)

80.2 (25–95)

Gender

Women

Men

8 (40%)

12 (60%)

Side

Right

Left

9 (45%)

11 (55%)

AO Classification

31 - A2.3 / A3.3

32 – A1a / A1b / A3a / C3i

6 / 8

3 / 1 / 1 / 1

Velocity

Low

High

18 (90%)

2 (10%)

For gender, side and velocity the values are given as number with percentage between brackets

2. Chimaera nail characteristics

The Chimaera nail (Fig. 2) is made of titanium alloy with anodized type II surface treatment. It is cannulated for guide-wire controlled insertion. Different lengths are available, from 280 mm to 460 mm, in 20 mm increments. The proximal diameter of the nail is 15.5 mm; distal diameter is 10 mm and 11 mm. There are two proximal nail CCD angles available: 125° or 130°. Angulations of the nail are a medio-lateral bend for valgus curvature of 5° and an anterior bend with a radius of 1500 mm. The lag screw is self-locking into the nail. The dynamic distal locking hole can be used to allow fracture compression up to 6 mm in the diaphysis direction.

3. Surgical Technique

The patients is placed in a supine position on a fracture table and the fracture is reduced under fluoroscopic guidance. A single-shot prophylactic antibiotic therapy is given 45 minutes before surgery. The CLN is inserted through the tip of the greater trochanter⁹. A supplementary lag screw can be used for rotational stability. Open reduction before nailing was needed in 75% (n = 15) of patients; 60% of those patients (n = 12) had one or two cerclages to help achieving and/or maintaining the reduction. The length of the implanted nail varied from 340 mm to 440 mm and the length of the cervical screws ranged from 90 to 120 mm. Distal locking consisted in two distal screws for 10 patients (50%) locked in static and dynamic or both in static mode. For 10 patients (50%) only one distal screw was placed: the screw was locked in dynamic or static mode depending on the operator’s own preference and fracture type. For transverse fractures, a dynamic distal locking method was chosen; for spiroid or communitive fractures, distal static locking method was chosen; for oblique fractures the operator chose which distal locking method was the most appropriated (depending on whether compression was needed or not). A board-certified orthopaedic surgeon supervised all surgeries.

4. Post-operative follow-up

At day 1 early mobilization was initiated with weight-bearing as tolerated and without limitation of the hip motion. All patients had the same reeducation protocol. Post-operative X-ray (Fig. 1) and red blood cell count were performed the day after the surgery.

5. Postoperative assessment

The primary outcome was mobility and return to social life. We used the mobility score of Parker and Palmer⁷ and the social function score of Jensen⁸ assessed at 3 months. Secondary outcomes were intraoperative fluoroscopy time and complications, adverse events, post-operative pain (evaluated during medical exam with interrogation (sleep on the affected side) and palpation), surgical time, perioperative blood loss, fluoroscopy time, tip-apex distance (TAD), Cleveland zone, material breakage, wound problems, length of hospital stay and readmission rate. The TAD¹⁰ and the Cleveland zone¹¹ were analyzed on the first post-operative AP pelvis X-ray and sagittal hip X-ray. Mal- and non-union were analyzed respectively at 3, 6 and 12 months.

6. 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 Stata 15.0 (StataCorp, College Station, TX, USA).

Clinical

Median operative time was 124 min (IQR 89–149). The median blood loss was 500 ml (IQR 260–1213). Median blood loss was 300 ml in closed reduction and was 500 ml in open reduction Median fluoroscopy time was 114 seconds (IQR, 95–172). (Table 2)

Table 2

Patients perioperative data
Number of Patients	20
Operative time (minutes)	124 (89–149)
Blood loss (ml)	500 (260–1213)
Fluoroscopy time (s)	114 (95–172)
Reduction Open Close	15 (75%) 5 (25%)
Cerclage Yes No	12 (60%) 8 (40%)

For operative time, blood loss and fluoroscopy time, the values are given as the median with IQR between brackets

We did not encounter any intraoperative fracture, cortical scraping or adverse event due to nail bending. We had one minor intra-operative complication which was the breakage of a cervical screw thread because the screw was turned too tight in the nail.

The Parker & Palmer⁷ mobility score was good to excellent at 3 months for most of the patients. It was equivalent or slightly modified compared to before the fall in respectively 54% of patients (maximum loss of 1 point of 9) with a median change of 3 points (median = 9 [IQR: 5.5-9] preoperatively to a median of 6 [IQR: 5.5-9] postoperatively). Jensen’s social score⁸ at 3 months was good to excellent for 87% of patient (maximum gain of 1 point) with no median change of the score (median score preoperative and postoperative unchanged at 2). (Table 3)

Table 3

Patients postoperative data
Number of Patients	13
Mobility score of Parker & Palmer⁷ 0-1 Point change 0-2 Points change 0-3 Points change	54% 77% 92%
Social function score of Jensen⁸ 0-1 Point change 0-2 Points change	87.5% 100%
Tip-Apex distance¹⁰ 10.0-24.9 mm > 25.0 mm	19 (95%) 1 (5%)
Cleveland Zone¹¹ 3 4 5 6	1 (5%) 1 (5%) 17 (85%) 1 (5%)
Complications Cephalic screw cut out Distal screw breakage Revision surgery	1 (5%) 4 (20%) 2 (10%)

Complications

There were neither wound healing problems or infections, nor lateral pain of the thigh due to lag screw irritation, nor bony malunion/nonunion during post-operative follow-up.

There were 2 postoperative complications: the first one was a cut out of the lag screw after 6 weeks (the TAD¹⁰ was 19.6 mm and according to Cleveland zone¹¹ the cephalic screw was in position 3), treated by revision total hip arthroplasty. The second complication was breakage of a single distal locking screw (screw deficiency) seven weeks post-operatively (Fig. 3) treated by revision of the screw and additional screw.

Radiologic

The median TAD¹⁰ was 16.4 mm (IQR 14.0-20.2); only one TAD was superior to 25 mm. The lag screw position was center-center in 85% of patients according to the Cleveland zone¹¹.

Recovery

All patients, except two, were able to walk weight bearing as tolerated within 7 days after the surgery. One patient didn’t walk because of dementia; the other patient because of general poor condition.

Primary Outcome

Intramedullary nailing has become the standard treatment for diaphyseal and/or an extra-capsular proximal femoral fracture due to the decreased risk of non-union and the low rate of complications⁵. Ricci et al.⁹ found that hip range of motion was similar to the unaffected side when using a femoral nail specially designed for trochanteric insertion which is the case for the CLN. Our study provides new data regarding the use of CLN in proximal and diaphyseal femoral fracture treatment. Post-operative analysis of functional scores showed that the CLN provides good to excellent mid-term functional and social results at 3 months post-operatively with the same or slightly modified score for the major part of the patients compared to preoperative score.

Secondary Outcome

Iatrogenic distal femoral shaft fracture is a well-known complication of long intramedullary nailing. For the long trochanteric Gamma nail (Stryker®, Michigan, USA) a close to 8% incidence has been reported¹². Bowing of the femur plus stress risers created by the rigidity of the implant and compressive loads at the tip of the nail seem to be the major factors for fracture around the nail¹³. One of the major advantages of the CLN is its radius. The native radius curve of the femur has been shown to be 110–120 cm¹⁴. The radius of the CLN is 1500 mm which is more anatomical than other nail like the original long Gamma Nail with a bowing of 2000 mm. Femoral bow increases with age¹⁵ and undergoes a morphological change: because of the increasing bow, the anterior tensile cortex becomes thinner, and the posterior cortex becomes relatively thicker¹⁵. Hence it is easy to perforate the anterior cortex either while reaming or during nail insertion of a “straight” nail in a curved femur. The use of a hammer increases the risk for this complication¹⁶. No fracture of the distal femur occurred in our group, which is lower than the results from other studies, with a reported incidence of 1%¹⁶. In our study, we attributed the lower rate of femoral shaft fractures and incidence of distal anterior cortical penetration to the design of the new CLN and its mechanical characteristics, with the distally positioned apex of the curvature of the nail which reduces the three-point loading at the femoral shaft¹³. Shetty et al.¹⁷ concluded that a cephalomedullary nail with a radius of curve of 1500 mm had its distal tip more towards the centre of the femoral canal when compared to a nail with radius of curve of 2000 mm and they did not have any case of anterior femoral penetration when using a nail with a ROC of 1500 mm.

One other major advantage is the self-retaining locking mechanism of the cephalic screw, which can slide on itself. Soucanye de Landevoisin E. et al¹⁸ presented 15.7% of patients with pain due to screw impingement on the fascia lata from whom 2% underwent reoperation. No cephalic screw back-out allowed by the device design occurred because of intranail fixation of the screw, preventing thus irritation of the fascia lata in our study. Compression of the fracture is still permitted by the self-telescoping effect of the screw.

Review of the surgical time indicates that the CLN is slightly longer to insert (average 119 minutes, median 124 minutes [IQR: 89–149]) than the Grosse-Kempf nail, the Synthes nails, the Russell Taylor nail¹⁹ and then the expandable (Fixion) or locked intramedullary nail of Sipahioglu S et al.²⁰ with an average of 60.9 min but slightly inferior to Koseoglu E. et al.²¹ in which the mean duration of operation was 122 minutes. These results may be influenced by the technical novelty of the implant and it may require a little adaptation time to progress.

Average per-operative bleeding was 670 ml, which is quite similar to Cameron et al¹⁹ who found out an average of 610 ml in their study of intra medullary nailing for femoral shaft fracture. Median operating blood loss was 500 ml (IQR 260–1213). We also have shown a difference between blood loss when open reduction was needed with a median difference of 200 ml between closed and open reduction.

Fluoroscopy time was in the average of other studies for intramedullary nailing of the femoral shaft fracture. Our median time was 114 s (IQR 95–172 s) with an average time of 139 s. Georgiannos D et al.²² average time for the similar procedure was 45 seconds and Koseoglu E. et al.²¹ average time was 283 seconds.

All TAD except one (TAD = 31 mm) were inferior to 25 mm according to Baumgaertner MR et al¹⁰ principle of the lag screw positioning. The cut out recorded was not due an excessive TAD (TAD = 19.6 mm). According to Cleveland M et al.¹¹, 3 lag screws were not positioned properly. It was the case for the only cut-out recorded where the lag screw was in position 3, which can explain the failure of the fixation in line with the bone quality of a 95 year old woman.

We do not report any nail breakage, in comparison with Georgiannos D et al.²² who found an incidence of nail breakage at the level of the cephalic screw of 2.4% for the long trochanteric gamma nail.

Complication

Georgiannos D et al. have shown that re-operation rate with the Long Gamma 3 nail was 10.6% and increasing up to 20.5% with the long trochanteric gamma nail²². Non statistical results with the CLN showed a lower rate of re-operation in our study. Only one patient required implant related re-operation: the distal broken screw which precipitated the failure of the nail fixation was changed and replaced by two distal screws with no further complication recorded after the second surgery.

We didn’t have any wound complication or bony nonunion/malunion

Study limitations

First limitation of the study is the small sample size; more patients are needed to validate our findings. Another limitation is the number of patients who withdrew before functional and social score recording due to concomitant illnesses affecting their general health and mortality rate. Furthermore, it is an uncontrolled study with no control group of our patients. However, we think that the strength of our study is the first clinical evaluation of a new nail.

The new Chimaera proximal long nail seems to be a valid implant for nailing of diaphyseal and trochanteric fractures of the femur within the limit of this study. Good to excellent functional outcomes were reported, with few per- and postoperative complications. The CLN is slightly longer to insert than other nails but the results may have been influenced by our lower experience with this nail. The CLN can be easily inserted, and provides stable fixation, which allows early full weight bearing of the patient and good social and functional outcomes.

Ethics approval and consent to participate

An informed consent was obtained from all subjects and/or their legal guardian.

Consent form to participate and to be published was obtained from all subjects and/or their legal guardian.

The protocol was approved by « cantonal commission for ethics and human research » (CER-VD). In accordance with the Declaration of Helsinki.

IRB: CER-VD 2018-00148

Consent to publish

Consent form to participate and to be published was obtained from all subjects and/or their legal guardian.

Availability of data and materials

All data generated or analyzed during the current study are included in this published article and its supplementary information files.

Consent for publication:

Not applicable

Competing interests

The authors have no conflict of interest

Fundings

No funding.

Acknowledgements

Not applicable

Authors’ contributions

A. Traverso, S. Steinmetz and T. Ngo wrote the manuscript.

O. Borens et S. Cherix prepared all auround the paper and help to construct the paper.

K. Moerenhout was the supervisor.

All authors reviewed the manuscript.

Authors’ information

Not applicable

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No competing interests reported.

Clinical and radiological outcomes of patients treated with the Orthofix Chimaera Long nailing system for proximal and diaphyseal femoral fracture

Status:

Version 1

Abstract

Figures

Highlights

Introduction

Materials and methods

1. Patients

2. Chimaera nail characteristics

3. Surgical Technique

4. Post-operative follow-up

5. Postoperative assessment

6. Statistical analysis

Results

Clinical

Complications

Radiologic

Recovery

Discussion

Primary Outcome

Secondary Outcome

Complication

Study limitations

Conclusion

Declarations

References

Additional Declarations

Status:

Version 1