Injury, Int. J. Care Injured 45S5 (2014) S2–S6

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Interprosthetic femoral fractures: proposed new classification system and treatment algorithm Robinson Esteves Santos Piresa,*, Paulo Roberto Barbosa de Toledo Lourençob, Pedro José Labronicic, Leonardo Rosa da Rochad, Daniel Balbachevskye, Francisco Ramiro Cavalcantef, Marco Antônio Percope de Andradea Federal University of Minas Gerais, Belo Horizonte - MG, Brazil Quinta D’Or Hospital, Rio de Janeiro – RJ, Brazil c Fluminense Federal University, Niterói – RJ, Brazil d National Institute of Orthopaedics and Traumatology (INTO), Rio de Janeiro – RJ, Brazil e Federal University of São Paulo, São Paulo – SP, Brazil f Orthopaedic Institute of Goiânia, Goiânia – GO, Brazil. a

b

keywords

abstract

Fracture Fracture fixation Hip fractures Osteoporotic fractures Periprosthetic fractures Interprosthetic fractures Hip prosthesis Knee prosthesis Knee replacement Hip replacement

Interprosthetic femoral fracture is a rare and challenging fragility fracture issue. Due to aging of the population, the incidence of this type of fracture is gradually and constantly increasing. There is no complete and specific interprosthetic femoral fracture classification system that indicates treatment and prognosis in the literature. The aim of the present study was to describe a new classification system for interprosthetic femoral fractures, and to present a case series and a treatment algorithm derived from the current evidence in the literature.

Introduction Interprosthetic femoral fractures are rare, occurring in 1.25% of patients who undergo hip and knee replacements [1]. By comparison, periprosthetic fracture incidence is 2.5% in the knee and 2% in the hip [2]. Several issues contribute to the challenging treatment of interprosthetic femoral fractures: poor bone quality, small interprosthetic fragment, prostheses instability, patient age, and clinical comorbidities [3-8]. Mortality and revision surgery rates associated with the treatment of interprosthetic femoral fractures have been reported to reach 50% in an observational study by Zuurmond et al [9]. There are several classifications in current use for knee and hip periprosthetic fractures; however, there is no complete and specific classification system for interprosthetic femoral fractures [10-13]. The aim of the present study was to describe a specific classification system for interprosthetic femoral fracture and to present a treatment algorithm for this important fragility * Corresponding author at: Department of Orthopaedic Surgery, Federal University of Minas Gerais, Belo Horizonte – MG, Brazil. Tel.: +55 31 3409-9757. E-mail address: [email protected] (R. Esteves Santos Pires). 0020-1383/$ – see front matter © 2014 Elsevier Ltd. All rights reserved.

© 2014 Elsevier Ltd. All rights reserved.

fracture issue. The authors also demonstrated an interprosthetic femoral fracture case series. The study was approved by the Institutional Ethics Committee and performed according to the standards of the Declaration of Helsinki. Patients and methods The following is a new classification system for inter­ prosthetic femoral fractures based on fracture site, viability of interprosthetic bone fragment, and prostheses stability. I.

Interprosthetic fracture surrounding hip (Figure 1)

IA: IB: IC: ID:

Stable prostheses Unstable hip prosthesis; stable knee prosthesis Stable hip prosthesis; unstable knee prosthesis Unstable hip and knee prostheses

II.

Interprosthetic fracture surrounding knee (Figure 2)

IIA: IIB: IIC: IID:

Stable prostheses Unstable hip prosthesis; stable knee prosthesis Stable hip prosthesis; unstable knee prosthesis Unstable hip and knee prostheses



III.

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Interprosthetic fracture with femoral extension stem (Figure 3)

IIIA: Stable prostheses with viable bone between the prostheses IIIB: Stable prostheses with unviable fragment due to lack of bone interval between prostheses ends IIIC: Unstable prostheses (hip, knee or both) with viable bone between the prostheses IIID: Unstable prostheses (hip, knee or both) with unviable fragment due to lack of bone interval between prostheses ends A literature review of current issues surrounding inter­ prosthetic femoral fracture, a treatment algorithm and a case series were also presented. The authors reviewed the database of three general hospitals and found six interprosthetic femoral fractures in six patients. The data collected included sex and age of patients, classification system, injury mechanism, treatment method, healing time and complications.

Fig. 1. Interprosthetic fracture surrounding hip.

Results Table 1 presents epidemiological data, treatment options and complications that occurred in the patients with interprosthetic femoral fracture. All patients were female and the average age was 75.8 years (range 71-86 years). The average healing time was 4.9 months (range 4-7.9 months). Treatment options included bridge-plating technique with soft tissue preservation, acetabular component revision plus percutaneous plate osteosynthesis, Ilizarov external fixation, and retrograde intramedullary nailing. There was only one complication reported: a pin tract infection in the patient who underwent Ilizarov external fixation. The patient was treated with local debridement and oral antibiotics and these were sufficient for infection control. Figure 4 shows an 86-year-old female who presented with interprosthetic femoral fracture surrounding the knee with stable hip and knee prostheses (IIA). The patient underwent minimally-invasive percutaneous plate osteosynthesis with distal femoral locked plate (less invasive stabilisation system [LISS®], DePuy Synthes). The fracture healed 6 months post-surgery, and the patient recovered to their pre-injury function level.

Fig. 2. Interprosthetic fracture surrounding knee.

Discussion Interprosthetic femoral fracture is a rare and challenging fragility fracture issue. Due to aging of the population, and the increasing number of arthroplasties, there is a trend towards increased incidence of interprosthetic femoral fracture [1,3-9]. There are several articles in the literature that discuss periprosthetic femoral fractures, but interprosthetic femoral fracture is only now just beginning to be addressed and few authors have described their experiences with this type of fracture [10-16]. Treatment options for interprosthetic femoral fracture include fixation using flat or precontoured plates, cerclage wires, autologous bone grafts with or without bone morphogenetic protein (BMP), and revision with stemmed prosthesis [14]. Hou et al [10] reported the outcomes of a case series of 13 patients with interprosthetic femoral fracture. Four fractures were treated with long-stemmed revisions because of loose prostheses. Two patients died prior to fracture healing. The remaining patients were treated with locked plates. The average fracture healing time was 4.7 ± 0.3 months. Average follow-

Fig. 3. Interprosthetic fracture with femoral extension stem.

up was 28 ± 4 months. All patients returned to preoperative functional status except for one patient who presented with a loose hip prosthesis three years after fracture healing. Mamczak et al [11] described a case series of 26 patients with interprosthetic femoral fracture who were all treated with plate fixation that spanned the interprosthetic zone, applied using soft tissue preserving techniques without adjuvant bone

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Table 1 Sex Patient

Trauma mechanism Age (years) Classification Treatment method

Healing time (weeks)

Complications

1

Female

Fall

86

IIA

LISS

16

None

2

Female

Fall

67

IIB

LISS + acetabular component revision

16

None

3

Female

Fall

80

IA

Bridge plating (LCP)

20

None

4

Female

Fall

71

IIA

Ilizarov

30

Pin tract infection

5

Female

Fall

77

IIA

Retrograde locked nail

16

None

6

Female

Fall

74

IIA

95° blade plate

20

None

Fig. 4. X-Ray in anteroposterior and lateral views showing interprosthetic femoral fracture type IIA (A and B). Images C, D, E and F show fracture healing after 6 months of fixation by applying a less invasive stabilisation system (LISS) spanning the hip prosthesis.

grafts. Nine of the fractures were surrounding the hip, and 17 were supracondylar. Five patients with six fractures were excluded from the study because of deviation from the original treatment protocol or lack of minimal follow-up. All remaining fractures healed. The complications were three malunions (one 9° extension, one 10° flexion, and one 10° valgus), two cases of painful implants (one required removal), and one total femur replacement in a patient who presented with a loose long-stem revision hip prosthesis. All reported complications occurred in supracondylar fracture patterns. The present study showed similar epidemiological data and healing times to previous studies. Only one complication was noted, this was a pin tract infection after external fixation with the Ilizarov method. There was no treatment protocol for this complication; treatment was determined only by surgeon preference. Lehmann [15] reported a 30% reduction in femoral shaft resistance with two intramedullary components. However, interprosthetic femoral fracture risk in this study was more credited to the component loosening causing a stress area than the remaining bone size between both prostheses. Interprosthetic femoral fracture fixation by applying retrograde intramedullary nailing led to poor results according to Soenen et al [3]. In the present case series, one patient presented a type IIA interprosthetic femoral fracture and underwent fixation with

retrograde intramedullary nailing. Despite the remaining bone interval between the hip prosthesis and retrograde nail, the patient presented no fracture after a 6-year follow-up. Prosthesis stability was probably more important to decrease fracture risk than the remaining bone interval. Cortical bone shaft thickness plays an important role in interprosthetic femoral fracture. The thicker the bone shaft, the lower the chances of such a fracture. Soenen et al [3] highlighted an individual management for the most challenging aspect of interprosthetic femoral fracture treatment: the interprosthetic fracture on total knee replacement with diaphyseal extension stem. The authors proposed this specific fracture pattern as an additional grade in the Vancouver and Société Française de Chirurgie Ortopédique et Traumatologique (SoFCOT) classifications. Interprosthetic femoral fracture in long-stemmed prosthesis remains a significant challenge for the orthopaedic surgeon. High complication rates in this specific fracture pattern result from two main issues: small bone interval between prostheses, which hinders fixation, and the presence of cement in the remaining bone, which compromises blood supply. However, interprosthetic femoral fracture is frequently classified using an association of classification systems, such as Vancouver plus Rorabeck, Vancouver plus SoFCOT, or Vancouver plus Su [12]. There is no complete and specific interprosthetic



R. Esteves Santos Pires et al. / Injury, Int. J. Care Injured 45 S5 (2014) S2–S6

Fig. 5. Treatment algorithm for Type I interprosthetic femoral fracture.

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Ochs et al [14] presented a helpful treatment algorithm based on the Platzer Classification. The authors proposed several treatment possibilities, including interprosthetic femoral fracture fixation by applying locking compression plate (LCP), bone graft, arthroplasty revision, and total femur replacement. The present study proposed an algorithm based on a new and complete classification system to help orthopaedic surgeons choose a more appropriate treatment for this challenging fracture pattern. Figures 5, 6 and 7 show the treatment protocol based on the new classification system for interprosthetic fracture. The classification proposed by the authors emphasises the most difficult interprosthetic femoral fracture pattern: the interprosthetic fracture with knee revision stem. Four subtypes comprise the type III interprosthetic femoral fracture according to prostheses stability and viability of the remaining bone fragment. Bone fragment viability was defined as at least 5cm with no cement and prosthesis components in the fracture site. The present study proposed a new, specific and complete classification system for interprosthetic femoral fracture. The authors demonstrated an effective treatment algorithm based on the current literature for this challenging and rare fracture pattern. A case series was presented to show the evaluation of six patients who underwent surgical treatment for interprosthetic femoral fracture. One weakness of the study was the small number of patients. Although interprosthetic femoral fracture is rare, some authors have published studies with larger numbers of patients. Furthermore, there was no standard treatment protocol during the study period; interprosthetic femoral fracture treatment was based only on surgeon preference. Also, the most difficult fracture pattern (Type III) was not represented in this case series. Conclusion

Fig. 6. Treatment algorithm for Type II interprosthetic femoral fracture.

The present case series showed similar epidemiological data, healing times, and complication rates to previous studies. The new classification proposal and treatment algorithm are potentially valuable tools for the treatment of interprosthetic femoral fracture. More studies are required with this treatment protocol with a higher evidence level, larger patient numbers, and longer follow-up to determine the real contribution to the improvement in outcome performance. Conflict of interest statement The authors declare that they have no conflict of interest. References

Fig. 7. Treatment algorithm for Type III interprosthetic femoral fracture.

femoral fracture classification system that indicates treatment and prognosis in the literature. Platzer et al [13] described the modified Vancouver classifi­ cation, which categorises interprosthetic fractures into three types depending on the fracture site and the vicinity of the prosthesis: Type I, no adjacency; Type II, adjacency to one prosthesis, and Type III, adjacency to both prostheses.

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