1 Background

The incidence of periprosthetic femoral fractures has been estimated between 1.5% and 4%.^1,2 According to the Swedish Registry, this kind of fractures is the third leading cause of revision hip arthroplasty after aseptic and septic loosening.³ Several periprosthetic femur fracture classifications have been used in the literature,^1,2,4–6 however, Vancouver classification² is the most common and reproducible classification for predicting the best treatment. It evaluate fracture site, implant stability and bone quality (see Figs. 3 and 4).

The management of these periprosthetic fractures is complex. The strategy include multiple factors such as the nature of the fracture, implant stability, bone quality, patient's age and surgeon's experience.

Vancouver type B fractures are those that compromise the bone around or just below the femoral stem. Type B1 have good bone stock and the femoral component is fixed; type B2 have good bone stock but the femoral implant is loose; and type B3 have poor bone quality and bone stock deficiency (severe comminution, osteolysis or osteopenia), as well as the femoral stem is loose.²

Tapered fluted stem began to be used in the 1980s and were originally described by Wagner.^4,5 Its design gives it axial and rotational stability in the femoral isthmus or below the bone defect. The design of these stems has evolved adding modularity, increasing their versatility and their indication in different cases of periprosthetic femur fractures.^6,7

Currently, the use of different cementless stems has been described, such as extensive porous coating stems^8–10 and modular fluted stems, both with good outcomes.^11–16 The modular tapered fluted stems have gained popularity in the last decade^12,15,17 due to the ease and reproducibility of their surgical technique.¹⁸ The literature reports a short-time successful survival around 87% with good clinical outcomes and functional scores.¹²

The purpose of this study is to report our experience in revision hip arthroplasty with the modular tapered fluted stems in patients with B2 and B3 periprosthetic fractures with a mid-term follow up. We evaluate survival rate, implant's complications, re-revision rate and mortality rate.

2 Methods

A multicenter, retrospective, observational study was conducted. We identified thirty six patients that underwent hip revision surgery secondary to periprosthetic femur fracture between 2007 and 2017.

We included in this analysis all patients with Vancouver type B2 and B3 periprosthetic femur fracture. One patient with Vancouver type B1 femur fracture was excluded. All surgeries were performed by senior surgeons at three level one trauma centers.

Demographic data as well as patient functional scores were obtained from the electronic medical record. The presence of implant subsidence, fracture consolidation and heterotopic bone ossification was evaluated.

The patients were evaluated clinically and radiologically at 3 and 6 weeks, then at 3 months and finally with an annual control during the first 3 years after surgery. Subsequently, the follow-up was every 3 years. Preoperative and postoperative Harris Hip Score was performed in all patients.¹⁹

Preoperative surgical planning included x-rays evaluation and proximal femoral bone loss, which was classified according to Paprosky and Burnett.²⁰ Preoperative planning was always carried out with proper templates. Five centimeters of diaphysis fixation was considered appropriated.²¹

Stem subsidence was measured from a fixed reference in the stem to fixed reference in the bone. The loosening was defined as a progressive stem subsidence or a progressive radiolucent line around the femoral component.²² The fracture healing was defined as a bone bridge across the fracture line visible on x-rays.

A posterolateral approach was used in all patients. Patients were allowed initial partial weight-bearing routinely in the postoperative period. All patients received antibiotic prophylaxis for 24 h, and thromboprophylaxis therapy for 28 days. Postoperative x-rays were analyzed to assess the stem stability, subsidence and loosening, as well as the fracture healing.

3 Results

Sixteen patients (44.4%) had Vancouver type B2 and 19 patients (52.7%) Vancouver type B3 periprosthetic femur fracture, which was not associated with gender (p = 0.675) and age (p = 0.76). Twenty-seven patients were female and nine male. Average age was 68 years (range 22, 85) (SD = 13.5), homogeneous between gender (p = 0.368). In all cases, modular tapered fluted stems were used.

Ninety seven percent reported previous surgeries, 75% and 17% had one and two previous surgeries in the same hip. There was no statistically significant differences between gender (p = 0.681).

Regarding acetabular cup revision, 75% of patient underwent to this procedure in the same surgery. There were no statically significant differences regarding gender (p = 0.50) and age (p = 0.35).

Average follow-up was 42 months (range 12, 96) (SD = 25.6). This value was conditioned by two patients whose survival times did not exceed 18 months after surgery. When these patients were not considered, the average implant survival was 50 months (SD 24.1), with 75 and 90 percentiles equal to 65 and 90 months, respectively. When acetabular revision was not performed, the follow-up time was, on average, 30% greater (p = 0.042) than patients with acetabular revision (95% CI: [35.5–72.3] months, without acetabular revision, 95% CI: [28.2–48.7] months, with revision] (Fig. 1).

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Fig. 1 Box Plots for the follow up time (months) for all classifications (upper left panel), related to: Acetabular Cup Revision (globally, upper right panel), Fracture Classification (without revision, lower left panel; with revision, lower right panel).

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There was no association between the Vancouver type classification with any postoperative complication evaluated (anterior thigh pain stress-shielding, stem subsidence, heterotopic bone ossification, instability episodes, and infection) (p = 0.856). Regarding these complications, only 3% of patients showed stress-shielding, 10% stem subsidence (range 12, 84 mm), 6% instability episodes, and 3% deep infection.

Average postoperative Harris Hip Score was 78.11 (SD = 12.4), the most of the patients between 73 and 86, with 15% of patients above 90 points. This assessment did not show statically differences significant between gender (p = 0.234, 95% CI: [75.4–90.75], 95% CI: [70.4–82.5] for male and female, respectively). Furthermore, this score was not associate with Vancouver classification (p = 0.62 for type B2 and p = 0.83 for type B3) or acetabular revision performed (p = 0.46). (Fig. 2)

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Fig. 2 Box Plot for Harris Hip Score related to the Acetabular Cup Revision.

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Fig. 3 Female, 77 years old. Vancouver type B2. Revision femoral component with modular fluted tapered stem. Consolidation 10 months.

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Fig. 4 Male, 83 years old. Vancouver type B3. Revision femoral component with modular fluted tapered stem and cemented acetabular cup. Consolidation 7 months.

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Regarding intraoperative complications, we observed anterior cortical perforation in a 5% of the patients. There were no cases of sciatic nerve palsy.

4 Discussion

Treatment goals of periprosthetic femur fractures include restoring leg alignment with a stable stem that allows early mobility and return to pre-fracture function.²³ Modular fluted tapered stems offer several advantages, including modularity, axial and rotational stability, and stress-shielding protection.^6,11,14 We observed a successful implant survival with low complication rate.

Average postoperative Harris Hip score in our series was 78.11(range 27,9; 97) (SD = 12.4). Abdel et al.,¹¹ reported similar results with an average HHS of 83 points.

Our average implant survival was 50 months (SD 24.1) and 25% of the sample exceeded 5.5 years. Similar results were reported in the literature^12,14,24 with a high success rate even in those patients with severe bone loss.

We observed that the subsidence rate and loosening rate were not related to Vancouver classification. We reported a subsidence rate of 10%, however, no patient needed a new surgery. Abdel et al.²⁵ showed that only 2.4% of the stems had a subsidence and the majorities were stabilized over time.

Subsidence stem rate in our series was similar to the literature.^14,22,24 Lopreite et al.²⁶ found a subsidence rate of 34,3% however with an excellent survival rate. Extensive porous coating stems have shown higher subsidence and loosening rates from 11% to 16%.^27–29 This complication is correlated with smaller diameter stems, osteoporosis, poor metaphyseal quality bone and extended femoral osteotomy (EFO) in the literature above. In contrast, Garabano et al.³⁰ concludes stem subsidence and integration was not significantly affected by EFO fracture/no fracture or union/non-union. Our results and the literature^18,21 suggest that inadequate selections of diameter and length stem are responsible for this.

Regarding mortality rate, Bhattacharyya et al.³¹ reported an 11% in these fractures. This is related to the complexity of the surgery, operative time and blood loss. Jennison et al.³² informed a 30 day mortality was 12.5% and 1 year mortality 28.1%; and time to surgery was the only significant risk factor for 30 day mortality. We reported in our series a rate of 2.78%.

Dislocation rate secondary to revision femoral component is high. Huang et al.³³ reported a 1.9% rate with modular tapered fluted stems and they did not report cases with non-modular stems. This rate is lower than previous literature reported which range from 2% to 21%.^{13,14,22,34–36} Abdel et al.¹¹ reported that instability is the most common complication (11%), but this can be reduced with the use of larger diameter femoral heads. Our study reported a postoperative dislocation rate of 6%. This percentage was directly related to the use of a head diameter smaller than 32 mm.

In conclusion, modular fluted tapered stems provide a reliable and durable solution in the mid-term for the management of femoral revisions in total hip arthroplasty secondary to Vancouver type B2 and B3 periprosthetic femur fracture, restoring hip biomechanic, leg lengths and femoral anteversion independently. Furthermore, these stems provide good implant stability, proximal femoral bone restoration and fracture healing, with a low complication rate.

As a limitations, the present study is a retrospective case series and we consider that a more extensive follow up is essential to ensure late complications associated with modularity such as corrosion and implant fracture.