 HIP

Is tantalum protective against infection in revision total hip arthroplasty?

A. T. Tokarski, T. A. Novack, J. Parvizi From The Rothman Institute, Philadelphia, United States

We hypothesised that the use of tantalum (Ta) acetabular components in revision total hip arthroplasty (THA) was protective against subsequent failure due to infection. We identified 966 patients (421 men, 545 women and 990 hips) who had undergone revision THA between 2000 and 2013. The mean follow up was 40.2 months (3 months to 13.1 years). The mean age of the men and women was 62.3 years (31 to 90) and 65.1 years (25 to 92), respectively. Titanium (Ti) acetabular components were used in 536 hips while Ta components were used in 454 hips. In total, 73 (7.3%) hips experienced subsequent acetabular failure. The incidence of failure was lower in the Ta group at 4.4% (20/454) compared with 9.9% (53/536) in the Ti group (p < 0.001, odds ratio 2.38; 95% CI 1.37 to 4.27). Among the 144 hips (64 Ta, 80 Ti) for which revision had been performed because of infection, failure due to a subsequent infection was lower in the Ta group at 3.1% (2/64) compared with 17.5% (14/80) for the Ti group (p = 0.006). Thus, the use of Ta acetabular components during revision THA was associated with a lower incidence of failure from all causes and Ta components were associated with a lower incidence of subsequent infection when used in patients with periprosthetic joint infection. Cite this article: Bone Joint J 2015;97-B:45–9.

 A. T. Tokarski, BS, Research Fellow  T. A. Novack, BS, Research Fellow  J. Parvizi, MD, FRCS, Orthopaedic Surgeon The Rothman Institute, 925 Chestnut Street, Philadelphia, 19107, USA. Correspondence should be sent to Dr J. Parvizi; e-mail: [email protected] ©2015 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.97B1. 34236 $2.00 Bone Joint J 2015;97-B:45–9. Received 7 April 2014; Accepted after revision 18 September 2014

Revision total hip arthroplasty (THA) can be a challenging problem.1-3 Failure of the acetabular component may occur as a result of aseptic loosening, osteolysis, fracture, or infection.1,4,5 Acetabular revision using an uncemented hemispherical component is widely practiced and has a favourable outcome.6-9 Most uncemented acetabular components used in this setting are made of titanium (Ti) or tantalum (Ta). In recent years, porous Ti components have also been used in an attempt to enhance the potential for osseointegration.10-15 Some previous studies have suggested that the use of a Ta acetabular component offers a better outcome with fewer further failures.16-20 Laboratory and animal studies have demonstrated higher potential for osseointegration with Ta components as well as other porous materials.21 A previous study from our institution also demonstrated a lower failure rate for Ta acetabular components compared with that of Ti when used in revision THA.16 This was despite the fact that Ta components are generally used in more complex reconstructive procedures at our institution. In the same study and during our subsequent observations, we noted that the use of a Ta acetabular component during revision THA performed for aseptic or septic

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failure was associated with a lower incidence of subsequent infection. The hypothesis of this study was that the use of a Ta acetabular component during revision THA may be protective against subsequent infection.

Patients and Methods After receiving approval from our Institutional Review Board, we performed a retrospective review of our database to identify all patients who had undergone revision THA between January 2000 and December 2013. During this time, 2879 revision THAs had been performed. Patients who did not have their acetabular component revised, or those undergoing revision using cemented acetabular components, antiprotrusio cages or ‘cup in a cage construct’, or patients without adequate follow-up, were excluded. Of the 1348 acetabular revisions using a Ta or Ti component, 358 were excluded because they did not achieve 90 days of followup. This left a total of 990 hips (433 men, 557 women; 966 patients) for inclusion in the study. There were 421 men with a mean age of 62.3 years (31 to 90) and 545 women with a mean age of 65.1 years (25 to 92). Various Ti acetabular components were used in 536 hips, which included 66 ingrowth surfaces. Ta 45

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A. T. TOKARSKI, T. A. NOVACK, J. PARVIZI

Table I. Distribution of demographics between patients with tantalum and titanium acetabular components Demographic Gender Male Female Mean age Mean BMI Mean Charlson Comorbidity Index22 Surgical indication Loosening Instability Infection Polyethylene wear Other Growth surface Ingrowth Ongrowth

Tantalum

Titanium

200 254 63.2 (26 to 92) 28.8 (16.6 to 46.9) 0.633

233 303 64.7 (25 to 91) 28.7 (12.9 to 53.8) 0.631

235 33 64 48 74

235 87 80 66 68

454 0

66 670

p-value 0.898

0.283 0.714 0.751 < 0.001

< 0.001

BMI, body mass index

acetabular components (all Zimmer trabecular metal components; Warsaw, Indiana) with ingrowth surfaces were used in the remaining 454 hips. In total, 520 hips were revised using ingrowth acetabular components and 470 were revised using ongrowth components. The revision surgery was performed by one of five fellowship-trained surgeons, all of whom were familiar with the use of both types of component. Ti components were not used in complex acetabular reconstruction with extensive bone loss. The indication for revision was aseptic loosening in 470 hips (47%), infection in 144 (15%), instability in 120 (12%), polyethylene wear in 114 (12%), and other indications in 142 hips (14%). For the purposes of this study, excision arthroplasty and implantation of an antibiotic impregnated cement spacer followed by reimplantation of components in the same joint were considered a onerevision procedure. The medical and radiographic records of all patients were reviewed and the age, gender, body mass index, Charlson Comorbidity Index (CCI),22 indication for revision surgery, type of growth surface (ingrowth vs ongrowth), the use of bone graft or trabecular metal augment in the acetabulum, if the femoral component was revised and the type of acetabular component which was used, was recorded. There was no difference in demographic details between patients receiving a Ta acetabular component and those receiving a Ti component (Table I). Patients were followed for a minimum of 90 days, and the mean follow up was 40.2 months (3 months to 13.1 years) based on the recommendations of The Center for Disease Control (CDC)23 to detect failures occurring as a result of infection. Patients who were not reviewed at least 90 days after their revision surgery were contacted by telephone to establish the outcome. Periprosthetic joint infection (PJI) was defined using the recent definition of the Musculoskeletal Infection Society.24,25

Statistical analysis. Fisher’s exact test and Wilcoxon rank sum test were used for categorical and continuous variables, respectively to determine if any of the demographic data were different between the Ta and Ti groups. Multivariate logistic regression (MVLR) was used to determine if any of the recorded parameters including age, gender, BMI, CCI, indication for revision surgery, growth surface and the type of component were independent predictive factors for subsequent failure. Odds ratios (OR) with 95% confidence intervals (CIs) were calculated. A p-value < 0.05 was considered to statistically significant. All analyses were assessed using R version 3.0 (R Foundation for Statistical Computing, Vienna, Austria).

Results At the latest follow-up, failure of the acetabular component had occurred in 73 hips (7.1%). The causes of failure were aseptic loosening (30 hips), infection (40 hips), instability (five hips) and periprosthetic fracture (one hip). The overall incidence of failure was significantly lower in hips with Ta acetabular components which were revised at 4.4% (20/ 454) compared with 9.9% (53/536) for Ti acetabular components (p < 0.001, MVLR). The incidence of infection in the Ta group at 2.9% (13/454) was lower, albeit not statistically significantly, than the incidence of infection at 5% (27/536) in the Ti group (p = 0.105, MVLR). However, the findings were notable, when analysis was applied to the cohort of 144 hips (64 Ta, and 80 Ti) which underwent initial revision for infection. When controlling for demographics, CCI, the use of bone graft and the need for femoral revision, the incidence of subsequent infection (recurrence or persistence) was significantly lower in the Ta group at 3.1% (2/64) compared with 17.5% (14/80) in the Ti group, (p = 0.007, MVLR). When controlling the same analysis with the type of surface (ongrowth or ingrowth), the incidence of subsequent infection was significantly lower THE BONE & JOINT JOURNAL

IS TANTALUM PROTECTIVE AGAINST INFECTION IN REVISION TOTAL HIP ARTHROPLASTY?

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1348 Acetabular revisions

990 90-day follow-up

536 Ti

454 Ta

64 Revisions for infection 2 Septic failure

390 Aseptic revisions 7 Aseptic failures

11 Septic failure

456 Aseptic revisions

80 Revisions for infection 14 Septic failures

1 Aseptic failure

13 Septic failures

25 Aseptic failures

Fig. 1 Flow chart showing the distribution of aseptic and septic revisions and subsequent aseptic and septic failures between the titanium and tantalum groups.

Table II. Factors contributing to further failure of the acetabular component Variable Gender Male Female Mean age (yrs) Mean BMI Mean CCI22 Type of component Ta Ti Use of acetabular bone graft or augment Yes No Revised femur Yes No Growth surface Ingrowth Ongrowth

Failed

Did not fail

37 36 64.4 28.6 0.64

396 512 64.2 28.6 0.63

20 53

434 483

p-value 0.271

0.029 0.699 0.029 < 0.001 0.016

23 50

210 707

31 42

401 516

26 47

494 423

0.902

0.103

BMI, body mass index; CCI, Charlson Comorbidity Index

(p < 0.001, MVLR) in the ingrowth group at 3.6% (3/83) compared with 21.3% for the ongrowth group (13/61). When both the type of metal (Ta or Ti) and the growth surface were controlled for, neither showed statistical significance (p = 0.664, MVLR) (Fig. 1). Ingrowth surfaces were highly associated with Ta surfaces, as demonstrated by Fisher’s exact test (p < 0.001). VOL. 97-B, No. 1, JANUARY 2015

The multivariate analysis revealed that young age (p = 0.029, OR 1.04; 95% CI 1.09 to 1.53), CCI per point increase (p = 0.003, OR 1.3; 95% CI 1.09 to 1.53), the use of acetabular bone graft or augment (p = 0.016, OR 1.9; 95% CI 1.13 to 3.30) and Ti acetabular components (p < 0.001, OR 2.7; 95% CI 1.56 to 4.66) were independent factors for subsequent failure of the acetabular component (Table II). There were also significantly more revisions for instability in the Ti group compared with the Ta group (p < 0.001, Fisher’s exact test).

Discussion The number of revision arthroplasties being performed in the United States is increasing;26 in particular, the number of revisions being performed for infection, with one projection estimating that $650 million of healthcare resources will be required to treat 26 000 patients with PJI in 2014.27 It is well-known that the incidence of PJI following revision THA is higher than that following primary THA.28-30 Although many theories for this observation can be offered, perhaps the most important is that revision procedures are more complex, taking longer to perform with more blood loss and the need for more allogeneic blood transfusion, all of which are known to increase the risk of subsequent infection.31,32 The consequences of PJI after revision surgery are equally more devastating as these patients often have compromised bone stock and/or local soft tissue, making further surgery exceedingly challenging. Currently orthopaedic surgeons are actively seeking strategies that can minimise the risk of PJI after joint arthroplasty, and particularly after revision. The findings of this study are encouraging in that the use of Ta components

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A. T. TOKARSKI, T. A. NOVACK, J. PARVIZI

may be protective against failure due to infection, at least in patients who are undergoing revision surgery for infection. There may be many reasons why Ta is more protective against infection. The first, and in our opinion the most important, reason may relate to the higher potential of Ta to osseointegrate21,33 thereby obliterating any dead space. The ability of osteoblasts to proliferate and integrate onto the surface of the uncemented component may then deprive infecting organisms access to the surface. The second reason may relate to the topographical three-dimensional structure of the surface of Ta that may be difficult for organisms to access and colonise. Finally, one may hypothesise that Ta, as an element, might carry a specific charge or have surface characteristics that are hostile to infecting organisms. Our study mirrors other publications showing a lower rate of failure for Ta acetabular components compared with Ti acetabular components used during revision THA.16,34 The fact that Ta performs better than Ti is even more impressive, as Ta acetabular components are generally used in more complex reconstruction, at least at our institution. Our intention was not just to demonstrate better survivorship for Ta acetabular components, as that has been shown in a report from our institution that included some of the patients in this cohort.16 The current investigation was designed to determine the incidence of failures due to infection following revision THA, particularly when the initial revision was performed for infection. We elected to use the three-month minimum follow-up, in compliance with the National Healthcare Safety Network, the surveillance arm of the CDC,23 that uses this period to determine if an infection occurring after surgery could be directly attributed to that procedure or not. We are certain that if we were to extend the period of follow-up, we would identify more failures not only due to infection, but also to other causes. The study has limitations. Due to its retrospective nature, patients were not randomised to receive either Ta or Ti acetabular components. The data generated are from a single institution that has a strict protocol for the management of patients requiring revision THA, particularly those with infection. It is possible that the findings of this study may not be applicable to patients who undergo surgical management for infection using different and less vigorous protocols. The other weakness of the study is that despite our attempts, 358 patients could not be contacted and were lost to follow-up. Thus, it is possible that the incidence of failure from all causes was underestimated as some patients may have sought treatment elsewhere. However, if this were true we suspect it would have been applicable to both groups of patients and should not bias the results unequally in favour of one type of component. We believe the findings of this study are encouraging and worth further exploration. Ta appeared to be protective against infection following revision THA, particular when

revision was performed for failure related to infection following the initial procedure. A. T. Tokarski: Contributed to study design, Study implementation. T. A. Novack: Study implementation. J. Parvizi: Contributed to study design, Refinement of study protocol, Approved the final manuscript. We are grateful to Zimmer Orthopedics whose funding enabled us to complete this study. The author or one or more of the authors have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article. In addition, benefits have been or will be directed to a research fund, foundation, educational institution, or other nonprofit organisation with which one or more of the authors are associated. This article was primary edited by G. Scott and first proof edited by J. Scott.

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