Periprosthetic joint infection (PJI) is a devastating complication after lower extremity arthroplasty. Currently, PJI occurs in 0.5% to 2.0% of patients who undergo THA or TKA and is the leading cause of arthroplasty failure . The appropriate surgical management of chronic PJI is controversial. For the past several decades, most patients with chronic PJI in Europe and North America have been treated with two-stage exchange [1, 8, 21, 25, 28], but single-stage exchange has been advocated by some because it may allow some patients to be treated without the morbidity associated with a second major surgical procedure [6, 7, 10, 11, 24]. Some systematic reviews found no differences in the risk of reinfection or persistent infection between single- and two-stage exchange for PJI [13, 16], and avoiding a second major procedure has appeared attractive in some small studies in terms of reduced mortality, improved functional scores, and lower healthcare costs when used in appropriately selected patients [2, 5, 12, 16, 18, 26].
However, good studies have suggested that single-stage exchange is not the right choice for all patients [14, 19, 23]. The International Consensus Meeting  and other studies have suggested that the best indications for this procedure are for chronic PJI in an immunocompetent host, with a preoperatively known nonvirulent or resistant pathogen, with an adequate soft tissue envelope and without a sinus tract [5, 6, 14, 17]. To our knowledge, no study has specifically explored the proportion of patients who might be good candidates for single-stage exchange based on the criteria articulated at the International Consensus Meeting . Those criteria, in principle, seek to identify patients whose infections are easier to manage; however, to our knowledge this contention has not been specifically evaluated.
Therefore, we asked: (1) What percentage of patients with chronic PJI treated at our institution met the International Consensus Meeting criteria for single-stage exchange arthroplasty? (2) Is the risk of persistent or recurrent infection lower for patients treated with two-stage exchange who met International Consensus Meeting criteria for single-stage exchange than it is among those who did not meet those inclusion criteria?
Patients and Methods
Between September 2012 and July 2016, a single referral center treated 120 patients with chronic PJI, defined by the Musculoskeletal Infection Society (MSIS) criteria (Fig. 1) . During this time, we used single-stage exchange only rarely in patients with chronic PJI (3%; four of 120), and these were done only in oncologic patients with mega-prosthetic implants; 7% (eight of 120) underwent other procedures (resection arthroplasty or arthrodesis). Of the remaining 108, 19% (20) would be indicated for single-stage exchange arthroplasty based on the International Consensus Meeting criteria; 81% (88 or 108) of patients at our institution met at least one of the International Consensus Meeting exclusion criteria for single-stage exchange arthroplasty (Fig. 2). Sixteen percent (17 of 108) of patients were lost to follow-up, leaving 91 patients to be evaluated as to the risk of reinfection.
Of the 108 included patients in the study the mean age was 63 ± 11 years, 46% (50) of patients were female, the median BMI was 34 kg/m2 (18-57), 24% (26) were THAs and 76% were TKAs (82) (Table 1).
To answer our first question, we applied the International Consensus Meeting indications for single-stage exchange, which were: (1) the presence of a known organism preoperatively, (2) the presence of a non-virulent or resistant pathogen, (3) an immunocompetent host, and (4) the presence of a sinus tract or inadequate soft tissue envelope. If patients did not meet all these criteria, they would be considered excluded from single-stage exchange. We then calculated the percentage of patients who would have met those criteria. To answer our second question, we compared those who would and would not have met inclusion criteria for single-stage exchange regarding the proportion who were determined to be infection-free at 2 years using the MSIS criteria.
A retrospective study was performed using an institutional review board-approved Joints Outcomes Registry Database. We assessed patients with MSIS-defined chronic PJI. Once defined as having chronic PJI we then assessed all patients undergoing two-stage exchange.
We attempted to mitigate selection bias by selecting all patients at a single-institution with MSIS-diagnosed chronic PJI who underwent two-stage exchange arthroplasty. Despite multiple operating surgeons, two-stage exchange was performed in a technically similar manner. We excluded single-stage exchanges, although rare at our institution, because they were all performed on chronic PJI in mega-prosthesis implants in oncologic patients, which we felt represented a different patient population that was not generalizable to the general public.
This was a retrospective study of 120 patients with chronic PJI who had readily available data. We selected the year 2012 as the start date because this was a date that the electronic medical record was universally used across our institutional hospitals, which allowed data to be readily available and consistent across years.
We compared the percentage of reinfection between patients considered candidates for single-stage exchange arthroplasty and those who were not using an unpaired t-test. Analysis was performed with GraphPad Prism version 8.3.0 for Mac (GraphPad Software, La Jolla, CA, USA).
Only 19% (20 of 108) met International Consensus Meeting criteria  for single-stage exchange. Of those who did not meet the criteria, 40% (43 of 108) had either an unknown organism preoperatively or dry aspiration precluding synovial fluid culture (only five of 43 patients with unknown organisms preoperatively had dry aspirations); 13% (14 of 108) had a draining sinus; 19% (21 of 108) had host immunocompromise; and 9% (10 of 108) had either a virulent, resistant, or polymicrobial infection. Of those who were contraindicated for single-stage exchange, 17% (15 of 88) were McPherson Type C hosts. Of patients indicated for single-stage exchange, only two of 20 was a Type C host (Table 1).
With the numbers available, there was no difference between those who met and did not meet those criteria in terms of the proportion who had persistent or recurrent infection 2 years after treatment (three of 15 versus 32% [24 of 76]; p = 0.38). The denominators here are smaller than 108 because of loss to follow-up before 2 years; however, there was no differential loss to follow-up between these two groups (five of 20 versus 12 of 88; p = 0.22).
Periprosthetic joint infection is a devastating complication after lower extremity arthroplasty and is the leading cause of arthroplasty failure . Treatment of chronic PJI with a single- or two-stage exchange continues to be debated, with studies citing comparable risks of reinfection and smaller studies suggesting less morbidity with single-stage exchange [9, 13, 16, 18, 26, 27]. However, to be considered a candidate for single-stage exchange, a patient should meet a specific set of indications. We sought to determine what percentage of patients at our institution met the International Consensus Meeting criteria for single-stage exchange. Because our institution treats patients with chronic PJI with two-stage exchange, we sought out to compare the proportion of patients experiencing reinfection after two-stage exchange in patients who met criteria for single-stage exchange (which should be a healthier group) with those who did not. We found that a low percentage of patients (19%) were candidates for single-stage exchange according to the International Consensus Meeting criteria, and there was no difference in risk of persistent or reinfection at 2-year follow-up between groups. It is possible that a small proportion of patients may benefit from a single-stage exchange, but our small sample size may have missed important differences in reinfection risk, and so our findings on that question must be considered preliminary.
There are several limitations of this study. First, the current study is limited by the fact that our numbers are relatively small, even though our institution is a tertiary referral center, which may make these numbers perhaps more applicable to a community-based surgeon. Secondly, despite finding no difference in the proportion of patients who experienced reinfection between candidates in the single versus two-stage cohorts, our study was underpowered, and the results should be viewed with caution. A larger study might have found a difference where we did not. It is very possible that candidates who qualify for a single-stage exchange may have a lower reinfection risk when compared with a larger number of patients. Loss to follow-up is always a concern in a study like this; five of 20 patients in the single-stage cohort were lost to follow-up versus 14% (12 of 88) in the two-stage cohort, but this did not represent a statistical difference (p = 0.21). Even so, it is possible that this would have affected the number of reinfection especially in the single-stage group specifically. Additionally, determining a host’s immunologic status was difficult because there were varying definitions in previous studies [3, 6, 15, 23]. Ultimately, we considered a host immunocompromised if she or he was currently taking chemotherapeutics, anti-rheumatic drugs, or corticosteroids, had a diagnosis of HIV or AIDS, had insulin-dependent diabetes mellitus, or was currently using intravenous drugs. Lastly, we did not specifically assess the soft-tissue status, but we assessed for the presence or absence of a draining sinus tract and believe this can act as a surrogate.
We found that only a small proportion—about 19%—of patients treated at our referral center for PJI during the study period would have been suitable candidates for single-stage exchange arthroplasty according to the International Consensus Meeting criteria . To our knowledge, no studies have what percentage of patients actually meet these criteria for single-stage exchange arthroplasty, and our suspicion that a very low number of patients actually meet these criteria was confirmed in this study. Small studies and systematic reviews assessing the proportion of patients who experienced reinfection and functional outcomes in patients undergoing two-stage versus single-stage exchange have shown comparable reinfection risks [13, 16] and potentially improved patient-reported outcomes, reduced total cost and length of stay, and earlier functional rehabilitation [2, 5, 12, 16, 18, 26] compared with single-stage exchange. However, we found that patients who qualified for the single-stage exchange were an entirely different patient population, which makes direct comparisons between the two cohorts very difficult. To know with confidence whether single or two-stage exchange is superior, one would need a randomized trial. Nonetheless, single-stage exchange may indeed have clinical and financial benefits, however, until further research clarifies the subject, we urge orthopaedic surgeons to adhere to the published inclusion criteria before considering broadening their indications for single-stage exchange.
With the numbers available, we found no differences in the risk of persistent infection or reinfection between those patients who would have met the International Consensus Meeting criteria  and those who would not have met the criteria. The data in this study support the use of single-stage exchange in the appropriately selected patient, as we found no difference in the proportion of patients who experienced reinfection. There are potential benefits to single-stage exchange, namely that if successful, it allows the patient to avoid a second operation, is less expensive, and it permits patients to have improved pain and function immediately after a single procedure. However, we emphasize that we expected to see a much lower reinfection risk in those who qualified for single-stage exchange, given that they were the most physiologically robust group. Had these patients actually undergone single-stage exchange, we may have seen a higher proportion of patients experiencing reinfection. Thus, we suggest that surgeons use caution in interpreting both our data and previous studies, given the small numbers. We will only know the answer with confidence if one or more large, randomized trials are performed to compare patients who are appropriate for single-stage exchange to receive either single- or two-stage exchange. We are aware of two such trials that are in progress now [4, 22].
In conclusion, we found only a small proportion of patients who present with chronic PJI to a referral center would have been suitable for single-stage direct exchange; with the numbers available, we found no difference in the reinfection risk after two-stage revision in those patients compared with those who would not have met those criteria. As a result, it is possible that a small proportion of patients may benefit from single-stage exchange, but our small sample size may have missed important differences in reinfection risk, and so our findings on that question must be considered preliminary. To answer these questions we will need large, randomized trials comparing single- with two-stage exchange in patients who are good candidates for the former procedure. We hope that two ongoing randomized clinical trials [4, 22] will clarify this topic in the near future.
1. Abdel MP, Barreira P, Battenberg A, Berry DJ, Blevins K, Font-Vizcarra L, Frommelt L, Goswami K, Greiner J, Janz V, Kendoff DO, Limberg AK, Manrique J, Moretti B, Murylev V, O'Byrne J, Petrie MJ, Porteous A, Saleri S, Sandiford NA, Sharma V, Shubnyakov I, Sporer S, Squire MW, Stockley I, Tibbo ME, Turgeon T, Varshneya A, Wellman S, Zahar A. Hip and Knee Section, Treatment, Two-Stage Exchange Spacer-Related: Proceedings of International Consensus on Orthopedic Infections. J Arthroplasty. 2019;34:S427-S438.
2. Bialecki J, Bucsi L, Fernando N, Foguet P, Guo S, Haddad F, Hansen E, Janvari K, Jones S, Keogh P, McHale S, Molloy R, Mont MA, Morgan-Jones R, Ohlmeier M, Saldana A, Sodhi N, Toms A, Walker R, Zahar A. Hip and Knee Section, Treatment, One Stage Exchange: Proceedings of International Consensus on Orthopedic Infections. J Arthroplasty. 2019;34:S421-s426.
3. Bori G, Navarro G, Morata L, Fernández-Valencia JA, Soriano A, Gallart X. Preliminary results after changing from two-stage to one-stage revision arthroplasty protocol using cementless arthroplasty for chronic infected hip replacements. J Arthroplasty. 2018;33:527-532.
4. Fehring TK. One stage versus two stage for periprosthetichip and knee infection. Clinical-Trials.Gov identifier: NCT02734134. https://clinicaltrials.gov/ct2/show/NCT02734134
. Updated October 3, 2019. Accessed January 1, 2020.
5. Gehrke T, Zahar A, Kendoff D. One-stage exchange: it all began here. Bone Joint J. 2013;95-:77-83.
6. George DA, Haddad FS. One-stage exchange arthroplasty: a surgical technique update. J Arthroplasty. 2017;32:S59-S62.
7. George DA, Konan S, Haddad FS. Single-stage hip and knee exchange for periprosthetic joint infection. J Arthroplasty. 2015;30:2264-2270.
8. George J, Miller EM, Curtis GL, Klika AK, Barsoum WK, Mont MA, Higuera CA. Success of two-stage reimplantation in patients requiring an interim spacer exchange. J Arthroplasty. 2018;33:S228-S232.
9. Gulhane S, Vanhegan IS, Haddad FS. Single stage revision: Regaining momentum. J Bone Joint Surg Br. 2012;94:120-122.
10. Haddad FS, Sukeik M, Alazzawi S. Is single-stage revision according to a strict protocol effective in treatment of chronic knee arthroplasty infections? Clin Orthop Relat Res. 2015;473:8-14.
11. Ji B, Wahafu T, Li G, Zhang X, Wang Y, Momin M, Cao L. Single-stage treatment of chronically infected total hip arthroplasty with cementless reconstruction: results in 126 patients with broad inclusion criteria. Bone Joint J. 2019;101:396-402.
12. Klouche S, Sariali E, Mamoudy P. Total hip arthroplasty revision due to infection: A cost analysis approach. Orthop Traumatol Surg Res. 2010;96:124-132.
13. Leonard HAC, Liddle AD, Burke Ó, Murray DW, Pandit H. Single- or two-stage revision for infected total hip arthroplasty? A systematic review of the literature. Clin Orthop Relat Res. 2014;472:1036-1042.
14. Lichstein P, Gehrke T, Lombardi A, Romano C, Stockley I, Babis G, Bialecki J, Bucsi L, Cai X, Cao L, de Beaubien B, Erhardt J, Goodman S, Jiranek W, Keogh P, Lewallen D, Manner P, Marczynski W, Mason JB, Mulhall K, Paprosky W, Patel P, Piccaluga F, Polkowski G, Pulido L, Stockley I, Suarez J, Thorey F, Tikhilov R, Velazquez JD, Winkler H. One-stage versus two-stage exchange. J Orthop Res. 2014;(32 Suppl 1):S141-146.
15. Lichstein P, Gehrke T, Lombardi A, Romano C, Stockley I, Babis G, Bialecki J, Bucsi L, Cai X, Cao L, de Beaubien B, Erhardt J, Goodman S, Jiranek W, Keogh P, Lewallen D, Manner P, Marczynski W, Mason JB, Mulhall K, Paprosky W, Patel P, Piccaluga F, Polkowski G, Pulido L, Stockley I, Suarez J, Thorey F, Tikhilov R, Velazquez JD, Winkler H. One-stage vs two-stage exchange. J Arthroplasty. 2014;29:108-111.
16. Nagra NS, Hamilton TW, Ganatra S, Murray DW, Pandit H. One-stage versus two-stage exchange arthroplasty for infected total knee arthroplasty: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2016;24:3106-3114.
17. Osmon DR, Berbari EF, Berendt AR, Lew D, Zimmerli W, Steckelberg JM, Rao N, Hanssen A, Wilson WR, Infectious Diseases Society of America. Diagnosis and management of prosthetic joint infection: clinical practice guidelines by the Infectious Diseases Society of America. Clin Infect Dis. 2013;56:e1-e25.
18. Oussedik SIS, Dodd MB, Haddad FS. Outcomes of revision total hip replacement for infection after grading according to a standard protocol. J Bone Joint Surg Br. 2010;92:1222-1226.
19. Parvizi J, Gehrke T, Chen AF. Proceedings of the International Consensus on Periprosthetic Joint Infection. Bone Joint J. 2013;95:1450-1452.
20. Parvizi J, Gehrke T, International Consensus Group on Periprosthetic Joint I. Definition of periprosthetic joint infection. J Arthroplasty. 2014;29:1331.
21. Petis SM, Perry KI, Mabry TM, Hanssen AD, Berry DJ, Abdel MP. Two-stage exchange protocol for periprosthetic joint infection following total knee arthroplasty in 245 knees without prior treatment for infection. J Bone Joint Surg Am. 2019;101:239-249.
22. Strange S, Whitehouse MR, Beswick AD, Board T, Burston A, Burston B, Carroll FE, Dieppe P, Garfield K, Gooberman-Hill R, Jones S, Kunutsor S, Lane A, Lenguerrand E, MacGowan A, Moore A, Noble S, Simon J, Stockley I, Taylor AH, Toms A, Webb J, Whittaker JP, Wilson M, Wylde V, Blom AW. One-stage or two-stage revision surgery for prosthetic hip joint infection - the INFORM trial: A study protocol for a randomised controlled trial. Trials. 2016;17:90.
23. Thakrar RR, Horriat S, Kayani B, Haddad FS. Indications for a single-stage exchange arthroplasty for chronic prosthetic joint infection: a systematic review. Bone Joint J. 2019;101:19-24.
24. Tibrewal S, Malagelada F, Jeyaseelan L, Posch F, Scott G. Single-stage revision for the infected total knee replacement: Results from a single centre. Bone Joint J. 2014;96:759-764.
25. Vadiee I, Backstein DJ. The effectiveness of repeat two-stage revision for the treatment of recalcitrant total knee arthroplasty infection. J Arthroplasty. 2019;34:369-374.
26. Wolf CF, Gu NY, Doctor JN, Manner PA, Leopold SS. Comparison of one and two-stage revision of total hip arthroplasty complicated by infection a markov expected-utility decision analysis. J Bone Joint Surg Am. 2011;93:631-639.
27. Zahar A, Gehrke TA. One-stage revision for infected total hip arthroplasty. Orthop Clin North Am. 2016;47:11-18.
28. Zmistowski B, Pourjafari A, Padegimas EM, Sheth M, Cox RM, Ramsey ML, Horneff JG 3rd, Namdari S. Treatment of periprosthetic joint infection of the elbow: 15-year experience at a single institution. J Shoulder Elbow Surg. 2018;27:1636-1641.