Orthopaedic Knowledge Update®: Musculoskeletal Infection 2 Print + Ebook (AAOS - American Academy of Orthopaedic Surgeons)

Chapter 16: Surgical Treatment of Hip and Knee Prosthetic Joint Infections

Spacer complications do occur. A 2019 study reported that, in a group of patients with varying types of hip spac ers, 48 of 185 patients (26%) were reported to have spacer complications. 34 Dislocation occurred in 17 patients (9%) and was associated with reduced femoral offset of greater than 5 mm and increased bone loss. Spacer fracture occurred in 14 of 185 patients (8%), 12% (12 of 97 patients) of molded versus 8% (2 of 23 patients) of handmade spacers. Periprosthetic fracture was associated with the use of an extended trochanteric osteotomy and increased offset greater than 5 mm. Stage Two Most patients receive 4 to 6 weeks of intravenous antibiotics after resection of the infected prosthesis. Reimplantation is delayed until the soft tissues have healed and the infection is treated. As of 2019, there was no consensus on the timing of reimplantation, 35 with some surgeons opting for a 2- to 6-week antibiotics holiday. The rationale for this is to allow for the emer gence of persistent infection before reimplantation. The 2018 ICM guidelines report limited evidence to support the use of an antibiotic holiday before reimplantation. 36 Although the Musculoskeletal Infection Society (MSIS) guidelines are very helpful in diagnosing PJI, they are not useful in the determination of persistent infection before reimplantation. 37 Serum erythrocyte sedimentation rate and C-reactive protein level are com monly assessed; however, they have a low sensitivity in this setting. 38 Declining serum erythrocyte sedimentation rate and C-reactive protein level are inferred to indicate appropriate response to treatment of the infection, 36 although this no association was shown with risk for reinfection. 39,40 Therefore, surgeons do not need to wait for these markers to normalize before reimplantation. 36 Synovial fluid analysis, reported in 2022, has also vary ing results, with white blood cell count and polymor phonuclear leukocyte percentage demonstrating high specificity (95%) and poor sensitivity (21%) in predicting persistent infection. 41 The synovial biomarker alpha- defensin has also shown poor sensitivity (7%) and poor overall accuracy (73%; area under the curve = 0.5) in detecting infection control with spacers. 42,43 Frozen sec tion and leukocyte esterase are two intraoperative metrics that are available. The utility of frozen section during the second-stage surgery has been debated. Original studies demonstrated that frozen section correlated with stan dard histology and had sensitivity, specificity, positive predictive value, and negative predictive values of 25%, 98%, 50%, and 95%, respectively. 44,45 Another analysis demonstrated the five neutrophils per high-power field method to have a high specificity (98%) and positive predictive value but a low sensitivity (28%). 46 Therefore, the test has limited benefit in this setting. Leukocyte

esterase is an appealing test as it is both quickly attain able intraoperatively and inexpensive. This test showed promising results in 2022, with a sensitivity, specificity, positive predictive value, and negative predictive value

of 82%, 99%, 90%, and 97%, respectively. 47 Outcomes Following Two-Stage Revision

Outcomes following two-stage revision arthroplasty as treatment for chronic PJI can be very successful. Several studies report 90% treatment success at 2-year follow-up and 80% to 90% at 5- to 10-year follow-up. 48 However, reports are highly variable and need to be taken in the context of the individual treatment protocols and defi nition of success. 49 A 2019 publication from the MSIS workgroup details tiers of outcomes to better differen tiate in the literature: (1) infection control with no con tinued antibiotics, (2) infection control with continued antibiotics, (3) need for revision surgery (with subgroups based on the type of surgical procedure), and (4) death (due to infection or not). 50 Many preoperative factors are associated with treat ment failure. A review of 108 two-stage revision TKAs for infection with 16 treatment failures analyzed 31 risk factors to identify associations with treatment failure. 48 Overall treatment success was 91% at 2 years, and mul tivariate analysis revealed four potential risk factors that may predict treatment failure: body mass index of 30 kg/m 2 or greater, surgical time greater than 4 hours, gout, and the presence of Enterococcus species during resection arthroplasty. Other studies demonstrated that body mass index greater than 40 kg/m 2 is associated with three- to fivefold increase in reinfection, revision, and reoperation rates. 51,52 Similar to all PJI treatment strategies, a two-stage revision also has a higher failure rate when infection with antibiotic-resistant organisms occurs. In 37 patients with PJI due to resistant organisms, 9 (24%) experienced reinfection, but only 4 (14%) were infected with the original organism. 53

Section 4: Prosthetic Joint Infections

One relative indication for two-stage revision for PJI is a previous failed surgery for infection, and this con tinues to be researched. In a retrospective review of 45 patients who have undergone two or more two-stage revision TKA for PJI, failure rates were compared using a PJI grading system 54 that accounts for host grade and extremity compromising factors. 55 Uncompromised hosts (MSIS type A) with an acceptable wound (MSIS type 1 or 2) had treatment success with 7 of 10 hosts, whereas type B2 hosts had success with 10 of 20, and type C3 had no treatment success with 2 hosts. This illustrates the importance of host factors in the treatment of PJI, and salvage strategies should be considered for those more compromised hosts that have a high likelihood for failure. Another study reported poor outcomes following a second attempt at two-stage treatment for recurrent PJI. Copyright © Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. 2023

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Orthopaedic Knowledge Update ® : Musculoskeletal Infection 2