Nowadays, chronic deep periprosthetic joint infections (PJIs) are typically treated with 2-stage exchange arthroplasty, but what about acute PJIs? In the December 6, 2017 edition of JBJS, Bryan et al. report on a retrospective cohort study of acute infections after hip arthroplasty. The results suggest we’ve come a long way in identifying patients with early infections and that contemporary irrigation-and-debridement protocols are more successful than older methods.
The researchers studied 6-year outcomes in 90 hips that had undergone either total or hemiarthroplasty and that were determined to have either acute early postoperative infections (n=66) or acute hematogenous infections (n=24). All the infected hips were managed with either irrigation, debridement, and modular head and liner exchange (70%) or with irrigation and debridement alone (30%). The authors stratified the patients into those without comorbidities (A), those with 1 or 2 comorbidities (B), and those with >2 comorbidities (C). Postoperatively, patients were treated with broad-spectrum intravenous antibiotics, followed by targeted therapy administered by infectious disease specialists.
Of the 90 acute infections, failure—defined as uneradicated infection, subsequent removal of any component for infection, unplanned second wound debridement for ongoing infection, or infection-related mortality—occurred in 15 hips (17%). Of those 15, 9 required component removal. The chances of treatment failure were slightly higher in cases of hematogenous infection (21%), compared with acute early postoperative infection (15%), but that difference was not statistically significant. Significant comorbidity-related failure-rate differences were found: failure occurred in 8% of the grade-A patients, 16% of grade-B patients, and 44% of grade-C patients. The most common infecting organism was methicillin-sensitive Staphylococcus aureus (MSSA).
From this overall 6-year success rate of 83%, the authors conclude that “with modern inclusion criteria for acute infection, modern surgical techniques, and modern antibiotic therapy…the rate of success was higher than in most historic reports.”
Total hip arthroplasty made its debut about 60 years ago. As with most new technologies, it was anticipated that advances and improvements would occur. However, the improvements have been incremental and in some cases have led to problems, particularly with regard to interchangeable parts, modularity, and the materials used for articulating surfaces. Some still believe that total hip arthroplasty was close to being optimized at the time that it was introduced.
Some may view these comments as somewhat provocative, but I would not be surprised if a lot of surgeons agree. The issue of trunnion wear is one example of these problems. One of the main contributing factors is the fact that each implant manufacturer uses tapers with their own specifications, which vary in terms of angle, diameter, straightness, roundness, and surface properties. Therefore, most femoral neck implant tapers are not necessarily compatible with each other. It is important to note that femoral heads should not be used interchangeably between designs as the cone angle may differ. ?If this is done, trunnionosis will be a likely outcome.
In the August 2016 issue of JBJS Reviews, Lanting et al. provide an important and very worthwhile discussion of the risk factors for trunnionosis. Trunnionosis may be enabled by the disruption of the protective oxidative layer on the metal by fretting, potentiating the corrosion of the exposed metal beneath the oxidative layer through an active combination of biochemical and electrochemical processes. Time in vivo consistently has been shown to be a risk factor for trunnionosis. Flexural rigidity of the trunnion has been demonstrated to have an important role in the development of trunnionosis. A flexible trunnion may allow fretting as well as point loading. Edge loading is known to make tribocorrosion more likely to occur. In the presence of any degree of angular mismatch, the effect of trunnionosis may be increased.
The role of design and manufacturing variables in the development of trunnion problems continues to be debated. Surgeon-related factors, especially the greater variability and taper assembly with smaller-incision surgery, also may contribute to this phenomenon. Patients presenting with unexplained pain who have modular neck-body implants should be considered to have an adverse local tissue reaction resulting from corrosion of the neck-stem interface as potential cause of the pain.
In most cases, I suspect that removal of the femoral head, cleaning of the taper, and replacement with a different femoral head (usually a ceramic head with a titanium adapter sleeve) represents adequate treatment based on care recommendations. In contrast, in cases involving adverse local tissue reactions associated with the modular neck designs, removal of the modular stem and neck may be required.
Thomas A. Einhorn, MD
Editor, JBJS Reviews
Heterotopic ossification (HO) is a known complication of hip arthroplasty. A double-blind, randomized, placebo-controlled trial by Beckmann et al. in the December 16, 2015 Journal of Bone & Joint Surgery showed that prophylaxis with naproxen dramatically reduced the prevalence of HO after hip arthroscopy, without serious medication-related side effects. These findings bolster findings from previous retrospective investigations that showed large reductions in HO prevalence among those taking nonsteroidal anti-inflammatory drugs (NSAIDs).
The patients in the study took naproxen (500 mg) or a placebo twice a day for three weeks following arthroscopic surgery for femoroacetabular impingement. After one year, the prevalence of radiographically determined HO in patients randomized to the naproxen group was 4% versus 46% in the patients randomized to the placebo group, an 11-fold difference. While the potential for serious GI and renal side effects with NSAIDs is well-documented, in this study only minor adverse reactions to study medication were reported in 42% of those taking naproxen and in 35% of those taking placebo.
Noting that the clinical consequences of HO following hip arthroscopy are “largely undetermined,” the authors still suggest a role for HO prophylaxis “because it could reduce the risk of developing symptomatic HO or requiring revision surgery for HO excision.”
In an accompanying commentary, Sverre Loken praises the authors for the well-designed study, but he cautions that “clinically relevant HO is uncommon, and this has to be weighed against the risk of serious side effects caused by NSAIDs.” He also emphasizes the observation Beckmann et al. make in the last paragraph of their study: that “the lowest dose and shortest duration of NSAID prophylaxis that still prevent HO remain to be determined.”