OrthoBuzz occasionally receives posts from guest bloggers. This guest post comes from Grigory Gershkovich, MD.
Shoulder arthroplasty continues to grow in popularity, and as the number of shoulder arthroplasties rises, so will the number of revisions. Infection is one major reason for shoulder arthroplasty failure, and Propionibacterium has been increasingly recognized as a major culprit.
However, Propionibacterium infection is difficult to diagnose. Despite improved detection techniques, diagnosis at the time of revision remains elusive because obvious signs of acute infection are often absent. The need to perform explantation in the setting of clinically apparent periprosthetic infection is obvious, but the appropriateness of single-stage revision with antibiotic treatment in shoulders with only apparent mechanical failures remains questionable.
Hsu et al. attempted to address this question in a study published in the December 21, 2016 issue of JBJS. The group retrospectively reviewed the outcomes of 55 shoulders that underwent revision arthroplasty due to continued pain, stiffness, or component loosening without obvious clinical infection. Mean follow up was 48 months. At least five cultures were obtained intraoperatively during each revision, and each case was treated with antibiotics as if were truly infected until the final culture results were received after three weeks. Shoulders were revised to either hemi-arthroplasty, total shoulder arthroplasty, or reverse total shoulder arthroplasty.
Hsu et al. analyzed outcomes according to two groups: the positive cohort (n=27), where shoulders had ≥ 2 cultures positive for Propionibacterium, and the control cohort (n=28), where shoulders had either 0 or 1 positive culture. The two groups were compared by before- and after-revision performance on the simple shoulder test (SST) and pain outcome scores.
Both groups improved postoperatively based on these patient-reported outcome measures, and no significant difference was found between the two groups. Three patients in each group required a return to the OR. Gastrointestinal side effects were the most commonly reported complication from prolonged antibiotic administration.
This study design was limited by its retrospective nature and the lack of a two-stage revision treatment comparison group. Furthermore, this study included only patients with no signs of clinical infection, and the findings may not be applicable to patients with perioperative signs of infection. The study also incorporated three revision surgery implant options, which could have influenced postoperative SST and pain scores. Larger, multicenter controlled trials will be needed to produce a more definitive answer to this complicated question.
Still, there are clear benefits of single-stage revision over two-stage revision, especially with regard to operative time, anesthesia risks, and patient recovery. Given the wide antibiotic sensitivity profile of Propionibacterium and these initial results from Hsu et al., single-stage revision with appropriate antibiotic therapy may be suitable for patients undergoing revision shoulder arthroplasty in the setting of suspected Propionibacterium infection.
Grigory Gershkovich, MD is chief resident at Albert Einstein Medical Center in Philadelphia. He will complete a hand fellowship at the University of Chicago in 2017-2018.
Of the hundreds of thousands of total knee arthroplasties (TKAs) performed annually around the world, very few result in failure so irreparable that transfemoral amputation is the last resort. But what does “very few” really mean? In the December 7, 2016 issue of The Journal of Bone & Joint Surgery, Gottfriedsen et al. determine the cumulative incidence of amputation for failed TKAs among nearly 93,000 registered knee replacements performed in Denmark from 1997 to 2013.
The authors used a competing-risk model (which took into account the competing risk of death) to avoid overestimating incidence. From a total of 115 amputations performed for causes related to failed TKA, they calculated a cumulative 15-year incidence of amputation of 0.32%. They noted a tendency toward decreasing incidence during the 2008-2013 period, relative to the 1997-2002 period.
The three most common causes of post-TKA amputation were periprosthetic infection (83%), soft-tissue deficiency (23%), and severe bone loss (18%). The authors add, however, that the latter two causes are “most likely the result of long-term infection together with several revision procedures, in which soft tissue and bone stock are gradually damaged.”
The authors encourage orthopaedists to consider newer treatment options to avoid amputation (such as skin grafts and muscle flaps for soft-tissue loss), but they also assert that, in each individual case, those contemporary approaches should be balanced against the “psychological and physical strains related to repeated surgery performed in an attempt to salvage the knee.”
Propionibacterium acnes is a frequently isolated pathogen in postoperative shoulder infections, but where exactly does it come from? According to a study by Falconer et al. in the October 19, 2016 Journal of Bone & Joint Surgery, P. acnes derives from the subdermal edges of the surgical incision and spreads through contact with the surgeon’s gloves and surgical instruments.
The authors obtained specimens for microbiological analysis at five different sites from 40 patients undergoing primary shoulder arthroplasty. Thirty-three percent of the patients had at least one culture specimen positive for P. acnes, and the most common site of P. acnes growth was the subdermal layer, followed by forceps.
The authors observed no clinical postoperative infections during the follow-up of 6 to 18 months, although that is a relatively short investigation period for a pathogen that often causes late-onset indolent infections. The authors conclude that “it is likely that surgeon handling of the skin and subdermal layer contaminates the rest of the surgical field.” Although the study did not investigate preventive techniques, based on the findings the authors suggest the following possible prophylactic approaches:
- Minimizing handling of the subdermal layer
- Changing gloves after the dermis is cut
- Avoiding contact between implants and the subdermal layer
- Repeating use of antibacterial agents once the wound is opened
Injuries to the musculoskeletal system are among the most common wounds of war. Compared with extremity injuries in the civilian population, injuries sustained in combat tend to be due to high-energy explosions and are associated with a greater degree of contamination and a longer timeline for recovery and healing. Importantly, the sequelae of musculoskeletal injuries sustained during combat tend to lead to more long-term disability than those affecting other organ systems.
In this month’s Editor’s Choice article, Rivera et al. review the current literature on combat injuries of the lower extremity and suggest that explosions are the most common mechanism of injury encountered by deployed service members. While exposure to an explosion does not necessarily result in a specific limb injury, the explosion mechanism does contribute to more severe injuries. Moreover, among service members who sustain open fractures of the tibia, foot, and ankle, infection is a common complication and is associated with more severe soft-tissue injury. As a result, surgeons who are deployed in combat settings are now performing more fasciotomies for limbs that are at risk. However, the outcomes and complication rates associated with these procedures are not well established, and the causes of late amputations are not always clear.
As part of a comprehensive review of this topic, Rivera et al. pose 3 important clinical questions that are ideal for translational research investigation. First, they ask, “What is the best way to manage and transport patients who have severe open fractures in order to minimize infection?” Indeed, while negative-pressure wound therapy (NPWT) appears to be a promising wound-care technique, additional study is needed in order to know how to best augment the standard of care for battlefield medicine. Second, “What is the best way to treat fasciotomy wounds and the late sequelae of the compartment syndrome?” In order to answer this question, a broader understanding of compartment syndrome detection and the indications for surgical treatment are needed. Finally, “What is the best way to select limbs for salvage and to optimize the reconstruction of injured tissues?” This question must explore not only the patient’s perspective but also the multitude of causes that lead to late amputation.
Thomas A. Einhorn, MD
Editor, JBJS Reviews
The incidence of primary total knee and hip arthroplasty is increasing steadily. While the success rates of these procedures are remarkable, failures do occur, and periprosthetic joint infection is the leading culprit in such failures. The standard treatment when deep infection strikes is a two-stage revision.
On Monday, November 14, 2016 at 8:00 PM EST, The Journal of Bone & Joint Surgery (JBJS) will host a complimentary webinar that examines prognostic factors affecting the success of two-stage revision arthroplasty for infected knees and hips.
- Tad M. Mabry, MD, coauthor of a matched cohort study in JBJS, will examine the impact of morbid obesity on the failure of two-stage revision TKA.
- JBJS author Antonia F. Chen, MD, will discuss results from a retrospective study that revealed an association between positive cultures at the time of knee/hip component reimplantation and the risk of subsequent treatment failure.
Moderated by JBJS Deputy Editor Charles R. Clark, MD, the webinar will include additional perspectives from two expert commentators—Daniel J. Berry, MD and Andrew A. Freiberg, MD. The last 15 minutes will be devoted to a live Q&A session, during which the audience can ask questions of all four panelists.
Seats are limited, so register now!
Infection, whether acute, chronic, local, or systemic, is something that all surgeons respect and fear. To counter infection, tissue injury activates an acute-phase response mediated by the liver and promotes coagulation, immunity, and tissue regeneration. However, microorganisms are able to survive and disseminate throughout tissues because of virulence factors that they express. These virulence factors help to modulate and hijack the acute-phase response.
In this month’s Editor’s Choice article, An et al. discuss how an understanding of virulence strategies of musculoskeletal pathogens will help to guide clinical diagnosis and decision-making through monitoring of acute-phase markers such as C-reactive protein, the erythrocyte sedimentation rate, and fibrinogen. As pathogenic bacteria possess virulence factors that allow them to invade, persist, and disseminate within the human body, this review focuses on the pathophysiology of musculoskeletal infection and the virulence factors that enable pathogens to thrive within the context of tissue damage.
The authors demonstrate that tissue injury ruptures anatomic compartment boundaries, leading to the contamination of microenvironments that require complex physiological processes for proper temporary repair. Certain organisms, such as Staphylococcus aureus and Streptococcus pyogenes, have evolved mechanisms for evading and hijacking the hemostatic, tissue regenerative, and antimicrobial properties of the acute-phase response. Indeed, a better understanding of the virulence strategies used by pathogenic microorganisms should enhance our ability to treat infections and improve patient outcomes in the future.
Thomas A. Einhorn, MD
Editor, JBJS Reviews
Many orthopaedists order cultures of tissue and synovial fluid samples during the reimplantation phase of two-stage exchange arthroplasties. Now, thanks to a retrospective study by Tan et al. in the August 3, 2016 JBJS, surgeons have some guidance on how to interpret the results from such cultures.The authors reviewed 267 cases of periprosthetic joint infections (186 knees and 81 hips) that were treated with two-stage exchange arthroplasty. Intraoperative tissue samples were obtained at the time of reimplantation, and 33 joints (12.4%) were found to have one or more positive cultures. Of those 33 cases, 15 (45.5%) had a subsequent arthroplasty failure, compared with 49 (20.9%) of the cases that were culture-negative at reimplantation. Failure rates did not differ between cases with 1 positive culture and those with ≥ 2 positive cultures.
After controlling for other variables, the authors determined that a positive intraoperative culture at the time of reimplantation was independently associated with >2.5 times the risk of subsequent treatment failure. These findings prompted Tan et al. to conclude that “even single positive cultures…should be treated aggressively.” They report that at their institution (the Rothman Institute in Philadelphia), “any positive culture at the time of reimplantation is now considered important…and is treated with systemic antibiotics.”
Among the limitations of this study is its inability to accurately assess the impact of antibiotic treatment in patients with positive cultures. The authors also stress the need for further evaluation of rapid intraoperative diagnostic tools that have shown promise in determining infection eradication more quickly than cultures can.