Michael M. Kheir

Are There Identifiable Risk Factors and Causes Associated with Unplanned Readmissions Following Total Knee Arthroplasty

We conducted a retrospective review of 3218 primary total knee arthroplasties (TKA) performed over two years at an urban academic hospital network using clinical and administrative data. Increased length of stay (LOS) was associated with readmission (P < 0.001). Readmission was not associated with age (P = 0.100), gender (P = 0.608), body mass index (P = 0.329), or staged bilateral procedures (P = 0.420). The most common readmitting diagnoses were post-operative infection (22.5%), hematoma (10.1%), pulmonary embolus (7.9%) and deep vein thrombosis (5.6%). Of readmissions, 53.9% were for surgical reasons and 46.1% were for medical reasons. Certain interventions described in previous literature may be more successful in minimizing unplanned readmissions by focusing on patients with extended LOS, elevated infection risk and low socioeconomic status.

Novel Effect of Berberine on Thermoregulation in Mice Model Induced by Hot and Cold Environmental Stimulation

The purpose of this study was to assess the effects of berberine (BBR) on thermoregulation in mice exposed to hot (40°C) and cold (4°C) environmental conditions. Four groups of mice were assembled with three different dosages of BBR (0.2, 0.4, and 0.8 mg/kg) and normal saline (control). In room temperature, our largest dosage of BBR (0.8 mg/kg) can reduce rectal temperatures (Tc) of normal mice. In hot conditions, BBR can antagonize the increasing core body temperature and inhibit the expression of HSP70 and TNFα in mice; conversely, in cold conditions, BBR can antagonize the decreasing core body temperature and enhance the expression of TRPM8. This study demonstrates the dual ability of BBR in maintaining thermal balance, which is of great relevance to the regulation of HSP70, TNFα and TRPM8.

Patients With Failed Prior Two-Stage Exchange Have Poor Outcomes After Further Surgical Intervention

BACKGROUND Failure of 2-stage exchange arthroplasty for the management of periprosthetic joint infection (PJI) poses a major clinical challenge. There is a paucity of information regarding the outcomes of further surgical intervention in these patients. Thus, we aim to report the clinical outcomes of subsequent surgery for a failed prior 2-stage exchange arthroplasty. METHODS Our institutional database was used to identify 60 patients (42 knees and 18 hips), with a failed prior 2-stage exchange, who underwent further surgical intervention between 1998 and 2012, and had a minimum 2-year follow-up. A retrospective review was performed to extract relevant clinical information, including mortality, microbiology, and subsequent surgeries. Musculoskeletal Infection Society criteria were used to define PJI, and treatment success was defined using Delphi criteria. RESULTS Irrigation and debridement (I&D) was performed after a failed 2-stage exchange in 61.7% of patients; 56.8% subsequently failed. Forty patients underwent an intended second 2-stage exchange; 6 cases required a spacer exchange. Reimplantation occurred only in 65% of cases, and 61.6% had infection controlled. The 14 cases that were not reimplanted resulted in 6 retained spacers, 5 amputations, 2 PJI-related mortalities, and 1 arthrodesis. CONCLUSION Further surgical intervention after a failed prior 2-stage exchange arthroplasty has poor outcomes. Although I&D has a high failure rate, many patients who are deemed candidates for a second 2-stage exchange either do not undergo reimplantation or fail after reimplantation. The management of PJI clearly remains imperfect, and there is a dire need for further innovations that may improve the care of these patients.

Direct anterior approach: Risk factor for early femoral failure of cementless total hip arthroplasty a multicenter study

Background: The direct anterior approach for total hip arthroplasty (THA) is marketed with claims of superiority over other approaches. Femoral exposure can be technically challenging and potentially lead to early failure. We examined whether surgical approach is associated with early THA failure. Methods: A retrospective review of 478 consecutive early revision THAs performed within 5 years after the primary THAs at 3 academic centers from 2011 through 2014 was carried out. Exclusion criteria resulted in a final analysis sample of 342 early-failure THAs. The surgical approach of the primary operation that was revised, the time to the revision, and the etiology of the failure leading to the revision were documented. Results: Analysis of the revisions due to early femoral failure showed them to be more common in patients who had undergone the direct anterior approach (57/112; 50.9%) than in those treated with the direct lateral (39/112; 34.8%) or the posterior (16/112; 14.3%) approach (p = 0.001). In multivariate regression analysis controlling for age, sex, laterality, Dorr bone type, body mass index (BMI) at revision, bilateral procedure (yes/no), and femoral stem type, the direct anterior approach remained a significant predictor of early femoral failure (p = 0.007). The majority of early revisions due to instability were associated with the posterior (19/40; 47.5%) or direct anterior (15/40; 37.5%) approach (p = 0.001 for the comparison with the direct lateral approach [6/40; 15.0%]). Conclusions: Despite claims of earlier recovery and improved outcomes with the direct anterior approach for THA, our findings indicate that that approach may confer a greater risk of early femoral failure and, along with the posterior approach, confer a greater risk of early instability compared with the direct lateral approach. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Diagnosing Periprosthetic Joint Infection: And the Winner Is?

BACKGROUND Diagnosis of periprosthetic joint infection (PJI) remains a challenge despite a wide variety of available diagnostic tests. The question that arises is which of these tests has a better performance for diagnosing PJI. Diagnostic odds ratio (DOR) has been described as the best indicator for test performance. METHODS To compare the performance of the standard diagnostic tests, the DOR of serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), synovial fluid (SF) white blood cell (WBC) count, SF polymorphonuclear (PMN%), and leukocyte esterase (LE) were calculated. RESULTS We obtained 4662 ESRs, 4392 CRPs, 836 SF WBC, 804 SF PMN%, and 659 LE results. LE had the highest DOR for diagnosing PJI: 30.06 (95% confidence interval [CI]: 17.8-50.7). The rest of the DORs in the descending order were SF WBC: 29.4 (95% CI: 20.2-42.8), CRP: 25.6 (95% CI: 19.5-33.7), SF PMN%: 25.5 (95% CI: 17.5-37.0), and ESR: 14.6 (95% CI: 11.5-18.6). CONCLUSION Based on our findings, it appears that among the minor diagnostic criteria, LE has the best performance.

Polymicrobial Periprosthetic Joint Infections: Outcome of Treatment and Identification of Risk Factors.

BACKGROUND The treatment outcomes of periprosthetic joint infection are frequently dependent on characteristics of the causative organism. The objective of this comparative study was to investigate the prevalence of and risk factors for development of polymicrobial periprosthetic joint infection, and the outcome of surgical treatment of these patients. METHODS All patients with polymicrobial, monomicrobial, or culture-negative periprosthetic joint infection treated from 2000 to 2014 were identified at a single institution. Ninety-five patients with a polymicrobial periprosthetic joint infection had a minimum follow-up of 12 months. We matched patients with a polymicrobial periprosthetic joint infection with the other cohorts using propensity score matching for several important parameters. Treatment success was defined according to the Delphi criteria; Kaplan-Meier survivorship curves were generated to demonstrate this. A multiple logistic regression analysis was performed to determine risk factors for a polymicrobial periprosthetic joint infection. RESULTS Overall, 10.3% (108 of 1,045) of the periprosthetic joint infections treated at our institution were polymicrobial in nature. Patients with a polymicrobial periprosthetic joint infection had a higher failure rate at 50.5% (48 of 95) compared with the monomicrobial periprosthetic joint infection cohort at 31.5% (63 of 200) and the culture-negative periprosthetic joint infection cohort at 30.2% (48 of 159) (p = 0.003). The survivorship of the polymicrobial periprosthetic joint infection group was 52.2% at the 2-year follow-up, 49.3% at the 5-year follow-up, and 46.8% at the 10-year follow-up. Patients with polymicrobial periprosthetic joint infection had a higher rate of amputation (odds ratio [OR], 3.80 [95% confidence interval (CI), 1.34 to 10.80]), arthrodesis (OR, 11.06 [95% CI, 1.27 to 96.00]), and periprosthetic joint infection-related mortality (OR, 7.88 [95% CI, 1.60 to 38.67]) compared with patients with monomicrobial periprosthetic joint infection. Isolation of gram-negative organisms (p < 0.01), enterococci (p < 0.01), Escherichia coli (p < 0.01), and atypical organisms (p < 0.01) was associated with polymicrobial periprosthetic joint infection. Only the presence of a sinus tract (OR, 2.20 [95% CI, 1.39 to 3.47]; p = 0.001) was a significant risk factor for polymicrobial periprosthetic joint infection on multivariate analysis. CONCLUSIONS This study reveals that polymicrobial periprosthetic joint infection, occurring at a relatively low rate, is associated with poor outcomes when compared with monomicrobial and culture-negative periprosthetic joint infection. Patients with polymicrobial infections were more likely to require a salvage procedure or to have periprosthetic joint infection-related mortality. Polymicrobial periprosthetic joint infection was associated with soft-tissue defects such as a sinus tract and certain types of organisms, which should be considered when administering antibiotics to these patients. LEVEL OF EVIDENCE Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Aspirin provides adequate VTE prophylaxis for patients undergoing hip preservation surgery, including periacetabular osteotomy

Abstract There are no clear guidelines regarding optimal venous thromboembolism (VTE) prophylaxis for patients undergoing hip preservation surgery (HPS), in particular pelvic osteotomy, which is considered to be a major orthopaedic procedure. The aim of this study was to determine the efficacy of aspirin for VTE prophylaxis in a large cohort of patients undergoing femoroacetabular osteoplasty (FAO) and periacetabular osteotomy (PAO). This was a retrospective study of prospectively collected data on patients undergoing HPS. A total of 603 patients (643 cases) underwent FAO and 80 patients (87 cases) underwent PAO between 2003 and 2016. The mean age of patients was 34.3 years (range 14.3–68.1 years). The type of VTE prophylaxis administered changed over time with earlier patients receiving warfarin (44 cases), followed by aspirin at 325 mg twice daily (448 cases), and most recently aspirin 81 mg twice daily (238 cases). The complications of symptomatic pulmonary embolism (PE), deep venous thrombosis (DVT) and major bleeding events within 90 days of surgery were documented. There were zero patients that developed major bleeding events or required evacuation of a hematoma. One patient who underwent FAO and received aspirin 325 mg, developed post-operative symptomatic DVT. One patient who underwent PAO and received aspirin 325 mg developed DVT and PE. This study demonstrates that the incidence of VTE following joint preservation procedure is acceptably low. Administration of aspirin to patients undergoing FAO or PAO appears to be adequate in reducing the risk of VTE. Only two patients in this cohort developed VTE following HPS.

The Alpha-Defensin Test for Diagnosing Periprosthetic Joint Infection in the Setting of an Adverse Local Tissue Reaction Secondary to a Failed Metal-on-Metal Bearing or Corrosion at the Head-Neck Junction.

BACKGROUND In patients with adverse local tissue reaction (ALTR) secondary to a failed metal-on-metal (MoM) bearing or corrosion at the head-neck junction in a metal-on-polyethylene bearing, ruling in or out periprosthetic joint infection (PJI) can be challenging. Alpha-defensin has emerged as an accurate test for PJI. The purpose of this multicenter, retrospective study was to evaluate the accuracy of the alpha-defensin synovial fluid test in detecting PJI in patients with ALTR. METHODS We reviewed medical records of 26 patients from 3 centers with ALTR that had an alpha-defensin test performed. Patients were assessed for PJI using the Musculoskeletal Infection Society criteria. Thirteen of these subjects had MoM total hip arthroplasty, 9 had ALTR secondary to head-neck corrosion, and 4 had MoM hip resurfacing. RESULTS Only 1 of the 26 patients met Musculoskeletal Infection Society criteria for infection. However, 9 hips were alpha-defensin positive, including 1 true positive and 8 that were falsely positive (31%). All 8 of the false positives were also Synovasure positive, although 5 of 8 had an accompanying warning stating the results may be falsely positive due to a low synovial C-reactive protein value. CONCLUSION Similar to synovial fluid white blood cell count, alpha-defensin testing is prone to false-positive results in the setting of ALTR. Therefore, we recommend an aggressive approach to ruling out PJI including routine aspiration of all hips with ALTR before revision surgery to integrate the synovial fluid blood cell count, differential, cultures and adjunctive tests like alpha-defensin to allow for accurate diagnosis preoperatively.

Determining the Role and Duration of the “Antibiotic Holiday” Period in Periprosthetic Joint Infection

BACKGROUND Two-stage exchange arthroplasty involves resection and reimplantation of new implants at a later stage. An antibiotic-free period is often advocated by surgeons before reimplantation. However, there is no conclusive evidence supporting the utility or duration of this practice. This study evaluated the utility and optimal duration of the antibiotic-free period before reimplantation. METHODS Electronic infection databases of 2 institutions were retrospectively reviewed from 2000 to 2014 to identify 785 patients who underwent 2-stage exchange arthroplasty, of which 409 were reimplanted without any surgeries between the first and second stage. Total joint arthroplasties that met the Musculoskeletal Infection Society criteria for periprosthetic joint infection (PJI) and had a minimum of 1-year follow-up were included. The antibiotic holiday period was defined as the time period off antibiotics before reimplantation. Treatment success was defined according to the Delphi consensus criteria. A multivariate analysis and Fisher exact test were performed. RESULTS The duration of the antibiotic-free period was not significantly associated with reinfection following reimplantation after controlling for potential confounders, including joint involvement, gender, institution, and comorbidities. However, the duration of spacer implantation was significantly associated with reinfection. Of the patients who failed treatment, 41.5% failed on antibiotics while 58.5% failed during the antibiotic-free period at a mean of 26.1 days. CONCLUSION The duration of an antibiotic-free period does not appear to significantly affect PJI rate after reimplantation. However, many patients fail during the antibiotic-free period. Further prospective studies are needed to determine the optimal timing of reimplantation for 2-stage exchange arthroplasty for PJI treatment.

Culturing Periprosthetic Joint Infection: Number of Samples, Growth Duration, and Organisms

BACKGROUND Owing to the difficulty isolating microorganisms in periprosthetic joint infection (PJI), current guidelines recommend that 3-5 intraoperative samples be cultured and maintained for 3-14 days. We investigated (1) the optimal number of culture samples and growth duration to diagnose PJI and (2) the microbiology profile at our institution. METHODS A retrospective review of 711 patients (329 hips, 382 knees) with PJI that met Musculoskeletal Infection Society criteria from 2000 to 2014 was performed. Two thousand two hundred ninety aerobic and anaerobic cultures were analyzed. A manual chart review collected demographic, surgical, and microbiological data. Microbiology profiles were trended. Logistic regression analysis was performed to determine statistical significance. RESULTS Obtaining 5 samples provided the greatest yield positive cultures for diagnosing PJI. The percentage of positive cultures overall was 62.6% and stratified by organism type: antibiotic resistant (80.0%), Staphylococcus aureus (76.0%), gram negative (58.9%), Pseudomonas (52.0%), variant PJI organisms (28.2%), Propionibacterium acnes (20.0%), and Escherichia coli (8.0%). Although most organisms were cultured in 5 days or less, 10.8 days were needed for Propionibacterium acnes, 6.6 for variant PJI organisms, and 5.2 for coagulase-negative Staphylococcus. At 3 days, only 42.2% of cultures turned positive compared with 95.0% at 8 days. There was a significant decrease in time in gram-positive PJIs and an increase in culture-negative PJIs. CONCLUSION The optimal number of cultures and growth duration depended on the type of organism. This study provides evidence that 5 samples should be obtained and held for at least 8 days given that the type of organisms is likely to be unknown at the time of surgery.