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Background: Two-stage exchange is the most common form of treatment of chronic infection following total hip arthroplasty (THA). We examined the prevalence of, and risk factors associated with, hip instability following 2-stage exchange as well as the fate of reimplanted hip prostheses that dislocated. Methods: Data on 515 2-stage exchange THAs performed between 2000 and 2014 at a single institution were retrospectively reviewed. Risk factors for instability as well as postoperative reoperations and revisions were analyzed. The impact of dislocation on these outcomes was evaluated as well. The mean age at the time of reimplantation was 65 years, and the mean duration of follow-up was 5 years (range, 2 to 15 years). Results: Dislocation occurred in 52 hips following reimplantation (cumulative probability = 8.9% at 1 year). There was a higher risk of instability in women (hazard ratio [HR] = 1.8, p = 0.038) and in those who had a history of dislocation prior to the 2-stage revision (HR = 5.1, p < 0.001). Younger age, body mass index, number of previous operations, spacer type, surgical approach, use of a constrained liner, femoral head diameter, and persistent or recurrent infection were not found to be significant risk factors. Patients with an absent or ununited greater trochanter or abductor deficiency also had a higher rate of dislocation (HR = 30, p < 0.001), as did patients who underwent reimplantation with a megaprosthesis (HR = 6.0, p < 0.001). The risk of additional reoperations (HR = 121, p < 0.001) and revision surgery (HR = 13, p < 0.001) was significantly higher in patients who experienced a dislocation after the 2-stage exchange. Conclusions: Dislocation after 2-stage exchange THA continues to be a major concern, with the 1-year cumulative probability found to be 9% in the present study. Female sex, a history of dislocation, an absent or ununited greater trochanter or abductor deficiency, and reimplantation with a megaprosthesis were identified as risk factors for dislocation. There is a remarkable 121-fold increase in the rate of reoperations and a 13-fold increase in the rate of revisions in hips that dislocated after 2-stage exchange THA. Level of Evidence: Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Background: For patients undergoing 2-stage exchange for the treatment of periprosthetic joint infection (PJI) following total knee arthroplasty, the long-term risk of reinfection and mechanical failure and long-term clinical outcomes are not well known. The purpose of our study was to determine the long-term clinical results of 2-stage exchange for PJI following total knee arthroplasty. Methods: We identified 245 knees that had undergone total knee arthroplasty and were subsequently treated with 2-stage exchange due to infection during the period of 1991 to 2006; the cohort had no prior treatment for PJI. Major, or 4 of 6 minor, Musculoskeletal Infection Society (MSIS) diagnostic criteria were fulfilled by 179 (73%) of the knees. The cumulative incidence of reinfection and of aseptic revision, accounting for the competing risk of death, were calculated. Risk factors for reinfection were evaluated using Cox proportional hazards regression. Knee Society Score (KSS) values were calculated. The mean age at spacer insertion was 68 years; 50% of the patients were female. The mean follow-up was 14 years (range, 2 to 25 years) following reimplantation. Results: The cumulative incidence of reinfection was 4% at 1 year, 14% at 5 years, 16% at 10 years, and 17% at 15 years. Factors that were predictive of reinfection included a body mass index of ≥30 kg/m 2 (hazard ratio [HR], 3.1; p < 0.01), previous revision surgery (HR, 2.8; p < 0.01), and a McPherson host grade of C (HR, 2.5; p = 0.04). The cumulative incidence of aseptic revision for loosening was 2% at 5 years, 5% at 10 years, and 7% at 15 years. Femoral (HR, 5.0; p = 0.04) and tibial (HR, 6.7; p < 0.01) bone-grafting at reimplantation were predictive of aseptic failure. The most common complications were wound-healing issues, requiring reoperation in 12 (5%) of the knees. The rate of death at 2 years following reimplantation was 11%. The mean KSS improved from 45 at PJI diagnosis to 76 at 10 years following reimplantation (p < 0.01). Conclusions: Long-term reinfection rates following 2-stage exchange for PJI after total knee arthroplasty were similar to those of shorter-term reports and were maintained out to 15 years. Mechanical failure rates were low if bone loss was addressed at the time of reimplantation. Improvements in clinical outcomes were maintained at long-term follow-up. Level of Evidence: Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Aims Concurrent hip and spine pathologies can alter the biomechanics of spinopelvic mobility in primary total hip arthroplasty (THA). This study examines how differences in pelvic orientation of patients with spine fusions can increase the risk of dislocation risk after THA. Patients and Methods We identified 84 patients (97 THAs) between 1998 and 2015 who had undergone spinal fusion prior to primary THA. Patients were stratified into three groups depending on the length of lumbar fusion and whether or not the sacrum was involved. Mean age was 71 years (40 to 87) and 54 patients (56%) were female. The mean body mass index (BMI) was 30 kg/m2 (19 to 45). Mean follow-up was six years (2 to 17). Patients were 1:2 matched to patients with primary THAs without spine fusion. Hazard ratios (HR) were calculated. Results Dislocation in the fusion group was 5.2% at one year versus 1.7% in controls but this did not reach statistical significance (HR 1.9; p = 0.33). Compared with controls, there was no significant difference in rate of dislocation in patients without a sacral fusion. When the sacrum was involved, the rate of dislocation was significantly higher than in controls (HR 4.5; p = 0.03), with a trend to more dislocations in longer lumbosacral fusions. Patient demographics and surgical characteristics of THA (i.e. surgical approach and femoral head diameter) did not significantly impact risk of dislocation (p > 0.05). Significant radiological differences were measured in mean anterior pelvic tilt between the one-level lumbar fusion group (22°), the multiple-level fusion group (27°), and the sacral fusion group (32°; p < 0.01). Ten-year survival was 93% in the fusion group and 95% in controls (HR 1.2; p = 0.8). Conclusion Lumbosacral spinal fusions prior to THA increase the risk of dislocation within the first six months. Fusions involving the sacrum with multiple levels of lumbar involvement notably increased the risk of postoperative dislocation compared with a control group and other lumbar fusions. Surgeons should take care with component positioning and may consider higher stability implants in this high-risk cohort.

Background: Limited data exist that show the long-term risks of reinfection and mechanical failure with a contemporary 2-stage exchange protocol for periprosthetic joint infection following total hip arthroplasty. The purpose of this study was to determine the long-term reinfection and mechanical failure rates of 2-stage exchange for periprosthetic joint infection after total hip arthroplasty. Methods: We identified 164 hips (162 patients) with infection after total hip arthroplasty between 1991 and 2006 treated with a 2-stage exchange protocol with no prior treatment for periprosthetic joint infection. With regard to Musculoskeletal Infection Society diagnostic criteria, at least 1 major criterion or 4 of 6 minor criteria were fulfilled in 129 hips (79%). The cumulative incidence with a competing risk of death was calculated for reinfection, aseptic revisions, and all-cause revisions. The risk factors for reinfection were evaluated using Cox proportional hazards regression. Harris hip scores were calculated. The mean age at the time of spacer insertion was 68 years, and 35% of the patients were female. Excluding the patients with <2 years of follow-up, the mean follow-up was 12 years (range, 2 to 21 years). Results: The cumulative incidence of recurrence of infection was 10% at 1 year, 14% at 5 years, and 15% at 10 and 15 years. Seventeen patients (11%) used chronic antibiotic suppression (>6 months), with 7 (41%) of these having recurrent infection at the time of the latest follow-up. Use of chronic antibiotic suppression was the only predictive factor for reinfection (hazard ratio, 4.5 [95% confidence interval (CI), 1.9 to 10.9]; p = 0.001). The cumulative incidence of aseptic femoral and acetabular revisions was 2.6% at 5 years and 3.3% at 10 and 15 years. The cumulative incidence of all-cause revisions was 15% at 5 years and 16% at 10 and 15 years. Dislocation was the most common complication, with 28 dislocations occurring in 20 patients (12%). The mean Harris hip score improved from 52 points prior to spacer insertion to 70 points at 15 years after reimplantation (p < 0.01). Conclusions: The rate of recurrence of infection of 15% for up to 15 years after total hip arthroplasty was similar to previous shorter-term reports of 2-stage exchange for periprosthetic joint infection. Surgeons should anticipate mitigating instability after reimplantation. Implant survivorship free of aseptic loosening and clinical outcomes were preserved for the long term. The role of chronic antibiotic suppression in the long-term treatment of periprosthetic joint infection requires further investigation. Level of Evidence: Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

AimsThe results of irrigation and debridement with component retention (IDCR) in the treatment of acutely infected total knee arthroplasties (TKAs) have been variable. The aim of this study was to assess the outcome after IDCR when combined with chronic antibiotic suppression. We also evaluated survivorship free from subsequent infection, removal of the components, and death, as well as the risk factors for failure.Patients and MethodsThis was a single-centre retrospective review of 134 infected primary TKAs that were treated with IDCR. Infections within four weeks of the procedure were defined as acute postoperative infections, and those occurring more than four weeks after the procedure with symptoms for less than three weeks were defined as acute haematogenous infections. Patients were treated with intravenous antibiotics for four to six weeks, followed by chronic oral antibiotic suppression. Estimates of survival were made using a competing risk analysis. The mean follow-up was five years (2.1 to 13).ResultsThe infection was an acute postoperative infection in 23 TKAs and an acute haematogenous infection in 111 TKAs. The incidence of subsequent infection was 36% in those with an acute postoperative infection and 33% in those with a haematogenous infection, five years postoperatively (p = 0.40). Age < 60 years increased the risk of subsequent infection (hazard ratio (HR) 2.4; p = 0.009) and removal of the components (HR 2.8; p = 0.007). Infection with a staphylococcal species increased the risk of subsequent infection (HR 3.6; p < 0.001), and removal of the components (HR 3.2; p = 0.002). Musculoskeletal Infection Society host type and local extremity grade, body mass index (BMI), the duration of symptoms, gender, and the presence of a monoblock tibial component had no significant effect on the outcome.ConclusionIn a rigorously defined group of acute periprosthetic infections after TKA treated with IDCR and chronic antibiotic suppression, the infection-free survival at five years was 66%. The greatest risk factor for failure was an infection with a staphylococcal species, followed by age of < 60 years. Cite this article: Bone Joint J 2018;100-B:1471–76.

Background: Increasing body mass index (BMI) has been shown to correlate with increased rates of complications after total knee arthroplasty. To our knowledge, body surface area, body mass, and height have not been investigated in this manner. BMI and body surface area are affected differently by changes in height, and they are affected similarly by changes in weight. The purpose of this study was to quantify revision for any reason, mechanical failure, aseptic loosening, polyethylene wear, reoperation, and any infection after total knee arthroplasty using BMI, body surface area, body mass, and height as continuous variables. Methods: Prospectively collected data from a single institution’s total joint registry were used to analyze 22,243 consecutive knees, in 16,106 patients, treated with a primary total knee arthroplasty from 1985 to 2012. The Kaplan-Meier survival method was used to evaluate revision and other common complications, with outcomes assessed using Cox regression analysis. Smoothing spline parameterization was used on physical parameters in these models. Results: Increasing BMI, body surface area, body mass, and height were associated with an increased risk of any revision surgical procedure, mechanical failure, and aseptic loosening after total knee arthroplasty. The risk of a revision surgical procedure was directly associated with each 1 standard deviation increase in BMI (hazard ratio [HR], 1.19; p < 0.01), body surface area (HR, 1.37; p < 0.01), body mass (HR, 1.30; p < 0.01), and height (HR, 1.22; p < 0.01). This association was especially demonstrated with revision for mechanical failure (BMI: HR, 1.15; p < 0.01; body surface area: HR, 1.35; p < 0.01; body mass: HR, 1.27; p < 0.01; and height: HR, 1.23; p < 0.01). The risk of failure in the subgroups of mechanical failure including a revision surgical procedure for aseptic loosening or polyethylene wear was also associated with increasing body surface area, body mass, and height. Increasing BMI (HR, 1.22; p < 0.01), body surface area (HR, 2.56; p < 0.01), and body mass (HR, 2.54; p < 0.01) were also associated with increased risk of any infection. Conclusions: Increasing BMI, body surface area, body mass, and height were strongly associated with the rates of revision, aseptic loosening, and other common complications following total knee arthroplasty. Body surface area and body mass appear to correlate more strongly with mechanical failure outcomes than BMI or height. Level of Evidence: Prognostic Level IV . See Instructions for Authors for a complete description of levels of evidence.

ABSTRACTTrauma, surgery, and other inflammatory conditions can lead to debilitating joint contractures. Adjunct pharmacologic modalities may permit clinical prevention and treatment of recalcitrant joint contractures. We investigated the therapeutic potential of rosiglitazone by intra‐articular delivery via oligo[poly(ethylene glycol)fumarate] (OPF) hydrogels in an established rabbit model of arthrofibrosis. OPF hydrogels loaded with rosiglitazone were characterized for drug elution properties upon soaking in minimum essential media (MEM) with 10% fetal bovine serum and measurements of drug concentrations via High Performance Liquid Chromatography (HPLC). Drug‐loaded scaffolds were surgically implanted into 24 skeletally mature female New Zealand White rabbits that were divided into equal groups receiving OPF hydrogels loaded with rosiglitazone (1.67 mg), or vehicle control (10 µl DMSO). After 8 weeks of joint immobilization, rabbits were allowed unrestricted cage activity for 16 weeks. Contracture angles of rabbit limbs treated with rosiglitazone showed statistically significant improvements in flexion compared to control animals (mean angles, respectively, 64.4° vs. 53.3°, p < 0.03). At time of sacrifice (week 24), animals in the rosiglitazone group continued to exhibit less joint contracture than controls (119.0° vs. 99.5°, p = 0.014). The intra‐articular delivery of rosiglitazone using implanted OPF hydrogels decreases flexion contractures in a rabbit model of arthrofibrosis without causing adverse effects (e.g., gross inflammation or arthritis). Statement of Clinical Significance: Post‐traumatic joint contractures are common and debilitating, with limited available treatment options. Pharmacologic interventions can potentially prevent and treat such contractures. This study is translational in that a commercially approved medication has been repurposed through a novel delivery device. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2949–2955, 2018.

ABSTRACTLocal, regional, and national registries have played an important role in the development of hip and knee arthroplasty and the treatment of patients with various maladies of these joints. Four arthroplasty registries stand out as leading forces behind the drive to popularize the use of registries and pursue the concept of evidence based medicine. The Mayo registry, started by Mark Coventry, is recognized as the oldest continuing registry for arthroplasty. The Harris Registry at Massachusetts General Hospital, along with the Mayo Registry, has greatly contributed to the advancement of arthroplasty surgery and have served an important role of identifying poorly performing implants and techniques in the United States. The Swedish Knee Arthroplasty Registry is the oldest national registry dedicated to joint arthroplasty and along with the Swedish Hip Arthroplasty Registry have established the infrastructure, analysis and reporting mechanisms, and leadership that has enabled other countries to subsequently develop national registries around the world. As more countries have adopted the concept of national registries, a new area of research is possible by pooling the resources of large registries as is now occurring with the Nordic countries. Several international organizations have been formed to promote future collaboration and develop international standards. The process of globalization of registries is a result of continued efforts over the past 50 years in improving and disseminating the knowledge gained from the early registries. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2319–2330, 2018.

Abstract: We previously compared the 15-year survivorship of total knee arthroplasty (TKA) implants that were mechanically aligned (0° ± 3° relative to the mechanical axis) compared with those that were outside that range and considered outliers. The original publication included 398 TKAs (292 in the aligned group and 106 in the outlier group) performed from 1985 to 1990. At the time of follow-up in the previous study, 138 patients (155 TKAs) had died and 59 knees had been revised. Since that publication, 49 additional patients (87 knees) have died. At 20 years, 57 (19.5%) of the 292 knees in the mechanically aligned group had been revised compared with 16 (15.1%) of the 106 knees in the outlier group (p = 0.97). Postoperative alignment within 0° ± 3° of the mechanical axis did not provide a functional advantage at 1, 5, 10, 15, and/or 20 years postoperatively as demonstrated by the Knee Society scores being similar between the groups (p ≥ 0.2 at all intervals). At 20 years, we once again did not find that neutral mechanical alignment provided better implant survivorship than that found in the outlier group. Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.