Novel Technique for the Identification of Hip Implants Using Artificial Intelligence.

BACKGROUND: The anticipated growth of total hip arthroplasty will result in an increased need for revision total hip arthroplasty. Preoperative planning, including identifying current implants, is critical for successful revision surgery. Artificial intelligence (AI) is promising for aiding clinical decision-making, including hip implant identification. However, previous studies have limitations such as small datasets, dissimilar stem designs, limited scalability, and the need for AI expertise. To address these limitations, we developed a novel technique to generate large datasets, tested radiographically similar stems, and demonstrated scalability utilizing a no-code machine learning solution. METHODS: We trained, validated, and tested an automated machine learning-implemented convolutional neural network to classify 9 radiographically similar femoral implants with a metaphyseal-fitting wedge taper design. Our novel technique uses computed tomography-derived projections of a 3-dimensional scanned implant model superimposed within a computed tomography pelvis volume. We employed computer-aided design modeling and MATLAB to process and manipulate the images. This generated 27,020 images for training (22,957) and validation (4,063) sets. We obtained 786 test images from various sources. The performance of the model was evaluated by calculating sensitivity, specificity, and accuracy. RESULTS: Our machine learning model discriminated the 9 implant models with a mean accuracy of 97.4%, sensitivity of 88.4%, and specificity of 98.5%. CONCLUSIONS: Our novel hip implant detection technique accurately identified 9 radiographically similar implants. The method generates large datasets, is scalable, and can include historic or obscure implants. The no-code machine learning model demonstrates the feasibility of obtaining meaningful results without AI expertise, encouraging further research in this area.

Highly Cross-Linked Polyethylene in Patients 50 Years of Age and Younger: A 20-year Follow-Up Analysis.

BACKGROUND: Highly cross-linked polyethylene (HXLPE) has been an excellent bearing for total hip arthroplasty (THA) due to improved wear characteristics compared to conventional materials. Patients 50 years of age or younger are at high risk for wear-related complications of their THA, and few studies have followed these patients who have HXPLE into the third decade. METHODS: In a retrospective review of 88 consecutive THAs performed in 77 patients aged 50 years and younger (mean 41; range, 20 to 50), in which HXLPE was utilized, they were evaluated for their clinical and radiographic results at an average of 20-year follow-up (range, 18 to 24). The current study reports on longer-term follow-up from our previously published series at shorter follow-up times. Patients were categorized by femoral head material: cobalt chrome (n = 14), ceramic (n = 30), and oxidized zirconium (n = 22) and by femoral head size: 26 mm (n = 12), 28 mm (n = 46), and 32 mm (n = 8). Harris Hip Scores were collected preoperatively and at the most recent follow-up. Radiographs were evaluated for linear and volumetric wear, radiolucent lines, and osteolysis. RESULTS: Mean Harris Hip Scores improved from 47.1 (standard deviation [SD] 8.8) preoperatively to 92.0 (SD 7.7) (P < .0001) at 20-year follow-up. There was one hip that was revised for recurrent instability, and no hip demonstrated radiographic evidence of loosening or osteolysis. The mean polyethylene linear wear rate was 0.017 (SD 0.012) mm/y, and the mean polyethylene volumetric wear rate was 3.15 (SD 2.8) mm3/year, with no significant differences based on articulation type or head size. CONCLUSIONS: Total hip arthroplasty with HXLPE in patients ≤ 50 years of age continues to demonstrate excellent long-term clinical and radiographic outcomes with low wear characteristics at 20-year follow-up, regardless of femoral head material or size.

Metaphyseal Fixation Using Cones and Sleeves for Severe Proximal Tibial Bone Loss.

BACKGROUND: Tibial bone defects are commonly encountered in revision total knee arthroplasty (rTKA) and can be managed with metaphyseal cones or sleeves. Few studies have directly compared tibial cones and sleeves in rTKA, and none have limited this comparison to the most severe tibial defects. The purpose of this study was to evaluate and compare the outcomes of metaphyseal cones and sleeves for tibial reconstruction in rTKA regarding implant fixation and clinical outcomes. METHODS: A retrospective review was conducted on patients undergoing rTKA in which metaphyseal cones or sleeves were utilized for addressing metaphyseal bone loss (34 cones and 18 sleeves). Tibial bone loss was classified according to the Anderson Orthopaedic Research Institute bone defect classification, with types 2B and 3 being included. Patient-reported outcomes and postoperative complications were collected, and a radiographic evaluation of osseointegration or loosening was performed. RESULTS: There were 52 knees included (34 cones, 18 sleeves), with a median follow-up of 41.0 months. All-cause implant survival was 100% at 2 years and 96% (95% confidence interval: 76 to 99%) at 4 years, with 98% of tibial components demonstrating osseointegration at the final follow-up. During follow-up, there were a total 11 revisions, of which 1 sleeve was revised secondary to implant loosening. Tibial sleeves had a higher risk of revision compared to tibial cones (P < .01), and sleeves fixed with a hybrid technique were more likely to need revision than cones fixed by the same method (P = .01). CONCLUSIONS: Porous metaphyseal tibial cones and tibial metaphyseal sleeves both performed well at a 41-month median follow-up with no difference in aseptic survivorship between the 2 constructs. Both demonstrate high rates of osseointegration, low rates of aseptic failure, and significant improvement in Knee Society Scores in patients with severe tibial defects in rTKA.

The Chitranjan S. Ranawat Award: Manipulation Under Anesthesia to Treat Postoperative Stiffness After Total Knee Arthroplasty: A Multicenter Randomized Clinical Trial.

BACKGROUND: Manipulation under anesthesia (MUA) occurs in 4% of patients after total knee arthroplasty (TKA). Anti-inflammatory medications may target arthrofibrosis pathogenesis, but the data are limited. This multicenter randomized clinical trial investigated the effect of adjuvant anti-inflammatory medications with MUA and physical therapy on range of motion (ROM) and outcomes. METHODS: There were 124 patients (124 TKAs) who developed stiffness after primary TKA for osteoarthritis enrolled across 15 institutions. All received MUA when ROM was < 90° at 4 to 12 weeks postoperatively. Randomization proceeded via a permuted block design. Controls received MUA and physical therapy, while the treatment group also received one dose of pre-MUA intravenous dexamethasone (8 mg) and 14 days of oral celecoxib (200 mg). The ROM and clinical outcomes were assessed at 6 weeks and 1 year. This trial was registered with ClinicalTrials.gov. RESULTS: The ROM significantly improved a mean of 46° from a pre-MUA ROM of 72 to 118° immediately after MUA (P < .001). The ROM was similar between the treatment and control groups at 6 weeks following MUA (101 versus 99°, respectively; P = .35) and at one year following MUA (108 versus 108°, respectively; P = .98). Clinical outcomes were similar at both end points. CONCLUSIONS: In this multicenter randomized clinical trial, the addition of intravenous dexamethasone and a short course of oral celecoxib after MUA did not improve ROM or outcomes. However, MUA provided a mean ROM improvement of 46° immediately, 28° at 6 weeks, and 37° at 1 year. Further investigation in regards to dosing, duration, and route of administration of anti-inflammatory medications remains warranted. LEVEL OF EVIDENCE: Level 1, RCT.

Increased Incidence of Methicillin-Resistant Staphylococcus aureus in Knee and Hip Prosthetic Joint Infection.

BACKGROUND: Periprosthetic joint infection (PJI) is a devastating complication of knee and hip arthroplasty. Past literature has shown that gram-positive bacteria are commonly responsible for these infections, although limited research exists studying the changes in the microbial profile of PJIs over time. This study sought to analyze the incidence and trends of pathogens responsible for PJI over three decades. METHODS: This is a multi-institutional retrospective review of patients who had a knee or hip PJI from 1990 to 2020. Patients with a known causative organism were included and those with insufficient culture sensitivity data were excluded. There were 731 eligible joint infections from 715 patients identified. Organisms were divided into multiple categories based on genus/species and 5-year increments were used to analyze the study period. The Cochran-Armitage trend tests were used to evaluate linear trends in microbial profile over time and a P-value <.05 was considered statistically significant. RESULTS: There was a statistically significant positive linear trend in the incidence of methicillin-resistant Staphylococcus aureus over time (P = .0088) as well as a statistically significant negative linear trend in the incidence of coagulase-negative staphylococci over time (P = .0018). There was no statistical significance between organism and affected joint (knee/hip). CONCLUSION: The incidence of methicillin-resistant Staphylococcus aureus PJI is increasing over time, whereas, coagulase-negative staphylococci PJI is decreasing, paralleling the global trend of antibiotic resistance. Identifying these trends may help with the prevention and treatment of PJI through methods such as remodeling perioperative protocols, modifying prophylactic/empiric antimicrobial approaches, or transitioning to alternative therapeutic strategies.

Long Term Results of Two-Stage Revision for Chronic Periprosthetic Knee Infection: A Multicenter Study.

BACKGROUND: Long-term reinfection and mortality rates and clinical outcomes with sufficient subject numbers remain limited for patients undergoing two-stage exchange arthroplasty for chronic periprosthetic knee infections. The purpose of this study was to determine the long-term reinfection, complication, and mortality following reimplantation for two-stage exchange following knee arthroplasty. METHODS: Retrospective review of 178 patients who underwent two-stage exchange knee arthroplasty for chronic PJI at three large tertiary referral institutions with an average of 6.63-year follow-up from reimplantation from 1990 to 2015. Rates of reinfection, mortality, and all-cause revision were calculated along with the cumulative incidence of reinfection with death as a competing factor. Risk factors for reinfection were determined using Cox multivariate regression analysis. RESULTS: Overall rate of infection eradication was 85.41%, with a mortality rate of 30.33%. Patients with minimum 5-year follow-up (n = 118, average 8.32 years) had an infection eradication rate of 88.98%, with a mortality rate of 33.05%. CONCLUSION: This is a large series with long-term follow-up evaluating outcomes of two-stage exchange knee arthroplasty resulting in adequate infection eradication and high mortality. Results were maintained at longer follow-up. This technique should be considered in patients with chronic PJI; however, realistic expectations regarding long-term outcomes must be discussed with patients.

Predictors of Reinfection in Prosthetic Joint Infections Following Two-Stage Reimplantation.

BACKGROUND: Two-stage reimplantation is an effective treatment for periprosthetic joint infection (PJI). Many factors are involved in the variable success of this procedure. The purpose of this study is to examine the relationship between patient risk factors, comorbidities, and the pathogen on reinfection rates following two-stage reimplantation. METHODS: We evaluated 158 patients treated for PJI from 2008-2019. Only patients who had completed a two-stage exchange were included. Patient demographics, comorbidities, laboratory values, time-to-reimplantation, pathogen, antibiotic sensitivities, host status, and reinfection rates were assessed. Multivariate analysis was performed to identify correlation between risk factors and reinfection. A P-value < .05 was considered statistically significant. RESULTS: 31 patients experienced a reinfection (19.6%). There was a statistically significant association between infection with Methicillin Sensitive Staphylococcus Aureus (MSSA) and reinfection (P = .046). Patients with a reinfection also had a significantly greater median serum C-reactive protein (CRP) level (12.65 g/dL) at the time of diagnosis compared to patients without a reinfection (5.0 g/dL) (P = .010). Median Erythrocyte Sedimentation Rate (ESR) (56 in no re-infection and 69 in re-infection) and time-to-reimplantation (101 days in no reinfection and 141 days in reinfection) demonstrated a trend toward an association with re-infection but were not statistically significant (P = .055 and P = .054 respectively). CONCLUSION: As the number of arthroplasties continue to rise, PJIs are increasing proportionately and represent a significant revision burden. Elevated C-reactive protein (CRP) levels and Methicillin Sensitive Staphylococcus aureus (MSSA) infection were strongly associated with failure of a two-stage reimplantation. While not statistically significant with our numbers, there were strong trends toward an association between elevated Erythrocyte Sedimentation Rate (ESR), longer time-to-reimplantation, and reinfection.

Two-Stage Reimplantation of a Prosthetic Hip Infection: Systematic Review of Long-Term Reinfection and Pathogen Outcomes.

BACKGROUND: Although two-stage exchange for chronic periprosthetic hip infections remains an effective option for infection eradication, long-term outcome reporting remains scarce. Compiling outcomes data for this standard of care is necessary to characterize long-term reinfection risk and identify bacteria associated with reinfection. The purpose of our study was to perform a systematic review to determine the long-term risk of reinfection after two-stage reimplantation. The second purpose was to identify the proportion of reinfections caused by the same or different organism(s) relative to the index infection. METHODS: We performed a systematic review of two-stage reimplantation randomized control trials, cohort studies, and case series for the treatment of periprosthetic joint infections, yielding 320 unique citations for abstract review, of which 138 were reviewed in full. We collected reinfection data including the timing of reinfection after successful reimplantation and the bacteria identified at reinfection. Meeting inclusion criteria were 28 studies with 2047 patients and 2055 hips that completed both reimplantation stages with just seven studies having greater than 24 month follow-up. RESULTS: Studies with longer average follow-up reported significantly higher all-time reinfection rates (P = .042). Among studies with at least 5 years of follow-up, the risk of reinfection was 10.25% (8.21-12.47). Among studies with minimum follow-up of at least 24 months, the 24-month rate of reinfection was 4.58% (2.17-7.66), which increased to 7.34% (4.44-10.82) by final follow-up. Only 12 studies reported index and recurrent pathogen data. In those studies, 3.00% (1.19-5.38) of all hips which completed both reimplantation stages were reinfected by a new pathogen, and 1.70% (0.52-3.35) of patients became reinfected by recurrent pathogens. CONCLUSION: While the majority of two stage reimplantation literature follows patients for two years, there is significant risk of reinfection into the long term. Further studies with detailed outcomes and long-term follow-up are needed to identify factors associated with late infections.

Late Reinfection May Recur More Than 5 Years After Reimplantation of THA and TKA: Analysis of Pathogen Factors.

BACKGROUND: Two-stage reimplantation has consistently yielded high rates of success for patients with chronic prosthetic joint infection, although results more than 5 years after reimplantation are not commonly reported. Numerous factors may contribute to the risk of reinfection, although these factors-as well as the at-risk period after reimplantation-are not well characterized. QUESTIONS/PURPOSES: (1) What is the risk of reinfection after reimplantation for prosthetic joint infection at a minimum of 5 years? (2) Is the bacteriology of the index infection associated with late reinfection? (3) Is the presence of bacteria at the time of reimplantation associated with late reinfection? METHODS: Between 1995 and 2010, we performed 97 two-stage revisions in 93 patients for prosthetic joint infection of the hip or knee, and all are included in this retrospective study. During that time, the indications for this procedure generally were (1) infections occurring more than 3 months after the index arthroplasty; and (2) more acute infections associated with prosthetic loosening or resistant organisms. One patient (1%) was lost to followup; all others have a minimum of 5 years of followup (mean, 11 years; range, 5-20 years) and all living patients have been seen within the last 2 years. Patients were considered free from infection if they did not have pain at rest or constitutional symptoms such as fever, chills, or malaise. The patients' bacteriology and resistance patterns of these organisms were observed with respect to recurrence of infection. Odds ratios and Fisher's exact test were performed to analyze the data. The incidence of reinfection was determined using cumulative incidence methods that considered death as a competing event. RESULTS: Reinfection occurred in 12 of the 97 joints resulting in implant revision. The estimated 10-year cumulative incidence of infection was 14% (95% confidence interval [CI], 7%-23%) and incidence of infection from the same organism was 5% (95% CI, 1%-11%). Five occurred early or within 2 years and three were resistant pathogens (methicillin-resistant Staphylococcus aureus, methicillin-resistant Staphylococcus epidermidis, or vancomycin-resistant Enterococcus). Seven late hematogenous infections occurred and all were > 4 years after reimplantation and involved nonresistant organisms. Three of the five (60%) early infections were caused by resistant bacteria, whereas all seven late infections were caused by different organisms or a combination of different organisms than were isolated in the original infection. The early reinfections were more often caused by resistant organisms, whereas late infections involved different organisms than were isolated in the original infection and none involved resistant organisms. With the numbers available, we found no difference between patients in whom bacteria were detected at the time of reimplantation and those in whom cultures were negative in terms of the risk of reinfection 5 years after reimplantation (18.6% [18 of 97] versus 81.4% [79 of 97], odds ratio 1.56 [95% CI, 0.38-6.44]; p = 0.54); however, with only 93 patients, we may have been underpowered to make this analysis. CONCLUSIONS: In our study, resistant organisms were more often associated with early reinfection, whereas late failures were more commonly associated with new pathogens. We believe the most important finding in our study is that substantial risk of late infection remains even among patients who seemed free from infection 2 years after reimplantation for prosthetic joint infections of the hip or knee. This highlights the importance of educating our patients about the ongoing risk of prosthetic joint infection. LEVEL OF EVIDENCE: Level III, therapeutic study.

Lessons Learned From Bundled Payment Programs.

To encourage the shift to value-based health care, the Center for Medicare & Medicaid Innovation created bundled payment programs in which episodes of care are paid for in a bundled fashion. Hip arthroplasty and knee arthroplasty were believed to be good procedures to pilot in bundled payment programs because these procedures had an easily defined episode of care and accounted for a considerable amount of the Medicare budget. Cost savings for hip and knee arthroplasty in bundled payment programs can be divided into cost savings achieved in the operating room, in the hospital, and in the postacute care period. Orthopaedic surgeons should be aware of the clinical results of hip and knee arthroplasty in bundled payment programs in various practice settings, including large healthcare systems, large academic centers, and private practices. Cost savings have been achieved in all phases of hip and knee arthroplasty in bundled payment programs. Almost all successful practice settings have developed an infrastructure to organize, administer, and manage patients through the different phases of patient care in bundled payment programs. Patient-reported outcomes and quality measures are being developed to determine the quality of the services provided in bundled payment programs.

Pharmacokinetic and Biodistribution Studies of HPMA Copolymer Conjugates in an Aseptic Implant Loosening Mouse Model.

N-(2-Hydroxypropyl) methacrylamide (HPMA) copolymers were previously found to represent a versatile delivery platform for the early detection and intervention of orthopedic implant loosening. In this article, we evaluated the impact of different structural parameters of the HPMA copolymeric system (e.g., molecular weight (MW), drug content) to its pharmacokinetics and biodistribution (PK/BD) profile. Using 125I, Alexa Fluor 488, and IRDye 800 CW-labeled HPMA copolymer-dexamethasone (P-Dex) conjugates with different MW and dexamethasone (Dex) contents, we found the MW to be the predominant impact factor on the PK/BD profiles of P-Dex, with Dex content as a secondary impact factor. In gamma counter-based PK/BD studies, increased MW of P-Dex reduced elimination, leading to lower clearance, longer half-life, and higher systemic exposure (AUC and MRT). In the semiquantitative live animal optical imaging evaluation, the distribution of P-Dex to the peri-implant inflammatory lesion increased when MW was increased. This result was further confirmed by FACS analyses of cells isolated from peri-implant regions after systemic administration of Alexa Fluor 488-labeled P-Dex. Since the in vitro cell culture study suggested that the internalization of P-Dex by macrophages is generally independent of P-Dex's MW and Dex content, the impact of the MW and Dex content on its PK/BD profile was most likely exerted at physiological and pathophysiological levels rather than at the cellular level. In both gamma counter-based PK/BD analyses and semiquantitative optical imaging analyses, P-Dex with 6 wt % Dex content showed fast clearance. Dynamic light scattering analyses unexpectedly revealed significant molecular aggregation of P-Dex at this Dex content level. The underlining mechanisms of the aggregation and fast in vivo clearance of the P-Dex warrant further investigation.

IL-12 promotes myeloid-derived suppressor cell recruitment and bacterial persistence during Staphylococcus aureus orthopedic implant infection.

Staphylococcus aureus is a leading cause of human prosthetic joint infections (PJIs) typified by biofilm formation. We recently identified a critical role for myeloid-derived suppressor cells (MDSCs) in S. aureus biofilm persistence. Proinflammatory signals induce MDSC recruitment and activation in tumor models; however, the mechanisms responsible for MDSC homing to sites of biofilm infection are unknown. In this study, we report that several cytokines (IL-12p40, IL-1ß, TNF-α, and G-CSF) and chemokines (CXCL2, CCL5) were significantly elevated in a mouse model of S. aureus PJI. This coincided with significantly increased MDSC infiltrates concomitant with reduced monocyte, macrophage, and T cell influx compared with uninfected animals. Of the cytokines detected, IL-12 was of particular interest based on its ability to possess either pro- or anti-inflammatory effects mediated through p35-p40 heterodimers or p40 homodimers, respectively. MDSC recruitment was significantly reduced in both p40 and p35 knockout mice, which resulted in enhanced monocyte and neutrophil influx and bacterial clearance. Adoptive transfer of wild-type MDSCs into infected p40 knockout animals worsened disease outcome, as evidenced by the return of S. aureus burdens to levels typical of wild-type mice. Tissues obtained from patients undergoing revision surgery for PJI revealed similar patterns of immune cell influx, with increased MDSC-like cells and significantly fewer T cells compared with aseptic revisions. These findings reveal a critical role for IL-12 in shaping the anti-inflammatory biofilm milieu by promoting MDSC recruitment.

Preventing Hospital Readmissions and Limiting the Complications Associated With Total Joint Arthroplasty.

Total joint arthroplasty is a highly successful surgical procedure for patients who have painful arthritic joints. The increasing prevalence of total joint arthroplasty is generating substantial expenditures in the American healthcare system. Healthcare payers, specifically the Centers for Medicare and Medicaid Services, currently target total joint arthroplasty as an area for healthcare cost-savings initiatives, which has resulted in increased scrutiny surrounding orthopaedic care, health resource utilization, and hospital readmissions. Identifying the complications associated with total hip and total knee arthroplasty that result in readmissions will be critically important for predictive modeling and to decrease the number of readmissions after total joint arthroplasty. In addition, improving perioperative optimization, providing seamless episodic care, and intensifying posthospital coordination of care may decrease the number of unnecessary hospital readmissions. Identified modifiable risk factors that substantially contribute to poor clinical outcomes after total joint arthroplasty include morbid obesity; poorly controlled diabetes and nutritional deficiencies; Staphylococcus aureus colonization; tobacco use; venous thromboembolic disease; cardiovascular disease; neurocognitive, psychological, and behavioral problems; and physical deconditioning and fall risk. Both clinical practice and research will be enhanced if defined total joint arthroplasty complications are standardized and stratification schemes are used to identify high-risk patients. Subsequently, clinical intervention will be warranted to address modifiable risk factors before proceeding with total joint arthroplasty.

Low wear rates seen in THAs with highly crosslinked polyethylene at 9 to 14 years in patients younger than age 50 years.

BACKGROUND: Patients 50 years or younger are at high risk for wear-related complications of their total hip arthroplasty (THA) because of their generally higher levels of activity. Highly crosslinked polyethylene (HXLPE) is believed to be more durable for this population than conventional polyethylene because of its improved wear; however, limited information is available on the wear of HXLPE in this population, particularly the wear of HXLPE when it articulates with alternative bearings like Oxinium (Smith & Nephew, Memphis, TN, USA). QUESTIONS/PURPOSES: The purpose of this study was to evaluate two questions relative to this population of patients undergoing THA. First, what was the linear and volumetric wear rate of HXLPE in patients 50 years or younger at a minimum followup of 9 years and was osteolysis observed in any of these hips? Given the potential for damage to the Oxinium femoral head surface, was the wear of HXLPE in the patients with this material similar to the other bearings or was there accelerated or runaway wear that was visible in any of the patients? METHODS: From November 1999 to April 2005, 105 THAs were performed in 95 patients 50 years of age or younger (mean, 42 years; range, 20-50 years). The mean body mass index was 30 kg/m(2) (range, 17-51 kg/m(2)).The mean followup was 12 years (range, 9-14 years). Two patients died, five patients (one bilateral) were lost to followup, and one hip was revised elsewhere for pain. The patients' information was not included in the study, which left 87 patients with 96 hips for analysis. Highly crosslinked polyethylene was the acetabular bearing for all of the hips. We analyzed the linear and volumetric wear of all of the hips using the Martell method. Eighty hips had the same diameter head (28 mm) allowing us to more accurately compare the different bearing materials. The type of femoral head used was related to our sequential use of materials beginning with cobalt chrome (14), ceramic (23) followed by Oxinium (43) in the hips with 28-mm heads. Although cobalt-chrome was used early in this study, our previous experience with ceramic on polyethylene encouraged us to use it as an alternative bearing. The Oxinium was used consecutively for the remaining hips. RESULTS: The mean wear of the HXLPE after 1 year of bedding-in (true linear wear)was 0.022 mm/year (95% confidence interval [CI], 0.015-0.030 mm/year). The mean volumetric wear of HXLPE after 1 year of bedding-in (true volumetric wear) was 9 mm(3)/year (95% CI, 4-14 mm(3)/year). None of the hip radiographs had evidence of loosening or osteolysis. Wear was not associated with femoral head material (p = 0.58 for linear wear/year versus head material and p = 0.52 for volumetric wear/year versus head material). CONCLUSIONS: In our study of patients 50 years of age or younger undergoing THA, the linear and volumetric wear rates of HXLPE were very low regardless of the bearing surface material. The laboratory concerns of Oxinium surface damage are serious but at this time we have not seen high wear of the HXLPE or osteolysis in this population. LEVEL OF EVIDENCE: Level III, therapeutic study.

How do I get out of this jam? Overcoming common intraoperative problems in primary total hip arthroplasty.

Prompt attention is typically required in managing intraoperative problems associated with total hip arthroplasty. There is often limited time for consultation or a review of the literature. The treating surgeon should be familiar with treatment options, favored treatment methods, and should be able to implement the most appropriate and optimal treatment for his or her patient. Common intraoperative complications associated with primary total hip arthroplasty include difficulty gaining sufficient exposure, problems with cup fixation, challenges with implant anteversion, intraoperative fracture of the femur, and difficulties with intraoperative limb length and hip instability.

Early diagnosis of orthopedic implant failure using macromolecular imaging agents.

PURPOSE: To develop and evaluate diagnostic tools for early detection of wear particle-induced orthopaedic implant loosening. METHODS: N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymer was tagged with a near infrared dye and used to detect the inflammation induced by polymethylmethacrylate (PMMA) particles in a murine peri-implant osteolysis model. It was established by inserting an implant into the distal femur and challenging with routine PMMA particles infusion. The osteolysis was evaluated by micro-CT and histological analysis at different time points. RESULTS: Significant peri-implant osteolysis was found 3-month post PMMA particle challenge by micro-CT and histological analysis. At 1-month post challenge, when there was no significant peri-implant bone loss, the HPMA copolymer-near infrared dye conjugate was found to specifically target the femur with PMMA particles deposition, but not the contralateral control femur with phosphate buffered saline (PBS) infusion. CONCLUSION: The results from this study demonstrate the feasibility of utilizing the macromolecular diagnostic agent to detect particle-induced peri-implant inflammation prior to the development of detectable osteolysis. Recognition of this early pathological event would provide the window of opportunity for prevention of peri-implant osteolysis and subsequent orthopaedic implant failure.

Inter- and intraobserver reliability of two-dimensional CT scan for total knee arthroplasty component malrotation.

BACKGROUND: Rotational malalignment of total knee arthroplasty (TKA) has been correlated with patellofemoral maltracking, knee instability, and stiffness. CT is the most accurate method to assess rotational alignment of prosthetic components after TKA, but inter- and intraobserver reliability of CT scans for this use has not been well documented. QUESTIONS/PURPOSES: The objective of this study was to determine the inter- and intraobserver reliability and the repeatability of the measurement of TKA component rotation using two-dimensional CT scans. METHODS: Fifty-two CT scans of TKAs being evaluated for revision surgery were measured by three different physicians. An orthopaedic resident and attending measured the same scans twice (more than 2 weeks apart) and a musculoskeletal radiologist measured them once. To assess interobserver reliability, intraclass correlation coefficients (ICCs) with two-way mixed-effects analysis of variance models as well as 95% confidence intervals for each were done. The repeatability coefficient was calculated as well, which is defined as the difference in measurements that include 95% of the values. This indicates the magnitude of variability among measurements in the same scale, which in this study is degrees. RESULTS: The interobserver ICC measurement for the femoral component was 0.386 (poor), and it was 0.670 (good) for the tibial component. The interobserver ICC for the combined rotation measurements was 0.617 (good). The intraobserver ICC for the femoral component was 0.606 (good), and it was 0.809 (very good) for the tibial component. The intraobserver ICC for combined rotation was 0.751 (good). The intraobserver repeatability coefficient for the femoral component was 0.49°, 10.64° for the tibial component, and 12.29° for combined rotation. CONCLUSIONS: In this study, the inter- and intraobserver reliability, and the repeatability, of TKA component rotation were variable. This raises concern about whether CT scan is diagnostic in the assessment of component malrotation after TKA.

Recurrent Periprosthetic Joint Infections: Diagnosis, Management, and Outcomes.

Periprosthetic joint infection (PJI) remains one of the most common complications after total joint arthroplasty. It is challenging to manage, associated with significant morbidity and mortality, and is a financial burden on the health care system. Failure of 2-stage management for chronic PJI is not uncommon. Repeat infections are oftentimes polymicrobial, multiple drug-resistant microorganisms, or new organisms. Optimizing the success of index 2-stage revision is the greatest prevention against failure of any subsequent management options and requires a robust team-based approach.

Cementless Total Knee Arthroplasty: Is it Safe in Demineralized Bone?

There is concern for cementless total knee arthroplasty (TKA) in patients with decreased bone mineral density (BMD) due to the potential increase in complications, namely failed in-growth or future aseptic loosening. Some data suggest that advances in cementless prostheses mitigate these risks; however this is not yet born out in long-term registry data. It is crucial to expand our understanding of the prevalence and etiology of osteoporosis in TKA patients, survivorship of cementless implants in decreased BMD, role of bone-modifying agents, indications and technical considerations for cementless TKA in patients with decreased BMD. The purpose of this study is to review current literature and expert opinion on such topics.

Long-term polyethylene wear rates and clinical outcomes of oxidized zirconium femoral heads on highly cross-linked polyethylene in total hip arthroplasty.

Aims: Oxidized zirconium (OxZi) and highly cross-linked polyethylene (HXLPE) were developed to minimize wear and risk of osteolysis in total hip arthroplasty (THA). However, retrieval studies have shown that scratched femoral heads may lead to runaway wear, and few reports of long-term results have been published. The purpose of this investigation is to report minimum ten-year wear rates and clinical outcomes of THA with OxZi femoral heads on HXLPE, and to compare them with a retrospective control group of cobalt chrome (CoCr) or ceramic heads on HXLPE. Methods: From 2003 to 2006, 108 THAs were performed on 96 patients using an OxZi head with a HXLPE liner with minimum ten-year follow-up. Harris Hip Scores (HHS) were collected preoperatively and at the most recent follow-up (mean 13.3 years). Linear and volumetric liner wear was measured on radiographs of 85 hips with a minimum ten-year follow-up (mean 14.5 years). This was compared to a retrospective control group of 45 THAs using ceramic or CoCr heads from October 1999 to February 2005, with a minimum of ten years' follow-up. Results: Average HHS improved from 50.8 to 91.9 and 51.0 to 89.8 in the OxZi group and control group, respectively (p = 0.644), with no osteolysis in either group. Linear and volumetric wear rates in the OxZi group averaged 0.03 mm/year and 3.46 mm3/year, respectively. There was no statistically significant difference in HHS scores, nor in linear or volumetric wear rate between the groups, and no revision for any indication. Conclusion: The radiological and clinical outcomes, and survivorship of THA with OxZi femoral heads and HXLPE liners, were excellent, and comparable to CoCr or ceramic heads at minimum ten-year follow-up. Wear rates are below what would be expected for development of osteolysis. OxZi-HXLPE is a durable bearing couple with excellent long-term outcomes.