A translational murine model of aseptic loosening with osseointegration failure.

An in vivo animal model of a weight-bearing intra-articular implant is crucial to the study of implant osseointegration and aseptic loosening caused by osseointegration failure. Osseointegration, defined as a direct structural and functional attachment between living bone tissue and the surface of a load-carrying implant, is essential for implant stability and considered a prerequisite for the long-term clinical success of implants in total joint arthroplasty. Compared to large animal models, murine models offer extensive genetic tools for tracing cell differentiation and proliferation. The 18- to 22-week-old C57BL/6J background mice underwent either press-fitted or loose implantation of a titanium implant, achieving osseointegration or fibrous integration. A protocol was developed for both versions of the procedure, including a description of the relevant anatomy. Samples were subjected to microcomputed tomography and underwent biomechanical testing to access osseointegration. Lastly, samples were fixed and embedded for histological evaluation. The absence of mineralized tissue and weakened maximum pull-out force in loose implantation samples indicated that these implants were less mechanically stable compared to the control at 4 weeks postoperation. Histological analysis demonstrated extensive fibrotic tissue in the peri-implant area of loose implantation samples and excellent implant osseointegration in press-fitted samples at 4 weeks. Both mechanically stable and unstable hemiarthroplasty models with either osseous ingrowth or a robust periprosthetic fibrosis were achieved in mice. We hope that this model can help address current limitations for in vivo study of aseptic loosening and lead to necessary translational benefits.

Capacity for large language model chatbots to aid in orthopedic management, research, and patient queries.

Large language model (LLM) chatbots possess a remarkable capacity to synthesize complex information into concise, digestible summaries across a wide range of orthopedic subject matter. As LLM chatbots become widely available they will serve as a powerful, accessible resource that patients, clinicians, and researchers may reference to obtain information about orthopedic science and clinical management. Here, we examined the performance of three well-known and easily accessible chatbots-ChatGPT, Bard, and Bing AI-in responding to inquiries relating to clinical management and orthopedic concepts. Although all three chatbots were found to be capable of generating relevant responses, ChatGPT outperformed Bard and BingAI in each category due to its ability to provide accurate and complete responses to orthopedic queries. Despite their promising applications in clinical management, shortcomings observed included incomplete responses, lack of context, and outdated information. Nonetheless, the ability for these LLM chatbots to address these inquires has largely yet to be evaluated and will be critical for understanding the risks and opportunities of LLM chatbots in orthopedics.

Head-to-Head Comparison of Kinematic Alignment Versus Mechanical Alignment for Total Knee Arthroplasty.

BACKGROUND: Seeing as there are many alignment strategies for total knee arthroplasty (TKA), we need to determine differences between them in a rigorous scientific way. Therefore, we sought to compare perioperative and postoperative functional outcomes in patients undergoing TKA for varus osteoarthritis with a mechanical alignment target vs a kinematic alignment target, both executed with the same implant and same technological guidance. METHODS: One hundred consecutive patients who underwent TKA using a mechanical alignment technique were 1:1 matched to 100 patients who underwent TKA using a kinematic alignment (KA) technique, using the same implant and robotic technology. Patient-reported outcomes were measured postoperatively at 1 and 2 years. Power analysis revealed 94 patients to detect a significant difference. RESULTS: Mean Visual Analog Scale scores were higher in the mechanical alignment group during the first 6 weeks (P = .04), but statistically similar at 1 year. Six-week Veterans RAND 12 Item Health Survey mental and physical components were statistically similar (P = .1). Patients did not differ in 6-week or 1-year knee range of motion (P > .43). Knee Injury and Osteoarthritis Outcome Score Joint Replacement was significantly better in the KA group at 6 weeks, 1 year, and 2 years (P = .09). Forgotten Joint Score at 1 and 2 years postoperatively were significantly higher in the KA group (P < .001). CONCLUSION: Patients undergoing TKA with KA experienced less pain in 6 weeks after surgery, and higher Forgotten Joint Scores at 1 and 2 years postoperatively. Alternative TKA alignment and balancing strategies should be considered to increase patient satisfaction.

RNA-seq Analysis of Peri-Implant Tissue Shows Differences in Immune, Notch, Wnt, and Angiogenesis Pathways in Aged Versus Young Mice.

The number of total joint replacements (TJRs) in the United States is increasing annually. Cementless implants are intended to improve upon traditional cemented implants by allowing bone growth directly on the surface to improve implant longevity. One major complication of TJR is implant loosening, which is related to deficient osseointegration in cementless TJRs. Although poor osseointegration in aged patients is typically attributed to decreased basal bone mass, little is known about the molecular pathways that compromise the growth of bone onto porous titanium implants. To identify the pathways important for osseointegration that are compromised by aging, we developed an approach for transcriptomic profiling of peri-implant tissue in young and aged mice using our murine model of osseointegration. Based on previous findings of changes of bone quality associated with aging, we hypothesized that aged mice have impaired activation of bone anabolic pathways at the bone-implant interface. We found that pathways most significantly downregulated in aged mice relative to young mice are related to angiogenic, Notch, and Wnt signaling. Downregulation of these pathways is associated with markedly increased expression of inflammatory and immune genes at the bone-implant interface in aged mice. These results identify osseointegration pathways affected by aging and suggest that an increased inflammatory response in aged mice may compromise peri-implant bone healing. Targeting the Notch and Wnt pathways, promoting angiogenesis, or modulating the immune response at the peri-implant site may enhance osseointegration and improve the outcome of joint replacement in older patients. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Accuracy of acetabular cup placement positively correlates with level of training.

BACKGROUND: Accurate acetabular component placement may reduce the risk of complication after total hip arthroplasty (THA). While surgeon experience and volume may reduce outliers, little is known how cup positioning accuracy and consistency relates to level of training (resident, fellow, attending) and whether trainee level impacts the magnitude and direction of cup placement errors. METHODS: Ninety patients undergoing posterolateral computer-assisted navigation THA were included for analysis. All surgery was performed by two fellowship-trained orthopaedic surgeons and assisted by a trainee (orthopedic resident (PGY 1-5) or fellow in adult reconstruction). In order to determine accuracy of cup placement in trainees and attendings, we used computer navigation to determine freehand cup placement by the trainee, then by the attending surgeon. Final cup inclination and version were determined and recorded by computer-assisted surgical navigation. Comparison of consistency in cup inclination and anteversion was made on values obtained by residents, fellows, and attendings and final values provided by the navigation system. In addition, to assess the role of training and repetition, acetabular cup inclination and version were compared between fellows during the first half and the second half of their training year. All comparisons were performed with the Student t-test except for comparison of rate of deviation from the safe zone, which were performed with the chi-square test. The level of significance was defined as p values ≤ 0.05 with 95% confidence interval, and trend toward significance was defined as p values ≤ 0.1. RESULTS: Inclination deviation from the final position and cup version deviation from the final position were statistically significant between resident vs attendings (p < 0.001 (inclination), p < 0.001 (version)), fellow vs attendings (p < 0.001 (inclination), p < 0.001 (version)), and all trainee vs attendings (p < 0.001 (inclination), p < 0.001 (version)). In all comparisons, the attending surgeons placed the cup closer to the final cup position than both resident and fellows. Proportion of inclination deviation from the safe zone of residents was significantly higher than of attendings (p < 0.001) but no significant difference was observed between fellows and attending (p = 1.00). Compared to residents, fellows demonstrated lower proportion of inclination deviation from the safe zone of 3.3% vs 23.3% for fellows vs residents (p = 0.002) and tended to implant the cups in a more horizontal position (45.6 ± 6.6° [SD] and 42.7 ± 4.3°, respectively, p = 0.04). Compared to fellow, residents tended to implant the cup in a more anteverted position than the final cup version (9.6 ± 6.7° and 6.74 ± 5.6° [SD], p = 0.034). There was no statistically significant difference in cup position between attendings' free-hand and final (computer assisted) cup placement. CONCLUSION: Accurate and consistent acetabular cup placement improves with level of training. Accurate and consistent acetabular cup version is harder to master as compared to acetabular cup inclination.

Outpatient Surgical Fixation of Proximal Humerus Fractures Can Be Performed Without Increased Rates of Short-Term Complications or Readmissions.

OBJECTIVE: To delineate differences in short-term complications between outpatient versus inpatient open reduction and internal fixation (ORIF) of proximal humerus fractures. DESIGN: Retrospective database review. SETTING: Hospitals participating in the American College of Surgeons National Surgical Quality Improvement Program database. PATIENTS: Patients in the National Surgical Quality Improvement Program database with proximal humerus fractures from 2005 to 2017. INTERVENTION: Proximal humerus fracture ORIF. MAIN OUTCOME MEASUREMENTS: Thirty-day readmission, reoperation, thromboembolic events, and other complications. RESULTS: In total, 920 outpatient and 2490 inpatient ORIF cases were identified. The proportion of outpatient proximal humerus fracture ORIF increased throughout the years from 6.67% in 2007 to 34.89% in 2017. Each outpatient case was propensity-score-matched with one inpatient case by age, sex, functional status, American Society of Anesthesiologists classification, smoking status, diabetes mellitus type, hypertension, chronic obstructive pulmonary disease, and dyspnea on exertion. After matching, there were 920 outpatient and 920 inpatient cases. Statistical analysis revealed no significant difference in complications including reoperation (1.63% vs. 2.50%), thromboembolic events (0.65% vs. 0.65%), and 30-day readmissions (2.93% vs. 2.69%) between outpatient versus matched inpatient procedures (all P > 0.05). The only significant finding was a lower rate of blood transfusion in outpatient procedures (0.54%) compared with inpatient procedures (4.02%) (P < 0.001). CONCLUSIONS: The perioperative outcomes assessed here support the conclusion that ORIF for proximal humerus fractures can be performed in the outpatient setting without increased rates of 30-day perioperative complications or readmissions compared with inpatient procedures. However, it is worth noting that the majority of outpatient cases were younger than the average geriatric proximal humerus fracture patient. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Trends of Prosthetic Joint Infection Organisms and Recurrence for a Single High-Volume Arthroplasty Surgeon Over 20 Years.

BACKGROUND: Prosthetic joint infection (PJI) is a morbid complication following total joint arthroplasty (TJA). PJI diagnosis and treatment has changed over time, and patient co-management with a high-volume musculoskeletal infectious disease (MSK ID) specialist has been implemented at our institution in the last decade. METHODS: We retrospectively evaluated all consecutive TJA patients treated for PJI between 1995 and 2018 by a single high-volume revision TJA surgeon. Microbial identities, antibiotic resistance, prior PJI, and MSK ID consultation were investigated. RESULTS: In total, 261 PJI patients (median age 66 years, interquartile range 57-75) were treated. One-year and 5-year reinfection rates were 15.8% (95% confidence interval [CI] 11.6-20.7) and 22.1% (95% CI 17.0-27.7), respectively. Microbial identities and antibiotic resistances did not change significantly over time. Despite seeing more prior PJI patients (53.3% vs 37.6%, P = .012), MSK ID-managed patients had similar infection rates as non-MSK ID-managed patients (hazard ratio [HR] 1.02, 95% CI 0.6-1.75, P = .93). Prior PJI was associated with higher reinfection risk (HR 2.39, 95% CI 1.39-4.12, P = .002) overall and in patients without MSK ID consultation, specifically (HR 2.78, 95% CI 1.37-5.65, P = .005). This risk was somewhat lower and did not reach significance in prior PJI patients with MSK ID consultation (HR 1.97, 95% CI 0.87-4.48, P = .106). CONCLUSION: We noted minimal differences in microbial/antibiotic resistances for PJI over 20 years in a single institution, suggesting current standards of PJI treatment remain encouragingly valid in most cases. MSK ID involvement was not associated with lower reinfection risk overall; however, in patients with prior PJI, the risk of reinfection appeared to be somewhat lower with MSK ID involvement. LEVEL OF EVIDENCE: Level IV-Case Series.