Lymphocyte Subset Ratio Cannot Diagnose Immune Failure of a TKA.

BACKGROUND: Up to 20% of patients are dissatisfied following total knee arthroplasty (TKA), most often due to pain and/or stiffness. The differential diagnosis includes immune reaction to the prosthesis. However, there is no consensus on diagnostic criteria for immune failure, an allergic reaction, to a TKA. Histologic evaluation could provide evidence as to whether an allergic reaction caused TKA failure. A recent study showed an increase in CD4+ lymphocytes compared to CD8+ lymphocytes in patients lymphocyte transformation testing (LTT) + for Ni. This finding is consistent with Ni sensitization, but can lymphocyte subsets be used to diagnose immune failure on a case-by-case basis? METHODS: Periprosthetic tissues from 18 revision cases of well-fixed, aseptic, but painful and/or stiff primary TKAs were analyzed. Six patients LTT- for Ni were matched as a cohort for age, sex, and body mass index (BMI), to 12 patients LTT + for Ni. Periprosthetic tissue biopsies underwent immunohistochemical IHC staining for CD4+ and CD8+ lymphocyte subsets and were compared by LTT status. The immunohistochemicalIHC results were also compared with periprosthetic histology. RESULTS: There was no relationship between LTT status and mean CD4+ cells/hpf or CD4+:CD8+ lymphocyte ratio. No relationship was found between LTT stimulation index (continuous or categorical) and CD4+:CD8+ ratio or aseptic lymphocyte-dominant vasculitis-associated lesion ALVAL score. CONCLUSION: Lymphocytes in periprosthetic tissue are highly variable in number, subtype ratio, and location, and have no relationship to LTT result or ALVAL score on a case-by-case basis. Based on these results, lymphocyte subsets cannot diagnose immune failure. Further work is needed to determine criteria for the diagnosis of immune failure of a TKA.

Periprosthetic Tissue Reaction Independent of LTT Result and Implanted Materials in Total Knee Arthroplasty.

BACKGROUND: An allergic reaction may rarely cause a painful or stiff total knee arthroplasty (TKA). However, no consensus diagnostic criteria for TKA immune failure exist. Lymphocyte transformation testing (LTT) measures immune sensitivity to various materials, but its role in diagnosing an allergic reaction to a TKA has not been established. This study compares TKA periprosthetic tissues in a) LTT-positive versus -negative patients and b) patients with conventional CoCrNi versus hypoallergenic implants. METHODS: Periprosthetic tissues from 26 revision cases of well-fixed, aseptic, but painful or stiff TKAs were analyzed. Twelve patients LTT positive for nickel (Ni) were matched as a cohort to 6 LTT-negative patients. In 4 patients LTT positive for Ni, tissue from first revision of CoCrNi implants was compared with tissue from subsequent revision of hypoallergenic implants. Histology was evaluated using the aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) score. RESULTS: No correlation was found between LTT and any ALVAL score component. The mean total ALVAL score was 3.8 ± 1.5 for LTT-negative patients and 3.3 ± 1.2 for LTT-positive patients (P = .44). The mean total ALVAL score at revision of CoCrNi implants was 3.0 ± 1.8 compared with 5.8 ± 0.5 at rerevision of hypoallergenic implants (P = .053). CONCLUSION: Periprosthetic TKA tissue reactions were indistinguishable between LTT-positive and -negative patients. LTT does not predict the periprosthetic tissue response. ALVAL scores of hypoallergenic revision implant tissue trended higher than primary CoCrNi implant tissue. A positive LTT may not indicate that a periprosthetic immune reaction is the cause of pain and stiffness after TKA. LEVEL OF EVIDENCE: 3, retrospective cohort study.

Survival in Mesenchymal Chondrosarcoma Varies Based on Age and Tumor Location: A Survival Analysis of the SEER Database.

BACKGROUND: Studies suggest that mesenchymal chondrosarcoma is associated with a poorer prognosis and a higher proportion of extraskeletal tumors than conventional chondrosarcoma. However, these investigations have been small heterogeneous cohorts, limiting analysis of prognostic factors. QUESTIONS/PURPOSES: (1) What is the 5- and 10-year survival rate of patients diagnosed with mesenchymal chondrosarcoma? (2) What is the effect of demographic and tumor characteristics on survival in patients with mesenchymal chondrosarcoma? METHODS: The Surveillance, Epidemiology, and End Results (SEER) database was used to identify all patients diagnosed with mesenchymal chondrosarcoma from 1973 to 2011. SEER reports survival data on over 8.2 million patients with cancer and has attained 98% completeness in reporting. Using variables within the database, this study designated each patient's tumor as skeletal or extraskeletal and cranial, axial, or appendicular, respectively. Overall survival (OS) was determined for the entire series as well as each group. Median survival was calculated using Kaplan-Meier methods. Cox proportional hazards regression was used to determine whether demographic and tumor variables affected survival. Two hundred five patients with mesenchymal chondrosarcoma were identified, including 82 (40%) skeletal and 123 (60%) extraskeletal. RESULTS: OS for the entire series was 51% (95% confidence interval [CI], 43%-58%) and 43% (95% CI, 35%-51%) at 5 and 10 years, respectively. No difference in OS was detected between extraskeletal and skeletal tumors. Kaplan-Meier analyses showed OS was worse for tumors in axial locations compared with appendicular and cranial locations. Appendicular tumors demonstrated an OS of 50% (95% CI, 36%-63%) at 5 years and 39% (95% CI, 26%-52%) at 10 years. OS for axial tumors was 37% (95% CI, 25%-49%) and 31% (95% CI, 20%-43%), whereas it was 74% (95% CI, 59%-84%) and 67% (95% CI, 50%-79%) for cranial tumors at 5 and 10 years, respectively. When controlling for age, sex, tumor origin, and tumor location, the presence of metastasis (hazard ratio [HR], 12.38; 95% CI, 5.75-26.65; p < 0.001) and 1-cm size increase (HR, 1.16; 95% CI, 1.09-1.23; p < 0.001) were both independently associated with an increased risk of death. Tumor location showed different behaviors depending on patient age. In comparison to cranial tumors at age 20 years, the HR was 5.56 (95% CI, 1.47-21.05; p = 0.01) for axial tumors and 6.26 (95% CI, 1.54-25.42; p = 0.01) for appendicular tumors. At age 60 years, those ratios were 0.10 (95% CI, 0.02-0.55; p = 0.01) and 0.14 (95% CI, 0.04-0.58; p = 0.01), respectively. CONCLUSIONS: Our data suggest that extraskeletal tumors are more common than previously reported; however, this factor does not have clear prognostic value. Presence of metastatic disease and increased tumor size are the main predictors of poor survival outcome. Cranial tumors appear to have a different clinical behavior with our data suggesting better overall survival in young patients (compared with axial and appendicular locations) and a worse survival outcome in older patients. LEVEL OF EVIDENCE: Level IV, prognostic study.

Evolving Effects of the COVID-19 Pandemic on Hip Fracture Outcomes: A Retrospective Comparison of Pre, Early, and Late Pandemic Timepoints.

INTRODUCTION: Hospital systems were strained during the COVID-19 pandemic, and although previous studies have shown that surgical outcomes in healthy hip fracture patients were unaffected in the initial months of the pandemic, subsequent data are limited. This study examined the evolution of hip fracture care throughout the COVID-19 pandemic. METHODS: A retrospective review (level III evidence) was done of surgically treated adult hip fractures at a Level 1 academic trauma center from January 2019 to September 2022, stratified into three groups: pre, early, and late pandemic. Continuous variables were evaluated with the Student t-test and one-way analysis of variance, categorical variables were evaluated with chi-squared, P < 0.05 considered significant. RESULTS: Late pandemic patients remained in the hospital 30.1 hours longer than early pandemic patients and 35.7 hours longer than prepandemic patients (P = 0.03). High-energy fractures decreased in the early pandemic, then increased in late pandemic (P < 0.01). Early pandemic patients experienced more myocardial infarctions (P < 0.01). No significant differences in time to surgery, revision surgery, 90-day mortality, or other adverse events were noted. CONCLUSION: To our knowledge, this is the longest study evaluating hip fracture outcomes throughout the COVID-19 pandemic. These results are indicative of an overburdened regional health system less capable of facilitating patient disposition.

Diagnosing the Severity of Knee Osteoarthritis Using Regression Scores From Artificial Intelligence Convolution Neural Networks.

BACKGROUND: This study focused on using deep learning neural networks to classify the severity of osteoarthritis in the knee. A continuous regression score of osteoarthritis severity has yet to be explored using artificial intelligence machine learning, which could offer a more nuanced assessment of osteoarthritis. MATERIALS AND METHODS: This study used 8260 radiographic images from The Osteoarthritis Initiative to develop and assess four neural network models (VGG16, EfficientNetV2 small, ResNet34, and DenseNet196). Each model generated a regressor score of the osteoarthritis severity based on Kellgren-Lawrence grading scale criteria. Primary performance outcomes assessed were area under the curve (AUC), accuracy, and mean absolute error (MAE) for each model. Secondary outcomes evaluated were precision, recall, and F-1 score. RESULTS: The EfficientNet model architecture yielded the strongest AUC (0.83), accuracy (71%), and MAE (0.42) compared with VGG16 (AUC: 0.74; accuracy: 57%; MAE: 0.54), ResNet34 (AUC: 0.76; accuracy: 60%; MAE: 0.53), and DenseNet196 (AUC: 0.78; accuracy: 62%; MAE: 0.49). CONCLUSION: Convolutional neural networks offer an automated and accurate way to quickly assess and diagnose knee radiographs for osteoarthritis. The regression score models evaluated in this study demonstrated superior AUC, accuracy, and MAE compared with standard convolutional neural network models. The EfficientNet model exhibited the best overall performance, including the highest AUC (0.83) noted in the literature. The artificial intelligence-generated regressor exhibits a finer progression of knee osteoarthritis by quantifying severity of various hallmark features. Potential applications for this technology include its use as a screening tool in determining patient suitability for orthopedic referral. [Orthopedics. 2024;47(5):e247-e254.].

The Biomechanical Effects of Intramedullary Fixation to the Level of the Physeal Scar on Distal Tibia Fracture Stability.

INTRODUCTION: The purpose of this study was to evaluate whether intramedullary nail contact with physeal scar improves construct mechanics when treating distal tibial shaft fractures. METHODS: Axially unstable extra-articular distal tibia fractures were created in 30 fresh frozen cadaveric specimens (15 pairs, mean age 79 years). Specimens underwent intramedullary nailing to the level of the physeal scar locked with one or two interlocks or short of the physeal scar locked with two interlocks (reference group). Specimens were subjected to 800N of axial load for 25,000 cycles. Primary outcomes were stiffness before and after cyclic loading. Secondary outcomes were load to failure, load at 3 mm displacement, plastic deformation, and total deformation. RESULTS: The physeal scar with one interlock cohort demonstrated 3.8% greater stiffness before cycling ( P = 0.75) and 1.7% greater stiffness after cycling ( P = 0.86) compared with the reference group. The physeal scar with two interlocks group exhibited 0.3% greater stiffness before cycling ( P = 0.98) and 8.4% greater stiffness after cycling ( P = 0.41) in relation to the reference group. No differences were identified regarding load to failure or load at 3 mm displacement. In specimens with two interlocks, those in contact with the physeal scar demonstrated significantly less plastic ( P = 0.02) and total ( P = 0.04) deformation. CONCLUSIONS: Constructs ending at the physeal scar demonstrated stiffness and load to failure similar to those without physeal scar contact. Less plastic and total deformation was noted in two-interlock constructs with physeal scar contact, suggesting a possible protective effect provided by the physeal scar. These data argue that physeal scar contact may offer a small mechanical benefit in nailing distal tibia fractures, but clinical relevance remains unknown.

A deep surgical site infection risk score for patients with open tibial shaft fractures treated with intramedullary nail.

OBJECTIVES: To identify deep infection risk factors in patients with open tibial shaft fractures and to develop a scoring algorithm to predict the baseline deep infection risk in this patient population. METHODS: A retrospective cohort study conducted at a single academic trauma center identified patients with open tibial shaft fractures treated with intramedullary nail fixation from December 2006 to October 2020. The primary outcome was a deep surgical site infection requiring surgical debridement. The outcome was identified by Current Procedural Terminology codes and confirmed with a medical chart review documenting evidence of a tibial draining wound or sinus tract. RESULTS: Deep surgical site infection occurred in 13% of patients (97/769). Factors that predicted deep surgical site infection were identified. Gustilo-Anderson type IIIB or IIIC was the strongest predictor with a 12-fold increase in the odds of deep infection (OR 11.8, p < 0.001). Additional factors included age >40 years (OR 1.7, p = 0.03), American Society of Anesthesiologists score ≥3 (OR 1.9, p < 0.01), Gustilo-Anderson type IIIA vs. type I or II (OR 2.8, p = 0.004), and gunshot wounds (OR 2.9, p = 0.02). The risk scoring model predicted patients who would develop an infection with an acceptable level of accuracy (AUC 0.79). The risk score categorized patients from a low probability of deep infection 2%-6% with <10 points to high risk (58%-69%) with >40 points. CONCLUSIONS: This risk score model predicts deep postoperative infection in patients with open tibial shaft fractures treated with intramedullary nails. The ability to accurately estimate deep infection risk at the time of presentation might aid patient expectation management and allow clinicians to focus infection prevention strategies on the high-risk subset of this population.

Compartment Syndrome in High-Energy Tibial Plateau Fractures.

High-energy tibial plateau fractures carry a high risk of associated acute compartment syndrome. Clinicians should be familiar with several demographic, clinical, and radiographic factors that are associated with compartment syndrome development after tibial plateau fracture. Once the diagnosis of compartment syndrome is made, emergent decompressive fasciotomies are needed. Fracture fixation complicates the treatment course and elements of postoperative management. Deep surgical site infection is a common complication, and controversy remains regarding the ideal timing of fixation and soft tissue closure for these complex injuries.

Functional Outcomes of Patella Fractures Treated With Anterior Plate Osteosynthesis at One Year.

OBJECTIVES: To evaluate the functional outcomes of patients with displaced patellar fractures treated with anterior plate constructs. DESIGN: Prospective cohort and retrospective clinical and radiographic assessment. SETTING: Level I Trauma Center. PATIENTS/PARTICIPANTS: Between 2014 and 2018, 18 patients who underwent operative intervention for an isolated, displaced patella fracture (OTA/AO 34C1-3) with a minimum of 1-year follow-up agreed to participate in the study. The mean follow-up was 19.5 ± 6.0 months. INTERVENTION: Patients were treated with 2.4 or 2.7-mm plates and supplemental screws or cerclage wires. MAIN OUTCOME MEASUREMENTS: Patients were evaluated with the Short Form-36 Survey and the Knee Injury and Osteoarthritis Outcome Scores and asked about symptomatic implants. The range of motion was assessed by goniometer. RESULTS: The cohort had no wound complications, infections, nonunion, loss of reduction, or implant failure. Active knee flexion was 131 ± 7 degrees. Five patients (28%) endorsed implant irritation. Only one patient (5.5%) underwent implant removal, which consisted of transverse screw removal alone. Twelve of the 14 patients (86%), who were previously employed, returned to work at 10 ± 7 weeks. All Knee Injury and Osteoarthritis Outcome Scores subscale scores and the Short Form-36 Survey scores for physical functioning, limitations due to physical health, limitations due to mental health, and social functioning were significantly lower than reference population norms (P < 0.05). CONCLUSIONS: Anterior plating provides reliable fixation for displaced patellar fractures and results in a low incidence of implant irritation. However, patients who had anterior fixation for displaced patella fractures continue to exhibit functional deficits at 1-year postoperatively. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.