Effects of Posterior Tibial Slope on a Posterior Cruciate Retaining Total Knee Arthroplasty Kinematics and Kinetics

BackgroundIt has been hypothesized that increasing posterior tibial slope can influence condylar rollback and play a role in increasing knee flexion. However, the effects of tibial slope on knee kinematics are not well studied. The objective of this study is to assess the effects of tibial slope on femorotibial kinematics and kinetics for a posterior cruciate retaining total knee arthroplasty design.MethodsA validated forward solution model of the knee was implemented to predict the femorotibial biomechanics of a posterior cruciate retaining total knee arthroplasty with varied posterior slopes of 0°-8° at 2° intervals. All analyses were conducted on a weight-bearing deep knee bend activity.ResultsIncreasing the tibial slope shifted the femoral component posteriorly at full extension but decreased the overall femoral rollback throughout flexion. With no tibial slope, the lateral condyle contacted the polyethylene 6 mm posterior of the midline, but as the slope increased to 8°, the femur shifted an extra 5 mm, to 11 mm posterior of the tibial midline. Similar shifts were observed for the medial condyle, ranging from 7 mm posterior to 13 mm posterior, respectively. Increasing posterior slope decreased the posterior cruciate ligament tension and femorotibial contact force.ConclusionThe results of this study revealed that, although increasing the tibial slope shifted the femur posteriorly at full extension and maximum flexion, it reduced the amount of femoral rollback. Despite the lack of rollback, a more posterior location of condyles suggests lower chances of bearing impingement of the posterior femur and may explain why increasing slope may lead to higher knee flexion.     

Early and Direct Rehab Transfer Leads to Significant Cost Savings and Decreased Hospital Length of Stay for Total Joint Arthroplasty in a Veteran Population

BackgroundTotal joint arthroplasty is the most common elective orthopedic procedure in the Veterans Affairs hospital system. In 2019, physical medicine and rehabilitation began screening patients before surgery to select candidates for direct transfer to acute rehab after surgery. The primary outcome of this study was to demonstrate that the accelerated program was successful in decreasing inpatient costs and length of stay (LOS). The secondary outcome was to show that there was no increase in complication, reoperation, and readmission rates.MethodsA retrospective review of total joint arthroplasty patients was conducted with three cohorts: 1) control (n = 193), 2) transfer to rehab orders on postop day #1 (n = 178), and 3) direct transfers to rehab (n = 173). To assess for demographic disparities between cohorts, multiple analysis of variance tests followed by a Bonferroni P-value correction were used. Differences between test groups regarding primary outcomes were assessed with analysis of variance tests followed by pairwise t-tests with Bonferroni P-value corrections.ResultsThere were no significant differences between the cohort demographics or comorbidities. The mean total LOS decreased from 7.0 days in the first cohort, to 6.9 in the second, and 6.0 in the third (P = .00034). The mean decrease in cost per patient was $14,006 between cohorts 1 and 3, equating to over $5.6 million in savings annually. There was no significant change in preintervention and postintervention short-term complications (P = .295).ConclusionsSignificant cost savings and decrease in total LOS was observed. In the current health care climate focused on value-based care, a similar intervention could be applied nationwide to improve Veterans Affair services.     

Are We Being Fooled by Fluoroscopy? Distortion May Affect Limb-Length Measurements in Direct Anterior Total Hip Arthroplasty

BackgroundDistortion is an intrinsic phenomenon associated with image-intensified fluoroscopy that is both poorly understood and infrequently appreciated by orthopedic surgeons. Little information exists regarding its potential influence on intraoperative parameters during orthopedic surgery, let alone during direct anterior (DA) total hip arthroplasty (THA). The purpose of this study was to quantify the amount of potential error caused by fluoroscopic distortion during DA THA.MethodsIntra-operative fluoroscopic pelvic images from 74 DA THAs were reviewed by two independent readers. All images were obtained using the same fluoroscopic C-arm unit with a radiopaque grid attached to the image intensifier. The vertical distortion from a straight central horizontal line at the peripheries of images were measured and summed to yield the combined vertical distortion similar to how a surgeon calculates a side to side comparison of limb lengths. Simple linear regression was used to evaluate associations between total distortion and patient demographics, operating theaters, and various operative parameters.ResultsThe average combined distortion was 10.0mm (range 2.0-20.0mm). There was a significant difference in the average distortion observed in different theaters (P < .001). There was no association between distortion and patient demographics or fluoroscopic time (all, P > .05).ConclusionFluoroscopic distortion is unpredictable and can cause a substantial amount of error when comparing limb lengths during DA THA. This is a critical finding as this amount of inaccuracy could lead to unintended implant positioning and limb-length discrepancies if unaccounted for.     

Understanding the Main Predictors of Length of Stay After Total Hip Arthroplasty: Patient-Related or Procedure-Related Risk Factors?

BackgroundRemoving total hip arthroplasty (THA) from the Centers for Medicare & Medicaid Services (CMS) inpatient-only list allows Medicare to cover outpatient THA, driving hospitals to recommend outpatient surgery for appropriate patients and raising safety concerns over which patients’ admissions should remain inpatient. Thus, we aimed to determine the influence of patient-related and procedure-related risk factors as predictors of >1-day Length of Stay (LOS) after THA.MethodsA prospective cohort of 5281 patients underwent primary THA from 2016 to 2019. Risk factors were categorized as patient-related or procedure-related. Multivariable cumulative link models identified significant predictors for 1-day, 2-day, and ≥3-day LOS. Discriminating 1-day LOS from >1-day LOS, we compared performance between two regression models.ResultsA>1-day LOS was significantly associated with age, female gender, higher body mass index, higher Charlson Comorbidity Index, Medicare status, and higher Hip disability and Osteoarthritis Outcome Physical Function Shortform(HOOS-PS) and lower Veterans RAND12 Mental Component (VR-12 MCS) scores via the initial regression model that contained patient factors only. A second regression model included procedure-related risk factors and indicated that procedure-related risk factors explain LOS more effectively than patient-related risk factors alone, as Akaike information criterion (AIC) increased by approximately 1100 units upon removal from the model.ConclusionAlthough patient-related risk factors alone provide predictive value for LOS following THA, procedure-related risk factors remain the main drivers of predicting LOS. These findings encourage examination of which specific procedural risk factors should be targeted to optimize LOS when choosing between inpatient and outpatient THA, especially within a Medicare population.     

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

BackgroundProsthetic 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.MethodsWe 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.ResultsIn 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).ConclusionWe 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 EvidenceLevel IV–Case Series.     

In Vivo Corrosion of Sleeved Ceramic Femoral Heads: A Retrieval Study

BackgroundThe purpose of this study was to evaluate a series of retrieved sleeved ceramic femoral heads used in total hip arthroplasty (THA) and determine qualitative and quantitative damage and corrosion patterns.MethodsAn IRB-approved implant retrieval database was utilized to identify all sleeved ceramic femoral heads collected from 1995 to 2004. There were 16 implants with an average duration of in situ of 70 months (range, 13-241 months). The femoral stem was known in 14 cases and was titanium alloy in each of those cases. None were revised for metal-related complications. Ten implants (63%) were from primary THAs, and 6 (38%) were from revision THAs. Damage and corrosion were qualitatively graded using a modified Goldberg method. A quantitative assessment was performed with a coordinate measurement machine (CMM).ResultsAmong the 16 retrieved implants, 1 (6%) demonstrated severe Grade 4 corrosion, 5 (31%) had moderate Grade 3 corrosion, 5 (31%) had mild Grade 2 corrosion, and 5 (31%) had no visible corrosion at the inner sleeve that interfaces with the stem trunnion. The only case of grade 4 corrosion occurred in the only head-sleeve in the study that was not factory assembled and was mated with a titanium molybdenum zirconium ferrous (TMZF) alloy stem. The mean maximum linear corrosion depth at the taper interface, as measured by the CMM, was 7.7 microns (range, 0.9-32.9 microns).ConclusionThis study is the first to quantify corrosion at the titanium interface of sleeved ceramic femoral heads. Potentially clinically significant damage and corrosion patterns were observed in a few failed retrievals; however, the majority of cases demonstrated minimal or no damage.     

Conical Primary Cementless Stem in Revision Hip Arthroplasty: 94 Consecutive Implantations at a Mean Follow-Up of 12.7 years

BackgroundRevision of a failed total hip arthroplasty (THA) poses technical challenges. The use of primary stems for revision can be advantageous for maintaining bone stock and reducing complications: small case series have reported promising results in the short-term to mid-term follow-up. The aim of this study was to evaluate the long-term clinical and functional results and survivorship of a consecutive series of THA femoral component revisions using a conical primary cementless stem (PCS).MethodsNinety-four stem revisions with a preoperative Paprosky I or II defect were analyzed at an average follow-up of 12.7 ± 5.4 years. Aseptic loosening was the reason for revision in 92.5% of cases. Twenty patients were lost to follow-up. Two subgroups were created: Group 1 (n = 59) underwent isolated stem revision; Group 2 (n = 15) underwent complete THA revision. All were evaluated preoperatively and postoperatively based on the Harris Hip Score (HHS), the Western Ontario and McMaster Universities Index (WOMAC) score, and the visual analog scale for pain (VAS). Residual trochanteric pain and length discrepancies were recorded. Radiographic evaluation included signs of osteolysis, subsidence, loosening, and heterotopic ossification.ResultsPCS survivorship was 100% at 5 years and 95.9% at 10 years. Overall, significant postoperative improvements (P < .01) were observed on the HHS (44.3 vs 86.9), WOMAC (42.8 vs 82.8), and VAS (7.0 vs 3.0). Postoperative scores on all scales were higher for Group 1 (P < .01). Three patients (4.1%) underwent further stem revision. Demarcation lines (1 mm) were found in 12 (16.2%) patients and significant heterotopic ossifications in 22 (29.7%).ConclusionThe use of PCS for stem revision in failed THA with a limited femoral bone defect is a reliable option for both isolated stem revision and concomitant cup revision in well-selected patients.     

Is a Titanium Implant for Total Knee Arthroplasty Better? A Randomized Controlled Study

BackgroundLighter weight and lower modulus are potential advantages of titanium (Ti) implants over cobalt chrome (CoCr) implants in total knee arthroplasty (TKA). This study was conducted to determine whether Ti implants in TKA resulted in better clinical outcomes and radiologic results.MethodsOne hundred and eight patients (216 knees) with knee arthritis warranting bilateral primary TKA were randomly allocated to undergo Ti rotating-platform TKA in one knee and CoCr rotating-platform TKA in the contralateral knee. The mean follow-up period was 5.3 years (range, 1-7 years). The weight of Ti implants was one-third lighter than that of CoCr implants (133.9 g vs 390.1 g, P < .01). Clinical outcomes were evaluated using clinical scores, patient preferences (lightness, comfort, naturalness, and satisfaction), gait analysis (kinetic and kinematic data), range of motion, and degree of pain. Radiologic results were evaluated based on the radiolucent line (RLL), degree of medial tibial bone loss, and loosening as seen on X-ray.ResultsNo significant differences were observed in clinical scores or patient preference. Regarding implant weight, approximately 70% of patients did not perceive the Ti implant as lighter. No significant differences were observed in gait analysis, range of motion, or degree of pain. The RLL was seen in 9% of the Ti implant group and 19% of the CoCr implant group.ConclusionThe lighter Ti implant did not show any clinical benefit over CoCr implants. The lightness of the Ti implant is not sufficient to matter or be noticeable. However, the Ti implant showed lower rate of RLL than the CoCr implant.Level of Evidencelevel I, randomized controlled trial.     

The Impact of Author Financial Conflicts on Robotic-Assisted Joint Arthroplasty Research

BackgroundRecent studies have suggested clinical superiority with robotic-assisted arthroplasty compared to traditional techniques. However, concerns exist regarding the author’s financial conflicts of interest (COI), which may influence research outcomes. This study aimed to determine whether COI relating to robotic-assisted arthroplasty influences the results of published outcomes following total hip (THA), total knee (TKA), and unicompartmental knee arthroplasty (UKA).MethodsWe performed a systematic review to identify all studies evaluating the use of robotics in THA, TKA, and UKA. An author’s financial COI was identified if they reported a relevant disclosure through the American Academy of Orthopedic Surgeons or within the study article. We then queried the Open Payments website to record all payments made from a robotic company in the year prior to publication. Each study was categorized as either favoring robotics (n = 42), neutral (n = 10), or favoring traditional techniques (n = 2). We then compared the number of conflicted authors, journal impact factor, level of evidence, and mean annual industry payment to each author.ResultsOf the 54 studies meeting inclusion criteria, 49 (91%) had an author financial COI. Conflicted studies were more likely to report favorable results of robotics than nonconflicted studies. When compared to studies favoring conventional techniques, those demonstrating favorable robotics outcomes had a higher number of conflicted authors and a higher mean industry payment per author. There was no difference in the level of evidence or journal impact factor.DiscussionNearly all studies comparing robotic THA, TKA, and UKA to conventional techniques involve financially conflicted authors. Further studies without COI may provide unbiased results.     

Minority Race and Ethnicity is Associated With Higher Complication Rates After Revision Surgery for Failed Total Hip and Knee Joint Arthroplasty

BackgroundRacial and ethnic disparities in access to hip and knee total joint arthroplasty (TJA) and postoperative outcomes have wide-reaching implications for patients and the health care system. The aim of this study is to evaluate the effect of ethnicity on clinical outcomes and complications following revision hip and knee TJA.MethodsA single-institution, retrospective analysis of a consecutive series of 4424 revision hip and knee TJA patients was evaluated. Student’s t-test and chi-squared analysis were used to identify significant differences in patient demographics and clinical outcomes between Caucasians and various ethnic minorities, including African Americans, Hispanics, and Asians.ResultsWhen compared with white patients, African American patients demonstrated a significantly higher BMI (P = .04), ASA score (P = .04), length of hospital stay (P = .06), and postoperative infection rates (P = .04). Hispanics demonstrated a significantly higher BMI (P = .04), when compared with white patients, alongside a significantly higher risk for postoperative infection (P < .01). African American demonstrated a significantly higher ASA score (P = .02; P = .03), when compared with Hispanics and Asians, alongside a significantly increased length of stay (P = .01) and higher risk for postoperative infection (P = .02).ConclusionThe study findings demonstrate an underutilization of revision TJA by ethnic minority groups, suggesting that disparities in access to orthopedic surgery increase from primary to revision surgery despite higher failure rates of minority ethnic groups reported after primary TJA surgery. In addition, inferior postoperative outcomes were associated with African Americans and Hispanics, when compared to white patients, with African Americans demonstrating the highest risk of postoperative complications.