Faculty Bibliography

Venous thromboembolism (VTE) is a rare, but serious complication following total knee arthroplasty (TKA). Current VTE guidelines recommend pharmacologic agents with or without intermittent pneumatic compression devices (IPCDs). At our institution, both 81-mg aspirin (ASA) twice a day (BID) and portable IPCDs were previously prescribed to TKA patients at standard risk for VTE, but the IPCDs were discontinued and patients were treated with ASA alone going forward. The aim of this study is to determine if discontinued use of outpatient IPCDs is safe and does not increase the rate of VTE or any other related complications in patients following TKA. A retrospective review of 2,219 consecutive TKA cases was conducted, identifying patients with VTE, bleeding complications, infection, and mortality within 90 days postoperatively. Patients were divided into two cohorts. Patients in cohort one received outpatient IPCDs for a period of 14 days (control), while those in cohort two did not (ASA alone). All study patients received inpatient IPCDs and were maintained on 81-mg ASA BID for 28 days. A posthoc power analysis was performed using a noninferiority margin of 0.25 (α = 0.05; power = 80%), which showed that our sample size was fully powered for noninferiority for our reported deep vein thrombosis (DVT) rates, but not for pulmonary embolism (PE) rates. A total of 867 controls and 1,352 patients treated with ASA alone were identified. Only two control patients were diagnosed with a PE (0.23%), while one patient in the ASA alone group had DVT (0.07%). There was no statistical difference between these rates (p = 0.33). Furthermore, no differences were found in bleeding complications (p = 0.12), infection (p = 0.97), or 90-day mortality rates (p = 0.42) between both groups. The discontinued use of outpatient portable IPCDs is noninferior to outpatient IPCD use for DVT prophylaxis. Our findings suggest that this protocol change may be safe and does not increase the rate of VTE in standard risk patients undergoing TKA while using 81-mg ASA BID.

Venous thromboembolism (VTE) events are rare, but serious complications of total joint replacement affect patients and health care systems due to the morbidity, mortality, and associated cost of its complications. There is currently no established universal standard of care for prophylaxis against VTE in patients undergoing revision total knee arthroplasty (rTKA). The aim of this study was to determine whether a protocol of 81-mg aspirin (ASA) bis in die (BID) is safe and/or sufficient in preventing VTE in patients undergoing rTKAs versus 325-mg ASA BID. In 2017, our institution adopted a new protocol for VTE prophylaxis for arthroplasty patients. Patients initially received 325-mg ASA BID for 1 month and then changed to a lower dose of 81-mg BID. A retrospective review from 2011 to 2019 was conducted identifying 1,438 consecutive rTKA patients and 90-day postoperative outcomes including VTE, gastrointestinal, and wound bleeding complications, acute periprosthetic joint infection, and mortality. In the 74 months prior to protocol implementation, 1,003 rTKAs were performed and nine VTE cases were diagnosed (0.90%). After 26 months of the protocol change, 435 rTKAs were performed with one VTE case identified (0.23%). There was no significant difference in rates or odds in postoperative pulmonary embolism (PE; p = 0.27), DVT (p = 0.35), and total VTE rates (p = 0.16) among patients using either protocol. There were also no differences in bleeding complications (p = 0.15) or infection rate (p = 0.36). No mortalities were observed. In the conclusion, 81-mg ASA BID is noninferior to 325-mg ASA BID in maintaining low rates of VTE and may be safe for use in patients undergoing rTKA.

Unicondylar knee arthroplasty (UKA), as an alternative to total knee arthroplasty (TKA), has been shown to be an effective option for patients with single-compartment end-stage knee osteoarthritis. Implant survival is contingent upon proper alignment, which has been improved with the advent of robotic-assisted surgery (r-UKA), but whether this outweighs the increased cost of the robotic-assist device has not been analyzed in the literature. The purpose of this study was to investigate the mid-term cost-effectiveness of r-UKA compared with UKA with traditional instrumentation (t-UKA) in the United States. A cost-effectiveness analysis using a four-state Markov model was performed using data from the 2018 National Joint Registry of England and Wales and a retrospective multicenter, cohort study on a cohort of 65-year-old patients having undergone r-UKA. The main outcome was cost per revision avoided and sensitivity analyses were conducted to evaluate the impact of using different model assumptions on the results. The Markov model illustrated that the benefit derived from r-UKA versus t-UKA was beneficial from a payer's perspective. The estimated incremental cost-effectiveness ratio (ICER) was $14,737 per revision avoided in a facility seeing 100 patients a year. Case volume was shown to be the primary variable affecting cost-effectiveness, with the value of r-UKA directly increasing with higher case volumes. Cost-effectiveness analyses demonstrated that the use of r-UKA is an effective alternative to t-UKA in patients with single-compartment knee osteoarthritis. While this study could benefit from longer follow-up clinical studies to illustrate the benefits of r-UKAs beyond the current 2 years time horizon, r-UKAs remained cost-effective, even after investigating several different assumptions.

AIMS/OBJECTIVE:In computer simulations, the shape of the range of motion (ROM) of a stem with a cylindrical neck design will be a perfect cone. However, many modern stems have rectangular/oval-shaped necks. We hypothesized that the rectangular/oval stem neck will affect the shape of the ROM and the prosthetic impingement. METHODS:Total hip arthroplasty (THA) motion while standing and sitting was simulated using a MATLAB model (one stem with a cylindrical neck and one stem with a rectangular neck). The primary predictor was the geometry of the neck (cylindrical vs rectangular) and the main outcome was the shape of ROM based on the prosthetic impingement between the neck and the liner. The secondary outcome was the difference in the ROM provided by each neck geometry and the effect of the pelvic tilt on this ROM. Multiple regression was used to analyze the data. RESULTS:The stem with a rectangular neck has increased internal and external rotation with a quatrefoil cross-section compared to a cone in a cylindrical neck. Modification of the cup orientation and pelvic tilt affected the direction of projection of the cone or quatrefoil shape. The mean increase in internal rotation with a rectangular neck was 3.4° (0° to 7.9°; p < 0.001); for external rotation, it was 2.8° (0.5° to 7.8°; p < 0.001). CONCLUSION/CONCLUSIONS: 2021;10(12):780-789.

Cementless fixation in total knee arthroplasty (TKA) offers the potential for biologically active osseointegration and the potential for life-long fixation. With early cementless TKA designs, several design issues were identified related to early failure, particularly with the tibial and patellar components. However, in the recent two decades, with improvements upon the early designs, particularly in porous metal technology as well as improved early biomechanical stability, interest was re-established in cementless TKA. The surgical technique for cementless TKA is more exacting than cemented technique, with an important emphasis on indications, accurate resections, and component alignment. Modern cementless TKA designs have demonstrated excellent early- and mid-term survivorship equivalent to cemented TKA. More long-term studies are needed to study this comparison. While implant cost maybe higher with cementless designs, there is emerging evidence that there may be an overall cost saving with the use of cementless components given the shorter operative time and the savings in the cost of supplies associated with the use of cement. As the population undergoing TKA is becoming younger and more active, interest in the use of cementless implants will likely increase.

The number of revision total knee arthroplasties (TKAs) is greatly increasing. It is important to know how to approach the painful and malfunctioning TKA to determine the etiology and establish surgical plan, and also how to perform a basic revision TKA. Following the conclusion of this chapter, the reader should feel familiar with the full spectrum of treatment for patients who may be indicated for revision TKA.

Recently, fructosamine has shown promising results in predicting adverse outcomes following total knee arthroplasty. The purpose of this study was to assess the utility of fructosamine to predict adverse outcomes following total hip arthroplasty (THA). A prospective multi-center study involving four institutions was conducted. All primary THA were evaluated for glycemic control using fructosamine levels prior to surgery. Adverse outcomes were assessed at a minimum 1 year from surgery. Primary outcome of interest was periprosthetic joint infection (PJI) based on the International Consensus Meeting (ICM) criteria. Secondary outcomes assessed were superficial infections, readmissions and death. Based on previous studies on the subject, fructosamine levels above 293 µmol/L were used to define inadequate glycemic control. Overall 1212 patients were enrolled in the present study and were available for follow up at a minimum 1 year from surgery. Of those, 54 patients (4.5%) had elevated fructosamine levels (> 293 µmol/L) and these patients were 6.7 times more likely to develop PJI compared to patients with fructosamine levels below 293 µmol/L (p = 0.002). Patients with elevated fructosamine were also associated with more readmissions (16.7% vs. 4.4%, p < 0.007) and a higher mortality rate (3.7% vs. 0.6%, p = 0.057). These associations remained statistically significant in a multi-regression analysis after adjusting for age, comorbidities and length of stay; Adjusted odds ratio were 6.37 (95% confidence interval 1.98-20.49, p = 0.002) for PJI and 2.68 (95% confidence interval 1.14-6.29, p = 0.023) for readmissions. Fructosamine is a good predictor of adverse outcomes in patients undergoing THA and should be used routinely to mitigate morbidity and mortality risk.

BACKGROUND:To create a safe zone, an understanding of the combined femoral and acetabular mating during hip motion is required. We investigated the position of the femoral head inside the acetabular liner during simulated hip motion. We hypothesized that cup and stem anteversions do not equally affect hip motion and combined hip anteversion. METHODS:Hip implant motion was simulated in standing, sitting, sit-to-stand, bending forward, squatting, and pivoting positions using the MATLAB software. A line passing through the center of the stem neck and the center of the prosthetic head exits at the polar axis (PA) of the prosthetic head. When the prosthetic head and liner are parallel, the PA faces the center of the liner (PA position = 0, 0). By simulating hip motion in 1-degree increments, the maximum distance of the PA from the liner center and the direction of its movement were measured (polar coordination system). RESULTS:The effect of modifying cup and stem anteversion on the direction and distance of the PA's change inside the acetabular liner was different. Stem anteversion influenced the PA position inside the liner more than cup anteversion during sitting, sit-to-stand, squatting, and bending forward (P = .0001). This effect was evident even when comparing stems with different neck angles (P = .0001). CONCLUSION:Cup anteversion, stem anteversion, and stem neck-shaft angle affected the PA position inside the liner and combined anteversion in different ways. Thus, focusing on cup orientation alone when assessing hip motion during different daily activities is inadequate.

BACKGROUND:Today, biological fixation of uncemented press-fit acetabular components plays an important role in total hip arthroplasty. Long-term stable fixation of these implants depends on the osseointegration of the acetabular cup bone tissue into the acetabular cup implant, and their ability to withstand functional loads. AIM/OBJECTIVE:To compare the strength of bone-implant osseointegration of four types of porous metal implants in normal and osteoporotic bone in rabbits. METHODS:The study was performed in 50 female California rabbits divided into non-ovariectomized (non-OVX) and ovariectomized groups (OVX) at 6 mo of age. Rabbits were sacrificed 8 wk after the implantation of four biomaterials [TTM, CONCELOC, Zimmer Biomet's Trabecular Metal (TANTALUM), and ATLANT] in a 5-mm diameter defect created in the left femur. A biomechanical evaluation of the femur was carried out by testing implant breakout force. The force was gradually increased until complete detachment of the implant from the bone occurred. RESULTS:= 0.001). CONCLUSION/CONCLUSIONS:= 0.001) in healthy and in osteoporotic bone.