Faculty Bibliography

INTRODUCTION: Proper ligament tension in flexion with posterior cruciate retaining (CR) total knee arthroplasty (TKA) has long been associated with clinical success. The purpose of this study was to determine the effect of varying levels of posterior cruciate ligament (PCL) release on the tibiofemoral kinematics and PCL strain. MATERIALS AND METHODS: A computational analysis was performed and varying levels of PCL release were simulated. Tibiofemoral kinematics was evaluated. The maximum PCL strain was determined for each bundle to evaluate the risk of rupture based on the failure strain. RESULTS: The femoral AP position shifted anteriorly as the PCL stiffness was reduced. PCL strain in both bundles increased as stiffness was reduced. The model predicts that the AL bundle should not rupture for a 75% release. Risk of PM bundle rupture is greater than AL bundle. DISCUSSION: Our findings suggest that a partial PCL release impacts tibiofemoral kinematics and ligament tension and strain. The relationship is dynamic and care should be taken when seeking optimal balance intra-operatively.

The potential for using mobile applications (apps) as an effective tool to monitor patients in an outpatient setting is promising. Past studies have investigated the use of applications in preoperative and postoperative settings as well as in monitoring and treating chronic illnesses such as diabetes, congestive heart failure (CHF), and multiple sclerosis. However, there is limited data on its specific use in the context of total knee arthroplasty. Given the complicated nature and crucial role of patient adherence to protocols during the preparatory and recovery phases of the procedure, the use of an app can serve as a helpful tool in aiding patients throughout this process. We present a pilot study to assess the efficacy of using such an app in order to monitor patient adherence to total knee arthroplasty-specific preoperative and postoperative protocols. Preoperative protocols used in this study included a 5-item medication protocol and multiple activity instructions. Postoperative patient protocols included following instructions on topics such as recording responses to quality-of-life questions, when and how to contact the clinical team if patients had non-emergent concerns or questions, and carrying out daily physical therapy (PT) exercises. Patients received and recorded responses to these preoperative and postoperative instructions using the iGetBetter program application installed on an iPad Mini, provided to the participants. Patient adherence was based on the data gathered from the patient responses inputted on this app. Adherence rates were comparable to those reported in various past studies that also investigated rates of adherence to health management-related instructions communicated through mobile apps.

INTRODUCTION: The clinical relevance of limb length discrepancy (LLD) after total hip arthroplasty gains attention as the number of total hip arthroplasties increases. Although several techniques are commonly used to assess LLD using a pelvic radiograph, their accuracy is not well established. This study measures LLD using different techniques viewing the pelvis and compares the measurements with the true LLD. METHOD: Pelvic landmarks used included the femoral head, lesser trochanter, acetabular teardrop, ischial tuberosity, and tibial plafond. The true LLD was determined by finding the difference in distance between the lowest point of the ischial tuberosity and the tibial plafond as well as the top of the femoral head to the center of the tibial plafond for each lower limb. RESULTS: Using pelvic landmarks to assess LLD is significantly different (P < .001) from the true LLD. The difference in distance from the center of the tibial plafond to the ischial tuberosity was not significantly different from the measurement from the top of the femoral head to the center of the tibial plafond (P = .08). Also, using the acetabular teardrop as a landmark has less reliability when compared to the ischial tuberosity. DISCUSSION: Owing to the extensive variety of pathologies that are associated with LLD, preoperative planning should include an assessment of any preexisting LLD. Although it may be reasonable to compare pelvic measurements preoperatively and postoperatively to assess for changes, the data from this study do not support the estimation of the true LLD using a pelvic radiograph.

BACKGROUND: Preoperative anemia is present in 20% of total joint arthroplasty patients. Current preoperative treatment options, including iron supplementation (FE) and erythropoietin (EPO), are expensive. Tranexamic acid (TXA) has been adopted as an intraoperative adjunct to decrease blood loss. Our hypothesis is that TXA is a cost-effective treatment compared to FE and EPO in anemic patients. METHODS: In this study, a cost analysis was performed, comparing the material costs of TXA and packed red blood cells (PRBCs) to the theoretical administration and material costs of FE and EPO per standard preoperative anemia protocol. RESULTS: A total of 243 patients were included in the study. Of this group, 18.5% (45/243) had preoperative anemia. The rate of transfusion was 6.7% (3/45), and 5 units of PRBCs was transfused. The combined cost of TXA and PRBCs was $5317.08. Even assuming a best-case scenario with FE or EPO treatment without a postoperative PRBC requirement, the cost of treatment would range from 2 to 17 times more than treatment with TXA. An additional 50 units of PRBC (1.1 units per patient) would need to be transfused for the cost of TXA treatment to be equivalent to FE or EPO treatment. CONCLUSION: Tranexamic acid is significantly less expensive than FE or EPO as a treatment option for total joint arthroplasty patients presenting with preoperative anemia. It is a cost-effective adjunct for limiting transfusion rates in this patient population. We recommend that new preoperative anemia levels that necessitate preoperative intervention be established.

BACKGROUND: With increasing health care expenditures, reform has largely focused on cost containment, particularly in elective procedures such as total hip and knee arthroplasty (THA and TKA, respectively). The primary objective of this study is to determine what financial value patients place on these highly successful procedures. METHODS: An anonymous survey was administered to 670 patients at 4 different institutions (2 private practice and 2 academic centers) in the outpatient setting over a 15-month period. Patients were asked what reimbursement a surgeon should receive for a primary total joint arthroplasty (TJA), their perception of how much Medicare actually reimburses for TJA, how much they would pay out of pocket for the procedure, and their opinion of current Medicare reimbursement rates. RESULTS: Of the 557 patients who participated in the survey (83% response rate), patients on average felt that orthopedic surgeons should be reimbursed $27,430 for a THA and $19,830 for a TKA. Patients would be willing to pay a significant amount of out-of-pocket costs for their procedure, mean of $14,397 for THA (50.3% of total costs) and $12,797 for TKA (46.3% of total costs). Although patients in private practice groups had higher education and household income (P < .001), patients in academic centers would be willing to pay more out-of-pocket costs ($15,922 vs $5782, P = .034 for THA, $14,419 vs $4556, P = .052 for TKA). CONCLUSION: Patients in both private practice and academic centers feel that surgeons are underpaid for primary THA and TKA. As controversy continues to surround orthopedic surgeons' participation in Medicare, many patients are still willing to pay a significant amount of out-of-pocket expenses for TJA.

BACKGROUND: Expenditures for postacute care in total joint arthroplasty (TJA) have risen dramatically over recent decades. Therefore, efforts are underway to better identify cost savings in postacute rehabilitation centers, such as skilled nursing facilities (SNFs). The primary purpose of this study was to analyze gait training achievements in post-TJA patients in the interval between hospital discharge and the patients' first 4 days at the SNF. Identification of potential losses in therapeutic progress may lead the way for improved patient care, outcomes, and cost savings. Our hypothesis is that patients discharged to an SNF will have a decline in gait achievements upon transfer from the hospital. METHODS: A total of 68 patients who underwent TJA were included. The total distance ambulated during physical therapy (PT) was recorded for the last day of hospital therapy and the first 4 days at the SNF as well as the reported visual analog scale (VAS) pain scores. RESULTS: There was a 73% decline in distance ambulated on SNF day 0 (Hospital: 138.6 ft vs SNF: 37.9 ft; P < .001) and a 50% decline on SNF day 1 (Hospital: 103.0 ft; SNF vs 51.1 ft; P < .001) compared to the last hospital session. There were no significant differences in distance walked on SNF days 3 and 4 relative to the last hospital session. The VAS pain scores did not significantly differ on SNF days 0 and 1 compared to the last hospital day but began to significantly decline on SNF day 3 (Hospital: 4.9; SNF: 3.3; P = .02) and day 4 (Hospital: 3.9; SNF: 2.3; P = .03). CONCLUSION: There was a significant decline in ambulatory proficiency in post-TJA patients on the day of and the day following hospital discharge to an SNF. These deficits cannot be attributed to heightened pain levels. Early and progressive ambulation is a recognized component of appropriate PT following TJA. This study therefore highlights the transition from hospital to SNF as a crucial and novel target for improvement in post-TJA care.

BACKGROUND: Effective use of prophylactic antibiotics decreases the incidence of surgical site infections (SSIs) after total joint arthroplasty (TJA). The purpose of this prospective study was to determine the viability of weight-based dosing protocols for cefazolin and vancomycin to determine if appropriate minimum inhibitory concentrations (MIC) are met. METHODS: Trabecular bone was harvested from discarded bone samples from 34 patients undergoing total knee arthroplasty (TKA) and total hip arthroplasty (THA). The cefazolin and vancomycin concentrations were determined in the trabecular bone using high-performance liquid chromatography. RESULTS: No difference was noted in bone concentration with respect to patient weight for cefazolin. Regarding vancomycin, a substantial difference was noted in trabecular bone concentrations with respect to patient weight with lower body mass index (BMI) achieving greater concentrations. Using the current weight-based protocol of antibiotic prophylaxis, 84% and 87% of patients receiving vancomycin and cefazolin, respectively, achieved bone concentrations above the MIC. CONCLUSIONS: Our assessment of trabecular concentration of cefazolin during TJA did not show any differences with respect to patient weight. However, vancomycin concentrations did show a difference with respect to BMI but this may be the result of the specific weight-based dosing protocol of vancomycin. Whereas the majority of cases were able to achieve adequate antibiotic concentrations in bone, further studies may be required to determine if increasing the pre-operative dosage of antibiotics is mandated given the findings of this pilot study.

INTRODUCTION: Increasing hip fracture incidence in the United States is leading to higher occurrences of conversion total hip arthroplasty (THA) for failed surgical treatment of the hip. In spite of studies showing higher complication rates in conversion THA, the Centers for Medicare and Medicaid services currently bundles conversion and primary THA under the same diagnosis-related group. We examined the cost of treatment of conversion THA compared with primary THA. Our hypothesis is that conversion THA will have higher cost and resource use than primary THA. METHODS: Fifty-one consecutive conversion THA patients (Current Procedure Terminology code 27132) and 105 matched primary THA patients (Current Procedure Terminology code 27130) were included in this study. The natural log-transformed costs for conversion and primary THA were compared using regression analysis. Age, gender, body mass index, American Society of Anesthesiologist, Charlson comorbidity score, and smoker status were controlled in the analysis. Conversion THA subgroups formed based on etiology were compared using analysis of variance analysis. RESULTS: Conversion and primary THAs were determined to be significantly different (P<.05) and greater in the following costs: hospital operating direct cost (29.2% greater), hospital operating total cost (28.8% greater), direct hospital cost (24.7% greater), and total hospital cost (26.4% greater). CONCLUSIONS: Based on greater hospital operating direct cost, hospital operating total cost, direct hospital cost, and total hospital cost, conversion THA has significantly greater cost and resource use than primary THA. In order to prevent disincentives for treating these complex surgical patients, reclassification of conversion THA is needed, as they do not fit together with primary THA.

The stability of a total knee arthroplasty is determined by the ability of the prosthesis components in concert with supportive bone and soft tissue structures to sufficiently resist deforming forces transmitted across the knee joint. Constrained prostheses are used in unstable knees due to their ability to resist varus and valgus transformative forces across the knee. Constraint requires inherent rigidity, which can facilitate early implant failure. The purpose of this study was to describe the comparative indications for surgery and postoperative outcomes of varus valgus constrained knee (VVK) and rotating-hinge knee (RHK) total knee arthroplasty prostheses. Seven retrospective observational studies describing 544 VVK and 254 RHK patients with an average follow-up of 66 months (range, 7-197 months) were evaluated. Patients in both groups experienced similar failure rates (P=.74), ranges of motion (P=.81), and Knee Society function scores (P=.29). Average Knee Society knee scores were 4.2 points higher in VVK patients compared with RHK patients, indicating minimal mid-term clinical differences may exist (P<.0001). Absent collateral ligament support is an almost universal indication for RHK implantation vs VVK. Constrained device implantation is routinely guided by inherent stability of the knee, and, when performed, similar postoperative outcomes can be achieved with VVK and RHK prostheses.

BACKGROUND: Efforts to mitigate costs while improving surgical care quality have received much scrutiny. This includes the challenging issue of readmission subsequent to hospital discharge. Initiatives attempting to preclude readmission after surgery require planned and unified efforts extending throughout the perioperative continuum. Patient optimization prior to discharge, enhanced disease monitoring, and seamless coordination of care between hospitals and community providers is integral to this process. The perioperative surgical home (PSH) has been proposed as a model to improve the delivery of perioperative healthcare via patient-centered risk stratification strategies that emphasize value and evidence-based processes. RESULTS: This case report seeks to specifically describe implementation of readmission reduction strategies via a PSH paradigm during total joint arthroplasty (TJA) procedures at the University of California Irvine (UCI) Health. An orthopedic surgeon open to collaborate within a PSH paradigm for TJA procedures was recruited to UCI Health in October of 2012. Institution specific data was then prospectively collected for 2 years post implementation of the novel program. A total of 328 unilateral, elective primary TJA (120 hip, 208 knee) procedures were collectively performed. Demographic analysis reveals the following: mean age of 64 +/- 12; BMI of 28.5 +/- 6.2; ASA Score distribution of 0.3 % class 1, 23 % class 2, 72 % class 3, and 4.3 % class 4; and 62.5 % female patients. In all, a 30-day unplanned readmission rate of 2.1 % (95 % CI 0.4-3.8) was observed during the study period. As a limitation of this case report, this reported rate does not reflect readmissions that may have occurred at facilities outside UCI Health. CONCLUSIONS: As healthcare evolves to emphasize value over volume, it is integral to invest efforts in longitudinal patient outcomes including patient disposition subsequent to hospital discharge. As outlined by this case management report, the PSH provides an institution-led means to implement a series of care initiatives that optimize the important metric of readmission following TJA, potentially adding further value to patients, surgical colleagues, and health systems.