We prospectively collected all data for inclusion in a joint registry. For this study, we retrospectively reviewed the records of all patients within our joint registry who underwent primary THA or primary TKA from June 1992 to June 2007 and had complete preoperative evaluation for all measures. Of the 1834 eligible patients, 1749 (739 patients who had THA and 1010 patients who had TKA) were included in the study. We excluded 85 patients (5%) secondary to having incomplete data at least 2 years postoperatively. Patients had surgery secondary to failed nonoperative treatments (medication, rehabilitation, and assistive devices), resulting in disabling pain. We obtained sociodemographic information from a self-administered questionnaire given to patients at their first office visit. The mean age of the cohort was 65.32 years (SD, 13.1 years); 68.1% were women. There were 1136 (65%) patients who were self-classified as white Hispanic, 392 (22%) as white non-Hispanic, 160 (9%) as African American non-Hispanic, and 61 (4%) as African American Hispanic (Table ). Of the 739 patients with THA, 98 (13%) had bilateral THAs and of the 1010 patients with TKA, 234 (23%) had bilateral TKAs (Table ). The underlying diagnosis was osteoarthritis (83%), rheumatoid arthritis (8%), avascular necrosis (7%), posttraumatic osteoarthritis (0.8%), femur neck fracture (0.5%), developmental dysplasia of the hip (0.5%), psoriatic arthritis (0.1%), and postseptic arthritis (0.1%). The minimum followup was 2 years (mean, 5.1 years; range, 2–16 years). All subjects gave written consent to be included in the joint registry, which the hospital’s institutional review board approved.
Bilateral distribution of THA and TKA by race/ethnicity
A single surgeon performed all surgeries (CJL). For THAs, the surgeon used a modified direct lateral approach (Hardinge) surgical technique and a press-fit technique for the femoral component and the acetabular components. In all patients, the surgeon used screws in the acetabular component for supplemental fixation. We permitted full weightbearing as tolerated on Postoperative Day 1 and utilized an abduction pillow at all times whenever in bed. If we operated on the patient in the morning, we initiated supervised physical therapy in the afternoon or on the next day if we operated after midday. Acute care services performed physical therapy two times per day until discharge and included transfer (sit-to-stand), gait (with standard walker), and bed mobility training. Therapeutic exercises included active and passive ROM, gluteal and quadriceps isometric exercises, and resistive exercises using weights or manual resistance. After acute care services, we typically discharged the patient for home health care, which included physical therapy three times per week for 4 weeks.
We treated each TKA in a similar manner. The surgeon approached all knees through a medial parapatellar incision. Once the desired implant position and soft tissue balance was achieved, the surgeon tested varus-valgus laxity and AP laxity in extension and in 90° of flexion. On completion of the procedure, we initiated continuous passive motion in the recovery unit starting at 0° to 30°, increasing 10° a day, and discontinued it when the patient reached the target of 85° to 90° of flexion. We encouraged patients to ambulate using a walker the first day after surgery. If we operated on the patient in the morning, we initiated supervised physical therapy in the afternoon or on the next day if we operated after midday. We used perioperative antibiotics for prophylaxis and a standard protocol of postoperative warfarin for thromboembolism prophylaxis. In the absence of complications, we discharged most patients 3 to 4 days postoperatively. Physical therapy and discharge disposition were similar to those used in THA.
We scheduled routine followup evaluation at 3 months, 6 months, 1 year, and yearly thereafter. At these intervals, we evaluated the patients using a long-arm goniometer for hip and knee ROM. We also took radiographs; AP and lateral radiographs were taken with the patient standing. Both before and after surgery, at 1-year intervals, we collected the patients’ Quality of Well-Being (QWB) scores, SF-36 scores, WOMAC scores, orthopaedic knee scores (Hospital for Special Surgery [HSS] score, Knee Society knee score [KSKS]), and orthopaedic hip scores (Harris hip score [HHS], Merle d’Aubigné-Postel score).
Kaplan and Bush [27
] developed the QWB index to assess general quality of life. The QWB combines preference-weighted values for symptoms and functioning. Symptoms are assessed by questions about the presence or absence of different symptoms complexes. Functioning is assessed by three separate domains (mobility, physical activity, and social activity). The four domain scores are combined into a total score that provides a numerical point-in-time expression of well-being ranging from 0 (for death) to 1.0 (for asymptomatic optimum functioning). This index is validated for use in a variety of populations, including African Americans and Hispanics. We used this outcome measure preoperatively and at each postoperative followup.
The SF-36 is a validated measure of general physical and mental health status assessed for content and construct in various populations, such as African Americans, Hispanics, and whites [4
]. The SF-36 contains eight different subscales. For this study, we used the physical function, bodily pain, social function, and physical component scores as outcome measures preoperatively and at each postoperative followup. All domains are scored separately on a 0- to 100-point scale, with higher numbers representing better health status. The pain and function subscales are the most sensitive to change in osteoarthritis patients after surgery.
The WOMAC is another current standard for evaluating results of TJA [7
]. It is designed to provide information on three dimensions: perception of pain, stiffness, and physical function. The WOMAC consists of 24 items (five for pain, two for stiffness, and 17 for function). Point values from 0 to 4 are assigned to each response, and scores are totaled for each category. We used the pain, physical function, and stiffness scores as outcome measures preoperatively and at each postoperative followup.
The HSS considers the following: (1) function or walking ability, (2) transfer ability, (3) ability to climb stairs, (4) ROM, (5) muscle strength, (6) flexion deformity, and (7) instability. The points are subtracted from the total score for residual extension lag, varus and valgus deformity, and use of external aids. A perfect score is 100 points and an arthrodesed knee achieves 60 points on this scale. An excellent result is scored between 85 and 100 points, good 70 to 81, fair 60 to 69, and poor less than 60 points [1
The KSKS is the evaluation system for knee rating and functional assessment. The main parameters evaluated in knee assessment are pain, stability, and ROM; 100 points are obtained by a well-aligned knee with no pain, 125º of motion, and negligible AP and mediolateral instability. Patient function is judged by walking distance and stair climbing, with deductions for walking aids. The maximum function score (100) is obtained by a patient who can walk an unlimited distance and go up and down stairs normally [26
The HHS is based on a scale of 100 points and the maximum possible scores are pain (44), function (47), ROM (5), and absence of deformity (4) [22
]. Of a total of 100 points, 100 to 90 points are considered excellent; 89 to 80, good; 79 to 70, fair; and less than 70, poor [22
The Merle d’Aubigné-Postel score is a functional hip score designed to provide information on three dimensions: pain, mobility, and ability to walk. All domains are scored separately on a 0- to 6-point scale, with higher numbers representing better functional grading status (a very good score is P [pain] + W [walking] = 11/12; good, 10; medium, 9; fair, 8; poor, 7 or less). If the mobility is reduced to 4, the result is classed one grade lower. If the mobility is reduced to 3 or less, the result is classed two grades lower [13
We stratified the patients into four classifications: African American non-Hispanic, African American Hispanic, white non-Hispanic, and white Hispanic. We used an analysis of covariance before and at postoperative followup to determine differences between groups who had TKA and THA. We entered all dependent measures into the model, with sex as the covariate. For the postoperative analyses, we used preoperative scores of all dependent measures as covariates in the model. We completed all pairwise comparisons as followups to determine differences among the four races by ethnicity subgroups. Also, we used a multivariate regression analysis to determine the influence of race, ethnicity, sex, and joint involvement on postoperative outcomes for individuals with TKA and THA (entire cohort). We entered all data into the joint registry via the Patient Analysis & Tracking System (Axis Clinical Software Inc, Portland, OR) and extracted data into Excel® (Microsoft Corp, Redmond, WA) to create spreadsheets. We completed all statistical analyses using SPSS® (Version 15.0; SPSS Inc, Chicago, IL).