Merrill A. Ritter

Postoperative alignment of total knee replacement. Its effect on survival.

Four hundred twenty-one posterior cruciate condylar total knee arthroplasties were performed between 1975 and 1983. Anatomic alignment of the knee was recorded on follow-up evaluations from two months to 13 years postoperatively. Patients were stratified into a normal group that was 5 degrees to 8 degrees anatomic valgus, a varus group that was from 4 degrees anatomic valgus to any degree of varus, and a valgus group that was more than 9 degrees anatomic valgus. There were eight failures, five in the varus group and three in the normal group. There were no failures in the valgus group. Kaplan-Meier survival curves showed no significant difference between normal and valgus groups; however, there was a statistical difference between the valgus and varus and the normal and varus groups. A surgeon should align a total knee prosthesis in neutral or a slight amount of anatomic valgus to give the patient the best chance for long-term survival.

Coronal alignment in total knee arthroplasty: just how important is it?

A recent study has challenged the premise that well-aligned total knee arthroplasties (TKAs) have better survival than outliers. This study examines the importance of overall coronal alignment as a predictor for revision. Patients with primary TKAs were stratified into neutral, varus, and valgus alignment groups based on the postoperative tibiofemoral angle. In 6070 knees (3992 patients), there were 51 failures (0.84%): 21 (0.5%) in the neutral group, 18 (1.8%) in the varus group, and 12 (1.5%) in the valgus group. The best survival was for overall alignment between 2.4 degrees and 7.2 degrees of valgus. Varus knees failed primarily by medial tibia collapse, whereas valgus knees failed from ligament instability. Outliers in overall alignment have a higher rate of revision than well-aligned knees. The goal of TKA should be to restore alignment within 2.4 degrees to 7.2 degrees of valgus.

The Chetranjan Ranawat Award: Tibial Component Failure Mechanisms in Total Knee Arthroplasty

The purpose of this study was to examine the failure mechanisms and factors associated with failure of a nonmodular metal backed cemented tibial component. Out of 3152 total knee replacements done for osteoarthritis, 41 tibial components had been revised (1.3%). Four distinct failure mechanisms were identified: 20 knees were revised for medial bone collapse, 13 for ligamentous imbalance, 6 for progressive radiolucencies, and 2 for pain. Factors associated with medial bone collapse were varus tibial component alignment more than 3.0°, Body Mass Index higher than 33.7, and overall postoperative varus limb alignment. Ligamentous imbalance was more prevalent in knees with preoperative valgus deformity. There were no knees revised for tibial component polyethylene wear or osteolysis. We conclude that the dominant failure mechanisms for this component design are related to preoperative deformity, technical factors of component alignment, overall limb alignment, and ligamentous imbalance.

Predicting range of motion after total knee arthroplasty. Clustering, log-linear regression, and regression tree analysis.

Background: Range of motion is a crucial measure of the outcome of total knee arthroplasty. The purpose of this study was to determine which factors are predictive of the postoperative range of motion. Methods: We retrospectively studied 3066 patients (4727 knees) who had a primary total knee arthroplasty with the same type of implant at the same center between 1983 and 1998. Statistical clustering analysis paired with log-linear regression was used to determine groupings along continuous variables. Regression tree analysis was used to characterize the combinations of variables influencing the postoperative range of motion. The variables considered were preoperative and intraoperative flexion and extension, preoperative alignment, age, gender, and soft-tissue releases. Results: Preoperative flexion was the strongest predictor of the postoperative flexion regardless of preoperative alignment. Other factors that were significantly related to reduced flexion were intraoperative flexion (p < 0.0001), gender (p < 0.0001), preoperative tibiofemoral alignment (p = 0.0005), age (p < 0.0001), and posterior capsular release (p < 0.0001). The removal of posterior osteophytes was related to the greatest increase in postoperative flexion in the group of patients with a varus tibiofemoral alignment preoperatively. Conclusions: The principal predictive factor of the postoperative range of motion was the preoperative range of motion. Removal of posterior osteophytes and release of the deep medial collateral ligament, the semimembranosus tendon, and the pes anserinus tendon in patients with large preoperative varus alignment and the attainment of a good intraoperative range of motion improved the likelihood that a good postoperative range of motion would be achieved. Level of Evidence: Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

Morbidly Obese, Diabetic, Younger, and Unilateral Joint Arthroplasty Patients Have Elevated Total Joint Arthroplasty Infection Rates

The study aims to delineate the deep infection rates and infection risk factors for primary total knee and total hip arthroplasty patients. A retrospective review was conducted on 6108 patients from 1991 to 2004. The deep infection cases were compared to the noninfected cohort whereby infection risk factors were identified. Of the 8494 joint arthroplasties, 43 (0.51%) developed a deep infection (30 total knee arthroplasties, 13 total hip arthroplasties). Patients with a body mass index greater than 50 had an increased odds ratio of infection of 21.3 (P < .0001). Diabetic patients were 3 times as likely to become infected compared to nondiabetic patients (P = .0027). Simultaneous bilateral total joint arthroplasties were found to have developed infection 3 times less frequently than those performed as unilateral procedures (P = .0024). The average age in our infection cohort was 64.3 and 68.4 in the noninfected cohort. In this retrospective review study, obesity, diabetes, and younger age were found to be risk factors for joint arthroplasty infection.

Long-term followup of anatomic graduated components posterior cruciate-retaining total knee replacement.

The purpose of the current study was to evaluate the authors’ 15-year experience with the Anatomic Graduated Components total knee replacement. This is a report of the survivorship of 4583 Anatomic Graduated Component total knee arthroplasties. Kaplan-Meier survival analyses were performed with the end point defined as radiographic loosening, revision, or both. This end point was subdivided into the best case scenario in which it was assumed that all the patients lost to followup were doing well throughout the study and a worst case scenario in which it was assumed that all patients lost to followup had failed results at their last clinic visit. There were six (0.18%) femoral, 21 (0.46%) tibial, and 180 (4.2%) all-polyethylene patellar component failures secondary to aseptic loosening. All femoral components and 90% of the tibial components were revised; however, only 15 patellar components were revised. The clinical survival rate with revision of one or more of the components was 98.86% at 15 years. Despite having nearly flat-on-flat geometry and retaining the posterior cruciate ligament, which should increase the stresses in the polyethylene and at the bone-cement interface, this total knee replacement has proved to have minimal wear and excellent longevity with time. The authors think this is a result of the direct compression molded polyethylene articulation and the nonmodular configuration that incorporates metal backing on the tibial component and eliminates back-sided tibial component polyethylene wear.

Impaction Bone-Grafting before Insertion of a Femoral Stem with Cement in Revision Total Hip Arthroplasty. A Minimum Two-Year Follow-up Study*

Impaction bone-grafting was performed before insertion of a collarless, polished, tapered femoral stem with cement in thirty-four revision total hip arthroplasties (thirty-four patients) that were done because of aseptic loosening. The average duration of follow-up was thirty months (range, twenty-four to forty-two months). The operation was the initial revision in twenty-eight patients (82 per cent). Twenty-two patients (65 per cent) also had revision of the acetabular component. Complications included four intraoperative and two postoperative fractures of the femur as well as one dislocation (at one month). Two patients (6 per cent) needed a repeat revision of the femoral stem because of aseptic loosening at twenty-six and thirty-six months postoperatively. Both of these patients had an associated fracture of the femur (one was intraoperative, and the other was postoperative). Subsidence was common (thirteen patients; 38 per cent) and averaged 10.1 millimeters (range, four to thirty-one millimeters). Although the study group was relatively small, with the numbers available subsidence was not found to be associated with the preoperative or postoperative hip score, segmental or cavitary femoral defects, femoral ectasia, intraoperative fracture of the femur, strut-grafting, trochanteric osteotomy, or varus position of the femoral component. Incorporation of the allograft into the trabecular bone and secondary remodeling were noted radiographically in thirty-two (94 per cent) and fourteen (41 per cent) of the patients, respectively, often within one year. Although the duration of follow-up was relatively short, no localized resorption of the allograft occurred and cortical repair was noted in one patient at three years. At the most recent follow-up evaluation, the Harris hip scores had improved from a preoperative average of 51 points (range, 32 to 90 points) to an average of 87 points (range, 65 to 100 points) and twenty-eight patients (82 per cent) had no or only slight pain. Despite the satisfactory early clinical results, we remain concerned about the high rate of fracture of the femur and the rate and extent of subsidence of the femoral component. On the basis of the worrisome findings after this two-year period, we recommend that impaction bone-grafting be used only when proximal femoral osteopenia is so severe that stability cannot be obtained with insertion of a long-stemmed femoral component without cement. In that setting, impaction bone-grafting may be considered instead of implantation of a massive proximal femoral allograft in combination with insertion of a femoral component with cement.

Comparative Outcomes of Total Joint Arthroplasty

A prospective pre- and postoperative general health/quality-of-life factor comparison, using the Rand SF-36 Health Status Questionnaire (TyPE Specification, Quality Quest [Health Outcomes Institute, Minneapolis, MN]), was carried out on a consecutive series of patients with diagnosed osteoarthritis undergoing total hip and knee arthroplasty between March 1991 and March 1994. Study groups consisted of 85 total hip arthroplasty patients, 93 total knee arthroplasty patients, and 65 single-stage bilateral total knee arthroplasty patients, all treated at the same specialty hospital, under the care of three senior orthopaedic surgeons. The average patient age was 69 years. Significant improvements in quality-of-life measures including physical functioning, social functioning, role functioning/physical problem, role functioning/emotional problem, mental health, energy/fatigue, pain, and change in health were noted in all hip and knee arthroplasty patients 6 months, 1 year, and 2 years after surgery (P < .05). There appeared to be no significant differences in quality-of-life measures between hip and knee arthroplasty patients. Results therefore indicate that total hip and knee arthroplasty significantly improve the functional status and quality of life among patients suffering from osteoarthritis.

Unwashed filtered shed blood collected after knee and hip arthroplasties. A source of autologous red blood cells.

We evaluated the results of twelve hematological and plasma protein determinations in 450 to 500-milliliter volumes of shed blood that had been collected with or without acid-citrate-dextrose anticoagulant (National Institutes of Health Formula A) from knees and hips during the first twelve hours after arthroplasty. We also evaluated the effects on the recipients when the blood was used for reinfusion. The findings in the units that had been obtained in less than four hours, in between four and six hours, and in more than six hours after the arthroplasty were similar whether or not the acid-citrate-dextrose anticoagulant had been used. The mean values for the collected units were: in the blood, a concentration of hemoglobin of 115 grams per liter, a hematocrit of 0.34, a white blood-cell count of 4.8 x 10(9) per liter, and a red blood-cell count of 3.7 x 10(12) per liter, and, in the plasma, a level of hemoglobin of 160 grams per liter, a level of fibrinogen of less than 0.2 gram per liter, a level of factor-V clotting protein of less than 10 per cent of normal, a level of factor-VIII clotting protein that was 45 per cent of normal, a level of antithrombin III that was 45 per cent of normal, a level of plasminogen that was 55 per cent of normal, a level of protein C that was 100 per cent of normal, and a level of fibrin-degradation products of 1000 micrograms per milliliter of plasma. The clinical response of the patient was assessed after the reinfusion of a total of 205 units of unwashed shed blood into 153 patients. In addition, in 126 of the 153 patients, hematological and plasma-protein measurements were analyzed before the autotransfusion and one and twenty-four hours afterward. Each of these patients had received one to four units of shed blood that had been filtered but not washed. Only two (2 per cent) of the ninety-nine patients who received shed blood that had been collected six hours or less after the operation had a febrile reaction, whereas twelve (22 per cent) of the fifty-four patients who received blood that had been collected six to twelve hours after the operation had such a reaction.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of total hip arthroplasty surgical approach on gait

This study examined the effect of the surgical approach used in total hip arthroplasty (THA) on gait mechanics six months following surgery. Quantitative gait analysis was performed on 29 subjects: 10 anterolateral (A‐L) and 10 posterolateral (P‐L) THA patients and nine able‐bodied, velocity‐matched subjects. Discriminant function analysis was used to determine the distinction of the groups with respect to sagittal plane hip range of motion, index of symmetry, trunk inclination, pelvic drop, hip abduction, and foot progression angles. The A‐L group had the largest trunk inclination (3.0 ± 2.4°) and the smallest hip range of motion (34.0 ± 7.4°). Both THA groups demonstrated greater asymmetry as expressed by the smaller symmetry index (0.97 ± 0.04 for A‐L and 0.98 ± 0.05 for the P‐L) than the able‐bodied group (0.99 ± 0.01). The classification procedure correctly classified 89% of the control group cases, 90% of the A‐L cases, and 50% of the P‐L cases. These results support the conclusion that six months following surgery, the gait of the majority (85%) of THA patients has not returned to normal. The A‐L patients displayed distinct gait patterns, while a small percentage (30%) of the P‐L patients demonstrated normal gait. While these differences are statistically significant, the clinical significance is unknown and linked to the duration that they persist.