Kenneth E. Davis

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.

Simultaneous bilateral, staged bilateral, and unilateral total knee arthroplasty. A survival analysis.

BACKGROUND The rates of perioperative morbidity and mortality are areas of concern associated with simultaneous bilateral total knee replacement. The purpose of this paper was to compare the rates of morbidity and mortality and the clinical outcome in large groups of consecutive patients undergoing simultaneous bilateral total knee replacement, unilateral total knee replacement, or staged bilateral total knee replacement. METHODS A total of 6200 total knee replacements, performed in 3998 patients between 1983 and 2000, consisted of 2050 simultaneous bilateral, 1796 unilateral, and 152 staged bilateral total knee replacements. A review of each group was conducted to compare the rates of morbidity and mortality, the survival of the prosthesis, and the clinical outcome. Kaplan-Meier survival analyses were performed with failure defined as revision because of aseptic loosening and as patient death. Complications and Knee Society scores were compared throughout the fifteen-year follow-up period (average, 4.3 years of follow-up). RESULTS The unilateral group had significantly lower Knee Society scores than the simultaneous bilateral group (p < 0.0001 up to twelve years, and p = 0.0067 at fifteen years) across all postoperative time-intervals. The percentage of patients who had thrombophlebitis was significantly higher in the simultaneous bilateral group (0.9%) than in the unilateral group (0.3%) (p = 0.0326). No significant differences were found with regard to prosthetic failure, cardiac complications, and the rates of death in the three groups. Ten years postoperatively, the simultaneous bilateral group had a significantly higher rate of patient survival than did the unilateral group (78.6% compared with 72.0%) (p = 0.0062). CONCLUSIONS The significantly higher rate of thrombophlebitis in the simultaneous bilateral group compared with that in the unilateral group may represent a greater risk to those patients. However, we believe that when there are adequate indications for bilateral total knee replacement, simultaneous bilateral arthroplasty is beneficial to patients, with a minimal increase in the risk of death or other complications compared with that associated with unilateral and staged procedures.

The Clinical Effect of Gender on Outcome of Total Knee Arthroplasty

The purpose of this study was to quantify the effect of sex on the clinical outcome and survivorship of a total knee arthroplasty (TKA) with clinical and radiographic follow-up. Seven thousand three hundred twenty-six primary AGC (Biomet, Warsaw, Ind) cruciate-retaining TKAs were performed from 1987 to 2004. Of these, 59.5% were performed on women. We examined preoperative and postoperative Knee Society knee score, function scores, pain scores, walking ability, stair-climbing ability, flexion, and implant survivorship based on sex. Female sex was associated with lower overall preoperative clinical scores for all parameters (P < .01). Improvement in Knee Society knee score and flexion was greater for women (P = .006), and there were equal pain relief and walking improvements for both sexes (P < .32). Stair and function score improvements were greater for men (P = .002). Implant survival was 98% for women and men at 15 years (P = .4684). We conclude that improvement after TKA is similar for men and women, with few clinically significant differences. Sex-specific implants would appear to offer no clinical advantage.

Implant position in knee surgery ☆: a comparison of minimally invasive, open unicompartmental, and total knee arthroplasty

This is a retrospective radiographic analysis of implant position in minimally invasive unicompartmental knee arthroplasty (UKA), open UKA, and total knee arthroplasty (TKA). Implant position and limb alignment were recorded in the AP and lateral planes. Of the 3 groups evaluated, the total knee group had the least variation and greatest accuracy of implant placement and limb alignment. UKA groups had small but significant differences in postoperative alignment and AP tibial position. Using contemporary instrumentation, UKA is less accurate than TKA in implant placement and limb alignment. Minimally invasive UKA was not as accurate as open UKA in AP tibial placement or postoperative limb alignment.

Total Knee Arthroplasty Has Higher Postoperative Morbidity Than Unicompartmental Knee Arthroplasty: A Multicenter Analysis

A total of 2235 primary total knee arthroplasties (TKAs) and 605 unicompartmental knee arthroplasties performed at 3 institutions over 5 years were reviewed to compare the incidence of postoperative complications between these groups. The overall risk of complications for patients undergoing TKA was 11.0%, compared with 4.3% for patients undergoing unicompartmental knee arthroplasty (P < .0001). Total knee arthroplasty was associated with increased rates of manipulation (odds ratio [OR], 13.0; P < .0001), transfusion (OR, 8.5; P = .036), intensive care unit admission (OR, 7.4; P = .049), discharge to a rehabilitation facility (OR, 5.2; P < .0001) and had longer hospital stays (mean, 3.3 vs 2.0 days; P < .0001). There was a trend toward an increased risk of deep infection (0.8% vs 0.2%, P = .13), readmission (4.2% vs 2.7%, P = .0795), thromboembolic events (1.0% vs 0.64%, P = .398), and any reoperation (1.4% vs 0.6%; P = .064). The increased risk of perioperative complications after TKA should be considered when counseling patients if they are an appropriate candidate for either procedure.

The Effect of Postoperative Range of Motion on Functional Activities After Posterior Cruciate-Retaining Total Knee Arthroplasty

BACKGROUND Range of motion is recognized as an important indicator of the success of a total knee replacement; however, an optimal range of motion has yet to be defined. This study was designed to determine the optimal range of motion for knee function after total knee arthroplasty with a posterior cruciate-retaining prosthesis. METHODS We retrospectively reviewed 5556 primary total knee arthroplasties performed with posterior cruciate-retaining prostheses between 1983 and 2003. The relationship between postoperative range of motion and pain, walking ability, stair-climbing ability, and knee function scores was examined at three to five years postoperatively. The relationship between a postoperative flexion contracture or hyperextension and knee function was also examined. RESULTS Patients with 128 degrees to 132 degrees of motion obtained the highest scores for pain, walking, and knee function and the highest Knee Society scores. The outcomes became substantially compromised with motion of <118 degrees . Patients with 133 degrees to 150 degrees of motion had the highest scores for stair-climbing. A postoperative flexion contracture and hyperextension were associated with lower scores for pain, walking, stair-climbing, and knee function. CONCLUSIONS The best functional results following total knee arthroplasty are achieved with 128 degrees to 132 degrees of motion. A postoperative flexion contracture and hyperextension of >or=10 degrees are associated with a poorer outcome except that stair-climbing is improved with more motion.

Long-term deterioration of joint evaluation scores

We investigated the long-term changes in the Harris Hip and Knee Society scores (HSS and KSS) to determine whether they result from overall functional decline rather than actual changes in the condition of the prosthesis. The HHS for 106 total hip arthroplasties with a minimum follow-up of ten years, no medical complications after operation and no evidence of radiological loosening, and the KSS for 264 total knee arthroplasties with a minimum follow-up of 12 years and no medical complications after operation or signs of radiographical loosening were evaluated. There were statistically significant drops in the functional scoring components of the joint evaluation systems despite no loosening of the prostheses or other significant medical complications. The HHS declined at an average of 0.67 points per year from between three and ten years after operation (p < 0.0001). Contributing to this were deterioration in gait and limp (p < 0.0004), the use of support aids (p < 0.0001), the distance walked (p < 0.0001) and the ability to climb stairs (p < 0.0455). The functional component of the KSS declined significantly at an average 0.88 points per year betwen the third and 12th years (p < 0.0001). There were significant declines in every component of the functional score including the distance walked (p < 0.0001), the ability to climb stairs (p < 0.0001) and the use of support aids (p < 0.0001). The knee score component of the KSS did not decline significantly (p < 0.9750). The combination of functional and pain scores within the HHS system leads to an inaccurate decline in the entire score. The decline of HHS and Knee Society functional scores in total joint arthroplasties, in the absence of implant-related problems, suggests that deterioration in the functional capacity of ageing patients is an important factor in longitudinal studies using these scoring systems.