Effect of polyethylene component thickness on range of motion and stability in primary total knee arthroplasty.

Total knee arthroplasty (TKA) is a common procedure with good survivorship and functional results. Optimal results are dependent on proper osseous cuts and soft tissue balancing. Soft tissue tensioning via the polyethylene spacer thickness is an important component of soft tissue balancing. Increased thickness increases soft tissue tension and, therefore, has the potential to increase stability but decrease range of motion (ROM). Decreased polyethylene thickness may decrease soft tissue tension and has the potential to increase ROM but decrease stability. Using computer-based navigation, the intraoperative effect of increasing and decreasing polyethylene thickness in 1-mm increments on ROM and coronal stability throughout the ROM of 35 patients was examined. It was found that increasing the polyethylene thickness by 1-mm increments had a statistically significant impact on the ability to achieve full extension but had no impact on flexion. Increased polyethylene thickness decreased coronal plane motion. Coronal plane laxity increased with increased flexion irrespective of polyethylene thickness. In this patient cohort, lateral laxity became >1° when the knee was flexed. However, medial structures prevented valgus angulation of >1° in all scenarios except when the polyethylene was diminished by 2 mm. Changes in polyethylene thickness had an impact on the ability to gain full extension and coronal plane motion.

The influence of the posterior cruciate ligament and component design on joint line position after primary total knee arthroplasty.

This study investigated the change in joint line position after posterior cruciate-retaining and posterior-stabilized total knee arthroplasty with AMK (DePuy, Warsaw, Ind) and Genesis II (Smith & Nephew, Memphis, Tenn) components. A total of 200 primary total knee arthroplasty patients were randomly selected so as to have 50 patients with each of the 4 prosthesis types. Joint line position was measured on preoperative and 2 year postoperative radiographs by both a lateral and an anteroposterior measurement method. Two-year follow-up functional data were assessed. There were no statistically significant differences in the joint line elevation between posterior-stabilized and posterior cruciate-retaining designs within the same implant system as measured on lateral radiographs. There were no differences in clinical functional outcomes in patients with variable joint line elevation.

Waiting times and patient perspectives for total hip and knee arthroplasty in rural and urban Ontario.

BACKGROUND: The demand for total hip and total knee arthroplasties is increasing as are the waiting times for these procedures. Because of the differences between rural and urban areas in terms of the provision of arthroplasty services and between the 2 patient groups, patient perspectives of waiting times may also be different. METHODS: To compare waiting times for initial orthopedic consultation and total hip and knee arthroplasties in rural Ontario (Stratford) and in urban Ontario (London), and to compare patient perspectives of these waiting times, we mailed a survey to all 260 patients who underwent total hip or total knee arthroplasty between June 1, 2000, and June 1, 2001. The survey asked for the length of wait for consultation and for surgery, acceptability of waiting time for surgery, the effect of waiting on health and what an acceptable waiting time would be. Of the 260 surveys mailed 202 (78%) were returned. We reviewed the charts of the respondents to determine the actual waiting times. RESULTS: The actual waiting times (mean [and standard deviation]) for initial consultation were significantly (p < 0.001) shorter in the rural (RUR) group (1.10 [0.53] mo) than the urban (URB) group (3.40 [1.34] mo). There was no significant difference in waiting times for surgery between RUR (8.45 [3.32] mo) and URB (9.32 [3.61] mo) groups. Surgical waiting times for both groups showed that 56% of all the patients had to wait longer than 9 months from the date surgery was recommended. Perceived waiting times for consultation were found to be 56.9% longer (p < 0.001) than the actual waiting times, but there was no significant difference between perceived and actual waiting times for surgery (p = 0.40). Fifty percent of the patients stated they were unhappy with the wait for surgery or found the wait unacceptable (56% of URB and 44% of RUR patients). There was no significant difference between RUR and URB in patients' acceptance of their wait for surgery (p = 0.09), but URB patients believed their wait for surgery made a greater contribution to health deterioration (p = 0.003). Thirty-eight percent of RUR and 54% of URB patients believed their surgical wait contributed to "a lot" or a "moderate" amount of deterioration in their health. CONCLUSIONS: Waiting times for hip or knee replacement surgery have increased to the point at which over 50% of surgical patients in 2000-2001 in RUR and URB orthopedic practices had waited longer than 9 months for surgery. In comparing these practices, there was a significantly longer wait in urban than rural practices for the initial consultation but no significant difference in waiting times for surgery.