Risk factors and outcomes in asymmetrical femoral component size for posterior referencing bilateral total knee arthroplasty: a matched pair analysis.

BACKGROUND: Theoretically, potential errors in femoral component (FC) sizing can affect postoperative functional outcomes after total knee arthroplasty (TKA), including range of motion (ROM), anterior knee pain, and flexion stability. Incidences of asymmetrical femoral components (AFC) in bilateral TKA have been reported; however; there is a lack of data on exactly why AFC size selection may differ in patients who have had posterior referencing system bilateral TKA. Therefore, this study was conducted to determine risk factors of AFC size selection in patients specifically undergoing posterior referencing bilateral TKA and to compare clinical outcomes between those with AFC or symmetrical femoral component (SFC) sizes. METHODS: We conducted a retrospective matched-pair study comparing thirty-four patients who had undergone simultaneous and staged bilateral TKA using AFC size (Group I) and thirty-five patients with SFC size (Group II). Patients were matched according to gender, body mass index, prosthesis type, and operative technique. Preoperative radiographic morphology of both distal femurs including anteroposterior/mediolateral diameters, anterior-posterior femoral offset, and postoperative radiographic data of FC comprising flexion and valgus angle were recorded. The postoperative functional outcomes including ROM, anterior knee pain, knee society score, and functional score at 6 weeks, 3, 6, 12 and 24 months were compared. RESULTS: There were no differences in morphology between left and right distal femurs from preoperative radiographic data in both groups. The postoperative radiograph showed a significantly greater FC flexion angle difference in Group I vs. Group II (2.18° ± 1.29° and 1.36° ± 1.08° P = 0.007), while the other parameters were the same. The postoperative clinical outcomes displayed no distinction between groups. CONCLUSION: The factor primarily associated with AFC size selection in bilateral TKAs is the difference in FC flexion angle but not the morphological diversity between sides. The postoperative functional outcomes were not inferior in AFC patients in comparison with SFC patients.

Is Regular Knee Radiograph Reliable Enough to Assess the Knee Prosthesis Position?

BACKGROUND: Proper knee alignment and prosthesis position may theoretically provide better surgical results and increase longevity of total knee arthroplasty. The 3-feet standing long radiograph (LR) is the gold standard for assessment of these parameters. However, the conventional standing regular knee radiograph (RR) is still being used because of convenience and lower cost. We conducted a study to investigate the accuracy of RR compared to LR in assessing the coronal plane prosthesis position. METHODS: We conducted a retrospective cross-sectional study in 100 knee radiographs in 88 patients with knee prostheses. The picture archiving and communications system was used to produce digitized radiographs and perform the angle measurements. LR images were cropped to the same size as the RRs to eradicate rotation error. The femoral component angle (FCA), tibial component angle (TCA), and tibiofemoral angle (TFA) were measured and analyzed by Student t-test. Pearson's correlation coefficient was used to assess interobserver and intraobserver reliability. RESULTS: The RR measurements resulted in a mean increment of 1.3° (95% confidence interval [CI], 0.9°-1.6°; P < .001) for FCA and 1.4° (95% CI, 1.0°-1.9°; P < .001) for TFA compared to LR. The TCAs were similar between 2 techniques (0.2° mean difference; 95% CI, 0°-0.4°; P = .11). RR provided very strong intraobserver reproducibility but only strong interobserver reliability for FCA and TCA while LR provided very strong correlation for all angles. CONCLUSION: RR overestimation of FCA and TFAs in a valgus alignment was minimal, suggesting RR could be an acceptable alternative to LR.

Comparison of Ramosetron With Ondansetron for Prevention of Intrathecal Morphine-Induced Nausea and Vomiting After Primary Total Knee Arthroplasty: A Randomized Control Trial.

BACKGROUND: Spinal anesthesia with intrathecal morphine is a reliable, easy to apply, and cost effective method for controlling pain after total knee arthroplasty (TKA). However, postoperative nausea and vomiting (PONV) is a major concern. 5-Hydroxytryptamine receptor 3 (5-HT3) antagonists like ondansetron and ramosetron are commonly used for preventing PONV, but the optimal choice remains unclear. We conducted a study to assess the effectiveness of ramosetron and ondansetron, hypothesizing that the longer acting ramosetron may be better than ondansetron in the first 48 hours after TKA, performed with spinal anesthesia and intrathecal morphine. METHODS: Patients were randomized preoperatively to either intravenous ondansetron (8 mg) or ramosetron (0.3 mg). The primary outcomes were the incidence rates of PONV. Secondary outcomes were the need for a rescue antiemetic (metoclopramide), pain score, patient satisfaction, and adverse drug reactions (ADRs) at 0-6, 6-12, 12-24, and 24-48 hours. RESULTS: Ninety patients were evaluable; 45 patients/arm. Compared with ondansetron, ramosetron was associated with significantly lower incidence rates of nausea at: (1) 12-18 hours: 3/45 vs 11/45 (P = .016), (2) 18-24 hours: 1/45 vs 9/45 (P = .005), and vomiting at 18-24 hours: 1/45 vs 6/45 (P = .044). There were no significant differences in the use of rescue-antiemetic medicine, pain score, patient satisfaction, and ADRs. CONCLUSION: Preoperative ramosetron provided more prolonged PONV prophylaxis than ondansetron after TKA in our setting, and had a similar ADR profile. Other trials are needed to confirm our results before ramosetron is adopted widely.