The performance of glomerular filtration rate (GFR) equations incorporating both cystatin C (CysC) and serum creatinine (Creat) in living kidney donors has not been studied before. From a population of 3,698 living kidney donors, 257 donors were randomly selected to undergo GFR measurement (mGFR) by the plasma disappearance of iohexol. GFR was estimated with the Modification of Diet in Renal Disease (MDRD) equation and the Chronic Kidney Disease Epidemiology Collaboration study eGFR(CKD-EPI-Creat) in 257 donors and the two newly developed equations using CysC with and without Creat, eGFR(CKD-EPI-CysC) and eGFR(CKD-EPI-Creat+CysC), in 215 donors. Mean mGFR was 71.8±11.8 mL/min/1.73 m. The eGFR(MDRD) exhibited least and only negative bias and the three other models were comparable in terms of bias. The eGFR(CKD-EPI-Creat+CysC) equation was most precise; r=0.64. Both eGFR(MDRD) and eGFR(CKD-EPI-Creat+CysC) had high percentage (94.4% and 92.6%, respectively) of estimates falling within 30% of mGFR versus estimates by eGFR(CKD-EPI-Creat) and eGFR(CKD-EPI-CysC) equations (87.2% and 85.1%, respectively). The eGFR(MDRD) was by far most accurate in identifying those with mGFR less than 60 mL/min/1.73 m whereas the CKD-EPI models were extremely accurate in classifying those with mGFR greater than or equal to 60 mL/min/1.73 m. eGFR(CKD-EPI-Creat+CysC) equation provides comparable accuracy to the eGFR(MDRD) in overall estimation of mGFR, but with higher precision. However, eGFR(CKD-EPI-Creat+CysC) clearly misses many of those with a post-donation GFR less than 60 mL/min/1.73 m and therefore eGFR(MDRD) is preferable in detecting donors with GFR less than 60 mL/min/1.73 m.

The objective of this retrospective review was to determine whether time efficiency could be gained by optimizing the navigation protocol based on a surgeon's specific technique and work flow. Three groups of 30 consecutive patients operated on by the same surgeon were studied. The groups were from three distinct periods between 2002 and 2008. The first group consisted of patients in which no navigation was performed (the control group); the second group consisted of patients in which navigation was performed using a standard protocol; and the third group consisted of patients in which navigation was performed using a customized protocol that eliminated certain steps. Statistical analysis considered analysis of variance for covariates of total time in the operating room, duration of the procedure, and tourniquet time. Chi-square analysis considered categorical variables of age, gender, body mass index (BMI), Knee Society score, and patellar resurfacing against the surgical group. Multiple linear regression analysis evaluated surgical time adjusted for preoperative deformity, BMI, and patellar resurfacing. In the adjusted model, the customized navigation protocol significantly reduced the surgical time by 10 minutes compared to the non-customized navigation. Not resurfacing the patella significantly reduced the surgical time by 9 minutes. Variables of age, gender, BMI, preoperative deformity and Knee Society score were not related to differences in operating time. Time efficiency may be gained with the use of improved computer navigation protocols and patellar non-resurfacing. [Level of evidence: Level 3.]