Range-precision improvement of a time-of-flight range sensor using dual reference plane sampling.

This study aimed to achieve high range precision in the sub-100 µm order with time-of-flight (TOF) range imaging for 3-D scanners. The precision of a TOF range imager was improved using dual reference plane sampling (DRPS). DRPS using two short-pulse lasers reduces driver jitter, which limits the range precision below sub-100 µm. A proof-of-concept measurement system implemented using a TOF range imager demonstrated the reduction in driver jitters, resulting in reduced column-to-column variation in range precision. The developed system also achieved a high precision of 52 µm using a single frame and 27 µm using a 10-frame average.

High and Varied Anterior Condyle of the Distal Femur Is Associated with Limited Flexion in Varus Knee Osteoarthritis.

OBJECTIVE: This study aimed to evaluate variations in anterior condylar height (ACH) of the distal femur in varus knee osteoarthritis and evaluate the association between ACH and knee flexion. DESIGN: Computed tomography (CT) images of 171 knees (143 patients; age 73.7 ± 8.3 years; 132 females, 39 males) with symptomatic primary knee osteoarthritis and varus alignment undergoing primary total knee arthroplasty, unilateral knee arthroplasty, or high tibial osteotomy were evaluated. Several other anatomic parameters were measured on CT or radiography. The ACH and knee flexion correlation was analyzed, and factors contributing to knee flexion were determined using multivariable regression analysis. RESULTS: Medial ACH (mean, 8.1 mm; range, -2.8 to 19.9 mm) was smaller (P < 0.001) but more variable (F = 1.8, P < 0.001) than lateral ACH (mean, 10.7 mm; range, 3.6-18.3 mm). Medial ACH was moderately correlated with flexion (r = -0.44, 95% confidence interval [CI], -0.55 to -0.32), whereas lateral ACH was weakly correlated (r = -0.38; 95% CI, -0.50 to -0.25). On multivariable linear regression analysis of knee flexion, body mass index (B [partial regression coefficient] = -1.1), patellofemoral Kellgren-Lawrence grade (B = -4.3), medial ACH (B = -1.2), medial posterior condylar offset (B = 1.2), age (B = -0.4), and varus alignment (B = -0.6) remained significant independent variables (adjusted R2 = 0.35). CONCLUSIONS: Wide variation and anteriorization of the anterior condyle of the distal femur was observed in advanced osteoarthritis, as an independent determinant of limited knee flexion.

A greater reduction in the distal femoral anterior condyle improves flexion after total knee arthroplasty in patients with osteoarthritis.

BACKGROUND: The effect of an anterior condylar height (ACH) change after total knee arthroplasty (TKA) is not well-known. The effect of an ACH change was evaluated on postoperative knee flexion, New Knee Society Scores (2011KSS), and patellofemoral contact force. METHODS: The study included 101 knees that underwent TKA. The medial or lateral ACH was measured using pre-operative and postoperative computed tomography. Pearson correlation between the change in ACH and knee flexion was calculated. The determinant of the change in flexion was evaluated using multivariable linear regression. The association between ACH and 2011KSS was assessed. Using the cases with the three highest and three lowest pre-operative medial ACHs, computer simulation was performed to detect the changes in patellofemoral contact forces. RESULTS: A postoperative reduction in ACH correlated with increased flexion at one year (medial ACH, R = 0.58; lateral ACH, R = 0.48). On multivariable linear regression, reductions in medial ACH (ß = 1.7, P < 0.001) and pre-operative flexion (ß = -0.3, P < 0.001) were associated with increased flexion. A decrease in ACH was associated with improvements in advanced activities (medial, R2 = 0.06; lateral, R2 = 0.08) in 2011KSS. On computer simulation, all three cases with reduced and increased medial ACHs showed decreased and increased patellofemoral contact forces, respectively. CONCLUSIONS: A change in ACH was an independent predictor of knee flexion after TKA. Greater reduction in ACH was associated with improved flexion after TKA, whereas an increase in postoperative ACH may be a risk factor for flexion loss.