To compare weight-bearing cone-beam (CBCT) and conventional CT based measurements of patellofemoral alignment and stability in patients surgically treated for recurrent patellar dislocation. These scans implied respectively single-leg up-right posture, the knee flexed, and lower limb muscles activation, versus supine position with the knee extended.
17 patients (11 males / 6 females) after surgical reconstruction with fascia lata allograft for recurrent patellofemoral dislocation were analyzed at 60-months follow-up. Tilt and congruence angles, and tibial tuberosity-trochlear groove (TT-TG) offset were measured on images obtained from CBCT and conventional CT scans by three independent and expert radiologists. Paired t-tests were performed to compare measurements obtained from the two scans. Interrater reliability was assessed using a two-way mixed-effects model intra-class correlation coefficient (ICC).
Only TT-TG offset was found significantly smaller (p < 0.001) in CBCT (mean 9.9 ±5.3mm) than in conventional CT (mean 15.9±4.9mm) scans. ICC for tilt and congruence angles and for TT-TG offset ranged between 0.80-0.94 with measurements in CBCT scans, between 0.52-0.78 in conventional CT.
In patients surgically treated for recurrent patellar dislocation, TT-TG offset was found overestimated with conventional CT. All measurements of patellofemoral stability and alignment were found more consistent when obtained with weight-bearing CBCT compared to conventional CT.
Study Design: Cross-sectional study; Level of evidence, 3.