Weight bearing versus conventional CT for the measurement of patellar alignment and stability in patients after surgical treatment for patellar recurrent dislocation

Abstract

Purpose To compare weight-bearing cone-beam computer tomography (CBCT) and conventional computer tomography (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. Methods A total of 17 patients (11 males/6 females) after surgical reconstruction with fascia lata allograft for recurrent patellofemoral dislocation were analyzed at 60-month 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. Inter-rater reliability was assessed using a two-way mixed-effects model intra-class correlation coefficient (ICC). Results Only TT-TG offset was found significantly smaller (p < 0.001) in CBCT (mean 9.9 ± 5.3 mm) than in conventional CT (mean 15.9 ± 4.9 mm) 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 and0.78 in conventional CT. Conclusion 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.

Cone‐beam CT imaging with laterally enlarged field of view based on independently movable source and detector

“…15 In this respect, note that the used Alderson phantom corresponded to a slim to normal weighted patient, and that the amount of body regions and anatomical details truncated on conventional full-scans will be strongly enhanced particularly of obese patients.A further important application of EnFOV imaging is particularly in orthopedics, since malpositions or -formations of the knees can in some cases only be diagnosed with imaging both knees under load. 11 There are some O-arm systems on the market that allow such weight-bearing volumetric imaging, as for instance the SCS MedSeries H22 (SCS Sophisticated Computertomographic Solu-tions, Germany) or the HiRise (CurveBeam AI, USA), but to the best of our knowledge corresponding in-depth scientific evaluations have not been performed so far. With the IRm, weight-bearing imaging becomes feasible from a technical perspective as well, since the system allows by a respective gantry tilt imaging of patients in lying, sitting, and standing positions in principle.…”

“…For instance, some pathophysiologies like malpositions of the knees can in orthopedics only be diagnosed by upright weight-bearing imaging. 11,12 In external beam radiation therapy, larger FOVs are particularly important for treatment planning. Only with the whole patient width visible on the scans, the delivered dose can be accurately modeled.…”

“…It may be unfeasible to capture the entire patient size within the FOV, which, however, is of pertinence for some applications. For instance, some pathophysiologies like malpositions of the knees can in orthopedics only be diagnosed by upright weight‐bearing imaging 11,12 . In external beam radiation therapy, larger FOVs are particularly important for treatment planning.…”

CT and MRI measurements of tibial tubercle lateralization in patients with patellar dislocation were not equivalent but could be interchangeable

“…The inter‐ and intraobserver reliability of the two imaging methods were evaluated. The intraclass correlation coefficient (ICC) [12] and the Bland–Altman 95% limits of agreement (LOA) [4] were calculated to assess the agreement between these two modalities. The values of TT–RA distance, TT–TG distance, and TT–PCL distance measured by two observers were averaged for analysis.…”

Functional Imaging of the Knee—A Comprehensive Review

“…44 A more comprehensive approach to patellofemoral kinematics is necessary to provide patient-specific treatments for patellar maltracking. In patients surgically treated for recurrent patellar dislocations, TT-TG offset was reduced on images obtained from weightbearing CT compared to conventional CT suggesting conflicting measurements may be obtained when a patient is in a recumbent, non-weightbearing position.. 45 Initial technical and qualitative assessment of the imaging performance of a cone beam scanner demonstrates excellent bone visualization and good soft-tissue visualization which can be produced with a radiation dose of 9 mGy, compared to 39.7 mGy for a typical multidetector CT. 58 There are several limitations worth noting. Current utilization of cone beam CT is limited to a few academic centers and mostly for studies evaluating foot and ankle pathologies.…”