Assessment of knee instability in ACL-injured knees using weight-bearing computed tomography (WBCT): a novel protocol and preliminary results

• Published in: Skeletal radiology 2024-08, Vol.53 (8), p.1611-1619
• Main Authors: Leão, Renata Vidal, Zelada, Sandro Ricardo Benites, Lobo, Carlos Felipe Teixeira, da Silva, Andre Giardino Moreira, Godoy-Santos, Alexandre Leme, Gobbi, Riccardo Gomes, Helito, Paulo Victor Partezani, Helito, Camilo Partezani
• Format: Article
• Language: English
• Subjects: Anterior cruciate ligament; Computed tomography; Image quality; Imaging; Injuries; Instability; Knee; Medical imaging; Medicine; Medicine & Public Health; Nuclear Medicine; Orthopedics; Pathology; Radiation; Radiation dosage; Radiology; Rotation; Stability; Stability analysis; Tomography
• ISSN: 0364-2348; 1432-2161; 1432-2161
• DOI: 10.1007/s00256-024-04562-1

Objective To propose a protocol for assessing knee instability in ACL-injured knees using weight-bearing computed tomography (WBCT). Materials and methods We enrolled five patients with unilateral chronic ACL tears referred for WBCT. Bilateral images were obtained in four positions: bilateral knee extension, bilateral knee flexion, single-leg stance with knee flexion and external rotation, and single-leg stance with knee flexion and internal rotation. The radiation dose, time for protocol acquisition, and patients’ tolerance of the procedure were recorded. A blinded senior radiologist assessed image quality and measured the anterior tibial translation (ATT) and femorotibial rotation (FTR) angle in the ACL-deficient and contralateral healthy knee. Results All five patients were male, aged 23–30 years old. The protocol resulted in a 16.2 mGy radiation dose and a 15-min acquisition time. The procedure was well-tolerated, and patient positioning was uneventful, providing good-quality images. In all positions, the mean ATT and FTR were greater in ACL-deficient knees versus the healthy knee, with more pronounced differences observed in the bilateral knee flexion position. Mean lateral ATT in the flexion position was 9.1±2.8 cm in the ACL-injured knees versus 4.0±1.8 cm in non-injured knees, and mean FTR angle in the bilateral flexion position was 13.5°±7.7 and 8.6°±4.6 in the injured and non-injured knees, respectively. Conclusion Our protocol quantitatively assesses knee instability with WBCT, measuring ATT and FTR in diverse knee positions. It employs reasonable radiation, is fast, well-tolerated, and yields high-quality images. Preliminary findings suggest ACL-deficient knees show elevated ATT and FTR, particularly in the 30° flexion position.