Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT, 84108, USA.
Department of Orthopaedics, Phramongkutklao Hospital and College of Medicine, 315 Rajavithi Road, Tung Phayathai, Ratchathewi, Bangkok, 10400, Thailand.
Skeletal Radiol. 2020 Oct;49(10):1615-1621. doi: 10.1007/s00256-020-03445-5. Epub 2020 May 11.
Subtle Lisfranc joint injuries remain challenging to diagnose. Although of questionable accuracy, the current gold standard to assess these injuries is through bilateral weight-bearing radiography. However, weight-bearing cone beam-computed tomography (CBCT), providing clearer visualization of bony landmarks, can also be utilized for evaluation. This study aims to establish the hypothesis that a specific weight-bearing CBCT finding (asymmetric lambda sign) can serve as an independent indicator of a subtle Lisfranc injury.
Weight-bearing CBCT images of 24 match-paired cadaveric legs were acquired, initially intact, and then following sequential dissection of each aspect (dorsal, interosseous, and plantar ligaments, respectively) of the Lisfranc ligamentous complex (LLC). All scans were taken in non- (NWB, 0 kg), partial- (PWB, 40 kg), and full-weight-bearing (FWB, 80 kg) manners. The lambda sign was then inspected axially for asymmetry (positive sign) by identifying three symmetrical joint spaces created between the medial cuneiform and the second metatarsal base (C1-M2), the medial and middle cuneiform (C1-C2), and the second metatarsal base and middle cuneiform (M2-C2).
A positive sign was observed in 25.6% (221/864) of all studies. Most notably, the fully dissected specimens demonstrated an asymmetric lambda sign in 33.3%, 72.2%, and 83.3% in NWB, PWB, and FWB conditions, respectively. The inter- and intra-observer reliability kappa value was calculated to be 0.843 and 0.912.
An asymmetric lambda sign is a simple and useful indicator for a complete LLC injury in PWB and FWB conditions using a cadaver model.
隐匿性跖跗关节损伤的诊断仍然具有挑战性。尽管存在准确性问题，但目前评估这些损伤的金标准是双侧负重 X 线检查。然而，提供更清晰的骨标志可视化的负重锥形束 CT（CBCT）也可用于评估。本研究旨在提出一个假设，即一个特定的负重 CBCT 发现（不对称的 lambda 征）可以作为隐匿性跖跗关节损伤的独立指标。
采集 24 对匹配的尸体腿的负重 CBCT 图像，最初是完整的，然后分别解剖跖跗韧带复合体（LLC）的各个方面（背侧、骨间和足底韧带）。所有扫描均在非负重（NWB，0 kg）、部分负重（PWB，40 kg）和完全负重（FWB，80 kg）状态下进行。然后通过识别内侧楔骨和第二跖骨基底（C1-M2）、内侧和中间楔骨（C1-C2）以及第二跖骨基底和中间楔骨（M2-C2）之间形成的三个对称关节间隙，轴向检查 lambda 征是否存在不对称（阳性征）。
在所有研究中，阳性征的发生率为 25.6%（221/864）。最值得注意的是，在完全解剖的标本中，NWB、PWB 和 FWB 条件下，lambda 征的不对称性分别为 33.3%、72.2%和 83.3%。观察者间和观察者内的kappa 值分别计算为 0.843 和 0.912。
在尸体模型中，使用负重 CBCT 时，不对称的 lambda 征是 PWB 和 FWB 条件下 LLC 完全损伤的简单而有用的指标。
