Bhimani Rohan, Mullen Marguerite A, Ashkani-Esfahani Soheil, O'Neill Colin, Waryasz Gergory R, Kerkhoffs Gino M M J, DiGiovanni Christopher W, Guss Daniel
Foot & Ankle Research and Innovation Laboratory, Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA.
Department of Orthopedic Surgery, Academic Medical Center, University of Amsterdam, Amsterdam Movement Sciences, the Netherlands.
Foot Ankle Orthop. 2025 Sep 28;10(3):24730114251373078. doi: 10.1177/24730114251373078. eCollection 2025 Jul.
The clinical treatment of Weber B fibular fractures has primarily focused on the symmetry of the medial clear space. Numerous radiographic studies demonstrate no change in tibiotalar contact area until the deltoid ligament is disrupted. In contrast, more recent studies using weightbearing CT scan (WBCT) and 3D volume analysis suggest that medial clear space (MCS) volume can in fact increase in the setting of a Weber B fibular fracture even if initial radiographs are reassuring, possibly because of a loss of fibular buttress. This study aims to evaluate the ability of WBCT to quantify the impact of isolated Weber B fractures on MCS volume (3D), as well as understand the implication of increasing fibular displacement among patients with a symmetric MCS distance (1D) on initial radiographs.
The study group included 18 patients with unilateral Weber B ankle fractures who underwent preoperative bilateral foot and ankle WBCT. The control group consisted of 60 patients with forefoot/midfoot conditions without ankle injury who underwent similar imaging. Measurements on WBCT images included (1) MCS distance; (2) syndesmotic area; (3) anterior, middle, and posterior distal tibiofibular distance; (4) fibular rotation; (5) distance from fibular tip to plafond; and (6) fibular fracture displacement. Additionally, volumetric measurements included (1) MCS volume, (2) syndesmotic joint volume from the tibial plafond extending to 3 cm and 5 cm proximally, and (3) lateral clear space volume were calculated. Area under the receiver operating characteristic (ROC) curve (AUC) analysis and Delong test were used, and optimal cutoff values to distinguish between stable and unstable Weber B fractures without syndesmotic instability and MCS widening were determined using Youden J statistic.
Among patients with unilateral Weber B ankle fractures, all WBCT measurements showed no side-to-side difference in any parameter, except MCS volume ( values < .001). When compared to the uninjured side, fibular displacement up to 2 mm and up to 4 mm was associated with MCS volume increases of 37.1% and 51.8%, respectively, compared with the contralateral uninjured side. Based on ROC analysis and Youden J statistic, a fibular fracture displacement of 2.3 mm was identified as the optimal threshold associated with a significant increase in MCS volume (AUC, 0.81; sensitivity, 77.8%; specificity, 80%). The control group showed no side-to-side difference in any of the measurements.
In this preliminary study using WBCT, 3D MCS volume measurements showed statistical differences in Weber B fibular fractures compared with the contralateral side, even when 1D distance measurements appeared symmetric. A displacement threshold of 2.3 mm was identified through ROC analysis, although the clinical significance of these volumetric changes remains unclear and requires validation through clinical outcome studies.
Level III, comparative diagnostic study.
Weber B型腓骨骨折的临床治疗主要集中在内侧间隙的对称性上。大量影像学研究表明，在三角韧带断裂之前，胫距关节接触面积没有变化。相比之下，最近使用负重CT扫描（WBCT）和三维容积分析的研究表明，即使最初的X线片显示正常，在Weber B型腓骨骨折的情况下，内侧间隙（MCS）容积实际上也可能增加，这可能是由于腓骨支撑作用丧失所致。本研究旨在评估WBCT量化孤立性Weber B型骨折对MCS容积（三维）影响的能力，并了解在初始X线片上MCS距离（一维）对称的患者中腓骨移位增加的影响。
研究组包括18例单侧Weber B型踝关节骨折患者，他们在术前接受了双侧足部和踝关节的WBCT检查。对照组由60例无前踝损伤的前足/中足疾病患者组成，他们接受了类似的影像学检查。对WBCT图像的测量包括：（1）MCS距离；（2）下胫腓联合面积；（3）胫腓骨远端前、中、后距离；（4）腓骨旋转；（5）腓骨尖至距骨穹窿的距离；（6）腓骨骨折移位。此外，还计算了容积测量值，包括：（1）MCS容积；（2）从胫骨穹窿向近端延伸3 cm和5 cm的下胫腓联合关节容积；（3）外侧间隙容积。使用受试者工作特征（ROC）曲线下面积（AUC）分析和德龙检验，并使用约登J统计量确定区分无下胫腓联合不稳定和MCS增宽的稳定和不稳定Weber B型骨折的最佳截断值。
在单侧Weber B型踝关节骨折患者中，除MCS容积外（P值<0.001），所有WBCT测量值在任何参数上均未显示出双侧差异。与未受伤侧相比，腓骨移位达2 mm和达4 mm时，MCS容积分别比健侧增加37.1%和51.8%。基于ROC分析和约登J统计量，确定腓骨骨折移位2.3 mm为与MCS容积显著增加相关的最佳阈值（AUC，0.81；敏感度，77.8%；特异度，80%）。对照组在任何测量值上均未显示出双侧差异。
在这项使用WBCT的初步研究中，即使一维距离测量显示对称，三维MCS容积测量在Weber B型腓骨骨折中与对侧相比仍显示出统计学差异。通过ROC分析确定了2.3 mm的移位阈值，尽管这些容积变化的临床意义仍不清楚，需要通过临床结局研究进行验证。
三级，比较诊断性研究。
