Overview of Weight Bearing Cone Beam Computed Tomography

, Francois Lintz2, Cesar de Cesar Netto3, Alexej Barg4, Arne Burssens5 and Scott Ellis6



(1)
Department for Foot and Ankle Surgery, Hospital Rummelsberg, Schwarzenbruck, Germany

(2)
Foot and Ankle Surgery Centre, Clinique de l’Union, Toulouse, France

(3)
Department of Orthopedics and Rehab, University of Iowa, Iowa City, IA, USA

(4)
University Orthopedic Center, University of Utah, Salt Lake City, UT, USA

(5)
Department of Orthopedics and Trauma, University Hospital of Ghent, Ghent, OVL, Belgium

(6)
Department of Orthopedic Surgery, Hospital for Special Surgery, New York, NY, USA

 



Keywords

Weight bearing CTLiterature reviewWBCT forefoot assessmentWBCT midfoot assessmentWBCT hindfoot assessment


General Thoughts on Foot and Ankle Imaging


Imaging remains highly valuable in diagnosing, treating, and assessing outcomes in patients with disorders of the foot and ankle [1]. Available modalities include conventional radiographs, fluoroscopy, computed tomography (CT), scintigraphy, single-photon emission computed tomography-CT (SPECT-CT), magnetic resonance imaging (MRI), and ultrasonography. Most diagnostic imaging workups start with conventional weight-bearing radiographs because pathologies such as subtle arch collapse and loss of cartilage are more reliably identified with weight-bearing. Further imaging may be required for better assessment of the underlying pathology as well as to guide treatment planning. The choice of the best imaging modality is usually based on several factors that include (1) reliability with regard to the diagnosis under consideration; (2) local availability; (3) patient concerns, such as cost, convenience, and discomfort; (4) safety risks including radiation dose (Table 2.1) and contrast sensitivity; and (5) cost [2].


Table 2.1

Typical effective radiation dose [2]































Average US background radiation/yr


3.0 mSv


Single trans-Atlantic flight


0.04 mSv


Radiograph: chest (p.a.)


0.02 mSv


Radiograph: foot (single exposure)


0.001 mSv


Conventional computed tomography: pelvis


15 mSv


Conventional computed tomography: ankle


0.07 mSv


Weight-bearing cone beam computed tomography: foot/ankle


0.01–0.03 mSv


Isotope (tc-99 m-MDP) bone scan


6.3 mSv



MDP methylene diphosphonate, mSV millisievert, p.a. posteroanterior


CT technology is commonly used to evaluate skeletal pathology. Modern multidetector CT technology provides high-resolution thin-slice images that can be obtained in any plane providing excellent visualization of fractures, degenerative changes, osseous union at a site of arthrodesis, internal fixation of fractures, or osteotomies [2]. One major limitation of conventional CT has been the inability to obtain weight-bearing images. Without weight-bearing during CT assessment, true alignment may not be fully appreciated. Pathology such as impingement, joint space narrowing, and malalignment that may be apparent only with load may also go undiagnosed [3].


The idea of visualizing the relative alignment of the bones of the foot and ankle with a weight-bearing CT (WBCT) imaging is not new. Several investigators have developed methods to simulate weight-bearing using custom-made loading frames to assess foot and ankle pathologies (Table 2.2). The limitations of simulated weight-bearing conditions have been well articulated by these authors. First, only partial weight bearing can be applied so the observed deformities or pathologies are potentially underestimated as compared to normal standing [38]. Second, the loading devices are generally passive, applying external loads without the muscle forces active when standing [911].


Table 2.2

Literature review addressing the use of simulated weight-bearing computed tomography in patients with foot and ankle disorders [1]











































































































Study


Patients


Study objectives


Methods


Findings


Ananthakrisnan et al. [3]


4 healthy controls


8 patients with flatfoot deformity and rupture of PTT


3D position of the talocalcaneal joint in patients with flatfoot deformity


75 N axial force with a custom loading frame in supine position


Patients with PTTD had decreased contact surface in talocalcaneal joint


Apostle et al. [4]


20 healthy controls


20 patients with peritalar subluxation


Morphology of the subtalar joint axis


75 N axial force with a custom loading frame in supine position


Subtalar joint axis orientation was more valgus in patients with peritalar subluxation


Ferri et al. [5]


8 healthy controls


15 patients with symptomatic flatfoot deformity


Forefoot and hindfoot alignment


Special loading device with load of 50% of body weight


Forefoot arch angle 29% lower in flatfeet during non-weight-bearing and 52% lower during weight-bearing


Geng et al. [12]


10 healthy controls


10 patients with HV deformity


Mobility of the 1st TMT joint


Special frame with full weight-bearing in supine position


1st TMT joint more dorsiflexed and more supinated in HV


Greisberg et al. [6]


37 patients with flatfoot deformity


Assessment of deformity and degenerative changes


75 N axial force with a custom loading frame in supine position


Mean TN angle −1° (10° to −34°)


Mean naviculocuneiform angle −15° (−1° to −30°)


Average TMT subluxation 9% (0–20%)


Katsui et al. [13]


142 patients with HV deformity (269 feet)


Alignment of the tibial sesamoid


Special frame with one third of patient’s weight loading


Sesamoid position: grade 1 (tibial sesamoid medial to axis of 1st metatarsal) 34 feet, grade 2 (tibial sesamoid below the axis of 1st metatarsal) 116 feet, grade 3 (tibial sesamoid lateral to axis of 1st metatarsal) 119 feet


Kido et al. [10]


21 healthy controls


21 patients with flatfoot deformity


Bone rotation of hindfoot joints


A custom foot loading device with 99.4 ± 11.6% of the body weight


Patients with flatfoot deformity: talus 1.7° more plantarflexed, navicular 2.3° more everted, calcaneus 1.1° more dorsiflexed and 1.7° more everted


Kido et al. [11]


20 healthy controls


24 patients with flatfoot deformity


Bone rotation of each joint in the medial longitudinal arch


Special frame with full weight-bearing in supine position


Patients with flatfoot deformity: 1st metatarsal more dorsiflexed, navicular and calcaneus more everted, and TN joint more rotated


Kim et al. [14]


138 patients (166 feet) with HV deformity


19 healthy controls (19 feet)


1st metatarsal pronation and sesamoid position


Special frame with half of full weight-bearing in supine position


Significant difference in α angle with 21.9° (HV group) vs. 13.8° (control group)


Kimura et al. [15]


10 patients with HV deformity


10 healthy controls


3D mobility of the first ray


Special frame with full weight-bearing in supine position


Patients with HV deformity: TN and 1st TMT joints more dorsiflexed


Ledoux et al. [7]


10 healthy controls


10 patients with pes cavus deformity


10 patients with asymptomatic pes planus deformity


10 patients with symptomatic pes planus deformity


Differences in bone-to-bone relationships between different foot types


Special frame with 20% of weight-bearing in supine position


Significant differences were found in all measurements regarding midfoot and hindfoot alignment


Malicky et al. [8]


5 healthy controls


19 patients with symptomatic flatfoot deformity with lateral pain


Osseous relationships in patients with flatfoot deformity and to evaluate subfibular impingement


75 N axial force with a custom loading frame in supine position


Prevalence of sinus tarsi impingement 92% vs. 0% in controls


Prevalence of calcaneofibular impingement 66% vs. 5% in controls


Van Bergeyk et al. [16]


12 healthy controls


11 patients with chronic lateral instability


Radiographic differences with respect to hindfoot varus/valgus between patients with chronic lateral instability and controls


Special frame with full weight-bearing in supine position


Hindfoot alignment angle was different in both groups: 6.4° ± 4° varus (patients with instability) vs. 2.7° ± 5° varus (controls)


Yoshioka et al. [17]


10 healthy controls


10 patients with stage II PTTD flatfoot deformity


Forefoot and hindfoot alignment


Special frame with full weight-bearing in supine position


Méary angle was significantly lower in flatfeet


1st metatarsal more everted in flatfeet


Calcaneus was more everted and abducted in flatfeet


Zhang et al. [18]


15 healthy controls


15 patients with stage II PTTD flatfoot deformity


Rotation and translation of hindfoot joints


Special frame with full weight-bearing in supine position


Significant differences in position of talus, navicular, and calcaneus between both groups



3D three-dimensional, HV hallux valgus, PTT posterior tibial tendon, PTTD posterior tibial tendon dysfunction, TMT tarsometatarsal, TN talonavicular


In the last decade, cone beam CT technology has helped with both supine and standing weight-bearing imaging of the lower extremity due to improved designs with flexible gantry movements [19, 20]. This imaging technology has several advantages, including the ability to obtain images with the patient standing, high contrast resolution and spatial resolution, fast image acquisition time, decreased radiation, a relatively small scanner size with portable design, and generally less capitalization cost than conventional CT scan technology [19, 20].


Studies on Normal Controls


Colin et al. [21] performed WBCT in 59 patients without any history of hindfoot or ankle pathology to describe the subtalar joint configuration. The shape of the posterior facet and the subtalar vertical angle was measured in three different coronal planes (center of the subtalar joint, 5 mm anterior, and 5 mm posterior to the center). In this patient cohort, the posterior facet was concave in 88% of feet and flat in the remaining 12%. In the middle coronal plane, the posterior facet was oriented in valgus in 90% and in varus in 10% of cases. However, substantial intraindividual differences in the subjects were observed with the subtalar vertical angle increasing in valgus when the measurement was performed more posteriorly [6].


Meanwhile, Lepojärvi et al. [22] used WBCT to investigate the normal anatomy and rotational dynamics of the distal tibiofibular joint under physiological conditions in a cross-sectional study including 32 asymptomatic subjects. Imaging acquisition was performed in three different positions of the ankle: neutral, internal, and external rotation. Measured parameters included sagittal translation of the fibula, anterior and posterior widths of the distal tibiofibular syndesmosis, tibiofibular clear space, and rotation of the fibula. In subjects with the ankle in a neutral position, the fibula was located anteriorly in the tibial incisura in 88% of all measurements. During ankle rotation, the mean anteroposterior motion was 1.5 mm, and the mean rotation of the fibula was 3° [22].


In another study, Lepojärvi et al. [23] performed WBCT in the same subject cohort to assess the rotational dynamics of the talus. The rotation of the talus, medial clear space, anterior and posterior widths of the tibiotalar joint, translation of the talus, and talar tilt were measured. When the ankle was rotated with a moment of 30 Nm, a talus rotation of 10° without substantial widening of the medial clear space was observed [23].


Studies on Pathologic Conditions


In total, eight studies were reviewed (Table 2.3). All were published between 2013 and 2017 with four prospective and four retrospective studies. All studies but one were single-center in design. For the included investigations, the level of evidence ranged from II to IV. There was one level II study, five level III studies, and two level IV studies.


Table 2.3

Description of eight studies included into systematic literature review [1]











































































Study


Study type


Data collection


Level of evidence


Conflict of interest


Subjects


Burssens et al. [9]


Multicenter


Retrospective


III


None


60 patients (30 valgus and 30 varus malalignment)


Cody et al. [24]


Single-center


Retrospective


III


None


45 patients with adult-acquired flatfoot deformity


17 healthy controls


Collan et al. [25]


Single-center


Prospective


II


None


10 patients with bilateral hallux valgus deformity


5 healthy controls


Hirschmann et al. [13]


Single-center


Prospective


IV


n.r.


22 patients with different hindfoot pathologies


Krähenbühl et al. [26]


Single-center


Retrospective


III


None


40 patients with subtalar osteoarthritis


20 healthy controls


Lintz et al. [27]


Multicenter


Retrospective


III


Yesa


135 patients: normal (57), varus (38), and valgus (40) alignment


Richter et al. [28]


Single-center


Prospective


IV


Yesb


30 patients with foot/ankle disorders


Richter et al. [29]


Single-center


Prospective


IV


Yesb


First study: 30 patients


Second study: 50 patients



n.r. not reported


aThe corresponding author received personal fees from CurveBeam during the conduct of the study


bThe corresponding author is a consultant of Stryker, Intercus, and CurveBeam, proprietor of R-innovation, and joint proprietor of 1st Worldwide Orthopedics

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Apr 25, 2020 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on Overview of Weight Bearing Cone Beam Computed Tomography
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