, Francois Lintz2, Cesar de Cesar Netto3, Alexej Barg4, Arne Burssens5 and Scott Ellis6
Keywords
Weight bearing CTLiterature reviewWBCT forefoot assessmentWBCT midfoot assessmentWBCT hindfoot assessmentGeneral Thoughts on Foot and Ankle Imaging
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 |
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].
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 |
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
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 |
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