Examples of Weight Bearing Computed Tomography

Fig. 22.1

(af) WBCT with implanted total ankle replacement (TAR) (STAR, Stryker, Kalamazoo, MI, USA). (a) show paracoronal reformation, (b) parasagittal reformation, and (c, d) axial reformations. The axial reformations (c, d) allow for assessment of rotational relationship between tibial component (c) and talar component (d). Especially for nonmobile bearing TAR models , incongruent rotational position of tibial and talar components might cause increased internal stress and wear. (e, f) show 3D reformations of TAR and surrounding bone (e) and TAR implant alone (f)


Fig. 22.2

(a, b) Subtle Lisfranc joint instability . (a) shows a lateral shift of the base of the second metatarsal in the second tarsometatarsal joint (arrow) which was not visible on conventional radiographs with weight-bearing or conventional CT without weight-bearing. (b) shows a 3D reformation


Fig. 22.3

(ac) Assessment of bilateral hallux valgus correction . (a) shows a virtual dorsoplantar weight-bearing radiograph, generated from the WBCT-3D-dataset. (b) shows a generated Metatarsal-Skyline view, and (c) a paracoronal reformation. The rotation of the first metatarsal head and its position in relation to the sesamoids is better visible on the paracoronal reformation (c) than on the metatarsal-skyline view (b) which represents the former visualization with conventional weight-bearing radiographs


Fig. 22.4

(ac) TAR (Salto, Wright Medical Group, Memphis, TN, USA). WBCT-based parasagittal (a), paracoronal (b), and axial (c) reformations allowing for optimal assessment of implant position and cyst size and location under weight-bearing conditions


Fig. 22.5

(ac) (STAR, Stryker, Kalamazoo, MI, USA). WBCT-based parasagittal (a), paracoronal (b), and axial (c) reformations allowing for optimal assessment of implant position and cyst size and location under weight-bearing conditions


Fig. 22.6

(ad) Charcot arthropathy at the hindfoot (Localization Sanders IV) before (a) and after bilateral hindfoot correction arthrodesis (bd). The preoperative paracoronal reformation (a) shows severe hindfoot valgus and destruction of ankle and subtalar joints. (b) shows a paracoronal reformation after bilateral hindfoot correction arthrodesis with retrograde arthrodesis nail (A3, Stryker, Kalamazoo, MI, USA). (c) shows a generated virtual hindfoot radiograph (so-called Saltzman view) showing the hindfoot axis and the entire implant. (d) shows a 3D reformation of the implants with best visibility of the locking screws


Fig. 22.7

(af) Charcot arthropathy at the midfoot (Localization Sanders II) before and after pan-correction-arthrodesis. (a, b) show axial and parasagittal reformations with severe destruction and deformity at and around the Lisfranc joint. (ce) show the healed situation after plan-correction-arthrodesis involving the following joints: subtalar, talonavicular, calcaneocuboid, innominate 1–3, intercuneiform 1–2, intercuneiform 2–3, and tarsometatarsal 1–5. Midfoot fusion bolts (MFB, Depuy Synthes, Raynham, MA, USA) were used for fixation. (c) shows a MFT in the medial column , i.e., first metatarsal, cuneiform 1, navicular, and talus. (d) shows a MFB in the lateral column , i.e., fifth metatarsal, cuboid, and calcaneus. (e) shows a MFB in the hindfoot , i.e., calcaneus and talus. (f) shows a 3D reformation of the three MFBs with their spatial relationship in relation to each other


Fig. 22.8

Shows a posttraumatic case of acquired flatfoot following chronic subluxation of the tibialis posterior tendon. The bilateral posterior skin view shows deviation of the hindfoot (a). The AP 3D rendering bone view shows lateralization of the forefoot and plantar drop of the talus comparative to the asymptomatic side (b). We have added a posterior 3D bone view showing the enlarged medial groove consequence of chronic subluxation of the posterior tibial tendon (c). (d, e) show the talocalcaneal lateral impingement in the sinus tarsi on the symptomatic (d) and asymptomatic (e) sides. Conventional measurements are possible very rapidly using pre-programed and readily available DRR (digitally reconstructed radiographs) incidences such as this lateral 2D view (f) showing medial arch angle, Meary’s angle, and navicular and medial cuneiform to floor distances. The TALAS (g) window shows the result of the semiautomatic hindfoot alignment software. In this case, the foot ankle offset value is 10.8%, advocating for a severe case of flatfoot


Fig. 22.9

Is a classic case of subfibular impingement . (a) shows the 3D rendering view on which the diagnosis is self-evident. We advocate for the use of the 3D rendering view to fulfill in the future the need for a “snapshot” view which before was provided by conventional radiographs. In the future, virtual reality and holographic projectors will probably provide for a comfortable and immediate interface valid for daily clinical use. (b, c) correspond to the coronal and sagittal views of the multiplanar windows. The TALAS (d) window in this case shows a major case of valgus, explaining this situation, with a close to 20% foot ankle offset. The FAO is given as a percentage of foot length, in order to be comparable across different patients. In this case, that means that the patient’s mass is distributed with an offset so large that it is actually projected outside, on the medial side of the plantar surface. In physical terms, this means the foot tilts on each step, explaining the major subfibular impingement


Fig. 22.10

Demonstrates the possibility in a large field of view cone beam WBCT to investigate dynamic postures such as varus in this case of chronic lateral ankle instability. An important intra-articular lateral talar tilt can be visualized and measured. The subtalar joint may be investigated in the MPR windows (c) or on the 3D rendering view (a, b). A distance mapping view (d, image courtesy of Pr Sorin Siegler, Drexel University, Philadelphia PA, USA) may be built from the harvested data. In this case the right side demonstrates good joint congruency, whereas the left side demonstrates approximation in the medial aspect of the tibiotalar joint and important distancing in the lateral aspect of the joint


Fig. 22.11

(af) Preoperative computer-assisted planning of an adult-acquired flatfoot deformity correction based on weightbearing CT images. Left AAFD in a 52-year-old male patient (a). Tenderness over deltoid ligament, tibialis posterior, and fascia plantaris +++ (b). Digitally reconstructed images AP and lateral of the left AAFD (c). A medializing calcaneus osteotomy is simulated on a generated 3D model with a calcaneus osteotomy angle in the axial plane (coaAx) 90° (perpendicular) to the lateral wall of the calcaneus (d). Note a lengthening of the calcaneus, which needs to be avoided in this case, as the patient presents with a marked fasciitis plantaris (e). The coaAx is changed to 71° which corresponds to an isometric translation of the calcaneus. A patient-specific instrument (PSI) is constructed to obtain the correct osteotomy plane (f)

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