Background The Distal Metatarsal Articular Angle (DMAA) was previously described as an increase in valgus deformity of the distal articular surface of the first metatarsal (M1) in hallux valgus (HV). Several studies have reported poor reliability of this measurement. Some authors have even called into question its existence and consider it to be the consequence of M1 pronation resulting in projection of the round-shaped lateral edge of M1 head. Our study aimed to compare the DMAA in HV and control populations, before and after computer correction of M1 pronation and plantarflexion with a dedicated weightbearing CT (WBCT) software. We hypothesized that after computerized correction, DMAA will not be increased in HV compared to controls. Methods: We performed a retrospective case-control study including 36 HV and 20 control feet. In both groups, DMAA was measured as initially described on conventional radiographs (XR-DMAA) and WBCT by measuring the angle between the distal articular surface and the longitudinal axis of M1. Then, the DMAA was measured after computerized correction of M1 plantarflexion and coronal plane rotation using the α angle (3d-DMAA). Results: The XR-DMAA and the 3d-DMAA showed higher significant mean values in HV group compared to controls (respectively 25.9 ± 7.3 vs 7.6 ± 4.2 degrees, P < .001, and 11.9 ± 4.9 vs 3.3 ± 2.9 degrees, P < .001). Comparing a small subset of precorrected juvenile HV (n=8) and nonjuvenile HV (n=28) demonstrated no significant difference in the measure DMAA values. On the other hand, the α angle was significantly higher in the juvenile HV group (21.6 ± 9.9 and 11.4 ± 3.7 degrees; P = .0046). Conclusion: Although the valgus deformity of M1 distal articular surface in HV is overestimated on conventional radiographs, comparing to controls showed that an 8.6 degrees increase remained after confounding factors’ correction. Clinical Relevance: After pronation computerized correction, an increase in valgus of M1 distal articular surface was still present in HV compared to controls. Level of Evidence: Level III, retrospective case-control study.
Background: The treatment of ankle osteoarthritis (OA) varies depending on the severity and distribution of the associated joint degeneration. Disease staging is typically based on subjective grading of appearance on conventional plain radiographs, with reported subpar reproducibility and reliability. The purpose of this study was to develop and describe computational methods to objectively quantify radiographic changes associated with ankle OA apparent on low-dose weightbearing CT (WBCT). Methods: Two patients with ankle OA and 1 healthy control who had all undergone WBCT of the foot and ankle were analyzed. The severity of OA in the ankle of each patient was scored using the Kellgren-Lawrence (KL) classification using plain radiographs. For each ankle, a volume of interest (VOI) was centered on the tibiotalar joint. Initial computation analysis used WBCT image intensity (Hounsfield units [HU]) profiles along lines perpendicular to the subchondral bone/cartilage interface of the distal tibia extending across the entire VOI. Graphical plots of the HU distributions were generated and recorded for each line. These plots were then used to calculate the joint space width (JSW) and HU contrast. Results: The average JSW was 3.89 mm for the control ankle, 3.06 mm for mild arthritis (KL 2), and 1.57 mm for severe arthritis (KL 4). The average HU contrast was 72.31 for control, 62.69 for mild arthritis, and 33.98 for severe arthritis. The use of 4 projections at different locations throughout the joint allowed us to visualize specifically which quadrants have reduced joint space width and contrast. Conclusion: In this technique report, we describe a novel methodology for objective quantitative assessment of OA using JSW and HU contrast. Clinical Relevance: Objective, software-based measurements are generally more reliable than subjective qualitative evaluations. This method may offer a starting point for the development of a more robust OA classification system or deeper understanding of the pathogenesis and response to ankle OA treatment.
We present a technical surgical description of a 36-year-old female diagnosed with Progressive Collapsing Foot Deformity (PCFD) treated with a medial displacement calcaneus osteotomy, a lateral column lengthening, and a modified Lapidus fusion. In order to increase the plantar flexion power of this arthrodesis and minimize the loss in ray length with joint preparation, a bone block structured graft was used. Fixation was performed using a post implant in the medial cuneiform with crossing screws though the surfaces and the graft. Forefoot varus was properly corrected intraoperatively by using the described surgical technique. Satisfactory functional short-term results and an excellent alignment was accomplished. Level of Evidence V; Therapeutic Studies; Expert Opinion.
Category: Midfoot/Forefoot Introduction/Purpose: The etiology of hallux rigidus has been unknown. Metatarsus primus elevates (MPE), elevated first metatarsal has been controversial. Recent studies have supported significantly elevated first metatarsal in hallux rigidus patients. Bouaicha reported MPE greater than 5 mm could be a predictive factor of hallux rigidus. Lateral weightbearing radiographs has been used to evaluate MPE, However, there are limitations of conventional radiography including variation in X-ray projection angle and foot position and superimposition of metatarsals. Cheung assessed foot alignment utilizing 3D reconstructions from WBCT and concluded that hallux rigidus patients had increased MPE. Our objective was to assess MPE and anatomical characteristics in foot alignment of hallux rigidus patients compared to a control group using WBCT. This is the first study measuring MPE on WBCT. Methods: This is a single-center, retrospective study from prospectively collected data. 20 patients with hallux rigidus and WBCT data were enrolled from October 2014 to December 2020. As a control group, 20 patients with various foot and ankle pathologies were selected. Measured WBCT parameters included 1st TMT joint version, HVA, IMA, DMAA, 1st and 2nd metatarsal lengths, Foot width, Sesamoid station and rotation angle, 1st-5th Metatarsal Angle, Metatarsus adductus angle, 2nd cuneiform-2nd metatarsal angle, Talus-1st Metatarsal Angel, 1st Metatarsal-Proximal Phalanx Angle, 1st and 2nd metatarsal declination angles and ratio, and MPE. MPE was measured as a direct distance between 1st and 2nd metatarsals using a line tangential to the first metatarsal and another perpendicular line at the metadiaphyseal junction to reach second metatarsal on parasagittal view. A Cut-off value of MPE was calculated using receiver operating characteristic curve. Two investigators independently assessed each WBCT. Results: Mean age was 43.3 in control group (45% male, 55% female) and 55.9 in HR group (60% male, 40% female). Significant differences were found in several facets of foot anatomy between HR and control groups including HVA (7.57 in control vs 14.05 in HR), DMAA (3.89 vs 8.06), forefoot width (92.96 vs 95.47), 1st MT declination angle (20.17 vs 17.82), 1st/2nd MT declination ratio (83.52 vs 76.02), and MPE (3.24 mm vs 5.40 mm). MPE was significantly higher in hallux rigidus group in all three parasagittal views (unmodified, parallel to 1st metatarsal and 2nd metatarsal). Dorsal subluxation/translation of the first metatarsal was observed at 1st TMT joint in the parasagittal view of WBCT in 9 (45%) patients of hallux rigidus group suggesting sagittal instability. No patient in control group had dorsal subluxation/translation. A cut-off value of MPE was 4.56 mm with 80% sensitivity and 90% specificity. Conclusion: To evaluate MPE on WBCT, we used a new direct measurement on parasagittal views. We found a significant difference in MPE in HR. Our WBCT results are consistent with other studies using conventional radiographs. A cut-off value of WBCT MPE for diagnosis of HR was 4.56 mm in our cohort. Considering 45% patients of the HR group had dorsal subluxation/translation of first metatarsal at 1st TMT and increased HVA, Hallux rigidus may be associated with first ray instability predominantly in sagittal plane with resultant MPE with varying degree of combined coronal plane instability resulting in increased HVA.
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