title: A New Measure of Tibial Sesamoid Position in Hallux Valgus in Relation to the Coronal Rotation of the First Metatarsal in CT Scans.
abstract: BACKGROUND
  We aimed to find a new radiographic measurement for evaluating first metatarsal pronation and sesamoid position in hallux valgus (HV) deformity.
  
  
  METHODS
  Data from a clinical study of 19 control patients (19 feet) with no HV deformity were compared with preoperative data of 138 patients (166 feet) with HV deformities. Using a weightbearing plain radiograph in anteroposterior (AP) view, the intermetatarsal angles (IMAs) and the hallux valgus angles (HVAs) of the control and study groups were measured. Using a semi-weightbearing coronal computed tomography (CT) axial view, the α angle was measured in the control and study groups. In addition, the tibial sesamoid grades in plain radiograph tangential view and the CT axial view were measured. The tibial sesamoid position in an AP view was checked preoperatively. Based on these measurements, 4 types of HV deformities were defined.
  
  
  RESULTS
  The mean values of the α angle in the control and HV deformity groups (control group µ = 13.8 degrees, study group µ = 21.9 degrees) was significantly different. Among 166 HV feet, 145 feet (87.3%) had an α angle of more than 15.8 degrees, which is the upper value of the 95% confidence interval of the control group, indicating the existence of abnormal first metatarsal pronation in HV deformity. Four types of HV deformities were defined based on their α angles and tibial sesamoid grades in CT axial view (CT 4 position). Among 25.9% (43/166) of the study group, abnormal first metatarsal pronation with an absence of sesamoid deviation from its articular facet was observed. The prominent characteristic of this group was that they had high grades in the AP 7 position (≥5); however, in the CT 4 position, their grade was 0. This group was defined as the "pseudo-sesamoid subluxation" group.
  
  
  CONCLUSIONS
  Patients with HV deformities had a more pronated first metatarsal than the control group, with a greater α angle. Pseudo-subluxation of the sesamoids existed in 25.9% of our study group. From our results, we suggest that the use of the CT axial view in assessments of HV deformity may benefit surgeons when they make operative choices to correct these deformities. With regard to the pseudo-sesamoid subluxation group, the use of the distal soft tissue procedure is not surgically recommended.
  
  
  METHODS
  Level III, retrospective comparative study.
authors: University of Western Australia, Podiatric Medicine Unit/School of Surgery, Faculty of Medicine, Dentistry and Health Science, Corner of Park and Crawley Ave, Perth, WA, Australia.
authors: Yejeong
authors: Y
authors: Kim
authors: Eulji Medical Center, Eulji University School of Medicine, Foot and Ankle Clinic, Department of Orthopedic Surgery, Seoul, South Korea jins33@hanmail.net.
authors: Jin Su
authors: JS
authors: Kim
authors: Eulji Medical Center, Eulji University School of Medicine, Foot and Ankle Clinic, Department of Orthopedic Surgery, Seoul, South Korea.
authors: Ki Won
authors: KW
authors: Young
authors: University of Western Australia, Podiatric Medicine Unit/School of Surgery, Faculty of Medicine, Dentistry and Health Science, Corner of Park and Crawley Ave, Perth, WA, Australia.
authors: Reza
authors: R
authors: Naraghi
authors: Eulji Medical Center, Eulji University School of Medicine, Foot and Ankle Clinic, Department of Orthopedic Surgery, Seoul, South Korea.
authors: Hun Ki
authors: HK
authors: Cho
authors: Eulji Medical Center, Eulji University School of Medicine, Foot and Ankle Clinic, Department of Orthopedic Surgery, Seoul, South Korea.
authors: Sang Young
authors: SY
authors: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006215:Hallux Valgus / Q000145:classification / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008682:Metatarsal Bones / Q000000981:diagnostic imaging*; D008875:Middle Aged; D011403:Pronation; D012716:Sesamoid Bones / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing; D055815:Young Adult
keywords: CT axial view; first metatarsal pronation; hallux valgus; sesamoid