Foot & Ankle International - 2017 FAI Supplement - 32S

change (P<0.001), as the heel ratio changed from 0.2±0.2 preoperatively to 0.3±0.2 postoperatively (P<0.001), the heel
angle changed from 11.4±7.0° preoperatively to 5.0±7.4°postoperatively (P<0.001), and the heel distance changed from
10.5±6.6mm preoperatively to 6.4±6.4mm postoperatively
(P<0.000).
Conclusion: Varus knee deformity tended to be associated
with valgus deformity of the ankle joint and hindfoot alignment. Alignment in the ankle joint and the hindfoot both
changed to a varus trend after correction of varus deformity
of the knee. Such changes in ankle joint and hindfoot alignment are considered to be due to the compensatory changes
following alterations in lower limb alignment. Therefore, it is
necessary to perform a meticulous examination of the ankle
joint as well as the knee joint and consider subsequent alteration of ankle joint and hindfoot alignment before surgical
correction of knee joint alignment.
Foot & Ankle International, 38(S1)
DOI: 10.1177/1071100717S00028
©The Author(s) 2017

Mobility Changes in the First TMT
Joint After Proximal First Metatarsal
Osteotomy for Hallux Valgus Evaluated
by Weightbearing CT and a 3D
Analysis System
Tadashi Kimura, MD,PhD, Makoto Kubota, MD,
Hidekazu Hattori, MD, Kazuhiko Minagawa, MD,
Naoki Suzuki, PhD, Asaki Hattori, PhD, Keishi
Marumo, MD, PhD
Category: Bunion
Keywords: Hallux valgus, Weight-bearing CT, proximal
first metatarsal osteotomy, TMT joint mobility
Introduction/Purpose: In a previous study, we found that
feet with hallux valgus show significantly greater threedimensional mobility than normal feet in all joints of the
first ray. Displacement was particularly pronounced in the

32S

first TMT joints, indicating that this is the primary cause of
first ray hypermobility. We developed a plate used specifically for proximal first metatarsal osteotomy to perform
three-dimensional correction of hallux valgus and associated deformities. In this study, we evaluated changes in
mobility of the first TMT joints after surgery in 3D using
weightbearing CT.
Methods: The subjects were 5 feet of 5 female patients with
hallux valgus (mean age 56 years, mean hallux valgus angle
38°). We performed non-weightbearing and weightbearing
(using a load equivalent to body weight) CT scans before surgery using an original loading device (Fig a). We reconstructed 3D models from captured images by segmentation
and defined axial coordinate system (Fig b). Next, we measured the three-dimensional displacement of the first metatarsal bone relative to the medial cuneiform bone under
weightbearing conditions. At 1 to 1.5 years after proximal
metatarsal osteotomy for all patients, we performed a followup CT scans using the same method and compared preoperative and postoperative displacement. Student's t-test was
performed to statistically compare data and statistical significance was set at p < 0.05.
Results: Postoperatively (when performing a follow up
CT), the mean hallux valgus angle improved from 38° to
10° and the mean first-second metatarsal angle improved
from 23° to 7°. The mean score on the Japanese Society for
Surgery of the Foot hallux scale improved from 62 points to
97 points. Displacement of the first metatarsal bone relative
to the medial cuneiform bone between non-weightbearing
and weightbearing conditions decreased significantly in all
directions, from 4.2° ± 1.8° to 1.6° ± 1.1° of dorsiflexion (p
= 0.02), 4.9° ± 1.8° to 0.7° ± 0.9° of inversion (p = 0.001),
and 4.4° ± 1.9° to 1.7° ± 0.8° of adduction (p = 0.01).
Conclusion: Displacement of the first TMT joints under
weightbearing conditions decreased after our surgery. This
indicates that the surgery corrected hallux valgus and associated pes planus and produced favorable functional outcomes
by improving the shape of the foot and hypermobility of the
first ray through correction of the orientation and tension of
surrounding tendons and ligaments and the plantar aponeurosis. In the future, we plan to further examine the pathology
and treatment of hallux valgus with a focus on postoperative
changes in soft tissue orientation.

Foot & Ankle International 38(1S)

Table of Contents for the Digital Edition of Foot & Ankle International - 2017 FAI Supplement