Foot & Ankle International - September 2019 - 1105

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Min et al
Table 1. Data Summary.
Parameter

Value (SD)

No. of patients
Mean age, y
Sex, M/F
Sides, right/left
Radiographic measurements
HVA, deg
IMA, deg
Modified MA, deg
AP talo-1st MT, deg
Lateral talo-1st MT, deg
1st tarsometatarsal instability, Y/N
Pedobarographic evaluation
1st tarsometatarsal instability, Y/N

57
59.7 (11.4)
6:51
32:25
31.9 (10.0)
14.6 (3.7)
19.4 (4.8)
7.7 (7.3)
18.7 (9.3)
15:42
26:31

Abbreviations: AP, anteroposterior; HVA, hallux valgus angle; IMA,
intermetatarsal angle; MA, metatarsus adductus angle; SD, standard
deviation; 1st MT, first metatarsal angle.

and sesamoid rotation angle are useful radiographic measurements for evaluating deformity and subluxation of the
metatarsophalangeal joint.2,5,27 However, instability of the
tarsometatarsal joint is relatively less focused on in the
evaluation and treatment of hallux valgus. Previous studies
have suggested the significant association or important role
of tarsometatarsal instability in the progression of hallux
valgus,11,20 and the first metatarsal tends to become
adducted, dorsiflexed, and pronated depending on aggravation of the hallux valgus at the tarsometatarsal joint.3,8,11,16
Although tarsometatarsal instability is considered to be
an important factor in the pathogenesis of hallux valgus,
there are no accurate and reliable methods for evaluating
the joint. Physical examination assessing first ray hypermobility showed conflicting results in its clinical utility and
reliability,3,8,14,16,28 and objective radiographic measurement
evaluating tarsometatarsal instability does not exist. Some
previous studies included foot pressure measurement along
with radiographic examination to evaluate stability of the
tarsometatarsal joint.6,30 The authors considered that pedobarographic examination could be a useful dynamic tool to
evaluate hypermobility of the tarsometatarsal joint.
Therefore, this study aimed to investigate the pedobarographic characteristics of tarsometatarsal instability and
identify radiographic factors associated with pedobarographic tarsometatarsal instability in hallux valgus.

Methods
This retrospective study was approved by the institutional
review board of our hospital, and the need for informed
consent was waived because of the study's retrospective
nature. Consecutive patients aged 20 years and older with
hallux valgus who visited our foot and ankle clinic (a

tertiary referral center) between November 2017 and June
2018 were enrolled. Exclusion criteria were (1) congenital
anomaly; (2) infection, tumor, fracture, or any other conditions that could alter the normal foot anatomy; (3) neuromuscular diseases; (4) previous foot and ankle surgeries;
and (5) inadequate radiographs.
All study patients underwent weightbearing anteroposterior (AP) and lateral foot radiography along with a pedobarographic examination. Hallux valgus was defined as an
HVA greater than 15 degrees.
Fifty-seven patients with hallux valgus were included in
the data analysis. The patients' mean age was 59.7 years
(SD, 11.4 years), and there were 6 male patients and 51
female patients. The mean HVA was 31.9 degrees (SD, 10.0
degrees) and the mean intermetatarsal angle (IMA) was
14.6 degrees (SD, 3.7 degrees). Fifteen patients showed
radiographic instability of the first tarsometatarsal joint,
and 26 showed pedobarographic instability (Table 1).

Radiographic Measurement
Foot radiographs were obtained using a UT 2000 X-ray
machine (Philips Research, Eindhoven, the Netherlands)
according to our protocol. AP foot radiographs were obtained
with the direction of the beam inclined at 15 degrees from the
vertical axis and centered between the patients' feet on the
midtarsal joint. The patients' feet were placed 5 cm apart, and
the medial borders of the feet were parallel. The lateral foot
radiographs were obtained separately for each foot with the
beam focusing on the medial cuneiform. AP and lateral foot
radiographs in the weightbearing view were obtained with
the patients standing barefoot. The radiograph settings were
60 kVp and 10 mAs at a source-to-image distance of 110 cm.
All radiographs were digitally acquired using a picture
archiving and communication system (PACS) (Infinitt,
Seoul, South Korea), and radiographic measurements were
performed using the PACS software.
Six radiographic indices of hallux valgus were determined,7,13,15,17,19,24 and the measurements were performed
by an orthopedic surgeon with 17 years of experience. The
6 measurements were the HVA, IMA, modified metatarsus
adductus angle, AP talo-first metatarsal angle, lateral talofirst metatarsal angle, and radiographic first tarsometatarsal
instability.
On AP radiographs, the HVA was measured between the
longitudinal axes of the proximal phalanx and first metatarsal
bone. The IMA was measured between the longitudinal axes
of the first and second metatarsal bones. The modified metatarsus adductus angle was the angle between the longitudinal
axes of the middle cuneiform and the second metatarsal. The
AP talo-first metatarsal angle was the angle between the longitudinal axes of the talus and the first metatarsal (Figure 1).
On lateral radiographs, the lateral talo-first metatarsal angle
was the angle between the longitudinal axes of the talus and

Foot & Ankle International - September 2019

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