Radiographic Evaluation of Congenital and Acquired Foot Deformities 1st MTP Angle

Purpose	Characterization of congenital and acquired foot deformities on radiographs
Tag(s)	bilateral foot, foot, x-rays, radiographs, congenital foot, pes, feet, 1st MTP angle, 1st metatarsophalangeal angle, weight-bearing
Panel	Pediatric
Define-AI ID	21010017
Originator	Pediatrics Panel
Lead	Viet Le & Alex Towbin
Panel Chair	Steven Blumer
Panel Reviewers	Pediatric Panel
License	Creative Commons 4.0
Status	Public Comment
RadElement Set	RDES206

Clinical Implementation

Value Proposition

Multiple angles and measurements can be used to evaluate abnormal development of the foot, but the task of obtaining these can be cumbersome and time-intensive. An automated method for obtaining a series of angle measurements and bony relationships, which can eventually be used to characterize foot deformities, should improve the radiologists’ workflow.

For our use case(s), we will first focus on automating the measurement of a series of different angles and bony associations on foot radiographs, which can then be compiled to determine the presence vs. absence of a foot deformity. If present, our hope is for the algorithm to further diagnose/characterize the specific foot deformity. Ultimately, this may be expanded to include additional modalities, such as CT.

For this particular use case, we will limit our evaluation to measuring the 1st metatarsophalangeal (MTP) angle to specifically evaluate the presence or absence of hallux valgus. Additional use cases include the AP and lateral talocalcaneal angles, talo-1st metatarsal angle, talonavicular axis, calcaneal pitch, intermetatarsal angle, Meary’s angle, and the tibial-calcaneal angle.

Narrative(s)

3-year-old female presents to the pediatrician with abnormal gait and in-toeing. Bilateral, weight-bearing 3-view foot radiographs are obtained for evaluation of foot deformities.

6-month-old male presents for contractures/abnormal positioning of the feet. Bilateral, 3-view simulated weight-bearing foot radiographs are obtained for evaluation of foot deformities.

Workflow Description

Radiographs of the foot/feet are ordered, obtained, sent to PACS and the algorithm is triggered.

The algorithm delivers the following outputs: 1st MTP angle, comparisons from any available prior studies, and normal vs. abnormal angle.

Considerations for Dataset Development

Procedures	XRAY, Foot RADIOGRAPH, Foot
Gender	Male, Female
Age (years)	0-18
Views	AP
Technique	Weight-bearing, Simulated weight-bearing, Erect
Anatomy	Foot
Confounders	Cast, Splint, Brace, Non-weight-bearing, Supine

Technical Specifications

Inputs

DICOM Study

Procedure	X-ray Foot Radiograph
Views	AP
Data Type	DICOM
Modality	X-ray
Body Region	Lower Extremity
Anatomic Focus	Foot

Primary Outputs

1st MTP Angle

RadElement ID	RDE1343
Definition	The angle between the axis of the 1st metatarsal shaft and the axis of the proximal phalanx of the 1st toe on weight-bearing AP foot radiograph.
Data Type	Numeric
Value Set	0-90
Units	Degrees

Secondary Outputs

Normal vs. Abnormal with Grading

RadElement ID	RDE1344
Definition	Normal for 1st MTP angle is <15 degrees. A 1st MTP angle >15 degrees is consistent with hallux valgus which can be graded as mild, moderate or severe.depending on the measurement of the 1st MTP angle.
Data Type	Categorical
Value Set	normal (<15) mild hallux valgus (15-20) moderate hallux valgus (21-40) severe hallux valgus (>40)
Units	N/A

Future Development Ideas

As mentioned in the Value Proposition, future development ideas include

Additional angle measurements
Bony relationships in the foot
Diagnosis of foot deformities if present (“diagnostic use cases”)
Improvement from prior studies if comparisons are available
Extrapolation to another imaging modality, such as CT