First Ray Pathology

Radiographic findings may include:

  • abnormal hallux abductus, intermetatarsal, and/or hallux interphalangeal angles
  • abnormal sesamoid position relative to the first metatarsal head
  • prominent first metatarsal head medially
  • osteophytes
  • unven joint space narrowing
  • subchondral sclerosis
  • loose osseous bodies

Differential Diagnosis:

  • hallux abductovalgus
  • hallux varus
  • os interphalangeus
  • bunion deformity
  • gouty arthritis
  • osteoarthritis
  • fracture
  • multipartite sesamoid
  • metatarsus primus elevatus

Here are presentations of first ray pathology and related variants (with *interpretations):

  • Case 1
  • *Case 1
  • Case 2
  • *Case 2
  • Case 3
  • *Case 3
  • Case 4a
  • *Case 4a
  • *Case 4b
  • Case 5
  • *Case 5
  • Case 6
  • *Case 6
HAV
HAV marked

Dorsoplantar foot view.
The hallux abductus (22 degrees) and intermetatarsal (15 degrees) angles are increased. The hallux interphalangeal angle is normal (5 degrees). The proximal articular set angle (PASA, 7 degrees) is high normal. The tibial sesamoid position is 6, and the first metatarsal head medial eminence is prominent. The proximal and distal articular set axes cross within the joint.
Other findings: A geographic decreased density presents in the medial aspect first metatarsal head and is bounded by a sclerotic margin. The fourth and fifth toes are in adductovarus position, and there are contractures at the lesser toe interphalangeal joints. The primary trabeculations are prominent in the lesser metatarsal heads.
Diagnoses: Hallux abductovalgus with bunion deformity. Subluxation, first metatarsophalangeal joint. Bone cyst. Toe deformities. Osteoporosis.

a Osteoarthritis DP view b Osteoarthritis lateral view
a Osteoarthritis DP view marked b Osteoarthritis lateral view marked

Dorsoplantar (a) and lateral (b) views.
The intermetatarsal and hallux abductus angles are normal (7 and 6 degrees, respectively). The interphalangeus angle is slightly increased (16 degrees). Other findings include osteophytes at the joint margins (arrows) and a loose osseous body superolaterally (arrowheads). The first metatarsal axis is greatly dorsiflexed relative to the talar axis.
Diagnosis: Osteoarthritis; hallux abductus interphalangeus; metatarsus primus elevatus.

HAV DP view
HAV DP view marked

Dorsoplantar foot view.
The hallux abductus (25 degrees) and intermetatarsal (17 degrees) angles are increased. The hallux interphalangeal angle is normal (0 degrees). The proximal articular set angle (PASA, 6 degrees) is high normal. The tibial sesamoid position is 7, and the first metatarsal head medial eminence is prominent. The proximal and distal articular set axes cross within the joint.
Other findings: The second toe angulates medially relative to the second metatarsal and is superimposed upon the hallux distally. The fourth toe is in adductovarus position.
Diagnoses: Hallux abductovalgus with bunion deformity and overlapping second toe. Subluxation, first metatarsophalangeal joint. Toe deformities.

a HAV DP view b post op hallux varus

Preop (a) and postop (b) studies of the same patient.

a HAV Dp view marked b post op hallux varus marked

Dorsoplantar foot views, pre-op (a) and post-op (b).
a) Pre-op findings: The hallux abductus (40 degrees) and intermetatarsal (18 degrees) angles are increased. The hallux interphalangeal angle is high normal 12 degrees). The proximal articular set angle (PASA, 26 degrees) is increased. The tibial sesamoid position is 7, and the first metatarsal head medial eminence is prominent. The proximal and distal articular set axes cross within the joint.
Other findings: The second toe angulates medially relative to the second metatarsal and is superimposed upon the hallux distally. The fifth toe is in adductovarus position.
Diagnoses: Hallux abductovalgus with bunion deformity and overlapping second toe. Subluxation, first metatarsophalangeal joint. Toe deformities.
b) Post-op findings are described with Case *4b.

a Pre-op HAV DP view b post-op hallux varus complication DP view
c post-op hallux varus complication lateral view

Pre-op dorsoplantar (a) foot view. Post-op dorsoplantar (b) and lateral (c) foot views.
Post-op findings: Compared to the pre-op view (a), the hallux proximal phalanx base is absent. The remaining phalanx angulates medially relative to the original first metatarsal pre-op axis (the diaphysis). The first metatarsal head medial eminence is also absent; the remaining surface angulates laterally relative to the medial cortex, and the tibial sesamoid is visible medial to the head. Increased soft tissue density and volume surrounds this operative area. A curvilinear decreased density runs across the first metatarsal proximal metadiaphysis, separating the base from the diaphysis. Ill-defined periosteal reaction is seen at its margins. A K-wire runs through the two segments from inferior-medial-anterior to superior-lateral-posterior, ending within the second metatarsal base. The intermetatarsal angle is decreased when compared to the pre-op study. The proximal articular set angle (PASA) was not addressed surgically and remains 26 degrees. The first metatarsal axis is greatly dorsiflexed compared to the talar axis in the lateral view.
Diagnoses: Post-op Keller bunionectomy and closing base wedge osteotomy with pin fixation. Soft tissue edema. Hallux varus. Metatarsus primus elevatus.

a Juvenile HAV DP view b Juvenile HAV lateral view
a Juvenile HAV DP view marked b Juvenile HAV lateral view marked

Dorsoplantar (a) and lateral (b) foot views.
The hallux abductus and proximal articular set (PASA) angles are greatly increased (41 & 54 degrees, respectively). The intermetatarsal angle is increased (17 degrees). The hallux interphalangusl angle is high normal (13 degrees). The tibial sesamoid (t) position is 7, and the first metatarsal head medial eminence is prominent, and there is increased soft tissue density and volume medial to it. The proximal and distal articular set axes cross outside the joint. The first metatarsal axis is greatly dorsiflexed relative to the talar axis (lateral view).
Other findings: A geographic increased density presents along the endosteal surface of the fourth metatarsal mid-diaphysis (arrow); adjacent to this finding along the periosteal surface is a small scalloped defect or lucent nidus. There is no gross evidence of adjacent soft tissue mass. When compared to a previous study from 2 years ago, there have been no changes.
Otherwise, all ossification centers appear as expected for this 12 year old male.
Diagnosis: Juvenile HAV deformity. Deviated first metatarsophalangeal joint. Metatarsus primus elevatus. Osteoid osteoma versus enostosis versus juxtacortical tumor or tumor-like lesion.

a sesamoid fracture dp view b sesamoid fracture axial
a sesamoid fracture dp view marked b sesamoid fracture axial marked

Dorsoplantar (a) and sesamoid axial (b) foot views.
A transversely-oriented linear decreased density runs partially through the fibular sesamoid (black arrow) in the dorsoplantar view. Also, mixed densities run vertically through the sesamoid where there is no superimposition of it upon the metatarsal head in this same view. In the axial view, white arrows point to multiple ill-defined, curvilinear decreased densities that divide the sesamoid into multiple segments.
Diagnosis: Comminuted fibular sesamoid fracture.

Should a radiographic study be ordered for suspicion of first ray pathology?

Yes, if clinically indicated.

What are the best views to order?

At a minimum order DP and lateral (or sesamoid axial) views. Obtain oblique views if necessary for further evaluation. The lateral oblique view is useful for isolating the tibial sesamoid.

Other information

It is dfficult to diagnose sesamoid fracture and osteonecrosis. Bone scintigraphy and/or MR may be a valuable resource.

I do not measure the distal articular set angle. In a preliminary study, I found that it the measurement can vary significantly depending upon the amount of hallux rotation in the coronal plane. [Christman RA: Radiographic evaluation of the distal articular set angle.  JAPMA 78 (7):352, 1988 (Jul)].

References:

  1. Christman RA: Foot and Ankle Radiology, 2nd edition, Lippincott Williams & Wilkins, 2015.