60 - Radiographic Planning for HAV Surgery Flashcards
Hallux abducto valgus (HAV) evaluation
- Clinical and radiographic pictures don’t always match
- May seem to have large deformity clinically but is smaller radiographically
- Use radiographs for surgical planning to choose best procedure
- Radiographs MUST be WB to evaluate foot correctly
- Angles will likely change with WB
Radiographic evaluation
NOTE: look at radiographs systematically***
- Soft tissue first
- Then bone and cartilage
- Then angles and alignment
Soft tissue evaluation on radiographs
o Edema
o Masses
o Air
o Foreign bodies
Bone and cartilage quality evaluation on radiographs
o Osteopenia o Cysts/Tumors o Erosions o Joint space narrowing o Exostosis
Example of radiograph evaluation (on slides)
- Example of osteoporotic bone and bone cysts within the 1st metatarsal head
- Example of joint space narrowing and exostosis
- AP radiographic views – straight down on top of the foot (This is where most of our x-ray measurements will be taken)
- Lateral radiographic view
- Sesamoid axial view – there is a block you put the foot up on, they go up on the ball of the foot (This is important in terms of the rotation of the 1st metatarsal)
Hallux interphalangeus angle
- Definition: Angle formed by the longitudinal bisection of proximal phalanx
and distal phalanx of the hallux - Normal angle is
Hallux abductus angle (HAA)
- Definition: Angle formed by bisection of the longitudinal axis of the proximal
phalanx and 1st metatarsal - Normal range is
Distal articular set angle (DASA)
- Definition: Angle formed by longitudinal bisection of the proximal phalanx of
the hallux and the perpendicular of the line formed by marking the medial and
lateral aspects of the cartilage of the base of the proximal phalanx - Looks at angular deviation of the cartilage of base of the proximal phalanx
- Normal is 0-8 degrees
Proximal articular set angle (PASA)
- Definition: Angle formed by a line perpendicular to longitudinal bisection of
the 1st met and a line formed by marking points of medial and lateral aspects
of 1st met head cartilage - Evaluates position of articular cartilage of the 1st met head
- Normal is 0-8 degrees
Intermetatarsus angle (IM)
- Definition: Angle formed by longitudinal bisection of the 1st metatarsal
and the second metatarsal - This angle is the “powerhouse” which determines which procedure to do
- Normal = 0-10 degrees
- Mild/moderate deformity = 10-15 degrees (In this case a head procedure is typically done)
- Severe deformity = > 15 degrees (In this case a more proximal procedure is typically done)
Metatarsus adductus angle
- Helps determine if all metatarsals are going off to the side or just the first one
- Definition: Angle formed by line perpendicular to midfoot bisection and
longitudinal bisection of the second
Metatarsus adductus angle: Points used to create perpendicular of midfoot are
o Medial most aspect of 1st met cuneiform joint or talonavicular joint
o Lateral most aspect of calcaneal cuboid joint or 4th met cuboid joint
(some texts will use 5th met cuboid joint)
Metatarsus adductus angle: Reference values for metatarsus adductus
o 0-15 = normal
o 16-25 = mild
o 26-35 = moderate
o > 35 severe
Metatarsus adductus angle: Alternative method to measure
o Angle formed by longitudinal bisections of the intermediate cuneiform and the 2nd metatarsal
o Normal is a little higher for this form of measurement
o Usually 5-10 degrees higher
Importance of metatarsus adductus angle
- In patients with increased met adductus, patient may have severe bunion deformity even with mildly increased IM angle
- If met adductus angle > 15 degrees
- True IM = (met adductus – 15) + IM
Now we are moving on to alignment and other considerations
FYI
Joint positions
Defined by the relationship of a line representing the effective
articular surface of the first metatarsal head and a line
representing the effective articular surface of the proximal phalanx:
o Congruous joint-lines are parallel
o Deviated joint-lines intersect outside the joint space
o Subluxed joint-lines intersect inside the joint space
Types of deformity WENT THROUGH ENTIRE CHART
- Structural deformity
- Positional deformity
- Combined deformity
Structural deformity
- Angle formula: PASA + DASA = HAA
- PASA/DASA abnormality: PASA +/- DASA abnormal
- Joint is congruent
Positional deformity
- Angle formula: positional deformity
- PASA/DASA abnormality: PASA + DASA
Combined deformity
- Angle formula: PASA + DASA
Notes on chart
- Structural deformity = deformity due to bone
- Positional deformity = deformity due to soft tissue contraction/adaptation
- HAA = hallux abductus angle
Shape of metatarsal head
- Round = most unstable
- Square (oblique) = relatively stable
- Square with ridge = most stable
Metatarsal protrusion distance
- A measurement for relative length of patterns of 1st and 2nd metatarsals
- Normal is +/- 2mm
Medial cuneiform obliquity
- May or may not be relevant. Study by Hatch et al that is awaiting publication, did not find correlation.
- If x ray angle different than 15, can change the perceived angle.
Tibial sesamoid position
- The is the relationship of the tibial sesamoid to the
bisection of the shaft of the first metatarsal: - Normal = positions 1,2,3
- Abnormal = positions 4,5,6,7
- Used an indication for removal of fibular sesamoid
What to look for in lateral view radiographs
- 1st ray elevation
- Hammer toes
- Hallux crossing over second
Conclusion
- Develop a systematic approach to evaluating radiographs
- Radiographic angles and alignment give you the guidelines needed for procedure choice
- Treat the patient, not the x-ray
CASE STUDY 1 (look at slides)
- Weight bearing x-rays: by appearance, IM angle looks to be above 15°
- Tibial sesamoid position looks to be a 7 (not touching midline)
- The 2nd metatarsal is protruding beyond the normal arc – positive for metatarsal protrusion
- 1st metatarsal elevatus is present (1st metatarsal is elevated)
- Procedure of choice: Lapidus because of high IM angle with phalanx wedge to straighten toe
CASE STUDY 2 (look at slides)
- Weight bearing x-rays
- By appearance, the IM angle looks to be below 15°
- Tibial sesamoid position looks to be at a 3 (at midline)
- There is not significant protrusion of the 2nd metatarsal – negative for metatarsal protrusion
- Procedure of choice: Austin
