61 - HAV 1 Flashcards
Introduction
- Bunions are a huge part of what we do – all day every day you will see this
- Covering all of bunion treatment is a daunting task
- I want you to be aware of what has been held tried and true in regards to bunion surgery in the eyes of many podiatrists, but what may not be evidence-based
- Some ideas that we will talk about today will be contradictory to what has been engrained
- It takes roughly 17 years for new evidence to become mainstream, so while new ideas are gaining steam, it is not mainstream currently
- New ideas will not be on your board exams and asked in clinical rotations for another 17 years
- I want you to be able to critically think about the evidence presented and form own opinions
- When I am talking about “old” versus “new” – I am not saying those who are doing old procedures are bad surgeons, I’m just saying that it is hard to change habit
- Until 2-3 years ago, bunion surgery was not a highlight of lecture series – many of them were based on complications (hallux varus and recurrence)
- Now we are seeing exciting engagement and discussion of bunions – are we best treating this?
- We will spend a lot more time talking about the concepts of bunion surgery, but not a lot of time talking about the step-by-step memorization of the procedures
- Make sure you review your surgical text on all of your bunion procedures – GERBERT
- When you are reviewing the surgical procedures, do not focus on exactly how you do the procedure, focus on the big picture
- If I have a low IM angle, what type of procedure do I do? What about a high IM angel? – Focus on this, not how you hold the saw blade, etc.
Bunion terminology
- Evolution of terminology has progressed in parallel with our changing understanding of the deformity itself
- Multiple terms exist, sometimes with multiple meanings
- Inconsistencies in interpretation can lead to confusion
Bunion (Durlacher 1845)
- Inflammation of the synovial bursa of the great toe, resulting in enlargement of the joint and lateral displacement of the toe
Hallux valgus (Heuter 1877)
- The distal portion of the great toe (hallux) is deviated away from the midline of the body (valgus)
- This descriptor refers to the transverse plane in the foot (historical perspective)
Valgus confusion
- Transverse plane valgus
- Frontal plane valgus
Hallux abducto valgus (1970)
- The great toe (hallux) is deviated away from the midline of the body in the transverse plane (abducto) and rotated away from the midline of the body in the frontal plane (valgus)
- *Tri plane description uses frontal plane definition of Valgus
Metatarsus primus varus (Truslow 1925)
- The distal portion of the first metatarsal (metatarsus primus) is deviated toward the midline of the body (varus)
- This descriptor refers to the transverse plane in the foot
- So “varus” means toward midline, NOT inverted in frontal plane
- ***Name Change to Highlight the True Level of the Deformity
Tri-axial orthogonal coordinate plane
- Justifies the frontal plane definition of Valgus used in the term HAV
- It uses transposition of the three cardinal planes used in the leg to the foot
- There is a change in designations of the three planes due to 90 degree
post embryologic rotation - Using this system Varus and Valgus are more appropriate frontal plane
descriptors than transverse plane descriptors in the foot
Coronal plane
- So, the transverse and sagittal planes are clear, what about the frontal???
- We have not historically talked about any significant research into the frontal plane
- No one has continued to stick with frontal plane research
- It is NOT well understood that there is frontal plane movement, but it has not been incorporated into treatment
Multiplanar 1st metatarsal position
- Range of Motion studies of the first ray create assumptions of position in a bunion
- Hicks
Hick’s orientation
o This creates inversion-dorsiflexion and gives the impression that the metatarsal is in a z-axis varus position in a bunion
o Found this from 5 cadavers and manipulated them – this is what our idea is based on
Tri-Plane Motion of the First Ray – Which way does it rotate?
o Adduction, Dorsiflexion, Inversion
o (Metatarsus Primus Varus(frontal))
Alternate observations to Hicks
o Adduction, Dorsiflexion, Eversion
o Metatarsus Primus Valgus
Dorsiflexion-inversion
WRONG
- Hicks
Dorsiflexion-eversion
All current research
Circumstantial association
- These studies all pursued understanding of the Normal ROM of the first ray
- Normal Range of motion is just that… Normal!
- Normal tells us nothing of what the metatarsal position is in the deformed foot.
- Even it were acceptable to apply normal ROM to deformity position, the lack of consensus in first ray ROM is enough to prevent the practice
Accurate terminology
- Use of the tri-axial orthogonal coordinate plane system to promote clarity in conversation.
- Accurate anatomic description of deformity in multiple planes to keep in the mind of the surgeon the complete nature of the deformity for appropriate planning.
Hallux Abducto Valgus
o Describes great toe segment of deformity
o Uses tri-axial orthogonal coordinate system
o Describes multi-planar position
Metatarsus Primus Adducto Valgus
o Describes metatarsal segment of deformity
o Uses tri-axial orthogonal coordinate system
o Describes multi-planar position
Summary
- There is a diversity of terms used to describe a bunion
- Use of the tri-axial orthogonal coordinate system and associated terms provides clarity in conversation
- Multi-planar position should be described to aid the surgeon in planning correction
- Bunion description: Hallux Abducto Valgus with Metatarsus Primus Adducto Valgus
Axial studies
- Let’s look at the evidence on the frontal plane position of the 1st Met in a bunion….
- Normal feet – Rectus position
- Bunion feet – Valgus position
- This is important because it leads to the surgical approach
Coronal plane observation
- Valgus metatarsal rotation (pronation) has been shown to be consistent in HAV
Literature findings on coronal plane observations
- Scranton. CORR 1980: Feet with Bunions averaged 14.5 degrees of eversion of the first metatarsal, 3.1 normal
- Talbot & Saltzman, FAI 1998: Pronation of metatarsal and subluxation
- Mortier. Orthop Traumatol Surg Res. 2012: Feet with Bunions have everted first metatarsals
- Okuda, JOS 2009, 2013: Supination improved correction of sesamoids
- Dayton, Feilmeier, Kauwe 2013, 2014, 2015: Direct correlation of PASA & TSP to pronation of the first metatarsal in frontal plane
- Kim FAI 2015: WB CT evaluation showing metatarsal pronation in HAV (87.3%) vs. control
Pronation of the first metatarsal is the THIRD plane of the deformity
- Metatarsus Primus Adducto Valgus
- Top: sesamoids are relatively parallel to the WB surface = no bunion
- Middle: sesamoids and met are slightly rotated = bunion present
- Bottom: sesamoids and met are severely rotated = severe bunion
Correlation of bunion severity and frontal plane rotation
- Left: tibial sesamoid position is normal (2-3), complex of metatarsal and sesamoids are parallel to the WB surface, so normal
- Middle: starting to see bunion (4 – midline), slight valgus rotation of met + sesamoid complex
- Left: bunion present, tibial sesamoid is 6, significant rotation of met + sesamoid complex
Sesamoid position
- We see the sesamoids as displaced , however they are in fact aligned and in their grooves on a pronated metatarsal in many cases
- This fact changes the anatomic basis of bunion correction
- If sesamoids are in fact in their grooves, then soft tissue balancing cannot provide alignment
- The real solution requires addressing the rotation
- NOTE: if we are going to be doing surgery on a patient, we should be trying our best to restore the normal anatomy as best as possible – this is the patient expectation
Example of sesamoid position
- You can see the change in sesamoid position real time after frontal plane rotation without opening the MTPJ
- Rotation dramatically changes all components of MTPJ alignment
- This is intraoperative – tibial sesamoid position is initially a 5
- When we rotate the 1st metatarsal in a valgus direction, the
tibial sesamoid position worsens - Then we rotate the 1st metatarsal in a varus direction, the
tibial sesamoid position is improved
Kim Study (2015)
- A new measure of tibial sesamoid position in hallux valgus in relation to the coronal rotation of the first metatarsal in CT scans
- This study did WB CT scans and found that 87% of patients with a bunion had pronation and eversion of the 1st metatarsal and sesamoids
- Some patients did in fact have subluxation of the sesamoids, but this typically happens in a very high IM angle in a long-standing deformity
- SUMMARY: most patients with a bunion are in PRONATION with or without subluxation of the sesamoids