Muller-Weiss Syndrome
Summary
Muller-Weiss Syndrome is a rare, spontaneous, debilitating Avascular Necrosis (AVN) of the tarsal navicular in adults. Unlike pediatric Kohler's disease (which resolves), Muller-Weiss causes progressive fragmentation and collapse of the lateral aspect of the navicular. This leads to a characteristic "Comma-Shaped" deformity and severe midfoot arthritis. Paradoxically, the foot collapses into Varus (high arch appearance), distinguishing it from the common flatfoot (PTTD). Management is challenging, often requiring complex fusion surgery. [1,2,3]
Key Facts
- The Demographic: Typically affects Middle-aged Women (40-60 years).
- The Shape: The lateral part of the navicular is compressed, while the medial part fragments or extrudes dorsally. On lateral X-ray, it looks like a "Comma".
- The Deformity: As the lateral navicular collapses, the forefoot adducts and the midfoot goes into Varus (Pes Cavovarus). This is the opposite of a flatfoot.
Clinical Pearls
"The Painful High Arch": If a middle-aged woman presents with a specific pain on the top of her arch and a foot that looks slightly "turned in" (Varus), think Muller-Weiss.
"It's not Kohler's": Kohler disease is a self-limiting AVN in children (boys) that heals perfectly. Muller-Weiss is a progressive destruction in adults that never heals.
"The Double Fusion": Simply fusing the Talonavicular joint is hard because the bone is dead. Often we must fuse the Naviculo-Cuneiform joints too (Double Arthrodesis) to bridge the gap.
Demographics
- Age: 40-60 years.
- Gender: Female > Male.
- Etiology: Idiopathic. Often associated with delayed ossification of the navicular in childhood?
- Bilateral: In 50% of cases.
Mechanism
- Lateral Compression: The force of the Talus head drives into the lateral aspect of the Navicular (Cuneiforms act as anvil).
- Ischemia: The vascular supply (watershed) is compromised.
- Fragmentation: The bone breaks into a dorsal-medial fragment and a plantar-lateral fragment.
- Varus Drift: The Talus head subluxes laterally, leading to hindfoot varus.
Classification (Maceira)
Based on Lateral X-ray:
- Stage 1: Normal X-ray. Bone edema on MRI.
- Stage 2: Dorsal angulation of the navicular (Comma shape begins).
- Stage 3: Navicular splits into two pieces. Hindfoot Varus begins.
- Stage 4: The two fragments separate. Talus head wedges between them.
- Stage 5: Total extrusion of the navicular. Talus articulates with Cuneiforms.
Symptoms
Signs
Imaging
- X-Ray:
- AP: Adduction of forefoot.
- Lateral: Comma-shaped navicular (dense, flattened). Talus head overriding.
- CT Scan:
- Essential for surgical planning. Shows the quality of the remaining bone stock.
- MRI:
- Shows early marrow edema (Stage 1).
CHRONIC MIDFOOT PAIN
↓
X-RAY: COMMA SHAPED NAVICULAR
↓
MULLER-WEISS CONFIRMED
↓
SYMPTOMATIC?
┌───────────┴───────────┐
MILD SEVERE
↓ ↓
CONSERVATIVE SURGICAL
(Stiff Shoe) (Arthrodesis)
↓
SINGLE OR TRIPLE?
(Depending on varus)
Indications
- Early stages (1-2).
- Low demand patients.
Protocol
- Stiff Soled Shoe: Rocker bottom sole (limit midfoot motion).
- Orthotics: Custom molded leather gauntlet (AFO) to lock the hindfoot.
- Injections: Steroid injections provide temporary relief but may accelerate bone necrosis.
Indications
- Intractable pain failing conservative care.
- Severe deformity preventing shoe wear.
Techniques
- Talonavicular-Cuneiform Fusion (TNC):
- The Gold Standard.
- Fuses the Talus to the Cuneiforms, bridging the dead Navicular.
- Requires substantial Bone Graft (Iliac Crest) to fill the defect.
- Triple Arthrodesis:
- If the Subtalar joint is also arthritic or the Varus is fixed.
- Fuses Talonavicular, Subtalar, and Calcaneocuboid joints.
- Talonavicular Fusion:
- Often fails because the navicular bone stock is too poor to hold screws.
Non-Union
- The primary risk. Trying to fuse dead bone is difficult.
- Rate: 10-20%.
Malunion
- Fusing the foot in Varus causes lateral ankle pain and instability.
Adjacent Joint Disease
- Ankle arthritis often develops years after midfoot fusion.
The "Anvil" Theory
- Maceira (2004): Described the biomechanics of the Cuneiforms acting as an anvil against which the talus crushes the navicular. This led to the understanding that simply removing the navicular doesn't work; the column must be stabilized.
The Condition
A bone in the middle of your foot (the Navicular) has died and collapsed. It's like a brick crumbling in an archway.
Why?
We don't know exactly why. It happens mostly in women. It is not an infection or cancer.
The Surgery
The crumbled bone cannot be fixed. We have to bypass it. We will fuse (glue) the ankle bone (Talus) directly to the forefoot bones (Cuneiforms), using a piece of bone from your hip to fill the gap. This will make your foot very stiff, but the pain will go away.
- Maceira E, Rochera R. Muller-Weiss disease: clinical and biomechanical features. Foot Ankle Clin. 2004.
- Fernandez-de-Retana P, et al. Muller-Weiss disease. Foot Ankle Clin. 2014.
- Doyle T, et al. Mueller-Weiss syndrome: imaging features. AJR. 2004.
Q1: What is the classic X-ray finding in Muller-Weiss? A: A "Comma-Shaped" deformity of the Tarsal Navicular on the lateral view, due to dorsal extrusion of the fragmented bone and compression of the lateral aspect.
Q2: How does the foot deformity differ from PTTD (Adult Acquired Flatfoot)? A: PTTD causes a Planovalgus (Flat + Valgus) deformity. Muller-Weiss causes a Pes Cavovarus (High Arch + Varus) deformity due to lateral column sparing and medial column collapse.
Q3: What is the Maceira Classification Stage 4? A: Separation of the two navicular fragments with the head of the talus protruding between them (creating a paradoxical articulation with the cuneiforms).
Q4: Why is isolated Talonavicular fusion discouraged? A: Because the navicular body is necrotic (dead bone). Screws usually pull out, and fusion fails. Bridging the fusion to the cuneiforms (TNC fusion) with bone graft improves stability.
(End of Topic)