Orthopedic Board Prep: Master Cavus Foot & Coleman Block Test with MCQs
Key Takeaway
The Coleman Block Test assesses the flexibility of hindfoot varus in a cavus foot. By elevating the lateral aspect of the foot (from calcaneus to fifth metatarsal head) with a 1cm block, it differentiates between flexible hindfoot varus secondary to a plantarflexed first ray and rigid deformities. Correction indicates flexibility.
A 14-year-old male presents with bilateral symptomatic cavovarus feet. On physical examination, you note clawing of the lesser toes, a prominent first metatarsal head, and a significant hindfoot varus. The hindfoot varus corrects partially when the foot is placed on a 1cm block elevating the fifth metatarsal (Coleman Block Test). What is the significance of this test, and how does it influence your surgical decision-making?
Candidate: The Coleman Block Test determines the flexibility of the hindfoot varus. If the hindfoot corrects to neutral or valgus, the varus is flexible and secondary to a plantarflexed first ray. This implies that correcting the forefoot deformity—such as a dorsiflexion osteotomy of the first metatarsal—may be sufficient to correct the hindfoot varus without requiring a formal calcaneal osteotomy.
Candidates often fail to describe the pathophysiology. A poor answer stops at "it's a flexible varus," without explaining that the hindfoot varus is a compensatory mechanism for the forefoot equinus. They often forget to mention that if the test remains positive (varus persists), a lateralizing calcaneal osteotomy (Dwyer) is mandatory.
The Coleman Block Test differentiates between flexible compensatory hindfoot varus and fixed hindfoot deformity. 1. Mechanism: By elevating the 5th metatarsal, you allow the 1st metatarsal to dorsiflex, removing the driving force of the forefoot equinus. 2. Interpretation: If the hindfoot corrects, the varus is flexible; the primary driver is the plantarflexed first ray. Surgical strategy: First ray dorsiflexion osteotomy + plantar fascia release. 3. Failure to correct: If the varus persists, the deformity is fixed/rigid within the subtalar joint. Surgical strategy: Must include a Dwyer (lateral closing wedge) calcaneal osteotomy to physically realign the hindfoot.
You have established the hindfoot varus is flexible. You are planning to address the claw toe deformity. Describe your systematic approach to these toes.
Candidate: I would assess if the claw toes are flexible or rigid. For flexible deformities, I would perform a Girdlestone-Taylor flexor-to-extensor tendon transfer. If they are rigid, I would consider an IPJ fusion or arthroplasty of the lesser toes, combined with an MTP joint release.
Ignoring the "big picture." A candidate who focuses only on the toes without mentioning that claw toes in cavus feet are a sign of intrinsic muscle weakness (often due to CMT) will likely lose marks. Failing to address the underlying neurological progression is a major oversight.
Structure the answer by flexibility and etiology: 1. Etiology: Explain that claw toes result from intrinsic muscle weakness (loss of MTP stabilization) and extrinsic overpowering (FDL/FHL). 2. Flexible: Flexor-to-extensor transfer (Girdlestone-Taylor) reroutes the FDL to the dorsal aspect of the proximal phalanx, converting a flexor into an MTP joint stabilizer. 3. Rigid: PIPJ fusion/resection arthroplasty is required to provide length and stability. 4. Caution: Always mention that surgery should only be performed after excluding progressive neurological deterioration, as surgical outcomes in advanced CMT can be complicated by post-operative stiffness and potential recurrence.
