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A mutation of PMP22 located at chromosome 17p12 most likely leads to an initial presentation highlighted by a:
Weak tibialis posterior
Weak peroneus longus
Strong peroneus brevis
Strong peroneus tertius
Weak tibialis anterior
Select Answer to see Preferred Response
Charcot-Marie-Tooth disease (CMT, also known as hereditary motor and sensory neuropathy/HMSN/or peroneal muscular atrophy) comprises a group of disorders caused by a mutation in the genes that affect the normal function of peripheral nerves. CMT is due to a mutation of PMP22 located at chromosome 17p12 and leads to symmetrical, predominantly distal limb-muscle wasting, weakness, and sensory loss, especially in the lower extremities.
The initial presentation is highlighted by a weakened tibialis anterior and peroneus brevis that is overpowered by a stronger peroneus longus/posterior tibialis, resulting in a plantar flexed first metatarsus and pronated forefoot. Hindfoot varus deformity develops secondarily. As the deformities become more fixed, an equinus contracture will often develop as well.
Illustrations A and B are radiographs demonstrating the significant pes cavus associated with Charcot-Marie-Tooth disease.
Answer 1&2: Peroneus longus and tibialis posterior is relatively stronger in CMT
Answer 3: Peroneus brevis is weakened in CMT
Answer 4: There is no known effect of the peroneus tertius in the pathophysiolgy of CMT
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Average 4.0 of 19 Ratings
A 32 year-old male complains of lateral foot pain and a progressively awkward gait. He has a family history of "foot problems" and reports some minor burning and numbness in both feet. He has no other medical problems, and takes no medications. Physical exam reveals bilateral cavus feet with clawing of the toes and intrinsic muscle wasting of the hands. A clinical photograph is shown in Figure A. Which of the following is responsible for the patients initial symptoms and awkward gait?
Weak gastrocnemius-soleus complex
Peroneus brevis overpowering the posterior tibial tendon
Tibialis anterior overpowering the peroneus longus
Plantar flexion of the first ray
Clawing of the toes
This patient is presenting with the history and clinical findings of Charcot-Marie-Tooth disease. Symptoms can vary, but the development of cavovarus deformity as seen in the clinical radiograph is common. The initial deforming force is the result of a weak anterior tibialis being overpowered by the unaffected peroneus longus, bringing the first ray into a plantarflexed position. This forces the hindfoot into varus position leading to lateral column overload and pain. The weakened tibialis anterior can also lead to a foot-drop deformity, and compound the gait difficulties. The reference by Ward et al listed below shows improved outcomes in treatment of flexible cavovarus foot deformities with soft-tissue and osteotomy procedures compared to triple arthodesis at an average of 26 years post-operatively.
Ward CM, Dolan LA, Bennett DL, Morcuende JA, Cooper RR
J Bone Joint Surg Am. 2008 Dec;90(12):2631-42. PMID: 19047708 (Link to Abstract)
Ward, JBJS 2008
Average 3.0 of 24 Ratings
The PMP22 (peripheral myelin protein 22) is found at the cytogenetic location found in Figure A. What pediatric congenital disorder is associated with a mutation of this gene?
Duchenne's/Becker's muscular dystrophies
Spinal muscular atrophy
Charcot-Marie-Tooth disease is a sensory motor demyelinating neuropathy that is autosomal dominant and is often due to a mutation of PMP22 (peripheral myelin protein 22) located at Chromosome 17p12. Orthopaedic manifestations include progressive distal muscle wasting/weakness (especially peroneal muscles), areflexia, hammertoes, hip dysplasia, and cavovarus foot deformities. Low nerve conduction velocities with prolonged distal latencies are noted in the peroneal, ulnar, and median nerves. Nerve pathology can show simultaneous demyelinization and remyelinization. There are several subtypes of the disease, but diagnosis is made commonly by DNA testing for a duplication of a portion of chromosome 17. Other pediatric congenital disorders and their associated genetic defect include Duchenne's/Becker's muscular dystrophies (dystrophin), Limb-girdle dystrophies (sarcoglycan and dystroglycan complex), myotonic dystrophy (myotonin), and spinal muscular atrophy (Survival motor neuron protein).
Average 2.0 of 30 Ratings
A 22-year-old woman is concerned about frequent ankle sprains and an awkward gait. Lower extremity nerve conduction velocities show prolonged distal latencies in the peroneal nerves. DNA testing shows a duplication on chromosome 17. Which of the following images is most likely the radiograph of this patient?
Charcot-Marie-Tooth disease (CMT), or Hereditary Motor Sensory Neuropathy, is a demyelinating disorder of the peripheral nervous system. Manifestations in the foot include pes cavovarus, claw toes, and frequent ankle sprains. The cause of the foot deformities in CMT is an imbalance of distal musculature, with the peroneus brevis and tibialis anterior being relatively overpowered by the peroneus longus.
The paper by Alexander et al. discussed the difficulties reconstructing cavovaus feet of CMT, with special focus on muscle imbalance causing the deformity.
Paulos et al studied over twenty patients with CMT who underwent plantar tissue releases and tendon transfers. With at least two year follow up, 85% were found to have acceptable results. Other described techniques include osteotomies as well.
Image C shows a high arched foot of a person with CMT.
Image A shows an accessory navicular.
Image B shows a calcaneonavicular coalition.
Image D shows a foot without pathology
Image E shows a ball-and-socket ankle, which can be associated with fibular hemimelia.
While other radiographic choices could represent a patient with frequent ankle spains, none of them except a patient with CMT would have abnormal nerve conduction studies.
Alexander IJ, Johnson KA.
Clin Orthop Relat Res. 1989 Sep;(246):273-81. PMID: 2766615 (Link to Abstract)
Alexander, CORR 1989
Paulos L, Coleman SS, Samuelson KM.
J Bone Joint Surg Am. 1980 Sep;62(6):942-53. PMID: 7430182 (Link to Abstract)
Paulos, JBJS 1980
Average 3.0 of 27 Ratings
A 5-year-old boy has bilateral cavus feet and genetic testing reveals duplication of the PMP (peripheral myelin protein) gene on chromosome 17. What is the most likely diagnosis?
Charcot-Marie-Tooth disease, a group of diseases that affect the peripheral nerve, is moderately common, with an incidence of 1 in 2500 individuals. All forms of the disease manifest as distal weakness primarily in the foot and ankle; somewhat later in life the hand may be affected as well. Most patients usually present toward the end of the first decade with progressive cavovarus deformities of the feet associated with dorsiflexion of the toes during the swing phase of gait and contracture of the plantar fascia. There are 30 genes that now have been described in association with the different forms of HMSN, CMT disease. 70% of patients show a duplication of the peripheral myelin protein (PMP) gene on chromosome 17
Nagai MK, Chan G, Guille JT, Kumar SJ, Scavina M, Mackenzie WG
J Pediatr Orthop. 2006 Jul-Aug;26(4):438-43. PMID: 16791058 (Link to Abstract)
Nagai, JPO 2006
Schwend RM, Drennan JC.
J Am Acad Orthop Surg. 2003 May-Jun;11(3):201-11. PMID: 12828450 (Link to Abstract)
Schwend, JAAOS 2003
Average 3.0 of 12 Ratings
Plantar flexion of the first ray is the initial deformity seen in which condition?
Juvenile hallux valgus
Charcot-Marie-Tooth (CMT) disease is a hereditary motor sensory neuropathy. These patients often develop a pes cavovarus deformity (Illustration A) with the intial stage being plantar flexion of the 1st ray.
A weakened tibialis anterior / peroneus brevis is overpowered by a stronger peroneus longus / posterior tibialis and results in a plantar flexed first metatarsal and pronated forefoot as described in the article by Mosca. Hindfoot varus deformity develops secondarily. As the deformities become more fixed, an equinus deformity can also develop.
Coleman block testing as described in CORR from 1977 can help determine if the hindfoot varus deformity is fixed or flexible. Hindfoot flexibility is noted by placing the lateral foot on a block to remove the plantar flexed first ray from contributing to the deformity and observing the hindfoot moving to a more neutral position.
Coleman SS, Chesnut WJ.
Clin Orthop Relat Res. 1977 Mar-Apr;(123):60-2. PMID: 852192 (Link to Abstract)
Coleman, CORR 1977
J Pediatr Orthop. 2001 Jul-Aug;21(4):423-4. PMID: 11433149 (Link to Abstract)
Mosca, JPO 2001
Average 3.0 of 17 Ratings
A 42-year-old woman with Charcot-Marie-Tooth disease complains of longstanding foot pain. Orthotics, bracing, and NSAIDs no longer provide relief. She has cavovarus hindfoot deformity that does not correct with Coleman block testing. Radiographs are notable for degenerative changes within the talocalcaneal and calcaneocuboid joints. Which of the following is the most appropriate treatment?
Split tibialis posterior transfer
Lateral closing wedge calcaneal osteotomy with peroneus longus to brevis transfer
First metatarsal dorsal closing wedge osteotomy
Achilles tendon lengthening
Charcot-Marie-Tooth disease is also known as hereditary motor sensory neuropathy. Characteristic deformity occurs when the weakened peroneal brevis and anterior tibalis succumb to the stronger posterior tibialis and peroneus longus resulting in a cavovarus foot. Coleman block testing is used to determine whether the deformity is flexible or rigid. An example of a correctable deformity is provided in Illustration A. Once the foot has become rigid and begins developing arthritic changes, triple arthrodesis is indicated. Flexible deformities without arthritic changes may be amenable to tendon transfers and dorsiflexion osteotomy of the first ray. Holmes et al reviews the evaluation, diagnosis, and treatment of the cavovarus foot in Charcot-Marie-Tooth disease.
Holmes JR, Hansen ST Jr.
Foot Ankle. 1993 Oct;14(8):476-86. PMID: 8253442 (Link to Abstract)
Average 3.0 of 16 Ratings
Lateral forefoot and heel posts would be the appropriate orthotic for the foot deformities associated with which of the following conditions?
Stage II posterior tibial tendon insufficiency
Stage III posterior tibial tendon insufficiency
Lateral forefoot and heel posts are most appropriate for cavovarus foot deformities. This deformity is typical of Charcot-Marie-Tooth (CMT) disease. Posting the lateral forefoot allows for flexion of the first metatarsal (correcting the forefoot driven, hindfoot varus deformity commonly seen in CMT), and posting the lateral heel corrects the varus hindfoot.
Cavovarus deformity can also be caused by poliomyelitis and cerebral palsy.
Schwend et al. reviewed cavus foot deformity in children. The goal of surgical management is to obtain a mobile plantigrade foot with correction of the cavus deformity.
The cavus deformity in Charcot-Marie-Tooth disease is caused by what muscular imbalance?
Peroneus brevis overpowering peroneus longus
Tibialis anterior overpowering tibialis posterior
Achilles overpowering tibialis anterior
Extrinsic toe flexors overpowering intrinsics
Peroneus longus overpowering tibialis anterior
The etiology of the abnormal foot posture in Charcot-Marie-Tooth disease usually results from peroneus longus overpowering tibialis anterior. The peroneus longus acts to plantarflex the first metatarsal raising the arch height and tilting the hindfoot into varus. Thus the Coleman block test allows one to check the hindfoot flexibility by eliminating the effect of the plantarflexed 1st ray and observing its effect on the hindfoot.
Additionally, the peroneus brevis is weak, allowing it to be over-powered by the posterior tibialis resulting in adduction of the foot and varus.
Bilateral pes cavovarus is the most common pathologic foot deformity seen with Charcot-Marie-Tooth disease. A passively correctable, and thus flexible, cavovarus foot may be appropriately treated with plantar fascial release, dorsal closing wedge osteotomy of the first metatarsal, and peroneus longus to peroneus brevis tendon transfer. A calcaneal osteotomy may also be indicated.
Holmes and Hansen present a Level 5 review of Charcot-Marie-Tooth disease. They report that the specific components of the disease process includes hindfoot varus, anterior or forefoot cavus, and often clawtoes. The study by Ward looks at long-term follow up of Cavovarus foot correction with (in part) peroneus longus to brevis transfer to eliminate that muscle imbalance.
Average 4.0 of 13 Ratings
A 17-year-old male complains of a foot deformity that has progressed over the past 1 year. He has pain along the lateral border of his foot with walking. His father has had similar problems with both feet throughout his life. A clinical photograph of the foot is provided in Figure A. Proper management of this patient should include evaluation for which of the following findings?
The patients clinical presentation is consistent with Charcot-Marie-Tooth disease (CMT), also known as hereditary motor sensory neuropathy. The cavovarus foot is secondary to peroneus brevis and anterior tibialis weakness. Acetabular dysplasia is known to occur in association with CMT.
Fuller et al review 4 familial cases of CMT. The patients demonstrated cavovarus foot deformities, decreased conduction velocities, acetabular dysplasia, and Trendelenburg gait.
Schwend et al review the evaluation, diagnosis, and treatment of cavus foot deformity in children. Management of the deformity is predicated upon proper diagnosis of the etiology for the cavus foot.
Fuller JE, DeLuca PA.
J Bone Joint Surg Am. 1995 Jul;77(7):1087-91. PMID: 7608233 (Link to Abstract)
Fuller, JBJS 1995
Average 2.0 of 55 Ratings
A 14-year-old male child presents with the increasing foot deformity shown in Figure A. On physical exam, it is noted that he is unable to walk on his heels and has decreased Achilles reflexes bilaterally. Coleman block testing reveals correctable hindfoot deformity. Which procedure is associated with improved clinical outcomes in patients with the above described condition?
Transfer of peroneus brevis to peroneus longus
Split anterior tibial tendon transfer to lateral column
Posterior tibial tendon transfer through the interosseous membrane to dorsum of the foot
Lateral column lengthening calcaneal osteotomy
The physical exam and clinical photo are consistent with a cavovarus foot deformity associated with Charcot-Marie-Tooth (CMT) disease. The Coleman block test reveals a flexible hindfoot deformity, which suggests that soft-tissue transfers and not osteotomies can correct the deformity. The posterior tibial tendon retains its strength in CMT and can aid in decreasing hindfoot varus while providing ankle dorsiflexion when transferred to the dorsum of the foot.
Wetmore and Drennan evaluated long-term outcomes in patient with CMT who had undergone triple arthrodesis. Nearly fifty-percent of patients had poor outcomes with only 24% having good and excellent results. This led to the recommendation that triple arthrodesis be reserved for a salvage procedure only in patients with CMT.
Roper and Tibrewal reviewed long term outcomes in patients with CMT undergoing a variety of soft-tissue procedures. At an average of 14 year follow-up, all 18 feet had avoided the need for triple arthrodesis while continuing to have satisfactory results.
Illustration A shows an example of the Coleman block test. This test is used to evaluate for flexibility of the hindfoot varus deformtiy. The illustration shows a flexible deformity with correction of the hindfoot varus.
Answer 1: Peroneal longus to brevis transfer can be utilized due to the fact that PL is typically preserved while PB is weakened in CMT.
Answer 2: The anterior tibial muscle is weakened and therefore transfer provides no benefit and can actually worsen the deformity.
Answer 3: Wetmore and Drennan revealed that poor outcomes are associated with triple arthrodesis in CMT.
Answer 5: Lateral column lengthening is used in pes planovalgus foot deformities.
Wetmore RS, Drennan JC.
J Bone Joint Surg Am. 1989 Mar;71(3):417-22. PMID: 2925716 (Link to Abstract)
Wetmore, JBJS 1989
Roper BA, Tibrewal SB.
J Bone Joint Surg Br. 1989 Jan;71(1):17-20. PMID: 2914996 (Link to Abstract)
Roper, BJJ 1989
Average 4.0 of 17 Ratings
A 24-year-old male with hereditary motor sensory neuropathy complains of worsening bilateral foot pain with ambulation and limited walking tolerance. Clinical photographs are shown in Figures A and B. The deformity corrects with Coleman block testing. Radiographs of the left foot are provided in Figures C-E. Which of the following is the best initial management for this patient?
Custom orthotics with posting of the lateral forefoot and lateral heel
Custom orthotics with posting of the medial forefoot and medial heel
Custom orthotics with medial heel posting and lateral forefoot recession
Gastrocnemius slide followed by dorsiflexion casting
Dorsal first metatarsal osteotomy with calcaneal slide osteotomy
The clinical presentation and photographs demonstrate a patient with bilateral cavovarus feet. The deformity is flexible as evidenced by correction with Coleman block testing. Illustration A provides an example of Coleman block testing. Radiographs demonstrate a high calcaneal pitch, but no arthritic changes. A flexible cavovarus foot can be passively corrected by posting of the lateral forefoot and lateral heel. Surgical interventions should be reserved for fixed deformities and failure of conservative treatment. Sammarco et al reviewed 21 feet with severe symptomatic cavovarus deformity who underwent lateral slide calcaneal osteotomy and dorsal closing wedge osteotomies of the metatarsal(s). The only complications encountered were delayed union and nonunion of the metatarsal osteotomy. Overall, patients did very well with pain reduction, preservation of motion, and enhanced ambulation.
Sammarco GJ, Taylor R
Foot Ankle Int. 2001 Jan;22(1):19-30. PMID: 11206819 (Link to Abstract)
Sammarco, FAI 2001
Average 4.0 of 18 Ratings