THUMB-IN-PALM DEFORMITY (CLASPED THUMB)

Thumb-in-palm deformity (clasped thumb) is a rare, progressive flexion and adduction deformity. Essentially, the thumb’s extensor tendon mechanism is deficient, or one or more of the extensor tendons is absent. The disorder is usually bilateral and has a familial tendency. The diagnosis is frequently delayed, because the thumb is naturally in the palm from birth to approximately 3 months of age. Once the child begins to use the thumb for grasping, the persistent flexion and adduction becomes obvious. The deformity impairs grasp-release and pinch functions.  The most common cause of thumb-in-palm deformity is cerebral palsy.

Pathophysiology

• About one-third of cases are genetically sporadic.
• There is a high percentage of positive consanguinity and family history.
  • Tsuyuguchi classification:*
    • Type I, flexible: thumb can be passively extended, with no other abnormality
    • Type II, comorbidity: thumb cannot be passively abducted or extended, and there are collateral ligament or thenar muscle abnormalities
    • Type III, joint contractures: features of type II are present along with arthrogryposis

* Several classifications are commonly used. The House classicication defines four types of thumb-in-palm.³

 Related Anatomy

• In thumb-in-palm (TIP) deformity:
  • Flexion adduction muscles of the thumb are the common primary deforming force
  • Extension abduction muscles of the thumb are weak or have poor voluntary control
  • Mobility at the interphalangeal (IP) joint may be unaffected
  • Mobility problems occur in the thumb CMC joint, the metacarpophalangeal (MP) joint and the thumb IP joint.
  • All nine muscles that contribute to normal thumb motor function can be part of motor imblaance that produces a thumb-in-palm deformity.
  • Laxity of the ulnar collateral ligament and the volar plate of the thumb MP joint may also be observed in thumb-in-palm deformity.

Incidence and Related Conditions

• Thumb-in-palm deformiy (TIP) is generally not isolated, but presents with a broad range of other musculoskeletal malformations, such as cerebral palsy, arthrogryposis, digitotalar dysmorphism, and Freeman–Sheldon syndrome.
• A variety of anomalies such as webbing, cleft palate, and ventricular septal defect also may be present.
• Thumb-in-palm deformiy (TIP) is one of several common manifestations of cerebral palsy.

Differential Diagnosis

• Arthrogryposis
• Cerebral palsy
• Digitotalar dysmorphism
• Dundar syndrome
• Freeman–Sheldon syndrome
• MASA syndrome
• Trigger thumb
• Traumatic brain injury
• Cerebral Vascular Accident (CVA)

The patient is usually a child 1–2 years old brought for examination due to flexed and adducted thumbs preventing grasping of objects. There may be a family history of clasped-thumb deformity, or of other anomalies (eg, CP, club feet, windblown deformity of the hands). 

• Muscle imbalance is common after the surgery, particularly in growing children. 
• The deformity can reoccur if surgery is performed between 7–10 years of age. 
• Over- or under-correction can occur if all of the deforming forces across the joint are not addressed. 
• Contractures or adhesions can result from prolonged immobilization. 

• Success of treatment depends on the lesion type.
• Conservative methods achieve good results in Tsuyuguchi type I and type II.
• Splinting and physical therapy: very successful in specific cases
• Tendon transfer: cosmetic and functional result can be excellent, with full mobility and much-improved grasping power
• Joint arthrodesis: stabilization good to excellent  

• Thumb-in-palm deformity (TIP) is the most complex problem of the upper extremity in patients with cerebral palsy.
• Because TIP deformity can manifest in a variety of ways in patients with cerebral palsy, individualized assessment and treatment are necessary.
• Pediatric trigger thumb appears quite similar, but treatment is vastly different; therefore, it is imperative to accurately differentiate the two disorders.
• While pediatric trigger thumb is typically unilateral, TIP tends to be bilateral.
• A trigger-thumb release procedure in a patient with TIP deformity is likely to worsen the flexion and adduction deformity and lead to a boutonnière posture.

New Article

1. Alewijnse JV, Smeulders MJ, Kreulen M. Short-term and long-term clinical results of the surgical correction of thumb-in-palm deformity in patients with cerebral palsy. J Pediatr Orthop 2015;35(8):825-30. PMID: 25575357
2. Van Heest AE. Surgical technique for thumb-in-palm deformity in cerebral palsy. J Hand Surg Am 2011;36:1526–31. PMID: 21816546
3. House JH, Gwathmey FW, Fidler MO. A dynamic approach to the thumb-in-palm deformity in cerebral palsy. J Bone Joint Surg Am 1981; 63A: 216-2225. PMID: 7462278

Reviews

1. Basu AP, Pearse J, Kelly S, et al. Early intervention to improve hand function in hemiplegic cerebral palsy. Front Neurol 2015;5:281 Epub. PMID: 25610423
2. Van Heest AE. Surgical technique for thumb-in-palm deformity in cerebral palsy. J Hand Surg Am 2011;36:1526–31. PMID: 21816546

Classics

1. Manske PR. Redirection of extensor pollicis longus in the treatment of spastic thumb-in-palm deformity. J Hand Surg Am 1985;10(4):553-60. PMID: 4020069
2. Matev I. Surgical treatment of spastic thumb-in-palm deformity. J Bone Joint Surg 1963;45B(4): 703-8. PMID: 14074317