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Delta Phalanx - observation

Exams and Signs

Description

  • Delta phalanx, or Type III clinodactyly, can be diagnosed by observing a patient with a triangular or trapezoidal shaped bone, usually in the thumb or middle finger, accompanied by a C-shaped epiphyseal plate.
  • Delta phalanx is also referred to as longitudinal epiphyseal bracket.1

Pathophysiology

  • Delta phalanx arises from the secondary center of ossification in a divergent epiphysis; the ossification center extends longitudinally along the diaphysis.1

Instructions

  1. Take a complete patient history. Typical history may include brachydactyly.
  2. Ask the parent or guardian if the patient has any difficulties with hand function in daily activities.
  3. Observe the proximal phalanx of the thumb and the middle phalanx of the little finger.
  4. Check for a triangular or trapezoidal shaped digit, with a C-shaped epiphyseal plate.
  5. Examine the contralateral hand.

Variations

  • When two adjacent delta bones have their convex parts facing each other, this is referred to as kissing delta phalanx.

Related Signs and Tests

  • Extensor tendon exam
  • Flexor tendon exam
  • Range of motion (ROM)
  • Sensory exam by root
  • Magnetic resonance imaging (MRI), without contrast, before 2 years of age
  • Radiographs after 2 years of age2

Diagnostic Performance Characteristics

  • Before the patient is 2 years old, use MRI without contrast to improve the reliability of the diagnosis. From 24-30 months, use radiographic evaluation to confirm the diagnosis.2
Definition of Positive Result
  • A positive result occurs when the patient presents with a triangular or trapezoidal shaped phalanx with a C-shaped epiphyseal plate.
Definition of Negative Result
  • A negative result occurs when the patient does not present with a triangular or trapezoidal shaped phalanx with a C-shaped epiphyseal plate.
Comments and Pearls
  • With clinodactyly secondary to a delta phalanx, early physiolysis can be a beneficial treatment. Because this treatment tends to show only gradual improvement, careful follow-up is required.3,4
Diagnoses Associated with Exams and Signs
References
  1. Choo AD, Mubarak SJ. Longitudinal epiphyseal bracket. J Child Orthop 2013;7(6):449-54. PMID: 24432108
  2. Johnson JM, Higgins TJ, Lemos D. Appearance of the delta phalanx (longitudinally bracketed epiphysis) with MR imaging. Pediatr Radiol 2011;41(3):394-6. PMID: 20972673
  3. Caouette-Laberge L, Laberge C, Egerszegi EP, et al. Physiolysis for correction of clinodactyly in children. J Hand Surg Am 2002;27(4):659-65. PMID: 12132092
  4. Medina JA, Lorea P, Elliot D, et al. Correction of clinodactyly by early physiolysis: 6-year results. J Hand Surg Am 2016;41(6):e123-7. PMID: 26972556
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