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DELTA PHALANX

Introduction

The delta phalanx, also known as a longitudinal epiphyseal bracket or clinodactyly with delta phalanx, is an uncommon deformity of the proximal phalanges and metacarpals. It is usually diagnosed by ~24 months of age, as restricted growth and angular deformities become evident. The defect is caused by a C-shaped secondary bone growth that extends along one side of the diaphysis, making straight longitudinal growth impossible. Curvature of the diaphysis and metaphysis produces a trapezoidal middle phalanx leading to angulation of the distal phalanx. The defect is also classified as Type III clinodactyly.1,3,5

Pathophysiology

  • Affects fingers more commonly than toes; most common in the proximal phalanx of the thumb and middle phalanx of the little finger
  • Caused by secondary center of ossification in aberrant epiphysis
  • Proximal-to-distal ossification causes unequal longitudinal growth of diaphysis, which is characterized by a triangular- or trapezoidal-shaped bone with a C-shaped epiphyseal plate, as the epiphysis curves from a normal transverse to a longitudinal orientation
  • Delta phalanges usually occur bilaterally. 
  • The mode of inheritance is thought to be autosomal dominant with incomplete penetrance.3

Related Anatomy

  • Proximal, Middle and Distal Phalanges
  • Metacarpals
  • Epiphyseal plate
  • Diaphysis of the middle phalanx

Incidence and Related Conditions

  • Delta phalanx is slightly more common in males than females.3
  • Clinodactyly in North America occurs at a rate of 1in 1000.4
  • Associated with numerous rare syndromes including:
    • Rubinstein-Taybi syndrome
    • Cenani-Lenz syndactyly
    • Isolated oligosyndactyly
    • Nievergelt syndrome syndactyly
  • Symphalangism
  • Triphalangeal thumb
  • Cleft hand
  • Hypoplastic hand
  • Apert's syndrome (index finger)
  • Poland's syndrome
  • Clinodactyly with no delta phalanx
  • Polydactyly

Differential Diagnosis

  • Type I clinodactyly
  • Type II clinodactyly
  • Camptodactyly
  • Kirner's deformity 2
ICD-10 Codes

  • DELTA PHALANX

    Diagnostic Guide Name

    DELTA PHALANX

    ICD 10 Diagnosis, Single Code, Left Code, Right Code and Bilateral Code

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    DELTA PHALANXQ68.1   

    ICD-10 Reference

    Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016 https://apps.who.int/iris/handle/10665/246208

Clinical Presentation Photos and Related Diagrams
Delta Phalanx
  • Delta phalanx left fifth finger in 2 year old infant
    Delta phalanx left fifth finger in 2 year old infant
Symptoms
Awkward angular deformity, usually bilateral, which interferes with the function of the deformed digit and/or the adjacent digit
Typical History

Patients presenting with delta phalanx are often infants or young children between the ages of 1 and 2 years when the parents note an angular deformity of the involved finger or thumb. The thumb and the little fingers are most frequently involved and associated deformities such as brachydactyly can occur. Delta phalanx can occur alone or as part of other congenital syndromes.

Positive Tests, Exams or Signs
Work-up Options
Images (X-Ray, MRI, etc.)
Delta Phalanx Imaging
  • Delta phalanx (arrow) left fifth finger X-ray
    Delta phalanx (arrow) left fifth finger X-ray
Treatment Options
Treatment Goals
  • Counsel the family and advise observation for minor deformities.
  • Rule out associated syndromes or other congenital deformities
  • Surgically correct severe deformities causing functional problems
Conservative

No effective non surgical alternatives to permanently correct the deformity; however, observation is appropriate for mild angulatory deformities with limited functional problems.

Operative
  • Excision
    • Removal of cartilaginous longitudinal epiphyseal bracket may prevent future soft tissue contractures and osseous deformities
    • Transverse resection of abnormal part of epiphyseal plate, with or without fat grafting, is suitable for initial correction in infants. The correction may not last and later osteotomies may be necessary especially in children over three years of age.3,5
  • Opening wedge osteotomy
  •   A wedge of bone is removed on the narrow side of the trapezoidal phalanx with the insertion of iliac crest bone into wedge gives satisfactory correction. But as bone growth continues, further correction may be necessary.
  • Reversed wedge osteotomy 
    • A wedge is removed from the mid-section of the delta phalanx
    • The wedge is reversed and replaced into the opening to straighten the bone and disrupt the longitudinal epiphysis.
  • Dome-shaped osteotomy
  • Resection and fat graft
    • Modified Langenskiöld procedure involves resection of the mid epiphysis and the underlying physis accompanied with a replacement fat graft
      • This technique addresses the pathological tissue and eliminates the need for pin fixation, as no bone is removed, but only useful in young children. Recurrence of deformity is common.
Treatment Photos and Diagrams
Surgical Treatment of Delta Phalanx
  • Surgical exposure of delta phalanx (arrow) left fifth finger
    Surgical exposure of delta phalanx (arrow) left fifth finger
Complications
  • Surgical complications are rare
  • Residual deformity after surgical treatment does occur
  • Recurrent deformity with growth also complicates surgical correction
Outcomes
  • Favorable results have been reported after closing wedge osteotomies.3
Key Educational Points
  • A kissing delta phalanx contains two duplicate longitudinal bracketed epiphyses or two adjacent delta bones with convex surfaces opposing each other.6
  • Radiological identification of the kissing delta phalanx may aid the diagnosis of rare congenital disorders
  • The degree of angulation required for the diagnosis of true clinodactyly is controversial; with criteria ranging from >8 degrees to greater than or equal to 15 degrees.3
References

Cited and New Articles

  1. Johnson J, Higgins T et al. Appearance of the delta phalanx (longitudinally bracketed epiphysis) with MR imaging. Pediatr Radiol 2011;41(3):394-6. PMID: 20972673
  2. Fairbank SM, Rozen WM, Coombs CJ. The pathogenesis of Kirner's deformity: A clinical, radiological and histological study. J Hand Surg Eur 2014 Epub. PMID: 25274771
  3. Ali M, Jackson T, Rayan GM. Closing wedge osteotomy of abnormal middle phalanx for clinodactyly. J Hand Surg 2009; 34A: 914-918.
  4. Dutta P. The inheritance of the radially curved little finger. Acta Genet Stat Med 1965; 15: 70-76.
  5. Vickers D. Clinodactyly of the little finger: a simple operative technique for reversal of the growth abnormality. J Hand Surg Br 1987;12:335–42. PMID: 3437200
  6. Elliot AM, Evans JA, Chudley AE, Reed MH. The duplicated longitudinal epiphysis or "kissing delta phalanx": evolution and variation in different disorders. Skeltdal radiology 2004; 33(6): 345-351.

Reviews

  1. Choo A, Mubarak S. Longitudinal epiphyseal bracket. J Child Orthop 2013;7(6):449-54. PMID: 24432108
  2. Sobel E, Levitz S et al. Longitudinal epiphyseal bracket: associated foot deformities with implications for treatment. J Am Podiatr Med Assoc 1996;86(4):147-55. PMID: 8920618

Classics

  1. Jones G. B. Delta phalanx. J Bone Joint Surg Br 1964;46:226–8. PMID: 14167628
  2. Vickers D. Clinodactyly of the little finger: a simple operative technique for reversal of the growth abnormality. J Hand Surg Br 1987;12:335–42. PMID: 3437200
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