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SYMPHALANGISM

Introduction

Symphalangism was first described by Harvey Cushing in 1916, when he identified a family in which 27% (84/313) of those examined exhibited dominantly inherited ankylosis of the IP joints of the hand. Symphalangism is a rare, congenital, autosomal dominant disorder of the middle phalanx characterized by ankylosis of either the proximal interphalangeal (PIP) or distal interphalangeal (DIP) joints of the finger(s), with PIP involvement being more common. Because many patients are either not severely affected or able to adapt to functioning with symphalangism, ongoing observation and conservative interventions like physical and occupational therapy are most commonly recommended. Surgery may be performed in rare cases when the condition causes extreme functional impairments or for cosmetic purposes; however, surgical outcomes are predominantly poor.1,2,3
 

Pathophysiology

  • Symphalangism is typically transmitted as an autosomal dominant trait by either sex, and it occurs due to failure of differentiation of the interphalangeal (IP) joint during the embryonic stage2
    • The abnormal genes responsible for causing symphalangism are localized on chromosome 17q221
    • Mutations in at least two genes—NOG and GDF5—have been identified as underlying causes of proximal symphalangism4
    • Symphalangism may also occur spontaneously in some cases
    • Infants with symphalangism may present with clinical fusion of the affected joint(s) early in life, but radiographic evidence of ankylosis is not seen until later childhood3

Related Anatomy

  • Symphalangism is typically classified into 3 types:
    • True symphalangism: involved digits are rigid but have normal length
    • Symbrachydactylism: affected digits are short and stiff
    • Symphalangism with associated anomalies (eg, Apert’s syndrome and Poland’s syndrome)5
    • Another classification system groups symphalangism into 3 separate grades based on the level of anatomical involvement:
      • Grade I: fibrous symphalangism
      • Grade II: cartilaginous symphalangism
      • Grade III: bony symphalangism6
      • Fusion between the proximal and middle phalanges at the PIP joint is the most common manifestation of symphalangism, although fusion at the DIP joint is also possible; involvement of the metacarpophalangeal (MP) joint is extremely rare5,6
      • The little finger is the digit most frequently affected by symphalangism, followed by the fourth, long, and index fingers; there have also been some reports of involvement of the thumb and hallux
        • Proximal symphalangism has been observed to always affect the second through fourth digits, while the distal type predominantly affects the fourth and fifth digits3
        • The index finger is generally only affected when other fingers are also involved5

Incidence

  • True symphalangism accounts for 0.03% of all congenital anomalies of the upper extremity7
  • Symphalangism occurs most commonly in Caucasians
  • Many additional skeletal anomalies have been reported in association with symphalangism, but there is great variability in their expression, which is indicative of the genetic heterogeneity of the disease3

Related Conditions

  • Proximal symphalangism is part of a spectrum of disorders that cause joint fusion, with multiple synostoses syndrome being at the most severe end of this spectrum4
  • Brachydactyly, camptodactyly, clinodactyly, syndactyly
  • Syndromes: Apert's, Nievergelt-Pearlman, Poland's, Herrmann, multiple synostoses syndrome
  • Conductive hearing loss
  • Taloscaphoid or radiohumeral fusion
  • Carpal and metacarpal anomalies (particularly carpal synostosis)
  • Pes planus
  • Bilateral hip dislocation
  • Tarsal coalitions (particularly talonavicular synostosis)
  • Congenital fusion of the cervical or thoracic spine

Differential Diagnosis

  • Arthrogryposis
ICD-10 Codes

  • SYMPHALANGISM

    Diagnostic Guide Name

    SYMPHALANGISM

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

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    SYMPHALANGISM Q70.02Q70.01 

    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

Symptoms
Stiff digits with compensatory hyperflexibility of the unaffected joints in the affected phalanx
Disability and functional loss in affected hand with difficulty making a fist, gripping and pinching impairments
Abnormal appearance of the finger(s) and hand with inability to perform activities that require fine manual dexterity
Absence of PIP joint skin creases at the affected joint(s)
Typical History

A 5-year-old girl presents with a little finger on her left (dominant) hand that has had abnormal curvature since birth. Her parents report that the girl’s finger has become stiff, and she has recently developed some difficulty making a complete fist and performing certain activities that require the use of this finger. 1,3,6

Positive Tests, Exams or Signs
Work-up Options
Treatment Options
Conservative
  • Treatment for symphalangism is based primarily on the type and severity of the deformity, as well as patient preference
    • Many patients are not severely affected and capable of still functioning without significant impairment, in which case, no treatment or ongoing observation is sufficient3
    • Physical and occupational therapies with structured exercises may be prescribed to improve hand and finger function
    • If surgery is performed, passive range of motion (ROM) exercises may be recommended after the procedure and continued for approximately 6 months6
Operative
  • Surgery is only recommended if the patient is still experiencing significant functional impairments after conservative treatments have failed to elicit improvements
  • Arthrodesis
    • May be used during adolescence to improve the function and cosmetic appearance of the hand
  • IP joint arthroplasty
    • One of many arthroplasties that may be used to attempt to correct the fusion
  • Angular osteotomy
  • Capsulectomy
  • Dorsal capsulotomy
  • Surgical soft tissue release
Complications
  • Osteoarthritis 
Outcomes
  • Many patients learn to adapt to the lack of IP flexion over time and go on to experience improved functional abilities
  • Most surgical outcomes are unsatisfactory due to the poor cosmetic appearance of a finger fused in flexion or the failure of surgery to significantly increase ROM and joint replacement attempts typically fail.3
    • Difficulty obtaining adequate ROM has even been reported when surgery has been performed before the age of 2 years
  • Dorsal capsulotomy and release of the dorsal half of collateral ligaments of affected joints has been found to make symphalangeal joints into mobile ones in grades I and II symphalangism.  Results in patients with grade I symphalangism were superior to those with grade II6
Key Educational Points
  • Diagnosis of symphalangism begins with a patient history and physical examination
  • Inspection of digits may reveal an absence or faintness of flexion and/or extension creases
  • The affected joint may be stiff, preventing active motion and allowing for only minimal passive motion6
  • Radiographic evidence of symphalangism will not be apparent until later childhood because the bone around the joint will be cartilage3
  • The age of a child when surgery is performed is extremely important, and it is believed that the earlier the operation is performed, the better the results; however, the indication for surgery are very limited6
  • More advanced MRI with higher resolution may be helpful for more accurately diagnosing symphalangism grades in the future6
References

Cited

  1. Durmus O, Cakar E, Ata E, et al. Symphalangism: ankylosis of the interphalangeal joints. Am J Phys Med Rehabil 2014;93(1):90-1. PMID: 22660373
  2. Steinberg AG, Reynolds EL. Further data on symphalangism. J Hered 1948;39(1):23-7. PMID: 18912544
  3. Letts M, Davidson D, Beaulé P. Symphalangism in children. Case report and review of the literature. Clin Orthop Relat Res 1999;(366):178-85. PMID: 10627733
  4. Leonidou A, Irving M, Holden S, et al. Recurrent missense mutation of GDF5 (p.R438L) causes proximal symphalangism in a British family. World J Orthop 2016;7(12):839-42. PMID: 28032038
  5. Pritchett JW. Bilateral symphalangism of the index fingers. J Hand Surg Am 1985;10(5):619-20. PMID: 4045134
  6. Baek GH, Lee HJ. Classification and surgical treatment of symphalangism in interphalangeal joints of the hand. Clin Orthop Surg 2012;4(1):58-65. PMID: 22379556
  7. Flatt AE. The care of congenital hand anomalies. St. Louis, 1977, The CV Mosby Co, 146-70.

New Articles

  1. Durmus O, Cakar E, Ata E, et al. Symphalangism: ankylosis of the interphalangeal joints. Am J Phys Med Rehabil 2014;93(1):90-1. PMID: 22660373
  2. Leonidou A, Irving M, Holden S, et al. Recurrent missense mutation of GDF5 (p.R438L) causes proximal symphalangism in a British family. World J Orthop 2016;7(12):839-42. PMID: 28032038

Review

  1. Letts M, Davidson D, Beaulé P. Symphalangism in children. Case report and review of the literature. Clin Orthop Relat Res 1999;(366):178-85. PMID: 10627733

Classics

  1. Cushing H. Hereditary Anchylosis of the Proximal Phalangeal Joints (Symphalangism). Proc Natl Acad Sci USA 1915;1(12):621-2. PMID: 16576087
  2. Steinberg AG, Reynolds EL. Further data on symphalangism. J Hered 1948;39(1):23-7. PMID: 18912544
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