CLINODACTYLY

Clinodactyly is a congenital angular deformity of the middle phalanx in the radioulnar plane that is usually bilateral and involves the small finger, although other digits also can be affected.¹ Clinodactyly is an autosomal dominant condition, and it occurs either in isolation or in association with other syndromes.² Unless clinodactyly is severe, it typically causes little-to-no functional impairment, especially if the little finger is involved. For this reason, observation alone is usually sufficient, and surgical intervention is reserved only for cases in which the deformity interferes with function or for cosmetic purposes. Surgical options for clinodactyly include closing, opening and reverse wedge osteotomies and physiolysis; treatment decisions should be based on the underlying pathology, age of the patient, as well as other factors. ^1,3

Pathophysiology

• Clinodactyly can be either congenital or acquired 
  • Congenital clinodactyly is commonly bilateral and occurs sporadically as an autosomal dominant trait, with variable expressivity and incomplete penetrance⁴ 
  • Acquired clinodactyly typically occurs secondary to physical or thermal trauma to the physis or phalanx, or due to abnormal scarring^3,5 
  • Clinodactyly is usually an isolated anomaly, although it may be part of a syndrome or chromosomal abnormality 
    • More than 60 syndromes are associated with clinodactyly, the most common of which is Down’s syndrome⁶ 
    • Other associated syndromes include Rubinstein-Taybi syndrome, Apert’s syndrome, and oculodentodigital dysplasia⁴ 

Related Anatomy

• The middle phalanx of the little finger is most commonly affected in clinodactyly, with deviation toward the fourth finger: instead of the typical rectangular phalangeal shape, the phalanx is trapezoidal or delta-shaped, which is usually due to a longitudinal epiphyseal bracket or C-shaped physeal plate.¹
• The degree of angulation constituting clinodactyly varies among different reports 
  • The condition has been defined by some as angulation of >8° in the finger long axis between the proximal and middle phalanges 
  • Others consider an angulation of >10° or ≥15° to be abnormal¹ 
  • One of the several classification systems used for clinodactyly groups it into four types:
    • 1) Simple: deformity of the middle phalanx with 15-45° angulation
    • 2) Simple complicated: deformity of the middle phalanx with 45-60° angulation
    • 3) Complex: deformities of the bone and soft tissue, with 15-45°angulation
    • 4) Complex complicated: deformities of bone and soft tissue, with 45-60° angulation and associated macrodactyly or polydactyly⁷

Exam Findings, Signs and Positive Tests

• Physical examination of the affected digit
• The physician should ask about activities of daily living and perform a range-of-motion test to determine if the condition is affecting the patient’s mobility and/or dexterity
• Clinodactyly may also be identified incidentally during presentation of an unrelated issue¹²

Work-Up Options

• X-rays are often needed to confirm the diagnosis
  • A C-shaped physis or longitudinally bracketed diaphysis is indicative of clinodactyly
  • The specific bony anomaly of the middle phalanx may be difficult to discern on plain radiographs⁴
  • Clinical deformity may be noted at a young age, but a radiographic diagnosis of clinodactyly cannot be made until the patient is skeletally mature and sufficient ossification of the epiphysis has occurred^4,12

Incidence and Related Conditions

• Clinodactyly has a reported incidence that ranges from 1-20% of the general population^8,9
• Incidence rates are significantly higher in individuals with Down’s syndrome (35-79%)¹⁰
• The gender distribution for clinodactyly of the little finger is ~15% for boys and ~8% for girls¹
• Brachydactyly, camptodactyly, polydactyly, syndactyly
• Apert’s syndrome, Down’s syndrome, Rubinstein-Taybi syndrome
• Kirner’s deformity
• Triphalangeal thumb
• Keratosis palmaris et plantaris
• Oculodentodigital dysplasia

Differential Diagnosis

• Brachydactyly
• Kirner deformity
• Camptodactyly
• Delta phalanx

The typical patient is a 9-year-old, right-or left-handed boy with Down’s syndrome. His parents noticed a minor deformity of his left little finger years earlier, as the digit was abnormally bent and deviated slightly towards the fourth finger. As the boy grew, the angulation of the deformity became larger and more noticeable.  Consequently, his parents took him to a physician for a clinical evaluation. The physician diagnosed the boy with clinodactyly based on his physical examination and patient history. Noting that the condition did not significantly impair his hand function, the physician recommended ongoing observation of the finger until or unless the boy developed severe functional limitations. ^1-4

Surgical Complications:

• Infection
• Nerve, artery, or extensor mechanism injury
• Incomplete correction of the deformity
• Loss of initial correction
• DIP joint stiffness
• Epiphyseal closure
• Nonunion

• Closing wedge osteotomy: corrects angular deformity, maintains motion of the PIP joint, and results in satisfactory appearance and functional outcomes¹
• Opening wedge osteotomy: increases phalangeal length, but is limited by the tightness of the soft tissues on the contracted side; they also carry a risk of stiffening the finger¹¹
• Reverse wedge osteotomy: maintains phalangeal length, but is also limited by the of the soft tissue tightness and a risk of finger stiffening¹¹
• The rate of correction after epiphyseal bar resection depends on the growth rate of the child; correction occurs slowly over a period of years and is usually seen clearly one year after surgery and can be observed on X-ray images¹¹
• Patient age at surgery is an important factor affecting the degree of correction: children who have surgery before age 6 show better outcomes²

• If the angular deformity of the digit continues to advance, it can interfere with normal hand function, in particular, scissoring may develop with growth, which can impair grip and complicate activities that require a high level of dexterity⁶
• The treatment most commonly used for clinodactyly is osteotomy of the middle phalanx to realign the digit, but controversy remains regarding the most appropriate type of osteotomy^1,6
• The most technically challenging portion of opening wedge osteotomy surgery is the correct placement of the longitudinal Kirschner wires⁴

Cited

1. Ali M, Jackson T, Rayan GM. Closing wedge osteotomy of abnormal middle phalanx for clinodactyly. J Hand Surg Am 2009;34(5):914-8. PMID: 19362790
2. Caouette-Laberge L, Laberge C, Egerszegi EP, Stanciu C. Physiolysis for correction of clinodactyly in children. J Hand Surg Am 2002;27(4):659-65. PMID: 12132092
3. Leung AK, Kao CP. Familial clinodactyly of the fifth finger. J Natl Med Assoc 2003;95(12):1198-200. PMID: 14717476
4. Goldfarb CA, Wall LB. Osteotomy for clinodactyly. J Hand Surg Am 2015;40(6):1220-4. PMID: 25892713
5. Horta R, Nascimento R, Monteiro D, et al. The Reverse Homodigital Flap Based on the Dorsal Branch of the Digital Artery for Reconstruction of Acquired Clinodactyly. J Hand Microsurg 2016;8(1):57-8. PMID: 27616830
6. Piper SL, Goldfarb CA, Wall LB. Outcomes of opening wedge osteotomy to correct angular deformity in little finger clinodactyly. J Hand Surg Am 2015;40(5):908-13. PMID: 25754787
7. Cooney WP. Camptodactyly and clinodactyly. In: Carter P, ed. Reconstruction of the child hand. Philadelphia: Lea & Febiger, 1991.
8. Dutta P. The inheritance of the radially curved little finger. Acta Genet Stat Med 1965;15:70–76. PMID: 14277138
9. Roche AF. Clinodactyly and brachymesophalangia of the fifth finger. Acta Paediatr 1961;50:387–391. PMID: 13742439
10. Flatt AE. The troubles with pinkies. Proc (Bayl Univ Med Cent) 2005;18(4):341-4. PMID: 16252026
11. Medina JA, Lorea P, Elliot D, Foucher G. Correction of Clinodactyly by Early Physiolysis: 6-Year Results. J Hand Surg Am 2016;41(6):e123-7. PMID: 26972556
12. Strauss NL, Goldfarb CA. Surgical correction of clinodactyly: two straightforward techniques. Tech Hand Up Extrem Surg 2010;14(1):54-7. PMID: 20216055

New Articles

1. Horta R, Nascimento R, Monteiro D, et al. The Reverse Homodigital Flap Based on the Dorsal Branch of the Digital Artery for Reconstruction of Acquired Clinodactyly. J Hand Microsurg 2016;8(1):57-8. PMID: 27616830
2. Medina JA, Lorea P, Elliot D, Foucher G. Correction of Clinodactyly by Early Physiolysis: 6-Year Results. J Hand Surg Am 2016;41(6):e123-7. PMID: 26972556
3. Piper SL, Goldfarb CA, Wall LB. Outcomes of opening wedge osteotomy to correct angular deformity in little finger clinodactyly. J Hand Surg Am 2015;40(5):908-13. PMID: 25754787

Review

1. Goldfarb CA, Wall LB. Osteotomy for clinodactyly. J Hand Surg Am 2015;40(6):1220-4. PMID: 25892713

Classics

1. Dutta P. The inheritance of the radially curved little finger. Acta Genet Stat Med 1965;15:70–76. PMID: 14277138
2. Hersh AH, Demarinis F, Stecher RM. On the inheritance and development of clinodactyly. Am J Hum Genet 1953;5(3):257-68. PMID: 13080251