Clinodactyly: Symptoms, Types, Causes and Treatment

Clinodactyly is a fascinating and sometimes perplexing condition affecting the fingers or toes, where one or more digits curve abnormally to one side. While often mild and painless, clinodactyly can sometimes pose functional and cosmetic concerns, especially when the angulation is more pronounced. Understanding clinodactyly requires exploring its symptoms, unique types, underlying causes, and the array of treatment options available. Let’s delve into each aspect to paint a full picture of this intriguing hand anomaly.

Symptoms of Clinodactyly

Clinodactyly typically presents as a sideways curvature of a finger—most often the little finger (fifth digit)—that is apparent from birth or becomes noticeable in early childhood. The degree of angulation can vary, and while some people experience no problems, others may notice functional or cosmetic concerns as the finger grows.

Symptom	Description	Frequency/Severity	Source(s)
Curved Digit	Lateral deviation, usually of the little finger	Common, variable	5 7 8
Angulation	Degree ranges from mild (20°) to severe (>40°)	Varies by case	5 8
Short Phalanx	Shortening of affected bones	Occasional	1 3
Functional Impact	Difficulty grasping, cosmetic concern	In severe cases	7 8

Table 1: Key Symptoms

The Appearance of Clinodactyly

Visually, clinodactyly is most noticeable as a sideways bend of the finger, typically at the middle phalanx. The angle of deviation can be subtle in some, while in others, it may be more pronounced and easily seen by the naked eye. The curvature most often affects the little finger, angling toward the ring finger, but other digits can be involved depending on the underlying anomaly 5 7 8.

Degrees of Angulation

The severity of clinodactyly is often described by the angle of deviation:

• Mild: 10–20 degrees
• Moderate: 20–40 degrees
• Severe: Greater than 40 degrees

Children may not experience any discomfort or limitations with mild forms, while those with more significant curvature might face challenges with grasping or fine motor tasks 5 8.

Associated Features

In some cases, the affected finger may also appear shorter than normal (brachydactyly), especially when underlying bone anomalies like a short or misshapen phalanx are present 1 3. While pain is rare, cosmetic concerns or embarrassment may prompt families to seek consultation.

Functional Limitations

Most people with clinodactyly experience no pain or loss of function. However, severe cases can result in:

• Difficulty making a fist or grasping objects
• Overlapping of the affected finger onto neighboring digits
• Reduced range of motion in the affected joint(s) 7 8

Types of Clinodactyly

Clinodactyly is not a one-size-fits-all condition. There are several subtypes, each distinguished by their anatomical cause, appearance, and sometimes genetic background.

Type	Description	Typical Digit(s)	Source(s)
Delta Phalanx	Abnormal, wedge-shaped (trapezoidal/triangular) phalanx	Little finger or thumb	2 5 6 7 8
Brachymesophalangism	Shortened middle phalanx	Usually fifth finger	1 3 7
Triphalangeal Thumb	Thumb with three phalanges, may curve	Thumb	2 7
Syndromic	Associated with genetic syndromes	Multiple digits	3 4

Table 2: Types of Clinodactyly

Delta Phalanx

A delta phalanx refers to an abnormally shaped bone—often wedge-like or trapezoidal—within the finger. This bone abnormality leads to uneven growth and results in lateral deviation. The delta phalanx is the most common structural cause of clinodactyly 2 5 6 7 8.

• Most often affects the middle phalanx of the little finger
• Can also be seen in the thumb (triphalangeal thumb)
• The abnormal bone has a longitudinal physis (growth plate) on one side, causing asymmetric growth

Brachymesophalangism

This subtype is characterized by an unusually short middle phalanx (brachydactyly). The fifth finger is usually affected, giving it both a shortened and curved appearance. This type can occur alone or as part of genetic syndromes 1 3 7.

Triphalangeal Thumb

A rarer form, the triphalangeal thumb, features an extra (third) phalanx in the thumb, sometimes leading to a curved, clinodactylous appearance. This is often due to a delta phalanx in the thumb and may require specific surgical intervention 2 7.

Syndromic Clinodactyly

Clinodactyly can be part of broader genetic syndromes, such as those involving HOXD13 or CDK13 gene mutations. In these cases, multiple digits may be affected, sometimes with additional features like hearing loss, cardiac anomalies, or intellectual disability 3 4.

Causes of Clinodactyly

The root causes of clinodactyly range from isolated, sporadic developmental anomalies to well-characterized genetic mutations. Understanding these origins is crucial for prognosis and family counseling.

Cause	Mechanism/Genetics	Clinical Context	Source(s)
Bone Abnormality	Delta phalanx (trapezoidal/triangular)	Most common, sporadic	2 5 6 7 8
Genetic Mutation	HOXD13, CDK13 mutations	Familial/syndromic cases	1 3 4
Syndromic	Part of broader genetic disorder	Multiple anomalies	3 4
Idiopathic	Unknown, no apparent cause	Sporadic cases	7

Table 3: Causes of Clinodactyly

Delta Phalanx and Abnormal Bone Growth

The most frequent anatomical cause is a delta phalanx, a wedge- or trapezoid-shaped bone with an abnormal longitudinal growth plate. This configuration causes uneven growth and results in the characteristic finger deviation 2 5 6 7 8.

Genetic Factors

Several genes have been implicated in familial and syndromic clinodactyly:

• HOXD13 mutations: These can lead to a spectrum of hand and foot deformities, including clinodactyly, brachydactyly (short digits), and synpolydactyly (fusion and duplication of digits). HOXD13 mutations may result in frameshift changes causing premature stop codons and altered protein function. Phenotypes can include classical clinodactyly, especially of the fifth finger 1 3.
• CDK13 mutations: Rare and associated with complex syndromes, including clinodactyly, intellectual disability, heart defects, and more. Both autosomal dominant and recessive patterns have been described 4.

Syndromic Associations

Clinodactyly is sometimes a feature of broader genetic disorders, such as:

• Wolfram-like syndrome
• Other congenital heart and developmental syndromes 4

Features may include:

• Hearing loss
• Cardiac malformations
• Intellectual disability
• Gastrointestinal tract abnormalities

Idiopathic Cases

In many instances, clinodactyly arises without a clear genetic or structural cause. These sporadic cases are typically mild and nonprogressive 7.

Treatment of Clinodactyly

Treatment for clinodactyly ranges from simple observation to surgical intervention, depending on the severity, symptoms, and impact on daily life. Many cases require no treatment at all, but for those with significant functional or cosmetic issues, several effective procedures are available.

Treatment	Indication	Key Outcome	Source(s)
Observation	Mild, asymptomatic cases	No intervention needed	5 7 8
Physiolysis	Growing children, delta phalanx, <6 years	Improved correction, growth	5 6
Osteotomy	Moderate-severe angulation (>15–30°), older children/adults	Correction of deformity	2 7 8
Wedge Resection	Delta phalanx of thumb/middle phalanx	Restored alignment	2 7
Joint Reconstruction	Triphalangeal thumb	Restored function	2 7

Table 4: Treatment Options

Observation

For most people with mild clinodactyly (deviation less than 15–20 degrees), especially if asymptomatic, simple observation is recommended. No treatment is necessary unless the curvature progresses or interferes with hand function 5 7 8.

Physiolysis

A minimally invasive surgical technique called physiolysis is particularly effective for young children with a delta phalanx. The procedure involves:

• Removing the abnormal longitudinal physis and replacing it with a fat graft
• Allowing for continued finger growth and gradual correction of the deformity

Studies show that physiolysis is most successful in children under six years of age and in those with a trapezoidal-shaped phalanx. The procedure is simple, with minimal complications, and often avoids the need for more invasive surgery later 5 6.

Osteotomy

Osteotomy is the surgical realignment of the bone and is indicated for moderate to severe angulation (usually greater than 15–30 degrees), especially in older children or adults:

• Closing wedge osteotomy involves removing a wedge-shaped piece of bone and fixing the finger in a straighter position
• Often combined with K-wire fixation for stability

Osteotomy provides excellent correction of the curvature and improves both function and appearance, with high satisfaction rates among patients and families 2 7 8.

Wedge Resection & Joint Reconstruction

For more complex cases, such as triphalangeal thumb or severe delta phalanx, additional procedures may be needed:

• Wedge resection of the abnormal bone
• Joint reconstruction to restore normal alignment and function 2 7

Timing and Outcomes

• Early intervention (before age 6) tends to yield the best results, particularly for physiolysis
• Severe cases benefit from surgical correction to prevent functional impairment and improve hand aesthetics
• Repeat procedures are generally avoided unless absolutely necessary, as multiple surgeries can lead to complications like premature growth plate fusion 5 6

Conclusion

Clinodactyly is a diverse and multifaceted condition, ranging from mild, asymptomatic curvature to more significant deformities that can impact hand function and appearance. Key takeaways from this comprehensive review include:

• Symptoms: Most commonly presents as a sideways curvature of the finger, typically the little finger, with variable severity and functional impact 5 7 8.
• Types: Includes delta phalanx, brachymesophalangism, triphalangeal thumb, and syndromic variants, each with distinctive features 1 2 3 4 5 6 7 8.
• Causes: Most often due to abnormal bone development, but can also result from genetic mutations or be part of broader syndromes 1 2 3 4 5 6 7 8.
• Treatment: Observation is sufficient for mild cases; surgical options like physiolysis and osteotomy are effective for more severe deformity, especially when timed appropriately 2 5 6 7 8.

In summary:

• Clinodactyly is usually harmless but can be functionally and cosmetically significant in some cases.
• Early identification and individualized treatment planning are crucial for the best outcomes.
• Advances in genetics and surgical techniques continue to improve understanding and management of this intriguing hand anomaly.

If you or a loved one is affected by clinodactyly, consult with a pediatric orthopedic or hand specialist to explore the most suitable approach tailored to your specific needs.