A Strongly Inherited Familial Symphalangism of All the Proximal Interphalangeal Joints

Abstract

Symphalangism is a rare congenital condition resulting in ankylosis of the interphalangeal joints to a varying degree. This can lead to significantly reduced function of the hand. The condition is difficult to assess in infants due to lack of radiographical evidence, and as such thorough history and examination is crucial. Treatment options include conservative and surgical management. It is difficult to achieve full range of movement in more advanced cases, but significant improvements have been noted in less severe cases. Best results are seen when patients are treated before the age of 2 years. This is a case of a inherited symphalangism with a strong family history, and their decision to manage this problem conservatively. In these cases, a strong input from physiotherapy and occupational therapy is the mainstay of management.

Introduction

Symphalangism is a rare congenital abnormality associated with ankylosis of interphalangeal joints of the fingers and/or toes, and can involve either the distal or, more commonly, the proximal joints. This can have obvious implications on function of the hand. It was first described by Harvey Cushing in 1916, ¹ who reported a case of hereditary fusion of the proximal interphalangeal joints (PIPJs), with one family having 84 members with the condition, and it has been described as an autosomal dominant disorder, ² however there are also sporadic cases reported as well. Most cases are associated with mutations of the NOG gene, ³ as well as a further associated mutation of the protein, Growth and Differentiation Factor 5 (GDF 5). ⁴

It is more common in the ulnar digits, and when not the inherited form it may be associated with syndactyly, brachydactyly, hearing loss and other syndromes.

As radiographs may be particularly difficult to interpret in infancy, the mainstay of assessment is patient history and physical exam, assessing for stiff joints and absence of flexion or extension creases overlying the joint.

Metacarpophalangeal joints (MCPJs) are rarely involved ⁵ and it is more often a problem of the distal aspect of the hand.

Flatt and Wood suggested a 3 tier classification system:

True symphalangism—fused digits of normal length

Symbrachydactylism—fused and short digits

Symphalangism with associated anomalies—fused digits + other anomalies such as Apert’s or Poland’s syndrome.

Furthermore, the degree of fusion can also be subcategorised as per Figure 1. These subcategories carry with them decreasing degrees of active and passive mobility, from normal range of movement, to 20°-30° passive movement in grade 1, and no movement in grade 4. Prior to fusion of the epiphyseal plate in grade 3, it may be possible to elicit a small a small degree of passive movement due to flexibility of the cartilage.

Figure 1.

A) Normal joint. B) Grade 1: fibrous symphalangism—mild joint space narrowing in distal interphalangeal joint. C) Grade 2: Cartilaginous symphalangism—only very small joint space. D) Grade 3: Bony symphalangism 5.

It is possible for one grade to progress to another as the child grows and as cartilaginous portions ossify.

There have previously been reports of attempts at mobilization, sadly these have often not yielded successful results. ⁶ Surgical options have also been suggested such as joint arthoplasties, ⁷ unfortunately many these options have not achieved significantly positive results either, and certainly are not appropriate for growing children. However another group has performed joint dorsal capsulotomy and release of dorsal half of both collateral ligaments in cases of Grade 1 or 2, and have shown a significantly improved range of movement, especially when surgery was performed before 2 years of age. ⁶

It would also be possible to perform an osteotomy later in life and fuse the finger in a more functional position, although this is only likely to be of benefit to a very select group.

A 7 week old baby was brought to the pediatric plastic surgery department having been referred for what appeared to be a lack of PIPJs across all fingers. Radiographs showed that a joint space was present, however there was almost no movement across the joint, with no significant skin creases on the volar aspect of the PIPJs. She was born of Caesarean section, is otherwise fit and well, and not on any medications. The neonatal team had no concerns with her in any other regard.

Her father has the same abnormality, as well as at least 2 further previous generations. As a family they have developed coping mechanisms with strong flexion at the distal-interphalangeal joints (DIPJs), and apparently function well day to day.

On examination, this child had no other chest wall or upper limb abnormality, with well developed thumbs and web spaces bilaterally. All other joints in the hands had good range of movement.

In light of the presence of PIP joint spaces, we offered to undertake a manipulation under anesthesia to see if we could initiate a degree of movement, and although has had limited success in the literature it was felt the least invasive option. We believed that as her flexor digitorum profundus muscle appeared particularly strong, that she may be able to maintain a range of movement herself if we could overcome any initially stiffness. However her parents were not keen to pursue this management plan, and were happy to leave her alone to learn to cope, as her previous generations had.

She is still currently under regular review in our clinic.

Discussion

Symphalangism accounts for about 0.03% of all congenital anomalies of the upper extremity, ⁸ and can result in significant disability in terms of hand function. It occurs most commonly in Caucasians, and is usually transmitted in an autosomal dominant manner, resulting in a failure of the differentiation of the interphalangeal joint during embryonic development.

Mild cases may not be severely affected and could be considered for conservative management only, including physical and occupational therapy to improve function. If surgery is to be performed, such as a dorsal capsulotomy and release of the dorsal half of the collateral ligaments, then post operative physiotherapy will be crucial to ensure a positive outcome is achieved.

The age of the child when surgery should be undertaken is crucial, and it is believed that the earlier the better. However, surgery is not without risk, and should not be considered without careful assessment. Hand surgery carries the risk of particularly problematic complications, including joint stiffness and scarring, and therefore should only proceed if the expected benefits outweigh the potential risks. Only grade 1 or 2 symphalangism should be considered, with outcomes worse the more severe the disease. ⁶

As seen in our case, it is possible for affected individuals to learn to adapt and function adequately with their daily activities, and fundamentally the decision to proceed with surgery is ultimately down to the patients themselves. If the decision is made to treat conservatively, then physiotherapy and occupational therapy will play an even more important role in achieving a high level of function.