A 2-year-old otherwise healthy girl presented with fixed ulnar deviation of the interphalangeal joint of the left thumb. She was born to non-consanguineous parents, after an uneventful pregnancy, with no exposure to teratogenic agents or maternal history of any illness. There was no family history of limb malformations.
Radiograph of the left thumb disclosed a triangular proximal phalanx with a longitudinal cleft and an additional separate distal ossicle (supernumerary middle phalanx) (Fig. 1). There was ulnar angulatory deformity of the digit distal to the morphologically abnormal proximal phalanx. The distal phalanx was unremarkable.
The delta phalanx (or longitudinally bracketed epiphysis), first described in 1964 by Blundell Jones, is a rare congenital abnormality that consists of a triangular/trapezoidal bone with a C-shaped epiphysis extending from its normal transverse position along the shorter side of the phalanx in a proximal to distal direction [1-5]. This abnormal configuration of the physeal plate may prevent the normal longitudinal growth of the digit, leading to progressive angulation and shortening of the affected finger, particularly if the bracket is complete [1-5].
This condition is thought to result from defective development of the primary ossification centre during the embryonic or early fetal period [3, 5, 6]. It most commonly involves the tubular bones with a proximal epiphyseal ossification centre, such as the phalanges, and also the first metacarpal and first metatarsal bones; therefore, the designation “delta phalanx” is considered a misnomer [2, 3, 5, 7-9].
Clinically, the abnormality most commonly manifests as clinodactyly (curvature of the digit more than 10 degrees off the longitudinal axis). It usually appears as an isolated finding, but can also occur as part of a wide variety of congenital malformation syndromes and dysplasias [2-9].
The most common example of a delta phalanx is found in the middle phalanx of both little fingers, producing clinodactyly toward the ring finger. A triphalangeal thumb that has a delta mid-phalanx and produces clinodactyly toward the index finger is uncommon [8]. The appearance in this case is that of a proximal delta phalanx with a supranumerary middle rudimentary phalanx, which, to our knowledge, has not previously been described in literature.
Radiographic appearances of the longitudinally bracketed epiphysis vary, depending on the degree of secondary ossification of the epiphysis [3, 5]. Although a cartilaginous bracket is present at birth; the involved bone is not ossified enough to demonstrate the bracket. Therefore, this abnormality is not seen on plain films until approximately 2 years of age [5-7].
An appropriate and prompt diagnosis allows early surgical intervention to reduce the deformity, improving the chance of adequate remodelling. Some authors have suggested MR imaging in early childhood deformities, in order to confirm the presence of an epiphyseal bracket before the ossification occurs. MRI can also provide a better assessment of the defect, degree and location of the bracket [6, 7].
When the deformity is minor, surgery or any other treatment may not be necessary. Reconstructive procedures for abnormalities with significant deforming potential include physiolysis, osteotomy, or both [2, 8].
Proximal delta phalanx in a triphalangeal left thumb
Based on the provided X-ray images, there is a noticeable abnormal bony structural change in the proximal and middle phalanges of the left thumb:
Taking into account the clinical history (2-year-old child, fixed ulnar deviation of the thumb, and no apparent family history) and radiological findings, the following possibilities should be considered:
These differentials are based on congenital digital developmental anomalies, yet the “C”-shaped epiphyseal extension and triangular/trapezoidal phalanx structure are highly indicative of a delta phalanx (longitudinal bracket epiphysis).
Considering the patient’s age, the nature of the thumb deformity, radiological findings, and the typical longitudinal bracket epiphysis (delta phalanx), the most likely diagnosis is:
Left thumb longitudinal bracket epiphysis (Delta phalanx) with an additional middle phalanx (supernumerary phalanx).
If further clarification of the cartilage and epiphyseal status is required, an MRI would help evaluate epiphyseal defects and the extent of the growth plate.
Whether surgery is performed depends on the severity of functional impairment and deformity progression. Rehabilitation exercises can help maintain joint mobility and hand function after either conservative or surgical management. Key principles include:
These rehabilitation approaches should be conducted under the guidance of specialist physicians or rehabilitation therapists, with adjustments made as the child grows and skeletal development progresses.
Disclaimer: This report is provided as a reference for medical analysis only and should not replace a clinical consultation with a professional physician. For specific diagnosis and treatment, please consult a legitimate medical institution or specialist.
Proximal delta phalanx in a triphalangeal left thumb
