Authors: Dina Aprilya, Oryza Satria, Maria Mayella Vianney
Categories: Case Report, Deformity, Exostosis, Mallet finger, Osteochondroma, Pediatric
Source: International Journal of Surgery Case Reports
Authors: Dina Aprilya, Oryza Satria, Maria Mayella Vianney
A terminal extensor tendon disruption, with or without bony avulsion, may lead to a mallet deformity. In most cases, trauma precedes deformity. Non-traumatic causes are less probable. Several reports showed non-traumatic causes include villonodular tumors or chronic inflammation/infection. Conversely, osteochondroma, a benign tumor, typically develops from the growth plate of the long bones during the first two decades of life.
We describe an unusual case of osteochondroma and mallet deformity in a child's finger. The child was only 4 years old at the time of the first presentation, and there was no clear injury before the symptom. The parent reported that the left little finger was crooked. Over the past year, the painless deformity has gradually progressed. At the physical examination, a palpated bony mass was found proximal to the angulated DIP joint. A radiograph was inconclusive and suggested an old fracture of the middle phalanx. Intraoperatively, a sessile-type exostosis at the epi-metaphysis of the middle phalanx pushed the intact terminal extensor ulnarwards.
After removing the exostosis, the biopsy confirmed the presence of osteochondroma. We reconstruct the terminal extensor tendon and skin. During the 2-year follow-up, there was no evidence of infection, deformity relapse, or tumor recurrence.
Our goal is to raise awareness of osteochondroma, an extremely rare cause of a non-traumatic mallet finger in a very young child. Surgical resection remains the mainstay treatment for the tumor, with additional soft tissue reconstruction to overcome the secondary deformity.
An injury to the terminal extensor tendon often results in a mallet finger, a common hand deformity. It usually occurs in sports (mostly contact sports) and work-related injuries, although other trivial daily activity injuries may occur in a non-athlete population [1,2]. Reports of pediatric mallet fingers are relatively uncommon. In a large group study of 99 mallet fingers in children, the most common cause is recreational injury and sports injury, with the mean age at presentation being 13.7 ± 2.4 years (male to female ratio = 7:3). A mallet finger's non-traumatic etiology is extremely rare. There were only four reported cases of non-traumatic mallet villonodular synovitis of the distal interphalangeal joint (DIPJ) in one adult and three solitary phalangeal osteochondromas in children [[3], [4], [5]].
On the other hand, osteochondroma is the most common benign bone tumor (20–50 % of benign bone tumors). Growing from an open epiphyseal growth plate, this bony exostosis may grow during childhood and stop growing, or no new lesions develop after the growth plates are closed. Osteochondroma is commonly encountered during the first decade of
life (> 80 % of patients), with a male-to-female ratio of 1. Patients with multiple osteochondromas (multiple hereditary exostosis/MHE) have a positive family history in 65 % of cases. They may have an earlier onset than solitary osteochondroma. Predilection sites of osteochondroma are long bones, particularly around the knee. Flat bones such as the sternum, costae, scapula, and pelvis are less common sites (< 5 %) [6]. Osteochondroma of the hand is an extremely rare entity, with only 0.2 % to 4 % of cases, which mostly caused a coronal deformity [4].
This case presents an unusual site of the osteochondroma at the distal end of the middle phalanx in a very young child who is presented as a mallet finger without a clear traumatic event. This case is reported according to the Surgical Case Report (SCARE) Guidelines [7].
A 5-year-old boy presented with an approximately 1-year history of a gradually bent left little finger. The precise start of the deformity rendered it nearly unrecognizable. Several doctors examined the patient before referring him to our center. Previous radiographs taken from the previous visit to the general practitioner and general orthopedic surgeon suggest a fracture, which brings confusion because no one in the family recalls any preceding injury, and the patient did not show any signs of trauma like crying or report pain surrounding the DIPJ. There is no previous history of bony masses on other body parts and no family history complaining of the same condition.
During the physical examination, we observed a mallet deformity and ulnar angulation of the left little finger. We palpated a lobulated mass with a hard consistency, which the parent did not recognize, proximal to the DIPJ. The joint was mobile; however, DIP extension lag was revealed during active finger extension (Fig. 1). A plain radiograph from the previous visit showed cortical irregularity at the dorsal middle phalangeal head. We took a magnetic resonance imaging (MRI) to confirm the findings of the last plain radiograph (Fig. 2). We decided to perform an excisional biopsy for the bony mass and mallet deformity correction.Fig. 1Little finger deformity at DIPJ consisting of (a) ulnar angulation and (b) 45^o^ extension lag.Fig. 1Fig. 2Pre-operative plain radiograph of the little finger (a & b) showed cortical irregularity at the dorsal metaphyseal region of the middle phalangeal head with metaphyseal enlargement compared to the same location at adjacent digits. (c) MRI showed a continuation of the medullary cavity and the exostosis. (d) Intra-operative image after mass excision, soft tissue reconstruction, and k-wire fixation.Fig. 2
An excisional biopsy was performed through a lazy S incision at the dorsal aspect of DIPJ. The proximal limb at the ulnar side was extended to accommodate better visualization. Intraoperatively, we found a hard lobulated mass at the dorsal aspect of the middle phalangeal head, pushing the whole terminal extensor complex ulnarly. After the mass excision, we covered the rough bony base with a thin layer of bone wax to ensure the tendons' smooth, gliding surface. The terminal extensor complex was centralized, and the radial side lateral band was stitched to adjacent soft tissue (Fig. 3). A 1.0 K-wire was inserted in a slight DIPJ hyperextension (Fig. 2c) and an excess skin dorsal to DIPJ was removed through an elliptical skin excision.Fig. 3Surgical mass excision and soft tissue reconstruction through a lazy S incision (a). Lobulated mass pushed the whole terminal extensor complex to the ulnar side (b) which is outlined with blue dotted lines (c). Rough bony trabeculae were exposed after mass excision (d) and covered with bone wax (e). Centralization of the terminal extensor complex (f). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)Fig. 3
A gross histopathological examination revealed a 0.7 × 0.5 × 0.2 cm whitish-colored mass with a firm consistency. Microscopically, the tumor was composed of a mature hyaline cartilage cap with an outer layer of dense fibrous perichondrium and an internal calcified matrix that undergoes enchondral ossification (Fig. 4). In deeper layers, the cellularity of cartilage increased, but there was no mitotic figure or nuclear atypia. Correlating the histopathology findings with clinical and radiological evidence, we concluded that the mass was an osteochondroma.Fig. 4Histopathological appearance with Hematoxylin-Eosin staining at 40× (a), 100× (b), and 400× magnification (c) showed a chondroid mass surrounded by an outer layer of dense fibrous tissue (perichondrium, black asterisk). The mass consisted of a hyaline cartilage cap (green asterisk) that merged with the underlying spongy bone filled with bone marrow fat (red asterisk) through an internal calcified matrix bridging both structures (yellow asterisk). Chondrocytes within the cartilage cap demonstrated no nuclear atypia or mitotic activity (c). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)Fig. 4
The K-wire was retained for two weeks, followed by a mallet splint with a slight modification of an additional play dough inserted at the middle phalanx with the affected finger buddy-tapped to the adjacent ring finger for another two weeks (Fig. 5). After the splint removal, active range of motion exercise was encouraged under buddy tape with play dough for another two weeks. The patient was healed uneventfully without infection, nail deformity, recurrence of the lesion, or extension lag at the 2-year follow-up.Fig. 5(a-b) The clinical appearance after skin closure. (c) Post-operative period with modified buddy taping with play dough inserted at the middle phalanx to tighten the radial collateral ligament. (d) Clinical picture at the latest follow-up.Fig. 5
Our patient had solitary osteochondroma (up to the publication of this article), which occurs spontaneously (primary osteochondroma). However, this patient's early onset of disease may raise susceptibility to developing other lesions, such as the typical presentation of multiple hereditary exostosis (MHE). While secondary osteochondroma can develop either due to childhood radiational exposure or trauma to the epiphyses (Salter-Harris fracture or surgery), none of the guardians could recall any traumatic events or pain symptoms (crying and irritability) that related to motions or physical touch to the affected finger [8,9].
The plain radiograph in our patient showed a cortical irregularity and appeared like a bony outgrowth at the dorsal epimetaphyseal surface of the middle phalanx. MRI confirmed the medullary connection between the lesion and the parent bone. Radiologically, the key features of osteochondroma are cortical and medullary continuity as well as the evidence of a cartilage cap. Outgrowing away from the epiphyses, osteochondroma lesions can be pedunculated or wide-based (sessile) located on the epimetaphyses region of long bones (predilection). They sometimes can make metaphyses appear wider [6]. Osteochondroma may mimic other conditions such as Trevor disease and parosteal chondroma or osteosarcoma. Trevor's disease is characterized by asymmetric excessive growth of epiphyses, which usually involves the lower limb [4]. The parosteal chondroma/juxtacortical chondroma, chondrosarcoma, and osteosarcoma develop in similar locations (near the epiphyseal plate) and age groups. The parosteal tumors develop on the bone surface but are unrelated to physeal plates. They can grow in any age group (particularly second to fourth decades) and present with a slow-growing palpable (and sometimes painful) mass. At the same time, the malignant form (parosteal chondrosarcoma/osteosarcoma) may produce a more aggressive nature. The parosteal tumor usually does not demonstrate the medullary continuity on plain films and MRIs that is seen with osteochondromas [8].
Histologically, the osteochondroma is characterized by the appearance of a cartilage cap (in children) that is composed of mature hyaline cartilage with overlying dense fibrous tissue called perichondrium. In pedunculated mass, marrow elements may be present within the stalk and connected with that of the native bone [10,11]. Meanwhile, the parosteal tumors develop through subperiosteal cartilage formation and consist of various histologic tissue types (hyaline cartilage, chondrogenic, and osteogenic cells) without evidence of permeation into the adjacent bone or soft tissue. In malignant form, spindle cell neoplasm with cytologic atypia may present. Further immunohistochemistry evaluations are sometimes needed to confirm the benign lesion from the low-grade malignancy [8].
Osteochondroma may appear cauliflower-like, sessile, or pedunculated. It is crucial to measure the size of the overlying glassy bluish-white cartilage cap perpendicular to the bone-cartilage interface at its thickest portion. Microscopically, it consists of three the outer layer is a fibrous tissue (perichondrium) that is usually continuous with the periosteum of the underlying bone. The second layer is dome-shaped, orderly, and arranged in vague columns. The third layer is the hyaline cartilage cap, which undergoes enchondral ossification [11,12]. While the deeper chondrocytes near the transition bone are larger, the superficial chondrocytes cluster together. There is no nuclear atypia or mitosis. The cartilage cap is usually thin (<2 cm) and may show degenerative myxoid or cystic changes, focal necrosis, nodularity, and calcification, but they do not indicate malignancy. The thickness decreases with age. A thick (2 cm) and irregular cap may be indicative of progression. Immunohistochemistry is no help, and molecular testing is not required to diagnose osteochondroma [12,13]. Excision is typically the preferred curative treatment, but incomplete removal can lead to recurrence. The lesion may recur if any perichondrium or cartilage cap remains behind. [11] Multiple recurrences – or recurrences after complete removal – should raise suspicion of progression. About 1 % of solitary osteochondromas and about 5 % of multiple osteochondromas have an estimated risk for progression into secondary peripheral chondrosarcoma [12].
Differential diagnoses for osteochondroma in children and young adults include periosteal chondroma and parosteal osteosarcoma. Periosteal chondroma shows lobules composed of cartilage; cellularity can be variable but generally low, without fibrous tissue that overlies the mass and no enchondral ossification. Meanwhile, parosteal osteosarcoma can mimic osteochondroma by showing a cartilage cap and enchondral ossification. However, the cartilage cap in parosteal osteosarcoma is more disorganized, and neoplastic spindle cells typically arrange as fascicles in intertrabecular spaces adjacent to the neoplastic bone, which is an area clue for parosteal osteosarcoma. In some cases, spindle cells infiltrate into fat and muscle fibers. In osteochondroma, benign adipose tissue and marrow elements are found in intertrabecular spaces [11].
A neglected phalangeal osteochondroma may lead to progressive deformity, limited motion, and stiffness. Deformities related to phalangeal osteochondroma may be caused by the exostosis growth, the reactive hyperplasia of articular cartilage, or secondary to changes induced by limitation of motion and mechanical imbalance (degenerative changes) [4]. Baek et al. [4] observed ten cases of solitary phalangeal osteochondroma (6 proximal phalanges and 4 middle phalanges) and analyzed the clinical pictures, which mostly caused a coronal deformity (6 out of 10 cases). One of their cases was similar to our case. However, the case was operated on earlier (at the age of 3), with less pre-operative extension lag (< 20^o^) and the distal metaphyseal morphology did not differ from other normal digits [4].
Phalangeal osteochondromas benefit from early surgical treatment of mass excision, including the entire overlying cartilaginous cap, to prevent recurrence. Secondary deformities were treated either by soft tissue reconstruction, corrective osteotomy, or both. Temporary
fixation with a K-wire and post-operative immobilization was used to ensure fibrosis healing to prevent deformity relapse in the early post-operative period [4].
In our patient, the osteochondroma led to the angulation and mallet deformity of the DIPJ. In the classic chronic mallet injury, particularly in childhood and adolescence, raises a specific concern regarding the open epiphyseal plate. Generally, a conservative approach is preferred, involving strict clinical and radiological evaluation, especially when fracture fragments are present. A chronic mallet typically requires surgical intervention, which may involve tendon plication, tendon repair with a tendon graft, threading a lateral band strip into the distal phalanx, and tenodermodesis [[12], [13], [14]]. These surgeries aim to reconstruct the disrupted extensor mechanism to correct the mallet deformity [12].
Fortunately, this patient's terminal extensor tendon and its complex were intact. After relocation to its original site, no extension lag was presented. We decided to tension the dorsal site by creating some DIPJ hyperextension, applying temporary fixation with K-wire, and tightening the dorsal skin. Considering the nature of the child, although we were fully aware of the existence of the distal epiphyseal plate, we cannot rely only on a splint to maintain the hyperextended DIPJ. Baek et al. [4] reported a similar case in a 3-year-old boy with a solitary osteochondroma on the middle phalanx of his index finger, which was treated with osseous mass excision, temporary
fixation of DIPJ with K-wire for 4 weeks and resulted in no recurrence of lesion and deformity relapse at two and a half years after surgery. Another report by Murase et al. [5] in two children (2 and 1 year) who were treated with surgical excision of the exostosis through a dorsal terminal extensor splitting approach in one patient and terminal tendon detachment in another patient. After the excision, the extensor was repaired without further plication or tensioning, and a 1 mm k-wire was used to maintain the DIPJ extension for 4 weeks. The latest follow-up (20 months and 3 months) revealed no recurrence in either case.
In a very young child, we reported an unusual presentation of a non-traumatic mallet finger due to osteochondroma. In the absence of trauma and even with no clinical evidence of a bony lump, we should consider this kind of lesion as the possible cause of a non-traumatic mallet finger, especially in pediatrics.
Informed consent was obtained from patient's guardian**.**
A written informed consent has been taken from the patient's guardian to publish this case report and accompanying images.
Consent for publication was obtained for patient's data included in the study**.**
Waived.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Dr. Oryza Satria
This study did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
All authors contributed to data analysis, drafting or revising the article, have agreed on the journal to which the article will be submitted, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.
None.