A 6-year-old boy presented with deformity of the left forearm (Figure 1a) for three months. Three years back he sustained an injury while playing and had accidentally hit the door. The boy had multiple cafe au lait spots on the back and cutaneous neurofibroma in his left knee (figures 1b and 1c).
A radiograph of the left forearm done three years back (Figure 2) showed a small expansile lytic lesion with ground glass matrix and cortical thinning in the diaphysis of the left radius. The margins were sclerosed with a narrow zone of transition and no periosteal reaction. The current radiograph (Figure 3) revealed enlargement of previously seen lesions with multiple lytic and ground glass areas. There was a malunited fracture in the distal meta-diaphyseal end of the left ulna. On MRI, the lesion measured 2.4 x 2 x 5.1 cm. It was T2 hyperintense, T1 hypointense with lobulated margins, and T1/T2 hypointense internal septations (Figures 4a and 4b). The lesion showed intense enhancement with a type 2 curve in the perfusion study (Figures 4c and 4d). A diagnosis of fibrous dysplasia (FD) in the radius and pseudoarthrosis in the distal ulna was made in a child with neurofibromatosis type 1.
Background
Pseudoarthrosis is typically described as the creation of a joint-like structure by fibrous hamartoma due to the unsuccessful healing between two bony ends, located away from the actual joints [1,2]. It is exemplified by anterolateral bending and non-union fracture in the diaphysis of long bones [3]. Pseudoarthrosis is associated with Jaffe–Campanacci syndrome, osteogenesis imperfecta, ankylosing spondylitis, the end stage of inflammatory arthritides, neurofibromatosis type 1, and FD [1–3].
Neurofibromatosis type 1 is the most common phacomatosis. Both mesodermal dysplasia and external pressure from the neurofibromas lead to various skeletal presentations [4]. Various skeletal findings in neurofibromatosis include non-dystrophic or dystrophic scoliosis, kyphosis, sphenoid dysplasia, dural ectasia, posterior vertebral body scalloping, thinning of the vertebral lamina and pedicles, ribs narrowing, and pseudoarthrosis [4].
Imaging Perspective
On a radiograph, FD shows ground glass opacity or radiolucency in the diaphysis with the widening of the medullary canal, endosteal scalloping, and cortical thinning. Shepherd crook deformity or bending of the affected bone is common. On CT, the lesion has an HU of 60–140 with better osseous delineation than the radiographs [5]. The lesion is T2 variable intense, T1 hypointense, and shows avid contrast enhancement [6,7].
Both non-ossifying fibroma (NOF) and FD are seen in neurofibromatosis and are morphologically similar; however, NOF is lytic, eccentric, and located at the metaphysis of long bones. MRI is useful from a surgical point of view to assess the line of resection and subtle soft tissue changes, and to look for non-enhancing cystic areas.
Outcome
Various treatment strategies include bracing, resection of the lesion, and bridging with vascularised tibial/fibular bone graft, Illizarov technique, and amputation. The continuous growth of the immature skeleton coupled with inherent mesodermal dysplasia hinders the normal healing process, and thus, the surgical results are not satisfactory [3]. A systematic review undertaken by Siebelt M et al. concluded that fibular bone graft had better outcomes for forearm pseudoarthrosis [8].
Take Home Message / Teaching Points
In a child with cafe au lait spots and bony deformity, one should suspect benign bone conditions like fibrous dysplasia (FD). Diagnosis can be made on the radiograph itself; however, an MRI is necessary for surgical planning.
Although pseudoarthrosis is more common in the tibial bone, few works of literature have reported pseudoarthrosis in the forearm in neurofibromatosis [9–13], but the involvement of radius with FD and pseudoarthrosis of the ulna in a neurofibromatosis type 1 was unique in our case. The pseudoarthrosis in the distal ulna was a sequelae of an untreated trauma in the past that had aggravated due to mesodermal dysplasia in this case.
Written informed patient consent for publication has been obtained.
Fibrous dysplasia and pseudoarthrosis in neurofibromatosis type 1
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
1. On the X-ray of the left forearm, the mid-shaft of the radius shows a “ground-glass” density change. The cortex is thinned, with an indentation of the medial cortex (endosteal scalloping). The overall radius alignment is curved, resulting in a certain degree of deformity.
2. The distal ulna shows separated fracture ends and a pseudoarthrosis appearance (no clear bony union), and the surrounding cortical edges appear irregular.
3. MRI indicates relatively well-defined margins for the left radial mid-shaft lesion. It appears hypointense on T1-weighted images, with heterogeneous signal enhancement on T2-weighted images, partially showing slightly prolonged T2 signal. Enhanced scans suggest a relatively active lesion, without significant extensive destruction or infiltration of the surrounding soft tissue.
4. Skin findings include multiple café-au-lait macules, and a subcutaneous neurofibroma is observed around the left knee. In conjunction with clinical signs and a history of trauma, these findings suggest skeletal changes associated with Neurofibromatosis Type 1 (NF1).
Given the patient’s background of neurofibromatosis, multiple café-au-lait macules, and the radiological findings indicating fibrous dysplasia of the radius and pseudoarthrosis of the ulna, the overall picture is more consistent with FD and pseudoarthrosis.
Combining the patient’s age, the clinical characteristics of Neurofibromatosis Type 1 (café-au-lait macules and subcutaneous fibromas), a history of trauma, and the imaging findings, the most likely diagnosis is:
“Neurofibromatosis (NF1) with fibrous dysplasia of the left radius and pseudoarthrosis of the ulna.”
1. Treatment Strategy:
- Conservative Treatment: If hand function is acceptable and the deformity is not progressing, consider bracing and regular follow-up. Pay attention to the risk of re-fracture, and supplementation with calcium or vitamin D may be necessary.
- Surgical Treatment: In cases of significant deformity or recurrent fractures, consider curettage of the lesion, bone grafting (vascularized fibular or tibial grafts when feasible), and internal fixation or even Ilizarov reconstruction. If the soft-tissue condition around the pseudoarthrosis is poor, or the deformity is severe, multiple surgical interventions may be required.
- Lesion Resection and Reconstruction: If the fibrous dysplasia is relatively localized, surgical removal/curettage and bone graft fusion may be performed to enhance skeletal stability.
2. Rehabilitation and Exercise Prescription:
Considering the patient is in a growth phase with risks of low bone mass and deformity, the exercise plan must be personalized and progressive, following the FITT-VP principle (Frequency, Intensity, Time, Type, Volume, and Progression):
- Early Phase (postoperative or initial conservative treatment):
· Focus on joint range of motion and basic muscle strength exercises, 1-2 times per day, around 10 minutes each session, with low to moderate intensity. The aim is to maintain joint flexibility and avoid disuse atrophy.
· Passive or assisted active exercises for the wrist and elbow joints may be performed with the help of healthcare providers or family members.
- Intermediate Phase (recovery period):
· Once the injured limb is stable, gradually increase muscle strength training (e.g., grip balls, low-resistance elastic bands), 3-4 times per week, 20 minutes per session, progressing from low to moderate intensity.
· Avoid high-impact activities and prevent excessive torsional or longitudinal stress on the forearm. Use braces or supports during running or jumping if necessary.
- Late Phase (functional consolidation):
· When forearm stability is regained, introduce low-intensity weight-bearing exercises (e.g., 1-2 kg dumbbells, medium-resistance bands), 3-4 times per week, 30 minutes each session, progressing from moderate intensity onwards.
· Emphasize coordination and endurance training of wrist and forearm muscles while continuing to avoid high-impact or heavy-load activities.
- Long-Term Maintenance:
· Continue regular medical follow-ups to monitor bone growth, deformity progression, and other manifestations of neurofibromatosis.
· Maintain sufficient nutrition and exposure to sunlight for bone health.
This report is for reference only based on current imaging and clinical data. It does not replace in-person specialist consultations or further examinations. If any symptoms worsen or if there are any concerns, please seek medical attention or consult a professional physician promptly.
Fibrous dysplasia and pseudoarthrosis in neurofibromatosis type 1
