Pediatric Tibial Osteofibrous Dysplasia: A Detailed Case Presentation

Patient Presentation and History

We present the case of a 10 year old male, otherwise healthy, who presented to the orthopedic oncology clinic with a chief complaint of progressive right lower leg bowing and mild, intermittent anterior shin pain over the past twelve months. The pain was described as dull, aching, exacerbated by prolonged weight bearing activity, and relieved with rest. There was no history of acute trauma, fall, or specific inciting injury. The bowing of the tibia was first noticed by his parents approximately 18 months prior and was initially thought to be a normal variant of growth, but it had become progressively more pronounced and symptomatic.

The patient denied any constitutional symptoms including fever, chills, night sweats, or unintentional weight loss. His past medical and surgical history was unremarkable, with no known drug allergies or significant family medical history of skeletal dysplasias, metabolic bone diseases, or musculoskeletal malignancies. There were no associated cutaneous manifestations such as café au lait macules, ruling against syndromic associations like Neurofibromatosis type 1 or McCune Albright syndrome. Developmentally, the patient was tracking along the 50th percentile for both height and weight. He actively participated in recreational sports with no significant limitations other than the occasional discomfort localized to the anterior leg. The insidious onset and progressive nature of the diaphyseal deformity, coupled with increasing, albeit mild, mechanical pain, raised strong clinical suspicion for an underlying primary bone lesion or dysplasia.

Further detailed history revealed that the pain did not awaken the patient from sleep, lacking the classic nocturnal presentation of osteoid osteoma. The pain was mechanically linked to the altered biomechanics of the bowed tibia, likely representing microtrabecular stress or periosteal tension rather than aggressive tumor expansion. Previous conservative management, including over the counter non steroidal anti inflammatory drugs and activity modification, provided only transient relief.

Clinical Examination Findings

On inspection of the right lower extremity in the standing position, a noticeable anterior bowing of the tibia was present, particularly localized to the mid diaphyseal region. There was mild, diffuse swelling over the anterior aspect of the shin, but no discrete, exophytic soft tissue mass, erythema, or localized warmth. Skin integrity was entirely intact, with no traumatic breaks, surgical scars, or draining sinuses.

Palpation revealed a firm, non tender, fusiform bony expansion along the anterior and anterolateral cortex of the mid diaphysis of the right tibia. There was no associated soft tissue mass or tenderness of the overlying anterior compartment musculature. The contralateral left lower extremity was entirely symmetrical, rectilinear, and non tender.

Range of motion of the right knee and ankle joints was full and pain free, with no intra articular effusions or ligamentous laxity. Strength testing of the major muscle groups around the ankle and knee, including the tibialis anterior, extensor hallucis longus, and gastrocnemius soleus complex, was graded 5 out of 5 bilaterally, with no motor deficits. Sensory examination to light touch and pinprick was intact throughout the distal right lower extremity in all dermatomal distributions, confirming no neurological compromise. Peripheral pulses, specifically the dorsalis pedis and posterior tibial arteries, were palpable, strong, and symmetrical bilaterally, indicating an intact vascular supply. There was no clinical evidence of acute or chronic exertional compartment syndrome.

Gait analysis demonstrated a subtle antalgic gait with a shortened stance phase on the right lower extremity, which the patient attributed to mild discomfort upon terminal stance. A leg length discrepancy evaluation utilizing block testing revealed a 1.5 centimeter overgrowth of the right lower extremity compared to the left, a common secondary finding in hyperemic pediatric bone lesions. The rotational profile, including the thigh foot angle and transmalleolar axis, remained within normal physiological limits.

Imaging and Diagnostics

Initial diagnostic workup commenced with orthogonal plain radiographs of the right tibia and fibula. These revealed significant anterior and slight lateral bowing of the mid diaphyseal right tibia. A well defined, eccentric, radiolucent lesion was identified within the anterior cortex, spanning approximately 8 centimeters longitudinally. The lesion demonstrated an undulating, soap bubble appearance with dense, sclerotic margins, and focal cortical thickening. There was no evidence of aggressive periosteal reaction, such as Codman triangles or sunburst patterns, nor was there overt cortical destruction. The fibula appeared unaffected. The appearances were highly suggestive of a benign, intracortical lesion, but the possibility of an aggressive benign or low grade malignant lesion, specifically adamantinoma, could not be definitively excluded based solely on plain radiographs.

To further characterize the lesion and delineate its precise anatomical extent, a Computed Tomography scan of the right lower leg was performed. The CT confirmed the eccentric, intracortical location of the lesion within the anterior tibial diaphysis. It clearly demonstrated the expanded and thickened cortex with multiple small lucencies separated by thin septa of sclerotic bone. The lesion exhibited ground glass attenuation in some areas, but predominantly showed a lobulated, bubbly architecture confined to the cortex, with minimal to no medullary extension. The endosteal margin was scalloped but intact.

Magnetic Resonance Imaging with and without intravenous gadolinium contrast was subsequently obtained to evaluate the medullary cavity and surrounding soft tissue envelope. The MRI demonstrated a cortically based lesion that was predominantly isointense to muscle on T1 weighted sequences and heterogeneously hyperintense on T2 weighted fat suppressed sequences. Following contrast administration, there was robust, heterogeneous enhancement of the intracortical lesion. Crucially, the MRI confirmed the absence of medullary involvement, skip lesions, or soft tissue extension, further supporting a diagnosis of osteofibrous dysplasia while mapping the exact margins for potential surgical intervention.

Given the diagnostic overlap between osteofibrous dysplasia and adamantinoma, an open incisional biopsy was performed. Histopathological analysis revealed a fibrous stroma containing trabeculae of woven bone. A critical diagnostic feature was the presence of prominent osteoblastic rimming around the bone trabeculae, which reliably differentiates osteofibrous dysplasia from fibrous dysplasia. Immunohistochemistry demonstrated scattered nests of cells positive for cytokeratin, a common finding in osteofibrous dysplasia that underscores its histogenetic relationship with adamantinoma, though no frankly malignant epithelial clusters or significant atypia were identified.

Differential Diagnosis

The clinical and radiographic presentation of an intracortical, lytic, diaphyseal tibial lesion in a pediatric patient presents a specific differential diagnosis. Distinguishing between these entities is critical, as their natural histories and required treatments vary drastically.

Osteofibrous Dysplasia versus Adamantinoma

The most critical distinction in this case is between osteofibrous dysplasia and adamantinoma. While osteofibrous dysplasia is a benign, self limiting fibro osseous lesion that often stabilizes or regresses after skeletal maturity, adamantinoma is a low grade malignant bone tumor with metastatic potential. Both predominantly affect the anterior tibia and share cytokeratin positivity. Osteofibrous dysplasia is generally considered a precursor or a regressive form of adamantinoma. The lack of medullary involvement and the absence of overt malignant epithelial nests on biopsy in our patient supported the benign diagnosis.

Osteofibrous Dysplasia versus Fibrous Dysplasia

Radiographically, fibrous dysplasia tends to be more centrally located within the medullary canal and exhibits a classic ground glass appearance, whereas osteofibrous dysplasia is strictly intracortical with a bubbly appearance. Histologically, the presence of active osteoblasts rimming the trabeculae of woven bone is the defining feature of osteofibrous dysplasia, which is notably absent in fibrous dysplasia.

Surgical Decision Making and Classification

Osteofibrous dysplasia is classically categorized using the Campanacci classification, which guides treatment algorithms based on the extent of tibial involvement:
* Campanacci Stage I: Small, localized lesions confined to the cortex.
* Campanacci Stage II: Larger lesions involving less than half the circumference of the tibia.
* Campanacci Stage III: Extensive lesions involving more than half the circumference of the tibia or presenting with secondary pseudoarthrosis.

Our patient presented with a Campanacci Stage II lesion that was progressively enlarging and causing significant anterior bowing. The surgical decision making in pediatric osteofibrous dysplasia is highly nuanced and historically controversial.

Intralesional curettage and bone grafting in patients under the age of 15 carries an unacceptably high recurrence rate, often cited between 70 and 100 percent. The aggressive recurrence is attributed to the active growth phase of the lesion during childhood. Therefore, the traditional paradigm dictates delaying definitive surgical intervention until skeletal maturity, at which point the lesion often spontaneously arrests or ossifies. During the observation period, patients are typically managed with functional bracing to prevent pathological fracture.

However, in this specific case, the patient exhibited progressive, symptomatic deformity with significant cortical thinning anteriorly, placing him at imminent risk for a pathological fracture. A pathological fracture through an osteofibrous dysplasia lesion can lead to a recalcitrant pseudoarthrosis, which is notoriously difficult to reconstruct.

Given the progressive bowing, the mechanical pain, and the impending structural failure of the anterior tibial cortex, the decision was made to proceed with surgical intervention. To avoid the near certain recurrence associated with curettage, a wide extraperiosteal segmental resection of the involved anterior cortex and reconstruction was planned. This approach provides definitive local control, allows for simultaneous correction of the mechanical axis, and provides a complete specimen for final pathological evaluation to definitively rule out adamantinoma.

Surgical Technique and Intervention

Preoperative Planning and Templating

Extensive preoperative templating was performed using weight bearing long leg radiographs and 3D CT reconstructions. The mechanical axis deviation was calculated, and the apex of the deformity was identified. The resection margins were planned to include the entire macroscopic lesion with a 1 centimeter normal bone margin proximally and distally, ensuring complete extraperiosteal excision. Reconstruction was planned utilizing a massive structural cortical allograft strut, augmented with autologous iliac crest bone graft at the host graft junctions, and stabilized with a customized, pre contoured locking plate.

Patient Positioning and Approach

The patient was placed supine on a radiolucent operating table. A bump was placed under the ipsilateral hip to internally rotate the leg to a neutral position. A sterile thigh tourniquet was applied. Prophylactic intravenous antibiotics were administered prior to inflation.

A longitudinal incision was made over the anterior crest of the tibia, extending from the proximal metaphysis to the distal diaphysis, ensuring adequate exposure of the planned resection margins. Full thickness fasciocutaneous flaps were elevated. The anterior compartment musculature was meticulously elevated off the lateral aspect of the tibia. It was critical to maintain an extraperiosteal dissection plane over the lesion to prevent tumor spillage and to ensure en bloc resection of the affected cortex.

Resection and Deformity Correction

Under fluoroscopic guidance, the proximal and distal osteotomy sites were marked. Using an oscillating saw equipped with continuous saline irrigation to prevent thermal necrosis, the anterior half of the tibial cortex containing the lesion was resected en bloc. The posterior cortex and medullary canal were carefully preserved to maintain structural continuity and vascularity. The resected specimen was sent for permanent pathological sectioning.

Following resection, the anterior bowing deformity was corrected. A closing wedge osteotomy of the intact posterior cortex was performed at the apex of the deformity to restore the mechanical axis of the tibia.

Reconstruction and Fixation Construct

A structural, freeze dried tibial cortical allograft was matched to the defect size. The allograft was meticulously contoured using a high speed burr to precisely fit the intercalary defect. To promote biological incorporation, the host graft interfaces were decorticated, and cancellous autograft harvested from the proximal tibia was packed into the junctions.

For fixation, a narrow, 4.5 millimeter titanium locking compression plate was pre contoured to match the corrected anatomical alignment of the tibia. The plate was applied to the anterolateral surface of the tibia, spanning the entire reconstructed segment. The construct was secured using a combination of non locking cortical screws for dynamic compression at the host graft interfaces and locking screws for rigid, angle stable fixation in the proximal and distal segments. Fluoroscopy confirmed excellent alignment, hardware placement, and restoration of the mechanical axis.

Soft Tissue Coverage and Closure

Adequate soft tissue coverage over the anterior tibia and hardware is paramount to prevent wound breakdown and secondary infection. The anterior compartment fascia was closed loosely to avoid compartment syndrome. The subcutaneous tissues were approximated with interrupted absorbable sutures, and the skin was closed with a running subcuticular suture. A sterile, non adherent dressing was applied, and the limb was placed in a well padded, bi valved long leg cast in neutral alignment.

Post Operative Protocol and Rehabilitation

The immediate postoperative course was uneventful. The patient was admitted for 48 hours for pain management and intravenous antibiotics. Strict elevation of the operative limb was maintained to mitigate postoperative edema. Neurovascular checks were performed every four hours, demonstrating no signs of compartment syndrome or vascular compromise.

Phase One Early Postoperative

The patient was discharged on postoperative day two. He was instructed to maintain strict non weight bearing status on the right lower extremity. At the two week follow up, the surgical incision was well healed, and the sutures were removed. The patient was transitioned to a custom molded, fracture brace. Range of motion exercises for the knee and ankle were initiated under the guidance of a physical therapist to prevent arthrofibrosis and maintain joint mechanics.

Phase Two Intermediate Rehabilitation

At six weeks postoperatively, plain radiographs demonstrated maintenance of alignment and early signs of callus formation at the host graft junctions. The patient was permitted to begin progressive touch down weight bearing, advancing to partial weight bearing in the fracture brace. Aquatic therapy was introduced to facilitate gait mechanics in a low impact environment.

Phase Three Advanced Rehabilitation and Surveillance

By three months postoperatively, radiographs showed progressing incorporation of the structural allograft. The patient was advanced to full weight bearing as tolerated and transitioned out of the fracture brace. Strengthening of the anterior compartment and gastrocnemius soleus complex was emphasized.

Given the nature of osteofibrous dysplasia and the theoretical risk of malignant transformation to adamantinoma, long term oncological surveillance is mandatory. The patient is scheduled for clinical and radiographic evaluation every six months for the first two years, and annually thereafter until skeletal maturity. Hardware removal is generally not recommended unless the plate becomes prominent or symptomatic, and only after complete radiographic incorporation of the allograft, which typically takes 18 to 24 months.

Clinical Pearls and Pitfalls

• Diagnostic Overlap: Always maintain a high index of suspicion for adamantinoma when evaluating an anterior tibial lesion with a bubbly appearance. The presence of cytokeratin positive cells in osteofibrous dysplasia necessitates expert musculoskeletal pathology review.
• Biopsy Technique: When performing a biopsy, ensure the tract is placed in line with the definitive surgical incision. Obtain adequate tissue from multiple areas of the lesion, as adamantinoma can present as focal malignant nests within a larger benign appearing fibro osseous background.
• Avoid Early Curettage: Intralesional curettage of osteofibrous dysplasia in young children is a pitfall, carrying a near universal recurrence rate. Delay surgical intervention until skeletal maturity if the mechanical integrity of the bone allows.
• Indications for Resection: Progressive deformity, impending pathological fracture, or Campanacci Stage III lesions warrant extraperiosteal segmental resection rather than observation or intralesional procedures.
• Preservation of Posterior Cortex: When performing an anterior cortical resection, meticulous preservation of the posterior cortex and its periosteal blood supply is critical for maintaining stability and promoting union of the intercalary reconstruction.
• Soft Tissue Management: The anterior tibia has a notoriously poor soft tissue envelope. Meticulous handling of the fasciocutaneous flaps and low profile fixation constructs are essential to prevent wound dehiscence and deep infection.