Patient Presentation & 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 year. The pain was described as dull, aching, worse with prolonged activity, and relieved with rest. There was no history of acute trauma, fall, or specific 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 more pronounced and symptomatic. The patient denies any fever, chills, night sweats, or weight loss. His past medical history is unremarkable, with no known allergies or significant family medical history. There are no associated skin lesions such as café-au-lait spots. Developmentally, he is on track. He participates in recreational sports with no significant limitations other than the occasional discomfort. The insidious onset and progressive nature of the deformity, coupled with increasing, albeit mild, pain, raised concerns regarding an underlying bone lesion.
Clinical Examination
On inspection of the right lower extremity, a noticeable anterior bowing of the tibia was present, particularly in the mid-diaphyseal region. There was mild, diffuse swelling over the anterior aspect of the shin, but no discrete palpable mass, erythema, or warmth. Skin integrity was intact, with no breaks, scars, or draining sinuses.
Palpation revealed a firm, non-tender 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 overlying musculature. The contralateral left lower extremity was symmetrical and non-tender.
Range of motion (ROM) of the right knee and ankle joints was full and pain-free, with no effusions or ligamentous laxity. Strength testing of the major muscle groups around the ankle and knee was graded 5/5 bilaterally, with no motor deficits. Sensory examination to light touch and pinprick was intact throughout the distal right lower extremity, confirming no neurological compromise. Peripheral pulses (dorsalis pedis and posterior tibial) were palpable, strong, and symmetrical bilaterally, indicating intact vascular supply. There was no evidence of compartment syndrome. The patient demonstrated an antalgic gait with a subtle limp on the right lower extremity, attributing it to the mild discomfort, but his ambulation was otherwise stable.
Imaging & Diagnostics
Initial diagnostic workup commenced with plain radiographs of the right tibia and fibula (anteroposterior and lateral views). These revealed significant anterior bowing of the mid-diaphyseal right tibia. A well-defined, eccentric, radiolucent lesion was identified within the anterior cortex, spanning approximately 8 cm longitudinally. The lesion demonstrated an undulating, "soap-bubble" or "bubbly" appearance with dense, sclerotic margins, and focal cortical thickening. There was no evidence of periosteal reaction or overt cortical destruction, nor was there any clear intramedullary involvement on plain films. The fibula appeared largely unaffected. The appearances were highly suggestive of a benign, intramedullary or intracortical lesion, but the possibility of an aggressive benign or low-grade malignant lesion could not be excluded definitively based solely on radiographs.
To further characterize the lesion and delineate its extent, a Computed Tomography (CT) scan of the right tibia 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 involvement. The CT scan provided excellent detail regarding the cortical integrity and the absence of significant soft tissue extension, reaffirming its intramural nature.
A Magnetic Resonance Imaging (MRI) scan of the right tibia, with and without intravenous gadolinium contrast, was subsequently obtained. The MRI confirmed the well-circumscribed, intracortical lesion. On T1-weighted images, the lesion appeared predominantly hypointense, and on T2-weighted and STIR sequences, it showed heterogeneous intermediate to high signal intensity, consistent with fibrous and osseous components. Post-contrast images revealed mild, patchy enhancement within the lesion, indicating vascularized fibrous tissue. Importantly, the MRI showed no evidence of aggressive features such as significant periosteal reaction, marrow edema extending beyond the lesion's immediate vicinity, or overt soft tissue mass, further supporting a benign process. The growth plates were open and not directly involved by the lesion. The bowing deformity was clearly visible on all sequences.
Given the imaging findings, which were highly suspicious for osteofibrous dysplasia (OFD) but also overlapped with other aggressive benign or low-grade malignant conditions, an image-guided core needle biopsy was deemed insufficient for definitive diagnosis, particularly to rule out adamantinoma. Therefore, an open incisional biopsy was planned for histological confirmation. Intraoperatively, the lesion appeared firm and gritty. Histopathological examination revealed a characteristic pattern of immature woven bone trabeculae rimmed by osteoblasts, haphazardly arranged within a cellular fibrous stroma composed of spindle cells. Crucially, there was no cellular atypia, pleomorphism, or significant mitotic activity. Areas of mature lamellar bone were also present at the periphery. Immunohistochemistry was performed, and while often not required for classic OFD, it was considered to further differentiate from adamantinoma. This confirmed the diagnosis of Osteofibrous Dysplasia.
Differential Diagnosis
The presentation of a slow-growing, cortical lesion with associated bowing in a child necessitates a thorough differential diagnosis, particularly given the overlap with potentially more aggressive entities. The primary differentials considered include:
| Feature | Osteofibrous Dysplasia (OFD) | Adamantinoma | Fibrous Dysplasia (FD) | Non-Ossifying Fibroma (NOF) / Fibrous Cortical Defect (FCD) |
|---|---|---|---|---|
| Age Group | Children/Adolescents (typically <20 years), most common <10 | Young adults (20-50 years), but can occur in adolescents | Any age, often diagnosed in children/adolescents or incidentally in adults | Children/Adolescents (very common, often incidental finding) |
| Location | Almost exclusively Tibia (anterior cortex, mid-diaphysis) | Almost exclusively Tibia (diaphysis/metadiaphysis), often eccentric | Any bone, commonly long bones (femur, tibia), ribs, craniofacial, pelvis | Long bones (tibia, femur), metaphysis/diaphysis |
| Clinical Pres. | Progressive bowing, mild pain, palpable cortical expansion | Pain, swelling, palpable mass, pathological fracture in 10-20% | Asymptomatic, pain, deformity (e.g., "shepherd's crook"), pathological fracture | Asymptomatic, incidental finding, pathological fracture (rare for FCD) |
| Radiographs | Eccentric, intracortical, "soap bubble" lucency with sclerotic margins, cortical thickening, bowing | Multicystic, expansile, "soap bubble" appearance, cortical destruction, often sclerotic reaction | "Ground-glass" matrix, endosteal scalloping, cortical thinning, bowing (femur) | Oval, lucent, eccentric, sclerotic rim, often appears to "migrate" from metaphysis |
| CT Findings | Confirms intracortical location, multiple small lucencies with sclerotic septa, cortical expansion | Better delineates cortical destruction, soft tissue extension, multilocular osteolytic areas | Confirms ground-glass matrix, cortical thinning, internal trabeculations | Well-defined, lucent defect, cortical scalloping, sclerotic border, often septated |
| MRI Findings | T1 hypointense, T2 heterogeneously hyperintense, patchy enhancement; no significant soft tissue mass | T1/T2 variable, often heterogeneous, enhancement; may show soft tissue extension | T1 low, T2 high, variable enhancement; characteristic "shepherd's crook" deformity if femur | T1 low, T2 high; no significant enhancement; often spontaneously resolve |
| Histology | Immature woven bone trabeculae rimmed by osteoblasts within a fibrous stroma; no atypia; often "Chinese character" bone pattern | Biphasic tumor with epithelial cells (basaloid, spindled, plexiform) and fibrous stroma; locally aggressive | Immature woven bone trabeculae without osteoblastic rimming, in a fibrous stroma | Spindle cell fibroblasts, histiocytes, hemosiderin, foamy macrophages (lipid-laden); no bone formation (except reactive) |
| Prognosis/Tx | Benign, often self-limiting, high recurrence if surgery in children. Curettage + grafting if symptomatic/unstable. | Malignant (low-grade), locally aggressive with metastatic potential. Wide en bloc resection. | Benign, often asymptomatic, surgery for pain, deformity, fracture. Curettage, osteotomy, grafting. | Benign, self-limiting; usually observation; curettage if symptomatic or risk of fracture. |
Surgical Decision Making & Classification
The decision for surgical intervention in Osteofibrous Dysplasia (OFD) is nuanced, balancing the benign nature and potential for spontaneous regression against symptomatic progression, risk of pathological fracture, and increasing deformity. In this particular case, the patient's progressive anterior tibial bowing and persistent, albeit mild, activity-related pain, despite conservative measures and observed over several months, indicated the need for intervention. Furthermore, the concern for ruling out adamantinoma, which shares significant radiographic similarities, necessitated an open biopsy.
Why Operative vs. Non-operative?
*
Non-operative management
is often the initial approach for asymptomatic or mildly symptomatic lesions in young children, as OFD has a documented potential for spontaneous regression or resolution in adolescence, particularly after skeletal maturity. Regular clinical and radiographic follow-up is crucial.
*
Operative intervention
becomes indicated for:
1.
Symptomatic lesions:
Persistent or increasing pain that significantly impacts daily activities.
2.
Progressive deformity:
Bowing that is worsening and likely to lead to functional impairment or significant cosmetic concern.
3.
Impending or actual pathological fracture:
Although OFD rarely causes complete cortical breach unless severe, cortical thinning and expansion can predispose to fracture.
4.
Diagnostic uncertainty:
As in our case, where adamantinoma could not be definitively excluded by imaging alone, an open biopsy was required. If the biopsy confirmed OFD, the surgical procedure could then be tailored.
5.
Large or extensive lesions:
Lesions that are significantly compromising the structural integrity of the bone.
There is no formal classification system for OFD that dictates treatment in the same way as fracture classifications. However, surgical planning often considers:
*
Age of the patient:
Younger patients (especially under 10 years) have a higher risk of recurrence post-curettage, which influences the choice of fixation and extent of resection.
*
Extent and location of the lesion:
Whether it's focal or diffuse, and its proximity to growth plates.
*
Severity of deformity:
The degree of angulation requiring corrective osteotomy.
*
Integrity of the remaining bone:
To assess the need for supplemental internal fixation after curettage and bone grafting.
Given the age of our patient (10 years), the progressive bowing, and the diagnostic imperative, a definitive open biopsy with subsequent intralesional curettage and bone grafting was chosen. The potential for recurrence in this age group was acknowledged, and a discussion was held with the family regarding this.
Surgical Technique / Intervention
The surgical intervention proceeded after definitive histopathological confirmation of Osteofibrous Dysplasia. The primary goal was thorough intralesional excision/curettage of the lesion, correction of the bowing deformity, structural reconstruction, and stabilization to prevent refracture.
Patient Positioning: The patient was positioned supine on the operating table. A high thigh tourniquet was applied to the right limb. The entire lower extremity was prepped and draped in a sterile fashion, allowing for visualization and manipulation of the knee and ankle. A small bump or bolster was placed under the ipsilateral hip to facilitate access to the iliac crest for bone graft harvest, if needed.
Surgical Approach: A straight longitudinal incision, approximately 12 cm in length, was made over the anterior aspect of the right mid-tibia, directly overlying the palpable cortical expansion and bowing. The incision extended through the skin and subcutaneous tissue. The periosteum was then carefully incised longitudinally and reflected subperiosteally to expose the underlying cortical lesion.
Lesion Excision and Curettage: A cortical window, approximately 6 cm in length and 1.5 cm in width, was created using an osteotome and small osteochondral instruments. This window was strategically placed over the most prominent and affected part of the anterior cortex to gain adequate access to the intracortical lesion. The lesion appeared as a firm, greyish-white, gritty fibrous mass with interspersed bony islands. Meticulous and thorough intralesional curettage was performed using various sizes of curettes. Care was taken to remove all macroscopic diseased tissue, extending into the sclerotic margins. High-speed burrs were used to meticulously debride the remaining sclerotic bone, ensuring complete removal of the lesion down to healthy, bleeding bone. Intraoperative fluoroscopy was used intermittently to confirm the extent of curettage and the absence of residual radiodense areas within the defect. Adjuvant therapies such as cryotherapy or phenol were consciously not employed, given the benign nature of OFD and the proximity to the growth plate in a pediatric patient, to minimize potential iatrogenic injury.
Deformity Correction (Osteotomy): Following curettage, the significant anterior bowing of the tibia required corrective osteotomy. A transverse osteotomy was performed through the previously created cortical window and extended through the posterior cortex, using an oscillating saw. The bowing deformity was then carefully corrected, achieving anatomical alignment of the tibia. This involved a gentle manual reduction, correcting the anterior angulation.
Bone Grafting: Autologous cancellous bone graft was harvested from the ipsilateral posterior iliac crest to fill the large cortical defect and osteotomy site. Approximately 20-30 mL of cancellous graft was packed tightly into the entire curetted cavity and around the osteotomy site. This served to provide structural support, promote osteoinduction and osteoconduction, and facilitate bone healing.
Fixation Construct: To maintain the corrected alignment and provide immediate stability, an intramedullary nail (IMN) was chosen, given the diaphyseal location and the age of the patient (growth plate sparing considerations were paramount). A reamed, cannulated titanium elastic nail (TEN) system, or a smaller diameter pediatric IMN, was utilized. The nail was inserted antegrade via a proximal tibial entry point, distal to the tibial tuberosity, ensuring not to violate the proximal tibial physis. The nail traversed the corrected osteotomy site and provided stable fixation. Distal and proximal interlocking screws were placed to prevent rotation and maintain length. The choice of an IMN provided robust internal fixation while allowing for early mobilization and potentially reducing the need for prolonged external immobilization. The cortical window fragment was not replaced.
Closure: The periosteum was loosely approximated over the grafted area. The subcutaneous tissues were closed in layers using absorbable sutures. The skin was closed with non-absorbable sutures in a running subcuticular fashion. A sterile dressing was applied.
Post-Operative Protocol & Rehabilitation
Immediate Post-Operative Period (Day 0-14):
*
Pain Management:
Multimodal analgesia regimen including NSAIDs, acetaminophen, and short-term oral opioids as needed.
*
Immobilization:
A well-padded knee immobilizer or a bulky soft dressing was applied to provide comfort and prevent gross movements, rather than rigid immobilization, as the intramedullary nail provided primary stability.
*
Elevation:
The operative limb was kept elevated above heart level to minimize swelling.
*
Weight-Bearing:
Strict non-weight-bearing (NWB) with crutches or a walker was prescribed for the initial 6 weeks to protect the bone graft and osteotomy site.
*
Range of Motion:
Gentle active and passive range of motion exercises for the knee and ankle were initiated immediately post-op, within the limits of comfort and avoiding stress on the osteotomy. Emphasis on quadriceps and hamstring setting exercises.
Early Rehabilitation (Weeks 2-6):
*
Wound Care:
Suture removal at 2 weeks. Monitor for signs of infection.
*
Physical Therapy:
* Continue full knee and ankle ROM exercises.
* Progressive strengthening exercises for hip, knee, and ankle musculature, initially isometric, then gradually isotonic.
* Maintain NWB status.
* Initiate gait training with crutches, focusing on proper mechanics while maintaining NWB on the operative limb.
Progressive Rehabilitation (Weeks 6-12):
*
Radiographic Assessment:
Follow-up X-rays at 6 weeks post-op to assess bone graft incorporation and osteotomy healing.
*
Weight-Bearing Progression:
If radiographic signs of early healing are favorable, transition to protected partial weight-bearing (PWB) in a controlled manner, typically with 25% body weight, gradually increasing to 50% over the next 2-4 weeks, under the guidance of a physical therapist.
*
Physical Therapy:
* Continue strengthening exercises, increasing resistance.
* Balance and proprioception training.
* Advance gait training to achieve a normal walking pattern with progressive weight-bearing.
Late Rehabilitation and Return to Activity (Months 3-6+):
*
Radiographic Assessment:
Further X-rays at 3 months and 6 months to monitor complete healing and graft remodeling.
*
Full Weight-Bearing:
Once full radiographic consolidation of the osteotomy and graft site is achieved (typically 3-4 months), full weight-bearing (FWB) without assistive devices is permitted.
*
Functional Training:
Progress to sport-specific drills, agility training, and plyometrics as appropriate, gradually increasing intensity.
*
Return to Activity:
Full unrestricted activity, including competitive sports, is usually permitted between 6-12 months post-surgery, contingent upon full bone healing, restoration of strength, and clearance from the surgeon.
*
Follow-up:
Long-term clinical and radiographic follow-up is critical for OFD, as recurrence can occur, particularly in younger patients. Annual follow-up with X-rays for at least 3-5 years post-surgery is recommended to monitor for recurrence, implant-related issues, or late complications.
Pearls & Pitfalls
Pearls (Crucial for FRCS/Board Exams)
- Clinical Suspicion: Always suspect Osteofibrous Dysplasia (OFD) in a child or adolescent presenting with progressive anterior bowing of the tibia and mild pain, especially if imaging shows an eccentric, intracortical, "soap-bubble" lesion with sclerotic margins.
- Key Differential: Adamantinoma is the most critical differential diagnosis due to similar radiographic features and tibial predilection. Always obtain a biopsy for definitive histological confirmation to differentiate these entities, as their management is vastly different.
- Histological Hallmark: The definitive diagnosis of OFD relies on histology demonstrating immature woven bone trabeculae rimmed by osteoblasts within a fibrous stroma. The absence of cellular atypia, pleomorphism, and high mitotic activity is critical.
- Conservative Management: For asymptomatic or mildly symptomatic OFD in young children, initial conservative management with careful observation is often appropriate, given the potential for spontaneous regression after skeletal maturity.
- Surgical Indications: Intervention is reserved for symptomatic lesions (pain), progressive deformity, impending/actual pathological fracture, or diagnostic uncertainty (to rule out adamantinoma).
- Surgical Principle: Intralesional curettage with meticulous debridement of the fibrous and bony components is the primary surgical technique. Adjuvant therapies (e.g., cryotherapy, phenol) are generally not indicated for OFD, particularly in children, due to potential growth plate damage and the lesion's benign nature.
- Deformity Correction & Grafting: For significant bowing, a corrective osteotomy is necessary. Bone grafting (autograft preferred) is essential to fill the defect, promote healing, and prevent refracture.
- Fixation in Children: When internal fixation is required in children, careful consideration of growth plate sparing techniques (e.g., flexible intramedullary nails, plates placed away from physes, or small-diameter reamed nails) is paramount.
- Recurrence: OFD, especially when operated on in younger patients (<10 years), has a reported recurrence rate of up to 50%. Long-term follow-up is therefore essential.
Pitfalls
- Misdiagnosis: Mistaking OFD for Fibrous Dysplasia (lacks osteoblastic rimming), Non-ossifying Fibroma (different histological features, different natural history), or even chronic osteomyelitis (lack of systemic symptoms, different imaging characteristics). More gravely, misdiagnosing an adamantinoma as OFD leads to inadequate treatment.
- Inadequate Biopsy: Performing only an image-guided core needle biopsy may not provide sufficient tissue for definitive differentiation, especially from adamantinoma. An open incisional biopsy may be necessary.
- Over-treatment: Aggressive surgical resection (e.g., wide en bloc resection) for a benign lesion like OFD is inappropriate and can lead to unnecessary morbidity, limb length discrepancy, or joint stiffness. This is reserved for true adamantinoma.
- Under-treatment: Failure to address significant progressive deformity or impending pathological fracture can lead to ongoing pain, functional impairment, and late complications.
- Ignoring Recurrence: Neglecting to counsel patients and families about the high recurrence rate in younger individuals, and failure to provide long-term follow-up, can lead to delayed identification and management of recurrences.
- Growth Plate Injury: Using inappropriate fixation techniques (e.g., large-diameter reamed nails or plates crossing physes) in skeletally immature patients can result in growth arrest or angular deformity.
