Orthopaedic Surgery - Chondroblastoma

Basics

Chondroblastoma is a benign bone tumor of cartilaginous origin that characteristically arises in the epiphysis of skeletally immature patients.

It most often develops in the epiphyses of long bones, particularly around major joints.

The proximal humerus is the most commonly involved site, followed by the proximal tibia and femur.

Synonyms

Chondroblastoma of the proximal humeral epiphysis has historically been referred to as a Codman tumor.

Another older term is epiphyseal chondromatous giant cell tumor.

Epidemiology

Chondroblastoma has a mild male predominance, with males affected approximately twice as often as females.

It occurs mainly in adolescents and young adults whose physes are still open or have only recently closed.

Incidence

Chondroblastoma is uncommon.

In large tumor series, it has accounted for approximately 1% of all skeletal neoplasms.

Risk Factors

No specific environmental, developmental, or lifestyle risk factors have been identified.

Genetics

No well-established hereditary predisposition has traditionally been recognized for chondroblastoma.

The tumor is generally considered sporadic.

Etiology

The precise cause remains uncertain.

The neoplastic cells are believed to arise from cartilage-producing precursor cells, or chondroblasts.

Some pathologic similarities exist between chondroblastoma and chondromyxoid fibroma, although they are distinct tumors.

Associated Conditions

Chondroblastomas may contain areas resembling an aneurysmal bone cyst (ABC).

These secondary aneurysmal changes can influence the radiographic appearance and may be associated with a greater risk of recurrence.

Diagnosis

Signs and Symptoms

The most common complaint is persistent mild to moderate pain near the involved joint.

Symptoms often develop gradually and may persist for months or even years before diagnosis.

Joint Stiffness

Because the tumor develops close to an articular surface, patients frequently experience stiffness and loss of motion in the adjacent joint.

Joint Effusion

An effusion may develop in the nearby joint.

This can make the presentation resemble an intra-articular or inflammatory disorder rather than a primary bone lesion.

Local Swelling

Visible or palpable swelling is uncommon.

The tumor usually remains contained within the bone unless it becomes unusually large or extends beyond the cortex.

Physical Examination

Examination may demonstrate a joint effusion and reduced range of motion.

A palpable soft-tissue mass is unusual.

Direct joint-line tenderness is also generally not a prominent feature.

Laboratory Tests

Routine laboratory investigations are usually normal.

Blood tests generally do not assist in establishing the diagnosis.

The erythrocyte sedimentation rate is typically normal, helping distinguish the lesion from some infectious or inflammatory conditions.

Imaging

Plain Radiographs

The classic radiographic appearance is a well-defined lytic lesion within the epiphysis.

The lesion usually has a thin surrounding rim of sclerosis.

Sclerotic Rim

The presence of a narrow sclerotic border is consistent with the relatively slow-growing and benign nature of the tumor.

The lesion may nevertheless enlarge sufficiently to expand or deform the surrounding bone.

Calcification

Small punctate calcifications may occasionally be visible within the lesion.

These reflect mineralization of the cartilaginous matrix.

Role of Radiographs

In a typical young patient with an epiphyseal lesion and characteristic symptoms, the combination of clinical history and plain radiographs may strongly suggest the diagnosis.

Definitive diagnosis, however, depends on histologic evaluation.

MRI

MRI is useful when plain radiographs are not definitive or when the full extent of the lesion must be determined.

The lesion generally has a well-demarcated margin on MRI.

Peritumoral Edema

Surrounding bone marrow and soft-tissue edema are commonly seen on MRI.

This edema can sometimes appear disproportionately extensive compared with the relatively small size of the benign tumor.

Pathological Findings

Histologic confirmation requires identification of characteristic chondroblasts.

These are small round or polygonal cells containing round or oval nuclei.

Chondroblast Appearance

Chondroblasts are often described as relatively plump cells, sometimes likened to the appearance of fried eggs on microscopy.

Chicken-Wire Calcification

One of the classic histologic features is fine calcification extending in a lattice-like pattern around individual chondroblasts.

This is referred to as “chicken-wire” calcification and is strongly associated with chondroblastoma.

Giant Cells

Multinucleated giant cells are commonly scattered throughout the tumor.

Their presence can create histologic resemblance to a giant cell tumor, particularly if the epiphyseal location is not considered.

Aneurysmal Bone Cyst Change

Secondary areas of aneurysmal bone cyst formation may also be present.

These regions contain blood-filled spaces and may contribute to expansion of the lesion.

Differential Diagnosis

Important differential diagnoses include enchondroma, giant cell tumor, osteomyelitis, and fibrous dysplasia.

Age, skeletal maturity, epiphyseal location, radiographic appearance, and histology help distinguish these conditions.

Giant Cell Tumor

Giant cell tumor is an especially important differential diagnosis because both lesions can involve the epiphysis and contain numerous giant cells.

Giant cell tumor typically occurs in skeletally mature patients, whereas chondroblastoma more commonly arises before or around skeletal maturity.

Osteomyelitis

Subacute osteomyelitis can occasionally mimic a well-defined lytic lesion.

Clinical evidence of infection, inflammatory markers, MRI findings, and tissue sampling may help differentiate infection from tumor.

Treatment

General Measures

Operative treatment is generally recommended because continued tumor growth can progressively damage the epiphysis and adjacent articular surface.

The aim is complete local removal while preserving the nearby joint whenever possible.

Surgical Challenges

Treatment may be technically difficult because chondroblastomas often lie immediately beneath the articular surface.

The surgeon must remove the tumor while minimizing damage to the joint cartilage, physis, and surrounding subchondral bone.

Bone Grafting

After removal of the lesion, the residual bone defect is commonly filled with bone graft or another suitable bone-defect substitute.

This provides structural support and promotes healing.

Activity

Pathologic fracture is not usually a major concern with typical chondroblastoma.

Therefore, strict activity restrictions are generally unnecessary unless symptoms, lesion size, postoperative status, or individual anatomy warrant protection.

Physical Therapy

Physical therapy may be useful after surgery to restore joint range of motion, strength, and function.

This is particularly important when preoperative stiffness or postoperative immobilization has limited movement.

Surgery

Because chondroblastoma is a benign tumor, local surgical treatment is usually adequate.

The standard procedure consists of thorough intralesional curettage followed by filling of the resulting defect.

Curettage

The tumor is removed by carefully curetting the lesion from the surrounding bone.

Meticulous removal is important because residual tumor increases the likelihood of recurrence.

Joint Preservation

When the lesion lies directly beneath the articular surface, surgery should preserve as much subchondral bone and cartilage as possible.

Damage to the joint surface may contribute to later stiffness or degenerative change.

Follow-Up

Long-term surveillance is important because recurrence is not uncommon.

Clinical evaluation should assess for recurrent pain, loss of motion, or new joint symptoms.

Prognosis

Overall prognosis is favorable because chondroblastoma is benign.

However, local recurrence remains an important concern.

Recurrence

The recurrence rate for conventional chondroblastoma has been reported at approximately 20% within 3 years.

Recurrence is more likely when the lesion contains substantial secondary aneurysmal bone cyst change.

Complications

The principal complications are local recurrence and joint stiffness.

Joint stiffness may result from the tumor itself, prolonged symptoms, surgical exposure, or postoperative scar formation.

Patient Monitoring

Because recurrence most often develops during the first several years after treatment, serial imaging is recommended.

Radiographs are commonly repeated approximately every 6–12 months for the first 2 years after excision.

Persistent or recurrent pain should prompt earlier reassessment and additional imaging.