Benign Bone Tumors of the Foot - Section 1

[intro][1] [2] [3] [4]

Osteochondroma

Osteochondroma may be the most common bone tumor in the foot, although that is not the case in my practice. This tumor affects teenages and young adults in their twenties, but occasionally may be see in older adults who have had delayed seeking medical advice. The male female ratio is 1.6 to 1. The tumor is almost always located on the metatarsals. The tumor presents as a painless lump that increases in size with growth of the patient.

In the distal tibia and fibula, osteochondromas may present as acute or recurrent ankle sprains, ankle pain, ankle stiffness, or a palpable mass. The lesion may cause plastic deformation of the ankle and varus deformity. The deformity will remodel after tumor removal, and younger patients remodel more completely. Substantial ankle varus did not remodel. (Chin el al JBJS 82A Sept 2000 1269 - 1278)

Radiologically, the tumor arises from the surface of the bone and the cortex and medullary cavity of the lesion is continuous with the cortex and medullary cavity of the bone. A CT scan can be very helpful in confirming this and may thus confirm the diagnosis. MRI is usually not necessary for diagnosis but may help define the nearby neurovascular structures in preparation for surgery. MRI will also allow precise measurement of the thickness of the cartilage cap on the lesion, which is an indicator of the potential for amlignant degeneration.

Treatment consists of simple excision by osteotomy through the base of the stalk. Surgeons do not need to remove every vestige of the stalk or base of the tumor to achieve complete resolution of the symptoms. The neurovascular bundle may be very near the intended osteotomy site. Damage to the neurovascular structures of the foot is not an acceptable complication from what should be a simple removal of a benign bone tumor.

Surgical treatment should be deferred until the patient is at or near skeletal maturity, if possible. The lesions are less likely to recur and are better defined so that complete removal can be easily accomplished and damage to the growth plate as well as recurrence can be avoided.

Enchondroma

Enchondromas comprise 10 - 15% of bone tumors in the foot. For unknown reasons, the bones of the hand and foot are very common locations for these tumors. Locations include the metacarpals and phalanges, and the cuneiform. Enchondroma is rare in the hindfoot.

Enchondromas present in the early adult years. Patients may have pain following activities, a swelling or lump on the bone, or a pathological fracture through the lesion. A few patients have multiple enchondromas and warrant special attention and possibly referral to a bone tumor specialist. Radiographically, the lesion is expansile and lytic, with a variable amount of matrix mineralization. The matrix has been described as "popcorn" or "stippled". The matrix consists of nodules of cartilage which tend to calcify at the periphery, so that on high quality radiographs "ring and arc" forms are visible. Clear demonstration of these helps confirm the diagnosis so that biopsy is not necessary.

Giant cell tumor is commonly mistaken for enchondroma, and both occur in the foot in similar locations. GCT has no matrix calcification and occurs exclusively in the metaphysis and epiphysis adjacent to the growth plate, often extending right up to the joint surface. In small bones that are completely filled with tumor, these lesions may be nearly impossible to distinguish. In enchondroma, MRI will show that the lesion has signal characteristics identical to cartilage. Treatment is very different so the surgeon should be careful to separate these two tumors.

Enchondroma may be highly expansile, especially in small bones such as the phalanges, so that the bone may be completely involved, deformed, and even destroyed. This is not considered a sign of malignancy in enchondromas of the foot or hand. This same behavior seen in a long bone such as the femur or humerus would be interpreted as a strong suggestion of malignancy.

Treatment depends on how expansile the lesion has become. Lesions inside the medullary cavity may remain totally latent, are usually asymptomatic, and not treatment other than intermittent radiographic follow-up is indicated. Expansile lesions cause cosmetic and functional loss and pathological fracture. Enchondromas recur very rarely following treatment, so that total eradication of the lesion is not necessary, rather the goal should be is restoring appearance and function. Curettage and bone grafting is usually adequate. Highly expansile lesions in the phalanges are probably best treated with amputation of the involved portion of the toe, since the function and cosmetic results are not likely to be acceptable following attempted curettage.

Benign bone tumors continued >>

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