This chapter will discuss the subject of distortions in the proper bone texture as a result of proliferation of various bone tissues or of aberrant creation of such.

Those benign cases can be sorted into groups according to the kind of tissue that composes them, i.e. cartilage, connecting tissue, bone, blood vessels etc.

Some of those cases are revealed through pain, formation of bony "bumps" in the limbs, malformation or fracture due to fragility of the bone. Many cases will not manifest themselves at all and will be detected by coincidence, usually following an x-ray performed due to a different reason. In most cases, the diagnosis is established by conventional x-ray studies, in others - the diagnosis can be confirmed by biopsy only.

Treatments of those bone defects are diverse, starting from a simple follow-up and up to surgical removal of the lesion in cases of disablement, pain or impending fracture due to bone weakness. Occasionally addition of substitute bone or bone graft is being used to fill a space created by the lesion or the biopsy.

The following demonstrates a few examples of the most common afflictions:

1.     Osteochondroma (derived from Greek: chondros = cartilage, osteon = bone)

This benign tumor, belonging to the group of cartilaginous tumors, is the most common to occur. It is often mushroom shaped, with a narrow or possible broad stem protruding above the bone surface. It is characterized by a cartilaginous area at its top (which does not show in the regular x-ray) and an osseous area (composed of bone) underneath to its base. The tumor is often positioned next to the growth plate, typically at the edges of long bones, but the tumor might involve any skeletal bone. Typically this is an isolated lesion and only rarely it comes in a widespread form, constituting a part of a disease which causes numerous afflictions of this kind. Normal growth factors encourage proliferation of the Osteochondroma and during puberty, parallel to the end of the natural growing process of the skeleton, its activity is stopped as well and the growth is halted. The defect is usually painless but might be manifested by a lump in the limb. Transformation into malignancy is less than 1%. If the bone lesion is irritating, it is commonly surgically removed.

2.     Osteoid Osteoma (derived from Latin: shaped like a bone tumor)

A bone lesion that belongs to the group of osseous (bone building) tumors. Typically afflicted bones are those of the thigh and the shank, but it can also be found in all other skeletal bones, including the vertebrae. As opposed to the majority of benign tumors, this bone lesion is characterized by severe pain, which typically occurs during night time. The origin of the tumor is a tiny, extremely active nucleus in the bone cortex (outer surface), which forms a bony-like tissue and secrets pain-arousing substances. On x-rays the nucleus manifests itself as a radiolucent zone of about 2mm in diameter surrounded by reactive bone formation, which looks like a calcification and condensation of the bone. Technetium bone scan is highly sensitive in detecting the lesion, and will be helpful in establishing the diagnosis. In cases in which the nucleus does not show up on regular x-rays, a CT might be helpful. Treatment can be conservative by the use of anti-inflammatory medications such as aspirin. The bone lesion is self-limited by nature, and its activity ceases after a few years. Sometimes the pain or the amount of drugs required for its relief are intolerable, in which cases, invasive treatment is recommended. This can be achieved by surgical excision of the active nucleus or by means of radio frequency ablation under imaging. Destroying the nucleus immediately brings to relief of pain, and full cure is achieved.

3.     Simple Bone Cyst

An osseous defect which is not a tumor. The cyst is caused by the lack of bone formation during growth. The cyst presents a void in the bony canal with the diameter of up to several centimeters. The most common locations for this occurrence are the arm and thigh bones at their proximal parts. Those defects go unnoticed and are detected randomly, following an x-ray or a fracture caused by weakening of the bone. Diagnosis is performed by an x-ray in which the defect is manifested by an ellipsoid void in the center of the medullary canal. Sometimes it demonstrates numerous partitions or lobules. If significant weakening of the bone is suspected, the void can be injected with steroids or bone marrow drawn from the ilium bone, or surgically curetted and filled with bone graft or a bone substitute.

4.     Non Ossifying Fibroma

5.     Aneurysmal Bone Cyst

Contrary to a simple bone cyst, this bone lesion contains proliferating tissue, is more active and therefore demonstrates a slow growth that causes local swelling of the bone. The treatment, depending on its activity, will include surgical curetting of the lesion and filling by bone graft or bone substitutes.