Massive Osteolysis (Gorham-Stout / Vanishing Bone Disease)

The single most important surgical principle: conventional bone graft is eaten by the disease. This is not a theoretical risk but the consistent experience since the condition was characterised - grafting has proved disappointing because the graft itself undergoes osteolysis, and there is no regeneration after the resorption to compensate. A cancellous or structural allograft placed into active disease is a further meal for the process, and the reconstruction fails. Four consequences follow, and together they are the answer to "how would you reconstruct this?":

Amputation retains a place in the rare limb rendered unreconstructable and painful by relentless progression, and saying so is not defeatism: it is the honest end of a spectrum in a disease with no reliable cure, and an examiner asking about the limits of reconstruction is asking whether the candidate knows it.

No consensus criteria exist, which is not the same as no criteria at all. The set that is actually cited, and the one to have ready when an examiner asks how the diagnosis is made, is the eight criteria described by Heffez and colleagues in 1983:

Criterion 4 is the one that costs time. Progressive resorption can only be shown by comparing images separated by an interval, which is why the average interval from first symptom to diagnosis in a systematic review of 206 patients was 3.5 years. A single radiograph, however striking, cannot make this diagnosis.

The blood tests are normal, and that is a finding rather than an absence of one. Serum calcium, phosphate, alkaline phosphatase and parathyroid hormone are characteristically within normal limits despite dramatic bone destruction. Normal calcium and PTH exclude hyperparathyroidism and its brown tumours; a normal alkaline phosphatase is consistent with criterion 3, since there is no osteoblastic response to raise it; and the absence of a paraprotein and of anaemia or renal impairment argues against myeloma. Record them, because "the biochemistry was normal" is part of the positive case, not a gap in the work-up.

The spine is involved in 46% of reported patients - more often than the ribs, the hip or the mandible - and it is the site at which the disease does harm by a mechanism entirely separate from the chylothorax.

What goes wrong. Vertebral body resorption removes anterior column support, so the segment collapses and kyphoses. Because there is no reparative response, the deformity does not stabilise the way a healed compression fracture does; the bone continues to disappear beneath any construct. Resorption of the posterior elements or extension of the angiomatous soft tissue into the canal adds direct compression. The result is progressive kyphotic deformity, instability and myelopathy or paraparesis, which in the reported literature sits alongside chylothorax as the reason patients die or are permanently disabled. Thoracic disease is particularly unforgiving because the canal is narrowest there and the cord's blood supply most tenuous.

What to do about it. Involvement of a vertebral body is an indication for baseline MRI of the whole spine - not a single level, because lesions are multiple in 77% of patients and a contiguous segment may be silently involved - and for serial neurological examination with a documented level rather than a global impression. Progressive deformity, instability or any neurological sign is an indication for stabilisation, and the operative principle is the same one that governs surgery anywhere in this disease: instrument beyond the affected segments into bone that is not involved, because fixation anchored in disease-bearing bone will loosen as that bone dissolves. Systemic therapy is started alongside, not instead of, stabilisation where the cord is threatened.

The chest and the spine are not separate problems here. Thoracic vertebral and rib disease frequently coexist, so a patient presenting with vertebral collapse needs the chest imaged for effusion, and a patient with a chylothorax needs the spine imaged for the lesion that will disable them later.