The progression and recurrence of some bone cysts could be related to continued high pressure within the cyst. This might explain the benefit of leaving Kirschner wires implanted into the cyst and, perhaps, injecting the cyst with cortico-steroid.
The following case seems to support this thesis.
A 38 year old opera singer presented with a fracture of the surgical neck of the humerus, associated with an extensive ’simple’ bone cyst. For some years she had been having an “aching discomfort” in the arm. The fracture was treated by forearm support for six weeks, and consolidated. A protecting support was supplied in anticipation of the cyst healing.
However the cyst remained, increasing slowly in size. Bone grafting was considered, but the patient wished to avoid a scar which would detract from her stage appearance, and she was unable to set aside time for a protracted convalescence.
At four years post-injury, needling the cyst demonstrated a pressure of about 90mm of clear fluid from within the cyst. A Spitz-Holtzer ventricular drain was inserted into the cyst, draining into the peritoneal cavity and left for 22 months.
Follow-up radiology over the year after inserting of the drain showed reduction in the size of the cyst, thickening of the cortex, reduction of scalloping and deposition of visible bone within the cyst and around the drain. The support was abandoned.
Since the “aching” pain experienced prior to the breakage had not reoccurred the patient declined further radiology.
The limb has withstood the rigours of bringing up children, as a single mother and all the loads of daily life with full upper limb function, over a 23 year post surgical follow-up.
Dr J P Driver-Jowitt 
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