Abstract
Vertebroplasty (VP) is a new prophylactic treatment for preventing osteoporotic compression fractures of vertebral bodies. During this procedure polymethylmethacrylate (PMMA) is injected into several vertebral bodies. However, there is the concern, that fat embolism (FE) and acute hypotension could occur as in a variety of other orthopaedic procedures.
This study was undertaken to investigate whether FE and acute hypotension are potential complications of VP using an animal model.
In six sheep 6.0 ml PMMA were injected unilaterally into L1. Transesophageal echocardiography was used to monitor the pulmonary artery for bone marrow and fat particles until 30 minutes postoperatively. Pulse, arterial and venous pressure were also recorded. Post mortem the lumbar spine and the lungs were harvested. The lungs were subjected to histological evaluation.
The first showers of echogenic material were visible approximately 7.0 seconds after the beginning of the cement injection and lasted for about 2.5 minutes.
Injection of bone cement elicited a very rapid decrease in heart rate after 2.0 seconds followed by a fall in mean arterial pressure after 6.0 seconds. A maximum fall in heart rate was accompanied by a delayed fall in mean arterial pressure of 33.0 mmHg (P=0.0003) at 36.0 seconds. Heat rate had returned to baseline by 89.0 seconds and had increased by 10.0 beats/min (P=0.02) at 25 minutes. Mean arterial pressure had recovered by 209.0 seconds and was not different to the baseline at 25 minutes.
The post mortem inspection revealed disseminated haemorrhages on the lung surface and throughout the parenchyma mainly in the caudal lobes of all six animals. No leakage of cement into the spinal cord was detected. In histology fat globules and bone marrow cells were observed in both the smaller and larger vessels throughout the lung.
This study clearly shows that VP resulted in a two-phase decrease in heart rate and arterial blood pressure. The first phase was probably due to an autonomic reflex and the second phase was due to the passage of fat emboli through the right heart and obstructing the lungs.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
