Precordial Doppler evaluation of simple bone cyst injection.

BACKGROUND: A randomized prospective trial of marrow-versus-steroids treatment of solitary bone cyst was ongoing. Protocol required contrast injection of the cyst. A subpopulation was noted to have large, rapid venous outflow of contrast material (omnipaque). Central embolization and resultant acute respiratory distress syndrome has been reported with bone marrow transplant. Particulate injection can result in bradycardia, low exhaled CO2, decreased SaO2 and voltage changes on electrocardiogram. METHODS: Precordial Doppler can measure flow and turbulence centrally after a peripheral cyst injection. Our cases were monitored with precordial Doppler as well as heart rate, ETCO2, blood pressure, electrocardiogram, and pulse oximetry. RESULTS: Five patients/7 injections were noted to have large and rapid outflow veins from solitary bone cyst. The Doppler showed increased signal in all 7 particulate injections (2 steroid injections, 5 bone marrow aspirates and cyst injections.) One marrow injection resulted in transient bradycardia and decreased blood pressure with no sequelae. One developed transient decrease in exhaled CO2. CONCLUSIONS: Rapid outflow has been reported in the past but precordial Doppler monitoring of injection into peripheral cysts is not reported. The potential for embolization with serious physiologic effects is a concern. Others have advocated injection of more particulate substances, such as calcium, sulfate, and demineralized bone matrix. This Doppler technique may be valuable for monitoring the potential harmful effects of these injections and lead to a better understanding of failure of cyst healing due to rapid outflow of material. LEVEL OF EVIDENCE: Level IV case series with poor reference standard.

Cyst index: a nonpredictor of simple bone cyst fracture.

PURPOSE: Treatment is indicated for simple bone cysts (SBC) with high risk of fracture. The cyst index was described as a method to determine if a cyst is at high risk or low risk of fracture. STUDY DESIGN: The cyst index of 32 femoral and humeral SBCs was determined by 8 reviewers. The risk group cyst index was compared with whether a fracture took place. Sensitivities, specificities, and positive and negative predictive values were calculated across varying cutoff levels. Intraobserver and interobserver reliability testing for 10 cysts was made. RESULTS: Receiver operator curves demonstrate that no cutoff value gave an acceptable level of both sensitivity and specificity. The mean value for the cyst index was significantly different for different observers (P < 0.05). CONCLUSIONS: This study does not validate the cyst index to be an accurate predictor of fracture. The test has low intraobserver and interobserver reliability. CLINICAL RELEVANCE: The cyst index cannot reliably discriminate between the patients that will fracture and those that will not.