Abstract
One of the major long term problems of total shoulder replacement is loosening of the glenoid component. Since 1997 we have been using atmospheric pressure to drive cement into the interstices of the glenoid trabecular bone by lowering the intraosseous pressure. This is achieved by introducing a wide bore needle into the base of the coracoid process and attaching it to surgical suction. During this period approximately 200 Tornier Aequalis shoulder replacements were performed by the senior author. For the purpose of this detailed study 20 consecutive cases were studied.
Good exposure of the glenoid is achieved using an extended approach and aggressive surgical releases. The surface is prepared according to the manufacturers recommendation. The base of the coracoid is now exposed and drilled with a 3.5mm AO drill bit, angled so as not to collide with the keel of the glenoid component. A Verres needle is hammered into the glenoid at this point and connected to a separate, second suction apparatus, placed on high suction during final lavage, cement insertion and cement curing. Blood and lavage fluid can be seen to be sucked from the glenoid during preparation and cementation.
Standard true antero-posterior radiographs were taken by the same experienced radiographer in the plane of the glenoid face two days following surgery, and at 3 months and one year. A Mitotoyu digital microcalliper with a resolution of 0.1mm was used to determine the depth of cement intrusion and presence of lucent lines. Three independent observers measured each radiograph. Analysis of interobserver error shows agreement between observers. For assessment the glenoid was divided into five zones – Superior flange; superior slope of keel; base of keel; inferior slope of keel; inferior flange.
No patient had a complete lucent line around the glenoid component. Four patients had a single zone lucent line (ranging from 1.1mm to 1.7mm) None of these patients had a lucent line around the keel, and those four areas of lucency under the superior or inferior flange were more likely due to incomplete removal of articular cartilage than a failure of cement technique.
The reported prevalence of glenoid lucent lines varies from 22% to 89%. The significance of glenoid lucent lines is controversial but several studies have reported a direct relationship between the presence of radiolucent lines and the development of loosening of cemented components.
Secure cement technique is more difficult in the shoulder than in the knee or hip. Access is tighter, bleeding more difficult to control and peroxide should not be contemplated because of close proximity of the axillary nerve to the glenoid. Classic socket pressurisers can not fit into such a small space. We have found that the second sucker technique is extremely effective in establishing a secure cement-bone interface during glenoid replacement.
These abstracts were prepared by Mr Cormac Kelly. Correspondence should be addressed to him c/o British Orthopaedic Association, Royal College of Surgeons, 35-43 Lincoln’s Inn Fields, London WC2A 3PN.
