Abstract
Introduction: An intra-medullary cement restrictor is an integral part of modern cementing technique in total hip arthroplasty. Failure of the restrictor to contain cement, flawed surgical technique or dislocation of the restrictor during pressurisation can all result in a deficient cement mantle. A radiographic analysis of hip replacements using a biodegradable restrictor was undertaken to determine the incidence of restrictor failure, the influence of femoral canal morphology on restrictor failure and to describe the cement mantle quality in successful and failed distal cement restriction.
Methods: x-rays from 299 consecutive hip replacements using the amberflex restrictor were analysed. The cortical index, canal-calcar ratio and femoral type, according to Dorr, were recorded. 3 modes of restrictor failure were identified:
-
Cement leakage –cement was seen to have escaped past the cement restrictor
-
Restrictor dislocation – the restrictor was 4 or more centimetres distal to the stem tip
-
Restrictor penetration –the tip of the femoral stem was resting on the restrictor All cement mantles were given a barrack grading.
Results: 84 cases of restrictor failure were observed – 44 dislocations, 24 leakages and 16 penetrations. The mode of failure was not correlated with femoral type, cortical index or canal-calcar ratio. A strong association was found between restrictor failure and grades c and d cement mantles using the chi squared test. A correlation between cortical index, canal-calcar ratio and femoral type was not observed.
Discussion: The ability of a cement restrictor to occlude the femoral canal and resist pressurisation is very important if a good quality cement mantle is to be achieved. Technical error was likely to be an important factor in many of the observed cases of restrictor failure, especially penetrative failure. Surgical technique is more important than femoral morphology in determining the successful use of this restrictor.
Correspondence should be addressed to The Secretary, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
