Abstract
There are good evidence that the distal canal restrictor improves pressurisation. Bone block and Hardinge restrictors are among the commonly used restrictors in UK.
During the introduction of cement, the restrictors tend to migrate. The effect may cause significant change in the size and thickness of the cement mantle. One of the determinants of early dramatic failure is the size of the cement mantle.
In our study, we compared the cement mantle thickness and amount of migration with Bone block restrictor and with Hardinge restrictor. The measurements were done in the standard AP x-ray of the hip taken in the post operative period. All cases were operated by one surgeon. The position of the either of the restrictor were maintained in all cases to 1.5 cm below the tip of the stem. Measurements were made for the cement mantle thickness, the distance between the tip of the stem and restrictor and canal diameter.
One observer who was not involved in the operative procedure evaluated 69 x-rays. Twenty seven cases of bone block restrictor and 42 cases of Hardinge restrictors were used.
At the end of our study, we conclude that both restrictors migrate with pressurisation. The amount of migration with Hardinge restrictor is more than bone block restrictor (21.5mm Vs 14.4mm) which is significant (p-0.007). The amount of migration had not affected the zone-4 cement mantle thickness (p-0.450). With the use of either restrictors, migration was influenced by the canal diameter (p-0.00). Canal diameter did not affect the cement mantle thickness ( p-0.368). We conclude that bone block restrictor is superior in withstanding pressurisation
Honorary Secretary Mr Bimal Singh. Correspondence should be addressed to BOSA (British Orthopaedic Specialists Association), c/o Royal College of Surgeons, 35 – 43 Lincoln’s Inn Fields, London WC2A 3PE.
