Aim: To study the influence of cement restrictors on the thickness and quality of femoral cement mantle.

Methods: In this prospective study, there are 49 cases of Hardinge restrictor and 33 cases bone block restrictor were used for Charnley hip replacement. The operation was carried out by one surgeon on 78 patients between 1 March 2003 and 30th April 2004. Each preoperative X-rays were templated for the placement of restrictor. Intraoperatively, a calibrated holder for the cement restrictor was used aiming at keeping the distal cement height within 2-3 cm of the tip of the femoral prosthesis. Postoperative X-rays were checked for cement mantle thickness and quality.

Results: The preoperative target of having a distal cement height of 2-3 cm was achieved as seen on postoperative X-ray in only 60.6% of the bone block group and 30.6% of the Hardinge group. Distal migration of the restrictors was associated with non-homogenous cement mantle in zones 3, 4 and 5 but did nor affect zone 2, 6, or7. As the restrictor remained within 20-30 mm, the thickness of mantle is maintained between 9mm and 21mm in zone 4. This finding is statistically significant with the p value of 0.001.

Conclusion: Though the bone block was marginally better than Hardinge restrictor, we conclude that the current available cement restrictors are not sufficiently good enough to offer a good cavity for cement intrusion in to the bone; further restrictors need to be developed and tested before clinical use.