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Canadian Journal of Surgery logoLink to Canadian Journal of Surgery
. 2001 Dec;44(6):421–427.

Standard anatomical medullary locking (AML) versus tricalcium phosphate-coated AML femoral prostheses

DWC (Bill) Johnston *,, Donna M Davies , Lauren A Beaupré , Guy Lavoie *
PMCID: PMC3692675  PMID: 11764874

Abstract

Objectives

To compare the preliminary rate and amount of bony ingrowth and calcar resorption between patients receiving either a standard anatomical medullary locking (AML) or a tricalcium phosphate (TCP)-coated AML femoral prosthesis and to compare preliminary clinical results.

Design

A prospective, randomized, double-blind clinical trial.

Setting

An acute care tertiary institution.

Patients

Between January 1993 and March 1995, 92 patients underwent primary total hip arthroplasty (THA). They were randomized to 2 groups of 46 — a control group or a treatment group. Of the 46 subjects enrolled in each group, no significant differences were seen preoperatively with respect to age, sex, diagnosis, clinical and radiographic assessment. Seventy-one patients were followed up for 24 months.

Interventions

Insertion of either a standard AML femoral implant (control group) or a TCP-coated AML femoral implant (treatment group).

Outcome measures

The degree of hypertrophy, calcar atrophy and the number of spot welds on standard postoperative radiographs at 6, 12 and 24 months. Clinically, assessment according to the Société internationale de chirurgie orthopédique et de traumatologie (SICOT) scale and a 100-point visual analogue scale (VAS) for pain.

Results

There were no prosthetic stem revisions in either group at the 24-month follow-up. Radiographically, bony ingrowth was not significantly different in the TCP-coated stem, by χ2 analysis of the degree of hypertrophy and number of spot welds present. Also by χ2 analysis, the degree of calcar atrophy was not significantly different between groups. The mean VAS score for pain at 24 months was 12.5 for the control and 12.1 for the treatment group. No significant differences were seen in any of the clinical categories of the SICOT Scale over the 24-month interval.

Conclusion

The objective of TCP-coating — to increase the rate and amount of bony ingrowth while reducing the rate of calcar resorption in non-cemented THA — was not achieved by 24 months postoperatively in our study.

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