The authors concluded that there was no clinical or radiologic evidence of benefits of application of hydroxyapatite coating on a femoral component in uncemented primary total hip arthroplasty. The authors’ conclusions reflected the evidence presented, but caution is warranted given a number of flaws in review processes and the small sizes of the reviewed studies.

To assess the clinical and radiographic effectiveness of hydroxyapatite coating in uncemented primary total hip arthroplasty.

MEDLINE and EMBASE were searched between January 1980 and September 2007 for articles written in English, German or French. Search terms were reported. Reference lists of identified articles were handsearched.

Randomised controlled trials (RCTs) that compared porous-coated femoral components with or without hydroxyapatite coating of identical geometry in primary uncemented total hip arthroplasty were eligible for inclusion. Only studies that assessed objective and validated clinical and radiographic outcomes were considered.

Included studies evaluated a varied number of hydroxyapatite-coated and porous-coated hips (range 28 to 318). Follow-up periods ranged from one to 10.5 years. Prostheses used were varied. Most patients were male and their mean age ranged from 45 to 64 years. Outcomes evaluated included: Harris Hip Score; Postel d’Aubigne; and a variety of radiographic outcomes, such as subsidence, radioactive lines and endosteal bone ingrowth (Spot Welds).

Two reviewers independently assessed studies for inclusion. Disagreements were resolved through discussion or referral to a third reviewer.

The methodological quality of the included studies was assessed using the following criteria: adequacy of randomisation; allocation concealment; blinding (of care providers, patients, outcome assessors); balance of baseline measures; control for cointerventions; adherence to interventions; outcome measures (reliability and timing of measurements); withdrawals and missing values; and intention-to-treat analysis.

Two reviewers independently assessed study quality. Inter-rater reliability of scores was assessed using Cohen’s Kappa.

Reviewers extracted mean scores and standard deviations for hydroxyapatite-coated and porous-coated femoral components to calculate a mean difference and 95% confidence interval (CI) for Harris Hip Score. For binary outcomes (radioactive lines, endosteal condensation), the number of patients with hydroxyapatite-coated and porous-coated femoral components was extracted and used to calculate relative risks (RRs) and 95% confidence intervals.

The authors stated neither how data were extracted for the review nor how many reviewers performed the data extraction.

A pooled weighted mean difference (WMD) with 95% CI was calculated for Harris Hip Score. Pooled relative risks with 95% confidence intervals were calculated for radiographic outcomes. Results were combined using the Mantel-Haenszel method. Statistical heterogeneity was assessed using the I² test. A random-effects model was applied when heterogeneity was detected (defined as I²=greater than 30%).

Eight RCTs (n=857) were included in the review. Inter-rater agreement in study quality assessment was high (Kappa=0.799). Allocation sequence generation was adequate in all studies. Allocation concealment was inadequate in one study. Only four studies were double-blinded.

Overall, there was no significant difference between hydroxyapatite-coated and porous-coated femoral components in both clinical and radiographic scores: Harris Hip Score (WMD 1.49, 95% CI -2.32 to 5.31; five RCTs); radioactive lines (RR 1.02, 95% CI 0.90 to 1.16; five RCTs); and endosteal condensation (RR 1.04, 95% CI 0.88 to 1.23; five RCTs). A random-effects model was used to compare Harris Hip Score due to the presence of significant heterogeneity (I²=32.1%).

There was no clinical or radiologic evidence of benefits of application of hydroxyapatite coating on a femoral component in uncemented primary total hip arthroplasty.

The review question was clearly stated. Two major databases were searched for publications in English, German and French, which raised the possibility of language bias. Relevant pre-1980 studies may have been missed given the restricted search strategy. No efforts were made to search for unpublished studies and publication bias was not assessed, hence the possibility of publication bias could not be excluded. Appropriate methods were used to minimise the risk of reviewer error and bias in study selection and validity assessment, but not explicitly with data extraction. Validity was assessed using appropriate criteria. The methods used to pool the results appeared appropriate. The authors’ conclusions reflected the evidence presented, but caution is warranted in the application of the conclusions given a number of flaws in the review processes and because the sample sizes were small (inadequate to detect differences in treatment effects).

The authors did not state any implications for practice or further research.

Not stated.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.