Purpose: To perform a comprehensive quantitative review of the published literature and to assess the methodology of studies comparing the surgical outcomes in minimally invasive hip arthroplasty (MIHA).
Methods: We conducted a comprehensive literature search using Medline, Embase, Cochrane, CINAHL and Google Scholar. The bibliographies of papers were also examined. All relevant articles in peer-reviewed journals were retrieved except those not mentioning outcomes, case reports, review of literature and letters to editors. Two authors independently scored the quality of the studies using a modified Coleman Methodology Score with 10 criteria which allow critical analysis of the design and implementation of a particular study. The results are recorded as a final score between 0 and 100. We collected data for year of publication, type of study, patient numbers, surgical method, follow-up, complications and patient satisfaction.
Results: Thirty-six studies met our inclusion criteria giving details of 6434 HAs, 78.5% (4031) of which were implanted using MIHA techniques. The only statistically significant outcome was a reduction in length of hospital stay (P = 0.02). With no significant difference noted between the two groups with respect to operating time, blood loss, dislocation and revision rates, neurological injury and incidence of peri-operative fracture, patient selection and surgeons' experience may have had a significant effect on outcome. For instance, studies reporting outcomes on an average patient age of 48 years had significantly different results to one reporting on patients with a mean age of over 70 years. Scores were predominantly low for quality of the studies, with patient number, follow-up time and validated outcome measures being the weakest areas.
Conclusion: At present, there is still a lack of quality evidence to advocate the expansion of MIHA. The better designed studies suggest that it should even be limited further to recognized expert centres. The complication rates and learning curve may be altered by changes in training and adapting surgical techniques. We emphasize the need for meticulous design in future studies comparing the outcomes of these two procedures.