The Impact of Maxillary Osteotomy on Speech Outcomes in Cleft Lip and Palate: An Evidence-Based Approach to Evaluating the Literature

Abstract

Objective To undertake a critical and systematic review of the literature on the impact of maxillary advancement on speech outcomes in order to identify current best evidence. Design and Main Outcome Measures The following databases were searched: PubMed, CINAHL, and The Cochrane Controlled Trials Register. In addition, reference lists were hand searched for additional articles. Using a predefined framework and set criteria, evidence was evaluated using the assignment of levels of evidence (at least Level III on the evidence hierarchy), calculation of post-hoc power (≥ 0.8), effect size (Cohen's d ≥ 0.5), and adaptation of the parameters as set out by The Cochrane Collaboration. Results Of the 40 studies identified, the majority (68%) fell within Level lll.ii, representing cohort-type studies and a fifth (20%) within Level IV, the weakest form of evidence. Power and effect size calculations were only possible in 9 studies for different speech outcomes, and only seven studies met the set criteria for best evidence. Accordingly, current best evidence for articulation exists only for a noncleft population, is conflicting for resonance and nasalance, and is mixed for velopharyngeal function depending on which instrumental measure is used. Conclusions There is an obvious need for further prospective research in the field with strong speech methodology such as the undertaking of interrater and intrarater reliability, adequate follow-up, and sufficient sample sizes based on a priori power analyses. Methodologic issues are discussed and recommendations made.