Missing data form a ubiquitous problem in scientific research, especially since most statistical analyses require complete data. To evaluate the performance of methods dealing with missing data, researchers perform simulation studies. An important aspect of these studies is the generation of missing values in a simulated, complete data set: the amputation procedure. We investigated the methodological validity and statistical nature of both the current amputation practice and a newly developed and implemented multivariate amputation procedure. We found that the current way of practice may not be appropriate for the generation of intuitive and reliable missing data problems. The multivariate amputation procedure, on the other hand, generates reliable amputations and allows for a proper regulation of missing data problems. The procedure has additional features to generate any missing data scenario precisely as intended. Hence, the multivariate amputation procedure is an efficient method to accurately evaluate missing data methodology.

ObjectivesThe aim of this study is to evaluate long-term facial growth in adults previously treated for an isolated unilateral complete cleft lip, alveolus and palate by two-stage palatoplasty.Materials and methodsUnilateral cleft lip and palate (UCLP) patients of 17 years and older treated by two-stage palatoplasty were invited for long-term follow-up. During follow-up, lateral cephalograms were obtained (n = 52). Medical history was acquired from their medical files. Outcome was compared to previously published normal values and the Eurocleft study.ResultsSoft and hard palate closure were performed at the age of 8 (SD 5.9) months and 3 (SD 2.2) years, respectively. The mean maxillary and mandibular angle (SNA, SNB) were 74.9° (SD 4.2) and 75.8° (SD 3.8). Maxillary and maxillomandibular relationships (SNA, ANB) were comparable to all Eurocleft Centres, except for Centre D. We observed a significantly steeper upper interincisor angle compared to the Eurocleft Centres.ConclusionsThis study describes the long-term craniofacial morphology in adults treated for a UCLP with hard palate closure at a mean age of 3 years. The mean maxillary angle SNA and mandibular angle SNPg were comparable to previous studies both applying early and delayed hard palate closure. The observed upper incisor proclination is likely caused by orthodontic overcorrection in response to the unfavourable jaw relationships. No clear growth benefit of this protocol could be demonstrated.Clinical relevanceThe present study shows the long-term craniofacial morphology of UCLP adults after the Utrecht treatment protocol which includes two-stage palate closure.

Missing data in scientific research go hand in hand with assumptions about the nature of the missingness. When dealing with missing values, a set of beliefs has to be formulated about the extent to which the observed data may also hold for the missing parts of the data. It is vital that the validity of these missingness assumptions is verified, tested, and that assumptions are adjusted when necessary. In this article, we demonstrate how observed data structures could a priori indicate whether it is likely that our beliefs about the missingness can be trusted. To this end, we simulate complete data and generate missing values according several types of MCAR, MAR, and MNAR mechanisms. We demonstrate that in scenarios where the data correlations are either low or very substantial, strictly different mechanisms yield equivalent statistical inferences. In addition, we show that the choice of quantity of scientific interest together with the distribution of the nonresponse govern the validity of the missingness assumptions.

OBJECTIVES In hypoplastic left heart complex patients, biventricular repair is preferred over staged-single ventricle palliation; however, there are too few studies to support either strategy. Therefore, we retrospectively characterized our patient cohort with hypoplastic left heart complex after biventricular repair to measure left-sided heart structures and assess our treatment strategy. METHODS Patients with hypoplastic left heart complex who had biventricular repair between 2004 and 2018 were retrospectively reviewed. Operative results were evaluated and echocardiographic mitral valve (MV) and aortic valve (AoV) dimensions, left ventricular length and left ventricular internal diastolic diameter (LVIDd) were measured preoperatively and during follow-up after 0.5, 1, 3, 5 and 10 years. RESULTS In 32 patients, the median age at surgery was 10 (interquartile range 5.0) days. The median follow-up was 6.19 (interquartile range 6.04) years. During the 10-year follow-up, the mean Z-scores increased from −2.82 to −1.49 and from −2.29 to 0.62 for MV and AoV, respectively. Analysis of variance results with post hoc paired t-tests showed that growth of left-sided heart structures was accelerated in the first year after repair, but was not equal, with the MV lagging behind the AoV (P = 0.033), resulting in significantly smaller MV Z-scores compared with AoV Z-scores at 10-year follow-up (P < 0.001). There were 2 (6%) early deaths. The major adverse events occurred in 4 (13%) patients. The surgical or catheter-based reintervention was required in 14 (44%) patients. CONCLUSIONS The growth rate of heart structures was most prominent during the first year after biventricular repair with lower growth rate of the MV compared with the AoV.