Statistical analysis
The trial was designed to detect an MCID in the DASH score of at least 10 points with a standard seviation (SD) of 18 (effect size d = 0.67). Our pretrial assumption was that the operative treatment arms (LP and HA) would gain an average improvement of 10 points of difference compared to nonoperative treatment (arms 1:1:1), and we used ANOVA (alpha = 0.05, power = 0.8). We assumed a common SD of 18 points and a between-group variance as 25 points. That would have led to an estimated sample size of 66 patients per group, making a total of 198 patients, including an estimated 10% dropout rate. We conducted a preinterim analysis and found no significant differences between the groups. The nonoperative treatment became more common during the study period in the Nordic countries, and in the cases needed, the reverse prosthesis was used. These factors led to a higher-than-expected exclusion rate toward the end of the trial, followed by a premature termination of the trial.The baseline characteristics were analyzed with descriptive statistics. The primary analysis was carried out with 95% confidence intervals (CIs) after all patients had completed the 2-year follow-up after initial treatment.The difference between groups was estimated using a linear mixed model allowing for repeated measures. Study group and time of assessment (baseline, 3, 6, 12, 24 months) were included as fixed factors, patients as random factors. The model included interactions between study group and time of assessment. The model was used to estimate the treatment effect as the absolute difference between the groups in DASH score (mean and 95% CIs) and Continuous outcomes were compared using the Student 