Inclusion Criteria:  Age older than 18 years Ineffective esophageal motility disorder according the Chicago classification (7), defined as ≥ 7/10 (70%) of swallows with weak contraction (distal contraction interval (DCI) between 100mmHg/s/cm and less than 450 mmHg/s/cm) or ≥ 5/10 (50%) of swallows with failed peristalsis (DCI <100mgHg/s/cm)Performance of partial fundoplication (180° anterior or 270° posterior) at Spital Limmattal Informed Consent as documented by signature  Exclusion Criteria:  Age under 18 years Pregnancy Normal preoperative esophageal motility Other specifically defined esophageal motility disorders such as Nutcracker or Jackhammer esophagus Preoperative presence of a hiatal hernia with migration of >20% of stomach in the chest Revisional surgery (after other procedures for reflux or at the hiatus)