Outcomes of augmented vs unaugmented Knapp procedure for double elevator palsy

Investigators used retrospective data to compare outcomes from an augmented version of the Knapp procedure vs. the standard Knapp procedure in patients with double elevator palsy (DEP).

Study design

This single-center retrospective chart review focused on 45 Turkish patients with congenital DEP, involving monocular elevation deficiency and no inferior rectus restriction. The augmented Knapp procedure involved the standard superior transposition of the medial and lateral rectus to the superior rectus insertion, with the addition of two Dacron augmentation sutures 8 mm from the superior rectus insertion that incorporated sclera and 25% of the respective horizontal rectus muscle belly. The primary objective was the reduction of the vertical deviation to >6 PD and improvement of duction deficiency to −1 or less at the 12-month follow-up point.

Outcomes

The augmented Knapp group had a greater postoperative reduction in hypotropia than the standard Knapp group, as well as a lower re-operation rate (54% vs. 12%, respectively). There were also greater improvements in elevation deficit in patients given the augmented Knapp procedure than in patients given the standard Knapp procedure. No additional complications or overcorrections were reported.

Limitations

It was unclear why the augmented Knapp procedure was chosen in some cases and the standard Knapp procedure in others. As the study was a retrospective review, surgeon-specific sources of bias were not addressed.

Clinical significance

The augmented Knapp procedure in this group's experience did not overcorrect patients with deviations >8 PD and elevation deficits of −2 or greater. The study design makes it difficult to say that the augmented procedure is superior to the standard Knapp procedure, though it could be considered for patients with large deviations and elevation deficits.