Editorial Commentary: Maximal Outcome Improvement: Another Arrow in the Quiver.

Clinically important outcome assessment has been a point of increasing emphasis in the orthopaedic literature. The minimal clinically important difference, patient acceptable symptom state, and substantial clinical benefit are the most reported in the hip preservation literature. Maximal outcome improvement (MOI) is now also being reported; however, its relation to patients undergoing hip preservation surgery is not well understood. The threshold values that represented satisfaction with surgery were 54.8%, 52.5%, 55.5%, and 55.8% of the MOI for the modified Harris Hip Score, Nonarthritic Hip Score, visual analog scale score for pain, and International Hip Outcome Tool-12 score, respectively. Although the MOI is helpful for characterizing outcome improvement, established measures such as substantial clinical benefit may be better used to grade outcomes in patients with high preoperative function.