UnitedHealth Group Inc. will reprocess claims using new medical guidelines as part of a settlement of two class actions that allege it wrongly limited coverage for spinal surgeries.

The settlement follows a policy change instituted in March under which United began treating lumbar artificial disc replacement surgery as a proven treatment that’s medically necessary if certain criteria are met. This policy change is a direct result of the litigation, and United will continue the policy unless new medical literature justifies...