I did one between third and fourth year and definitely do not regret it. In my opinion there are several benefits.
1. Publications - I had a very productive year and every interviewer I have had was thoroughly impressed with my CV. Definitely worthwhile especially if research is weak for you.
2. I think it is better to strengthen your application BEFORE you potentially don't match (if this is something you are concerned about). I believe it is harder as a re-applicant, and you have less time to improve your CV (ERAS submitted 9/15). Also it shows dedication to Orthopedics by being willing to take an extra year to ensure you match.
3. Decompress some of the stressful things you need to do mid third year to early 4th year (schedule aways, write personal statement, fill out ERAS, get letters of recommendation, take step 2 etc.) Made my life way easier for sure.
4. An opportunity to make connections, get a strong letter of recommendation, and have someone else willing to go to bat for you and make calls since they know you very well after 1 year.