Surgery stats help



hey everyone, first time poster here. I used to be a stats geek but four years of medical school and five years of residency have helped wipe that from my brain. Now I need some help for a research project.

We are comparing outcomes for different surgical approaches. I'm using SPSS to analyze the data. To keep it simple, we have two diagnoses (nominal data) four surgical approaches (nominal data) and outcome variables (scale data) at baseline, 3 months and 12 months. I used the paired samples t test to show that the outcomes at 3 months and 12 months are significantly different from baseline. However, I'm having trouble doing my subgroup analysis. I want to see if the different approaches lead to better or worse outcomes at 3 & 12 months. So, are the outcomes from approach 1 at 3 months & 12 months significantly better than approach 2, etc.

Thanks and any help at all is greatly appreciated!