A session heavy in in-office procedures requires room turnover, instrument reprocessing, chaperoning and post-procedure instruction that a consultation session does not. Write down what a representative session actually requires, task by task, with honest time estimates. Sum it. That is your requirement.
Then do the same for the non-clinical spine: check-in, eligibility, prior authorization, referrals, results management, scheduling and phones. Under-resourcing this side is the most expensive staffing decision most practices make, because the cost shows up sixty days later as denials owned by someone else.