This will be a multi-site study with all patients either receiving the CMRH or the MRH. Sequential enrollment of all patients meeting inclusion criteria and agreeing to be in the study will be enrolled. The patients will sign an informed consent agreeing to accept either the investigational or control device. In addition, the surgeon will not know which device the patient is to receive until the day of surgery in an attempt to further reduce bias. The surgeon will open an envelope at the time of surgery to determine if a CMRH or MRH will be implanted.