This is an open-label, single-arm safety study to evaluate the safety of hydromorphone hydrochloride given by continuous intrathecal infusion using an implantable pump device. This study will enroll both subjects on a current opioid intrathecal medication as well as naïve subjects now current on intrathecal opioid medications. All subjects currently on intrathecal opioid treatment will be converted from their current intrathecal therapy to intrathecal hydromorphone hydrochloride according to standard medical practice. After an optimal dose for pain relief is achieved, subjects will remain on therapy for a total of 12 months or until discontinuation from the study. During this continuous dosing period, dose adjustments (up or down) are permitted to manage pain or side effects provided a maximum dose of 10 mg/day is not exceeded. Subjects will be assessed for pain intensity using a visual analog scale of pain intensity (VASPI) instrument at each study visit.