A surgical treatment can involve creating a pattern of perforations in a tissue structure to allow lengthening of that tissue structure. For example, a pattern of perforations can be created in the transverse carpal ligament of a patient suffering from carpal tunnel syndrome (CTS) that allows the carpal ligament to lengthen slightly. This lengthening can relieve pressure on the median nerve, thereby reducing the symptoms of CTS while maintaining the structural integrity of the wrist. A surgical instrument for use in perforating a tissue structure (such as the transverse ligament) can be an elongate structure with one or more retractable blades. Such a tool can be used in either an open or minimally invasive procedure to create a desired pattern of perforations in the tissue structure.