20 C.F.R. § 10.310
What are the basic rules for obtaining medical care?
(a) The employee is entitled to receive all medical services, appliances or supplies which a qualified physician prescribes or recommends and which OWCP considers necessary to treat the work-related injury. Billing for these services is described in subpart I of this part. The employee need not be disabled to receive such treatment. If there is any doubt as to whether a specific service, appliance or supply is necessary to treat the work-related injury, the employee should consult OWCP prior to obtaining it through the automated authorization process described in § 10.800. OWCP may also utilize the services of a field nurse to facilitate and coordinate medical care for the employee. OWCP may contract with a specific provider or providers to supply such services or appliances, including durable medical equipment and prescribed medications.
(b) Any qualified physician or qualified hospital may provide such services, appliances and supplies. Non-physician providers such as physicians' assistants, nurse practitioners and physical therapists may also provide authorized services for injured employees to the extent allowed by applicable Federal and State law.
(c) Where OWCP has not contracted for the provision of appliances or supplies, only a supplier of durable medical equipment that is registered in Medicare's Durable Medical Equipment, Prosthetics, Orthotics and Supplies Accreditation process may furnish such appliances and supplies. OWCP may apply a test of cost-effectiveness to appliances and supplies, may offset the cost of prior rental payments against a future purchase price, and may provide refurbished appliances where appropriate.