Maryland has no statute that expressly prohibits caging a dog inside a home. It does have a general law that prohibits abuse of any animal, however. Maryland Code § 10-604(a) provides as follows:
§ 10-604. Abuse or neglect of animal
(a) Prohibited. -- A person may not:
(1) overdrive or overload an animal;
(2) deprive an animal of necessary sustenance;
(3) inflict unnecessary suffering or pain on an animal;
(4) cause, procure, or authorize an act prohibited under item (1), (2), or (3) of this subsection; or
(5) if the person has charge or custody of an animal, as owner or otherwise, unnecessarily fail to provide the animal with nutritious food in sufficient quantity, necessary veterinary care, proper drink, air, space, shelter, or protection from the weather.
Violation of that law is a misdemeanor criminal offense. It seems to me that in some circumstances caging a dog might be a violation of this provision, but the details of what is being done would matter greatly. It would be up to the local DA whether he or she thought the circumstances of the dog's treatment were egregious enough to warrant trying to prosecute the homeowners for abuse under this section.
Maryland does have a specific statute that addresses keeping dogs tied up OUTSIDE, however. Maryland Code § 10-623 provides as follows:
§ 10-623. Leaving dogs outside and unattended by use of restraints
(a) Definitions. --
(1) In this section the following words have the meanings indicated.
(2) "Collar" means a device constructed of nylon, leather, or similar material specifically designed to be used around the neck of a dog.
(3) "Restraint" means a chain, rope, tether, leash, cable, or other device that attaches a dog to a stationary object or trolley system.
(b) Prohibited. -- A person may not leave a dog outside and unattended by use of a restraint:
(1) that unreasonably limits the movement of the dog;
(2) that uses a collar that:
(i) is made primarily of metal; or
(ii) is not at least as large as the circumference of the dog's neck plus 1 inch;
(3) that restricts the access of the dog to suitable and sufficient clean water or appropriate shelter;
(4) in unsafe or unsanitary conditions; or
(5) that causes injury to the dog.
(c) Penalties. -- A person who violates this section is guilty of a misdemeanor and on conviction is subject to imprisonment not exceeding 90 days or a fine not exceeding $ 1,000 or both.
You may read all the crimes in Maryland relating to treatment of animals in Title 10, Substitle 6 of the Maryland Code.