More than two dozen orthopedic practices in the region have teamed up to form a joint corporation, hoping to avoid the financial and regulatory pressures that have driven many doctors from private practice. Called the Centers for Advanced Orthopaedics, the new consortium consists of 25 practices and 130 physicians. It spans more than 30 Zip codes of Virginia, Maryland, West Virginia, Pennsylvania and the District of Columbia. Collectively, the members bring in more than $150 million in annual revenue and employ about 1,200 people. Under the new structure, the group will share administrative, technology and marketing costs, as well as reimbursement contracts with insurers and employee benefit plans.