Complex sentence: Additionally, the Spurs' deep playoff runs (they only missed the playoffs once in their nine years there) tied up the Alamodome for most of the winter and spring, making it difficult to accommodate conventions, concerts or even a prospective football team.
Split into simpler sentences: Additionally, the Spurs tied up the Alamodome for most of the winter and spring due to their deep playoff runs (they only missed the playoffs once in their nine years there). With the Alamodome booked solid well into April, it was difficult to accommodate conventions, concerts or even a prospective football team.