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06/06/08 12:44 PM ET

Ortiz sporting a Munster cast

Red Sox slugger has a partially torn wrist tendon sheath

Google the phrase "Munster Cast" and see what you come up with.

You'll find a reference or two to Fred Gwynne and Yvonne De Carlo, stars of the '60s TV sitcom "The Munsters." You'll also find a cast of a different kind. That would likely be the type of cast that Red Sox star David Ortiz will be sporting for the next four weeks, according to Dr. Charles Day, Chief of Orthopedic Hand Surgery at Beth Israel Deaconess Medical Center.

"With the type of injury that David Ortiz has, a partially torn wrist tendon sheath, the first thing that needs to happen is the wrist needs to be stabilized," says Dr. Day. "That's a bit more involved than a cast for a broken wrist."

Ortiz's partial tear occurred on the sheath that holds the extensor carpi ulnaris or ECU tendon in place within the wrist joint. (If you were to hold out your arm as if to shake somebody's hand, the tendon would be located at the bottom of the hand, in line with your little finger). If that sheath becomes unstable, the tendon can "snap" over the bone when the wrist is rotated. It's a painful experience and can lead to a tendon tear.

"It is similar in some respects to the type of injury which Curt Schilling had in his ankle in the 2004 season, however, the wrist is a more complex joint than the ankle," explains Dr. Day. "In just a two-inch cross-section of the wrist, you'll find 15 bones and 24 tendons. And we're able to rotate the wrist nearly 180 degrees. That's why immobilizing the joint isn't a simple job."

A Munster cast -- which starts just above the elbow and extends all the way down to the hand -- prevents the wrist from rotating and gives the partially torn sheath a chance to heal itself. It's the first line of treatment.

"If this were a full sheath rupture it would be a completely different story. Surgery would be a likely option," Dr. Day says. "With a partial tear, I would put the chances of the tear healing itself at about 90 percent with the proper immobilization for four weeks. But remember, he won't come out of the cast and immediately be in the lineup the next day."

Once the cast comes off, it will most likely be replaced by a splint that can be removed for treatment and rehab. It might be two weeks or more before the injury is fully healed.

"You or I in a similar situation would be back to doing normal activities pretty quickly after immobilization. We'd be driving and typing with perhaps a little discomfort," says Dr. Day. "But then most of us don't subject our wrists to the kind of stress a Major League hitter does. If the tear is not fully healed, an awkward swing could re-aggravate the injury."

Dr. Days sees about six to eight of these injuries a year. It can be the result of a person extending his arms and twisting his wrist to catch himself as he falls, for instance. And golfers who do more than a bit of damage to the course sometimes end up with a damaged wrist. In other words, a big divot can sometimes lead to a tendon sheath tear.

So, be careful out there. After all, it's tough to work the remote to find the cast of "The Munsters" when you are wearing a Munster cast.

Gary Gillis is a contributor to MLB.com. The BID Injury Report is a regular column on redsox.com. Beth Israel Deaconess Medical Center is the official hospital of The Boston Red Sox. This story was not subject to the approval of Major League Baseball or its clubs.