Dr. Jeffrey Dugas, who performed the procedure, said Ambrose has already started physical therapy, but it remains unclear when the wrestler will be healthy enough to return to the ring.
Dugas said Ambrose "basically tore about 50 percent of the triceps tendon away from the bone."
Samoa Joe, Sheamus and Cesaro attacked Ambrose and Seth Rollins backstage on Raw on Monday. It would appear Ambrose's injury came before the attack, since a WWE trainer was already examining the arm. Of course, the segment does give WWE a way to explain Ambrose's absence.
Losing Ambrose for an extended period may force WWE to all but abandon The Shield's reunion. The group isn't the same with only two of its three members, which was made clear when a bout of viral meningitis sidelined Roman Reigns for The Shield's first match back at TLC: Tables, Ladders & Chairs in October.
The injury may also jeopardize Ambrose's involvement in WrestleMania 34 on April 8.
Given the scale of the event, WWE will probably want to start the build for any WrestleMania match more than a month out, which leaves early March as the cutoff point for Ambrose to get back to 100 percent. Judging by Dugas' comments, a little over two months may be unrealistic for Ambrose's arm to fully heal.
At the time, Ambrose's win over Baron Corbin to retain the Intercontinental Championship on the WrestleMania 33 pre-show felt like a big step down, since he had wrestled Brock Lesnar in a defeat a year earlier. Now, Ambrose may be lucky to get on the WrestleMania altogether.