Ballet superstar Natalia Makarova is not expected to be released from George Washington University Hospital for several days, after sustaining a broken shoulder and a severe scalp laceration Saturday night while performing in "On Your Toes." The 42-year-old performer, who was making her musical comedy debut in the Kennedy Center Opera House, was accidentally struck a glancing blow by a piece of falling scenery during a scene change in the second act. She will not return to the show.

Dr. Max H. Cohen, a clinical assistant professor of surgery at George Washington University who was in the audience at the time of the accident and has been caring for Makarova since then, estimated that it would probably take "from 8 to 10" weeks for her broken right shoulder to mend. Although severe blows to the head can result in paralysis, Cohen said yesterday that X-ray films of the cervical spine (the vertebrae of the neck), taken upon Makarova's arrival at the hospital, have revealed "no bone injury. So far she appears to be doing well. She's had no abnormal alterations in her mental state or neurological signs." Last night she was listed in good condition.

Makarova's husband, San Francisco industrialist Edward Karkar, immediately flew to Washington and was at her bedside last night. Karkar refused comment, saying he didn't want to make it into a "media event," according to a spokesman. The spokesman added Karkar insisted his wife remain hospitalized.

The accident brought Saturday night's performance to an abrupt halt. The curtain was lowered and a stunned audience of 1,800 was asked to leave the hall. At yesterday's matinee and evening performances, Makarova's understudy, Starr Danias, took over the lead role, that of a temperamental ballerina in a beleaguered Russian dance troupe in New York. Danias will continue in the role until Valentina Koslova joins the cast "in two or three days -- certainly by the first of next week," according to Kennedy Center chairman Roger L. Stevens. (Because of prior commitments, Makarova was scheduled to play only the first four weeks of the six-week run, and Koslova and her husband, Leonid Koslov, who will replace George de la Pen a, have already been rehearsing for the final two weeks.)

There were conflicting accounts in the hours following the accident. Stevens, who had been watching the show from the presidential box, said yesterday.

"It's one of those things that happens so fast you're not prepared for it. There were 50 people backstage afterwards and they all had different stories of what occurred. We haven't had an accident of this sort since the Center opened."

Yesterday morning Kennedy Center stagehands met with Judy Moor, general manager of theaters, and her staff to determine what went wrong. By yesterday afternoon Center officials described it this way:

Makarova had just played a brief scene in front of a canvas drop, representing the outside of the Cosmopolitan Opera House. The drop, the bottom of which is weighted by two metal pipes in a "batten pocket," was being raised for the following scene in a rehearsal hall, when the canvas began to rip. The pocket, containing both a 48-foot pipe and a 21-foot pipe, fell diagonally, first hitting the floor stage left with a resounding bang. Makarova, standing on the opposite side of the stage, was struck by the other ends of the pipes as the canvas continued to rip.

"That's why she's alive," said Tom Kendrick, the Center's operations director. "If she'd been on the other end, it certainly would have been far more serious."

Danias, the understudy, who was waiting in her dressing room beneath the stage, recalled yesterday, "I heard a tremendous crash and rushed upstairs imagining the entire company had been destroyed, but the injury to Makarova is pain enough."

A stagehand promptly summoned the on-duty nurse at the Kennedy Center, who grabbed all the available ice and ran backstage.

Cohen, who was sitting in the front row with his wife, also dashed backstage. Makarova "was woozy, but relatively quiet, complaining of pain in her right arm. She had some bleeding from the right scalp area, which was partially obscured by a blond wig. Very briefly and transiently, she lost contact, which is one of the reasons we have kept her in the hospital -- to make sure she has no underlying neurological problems."

Within minutes after the accident, Makarova -- still in her costume, a white skirted leotard with a white scarf in her hair -- was rushed to GW Hospital by ambulance, where a team of five physicians and three nurses evaluated her injuries. She received six stitches for the 3 1/2-inch laceration in her scalp, and after Cohen consulted with two orthopedic surgeons, her right shoulder was immobilized in a sling. She has been advised to wear it for two weeks.

"She was quiet and distressed and concerned about the impact of the injuries on her future course," said Cohen, "but she was also very poised throughout."

Dina Makarova (no relation), a Russian-speaking American, Makarova's longtime factotum and one-time interpreter for Mikhail Baryshnikov, was at the star's side, initially providing translations. But "by speaking English very slowly," Cohen said, "we found that her comprehension was complete."

Hospital officials checked her vital signs hourly throughout the night. "She's gotten some sleep, but she's still in a fair amount of pain and will be in the hospital for several more days," said Cohen, who noted that the average rehabilitation time for injuries of this sort is 8 to 10 weeks, although "because of her profession she does have increased stress on that area."

The accident provided an ironic counterpoint to the story of Rodgers and Hart's "On Your Toes." In a scene played just before the accident occurred, George de la Pen a, who plays a pugnacious dancer in the troupe, is knocked unconscious in a fight with a vaudeville hoofer, played by Lara Teeter. Coming right afterward, the accident, which sent Makarova slumping to the floor, at first seemed to some members of the audience just another twist in the 1936 backstage musical.

Several fellow performers rushed to Makarova's side and began struggling with the canvas-wrapped pipes that lay over her body. The curtain was lowered and the audience waited in shock. Some claimed to hear moans of "My arm, my arm" coming from the body microphone Makarova was still wearing.

"On Your Toes" received mixed reviews when it opened last Tuesday, but interest in the musical, directed by George Abbott and choreographed by George Balanchine, has been running high. As of last Friday, the Kennedy Center had an advance ticket sale of nearly $1 million. Stevens refused to speculate on the effect Makarova's removal from the cast would have on the fortunes of the show, saying only, "Up to now, we seem to have had a terribly strong box office."

Makarova was scheduled to be the guest of honor Saturday at an after-theater party for 80 at the Rive Gauche restaurant hosted by Mrs. Gordon Getty, daughter-in-law of the late financier J. Paul Getty. According to a restaurant spokesman, 55 of the guests showed up and the mood was downbeat. "The accident was all they were talking about," he said.

Makarova's next appearance was to have been in "The Firebird," a new ballet premiering in Vienna. She was to have traveled there on Jan. 1.

Danias, the 33-year-old understudy, has danced with the Joffrey Ballet and as a soloist with the American Ballet Theatre. She appeared in the film "The Turning Point" and was playing Lola, a small part in "On Your Toes.