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Anne Palmer, 64, was in pain for months after falling off a ladder this winter and injuring her shoulder.

The accident forced her to confront the fact the cartilage in her shoulder had completely worn away, she had bone spurs in the joint and she needed a complete joint replacement.

Right after Dr. Gareth Hammond with Animas Orthopedic Associates replaced her shoulder joint in July, she could feel the difference, she said.

“There was no sound like gravel grinding. … You could feel that immediately – how smooth it felt,” she said.

To help ensure Palmer’s new joint was properly aligned, Hammond used a guide designed specifically for her anatomy using a computer-based model of her shoulder, he said.

The new patient-specific guides bring far more precision to a traditionally tricky surgery, typically done to relieve pain from arthritis and restore range of motion, he said.

Candidates for shoulder replacement surgery are usually 60 years old or older and have arthritis in the shoulder caused by old injuries, wear and tear or disease, such as rheumatoid arthritis, he said.

Palmer described her own shoulder joint as cratered like a moon from use and arthritis, but the new metal and plastic surfaces in the joint have relieved her pain, she said.

Shoulder replacement surgery is less common than hip or knee replacement. About 53,000 Americans have shoulder replacement surgery annually, according to the Agency for Healthcare Research and Quality. Hammond completes about 30 to 50 shoulder-replacement surgeries a year, he said.

Nationally, shoulder replacement surgery is expected to become far more common, in part, because technology has made it easier for surgeons to complete and to ensure joints are better aligned.

“Joint replacement, when I was training, was very much like carpentry,” he said.

Now, Hammond takes a CT scan of a patient’s shoulder ahead of time that allows him to complete the surgery virtually before doing it in real life.

To replace a shoulder joint, a surgeon must replace the ball at the top of the arm bone with a metal implant. The socket must also be smoothed and a plastic implant put in to receive the new metal ball.

Lining up the new plastic socket can be tricky because the surgeon can only see a tiny portion of the bone and the rest of the shoulder blade is hidden from view.

“It’s very easy to get disoriented. … You have no idea which way the shoulder blade is really facing because it’s hidden in the patient’s back and they are all covered by drapes,” he said.

The computer-built guides eliminate uncertainty for surgeons by identifying a “keystone” point that the joint replacement can be built around, he said.

The computer model identifies the keystone point and is used to design the custom-made guide for surgery.

The guide is either 3D-printed or built in the operating room to the specifications of the patient’s socket. It is placed on the socket, and then it allows the surgeon to fire a pin into the bone identifying the keystone point needed to align the implant, Hammond said.

Before computer modeling, surgeons would use landmarks in the patient’s anatomy and manual guides to align implants that hadn’t been shaped to the patient’s bone.

A custom device to guide a shoulder replacement typically adds a few hundred dollars to the cost of a surgery, Hammond said. But most patients want him to use the device because it will help their shoulder joint feel balanced, he said. A poorly balanced shoulder can feel as if it’s slipping and the range of motion can be limited, he said.

The well-aligned implants are also expected to last longer, but studies have not been completed to prove that they will, he said.

Shoulder replacements can help patients return to sports such as tennis, golf, swimming and other sports, Hammond said. But patients should avoid activities such as climbing or lifting heavy weights.

Six weeks after her surgery, Palmer said she was returning to regular activities, after about six months of limited motion following her fall. She can now reach the top of the file cabinet in her workplace and saddle her horse. However, it will take six months to a year for the replaced joint to heal completely, Hammond said.

“There is life after shoulder surgery,” Palmer said.

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