For certain shoulder injuries

DEAR DOCTOR » My doctor at the local bone and joint clinic said I was a good candidate for an experimental injection of PRP for arthritis in my right shoulder. What is your opinion? I’m 71.

DEAR READER » Unlike your doctor, I’m not familiar with your medical history or your shoulder condition, so I can’t offer a specific medical opinion. What I can do is explain a bit more about this procedure and its potential.

First, some background: Because tendons, ligaments and cartilage have limited blood flow, the body’s ability to repair them is limited. Autologous platelet-rich plasma (PRP) aims to compensate for this. It’s prepared by removing about 30 to 60 cubic centimeters of blood from your arm. The blood is then filtered through a process called plasmapheresis, which concentrates the platelets. The wonderful thing about platelets is that they’re usually the first blood component to arrive at the site of an injury, bringing molecules that encourage healing. Thus, platelet injections have the potential to improve healing of an area with normally poor blood flow.

Most studies of PRP for the shoulder have involved people having surgical repair of the joint, with surgeons using PRP to bolster a rotator cuff repair or to boost healing after shoulder replacement. A 2015 study combined data from eight studies comparing arthroscopic surgery for rotator cuff tendon tears with PRP and without PRP. Of 464 patients, 234 had PRP injections. The authors found no difference in the rates of tendons re-tearing after surgery, nor did they find any significant MRI changes in the PRP group. Further, the studies did not find any difference in range of motion or pain with the use of PRP.

Another 2015 analysis — this one of 11 studies with a total of 597 patients — also failed to show MRI or symptom benefit with the use of PRP. However, PRP did show benefit among people who had rotator cuff tendon tears greater than 3 centimeters. A 2016 study showed benefit in the use of PRP in the first month after surgery, but no significant benefit after six months.

Also, there are small studies that show PRP can help people who are not having shoulder surgery. Some studies have compared PRP to steroid injections in the shoulder for partial rotator cuff tears or for impingement syndrome and found that PRP was equivalent or even more helpful than steroid injections. However, a study from Iran found that while PRP did ease pain and improve mobility of the shoulder, it was not superior to physical therapy.

As for arthritis of the shoulder, I haven’t found good studies to support the use of PRP. Some studies show benefit for arthritis of the knees, but their poor design and lack of comparison subjects make conclusions difficult.

That said, while I don’t know the degree of your shoulder arthritis, if you have impingement of the shoulder or a partial tear of your rotator cuff tendon, PRP in addition to physical therapy may have benefit.

I’m with your doctor on this: It’s worth a try.