PRP IN PRACTICE: Tips on safe injection techniques

By Paul Basilio

Platelet-rich-plasma (PRP) has increasingly been used in equine medicine for the treatment of joints, bursae and soft tissue injuries.

During the past 5 years, A. Kent Allen, DVM, ISELP, and his colleagues at Virginia Equine Imaging, have used PRP in more than 400 horses totaling about 800 individual joints, and he’s confident in the beneficial effects of PRP in equine practice.

He recently passed along some helpful tips dur- ing the Equine Regenerative Medicine and Orthobiologics Online Summit

Volume, frequency, and gain

“You want to be comfortable with ultrasound-guided injections and have a plan for reducing the pain of the needle passage,” Dr. Allen said. “Whether it’s a regional nerve block or a skin block, come up with a plan beforehand on how you can reduce the pain of this injection technique.”

It is crucial to avoid over-pressurizing the lesion, joint, or bursa by keeping an eye on the volume that is being injected. If there is any resistance on the plunger of the syringe or if tissue separation starts to become evident, back off and perhaps draw the syringe out slightly.

“Those situations will look very much like a flarelike syndrome, but they come from pressurizing that joint and structure,” he added.

For the ultrasound probe, make sure it is positioned well enough to easily see the needle passage. For guided injections, the frequency should be set a little lower and the gain should be set a little higher than what practitioners typically set for ultrasound imaging.

“That accentuates the needle,” Dr. Allen explained. “The needle is passing in the thin plane of the probe, which is only about 2 mm thick. You have to stay in that plane, so anything that helps you see that a little better is something you need to do.”

For sacroiliac injections, he also recommended clipping the haircoat—particularly in the winter.

If the PRP is not flowing easily into the lesion, scarring that was not appreciated beforehand may be giving the needle a bumpy ride.

“You think you’re going into a fairly hypoechoic lesion and the PRP is going to flow easily, but once you get the needle in there you may find that it’s not happening,” he said. “Always be prepared to have a secondary plan for depositing the PRP perilesionally.”

Using a reasonable needle gauge (eg, 20-gauge) with the horse in a non-weightbearing stance, it’s possible to put a small amount of air into the syringe to see the air bubbles flow, which will help you track where the injection is going.

“Sometimes if you’re doing a tendon with a fairly long lesion, this allows you to see where you’ve gotten the PRP in and where you have not,” Dr. Allen explained. “Then you can reposition the needle appropriately.”

Recheck and plan

To monitor the success of the treatment, Dr. Allen usually rechecks the horse in 30-day intervals to assess the progress. “If it didn’t work, you may want to consider another PRP injection or you may want to rethink your treatment plan,” he said.

A structured rehab plan is also important for the success of the treatment. Dr. Allen recommends keeping the horse quiet via sedation on a small paddock turnout.

For neck and back lesions, improvement can be monitored by checking in with trainers and riders to see if the horse is tripping less or appears to be comfortable.

“It is not uncommon to see significant filling of the lesion at 30 to 60 days,” he said. “The horse still won’t be able to go back to full work despite the tissue appearance, and it will still need the standard term of rehabilitation. Don’t be fooled by that. If good things are happening in that lesion, it doesn’t mean the horse still doesn’t need an appropriate rehab time frame.”

Contraindications

Concurrent NSAID use should be avoided with PRP injections. In human medicine, good evidence has shown that naproxen affects the quality of PRP treatment. “You’ll want to talk to the client beforehand if you’re doing a PRP injection,” Dr. A. Kent Allen said. “Have the receptionist ask the owner if the horse is on any NSAIDs and have them ask the owner to discontinue them. I prefer a week [NSAID washout period] before and after PRP injections.”

A similar approach should be taken with corticosteroids. In an ideal world, Dr. Allen would like to see a horse go off corticosteroids for about 30 days, but that is not always feasible.

Infections are rare with PRP injections, but a sterile technique with sleeve covers can decrease the risk.