Insertional tibialis posterior tendinitis is a common cause of medial arch pain in adults. We tend to think about this condition in pediatric patients with a large navicular tuberosity and/or an os tibiale externum associated with a flat foot (Kidner foot type). When you have an adult with navicular tuberosity pain who has a normal X-ray and no os tibiale externum, you probably ask yourself, “Now what I am going to do with that?”
I have personally found it difficult to treat this condition in adults. Conservative treatments initially include rest, icing, non-steroidal anti-inflammatory medication (NSAIDs) and supportive shoes with orthotics. The second line of treatment will usually involve fracture boot immobilization for a month or more with a prednisone taper dose. I prefer prednisone 60/40/20/10/5 mg for three days each.
If that treatment fails, physical therapy may be a last ditch effort to treat the condition without surgery. I caution you about cortisone injections at the attachment area of any tendon. You may get lucky but rupture is a common occurrence. Most of my patients who have presented to my office with a tibialis anterior tendon rupture had prior cortisone injections in the medial arch.
When it comes surgery, if there is a large os tibiale externum, it is easy for us to show our patients and say, “See that extra bone? That is what is causing your pain.” What about the patient who does not have an os tibiale externum? Now what do you do? Is it the bone that is causing the pain? Is it the tendon? Is it both?
Just like any other insertional tendinitis, whether it is the Achilles, tibialis anterior or peroneus brevis tendons, it is usually the tendon that is the problem. If you get a magnetic resonance image (MRI), you will generally see distal tendinosis.
As far as surgery goes, I have some tips for you. If there is an os tibiale externum, you need to be very aggressive in the amount of bone that you remove. Just removing the accessory bone and reattaching the tendon is not good enough. I do my best to get the navicular bone as flush to the cuneiform as possible. I will position the saw dorsal to plantar, using the cuneiform as a reference. Then by inverting the foot, you will “cover up” the talar head so you avoid the talus with the saw. After removing the navicular bone and/or os tibiale externum, I will use a rotary burr or hand rasp to remove any sharp edges. I will use radiofrequency Coblation on the distal tibialis posterior tendon as tendinosis is invariably part (if not all) of the problem.
I recommend making the skin incision along the anterior (dorsal) aspect of the tibialis posterior tendon and extending to the naviculocuneiform joint. After dissecting down to the tendon sheath and insertion site on the navicular tuberosity, I will score the periosteum on the dorsal aspect of the navicular tuberosity. I extend the incision enough to where I can see the cuneiform. Then I carry the incision over the navicular tuberosity and reflect the periosteum and tendon inferiorly. This will allow for adequate exposure of bone to resect, leaving a layer (like a sleeve) of tissue for easy closure, and preserving most of the tendon attachment. At this point, you are ready for bone resection as I discussed above.
I generally use a bioresorbable 5-mm corkscrew anchor to reattach the tendon and periosteum. I always check my bone tap under fluoroscopy to ensure the proper location. Remember to angle the tap distally or else you will encounter the talonavicular joint if you are too perpendicular to the bone.
I generally have patients non-weightbearing for a minimum of four weeks and maximum of six weeks depending on the amount of tendon that I reflected. Then the patient can ambulate in a fracture boot and start physical therapy for rehabilitation.
I personally feel that bleeding bone of the navicular and radiofrequency Coblation of the distal tendon are what helps rejuvenate the tendon. It is essentially the same process as for insertional Achilles tendinitis/tendinosis but we will save that for another day.