Ulnar Impaction Syndrome (Ulnar Abutment), what does this mean?
In our Facebook group, "TFCC and Ulnar-Sided Wrist Pain" there has been a lot of discussion about Ulnar impaction.
Ulnar impaction syndrome (UIS) also has a couple of other names, all of which refer to the same issue. The other names are Ulnar abutment and ulnocarpal loading.
In an interesting article published by PubMed.gov, the authors write, "The relationship between triangular fibrocartilage complex (TFCC) tear and ulnar impaction syndrome has not been fully understood. We hypothesized that a TFCC tear could change the ulnar variance, which may be the cause of ulnar impaction syndrome." They concluded, "Ulnar variance may be changed after a TFCC tear. In our study, it decreased after TFCC foveal repair. However, as time went on, the ulnar variance increased again, which could be one of the causes of ulnar impaction syndrome and ulnar-sided wrist pain."
In a nutshell, UIS occurs when the ulna hits the lunate and causes damage to the lunate bone where they meet. See the red colored areas on the image. Once you read through this article and understand the condition a little better, you can appreciate photos found here. https://radiopaedia.org/
How does it happen?
The most common causes of Ulnar Impaction Syndrome are thought to be:
- The result of a long ulna - called Positive Ulnar Variance
- Birth defect - Madelungs deformity (rare)
- Premature growth plate closure (common in gymnasts)
- Fractured ulna with difficult healing
- Monteggia Fracture dislocation
- Essex - Lopresti fracture dislocation
But how does it REALLY happen?
In my experience, I see patients diagnosed with ulnar impaction AFTER they've been diagnosed with TFCC tears. It's something that arises 6 months or more after having an untreated and significant TFCC tear. The incidence of UIS increases with the severity of the primary TFCC injury.
When the TFCC is injured, there is a spreading of the space between the distal radius and the ulna. This gap changes how the radius and ulna respond to weight bearing loads.
In a normal, uninjured wrist, when called into action, the small ulna bears 20% of the weight, and the bigger radius bears 80% of it.
In wrists with TFCC injuries, that gap changes the dynamics of weight bearing and now the ulna must bear 40% of the weight and the radius only bears 60%.
It's clear that patients with UIS have a loss of weight bearing ability under 45 lbs of weight. This incidence increases exponentially when the loss of weight bearing tolerance drops below 20#. This is a red DANGER zone.
Can it heal? Is there hope?
If a patient has been diagnosed with UIS, it's serious! Dramatic changes to all daily life must be made, and treatment must start. You don't want to use the wrist and aggravate where the ulna bone is deteriorating.
The great news is that I have witnessed many cases of UIS RESOLVE by using the WristWidget® and a strict protocol. The biggest investment is time. It takes time for the ulna to recover. Like any fracture or injury to the bone, full healing, where the injury becomes calcified, takes 4 weeks to a year. Fortunately, you are able to watch this incredible healing process by performing the Weight Bearing Test each week.
In severe cases of TFCC tears, the treatment for TFCC healing is 3 months. If the lunate bone is involved, I anticipate 6 months to return to normal weight bearing tolerance.
There is a lot of reason to worry when you have been diagnosed with Ulnar Impaction Syndrome. BUT there is also great hope that this too can heal.
Wendy Medeiros, OTR, CHT (retired 2014)