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April 05, 2019 8 min read

Answer a fun quick question about wrist instability, learn more about what defines this particular condition, and find some helpful tips on the best hand therapy treatment.

Answer this Quick Question

What does DISI stand for?

  1. Dorsal Intercalated Segment Instability
  2. Dorsal Instability Scaphoid Interval
  3. Dissociative Intercalated Segment Instability
  4. Divergent Interval Segment Instability

Answer: a)  Dorsal Intercalated Segment Instability

 

DISI Defined

Definition:
This sounds complicated and scary, but it’s really not – I am going to try and simplify it through a few basic principles. Normal wrist kinematics are this: the proximal carpal row consists of the scaphoid, lunate and triquetrum, which are connected to each other by the scapholunate and lunotriquetral ligaments respectively.

The scaphoid has a tendency to want to flex (move volarly), whereas the triquetrum has a tendency to want to extend (move dorsally). In a stable normal wrist the lunate sits in the middle, “balanced” by the forces tending to act on the adjacent bones.

I’m not sure who came up with the idea of the “promiscuous lunate” but I first heard it described by Sarah Mee at a Hand Therapy conference in Napier, New Zealand. It is a great concept, as it makes this easy to understand. Basically the lunate will go with whoever it’s attached to.

So, if the scapholunate ligament is disrupted, the lunate will displace dorsally with the triquetrum, i.e. DISI. If the lunotriquetral ligament is disrupted, the lunate will displace volarly with the scaphoid, i.e. VISI. A DISI may also be the result of an unstable scaphoid fracture.

TOO EASY!

Dorsal Intercalated Segment Instability


  

 

Clinical signs and symptoms:

If your client is referred to you with the diagnosis of DISI already made, chances are he / she has a scapholunate ligament disruption. If you are the first person to see the client or make the diagnosis, look out for the following:

  1. History of injury: often a fall onto outstretched hand, usually with wrist extended and sometimes ulnar deviated (if they can remember those details!)

  2. Pain: usually central dorsal wrist, over the SLL. There may be swelling in this area. Often pain is worse when gripping firmly, as the capitate pushes downward, forcing apart the scaphoid and lunate.

  3. X-rays: Remember always to compare to the unaffected side. In pre-dynamic SLL injuries, there may be nothing to see on x-ray. But in the case of dynamic instability, there is likely a widened scapholunate interval (known as the “Terry Thomas sign”, named after a comedian with a big gap between his front teeth!) in a clenched fist view (because with gripping the capitate forces the scaphoid and lunate apart if the ligament is injured) or with the wrist ulnar deviated.

Deviated

In the case of a static injury, where the SLL is completed disrupted, the Terry Thomas sign may be evident on a non-stressed view too. On a lateral view you will also see an increase scapholunate angle (normal is 30-60deg, whereas >60deg indicates DISI). The ring sign is also an important diagnostic finding indicating DISI, where the scaphoid is flexed volarly but the lunate is extended dorsally.

It may take up to 12 months before dynamic instability develops and dissociation becomes evident on x-ray.

Wrist Xray


 

Clinical tests:

Watson’s shift test: Client’s wrist is in ulnar deviation and slight extension. Therapist puts thumb on client’s scaphoid tubercle and IF on the anatomical snuffbox (i.e. holding the scaphoid). Therapist’s thumb blocks the scaphoid from flexing, as you radially deviate the client’s wrist. Instability will cause the scaphoid to sublux dorsally. When pressure is removed, there will be a painful clunk in a positive test.

Hand Therapy for DISI

Not all scapholunate ligament injuries result in DISI. Management depends on the severity of the tear, time since injury, and presence of arthritis. Severity increases from partial tears to dynamic instability to static instability to SLAC (scapho-lunate advanced collapse) wrist arthritis.

With a Grade 1 tear, there will not be instability, thus this is not a DISI. Some Grade 2 tears do result in instability over time, but can be managed conservatively if diagnosed early. The goal of hand therapy for these clients is stability rather than mobility.

Non-surgical

  • Splinting: Grade 1 and 2 tears are managed initially with period of splinting or casting until the wrist is stiff / stable, anywhere between 3-12 weeks depending on severity of injury and symptoms.
  • ROM: At the point where the wrist feels stable again, you can initiate gentle AROM, however continue with splinting between exercise sessions. Dart thrower’s motion is a great place to start, as this places the least stress on the healing SLL.
  • Strength: Once the wrist feels stable, isometric strengthening in dart throwers motion positions is a good place to start. Be careful with grip strengthening though, remembering that with firm grip the capitate pushes the scaphoid and lunate apart, stressing the SLL.
  • Education: As with all hand therapy, education is key. The client needs to understand the condition, biomechanics and normal healing timeframes, in order to understand their management and take on board advice around activity modification.

Surgical

If there is dynamic or static instability, Grade 3 tear / complete disruption, they will require surgery. This will correct / improve the mechanics of the wrist, and prevent it from developing into a SLAC wrist. Goals of surgery are to reduce pain, increase function and improve wrist alignment. The ligament may be repaired in some cases, or reconstructed. Surgery may include a capsulodesis, bone-ligament-bone graft, tendon weave, or RASL.

Hand therapy should focus on strength, dexterity, proprioception and stability. Post op management depends on your surgeon’s preference, or their specific protocols. However, most commonly the client would be immobilised in a cast for 6-8 weeks, and thereafter in a removable thermoplastic splint, which is worn for a further 4 weeks between exercise sessions.

AROM can usually commence in the DTM arc around 6-8 weeks post-op. PROM is delayed as to avoid destabilising the repair. Isometric strengthening in dart throwers motion positions may be commenced around 8+ weeks. Again be careful with grip strengthening, as firm grip stresses the repaired SLL.

Many can return to normal activity by ~4 month post op, while others may take 6-12 months to reach full capacity. 

Here are my top 3 hand therapy techniques for DISI:

  1. Dart throwers motion. This movement has been shown through in vivo testing to place the least stress on the scapholunate ligament. Rather than moving from pure flexion to pure extension, it is the more natural arc of movement from extension with radial deviation through to flexion with ulnar deviation. It is the same motion that is used when throwing a dart. This is my “go-to” arc of motion for scapholunate ligament injuries of any grade, and an essential part of my DISI post-op toolbox.
  1. The joint position sensors are almost always injured when there is an injury to ligament and joint capsule. Proprioception retraining is essential to regaining normal function in a DISI wrist post operatively. It also helps to prevent future re-injury. You only have to use your imagination to come up with some great ideas for wrist proprioception retraining. As with any hand therapy, finding something that is meaningful to the client will enhance their motivation and compliance. Ideas may include:
    • weight-bearing gently through a large soft-ish ball on a table top or against a wall, with your upper limb in varying positions – perhaps “draw” shapes or “write” letters and numbers on the wall or table with the ball.
    • Rolling a tennis ball around on a tennis racquet clockwise or anti-clockwise, not letting it fall off. The further down the handle you hold the tennis racquet, the longer the lever. It may be easier to start with a small ball rolling around in an upturned Frisbee. This also allows you to alternate between a wide span grasp under the whole Frisbee or a lateral pinch grasp on the edge.
    • Slosh pipe (a length of tubing / spouting half-filled with water, with caps on either end): tilt the pipe from side to side, while keeping the water level steady. You can fabricate some handles out of thermoplastic to change the type or position of grip used.
    • Bathroom scales: taking weight through the unaffected hand to a certain level (e.g. 5kg) and then trying to mimic that with the affected hand. Try with eyes closed, the eyes open, then eyes closed again to integrate the pressure sensors’ feedback.
  1. Isometric strengthening. For the most part, when we are using our hands for a strength tasks, our wrists stay stable. Think about holding a drill, lifting a large item, pushing a trolley, etc. So it is best to do strengthening in the same way. Think of client centred activities (relating to your client’s goals / activities / lifestyle) that require the wrist to be strong and stable. You may start with simply squeezing a sponge / small ball / putty with wrist in mid-position, or resisting / blocking wrist movement while contracting the muscles, and progress to tool use, lifting and pouring a full jug, or sports-specific hand grips with the wrist in a stable position.

You could also try:

  1. Proximal stability. Good proximal stability is vital for good distal ability (strength, co-ordination, dexterity). Work on the core as well as the shoulder girdle and scapulo-thoracic stability. The Swiss ball is an excellent tool to use for this, as is a Pilates board if you have one. For clients at home, theraband exercises are inexpensive and easy to replicate.
  1. Scar management.After surgery, a smooth, flat, pale, pliable scar will result in better ROM outcomes than a red, raised, tight, contracted, unrelenting scar. As soon as the wound has healed and sutures are removed, start with paper taping the scar to stop it from raising or widening. For a scar that looks very active (red, raised, firm) you could try using contact media such as hydrocolloid dressings (worn full time for up to a week), or silicone gel sheeting (according to manufacturer’s guidelines, but most can be worn overnight, or up to 23 hours per day – if this does not interfere with function).
  1. Splint progression.While awaiting surgery for a DISI, most clients will benefit from a splint to support and protect, and keep them comfortable. Post operatively most will be in a cast for 6-8 weeks. Once the cast is removed, they still need protection between exercise sessions. You may elect to make a removable thermoplastic wrist splint, or you may choose an off-the-shelf option, which many clients find more comfortable. Suitable options may include the Jura Black Wrist Brace or the Procool D-ring wrist brace. 
    As treatment progresses, they may be able to function with less support, and could progress to something like the Ventroprene Neobracewhich is shorter and less restrictive.
    Then for a return to work or sports they may be able to perform in a light support such as the Thera P wrist splint universal.


Suitable supports

My professional favourite for DISI post cast removal is: Jura Black Wrist Brace or the Procool D-ring wrist brace. 


View our full range of wrist supports

We have an excellent range of wrist supports  that may be suitable for your clients.
 

What are your tips for treating clients with a DISI deformity?

This blog is a discussion format. We have listed our views above but would love to know what you think, what your comments are or how you best treat DISI deformity in your practice. Add your comments below in the comments box or feel free to email Alison@handtherapyproducts.com


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