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Scaphoid and Scapholunate Ligament Injuries

The Achilles' heel of the wrist

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Vol. 26 • Issue 18 • Page 28

Rehabilitation, Disablilty And Participation

Sometimes the mode of injury is hard to forget-a fall on an outstretched hand while roller blading, for example-whereas for other patients it is easily forgotten. Your patient may not recognize the exact moment the integrity of her wrist was compromised, but the consequences of a scaphoid injury are hard to ignore.

An injury to this small region can cause significant discomfort while performing fine-motor and resistive pinch activities, as well as range of motion and resistive tasks that produce loading forces to the wrist. Pain and instability can cause even the simplest tasks to become intolerable, and a delay in treatment can have crippling effects. I have heard more than a few patients recall that their injury caused significant pain but they didn't comprehend the damage done, citing the all-too-common lament, "I knew it was bad, but I didn't know it was that bad."

Scaphoid injuries can be that bad. The scaphoid bone is the most lateral carpal bone in the proximal row of the wrist, and it articulates with four other carpal bones-the trapezium, trapezoid, lunate and capitates, and the radius.1 It is the most commonly injured carpal bone. The injury may be initially dismissed as a serious sprain or a bad case of tendinitis. Prompt diagnosis and treatment yield the best result, which is especially crucial considering the limited blood supply to the proximal portion of the scaphoid.

A scaphoid fracture left untreated or one that fails to heal can lead to arthritis, scaphoid non-union advanced collapse (SNAC), and avascular necrosis (a scenario known as Preiser's disease).4

Similarly, a tear to the most commonly injured wrist ligament-the scapholunate ligament-can lead to instability between the scaphoid and lunate, which is classified as a carpal instability dissociative (CID) or instability between same-row carpal bones. The unfortunate sequelae of a continued breech is a scapholunate advanced collapse (SLAC) wrist, and arthritis. Worse yet, patients may unknowingly incur irreparable damage to their wrists by using their affected hands during heavy ADL or trying to strengthen their wrists while
they are acutely symptomatic.4

Looking for Clues

The physician has numerous options to choose from in order to diagnose either scaphoid or scapholunate ligament injuries, and should be consulted in cases where more information regarding a patient's condition is required.

Diagnostics include: CT scan, ultrasound, MRI, fluoroscope, arthrogram, arthroscope and plain film/X-ray.

A dynamic scapholunate ligament instability is only seen on diagnostics that display movement, such as a fluroscope, whereas a static instability may simply demonstrate a gap between the scaphoid and lunate. A significant scapholunate ligament tear may be noted on plain films as a dorsal intercalated segment instability (DISI) deformity whereby the position of the lunate is dorsiflexed in relation to the scaphoid while the wrist is in the neutral position. A suspected scaphoid fracture may not be detected on plain films, requiring further work-up with a bone scan or MRI.1,4

Provocative tests performed in the clinic may yield clues that a "simple wrist injury" may not be as simple as it appears. By applying pressure in the anatomical snuffbox at the base of the thumb, you can feel for the structural integrity of the scaphoid, as well as gauge the representation of your patient's pain.

Provocative tests such as the Watson's Test or Scaphoid Shift Test are maneuvers used to evaluate scapholunate ligament instability. However, variables as reported in a study by Wolf, et al. in the Journal of Hand Surgery, such as the "midcarpal shift"-a significant movement between the capitate and lunate-can skew the results of these tests. The study concluded that the Scaphoid Shift Test can be helpful in diagnosing scapholunate ligament injuries; however, it is not exclusively definitive, due to variables in wrist anatomy. Fluoroscopy was defined as the most reliable option.2

Treatment Options

Following diagnosis, the physician will determine the most appropriate course of action (conservative or surgical management). Regardless, the patient may be left with a protective phase of immobilization that trumps most others in the hand. Conservative management of a scaphoid fracture often necessitates a prolonged period in a cast. A scaphoid fracture can take up to 20 weeks to heal, though it may do so in a little more than a month.4 Likewise, a scapholunate ligament tear will also need an extended period of immobilization of up to eight weeks, and even further time before loading and resistive activities can be initiated.4,5

Surgical management will depend on the precise area injured as well as its severity. The physician may choose internal fixation, such as a Herbert screw, to correct a scaphoid fracture which will otherwise not heal naturally. A scapholunate ligament tear may be repaired with a variety of techniques, including capsulodesis, reconstruction and Kirshener wire or open reduction and pinning, which both require eight weeks of cast immobilization.4

Unfortunately, a delay in proper treatment may cause the surfaces of the bones to erode or to interrupt the vascular supply, necessitating a procedure that salvages wrist function. These procedures are dependant upon the amount of damage to the wrist, the age and normal activity of the patient. They include:

• proximal row carpectomy: The scaphoid, lunate and triquetrum are excised. This procedure allows for an approximate 80-degree return in total arc of motion for wrist flexion and extension;4

• arthroplasty: The carpus is replaced by metal or plastic prosthesis. This generally nets a 35-degree return in wrist flexion and extension each;4

• total arthrodesis: Severe damage may not be able to be corrected, and a total fusion may be necessary to relieve pain and improve function. It requires approximately 12 weeks of immobilization for the fusion to become solid;4

• partial arthrodesis: Two common types of partial fusion are the scaphoid-trapezium-trapezoid (STT) fusion, which provides an approximate 40-60 degree return in wrist flexion and extension, and the four-corner scaphoid-lunate-capitate-trapezium fusion, which provides an approximate 3-degree return in wrist extension and 36-degree return in wrist flexion.3,4

The initial occupational therapy evaluation should include a comprehensive ADL assessment and AROM measurements of the wrist and thumb; but don't forget to assess range of motion of the index, long, ring and little fingers as well as more proximal joints of the upper extremity, due to the potential for disuse stiffness. It is always nice to see a patient who is able to keep all uninvolved/uncasted joints freely moving; but as we all know, that is not always the case. Sadly, it is not uncommon to see stiff index fingers, elbows and even shoulders at the initial OT evaluation when, in most cases, this scenario could have been prevented. Strength testing is usually reserved until healing is more thorough.

Occupational therapy for treatment of a scaphoid fracture or scapholunate ligament injury will initially need to focus on pain and edema management as well as scar reduction for the post-operative patient, once he is released from the continuous immobilization phase of treatment. Once the physician confirms the stability of the wrist, the patient may be ready for a splint schedule that allows for light ADL, such as bathing, feeding and dressing out of the splint, as well as AROM exercises targeted at improving wrist AROM (with the exception of total wrist arthrodesis) and thumb ROM.

Progressive ROM, strengthening and loading activities and exercises are the last phase of treatment when the wrist can withstand it.4 As always, the timing and progression of exercises depend on many factors, such as the type of scaphoid or scapholunate ligament injury, the type of repair, and the state of the patient's healing process.

Scaphoid and scapholunate ligament injuries may appear small, but they can have a large impact on your patients' lives. A comprehensive approach, timed precisely, will help get them back in shape quickly.

References available at www.advanceweb.com/OT or upon request.

Amy Roux, OTR/L, CHT, has been a certified hand therapist since 2001, and has worked for UMASS Health Alliance since 1993.




     

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