Wrist osteoarthritis

Scapholunate advanced collapse (SLAC) is a predictable pattern of wrist osteoarthritis that results from untreated long-standing scapholunate ligament rupture and the associated carpal malalignment.[4] The misalignment is described as dorsal intercalated segment instability (DISI) which is where the lunate angulates towards the dorsal side of the hand.[2][5]

Scaphoid nonunion advanced collapse

Scaphoid fracture non-union changes the shape of the scaphoid bone and results in DISI malalignment.[2][5] Scaphoid Non-union Advanced collapse (SNAC) is the pattern of osteoarthritis that develops in relation to the malalignment.

Post-traumatic osteoarthritis can be classified into four stages.[1][6] These stages are similar between SLAC and SNAC wrists. Each stage has a different treatment.

• Stage I: the osteoarthritis is only localized in the distal scaphoid and radial styloid.
• Stage II: the osteoarthritis is localized in the entire radioscaphoid joint.
• Stage III: the osteoarthritis is localized in the entire radioscaphoid joint with involvement of the capitolunate joint.
• Stage IV: the osteoarthritis is located in the entire radiocarpal joint and in the intercarpal joints. It also may involve the distal radio-ulnar joint (DRUJ).

• 
  Stage I
• 
  Stage II
• 
  Stage III
• 
  Stage IV

From lateral to medial and when viewed from anterior, the proximal row is formed by the:

• Scaphoid
• Lunate
• Triquetral
• Pisiform

From lateral to medial and when viewed from anterior, the distal row is formed by the:

• Trapezium
• Trapezoid
• Capitate
• Hamate

The person may or may not recall an old wrist injury. [7]

Examination may identify limited passive wrist motion, pain at the extremes of wrist motion, tenderness at the radioscaphoid joint, and dorsal radial prominence.[2] Activities that use forceful wrist extension such as rising from a chair or push-ups may be painful.
In the absence of gout, chondrocalcinosis, rheumatoid arthritis, or prior distal radius fracture, a person with gradual onset limited motion and pain in the wrist likely has wrist osteoarthritis.

Radiographs can confirm the diagnosis of wrist osteoarthritis. The earliest sign is narrowing of the joint space between the radius and the scaphoid and an osteophyte off the tip of the radial styloid. [9]

SLAC

Because SLAC results from scapholunate ligament rupture, there is a larger space between the two bones, also known as the Terry Thomas sign.[10] Scaphoid instability due to the ligament rupture can be stactic or dynamic.[11] When the X-ray is diagnostic and there is a convincing Terry Thomas sign it is a static scaphoid instability. When the scaphoid is made unstable by either the patient or by manipulation by the examining physician it is a dynamic instability.[11]

SNAC

In order to diagnose a SNAC wrist you need a PA view X-ray and a lateral view X-ray. As in SLAC, the lateral view X-ray is performed to see if there is a DISI.[12] Computed tomography (CT) or Magnetic Resonance Imaging (MRI) are rarely used to diagnose SNAC or SLAC wrist osteoarthritis because there is no additional value.[7] Also, these techniques are much more expensive than a standard X-ray. CT or MRI may be used if there is a strong suspicion for another underlying pathology or disease.[7]

For stage I, normally, nonsurgical treatment is sufficient. Injections of corticosteroid may be considered. Keep in mind that corticosteroids provide, at best, temporary alleviation of discomfort. And corticosteroid injection harms cartilage. Since people with Stage 1 arthritis have good cartilage, one might be cautious with corticosteroid injection.

Surgical options for mild arthritis may include neurectomy of the anterior and posterior interosseous nerves, or radial styloidectomy, in which the radial styloid is surgically removed from the distal radius.

The surgical options for stage II and III wrist osteoarthritis are excision of some of the bones with or without fusion (arthrodesis) of the others. The idea is to try to alleviate pain while maintaining some wrist motion.

One technique is to remove one row of carpal bones. The bones closer to the forearm (proximal) are removed: scaphoid, lunate, and triquetrum.[14] It is important that the radioscaphocapitate ligament is left intact, because if the ligament is not preserved the capitate bone will translate to the ulnar side of the wrist and move away from the distal radius.[1][15]

The new articulation of the capitate with the lunate fossa of the distal radius is not as congruent as the former scaphoid-lunate-radius joint.[16][17] This and other issues contribute to potential to develop arthritis over the years. In part based on these concerns, some surgeon prefer to maintain the lunate in patients younger than 40 years proximal row carpectomy. [6][18]

A surgery called four-corner arthrodesis is an option.[6] The capitate, lunate, hamate and triquetrum are fused together in this procedure and the scaphoid is excised.[1][14] Before the arthrodesis is executed, the lunate must be reduced out of DISI position.[14] Because the radiolunate joint is typically preserved in stage II SLAC and SNAC wrists, this joint can be the only remaining joint of the proximal wrist. Both procedures are often combined with wrist denervation, as described in the text of treatment stage I.

In Stage III wrist osteoarthritis, some surgeons offer patients proximal row carpectomy and interpose some of the wrist capsule to account for the arthritis in the capitate. Four-corner arthrodesis, as described above in stage II, is also an option.

In this stage there are two surgical treatment options; total wrist arthroplasty and total wrist arthrodesis. Total wrist arthrodesis has become the standard surgical treatment for patients with stage IV wrist osteoarthritis. During this procedure the carpal bones are all fused together and are then fastened to the distal radius.[14] Patients who still want to undertake heavy labor benefit the most of this surgical approach,[19] because after surgery and recovery this is still possible. However, the arc of motion is extremely diminished by this type of surgery.

The best option for those who wish for a motion-sparing procedure is total wrist arthroplasty. However, impact loading should be avoided, an object heavier than 4.5 kg should not be lifted.[20] So, this surgical approach has postoperative activity restrictions. Nevertheless, patients with a total wrist arthrodesis on one side and a total wrist arthroplasty on the other, prefer the total wrist arthroplasty.[21] The procedure exists of a couple of elements. First, the proximal row is removed and the distal row is fastened to the metacarpals. Then, one side of the arthroplasty is placed upon the distal row and the other side on the distal radius. Additionally, the head of the ulna is removed.[14]