Kienbock's Disease

• Kienbock's disease is Osteonecrosis Of The Lunate.
• By a mechanism that still is not entirely understood, the blood flow to the lunate bone of the wrist is compromised to such an extent that osteonecrosis ensues and collapse and fragmentation of the bone occurs over time.
• The end result can be degenerative arthritis of the radio-carpal joint and pain. 

Pathogenesis

• Various predisposing factors exist.
• About 75% of patients have a shorter ulna compared to the radius, as measured at the wrist (Ulnar Negative Variance).
• The slope of the distal radius articular surface is found to be more horizontal.
• Approximately 25% of lunate are thought to have a single vessel blood supply.
• Repetitive micro-fracture of the bone or a single fracture have been suggested as the cause of osteonecrosis of the lunate.

Incidence

• More common in Males that females.
• It occurs more frequently between the ages of 15 and 40 years and in the dominant wrist of men engaged in manual labor. 

Clinical features

• Half of patients relate a history of trauma.
  
• Most complain of dorsal wrist pain and stiffness.
  
• Physical examination may reveal
  
  • →  Diminished range of motion,
    
  • →  Grip weakness, and
    
  • →  Tenderness over the radio-carpal joint.
    
• Some patients present with symptoms of carpal tunnel syndrome.
  
• Untreated, the disease usually results in
  
  • →  fragmentation of the lunate,
    
  • →  collapse with shortening of the carpus, and
    
  • →  secondary arthritic changes throughout the proximal carpal area.
    
• Symptoms can develop 18 months before radiographs show evidence of the disease.
  

Radiographic Staging

•  Stage 0: Normal plain radiographs of the wrist with abnormal MRI scan of the lunate.
  
•  Stage 1: Fracture of the lunate without collapse of the bone.
  
•  Stage 2: Sclerosis of the lunate without collapse of the bone.
  
•  Stage 3a: Lunate collapse without loss of height of the wrist.
  
•  Stage 3b: Collapse of the wrist. Fixed rotation of the scaphoid with IIIA changes.
  
•  Stage 4: Degenerative changes of the wrist joint secondary to Keinbock's disease.
  

Radiographic Classification of Kienbock's disease

Management

• In patients with stage 0 and stage 1 disease, Immobilization And Non-Operative Support may suffice. 

• Patients with stage 2 and stage 3a disease who continue with symptoms are generally indicated for Surgery.

• The surgical procedures for patients with stage 2 and stage 3a Kienbock's disease can be divided into two broad categories:
  
1. Joint-Leveling Procedures
   
2. Revascularization Procedures 

• The most commonly performed among these procedures is the Radial Shortening
  Osteotomy.
  
• →  This procedure is indicated in patients who have a short ulna and the goal of surgery is to shorten the radius to “level” it with the ulna.
  
• →  The exact reason why this procedure is effective is still unknown.

• The most commonly performed revascularization procedures for Keinbock's disease is a Pedicled Vascularized Bone Graft harvested from the dorsal distal radius.

• For patients with symptomatic stage 4 & some pts with stage 3b disease, reconstructive salvage surgery of the wrist is indicated.
  
• This salvage surgery may include
  

1. A PARTIAL (maintains some element of wrist range of motion),or a Complete Wrist Fusion, or
   
2. A Proximal Row Carpectomy (removal of the lunate bone along with the scaphoid and
   triquetral bone).
   
   • →  Proximal row carpectomy allows the capitate to articulate in the lunate fossa.
     
   • →  A prerequisite for this operation is maintenance of a good distal radius articular surface.