Controversy surround the etiology of kienboecks disease (lunatomalacia).
Few of the theories are (a) In manual workers chronic repetitive trauma is considered to damage supplying arteries of the lunate . : Arteries entering the lunate from the dorsal and palmar pole form an intraosseous vascular network with the proximal pole supplied by terminal arteries only . (b)Another theory of compression or avulsion fractures as the primary cause of lunatomalacia is nowadays rejected by many authors. (c)According to an observation by Hulten , lunatomalacia is associated with a negative ulnar variance in 78% of the test population. Due to inadequate force transmission from the ulna to the wrist, the lunate is exposed to an increased axial load in the radiolunate articular cornpartnient. (d)Most recently, the possibility of venous congestion is discussed as a cause of lunatomalacia with intraosseous measurements showing significantly higher pressures .
MRI Staging with signal on T1
Stage 1- Low signal, and shows homogenous enhancement refd as edema considered as prognostically good
2-Low signal on T1 shows pathcy inhomogenous enhancement and is refd as partial necrosis
3-Low signal on T1 absent enhancement and refd as complete necrosis
Differential diagnosis includes the rare fractures of the lunate without consecutive necrosis, the ulnolunar impaction syndrome, and intraosseous ganglia originating from the scapholunar or lunotriquetral ligament
Staging classification of Kienbock's disease on radiological and MRI criteria.Stage (MRI and conventional radiography) Lichtman and Ross
I Normal radiographic appearance,diagnosis by MRI
II Increased spongiosal sclerosis,initial fracture of the proximal pole possible
III (a) Lunate collapse without carpal instabilityIII (b) Progessive lunate collapse with carpal instability
IV Progessive carpal collapse and ostcoarthritis (SLAC wrist) in our case proximal pole of scaphoid shows the fracture but marrow signal is normal and no AVN is seen.
Case by Dr MGK Murthy, Sr Consultant Radiologist