Robert Kienbock; a Viennese radiologist described 16 cases of avascular necrosis of lunate in 1910. Similar changes of lunate in anatomical specimen was reported by Peste in 1843, but Kienbock’s report was the first clinical report.
The cause of Kienbock disease is thought to be due to mechanical or vascular causes. Negative ulnar variance was identified by Olle Hulten in 1927 as a predisposing factor for Kienbock disease. He reported 74% incidence of negative ulnar variance in patients with Kienbock disease. In the normal population 61% have neutral, 26% negative and 13% have positive ulnar variance. But many other researchers found that negative ulnar variance is not significantly higher in those with Kienbock’s disease. According to Nakamura et al ulnar variance tends to become more positive with age.
Negative ulnar variance results in overloading of the radial portion of lunate leading to stress fractures. The lunate is sandwiched between rigid capitate and the radius and elastic TFCC; which may lead to stress fractures due to so called nutcracker effect. Other morphological associations reported are flattened radial inclination and smaller size of lunate.
Blood supply to the lunate may be a key factor in pathogenesis. Three patterns of extraosseous blood supply has been described for lunate. Multiple vessels, one volar and one dorsal vessel each and a single dorsal blood vessel in 7%. In addition 31% of cases showed single path of intraosseous supply through the bone with no significant arborization. Lunate with a single blood vessel supply may be at risk for avascular necrosis in presence of trauma.
Proximal portion of lunate is a terminal perfusion zone dependent on intraosseous retrograde blood supply. In Kienbock disease, the pathoanatomical changes show zone of necrosis in the proximal portion, zone of reparation in the middle layer with fibrovascular reparative tissue and zone of viability in the distal portion. Disruption of venous outflow has also been thought to be a cause of Kienbock disease.
The causation of Kienbock disease appears to be multifactorial. Vascular patterns, anatomical variations when combined with repetitive trauma may be the reason. Lunate with negative ulnar variance, single blood vessels and poor intraosseous anastomoses may be at risk for Kienbock disease in the setting of repetitive trauma.
Seen most commonly in young adults between 20-45 years. But it has been reported in children and older persons. It is more common in males. Often there is history of minor trauma or repetitive trauma. Usually unilateral and patients present with dorsal wrist pain, weakness and restricted range of movement. There may be dorsal tenderness localised to lunate. Swelling and fullness may be seen in presence of synovitis. Restricted range of motion may be seen. In presence of synovitis, anteroposterior translation when doing drawer test may be diminished.
Diagnosis is mainly by x-ray. On the x-ray assess the sclerosis and collapse of lunate, carpal collapse by assessment of carpal height, rotation of scaphoid by the ring sign and angles such as radio-scaphoid angle or scapho-lunate angle. Assess the width of lunate on the lateral view to assess lunate collapse. Assess the ulnar variance on the AP view taken as per the method described by Palmer, Glisson and Werner; in 90 degree shoulder abduction, 90 degree elbow flexion and forearm neutral rotation. Draw the mid-diaphyseal axis of radius and draw a perpendicular at the level of medial corner of distal articular surface of radius, draw a line parallel to the distal articular surface of ulna and measure the distance between the 2 lines. MRI is an excellent investigation to assess the vascularity
X-ray based classification was first described by Decoulx in 1957. Most commonly used classification is the Lichtman’s classification.
I- Normal X-ray with positive bone scan
II- Sclerosis with normal size and shape
IIIA- Lunate collapse with proximal migration of capitate, scaphoid normal
IIIB- Carpal collapse with fixed scaphoid rotation
IV- Radiocarpal Arthitis
Coronal lunate fracture is now considered as stage IIIC and is associated with poor prognosis.
Bain & Begg Arthroscopic classification
Based on number of nonfunctional articular surface.
0- Articular surfaces are normal
1- Proximal surface of lunate abnormal
2A- Proximal surface of lunate and lunate fossa of radius abnormal.
2B- vertical fracture of lunate.
3- Lunate fossa of radius and proximal and distal surfaces of lunate abnormal.
4- Lunate fossa of radius and proximal and distal surfaces of lunate and the proximal surface of capitate abnormal.
Lunate stress test- Done in those symptomatic patients with normal MRI. Repeated axial loading of wrist followed by Gadolinium enhanced fat suppressed T1 sequences will show Schmitt and Lanz pattern A pattern (bone marrow edema).
Schmitt and Lanz MRI patterns
N- Normal signal
A- Marrow edema with viable and intact bony trabeculae
B- Early marrow necrosis with fibro-vascular reparative tissue
C- Necrotic bone marrow with collapse
Only 25% of MRI signal changes seen in lunate are caused by Kienbock disease. Other causes for altered signal on MRI are ulnar impaction syndrome, TFCC lesion, intraosseous cysts fibrocartilaginous type lunotriquestral fusion, trauma and inflammatory lesions.
Integrated classification system combines osseous changes determined by X-ray, vascular changes identified by MRI and chondral changes identified by arthroscopy.
Pathological phases of Kienbock disease are;
Early vascular phase- Ischaemia, necrosis, revascularization
Intermediate osseous phase- Sclerosis, subchondral collapse, coronal fracture, remodelling
Late chondral phase- Subchondral collapse, articular surface collapse, degeneration of opposing articular surface.
Kienbock disease may be due to multiple factors such as repetitive loading, vascular risk and mechanical predisposition. As a result treatments designed so far have been aimed at correction of abnormal biomechanics or at revascularization. Persson first described step cut lengthening osteotomy of ulna to treat Kienbock disease. Hori reported that transposition of an arteriovenous pedicle resulted in formation of new bone. Since then many vascularised pedicle grafts have been described. Illarramendi in 2001 described radius and ulna metaphyseal core decompression for Kienbock disease. Mehrpour et al in 2011 described core decompression of lunate.
Before deciding on treatment, the involved wrist should be thoroughly evaluated to determine the stage of disease and the biological and biomechanical effects of collapsed lunate. Treatment is conservative in children and in old persons over 60 years.
Surgical treatment can be classified into revascularization procedures, joint decompression procedures and salvage procedures.
Choice of surgery depends on the stage of disease, range of movement of wrist, ulnar variance, shape of sigmoid notch and the presence of coronal fracture of lunate.
Treatment is mainly based on the stage of disease.
Treatment recommendations based of Lichtman’s classification
I – Immobilization
II &IIIA with negative ulnar variance- Radial shortening
II &IIIA with positive ulnar variance- Lateral wedge osteotomy of radius or Capitate shortening
IIIB- Proximal row carpectomy or triscaphe fusion
IV- Wrist arthrodesis
Stage I is managed mainly by immobilization for 3 months. Then the patient is reassessed, and if symptoms have improved and if there is radiologic evidence of healing the patient is progressively mobilised.
In stage II and IIIA, the patient can be managed either by revascularization procedure or joint levelling procedures. In patients with negative ulnar variance, radius shortening or ulnar lengthening is preferred. If ulnar variance is neutral or positive, then lateral wedge osteotomy of radius or capitate shortening osteotomy is done.
In stage IIIB, treatment can be by intercarpal fusion, preferably STT fusion with or without lunate excision/replacement.
In stage IV the treatment is determined by the condition of articular cartilage of proximal pole of capitate. If the proximal pole of capitate is normal then proximal row carpectomy is preferred and if abnormal then either wrist fusion or wrist denervation can be done.
Revascularization may be by direct vessel implantation or indirectly by vascularised bone graft (VBG). Vascularised bone graft may be pedicled or free. Revascularization needs removal of dead bone, replacement of dead bone by living bone and protection of lunate by immobilisation till it heals. Saffar’s technique is use of pisiform bone pedicled on the ulnar artery. Another technique is removal of dead bone, filling of defect by cancellous graft and direct transplantation of vessels such as posterior interosseus artery. Mayo group after study of blood supply designed 4,5 extensor retinaculum vascularised bone graft from radius. Because of anatomic variations, it is better to be aware of multiple sources of pedicled bone graft. Either external fixation or temporary pinning of scapho-trapezo-trapezoid joint is necessary along with VBG to unload the lunate. Stage I and II is a good indication for VBG. Smoking and oldage are considered as contraindications for VBG.
Joint decompression may be done in presence of osseous stage 1, 2, 3A. Joint decompression may be done by radial shortening, ulnar lengthening, intercarpal arthrodesis or capitate shortening. Radial shortening or ulnar lengthening are indicated only in presence of negative ulnar variance. Satisfactory pain is seen in majority of patients but the fate of lunate is unclear as many show further collapse. Joint levelling is thought to act by unloading of lunate. Many think that it may be due to biological changes of healing after osteotomy. The negative ulnar variance should be measured and the amount
of joint levelling should be such that postoperatively there should be neutral or 1mm positive ulnar variance. Radial shortening should not be more than 4mm. It has more predictable results than ulnar lengthening. Morphological study of sigmoid notch show 3 types of sigmoid notch. Joint levelling may lead to DRUJ symptoms in some morphological patterns. Signs of revascularization is found in one third of patients, significant pain relief is seen in over 90%, grip strength improve in 75% and range of movement improve in over 50%.
In those patients with neutral or positive ulnar variance, capitate shortening osteotomy with or without capito-hamate fusion (Almquist procedure) will unload the lunate theoretically, but clinical and radiological results of the procedure have been poor.
In the absence of negative ulnar variance, lateral wedge osteotomy of radius to reduce radial inclination should be done to reduce radial inclination. Other osteotomies meant for joint decompression are lateral closing wedge osteotomy of radius, lateral opening wedge osteotomy and medial closing wedge osteotomy of radius. Radial opening wedge osteotomy causes better decompression than closing wedge osteotomy.
Salvage procedures can be denervation, arthroplasty or arthrodesis. Arthroplasty may be by proximal row carpectomy, excision of lunate, excision of lunate with intercarpal fusion, excision and replacement with biological tissue such as palmaris longus, pisiform or head of capitate (Graner’s procedure), or by prosthetic replacement. It is indicated in presence of osteoarthritis (Stage4) or in presence of carpal collapse with fixed scaphoid rotation. Proximal row carpectomy is the procedure of first choice as the functional results are good. Proximal row carpectomy is contraindicated in presence of degenerative changes involving lunate fossa of radius, degenerative changes involving proximal pole of capitate and previous intercarpal fusions; wrist arthrodesis is the procedure that needs to be considered in these circumstances.
An important consequence of lunate collapse is change in the intercarpal relationship in particular rotatory subluxation of scaphoid. Prevention of rotatory subluxation of scaphoid as well as decompression of lunate can be achieved by intercarpal fusions such as scaphotrapezotrapezoid (STT) fusion or scaphocapitate fusion.
Use of arthroscopy in the treatment was described by Menth Chiari in 1999.
Copyright @Dr Rajesh Purushothaman, Associate Professor, Government Medical College, Kozhikode, Kerala, India