Kienböck Disease

Kienböck disease is avascular necrosis (AVN) of the lunate — the central carpal bone. The lunate has a tenuous blood supply (often a single palmar vessel with variable dorsal contributions), making it vulnerable to ischaemia following trauma or in conditions that compromise its perfusion. The disease follows a characteristic progressive course from early oedema and subchondral changes to collapse, fragmentation, and ultimately carpal instability and wrist arthritis. Early-stage disease in a young patient offers the best opportunity for joint-preserving intervention.

• Epidemiology: peak incidence in young adults aged 20–40 years; male predominance; typically unilateral; dominant hand more commonly affected; associated with manual workers and certain occupations involving vibration tool use
• Aetiology — ulnar negative variance: the association between negative ulnar variance (the ulna is shorter than the radius at the wrist) and Kienböck disease is well established; in ulnar negative variance, the lunate bears more of the compressive load across the wrist (the radiolunate contact force is increased when the ulna is short); this biomechanical overload is proposed as a contributing factor; the normal ulnar variance is neutral; negative variance is present in the majority of Kienböck patients; ulnar lengthening (joint-levelling procedure) is one of the primary surgical treatments for early-stage disease in patients with negative ulnar variance
• Blood supply of the lunate: receives blood from dorsal and volar vessels; approximately 20–30% of lunates have a single palmar nutrient vessel only (no dorsal supply) — these are most vulnerable to AVN; the specific vascular anatomy can be assessed on MRI and is relevant to surgical planning (revascularisation procedures)
• The lunate`s central position in the proximal carpal row makes its AVN particularly destructive — as it collapses, the carpal alignment is lost and secondary arthritis of the radiocarpal and midcarpal joints follows predictably

• History: insidious onset of dorsal wrist pain and stiffness; weakness of grip; the onset may follow a trivial injury or occur without any identifiable trauma; symptoms are often present for months before diagnosis; point tenderness over the dorsal lunate (just distal to Lister`s tubercle, slightly ulnar) is characteristic
• Examination: dorsal wrist swelling; grip weakness; reduced wrist range of motion (flexion-extension both reduced); tenderness directly over the lunate on dorsal palpation; no specific clinical test reliably diagnoses Kienböck — the diagnosis is radiological/MRI-based
• Differential diagnosis: scaphoid fracture/non-union; SL instability; dorsal ganglion; dorsal wrist impingement; inflammatory arthritis; wrist fractures; the key differentiating investigation is imaging (plain X-ray and MRI)

• Plain radiographs (PA and lateral views): assess lunate density (sclerosis = Stage II); lunate shape and height (collapse = Stage III); carpal alignment (scaphoid rotation, DISI deformity = Stage IIIB); generalised OA changes (Stage IV); measure ulnar variance (negative variance = ulnar shorter than radius — key for surgical planning); Stage I disease has normal X-rays — MRI is required for diagnosis at Stage I
• MRI: the gold standard for early diagnosis and staging; Stage I — diffuse low T1 signal throughout the lunate (avascular bone is low T1 because it lacks normal fat signal); high T2 in Stage I (oedema); low T1 AND low T2 in established AVN (the dead bone has no perfusion or oedema signal); MRI also assesses the extent of articular cartilage preservation (critical for surgical decision-making)
• CT scan: best assessment of lunate morphology, collapse pattern, and fracture lines within the lunate; useful for pre-operative planning (estimating the degree of collapse and fragmentation); staging alongside MRI in Stages II–III
• Bone scan: increased uptake in the lunate (even before X-ray changes); historically useful; now largely superseded by MRI for sensitivity and specificity

• Radial shortening osteotomy (RSO): the most commonly performed joint-levelling procedure for Kienböck disease in patients with negative ulnar variance; the radius is shortened (typically 2–4 mm) to convert the negative variance to neutral; this reduces the compressive load on the lunate by redistributing force to the ulna; performed at Stage I, II, and IIIA; the osteotomy is fixed with a locking plate; outcomes are good at Stages I–II with approximately 70–80% pain relief; RSO is not appropriate if ulnar variance is already neutral or positive (would create ulnar positive variance and ulnar impaction syndrome)
• Ulnar lengthening osteotomy: an alternative joint-levelling procedure achieving the same biomechanical effect (correcting negative variance) by lengthening the ulna rather than shortening the radius; technically more demanding; less commonly used than RSO
• Revascularisation procedures: pedicled vascularised bone grafts from the distal radius (4,5 ICSRA pedicle — 4th and 5th extensor compartment artery) or the pronator quadratus; the graft carries a vascular pedicle that introduces new blood supply into the avascular lunate; used for Stage I–IIIA disease; technically demanding; results are modest but justified in young patients who have failed or are not suitable for joint-levelling alone; free vascularised grafts (from the knee — osteocartilaginous rib graft) for selected cases
• Scaphocapitate fusion (capitate shortening): for Stage IIIA/B; the scaphoid and capitate are fused, effectively unloading the lunate by transferring wrist forces through the scaphotrapeziotrapezoid and midcarpal joints; preserves some wrist motion; the `capitolunate unloading` is the mechanism of pain relief
• Proximal row carpectomy (PRC): for Stage IIIB/IV (if the radiolunate fossa cartilage and capitate head are preserved); removes the scaphoid, lunate, and triquetrum; the capitate articulates with the radiolunate fossa; provides 60–70% of normal wrist motion; reliable pain relief; contraindicated if capitate head or lunate fossa has OA changes

• Neutral or positive ulnar variance and Kienböck: approximately 20–30% of patients with Kienböck disease have neutral or positive ulnar variance; in these patients, radial shortening is inappropriate (would create positive variance and ulnar impaction); alternative joint-levelling is not applicable; management options for neutral variance Kienböck include: capitate shortening osteotomy (reduces the length of the capitate, unloading the lunate without altering radial or ulnar length); STT (scaphotrapeziotrapezoid) fusion; revascularisation; or conservative management if Stage I–II with watchful waiting
• Lichtman Stage IIIA vs IIIB distinction: this distinction is critical for surgical decision-making; in Stage IIIA, the lunate has collapsed but the scaphoid remains in its normal position — carpal alignment is maintained; joint-levelling (RSO) can still be effective; in Stage IIIB, the scaphoid has rotated into a fixed flexed position (the SL ligament has stretched due to lunate collapse, allowing scaphoid rotation); joint-levelling alone is insufficient — the carpal malalignment requires direct correction (scaphocapitate fusion, STT fusion) or salvage surgery (PRC)
• The `lunate type` and surgical planning: lunates are classified by the presence or absence of a medial facet (Type I — no medial facet, articulates only with the radius; Type II — has a medial facet articulating with the hamate); Type II lunates have an additional articular surface and may have a more protected blood supply; this distinction affects the biomechanics of load transfer and is relevant to decision-making in capitate shortening procedures

• Kienböck disease: AVN of the lunate; young adults 20–40 years; associated with negative ulnar variance; insidious dorsal wrist pain + grip weakness; Lichtman Stage I–IV
• Stage I: normal X-ray; MRI shows low T1 (avascular lunate), high T2 (oedema); best prognosis; most treatable; the only stage diagnosable on MRI alone
• Stage II: lunate sclerosis on X-ray; shape preserved; Stage IIIA: lunate collapse + normal carpal alignment; Stage IIIB: collapse + fixed scaphoid rotation (DISI); Stage IV: pan-carpal OA
• Negative ulnar variance: ulna shorter than radius; increases radiolunate compressive load; present in majority of Kienböck patients; key measurement on PA X-ray
• Radial shortening osteotomy: shortens radius 2–4 mm to neutral variance; reduces lunate load; Stages I–IIIA with negative variance; 70–80% pain relief; contraindicated if variance already neutral/positive
• Neutral/positive variance: RSO contraindicated; use capitate shortening or STT fusion instead
• Stage IIIB and IV: PRC (if capitate head + lunate fossa preserved) or total wrist arthrodesis; joint-levelling ineffective for fixed carpal malalignment
• PRC: removes scaphoid, lunate, triquetrum; capitate on radial fossa; 60–70% wrist motion; contraindicated if capitate OA (Stage IV)
• Revascularisation: pedicled vascularised graft (4,5 ICSRA); for Stages I–IIIA; introduces new blood supply into avascular lunate; useful adjunct in young patients
• MRI low T1 + low T2: established AVN (dead bone — no fat signal, no oedema); Stage I = low T1, HIGH T2 (oedema still present = reversible ischaemia)