A Case Report With Atypical Findings and Literature Review
STEPHEN L. STUCKEY, M. MED., F.R.A.C.R., VICTOR KALFF, F.R.A.C.P., AND GREG HOY, F.R.A.C.S.
The authors present an 18-year-old man who had a 5-month history of a painful left wrist. Despite the prolonged history, discrete photopenia on the blood-pool phase and photopenia relative to the remainder of the ipsilateral carpus on the delayed phase of a bone scan in the region of the lunate was shown. When Kienbock's disease is seen in its late phase, the bone scan findings may be atypical in that they may not show the usual three-phase bone scintigraphic evidence of bone remodeling expected in delayed diagnosis avascular necrosis. A review of the previous literature is presented. Key Words: Kienbock's Disease, Bone Scan.
Photopenic bone scan abnormalities in early avascular necrosis, particularly in the femoral head, are a wellrecognized phenomenon. Photopenic bone scan abnormalities have rarely been documented in carpal avascular necrosis. We describe a patient with Kienbock's disease (lunatornalacia or avascular necrosis of the lunate) in whom we found the apparently rare finding of lunate-relative photopenia on bone scan after 5 months of symptoms. The finding of a relatively photopenic abnormality in the carpus, despite the presence of prolonged symptoms, is consistent with avascular necrosis. Awareness of this appearance should improve accuracy in wrist and hand scintigraphic interpretation.
Case Report
An 18-year-old, right-handed man had a 5-month history of pain in the left wrist. There was no history of previous trauma, repetitive injury, or overuse. Examination showed marked limitation of wrist movement. Plain radiographs of the left wrist showed the possibility of minor increased density in the left lunate with ulna neutral variance. Ultrasound studies showed soft tissue thickening over the dorsal capsule of the radiocarpal joint. A three-phase(initial blood flow, early blood pool, and 3-hour delayed) bone scan of the hands and wrists was performed with 700 MBq of Tc-99m MDP (Fig. 2 A,B). Relative photopenia in the left lunate, compared with increased left carpus tracer and the right lunate region, was clearly identified on the bloodpool phase. The delayed phase showed slightly increased tracer in the region of the left lunate when compared with the contralateral lunate region. However, this increase was difficult to appreciate because of markedly increased surrounding ipsilateral carpal tracer. The delayed phase also showed increased tracer in the distal radius and ulna epiphyseal plates and in a periarticular distribution involving the small joints of the left hand. The bone scan findings were thought to be consistent with avascular necrosis of the lunate. The associated findings in the wrist were considered evidence of a reactive carpal synovitis or possibly a form of reflex-sympathetic dystrophy, with increased uptake in the small joints of the hand and distal radius and ulna epiphyseal plates relating to hyperemia. In view of the long duration of symptoms, the findings were considered atypical, and an MRI was performed to further substantiate the diagnosis. The MRI-T1 sequence showed reducedsignal intensity in the proximal half of the left lunate that was consistent with avascular necrosis with no evidence of an associated fracture.
The patient underwent a left radius shortening and distal transverse osteotomy, with protective buttress plating, which resulted in minimal ulnar positive variance. The postoperative course was uncomplicated. At 6 months, there was full range of motion in the left wrist, no irritability, and minimal pain, which occurred only with forced extension. There was no evidence of contralateral disease at clinical follow-up.
Discussion
Kienbock's disease, although of uncertain cause, involves interruption of the vascular supply to the lunate and eventually avascular necrosis. Kienbock's disease is more common in those with an ulna minus variance i.e., a relatively short ulna compared with the radius, and occurs in virtually any age group that has with wrist pain, weakness, and reduced motion. Treatment of Kien bocks disease may involve immobilization, decompression of the lunate, removal, replacement, or revascularization of the lunate or radius-shortening procedures. Treatment is largely based on the radiologic findings and particular stage. Imaging of Kienbock's disease initially is performed with plain radiographs, which are normal early in the course of the disease. Later, plain radiographs show the classical findings of avascular necrosis with relative increased density and eventually subchondral collapse, fragmentation, and secondary osteoarthritis.
There is limited radionuclide imaging literature on the bone scan appearances of Kienbock's disease. Duong et al were the first to describe a case of Kienbock's disease with correlation of clinical, radiographic, scintigraphic, and pathologic findings. In this article, the scan results of a patient who had symptoms for an 8-month period showed lunate-region photopenia relative to the increased tracer in the remainder of the ipsilateral wrist on the blood-pool and delayed phases of the bone scan examination. As subsequent reports showed, the patient was atypical in terms of duration of his symptoms and corresponding scintigraphic findings.
In a series of 21 patients, comparing the role of plain radiographs, radionuclide imaging, and MRI in carpal avascular necrosis, 4 patients were thought to have Kienbock's disease. All four patients had delayed bone scan abnormalities of increased lunate tracer and only three had positive MRI results . However, bone scan abnormalities needed correlation with anatomic imaging to increase specificity. Sowa et al described the wrists (total, 14) in 12 patients with lunate avascular necrosis (4). Twelve wrists showed increased delayed tracer in the lunate. In one case, increased tracer was noted in the trapezoid rather than in the lunate, and bone scintigraphy was not performed in one case . Focal, increased blood pool in the region of the lunate was noted in five of the 12 wrists with Kienbock's disease in which bone scintigraphy was performed. Focal, increased blood pool was also noted close to the lunate or in the entire carpus in another 3 of these 12 wrists. Magnetic resonance imaging and scintigraphy had comparable sensitivity; however, MRI was more specific. Amadio et al (5) reported a case of false-negative imaging (e.g., plain radiographs, tomography, bone scan, and MRI) after 3 months of symptoms, which was positive for Kienbock's disease on review imaging at 1 year. Their review showed the delay in diagnosis of Kienbock's disease is between 1 month and 10 years, and it averages 14-26 months. They suggested that in some instances. avascular necrosis may develop during a prolonged period. Other examples in the literature and textbooks that are not dedicated to the topic of Kienbock's disease only give examples of increased blood pool and delayed tracer in the lunate .
Thus, the appearance of relative photopenic abnormalities in Kienbock's disease has only been clearly described by Duong et al in their initial case report of the scintigraphic findings in Kienbock's disease. The appearances of reduced blood-pool and reduced delayed uptake relative to the remainder of the ipsilateral wrist in a patient with prolonged symptoms is probably particularly rare. However, it is noteworthy because future cases will not require MRI to confirm the diagnosis. The pathogenesis of these appearances could relate to ischemic necrosis in which revascularization and subsequent repair has not occurred, and the evolution of the disease has been protracted. An intermittent, temporary, or partial vascular impediment that eventually progresses to complete obstruction and, thereby, to worsening of symptoms, presentation, and the scan appearances is hypothesized. These complex alterations are probably further complicated in these cases by a superimposed, reactive carpal synovitis or reflex-sympathetic dystrophy, which provides the high-background carpal tracer levels.
Conclusion
A case of Kienbock's disease with atypical scintigraphic findings relative to symptom duration and the previously published literature is presented showing that decreased tracer relative to the remaining carpus may occur in Kienbock's disease, despite a delayed presentation.