What Is the Radiographic Prevalence of Incidental Kienböck Disease?

BACKGROUND

Kienböck disease is characterized by osteonecrosis of the lunate. Not all patients with radiographic evidence of the disease experience symptoms bothersome enough to consult a doctor. Little research has been performed on the prevalence of Kienböck disease, and the prevalence in the asymptomatic population is unclear. Knowledge of the natural course of the disease and how often patients are not bothered by the symptoms is important, because it might influence the decision as to whether disease-modifying treatment would be beneficial.

QUESTIONS/PURPOSES: (1) What is the prevalence of incidental and symptomatic Kienböck disease? (2) What are the factors associated with incidental and symptomatic Kienböck disease? (3) Are there differences in Lichtman stage distribution between incidentally discovered and symptomatic Kienböck disease?

METHODS

We retrospectively searched radiology reports of all MRI scans, CT scans, and radiographs that included the wrists of 51,071 patients obtained over an 11-year period at one institution to screen for Kienböck disease and avascular necrosis of the lunate. Corresponding MR images, CT scans, or radiographs were reviewed by an orthopaedic hand surgeon to confirm the presence of Kienböck disease when the report was inconclusive. The medical record was reviewed to determine whether the radiographic Kienböck disease was incidental. Prevalences were calculated for both symptomatic and incidental Kienböck disease. Additionally, we assessed the association of age, sex, and race with incidental and symptomatic Kienböck disease as well as the radiographic severity according to the Lichtman classification and calculated odds ratios.

RESULTS

We identified 51 cases (0.10%) of incidental Kienböck disease and 87 cases (0.17%) of symptomatic Kienböck disease out of 51,071 patients. Patients with incidental Kienböck were older (mean, 54 years; SD, 17; mean difference, -6.1; 95% confidence interval [CI], -11 to -0.96; p = 0.020) and patients with symptomatic Kienböck disease were younger (mean, 43 years; SD, 14; mean difference, 5.1; 95% CI, 1.2-9.0; p = 0.010) compared with the group of patients without Kienböck disease (mean, 48 years; SD, 19). Lunate collapse (Lichtman Stages III and IV) was seen in nine of 51 patients (18%) with incidental Kienböck disease and in 44 of 87 patients (51%) with symptomatic Kienböck disease (odds ratio, 0.21; 95% CI, 0.086-0.51; p < 0.001). Our study did not identify any other factors associated with Kienböck disease.

CONCLUSIONS

We found that Kienböck disease is diagnosed on radiographs in a notable number of asymptomatic patients and that asymptomatic patients are more likely to have precollapse stages of the disease. This suggests that symptoms and disability do not correlate with pathophysiology, progression, or activity. Patients and surgeons benefit from awareness that symptoms are not a good indicator of the severity or prognosis of pathophysiology and that lunate osteonecrosis can exist with no or insufficient symptoms. This is important when considering treatment, because we cannot distinguish active disease at risk of collapse that could merit disease-modifying treatment from disease that will not progress.

LEVEL OF EVIDENCE

Level III, prognostic study.