Background/Purpose:

Prior studies have demonstrated that monosodium urate (MSU) deposits on dual-energy CT (DECT) are commonly found in joints as well as tendons of the feet and ankles of gout patients. However, no study has systematically evaluated the prevalence of MSU deposition in other joints or tendons, particularly in the knee joints. The aim of this study was to determine the prevalence of MSU deposition among multiple sites in the knees, feet/ankles, and hands/wrists among gout patients treated with urate-lowering therapy (ULT).

Methods:

Using standardized acquisition protocols, DECT of the bilateral feet/ankles, knees, and hands/wrists were obtained on 153 patients with a known diagnosis of gout and on allopurinol at a dose of at least 300mg daily for at least 3 months. The patients were prospectively recruited as a part of a non-interventional multi-center study conducted in the US and New Zealand. All patients met 1977 ARA gout classification criteria. The presence of MSU deposition was evaluated at 12 sites in the feet/ankles, 4 sites in the knees, and 15 sites in the hands/wrists by two radiologists familiar with DECT interpretation. To account for the larger number of sites in the feet/ankles and hands/wrists, they were then grouped into 4 sub-regions in the feet/ankles (first MTP, other toes, tarsals, tendons) and 3 sub-regions in the hands/wrists (IP joints, MCPs, carpals).

Results:

Among 153 gout patients (92% male) with mean duration of allopurinol therapy of 5 years and average allopurinol dose of 333mg daily, mean serum uric acid (SUA) was 6.1mg/dL and 51% of patients had SUA < 6mg/dL. The most commonly involved region was the feet/ankles followed closely by the knees; the hands/wrists had less MSU deposition (61%, 57%, and 23% respectively). The three most commonly affected sub-regions were the lateral tibiofemoral, patellofemoral, and medial tibiofemoral compartments of the knees (42%, 39%, and 37% respectively), followed by the first MTP joint (35%) (Table). The prevalence in the cruciate ligaments was similar to that of Achilles tendons (25% and 26%, respectively).

Conclusion:

Among patients with gout on ULT, there was a considerable prevalence of MSU deposition in all three compartments and the cruciate ligament of the knee joint. While these findings could reflect the higher frequency of involvement at these sites, they may also reflect larger volume MSU deposits in the knees which takes longer to resolve on ULT. DECT of the knees adds substantial value when assessing MSU burden and response to therapy among treated gout patients.

Table – Prevalence of MSU deposits

MTP = metatarsophalangeal joint; MCP = metacarpophalangeal joint; IP = interphalangeal joint