New classification strategy for ankle gouty arthritis based on arthroscopic view

Baozhou Zhang et al conducted a study to evaluate the clinical outcomes, patient-reported outcomes, and recurrence rate of patients diagnosed with ankle gouty arthritis who underwent arthroscopic surgery based on the new classification. It has been published in ‘International Orthopaedics.’

A total of 51 patients diagnosed with ankle gouty arthritis were included in this retrospective study. A new classification was proposed based on the location and extent of MSU crystal deposition under an arthroscopy view. Patients are classified into different types and underwent arthroscopic surgery accordingly.

 Type I is characterised by the visibility of hyperplasia synovial tissue. Crystalline deposits of MSU may occasionally adhere to this proliferating synovium, yet they spare both bony and cartilaginous structures.

 Type II is defined by the observable deposition of MSU crystals on bony or soft tissue structures surrounding the joint under arthroscopy, yet the joint cartilage remains unaffected.

 Type III is typified by the arthroscopically visible deposition of MSU crystals on the surface of the articular cartilage. Depending on the extent of crystal deposition on the cartilage surface, it is further subdivided into Type III A and Type III B. Type III A - the crystal deposition on the cartilage surface appears spotty, with the longest diameter less than 3 mm, and the total area smaller than 10% of the joint surface. Type III B -flaky crystal deposition on the cartilage surface, covering more than 10% of the joint surface.

 Type IV constitutes a unique classification, described as the combination of a subchondral cyst resulting from an osteochondral lesion of the talus (OLT) and MSU crystal deposition.

The primary outcome measure was the American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score. The secondary outcomes included the visual analog pain scale (VAS), serum uric acid levels, and the recurrence rate of ankle gouty arthritis at one year postoperatively.

Key findings of the study were:

• The final cohort comprised 51 patients, predominantly male (n=50) with a single female participant.

• Based on the new classification,

5 patients were Type I- Synovium removal,

24 patients were Type II- Crystal deposition debridement, osteophyte removal, and ligament repair,

5 were Type III A - Scraping of damaged cartilage, 6 were Type III B - Selective scraping of damaged cartilage, and

11 were Type IV - Clearing unstable cartilage and MSU crystal deposits.

• The average follow-up time was 23.5±10.9 months.

• The AOFAS hindfoot-ankle score improved significantly from 70.3±15.9 to 85.6±13.0 (p<0.01).

• The mean serum uric acid level was significantly decreased from 442.0±109.2 to 540.5±132.4 (p< 0.01).

• The average VAS scale decreased from 3.8±1.9 to 1.4±1.7 (p< 0.01).

• The median of recurrences in one year postoperatively was significantly decreased from 1.5 (1, 3.75) to 0 (0, 0.75) (p< 0.01).

The authors concluded that – “A new classification strategy for ankle gouty arthritis based on arthroscopic view was proposed. Patients with ankle gouty arthritis showed significant improvement in ankle function and pain relief after undergoing arthroscopic surgery driven by the new classification.” 

Further reading on surgical procedures based on the classification:

Arthroscopic surgery for ankle gouty arthritis: a retrospective analysis of clinical outcomes at six month follow up based on a novel classification system

Baozhou Zhang, Ying Li et al

International Orthopaedics

https://doi.org/10.1007/s00264-023-06057-5