Prevalence of Pseudoerosions and Morphology of Joint Capsules and Recesses of the Hand and Wrist: Ultrasound Findings in 100 Asymptomatic Volunteers

Purpose: The presence of synovial hypertrophy and cortical erosions can indicate an inflammatory arthritis. Such hypertrophy must be differentiated from the normal dorsal joint recess and capsule. Additionally, cortical depressions have been described in several metacarpal (MC) heads simulating erosions, and we have noted similar “pseudoerosions” more frequently and also present at the wrist. The purpose of the study was to evaluate the frequency and location of pseudoerosions, as well as dorsal joint capsule and recess morphology of the hand and wrist in asymptomatic volunteers.

Methods and Materials: After institutional review board approval and obtaining informed consent, 100 subjects without hand or wrist symptoms were examined bilaterally with ultrasound. Dorsal metacarpal heads, lunate, triquetrum, and distal ulna were examined. Cortical depressions were characterized with regard to location (central, marginal, and both), morphology (irregularity and ring-down artifact), and dimensions (length and depth). The dorsal capsules and recesses of the metacarpophalangeal, radiocarpal, and midcarpal joints were also characterized with regard to echogenicity, fibrillar pattern, hyperemia, and measurements. The evaluation was performed by two fellowship-trained musculoskeletal radiologists in consensus.

Results: A total of 52 male and 48 female subjects were included (mean age: 47 ± 16 years). MC heads showed a central pseudoerosion at various frequencies (MC1: 21.5%; MC2: 92%; MC3: 85.5%; MC4: 59.5%; MC5: 81%). One marginal erosion was present at an MC5 and a marginal plus central at an MC2. Pseudoerosions were present at the lunate (82%), triquetrum (84%), and distal ulna (20%), and they were multiple (lunate: 40%; triquetrum: 27%; ulna 5%). Ring-down artifact (30.3–49.7%) was present more than cortical irregularity (12.6–27.9%). Mean pseudoerosion length and depth of MC was 3 mm (range: 0.6–9 mm) and 0.7 mm (range: 0.2–8 mm). Dimensions for pseudoerosions varied slightly for the lunate (length: 2.1 mm; depth: 0.8 mm), triquetrum (length: 1.7 mm; depth: 1.0 mm), and ulna (length: 1.7 mm; depth: 1.1 mm). Dorsal capsules and recesses at the metacarpophalangeal joints were isoechoic to subdermal fat and fibrillar measuring 3.1 to 6.3 mm in maximal thickness. The dorsal capsules and recesses of the radiocarpal and midcarpal joints were hypoechoic to subdermal fat, nonfibrillar with maximum thickness of 3.9 and 3.4 mm, respectively. No flow on color Doppler imaging was noted.

Conclusion: Pseudoerosions are a typical finding of MC heads, lunate, triquetrum, and distal ulna in asymptomatic patients and should not be misinterpreted as inflammatory arthritis. The appearances of dorsal joint capsules and recesses are different between the MC and wrist joints, and their characteristics should not be confused with synovial hypertrophy.

Fig. 1 (a) Sagittal and (b) axial ultrasound of a 47-year-old asymptomatic man shows a central irregular pseudoerosion with ring-down artifact at the third metacarpal head.

No conflict of interest has been declared by the author(s).