Normal Yune Soft Tissue Index Size on Radiography
The Yune Soft Tissue Index is a radiographic ratio used to assess the relative thickness of soft tissues over the distal phalanx of the hand on posteroanterior (PA) projection. It provides an objective, reproducible measure of peripheral soft tissue overgrowth. Accurate evaluation of this index is particularly relevant in the workup of systemic conditions associated with acral soft tissue hypertrophy.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Posteroanterior | >0.2 |
Clinical Significance
A Yune Soft Tissue Index greater than 0.2 is considered the normal threshold on PA radiography. The index quantifies the proportion of soft tissue padding relative to the underlying bony phalanx width. Values exceeding this threshold raise concern for pathological soft tissue enlargement at the fingertip.
The most important clinical application is in the screening and monitoring of acromegaly, where excess growth hormone leads to characteristic acral soft tissue and bony overgrowth. Beyond acromegaly, abnormal values may be encountered in several other clinical scenarios. Careful correlation with clinical findings and additional imaging is essential, as overlying edema, trauma, or obesity can confound measurements.
- Acromegaly — excess GH/IGF-1 causing acral overgrowth
- Pachydermoperiostosis — primary hypertrophic osteoarthropathy
- Peripheral edema — systemic or local causes mimicking true soft tissue hypertrophy
- Myxedema (hypothyroidism) — non-pitting soft tissue thickening
- Chronic clubbing — subperiosteal soft tissue proliferation at distal phalanges
Reference: Schmitt R, Lanz U. Diagnostic Imaging of the Hand. TIS. (2008).
Imaging Notes
The Yune Soft Tissue Index is measured on a standard posteroanterior (PA) hand radiograph. The index is calculated by dividing the maximum soft tissue width of the distal phalanx (measured from skin edge to cortex) by the total width at the same level (skin edge to skin edge). A technically adequate PA projection with the hand flat against the detector and no rotation is essential to avoid measurement error. Consistent exposure settings and patient positioning improve reproducibility across serial examinations.
When assessing for acromegaly, it is advisable to evaluate multiple digits and correlate with additional radiographic features such as terminal phalangeal tufting, joint space widening, and heel pad thickness. Single-digit measurements should be interpreted cautiously in the presence of localized pathology, trauma, or asymmetric edema.