Abstract
Background
The periarticular ligament anatomy of the scaphotrapeziotrapezoid (STT) joint varies
in the literature, complicating standardization. Preservation of this ligamentous
array is critical in preventing intracarpal malalignment.
Purpose
This study aims to map ligament insertion sites on the bony components of the STT
joint and define resection margins for the scaphoid, trapezium, and trapezoid during
arthroplasty.
Materials and Methods
We examined 26 cadaveric wrists. Needles marked the STT joint before arthrotomy, allowing
precise observation of ligament positioning intact. Ligament insertion sites on the
scaphoid, trapezium, and trapezoid were measured with micrometric calipers. We recorded
STT arthritis presence and distribution on the scaphoid, trapezium, and trapezoid
articular surfaces. Each surface was divided into four quadrants voloulnar (VU), voloradial
(VR), dorsoulnar (DU), and dorsoradial (DR).
Results
The dorsal intercarpal ligament (DIC) was the only extrinsic dorsal ligament of the
STT joint. The average insertion distance from the articular surface was 3.033 mm
(standard deviation [SD] = 0.693) on the trapezium and trapezoid, compared to 1.918 mm
(SD = 0.329) on the scaphoid. This difference was statistically significant (p < 0.001). The palmar ligament organization resembled a rigid tripod anchored by the
RS (radioscaphoid), ST (scaphotrapezial), and SC (scaphacapitate) ligaments around
the scaphoid tubercle. Palmar ligament insertion points averaged 0.58 mm (SD = 0.32)
from the articular surface, with no significant difference between the scaphoid and
the trapezoid–trapezium complex (p = 0.558). STT arthritis was present in 80.8% of wrists. The VU sides of the STT were
most affected, particularly the volar side of the trapezoid.
Conclusion
The DIC ligament and palmar ligamentous tripod, formed by the RS, SC, and ST ligaments,
could acts as a mechanical lock preventing dorsal scaphoid translation. While distal
scaphoid pole resection is standard, our findings suggest prioritizing proximal trapezium
and trapezoid resections in arthroplasty to avoid instability.
Keywords
STT joint - wrist ligaments - arthroplasty - anatomy - arthritis
