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J Wrist Surg 2021; 10(04): 276-279
DOI: 10.1055/s-0040-1719031
Special Review: Anatomy of the Watershed Line of the Distal Radius

Bony Anatomy around the Watershed Line of the Distal Radius

Kenny Tay 
1   SingHealth-Duke NUS Musculoskeletal Sciences Academic Clinical Programme, Singapore
2   Department of Orthopaedic Surgery, Singapore General Hospital, Singapore
,
Hamid Rahmatullah Bin Abd Razak
3   Department of Orthopaedic Surgery, Sengkang General Hospital, Singapore
,
Andy Khye Soon Yew
2   Department of Orthopaedic Surgery, Singapore General Hospital, Singapore
,
Joyce Suang Bee Koh
1   SingHealth-Duke NUS Musculoskeletal Sciences Academic Clinical Programme, Singapore
2   Department of Orthopaedic Surgery, Singapore General Hospital, Singapore
,
Tet S. Howe
1   SingHealth-Duke NUS Musculoskeletal Sciences Academic Clinical Programme, Singapore
2   Department of Orthopaedic Surgery, Singapore General Hospital, Singapore
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Abstract

Background An important surgical landmark in the distal radius is the watershed line. The watershed line is a landmark for the positioning of volar locking plates (VLP) in the distal radius. Inconsistencies remain in the literature as to the presence and dimensions of landmarks in this compact area. We studied the detailed anatomy and dimensions of the distal radius with reference to bony anatomy around the watershed line, with special attention to the area between the pronator quadratus (PQ) and radial styloid.

Materials and Methods The distal radius regions of 31 cadavers (23 right sided and 8 left sided) were dissected and studied. The heights at the junction of the scaphoid and lunate fossa, at the radial styloid, at the midpoint in between, and the widths of the PQ line, scaphoid, and lunate fossa were measured. The angle subtended by the pronator fossa and the radial styloid was also recorded.

Results The mean heights at the junction of the scaphoid and lunate fossa, radial styloid, and midpoint in between were 5.1, 15.7, and 8.2 mm, respectively. The widths of the PQ line, scaphoid, and lunate fossa were 27, 19.4, and 10.6 mm, respectively. The mean angulation between the pronator fossa and the radial styloid was 128.9 degrees.

Conclusion The area between the PQ and watershed line comprises a narrow area of bone which tapers to a point at its medial extent largely below the lunate fossa, thus it can hardly contain any implant proximal to the lunate fossa. The anterior orientation of this area and the concave anatomy of the articular surface mean careful screw direction is imperative to avoid inadvertent joint penetration. An angulation exists between the pronator fossa and the radial styloid, below the scaphoid fossa.

Keywords

anatomy - distal radius - watershed line

Ethical Approval

This is to state that no clinical patients or patient identifiable data were utilized in this study, hence no ethical committee was required at our institution.




Publication History

Received: 29 April 2020

Accepted: 01 September 2020

Article published online:
04 November 2020

© 2020. Thieme. All rights reserved.

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