DISTAL RADIAL SIGMOID NOTCH

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Thank you for attention

3 Coronal types x 4 Transverse Types = 12 combination

I > ABCD

II > ABCD

III > ABCD

Take Home Massage

%

Relative Lax wrist

Introduction

1The distal radioulnar joint (DRUJ) is a diarthrodial, synovial articulation that provides the distal link between the radius and the ulna and a pivot for pronation and supination ( Fig. 14.1 ). Because the radii of curvature of the articular surfaces of the radius and ulna are different, the soft tissues are critical for guiding and restraining the joint; pathologic alterations of the soft tissues can adversely influence joint motion or stability. During normal forearm motion, the DRUJ moves synchronously with the proximal radioulnar joint (PRUJ), and any injury or deformity involving the radius or ulna can alter the function of both joints.

The articular contour of the DRUJ varies considerably among individuals in both the coronal and transverse (axial) planes. In the coronal plane, the slopes of the opposing articular surfaces of the notch and ulnar head may be parallel (55%), oblique (33%), or reverse oblique (33%) relative to the long axis of the radius and ulna 4 ( Fig. 14.3 ). A recent study of 1000 radiographs indicated a slightly lower prevalence of reverse oblique morphology at 6%, noting its negative correlation with ulnar positive variance. 6 An evaluation of both magnetic resonance imaging (MRI) and radiographs in 100 wrists from 98 asymptomatic patients revealed a mean difference of 12 degrees when comparing the inclination of the subchondral bone with the articular cartilage, leading to a change in Tolat inclination type in 66% of the wrists. Of interest, no reverse-types were identified when using the cartilage inclination to classify sigmoid notch morphology. 7 Although the slope has no proven impact on joint function in its natural state, acquired changes in lengths of the radius or ulna may alter peak DRUJ articular pressures. A shortening osteotomy through the ulnar shaft for the treatment of ulnar impaction syndrome in a patient with a reverse oblique slope of the DRUJ may have the potential to increase articular pressures at the proximal edge of the notch and the opposing surface of the ulnar head

The ulna is the stable unit of the forearm and supports loads transmitted from the radius and carpus. The ulnar head serves as the articular seat around which the radius rotates via the sigmoid notch. The surface of the ulnar head that faces the sigmoid notch forms a slightly asymmetric, partial cylinder of about a 130-degree arc. The articular cartilage coverage of this arc ranges from 50 to 130 degrees and is located on the dorsal, lateral, palmar, and distal surfaces. 10 Due to a slight asymmetry in its curvature, there is a small cam effect at the DRUJ during forearm rotation. Generally, the ulnar head articular surface is inclined and shaped to match the slope of the sigmoid notch, but radiographic appearance of a mismatch is common. In a radiographic study, the mean inclination of the sigmoid notch was found to be 8 degrees, ranging from −24 to 27 degrees, whereas the inclination of the opposing ulnar head surface averaged 21 degrees, ranging from −14 to 41 degrees. 8 These morphologic differences may contribute to the development of adverse symptoms after ulnar shortening osteotomy or changes in radial length following distal radius fracture.

- Reverse oblique Type - Associated with Ulnar plus variance - High rist to osteoarthritis - common in females.

- Flat Type - Laxity ^ (lead to Soft tissue injury )

- These Pts with morphology shoulrd be suspected about injury (High risk pts).

- 12 types Combination possible between CoronaL & Transverse plane view.

- No consensus (Relation Ulnar variance to DRUJ type "Coronal type").

The sigmoid notch of the radius is a shallow concavity that articulates with the ulnar head. Computed tomographic data from 100 cadaver forearms demonstrated that the radius of curvature of the sigmoid notch averaged 18.2 ± 8.5 mm compared with only 8.2 ± 1.3 mm for the ulnar head. 1 The dorsal and palmar rims of the sigmoid notch contribute substantially to DRUJ stability. Typically, the dorsal bony rim is angled acutely, whereas the palmar rim is more rounded. The palmar rim is augmented by a fibrocartilaginous lip, which is prominent in 80% and subtle in 18% ( Fig. 14.2 ). The importance of these variations in sigmoid notch morphology has been shown clinically and in biomechanical investigations, in which posttraumatic rim deficiencies substantially reduce joint stability. 2345

A

Deserve More Study

Transverse

Type

Coronal Types

In the axial plane, the average sigmoid notch subtends an arc of approximately 50 degrees (see Fig. 14.2 ). Based on an anatomic study of 50 cadavers, four different sigmoid notch shapes were described: flat face (42%), ski slope (14%), “C” type (30%), and “S” type (14%) 4 ( Fig. 14.4 ). The shape has potential implications for risk of traumatic instability and its treatment alternatives. A flat sigmoid notch may be more prone to instability and less responsive to treatment by soft tissue repair alone. 4 In a study of 58 patients and 118 control subjects, investigators identified a negative association between the depth and version angle of the sigmoid notch with triangular fibrocartilage complex (TFCC) foveal injury, 9 implying that increasing articular constraints will enhance the inherent stability of the DRUJ, reducing strain on the soft tissue stabilizers during mechanical loading.

B

A

I

- If there is Correlation between Coronal and Transverse plane views.

- If there is Different morphological anatomy of Palmar labrum (Fibrocartilage lip) in different type of Sigmoid notch ?

- No classification system exists for disruption patterns of the sigmoid notch of the radius associated with distal radius fractures

- Read to paper TOLAT + ULNAR VARIANT and xray

II

III

C

D

1993

Conclusion

Anatomy of DRUJ

- Ulnar Zero > has Parallel type

- Ulnar minus > has Oblique orientation

- As well Ulnar plus > has Reverse Oblique

- Distal link between the radius & ulna

- Pivot for pronation & supination

Clinical Implication

+

Tolat's Classification

Anatomy Details Sigmoid notch

Coronal Plane View

Transverse Plane view

66%

42%

14%

33%

- Shallow concavity that articulates with the ulnar head

- The dorsal & palamar rims of the sigmoid notch increase stability of DRUJ

- The palmar rim is augmented by a fibrocartilaginous lip (Labrum)

- The soft tissues are critical for guiding and restraining the joint

14%

33%

or 33%

^ Female ^ Ulnar-sided pathology

DISTAL RADIAL SIGMOID NOTCH

Clinical Implication

Classification & Clinical Implication

LT

• ulnar positive, reverse inclination morphology was more likely to be present in relatively stiff wrists

• Females were more likely to have Reverse oblique type.

• Reverse Oblique & Oblique more likely to have DRUJ arthritis

2022

Dr. Waheeb - Jerusalem

Flat type has more prone to instability

Flat-Face (has less depth & Version angle)

^^^ TFCC foveal injury

Framework

Deserve More Study

• Anatomy of DRUJ (Distal Radio-ulnar joint).

• Anatomy of Sigmoid Notch (Distal Radial Sigmoid Notch).

• Tolat's Classification & Clinical Implication.

• Deserve More Study

• Take home massage

- New study with more amount of patient.

- Update Tolat's Classification.