slac & snac wrist

PRESENTED BY:

DR.N.BENTHUNGO TUNGOEP.G, MS(ORTHOPEDICS)

CENTRAL INSTITUTE OF ORTHOPEDICSVMMC & SAFDARJUNG HOSPITAL

NEW DELHI

SNAC & SLAC WRIST

INTRODUCTION

Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) are the two most common patterns of post-traumatic wrist arthritis.

ETIOLOGY OF SLAC

TRAUMATIC CAUSES: Scaphoid fracture non union, Scapholunate ligament dissosciation

ATRAUMATIC CAUSES: CPPD(calcium pyro phosphate dehydrate) diseases Rheumatoid arthritis Neuropathic diseases Beta 2 microglobulin assosciated amyloid deposition

disease

SCAPHO LUNATE LIGAMENTOUS COMPLEX

The scapholunate ligament complex is a U-shaped ligamentous complex joining thelunate and the scaphoid.

It is divided into dorsal, volar and intermediate components with surrounding secondary stabilisers.

Dorsal component

blends with joint capsule, scaphotriquetral and intercarpal ligaments

strongest portion of the complexcontrols flexion/extension

Volar componentoblique collagen fibresblends with extrinsic volar radioscapholunate ligamentcontrols rotational motionmajor proprioceptive role

Intermediate/interosseous componentlocated proximally and centrally and therefore may

be referred to as the central or proximal componentfibrocartilageweakest portion of the complexextends a few millimeters into the joint, akin to a

meniscus

Secondary stabilisersscapho-trapezial-trapezoidal ligamentradio-scapho-capitiate ligament

RADIOGRAPHIC FEATURES

The pattern is that of a progressive osteoarthritis affecting initially the articulation between the radial styloid and the scaphoid. In later stages of the disease, osteoarthritis affects the whole radioscaphoid articulation, then the articulation between lunate and capitate. Finally it may involve other intercarpal joints. In addition there is widening of the space between scaphoid and lunate as well as proximal migration of the scaphoid and the capitate

CT FINDINGS:  angulations of the scaphoid and lunate bones (increased scapholunate angle and dorsal or volar intercalated segment instability deformity), radioscaphoid incongruity, cartilage loss, and subchondral bone degenerative changes.

SCAPHOLUNATE DISSOSCIATION(TERRY THOMAS SIGN)

SLAC

Watson staging (often used by hand surgeons)

I: osteoarthritis of the articulation between the radial styloid and the scaphoid

II: osteoarthritis involving the whole radioscaphoid articulation

III: osteoarthritis of the radioscaphoid and capitolunate articulations

IV: osteoarthritis of the radiocarpal and intercarpal articulations +/- distal radioulnar joint (DRUJ)

NOTE: Note that the radiolunate joint is almost preserved until very last stages of the disease. It is also worth noting that the scaphoid fossa in the radius may be deep / preserved in cases of CPPD in contrast to post-traumatic SLAC wris

SURGICAL TREATMENT

Surgical treatment for SLAC wrist includes  four-corner arthrodesis, capitolunate arthrodesis, complete wrist arthrodesis, scaphoidectomy, proximal row carpectomy (PRC), denervation, radial styloidectomy

SNAC(scaphoid non union advcance collapse)

In a SNAC wrist, the proximal scaphoid fragment usually remains attached to the lunate (which rotate together during extension), while the distal scaphoid fragment rotates into flexion. This results in abnormal contact in the radioscaphoid compartment, characterised by early styloid osteoarthritis between the distal scaphoid fragment and the radial styloid process

Jupiter et al classification of non union based on the extent of arthosis:1. nonunions without arthrosis,2. nonunions with radiocarpal arthrosis, 3. nonunions with advanced radiocarpal and

intercarpal arthrosis

Radiographic findings of SNAC

radioscaphoid narrowing, capitolunate narrowing, cyst formation, pronounced dorsal intercalated segment

instability(DISI)

Note: The radiolunate joint usually is spared in early stages but may show degenerative changes as the arthritis becomes more diffuse.

Effect of SLAC & SNAC ON JOINT KINEMATICS:

Both of these processes lead to abnormal joint kinematics, since the lunate is unrestrained by the distal scaphoid and, therefore, assumes an extended posture.

Over time, this may result in a dorsal intercalated segment instability (DISI) deformity, which invariably progresses to degenerative arthritis at the radioscaphoid articulation, followed by carpal collapse and midcarpal arthritis

DISI(dorsal intercalated segment instability )

CAUSES:1. wrist trauma +/- fracture Scaphoid fracture: bony DISI distal radius fracture: compensatory DISI radius malunion: adaptive DISI

2.Scapholunate ligament sissosciation: ligamentous DISI

Radiographic features

On an AP view the normal trapezoidal configuration of the scaphoid may be lost and it may appear triangular.

On lateral plain film typically shows a dorsal tilt of the lunate:

scapholunate angle > 60º: sign of scapholunate ligament dissociation

capitolunate angle  > 30º:  the capitate is displaced posteriorly compared to the distal radius

DIFFERENTIAL DIAGNOSIS

CARPAL TUNNEL SYNDROMETRIGGER FINGERDE QUERVANS TENOSYNOVITISFCR TENDONITIS

NON OPERATIVE MANAGEMENT

WRIST IMMOBILIZATION WITH SPLINTSNSAIDSCORTICO STEROIDS INJECTIONS

OPERATIVE MANAGEMENT

RADIAL STYLOIDECTOMYWRIST DENERVATIONSCAPHOID EXCISIONPROXIMAL ROW CARPECTOMYARTHODESIS

Four corner arthodesis Capito-lunate arthodesis Wrist arthodesis

Four corner arthodesis

THANK YOU