The SLAC Wrist

Alvin S. Chen, Harvard Medical School Year III

Gillian Lieberman, MD

Radiology Core Clerkship

Overview Wrist: Normal Anatomy & Biomechanics

Approach to Wrist Imaging: Menu of Tests & Efficacious Use

Index Patient

SLAC Wrist: Clinical Implications & Radiographic Diagnosis

SLAC Wrist: Treatment

Alvin Chen, Gillian Lieberman

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Normal Anatomy of the Wrist: PA

Source: http://radiologymasterclass.co.uk


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Normal Anatomy of the Wrist: PA

Note: • Pisiform and

Triquetrum overlap • The other carpal

bones partly overlap



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Normal Anatomy of the Wrist: Lateral



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Normal Anatomy of the Wrist: Lateral

Note: • The scaphoid is

difficult to see clearly on this view

• This view is essential to check for alignment of the radius, lunate and capitate



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Normal Anatomy of the Wrist: Ligaments

Source: Netter’s Atlas of Anatomy, 4e


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Source: Netter’s Atlas of Anatomy, 4e


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Coronal T-1 weighted MRI showing normal SL ligament (arrow) (S, scaphoid; L, lunate; T, triquetrum)

Source: www.orthobullets.com


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Three distinct biomechanical concepts have been proposed, but the “intercalated row” concept is most widely accepted

The wrist is comprised of radius/ulna, proximal and distal rows

Scaphoid serves as a bridge between rows

The proximal carpal row has no tendinous attachments so its position is determined by the position of the radius and distal carpal row

Disruption (fracture or ligamentous injury) leads to instability in wrist motion

Wrist Biomechanics


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Wrist Biomechanics

Source: www.wikiradiography.com


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• True axis of scaphoid is the line through the mid-points of its proximal and distal pole

• A parallel line bordering the ventral points of the proximal and distal poles of the bone can be used as a good proxy

Wrist Biomechanics – Scaphoid Axis

Source: www.radiologyassistant.nl


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Wrist Biomechanics – Lunate Axis

• Lunate axis runs through midpoints of the convex proximal and concave distal joint surfaces

• Best approximated by tracing the perpendicular line to a line joining the distal palmar and dorsal borders

• Normal SL angle: 30-60⁰ • Borderline: 60-80⁰ • Abnormal: >80⁰ (indicates

wrist instability)

Source: www.radiologyassistant.nl


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Wrist Biomechanics – Capitate Axis

• Capitate axis joins the midportion of the proximal convexity of the third metacarpal and that of the proximal surface of the capitate

• Normal CL angle: <30⁰ • Abnormal: >30⁰ (indicates wrist

instability)


14 Source: www.radiologyassistant.nl



Index Patient




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Menu of Tests & Efficacious Use Plain film (X-ray) – Wrist Series

Standard: AP, Lateral, and Oblique Obtain scaphoid view (semipronated oblique) if there is

suspicion for scaphoid fracture Obtain ‘clenched fist’ view if there is suspicion for

ligamentous injury, especially SL ligament

MRI: if suspicion for fracture or ligamentous injury but radiographs negative More sensitive than plain film for detecting fracture, ligament

tears, edema and arthritis Allows for early detection of AVN MR Arthrography can be used in suspected intercarpal

ligament or TFCC tears


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Menu of Tests & Efficacious Use Less commonly used tests:

Conventional CT Scan Allows for 3-D visualization of carpal bones, soft tissue detail Can assess nonunion of fractures, usually scaphoid waist fx Utilized to better define a previously detected fracture or assess the distal

radial ulnar joint

Fluoroscopy Useful for dynamic detection of abnormal bony motion and

ligamentous/capsular injury

Bone Scintigraphy Can be used to work-up occult fractures; high sensitivity, low specificity

Ultrasound Limited use in trauma setting, may allow for evaluation of extensor or flexor

tendons to exclude rupture Can visualize foreign bodies, cysts or effusions

Arthroscopy Allows for direct visualization of wrist structures, gold-standard, invasive


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Index Patient




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Index Patient: History of Present Illness 49 yo AA man w/PMHx ulcerative colitis and ankylosing

spondylitis presenting with 9 months of insidious onset right wrist pain

Reports swelling and erythema of the right wrist over the dorsal surface

Worse with palpation and flexion/extension

Has tried Tylenol with minimal relief

Does not remember specific trauma that may have caused this, but has had a few falls over the past year

SocHx: works as a secretary at a local hospital

ROS, FMHx non-contributory


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Index Patient: Physical Examination Vital signs within normal limits

General: obese man in NAD

HEENT/Neck: no malar rash, no lymphadenopathy

Cardiopulmonary exam: normal

Joint exam: right-sided 2+ edema in medial dorsal aspect of wrist, tender to palpation, significantly decreased ROM, positive Watson scaphoid shift test


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Watson Scaphoid Shift Test With firm pressure over

the palmar tuberosity of the scaphoid, the wrist is moved from ulnar to radial deviation

Dorsal wrist pain or a clunk during this maneuver may indicate instability of SL ligament

Sens: 86%, Spec: 57%


Source: http://www.maitrise-orthop.com/corpusmaitri/orthopaedic/dumontier_synth/dumontier_us.shtml 21

Index Patient: Differential Diagnosis Scapholunate Advanced Collapse (SLAC) Scaphoid Non-Union Advanced Collapse (SNAC) Carpal fracture (scaphoid, lunate, triquetral, etc.) Carpal arthritis (OA vs. RA) Wrist tendonitis Carpal tunnel syndrome Chronic osteomyelitis De Quervain tenosynovitis Kienbock’s disease Scaphotrapezoid-trapezial (STT) joint arthritis Ulnar nerve entrapment


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Index Patient: Plain Films

Source: PACS, BIDMC


Please pause to evaluate, continue to view findings

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Index Patient: Plain Films

Source: PACS, BIDMC


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Please pause to evaluate, continue to view findings

Index Patient: Plain Film Interpretation Abnormal sclerosis of scaphoid

Degenerative changes in the radiocarpal joint involving the scaphoid fossa with subchondral sclerosis and marginal osteophytes

Widening of the scapholunate interval with proximal displacement of the capitate

No acute fracture or dislocation seen

Appearance of scaphoid reflects degenerative change vs. AVN

Appearance consistent with possible SLAC wrist

To better characterize underlying cause of degenerative arthritis and possible ligamentous injury, an MRI was ordered


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Index Patient: Coronal T1-weighted MRI

Source: PACS, BIDMC


Please scroll through sequences to evaluate, findings will be provided on summary slide following these images

Slice 1

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Source: PACS, BIDMC


Slice 2

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Source: PACS, BIDMC


Slice 3

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Source: PACS, BIDMC


Slice 4

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Source: PACS, BIDMC


Slice 5

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Index Patient: Coronal T2-weighted FS MRI

Source: PACS, BIDMC


Slice 1

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Source: PACS, BIDMC


Slice 2

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Source: PACS, BIDMC


Slice 3

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Source: PACS, BIDMC


Slice 4

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Source: PACS, BIDMC


Slice 5

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Source: PACS, BIDMC


Slice 6

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Index Patient: Sagittal T1-weighted MRI

Source: PACS, BIDMC


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Index Patient: Sagittal T1-weighted MRI

Source: PACS, BIDMC

Widened CL angle!!


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Index Patient: MRI Interpretation Widening of SL interval consistent with SL ligament tear

Severe radio-scaphoid osteoarthritis, but no definite thinning of capitate cartilage and proximal migration of the capitate, consistent with stage II SLAC wrist

Peripheral low signal intensity associated with T2 hyperintense signal within subchondral aspects of the scpahoid, lunate, trapezoid, capitate, and hamate consistent with subchondral cysts vs. erosions vs. synovitis

Dorsal intercalated segment instability (DISI) deformity (CL angle > 30⁰) noted on sagittal view, dorsiflexion of lunate with posterior subluxation of distal carpal row


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Index Patient




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SLAC Wrist: Etiology A condition of progressive wrist instability causing

advanced arthritis of radiocarpal and midcarpal joints

Describes the specific pattern of degenerative arthritis seen in chronic dissociation between the scaphoid and lunate

Chronic SL ligament injury creates a DISI deformity – scaphoid becomes flexed volarly and lunate is extended dorsally

Leads to aberrant force distribution across midcarpal and radiocarpal joints and malalignment of concentric joint surfaces

Initially presents as arthritis of radioscaphoid joint, then progressing to arthritis of capitolunate joint


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SLAC Wrist: Etiology Causes can be traumatic or atraumatic

Scaphoid fracture (SNAC wrist)

Scapholunate ligament tear

Kienbock’s disease (avascular necrosis of lunate)

Calcium pyrophosphate dehydrate deposition disease

Rheumatoid arthritis

Neuropathic diseases

β2-microglobulin associated amyloid deposition disease

Extra-intestinal manifestation of IBD


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SLAC Wrist: Presentation Symptoms

Difficulty bearing weight across wrist

Pain over dorsal surface of wrist, specifically in region of SL interval

Progressive hand weakness

Wrist stiffness

Physical Exam Tenderness to palpation over dorsal aspect of wrist

Significantly decreased ROM

Weakened grip strength

Positive Watson scaphoid shift test


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SLAC Wrist: Radiographic Diagnosis • Stage I SLAC Wrist: arthritis

between scaphoid and radial styloid

• >3 mm diastasis between scaphoid and lunate (‘Terry Thomas sign’)

• PA radiograph shows radial styloid beaking, sclerosis and joint space narrowing between scaphoid and radial styloid



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SLAC Wrist: Radiographic Diagnosis • Stage II SLAC Wrist: arthritis

between scaphoid and entire scaphoid facet of the radius

• >3 mm diastasis between scaphoid and lunate (‘Terry Thomas sign’)

• PA radiograph shows sclerosis and joint space narrowing between the scaphoid and the entire scaphoid fossa of distal radius



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SLAC Wrist: Radiographic Diagnosis • Stage III SLAC Wrist: arthritis

between capitate and lunate • >3 mm diastasis between

scaphoid and lunate (‘Terry Thomas sign’)

• PA radiograph shows sclerosis and joint space narrowing between the lunate and capitate with subchondral cyst formation

• Eventually, the capitate will migrate into the void created by the SL dissociation



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SLAC Wrist: Radiographic Diagnosis • Stage III SLAC Wrist: arthritis

between capitate and lunate • >3 mm diastasis between

scaphoid and lunate (‘Terry Thomas sign’)

• PA radiograph shows sclerosis and joint space narrowing between the lunate and capitate with subchondral cyst formation

• Eventually, the capitate will migrate into the void created by the SL dissociation



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SLAC Wrist: Radiographic Diagnosis • In scapholunate ligament injury,

can also see ‘cortical ring sign’ caused by scaphoid malalignment

• May be present in any of the three stages of SLAC wrist



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SLAC Wrist: Radiographic Diagnosis


Normal Carpal Alignment DISI

• Dorsal intercalated segmental instability (DISI) is easily diagnosed on lateral plain film

• DISI is caused by disruption of the SL articulation

• Lunate becomes angulated dorsally

• Radiographs are consistent with DISI pattern when scapholunate angle > 80⁰ or capitolunate angle > 30⁰

Source: www.wikiradiography.com 49

SLAC Wrist: Radiographic Diagnosis


• MRI is unnecessary for staging but would show: • Thinning of articular

surfaces of the proximal scaphoid

• Synovitis of the scaphoid facet of distal radius and capitolunate joint

• Complete or partial rupture of the SL ligament

Source: PACS, BIDMC 50



Index Patient




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SLAC Wrist: Treatment Non-operative:

Address underlying cause (e.g. treatment of rheumatologic disease)

NSAIDs Wrist immobilization with splints Corticosteroid injections

Operative Radial styloidectomy Anterior and posterior interosseous nerve denervation Distal scaphoid pole excision Proximal row carpectomy Four-corner arthrodesis Capitolunate arthrodesis


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SLAC Wrist: Radial styloidectomy


Source: http://www.msdlatinamerica.com/ebooks/HandSurgery

• Indicated for Stage I disease • Excision of radial styloid • Prevents impingement

between proximal scaphoid and radial styloid

• May be performed open or arthroscopically via 1,2 portal

• Can be combined with other procedures for maximal relief in symptoms

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SLAC Wrist: Proximal Row Carpectomy


Source: Strauch, RJ. SLAC and SNAC Arthritis – Update on Evaluation and Treatment. J Hand Surg. 2011; 36A: 729-735

• Indicated for Stage II disease • Excision of entire proximal row of

carpal bones while preserving radioscaphocapitate (RSC) ligament (to prevent ulnar subluxation)

• Contraindicated if RSC ligament is incompetent

• Results in capitate articulating with lunate fossa of radius

• Provides relative preservation of strength and motion

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SLAC Wrist: Four-corner arthrodesis


Source: Dacho et al. Long-Term Results of Midcarpal Arthrodesis in the Treatment of SNAC-Wrist and SLAC-Wrist. Annals of Plastic Surgery. 56(2); Feb. 2006

• Indicated for Stage II & III disease • After removal of cartilagenous

structures, the capitate, lunate, hamate and triquetrum are fused using cancellous bone graft from either the radius or iliac crest

• Can also be fixed using circular plates • Preserved articulation between lunate

and distal radius • Also provides relative preservation of

strength and motion • Similar long-term results between PRC

and four-corner fusion

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SLAC Wrist: Four-corner arthrodesis



AP film showing circular plate fixation for 4-corner fusion for SLAC wrist

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SLAC Wrist: Capitolunate arthrodesis



AP film showing solid capitolunate fusion using cannulated screws for SLAC wrist

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Back to our patient… Upon consultation with his rheumatologist, his

symptoms were thought to be extra-intestinal manifestations of his ulcerative colitis

His colitis had been dormant for several years, and he had been off treatment during this same time period

He was restarted on Sulfasalazine 500 mg QID

On one month follow-up, his symptoms had decreased significantly and his right wrist ROM was back to normal


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Summary Scapholunate dissociation or ligament injury can lead

to DISI deformity and eventually SLAC wrist

Plain films (PA, lateral, oblique) are the study of choice for diagnosing and staging of SLAC wrist

MRI can be used to elucidate the etiology of SLAC wrist, but is usually not necessary

Several surgical techniques, including radial styloidectomy, denervation, proximal row carpectomy, and 4-corner fusion, have been shown to have positive outcomes in patients with SLAC wrist


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References Watson HK, Ballet FL. The SLAC wrist: scapholunate advance collapse

pattern of degenerative arthritis. J Hand Surg [Am]. 1984;9A:358-65.

Watson HK, Ryu J. Evolution of arthritis of the wrist. Clin Orthop Relat Res. 1986;202:57:67.

Dacho A, Grundel J, Holle G, Germann G, et al. Long-term results of midcarpal arthrodesis in the treatment of scaphoid nonunion advanced collapse (SNAC-wrist) and scapholunate advanced collapse (SLAC-wrist). Ann Plast Surg. 2006;56(2):139-44.

Shah CM, Stern PJ. Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) wrist arthritis. Curr Rev Musculoskelet Med (2013). 6:9-17

Strauch, RJ. Scapholunate Advanced Collapse and Scaphoid Nonunion Advanced Collapse Arthritis – Update on Evaluation and Treatment. J Hand Surg. 2011; 36A: 729-735


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References Dacho A, Baumeister S, Germann G, Sauerbier M. Comparison or

proximal row carpectomy and midcarpal arthrodesis for the treatment of scaphoid nonunion advanced collapse (SNAC-wrist) and scapholunate advanced collapse (SLAC-wrist) in stage II. J Plastic, Recon & Anes Surg. (2008) 61, 1210-1218.

Cha SM, Shin HD, Kim KC. Clinical and Radiological Outcomes of Scaphoidectomy and 4-Corner Fusion in Scapholunate Advanced Collapse at 5 and 10 years. Ann Plastic Surg. (2013). 71(2);166-169.

Wyrick JD, Stern PJ, Kiefhaber TR. Motion-preserving procedures in the treatment of scapholunate advanced collapse wrist: proximal row carpectomy versus four-corner arthrodesis. J Hand Surg Am. 1995; 20:965:970.

Jebson PJ, Hayes EP, Engber WD. Proximal row carpectomy: a minimum 10-year follow-up study. J Hand Surg Am. 2003:28:561:569.


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Image & Web References Vitale M. SLAC (Scaphoid Lunate Advanced Collapse). Orthobullets. Accessed

4/17/14. http://www.orthobullets.com/hand/6043/slac-scaphoid-lunate-advanced-collapse

Gilula L, Chesaru I. Wrist – Carpal Instability. Radiology Assistant. Accessed 4/17/14. http://www.radiologyassistant.nl/en /p42a29ec06b 9e8/wrist-carpal-instability.html#i430347c574459

DISI and VISI Deformities. Wiki Radiography. Accessed 4/18/14. http://www.wikiradiography.com/page/DISI+and+VISI+Deformities

Wheeless CR. Scapholunate Advanced Collapse (SLAC). Wheeless Textbook of Orthopaedics. Accessed 4/17/14. http://www.wheelessonline.com/ortho/scapholunate_advanced_collapse_slac

Trauma X-ray – Upper Limb. Radiology Masterclass. Accessed 4/19/14. http://radiologymasterclass.co.uk/tutorials/musculoskeletal/x-ray_trauma_upper_limb/wrist_trauma_x-ray.html

Imbriglia, JE. Proximal Row Carpectomy. Hand Surgery 1st Edition. Accessed 4/21/14. http://www.msdlatinamerica.com/ebooks/HandSurgery/sid925688.html

Netter, F. Atlas of Human Anatomy. 4th Edition. 2006.


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http://www.wikiradiography.com/page/DISI+and+VISI+Deformities

http://www.wikiradiography.com/page/DISI+and+VISI+Deformities

http://www.wheelessonline.com/ortho/scapholunate_advanced_collapse_slac

http://www.wheelessonline.com/ortho/scapholunate_advanced_collapse_slac

http://radiologymasterclass.co.uk/tutorials/musculoskeletal/x-ray_trauma_upper_limb/wrist_trauma_x-ray.html






http://www.msdlatinamerica.com/ebooks/HandSurgery/sid925688.html

http://www.msdlatinamerica.com/ebooks/HandSurgery/sid925688.html

Acknowledgements Dr. Justin Kung

Dr. Omer Awan

Dr. Gunjan Senapati

Dr. Jawad Hussain

Dr. Gillian Lieberman

Megan Garber


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The SLAC Wrist

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