Summary Scaphotrapeziotrapezoidal (STT) arthritis is the second most common location for carpal arthritis, and a strong association exists between STT and thumb carpal-metacarpal joint arthritis. STT arthritis us diagnosed clinically with with pain and weakness in grip strength with radiographs showing narrowing and subchondral sclerosis at the STT articulations. Treatment is initially nonsurgical, with surgery being reserved only for those who fail initial nonoperative management. Science Epidemiology Incidence 16% of US population Demographics Most common among females >50 years Location Junction of Scaphoid, Trapezoid, and Trapezium (STT) Only the radioscaphoid joint is more commonly affected with OA in the carpus Risk factors STT arthritis often found with concomitant basilar thumb arthritis Pathophysiology Rigidity of STT joint restricts motion to primarily flexion-extension. Any change to the restricted kinematic pattern fosters an environment which predisposes to the development of STT arthritis Combination of morphology of the Trapezium, wide circumduction of motion, strenuous use, and high compressive forces during pinch and grasp exhibited at STT joint lead to cartilage erosion and subsequent development of arthritis Instability at the STT joint or within the carpus (particular DISI and midcarpal instability), is associated with STT arthritis Wrists with type II lunates, which confer more rigid carpal kinematics, is associated with STT arthritis Associated orthopedic conditions Basilar thumb arthritis Carpal instability, specifically DISI Every one stage increase in the Eaton-Glickel stage in STT arthritis is associated with an average change in capitolunate angle of 7 degrees. Prognosis Nonsurgical measures are the mainstay of treatment. However, there is little prospective evidence which has demonstrated the effectiveness of nonsurgical management Anatomy Osteology Scaphoid bridges the proximal and distal carpal rows on its radial side. Ligaments Trapeziotrapezoid Trapezoid-capitate STT ligaments Major anatomic stabilizer of the STT joint Capitate-trapezium Biomechanics Scaphoid articulates with scaphoid fossa of distal radius, the lunate, the capitate, the trapezium and the trapezoid Trapezoid articulates with the trapezium and the scaphoid, in addition to the capitate and the base of the second metacarpal Classification White and Colleagues Stage I • Joint narrowing when compared to other intercarpal joints in the same radiograph, with or without subcortical sclerosis Stage II • Stage I changes, in addition to cyst-like lucencies, with or without osteophyte formation Stage III • Complete joint space obliteration with bone-on-bone articulation, with no apparent joint-space within the cartilage Presentation History Pain and weakness in grip strength Atraumatic in nature Often presents in a patient's sixth or seventh decade of life Symptoms Pain Sharper than the pain associated with basilar thumb arthritis Can have tendonitis along the flexor carpi radialis tendon Physical exam inspection Painful bony prominence just distal to the radioscaphoid joint Can be confused with the prominence observed in SLAC wrist Prominence in STT arthritis is slightly more distal and ulnar than the changes seen in SLAC wrist Motion Range of motion is grossly preserved Provocative tests Radial grind test: pain along the STT articulation with radial deviation of the wrist Imaging Radiographs recommended views AP, lateral and oblique views of the wrist optional views STT view, in which the wrist in placed in maximal extension and ulnar deviation with the palm facing the cassette Amount of arthritis is best conferred when beam is directed perpendicular and approximal 2.5 cm medial to the base of the thumb carpometacarpal joint findings STT joint space narrowing STT osteophyte formation Differential Differentiating between concomitant basilar thumb arthritis and STT arthritis can be difficult Concomitant basilar thumb arthritis and STT arthritis occurs in up to 60% of cadaver specimens Basilar thumb pain in STT arthritis is typically more proximal and medical than the trapezial-metacarpal symptoms Provocative examination maneuvers for basilar thumb arthritis are typically negative in STT arthritis (i.e. hyperadduction/hyperextension or the thumb CMC grind test Can also utilize focal injection of local corticosteroid to aid in differentiation Treatment Nonoperative Brace use, NSAID, injection Indications include patients seen initially with STT arthritis Limited long-term evidence Exhaustion of nonoperative management should be reached prior to progressing to operative treatment Operative Distal pole of scaphoid excision Indications Patients desiring preservation of range or motion and not amenable to prolonged immobilization Patients at higher risk of nonunion Outcomes As compared to contralateral wrist: Flexion/extension (79-88%), radioulnar deviation (100-85%), grip strength (85%), and pinch strength (93%) At average follow-up of three years, no patients demonstrated increased symptoms of progression of degenerative changes Mean pain VAS improvement from 7.5 to 0.6 May predispose to carpal instability (DISI posture and development of CL arthritis) Complications include persistent pain (mild: 44%) and capitate AVN STT fusion Indications STT fusion is ideal treatment for young, heavy laborer Most common surgical treatment for STT arthritis Techniques Kirschner wires Headless compression screws Staple fixation Circular plate Outcomes As compared to contralateral wrist: Flexion/extension ROM (93%), radioulnar deviation ROM (81%), grip strength (80%), and pinch strength (70%) Overall complications rate ranges from 13-78% and include nonunion (4-31%), persistent pain (mild: 30% and moderate: 5%), FCR tendonitis, radial styloid overgrowth, pin tract infections and loss of ROM Most common reason for return to OR is secondary radial styloidectomy from radial styloid overgrowth Pyrocarbon implant arthroplasty Indications Theoretically decreased risk of carpal instability as scaphoid length is preserved, improved grip strength, technically less complex as compared to STT fusion Outcomes Significant increases in DASH, VAS, grip/pinch strength, and ROM. Very limited series have not reported complications and have short follow-up and small sample sizes Techniques Distal pole of scaphoid excision Technique Removes arthritic articulation May be backfilled with tendon interposition Approach: volar, dorsal or arthroscopic Complications May predispose to carpal instability, specifically DISI posture and development of capitolunate arthritis Persistent pain (44% of patients have residual mild pain) Avascular necrosis of the capitate Flexor tendon Rupture STT fusion Options Kirschner wires are the most common method of internal fixation Alternative techniques include headless compression screws, staples and plate/screw constructions Headless compression screws are gaining in popularity Ideal radioscaphoid angle in which to fuse varies between 45 and 60 degrees of palmar flexion Technique Kirschner Wires 6-8cm dorsal incision centered over the STT joint The dorsal capsule is incised between ECRL and ECRB The articular surface is removed and decorticated, including the volar lip of the scaphoid The scaphoid is positioned at 45-60 degrees of flexion and the wrist is placed in maximal radial deviation It is not necessary to correct abnormal rotation of the lunate Cancellous bone graft is packed into the STT joint The Scaphotrapezoid joint is pinned proximal to distal while the Scaphotrapezial joint is pinned radial to ulnar The wrist is then immobilized for 6-8 weeks Staple Fixation Scaphotrapezial and Scaphotrapezoid joints reduced with k-wires then compressed with staples Circular Plate A 4-corner fusion plate can be used to fuse the STT joint Complications Nonunion Radial styloid impingement Adjacent joint arthrosis and degeneration Reflex Sympathetic Dystrophy Pyrocarbon Implant Arthroplasty Indications Patients with a desire to maintain relatively normal carpal kinematics Technique Ensure implant is sized correctly Resent approximately 3-4mm of distal scaphoid Identify and protect the sensory branch of the radial nerve Complications Implant loosening Scaphoid bone loss Complications Flexor Tendon Rupture Associated with distal scaphoid excision Thought to be associated with sharp bony remnant of distal scaphoid Dorsal Intercalated Segment Instability and Midcarpal Misalignment Occurs with distal scaphoid excision, often in the setting of comorbid midcarpal instability Lower incidence with pyrocarbon implant Nonunion Nonunion rates in STT fusion vary from 4% to 31% Can use vascularized bone graft from the distal radius to augment the fusion Radial Styloid Impingement Occurs in 33% of STT fusions Incidence is higher in patients treated for rotary subluxation of scaphoid Can treat with partial radial styloidectomy Can perform prophylactically with all STT fusions Adjacent Joint Arthrosis and Degeneration Occurs at the radiocarpal joint in 42% of patients and at the trapezial-metacarpal joint in 28% of patients following STT fusion Reflex Sympathetic Dystrophy Occurs following STT fusion Incidence is approximately 3.6% Can prevent with high-dose vitamin C