75: Scaphotrapeziotrapezoid Arthrodesis and Lunate Excision with Replacement by Palmaris Longus Tendon

Published on 18/04/2015 by admin

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Procedure 75 Scaphotrapeziotrapezoid Arthrodesis and Lunate Excision with Replacement by Palmaris Longus Tendon

Akio Minami

Indications

image Advanced avascular necrosis of the lunate from late stage IIIA to early stage IV according to the Lichtman preoperative 5-stage classification.

image This procedure is mainly indicated for stage IIIB Kienböck disease, which is associated with carpal collapse with a fixed palmar scaphoid flexion.

image A radiograph showing generalized arthrosis is not suitable for scaphotrapeziotrapezoid (STT) arthrodesis and lunate excision with replacement by the palmaris longus tendon.

image This procedure is contraindicated in patients with preoperative advanced osteoarthrosis between the radius and scaphoid because of the risk for further progression of osteoarthrosis at the radioscaphoid joint.

Examination/Imaging

Clinical Examination

image A complete examination of the involved and contralateral extremity is indicated, especially if the patient has a history of autoimmune disease or infection.

image Documentation of baseline pinch and grip strength is helpful.

image Attention to soft tissue swelling must be given because some patients have associated capsular inflammation, thickening, and synovitis.

image Pain can be elicited in all directions of motion, and frequently there is a notable decrease in the arc of motion, particularly in extension.

image Degree of pain, range of motion of the wrist, and grip strength of both wrists should be meticulously measured preoperatively to evaluate postoperative results.

Imaging

Plain Radiographs

image Staging: Lichtman modification of Stahl staging

• Stage 0: Radiographs are normal, and magnetic resonance imaging (MRI) may show lunate density changes, edema, or fracture (according to the Amadio modified Lichtman staging based on MRI findings).
• Stage I: Radiographs are normal, but bone scan or tomograms may reveal a sclerotic line representative of a lunate fracture. Occasionally, an indistinct line consistent with the fracture may be visible on plain films (Fig. 75-1A).
• Stage II: Lunate density changes are apparent, but carpal alignment remains normal, and lunate size is preserved (Fig. 75-1B).
• Stage IIIA: Plain films demonstrate lunate collapse, fragmentation, and displacement; on anteroposterior and lateral views, lunate elongation may be seen without static carpal collapse (Fig. 75-1C).
• Stage IIIB: Lunate collapse is accompanied by carpal collapse with a fixed palmar scaphoid flexion (Fig. 75-1D).
• Stage IV: All stage III findings are present plus generalized arthritis (Fig. 75-1E).

image Posteroanterior (PA) and lateral radiographs with the wrist in neutral rotation and neutral flexion-extension (Fig. 75-2).

image Ulnar variance radiographic views with the wrist in full pronation and full supination. The carpal height ratio is measured from PA view with the wrist in neutral position. The Stahl index is also measured from lateral view.

image Lunate sclerosis, carpal instability patterns, and fragmentation are seen.

image Shortened scaphoid in the long axis and cortical ring sign of the scaphoid are seen in stage IIIB, which indicates scaphoid in flexed position.

image Evaluation of relationship among scaphoid, trapezium, and trapezoid.

image

FIGURE 75-1

image

FIGURE 75-2

Computed Tomography

image Computed tomography (CT) is needed to evaluate precisely the bony architecture of the lunate and the remainder of the carpus to determine which procedure is indicated and to determine whether arthritic changes of the midcarpal and radiocarpal joints are present.

image A CT scan is useful for evaluation of fragmentation or fracture patterns and associated collapse.

Magnetic Resonance Imaging

image MRI will show decreased uptake in both T1- and T2-weighted images. Gadolinium contrast has improved diagnosis and evaluation of lunate vascularity (Fig. 75-3).

image It is important to differentiate between ulnar impaction of the lunate and true Kienböck disease.

image Stage 0 has been proposed when lunate edema is visible on MRI only. MRI can show the degree of devascularization or revascularization.

image

FIGURE 75-3

Bone Scan

image A three-phase bone scan is useful to determine the blood flow to the lunate. This scan is highly sensitive, but specificity is low.

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