Procedures for avascular necrosis of the lunate (Kienböck disease)

Introduction

Kienböck disease describes the avascular necrosis of the lunate. Although its cause and natural history are uncertain, it is thought to progress through four stages: necrosis and subsequent collapse of the lunate, leading to changes in biomechanics of the other carpal bones and finally to the development of arthritis.
Nonoperative management of Kienböck disease is controversial and is usually indicated only in stage I disease.
Operative treatments fall into 3 categories: (1) strategies to off-load the lunate (see “Capitate Shortening” or “Radius Shortening”), (2) strategies to revascularize the lunate (see “Pedicled Vascularized Bone Grafts From the Middle Finger Metacarpal or Distal Radius” and “Free Osteochondral Flaps”), and (3) salvage arthrodesis procedures (see Chapter 53 Total Wrist Fusion and proximal row carpectomy [PRC] in Chapter 27 Salvage Procedures for Scaphoid Nonunion).

Indications

The treatment of Kienböck disease is guided by its stage. The most common staging system is the Lichtman classification ( Fig. 31.1 ).
- Stage I: Plain x-ray negative or single linear fracture; decreased signal in lunate on T1-weighted magnetic resonance imaging (MRI).
- Stage II: Multiple fractures and/or sclerosis seen within the lunate but no evidence of lunate collapse.
- Stage IIIA: Lunate collapse but the carpal alignment has been maintained.
- Stage IIIB: Lunate collapse with fixed scaphoid flexion.
- Stage IV: Arthritis around the lunate.
If the patient has stage IV disease, salvage procedures are performed (wrist denervation, PRC, or limited arthrodesis, depending on the arthritic surfaces).
If a patient has stage I, II, or IIIA disease, a combination of lunate off-loading and revascularization is performed during a single surgical session. We prefer to perform a capitate shortening osteotomy and pedicled bone flap from the middle finger metacarpal in most situations because it is relatively simple, requires a limited exposure, and avoids donor site morbidity. Osteochondral flaps may also be considered.
If a patient has stage IIIB disease, then the biomechanical changes may progress to arthritis even with off-loading or revascularization procedures. Treatment at this stage is controversial. Though some surgeons perform off-loading and revascularization procedures, others recommend salvage procedures when symptoms are intolerable.

Contraindications

Performing a radial shortening osteotomy in patients with ulnar negative variance can lead to ulnocarpal abutment syndrome. Capitate shortening osteotomy should be performed in these patients instead.
One contraindication is evidence of wrist arthritis.
Another is flexion of the scaphoid with radioscaphoid angle greater than 60 degrees because this indicates stage IIIB disease. This is controversial, however, because some surgeons achieve good results with off-loading and revascularizing procedures in patients with stage IIIB disease.

Clinical examination

Kienböck disease is difficult to diagnosis early because patients typically present with vague dorsal wrist pain and limited range of motion (ROM), with or without antecedent trauma.
A thorough wrist examination is necessary to assess ROM, locations of point tenderness, and any soft tissue defects.
The wrist should be examined dorsally and volarly with direct palpation over bone intervals and the carpus to identify pain and inflammation. The pain may be localized to the radiolunate joint. It often increases with activity and is relieved with rest and immobilization.
Test for pain with axial loading or inherent joint instability because these are relative contraindications to PRC.
Check for tendon excursion because the overall kinematics at the wrist will change with shortening.
Tenderness is common over the dorsal lunate, which can be palpated just distal and ulnar to the Lister tubercle.

CLINICAL EXAMINATION PEARLS

Kienböck disease should be suspected in any young person with vague wrist pain.

Imaging

Radiographs

Standard radiographs are always obtained to (1) rule out other pathology, (2) diagnose stage II or later Kienböck disease, and (3) determine ulnar variance. The lunate may appear normal on x-rays despite the presence of stage I disease.
Radiographs can show lunate sclerosis in stage II or lunate collapse in stage III and beyond ( Fig. 31.2 ). Stage IIIA has normal overall carpal alignment, whereas stage IIIB has carpal collapse with scaphoid flexion.
Two measurements are used to distinguish stage IIIA from stage IIIB ( Fig. 31.3 ): (1) The radioscaphoid angle reflects scaphoid flexion. It is measured between the long axis of the radius and the axis of the scaphoid and should be between 30 and 60 degrees. (2) Carpal height ratio reflects collapse of the carpus onto a collapsed lunate and flexed scaphoid; it is the ratio of carpal height to middle finger metacarpal height. The range is 0.52 plus or minus 0.02; less than 0.45 generally indicates carpal collapse.
Stage IV disease demonstrates arthritis and is treated with observation, rest, and splinting, or salvage operations such as wrist denervation, PRC, or limited wrist fusion.
Ulnar variance is measured on a neutral rotation posteroanterior (PA) view. When the distal radius and ulna are measured at the same level, this is termed neutral variance. If the ulnar articular surface is distal to the articular surface of the radius, this is called positive variance. Negative ulnar variance exists when the ulna is proximal to the radius. Normal variance is considered −2 mm to +2 mm. Pronation (up to +1 mm) and power grip (up to +2.5 mm) may change the articular relationship.
Shortening the radius can decrease the lunate strain by up to 70%, and 90% of this can be accomplished with 2 mm of radial shortening.
If x-rays demonstrate ulnar neutral or ulnar positive variance, shortening of the radius could lead to ulnocarpal abutment and subsequent wrist pain. In these patients, a capitate shortening should be considered.

Magnetic resonance imaging

Stage I disease is only reliably detected with MRI imaging that demonstrates decreased T1 signal diffusely throughout the lunate ( Fig. 31.4 ). The decrease in signal intensity must be seen uniformly throughout the lunate to diagnose avascular necrosis of the lunate. Ulnar impaction syndrome, fractures, interosseous ganglions, or enchondromas may cause focal decrease in signal on T1 or hyperintense signal on T2.

FIGURE 31.4, T1-weighted MRI showing avascular necrosis of the lunate with collapse, indicating stage IIIA disease. Stage I disease is indicated by a normal x-ray and the same MRI appearance of the lunate but no collapse. MRI, Magnetic resonance imaging.

Surgical anatomy

There is a rich anastomotic network of arteries at the dorsal wrist that provides several pedicled bone flap options ( Fig. 31.5 ).
Pedicled bone flaps either travel above or below the extensor retinaculum. We use the fourth extensor compartment artery (ECA) bone flap, which travels below the extensor retinaculum. Other surgeons use bone flaps that travel above the extensor retinaculum, or “supraretinacular” SRA flaps: the 1,2- and 2,3-intercompartmental supraretinacular artery (ICSRA).
For the revascularization procedures presented in this chapter, it is necessary to bur out the necrotic lunate to receive the pedicled bone flap. It is challenging to fit the flap within the lunate because the lunate is curved and the bone flap is a cube ( Fig. 31.6 ).

Capitate shortening osteotomy

Positioning

All procedures in this chapter require the same positioning: general anesthetic or a block and monitored anesthesia care, supine on the operating room table with a tourniquet.
Prophylactic antibiotics are administered.

Step 1: Markings

The incision is designed over the fourth extensor compartment, from the distal radius to the mid-third metacarpal ( Fig. 31.7 ).

FIGURE 31.7, Dorsal wrist markings, showing the metacarpal, capitate, and collapsed lunate, with a dorsal wrist incision placed in line with these structures.

STEP 1 PEARLS

Use long incisions to achieve better visualization.
Confirm markings are over the capitate with fluoroscopy before incision.

Step 2: Expose the dorsal wrist capsule

The tourniquet is inflated with minimal exsanguination to help identify vessels.
A standard dorsal approach to the wrist is used to expose the dorsal wrist capsule. Incise through the skin and take care to protect the subcutaneous nerves and veins.
Identify and transpose the extensor pollicis longus (EPL) to protect it, then enter the fourth extensor compartment. Use self-retaining retractors to retract the fourth extensor tendons and expose the dorsal wrist capsule.

STEP 2 PEARLS

Elevate thick subcutaneous flaps that contain all structures superficial to the extensor retinaculum. This will ensure that the radial sensory and dorsal cutaneous ulnar nerves are raised in the skin flaps.
Cauterize any crossing veins. There is no benefit to preserving them, and they can often bleed when the tourniquet is taken down.

STEP 2 PITFALLS

The EPL tendon is more easily transected than the fourth extensor tendons because it crosses the dorsal wrist at an angle and is more superficial, whereas the other extensor tendons are longitudinal and deeper.

Step 3: Confirm anatomy with fluoroscopy

Use fluoroscopy to identify the third carpometacarpal (CMC) joint, between the distal capitate and third metacarpal; this will form the distal position of wrist capsulotomy. Mark with a marking pen.

STEP 3 PEARLS

The pedicles for local bone flaps are close to the capsulotomy incisions required to access the wrist; precise cuts in the wrist capsule can be made at the distal capitate using fluoroscopic guidance.
The dorsal interosseous muscles appear distal to the metacarpal bases. The bases articulate with each other, and then narrow to form the shafts, between which are the interossei. Therefore the CMC joint is proximal to the interossei.

STEP 3 PITFALLS

The third metacarpal bone flap is taken from the white-appearing metacarpal base ( Fig. 31.8 ). Recognize that this is not the capitate, and design a capsule incision proximal to it.

FIGURE 31.8, Plan a dorsal wrist capsule incision to protect the pedicled bone flap from the third metacarpal base. The white structure indicated at left is the third metacarpal base, and the capsule incision is placed proximal to this.

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