The decision to operate must not be made on the basis of the X-ray appearances alone. However, function is not always the only consideration. Although it is generally not a good idea to perform an arthroplasty in patients who have good function, some patients still ask for surgery to ‘improve’ the appearance of their hands.
Indications
• Painful or stiff joints unresponsive to medical treatment
• Deformity and/or loss of range of movement affecting activities of daily living
• Failure of conservative measures. Before this can be said, patients must have had an adequate trial of:
– Regular non-steroidal anti-inflammatory drugs (NSAIDs) and splintage
– Steroid injections (administer at least one or two of these)
– Using home or work aids
– Appropriate alterations to their home or work circumstances
• To ‘improve’ the appearance of the hand
• MCP joint in preference to PIP joint
• Index or middle finger PIP joints
Contraindications
• Absent or poor flexor or extensor tendon function
• Absent or poor nerve function (e.g. peripheral neuropathy)
• Patients with significant vascular compromise (e.g. scleroderma, Raynaud’s phenomenon)
• Patients with poor skin cover over the joint
• Patient unwilling or unable to comply with postoperative hand therapy
• Heavy smoker and unwilling to stop preopera - tively
• DIP joint – an arthrodesis is recommended
• PIP joint of ring and little fingers – joint instability is often worse in these digits.
Operative planning
The choice is between a replacement arthroplasty or a resurfacing/interposition arthroplasty. A re - placement arthroplasty excises the joint completely and replaces it with an artificial or autologous joint (usually taken from the foot). Artificial joints do better in older/lower-demand patients. A resurfacing/ interposition arthroplasty is less destructive and tries to restore the normal shape of the joint using either autologous or artificial materials and is more suitable for young or active patients.
In general, replacement arthroplasty works best for the MCP joints and not the PIP joints. If PIP joint arthroplasty must be considered, then this is best done in the index and middle fingers only. DIP joint arthroplasty is rarely successful. These patients are better served by an arthrodesis.
Many types of artificial material have been described for replacement arthroplasty. The only material that has withstood the test of time is silicone, e.g. Swanson’s implant (Fig. 9.8). The technique for insertion is described here.
Anaesthesia and positioning
Local, regional or general anaesthesia can be used. The position is supine with the hand on an arm table.
Consent and risks
• Flexor tendon/neurovascular injury
• Instability (only for PIP joint arthroplasty)
• Recurrent deformity (affects one-third of arthroplasties)
• Dislocation, loosening or fracture of the implant (implant failure affects one-third of implants)
• Infection necessitating removal of implant
• Loss of range of movement
• Ongoing pain
• Dislocation, fracture or extrusion of the implant (7–15 per cent).
• Silicone synovitis
Arthroplasty in the hand 125
Figure 9.8Swanson’s implant in place
SURGICAL TECHNIQUE
Metacarpophalangeal joint
Landmarks and incision
A longitudinal incision (straight or curvilinear) is made over the dorsum of the joint. Any curvature in the incision is usually towards the radial side. This makes it easier to access and reef the radial saggital bands of the extensor hood. Reefing of the extensor hood allows ulnar subluxation of the extensors to be corrected in rheumatoid arthritis.
Dissection
The skin and subcutaneous fat are widely degloved over the joint to expose the extensor tendons and the saggital bands. The sagittal bands are divided longitudinally on the radial side, leaving a minimum 2–3 mm fringe along the edge of the extensor tendon: this allows the bands to be reefed at a later stage. The extensor mechanism is now freed from the underlying capsule and retracted ulnarly. The joint capsule is often flimsy in these patients and it is often easiest to simply excise it. After excising the capsule and any associated synovial tissue, any remnants of the collateral ligaments can also be excised.
Procedure
The volar plate must be freed from the neck of the metacarpal to allow the base of the proximal phalanx to come into correct alignment with the metacarpal. The metacarpal head is now excised with an oscillating saw. In the rheumatoid patient, the metacarpal head is often excised with a slight radial tilt to help correct any ulnar drift. The amount of bone excised is determined by the need to accommodate intrinsic muscle tightness: the
tighter the intrinsics, the more bone that needs to be excised (up to a limit – excessive shortening is best avoided). The base of the proximal phalanx is not excised unless there is severe deformity. However, any osteophytes must be removed with bone nibblers since these may interfere with flexion. The base of the proximal phalanx is now pierced with an awl. This opening is enlarged and the medullary cavities of the proximal phalanx and metacarpal are now reamed by hand using progressively larger reamers. Sizers are used to determine the correct size of Swanson’s implant which should be used. In general, the largest implant that fits should be selected. The implant fits when the long stem fits snugly in the metacarpal and the short stem fits snugly in the proximal phalanx. There should be no compression of the mid-section with the fingers in extension. Generally, size 3 or 4 implants are used for the MCP joints.
The sizer is removed and the wound is washed out with saline. The appropriate permanent implant is inserted using a ‘no touch’ technique. The implants are usually supplied with stainless steel ‘grommets’. These should not be used.
Closure
It is not necessary to formally repair the collateral ligaments – scar tissue forms rapidly around the implant and confers some stability to the joint. The sagittal bands are repaired with 4/0 or 5/0 PDS and are reefed as necessary if there is significant subluxation of the extensor tendons into the ulnar gutters.
The skin is then closed with absorbable sutures. The author recommends using interrupted 5/0 Monocryl for the dermis (to approximate the wound edges) then a running subcuticular 5/0 Monocryl suture for final closure.