Proximal Interphalangeal and Metacarpophalangeal Joint Silicone Implant Arthroplasty



Proximal Interphalangeal and Metacarpophalangeal Joint Silicone Implant Arthroplasty


Charles A. Goldfarb





ANATOMY


Metacarpophalangeal Joint



  • The MCP joint is condyloid with motion in three planes: flexion-extension, abduction-adduction, and rotation.


  • The head of the metacarpal is wider on its volar aspect, providing greater stability in flexion. The radial condyle is larger as well, contributing to the ulnar deviation posture most commonly seen in RA patients.


  • Collateral ligaments arise dorsal to the center of rotation; this, together with the shape of the metacarpal head, contributes to the cam effect that is manifest by collateral ligament laxity in extension and tightness in flexion.


  • Hyperextension of the MCP joints is common; however, the volar plate limits excessive motion.


Proximal Interphalangeal Joint



  • The PIP joint is a hinge joint with an average arc of motion of 0 to 100 degrees of flexion.


  • The bony anatomy is crucial to PIP joint stability in all positions; the base of the middle phalanx is wider volarly, thus helping to prevent dorsal dislocation. The PIP joint is more stable in all positions compared to the MCP joint.


  • The proper collateral ligaments originate from the center of rotation of the proximal phalanx head and insert onto the volar base of the middle phalanx; they provide stability in all positions. The accessory collateral ligaments insert onto the volar plate and provide more stability in extension. There is no significant cam effect with the PIP joint.


  • The volar plate resists hyperextension and is a key supporting structure of the joint.


PATHOGENESIS



  • Arthritis of the MCP or PIP joints may be idiopathic, posttraumatic, or inflammatory (RA).


  • Idiopathic osteoarthritis involves the distal interphalangeal joint most commonly, but the PIP joint is also affected; the MCP joint is less commonly involved.


  • The PIP joint is the most frequently traumatized finger joint and, thus, has the highest incidence of posttraumatic arthritis. Given the shortcomings of the salvage procedures for PIP joint arthritis, an anatomic joint reduction and aggressive restoration of the normal anatomy after trauma is critical to reduce the risk of arthritis.


  • The bony congruity of the PIP joint makes it poorly tolerant of any loss of cartilage; deformity and loss of motion may progress quickly.


  • Inflammatory arthritis (RA) most commonly affects the MCP joint but may also involve the PIP joint. In RA, a proliferative synovitis compromises the soft tissue support of the affected joint and may lead to the characteristic deformities at the MCP joint, including volar subluxation (and a flexed posture) and ulnar deviation. The PIP joint is less predictable because attenuation of the volar supporting structures may lead to joint hyperextension, whereas compromise of the central slip insertion will lead to a joint flexion deformity.


  • The efficacy of the disease-modifying antirheumatic drugs has dramatically decreased the need for joint arthroplasty in these patients.


NATURAL HISTORY



  • The natural history of osteoarthritis or posttraumatic arthritis of the PIP joint is progression with loss of motion, pain, and, in some patients, deformity. The MCP joint is less commonly affected and is also more tolerant of arthritis, given its increased mobility in all planes.


  • In the patient with severe RA not controllable by disease-modifying antirheumatic drugs, joint inflammation will lead to progression of the arthritis.


  • The functional effect of the arthritis depends on the degree of involvement, the specific joint, and the involvement of the adjacent joints.


PATIENT HISTORY AND PHYSICAL FINDINGS



  • It is vital that the surgeon understand how the arthritis specifically affects the function of a particular patient. This depends on many factors, including adjacent joint involvement, specific patient activities, and the degree of pain experienced.



IMAGING AND OTHER DIAGNOSTIC STUDIES



  • Posteroanterior and lateral plain radiographs provide sufficient diagnostic information. Occasionally, oblique radiographs are helpful (FIG 1).






    FIG 1A. RA affecting hand, with most notable disease affecting MCP joints. The wrist is also affected. B. Isolated osteoarthritis of the MCP joint of the long finger. C. Posttraumatic arthritis affecting the small finger PIP joint.


  • Magnetic resonance imaging (MRI) and computed tomography (CT) are of limited use in the evaluation of the MCP and PIP joints.




NONOPERATIVE MANAGEMENT



  • Anti-inflammatory medications


  • Steroid injections


  • Hand therapy to address contractures, including splinting


SURGICAL MANAGEMENT



  • Surgery is considered if nonoperative management fails. Given the limitations of silicone implant arthroplasty as noted in the following text, the decision for surgical intervention should be patient driven.


  • The best outcome is expected in patients with joint-based pain and a well-preserved arc of motion and minimal deformity. Patients without pain and presenting with deformity or a lack of motion are not ideal candidates for arthroplasty, especially if the adjacent joints are functioning well. Joint arthroplasty, of any variety, does not reliably increase motion at long-term follow-up.


  • In RA, an ulnar drift and volar subluxation of the MCP joints with a flexion posture of the joints may lead to weakness and a loss of the ability to grasp larger objects. These deformities are also unsightly. Surgical intervention in these patients can be expected to improve the appearance and function of the hand.


Preoperative Planning



  • All imaging studies are reviewed.


  • Involvement of adjacent joints is assessed.



  • Multiple MCP or PIP joints can be treated with silicone arthroplasty at the same surgical setting, but we do not typically recommend MCP and PIP joint silicone arthroplasty in the same finger.



    • In patients with symptomatic disease at both the MCP joint and the PIP joint, the MCP is typically treated with silicone implant arthroplasty and the PIP joint is fused.


  • An assessment of the ligamentous stability of the MCP and PIP joints is performed under anesthesia.


  • MCP and PIP arthroplasty is performed cautiously in the index (or long) finger, as pinch forces may be problematic for joint stability if the collateral ligaments are elongated or compromised with surgery.


  • Templating is performed to ensure that appropriate-sized implants are available.


Positioning



  • The patient is supine with the extremity on an arm table.


  • A nonsterile arm tourniquet is used.


  • General or axillary block anesthesia is used.


Approach



  • The MCP joint is approached from dorsally with a midline incision.


  • The PIP joint may be approached from either the dorsal or volar approach.


Jul 22, 2016 | Posted by in ORTHOPEDIC | Comments Off on Proximal Interphalangeal and Metacarpophalangeal Joint Silicone Implant Arthroplasty
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