59: Pyrocarbon Implant Arthroplasty of the Proximal Interphalangeal and Metacarpophalangeal Joints

Published on 18/04/2015 by admin

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Procedure 59 Pyrocarbon Implant Arthroplasty of the Proximal Interphalangeal and Metacarpophalangeal Joints

Nathan S. Taylor, Kevin C. Chung

imageSee Video 42: Pyrocarbon Implant Arthroplasty (Proximal Interphalangeal Joint)

See Video 43: Pyrocarbon Implant Arthroplasty (Metacarpophalangeal Joint)

Indications

image Painful osteoarthritis of the proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints is found.

image The patient should understand that normal full motion of the joint cannot be restored; therefore, surface replacement arthroplasty should be performed when the arthritic pain has become intolerable.

Examination/Imaging

Clinical Examination

image The patient’s joints are assessed for the following:

• Intact extensor apparatus
• Intact collateral ligaments
• Good bone stock of the finger

image If the extensor tendon is not intact, it should be reconstructed at the time of surface replacement arthroplasty.

Imaging

image Three views of the hand are essential to evaluate the structural integrity of the small joints of the hand and adequate bone stock.

image Occasionally, computed tomography scans of the joints may be necessary to assess the articular cartilage.

Surgical Anatomy

image The MCP joints of the fingers are condylar joints (Fig. 59-1), and specific MCP pyrocarbon implants are designed to mirror the anatomic construct. At the MCP joint, excellent soft tissue support and stability provided by the intermetacarpal ligaments give its stable construct. The best indication for pyrocarbon implant arthroplasty is an osteoarthritic MCP joint. Unfortunately, this situation is not often encountered. We generally do not recommend placing pyrocarbon implants in the rheumatoid hand because of the lack of adequate ligamentous support.

image The PIP joints for the fingers are ginglymoid joints that function essentially as hinge joints (Fig. 59-2). Destruction of the PIP joints often weakens the soft tissue support around the joints and may not be sufficiently tight to stabilize the pyrocarbon implants.

image Preserving bone and collateral ligament origins and insertions helps stabilize the arthroplasty.

image

FIGURE 59-1

image

FIGURE 59-2

Positioning

image The procedure is performed under tourniquet control with the patient in the supine position and the extremity abducted with the hand on a hand table.

Exposures

MCP Joint Approach

image A dorsal lazy S-shaped incision is made over the MCP joint for single joint replacement (Fig. 59-3A and B).

image If there is no subluxation of the extensor mechanism, it can be split in the midline to expose the joint capsule. We prefer to incise the radial sagittal band to expose the joint so that the extensor tendon is not disrupted (Fig. 59-3C). The incised sagittal band should be imbricated to centralize the extensor mechanism at the conclusion of the procedure.

image

FIGURE 59-3

PIP Joint Approach

image The PIP joint is approached using a lazy S-shaped incision (Fig. 59-4), which provides wide exposure of the joint.

image Two incisions may be used to expose the extensor mechanism.

• The widest exposure is obtained with a chevron incision that detaches the extensor tendon proximally, with the central tendon remaining inserted distally (Fig. 59-5A). The tendon is reflected distally, and the entire joint is fully exposed (Fig. 59-5B).
• Our preference is to split the extensor tendon in the midline to maintain tendon integrity and provide adequate exposure (Fig. 59-6A and B). This incision will require traction on the split extensor tendon during the surgical procedure, but the tendon can be closed in a side-to-side fashion that will not stretch out during therapy.
image

FIGURE 59-4

image

FIGURE 59-5

image

FIGURE 59-6

Pearls

After the PIP joint arthroplasty, the lazy S-shaped incision can be closed by recruiting lateral skin to decrease tension of the skin flap during flexion of the PIP joint.

Pitfalls

The chevron incision exposure must be performed cautiously because the subsequent tendon repair may stretch out during therapy, resulting in an extension lag.

Procedure

PIP Joint Arthroplasty

Step 1

image The manufacturer’s manual recommends placing the starter awl first to make the tunnel ready for broaching. However, the osteoarthritic PIP joint is usually very tight, and getting precise placement of the awl is difficult. We have modified this key step by making a freehand cut of the head of the proximal phalanx first, which will fully expose the medullary cavity for precise broaching. Experience is necessary to avoid too much head resection, cutting just at the distal neck of the proximal phalanx (Fig. 59-7A to D).

image

FIGURE 59-7

Step 1 Pearls

One must be careful to identify the proximal insertion of the collateral ligaments to avoid damaging these during the vertical proximal osteotomy.

Preservation of as much bone stock as possible will help stabilize the implant.

Step 1 Pitfalls

Injury to the collateral ligaments will contribute to instability of the construct.

Step 2

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