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

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

Nathan S. Taylor, Kevin C. Chung

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

See Video 43: Pyrocarbon Implant Arthroplasty (Metacarpophalangeal Joint)

Indications

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

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.

Surgical Anatomy

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.

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.

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

FIGURE 59-1

FIGURE 59-2

Positioning

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

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

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.

FIGURE 59-3

PIP Joint Approach

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

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.

FIGURE 59-4

FIGURE 59-5

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

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).

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

A series of broaches are sequentially inserted into the proximal phalanx, starting with a no. 10 broach and increasing to the largest broach that can be accommodated within the medullary canal. The broach must be fully inserted into the medullary canal to fully accommodate the implant, which can be confirmed fluoroscopically (Fig. 59-8A and B).

FIGURE 59-8

Step 2 Pearls

The hard bone in osteoarthritis makes broaching difficult. Using a mallet to tap the broach into the bone can be helpful to facilitate seating the broach at the required depth, but tapping must be done carefully to avoid fracture.

Step 3

An oblique cutting guide is then placed into the cut proximal phalanx to complete the volar oblique osteotomy (Fig. 59-9A and B). The proximal phalanx is now ready to accommodate the trial proximal phalanx implant. The pyrocarbon implant is press-fit, and cement is not used.

FIGURE 59-9

Step 3 Pearls

The PIP pyrocarbon implant components can be mixed one size up or one size down. For example, a no. 30 proximal implant may fit with a no. 20 distal implant, and vice versa.

The middle phalanx can be difficult to broach to a larger size. Therefore, the size of the distal component is often one size down from the proximal component.

Step 4

A small oval bur is used to remove the articular surface of the middle phalanx and create a gentle trough that can accommodate the middle phalanx implant. Bone is not resected from the middle phalanx.

Step 5

The medullary canal is broached sequentially to obtain the largest implant that can be accommodated within the medullary cavity.

Step 5 Pearls

Using a side-cutting bur can enlarge the hole in the middle phalanx sufficiently to make broaching a bit easier. The bone is hard, and the bur can widen the medullary cavity to seat a larger implant.

Step 6

After adequate placement of the trial implant with the PIP joint moving smoothly, the implant is press-fit into the medullary cavity by tapping it in gently (Fig. 59-10A to C).

FIGURE 59-10

Step 6 Pearls

If the implant is excessively tight, additional bone should be resected from the proximal phalanx, taking care to preserve the collateral ligaments.

Step 7

The extensor tendon is closed with 3-0 horizontal-mattress braided permanent suture. The tourniquet is released, and all bleeding points are cauterized. The skin is closed with 4-0 horizontal mattress nylon suture, and the finger is splinted in full extension.

Procedure

MCP Joint Arthroplasty

Step 1

The sequence of steps for the MCP joint arthroplasty is similar to that for PIP joint arthroplasty. A starter awl enters the metacarpal head one third of the distance from the dorsal cortex and slightly ulnar to the midline and can be advanced to one half or two thirds of the metacarpal bone length (Fig. 59-11A to D). The implant fits the anatomic shape of the head of the metacarpal, and the cam design of the implant requires the center of axis to enter one third from the dorsal cortex. The proximal implant has a condylar shape, and its stem will reside more dorsally from the midaxis of the joint.

FIGURE 59-11

Step 1 Pearls

Radial positioning of the metacarpal component should be avoided because this will further increase the radial deviating moment arm and contribute to ulnar drift. Fluoroscopy must be used liberally to ensure that all the instruments are in the precise location to permit perfect seating of the implant.

Step 2

A proximal osteotomy is made using a proximal osteotomy guide, which has a 27.5-degree distal tilted axial slot for the saw blade (Fig. 59-12A). A conservative osteotomy 1.5 mm distal to the collateral ligament attachment site is recommended to protect the collateral ligaments. The osteotomy is partially made over the dorsal cortex, and complete osteotomy is performed freehand after removal of the alignment guide (Fig. 59-12B).

FIGURE 59-12

Step 2 Pearls

One should identify the proximal insertion of the collateral ligaments and protect these to maintain ligamentous support.

Every effort should be made to preserve as much bone stock as possible.

Step 3

A medullary canal is created over the base of the proximal phalanx using the starter awl. The starter can be advanced one half to two thirds of the length of proximal phalanx (Fig. 59-13A and B).

FIGURE 59-13

Step 4

A 5-degree distally tilted osteotomy is made using the osteotomy guide (Fig. 59-14A and B).

FIGURE 59-14

Step 5

A broach is inserted as described previously (Fig. 59-15A and B). Mismatch is not permitted between the proximal and distal components of the implant in MCP joint pyrocarbon arthroplasty.

FIGURE 59-15

Step 5 Pearls

In cases of significantly sclerotic bone, such as in osteoarthritis, the canal may need to be enlarged with a side-cutting bur.

Broaching is stopped when the reamer is seated just below the bone edge.

Step 6

A trial implant is inserted using a proximal and a distal impactor (Fig. 59-16A and B). The implant is press-fit into the medullary cavity by tapping it in gently (Fig. 59-17A and B).

FIGURE 59-16

FIGURE 59-17

Step 6 Pearls

Final implants tend to be slightly larger than trial components to be press-fit securely.

The MCP joint should move passively through a 0- to 90-degree arc without significant tension.

Step 7

The incised sagittal band is repaired with 3-0 horizontal-mattress braided permanent suture (Fig. 59-18). The tourniquet is released, and all bleeding points are cauterized. The skin is closed with 4-0 horizontal mattress nylon suture, and the finger is splinted in full extension.

FIGURE 59-18

Step 7 Pearls

The dorsal capsule can be trimmed to provide a better-fitting repair over the prosthesis.

A final fluoroscopic examination should be performed to ensure that there has been no subluxation during dressing application.

Postoperative Care and Expected Outcomes

The joint should be kept in extension for 3 weeks after the operation to consolidate the soft tissue support.

One week after the operation, flexion and extension exercises are started in a dynamic splint. A static resting splint can be worn at night for 2 months after the 3-week exercise program.

Expected outcomes of this procedure include improvement in pain, improved aesthetic appearance of the hand and fingers, increased ability to perform activities of daily living, improved key pinch strength, minimal change in active arc of motion, and minimal improvement in grip strength.

Case Studies

Figure 59-19 (A to F) shows the long-term result of a PIP joint pyrocarbon implant arthroplasty in a 53-year-old man with severe osteoarthritis and pain over the left index finger PIP joint limiting motion. The patient refused PIP joint fusion; therefore, a pyrocarbon implant arthroplasty was performed.

A 70-year-old woman presented with right index finger severe osteoarthritis and pain. She refused PIP joint fusion and opted for a pyrocarbon implant arthroplasty to preserve some motion (Fig. 59-20A). About 18 months after pyrocarbon arthroplasty, she began to experience chronic pain and swelling related to instability and recurrent dislocation of the joint that she was always able to reduce herself (Fig. 59-20B). Because of her persistent symptoms related to the recurrent dislocation, the implant was removed, and a PIP joint fusion was performed. This case illustrates that pyrocarbon arthroplasty can cause long-term problems relating to implant subsidence and dislocation. These complications must be explained carefully to the patient. Because there is no better alternative, and silicone implant for the PIP joint is often associated with joint instability, the pyrocarbon arthroplasty option is still a reasonable solution in lieu of joint fusion.

A 59-year-old woman with a history of severe osteoarthritis of all finger joints presented for pyrocarbon arthroplasty of her right ring finger PIP joint (Fig. 59-21A). Two weeks after the arthroplasty, the joint was dislocated (Fig. 59-21B). The joint was reduced, and an external fixator was used to maintain reduction for 6 weeks (Fig. 59-21C). After removal of the external fixator, the joint was stable and had good motion (Fig. 59-21D). This case illustrates that poor ligamentous support in the PIP joint is unable to maintain joint reduction after implant arthroplasty. The use of an external fixator to reduce the joint permits tightening of the ligament support and can remedy the dislocation complication, if this complication is detected within the first 2 weeks after surgery.