Proximal interphalangeal arthroplasty

Indications

Implant arthroplasty is indicated for patients with severe pain, deformity, and loss of motion in the proximal interphalangeal (PIP) joint who have failed nonoperative treatment (splinting, antiinflammatory medication, steroid injection, and/or hand therapy).
Silicone implants may be used in patients with inflammatory arthritis, posttraumatic arthritis, or osteoarthritis (OA).
Silicone implants act as spacers after joint resection. They are supported by the surrounding ligamentous structures and become encapsulated by fibrous tissue shortly after insertion. The result is reduced pain and maintained range of motion (ROM).
Silicone is biologically inert and has many properties that are ideal for small joint reconstruction. Unlike rigid implants, silicone implants are softer than bone and do not cause bony resorption.

PIP joint arthroplasty is contraindicated when there is active infection, ligamentous instability, severe angular deformity of the bone, or significant periarticular bone loss.
Implant arthroplasty of the index finger PIP joint can be considered but because of lateral stress on the joint during pinch, arthrodesis may be preferred in active patients who require joint rigidity during pinch.

The fingers are inspected for collinearity and symmetry. Deviation of the finger at the PIP joint may indicate asymmetric articular compression, ligamentous damage, or periarticular bone loss ( Fig. 42.1 ).
Active ROM is assessed ( Fig. 42.2 A–C ). Implant arthroplasty is effective for treating pain, which is the major indication. Patients must understand that motion may not change or may decrease, but pain should improve. Patients with 60 degrees or more of active PIP motion arc should be discouraged from undergoing implant arthroplasty if the pain is tolerable.
Passive ROM is evaluated, and the PIP joint is manually stressed in all directions. The implant relies on the ligamentous support of the PIP joint. If a joint is extremely unstable, fusion is a more predictable option.

Standard three-view x-rays are required ( Fig. 42.3 ). The articular surfaces of the proximal and middle phalanges are examined. Implant arthroplasty is indicated if there is articular surface damage and joint space loss.
Bone stock and quality must be sufficient to support an implant. Some patients are better served with a fusion if the bone quality is poor.

The PIP joint is a gliding hinge joint composed of the bicondylar head of the proximal phalanx and the concave base of the middle phalanx.
The volar plate, collateral ligaments, and extensor mechanism stabilize the joint on all sides ( Fig. 42.4 ).
The volar approach places the digital neurovascular bundles and flexor tendons at risk. These must be protected during elevation of the skin flaps.
The A3 pulley is located directly over the proximal interphalangeal joint and must be divided for joint exposure. The A2 pulley and A4 pulley, which are proximal and distal, are preserved.
Shotgun hyperextension of the PIP joint requires release and elevation of the volar plate and partial release of the collateral ligaments. The typical shotgun approach is not needed. The volar plate should be detached proximally to expose the head of the proximal phalanx. Access to the PIP joint is necessary to insert the implant after sawing just proximal to the head of the proximal phalanx and then removing it.

The patient is positioned supine with the arm supported on a hand table. An upper arm tourniquet is placed.
The procedure is performed under general or regional anesthesia.
Preoperative antibiotics are administered.
Intraoperative fluoroscopy, a narrow oscillating saw, an arthroplasty set with an awl and broaches, implant sizers, and multiple sizes of final implants must be available.

Dorsal, lateral, and volar approaches to the PIP joint are described in the literature. Studies have shown favorable results with the volar approach, and this is our preferred technique. It is technically more challenging but achieves better motion and less extensor lag postoperatively.
A Bruner incision is designed from the distal interphalangeal (DIP) flexion crease to the metacarpophalangeal (MCP) flexion crease ( Fig. 42.5 ).
The skin is incised, and the flap is elevated at the level of the flexor tendon sheath ( Fig. 42.6 ). The neurovascular bundles must be identified and protected.

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