MP and PIP Joint Arthroplasty
Lindley B. Wall, MD
Rhonda K. Powell, OTD, OTR/L, CHT
Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Powell and Dr. Wall.
Introduction
Function of the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of the hand are important for activities of daily living (ADLs) and are susceptible to degenerative changes. Arthroplasty of the small joints of the hand, specifically the MCP and PIP joints, is an established and accepted treatment for symptomatic arthritis. Small joint arthroplasty can reliably treat pain, restore joint motion, and improve overall hand function. Silicone and resurfacing (pyrocarbon or metallic) implants are available for both the MCP and PIP joints.
Metacarpophalangeal Joint Arthroplasty
Relevant Anatomy
The MCP joint has a CAM-like structure that is stabilized by the proper and accessory collateral ligaments. The joint is more stable to varus and valgus stress in a flexed position compared to extension. The volar plate also stabilizes the MCP joint by limiting joint hyperextension. The extensor tendon is located dorsal to the joint, and is maintained in a central position by the radial and ulnar sagittal bands.
Patient Evaluation
The preoperative evaluation assesses digit range of motion (ROM), grip-and-pinch strength, as well as consideration of functional needs and overall goals. The alignment, active range of motion (AROM) and passive range of motion (PROM), stability, and degree of laxity of the involved joints are evaluated. Radiographs of the hand, including a posterior-anterior (PA) and lateral image, are also obtained to assess for degenerative changes, including joint space narrowing, osteophyte formation, and subchondral sclerosis.
Indications and Contraindications
Silicone MCP arthroplasty has been utilized for over 50 years with acceptable levels of pain relief and restoration of joint motion. Silicone is a synthetic polymer that can be fashioned into different structures and provides a flexible rubber-like form. The silicone arthroplasty is a constrained implant that bridges from the metacarpal to the proximal phalanx and acts as a hinge joint while providing inherent stability. This arthroplasty is most commonly utilized in the setting of rheumatoid arthritis and other conditions with ligament or capsular laxity and deficiency. Patients must have adequate bone stock to support the implant and functioning flexor and extensor tendons to allow for active joint ROM.
Resurfacing arthroplasties are a newer-generation arthroplasty for the painful arthritic MCP joint, fabricated from pyrocarbon, cobalt chrome with polyethylene, or other composite materials. Pyrocarbon is a synthetic material consisting of a graphite core coated by a pyrolytic carbon layer. These implants are unconstrained and require stability from the surrounding collateral ligaments and capsule. Therefore, these implants are ideal for osteoarthritic joints or posttraumatic joints with competent ligamentous support. Joints affected by inflammatory arthritis and compromised soft-tissue structures are a relative contraindication to pyrocarbon implants because of the risk of instability.
Arthroplasty is generally contraindicated in a previously infected joint because of increased risk of joint loosening and failure.
Surgical Procedure
The surgical techniques used for silicone and resurfacing arthroplasty are similar. A dorsal approach to the MCP joint is utilized. A longitudinal incision is made centrally over a single involved joint. If all or multiple MCP joints are being addressed at one time, then a transverse incision centered over the joints is preferred. Care is taken to preserve small sensory nerves.
In the rheumatoid patient, the extensor tendon is usually subluxated ulnarly, thus the extensor hood is incised on the ulnar side of the extensor tendon. If the tendon is not subluxated, it can be incised longitudinally and repaired at closure. The joint capsule is then incised and synovectomy is performed to remove any extensive synovitis.
In the rheumatoid patient, the extensor tendon is usually subluxated ulnarly, thus the extensor hood is incised on the ulnar side of the extensor tendon. If the tendon is not subluxated, it can be incised longitudinally and repaired at closure. The joint capsule is then incised and synovectomy is performed to remove any extensive synovitis.
 Figure 27.1 Lateral, oblique, and posteroanterior radiographs of a metacarpophalangeal joint pyrocabon arthroplasty of the middle finger. |
The metacarpal bone resection is performed just distal to the origin of the collateral ligaments. With silicone implants, the distal portion may simply be placed in the proximal phalanx canal without resection of the subchondral bone. For resurfacing implants, an alignment awl is used with fluoroscopic assistance to make both the metacarpal and phalanx osteotomies. An awl and sequentially increasing-sized broaches are used to open the intramedullary canals. Trial implants are used to assess the appropriate implant size. The joint is assessed for stability and ROM. Implant placement is confirmed with fluoroscopy; both the PA and lateral images are used to assess the implant position. The dorsal capsule and extensor tendon are repaired. The hand is placed into a bulky padded postoperative volar slab splint with the MCP joints flexed and PIP joints extended. If a joint is felt to be looser than intended, then the implant size should be reconsidered or postoperative rehabilitation should be more conservative. Radiographic images of the two MCP arthroplasties can be seen in Figures 27.1 and 27.2.
 Figure 27.2 Posteroanterior radiograph of 4 silicone metacarpophalangeal joint arthroplasties involving the index, middle, ring, and small finger metacarpophalangeal joints. |
Complications
Potential complications in small joint arthroplasty include dislocation, instability, neuroma formation, infection, and stiffness. Specifically, silicone arthroplasties can fracture over time and can result in a silicone synovitis that can necessitate revision arthroplasty or joint arthrodesis. Resurfacing implants can also fracture, but are more likely to fail secondary to loosening of the implant, thus requiring revision or arthrodesis.
Postoperative Rehabilitation
Introduction
The goal of surgery and therapy is to reduce pain in the MCP joints and improve hand function. Patient goals also may include improving the appearance of their hands. Patient education should include potential difficulty with ADLs immediately postoperatively and an overall description of the rehabilitation program, including interventions provided, orthoses that will be worn by the patient, and approximate frequency and duration of therapy visits. Patients may need to consider arranging for transportation to therapy appointments, or planning for expected copayments of therapy visits.
Collaboration and communication between the therapist, surgeon, and patient are important to coordinate the postoperative care and rehabilitation. Details of the surgical procedure help to identify points of concern that will help to safely guide the recovery. Consideration of other related comorbidities and functional limitations—especially in patients with polyarticular involvement, such as with inflammatory arthritis—is also important.
Therapy is usually initiated 1 to 2 weeks postoperatively, depending on surgeon preference. As the initial goal is to allow the implant to become encapsulated, the main reason to start therapy sooner than the date of suture removal is to provide wound care. Initial postoperative evaluation includes assessment of wound healing (including swelling and edema), alignment of digits, ROM (including active flexion and passive extension of digits), and ADL status.
Interventions
Wound care: After the bulky dressing is removed, a light compressive dressing is applied. Dressings are changed in the therapy or physician clinics, and are maintained until the wound is sealed. Scar massage is initiated after suture removal, which usually occurs at 2 weeks, when the wounds are fully closed.
Edema management: Light compressive wraps such as a self-adherent wrap can be applied to the digits and hand. Active ROM of the shoulder, elbow, wrist, and digits will assist in minimizing edema of the upper extremity. The patient should continue to keep the hand elevated while sedentary for the first few weeks after surgery.
Orthoses: Two orthoses are fabricated; one for daytime use and one for sleeping.
Day orthosis for ROM (Figure 27.3)
A dorsal forearm-based dynamic digit extension orthosis is fabricated.
Dynamic MCP extension is achieved through an outrigger attachment with finger slings that encompass the proximal phalanges, and rubber band tension that passively extends the MCP joints.
Orthosis supports the wrist in neutral, MCP joints at 0° to slight flexion, and allows active MCP joint flexion to 70° with dynamic return to the resting position, while maintaining neutral coronal plane alignment of the digits.
It is imperative that the dynamic extension tension is adjusted to avoid any hyperextension of the MCP joints, with careful attention to the small finger, which is most vulnerable to hyperextension.
Imaging with plain radiographs or fluoroscopy can be used to confirm that the MCP joint is not resting in hyperextension within the orthosis.
Patients should be able to demonstrate and report ease of flexion against the rubber band tension as forceful flexion can create deforming forces through the joints. Forty percent more force is required to actively flex the fingers with the low-profile outrigger (see Figure 27.3). However, most patients prefer the appearance of the lower-profile outrigger. Force application needs to be carefully monitored.Related posts:
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