49 Revision of Subsided Pyrocarbon Implants
49.1 Patient History Leading to the Specific Problem
A 55-year-old woman presents with a painful right middle finger metacarpophalangeal (MCP) joint. She has a history of osteoarthritis and underwent arthroplasty of this joint 6 years ago; one revision procedure was required 5 years ago for subsidence. Cement was used to secure the implant at the time of revision. Although she initially enjoyed pain-free motion, she has noticed increasing pain, limitation in motion, and shortening of the digit over time (▶Fig. 49.1).
Fig. 49.1 (a–c) Radiographs demonstrating pyrocarbon metacarpophalangeal joint arthroplasty with subsidence. (d) The patient’s right middle finger is shortened and deviated ulnarly.
49.2 Anatomic Description of the Patient’s Current Status
▶Fig. 49.1 shows the characteristic silhouette of a pyrolytic carbon (pyrocarbon) implant arthroplasty at the middle finger MCP joint. Although most authors have reported a large proportion of good and excellent results with this implant in this location, occasional problems do occur.
Currently, both components of the implant have subsided dramatically, such that there is now an encasement of bone around the implant, and impingement of the metacarpal bone against the proximal phalanx bone with hand use. Furthermore, there is subluxation of the joint such that the two components of this surface replacement arthroplasty are no longer properly articulating with each other. This has led to a reduction in possible range of motion and overall shortening of the digit, in addition to an increase in pain from the bony impingement.
While this degree of subsidence is relatively uncommon, a similar situation can arise if an undersized implant is utilized, leading to bony impingement with ulnar and/or radial deviation (▶Fig. 49.2).
Fig. 49.2 Radiograph showing an undersized pyrocarbon implant, with bony impingement on the ulnar side of the metacarpophalangeal joint.
49.3 Recommended Solution to the Problem
• Bony resection should be minimized, although some bone resection may be required to extract the existing implant.
• Implants cemented in place may present unique removal challenges. Extraction can be sometimes be facilitated by creation of a dorsal longitudinal osteotomy and use of a bone tamp to dislodge the implant. Residual cement can be removed with an appropriate high-speed burr if needed.
• Given the failure of two previous attempts at surface replacement arthroplasty, conversion to a hinged silicone arthroplasty is appropriate.
• Using a larger silicone implant can help partially correct the bone deficit and restore some length to the digit.
49.4 Technique
The surgery is performed in the operating room with the patient in the supine position. Although multiple types of anesthesia would suffice, we prefer light sedation plus a regional block (supraclavicular technique), due to the extended period of comfort provided for many hours after surgery. Bier block or WALANT (wide-awake local anesthesia and no tourniquet) are two other good options; general anesthesia is probably not indicated for most patients. The hand is prepped and draped in sterile fashion. Use of a tourniquet makes visualization easier, although the need for a tourniquet could be reduced with use of a local anesthetic containing epinephrine.
A dorsal longitudinal incision provides excellent visualization of the involved structures; in this case, the previous scar was utilized (▶Fig. 49.3a). The extensor tendon is split longitudinally, and the joint capsule is opened. In this case, the capsule was very thin dorsally, and the metacarpal component of the implant was readily identified, surrounded by chronic synovitis (▶Fig. 49.3b). The implants were easily removed, as the cement was not adherent to the surrounding bone (▶Fig. 49.3c).
Minimal bone resection was performed to remove cortical prominences around the medullary openings, which were then carefully broached up to the maximum size silicone implant that could be inserted without compromising the already atrophic bone (▶Fig. 49.4a). Only minimal broaching was required due to the bony resorption and remodeling resulting from the previous implant. Residual collateral ligaments on the radial and ulnar sides of the joint were carefully preserved. After installing the silicone implant, intraoperative fluoroscopy revealed a well-seated implant without any residual bony impingement (▶Fig. 49.4b).
Capsular closure was performed, followed by repair of the split extensor tendon with nonresorbable sutures. Routine skin closure was performed. The patient was immobilized in a volar resting splint with the fingers in position of function. Occupational therapy was initiated on postoperative day 5, beginning with active flexion and active-assisted extension using a dynamic orthosis.
