20.2.1 Characteristics of the Implant

Pyrodisk implant (Integra Life Sciences, Plainsboro, NJ, USA) (Fig. 20.1) is a nonanatomical interposition shaped as a biconvex disk with a central hole to allow stabilization with an autograft tendon, transferred and passed through the trapezium, the implant, and the thumb metacarpal. Six available sizes exist with various combinations of diameters (14 mm, 16 mm, 18 mm) and heights (5.5 mm, 7 mm, 8 mm, 9 mm).

20.2.2 Indications

Pyrodisk implant may be indicated for the treatment of any stages of OA. In the early stages (Eaton’s stage1, 2, and 3), Pyrodisk implant is originally used after partial trapeziectomy. The implant is positioned between the metacarpal and the remaining trapezium (Fig. 20.2). More severe stages of OA may require total trapeziectomy with interposition of Pyrodisk articulated between the metacarpal and the scaphoid (Fig. 20.3).

20.2.3 Surgical Technique

The approach is dorsal over the trapezium. Two to 3 mm of bone is removed with an oscillating saw from the metacarpal base perpendicular from its long axis. The trapezial surface is flattened with the saw with a cut parallel to the metacarpal cut. A reamer is used to dig a small concavity on the trapezium and metacarpal surfaces. In each bone a 3.2-mm drill hole is created obliquely toward the center of the TMC joint in the middle of the cavities starting for the trapezium from the center of the scaphotrapezial joint and for the metacarpal from its dorsal radial aspect. The proper implant diameter is determined by selecting the size that provides the best fit to the diameter of the thumb metacarpal base without overhang. If the best size falls between two available sizes, then the smaller size is chosen. The goal is to achieve a gentle rocking motion of the biconvex disk on the concave surfaces of both the thumb metacarpal base and the trapezium.

Intraoperative fluoroscopy confirms proper sizing.

One of the bundles of the abductor pollicis longus tendon or half of the flexor carpi radialis (FCR) tendon ⁴ is used as a stabilizer tendon. The distal stump of the distally based tendon is passed through the trapezium, into the resected joint through the selected Pyrodisk implant and into the thumb metacarpal base to exit dorsally through the prepared passage. Gentle traction is applied to the tendon prior to closure to enhance stability. The remaining tendon then is folded back and incorporated into a secure capsular closure.

After surgery, the wrist and thumb are immobilized in a thumb spica plaster orthosis for 3 weeks. A removable orthosis is used during the next 8 to 9 weeks during which the patient performs active range of motion exercises and uses the hand for daily activities. After 11 to 12 weeks, unrestricted activities are allowed.

20.2.4 Results in the Literature

A retrospective series by Barrera-Ochoa et al ² included 19 patients reviewed at a minimum 5-year follow-up. Eighty-nine percent of patients were satisfied or very satisfied, pain measured 1.7 (visual analog scale [VAS]), Quick-DASH scored 20.2, mobility was not significantly improved, and grip strength (20 kg) increased significantly. The failure rate was 10.5%, associated with painful instabilities, revised by trapeziectomy after 1 year. Long-term outcomes of reported similar results with a survival rate of 94% at 8 years. ⁵

The series by Mariconda et al ⁷ included 27 patients reviewed at an average follow-up of 37 months. It showed better results on pain and Quick-DASH score. Ninety-six percent of patients were satisfied or very satisfied. There were no complications or revisions. Radiologically, one implant was dislocated and no bone subsidence was noted.

In indications of perfectly centered rhizarthrosis, Odella et al ⁷ generally obtained good pain results with Pyrodisk. However their results on strength (a 20% loss) were in contradiction with those of Barrera-Ochoa et al (a 26% gain). ² They also reported a failure rate of 3% and 3% implant dislocation.

A recent retrospective comparative series ² of ligament reconstruction and tendon interposition (LRTI) (19 cases) versus Pyrodisk (20 cases) showed a significant better key pinch strength (1.8 kg higher) with the Pyrodisk after a minimum follow-up of 2 years. No differences were found in other functional criteria or in complication rates.

20.2.5 Author’s Experience

The Pyrodisk implant can also be used after total trapeziectomy (Fig. 20.4), as proposed by Vitale et al ⁸ and Chaise. ⁹ Like the Pi2 implantation (see Chapter 19), a partial trapezoidectomy is required to medialize the implant and for the treatment of an associated scaphotrapezoid OA (Fig. 20.4). To stabilize the implant a strip of the FCR tendon, ⁸ or a ligamentoplasty with a thread of Goretex CV/0 ⁹ may be used. This latter implant stabilization technique is simpler and less invasive than that used for the Pi2 implant (see Chapter 19). However, in our experience of more than 80 implants, the failure rate (revised by implant) for chronic pain enduring beyond 1 year was 6% and we found that the overall clinical results, especially regarding pain, seemed inferior to those of the Pi2 implant. Since the Pyrodisk implant is more constrained than the Pi2, pain originating in the bone may be associated with excessive stress peaks. Failure to stabilize the implant and the base of the metacarpal with the follow-up may occur with the follow-up as shown in some cases of our series (Fig. 20.5). It may be due to frictional wear of the ligamentoplasty in the articulating surfaces and can be facilitated by the biconvex shape of the implant.

20.3.1 Characteristics of the Implant

Pyrocardan implant (Wright Medical-Tornier SAS, Bioprofile, Grenoble, France) (Fig. 20.6) is an intra-articular interfacing unconstrained interposition of the TMC joint. ³ It is rectangular-shaped with two perpendicularly opposing tubular concave faces. This geometry is supposed to replicate the carpometacarpal (CMC) joint movements. The implant has a 1-mm central thickness regardless of size. There are 7 variants, between 12 and 18 mm wide. The thickness of the exterior edges is proportional to the implant size. Its placement requires minimal intra-articular bone resection that respects the capsuloligamentary muscle insertions outside the joint space area. ¹⁰ Stabilization ligamentoplasty is, therefore, not necessary.