22 STT and Peritrapezium Joints Arthroplasties

Philippe Bellemère


STT joint arthroplasty has been proposed alternatively to the simple resection arthroplasty for the treatment of STT osteoarthritis. Pyrocarbon free interposition of the STT joint has replaced silicon interposition which is not used anymore. Aim of pyrocarbon STT arthroplasty is to relieve pain and preserve wrist motion and function by maintaining height and kinematic of the scaphoid.

Severe midcarpal instability associated with STT joint destruction is a contraindication of pyrocarbon interposition. Pyrocarbon interposition of the STT joint may use two types of implants: a concave-convex-shaped disk (STPI); and a thinner one (Pyrocardan), rectangular and biconcave-shaped. Open or arthroscopic implantation of these implants are possible. STPI interposition requires distal scaphoid resection while Pyrocardan interposition spares the scaphoid but remodels the articular trapeziotrapezoid surface.

Pyrocarbon implants for STT arthroplasty give reliable outcomes. Pain relief is effective, wrist and thumb motion and strength are preserved, and intracarpal stability of the wrist does not deteriorate. Complications are rare. The most frequent is implant instability more likely encountered with STPI interposition especially after inappropriate scaphoid preparation on its medial side. Thin implant like Pyrocardan seems particularly adapted to the anatomy and the kinematic of the narrow STT joint.

In select cases of pantrapezium osteoarthritis, double arthroplasty of STT and TM joints with Pyrocardan implant may be an efficient trapezium-preserving procedure.

22 STT and Peritrapezium Joints Arthroplasties

22.1 Introduction

Scaphotrapeziotrapezoid (STT) osteoarthritis (OA) is the second most frequent arthritic location in the wrist and is mainly isolated and idiopathic (Fig. 22.1). 1 Painful STT OA must be initially treated conservatively with medical treatment. When it fails, surgical treatment is recommended. Several surgical techniques may be proposed: triscaphoid arthrodesis, bone resection (trapeziectomy with partial trapezoidal excision or distal pole of the scaphoid) with or without suspension ligamentoplasty and tendon interposition, arthroscopic debridement or partial joint resection with or without interposition, and arthroplasty using a pyrocarbon implant interposition. Silicone implant interposition arthroplasty is not used anymore in STT joint.

Fig. 22.1 Isolated idiopathic osteoarthritis of the scaphotrapeziotrapezoid (STT) joint.

Radiographic occurrence of concomitant STT OA to painful trapeziometacarpal (TM) has been found in 60%. 2 Such peritrapezial OA may be symptomatic at the STT and TM levels and trapeziectomy with partial trapezoidal excision with or without suspension ligamentoplasty and tendon interposition is the classical surgical option after failed medical treatment. Nevertheless, in some conditions, a double implant arthroplasty of the STT and TM joints may be proposed. 3

22.2 Pyrocarbon Implants for STT Arthroplasty

STT implant interposition arthroplasty aims to relieve pain and preserve wrist motion and function. The mechanical goals of the implant are to maintain scaphoid mobility and scaphoid length. Therefore the implant allows compressive forces to be dissipated from the implant to the scaphoid, hence limiting the likelihood of intracarpal instabilities, especially a dorsal intercalated segment instability (DISI) malalignment, exacerbated by excessive scaphoid flexion or height loss.

22.2.1 Indications

Failure or conservative treatment (splinting, anti-inflammatory drugs, intra-articular corticoid injections, and physiotherapy) of painful idiopathic STT OA is an indication of STT arthroplasty. Some authors limit their indication of STT pyrocarbon spacer after resection arthroplasty in case of wide scapholunate angle or in the presence of DISI deformity to give more stability and height to the scaphoid. 4 Chronic inflammatory process such as chondrocalcinosis and rheumatoid arthritis may induce preoperative distal resorption of the scaphoid and midcarpal instability with important dorsal subluxation of the capitate and DISI malrotation. Clinical signs of midcarpal instability may be present and such instable wrist is a contraindication of pyrocarbon interposition in the STT joint. STT arthrodesis may be a better option. 5

22.2.2 STPI

The first pyrocarbon implant for the STT joint, called STPI (Scaphoid Trapezium Pyrocarbon Implant) (Wright Medical-Tornier SAS, Bioprofile, Grenoble, France) was proposed in 2000 by Péquignot et al. 6 This discoid implant has two joint surfaces, one convex for the trapeziotrapezoidal surface, and the other concave for the distal scaphoid articular surface (Fig. 22.2). This implant is available in three sizes varying in diameter and thickness (from 3 to 4 mm). It is a mobile spacer requiring for its implantation the resection of the distal scaphoid (Fig. 22.3).

Fig. 22.2 STPI (scaphotrapezial pyrocarbon implant).
Fig. 22.3 Radiographic view of the scaphoid trapezium pyrocarbon implant (STPI) in the scaphotrapeziotrapezoid (STT) joint.

Surgical Technique

Dorsal implantation is recommended by Péquignot. The capsular approach is between the tendons of the extensor pollicis longus on the radial side and the extensor carpi radialis brevis on the ulnar side. Capsular incision is made longitudinally and the distal portion of the scaphoid is exposed.

Palmar implantation is another option made with a longitudinal skin incision on the volar aspect between the flexor carpi radialis (FCR) tendon and the radial artery. 7 After reaching the plane of radiocarpal joint, a longitudinal incision is made on the STT joint distal to the radioscaphocapitate ligament.

Whatever the side of the approach chosen, about one-quarter of the scaphoid length (3 to 4 mm) is removed distally after a bone cut is made with an oscillating saw perpendicularly to the axis of the scaphoid.

The appropriate implant size is chosen using trial implants under fluoroscopic control to confirm that enough bone has been removed on the medial side and to check the absence of impingement of the implant especially on its radial side. The implant should be mobile and self-stabilizing.

After closure of the capsule, no ligamentoplasty is required.

Postoperative permanent splinting of the wrist does not exceed 2 to 3 weeks. After this time period passive and active motion exercises of the wrist and the thumb are allowed, and a removable splint is worn for protection for 3 weeks.

Arthroscopic implantation of the STPI spacer has been proposed after arthroscopic debridement and partial resection of the STT joint especially in case of instability of the scaphoid seen with DISI deformity. 8 , 9 The arthroscopic portals are located dorsally. One STT portal (ulnar to the tendons of the first compartment) is used as the working portal with a 2.5-mm shaver and burr and occasionally a 3.5-burr, and the second arthroscopic portal (radial to the tendons of the third compartment) is used as the viewing portal using a 1.9-mm arthroscope. A volar portal can be used as if there is difficulty visualizing the dorsoulnar portion of the STT joint. 10 Joint debridement, synovectomy, and resection of 3 to 4 mm of the distal scaphoid are performed. A small transverse incision can join the two dorsal arthroscopic portals for inserting the implant (Fig. 22.4). Postoperative protocol is same as the open procedure.

Fig. 22.4 Arthroscopic view of a pyrocarbon implant in the scaphotrapeziotrapezoid (STT) joint. The scaphoid is at the bottom, trapezoid at the top, and capitate on the right. (This image is provided courtesy of Christophe Mathoulin, Institut de la Main, clinique Bizet, Paris, France.)

Results of the Literature

Several STPI interposition studies have been published 6 , 7 , 8 , 9 , 11 with small cohort and an average follow-up of 1.5 to over 6 years. Satisfactory short- and medium-term clinical results were achieved in all the studies; these studies found much improvement in pain and function.

Mobility was not significantly changed, and the grip strength was preserved or even improved. Implant instability was reported in two arthroscopy studies 8 , 9 and one open surgery study 7 at a rate of 20, 15.4, and 4%, respectively. These were attributed to technical errors related to insufficient medial scaphoid resection.

Pre-existing intracarpal misalignment was controlled or corrected in all series. No failure requiring conversion of this arthroplasty to another surgical solution has been reported in the literature.

Author’s Experience

Good clinical results were also achieved in our experience of 24 STPI interposition. However, two cases of implant luxation required reoperation for repositioning. We do not use the STPI implant anymore because we find this implant to be thick and potentially instable. We prefer to use a thinner and more stable pyrocarbon implant such as the Pyrocardan. 12

22.2.3 Pyrocardan Implant in STT Joint

Since March 2010, we have used the Pyrocardan implant (Wright Medical-Tornier SAS, Bioprofile, Grenoble, France) in the STT joint because its two concave surfaces make it stable under axial loads, its rectangular shape is closer to that of the STT joint, its minimal thickness reduces bone resection, and its implantation saves the scaphoid surface and its distal ligament attachments, thereby preserving its height and kinematics (Fig. 22.5). The Pyrocardan implant is available in seven sizes, defined by the longest implant length, from 12 mm (XXS) to 18 mm (XXL). The implant is 1 mm thick at its center. The thickness of the exterior edges is proportional to the implant size (see Fig. 22.6).

Fig. 22.5 Pyrocardan implant.
Fig. 22.6 Radiographic views of the Pyrocardan implant in the scaphotrapeziotrapezoid (STT) joint. (a) Anteroposterior (A-P) view. (b) Lateral view.

Surgical Technique (Fig. 22.7)
Fig. 22.7 Drawing of the principles of the procedure of Pyrocardan implant in scaphotrapeziotrapezoid (STT) joint.

The approach is an anterior curved incision of about 4 cm centered on the scaphotrapezoid space, delimited by the FCR tendon, and the volar tubercles of the scaphoid and trapezium (Fig. 22.8A). 13 The FCR sheath is opened to treat tenosynovitis or to remove the synovial cysts often associated with arthritis. Partial detachment of the proximal insertions of the thenar muscles from the trapezium tubercle is required to access the STT joint, which is then opened longitudinally between the distal flange of the FCR tendon and the scaphoid and trapezium tubercles. Axial traction is placed on the thumb to expose the STT joint space. The aim of joint preparation is to spare the articular surface of the scaphoid and the ligament insertions at the distal pole, while removing the double concavity of the trapeziotrapezoid surface. Resection is performed using a thin oscillating saw, starting with the extremities of the lateral edge of the trapezium, followed by the medial edge, which is relative to the trapezoid (Fig. 22.8b). The articular trapeziotrapezoid surface is then remodeled using a reamer to obtain a slight mediolateral and anteroposterior convexity (Fig. 22.8c). The trial implant is then positioned along its long axis mediolaterally with its concavity facing the new trapeziotrapezoid surface. The size of the implant is chosen to ensure optimal trapeziotrapezoid articular coverage over the scaphoid. A majority of implants used in our practice range from size 14 to size 15. Fluoroscopic control is required to check the bone preparation, especially of the most medial part of the joint and the position of the trial implant during flexion–extension and ulnar and radial deviation movements of the wrist. Kinematics of the distal pole of the scaphoid on the implant surface is also evaluated under visual examination. The final implant is inserted and the articular capsule is closed with resorbable suture. No ligamentoplasty is required even in case the capsule is not closable.

Arthroscopic implantation of Pyrocardan implant in STT joint is also possible but has not yet been reported in the literature.

Fig. 22.8 Surgical technique. (a) Palmar incision allowing the access of the flexor carpi radialis (FCR) tendon and the scaphotrapeziotrapezoid (STT) joint. (b) Bones resection (dotted line) of the trapezium and trapezoid on a cadaveric specimen. Tpd, trapezoid; Tpz, trapezium. (c) Pyrocardan implant in the STT joint.

Postoperative permanent splinting of the wrist does not exceed 2 to 3 weeks. After this time period passive and active motion exercises of the wrist and the thumb are allowed, and a removable splint is worn for protection for 3 weeks.

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May 4, 2022 | Posted by in ORTHOPEDIC | Comments Off on 22 STT and Peritrapezium Joints Arthroplasties
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