19.1 Introduction

Today’s bioindustrial proficiency in pyrocarbon technology has led to its use in the field of orthopedics, most particularly in hand and wrist surgery with the development of joint prostheses or hemiprostheses and new implants. ^{1 , 2 , 3}

19.2 Characteristic of Implants

19.2.1 Pi²

Whright Pi² implant is a free spacer because there is no bone or ligament fixation (Fig. 19.1). It can therefore be mobile, and its shape allows it to adapt its position to thumb movements. Implant stability is based to a large extent on the soft tissues, which prevent it from coming out of its trapezium fossa. The implant is oval with two axes. When the implant is positioned, its largest axis is perpendicular to the thumb column. The implant comes in two sizes (thickness by length): 9 × 13 mm and 9 × 15 mm. The 9-mm thickness was chosen to be slightly smaller than the trapezium height, which is on average 11 mm. The implant thus maintains a certain height in its trapezium compartment without being subjected to or subjecting the scaphoid or the metacarpal base to excessive stresses that could result in bone resorption.

19.2.2 Nugrip

Ascension NuGrip^TM CMC Implant is not a free spacer but a pyrocarbon hemiprosthesis. This is the second-generation PyroHemiSpher implant that has been specifically designed for the treatment of osteoarthritis in the thumb carpometacarpal joint (Fig. 19.2).

19.3 Results in the Literature

19.4 Indications/Contraindications

19.5 Pi² Implant: Author’s Own Experience and Preferred Technique

This procedure does not simply remove the trapezium and replace it with an implant. The technique requires several surgical stages whose sequence and execution must be scrupulously respected. ¹⁴ The intervention takes place under locoregional anesthesia with a pneumatic tourniquet at the root of the arm.

19.5.1 Anteroexternal Approach

We use a modified anterior Gedda-Moberg approach (Fig. 19.3), i.e., slightly medial and centered in a V on the trapezium tubercle. It provides easy access to the abductor pollicis longus (APL) tendon as well as to the flexor carpi radialis (FCR) tendon, which will be used to stabilize the implant. The fascia of the external thenar muscles is detached on its external edge, so that the muscles can be retracted internally, and the trapeziometacarpal joint can be approached as well as the trapezium tubercle. There often is an accessory tendon of the APL, highly variable in size, which is frequently inserted on the thenar muscle fascia or more rarely on the trapezium. This accessory tendon can be left in place or resected.

19.5.2 Nontraumatic Trapeziectomy

Before proceeding to the trapeziectomy, it is important to identify the FCR tendon immediately above the trapezium tubercle. This tendon should be preserved for the duration of the trapeziectomy. This should be done as gently as possible by disinsertion of the soft peritrapezial tissues at the bone level using a no. 15 blade or a fine periosteal elevator. We use a “corkscrew” screwed into the trapezium and handled like a joystick to expose each facet of the trapezium as much as possible and release them from the surrounding soft tissue (Fig. 19.4). This allows the trapezium to be extracted in the majority of cases in a single piece. The corkscrew is never used as an extractor, which would tear and weaken soft tissue environment. The internal osteophyte of the trapezium, often fractured during trapeziectomy, is removed with the same care as the trapezium.

Related posts:

18 Silicone Implants and Total Joint Prostheses for Osteoarthritis of the Trapeziometacarpal Joint: A Systematic Review 20 Pyrocardan and Pyrodisk Arthroplasties of the Thumb CMC Joint 21 Total Thumb CMC Arthroplasty 22 STT and Peritrapezium Joints Arthroplasties 23 Thumb IP Joint Arthroplasty: An Alternative to Arthrodesis Section 2 Arthroplasty of Finger Joints

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