INTRODUCTION
∗ I dedicate this chapter to all EWAS members (European Wrist Arthroscopy Society) who, for 3 years, without a let-up in their efforts, allowed the creation of one of the most dynamic and nicest scientific societies.
Pyrolytic carbon (pyrocarbon) was developed in the 1960s from a collaboration between the CEA (French Commission for Atomic Energy) and General Atomics (US) for nuclear applications as a coating for nuclear fuel. In the 1970s, the hemocompatibility of pyrocarbon was established, and it was used initially for the fabrication of heart valves. This material has the nearest Young’s modulus to bone and does not cause adverse reaction in surrounding tissues. Pyrocarbon was used in the manufacture of carpal implants in the 1990s.STRUCTURE
Pyrolytic carbon belongs to the family of turbostratic carbons, which have a similar structure to graphite. Graphite consists of carbon atoms that are covalently bonded in hexagonal arrays. These arrays are stacked and held together by weak interlayer binding. Pyrolytic carbon and other turbostratic carbons differ from graphite in that the layers of the former are disordered, resulting in wrinkles or distortions within layers. This gives pyrolytic carbon an improved durability compared with graphite.
THE SCAPHOID TRAPEZIUM INTERPOSITION IMPLANT FOR ISOLATED OSTEOARTHRITIS OF THE SCAPHOTRAPEZIOTRAPEZOID JOINT
Osteoarthritis of the scaphotrapeziotrapezoid (STT) joint is less well known than other types of arthritis of the wrist. It represents only 13% of osteoarthritic lesions of the wrist. The involvement of this isolated articulation is rare, but very difficult to treat. The only treatment that was previously proposed was arthrodesis of the STT joint, which is technically difficult and is associated with numerous complications. Pseudarthrosis is not uncommon, and arthrodesis of the STT joint has been shown to lead to radioscaphoid osteoarthritis. Techniques associated with resection of the distal pole of the scaphoid and interposition of biologic tissue such as tendons (flexor carpi radialis) were described in the 1990s. A modification of the previous technique by distal scaphoid resection and capsular interposition arthroplasty was described by Garcia-Elias and colleagues. This led to the development of arthroscopic techniques to prevent extensive scarring and to prevent instability due to ligament injuries.
The anatomy of the STT joint is simple. The convexity of the distal pole of the scaphoid articulates with the concavity of the proximal part of the trapezium and the trapezoid. The STT joint is stabilized by the scaphotrapezial ligament, which is more consistent on the palmar side. Two important structures are involved in the stabilization of the STT joint, namely the dorsal STT ligament and the palmar scaphocapitate ligament. This articulation has a very close relation to the radial artery that passes in front of the joint and also to the dorsal branch of the radial artery that crosses on the dorsal aspect. The terminal branches of the superficial radial nerve are also in close proximity to the joint.
Composition of the Implant
The scaphoid trapezium interposition implant (STPI; BIOProfile, Grenoble, France) is made of graphite coated with pyrocarbon. This prosthesis has a button-like shape, with one convex and one concave surface. The former faces the remaining part of the scaphoid, whereas the latter faces the trapezium and the trapezoid. Two sizes are available. Sizing is done using two templates.
Indications and Contraindications
The ideal candidate for STPI is a middle-aged patient with isolated arthritis of the STT joint. Sufficient resection of the distal pole of the scaphoid (3 mm) and isolated involvement of the STT joint are the keys to a successful outcome.
Contraindications to the placement of an STPI are wrist instability due to ligament injury and basal joint arthritis.
Preoperative Physical Examination and Imaging
The surgeon should document the location of pain, range of motion, strength (key pinch and grip), and functional status. The contralateral unaffected side is also examined for comparison. Simple radiographs (frontal, lateral, and oblique views) are most often sufficient. Comparative x-rays of the opposite side are also made.
Surgical Technique
Patients are operated on in the supine position under local-regional anesthesia and tourniquet control on an outpatient basis. Traction is applied in the axis of the thumb by a Chinese finger trap. Traction of 2 to 3 pounds is sufficient. The joint is first injected with normal saline via a radial midcarpal portal. The radial midcarpal portal is used because it provides good visualization of the STT joint ( Fig. 23-1 ). The STT joint is then identified via the 1-2 portal using a hypodermic needle. Particular attention is paid to the position of the radial artery and the branches of the radial nerve. A small transverse skin incision followed by blunt soft tissue dissection with a fine artery forceps prevents injury to the important structures. A Spanish team has described a palmar portal, but we have no experience with this technique. It is possible to perform a direct dorsal approach, taking into account the axis of the trapezium and the rounded shape of the joint. A 2.5-mm arthroscopic burr is inserted via the first 1-2 radiocarpal portal. The distal scaphoid is resected under direct vision starting from the dorsoradial aspect palmarly to the scaphoid tubercle ( Fig. 23-2 ). A resection of at least 2 to 3 mm of the distal pole of the scaphoid is necessary. Great care must be taken to preserve the scaphotrapezial and scaphocapitate ligaments to avoid a dorsal intercalated segmental instability (DISI) deformity.
If the STPI is not implanted, the portals are left open or closed by using Steri-Strips. If an STPI is implanted, the STT portal is slightly enlarged to pass the implant through. There are two sizes (small and large) ( Fig. 23-3 ). The template implants are inserted under arthroscopic control. Once the definitive implant is in place, the capsule is sutured with a resorbable suture, and the skin is closed with interrupted sutures. The hand is immobilized with a splint in all cases for a period of 3 weeks. In most cases, there is no need for a postoperative rehabilitation program.
Results
From 2002 to 2005, we operated on 26 patients with isolated osteoarthritis of the STT joint. All patients had received medical treatment before the operation, including a thumb spica splint, nonsteroidal anti-inflammatory medication, and corticosteroid injections, with no improvement. The average duration of conservative treatment was 8 months (range 3 to 18). X-rays revealed an obliteration of the STT joint space in all cases. Reactive cystic changes were seen in the distal pole of the scaphoid in some cases. Anteroposterior and lateral x-rays of the wrist were performed to measure the scapholunate angle and to rule out a static carpal instability pattern, which is an absolute contraindication to performing the procedure.
The first carpometacarpal joint was assessed to verify that it was free of any osteoarthritic changes, which would also constitute a contraindication. Grip-and-pinch strength testing was performed in all patients before and after surgery using a JAMAR Hydraulic Hand Dynamometer and a JAMAR Hydraulic Pinch Gauge (Asimow Engineering CO., Los Angeles, CA). Pain was assessed using a visual analogue scale (VAS) (100-mm line with verbal anchors of 0 as “no pain” and 100 as the “worst possible pain”). The level of patient satisfaction after the procedure was also analyzed using the Green-O’Brien score. Whenever possible, the analysis was compared with the contralateral side.
Surgical Outcome
Isolated Resection of the Distal Pole of the Scaphoid
We performed surgery on 13 women whose average age was 58 years (range 52 to 64). An analysis using the Green-O’Brien score showed an improvement from an average of 50 points preoperatively to 90 points postoperatively. We had only one complication, consisting of a transient dysesthesia on the dorsal side of the thumb due to irritation of a sensory radial nerve branch. The dysesthesia resolved spontaneously. In the short term, we have observed a progressive reduction in the scaphotrapezial space, but it did not lead to a recurrence of pain. A long-term follow-up is necessary to see if the patients remain pain free ( Fig. 23-4 A–D).
Implantation with the Scaphoid Trapezium Interposition Implant
We operated on 13 patients with STPI. There were 12 women and 1 man. The average age was 62 years (range 48 to 79 years). All patients had disabling pain for several months before surgery with a significant decline in pinch grip strength, and they did not respond to conservative therapy. All patients had a fairly significant restriction in range of motion before surgery. The average follow-up was 20 months (range 11 to 27). The postoperative range of motion improved in all cases. The pain disappeared completely in 12 cases and was reduced in one patient. Two of the 13 implants dislocated, which was attributed to inadequate resection of the distal pole of the scaphoid. These patients were reoperated using the same technique with revision of the resection, and reimplantation of the STPI. The patients had no further problems and were satisfied with the outcome. The patients had no complications related to infection and no recurrence of painful phenomena. Both grip and pinch strength increased in all cases ( Fig. 23-5 A–C).
Discussion
Our results of resection alone are comparable to those found in the literature. Nevertheless, it appears that, over time, there is a reduction in pinch strength. The results of our series with the STPI are similar to those reported by Pegoli and colleagues. The implantation of an interposition prosthesis (STPI) seems to prevent this kind of problem. It requires, however, a meticulous surgical technique, particularly with respect to the resection of the distal pole of the scaphoid. Conceptually, a resection of the proximal portion of the trapezium and the trapezoid seems more logical. From a technical point of view, however, the proximal portions of the trapezium and the trapezoid are much more compact and more difficult to resect with a small 2.5-mm burr. In our two series, the scapholunate angle was unchanged even at a long-term follow-up of 4 years. This procedure cannot be performed in patients with pantrapezial arthritis, who generally require a trapeziectomy associated with a ligament reconstruction and/or interposition arthroplasty.
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Management of Soft Tissue Contractures Around the Distal Radioulnar Joint
Lunotriquetral Ligament Instability/Tear: Acute and Chronic
Arthroscopic Trapeziometacarpal Arthroplasty
Bone Tumors of the Hand and Wrist
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