The wrist is a frequent source of pain, the clinical and radiographic investigation of which remains difficult (See Maîtrise Orthopédique n°49). Accordingly, arthroscopic diagnosis is still indicated in some cases. However, as in other joints, wrist arthroscopy is, above all, a therapeutic act. Although its use is not yet widespread in France, probably because of the material cost, wrist arthroscopy is an ever-growing part of the therapeutic arsenal of hand surgeons. In certain indications, the results of arthroscopic treatment are now superior to those of open techniques. At present, the number of patients in published series and follow-up are sufficiently extensive for arthroscopy of the wrist to warrant more widespread attention. Even if you have few indications in your practice, this short article is designed to illustrate what one sees in an arthroscope and how it can be used. This is only an introduction, which is in no way intended to replace regularly organized theoretical and practical courses, notably those of the Société Française d'Arthroscopie. For didactic reasons, all the inner views of the joints are those of a right wrist.
Regional anesthesia is sufficient. The patient is placed in the supine position on a table with an arm support and an inflatable cuff. The wrist must be placed in traction, using either a system such as that used for shoulder traction or fingertraps (The arm should be blocked proximal to the elbow under the inflatable cuff.)
Another possibility is to use a swiveling arm support, entirely sterilizable and placed on the table facilitating ulnar and radial deviation. Traction should not exceed 3 to 5 kg, depending on the patients.
In any event, the wrist must be free, especially if one uses an image intensifier.
The material used must be adapted. An endoscope 2.7 mm in diameter is ideal. A 3-mm endoscope can also be used, but this may hinder insertion into the mediocarpal joint in certain patients. The 1.9-mm endoscopes are fragile and their field of view is more limited. They are especially useful in the scaphoid-trapezium-trapezoid joint and indispensable if one intends to perform arthroscopy of the trapezium-metacarpal joint.
A small hook, a shaver with a 3-mm resector, and a 3-mm burr are indispensable. The shaver can, in some cases, be replaced by electrocautery of appropriate size. Needles for suturing or more sophisticated devices are also useful for intraarticular sutures. If one uses a drill, it should be waterproof.
Irrigation is best performed using a pump with sensors (but there is a risk of fluid diffusion, notably in fractures). Otherwise, one can use drip infusion, in some cases even a simple system of irrigation by an assistant with a syringe.
The surgeon sits at the posterior side of the wrist (practically all portals are posterior), the video system being placed in front of the surgeon, on the other side of the patient in most cases.
For the radiocarpal joint, the portals bear the names of the compartments of the underlying extensors. These consist of the 1-2 portal (between the abductor pollicis longus and extensor carpi radialis), the 3-4 portal (between the extensor pollicis longus and extensor digitorum communis), the 4-5 portal (between the extensor digitorum communis and extensor digiti minimi), the 6R portal (radial at the extensor carpi ulnaris) and the 6U portal (ulnar at the extensor carpi ulnaris).
There are several portals. One should always use at least two per joint, and they are interchangeable. The portals should be drawn on the skin before fluid distension using bony landmarks of the hand: Lister's tubercle, distal radioulnar joint, capitate neck, the second and third carpometacarpal joint, as well as tendinous landmarks: extensor carpi ulnaris, extensor pollicis longus, and the common extensor.
The anterior 3-4 portal is the most useful and easiest to draw on the skin. It is situated approximately 1 cm under the Lister's tubercle, which is always palpable (except in radial fractures). This portal is situated immediately distal to the angle in the extensor pollicis longus. The anterior 3-4 portal is not dangerous, tendons (8 mm) and nerves (16 mm) being situated at a distance. The instrument should be inserted straight ahead, with a proximal tilt of roughly 10° to take into account the slight sagittal angle of the radius.
For a triangular approach, an ulnar portal is needed, either 4-5 or 6R. The choice depends on the surgeon and on the lesion being treated. The 4-5 portal is situated approximately 1 cm distal to the radioulnar joint line (it is necessary to take into account the ulnar length on preoperative films). The tendons (7 mm) are at a distance and the risks are low. The 6R portal is immediately radial to the extensor carpi ulnaris. Tendons (4 mm) and nerves (7 mm) are closer, but the risks are minimal. Insertion is aimed slightly laterally, toward the center of the wrist.
For the mediocarpal joint, three portals are useful, but only two are commonly used: the radial midcarpal (RMC) and ulnar midcarpal (UMC) portals. The STT portal is used only for the procedures involving this joint.
The STT portal leads directly to the STT joint. This portal is found directly by palpating the joint line, but it is dangerous, because of the proximity of the radial artery. This risk is reduced by insertion medial to the extensor pollicis longus tendon.
Normal Radiocarpal arthroscopy
Before penetrating the radiocarpal joint, it must be distended. Fluid is injected into the 3-4 joint in most cases, given the straightforwardness there. One should see the return of fluid to be certain of the intraarticular placement. Very often the capsule swells and the wrist moves slightly.
The first elements seen upon penetration through the 3-4 portal are the capillaries of the anterior capsule. By pulling the arthroscope slightly back, a vascularized "ball" sparsely covered with filaments comes into view. It is a fatty structure, which accompanies the Testut and Kuentz radial scapholunate ligament. In the 3-4 portal, this is the primary landmark, which permits orientation in the radiocarpal joint.
By turning the arthroscope toward the lateral side of the wrist, a curtain of two oblique ligaments appears. The medialmost ligament is the radiolunate ligament, the lateralmost ligament is the radial scaphocapitate ligament, and between the two begins Poirier's space, where anterior synovial cysts develop. More laterally, one may begin to see the lateral edge of the scaphoid, which can be followed to its distal third.
Turning toward the medial side, one is blocked by the projection of the convex proximal aspect of the lunate. The anterior ulnocarpal ligaments are often poorly visible through this portal, as is the lunotriquetral joint line.
Far on the medial side coursing in a deep direction, one sees a cavity, which is often sparsely lined with filaments. This cavity is the prestyloid recess, where the greatest amount of synovial proliferation is situated in rheumatoid arthritis. This cavity constitutes the medial limit of the triangular fibrocartilage complex (TFCC), a set of anatomic structures including the triangular ligament.
Turning the arthroscope 180°, one brings into view the proximal portion of the joint with, laterally to medially, first the radial styloid, 4 mm to 5 mm of which is intraarticular.
Then the scaphoid fossa of the radius, separated from the lunate fossa by a marked crest.
More medially, the junction between the articular surfaces of the radius and the TFCC is difficult to see, but palpation permits clear distinction of the limits. Radial surfaces are hard, while the ligament can be depressed, but preserves a physiological tension, which has been referred to as the “trampoline” effect. There is often a certain degree of synovitis, which partially hides the ulnar insertion of the TFCC, and which one has to resect for a clear view.
This portal permits complete exploration of the radiocarpal joint, the medial portal providing a pathway for instruments. However, it is important to change arthroscopes and instruments to get a complete view from two different angles.
Medial portals show the same structures from a different angle. Insertion is still oriented toward the center of the wrist. Consequently, the same landmarks are used: laterally, the convex aspect of the lunate above, the scapholunate “buttocks” with the scapholunate ligament between the two, and further back, the radius and the radial styloid.
From the medial portals are best seen the posterior capsule and the scapholunate ligament, the latter on the posterior aspect, which has greater physiological significance.
Medially, there is a better view of the TFCC, the synovial recess and, in some cases, the pisotriquetral joint. The lunotriquetral joint line, very oblique, is always difficult to see, but one can probe the lunotriquetral ligament with a hook palpator.
The arthroscope is directed upward. Moving it medially, one brings into view the capitate-hamate junction, then the superior aspect of the hamate.
Especially in subjects with pronounced laxity, it is possible to see the triquetrocapitate ligament, the internal branch of 5th ligament. Laterally, the head of the capitate can be bypassed to penetrate into the scaphocapitate joint space.
If one turns the arthroscope 180°, one has a better view of the inferior aspect of the proximal row of carpal bones. Laterally, the scaphoid is separated from the lunate by a space of approximately 1 mm into which it is not usually possible to introduce the hook palpator. Both articular surfaces are at the same level.
In 45% to 63% of cases, the inferior articular surface of the lunate displays two facets.
In this configuration, the lunotriquetral joint line articulating with its counterpart capitate hamate has a crenellated aspect, and the hook of the hamate bears two articular facets (type 2 configuration).
This complex resembles the pelvis and thighs of a woman seen from the front, while the first row is similar to her intimate region, i.e., another way of distinguishing between the two joint lines.
More medially, the lunotriquetral joint space is also flush, and it is not possible to slip a hook into it.
Arthroscopic diagnosis remains useful in the work-up of ligamentous lesions (determination of severity and search for associated degenerative osteoarthritis) and in certain chronic painful wrists (to look for chondral lesions difficult to see on imaging studies). However, arthroscopy is above all a technique of therapeutic interest, providing numerous possibilities, some of which remain anecdotal.
Arthroscopy has several advantages: primarily diagnostic. Most of the ligamentous tears seen in arthrography are bilateral; rupture is not synonymous with instability.
The degree of instability may be better evaluated through mediocarpal portals. These signs of instability include joint dislocation and abnormal mobility between bones during passive wrist movements.
Normally, it is impossible to slip a hook or other instruments between the bones.
The existence of a spontaneous abnormally wide joint space and the possibility of introducing a hook are also signs of instability.
In certain cases, the radiocarpal joint is visible through the mediocarpal portal, reflecting severe lesions.
On the contrary, the joint space may contain post-traumatic fibrous scarring, which is necessary to excise to expose the lesions. Whipple suggested arthroscopic treatment of scapholunate injuries by creating fibrous nonunion. This involves freshening of the scapholunate joint with a shaver through a mediocarpal portal, then inserting 4 to 6 fine scapholunate pins attempting to obtain an osteofibrous syndesmosis.
Ligamentous lesions of the TFCC are frequent and one of the best therapeutic indications. These lesions are either traumatic (Palmer type 1) or degenerative (Palmer type 2) and, in this case, involve a long ulna.
The surgeon should pronate the forearm to be certain to have harmoniously resected 1 to 2 mm of the distal portion of the ulna. This is sufficient to relieve internal hyperpressure.
Treatment assisted by arthroscopy of radial fractures
As in the knee, arthroscopic verification of radial surfaces has been proposed in the management of fractures of the radius, involvement of the articular surface being suggestive of poor prognosis. Arthroscopy permits assessment of associated ligamentous lesions, and contributes to the quality of articular reduction. In a series of 105 fractures, Doi showed that the quality of outcome was better in the group managed with arthroscopic verification.
From a practical standpoint, the surgeon should wrap the forearm with elastic banding to avoid fluid diffusion, a theoretical source of compartment syndrome, even though this complication has yet to be reported with this technique.
After washing, which should be abundant, the articular surfaces are “tacked” with pins of 0.12 mm used for manipulating the fragments.
One begins by restoring the length of the lateral column, onto which the fragments are returned. Once the reduction is obtained, the pins are pushed under fluoroscopic guidance. This procedure is long and demanding. The indications are still limited, but in young subjects, the initial published results are promising.
These lesions are frequent in the wrist, and difficult to delineate with conventional imaging studies. In a series of 54 cases of chondral lesions, Koman reported 34 that had failed to be detected preoperatively. In most cases these lesions were situated on the hook of the hamate, perhaps favored by an anatomic predisposition (lunate of type 2), on the posterior aspect of the triquetrum, or on the radial styloid.
The treatment of synovial cysts
A capsulectomy centered on the insertion of the capsule across from the scapholunate joint can be used to empty the cyst arthroscopically. We often inject the cyst with methylene blue preoperatively to facilitate localization of the cyst and its neck during the intervention. There is a risk involving the extensor tendons, which one always sees at the end of the procedure.
When proximal, cysts near the radial artery arise from the radiocarpal joint between the radiolunate ligament and the radial scaphocapitate ligament. They are also accessible to rather simple arthroscopic treatment, because a shaver inserted through the 3-4 portal arrives directly on the capsule. The radial artery, in danger in conventional surgery, is in this technique at a distance, because the artery is separated from the capsule by the thickness of the cyst.
Resection of the distal end has been proposed and can, in some cases, be achieved arthroscopically if the joint space is not too tight.
In our opinion, wrist arthroscopy warrants more widespread use. Although its development is less rapid than that of shoulder or elbow arthroscopy, wrist arthroscopy is a promising technique. With quite limited morbidity, it permits a substantial number of technical procedures in a large range of domains, from traumatology to the treatment of cysts. The indications still need to be clarified, but orthopedic hand specialists should master the technique wrist arthroscopy. For those who wish to learn more, numerous books and articles are now available and several courses are organized every year in France.