Wrist kinetics after scaphoidectomy.

BACKGROUND: The scaphoid cannot be excised without generating substantial carpal dysfunction. The extent and nature of such a destabilizing procedure, however, has never been properly studied in the laboratory. METHODS: We used a six-degrees-of-freedom motion tracking device to quantify the changes in carpal alignment produced by isometric simultaneous loading of five wrist motor tendons in 12 fresh normal cadaver arms, before and after excising the entire scaphoid. FINDINGS: In the intact wrist, tendon loading consistently extended and supinated the capitate while flexing the triquetrum. After scaphoidectomy, the opposite rotations were always found: the capitate collapsed into flexion and pronation, whereas the triquetrum migrated proximally, while extending and radial deviating. All these changes were statistically significant. INTERPRETATION: Unless it is supplemented by some sort of midcarpal stabilization, scaphoidectomy alone is much too aggressive as a procedure to be considered a treatment option for wrist osteoarthritis. LEVEL OF EVIDENCE: Laboratory study. Not applicable.

Divergent Axial Carpal Dislocation and Its Pathomechanics.

Background Axial carpal dislocations and fracture dislocations are 1.4 to 2.08% of all the fractures and dislocations of the wrist. These injuries are caused by high-energy blast or compression mechanisms. Only 11 cases of axial-radial-ulnar (ARU) fracture dislocations have been described in the literature. Case Description We describe a case with a traumatic transtrapezoid, peritrapezium, transhamate, peripisiform ARU in a patient with acute compartment syndrome, traumatic transverse flexor retinaculum (TFR) rupture, and radial nerve palsy. Literature Review The ARU fractures are injuries where the carpus is torn into three columns. ARU injuries have a high incidence of neurovascular, soft-tissue cover, and muscular-associated injuries. Depending on the injuries mentioned earlier, a bad functional prognosis can be expected. Nearly without exception, in ARU cases, a traumatic TFR rupture takes place. Garcia-Elias mentioned that the injury pattern is given by the speed, magnitude, and energy entry point. Clinical Relevance We describe a case of an ARU injury which has not been previously described. In an analysis of the 12 ARU cases previously reported, we observed that when two or more applied forces converge, an ARU injury pattern can occur. That suggests that in ARU injuries, one side of the injury occurs before the other. Due to the extensive carpal damage, in patients with ARU, a restricted range of motion is more likely to happen than residual instability. Thus, in all these cases, an early mobilization and intensive rehabilitation is highly necessary.

The effect of individual isometric muscle loading on the alignment of the base of the thumb metacarpal: a cadaveric study.

Stability of the thumb carpometacarpal joint relies upon equilibrium between its ligaments, muscular support and joint congruity. We wanted to identify the muscles important in preventing or increasing dorsoradial subluxation of this joint. In ten cadaveric hands, a Fastrak® motion tracking device was used to assess the effects of individual isometric muscle loading on the base of the thumb metacarpal relative to the radius and to the base of the middle finger metacarpal. We found that the first dorsal interosseous muscle caused the least dorsoradial translation and highest distal migration of the base of the first metacarpal, whereas abductor pollicis longus was the primary destabilizer, increasing dorsoradial misalignment. The findings show different impacts of these muscles on joint alignment and stability, which suggests that treatment should be targeted to enhance the action of the primary stabilizing muscle, the first dorsal interosseous muscle.

Histological assessment of the triangular fibrocartilage complex.

The morphological structure of the seven components of triangular fibrocartilage complexes of 11 cadaver wrists of elderly people was assessed microscopically, after staining with Hematoxylin-Eosin and Elastica van Gieson. The articular disc consisted of tight interlaced fibrocartilage without blood vessels except in its ulnar part. Volar and dorsal radioulnar ligaments showed densely parallel collagen bundles. The subsheath of the extensor carpi ulnaris muscle, the ulnotriquetral and ulnolunate ligament showed mainly mixed tight and loose parallel tissue. The ulnolunate ligament contained tighter parallel collagen bundles and clearly less elastic fibres than the ulnotriquetral ligament. The ulnocarpal meniscoid had an irregular morphological composition and loose connective tissue predominated. The structure of the articular disc indicates a buffering function. The tight structure of radioulnar and ulnolunate ligaments reflects a central stabilizing role, whereas the ulnotriquetral ligament and ulnocarpal meniscoid have less stabilizing functions.

Tendinopathies of the Extensor Carpi Ulnaris.

To improve its mechanical advantage, the extensor carpi ulnaris (ECU) muscle uses, as if it was a pulley, the 6(th) extensor compartment, a dorsal fibro-osseous tunnel formed by the ulnar sulcus and the ECU tendon sub-sheath. Rupture or insufficiency of that sheath may allow anteromedial ECU tendon subluxation and subsequent destabilization of the distal radioulnar and ulnocarpal joints. Sometimes, it is not sheath problem, but excessive friction between the sheath and the tendon what causes a painful degeneration of the tendon (tendinosis) with or without tendon entrapment. The term "ECU tendinopathy" has been chosen to designate all painful ECU anomalies resulting from a dysfunctional 6(th) extensor compartment. ECU tendinopathies are frequent among sportsmen using bats, sticks or clubs. There are 2 major types of tendinopathy: 1) constrained tendinopathies, where there is entrapment of a thickened overused tendon, and 2) unconstrained tendinopathies, where a ruptured ECU sub-sheath allows the ECU to sublux in a volar direction, a position precluding all its stabilizing potential. In the first type, the goal of the treatment is to avoid further degeneration and subsequent rupture of the diseased tendon; in the second, to re-establish the normal connections between the ulna and the ECU tendon. This article reviews the management of the most frequent ECU tendinopathies.

Dart-throwing motion in patients with scapholunate instability: a dynamic four-dimensional computed tomography study.

When the normal wrist rotates along the 'dart-throwing' plane, the proximal row remains still, with most motion occurring at the midcarpal joint. Whether this behaviour is maintained when the scapholunate ligaments are torn is not known. If this is the case, patients having a scapholunate ligament repair could benefit from early dart-throwing exercises without the risk of pulling the sutures apart. Using dynamic computer tomography, we analysed the carpal behaviour of six normal wrists and six wrists with scapholunate instability during dart-throwing motion. In the normal wrists, the scaphoid and lunate did not flex or extend, but translated along the frontal plane an average 5.9 and 5.6 mm, respectively. When the scapholunate ligaments were torn, the scaphoid shifted towards the radial styloid considerably more than the lunate (12.8 mm versus 4.8 mm; p = 0.005), inducing a scapholunate gap. Based on these findings, we cannot recommend dart-throwing exercises after scapholunate ligament repair, unless the joint is stabilized with wires or screws.

[Muscular control of scapholunate instability. An experimental study]. / Control muscular de la inestabilidad escafolunar. Estudio experimental.

PURPOSE: As long as the neuromuscular stabilizers are intact, a lesion of the scapholunate ligament may or may not progress to a carpal instability. The mechanisms by which the muscles compensate this defect are not very well known. We designed an experimental study with the aim of clarifying these mechanisms. MATERIAL AND METHOD: Using 10 fresh wrists, with no pre-existing lesions, we studied the movements of the scaphoid, triquetrum and capitate produced by the isometrical loading of the muscles which move the wrist, each of them isolated or combined, before and after cutting off the scapholunate ligaments. To do this, we placed sensors in each of these bones and used the Fastrack system to record these movements. RESULTS: The simultaneous loading of the muscles of the wrist produce rotational movements in flexion and supination of the proximal carpal row. After cutting off the scapholunate ligaments, the scaphoid rotates in pronation and flexion, while the triquetrum rotates in pronation and extension. In this situation of a scapholunate lesion, the muscles that worsen the carpal dexasation are the extensor carpi ulnaris and flexor carpi ulnaris. On the other hand, the isolated loading of the radial muscles reduce the scapholunate diastasis, thus improving the carpal alignment. CONCLUSION: In dynamic scapholunate instabilities, isometric contraction of the ulnar carpal muscles must be avoided, as it promotes the scapholunate diastasis. The rest of the muscles have the opposite effect, stabilizing the carpus when primary stabilizers have failed.

[Carpal dynamic stability mechanisms. Experimental study]. / Mecanismos de estabilización dinámica del carpo. Estudio experimental.

OBJECTIVE: To evaluate, experimentally in cadavers, the effect of the motor muscles in the wrist in the kinetic behaviour of the carpal, under axial load, and the wrist in a neutral position. MATERIAL AND METHOD: The changes in the spatial orientation of the carpal bones were recorded with a movement trajectory gauge that functions with electromagnetic fields. A total of 30 fresh cadaver wrists were used, in which the principal motor tendons were isolated and subjected to loads proportional to the area of the physiological section of each muscle. The experiment was performed under isometric load conditions of all the tendons, and separately from each tendon. RESULTS: The simultaneous load of all the tendons studied caused a three-dimensional change of the carpal bones. The flexor carpi radialis led to supination of the scaphoids and pronation of the pyramidal. Conversely, the isolated load of the flexor carpi ulnaris, abductor pollicis longus and the extensor carpi radialis longus, caused a supination movement of the 2 carpal rows. Only the extensor carpi ulnaris led to a marked pronation of the carpal. COMMENTS AND CONCLUSIONS: The forearm muscles, as well as the movements of the wrist, cause pronation/supination/supination, flexion/extension and radial/cubital inclination movements. It is proposed that the most important movements in the dynamic stabilisation of the carpal are the intercarpal pronation and supination movements provoked by these muscles. Depending on the carpal injury mechanism or instability, the stimulating of one muscle group or the other may be beneficial.

Dorsal scapholunate ligament injury: a classification of clinical forms.

The dorsal scapholunate (SL) ligament may disrupt in variety of ways. Each form of injury requires specific fixation. To investigate the incidence of each type of ligament failure, the records of 45 patients with adequate information, good quality pictures, or videos demonstrating injury characteristics were reviewed. Four types of SL injury were found: type 1 (lateral avulsion from the scaphoid) was the most frequent, present in 19 patients (42%); type 2 (medial avulsion from the lunate) was the least frequent, with 7 cases (16%); type 3 (mid-substance rupture) was found on 9 occasions (20%); and type 4 (partial rupture plus elongation) was observed on 10 occasions (22%). Based on our observations, we submit that an arthroscopically assisted SL capsuloplasty may not be possible in all cases, particularly not when the ligament has avulsed off the bone (60% of the cases), leaving no ligament remnant on one side. Most patients will require ligament reattachment techniques using transosseous sutures, bone anchors, or ligament reconstruction.

[Relationship between midcarpal inclination angle and scaphoid kinematic]. / Relation entre l'angle d'inclinaison médiocarpienne et la cinématique du scaphoïde.

OBJECTIVE: To investigate if there is a correlation between the so-called midcarpal inclination angle and the kinematic behavior of the scaphoid. PATIENTS AND METHODS: The population studied was 60 patients with postero-anterior radiographs of the wrist in full radial and ulnar deviation. Each patient was assessed for the type of lunate by two independent observers. For each pair of radiographs the Midcarpal Inclination Angle and the Scaphoid Flexion Index (SFI) was determined. RESULTS: Twenty-three cases were classified as lunate type I, 19 cases as type II. The average midcarpal inclination angle was 55.2° (SD±6.1) for wrists with a lunate type I and 63.8° (DE±6.3) for type II (p<0.0001). There was a significant linear relationship between the midcarpal inclination angle and the Scaphoid Flexion Index (p=0.02). CONCLUSIONS: The wrists with a midcarpal inclination angle greater than 60° (type II lunate) had a scaphoid rotating according to a "columnar pattern", during radioulnar inclinations (predominant rotation along the sagittal plane), while the wrists with a lunate type I behave according to a "row pattern".

Role of the extensor carpi ulnaris and its sheath on dynamic carpal stability.

Ten cadaveric forearms were tested using a wrist testing apparatus specifically designed to investigate the mechanisms of muscle stabilization of the wrist. The specimens were set in a jig allowing the distal row to migrate proximally and rotate around the axis of pronosupination. The extensor carpi ulnaris (ECU) was loaded with specific weights. Reactive rotations of the scaphoid, triquetrum, and capitate were measured by an electromagnetic motion tracking device. Loading the ECU caused pronation of both proximal and distal rows. After sectioning its sheath, the overall direction of the movement remained unchanged, but there was a 40% and 50% decrease of the pronation power over the distal and proximal carpal row, respectively. In addition to stabilizing the distal radiolunar joint, the ECU is an important structure that contributes to the dynamic stability of the wrist. Furthermore, its sheath plays a crucial role in maintaining the effect of the ECU muscle on the carpus.

Relationship between thumb laxity and trapezium kinematics.

OBJECTIVES: To investigate the relationship between thumb laxity (passive mobility), shape of the trapezium and trapezial mobility relative to the second metacarpal. METHODS: Sixty normal volunteers were assessed for the amount of thumb laxity by measuring the shortest distance of the thumb nail to the radius when the thumb was forcefully approximated to the forearm with the wrist in flexion. The inclination of the distal surface of the trapezium (angle ß) and the mobility of the trapezium relative to the II metacarpal (Δangle α) were assessed using dynamic X-rays in maximal radial and ulnar deviation. RESULTS: There was no statistical correlation between thumb laxity and shape of the trapezium (angle ß). However, trapezium mobility (Δangle α) and thumb laxity were strongly correlated (P=0.018), with the more lax individuals registering higher trapezium mobility. CONCLUSION: This investigation does not support the concept of thumb hypermobility being associated to a trapezium with more pronounced inclination of its distal articular surface. However, it has been found that the higher the thumb mobility, the more the trapezium tilts under load.

Effects of forearm muscles on carpal stability.

Thirty cadaveric forearms were tested using a wrist testing apparatus specifically designed to investigate the mechanisms of muscle stabilization of the wrist. The specimens were set in a jig allowing the distal row to migrate proximally and to rotate around the pronosupination forearm axis. Five wrist motor tendons (FCR, FCU, ECU, ECRL and APL) were loaded with specific weights. Reactive rotations of the scaphoid, triquetrum and capitate were measured by an electromagnetic motion tracking device. When all five tendons were loaded simultaneously, the capitate supinated and the proximal row predominantly supinated and flexed. By contrast, when the ECU was loaded in isolation, it caused pronation to both proximal and distal rows. The FCR exhibited a mixed effect pronating the capitate and triquetrum, whilst supinating the scaphoid. Based on this, a hypothesis is proposed linking wrist stability to the balance of wrist pronators (ECU and FCR) and supinators (FCU, ECRL and APL).

The role of the flexor carpi radialis muscle in scapholunate instability.

PURPOSE: The flexor carpi radialis (FCR) muscle has been suggested to act as a dynamic scaphoid stabilizer. Because the FCR tendon uses the scaphoid tuberosity as a pulley to reach its distal insertion onto the second metacarpal, it has been hypothesized that FCR muscle contraction generates a dorsally directed vector that resists the scaphoid from rotating into flexion. The purpose of the present study was to validate that hypothesis and clarify the role of the FCR as a dynamic scaphoid stabilizer. METHODS: Ten fresh cadaver wrist specimens were tested. A custom-designed testing apparatus was used to hold the forearm and wrist vertically, in neutral forearm rotation. A 6-degree-of-freedom, electromagnetic motion-tracking device, with sensors attached to the scaphoid, triquetrum, capitate, and radius, was used to monitor spatial changes in carpal alignment as a result of isometrically loading the FCR in 5 different wrist positions. RESULTS: In all specimens and all wrist positions, the scaphoid consistently rotated into flexion when the FCR was loaded. It also exhibited variable degrees of pronation or supination, depending on whether the wrist was in flexion or extension. When the wrist was loaded in neutral position, the scaphoid consistently supinated and the triquetrum pronated, these differences being statistically significant (p < .05). CONCLUSIONS: The scaphoid consistently rotated into flexion and supination when the FCR was loaded, while the triquetrum rotated in flexion and pronation. The positive effects of FCR muscle re-education in dynamic scapholunate instabilities can be explained not by this muscle's capability of extending the scaphoid, as has often been hypothesized, but by its ability to induce supination to the scaphoid and pronation to the triquetrum. Such opposite rotations are likely to result in a dorsal coaptation of the scapholunate joint with relaxation of the dorsal scapholunate ligament.

Long-term results of lunocapitate arthrodesis with scaphoid excision for SLAC and SNAC wrists.

When treating the degenerative arthritis that follows scapholunate instability or scaphoid pseudarthrosis, excision of the scaphoid must be combined with a stabilisation of the midcarpal joint. Two alternatives have been proposed for that purpose: fusing the lunate, triquetrum, capitate and hamate (four corner fusion), 4CF; or limiting the arthrodesis to the lunate and capitate, preserving or excising the triquetrum. Previous reports have attributed a high level of complications to lunocapitate arthrodesis, mainly in respect of nonunion. We have reviewed 17 patients who had been treated with a lunocapitate fusion, after an 8 to 12-year follow-up period, and found similar results compared with 4CF, even with a major degree of motion in ulnar-radial deviation. Recent work on the innervation of the radiotriquetral ligaments has given relevance to the preservation of lunotriquetral motion in maintaining proprioception. Also if the triquetrum is excised to gain more motion, the proprioceptive role of the radiotriquetral ligaments is compromised.

[Radio-scapho-lunate arthrodesis with distal scaphoid excision]. / Arthrodèse radioscapholunaire avec excision du scaphoïde.

Painful dysfunction of the radio-scapho-lunate joint may occur secondary to a number of post-traumatic, inflammatory and non-inflammatory conditions. When symptomatic, this problem may necessitate fusing the radio-scapho-lunate joint. The goal of this study is to describe precisely the technical steps of radio-scapho-lunate fusion with distal scaphoidectomy and to present the results in a clinical series. Sixteen patients presented with degeneration of the radio-scapho-lunate joint combined with a normal midcarpal joint. Radio-scapho-lunate fusion with distal scaphoidectomy was performed in all patients. At an average follow-up of 37 months, complete relief of pain was obtained in 10 patients, three had slight pain with strenuous loading, and three had occasional pain with regular activities. The average range of passive motion at follow-up was 32 degrees of flexion and 35 degrees of extension. The average postoperative grip strength was 76%. In all cases a solid fusion was obtained. In two patients who had originally suffered a perilunate dislocation, midcarpal degenerative arthritis was noted. We suggest that in cases of radio-scapho-lunate osteoarthritis without degenerative change in the midcarpal joint, radio-scapho-lunate fusion is a possible solution. However, it is necessary to perform distal scaphoidectomy in order to avoid scapho-trapezo-trapezoid impingement. Provided all the technical principles are respected, complications such as ulnocarpal impingement or nonunion, are rare.

The non-dissociative clunking wrist: a personal view.

Clunking of the wrist is often the result of a combined radiocarpal and midcarpal ligament insufficiency, coupled with inadequate neuromuscular coordination. When symptomatic, these wrists may benefit from splinting, isometric exercising of specific muscles and advice on activity modification. Failing this, different surgical strategies have been proposed, depending on the location of dysfunction. When the clunking derives from an isolated injury of one joint, reconstruction of its inadequate ligaments may be an effective solution. However, soft tissue procedures tend to fail when clunking results from multilevel instability. In these cases, partial carpal arthrodesis is an alternative. Although effective in eliminating the clunking, midcarpal fusion is associated with alteration of the so-called "dart-throwing" motion, the most common rotation in daily activities, and hence is not recommended. Radiolunate fusion, by contrast, appears to be a less morbid alternative, with the benefit of eliminating the painful clunking while preserving a good range of dart-throwing motion.