Wrist carpal bones

Joints such as the ankle and wrist consist of many small bones, and their surfaces must be determined accurately. This may be done via cadaveric examination or noninvasive means. The cadaveric system generally consists of the following (or a modification) The ligaments and tendons are stained to display the attachments (insertions) into the bones the construct is then embedded in Plexiglas, and sequential pictures or scans are taken as the construct is either sliced or milled. Slices on the order of a fraction of a millimeter are needed to fully describe the surfaces of wrist carpal bones. Noninvasive measures, such as modem high-sensitivity computed tomographic (CT) scans, may also be able to record geometries at the required level of detail. 

The wrist functions by allowing changes of orientation of the hand relative to the forearm. The wrist joint complex consists of multiple articulations of eight carpal bones with the distal radius, the structures of the ulnocarpal space, the metacarpals, and each other. This collection of bones and soft tissues is capable of a substantial arc of motion that augments hand and finger function. 

Fractures and dislocations of the carpal bones are rare, and a child with a painful wrist following trauma is much more likely to have injured the distal radius (Fig. 19.33). Carpal bone fractures are uncom-... 

Carpal T mnel An internal passage in the wrist between the extensor retinaculum and the carpal bones through which the median nerve, finger flexor tendons, and blood vessels pass from the arm to the hand. 

WRULDs describe a group of illnesses which can affect the neck, shoulders, arms, elbows, wrists, hands and fingers. Tenosynovitis (affecting the tendons), carpal tunnel syndrome (affecting the tendons which pass through the carpal bone in the hand) and frozen shoulder are all examples of WRULDs which differ in the manifestation and site of the illness. The term repetitive strain injury (RSI) is commonly used to describe WRULDs. 

The wrist or carpus is the distal articulation of the radius and the articular disk with the proximal row of carpal bones. The disk joins the ulna and radius and lies between the ulna and the proximal row of carpal bones. Laterally to medially, these bones are the scaphoid (navicular), lunate, and the triquetrum. A small bone, the pisiform, lies slightly anterior to the triquetrum. 

The wrist and hand joints should be palpated for swelling, asymmetries, and tenderness. The skin of the wrist and hand shonld be evalnated for temperature and moisture changes. Tendons or joints may be tender. The anatomic snuffbox should be palpated. In case of trauma, any tenderness in this area should be noted, because the navicular is the most commonly fractured of the carpal bones. 

There were several limitations with constructive recommendations found in this study. Regarding the model of wrist after arthroplasty, it was preferable to perform microstudy analysis for the fixation area. This project has simplified the screw by removing the threads. Hence, it is an advantageous if the threads could be constructed accurately. Screw threads have a crucial effect in determining the effects for fixation [32]. The effects on small carpal bones could be successfully investigated if microstudy analysis was carried out. 

Wrist affected with Rheumatoid Arthritis was commonly associated with carpal bones instability. In addition, stability of the wrist arthroplasty was still arguable due to some clinical reported the failure of the wrist arthroplasty due to weak fixation in which lead to instability. One of the suggested methods to enhance the fixation was to use bone graft. It was clearly observed in the results that the displacement of the bones as well as implants in the model fixed with bone graft is low. Since this study was established under semi-static condition, the low displacement significantly indicated the stability of the implant fixation. Thus, the fixation with bone graft found to be relatively... 

This presented paper was successfully illustrated the biomechanical behaviour of the two main fixation methods of the wrist arthroplasty, with and without bone graft. Based on the results and presented discussions, it can be concluded that wrist arthroplasty with carpal component fixed with bone graft successfully restore the stability of the carpal bones of the wrist with Rheumatoid Arthritis. This stability was interpreted with lower carpal displacement as well as considerably sufficient stresses value to provide fixation. 

Fig. 10.1. Schematic drawing of a coronal view through the wrist outlines the relation among carpal bones and wrist joint spaces. Distal to the radius (R) and ulna fLl),the proximal row of carpal bones includes the scaphoid (S), lunate (L), triquetrum (T) and pisiform (P), whereas the distal row is formed by the trapezium fTzj, trapezoid (Tdj, capitate (C) and hamate (H). The distal radio-ulnar joint (1) is separated from the radiocarpal joint (2) by the triangular fibrocartilage (curved arrow). The scapholunate (straight arrow) and lunotriquetral (arrowhead) ligaments separate the radiocarpal from the mid-carpal fSj joint. The carpometacarpal joint spaces (4) lie ahead of the distal carpal row...

The wrist is crossed by flexor and extensor tendons which course along its ventral and dorsal aspects respectively. Among them, nine flexor tendons and nine extensor tendons move toward the fingers without any attachment to the carpal bones two primary wrist flexors and three wrist extensors insert onto the distal carpal row and the metacarpals and one tendon, the palmaris longus tendon, attaches to the transverse carpal ligament and to the palmar aponeurosis. 

The diagnosis of dislocation of carpal bones may be challenging on plain films. Dislocations affect mostly the lunate which, being free from tendon attachments, is prone to volar dislocation, a condition commonly referred to as perilunate dorsal dislocation of the wrist. Even if radiographic examination can recognize the displacement of the lunate, in some cases this condition goes unnoticed at the first examination and US can be required to assess... 

It has been shown that in the dynamic tasks involving upper extremities, the posture of the hand itself has very little predictive power for the risk of musculoskeletal disorders. Rather, it is the velocity and acceleration of the joint that significantly differentiate the musculoskeletal disorders risk levels (Schoenmarklin and Marras 1990). This is because the tendon force, which is a risk factor of musculoskeletal disorders, is affected by wrist acceleration. The acceleration of the wrist in a dynamic task requires transmission of the forearm forces to the tendons. Some of this force is lost to friction against the ligaments and bones in the carpal tunnel. This frictional force can irritate the tendons synovial membranes and cause tenosynovitis or carpal tunnel syndrom (CTS). These new research results clearly demonstrate the importance of dynamic components in assessing CTD risk of highly repetitive jobs. 

Linscheid et al. popularized a different concept, the slider/crank theory where the scaphoid was seen as the bone that bridged the proximal and distal carpal row and, by bringing it back into its correct anatomic position, the stability of the wrist could be re-established. 

The ossific nucleus of the scaphoid appears around 4-6 years of age, and ossification is complete at 13-15 years. As in adults, the scaphoid is the most frequently injured carpal hone. The incidence of fractures is extremely low in the first decade, thereafter rising to a peak in the late teens to mid twenties (Grad 1986). Unlike adults, fractures of the distal pole are more common than of the waist (Fig. 19.34). These fractures represent ligamentous avulsion injuries, with failure through the bone rather than the stronger soft tissues. Middle third fractures occur in older children and adolescents, whilst proximal pole fractures are rare. Many fractures are the result of direct trauma to the wrist rather than a fall on the outstretched hand (Vahvanen and Westerlund 1980). 

An anatomic feature in the wrist formed by the wrist bones and the trans-carpal ligament through which the median nerve and the nine digital flexor tendons pass. 

As with many of the arthritic conditions, the primary dysfunction of the wrist and hand occur with the secondary motions more than the primary motions. Some dysfunctions of the carpal joints occur involving multiple joints. One of the most typical of the carpal dysfunctions involves restriction of glide of the lunate bone. It tends to have a preferential glide into the ventral direction and can contribute to the narrowing of the space of the carpal tunnel. The dysfunctions of... 

Somatic dysfunction can occur between any of the carpal or hand bones. Tender points lie over the dorsal and volar surfaces of the wrist A common tender point ofthe hand is found in the thenar eminence. 

Fig. 4 has the information on the stress distribution of the carpal side of the wrist arthroplasty fixed with and without bone graft. It was clearly observed that the one fixed with bone graft has relatively 10 times higher stress compared to implant fixation without bone graft. In general, the implant has higher stresses compared to the bone and bone graft. 

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