الفهرس 
FUNCTIONAL ANATOMY OF THEOnly 14 pages are availabe for public view
 |  | from | 114 |  |  |
| | | from | 114 | | |
Abstract
The hand accounts for about 90 percent of upper limb function. The thumb is the most functionally important of the digits. The thumb plays a critical role in many daily manipulative tasks based on its unique anatomical and biomechanical characteristics. A hand deprived of the thumb loses approximately 40% of its function and corresponds to a total body loss of 22%, which in terms of disability is similar to the loss of an eye ( Sastre and Arambula, 2000).
The thumb forms the lateral ray of the hand, which involves the trapezium, first metacarpal bone, two phalanges ”proximal and distal”. There are several extrinsic and intrinsic hand muscles that contribute to the motion and stability of the thumb. (Mathers, 1996).
One of the most important functional aspects of the thumb is its extensive mobility. The carpometacarpal joint permits a wide range of motion and is largely responsible for the characteristic dexterity of human prehension (Neumann and Bielefeld, 2003).
The basic active movements of the thumb are flexion-extension, abduction–adduction, opposition which describes normal pulp-to-pulp contact between the thumb and another opposable digit and circumduction which describes the angular motion of the first metacarpal bone. from different positions of the arc of circumduction, numerous types of pinch grip (precision, oppositional, key, directional, hook, span, power grip) are possible (Standring, 2005).
There are many types of traumatic injuries to the thumb. Crush avulsion injuries and amputations injuries are the most serious due to the need for complex reconstructive techniques (Valauri and Buncke, 1989).
Traumatic thumb amputations has many classifications, the most practical classifications are according to the level of thumb loss, putting in consideration it’s relation to soft tissue loss (Lee and Salyapongse, 2005).
In traumatic thumb loss, emergency replantation should be considered for all thumb amputations proximal to the base of the distal phalanx. If replantation is impossible or fails, several methods of thumb reconstruction may be used (Christopher, 2006).
Amputations in the distal third of the thumb are well-tolerated. First-web-space deepening will generally provide excellent results for amputations at the distal half of the middle third. In the proximal half of the middle third, Distraction lengthening of the first metacarpal is a reliable technique that provides up to 3 cm of length. Microvascular toe transfer is an excellent option for elective reconstruction. However, the other options also are available and may be more appropriate in some cases. Less ideal options include the various types of osteoplastic reconstruction (Muzaffar et al, 2005).
In the proximal third of the thumb, reconstructive options are more limited, including microvascular toe transfer and pollicization which can be done using either a damaged finger or normal finger (Sabapathy, 2004).