The Human Wrist
Wednesday, 25 November 2009 10:45
Author: Jonathan Blood Smyth
The wrist-hand complex is a highly complicated tool which allows for the precise use of the hand and its very important role in human function, with the wrist a vital link in this process. The shoulder and scapula allow crude arm positioning, the elbow allows the distance from the body to be varied, the forearm sets the angle at which the wrist will be positioned and the wrist finishes off the last detail of hand positioning. As the joints get closer to the hand the smaller and more precise their movements.
The wrist-hand complex is a highly complicated tool which allows for the precise use of the hand and its very important role in human function, with the wrist a vital link in this process. The shoulder and scapula allow crude arm positioning, the elbow allows the distance from the body to be varied, the forearm sets the angle at which the wrist will be positioned and the wrist finishes off the last detail of hand positioning. As the joints get closer to the hand the smaller and more precise their movements.
The wrist bones are a grouping of eight small bones called the carpal bones and which are arranged in two rows between the metacarpals and the ulna and radius of the forearm. From the end row of carpal bones the metacarpals run down the hand to the junction with the phalanges at the knuckles, making a mobile central hand area. Running virtually parallel to each other and being long and narrow the metacarpals can alter their positioning, either becoming flattened to support something large or rotated round to cup the palm for increased grasping ability.
The neat, close group of carpal bones allows the wrist to perform a conical range of movement facing forwards, with a full 360 degree rotation possible. The bones can move as a group or to some degree individually to permit fine control of the thumb, fingers and hand. The rows are somewhat irregular but on average there are two bones in line with each metacarpal between it and the forearm. This pattern creates a series of joints in line with each other and permits a great variety of individual movements to translate into precise and varied positioning.
The thumb is the most manoeuvrable and astonishing part of the human hand. We possess an "opposable thumb" which is absent from apes and allows us to achieve the high levels of precision movements we require. On the outside of the hand the thumb's metacarpal is not flat in the same plane as the others in the palm but is turned inwards, giving it the function of crossing the palm to allow the thumb to meet the ends of the fingers in gripping. Much of the specialised thumb movement comes from the junction of its carpal and metacarpal bones.
The movements of the carpal bones can be in unison in small amounts as they move together to allow a movement to occur. As the hands move small amplitudes of movement occur between the individual carpal bones and the carpal rows. The metacarpals are able to rotate around their long axes which allows the palm to be curled into a cupped position. As the palm moulds round to assist gripping it also allows the fingers to align so that they can effectively grip at the correct angle. Any loss of the accessory movements of the carpals and metacarpals can reduce the ability of the hand to function adequately.
Using the hands very heavily such as in gripping and holding heavy objects, hauling ropes or operating heavy machinery can adversely affect wrist function. The longitudinal forces which are generated across the wrist are very high as the hand grasping power is applied, compressing the carpal bones between the forearm and the metacarpals. The carpal bones can then suffer a reduction in the accessory movements possible between them. If the wrist is forcibly extended this may dislodge the lunate bone, one of the wrist bones, forwards and cause pain.
The commonest reason for the wrist to be extended forcibly is a FOOSH or a fall on the outstretched hand, which can result in a Colles fracture which involves the last inch of the radius and ulna near the wrist. The fracture, commonest in older females, is the most obvious part of the overall injury which results also in wrist sprain and soft tissue injury. Five to six weeks will be enough to heal the fracture but there may be weakness, pain and difficulty with use in the hand for a longer period, partly related to a upset in the inter carpal movements.
The wrist-hand complex is a highly complicated tool which allows for the precise use of the hand and its very important role in human function, with the wrist a vital link in this process. The shoulder and scapula allow crude arm positioning, the elbow allows the distance from the body to be varied, the forearm sets the angle at which the wrist will be positioned and the wrist finishes off the last detail of hand positioning. As the joints get closer to the hand the smaller and more precise their movements.
The wrist bones are a grouping of eight small bones called the carpal bones and which are arranged in two rows between the metacarpals and the ulna and radius of the forearm. From the end row of carpal bones the metacarpals run down the hand to the junction with the phalanges at the knuckles, making a mobile central hand area. Running virtually parallel to each other and being long and narrow the metacarpals can alter their positioning, either becoming flattened to support something large or rotated round to cup the palm for increased grasping ability.
The neat, close group of carpal bones allows the wrist to perform a conical range of movement facing forwards, with a full 360 degree rotation possible. The bones can move as a group or to some degree individually to permit fine control of the thumb, fingers and hand. The rows are somewhat irregular but on average there are two bones in line with each metacarpal between it and the forearm. This pattern creates a series of joints in line with each other and permits a great variety of individual movements to translate into precise and varied positioning.
The thumb is the most manoeuvrable and astonishing part of the human hand. We possess an "opposable thumb" which is absent from apes and allows us to achieve the high levels of precision movements we require. On the outside of the hand the thumb's metacarpal is not flat in the same plane as the others in the palm but is turned inwards, giving it the function of crossing the palm to allow the thumb to meet the ends of the fingers in gripping. Much of the specialised thumb movement comes from the junction of its carpal and metacarpal bones.
The movements of the carpal bones can be in unison in small amounts as they move together to allow a movement to occur. As the hands move small amplitudes of movement occur between the individual carpal bones and the carpal rows. The metacarpals are able to rotate around their long axes which allows the palm to be curled into a cupped position. As the palm moulds round to assist gripping it also allows the fingers to align so that they can effectively grip at the correct angle. Any loss of the accessory movements of the carpals and metacarpals can reduce the ability of the hand to function adequately.
Using the hands very heavily such as in gripping and holding heavy objects, hauling ropes or operating heavy machinery can adversely affect wrist function. The longitudinal forces which are generated across the wrist are very high as the hand grasping power is applied, compressing the carpal bones between the forearm and the metacarpals. The carpal bones can then suffer a reduction in the accessory movements possible between them. If the wrist is forcibly extended this may dislodge the lunate bone, one of the wrist bones, forwards and cause pain.
The commonest reason for the wrist to be extended forcibly is a FOOSH or a fall on the outstretched hand, which can result in a Colles fracture which involves the last inch of the radius and ulna near the wrist. The fracture, commonest in older females, is the most obvious part of the overall injury which results also in wrist sprain and soft tissue injury. Five to six weeks will be enough to heal the fracture but there may be weakness, pain and difficulty with use in the hand for a longer period, partly related to a upset in the inter carpal movements.
About the Author:
Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapists, physiotherapy, Physiotherapists in Bournemouth, back pain, orthopaedic conditions, neck pain and injury management. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.
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