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Thumb Fracture -
Introduction and Case Report



The thumb is indeed our most important finger, the one that distinguishes us (and primates) from other species by conferring our superiority in a multitude of manual functions including pinch, grasp and fine movement. Unlike other fingers, the thumb is capable of full opposition, allowing a prehensile activity that is required to handle objects with fine precision. For this reason, an injury, the loss or a degree of deficit in the function of the thumb can have enormous implications for the individual, particularly when the hand is required in manual work.
In evolutionary terms, around 3.2 million years ago, the hand of the famous hominid ‘Lucy’, presented, unlike apes, a thumb capable of full opposition. Over time in the evolution of primates, the finger bones straightened and the distal phalange of the thumb became thicker and stronger with an increased angle from the index finger to facilitate prehensile activity (see attached article). Interestingly, the development of the human hand parallels the increase in brain size and the passage to an erect bipedal gait. The importance of the thumb in our daily activities is demonstrated by the area of the brain cortex controlling its function, which occupies 50% of the entire cortical area controlling the hand. It is conceivable that the development of a prehensile thumb was critical for the development of the human species.
The impairment assessment of the hand is a challenging exercise as described in the AMA guideline 4th Edition on Table I, page 318. Overall, the hand is a sophisticated part of the body equipped with 29 bones, 29 joints, 123 ligaments, 34 muscles, 48 nerves and 30 arteries that allow for the versatility of its functions. Also, the thumb displays a distinctive range of movement compared to the second & third finger, or the fourth & fifth finger. Sensitivity of the skin on the fingers is also important to guide the individual in several fine motor tasks.

To illustrate the impact of thumb impairment on the overall impairment of an individual, we report today a specific case study with a step by step explanation of the medical examination and calculation of impairment. In addition, see below for the extended description of the pathology: Thumb Fracture to illustrate what it is, the causes and risk factors leading to the pathology, the means of treatment and how to prevent it.  

Case Report

A 46-year-old laborer falls from a scaffolding and suffers an injury to his right thumb. He is transported to the hospital and x-rays reveal a comminuted intraarticular metacarpo-phalyngeal joint (MCP) joint fracture with multiple fragments. The hand surgeon decides to stabilize the fracture with an external fixator for 8 weeks. To adjust some of the fragments he had to open the MCP joint of the thumb. After six months, the worker is seen by an independent medical examiner who finds a scar of 2cm over the MCP joint and severe movement restrictions of the workers thumb, with ankylosis of the metacarpal –phalyngeal joint ankylosed in 0°, reduced mobility in the interphalangeal joint with extension 0° and flexion of 40°, lack of adduction of 8 cm, lack of radial abduction of 30° and a lack of opposition of 0 cm.    

Permanent impairment in accordance with the AMA Guideline 4th Edition


Right thumb movements


For the orthopaedic component, the combined Whole Person Impairment (WPI) is 19 %.
Please see Table 1, page 3/18, which distinguished between thumb, 2nd and 3rd finger and 4th and 5th finger impairment when converting from thumb/finger impairment to hand impairment. 
In general, finger injuries are regarded as severe and depending on the reaming movement restrictions the awarded permanent impairment is high, in particular if the thumb is involved. 

Thumb Fracture

The thumb is formed by the metacarpal bone, the proximal and distal phalanges. A thumb fracture can occur in any of these three bones.
Read the full pathology
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