Homework Week 10

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Rutgers University *

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208

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Mechanical Engineering

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Feb 20, 2024

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Homework Week 10 1. What are the carpal bones in the proximal and distal row of the wrist? 1. The proximal row of carpal bones are the scaphoid, lunate, triquetrum, and pisiform. The distal row of carpal bones comprises the trapezium, trapezoid, capitate, and hamate. 2. Describe the pisiform? 1. Pisiform is a sesamoid bone which mechanically enhances the FCU. It i s one of eight and smallest carpal bones that forms part of the wrist joint. It’s shaped like a small pea bone. It develops in a tendon and is a sesamoid bone 2. Describe the articulation of the wrist to the hand 1. The scaphoid and the lunate are the two bones which actually articulate with the radius and ulna to form the wrist joint. Each ray articulates with a carpal bone forming a CMC joint. MCP is the next joint, followed by PIP and DIP with thumb only IP 3. Describe the arches of the hand 1. There are three arches, the proximal arch, distal transverse arch, and longitudinal arch. There are a few curves inside the palm of your hand that empower the hand to get a handle on objects of various sizes and shapes. These curves direct the gifted development of your fingers and control the force of your grip. In your grasp there are three primary curves, two cross over and one longitudinal curve. Arches allow for flattening or cupping of the palm to grab objects. 4. What is the importance of the radial nerve, median nerve, and ulnar nerve? 1. Radial nerve: innervates any of the muscles that extend the wrist, helps with Wrist Drop, decreased ability to grasp. Median nerve: innervates any of the muscles that flex the wrist, helps with Wrist flexors on the radial side, fine motor activities, sensation loss in the first three digits is a problem. Ulnar nerve: innervates ulnar nerve flexors and hand intrinsic. Ulnar nerve protects the upper limb since we lean on it getting sensation back to the CNS, which also supplies blood ulnar and radial arteries. 5. Describe the TFCC and its importance 1. It is the main stabilizer of distal radioulnar joint, in addition to contributing to ulnocarpal stability. It is important in loading & stabilizing of distal radioulnar joint. It is an organization of tendons, ligaments, and ligament that sits between the ulna and span bones on the little finger side of the wrist. The TFCC balances out and pads the wrist, especially when an individual turns their hand or handles something with it. TFCC normally not only stabilizes the ulnar head in sigmoid notch of radius but also acts as a buttress to support proximal carpal row. 6. Describe the digital collateral ligaments?

1. Starts from small depressions one or the other side of the metacarpal head and their origins lie approximately one-third of the way down from the dorsal surface of the metacarpal head. The ligaments course obliquely to insert at the palmar aspect of the proximal phalanx. It functions into flexion, digits enforced with two firm collateral ligaments and thick reinforced anterior capsule or volar plate. It is slack during extension and taut during flexion of digits. 7. Describe the volar plate? 1. It reinforces the joint anteriorly. It limits hyperextension of the MCP. It is a thick ligament that connects two bones in the finger. There are other ligaments to each side of the joint as well. As the volar plate is stretched and torn, it may also pull off a small piece of bone. It prevents impingement of the flexor tendons during MCP flexion. 8. Describe where flexion and extension occur in the wrist 1. Occur in the sagittal plane, they refer to increasing and decreasing the angle between two body parts: Flexion refers to a movement that decreases the angle between two body parts. 9. Describe what occurs with the 2 nd and 3 rd metacarpal and 4 th and 5 th metacarpal 1. 2nd and 3 rd : The second metacarpal articulates with the trapezium, trapezoid and capitate . The third articulates with the capitate . The metacarpal bone 2 is the one with the largest base and the longest shaft. Its base shows several areas for the articulations with the carpal bones. The metacarpal bone 3 is located at the base of the middle finger. It differs from the others by a styloid process that projects proximally from the laterodorsally edge of its base. This process participates in the joint with the capitate bone. The lateral surface of the base articulates with the second metacarpal, while the medial surface articulates with the fourth metacarpal via two oval articular surfaces. The 3rd metacarpal is distinguished by a styloid process on the lateral side of its base. 2nd metacarpal fractures is lower than the incidence rate of 5th metacarpal fractures. 4th and 5 th : the fourth and fifth articulate with the hamate . The metacarpal bone 4 shows a few specificities of its base. The metacarpal bone 5 is the smallest of all five metacarpals. Its base slightly differs from the other metacarpals, as its lateral part is non-articular and instead features a tubercle for the attachment of the extensor carpi ulnaris muscle. The lateral side of the base, however, articulates with the hamate bone. 10. Describe functional wrist motion 1. Wrist has three degrees of freedom 1. Flexion – extension 2. Radioulnar deviation 3. Rotation 1. The normal functional range of wrist motion is 5 degrees of flexion, 30 degrees of extension, 10 degrees of radial deviation, and 15 degrees of ulnar deviation 11. What are the differences between power and precision grip?

1. Power grip is used when an object must be held forcefully. Precision grip is used when an object must be manipulated finely. A power grip involves an ISOMETRIC contraction with no movement occurring between the hand and the object being held.

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