ScrewA screw and a bolt (see Differentiation between bolt and screw below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a male thread (external thread). Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread (internal thread) in a matching part. Screws are often self-threading (also known as self-tapping) where the thread cuts into the material when the screw is turned, creating an internal thread that helps pull fastened materials together and prevents pull-out.
Rotator cuff tearRotator cuff tendinopathy is a process of senescence. The pathophysiology is mucoid degeneration. Most people develop rotator cuff tendinopathy within their lifetime. As part of rotator cuff tendinopathy, the tendon can thin and develop a defect. This defect is often referred to as a rotator cuff tear. Acute, traumatic rupture of the rotator cuff tendons can also occur, but is less common. Traumatic rupture of the rotator cuff usually involves the tendons of more than one muscle.
Screw threadA screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. A screw thread is the essential feature of the screw as a simple machine and also as a threaded fastener. The mechanical advantage of a screw thread depends on its lead, which is the linear distance the screw travels in one revolution.
Screw theoryScrew theory is the algebraic calculation of pairs of vectors, such as forces and moments or angular and linear velocity, that arise in the kinematics and dynamics of rigid bodies. The mathematical framework was developed by Sir Robert Stawell Ball in 1876 for application in kinematics and statics of mechanisms (rigid body mechanics). Screw theory provides a mathematical formulation for the geometry of lines which is central to rigid body dynamics, where lines form the screw axes of spatial movement and the lines of action of forces.
Screw-cutting latheA screw-cutting lathe is a machine (specifically, a lathe) capable of cutting very accurate screw threads via single-point screw-cutting, which is the process of guiding the linear motion of the tool bit in a precisely known ratio to the rotating motion of the workpiece. This is accomplished by gearing the leadscrew (which drives the tool bit's movement) to the spindle with a certain gear ratio for each thread pitch. Every degree of spindle rotation is matched by a certain distance of linear tool travel, depending on the desired thread pitch (English or metric, fine or coarse, etc.
ShoulderThe human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The shoulder joint, also known as the glenohumeral joint, is the major joint of the shoulder, but can more broadly include the acromioclavicular joint. In human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula, and the head sits in the glenoid cavity.
Joint replacementReplacement arthroplasty (from Greek arthron, joint, limb, articulate, + plassein, to form, mould, forge, feign, make an image of), or joint replacement surgery, is a procedure of orthopedic surgery in which an arthritic or dysfunctional joint surface is replaced with an orthopedic prosthesis. Joint replacement is considered as a treatment when severe joint pain or dysfunction is not alleviated by less-invasive therapies. It is a form of arthroplasty, and is often indicated from various joint diseases, including osteoarthritis and rheumatoid arthritis.
Upper limbThe upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the arm, forearm and hand, and is primarily used for climbing, lifting and manipulating objects. In formal usage, the term "arm" only refers to the structures from the shoulder to the elbow, explicitly excluding the forearm, and thus "upper limb" and "arm" are not synonymous.
ForceIn physics, a force is an influence that can cause an object to change its velocity, i.e., to accelerate, unless counterbalanced by other forces. The concept of force makes the everyday notion of pushing or pulling mathematically precise. Because the magnitude and direction of a force are both important, force is a vector quantity. It is measured in the SI unit of newton (N) and often represented by the symbol F.
Hip replacementHip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant, that is, a hip prosthesis. Hip replacement surgery can be performed as a total replacement or a hemi (half) replacement. Such joint replacement orthopaedic surgery is generally conducted to relieve arthritis pain or in some hip fractures. A total hip replacement (total hip arthroplasty or THA) consists of replacing both the acetabulum and the femoral head while hemiarthroplasty generally only replaces the femoral head.
