A Better Joint Project

Kaitlin Rhind

Anatomy/ Physiology

Mr. Orre

5 May, 2017

Abstract:

I chose to do my project on wrist dislocation. A dislocation, or subluxation occurs when a bone moves from its normal position within a joint due to trauma.

As I explored this injury, I realized how complex the wrist is and how many joints work together in order to connect the hand and forearm. I read into the anatomy of the wrist further and chose a specific joint that stood out to me, which is the radiocarpal joint. I learned about the different tendons and muscles associated with it before trying to think of improvements to avoid this common dislocation. My goal was to find a solution to hyperextension and excessive movement which can cause abnormal movement of the wrist. I wanted to understand how this dislocation is treated, and researched different surgeries and treatment options in order to gain a better sense for the support structures that can be inserted for rehabilitation.

Main Body:

The Tendons and Ligaments of the Hand

The radiocarpal joint of the wrist sits between the distal radius, articular disk and proximal carpals. This synovial ellipsoid joint is composed of a convex bone fitting into a concave bone, and aids in movements such as extension, abduction and adduction. It is an incongruent joint, and has an unleveled surface, which allows for a greater range of motion. The radiocarpal joint absorbs about 80% of force placed on the wrist. The distal radius and articular disk are separated from the proximal carpals by synovial fluid which lubricates the joint, and an articular capsule, a fibrous connective tissue that provides additional support and reduces any excessive movements. The articular disc is also a tough connective tissue that provides shock support and stability between the bones. Muscles that are involved in flexion and radial deviation are the flexor carpi radialis and flexor carpi ulnaris which attach to the palmar side of the metacarpals. The anterior side of the wrist is composed of a flexor retinaculum, which protects the median nerve and flexor muscle tendons. The palmar extensor retinaculum tissues are much thinner than the flexor retinaculum, and prevent herniation, or excessive movement in the direction of least resistance. These tissues work together with the palmar radiocarpal ligament, the largest ligament in the wrist, to prevent extreme extension. There are 8 carpals in the hand that helps with free movement, and 5 metacarpals; the Radiocarpal ligament connects the dorsal end of the radius and carpals, and the ulnar collateral ligament resists extreme radial deviation.

Muscles of the Hand

Radiocarpal dislocation is caused by a high energy impact and is often occurrent with additional injuries such as fractures. Although it is not a common dislocation, as the joint impacted from the ulna side shifts towards the thumb in an upward direction, the chance of dislocation increases with the severity of impact. In gymnastics, the excessive load placed on the joint in floor routines and vault passes can result in wrist injuries. An outstretched hand absorbing a fall can cause the ligaments and capsule protecting the radiocarpal joint to rupture and dislocate the carpals from the radius. After sustaining this injury, one treatment path is to surgically insert a distal plate that connects from the diaphysis of the radius to the metacarpal of the long middle finger, forcing a lateral realignment. In order to prevent the dislocation of the radiocarpal joint, the ovial surface of the ellipsoid joint needs to be congruent. The difference of size between the ulna and radius creates an uneven socket for the carpals to sit in. By removing the first row of carpals, including the scaphoid, triquetrum, pisiform, and lunate, the radius will no longer sit higher than the ulna, however, there will still be a row of carpals to connect to the metacarpals. This reduces the number of interjoint spaces, and creates a stronger joint. In order to reduce the chance of ligament rupture, the distal radiocarpal and ulnar collateral ligaments will connect to the capitate and trapezium carpals instead and have much denser connective tissue. Although this will slightly reduce the flexion and extension range of motion of the wrist with four less joints and stronger ligaments, the chance of dislocation will decrease drastically.

Radiocarpal Dislocation of the Right Hand Anterior View

Realignment of the Radiocarpal Joint

The recreated joint without 4 carpals  creating a smoother surface for the joint to fit within.

Discussion:

I chose to improve the wrist joint because as a gymnast, I sustained a lot of injuries to my wrists. A lot of the exercises require you to bear all of your body weight onto your hands which can easily cause stress fractures and dislocations. I was young when this happened, and did not understand the wrist or the many components and dysfunctions that can occur, and so I wanted to understand its anatomy in-depth. There are many different conditions under which radiocarpal dislocation can occur, and even though I am trying to prevent this particular injury, it will not protect against all dislocations. In addition, by adding stronger ligaments to the palmar and anterior sides of the wrist, range of motion is reduced due to the higher tension, which can be undesirable. Since it is not possible to naturally redesign this joint, it is important to take precautions to avoid overstressing joints or allowing extreme deviation from natural anatomical position. Weight lifting requires wrists to have a large range of motion while flexing, extending and hyperextending the hands when picking up barbells or weights. Also, uneven bars in gymnastics places heavy strain on wrists when hanging because of the firm grasp it takes to hold on to the bar. To prevent dislocations and fractures during high intensity activities such as this, athletes will wear wrist wraps that support the hand from over extending or flexing and keeps the bones and ligaments aligned.

Works Cited:

https://www.epainassist.com/joint-pain/wrist-pain/wrist-joint-dislocation

https://www.epainassist.com/joint-pain/wrist-pain/understanding-wrist-joint-or-radiocarpal-joint

http://www.mccc.edu/~behrensb/documents/WristBIG.pdf

http://www.coa.org/docs/2014annualmeeting/presentations/GhiassiRevised.pdf

https://commons.wikimedia.org/wiki/File:Medical_X-Ray_imaging_VNH07_nevit.jpg

https://commons.wikimedia.org/wiki/File:Sobo_1909_203.png

https://clinicalgate.com/forearm-wrist-and-hand-2/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4208958/

Anatomy of Movement by Blandine Calais-Germain