A youthful hand has smooth contours covered by supple skin with minimal appearance of dorsal veins. As we age, changes to the back of hand include:
Prominence of dorsal veins
Visibility of tendons
Soft tissue volume loss
Bone and joint changes
The dorsum of the hand can be divided into 7 layers as follow:
Superficial fat layer (target layer for dermal filler injections)
Dorsal Superficial Fascia
Intermediate fat layer (veins and sensory nerves are located here)
Intermediate Superficial Fascia
Deep fat layer (contains interosseous muscles, metacarpal bones, extensor tendons and perforator vessels)
Deep Superficial Fascia
Three nerves control function in our hands: the median, ulnar, and radial nerves. Each of these nerves is responsible for both sensory and motor function in different parts of the hand.
The median nerve. This nerve originates at the shoulder, and controls the muscles we need to perform fine precision hand movements and pinching functions. The median nerve is the only nerve that enters the hand through the carpal tunnel; a spaced formed by the carpal bones of the wrist. This nerve controls sensation in the thumb, index finger, middle finger, and one side of the ring finger.
The ulnar nerve. The ulnar nerve runs through the arm into the hand and is the largest unprotected nerve in the human body. It connects to the little finger and adjacent side of the ring finger of the hand, providing sensation on the palm side of the hand. The ulnar nerve enables us to grasp objects. It travels along the elbow, between the bone and overlying skin at the cubital tunnel. When we bump our “funny bone,” the painful sensation we feel comes from impact against this nerve. The ulnar nerve enters the palm of the hand through the Guyon’s canal.
The radial nerve. This nerve runs through the arm and controls our ability to extend our wrist and control the position of our hand. It also provides sensory feedback from the back of the little finger and adjacent half of the ring finger.
Before injecting dermal fillers to rejuvenate the hand, a thorough hand examination must be carried out to identify potential issues that may affect treatment. Dermal filler injections for hand rejuvenation is contraindicated in the presence of any damage or disease affecting nerves, blood vessels, muscles or extreme joint swelling (e.g. arthritis).
How to perform modified Allen’s test
Instruct the patient to clench his or her fist (elevated above heart level); if the patient is unable to do this, close the person’s hand tightly.
Using your fingers, apply occlusive pressure to both the ulnar and radial arteries, to obstruct blood flow to the hand.
While applying occlusive pressure to both arteries, have the patient relax his or her hand, and check whether the palm and fingers have blanched. If this is not the case, you have not completely occluded the arteries with your fingers.
If the plam and fingers have blanched, release the occlusive pressure on the ulnar artery only to determine whether the modified Allen test is positive or negative.
Positive modified Allen test – If the hand flushes within 5-15 seconds it indicates that the ulnar artery has good blood flow; this normal flushing of the hand is considered to be a positive test.
Using a 22/25G cannula, inject dermal filler (medium viscosity) into the superficial fat layer, in a fan shape covering the entire dorsum.