Anatomy clinical correlates: Wrist and hand

In everyday life, we rely on our hands for a variety of reasons, from vigorously typing out notes while watching an Osmosis video to playing musical instruments or participating in sports.Unfortunately, since we use them so much, the hands are quite prone to injury.Alright, let's start by looking at distal forearm fractures.There’s two kinds: Colles fracture, which are a direct result of falling on an extended wrist, and Smith fracture, which results from falling on a flexed wrist, or a direct blow to the posterior forearm.With Colles fractures, the displaced radial fragment moves posteriorly, or dorsally, and the ulnar styloid process can also become fractured.Clinically, when the distal radial segment moves dorsally this is called a “dinner fork deformity” because when viewed laterally, the hand and wrist are slightly curved anteriorly making it look like a fork.With Smith fractures, on the other hand, the displaced distal radial fragment moves anteriorly, or ventrally, which clinically translates as a “garden spade” deformity.Next, let’s look at carpal bone fractures, of which the most common are scaphoid fractures.Scaphoid fractures occur as a result of falling on the lateral side of an outstretched hand in abduction.Clinically, this results in pain and tenderness on the lateral side of the wrist and hand, in a location called the anatomical snuffbox, which is where you can palpate the scaphoid bone between the tendons of extensor pollicis longus on the medial side and extensor pollicis brevis and abductor pollicis longus on the lateral side.The big problem with these fractures is that because the blood vessels supply the distal part of the scaphoid first then come back and supply the proximal part, a fracture in the middle of this bone disrupts the blood supply.This can cause avascular necrosis and non union of the proximal fragment of the scaphoid, which is basically when the bone dies off because of lack of blood, and degenerative wrist joint disease.Initial X-rays often miss scaphoid fractures at first, so when there is tenderness on palpation of the anatomical snuffbox in a patient who fell on an outstretched hand, it’s important to still treat it as a fracture to avoid this complication.When still suspecting a scaphoid fracture after an initial negative x-ray, a CT or MRI scan can be done, or a follow up x ray can be done in 7-14 days.Management for a non-displaced scaphoid fracture is immobilization with a cast or thumb spica splint, where displaced fractures may need to be treated surgically.Furthermore, serial x-rays should be done during recovery to monitor for osteonecrosis of the proximal segment.Another carpal bone, called the lunate, can also be subject to injury.The lunate is found in the proximal row of carpal bones medial to the scaphoid, and is susceptible to volar, or anterior dislocation into the carpal tunnel during a fall on an outstretched hand, though less likely to be injured than the scaphoid bone.Lunate bone dislocation can result in compression of the median nerve within the carpal tunnel, resulting in median nerve compression signs and symptoms.This includes pain and paraesthesia in the radial 3 and a half digits, weakness of the first and second lumbrical, thenar atrophy, and weakness of thumb abduction and opposition of the affected hand.On a lateral x-ray of the hand, volar lunate dislocation can be recognized by the ‘spilled teacup’ sign.Another common pathology of the hand that you probably have heard of is carpal tunnel syndrome.Carpal tunnel syndrome occurs when the median nerve is compressed within the carpal tunnel, which is a space created by the transverse carpal ligament forming the roof of the carpal tunnel, and the carpal bones forming the floor.The median nerve, along with 9 flexor tendons enter the hand through the carpal tunnel, and increased pressure in this space can compress the median nerve, resulting in median nerve compression signs and symptoms.Risk factors for carpal tunnel are pregnancy, edema, obesity, rheumatoid arthritis, hypothyroidism, diabetes, acromegaly, and may be associated with repetitive use of the hands and wrist.There are two popular clinical tests used to test for carpal tunnel syndrome.The first is Phalen maneuver, where both wrists are flexed to 90 degrees, and the dorsal surfaces of the hands are pressed together.A positive test is when the symptoms of carpal tunnel are reproduced in prolonged position of up to 60 seconds.The second is the Tinel sign, which is performed by repeatedly percussing firmly over the carpal tunnel, and if carpal tunnel symptoms appear, that’s a positive test.To confirm the diagnosis of carpal tunnel syndrome, a nerve conduction study frequently combined with electromyography is used to assess the degree of nerve damage and muscle denervation.The management of carpal tunnel syndrome is typically non surgical.Initially, a wrist splint can be used to immobilize the wrist in a neutral position to prevent excess flexion or extension that can worsen symptoms.If this does not work, steroid injections can be used to reduce inflammation.Significant impairment may require surgical decompression of the median nerve with a longitudinal incision through the transverse carpal ligament to decrease pressure.However, it is important to avoid the recurrent branch of the median nerve, which is susceptible to injury during this operation, or any superficial laceration of the palm in general.Injury to the recurrent branch of the median nerve would lead to dysfunction of the three thenar muscles which it supplies, but no sensory deficits, resulting in thumb movement dysfunction and loss of the thumb’s overall usefulness.Another nerve, called the ulnar nerve, is also susceptible to compression within the ulnar canal, or Guyon canal, which is the space where the ulnar nerve enters the wrist.The ulnar canal has a roof, made up by the thickened superficial palmar fascia, a floor made up by the transverse carpal ligament, a medial wall, consisting of the pisiform and pisohamate ligament, and a lateral wall made up by the hook of the hamate.Fracture of the hook of the hamate can cause compression to the ulnar nerve at the wrist, resulting in sensory loss to the medial 1 and a half digits, weakness in abduction and adduction in digits 2-5, weakness in adduction of the thumb, weakness in flexion of the fourth and fifth digits as well as weakness in opposition of the 5th digit.Atrophy of the hypothenar muscles will eventually occur, and injury to the distal ulnar nerve can result in an ulnar claw deformity when the hand is at rest.Now let’s switch gears and look at the bones of the hand.Some of the most common injuries at this site include fractures of the 5th metacarpal, also called “boxer’s fractures”, and injuries of the fingertip, called “mallet finger”, also called “baseball” finger.Let’s look at them one by one.5th metacarpal fractures occur when throwing a punch with a closed and abducted fist.Fingertip injuries are caused by damage to the extensor tendon at the distal interphalangeal joint, and it’s called a “baseball” finger because it’s often the result of a forceful impact of an object, like a baseball, with the fingertips.Clinically, mallet finger results in drooping, and inability to extend the fingertip.Alright, now, we’re still in the hand region, so let’s talk about Dupuytren contracture, which is when the palmar fascia and aponeurosis gradually thickens, shortens and becomes fibrotic, until the 4th and 5th fingers are pulled into permanent partial flexion.Some risk factors for developing Dupuytren contracture include family history, alcohol dependence, smoking, liver or thyroid disease and diabetes.Up next, there’s tenosynovitis, which is the inflammation of the sheath surrounding a tendon.One form is de Quervain tenosynovitis, which affects the tendons of the abductor pollicis longus and extensor pollicis brevis, which have the same common tendon sheath, because of repetitive forceful movements of the hands during gripping and wringing, like when squeezing water out of clothes.Clinically, this causes sharp pain on the lateral side of the wrist, which can be elicited using Finkelstein test, where the examiner grasps and ulnar deviates the hand when the person has their thumb held within their fist.It most commonly occurs in women between the age of 30 and 50, and it also has a higher frequency 4-6 weeks postpartum.Golf and racquet sport players are also at risk.These injuries can be managed conservatively, with analgesics such as non-steroidal anti inflammatories and thumb spica splinting.Another form of tenosynovitis is known as “trigger finger”, or stenosing tenosynovitis, which can affect one or multiple fingers, causing them to snap or lock into place during flexion making it hard to extend these fingers, leaving them in the classic ‘trigger’ position.Finally, one last condition that can affect the wrist is a ganglion cyst, which is a small mass typically filled with mucinous fluid which can overlie the joints or tendon sheaths in the upper and lower limbs, but most commonly they affect the wrist.These are generally harmless lesions which communicate with the underlying joint, and those with underlying joint disorders or previous injury are more at risk.They are typically diagnosed clinically, and are confirmed using transillumination of the mass with a light pressed up against it.Rarely, an ultrasound or MRI is needed to confirm diagnosis.They are often asymptomatic but can produce some pain and tenderness, and if they get large enough can cause local compression on nerves such as the median nerve.Typically they resolve on their own, but aspiration or surgical removal are sometimes necessary.Alright, as a quick recap.Distal forearm fractures include Colles and Smith fractures.Colles fractures result from falling on an extended wrist, and this may result in a “dinner fork deformity”, whereas Smith fractures usually result from falling on a flexed wrist, causing a “garden spade” deformity.In the hand region, the most common carpal fracture is a scaphoid fracture, and often result from a fall on an outstretched hand.This mechanism of injury can also result in lunate bone volar dislocation which may also compress the median nerve.Nerve compression can also affect the median nerve as it travels through the carpal tunnel, or the ulnar nerve as it passes through the ulnar canal.Superficial laceration of the palm can cause damage to the recurrent branch of the median nerve which innervates the thenar muscles controlling movement of the thumb.Ganglion cysts are mucinous filled lesions mostly overlying the wrist.Fractures of the 5th metacarpal is called “boxer’s fractures' and injury to the fingertips is called “mallet finger”, also called “baseball” finger.Dupuytren contracture is when the palmar fascia and aponeurosis gradually thickens, shortens and becomes fibrotic, until the 4th and 5th fingers are pulled into permanent partial flexion.Sharp pain on the lateral side of the wrist during ulnar deviation is called de Quervian tenosynovitis, and trigger finger is when one or more fingers can ‘catch’ or ‘lock’ into flexion and have difficulty