Musculoskeletal anatomy fill in the blanks

A fracture of the [blank_start]surgical neck of humerus[blank_end] places the axillary nerve at risk of injury. This nerve passes through the [blank_start]quadrangular space[blank_end], the lateral border of which is the [blank_start]surgical neck of humerus[blank_end]. This nerve innervates the [blank_start]deltoid muscle[blank_end] and the [blank_start]teres minor muscle[blank_end]. The clinical features of injury to this nerve include weakness of shoulder [blank_start]abduction[blank_end] and sensory loss in the [blank_start]lateral upper arm[blank_end].

Laceration of the [blank_start]profunda brachii artery[blank_end] might occur if one suffers a midshaft fracture of the humerus. This artery accompanies the [blank_start]radial nerve[blank_end] in the [blank_start]spiral groove[blank_end] of the humerus. A [blank_start]surgical neck fracture[blank_end] may lacerate the [blank_start]posterior circumflex humeral artery[blank_end], which accompanies the axillary nerve through the quadrangular space.

Weakness of [blank_start]internal rotation[blank_end] of the arm may result from a lesion to the [blank_start]posterior cord[blank_end] of the brachial plexus and one or more of the subscapular nerves, or injury to the lateral or medial pectoral nerves. The major [blank_start]internal rotators[blank_end] of the arm at the shoulder are the [blank_start]subscapularis muscle[blank_end], innervated by the upper subscapular nerve and lower subscapular nerve, the [blank_start]latissimus dorsi muscle[blank_end], innervated by the middle subscapular nerve, [blank_start]teres major[blank_end], innervated by the lower subscapular nerve, and the [blank_start]pectoralis major muscle[blank_end], innervated by the lateral and medial pectoral nerves.

Weakness in the ability to [blank_start]elevate the scapula[blank_end] may result from a lesion of the [blank_start]accessory nerve[blank_end]; this nerve may be lacerated by a wound to the lateral neck, but not by a humeral fracture. This nerve innervates the trapezius muscle.

Winging of the scapula results from an injury to the [blank_start]long thoracic nerve[blank_end], which innervates the [blank_start]serratus anterior muscle[blank_end]. This presents as protrusion of the [blank_start]medial border[blank_end] of the scapula when the patient [blank_start]pushes[blank_end] against a wall. There will be no [blank_start]sensory[blank_end] deficits. The nerve is subject to injury during axillary surgery, such as axillary node dissection for breast cancer.

This patient has weakness of the anterior compartment muscles (loss of [blank_start]dorsiflexion[blank_end] ) and lateral compartment muscles ( unopposed [blank_start]inversion[blank_end] ) of the leg. These muscles are innervated by the [blank_start]deep peroneal nerve[blank_end] and [blank_start]superficial peroneal nerve[blank_end], respectively. Both of these nerves are branches of the [blank_start]common peroneal nerve[blank_end] . Also, the [blank_start]superficial peroneal nerve[blank_end] and [blank_start]deep peroneal nerve[blank_end] provide sensory innervation to the [blank_start]dorsum[blank_end] of the foot. The [blank_start]superficial peroneal nerve[blank_end] provides sensory innervation to most of the [blank_start]dorsum[blank_end] of the foot. The deep peroneal nerve provides sensory innervation to the webspace between the [blank_start]first and second digit[blank_end]. The [blank_start]common peroneal nerve[blank_end] is superficially located at the neck of the fibula. The patient likely compressed this nerve by lying on her [blank_start]right side[blank_end] or supine with the right leg [blank_start]externally rotated[blank_end] for long periods of time.

The [blank_start]femoral nerve[blank_end] innervates the muscles and the skin of the anterior thigh. Weakness of these muscles would cause weakness of [blank_start]knee extension[blank_end]. The [blank_start]obturator nerve[blank_end] innervates the muscles of the medial thigh and the skin in this region. Weakness of these muscles would cause weakness of [blank_start]hip adduction[blank_end]. The sciatic nerve divides to become the [blank_start]tibial nerve[blank_end] and the [blank_start]common peroneal nerve[blank_end]. The [blank_start]tibial nerve[blank_end] innervates the muscles of the calf and the skin of the s[blank_start]ole of the foot.[blank_end] The calf muscles are responsible for [blank_start]plantar flexion[blank_end] and sensation on the [blank_start]sole of the foot[blank_end].

The [blank_start]common peroneal nerve[blank_end] is susceptible to compression injury due to its superficial location at the [blank_start]neck of the fibula[blank_end]. Deficits include weakness of anterior compartment muscles ([blank_start]foot drop[blank_end]) and weakness of lateral compartment muscles ([blank_start]unopposed inversion[blank_end]). Loss of sensation on the [blank_start]dorsum of the foot[blank_end] may also be present.

The [blank_start]hamate bone[blank_end] is the small bone in the distal row of carpal bones in the wrist that sits directly proximal to the little and ring fingers (5th and 4th digits). It has a bony protrusion, the [blank_start]hook of the hamate[blank_end], which is very vulnerable to trauma of the palm, particularly in the settings of a person hitting the ground forcibly with a stick (including a golf club) or falling on an [blank_start]outstretched hand[blank_end]. An x-ray or CT scan of the wrist can confirm the diagnosis. Therapy involves [blank_start]open reduction with fixation[blank_end] or [blank_start]excision of the bone fragment[blank_end].

The [blank_start]ulnar nerve[blank_end] crosses the wrist immediately lateral to the hook of the hamate and can be injured in such a fracture. If that occurs, there will be sensory symptoms on the [blank_start]medial[blank_end] side of the hand on both the dorsal and palmar surfaces of the hand and there could be motor loss in many of the [blank_start]intrinsic muscle[blank_end] of the hand (not including the [blank_start]thenar muscles[blank_end] or the [blank_start]first two lumbrical muscles[blank_end]). Because the [blank_start]flexor digiti minimi[blank_end] and [blank_start]opponens digiti minimi[blank_end] have their origins on the hook of the hamate, [blank_start]flexion[blank_end] of the fifth digit against resistance causes pain at the fracture site.

Carpal tunnel syndrome results from compression of the [blank_start]median nerve[blank_end] within the [blank_start]carpal tunnel[blank_end]. It results in sensory disturbance of the palmar surface of the [blank_start]lateral 3.5 digits[blank_end] and weakness of the [blank_start]thenar muscles[blank_end]. It is often the result of swelling of the [blank_start]synovial tendon sheaths[blank_end] of the [blank_start]digital flexors[blank_end] within the carpal tunnel.

Cubital tunnel syndrome causes paresthesias and numbness on the [blank_start]ulnar[blank_end] side of the hand due to compression of the [blank_start]ulnar nerve[blank_end] at the [blank_start]elbow[blank_end].

Lunate dislocation is an [blank_start]anterior[blank_end] displacement of the lunate with respect to the rest of the carpals. It can occur in severe trauma of the hand and is usually accompanied by compression of the [blank_start]median nerve[blank_end], with resulting pain and numbness on the [blank_start]palmar[blank_end] aspect of the hand. Scapholunate ligament rupture causes pain in the [blank_start]mid-wrist[blank_end] and can result from a fall onto an [blank_start]outstretched hand[blank_end].

The [blank_start]hamate[blank_end] is a wedge-shaped carpal bone with a hooklike process on its [blank_start]palmar surface[blank_end]. It is located in the [blank_start]distal[blank_end] carpal row on the [blank_start]ulnar[blank_end] side. The [blank_start]hook of the hamate[blank_end] may be fractured when a person falls on an outstretched hand, or hits the ground with a stick (i.e., a golf club) in the hand.

Clawing of the ring and little fingers is characteristic of an [blank_start]ulnar nerve[blank_end] lesion. [blank_start]Ulnar nerve[blank_end] lesions can also produce wasting of the [blank_start]hypothenar[blank_end] eminence and [blank_start]interosseous[blank_end] muscles. The latter causes "[blank_start]guttering[blank_end]" between the extensor tendons on the back of the hand. The [blank_start]dorsal interosseaous[blank_end] muscles abduct digits 2-5 and the [blank_start]palmar interosseous[blank_end] muscles adduct digits 2-5. [blank_start]Ulnar[blank_end] lesions also cause loss of sensation to the [blank_start]medial[blank_end] side of the hand (both palm and dorsal surface) and both the palmar and dorsal surfaces of the [blank_start]little[blank_end] finger and the medial half of the [blank_start]fourth[blank_end] finger. Sensation on the back of the thumb is provided by the [blank_start]radial nerve[blank_end] Sensation on the palmar side of the forefinger is provided by the [blank_start]median nerve[blank_end] Wasting of the thenar eminence is associated with lesions of the [blank_start]median nerve[blank_end] "Wrist drop" is associated with lesions of the [blank_start]radial nerve[blank_end].

Ulnar nerve lesions can produce: 1. [blank_start]Clawing[blank_end] of the [blank_start]4th[blank_end] and [blank_start]5th[blank_end] digits 2. [blank_start]Wasting[blank_end] of the [blank_start]hypothenar[blank_end] eminence and [blank_start]dorsal interosseous[blank_end] muscles 3. Loss of [blank_start]sensation[blank_end] to the [blank_start]medial[blank_end] side of the hand (both palm and dorsal surface) and both the palmar and dorsal surfaces of the [blank_start]5th[blank_end] digit and the [blank_start]medial half[blank_end] of the [blank_start]4th[blank_end] digit.

Loss of elbow flexion indicates denervation to the [blank_start]biceps brachii[blank_end]. Herniation of the C5 intervertebral disc occurs secondary to the tough, [blank_start]fibrous[blank_end] covering of the intervertebral disc becoming compromised, allowing the [blank_start]inner nucleus pulposus[blank_end] to bulge out and [blank_start]compress[blank_end] the spinal nerve. This characteristically produces the radiating symptoms that we see in this patient. As shown in the figure of the brachial plexus below, the C5 nerve root significantly contributes to the [blank_start]upper trunk[blank_end], which in turn contributes to the [blank_start]lateral[blank_end] and [blank_start]posterior[blank_end] cords for the [blank_start]anterior[blank_end] and [blank_start]posterior[blank_end] division nerve fibers, respectively. Only certain nerves branching from these cords receive input directly from C5, and typically these nerves innervate more proximal muscles. Specifically, C5 makes contributions to the s[blank_start]uprascapular nerve[blank_end], m[blank_start]usculocutaneous nerve[blank_end], a[blank_start]xillary nerve[blank_end], l[blank_start]ower subscapular nerve[blank_end], u[blank_start]pper subscapular nerve[blank_end], l[blank_start]ateral pectoral nerve[blank_end], l[blank_start]ong thoracic nerve[blank_end], and part of the p[blank_start]hrenic nerve[blank_end]. The [blank_start]musculocutaneous[blank_end] nerve provides innervation to major flexors of the elbow including the [blank_start]biceps brachii[blank_end] and [blank_start]brachialis[blank_end]. Loss of sensation in the [blank_start]lateral upper arm[blank_end] is in the region of the C5 dermatome. C5 contributions to the axillary nerve are responsible for sensation in this region.