Episode 29 – Peripheral Nerve Injuries

Watch the video version of this Q&A episode on YouTube - https://youtu.be/HvzBa6ZaRsQ

A physical therapist examines a patient following a traumatic crush injury to the forearm. The patient displays a wrist drop deformity and is unable to strongly grasp objects with their hand. Which nerve was MOST likely affected?

1. Median nerve
2. Ulnar nerve
3. Radial nerve
4. Musculocutaneous nerve

Welcome back to the Scorebuilders’ Question and Answer Podcast! This podcast provides members of the Scorebuilders’ team with the opportunity to explore challenging multiple-choice examination questions with students actively preparing for the licensing examination. My name is Scott Giles and I will be your host for today’s journey.

Ready? Let’s go!

A physical therapist examines a patient following a traumatic crush injury to the forearm. The patient displays a wrist drop deformity and is unable to strongly grasp objects with their hand. Which nerve was MOST likely affected?

1. Median nerve
2. Ulnar nerve
3. Radial nerve
4. Musculocutaneous nerve

Wrist Drop Deformity
A wrist drop deformity is characterized by an inability to actively extend the wrist and fingers, resulting in the wrist being flaccidly held in a flexed position. Patients with wrist drop deformity have diminished grip strength since they are unable to actively extend their wrist.

Let’s explore each of the options:

Option 1 - Median nerve
The median nerve innervates the forearm pronators, most of the wrist flexors, first and second lumbricals, and muscles of the thenar eminence. Injury to the median nerve often causes weakness with wrist flexion and forearm pronation.

Option 2 - Ulnar nerve
The ulnar nerve innervates the flexor carpi ulnaris, flexor digitorum profundus, third and fourth lumbricals, muscles of the hypothenar eminence, interossei, and other small muscles within the hand. Injury to the ulnar nerve often causes weakness with wrist flexion and flexion of the ulnar half of the digits, resulting in a claw hand deformity.

Option 3 - Radial nerve
The radial nerve innervates the triceps, brachioradialis, wrist extensors, and finger extensors. Injury to the radial nerve often causes weakness with wrist and finger extension, resulting in a wrist drop deformity…… B-I-N-G-O, B-I-N-G-O, B-I-N-G-O and Bingo was his name-o!

Option 4 - Musculocutaneous nerve
The musculocutaneous nerve innervates the coracobrachialis, biceps brachii, and brachialis. Injury to the musculocutaneous nerve often causes weakness with elbow flexion and forearm supination.

The correct answer is Option 3

Let’s explore the all student data:
32% of students selected Option 1, Median nerve
7% of students selected Option 2, Ulnar nerve
59% of students selected Option 3, Radial nerve, the correct response
2% of students selected Option 4, Musculocutaneous nerve

System Classification
This question is a Neuromuscular and Nervous Systems question which represents approximately 24% of all exam items.

Content Outline Classification
This question is a Physical Therapy Examination question which represents approximately 24% of all exam items.

Level Classification
This question is a Level 2 question since the question requires students to integrate numerous pieces of information or to apply knowledge in a given clinical scenario. Remediation of Level 2 questions occurs by increasing flexibility with academic content and by carefully analyzing decision making processes when answering applied examination questions.

Academic Focus Area
Looking to review related academic content? Check out page 260, 270-271 in PTEXAM: The Complete Study Guide.

Bonus Thought
Our best selling review book PTEXAM: The Complete Study Guide is loaded with features to supercharge your academic review. One of these features is called Consider This. It’s designed to offer candidates valuable application driven information related to selected academic content.

Candidates use this essential information to increase the breadth and depth of their content knowledge.

Why am I sharing this seemingly unrelated piece of information at this point in time? Because, upon discussing peripheral nerve injuries my mind immediately flashed to a related Consider This dealing with peripheral nerve injury etiologies. Let’s explore this related content on page 271 of the review book. 

Upper Extremity – Peripheral Nerve Etiologies
Axillary Nerve

• fracture of the neck of the humerus
• anterior dislocation of the shoulder

Musculocutaneous Nerve

• fracture of the clavicle

Radial Nerve

• compression of the nerve in the radial tunnel
• fracture of the humerus

Median Nerve

• compression in the carpal tunnel
• pronator teres entrapment 

Ulnar Nerve

• compression in the cubital tunnel
• entrapment in Guyon’s canal 

Lower Extremity – Peripheral Nerve Etiologies
Femoral Nerve

• total hip arthroplasty
• displaced acetabular fracture
• anterior dislocation of the femur
• hysterectomy
• appendectomy 

Sciatic Nerve

• blunt force trauma to the buttocks
• total hip arthroplasty
• accidental injection to the nerve

Obturator Nerve

• fixation of a femur fracture
• total hip arthroplasty

Fibular Nerve

• femur, tibia or fibula fracture
• positioning during surgical procedures

Tibial Nerve

• tarsal tunnel entrapment
• popliteal fossa compression

Sural Nerve

• fracture of the calcaneus or lateral malleolus

Thanks for joining us on the Scorebuilders Q and A podcast! See you next week!