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9. Shoulder and Elbow MCQs

Practice Set 58 of 197

This practice set contains high-yield board review questions covering key concepts in 9. Shoulder and Elbow. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1141

Topic: 9. Shoulder and Elbow
Late surgical treatment of posttraumatic cubitus varus (gunstock deformity) is usually necessitated by the patient reporting problems related to
. tardy ulnar nerve palsy.
. posterior glenohumeral subluxation.
. posterolateral rotatory subluxation of the elbow.
. poor appearance.
. snapping medial triceps.

Correct Answer & Explanation

. poor appearance.

Explanation

DISCUSSION: Cubitus varus, elbow hyperextension, and internal rotation are all typical components of the gunstock deformity. This deformity results from malunion of a supracondylar fracture of the humerus. All of the problems listed above have been reported as sequelae of a gunstock deformity, although the malunion usually causes no functional limitations. Unacceptable appearance is the most common reason why patients or parents request corrective osteotomy. REFERENCES: O’Driscoll SW, Spinner RJ, McKee MD, et al: Tardy posterolateral rotatory instability of the elbow due to cubitus varus. J Bone Joint Surg Am 2001;83:1358-1369. Gurkan I, Bayrakci K, Tasbas B, et al: Posterior instability of the shoulder after supracondylar fractures recovered with cubitus varus deformity. J Pediatr Orthop 2002;22:198-202. Spinner RJ, O’Driscoll SW, Davids JR, et al: Cubitus varus associated with dislocation of both the medial portion of the triceps and the ulnar nerve. J Hand Surg 1999;24:718-726.

Question 1142

Topic: 9. Shoulder and Elbow

A 51-year-old butcher has an 18-month history of recalcitrant medial elbow pain, which is affecting his occupational demands. He describes the pain as mainly anterior and distal to the medial epicondyle. His symptoms are exacerbated with resisted wrist flexion and forearm pronation. On examination, he is also found to have a positive Tinel's sign at the elbow with weakness of intrinsic strength. He has attempted physical therapy, activity modification, bracing, and anti-inflammatory medication without any significant improvement. Presurgical counseling should include the understanding that

. concomitant ulnar neuropathy is a potential poor prognostic factor.
. a change in occupation will likely be required after surgery.
. weakness in wrist flexion strength will result postoperatively.
. prior corticosteriod injections are a potential poor prognostic factor.

Correct Answer & Explanation

. concomitant ulnar neuropathy is a potential poor prognostic factor.

Explanation

Although less common in comparison with lateral elbow tendinopathy, medial elbow tendinopathy remains a significant cause of elbow disability. Fortunately, most patients can anticipate resolution of symptoms with nonsurgical management. For patients with recalcitrant symptoms, surgical intervention should be discussed as a treatment alternative. The literature reports successful results with surgical intervention via debridementof pathologic tissue, release of the flexor carpi radialis - pronator teres origin, and/or repair of the flexor carpi radialis - pronator teres origin. Several authors have raised concern of the impact of concomitant ulnar neuropathy on results following surgical treatment for medial epicondylitis. Kurvers and Verhaar and Gabel and Morrey, among others, have reported a statistically significant association between concomitant ulnar neuropathy and worse outcomes following surgery. Most patients can anticipate a return to prior activity levels after surgery without any consistently reported loss of flexor/pronator strength. Prior corticosteroid injectionshave not been found to impact results.

Question 1143

Topic: 9. Shoulder and Elbow

A 13-year-old right-hand dominant pitcher was treated for Little League shoulder. What finding increases his risk of recurrence?

. Hyperlaxity
. Rotator cuff weakness
. Increased height
. Glenohumeral internal rotation deficit

Correct Answer & Explanation

. Hyperlaxity

Explanation

Little League shoulder is a physeal injury increasingly seen in young throwers. The primary treatment is refraining from throwing with rehabilitation, followed by a throwing program. The risk of recurrence is approximately 7%. The risk of recurrence is three times higher in athletes with glenohumeral internal rotation deficit. Hyperlaxity,rotator cuff weakness, and increased height have not been shown to correlate with recurrent symptoms.

Question 1144

Topic: 9. Shoulder and Elbow
Figure 40 shows the radiograph of a 16-year-old wrestler who injured his elbow when he was thrown to the mat by his opponent. Closed reduction is readily accomplished, and the elbow seems stable. Management should now consist of application of a splint for
. 2 to 5 days, followed by initiation of assisted motion.
. 14 to 21 days, followed by initiation of assisted motion.
. 4 weeks, followed by active motion.
. 6 weeks, followed by physical therapy.
. 8 weeks, followed by active motion of the elbow.

Correct Answer & Explanation

. 2 to 5 days, followed by initiation of assisted motion.

Explanation

DISCUSSION: Flexion contractures are the most common complication of elbow dislocations. About 15% of patients lose more than 30 degrees of flexion. The risk of contracture is proportional to the duration of immobilization. Elbows should be moved within the first few days after reduction. The splinting is for comfort and protection only while the pain subsides.

Question 1145

Topic: 9. Shoulder and Elbow

An active 65-year-old man has pain in the left shoulder 5 years after undergoing a hemiarthroplasty. He has a remote history of two previous instability operations. Examination reveals that forward elevation is 140 degrees and external rotation is 40 degrees. Serologic studies for infection are negative. AP and axillary radiographs are shown in Figures 7a and 7b. What surgical procedure will provide the most predictable pain relief and function? Review Topic

. Conversion to a reverse total shoulder arthroplasty
. Conversion to a standard total shoulder arthroplasty
. Conversion to a glenohumeral fusion
. Resection arthroplasty
. Biologic resurfacing of the glenoid

Correct Answer & Explanation

. Conversion to a reverse total shoulder arthroplasty

Explanation

The radiographs show glenoid arthrosis, which is common after a hemiarthroplasty. Conversion to a conventional total shoulder arthroplasty with placement of a glenoid component predictably decreases pain and improves function. There is no indication for a reverse total shoulder arthroplasty because the patient has 140 degrees of elevation with an intact rotator cuff. Biologic resurfacing has more unpredictable results and is usually reserved for younger patients in whom a prosthetic glenoid component might not be desired. Both resection arthroplasty and arthrodesis are associated with poor function.

Question 1146

Topic: 9. Shoulder and Elbow

A 52-year-old man sustained the left elbow injury shown in Figure A while playing basketball 2.5 months ago. He underwent the procedure shown in Figure B. Post-operatively he was mobilized in a hinged brace. On examination today, his arc of elbow flexion is 75 degrees with loss of 45 degrees of full extension. His Disabilities of the Arm, Shoulder and Hand (DASH) Outcome Measure score is 45 points. What initial treatment option will likely provide the greatest improvement in this patients DASH score and functional range of motion? Review Topic

. Self-directed exercise therapy
. Supervised exercise therapy
. Supervised exercise therapy with static progressive elbow splinting
. Continuous passive motion device
. Closed manipulation under anesthesia

Correct Answer & Explanation

. Self-directed exercise therapy

Explanation

The clinical presentation is consistent with post-traumatic elbow stiffness following an elbow fracture-dislocation. Supervised exercise therapy with static elbow splinting over a 6 month period has shown to have a significant improvement on DASH scores and functional range of motion (ROM) in patients with post-traumatic elbow stiffness.Post-traumatic elbow stiffness is often difficult to manage. The ultimate goal of treatment is to restore a functional range of elbow motion (30° to 130°). Nonoperative modalities are considered the first-line of treatment. Aggressive physical therapy has traditionally been advocated. However, the use of static progressive elbow splinting with a turnbuckle, alongside aggressive physical therapy, has shown to provide better functional outcomes. Treatment is usually maintained over a period of 6-12 months. Surgery is considered when nonoperative therapy fails.Doornberg et al. looked at a retrospective case series of 29 patients with posttraumatic elbow stiffness. They showed that static progressive splinting can help gain additional motion when standard exercises fail to produce additional improvements.Lindenhovius et al. randomized sixty-six patients with post-traumatic elbow stiffness into static progressive elbow splint therapy or dynamic elbow splinting over a 12 month period. There was no significant difference in outcomes between treatment modalities. ROM increased by 40° vs. 39° at six months, respectively. DASH scores improved from 50 vs 45 at enrollment to 32 vs. 25 at six months, respectively.Figure A shows a posterior elbow dislocation with an associated medial epicondyle fracture. Figure B shows ORIF of the fracture seen in Figure A. Illustration A shows a static progressive turnbuckle elbow splint used for post-traumatic elbow stiffness.Incorrect Answers:

Question 1147

Topic: Elbow & Forearm
A 30-year-old firefighter sustained a longitudinal pulling injury to the arm while attempting to move a heavy object during a fire. Figure 45 shows an MRI scan of the elbow. Initial management should consist of
. rest and a sling followed by a gradual return to activities.
. physical therapy and extension-block bracing.
. repair of the biceps tendon to the brachialis muscle.
. repair of the common flexor origin.
. anatomic repair of the distal biceps tendon.

Correct Answer & Explanation

. anatomic repair of the distal biceps tendon.

Explanation

DISCUSSION: Because the MRI scan shows a complete rupture of the distal biceps tendon, the preferred treatment is anatomic repair of the tendon to the radial tuberosity either with the use of suture anchors or transosseous sutures through a two-incision technique. Several studies have documented superior results with anatomic repair of the distal biceps tendon when compared with results of nonsurgical management or repair of the tendon by attachment to the brachialis muscle. Patients undergoing anatomic repair of the distal biceps tendon through a two-incision technique typically regain a functional range of motion and nearly normal strength.

Question 1148

Topic: 9. Shoulder and Elbow

A 71-year-old woman reports the insidious onset of shoulder pain at night and when moving her shoulder. She cannot raise her arm above shoulder level. Physical therapy has failed to provide pain relief or improve function. An injection relieved her pain in the office, but she could not raise her arm above shoulder level. A radiograph is shown in Figure 21. What surgical procedure will provide the best chance of restoring above shoulder function and pain relief? Review Topic

. Reverse total shoulder arthroplasty
. Hemiarthroplasty of the shoulder
. Arthroscopic biceps tenolysis
. Open subacromial debridement
. Total shoulder arthroplasty

Correct Answer & Explanation

. Reverse total shoulder arthroplasty

Explanation

The radiograph shows complete loss of the acromiohumeral space. The glenohumeral joint space is also severely narrowed, which is consistent with rotator cuff tear arthropathy. In patients who have pain that limits elevation, pain-reducing procedures such as biceps tenolysis, open debridement, or hemiarthroplasty may allow the patient to regain the shoulder function. If the patient cannot elevate the arm after a successful local anesthetic injection, then pain is not the reason for the patient's loss of elevation. In this situation, a reverse total shoulder arthroplasty will most reliably restore function and provide pain relief.

Question 1149

Topic: 9. Shoulder and Elbow

Figures 100a and 100b are the MRI scans of a 45-year-old man who has had elbow and proximal forearm pain for the past 8 months. He can recall no specific trauma and symptoms have not lessened despite his adopting job modifications that limit lifting. He has discomfort with resisted elbow extension and pronation. The biceps tendon can be easily palpated. Treatment should consist of which of the following? Review Topic

. Release of the lacertus and transfer of the biceps to the brachialis tendon
. Open detachment, debridement, and reattachment of the biceps tendon
. Anterior exploration and decompression of the posterior interosseous nerve
. Excision of the anterior intramuscular lipoma
. Endoscopic debridement of the biceps tendon

Correct Answer & Explanation

. Release of the lacertus and transfer of the biceps to the brachialis tendon

Explanation

The MRI findings are most consistent with a partial tear of the biceps tendon. In the setting of prolonged symptoms that are resistant to nonsurgical interventions like rest,physical therapy, and modality, surgical treatment is indicated. Exploration, debridement, and reattachment with one of a variety of techniques are the standards of care. No lipomatous mass is seen on the MRI scan. There is no weakness in finger extension to suggest posterior interosseous nerve palsy. Transfer of the biceps would result in loss of supination strength. Endoscopic biceps tendon surgery is reserved for long-head pathology.

Question 1150

Topic: 9. Shoulder and Elbow

A 13-year-old pitcher reports the immediate onset of medial elbow pain after throwing a pitch. Upon examination, the patient is tender to palpation at the medial epicondyle and has pain and instability with valgus testing of the elbow. What would be the most appropriate initial diagnostic test for this patient?

. MRI arthrogram
. CT scan with 3-dimensional reconstructions
. Plain radiographs of both elbows
. Ultrasonography

Correct Answer & Explanation

. MRI arthrogram

Explanation

The patient has an acute avulsion fracture of the medial epicondyle, which can occur in response to the valgus load placed on the elbow while throwing. Diagnosis is confirmed by radiograph, with comparison views of the uninjured elbow to evaluate for physeal closure versus injury. In older pitchers, the UCL fails rather than the bone of the medial epicondyle. Advanced imaging may be necessary to confirm the diagnosis of an UCLinjury and/or bony injury.

Question 1151

Topic: 9. Shoulder and Elbow

A 51-year-old butcher has an 18-month history of recalcitrant medial elbow pain, which is affecting his occupational demands. He describes the pain as mainly anterior and distal to the medial epicondyle. His symptoms are exacerbated with resisted wrist flexion and forearm pronation. On examination, he is also found to have a positive Tinel’s sign at the elbow with weakness of intrinsic strength. He has attempted physical therapy, activity modification, bracing, and anti-inflammatory medication without any significant improvement. Presurgical counseling should include the understanding that

. concomitant ulnar neuropathy is a potential poor prognostic factor.
. a change in occupation will likely be required after surgery.
. weakness in wrist flexion strength will result postoperatively.
. prior corticosteriod injections are a potential poor prognostic factor.

Correct Answer & Explanation

. concomitant ulnar neuropathy is a potential poor prognostic factor.

Explanation

Although less common in comparison with lateral elbow tendinopathy, medial elbow tendinopathy remains a significant cause of elbow disability. Fortunately, most patients can anticipate resolution of symptoms with nonsurgical management. For patients with recalcitrant symptoms, surgical intervention should be discussed as a treatment alternative. The literature reports successful results with surgical intervention via debridementof pathologic tissue, release of the flexor carpi radialis - pronator teres origin, and/or repair of the flexor carpi radialis - pronator teres origin. Several authors have raised concern of the impact of concomitant ulnar neuropathy on results following surgical treatment for medial epicondylitis. Kurvers and Verhaar and Gabel and Morrey, among others, have reported a statistically significant association between concomitant ulnar neuropathy and worse outcomes following surgery. Most patients can anticipate a return to prior activity levels after surgery without any consistently reported loss of flexor/pronator strength. Prior corticosteroid injectionshave not been found to impact results.

Question 1152

Topic: 9. Shoulder and Elbow
An MRI arthrogram of the elbow is shown in Figure 6. Based on these findings, what is the most likely diagnosis?
. Rupture of the medial collateral ligament
. Rupture of the lateral collateral ligament
. Intra-articular loose body
. Flexor-pronator injury
. Extensor origin avulsion

Correct Answer & Explanation

. Rupture of the medial collateral ligament

Explanation

DISCUSSION: MRI arthrography is the imaging study of choice for evaluation of medial collateral ligament injuries. REFERENCES: Carrino JA, Morrison WB, Zou KH, et al: Noncontrast MR imaging and MR arthrography of the ulnar collateral ligament of the elbow: Prospective evaluation of two-dimensional pulse sequences for detection of complete tears. Skeletal Radiol 2001;30:625-632. Munshi M, Pretterklieber ML, Chung CB, et al: Anterior bundle of ulnar collateral ligament: Evaluation of anatomic relationships by using MR imaging, MR arthrography, and gross anatomic and histologic analysis. Radiology 2004;231:797-803.

Question 1153

Topic: 9. Shoulder and Elbow
When elevating the arm, the ratio of scapulothoracic to glenohumeral motion over the total range of motion is best described as
. 1:2, and in the first 30 degrees the ratio is 1:5.
. 1:2, and in the first 30 degrees the ratio is variable.
. 2:1, and in the first 30 degrees the ratio is variable.
. 2:1, and in the first 30 degrees the ratio is 3:1.
. highly variable and no definitive statement can be made about the ratios.

Correct Answer & Explanation

. 1:2, and in the first 30 degrees the ratio is variable.

Explanation

DISCUSSION: The ratio of scapulothoracic to glenohumeral motion with elevation has been shown to vary depending on what portion of elevation is examined, how much load is on the arm, and the technique used to measure increments of elevation. However, almost every study shows that the ratio of scapulothoracic to glenohumeral motion is 1:2 for the contributions over a full range of elevation to 170 degrees. In the first 30 degrees of elevation, there is significant variability in the ratio, and there may be significant variability up to around 60 degrees. REFERENCES: Inman VT, Saunders JR, Abbott LC: Observations of the function of the shoulder joint. Clin Orthop 1996;330:3-12. Freedman L, Munro RH: Abduction of the arm in the scapular plane: Scapular and glenohumeral movements. J Bone Joint Surg Am 1966;18:1503.

Question 1154

Topic: 9. Shoulder and Elbow

A total shoulder arthroplasty (TSA) would be the most appropriate treatment in which of the following arthritic patients? Review Topic

. A 75-year-old female with a longstanding history of brachial plexus palsy
. A 63-year-old male with a 6 month history of shoulder pain and inability to abduct past 30 degrees
. A 67-year-old female with chronic shoulder pain and evidence of significant proximal migration of the humerus on x-ray
. A 70-year-old female with severe shoulder pain and radiographic evidence of glenoid erosion to the coracoid process
. A 72-year-old male who is 9 months status post right TKA for OA with debilitating shoulder pain and an MRI demonstrating an intact rotator cuff

Correct Answer & Explanation

. A 75-year-old female with a longstanding history of brachial plexus palsy

Explanation

A total shoulder arthroplasty (TSA) is indicated in the 72 year old male with debilitating shoulder pain and an intact rotator cuff on MRI. The other patient scenarios are examples of contraindications for TSA.A TSA involves replacement of the humeral head with a metal head and resurfacing of the glenoid to a cemented all-polyethylene surface. In order to achieve optimal results, patients must be selected carefully. Patients with an irreparable rotator cuff tear, non-functioning deltoid, inadequate glenoid bone stock and brachial plexopathyare poor candidates for TSA.Edwards et al. conducted a multicenter randomized controlled trial to compare TSA versus hemiarthroplasty in patients with primary osteoarthritis of the shoulder. They found that TSA provided better scores for pain, mobility, and activity than hemiarthroplasty at 2 year follow-up.Boileau et al. followed 45 consecutive patients who underwent reverse TSA (rTSA) for cuff tear arthropathy (CTA), post-traumatic arthritis, and failure of revision arthroplasty. After a mean follow-up of 40 months, they found that the reverse prosthesis improved function and was able to restore active elevation in patients with incongruent cuff-deficient shoulders. They also found that the results were less predictable and complication and revision rates were higher in patients undergoing revision surgery as compared to those patients undergoing rTSA for CTA.Illustrations A and B show the preoperative and postoperative x-rays of a patient with characteristic OA of the glenohumeral joint that was treated with TSA.Incorrect Answers:

Question 1155

Topic: 9. Shoulder and Elbow

Figures 28a and 28b are the MR images of a 30-year-old man who has right shoulder pain and difficulty throwing a football. His history includes a shoulder injury from a skiing accident 2 years ago. He has not had a recent shoulder injury. Which shoulder motion is most likely to demonstrate weakness?

. Shoulder abduction
. Shoulder internal rotation
. Shoulder external rotation
. Shoulder adduction

Correct Answer & Explanation

. Shoulder abduction

Explanation

DISCUSSIONThe MR images reveal a large paralabral cyst extending into the spinoglenoid notch. This cyst can be expected to compress the branch of the suprascapular nerve to the infraspinatus. Compression of this branch could lead to weakness in the infraspinatus, which would manifest as external rotation weakness. Shoulder abduction would be unaffected because the axillary and main suprascapular nerves would be intact. Shoulder internal rotation and adduction would be unaffected because the subscapularis and pectoralis would be unaffected.

Question 1156

Topic: 9. Shoulder and Elbow

A 26-year-old mixed martial arts fighter sustains a posterolateral elbow dislocation. The primary stabilizers of the elbow joint are the

. radiocapitellar joint, the posterior band of the medial collateral ligament, and the annular ligament.
. ulnohumeral joint, the anterior band of the medial collateral ligament, and the lateral ulnar collateral ligament.
. radiocapitellar joint, the anterior band of the medial collateral ligament, and the radial collateral ligament.
. ulnohumeral joint, the anterior band of the medial collateral ligament, and the posterior band of the medial collateral ligament.

Correct Answer & Explanation

. radiocapitellar joint, the posterior band of the medial collateral ligament, and the annular ligament.

Explanation

The primary stabilizers of the elbow are the ulnohumeral joint, the lateral collateral ligament (lateral epicondyle to the crista supinatoris), and the anterior band of the medial collateral ligament (anterior inferior medial epicondyle to the sublime tubercle). Secondary stabilizers are the radial head, the common flexor andextensor origins, and the joint capsule. The muscles that cross the elbow joint act as dynamic stabilizers.

Question 1157

Topic: 9. Shoulder and Elbow
A 21-year-old hockey player who has recurrent shoulder subluxations undergoes an anterior capsulorrhaphy under general anesthesia, and an interscalene block is used to relieve postoperative pain. At the 1-week follow-up examination, he reports loss of sensation over the lateral region of the shoulder and is unable to actively contract the deltoid muscle. The remainder of the examination is normal. What is the best course of action at this time?
. Early exploration and possible repair of the axillary nerve
. Urgent electromyography to assess for level of nerve injury
. Continued normal postoperative care and observation of the nerve injury
. Consultation with the anesthesiologist regarding a complication of the interscalene block
. MRI to evaluate for a possible hematoma compressing the neurovascular bundle

Correct Answer & Explanation

. Continued normal postoperative care and observation of the nerve injury

Explanation

DISCUSSION: The patient has an axillary nerve injury, which is relatively uncommon after surgery for instability. This type of injury generally is the result of a stretch injury rather than transection or a hematoma. Therefore, observation is indicated in the early postoperative period. After approximately 6 weeks, electromyography can be used to confirm and document the point of injury. Interscalene blocks can cause prolonged nerve injury but usually are not limited to the axillary nerve.

Question 1158

Topic: 9. Shoulder and Elbow
The medial collateral ligament complex of the elbow originates on what portion of the medial epicondyle?
. Anterior and inferior
. Anterior and superior
. Anterior and central
. Posterior and superior
. Posterior and inferior

Correct Answer & Explanation

. Anterior and inferior

Explanation

DISCUSSION: The medial collateral ligament complex of the elbow consists of three portions: the anterior bundle, the posterior bundle, and a transverse component that has little biomechanic significance. The origin of the ligament is from the central two thirds of the anteroinferior undersurface of the medial epicondyle.

Question 1159

Topic: 9. Shoulder and Elbow

Which of the following preoperative findings is a predictor of poor outcome following arthroscopic debridement for glenohumeral arthritis? Review Topic

. Shoulder stiffness
. History of infection
. Nonconcentric joint space on preoperative radiographs
. Intra-articular loose bodies
. History of instability

Correct Answer & Explanation

. Shoulder stiffness

Explanation

Studies have shown that patients with moderate to severe degenerative changes of the glenohumeral joint fare worse than those with a concentric joint space. Preoperative stiffness and presence of loose bodies have correlated with successful results. A history of infection or instability, in the absence of degenerative changes has not been correlated with poorer outcomes.

Question 1160

Topic: 9. Shoulder and Elbow
A 19-year-old collegiate offensive lineman injures his left elbow in a scrimmage. He reports reaching out with his left arm to prevent the defensive player from getting around him, and, as he grabbed the player, his elbow was forced into extension. He had immediate pain and weakness and heard a “pop.” He has mild swelling in the antecubital fossa and a prominent-appearing biceps muscle belly. His hook test result is abnormal at the elbow. The athlete undergoes repair of the injury, and postsurgical radiographs are shown in Figures 1 and 2. At his first postsurgical visit, he reports no pain but describes weakness in his hand and decreased sensation over his lateral forearm. Upon examination, he has decreased 2-point discrimination over the lateral forearm and an inability to actively extend his thumb and fingers at the metacarpophalangeal joints. He can extend at the finger interphalangeal joints. He can extend his wrist weakly, and it deviates radially as he extends. His distal sensation is intact. Considering his examination findings, which two nerves are injured?
. PIN and radial nerve
. PIN and lateral antebrachial cutaneous nerve (LABCN)
. Median nerve and LABCN
. Radial nerve and LABCN

Correct Answer & Explanation

. PIN and lateral antebrachial cutaneous nerve (LABCN)

Explanation

The most troubling complication for most surgeons is the development of a posterior interosseous nerve (PIN) palsy, which this patient clearly demonstrates in addition to the more common LABCN upon postsurgical examination. Because the LABCN injury is typically a neuropraxia from retraction, a period of observation is indicated. PIN injury can result from excessive traction during surgical exposure or from entrapment by the fixation button.

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