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Musculoskeletal Trauma Scored and Recorded Self-Assessment Examination 2015

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Figure 1a Figure 1b

CLINICAL SITUATION FOR QUESTIONS 1 THROUGH 3

Figures 1a and 1b are the radiographs of a 70-year-old retired man who falls

while skiing and injures his right hip. He had no preceding hip pain. After

the fall, he is unable to ambulate and is transferred down the mountain by

the ski patrol and taken to a hospital.

Question 1 of 101

The major blood supply to the femoral head comes from which vessel?

1 - Lateral femoral circumflex artery

2 - Medial femoral circumflex artery

3 - Artery of the ligamentum teres

4 - Inferior gluteal artery

PREFERRED RESPONSE: 2 - Medial femoral circumflex artery

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Question 2 of 101

A formal multidisciplinary team approach to the comanagement of geriatric

patients with hip fracture has been shown to lead to

1 - decreased intraoperative blood loss.

2 - decreased surgical time.

3 - decreased inpatient mortality.

4 - decreased per-patient costs.

PREFERRED RESPONSE: 4 - decreased per-patient costs.

Question 3 of 101

Which factor is a potential disadvantage of total hip arthroplasty compared

to hemiarthroplasty for treatment of displaced femoral neck fracture in older

patients with higher functional demands?

1 - Increased long-term overall costs

2 - Increased risk for dislocation

3 - Increased risk for revision surgery

4 - Decreased postsurgical function

PREFERRED RESPONSE: 2 - Increased risk for dislocation

DISCUSSION

The main source of blood supply to the femoral head is the deep branch of

the medial femoral circumflex artery. The lateral femoral circumflex artery

and artery of the ligamentum teres contribute to a lesser degree, while the

inferior gluteal artery has a minimal contribution. This vascular supply is

compromised with displaced femoral neck fractures and results in a high rate

of osteonecrosis. This is a reason to consider arthroplasty for older patientswho may not be able to tolerate multiple procedures.

Studies evaluating comanagement protocols for the treatment of hip

fractures in patients older than age 60 have demonstrated significant

improvements in mortality, length of stay, complication and readmission

rates, and ambulatory status at time of discharge while decreasing costs.

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Surgical time, blood loss, time to surgery, and inpatient mortality have not

been altered.

Total hip arthroplasty is more frequently recommended for primary

treatment of displaced femoral neck fractures in older, active patients whowould have otherwise been treated with hemiarthroplasty. Risk for

acetabular erosion is alleviated, implant survival is longer, and revision

surgery rates are lower, as are overall long-term costs. Postsurgical function

is not compromised and may actually be better. Dislocation rates are

increased (up to 10%), although these rates may be lessened with recent

improvements in component design that allow for use of larger femoral

heads.

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Musculoskeletal Trauma Scored and Recorded Self-Assessment

Examination 2015

Figure 4a Figure 4b Figure 4c

Question 4 of 101

A 30-year-old man was involved in a high-speed motorcycle collision and

sustained the injury shown in Figure 4a. Hypotension ensued shortly after

arrival in the emergency department. Figure 4b is the initial contrast pelvic

CT image with an unrecognized blush consistent with arterial bleeding.

During surgical repair, the patient was noted to have active bleeding and an

angiogram was obtained (Figure 4c). Which structure is the likely cause of

his bleeding?

1 - Superior gluteal artery2 - Branch of the external iliac artery

3 - Branch of the pudendal artery

4 - Branch of the femoral artery

PREFERRED RESPONSE: 3 - Branch of the pudendal artery

DISCUSSION

Pelvic bleeding occurs predominantly from disruption of the posterior

venous plexus and bleeding from the fractured bone. Occasionally arterial bleeding is seen, with injury to the superior gluteal artery most common.

Anterior pelvic bleeding occurs from injury to the obturator artery

(commonly from a pubic bone fracture laceration) and less frequently from

the pudendal artery near the symphysis. The location of the bleeding on CT

and angiography images does not correspond to the superior gluteal, external

iliac, or femoral arteries.

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Figure 5a Figure 5b

RESPONSES FOR QUESTIONS 5 THROUGH 8

1 - Avascular necrosis, head collapse, and screw penetration

2 - Fixation failure and varus collapse

3 - Humeral stem loosening

4 - Glenoid component loosening

5 - Hardware failure (breakage of plate or screws)

6 - Shoulder dislocation

Please choose from the responses to identify the most likely complication in

each scenario.


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Question 5 of 101

An active 79-year-old woman with the radiograph and intraoperative image

shown in Figures 5a and 5b undergoes open reduction and internal fixation

(ORIF) of her proximal humerus fracture.







PREFERRED RESPONSE: 1 - Avascular necrosis, head collapse, and

screw penetration

Question 6 of 101

A 73-year-old woman sustains a displaced 3-part proximal humerus fracture.

At the time of surgery, she has a massive rotator cuff tear in addition to the

proximal humerus fracture. She is treated with total shoulder arthroplasty

(TSA).


2 - Fixation failure and varus collapse3 - Humeral stem loosening




PREFERRED RESPONSE: 4 - Glenoid component loosening

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Question 7 of 101

An 82-year-old woman with osteoporosis has increased pain and difficulty

using her arm 3 weeks after undergoing ORIF of her 4-part proximal

humerus fracture.







PREFERRED RESPONSE: 2 - Fixation failure and varus collapse

Question 8 of 101

A 79-year-old woman with a massive rotator cuff tear presents to the

emergency department with pain and difficulty moving her arm 7 weeks

after undergoing reverse TSA for a displaced 4-part proximal humerus

fracture.

1 - Avascular necrosis, head collapse, and screw penetration2 - Fixation failure and varus collapse





PREFERRED RESPONSE: 6 - Shoulder dislocation

DISCUSSION

The complication rate is high after surgical treatment of proximal humerus

fractures, particularly in elderly patients with osteoporotic bone. In patients

treated with ORIF, common complications include varus malunion (16%),

avascular necrosis (10%), screw penetration (8%), and infection (4%). In

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cases involving a dislocation of the humeral head, avascular necrosis is more

common. In patients treated with hemiarthroplasty or TSA, complications

include component loosening, infection, and dislocation. TSA is associated

with glenoid loosening in patients with rotator cuff incompetence and should

be avoided in these patients. Reverse TSA is a potential solution for this population. Dislocation and postoperative infection are potential

complications after reverse TSA.

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Examination 2015

Figure 9a Figure 9b

Figure 9c Figure 9d

Question 9 of 101

Figures 9a through 9d are the radiographs of a 21-year-old woman who is

involved in a high-speed motor vehicle collision and sustains an isolated

right closed-foot injury. Before surgery, the patient is advised about the

relatively poor long-term outcomes associated with this injury. What is the

most common reason for functional limitations after surgical treatment in

this scenario?

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1 - Subtalar arthritis

2 - Osteonecrosis

3 - Nonunion

4 - Varus malunion

PREFERRED RESPONSE: 1 - Subtalar arthritis

DISCUSSION

When a displaced talar neck fracture occurs, the rate of osteonecrosis is

high; however, many revascularize the talus without collapse. A nonunion

can occur but is less common than osteonecrosis and arthritis. A varus

malunion can be debilitating and lead to subtalar arthritis. In a fracture with

the talar body dislocated posteromedially (such as in this example)

neurologic deficits in the tibial nerve distribution are common but typicallyimprove with urgent reduction. Studies show that posttraumatic subtalar

arthritis is common after this injury and is the most likely cause of long-term

functional impairment.

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Examination 2015



Figure 10a is the radiograph of a 30-year-old man who sustained an injury in

a motor vehicle collision.

Question 10 of 101

This patient underwent fixation and his radiographs (Figures 10b and 10c) at

6 weeks are shown. What was the failure mode for this implant?

1 - Varus collapse and hardware failure

2 - Screw cut out in the femoral head

3 - Failure of distal screws and loss of fixation

4 - Lack of patient compliance

PREFERRED RESPONSE: 1 - Varus collapse and hardware failure


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Question 11 of 101

The biomechanical reason for implant failure in this case is related to

1 - lack of medial cortical contact secondary to comminution.

2 - lack of friction fit of plate to bone.

3 - varus malreduction of the fracture.

4 - poor bone quality in the femoral head and diaphysis.

PREFERRED RESPONSE: 1 - lack of medial cortical contact secondary

to comminution.

Question 12 of 101

Among the options listed below, what is the best treatment for the

complication shown in Figure 10c?

1 - Removal of hardware and bone grafting

2 - Removal of hardware and total hip arthroplasty (THA)

3 - Removal of hardware and revision using a first-generation femoral nail

4 - Removal of hardware and revision using a second-generation femoral nail

PREFERRED RESPONSE: 4 - Removal of hardware and revision using

a second-generation femoral nail

DISCUSSION

Proximal femur fractures can be treated using a variety of implants including

intramedullary nails, blade plates, and locking plates (now precontoured

proximal femur plates). The comminution and lack of medial cortical

support may predispose these fractures to nonunion.

The recent popularity of locking plates for proximal femur treatment has

increased their use for this fracture; however, a disproportionately high rate

of failure of these plates, including early implant failure with plate and screw

breakage, cut out with varus collapse, and nonunion have been reported.?

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Malreduction predisposes these fractures to failure. The initial postoperative

radiographs do not reveal a varus malreduction because the tip of the greater

trochanter is below the center of the femoral head.

Once failure occurs, the best fixation method among the options detailed isan intramedullary nail (second generation with screws into the femoral head)

and restoration of alignment. THA is usually not recommended for treatment

of subtrochanteric femur fractures in young patients.

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Examination 2015

Question 13 of 101

Which medication or supplement is recommended to promote healing of

atypical subtrochanteric fractures?

1 - Bisphosphonates

2 - Teriparatide

3 - Vitamin D

4 - Glucosamine chondroitin

PREFERRED RESPONSE: 2 - Teriparatide

DISCUSSION

Use of teriparatide in association with fracture fixation promotes healing

because these fractures are associated with delayed healing. The other

responses are not associated with healing of these fractures.

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Examination 2015

Figure 14a Figure 14b

estion 14 of 101

An 18-year-old man was involved in an altercation during which he

sustained the injuries shown in Figures 14a and 14b. His Glasgow Coma

Scale (GCS) score is 11 (a GCS score of 9-12 indicates moderate head

injury). The neurosurgeons elect to not place an intracranial pressure (ICP)

monitor. The patient responds appropriately to stimuli and is

hemodynamically stable. What is the most appropriate initial treatment?

1 - Knee immobilizer

2 - Immediate spanning external fixation

3 - Immediate intramedullary nailing

4 - Immediate plate fixation

PREFERRED RESPONSE: 2 - Immediate spanning external fixation


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DISCUSSION

Although management of femoral shaft fractures in patients with head

injuries remains controversial, most practitioners agree that "damage-control

principles" are appropriate for patients with evolving head injuries. This patient has a subarachnoid hemorrhage and a decreased GCS but is

responding appropriately. The best treatment is a damage-control approach

for the femur that will cause minimal blood loss and allow the brain injury

(and swelling) to equilibrate. External fixation can be performed

expeditiously and with minimal blood loss, which will reduce further injury

to the brain. Special attention should be paid to maintaining cerebral

perfusion pressure higher than 70 mmHg. Admission to the intensive care

unit is recommended for monitoring of this injury. Knee immobilizers are

not tolerated well by young muscular men with femur shaft fractures. A

GCS score of 11 or higher can be observed without ICP monitoring.

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Examination 2015

Figure 15

Question 15 of 101

The most common reason for proximal femur fracture fixation failure

(Figure 15) is secondary to which common deformity?

1 - Varus

2 - Valgus

3 - Malrotation

4 - Shortening

PREFERRED RESPONSE: 1 - Varus

DISCUSSION

Malposition of a proximal lag screw may result in cut-out similar to that

seen with a sliding hip screw. Varus malreduction also can result in implant

failure. Studies have shown no difference in complication or healing rates

when comparing short and long cephallomedullary nails.

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Examination 2015


A 23-year-old man sustains multiple injuries in a high-speed motor vehicle

collision. Among his injuries are a right transverse-posterior wall acetabular

fracture, a left open tibia fracture with compartment syndrome, and a right

calcaneus fracture.

Question 16 of 101

After initial evaluation he is taken to the operating room urgently and

undergoes debridement of his open tibia fracture, 4-compartment

fasciotomy, and intramedullary nailing of the fracture. Negative pressurewound therapy (NPWT) is chosen for the open wound and fasciotomy sites.

NPWT in this scenario will

1 - remove bacteria from the wound and decrease risk for infection.

2 - promote wound contraction, making primary closure less likely.

3 - promote local wound perfusion.

4 - decrease compartment pressures.

PREFERRED RESPONSE: 3 - promote local wound perfusion.

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Question 17 of 101

Nine hours after surgery you are contacted because the patient has continued

tachycardia and ongoing resuscitation needs. The NPWT canister has been

emptied 3 times in the last 8 hours and contains sanguinous fluid. In additionto continued resuscitation, what is the most appropriate next step??

1 - Order the NPWT applied to wall suction to allow less frequent emptying

of the canister.

2 - Clamp off the suction device and return to the operating room for wound

exploration.

3 - Turn the suction down from -125 mm Hg to -50 mm Hg.

4 - Take the patient for angiography and possible embolization.

PREFERRED RESPONSE: 2 - Clamp off the suction device and return tothe operating room for wound exploration.

Question 18 of 101

On postinjury day 3 the patient undergoes open reduction and internal

fixation of his right acetabular fracture via a Kocher-Langenbeck approach.

On postoperative day 5 he is noted to have persistent serous drainage

without any localized signs of infection. Incisional NPWT used in this

setting would likely result in

1. infection.

2. a sealed wound (more rapidly than sealing would occur with a

compressive dressing).

3. hematoma formation.

4. it can electively delay flap coverage for 3 to 4 weeks.

PREFERRED RESPONSE: 2 - a sealed wound (more rapidly than sealing

would occur with a compressive dressing).

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Question 19 of 101

The patient undergoes repeat debridements for the open tibia fracture and

associated compartment syndrome. It becomes apparent that the medial open

fracture wound is not amenable to primary closure. NPWT is useful in thissetting because

1 - it will stabilize the soft-tissue environment while the patient awaits

flap coverage.

2 - it will promote granulation of the wound over the exposed fracture site

to prevent flap coverage.

3 - it will promote fracture healing.

4 - it can electively delay flap coverage for 3 to 4 weeks.

PREFERRED RESPONSE: 1 - it will stabilize the soft-tissue environment

while the patient awaits flap coverage.

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Question 20 of 101

The patient subsequently requires split-thickness skin grafting over his

lateral fasciotomy wound during soft-tissue reconstruction. In this setting,

NPWT

1 - will likely improve incorporation of the graft.

2 - will provide an inconsistent bolster to the graft.

3 - should be used directly over the skin graft.

4 - should be used at the donor site to promote faster healing.

PREFERRED RESPONSE: 1 - will likely improve incorporation of the

graft.

DISCUSSION

NPWT increases wound perfusion. The dressing may help decrease risk for

wound infection, but will not do so by removing bacteria. It also helps to

prevent wound contracture to improve the likelihood of primary wound

closure. NPWT can help to improve tissue edema and will not elevate

compartment pressure.

Hemorrhage is the most common major complication associated with NPWT. This risk is highest when NPWT is used in areas of major vessels

and vessels that have been ligated and for patients undergoing

anticoagulation therapy. Specialized white polyvinyl alcohol sponges are

available to prevent adherence to vessels, exposed nerves, or exposed bone.

NPWT should not be used directly over exposed major vessels. If major

bleeding occurs, a return to the operating room for wound exploration is

recommended.

Incisional NPWT is an effective treatment for persistent serous drainage.

Wounds that drain persistently seal more quickly and pose lower risk for

infection when incisional NPWT is used vs compressive dressings.

Incisional NPWT has also demonstrated benefit when used on high-risk

postsurgical wounds of the tibial plateau, pilon, and calcaneus. It has not

been shown to contribute to increased risk for wound dehiscence or

hematoma.

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NPWT stabilizes the soft-tissue environment and does not necessitate

frequent dressing changes. Despite this benefit, a delay of flap coverage after

NPWT still poses higher risk for infection than early coverage.

Consequently, flaps should not be delayed for long. NPWT promotes the

formation of granulation tissue and can be used over exposed bone, but itwould not be expected to form granulation tissue over an exposed fracture

site or hardware or promote fracture healing.

NPWT provides an excellent bolster for a skin graft and improves skin graft

incorporation. It needs to be applied with nonadherent dressings to prevent

adherence to the skin graft. NPWT is generally not used at skin grafting

donor sites.

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Examination 2015

Question 21 of 101

Preventing "missed" femoral neck fractures associated with ipsilateral

femoral shaft fractures is best achieved with

1 - an examination.

2 - dedicated anteroposterior and lateral hip radiographs.

3 - thin-cut pelvic CT images with coronal and sagittal reconstructions.

4 - MRI.

PREFERRED RESPONSE: 3 - thin-cut pelvic CT images with coronal

and sagittal reconstructions.

DISCUSSION

Ipsilateral femoral neck and shaft fractures occur in up to 6% of femur

fractures. A femoral neck fracture is often vertical and nondisplaced. A high

degree of suspicion is necessary to avoid "missed" femoral neck fractures in

patients with this condition. Although an examination and dedicated hip

radiographs help to avoid missed injuries, a significant decrease in missedinjuries has been described with the use of thin-cut pelvic CT images. In

patients who undergo trauma, a pelvic CT scan is often performed to assess

for associated injuries and is easily reviewed to examine the femoral neck.

Although MRI is advocated to identify isolated occult femoral neck

fractures, CT has been described as the method of choice with which to

identify ipsilateral femoral neck and shaft fractures in the trauma population.

Currently, no literature supports the use of MRI in this population.

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Examination 2015

Figure 22


Figure 22 is the anteroposterior radiograph of a 44-year-old firefighter who

falls from his road bike and sustains a closed midshaft clavicle fracture. He

chooses surgical treatment with open reduction and internal fixation (ORIF).

Question 22 of 101

What is the most common complication of nonsurgical treatment for this

injury?

1 - Anterior chest wall numbness

2 - Symptomatic malunion

3 - Nonunion

4 - Pneumothorax

PREFERRED RESPONSE: 3 - Nonunion


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Question 23 of 101

Which variable is a risk factor for nonunion of displaced clavicle fractures?

1 - Adolescence

2 - Displacement exceeding 100%

3 - Transverse fracture

4 - Male gender

PREFERRED RESPONSE: 2 - Displacement exceeding 100%

Question 24 of 101

The patient decides to undergo surgery with open reduction and plate

fixation. What is the most common reason for revision surgery after plate

fixation of a clavicle fracture?

1 - Supraclavicular nerve entrapment

2 - Symptomatic malunion

3 - Nonunion

4 - Hardware irritation/prominence

PREFERRED RESPONSE: 4 - Hardware irritation/prominence

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Question 25 of 101

Which structure(s) is/are most at risk with surgical treatment of displacedclavicle fractures with ORIF?

1 - Subclavian artery

2 - Subclavian vein

3 - Brachial plexus

4 - Supraclavicular nerves

PREFERRED RESPONSE: 4 - Supraclavicular nerves

DISCUSSION

Complications associated with nonsurgical treatment of displaced midshaft

clavicle fractures are uncommon. Although intrathoracic and local vascular

complications have been reported with clavicle fracture, subclavian artery

aneurysm and pneumothorax are rare. Malunion to some degree is inevitable

with nonsurgical treatment of displaced clavicle fractures, but only about 9%

of patients develop symptomatic malunion. Nonunion occurs in about 15%

of patients.

Previously identified risk factors for nonunion of clavicle fractures include

female gender, displacement exceeding 100%, comminution, and advanced

age. Research demonstrates the strongest risk factors are smoking,

comminution, and fracture displacement. Rate of nonunion in 1 study was

approximately 13%. Murray and associates showed that by estimating the

risk of nonunion using their model and operating only on fractures with at

least a 40% chance of nonunion, they would only need to operate on 1.7

patients to prevent 1 nonunion (decreased from 7.5 procedures per nonunion

if operating on all displaced midshaft fractures). This data could potentially

be used to limit unnecessary procedures and decrease costs associated with

treatment of clavicle fractures.

Hardware removal is the most common reason for revision surgery.

Symptomatic malunion and supraclavicular nerve entrapment are rare after

surgery. Nonunion is uncommon (in fewer than 2% of cases). The main

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reason for revision surgery is hardware removal to address local

irritation/prominent hardware or infection.

An anatomical study demonstrated that in 97% of clavicles, 2 to 3 branches

of the supraclavicular nerve were crossing the clavicle with wide locationvariability in the zone in which most clavicle fractures occur and surgery

would take place. The subclavian vein and artery and brachial are rarely

injured, although there are case reports of injury to all either by the displaced

fracture fragments or errant hardware.

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Examination 2015

Figure 26a Figure 26b Figure 26c Figure 27

CLINICAL SITUATION FOR QUESTIONS 26 AND 27

Figures 26a through 26c are the radiographs of a 50-year-old athlete who

sustained an injury to his right foot; the foot was plantar flexed and another player landed on the posterior aspect of his heel. After sustaining the injury

he was unable to bear weight, and 3 days later he was seen in the emergency

department because of persistent pain and tenderness over his midfoot.

Question 26 of 101

CT images reveal a purely ligamentous injury. Which treatment produces the

best results?

1 - Open reduction and internal fixation (ORIF) of the fracture2 - Early fusion of the first and second tarsometatarsal joints

3 - Nonweight-bearing activity for 6 weeks

4 - Weight bearing with a camwalker

PREFERRED RESPONSE: 2 - Early fusion of the first and second

tarsometatarsal joints

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Question 27 of 101

ORIF of the injury was chosen (as illustrated in Figure 27). Long-term

results may include

1 - improved American Orthopaedic Foot & Ankle Society (AOFAS) scores

as compared to scores obtained following fusion.

2 - pes planovalgus.

3 - persistent pain and arthritis.

4 - hindfoot pain.

PREFERRED RESPONSE: 3 - persistent pain and arthritis.

DISCUSSION

The injury mechanism describes axial loading to a plantar-flexed foot and is

classic for Lisfranc injury. If the initial films are not diagnostic as in this

case, weight-bearing films are a reasonable next step. Radiographic

widening of 2 mm or more between the second metatarsal base and medial

cuneiform (as compared to the other side) is diagnostic; occasionally, a

"fleck" sign (a small bony fragment noted in the Lisfranc joint) may indicate

an avulsion fracture. Clinical signs include plantar ecchymosis, tenderness

over the Lisfranc joint, and an inability to bear weight. Anatomic ORIF orfusion are the options for treatment, and results for ligamentous injuries are

better when fusion is performed. Better AOFAS scores have been

demonstrated with fusion, and a higher incidence of pain and arthritis have

been noted with fixation. No significant difference has been seen regarding

hardware failure, and hindfoot pain is not a consideration.

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Examination 2015

Question 28 of 101

A 67-year-old right-hand-dominant man who is an avid golfer sustains an

unstable distal radius fracture on his right side. He undergoes a closed

reduction with acceptable alignment. After discussing surgical vs

nonsurgical management and recovery, the patient decides to have surgery.

He made this decision because he was told that his

1 - functional outcome at 1 year would be worse with nonsurgical

management.

2 - radiographs will look better after surgery.

3 - grip strength will be better with surgical intervention.4 - overall long-term outcome can improve with formal occupational therapy

after surgery.

PREFERRED RESPONSE: 3 - grip strength will be better with surgical

intervention.

DISCUSSION

The optimal treatment of distal radius fractures in elderly patients remains

controversial. Both surgical and nonsurgical management of distal radius

fractures produce identical functional outcomes at 1 year. Although many

patients have better motion early with surgery, only grip strength has been

shown to be significantly better at 1 year. Radiographic outcome has not

been correlated with functional outcome, and complications are also

equivalent. Independent prescribed therapy has been better than formal

occupational therapy for range of motion, but no differences in functional

outcome were seen as assessed by Disabilities of the Arm, Shoulder and

Hand scores.

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Figure 29

Question 29 of 101

Figure 29 is the anteroposterior radiograph of a 60-year-old man who is

involved in a motorcycle collision and airlifted to a trauma center. The

patient is hypotensive and tachycardic upon arrival and fluid resuscitation is

underway. He has a scrotal hematoma and his bilateral lower extremities are

externally rotated. What is the first step in managing this scenario?

1 - Obtain CT images of the pelvis

2 - Angiography

3 - Place external fixation

4 - Apply a pelvic binder

PREFERRED RESPONSE: 4 - Apply a pelvic binder

DISCUSSION

A pelvic binder or sheet can be applied right away to reduce and stabilize the pelvis more quickly than is possible with an external fixator. Pelvic ring

injuries are associated with a high incidence of mortality mainly because of

the potential for retroperitoneal hemorrhage. A pelvic circumferential

compression device allows for force-controlled circumferential compression.

It can effectively reduce pelvic ring injuries and poses minimal risk for

overcompression and complications. Reduction of external rotation injuries


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is comparable to definitive fixation reduction and does not cause significant

overcompression of internal rotation injuries. Angiography is used to assess

persistent hemodynamic instability after initial stabilization of the pelvic

ring with the binder or sheet. CT images should be obtained after initial

resuscitation.

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Examination 2015

Question 30 of 101

An 82-year-old woman falls from a standing height and sustains a proximal

humerus fracture. Which factor is the best predictor of ischemia of the

humeral head?

1 - Fracture pattern involving 4 parts

2 - Humeral head angulation exceeding 45 degrees

3 - Posteromedial calcar length of less than 8 mm attached to the humeral

head

4 - Glenohumeral dislocation

PREFERRED RESPONSE: 3 - Posteromedial calcar length of less than 8

mm attached to the humeral head

DISCUSSION

Humeral head ischemia that occurs following proximal humerus fractures is

closely associated with the amount of posteromedial calcar bone attached to

the humeral head. Fractures that exit within 8 mm of the posteromedial edgeof the head more commonly are ischemic (compared to fractures that have

more than 8 mm of posteromedial calcar still attached). Four-part fracture

patterns are a moderate predictor of humeral head ischemia, with an

accuracy of 0.67. Angulation of the humeral head exceeding 45 degrees also

is a moderate predictor of humeral head perfusion, with an accuracy of 0.62.

Glenohumeral dislocation is a poor predictor of humeral head ischemia.

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Examination 2015

Question 31 of 101

An atypical bisphosphonate-associated femur fracture would show which

features?

1. Lateral cortical thickening at the subtrochanteric region with a

fracture line extending to the medial side.

2. Lateral cortical thickening at the supracondylar region with a fracture

line extending to the medial side.

3. Stress fracture of the femoral neck.

4. Reverse obliquity intertrochanteric femur fracture.

PREFERRED RESPONSE: 1 - Lateral cortical thickening at the

subtrochanteric region with a fracture line extending to the medial side

DISCUSSION

Patients sustaining atypical femur fractures have classic radiographic

findings including medial beaking, lateral cortical thickening, and transverse

or short oblique proximal (subtrochanteric) femur fracture.

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1. Open reduction and internal fixation with a proximal humerus locking

plate.

2. Nonsurgical treatment.

3. Arthroplasty

Match the appropriate treatment listed with the clinical scenario described.

Question 32 of 101

A 78-year-old right-hand-dominant woman who lives independently falls

down the stairs at her home. She has an isolated injury to her left shoulderand a history of hypertension and atrial fibrillation. Imaging reveals a

proximal humerus fracture with a displaced fracture splitting the humeral

head and a large displaced greater tuberosity fragment.

1. Open reduction and internal fixation with a proximal humerus

locking plate.

2. Nonsurgical treatment.

3. Arthroplasty

PREFERRED RESPONSE: 3 - Arthroplasty

Question 33 of 101

A 72-year-old right-hand-dominant woman sustains an isolated injury to her

right shoulder after a fall while walking her dog. She lives independently

and has a history of hypercholesterolemia. Her activities include walking,

aerobics, and yoga. Imaging reveals a proximal humerus fracture with

fracture of the surgical neck that is displaced 2 cm.

1 - Open reduction and internal fixation with a proximal humerus locking plate2 - Nonsurgical treatment

3 - Arthroplasty

PREFERRED RESPONSE: 1 - Open reduction and internal fixation with a

proximal humerus locking plate

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Question 34 of 101

An 81-year-old left-hand-dominant woman who lives independently has a

slip-and-fall accident while shopping. She has an isolated injury to her left

shoulder and a history of coronary artery disease and hypertension. Imagingreveals a proximal humerus fracture with 50% translation at the surgical

neck.

1 - Open reduction and internal fixation with a proximal humerus locking

plate

2 - Nonsurgical treatment

3 - Arthroplasty

PREFERRED RESPONSE: 2 - Nonsurgical treatment

Question 35 of 101

An 80-year-old right-hand-dominant woman who lives independently falls

in her home. She has an isolated injury to her right shoulder and a history of

a total hip replacement for a femoral neck fracture (3 years prior). She has

had a prior failed rotator cuff repair. Her daily activities include volunteering

at her church and caring for her grandchildren. Imaging reveals a displaced

proximal humerus fracture with comminution and 50% translation withvarus angulation at the surgical neck. She also has displacement and

comminution of the greater tuberosity.

1 - Open reduction and internal fixation with a proximal humerus locking

plate


3 - Arthroplasty

PREFERRED RESPONSE: 3 - Arthroplasty

DISCUSSION

Treatment of proximal humerus fractures in elderly patients is controversial

and requires consideration of the patient's functional demands and fracture

characteristics. The majority of fractures can be treated nonsurgically.

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Nonsurgically treated fractures should be briefly immobilized before

beginning pendulum exercises and elbow range of motion.

Some patients are surgical candidates based upon functional demands and

degree of displacement. Fractures that are reconstructible can besuccessfully treated with reduction and fixation or intramedullary nailing. If

there is tuberosity involvement, plate fixation is preferable to intramedullary

nailing. Factors that make fixation challenging and vulnerable to failure

include poor bone quality and significant varus alignment. Relative

indications for arthroplasty, especially in patients with poor bone quality,

include initial varus alignment, head-splitting fractures, and 4-part fractures.

Traditionally, hemiarthroplasty has produced reliable pain relief and

unreliable function because of the difficulty associated with reconstruction

of the tuberosities to restore rotator cuff function. Reverse shoulder

arthroplasty may be a better option for patients who are arthroplastycandidates who have tuberosities that will not be reliably reconstructed or

for those who have a pre-existing rotator cuff deficiency.

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Examination 2015

Figure 36

Question 36 of 101

Two femoral shaft fractures are shown in Figure 36. Each is fixed identically

with the same intramedullary nail and interlocking screws. The fracture gapstrain is higher in

1 - A.

2 - B.

3 - neither; the strain is identical in A and B.

4 - neither; the strain is dependent on femur length.

PREFERRED RESPONSE: 1 - A.

DISCUSSION

Fracture gap strain is defined as deformation of granulation tissue within the

fracture gap when a given force is applied. Normal strain is the change in

length (? l) divided by the original length (l) when a given load is applied.


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The amount of deformation that a tissue can tolerate while functioning varies

greatly. Intact bone has a normal strain tolerance of 2% (before it fractures),

whereas granulation tissue has a strain tolerance of 100%. Bony bridging

between the distal and proximal callus can only occur when local strain (ie,

deformation) is less severe than the forming bone can tolerate. Therefore,treatment of fractures must optimize the strain environment to enable

healing.

Comminution, as shown in B, results in distribution of the motion between

multiple fracture fragments. As a result, each fracture gap experiences less

motion and strain is decreased. In simple fracture patterns as shown in A,

small amounts of motion or even a small fracture gap results in a high-strain

environment. Strain is dependent upon the length of the fracture gap but not

on the length of the bone.

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Figure 37

Question 37 of 101

Figure 37 is the radiograph of a 31-year-old woman who has acute right hip

pain after a fall. The treatment variables that are most important to maximize

clinical outcome are

1 - timing of fixation and capsulotomy.

2 - timing of fixation and choice of implants.3 - quality of reduction and fixation.

4 - choice of open reduction and capsulotomy.

PREFERRED RESPONSE: 3 - quality of reduction and fixation.

DISCUSSION

Femoral neck fractures are potentially devastating injuries for physiologically

young patients. Studies have demonstrated that the timing of fixation is not as

critical to outcome or to avascular necrosis prevention as other factors.

Experimental evidence supports capsulotomy to improve femoral head blood flow.

Relative biomechanical advantages are associated with different implants;

however, a surgeon can obtain good fixation with a variety of devices. For a

physiologically young patient, an open reduction is often required to obtain the

desired anatomic reduction; however, if the desired result can be achieved with

closed reduction, open reduction is not required. Anatomic reduction of the

fracture and biomechanically sound fixation consistently yield optimal results.


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Examination 2015


Question 38 of 101

A 55-year-old man fell off a bicycle and sustained the injury shown in

Figures 38a through 38c. Which fracture pattern best describes this injury?

1 - Anterior column posterior hemitransverse2 - Anterior column

3 - Anterior wall

4 - Associated both-column

PREFERRED RESPONSE: 2 - Anterior column

DISCUSSION

This is an anterior column fracture with dome impaction. The obturator

oblique view and both CT images show disruption of the anterior column.

Both CT images also reveal an intact posterior column, which eliminates

anterior column posterior hemitransverse and associated both-column

fracture types as correct responses. An anterior wall fracture would not

extend up into the ilium.


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Figure 39


Figure 39 is the standing radiograph of a 20-year-old college student who

injures his foot while playing intramural football. Initial radiograph findings

are reportedly normal, but 1 week after injury he still cannot bear weight.

You see him in the clinic and note swelling of his foot and plantar

ecchymosis.

Question 39 of 101

What is the strongest structure supporting the tarsometatarsal (TMT)

complex of the midfoot?

1 - Oblique interosseous ligament

2 - Deep band of the plantar oblique ligament

3 - Dorsal oblique ligament

4 - First TMT ligament

PREFERRED RESPONSE: 1 - Oblique interosseous ligament


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Question 40 of 101

What radiographic finding is consistent with a Lisfranc injury?

1 - Dorsal and plantar aspects of the metatarsals (MTs) correspond with thecuneiforms and cuboid on the lateral view.

2 - The medial border of the second MT is aligned with the medial border of

the middle cuneiform on the anteroposterior view.

3 - The medial border of the fourth MT is aligned with the medial border of

the cuboid on the oblique view.

4 - Diastasis between the first and second MT is 3.5 mm.

PREFERRED RESPONSE: 4 - Diastasis between the first and second MT

is 3.5 mm.

Question 41 of 101

Primary arthrodesis is associated with which outcome when compared to

outcomes associated with open reduction and internal fixation (ORIF)

without arthrodesis?

1 - Decreased secondary surgeries

2 - Increased pain3 - Increased risk for infection

4 - Poorer function at 2-year follow-up

PREFERRED RESPONSE: 1 - Decreased secondary surgeries

DISCUSSION

There are longitudinal, oblique, and transverse ligaments at the TMTcomplex that are further defined by their location as dorsal, interosseous, or

plantar. There are 3 ligaments between the medial cuneiform and the second

MT base, the most important of which is the oblique interosseous ligament,

which is also known as the Lisfranc ligament. Plantar and dorsal oblique

ligaments contribute to stability to a lesser degree. The dorsal ligaments are

weakest and may be the first to fail in a Lisfranc injury.

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The second MT base should be aligned with the middle cuneiform at the

medial borders, and the fourth MT base should be aligned with the cuboid at

the medial borders on the oblique view. The dorsal and plantar aspects of the

MTs should align with the cuneiforms/cuboid on the lateral view. Any

malalignment should raise the suspicion of a Lisfranc injury. Diastasis between the second MT and the first MT/medial cuneiform complex of more

than 2 mm indicates injury, as does TMT joint subluxation of 2 mm more

than seen on the uninjured contralateral side. Diastasis between the first and

second MT up to 2.7 mm can be normal. Another radiographic sign of injury

includes avulsion fracture of the second MT base or medial cuneiform.

Additional imaging studies that may be helpful in identifying subtle injuries

include weight-bearing radiographs and CT or MRI images.

Two prospective randomized studies compared primary fusion with ORIF

Lisfranc injuries. The second study included fracture-dislocations, whereasthe first looked at primarily ligamentous injuries. Results conflicted with an

earlier study demonstrating improved results (less pain, better function) with

primary fusion, while a more recent study showed no difference. Neither

study showed worse results with primary fusion, and the rate of secondary

surgery was more common in the ORIF group (salvage arthrodesis or

hardware removal).

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Question 42 of 101

Which ligament attaches to the bony fragment identified by the CT image

arrows in Figures 42a and 42b?

1 - Posterior tibiotalar ligament

2 - Posterior-inferior tibiofibular ligament (PITFL)

3 - Interosseous ligament (IOL)

4 - Anterior-inferior tibiofibular ligament (AITFL) ?

PREFERRED RESPONSE: 2 - Posterior-inferior tibiofibular ligament

(PITFL)

DISCUSSION

The distal tibiofibular syndesmosis is a ligamentous complex that consists of the

AITFL, PITFL, intertransverse ligament (ITL), and IOL. The PITFL originates on

the posterior inferior aspect of the tibia (Volkmann tubercle) and inserts on the

lateral malleolus. The AITFL originates on the anterolateral aspect of the tibia

(Chaput tubercle) and inserts on the distal anterior aspect of the fibula (Wagstaffe

tubercle). The ITL is a group of fibers running transversely just inferior to the

PITFL. As a group, these structures maintain the appropriate tibial plafond and

talus relationship throughout physiologic range of motion.


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A 46-year-old healthy right-hand-dominant man falls and sustains the injury

shown in Figures 43a and 43b.

Question 43 of 101

What is the treatment of choice?


2 - Open reduction and internal fixation (ORIF)3 - Hemiarthroplasty

4 - Total shoulder arthroplasty (TSA)

PREFERRED RESPONSE: 2 - Open reduction and internal fixation

(ORIF)


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Question 44 of 101

If the patient undergoes ORIF, which strategy is essential to minimize

fixation failure?

1 - Use of all locking screws

2 - Use of cancellous allograft for defect management

3 - Achieving at least 3 points of fixation in the humeral head

4 - Restoration of medial cortical support

PREFERRED RESPONSE: 4 - Restoration of medial cortical support

Question 45 of 101

A similar fracture is treated with ORIF and a locking plate for an active 73-

year-old right-hand-dominant woman. Which patient characteristic is most

likely to contribute to possible fixation failure?

1 - Hand dominance

2 - Level of activity

3 - Osteoporosis

4 - Rotator cuff incompetence

PREFERRED RESPONSE: 3 - Osteoporosis

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Question 46 of 101

The 73-year-old patient undergoes shoulder hemiarthroplasty. What is a risk

factor for a poor outcome?

1 - Tuberosity nonunion

2 - Hand dominance

3 - Female gender

4 - BMI higher than 30

PREFERRED RESPONSE: 1 - Tuberosity nonunion

DISCUSSION

Surgical treatment is favored for young, active patients with displaced

proximal humerus fractures. Nonsurgical treatment is favored to treat

fractures with minimal displacement among low-demand elderly patients.

When ORIF is used, a number of strategies are employed to prevent failure,

including restoration of medial cortical support (medial calcar),

incorporation of the rotator cuff into the construct, and placement of screws

of adequate length to gain purchase in the subchondral bone of the humeral

head. Intramedullary allograft is not routinely required but is useful when

dealing with osteoporotic bone. Cancellous allograft has not been shown to prevent failure. Varus collapse and failure of fixation are more prevalent in

patients with osteoporotic bone, and, in these cases, strategies for

supplemental fixation are advisable. In cases of severe osteoporosis,

comminution, or poor bone quality, shoulder arthroplasty may be a better

choice. Without a functioning rotator cuff, as would happen with a

tuberosity nonunion, outcomes after shoulder hemiarthroplasty and TSA are

poor.

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50


Examination 2015



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1 - Stress distribution

2 - Stress concentration

For each pattern detailed or depicted, select the appropriate condition.

Question 47 of 101

A simple fracture pattern that is nonanatomically reduced with a 3-mm gap

and treated with an 8-hole locking plate with 4 bicortical locking screws

placed on each side of the fracture



PREFERRED RESPONSE: 2 - Stress concentration

Question 48 of 101

A multifragmentary fracture pattern that is bridge plated to restore length

and alignment and treated with a 12-hole locking plate with 4 bicortical

locking screws placed on each side of the fracture



PREFERRED RESPONSE: 1 - Stress distribution

Question 49 of 101

Figures 49a through 49c



PREFERRED RESPONSE: 2 - Stress concentration

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Question 50 of 101

Figures 50a and 50b

1 - Stress distribution2 - Stress concentration

PREFERRED RESPONSE: 1 - Stress distribution

Figure 50c Figure 50d

DISCUSSION

When comparing stress distribution and stress concentration, the focus is

primarily on the implant. Stress is equal to force divided by the area over

which that force is distributed. When the area is small, concentration ofstress occurs. When the area is large, distribution of stress occurs. The

practical importance is most easily understood via an analogy (Figures 50c

and 50d). Consider a ruler. If the goal were to break the ruler, placing your

thumbs close together would be a logical choice. This hand position

concentrates the forces over a small area (stress concentration). Now

imagine that the ruler is a bone and your thumbs are screws placed on each

side of a fracture. If a bending load is applied, the same small area of the

plate is cycled. Metal can sustain a limited number of cycles before fatigue

failure occurs. If the bone does not heal before this time, construct failure

ensues. In a scenario in which prolonged healing times are expected, leaving

a larger segment of the plate unsupported (ie, moving the center screws

further away from each other) would distribute implant stress. This must be

balanced with the goal of stability and the basic science of bone healing.

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Examination 2015

Figure 51a Figure 51b Figure 52a

Figure 52b Figure 52c Figure 52d


Figures 51a and 51b are the radiographs of a 55-year-old man who was

involved in a motor vehicle collision. The patient has pain and deformity of

his right knee. Examination reveals crepitus and swelling about the knee

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54

with gross motion of the distal femur. There is an 8-cm lateral open wound

with exposed bone and gross contamination.

Question 51 of 101

Immediate surgical treatment should consist of irrigation and debridement of

the fracture and

1 - bridging external fixation.

2 - a retrograde intramedullary nail.

3 - a tibial traction pin.

4 - open reduction and internal fixation (ORIF) with plate fixation.

PREFERRED RESPONSE: 1 - bridging external fixation.

Question 52 of 101

The patient undergoes ORIF as shown in Figures 52a and 52b. Three months

later, he develops a deformity and pain. Radiographs are shown in Figures

52c and 52d. Early hardware failure in the management of distal femur

fractures has been linked to

1 - the use of nonlocking screws in the proximal fragment.

2 - the length of the plate used.

3 - distal placement of the plate.

4 - comminution of the fracture.

PREFERRED RESPONSE: 2 - the length of the plate used.

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Question 53 of 101

When applying a locking plate to the lateral aspect of the distal femur,

medial translation of the distal femur occurs with respect to the diaphysis

("golf-club deformity"). This deformity was created by

1 - placement of the plate too posterior.

2 - placement of the plate too proximal.

3 - placement of the plate too anteriorly on the shaft.

4 - placement of the plate too anteriorly on the condyles.

PREFERRED RESPONSE: 1 - placement of the plate too posterior.

DISCUSSION

This patient should undergo immediate irrigation and debridement of the

fracture. Secondary to gross contamination, there is concern for initial

definitive treatment. ?

Because of the contamination, temporary stabilization will allow for better

soft-tissue management and a second look prior to definitive internal

fixation. Tibial traction pin placement for skeletal traction is less than ideal

because it confines patients to bed rest. With external fixation, a patient canmobilize.

Obtaining CT images prior to ORIF will aid in preoperative planning.

Locked plating of supracondylar distal femur fractures has not been without

complications. In a large study of patients undergoing surgical fixation, it

was found that a key failure factor was plate length. A plate longer than 9

holes (shaft) that allows for at least 8 holes proximal to the fracture is ideal.

Other risk factors that led to implant failure in this study were obesity, open

fractures, smoking, and younger age. There has not been an association with

early failure using nonlocked screws or the degree of comminution. Both

may be factors in long-term failure if there is delayed healing or nonunion

development. ?

The golf-club deformity has been a long-standing problem in the

management of distal femur fractures when a plate is applied too posteriorly.

This was true when 95-degree dynamic condylar plates or blade plates were

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used, and this still holds true for locking plates. Distal placement of the plate

also leads to this deformity because in both situations medialization of the

condyles occurs. Placing the plate too anterior on the shaft can lead to

compromised fixation and early failure, whereas placement anterior on the

condyles can lead to hardware pain or intra-articular screw penetration intothe patella-femoral joint. Proximal placement of the plate would not result in

the deformity and is not a common problem because of the contour of the

plate. If the plate were applied too proximal, the condyles would be

lateralized and/or insufficient points of fixation could occur.

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Question 54 of 101

A 53-year-old man is involved in a motor vehicle collision and sustains the

closed distal femur fracture seen in Figures 54a and 54b. A precontoured

distal femoral locking plate is selected for fixation. A locking construct

should be used to

1 - make the construct as rigid as possible and minimize strain to promote

primary bone healing.

2 - make the construct as rigid as possible and provide a high-strain

environment to promote primary bone healing.

3 - provide a fixed-angle construct and bridge the area of comminution to

minimize strain and promote secondary bone healing.

4 - provide a fixed-angle construct and bridge the area of comminution to

provide a high-strain environment and promote secondary bone healing.

PREFERRED RESPONSE: 3 - provide a fixed-angle construct and bridge

the area of comminution to minimize strain and promote secondary bone

healing.


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DISCUSSION

This patient has a comminuted distal femur fracture. A fixed-angle device

such as a locking plate is preferred to confer angular stability to the construct

and prevent varus collapse. The strategy to promote union of the fracture isto provide a low-strain environment to allow bone healing. Strain is

determined by the amount of motion over the length of a fracture. In the case

of a noncomminuted fracture, the fracture surfaces can be compressed and

rigid fixation applied to abolish strain and promote primary bone healing

without callus. In the case of a comminuted fracture, the preferred fixation

strategy focuses on distributing motion along the length of the fracture to

provide a low-strain environment that will promote secondary bone healing

and callus formation.

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Examination 2015

Question 55 of 101

An 83-year-old right-hand-dominant woman sustains a displaced right extra-

articular distal radius fracture and is treated with closed reduction and

casting. At her 4-week follow-up visit, radiographs demonstrate a volar tilt

of -5 degrees and 4 mm of positive ulnar variance. Which treatment is

recommended?

1 - No additional reduction and continued treatment in the cast

2 - Repeat closed reduction and cast application

3 - Closed reduction and percutaneous skeletal fixation

4 - Open reduction and internal fixation

PREFERRED RESPONSE: 1 - No additional reduction and continued

treatment in the cast

DISCUSSION

Studies demonstrate that surgical treatment of distal radius fractures in

elderly people does not result in improved outcomes. Although nonsurgicaltreatment resulted in worse radiographic findings for this patient, these

findings did not translate into worse functional outcomes.

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Examination 2015

Figure 56

Question 56 of 101

Figure 56 is the radiograph of a 62-year-old noninsulin-dependent woman

with diabetes who twisted her ankle while walking and felt a pop. At the

emergency department she describes heel pain. What is the best course of

action?

1 - Protected weight-bearing activity for 6 weeks

2 - Closed reduction and cast application

3 - Urgent open reduction and internal fixation

4 - Excision of the calcaneal tuberosity

PREFERRED RESPONSE: 3 - Urgent open reduction and internal fixation

DISCUSSION

The radiograph reveals a displaced calcaneal tuberosity fracture.

Displacement of a large tuberosity fragment necessitates urgent fracture

reduction and stabilization. Delayed reduction results in compromise of the

skin and soft tissues at the posterior heel. This injury occurs frequently in

patients with diabetes. Protected weight-bearing activity does not address thedisplaced fragment or the threatened skin. Closed reduction, if possible, will

not maintain the tuberosity fragment in a reduced position and will likely

result in redisplacement. The fragment is large enough that it may be fixed

and not excised. The Achilles tendon inserts on the displaced tuberosity

fragment, so tuberosity reduction and fixation is necessary to achieve proper

Achilles function.


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Examination 2015


1 - High strain

2 - Low strain

For each fracture detailed, select the appropriate description.

Question 57 of 101

A simple fracture pattern that is anatomically reduced and compressed and

treated with an 8-hole conventional plate with 4 bicortical conventional

screws placed on each side of the fracture

1 - High strain

2 - Low strain

PREFERRED RESPONSE: 2 - Low strain

Question 58 of 101

A multifragmentary fracture pattern that is bridge plated, restoring length

and alignment, and treated with a 12-hole locking plate with 4 bicortical

locking screws placed on each side of the fracture

1 - High strain

2 - Low strain

PREFERRED RESPONSE: 2 - Low strain

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Question 59 of 101

A transverse humeral shaft fracture that occurs between a stiff arthritic

shoulder joint; a stiff, arthritic elbow joint is treated nonsurgically in a

hanging-arm cast

1 - High strain

2 - Low strain

PREFERRED RESPONSE: 1 - High strain

DISCUSSION

In 1977, Perren and Cordey penned a German manuscript that first described

an interpretation of mechanical influences on tissue differentiation. This

became known as the Strain Theory of Perren. In 1980, a second manuscript

by the same authors was published in English. Within this manuscript,

Perren wrote, "These thoughts about the mechanical influences on tissue

differentiation are not intended as conclusive evidence since precise data are

still not available, but we hope that they will stimulate thought and provide a

basis for discussion." More than 30 years later, these thoughts continue to

stimulate discussion and research on cell mechanotransduction. This theory

is still being manipulated in surgical theatres all around the world in anattempt to more consistently achieve fracture healing. Strain is a magnitude

of deformation. As typically defined, it is the change in dimension of a

deformed object during loading divided by its original dimension. This is

difficult to work with intraoperatively. The fraction below illustrates a

simpler way to regard this concept:

Strain = Magnitude of displacement between fragments during loading /

Total resting distance between fragments after stabilization

By remembering that low strain generally leads to bone formation and

healing, it is possible to manipulate this fraction intraoperatively to achieve

success. When a simple fracture pattern is anatomically reduced and

compressed, then the total resting distance between fragments after

stabilization approaches 0. This means the numerator must be near

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Aaos 2015 Trauma