OITE & ABOS Orthopedic Board MCQs: Arthroplasty & Trauma

Question 1

In a reverse total shoulder arthroplasty, moving the center of rotation medially and distally compared to the native shoulder achieves which of the following biomechanical outcomes?

Explanation

Reverse total shoulder arthroplasty fundamentally alters shoulder biomechanics by medializing and distalizing the center of rotation. Medialization reduces torque and shear forces on the glenoid baseplate, minimizing the risk of aseptic loosening. Distalization of the humerus increases the resting tension and moment arm of the deltoid muscle, which is critical for restoring active elevation in the absence of a functional rotator cuff.

Question 2

According to the 2018 International Consensus Meeting (ICM) criteria for periprosthetic joint infection (PJI), which of the following represents a definitive (major) criterion for the diagnosis of PJI?

Explanation

According to the 2018 ICM criteria, the two major criteria (either of which is definitive for the diagnosis of PJI) are: 1) Two positive periprosthetic cultures with phenotypically identical organisms, or 2) A sinus tract communicating with the joint. The other options represent minor criteria or diagnostic biomarkers that contribute to an aggregate score but are not definitively diagnostic on their own.

Question 3

A 35-year-old male presents with a pelvic injury following a motor vehicle collision. Plain radiographs of the pelvis show disruption of both the iliopectineal and ilioischial lines, but the obturator ring remains completely intact. According to the Letournel and Judet classification, what is the diagnosis?

Explanation

A transverse acetabular fracture separates the innominate bone into upper (iliac) and lower (ischiopubic) segments. It crosses both the anterior column (disrupting the iliopectineal line) and the posterior column (disrupting the ilioischial line) but distinctly leaves the obturator ring intact. T-type and both column fractures also involve both columns but extend into and disrupt the obturator ring.

Question 4

A 28-year-old female sustains a knee injury. Imaging reveals a fracture involving the medial tibial plateau with a coronal plane fracture line separating the posteromedial aspect of the condyle. According to the Moore classification of fracture-dislocations of the knee, which type is this?

Explanation

The Moore classification describes fracture-dislocations of the proximal tibia. Type I is a split fracture of the medial plateau in the coronal plane (posteromedial fragment). Type II is an entire medial condyle fracture with the fracture line extending into the opposite compartment. Type III is a rim avulsion (often associated with lateral capsular avulsion/Segond fracture). Type IV is a rim compression. Type V is a four-part fracture.

Question 5

During a primary posterior-stabilized total knee arthroplasty utilizing a measured resection technique, the surgeon evaluates the gaps. The extension gap is symmetric and perfectly balanced. However, the flexion gap is tight medially and loose laterally. What is the most appropriate corrective action?

Explanation

A flexion gap that is tight medially and loose laterally signifies internal rotation of the femoral component relative to the surgical epicondylar axis. Externally rotating the femoral component will decrease the medial posterior condyle thickness (thereby opening the medial flexion gap) and increase the lateral posterior condyle thickness (tightening the lateral flexion gap) without affecting the extension gap.

Question 6

A 65-year-old male with primary glenohumeral osteoarthritis is undergoing evaluation for a total shoulder arthroplasty. A CT scan of his shoulder reveals biconcave glenoid wear with retroversion of 20 degrees and posterior subluxation of the humeral head. Which Walch classification describes this glenoid morphology?

Explanation

The Walch classification describes glenoid morphology in osteoarthritis. Type B2 is characterized by a biconcave glenoid with posterior subluxation of the humeral head and varying degrees of retroversion. Type B1 is posterior joint space narrowing without biconcavity. Type B3 is a monoconcave glenoid with severe retroversion (>15 degrees) and posterior subluxation. Type A represents central wear, and Type C is dysplastic.

Question 7

In a patient with an anteroposterior compression (APC) pelvic ring injury, at what threshold of pubic symphysis diastasis are the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments typically disrupted, signifying an APC II injury?

Explanation

A symphyseal diastasis greater than 2.5 cm is the classic threshold indicating rupture of the pelvic floor ligaments (sacrotuberous and sacrospinous) and the anterior sacroiliac ligaments. This injury pattern defines an APC II pelvic ring injury. A diastasis of less than 2.5 cm (APC I) usually indicates the posterior ligaments remain intact.

Question 8

A 40-year-old male undergoes a total hip arthroplasty using a ceramic-on-ceramic bearing. Which of the following is a recognized complication specifically associated with this bearing surface compared to standard metal-on-polyethylene?

Explanation

Squeaking is a well-documented complication specific to ceramic-on-ceramic (CoC) bearings, occurring in up to 10% of patients. It is associated with microseparation, edge loading, and certain patient or implant characteristics. ALVAL is seen in metal-on-metal bearings. Volumetric wear and debris-induced osteolysis are classic complications of metal-on-polyethylene bearings.

Question 9

Inferior scapular notching is a well-recognized complication after reverse total shoulder arthroplasty. Which surgical modification of the baseplate and glenosphere is most effective at reducing the incidence of this complication?

Explanation

Scapular notching occurs when the humeral component impinges on the inferior scapular neck during arm adduction. Inferior placement of the baseplate on the glenoid, using an eccentric glenosphere with inferior offset, and increasing the lateral offset of the glenosphere are the primary surgical strategies to prevent this mechanical impingement.

Question 10

A 32-year-old male sustains a distal femur fracture in a motorcycle collision. CT imaging reveals a coronal plane fracture of the lateral femoral condyle. What is the most common mechanism of injury leading to this specific fracture pattern (Hoffa fracture)?

Explanation

Hoffa fractures are coronal shear fractures of the distal femoral condyles, most commonly affecting the lateral condyle. The classic mechanism of injury is an axial load transmitted through the femoral condyle while the knee is in 90 degrees or more of flexion, driving the posterior aspect of the condyle proximally.

Question 11

A 62-year-old female presents with a painful, swollen, and stiff knee 2 years after a primary TKA. Comprehensive infection workup is negative. She notes a history of severe contact dermatitis to cheap jewelry, and patch testing confirms a profound nickel allergy. If revision arthroplasty is pursued, which femoral component material is the most appropriate choice?

Explanation

In patients with symptomatic, documented metal hypersensitivity (most commonly nickel, cobalt, or chromium) who require knee arthroplasty or revision, standard cobalt-chromium components (which contain nickel) should be avoided. Oxidized zirconium (Oxinium) or pure titanium components lack nickel and are the implants of choice to avoid hypersensitivity reactions.

Question 12

During surgical planning for a 4-part proximal humerus fracture, understanding the vascular anatomy is critical. Which vessel has been shown in quantitative studies to supply the majority of the blood to the native humeral head?

Explanation

Historically, the anterior humeral circumflex artery (specifically its arcuate branch) was believed to be the primary blood supply to the humeral head. However, landmark cadaveric studies by Brooks et al. and Hettrich et al. established that the posterior humeral circumflex artery provides approximately 64% of the blood supply to the humeral head, making it the major vascular contributor.

Question 13

A 45-year-old roofer falls 15 feet and sustains a closed intra-articular calcaneus fracture. On the lateral radiograph, Bohler's angle is measured at 5 degrees. What is the normal physiological range for Bohler's angle?

Explanation

Bohler's angle is measured on a lateral radiograph by drawing one line from the highest point of the anterior process to the highest point of the posterior facet, and a second line from the highest point of the posterior facet to the highest point of the calcaneal tuberosity. The normal range is 20 to 40 degrees. A decreased angle (<20 degrees) indicates collapse of the posterior facet, which is typical in intra-articular calcaneus fractures.

Question 14

When comparing the direct anterior approach to the posterior approach for primary total hip arthroplasty, the direct anterior approach is associated with a higher risk of iatrogenic injury to which of the following nerves?

Explanation

The direct anterior approach utilizes the internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). The lateral femoral cutaneous nerve crosses the surgical field anteriorly and is at the highest risk for neuropraxia or transection during this approach.

Question 15

A 55-year-old female presents with a highly comminuted distal radius fracture involving a displaced volar marginal fragment of the lunate facet (volar ulnar corner). Which of the following carpal ligaments originates from this specific fracture fragment, making its anatomical stabilization critical to prevent volar carpal subluxation?

Explanation

The short radiolunate ligament securely attaches the volar marginal fragment of the lunate facet (often termed the 'tear-drop' fragment) to the lunate. If this volar ulnar corner is not recognized and rigidly fixed, the entire carpus can subluxate volarly with the lunate, leading to catastrophic radiocarpal instability and poor functional outcomes.

Question 16

During a Latarjet procedure for recurrent anterior shoulder instability, the coracoid process is transferred to the anterior glenoid rim. The 'sling effect' provided by this procedure, which contributes significantly to stability when the arm is abducted and externally rotated, is created by which of the following?

Explanation

The Latarjet procedure stabilizes the shoulder via a triple-blocking effect. The 'sling effect' is the dynamic stabilization provided by the conjoined tendon (short head of the biceps and coracobrachialis), which passes through the lower portion of the split subscapularis muscle. When the arm is placed in abduction and external rotation, the conjoined tendon acts as a sling to tension the inferior capsule and lower subscapularis, preventing anterior translation of the humeral head.

Question 17

A 24-year-old male is admitted with a comminuted midshaft tibia fracture. He develops severe leg pain out of proportion to the injury. Which of the following pressure readings or thresholds is most widely accepted as an absolute indication for emergent fasciotomy for acute compartment syndrome?

Explanation

A Delta P (diastolic blood pressure minus absolute compartment pressure) of less than or equal to 30 mmHg is the most reliable objective threshold for diagnosing acute compartment syndrome. Using a Delta P rather than an absolute pressure accounts for the patient's systemic perfusion pressure and minimizes unnecessary fasciotomies.

Question 18

A 70-year-old female sustains recurrent posterior dislocations following a right total hip arthroplasty via a posterior approach. CT scan demonstrates the acetabular cup is placed in 45 degrees of abduction and 5 degrees of retroversion. The femoral stem has 15 degrees of anteversion. What is the most likely cause of her posterior instability?

Explanation

The acetabular component should typically be placed in 15-20 degrees of anteversion and 40-45 degrees of abduction (the Lewinnek safe zone). This patient's cup is placed in 5 degrees of retroversion, which severely predisposes her to posterior dislocation, particularly with hip flexion and internal rotation. The combined anteversion is only 10 degrees (15 femoral + (-5) acetabular), which is below the ideal 25-40 degrees.

Question 19

In the initial management of a severely polytraumatized patient, which of the following physiological parameters is most suggestive that the patient is in an 'in extremis' state, favoring Damage Control Orthopedics (DCO) over Early Total Care (ETC)?

Explanation

Parameters favoring Damage Control Orthopedics over Early Total Care include elements of the 'lethal triad' (hypothermia, coagulopathy, acidosis). Specific thresholds for 'in extremis' or borderline patients include: hypothermia (< 32-35 C), coagulopathy (platelets < 90,000/uL, INR > 1.5), and severe acidosis (pH < 7.24, base deficit more negative than -6, lactate > 2.5 mmol/L). A platelet count of 70,000/uL indicates significant coagulopathy, warranting DCO.

Question 20

A 68-year-old male presents with vague shoulder pain 18 months after a primary reverse total shoulder arthroplasty. Inflammatory markers are minimally elevated. A joint aspirate is obtained and grows Cutibacterium (formerly Propionibacterium) acnes after 10 days of incubation. Which of the following characteristics best describes this organism?

Explanation

Cutibacterium acnes is a slow-growing, Gram-positive, anaerobic (to aerotolerant) bacillus that resides as normal flora deep within the sebaceous glands of the skin, particularly around the shoulder. It is a notorious cause of indolent periprosthetic joint infections following shoulder arthroplasty and typically requires extended culture incubation (often up to 14 days) to be detected.

Question 21

A 65-year-old male with long-standing ankylosing spondylitis and a completely fused lumbar spine is scheduled for a total hip arthroplasty (THA). Due to his severe spinopelvic stiffness, how should the acetabular component be positioned compared to a patient with normal spinopelvic mobility to minimize dislocation risk?

Explanation

Patients with a stiff spine (e.g., due to ankylosing spondylitis or long spinal fusions) lack normal compensatory spinopelvic mobility. Normally, when a patient moves from standing to sitting, the pelvis tilts posteriorly, increasing acetabular anteversion and accommodating hip flexion. In a stiff spine, the pelvis does not tilt posteriorly during sitting, leading to anterior impingement and a high risk of posterior dislocation. To compensate for this lack of dynamic 'opening' of the cup, the acetabular component must be placed in relatively increased anteversion and increased inclination.

Question 22

A 68-year-old female presents with an audible and palpable 'pop' over the anterior aspect of her knee when rising from a chair. She underwent a posterior-stabilized total knee arthroplasty (TKA) one year ago. She is diagnosed with patellar clunk syndrome. At approximately which range of knee flexion does this phenomenon classically occur during active extension?

Explanation

Patellar clunk syndrome is a complication primarily seen in posterior-stabilized (PS) TKA designs. It occurs due to the formation of a fibrous nodule at the superior pole of the patella. As the knee actively extends from a flexed position, the nodule gets caught in the intercondylar box of the femoral component and then abruptly 'clunks' out of the box. This typically occurs between 30 to 45 degrees of flexion during active extension.

Question 23

Scapular notching is a well-recognized radiologic finding following reverse total shoulder arthroplasty (RTSA). Which of the following modifications in glenosphere positioning has been biomechanically and clinically proven to decrease the incidence of inferior scapular notching?

Explanation

Scapular notching occurs when the medial aspect of the humeral component impinges against the inferior scapular neck during adduction. Placing the glenosphere flush or with a slight inferior overhang (2-4 mm) and applying inferior tilt minimizes this impingement by lowering the humerus relative to the scapular neck and improving the clearance for the humeral cup.

Question 24

A 40-year-old male sustains a coronal shear fracture of the lateral femoral condyle (Hoffa fracture). Biomechanical studies have demonstrated that which of the following screw configurations provides the most stable construct against vertical shear forces?

Explanation

A Hoffa fracture is a coronal plane fracture of the femoral condyle (most commonly lateral). While an anterior-to-posterior (AP) approach is frequently used clinically due to ease of surgical access, biomechanical studies demonstrate that posterior-to-anterior (PA) directed lag screws placed perpendicular to the fracture plane offer superior pull-out strength and structural stability compared to AP screws.

Question 25

During the surgical management of an anterior pelvic ring injury via an ilioinguinal approach, the surgeon encounters significant hemorrhage over the superior pubic ramus. This is most likely originating from the corona mortis, an anastomotic vascular connection typically linking which two vessel systems?

Explanation

The corona mortis ('crown of death') is a vascular anastomosis between the external iliac (or inferior epigastric) vessels and the internal iliac (obturator) vessels. It is located on the posterior aspect of the superior pubic ramus, approximately 5 cm from the pubic symphysis, and can cause life-threatening hemorrhage if inadvertently disrupted during anterior pelvic ring surgery.

Question 26

A patient is being evaluated for a suspected periprosthetic joint infection (PJI) following a total hip arthroplasty. The synovial fluid alpha-defensin immunoassay returns positive. What is the primary biological source of alpha-defensin in the synovial fluid?

Explanation

Alpha-defensin is an antimicrobial peptide released predominantly by human neutrophils in response to the presence of pathogens. It has proven to be a highly sensitive and specific biomarker for diagnosing periprosthetic joint infections, as its levels rise dramatically in the presence of an active bacterial infection regardless of prior antibiotic use.

Question 27

Recent quantitative anatomic studies evaluating the vascularity of the proximal humerus have challenged historical teachings regarding the primary blood supply to the humeral head. Based on contemporary understanding (e.g., Hertel et al.), which artery provides the predominant blood supply to the humeral head?

Explanation

Historically, the arcuate artery (a branch of the ascending branch of the anterior humeral circumflex artery) was thought to be the principal blood supply to the humeral head. However, modern cadaveric studies using advanced perfusion techniques have definitively demonstrated that the posterior humeral circumflex artery provides the vast majority (up to 64%) of the robust intraosseous blood supply to the humeral head.

Question 28

A 55-year-old male presents with groin pain and a palpable anterior hip mass 4 years after a total hip arthroplasty. Aspiration yields sterile, turbid fluid. MRI reveals a large cystic pseudotumor. Which combination of modular femoral head and stem characteristics places the patient at the highest risk for mechanically assisted crevice corrosion (trunnionosis)?

Explanation

Mechanically assisted crevice corrosion (MACC) at the modular head-neck junction (trunnionosis) is a recognized cause of adverse local tissue reaction (ALTR). The risk is significantly amplified by the use of large diameter (e.g., >36 mm) Cobalt-Chromium (CoCr) heads on Titanium (Ti) alloy stems with short, thin trunnions due to the increased frictional torque, micro-motion, and galvanic/fretting corrosion occurring at the mixed-metal interface.

Question 29

A surgeon is utilizing a posteromedial approach to internally fix a complex shear fracture of the medial tibial plateau. To correctly perform the deep dissection and avoid damaging vital structures, the internervous/intermuscular interval should be developed between which of the following structures?

Explanation

The posteromedial approach to the proximal tibia utilizes an intermuscular interval between the medial head of the gastrocnemius (which is retracted laterally/posteriorly to protect the neurovascular bundle) and the pes anserinus tendons (semitendinosus, gracilis, and sartorius, which are retracted medially/anteriorly). The semimembranosus tendon lies deep and must be carefully managed in this plane.

Question 30

A 62-year-old male is 5 weeks postoperative from a deltopectoral anatomic total shoulder arthroplasty. He reports a sudden 'pop' accompanied by pain and weakness while pushing a heavy door. Physical exam reveals increased passive external rotation compared to the contralateral side and a positive bear-hug test. What is the most appropriate management?

Explanation

The patient's presentation (sudden pop, weakness, increased passive ER, positive bear-hug test) in the early postoperative period following an anatomic TSA via a deltopectoral approach is highly suspicious for an acute subscapularis tendon failure. Untreated, this can lead to anterior instability and devastating functional loss. Early surgical repair is the standard of care for acute traumatic failure of the subscapularis repair following TSA.

Question 31

A 26-year-old previously healthy male sustains a high-energy Pauwels type III (vertical) femoral neck fracture. To minimize the risk of varus collapse and nonunion, which of the following internal fixation constructs provides the greatest biomechanical stability against vertical shear forces?

Explanation

Pauwels type III femoral neck fractures have a vertical fracture line (angle >50 degrees), which subjects the fracture to immense vertical shear forces. Biomechanical studies have shown that multiple cannulated screws have a high failure rate due to varus collapse. A fixed-angle construct, such as a sliding hip screw (with an anti-rotation screw) or a modern femoral neck system, provides superior biomechanical stability against shear forces compared to parallel cannulated screws.

Question 32

A 72-year-old female with severe rheumatoid arthritis undergoes TKA for end-stage valgus osteoarthritis (Krackow Type II). Intraoperatively, after appropriate soft tissue balancing, the medial collateral ligament (MCL) is found to be completely attenuated and incompetent, resulting in gross coronal instability. Which implant constraint is definitively required?

Explanation

In the setting of total knee arthroplasty, coronal plane stability depends on collateral ligament competence. A constrained condylar knee (CCK) relies on the presence of functional collateral ligaments to prevent catastrophic post-failure. If the medial collateral ligament (MCL) is completely absent or incompetent, a CCK will fail, and a rotating hinge prosthesis is required to substitute for the absent collateral stability.

Question 33

The Sanders classification system is widely used for guiding the management of intra-articular calcaneus fractures. This classification is determined by the number and location of primary fracture lines through which of the following structures on a coronal CT scan?

Explanation

The Sanders classification system utilizes coronal CT images at the widest portion of the posterior facet of the calcaneus. It classifies fractures into types I through IV based strictly on the number and location of articular fracture lines through the posterior articular facet. The classification helps guide surgical decision-making and provides prognostic information.

Question 34

When counseling a 35-year-old male with an acute, closed midshaft clavicle fracture regarding non-operative management, which of the following represents the most significant independent predictor for the development of a nonunion?

Explanation

While several factors influence midshaft clavicle fracture healing (including advanced age, female gender, and comminution), the degree of initial displacement and fracture shortening is widely considered the strongest predictor of nonunion. Specifically, shortening greater than 20 mm (2 cm) or 100% displacement dramatically increases the nonunion risk in non-operatively treated clavicle fractures.

Question 35

A 40-year-old male with a ceramic-on-ceramic total hip arthroplasty complains of a highly audible 'squeaking' sound coming from his hip during ambulation. Radiographic evaluation of component positioning is most likely to reveal which of the following?

Explanation

Squeaking in ceramic-on-ceramic THA is a phenomenon strongly linked to edge loading, stripe wear, and micro-separation. Edge loading occurs when the femoral head articulates against the rim of the acetabular liner rather than the dome. This is most strongly associated with component malpositioning, particularly when the acetabular cup is placed in excessive anteversion combined with excessive (steep) inclination.

Question 36

A 30-year-old male develops isolated anterior compartment syndrome of the leg following a high-energy tibia fracture. If decompression is delayed, which of the following specific sensory and motor deficits is most likely to be present on physical examination?

Explanation

The anterior compartment of the leg contains the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius muscles, as well as the deep peroneal nerve and anterior tibial artery. Ischemia to this compartment results in weakness of ankle dorsiflexion and great toe extension, along with diminished sensation in the autonomous zone of the deep peroneal nerve (the first dorsal web space).

Question 37

During a Latarjet procedure for recurrent anterior shoulder instability, the conjoined tendon is aggressively retracted medially to facilitate exposure of the subscapularis. Over-retraction or aggressive manipulation of the conjoined tendon places which of the following nerves at greatest risk of stretch injury?

Explanation

The musculocutaneous nerve enters the coracobrachialis (part of the conjoined tendon) approximately 5 to 8 cm distal to the tip of the coracoid process, though its course can be variable. Aggressive medial and distal retraction of the conjoined tendon during the Latarjet procedure or a deltopectoral approach puts the musculocutaneous nerve at significant risk for a neuropraxic stretch injury.

Question 38

The direct anterior approach (DAA) to the hip is popular for its theoretical advantage of utilizing a true internervous and intermuscular plane. The superficial surgical interval in the DAA is between muscles supplied by which two nerves?

Explanation

The direct anterior approach (Smith-Petersen) exploits the internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve) superficially. Deep to this, the interval is between the rectus femoris (femoral nerve) and the gluteus medius/minimus (superior gluteal nerve).

Question 39

A 55-year-old woman presents to the clinic unable to actively extend the interphalangeal joint of her thumb. She was treated non-operatively 6 weeks ago for a non-displaced distal radius fracture. What is the primary pathophysiological cause of this late complication?

Explanation

Spontaneous rupture of the extensor pollicis longus (EPL) tendon is a classic complication that occurs weeks after a non-displaced distal radius fracture. It is primarily caused by mechanical attrition from bony irregularity at Lister's tubercle, compounded by localized ischemia of the tendon within the unyielding third extensor compartment due to fracture hematoma and swelling.

Question 40

In the setting of a massive, irreparable posterosuperior rotator cuff tear in a young, active laborer without significant glenohumeral arthritis or pseudoparalysis, a lower trapezius tendon transfer (often augmented with an Achilles allograft) may be performed. This specific transfer primarily aims to restore which of the following shoulder biomechanical functions?

Explanation

The lower trapezius tendon transfer is performed to recreate the vector of the infraspinatus. Because the line of pull of the lower trapezius closely matches that of the infraspinatus, it is highly effective at restoring active external rotation, particularly with the arm abducted to 90 degrees. It has largely replaced the latissimus dorsi transfer for massive tears primarily involving severe loss of external rotation.

Question 41

Which design feature of a reverse total shoulder arthroplasty (RTSA) implant most effectively decreases the incidence of scapular notching?

Explanation

Scapular notching in RTSA is a common complication caused by impingement of the humeral component on the inferior scapular neck. Inferior placement of the glenosphere with a slight overhang past the inferior glenoid margin biomechanically reduces this impingement.

Question 42

According to Hertel's criteria, which combination of radiographic findings best predicts ischemia of the humeral head following a proximal humerus fracture?

Explanation

Hertel described predictors for humeral head ischemia in proximal humerus fractures. A short calcar segment (<8 mm), a disrupted medial hinge, and an anatomical neck fracture are the strongest positive predictive factors for avascular necrosis.

Question 43

During an ilioinguinal approach for a transverse acetabular fracture, significant arterial hemorrhage occurs near the superior pubic ramus. The bleeding is most likely originating from an anastomosis between which two vessels?

Explanation

This anastomosis is known as the corona mortis (crown of death). It is a vascular connection between the inferior epigastric (or external iliac) and obturator vessels, crossing the superior pubic ramus where it is vulnerable during pelvic surgery.

Question 44

A 45-year-old active male underwent a ceramic-on-ceramic total hip arthroplasty 2 years ago. He now complains of a squeaking noise with deep flexion. Which of the following component factors is most strongly associated with this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic bearings is strongly associated with edge loading. This typically occurs when the acetabular component is placed in excessive abduction (>50 degrees) or malversion, leading to concentrated contact stresses and fluid film disruption.

Question 45

During a posterior-stabilized total knee arthroplasty, the surgeon notes that the knee is tight in flexion but perfectly balanced in extension. Which of the following is the most appropriate next step to balance the knee?

Explanation

A knee that is tight in flexion and balanced in extension requires an increase in the flexion gap without altering the extension gap. Downsizing the femoral component achieves this by reducing the posterior condylar offset.

Question 46

A 40-year-old male sustains a high-energy Schatzker IV tibial plateau fracture. Which associated injury should the surgeon have the highest index of suspicion for compared to lateral-sided plateau fractures?

Explanation

Schatzker IV (medial plateau) fractures are often high-energy injuries involving varus forces and are frequently considered fracture-dislocations of the knee. They carry a significantly higher risk of popliteal artery injury and multiple ligamentous disruptions than simple lateral plateau fractures.

Question 47

A 72-year-old female presents with severe primary glenohumeral osteoarthritis. MRI demonstrates an intact rotator cuff, but a CT scan reveals a Walch B3 glenoid with 25 degrees of retroversion. Which of the following is the most appropriate surgical treatment?

Explanation

In elderly patients with severe glenoid retroversion (Walch B2 or B3, often >15-20 degrees) and posterior subluxation, reverse total shoulder arthroplasty is increasingly preferred even with an intact rotator cuff to prevent the high rate of early glenoid loosening seen in anatomic TSA.

Question 48

A 70-year-old female on alendronate for 8 years presents with vague thigh pain. Radiographs reveal a thickened lateral cortex with a transverse radiolucent line in the subtrochanteric region of her femur. What is the most appropriate prophylactic surgical management?

Explanation

This patient has an impending atypical femur fracture associated with long-term bisphosphonate use. The gold standard surgical management for a symptomatic, impending atypical subtrochanteric fracture is full-length intramedullary nailing (cephalomedullary nail).

Question 49

A 65-year-old male presents with severe acute left hip pain 3 weeks after a primary total hip arthroplasty. Aspiration yields 35,000 WBCs/uL (92% PMNs). The implant is radiographically well-fixed. What is the most appropriate next step in management?

Explanation

In the setting of an acute early periprosthetic joint infection (<4 weeks post-op) with well-fixed components and a known or highly suspected organism, DAIR with modular component exchange is the standard of care.

Question 50

In the surgical management of a 'terrible triad' injury of the elbow, what is the generally recommended sequence of repair to best restore concentric stability?

Explanation

The terrible triad consists of an elbow dislocation, radial head fracture, and coronoid fracture. The standard sequence of repair is deep to superficial: coronoid fixation first, followed by radial head repair or arthroplasty, and finally lateral collateral ligament (LCL) repair, and finally evaluating the need for MCL repair or hinged ex-fix.

Question 51

A 68-year-old female complains of a painful 'catching' sensation in her knee when extending from a flexed position, one year following a posterior-stabilized total knee arthroplasty. What is the most likely etiology?

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized TKA designs when a fibrous nodule forms at the superior pole of the patella and catches in the intercondylar box of the femoral component during active extension.

Question 52

A patient sustains a Hawkins Type III talar neck fracture. Which of the following accurately describes the displacement pattern and the associated risk of avascular necrosis (AVN)?

Explanation

A Hawkins Type III fracture involves a displaced talar neck fracture with both subtalar and tibiotalar joint dislocation. This disrupts multiple blood supplies to the talus, carrying an AVN risk of approximately 70-100%.

Question 53

In a reverse total shoulder arthroplasty, the center of rotation is moved medially and distally compared to native anatomy. How does this specific alteration biomechanically affect the deltoid muscle?

Explanation

Medializing and distalizing the center of rotation in an RTSA lengthens the deltoid lever arm and increases deltoid tension. This maximizes the mechanical advantage of the deltoid, allowing it to initiate and maintain forward elevation in the absence of a functioning supraspinatus.

Question 54

The direct anterior (Smith-Petersen) approach for total hip arthroplasty utilizes a true internervous plane between which of the following muscle groups?

Explanation

The direct anterior approach utilizes the internervous and intermuscular plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve) superficially, and the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve) deep.

Question 55

A 28-year-old male sustains a vertically oriented (Pauwels type III) femoral neck fracture. Which of the following fixation constructs provides the most biomechanically stable fixation for this specific fracture pattern?

Explanation

Pauwels type III fractures experience high shear forces and varus stress. A sliding hip screw with an anti-rotation screw provides superior biomechanical stability compared to multiple cancellous screws by allowing controlled compression and resisting shear.

Question 56

During a posterior-stabilized total knee arthroplasty, trial reduction demonstrates the knee is balanced in extension but significantly tight in flexion. Which of the following maneuvers is the most appropriate next step?

Explanation

A knee that is tight in flexion and balanced in extension requires increasing the flexion gap without altering the extension gap. Downsizing the femoral component using a posterior referencing system decreases the posterior condylar offset, thereby increasing the flexion gap.

Question 57

In reverse total shoulder arthroplasty (RTSA), inferior scapular notching is a recognized complication. Which of the following baseplate and glenosphere configurations minimizes the risk of this complication?

Explanation

Inferior scapular notching is caused by mechanical impingement of the humeral component against the scapular neck. Inferior placement of the baseplate with inferior overhang of the glenosphere, along with a slightly inferior tilt, reduces impingement and minimizes notching.

Question 58

A 45-year-old male presents with a Schatzker type IV medial tibial plateau fracture. An open reduction and internal fixation via a posteromedial approach is planned. Which internervous/intermuscular interval is primarily utilized in this approach?

Explanation

The standard posteromedial approach to the tibial plateau utilizes the interval between the pes anserinus tendons anteriorly and the medial head of the gastrocnemius posteriorly. This allows excellent and safe visualization of the posteromedial fracture fragment.

Question 59

A 65-year-old female with a history of an L2-pelvis spinal fusion is undergoing a primary total hip arthroplasty. How does her spinal fusion alter normal spinopelvic kinematics during the transition from standing to sitting?

Explanation

In a patient with a stiff or fused lumbar spine, the pelvis fails to retrovert when transitioning from standing to sitting. This lack of posterior pelvic tilt prevents the expected increase in functional acetabular anteversion, leading to anterior impingement and posterior dislocation.

Question 60

According to the Hertel criteria, which of the following radiographic findings is the strongest predictor of humeral head ischemia following a proximal humerus fracture?

Explanation

Hertel criteria for humeral head ischemia include a short metaphyseal head extension (< 8 mm) and disruption of the medial hinge (< 2 mm). An anatomic neck fracture combined with an absent or severely disrupted medial hinge has the highest predictive value for ischemia.

Question 61

A 30-year-old male arrives in the trauma bay in hemorrhagic shock following a motorcycle accident. Radiographs reveal an anteroposterior compression (APC) type III pelvic ring injury. What is the correct anatomical landmark for the application of a circumferential pelvic sheet or binder?

Explanation

Pelvic binders should be centered directly over the greater trochanters. Placement higher over the iliac crests or abdomen is ineffective for reducing the pelvic volume and can paradoxically widen the pelvis in open-book injuries.

Question 62

A 65-year-old female complains of giving way and recurrent effusions 2 years after a primary TKA. Examination reveals symmetrical extension gap stability, but instability to varus and valgus stress at 90 degrees of flexion. Which intraoperative error most likely caused this presentation?

Explanation

Undersizing the femoral component (specifically the anteroposterior dimension) increases the flexion gap without affecting the extension gap. This mismatch leads to isolated flexion instability.

Question 63

A 55-year-old male with a ceramic-on-ceramic total hip arthroplasty presents with a high-pitched squeaking sound during hip flexion. Which of the following factors is most strongly associated with this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic THA is predominantly associated with edge loading. This often results from acetabular cup malposition, such as excessive steepness or anteversion, which leads to stripe wear and microseparation.

Question 64

When fixing a 3-part proximal humerus fracture with a locking plate, which of the following surgical techniques best minimizes the risk of varus collapse and subsequent screw cutout?

Explanation

The placement of an inferomedial calcar screw into the inferomedial quadrant of the humeral head mechanically supports the medial hinge. This significantly reduces the risk of varus collapse and superior screw cutout.

Question 65

A 22-year-old rugby player undergoes a Latarjet procedure for recurrent anterior shoulder instability with 25% glenoid bone loss. Which muscle or tendon must be split to pass the coracoid graft to the anterior glenoid neck?

Explanation

During the Latarjet procedure, the coracoid process with the attached conjoint tendon is passed through a horizontal split in the subscapularis muscle to reach the anterior glenoid rim. This creates a dynamic sling effect that contributes to stability.

Question 66

A 30-year-old male sustains a Hawkins type III talar neck fracture. Six weeks postoperatively, an AP radiograph of the ankle demonstrates a subchondral radiolucent band in the talar dome. What does this radiographic finding indicate?

Explanation

This finding is the Hawkins sign, which represents subchondral osteopenia secondary to hyperemia from disuse. It is a highly reliable indicator that the vascular supply to the talar body is intact, thereby ruling out avascular necrosis.

Question 67

In total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) compared to conventional ultra-high molecular weight polyethylene (UHMWPE) alters the wear profile. Which of the following trade-offs is most characteristic of increasing the radiation dose during HXLPE manufacturing?

Explanation

Highly cross-linking polyethylene significantly decreases the volumetric wear rate, lowering the risk of osteolysis. However, it inversely decreases the material's mechanical properties, such as fatigue strength and fracture toughness.

Question 68

A 25-year-old male sustains a displaced Pauwels type III femoral neck fracture. Which of the following fixation constructs provides the most biomechanically stable construct against vertical shear forces?

Explanation

A Pauwels type III fracture has a highly vertical fracture line that experiences significant shear forces. A fixed-angle construct like a dynamic hip screw (DHS), supplemented with a derotation screw, provides superior biomechanical resistance to shear compared to multiple cancellous screws.

Question 69

A patient presents with a painful popping sensation at the superior pole of the patella when extending the knee from 45 degrees to full extension, 1 year after a posterior-stabilized TKA. What is the most appropriate management?

Explanation

This is the classic presentation of patellar clunk syndrome, caused by a fibrotic nodule forming at the superior pole of the patella that catches in the intercondylar box of a posterior-stabilized femur. Arthroscopic excision of the nodule provides excellent results.

Question 70

What is the most common neurologic complication following a reverse total shoulder arthroplasty (RSA) for rotator cuff arthropathy, and what is its most common mechanism?

Explanation

Axillary nerve neurapraxia is the most common neurologic complication following RSA. It typically results from overstretching during inferior capsular release or direct retractor compression at the inferior glenoid neck.

Question 71

A 40-year-old male presents with a posteromedial shear fracture of the tibial plateau (Schatzker IV). Which surgical approach is most appropriate for direct visualization and buttress plating of this specific fragment?

Explanation

Posteromedial tibial plateau fractures require a posteromedial approach between the pes anserinus and the medial head of the gastrocnemius. This allows for biomechanically superior anti-glide or buttress plating of the posteromedial fragment.

Question 72

In the workup of a suspected periprosthetic joint infection (PJI), a synovial fluid alpha-defensin test is ordered. What is the primary physiological role of alpha-defensin in this context?

Explanation

Alpha-defensin is an antimicrobial peptide released by host neutrophils in response to pathogens. Its measurement in synovial fluid is a highly specific and sensitive biomarker for diagnosing periprosthetic joint infection.

Question 73

A 32-year-old female presents with an anteroposterior compression (APC) type II pelvic ring injury following a crush accident. Which specific ligamentous structures are completely disrupted in an APC-II injury compared to an APC-I injury?

Explanation

According to the Young-Burgess classification, an APC-II injury involves symphyseal diastasis with disruption of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments. This results in rotational instability while maintaining vertical stability since the posterior SI ligaments remain intact.

Question 74

During volar locking plate fixation of a distal radius fracture, the surgeon accidentally places a screw that protrudes through the dorsal cortex of the distal radius into the third extensor compartment. Which tendon is at the highest risk for attrition and rupture?

Explanation

Prominent dorsal screws protruding through the third extensor compartment specifically place the Extensor Pollicis Longus (EPL) tendon at risk for attritional rupture. Proper screw length measurement is critical to avoid this complication.

Question 75

A 62-year-old male with a metal-on-polyethylene total hip arthroplasty presents with groin pain and a large cystic mass 5 years postoperatively. Blood tests show elevated cobalt levels but normal chromium levels. What is the most likely etiology of his symptoms?

Explanation

Mechanically assisted crevice corrosion at the modular head-neck junction (trunnionosis) typically presents with an adverse local tissue reaction. It is characterized by elevated serum cobalt levels out of proportion to chromium levels.

Question 76

A 28-year-old male sustains a transverse subtrochanteric femur fracture. Which muscle group is primarily responsible for the characteristic flexion and external rotation deformity of the proximal fragment?

Explanation

The proximal fragment in a subtrochanteric fracture is characteristically flexed by the iliopsoas, abducted by the gluteus medius and minimus, and externally rotated by the short external rotators.

Question 77

A 45-year-old construction worker undergoes open reduction and internal fixation of a displaced intra-articular calcaneus fracture via an extensile lateral approach. Which nerve is at the greatest risk of iatrogenic injury during the inferior limb of this incision?

Explanation

The sural nerve crosses the lateral border of the foot and is at high risk of transection or traction injury during the development of the full-thickness flap in an extensile lateral approach to the calcaneus.

Question 78

In an anatomic total shoulder arthroplasty, the phenomenon of 'rocking horse' loosening of the glenoid component is most commonly caused by which of the following?

Explanation

Eccentric loading of the glenoid component, most commonly due to superior migration of the humeral head in the setting of rotator cuff deficiency, creates a rocking horse effect that leads to premature aseptic glenoid loosening.

Question 79

During a revision THA, the surgeon notes massive acetabular bone loss with superior migration of the hip center by 4 cm, but the teardrop and Kohler's line remain intact. According to the Paprosky classification, what type of defect is this, and what is the preferred management?

Explanation

A Paprosky 3A defect is characterized by greater than 3 cm of superior migration with intact medial wall structures (Kohler's line). Management typically involves a hemispherical cup supplemented with structural allograft or highly porous metal augments to address the superior defect.

Question 80

A 35-year-old farmer sustains a severe open tibia fracture (Gustilo-Anderson Type IIIA) contaminated with soil and farm debris. According to current guidelines, which of the following antibiotic regimens is most appropriate for initial management?

Explanation

For open fractures heavily contaminated with farm soil or displaying gross crush injury, high-dose penicillin should be added to the standard regimen (a first-generation cephalosporin and/or aminoglycoside) to cover for Clostridium species.

Question 81

In a reverse total shoulder arthroplasty, inferior tilt of the glenosphere baseplate is often recommended. What is the primary biomechanical advantage of placing the baseplate with an inferior tilt?

Explanation

Inferior tilt of the glenosphere reduces the mechanical impingement of the humeral polyethylene cup against the inferior scapular neck during adduction. This significantly decreases the incidence of inferior scapular notching.

Orthopedic Surgery Board Review MCQs: Arthroplasty, Trauma & Spine Part 255

OITE & ABOS Orthopedic Board Exam MCQs: Arthroplasty, Shoulder & Trauma | Part 30

Key Takeaway

OITE & ABOS Orthopedic Board Exam MCQs: Arthroplasty, Shoulder & Trauma | Part 30

Chapter Index