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Total Hip Arthroplasty (THA) MCQs

Practice Set 29 of 36

This practice set contains high-yield board review questions covering key concepts in Total Hip Arthroplasty (THA). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 561

Topic: Total Hip Arthroplasty (THA)

During a direct lateral (Hardinge) approach to the hip, proximal splitting of the gluteus medius is limited to prevent denervation of the anterior portion of the muscle. The superior gluteal nerve is at greatest risk if the split extends more than what distance proximal to the tip of the greater trochanter?

. 1 cm
. 3 cm
. 5 cm
. 8 cm
. 10 cm

Correct Answer & Explanation

. 1 cm

Explanation

The superior gluteal nerve innervates the gluteus medius, gluteus minimus, and tensor fasciae latae. It is located approximately 5 cm proximal to the tip of the greater trochanter, marking the superior limit of the "safe zone" for splitting the gluteus medius.

Question 562

Topic: Total Hip Arthroplasty (THA)

A 55-year-old male who underwent a ceramic-on-ceramic total hip arthroplasty 2 years ago presents complaining of an audible squeaking sound during ambulation. Radiographs show secure components. Which of the following factors is most strongly associated with the development of this phenomenon?

. Acetabular component retroversion
. Acetabular cup inclination greater than 50 degrees
. Femoral stem varus alignment
. Femoral stem retroversion
. Increased femoral offset

Correct Answer & Explanation

. Acetabular cup inclination greater than 50 degrees

Explanation

Squeaking in ceramic-on-ceramic hips is highly associated with component malposition, particularly excessive acetabular inclination (>50 degrees) or anteversion. This leads to edge loading, disruption of the fluid film lubrication, and stripe wear.

Question 563

Topic: Total Hip Arthroplasty (THA)

A patient experiences recurrent posterior dislocations of a total hip arthroplasty. CT evaluation reveals a combined anteversion (Widmer technique) of 15 degrees, with the acetabular cup at 5 degrees and the femoral stem at 10 degrees. What is the most appropriate revision strategy?

. Exchange the modular head to a larger diameter
. Revise the acetabular component to increase anteversion
. Revise the femoral stem to decrease anteversion
. Increase the femoral offset using a different modular neck
. Apply a constrained acetabular liner without changing version

Correct Answer & Explanation

. Exchange the modular head to a larger diameter

Explanation

The normal target for combined anteversion in THA is roughly 25 to 45 degrees. A combined anteversion of 15 degrees is too low and predisposes the patient to posterior dislocation. Revising the acetabular component to increase its version will restore appropriate stability.

Question 564

Topic: Total Hip Arthroplasty (THA)

A 45-year-old man undergoes THA with a ceramic-on-ceramic (CoC) articulation. Postoperatively, he complains of a loud, high-pitched squeaking noise during gait. Which of the following component positions is most strongly associated with this phenomenon?

. Insufficient femoral offset
. Excessive acetabular anteversion and inclination leading to edge loading
. Excessive acetabular retroversion leading to posterior impingement
. Femoral stem varus positioning
. Loss of fluid film lubrication secondary to large head size (>40mm)

Correct Answer & Explanation

. Insufficient femoral offset

Explanation

Squeaking in CoC bearings is heavily linked to stripe wear and edge loading. Edge loading most commonly occurs due to component malposition, specifically excessive cup steepness (inclination) or excessive anteversion.

Question 565

Topic: Total Hip Arthroplasty (THA)

Mechanically assisted crevice corrosion (MACC), or trunnionosis, has been identified as a cause of adverse local tissue reactions in non-metal-on-metal THA. Which combination of implant factors confers the highest risk for trunnionosis?

. Small femoral head diameter and short neck offset
. Ceramic femoral head and a standard titanium neck
. Large metallic femoral head diameter and a large offset neck
. Use of a 12/14 trunnion instead of a 11/13 trunnion
. Highly cross-linked polyethylene liner with a 28mm head

Correct Answer & Explanation

. Large metallic femoral head diameter and a large offset neck

Explanation

Trunnionosis is exacerbated by increased frictional torque and bending moments at the head-neck junction. Large diameter metallic heads (>36mm) and long/high-offset necks significantly increase these mechanical stresses, accelerating MACC.

Question 566

Topic: Total Hip Arthroplasty (THA)

To minimize the risk of posterior dislocation following a primary THA, surgeons aim for an optimal 'combined anteversion' of the acetabular and femoral components. Based on classic principles, what is the generally accepted target range for combined anteversion?

. 5 to 15 degrees
. 25 to 45 degrees
. 50 to 65 degrees
. 70 to 85 degrees
. -10 to 0 degrees

Correct Answer & Explanation

. 25 to 45 degrees

Explanation

Combined anteversion (acetabular anteversion + femoral anteversion) is targeted between 25 and 45 degrees (often cited as the Ranawat or Widmer safe zones) to optimize stability and prevent both anterior and posterior impingement.

Question 567

Topic: Total Hip Arthroplasty (THA)

During acetabular component fixation in THA, screw placement is targeted to specific anatomic zones to avoid neurovascular injury. According to Wasielewski's quadrant system, which quadrant is considered the 'safe zone' for placing screws?

. Anterosuperior quadrant
. Anteroinferior quadrant
. Posterosuperior quadrant
. Posteroinferior quadrant
. Central (cotyloid fossa) region

Correct Answer & Explanation

. Posterosuperior quadrant

Explanation

The posterosuperior quadrant is the safe zone for screw placement, providing excellent bone stock (ilium) while avoiding major neurovascular structures. The anterosuperior/anteroinferior quadrants risk injury to the external iliac vessels and obturator nerve.

Question 568

Topic: Total Hip Arthroplasty (THA)

Intraoperatively during a THA, the surgeon tests the hip and notes it is stable in all positions, but the leg is 15 mm longer than the contralateral side, and the surrounding soft tissues are extremely tight. What is the most appropriate surgical adjustment?

. Increase the acetabular offset
. Increase the neck length of the femoral head
. Change to a high-offset femoral stem
. Recut the femoral neck more distally and advance the stem
. Release the iliopsoas tendon completely

Correct Answer & Explanation

. Recut the femoral neck more distally and advance the stem

Explanation

If the hip is stable but the leg is too long with tight soft tissues, the center of rotation has been elevated too far superiorly. The appropriate step is to lower the stem by recutting the femoral neck more distally, decreasing leg length while maintaining stability.

Question 569

Topic: Total Hip Arthroplasty (THA)

Figures 2a and 2b are the radiographs of a 56-year-old woman who has groin pain and decreased function 15 months after a total hip replacement using the posterolateral approach. Findings from the workup for infection are negative and physical examination localizes pain to the hip joint. Records show the patient underwent total hip surgery with a metal-on-metal bearing.
The patient undergoes cup revision to a more optimal position using a 36-mm metal-polyethylene bearing. Abductor muscle damage from gross metal debris and inflammation are encountered during surgery. After cup revision, repair of abductors, and hip brace use for several weeks, the patient has no more pain.Several months after surgery, the patent returns with a history of multiple hip dislocations that have proven refractory to treatment including hip precautions, bracing, and exercise. Radiographs perfectly positioned components; the patient has no pain, and examination under anesthesia shows show hip instability.

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Before recommending revision total hip arthroplasty, what other step(s) should be included in the workup?

. Aspiration of the hip joint and diagnostic injection of an anesthetic
. Draw an erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
. Three-phase bone scan of the hip
. Lumbar spine radiographs

Correct Answer & Explanation

. Draw an erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)

Explanation

The differential diagnosis of pain after a total hip arthroplasty encompasses a number of etiologies, but the question is directed to a basic and essential part of the workup (ie, definitively considering and ruling in or out the possibility of deep sepsis). Radiographs may point to other, obvious sources of pain, but the orthopaedic surgeon must not overlook the possibility that deep sepsis is the predominant cause of the symptoms. Accordingly, ESR and CRP are logical next steps in the workup in this clinical scenario. Radiographs show increased anteversion of the metal socket, and pain etiologies can include psoas irritation, hip instability, or adverse tissue reaction to metal debris generated by suboptimal implant position leading to higher bearing contact stresses and/or impingement. Once other common etiologies of hip pain have been excluded such as deep infection or lumbar pathology, the most likely cause of hip symptoms should be considered. Here the evidence points to a malpositioned acetabular component. Systemic ion dissemination may occur in this patient but will not produce hip pain. Head-neck taper corrosion can generate metallic debris, but a more likely source of local metallic debris is edge loading or impingement of the metal-metal bearing. Leg length inequality can be distressing to a patient but will usually not result in hip pain. Component malposition is the best answer. Among the spectrum of clinical presentations following failed metalmetal total hip replacements, abductor damage from localized inflammation is one finding that can lead to hip instability. A reasonable treatment option is to repair the abductors as best as possible, with augmentation of soft-tissue repair using graft tissue, a large-diameter femoral head, and a constrained polyethylene liner. This is a challenging clinical scenario because chronic hip instability with deficient abductors is difficult to control and is an indication for the use of constrained components. Revision to a larger head and increased leg lengths will not address the underlying cause of instability. Hip resection is not necessary because this is not a septic total hip.

Question 570

Topic: Total Hip Arthroplasty (THA)

Figures 2a and 2b are the radiographs of a 56-year-old woman who has groin pain and decreased function 15 months after a total hip replacement using the posterolateral approach. Findings from the workup for infection are negative and physical examination localizes pain to the hip joint. Records show the patient underwent total hip surgery with a metal-on-metal bearing.
The patient undergoes cup revision to a more optimal position using a 36-mm metal-polyethylene bearing. Abductor muscle damage from gross metal debris and inflammation are encountered during surgery. After cup revision, repair of abductors, and hip brace use for several weeks, the patient has no more pain.Several months after surgery, the patent returns with a history of multiple hip dislocations that have proven refractory to treatment including hip precautions, bracing, and exercise. Radiographs perfectly positioned components; the patient has no pain, and examination under anesthesia shows show hip instability.

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Before this patient’s most recent revision surgery, her symptoms were most likely related to

. systemic metal ion debris.
. component malposition.
. leg length inequality.
. Head-neck taper corrosion.

Correct Answer & Explanation

. component malposition.

Explanation

The differential diagnosis of pain after a total hip arthroplasty encompasses a number of etiologies, but the question is directed to a basic and essential part of the workup (ie, definitively considering and ruling in or out the possibility of deep sepsis). Radiographs may point to other, obvious sources of pain, but the orthopaedic surgeon must not overlook the possibility that deep sepsis is the predominant cause of the symptoms. Accordingly, ESR and CRP are logical next steps in the workup in this clinical scenario. Radiographs show increased anteversion of the metal socket, and pain etiologies can include psoas irritation, hip instability, or adverse tissue reaction to metal debris generated by suboptimal implant position leading to higher bearing contact stresses and/or impingement. Once other common etiologies of hip pain have been excluded such as deep infection or lumbar pathology, the most likely cause of hip symptoms should be considered. Here the evidence points to a malpositioned acetabular component. Systemic ion dissemination may occur in this patient but will not produce hip pain. Head-neck taper corrosion can generate metallic debris, but a more likely source of local metallic debris is edge loading or impingement of the metal-metal bearing. Leg length inequality can be distressing to a patient but will usually not result in hip pain. Component malposition is the best answer. Among the spectrum of clinical presentations following failed metalmetal total hip replacements, abductor damage from localized inflammation is one finding that can lead to hip instability. A reasonable treatment option is to repair the abductors as best as possible, with augmentation of soft-tissue repair using graft tissue, a large-diameter femoral head, and a constrained polyethylene liner. This is a challenging clinical scenario because chronic hip instability with deficient abductors is difficult to control and is an indication for the use of constrained components. Revision to a larger head and increased leg lengths will not address the underlying cause of instability. Hip resection is not necessary because this is not a septic total hip.

Question 571

Topic: Total Hip Arthroplasty (THA)

Figures 2a and 2b are the radiographs of a 56-year-old woman who has groin pain and decreased function 15 months after a total hip replacement using the posterolateral approach. Findings from the workup for infection are negative and physical examination localizes pain to the hip joint. Records show the patient underwent total hip surgery with a metal-on-metal bearing.
The patient undergoes cup revision to a more optimal position using a 36-mm metal-polyethylene bearing. Abductor muscle damage from gross metal debris and inflammation are encountered during surgery. After cup revision, repair of abductors, and hip brace use for several weeks, the patient has no more pain.Several months after surgery, the patent returns with a history of multiple hip dislocations that have proven refractory to treatment including hip precautions, bracing, and exercise. Radiographs perfectly positioned components; the patient has no pain, and examination under anesthesia shows show hip instability.

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After revision surgery, this patient’s total hip remains unstable and unresponsive to nonsurgical treatment.What is the most appropriate surgical option?

. Trochanteric advancement
. Revision to a constrained polyethylene liner
. Revision to the largest head size and increase leg length
. Resection with repeat abductor repair, with staged reimplantation

Correct Answer & Explanation

. Revision to a constrained polyethylene liner

Explanation

The differential diagnosis of pain after a total hip arthroplasty encompasses a number of etiologies, but the question is directed to a basic and essential part of the workup (ie, definitively considering and ruling in or out the possibility of deep sepsis). Radiographs may point to other, obvious sources of pain, but the orthopaedic surgeon must not overlook the possibility that deep sepsis is the predominant cause of the symptoms. Accordingly, ESR and CRP are logical next steps in the workup in this clinical scenario. Radiographs show increased anteversion of the metal socket, and pain etiologies can include psoas irritation, hip instability, or adverse tissue reaction to metal debris generated by suboptimal implant position leading to higher bearing contact stresses and/or impingement. Once other common etiologies of hip pain have been excluded such as deep infection or lumbar pathology, the most likely cause of hip symptoms should be considered. Here the evidence points to a malpositioned acetabular component. Systemic ion dissemination may occur in this patient but will not produce hip pain. Head-neck taper corrosion can generate metallic debris, but a more likely source of local metallic debris is edge loading or impingement of the metal-metal bearing. Leg length inequality can be distressing to a patient but will usually not result in hip pain. Component malposition is the best answer. Among the spectrum of clinical presentations following failed metalmetal total hip replacements, abductor damage from localized inflammation is one finding that can lead to hip instability. A reasonable treatment option is to repair the abductors as best as possible, with augmentation of soft-tissue repair using graft tissue, a large-diameter femoral head, and a constrained polyethylene liner. This is a challenging clinical scenario because chronic hip instability with deficient abductors is difficult to control and is an indication for the use of constrained components. Revision to a larger head and increased leg lengths will not address the underlying cause of instability. Hip resection is not necessary because this is not a septic total hip.

Question 572

Topic: Total Hip Arthroplasty (THA)
A 70-year-old man underwent removal of an infected total hip arthroplasty (THA) and insertion of an articulating antibiotic-loaded spacer to treat a deep periprosthetic hip infection. He was in a nursing home receiving intravenous antibiotics 3 weeks after surgery when he tripped and fell. Examination shows swelling in the mid and distal thigh, intact skin and neurovascular structures, and severe pain with knee or hip movement. Radiographs of the femur show a fracture below the implant. What is the most appropriate treatment for the fracture?
. Balanced traction to address concern regarding persistent infection with reoperation
. Open reduction and internal fixation of the fracture with a lateral plate and screws
. Removal of the articulating spacer and revision to a longer-stem antibiotic-loaded articulating spacer
. Removal of the articulating spacer and reimplantation using a long-stem fluted uncemented hip replacement

Correct Answer & Explanation

. Open reduction and internal fixation of the fracture with a lateral plate and screws

Explanation

This patient has a type C periprosthetic femoral fracture. The articulating spacer is not involved in the fracture, which is well distal to the implant. The most appropriate treatment is open reduction and internal fixation of the fracture. Traction is not appropriate for this fracture because it can be treated surgically despite the history of previous hip infection. Traction would also be needed for at least 5 weeks to delay surgical treatment of the periprosthetic fracture until the time of second-stage revision THA. The fracture is fairly distal and revision to a longer antibiotic-loaded implant or uncemented stem is not suitable for this fracture pattern because it extends well past the isthmus. A femoral stem in the distal fragment would provide little stability for the fracture. Additionally, removing the articulating spacer and reimplantation using a long-stem fluted uncemented hip replacement is not appropriate because it would be premature to reimplant this man’s hip while he is still receiving treatment for his deep-hip infection.

Question 573

Topic: Total Hip Arthroplasty (THA)
The anteroposterior hip radiograph of a 74-year-old healthy and active man who was seen in the office 18 months after a primary uncemented total hip replacement with a history of 3 hip dislocations. The last dislocation occurred 1 week ago and he was treated in the emergency department with a closed reduction and application of a hip abduction brace. All episodes of dislocation occurred when bending forward. Aside from the episodes of dislocation, his hip functions well. Examination revealed a normal gait with good abductor strength and pain-free hip movement. What is the most appropriate next treatment step?
. Prescribe physical therapy to work on abductor strengthening and reinforce hip position precautions.
. Recommend revision of the acetabular component to change cup position and increase the head and liner size.
. Recommend revision of the head and liner to a larger size using an elevated or oblique liner.
. Continue use of the hip abduction brace for 6 weeks and follow with physical therapy.

Correct Answer & Explanation

. Recommend revision of the acetabular component to change cup position and increase the head and liner size.

Explanation

This patient has had 3 hip dislocations since his hip replacement, and the radiograph shows an under-anteverted cup. He will likely continue to dislocate and surgery is indicated. The anteroposterior radiograph indicates that the cup is vertically oriented and not anteverted. His acetabular component is malpositioned and should be revised to provide the highest likelihood for success. A simple head and liner exchange with a malpositioned implant is less likely to succeed. Additionally, the radiograph shows sufficient acetabular bone stock medial to the cup. The addition of acetabular revision carries a low risk for increased morbidity and will allow a large cup with a larger femoral head with sufficient polyethylene thickness.

Question 574

Topic: Total Hip Arthroplasty (THA)
What clinical outcome is associated with total hip replacements that have metal-metal bearings (compared to total hip replacements with metal-polyethylene bearings)?
. Soft-tissue sarcomas
. Similar revision rates at 5 years
. Increased nephrotoxicity
. Pseudotumors

Correct Answer & Explanation

. Pseudotumors

Explanation

Patients with metal-metal total hip bearings have higher levels of cobalt and chromium in the bloodstream, but systemic migration of wear debris from total hip bearings is also common to total hip arthroplasties with polyethylene bearings. There is no direct evidence that patients with metal-metal total hip arthroplasties experience a higher incidence of cancer. Chromosome abnormalities have been detected in patients with metal-metal hip bearings, and the clinical consequences of this finding remain unknown. Also, pseudotumors can form around the periprosthetic joint space in response to localized metal ion debris and the host inflammatory response, although these tumors are not specific for failed metal-metal total hip arthroplasties. Metal-on-metal hip replacements have higher revision rates compared to conventional hip replacements in multiple registry studies. Although metal-on-metal articulations have not been shown to cause renal failure, they are not recommended in patients with chronic renal insufficiency.

Question 575

Topic: Total Hip Arthroplasty (THA)

A 49-year-old active man has groin pain 3 years after undergoing an uneventful total hip replacement using a cobalt-chrome femoral head articulating against a cobalt-chrome acetabular insert. The pain intensifies with activity and travels down his thigh. Examination and radiographic evaluation are not particularly helpful; there is no evidence of spinal or vascular disease. What is the next step in the evaluation of this patient?

. A 3-phase bone scan
. Measurement of synovial metal ions levels
. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and possible hip aspiration
. Bearing exchange to a metal-polyethylene combination

Correct Answer & Explanation

. A 3-phase bone scan

Explanation

ESR, CRP, and possible hip aspiration is the most logical next step even though at some point, bearing exchange may emerge as the ultimate treatment for a metal-metal adverse reaction in this patient. But the initial workup of a patient with a painful total hip that was otherwise functioning well must include the differential diagnosis of infection, which must be excluded with an appropriate laboratory workup, clinical history, and hip aspiration. The latter study may also help to diagnose a reaction to the metal bearing;cobalt and chromium levels in the aspirate can be investigated, and the color and quantity of the aspirate can be examined along with the cell count. Serum levels of metal ions at this stage could be both helpful and difficult to interpret.

Question 576

Topic: Total Hip Arthroplasty (THA)
This is a radiograph of a 72-year-old man who underwent an open reduction and internal fixation of a right femoral neck fracture. After 3 months he started to develop pain, and during the next 8 months he complained of progressive pain and shortening of the hip. What is the most appropriate treatment?
. Girdlestone
. Total hip replacement
. Hardware removal
. Hardware removal with revision open reduction and internal fixation

Correct Answer & Explanation

. Total hip replacement

Explanation

Even though a relatively short amount of time has passed since the index surgery, this patient has developed significant osteonecrosis that has caused collapse of the bony structures and the hardware to become prominent. Total hip replacement gives the most efficient pain relief. Hardware removal with or without re-reduction does not provide reliable pain relief. A Girdlestone procedure does not allow the patient to function.

Question 577

Topic: Total Hip Arthroplasty (THA)

A 59-year-old active woman underwent elective total hip replacement using a posterior approach. She had minimal pain and was discharged to home 2 days after surgery. Four weeks later she dislocated her hip while shaving her legs. She underwent a closed reduction in the emergency department. Postreduction radiographs show a reduced hip with well-fixed components in satisfactory alignment. What is the most appropriate management of this condition from this point forward?

. Observation and patient education regarding hip dislocation precautions
. Revision to a larger-diameter femoral head
. Revision to a constrained acetabular component
. Application of a hip orthosis for 3 months

Correct Answer & Explanation

. Observation and patient education regarding hip dislocation precautions

Explanation

First-time early dislocations are often successfully treated without revision surgery, especially when there is no component malalignment. In this clinical scenario, it appears the patient would benefit from better education about dislocation precautions. Hip orthoses are of questionable benefit unless the patient is cognitively impaired. Revision surgery can be successful, but is usually reserved for patients with recurrent dislocations. Question 43

Question 578

Topic: Total Hip Arthroplasty (THA)
What is the most common complication after a total hip replacement done through the anterior (Smith-Peterson) approach?
. Lateral femoral cutaneous nerve injury
. Heterotopic ossification
. Femoral nerve palsy
. Anterior dislocation

Correct Answer & Explanation

. Lateral femoral cutaneous nerve injury

Explanation

The incidence of lateral femoral cutaneous nerve injury is much higher than that of other complications after anterior-approach total hip replacement. This injury is usually clinically inconsequential, presenting as thigh numbness.

Question 579

Topic: Total Hip Arthroplasty (THA)

A 68-year-old woman with a 9-year history of type II diabetes is seen 11 weeks after an uncemented left total hip replacement. When seen 6 weeks after surgery, some mild erythema and induration at the distal incision was noted, but no drainage. She states that drainage started 2 weeks ago. Examination shows turbid drainage coming from the distal third of the incision with mild surrounding erythema. Hip range of motion causes mild discomfort. Investigations reveal an erythrocyte sedimentation rate of 45 mm/h(reference range, 0-20 mm/h) and C-reactive protein of 54 mg/L (reference range, 0.08-3.1 mg/L). A rapid polymerase chain reaction of the swabbed fluid is positive for methicillin-resistant Staphylococcus aureus.Hip aspiration under fluoroscopy is attempted but no fluid is obtained. What is the most appropriate treatment?

. Debridement of the skin and superficial tissues
. Debridement and removal of the implants and insertion of an antibiotic spacer
. Debridement of superficial and deep tissues including the joint with exchange of the modular head and liner
. Prescription for sulfamethoxazole and trimethoprim (Bactrim DS), 1 tablet, twice daily for 14 days, and then re-evaluate the patient

Correct Answer & Explanation

. Debridement of the skin and superficial tissues

Explanation

This case illustrates the treatment choices to address a postsurgical deep infection at 11 weeks postsurgery.Considering the progression of symptoms and persistent drainage, one needs to assume the infection is deep. Wound drainage beginning at 9 weeks after surgery is unlikely to be the result of a superficial infection. The absence of fluid on the attempted aspiration may occur in situations in which a sinus tract allows most of the fluid to escape the joint. Injection of contrast could confirm the presence of a sinus tract. Debridement and removal of the implants and insertion of an antibiotic spacer are most appropriate because the results of a single debridement at 11 weeks with a resistant organism are poor for curing or controlling infection. The use of antibiotics alone or a superficial debridement is inadequate in this setting.

Question 580

Topic: Total Hip Arthroplasty (THA)

During pre-operative templating for a primary total hip arthroplasty (THA), the surgeon decides to use a high-offset femoral stem instead of a standard-offset stem of the same neck length. What is the primary biomechanical effect of this decision?

. Increases global leg length
. Decreases the abductor moment arm
. Decreases the joint reaction force across the hip
. Increases the risk of bony impingement during abduction
. Decreases soft tissue tension in the gluteus medius

Correct Answer & Explanation

. Increases global leg length

Explanation

Increasing the femoral offset lateralizes the proximal femur, which increases the abductor moment arm. By increasing the abductor moment arm, less force is required by the abductor muscles to maintain the pelvis level during single-leg stance. This subsequently decreases the overall joint reaction force across the hip joint, reducing wear rates. It does not independently increase leg length.

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