summary THA Dislocation is a complication following THA and may occur due to patient noncomplicance with post-operative restrictions, implant malposition, or soft-tissue deficiency. Diagnosis can be made with plain radiographs of the hip. CT of the pelvis can assist with assessing for implant malpositioning. Treatment is closed reduction of the hip. Surgical management with possible revision THA is indicated for irreducible dislocations, recurrent instability, and implant malposition. Epidemiology Incidence 1-3% 70% occur within first month 75-90% posterior Etiology Mechanism anterior extension and external rotation of hip posterior flexion, internal rotation, adduction of hip Risk factors prior hip surgery (greatest risk factor) female sex >70-80 years of age posterior surgical approach repairing capsule and reconstructing external rotators brings dislocation rate close to anterior approach malpositioning of components ideal positioning of acetabular component is 40 degrees of abduction and 15 degrees anteversion in general, excessive anteversion increases risk of anterior hip dislocation; excessive retroversion increases risk of posterior hip dislocation spastic or neuromuscular disease (Parkinson's) drug or alcohol abuse decreased femoral offset (decreases tissue tension and stability) decreased femoral head to neck ratio prior spinal fusion or fixed spinopelvic alignment polyethylene wear common cause of late instability occuring >5 years after procedure Presentation History often reports activity that puts patient in a position that provokes dislocation (hip flexion, adduction, internal rotation) shoe tying sitting in low seat or toilet Imaging Radiographs recommended views AP cross-table lateral findings increased acetabular inclination > 60° increased acetabular anteversion > 20° aceabular retroversion look for eccentric position of femoral head as an indication of polyethylene wear and risk for impending dislocation CT scan indications to assess for implant malposition Treatment Nonoperative closed reduction and immobilization indications two-thirds of early dislocations can be treated with closed reduction and immobilization technique immobilize with hip spica cast, hip abduction brace, or knee immobilizer Operative polyethylene exchange indications stable well-aligned implants with extensive polyethylene wear thought to be sole reason for dislocation revision THA indications indicated if 2 or more dislocations with evidence of implant malalignment vertical acetabular component acetabular retroversion implant failure polyethylene wear techniques see below conversion to hemiarthroplasty with larger femoral head indications for soft tissue deficiency or dysfunction contraindicated if acetabular bone is compromised older technique rarely used with development of dual mobility implants resection arthroplasty indications when all options have been exhausted significant bone loss and soft tissue deficiency psychiatric patients who are dislocating for secondary gain Technique Revision THA techniques to prevent future dislocation during THA include realign components indicated if malalignment explains dislocation retroverted acetabulum vertical acetabulum short femoral neck lack of femoral neck offset retroverted femoral component head enlargement optimize head-neck ratio utilization of a lateralized liner increases femoral offset trochanteric osteotomy and advancement places abductor complex under tension which increases hip compression force conversion to a constrained acetabular component indications recurrent instability with a well positioned acetabular component due to soft tissue deficiency or dysfunction conversion to dual mobility implant conversion to tripolar construct
QUESTIONS 1 of 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (SBQ16HK.10) A 56-year-old male undergoes a total hip arthroplasty (THA). Which of the following would increase the patient's risk for dislocation or instability? QID: 211218 Type & Select Correct Answer 1 Acetabular cup anteversion of 16 degrees 4% (79/1757) 2 Acetabular cup abduction of 45 degrees 3% (50/1757) 3 High femoral offset 3% (52/1757) 4 Male sex 2% (42/1757) 5 Reduced femoral head to neck ratio 87% (1527/1757) L 1 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ13.197) Figures A and B show pre- and post-operative radiographs of a sedentary 75-year-old female who underwent surgery on her left hip. Based on the radiographic findings, what was the most likely indication for revision surgery? QID: 4832 FIGURES: A B Type & Select Correct Answer 1 Left acetabular fracture 1% (28/4878) 2 Left acetabular cup osteolysis 11% (521/4878) 3 Left femoral stem osteolysis 3% (122/4878) 4 Left hip instability 85% (4152/4878) 5 Left femoral stem valgus malalignment 1% (35/4878) L 2 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ11.26) A 73-year-old female undergoes a total hip arthroplasty (THA) using a cemented stem design shown in Figure A. She returns to clinic 3 years post-operatively with signifcant thigh pain. Current radiographs, shown in Figure B, demonstrate femoral subsidence. What affect does this have on the biomechanics of her THA? QID: 3449 FIGURES: A B Type & Select Correct Answer 1 Excursion distance is decreased 4% (185/4575) 2 Primary arc range is increased 2% (88/4575) 3 Abductor complex tension is decreased 87% (3963/4575) 4 Joint reactive forces are decreased 4% (165/4575) 5 Femoral offset is increased 3% (144/4575) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ10.15) All of the following are independent risk factors for dislocation after total hip arthroplasty EXCEPT? QID: 3103 Type & Select Correct Answer 1 Female gender 10% (335/3296) 2 Osteonecrosis 30% (1001/3296) 3 Inflammatory arthritis 12% (391/3296) 4 Post traumatic osteoarthritis 35% (1158/3296) 5 Age >70 12% (396/3296) L 5 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic (OBQ10.236) A 65-year-old male with chronic right hip pain undergoes the procedure seen in Figure A utilizing a posterior approach. Which of the following hip positions would put the patient at the greatest risk for dislocation? QID: 3335 FIGURES: A Type & Select Correct Answer 1 Abduction and external rotation 1% (20/3071) 2 Flexion and external rotation 3% (86/3071) 3 Flexion and internal rotation 95% (2903/3071) 4 Extension and internal rotation 1% (35/3071) 5 Extension and external rotation 1% (19/3071) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ10.98) A 68-year-old male 2 weeks status post left total hip arthroplasty experiences a painful clunk getting out of bed in the morning. He is unable to bear any weight on the left leg. A radiograph is provided in figure A. Following closed reduction under sedation, the hip continues to dislocate with flexion up to 90 degrees. Each of the following operative interventions will increase the stability of the hip EXCEPT: QID: 3192 FIGURES: A Type & Select Correct Answer 1 Revising the acetabular component to a more medialized position 79% (2677/3372) 2 Advancing the trochanter distal on the femur 10% (351/3372) 3 Converting to a femoral component with extended offset 3% (110/3372) 4 Replacing the acetabular polyethylene with a constrained liner 4% (144/3372) 5 Replacing the femoral head with a larger size 2% (81/3372) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic (OBQ09.202) Which of the following situations is appropriate for revision of a total hip arthroplasty to a constrained acetabular liner? QID: 3015 Type & Select Correct Answer 1 Periprosthetic acetabular fracture with resulting pelvic discontinuity 1% (28/2519) 2 Chronically infected total hip arthroplasty 0% (9/2519) 3 Recurrent dislocations in a patient whose femoral component is positioned in 15° retroversion 4% (89/2519) 4 Recurrent dislocations in a patient whose cup is positioned in 10° retroversion and 60° abduction 9% (219/2519) 5 Recurrent dislocations in a patient whose cup is positioned in 20° anteversion and 40° abduction 86% (2165/2519) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic (OBQ09.269) All of the following are acceptable indications for use of a constrained acetabular component EXCEPT: QID: 3082 Type & Select Correct Answer 1 Recurrent dislocations due to abductor insufficiency 4% (89/2137) 2 Recurrent dislocations due to unsalvageable capsular attenuation 1% (22/2137) 3 Recurrent dislocations due to severe polyethylene wear 83% (1770/2137) 4 Recurrent late dislocations without component loosening or malposition 7% (151/2137) 5 Recurrent dislocations due to cognitive or neuromuscular disease 5% (101/2137) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ09.126) A 60-year-old male had a total hip replacement 8 years ago. There is evidence of eccentric polyethylene wear and some retroacetbular osteolysis. You discuss treatment options of acetabular revision if the component is found to be loose intra-operatively versus isolated polyethylene exchange if the acetabular component is stable intra-operatively with the patient. What is the most common complication of isolated polyethylene exchange with bone grafting that should be disclosed? QID: 2939 Type & Select Correct Answer 1 Sciatic nerve injury 2% (46/2135) 2 Intraoperative acetabular fracture 9% (201/2135) 3 Postoperative hip instability 67% (1426/2135) 4 Infection 10% (220/2135) 5 Catastrophic implant failure 11% (227/2135) L 3 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ09.5) A 70-year-old man underwent total hip arthroplasty 4 months ago and has experienced 3 dislocations. Radiographs reveal no failure of the hardware and an acetabular component that has an abduction angle of 40 degrees and a version of 10 degrees retroverted. What is the most appropriate treatment for the recurrent dislocations? QID: 2818 Type & Select Correct Answer 1 hip abduction brace 1% (29/2731) 2 revision of the acetabular liner to a constrained type 9% (233/2731) 3 revision of the entire acetabular component 86% (2343/2731) 4 revision of the femoral head to a larger size 3% (77/2731) 5 revision to an extended offset prosthesis 1% (30/2731) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ08.260) What is the most common complication after revision of a total hip polyethylene liner in a patient with well-fixed femoral and acetabular shell components? QID: 646 Type & Select Correct Answer 1 dislocation 81% (3020/3735) 2 failure of the femoral component 0% (16/3735) 3 extensive osteolysis 6% (216/3735) 4 failure of the fixation between the liner and the acetabular shell 10% (389/3735) 5 fracture of the polyethylene 2% (79/3735) L 2 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic This is an AAOS Self Assessment Exam (SAE) question. Orthobullets was not involved in the editorial process and does not have the ability to alter the question. If you prefer to hide SAE questions, simply turn them off in your Learning Goals. (SAE07HK.90) A 68-year-old woman who underwent a right total hip arthroplasty 1 year ago has dislocated her hip five times since surgery. Radiographs show a retroverted acetabular component. What is the best treatment for this patient? QID: 6050 Type & Select Correct Answer 1 Use a constrained acetabular liner 3% (16/534) 2 Revise the femoral component to provide greater femoral offset 1% (3/534) 3 Revise the femoral head from a 28-mm head size to a 36-mm head size 1% (7/534) 4 Revise the acetabular component to 15 degrees of anteversion and 45 degrees of abduction 95% (506/534) 5 Perform a greater trochanteric osteotomy to improve soft-tissue tension 0% (1/534) L 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic This is an AAOS Self Assessment Exam (SAE) question. Orthobullets was not involved in the editorial process and does not have the ability to alter the question. If you prefer to hide SAE questions, simply turn them off in your Learning Goals. (SAE07HK.48) Figure 27 shows the AP radiograph of a patient who has late instability. The problem most likely occurred as a result of QID: 6008 FIGURES: A Type & Select Correct Answer 1 greater trochanter detachment. 12% (62/518) 2 femoral stem loosening. 8% (41/518) 3 wear. 45% (232/518) 4 osteolysis. 33% (173/518) 5 infection. 1% (7/518) L 4 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic This is an AAOS Self Assessment Exam (SAE) question. Orthobullets was not involved in the editorial process and does not have the ability to alter the question. If you prefer to hide SAE questions, simply turn them off in your Learning Goals. (SAE07HK.26) A 59-year-old woman who underwent a total hip arthroplasty 5 years ago now has recurrent dislocation following bariatric surgery and a weight loss of 200 lb. An attempt at converting to a larger head size and trochanteric advancement has failed. Her components are well aligned. What is the best course of action? QID: 5986 Type & Select Correct Answer 1 Resection arthroplasty 1% (3/396) 2 Hip abduction brace 3% (10/396) 3 Constrained acetabular liner 86% (339/396) 4 Thermal ablation of the posterior capsule 0% (1/396) 5 Conversion to a bipolar prosthesis 11% (42/396) L 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic This is an AAOS Self Assessment Exam (SAE) question. Orthobullets was not involved in the editorial process and does not have the ability to alter the question. If you prefer to hide SAE questions, simply turn them off in your Learning Goals. (SAE07HK.23) At the time of the revision surgery shown in Figure 14, the acetabular component was found to be stable. Polyethylene exchange with a standard ultra-high molecular weight polyethylene liner and grafting was performed. The patient is at significantly increased risk for QID: 5983 FIGURES: A Type & Select Correct Answer 1 loosening of the femoral component. 1% (7/653) 2 loosening of the acetabular component. 18% (119/653) 3 prosthetic hip dislocation. 44% (286/653) 4 rapid wear of the polyethylene. 15% (99/653) 5 continued expansion of the lytic defects. 22% (141/653) L 4 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ06.18) A 64-year-old healthy female patient underwent right total hip replacement (THR) through a posterior approach 6 months ago. She has now dislocated posteriorly 3 times, each followed by closed reduction under anesthesia in the operating room. A radiograph is provided in Figure A. Treatment should include: QID: 29 FIGURES: A Type & Select Correct Answer 1 Hip spica casting 0% (3/2962) 2 Revision of the femoral component to a modular stem with retention of the acetabular component 1% (42/2962) 3 Revision of the acetabular component 95% (2816/2962) 4 Hip abduction bracing 1% (22/2962) 5 Revision to a constrained liner with retention of the acetabular and femoral prostheses 2% (66/2962) L 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ04.64) A 62-year-old woman presents for her 1-year follow-up after a revision right total hip arthroplasty. She has no complaints of pain and has returned to all her activities of daily living. An AP radiograph is shown in Figure A. The black arrow in the radiograph indicates she is at higher risk for which of the following? QID: 1169 FIGURES: A Type & Select Correct Answer 1 Aseptic loosening 21% (372/1766) 2 Aseptic lymphocytic vasculitis-associated lesions (ALVAL) 1% (18/1766) 3 Dislocation 56% (986/1766) 4 Third body wear 17% (292/1766) 5 Catastrophic ceramic bearing failure 5% (82/1766) L 4 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic
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