summary Four important variables that help determine the stability of THA component design component position soft-tissue tensioning soft tissue function Component Design Femoral component design large femoral heads decreased dislocation rates due to head-neck ratio increased definition diameter of femoral head/diameter of femoral neck importance larger head-neck ratios allow greater arc range of motion prior to impingement skirts can be avoided definition skirts are attachments used to extend the length of the femoral neck importance skirts decrease the head-neck ratio jump-distance is increased definition amount of translation prior to dislocation importance large femoral heads are seated deeper within the acetabulum, increasing jump-distance increase in jump-distance increases joint stability a larger femoral head will not compensate for abductor deficiency or a vertically positioned cup femoral offset see "soft tissue tensioning" below Acetabular component design elevated rim liner a posteriorly placed elevated rim liner may increase joint stability lateralized liner increases soft-tissue tension by increasing offset has been shown to increase the risk of acetabular component loosening Component Position Acetabular position recommendations anteversion 5° - 25° abduction 30° - 50° medialization of the cup increases moment arm of the abductors (gluteus medius & gluteus minimus) increased moment arm leads to decreased joint reactive forces caveats surgical approach may affect optimal position of implants posterior approach should err towards more anteversion anterior approach should err towards less anteversion hypertrophy of the anterior inferior iliac spine may cause component impingement and instability complications excessive retroversion posterior dislocation excessive anteversion anterior dislocation excessive abduction (high theta angle, vertical cup) posterior superior dislocation eccentric polyethylene wear and late instability excessive adduction (low theta angle, horizontal cup) impingement in flexion inferior dislocation Femoral stem position recommendations 10°- 15° of anteversion caveats more difficult to adjust femoral component version in uncemented femoral components Combined version definition femoral component anteversion plus acetabular component anteversion recommendations 37 degrees Soft Tissue Tensioning Abductor Integrity gluteus medius serves as the major hip abductor muscle; insufficiency/tear leads to Trendelenburg gait gluteus maximus and/or fascia lata transfers can be utilized in chronic abductor insufficiency Restoration of offset definition perpendicular distance from femoral head center of rotation to the axis of the femur importance increased offset leads to decreased impingement decreased joint reaction force increases soft tissue tension without increasing leg length decreased offset may lead to instability abductor weakness gluteus medius lurch increasing offset improves hip stability techniques to increase offset increasing length of femoral neck decreasing neck-shaft angle medializing the femoral neck while increasing femoral neck length trochanteric advancement alteration of the acetabular liner (see "component design" above) Soft Tissue Function Three main factors controlling proper soft tissue function central nervous system pathology that affects the central nervous system stroke cerebellar dysfunction dementia MS Parkinson's myelopathy delirium alcoholism peripheral nervous system pathology that affects the peripheral nervous system spinal stenosis (gluteus medius is L5) peripheral neuropathy radiculopathy paralysis/paresis local soft tissue integrity trauma myoligamentous disruption deconditioning aging process poor health irradiation osteolysis collagen abnormalities myopathy malignancy infection
QUESTIONS 1 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Previous Next 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 (OBQ18.208) A 70-year-old healthy woman presents with recurrent left prosthetic hip dislocations after undergoing total hip arthroplasty 6 months ago. Workup for infection has been negative. Radiographs from her visit today are depicted in Figure A. Which of the following will most definitively prevent further dislocations? QID: 213104 FIGURES: A Type & Select Correct Answer 1 Exchange polyethylene liner to a lipped acetabular liner 1% (33/2459) 2 Exchange polyethylene liner to a thinner liner and increase the size of femoral head component 2% (45/2459) 3 Cemented acetabular component revision 10% (238/2459) 4 Uncemented acetabular component revision 81% (1995/2459) 5 Exchange polyethylene liner to a constrained acetabular liner 5% (122/2459) L 3 Question Complexity A 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 (OBQ09.160) A 65-year-old female undergoes total hip arthroplasty. Instability of the prosthesis with straight hip flexion is identified during intra-operative range of motion testing. A fluoroscopic image is shown in figure A. Impingement is caused by the structure labeled with the asterisk. Which muscle originates upon this structure? QID: 2973 FIGURES: A Type & Select Correct Answer 1 Sartorius 4% (125/3411) 2 Direct head of the rectus femoris 68% (2312/3411) 3 Reflected head of the rectus femoris 24% (825/3411) 4 Obturator externus 2% (70/3411) 5 Obturator internus 2% (58/3411) L 3 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (SBQ08OS.108.1) What is an advantage of utilizing a 36-mm instead of a 28-mm femoral head in the setting of a revision total hip arthroplasty? QID: 210084 Type & Select Correct Answer 1 Compensating for abductor deficiency 13% (372/2961) 2 Decreasing volumetric wear 9% (269/2961) 3 Decreasing trunion stress 3% (82/2961) 4 Delaying neck-socket impingement 70% (2081/2961) 5 Compensating for vertical cup placement 4% (121/2961) L 3 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 (OBQ07.117) Figure A depicts an individual seen from behind during a single-leg stance on the left lower extremity. Which of the following modifications during a left-sided total hip arthroplasty would exacerbate the abnormal findings present in Figure A? QID: 778 FIGURES: A Type & Select Correct Answer 1 Decreasing femoral offset 84% (3118/3716) 2 Changing from a standard offset neck to an extended offset neck 8% (298/3716) 3 Increasing femoral head size 1% (29/3716) 4 Increasing femoral neck length 5% (179/3716) 5 Moving acetabular cup inferiorly 2% (73/3716) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic (OBQ07.213) In total hip arthroplasty, which of the following techniques will lead to improved stability by increasing the abductor tension? QID: 874 Type & Select Correct Answer 1 Use of a high offset femoral component 94% (4069/4342) 2 Decreasing neck length 0% (17/4342) 3 Use of a low offset femoral component 1% (62/4342) 4 Increasing the head size 1% (50/4342) 5 Medializing the acetabular component 3% (133/4342) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic (OBQ06.2) During total hip arthroplasty, which of the following techniques increases range of motion prior to impingement? QID: 13 Type & Select Correct Answer 1 Using implants with a smaller femoral head 4% (204/4782) 2 Using implants with a larger femoral head to neck ratio 93% (4457/4782) 3 Using a ultra high molecular weight polyethylene liner on the acetabulum 1% (37/4782) 4 Decreasing femoral offset 1% (57/4782) 5 Cementing the femoral stem 0% (5/4782) L 1 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic (OBQ05.268) A surgeon is planning to revise a left hip resurfacing component to a total hip arthroplasty. He wishes to decrease the joint reaction force of the left hip by increasing the femoral offset. Which of the following labeled measurements found in Figure A best describes femoral offset? QID: 1154 FIGURES: A Type & Select Correct Answer 1 Line 1 2% (68/2786) 2 Line 2 1% (29/2786) 3 Line 4 95% (2644/2786) 4 Line 5 1% (15/2786) 5 Line A 1% (21/2786) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ05.245) The schematic shown in Figure A displays a ceramic-on-ceramic total hip arthroplasty articulation with impingement. Which of the following modifications would increase the primary arc range of motion? QID: 1131 FIGURES: A Type & Select Correct Answer 1 Addition of a collar on the femoral head 1% (26/2666) 2 Exchanging the ceramic liner with a hooded polyethylene liner 1% (27/2666) 3 Increasing the femoral head size 92% (2447/2666) 4 Increasing the femoral offset 3% (93/2666) 5 Increasing the acetabular anteversion 3% (67/2666) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ04.269) Which of the following factors is most likely to increase the risk of hip dislocation after a total hip arthroplasty (THA)? QID: 1374 Type & Select Correct Answer 1 Large head-to-neck ratio 2% (86/3578) 2 Use of a skirted femoral head 79% (2817/3578) 3 Femoral component in 15 degrees of anteversion 4% (128/3578) 4 Acetabular cup in 15 degrees of anteversion 3% (115/3578) 5 Acetabular cup in 50 degrees of abduction 12% (420/3578) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic
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