In Judet views of the pelvis, the right obturator oblique view shows? cassette.
Core decompression following avascular necrosis (AVN) of the femoral head is more likely to be successful if the patient has not progressed beyond?
FICAT II. As long as the femoral head is in the pre-collapse phase and has minimal involvement (<30% ideally) core decompression is likely to be beneficial. Results are still not fully conclusive, but current thinking is that pre-collapse heads may be decompressed successfully, but once the collapse (crescent sign, FICAT III) has appeared, salvage is not possible in this way. Whether or not there should be addition of other products such as bone morphogenic protein or growth factors is still controversial.
In which situation following deep infection of a total hip replacement could single- stage revision be considered? raised. commenced antibiotics. and the patient is commenced on antibiotics.
There is a known organism from preoperative aspirate and the patient has commenced antibiotics. Selected patients may undergo single-stage revision, with reported better functional outcome than two-stage revisions. The prerequisites for this are healthy soft tissues, minimal bone loss allowing for cement to be inserted, and a known pathogen with sensitivities. Significant severe bone loss, an unidentified pathogen and the presence of multi-resistant bacteria are contraindications to single-stage revision surgery.
In planning total hip replacement for a patient with Paget’s disease, which of the following is not an expected finding?
Valgus deformity of femoral neck. All the above are seen due to remodelling of bone and high vascularity, except a valgus deformity. Typically, varus deformity is seen due to initially osteoporotic change which causes deformity under loading before remodelling into its final shape; this is also responsible for anterolateral diaphyseal bowing. Stress fractures may also be seen on the convex side of the femoral diaphysis. Bone may have lytic lesions or be unusually dense, depending on the activity of the disease process.
The following are known causes of sciatic nerve dysfunction following total hip replacement except? 72
Pressure from straps of abduction wedge pillow. Straps from an abduction wedge pillow may cause local pressure to the common peroneal nerve, rather than the sciatic nerve, at the level of the fibular neck resulting in foot drop. The most commonly injured part of the sciatic nerve is the region which goes on to become the common peroneal nerve. In one study, peroneal palsy was found more commonly after average lengthening of 2.7 cm and sciatic palsy with average lengthening of over 4.4 cm.
Which of the following is true regarding labral tears of the acetabulum? femoro-acetabular impingement.
They are associated with degenerate changes and cysts when due to femoro-acetabular impingement. Labral tears are often associated with subtle abnormalities of hip anatomy causing femoro-acetabular impingement (FAI). Painful clicking, snapping and similar symptoms are often due to labral tears in association with FAI. Labral tears may present as groin pain usually in certain positions and repetitive movements such as running.
For infection following total hip replacement, wound washout and exchange of accessible components is acceptable management if?
Infection is within 3 weeks of surgery. Phillips et al found 41% of infections were successfully treated with debridement and antibiotics. Crockarell et al. found debridement successful only if performed within 2 weeks of onset of symptoms. 84
Which of the following is not one of the trabecular patterns in the proximal femur?
Lesser trochanter group. There are four main trabecular patterns in the proximal femur. There are two compressive, one tensile, and one greater trochanteric group but none relating specifically to the lesser trochanter.
What is meralgia paraesthetica due to?
Compression of the lateral cutaneous nerve of thigh. The lateral cutaneous nerve of thigh may typically be compressed at several locations, such as the inguinal ligament, by tight belts (e.g. weightlifter’s belt), resulting in pain in the anterolateral part of the thigh.
Which of the following is the greatest risk factor for heterotopic ossification following elective total hip replacement?
Previous formation of heterotopic ossification. Although the exact aetiology is poorly understood, if there is a history of heterotopic ossification, then it is very likely to recur at a new site of surgery. Other factors include: ankylosing spondylitis, hypertrophic osteoarthritis, and diffuse idiopathic skeletal hyperostosis, with weaker evidence for extensive soft tissue handling/stripping, or bone debris from reamings. Although patients with head injuries are found to produce extensive calcific deposits a patient would not have elective total hip replacement so soon after significant head injury. Over-expression of bone morphogenetic protein-4 BMP-4) may be implicated in the pathogenesis of heterotopic ossification.
A patient is to have primary total hip replacement and takes methotrexate for rheumatoid arthritis. Methotrexate should be? following surgery. 73
Continued as usual. Although there is a higher rate of infection in general in rheumatoid patients, continuing their methotrexate at the normal dose has not been shown to affect their risk of infection. Grennan et al found that methotrexate made no difference to early infection following elective orthopaedic surgery when two groups were compared, one which continued and a group that didn’t; other drugs such as penicillamine, indomethacin, ciclosporin, hydroxychloroquine, chloroquine and prednisolone did increase the early infection risk post-operatively. Conversely, discontinuing their methotrexate may result in disease flare that impedes their post-operative rehabilitation.
A 72-year-old patient is suspected to have an infected total hip replacement, rather than aseptic loosening, 8 years following surgery. Which of the following would be a useful investigation to differentiate between them?
Hip aspiration. Although a radio-labelled white cell scan is more likely to be positive in infection rather than inflammation, it cannot be used to definitively differentiate between the two. A radionuclide bone scan would appear hot in both conditions. A positive hip aspirate would both identify infection, as well as guide antibiotic treatment. Von Rothenburg et al found a Tc-99m-labelled scan had sensitivity of 93% but specificity of 65%. Therefore, a positive result (positive predictive value 63%) may not definitely mean an infection, whereas a negative result (negative predictive value 94%) is likely to help rule out infection.
Which of the following is true regarding impaction grafting for revision total hip replacement with femoral bone loss? revision. amount of allograft used.
It is best with a polished tapered stem. Polished tapered stems such as the Exeter stem are best suited to impaction grafting, as subsidence is expected. This is thought to allow subsidence in the cement mantle, and subject the cement to creep, thereby distributing load evenly and encouraging bone to remodel. Although earlier studies have waned against subsidence, Wraighte et al showed that there was no link between subsidence (median 2 mm at 1 year; up to total 10 mm in some patients) and 10-year survival. 85
What is the effect of repairing the posterior capsule in the posterior approach for total hip replacement?
Reduce dislocation by a magnitude of 10. Although there are many studies, most conclude that there is a beneficial effect of repairing the posterior soft tissue structures. A meta-analysis by Kwon et al found that the rate of dislocation reduced from 4.46% to 0.49% if repaired.
Which of the following is the most important prognostic indicator for the success of a hydroxyapatite (HA)-coated stem?
Thickness of HA of at least 50 mm. Although all these factors are important when considering cementless fixation, they are not all relevant to hydroxyapatite-coated stems, and apply also to other stems such as porous- coated and grit-blasted stems. In a canine model, it has been shown that there is greater total bone apposition and bone ingrowth in implants coated with minimum 50 mm hydroxyapatite at the level of the isthmus and the calcar, although there was no difference between having 50 or 100 mm thickness coating on the amount of bony ingrowth.
A 27-year-old patient presents with groin pain and clicking. He has a history of mild developmental dysplasia of the hip (DDH) as a child. Which of the following is the most likely finding on a plain radiograph?
Femoral head/neck junction prominence. The patient is likely to be suffering from cam-type femoro-acetabular impingement, often presenting secondary to DDH, Perthes, or slipped upper femoral epiphysis, with a head/ neck junction prominence that may also lead to labral degeneration, cysts and tear. Degenerate changes at the articular surface in mild DDH is rare in a patient of this age, although cysts may be seen at the head/neck junction if there is impingement.
A 74-year-old patient has developed degenerate change in her hip requiring total hip replacement. She has previously had a pertrochanteric femoral fracture fixed with a dynamic hip screw device. What is the correct surgical management? 74 fully coated uncemented stem. diaphyseal fracture. cemented stem. lowest screw hole.
Remove metalwork, insert cemented stem passing two cortical thicknesses below lowest screw hole. There is no need to reinforce the femur externally. A well-cemented stem must pass well past the lowest screw hole to reduce the risk of a stress riser. Hip resurfacing in a patient of this age is not recommended.
Following total hip replacement, deep infection is?
Less in ceramic than polyethylene cups. The Swedish Hip Registry reports that deep infections are slightly lower with ceramic components. The exact mechanism is unclear, but may be due to bacterial adhesion being poorer on the smoother surface of ceramic components.
Which of the following is true of the centre-edge angle of Wiberg? acetabulum.
If less than 15º, it is one of the indications for pelvic osteotomy. This is the angle between a vertical line through the centre of the femoral head and a line connecting the centre of the femoral head to the edge of the acetabulum, used in patients over the age of 5, and useful in adults. Greater than 25º is considered normal, and less than 20 is considered a dysplastic acetabulum. Less than 15º is marked dysplasia, and the patient may benefit from osteotomy of the acetabulum.
A 40-year-old patient is developing avascular necrosis of the femoral head. The contour is normal (i.e. no collapse), although structural changes are evident on MRI. What is the preferred treatment?
Vascularized fibular graft. As long as there is no collapse of the femoral head, vascularized fibular graft has been shown to be superior to non-vascularized by reducing progression to collapse, as well as having better Harris Hip Scores.
Which nerve is at risk during the ilio-inguinal approach to the pelvis, and often needs to be divided?
Lateral cutaneous nerve of thigh. The ilio-inguinal approach is an exam favourite. It affords exposure to the inner aspect of the pelvis from the sacroiliac joint all the way to pubic symphysis. The lateral cutaneous nerve of thigh often is in the way and must be sacrificed. Although infrequently used by 86 most surgeons, it would be worth memorizing the concepts of this approach, particularly the structures at risk in the three ‘windows’: Lateral – between the iliac wing and the iliopsoas muscle; Middle – between the femoral nerve (iliopsoas muscle) and the external iliac vessels; Medial – between the lymphatics and the rectus abdominus at the level of the pubic tubercle.
What type of lubrication is found in hard-on-hard total hip replacements at the point when the two articulating surfaces are not in contact? 75
Hydrodynamic. Although the majority of lubrication in total hip replacements is boundary lubrication, hard-on-hard bearing surfaces, such as metal-on-metal, have been found to have hydrodynamic lubrication during the motion phase of the gait cycle, particularly effective when the prosthesis is polar bearing with high conformity.
When cementing a femoral stem, what is thought to be the most likely cause for severe hypotension related to ‘bone cement implantation syndrome’ (BCIS)? monomer, as opposed to small area in acetabulum.
Multiple emboli. Donaldson et al have attempted to define this poorly understood phenomenon: “BCIS is characterized by hypoxia, hypotension or both and/or unexpected loss of consciousness occurring around the time of cementation, prosthesis insertion, reduction of the joint or, occasionally, limb tourniquet deflation in a patient undergoing cemented bone surgery.” Current thinking on aetiology leans towards multiple embolic showers of fat, marrow, cement particles, air, bone particles and platelet/fibrin aggregate. Previous theories of methylmethacrylate monomers entering the circulation and causing significant vasodilatation have now largely been discounted in favour of the embolic theory.
In the posterior thigh, the sciatic nerve lies between which two muscles?
Gluteus maximus and adductor magnus. The sciatic nerve passes through the interval between piriformis and superior gemellus to lie under gluteus maximus, and passes over the gemelli, obturator internus, and quadratus femoris, before passing over the posterior surface of adductor magnus until it divides into its terminal branches. Cross-sectional anatomy of the limbs at different levels is a popular exam question, and it is worth memorizing the major structures in relation to each other.
Which type of pelvic injury is most likely to result in urethral/bladder injury? 76
Inwardly displaced parasymphyseal fracture >1 cm. The single biggest predictor of urethral injury is pubic symphysis diastasis, especially of >1 cm, along with medially displaced medial 1/3 fracture. However, inward displacement didn’t result in a large number of patients having urethral injury. It would appear that the traction caused to the urethra is more significant than compression. 87 1. After cementing in a total knee replacement for a valgus knee, you find that it remains tight laterally in extension. The next most appropriate step is to? a. Carry out a medial release. b. Carry out a medial release and increase the size of the polyethylene insert. c. Release the iliotibial band. d. Release popliteus. e. Decrease the size of the polyethylene insert. 2. Which of the following statements regarding anterior cruciate ligament (ACL) grafts is false? a. The maximum load to failure of a patellar tendon graft is approximately 2600 newtons. b. The use of an autologous hamstring graft results in a 50% loss of hamstring strength. c. The maximum load to failure of a quadruple hamstring graft is approximately 4500 newtons. d. Allograft processing does not always alter the mechanical properties of the graft. e. The maximum load to failure of the native ACL is approximately 2100 newtons. 3. Which of the following is considered to be the primary stabilizer of knee to external rotation? a. Anterior cruciate ligament (ACL). b. Posterior cruciate ligament (PCL). c. Lateral collateral ligament (LCL). d. Medial collateral ligament (MCL). e. Patellar tendon. 4. A 34-year-old man presents with a 3 month history of knee pain, with an inability to squat. The most likely diagnosis is? a. Primary osteoarthritis. b. Osteochondral defect. c. Loose body. d. Posterior horn meniscal tear. e. Pigmented villonodular synovitis. # Cambridge University Press 2012. 93
