MCQs-Hip Recon. 1
– Between uncemented and cemented stems – the uncemented have a higher incidence of thigh pain
– For acetabular osteotomies – the Salter, Steel, and Ganz all redirect the acetabulum and move the teardrop. The Chiari does not move the teardrop, but it does not redirect the acetabulum either. The only ones to redirect the acetabulum but not move the teardrop (leave the medial wall in its original position) are the dial or spherical osteotomy. These are intra-articular osteotomies.
– Ficat I AVN – x-rays normal, MRI positive
– Ficat II – sclerosis of head, maybe some fragmentation/cystic lesions
– Ficat III – subsclerotic lucency (cresent sign) with some collapse of the head
– Ficat IV – arthritis on both femoral and acetabular sides.
– elevated rim liners are associated with impingement and possible earlier loosening
– cement failure often due to microfracture and fragmentation (more so than osteolysis). This is found particularly around sharp corners of the stem, near cement voids, and in areas of inadequate cement mantle. Hence, the importance of good cementing technique.
– when looking to do a varus osteotomy of the femur, look at the abduction view. Ask: does the head reduce? (look at the Shentons line, look at the relationship between the inferior head and the teardrop). Then ask, is it congruent? (look at the weight-bearing area of the acetabulum and the femoral head). Then as, is it covered? (Tilt the x-ray so that the femur is pointing down to the floor, and measure the center edge angle).
– in normal adult cartilage, the tangential zone consists of a high concentration of collagen fibers – the tangential zone is like the “skin” of the cartilage. There are fibers running at 90 degrees to one another, but parallel to the joint surface. There is little intervening proteoglycan matrix in this layer.
– a contraindication to performing a valgus intertrochanteric osteotomy is limited adduction (ie. an abduction contracture); when performing the osteotomy, the leg will be abducted – if the patient has limited adduction preop, he/she will never get their leg back to neutral.
– conversely, a contraindication to performing a varus osteotomy is limited abduction (an adduction contracture); when performing the osteotomy, the leg will be adducted – if the patient has limited abduction, they will be able to spread their legs beyond neutral.
– “rapidly destructive osteoarthritis” is a concept more known in the European literature – it consists of rapid progressive destruction of the femora head with such severe flattening as to look like it had been “sheared off”. It mimics septic arthritis, rheumatoid, seronegative, osteonecrosis, and neuropathic. The tip off is that there are no signs of infection – but rule this out!
– for cemented femoral components, it is important that the medial border be broad and rounded in order to avoid stress concentration in the cement.
– in rheumatoids, do their hip replacement before knee – rehab is easier, you eliminate their referred pain, and you place a lot of stress on the total knee during a total hip replacement and risk fracturing it.
– reducing cement porosity improves the compressive modulus of cement
– total hip replacement after arthrodesis is associated with higher rate of mechanical failure and loosening (40% higher).
– osteonecrosis is dark on T1 – I think. The marrow is fatty and normally fat is bright on T1 – this is replaced by low intensity of the necrotic segment.
– line to line reaming and dome contact can result in greater acetabular lucency with uncemented cups – better to under-ream by 1-3 mm (if you under-ream by 4 mm, there is an increased chance of fracture)
– for uncemented cups, there may be some stress shielding in DeLee zone 2 (the central zone) because the cups are generally put in to achieve RIM FIT and hence the bonding would be more at the rim (zones 1 and 3) than in the center.
– the preferred method of reconstructing a dysplastic acetabulum in a high