MCQs-Hip Recon. 2
dislocation is with structural autograft and cementless acetabular component. (use the femoral head as the shelf autograft).
– for antibiotic loaded cement, the local level of antibiotic cease to be significant at 6 weeks.
– compared to cobalt chrome, titanium hip stems are advantageous because they are less stiff (when comparing stems of equal size and shape). The stiffness depends on a material factor (modulus) and a geometric factor (size and shape). Titanium does have a lower modulus than cobalt chrome, but in order to make an estimation of stiffness you have to know the size and shape characteristics, particularly the radius. Even though titanium has a lower modulus, if the titanium stem were wider, it may still be stiffer than a cobalt chrome stem. NOTE THE DIFFERENCE BETWEEN THE TWO.
– if you shorten the hip, you decrease the soft tissue tension about the hip and increase the risk of dislocation.
– core decompression for AVN has the greatest chance of success in Ficat I. Is also recommended for II and early III.
– patients on NSAIDS have risks of GI system (bleeding), increased blood pressure, bone marrow suppression, liver damage, and kidney damage. They should have a blood count and chemistries every 6 months.
– the most efficient way of determining whether someone has an occult hip fracture is an MRI (if early). Bone scanning tends to be hotter a day later I think.
– ceramic heads may reduce long term loosening because they are more polished than metal heads and thus produce less poly wear. They are harder (allows them to be more polished) and do deform less.
– for the young patient with dysplasia, an incongruent joint that is uncovered, with some joint space narrowing – do a Chiari.
– when doing the acetabular reconstruction, if there is less than 50-70% host bone contact, you have to think about doing something other than a simple uncemented reconstruction – options include structural allograft with cage and cemented cup, or impaction allograft with cage and cemented cup
– hybrid hip replacements are en vogue because of the high incidence of acetabular failure at 10 years with cemented cups.
– a femoral varus osteotomy will decrease the abductor force by lateralizing the GT and increasing the lever arm of the abductors. Although you might lateralize the shaft and put the adductors on more stretch, in reality you tend to shorten the femur and thus there is more slack in the adductors – hence adductor force is also diminished. Also, you often tend to medialize the shaft when you apply the fixation.
– for acetabular cups, it is felt that the poly should be at the very least 6-8 mm. Smaller head sizes should be used with smaller cups. The size of the head in and of itself does not affect dislocation rates – it is the ratio of the head:neck width. So if the cup is going to be small, you better plan on a smaller head.
– for fixing valgus or varus intertrochanteric osteotomies, the optimal fixation device is some sort of fixed angle device.
– in the failing cement-bone interface, the histology is of PLUMP active MACROPHAGES with intracellular and extracellular polyethylene, and a fibrous membrane.
– for protrusio – best reconstruction is to use an ingrowth cup with rim fit and bone graft beneath it
– acetabular rim syndrome is seen in young patients with groin pain, intermittent mechanical symptoms, and a sensation of clicking or locking. They often have a congruent but shallow acetabulum which leaves part of the femoral head uncovered – this causes shear stress on the labrum which will eventually tear, and lead to progressive localized degeneration. This is a good indication for osteotomy. A Ganz type I dysplasia has acetabular incongruency, shallowness, and uncovering. A Ganz type II dysplasia has acetabular congruency, shallowness, and uncovering.
– in a young patient who has a SCFE and you are considering osteotomy on. Look at the range of motion to decide what he is lacking – look at flex/ext, rotation,