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Insertion of Cemented Femoral Stem

- See:
       - characteristics of cemented femoral stems
       - loosening cemented femoral component:
       - collar: in THR
       - optimal cementing technique
       - removal of cemented femoral stems:

- Preparation for Insertion:
    - calcar planer:
         - this step is necessary to maximize contact w/ the femoral collar;
         - countersink final broach size approx 2 mm below femoral neck cut;
         - for prosthesis w/ collar, use calcar planer to make final adjustments of collar against medial aspect of femoral neck cortex;
    - medullary brush (optional)
         - stems placed in valgus will have a thicker mantale of soft medial cancellous bone;
         - failure to remove soft cancellous bone from medial surface of femoral neck will prevent the cement column from resting on a dense 
                 cancellous support bed and may lead to early loosening;
    - cement restrictor is inserted;
    - medullary canal is irrigated w/ pusatile lavage;
         - ref: Medullary lavage reduces embolic phenomena and cardiopulmonary changes during cemented hemiarthroplasty.
    - epinephrine soaked sponge is inserted into medullary canal;
    - "illegal" sponge is placed in the acetabulum;
    - apply the stem centralizer to the stem;
    - cementing: preparation and technique:

- Insertion Technique:
    - the leg is placed in secure position, and prosthesis is inserted;
    - prosthesis must be inserted w/ proper anteversion all the way down
         - it is illegal to rotate the femoral component w/in canal because this will create voids w/in the cement;
    - the prosthesis must be inserted w/ great care to maintain proper anteversion, and and care not to put the component in varus;
           - this is best performed by placing a finger on the femoral neck where the collar is planned to rest;
                  - when the component is inserted, the cement wells over the side obstructing the view of the femoral neck;
                  - w/ the finger on the femoral neck, there is no question of the proper amount of anteversion;
    - cement handling characteristics:
           - in the study by Shepard MF, et al, the authors sought to determine whether the time to cementation influenced the cement-prosthesis 
                  bond of four roughened cobalt chrome surfaces (60 grit-blasted, 10 grit-blasted, 10 grit-blasted with polymethylmethacrylate 
                  precoating, glass bead-blasted) and one polished cobalt chrome surface;
                  - roughened and polymethylmethacrylate precoated surfaces:
                         - had significantly greater tensile and shear strengths at early cementation times compared with polished surfaces;
                         - roughened components had significant decreases in tensile and shear strengths as cementation time increased from 2 to 4
                                  minutes and 2 to 6 minutes;
                         - the authors recommend that when using a roughened or precoated cemented femoral component, the surgeon should 
                                 consider cementing earlier with wetter cement to maximize the cement-prosthesis bond;
                  - polished surface stems:
                         - tensile and shear strengths for the polished surface were significantly lower than for the roughened surfaces and did not 
                                 change with longer cementation times;
                         - the authors recommend that when implanting a polished femoral component, it is prefer able that the cement is
                                 doughy, because the cement-prosthesis bond is not influenced by the wetness of the cement and it is easier to 
                                 maintain the orientation of the femoral component;
                  - ref: Influence of Cement Technique on the Interface Strength of Femoral Components.  
    - at first the prosthesis is inserted by hand but at the last 2 cm may require a stem impactor and mallet;
    - excess cement is removed;
         - reference:
                 Obturator-nerve palsy resulting from intrapelvic extrusion of cement during total hip replacement. Report of four cases.
    - remove debris from acetabulum & recheck leg length w/ trial head;
    - wipe clean the femoral stem and impact on the femoral head;
    - reduce the hip;


- Final Reduction:
    - remove sponge and ensure that no foreign body remains;
    - after reduction ensuring that there is no interposing soft tissue;
    - stability is rechecked;
         - some degree of anterior instability is accetable
         - posterior instability is nevere acceptable;
               - ensure that there are no impinging anterior osteophytes by placing finger between femoral neck & anterior acetabulum

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