• ,V7--Schai, Pascal A, Thornhill ot al. : Total knee-arthropiasty \vilh !he PI-'C system results at a minimum of Ion years and survivorship analysis. JB.1S, 80B. 1WS; 850-858.
  38-lnsall JN, Clarke 111) : Historic development, classification, and characteristics of knee prostheses. In: Surgry of the knee. By Insall JN and Scott WN Churchill livingstone, 2004; 1516-1552.
  39-Bouhm, Paul, Holy, Tatjna: Is there a future for hinged prosthesis in primary total knee arthroplasty a 20- year survivorship analysis of the Blauth prosthesis. JRJS, SOB, 1998; 302-309.
  40-Petrou G, Petou H, Tikerklis C ct al. : Medium-term results with a primary cemented rotating-hing total knee replacement. JBJS, 86B. 2004; 813-817.
  41 -HeiinkFl^rTl^enr~S~
  developed ceramics offer new solutions. Biomaterials, 23 ,
  1539-1551.
  42-Huang CH, Ming H, Liau JJ et al. : Osteolysis in failed total knee arthroplasty: A comparison of mobile-bearing and fixed-bearing knees. JBJS, 84A, 2002; 2224-2229.
  43-Lachiewicz PF, Soileau E : The rates of osteolysis and loosening associated with a modular posterior stabilized knee replacement. JBJS, 86A, 2004; 525-530.
  44-Callaghafi JJ: Mobile-bearing knee replacement: Cinical results. A' review of the literature. Clin Orthop, 392, 2001; 221-226.
  45-Wilson CJ, Fitzgerald B, Tait GR : Five year review of the rotaglide total knee arthroplasty.The Knee, 10, 2003; 167-171.

• TNI-'-u also stiniuialcs bone resorption thiough a mechanism \vhirh ,.., at least partially dependent upon the produetion of prostaghmdin !-..' (P(n-2) by cells in bone. Ofthe mediators studied, TNI^;-u is by far i !•,•_• most consistently released; it is released by both monocyles and macrophages in response to polymethyhnethacrylate, titanium, and polyethylene (l).
  in a study by Baldwin L. et al.. they used the techniques o! iminunoliistoeheniistry and reverse transcription polymerase chain reaction to identify the inflammatory cell types, cytokin.es and chcmokines within the interface ^fissue surrounding failed Accord Knee proslheses. Many T cells were identified within the tissue; however, the classical marker of activation, CD25 was expressed on very few cells. Molecular analysis failed"to detect the synthesis of either T-helper ! (Thl) or T-helper 2 (Th2) cytokines (68).
  These results suggest that the T cells are being actively recruited to the
  site   of inflammation   along  the  chemokine  gradients   but   are  not
  participating in a classical immune response (68).
  Ultra-high molecular weight polyethylene particle:; - isolated from human tissue stimulated osteoblast,proliferation and prostaglandin-H2 production and inhibited ceil differentiation and matrix production. These 'results indicate that particles of wear debris inhibit cell functions associated with bone formation and that osteoblasts may produce factors in response to wear debris that influence neighboring cells, such as osteoclasts and macrophages (69).
  prior studies  have demonstrated that particles of wear debris  induce eytokine secretion in,macrophages, which  initiates the _i production of promflamaiory cytokines. such as TNF-a (tumor necrosis factor-a), IL-l(intcrieukin-l), and IL-6 (interleukin-6) (70).
  More importantly, these factors directly or indirectly stimulate RANK-ligand expression in osteoblasts and stromal cells, leading to osteoclast formation and activation (71).

• II-Joint aspiration :

  Joint aspiration should bo per formed to ru[e_tnH_ injection before revision surgery is considered, even ifthe surgeon beiie\'es that no infection exists (10).
  
  
  Synovial fluid analysis should be done to assess the differential leukocyte count and the protein and glucose concentrations in order to help determine the presence or absence of infection (10).
  
  
  The aspirate should be examined-for ce!li% organisms, and metallic and polyethylene debris as well as sent for aerobic, anaerobic, and fungal cultures (93).

  The results of aspiration of the knee should be correlated with the finding of the physical and radiographic examinations to completely assess the presence or absence of infection. Suspicion of infection should be high and, even at the time of surgery, clinical judgment is important in determining the presence or absence of infection (10).
  
  
  
  

• 
  
• somelimcs difficult (o identify both epicondyles, especially the medial (Hie (92).

  When ihe femoral component has not migrated, preoperative ("f will 'mernsurc-lhc aivgle-b-e4ween ihe transverse axis of the component and the epicondylar line. This procedure helps to rotate the new femoral component appropriately (92).

  c-Distal femur position:

  The key to this step is restoring the distance from the joint line, distally and posteriorly. The epicondyles are a useful landmark to determine the joint line (93).

  The joint line on average is 25 mm from the lateral epicondyle and 30 mm from the medial epicondyle. Because the tibial cut. is established at 90 degrees to the tibial shaft, the joint line of the prosthetic knee, of average size, is 30 mm from both epicondyles (93).

  The distance from the epicondyles to the posterior joint line is similar to that of the distal joint line and is helpful in confirming the correct femoral component size (93).

  II-Rebuild the flexion space:

  a-Create a flat tibial surface:

  «.

  The key in selecting the correct size tibial component is to choose a size that will cover the entire proximal tibia without overhanging. The tibial surface should be perpendicular to the tibial shaft. This should be accomplished with minima! bone resection; when necessary, appropriate wedge or block augmentation should be added (93).

  b-Balance the flexion space:

  This step requires choosing the correct tibial polyethylene articulation. The provisional femoral component needs to be in place. The size of the polyethylene chosen should fill the flexion space (93).
  
  
  
  

  •**•#"•;•••

  
  
  
  

• 
  
• so    an    examination   of   those   regions   is   mandatory.    A    eonip!r'_a-neurovascular examination of the extremities should be performed (10,.
  XII-Examination of the knee :
  Hxamination of the knee should include an assessment of the quality, color, temperature of the skin near the incision, an assessment of iSu­stains of the incision, and a determination of the presence or absence of an effusion (101.
  The stability of the total knee replacement should be evaluated., and the overall alignment of the extremity and the alignment of the foot should be recorded (10).
  2-Radiological
  Radiological methods of detecting loosening with or without infection have included plain radiography, arthrography and radionuclide studies
  (83).
  The clinical need for revision may be predicted radiologicaliy 3 years after operation in symptomless patients by noting a change in component position combined with progressive radiolucent lines and osteolysis. Thus, radiological follow-up should be continued for a minimum of 3 years after knee replacement (53).
  The use of a stem enabled the detection of raclioluccnt lines which \ve believe were missed around prosihes'es with condylar pegs. Thus, (lie use of a stem improves the prediction" of failure (but does not improve fixation) (63).

• Small (less than 5mm) uneontaincd detects can also be repaired with cement alone or eement and screws.
  Intermediate (5 to ULinm) imcontnined detects can be managed with modular wedges.
  Large (greater than 10 mm) uneontained defects arc best managed with modular augments or structural allourafts (93V
  5-Prosthetic selection :
  Implant selection is based primarily on the severity of bone loss and the status of the ligamentous and soft-tissue stabilizing structures at the time of revision surgery (95).-"
  The goal is to provide a stable knee and a stable implant with an axis of _rotatign near the normal axis with the use of the least-constrained implant ^xpectecftcTachieveTfns
  In the setting of ligamentous loss or insufficiency, increasing constraint from a posterior stabilized prosthesis to a nonlinked constrained or rotating-hinge prosthesis may be necessary (95).
  In the setting of massive segmental bone loss, a modular segmental replacement prosthesis or an allografi-prosthesis composite may be required (95).
  The primary advantages of canal filling cementless stems are ease of removal and greater retention of bone stock should rerevision become necessary (97).
  The results associated with canal-filling cementless steins have been comparable with those associated with cemented stems. Nelson et al. recommend the use of cementless stems for patients undergoing revision total knee arthroplasty (97).

• 
  
• Rocking or torsion ot" the posterior stabilized femoral, component
  during removal may result in a fracture of the femur through the area of
  the jntercondylar notch (87).                          
  In a revision setting, where infection has been ruled out, it is better to leave remaining well-fixed cement in the canal rather than riskin<> excessive bone loss or perforating the canal trying to remove it (93).
  4-Reconstniction :
  When performing revisions, Brassard et al.. prefer to use a three-step method. The three steps are recreating the femur, rebuilding the flexion space, and rebuilding the extension space. The femur is prepared first because of the availability of more reliable anatomical landmarks (93).
  I-Recreate the femur:
  a-Size the femur:
  It is helpful preoperatively to procure the operative notes from the previous procedure. Another useful preoperative step is to template the opposite side in order to obtain a relative idea of the sizes (93).
  There usually posterior bone loss, so templating intraoperatively runs the risk of undersizing the federal component. The epicondylar width of the femur can also be helpful in selecting the appropriate size (93).
  b-Fcmoral component rotation:
  With 90 degree flexion, the rotation of the femoral component and the stability in flexion should be determined. Rotational landmarks are identified. In revision surgery, the posterior aspect of the femoral condyles and Whiteside lines are not available. The epicondylar axis may be used and is considered by many authors as the best landmark but it is