الفهرس 
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Abstract
TKA is a common and highly effective procedure used in treatment of advanced osteoarthritis of knee joint (primary cases) and revision of failed primary cases. The number of revision arthroplasties continues to rise in parallel to the trend for increasing numbers of primary procedures.
Revision knee arthroplasty and also difficult primary cases with bone defects are a technically challenging procedure, with one of the most difficult issues that is frequently encountered being loss of bone. Accurately identifying and characterizing bone loss in primary and revision cases is very important in management of bone defects.
In primary cases especially in severe varus deformity bone loss occurs most commonly on the tibial side of the joint. Most often it is localized posteriorly on the plateau due to the frequently associated flexion contracture and deficient ACL.
In revision cases avoiding bone loss at the time of extraction of prostheses, and careful advanced planning for appropriate equipment and graft materials to be available at the time of revision surgery are all essential prerequisites for a successful outcome after revision knee arthroplasty.
The purpose of our study is to evaluate management of bone defects in TKR whether primary or revision procedure.
The management of bone deficiency in TKR is one of the most important items to provide proper alignment & stability, and bone defects will vary depending upon the location and degree of the bone loss. Bone defects are classified according to AORIC classification (which was used in our study) into:
In type-I defects, the metaphyseal bone is intact, with minor bone defects. (Occurs in 2 cases of our study managed by impaction bone graft)
In type-II defects, there is metaphyseal bone damage and cancellous bone loss in one femoral/tibial condyle (type IIA) or both femoral/tibial condyles (type IIB); bone grafting (in 1 case) or metal augmentation (in 17 cases) is needed.
In type-III defects, not included in our study.
Management of bone defects in TKR in both primary and revision cases are a challenging procedure which is dependent on preoperative preparation of the patient in the form of:-
Assessment of the size of the defect by plain x.ray.
Evaluation of the general condition of the patient to decrease the risk of infection.
Good preoperative preparation of the instruments used in the operation & methods used for management of bone defects whether bone graft or metal augments.
The selection for the augment technique is based on the defect size, the patient age and life expectancy. In general, the metal augments can address most of the defects.
The use of autograft is appropriate for the filling of cavitary defects as well as small defects involving less than one fourth of the cortical rim & should be considered in younger patients
Follow up assessment of our patients was done by clinical, radiological and functional evaluation:-
Clinical: ROM and stability.
Radiological: plain x-ray and assessment of component alignment by calculation of anatomic tibio-femoral, ALDFA & MPTA angles.
Functional: WOMAC score.
In our study we had achieved the following:-
(1) Correction of limb alignment.
(2) Correction of implant position.
(3) Flexion and extension gap balancing.
(4) Joint line restoration.
(5) Central patellar tracking.
(6) Adequate range of motion.
(7) Ligamentous stability.