الفهرس 
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Abstract
SUMMARY
Management of acetabular bone stock loss in revision of a
previous hip arthroplasty, or in primary deficiencies resulting from
either an abnormality in growth or a condition that alters the shape
of the acetabulum, is recently considered one of the major surgical
challenges in arthroplasty. That is why many orthopedic clinicians
and researchers are working daily all over the world for finding a
variety of solutions for this condition.
Deficiency of the acetabular bone stock may result from a
number of factors: (1) osteolysis caused by wear, loosening, or
infection, (2) excessive bone resection at the time of previous
surgery, especially if the patient has had a resurfacing procedure or
previous acetabular revision, (3) preexisting bone deficit from
acetabular fracture or dysplasia that was not corrected at the time
of previous surgery, and (4) inadvertent destruction of bone during
removal of a previous component or cement. Some benign tumours
affect the hip bone and can cause acetabular bone stock defect.
Malignant tumours and more commonly bone metastases which
can cause acetabular lesions are mostly ossific and not lytic
lesions, while acetabular defects in such cases are caused after
tumour resection.
So, bone deficiency in the acetabulum can be encountered
in primary and in revision cases acetabular reconstruction.
Many classification schemes have been formulated to
describe acetabular deficiencies. The most commonly used
schemes are those that are easy to remember, easy to reproduce,
and are most useful in guiding treatment options. The classification
systems referred to most often in the literature are those developed
by the American Academy of Orthopedic Surgeons (AAOS)
Committee on the Hip. In primary arthroplasty, hip dysplasia is the
most common disease that results in primary acetabular deficiency
and hips with dysplasia can be classified on the plain radiographs
using the classification by Crowe et al. Another commonly used
classification is Paprosky classification system which is based on
the severity of bone loss and the ability to obtain cementless
fixation for a given bone loss pattern. Pathological fractures and
defects due to acetabular bone metastasis are subdivided into four
groups according to Harrington’s Classification in acetabular
metastasis defects.
Although in many cases acetabular defects are discovered
intraoperatively, specially in revision cases, when the condition is
suspected preoperatively it is important to understand the nature
and extent of the bone deficiency before undertaking the
reconstruction operation so that special equipment can be obtained,
if necessary, the type and amount of allograft, if needed, the type
and size of protrusion shell, and the presence or absence of column
defects, should be anticipated. So, in addition to clinical evaluation
by giving a hip score, a variety of imaging techniques are used to
evaluate the condition. Significant tests to diagnose deep infection
if suspected should be done in addition to routine preoperative
investigations.
Acetabular bone stock deficiency in primary and revision
total hip arthroplasties can usually be effectively managed by
combining the use of appropriately designed implants and
structural or nonstructural bone grafts or bone graft substitutes. The
objectives of acetabular reconstruction are (1) to restore the center of rotation
of the hip to its anatomical location, (2) to establish normal joint mechanics,
(3) to reestablish the structural integrity of the acetabulum, and (4) to obtain
initial rigid fixation of bone graft, adequate containment of the new prosthesis,
and rigid fixation of the revision prosthesis to host bone. Currently, most
acetabular revisions are done with cementless components.
Morcellized or structural grafts are used to augment host
bone stock, and immediate rigid fixation may be obtained using
cementless socket with screws. While a variety of acetabular
prosthesis can be used according to shape and site of the defect as,
placement of the cup at a high hip center, oblong cups, or
reinforcement rings may often prove useful alternatives in the
The plane of reconstruction; type of grafting, prosthetic
selection, can be based on the kind and severity of the acetabular
defect determined according to any of the famous classifications
being used. Although special conditions of acetabular defects such
as those caused by severe infection or malignancy need different
special plans according to the situation. Daily many improvements
and modulations are practiced by orthopedic authors with the help
of prosthesis producers seeking for better results in acetabular
defects management.
Complications of reconstruction arthroplasty of the
acetablum include thromboembolic disease or blood clots in the
veins of the legs, bleeding, loosening of the implants, wear of the
components, osteolysis, nerve or vessel damage, postoperative
infections, periprosthetic or prosthetic fractures, prosthesis
dislocation, bone graft failure, and dislocation of the prosthetic
liner.