Masri Ba

Primary total hip arthroplasty after infection.

Only a few of the more than 200,000 total hip arthroplasties performed annually in the United States are done after an infection of the hip joint or the proximal aspect of the femur.nnAlthough some infections produce severe early destruction of the hip joint, most patients, if treated promptly, regain good hip function and do not present again until much later in life, when secondary degenerative changes have occurred1. It is therefore necessary to be aware of the possibility of a previous infection and to inquire about it specifically.nnThe first recurrence of bone infection may be delayed for many decades. Gallie2 reported a case of femoral osteomyelitis in a ten-year-old girl that did not recur until after nearly eighty years. The risk that a previous infection of the hip region poses to a hip prosthesis is multifactorial. The type of infection (osteomyelitis or septic arthritis), the level of activity of the infection (active or quiescent), the time since the infection (recent or historical), the organism (pyogenic, tuberculous, or fungal), and the reconstruction technique all contribute to the outcome.nn### OsteomyelitisnnEver since Staphylococcus aureus was first isolated from osteomyelitis by Pasteur3 in the late nineteenth century, it has remained the predominant infecting organism, implicated in approximately 90% of infections where an organism is isolated (range, 88% [140 of 159] to 95% [392 of 411])4,5. The infecting organisms in the remaining cases are largely Staphylococcus epidermidis and streptococci.nnMore recently, there has been a shift in the prevalence of certain causative organisms, with fewer infections caused by Staphylococcus aureus . There has also been a significant increase (from eight of sixty-five cases to eight of nineteen cases; p < 0.001) in the proportion of cases that are subacute and that have a greater tendency …

Allograft impaction and cement penetration after revision hip replacement: A HISTOMORPHOMETRIC ANALYSIS IN THE CADAVER FEMUR

We studied various aspects of graft impaction and penetration of cement in an experimental model. Cancellous bone was removed proximally and local diaphyseal lytic defects were simulated in six human cadaver femora. After impaction grafting the specimens were sectioned and prepared for histomorphometric analysis. The porosity of the graft was lowest in Gruen zone 4 (52%) and highest in Gruen zone 1 (76%). At the levels of Gruen zones 6 and 2 the entire cross-section was almost filled with cement. Cement sometimes reached the endosteal surface in other Gruen zones. The mean peak impaction forces exerted with the impactors were negatively correlated with the porosity of the graft.

Role and results of tapered fluted modular titanium stems in revision total hip arthroplasty

Tapered, fluted, modular, titanium stems have a long history in Europe and are increasing in popularity in North America. We have reviewed the results at our institution looking at stem survival and clinical outcomes. Radiological outcomes and quality of life assessments have been performed and compared to cylindrical non-modular cobalt chromium stems. Survival at five years was 94%. This fell to 85% at ten years due to stem breakage with older designs. Review of radiology showed maintenance or improvement of bone stock in 87% of cases. Outcome scores were superior in tapered stems despite worse pre-operative femoral deficiency. Tapered stems have proved to be a useful alternative in revision total hip arthroplasty across the spectrum of femoral bone deficiency.

Structural proximal femoral allografts for failed total hip replacements

There are few medium- and long-term data on the outcome of the use of proximal femoral structural allografts in revision hip arthroplasty. This is a study of a consecutive series of 40 proximal femoral allografts performed for failed total hip replacements using the same technique with a minimum follow-up of five years (mean 8.8 years; range 5 to 11.5 years). In all cases the stem was cemented into both the allograft and the host femur. The proximal femur of the host was resected in 37 cases.nnThere were four early revisions (10%), two for infection, one for nonunion of the allograft-host junction, and one for allograft resorption noted at the time of revision of a failed acetabular reconstruction. Junctional nonunion was seen in three patients (8%), two of whom were managed successfully by bone grafting, and bone grafting and plating respectively. Instability was observed in four (10%). Trochanteric nonunion was seen in 18 patients (46%) and trochanteric escape in ten of these (27%). The mean Harris hip score improved from 39 to 79. Severe resorption involving the full thickness of the allograft was seen in seven patients (17.5%). This progressed rapidly and silently, but has yet to cause failure of any of the reconstructions.nnProfound resorption of the allograft may be related to a combination of factors, including a slow form of immune rejection, stress shielding and resorption due to mechanical disuse with solid cemented distal fixation, and the absence of any masking or protective effect which may be provided by the retention of the bivalved host bone as a vascularised onlay autograft. Although continued surveillance is warranted, the very good medium-term clinical results justify the continued use of structural allografts for failed total hip replacements with severe loss of proximal femoral bone.

Instructional Course Lectures, The American Academy of Orthopaedic Surgeons - Primary Total Replacement of the Dysplastic Hip*†

Developmental abnormalities following such childhood conditions as congenital dislocation and dysplasia of the hip, Legg-Calve-Perthes disease, and slipped capital femoral epiphysis are the most common cause of secondary osteoarthritis of the hip3,43 and may be a cause of degeneration in a large portion of patients with so-called idiopathic osteoarthritis of the hip43. Despite concerted screening programs, a large number of patients still have the sequelae of dysplasia or dislocation of the hip in adulthood37,117.nnThe severity of hip dysplasia varies widely, ranging from the shallow acetabulum to the completely dislocated and so-called high-riding hip. Osteoarthritis of the hip secondary to hip dysplasia, therefore, presents a broad spectrum of reconstructive challenges. Hips that have mild anatomical abnormalities can be treated with standard primary total hip replacements, but until recently others would have been labeled unreconstructible16. Because patients who have hip dysplasia are often young and active, it is critical to understand the complexities of total hip replacement in this group and to plan any interventions meticulously. To this end, the nature and the extent of the preoperative deformities and abnormalities must be understood, and the problems that have been obstacles to obtaining satisfactory fixation with acceptable long-term function must be addressed. In this paper, we present an overview of the classification and assessment of the dysplastic hip with secondary osteoarthritis and summarize the current knowledge about total hip arthroplasty in patients who have this disorder.nnA thorough understanding of both the clinical and the radiographic anatomy of the dysplastic hip is necessary in order to plan and perform a reconstruction of the hip that will yield satisfactory long-term results. This anatomy may be distorted by the primary disorder and by the effects of previous operations.nnThe anatomical abnormalities that are …

Cement penetration and primary stability of the femoral component after impaction allografting: A BIOMECHANICAL STUDY IN THE CADAVERIC FEMUR

This study explored the relationship between the initial stability of the femoral component and penetration of cement into the graft bed following impaction allografting. Impaction allografting was carried out in human cadaveric femurs. In one group the cement was pressurised conventionally but in the other it was not pressurised. Migration and micromotion of the implant were measured under simulated walking loads. The specimens were then cross-sectioned and penetration of the cement measured. Around the distal half of the implant we found approximately 70% and 40% of contact of the cement with the endosteum in the pressure and no-pressure groups, respectively. The distal migration/micromotion, and valgus/varus migration were significantly higher in the no-pressure group than in that subjected to pressure. These motion components correlated negatively with the mean area of cement and its contact with the endosteum. The presence of cement at the endosteum appears to play an important role in the initial stability of the implant following impaction allografting.

Instructional Course Lectures, The American Academy of Orthopaedic Surgeons - Femoral Bone Loss in Total Hip Arthroplasty: Classification and Preoperative Planning*†

A single comprehensive classification system that can adequately describe all types of bone loss associated with hip arthroplasty should become a standard for reporting purposes. There is a need for a critical appraisal of the classification systems currently in use and, through a consensus, for development of a system that will permit comparison between the reported results of different techniques. Although no one classification system is ideal, the one proposed by the AAOS Committee on the Hip is the most comprehensive and the most consistently used. It addresses not only revision total hip arthroplasty but also primary hip replacement. It also addresses other conditions related to problems with the bone stock, such as those resulting from a previous hip arthrodesis on the acetabular side and femoral stenosis and malalignment on the femoral side. The only drawback to this classification system is its complexity; however, the problem of acetabular and femoral bone loss is of sufficient complexity and variety that a simple classification system, although ideal, cannot be comprehensive. Regardless of the absence of a common language and a comprehensive classification system that is applicable to all types of reconstructions, it is clear that femoral bone loss is a problem that will continue to challenge orthopaedic surgeons. It is only by careful and methodical analysis of patients who have femoral bone loss and by meticulous attention being paid to detail in preoperative evaluation and investigation, surgical planning, and the recording of outcomes that we will be able to improve our treatment of this difficult problem.