Rheumatology: 10. Joint replacement of the hip and knee--when to refer and what to expect.
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Adolescent↗
Biomedical subjects
B A Masri
Publications and source records attributed to B A Masri.
The reliability and validity of the Vancouver classification of femoral fractures after hip replacement.
This study assessed the reliability and validity of a new classification system for fractures of the femur after hip arthroplasty. Forty radiographs were evaluated by 6 observers, 3 experts and 3 nonexperts. Each observer read the radiographs on 2 separate occasions and classified each case as to its type (A, B, C) and subtype (B1, B2, B3). Reliability was assessed by looking at the intraobserver and interobserver agreement using the kappa statistic. Validity was assessed within the B group by looking at the agreement between the radiographic classification and the intraoperative findings. Our findings suggest that this classification system is reliable and valid. Intraobserver agreement was consistent across observers, ranging from 0.73 to 0.83. There was a negligible difference between experts and nonexperts. Interobserver agreement was 0.61 for the first reading and 0.64 for the second reading by kappa analysis, indicating substantial agreement between observers. Validity analysis revealed an observed agreement kappa value of 0.78, indicating substantial agreement. This study has shown that this classification is reliable and valid.
Arthroplasty, Replacement, Hip↗
Circumferential allograft replacement of the proximal femur. A critical analysis.
The use of proximal femoral structural allografts in revision hip arthroplasty remains controversial. The current study constitutes the mean 8.8 years followup (range, 3-12.5 years) of a consecutive series of 55 proximal femoral allografts in 51 patients. In 46 patients the implant was cemented into the allograft and the distal femur, and the host proximal femur was resected at the time of reconstruction in all but seven patients. Five patients underwent revision surgery for acetabular failure, and six additional patients underwent revision surgery for failure of the proximal femoral allograft. Three patients underwent successful revision surgery and had additional proximal femoral allografts. Failure was caused by graft fracture in one patient, by deep infection in two patients, and by junctional nonunion in three patients. Junctional nonunion was seen in five patients (9%), two of whom were treated successfully with bone grafting and bone grafting and plating, respectively. Instability was observed in six patients (11%). Trochanteric nonunion was seen in 22 patients (43%) and trochanteric escape was seen in 14 patients (27%). The mean Harris hip score improved from 39 to 79 points. Resorption involving the full thickness of the allograft in at least one zone was seen in seven patients. This progressed rapidly and silently within the first 3 years but has yet to lead to the failure of any of the reconstructions. Infection was ruled out in every case. Allograft resorption was seen in seven patients and may be related to a combination of factors. It is most likely that this is an immunologic problem of slow rejection, but it is possible that the distal cement fixation led to stress shielding and resorption attributable to mechanical disuse. The possible protective role of retaining the bivalved host bone as a vascularized onlay autograft remains to be clarified. Although these results justify the continued use of structural allografts for selected patients, continued followup is warranted.
Adult↗
Structural proximal femoral allografts for failed total hip replacements: a minimum review of five years.
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. There 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. Profound 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.
Adult↗
The PROSTALAC functional spacer in two-stage revision for infected knee replacements. Prosthesis of antibiotic-loaded acrylic cement.
The PROSTALAC functional spacer is made of antibiotic-loaded acrylic cement but has a small metal-on-polythene articular surface. We have used it as an interim spacer in two-stage exchange arthroplasty for infected total knee replacement. PROSTALAC allows continuous rehabilitation between stages as it maintains good alignment and stability of the knee and a reasonable range of movement. It also helps to maintain the soft-tissue planes, which facilitates the second-stage procedure. We reviewed 45 consecutive patients, treated over a period of nine years. The mean follow-up was for 48 months (20 to 112). At final review, there was no evidence of infection in 41 patients (91%); only one had a recurrent infection with the same organism. There was improvement in the Hospital for Special Surgery knee score between stages and at final review. The range of movement was maintained between stages. Complications were primarily related to the extensor mechanism and stability of the knee between stages. Both of these problems decreased with refinement of the design of the implant. The rate of cure of the infection in our patients was similar to that using other methods. Movement of the knee does not appear to hinder control of infection.
Adult↗
Primary total replacement of the dysplastic hip.
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Adult↗
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.
Arthroplasty, Replacement, Hip↗
Femoral bone loss in patients managed with revision hip replacement: results of circumferential allograft replacement.
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Arthroplasty, Replacement, Hip↗
Popliteal vascular malformation simulating a soft tissue sarcoma.
Differentiation of vascular abnormalities from soft tissue sarcomas may be difficult on clinical grounds, but is usually possible on imaging criteria. We report the MRI and digital subtraction angiography (DSA) findings in a patient presenting with a mass behind the knee. We discuss differentiating features and review the literature of similar cases.
Aneurysm, False↗
The prevention of periprosthetic fractures in total hip and knee arthroplasty.
Periprosthetic fractures in total hip and total knee arthroplasty lead to considerable morbidity in terms of component fixation, bone loss, and subsequent function. The management of these fractures is technically demanding and may result in suboptimal fixation owing to poor bone stock. The prevention, early recognition, and appropriate management of such fractures are therefore critical. The pathogenesis of periprosthetic factors is multifactorial. There are a number of intrinsic patient influences such as bone stock, biomechanics, and compliance. There are also a host of extrinsic factors over which the surgeon has more control. The prevention of periprosthetic fractures requires careful preoperative planning and templating, the availability of the necessary expertise and equipment, and knowledge of the potential pitfalls so that these can be avoided both intraoperatively and in follow-up.
Acetabulum↗
Classification of the hip.
A number of classification systems have been proposed for periprosthetic fractures of the femur following total hip replacement. Most of these rely purely on the site and pattern of the fracture. However, it is only after consideration of other important factors, including the stability of the prosthesis as well as the quality of the surrounding bone stock, that appropriate management can be instituted. The authors have developed a new classification system that addresses these other important factors. The authors believe that only after classifying a periprosthetic fracture with specific reference to fracture site, stability of the implant, and quality of the surrounding bone stock, can one make a rational decision towards a treatment algorithm.
Acetabulum↗
The treatment of periprosthetic fractures of the femur using cortical onlay allograft struts.
Periprosthetic fractures of the femur are a complex problem to treat. Careful planning is essential before embarking on such a technically demanding procedure. There are many factors to be considered, including the premorbid condition of the patient and previous experience and training of the surgeon. Important factors relating directly to the fracture include the site, stability of the implant, and the state of the surrounding bone stock.
Animals↗
The role of intraoperative gram stain in the diagnosis of infection during revision total hip arthroplasty.
A total of 202 revision hip arthroplasties in 178 patients, over a 2-year period, were evaluated prospectively. Intraoperative Gram stains were obtained from periprosthetic tissues in all cases. Of these, a definitive diagnosis of infection, using defined criteria, was established in 35 cases. Of these 35 patients, 17 had received antibiotics before surgery. The intraoperative cultures were positive in 8 of the 17 patients who had received antibiotics and 17 of the 18 patients who had not received preoperative antibiotics. In 1 infected case, intraoperative cultures of periprosthetic tissues failed to reveal bacterial growth, despite the fact that the patient received no preoperative antibiotics. Overall, there were 5 true-positive Gram stain results, 172 true-negative results, 3 false-positive results, and 22 false-negative results. The sensitivity of the Gram stain was 19%, specificity was 98%, predictive value of a positive test was 63%, and predictive value of a negative test was 89%. These results suggest that the intraoperative Gram stain is not a sensitive tool for the diagnosis of infection and should not be used when attempting to diagnose infection intraoperatively.
Antibiotic Prophylaxis↗
The in vitro elution characteristics of antibiotic-loaded CMW and Palacos-R bone cements.
An in vitro study was carried out comparing the elution characteristics of Palacos-R and CMW acrylic cements. Three groups of 6 antibiotic-loaded cement disks were prepared, incorporating 1.0 g vancomycin and 2.4 g tobramycin per 40 g packet of cement. Palacos-R bone cement was used for group 1, CMW 1 for group 2, and CMW 3 for group 3. The disks were placed in saline baths for 9 weeks. The baths were periodically sampled and elution rates calculated. CMW 1 released 24% less tobramycin and 36% less vancomycin than Palacos-R over the total study period (P < .05). CMW 3 released 34% less tobramycin and 38% less vancomycin than Palacos-R (P < .05). There was no significant difference in antibiotic release between CMW 1 and CMW 3. The in vitro elution characteristics of Palacos-R are superior to CMW.
Acrylic Resins↗
The treatment of the infected hip replacement. The complex case.
The treatment of the infected total hip replacement remains expensive, leads to a long difficult course for the patient, and frequently results in a suboptimal functional outcome. Various treatment techniques are available, and may be suitable for the more straightforward case. These include one-stage exchange arthroplasty, two-stage exchange arthroplasty, resection arthroplasty, and debridement and irrigation. The complex infected total hip replacement encompasses numerous host and organism factors. These include unusual or multiple organisms, diagnostic difficulties, bone loss, immunocompromise, and reinfection. In the authors' experience, the problem of the complex infected hip replacement is best addressed using the prosthesis of antibiotic-loaded acrylic cement approach. This interval arthroplasty is a modular, custom-made, immediate fit, antibiotic selective, temporary spacer system that allows the surgeon to reconstruct even the most deficient bone stock safely and effectively using two-stage exchange arthroplasty. It affords the patient rapid pain relief, allows them to mobilize quickly while successfully eradicating infection in 96% of hips with severe bone loss, and sets an appropriate soft tissue environment for a relatively straightforward second stage procedure. The prosthesis of antibiotic-loaded acrylic cement system affords the benefits of two-stage exchange without the functional disadvantages of an excision arthroplasty particularly when the proximal femur is severely deficient. It allows flexibility for the interval period and the type of fixation used, and the potential for allograft reconstruction at the final stage.
Anti-Bacterial Agents↗
The quadriceps myocutaneous flap for operation on the distal femur.
We describe a U-shaped approach to the distal femur which, having divided the extensor mechanism and elevated the entire quadriceps muscle, gives excellent exposure and allows a number of reconstructive options. It was used in 14 patients, 13 of whom were followed up for a mean of 3.5 years (1 to 11). There was no case of flap necrosis, and complications related to the reconstruction were acceptable.
Adolescent↗
Prospective analysis of preoperative and intraoperative investigations for the diagnosis of infection at the sites of two hundred and two revision total hip arthroplasties.
BACKGROUND: Total hip arthroplasty is a commonly performed procedure in the United States and Canada that is associated with a definite risk of postoperative infection. Moreover, diagnosing an infection after total hip arthroplasty can present a challenge as there are no preoperative tests that are consistently sensitive and specific for infection in patients who need a revision arthroplasty. The present prospective study was performed to evaluate a variety of investigations for the diagnosis of infection at the site of a previous arthroplasty in order to determine if any combination of diagnostic studies could be used to determine which patients are at risk for a postoperative wound infection. METHODS: We prospectively analyzed the preoperative and intraoperative investigations used for the diagnosis of infection in 178 patients who had a total of 202 revision hip replacements. Clinical data were collected preoperatively. Investigations to determine the presence or absence of infection included a white blood-cell count, measurement of the erythrocyte sedimentation rate, measurement of the level of C-reactive protein, preoperative aspiration of the joint, intraoperative gram-staining and culture of periprosthetic tissue, a white blood-cell count in synovial fluid, and examination of intraoperative frozen sections. Frozen sections were analyzed in a blinded fashion without knowledge of clinical or laboratory data. Patients receiving antibiotics at the time of aspiration or collection of specimens for intraoperative culture were excluded from the analysis of those investigations, regardless of the results of the cultures. A positive result (suggestive of infection) was clearly defined for each of the investigations. RESULTS: Thirty-five hips (17 percent) were determined to be infected on the basis of clinical findings and positive results, according to the defined criteria, of investigations. With inflammatory conditions excluded, the sensitivity, specificity, positive predictive value, and negative predictive value were 0.82, 0.85, 0.58, and 0.95, respectively, for the erythrocyte sedimentation rate and 0.96, 0.92, 0.74, and 0.99, respectively, for the level of C-reactive protein. All patients who had a periprosthetic infection had an elevated erythrocyte sedimentation rate or level of C-reactive protein, but not always both. When patients who were receiving antibiotics were excluded, the results of aspiration of the joint were 0.86 for sensitivity, 0.94 for specificity, 0.67 for the positive predictive value, and 0.98 for the negative predictive value. Intraoperative studies revealed sensitivities, specificities, positive predictive values, and negative predictive values of 0.19, 0.98, 0.63, and 0.89, respectively, for gram-staining of specimens of the most inflamed-appearing tissue; 0.36, 0.99, 0.91, and 0.90, respectively, for the white bloodcell count in synovial fluid; and 0.89, 0.85, 0.52, and 0.98, respectively, for a neutrophil count in synovial fluid of more than 80 percent. The sensitivity, specificity, positive predictive value, and negative predictive value were 0.80, 0.94, 0.74, and 0.96, respectively, for the frozen sections and 0.94, 0.97, 0.77, and 0.99, respectively, for the intraoperative cultures. CONCLUSIONS: The combination of a normal erythrocyte sedimentation rate and C-reactive protein level is reliable for predicting the absence of infection. Aspiration should be used when the erythrocyte sedimentation rate or the C-reactive protein level is elevated or when a clinical suspicion of infection remains. We found the gram stain to be unreliable. Examination of intraoperative frozen sections is useful in equivocal cases or when hematological markers may be falsely elevated because of an inflammatory or other condition.
Aged↗
Use of reconstruction rings for the management of acetabular bone loss during revision hip surgery.
Aseptic loosening remains the leading cause of failure after total hip replacement. Extensive bone loss and acetabular bone stock deficiency are frequently encountered. Simple autografting techniques are often not possible, and copious amounts of allograft may be required to reconstruct the defect. The mechanically stable environment that is a prerequisite for successful graft incorporation cannot be achieved with routine acetabular fixation techniques alone. A reconstruction ring that is secured to the surrounding pelvis provides a more rigid construct. Several types of reconstruction rings are available for the management of acetabular bone loss during revision hip surgery. Early results suggest that these devices may prove to be a useful alternative for treatment of a difficult problem.
Acetabulum↗