Victor M. Goldberg

Distal femoral replacement with allograft/prosthetic reconstruction for treatment of supracondylar fractures in patients with total knee arthroplasty.

Large-segment distal femoral allografts were used in conjunction with non-linked total knee prostheses to reconstruct bone deficits following supracondylar fracture of the femur in seven patients with previous total knee arthroplasties. Three patients with multiple medical problems died of unrelated causes prior to a minimum 2 year follow-up. Indications for surgery were previously failed attempts at osteosynthesis and significant fracture comminution, osteopenia, and intercondylar extension or femoral component loosening. Specifics of the surgical technique included subperiosteal excision of the involved distal femur with retention of a soft tissue sleeve containing the collateral ligaments and reconstruction with a large-segment allograft and a stemmed, semiconstrained total knee prosthesis. Cement fixation using pressurized technique with intramedullary plugging of the tibial and femoral canal was routinely used to secure the prosthesis/allograft construct to the host bone. Postoperative complications included one dislocation, which was successfully treated closed, and one popliteal artery injury, which was successfully repaired. There were no postoperative infections. Two patients, however, had some degree of persistent instability, warranting bracing at the time of last follow-up. Using the Knee Society rating system, the average knee score for these patients was 71, and the average pain score and function score were 33 and 49, respectively. Range of motion averaged 96 degrees. All of the femoral components were well fixed at last follow-up. Results of this study indicate that large-segment distal femoral allografts used in conjunction with nonlinked knee prostheses can be an acceptable method of treatment of these difficult reconstructive problems.

In vivo degradation of polyethylene liners after gamma sterilization in air.

BACKGROUND Ultra-high molecular weight polyethylene degrades during storage in air following gamma sterilization, but the extent of in vivo degradation remains unclear. The purpose of this study was to quantify the extent to which the mechanical properties and oxidation of conventional polyethylene acetabular liners treated with gamma sterilization in air change in vivo. METHODS Fourteen modular cementless acetabular liners were revised at an average of 10.3 years (range, 5.9 to 13.5 years) after implantation. All liners, which had been machined from GUR 415 resin, had been gamma-sterilized in air; the average shelf life was 0.3 year (range, 0.0 to 0.8 year). After removal, the components were expeditiously frozen to minimize ex vivo changes to the polyethylene prior to characterization. The average duration between freezing and testing was 0.6 year. Mechanical properties and oxidation were measured with use of the small-punch test and Fourier transform infrared spectroscopy, respectively, in the loaded and unloaded regions of the liners. RESULTS There was substantial regional variation in the mechanical properties and oxidation of the retrieved liners. The ultimate load was observed to vary by >90% near the surface. On the average, the rim and the unloaded bearing showed evidence of severe oxidation near the surface after long-term in vivo aging, but these trends were not typically observed on the loaded bearing surface or near the backside of the liners. CONCLUSIONS The mechanical properties of polyethylene that has been gamma-sterilized in air may decrease substantially in vivo, depending on the location in the liner. The most severe oxidation was observed at the rim, suggesting that the femoral head inhibits access of oxygen-containing body fluids to the bearing surface. This is perhaps why in vivo oxidation has not been associated with clinical performance to date.

Inhibition of the PI3K-Akt Signaling Pathway Reduces Tumor Necrosis Factor-α Production in Response to Titanium Particles in Vitro

BACKGROUND Wear debris contributes to implant loosening after total joint arthroplasty, and few advances have been made in our ability to inhibit the biological response to wear particles. Bacterial endotoxins augment the effects of wear particles in vitro and in vivo. The cytokine, tumor necrosis factor-alpha (TNF-alpha), is produced by macrophages in response to bacterial endotoxins and wear particles, and it increases osteoclast activity resulting in bone resorption and implant loosening. The phosphoinositol-3-kinase (PI3K)-Akt intracellular signal transduction pathway contributes to cytokine production in response to soluble endotoxin. We investigated the role of the PI3K-Akt pathway in the production of TNF-alpha in response to wear particles with adherent endotoxin and so-called endotoxin-free wear particles. METHODS Cultured RAW264.7 murine macrophages were incubated with titanium particles with adherent endotoxin or with endotoxin-free titanium particles in the presence and absence of specific inhibitors of PI3K (LY294002) or Akt (SH-5). Akt activation was assessed with use of Western blot. TNF-alpha production was measured with use of enzyme-linked immunosorbent assay. Cytotoxicity was determined by measuring lactic dehydrogenase release. RESULTS Titanium particles with adherent endotoxin increased Akt activation, whereas endotoxin-free titanium particles did not. The PI3K inhibitor reduced TNF-alpha production by 70% in response to titanium with adherent endotoxin without increasing cytotoxicity. Similarly, the Akt inhibitor reduced TNF-alpha production by 83% in response to titanium particles with adherent endotoxin without increasing cytotoxicity. High concentrations of endotoxin-free titanium particles resulted in a small delayed increase in TNF-alpha production that was completely blocked by the PI3K inhibitor. CONCLUSIONS Inhibition of the PI3K-Akt pathway reduces macrophage TNF-alpha production in response to titanium particles with adherent endotoxin and endotoxin-free particles in vitro.

Clinical and Histologic Results Related to a Low-Modulus Composite Total Hip Replacement Stem

BACKGROUND Osteolysis secondary to stress shielding in patients with a total hip arthroplasty has been attributed to greater stiffness of the prosthetic femoral stem compared with the stiffness of the femur. This concern led to the development of a composite femoral stem implant with a structural stiffness similar to that of the native femur. The stem consists of a cobalt-chromium-alloy core surrounded by polyaryletherketone and titanium mesh for bone ingrowth. The purpose of this study was to determine the intermediate-term clinical, radiographic, and histologic results of the use of this stem. METHODS Twenty-eight patients (nineteen men and nine women) with an average age of 51.3 years underwent primary total hip arthroplasty with the Epoch stem and were followed for an average of 6.2 years. Harris hip scores were determined and radiographic studies were performed preoperatively, postoperatively, and at two-year intervals thereafter. In addition, dual x-ray absorptiometry scans were made up to two years postoperatively to evaluate osseous resorption. Two femora obtained at autopsy thirteen and forty-eight months after surgery were analyzed for bone ingrowth and ongrowth. RESULTS The Harris hip scores averaged 56 points preoperatively and improved to 97 points at the time of the last follow-up. Dual x-ray absorptiometry scans demonstrated the greatest decrease in mean bone density (27.5%) in Gruen zone 7 at two years. Radiographs demonstrated no instances of migration, and only one hip had osteolysis. All stems had stable osseous fixation. Histologic evaluation of the two femora that had been retrieved at autopsy at thirteen and forty-eight months showed the mean bone ingrowth (and standard deviation) along the entire length of the stem to be 49.62% +/- 13.04% and 73.57% +/- 8.48%, respectively, and the mean bone ongrowth to be 54.18% +/- 7.68% and 80.92% +/- 6.06%, respectively. CONCLUSIONS Intermediate-term follow-up of hips treated with the Epoch stem indicated excellent clinical success, radiographic evidence of osseous integration, and histologic findings of osseous ingrowth and ongrowth. Although the implant has been associated with excellent results in both the short and the intermediate term, longer follow-up will be necessary to assess the long-term function of the implant.

Clinical and Radiographic Outcomes of Total Hip Arthroplasty with Insertion of an Anatomically Designed Femoral Component without Cement for the Treatment of Primary Osteoarthritis. A Study with a Minimum of Six Years of Follow-up*

We evaluated the clinical and radiographic outcomes of 100 consecutive primary total hip arthroplasties in which a proximally coated anatomically designed femoral component was fixed without cement for the treatment of primary osteoarthritis. The minimum duration of follow-up was six years (average, 7.1 years). The eighty-eight patients who had the arthroplasties were followed prospectively with a standard clinical evaluation that involved use of the Harris hip score and a radiographic evaluation based on the criteria of the Hip Society. Bone ingrowth was evaluated with the method of Engh et al. The average age of the patients at the time of the operation was 62.6 years (range, thirty-nine to eighty-four years). Fifty-one patients were men and thirty-seven were women. The average preoperative Harris hip score was 48 points, with an average pain score of 15 points and an average function score of 26 points. Nonmechanical complications that necessitated a revision operation included one deep hematogenous infection, one late periprosthetic fracture, and a 0.5-inch (1.27-centimeter) limb-length discrepancy. At the time of the most recent follow-up, the average Harris hip score was 96 points, with an average pain score of 42 points and an average function score of 45 points. The prevalence of pain in the anterior part of the thigh was 5 percent (five hips). One patient had a revision of the femoral component because of aseptic loosening, and one had a revision of the acetabular component because of recurrent dislocations. Radiographic assessment revealed consistent evidence of proximal bone ingrowth. No complete radiolucent line was identified, except around the stem that had loosened. Twenty-seven femoral components were associated with slight pedestal formation. No osteolytic lesion of the femur was identified. Nonprogressive pelvic osteolysis was identified in four hips, but none of the lesions were more than two millimeters in diameter. None of the acetabular components migrated, and no radiolucent line of more than two millimeters in thickness was seen around any acetabular cup. The data from this study, in which the minimum duration of follow-up was six years, indicate that the anatomically designed prosthesis can provide good results, with low prevalences of pain in the thigh and loosening of the component, in younger, active patients.

Evaluation of Contemporary Software Methods Used to Quantify Polyethylene Wear After Total Hip Arthroplasty

BACKGROUND Radiographic measurements of the wear of total hip arthroplasty implants are indirect measurements based on radiographic determinations of the location of the femoral head relative to the acetabular component. Using the simplest case of zero wear, we assessed the reproducibility and accuracy of two software applications designed to quantify wear from clinical radiographs. METHODS After a cobalt-chromium head was glued into the polyethylene liner of a titanium shell, one cross-table lateral radiograph and three anteroposterior pelvic radiographs were made for twelve permutations of acetabular component angulation. The three anteroposterior radiographs differed only with regard to the cephalocaudal positioning of the prosthesis relative to the x-ray tube. To assess method reproducibility, each anteroposterior radiograph was assumed to be both the initial and the latest follow-up radiograph of a wear analysis. To assess method accuracy, each anteroposterior radiograph was paired in a wear analysis with each of the two anteroposterior radiographs made when the component was in the same angulation but at a different cephalocaudal position relative to the tube (one radiograph was the initial follow-up radiograph while the second was the latest follow-up radiograph). The analyses of reproducibility and accuracy were performed both with and without inclusion of the lateral radiograph made with the component in the same angulation. RESULTS Both methods fared well in the reproducibility analyses, with mean linear and volumetric wear values of 0.00 to 0.07 mm and 0 to 24 mm(3), respectively. In the accuracy analyses, the mean linear and volumetric wear values derived with the two methods were 0.26 to 0.40 mm and 78 to 126 mm(3), respectively. CONCLUSIONS Whereas the results of the reproducibility analyses showed that the methods were consistent in determining the relative positions of the head and shell from a given anteroposterior radiograph or pair of anteroposterior and lateral radiographs, the non-zero wear results obtained in the accuracy analyses proved that these positional determinations were often inaccurate. Thus, while contemporary software methods may yield reproducible results, their accuracy is limited by their inability to correctly determine the position of the head relative to the acetabular component.

Use of an antibiotic impregnated polymethyl methacrylate intramedullary spacer for complicated revision total hip arthroplasty

Revision total hip arthroplasty is frequently necessary in the presence of significant proximal femoral bone loss, periprosthetic fracture, or infection. In these situations, optimal reconstruction may sometimes warrant the use of special implants, including bone grafts. The emergent presentation of these cases or unexpected findings at the time of surgery can preclude the use of these treatment options. In cases of periprosthetic sepsis, delayed reimplantation may be the most successful approach to eradicate infection. In seven of these complicated revision total hip arthroplasties, the authors used an antibiotic-impregnated intramedullary polymethyl methacrylate spacer with delayed prosthetic reimplantation to allow for the use of these methods. Benefits of this technique include uncompromised radiographic evaluation of the proximal femur for design of a custom implant, if needed, stabilization of the proximal femur facilitating early mobilization of the patient in the case of periprosthetic fracture, and local delivery of antibiotics to the wound in the case of infection. The authors ability to reconstruct these total hip arthroplasties complicated by bone deficiency, fracture, and sepsis, was significantly improved with this use of this technique.