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Biomedical subjects

Michael D Ries

Publications and source records attributed to Michael D Ries.

15 recordsLinked to original sources
PubMed2003

Structural degradation of acrylic bone cements due to in vivo and simulated aging.

Acrylic bone cement is the primary load-bearing material used for the attachment of orthopedic devices to adjoining bone. Degradation of acrylic-based cements in vivo results in a loss of structural integrity of the bone-cement-prosthesis interface and limits the longevity of cemented orthopedic implants. The purpose of this study is to investigate the effect of in vivo aging on the structure of the acrylic bone cement and to develop an in vitro artificial aging protocol that mimics the observed degradation. Three sets of retrievals are examined in this study: Palacos brand cement retrieved from hip replacements, and Simplex brand cement retrieved from both hip and knee replacement surgeries. In vitro aging is performed using oxidative and acidic environments on three acrylic-based cements: Palacos, Simplex, and CORE. Gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR) are used to examine the evolution of molecular weight and chemical species within the acrylic cements due to both in vivo and simulated aging. GPC analysis indicates that molecular weight is degraded in the hip retrievals but not in the knee retrievals. Artificial aging in an oxidative environment best reproduces this degradation mechanism. FTIR analysis indicates that there exists a chemical evolution within the cement due to in vivo and in vitro aging. These findings are consistent with scission-based degradation schemes in the cement. Based on the results of this study, a pathway for structural degradation of acrylic bone cement is proposed. The findings from this investigation have broad applicability to acrylic-based cements and may provide guidance for the development of new bone cements that resist degradation in the body.

Acrylates↗
PubMed2003

Effect of cementless bowed stem distal surface contour and coronal slot on femoral bone strains and torsional stability.

Six pairs of unembalmed cadaver femurs were instrumented with strain gauges and prepared with flexible reamers for insertion of long bowed cementless femoral stems. A fully porous-coated cobalt chrome stem was inserted into each left femur, and a distally fluted, slotted, stem of the same implant geometry and implant material was inserted into each right femur. Bone strains were measured during stem insertion and torsional stability tested after the stems were fully seated. Distal strains were significantly higher (p < 0.05) for the fully porous compared to the distally fluted, slotted stem. Three fractures occurred in femurs with fully porous-coated stems. There was no difference in torsional stability between the two stem geometries. Our data demonstrate that a long bowed cementless stem with a distal coronal slot and flutes is associated with decreased bone strains and fracture risk during stem insertion compared to a fully porous-coated stem.

Biomechanical Phenomena↗
PubMed2003

Combined vertical and horizontal cable fixation of an extended trochanteric osteotomy site.

BACKGROUND: The use of an extended trochanteric osteotomy facilitates exposure and aids in the removal of a well-fixed femoral implant and cement during revision total hip arthroplasty. Occasionally, nonunion, fracture, and trochanteric migration have been reported following osteotomy. We evaluated the rate of healing of the osteotomy site and of implant stability when fixation was accomplished with use of vertical trochanteric and horizontal metaphyseal cable fixation (combined cable fixation). METHODS: The clinical and radiographic results of revision total hip arthroplasty with use of an extended trochanteric osteotomy followed by implantation of a distally porous-coated component and combined cable fixation of the osteotomy site in forty-two consecutive patients (forty-three hips) were reviewed. Intraoperative fracture at the osteotomy site occurred in five hips (12%). RESULTS: All osteotomy sites healed by six months, with an average time to union of fifteen weeks. One implant subsided 5 mm in a patient in whom a fracture had occurred at the time of the osteotomy. No trochanteric migration occurred. Two patients required a reoperation: one because of instability, and another because of recurrent infection. CONCLUSIONS: The extended trochanteric osteotomy facilitates revision of a well-fixed femoral component. Despite occasional intraoperative fracture at the osteotomy site, combined vertical trochanteric and horizontal metaphyseal cable fixation resulted in an excellent rate of healing and implant stability.

Adult↗
PubMed2003

Complications in primary total hip arthroplasty: avoidance and management: wear.

Many factors, including polyethylene processing, sterilization method, counterface material, femoral head size, femoral offset, acetabular component position, implant design, and patient activity level, affect the rate of wear in total hip arthroplasty. For patients with life expectancy that exceeds the longevity of the conventional implant materials, an alternative bearing surface (highly cross-linked polyethylene, metal-on-metal, or ceramic-on-ceramic) may be considered. Although laboratory wear tests with these materials are very favorable, clinical outcomes have not been clearly established. When osteolysis does develop in response to particulate debris, the location and progression of the lesions may be quite variable. Asymptomatic stable lesions can be followed clinically and radiographically while symptomatic or enlarging lesions or those that may compromise the integrity of the periprosthetic bone stock require surgery. If acetabular component revision is necessary and an adequate rim of host bone is maintained to support a revision acetabular component, defects can be filled with particulate bone graft. Large segmental defects generally require structural allografts. If the acetabular shell is well fixed in good position and the osteolytic defects are accessible, treatment with curettage and bone grafting of the lesions with liner revision is appropriate to avoid use of a structural allograft. Proximal femoral defects around a well-fixed stem can be managed in a similar manner with curettage and bone grafting. Distal lesions associated with risk of periprosthetic femur fracture or implant loosening require stem revision. Osteoclastic resportion of bone in response to particulate debris can be impaired with use of some drugs such as alendronate. However, the safety and efficacy of alendronate in the clinical management of osteolysis associated with total hip arthroplasty has not been established.

Arthroplasty, Replacement, Hip↗
PubMed2002

Retrieved glenoid components: a classification system for surface damage analysis.

There have been many reports describing modes of damage in retrieved total hip and total knee arthroplasty components. The most common mechanism in total hip arthroplasties has been shown to be surface wear. Fatigue failure shown as pitting and delamination are observed more often in total knee components. There has been no previous analysis of retrieved polyethylene glenoid components. This study evaluated the wear mechanisms contributing to failure of total shoulder glenoid components. Polyethylene glenoid components from 10 consecutive total shoulder arthroplasties have been retrieved and analyzed. Wear mechanisms were analyzed under low-power magnification, and a classification system was designed for total shoulder arthroplasties. This classification system is an adaptation of previous models of hip and knee surface damage. The severity of each damage mode was graded in 4 separate quadrants. The most prevalent damage modes were abrasion, pitting, and delamination. These data show a combination of abrasive wear and fatigue in retrieved total shoulder specimens. Surface wear and subsurface fatigue failure mechanisms both contribute to glenoid implant failure.

Aged↗
PubMed2002

Association between human immunodeficiency virus and osteonecrosis of the femoral head.

The records of a consecutive series of 50 patients treated operatively for osteonecrosis of the femoral head were reviewed to determine the prevalence of human immunodeficiency virus (HIV) as an isolated risk factor for osteonecrosis. Twelve patients had a history of trauma to the hip and were excluded from the study. The remaining 38 patients were treated operatively for nontraumatic osteonecrosis of the femoral head. Of these, 7 patients were HIV positive, and 31 were HIV negative. Of the 7 patients who were HIV positive, 4 (57%) had none of the known risk factors for osteonecrosis. Of the 31 patients who were HIV negative, 4 (13%) had none of the known risk factors for osteonecrosis. The difference between the groups was statistically significant, suggesting that HIV infection is a risk factor for the development of osteonecrosis of the femoral head.

Adult↗
PubMed2002

Impact biomechanics and pelvic deformation during insertion of press-fit acetabular cups.

Five fresh cadaver pelves were cleaned of soft tissue and instrumented with strain gauges. The acetabula were reamed, and a cementless cup, oversized at the periphery, was inserted. The applied force and cup acceleration were measured during insertion and used to calculate an effective mass of the cup, insertion device, and pelvis during each impact. Periacetabular strains increased variably during cup seating. After the cups were seated, strains continued to increase with postseating impacts. The effective mass remained constant throughout the test, indicating that cup seating is not associated with a change in acceleration. This finding implies that an accurate assessment of cup seating cannot be inferred by surgeon proprioception during impaction, and use of an apical hole in the cup is necessary to determine when the cup has seated.

Acetabulum↗
PubMed2002

Skin necrosis after total knee arthroplasty.

Nine patients were treated for skin necrosis after total knee arthroplasty. Eight patients had predisposing factors, which may have increased their risk of developing wound complications. Seven patients developed necrosis over the patellar tendon or tibial tubercle, of whom 6 were treated with muscle flap coverage. Two patients developed necrosis over the patella, both of whom were treated with local wound care and skin grafting. Successful wound healing and salvage of the total knee arthroplasty was achieved in all cases. Treatment of necrosis over the patellar tendon or tibial tubercle usually requires muscle flap coverage, whereas necrosis over the patella may be treated with local wound care and skin grafting.

Adult↗
PubMed2002

Total knee arthroplasty in hemophilic arthropathy.

BACKGROUND: Arthropathy of the knee frequently develops in patients with hemophilia, who may require a total knee arthroplasty at a young age. Hemophilic patients, who require regular intravenous replacement of coagulation factor, have a higher prevalence of human immunodeficiency virus (HIV) infection, which can compromise the outcome of the arthroplasty. The purpose of this study was to evaluate prosthetic survival following total knee arthroplasty and identify factors associated with failures of the arthroplasties in hemophilic patients. METHODS: The results of fifty-three total knee arthroplasties performed in thirty-eight patients (twenty-nine of whom were seropositive for HIV) to treat hemophilic arthropathy between 1976 and 1998 were retrospectively reviewed. Inpatient and outpatient medical records were studied to determine the HIV status, CD4 lymphocyte count, type of prosthesis, duration of prosthetic survival, cause of failure, and cause of death. If an arthroplasty failed, the outcome of the treatment of the failed arthroplasty was also determined. RESULTS: The rate of survival of the prostheses was 90% after five years. Eleven total knee arthroplasties failed. The most common cause of failure was infection (seven knees), which developed at an average of sixty months (range, three to 138 months) after the arthroplasty. There was no significant difference in the CD4 lymphocyte counts between the patients in whom infection developed and those in whom it did not. The HIV status also did not appear to be related to the development of infection. Thirteen patients died, and the most common cause of death was complications associated with acquired immunodeficiency syndrome (AIDS). CONCLUSIONS: Total knee arthroplasty performed to treat hemophilic arthropathy has a high risk of failure as a result of infection. Most infections developed late and were frequently caused by Staphylococcus epidermidis, suggesting that a likely cause of failure due to infection was hematogenous spread during administration of coagulation factor. It may be difficult to salvage a prosthesis complicated by infection. However, the life expectancy of hemophilic patients is lower than that of the general population of patients treated with total knee arthroplasty, and the improvement in the quality of life after total knee arthroplasty for hemophilic arthropathy may outweigh the risk of failure.

Adult↗
PubMed2000

Management of Contained Medial [Protrusiol] Acetabular Defects in Revision Total Hip Arthroplasty.

Medial migration of the acetabular cup and protrusio of the medial wall is a well recognized failure mechanism of acetabular fixation in cemented total hip arthroplasty. In the protruded acetabulum, a medialized position of the acetabular component is associated with increased medial cortical bone stresses, while more lateral positioning reduces the medial stresses. Use of a protrusio ring or medial wire mesh may limit medial migration. However, late failure of acetabular revision reconstructions can occur when cemented protrusio rings or wire mesh reinforcement are used without bone grafting.

Journal Article↗