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Biomedical subjects

R L Barrack

Publications and source records attributed to R L Barrack.

At least 19 recordsLinked to original sources
PubMed2001

Virtual reality computer animation of the effect of component position and design on stability after total hip arthroplasty.

Virtual reality technology was utilized to assess the effect of component orientation and component design on the range of motion prior to impingement following total hip arthroplasty. Components were digitized, oriented in the pelvis, and computer animations were performed to assess the likelihood of dislocation with different combinations of component orientation.

Arthroplasty, Replacement, Hip↗
PubMed2001

Failed cementless total knee arthroplasty presenting as osteolysis of the fibular head.

Large osteolytic lesions can occur adjacent to cementless total knee arthroplasty components. This occurrence frequently is related to suboptimal design features leading to the generation of metal or polyethylene wear debris. Occasionally, such lesions can mimic a bone tumor. A case of a lytic lesion of the fibular head adjacent to a failed cementless knee arthroplasty is described along with a description of the damaged retrieved component that led to the failure.

Fibula↗
PubMed2001

Radiographic wear measurements in a cementless metal-backed modular cobalt-chromium acetabular component.

Linear polyethylene wear was measured radiographically and correlated with direct measurements of wear from 21 of 24 liners retrieved at revision. An optical comparator was used to assess linear wear using the shadowgraph technique. Postoperative and prerevision radiographs were reviewed to measure the amount of linear wear radiographically. Seven radiographic methods described in the literature were used: 5 were manual techniques, and 2 techniques used a computer-assisted digitizer. Linear regression analysis showed that there was a statistically significant correlation between the radiographic measurements compared with the direct measurement for 4 of the 5 manual techniques but only 1 of the 2 computerized techniques. Based on these results, radiographic wear measurements of cementless, modular components should be considered qualitative rather than quantitative. There is a significant difference in the measurements obtained among various published techniques. The addition of computer digitization to enhance manual methodology does not improve accuracy.

Acetabulum↗
PubMed2001

Stem design and dislocation after revision total hip arthroplasty: clinical results and computer modeling.

The effect of the size and shape of the neck and the taper of the femoral stem on dislocation rate after revision total hip arthroplasty was examined. Design I had a large (14/16), long taper with a circular neck cross-section; a fixed 42-mm offset; and a neck that was anteverted relative to the stem. Design II was characterized by a smaller (12/14), shorter taper; a trapezoidal neck cross-section; a progressive (40-50 mm) offset; and no neck anteversion relative to the stem. The stems were digitized and placed through a range of motion using virtual reality software, and the cross-sectional area of the neck, length of the taper, and total arc of motion before impingement between the neck and liner were compared. The dislocation rate at a minimum of 2 years' follow-up was 15.4% (8 of 52) for design I compared with 4.3% (2 of 46) for design II. This finding was consistent with the results of computer modeling, which showed that design I had a cross-sectional area that was 32% greater and a total arc of motion that was 76% less compared with design II. The results suggest that neck and taper design may be an important factor in dislocation after revision total hip arthroplasty.

Arthroplasty, Replacement, Hip↗
PubMed2001

The use of osteogenic protein-1 in reconstructive surgery of the hip.

Osteogenic proteins (OPs), also referred to as bone morphogenetic proteins (BMPs), are a family of bone matrix polypeptides that induce a sequence of cellular events that lead to the formation of new bone. This article reports the use of recombinant human OP-1 (rhOP-1, rhBMP-7) in preclinical animal models and initial human clinical experience in hip reconstructive surgery. The use of rhOP-1 in conjunction with morcellized cancellous bone and cortical strut allograft in preclinical models dramatically improved the biologic activity of the graft, resulting in greater and earlier new bone formation and graft incorporation. The clinical use of rhOP-1 in hip reconstructive procedures also resulted in greater and earlier new bone formation in the more challenging biologic environment compared with allograft bone alone.

Animals↗
PubMed2001

Patella in total knee arthroplasty.

The patella is a reliable guide to the success or failure of a total knee replacement. Patients who do not experience peripatellar symptoms or a patellar complication usually have a successful result. Conversely, peripatellar symptoms or complications usually reflect an underlying problem with surgical technique, component designs, or both. Current designs still do not replicate normal kinematics, and current instrumentation and techniques significantly alter the anatomy of the patellofemoral articulation in a substantial percentage of patients. Reproducing extensor mechanism balance and using components that provide adequate congruency and contact area through a physiologic arc of motion should lead to a successful result with minimal patellar symptoms or complications whether or not the patella is resurfaced. Attempting to achieve normal patellofemoral kinematics and minimize patellar complications has led to a better understanding of total knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMed2001

The impact of the Tulane-HCA joint venture on academic and clinical missions.

As with any joint venture in any given industry, positive and negative impacts are felt. Tulane University School of Medicine experienced impacts on its academic and clinical missions as a result of the joint venture between Tulane University and HCA, a for-profit public company. The laws of business had entered the halls of medicine. Although patients, personnel, and physicians experienced culture shock and inconveniences, Tulane University School of Medicine has been able to maintain viable training programs, and its faculty physicians have a hospital and corporately run clinics across the street. In addition, multidisciplinary centers of excellence, long spoken of in the academic realm, came to fruition through the corporate world. This may not have been the case, had Tulane University not entered into ajoint venture with HCA. Is it worth the effort? For Tulane University, whether one likes the entire package or not, the answer must be yes. The greatest impact is that the orthopaedic surgeons still are in a position to fulfill their academic and clinical missions.

Academic Medical Centers↗
PubMed2001

Improved cartilage repair after treatment with low-intensity pulsed ultrasound.

Low-intensity pulsed ultrasound accelerates bone healing via upregulation of cartilage formation and maturation phases of endchondral bone formation. The current authors evaluated the effect of ultrasound therapy on the repair of full-thickness osteochondral defects. Bilateral, 3.2 mm diameter by 5.0 mm deep osteochondral defects were created in the patellar groove of 106 adult male New Zealand rabbits. The defects were treated with daily low-intensity pulsed ultrasound therapy on the right knee. The left knee was not treated. In Part I, the effect of ultrasound therapy was evaluated at 4, 8, 12, 24, and 52 weeks after surgery. In Part II, the effect of the length of treatment (5, 10, or 40 minutes of daily ultrasound therapy) compared with standard 20 minute therapy was evaluated. The repair cartilage was evaluated and graded on a standard scale for the gross and histologic appearance. Ultrasound treatment significantly improved the morphologic features and histologic characteristics of the repair cartilage compared with nontreated controls. Earlier, better repair with less degenerative changes at later times was observed in defects treated with ultrasound. Doubling the treatment time to 40 minutes daily significantly increased the histologic quality of the repair cartilage. In the current animal model, daily low-intensity pulsed ultrasound had a significant positive effect on the healing of osteochondral defects.

Animals↗
PubMed2001

Component rotation and anterior knee pain after total knee arthroplasty.

All patients undergoing cruciate-retaining primary total knee arthroplasty for degenerative osteoarthritis at one center were studied prospectively. Clinical and radiographic followup was obtained at a minimum 5 years in 102 knees in 73 patients. Patients were asked specifically about the presence of the pain in the anterior aspect of the knee in the vicinity of the patella and rated the severity of the pain on a visual analog scale. Significant anterior knee pain rating at least 3 of 10 on the visual analog scale was present in 16 knees (13 patients). Eleven patients with 14 symptomatic knees agreed to undergo computed tomography scanning to accurately determine the rotation of the tibial and femoral components. The epicondylar axis and tibial tubercle were used as references using a previously validated technique. A control group of 11 asymptomatic patients (14 knees), matched for age, gender, and length of followup also underwent computed tomography scanning. All patients in both groups had normal axial alignment. There was a highly significant difference in tibial component rotation between the two groups with the patients with anterior knee pain averaging 6.2 degrees internal rotation compared with 0.4 degrees external rotation in the control group. There also was a significant difference in combined component rotation with the patients with anterior knee pain averaging 4.7 degrees internal rotation compared with 2.6 degrees external rotation in the control group. There was no significant difference in the degree of radiographic patellar tilt or patellar subluxation between the two groups. Patients with combined component internal rotation were more than five times as likely to experience anterior knee pain after total knee arthroplasty compared with those with combined component external rotation. Component malrotation is a significant factor in the development of anterior knee pain after total knee arthroplasty.

Aged↗
PubMed2001

Use of recombinant human erythropoietin in two-stage total knee arthroplasty for infection.

A multicenter prospective study was conducted to determine whether epoetin alfa could be used to lower transfusion requirements after two-stage exchange arthroplasty for infection. Forty-one consecutive patients undergoing successful two-stage exchange arthroplasty for an infected total knee arthroplasty were enrolled in a prospective study. Epoetin alfa (40,000 units) was administered subcutaneously after prosthesis resection and antibiotic spacer placement. Although there was no difference in the hemoglobin levels before resection arthroplasty or on postoperative Day 3 between the study group and the control group, hemoglobin levels before reimplantation were higher in the patients who received epoetin alfa (12.4 mg/dL; range, 9.3-15.1 mg/dL) compared with the control group (11.3 mg/dL; range, 8.1-14.4 mg/dL). Average increase in hemoglobin level in the interval between stages was higher in the treatment group (3.2 mg/dL; range, -0.7-6.8 mg/dL) than the control group (1.7 mg/dL; range, -1.9-6 mg/dL). The transfusion rate decreased from 83% of patients in the control group to 34% in the study group during reimplantation. In addition, overall incidence of transfusion for either stage improved from 89% in the control group to 44% in the patients treated with epoetin alfa. Perioperative epoetin alfa statistically increased the hemoglobin levels and decreased transfusion rates for patients undergoing two-stage revision for infected total knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMed2001

Evolution of the rotating hinge for complex total knee arthroplasty.

Initial rotating hinge total knee designs were associated with a high failure rate. More recent designs have improved the patellofemoral articulation and the rotating hinge mechanism, added modular canal filling slotted fluted stems and metaphyseal sleeves, and improved the articulation between the mobile-bearing element and the tibial component. A series of patients with complex problems was studied. They underwent knee arthroplasty using a second generation rotating hinge component incorporating the design features listed above. Indications for surgery included medial collateral ligament disruption, revision of a previous hinged component with a massive bone loss, comminuted distal femur fracture or distal femoral nonunion in elderly patients, extensor mechanism disruption requiring reconstruction in an unstable knee, and ankylosis requiring femoral peel exposure with moderate residual flexion extension gap imbalance. A series of 23 knees in 22 patients was evaluated at the 2- to 9-year followup. The clinical results, range of motion, and satisfaction were comparable with that of a standard condylar revision knee arthroplasty despite the fact that the cases were more complex. These results warrant continued investigation of the role of rotating hinge in complex total knee arthroplasty.

Arthritis, Rheumatoid↗
PubMed2001

Modular, mobile-bearing hinge total knee arthroplasty.

Early reports of hinge total knee arthroplasty showed high rates of complications and implant failure. Third-generation modular, mobile-bearing, hinge knee arthroplasty systems have evolved to decrease the deleterious stresses that contributed to the failures of earlier designs. The combined series of Barrack et al and Jones et al documents midterm results using the S-ROM Hinge Knee System for patients with significant soft and hard tissue deficiencies not suitable for standard, less constrained, revision knee systems. The combined series included 30 knees with a mean followup of 49 months. Knee Society clinical scores improved from 52 to 134 points. There were no mechanical failures of the implants. The knee system used provides press-fit diaphyseal stems and metaphyseal filling and loading sleeves, all of which showed apposition and positive remodeling of bone at followup radiographic analysis. The excellent midterm results of this modular, mobile-bearing, linked knee system suggest the orthopaedic surgeon can display increasing confidence in the selection of such a knee system when confronted with catastrophic, salvage knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMed2001

The effect of osteogenic protein-1 on the healing of segmental bone defects treated with autograft or allograft bone.

BACKGROUND: Large amounts of bone graft are frequently used to elicit the healing of bone defects resulting from reconstructive procedures. Autograft and allograft bone are often used, but each has its limitations. Bone morphogenetic proteins (BMPs) improve the healing of segmental bone defects treated with autograft or allograft. The objective of the present study was to determine the effect of implantation of a recombinant osteogenic protein-1 (OP-1) in combination with bone graft on the healing of a critical-sized (2.5-cm) segmental defect in canine ulnae. METHODS: Either autograft bone, allograft bone, osteogenic protein-1 (OP-1) mixed with type-1 bovine collagen, or various combinations of OP-1 and collagen (OP-1 device) mixed with allograft or autograft were implanted in the segmental bone defects. The combinations included 67% bone graft with 33% OP-1 device and 33% bone graft with 67% OP-1 device. The healing of the defects was assessed with radiographic, biomechanical, and histological studies. The animals were killed at twelve weeks postoperatively. RESULTS: The use of the OP-1 device alone or any combination of autograft or allograft bone and the OP-1 device demonstrated improved healing on radiographic, mechanical, and histological studies compared with that demonstrated after use of autograft or allograft bone alone. The highest radiographic and histological grades and the greatest mechanical strength were achieved with the use of 33% allograft and 67% OP-1 device, although no significant differences were observed among the different groups containing the OP-1 device. At twelve weeks postoperatively, the defects treated with any amount of the OP-1 device obtained greater mechanical strength than that obtained by autograft bone alone. CONCLUSIONS: Major bone defects may be treated with allograft bone combined with the OP-1 device, instead of autograft alone, to avoid complications associated with the use of autograft. The combination of allograft bone and the OP-1 device resulted in optimum healing of the defect, according to the radiographic, mechanical, and histological parameters measured in this study. CLINICAL RELEVANCE: The combination of freeze-dried allograft bone with the OP-1 device is an attractive graft material for the treatment of large bone defects. Although similar results were observed when autogenous bone graft was used in combination with the OP-1 device, the results of the present study suggest that allograft, because of its relatively unlimited supply, can be substituted without reduced efficacy. In addition, avoiding the need to harvest autogenous bone eliminates the additional operative time and risk associated with a second surgical procedure.

Animals↗
PubMed2001

The use of modularity in revision total hip replacement.

A study was undertaken to establish the pattern of components revised in recent years during total hip revision to establish how often a modular feature of a retained component was used. All total hip revisions performed by the total joint service of the University Hospital between 1991 and 1995 were reviewed. Revisions involving a surface replacement, endoprosthesis, bipolar stem, or infection were excluded because retention of components is not an option in these cases. This left 158 cases for review. If a modular femoral or acetabular component was retained, it was determined whether a different length of modular head or different liner type was replanted, thus using a modular feature of the component. The most common pattern of component revision was to revise all components, which was done in 77 of 158 cases (48.7%). The second most common pattern was to revise a socket and leave the stem in place (53/158, 33.5%). The third most common was to revise the stem and leave the socket in place (22/158, 13.9%). The least common was to retain both the stem and socket and exchange the head and liner (6/158, 3.8%). Of the 59 cases in which the stem was retained, a modular head of a different length was used in 52 (88%). Of the 28 cases in which a socket was retained, a different liner type was used in 14 (50%). The modular aspect of the retained component was a valuable asset at the time of revision in a high percentage of cases (66/158, 41.8%).

Arthroplasty, Replacement, Hip↗
PubMed2001

Patellar resurfacing in total knee arthroplasty. A prospective, randomized, double-blind study with five to seven years of follow-up.

BACKGROUND: Whether to resurface the patella during a primary total knee arthroplasty performed for the treatment of degenerative osteoarthritis remains a controversial issue. Parameters that have been suggested as being useful in guiding this decision include patient height and weight, the presence of anterior knee pain preoperatively, and the grade of chondromalacia encountered intraoperatively. The purpose of this study was to determine whether these parameters were predictive of the clinical result following total knee arthroplasty with or without patellar resurfacing. METHODS: Eighty-six patients (118 knees) undergoing primary total knee arthroplasty for the treatment of osteoarthritis were enrolled in a prospective, randomized, double-blind study. All patients received the same posterior-cruciate-sparing total knee prosthetic components. Patients were randomized to treatment with or without resurfacing of the patella. Evaluations consisted of the determination of a Knee Society clinical score, the completion of a patient satisfaction questionnaire, specific questions relating to patellofemoral symptoms, and radiographs. Sixty-seven patients (ninety-three knees) were followed for a minimum of five years (range, sixty to eighty-four months; average, 70.5 months). RESULTS: With the numbers available, there was no significant difference between the groups treated with and without resurfacing with regard to the overall Knee Society score or the pain and function subscores. Obesity, the degree of patellar chondromalacia, and the presence of preoperative anterior knee pain did not predict postoperative clinical scores or the presence of postoperative anterior knee pain. CONCLUSIONS: The occurrence of anterior knee pain could not be predicted with any clinical or radiographic parameter studied. On the basis of these results, it seems likely that postoperative anterior knee pain is related either to the component design or to the details of the surgical technique, such as component rotation, rather than to whether or not the patella is resurfaced.

Arthroplasty, Replacement, Knee↗