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H E Rubash

Publications and source records attributed to H E Rubash.

At least 19 recordsLinked to original sources
PubMed2006

Determination of in-vivo articular cartilage contact areas of human talocrural joint under weightbearing conditions.

OBJECTIVE: The knowledge of in-vivo cartilage contact biomechanics is important to the understanding of the pathogenesis of joint diseases such as osteoarthritis. This study investigated the in-vivo contact areas of human talocrural joint under weightbearing conditions that simulated the stance phase of walking using a combined magnetic resonance (MR) and dual-orthogonal fluoroscopic imaging technique. DESIGN: Nine healthy ankles of living subjects were recruited for this study. The in-vivo talocrural joint positions were recorded using the dual-orthogonal fluoroscopic images at three ankle positions that simulated those occurring during the stance phase of walking: heel strike, mid-stance, and toe off. Three-dimensional (3D) models of the talocrural joints were created from MR images and used to reproduce the in-vivo ankle positions recorded on the fluoroscopic images. The talocrural cartilage contact area was defined as the overlap area of the distal tibial and the proximal talar cartilage surfaces. The method was validated using an in-vitro experimental setup to evaluate its accuracy in determination of cartilage contact area. RESULTS: The validation study demonstrated that the articular cartilage contact area of the talocrural joint determined using the imaging technique was approximately 4% lower than that of the experimental measurement. In the nine living ankles, the average cartilage coverage area was 964.9+/-156.1 mm(2) on the distal tibia and 1304.8+/-208.4 mm(2) on the proximal talus. The average talocrural cartilage contact areas were 272.7+/-61.1 mm(2) at heel strike, 416.8+/-51.7 mm(2) at mid-stance, and 335.7+/-64.5 mm(2) at toe off. The contact area at mid-stance was significantly larger than those at heel strike and toe off, while the contact area at toe off was significantly larger than that at heel strike. CONCLUSION: The combined dual fluoroscopic and MR imaging technique was shown to be capable of determining in-vivo talocrural cartilage contact areas. During the simulated stance phase of walking, the contact areas were less than 44% and 31% of the cartilage coverage areas of the distal tibia and the proximal talus, respectively. These data may be useful for understanding in-vivo biomechanical function of the cartilage as well as the etiology of osteoarthritis.

Adult↗
PubMed2004

Effect of the posterior cruciate ligament on posterior stability of the knee in high flexion.

Most biomechanical studies of the knee have focused on knee flexion angles between 0 degrees and 120 degrees. The posterior cruciate ligament (PCL) has been shown to constrain posterior laxity of the knee in this range of flexion. However, little is known about PCL function in higher flexion angles (greater than 120 degrees ). This in vitro study examined knee kinematics before and after cutting the PCL at high flexion under a posterior tibial load and various muscle loads. The results demonstrated that although the PCL plays an important role in constraining posterior tibial translation at low flexion angles, the PCL had little effect in constraining tibial translation at 150 degrees of flexion under the applied loads.

Aged↗
PubMed2001

Rotational instability and malrotation after total knee arthroplasty.

Total knee arthroplasty has become the standard treatment for various disabling disorders of the knee and has proven long-term success. Surgical technique and prosthetic design have evolved to produce consistent and excellent results. Despite the current success of total knee arthroplasty, complications remain.

Arthroplasty, Replacement, Knee↗
PubMed2001

The effect of component placement on knee kinetics after arthroplasty with an unconstrained prosthesis.

The mechanical success of a total knee replacement demands stable patellar tracking without subluxation and, stable tracking, in turn, can depend largely on the medial-lateral forces restraining the patella. Patellar button medialization has been advocated as a means of reducing subluxation, and experimental evidence has shown femoral component rotation also affects medial-lateral forces. Surgeons have choices in femoral component rotation and patellar button medialization and must frequently make intra-operative decisions concerning component placement because of anatomical variations among patients. Thus, in seeking to minimize medial-lateral patellar force, we examined the effects of patellar button medialization and external femoral component rotation. The study used an unconstrained total knee system implanted in nine cadaveric specimens tested on a knee simulator operating through flexion angles up to 100 degrees. Tests included all combinations of external femoral component rotation of 0 degree, 2.5 degrees, and 5 degrees and patellar placement at the geometric center and at 3.75 mm medial to the geometric center. A video-based motion analysis system tracked patellar and tibial kinematics while a six-component load cell measured patellofemoral loads. Repeated measures analysis of variance revealed a statistically significant decrease in the average medial-lateral force with button medialization but no significant change with femoral component rotation. Neither femoral component rotation nor patellar button medialization had an effect on the normal component of the patellar reaction force. External femoral component rotation did cause significant increases in lateral patellar tilt, in tibial varus angle, and in external tibial rotation. Button medialization caused significant increases in lateral patellar tracking, lateral patellar tilt and external tibial rotation. The results in medial-lateral patellar forces quantify the benefit of patellar button medialization and discount any benefit of femoral rotation. The change in tibial kinematics with patellar button medialization and femoral component rotation cannot be measured in vivo with current technology, and the precise clinical implications are unknown.

Anterior Cruciate Ligament↗
PubMed2001

An electronic database for outcome studies that includes digital radiographs.

We report on acquisition of key data from the clinical medical record, surgical data, radiologic studies, and patient surveys for a novel digital total hip arthroplasty (THA) registry that includes electronic capture of digital radiographic images into a database on an internet platform for query. We now have the ability to collect demographic and operative data, including the operative note, discharge summary, surgery data, and Digital Imaging Communications in Medicine (DICOM) radiology images. Steps are being completed to assemble office encounters, hospital procedural codes, and implant bar codes. Two examples include a THA surgery record and a THA outcome study with plain radiograph set. Analysis of such data could suggest ways to improve clinical practice.

Arthroplasty, Replacement, Hip↗
PubMed2001

Cruciate-retaining and cruciate-substituting total knee arthroplasty: an in vitro comparison of the kinematics under muscle loads.

The kinematics of posterior cruciate ligament (PCL)-retaining (PCR) and PCL-substituting (PS) total knee arthroplasty (TKA) were compared directly in a robotic, in vitro study, and the forces in the PCL and cam-spine mechanism were measured from 0 degrees to 120 degrees of flexion. The forces in the PCL after PCR TKA and in cam-spine contact after PS TKA increased only at a flexion of > or =90 degrees. Posterior translation of the lateral femoral condyle was significantly greater than translation of the medial femoral condyle in the intact knees, consistent with femoral rollback and internal tibial rotation. The PCR and PS TKAs partially restored these kinematics when the knee flexed >60 degrees (ie, when the forces increased in the PCL and cam-spine mechanism), whereas the PCL-deficient TKA failed to do so. The results reflect the importance of the PCL and cam-spine mechanism after PCL retention and substitution in TKA and confirm the necessity for either one, if knee kinematics are to be restored even partially.

Analysis of Variance↗
PubMed2001

Biochemical analyses of human macrophages activated by polyethylene particles retrieved from interface membranes after failed total hip arthroplasty.

Human monocyte/macrophages (M/M) were exposed to retrieved ultra-high molecular weight polyethylene (UHMWPE) particles isolated after enzymatic digestion of revision total hip arthroplasty interface membrane tissue samples. The cellular response of human M/M to UHMWPE was compared with the response of these cells to latex particles and culture medium alone. We incubated macrophages in good contact with polyethylene particles using an inverted culture system. Chamber slides on which macrophages were attached were filled with polyethylene particle suspension and sealed with plastic sheets. After the slides were inverted, the incubation was completed. Retrieved UHMWPE particulate debris stimulated human M/M to secrete interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha. Human M/M exposed to retrieved UHMWPE particles secreted significantly more IL-1beta, IL-6, and TNF-alpha compared with M/M exposed to latex particles (P<.05).

Aged↗
PubMed2001

Classification of osteonecrosis of the femoral head. Reliability, reproducibility, and prognostic value.

The purpose of the current investigation was to determine interobserver and intraobserver reliability of the classification system of Steinberg et al for osteonecrosis of the femoral head. Sixty-five anteroposterior and lateral radiographs of hips were selected randomly from a pool of patients with confirmed osteonecrosis of the femoral head. Six fellowship-trained observers viewed the radiographs (Reading 1). The observers used six main stages of the classification excluding A, B, and C subgroups. The same observers viewed the radiographs 4 months later in reverse order (Reading 2). Reading 1 was used to calculate interobserver kappa values. Reading 2 was used to calculate intraobserver kappa values. Stage-specific kappa values for interobserver variation between all viewers were as follows: Stage I, k = 0.64; Stage II, k = 0.51; Stage III, k = 0.21; Stage IV, k = 0.49; Stage V, k = 0.36; and Stage VI, k = 0.80. Stage-specific kappa values for intraobserver variation between all viewers were as follows: Stage I, k = 0.74; Stage II, k = 0.60; Stage III, k = 0.46; Stage IV, k = 0.59; Stage V, k = 0.27; and Stage VI, k = 0.78. An average of 10 of 21 (48%) of these errors involved Stage III. An average of 6.3 of 21 (30%) intraobserver errors involved Stage V. The presence of the crescent sign in Stage III and joint space narrowing in Stage V markedly diminished the overall reliability of any four- to six-stage classification system. Based on the authors' experience and analysis of the current classifications of osteonecrosis of the femoral head, an easy and reproducible Pittsburgh classification system is proposed.

Female↗
PubMed2001

Optimizing femoral component rotation in total knee arthroplasty.

Femoral component rotation is important in total knee arthroplasty to optimize patellofemoral and tibiofemoral kinematics. More recently, the epicondylar axis has been cited as the definitive landmark for femoral component rotation. However, there are few studies to support the validity of this rotational landmark and its effect on the patellofemoral and tibiofemoral articulations. In the current study, a total knee arthroplasty was done in 11 knees from cadavers. The knees were tested with various femoral component rotations from 5 degrees internal rotation to 5 degrees external rotation referenced to the epicondylar axis and to the posterior femoral condyles. Each knee acted as its own internal control. The knees were actively ranged from 0 degrees to 100 degrees by a force on the quadriceps tendon in an Oxford knee simulator. Three-dimensional kinematics of all three components were measured whereas a multiaxial transducer imbedded in the patella measured patellofemoral forces. Femoral component rotation parallel to the epicondylar axis resulted in the most normal patellar tracking and minimized patellofemoral shear forces early in flexion. This optimal rotation also minimized tibiofemoral wear motions. These beneficial effects of femoral rotation were less reproducibly related to the posterior condyles. Rotating the femoral component either internal or external to the epicondylar axis worsened knee function by increasing tibiofemoral wear motion and significantly worsening patellar tracking with increased shear forces early in flexion. Based on the current study, the femoral component should be rotationally aligned parallel to the epicondylar axis to avoid patellofemoral and tibiofemoral complications.

Analysis of Variance↗
PubMed2000

Quantitative analysis of ultrahigh molecular weight polyethylene (UHMWPE) wear debris associated with total knee replacements.

The size and morphology of particulate wear debris retrieved from tissues around 18 failed total knee replacements (TKR) were characterized. Interfacial membranes from nine cemented and nine uncemented TKR were harvested from below the tibial components during revision surgery. Wear debris were extracted using papain and potassium hydroxide digestion. Ultrahigh molecular weight polyethylene (UHMWPE) particles from around cemented or uncemented TKR were similar in size and morphology. The mean size was 1.7 +/- 0. 7 microm with a range of 0.1-18 microm. Thirty-six percent of the particles were less than 1 microm and 90% were less than 3 microm. Morphologically the particles were predominantly spherical with occasional fibrillar attachments and flakes. Particles from TKR were greater than threefold larger than previously characterized particles from total hip replacements, which were 0.5 microm in mean size. Differences in joint conformity and wear patterns between the hip and knee articulations may explain the disparity in size of the wear debris. Since particle size represents an important variable influencing the magnitude of the biological response, it is possible that in vivo the larger TKR debris results in a diminished mediator release, which in turn may account for the lower incidence of osteolysis and aseptic loosening in some designs of TKR.

Aged↗
PubMed2000

Revision total knee arthroplasty: current rationale and techniques for femoral component revision.

Revision total knee arthroplasty often requires solutions for the multiple complexities that exist on the femoral side, including the treatment of bone loss, component position, ligamentous laxity, and component stability. Surgical decisions regarding the proper use of bone grafts, component augmentation, proper axial and rotational alignment, and femoral stems must be addressed systematically to achieve consistently successful outcomes. A review of currently used femoral revision techniques and their rationale and a classification system of femoral deficiencies designed to guide the surgical decision making process are presented.

Arthroplasty, Replacement, Knee↗
PubMed1999

Short-term effects of bisphosphonates on the biomechanical properties of canine bone.

Periprosthetic osteolysis and aseptic loosening of total joint replacements are believed to be initiated often by abnormal bone resorption induced by prosthetic wear debris. Bisphosphonates can inhibit bone resorption and have been successfully used clinically to treat osteoporosis and Paget's disease. In a recent study it also was shown that a third generation bisphosphonate (alendronate) is effective in preventing wear debris-induced periprosthetic osteolysis. Since inhibition of bone resorption by alendronate may disrupt the delicate balance between bone resorption and formation in normal bone remodeling, it is possible that continuous alendronate therapy may have an adverse effect on the biomechanical properties of bone. Thus the purpose of the present study was to examine the effects of systemic alendronate administration on the biomechanical properties of normal bone using a canine total hip arthroplasty model. We evaluated the biomechanical properties of femora from canines that had received total hip replacements on one side and had been given oral alendronate daily for 23 weeks. The biomechanical properties assessed were fracture toughness, elastic modulus, tensile strength, microhardness, porosity, and weight fractions of the mineral and organic phases of bone. Also, bone microstructure was examined using optical microscopy. Our results indicate that in the short term alendronate therapy does not have any adverse effects on the intrinsic biomechanical properties of canine bone. However, the long-term effects of alendronate therapy still need to be investigated.

Alendronate↗
PubMed1999

Fabrication of submicron titanium-alloy particles for biological response studies.

Biologic response to generated wear particles and subsequent aseptic loosening is a critical factor limiting the long-term survival of total hip replacements. To better understand the sequence of events leading to aseptic loosening and the role of the individual material components, fabricating metal particles similar to those present clinically is very important. We describe a simple milling technique to generate significant amounts of fine titanium-alloy (TiAlV) debris. A TiAlV rod was milled against a TiAlV plate in distilled water supplemented with antibiotics. The resulting debris were sedimented in alcohol and the fine debris were separated. Scanning electron microscopy analysis and particle size analysis demonstrated that the mean size of particles was 1.1 +/- 0.9 microm (range 0.2-4.2 microm). Sixty-two percent were smaller than 1.0 microm, and 85% were smaller than 2.0 microm. The particles generated had varying shapes, including angular or shard-like shapes with jagged and irregular outlines.

Alloys↗
PubMed1999

Fixation, polyethylene wear, and pelvic osteolysis in primary total hip replacement.

A multicenter retrospective review was performed analyzing 1081 primary total hip replacements in 944 patients using the Harris Galante-I cementless acetabular component with screw fixation. All patients were followed up for a minimum of 5 years with a mean followup of 81 months. Linear polyethylene wear averaged 0.11 mm/year (range, 0-0.86 mm/year). Pelvic osteolysis was seen in 25 patients (2.3%). Migration of the acetabular component was seen in four hips. A subgroup of patients was reanalyzed at a minimum followup of 10 years. The mean linear polyethylene wear rate remained 0.11 mm/year. In this group, only one socket had migrated. There was an association between wear rate and age. On average, younger patients had higher wear rates. The risk for having pelvic osteolysis develop and the need for revision surgery also was age-related. Twenty-two percent of hip replacements (15 hips) in patients younger than 50 years of age at the time of their index operation had pelvic osteolysis develop. In contrast, for patients older than 50 years of age at the time of surgery only 7.8% (eight hips) had osteolysis of the pelvis develop. For patients older than 70 years of age at the time of primary total hip replacement, none had pelvic osteolysis develop.

Adolescent↗
PubMed1999

Prediction of antagonistic muscle forces using inverse dynamic optimization during flexion/extension of the knee.

This paper examined the feasibility of using different optimization criteria in inverse dynamic optimization to predict antagonistic muscle forces and joint reaction forces during isokinetic flexion/extension and isometric extension exercises of the knee. Both quadriceps and hamstrings muscle groups were included in this study. The knee joint motion included flexion/extension, varus/valgus, and internal/external rotations. Four linear, nonlinear, and physiological optimization criteria were utilized in the optimization procedure. All optimization criteria adopted in this paper were shown to be able to predict antagonistic muscle contraction during flexion and extension of the knee. The predicted muscle forces were compared in temporal patterns with EMG activities (averaged data measured from five subjects). Joint reaction forces were predicted to be similar using all optimization criteria. In comparison with previous studies, these results suggested that the kinematic information involved in the inverse dynamic optimization plays an important role in prediction of the recruitment of antagonistic muscles rather than the selection of a particular optimization criterion. Therefore, it might be concluded that a properly formulated inverse dynamic optimization procedure should describe the knee joint rotation in three orthogonal planes.

Algorithms↗
PubMed1999

An analysis of blood management in patients having a total hip or knee arthroplasty.

Three hundred and thirty orthopaedic surgeons in the United States participated in a study of transfusion requirements associated with total joint arthroplasty. A total of 9482 patients (3920 patients who had a total hip replacement and 5562 patients who had a total knee replacement) were evaluated prospectively from September 1996 through June 1997. Of those patients, 4409 (46 percent [57 percent of the patients who had a hip replacement and 39 percent of the patients who had a knee replacement]) had a blood transfusion. Two thousand eight hundred and ninety patients (66 percent) received autologous blood, and 1519 patients (34 percent) received allogenic blood. Ordered logistic regression analysis showed the most important predictors of the transfusion of allogenic blood to be a low baseline hemoglobin level and a lack of predonated autologous blood. Preoperative donation of autologous blood decreases the risk of transfusion of allogenic blood; however, inefficiencies in the procedures for obtaining autologous blood were identified. Sixty-one percent (5741) of the patients had predonated blood for autologous transfusion, but 4464 (45 percent) of the 9920 units of the predonated autologous blood were not used. Primary procedures and revision total knee arthroplasty were associated with the greatest number of wasted autologous units. Of the 5741 patients who had predonated blood, 503 (9 percent) needed a transfusion of allogenic blood. The frequency of allogenic blood transfusion varied with respect to the type of operative procedure (revision total hip arthroplasty and bilateral total knee arthroplasty were associated with the highest prevalence of such transfusions) and with a baseline hemoglobin level of 130 grams per liter or less. Transfusion of allogenic blood was also associated with infection (p < or = 0.001), fluid overload (p < or = 0.001), and increased duration of hospitalization (p < or = 0.01). These latter findings warrant further evaluation in controlled studies.

Aged↗
PubMed1999

Micromotion measurements with hip center and modular neck length alterations.

Hip center relocation often is necessary because of acetabular deformity or in revision surgery. Superolateral relocation of the acetabular component increases the hip joint reaction forces and has been associated with early femoral implant loosening. In addition, relocation can necessitate the use of extended femoral neck lengths. The purpose of this study was to compare the initial stability (micromotion) of an anatomically placed femoral component with that of a superolaterally relocated component and with a component having an extended neck length. A six-degree of freedom device was constructed to measure three-dimensional micromotion at the proximal and distal regions of the femoral component. The instrumented femur was loaded using a unique loading device that included musculature necessary to simulate stairclimbing. Results showed that superolateral relocation of the hip center (25 mm) only moderately increased femoral component micromotion (13%). However, it was found that extending the neck length 12.5 mm produced a dramatic increase in micromotion (38%). Clinically this suggests that hip center lateralization and the use of long modular neck lengths should be avoided.

Acetabulum↗