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Biomedical subjects

H E Rubash

Publications and source records attributed to H E Rubash.

At least 55 records · Page 3Linked to original sources
PubMed1996

Physical modelling of hip joint forces in stair climbing.

A test device has been developed and validated to simulate physiologic loading of the hip during stair climbing. Forces about the hip joint were measured in static simulations of stair climbing using simulated extensor, abductor and adductor muscle groups to support the joint. Femoral flexion angle (to model step length and height) and applied hip flexion moment (to model trunk lean) were varied to examine the effects of different loading conditions on the hip. In stair climbing the maximum total joint force was six times body weight at 34 degrees of femoral flexion and 60 N m of hip flexion moment. Joint forces increased with hip flexion moment and varied little with femoral flexion angle, except for the posteriorly directed force. This component, which twists implants about the femoral shaft, increased with femoral flexion angle but changed little with hip flexion moment.

Biomechanical Phenomena↗
PubMed1995

Aseptic loosening in uncemented total hip arthroplasty in a canine model.

An in vivo canine model was developed to investigate the histologic and biochemical parameters associated with aseptic loosening. Thirty-eight canines had cementless total hip arthroplasty. Experimental groups were designed specifically to investigate the relative contributions of implant motion and particulate debris (cobalt chrome alloy, titanium aluminum vanadium, and polyethylene) on the resultant periprosthetic tissues. Tissues from a stable, well-ingrown prosthesis provided a control. Importantly, the histologic and biochemical characteristics of the experimentally induced membranes consistently correlated with previous in vitro reports of tissues retrieved at revision surgery for aseptic loosening. Implant motion and all 3 particulate debris groups resulted in increased numbers of macrophages in the periprosthetic membranes. The histologic findings paralleled the increase in levels of biochemical mediators of bone resorption as measured by collagenase, gelatinase, prostaglandin E2, and interleukin-1 activity. The most striking results were seen in the histology and biochemistry of the particle groups with highly cellular membranes showing increased biochemical activity when compared with controls. The clinical relevance of this work lies in the description of an in vivo model of aseptic loosening that can be used to investigate the effects of numerous variables implicated in aseptic loosening. Ultimately, the model may serve as a basis for developing therapeutic interventions.

Alloys↗
PubMed1994

In vivo and in vitro analysis of membranes from hip prostheses inserted without cement.

Biochemical, histological, and immunohistochemical studies of interface membranes surrounding failed hip prostheses that had been inserted without cement were done to examine specific factors involved in the development of aseptic loosening. Membranes from sixty-four femoral components were obtained from sixty-three patients during revision arthroplasty. Fifty-seven membranes were from implants that articulated with polyethylene (thirty-two were made of cobalt-chromium alloy and twenty-five, titanium alloy), and seven were from unipolar endoprostheses made of cobalt-chromium alloy that did not articulate with polyethylene. The membranes from implants with a polyethylene articulation produced significantly higher levels of collagenase and interleukin-1 (p < 0.05). However, there was no significant difference in the levels of prostaglandin E2 between the three groups. Furthermore, membranes from implants with roentgenographic evidence of focal osteolysis (endosteal erosion) released significantly higher levels of interleukin-1 (p < 0.05) than did membranes from implants without focal osteolysis. Although the membranes from the titanium-alloy implants tended to contain more metal debris than those from the cobalt-chromium-alloy implants, the biochemical findings were not significantly different between these two groups. Many macrophages that were filled with polyethylene and metal debris were present in the membranes from both groups with a polyethylene articulation. Few T lymphocytes or B lymphocytes were identified in the three groups.

Adult↗
PubMed1994

The characterization of cytokines in the interface tissue obtained from failed cementless total hip arthroplasty with and without femoral osteolysis.

The histologic, biochemical, and immunohistologic characteristics of the interface membranes surrounding the femoral component of failed cementless total hip arthroplasty (THA) in patients with (Group I) and without (Group II) radiographic evidence of focal endosteal erosion (osteolysis) were studied. Group I membranes had more macrophages and small particles of polyethylene debris in the membrane, but both groups had similar amounts of metal particles. A greater activity level of interleukin-1 (IL-1), tumor necrosis factor (TNF), and interleukin-6 (IL-6) was seen in the culture supernatant of the membranes from Group I than in that of Group II. Group I membranes also had more cells (macrophages, fibroblasts, and endothelial cells) that stained positively with anti-IL-6 antibody. These results suggest that IL-6, IL-1, and TNF play a role in the focal femoral osteolysis observed in patients with failed cementless hip prostheses.

Aged↗
PubMed1994

Comparison of interface membranes obtained from failed cemented and cementless hip and knee prostheses.

Biochemical and histologic analyses were performed on interface membranes obtained at revision of aseptically loosened hip implants (n = 36) and knee implants (n = 16). Clinical failure occurred sooner in patients with uncemented total hip implants (Group 1) than in patients with cemented implants (Group 2) (p < 0.02). There was no difference in time to revision between the patients with uncemented implants (Group 3) and patients with cemented total knee implants (Group 4). Histologically, more small (< 5 mu) polyethylene particles were found within macrophages and fibroblasts in membranes from Groups 1 and 2. Polyethylene particles from failed total knees (> 10-100 mu) were larger than those from failed total hips. Large polyethylene fragments and foreign-body giant cells were more common in failed knees than failed total hip membranes. Biochemically, proteinase and cytokine activity in the tissue culture supernatant from all groups was higher than in the control tissue (p < 0.01). The activities of stromelysin, prostaglandin E2, interleukin-1 alpha, interleukin-1 beta, and tumor necrosis factor-alpha were higher in Groups 1 and 2 than in Groups 3 and 4 (p < 0.05). These findings support the hypothesis that interface membranes enveloping femoral (hip) and tibial (knee) components of failed total joint implants may promote bone resorption and aseptic loosening. The reason for slower failure of knee implants as compared with hip prostheses may be the lower level of biochemical activity and macrophage density that correlates closely with larger polyethylene particles.

Aged↗
PubMed1994

A biochemical, histologic, and immunohistologic analysis of membranes obtained from failed cemented and cementless total knee arthroplasty.

Biochemical, histologic, and immunohistochemical analyses were performed on 34 interface membranes obtained from 33 patients during revision total knee arthroplasty. The membranes had surrounded components of cementless (n = 11) and cemented (n = 23) knee prostheses that were aseptically loose. None of these implant failures was caused by catastrophic polyethylene erosion leading to metal-to-metal contact. The histologic findings were similar in the membranes from cemented and cementless knee components: small polyethylene debris within macrophages and large birefringent polyethylene debris within foreign-body giant cells. Metallic debris was seen in membranes from both groups, but cemented membranes had more polymethylmethacrylate particles and more hyalinization. Intracytoplasmic asteroid bodies were observed in several foreign-body giant cells in both types of membranes. No significant differences were found between the two groups in levels of collagenase, prostaglandin E2 (PGE2), interleukin-1 (IL-1), interleukin-6 (IL-6), or tumor necrosis factor-alpha (TNF-alpha), nor in the population of inflammatory cells stained with IL-1, IL-6, and TNF-alpha antibodies. Membranes that had surrounded components with radiographic evidence of diffuse or localized periprosthetic bone loss released significantly more collagenase, IL-1, IL-6, and TNF than did membranes from components without bone loss. These two groups, however, did not have significantly different PGE2 levels. These findings suggest that polyethylene and metal debris may play a role in macrophage activation and the release of mediators of bone resorption in the membranes surrounding failed cemented and cementless total knee implants.

Aged↗
PubMed1994

Primary total hip arthroplasty in the older patient: optimizing the results.

Preoperative planning is the first step in adult reconstructive surgery of the hip. When executed properly, it provides a template of the procedure for the whole surgical team. Thorough planning also helps the team anticipate intraoperative problems and avert complications. It reduces surgical trial and error, thus reducing operative time. Planning shortens the learning curve for a new implant system, improves technical skills for performing THA, and ultimately can improve the clinical results.

Acetabulum↗
PubMed1994

Fixing the cup.

Explore the source record for details and available documents.

Acetabulum↗
PubMed1993

Preventing distal voids during cementation of the femoral component in total hip arthroplasty.

Cement voids have been noted in close approximation to the unfilled hole in the distal end of the femoral prosthesis. These cement voids result from the displacement of cement by the expansion of air trapped in the distal prosthesis. Voids in the distal cement have been shown to lead to an increased incidence of cement failures. This potentially deleterious situation can easily be avoided by plugging the hole in the distal stem. This may be accomplished three ways: using a centralizer, using the plastic plug supplied with the prosthesis, or filling the hole with cement prior to implanting the prosthesis.

Cementation↗
PubMed1993

Total knee arthroplasty in patellectomized patients.

Thirty-two total knee arthroplasties (TKAs) in patellectomized patients were evaluated with recent clinical and radiographic examinations. Eighteen patients had a primary TKA with a mean follow-up period of 49 months, and 14 patients had a revision TKA with a mean follow-up period of 36 months. A control group of 13 TKA patients with intact patellae were randomly generated but matched for age, sex, follow-up data, diagnosis, and prosthesis. Posterior cruciate ligament-retaining types of prostheses were used in the primary knees, while the revision knees underwent arthroplasties with the more constrained, posterior cruciate ligament-substituting prostheses. All knees were evaluated based on the Knee Society's clinical and radiographic scoring system. In addition, 18 patients (9 primary, 9 revision) underwent isokinetic dynamometer testing for quantitation of peak quadriceps and hamstring torque. The knee score, indicative of pain relief, averaged 82.5 in the primary group (16 good/excellent, 1 fair, 1 poor), 86.5 in the revision group (12 good/excellent, 1 fair, 1 poor), and 93.9 in the control group (13/13 excellent). The function score averaged 59.7 in the primary group (6 good/excellent, 6 fair, 6 poor), 60.0 in the revision group (5 good/excellent, 2 fair, 7 poor), and 80.9 in the control group (12 good/excellent, 1 fair). The lower function scores predominantly reflected the patients' difficulty in independently climbing or descending stairs. This was also reflected in their higher flexion to extension peak torque ratios. There was one failure in the primary group requiring a revision and one failure in the revision group requiring a knee fusion. There was no radiographic evidence of impending failure in any of the remaining knees. No clinical or radiographic differences were found between the patients with osteoarthritis or rheumatoid arthritis. Although the knee and function scores were lower in the patellectomized patients, the overall results were generally satisfactory without a high incidence of failures. Satisfactory results were obtained in the primary TKAs using the minimally constrained prostheses when the posterior cruciate ligament was intact. Revision TKAs, in which the posterior cruciate ligament was absent, also demonstrated satisfactory results with the more constrained, posterior cruciate ligament-substituting prostheses.

Aged↗
PubMed1993

Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis.

The posterior condylar surfaces of the femur are routinely used as the reference for the rotational orientation of the femoral component during most primary total knee arthroplasties. The purpose of this investigation was to identify a clearly discernible, reproducible secondary anatomic axis useful for determining the rotational orientation of the femoral component when the posterior condylar surfaces cannot be used. Seventy-five embalmed anatomic specimen femurs were studied. A surgical epicondylar axis was defined as the line connecting the lateral epicondylar prominence and the medial sulcus of the medial epicondyle. The posterior condylar angle was measured as the angle between the posterior condylar surfaces and the surgical epicondylar axis. Measurement of the posterior condylar angle referenced from the surgical epicondylar axis yielded a mean posterior condylar angle of 3.5 degrees (+/- 1.2 degrees) of internal rotation for males and a mean posterior condylar angle of 0.3 degree (+/- 1.2 degrees) of internal rotation for females. Thus, rotational alignment of the femoral component can be accurately estimated using the posterior condylar angle. The posterior condylar angle, referenced from the surgical epicondylar axis, provides a visual rotational alignment check during primary arthroplasty and may improve alignment of the femoral component at revision.

Biometry↗
PubMed1993

Avoiding neurologic and vascular injuries with screw fixation of the tibial component in total knee arthroplasty.

This investigation determined the position of neurologic and vascular structures at risk during screw fixation of an uncemented tibial component in total knee arthroplasty relative to the cut surface of the tibial plateau. Sixteen anatomic specimens of the lower extremities were studied by systematically placing screws about the tibial plateau followed by computed tomographic scanning with three-dimensional reconstruction and anatomic dissection. The structures at risk during screw preparation and placement were the tibial nerve, popliteal artery, popliteal vein, anterior tibial artery, and common peroneal nerve with its superficial and deep branches. The application of a clock system to the cut surface of the tibial plateau with the six o'clock position defined as directly anterior and the three o'clock position defined as lateral identified the entire region between the 11 o'clock and three o'clock positions as a location where potential injury to vital structures can occur during screw placement. The risk of injury to these structures may be minimized by directing screws radially inward to avoid violation of the tibial cortex. Any penetration of the cortex between the 11 o'clock and three o'clock positions may have potentially devastating consequences because of the close proximity of neurologic and vascular structures.

Blood Vessels↗
PubMed1993

A histologic and biochemical comparison of the interface tissues in cementless and cemented hip prostheses.

Thirty-four membranes from 20 cementless and 14 cemented prostheses from 33 patients excised during revision arthroplasty were analyzed for foreign-body reactive processes. As a control, identical analyses were performed using adjacent pseudocapsular tissue taken from 12 patients during revision arthroplasty. Histologically, cementless membranes tended to contain more metal debris, and cemented membranes contained more foreign-body giant cells. Collagenase, gelatinase, prostaglandin E2, and interleukin-1 were measured in conditioned media taken from organ cultures of each interface membrane. Both cementless and cemented membranes released significant levels of gelatinase and collagenase, prostaglandin E2, and interleukin-1 into the conditioned media when compared with control tissues. However, the tissue concentrations were not significantly different between cementless and cemented membranes. Although histologic differences between cementless and cemented interface membranes exist, both share a similar capacity to release bioactive products that can induce bone resorption and cause aseptic loosening of the hip prostheses.

Adult↗
PubMed1993

Femoral windows in revision total hip arthroplasty.

In 21 revision total hip arthroplasties (THA), a 2-5-cm window was cut into the anterolateral cortex of the femur, and the cement distal to the window was removed under direct vision. In each case, a cemented THA was revised to a noncemented implant that bypassed the window by at least two femur diameters. The section of cortical bone was replaced; autogeneic bone graft was applied to the osteotomy site, and cerclage wires were used to hold the window in place. Postoperatively, all patients were maintained at partial weight-bearing (touchdown) for six weeks and then advanced as they were able. The mean follow-up time in this series was 22 months. Access to the femoral cement was greatly facilitated by the use of a femoral window. There were no intraoperative femoral fractures or inadvertent femoral perforations during cement removal. The mean healing time for the windows was 17 weeks. There was no association of femoral thigh pain or implant loosening with femoral windows. The windows heal rapidly and have not been associated with perioperative femoral fractures.

Adult↗
PubMed1992

Neural and vascular injury in total hip arthroplasty.

Complete awareness of the anatomy of the pelvis and proximal femur is required if neurologic and vascular complications are to be avoided following total hip arthroplasty. Avoidance of the anterior quadrants for acetabular screw fixation is critical. Cementing techniques are important, and all acetabular and femoral defects should be bone grafted to avoid inadvertent cement migration. Knowledge of the location of pertinent neural and vascular structures should guide retractor placement. Planned lengthening of an extremity during total hip arthroplasty poses a significant risk to neurologic structures, and SSEP monitoring should be considered. In difficult revision procedures and complex primary total hip arthroplasty, preoperative neural and vascular assessment and SSEP monitoring should be done. With the occurrence of a postoperative nerve palsy, careful review of the procedure should be performed to determine the cause of the injury. In this manner the surgeon can best offer appropriate counseling to the patient as to the likelihood of neurologic recovery.

Blood Vessels↗
PubMed1992

Bone remodeling around total hip implants.

This chapter reviews the research in the computer simulation of bone remodeling caused by hip implants and also attempts to give nonmedical personnel a basic introduction to total hip arthroplasty and implant-induced bone resorption. First, a short discussion of the hip arthroplasty procedure and the results of follow-up studies are presented to motivate the study of hip prostheses. Current implant materials and technologies and future trends in implant design are reviewed. A description of what are believed to be the mechanisms of bone resorption due to femoral implantation is presented. Different mathematical theories of bone remodeling and their application to the problem of implant analysis are presented, and recent advances in the finite element modeling of bone resorption and implant micromotion are discussed.

Algorithms↗
PubMed1992

Porous-coated uncemented components in experimental total hip arthroplasty in dogs. Effect of plasma-sprayed calcium phosphate coatings on bone ingrowth.

The effect of a thin plasma-sprayed, calcium phosphate ceramic coating on bone ingrowth into titanium fiber mesh porous-surfaced prostheses was examined in a controlled canine cementless total hip arthroplasty model. Bone ingrowth was quantified using backscattered scanning electron microscopy of undemineralized sections. When good contact between the bone and porous coating was present, the calcium phosphate-coated prostheses contained significantly higher amounts of bone ingrowth at three weeks postimplantation than the uncoated control prostheses. At six weeks, however, there was no significant difference in the amount of bone ingrowth between the coated prostheses and uncoated prostheses. The ingrown bone seemed to be more intimately associated with the calcium phosphate-coated porous surfaces than the uncoated porous surfaces. When gaps at the bone-porous coating interface occurred, the calcium phosphate coating did not enhance bone ingrowth across those gaps. Plasma-sprayed calcium phosphate coatings may be useful in enhancing the early ingrowth of bone into porous-surfaced joint replacement prostheses, but they may lack long-term effectiveness. The coatings were not effective in enhancing bone ingrowth across gaps between the porous surface and the bone bed prepared at surgery.

Acetabulum↗