Biomedical subjects

D A Heck

Publications and source records attributed to D A Heck.

36 records · Page 2Linked to original sources

PubMed1993

Unicompartmental knee arthroplasty. A multicenter investigation with long-term follow-up evaluation.

Nonmental-backed, cemented, unicompartmental knee arthroplasty has a survivorship rate in this multicenter investigation at ten years of 91.4% (+/- 2.8). High levels of patient weight were associated with increased need for revision arthroplasty. Overall, men had a lower revision rate (2.4%) compared with women (3.9%). Valgus postoperative alignment was minimally associated with progression of disease as a cause for revision. No difference in revision rates between medial and lateral compartmental arthroplasty was noted. The theoretical clinical benefits of the use of metal-backed tibial components will need to be reevaluated in light of these findings.

Adult↗

PubMed1992

Comparative analysis of total knee arthroplasty in two health care delivery systems.

A prospective, concurrent comparison of patients undergoing total knee arthroplasty in two different health care delivery systems was carried out. All patients had osteoarthritis, and received treatment between September 1983 and September 1987 under the supervision of a single staff physician. There were 26 total knee arthroplasties performed at the University Hospital (UH) and 22 performed at the Department of Veterans Affairs Medical Center (VAMC). The average patient age at the UH was 73 years (range, 58-87 years). The corresponding average age at the VAMC was 67 years (range, 56-78 years). Statistically significant differences between the two health care delivery systems were noted in preoperative length of hospital stay (P less than .001), postoperative length of hospital stay (P less than .001), total length of hospital stay (P less than .001), and postoperative knee range of motion at 1 and 2 years. Overall complications in the UH patient group (23% of knees) were lower than the VAMC (68% of the knees) (P = .05). Our university health care delivery system has both short- and long-term patient benefits as compared to the VAMC studied.

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PubMed1992

Gross polyethylene failure in total knee arthroplasty.

A total of 12 total knee replacements in nine patients with evidence of gross polyethylene failure at the time of revision surgery were identified. There were nine tibial and three patellar component failures. The average time from index to revision arthroplasty was 6 years (range: 0.75 to 9.63). A retrospective cohort group was identified based on date of operation. The average patient weight of the initial group was 89.6 kg (range: 76 to 104 kg), compared with 74.8 kg (range: 47 to 108 kg) (P = .045) in the control group. There was a male sex preponderance in the failure group (P = .045). The average height of the study group was 176 cm, compared to 161 cm for the control group (P = .003). Using the modified OASDI scale, the failure group had a higher activity level (P = .023). Pre-revision limb alignment in patients with failed TKA was statistically different from controls and served as an indication of polyethylene failure (P = .04). The selection of modular prosthetic component systems that allow for easy polyethylene revision is indicated in the high risk patient group identified. Close follow up is needed to minimize the sequela of polyethylene failure.

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PubMed1992

Prevalence of cartilage shards in synovium and their association with synovitis in patients with early and endstage osteoarthritis.

It has been suggested that incorporation of shards of fibrillated cartilage into the synovium is a cause of synovitis in osteoarthritis (OA). We examined the prevalence with which fragments of cartilage are seen in synovium, and their association with synovitis, in patients with endstage OA and early OA of the knee. Samples of synovium were obtained from 12 patients with endstage OA who were undergoing knee joint replacement and 30 with only mild/moderate radiographic changes of OA who exhibited articular cartilage changes of OA at arthroscopy. The presence of cartilage shards was sought in synovium from the medial and lateral tibiofemoral compartments and the suprapatellar pouch of each patient. Comparable volumes of the synovial lining from patients with endstage and early OA were examined, and tissue mononuclear cell infiltration was graded as an indicator of synovitis. Cartilage shards were seen in synovium from 7 of 12 patients with endstage OA, all of whom had synovitis. No topographic relationship was found between shards and mononuclear cell infiltration. In contrast, cartilage fragments were not seen in synovium from any of the 30 patients with early OA, although 9 of them had full thickness cartilage ulcers and 17 had evidence of synovitis.

Adult↗

PubMed1991

Stiffening of the femoral head due to inter-trabecular fluid and intraosseous pressure.

The mechanical properties of cancellous bone, as measured from bone plug samples have been widely documented. However, few tests have been attempted to explore the effects the intertrabecular contents may have on the load bearing capabilities. In this study, canine femoral heads were subjected to dynamic compressive strain cycles. The femoral heads were tested intact, as well as with disrupted boundary conditions of the continuous, intraosseous fluid space. A significant reduction in mechanical stiffness was observed when the fluid compartment boundary was disrupted by drilling a hole part way into the femoral neck. A finite element model of a typical femoral head showed that the stiffness change was not due to removal of material from the neck, hydraulic effects notwithstanding. Refilling the hole in the neck with saline solution and sealing the boundary restored the stiffness to the intact baseline level. However, an increase in the fluid pressure did not cause a statistically significant increase in the stiffness of the femoral head.

Animals↗

PubMed1991

A comparison of tricompartmental and unicompartmental arthroplasty for the treatment of gonarthrosis.

An historical prospective study was performed to compare two surgical management alternatives in the treatment of patients with knee arthritis. There were 120 unicompartmental and 81 tricompartmental knee arthroplasties in 98 and 66 patients, respectively. All living patients were available for follow-up observation, and survivorship data on all arthroplasties were obtained. The average follow-up interval was 78 months (range, eight-162 months) in the unicompartmental series and 68 months (range, two- 186 months) in the tricompartmental group. Patients receiving the unicompartmental arthroplasty were treated with nonmetal-backed polyethylene tibial components. Prosthetic survivorship was 92% at ten years in the unicompartmental patient group. There were no statistically significant differences in aseptic loosening between these two patient groups. In appropriately selected patients unicompartmental arthroplasty was associated with better range of motion and ambulatory function than patients being treated with tricompartmental knee replacement.

Adult↗

PubMed1991

The effect of intertrabecular fluid on femoral head mechanics.

The effect of intraosseous fluid on the mechanical characteristics of bone is unclear. To determine the potential effects of alteration in the fluid boundary conditions of the femoral head, a decompression procedure was performed. The stiffness of femoral heads from normal adult mongrel dogs was measured after the heads were subjected to a physiologic mechanical load. When the fluid boundary conditions were altered by drilling the femoral neck, femoral head stiffness was reduced by more than 30% (p = 0.045). Refilling of the femoral specimen with saline restored the stiffness to the baseline value. These observations demonstrate that in vitro changes of fluid boundary conditions can alter the mechanical integrity of the femoral head. Alteration in osseous fluid boundary conditions in vivo could affect joint integrity and be of pathogenetic significance in joint disease.

Animals↗

PubMed1990

Synovial inflammation in patients with early osteoarthritis of the knee.

While synovitis is common in advanced osteoarthritis (OA), its prevalence and severity in patients with early or mild OA are uncertain. In our study synovial biopsies from patients with arthroscopic evidence of OA whose radiographs were normal, or showed only mild/moderate changes of OA, were examined to determine the prevalence and severity of lining cell proliferation and mononuclear cell infiltration. Synovitis was present in only 16 of 29 patients (55%) who underwent arthroscopy because of chronic knee pain and were found to have OA; no synovium from 50% of the 22 patients in this group with full thickness cartilage ulceration showed infiltration with mononuclear cells. Similarly, no evidence of synovitis was seen in biopsies from 7 of 14 additional patients with OA who did not have knee pain but who underwent arthroscopy to evaluate joint instability. An association was seen between synovial mononuclear cell infiltration and thickness of the synovial lining cell layer (p less than 0.03), but lining cell hyperplasia was found in samples from only 12% of the patients with OA in our series. The severity of OA cartilage lesions was unrelated to severity of synovitis and no topographic relationship was found between cartilage ulceration and synovitis.

Adult↗

PubMed1989

Gait alterations in dogs after transection of the anterior cruciate ligament.

We calculated mean peak vertical forces (MFz) of each limb of 9 adult mongrel dogs before and 2 weeks, 6 weeks, and 12 weeks after left anterior cruciate ligament transection (ACLT). Five additional dogs were studied before and 2 weeks and 6 weeks after sham ACLT. The gaits of 3 dogs that had undergone ACLT 2.5 years previously were also analyzed. Preoperatively, there were no differences in the MFz of the right and left hind limbs of the 9 dogs; we found that each limb exerted approximately 70% of the dog's static body weight on the force plate. Two weeks following ACLT, the MFz of the operated limbs decreased to 25% of the static body weight, while at 6 weeks and 12 weeks after surgery, the MFz generated by the operated limbs rose to about 32% and 37% of static body weight, respectively. No change was noted in the MFz of the contralateral hind limbs. In the 3 dogs that had undergone ACLT 2.5 years earlier, the MFz in the unstable stifle joint was 50% of static body weight. At both 2 weeks and 6 weeks after surgery, the MFz values for all 4 limbs of the animals subjected to sham ACLT were comparable with baseline values. These observations indicate that the osteoarthritic changes seen in the unstable limb are associated with decreased loading of that limb, without increased (compensatory) loading of the contralateral hind limb.

Animals↗

PubMed1988

Component wear of total knee prostheses using Ti-6A1-4V, titanium nitride coated Ti-6A1-4V, and cobalt-chromium-molybdenum femoral components.

A knee simulator was used to study the wear of carbon fiber reinforced UHMWPE (Poly Two) (Poly Two is a registered trademark of Zimmer, USA) tibial and patellar components against Ti-6A1-4V, titanium nitride (TiN)-coated Ti-6A1-4V, and cobalt-chromium-molybdenum femoral components. The prostheses tested were regular sized Miller-Galante total knees mounted on 316L stainless steel fixtures using bone cement. An environmental chamber surrounded the knee and maintained bovine serum lubricant at 37 degrees C. The specimens were tested using consecutive blocks of 464 level walking steps, 8 ascending stairs and 8 descending stairs for a total of 100,000 steps. The wear mechanisms found on the tibial components were scratching, carbon-fiber associated damage, surface deformation, pitting, minor abrasion, and delamination. Three forms of carbon fiber associated damage were identified; fibers pulled from the surface, broken fibers, and UHMWPE removed from the surface fibers. The SEM evaluation revealed a pit forming mechanism. No correlation was found between femoral component material and tibial surface damage. Visual examination of the femoral components revealed no signs of wear or scratching on the cobalt-chromium-molybdenum or TiN-coated Ti-6A1-4V components. There were, however, many light surface scratches on the uncoated Ti-6A1-4V components, which were also observed in a supplementary test of an uncoated Ti-6A1-4V component tested with a conventional polyethylene tibial component.

Alloys↗

PubMed1988

Fracture of the femoral neck after internal fixation.

A case of femoral neck fracture despite the presence of a previously inserted sliding screw and sideplate is reported. Internal fixation in itself did not prevent subsequent fracture. A critical factor in the mechanism of this fracture was the patient's underlying disease, felt to be alcoholic osteomalacia.

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PubMed1988

Degenerative arthritis of the knee secondary to fracture malunion.

Degenerative arthritis of the knee is a complication of femoral or tibial fractures potentially avoidable by the correction of various degrees of malalignment. To better clarify the malalignment problem, the records of 14 patients (15 limbs), with degenerative arthritis of the knee and a history of tibial or femoral fracture were retrospectively reviewed. The average follow-up was 31.7 years. Static biomechanical frontal plane analyses were evaluated. The calculated increased force on either the medial or lateral tibial plateau, due to the malunion, was strongly associated with presence of a varus or valgus deformity at the knee (p less than 0.0005). A normal tibial plateau force for the malaligned condition multiplied by the time since fracture correlated directly with the amount of subsequent varus or valgus deformity at the knee (p less than 0.01). Lower limb fracture alignment should be restored to as near normal as possible to reduce the likelihood of gonarthrosis.

Adult↗

PubMed1986

In vivo construction of a metal-backed, high-molecular-weight polyethylene cup during McKee-Farrar revision total joint arthroplasty. A case report.

The need for revision total hip arthroplasty after metal-to-metal articulating prostheses is well known. An alternative to conventional acetabular revision in the clinical circumstance of isolated femoral component loosening is in vivo construction of a metal-backed, high-molecular-weight polyethylene (HMWPE) acetabular component. This surgical approach reduces the likelihood of intraoperative acetabular bone loss, should minimize subsequent loosening, and virtually eliminates the source of metallic wear debris. Follow-up evaluation after 3 years revealed maintenance of the acetabular component position and a satisfactory clinical result. In vivo construction of a metal-backed HMWPE acetabular component is an effective alternative in the management of this potentially difficult orthopedic problem.

Acetabulum↗

PubMed1986

Orthopedic grand rounds. Retained wooden foreign body in the foot detected by computed tomography.

A 20-year-old female presented with a 12-week history of a penetrating wound by a pointed wooden slat to the dorsum of her right foot. She had persistent pain, swelling, and an open wound. Initial radiographs were normal, and three surgical explorations failed to find a foreign body. Later radiographs showed erosion of the second metatarsal. Computed tomography detected and localized the wooden foreign body. Removal of the foreign body was followed by healing of the foot.

Adult↗

PubMed1986

General considerations in total knee arthroplasty.

Total knee replacement is a powerful but complex surgical procedure. Recognizing and addressing all planes of motion at the knee is mandatory for good results. Accurate alignment of the prosthetic component and the limb is crucial. Close attention to surgical detail and prosthetic interaction is necessary. Current prosthetic replacement fails to return the bone to its normal strain environment. Clinical results with current resurfacing components rival or exceed those obtained with conventional total hip replacement in properly selected patients.

Biocompatible Materials↗

PubMed1986

The effect of load alteration on the biological and biomechanical performance of a titanium fiber-metal segmental prosthesis.

The effect of overloading and underloading on tissue ingrowth into the porous-coated titanium segmental prosthesis was studied in a canine femoral model. The prosthesis has modular components that are connected by a conical coupling joint. One of the dog's hind legs was immobilized and suspended for three weeks using an external fixator to minimize loading and prevent weight-bearing, while the contralateral leg was allowed to bear weight freely, simulating an overloading situation. Five dogs reached the final study period of twelve weeks without complication. There were no significant differences between the non-weight-bearing and weight-bearing sides on radiographic assessments. However, the immobilized side had significantly higher stem-push-out strength and energy to failure. Bone ingrowth was variable, and a fibrous layer was commonly demonstrated at the prosthetic stem-bone interface. The orientation of the fibrous tissue was more organized, in a penetrating pattern, on the immobilized side. The mean concentration of titanium was insignificant in all tissue examined. Reduced implant loading for the porous-coated segmental bone prosthesis during the initial period of implantation was found to be beneficial as compared with an overloading situation in achieving intramedullary fixation.

Animals↗

PubMed1986

Titanium fibermetal segmental replacement prostheses. A radiographic analysis and review of current status.

Thirteen patients with titanium fibermetal segmental bone/joint prostheses at a minimum follow-up period of six months were reviewed. Detailed radiographic data were analyzed quantitatively in terms of stem/bone interface radiolucency and bone bridging over the segmental portion of the prosthesis at predefined zones. Although stem radiolucent lines were common in this series, only one case had clinical loosening and required reoperation. There were two cases of stem fracture; one achieved extracortical bone union without revision, and the other case required implant removal and revision. Analysis of the retrieved specimen revealed histologic evidence of bony ingrowth. The use of a long side plate for initial implant fixation might have been partially responsible for this complication because of inhibition of new bone formation over the porous-coated segment. Sequential study of radiograms at different follow-up time periods with the same zonal analysis criteria revealed that no progression of radiolucency occurred at the bone/prosthesis interface, and bone formation over the segmental portion either increased or stabilized with time. The patients' functional results and implant performance seemed to indicate that the porous-coated segmental prosthetic system was effective in bridging skeletal/joint defects. However, further improvements are needed in prosthetic design and implant quality control in order to minimize device-related complications.

Adolescent↗

PubMedDate not supplied

Management of osteoarthritis of the knee by primary care physicians.

BACKGROUND: Most patients with osteoarthritis (OA) are treated by primary care physicians (in this article, primary care physicians are family physicians and general internists). OBJECTIVE: To describe and compare the self-reported practice patterns of family physicians and general internists for the evaluation and management of severe OA of the knee, including factors that might influence referral for total knee replacement. DESIGN, SETTING, AND PARTICIPANTS: A survey was developed and mailed to randomly selected community family physicians and general internists practicing in Indiana. MAIN OUTCOME MEASURE: Self-reported physician practice patterns regarding OA of the knee. RESULTS: Physical examination was the most common method of evaluating OA of the knee. Family physicians were more likely to examine for crepitation, joint stability, and quadriceps muscle strength than were general internists (P<.05). Patients with OA of the knee treated by family physicians were more likely to receive nonsteroidal anti-inflammatory drugs or oral corticosteroids and were less likely to receive aspirin, acetaminophen, or narcotics compared with patients treated by general internists. Six patient characteristics were rated as positive factors favoring a referral for possible total knee replacement, 8 characteristics were rated as negative, and 5 were rated as not a factor in the decision about referral. CONCLUSIONS: Results from this study suggest that additional research is needed to determine the evaluative techniques for OA of the knee that provide the most useful information for management decisions, the management techniques that maximize patient outcomes, and the criteria that should be used to select patients who would benefit most from referral for possible total knee replacement.

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