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Biomedical subjects

R G Volz

Publications and source records attributed to R G Volz.

At least 19 recordsLinked to original sources
PubMed1995

Tibiofemoral contact stress and stress distribution evaluation of total knee arthroplasties.

The Fuji film (Itochu, Los Angeles, CA) area analysis technique demonstrates that a more accurate assessment of tibiofemoral contact stresses is possible when the film is used at 37 degrees C and at the upper end of its sensitivity range (in this case, a 2,000-N load). An AMK with a regular and Hylamer-M insert (DePuy, Warsaw, IN), an MG II (Zimmer, Warsaw, IN), an Omnifit (Osteonics, Allendale, NJ), an Ortholoc III (Dow Corning Wright, Midland, MI), a PCA II (Howmedica, Rutherford, NJ), and a PFC (Johnson & Johnson Orthopaedics, Raynham, MA) had average contact stresses that varied only 12% at 60 degrees flexion. At 0 degrees, 15 degrees and 60 degrees flexion, stresses ranged from 13 to 25 MPa. Contact area distribution ratios, which were smaller at 37 degrees C than at 24 degrees C, provide a quantitative means of grouping implants according to the shape of the tibiofemoral contact area. The Omnifit, MG II, PCA II, and PFC had small ratios (symmetric areas). The AMK and Ortholoc III had large ratios (asymmetric contact areas). If the impression is reflective of wear, it would be expected to be focal in knees with small ratios and contact areas, and uniform in knees with large ratios and contact areas, whereas large ratios and small areas would imply a linear wear pattern. Calibrated electrical resistance contact stress measurements indicated that the Fuji film measurements underestimated the magnitude of contact stresses. They also provided a means of quantifying the rate of area increase during initial loading of the knees, with the highest area increase noted for the knee with the roughest insert (Ortholoc III) and the lowest area increase for the knee with the smoothest insert (PCA II).

Electric Impedance↗
PubMed1994

Ciprofloxacin attachment to porous-coated titanium surfaces.

A simple and effective method for attaching ciprofloxacin HCl salt to the surface of porous-coated titanium based orthopedic materials was developed. The method utilizes the electrophoretic migration of both fine ciprofloxacin HCl particles and ciprofloxacin ions to deposit the antibiotic salt on a positively biased surface. The quantity of antibiotic deposited can be easily and effectively controlled by varying the time of deposition and applied voltage. In vitro tests have indicated that the antimicrobial activity of the treated surfaces is retained for a period of 5 days. The method allows a significant amount of antibiotic to be deposited and could theoretically be used to deliver antibiotics to the tissues surrounding prosthetic devices in order to prevent postoperative infections.

Biocompatible Materials↗
PubMed1993

Gentamicin sulfate attachment and release from anodized Ti-6A1-4V orthopedic materials.

A novel method has been developed to attach, retain, and release antibiotics from titanium based materials. This technique consists of forming porous surface coatings by anodizing and using the surface chemical properties of the oxide coatings to attach antibiotics. Coatings with pores in the size range 0.1-0.5 micron have been formed in acid solutions. The attachment and retainment of gentamicin sulfate, a cationic antibiotic, to the coatings has been investigated using microbiological methods. In vitro test results have shown that the duration of antimicrobial activity on the surface of anodized materials is dependent on the porosity and isoelectric point of the coatings. Using microporous oxide coatings formed in phosphoric acid solutions, it has been found that antimicrobial activity could be retained for more than 2 weeks.

Alloys↗
PubMed1993

Comparison of the subvastus and paramedian surgical approaches in bilateral knee arthroplasty.

A prospective randomized study was performed on 20 patients undergoing one-stage bilateral knee arthroplasty. One knee was exposed using a standard median parapatellar arthrotomy and the other knee with a subvastus arthrotomy. All patients underwent quantitative strength testing before surgery and at 1 week, 1 month, and 3 months after surgery. The knees were also evaluated for range of motion, and patients, who were blinded as to the approach used, completed questionnaires at each evaluation period as to their preference, if any, regarding knee pain and level of function. There was no difference in the range of motion between knees exposed with the paramedian or subvastus arthrotomy at any time period. The subvastus knees demonstrated significantly greater strength at the 1-week and 1-month intervals, but there was no strength difference at the 3-month interval. There were more lateral releases performed in the paramedium knees, and three minor complications were related to the subvastus approach. Patients who expressed a preference chose the subvastus knee 4:1 over the paramedian knee. The subvastus approach offers a reasonable alternative to the paramedian arthrotomy and preserves greater quadriceps strength in the early postoperative period.

Aged↗
PubMed1991

Postoperative blood salvage in total hip and knee arthroplasty. A randomised controlled trial.

We undertook a prospective controlled clinical trial of 109 patients to determine whether postoperative blood salvage in patients undergoing total hip or knee arthroplasty decreased the need for transfusion with banked blood. The average amount of blood collected in our series was 493 ml, most of which was collected in the first four postoperative hours. In patients undergoing bilateral total knee arthroplasty, there was a 54% reduction in banked blood utilisation. None of our patients developed adverse effects from the reinfused material. The cost of collecting and processing wound drainage using the Haemolite cell washer was $175 per patient, regardless of the volume processed, compared to $125 for a unit of banked blood. By reducing the requirement for homologous transfusion, blood salvage diminishes the risks of transmission of HIV and hepatitis viruses. In those cases where the equivalent of two units of blood are reinfused, blood salvage saves money. However, due to the small amounts of blood collected in unilateral hip or knee arthroplasty, we do not recommend its routine application in these cases.

Blood Specimen Collection↗
PubMed1991

The role of fixation and bone quality on the mechanical stability of tibial knee components.

Tibial component loosening remains one of the major causes of failure of cemented and noncemented total knee arthroplasties. In this study, the authors identified the role of implant design, method of fixation, and bone density as it related to implant stability. The physical properties of "good" and "bad" bone were simulated using a "good" and "bad" foam model of the proximal tibia, fabricated in the laboratory from DARO RF-100 foam. A generic tibial component permitting various fixation designs was implanted into "good" and "bad" variable density foam tibial models in both cemented and noncemented modes. The mechanical stability of the implants was determined using a Materials Testing Machine by the application of an eccentrically applied cyclic load. The micromotion (subsidence and lift-off) of the tibial implants was recorded using two Linear Variable Differential Transformers. Statistically significant differences in implant stability were recorded as a function of fixation method. The most rigid implant fixation was achieved using four peripherally placed, 6.5-mm cancellous screws. The addition of a central stem added stability only in the case of "poor" quality foam. The mechanical stability of noncemented implants related directly to the density of the foam. Implant stability was greatly enhanced in "poor" quality foam by the use of cement. The method of implant fixation and bone density are critical determinants to tibial implant stability.

Biomechanical Phenomena↗
PubMed1990

The current status of total joint replacement.

The last two decades have witnessed tremendous strides in the evolution of acceptable and successful methods of prosthetic replacement for the arthritic joint. By and large, these techniques are predictable and durable, though not always to the complete satisfaction of the patient and surgeon. Despite the recent emphasis on alternative forms of implant fixation, cemented total joint replacements remain the standard by which all others are judged. In some settings, non-cemented implants appear to function as well as cemented ones in providing pain relief. The acetabular component in the hip and the femoral component in knee replacement are two such areas. This has resulted in the emergence of the "hybrid" joint replacement where one component is cemented while the other is not. The long-term function and durability of these non-cemented components remains to be seen. The future of joint replacement lies in the development of new "composite" materials which can more closely match the structural characteristics of the bone into which they are being implanted. Until we better understand and are able to prevent the disease processes which lead to total joint replacement, this area will continue to be the focus of intense research and development.

Humans↗
PubMed1989

Total joint replacement: where are we today, and where are we headed?

With the advent of noncemented total joint prostheses, today's orthopedic surgeons are asking questions about the predictability and performance of newer biologically fixed implants. Reported experience to date has failed to document any improved parameters of performance; instead, problems of prolonged convalescence, postoperative pain, and difficulties in revision procedures have been noted. Other issues of concern relate to the potential harmful effects of ion leaching, and problems of stress shielding and stress overload due to the physical properties of the materials presently available. Current investigative efforts to resolve these problems look promising, though surgeons should realize that science is a long way from producing the perfect total joint prosthesis.

Aging↗
PubMed1988

The mechanical stability of various noncemented tibial components.

Four different porous-coated tibial prosthetic implants were tested for their mechanical stability following implantation into paired cadaver tibias: Porous Coated Anatomic (PCA), Miller-Galante, Whiteside, and Anatomic Modular Knee (AMK). Following implantation the test sample was loaded eccentrically over the medial tibial plateau at 40 cycles per minute for 300,000 cycles, using an MTS machine. This represents the number of steps taken by the average person in a six- to 12-month period. Load varied sinusoidally from 5 to 115 kg. Subsidence and lift-off of the tibial plate from its bony bed was recorded for each implant, using linear variable differential transformers. The greatest degree of mechanical stability was observed with the AMK design, which is secured to the bone bed using four peripherally placed 6.5-mm cancellous screws. No motion in excess of 100 micron was observed. The central-stemmed Whiteside design and the cortical screw fixated Miller-Galante designs provided slightly less stability, each demonstrating approximately 200 micron of lift-off on the unweighted side. The PCA design exhibited the greatest amount of micromotion with subsidence and lift-off displacements of 500 micron (0.5 mm).

Biomechanical Phenomena↗
PubMed1988

Fracture/dissociation of the polyethylene in metal-backed patellar components in total knee arthroplasty.

We encountered a complication that is unique to the use of a metal-backed patellar component in total knee replacement--namely, fracture and separation of the polyethylene bearing from its metal counterpart. The cases of seventeen patients who were treated at several institutions were studied. Patellar malalignment, especially in heavy patients who had a high level of activity, was a contributory cause of the complication, but we thought that deficiencies in the design of the prosthesis were also an important factor.

Aged↗
PubMed1987

Cementing technique and the effects of bleeding.

We report the results of simple laboratory experiments which showed that bleeding pressures known to occur at the bone surface during total hip arthroplasty may compromise the integrity of the bone-cement interface and the cement itself. Such undesirable effects can be prevented by maintaining adequate pressure on the cement until its increased viscosity can resist displacement caused by the bleeding pressure.

Blood Pressure↗
PubMed1987

Medical and economic parameters of motorcycle-induced trauma.

A retrospective study was conducted on all patients injured in a motorcycle accident who were admitted to the authors' institution during a one-year period. The 71 patients evaluated averaged 26 years of age; 79% were men, 75% were not wearing a helmet, and 24% were legally intoxicated. Sixty-six percent required surgical intervention and 36% a second procedure. There were 167 fractures, with an average of 2.4 per patient. The 27 patients requiring a blood transfusion averaged 10.5 units per patient. Motorcyclists not wearing a helmet had an increased risk of head injury (p less than .01). Those with head injuries had an increased need for intensive care (p less than .0001) and a ventilator (p less than .001). Patients with head injuries more commonly sustained fractures about the shoulder (p less than .015) than fractures to the lower extremity (p less than .005). The average hospital stay was 13 days, with a cost of $16,408 per patient. The cost was significantly higher in patients with a head injury ($21,945) than in patients without a head injury ($11,941). Patients sustaining a head injury were less likely to return to baseline functioning (p less than .001).

Accidents, Traffic↗
PubMed1984

Efficacy of a topical antibiotic irrigant in decreasing or eliminating bacterial contamination in surgical wounds.

Using a simple in vitro system, the authors showed that colony counts of Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas species can be reduced by 12%-56% with saline irrigation; the reduction of colony numbers, however, especially for S. aureus, was not always statistically significant. However, even if it were statistically significant, the amount of reduction would not be clinically significant. A topical antibiotic irrigant containing bacitracin/neomycin was effective against S. aureus, S. epidermidis-, and E. coli-treated agar plates. Except for a single plate containing Pseudomonas organisms, the growth of Pseudomonas colonies was also prevented by antibiotic irrigation. Tissue samples of muscle, fat, and bone obtained during operation showed antibiotic levels comparable with, and in most cases greater than, those found in the blood agar plates. These data may be clinically significant and suggest that bacitracin/neomycin irrigation can be safely used to reduce the incidence of postoperative infection.

Adipose Tissue↗
PubMed1984

The surgical treatment of the arthritic patient.

For the past several decades, the surgical approach to the arthritic patient has changed dramatically: no longer is the severely disabled arthritic patient left to a life of incapacitation and suffering. Today, the orthopedic surgeon's armamentarium includes procedures aimed not only at temporizing or arresting the early stages of inflammatory arthritis (synovectomy) but also more definitive and curative procedures such as osteotomy, arthrodesis, or total joint replacement. The most dramatic results, however, are achievable after total joint replacement. Through these techniques, patients previously considered too disabled to be rehabilitated can now be restored to useful pain-free lifestyles. The vast amount of research presently underway in the areas of more refined prosthetic designs and fabrications offers the promise of even more exciting and dramatic forms of treatment in the near future.

Arthritis↗
PubMed1984

Traumatic laceration of the radial nerve following supracondylar fracture of the elbow. A case report.

Traumatic laceration of the median, ulnar, or radial nerve is an extremely rare complication of supracondylar fracture of the humerus in children. A recent review of the literature disclosed only two reported cases of a laceration involving the radial nerve; a third such injury in an 8-year-old boy is reported in the present paper. Traumatic neuropraxia of one or more of the three adjacent peripheral nerves is a more common complication of supracondylar fracture, with the great majority of these lesions responding to conservative treatment. Vascular compromise secondary to traumatic laceration of the brachial artery is a more frequently observed injury, with an incidence in some series as high as 10%. Clinical findings that suggest vascular injury, therefore, warrant a more aggressive approach, either by arteriography or surgical exploration.

Child↗