Percutaneous vertebroplasty guided by a combination of CT and fluoroscopy

We describe the technique of percutaneous vertebroplasty using methyl methacrylate. We injected under the guidance of CT and fluoroscopy a group of 10 patients with back pain caused by a variety of vertebral lesions including severe osteoporosis (n = 4), hemangiomas (n = 5) and metastasis (n = 1). Over varying periods of follow-up (ranging from 4 to 17 months) none of the injected vertebral bodies demonstrated compression. All patients had relief of back pain; none had complications related to the technique. We emphasize that the efficacy of this technique in preventing vertebral collapse could not be evaluated in this small sample; a well-controlled study would be required to determine the proper indications and efficacy of this treatment.

[Local antibiotic administration in osteomyelitis treatment--a comparative study with two different carrier substances]

Two antibiotic carriers (collagen sponge/PMMA-beads--loaded with gentamicin) for the treatment of osteomyelitis of long bones are compared in a randomised prospective study of 20 patients in respect of efficacy, safety and biocompatibility. In addition, the concentration of gentamicin in serum, urine and wound exudate was measured. This revealed marked differences. Gentamicin was released rapidly from the collagen sponge, leading to high levels in wound exudate and urine within the first 48 hours, with measurable but non-toxic concentrations in the serum. The liberation of gentamicin from the PMMA beads was much slower. This resulted in low steady levels in wound exudate and urine, and no detectable concentrations in the serum. The clinical outcome showed no differences between both methods of application. In 80% of the collagen sponge group and in 90% of the PMMA-beads group the osteomyelitis was completely allayed with disappearance of all infectious parameters. The number of re-operations was significantly higher in the PMMA group. It is recommended to use collagen sponges for the local treatment of osteomyelitis in cases that can probably be eradicated in a single surgical procedure, whereas PMMA beads should be applied in larger defects requiring a space-occupying function for further reconstructive operations.

Antibiotic bead chains

Gentamicin-PMMA chains are an effective drug delivery system for local antibiotic therapy in bone and soft-tissue infections. The gentamicin concentrations at the site of infection are far higher than after systemic application of the same antibiotic and far above the minimal inhibitory concentrations of most common pathogens. Because of the very low concentrations in the serum and urine after implantation of the antibiotic bead chains, toxic side effects are not to be feared. Radical debridement with removal of all sequestrated bone fragments and removal of all alloplastic implants is mandatory before implantation of gentamicin-PMMA chains into the infected bone cavity. Primary wound closure is necessary to achieve high local concentrations. The chains can be used for temporary or permanent filling of osteomyelitic cavities. Guidelines are given for the clinical application in sequestrating osteomyelitis, infected osteosynthesis, and infected pseudarthrosis. There are distinct advantages of this new form of antibiotic therapy in chronic osteomyelitis, such as increased patient comfort by primary wound closure, no need for prolonged systemic antibiotic therapy with toxic side effects, no irrigation-suction-drainage, early ambulation, shortening of hospitalization, and reduced cost.

Methyl methacrylate: inhalation developmental toxicity study in rats

Methyl methacrylate (99.9% pure) was administered by vapor inhalation exposure to five groups (27 rats/group) of presumed pregnant rats (Crl:CD) at concentrations of 0 (control), 99, 304, 1,178, and 2,028 ppm for 6 hr/day on days 6-15 of gestation (G). Maternal body weight, feed consumption, and clinical signs were recorded throughout gestation. Dams were euthanized on day 20 G. Each uterus was weighed and corpora lutea, implantation sites and resorptions were counted. The number of fetuses per litter were counted and their location within the uterus recorded. All fetuses were weighed, sexed and examined for external and skeletal alterations. One half of the fetuses from each litter were examined for visceral alterations. No treatment-related deaths were noted at any concentration tested. Treatment-related effects on maternal body weight and feed consumption were noted at all exposure levels. The decreases in maternal body weight at 99 and 304 ppm were minimal and transient since they returned to control values by the next weighing period. When exposure was discontinued, body weight gain and feed consumption in all exposure groups returned to control values. There were no treatment-related changes in the number of litters produced or in the mean number per litter of corpora lutea, implantations, resorptions, live or dead fetuses, or sex ratio. Fetal body weights were similar between the control and treated groups. There were no treatment-related increases in the type or incidence of external, visceral, or skeletal malformations, developmental variations, or variations indicative of retarded development. Exposure to methyl methacrylate concentrations up to 2,028 ppm resulted in no embryo or fetal toxicity or malformations even at exposure levels that resulted in maternal toxicity.

[Local preventive antibiotic treatment in intramedullary nailing with gentamycin impregnated biomaterials]

The benefit of antibiotics applied intravenously to avoid postoperative infection after intramedullary nailing has not yet been proven. Local antibiotic-releasing systems might be more effective because of the high concentration available in the compartments of interest. We report on the pharmacokinetic results of ten patients with intramedullary nailing of the tibia, respectively 15 patients undergoing the same procedure at the femur, in whom we used gentamicin-impregnated biomaterials for perioperative prophylaxis. The elution of gentamicin from a collagen sponge was complete and pharmacokinetic data suggest this drug releasing system is superior to PMMA beads in respect of the studied indication.

[Treatment of infected intramedullary osteosynthesis. A comparison of various therapeutic procedures]

A retrospective study was undertaken of the results of three different treatment regimens in 24 patients with postoperative infection subsequent to intramedullary nailing treated in our hospital between 1980 and 1989. In all cases, the nail was first removed. There- after, 9 patients were treated with continuous sump drainage (A), 9 patients received gentamicin PMMA chains and secondary cancellous bone grafts (B), and 6 patients were treated with local myoplasty (C). The results of a follow-up examination performed 27 months after the end of treatment showed 5 patients in group A with signs of residual infection. In groups B and C, no patient had clinical or radiological signs of residual infection at follow-up. These results confirm the positive effects of local antibiotic treatment and local myoplasty in posttraumatic bone infection.

Interaction of serum components with poly(methylmethacrylate) nanoparticles and the resulting body distribution after intravenous injection in rats

Radiolabelled poly(methylmethacrylate) (PMMA) nanoparticles were coated with rat serum albumin (RSA), serum and inactivated serum, to examine the influence of these blood components on the body distribution of a model colloidal drug carrier. The particles were incubated overnight at 37 degrees C either in a 1% solution of RSA in phosphate buffered saline (PBS) or in serum obtained from the rats. A suspension of nanoparticles in PBS was used as a control. Serum complement inactivation was achieved by storage at 56 degrees C for 30 min. The suspensions were then injected intravenously via the tail vein of Wistar rats. The animals were sacrificed at five different time points (30 min, 2 h, 6 h, 24 h, and 7 d after injection) and two samples of each organ and two blood samples were weighed into scintillation vials. The radioactivity of each sample was then measured in a Beckman scintillation counter. Coating with RSA led to no significant change in the body distribution of the particles, whereas incubation in serum, especially with complement inactivation prior to injection, very significantly reduced the uptake of particles into the organs of the reticuloendothelial system (RES), e.g., liver, spleen, and bone marrow. At the same time, much higher concentrations of nanoparticles were observed in the serum and in non-RES organs and peripheral tissues (kidneys, muscles, and intestine). This effect was most pronounced after 30 min, but was still observable after 7 d.

[Treatment of chronic osteitis of the tibia]

Since the beginning of May 1990, we have been using the original Ilisarov apparatus in our treatment of osteomyelitis. It has been used both statically and dynamically after corticotomy for segment transport and lengthening. So far we have treated 24 patients, of whom 13 had defect osteomyelitis, 9 had unstable infections and 2 had stable osteomyelitis with deformities. On average the bone defects measured 7.6 cm, and nine patients had soft tissue defects larger than 6 cm2. The Ilisarov apparatus performed a holding function in seven cases after defect grafting using autogeneic spongiosa. It was used in four cases for gradual compression, in seven cases for segment or fragment transport, in three cases for secondary lengthening and in three cases for correction. In all cases the infections were eliminated and stability was obtained. The duration of segment transport corresponded to the defect size, with a daily lengthening of approximately 1 mm. The fixation times ranged from 112 to 483 days (mean: 240 days). Apart from one special situation, no bone regeneration problems were observed. Some of the complications we encountered must be regarded as beginners' mistakes. We observed problems with segment transport (early corticotomy healing, deformity, non-union at the docking site) and problems with equipment, which has now been improved. For closure of the soft tissue defects it was sufficient to use mesh grafting. Its versatility and advantages as a stabilizing apparatus have made the Ilisarov fixator the instrument of our choice, especially in the treatment of circular infected defects larger than 3 cm.

[Treatment of chronic osteitis of the femur]

Since May 1990, we have treated seven patients with chronic osteomyelitis of the femur. The Ilisarov apparatus was used in three of these cases for fixation and in four cases for segment transport. The treatment of four patients is now complete. We have not found any problems in bone regeneration. The use of pins in the proximal and middle thirds of the femur has proved problematic due to the soft tissue damage. Instead of this, we recommend using Schanz screws, which can be fixed to the arch with the AO lock. Moreover, it is easier to shorten the 180 degrees arch to 90 degrees or 120 degrees using the Schanz screws. To prevent problems, it is better to assemble the apparatus before use and to take into consideration the anatomical and functional situation.

[Technical recommendation for connecting osteosynthesis]

In patients with pathological fractures an operative stabilisation is indicated without delay although 40 to 50% of the patients survive only three to four months. Generally palliative operations are practiced. Mostly a connecting osteosynthesis is carried out in which after resection of the tumorous bone the stability can be achieved by the application of plates and filling of the bone defect with cement. In three examplary cases a technical improvement of the impaction of bone cement is described. Using an exactly cutted packing ring of a single use syringe after the application of the plate the bone cement can be filled in easily. By the casting a penetration of the bone cement into the soft tissues can be avoided. An additional effect is that pins of cement extend into the bone narrow with a sufficient support of the filling on the cortical bone. After the removal of the casting the screws can be inserted in the overbridged defect while the polymerisation has nearly finished.

Human growth hormone in polymethyl methacrylate. A controlled study of 15 hip arthroplasties

Growth hormone-loaded polymethyl methacrylate (PMMA) was used in 15 hip replacements. The levels of growth hormone and insulin growth factor-I from the hip and the blood were measured before, and after, implanting PMMA containing 20 mg of growth hormone. Low levels of growth hormone and insulin growth factor-I were found in the femur initially, but very high local levels were found after implanting the growth hormone-loaded PMMA. These results were compared with the low levels found in 15 patients in a control group undergoing cemented or cementless hip replacement without added growth hormone. The local levels of growth hormone and insulin growth factor-I declined rapidly during the first 72 hours and were near normal at the end of this time. Systemic levels of growth hormone and insulin growth factor-I were not affected by the implantation of growth hormone-loaded PMMA. No complications or adverse reactions were noted. However, randomized studies with long-term follow-up are mandatory before the use of growth hormone-loaded PMMA is justified.

Acetabular cement temperature in arthroplasty. Effect of water cooling in 19 cases

In 19 patients who underwent total hip arthroplasty the temperature was studied at the bone-cement interface in the acetabulum during the polymethyl methacrylate curing process. To evaluate the effect of fluid cooling, the patients were randomized into two groups: one group with no irrigation, the other with continuous irrigation with Ringer solution during cement curing. The temperature was recorded with a thermocouple at the bone-cement interface. Without water cooling, the median maximum temperature was 49 (41-67) degrees C. In 9 out of 11 patients the temperature elevations were sufficient to cause impaired bone regeneration or thermal necrosis of bone. Continuous water irrigation reduced the amount of heat at the bone-cement interface; median maximum temperature was 41 (37-48) degrees C.

Experimental hydroxyapatite cement cranioplasty

Hydroxyapatite cement is a calcium phosphate-based material that when mixed with water forms a dense paste that sets within 15 minutes and isothermically converts in vivo to a microporous hydroxyapatite implant. This cement was used to reconstruct bilateral 2.5-cm-diameter full-thickness critical-sized parietal skull defects in six cats. One side was reconstructed with 100 percent hydroxyapatite cement, and the other with a mixture of 50 percent hydroxyapatite cement and 50 percent ground autogenous bone by weight. These animals were sacrificed at 6 and 12 months after implantation. Positive and negative controls also were prepared. The anatomic contour of the soft tissue overlying all hydroxyapatite cement implants was well maintained, there were no wound infections or structural failures, and the implants were well tolerated histologically. None of the negative (unreconstructed) control defects was completely filled with repair bone, and all positive (methyl methacrylate) controls demonstrated foreign-body giant-cell formation and fibrous encapsulation of the implants. Examination of decalcified and undecalcified sections revealed progressive but variable replacement of the cement by new bone and soft tissue without a change in the shape or volume of the hydroxyapatite cement-reconstructed areas. New bone comprised 77.3 and 64.7 percent of the tissue replacing the hydroxyapatite cement and hydroxyapatite cement-bone implants, respectively. Replacement of the hydroxyapatite cement implants by new bone is postulated to occur by a combination of osteoconduction and implant resorption. These results indicate that further experimental research leading to the possible application of hydroxyapatite cement for full-thickness calvarial defect reconstruction in humans is warranted.

Implantation of antibiotic-releasing carriers and in situ reconstruction for treatment of mycotic aneurysm

Four patients with mycotic aneurysm of the extracranial carotid artery, the innominate artery, the ascending aorta, and the infrarenal aorta were treated with local implantation of antibiotic-releasing carriers after resection of the aneurysm, excision of all infected tissue, and in situ reconstruction by prosthetic graft replacement in two patients and patch plasty in two patients. The patient with a mycotic aneurysm of the ascending aorta was operated on again 1 month after the first operation because of a second mycotic aneurysm located on the aortic arch. No early or late signs of recurrent infection were seen on clinical and laboratory postoperative follow-up done between 9 and 16 months or on duplex scan or computed tomography done at these times. Implantation of antibiotic-releasing carriers after débridement of all infected tissue and in situ reconstruction for treatment of mycotic aneurysm was performed successfully in four patients with this life-threatening condition.

Cranioplasty using gentamicin-loaded acrylic cement: a test of neurotoxicity

Cranioplasty represents a formidable challenge for neuro-surgeons, with a significant morbidity from both early and late wound infections. Polymethylmethacrylate (PMMA) is one of the most widely used materials in this setting. Despite the advantages of this material, such as ease of handling and inert biochemical properties, it is still a foreign body that is prone to infection. We present an animal model using a gentamicin-impregnated PMMA patch to assess the neurotoxicity as well as the efficacy of using this as an alternative material to lessen the infectious morbidity in this clinical setting. In part two of our experiment, we used a PMMA patch of similar weight and surface area in a physiological saline solution to determine the rate of gentamicin elution from the patch. The results obtained appear promising with no evidence of neurotoxicity and warrant further study to assess the clinical efficacy of PMMA in this setting.

Tobramycin-impregnated cement in total hip replacements

The clinical effect of adding 1.2 g of tobramycin powder to each 40-g pack of powdered polymethylmethacrylate used in hip replacement surgery was investigated. Fifteen patients underwent total hip replacement in which a cemented femoral prosthesis and a cementless acetabular prosthesis were used. Postoperatively, the tobramycin levels in the blood and in the wound drainage fluid were measured. The serum tobramycin concentrations were low, whereas the wound drainage fluid contained highly effective antibacterial concentrations. There was no evidence of reaction or toxicity to the antibiotic-impregnated bone cement.

Ciprofloxacin-impregnated poly-L-lactic acid drug carrier. New aspects of a resorbable drug delivery system in local antimicrobial treatment of bone infections

Resorbable poly-L-lactic acid (PLLA) cylinders (3.5 mm diameter, 5 mm in length) carrying 6% of weight ciprofloxacin (Ciprobay, Bayer AG, Leverkusen, FRG) were investigated in vitro to explore their properties as a slow-release antibiotic deposit. Forty bioactive cylinders stored in test tubes were covered with phosphate buffer (pH 7.4 at 37 degrees C) and 40 with fresh human blood plasma and tested under various conditions. For comparison a gentamicin-polymethylmethacrylate (PMMA) chain (Septopal, E. Merck, Darmstadt, FRG) was exposed to similar test conditions. The quantities of ciprofloxacin and gentamicin released were analysed by a microbiological method (bioassay). The concentrations of ciprofloxacin released were analysed by a microbiological method (bioassay). The concentrations of ciprofloxacin released from 40 cylinder were initially very high (up to 180 mg/l) but they decreased rapidly within the first 5 days (4.2-22.5 mg/l). Early release of gentamicin reached up to 227.5 mg/l but dropped to of 22 mg/l on the 14th day. Complete degradation of the PLLA-cylinders was not seen in the observed period of 92 days. The mean loss of mass was 8.4%. The recovery of incorporated ciprofloxacin was 6.5% on average.

[Genotoxic effect of acrylates]

Study of mutagenic activity of butylacrylate and methyl methacrylate on bone marrow cells of rat was carried out. Mutagenic activity of both of them was noted, but the butylacrylate was more active.

[Experimental study of surgical cement reinforced with wire mesh]

We have used wire mesh in association with PMMA cement in six patients to reinforce a deficient medial acetabular wall. None of these cups show signs of loosening. We therefore investigated experimentally the mechanical characteristics of HDP cups embedded in cement reinforced with wire mesh. The mesh appears to increase the resistance of the cement to tensile stress and associated loading forces at the bone/cement interface by the "stiffening" affect of the metal framework.

Local gentamicin application for perineal wound healing following abdominoperineal rectum excision

A major complication of abdominoperineal rectum excision for rectal or anal carcinoma is local wound infection. The main reason for this infection is that systemically administered antibiotic prophylaxis does not reach sufficiently high concentrations of antibiotic in the tissue of the sacroperineal wound. Since gentamicin-polymethylmethacrylate (PMMA) in the form of chains of beads has been confirmed as a useful tool in the treatment of local infection in bone and soft tissue surgery, we have evaluated its effect on the abdominoperineal rectum excision in a prospective, randomized trial. Forty-four patients with rectal or anal carcinoma entered the study. Only patients with stage Dukes D were excluded from the trial. Following randomized selection, the patients were treated either with local gentamicin and drainage (Group A) or drainage alone (Group B), using the Lloyd-Davies procedure. The two groups were comparable regarding age, sex, tumor stage and level, and risk factors predisposing for an infectious complication (anemia, nutritional status, blood transfusion). The postoperative mortality rate was 0% in both series. Analysis of local perineal wound healing revealed a statistically significant higher percentage of primary wound healing in Group A than in Group B (87% versus 46%; p less than 0.01). This led to a significantly shorter hospitalization period for patients in Group A (p less than 0.01). Gentamicin-PMMA chains have been demonstrated to exert a favorable effect on local wound healing and the postoperative outcome of patients with abdominoperineal rectum excision.

High antibody titres in mice with polymethylmethacrylate nanoparticles as adjuvant for HIV vaccines

The aim of the present study was to determine the effect of polymethylmethacrylate (PMMA) nanoparticles as adjuvants for an HIV-2 whole-virus vaccine in mice. The data clearly revealed that PMMA nanoparticles induced 10-100-fold higher antibody titres than aluminium hydroxide or an aqueous vaccine control preparation as measured by enzyme-linked immunosorbent assay. Moreover, the high antibody titres obtained with PMMA as adjuvant appeared to be stable for between 10 and 20 weeks after immunization. In contrast, the titres of the control preparations, fluid or aluminium hydroxide formulations, decreased after 10 weeks.

Antibiotic-impregnated beads. Part II: Factors in antibiotic selection

Part I of this series discussed the advantages of implanted antibiotic-impregnated polymethylmethacrylate beads over systemic therapy for managing chronic osteomyelitis and acute musculoskeletal infections. Numerous antibiotics are available for use in polymethylmethacrylate. However, specific characteristics should be considered prior to therapeutic selection: the antibiotic should be water-soluble, bactericidal, nontoxic to tissues, and readily available in powder form. In this concluding segment, the organisms most commonly cultured from orthopaedic infections and appropriate combinations of antibiotics and bone cements are outlined.

Antibiotic-impregnated beads. Part I: Bead implantation versus systemic therapy

Parenteral antibiotic therapy for acute bone infections, soft-tissue infections, and osteomyelitis may result in high serum concentrations associated with nephrotoxic, ototoxic, and allergic complications. Conversely, the local release of antibiotics into the wound with the use of antibiotic-impregnated cement or antibiotic-impregnated polymethylmethacrylate beads has been found effective and does not induce negative effects or result in systemic concentrations of clinical significance. The antibiotic-impregnated cement beads are fabricated on a surgical steel wire, and they have bimodal elution properties. They provide local antibiotic concentrations that surpass the minimum inhibitory concentrations for pathogens commonly isolated in orthopaedic infections. Their use effectively controls chronic osteomyelitis and acute musculoskeletal infections. Compared with systemic antibiotic therapy, the incidence of nephrotoxic, ototoxic, and hypersensitivity reactions is significantly diminished. The beads release 5% of the antibiotic within the first 24 hours. The sustained elution then progressively diminishes to undetectable levels within a few weeks or months.