Canine Total Hip Arthroplasty Research Articles

In vivo evaluation of temperature-responsive antimicrobial-loaded PNIPAAm hydrogels for prevention of surgical site infection.

Surgical site infections (SSIs) are a persistent clinical challenge. Local antimicrobial delivery may reduce the risk of SSI by increasing drug concentrations and distribution in vulnerable surgical sites compared to what is achieved using systemic antimicrobial prophylaxis alone. In this work, we describe a comprehensive in vivo evaluation of the safety and efficacy of poly(N-isopropylacrylamide-co-dimethylbutyrolactone acrylamide-co-Jeffamine M-1000 acrylamide) [PNDJ], an injectable temperature-responsive hydrogel carrier for antimicrobial delivery in surgical sites. Biodistribution data indicate that PNDJ is primarily cleared via the liver and kidneys following drug delivery. Antimicrobial-loaded PNDJ was generally well-tolerated locally and systemically when applied in bone, muscle, articulating joints, and intraperitoneal space, although mild renal toxicity consistent with the released antimicrobials was identified at high doses in rats. Dosing of PNDJ at bone-implant interfaces did not affect normal tissue healing and function of orthopedic implants in a transcortical plug model in rabbits and in canine total hip arthroplasty. Finally, PNDJ was effective at preventing recurrence of implant-associated MSSA and MRSA osteomyelitis in rabbits, showing a trend toward outperforming commercially available antimicrobial-loaded bone cement and systemic antimicrobial administration. These studies indicate that antimicrobial-loaded PNDJ hydrogels are well-tolerated and could reduce incidence of SSI in a variety of surgical procedures.

Evaluation of the Femoral Stem Implant in Canine Total Hip Arthroplasty: A Cadaver Study

Evaluation of the Femoral Stem Implant in Canine Total Hip Arthroplasty: A Cadaver Study

In vitro and in vivo investigations of a-C/a-C:Ti nanomultilayer coated Ti6Al4V alloy as artificial femoral head

Hydrogen-free a-C/a-C:Ti nanomultilayer (a-C NM) films were deposited on medical Ti6Al4V by the magnetron sputtering technique under bias-graded voltage. Cell tests and implantations were performed for the a-C NM films coated Ti6Al4V with the uncoated Ti6Al4V as the control. The canine total hip arthroplasty (THA) surgeries were conducted for 12 dogs using the coated femoral heads, with the CoCr heads as the control. Results of cell tests showed that the coated Ti6Al4V had no cytotoxicity, and there was no statistical difference of the cell attachment rates between the coated and uncoated sample (P = 0.091). No significant difference of the tissue response around the coated and uncoated implants were observed after the intramuscular (P = 0.679) and intraosseous implantations (P = 0.122). After two years of successful canine THA, the polyethylene wear particles isolated from periprosthetic soft tissue showed similar sizes, shapes and counts in the two groups (all of the P values >0.05). The retrieved femoral heads showed slightly change of the surface roughness, but no statistical differences between groups (P = 0.696). However, the systemic metal ion analysis indicated that the content of Co and Cr ions released in the coated group (Co: 0.71 ± 0.06 μg/L, Cr: 0.52 ± 0.05 μg/L) were significant lower than that in the control (Co: 1.98 ± 0.16 μg/L, Cr: 1.17 ± 0.19 μg/L) (both P < 0.005). Histological analysis of the periprosthetic tissue in CoCr group showed a severer histiocyte response than that in the coated group (P = 0.029). The head-taper interfaces showed galvanic corrosion attack in the CoCr group, but not in the coated Ti6Al4V group. Therefore, the a-C NM films coated Ti6Al4V exhibited good biocompatibility as an implant material. Compared with the CoCr, the coated Ti6Al4V femoral head could provide comparable in vivo wear properties, release less harmful metal ions and reduce the inflammatory response in periprosthetic tissue, which may help to prolong the longevity of prostheses.

In vitro and in vivo evaluations of the fully porous Ti6Al4V acetabular cups fabricated by a sintering technique.

A type of canine fully porous Ti6Al4V acetabular cup was fabricated by a well-controlled powder sintering technique. The traditional hydroxyapatite-coated (HA-coated) cups were also prepared as the control. The characteristics, mechanical and biological properties of the two types of cups were evaluated by scanning electron microscopy, mechanical tests, finite element analysis and canine total hip arthroplasty (THA). Results showed that the porous cup had high porosity and large pore size with good mechanical properties without obvious stress shielding, and it had sufficient safety for implantation according to the finite element analysis. Both groups showed good biocompatibility and osteogenic ability after the THA surgeries, but the porous group had more bone ingrowth and higher bone–implant contact rate according to the micro-CT and histopathologic results. Therefore, the canine fully porous Ti6Al4V acetabular cup fabricated by the sintering technique could provide sufficient space and adequate mechanical support without obvious stress shielding effect for bone ingrowth. Compared with the traditional HA-coated cup, the porous cup may be more effective in achieving in vivo stability, which could contribute to reducing the risk of aseptic loosening.

Severe Polyethylene Wear Requiring Revision Total Hip Arthroplasty in Three Dogs.

To describe the occurrence of severe polyethylene wear of the acetabular component in 3 dogs that ultimately led to implant failure, and to report the outcome of revision of total hip arthroplasty (THA) in these cases. Case report Dogs (n=3). Three dogs with hip dysplasia underwent routine THA before 2 years of age. All dogs became acutely lame 4-5 years after THA. Radiographs revealed acetabular cup wear in all cases, shell fragmentation in 2 cases, and additional stem failure in 1 case. All dogs underwent successful revision surgery, during which severe polyethylene wear and metallosis was observed. Revision surgery provided an excellent clinical outcome in all dogs from 10 months to 4 years post revision. Polyethylene wear and implant failure may be a significant long-term complication of THA not previously recognized, which may be especially true when placed at an early age in a large breed, active dog, or in a dog with significant morbidity associated with other limbs. A successful revision was achieved in all 3 dogs. Additional investigation is warranted to document the risk factors associated with severe polyethylene wear in canine THA.

Risk factors for loosening of cementless threaded femoral implants in canine total hip arthroplasty

To determine the incidence and potential risk factors of femoral implant loosening in the canine Helica® total hip replacement (THR) system. Sixteen dogs with a Helica THR were included. Medical records were reviewed for signalment and size of implants. Stem angle, stem collar to lateral cortex distance, tip to cortex distance, stem collar to lateral cortex distance at a stem angle of 150°, lever arm distance, and the distance on the diaphysis measurements were calculated from the one year postoperative radiographs. Three ratios were determined from these measurements to take into account the size of the femur in relation to the size of the implant. Femoral implant loosening was identified by radiographic and clinical signs, and confirmed at the time of surgical explantation. Differences in the successful and femoral stem failure groups were compared using either a students t-test or a Mann Whitney test. Significance was set at p <0.003. Six of the 16 dogs had loosening of the femoral prostheses within one year post-implantation. One dog had evidence of a septic cause for loosening. No significant risk factors could be identified in this group of dogs with Helica stem loosening. Helica femoral stem loosening was a common complication within one year post-implantation in this group of dogs. No risk factors were identified to potentially decrease the incidence of loosening. Therefore, due to this unacceptably high complication rate, the authors do not recommend this model of the Helica THR.

Effects of Simvastatin on Osseointegration in a Canine Total Hip Arthroplasty Model: An Experimental Study

Simvastatin was recently demonstrated to stimulate bone morphogenetic protein–2 expression, leading to bone formation. The present study was designed to evaluate whether simvastatin administered by injection could promote osseointegration in a canine total hip arthroplasty model. Fifteen dogs were divided into 3 groups of 5 dogs each: group 1 (high-dosage simvastatin, 6.0 mg/[kg d]), group 2 (low-dosage simvastatin, 3.0 mg/[kg d]), and a control group (isotonic saline, 3.0 mg/[kg d]). Osseointegration was assessed by using the push-out test, scanning electron microscopy, energy-dispersive spectrometer microanalysis, and histomorphometric examination. The results showed higher mechanical strength, greater area of bone covering the femoral component, and higher bone-implant contact in group 1 than in the other 2 groups. Our findings indicate that simvastatin administered by injection could contribute significantly to osseointegration in a canine total hip arthroplasty model.

Influence of Canal Preparation Depth on the Incidence of Femoral Medullary Infarction with Zurich Cementless Canine Total Hip Arthroplasty

To determine the incidence of femoral medullary infarction after modifying the depth of femoral reaming and filing when performing total hip replacement (THR) using the Zurich Cementless Total Hip Replacement system (ZCTHR). Case series. Dogs (n=31) that had ZCTHR (34). Thirty-one dogs (34 THR) had ZCTHR (May 2003-September 2006) and with >1 year radiographic (craniocaudal, mediolateral views) follow-up after THR were evaluated for the presence of femoral medullary infarcts. Incidence was compared with a previous study performed before the technique modification. Femoral medullary infarction occurred in 1 femur (2.9%; dog <18 months at THR) compared with 19.5% before the technique change, a significant decrease (P<.001). Limiting the depth of reaming and filing of the medullary canal resulted in a significant decrease in the incidence of femoral medullary infarction. Depth of reaming and filing the medullary canal should be limited when performing THR using the ZCTHR.

Femoral Medullary Infarction Prevalence with the Zurich Cementless Canine Total Hip Arthroplasty

To document the prevalence of femoral medullary infarction associated with the Zurich Cementless Total Hip Replacement (ZCTHR) system in dogs. Case series. Dogs (n=35) with 41 ZCTHR implants. Medical records (February 1999-December 2002) were reviewed for dogs that had ZCTHR and at least 1 year follow-up with radiographic evaluation. Thirty-five dogs (41 ZCTHR) met the inclusion criteria. Femoral morphologic data, implant to bone relationships, and medullary infarcts were recorded. Data were analyzed for associations between infarct occurrence and morphologic details and dog characteristics. Eight of 41 femurs had radiographic evidence of infarcts (19.5%). Dogs with infarcts were significantly younger (mean [+/-SD] age, 18.5+/-5.2 months) compared with those without infarction (mean age, 44.4+/-5.6 months; P=.027). None of the other variables were significantly different between dogs with and without infarcts. Three femurs with infarcts ultimately developed stem loosening. A higher prevalence of femoral medullary infarcts was identified with ZCTHR compared with incidence reported for other total hip systems. Younger dogs were more likely to develop infarction. Femoral infarction appears to be associated with stem loosening. Adjustments in surgical technique or delaying surgery beyond 18 months of age may reduce incidence of infarction but needs further evaluation.

Long-Term Follow-Up Study of Bioactive Bone Cement in Canine Total Hip Arthroplasty

We report a long-term study of bioactive bone cement (BABC) in a canine total hip arthroplasty (THA) at follow-up of 8 years. Previous studies have shown excellent biomechanical and histological results at follow-up of 6, 12, and 24 months. In the present study, THA was performed in a beagle dog using BABC consisting of an apatite- and wollastonite-containing glass ceramic (AW-GC) powder and SiO2 powder as the filler and a bisphenol-a-glycidyl methacrylate (Bis-GMA) based resin as the organic matrix. Histological examination showed direct bonding between BABC and bone without any intervening soft tissue layer at the BABC-bone interface. A reactive layer, through which BABC bonded to the bone, was observed thicker at 8 years than it was at 24 weeks. No adverse effects of BABC were observed. BABC maintained the high bioactivity and direct bonding to bone in a canine THA at follow-up of 8 years.

Effect of Oral Alendronate on Net Bone Ingrowth Into Canine Cementless Total Hips

Alendronate has been shown to prevent osteolysis in a canine total hip arthroplasty (THA) model. However, the effect of alendronate on bone ingrowth and remodeling around canine cementless hip replacement components remains unclear. We hypothesized that oral alendronate would increase net bone ingrowth into the porous surface of THA components when intimate bone/implant contact exists. To test this hypothesis, six mature dogs received unilateral cementless THA and were treated with five milligrams of oral alendronate daily from day seven to day eighty-four postoperatively. Six comparable dogs served as controls. Quantitative analysis of net bone ingrowth into the porous surface did not show a significant difference between the two groups, (control 7.9 ± 1.5, alendronate 7.5 ± 1.4, P < 0.6). These results did not support the hypothesis that oral alendronate would increase net new bone formation into the porous surface of THA components.

Osteoblast proliferation and maturation by bisphosphonates

Aseptic loosening and osteolysis are currently the most common causes of failure of total joint replacements. Osteolysis is initiated by a macrophage response to wear debris, resulting in localized, osteoclastic peri-implant bone loss. We have previously inhibited osteoclast-mediated bone resorption in a canine total hip arthroplasty model using oral bisphosphonate therapy. Based on serendipitous observations from our canine study, we hypothesized that bisphosphonates have an anabolic effect on osteoblasts, in a manner distinct from their inhibitory effect on osteoclastic bone resorption. We studied the anabolic effects of two FDA-approved bisphosphonates (alendronate and risedronate) on two in vitro models: a primary human trabecular bone cell culture and the MG-63 osteoblast-like cell line. Following treatment with bisphosphonates at varying concentrations and time periods, cells were assayed for proliferation effects and results were quantified using the methods of direct cell count, and the colorimetric MTT (3-dimethylthiazol-2,5-diphenyltetrazolium bromide) assay at 24, 48, and 72 h. The effect of bisphosphonates on the maturation of osteoblasts were tested with alkaline phosphatase bioassay and reverse transcription-polymerase chain reaction for markers of osteoblast differentiation. Results from both the primary human trabecular bone cell culture and the MG-63 osteoblast-like cell line showed that both bisphosphonates significantly increased the cell number over controls, attaining peak levels at a concentration of 10 −8 m. Alkaline phosphatase activity was also increased, representing earlier commitment of osteoprogenitor cells towards the osteoblastic phenotype. Bisphosphonates also enhanced gene expression of BMP-2, Type I collagen and osteocalcin. In summary, bisphosphonates, aside from their role as inhibitors of osteoclastic bone resorption, are promoters of osteoblast proliferation and maturation.

Radiographic evaluation of mechanically tested cemented total hip arthroplasty femoral components retrieved post-mortem

SummaryGuidelines for assessing total hip arthroplasty (THA) radiographs for femoral implant stability have not been published; therefore, often the determination is subjective. The aim of this study was to identify radiographic criteria for veterinary clinicians to use when evaluating radiographs for femoral implant stability. Specific objectives were to: identify radiographic features associated with canine THA femoral implant loosening, evaluate whether technical recommendations for human femoral component implantation apply to dogs, and evaluate the effectiveness of radiographs for identifying canine THA implant loosening. Post-operative, follow-up, and post-mortem contact radiographs of canine implanted femora retrieved postmortem and mechanically tested for implant stability were evaluated. Based on the results, radiographic evaluation is not an effective means of assessing canine femoral implant stability; however, certain radiographic findings including implant retroversion, cement mantle cracks, or the appearance of cementmetal interface radiolucencies, may be indicative of implant loosening. It was also found that femoral implants completely surrounded by cement mantle of any thickness were less likely to loosen than those with an area lacking cement between the implant and bone. There was also a trend suggesting an association between inferior cement mantle quality and femoral implant loosening. In order to improve cement mantle quality and ensure that implants are completely surrounded by cement mantle, the use of modern cementing techniques is recommended.

Effects of calcium ion implantation on osseointegration of surface-blasted titanium alloy femoral implants in a canine total hip arthroplasty model

Osteoconductivity of titanium-alloy implants may be improved when surface-modified by calcium ion (Ca 2+) implantation. We studied the effects of Ca 2+ implantation on osseointegration of a grit-blasted titanium-alloy stem using a canine total hip arthroplasty model. Fifteen dogs underwent bilateral hip arthroplasties and were sacrificed at 1, 6, and 12 months postoperatively. The hip components were evaluated by radiographic, qualitative, and quantitative histology methods. Radiographically and histologically, both Ca 2+-implanted and non—Ca 2+-implanted stems were well integrated. Ca 2+-implanted stems had greater new bone apposition than non—Ca 2+-implanted stems, although the difference was significant only at 1 month (15.8% ± 3.5% of the implant perimeter for non—Ca 2+-implanted, 25.4% ± 4.7% for Ca 2+-implanted, P<.05). This result could be related to chronological decrease of the dissolution rate of calcium ions from Ca 2+-implanted surface. Although further improvement of the Ca 2+ implantation technique for a sustained osteoconductive effect is necessary, Ca 2+ implantation may be beneficial for early fixation of titanium-alloy implants.

The effect of different cement insertion techniques on the bone–cement interface

Since the introduction of cemented total hip arthroplasty, the method of cement usage has evolved through several generations. These changes may have been responsible for an improvement in femoral component longevity. The nature of the bone–cement interface in first-generation cementing techniques has been described, but the bone–cement interface in more recent cementing techniques has not. This article describes the bone–cement interface after 2 different cementing techniques in a canine total hip arthroplasty model. Copyright 2002, Elsevier Science (USA). All rights reserved.

Cementless acetabular fixation in total hip arthroplasty using polyglycolide-lactide screws: An in vivo canine study

Bone ingrowth into cementless acetabular components was evaluated in a canine total hip arthroplasty model, comparing components initially stabilized with polyglycolide-lactide screws with those initially stabilized with titanium screws. The acetabular shell was anchored with 2 polyglycolide-lactide screws in 16 dogs and with 2 titanium screws in 12 dogs. The dogs were followed and sacrificed at 7 weeks, 14 weeks, 10 months, or 15 months. Histomorphometric analysis of bone ingrowth into the weight-bearing dome of the acetabular shell was conducted. No difference was detected in mean bone ingrowth into the acetabular shell comparing the 2 screw groups. The results of this study do not support a significant advantage to the use of biodegradable screws for the initial stabilization of cementless acetabular components in canine total hip arthroplasty.

Femoral medullary infarction secondary to canine total hip arthroplasty.

To evaluate the prevalence of femoral intramedullary infarction after total hip arthroplasty (THA) and to determine whether any specific femoral morphology predisposes to bone infarction. Retrospective clinical study. All dogs from our hospital population undergoing THA between 1984 and 1997 with radiographic follow-up available at 1 year or more postoperatively. A case control study was conducted within the THA group to determine risk factors predisposing to femoral infarction after THA. Medical records and radiographs were reviewed. Data were collected on clinical parameters, femoral morphology, prosthesis, and bone changes. Radiographic diagnosis was confirmed using histopathology in 11 femora. Radiographs of 50 age-matched control dogs weighing more than 20 kg with coxofemoral degenerative joint disease were randomly chosen to determine the prevalence of bone infarction in nonoperated dogs. Ninety-one dogs with 110 THA were included in the study. Fifteen of the 110 femora with THA had radiographic evidence of infarction (14%). Infarction was not present in any femora in the control group. There was no significant difference in the prevalence of infarction between dogs that received cemented or uncemented prostheses. Clinical signs were not reported in any patient that developed femoral infarction. Young age (P = .03) and a distance between the greater trochanter and nutrient foramen greater than 79 mm (P = .008) predisposed dogs to femoral infarction. Over time, three infarcts decreased in size radiographically, five remained unchanged, and three expanded. An osteosarcoma developed at the site of a bone infarct in one dog. Femoral intramedullary infarction occurred in 15 of 110 THA. Young age at the time of THA and a greater distance between the greater trochanter and the nutrient foramen predisposed to infarction. Intramedullary infarction occurs after canine THA. These bone infarcts do not appear to cause clinical signs; however, they may present a diagnostic challenge. Malignant transformation could potentially result from medullary infarction.

Evaluation of bioactive bone cement in canine total hip arthroplasty.

Total hip arthroplasties (THAs) were performed in beagle dogs using a bioactive bone cement (BABC) consisting of a silane-treated apatite- and wollastonite-containing glass-ceramic (AW glass-ceramic) powder and a silica glass powder as the filling particles and a bisphenol-A-glycidyl dimethacrylate-based resin (Bis-GMA-based resin) as the organic matrix. The outcomes were compared with the results of polymethylmethacrylate (PMMA) bone cement. The mechanical properties of the BABC were stronger than those of PMMA bone cement. The bonding strength of the BABC to bone in the dogs' femora increased with time and reached 3.7 MPa at 24 months after implantation whereas that of PMMA bone cement was 2.0 MPa (p < 0.05). Histological examination showed direct bonding between the BABC and the femoral bone for up to 24 months after implantation. However, with PMMA bone cement an intervening soft-tissue layer consistently was observed at the bone-cement interface. Direct bonding at the interface between the BABC and the bone through a calcium phosphorous layer 30 microm-thick was revealed by scanning electron microscopy. Femoral bone resorption was observed at 24 months after implantation in the BABC group, but it was not observed in the PMMA bone cement group. Direct bonding between BABC and the bone may have accelerated femoral bone resorption. Cement fractures of the BABC were observed on the acetabular side 24 months after implantation. Weak bonding between the BABC and an acetabular component made of ultrahigh molecular weight polyethylene (UHMWPE), relatively high elastic characteristics of BABC, and weakness of the calcium phosphorous layer formed on the surface of this cement seemed to lead to failure at 24 months on the acetabular side.

Use of a polyglycolide lactide cement plug restrictor in total hip arthroplasty.

The use of a polyglycolide lactide cement plug restrictor in cemented femoral fixation during total hip arthroplasty was evaluated. Femoral cement pressurization was evaluated in vitro in a cadaveric model and the host response to polymer degradation was evaluated in vivo in a canine total hip arthroplasty model. Sixteen embalmed anatomic specimen femurs were prepared for cement femoral fixation. The intramedullary canal was plugged with either an ultrahigh molecular weight polyethylene cement plug restrictor or a polyglycolide lactide cement plug restrictor. Peak pressures in the proximal, mid, and distal portions of the cement mantle were recorded during cement insertion, cement pressurization, and implant insertion. There was no difference between the two plug groups in peak pressures throughout the cement mantle during cement insertion, pressurization, or implant insertion. Total hip arthroplasty using a cementless acetabular component and a cemented femoral stem was performed in 24 dogs. The femoral intramedullary canal was plugged with a polyethylene or a biodegradable cement plug restrictor. The dogs were sacrificed at 7 weeks, 10 months, or 15 months. Radiographically, no osteolytic lesions were seen around either plug type. Histomorphometrically, the polyglycolide lactide plugs appeared intact at 7 weeks and partially degraded by 10 and 15 months. In both plug groups, a mild fibrohistiocytic reaction with infiltration of fibrocytes, histocytes, and endothelial cells was seen. No osteolysis was observed. The results of the current study show that femoral cement pressurization can be attained in vitro using a biodegradable cement plug restrictor and that for as long as 15 months in the in vivo canine model there were no adverse reactions associated with use of these plugs compared with conventional ultrahigh molecular weight polyethylene plugs.

The wear of a polyethylene socket articulating with a zirconia ceramic femoral head in canine total hip arthroplasty

Wear of yttria-zirconia (zirconia) in the femoral head was investigated in mature mongrel dogs weighing 10 to 13 kg. Two dogs, which were used as a control group, were sacrificed 18 months after implantation of the uncemented modular hip system with an alumina ceramic (alumina) femoral head. A zirconia femoral head was implanted in five dogs: one was sacrificed 12 months after implantation, two at 18 months, and two at 24 months. In each femoral head and polyethylene (PE) socket, the surface was observed by means of scanning electron microscopy (SEM); the mean articulation surface roughness on the femoral head and PE socket and the thickness of the PE socket were measured. Wear was not seen on the surface of either the zirconia or the alumina heads. In both groups, minute white spots on the smooth surface of the PE socket were visible by SEM. In the alumina and zirconia groups the mean roughness was 0.1 microm. The mean thickness of the PE socket was reduced by 0.2 mm in the alumina group. In the zirconia group it was reduced by 0.2 to 0.3 mm. However, the mechanical strength of zirconia is known to be greater than that of alumina and it may be possible to reduce the diameter of the femoral head. The smaller zirconia head may contribute to the reduction of the wear of the PE socket in an uncemented modular total hip system.