Quantitative computer-assisted osteodensitometry in total hip arthroplasty

No Impact of Contact Between the Medial Collar of a Hydroxyapatite-Coated Triple-Tapered Stem and the Femoral Neck on Periprosthetic Bone Mineral Density

BACKGROUND

Hydroxyapatite-coated, triple-tapered, shorter-length stems with a medial collar have been reported with good results for a few years. We investigated whether contact between the medial collar and femoral neck affects clinical outcomes and changes in bone mineral density (BMD) in patients who have this type of stem in their total hip arthroplasty construct.

METHODS

This was a retrospective, single-center study involving 62 patients scheduled for unilateral total hip arthroplasty using a hydroxyapatite-coated, triple-tapered, shorter-length stem who were followed for at least 1 year postoperatively. All patients had a Dorr type B femoral canal shape. Contact between the medial collar and the femoral neck was evaluated by computed tomography at the third postoperative month, and patients were classified into 2 groups. Postoperative clinical outcomes were investigated by the Western Ontario and McMaster Universities Arthritis Index and the Japanese Orthopaedic Association scores; radiological evaluation included stem fixation, spot welds and cortical hypertrophy, postoperative 3-dimensional stem alignment, and periprosthetic BMD changes.

RESULTS

There were 51 patients in the Contact + group (collar and neck contact) and 11 in the Contact-group (no contact). There were no differences between the 2 groups in the improvement of Western Ontario and McMaster Universities Arthritis Index and Japanese Orthopaedic Association scores, stem fixation, occurrence of cortical hypertrophy, or 3-dimensional stem alignment. Radiolucent lines were present in zones 3, 4, and 5 in 6 patients (12%) in the Contact + group only, who had no statistical difference between the 2 groups. Bone mineral density (BMD) decreased most in zone 7 in both groups, with no difference between the 2 groups.

CONCLUSIONS

The presence or absence of contact between the medial collar and femoral neck did not affect postoperative BMD changes or radiological or clinical results.

LEVEL OF EVIDENCE

Therapeutic Level III.

Bone Quality Assessment Before Total Hip Arthroplasty: The Role of Densitometry

Background Total hip arthroplasty (THA) is effective in the treatment of hip osteoarthritis. Radiographic evaluation, standard in THA planning, is sufficient in examining hip anatomy, although it may not precisely assess bone quality. A routinely implemented method in bone quality assessment is densitometry. The technique allows for a measurement of bone mineral density (BMD). Methodology In the study, we included 26 participants who qualified for THA. All the patients were preoperatively examined with radiographs and densitometry of the affected hip. On the preoperative anteroposterior radiograph, we measured the canal-to-calcar isthmus ratio (CC ratio) and the cortical index (CI). Intraoperatively, during the THA procedure, we measured the thickness of the cortical bone and the diameter of the femoral neck in the line of neck resection. Results The examination with Pearson's correlation coefficient revealed that BMD significantly positively correlates with the intraoperatively measured diameter of the femoral neck (r = 0.5, P = 0.009), and with the measured thickness of the cortical bone (r = 0.47, P = 0.015), CI significantly positively correlates with the intraoperatively measured diameter of the femoral neck (r = 0.6, P = 0.001), and with the CC ratio (r = 0.44, P = 0.024), the intraoperatively measured diameter of the femoral neck significantly positively correlates with the intraoperatively measured thickness of the cortical bone (r = 0.59, P = 0.001). All of the other correlations were not statistically significant. Conclusions BMD measurements can be used in THA planning as they positively correlate with intraoperative measurements. The radiological parameters (CC ratio and CI) may not be as precise in bone quality assessment.

Bone remodeling and cortical thinning distal to the femoral stem: a retrospective review

INTRODUCTION

There is a paucity of information on the bone remodeling that occurs distal to the femoral stem following total hip arthroplasty as most previous studies have focused on proximal changes. In this study, we report the cortical thinning that occur distal to the femoral stem after primary total hip arthroplasty.

METHODS

A retrospective review was performed at one institution over a 5-year period. 156 primary total hip arthroplasty procedures were included. The Cortical Thickness Index (CTI) was measured on both operative and non-operative hips at 1 cm, 3 cm and 5 cm below the prosthetic stem tip on anteroposterior radiographic images pre-operatively as well as at 6 months, 12 months and 24 months post-operatively. The difference in average CTI was measured using paired t-tests.

RESULTS

There were statistically significant decreases in CTI distal to the femoral stem at 12 months and 24 months (-1.3% and -2.8%, respectively). Greater losses were seen in female patients, patients older than 75, and patients with BMI less than 35 at 6 months postoperative. There were no differences in CTI at any time point on the non-operative side.

CONCLUSION

The current study demonstrates that patients undergo bone loss as measured by CTI distal to the stem in the first 2 years following total hip arthroplasty. Comparison to the contralateral non-operative side confirms that this change is greater than expected for the natural aging process. A greater understanding of these changes will help optimize post-operative management and direct future innovations in implant design.

A semiautomated method to quantitatively assess osteolytic lesion volume and bone mineral density within acetabular regions of interest from CT

The objectives of this study were to (1) develop a semiautomated method to obtain lesion volume and bone mineral density (BMD) in terms of Hounsfield units from pelvic computed tomography (CT) scans in three regions of interest, and (2) assess accuracy and reliability of the method based on cadaveric CT scans. Image artefacts due to metal implants reduce CT clarity and are more severe with more than one implant in situ. Therefore, accuracy and reliability tests were performed with varying numbers of total hip arthroplasties implanted. To test the accuracy of lesion size measurements, microcomputed tomography was used as a reference. Mean absolute error ranged from 36 to 284 mm³ after five measurements. Intra- and inter-operator reliability of the entire method was measured for a selection of parameters. All coefficient of variation values were good to excellent for CT scans of the native pelvic anatomy and a CT scans of the same pelvis with one and two implants in situ. Accuracy of quantifying lesion volume decreased with decreasing CT image clarity by 0.6%-3.6% mean absolute relative error. Reliability of lesion volume measurement decreased with decreasing CT clarity. This was also the case for reliability of BMD measurements in the region most disrupted by metal artefact. The presented method proposes an approach for quantifying bone loss which has been proven to be accurate, reliable, and clinically applicable.

Preserved periprosthetic bone stock at 5 years post-operatively with uncemented short hip stem in both collared and collarless version

INTRODUCTION

Previous bone density studies have generally shown bone resorption around both cemented and uncemented total hip arthroplasty (THA) stems. This is presumed to be due to stress shielding. Short stems have been introduced partly to preserve bone in the proximal femur by a more physiological loading of the bone. The purpose of this study was to evaluate bone remodeling around a short, fully hydroxyapatite-coated titanium stem that comes in a collared and collarless version.

PATIENTS AND METHODS

A prospective cohort of 50 patients included in a study evaluating the Furlong Evolution stem has been followed for 5 years. Examination was done with dual energy X-ray absorptiometry (DXA) postoperatively, at 1, 2 and 5 years. Clinical outcome was followed with radiography and both general and hip specific outcome measures.

RESULTS

The two versions of the stem behaved similarly regarding bone remodeling. After an initial decrease up to 1 year, bone mineral density (BMD) increased in all Gruen zones up to 2 years and at 5 years bone stock was still preserved compared with postoperatively (net BMD + 1.2% (95% CI - 0.4 to 2.8)). Increase in BMD occurred mainly in the greater trochanter and distally around the stem with a decrease in the calcar area. Both versions showed excellent clinical outcome up to 5 years.

CONCLUSION

This short stem seems to preserve proximal bone stock up to 5 years, exhibiting similar behaviour both with and without a collar.

TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION

ClinicalTrials.gov, (identifier: NCT01894854). July 10, 2013.

Image-based analysis of trabecular bone in osteoporotic rabbits: correlation of morphological features and bone mineral density profile

OBJECTIVE

To analyse a set of morphological features from digital radiographs (RX) and bone mineral density (BMD) values estimated from quantitative computerized tomography scans (QCT scans) of the knee joint of an osteoporotic rabbits, and to determine the relationship and correlation of these variables to be considered as an alternative diagnosis method.

METHODS

The knee joint of rabbits (N = 9 ovariectomized and injected with of methylprednisolone sodium succinate (OVX + MPSS) and 3 sham operated healthy controls) were subjected to radiographic examination before the beginning of the study and after 6 weeks; after sacrifice, they were immediately scanned with a 64-channel CT. A set of morphological features was extracted from RX images and then subjected to Principal Component Analysis (PCA); BMD-values were calculated at different depths from the articular surface of the femur and the tibia. The selected morphological variables and the BMD values were correlated in order to determine useful information in medical diagnostics.

RESULTS

Ten morphological variables explained 80.39% of the total variability, but only some of them demonstrated significant differences between baseline and OVX + SSMP states and between OVX + SSMP and control. Spearman analysis showed higher positive and negative correlation of these parameters among them (r = 0.67, 0.81, 0.83 and 1); and a moderate correlation with the BMD values (r = 0.50, 0.52, 0.52 and 0.55) during the progression of osteoporosis (OP).

CONCLUSION

The Spearman's rank test supported the overall significant correlation between both, the morphological features and BMD values, making them as a reliable alternative option to the diagnosis of osteoporosis.

Texture analysis of trabecular bone around RM-Pressfit cementless acetabulum in a series of 46 patients during a 5 year period

BACKGROUND

Cementless total hip arthroplasty (THA) is a common procedure producing excellent clinical results. Their long-term survival is nevertheless burdened by loosening of the acetabular part caused by changes in the distribution of strains around the cup. In this context the RM-Pressfit® cup has been developed, resulting in a more harmonious distribution of the strains.

HYPOTHESIS

Texture analysis of X-ray films can evaluate the evolution of trabecular bone micro-architecture during the five years following THA with a RM-Pressfit® cup.

MATERIAL AND METHOD

A monocentric series of 46 hips was reviewed regularly within five years post- surgery. Radiographic evaluation of the operated hip was done on frontal digitized radiographs of the pelvis to follow evolution of bone micro-architecture in the #2 zone of De Lee and Charnley. Texture analysis using fractal algorithms was done at D0, 6 months, 1, 2 and 5 years post-THA. The fractal methods used included the skyscrapers and the dynamic blanket methods with 3 different structuring elements (a cross, a horizontal and a vertical vector).

RESULTS

The RM-Pressfit® caused significant changes in the distribution of strains around the acetabulum that preserved the bone volume over a 5-year period post-surgery. This corresponds to an improvement of the trabecular micro-architecture around the acetabular cups.

CONCLUSION

A statistically significant increase in the four fractal dimensions considered corresponded to an improved trabecular bone micro-architecture revealed by texture analysis, a non-invasive method that can be used on digitized X-ray images.

LEVEL OF EVIDENCE

IIIb, Case control study, retrospective design.

Demineralized Bone Matrix Coating Si-Ca-P Ceramic Does Not Improve the Osseointegration of the Scaffold

The aim of this study was to manufacture and evaluate the effect of a biphasic calcium silicophosphate (CSP) scaffold ceramic, coated with a natural demineralized bone matrix (DBM), to evaluate the efficiency of this novel ceramic material in bone regeneration. The DBM-coated CSP ceramic was made by coating a CSP scaffold with gel DBM, produced by the partial sintering of different-sized porous granules. These scaffolds were used to reconstruct defects in rabbit tibiae, where CSP scaffolds acted as the control material. Micro-CT and histological analyses were performed to evaluate new bone formation at 1, 3, and 5 months post-surgery. The present research results showed a correlation among the data obtained by micro-CT and the histomorphological results, the gradual disintegration of the biomaterial, and the presence of free scaffold fragments dispersed inside the medullary cavity occupied by hematopoietic bone marrow over the 5-month study period. No difference was found between the DBM-coated and uncoated implants. The new bone tissue inside the implants increased with implantation time. Slightly less new bone formation was observed in the DBM-coated samples, but it was not statistically significant. Both the DBM-coated and the CSP scaffolds gave excellent bone tissue responses and good osteoconductivity.

Cancellous and cortical bone mineral density around an elastic press-fit socket in total hip arthroplasty

Background and purpose - The acetabular component has remained the weakest link in hip arthroplasty for achievement of long-term survival. One of the possible explanatory factors for acetabular failure has been acetabular stress shielding. For this, we investigated the effects of a cementless elastic socket on acetabular bone mineral density (BMD). Patients and methods - During 2008-2009, we performed a single-center prospective cohort trial on 25 patients (mean age 64 (SD 4), 18 females) in whom we implanted a cementless elastic press-fit socket. Using quantitative BMD measurements on CT, we determined the change in BMD surrounding the acetabular component over a 2-year follow-up period. Results - We found a statistically significant decrease in cancellous BMD (-14% to -35%) and a stable level of cortical BMD (5% to -5%) surrounding the elastic press-fit cup during the follow-up period. The main decrease was seen during the first 6 months after implantation. During the second year, cancellous BMD showed a further decrease in the medial and lower acetabular regions. Interpretation - We found no evidence that an elastic press-fit socket would prevent acetabular stress shielding during a 2-year follow-up.

Building healthy bones throughout life: an evidence-informed strategy to prevent osteoporosis in Australia

Osteoporosis imposes a tremendous burden on Australia: 1.2 million Australians have osteoporosis and 6.3 million have osteopenia. In the 2007–08 financial year, 82 000 Australians suffered fragility fractures, of which > 17 000 were hip fractures. In the 2000–01 financial year, direct costs were estimated at $1.9 billion per year and an additional $5.6 billion on indirect costs. Osteoporosis was designated a National Health Priority Area in 2002; however, implementation of national plans has not yet matched the rhetoric in terms of urgency. Building healthy bones throughout life, the Osteoporosis Australia strategy to prevent osteoporosis throughout the life cycle, presents an evidence-informed set of recommendations for consumers, health care professionals and policymakers. The strategy was adopted by consensus at the Osteoporosis Australia Summit in Sydney, 20 October 2011. Primary objectives throughout the life cycle are: to maximise peak bone mass during childhood and adolescence to prevent premature bone loss and improve or maintain muscle mass, strength and functional capacity in healthy adults to prevent and treat osteoporosis in order to minimise the risk of suffering fragility fractures, and reduce falls risk, in older people. The recommendations focus on three affordable and important interventions — to ensure people have adequate calcium intake, vitamin D levels and appropriate physical activity throughout their lives. Recommendations relevant to all stages of life include: daily dietary calcium intakes should be consistent with Australian and New Zealand guidelines serum levels of vitamin D in the general population should be above 50nmol/L in winter or early spring for optimal bone health regular weight-bearing physical activity, muscle strengthening exercises and challenging balance/mobility activities should be conducted in a safe environment.

Mid-term study of bone remodeling after femoral cemented stem implantation: comparison between DXA and finite element simulation

This five-year prospective study was designed to investigate periprosthetic bone remodeling associated with two cemented stem models, ABG-II (Stryker) and VerSys (Zimmer), randomly implanted in patients older than 75 years. The sample consisted of 64 cases (32, ABG-II; 32, VerSys). Inclusion criterion was diagnosis of osteoarthritis recommended for cemented total hip arthroplasty. Besides clinical study, Finite Element (FE) simulation was used to analyze biomechanical changes caused by hip arthroplasty. Bone Mineral Density (BMD) measurements showed a progressive increase in bone mass throughout the entire follow-up period for both stems, well correlated with FE results except in Gruen zones 4, 5, 6 for ABG-II and in zones 4, 5 for VerSys, denoting that remodeling in those zones does not depend on mechanical factors but rather on biological or physiological ones.

Surgical treatment options in patients with impaired bone quality

BACKGROUND

Bone quality should play an important role in decision-making for orthopaedic treatment options, implant selection, and affect ultimate surgical outcomes. The development of decision-making tools, currently typified by clinical guidelines, is highly dependent on the precise definition of the term(s) and the appropriate design of basic and clinical studies. This review was performed to determine the extent to which the issue of bone quality has been subjected to this type of process.

QUESTIONS/PURPOSES

We address the following issues: (1) current methods of clinically assessing bone quality; (2) emerging technologies; (3) how bone quality connects with surgical decision-making and the ultimate surgical outcome; and (4) gaps in knowledge that need to be closed to better characterize bone quality for more relevance to clinical decision-making.

METHODS

PubMed was used to identify selected papers relevant to our discussion. Additional sources were found using the references cited by identified papers.

RESULTS

Bone mineral density remains the most commonly validated clinical reference; however, it has had limited specificity for surgical decision-making. Other structural and geometric measures have not yet received enough study to provide definitive clinical applicability. A major gap remains between the basic research agenda for understanding bone quality and the transfer of these concepts to evidence-based practice.

CONCLUSIONS

Basic bone quality needs better definition through the systematic study of emerging technologies that offer a more precise clinical characterization of bone. Collaboration between basic scientists and clinicians needs to improve to facilitate the development of key questions for sound clinical studies.

Quantitative computed tomography-assisted osteodensitometry of the pelvis after press-fit cup fixation: a prospective ten-year follow-up

BACKGROUND

As a follow-up of a previously reported three-year study, we analyzed the periprosthetic acetabular cortical and cancellous bone density changes at ten years after implantation of a press-fit cup.

METHODS

Prospective clinical, radiographic, and quantitative computed tomography examinations were performed within ten days and at mean periods of one, three, and ten years after total hip arthroplasty with a press-fit cup, a femoral stem with a tapered design, and alumina-alumina pairing. Periacetabular cortical and cancellous bone density (mg CaHA/mL) in the cranial, ventral, and dorsal regions about the cup were measured for twenty-four hips in vivo.

RESULTS

All acetabular cups showed radiographic signs of stable ingrowth, and no acetabular component had to be revised. The loss of periacetabular cancellous bone density about the cup was as much as -37% cranially, -60% ventrally, and -71% dorsally; the decrease was progressive between the one-year and three-year examinations only. In contrast, cortical bone density above the dome of the acetabular cup remained constant throughout the ten-year follow-up. A moderate change in cortical bone density of -5% to -18% was seen at the level of the cup ten years postoperatively.

CONCLUSIONS

Both periacetabular cortical and cancellous bone density changes were nonprogressive between the three-year and ten-year examinations after press-fit cup fixation.

Relationships of hip joint volume ratios with degrees of joint laxity and degenerative disease from youth to maturity in a canine population predisposed to hip joint osteoarthritis

OBJECTIVE

To assess relationships of acetabular volume (AV), femoral head volume (FV), and portion of the femoral head within in the acetabulum (FVIA) with each other and with degrees of hip joint laxity and degenerative joint disease from youth to maturity in dogs predisposed to developing hip joint osteoarthritis (OA).

ANIMALS

46 mixed-breed half- or full-sibling hound-type dogs.

PROCEDURES

The distraction index (DI), AV, FV, FVIA, and degree of osteoarthritis (OA score) were quantified in 1 hip joint at 16, 32, and 104 weeks of age. Relationships among variables were evaluated within and between ages. Ratios corresponding to OA scores were compared within ages. Differences among 16-week ratios corresponding to 32-week OA scores and among 16- and 32-week ratios corresponding to 104-week OA scores were evaluated.

RESULTS

Significant positive relationships existed between FV and AV across ages as well as between FVIA/FV and FVIA/AV and between DI and OA score across and within most ages. Such relationships also existed within these variables across most ages. Negative relationships of DI and OA scores with FVIA/FV and FVIA/AV within and among all ages were significant. Sixteen-week AVs, FVs, and FVIAs were greater and FV/AVs and OA scores were less than 32- and 104-week values. The 32-week FVIA/FV was less than 16- and 104-week values, and the 32-week FVIA/AV was less than the 104-week value. The FVIA/FV and FVIA/AV were lower and the DI was higher with higher OA scores within and among most ages.

CONCLUSIONS AND CLINICAL RELEVANCE

Structural volumes in lax canine hip joints changed predictably relative to each other during growth, despite degenerative changes. Measures developed in this study may augment current diagnosis and treatment strategies for hip dysplasia in dogs.

Femoral bone density changes after total hip arthroplasty with uncemented taper-design stem: a five year follow-up study

We measured bone density (BD) changes to assess adaptive bone remodelling five years after uncemented total hip arthroplasty with taper-design femoral component using quantitative computed-tomography-assisted osteodensitometry (qCT). Nineteen consecutive patients (21 hips) with degenerative joint disease were enrolled in the study. A press-fit cup and a tapered uncemented stem ceramic-ceramic pairing were used in all patients. Serial clinical, radiological and qCT osteodensitometry assessments were performed after the index operation and at the one, two and five year follow-ups. At the latest follow-up, the clinical outcome was rated satisfactory in all hips. The radiological assessment showed signs of osteointegration with stable fixation of all cups and stems. Overall, there was evidence of a BD loss at year five (p = 0.004). We estimate that BD loss was between 2.2% and 12.1% in comparison with baseline postoperative values. Progressive loss of BD in the metaphyseal region was observed in all hips. We found unremarkable BD changes of diaphyseal cortical BD throughout the five year follow-up period. qCT osteodensitometry technology allows differentiation of cortical and cancellous BD changes over time. Periprosthetic BD changes at the five year follow-up are suggestive of stable stem osteointegration with proximal femoral diaphysis load transfer and metaphyseal stress shielding.

Loss of tibial bone density in patients with rotating- or fixed-platform TKA

Little is known about tibial bone remodeling with TKA and its clinical relevance. We performed a randomized clinical trial to compare tibial bone density changes in cemented components with different bearing designs. Bone density changes were assessed using quantitative computed tomography (qCT)-assisted osteodensitometry. Twenty-eight rotating-platform and 26 fixed-platform cemented TKAs were included. The nonoperated contralateral side was used as a control. CT scans were performed postoperatively and 1 year and 2 years after the index operation. Cancellous bone density loss (up to 12.6% at 2 years) was observed in all proximal tibial regions in both cohorts. In contrast, we found lower cortical bone density loss (up to 3.6% at 2 years). We found no differences in bone loss between fixed- and rotating-platform implants. The decrease of cancellous bone density after TKA suggests stress transfer to the cortical bone.

Five-year DEXA study of 88 hips with cemented femoral stem

We performed repeated dual-energy X-ray absorptiometry (DEXA) measurements over five years in a homogeneous patient population to study the effect of a cemented stem on proximal femoral bone remodelling. Data from 88 patients (88 hips) implanted with total hip arthroplasty (THA) prostheses were extracted from three randomised studies. Femoral bone mineral density (BMD) was measured using a Lunar DPX-IQ densitometer for five years postoperatively. At one year the BMD changes had decreased between -2.0% [region of interest (ROI) 1] and -11.5% (ROI 7). During the follow-up period the BMD initially increased during the second year and thereafter decreased again in ROIs 5, 6 and 7. The loss of BMD at five years was more pronounced in region 7 (12.9%) and decreased with increasing age, total hip replacement (THR) on the right side and decreasing weight of the patient. We found that after the initial phase of early bone loss a period of recovery follows. Thereafter the BMD decreases again, which probably reflects the normal ageing of bone after uncomplicated cemented THA.

Quantitative CT-assisted osteodensitometry of femoral adaptive bone remodelling after uncemented total hip arthroplasty

The aim of this prospective study was to measure bone density changes and to assess adaptive bone remodelling after uncemented total hip arthroplasty with a taper-design femoral component using quantitative computer-tomography-assisted osteodensitometry. This method is able to differentiate cortical and cancellous bone structures. Twenty-seven consecutive patients (29 hips) with degenerative joint disease were enrolled in the study. Serial clinical, radiological and CT-osteodensitometry assessments were performed after the index operation. At the 2-year follow-up, the clinical outcome was rated satisfactory in all hips. The radiological assessment showed signs of osteointegration and stable fixation of all cups and stems. We observed a -17% decrease of cortical bone density and -22% decrease of cancellous bone density in the greater trochanter and femoral neck region. Cortical and cancellous bone density decrease at the level of the lesser trochanter was -9% and respectively -4%. We observed small changes of cortical bone density in the diaphyseal regions; in contrast, cancellous bone density increased (range 6% to 27%) in the diaphyseal regions. Overall, a trend of bone density recovery was observed throughout the follow-up period. Periprosthetic bone density changes at the 2-year follow-up are suggestive of stable osteointegration with proximal femoral diaphysis load transfer and moderate metaphyseal stress-shielding.

Retroacetabular stress-shielding in THA

We conducted a randomized clinical trial to compare periacetabular bone density changes after total hip arthroplasty using press-fit components with soft and hard liner materials. Bone density changes were assessed using quantitative computed tomography-assisted osteodensitometry. Twenty press-fit cups with alumina ceramic liners and 20 press-fit cups with highly cross-linked polyethylene liners were included; the nonoperated contralateral side was used as the control. Computed tomography scans were performed postoperatively and 1 year after the index operation. At the 1-year followup, we found no differences of periacetabular bone density changes between the alumina and polyethylene liner cohorts. However, we observed marked periacetabular cancellous bone density loss (up to -34%) in both cohorts. In contrast, we observed only moderate cortical bone density changes. The decrease of periacetabular cancellous bone density with retention of cortical bone density after THA suggests stress transfer to the cortical bone.

Nanosurfaces and nanostructures for artificial orthopedic implants

Nanomaterials and structures, such as nanoparticles, nanofibers, nanosurfaces, nanocoatings, nanoscaffolds and nanocomposites, are considered for various applications in orthopedics and traumatology. This review looks at proposed nanotechnology inspired applications for implants from the perspective of the orthopedic industry. Investigations support consistently the theory that most nanomaterials in various physical forms are able to enhance the cell response selectively for biological tissue integration or increase the strength and wear resistance of current orthopedic materials. At this stage, most of the studies are at the laboratory scale or in early in vivo testing. Significant basic and applied research and development is needed to realize their full clinical potential and biological, manufacturing, economic and regulatory issues have to be addressed. Nevertheless, a crucial factor for success is well-coordinated multimethod and multidiscipline teamwork with profound industrial and medical expertise.

Osseointegration in arthroplasty: can simvastatin promote bone response to implants?

Cementless fixation depends on bone ingrowth for long-term success. Simvastatin as a lipid lowering agent has been demonstrated to have osteoanabolic effects. This study was designed to measure the possible effect of simvastatin on implant osseointegration. Bilateral femoral implantation of titanium cylinders was performed in 20 rabbits. Blood lipid levels were measured pre- and postoperatively. Scanning electron microscopy (SEM) was used to measure the percentage of the surface of each implant in contact with bone and mechanical pull-out testing was performed. The blood lipid levels were significantly reduced in the simvastatin group. Histomorphometric examination revealed increased bone ingrowth and mechanical examination showed increased interface strength in the simvastatin group. Mechanical and histological data showed superior stability and osseous adaptation at the bone/implant interface for the simvastatin group. We conclude that simvastatin has potential as a means of enhancing bone ingrowth, which is a key factor in the longevity of cementless implants.