THA with hydroxyapatite granules at cement-bone interface: 15- to 20-year results

Biomaterial-based strategies for bone cement: modulating the bone microenvironment and promoting regeneration

Osteoporotic bone defect and fracture healing remain significant challenges in clinical practice. While traditional therapeutic approaches provide some regulation of bone homeostasis, they often present limitations and adverse effects. In orthopedic procedures, bone cement serves as a crucial material for stabilizing osteoporotic bone and securing implants. However, with the exception of magnesium phosphate cement, most cement variants lack substantial bone regenerative properties. Recent developments in biomaterial science have opened new avenues for enhancing bone cement functionality through innovative modifications. These advanced materials demonstrate promising capabilities in modulating the bone microenvironment through their distinct physicochemical properties. This review provides a systematic analysis of contemporary biomaterial-based modifications of bone cement, focusing on their influence on the bone healing microenvironment. The discussion begins with an examination of bone microenvironment pathology, followed by an evaluation of various biomaterial modifications and their effects on cement properties. The review then explores regulatory strategies targeting specific microenvironmental elements, including inflammatory response, oxidative stress, osteoblast-osteoclast homeostasis, vascular network formation, and osteocyte-mediated processes. The concluding section addresses current technical challenges and emerging research directions, providing insights for the development of next-generation biomaterials with enhanced functionality and therapeutic potential.

Multi-center study of use of the Exeter stem in Japan: a 10-year follow-up report

PURPOSE

Since the introduction of the Exeter stem for clinical use in Japan in 1996, the number of stems used has continued to rise owing to its favorable results. We investigated the outcomes of patients who had previously undergone total hip arthroplasty with the Exeter stem in Japan with a 10-year + follow-up period.

METHODS

This retrospective cohort study used clinical and radiographic data of 682 cases of primary total hip arthroplasty performed using the Exeter stem.

RESULTS

The mean postoperative follow-up period was 13.3 years. Femoral-side revision was required in 14 hips, with no cases of aseptic stem loosening-associated revision observed. Kaplan-Meier survival analysis predicted 97.3% 15-year survival when revision for any reason was used as the endpoint.

CONCLUSION

The obtained findings suggested the excellent long-term stability of the Exeter stem for primary total hip arthroplasty in Japan.

Minimum 10-Year Follow-Up of Total Hip Arthroplasty With a Collarless Triple-Tapered Polished Cemented Stem With Line-to-Line Implantation Using a Direct Anterior Approach

BACKGROUND

The Trilliance stem (B. Braun-Aesculap, Tuttlingen, Germany), a novel collarless triple-tapered polished stem, was introduced in 2009. The aim of this study is to evaluate the long-term clinical and radiological results of the Trilliance stem with line-to-line implantation in primary total hip arthroplasty using a direct anterior approach.

METHODS

A consecutive retrospective series of 130 patients (151 hips) who underwent total hip arthroplasty between February 2009 and August 2011 were evaluated for a minimum of 10 years. Of these, 87.4% had a diagnosis of secondary osteoarthritis based on developmental hip dysplasia. Clinical and radiological results, complications were evaluated and survival analysis was performed.

RESULTS

The mean follow-up was 10.7 years (range, 10.0-12.1). Thirteen hips (13 patients, 6.8%) were lost to follow-up. Adequate cementation (Barrack grade A) was achieved in 136 hips (93.8%) 1 week post-operatively. Nearly all (144 hips, 99.3%) had been inserted within the range of 3°. No significant differences were identified between high- (≥30 procedures/year) and low- (<30 procedures/year) volume surgeons. The Kaplan-Meier survival analysis with revision of the femoral component for aseptic loosening, revision of the femoral component for any reason and revision of either component for any reason as the end points, cumulative survivorship was 100.0%, 97.6% (95% confidence interval (CI) 95.4-100.0) and 96.5% (95% CI 93.8-99.3) at 10 years, respectively.

CONCLUSION

The Trilliance stem with line-to-line implantation using a direct anterior approach has an excellent clinical and radiological outcome at a minimum of 10 years' follow-up.

LEVEL OF EVIDENCE

Level IV, Retrospective cohort study.

The influence of anterior and posterior knot placement on hip function after total hip arthroplasty using a modified Dall's approach: a prospective non-randomised comparative study

BACKGROUND

The direct lateral modified Dall's approach for total hip arthroplasty (THA) provides an excellent vision of the hip joint by osteotomising the greater trochanter (GT). A robust method for the reattachment of osteotomised fragments is essential to prevent complications around the GT. Ultra-high molecular weight polyethylene cables are reported to be useful for reattachment; but the optimal suture method of these cables is unknown. The purpose of this study was to investigate the influence of the knot position on hip function after primary THA.

METHODS

In a prospective non-randomised study 216 primary THA were included, being scheduled for an operation with a modified Dall's approach. They were divided into 2 groups, anterior (A) and posterior (P) according to the knot position for the GT. Hip function was assessed using the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ), pain visual analogue scale (VAS), satisfaction VAS and Merle d'Aubigne-Postel hip score at 3 and 6 months postoperatively. A logistic regression analysis was used to investigate factors influenced by the knot position.

RESULTS

Patient demographics were comparable between the 2 groups. Differences of the knot position did not affect the radiological failure rate of GT reattachment. Regression analysis showed a significantly positive impact on pain VAS and flexion range at 6 months postoperatively for posterior knot position.

CONCLUSIONS

For the reattachment of osteotomised fragments, the posterior knot may be superior to the anterior knot.

Good result for twelve years after bilateral hip and knee arthroplasties for ankylosis with juvenile idiopathic arthritis: a case report

Juvenile idiopathic arthritis (JIA) can lead to joint deformity and bone destruction, which can cause gait disturbances. To the best of our knowledge, there are no case reports with over 10 years of follow-up on quadruple joint arthroplasties (QJA) for bilateral hip and knee ankylosis associated with JIA. We present the case of a 29-year-old woman with JIA. The patient suffered from bilateral ankylosis of the hips and knees and developed a swing gait requiring double crutches. We performed staged QJA with careful attention to postoperative rehabilitation and her physical features, which included excessive pelvic anteversion, poor bone quality, and short statue of bones. Twelve years after surgery, the patient was able to walk without any support and showed good clinical functional scores. In addition, no radiological loosening following QJA was observed. We hereby introduce a surgical strategy for total hip arthroplasty for excessive pelvic anteversion, which involves two methods to calculate pelvic tilt on a pelvic anteroposterior radiograph. These methods were able to approximately predict postoperative pelvic changes.

Risk factors for a radiolucent line around the acetabular component with an interface bioactive bone cement technique after primary cemented total hip arthroplasty

Aims

The main aims were to identify risk factors predictive of a radiolucent line (RLL) around the acetabular component with an interface bioactive bone cement (IBBC) technique in the first year after THA, and evaluate whether these risk factors influence the development of RLLs at five and ten years after THA.

Methods

A retrospective review was undertaken of 980 primary cemented THAs in 876 patients using cemented acetabular components with the IBBC technique. The outcome variable was any RLLs that could be observed around the acetabular component at the first year after THA. Univariate analyses with univariate logistic regression and multivariate analyses with exact logistic regression were performed to identify risk factors for any RLLs based on radiological classification of hip osteoarthritis.

Results

RLLs were detected in 27.2% of patients one year postoperatively. In multivariate regression analysis controlling for confounders, atrophic osteoarthritis (odds ratio (OR) 2.17 (95% confidence interval (CI), 1.04 to 4.49); p = 0.038) and 26 mm (OR 3.23 (95% CI 1.85 to 5.66); p < 0.001) or 28 mm head diameter (OR 3.64 (95% CI 2.07 to 6.41); p < 0.001) had a significantly greater risk for any RLLs one year after surgery. Structural bone graft (OR 0.19 (95% CI 0.13 to 0.29) p < 0.001) and location of the hip centre within the true acetabular region (OR 0.15 (95% CI 0.09 to 0.24); p < 0.001) were significantly less prognostic. Improvement of the cement-bone interface including complete disappearance and poorly defined RLLs was identified in 15.1% of patients. Kaplan-Meier survival analysis for the acetabular component at ten years with revision of the acetabular component for aseptic loosening as the end point was 100.0% with a RLL and 99.1% without a RLL (95% CI 97.9 to 100). With revision of the acetabular component for any reason as the end point, the survival rate was 99.2% with a RLL (95% CI 97.6 to 100) and 96.5% without a RLL (95% CI 93.4 to 99.7).

Conclusion

This study demonstrates that acetabular bone quality, head diameter, structural bone graft, and hip centre position may influence the presence of the any RLL.

Cite this article: Bone Joint Open 2021;2(5):278–292.

Influence of the knot position on the union of the greater trochanter after bipolar hip arthroplasty via the modified Dall approach: a prospective non-randomized study

Background

In our institute, all elderly patients with displaced femoral neck fracture were treated with cemented bipolar hemiarthroplasty (BHA) using the modified Dall approach. To our knowledge, there are no reports on the knot position of the greater trochanter reattachment. The aim of this study was to determine influence of two knot positions (anterior or posterior) on the complications of the greater trochanter.

Methods

This is a prospective non-randomized study conducted on 95 elderly patients (95 hips) from September 2013 to December 2017. The knot position was changed from anterior to posterior alternately. The X-ray images obtained immediately after the operation were compared with those obtained at 3 months postoperatively; thereafter, the status of the greater trochanter was classified into three types: type A, no apparent shifting and fracture; type C, over 1-mm shifting of the fragment; and type F, fracture of the greater trochanter.

Results

Regarding age at operation, sex, BMI, size of the greater trochanteric fragment, stem type, and surgeon, there was no significant difference between two groups. In the anterior group, 34 hips (72.3%), 5 hips (10.6%), and 8 hips (17.0%) were classified under type A, C, and F, respectively. In the posterior group, 44 hips (91.7%), 1 hip (2.1%), and 3 hips (6.3%) were classified under type A, C, and F, respectively. There were significantly fewer greater trochanteric complications in the posterior group.

Conclusions

The posterior knot position improved the union of the greater trochanter after BHA compared with the anterior knot position.

Trial registration

We had approved IRB at our hospital clinical research review committee. Retrospectively registered.

Minimum 5 year follow-up of clinical and radiographic results of cemented acetabular components with an interface bioactive bone cement technique in primary cemented total hip arthroplasty

INTRODUCTION

A well-fixed cement-bone interface is a crucial factor for acetabular and femoral components in cemented total hip arthroplasty (THA). The aim of the present study was to evaluate the middle-term clinical and radiological results of fixing the acetabular component with an interface bioactive bone cement (IBBC) technique in primary cemented THA.

MATERIALS AND METHODS

We undertook a retrospective review was undertaken of 193 primary cemented THAs in 174 patients using acetabular components cemented with an IBBC technique and followed for a minimum of 5 years (mean 8.3 years; range 5-17 years). Baseline data, clinical and radiological outcomes were evaluated.

RESULTS

Japanese Orthopedic Association hip score and modified Harris hip scores demonstrated significant clinical improvement in all patients (p < 0.001). Radiolucent lines were detected in 15 hips (7.8%) at the first year and 24 hips (12.4%) at the final post-operative follow-up. The Kaplan-Meier survivorship with radiographic loosening as the end point was 97.8% [95% confidence interval (CI) 95.2-100]. With revision of the acetabular component for aseptic loosening as the end point, component survival was 99.0% (95% CI 97.5-100). With revision of the acetabular component for any reason as the end point, component survival was 97.0% (95% CI 93.9-100).

CONCLUSIONS

Clinical and radiological results of the acetabular component with the IBBC technique in primary cemented THA were excellent.

Prospective, comparative study of cemented, smooth-surfaced titanium stems and polish-surfaced, stainless steel stems at a minimum follow-up of 10 years

BACKGROUND

Excellent results have been reported with cemented total hip arthroplasty (THA) using both smooth-surfaced and polished-surfaced stems. However, the superiority of polished-surfaced over smooth-surfaced in cemented THA, or vice versa, is still debated.

MATERIALS AND METHODS

Forty-six smooth-surfaced, triple-tapered, titanium-alloy stem (Group C) and 46 Exeter stems (Group T) have been fixed consecutively at different periods at our institute and prospectively evaluated clinically and radiologically. The area and location demonstrating cortical hypertrophy (CH) was measured in the serial radiograph and compared.

RESULTS

The mean postoperative follow-up period was 12.4 years for group C and 10.8 years for group T. No significant difference of clinical results was found between both groups. CH was observed in 8 hips (18.6%) of group C and in 7 hips (17.1%) of group T (NS). Among the hips in which distribution of CH was observed at the medial side, a significantly low proportion belonged to group C (adjusted standardized residual = - 2.3) and a significantly high proportion belonged to group T (adjusted standardized residual = 2.3). The largest area of CH found in each group was 166.1 mm² in group C and 227.6 mm² in group T (NS). The peak location of CH was 100.4% in group C and 84.3% in group T (p = 0.02).

CONCLUSION

Medium-term results of both stems were excellent. CH was observed medially and proximally in group T and laterally and distally in group C.

A case report of idiopathic iliopsoas hematoma which occurred soon after transfer to the wheelchair after total hip arthroplasty

A 79-year-old woman was diagnosed with osteoarthritis of the left hip and scheduled for total hip arthroplasty. As two lesions were detected in branches of the coronary arteries, she was treated with catheter treatment. The patient was receiving anticoagulant treatment, which was suspended eight days before the operation; however, heparin was started at 6 days before the operation and was stopped 9 hours before the operation. On the 2nd postoperative day soon after transfer to the wheel chair, she was feeling unwell and was suffering from severe pain in her left buttock and left thigh. Her blood pressure had decreased to 70 mmHg. During abdominal contrast-enhanced CT, a hematoma was detected in the left iliopsoas muscle. Catheter therapy was started by the cardiovascular department and bleeding had stopped spontaneously. The patient was able to walk with a cane and was discharged on the 40th postoperative day.

Abbreviations: THA: total hip arthroplasty, CT: computed tomography, JOA score: Japanese Orthopaedic Association hip score, HA: hydroxyapatite, PMMA: polymethyl-methacrylate, APTT: activated partial thromboplastin time

Total Hip Arthroplasty around the Inception of the Interface Bioactive Bone Cement Technique

Background

To augment cement-bone fixation, Dr. Hironobu Oonishi attempted additional physicochemical bonding through interposition of osteoconductive crystal hydroxyapatite (HA) granules at the cement-bone interface in 1982. He first used the interface bioactive bone cement (IBBC) technique in 12 selected patients (12 hips) in 1982 (first stage) and followed them for 2 years. In 1985, the technique was applied in 25 total hip arthroplasty (THA) patients (second stage) and the effects were investigated by comparing the side with the IBBC technique and the other side without the IBBC technique. He has employed this technique in all THA patients since 1987 (third stage).

Methods

In the IBBC technique, HA granules (2 to 3 g) were smeared on the bone surface just before the acetabular and femoral components were cemented. In the first stage, 12 hips were operated using the IBBC technique in 1982. In the second stage, THA was performed without the IBBC technique on one side and with the IBBC technique on the other side within 1 year in 25 patients. In the third stage, THA was performed with the IBBC technique in 285 hips in 1987.

Results

In the first stage patients, implant loosening was not detected at 30 years after operation. In the second stage patients, revision was required in 7 hips without the IBBC technique due to cup loosening (5 hips) and stem loosening (2 hips), whereas no hip was revised after THA with the IBBC technique at 26 years after operation. In the third stage patients, the incidence of radiolucent lines and osteolysis was very few at 25 years after operation.

Conclusions

The long-term follow-up of THA performed around the inception of the IBBC technique has revealed low incidences of radiolucent lines, osteolysis, and revision surgery.

Acrylic bone cement in total joint arthroplasty: A review

Acrylic bone cement has a variety of applications in orthopedic surgery. Primary uses in total arthroplasties are limited to prostheses fixation and antibiotic delivery. With the large number of total joint arthroplasties expected to continue to rise, understanding the role bone cement plays in the success of total joint arthroplasty can have a significant impact on daily practice. The literature is inconclusive on whether cemented or cementless fixation technique is superior, and choice of fixation type is mainly determined by surgeon preference and experience. Surgeons should understand that if poor techniques exist, short-term outcomes of the replaced joint may be at risk. Statement of clinical significance: This article attempts to clarify some points of bone cement use through a review of the mechanical properties related to bone cement, a comparison to alternative materials, influence of additives, and the effects on surgical outcomes. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:737-744, 2016.

Monitoring of blood pressure during total hip arthroplasty using the interface bioactive bone cement (IBBC) technique

BACKGROUND

Cement implantation syndrome, which is characterized by hypotension, hypoxemia, and cardiac arrhythmia or arrest, has been reported in the literature. The purpose of the present study was to monitor the blood pressure changes that occur after cementing during primary total hip arthroplasty (THA).

METHODS

The present study examined 178 cases in which 204 joints were treated with primary THA. Study subjects had a mean age at the time of surgery of 64.5 years (range 35-89). Under general anesthesia, both hip components were cemented in place using an anterolateral approach. After cementing, systolic arterial blood pressure was measured at 1-min intervals for 5 min and then again at 10 min. The maximum regulation ratio (MRR) was calculated as follows: (maximum change in blood pressure - blood pressure before cement application) divided by blood pressure before cement application.

RESULTS

No major complications, such as cardiac arrest, occurred in most cases; blood pressure increased until 4 mins on the acetabular side and until 2 min on the femoral side, and then gradually returned to the level observed prior to cement application. On the acetabular side, the mean MRR was 11.2 % [standard deviation (SD): 15.9; range -26 to -80], whereas it was 6.4 % (SD: 14.9; range -31 to -65) on the femoral side. Correlations were detected between MRR classification on the acetabular side and the subject's age at the time of the operation or bleeding control status on the acetabular side. When bleeding control was judged as complete, the tendency for blood pressure to decrease was reduced. Conversely, when bleeding control was judged as good, blood pressure showed a greater tendency to decrease.

CONCLUSION

In the present study, no episodes of major hypotension occurred. During THA involving the interface bioactive bone cement (IBBC) technique, when bleeding control on the acetabular side was judged as complete the tendency for blood pressure to decrease was reduced.

Inflammatory cell response to calcium phosphate biomaterial particles: an overview

Bone is a metabolically active and highly organized tissue consisting of a mineral phase of hydroxyapatite (HA) and amorphous calcium phosphate (CaP) crystals deposited in an organic matrix. One objective of bone tissue engineering is to mimic the chemical and structural properties of this complex tissue. CaP ceramics, such as sintered HA and beta-tricalcium phosphate, are widely used as bone substitutes or prosthesis coatings because of their osteoconductive properties. These ceramic interactions with tissues induce a cell response that can be different according to the composition of the material. In this review, we discuss inflammatory cell responses to CaP materials to provide a comprehensive overview of mechanisms governing the integration or loosening of implants, which remains a major concern in tissue engineering. A focus on the effects of the functionalization of CaP biomaterials highlights potential ways to increase tissue integration and limit rejection processes.

Interface micromechanics of transverse sections from retrieved cemented hip reconstructions: an experimental and finite element comparison

In finite element analysis (FEA) models of cemented hip reconstructions, it is crucial to include the cement-bone interface mechanics. Recently, a micromechanical cohesive model was generated which reproduces the behavior of the cement-bone interface. The goal was to investigate whether this cohesive model was directly applicable on a macro level. From transverse sections of retrieved cemented hip reconstructions, two FEA-models were generated. The cement-bone interface was modeled with cohesive elements. A torque was applied and the cement-bone interface micromotions, global stiffness and stem translation were monitored. A sensitivity analysis was performed to investigate whether the cohesive model could be improved. All results were compared with experimental findings. That the original cohesive model resulted in a too compliant macromechanical response; the motions were too large and the global stiffness too small. When the cohesive model was modified, the match with the experimental response improved considerably.

Multi-center study of use of the Exeter stem in Japan: evaluation of 1000 primary THA

BACKGROUND

The Exeter stem was introduced to the Japanese market in 1996. Since then, owing to excellent clinical results, the number of stems used has increased year by year and more than 2000 stems were implanted in 2009. The objective of this study was to prove the efficacy of the Exeter stem for Japanese patients by evaluating the short-term results of four major dedicated hip centers.

METHODS

We performed a retrospective study of clinical and radiographic results of 1000 primary total hip arthroplasties (THA) performed using the Exeter stem on 881 patients who were followed-up for at least 2 years after surgery. The average age of the patients at operation was 62.3 years (range 23-89 years). Mean postoperative follow-up period was 4.0 (range 2-9) years.

RESULTS

Thirty postoperative complications were observed, including 9 infections, 14 dislocations, 5 cases of deep vein thrombosis, and 2 cases of sciatic nerve palsy. No symptomatic pulmonary embolization or femoral fractures were observed. Re-operations for infection and dislocation were performed in 8 and 6 hips, respectively. According to Barrack's classification, the postoperative cementing grade was judged as A for 735 hips, B for 246 hips, and C for 4 hips. At final follow-up, no radiolucent line was observed at the bone-cement interface. Cortical hypertrophy was observed in 9.5 % of cases in Gruen zones 2-6. Kaplan-Meier survival analysis predicted 100 % survival at 5 years when a radiolucent line at the bone-cement interface of the femur was used as the endpoint, 98.8 % when re-operation was required for any reason.

CONCLUSIONS

This study revealed that excellent short-term results were achieved by fixing the Exeter stem with modern cementing techniques for primary THA in Japanese patients.

Osteoconduction of impacted porous titanium particles with a calcium-phosphate coating is comparable to osteoconduction of impacted allograft bone particles: in vivo study in a nonloaded goat model

AIMS

Impaction grafting restores bone defects in hip arthroplasty. Defects are reconstructed with bone particles (BoP) as substitute materials with adequate mechanical and biological properties are not yet available. Ceramic particles (CeP) have mechanical drawbacks as opposed to porous titanium particles (TiP). In this in vivo study, bone ingrowth and bone volume in coated and noncoated TiP were compared to porous biphasic calcium-phospate CeP and allograft BoP. Coatings consisted of silicated calcium-phosphate and carbonated apatite. Materials were implanted in goats and impacted in cylindrical defects (diameter 8 mm) in the cancellous bone of the femur. On the basis of fluorochrome labeling and histology, bone ingrowth distance was measured at 4, 8, and 12 weeks. Cross-sectional bone area was measured at 12 weeks.

FINDINGS

TiP created a coherent matrix of entangled particles. CeP pulverized and were noncoherent. Bone ingrowth in TiP improved significantly by the coatings to levels comparable to BoP and CeP. Cross-sectional bone area was smaller in CeP and TiP compared to BoP.

CONCLUSIONS

The osteoconductive properties of impacted TiP with a calcium-phosphate coating are comparable to impacted allograft bone and impacted biphasic ceramics. A more realistic loaded in vivo study should prove that coated TiP is an attractive alternative to allograft bone.

Outcomes of Charnley total hip arthroplasty using improved cementing with so-called second- and third-generation techniques

BACKGROUND

Techniques of cemented total hip arthroplasty have developed over time. We present the outcomes of Charnley total hip arthroplasty performed using improved second- and third-generation cementing techniques.

METHODS

We reviewed the radiologic results of 91 Charnley total hip arthroplasties performed using second- and third-generation cementing techniques. Second-generation techniques involved making multiple anchor holes, a double-cementing method on the acetabular side and an intramedullary plug, and retrograde filling with a cement gun on the femoral side in 57 hips. Third-generation techniques involved additional vacuum mixing and cement pressurization in 34 hips.

RESULTS

Joint survival rates at 20 years when using second-generation techniques were 89% for the socket and 94% for the stem with aseptic loosening as the end point; the survival rates at 10 years when using third-generation techniques were 97 and 100%, respectively. According to our radiographic evaluation system for the clear zone at 5 years, there was less clear zone in the acetabular side with the third-generation techniques than with second-generation techniques. In the femoral side, there was very little development of the clear zone, but the difference between generations was not significant.

CONCLUSIONS

Second- and third-generation cementing techniques showed excellent survivorship. The clear zone scores at 5 years indicated that third-generation techniques were effective, especially in the acetabular side, and may produce better long-term results than second-generation techniques.

The effect of impaction and a bioceramic coating on bone ingrowth in porous titanium particles

BACKGROUND AND PURPOSE

Porous titanium (Ti) particles can be impacted like cancellous allograft bone particles, and may therefore be used as bone substitute in impaction grafting. We evaluated the effect of impaction and of a thin silicated biphasic calcium phosphate coating on osteoconduction by Ti particles.

METHODS

The bone conduction chamber of Aspenberg was used in goats and filled with various groups of coated or uncoated small Ti particles (diameter 1.0-1.4 mm). Impacted allograft bone particles and empty chambers were used in control groups. Fluorochromes were administered at 4, 8, and 12 weeks. Maximum bone ingrowth distance was evaluated by histomorphometric analysis.

RESULTS

Histology of Ti particle graft cylinders showed a dense matrix with narrow inter-particle and intra-particle pores (< 100 μm), occluding the lumen of the bone chamber. Bone ingrowth distances gradually increased with time in all groups. Maximum bone ingrowth distance was higher in originally empty chambers than those with allograft bone particles (p = 0.01) and Ti particles (p < 0.001). Maximum bone ingrowth in allograft bone particles was higher than in all Ti groups (p ≤ 0.001). Impaction reduced osteoconduction and the coating partially compensated for the negative effect of impaction, but these differences were not statistically significant. No osteolytic reactions were found.

INTERPRETATION

Osteoconduction in the bone conduction chamber was reduced more by the insertion of small Ti particles than by insertion of small allograft bone particles. The osteoconductive potential of porous Ti particles should be studied further with larger-sized particles, which may allow bone ingrowth after impaction through larger inter-particle pores.

Morphology based cohesive zone modeling of the cement-bone interface from postmortem retrievals

In cemented total hip arthroplasty, the cement-bone interface can be considerably degenerated after less than one year in vivo service; this makes the interface much weaker relative to the direct post-operative situation. It is, however, still unknown how these degenerated interfaces behave under mixed-mode loading and how this is related to the interface morphology. In this study, we used a finite element (FE) approach to analyze the mixed-mode response of the cement-bone interface taken from postmortem retrievals. We investigated whether it was feasible to generate a fully elastic and a failure cohesive model based on only morphological input parameters. Computed tomography-based FE-models of postmortem cement-bone interfaces were generated and the interface morphology was determined. The models were loaded until failure in multiple directions by allowing cracking of the bone and cement components and including periodic boundary conditions. The resulting stiffness was related to the interface morphology. A closed form mixed-mode cohesive model that included failure was determined and related to the interface morphology. The responses of the FE-simulations compare satisfactorily with experimental observations, albeit the magnitude of the strength and stiffness are somewhat overestimated. Surprisingly, the FE-simulations predict no failure under shear loading and a considerable normal compression is generated which prevents dilation of the interface. The obtained mixed-mode stiffness response could subsequently be related to the interface morphology and subsequently be formulated into an elastic cohesive zone model. Finally, the acquired data could be used as an input for a cohesive model that also includes interface failure.