Influence of the cementing technique on the cement mantle in hip resurfacing: an in vitro computed tomography scan-based analysis

Towards the First Generation of Biomimetic Fixation for Resurfacing Arthroplasty Endoprostheses

This paper presents advances in designs of resurfacing arthroplasty endoprostheses that occurred through their historical generations. The critical characteristics of contemporary generation hip resurfacing arthroplasty endoprostheses are given and the failures resulting from the specific generation cemented and short stem fixation of the femoral component are reviewed. On the background of these failures, the critical need arises for an alternative approach to the fixation of components of resurfacing arthroplasty leading towards the first generation of biomimetic fixation for resurfacing arthroplasty endoprostheses. The state of the art of the completed bioengineering research on the first biomimetic fixation for resurfacing arthroplasty endoprostheses is presented. This new design type of completely cementless and stemless resurfacing arthroplasty endoprostheses of the hip joint (and other joints), where endoprosthesis components are embedded in the surrounding bone via the prototype biomimetic multi-spiked connecting scaffold (MSC-Scaffold), initiates the first at all generations of biomimetic endoprostheses of diarthrodial joints.

A comparison of 2 cementing techniques in hip resurfacing using human femoral heads

INTRODUCTION

Hip resurfacing remains a valid option in young male patients. The creation of the optimum cement mantle aids fixation of the femoral component. If the cement mantle is too thick the prosthesis can remain proud leading to early failure or if it penetrates too far into the femoral head, it may cause osteonecrosis.

METHOD

18 of 96 femoral heads collected from patients undergoing total hip arthroplasty were matched for their surface porosity. They were randomly allocated into 2 different cementing groups. Group 1 had the traditional bolus of cement technique, while group 2 had a modified cementing technique (swirl) where the inside of the femoral component was lined with an even layer of low viscosity cement.

RESULTS

The traditional bolus technique had significantly greater cement mantle thickness in 3 of 4 zones of penetration (p = 0.002), greater and larger air bubble formation (6 of 9 in bolus technique vs. 1 in 9 in swirl technique, p = 0.05) and more incomplete cement mantles compared with the swirl technique. There was no relationship to femoral head porosity.

CONCLUSION

The swirl technique should be used to cement the femoral component in hip resurfacing. Long-term clinical studies would conform if this translates into increased survivorship of the femoral component.

The porosity of the bone cement interface of 96 human femoral heads prepared for hip resurfacing

PURPOSE

The porosity of the femoral head prepared for hip resurfacing has not been previously described. This is important as greater pore size increases the penetration of bone cement and excessive cement penetration can cause osteonecrosis.

METHODS

96 osteoarthritic femoral heads were harvested at total hip arthroplasty and prepared for hip resurfacing. The porosity of the bone cement interface in hip resurfacing was calculated from digitised black and white photographs using MatLab software.

RESULTS

The mean porosity was 0.63. Increased porosity was associated with larger femoral heads in both the coronal and sagittal dimensions and cysts in the femoral head. It was not associated with gender, age, body mass index (BMI), smoking, alcohol or corticosteroid consumption.

CONCLUSION

The porosity of the femoral head has been shown to be 0.63. Future studies of cementing techniques in hip resurfacing should include this porosity in their designs. The surgeon prior to hip resurfacing should consider altering his cementing technique when cysts are present on the preoperative radiographs.

Biomimetic Multispiked Connecting Ti-Alloy Scaffold Prototype for Entirely-Cementless Resurfacing Arthroplasty Endoprostheses-Exemplary Results of Implantation of the Ca-P Surface-Modified Scaffold Prototypes in Animal Model and Osteoblast Culture Evaluation

We present here—designed, manufactured, and tested by our research team—the Ti-alloy prototype of the multispiked connecting scaffold (MSC-Scaffold) interfacing the components of resurfacing arthroplasty (RA) endoprostheses with bone. The spikes of the MSC-Scaffold prototype mimic the interdigitations of the articular subchondral bone, which is the natural biostructure interfacing the articular cartilage with the periarticular trabecular bone. To enhance the osteoinduction/osteointegration potential of the MSC-Scaffold, the attempts to modify its bone contacting surfaces by the process of electrochemical cathodic deposition of Ca-P was performed with further immersion of the MSC-Scaffold prototypes in SBF in order to transform the amorphous calcium-phosphate coating in hydroxyapatite-like (HA-like) coating. The pilot experimental study of biointegration of unmodified and Ca-P surface-modified MSC-Scaffold prototypes was conducted in an animal model (swine) and in osteoblast cell culture. On the basis of a microscope-histological method the biointegration was proven by the presence of trabeculae in the interspike spaces of the MSC-Scaffold prototype on longitudinal and cross-sections of bone-implant specimens. The percentage of trabeculae in the area between the spikes of specimen containing Ca-P surface modified scaffold prototype observed in microCT reconstructions of the explanted joints was visibly higher than in the case of unmodified MSC-Scaffold prototypes. Significantly higher Alkaline Phosphatase (ALP) activity and the cellular proliferation in the case of Ca-P-modified MSC-Scaffold pre-prototypes, in comparison with unmodified pre-prototypes, was found in osteoblast cell cultures. The obtained results of experimental implantation in an animal model and osteoblast cell culture evaluations of Ca-P surface-modified and non-modified biomimetic MSC-Scaffold prototypes for biomimetic entirely-cementless RA endoprostheses indicate the enhancement of the osteoinduction/osteointegration potential by the Ca-P surface modification of the Ti-alloy MSC-Scaffold prototype. Planned further research on the prototype of this biomimetic MSC-Scaffold for a new generation of RA endoprostheses is also given.

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.

Cement applicator use for hip resurfacing arthroplasty

We compared the manufacturer recommended cementing technique for a femoral hip resurfacing implant (BHR, S&N) to a newly designed cement applicator on 20 porous carbon foam specimens. Substantial design changes and improvements of the cement applicator were necessary: The diameter and number of the cement escaping holes at the top of the applicator were optimized for medium viscosity cement. It was necessary to add four separate air inlet holes with large diameters. The inner shape of the applicator had to be adapted to the BHR design with a circular extending chamfer in the proximal region, a parallel inner wall and a second chamfer distally. The interface temperatures showed no risk for heat necrosis using both techniques. The cement penetration depth was more uniform and significantly reduced for the applicator cementing technique (4.34 ± 1.42 mm, 6.42 ± 0.43 mm, p = 0.001). The cement-applicator showed no cement defects compared to a large defect length (0.0 ± 0.0 mm, 10.36 ± 1.10 mm, p < 0.001) with the manufacturer recommended cementing technique. The cement applicator technique appears to be effective for a homogenous cement distribution without cement defects and safe with a lower risk of polar over-penetration.

Four decades of finite element analysis of orthopaedic devices: where are we now and what are the opportunities?

Finite element has been used for more than four decades to study and evaluate the mechanical behaviour total joint replacements. In Huiskes seminal paper "Failed innovation in total hip replacement: diagnosis and proposals for a cure", finite element modelling was one of the potential cures to avoid poorly performing designs reaching the market place. The size and sophistication of models has increased significantly since that paper and a range of techniques are available from predicting the initial mechanical environment through to advanced adaptive simulations including bone adaptation, tissue differentiation, damage accumulation and wear. However, are we any closer to FE becoming an effective screening tool for new devices? This review contains a critical analysis of currently available finite element modelling techniques including (i) development of the basic model, the application of appropriate material properties, loading and boundary conditions, (ii) describing the initial mechanical environment of the bone-implant system, (iii) capturing the time dependent behaviour in adaptive simulations, (iv) the design and implementation of computer based experiments and (v) determining suitable performance metrics. The development of the underlying tools and techniques appears to have plateaued and further advances appear to be limited either by a lack of data to populate the models or the need to better understand the fundamentals of the mechanical and biological processes. There has been progress in the design of computer based experiments. Historically, FE has been used in a similar way to in vitro tests, by running only a limited set of analyses, typically of a single bone segment or joint under idealised conditions. The power of finite element is the ability to run multiple simulations and explore the performance of a device under a variety of conditions. There has been increasing usage of design of experiments, probabilistic techniques and more recently population based modelling to account for patient and surgical variability. In order to have effective screening methods, we need to continue to develop these approaches to examine the behaviour and performance of total joint replacements and benchmark them for devices with known clinical performance. Finite element will increasingly be used in the design, development and pre-clinical testing of total joint replacements. However, simulations must include holistic, closely corroborated, multi-domain analyses which account for real world variability.

Impact of implant size on cement filling in hip resurfacing arthroplasty

Larger proportions of cement within femoral resurfacing implants might result in thermal bone necrosis. We postulate that smaller components are filled with proportionally more cement, causing an elevated failure rate. A total of 19 femoral heads were fitted with polymeric replicas of ReCap (Biomet) resurfacing components fixed with low-viscosity cement. Two specimens were used for each even size between 40 and 56 mm and one for size 58 mm. All specimens were imaged with computed tomography, and the cement thickness and bone density were analyzed. The average cement mantle thickness was 2.63 mm and was not correlated with the implant size. However, specimen with low bone density had thicker cement mantles regardless of size. The average filling index was 36.65% and was correlated to both implant size and bone density. Smaller implants and specimens with lower bone density contained proportionally more cement than larger implants. According to a linear regression model, bone density but not implant size influenced cement thickness. However, both implant size and bone density had a significant impact on the filling index. Large proportions of cement within the resurfacing head have the potential to generate thermal bone necrosis and implant failure. When considering hip resurfacing in patients with a small femoral head and/or osteoporotic bone, extra care should be taken to avoid thermal bone necrosis, and alternative cementing techniques or even cementless implants should be considered. This study should help delimiting the indications for hip resurfacing and to choose an optimal cementing technique taking implant size into account.

What is the upper limit of cement penetration for different femoral hip resurfacing components?

We used a validated femoral resurfacing model to obtain measurements of pressure and temperature and quantify cement distribution as a function of inner geometry and cementing technique of five different femoral hip resurfacing components. The purpose was to investigate if manufacture cementing recommendations are reliable. ASR showed only with the recommended manual cementing technique low cement pressures of 58.0±50.2kPa and low interface temperatures of 33.3±4.1°C. BHR had large cement defects of 10.4±1.1mm. Conserve Plus caused the smallest cement penetration depths of 2.9±0.6mm. Durom was tolerant against changes of the cementing technique but showed the widest spread of temperature data 42.8±7.0°C. ReCap showed the highest risk for incomplete seating with a cement mantle thickness of 4.3±0.9mm. Polymerization heat did not exceed the threshold of 45°C with a cement penetration depth of less than 4.2mm in any circumstances of this study.

Is it Time for Cementless Hip Resurfacing?

BACKGROUND

Metal-on-metal bearing with cemented femoral component and cementless acetabular fixation is the current standard in surface replacement arthroplasty (RSA) of the hip. Because of concerns about the long-term survivorship of cemented stems in conventional hip arthroplasty, it seems logical to achieve cementless fixation on the femoral side with RSA.

QUESTIONS/PURPOSES

The goals of this review were to evaluate clinical and radiological data reported from previously published cementless RSA series. In addition, we intend to review author's preliminary experience with Conserve Plus cementless devices specifically assessing the clinical outcomes, the complications rate, the survivorship, and the metallic ions levels measured in follow-up.

METHODS

A references search was done with PubMed using the key words "cementless hip resurfacing", "cementless hip resurfacing prosthesis", and "femoral cementless hip resurfacing". Additionally, the clinical outcomes, the complications rate, the survivorship, and the metallic ions levels were measured in 94 cementless Conserve Plus(©) devices in 90 patients (68 males and 22 females) with a mean age of 41.1 years (18-59). Mean follow-up was 13.1 months (8-16).

RESULTS

No revision was performed during the observed follow-up. Neither radiological signs of loosening nor neck narrowing >10% were evident. Chromium and cobalt levels in whole blood samples rose respectively from 0.53 μg/l (0.1-1.7) to 1.7 μg/l (0.6-2.9) and from 0.54 μg/l (0.1-1.4) to 1.98 μg/l (0.1-2.8).

CONCLUSIONS

Cementless "fit and fill" femoral-side fixation, which seems to be potentially evolved and design-related, should be considered for future hip-resurfacing device generations.

Effect of cementing technique and cement type on thermal necrosis in hip resurfacing arthroplasty--a numerical study

Femoral fractures within resurfacing implants have been associated with bone necrosis, possibly resulting from heat generated by cement polymerization. The amount of heat generated depends on cement mantle volume and type of cement. Using finite element analysis, the effect of cement type and volume on thermal necrosis was analyzed. Based on CT-data of earlier implantations, two different models were created: a thick mantle model, representing a low-viscosity "cement filling" technique, and a thin mantle model, representing a high viscosity "cement packing" technique. Six cement types were analyzed. The polymerization heat generation and its effect on bone necrosis were predicted. In the thin cement mantle models, no thermal necrosis was predicted. Thick cement mantle models produced thermal necrosis at the cement-bone interface depending on cement type. In the worst case, 6% of the bone at the cement-bone interface became necrotic, covering almost the entire cross-sectional area. The current findings suggest a potential thermal drawback of thick cement mantles, although it is unclear whether thermal bone necrosis significantly affects implant fixation or increases the fracture risk. Furthermore, our study showed distinct differences between the heat generated and resulting thermal damage caused by the various cement types.

Fixation of trapezial implants in a trapeziometacarpal total joint prosthesis tested in a model of porcine bone

High aseptic loosening rates have been reported in total joint prostheses of the carpometacarpal joint of the thumb, particularly in the trapezial component. The primary fixation of new implants may be tested in cadaver bones, but the anatomy of the pig is in many ways similar to that of the human, so we compared the central carpal bone from the forefoot of 6-month-old pigs, which has a saddle joint surface similar to the trapezium, to the trapezium in patients with carpometacarpal osteoarthritis. The mean (SD) bone mineral density of the 13 pig forefoot bones was 0.88 (0.12) g/cm(2) compared with 0.63 (0.16) g/cm(2) in the 31 human trapeziums. The measured size of the porcine bones was slightly larger than that of the human trapeziums. The similarity in form, size, and bone mineral density means that the central bone of the forefoot of 6-month-old pigs may be used for fixation tests in trapezial implants.

Metal-on-metal hip resurfacing with uncemented fixation of the femoral component. A minimum 2 year follow up

The current generation of metal-on-metal hip resurfacing designs has largely been characterized by cemented femoral fixation using a cementless cup. We present the clinical results of 135 entirely uncemented metal-on-metal hip resurfacing procedures. The primary outcome measures were revision for any cause and the Oxford hip score at the latest follow up. The average length of followup was 2.9 years. The mean Oxford hip score was 18.4 and no patient required revision of either component during the study period. Uncemented femoral fixation may be comparable to fixation with cement in metal-on-metal hip resurfacing.

Primary cup fixation with different designs of trapeziometacarpal total joint trapezium components: a radiostereometric analysis in a pig bone model

High loosening rates of the trapezium components of trapeziometacarpal total joint prostheses have been reported. The purpose of this study was to compare the primary press fit fixation of two different, uncemented cup designs (MOTEC and Elektra) with the primary fixation of a cemented polyethylene cup (DLC) in a pig bone model. We did a push out test to measure the maximal load strength of the implants and a low-pressure cyclic loading test combined with radiostereometric analysis to measure the micromotion of the implants. There was no significant difference in fixation strength between the two uncemented screw cup designs or between the two uncemented screw cups and the cemented polyethylene cup. However, we found that threading of the bone before insertion of the Electra screw cup weakens the primary fixation strength of the implant. The results indicate that focus should be on the insertion technique as well as on the cup design of uncemented trapezium cup implants. Further studies of trapezium implant migration in a clinical setting are needed.

Effects of impaction on cement mantle and trabecular bone in hip resurfacing

INTRODUCTION

Failures involving the femoral part in hip resurfacing remain problematic in terms of overall implant survival. In this context, effects of impaction strength on cement mantle morphology and trabecular bone damage have not been studied to date.

MATERIALS AND METHODS

Sixteen paired cadaveric femora that had undergone hard and gently impacted hip resurfacing using a manual packing cementing technique in a previous study, were evaluated morphologically. The earlier study had revealed lower failure loads for hard impacted heads. A central slice of each femoral head underwent microradiography.

RESULTS

Overall cement mantle thickness averaged 2.0 mm (range 0-5 mm) in the hard and in the low impact group with no significant difference between groups (p = 0.299). No signs of damage in the bone remnants inside the prosthesis of the fractured proximal femurs were detected in the microradiographic analysis.

CONCLUSION

Cement mantle thickness was not influenced by impaction strength when using a manual packing cementing technique. No trabecular damage underneath the implant was detected despite lower failure loads, confirming the difficulty to identify small trabecular damage in an in vitro study.

The influence of cementing technique in hip resurfacing arthroplasty on the initial stability of the femoral component

PURPOSE

In clinical and retrieval analyses, over-penetration of cement, incomplete seating of the prosthesis with a resultant polar cement mass, or both, have been associated with early femoral failures of resurfacing arthroplasties. We used human bone specimens to experimentally compare the initial stability of different cementing techniques.

METHODS

Twenty-six pairs of fresh frozen femora were prepared for resurfacing using original instruments (DePuy ASR). ASR femoral resurfacing prostheses were implanted using two different cementing techniques: (1) component filling and (2) cement applicator. Real-time measurements of pressure and temperature during implantation, analyses of cement penetration and micro motions under torque application were performed.

RESULTS

Applicator use reduced significantly the cement penetration depth (9.2 mm vs 5.3 mm with the applicator, p = 0.001), polar mantle (8.1 mm vs 2.6 mm, p = 0.008), cement defects (3.7 mm vs 0.1 mm, p = 0.008) and interface temperatures (40.3°C vs 33.1°C, p < 0.001 ). Initial rotational stability showed statistically significant less extreme values with the cement applicator technique (range 3.4-51.7 m°/Nm, 11.0-29.7 m°/Nm, p = 0.024).

CONCLUSIONS

The cement applicator technique significantly reduces cement defects, incomplete seating, over-penetration and interface temperatures with a more consistent initial stability of the ASR femoral resurfacing prostheses.

Birmingham hip resurfacing: the prevalence of failure

Despite the increasing interest and subsequent published literature on hip resurfacing arthroplasty, little is known about the prevalence of its complications and in particular the less common modes of failure. The aim of this study was to identify the prevalence of failure of hip resurfacing arthroplasty and to analyse the reasons for it. From a multi-surgeon series (141 surgeons) of 5000 Birmingham hip resurfacings we have analysed the modes, prevalence, gender differences and times to failure of any hip requiring revision. To date 182 hips have been revised (3.6%). The most common cause for revision was a fracture of the neck of the femur (54 hips, prevalence 1.1%), followed by loosening of the acetabular component (32 hips, 0.6%), collapse of the femoral head/avascular necrosis (30 hips, 0.6%), loosening of the femoral component (19 hips, 0.4%), infection (17 hips, 0.3%), pain with aseptic lymphocytic vascular and associated lesions (ALVAL)/metallosis (15 hips, 0.3%), loosening of both components (five hips, 0.1%), dislocation (five hips, 0.1%) and malposition of the acetabular component (three hips, 0.1%). In two cases the cause of failure was unknown. Comparing men with women, we found the prevalence of revision to be significantly higher in women (women = 5.7%; men = 2.6%, p < 0.001). When analysing the individual modes of failure women had significantly more revisions for loosening of the acetabular component, dislocation, infection and pain/ALVAL/metallosis (p < 0.001, p = 0.004, p = 0.008, p = 0.01 respectively). The mean time to failure was 2.9 years (0.003 to 11.0) for all causes, with revision for fracture of the neck of the femur occurring earlier than other causes (mean 1.5 years, 0.02 to 11.0). There was a significantly shorter time to failure in men (mean 2.1 years, 0.4 to 8.7) compared with women (mean 3.6 years, 0.003 to 11.0) (p < 0.001).