Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine (P I MECH ENG H)

Publications in this journal

• Article: Evaluation of phytochemicalincorporated porous polymeric sponges for bone tissue engineering: A novel perspective.

  Ravi N Raghavan, N Somanathan, Thottapalli P Sastry
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  ABSTRACT: Porous polymeric scaffolds are extensively studied for delivery of bone growth factors. Since phytochemicals are known to produce changes in cell signalling and other metabolic pathways, osteogenic phytochemicals, that is, extracts of Cissus quadrangularis and Butea monosperma, are incorporated into sulphonated poly(aryl ether ketone) sponges. The results have shown that the scaffolds with phytochemicals enhanced the proliferation and alkaline phosphatase activity of the cells compared to cells treated on scaffolds without phytochemicals. Hence, these phytochemicals can be evaluated to augment, if not substitute the use of bone morphogenetic proteins in scaffolds.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 06/2013;
• Article: An in vitro approach to the evaluation of foot-ankle kinematics: Performance evaluation of a custom-built gait simulator.

  Koen Peeters, Tassos Natsakis, Josefien Burg, Pieter Spaepen, Ilse Jonkers, Greta Dereymaeker, Jos Vander Sloten
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  ABSTRACT: Despite their well-known limitations, in vitro experiments have several benefits over in vivo techniques when exploring foot biomechanics under conditions characteristic of gait. In this study, we present a new setup for dynamic in vitro gait simulation that integrates a numerical model for generating the tibial kinematics control input, and we present an innovative methodology to measure full three-dimensional joint kinematics during gait simulations. The gait simulator applies forces to the tendons. Tibial kinematics in the sagittal plane is controlled using a numerical model that takes into account foot morphology. The methodology is validated by comparing joint rotations measured during gait simulation with those measured in vivo. In addition, reliability and accuracy of the control system as well as simulation input and output repeatability are quantified. The results reflect good control performance and repeatability of the control inputs, vertical ground reaction force, center of pressure displacement, and joint rotations and translations. In addition, there is a good correspondence to in vivo kinematics for most patterns of motion at the ankle, subtalar, and Chopart's joints. Therefore, these results show the relevance and validity of including specimen-specific information for defining the control inputs.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 06/2013;
• Article: Clinical failure analysis of contemporary ceramic-on-ceramic total hip replacements.

  Jan-M Brandt, Trevor C Gascoyne, Leah E Guenther, Andrew Allen, David R Hedden, Thomas R Turgeon, Eric R Bohm
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  ABSTRACT: The present study investigates the performance of ceramic-on-ceramic total hip replacements by combining a retrieval analysis with a survivorship analysis to elucidate mechanisms that led to clinical failure. Semiquantitative surface damage assessment, contact profilometry, contour measurements, and scanning electron microscopy were performed to characterize the types and quantify the extent of surface damage on the retrieved ceramic components. The implantation period was positively correlated with both damage scores of the femoral heads (R = 0.573, p < 0.001) and the acetabular cups (R = 0.592, p < 0.001). Increased maximal out-of-roundness values of the femoral heads correlated with both increased metal transfer damage score (R = 0.384, p = 0.023) and increased stripe damage score (R = 0.729, p ≤ 0.001) of the acetabular liners. The damage rate (damage score/year) for both the retrieved heads and acetabular liners was at least 2.2-fold greater at inclination angles of >45° than the damage rate at inclination angles of ≤45°. For the retrieved femoral heads only, the linear wear rate of 25.5 ± 21.3 µm/year at inclination angles of >45° was 6-fold greater than the linear wear rate of 4.2 ± 2.3 µm/year at inclination angles of ≤45°. Metal transfer on the ceramic bearing surface could possibly contribute to fluid-film starvation and, in combination with an increased inclination angle, may facilitate an adhesive wear mechanism associated with stripe surface damage. At our institution, the clinical survivorship of ceramic-on-ceramic total hip replacements was 98.9% (a total of 9 out of 815 patients were revised within 10 years after total hip arthroplasty) with revision as the end point, suggesting their safe use in younger patients.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 06/2013;
• Article: Contribution of posterolateral corner structures to knee joint translational and rotational stabilities: A computational study.

  Yoon Hyuk Kim, Purevsuren Tserenchimed, Kyungsoo Kim, Kwang-Jun Oh
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  ABSTRACT: It has been reported that posterolateral corner structures, including the lateral collateral ligament, the popliteus tendon, and the popliteofibular ligament, may play important roles in reducing external rotational and posterior translational instabilities. However, there are few studies focusing on the quantitative influence of posterolateral corner structures on knee joint stability, due to the difficulty of controlling experimental conditions. In this study, a knee model that included posterolateral corner structures was developed. It was validated by comparison to previous experimental studies using the posterior drawer test, dial test, and varus stress test. The posterior translation, external rotation, and varus rotation were then predicted in order to investigate the contribution of posterolateral corner structures to translational and rotational stabilities. Our results indicate that posterolateral corner structures, including the popliteofibular ligament and the popliteus tendon, could contribute to posterior translational and external rotational stabilities, as clinical observations had suggested. Therefore, the addition of posterolateral corner structures to knee joint models may improve the utility of such models.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 06/2013;
• Article: Detection of looseness degree of dental posts using natural frequency analysis.

  Sung-Chih Hsieh, Shu-Li Lin, Yung-Kai Huang, Wei-Jen Chang, Chia-Chun Yuan, Yi-June Lo, Sheng-Yang Lee, Haw-Ming Huang
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  ABSTRACT: This study examines the relationship between the retention force and natural frequency of dental posts cemented with zinc phosphate cement. Forty-two decoronated maxillary incisors were collected and embedded in resin blocks. The 7-mm post spaces were prepared for all test samples prior to cementing the 13-mm Para-Posts with zinc phosphate cement. The natural frequency values and retention forces of the zinc phosphate cement-cemented Para-Posts in various liquid/powder mixing ratios were measured. Thereafter, the natural frequency values of the zinc phosphate cement-cemented posts were continuously detected during ultrasonic vibration. Moreover, both the natural frequency values and the dislodgement forces in response to ultrasonic vibrations were measured for the pretreated post samples. Results showed that the natural frequency values of the posts significantly decreased from 8.8 ± 0.8 to 5.0 ± 0.5 kHz (P < 0.05) before and after ultrasound treatment, respectively. The natural frequency values and the dislodgement forces of tested posts had a highly linear relationship (R(2) = 0.99, P < 0.05). These findings suggest that natural frequency is a variable for monitoring the stability status of zinc phosphate cement-cemented dental posts.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013;
• Article: A biomechanical evaluation of hinged total knee replacement prostheses.

  Robin Long, Sabina Gheduzzi, Thomas A Bucher, Andrew D Toms, Anthony W Miles
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  ABSTRACT: The number of total knee replacements being performed worldwide is undergoing an unprecedented increase. Hinged total knee replacements, used in complex salvage and revision procedures, currently account for a small but growing proportion of prostheses implanted. Modern hinged prostheses share the same basic configuration, allowing flexion-extension and tibial rotation. One aspect on which designs differ is the anteroposterior location of the hinge. A more posterior hinge is designed to increase the patellar tendon moment arm, reducing the quadriceps force required for a given activity and benefiting the patient. Five commonly used total knee replacements were evaluated in terms of quadriceps force and patellar tendon moment arm using a laboratory-based rig. Significant differences were identified between the five prostheses in quadriceps force and patellar tendon moment arm. Analysis of the correlation between these two parameters indicates that while patellar tendon moment arm influences quadriceps force, it is not the only factor. Also important is the lever function of the patella, and it is suggested here that the non-physiological nature of the prosthetic patellofemoral geometry may result in unnatural joint function. Thus, a thorough understanding of the resulting kinematic function of hinged total knee replacements is becoming increasingly important in complex revision total knee replacement to meet rising patient expectations and functional demands.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013;
• Article: A critical study on the experimental determination of stiffness and viscosity of the human triceps surae by free vibration methods.

  Federico Paris-Garcia, Alberto Barroso, José Canas, Juan Ribas, Federico Paris
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  ABSTRACT: Muscles and tendons play an important role in human performance. Their mechanical behaviour can be described by analytical/numerical models including springs and dampers. Free vibration techniques are a widely used approach to the in vivo determination of stiffness and viscosity of muscle-tendon complexes involved in sport movements. By considering the data reported in the literature, it appears that the visco-elastic properties of the triceps surae muscle-tendon complexes are independent of the modality in which free vibration is induced as well as they do not depend on the composition of the population of subjects submitted to the experiments. This research will critically discuss this important aspect focussing in particular on two studies documented in the literature. For this purpose, two equipments will be developed to reproduce literature experiments under the assumption that the oscillating part of the body behaves as a single-degree-of-freedom system: The governing degree of freedom is associated with the vertical displacement of the lower leg or with the rotation of the foot around the ankle articulation. Unlike literature, measurements are now conducted on the same population of subjects in order to draw more general conclusions on the real equivalence of results and validity of the mechanical properties determined experimentally. Free vibration tests are accurately simulated by analytical models describing the response of each vibrating system. It is found that if the two measurement protocols are applied to the same population of individuals as it is done in this study, values of visco-elastic properties of muscle-tendon complexes extracted from experimental data are significantly different, the differences presenting a convincing consistency. This result is in contrast with the literature and confirms the need to evaluate results of free vibration techniques by taking homogeneous bases of comparison.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013;
• Article: A biomechanical study of the recovery in spinal stability of flexion/extension and torsion after the resection of different posterior lumbar structures in a sheep model.

  Haobo Jia, Shaowen Zhu, Jianxiong Ma, Jie Wang, Rui Feng, Dan Xing, Yang Yang, Baoyi Ma, Yang Chen, Jingtao Yu, Xinlong Ma
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  ABSTRACT: Posterior lumbar structures are vital for spinal stability, and many researchers thought that laminectomy and facetectomy would lead to severe spinal instability. However, because living organisms have compensatory repair capacities, their long-term condition after injuries may change over time. To study the changes in the lumbar biomechanical stability of flexion/extension and torsion at different time points after the resection of various posterior structures, as well as to assess the capacity for self-healing, sheep that had undergone laminectomy or facetectomy were used as an experimental animal model. The injured sheep models included three groups: laminectomy only, laminectomy plus left total facetectomy, and laminectomy plus bilateral facetectomy. Eight nonoperative sheep were used as the control group. At 0, 6, 12, 24, and 36 weeks after injury, the lumbar specimens were harvested for biomechanical testing using the Instron 8874 servohydraulic biomechanical testing system. The changes in the injured lumbar spine were also analyzed through radiological examination. The lumbar stability in flexion/extension and torsion was severely decreased after the three types of surgery. After 6 weeks, the flexion/extension mechanical parameters recovered substantially; each parameter had returned to normal levels by 12 weeks and exceeded the intact group by 24 and 36 weeks. Torsional stiffness also recovered gradually over time. All injury groups demonstrated decreased intervertebral space and degeneration or even fusion in the small joints of the surgical segment or in adjacent segments. These results indicate that the body has the ability to repair the mechanical instability to a certain extent.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013;
• Article: Application of design rationale for a robotic system for single-incision laparoscopic surgery and natural orifice transluminal endoscopic surgery.

  Wei Yao, Peter Rn Childs
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  ABSTRACT: Current endoscopes and instruments are inadequate in some respects for complex intra-abdominal surgery because they are too flexible and cannot provide robust grasping and anatomic retraction. Minimal invasive surgery devices represent a sophisticated class of mechanical instruments making use of a range of mechanisms integrated into modular platforms that can be combined to undertake complex medical procedures. Although the machine elements concerned represent classic mechanical engineering devices, issues of miniaturization, surgical procedure compliance and location control conspire to present a design challenge. In order to capture, document and resolve the design requirements for this complex application, quality functional deployment has been applied in combination with design rationale, captured through issue-based information system mapping. This article reports the use of these tools to produce robot designs with improved dexterity and triangulation that are basic requirements in laparoscopy.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013;
• Article: Apparent elastic modulus of ex vivo trabecular bovine bone increases with dynamic loading.

  Juan Vivanco, Sylvana Garcia, Heidi L Ploeg, Gwen Alvarez, Diane Cullen, Everett L Smith
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  ABSTRACT: Although it is widely known that bone tissue responds to mechanical stimuli, the underlying biological control is still not completely understood. The purpose of this study was to validate required methods necessary to maintain active osteocytes and minimize bone tissue injury in an ex vivo three-dimensional model that could mimic in vivo cellular function. The response of 22 bovine trabecular bone cores to uniaxial compressive load was investigated by using the ZETOS bone loading and bioreactor system while perfused with culture medium for 21 days. Two groups were formed, the "treatment" group (n = 12) was stimulated with a physiological compressive strain (4000 µε) in the form of a "jump" wave, while the "control" group (n = 10) was loaded only during three measurements for apparent elastic modulus on days 3, 10, and 21. At the end of the experiment, apoptosis and active osteocytes were quantified with histological analysis, and bone formation was identified by means of the calcium-binding dye, calcein. It was demonstrated that the treatment group increased the elastic modulus by 61%, whereas the control group increased by 28% (p < 0.05). Of the total osteocytes observed at the end of 21 days, 1.7% (±0.3%) stained positive for apoptosis in the loaded group, whereas 2.7% (±0.4%) stained positive in the control group. Apoptosis in the center of the bone cores of both groups at the end of 21 days was similar to that observed in vivo. Therefore, the three-dimensional model used in this research permitted the investigation of physiological responses to mechanical loads on morphology adaptation of trabecular bone in a controlled defined load and chemical environment.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013;
• Article: Rotator cuff repair: A biomechanical ex vivo ovine study.

  Ilias Bisbinas, Evangelos Magnissalis, Ioannis Gigis, Theodoros Beslikas, Ippokratis Hatzokos, Ioannis Christoforidis
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  ABSTRACT: The purpose of this study was to assess load to failure of sutures, suturing techniques, and suture anchors used in rotator cuff surgery in order to explore their weaknesses. Ten types of sutures (absorbable and nonabsorbable), four types of suturing techniques, and eight types of suture anchors (bioabsorbable and metallic) were tested. Material Testing Machine and attached load cell were used to test the biomaterials in ex vivo ovine tissues. The results show that the mean load to failure and stiffness were higher in nonabsorbable sutures. Massive cuff tear and modified Mason-Allen suturing techniques had higher failure strength and stiffness when compared to simple and mattress techniques, but there was no substantial difference between them. Metallic suture anchors had higher failure strength when compared to bioabsorbable ones. Often either in metallic or in bioabsorbable anchors, the eyelet fails first. The failure sequence in ovine tissues is found to be in the following order: simple and mattress suturing techniques, nonabsorbable sutures, massive cuff tear and modified Mason-Allen suturing techniques, bioabsorbable anchors, and metallic anchors. Thus, it is concluded that metallic anchors mounted with modern nonabsorbable sutures will fail last. If we use simple and mattress techniques, the tendon-suture level will fail first, but it will improve substantially using more sophisticated suturing techniques (massive cuff tear or modified Mason-Allen).
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013; 227(5):560-70.
• Article: Using additive manufacturing in accuracy evaluation of reconstructions from computed tomography.

  Erin J Smith, Joseph A Anstey, Gabriel Venne, Randy E Ellis
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  ABSTRACT: Bone models derived from patient imaging and fabricated using additive manufacturing technology have many potential uses including surgical planning, training, and research. This study evaluated the accuracy of bone surface reconstruction of two diarthrodial joints, the hip and shoulder, from computed tomography. Image segmentation of the tomographic series was used to develop a three-dimensional virtual model, which was fabricated using fused deposition modelling. Laser scanning was used to compare cadaver bones, printed models, and intermediate segmentations. The overall bone reconstruction process had a reproducibility of 0.3 ± 0.4 mm. Production of the model had an accuracy of 0.1 ± 0.1 mm, while the segmentation had an accuracy of 0.3 ± 0.4 mm, indicating that segmentation accuracy was the key factor in reconstruction. Generally, the shape of the articular surfaces was reproduced accurately, with poorer accuracy near the periphery of the articular surfaces, particularly in regions with periosteum covering and where osteophytes were apparent.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013; 227(5):551-9.
• Article: Shortening of an anatomical stem, how short is short enough? An in vitro study of load transfer and primary stability.

  Per Olav Ostbyhaug, Jomar Klaksvik, Pål Romundstad, Arild Aamodt
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  ABSTRACT: An anatomical stem should be short enough to avoid distal locking and distal load transfer but long enough to ensure adequate primary stability of the stem. In this in vitro study, the cortical strains in the femur and the primary stability of the stem were measured after insertion of Anatomic Benoist Girard-I anatomical stems with gradually reduced stem length in six human cadaver femurs in order to find the optimal stem length. A shortening of 40-50 mm, corresponding to a stem extending 30-40 mm below the lesser trochanter, did not affect stem stability but nearly normalized the load distribution in the lower metaphysis and upper diaphysis. The large strain shielding observed in the calcar region was not influenced by shortening of the stem.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013; 227(5):481-9.
• Article: Effect of simplifications of bone and components inclination on the elastohydrodynamic lubrication modeling of metal-on-metal hip resurfacing prosthesis.

  Qingen Meng, Feng Liu, John Fisher, Zhongmin Jin
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  ABSTRACT: It is important to study the lubrication mechanism of metal-on-metal hip resurfacing prosthesis in order to understand its overall tribological performance, thereby minimize the wear particles. Previous elastohydrodynamic lubrication studies of metal-on-metal hip resurfacing prosthesis neglected the effects of the orientations of the cup and head. Simplified pelvic and femoral bone models were also adopted for the previous studies. These simplifications may lead to unrealistic predictions. For the first time, an elastohydrodynamic lubrication model was developed and solved for a full metal-on-metal hip resurfacing arthroplasty. The effects of the orientations of components and the realistic bones on the lubrication performance of metal-on-metal hip resurfacing prosthesis were investigated by comparing the full model with simplified models. It was found that the orientation of the head played a very important role in the prediction of pressure distributions and film profiles of the metal-on-metal hip resurfacing prosthesis. The inclination of the hemispherical cup up to 45° had no appreciable effect on the lubrication performance of the metal-on-metal hip resurfacing prosthesis. Moreover, the combined effect of material properties and structures of bones was negligible. Future studies should focus on higher inclination angles, smaller coverage angle and microseparation related to the occurrences of edge loading.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013; 227(5):523-34.
• Article: Comparative wear tests of ultra-high molecular weight polyethylene and cross-linked polyethylene.

  A P Harsha, Tom J Joyce
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  ABSTRACT: Wear particle-induced osteolysis is a major concern in hip implant failure. Therefore, recent research work has focussed on wear-resistant materials, one of the most important of which is cross-linked polyethylene. In view of this, the objective of this study was to compare the in vitro wear performance of cross-linked polyethylene to traditional ultra-high molecular weight polyethylene. In order to mimic appropriate in vivo conditions, a novel high-capacity wear tester called a circularly translating pin-on-disc was used. The results of this in vitro study demonstrated that the wear rate for cross-linked polyethylene was about 80% lower than that of conventional ultra-high molecular weight polyethylene. This difference closely matches in vivo results reported in the literature for total hip replacements that use the two biopolymers. The in vitro results were also verified against ASTM F732-00 (standard test method for wear testing of polymeric materials for use in total joint prostheses). The 50-station circularly translating pin-on-disc proved to be a reliable device for in vitro wear studies of orthopaedic biopolymers.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013; 227(5):600-8.
• Article: Distal stem features improve the torsional resistance of long-stem cemented revision hip stems: An in vitro biomechanical study.

  Timothy P Holsgrove, Timothy G Petheram, Anthony W Miles, Andrew J Timperley
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  ABSTRACT: When proximal bone stock is compromised at revision hip arthroplasty, distal fixation is often relied upon for stability of the femoral component. In such circumstances, torsional forces can result in debonding and loosening. This study compared the torsional behaviour of a cemented, polished and featureless (plain) stem with cemented, polished stems featuring fins or flutes. The finned stem construct was found to be significantly stiffer than the fluted stem. The maximum torque of the finned and fluted stems was significantly higher than the plain stem, with no difference between the finned and fluted stems. Distal stem features may provide a more reliable and greater resistance to torque in polished, cemented revision hip stems. Finned stem features may also increase the stiffness of the construct.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013; 227(5):503-9.
• Article: The use of muscle dynamometer for correction of muscle imbalances in the area of deep stabilising spine system.

  Renata Malátová, Jitka Rokytová, Jan Stumbauer
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  ABSTRACT: Dorsal pain caused by spine dysfunctions belongs to most frequent chronic illnesses. The muscles of the deep stabilising spine system work as a single functional unit where a dysfunction of only one muscle causes dysfunction of the whole system. Non-invasive, objective and statistically measurable evaluation of the condition of deep stabilising spine system has been made possible by the construction of muscular dynamometer. The aim of our work has been the assessment of deep stabilising spine system by diaphragm test and muscular dynamometer measurements. Based on an initial examination, a 6-week intervention programme was established including instructions on physiological body posture and correct basic body stabilisation for the given exercises and muscle strengthening. Consecutive measurements are then compared with the initial ones. It was presumed that a smaller number of the tested subjects would be able to correctly activate the deep stabilising spine system muscles before the intervention programme when compared to those after the intervention programme. A positive change of 87% has been found. It is clear that if a person actively approaches the programme, then positive adaptation changes on the deep stabilising spine system are seen only after 6 weeks. With the muscular dynamometer, activation of deep stabilising spine system can be objectively measured. Changes between the initial condition of a subject and the difference after some exercise or rehabilitation are especially noticeable. Also, the effect of given therapy or correct performance of the exercise can be followed and observed.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013;
• Article: Bone remodelling around uncemented metallic and ceramic acetabular components.

  Rajesh Ghosh, Kaushik Mukherjee, Sanjay Gupta
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  ABSTRACT: Stress shielding-induced bone resorption around cementless acetabular components has been indicated as a potential failure mechanism that may threaten long-term fixation. Using a bone remodelling algorithm in combination with three-dimensional finite element models of intact and implanted pelvises and musculoskeletal loading during normal walking, the objectives of the study were to investigate the deviations in load transfer due to implantation and bone adaptation around cementless metallic and ceramic acetabular components. Variations in implant-bone interfacial condition affected strain shielding and bone remodelling; strain shielding was higher for the bonded condition as compared to the debonded condition. For bonded interfacial condition, severe bone resorption, 20%-50% bone density reduction, was observed within the acetabulum. Considering debonded implant-bone interface, bone density increase of 50%-60% was observed around the supero-posterior part of acetabulum, whereas bone density reductions were low (2%-15%) in other locations. The implant-bone interface appeared less likely to fail, post-operatively and after bone remodelling. Moreover, the implant-bone micromotion was found to be low, less than 100 µm. Strain shielding and bone remodelling were almost similar for the metallic and ceramic components. Based on the results of this study, the ceramic acetabular component appeared to be a viable alternative to metal.
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013; 227(5):490-502.
• Article: Wear of 36-mm BIOLOX(R) delta ceramic-on-ceramic bearing in total hip replacements under edge loading conditions.

  Mazen Al-Hajjar, John Fisher, Joanne L Tipper, Sophie Williams, Louise M Jennings
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  ABSTRACT: Ceramic-on-ceramic bearings have become of great interest due to the substantial improvements in the manufacturing techniques and material properties and due to polyethylene wear debris-induced osteolysis and the issues with metal wear debris and ion release by metal-on-metal bearings. Edge loading conditions due to translational malpositioning (microseparation conditions) have been shown to replicate clinically relevant wear mechanisms and increase the wear of ceramic-on-ceramic bearings; thus, it was necessary to test new bearing materials and designs under these adverse conditions. The aim of this study was to assess the effect of increasing head size on the wear of BIOLOX(®) delta ceramic-on-ceramic bearings under edge loading conditions due to rotational (steep cup inclination angle) and translational (microseparation) malpositioning. In this study, six 36-mm ceramic-on-ceramic bearings (BIOLOX delta, CeramTec, Germany) were tested under standard and edge loading conditions using the Leeds II hip simulator and compared to the 28-mm bearings tested and published previously under identical conditions. The mean wear rate under standard gait conditions was below 0.1 mm(3)/million cycles for both the 28-mm and the 36-mm ceramic-on-ceramic bearings, and increasing the inclination angle did not affect the wear rates. The introduction of microseparation to the gait cycle increased the wear rate of ceramic-on-ceramic bearing and resulted in stripe wear on the femoral heads. Under microseparation conditions, the wear rate of size 36-mm bearings (0.22 mm(3)/million cycles) was significantly higher (p = 0.004) than that for size 28-mm bearings (0.13 mm(3)/million cycles). This was due to the larger contact area for the larger bearings and deprived lubrication under edge loading conditions. The wear rate of BIOLOX delta ceramic-on-ceramic bearings under microseparation conditions was still very low (<0.25 mm(3)/million cycles) compared to earlier generation ceramic-on-ceramic bearings (BIOLOX forte, 1.84 mm(3)/million cycles) and other bearing materials such as metal-on-metal bearings (2-8 mm(3)/million cycles).
  Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 05/2013; 227(5):535-42.