Nico Verdonschot | Radboudumc Nijmegen - The Netherlands (original) (raw)

Papers by Nico Verdonschot

Journal of Biomedical Materials Research, 2001

In reconstructive surgery human bone defects are sometimes filled with the use of the impaction b... more In reconstructive surgery human bone defects are sometimes filled with the use of the impaction bone grafting technique. Currently different types of biomaterial particles are being developed as bone-substitute materials. Before these biomaterials can be applied their mechanical and biological behavior should be characterized. In this study the timedependent mechanical behavior of biomaterial particles with different tri-calcium-phosphate/ hydroxy-apatite (TCP:HA) ratios, particle sizes, and porosities is determined and compared to the behavior of human bone grafts, the latter being the standard material currently used to augment bone defects. The mechanical properties were assessed with the use of dynamic confined compression creep tests with a loading and unloading phase. Different graft material groups were tested, consisting of 100% human bone grafts, 100% biomaterial particles, and 50:50 weight mixtures of human grafts and biomaterial particles. No damage to the particles was observed by the impaction in the test chamber or by the dynamic load. Relative to the human graft material, the biomaterial particles hardly deformed under loading, were much stiffer, and showed almost no viscoelastic behavior. The mixtures showed intermediate results. Particle size and porosity influenced the behavior of the biomaterial particles. TCP:HA ratio did not have a great effect. The conclusion is that the application of these particles should be done with great care, as their mechanical behavior is drastically different than that of the human graft material. Mixing it with human bone grafts gave the material some biphasic, viscoelastic behavior that may be important for its biological response.

The American Journal of Sports Medicine

There is some confusion about the relationship between the tension placed on the graft and the jo... more There is some confusion about the relationship between the tension placed on the graft and the joint position used in the fixation of anterior cruciate ligament grafts. This is because of deficiency in accurate basic science about this important interaction in the normal and reconstructed anterior cruciate ligament. If the normal femoral attachment of the anterior cruciate ligament can be preserved and the tibial insertion isolated and tested, an accurate force-flexion curve of the human anterior cruciate ligament can be mapped out and used as a standard for proper graft tensioning protocols in anterior cruciate ligament reconstruction. Controlled laboratory study. In 10 fresh-frozen human cadaveric knees, an isolated bone plug containing the tibial anterior cruciate ligament insertion was connected with a custom-made tensiometer. The knees were moved through the whole range of motion; the starting point chosen was an anterior cruciate ligament tension of 10 N, which was applied at ...

Acta orthopaedica Belgica, 2004

During total hip arthroplasty the final clinical position of the cementless CLS stem (Centerpulse... more During total hip arthroplasty the final clinical position of the cementless CLS stem (Centerpulse) is not always identical to the position of the final rasp with which a successful trial reduction was performed. Therefore, the rasp-stem correspondence of CLS system (Centerpulse) was investigated in a laboratory study and compared to the CBC-T system (Mathys). Both systems showed an average rasp-stem mismatch below 2 mm in three orthogonal directions. It was found that this mismatch related to geometric differences at the corners between rasp and stem. The measured mismatch is not expected to have adverse clinical consequences.

Bio-medical materials and engineering, 2015

There is considerable interest to develop accurate subject-specific biomechanical models of the k... more There is considerable interest to develop accurate subject-specific biomechanical models of the knee. Most of the existing models currently do not include a representation of the posterior knee capsule. In order to incorporate the posterior capsule in knee models, data is needed on its mechanical properties. To quantify the mechanical properties of the human posterior knee capsule through semi-static tensile tests. Fifteen posterior knee capsule specimens (5 knees, 3 male, 2 female; age 79.2±7.9 years) were used to perform tensile tests. A medial, central and lateral specimen was taken from each knee. The cross-sectional area was measured, after which semi-static tensile tests were performed to quantify the material properties. The stiffness of the capsule was randomly distributed over the regions. The global Young's modulus and yield strength was 8.58±10.77 MPa and 1.75±1.89 MPa, respectively. A strong correlation (ρ=0.900) was found between Young's modulus and yield streng...

$Research paper thumbnail of Towards clinical application of biomechanical tools for the prediction of fracture risk in metastatic bone disease$

Journal of biomechanics, Jan 18, 2015

Current clinical practice lacks an accurate predictor for the pathological fracture risk in metas... more Current clinical practice lacks an accurate predictor for the pathological fracture risk in metastatic bone disease, but biomechanical tools are under development to improve these predictions. In this paper we explain the limitations of currently used clinical guidelines and provide an overview of more objective and quantitative approaches that have been proposed for fracture risk assessment in metastatic bone disease. Currently, such mechanical models are as sensitive and specific as clinical guidelines, but there are a number of opportunities to further improve their predictive capacity. Hence, they are a promising tool to decrease the numbers of over- and undertreated patients.

Acta orthopaedica Belgica, 2002

Prosthetic migration has been identified as a marker for future revision of cemented total hip re... more Prosthetic migration has been identified as a marker for future revision of cemented total hip reconstructions. This could be tested at a pre-clinical stage with dynamic loading experiments. The purpose of this study was to assess the effects of resting periods, which are a considerable part of the daily activity cycle, on the migration characteristics of femoral cemented stems. Ten polished Exeter stems were implanted in composite femurs and loaded either with a continuous load or a discontinuous load. Continuous loading involved 345,600 loading cycles at 1 Hz, whereas the discontinuous loading involved loading at 1 Hz for 2.5 hours and a resting period of 21.5 hours for a period of four days. Hence, a total of 36,000 loading cycles were applied to these reconstructions. The subsidence patterns of the prostheses were considerably affected by the resting periods. The prostheses exhibited a step-wise migration pattern with migration steps of about 50 microns after every resting perio...

The Journal of Arthroplasty, 2015

We investigated the effect of surface morphology on the mechanical performance of uncemented femo... more We investigated the effect of surface morphology on the mechanical performance of uncemented femoral knee prosthesis. Eighteen implants were implanted on nine paired femurs and then pushed-off (left legs: a novel surface morphology; right legs: Porocoat as baseline). Bone mineral density (BMD) and anteroposterior dimension were not significantly different between groups. The insertion force was not significantly different, however, the loosening force was significantly higher in the novel group (P=0.007). BMD had a direct relationship with the insertion and loosening force (P&amp;amp;amp;amp;amp;amp;amp;lt;0.001). The effect of surface morphology on implant alignment was very small. We conclude that the surface properties create a higher frictional resistance, thereby providing a better inherent stability of implants featuring the novel surface morphology.

Journal of the Mechanical Behavior of Biomedical Materials, 2015

Initial fixation of press-fit implants depends on interference fit, surface morphology, and bone ... more Initial fixation of press-fit implants depends on interference fit, surface morphology, and bone material properties. To understand the biomechanical effect of each factor and their interactions, the pull-out strength of seven types of CoCrMo tapered implants, with four different interference fits, three different surface morphologies (low, medium and high roughness), and at two time points (0 and 30 min) were tested in trabecular bone with varying density. The effect of interference fit on pull-out strength depended on the surface morphology and time. In contrast with our expectations, samples with a higher roughness had a lower pull-out strength. We found a similar magnitude of bone damage for the different surface morphologies, but the type of damage was different, with bone compaction versus bone abrasion for low and high frictional surfaces, respectively. This explains a reduced sensitivity of fixation strength to bone mineral density in the latter group. In addition, a reduction in fixation strength after a waiting period only occurred for the low frictional specimens. Our study demonstrates that it is essential to evaluate the interplay between different factors and emphasizes the importance of testing in natural bone in order to optimize the initial stability of press-fit implants.

Femoral fractures within resurfacing implants have been associated with bone necrosis, possibly r... more 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 &amp;amp;amp;amp;amp;quot;cement filling&amp;amp;amp;amp;amp;quot; technique, and a thin mantle model, representing a high viscosity &amp;amp;amp;amp;amp;quot;cement packing&amp;amp;amp;amp;amp;quot; 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.

Journal of orthopaedic research : official publication of the Orthopaedic Research Society, Jan 9, 2014

In musculoskeletal modelling, several optimization techniques are used to calculate muscle forces... more In musculoskeletal modelling, several optimization techniques are used to calculate muscle forces, which strongly influence resultant hip contact forces (HCF). The goal of this study was to calculate muscle forces using four different optimization techniques, i.e., two different static optimization techniques, computed muscle control (CMC) and the physiological inverse approach (PIA). We investigated their subsequent effects on HCFs during gait and sit to stand and found that at the first peak in gait at 15-20% of the gait cycle, CMC calculated the highest HCFs (median 3.9 times peak GRF (pGRF)). When comparing calculated HCFs to experimental HCFs reported in literature, the former were up to 238% larger. Both static optimization techniques produced lower HCFs (median 3.0 and 3.1 pGRF), while PIA included muscle dynamics without an excessive increase in HCF (median 3.2 pGRF). The increased HCFs in CMC were potentially caused by higher muscle forces resulting from co-contraction of a...

Sarcoma, 2014

Accurate predictions of functional outcome after limb salvage surgery (LSS) in the lower limb are... more Accurate predictions of functional outcome after limb salvage surgery (LSS) in the lower limb are important for several reasons, including informing the patient preoperatively and, in some cases, deciding between amputation and LSS. This study aimed to elucidate the correlation between surgeon-predicted and patient-reported functional outcome of LSS in the Netherlands. Twentythree patients (between six months and ten years after surgery) and five independent orthopedic oncologists completed the Toronto Extremity Salvage Score (TESS) and the RAND-36 physical functioning subscale (RAND-36 PFS). The orthopedic oncologists made their predictions based on case descriptions (including MRI scans) that reflected the preoperative status. The correlation between patient-reported and surgeon-predicted functional outcome was "very poor" to "poor" on both scores ( 2 values ranged from 0.014 to 0.354). Patient-reported functional outcome was generally underestimated, by 8.7% on the TESS and 8.3% on the RAND-36 PFS. The most difficult and least difficult tasks on the RAND-36 PFS were also the most difficult and least difficult to predict, respectively. Most questions had a "poor" intersurgeon agreement. It was difficult to accurately predict the patient-reported functional outcome of LSS. Surgeons' ability to predict functional scores can be improved the most by focusing on accurately predicting more demanding tasks.

Clinical Orthopaedics and Related Research, 2003

Rigorous preclinical testing of cemented hip prostheses against the damage accumulation failure s... more Rigorous preclinical testing of cemented hip prostheses against the damage accumulation failure scenario will reduce the incidence of aseptic loosening. For that purpose, a finite element simulation is proposed that predicts damage accumulation in the cement mantle and prosthetic migration. If the simulation is to become a convincing preclinical test, it should be able to distinguish between implants in a clinically relevant way, based on accurate predictions of long-term failure mechanisms of cemented hip prostheses. The algorithm was used to simulate long-term fatigue experiments on femoral reconstructions with Mueller Curved and Lubinus SPII stems. Clinically, the Mueller Curved system performs inferior to the Lubinus SPII system. The finite element simulation predicted much more cement damage around the Mueller Curved stem and showed that the entire cement mantle was involved in the failure process, which was not the case around the Lubinus SPII stem. In addition, the Mueller Curved stem was predicted to migrate more than the Lubinus SPII. The predictions showed excellent agreement with the experimental findings: similar damage locations in the cement, more damage for the Mueller Curved, similar prosthetic migration directions, and more migration for the Mueller Curved stem. This is the first time that a finite element simulation is able to differentiate between a clinically superior and an inferior implant, based on accurate simulation of the long-term failure mechanisms in a cemented reconstruction. Its use for preclinical testing purposes is corroborated.

Acta Orthopaedica, 2001

We report a long-term review of 41 acetabular reconstructions using impacted morsellized bone gra... more We report a long-term review of 41 acetabular reconstructions using impacted morsellized bone grafts and a cemented total hip arthroplasty (THA) in patients younger than 50 (22-49; average 38) years. Reconstruction was performed in 23 primary THA (19 patients) and 18 revision THA (17 patients). 3 patients were lost to follow-up and 3 (4 hips) died within 10 years of surgery; none had a revision. Thus, 34 hips (30 patients) were reviewed with an average follow-up of 13 (10-18) years. In 2 hips, a revision was performed for aseptic loosening of the acetabular component 7 and 11 years after surgery. One additional cup was revised after 12 years during a femoral stem revision due to wear and matching problems, but was well fixed. The survival rate of the acetabular reconstruction technique was 94% (95% CI: 90-98%).

Clinical Orthopaedics and Related Research, 2005

Reconstructing large loaded bone defects with ceramic bone graft extenders is tempting considerin... more Reconstructing large loaded bone defects with ceramic bone graft extenders is tempting considering the expected future donor bone shortage. However, whether there are negative effects is unknown. Standardized large defects in the acetabulum of goats were created and subsequently reconstructed with metal mesh and impacted morselized cancellous bone grafts or a 50/50% volume mixture of tricalcium phosphate-hydroxyapatite granules and morselized

Journal of Bone and Joint Surgery-british Volume, 2000

The properties of impacted morsellised bone graft (MBG) in revision total knee arthroplasty (TKA)... more The properties of impacted morsellised bone graft (MBG) in revision total knee arthroplasty (TKA) were studied in 12 horses. The left hind metatarsophalangeal joint was replaced by a human TKA. The horses were then randomly divided into graft and control groups. In the graft group, a unicondylar, lateral uncontained defect was created in the third metatarsal bone and reconstructed using autologous MBG before cementing the TKA. In the control group, a cemented TKA was implanted without the bone resection and grafting procedure. After four to eight months, the animals were killed and a biomechanical loading test was performed with a cyclic load equivalent to the horse's body-weight to study mechanical stability. After removal of the prosthesis, the distal third metatarsal bone was studied radiologically, histologically and by quantitative and micro CT. Biomechanical testing showed that the differences in deformation between the graft and the control condyles were not significant for either elastic or time-dependent deformations. The differences in bone mineral density (BMD) between the graft and the control condyles were not significant. The BMD of the MBG was significantly lower than that in the other regions in the same limb. Micro CT showed a significant difference in the degree of anisotropy between the graft and host bone, even although the structure of the area of the MBG had trabecular orientation in the direction of the axial load. Histological analysis revealed that all the grafts were revascularised and completely incorporated into a new trabecular structure with few or no remnants of graft. Our study provides a basis for the clinical application of this technique with MBG in revision TKA.

Acta Orthopaedica, 2007

BACKGROUND: A medialization of the femoral component in a total knee arthroplasty (TKA) causes ab... more BACKGROUND: A medialization of the femoral component in a total knee arthroplasty (TKA) causes abnormal patellar tracking, which could result in patellar instability, pain, wear, and failure. Previous reports defined medialization in relation to the neutral position of the femoral component, but omitted to compare it to the anatomical position of the trochlea. We assessed intraoperatively whether there is a

$Research paper thumbnail of Retrograde bridging nail in periprosthetic femoral fracture treatment which allows direct weight bearing$

Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2008

The bridging nail is a retrograde intramedullary femoral nail designed to stabilize periprostheti... more The bridging nail is a retrograde intramedullary femoral nail designed to stabilize periprosthetic femoral fractures. It offers a minimal invasive surgical approach in combination with early mobilization. The goal of this study was to evaluate the osteosynthesis under full weight-bearing conditions. Three groups of five composite fibreglass femora were prepared with a cemented hip stem. Group 1 underwent cyclic axial loading with 1500 N during 150 000 cycles. After completion, linear loading to failure was conducted. Groups 2 and 3 were submitted to linear increased torsional loading with and without an axial load respectively. Failure was defined as rotational movement of the connection (slippage). In the axial cyclic loading configuration, one specimen failed after 122 000 cycles. Four specimens passed 150 000 cycles and failed after linearly increasing the axial loading of 1940-2600 N (mean, 2408 N +/- 313 standard deviation (SD)). Slippage was first detected at a torque varying between 2.5 and 8.2 Nm (mean, 5.1 Nm +/- 2.1 SD) in group 2 and between 10.0 and 15.4 Nm (mean, 13.0 N m +/- 2.3 SD) in group 3. In conclusion the bridging nail offers a stable connection with the stem of a hip arthroplasty which can resist high repetitive loads, representative of direct full axial weight bearing. The biomechanical results support the clinical experience of a stable osteosynthesis enabling early post-operative mobilization.

Physics in Medicine and Biology, 2010

Bone specific, CT-based finite element (FE) analyses have great potential to accurately predict t... more Bone specific, CT-based finite element (FE) analyses have great potential to accurately predict the fracture risk of deteriorated bones. However, it has been shown that differences exist between FE-models of femora scanned in a water basin or scanned in situ within the human body, as caused by differences in measured bone mineral densities (BMD). In this study we hypothesized that these differences can be reduced by re-creating the patient CT-conditions by using an anatomically shaped physical model of the lower body. BMD distributions were obtained from four different femora that were scanned under three conditions: (1) in situ within the cadaver body, (2) in a water basin and (3) in the body model. The BMD of the three scanning protocols were compared at two locations: proximally, in the trabecular bone of the femoral head, and in the cortical bone of the femoral shaft. Proximally, no significant differences in BMD were found between the in situ scans and the scans in the body model, whereas the densities from the water basin scans were on average 10.8% lower than in situ. In the femoral shaft the differences between the three scanning protocols were insignificant. In conclusion, the body model better approached the in situ situation than a water basin. Future studies can use this body model to mimic patient situations and to develop protocols to improve the performance of the FE-models in actual patients.

Orthopedic Clinics of North America, 2005

Medical Engineering & Physics, 2014

This study assessed whether the Symax™ implant, a modification of the Omnifit(®) stem (in terms o... more This study assessed whether the Symax™ implant, a modification of the Omnifit(®) stem (in terms of shape, proximal coating and distal surface treatment), would yield improved bone remodelling in a clinical DEXA study, and if these results could be predicted in a finite element (FE) simulation study. In a randomized clinical trial, 2 year DEXA measurements between the uncemented Symax™ and Omnifit(®) stem (both n=25) showed bone mineral density (BMD) loss in Gruen zone 7 of 14% and 20%, respectively (p&amp;amp;amp;amp;amp;amp;amp;lt;0.05). In contrast, the FE models predicted a 28% (Symax™) and 26% (Omnifit(®)) bone loss. When the distal treatment to the Symax™ was not modelled in the simulation, bone loss of 35% was predicted, suggesting the benefit of this surface treatment for proximal bone maintenance. The theoretical concept for enhanced proximal bone loading by the Symax™, and the predicted remodelling pattern were confirmed by DEXA-results, but there was no quantitative match between clinical and FE findings. This was due to a simulation based on incomplete assumptions concerning the yet unknown biological and mechanical effects of the new coating and surface treatment. Study listed under ClinicalTrials.gov with number NCT01695213.