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Biomedical subjects

Nico Verdonschot

Publications and source records attributed to Nico Verdonschot.

At least 19 recordsLinked to original sources
PubMed2007

Comparison of techniques for correction of magnification of pelvic X-rays for hip surgery planning.

The aim of this study was to develop an accurate method for correction of magnification of pelvic x-rays to enhance accuracy of hip surgery planning. All investigated methods aim at estimating the anteroposterior location of the hip joint in supine position to correctly position a reference object for correction of magnification. An existing method-which is currently being used in clinical practice in our clinics-is based on estimating the position of the hip joint by palpation of the greater trochanter. It is only moderately accurate and difficult to execute reliably in clinical practice. To develop a new method, 99 patients who already had a hip implant in situ were included; this enabled determining the true location of the hip joint deducted from the magnification of the prosthesis. Physical examination was used to obtain predictor variables possibly associated with the height of the hip joint. This included a simple dynamic hip joint examination to estimate the position of the center of rotation. Prediction equations were then constructed using regression analysis. The performance of these prediction equations was compared with the performance of the existing protocol. The mean absolute error in predicting the height of the hip joint center using the old method was 20 mm (range -79 mm to +46 mm). This was 11 mm for the new method (-32 mm to +39 mm). The prediction equation is: height (mm) = 34 + 1/2 abdominal circumference (cm). The newly developed prediction equation is a superior method for predicting the height of the hip joint center for correction of magnification of pelvic x-rays. We recommend its implementation in the departments of radiology and orthopedic surgery.

Aged↗
PubMed2007

Finite element-based preclinical testing of cemented total hip implants.

We developed a finite element model to preclinically test cemented hip implants for damage accumulation, including cement crack formation, creep, and stem migration. Using this model, we simulated the mechanical failure processes of four cemented total hip arthroplasty implants (Lubinus SPII, Mueller Curved, Exeter and Charnley, all with known clinical results) during cyclic normal walking and stair-climbing loads. These four implants were selected to ascertain whether the simulation predicted greater damage development around clinically inferior stems, whether clinically inferior designs could be identified by an initial stress analysis without the prediction of cement damage, and whether the simulation could predict high implant subsidence rates in combination with minimal cement damage. Based on the predicted cement crack patterns and crack formation rates, the simulation correctly identified the clinically inferior implant designs. Based only on the initial stress analysis under a stair-climbing load, it was not possible to identify clinically inferior designs. High subsidence values and minimal cement damage were predicted for the Exeter implant, similar to clinical findings. Our findings suggest the simulation may be effective in differentiating between a range of implants and design features.

Bone Cements↗
PubMed2006

Biomechanical analysis of the percutaneous compression plate and sliding hip screw in intracapsular hip fractures: experimental assessment using synthetic and cadaver bones.

We compared the mechanical behaviour of osteosynthesis with the percutaneous compression plate (PCCP) compared with the standard osteosynthesis sliding hip screw (SHS) in intracapsular hip fractures. We created 10 stable and 10 unstable intracapsular hip fractures in 20 synthetic femurs. Each fracture was fixed with either the SHS or PCCP. In six pairs of cadaver femurs, we created unstable intracapsular hip fractures and fixed them with the SHS or PCCP, at random on the left or right side. All femoral heads were exposed to a cyclic, combined axial and torque load until failure. In each group, the PCCP resisted a significantly higher load than the SHS. Clinical prospective studies are needed to confirm these in vitro findings that the PCCP is more stable than the SHS.

Biomechanical Phenomena↗
PubMed2006

Asymmetrical total knee arthroplasty does not improve patella tracking: a study without patella resurfacing.

It is often suggested that patella tracking after total knee arthroplasty (TKA) with an asymmetrical patella groove is more physiological than with a symmetrical patella groove. Therefore, this study tried to address two questions: what is the effect of TKA on patella tracking, and is patella tracking after asymmetrical TKA more physiological than patella tracking after symmetrical TKA? The patellar and tibial kinematics of five cadaveric knee specimens were measured in the intact situation, after the incision and suturing of a zipper, and after placement of a symmetrical TKA and an asymmetrical TKA, respectively. The patellae were not resurfaced. The flexion-extension kinematics were measured with an internal and external tibial moment to determine the envelope of motion (laxity bandwidth) of the tibio-femoral and patello-femoral articulation. The kinematics after TKA showed statistically significant changes in comparison to the intact situation: patellar medio-lateral translation, patellar tilt and tibial rotation were significantly affected. No statistically significant differences in knee kinematics were found between the symmetrical and the asymmetrical TKAs. We conclude that conventional TKA significantly changes physiological patello-femoral kinematics, and TKA with an asymmetrical patella groove does not improve the non-physiological tracking of the patella.

Arthroplasty, Replacement, Knee↗
PubMed2006

Larger bone graft size and washing of bone grafts prior to impaction enhances the initial stability of cemented cups: experiments using a synthetic acetabular model.

BACKGROUND: Bone defects after failed total hip arthroplasty can be reconstructed with impacted morselized bone grafts and a cemented cup. On the acetabular side, the effects on initial cup stability of washing bone grafts prior to impaction and bone graft size remain unclear. Related to these variables, cement penetration and inter-particle shear resistance have been suggested to be critical factors to ensure initial cup stability. METHODS: Using a synthetic acetabular model, we studied the effects of (1) washing bone grafts prior to impaction, and (2) bone graft size on the initial stability of cemented cups. In addition, cement penetration was measured using CT scans. RESULTS: Reconstructions with large, washed bone grafts provided the highest stability during mechanical compression and in a lever-out situation. Washing of the bone grafts had a positive effect on initial cup stability, but the size of the bone grafts appeared to be more important. Cement penetration was affected by bone graft size but not by washing. INTERPRETATION: From a mechanical standpoint, large bone grafts that have been washed prior to impaction may be preferable in order to obtain optimal cup stability using the bone impaction grafting technique.

Acetabulum↗
PubMed2006

Press-fit stability of an osteochondral autograft: Influence of different plug length and perfect depth alignment.

BACKGROUND: Osteochondral autologous transplantation is used for the treatment of full-thickness articular cartilage lesions of a joint. Press-fit stability is an important factor for good survival of the transplanted plugs. MATERIAL AND METHODS: 36 plugs of three different lengths were transplanted in fresh-frozen human knees. On one condyle, 3 plugs were exactly matched to the depth of the recipient site ("bottomed" plugs) and on the opposite condyle 3 plugs were 5 mm shorter than the depth of the recipient site ("unbottomed" plugs). Plugs were left protruding and then pushed in until flush, and then to 2 mm below flush level, using a loading apparatus. RESULTS: Longer plugs needed higher forces to begin displacement. At flush level, bottomed plugs needed significantly higher forces than unbottomed plugs to become displaced below flush level (mean forces of 404 N and 131 N, respectively). Shorter bottomed plugs required higher forces than longer bottomed ones. INTERPRETATION: Bottomed plugs generally provide much more stability than unbottomed ones. Short bottomed plugs are more stable than long bottomed plugs. Thus, in clinical practice it is advisable to use short bottomed plugs. If, however, unbottomed plugs are still chosen, the longer the plug the higher the resulting stability will be because of higher frictional forces.

Biomechanical Phenomena↗
PubMed2006

Correction of error in two-dimensional wear measurements of cemented hip arthroplasties.

The irregularity of individual wear patterns of total hip prostheses seen during patient followup may result partially from differences in radiographic projection of the components between radiographs. A method to adjust for this source of error would increase the value of individual wear curves. We developed and tested a method to correct for this source of error. The influence of patient position on validity of wear measurements was investigated with controlled manipulation of a cadaveric pelvis. Without correction, the error exceeded 0.2 mm if differences in cup projection were as small as 5 degrees. When using the described correction method, cup positioning differences could be greater than 20 degrees before introducing an error exceeding 0.2 mm. For followup of patients in clinical practice, we recommend using the correction method to enhance accuracy of the results.

Arthroplasty, Replacement, Hip↗
PubMed2006

Femoral component revision with use of impaction bone-grafting and a cemented polished stem. Surgical technique.

BACKGROUND: The purpose of this study was to evaluate the clinical and radiographic outcomes of revision of the femoral component of a hip arthroplasty with use of an impaction bone-grafting technique and a cemented polished stem. METHODS: Thirty-three consecutive femoral reconstructions that were performed between March 1991 and February 1996 with use of the X-change femoral revision system, fresh-frozen morselized allograft, and a cemented polished Exeter stem were followed prospectively. Femoral bone stock defects were classified according to the Endoklinik classification. The average age of the patients at the time of the femoral component revision was sixty-three years. No patient was lost to follow-up, which was performed at a minimum of eight years, but eight patients had died. None of the deaths was related to the surgery. RESULTS: No femoral reconstruction had been rerevised at a mean of 10.4 years postoperatively. There was one unrecognized intraoperative fracture, which healed following nonoperative treatment. There were three postoperative femoral fractures, all through cortical defects at the level of the tip of the prostheses. All fractures healed after plate fixation, and all femoral implants were left in situ. The average subsidence of the stem within the cement mantle was 3 mm; seven stems migrated 5 mm. The average Harris hip score improved from 49 points prior to surgery to 85 points (range, 68 to 100 points) at the time of this review. Subsidence did not affect the Harris hip score. Kaplan-Meier analysis, with an end point of femoral revision for any reason, showed a survival rate of 100% (one-sided 95% confidence interval, 100% to 91.3%). CONCLUSIONS: Femoral revision with use of an impaction bone-grafting technique and a cemented polished stem resulted in an excellent prosthetic survival rate at eight to thirteen years postoperatively. The major problem that occurred was a femoral fracture in four patients.

Adult↗
PubMed2005

The use of a bioresorbable nano-crystalline hydroxyapatite paste in acetabular bone impaction grafting.

Calcium phosphates such as TCP-HA granules are considered promising bone graft substitutes. In the future, they may completely replace allograft bone for impaction grafting procedures. Mechanically, acetabular reconstructions with TCP-HA granules show high stability, however this is partly caused by excessive cement penetration, which is unfavourable from a biological perspective. It has been hypothesised that mixtures of morselised cancellous bone grafts (MCB) and/or TCP-HA granules with a nano-crystalline hydroxyapatite paste (Ostim) may reduce cement penetration while maintaining adequate implant stability and biocompatibility of the graft mixture. To investigate this hypothesis, destructive lever-out tests and in vivo animal test were performed with various combinations of materials. Mechanically, the addition of 10% Ostim to mixtures of MCB and/or TCP-HA granules reduced cement penetration and resulted in a mechanical stability comparable to pure allograft (the current gold standard). Biologically, the application of Ostim with MCB or TCP-HA granules did not hamper the biocompatibility of the materials. Ostim was mostly osseous-integrated with MCB or TCP-HA granules after 8 weeks. Also, non-osseous-integrated Ostim remnants were observed. In tartrate resistant acid phosphatase stained sections, these few non-osseous integrated Ostim remnants were actively being resorbed by osteoclasts. In conclusion, Ostim HA-paste could be a valuable addition when TCP-HA ceramic granules are being used for acetabular bone impaction grafting procedures.

Absorbable Implants↗
PubMed2005

ACL graft can replicate the normal ligament's tension curve.

UNLABELLED: The anatomical femoral insertion of the normal anterior cruciate ligament (ACL) lies on the deep portion of the lateral wall of the intercondylar fossa. Following the deep bone-cartilage border, it stretches from 11 o'clock high in the notch all the way down to its lowest border at 8 o'clock. The tension curve of the normal ACL during passive flexion-extension shows a characteristic pattern with two tension peaks, one in full extension and the other in deep flexion. Low tension in mid-flexion is measured between those two peaks. Standard ACL reconstructions use a femoral insertion at 11 o'clock, which results in non-physiological tension curves with one peak in full extension only. The hypothesis was that it is possible to reproduce the typical tension curve of the normal ACL by placing the femoral tunnel into the low part of the normal ACL footprint. In a controlled laboratory study, three different femoral tunnel positions at 9, 10 and 11 o'clock were tested in four cadaver knees while using the identical standard tibial tunnel each time. The tension curve was measured during passive flexion-extension with a custom-made tension measurement device, using an artificial Dacron graft. The tension curve of grafts in the 9 o'clock tunnels showed the characteristic pattern of the normal ACL's tension curve with tension peaks in extension as well as in deep flexion. The tunnels in the 10 and 11 o'clock positions failed to reproduce the normal ACL's tension curve with high-tension values in extension only. CLINICAL RELEVANCE: If an ACL graft is placed low within the normal femoral footprint, the physiological tension curve of the normal ACL can be reproduced.

Aged↗
PubMed2005

The remains of anterior cruciate ligament graft tension after cyclic knee motion.

BACKGROUND: There is sometimes a return of excess knee laxity after anterior cruciate ligament reconstruction. One of the contributing factors might be a loss in graft tension. It is unknown whether the tension imposed on an anterior cruciate ligament graft degrades with time and, if so, the effect of that loss of tension on knee laxity. HYPOTHESES: The pretension in the anterior cruciate ligament graft reduces significantly within the first 500 motion cycles, and this decrease in graft tension causes an increase in knee laxity. STUDY DESIGN: Controlled laboratory study. METHODS: This study measured the remains of bone-patellar tendon-bone graft pretension after cyclical flexion-extension and the effect of any tension loss on knee laxity, using 8 cadaveric knees. A tension transducer was inserted into the graft and calibrated in situ. The reconstruction tension was 40 N at 20 degrees of flexion. In test 1, the graft tension was measured under cyclical flexion-extension in a motorized rig up to 1500 cycles. Test 2, with a new graft, also included anteroposterior and internal-external rotational knee laxity measurements at 0, 500, and 1500 cycles. RESULTS: The graft tension at 0 degrees of flexion dropped from 208 N, by 25% after 50 cycles, 41% by 500, and 46% by 1500 cycles. Anterior laxity increased from +1.4 to +2.8 mm by 500 cycles, and performing these laxity tests also caused significant tension losses. CLINICAL RELEVANCE: These results provide one possible explanation for early slackening of anterior cruciate ligament reconstructions.

Aged↗
PubMed2005

Accuracy and initial stability of open- and closed-wedge high tibial osteotomy: a cadaveric RSA study.

We analyzed the difference in angle-correction accuracy and initial stability between open-wedge (OWO) and closed-wedge tibial valgus osteotomy (CWO). Five fresh-frozen pairs of human cadaver lower limbs were used; their bone mineral density (BMD) was measured with DEXA and a planned 7 degrees valgus osteotomy was performed, either with an open (right knees) or closed (left knees) technique. All knees for osteotomy were fixed with a rigid locked plate. In OWO, tricalcium phosphate (TCP) wedges were inserted. The knees were subjected to an increasing cyclic axial load until failure, while measuring the relative displacement of the bony segments with roentgen stereophotogrammetric analysis. The mean postoperative valgus correction angle was 9.5 degrees +/-2.8 degrees for CWO (over-correction of 2.5 degrees ) and 6.2 degrees +/-2.0 degrees for OWO (under-correction of 0.8 degrees ) (P =0.08). The data of displacement under load bearing showed no significant differences in rotations and translations in any direction. No significant correlation between BMD and the moment of failure was found (P =0.27). This study has shown that both methods gave an acceptable correction with a high variation of postoperative correction angles. There was a tendency for over-correction in the CWO group but no significant difference was found. There was no difference in initial stability between CWO and OWO with a rigid locked-plate fixation.

Bone Plates↗
PubMed2005

The accuracy of measuring the kinematics of rising from a chair with accelerometers and gyroscopes.

The purpose of this study was to assess the accuracy of measuring angle and angular velocity of the upper body and upper leg during rising from a chair with accelerometers, using low-pass filtering of the accelerometer signal. Also, the improvement in accuracy of the measurement with additional use of high-pass filtered gyroscopes was assessed. Two uni-axial accelerometers and one gyroscope (DynaPort) per segment were used to measure angles and angular velocities of upper body and upper leg. Calculated angles and angular velocities were compared to a high-quality optical motion analysis system (Optotrak), using root mean squared error (RMS) and correlation coefficient (r) as parameters. The results for the sensors showed that two uni-axial accelerometers give a reasonable accurate measurement of the kinematics of rising from a chair (RMS = 2.9, 3.5, and 2.6 degrees for angle and RMS = 9.4, 18.4, and 11.5 degrees /s for angular velocity for thorax, pelvis, and upper leg, respectively). Additional use of gyroscopes improved the accuracy significantly (RMS = 0.8, 1.1, and 1.7 degrees for angle and RMS = 2.6, 4.0 and 4.9 degrees /s for angular velocity for thorax, pelvis and upper leg, respectively). The low-pass Butterworth filter had optimal cut-off frequencies of 1.05, 1.3, and 1.05 for thorax, pelvis, and upper leg, respectively. For the combined signal, the optimal cut-off frequencies were 0.18, 0.2, and 0,38 for thorax, pelvis and upper leg, respectively. The filters showed no subject specificity. This study provides an accurate, inexpensive and simple method to measure the kinematics of movements similar to rising from a chair.

Acceleration↗
PubMed2005

The contradictory effects of pores on fatigue cracking of bone cement.

The beneficial effect of porosity reduction on the fatigue life of bone cement has been demonstrated in numerous experimental studies. Clinically, however, it seems that the beneficial effect of porosity reduction of cement around total hip replacement components can only be found in large follow-up studies. Little is known about the actual mechanical effect of a pore on fatigue crack formation in cement mantles. We studied the effect of pores on the crack formation process in a finite element model of a transverse slice of a total hip reconstruction. We created models with a single large pore and models with multiple pores at levels of 2, 4, and 9%. The models were cyclically torque-loaded, causing macrocracks to appear in the cement mantle. In all models, we found that pores acted as microcrack initiators. However, pores could have both a detrimental and a beneficial effect on the macrocrack propagation in the cement mantle. Both effects were seen in the models with a single large pore and in the models with multiple pores. Pores would either accelerate, deviate, or decelerate the macrocrack propagation in the cement mantle. The effect of the pores depended on the location of the pores with respect to the stress intensities in the model, but was independent of the pore size or the level of porosity. The results may explain why the beneficial effect of vacuum mixing is difficult to demonstrate clinically. Stress intensities that are present in a cement mantle in an in vivo situation may overshadow the detrimental effect of a pore, while the beneficial effect may become more pronounced.

Bone Cements↗
PubMed2005

No negative effects of bone impaction grafting with bone and ceramic mixtures.

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 cancellous bone grafts using the bone impaction grafting technique. Subsequently, a cemented total hip prosthesis was inserted. Clinically, no differences were observed between groups. Most of the morselized cancellous bone graft had been resorbed and incorporated into new bone after 15 weeks. The large tricalcium phosphate-hydroxyapatite granules were integrated, the smaller crushed tricalcium phosphate-hydroxyapatite granules were surrounded by osteoclasts or engulfed by macrophages and giant cells. The cement penetration into the reconstructive layer and the quality of the bone based on a semiquantitative score were similar in both groups. We found no suggestion of tricalcium-hydroxyapatite granule-induced third-body wear in this short-term followup study. No negative effects were observed in this study, and therefore, it seems reasonable to use tricalcium-hydroxyapatite granules in a 50/50% volume mix with morselized cancellous bone graft as a bone graft extender in acetabular revision surgery with the bone impaction grafting technique.

Acetabulum↗
PubMed2005

The normal anterior cruciate ligament as a model for tensioning strategies in anterior cruciate ligament grafts.

BACKGROUND: 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. HYPOTHESIS: 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. STUDY DESIGN: Controlled laboratory study. METHODS: 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 10 degrees of knee flexion and resulted in a baseline curve. This curve was compared with the results recorded when the starting point was below the baseline curve, similar to, or above it. RESULTS: The anterior cruciate ligament showed low tension close to slackness in midflexion after starting with 10 N at 10 degrees of flexion. Starting points below the baseline curve shifted the whole curve downward; those above the baseline curve increased the force in the anterior cruciate ligament, resulting in a tight anterior cruciate ligament in midflexion. CLINICAL RELEVANCE: The normal anterior cruciate ligament shows a physiological laxity in midflexion. This study gives guidelines for tensioning protocols in anterior cruciate ligament grafts to replicate the force-flexion curve characteristics of the normal anterior cruciate ligament.

Aged↗
PubMed2005

Femoral component revision with use of impaction bone-grafting and a cemented polished stem.

BACKGROUND: The purpose of this study was to evaluate the clinical and radiographic outcomes of revision of the femoral component of a hip arthroplasty with use of an impaction bone-grafting technique and a cemented polished stem. METHODS: Thirty-three consecutive femoral reconstructions that were performed between March 1991 and February 1996 with use of the X-change femoral revision system, fresh-frozen morselized allograft, and a cemented polished Exeter stem were followed prospectively. Femoral bone stock defects were classified according to the Endoklinik classification. The average age of the patients at the time of the femoral component revision was sixty-three years. No patient was lost to follow-up, which was performed at a minimum of eight years, but eight patients had died. None of the deaths was related to the surgery. RESULTS: No femoral reconstruction had been rerevised at a mean of 10.4 years postoperatively. There was one unrecognized intraoperative fracture, which healed following nonoperative treatment. There were three postoperative femoral fractures, all through cortical defects at the level of the tip of the prostheses. All fractures healed after plate fixation, and all femoral implants were left in situ. The average subsidence of the stem within the cement mantle was 3 mm; seven stems migrated > or =5 mm. The average Harris hip score improved from 49 points prior to surgery to 85 points (range, 68 to 100 points) at the time of this review. Subsidence did not affect the Harris hip score. Kaplan-Meier analysis, with an end point of femoral revision for any reason, showed a survival rate of 100% (one-sided 95% confidence interval, 100% to 91.3%). CONCLUSIONS: Femoral revision with use of an impaction bone-grafting technique and a cemented polished stem resulted in an excellent prosthetic survival rate at eight to thirteen years postoperatively. The major problem that occurred was a femoral fracture in four patients.

Adult↗