Biomedical subjects

E Hille

Publications and source records attributed to E Hille.

At least 19 recordsLinked to original sources

PubMed2006

Migration and cyclic motion of a new short-stemmed hip prosthesis--a biomechanical in vitro study.

BACKGROUND: Uncemented, short-stemmed hip prostheses have been developed to reduce the risk of stress shielding and to preserve femural bone stock. The long-term success of these implants is yet uncertain. Prerequisite for osseointegration is sufficient primary stability. In this study the cyclic motion and migration patterns of a new short-stemmed hip implant were compared with those for two clinically successful shaft prostheses. METHODS: The prostheses were implanted in paired fresh human femura and loaded dynamically (gait cycle) with increasing load (max 2,100 N) up to 15,000 cycles. Relative displacements between prosthesis and bone were recorded using a 3D-video analysis system. FINDINGS: The short stem displayed a biphasic migration pattern with stabilisation at maximum load. Initial migration was predominantly into varus and was greater than that for the shaft prostheses. Failure occurred in cases of poor bone quality and malpositioning. Cyclic motion of the short prosthesis was less than that for the shaft prostheses. Surface finish showed no effect. System stiffness for the new stem was lower than for the shaft prostheses. INTERPRETATION: The new stem tended to migrate initially more than the shaft prostheses, but stabilised when cortical contact was achieved or the cancellous bone was compacted sufficiently. Bone quality and correct positioning were important factors for the short stem. The lower cyclic motion of the new stem should be favourable for bony ingrowth. The lower system bending stiffness with the new implant indicated a more physiological loading of the bone and should thereby reduce the effects of stress shielding.

Adult↗

PubMed2005

[Comparison of total hip replacements cup orientation and position. Navigation vs. conventional manual implantation of hip prostheses].

BACKGROUND: Aim of this in-vitro study was to compare the hip cup placement for total hip replacement when using different navigation systems compared with the traditional, non-navigated technique. METHODS: Five different navigation systems were used: the CT-less systems Navitrack, Orthopilot and Surgetics Station, as well as the CT-based Navitrack and VectorVision. Three different surgeons carried out five cup implantations using all navigation systems and the manual approach on a surgery dummy. Cup orientation (inclination and anteversion) and the cup position (achieved cup center) were determined with a coordinate measuring machine. RESULTS: In the manual group the variability of the cup orientation was higher in comparison and hardly influenced by the surgeon. Navigation was identified as a significant factor for smaller deviations from planned inclination and anteversion angles (p<0,001 for both). Cup position was not affected by surgeon in the manual group (p=0,966). Compared with manual technique, the cup misplacement vector was significantly smaller in the CT-Navitrack group (p<0,001) but higher in the Navitrack (CT-less) and VectorVision group (p<0,001). CONCLUSIONS: The use of computer navigation will help the surgeon to orientate the acetabular component more accurately but not necessarily with regard to cup positioning.

Acetabulum↗

PubMed2003

[Laser-evoked potentials: diagnostic approach to the dorsal root].

Functional diagnostics of the dorsal root are especially effective via nociceptive fibers on account of less intersegmental overlap compared to large-diameter fibers of the mechanoreceptive afferents. Laser-evoked potentials (LEP) are induced by short, painful heat stimuli. The aim of this work was to describe changes of the LEP in cases of dorsal root damage. The recorded LEP changes will be discussed with regard to their prognostic value as well as pathophysiologic aspects of dorsal root damage. Dorsal root function was tested in 21 patients suffering from clinically proven radiculopathy in one of the segments L4 to S1. Mechanosensibility and thermosensibility were clinically investigated. LEP were induced by slightly painful stimuli (80 on the affected and 80 on the contralateral unaffected dermatome). The LEP were evaluated by amplitude of the averaged electroencephalogram (EEG). In addition, a subjective pain rating was recorded after each stimulus. Investigation of dorsal root function by LEP in patients with radiculopathy yields two typical changes of the amplitude. On the one hand, there were significant reductions of amplitude, and on the other hand, a complete loss of LEP was found. LEP changes allow a graduation of patients who show no obvious differences in their clinical appearance. Which mechanisms are responsible as concerns deafferentiation and neuropathy of the dorsal root fibers are discussed. With regard to the LEP changes, a prognostic relevance in patients with dorsal root affections is likely. This question will be addressed in a prospective study soon.

Adult↗

PubMed2001

The effect of interfacial parameters on cup-bone relative micromotions. A finite element investigation.

Achieving stability is a prerequisite for allowing bone to grow into the porous surface of non-cemented acetabular cups. The purpose of this study is to estimate the effects of interfacial characteristics on relative cyclical micromotion between cup and bone during gait in the immediate postoperative phase. The technique used is finite element analysis. Six models with different interfacial characteristics are created in order to study the effects of fixation technique. These include representation of a 1 mm press-fit, 2 mm press-fits (with and without an initial polar gap) and exact-fit conditions (with and without additional screw fixation). Although direct validation of the model has not been performed, the calculated micromotions under a static load of 1112 N are compared with appropriate experimental data. Generally, the model tends to underestimate micromotion and this underestimate is significant in the case of relative surface-normal micromotion in polar regions for models with low- and no-interference. The most likely cause of this significant underestimate is a failure of the model to accurately represent penetration of rough contacting surfaces under compression. Other types of micromotion, although low, are within standard deviations reported by Kwong et al. (1994 Journal of Arthroplasty 9, 163-170). Quasi-static joint contact and muscle forces, representative of the stance phase of gait are then applied and maximum micromotions are found to occur consistently prior to toe off: this being the point of maximum force. With regard to the press-fit simulations, good cup-bone contact in the superior region of the interface is required for stability and the greatest micromotions occur in the models with the larger interference and larger polar gaps. In contrast to the press-fit models, muscle activity in exact-fit models influences the calculations. Specifically, the early activity of m.semimembranosus modelled causes opening of the peripheral seal. Taken together it is found that polar gaps reduce the stability of the model and lack of pre-compresssion in the periphery allows this region of the interface to be opened up.

Acetabulum↗

PubMed2000

The use of water-jetting technology in prostheses revision surgery-first results of parameter studies on bone and bone cement.

Water-jet cutting techniques have been used in industrial applications for many different materials. Recently these techniques have been developed into a revolutionary cutting tool for soft tissues in visceral surgery. The present study investigates the usage of this cutting technology for the revision surgery of endoprostheses. In the first part of the study, samples of bovine bone and acrylic bone cement (PMMA) were cut using an industrial jet cutting device with pure water. Below 400 bar, only PMMA was cut; above 400 bar, bone was also cut, but only pressures above 800 bar resulted in clinically useful rates of material removal (cut depth 2. 4 mm at 10 mm/min traverse speed). In the second part of the study, the effect of adding biocompatible abrasives to the water in order to reduce the required pressure was investigated, resulting in a significantly higher removal of material. At 600 bar, PMMA was cut 5. 2 mm deep with plain water and 15.2 mm deep with added abrasives. The quality of the cuts was increased by the abrasive. Though there was no clear selectivity between bone and PMMA any more, the rate of material removal at similar pressures was significantly higher for PMMA than for bone (600 bar: 1.6 mm cut depth for bone samples, 15.2 mm for PMMA). The measured cut depths with either method were not influenced by a change of the cutting direction with respect to the main direction of the osteons in the bone. However, a reduction of the jet surface angle (90 degrees to 23 degrees ) resulted for bone in a significantly lower cut depth at 600 bar (plain water: 0.62 mm vs. 0.06 mm; abrasive: 1.61 mm vs. 0.60 mm). The laboratory experiments indicate that abrasive water jets may be suitable for cutting biomaterials like bone and bone cement.

Analysis of Variance↗

PubMed2000

Interfacial conditions between a press-fit acetabular cup and bone during daily activities: implications for achieving bone in-growth.

Interfacial gaps and relative micromotions during activities are widely believed to restrict the boney in-growth process of non-cemented acetabular cups. Using finite element modeling of the cup-bone system, relative micromotions and interfacial gaps are calculated for walking slow, normal and fast and for climbing upstairs, downstairs and standing up from a chair. A 2mm press-fit is simulated and interfacial conditions in the immediate postoperative period (i.e. prior to boney in-growth) calculated between paired nodes covering the whole of the interface. In regions of 'safe' micromotions and 'allowable' gaps, boney in-growth is simulated by specifying zero relative displacement between nodal pairs. The modified model is then resubjected to the loads associated with climbing upstairs, which was shown to be the worst activity. Interfacial conditions are recalculated for subsequent iterations. The procedure is repeated until no further in-growth is predicted. The final pattern of in-growth calculated with the model compares reasonably well with histological evidence from explanted canine cups (Cha et al., 1998. Transactions of the Orthopaedic Research Society, 23, p. 373). Bridging between adjacent regions of in-growth is observed. Notably, in-growth occurs at most of the periphery but not in the polar region. The lack of polar in-growth is caused by the interfacial gap assumed to exist after cup implantation. It is suggested that increasing/decreasing hip-joint loads would have little effect on this lack of polar in-growth. However, excessive micromotions as a result of high hip-joint loads cause a lack of in-growth in the anterior region of the periphery in the model. Although such results were not found in the canine study, if relevant to the general human population, the avoidance of harsh weight-bearing activities may encourage complete peripheral in-growth but is speculated to do little for polar in-growth.

Acetabulum↗

PubMed2000

[Water jet cutting for bones and bone cement--parameter study of possibilities and limits of a new method].

Water jet techniques have been used in industrial cutting, drilling and cleaning applications for more than 30 years. Plain water is typically used for the cutting of non-metallic materials. The addition of abrasive substances to the stream allows almost any material to be cut. The first medical applications were reported in the early 1980s, when the water jet was used to cut organs. The present study investigates the use of water jet cutting technology for endoprosthesis revision surgery. Bone and PMMA (polymethylmethacrylate) samples were cut at different pressures using an industrial water jet cutting device. Using plain water at 400 bar, PMMA was cut selectively without damaging the bone; above 400 bar, bone was also cut, but the cutting depths in PMMA were significantly greater (p < 0.05). Adding a water-soluble abrasive disaccharide to the water results in a significantly higher removal rate for both materials (p < 0.05), but selectivity is lost, although the differences in cutting depth between the two materials was significant (p < 0.05). With an abrasive, the quality of the cut was better for both materials. The water jet technology--in particular the abrasive technique--can be used to cut biomaterials such as bone and bone cement. The diameter of the jet is a great advantage when working in the confined area at the prosthesis interface. The cutting process is essentially cold, thus eliminating a thermal effect, and the jet reaction forces are relatively low. Accurate manipulation of the hydro jet nozzle is possible both manually and by robot. The results obtained show that it is possible to remove prostheses with this cutting technique, rapidly and with little damage to the surrounding tissue. Problem areas are the development of sterile pumps and the "depth control" of the jet.

Animals↗

PubMed1999

The influence of friction and interference on the seating of a hemispherical press-fit cup: a finite element investigation.

The formation of gaps in the polar region of acetabular cups is seen as a drawback of press-fit fixation of non-cemented acetabular cups. Recent findings indicate a link between long-term polar gaps and the gaps present directly after implantation. In this study the process of press-fitting is simulated with a linear-elastic two-dimensional axisymmetric finite-element model. The aim of this paper is to investigate the possible importance of friction and interference on the formation of these gaps. A range of cup-bone friction coefficients (mu = 0.1-0.5) is assigned to the cup-bone interface in order to represent the unknown amount of friction occurring during press-fitting. The cup is modeled with a radius of 27 mm, whereas the radius of the cavity is varied between 26.50 and 26.75 mm, thus, creating 0.50 and 0.25 mm radial interference fits. The difference in cavity radius represents the discrepancy between the radius of the last-reamer-used and radius of the cavity it creates. The subchondral plate is considered as being completely removed during reaming. The effects of impact blows via the surgeon's mallet during surgery are modeled as a series of four load pulses, in which peak force is gradually increased from 0.5 to 4.0 kN. The effects of load removal as well as those of load application are investigated. On load application, the cup penetrates into the cavity, and on load removal, the cup rebounds. Depending on the friction, interference and load applied, the position of the cup after the load pulse is somewhere between its position at peak force and its position at the beginning of the pulse. Although the simplifications and conditions involved in the creation of the model necessitate caution when interpreting the results for all clinical cases, it is found that the seating of hemispherical cups in trabecular bone could be more satisfactory for intermediate values of friction (mu = 0.2-0.3) and smaller interference fits (0.25 mm).

Acetabulum↗

PubMed1998

Intramuscular pressure in the erector spinae and intra-abdominal pressure related to posture and load.

STUDY DESIGN: Intramuscular pressures in both Erectors Spinae and intra-abdominal pressures were measured during different holding tasks. OBJECTIVES: To investigate the potential for using intramuscular pressure measurements in both Erectors Spinae to better quantitate the role of muscles during different lifting tasks in vivo. SUMMARY OF BACKGROUND DATA: Intramuscular pressure and intra-abdominal pressure were measured previously under isometric and dynamic conditions. However, no previous study systematically has addressed the relation between intramuscular and intra-abdominal pressures and different loads, tasks, and postures. METHODS: Intramuscular and intra-abdominal were measured simultaneously with microtip pressure transducers in 10 healthy volunteers performing 24 different static holding tasks. Tasks included different weights (10 kg and 20 kg), postures (squat or back lift), and positions of the weight. RESULTS: Intramuscular pressures were dependent on posture. Kyphotic back posture produced intramuscular pressures of 120-130 mm Hg, compared with the 10-25 mm Hg produced when volunteers were in the erect position (P < 0.001). Holding a 10-kg weight at the thighs close to the body produced significantly (P < 0.001) lower intramuscular pressures (25-32 mm Hg) than that produced by holding it 25 cm in front of the body (47-56 mm Hg). In all tasks, intramuscular pressures were significantly higher with the 20-kg weight than with the 10-kg weight (P < 0.001). Highest values (> 300 mm Hg) were measured when the 20-kg weight was held in the kyphotic posture above the floor and 25 cm away from the body. CONCLUSIONS: Intramuscular pressure measurements in the erector spinae seem to be a valuable tool for quantitating the role of back muscles during different lifting tasks.

Abdomen↗

PubMed1998

[Effect of surface hardness of the femur head prosthesis on abrasive wear forces in pairing with polyethylene for artificial hip joints].

The problem of wear has become a major issue in total joint replacement. A correlation between biomaterial hardness and abrasive wear mechanisms may be assumed. To investigate the effect of hardness, cobalt-chromium (CoCr) femoral heads coated with hard amorphous-hydrogenated carbon (a-CH) were tested against uncoated heads under conditions of abrasive wear. The heads were paired with polyethylene (UHMWPE) discs in a ball-on-disc machine. The abrasive wear resistance of the heads increased with surface hardness, and qualitatively differing patterns of wear were observed on the UHMWPE surfaces, depending on the abrasive wear of the matching areas of the heads. Accordingly, when evaluating biomaterials for their suitability for use in total joint replacement, hardness should be considered one of the relevant factors among the material properties with an influence on wear.

Chromium Alloys↗

PubMed1994

[Function of the trunk musculature in elite rowers].

In sports medicine, disorders of muscle function and muscular imbalance play an important role in both risk of injury and lack of improvement. They are highly important for the trunk muscle function, since low back pain is one of the most common disorders of sportsmen and is usually diagnosed as "functional disorder" without further specification. Despite its relevance, little is known about the specific capabilities of trunk muscle function in elite sportsmen. This study describes the measurement of trunk muscle torque, velocity, endurance and coordination in elite sportsmen. The study was performed by clinical examination and an isoinertial testing device (ISOSTATION-B200, Isotechnologies, Hillsborough, NC, USA). The results of a study of 20 German elite male rowers are presented and the relevance of these results is discussed in respect of their implications for training and therapy in injured athletes. Mean torques in extension and flexion were 319 Nm and 295 Nm, respectively. Elite rowers were stronger in isometric torque in all planes compared to normals and other sports groups, such as tennis players and swimmers. The better the rowing performance was, the lower was the extension/flexion ratio, the coordination and the decrease in velocity during endurance testing. This testing procedure is a useful tool in the measurement of trunk performance in elite sportsmen.

Adult↗

PubMed1994

The analgesic effect of acupuncture in chronic tennis elbow pain.

The immediate analgesic effect of a single non-segmental acupuncture stimulation treatment on chronic tennis elbow pain was studied in a placebo-controlled single-blind trial completed by 48 patients. Before and after treatment, all patients were examined physically by an unbiased independent examiner. Eleven-point box scales were used [13] for pain measurement. Patients in the verum group were treated at non-segmental distal points (homolateral leg) for elbow pain following Chinese acupuncture rules, whereas patients in the placebo group were treated with placebo acupuncture avoiding penetration of the skin with an acupuncture needle. Overall reduction in the pain score was 55.8% (S = 2.95) in the verum group and 15% (S = 2.77) in the placebo group. After one treatment 19 out of 24 patients in the verum group (79.2%) reported pain relief of at least 50% (placebo group: six patients out of 24). The average duration of analgesia after one treatment was 20.2 h in the verum group (S = 21.54) and 1.4 h (S = 3.50) in the placebo group. The results are statistically significant (P < 0.01); they show that non-segmental verum acupuncture has an intrinsic analgesic effect in the clinical treatment of tennis elbow pain which exceeds that of placebo acupuncture.

Acupuncture Analgesia↗

PubMed1990

[The value of arthroscopic labrum stapling in anterior shoulder dislocation].

Shoulder luxations are common injuries in relation to sports. Isokinetic strength was evaluated in 24 patients on the average 1 year after performing arthroscopic stabilisation of an anterior shoulder luxation. Using the Merac (Universal Gym Equip., Cedar Rapids, Iowa, USA), test data were gathered on both shoulders in flexion-extension, abduction-adduction and in the supine 90 degrees abducted test position in external-internal rotation. Tests were performed at 60, 180 and 500 deg/sec. Means and standard deviations for peak torque, total work, peak torque to body weight ratios and agonist/antagonist ratios are presented. Our one year follow-up showed, that 82% of all patients were free from complaints and had almost the same data as on the non-operated shoulders. Arthroscopic stabilisation of anterior shoulder luxations in combination with intensive physiotherapy gave excellent results in most cases.

Adult↗

PubMed1990

[The "patellofemoral joint" problem].

In the differential diagnosis of femoropatellar joint disease, three conditions must be considered: (1) peripatellar irritation; (2) chondromalacia of the patella; (3) femoropatellar arthrosis. In approximately 90% of the cases, peripatellar irritation and chondromalacia of the patella can be kept under control by active extension and strengthening exercises for the femoral flexor and extensor musculature. In therapy-resistant cases, arthroscopic surgery can provide the opportunity to influence the pathological gliding process positively. The operative procedure is planned on the basis of clinical and radiological examinations and computed tomography investigations. Dysplasia of the patella, including a lax patella, not only requires lateral release, but also medial tightening whereas patellar insufficiency can be treated successfully by lateral release alone. In our new staging procedure, chondromalacia and femoropatellar arthrosis are differentiated. Stage III chondromalacia is simply smoothed out via arthroscopy. In the treatment of femoropatellar arthrosis, on the other hand, restitution of the cartilage defect is of most importance. The age of the patient and staging of the cartilage defect determine which therapeutic procedure is to be used. The "release" operations in the treatment of femoropatellar arthrosis serve to relieve the damaged cartilage area and depend on the axial positioning of the knee joint.

Arthroscopy↗

PubMed1989

[Chip fracture of the lateral tibial condyle--a roentgenologic sign of anterior cruciate ligament injury].

A case report serves as basis for describing the importance of the so-called chip fracture as the first roentgenological pointer to a rupture of the anterior cruciate ligament in a handball player. The paper discusses the biomechanical changes resulting from an ACL rupture and underlines the importance of early arthroscopic diagnosis or of arthroscopic surgery for regaining knee stability and for preventing secondary subsequent damage.

Adult↗

PubMed1988

Experimental stress-induced changes in growing long bones.

Animal experiments were carried out to determine what changes result from the controlled overloading of a bone. Forty-four guinea-pigs were used and a partial resection of the right ulna was done so that subsequently the radius would be overloaded. Exercise was carried out daily on a treadmill. The animals were divided into four groups and were sacrificed at varying intervals from 15 to 60 days. Morphometric studies indicated that there was an immediate stress-induced growth in thickness of the diaphysis, which also occurred in the metaphysis after some delay. Calculations were made to determine the stress-induced changes in the bone. The results showed that the geometry of the metaphysis and diaphysis was able to accommodate to sudden pressure, bending and torsional stresses. Autoradiography did not demonstrate increased mitoses in the overloaded bone, but the density of osteocytes was reduced compared to normal. This, with a simultaneous increase in bone weight, indicates that there is an increased production of intercellular substance by the existing osteocytes which give rise to hypertrophy.

Animals↗

PubMed1987

[Selective paralysis of the infraspinatus muscle, caused by compression of the infraspinatus branch of the supraspinatus muscle].

This is the case of a thirty-year-old athlete suffering from a painful right shoulder while moving and working with his right arm and showing a massive atrophy of his right infraspinatus muscle. After careful examination an isolated compression of the inferior branch of the suprascapular nerve was suspected. The entrapment of the nerve at the spinoglenoid notch by a large and hypertrophied ligament was demonstrated by an open revision.

Adult↗

PubMed1985

Pressure and contract-surface measurements within the femoropatellar joint and their variations following lateral release.

The Pressure Measurement Foil (PMF), of Prescale, developed by the Fuji company permits the determination of the contact surfaces and of the pressure pattern within the femoropatellar joint. We measured contact surfaces and pressure distribution between patella and femoral condyles at different degrees of knee joint flexion before and after a lateral release. At a external load of 1000 N, only 12% of patellar surfaces established contact in extension, which was increased to 25% on flexion of 120 degrees. Superimposition of all function-related contacts showed that contact was established with the entire patellar surface. With increasing degree of flexion the mean pressures across the pressure zones showed only minor variations, owing to the flexion- dependent enlargement of the contact surfaces. Lateral release does not influence articular mechanics; it was at least not possible to change the retropatellar pressure to any measurement extent by releasing the lateral patellar connection.

Biomechanical Phenomena↗