Gait analysis in tumor patients after distal femoral resection and implantation of a megaprosthesis.

We analysed nine patients who had had a megaprosthesis implanted into the distal femur and knee joint for treatment of sarcomas. Data obtained from the leg operated on were compared with those from the contralateral side and healthy volunteers. Gait data, kinematics, ground reaction forces and the EMG from five muscles around the knee joint were analysed by means of a video-based analysis system recording data from reflection markers ; a Kistler-plate recorded the GRF and a ten channel surface EMG the muscle activity. Muscle around the knee showed a cocontraction between the extensor and flexor muscles in the thigh and the calf in the operated leg as well as contralaterally. Gait characteristics exhibited a reduced speed, -cadence, and a shorter step. This correlated with a reduced flexion in the hip and knee joint. The GRF exhibited significant changes in the data representing the reduced gait dynamic.

Hip contact forces and gait patterns from routine activities.

In vivo loads acting at the hip joint have so far only been measured in few patients and without detailed documentation of gait data. Such information is required to test and improve wear, strength and fixation stability of hip implants. Measurements of hip contact forces with instrumented implants and synchronous analyses of gait patterns and ground reaction forces were performed in four patients during the most frequent activities of daily living. From the individual data sets an average was calculated. The paper focuses on the loading of the femoral implant component but complete data are additionally stored on an associated compact disc. It contains complete gait and hip contact force data as well as calculated muscle activities during walking and stair climbing and the frequencies of daily activities observed in hip patients. The mechanical loading and function of the hip joint and proximal femur is thereby completely documented. The average patient loaded his hip joint with 238% BW (percent of body weight) when walking at about 4 km/h and with slightly less when standing on one leg. This is below the levels previously reported for two other patients (Bergmann et al., Clinical Biomechanics 26 (1993) 969-990). When climbing upstairs the joint contact force is 251% BW which is less than 260% BW when going downstairs. Inwards torsion of the implant is probably critical for the stem fixation. On average it is 23% larger when going upstairs than during normal level walking. The inter- and intra-individual variations during stair climbing are large and the highest torque values are 83% larger than during normal walking. Because the hip joint loading during all other common activities of most hip patients are comparably small (except during stumbling), implants should mainly be tested with loading conditions that mimic walking and stair climbing.

Musculo-skeletal loading conditions at the hip during walking and stair climbing.

Musculo-skeletal loading plays an important role in the primary stability of joint replacements and in the biological processes involved in fracture healing. However, current knowledge of musculo-skeletal loading is still limited. In the past, a number of musculo-skeletal models have been developed to estimate loading conditions at the hip. So far, a cycle-to-cycle validation of predicted musculo-skeletal loading by in vivo measurements has not been possible. The aim of this study was to determine the musculo-skeletal loading conditions during walking and climbing stairs for a number of patients and compare these findings to in vivo data. Following total hip arthroplasty, four patients underwent gait analysis during walking and stair climbing. An instrumented femoral prosthesis enabled simultaneous measurement of in vivo hip contact forces. On the basis of CT and X-ray data, individual musculo-skeletal models of the lower extremity were developed for each patient. Muscle and joint contact forces were calculated using an optimization algorithm. The calculated peak hip contact forces both over- and under-estimated the measured forces. They differed by a mean of 12% during walking and 14% during stair climbing. For the first time, a cycle-to-cycle validation of predicted musculo-skeletal loading was possible for walking and climbing stairs in several patients. In all cases, the comparison of in vivo measured and calculated hip contact forces showed good agreement.Thus, the authors consider the presented approach as a useful means to determine valid conditions for the analysis of prosthesis loading, bone modeling or remodeling processes around implants and fracture stability following internal fixation.

Computer navigation of parapedicular screw fixation in the thoracic spine: a cadaver study.

STUDY DESIGN: An in vitro study to investigate the advantages of computer assistance for the purpose of parapedicular screw fixation in the upper and middle thoracic spine. OBJECTIVES: To evaluate the feasibility and application accuracy of parapedicuar screw insertion with the assistance of an optoelectronic navigation system. SUMMARY OF BACKGROUND DATA: Because of anatomic limitations, thoracic pedicle screw insertion in the upper and middle thoracic spine remains a matter of controversy. The technique of parapedicular screw insertion has been described as an alternative, although the exact screw position is difficult to control. With the assistance of computer navigation for the screw placement, it might become possible to overcome these challenges. METHODS: Four human specimens were harvested for this study; 6-mm screws were inserted from T2 to T8 with the assistance of a CT-based optoelectronic navigation system. During surgery virtual images of the screw position were documented and compared with postoperative contact radiographs to determine the application accuracy. The following measurements were obtained: axial and sagittal screw angles as well as the screw distances to the anterior vertebral cortex and the medial pedicle wall. RESULTS: All 54 screws were inserted in a parapedicular technique without violation of the medial pedicle wall or the anterior or lateral vertebral cortex. The mean +/- standard deviation difference between the virtual images and the radiographs was 1.0 +/- 0.94 mm for the distance to the medial pedicle wall and 1.9 +/- 1.44 mm for the distance to the anterior cortex. The angular measurements showed a difference of 1.6 +/- 1.1 degrees for the transverse screw angle and 2.1 +/- 1.6 degrees for the sagittal screw orientation. CONCLUSION: With the assistance of computer navigation it is possible to achieve a safe and reliable parapedicular screw insertion in the upper and middle thoracic spine in vitro. The application accuracy varies for the linear and angular measurements and is higher in the axial than in the sagittal plane. It is important for the surgeon to understand these limitations when using computer navigation in spinal surgery.

Determination of the in vivo loading of the lumbar spine with a new approach directly at the workplace--first results for nurses.

OBJECTIVE: To determine the magnitude of workplace loading for nurses with and without a history of low back pain. DESIGN: A measurement system for the assessment of workplace loading as well as a model for the calculation of lumbo-sacral junction loading was designed and applied to a group of 12 nurses with and without a history of low back pain. BACKGROUND: Disagreement exists regarding the key factors in the aetiology of low back pain. Traditionally workplace loading is viewed as the dominant influence. Data for workplace loading in jobs with non-uniform tasks, however, do rarely exist. METHODS: A three-dimensional inverse-dynamic and force distribution model as well as the respective data acquisition system was used to assess the workplace loading of 12 nurses from surgical departments of two hospitals. The nurses were assigned to two groups based on their history of low back pain (with/without). Workplace loading was measured continuously for 4 h. RESULTS: No differences in workplace loading between nurses with/without a history of low back pain were found. Maximum values of the compressive force at the lumbo-sacral junction were high and well above suggested workplace load limits. High values occurred only during short-time periods (about 0.4% of total shift duration). CONCLUSIONS: A system for the assessment of overall workplace loading has been developed. First results for nurses suggest that critical loadings do exist at the workplace, even so they might not be the decisive factor for the development of low back pain. RELEVANCE: Preventative measures for low back pain in nursing have to include prevention of critical workplace loading. This approach by itself, however, is probably not sufficient.

Influence of femoral anteversion on proximal femoral loading: measurement and simulation in four patients.

OBJECTIVE: The aim of this study was to determine the loading of the proximal femur during daily activities and to quantify the influence of femoral anteversion. DESIGN: This study combined experimental and analytical approaches to determine the in vivo loading at the hip joint. A numerical musculo-skeletal model was validated against measured in vivo hip contact forces and then used to analyse the influence of anteversion on the loading conditions in the femur. BACKGROUND: Musculo-skeletal loading of long bones is essential for joint replacement and fracture healing. Although joint contact forces have previously been measured in selected patients, the interaction between femoral anteversion and the associated musculo-skeletal loading environment remains unknown. METHODS: The gait of four patients with force measuring hip prostheses was analysed during walking and stair-climbing. Musculo-skeletal loading was determined using individual numerical models by minimising the sum of the muscle forces. RESULTS: Experimentally and numerically determined hip contact forces agreed both qualitatively and quantitatively. Muscle activity resulted in compression of the femur and small shear forces in the meta- and epi-physeal regions. Increasing the anteversion to an angle of 30 degrees increased hip contact forces and bending moments up to 28%. CONCLUSIONS: This study has shown that femoral anteversion has a strong influence on the musculo-skeletal loading environment in the proximal femur. RELEVANCE: Detailed musculo-skeletal modelling may allow pre-surgical, patient specific optimisation of loading on implant, bone and soft tissues.

[A CAE (computer aided engineering) approach to dynamic whole body modeling--the forces iin the lumbar spine in asymmetrical lifting]. / Ein CAE-basierter Zugang zur dynamischen Ganzkörpermodellierung--Die Kräfte in der lumbalen Wirbelsäule beim asymmetrischen Heben.

Biomechanical models of the human body play an important role in the analysis of the mechanical loading of the musculo-skeletal system. The whole-body model presented in this paper is based on a CAE (Computer Aided Engineering) program that permits the dynamic simulation of complex systems of rigid bodies. The model we developed on this basis consisted of 19 segments and 18 joints. The experimental data are derived from the 3D motion analysis system VICON, which is provided with 5 cameras, a force-plate and a 10-channel EMG recorder. The kinematic data are fed into the simulator after first being processed in a special manner to generate drivers for joint angles. The model was first used to calculate the compression forces generated within the lumbar spine during the asymmetric lifting and putting down of a 15 kg stone. The quasistatic calculation shows a dynamic contribution to the compression forces generated during the lifting of 11%. Increasing or decreasing the inertial moments of the segments by the factor 2 had an effect of less than 1% with the identical movement.

[Tensile strength of bone fixation of hydroxyapatite coated Schanz screws of the Heidelberg External Fixation System (HEFS)--comparative torque measurements in clinical use and in cadaver tibia]. / Zur knöchernen Verankerungsfestigkeit hydroxylapatitbeschichteter Schanz-Schrauben des Heidelberg External Fixation Systems (HEFS)--Vergleichende Drehmomentmessungen im klinischen Einsatz und an der Leichentibia.

It is claimed in the literature that hydroxyapatite(HA)-coated screws of external fixators have superior fixation strength in bone, which is postulated to lead to a substantial decrease in loosening and infection rates. We report on a study of the maximum torque values developed while inserting and removing 30 HA-coated Schanz screws of 8 Heidelberg external fixation systems applied to the tibia to correct leg length differences and axial deformities. The infection rate was determined in accordance with defined criteria, and was found to be about 20% for the HA-coated screws. Screws without infection showed an extraction torque above insertion torque, screws with infection an extraction torque below. A significant correlation (p = 0.05) was seen between infection and decrease in fixation strength (quotient: loosening torque/tightening torque). To exclude the impact of such biological processes as osteointegration and bone remodelling, the clinical results were compared with the torques measured for coated and uncoated Schanz screws in a human cadaveric tibia. A significantly higher fixation strength in bone was found for HA-coated screws in comparison with uncoated screws (p = 0.002). These data warrant a clinical study directly comparing HA-coated and uncoated Schanz screws.

TNF-alpha alters visfatin and adiponectin levels in human fat.

Adiponectin and visfatin are newly discovered adipokines that are strongly expressed in human visceral adipose tissue. To identify new regulatory mechanisms in fat, the effect of TNF-alpha (TNF) on adiponectin, on its two receptors, and on visfatin was investigated by incubating human visceral adipose tissue from patients without diabetes mellitus with TNF for 24, 48 and 72 hours. The mRNA expression of visfatin, adiponectin, and its two receptors, as well as the protein expression of adiponectin were determined. A decrease of adiponectin mRNA expression of 97% after incubation with TNF (5.75 nmol/l) for 24 hours, a decrease of 91% after 48 hours, and a decrease of 96% after 72 hours were measured. The reduction of protein expression was measured to be 42% after 24 hours, 28% after 48 hours, and 39% after 72 hours of incubation with TNF (5.75 nmol/l). The mRNA level of adiponectin receptor 1 (AdipoR1) was elevated about 72% after 48 hours of incubation and 67% after 72 hours of incubation, whereas the mRNA expression of adiponectin receptor 2 (AdipoR2) was not altered significantly. The visfatin mRNA level was found to be highly increased by 255% after 24 hours and 335% after 48 hours and 341% after 72 hours of incubation with TNF (5.75 nmol/l). Our results support the concept of visceral adipose tissue as an endocrine organ. We demonstrate that TNF has regulatory functions on adiponectin, AdipoR1 and on visfatin in human visceral adipose tissue. TNF levels are elevated in states of obesity and insulin resistance. Due to this fact TNF could be the reason that there is a decrease in the level of adiponectin, whereas there is an increase in the level of visfatin in states of obesity and insulin resistance.

[Treatment of chronic plantar fasciitis with botulinum toxin A--an open pilot study on 25 patients with a 14-week-follow-up]. / Behandlung der chronischen Plantarfasziitis mit Botulinumtoxin A--Eine offene Pilotstudie an 25 Patienten mit einem Beobachtungszeitraum über 14 Wochen.

AIM: The conservative and operative treatments of plantar fasciitis tend to be tedious. Unsatisfactory results are common in chronic cases. This study was performed in order to test the hypothesis that the analgesic and anti-inflammatory effect of a single injection of Botulinum toxin A (BoNT A) induces a significant reduction of symptoms. METHOD: 25 patients were included and followed-up for 14 weeks. Prior to injection, all of them had undergone at least two trials of conservative treatment. To determine the optimal treatment dose, 6 patients were injected subfascially with 100 units BoNT A (Dysport), another 6 with 200 units BoNT A. As result of this pre-trial, another 13 patients were treated with the higher dose. The patients documented maximum pain and continuous pain on a visual analogue scale. The strength of the lower leg and foot muscles was clinically assessed. RESULTS: A significant reduction of maximum and continuous pain was seen 2 weeks after injection in the group of 19 patients treated with 200 units BoNT A and persisted until the end of the follow-up. Adverse effects such as weakness of the muscles or systemic reactions have not been observed. CONCLUSION: This pilot study shows the efficacy of a single application of 200 units BoNT A as a treatment option for chronic plantar fasciitis.

The fixation strength of hydroxyapatite-coated Schanz screws and standard stainless steel Schanz screws in lower extremity lengthening : a comparison based on a new torque value index: the fixation index.

INTRODUCTION: Lengthening procedures are often complicated by loosening of pins. It has been reported that coating with hydroxyapatite improves fixation and reduces the rate of pin-track infection. MATERIALS AND METHODS: We compared 47 hydroxyapatite-coated Schanz screws (HA screws) in 12 monolateral fixators mounted at the University Hospital Hamburg-Eppendorf with 45 standard stainless steel screws in 9 monolateral fixators mounted at the St Josefs-Hospital Wiesbaden by measuring the insertion and extraction torque values. The average implantation period was 7 months for the hydroxyapatite-coated screws and 5.4 months for the uncoated screws. We established the quotient of the maximum extraction torque over insertion torque which shows the change in the fixation strength with respect to time, the fixation index. It eliminates the influence of the varying pin-bone contact. RESULTS: There was no significant difference in the rate of infection. In the Schanz screws without signs of infection the index was 1.92 for the HA screws and 0.76 for the stainless steel screws (P = 0.0002) giving evidence of the improvement of the fixation by the coating. CONCLUSION: HA coating resulted in improved fixation of Schanz screws in bone and may be useful in prolonged external fixation of the lower leg. The fixation index proved to be a simple tool for the evaluation of the fixation strength of Schanz screws.

First inventory of resorption lacunae on rods and plates of trabecular bone as observed by scanning electron microscopy.

In the present study a novel systematic distribution scheme of resorption lacunae (RL) was applied using scanning electron microscopy. RL, classified as either reticulate patch resorption lacunae (RPR) or as longitudinally extended resorption lacunae (LER) [11, were analyzed and quantified according to their localizations on rods (middle, nodes or both) and plates (central or peripheral) in standardized segments from the femoral head of 24 Caucasian subjects without bone disease. Age and gender variations were explored. No clear gender-related distribution pattern could be detected on plates. On rods of males, however, the distribution of RL tended to be higher at the nodes, but seemed to be more prevalent in the middle or extended from the middle to the nodes of rods in females. Certain other non-conclusive tendencies in relation to age, gender, type of RL and localization were observed.

Treatment of lateralisation and subluxation of the hip in cerebral palsy with Botulinum toxin A: preliminary results based on the analysis of migration percentage data.

It has been reported that cerebral palsy patients with adductor spasm and lateralisation/subluxation of the hip can be treated with Botulinum toxin A, but statistical evaluation is lacking. We present the radiological results in 5 patients. The follow-up ranged from 18 (5 patients) to 24 months (4 patients). Reimers' migration percentage was chosen as parameter for lateralisation/subluxation. Statistical analysis was performed by the Wilcoxon test. The migration percentage improved from 51% to 44% at 9 months, 37% at 18 months, and 34% at 24 months. The improvement was significant from the 9th to the 18th month (p=0.04).

[Therapy for chronic radial epicondylitis with botulinum toxin A]. / Therapie der chronischen Epicondylopathia humeri radialis mit Botulinumtoxin A -- eine Therapiestudie mit 2 Jahren Nachuntersuchungszeitraum.

AIM: Chronic radial epicondylitis (tennis elbow) is not a serious disease but patients may suffer greatly. If standard conservative and possibly operative treatment modalities have not been effective, patients need further therapy. First trials with injection of Botulinum toxin A (Btx A) have shown promising results. The purpose of the study was to clarify if a single injection of Btx A could be an efficient therapy for chronic radial epicondylitis. METHODS: In this study 16 patients received injections into the forearm extensors. The site of injection was determined by local tenderness and pain provocation on finger and wrist extension. RESULTS: A significant clinical improvement was already seen at 2 weeks following injection. The effect was noted up to the last follow-up at 2 years. Continuous and maximal pain during the last 48 h, as self-assessed on a visual analogue scale, was also significantly reduced. In a few cases a significant decrease of muscle strength was seen for the third finger two weeks after injection. It slowly returned thereafter. CONCLUSION: A single injection of Btx A was effective as therapy for chronic tennis elbow. It can be carried out in an out-patient setting, and allows the patient to continue working.