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Biomedical subjects

M Thomsen

Publications and source records attributed to M Thomsen.

At least 19 recordsLinked to original sources
PubMed2006

[Proximal fracture of the femur in elderly patients. The influence of surgical care and patient characteristics on post-operative mortality].

In a retrospective study, 1.173 fractures of the proximal femur, which had been treated surgically, were analysed in two periods from 1975 to 1991 and from 1992 to 2000. The influence on mortality of preoperative risk factors and primary treatment with total hip replacement (THR), even in cases of pertrochanteric fractures, was analysed by stepwise logistic regression. In the later period, mortality within 90 days was 13.1%, and within 1 year 22.2%. Rejection of hemiendoprosthesis in high-risk patients with intracapsular fractures increased the mortality rate from 6.3% to 11.8%. The introduction of dynamic hip screws instead of Ender nails led to a reduction of mortality from 16.5 to 7.1%. Higher mortality after THR (27.6%) compared to osteosynthesis (15.5%) in pertrochanteric femur and lateral neck fractures was due to higher age and increased risk factors. Although the influence of some risk factors could be reduced, age, sex and morbidity influenced the outcome more than surgical treatment. THP, even after pertrochanteric fractures, is reasonable if it guarantees a quick and enduring mobilisation of the patient. Bicentric bipolar prostheses are recommended for high risk patients.

Aged↗
PubMed2006

[Allergy towards bone cement].

Bone cements based on polymethylmethacrylate are typically used for fixation of artificial joints. Intolerance reactions to endoprostheses not explained by infection or mechanical failure may lead to allergological diagnostics, which mostly focuses on metal allergy. However, also bone cement components may provoke hypersensitivity reactions leading to eczema, implant loosening, or fistula formation. Elicitors of such reactions encompass acrylates and additives such as benzoyl peroxide, N,N-dimethyl-p-toluidine, hydroquinone, or antibiotics (particularly gentamicin). Upon repeated contact with bone cement components, e.g., acrylate monomers, also in medical personnel occasionally hand eczema or even asthma may develop. Therefore, in the case of suspected hypersensitivity reactions to arthroplasty, the allergological diagnostics should include bone cement components.

Bone Cements↗
PubMed2005

[Post-traumatic shoulder instability in adolescence].

BACKGROUND: Post-traumatic shoulder instability in adolescence represents a very rare condition. However, most of these patients develop recurrent shoulder dislocations over time. METHODS: We report about a retrospective study, which included 32 patients younger than 16 years of age. The mean follow-up was 5 years. Our evaluation focussed on patients' age at the time of first shoulder dislocation, type of injury, and the results after conservative and operative treatment. RESULTS: After the first dislocation, all shoulders were immobilized for 3 weeks and were treated with physiotherapy afterwards. Of these 32 patients, 30 (94%) developed recurrent shoulder dislocations. Eight patients remained in a conservative regimen (age <15 years) and 21 patients were operated for persistent shoulder instability (age >15 years). The recurrence rate was 8 of 21 patients (36.5%) in the operative group and 4 of 8 patients in the conservative group. At the time of follow-up, 4 of 8 conservatively treated patients had returned to their former sports activities and 15 of 21 (71%) in the operated group. CONCLUSIONS: Our results on post-traumatic shoulder instability in adolescence show high recurrence rates in both conservative and operative groups. After adolescence, including ossification of the glenoid, operative treatment is able to decrease the recurrence rate and to increase the sports ability of these young patients.

Adolescent↗
PubMed2005

[Fixed posterior subluxation with lateral rotation of the knee joint caused by congenital dislocation of the patella in combination with aplasia of the posterior cruciate ligament. Case report and review of the literature].

Congenital dislocation of the patella is very rare. In this anomaly, the patella is dislocated to the side of the lateral femoral condylus and cannot be repositioned manually. Diagnosis is often made by clinical examination and observation of an abnormal gait. We describe the long-term course of treatment in a young girl with fixed posterior subluxation with lateral rotation of the knee joint caused by congenital dislocation of the patella in combination with aplasia of the posterior cruciate ligament. These anomalies of the knee joint were corrected incrementally. First, recentralization of the patella was performed by open surgery. Subsequently, distraction of the shortened ischiocrural muscles and the posterior capsules and ligaments was conducted. This is the first case to be described, to the best of our knowledge, of a patient with congenital dislocation of the patella in combination with aplasia of the posterior cruciate ligament. We describe the successful treatment of such a fixed posterior subluxation and lateral rotation of the knee joint.

Child↗
PubMed2005

Reconstitution of a human immune system in immunodeficient mice: models of human alloreaction in vivo.

Rodents have been widely used for studies in transplantation immunology because of their short reproduction period and the relative ease of generating inbred mutant or transgenic strains. However, although many biological mechanisms are similar between rodents and humans, several features clearly distinguish the immune system in these species. Consequently, it is rarely possible to extrapolate observations from rodent models directly into clinical practice. In vitro studies with human cells are useful for elucidation of basic mechanisms, but in order to study complex biological phenomena, in vivo studies are indispensable. In later years, a number of interesting models have been described where immunodeficient mice have been reconstituted with human cells, so-called humanized mice, in order to study human immune responses in vivo. This has opened a new field of experimental immunology that has been applied to areas such as cancer, autoimmunity, allergy, infections, and transplantation biology. In this review, we shall concentrate on the use of severe combined immunodeficient mice reconstituted with human immune or stem cells for studies of human alloreaction in vivo.

Animals↗
PubMed2005

Continuous passive motion versus immobilisation in a cast after surgical treatment of idiopathic club foot in infants: a prospective, blinded, randomised, clinical study.

Continuous passive motion has been shown to be effective in the conservative treatment of idiopathic club foot. We wished to determine whether its use after operation could improve the results in resistant club feet which required an extensive soft-tissue release. There were 50 feet in the study. Posteromedial lateral release was performed in 39 feet but two were excluded due to early relapse. The mean age at surgery was eight months (5 to 12). Each foot was assigned a Dimeglio club foot score, which was used as a primary outcome measure, before operation and at 6, 12, 18 and 44 months after. Nineteen feet were randomly selected to receive continuous passive motion and 18 had standard immobilisation in a cast. After surgery and subsequent immobilisation in a cast the Dimeglio club foot score improved from 10.3 before to 4.17 by 12 months and to 3.89 at 48 months. After operation followed by continuous passive motion the score improved from 9.68 before to 3.11 after 12 months, but deteriorated to 4.47 at 48 months. Analysis of variance adjusted for baseline values indicated a significantly better score in those having continuous passive motion up to one year after surgery, but after 18 and 48 months the outcomes were the same in both groups.

Child, Preschool↗
PubMed2003

[Ceramic couplings in orthopedic surgery].

Ceramic materials have been used as a coupling in total hip arthroplasty since the 1970s to solve the problem of polyethylene particle disease. Several problems with the material and the design have been identified and solved. Using inlays and ceramic heads of the latest generation offers the possibility of reducing the wear rate to as low as 0.001 mm per year. The problem of ceramic fractures is rare. Recently due to the manufacturing process some zirconia ceramic heads have been problematic. New developments with other ceramics are discussed.

Aluminum Oxide↗
PubMed2003

[Polyethylene as an implant material].

Since the early 1960s, ultrahigh-molecular weight polyethylene (UHMWPE) has been one of the most frequently and successfully used materials in total joint replacement. However, in the course of clinical usage, various weaknesses of the material became apparent including wear and aging properties. As a result of research on this polymer, several improvements in the quality of the raw material, the processing, and the sterilization have been introduced. These changes paired with an improved knowledge of the viscoelastic behavior of UHMWPE have led to an improved design of the components to meet the requirements of the given material characteristics and in turn to better clinical results. In the 1990s, investigations focused on the influence of radiation on the molecular structures of polyethylene. Gamma radiation treatment in air leads to an important decrease in the molecular weight with reduced tribological behavior and accelerated aging. In contrast, a nitrogen atmosphere during irradiation and storage can improve the linkage of the polyethylene and promote the positive effects of radiation treatment. This effect can be further intensified by increased radiation levels. Such highly cross-linked polyethylenes demonstrate extremely low wear rates in vitro;however, other material properties are also changed. First reports on fissures in highly cross-linked polyethylene explants demonstrate that only long-term clinical trials can allow a final verdict on the clinical potential of highly cross-linked polyethylenes.

Elasticity↗
PubMed2003

[Myoelectric prostheses for kindergarten age children. Analysis of first reactions and experiences].

During the last few decades myoelectric prostheses were generally provided for adolescent or adult patients. Since 1991 the availability of smaller sized electric hands in conjunction with technical improvements enabled the introduction of myoelectric prostheses for preschool children.However, this progress remained widely unnoticed in Germany. This study presents the authors' experiences with prosthetic devices for preschool children with unilateral upper limb deficiency (congenital and traumatic). Twenty children received a myoelectric prosthesis between the ages of 2 and 5 years (3.9+/-1.1 years). The follow-up period was 1.7 years. The prosthesis was worn for an average of 5.6 h/day. Our hospital-based intensive training program positively influenced the acceptance rate. All children with a below-hand amputation rejected their prosthesis.However, the general dropout rate in preschool children is conspicuously lower compared to adults. In this study 2.4+/-2.9 repairs per year per patient were required. The susceptibility for repairs in this age group is much higher for myoelectric prostheses compare to body-powered devices. Since the correct indication and the intensive training program significantly influence the acceptance rate, the introduction of myoelectric prostheses to preschool children should take place at specialized centers with an interdisciplinary team composed of orthopedists,occupational therapists,and technicians.

Arm↗
PubMed2003

[Conservative and functionally oriented treatment of idiopathic clubfoot].

The article describes current conservative treatment of idiopathic clubfoot, especially plaster cast manipulation, functional mobilization, and orthosis. New procedures such as mobilization of the foot on a continuous passive motion machine and the use of botulinum toxin are presented and discussed.

Casts, Surgical↗
PubMed2003

Pattern of periprosthetic bone remodeling around stable uncemented tapered hip stems: a prospective 84-month follow-up study and a median 156-month cross-sectional study with DXA.

Bone resorption in the proximal femur is commonly seen after total hip arthroplasty (THA). With dual energy X-ray absorptiometry (DXA), the amount of bone mass (BMD) after implantation of a total hip stem can be precisely determined. However, prospective evaluation of the change of bone mass around the stem is only available for selected stems and short-term follow-up (up to 36 months). We analyzed BMD in patients who had undergone uncemented THA by DXA. Only patients with good clinical outcome (Merle d' Aubigné score > 12) were included to obtain normative data for regular bone response. Two separate studies were performed: a prospective longitudinal study over 84 months with baseline values acquired within the first postoperative week (group A) (n = 26 patients) and a separate cross-sectional study, median follow-up 156 (124-178) months (group B) (n = 35 patients). Regions of interest were defined according to Gruen (ROI 1-7) and as net average ROI (net avg) for the periprosthetic femoral bone. After the initial remodeling process (12 months), BMD was compared to the 84-month (longitudinal) and the 156-month (cross-sectional) follow-up values to determine long-term periprosthetic changes of bone mineral density. The longitudinal study (group A), after the initial bone remodeling, showed no relevant further bone loss for women and men with BMD values 1.19 +/- 0.15 and 1.40 +/- 0.19, respectively, 12 months (women 89.8%, men 93.6%), and 1.19 +/- 0.13 and 1.36 +/- 0.18, respectively, after 84 months (women 90.0%, men 91.3%) (P = 0.98, P = 0.08,) respectively. The distribution of the BMD around the stem changed during the first 12 months. The ROIs around the proximal stem (ROI 1 and 7) showed the lowest absolute values at the 12-month follow-up and BMD in ROI 7 decreased most during the further follow-up until 84 months. The cross-sectional study (group B) showed no significant difference in BMD (net avg) values at a median of 156 months follow-up compared to the 12-month values (group A) (women: P = 0.77, men: P = 0.44). Initial BMD, implant diameter, and body mass index did not influence BMD loss (net avg) in this study, whereas age showed a weak correlation with BMD loss. The results show that after the initial remodeling process, no relevant further bone loss (net avg) occurs up to 84 months postsurgery, and values after a median of 156 months are similar. Normative long-term changes in the periprosthetic bone can be demonstrated in defined ROIs after implantation of a tapered corundum-blasted titanium stem with a good clinical result.

Absorptiometry, Photon↗
PubMed2003

A ten- to 15-year follow-up of the cementless spotorno stem.

We followed the first 354 consecutive implantations of a cementless, double-tapered straight femoral stem in 326 patients. Follow-up was at a mean of 12 years (10 to 15). The mean age of the patients was 57 years (13 to 81). At follow-up, 56 patients (59 hips) had died, and eight (eight hips) had been lost to follow-up. Twenty-five hips underwent femoral revision, eight for infection, three for periprosthetic fracture and 14 for aseptic loosening. The overall survival was 92% at 12 years (95% CI 88 to 95). Survival with femoral revision for aseptic loosening as an endpoint was 95% (95% CI 92 to 98). The median Harris hip score at follow-up was 84 points (23 to 100). Radiolucent lines (< 2 mm) in Gruen zones 1 and 7 were present in 38 (16%) and 34 hips (14%), respectively. Radiolucencies in zones 2 to 6 were found in five hips (2%). The results for mid- to long-term survival with this femoral component are encouraging and compare with those achieved in primary cemented total hip arthroplasty. The high rate of loosening of the cup and the high rate of pain are, however, a source of concern.

Adolescent↗
PubMed2002

[Biomechanics of the tibiofemoral joint and knee braces].

We investigated whether the kinematics of modern knee braces reflect the natural movement of the knee, especially with regard to the roll-glide ratio. Seven commercially available modern knee braces were analyzed in a new measuring unit with a 6-D positional registration system, which had been developed for this study. The results were compared to the theoretically postulated joint movements. All knee braces produced a roll-glide ratio different from the natural movement of the knee. Only the Townsend brace protected the anterior cruciate ligament at the beginning of the movement.Biomechanically, none of the knee braces tested provided efficient protection for the knee movement. We propose a new functional external joint, which allows restoration of the natural roll-glide mechanism of the articulating surfaces.

Anterior Cruciate Ligament↗
PubMed2002

[Influence of implant position of a hip prosthesis on alignment exemplified by the CLS shaft].

We performed a clinical and radiological analysis to evaluate the significance of the stem position of cementless CLS components with respect to function and survival. We used patient material from a multi-center study of 3,732 CLS stems with a mean follow-up of 43 months (range: 12-142 months). The clinical outcome was assessed using Merle D'Aubigné Scores and stem alignment was determined as the deviation of the longitudinal stem axis from the longitudinal femur axis. We found no correlation between stem alignment and function, survival, implant migration or periprosthetic radiolucent lines. In patients with rheumatoid arthritis and hip ankylosis the neutral stem position was less often achieved than in patients with other diagnoses. The results of our study cast doubt on whether the varus position of the femoral component of cementless tapered CLS-type stem designs is as critical as in cemented total hip arthroplasty.

Aged↗