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Biomedical subjects

R Forst

Publications and source records attributed to R Forst.

At least 19 recordsLinked to original sources
PubMed2006

Results of primary extensor tendon repair in relation to the zone of injury and pre-operative outcome estimation.

INTRODUCTION: The outcome of primary extensor repair in hand surgery has been widely explored, but little systematic effort has been made to investigate the influence of the anatomical zone of tendon injury. Therefore, the aim of our study was to assess the outcome of primary extensor tendon repair with a special focus on the pre-operative state and Verdan's anatomical zones. Our hypothesis being tested was that the outcome after primary extensor repair depends on the complexity of trauma and the site of lesion. MATERIALS AND METHODS: One hundred and seventy seven patients with 203 extensor tendon repairs were studied. After tendon repair and a 6-week protective immobilization, physiotherapy was carried out. A score proposed by Geldmacher and Schwarzbach was applied to estimate the outcome pre-operatively and to assess the results in a follow-up after a mean of 13 months. Correlations were tested between the anatomical zone of tendon injury, the pre-operative expectation and the results as considered both by the patient and the physician. RESULTS: In Verdan's zones 1, 2, 4 and 5, excellent or good results were obtained in the vast majority of patients. Due to a higher frequency of complex injuries with concomitant soft tissue and bony injuries, the outcome was significantly worse after tendon repair in zones 3 and 6, as expected after the pre-operative estimation. In addition, a strong correlation was found for all anatomical zones between the pre-operative estimation and the outcome as judged both by the physician and the patient. CONCLUSION: Recovery of finger function after primary extensor tendon repair depends on the complexity of trauma and the anatomical zone of tendon injury. Static splinting is an appropriate tool after primary extensor tendon repair in Verdan's zone 1, 2, 4 and 5, whereas injuries in zones 3 and 6 may demand for a different treatment regimen.

Adult↗
PubMed2006

The phenomenon and efficiency of ligamentotaxis after dorsal stabilization of thoracolumbar burst fractures.

Thirty-six consecutive patients with burst fractures of the thoracolumbar spine and with a fractured posterior vertebral surface dislocated into the spinal canal without neurological symptoms were treated with the AO internal fixator. Computed tomography-aided planimetry of the spinal canal was undertaken preoperatively and within 1 week postoperatively to elucidate the effect of kyphosis correction and distraction on spinal canal widening (ligamentotaxis). The stenosis of the spinal canal area (SCA) was reduced from 29% preoperatively to 19% postoperatively (+10%) of the estimated original area, and the stenosis of the mid-sagittal diameter (MSD) reduced from 31 to 23% (+8%). The widening of the SCA was greater at the level of L1/L2 (+13%) than at L3/L4 (+6%). High preoperative canal compromise was associated with greater absolute spinal canal widening. Large trapezoid-shaped fragments resisted reduction by ligamentotaxis. Even though the effect of ligamentotaxis after operative treatment with the internal fixator was proven, a certain stenosis of the spinal canal remains in most cases. Especially for patients with fracture-related neurological symptoms, ligamentotaxis alone does not seem sufficient for the requested spinal decompression. Even an exact analysis of preoperative CT scans under consideration of the fracture level will not always allow an exact prognosis of the expected effect of ligamentotaxis.

Adolescent↗
PubMed2006

[Insoles for the rheumatic foot. A clinical and pedobarographic analysis].

BACKGROUND: Insoles are regarded as an appropriate tool for the management of rheumatic foot disorders. However, a quality control for this purpose has not been established. In our study, the clinical effectiveness of insoles used in patients with rheumatic foot disorders was addressed. In addition, we sought to establish pedobarography as a means of quality control for orthotic management of the rheumatic foot. MATERIAL AND METHODS: Our study included 20 rheumatoid arthritis patients with painful rheumatic foot deformities who were provided with insoles. Clinical data were obtained by physical examination and a 100-mm pain scale. Pedobarography was performed using the novel pedar cable system with new and individually designed insoles and after a 6-month follow-up. A shoe-only trial served as control. The parameters maximum force, peak pressure, force-time integral, and average pressure were analyzed in anatomical regions and an individually defined overloaded forefoot region. RESULTS: Clinical improvement was significant after a 6-month follow-up in spite of a heterogeneous group of patients. However, our results could not confirm consistent changes in plantar pressure distribution. CONCLUSION: As a conclusion, further efforts are necessary to establish a quality control for orthotic management of the rheumatic foot.

Adult↗
PubMed2005

[Myofascial pain syndrome].

The myofascial pain syndrome is an autonomous clinical picture with well-defined clinical and morphological features. The myofascial pain is initiated through trigger points in the musculature which induce a typical referred pain into a specific body region typical for each muscle. Untreated, the myofascial pain syndrome leads to a reduced extensibility of the involved muscle with consecutive decrease of the range of motion and development of a muscular imbalance resulting in a disturbance of complex movement and evolution of a chronic pain disease. An early started and aimed therapy can prevent effectively the chronification. It includes beside the local treatment of the trigger point (e. g. spray-and-stretch, infiltration, acupuncture), the pharmacological and psychotherapy, the physiotherapy and the different procedures of the physical therapy.

Exercise Therapy↗
PubMed2005

[Femoral neck prosthesis in the case of femoral neck fracture and ipsilateral long stem-knee tumour prosthesis].

Femoral neck fracture in the case of a previously implanted ipsilateral tumour knee-prosthesis represents a challenging situation because of the long proximal stem of the knee implant. Avoiding total femur replacement, we implanted a femoral neck prosthesis (Eska Cut 2000) in a 65 year old patient to preserve as much of the femur free of implant as possible, minimizing the risk of a periprosthetic or interprosthetic fracture. At 2.5 years postoperatively, there were no signs of loosening, migration or periprosthetic fracture with a good functional result. In our case, the femoral neck prosthesis avoided the implantation of a total femur replacement. Nevertheless, this prosthesis must be considered critically and cannot be recommended as the standard implant for femoral neck fracture in the case of an ipsilateral long stem-knee prosthesis.

Aged↗
PubMed2005

[Allergic potential of titanium implants].

AIM: The aim of this investigation is to evaluate the allergic potential of titanium and titanium alloys for surgical implant applications. MATERIALS AND METHODS: Discs cut from rods supplied by five different titanium suppliers in several diameters were investigated. The samples were cp-Titanium as well as Ti6Al4 V and Ti6Al7Nb, 6 mm thick with a diameter of between 6 and 60 mm. The material was checked by optical spectral analysis. RESULTS: In all samples except iodidtitanium, a Nickel content of 0.012-0,034 wt% could be detected. CONCLUSION: The low nickel content in the implant material results from the production process. The nickel atoms are in solid solution in the titanium lattice. Nickel allergic patients may develop hypersensitivity reactions even due to this low nickel content. Hence, this reaction may be falsely attributed to the titanium material itself. Measurements of ion concentration in the body are helpful for quantifying the maximum content of nickel in titanium materials for surgical implant applications. In addition, technical questions related to the production of nickel free titanium materials for allergic patients have to be solved.

Biocompatible Materials↗
PubMed2001

Spinal stabilization in Duchenne muscular dystrophy: principles of treatment and record of 31 operative treated cases.

The aim of this study was to report results of prophylactic spinal stabilization in patients with Duchenne muscular dystrophy. There is still debate regarding the ideal instrumentation. A prospective study of a consecutive series of 31 patients stabilized with the ISOLA system from D2 to S1 will be presented. The mean follow-up was 22 months (range, 1-60 months). The evaluation of the Cobb angle and pelvic obliquity revealed the following: 1) Cobb angle: preoperation, 48.6 degrees (range, 22-82 degrees); postoperation, 12.5 degrees (range, 0-30 degrees); follow-up, 12.5 degrees (range, 0-42 degrees); and 2) pelvic obliquity: preoperation, 18.2 degrees (range, 3-40 degrees); postoperation, 3.8 degrees (range, 0-13 degrees); follow-up, 5.1 degrees (range, 0-14 degrees). Spinal stabilization with the ISOLA system was found to be a suitable treatment for scoliosis owing to Duchenne muscular dystrophy. It should be carried out after loss of ambulation as soon as a progressive curve of more than 20 degrees is documented. The complication rate was found to be high.

Adolescent↗
PubMed2000

Value of myofibrillar protein catabolic rate in Duchenne muscular dystrophy. A study after lower limb surgery.

Previous studies have shown a decreased progression of the course in Duchenne muscular dystrophy (DMD) patients treated by lower limb surgery in early childhood. The use of 3-methylhistidine (3-MH) excretion and 3-MH/creatinine excretion ratio as an appropriate indicator for the myofibrillar protein catabolic rate (MPCR) in muscle disorders is discussed controversially. To explore this issue we studied the renal excretion of (3-MH) over a period up to 24 months (on average 20.8 +/- 1.4) after operation in 15 consecutive DMD patients with an average age at operation of 8.75 (+/- 2.43 years) to evaluate the myofibrillar protein catabolic rate. No significant change of the MPCR could be found in our population over the follow-up period. However, the formula for the calculation of the MPCR contains quantities which are not precisely known in DMD or assumed to be constant over the progressive course of DMD. Summarizing MPCR cannot be recommended for the assessment of therapeutic efficacy in DMD.

Adolescent↗
PubMed2000

A modular femoral implant for uncemented stem revision in THR.

We present the early results of 142 uncemented femoral stem revisions using the modular MRP-Titan system. There were 70 cases with marked preoperative femoral bone defects (Paprosky type 2C and type 3); and bone grafts were used in 31 cases. At a mean follow-up of 2.3 years five cases were re-revised due to dislocation and two due to aseptic loosening. The mean Harris hip score improved from 37.4 preoperatively to 92.4. In 122 cases progressive bone regeneration on X-ray was seen; and no further osteolysis was observed.

Adult↗
PubMed2000

Critical evaluation of known bone material properties to realize anisotropic FE-simulation of the proximal femur.

PURPOSE: In a meta-analysis of the literature we evaluated the present knowledge of the material properties of cortical and cancellous bone to answer the question whether the available data are sufficient to realize anisotropic finite element (FE)-models of the proximal femur. MATERIAL AND METHOD: All studies that met the following criteria were analyzed: Young's modulus, tensile, compressive and torsional strengths, Poisson's ratio, the shear modulus and the viscoelastic properties had to be determined experimentally. The experiments had to be carried out in a moist environment and at room temperature with freshly removed and untreated human cadaverous femurs. All material properties had to be determined in defined load directions (axial, transverse) and should have been correlated to apparent density (g/cm(3)), reflecting the individually variable and age-dependent changes of bone material properties. RESULTS: Differences in Young's modulus of cortical [cancellous] bone at a rate of between 33% (58%) (at low apparent density) and 62% (80%) (at high apparent density), are higher in the axial than in the transverse load direction. Similar results have been seen for the compressive strength of femoral bone. For the tensile and torsional strengths, Poisson's ratio and the shear modulus, only ultimate values have been found without a correlation to apparent density. For the viscoelastic behaviour of bone only data of cortical bone and in axial load direction have been described up to now. CONCLUSIONS: Anisotropic FE-models of the femur could be realized for most part with the summarized material properties of bone if characterized by apparent density and load directions. Because several mechanical properties have not been correlated to these main criteria, further experimental investigations will be necessary in future.

Anisotropy↗
PubMed1999

Errors of computer-assisted migration analysis in conventional radiographs of femoral hip implants--an experimental study.

Several methods have been described in the literature in order to analyze migration of femoral hip implants in conventional radiographs. However, no measurements were done regarding the potential errors inherent in such unstandardized radiographs of daily routine. In order to quantify this lack of reproducibility, we carried out experimental examinations with radiographs of a hip revision prosthesis, where different variables of technical X-ray conditions and femoral positions were changed. All radiographs were analyzed with a computer-assisted processing system by different procedures. At first, the radiographs were calibrated geometrically. Then, particular reference distances between defined points of the implant and cortical bone structures were analyzed quantitatively. The error of the axial migration analysis was up to 11.11 mm concerning different femoral positions, up to 8.29 mm in the case of different source-to-film distances and up to 2.21 mm due to different lateral localizations of the central X-ray focus. Significant errors for the migration analysis in the transverse and rotational planes were only found under conditions of varying the femoral position, and not under different technical X-ray conditions. From these experimental results, we derived the following criteria to minimize failure in a quantitative radiographic migration analysis: (1) the patient's leg has to be placed into an antirotation device to ensure identical object position; (2) the same source-to-film distance has to be used; (3) the central X-ray focus has to be localized on the center of the film-cassette; (4) film-screen systems should be of the same type and size; (5) the object has to be placed in the same position as in previous radiographs. As a conclusion, only if these standardization criteria are respected in the daily routine of conventional radiographs will an effective and meaningful use of migration analysis systems be possible to prove or to exclude mechanical failure of femoral hip implants in prospective longitudinal follow-up series.

Cadaver↗
PubMed1999

Pain therapy following joint replacement.A randomized study of patient-controlled analgesia versus conventional pain therapy.

A prospective randomized trial in 42 patients undergoing elective total hip or knee arthroplasty under general anaesthesia was carried out to evaluate the efficacy of patient-controlled analgesia (PCA) versus demanded conventional pain therapy (CPT) for controlling postoperative pain. Four patients had to be excluded from the study (2 postoperative confusion, 1 elevated piritramid dosage caused by chronic pain therapy, 1 stressed by PCA pump handling). PCA group (n = 19) received piritramid via PCA pump, CPT group (n = 19) received tramadol (oral or intramuscularly) or piritramid intravenously. PCA or CPT was started in the intensive care unit. Pain was measured with a standard 100 mm visual analogue scale (VAS) for 60 h postoperatively. Over this period of time, no significant differences were found in the pain score of both groups, nor did the incidence of side-effects differ significantly. The PCA group required on average twice as much piritramid-equivalent than the CPT group (P < 0.001). Patient satisfaction was good in both groups, but significantly better in the PCA group (P < 0.01), although the measured postoperative individual pain scores were above the preoperatively determined individual subjective pain threshold in the majority of both groups. From these results we draw the conclusion that even if the patients feel satisfied by the pain therapy administered, the majority are objectively treated below their individual subjective pain threshold.

Administration, Oral↗
PubMed1999

Lower limb surgery in Duchenne muscular dystrophy.

Two hundred and thirteen of 428 patients with Duchenne muscular dystrophy (DMD) of a prospective and open study were operated on bilaterally with hip and knee release, aponeurectomy of the iliotibial band and Achilles tendon lengthening. In 87 patients the operation was carried out during early restrictions of the lower limb joint mobility at an average age of 6.56 years (4.02-8.26, SD 1.42). The follow-up was on average 5.4 years (0.25-9.01, SD 2.7). This group was compared to a control group (natural history) consisting of 100 non-operated DMD patients. A significant (P < 0.001) release of the contractures could be obtained. Loss of walking ability occurred in the control group at an average of 9.29 years (5.85-13.63, SD 1.98) and in the operated group at an average of 10.55 years (8.17-14.39, SD 1.76). This shows that early lower limb surgery leads to a prolongation of independent ambulation of 1.25 years on average. In contrast to the patients of the control group all treated patients between ages 6 and 8 years could walk independently. The positive influence of early lower limb surgery could also be shown by the development of Hammersmith motor ability score, CIDD (Council of Investigation of Duchenne Dystrophy) grading and Vignos scale. Nevertheless, in consideration of the well-known course of DMD not only the prolongation of ambulation but also the achieved prolongation of assisted standing ability with no or mild contractures are aims of lower limb surgery. Since no improvement of muscle strength could be observed after lower limb surgery, further studies have to investigate if additionally administered steroids can prolong ambulation after early lower limb surgery.

Adolescent↗
PubMed1998

Spontaneous osteonecrosis of the femoral condyle: causal treatment by early core decompression.

In 16 patients with an average age of 64.6 +/- 9.8 years and sudden onset of severe knee pain, the initial stage of Ahlbäck disease (spontaneous osteonecrosis of a femoral condyle) was verified by magnetic resonance imaging (MRI) and subsequent histology. The first radiological sign of osteonecrosis (flattening of the affected femoral condyle) was present in only one case. All patients were treated surgically by extra-articular drilling into the affected femoral condyle to achieve core decompression. The knee pain disappeared immediately after surgery in all patients. Successful healing was confirmed by normalization of the bone marrow signal on MRI (on average, 35.8 months follow-up). Core decompression by extra-articular drilling into the femoral condyle can be recommended as an effective treatment in initial osteonecrosis of the knee (still radiologically invisible). However, if radiologically a flattening of the affected femoral condyle becomes apparent, progression of this disease cannot be avoided.

Aged↗
PubMed1998

Stability of different wiring techniques in segmental spinal instrumentation. An experimental study.

The pullout force of sublaminar and transspinous wires for segmental instrumentation which had been inserted into different segments of human cadaver spines were compared. Four different types of wiring were tested: single and double sublaminar wires, button-wires according to Drummond's technique and button-wires with the additional use of two crimps for each spinous process. A total of 50 tests were performed. In all attempts the bone proved to be the limiting factor. None of the 300 fixed wires failed. Typical types of fractures appeared with different wiring techniques. There was no statistically significant difference between the sublaminar wiring techniques tested. However, there were significant differences between sublaminar and transspinous wiring. The transspinous techniques achieved between 30% and 45% of the pull-out strength of sublaminar techniques. The forces decreased with increasing cranialisation. In all techniques the values in the upper segment (D5-D3) were almost half those of the lower segment (L5-L3). The differences of the transspinous techniques increased cranially, in favour of the technique with additional crimps. Thus, the crimps have the strongest effect on weak spinous processes. This study demonstrates that in non-dynamic testing, the stability of the bone and not the type of wiring is the limiting parameter in segmental spinal stabilisation. As the wires are inserted in different areas, the transspinous technique shows significantly lower tension forces in comparison with sublaminar wiring.

Biomechanical Phenomena↗
PubMed1998

Femoral nerve lesion in total hip replacement: an experimental study.

A total of 20 hip joints of 10 non-fixed corpses were examined within 48 h of death to measure the pressure below the inguinal ligament simulating the surgical conditions during total hip arthroplasty. The purpose of this study was to assess the influence of various leg positions and insertion techniques of retractors during the surgical procedure for total hip replacement in order to detect supposed causes for indirect pressure injuries of the femoral nerve. The obtained results verified no increase of pressure in the inguinal canal which could explain an indirect injury of the femoral nerve. If the retractor is inserted correctly at the anterior acetabular rim, the pressure in the lacuna musculorum can even be reduced, and furthermore, the femoral nerve is protected by the iliopsoas muscle. Femoral nerve lesions which have been published so far can only be explained by an incorrect use of instruments or implants (e.g., screws, cement, acetabular cup) or an extreme postoperative leg length discrepancy.

Arthroplasty, Replacement, Hip↗
PubMed1998

Platelet function deficiency in Duchenne muscular dystrophy.

Platelet function and plasmatic coagulation of 51 patients with Duchenne muscular dystrophy (DMD) were studied in order to find an explanation for the known substantial blood loss in spinal surgery of these very patients. A normal plasmatic coagulation and a slight but not significant increase of bleeding time was found. However, a significant deficiency of platelet adhesion and ristocetin induced aggregation (P < 0.001) as well as a marked reduction of expression of glycoprotein i.v. (synonyms: GPIV, GPIIIb, CD36) to 50% were detected. We conclude from our study, that this finding of deficiency of platelet function in DMD patients is of no importance in everyday life and minor operations, e.g. lower limb surgery. In major spinal surgery, however, the platelet function deficiency occurs. A decompensation of platelet adhesion as well as aggregation capacity can be assumed due to the unavoidable intraoperative dilution effect by the inevitable volume replacement.

Adolescent↗