Biomedical subjects

M von Knoch

Publications and source records attributed to M von Knoch.

31 records · Page 2Linked to original sources

PubMed1999

Lateral approach with osteotomy of the tibial tubercle in primary total knee arthroplasty.

In a prospective study of 51 patients (61 cases) with primary total knee arthroplasty (valgus knees and/or knees that had undergone previous nonarthroplasty surgery), a lateral approach with osteotomy of the tibial tubercle was performed. In a lateral approach, lateral release techniques form part of the approach. In addition, the medial blood supply to the patella is preserved. An additional tibial osteotomy grants wide exposure with little tension on the extensor mechanism during eversion of the patella. The patients were followed up clinically (51 patients, 61 cases) and radiologically (44 patients, 52 cases) for 1 year. No postoperative tibial fractures, no delayed unions, and no nonunions at the site of the osteotomy were seen. No patellar necrosis occurred. The results after 1 year were good or excellent in 45 (88%) patients, fair in four (8%), and poor in two (4%). Complications related to technique were hematoma (four patients) and compartment syndrome (one patient). These complications occurred early in the series and were eliminated by technical modifications.

Aged↗

PubMed1997

Incidence of late bead shedding from uncemented porous coated cups. A radiographic evaluation.

A radiographic study was performed on late head separation from the porous surface of clinically well functioning and radiographically stable Arthropor uncemented acetabular components. Of 104 cups in 102 patients, 11 (10.6%) showed bead separation from the porous coated surface. Bead shedding occurred at an average of 4.2 years (range, 2-7 years). In each case the phenomenon was progressive. In the group that shed beads, there was a higher prevalence of acetabular radiolucencies (63.6% versus 25.8%) and of osteolysis (45.5% versus 10.8%). These differences were statistically significant. The group that shed beads also had a higher polyethylene wear rate (0.21 mm/year versus 0.16 mm/year) and were younger (49.5 years versus 59.5 years). All cups that shed beads remained clinically and radiographically stable. Thus, the clinical impact of these observations is uncertain. However, the higher prevalence of acetabular lucencies and osteolysis in these patients, in combination with an increased polyethylene wear rate, require thorough clinical and radiographic followup to uncover potential loosening problems of these acetabular components.

Acetabulum↗

PubMedDate not supplied

[Knee flexion after rotational knee endoprosthesis].

UNLABELLED: In the presented study the question was evaluated if--after rotational knee arthroplasty--range of motion must be restored at discharge or if range of motion can also be restored with delay during the first postoperative year. METHOD: A retrospective study was performed on 45 patients. These had been rehabilitated with a specific therapeutical concept which did not include early restoration at discharge of complete range of motion as the key principle. RESULTS: The mean range of motion was 60 degrees +/- 21 degrees at discharge. At the date of presentation 12 to 18 months postoperatively the mean range of motion had improved to 110 degrees +/- 19 degrees. CONCLUSIONS: The presented study indicates that complete restoration of range of motion after rotational knee arthroplasty may not necessarily be restored at discharge.

Aftercare↗

PubMedDate not supplied

[Polyethylene content and cell size of foreign body giant cells in aseptic hip prosthesis loosening--a histomorphometric study].

INTRODUCTION: In aseptic loosening of cementless hip arthroplasty polyethylene particles are phagocytized by macrophages and foreign-body giant cells. This initiates an osteolytic cascade. In this study, the authors investigated if there are correlations between the size of foreign-body giant cells and the polyethylene loading and number of intracellular particles as determined by light microscopy. MATERIAL AND METHOD: Histological specimens were processed from tissues retrieved during revision surgery of 7 cases of cementless hip arthroplasty which had become aseptically loose. The specimens were analyzed by histolomorphology and histomorphometry. The cell size, polyethylene loading and intracellular particle number of 111 foreign-body giant cells were determined. A regression analysis was performed to investigate if there was a correlation between these variables. RESULTS: The mean cell size was 1417 +/- 487 micron 2, the mean polyethylene loading was 49 +/- 42 micron 2 and the mean intracellular particle number was 10.4 +/- 5.4. The cell size correlated with both the intracellular particle number (r = 0.25) and the polyethylene loading (r = 0.39). CONCLUSIONS: In the cellular reaction to polyethylene particles in aseptic loosening of cementless total hip arthroplasty, the size of foreign-body giant cells correlates with intracellular polyethylene loading and intracellular polyethylene particle number as determined by light microscopy. The presence of large foreign body giant cells might be associated with a high particle load of the tissue and a high osteolytic activity.

Aged↗

PubMedDate not supplied

[Fracture behavior of AO 3.5 mm cortical titanium screws Synthes screws) combined with LC-DCP plates].

AIM: It was investigated if AO 3.5-mm titanium cortical screws used in combination with LC-DCP plates for osteosynthesis are likely to break during surgery. METHOD: The moments of torque that lead to breakage of the screw were determined experimentally in a hardwood model. The insertion angle was variable: 90 degrees in centric (n = 30) and excentric (n = 30) positioning, 70 degrees (n = 30) and 50 degrees (n = 30). Minimal moments that led to screw breakage were compared to insertion moments that were measured intraoperatively in 7 fracture operations (radial, ulnar, tibial, fibular; 32 screws). RESULTS: Minimal moments that led to screw breakage were 2.6 Nm (90 degrees centric), 2.8 Nm (90 degrees eccentric), 2.7 Nm (70 degrees) and 2.4 Nm (50 degrees). The maximal intraoperatively measured insertion moment was 2.25 Nm (radius). CONCLUSIONS: In this investigation, minimal moments that led to screw breakage in an experimental setting were higher than maximal insertion moments that were recorded during surgery. It is concluded that screw breakage related to the given implant combination is unlikely if correct surgical technique is performed.

Bone Plates↗

PubMedDate not supplied

[Size and shape of commercially available polyethylene particles for in-vitro and in-vivo-experiments].

AIM: The longevity of total hip arthroplasty is sometimes limited by osteolysis and aseptic loosening. Aseptic loosening may be caused by the biologic reaction to polyethylene wear particles. Particles of less than 1 micro m diameter are of particular importance. These particles are not easily available for experimental use. METHOD: We performed a morphologic analysis of commercially available, very small polyethylene particles (Ceridust(R)) in order to determine the specific size distribution. We measured 1 978 particles. Size analysis was performed using an electron microscope. Particle size was described as the equivalent circle diameter (ECD). Particle morphology was described as feret ratio. In addition, Ceridust(R) particles were compared to different particles stemming from a hip simulator experiment. RESULTS: More than 35 % of the particles were less than 1 micro m in size. The particle size was 1.75 micro m +/- 1.43 micro m (median 1.42 micro m). The minimum was 0.06 micro m, the maximum was 11.06 micro m. The feret ratio was 0.58 +/- 0.17 (median 0.63). The minimum was 0.07, the maximum was 0.93. The majority of Ceridust(R) particles had a rough surface. Compared to polyethylene particles stemming from a hip simulator experiment, Ceridust(R) particles had a rougher surface, were less longitudinal, and had a more even size distribution. CONCLUSIONS: The pure, commercially available polyethylene particles analyzed here are suitable for in vitro and in vivo experiments due to their easy availability, minor costs, and large fraction of very small particles.

Biocompatible Materials↗

PubMedDate not supplied

[Cup placement in hip replacement surgery -- A comparison of free-hand and computer assisted cup placement in total hip arthroplasty -- a multi-center study].

AIM: The purpose of the current study was to determine the accuracy of free hand and computer-assisted (CAS) cup placement. MATERIAL AND METHODS: Between June 1985 and August 2001, 105 free-hand and from March to November 1999 80 total hip arthroplasties under computer assistance were implanted in the above mentioned centers. To determine the accuracy of the cups, the inclination and anteversion angles were measured. In all cases the cup position was measured with a CT-investigation of the pelvis. Statistical analysis was performed with the F-test. RESULTS: With regard to the inclination and anteversion angles the variability of the cup position was significantly higher in the group of free hand implanted cups. In the CAS group we could not find any "extreme" positions. CONCLUSION: Using computer-assisted surgery a significantly higher reproducible cup position can be obtained. Long time survey may present a lowering of the rate of early and late complications caused by better prostheses alignment in the follow up.

Adult↗

PubMedDate not supplied

[Revision of failed acetabular cups with extensive structural allografts].

AIM: Structural allografts are used with encouraging results for revision of failed total hip arthroplasty and in the surgery of bone tumours. The aim of the present study is to describe the clinical and radiological results achieved with structural allografts in revision of a total hip arthroplasty. MATERIAL AND METHODS: 15 patients (12 female and 3 male patients) were revised with an acetabular defect situation of type 3 A or 3 B according to the Paprosky classification. Five fresh-frozen acetabula, nine distal femora and one proximal tibia were used for acetabular reconstruction. The rigid graft fixation was performed with 2 > or = AO screws. In one case a cemented acetabular ring was implanted, four cementless cups and ten cemented polyethylene acetabular components were used. The mean follow-up was 7.9 years (1.6-11.0 years). RESULTS: A stable osseointegration of fifteen transplanted structural allografts was achieved in thirteen cases. Two allografts (one aseptic loosening, one deep infection) failed to osseointegrate. In one case the migration of a cementless cup was registered. Revision surgery of this female patient was performed successfully with a cemented reconstruction ring. The mean Harris hip score at the latest follow-up was 81.4 points (70-99 points). CONCLUSION: For reconstruction of acetabular bone stock and restoration of the bone anatomy structural allografts can be recommended. The use of cementless cups in combination with structural grafts is to be evaluated as critical.

Acetabulum↗

PubMedDate not supplied

[Follow-up study after dynamic and static stabilisation of the lumbar spine].

INTRODUCTION: The clinical indication for graf's ligamentoplasty and dorsoventral fusion may be described as the "lumbar instability syndrome". A follow-up comparison between Graf's ligamentoplasty and instrumental dorsoventral fusion in a consecutive series of 52 patients was performed. METHODS: 52 patients operated on for low back pain were recalled for a clinical and radiological review (at mean 79 months postoperatively). 26 patients underwent Graf' ligamentoplasty and 26 patients underwent dorsoventral fusion. We evaluated the surgical results and measured an objective outcome using the Oswestry Score, Low Back Outcome Score (LBOS) and Visual Analogue Scale (VAS). For radiological evaluation the Mimura and the Pathria Scores were used. RESULTS: There was no statistically significant difference between the two groups, when measured by the Oswestry Score, LBOS and VAS at the latest follow-up. The difference between the preoperative and actual VAS in each group was statistically significant (p < 0.001). Furthermore, there was no provable preoperative parameter in favour of either one of these therapies. CONCLUSION: Both methods for stabilisation methods of the lumbar spine had a comparable clinical outcome.

Adult↗

PubMedDate not supplied

[Localization of the neurokinin 1 receptor in hip joints of patients with painful osteoarthritis].

INTRODUCTION: Recent studies on osteoarthritis have focused on nociceptive substance P (SP) containing afferent nerve fibres. The effects of SP are known to be mainly mediated by the tachykinin receptor neurokinin 1 (NK1-R). AIM: The aim of the present study was to demonstrate the NK1-R in human joint tissues. METHODS: The hip joint capsule of three patients with painful hip osteoarthritis (Group 1), three patients with femoral neck fracture showing no cartilage destruction (Group 2, controls) and the soft tissue of the fossa acetabuli of Group 1 were resected during hip arthroplasty implantation. The tissue samples were cut into small blocks and immersion-fixed in Zamboni's fixative. The specimens were frozen, cut into 50 microm sections and immunostained using a standard immunohistochemical staining protocol. RESULTS: In Groups 1 and 2 the NK1-receptor was localised in the wall of venous vessels, on Schwann cells of nerve bundles and on nerve fibres. In the osteoarthritis group the staining pattern was similar but the number of NK1-bearing cell structures seemed to be enhanced. CONCLUSIONS: The present study provides the first evidence of NK1-R in the human hip joint. In patients with painful osteoarthritis the density of NK1-R-positive cell structures seemed to be increased. The localisation of the NK1 receptor on different cell types suggests multiple effects of SP in normal and osteoarthritic joints.

Acetabulum↗

PubMedDate not supplied

[Effects of bisphosphonates in arthroplasty].

AIM: This study presents an overview of the general effects of bisphosphonates and in particular of their effects on different problems in joint arthroplasty. METHOD: First the chemical properties are described, then the biological effects. It is already known that bisphosphonates have effects on orthopaedic diseases and an increasing number of studies are investigating what effects can be achieved in joint arthroplasty with these substances. RESULTS: The bisphosphonates group was derived from industrial pyrophosphate which is used to prevent calcification. Bisphosphonates inhibit bone mineralisation and resorption. Several direct and indirect mechanisms are responsible for these effects. The inhibition of bone resorption is used to benefit patients suffering from various diseases causing increased bone resorption. Treatment with bisphosphonates results in greater bone density and improved mechanical bone quality. Indications for this treatment include osteoporosis, tumour-associated osseo-destruction, fibrous dysplasia and Paget's disease. Recent studies have shown that osseo-integration of metal implants is accelerated and periprosthetic bone loss, which is caused by various different mechanisms during the lifetime of an implant, can be reduced. CONCLUSION: Bisphosphonates have been an established element in the treatment of bone metabolic disorders for many years. Their use in joint arthroplasty could become increasingly important.

Animals↗

PubMedDate not supplied

[Influence of the x-ray technique on evaluation of cup anteversion after total hip arthroplasty].

AIM: Total hip arthroplasty (THA) is a standard procedure in orthopaedic surgery. Planar radiography of the implant is routinely performed to ensure that the operation has achieved the desired result. This study investigates the influence of varying the X-ray beam on the analysis of the radiograph. METHOD: Twenty-three patients were analysed after implantation of a total hip replacement. Besides a CT scan of the pelvis, symphysis- and hip-centred radiographs were available. The cup anteversion was calculated using two published algorithms. The CT-based data were the gold standard. RESULTS: Our study revealed a significant major error in the analysis of the symphysis-centred radiographs when compared with the hip-centered radiographs. Widmer's algorithm showed a significant superiority over Pradhan's formula. CONCLUSION: The best approximation of the anteversion angle was achieved using Widmer's technique by centering the X-ray beam onto the hip.

Acetabulum↗

PubMedDate not supplied

[Surgical treatment of congenital clavicular pseudarthrosis].

INTRODUCTION: Congenital pseudarthrosis of the clavicle is an extremely rare disease of unknown histogenesis. The method of treatment is still discussed controversely. CASES: Two cases of a congenital pseudarthrosis of the right clavicle were presented, revealing the typical clinical, radiologic and histopathologic features. Surgical treatment was performed at the age of 4 and 7 years, consisting of a partial resection of the bony ends of both segments of the clavicle, partial excision of the dense fibrous tissue lying within the defective area in the middle third of the clavicles by forming a continuous sleeve for interposing autogeneous spongiosa from the iliac crest and internal fixation with a Kirschner wire. Both cases showed a successful solid bone union in X-ray controls after 8 weeks. CONCLUSIONS: According to the histopathological findings we assume an abnormal ineffective chondral instead of an endesmal ossification resulting from a damage during embryogenesis as the underlying pathogenetic mechanism of congenital pseudarthrosis of the clavicle. Since chondral ossification proves to be ineffective also after birth, spontaneous bony union cannot be expected. Therefore, reconstructive surgery is the treatment of choice.

Bone Transplantation↗