Biomedical subjects

M von Knoch

Publications and source records attributed to M von Knoch.

At least 19 recordsLinked to original sources

PubMed2007

[Endosteal reaction in the region surrounding the stem of a cement-free prosthesis. An early radiological sign of imminent fracture of the femoral shaft?].

Periprosthetic fractures are familiar complications after total hip arthroplasty and have often been reported in the literature. The most frequent localization of such fractures is the middle third of the shaft. In the case described here a minor trauma resulted in a periprosthetic fracture with fracture of the femur and of the femoral component of a Lord prosthesis. A radiograph taken prior to trauma showed an endosteal reaction at the level at which the fracture later occurred. This might have been an indication that the stem of the prosthesis was already broken; had this radiological sign been correctly interpreted, it is possible that the fracture could have been avoided.

Aged↗

PubMed2007

[Structural femoral head allografts in revision surgery of loosened acetabular cups].

BACKGROUND: Treatment of acetabular bone defects presents a great challenge in revision total hip arthroplasty (THA). Many methods of acetabular reconstruction have been described. The purpose of this study was to evaluate the midterm results of structural femoral head allografts for acetabular reconstruction. METHODS: Thirty-six patients (33 females and 3 males) with acetabular defects ranging from type 2C to type 3B according to Paprosky's classification were included in the study. In all cases acetabular defects were closed using allografts from femoral heads. In 13 cases an uncemented press-fit cup, in 17 cases a cemented polyethylene socket, and in 6 cases a Burch-Schneider antiprotrusion cage was implanted. The mean follow-up period was 84.2 months (range: 5-147). RESULTS: Four acetabular components failed. All 36 grafts were osseointegrated radiographically and formed a mechanically stable construction. The mean Harris Hip Score at the most recent follow-up was 79.8 points. The distance from the obturator line to the prosthesis head center was 3.73 cm (1.17-5.80 cm) preoperatively and 2.79 cm (0.85-4.8 cm) postoperatively (p<0.05). The distance from the teardrop figure to the prosthesis head center was 3.02 cm (1.0-5.8 cm) preoperatively and 3.25 cm (1.6-4.8 cm) postoperatively (p<0.001). CONCLUSIONS: Closure of acetabular defects of types 2C to 3B according to Paprosky's classification can be satisfactorily accomplished using femoral head allografts. These allografts may facilitate future revision surgery. Femoral heads are readily available due to widespread primary total hip replacement surgery. However, the use of structural femoral head allografts for acetabular reconstruction is cost intensive. Individual patient-related aspects, such as the function of revision arthroplasty, have to be considered when planning revision arthroplasty using femoral head allografts.

Acetabulum↗

PubMed2006

Reinforcement of deficient femur with inlay strut grafts in revision hip arthroplasty: a small series.

Failure of the femoral component due to severe loss of femoral bone is an important long-term complication of total hip arthroplasty. We treated four patients with a type IV femoral defect (Paprosky classification) because of aseptic and septic loosening. To enhance bone stock and create a stable prosthetic reconstruction we used femoral allografts as inlay strut grafts alone or combined with onlay strut grafts and impaction grafting. At a mean follow-up of 11 years all four patients presented good or excellent results with Harris Hip Score between 86 and 95 points. Radiologically, no migration of the stems were found and the struts showed signs of incorporation. Inlay strut grafts are a reliable method for bone reconstruction of deficient femoral bone stock in failed total hip replacement.

Aged↗

PubMed2006

Trochleaplasty for recurrent patellar dislocation in association with trochlear dysplasia. A 4- to 14-year follow-up study.

We investigated the clinical and radiological outcome of trochleaplasty for recurrent patellar dislocation in association with trochlear dysplasia in 38 consecutive patients (45 knees) with a mean follow-up of 8.3 years (4 to 14). None had recurrence of dislocation after trochleaplasty. Post-operatively, patellofemoral pain, present pre-operatively in only 35 knees, became worse in 15 (33.4%), remained unchanged in four (8.8%) and improved in 22 (49%). Four knees which had no pain pre-operatively (8.8%) continued to have no pain. A total of 33 knees were available for radiological assessment. Post-operatively, all but two knees (93.9%) had correction of trochlear dysplasia radiologically but degenerative changes of the patellofemoral joint developed in 30% (10) of the knees. We conclude that recurrent patellar dislocation associated with trochlear dysplasia can be treated successfully by trochleaplasty, but the impact on patellofemoral pain and the development of patellofemoral osteoarthritis is less predictable. Overall, subjective patient satisfaction with restored patellofemoral stability after trochleaplasty appeared to outweigh its possible sequelae.

Adolescent↗

PubMed2005

[A comparison of the antiresorptive effects of bisphosphonates and statins on polyethylene particle-induced osteolysis].

An ongoing unraveling of the molecular mechanisms in aseptic loosening of hip arthroplasty has opened up novel potential pharmacological interventions. In this study the antiresorptive effects of the bisphosphonate zoledronate and the statin simvastatin on ultra high molecular weighted polyethylene (UHMWPE) particle-induced osteolysis were compared. Two previous studies of our group based on the murine calvarial model of UHWMPE particle-induced osteolysis were pooled to form four study groups. Animals in group I (n=14) underwent sham surgery only. In groups II (n=14), III (n=7) and IV (n=7) UHMWPE particles were implanted on the calvariae. Animals in groups III and IV were additionally treated with zoledronate (single 25 microg/kg s.c. injection) and simvastatin (120 mg/day p.o. for 14 days), respectively. After two weeks, calvaria were processed for undecalcified histomorphometry. Bone resorption was measured using Giemsa staining. Osteoclast numbers were determined using TRAP-staining. UHMWPE particle implantation resulted in a grossly pronounced osteolytic activity with significantly increased values of bone resorption (p < 0.001) and osteoclast numbers (p < 0.001). Additional treatment with zoledronate or simvastatin counteracted the particle-induced effects. A comparison of the two medical treatments revealed no statistically significant differences in bone resorption (p = 0.63) and osteoclast numbers (p = 0.41). A single dose of the bisphosphonate zoledronate decreased UHMWPE particle-induced osteolysis in a murine calvarial model as effectively as a daily treatment with simvastin. Both drug groups may have a preventive and therapeutic role as antiresorptive agents in wear particle-induced bone resorption following total joint replacement.

Animals↗

PubMed2004

The accuracy of free-hand cup positioning--a CT based measurement of cup placement in 105 total hip arthroplasties.

We studied 105 patients who received a total hip arthroplasty between June 1985 and August 2001 using freehand positioning of the acetabular cup. Using pelvic CT scan and the hip-plan module of SurgiGATE-System (Medivision, Oberdorf, Switzerland), we measured the angles of inclination and anteversion of the cup. Mean inclination angle was 45.8 degrees +/-10.1 degrees (range: 23.0-71.5 degrees ) and mean anteversion angle was 27.3 degrees +/-15.0 degrees (range: -23.5 degrees to 59.0 degrees ). We compared the results to the "safe" position as defined by Lewinnek et al. and found that only 27/105 cups were implanted within the limits of the safe position. We conclude that a safe position as defined by Lewinnek et al. [13] was only achieved in a minority of the cups that were implanted freehand.

Adult↗

PubMed2004

Decrease in particle-induced osteolysis in obese (ob/ob) mice.

There may be variability in the susceptibility of different individuals to osteolysis from wear debris, and it is not clear whether some individuals may have a genetic predisposition for a more marked osteolytic response. The purpose of this study in mice was to determine whether genetically determined obesity can alter the response to particulate debris. Polyethylene particles were implanted onto the calvaria of seven wild-type mice and seven obese mice (ob/ob). Calvaria from unimplanted wild-type and obese mice served as controls. Calvaria were harvested after 7 days, stained with toluidine blue and for tartrate-specific alkaline phosphatase, and analyzed by histomorphometry. The osteoclast number per mm total bone perimeter was 8.000+/-3.464 in wild-type animals with particles and 2.857+/-1.676 in ob/ob animals with particles (p=0.002; Fisher's PLSD). Bone resorption was 1.895+/-0.713 mm/mm(2) in wild-type animals with particles and 1.265+/-0.494 mm/mm(2) in ob/ob animals with particles (p=0.0438; Fisher's PLSD). Particles induced a diminished osteolytic response in genetically determined obese mice, suggesting that obesity may have a protective role against particle-induced bone resorption-similar to obesity and osteoporosis. These important new findings may help to stimulate clinical studies which may define criteria to better identify patients at risk to develop particle-induced osteolysis.

Animals↗

PubMed2004

[Titanium as an implant material for rods of transpedicular instrumentation of the lumbar spine].

BACKGROUND AND AIM: Titanium alloys are increasingly being used as an implant material in orthopaedics and for spinal instrumentation. In this study a metallographic analysis and mechanical testing were performed to evaluate the resistance of rods of Ti-A16-V4 in particular to tensile forces. METHOD: The surface texture of unprepared Ti-A16-V4 and a rod of the same material for spinal instrumentation were evaluated in a metallographic analysis using light microscopy and electron microscopy. Tensile strength measurements were performed on 2 rods, and the strength of the connection between rod and pedicle screws was tested in 9 cases. An electron microscopic analysis of surface changes of the connections between rod and pedicle screws after loading was performed. RESULTS: The titanium alloy Ti-A16-V4 has a mill-annealed appearance, which has a high resistance to tearing under stress. Titanium rods show high tensile strength before failure under loading. The connection between rod and pedicle screws also as high resistance to tensile loads (> 27 kN) with only little deformation of the connecting surface and no tearing. CONCLUSION: The titanium alloy Ti-A16-V4 is an appropriate material for dorsal spinal instrumentation rods because of its low weight, high biocompability and high tensile strength.

Alloys↗

PubMed2003

Periprosthetic fractures with extensive bone loss treated with onlay strut allografts.

We reviewed a consecutive series of 19 patients with comminuted periprosthetic fractures, loosening of the femoral stem (Vancouver type B3) and significant loss of bone stock (Paprosky type III and IV). Sixteen porous-coated long stems and three Exeter stems, all with impaction grafting, were used. Large femoral onlay strut allografts were applied to maintain fracture reduction and improve stability. There was one early re-fracture at the tip of the femoral stem. Eighteen fractures healed without deformity and shortening. At the last follow-up at mean 3.7 (2.0-7.5) years, the mean Harris hip score was 76.4 (57.5-92.0). There was ingrowth of all strut grafts and significant augmentation of periprosthetic bone.

Adult↗

PubMed2002

Spontaneous fusion of 'os acetabuli' after triple pelvic osteotomy.

In acetabular dysplasia, an overloading of the acetabular rim can cause a stress fracture, creating an 'os acetabuli', or a lesion of the acetabular labrum. At puberty, the os acetabuli seems to be the epiphysis of the os pubis. We present the case of a 14-year-old girl with acetabular dysplasia and spontaneous fusion of an 'os acetabuli' after biomechanical correction by triple pelvic osteotomy. Our report supports the correctness of the biomechanical principle: reorientation of the acetabulum results in a better coverage of the femoral head, reduces the stress at the acetabular rim, shifts the os acetabuli out of the stress region, and may allow union of the bony fragment with the acetabulum.

Acetabulum↗

PubMed2002

[Holistic thinking in medicine--do we need a medical philosophy? Current efforts to think beyond the limits of school medicine, needs for systematic standardization].

The increasing debate dealing with topics of medicine and with medicine itself necessitates a scientific and systematic approach to the reality of medicine as a whole. This can be accomplished by the philosophy of medicine. For the purpose of reorientation of this discipline a division into notices of medicine, aesthetics of medicine and ethics of medicine is proposed.

Austria↗

PubMed2002

[Surface cleaning of cemented orthopedic implants with conservation of surface properties].

Prior to the analysis of explanted cemented orthopedic implants, complete removal of foreign material, blood and residual tissue and thorough cleaning of the surface without compromising its characteristics is essential. We describe a reprocessing procedure comprising the following 4 steps: 1) retrieval and storage, 2) removal of residual bone cement, 3) chemical cleaning in an enzymatic solution, and 4) mechanical cleaning in an ultrasound bath.

Bone Cements↗

PubMed2001

Total knee arthroplasty in a patient with chronic occlusion of the superficial femoral artery.

In a 67-year-old patient with severe valgus gonarthrosis and chronic occlusion of the superficial femoral artery on the same side, total knee replacement was performed without preceding angioplasty because the collateral circulation was intact. No tourniquet was used. To leave the peripatellar arterial ring intact on one side in this case of lateral patellar maltracking, a lateral approach was used. In this approach, a lateral release forms part of the approach itself. To achieve gentle eversion of the patella, the tibial tubercle was osteotomized. One year postoperatively, the patient was satisfied with the outcome and showed no clinical signs of any vascular deterioration. It is concluded that total knee replacement may be possible in the presence of chronic occlusion of the superficial femoral artery provided that the collateral circulation is intact.

Aged↗

PubMed2001

Intracellular measurement of polyethylene particles. A histomorphometric study.

A histological and histomorphometric study was carried out on pseudo-capsules retrieved from patients during revision surgery of cementless total hip replacement. Polyethylene loading and areal polyethylene particle size in different cells of the reticuloendothelial cell line were determined within the tissue by histomorphometry. In the reticuloendothelial cell line, foreign-body giant cells are considered to be the result of confluence of mononuclear macrophages caused by large particles or other unknown stimuli. The aim of this study was to investigate whether polyethylene particle size and polyethylene loading are different in mononuclear macrophages and foreign-body giant cells. The specimens were examined under the light-optical microscope with plain and polarized light. The polyethylene loading of 329 macrophages (mononuclear), 81 small foreign-body giant cells (2-5 visible nuclei), and 103 large foreign-body giant cells (6 or more visible nuclei) was determined and the intracellular polyethylene particle size analyzed by histomorphometry. The mean polyethylene loading was 13 +/- 8 microm2, 25 +/- 16 microm2, and 49 +/- 42 microm2, respectively. This difference was statistically significant (Student's t-test, P < 0.05). The mean polyethylene particle size was 2.34 +/- 3.2 microm2, 3.02 +/- 3.46 microm2, and 4.70 +/- 11.25 microm2, respectively. This difference was statistically significant between macrophages and large foreign-body giant cells (t-test, P < 0.05). The findings of this light-optical study show that the mean intracellular polyethylene particle size is greater in foreign-body giant cells. In addition, absolute polyethylene loading tends to be higher in foreign-body giant cells than in mononuclear macrophages.

Female↗

PubMed2001

Magnetic resonance arthrography of the acetabular labrum: value of radial reconstructions.

The intention was to compare the sensitivity and specificity of radial planes with oblique coronal and oblique axial planes for the detection of labral abnormalities of the acetabulum on magnetic resonance arthrography (MRa). Twenty cadaveric hip joints were examined by radiography and MRa. For MRa, 15 ml of a solution of iodinated contrast material and gadolinium diethylene triamine tetra-acetic acid (Gd-DTPA; 100:1) were injected under fluoroscopic guidance. MRI was performed on a 1.5-T MR scanner with a fat-suppressed 3D-FLASH sequence (TR/TE/flip-angle 42 ms/10 ms/40 degrees; field of view 16 cm, matrix 256 x 256, section thickness 1.5 mm, pixel size 0.7 x 0.7 mm). Multiplanar image reconstructions were done perpendicular to the acetabulum in oblique coronal and oblique axial planes and in radial planes. Macroscopic and histopathologic examination of the labral specimens was performed. Labral lesions were found in 15/20 hips (75%) on pathologic examination. Six hips demonstrated labral degeneration. The labrum was partially detached in 7 hips and completely detached in 2 hips. A flap-like labrum was found in 2 cases, 1 with partial detachment of the labrum and 1 with a degenerated labrum. Using oblique coronal and oblique axial reconstructions, pathologic findings were confirmed by MRa in 9/15 specimens (sensitivity 60%). There were no false-positive findings (specificity 100%, accuracy 70%). Also, 3/6 labral degenerations without detachment, 4/7 partial detachments, and 2/2 complete detachments were correctly diagnosed. Two flap-like labra were not recognized. With radial reconstructions, pathologic findings were correctly confirmed in 12/15 specimens (sensitivity 80%) without false-positive findings (specificity 100%, accuracy 85%). Also, 3/6 labral degenerations without detachment, 6/7 partial detachments, 2/2 complete detachments, and 1/2 flap-like labra were correctly diagnosed. MRa of the acetabular labrum using radial reconstructions is well suited to delineate the acetabular labrum and to diagnose labral detachments. Radial reconstructions allow for perpendicular display of the whole acetabular circumference and are more accurate for the diagnosis of acetabular labral lesions, when compared with oblique coronal and oblique axial reconstructions.

Acetabulum↗

PubMed2001

Skeletal cystic angiomatosis with severe hip joint deformation resembling massive osteolysis.

An aggressive destruction pattern resulting in joint deformation has not been described in skeletal cystic angiomatosis (SCA) so far. We present the case of a 6-year-old boy with such findings strongly resembling Gorham's disease (massive osteolysis). Since the prognosis of the latter entity tends to be less favorable than in SCA, particularly SCA without extraskeletal involvement, careful differentiation of both disorders appears to be important.

Angiomatosis↗

PubMed2000

Migration of polyethylene wear debris in one type of uncemented femoral component with circumferential porous coating: an autopsy study of 5 femurs.

This autopsy study analyzed the migration of polyethylene wear debris adjacent to uncemented femoral components with circumferential porous coating. Five femoral specimens retrieved at autopsy from 3 patients were investigated. Two stems were 40% porous coated, 2 were 80% porous coated, and 1 was 100% porous coated. The implants' time in situ ranged from 53 to 132 months (average, 94.8 months). All patients were followed clinically and radiographically until death. Radiographically, 3 of the stems were bone ingrown with proximal bone loss, 1 stem was mainly fibrous encapsulated, and 1 stem was completely fibrous encapsulated. Histologic examination of bone adjacent to the middle and distal sections of the femoral implant revealed no polyethylene wear debris or granulation tissue in any of the specimens. In 2 bone-ingrown cases, a small number of polyethylene particles and small areas of granulation tissue were present at the proximal level. This granulation tissue, however, did not cause major osteolysis. The findings in this study imply that circumferential porous coating of cementless femoral components could prevent distal migration of polyethylene wear debris along the bone-implant interface in both bone-ingrown and fibrous-encapsulated femoral implants.

Aged↗

PubMed1999

Unsuccessful surgical treatment of hip dislocation in congenital sensory neuropathy with anhidrosis. A case report.

A six-year-old girl with congenital sensory neuropathy with anhidrosis (CSNA) presented with bilateral hip dysplasia and subluxation on the right side. Conservative treatment of the hips by closed reduction and a plaster cast was unsuccessful. When aged seven years the patient had an intertrochanteric varus rotation osteotomy on the right side, but subluxation was again evident after five months. A Salter-type pelvic osteotomy was carried out followed by immobilisation, but one year later subluxation was present in the right hip and dislocation in the left. At the age of nine years, the right femoral head resembled a Charcot joint, although walking ability was preserved. In patients with CSNA, surgery may not always be advisable.

Child↗