Biomedical subjects

R P Pitto

Publications and source records attributed to R P Pitto.

At least 37 records · Page 2Linked to original sources

PubMed2000

Osteodensitometry in uncemented total hip arthroplasty using computertomography.

The aim of this investigation was to evaluate a new method developed for the measurement of bone mineral density and bone remodelling phenomena after total hip arthroplasty using computer tomography. Computertomography is a radiological technique to examine bone structures in high resolution. Using an extended scale it is possible to investigate bone scans and implants with fewer metal artifacts. For osteodensitometry measurement a special software (IMPact HIP) for the analysis of the data was used. The measured parameters were the overall bone mineral density (mg Calcium-Hydroxyapatite/ml) and the cortical bone structure. A standard scan mode enable to compare the computertomography scans at follow-up. Nineteen total hip arthroplasty patients (20 hips) with a mean age of 58 years (31-70) were operated on using an uncemented titanium alloy stem with a tapered design. The periprosthetic bone was assessed using computertomography-assisted osteodensitometry two weeks and one year after surgery. We observed a decrease of the overall bone mineral density (15%) and of the cortical bone structure (20%) one year after insertion of the stem in the proximal part of the femur. The area corresponds to the Gruen zones 1 and 7. On the other hand, a decrease of mineral density of 5% for the overall bone and of 3% for the cortical bone was found at the level of the tip of the stem, which corresponds to the Gruen zones 3, 4 and 5. Computertomography-assisted osteodensitometry allows to investigate the bone remodelling after total hip arthroplasty by separating the analysis of the overall bone mineral density and of the cortical structure. The present method is a reliable tool for quality-control in total hip arthroplasty.

Absorptiometry, Photon↗

PubMed2000

The Morse taper junction in modular revision hip replacement--a biomechanical and retrieval analysis.

All biomaterials used for total joint surgery are subjected to wear mechanisms. Morse taper junctions of modular hip revision implants are predilection sites for both fretting and crevice corrosion, dissociation and breakage of the components. The aim of this study is to quantify wear and study metallurgical changes of Morse taper junctions of in-vitro and in-vivo loaded modular revision stems. Three modular revision stems (MRP-Titan, Peter Brehm GmbH, Germany) were loaded by a servohydraulic testing machine. The loads and conditions used exceeded by far the values required by ISO-standard 7206. The tests were performed with maximum axial loads of 3,500 N to 4,000 N over 10-12 x 10(6) cycles at 2 Hz. Additionally, the female part of the taper junctions were coated with blood and bone debris. The free length of the implant was set to 200 mm. One other MRP stem was investigated after retrieval following 5.5 years of in-vivo use. All contact surfaces of the modular elements were assessed by visual inspection, optical microscopy and scanning electron microscopy (SEM). The degree of plastic deformation of the male part of the morse taper junction was determined by contouroscopy. None of the morse taper junctions broke or failed mechanically. Corrosion and wear affected all tapers, especially at the medial side. The retrieved implant showed no cracks and the amount of debris measured only one third of that for the stems tested in-vitro. The present retrieval and laboratory investigations have proven, that the morse taper junctions of the MRP-titanium stem are stable and resistant to relevant wear mechanisms. The longevity of the junctions for clinical use is given. If an optimal taper design is selected, the advantages of modular femoral components in total hip revision arthroplasty will outweigh the possible risks.

Biomechanical Phenomena↗

PubMed1999

Prophylaxis of secondary osteoarthrosis with spherical osteotomy in residual acetabular dysplasia. Analysis of predictive factors of success.

The aim of this study was to evaluate whether or not spherical acetabular osteotomy prevents progression of osteoarthrosis in hip joints with residual dysplasia and which radiological parameters can be used postoperatively as predictive factors concerning the outcome. Sixty-eight out of 78 joints were re-investigated with a mean follow-up of 11.2 years after the index operation. Twenty-three Wagner type 1 and 45 type II osteotomies were performed. At surgery, the mean age of the patients was 26 years; 90% of joints showed no or mild degenerative changes, 26% presented with a good or excellent Harris hip score. At follow-up, 28% of patients had improved in function, mean Harris hip score rated 75 points. The mean center-edge (CE) angle improved from -4 degrees to 18 degrees, and the anterior center-edge (ACE) angle from -4 degrees to 26 degrees. The weight-bearing zone of the acetabulum showed an acetabular index (AC) angle of 27 degrees preoperatively and 14 degrees postoperatively. Statistical analysis proved a significant correlation between the normal postoperative values of the acetabulum/femoral-head index of Heyman and Herndon and the absence of degenerative joint changes at follow-up. 73.5% of the hips had not markedly progressed to secondary osteoarthrosis, but 26.5% of joints had deteriorated: 7.4% of them due to perioperative complications and early postoperative trauma. In 8.8% (severe dysplasia) only partial reorientation was possible, which explains the progression of arthrosis, but 10.2% progressed despite sufficient correction.

Acetabulum↗

PubMed1999

Relevance of the drainage along the linea aspera for the reduction of fat embolism during cemented total hip arthroplasty. A prospective, randomized clinical trial.

The aim of this study was to assess the relevance of drainage placed along the linea aspera for the prevention of fat embolism and cardiopulmonary impairment during the insertion of a cemented stem. We studied 40 patients with coxarthrosis randomly allocated to total hip arthroplasty with proximal drainage or without it. The venting hole for the drainage of the medullary cavity was placed posteriorly, between the greater and the smaller trochanter, in the prolongation of the linea aspera. The heart was monitored intraoperatively by a echocardiography probe positioned in the patient's oesophagus. During the operation we monitored the hemodynamics and blood gas values. Severe embolic events were observed in 85% of the control group and in 20% of the drainage group (P = 0.01). Embolism occurred during the insertion of the femoral component and continued after reduction of the hip joint. After major embolism, the pulmonary shunt values increased significantly in the control group (+22.7%), but there were no marked changes in the drainage group (+7.1%). The logical therapeutic measure to avoid intravasation of bone marrow, fat, and bone debris during the insertion of the femoral component is to prevent the rise of intraosseous pressure. The drainage of the venous system located along the linea aspera significantly reduces the risk of intraoperative embolism and cardiopulmonary impairment.

Aged↗

PubMed1999

Long-term results of spherical acetabular osteotomy.

We have examined the effect of the Wagner spherical acetabular osteotomy on preserving the joint in 38 hips with a mean follow-up of 17 years. At the time of the initial operation, 55% of patients had clinical symptoms and 30 joints showed minimal or absent radiological signs of osteoarthritis. At follow-up, 54% of patients had a good functional result. The osteotomy improved the mean centre-edge angle from -3 degrees to +15 degrees, the mean anterior centre-edge angle to 23 degrees and the acetabular head index to 75%. The obliquity of the acetabular roof decreased from 28 degrees to 16 degrees. One patient improved, but 14 deteriorated with joint degeneration. Of these, one progressed because of postoperative deep-tissue infection and five due to undercorrection. One patient needed total joint replacement after 14 years. At 17 years after operation, Wagner osteotomy had prevented progression of secondary arthritis in 63% of cases.

Acetabulum↗

PubMed1999

[Primary stability of press-fit acetabulum cups using a new acetabulum reamer].

The aim of the present study was to assess the initial stability of uncemented press-fit acetabular components using a newly developed reamer designed to optimize the surgical preparation of the acetabulum. Ten synthetic human pelves were used to investigate the stability of 20 uncemented press-fit acetabular components, each of which was tested in a servohydraulic testing machine for 6 cycles under an axial load of 2.4 kN. The results of the micrometric measurements revealed satisfactory stability for a reaming depth of 2 mm, and a press-fit of 2 mm. Micromotion was less than 200 microns in all the anatomical sections of the acetabulum (ischium 63 microns, pubis 150 microns, ilium 85 microns). A press-fit of 4 mm and the smaller reaming depth of 1 mm were associated with a substantial decrease in mechanical stability.

Acetabulum↗

PubMed1999

[3-dimensional registration of micro-movements of vertebral implants by a specially adapted measuring system using magnetic transducers].

The aim of this study was to develop a biomechanical experimental set-up to quantify motion of ventrally inserted spinal implants at the implant/bone interface. The model we used was the vertebral column of the calf. Lumbar vertebrae L2 to L4 were "instrumented" with a screw-rod system. The adjacent vertebrae L1 and L5 were connected to a servohydraulic testing machine and axial compression applied. Shortening of the specimen and three-dimensional movement of the most cranial implant relative to the bone was recorded using 3 electromagnetic transducers. 100,000 cycles of axial loading varying between -0.5 kN and -1 kN were applied. Static shortening of the specimen of 8.5 mm and an elastic movement of 180 to 280 microns were measured. The greatest amplitude of single-plane motion was recorded in the sagittal plane in both static and elastic modes. Implant motion within each cycle was recorded accurately as load-displacement curves within a range of 1.35 to 30 microns. With this test set-up, primary stability of different spinal implant systems can be compared. The use of electromagnetic transducers permits three-dimensional implant motion analysis even when only a mono-axial servohydraulic testing machine is available.

Animals↗

PubMed1999

[New instruments for preparation of the prosthesis socket and primary stability of the acetabular Press-fit cups].

The aim of the present study was to develop surgical instruments necessary to achieve a precisely reamed surface and stable initial fixation. The instruments used to prepare the socket were a gauge-drill guide, a liner for the spigot hole and two spigotted reamers of different design and indentation intended to achieve a precisely reamed surface while preserving subchondral bone. For each reamer we implanted in a synthetic hip model 10 uncemented cups with 2 mm press-fit and loaded at 2.4 kN in the physiological axis (Mod. 8501, Instron, Canton, MA, USA). The micromotion between implant and bone socket was measured using an inductive micrometric measuring system (MultiNCDT-500, Micro-Epsilon, Ortenburg, Germany) and compared with that seen after using conventional instruments. The use of the new reamer of elliptical design significantly reduced the standard deviations of the measured values (p < 0.01 at the ischium and pubis) and also reduced maximum movement (p < 0.01 at the ischium); at the same time, all the components showed overall limited movement (< 150 microns at the ischium, pubis and ilium) under maximum loading (2.4 kN). Manufacturing tolerances, the quality and wear of the instruments, acetabular bone stock and surgical technique all impact on the degree of press-fit obtainable at surgery. The results of our study show that press-fit and initial stability can be optimized by using adequate instruments to prepare the socket.

Acetabulum↗

PubMed1999

[Performance of vacuum pumps used during implantation of hip endoprostheses with an innovative cementing technique--a comparative study].

The increase in intramedullary pressure during implantation of a cemented total hip prosthesis is the decisive pathogenic factor in the development of an embolism. The logical countermeasure aimed at preventing bone marrow and fat emboli is reduction of pressure. Drainage of the femoral canal enabled by the bone-vacuum cementing technique substantially reduces intraoperative fat embolism and cardiopulmonary events. The aim of the present study was to compare the efficiency of two suction pumps used with this technique. In-vitro and In-vivo measurements of pressure were obtained to characterize the properties of the Vakufix pump and the Sterivap pump. In vitro experiments showed that the length of the suction tube has no influence on the performance of the pumps. A useful vacuum in the medullary canal was achieved In-vivo with both pumps (mean-209.3 mbar). The vacuum obtained with the Vakufix pump was higher (+16%) than that obtained with the Sterivap pump. Owing to the complexity of the system, we would not recommend the use of the Sterivap pump for evacuating the femoral canal.

Aged↗

PubMed1999

Comparison of fixation of the femoral component without cement and fixation with use of a bone-vacuum cementing technique for the prevention of fat embolism during total hip arthroplasty. A prospective, randomized clinical trial.

BACKGROUND: Acute hypotension, hypoxemia, cardiac arrest, and sudden death are well recognized complications during total hip arthroplasty, and they have been attributed to embolization of fat and bone marrow. An increase in intramedullary pressure in the femur is the most important pathogenic factor for the development of embolic events. Intravasation of fat, bone marrow, and bone debris during the implantation of a femoral component, and the embolization of these elements through the venous system located along the linea aspera and through the metaphyseal vessels, have been demonstrated experimentally and clinically. The purpose of the present study was to compare the effects of fixation of the femoral component without cement with those of fixation with a bone-vacuum cementing technique on the severity of embolic phenomena and cardiopulmonary impairment during total hip arthroplasty. Fixation with a conventional cementing technique was also evaluated as a control. METHODS: Sixty patients (sixty hips) were entered into a prospective, randomized clinical trial. The patients were assigned to one of three groups. Group 1 consisted of twenty patients who had the femoral component inserted without cement, Group 2 comprised twenty patients who had the component inserted with a conventional cementing technique, and Group 3 included twenty patients who had fixation with the so-called bone-vacuum cementing technique. In the hips in Group 3, a suction of -800 millibars (-80,000 pascals) was applied to a proximal drainage cannula placed along the linea aspera and a distal drainage cannula placed in the diaphysis in order to produce a vacuum in the medullary cavity of the femur during the application of cement and the insertion of the stem. Transesophageal echocardiography and hemodynamic and blood-gas analysis were performed during the operation. RESULTS: Severe embolic events (defined as a cascade of fine echogenic particles of less than five millimeters in diameter) were observed in seventeen (85 percent) of the twenty patients during insertion of the stem with use of a conventional cementing technique but in none of the patients who had the stem inserted without cement (p < 0.05). Insertion of the femoral component with the bone-vacuum cementing technique prevented embolic phenomena in all but one patient (5 percent). Arterial oxygen saturation decreased significantly (p < 0.05) from a mean of 99.5 to 92.9 percent after insertion of the stem with a conventional cementing technique, but only slight changes were observed in the patients who had fixation of the component without cement and in those who were managed with the bone-vacuum cementing technique. Intraoperative pulmonary shunt values increased a mean of 24 percent (p < 0.05) when the femoral component was inserted with a conventional cementing technique, but with the numbers available we did not detect a significant change in those values when the component was fixed without cement or when it was inserted with use of the bone-vacuum cementing technique. CONCLUSIONS: The present study showed that severe embolic events and intraoperative pulmonary impairment are common when a femoral component is fixed with use of a conventional cementing technique. The results clearly demonstrated a low risk of embolism during total hip arthroplasty when the femoral component was fixed without cement and when it was fixed with the bone-vacuum cementing technique. The ability of a patient to withstand an embolic event should be considered before fixation of the femoral component with use of a conventional cementing technique is planned.

Aged↗

PubMed1998

Impaction grafting and acetabular reinforcement in revision hip replacement.

A substantial loss of bone stock is frequently encountered at revision of a hip replacement. A mix of autologous and homologous bone chips is a biological method of filling the cavities. Reinforcement implants can be used to anchor the new prosthesis and to impact the bone graft, protecting it during healing. The goals of this study were to evaluate the clinical and radiological results after revision of cups with aseptic loosening. Follow-up examination of 81 revisions in 78 patients at 6.5 years (range 3 to 9 years) showed that 93% of the patients were satisfied with their results. One patient underwent a further revision because of recurrent dislocation of the femoral head, and one had a superficial infection. All the grafts were fused at 3 months after the operation. The bone stock had increased in every case, but 6 of them show some degree of graft resorption. No implant showed impending signs of loosening. These results were encouraging. The reinforcement implants allow sufficient primary fixation and secondary stability can be achieved with the impaction grafting. Careful preoperative evaluation and assessment at operation is important to match bone defects with the grafts and selection of the prosthesis.

Arthroplasty, Replacement, Hip↗

PubMed1998

The John Charnley Award. Prophylaxis of fat and bone marrow embolism in cemented total hip arthroplasty.

The efficiency of a new cementing technique developed to prevent the risk of intraoperative pulmonary embolism was assessed. Seventy patients with coxarthrosis entered into a prospective, randomized clinical trial. In the control group of 35 cases the total hip replacement was cemented conventionally. In the second group a proximal drainage placed along the Linea aspera, and a distal drainage placed in the diaphysis, created a vacuum in the medullary cavity of the femur during the insertion of the stem. The operation was performed with the patient under blood gas analysis and hemodynamic and transesophageal echocardiography monitoring. Severe transatrial embolic events were observed during the insertion of the femoral component in 94% of the cases of the control group and in 14% of the cases of the vacuum group; the difference is statistically significant. A significant decrease of arterial partial pressure of O2 (-40.8 mm Hg) and increase of the pulmonary shunt values (+28.3%) occurred 5 minutes after the observation of embolic events in the cases operated on conventionally, but these parameters showed minimal changes in the vacuum group. The rise of intramedullary pressure in the femur is the most decisive pathogenic factor of pulmonary embolism during total hip arthroplasty. The logical prophylactic measure to prevent intravasation of fat and bone marrow is to create sufficient drainage. The cohorted investigation showed the value of the vacuum cementing technique for a substantial reduction of intraoperative embolism and pulmonary impairment.

Aged↗

PubMed1998

[Effect of socket preparation on primary stability of an elliptical acetabular component].

The aim of this investigation was to examine, with the aid of a valid micrometric measuring system, the initial stability of an elliptical press-fit acetabular component with regard to the size of the reamer used to prepare the socket, and the depth of reaming. All 10 implanted cups showed marked movement (> 500 microns) at the first loading after implantation. Only the implant with a press-fit of 1 mm and a reaming depth of 2 mm showed small elastic micromovement (< 130 microns) at all three measuring points during cyclic loading. The results indicate that press fit and stability need to be optimized using adequate surgical instrumentation and techniques, and that it is necessary to develop new methods to optimize the cementless anchorage of acetabular components.

Acetabulum↗

PubMed1997

[Factors affecting the primary stability of acetabular components. An in vitro study].

The aim of the present study was to investigate the micromotion under physiological loading of various acetabular components with and without screws, to determine the most suitable anchoring, cup design and optimal surface structure. Six acetabular components with varying cup geometry and surface configuration were implanted with a 2 mm press-fit into polyethylene pelves. In the first set of trials, the uncemented cups with two peripheral screws were tested under an axial load of 240 kg (2,354 N). The screws were then removed and the cups, held in place only by press fit, were tested again. None of the uncemented cups achieved the high initial stability of the cemented reference cups. It was not possible to determine an optimal cup design. In this study, titanium plasma-spray-coated cups achieved the best results. Stability is determined only in part by the configuration of the prosthesis. Of equal importance is the quality of the preparation of the cup bed. The use of screws cannot be unreservedly recommended. With a good press fit, the use of screws enhances stability only minimally.

Acetabulum↗

PubMed1995

Total hip replacement with bone grafting using the removed femoral head in severe acetabular dysplasia.

We carried out total hip replacement and femoral head bone-grafting in 21 hips with congenital dysplasia or dislocation, obtaining as much support of the cup by the host bone as was possible. A Charnley small or extra small cup was implanted in 20 cases and a miniature femoral component in 15. The results of 20 hips were reviewed prospectively at an average of 10 years. Nineteen patients had no pain. Three cups showed radiological signs of loosening, one was causing other symptoms. All the stems, except one, were radiologically stable and were symptomless. The graft had fused without resorption in 18 cases. Two grafts showed severe resorption with loosening of the cup. Satisfactory long term results of total hip replacement and femoral head bone-grafting can be achieved using special surgical techniques and the appropriate components. Medialisation of the hip and the use of small cups are important in allowing sufficient support of the prosthesis by bone so that the distribution of load on the graft is minimised. The grafted femoral head provides suitable bone stock for reconstruction of the acetabulum.

Adult↗

PubMed1994

The mortality and social prognosis of hip fractures. A prospective multifactorial study.

A prospective 5-year study was carried out of 143 patients with trochanteric fractures treated by Ender nailing. A detailed proforma was used for multifactorial analysis in order to identify the prognostic indicators of social function and quality of life of the patients. Their mean age was 81 years and the female: male ratio 7:1. The mortality rate 6 months after injury was 23%, and at the end of 5 years 45.5%. The patients surviving the first 6 months had the same life expectancy as the general population. Dementia, associated disease, medical complications, total dependency and age were the most significant predictors of mortality. These factors, with pressure sores and poor rehabilitation, were also significant in determining the prognosis of social function. Deterioration of health status was seen in 36% during the first 6 months after injury and 40% showed deterioration of their social condition within this period. Later, most survivors recovered and were restored to their previous state. Postoperative geriatric care is essential to achieve this aim.

Aged↗

PubMed1991

Extraforaminal lumbar disk herniation. Clinical features and computerized tomography.

Disk herniation lateral to the intervertebral foramen is defined as extraforaminal. Its particular anatomical site makes its clinical and neurologic features completely different from those of posteromedial and posterolateral disk herniations. Prior to the advent of computerized tomography, only diskography was capable of preoperatively identifying this rare disease. We present 5 cases of extraforaminal disk herniation, the clinical and tomographic diagnosis of which was confirmed at surgery. All patients had severe motor deficit and reported sciatica as prevalent over low back pain. The herniated disk was L4-5 in 2 cases and L5-S1 in 3 cases. The CT scan suggested disk protrusion in 2 cases, extrusion in 2 cases, and sequestration in 1 case. Four of these findings were confirmed intraoperatively. Diskectomy was done after hemilaminectomy and partial or total facetectomy. The clinical result was excellent in 2 cases and good in 3 cases after an average follow-up of 10 months. The use of CT scan as part of the routine diagnostic procedure in patients with radicular pain has lowered the number of cases which the surgical findings were inexplicably negative for disk herniation without having to resort to more complex and invasive diagnostic techniques such as myelo-CT and disk-CT. Moreover, preliminary tomographic localization of the extraforaminal disk herniation makes it possible to operate on the affected level using more conservative techniques. In any case, thorough clinical examination is essential for both correct interpretation of the CT scan and appropriate choice of treatment.

Adult↗

PubMed1991

Verified causes of failure in the treatment of femoral neck fractures with multiple Knowles pins.

The authors examine 152 cases of femoral neck fractures treated with Knowles pins in order to analyze the incidence and causes of nonunion and avascular necrosis. The displaced fractures were all treated with closed reduction, and weight-bearing was permitted after 30-45 days. Seventy fractures were followed up after an average of four years. Criteria are proposed for evaluating the quality of both the reduction and the internal fixation. Healing was achieved in all cases of Garden grade I and II fractures; the incidence of avascular necrosis was 4.1%. In the displaced fractures the incidence of nonunion was 15.2% and avascular necrosis 13%. Technical errors in either reduction or internal fixation were present in 50% of the necroses and in 100% of the nonunions. The quality of the reduction was the most important factor in fracture healing, yet an accurate reduction and a valid fixation could not completely overcome the risk of avascular necrosis in the femoral head.

Adult↗