PubMed Health⌕ Search

Biomedical subjects

R P Pitto

Publications and source records attributed to R P Pitto.

At least 19 recordsLinked to original sources
PubMed2006

Quantitative computer-assisted osteodensitometry in total hip arthroplasty.

Several factors can cause bone loss and fixation failure following total hip arthroplasty (THA), including polyethylene wear debris, implant micromotion and stress shielding. Various techniques have been used in an effort to detect bone density loss in vivo, all with varying success. Quantitative computed tomography (qCT)-assisted osteodensitometry has been shown to be useful in assessing the in vivo structural bone changes after THA. It has a high resolution, accuracy and reproducibility, thereby making it a useful tool for research purposes, and it is able to differentiate between cortical and cancellous bone structures and assess the bone/implant interface. This technique also provides valuable information about the pattern of stress shielding which occurs around the prosthesis and can show early bony changes, which may prove informative about the quality of implant fixation and surrounding bone adaptation. In conjunction with finite-element analysis, qCT is able to generate accurate patient-specific meshes on which to model implants and their effect on bone remodelling. This technology can be useful to predict bone remodelling and the quality of implant fixation using prostheses with different design and/or biomaterials. In the future, this tool could be used for pre-clinical validation of new implants before their introduction in the market-place.

Absorptiometry, Photon↗
PubMed2006

Accuracy of a computer-assisted navigation system for total knee replacement.

The object of this study was to develop a method to assess the accuracy of an image-free total knee replacement navigation system in legs with normal or abnormal mechanical axes. A phantom leg was constructed with simulated hip and knee joints and provided a means to locate the centre of the ankle joint. Additional joints located at the midshaft of the tibia and femur allowed deformation in the flexion/extension, varus/valgus and rotational planes. Using a digital caliper unit to measure the coordinates precisely, a software program was developed to convert these local coordinates into a determination of actual leg alignment. At specific points in the procedure, information was compared between the digital caliper measurements and the image-free navigation system. Repeated serial measurements were undertaken. In the setting of normal alignment the mean error of the system was within 0.5 degrees . In the setting of abnormal plane alignment in both the femur and the tibia, the error was within 1 degrees . This is the first study designed to assess the accuracy of a clinically-validated navigation system. It demonstrates in vitro accuracy of the image-free navigation system in both normal and abnormal leg alignment settings.

Arthroplasty, Replacement, Knee↗
PubMed2005

Pre-formed articulating knee spacer in two-stage revision for the infected total knee arthroplasty.

We performed a prospective study to assess safety and effectiveness of a pre-formed articulating spacer made of gentamicin-impregnated acrylic cement in the management of infected total knee arthroplasty. Twenty-one consecutive patients with unilateral deep infection were treated by two-stage revision in two centres. Two patients were excluded, and 19 patients remained available for assessment. The mean implantation time of the spacer was 12 weeks. The rehabilitation programme between stages consisted in early range of motion exercises and partial weight bearing. Mean follow-up after removal of the spacer and insertion of the final prosthesis was 24 (range, 12-43) months. No patient had recurrence of infection at the latest follow-up. The mean Knee Society functional score during spacer management was rated 75 points and was rated 84 points at the latest follow-up. No device-related complication was observed.

Aged↗
PubMed2004

Antibiotic-loaded bone cement spacers in two-stage management of infected total knee arthroplasty.

We reviewed the current use of spacers in the management of the infected knee prosthesis. There are two types of temporary spacers: block or non-articulating spacers and articulating or mobile spacers. Generally, spacers improve mobilisation and hasten recovery with shorter hospital stay between stages. Furthermore, spacers facilitate the second-stage procedure by maintaining joint space, and articulating spacers may also maintain range of motion. Last but not the least, the cost of spacers represents only a small fraction of the total expenses for management of infected knee arthroplasties.

Anti-Bacterial Agents↗
PubMed2004

Mechanical prophylaxis of deep-vein thrombosis after total hip replacement a randomised clinical trial.

Routine prophylaxis for venous thromboembolic disease after total hip replacement (THR) is recommended. Pneumatic compression with foot pumps seems to provide an alternative to chemical agents. However, the overall number of patients investigated in randomised clinical trials has been too small to draw evidence-based conclusions. This randomised clinical trial was carried out to compare the effectiveness and safety of mechanical versus chemical prophylaxis of DVT in patients after THR. Inclusion criteria were osteoarthritis of the hip and age less than 80 years. Exclusion criteria included a history of thromboembolic disease, heart disease, and bleeding diatheses. There were 216 consecutive patients considered for inclusion in the trial who were randomised either for management with the A-V Impulse System foot pump. We excluded 16 patients who did not tolerate continuous use of the foot pump or with low-molecular-weight heparin (LMWH). Patients were monitored for DVT using serial duplex sonography at 3, 10 and 45 days after surgery. DVT was detected in three of 100 patients in the foot-pump group and with six of 100 patients in the LMWH group (p < 0.05). The mean post-operative drainage was 259 ml in the foot-pump group and 328 ml in the LMWH group (p < 0.05). Patients in the foot-pump group had less swelling of the thigh (10 mm compared with 15 mm; p < 0.05). One patient developed heparin-induced thrombocytopenia. This study confirms the effectiveness and safety of mechanical prophylaxis of DVT in THR. Some patients cannot tolerate the foot pump.

Anticoagulants↗
PubMed2003

Anterior vertebral body screw pullout testing with the hollow modular anchorage system--a comparative in vitro study.

Pullout of implants at the proximal and distal ends of multilevel constructs represents a common spinal surgery problem. One goal concerning the development of new spinal implants is to achieve stable fixation together with the least invasive approach to the spinal column. This biomechanical study measures the influence of different modes of implantation and different screw designs, including a new monocortical system, on the maximum pullout strength of screws inserted ventrolaterally into calf vertebrae. The force pullout of eight different groups were tested and compared. Included were three bicortical used single screws (USS, Zielke-VDS, single KASS). To further increase pullout strength either a second screw (KASS) or a pullout-resistant nut can be added (USS with pullout nut). A completely new concept of anchorage represents the Hollow Modular Anchorage System (MACS-HMA). This hollow titanium implant has an increased outside diameter and is designed for monocortical use. Additionally two screw systems suitable for bicortical use were tested in monocortical mode of anchorage (USS, single KASS). We selected seven vertebrae equal in mean size and bone mineral density for each of the eight groups. The vertebral body and implant were connected to both ends of a servohydraulic testing machine. Displacement controlled distraction was applied until failure at the metal-bone-interface occurred. The maximum axial pullout force was recorded. Mean BMD was 312 +/- 55 mg CaHA/ml in cancellous bone and 498 +/- 98 mg CaHA/ml in cortical bone. The highest resistance to pullout found, measured 4.2 kN (KASS) and 4.0 kN (USS with pullout nut). The mean pullout strength of Zielke-VDS was 2.1 kN, of single KASS 2.5 kN, of MACS-HMA 2.6 kN and of USS 3.2 kN. There was no statistically significant difference (t-test, p > 0.05) between bicortical screws and the new monocortical implant. For the strongest fixation at the proximal or distal end of long spinal constructs the addition of a second screw or a pullout-resistant nut behind the opposite cortex offers even stronger fixation.

Animals↗
PubMed2002

A computed tomography assessment of femoral and acetabular bone changes after total hip arthroplasty.

Using computed tomography-assisted (CT) osteodensitometry, we studied the bone changes that occurred in 12 patients at 2 weeks and again at 1 year after total hip arthroplasty with insertion of a press-fit acetabular cup and an uncemented femoral tapered stem. There was a greater decrease in full bone density (BD) lateral to the femoral stem when compared to the medial side, at the proximal end of the femur this difference was significant (-22.1% versus -16.2%) ( P<0.001). At the tip of the stem cortical BD had decreased between 2.3% and 1.9% only. Proximal to the cup, the cortical BD increased by about 3.4% ( P< or =0.05), while the full BD decreased markedly by 8% ( P< or =0.001). These changes represent a response to a decrease in regional bone stress induced by the presence of the press-fit implant, and this might be considered as retro-acetabular stress shielding. No focal bone resorption was found.

Acetabulum↗
PubMed2002

[The MACS-HMA hollow screw. An alternative possibility for stable implant anchoring in the vertebral body also for long fusions].

Our biomechanical in vitro tests compared the stability of the MACS HMA (Aesculap, Tuttlingen) implants to three established systems. The MACS HMA is a modular system consisting of porous hollow titanium screws with an outer diameter of 12 mm for monocortical use. We report the preliminary results of MACS HMA used for correction of scoliosis. All other implant systems used are designed with bicortical screws; one is for application with two screws/two rods and one uses a pullout-resistant nut behind the opposite cortex to increase stability. Significantly increased motion in the craniocaudal direction was recognized for bicortical standard screws (20 +/- 17 microns) compared to MACS HMA (10 +/- 11 microns) or the dual screw system (12 +/- 6 microns). Two-tailed t-test showed significantly higher stability for the dual screw system (4.2 kN) and the system with pullout-resistant nut (4.0 kN) compared to all other systems (p < 0.025 or higher). Bicortical implants (2.1-3.2 kN) and MACS HMA (2.6 kN) did not reveal significant differences in pullout strength. All biomechanical tests and in vivo use demonstrated favorable performance of MACS HMA implants.

Adolescent↗
PubMed2002

Alternative bearing surfaces in total hip arthroplasty: zirconia-alumina pairing. Contribution or caveat?

The aim of the present study was to evaluate the zirconia and alumina articulation in total hip arthroplasty in regard to clinical and radiological outcome. This is the first report concerning the clinical application of a hybrid ceramic articulation. Owing to ethical reasons, a limited number of patients was enrolled in the study. Ten consecutive patients with degenerative arthritis were randomly allocated after informed consent to hybrid total hip arthroplasty treatment using an alumina femoral head and an alumina acetabular liner (5 hips), or using a zirconia femoral head and an alumina acetabular liner (5 hips). The median age of patients at index operation was 57.8 years. Current criteria were used for clinical and radiological assessment. The mean follow-up was 5.1 years (5 to 5.3 years). No hip required revision, and no clinical and radiological differences were observed between the two groups of hips. The median preoperative Harris hip score was rated 55.3 points in the control group of hips with alumina head, and 55.6 in the group of hips with zirconia head. The median Harris hip score increased to 94.9 points at the time of follow-up in the control group, and 96 points in the zirconia group. No radiological signs of cup loosening or focal acetabular osteolysis were detected at follow-up. All stems showed stable fixation without radiolucent lines or focal osteolysis. Zirconia femoral heads and alumina acetabular liners have been successfully used in the present series of 5 total hip arthroplasties with a mean follow-up of 5.1 years. Nevertheless, the use of femoral heads made of zirconia in total hip arthroplasties remains an important clinical concern due to the potential genesis of wear microparticles which can lead to progressive osteolysis. Further in-vitro and in-vivo investigations are required to define the value of this alternative bearing surface.

Aged↗
PubMed2001

The clinical relevance of embolic events detected by transesophageal echocardiography during cemented total hip arthroplasty: a randomized clinical trial.

UNLABELLED: The first aim of this prospective clinical study was to characterize the relationship between embolic events observed during cemented total hip arthroplasty using transesophageal echocardiography (TEE), and changes in cardiopulmonary function. The second aim was to assess the efficiency of a modified cementing technique that was developed to reduce the risk of embolism. The modification consists in a vacuum drainage placed in the proximal femur to reduce the increase of intramedullary pressure during insertion of the prosthesis. One hundred twenty patients were randomized into two groups. Group 1 received a total hip arthroplasty cemented conventionally, whereas Group 2 was cemented with the modified technique. Continuous TEE, hemodynamic monitoring, and blood gas analysis were done during the perioperative period. Severe embolic events were imaged during the insertion of the femoral component and the reduction of the hip joint. Embolism occurred in 93.3% of patients operated on with the conventional cementing technique, compared with 13.3% of patients operated on with the modified technique (P < 0.05). Intraoperative shunt values during insertion of the femoral component increased from 8.2% to 10.3% (P < 0.05) in Group 1 patients, whereas there was no significant change in Group 2 patients. We observed no clinical signs of fat embolism syndrome in any study patient. The results of the study indicate that embolic events observed using TEE can cause increased pulmonary shunt values during hip arthroplasty, especially in patients with systemic disease (ASA physical status III). The modified surgical technique effectively reduced the incidence of embolization during cemented hip arthroplasty. IMPLICATIONS: Use of conventional cementing techniques is associated with echocardiographic evidence of embolism in 93% of patients and with a significant increase in pulmonary shunting. The incidence of embolism and change in shunting are reduced with a modified cementing technique that limits increases in intramedullary pressure.

Aged↗
PubMed2001

Initial stability of modular acetabular components. Comparative in-vitro study with polyethylene and ceramic liners.

Modular acetabular components with alumina ceramic liners are currently used in total hip arthroplasty, but concerns have emerged regarding their high stiffness, which could cause impairment of stability, stress-shielding phenomena, and loosening. The purpose of the present biomechanical investigation was to compare the in-vitro initial stability of a modular press-fit acetabular component using a polyethylene liner and using an alumina liner. The initial stability was investigated by measuring the micromotion between the implant and the acetabulum during the application of physiological load (2.39 kN). The micromotion of the acetabular component was investigated in 10 acetabuli using a polyethylene liner and in 10 acetabuli using an alumina liner. Micromotion was assessed at the level of the Os ilium, Os pubis, and Os ischium using 3 electromagnetic transducers. The transducers have a sensitivity of 1 micron and a range of measurement of 500 microns. All implants have been fixed on human pelves made of polyurethane. Measurement of implant micromotion showed stable conditions at the level of the three main sectors of the acetabulum during all tests. No statistically significant differences of results were observed between the group of specimens with polyethylene liner and the group of specimens with alumina liner. The mean micromotion values of the uncemented cups were similar to the mean micromotion values of 10 cemented cups investigated to achieve comparative data of stability. In conclusion, the modular acetabular components inserted using an alumina liner showed a satisfactory initial stability in-vitro. The results do not contrast with those achieved using the same cup inserted with a polyethylene liner.

Acetabulum↗
PubMed2001

[Hemodynamics of the lower extremity with pneumatic foot compression. Effect on leg position].

External pneumatic compression of the foot is being used more and more to increase the venous blood flow in the lower limbs and thus reduce the risk of postoperative deep venous thrombosis. We have investigated the efficacy of the foot pump pneumatic compression device (A-V Impulse, Novamedix, Andover, England) in 10 healthy subjects and in 10 patients undergoing total hip arthroplasty. The velocity of venous blood flow in the common femoral artery was measured in the horizontal, Trendelenburg (head-down, foot-up) and reverse Trendelenburg (head-up and foot-down) positions using a duplex ultrasound unit (Sonoline Elegra, Siemens, Erlangen, Germany) with a 5 MHz linear array probe. Application of the foot pump produced an increase in venous blood flow velocity in all healthy subjects and in all patients. In healthy subjects the mean increase in the horizontal position was 31.18% (SD = 15.86%), and in the Trendelenburg position 20.72 (SD = 15.69%) (right limb). In the reverse Trendelenburg position, the foot pump produced a mean increase of 94.08% (SD = 55.00%). The difference is statistically significant (p < 0.005). In patients with a total hip arthroplasty, the mean increase in the horizontal position was 28.67% (SD = 9.95%), and in the Trendelenburg position 20.34% (SD = 17.85%) (operated limb). In the reverse Trendelenburg, the foot pump produced a mean increase of 91.55% (SD = 42.38%). The difference is statistically significant (p < 0.005). There was no noteworthy difference in results between the controls and patients. Pneumatic compression devices designed to reduce venous stasis are effective in decreasing the rate of deep venous thrombosis after surgery on the lower limb. The results of the present study show that the efficiency of the foot pump in increasing venous return is improved by adopting the reverse Trendelenburg position. This may increase its thromboprophylactic effect.

Adult↗
PubMed2001

Fat and bone marrow embolism in total hip arthroplasty.

A number of cardiovascular and pulmonary complications have been reported to occur occasionally after insertion of a total hip prosthesis. Of the proposed causes of these reactions, the possibility of fat embolism has received considerable support. The increase in intramedullary pressure, produced by the mechanical compression of the femoral canal during the insertion of the stem, seems to be the decisive pathogenic factor for the development of emboli. Surgeons' proclivity to deny the clinical relevance of intraoperative emboli is directly related to their awareness of and their attempt to avoid this phenomenon. Depending on the preoperative clinical condition of the patient, the cardiorespiratory impairment may be subclinical for those with good reserve, or clinical for those with poor reserve. In cases with preexisting cardiorespiratory diseases, severe embolism can also lead to death. Moreover, tissue thromboplastin from bone marrow forced into the draining veins of the proximal femur during insertion of the stem leads to activation of the clotting cascade, lesions of the venous endothelium, and thrombogenesis. A correlation was found between the embolic events observed using transesophageal echocardiography and the cardiopulmonary function of the patients during the perioperative period. A modified surgical technique was designed to reduce the intramedullary pressure during insertion of the stem to prevent intraoperative embolic events. Surgical prevention of fat and bone marrow embolism can also reduce the incidence of postoperative deep vein thrombosis.

Arthroplasty, Replacement, Hip↗
PubMed2000

Total hip arthroplasty using an uncemented femoral component with taper design: outcome at 10-year follow-up.

The aim of this study was to assess the clinical and radiological outcome of the cementless-system (CLS) femoral component designed by Spotorno with a taper design. Ninety-four patients (107 hips) were operated on from January 1987 to December 1988. The female/male ratio was 2/1, the mean age was 51 years (range 20-77 years). Clinical follow-up was obtained in 89 hips (83%). Five patients (7 hips, 6.5%) could not be traced. Nine patients (11 hips, 10%) had died before the minimum time of follow-up required for this study (10 years). All these hips still had their stem in place at the time of the last intermediate inquiry. The mean follow-up was 10.3 +/- 0.3 years. No stem required revision. According to the Harris score, 84% of hips were rated good or excellent, 14% fair, and 2% poor. The average Harris hip score was 88 at the time of the last follow-up. Fifteen patients (17%) reported occasional thigh pain. All patients reported complete relief of pain within the first 6 months after the operation. Radiologically, 95% of stems showed stable fixation by bony ingrowth, 5% by fibrous ingrowth. Seven (9%) uncemented acetabular components showed progressive migration. Three of those cups had been replaced in the meantime. Fifty-one (65%) of the CLS stems induced either no change in femoral bone density or only patchy loss of bone density localized to zone 1 or 7 according to Gruen, while 27 (35%) of the hips showed some reduction of bone density in the proximal diaphysis of the femur (zone 2 or 6). Severe progressive osteolysis of the femoral cortex underneath the lesser trochanter was found in 4 hips (5%) with coexistent loosening of the cup. In all of these hips, the Mecron cup had been used. At a mean follow-up of 10 years, the results of the CLS femoral component are comparable with those of modern techniques of cementing in primary total hip arthroplasty and with the long-term outcomes of other uncemented stems with tapered design. The long-term fixation of the cup remains an unsolved problem.

Adult↗
PubMed2000

Transesophageal echocardiography and clinical features of fat embolism during cemented total hip arthroplasty. A randomized study in patients with a femoral neck fracture.

Forty patients suffering from a medial femoral neck fracture participated in a prospective, randomized study. In 20 patients, the femoral component was cemented using a contemporary technique. In the patient group operated on with the bone vacuum technique, the medullary cavity was drained during the insertion of the stem. The proximal draining hole was placed in the intertrochanteric region, along the prolongation of the linea aspera. The distal hole was placed 2 cm below the tip of the femoral component. Embolic phenomena were documented intraoperatively by continuous transesophageal echocardiographic imaging of the right atrium and ventricle. The clinical relevance of the emboli was noted simultaneously by recording hemodynamic and blood gas parameters. Patients of the control group showed severer and longer-lasting episodes of embolism than patients of the bone vacuum group. Ongoing emboli were first seen during the injection of the cement, and continued during stem insertion. Massive emboli of small particles could be verified in 19 patients (95%) of the control group and in 1 patient (5%) of the bone vacuum group (P < 0.05). During massive emboli, a distinct decrease in the arterial oxygen saturation and the end-expiratory carbon dioxide level was observed. The calculated average pulmonary shunt volume showed an increase after the insertion of the stem using the contemporary technique (36.5%; P < 0.05). These distinct hemodynamic changes were not observed in the bone vacuum group. This study was able to show a clearly reduced risk of pulmonary emboli using the bone vacuum cementing technique. The presence of pre-existing disease greatly magnified the clinical relevance of fat embolism.

Aged↗
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↗