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Biomedical subjects

P Regazzoni

Publications and source records attributed to P Regazzoni.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Radiation exposure of the patient by intraoperative imaging of intramedullary osteosyntheses].

MATERIAL AND METHOD: 39 patients with pertrochanteric femur fracture (n = 32) or lower leg fracture (n = 7) were treated with closed intramedullary nailing. The related radiation exposure of the patients was calculated. RESULTS: Osteosynthesis of pertrochanteric fractures took less fluoroscopic time than osteosynthesis of lower leg fractures. The effective dose was 14 mSv for nailing osteosynthesis of proximal pertrochanteric fractures and less than 0.1 mSv for osteosynthesis of distal lower leg fractures. CONCLUSION: Radiation exposure of the patient due to intraoperative fluoroscopic imaging during osteosynthesis can be estimated based on the data given above. Intraoperative observations imply, consequent application of radiation protection by the orthopaedic surgeons may reduce intraoperative radiation exposure even more.

Female↗
PubMed2001

[Computer assisted surgery, 2001 development and prospects. Results of a congress at Reisensburg Castle, 23-24 November 2000]].

The progress in computer assisted surgery (CAS) is influenced by new technologies in imaging as well as by the input of the users. At present, CAS procedures are established in dorsal spine instrumentation, prosthetics and long bone surgery. Present status and future of CAS was a topic of an expert meeting at the Reisensburg castle. Imaging will speed up in the future using multi-detector techniques. C-arm navigation will gain more information using the 3D technology intraoperatively. CT based navigation procedures are standard in spine and will be established in pelvic surgery. CAS in robotics at the moment means the use of robot-assistance. A new concept is the modality-based navigated surgery, which can be used at various skeletal locations. Visualization of patient data will improve using 3D semi-transparencies with real time update. In the future it will be mandatory to find algorithms to fuse the different possibilities and techniques. A new concept of surgical training is necessary to teach CAS procedures. Therefore discussion must go on to improve these systems.

Forecasting↗
PubMed2001

Minimally invasive fracture stabilization of distal femoral fractures with the LISS: a prospective multicenter study. Results of a clinical study with special emphasis on difficult cases.

The LISS-DF (Less invasive stabilization system-distal femur) is a new type of implant system for the treatment of distal femoral fractures according to the principles of "Minimally Invasive Surgery". A plate, pre-contoured to the anatomy, is inserted through a minimally invasive incision into the epiperiosteal space by means of an aiming device after indirect, closed fracture reduction. The implant is stabilized by insertion of screws which lock into the plate holes and prevent tilting. This is performed with the aid of an aiming device and through stab incisions. It is not necessary for a large area to be exposed at the fracture site. As part of an AO prospective multicenter study, the new system was applied to 112 patients with 116 fractures. The time to follow-up was on average 13.7 months (minimum 7 months, maximum 33 months). Fractures treated were distal femoral shaft and supracondylar femoral fractures. Eight patients died during the study of causes unrelated to the implant. Of the remaining 104 patients with 107 fractures, 96 patients with 99 fractures were available for complete follow-up (93% follow-up rate). In 90% of all cases treated and followed up, the fracture had consolidated during the period of observation. Twenty-three revision operations were necessary in 21 patients. In two cases, implant failure occurred as the result of a pseudarthrosis. The complications can be attributed in nearly all cases to the severity of the trauma and/or a lack of experience when applying the new style implant to a wider range of indications. The results of the study show that with a sound knowledge of the operative technique and careful preoperative planning this system represents an excellent, safe procedure for the treatment of almost all distal femoral fracture types including periprosthetic fractures of the distal femur. There is generally no need for primary cancellous bone grafting.

Adolescent↗
PubMed2000

Surgical navigation based on fluoroscopy--clinical application for computer-assisted distal locking of intramedullary implants.

OBJECTIVE: Fluoroscopy is used to guide surgical instruments during orthopedic procedures. Radiation exposure and lack of spatial information are drawbacks of this method. Improvements are expected when fluoroscopy-based surgical navigation is used for intraoperative guidance, e.g., in computer-assisted distal locking of intramedullary implants. PATIENTS AND METHODS: The method was applied to 42 interlocking procedures during implantation of the short proximal femoral nail in 27 patients with pertrochanteric femoral fractures. Precision of interlocking, exposure time, operating time, and number of personnel required for computer-assisted distal locking were recorded. RESULTS: One misplaced interlocking screw was observed (2.3%), and contact between the drill bit and the nail during drilling was noticed in 8 cases (19%). The average exposure time was 16 seconds (range 4-42 seconds), and the procedure took an average of 43 min (range 20-70 min). The number of persons required for computer-assisted distal locking was reduced from three to one within the course of the study. CONCLUSIONS: Fluoroscopy-based surgical navigation provided precise intraoperative guidance for computer-assisted distal locking with minimal use of fluoroscopy. The complex system and related procedure times may be drawbacks in this application. Clinical studies are underway to define implants and surgical procedures where intraoperative guidance by fluoroscopy-based surgical navigation is beneficial for the patient and/or surgeon.

Computer Simulation↗
PubMed2000

The multifunctional therapy room of the future: image guidance, interdisciplinarity, integration and impact on patient pathways.

With few exceptions the interventional rooms of the present are either imaging suites or sterile operating rooms. Their users are restricted to either percutaneous procedures or to two-staged image-guided surgery without intra-operative imaging control. Since interventional therapy of the future will be minimally invasive and since minimally invasive therapy is essentially image-guided therapy, a new physical place for these activities has to be devised: the multifunctional therapy room of the future integrates sophisticated imaging and image guidance modalities together with advanced surgical and life-support equipment in a sterile environment [1, 2, 3]. Even given a high degree of integration, this will be a complex and costly piece of medical technology. These two factors--complexity and cost-- require interdisciplinary technological and medical collaboration to bring it into existence, distribute its cost and maximize usage and medical benefit. Yet another dimension of multifunctionality will be introduced and a significant impact on the care of vitally threatened patients will be exerted by using this room not only for elective image-guided therapy but also for emergent one-stop diagnosis and treatment. Motivation, technology, implementation strategies and funding of this image-guided, integrated and interdisciplinary therapy room, as well as a comprehensive approach combining emergency care and elective computer-assisted therapy (CAT), are discussed in this paper.

Critical Pathways↗
PubMed2000

The epidemiology of diaphyseal fractures of the tibia.

AO Documentation collected reports of nearly five thousand diaphyseal tibial fractures occurring in the 1980s. The following conclusions can be drawn: i. The number of fractures affecting men is twice that affecting women. ii. These fractures occurred mainly in younger people (under 40 years of age) and no increase occurred in elderly people. iii. Most bending fractures occurred in young men (20-30 yrs) and the torsion fractures affected men and women of about 40 equally. iv. The number of simple fractures (type A) is about the same as for fractures with one fragment (type B).

Adolescent↗
PubMed2000

A biomechanical enigma: why are tibial fractures not more frequent in the elderly?

Epidemiology revealed that diaphyseal fractures of the tibia affect young people, particularly young men; no increase was noticed for the elderly. This indicates that osteoporosis does not lead to increased bone fragility. Obviously, this is a biomechanical enigma. Torque measurements were carried out on human cadaveric tibiae and revealed a great correlation between the polar moment of inertia of the cortical bone at the tibial isthmus and the ultimate torque at failure (r = 0.83) and a lesser correlation between the cross-sectional density at the isthmus and the torque at failure (r = 0.57). Therefore, the size is more important than the degree of osteoporosis. We can speculate that endosteal resorption due to osteoporosis is compensated for by periosteal apposition and therefore does not lead to bone weakness.

Age Factors↗
PubMed2000

Prevention of malunions in the rotation of complex fractures of the distal femur treated using the Dynamic Condylar Screw (DCS): an anatomical graphic analysis using computed tomography on cadaveric specimens.

The AO ASIF dynamic condylar screw is a popular method for the treatment of severe distal femoral fractures. Two methods of application have been presented by the AO group, one in the AO manual and the other in the teaching video tapes. The small difference in the techniques suggested that one of these methods might present a risk of rotational malunion in cases of severe comminuted fractures. The question of determining which method was less appropriate was investigated on human cadaveric specimens using a graphic analysis of computed tomograms. We found disadvantages for both methods and propose a third method combining the advantages of the two original methods.

Adult↗
PubMed2000

Comparison of three different plating techniques for the dorsum of the distal radius: a biomechanical study.

Three different plating techniques were used on experimentally produced dorsally displaced distal radius fractures in cadavers and were tested in 4-point bending: a AO 3.5-mm T plate (group 1), two 2. 0-mm titanium plates 60 degrees to each other (group 2), and the AO pi plate (group 3). A metaphyseal defect was simulated by a dorsally open wedge osteotomy. The tests show that the 2-mm double-plating technique has superior stiffness and statistically equivalent bending and bone gap to failure compared with the AO 3.5-mm T plate or the pi plate when applied to the unstable distal radius fracture model. (J Hand Surg 2000; 25A:29-33.

Biomechanical Phenomena↗
PubMed2000

A whole-body registration-free navigation system for image-guided surgery and interventional radiology.

RATIONALE AND OBJECTIVES: To develop and test an image-guided navigation system in which the base of reference is taken from the imaging modality, here, a helical CT scanner. METHODS: An optical digitizer together with a calibration device is used to measure the transformation matrix between the digitizer reference system and a CT reference system. During intervention, it tracks radiological and surgical tools with tool references. A specific software visually integrates the current tool position with the corresponding image information. In vitro accuracy tests were performed. RESULTS: With helical CT, freehand positioning accuracy was 1.9 +/- 1.1 mm (mean +/- SD) in vitro (n = 718). CONCLUSIONS: The navigation system developed by the authors appears to be feasible for radiological interventions as well as for minimally invasive surgery. It is not limited to a certain procedure, can be used in every region of the body, and is functional after imaging. Intraprocedural scans can be integrated immediately.

Equipment Design↗
PubMed2000

Arthroscopic findings in acute fractures of the ankle.

We have evaluated prospectively the arthroscopic findings in acute fractures of the ankle in 288 consecutive patients (148 men and 140 women) with a mean age of 45.6 years. According to the AO-Danis-Weber classification there were 14 type-A fractures, 198 type B and 76 type C. Lesions of the cartilage were found in 228 ankles (79.2%), more often on the talus (69.4%) than on the distal tibia (45.8%), the fibula (45.1%), or the medial malleolus (41.3%). There were more lesions in men than in women and in general they were more severe in men (p < 0.05). They also tended to be worse in patients under 30 years and in those over 60 years of age. The frequency and severity of the lesions increased from type-B to type-C fractures (p < 0.05). Within each type of fracture the lesions increased from subgroups 1 to 3 (p < 0.05). The anterior tibiofibular ligament was injured with increased frequency from type-B.1 to type-C3 fractures (p < 0.05), but it was not torn in all cases. While lateral ligamentous injuries were seen more often in type-B than in type-C fractures (p < 0.05), no difference was noted in the frequency of deltoid ligamentous lesions. Our findings show that arthroscopy is useful in identifying associated intra-articular lesions in acute fractures of the ankle.

Acute Disease↗
PubMed2000

Fractures of the distal radius treated by internal fixation and early function. A prospective study of 73 consecutive patients.

Stable fixation of fractures of the distal radius can be achieved by using two 2.0 mm titanium plates placed on the radial and intermediate columns angled 50 degrees to 70 degrees apart. We describe our results with this method in a prospective series of 74 fractures (58 severely comminuted) in 73 consecutive patients. Early postoperative mobilisation was possible in all except four wrists. All of the 73 patients, except two with other injuries, returned to work and daily activities with no limitations. The anatomical results were excellent or good in 72 patients and fair in one. Our discussion includes details of important technical considerations based on an analysis of the specific complications which were seen early in the series.

Adult↗
PubMed1999

[Distal radius fractures].

Fractures of the distal end of the radius are the most common fractures in humans. The variants of type of fracture and associated injuries are numerous, depending on the mechanism of injury, the amount of energy absorbed and the quality of the bone. Treatment concepts evolve as our understanding of the physiopathology of this heterogeneous group of injuries increases. It is now commonly accepted that extraarticular anatomy and joint congruency, as well as ligamentous integrity, should be restored to obtain a good functional result. This paper provides an overview of current knowledge and discusses possible future trends.

External Fixators↗
PubMed1999

The mechanics of internal fixation of fractures of the distal femur: a comparison of the condylar screw (DCS) with the condylar plate (CP).

Distal femoral fractures are rare and usually complex. Mostly, they are fixed with the Dynamic Condylar Screw (DCS) or the 95 degrees condylar plate (CP). The simplicity of applying the DCS compared with the CP led us to investigate whether any possible mechanical deficiencies of the CP would detract from its technical advantages, thus limiting the indications for its use in the treatment of fractures of the distal femur. An in vitro investigation was carried out to measure the stability of a Y-osteotomy (with and without medial metaphyseal bone defect) stabilized either with the CP or the DCS. 8 pairs of human cadaveric femora classified according to their bone density were used. CP and DCS were applied to 1 bone in each pair by means of three lag screws (anterior, posterior and through the plate). Physiological loading was simulated and measurements were taken at the level of the osteotomy in the frontal and sagittal planes in order to assess rotational instability and the amount of gap opening in the vertical branch of the osteotomy. There was no relevant difference in the mechanical properties of the two fixations for fractures without medial defect, even if the stability of the fixation was reduced by removing the distal screw. Furthermore, interfragmental movement was minimal. In the frontal plane, simulated closure resulted in closure of the medial branch of the osteotomy in every case without any opening of the vertical branch of the osteotomy. In the sagittal plane, the closure of all branches of the osteotomy was confirmed for 11 bones and a rotation of the condyle was observed in 5 bones (3 CP, 2 DCS). Removing the distal lag screw did not increase the instability. Even in osteoporotic bones, the DCS provided the same stability as the CP. For simple Y-osteotomies, the CP did not offer any technical or mechanical advantages. The stability in the frontal plane however was significantly reduced in osteotomies with medial defect. The amplitude of interfragmental movement on all bones fixed by the CP, except for 1 pair, was greater than those fixed by the DCS. The absence of the anterior lag screw did not reduce stability. However, the absence of the lag screw within the implant considerably weakend the fixation--more so for the CP than for the DCS. Instability reached a maximum without any lag screw at all, which again was more pronounced for the CP than for the DCS. The Dynamic Condylar Screw (DCS) must be regarded as the implant of choice both technically and mechanically even in osteoporotic bones, but the distal condylar block must be at least 4 cm in length.

Biomechanical Phenomena↗
PubMed1999

Avascular necrosis of the femoral head after open reduction and internal fixation of femoral neck fractures: an inevitable complication?

Between 1980 and 1989 71 patients with a femoral neck fracture were treated at the University Hospital of Basel by a Dynamic Hip Screw (n = 54) or by three compression screws (n = 17). Fifty out of 71 patients (70%) were reviewed clinically and radiologically after an average of 116 months. 32/50 fractures (64%) had united. In 18/50 (36%) either avascular necrosis (12) or secondary fracture dislocation (6) had resulted in failure after an average of 29 months following injury. Despite these results, the patients assessment had been very good or good in 44 patients (88%) and fair only in six patients (12%). The cause of secondary dislocation proved to be mainly due to a technical failure at surgery. The incidence of avascular necrosis was significantly higher in displaced fractures compared to non-displaced fractures (p < 0.05), regardless of the quality of the reduction achieved (varus or valgus) or the time delay between accident and operation. However it was interesting to note, that more than one third of all avascular necrosis became apparent more than 3 years (4-10 years) after the accident.

Adult↗
PubMed1998

Clinical results using the trochanter stabilizing plate (TSP): the modular extension of the dynamic hip screw (DHS) for internal fixation of selected unstable intertrochanteric fractures.

OBJECTIVE: To evaluate whether the implantation of the modular trochanter stabilizing plate (TSP) in addition to the dynamic hip screw (DHS) prevents excessive telescoping and limb shortening in four-part and selected three-part trochanteric fractures. DESIGN: Prospective clinical study. SETTING: The study was conducted at the trauma unit of the Surgical Department of the University of Basel, Switzerland. PATIENTS: Forty-six consecutive patients with unstable intertrochanteric fractures were treated with an additional TSP super-imposed on the regular DHS at our institution between July 1991 and July 1993. Five patients died before the first follow-up, one patient was lost to follow-up, and another patient refused follow-up. Thus, thirty-nine patients were followed for at least twelve months (mean 14 months, range 12 to 20 months). INTERVENTION: The fractures treated were classified according to the OTA classification, which is based on the AO classification. Seventeen were 31-A2.2, seven were 31-A2.3, and fourteen were 31-A3.3 fractures. RESULTS: Lateralization of the greater trochanter was successfully prevented in all fractures. Limited fracture impaction was found in 90 percent (n = 35) of the patients with telescoping of 9.5 millimeters (range 0 to 30 millimeters), resulting in mean limb shortening of 5.37 millimeters (range 0 to 14.9 millimeters). Four patients suffered limb shortening exceeding fifteen millimeters (range 15.6 to 21.3 millimeters). Functional results were excellent and good in 87 percent of patients and fair in 13 percent according to the Salvati-Wilson score. All fractures had healed six months after the operation. Three complications required a secondary procedure: one from not inserting a second screw parallel to the gliding hip screw to prevent rotation of the head-neck fragment ("antirotation screw"), one because of deep infection, and one because of a refracture after premature implant removal. CONCLUSION: In unstable pertrochanteric fractures with small or missing lateral cortical buttress, the addition of a TSP to the DHS effectively supports the unstable greater trochanter fragment and can prevent rotation of the head-neck fragment. Excessive fracture impaction and consecutive limb shortening was prevented by this additional implant in 90 percent of these patients.

Adult↗
PubMed1997

[4-fragment fractures of the proximal humerus. Alternative strategies for surgical treatment].

The operative treatment of dislocated fractures of the proximal humerus has been evolving in recent years. Replacement using endoprostheses often results in only moderate functional outcome, and with the high risk of aseptic necrosis with ORIF, new methods of minimally invasive stabilisation have been developed. These methods reduce the opening of the fracture site to a minimum and thereby limit the risk of iatrogenic damage to local vascularity and the rotator cuff. This study reviewed 18 patients operated on with minimal osteosynthesis for dislocated four-part fractures of the proximal humerus from March 1991 to October 1994. Only tension band wiring with resorbable cords from woven polydioxanone was applied. After an average follow-up of 26 months (20-37 months), 72% (n = 13) of the four-part fractures were rated as good and very good results according to the Neer Score. In 16.7%, a complete head necrosis occurred, requiring a prosthetic replacement. Two patients with partial necrosis (11.1%) had a good functional outcome. With regard to these results, we recommend head-preserving tension band wiring with resorbable cords and preservation of the articular surface. At the present time the procedure seems comparable with prosthetic replacement in respect of shoulder function.

Adult↗