Biomedical subjects

C Krettek

Publications and source records attributed to C Krettek.

At least 217 records · Page 12Linked to original sources

PubMed1996

[A new roentgen ray-free aiming technique for distal locking screw boring of the unreamed tibial nail].

A mechanical aiming device for the placement of distal locking screws of the unreamed tibial nail (UTN) has been developed. At the level of the distal nail end, a roughly placed "contact hole" is drilled (diameter, 6.0 mm). An asymmetric spacer is inserted through this contact hole, placed directly onto the nail and connected with the aiming arm. By this re-adjustment, the direction and the plane of both distal transverse holes are defined and can be drilled. A medial spacer re-adjusts the aiming arm for the aphole.

Biomechanical Phenomena↗

PubMed1995

Outcome of tibial shaft fractures with severe soft tissue injury treated by unreamed nailing versus external fixation.

MATERIALS: Between 1987 and 1991, 114 fresh tibial shaft fractures with severe soft tissue injury, which met the inclusion criteria, were treated and retrospectively reviewed. There were 48 cases in the unreamed nail (unreamed tibial nail (UTN)) group and 66 cases in the external fixation (EF) group. METHODS: Soft tissue injury was classified by the Gustilo and Tscherne methods. There were 18 AO type A, 56 type B, and 40 type C fractures. There were no significant difference in fracture type, soft tissue injury, age, and additional injury between the groups. Outcome was assessed using the Karlström score after 28 months. RESULTS: There were a significantly higher number of reoperations in the EF group. Mean time to bony healing was 25.8 weeks. In the EF group, there was a 26% rate of pin tract infection, whereas 19% of cases had bolt breakages in the UTN group. In the UTN group, 40% had good results, compared with 27% in the EF group. In the UTN group, there were significantly fewer ante- and recurvatum deformities of more than five degrees. CONCLUSIONS: Treatment of tibial fractures by UTN, compared with EF, gave a lower reoperation rate and better functional outcome.

External Fixators↗

PubMed1995

[Stress and fracture healing].

Stress is an important factor in fracture healing, but it is not the only one. The exact amount of stress, displacement or strain needed or tolerated in fracture healing is not yet clear. There are numerous modifying factors influencing fracture healing like fracture type, soft tissue injury, vitality of fragments, type of osteosynthesis, soft tissue handling, localization of injury, activity level and weight of the patient, local geometry and muscular topography. However, despite our large deficits in knowledge of the process of fracture healing, typical patterns of failure or disturbed healing can be recognized. This could help bringing stress and fracture healing in balance and includes an analysis of pathological stress and our efforts to neutralize, canalize or use it to our advantage.

Bony Callus↗

PubMed1995

[Functional treatment of acute rupture of the Achilles tendon. An experimental biomechanical study].

In 84 adult rabbits the biomechanical properties of healing Achilles tendon rupture were examined 2, 4, 8 and 12 weeks (21 each group) after the injury. For the first time a mop-end-tear was performed. The following treatment modalities were applied (7 rabbits in each subgroup): (a) operative functional treatment (resorbable suture; Kleinert techniques); (b) operative functional treatment (fibrin glue); (c) primary functional treatment (conservative). The functional after treatment in all groups was performed with a specially developed orthesis, which was taped to the limb. For biomechanical testing a newly developed fixation technique (cryo-clamp) was applied, which guaranteed secure intratendineal rupture. After 2 weeks the fibrin glue-treated tendon ruptures showed the best results with regard to stiffness, tensile stress and max. rupture force. These results and a higher tensile stress of the sutured tendons were significantly different from those in the conservatively treated groups. After 4 weeks the stiffness in the fibrin group and the energy and rupture force in the suture group were significantly higher than in the group treated conservatively. The 8-week results revealed comparable biomechanical properties. The only significant difference was a higher energy in the fibrin glue group than in the conservative treatment group. The experiment revealed no significant biomechanical differences after 3 months. Compared with the results recorded for plaster immobilization in the literature, the functional treatment resulted in a significantly faster course of healing.

Achilles Tendon↗

PubMed1995

Nonreamed interlocking nailing of closed tibial fractures with severe soft tissue injury.

Closed tibial shaft fractures with severe soft tissue trauma require urgent surgical treatment to minimize complications such as soft tissue necrosis, infection, compartment syndrome, and nonunion. Although time to union and complications are similar to open tibial fractures, these injuries often are treated as low energy closed fractures. The method of internal fixation depends not only on the fracture pattern, but also on the condition of the soft tissues. Unlike plate osteosynthesis, the authors believe that virtually all complex closed tibial fractures may be treated with an unreamed tibial nail if proximal and distal interlocking is possible. With severe closed soft tissue trauma (Grades 2 and 3), an unreamed nail may have biologic and mechanical advantages. In a prospective study, 21 closed tibial shaft fractures with severe soft tissue trauma (Grades 2 and 3) were treated with an unreamed nail. The mean followup was 29 months. All fractures healed in an average time of 23 weeks. However, 3 patients required a bone graft, and in 3 patients the fixation was revised. One infection occurred after an exchange reamed nailing. Because of the low infection and low nonunion rate, the authors recommend unreamed interlocking tibial nails for closed tibial shaft fractures with severe soft tissue trauma.

Adolescent↗

PubMed1995

[Biomechanical studies of human Achilles tendon rupture].

The biomechanical properties of human Achilles tendon are described with a computer-controlled material-testing machine. With an optimized fixation device for the muscle-tendon-calcaneus system the rupture was intratendineal. The tendons were compared for different rupture speed (1000 mm/min vs 100 mm/min), sex and age ( < 35 years vs > 35 years). The tendons ruptured at 1000 mm/min had better results in terms of maximum rupture force, stiffness and tensile stress, while the results for elongation and energy were less good. None of these differences were statistically significant. Significant differences were found between the sexes: male tendons had higher maximum rupture force and stiffness and a larger cross-sectional area. In the younger tendons significantly higher tensile rupture stress and lower stiffness were found.

Achilles Tendon↗

PubMed1994

Routine application of the pinless external fixator.

One serious disadvantage of conventional fixator systems is the need to open the medullary space, hence creating a direct communication with the exterior. The new pinless external fixator does not have this major disadvantage, because the fixator clamps simply rest on the cortical bone without penetrating it. Clinically, this easily managed system is intended for fractures of the tibia in cases in which primary internal fixation is precluded either by precarious local or general conditions or by infrastructural problems. In such situations the new pinless fixator is an excellent device with which to achieve good stabilization of the fracture rapidly, while leaving open all options for subsequent alteration of treatment. If the surgeon decides to convert to locked intramedullary nailing, the pinless fixator facilitates the new approach, because it can be used as a distractor and makes it unnecessary to transfer the patient to a fracture table.

Adult↗

PubMed1994

[Biomechanical comparison of various emergency stabilization measures of the pelvic ring].

Massive bleeding with shock is still the most frequent reason for early death after complex pelvic trauma. For hemostasis, fracture stabilization in the pelvic ring is an important aspect. By use of the external fixator and introduction of emergency pelvic c-clamps, attempts were made to include pelvic ring stabilization on the early resuscitation algorithm. This biomechanical study compared a simple anterior external fixator (one supraacetabular pin on each side), the emergency pelvic c-clamp (Ganz) and the Browner modification of the clamp ("ACE clamp"). Two fresh-frozen human cadaver pelves were loaded in a one-leg stance model. The displacement and rotations on the site with the fracture were measured with a 3D measurement system. Fracture models included a Tile type B injury and two Tile type C instabilities (pure SI dislocation; transforaminal sacrum fracture). In type B injuries all methods withstood loading with 100% of the body weight (640/700 N). In C-type injuries with SI dislocation the external fixator showed no significant holding force, whereas the two c-clamps withstood loading of 112 N and 160 N. In the transforaminal fracture model no one method withstood a load of more than 40 N. The combination of the clamps with the external fixator increased the holding strength to 66 N and 103 N. Although a single-leg-stance model does not reflect the emergency situation, in which the patient is normally in a supine position, the data recorded are comparable to those observed in earlier investigations.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗

PubMed1994

[Osteosynthesis of femur shaft fractures with the unreamed AO-femur nail. Surgical technique and initial clinical results standard lock fixation].

Nailing technique has changed in recent years in some important aspects which are not limited to the omitted reaming procedure. These changes concern patient positioning, reduction technique and determination of implant length and diameter. Approach and exposure techniques have been modified to new, less invasive procedures, in order to fulfill technical, functional and aesthetic requirements. Techniques and tricks have been developed for avoidance of fragment diastasis, axial and torsional malalignment and leg length differences. Finally, simple algorithms have been elaborated for the management of bilateral femoral shaft or ipsilateral tibial shaft fractures and the number and location of locking bolts. These algorithms, techniques and procedures were developed in a series of 108 femoral shafts, which were stabilized wit the AO unreamed femoral nail (UFN) in a prospective study between 1991 and 1994. Of these, 39 cases with a mean follow-up of 19.3 (range 8-40) months after trauma were reviewed. Fractures were classified according to Müller (1990): 6 type A, 21 type B and 12 type C. Closed soft tissue damage was classified according to our classification: C0/I, n = 14; CII, n = 15 (Tscherne 1982). Among 10 open fractures 4 were OI, 4OII, 1OIIIA and 1OIIIB (Gustilo 1976). The major complications were breakage of locking bolts (n = 2), one nail breakage after 9 weeks and one case of osteitis.

Adolescent↗

PubMed1994

[Current status of surgical technique for unreamed nailing of tibial shaft fractures with the UTN (unreamed tibia nail)].

Nailing technique has changed in recent years in some important aspects which are not limited to the omitted reaming procedure. These changes concern patient positioning, reduction technique, the use of temporary stabilizers such as the 'Pinless', and determination of implant length and diameter. Approach and exposure techniques have been modified to new, less invasive procedures, in order to fulfill technical, functional and aesthetic requirements. Techniques and tricks have been developed for avoidance of fragment diastasis and axial and torsional malalignment. Finally, simple algorithms are described for the management of large bone defects, bilateral tibia shaft or ipsilateral femoral shaft fractures, number and location of locking bolts, the 'when and how' of patient mobilization and load bearing, and primary and secondary dynamization. These algorithms, techniques and procedures were developed in a series of 152 tibia shafts, which were stabilized with the AO unreamed tibia nail (UTN) in a prospective study between March 1989 and June 1994. Of these, 75 cases with a mean follow-up of 19.4 +/- 6.3 (range 11-37) months after trauma were reviewed. Fractures were classified according to Müller (1990): 14 type A, 37 type B and 24 type C. Closed soft tissue damage was categorized according to our classification: C0/1, n = 5; C2, n = 12; C3, n = 9 (Tscherne 1982). Among 49 open fractures 8 were OI, 18 OII, 10 OIIIA and 13 OIIIB (Gustilo 1976). The main minor intraoperative complication was drill bit breakage (n = 10), most frequently at the proximal locking holes. The main postoperative complication was breakage of locking bolts (n = 16), mainly between weeks 6 and 20. Minor secondary reinterventions were, in most cases, secondary dynamization under local anaesthesia. Major reintervention were: soft tissue reconstructions (n = 5), isolated cancellous bone graft (n = 6), and change of treatment (n = 12). There were nine changes to a reamed nail, two changes, in very proximal fractures, to plate osteosyntheses. There were three deep infections. Mean time to union was 23.9 weeks (range 10-48 weeks, n = 73); in two cases non-union was observed. The overall result was judged with the Karlström-Olerud score, which was applicable in 66 of 75 cases; excellent, n = 2; good, n = 22; satisfactory, n = 24; fair, n = 9; poor, n = 9. In the remaining nine cases no scoring was attempted because of severe injuries around the knee or ankle.

Adolescent↗

PubMed1994

[Biomechanical studies of 9 tibial interlocking nails in a bone-implant unit].

Various different interlocking intramedullary nail designs are now available for the tibia the designs resulting from a different approaches to achieving stability for fracture fixation. During recent years small-diameter unreamed interlocking nails have been developed. So far there are no data on stiffness of different nail designs that can justify the use of certain nail types. We compared different nail types in the bone-implant complex (BIC) with reference to stiffness under axial load, bending and torsion of the BIC. We simulated comminuted mid-shaft fractures by a 2-cm defect osteotomy in paired human cadaver tibiae. We fixed each tibia with one of nine different interlocking nails (AO Unreamed Tibial Nail 9 mm [UTN9], AO Unreamed Tibial Nail 8 mm [UTN8], Russell & Taylor Delta Tibial Nail 9 mm [RTD], Russell & Taylor Reconstruction Tibial Nail 11 mm [RTR], Brooker & Wills Nail 11 mm [B-W], Grosse & Kempf Tibial Nail 11 mm [G-K], AO Universal Tibial Nail 11 mm [AOU], Klemm & Schellmann Tibial Nail 11 mm [K-S], Börner & Mattheck Tibial Nail 11 mm [B-M]) according to the manufacturers' recommendations. Each BIC was tested mechanically using a Zwick universal testing machine. Torque testing was performed with a maximum moment of 5 Nm in both directions. Maximum axial load was 1100 N. Four-point bending was done up to a moment of 66 Nm. For each implant bending and torque stiffness of the nail were calculated and compared with the test results obtained in the cadaver study. A P-value less than 0.05 (least significance difference test, ANOVA) was considered significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

[A new procedure for determination of leg length and differences in leg length using sonography. I. Development and experimental studies].

The precise measurement of leg length and leg length discrepancies (LLD) plays an important role in the examination of lumbar spine and lower extremities. Those real LLD which may be posttraumatic or idiopathic, can sometimes hardly be differentiated from LLD caused by spinal scoliosis or malposition. Although there is no final agreement, to which extent a LLD becomes clinically significant, most authors state that clinical assessment of LLD by tape measure or lengthening of the short leg with blocks of known thickness is highly unreliable. Radiological methods are necessary for precise detection of LLD less than 10 mm. Since previously reported non-invasive, ultrasound-supported leg-length measurement methods proved to be complicated and unhandy, a new method was developed. To avoid radiation exposure accuracy and precision were tested on human cadavers and were compared to clinical assessments by tape measurement. A measurement device was constructed consisting of a wire rope meter and a length millimeter digital display. Measurements were taken with the examined person in supine position. The device was placed beyond their feet and the end of the rope was hinged with a metal brace to a convenient transducer in exact middle position. Thus the middle of the ultrasound monitor concords with the end of the rope. The medial knee joint and ventral hip joint were used as standardised sonographic landmarks. Ten not pre-selected mortants were measured in this manner and additionally clinical LLD was obtained with a tape measure (medial ankle to anterior superior iliac spine). Afterwards all distances were anatomically prepared and measured with a meter stick.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗

PubMed1993

Acute effects of the heavy metal antidotes DMPS and DMSA on circulation, respiration, and blood homoeostasis in dogs.

The heavy metal antidotes sodium-2,3-dimercaptopropane-1-sulfonate (DMPS) and meso-2,3-dimercaptosuccinic acid (DMSA) were investigated in anaesthetized dogs for their effects on a variety of physiological variables and parameters. In addition, the influence of both dithiols on oxygen consumption and ferrihaemoglobin production was studied in blood and red blood cells in vitro. DMPS (15 and 75 mg/kg i.v.) did not affect respiration, central venous pressure, left ventricular pressure or cardiac output and showed only marginal, statistically non-significant effects on aortic and effective perfusion pressure. In contrast to the slight, non-significant changes due to DMPS (15 mg/kg i.v.), an equimolar dose of DMSA (12 mg/kg i.v.) led to a slight transient decrease in femoral blood pressure with strong reflex tachycardia and increase in blood flow. The higher DMPS dose (75 mg/kg i.v.), however, caused marked decreases in femoral blood pressure and blood flow, strong changes in blood gases and pH, and lactacidosis. Most of the physiological variables and parameters did not return to the initial level by 60 min. The R-spike of the electrocardiogram decreased, and the T-wave increased. Experiments on the denervated hind leg indicate that DMPS may be a direct vasodilator. The fall of blood pressure due to DMPS was markedly reduced when 30% ferrihaemoglobin had been formed by 4-dimethylaminophenol.HCl (DMAP). The highest DMPS dose (150 mg/kg i.v.) provoked circulatory failure and respiratory arrest. Artificial ventilation with room air restored spontaneous respiration, but one of three animals did not survive this dose for more than 90 min. DMPS and DMSA reacted with oxygen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Biophysical properties of the gelatin-resorcin-formaldehyde/glutaraldehyde adhesive.

Refixation of dissected aortic layers with gelatin-resorcin-formaldehyde/glutaraldehyde (GRFG) adhesive represents a new option in the surgical treatment of aortic dissection. Because of its ability to reinforce the delicate structures of the acutely dissected aortic wall, GRFG has been used increasingly in recent years. However, the biomechanical properties of the adhesive are still unclear, and little is known regarding the optimal mode of its application. In an ex vivo study, aortic specimens from sheep were glued with warm (45 degrees C) adhesive under wet and dry conditions and submitted to defined degrees of compression (5 Newtons [N], 20 N). Bonded specimens were retracted to assess tensile strength and elasticity compared with two reference adhesives: cyanoacrylate gel and fibrin glue. Gelatin-resorcin-formaldehyde/glutaraldehyde and cyanoacrylate gel showed similar results at 5 N. Both provided better adhesion when applied under dry conditions (GRFG 5 N: dry, 3.5 +/- 1.6 N/cm2; wet, 1.4 +/- 1.0 N/cm2; cyanoacrylate gel 5 N: dry, 4.8 +/- 1.8 N/cm2; wet, 3.2 +/- 1.3 N/cm2). At 20 N, GRFG tensile strength was significantly increased for either condition compared with values at 5 N (GRFG 20 N: dry, 17.1 +/- 4.2 N/cm2; wet, 4.8 +/- 1.8 N/cm2). Fibrin glue demonstrated only weak adhesive properties even under dry conditions (fibrin glue 5 N: dry, 0.8 +/- 0.3 N/cm2). Gelatin-resorcin-formaldehyde/glutaraldehyde has good adhesive properties both in wet and dry tissue. Bonding capacity can be substantially increased when applied on dry surfaces and at increased pressures.

Adhesiveness↗

PubMed1993

A new solid unreamed tibial nail for shaft fractures with severe soft tissue injury.

In a prospective study, 51 tibial shaft fractures with severe open or closed soft tissue damage were treated with a new, thin (8 mm or 9 mm) solid locking nail, inserted without reaming. At 6 months or more after trauma, 43 cases were reviewed. Fractures were classified according to Müller with six type A, 25 type B, and 12 type C fractures. In 13 cases there was group II (n = 8) or group III (n = 5) closed soft tissue damage (Tscherne). Of 30 open fractures, 16 were group OII, six were group OIIIA and eight were group OIIIB (Gustilo). Postoperative treatment in 42 of 44 cases was possible without additional cast or brace. Full weight bearing was achieved in 26 cases within 12 weeks, and in 42 cases within 26 weeks. In 43 cases, fracture healing occurred with a mean of 21.9 weeks (range 12-40 weeks). There was one case with valgus of 6 degrees and three cases with anterecurvatum deformities of 5 degrees to 10 degrees. In four cases there was an external rotation malalignment between 10 degrees and 20 degrees. In three cases we found an internal rotation deformity of 10 degrees to 20 degrees. Shortening between 0.5 and 1.0 cm was found in five cases, and in one case shortening was 1.5 cm. None of the patients had an osteomyelitis.

Adolescent↗

PubMed1993

Influences of different methods of intramedullary femoral nailing on lung function in patients with multiple trauma.

We investigated the effects of primary (< or = 24 h) intramedullary femoral nailing on lung function and pulmonary hemodynamics in patients with multiple trauma. Two groups were separated: the group with primary femoral nailing with reaming (group RFN) was submitted to femoral nailing after reaming of the medullary canal; in the group with unreamed femoral nailing (group UFN) a small-diameter solid nail was inserted without reaming. Lung function was assessed by oxygenation ratio (PaO2/FIO2), and pulmonary hemodynamics by intraoperative pulmonary artery catheter measurements. Central venous blood concentrations of elastase and the platelet count were determined during and 3 days after surgery. Lung function was stable in UFN patients (n = 14), but deteriorated in RFN patients (n = 17) from 353 +/- 24 (PaO2/FIO2 preoperatively) to 260 +/- 28 (PaO2/FIO2 postoperatively) (p < 0.05) and improved only after 48 hours. Pulmonary artery pressure (PAP) did not change during surgery in UFN patients; in RFN patients PAP increased from 27.2 +/- 3.1 mm Hg (preoperatively) to 36.3 +/- 4.1 mm Hg (p < 0.05) upon reaming and normalized 1 hour after insertion of the nail. Femoral nailing after reaming represents a potential risk with respect to lung function disturbances. This might trigger the development of adult respiratory distress syndrome (ARDS), especially in patients at extra risk of this complication (additional lung contusion, "borderline patient"). In these cases unreamed femoral nailing might offer an alternative by allowing primary intramedullary stabilization without the risk of adverse effects to the lung.

Adult↗

PubMed1992

[Effects of different intramedullary stabilizing procedures of the femur on lung function in polytrauma].

We investigated the effects of primary (< 24 h) intramedullary femoral nailing on lung function and pulmonary hemodynamics in multiple trauma patients. The standard procedure following reaming of the medullary canal (AFN) was compared with a new procedure using a small, solid nail without prior reaming (UFN). Pulmonary hemodynamics were determined using a pulmonary artery catheter. Global lung function was assessed by means of the oxygenation ratio (PaO2/FiO2). Concentrations of elastase and the platelet count as a general parameter of the clinical course were determined from central venous blood during and 3 days after surgery. The lung function was stable in UFN patients (n = 6), but decreased significantly in AFN patients (n = 10) from 353 +/- 24 (PaO2/FiO2 preoperative) to 260 +/- 28 (PaO2/FiO2 postoperative) and did not improve until 48 h later. Pulmonary artery pressure (Pap) remained within normal limits in UFN patients, whereas in AFN patients Pap increased from 27.4 +/- 3 mm Hg (preoperative) to 37 +/- 3 mm Hg during reaming and did not normalize until 1 h after insertion of the nail. The platelet count remained unchanged in UFN patients and dropped in AFN patients from 143 +/- 25 x 1000 cells/ml blood (preoperative) to 87.5 +/- 15 x 1000 cells/ml blood 2 days after surgery. Our measurements did not show an increase in central venous triglycerides in the AFN group, probably because bone marrow does not become immediately soluble. There was no significant difference between the increase of elactase levels in the two groups. The femoral nailing procedure with reaming in multiple trauma patients involves a potential risk to the lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

[Osteosynthesis of distal radius fractures with biodegradable fracture rods. Results of two years follow-up].

Forty distal fractures of the radius were stabilized with biodegradable polyglycolic acid rods (Biofix). A forearm plaster cast was fit for 4 weeks. Nine patients developed late (4 to 16 weeks) aseptic inflammatory reactions at the pin site, which were treated by débridement. The histological specimens showed giant-cell phagocytosing fragmented polyermic debris. In two cases a bacterial wound infection occurred secondary to débridement. All local reactions healed within 4 weeks. A classification system and treatment regimen for these inflammatory reactions are proposed. Thirty-four patients (including those with local foreign body reaction) were available for the 2-year follow-up. The anatomical results of fracture reduction on the postoperative and follow-up radiograms were the same, confirming good mechanical fracture stabilization. According to the Sarmiento score, the overall results were excellent and good in 31 cases. In one of the three fair cases, the result was clearly due to the initial local foreign-body reaction. Because of the high incidence of local inflammatory reaction, for now clinical application of biodegradable implants seems problematic despite the good overall 2-year results. This should only be advocated for well-controlled prospective studies using implants with improved biocompatibility.

Adult↗