The effect of intermittent intraabdominal pressure elevations and low cardiac output on the femoral to carotid arterial blood pressure difference in piglets.

BACKGROUND: Our previous work in a laparoscopic setting in piglets revealed that the systolic femoral artery pressure was approximately 5 % higher than its carotid counterpart, whereas the mean and diastolic values showed no significant difference. This remained idem when the intraabdominal pressure (IAP) was gradually increased. In this study, we aimed to investigate the effect of (1) intermittent IAP elevations and (2) a low cardiac output (CO) on the blood pressure (BP) difference cranially (carotid artery) and caudally (femoral artery) of a capnoperitoneum (ΔP = P a fem-P a carot). METHODS: A total of twenty-two piglets (mean body weight 11.0 kg; range 8.9-13.3 kg) were studied. Of these, 14 underwent intermittent IAP elevations at 8 and 16 mmHg, and ΔP was measured. In another 8 piglets, a model of reduced CO was created by introducing an air embolism (2 ml/kg over 30 s) in the inferior caval vein (VCI) at 12 mmHg IAP to further assess the influence of this variable on ΔP. RESULTS: Systolic ΔP remained at a mean of 5.6 mmHg and was not significantly affected by insufflation or exsufflation up to an IAP of 16 mmHg. Diastolic and mean values showed no differences between P a carot and P a fem. P a fem, systol remained higher than its carotid counterpart as long as the cardiac index (CI) was above 1.5 l/min/m2, but fell significantly below P a carot, systol at a low CI. There was no CO-dependent effect on diastolic and mean ΔP. Repeated IAP elevations do not significantly influence ΔP. CONCLUSIONS: Intermittent IAP elevations do not significantly influence ΔP. Despite of a CO-dependent inversion of systolic ΔP, mean BP measurements at the leg during laparoscopy remain representative even at low CO values.

Locking-plate osteosynthesis versus intramedullary nailing for fixation of olecranon fractures: a biomechanical study.

PURPOSE: Intramedullary nailing and locked plating for fixation of olecranon fractures has recently gained popularity. However, these two new technologies have not been compared for their biomechanical efficacy. The aim of this study was to evaluate the biomechanical stability of two newly designed fracture fixation devices for treating olecranon fractures during dynamic continuous loading: the ION intramedullary locking nail and the LCP precontoured locking compression plate. METHODS: Simulated oblique olecranon fractures were created in eight pairs of fresh-frozen cadaver ulnae and stabilised using either the LCP or ION. Specimens were then subjected to continuous dynamic loading (from 25 to 200 N), with a continuous angle alteration between 0° and 90° of flexion, to perform a matched-pairs comparison. Significant differences in the distance between markers surrounding the fracture gap was determined using the Wilcoxon test after four and 300 loading cycles. RESULTS: The ION resulted in significantly less displacement in the fracture gap at 0° extension (P = 0.036), 45° flexion (P = 0.035) and 90° flexion (P = 0.017) after 300 cycles of continuous loading. The measured displacements were small and were probably not of clinical significance. No mechanical failure or hardware migration was seen with either fixation technique. CONCLUSION: This study shows significantly less micromotion for the ION than for the LCP in treating oblique olecranon fractures after 300 cycles of dynamic loading. Both implant types could be appropriate surgical techniques for fixation of selected olecranon fractures and osteotomies.

Biomechanical comparison of dorsal nail plate versus screw and K-wire construct for extra-articular distal radius fractures in a cadaver bone model.

PURPOSE: The purpose of the study was to compare the biomechanical stability of distal radius fracture fixation with 2 new implants, the DNP (Hand Innovations LLC, Miami, FL), a dorsal locked hybrid of nail and plate, and the XSCREW (Zimmer, Freiburg, Germany), an implant combining a cannulated screw and K-wires, in a cadaver bone distal radius fracture model. METHODS: Eight pairs of fresh-frozen cadaver radii were used. To simulate an extra-articular distal radius fracture, a 5-mm volar open wedge osteotomy was made. Axial loads of 10 to 100 N and torque loads of -1.5 to 1.5 Nm were applied by a testing machine to the intact radii and to the radii after each device was fixed as recommended by the manufacturer. One thousand cycles in torque and failure tests were performed. RESULTS: With a median of 136.0 N/mm, the axial stiffness of XSCREW-fixed specimens was higher than that of DNP-fixed specimens, with a median of 69.5 N/mm, but differences were not statistically significant. With a median of 0.163 Nm/ degrees , the torque stiffness of XSCREW-fixed specimens was significantly higher than that of DNP-fixed specimens, with a median of 0.068 Nm/ degrees . The XSCREW-group reached 33% of the axial stiffness and 49% of the torque stiffness of the intact radii, and the DNP-group reached 14% of the axial stiffness and 20% of the torque stiffness of the intact radii. CONCLUSIONS: In this human cadaver bone biomechanical study, the XSCREW provided more stability than the DNP in torque stiffness but not in axial stiffness.

Evaluation of severely displaced radial neck fractures in children treated with elastic stable intramedullary nailing.

BACKGROUND: We performed a retrospective case study of 28 consecutive severely displaced radial neck fractures (Judet types III and IV) in children treated with elastic stable intramedullary nailing using the Metaizeau technique. METHODS: We reviewed all preoperative radiographs and classified the injuries according to Judet. All patients were asked to return for later assessment. They underwent physical examination; radiographs were taken; and they were asked for subjective assessment. An evaluation of clinical results was performed using the Mayo Elbow Performance Score (MEPS). RESULTS: According to Judet classification there were 13 type III and 15 type IV fractures. Using the MEPS, excellent results were achieved in 23 cases (82%) and good results in 5 cases (18%). The average MEPS was 97 points. Five patients complained of mild pain. Three malunions were observed. CONCLUSIONS: Elastic stable intramedullary nailing is a minimally invasive technique, allowing stable fixation and providing excellent to good outcomes with a low complication rate. LEVEL OF EVIDENCE: We performed a retrospective level 4 study of case series.

[Biomechanical study of four palmar locking plates and one non-locking palmar plate for distal radius fractures: stiffness and load to failure tests in a cadaver model]. / Biomechanische Studie zu vier winkelstabilen distalen palmaren Radiusplatten und einer nichtwinkelstabilen Radiusplatte: Steifigkeit und Versagenstests am Kadavermodell.

Five different palmar fixation plate designs were compared in a distal radial osteotomy cadaver model with regard to their biomechanical properties. A metaphyseal osteotomy gap of 1 cm was performed and the osteosynthesis was plated according to the manufacturer's instructions. Axial load was applied to the construct by a pneumatic material testing machine. Five implant groups with eight cadavers each were tested concerning stiffness. None of the constructs developed deformity and movement of the fracture gap larger than 2 mm with a load of 100 N. Increasing the load to 250 N revealed significant differences in stiffness and failure load between the different plates. The mean stiffness under axial load (mean+/-standard deviation) was 356.4+/- 138.6 N/mm for the radius correction plate without lateral tongue, 299.7+/-86.3 N/mm for the radius correction plate with lateral tongue, 132.8+/-41.5 N/mm for the distal volar radius plate, 112.5+/-40.2 N/mm for the 3.5 mm titanium locking compression plate and 91.9+/-29.2 N/mm for the standard stainless steel 3.5 mm T-Plate. The non-angular stable implant (STP plate) had the lowest stiffness. Unexpectedly, there were differences over 100% concerning the stiffness between the at first glance nearly similar angular stable implants. Additionally, a review of the literature concerning biomechanical investigations of the distal radial fracture was performed.

Impact of Different Screw Designs on Durability of Fracture Fixation: In Vitro Study with Cyclic Loading of Scaphoid Bones.

PURPOSE: The use of new headless compression screws (HCSs) for scaphoid fixation is growing, but the nonunion rate has remained constant. The aim of this study was to compare the stability of fixation resulting from four modern HCSs using a simulated fracture model to determine the optimal screw design(s). METHODS: We tested 40 fresh-frozen cadaver scaphoids treated with the Acumed Acutrak 2 mini (AA), the KLS Martin HBS2 midi (MH), the Stryker TwinFix (ST) and the Synthes HCS 3.0 with a long thread (SH). The bones with simulated fractures and implanted screws were loaded uniaxially into flexion for 2000 cycles with a constant bending moment of 800 Nmm. The angulation of the fracture fragments was measured continuously. Data were assessed statistically using the univariate ANOVA test and linear regression analysis, and the significance level was set at p < 0.05. RESULTS: The median angulation of bone fragments φ allowed by each screw was 0.89° for AA, 1.12° for ST, 1.44° for SH and 2.36° for MH. With regards to linear regression, the most reliable curve was achieved by MH, with a coefficient of determination of R2 = 0.827. This was followed by AA (R2 = 0.354), SH (R2 = 0.247) and ST (R2 = 0.019). Data assessed using an adapted ANOVA model showed no statistically significant difference (p = 0.291) between the screws. CONCLUSIONS: The continuous development of HCSs has resulted in very comparable implants, and thus, at this time, other factors, such as surgeons' experience, ease of handling and price, should be taken into consideration.

Are there any differences in various polyaxial locking systems? A mechanical study of different locking screws in multidirectional angular stable distal radius plates.

Numerous angular stable plates for the distal radius exist, and technically based comparisons of the polyaxial locking interfaces are lacking. The aim of this mechanical study was to investigate three different locking interfaces of angular stable volar plates by cantilever bending: VA-LCP Two-Column Distal Radius Plates 2.4 mm (Synthes® GmbH, Oberdorf, Switzerland), IXOS® P4 (Martin, Tuttlingen, Germany) and VariAX™ (Stryker®, Duisburg, Germany). We assessed the strength of 0°, 5°, 10° and 15° screw locking angles and tested the bending strength from 10° to 5° angles by cyclic loading until breakage. The final setup repeated the above assessments by inclusion of four locking screws. The single screw-plate interfaces of the VA-LCP showed the highest bending moment at an angle of 0° and 5°, the IXOS® P4 at an angle of 10° and 15° and the VariAX™ when changing the insertion angle from 10° into 5°. The strength of polyaxial locking interfaces and mechanism of failure proved to be different among the examined plates.

Volar fixed-angle plating of distal radius fractures: screws versus pegs--a biomechanical study in a cadaveric model.

OBJECTIVES: The purpose of this biomechanical study was to determine whether a multidirectional fixed-angle plate with locking screws or with locking pegs in the distal fragment would optimize fixation of Orthopaedic Trauma Association (OTA) type A3 distal radius fractures. METHODS: Eight pairs of fresh-frozen human distal radii were used. Extra-articular distal radius fractures were created and stabilized with a multidirectional volar fixed-angle plate. The radii were randomized into 2 matched-paired groups. The distal fragment in Group I was stabilized with 7 locking screws. The distal fragment in Group II was fixed with 7 locking pegs. The proximal fragment in both groups was fixed with 3 screws. The specimens were tested under torsion and axial compression during static and cyclic tests. Finally, load-to-failure tests were performed under torsion. RESULTS: After 1000 cycles, 99% of the median torsional stiffness remained in the group using screws, whereas only 76% of the median stiffness under torsion remained in the group using pegs (P = 0.018). Under axial compression, median stiffness remained at 93% in the group using screws after 1000 cycles compared with a median of 0% in the group using pegs (P = 0.018). CONCLUSIONS: This biomechanical study showed a statistically significant difference between the locking screw and locking smooth peg configuration with regard to stiffness of the constructs after 1000 cycles. The use of locking screws as opposed to smooth locking pegs for OTA type A3 extra-articular distal radius fractures optimizes construct stability.

Embolism risk analysis--helium versus carbon dioxide.

BACKGROUND: Helium is used as an insufflation gas to avoid the negative properties of carbon dioxide (CO(2)), such as CO(2) accumulation, acidosis, and tachycardia, particularly in the case of insufficient respiratory function, seen also in infancy. Any laparoscopic procedure carries the risk of a gas embolism. MATERIALS AND METHODS: Seven anesthetized piglets (weighing 9.9-12.8 kg), randomized into three groups, served as models for pre-teenage children. Three piglets received a CO(2) embolism, followed by a helium embolism of 2 mL/kg, respectively. Helium was administered to three piglets, whereas both gases were repeatedly administered alternately to one piglet. The embolisms were administered for 30 seconds via a central venous line. Cardiac output was measured using the thermodilution method. The observation period for each embolism was 60 minutes in Groups 1 and 2 and 15 minutes in Group 3. RESULTS: All animals survived CO(2) embolisms. Four of the six piglets died after helium embolisms. Following helium embolisms there was a prompt initial decrease in the end-tidal CO(2) pressure and an initial increase in the pulmonary arterial pressure. A further decrease in arterial blood pressure was prevented by a compensatory increase in the heart rate and appeared just before death. After only 5 minutes cardiac output showed a 25% decline from the initial value. Helium embolisms led to a severe increase in the pulmonary dead space. CONCLUSIONS: Embolisms with the smallest amounts of helium administered via direct venous puncture have an immediate lethal impact. Extended perioperative monitoring and trocar placement under vision should be performed.

Intramedullary nailing vs. palmar locked plating for unstable dorsally comminuted distal radius fractures: a biomechanical study.

BACKGROUND: The purpose of this study was to compare the stability of a 2.4mm palmar locking compression plate and a new intramedullary nail-plate-hybrid Targon DR for dorsally comminuted distal radius fractures. METHODS: An extraarticular 10mm dorsally open wedge osteotomy was created in 8 pairs of fresh frozen human radii to simulate an AO-A3-fracture. The fractures were stabilized using one of the fixation methods. The specimens were loaded axially with 200 N and dorsal-excentrically with 80 N. 2000cycles of dynamic loading and axial loading-to-failure were performed. FINDINGS: Axial loading revealed that intramedullary osteosynthesis (Targon DR: 369 N/mm) was significantly (p=0.017) stiffer than plate osteosynthesis (Locking compression plate: 131 N/mm). With 214 N/mm the intramedullary nail also showed higher stability during dorsal excentric loading than the Locking compression plate with 51 N/mm (p=0.012). After 2000 cycles of axial loading with 80 N the Targon DR-group was significantly stiffer than the Locking compression plate-group under both loading patterns. Neither group showed significant changes in stiffness after 2000 cycles. Under dorsal excentric loading the Targon DR-group was still significantly stiffer with 212 N/mm than the Locking compression plate-group with 45 N/mm (p=0.012). The load to failure tests demonstrated higher stability of intramedullary nailing (625 N) when compared to plate osteosynthesis (403 N) (p<0.025). INTERPRETATION: The study shows that intramedullary fixation of a distal AO-A3 radial fracture is biomechanically more stable than volar fixed-angle plating under axial and dorsal-excentric loading in an experimental setup.

Osteosynthesis of Proximal Humeral Fractures with the Fixed Angle PHILOS-plate.

In a retrospective study we analyzed the functional and radiological outcome of 30 proximal humeral fractures, treated by PHILOS-plate, a fixed-angle device. Two of them were characterized as type Neer III, 14 as type Neer IV, 5 as type Neer V and 9 as type Neer VI. There were 2 2-part, 16 3-part and 12 4-part fractures. According to the constant-score, the normalized constant-score and the UCLA-score, good to excellent results were obtained in 66.7, 76.7 and 76.7%. Twenty-six (86.7%) patients had no or mild pain. Active forward flexion and active abduction over 90° was possible in 26 (86.7%) cases. Four (13.3%) patients developed partial avascular necrosis. Screw perforation was seen in 3 (10%) cases, delayed union in 1 (3.3%) case, malunion in 1 case and a loosening of plate and screws in another one. A secondary varus displacement of 5°-35° with a mean of 7° was found in 19 (63.3%) cases. The average time to union was 75 days. Fixation with PHILOS-plate is an adequate treatment for displaced 2- to 4-part fractures. Even in dislocated or 4-part fractures or in patients over 65 years good to excellent results were seen in the majority of cases.

Anatomical Course of the Superficial Branch of the Radial Nerve and Clinical Significance for Surgical Approaches in the Distal Forearm.

10 embalmed cadaver forearms and wrists were dissected to determine the anatomical course of the superficial branch of the radial nerve in the distal forearm. The superficial radial nerve bifurcated in two branches at a mean of 54,7 mm proximal to the radial styloid. From the styloid process of the radius, the mean distance to the closest dorsal branch of the superficial radial nerve was 3,5 mm and the mean distance to the closest volar branch was 9,8 mm. The mean distance between the closest branch of the superficial radial nerve and Lister?s tubercle was 16,4 mm. The crossing point between the nerve and the cephalic vein was located at a mean of 54,3 mm proximal to the styloid process. At the level of styloid process the mean distance between the closest dorsal branch of the superficial radial nerve and the first dorsal compartment was 15,2 mm and between the closest volar branch and the first dorsal compartment 4,4 mm. Detailed knowledge of anatomic characteristics of the superficial branch of the radial nerve may help prevent injury during operations and treat traumatic lesions of the nerve. Because of great variations in the course of the superficial radial nerve we could not define an absolute safe zone for surgical procedures on the distal forearm. Iatrogenic lesions of the superficial radial nerve are described complications of percutaneous procedures. Therefore open surgical approaches are recommended.

Pediatric fractures of the carpal scaphoid: a retrospective clinical and radiological study.

A retrospective study was undertaken of 22 carpal scaphoid fracture patients younger than 18 years. Of these, 17 patients received conservative treatment, and 5 received treatment involving screw fixation with or without a bone graft from the iliac crest. Clinical outcomes were evaluated using the Cooney score. Radiographs were analyzed with respect to the site of the fracture, the course of the fracture gap, displacement, and time to union. According to the Cooney score, in 94% of patients, good or excellent results were obtained. A total of 94% of patients considered their result as good or excellent. All fractures healed. Malunion was evident in 1 case.