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Objectives: Placement of a proximal humerus locking plate through a percutaneous transdeltoid approach bears the advantages of a minimally invasive approach but may compromise the anterior branches of the axillary nerve. This anatomic study aimed to develop a risk profile for 6 types of modern proximal humerus locking plates as to their interference with the axillary nerve., Materials and Methods: In this study six different implants (Arthrex®, DePuy®, Königsee®, Smith & Nephew®, Stryker® and Synthes®) were placed on the intact proximal humerus of 33 embalmed cadaveric upper extremities and the relative positioning between the axillary nerve and the screw holes was determined., Results: All locking plates displayed an area of risk which concerned 3 out of 7 (Arthrex®), 4 out of 10 (DePuy®), 2 out of 9 (Königsee®), 3 out of 11 (Smith & Nephew®), 3 out of 11 (Stryker®) and 6 out of 12 (Synthes®) screw holes of the plate., Conclusions: Using the anterolateral percutaneous deltoid splitting approach the relative position of the axillary nerve to the holes of a specific implant is of relevance for avoidance of iatrogenic lesions to the nerve.

Purpose: A bilateral fixed-angle plate was biomechanically compared to the two currently preferred methods of osteosynthesis for transverse patella fractures. It was hypothesized that the new angle-stable implant would provide a secure and sustainable fracture fixation, superior to the established standard techniques., Methods: Twenty-one identical patellae made of polyurethane foam (Sawbones(®)), osteotomized to create a transverse two-part fracture, were fixed with modified anterior tension wiring, cannulated lag screws with anterior tension wiring or bilateral polyaxial 2.7-mm fixed-angle plates. The testing protocol consisted of 10,000 repetitive cycles using a non-destructive physiological load between 100 and 300 N at a simulated knee flexion of 60°., Results: All 21 Sawbone(®)-patellae sustained repetitive loading up to 10,000 cycles without failing. The anterior tension wire group displayed significant displacement of the fracture gap (0.7 ± 0.2 mm) during cyclic loading, while both lag screws with tension wiring and bilateral fixed-angle plates showed no fracture gap widening at all (p < 0.01)., Conclusion: The bilateral fixed-angle plate and cannulated lag screws with anterior tension wiring preserved a constantly reduced fracture gap over 10,000 tensile cycles in contrast to modified anterior tension wiring, which exhibited significant widening of the gap after initial loading. Results of in vitro testing indicate that bilateral fixed-angle plates provide sustainable fixation stability offering a promising new option in the treatment for transverse patella fractures.

Purpose: Displaced tibial eminence fractures require surgical fixation in order to obtain a stable knee joint. Suture fixation with FiberWire(®) seems to be the most favorable therapeutic option. Biomechanical studies show failure of this technique most commonly due to a suture cutout with subsequent fracture of the tibial eminence fragment. The goal of this study is to compare the biomechanical properties of three different techniques of suture fixation using FiberWire(®)., Methods: Bone mineral density was evaluated in 18 human knee specimens by pqCT, and three similar groups were formed. A standardized anterior tibial eminence fracture was created, and suture fixation was performed using one of three different techniques in 6 specimens each. Cyclic and destructive testing was conducted., Results: Significant differences between the three techniques could be shown neither in the cycles needed to achieve a steady state nor in a failure load or initial stiffness. Almost all specimens failed by suture cutout., Conclusion: The presented modification of the existing technique for suture fixation of tibial eminence fractures did not lead to an increased initial stability nor did it lower the rate of suture cutout. All tested suture techniques showed comparable initial stiffness and failure load.

Introduction: Operative treatment of patella fractures is frequently associated with implant failure and secondary dislocation which can be attributed to the employed hardware. Therefore, a 2.7 mm fixed-angle plate designed for the treatment of patella fractures was tested biomechanically against the currently preferred methods of fixation. It was hypothesized that under simulated cyclic loading fixed-angle plating would be superior to modified anterior tension wiring or cannulated lag screws with anterior tension wiring., Materials and Methods: Eighteen human cadaver knees, matched by bone mineral density and age, were divided into three groups of six. After setting a transverse patella fracture each group received one of the osteosyntheses mentioned above. Repetitive testing over 100 cycles was performed at non-destructive loads by simulating knee motion from 90° flexion to full extension., Results: Anterior tension wiring as well as lag screws with tension wiring showed significant fracture displacement after the initial cycle already. Both constructs, lag screws plus wiring (3.7 ± 2.7 mm) as well as tension wiring alone (7.1 ± 2.2 mm) displayed fracture displacement of >2 mm which is clinically regarded as failure. Those patellae stabilized with fixed-angle plates showed no significant fracture gap widening after completion of 100 cycles (0.7 ± 0.5 mm). The differences between the fixed-angle plate group and the other two groups were statistically significant (p<0.05)., Conclusion: In contrast to modified anterior tension wiring and cannulated lag screws with anterior tension wiring the bilateral fixed-angle plate was the only fixation device to stabilize transverse patella fractures securely and sustainably., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Aim: The aim of the present study was to compare the primary fixation stability and initial fixation stiffness of two established fixation techniques, the tension band wiring technique and interfragmentary screw fixation, with a mini-screw fragment fixation system in a model of transverse patella fracture. It was hypothesised that the biomechanical loading performance of the fragment fixation system would not significantly differ from the loading characteristics of the two established methods currently investigated., Materials and Methods: Ninety-six calf patellae were used in this biomechanical model. A standardized transverse patella fracture was induced and three different fixation methods, including the modified tension band wiring technique, interfragmentary screw fixation, and the mini-screw fragment fixation system, were used for fragment fixation. Specimens were mounted to a loading rig which was secured within a material testing machine. In each fixation group, eight specimens were loaded to failure at a simulated knee angle of either 0 degrees or 45 degrees . Another eight specimens were submitted to a polycyclic loading protocol consisting of 30 cycles between 20N and 300N at a simulated knee angle of 0 degrees or 45 degrees . The residual displacement between the first and the last cycle was recorded. Differences in the biomechanical performance between the three fixation groups were evaluated., Results: No significant differences between the three fixation groups were observed in the parameters maximum load to failure and linear fixation stiffness with monocyclic loading. Specimens being loaded at 45 degrees showed significantly lower maximum failure loads and linear stiffness when compared with 0 degrees . During polycyclic loading, no significant differences in the residual displacement were observed between the groups at 0 degrees loading angle, while at 45 degrees , residual displacement was significantly higher with tension band fixation when compared with interfragmentary screw fixation or the fragment fixation system., Conclusion: The biomechanical performance of the fragment fixation system was comparable to interfragmentary screw fixation and superior to the tension band wiring technique. Given the advantages of a system which provides interfragmentary compression and which simplifies fracture fixation after open or closed reduction, we believe the fragment fixation system to be an adequate alternative in the osteosynthesis of transverse patella fractures., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Unlabelled: This study aims to describe the first clinical results in the treatment of dislocated olecranon fractures with 2.2-mm, fine-threaded wires with a washer. Furthermore, in the second part of the article, the stability of these new implants has been compared to standard tension band wiring in a sawbone model., Patients: The radiological and clinical outcomes in 24 patients (mean age: 53.6 years) with 24 isolated Mayo type I and II fractures of the olecranon were evaluated in a prospective study after open reduction and internal fixation (ORIF) with a new fixation device (FFS; Orthofix). The quality of reduction with the implementation of 24 FFS constructions was compared with 24 tension band-wiring procedures performed by six different surgeons in a standard sawbone Mayo type IIa fracture model. Stability was tested in all constructs using a single cycle load to failure protocol (group I), cyclic loading for 300 cycles between 10 and 500 N (group II) and incremental sinusoidal loading from 10 to 200 N with an incremental increase of 10 N per cycle (group III) in a laboratory study., Results: The Morrey elbow score was excellent in 23 patients and good in one patient, with mean DASH score of 1.6. No implant migration, secondary dislocation or nonunion was observed. In the sawbone model, the quality of reduction was the same with the FFS implants compared to the tension band wiring in the sawbone model. Here, bending moments in all three groups showed no significant difference, whereas displacement at failure was significantly greater in the tension band-wiring group at a single cycle load (p=0.017)., Conclusion: Clinical results were comparable to tension band wiring and stability of the implants in the sawbone model was the same; thus, we conclude that the FFS technique can serve as an alternative treatment option for isolated olecranon fractures.

Background: The purpose of the current work was to study the arterial blood supply of the humerus to evaluate impairments of the blood supply after humeral fractures and different methods of fracture treatment., Methods: Arterial blood supply of the humerus was studied by corrosion injection technique in 6 cadaver preparations and is compared with the existing literature., Results: Humeral head arteries originate from the circumflex humeral arteries. The major vessel enters the greater tubercle. Another group of vessels accesses the head from medially. The nutrient artery for the shaft enters into the medial third of the shaft. At the distal humerus there are multiple anastomoses with penetrating branches into both condyles and proximal to the radial, coronoid, and olecranon fossae., Conclusions: Fragments of a proximal humeral fracture usually have an independent blood supply. The medial vessels to the head gain high importance in fractures of the anatomical neck. The nutrient artery lies regularly medial to the humeral mid-shaft and is at risk at open reduction of this region. The abundant vessels at the entire distal humerus ensure sufficient vascularization of the fragments after fracture.

Aims: Comparison of the degradation of poly(D,L)lactide (Resorb X) or poly(lactide-co-glycolide) (LactoSorb) in vivo., Material and Methods: LactoSorb and Resorb X osteosynthesis plates were fixed at the lateral aspect of the femora of 26 Chinchilla rabbits using the respective osteosynthesis screws. After intraperitoneal injection of fluorochromes the screw plate bone blocks were resected after 1, 6, 12, 14, 16, 21, 26 months and radiologic, histologic as well as fluorescence microscopic examinations were carried out., Results: Newly formed bone was detectable above and beneath the polymers 1 month after the implantation. The implants were totally covered by newly formed bone after 6 months. While the LactoSorb screws were found to be as birefringent as after 1 month, in the Resorb X screws a continuous resorption by phagocytizing marrow cells starting from the periphery was detectable. Resorb X was totally resorbed in histologic slides 12 months after implantation, while total resorption of LactoSorb lasted 14 months; both polymers were replaced by marrow cells. Bone remodeling was not finished 26 months after implantation in both polymers., Conclusion: Resorption of Resorb X was finished earlier than the resorption of LactoSorb. Both materials were found by fluorescence microscope to be completely resorbed after 12 or 14 months, but bone remodeling of the screw holes was not yet finished 26 months after implantation.

For osteosynthesis in the epiphyseal region of long bones, specialized screw types are available to achieve a better purchase in cancellous bone. Typically, the cancellous bone screw has a large outer thread diameter with a relatively small core diameter and a great pitch. Due to its dimensions, this screw type is not suited for the cancellous bone areas in hand and foot surgery, respectively. Fine machine screws are better adapted to the bone dimensions in this part of the skeleton. To compare the holding power of fine machine screws with the holding power of other screw types available in the market, a biomechanical study was undertaken. Different screw types were compared: 4 mm cancellous screw, 3.5 and 2.7 mm cortical screws and three different diameters of a fine machine screw (2.2, 1.6 and 1.2 mm). Both cortical screws were tested in pretapped and self-tapping version. Polyurethane foam and bovine cancellous bone were tested. The screws were applied according to the manufacturer's instructions and an axial extraction force was applied. The 4 mm cancellous bone screws were superior to all the other screws in both test materials (P<0.05). The 3.5 mm cortical screw showed a significant difference compared to the 2.7 mm cortical screw in both materials. A significant difference between the self-tapping and pretapped screws of the same diameter was only found in the 3.5 mm cortical screws in polyurethane foam (P<0.05). Interestingly, the maximum holding power of the 2.2 mm fine machine screws in homogeneous test material (polyurethane foam) was as high as the holding power of the 2.7 mm cortical screws (P<0.05). In natural bovine cancellous bone, the result was even more striking. There was no significant difference between the 2.2 mm fine machine screws and the 3.5 mm cortical screws (P<0.05). Relative to their thread diameter, the fine machine screws were superior to conventional cancellous and cortical screws in cancellous bone. The high holding power of this screw type is at least partly due to the impaction effect of the drilling debris between the thread and the abutting spongy bone structure.

Percutaneous application of Kirschner wires, fixator pins, or other implants near the metacarpophalangeal joint may lead to postoperative disability of movement with subsequent joint stiffness. To determine the best location for the application of implants into the metacarpal head and the basis of the proximal phalanx, 57 Kirschner wires were introduced into the metacarpal head and into the bases of the proximal phalanx and the resulting stiffness has been measured. Kirschner wires inserted at the level of the dorsal tubercle or proximal to the tubercle, do not lead to a noteworthy stiffness. Whenever possible, this tubercle should be taken as the distal border for inserting implants. If the position of the fracture line makes it necessary to implant wires into the metacarpal head itself, a more dorsal application is preferable. If a palmar placement cannot be avoided, the implantation should be done in neutral position of the metacarpophalangeal joint, because a transfixation of the tense collateral ligament in flexion leads to a maximum of postoperative stiffness. The application of wires into the basis of the proximal phalanx does not influence the range of movement of the metacarpophalangeal joint.

The four ulnar metacarpal bones are connected to each other at their proximal and distal ends by strong ligaments. The second and fifth metacarpal bones are the frame of the metacarpus. Surgically, this is of great importance. A fracture of these two bones often requires stabilization, whereas a fracture of the third and fourth metacarpal bones with intact ligaments seldom requires surgery except in cases of severe fragment dislocation. Using external fixation for these purposes it seems to be of utmost interest to define secure pintracks through the soft tissue. In an anatomical study using formalin fixed specimen it clearly could be demonstrated that the second and fifth metacarpal bones are best suited for external fixation. The second metacarpal bone should always be fixed from the radial side because the fixator pins can be inserted within a wide range of angles without the risk of violating the extensor tendons. Variations of tendons and ligaments are seldom located on the radial side of the second metacarpal bone and therefore, finger movement is unhindered after pin application. A similar consideration is true for the fifth metacarpal bone which should be fixed from the ulnar side. With respect to the extensor tendon which covers the entire dorsal surface of the fifth metacarpal bone, the angle of the pins should be 40 to 90 degrees from the dorsal side. For the third metacarpal bone, fixation from the radial side is preferable taking topographical and biomechanical considerations into account. The radial corridor to the fourth metacarpal bone is smaller than the ulnar corridor, but there is much less morphological variability of the extensor tendons than on the ulnar side where strong fibres often cross the fourth intermetacarpal space. Because in the proximal fourth of the metacarpal bones the tendons are located very close to each other, a small skin incision and preparation to the bone surface is advisable to exclude violation of the tendons when inserting fixator screws into the third and fourth metacarpal bones. Using formalin-alcohol fixed cadaver specimens for the research gives an idea of the anatomical situation in the dorsal metacarpus but cannot answer the question whether the tendons in the lax subcutaneous tissue of the living will automatically slip aside when the fixator pin approaches. This should be item to subsequent studies in fresh frozen specimens and follow-up studies in a larger amount of patients treated with external fixation.

In a comparative, experimental examination of 60 human cadaver radii, the stability of various, widely used internal fixation procedures of a distal radius fracture loco typico using a dorsal wedge was determined. The use of 2.5-mm Kirschner wires (K-wires) delivered a 10% greater stability than 1.8-mm K-wires. The 2.7-mm polylactide rods achieved a slightly greater stability than 1.8-mm K-wires under accurate pinning conditions. Polylactide rods (35 mm length, 2 mm diameter) and polyglycolide rods (60 mm length, 2 mm diameter) proved to be 20% less solid than 1.8-mm K-wires and almost 45% less than plate fixation. The short polylactide pins, however, did not have enough hold in the proximal cortical bone. The 2.7-mm polylactide rods (60 mm length) complied with the stability prerequisites necessary for comparable substitution for K-wires in distal radius fractures.