[Biomechanical comparison of six different fixation techniques for treatment of metacarpal neck fractures]. / Biomechanischer Vergleich sechs verschiedener Fixationstechniken zur Versorgung von Halsfrakturen der Metakarpale.

PURPOSE: The purpose of this study was to evaluate the primary stability of commonly used fixation techniques for metacarpal neck fractures and to compare it with that of an innovative osteosynthesis device: IlluminOss™, the photodynamic bone stabilization system™. MATERIAL AND METHODS: Metacarpal neck fractures were created on the second to fifth metacarpal bones of 24 freshly frozen human cadavers using a band saw. Specimens were randomly assigned to one of six groups and treated with (1) K-wire fixation, (2) dorsal plating, (3) external fixation, (4) cross-threaded K­wire fixation, (5) IlluminOss™ and (6) locked IlluminOss™. In each group 16 specimens each underwent either monocyclic or polycyclic loading protocols. RESULTS: During monocyclic loading none of the specimens failed prior to a maximum deformation of 3 mm. With intramedullary K­wire fixation the mean loads were significantly lower than those of the other techniques. Mean loads causing 2 mm deformation with external fixation were significantly lower than those with dorsal plate osteosynthesis. The mean linear stiffness of the K­wire osteosynthesis was significantly lower than for the other fixation techniques and all methods of external fixation were significantly lower than dorsal plates. There were no significant differences with respect to the linear stiffness between the groups with dorsal plates, fragment fixation system (FFS), IlluminOss™ and locked IlluminOss™. During polycyclic testing the loss of resistance in dorsal plate osteosynthesis was significantly lower than with K­wire and IlluminOss™ fixation. No significant differences in loss of resistance could be shown between dorsal plate osteosynthesis, external fixation, FFS and locked IlluminOss™. CONCLUSION: In summary, IlluminOss™ can be used as an intramedullary stabilization system for treatment of metacarpal neck fractures. In combination with locking screws the biomechanical characteristics of IlluminOss™ are comparable to the other fixation techniques.

[Knee laxity in anterior cruciate ligament reconstruction : The influence of graft rotation using interference screw fixation]. / Kniegelenklaxizität beim vorderen Kreuzbandersatz : Einfluss der Transplantatrotation um die Interferenzschraube.

BACKGROUND: The use of interference screws for femoral graft fixation in anterior cruciate ligament (ACL) reconstruction with hamstring grafts can result in rotation of the graft around the screw leading to changes in the final position of the graft within the bone tunnel. MATERIAL AND METHODS: In a prospective study 107 patients (54 right and 53 left knees) underwent ACL reconstruction with a hamstring tendon autograft. Femoral fixation of the graft was performed with a standard right-thread screw in all cases. Patients were assessed at 6 months postoperatively with the international knee documentation committee (IKDC) standard evaluation including instrumented laxity measurements and the results were compared between right and left knees. RESULTS: A significantly higher postoperative anterior laxity was observed in left knees with a negative Lachman test in only 64 % of the cases compared with 87 % in the group of right knees. Accordingly, instrumented laxity measurements of the reconstructed knee compared with the contralateral knee revealed significant differences between left and right knees (left knees 1.8±1.2 mm and right knees 1.0±1.4 mm). CONCLUSIONS: This study demonstrates the importance of femoral graft positioning and its sensitivity to multiple influencing factors. The use of standard right-thread interference screws for femoral graft fixation in the mirrored situation of right and left knees may produce a systematic error in ACL reconstruction. Due to a possible rotation of the graft around the screw, the final position of the transplant may vary thus leading to significant changes in anterior translation of the operated knee.

[Knee laxity in anterior cruciate ligament reconstruction. The influence of graft rotation using interference screw fixation]. / Kniegelenklaxizität beim vorderen Kreuzbandersatz. Einfluss der Transplantatrotation um die Interferenzschraube.

BACKGROUND: The use of interference screws for femoral graft fixation in anterior cruciate ligament (ACL) reconstruction with hamstring grafts can result in rotation of the graft around the screw leading to changes in the final position of the graft within the bone tunnel. MATERIAL AND METHODS: In a prospective study 107 patients (54 right and 53 left knees) underwent ACL reconstruction with a hamstring tendon autograft. Femoral fixation of the graft was performed with a standard right-thread screw in all cases. Patients were assessed at 6 months postoperatively with the international knee documentation committee (IKDC) standard evaluation including instrumented laxity measurements and the results were compared between right and left knees. RESULTS: A significantly higher postoperative anterior laxity was observed in left knees with a negative Lachman test in only 64 % of the cases compared with 87 % in the group of right knees. Accordingly, instrumented laxity measurements of the reconstructed knee compared with the contralateral knee revealed significant differences between left and right knees (left knees 1.8±1.2 mm and right knees 1.0±1.4 mm) CONCLUSIONS: This study demonstrates the importance of femoral graft positioning and its sensitivity to multiple influencing factors. The use of standard right-thread interference screws for femoral graft fixation in the mirrored situation of right and left knees may produce a systematic error in ACL reconstruction. Due to a possible rotation of the graft around the screw, the final position of the transplant may vary thus leading to significant changes in anterior translation of the operated knee.

Biomechanical evaluation of the primary stability of pedicle screws after augmentation with an innovative bone stabilizing system.

INTRODUCTION: In today's aging population, diminished bone quality often affects the outcome of surgical treatment. This occurs especially when surgical implants must be fixed to bone, as it occurs when lumbar fusion is performed with pedicle screws. Besides Polymethylmethacrylate (PMMA) injection, several techniques have been developed to augment pedicle screws. The aim of the current study was to evaluate the primary stability of an innovative system (IlluminOss™) for the augmentation of pedicle screws in an experimental cadaveric setup. IlluminOss™ is an innovative technology featuring cement with similar biochemical characteristics to aluminum-free glass-polyalkenoate cement (GPC). MATERIALS AND METHODS: IlluminOss™ was inserted transpedicularly via a balloon/catheter system in 40 human cadaveric lumbar vertebrae. For comparability, each vertebra was treated bilaterally with pedicle screws, augmented and non-augmented. The maximum failure load during pull out test was documented by a universal material testing machine. RESULTS: The results showed significantly higher failure loads for the augmented pedicle screws (Median 555.0 ± 261.0 N, Min. 220.0 N, Max. 1,500.0 N), compared to the native screws (Median 325.0 ± 312.1 N, Min. 29.0 N, Max. 1,400.0 N). CONCLUSIONS: Based on these data, we conclude the IlluminOss™ system can be used to augment primary screw stability regarding axial traction, compared to native screws. The IlluminOss™ monomer offers ease of control for use in biological tissues. In contrast to PMMA, no relevant heat is generated during the hardening process and there is no risk of embolism. Further studies are necessary to evaluate the usefulness of the IlluminOss™ system in the in vivo augmentation of pedicle screws in the future.

[Treatment of proximal humerus fractures: relative position of different locking plates to the axillary nerve]. / Versorgung von Humeruskopffrakturen: Lagebeziehung proximaler Verriegelungsplatten zum N. axillaris.

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.

[Fixator with motion capacity and distraction arthrodiatasis in post-traumatic elbow stiffness]. / Bewegungsfixateur und Distraktionsarthroplastik zur Behandlung der posttraumatischen Ellenbogensteife.

Elbow stiffness may result from trauma, burns and head injuries. It is defined as a total range of motion of <100° with no relevant loss of forearm rotation. Of particular relevance is the flexion deficit. A detailed analysis regarding the development of the elbow stiffness is required together with an exact diagnosis in order to plan the surgical intervention. Closed distraction of the elbow joint as arthrodiatasis with an external fixator is described and evaluated. Adequate long-term results can be achieved with this technique, which reflects proper selection of patients as well as coordination between surgeon, aftercare and physiotherapist. Contraindications are poor compliance, poorly controlled diabetes mellitus, active hepatitis B and C infection, HIV infection and acute articular infection.

[External fixation with motion capacity in acute dislocations and fracture dislocations of the elbow. Fixation with motion capacity]. / Die Behandlung der akuten Luxation und Luxationsfraktur des Ellenbogens. Bewegungsfixateur.

Dislocations and fracture dislocations with their typical fracture patterns may substantially affect the complex anatomy and integrity of the elbow joint. The more components of the joint are injured, the more technically demanding is the therapy. Standardized diagnostic and therapeutic algorithms help to avoid misinterpretations regarding the severity of the injury and the subsequent complications. In elbow dislocations and fracture dislocations with persistent instability the hinged external fixator is an excellent device to improve joint stability and allows physiotherapeutic assistance at an early stage.

Biomechanical comparison of tension band- and interfragmentary screw fixation with a new implant in transverse patella fractures.

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.

Management of obstetric complications at a small rural hospital.

To determine if there is a way of identifying obstetric patients in whom complications will develop, the experience of one small hospital was reviewed. It was found that there is no satisfactory method presently available that allows a hospital to select such patients so that they can be referred to a large centre. While the scoring system designed by Goodwin, Dunne and Thomas for assessing antepartum fetal risk is fairly effective in selecting fetuses at risk, its results do not correlate well with the frequency of obstetric complications. Since in a significant proportion of obstetric patients complications develop that require emergency intervention, it is important that hospital staff maintain their ability to do safe cesarean sections and to obtain blood for transfusion quickly. Hospitals in which there are fewer than 100 deliveries per year probably do not have a sufficient caseload to maintain the ability to do safe cesarean sections; it is therefore suggested that they discontinue obstetric practice. At hospitals with a larger caseload elective cesarean sections should be done so that the ability to do emergency procedures can be maintained.