Sascha Rausch

Evaluation of a polyaxial angle-stable volar plate in a distal radius C-fracture model – A biomechanical study

INTRODUCTION Polyaxial angle-stable plating is thought to be particularly beneficial in the management of complex intra-articular fractures of the distal radius. The purpose of the present study was to investigate whether the technique provides stability to match that of conventional (fixed-angle) angle-stable constructs. MATERIAL AND METHODS In seven pairs of human cadaver radii, an Arbeitsgemeinschaft für Osteosynthese (AO) 23 C2.1 intra-articular fracture was created. One radius of each pair received a juxta-articular 2.4-mm locking compression plate (LCP) Volar Distal Radius Plate, whilst the contralateral one received a 2.4-mm Variable Angle Locking Compression Plate (LCP) Two-Column Volar Distal Radius Plate (both plates: Synthes, Oberdorf, Switzerland). Parameters tested were construct stiffness (static axial loading with 150 N), range of motion and secondary loss of reduction (dynamic 150 N axial loading over 5000 cycles). Stiffness and range of motion were measured both pre- and post-cycling. RESULTS The polyaxial constructs were significantly stiffer, both before and after cyclic testing. However, the two-column plates showed a significant loss of stiffness during cyclic testing. The range of motion was significantly greater, both initially and at the end of cyclic testing, in the fixed-angle constructs. The conventional constructs had significantly greater secondary loss of reduction. CONCLUSION The polyaxial two-column plate tested in this study provides a biomechanically sound construct for the management of intra-articular fractures of the distal radius.

Navigation in femoral-shaft fractures--from lab tests to clinical routine.

INTRODUCTION This study evaluates the use of a navigation system (BrainLAB, Feldkirchen, Germany) to intra-operatively check for correct length, axis and rotation in intramedullary nailing of femoral-shaft fractures in an experimental setting and in clinical routine. MATERIALS AND METHODS We tested the navigation system in two experimental settings before introducing it into clinical routine. In the first experiment, 10 osteotomised model femora were fixed with intramedullary nails by using a navigation system. The goal was a locking fixation in predefined values for length and rotation. In the second experiment, eight examiners assessed values for rotation and length of one femur 10 times to examine the accuracy and reproducibility of that determination. Following this, we navigated 40 femoral nailing procedures in our department. Preoperatively, we assessed values of femur geometry on the contralateral side in a computed tomography (CT) scan and reproduced these values intra-operatively on the fractured side, guided by the navigation system. During the intervention, we recorded the length of the procedure steps and the fluoroscopy time. We verified the intra-operative values achieved with the navigation system in a postoperative CT scan and documented differences in rotation and length. After the assessment, we analysed the data for different findings on femur geometry, fluoroscopy time and procedure duration. RESULTS The experimental evaluation showed a range of ±5° for anteversion differences and ±2.3 mm for length differences. We estimated this accuracy as sufficient to use the system in clinical routine. The navigation system was used for 40 fracture fixations. All our criteria for restoring femoral geometry could be achieved by navigation guidance in these procedures. Setting up the system took on average 33±11.5 min. An additional fluoroscopy time of 36±22 s was needed to acquire the reference X-rays and to verify pin placement. The differences between anteversion values assessed in intra-operative planning steps on the navigation system and values assessed with a postoperative CT were on average 5.4±3.5°, whilst femur length differed on average by 4±4 mm. DISCUSSION Many authors judge intra-operative control of anteversion in femoral-shaft fracture fixation as problematic. Neither our experimental navigation assessment nor our clinical navigated evaluation showed relevant anteversion differences to a postoperative CT assessment of femur geometry. After initial training, guidance by a navigation system achieves consistent results in a clinical situation. CONCLUSIONS The use of a navigation system to align axis, length and rotation led to a secure way of avoiding any relevant malalignment in complex femur-shaft fractures whilst exposing patients to an acceptable amount of additional procedure sequences. Malalignment can be avoided by using a navigation system in the operative treatment of femoral-shaft fractures and may be integrated into clinical routine in specialised centres.

Volar versus dorsal latest-generation variable-angle locking plates for the fixation of AO type 23C 2.1 distal radius fractures: A biomechanical study in cadavers

INTRODUCTION Anatomicaly preformed variable-angle locking plates are technologically mature and appear to be optimal for the fixation of distal radius fractures. However, there is still much argument about whether volar plating is equivalent to dorsal (buttressing) plating, especially in the management of intra-articular extension fractures. This biomechanical study was performed to determine, in a simple intra-articular fracture model, whether dorsal or volar plate constructs would be more stable. MATERIALS AND METHODS Six pairs of fresh frozen radii were examined with dual-energy absorptiometry (DXA) to determine their bone mineral density (BMD). An AO type 23 C2.1 fracture was created. Volar fixation was with a 2.4mm Variable-Angle LCP Two-Column Volar Distal Radius Plate; dorsal fixation was with two orthogonal 2.4 mm Variable-Angle LCP Dorsal Distal Radius Plates (both devices: Synthes, Oberdorf, Switzerland). Biomechanical testing used a proven protocol involving static tests of stiffness, and a cyclic test to obtain range of motion (ROM), maximum deformation, and subsidence data. RESULTS None of the constructs failed during biomechanical testing. The two groups (volar and dorsal plating, respectively) did not differ significantly in terms of initial (pre-cyclic-testing) and final (post-cyclic-testing) stiffness. Equally, there was no significant difference between the subsidence values in the two groups. The post-cyclic-testing ROM was significantly greater in the dorsal-plate group as compared with the volar-plate group. The volar constructs showed a significant decrease in the ROM between pre- and post-cyclic testing. CONCLUSION Biomechanically, volar plating with a modern variable-angle locking plate is equivalent to dorsal plating with two modern variable-angle locking plates.

Biomechanical comparison of a lateral polyaxial locking plate with a posterolateral polyaxial locking plate applied to the distal fibula.

BACKGROUND Polyaxial locking plates are becoming popular for the fixation of distal fibula fractures. This study establishes how construct stiffness and plate loosening, measured as range of motion, differs between lateral and posterolateral plate location. METHODS Seven matched pairs of cadaver fibulae were osteotomized in standardized fashion to produce a Weber type B distal fibula fracture. The fragments were fixated with an interfragmentary lag screw and polyaxial locking plates, with one fibula in each pair receiving a posterolateral anti-glide-plate, and the other a lateral neutralization-plate. In a biomechanical test, the bending and torsional stiffnesses of the constructs and the ranges of motion (ROM) were measured and subjected to a paired comparison. RESULTS The laterally plated group had a higher median (interquartile range) bending stiffness (29.2 (19.7) N/mm) and a smaller range of motion (2.06 (1.99) mm) than the posterolaterally plated group (14.6 (20.6) N/mm, and 4.11 (3.28) mm, respectively); however, the results were not statistically significant (pbending=0.314; pROM=0.325). Similarly, the torsional stiffness did not differ significantly between the two groups (laterally plated: 426 (259) Nmm/°; posterolaterally plated: 248 (399) Nmm/°; ptorsion=0.900). The range of motion measurements between the two groups under torsional loading were also statistically insignificant (laterally plated: 8.88 (6.30) mm; posterolaterally plated: 15.34 (12.64) mm; pROM=0.900). CONCLUSION In biomechanical cadaver-model tests of Weber type B fracture fixation with polyaxial locking plates, laterally plated constructs and posterolaterally plated constructs performed without significantly difference. Therefore, other considerations, such as access morbidity, associated injuries, patient anatomy, or surgeons preference, may guide the choice of plating pattern. Further clinical studies will be needed for the establishment of definitive recommendations. CLINICAL RELEVANCE Information on the behavior of polyaxial locking plates is relevant to surgeons performing internal fixation of distal fibula fractures.

Utility of the Cortical Thickness of the Distal Radius as a Predictor of Distal-Radius Bone Density

BACKGROUND Bone density is an important factor in the management of fractures of the distal radius. OBJECTIVES The aim of this study was to establish whether standard anteroposterior (AP) radiographs would provide the attending physician with a prediction of bone density. PATIENTS AND METHODS Six pairs of human cadaveric radii were harvested. The mean donor age was 74 years. Standardized AP radiographs were taken of the radii. The outside diameter and the inside diameter of the cortical shell at the metaphyseal / diaphyseal junction were measured and their ratio was calculated. Dual-energy x-ray absorptiometry (DXA) was used to obtain the bone mineral density (BMD) of the distal parts of the radii. The correlation of the BMD values with these ratios was studied. RESULTS The mean BMD was 0.559 (SD = 0.236) g / cm(2). The mean outside diameter/inside diameter ratio was 1.24 (SD = 0.013); the ratio significantly correlated with the total BMD (P = 0.001; R(2) = 0.710). In the BMD subregions, the correlation was also significant. CONCLUSIONS The outside diameter/inside diameter ratio at the metaphyseal/diaphyseal junction of the distal radius on AP radiographs is suitable for use as a predictor of distal-radius bone density. Further studies should be performed, and clinical utility evaluated.

Biomorphometric analysis of ilio‐sacro‐iliacal corridors for an intra‐osseous implant to fix posterior pelvic ring fractures

It is hypothesized that ilio‐sacro‐iliacal corridors for a new envisioned pelvic ring implant (trans‐sacral nail with two iliacal bolts = ISI‐nail: ilio‐sacro‐iliacal nail) exists on the level of S1‐ or S2‐vertebra in each patient. The corridors of 84 healthy human pelves (42x ♂; 42x ♀, 18–85 years) were measured in high resolution CT scans using the Merlin Diagnostic Workcenter Software. Trans‐sacral corridors (≥9 mm diameter) on the level of S1 and S2 were found in 62% and 54% of pelves with a mean length [mm ± SD] of 164 ± 12.9 and 142 ±  10.2. Corresponding iliac corridors were present in all specimens in caudally tilted axial planes of 37.8 ± 0.67° and 53.7 ± 0.94° in relation to the operating table plane and divergent angulations of 69.0 ± 0.49° and 70.1 ± 0.32° in relation to the sagittal midline plane. Sacral dysmorphism, with compensatory larger S2 corridors were prevalent in 24% of pelves; ilio‐sacro‐iliacal osseous corridors for the envisioned implant were found in 88% of pelves on the level of S1 or S2. In the remaining 12% with too narrow corridors for any trans‐sacral implant (screws, bars, ISI nail) alternative fixation methods have to be considered. Expected advantages of the envisioned ISI nail compared to available fixation devices are discussed.

Anatomical Evaluation of Different Approaches for Tibiotalocalcaneal Arthrodesis

Background: The transfibular approach is commonly used for tibiotalocalcaneal arthrodesis. However, the medial and the posterolateral approaches are available as alternatives. The present study was performed to assess the effects of the 3 approaches on the neurovascular structures encountered and to quantify the extent of cartilage in the different joint compartments that could be surgically debrided. Methods: This cadaver study was performed in 6 pairs of formalin-fixed legs (mean donor age: 80 years; 4 females, 2 males). For each approach, 4 specimens were selected. The neurovascular structures at risk and the debrided portions of the articular cartilage were compared. Results: Arterial structures were least compromised by the transfibular approach. The posterolateral approach was particularly likely to damage the lateral malleolar branches of the peroneal artery. Venous structures were at risk mainly from the medial approach, which was also the most risk-bearing of the 3 approaches in terms of nerve damage. The proportions of cartilage-debrided joint surfaces of the tibia in the ankle joint, and of the talus and the calcaneus in the subtalar joint, did not differ notably. The proportions of debrided surfaces of the talus in the ankle joint differed notably among the 3 approaches. Conclusions: The medial approach could be a valid alternative to the lateral transfibular approach for tibiotalocalcaneal arthrodesis. Care should be taken, however, to prevent damage to the saphenous nerve and other neurological structures. Clinical Relevance: Access morbidity and feasibility of adequate cartilage debridement are relevant to the clinical outcome of hindfoot arthrodesis.

Percutaneous navigated screw fixation of glenoid fractures

BackgroundOpen or percutaneous arthroscopic-based procedures are reported to fix unstable or displaced intra-articular glenoid fractures. Approach related morbidity has to be considered for open procedures, and arthroscopic-based procedures are demanding. Therefore an alternative percutaneous navigated approach is described.Technical procedureIn an experimental setting an operative workflow was simulated to evaluate the best position of the patient on the operation table, the operating room set up and the fixation technique for the dynamic reference base of the navigation system. Based on two clinical cases, screw fixation of glenoid fractures via a posterior percutaneous approach is described, using a 2D-fluoroscopic based navigation system. Compared to the common approaches, the advantages and disadvantages of this procedure are discussed.ConclusionThe described technique of percutaneous navigated screw fixation of glenoid fractures is an alternative minimal invasive procedure. A reduction of approach related morbidity and more rapid return to function could be expected. The intraoperative results and postoperative functional outcome of both cases are promising.

Biomechanical analysis of polyaxial locking vs. non-locking plate fixation of unstable fractures of the distal fibula: A cadaver study with a bone only model

BACKGROUND Open reduction and internal fixation is the current standard of treatment of displaced distal fibula fractures, whereupon using a lag screw often is impossible because of a multifragmantary fracturezone. This study investigates in what extend polyaxial-locking plating is superior to non-locking constructs in unstable distal fibula fractures. METHODS Seven pairs of human cadaver fibulae were double osteotomized in standardized fashion with a 5mm gap. This gap simulated an area of comminution, where both main fragments were no longer in direct contact. One fibula of the pair was managed using a 3.5-mm screw in a polyaxial-locking construct and the other fibula in a non-locking construct.

Adjustment of traumatic femur shortening assisted by an intramedullar skeletal kinetic distractor: a case report

IntroductionDistal comminuted femoral fractures with joint involvement are highly challenging for the surgeon. We present a potential therapeutic concept that aims especially at the treatment of posttraumatic leg length discrepancy.Case presentationThis case report describes a polytraumatized 19-year-old German woman. Among other injuries she had a third grade open distal comminuted femoral fracture with a long distance metaphyseal osseous defect. As a primary care procedure an external fixation was applied at first. On day 13, an open reconstruction of her distal femur and the articular surface was performed by screw osteosynthesis, shortening and intramedullary nailing. Due to delayed osseous consolidation an autologous cancellous bone grafting was performed twice. In addition to the second cancellous bone graft an allogeneic cortical bone graft was implemented. A 6.5cm posttraumatic leg length shortening after osseous consolidation was the result. The entire leg length shortening was successfully treated 16 months after her accident with the help of an intramedullar skeletal kinetic distractor.ConclusionsWith the help of the current case report of a patient with polytrauma and a third grade open distal comminuted femoral fracture with joint involvement and a long distance osseous defect, we present a potential therapeutic concept that aims especially at the treatment of posttraumatic leg length discrepancy.