Superior fixation strength of coronoid process replacement using individually designed 3D printed prosthesis with curved cemented intramedullary stem

BACKGROUND

Coronoid fractures frequently occur as part of complex elbow injuries and account for 2-15% of the cases with dislocations. Comminuted fractures and non-unions necessitate surgical treatment. Considering the latest technological advancements, the aim of this study was to investigate the fixation strength of coronoid replacement using an individualized 3D printed prosthesis with curved cemented intramedullary stem versus both radial head grafted reconstruction and coronoid fixation.

METHODS

Twenty-four human cadaveric paired forearms were stripped of soft tissue and their CT scanned ulnas were randomized to four groups for coronoid replacement (prosthesis group), radial head grafted reconstruction (radial head group), fixation (fixation group) or no treatment (intact group). The ulnas in all groups except the intact one were osteotomized at 40% of the coronoid height and either replaced with a 3D printed stainless-steel coronoid prosthesis with curved cemented intramedullary stem, individually designed based on the contralateral scan (prosthesis group), reconstructed with an ipsilateral radial head autograft fixed with two anteroposterior screws (radial head group), or coronoid process fixed in situ with two anteroposterior screws (fixation group). All specimens were biomechanically tested under ramped quasi-static axial loading.

RESULTS

Bone mineral density was not significantly different among the groups (p=0.95). Stiffness and failure load in the prosthesis group was significantly higher compared to all other groups (p≤0.04) and in addition it was significantly lower in the fixation group compared to the intact group (=0.03), with no further detected significant differences among the groups (p≥0.72). Absorbed energy to failure in the prosthesis group was significantly more compared to both radial head and fixation groups (p≤0.04) but not versus the intact group. Failure deformation at the osteotomy site was not significantly different among the groups (p=0.26).

CONCLUSIONS

Coronoid process replacement using an anatomically shaped individually designed 3D printed prosthesis with curved cemented intramedullary stem seems to be an effective method to restore the coronoid buttress function under axial loading. This method provides superior fixation strength over both radial head grafted reconstruction and screw fixation.

Comminuted intraarticular calcaneal fractures: Multiplanar VA locked plating and interlocked nailing incorporate longitudinal strut and provide superior stability - a biomechanical cadaveric study

Treatment of comminuted intraarticular calcaneal fractures remains controversial and challenging. The aim of this study was to investigate the biomechanical performance of three different methods for fixation of such fractures. Comminuted calcaneal fractures, including Sanders III AB fracture of the posterior facet and Kinner II B fracture of the calcaneocuboid joint (CCJ) articular calcaneal surface, were created in 18 human cadaveric lower legs by osteotomizing. The ankle joint, medial soft tissues and midtarsal bones along with their ligaments were preserved. The specimens were randomized to three groups for fixation with either (1) 2.7 mm variable-angle locking lateral calcaneal plate (Group 1), (2) 2.7 mm variable-angle locking anterolateral calcaneal plate in combination with one 4.5 mm and one 6.5 mm cannulated screws (Group 2), or (3) interlocking calcaneal nail with 3.5 mm screws in combination with three separate 4.0 mm cannulated screws (Group 3). All specimens were biomechanically tested to failure under axial loading in midstance foot position. Each test commenced with a quasi-static compression ramp from 50 to 200 N, followed by progressively increasing cyclic loading at 2 Hz. Starting from 200 N, the peak load of each cycle increased at a rate of 0.2 N/cycle. Interfragmentary movements were captured by motion tracking. In addition, mediolateral X-rays were taken every 250 cycles with a triggered C-arm. Böhler angle after 5000 cycles (1200 N peak load) increased significantly more in Group 1 compared to both other groups (P ≤ 0.020). Varus deformation of 10° between the calcaneal tuberosity and the lateral calcaneal fragments was reached at significantly lower number of cycles in Group 1 compared the other groups (P ≤ 0.017). Both cycles to 10° plantar gapping between the anterior process and the calcaneal tuberosity fragments, and 2 mm displacement at the CCJ articular calcaneal surface revealed no significant differences among the groups (P ≥ 0.773). From a biomechanical perspective, treatment of comminuted intraarticular calcaneal fractures using anterolateral variable-angle locking plate with additional longitudinal screws or interlocked nail in combination with separate transversal screws provides superior stability as opposed to lateral variable-angle locked plating only.

Volar versus combined dorsal and volar plate fixation of complex intraarticular distal radius fractures with small dorsoulnar fragment - a biomechanical study

Complex intraarticular distal radius fractures (DRFs), commonly managed with volar locking plates, are challenging. Combined volar and dorsal plating is frequently applied for treatment, however, biomechanical investigations are scant. The aim of this biomechanical study was to investigate volar plating versus double plating in DRFs with different degrees of lunate facet comminution.Thirty artificial radii with simulated AO/OTA 23-C2.1 and C3.1 DRFs, including dorsal defect and lunate facet comminution, were assigned to 3 groups: Group 1 with two equally-sized lunate facet fragments; Group 2 with small dorsal and large volar fragment; Group 3 with three equally-sized fragments. The specimens underwent volar and double locked plating and non-destructive ramped loading in 0° neutral position, 40° flexion and 40° extension.In each tested position, stiffness: (1) did not significantly differ among groups with same fixation method (p ≥ 0.15); (2) increased significantly after supplemental dorsal plating in Group 2 and Group 3 (p ≤ 0.02).Interfragmentary displacements between styloid process and lunate facet in neutral position were below 0.5 mm, being not significantly different among groups and plating techniques (p ≥ 0.63).Following volar plating, angular displacement of the lunate facet to radius shaft was significantly lower in Group 1 versus both Group 2 and Group 3 (p < 0.01). It decreased significantly after supplemental dorsal plating in Group 2 and Group 3 (p < 0.01), but not in Group 1 (p ≥ 0.13), and did not differ significantly among the three groups after double plating (p ≥ 0.74).Comminution of the lunate facet within its dorsal third significantly affected the biomechanical outcomes related to complex intraarticular DRFs treated with volar and double locked plates.Double plating demonstrates superior stability versus volar plating only for lunate facet comminution within its dorsal third. In contrast, volar plating could achieve stability comparable with double plating when the dorsal third of the lunate facet is not separated by the fracture pattern. Both fixation methods indicated achievable absolute stability between the articular fragments.

Two reconstruction plates provide superior stability of displaced midshaft clavicle fractures in comparison to single plating - A biomechanical study

BACKGROUND

Displaced midshaft fractures are the most common surgically treated clavicle fractures. However, they are associated with high complication rates following plating due to fixation failure in terms of plate breakage, screw breakage and/or screw loosening. The aim of this study was to compare the biomechanical competence of three different plating techniques for fixation of displaced midshaft clavicle fractures.

METHODS

Displaced midshaft fractures type 2B according to the Robinson classification were simulated by standardized osteotomy gap in 18 synthetic clavicles, assigned to three groups (n = 6) for plating with either superiorly placed Dynamic Compression Plate (width/thickness 11.0/4.0 mm), locked Superior Anterior Clavicle Locking Compression Plate (width/thickness 10.2/2.0 mm), or two non-locked Reconstruction Plates placed superiorly and anteriorly (width/thickness 10.0/2.8 mm). Each specimen was cyclically tested at 3 Hz under craniocaudal cantilever bending, superimposed with torsion around the shaft axis over 720'000 cycles or until failure occurred. The latter was defined by plate breakage, screw breakage or screw loosening.

FINDINGS

Initial construct stiffness (N/mm) and cycles to failure in group Reconstruction Plates (22.30 ± 4.07; 712'778 ± 17'691) were significantly higher compared with both groups Compression Plate (12.53 ± 2.09; 348'541 ± 212'941) and Locking Plate (4.19 ± 0.46; 19'536 ± 3'586), p ≤ 0.019. In addition, these two outcomes were significantly higher in group Compression Plate versus Locking Plate, p ≤ 0.029.

INTERPRETATION

Double plating of unstable midshaft clavicle fractures with reconstruction plates seems to provide superior fixation stability under dynamic loading, when compared to single compression or locked plating, whereas the latter is associated with inferior performance.

A Unique Complication after a Routine Operation - Late Pseudoaneurysm of the Brachial Artery after Plate Fixation of Humeral Shaft Fracture. A Case Report and Review of the Literature

We report an extremely rare case of an 82-year-old woman with pseudoaneurysm of the brachial artery developed 22 months after a plate osteosynthesis with angularly stable locking plates for the proximal humerus. The condition was initially misdiagnosed as a tumor by the attending physician, and the patient was referred to an oncological unit. The case was successfully managed by a multidisciplinary team consisting of orthopedic and vascular surgeons.An up-to-date review of the available literature is also provided. The pseudo-aneurysms of the axillary and the distal peripheral arteries of the upper limb are a rare but potentially dangerous complication because the thromboembolism could lead to gangrene and amputation of the extremity. Despite casuistic, they should be taken into consideration in the differential diagnosis after plate osteosynthesis. Proper operative technique and constant vigilance when orthopedic implants are used are of paramount importance, which is actually the emphasis of this report.

Does Supplemental Intramedullary Grafting Increase Stability of Plated Proximal Humerus Fractures?

OBJECTIVES

To investigate the biomechanical competence of locked plating augmented with supplemental intramedullary graft in comparison to conventional locked plate fixation in proximal humerus fractures (PHF).

METHODS

Complex four-part PHFs were set in 30 artificial humeri assigned to 3 study groups (n = 10 in each group). Group 1 was characterized by loss of medial support, group 2 by simulated severe cancellous bone damage due to osteoporosis, and group 3 by combination of the 2 features. After locked plating, each specimen underwent nondestructive quasi-static mechanical testing in 25 degrees lateral angulation under axial loading between 150 and 400 N in 50-N increments, accompanied by consecutive anteroposterior x-ray imaging. Subsequently, an additional 3D-printed intramedullary graft was inserted into each specimen and all tests were repeated.

RESULTS

Grafting resulted in significantly higher axial stiffness compared with no graft in groups 1 and 3 (P < 0.01) but not in group 2 (P = 0.12). Nongrafted specimens represented significantly higher stiffness in group 2 compared with groups 1 and 3 (P < 0.01), whereas no significant differences were detected among the 3 groups in the grafted state (P > 0.99). Varus deformation decreased significantly in each group after graft insertion (P ≤ 0.04). Nongrafted specimens in group 2 showed significantly lower varus deformation compared with groups 1 and 3 (P ≤ 0.04). No significant differences were registered among the 3 groups after grafting (P ≥ 0.65).

CONCLUSIONS

From a biomechanical perspective, locked plating augmented with intramedullary graft has the potential to increase significantly the stability against varus collapse in unstable PHFs when compared with conventional locked plate fixation.

Is augmented LISS plating biomechanically advantageous over conventional LISS plating in unstable osteoporotic distal femoral fractures?

Treatment of complex osteoporotic distal femur fractures with the Less Invasive Stabilization System (LISS) has been associated with high complication rates. The aim of this study was to investigate the biomechanical competence of two different techniques of augmented versus conventional LISS plating. Unstable distal femoral fracture AO/OTA 33-A3 was created via osteotomies in artificial femora simulating osteoporotic bone. Three study groups, consisting of 10 specimens each, were created for fixation with either LISS plate, LISS plate with additional polylactide intramedullary graft, or LISS plate plus medial locking plate (double plating). All specimens were non-destructively tested under axial (20-150 N) and torsional (0-4 Nm) quasi-static loading. Each bone-implant construct was tested with two different working length (WL) configurations (long and short) of the LISS plate. Relative movements between the most medial superior and inferior osteotomy aspects were investigated via three-dimensional motion tracking analysis. Double plating revealed significantly smaller longitudinal and shear displacement than the other two techniques (p ≤ 0.001). In addition, LISS plus graft fixation was with significantly less longitudinal displacement in comparison to conventional LISS plating (p < 0.001). Long WL resulted in significantly higher longitudinal and shear displacement compared to short WL for LISS and LISS plus graft (p ≤ 0.032), but not for double plating (p > 0.999). In conclusion, intramedullary grafting resulted in significantly increased fracture stability under axial loading in comparison to conventional LISS plating. Although it was not efficient enough to provide comparable stability to double plating, intramedullary grafting may be considered as a useful biological alternative to the latter in a surgeon's armamentarium. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2604-2611, 2018.