Treatment of Metaphyseal Defects in Plated Proximal Humerus Fractures with a New Augmentation Technique-A Biomechanical Cadaveric Study.

Background and Objectives: Unstable proximal humerus fractures (PHFs) with metaphyseal defects-weakening the osteosynthesis construct-are challenging to treat. A new augmentation technique of plated complex PHFs with metaphyseal defects was recently introduced in the clinical practice. This biomechanical study aimed to analyze the stability of plated unstable PHFs augmented via implementation of this technique versus no augmentation. Materials and Methods: Three-part AO/OTA 11-B1.1 unstable PHFs with metaphyseal defects were created in sixteen paired human cadaveric humeri (average donor age 76 years, range 66-92 years), pairwise assigned to two groups for locked plate fixation with identical implant configuration. In one of the groups, six-milliliter polymethylmethacrylate bone cement with medium viscosity (seven minutes after mixing) was placed manually through the lateral window in the defect of the humerus head after its anatomical reduction to the shaft and prior to the anatomical reduction of the greater tuberosity fragment. All specimens were tested biomechanically in a 25° adduction, applying progressively increasing cyclic loading at 2 Hz until failure. Interfragmentary movements were monitored by motion tracking and X-ray imaging. Results: Initial stiffness was not significantly different between the groups, p = 0.467. Varus deformation of the humerus head fragment, fracture displacement at the medial humerus head aspect, and proximal screw migration and cut-out were significantly smaller in the augmented group after 2000, 4000, 6000, 8000 and 10,000 cycles, p ≤ 0.019. Cycles to 5° varus deformation of the humerus head fragment-set as a clinically relevant failure criterion-and failure load were significantly higher in the augmented group, p = 0.018. Conclusions: From a biomechanical standpoint, augmentation with polymethylmethacrylate bone cement placed in the metaphyseal humerus head defect of plated unstable PHFs considerably enhances fixation stability and can reduce the risk of postoperative complications.

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 nonunions 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 (IM) stem vs. both radial head grafted reconstruction and coronoid fixation. METHODS: Twenty-four human cadaveric paired forearms were stripped of soft tissue and their computed tomography scanned ulnas were randomized to 4 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 the coronoid process was either replaced with a 3D printed stainless-steel prosthesis with curved cemented IM stem individually designed based on the contralateral scan (prosthesis group), reconstructed with an ipsilateral radial head autograft fixed with 2 anteroposterior screws (radial head group), or fixed in situ with 2 anteroposterior screws (fixation group). All specimens were biomechanically tested under ramped quasistatic axial loading. RESULTS: Bone mineral density was not significantly different among the groups (P = .95). Stiffness and failure load in the prosthesis group was significantly higher compared to all other groups (P ≤ .04) and in addition, it was significantly lower in the fixation group compared to the intact group (P = .03), with no further detected significant differences among the groups (P ≥ .72). Absorbed energy to failure in the prosthesis group was significantly more compared to both radial head and fixation groups (P ≤ .04) but not vs. the intact group. Failure deformation at the osteotomy site was not significantly different among the groups (P = .26). CONCLUSIONS: Coronoid process replacement using an anatomically shaped, individually designed 3D printed prosthesis with curved cemented IM 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.

A Novel Technique for Treatment of Metaphyseal Voids in Proximal Humerus Fractures in Elderly Patients.

Background and Objectives: The treatment of proximal humerus fractures in elderly patients is challenging, with reported high complication rates mostly related to implant failure involving screw cut-out and penetration. Metaphyseal defects are common in osteoporotic bone and weaken the osteosynthesis construct. A novel technique for augmentation with polymethylmethacrylate (PMMA) bone cement was developed for the treatment of patients in advanced age with complex proximal humerus fractures and metaphyseal voids, whereby the cement was allowed to partially cure for 5-7 min after mixing to achieve medium viscosity, and then it was manually placed into the defect through the traumatic lateral window with a volume of 4-6 mL per patient. The aim of this retrospective clinical study was to assess this technique versus autologous bone graft augmentation and no augmentation. Materials and Methods: The outcomes of 120 patients with plated Neer three- and four-part fractures, assigned to groups of 63 cases with no augmentation, 28 with bone graft augmentation and 29 with cement augmentation, were assessed in this study. DASH, CS, pain scores and range of motion were analyzed at 3, 6 and 12 months. Statistical analysis was performed with factors for treatment and age groups, Neer fracture types and follow-up periods, and with the consideration of age as a covariate. Results: DASH and CS improved following cement augmentation at three and six months compared to bone grafting, being significant when correcting for age as a covariate (p ≤ 0.007). While the age group had a significant effect on both these scores with worsened values at a higher age for non-augmented and grafted patients (p ≤ 0.044), this was not the case for cement augmented patients (p ≥ 0.128). Cement augmentation demonstrated good clinical results at 12 months with a mean DASH of 10.21 and mean CS percentage of 84.83% versus the contralateral side, not being significantly different among the techniques (p ≥ 0.372), despite the cement augmented group representing the older population with more four-part fractures. There were no concerning adverse events specifically related to the novel technique. Conclusions: This study has detailed a novel technique for the treatment of metaphyseal defects with PMMA cement augmentation in elderly patients with complex proximal humerus fractures and follow-up to one year, whereby the cement was allowed to partially cure to achieve medium viscosity, and then it was manually placed into the defect through the traumatic lateral window. The results demonstrate clinically equivalent short-term results to 6 months compared to augmentation with bone graft or no augmentation-despite the patient group being older and with a higher rate of more severe fracture patterns. The technique appears to be safe with no specifically related adverse events and can be added in the surgeon's armamentarium for the treatment of these difficult to manage fractures.

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.

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.

Complications after interlocking intramedullary nailing of humeral shaft fractures.

INTRODUCTION: IM nails have gained popularity for stabilization of humeral shaft fractures (HSF). The initial enthusiasm was tempered by a number of specific complications and thus indications need to be re-evaluated. PATIENTS AND METHODS: This retrospective study includes 111 patients with HSF subjected to a treatment protocol of IM fixation with first and second generation of humeral nails. Antegrade approach was used in 105 (94.5%) and retrograde in 6 (5.5%) patients. Reaming was performed in 51 (45.9%) fractures. The study covers a period of 10 years. Mean follow-up time was 3.5 (1-6) years. This investigation is directed at technical errors and complications, especially those corrected by secondary surgery. RESULTS: We registered 52 (46.85%) intra-operative complications in 40 (36.04%) patients, on average 1.3 per patient. The most common were: distraction n=5 (4.5%), long proximal locking screws n=9 (8.1%), additional diaphyseal fracture n=7 (6.3%) and countersinking of the nail in the humeral head n=8 (7.2%). The number of postoperative complications was 40 (36.0%) related to 19 (17.1%) patients. Technical errors, such as distraction, longer nail and additional fractures have affected time to union and resulted in chronic shoulder pain. 36 (32.5%) secondary surgeries were needed to address these problems. When first generation nails are used, the intra-operative complication related risk increases 1.58 times, and the postoperative complication related risk is 1.67 times higher compared to second generation nails. According to Constant-Murley score excellent and very good functional results were achieved in 93 (83.78%) patients. While reaming did not influence the clinical results for both nail generations, overall better results were achieved with second generation nails. Postoperative shoulder pain has been registered in 18 (16.2%) patients. CONCLUSION: We registered a number of technical errors and complications, which we consider technique specific. The analysis and avoidance of these complications, related only to IM nailing of the humerus, will allow IM nails to successfully bridge the gap between functional bracing and plating.