Augmented screws in angular stable plating of the proximal humerus: what to do when revision is needed?

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.

[Cement augmentation and bone graft substitutes-Materials and biomechanics]

BACKGROUND

Materials with different characteristics are used for cement augmentation and as bone graft substitutes.

OBJECTIVE

Cement augmentation and bone graft substitutes are the subject of current research. The evaluation of new knowledge allows its specific application.

MATERIAL AND METHODS

Selective literature search and outline of experimental research results on cement augmentation and bone graft substitutes.

RESULTS

Augmentation and bone graft substitutes are essential components of current trauma surgical procedures. Despite intensive research all materials have specific disadvantages. Cement augmentation of implants enhances not only the anchorage but also influences the failure mode.

CONCLUSION

Cement augmentation has large potential especially in osteoporotic bone. In load-bearing regions acrylic-based cements remain the standard of choice. Ceramic cements are preferred in non-load-bearing areas. Their combination with resorbable metals offers still largely unexplored potential. Virtual biomechanics can help improve the targeted application of cement augmentation.

Primary stability of cement augmentation in locking plate fixation for proximal humeral fractures: A comparison of absorbable versus non-absorbable cement

BACKGROUND

Cement augmentation has been suggested to increase the stability of screw anchoring in osteoporotic humeral fractures. Initial results are promising but may be jeopardized by cement leakage into the joint and difficult implant removal. Absorbable cement might have advantages in this regard, but it is unclear if the primary stability of both techniques is equivalent to each other. Therefore, this study aimed to compare its primary stability with that of non-absorbable cement augmentation.

METHODS

Nineteen cadaveric humeri with two-part fracture models were treated with locking plate osteosynthesis and cement augmentation using either absorbable calcium phosphate cement (group 1) or polymethylmethacrylate (group 2). Fracture movement, stiffness, failure mode, and ultimate load under cyclic compressive loading were examined and compared between the groups.

FINDINGS

The absolute and relative stiffness values in group 1 were significantly smaller than those in group 2 after 50 cycles (group 1: 114 ± 38 N/mm and 94 ± 8% vs. group 2: 188 ± 71 N/mm and 106 ± 9%; p₅₀ = 0.022), 2000 cycles (group 1: 97 ± 34 N/mm and 81 ± 15% vs. group 2: 153 ± 47 N/mm and 88 ± 15%; p₂₀₀₀ = 0.028), and 5000 cycles (group 1: 98 ± 40 N/mm and 81 ± 22% vs. group 2: 158 ± 40 N/mm and 92 ± 16%; p₅₀₀₀ = 0.028). The failure load was not statistically significantly different between the groups.

INTERPRETATION

Although the PMAA group showed higher values for absolute and relative stiffness, no statistically significant difference was found in the primary stability between absorbable and non-absorbable cement augmentation supporting plate osteosynthesis in proximal humeral fractures. In view of the potential advantages of bio-absorbable cement during the healing process, its use should be considered for the augmentation and stabilization of osteoporotic fractures.

Is Kummell's Disease a Misdiagnosed and/or an Underreported Complication of Osteoporotic Vertebral Compression Fractures? A Pattern of the Condition and Available Treatment Modalities

This narrative review provides the outcomes of minimally invasive surgery (MIS) and describes the available conservative treatment options for patients with osteoporotic vertebral compression fractures (OVCFs) that have risk factors for Kummell's disease (KD). It aims to explore the evidence, emphasize the possible therapy complications, and aims to propose the most efficient clinical strategies for maintaining a good overall condition of individuals who may suffer from neurological deficits from a late-diagnosed OVCF complication. The secondary objective is to sum up the diagnostic particularities concerning individuals prone to OVCFs and KD, as the major risk factor for developing these severe conditions remains osteoporosis. Findings of our narrative review are based on the results found in PubMed, Embase, and Google Scholar from the beginning of their inception to December 2020, described independently by two authors. All of the studies included in the review focus on reporting the following treatment methods: conservative methods, vertebroplasty, kyphoplasty, targeted percutaneous vertebroplasty, frontal and side-opening cannula vertebroplasty, SpineJack, bone-feeling mesh container treatment, and the difference in the cement viscosity used (high vs. low) and the approach used (unilateral vs. bilateral). The comparison of randomized control trials (RCTs) as well as prospective and retrospective case series showed a comparable efficacy of kyphoplasty and vertebroplasty, and described cement-augmented screw fixation and the SpineJack system as effective and safe. Although it should be noted that several studies revealed inconsistent results in regards to the efficacy of using back braces and analgesics in patients who had vertebral fractures that were overlooked or not enrolled in any active surveillance program to track the patient's deterioration immediately. Nevertheless there are non-standardized guidelines for treating patients with OVCFs and their complications already established. Using these guidelines, a treatment plan can be planned that takes into consideration the patients' comorbidities and susceptibilities. However, the primary approach remains the management of osteoporosis and that is why prophylaxis and prevention play a crucial role. These measures reduce the risk of disease progression. Unfortunately, in the majority of cases these measures are not taken into account and KD develops.

Cement augmentation of calcar screws may provide the greatest reduction in predicted screw cut-out risk for proximal humerus plating based on validated parametric computational modelling: Augmenting proximal humerus fracture plating

Aims

Fixation of osteoporotic proximal humerus fractures remains challenging even with state-of-the-art locking plates. Despite the demonstrated biomechanical benefit of screw tip augmentation with bone cement, the clinical findings have remained unclear, potentially as the optimal augmentation combinations are unknown. The aim of this study was to systematically evaluate the biomechanical benefits of the augmentation options in a humeral locking plate using finite element analysis (FEA).

Methods

A total of 64 cement augmentation configurations were analyzed using six screws of a locking plate to virtually fix unstable three-part fractures in 24 low-density proximal humerus models under three physiological loading cases (4,608 simulations). The biomechanical benefit of augmentation was evaluated through an established FEA methodology using the average peri-screw bone strain as a validated predictor of cyclic cut-out failure.

Results

The biomechanical benefit was already significant with a single cemented screw and increased with the number of augmented screws, but the configuration was highly influential. The best two-screw (mean 23%, SD 3% reduction) and the worst four-screw (mean 22%, SD 5%) combinations performed similarly. The largest benefits were achieved with augmenting screws purchasing into the calcar and having posteriorly located tips. Local bone mineral density was not directly related to the improvement.

Conclusion

The number and configuration of cemented screws strongly determined how augmentation can alleviate the predicted risk of cut-out failure. Screws purchasing in the calcar and posterior humeral head regions may be prioritized. Although requiring clinical corroborations, these findings may explain the controversial results of previous clinical studies not controlling the choices of screw augmentation.

Cement augmentation of humeral head screws reduces early implant-related complications after locked plating of proximal humeral fractures

Background

Cement augmentation (CA) of humeral head screws in locked plating of proximal humeral fractures (PHF) was found to be biomechanically beneficial. However, clinical outcomes of this treatment have not been well evaluated to date.

Objectives

To assess outcomes of locked plating of PHF with additional CA and to compare them with outcomes of conventional locked plating without CA.

Methods

24 patients (mean age, 74.2 ± 10.1 years; 22 female) with displaced PHF were prospectively enrolled and treated with locked plating and additional CA. The Constant score (CS), the Simple Shoulder Test (SST), and the Simple Shoulder Value (SSV) were assessed 3 and 12 months postoperatively. Fracture healing and potential complications were evaluated on postoperative radiographs. The CS and complications were compared with the outcomes of a matched group of 24 patients (mean age, 73.9 ± 9.4 years; 22 female) with locked plating of displaced PHF without CA.

Results

At the 3‑month follow-up, the mean CS was 59.9 ± 15.6 points, the mean SST was 7.5 ± 2.7 points, and the mean SSV was 63.9 ± 21.7%. All scores significantly improved by the 12-month follow-up (p < 0.05; CS, 72.9 ± 17.7; SST, 9.2 ± 3.2; SSV, 77.2 ± 17.3%). There were two cases (8%) of biological complications (n = 1 varus malunion and n = 1 humeral head necrosis). Compared with locked plating without CA, no significant differences were observed between the CS at the 3‑ (57.8 ± 13.4 points; p = 0.62) and 12-month (73.0 ± 12.8 points; p = 0.99) follow-up. However, patients without CA had a significantly increased risk of early loss of reduction and articular screw perforation (p = 0.037).

Conclusion

Locked plating of proximal humeral fractures with trauma cement augmentation of humeral head screws could be translated from the ex-vivo lab setting into the clinical situation without additional complications. Locked plating of displaced PHF with additional cement augmentation showed similar clinical outcomes but reduced the rate of early implant-related complications compared to locked plating without additional CA.

The use of augmentation techniques in osteoporotic fracture fixation

There are an increasing number of fragility fractures, which present a surgical challenge given the reduced bone quality of underlying osteoporosis. Particularly in aged patients, there is a need for early weight bearing and mobilization to avoid further complications such as loss of function or autonomy. As an attempt to improve fracture stability and ultimate healing, the use of biomaterials for augmentation of osseous voids and fracture fixation is a promising treatment option. Augmentation techniques can be applied in various locations, and fractures of the metaphyseal regions such as proximal humerus, femur, tibia and the distal radius remain the most common areas for its use. The current review, based on the available mechanical and biological data, provides an overview of the relevant treatment options and different composites used for augmentation of osteoporotic fractures.

How to enhance the stability of locking plate fixation of proximal humerus fractures? An overview of current biomechanical and clinical data

BACKGROUND

The complication rate after locking plate fixation of proximal humerus fractures is high. In addition to low bone mineral density, a lack of medial support has been identified as one of the most important factors accounting for mechanical instability. As a result of the high failure rate, different strategies have been developed to enhance the mechanical stability of locking plate fixation of proximal humerus fractures. The aim of the present article is to give an overview of the current biomechanical and clinical studies that focus on how to increase the stability of locking plate fixation of proximal humerus fractures.

METHODS

A comprehensive search of the Medline databases using specific search terms with regard to the stability of locking plate fixation of proximal humerus fractures was performed. After screening of the articles for eligibility, they were subdivided according to clinical and biomechanical aspects.

RESULTS

Medial support screws, filling of bone voids and screw-tip augmentation with bone cement as well as the application of bone grafts are currently the most frequently assessed and performed methods. Although the evidence is weak, all of the mentioned strategies appear to have a positive effect on achieving and maintaining a stable reduction even of complex fractures.

CONCLUSION

Further clinical studies with a higher number of patients and a higher level of evidence are required to develop a standardised treatment algorithm with regard to cement augmentation and bone grafting. Although these measures are likely to have a stabilising effect on locking plate fixation, its general use cannot be fully recommended yet.