[Infected nonunion: diagnostic and therapeutic work-up]

Low-grade infections in nonunion of the femur and tibia without clinical suspicion of infection - Incidence, microbiology, treatment, and outcome

Treatment algorithms for fracture nonunion depend on the presence or absence of bacterial infection. However, it is often impossible to identify infection preoperatively. While some infections may present with clinical signs of infection, low-grade infections lack infection signs and have a clinical presentation similar to aseptic nonunion. The clinical relevance of low-grade infection in nonunion is not entirely clear. Therefore, the aim of this study was to evaluate the role of low-grade infection in the development and management of lower extremity nonunion. A prospective multicenter clinical study enrolled patients with femoral or tibial shaft nonunion and regular healed fractures, scheduled for nonunion revision and routine implant removal, respectively. Preoperatively, serum markers including C-reactive protein (CRP), leukocytes, and procalcitonin were determined, clinical infection signs were recorded, and a suspected septic or aseptic diagnosis was made prior to surgery and further diagnostics. Tissue samples were collected for microbiology and histopathology, and osteosynthesis material for sonication. Nonunion patients were followed for twelve months, during which the definitive diagnosis of "septic" or "aseptic" nonunion was made according to diagnostic criteria for fracture-related infection. One hundred and ten patients with nonunion and 34 patients with regular healed fractures were included. Sixty-two nonunion patients were diagnosed as aseptic, 22 with expected and confirmed infection, and 23 with unexpected low-grade infection. Three patients had an unclear diagnosis. Low-grade infection was detected in 28 % of presumed aseptic nonunion patients. Sensitivity and specificity for the suspected diagnosis were 49 % and 95 %, respectively. The suspected diagnosis had a significant impact on revision strategy. All medians of the preoperative blood values were within the reference ranges except for CRP, which was slightly elevated in the expected and confirmed infected nonunion group. Expected and confirmed septic nonunion and unexpected low-grade infected nonunion demonstrated a similar bacterial spectrum. While 10 % of patients with aseptic nonunion required follow-up surgeries, re-operation rates were higher in patients with low-grade infection and expected and confirmed infection at 30 % and 64 %, respectively. Patients with low-grade infections were treated less frequently with systemic antibiotics and for a shorter duration than patients with expected and confirmed infections, with no significant difference in healing rate which was 83 % in low-grade and 62 % in expected and confirmed infections. The healing rate of aseptic nonunion was 90 %. A limitation of this study is the limited number of tissue samples for microbiological and histopathological diagnostics in the suspected aseptic nonunion cohort, which may have led to an underestimation of the low-grade infection rate. Our findings suggest that unexpected low-grade infection is frequently associated with nonunion. While expected and confirmed infected nonunion differs significantly from aseptic nonunion, low-grade infected nonunion is very similar to aseptic nonunion, except for intraoperative bacterial detection. In addition to antibiotic therapy, surgical nonunion revision with implant exchange and debridement appears to be highly effective in achieving consolidation of low-grade infected nonunion.

Exploration of the Biological Function of Ferroptosis in Bone Nonunion: An Analysis of Bioinformatics Combined Mendelian Randomization

To deeply investigate the mechanism of ferroptosis-related genes in the process of bone nonunion based on the GEO database. And using Mendelian randomization to explore the causal association of 15 trace elements with the occurrence of bone nonunion. Bone nonunion RNA-seq data were retrieved and downloaded from the GEO database. The differentially expressed genes in bone nonunion were identified using two differential expression analysis methods, "limma" and "WGCNA". Random Forest Tree, Support Vector Machine, and Lasso-cox were used to analyze and screen the genes related to ferroptosis in bone nonunion; A risk model of bone nonunion was constructed based on the screened ferroptosis-related genes; based on this, the pathway mechanism of ferroptosis-related genes involved in the occurrence and development of bone nonunion was further investigated. Mendelian randomization analysis was performed using inverse variance weighting as the main analysis method, and weighted median, Weighted mode, Mr-Egger, and Simple mode were used as complementary methods. Heterogeneity was detected using Cochran's Q test and funnel plot analysis, horizontal pleiotropy was detected using Mr-Egger intercept, and sensitivity analyses were performed using the "leave-one-out" method. PTGS2/PRKCA/MAPK14 all showed excellent diagnostic efficacy for bone nonunion. The risk prediction model based on PTGS2, PRKCA, and MAPK14 showed good predictive efficacy and clinical benefit rate for bone nonunion. Ferroptosis core gene PRKCA may be involved in the VEGF signaling pathway to affect the cell cycle and inhibit fracture healing. MR analysis suggests that Potassium and Vitamin E are protective factors for the development of bone nonunion. Ferroptosis genes PTGS2/PRKCA/MAPK14 are potential diagnostic targets for bone nonunion. The down-regulation of PRKCA expression may inhibit fracture healing through the VEGF signaling pathway during the growth of blood vessels at fracture breaks. The results of MR suggested that Potassium and Vitamin E have a promoting effect on fracture healing.

[Non-unions of the upper extremities]

The diagnosis and treatment of non-unions still represents an interdisciplinary challenge. Therefore, prevention, early detection and specific treatment are of great importance. Non-unions of the upper extremities, although less common than that of the lower extremities, requires special attention for successful treatment due to the central role of the shoulder girdle and arm in day to day activities. Successful treatment of non-unions requires a comprehensive evaluation of the patient's medical history, a thorough clinical examination and in particular radiological imaging. In order to effectively treat the pseudarthrosis it is crucial to distinguish between pseudarthroses that are suspected to be due to infections and those that are not. This article presents a treatment algorithm for managing both pseudarthrosis due to infection and pseudarthrosis without infection in the upper extremities.

[Nonunions after intertrochanteric and subtrochanteric femoral fractures]

INTRODUCTION

The overall frequency of proximal femoral fractures means that we are repeatedly confronted with failed healing and implant failure, despite a relatively low nonunion rate especially in intertrochanteric fractures (< 5%). The aim of this paper is to present our approach to treating these nonunions of the proximal femur and discuss the treatment results.

MATERIAL AND METHODS

Between 2009 and 2023, patients with nonunion of the proximal femur were retrospectively identified and analyzed. Age, gender, time to revision, the Weber-Cech classification of pseudarthrosis and radiographic imaging before and after revision were analyzed.

RESULTS

A total of 66 patients were analyzed. The mean age was 58 years (range 25-88 years). The overall healing rate was 88% with a mean consolidation time of 8 months (range 2-29 months). The main osteosynthesis procedures were plate osteosynthesis (n = 45, of which 44 were blade plates), and nail replacement (n = 12). Other procedures included augmentative plate osteosyntheses (n = 4), isolated cancellous bone graft (n = 2), nail dynamization (n = 2), and the use of a dynamic hip screw (n = 1).

DISCUSSION

The analysis of our treatment data as well as the current literature, revealed a trend towards intramedullary revision procedures. Implants that can be used to correct the CCD angle, such as the blade plate, remain a predictable option to achieve correction, especially in nonunions with an increased degree of varus. Particularly in the subtrochanteric region, fractures can also be treated in a targeted manner by a combination of mechanical and biological methods with a reamed nail change to a larger caliber implant.

Long-Term Outcomes Following Single-Stage Reamed Intramedullary Exchange Nailing in Apparently Aseptic Femoral Shaft Nonunion with Unsuspected Proof of Bacteria

Background: The aim of this study was to evaluate detection rates and risk factors for unsuspected proof of bacteria, as well as clinical and radiologic outcomes following femoral shaft nonunion without clinical signs of infection treated by a single-stage surgical revision procedure including reamed intramedullary exchange nailing. Methods: A retrospective cohort study was performed in a European level I trauma center between January 2015 and December 2022. Fifty-eight patients were included who underwent reamed intramedullary exchange nailing as a single-step procedure for surgical revision of posttraumatic diaphyseal femoral nonunion without any indications of infection in medical history and without clinical signs of local infection. Clinical details of the patients were analyzed and functional and radiologic long-term outcomes were determined. Results: In all patients, with and without proof of bacteria osseous, healing could be observed. The physical component summary of the SF-12 demonstrated significantly better results at least one year after the final surgical revision in case of a negative bacterial culture during exchange nailing. Conclusions: Clinical long-term outcomes demonstrated a trend towards better results following femoral shaft nonunion revision if there was no evidence for the presence of low-grade infected nonunion. In this case, a single-stage surgical procedure may be recommended.

[Diagnostic and therapeutic work-up of infected tibial nonunion]

BACKGROUND

The failure of bone fracture healing is one of the major complications of fracture treatment, especially of the tibia due to its limited soft tissue coverage and high rate of open injuries. Although implant development is constantly progressing and modern surgical techniques are continuously improving, infected tibial nonunion plays a decisive role in terms of its variable clinical presentation.

OBJECTIVE

This article provides guidelines for the successful surgical treatment of infected tibial nonunion.

MATERIAL AND METHOD

Strategies are presented to identify infection as a cause of failure of fracture healing and to achieve infection and bone healing.

RESULTS

A significant amount of tibial nonunions primarily thought to be aseptic ultimately turn out to be infected nonunions.

CONCLUSION

The treatment of infected tibial nonunion requires extensive clinical, radiological and laboratory diagnostics as well as a profound biomechanical and biological understanding of the bone situation. This is the only way to achieve rapid osseous healing with as few revision interventions as possible.

Medial augmentation plating of aseptic distal femoral nonunions

BACKGROUND

Distal femur nonunions are well-recognized contributors to persistent functional disability, with limited data regarding their treatment options. In the current study, we asked whether additional medial augmentation plating is a feasible treatment option for patients with aseptic distal femoral nonunion and intact lateral implants.

METHODS

We conducted a single-center, retrospective study including 20 patients treated for aseptic distal femoral nonunion between 2002 and 2017. The treatment procedure included a medial approach to the distal femur, debridement of the nonunion site, bone grafting and medial augmentation plating utilizing a large-fragment titanium plate. Outcome measures were bone-related and functional results, measured by the Hospital for Special Surgery Knee Rating Scale (HSS) and the German Short Musculoskeletal Function Assessment questionnaire (SMFA-D).

RESULTS

Eighteen of 20 nonunions showed osseous healing at 8.16 ± 5.23 (range: 3-21) months after augmentation plating. Regarding functional results, the mean HSS score was 74.17 ± 11.12 (range: 57-87). The mean SMFA-D functional index was 47.38 ± 16.78 (range 25.74-71.32) at the last follow-up. Index procedure-associated complications included two cases of persistent nonunion and one case of infection.

CONCLUSIONS

According to the assessed outcome measures, augmentation plating is a feasible treatment option, with a high proportion of patients achieving bony union and good functional outcomes and a few patients experiencing complications.

[Update on non-unions 2022 : Imaging diagnostics, classification and treatment algorithms]

BACKGROUND

Fracture healing is a complex regenerative process. An unconsolidated fracture that will not heal without further surgical intervention is called non-union. The causes are multifactorial. Diagnostic imaging is a central pillar and provides insights into the morphology and biology of the fracture as a basis for optimal surgical treatment decisions.

AIM

Knowledge of fracture healing, targeted radiological and nuclear medical diagnostics, and interdisciplinary standardized classification are of high importance for optimal treatment.

METHODS

In this article, the proven and modern diagnostic procedures are presented, an overview of the currently used scoring and classification models is given and the optimal therapeutic approach based on the extended "diamond concept" is addressed. A possible diagnostic and therapeutic approach is shown using an algorithm.

CONCLUSION

For successful treatment of pseudarthrosis, targeted radiological and nuclear medical diagnostics with old established but also newest methods, such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and hybrid imaging, are necessary. An exact classification of non-unions using additional classification models makes it possible to determine and carry out the optimal surgical treatment at an early stage.