Methodological principles of diagnosis verification and treatment tactics determination in combat limb injuries with bone defects

Objective. To develop a classification system for long bone defects resulting from combat limb injuries, establish criteria for predicting pathological fractures, and determine indicators for assessing the feasibility of converting the fixation method in combat-related injuries. Methods. The modern literature regarding the treatment of combat-related long bone defects resulting was analyzed in three databases: PubMed, Scopus, and Web of Science. The analysis was conducted using keywords such as combat injuries, bone defect, non-union, auto- and allograft transplantation, Ilizarov method — bone transport, Masquelet method — induced membrane, and fixation method replacement. The clinical material used for this study was derived from the evaluation and treatment of 457 patients with long bone defects at the III–IV medical intervention stage. Results. The determination of modern perspectives on the fundamental issues of combat injuries, combined with the analysis of treatment outcomes for such patients, enabled the development and validation of a classification of bone defects that incorporates the volume of bone tissue loss. Furthermore, a prognostic table for the risk of pathological fractures in cases of bone defects and a scoring scale for assessing the feasibility of fixation method conversion have been introduced and applied. Conclusions. The proposed classification allows the verification of all types of long bone defects. Its application in clinical practice offers the possibility of obtaining optimal and standardized treatment methods for different types of bone defects, thus improving outcomes by choice of appropriate technologies for their replacement. The objectification of fracture risk factors identification for bone defects enables the choice of the method and means of segment stabilization. The assessment of the feasibility of the fixation method change allows the evaluation of the patientʼs condition and the local status, facilitating the determination of the potential for method conversion — transition from external fixation devices to intramedullary osteosynthesis, significantly reducing complications during this stage.


The determination of modern perspectives on the fundamental issues of combat injuries, combined with the analysis of treatment outcomes for such patients, enabled the development and validation of a classification of bone defects that incorporates the volume of bone tissue loss. Furthermore, a prognostic table for the risk of pathological fractures in cases of bone defects and a scoring scale for assessing the feasibility of fixation method conversion have been introduced and applied. Conclusions. The proposed classification allows the verification of all types of long bone defects. Its application in clinical
practice offers the possibility of obtaining optimal and standardized treatment methods for different types of bone defects, thus improving outcomes by choice of appropriate technologies for their replacement.The objectification of fracture risk factors identification for bone defects enables the choice of the method and means of segment stabilization.The assessment of the feasibility of the fixation method change allows the evaluation of the patientʼs condition and the local status, facilitating the determination of the potential for method conversion -transition from external fixation devices to intramedullary osteosynthesis, significantly reducing complications during this stage.

ОРИГІНАЛЬНІ СТАТТІ Introduction
Bone defects represent a pathological condition characterized by a loss of a portion of bone tissue that lacks the capacity for self-regeneration, even when subjected to appropriate care and surgical stabilization [1].
Bone tissue defects can arise from various causes, such as tumors affecting the musculoskeletal system, infections, high-energy injuries, osteofibrous dysplasias, or congenital abnormalities, for instance, the Adams-Oliver syndrome [2].
According to statistical data, bone defects occur in approximately 0.4 % of all individuals with bone fractures, which translates to roughly one million cases of skeletal trauma.Bone defects most commonly develop in open high-energy injuries, constituting 11.4 % of all open fractures.[3].
A current significant concern is the treatment of bone defects caused by combat injuries, which occur due to the use of firearms or explosives.These injuries result from high-energy impacts and lead to complex structural damage [4].
Systematic studies of injuries among NATO allied forces in Iraq and Afghanistan reveal that limb injuries are the most common, accounting for approximately 39 to 49 % of all injuries, surpassing other types [5].The treatment of such injuries necessitates a step-by-step and timely approach regarding soft tissue defects, bone tissue issues, infectious complications, and the long-term duration of restorative care [6].
To improve treatment outcomes, it is essential to establish methodological principles for diagnosis verification and develop a classification system for bone tissue defects, serving as the basis for the bone defect repair procedural algorithm and replacement technologies.Additionally, it's crucial to determine objective criteria for the choice between fixation methods, such as external fixation devices or intramedullary osteosynthesis.
Objective: to develop a classification system for long bone defects resulting from combat limb injuries, establish criteria for predicting pathological fractures, and determine indicators for assessing the feasibility of converting the fixation method in combat-related injuries.

Material and methods
The modern literature regarding the treatment of combat-related long bone defects resulting was analyzed in three databases: PubMed, Scopus, and Web of Science.The analysis was conducted using keywords such as combat injuries, bone defect, nonunion, auto-and allograft transplantation, Ilizarov method -bone transport (BT), Masquelet methodinduced membrane, and fixation method replacement.
The article inclusion criteria involved full-text articles with clinical studies confirming the treatment of patients with segmental bone defects and non-union using DO (Distraction Osteogenesis), IMT (Intramedullary Transport), FVFG (Free Vascularized Fibular Graft), or auto-and allograft transplantation.Articles were selected if they presented treatment results based on a sufficient number of patients (no less than twenty) and included comparative studies of the mentioned methods, provided they contained quantitative data for method evaluation.
The article non-inclusion criteria involved case reports, pilot studies, and preliminary research.
The clinical material is based on the examination and treatment of 457 patients with combat long bone defects at the III-IV medical intervention stage.
The work was carried out with the grant support of the Ministry of Health of Ukraine, project 0123U101089.
The work was performed in compliance with the current legislation and the article was approved at a meeting of the Bioethics Committee of the SI «Institute of Traumatology and Ortopedics» NAMS of Ukraine (Protocol № 4 dated 14.11.2023).

Results
When developing the classification of long bone defects, the numerical coding for the humerus, femur, forearm bones, tibia, and their segments, we used the AO/ASIF classification of long bone fractures [7].
This approach is driven by the fact that the AO/ ASIF classification is well-known and widely used, which simplifies the implementation and use of the proposed classification.
Figure 1 displays the numbering of long bones of the skeleton and their segments.
This approach also applies to the epimetaphyseal areas, as shown in figure 2.

Classification of bone tissue defects in firearm injuries
Epimetaphyseal defects of type A involve defects in the bone tissue of the epimetaphyseal area, characterized by the preservation of the articular surface and the integrity of the cortical layers (fig.3).
Type B epimetaphyseal defects encompass defects in the bone tissue of the epimetaphyseal area and the cortical layer with the preservation of the articular surface and without complete bone disintegration (fig.4).
Type C epimetaphyseal defects encompass defects in the bone tissue of the epimetaphyseal area and the articular surface (fig.5).
Type D epimetaphyseal defects encompass defects in the epimetaphyseal area, articular surface, and the cortical layer (fig.6).
Type A diaphyseal defects involve bone defects without compromising the integrity of the bone (fig.7).
Type B diaphyseal defects encompass bone defects with compromised bone integrity, but with preserved contact in the cortical layer (fig.8).
Type C diaphyseal defects encompass bone defects with a compromised bone integrity and a complete defect of the segmentʼs area (fig.9).
An essential aspect of preoperative planning for bone defects is determining the volume of bone tissue loss (V cm³).
V.1 -bone tissue loss up to 15 cm³ V.2 -bone tissue loss from 16 cm³ to 40 cm³ V.3 -bone tissue loss exceeding 40 cm³ A table was developed to predict fractures in bone defects, specifically to determine the extent of surgical intervention required, whether external or internal stabilization of the segment area is necessary.The table includes defects of types A, B, and C for epimetaphyseal areas and excludes type D. For defects in the diaphyseal area, type A defects are included, while types B and C are excluded.
The primary criteria were identified and assessed using the Harrington methodology [8].For ease of calculation, numerical characteristics were converted into scores represented by rounded numbers (table 1).An important step in the staged treatment of patients with gunshot injuries to long bones is determining the feasibility of changing the fixation method (conversion): external fixation apparatus to intramedullary osteosynthesis.To facilitate this, a scoring system, the «Assessment of the Possibility of Changing the Fixation Method» scale, has been developed (table 2).
According to the scale: «0» -a score that indicates confidence in performing conversion, «1» -a score that significantly does not affect conversion planning, «2» -characterizes the possible impact of this characteristic on conversion planning, «3» -allows for doubts about the feasibility of conversion, «5» -indicates the impossibility of performing conversion.The final stage involves summing up all the obtained indicators and conducting an evaluation.In the range from 0 to 7, conversion is possible; from 8 to 10, itʼs questionable (the sum of scores doesnʼt rule it out, but may require additional examination or adjustment of therapeutic appointments); and over 10, conversion is contraindicated.

Discussion
Segmental loss of bone tissue following trauma remains a challenging problem for orthopedic surgeons.The presence of bone defects, combined with infection, significant changes in soft components, and/or their deficiency, create extremely unfavorable conditions for bone regeneration.
The classification of bone defects is an important component in addressing this issue.Its necessity is objectively driven because classification allows for standardizing approaches to treatment, establishing a system for regenerative therapy, defining the types of grafts based on the defectʼs characteristics, and evaluating results.This provides a foundation for further research and determining the most optimal methods.Attempts to systematize bone defects and present the data as an effective and practical classification are not new in modern orthopedics and traumatology.Two of the most well-known classifications, F. Waldvogel and G. Cierny, J. T. Mader, have been in use for over 40 years [9,10].
Despite the fact that the Cierny and Mader classification was used to determine the surgical treatment strategy based on the bone defect model, the presented indicators showed little correlation with the prognosis after a 2-year observation among candidates for surgical intervention [11].
Considerable attention is given not only to the localization of the defect but also to its length.For example, L. Gordon and C. L. Romano used a 3 cm bone defect, while J. W. May and J. B. Jupiter used a 6 cm bone defect for their classification [12][13][14].
The parameters for defining small, medium, and large bone defects have remained largely unchanged over the last 30-40 years.The changes mainly relate to their encoding.For example, open fractures are classified based on orthogonal radiographs, assessing the degree and local geometry of bone loss, including: D1 -incomplete defects, D2 -minor/subcritical (complete) defects (< 2 cm), and D3 -segmental/ critical defects -defect size (≥ 2 cm).
The determination of the critical size of a bone defect is a topic of debate, and there is no universally agreed-upon definition of what constitutes a critical bone defect.By definition, a critical size bone defect is one that will not spontaneously heal.The SPRINT study identified a critical size defect as one that involves > 50 % of the cortical diameter of a long bone and > 1 cm in length [16].
However, D. W. Sanders et al., when evaluating patients with a «critical size defect» according to the SPRINT definition, found that defects in the diaphysis of long bones larger than 1 cm, and with a circumference involving > 50 % of the cortical area, healed without additional surgical intervention in 47 % of cases.Therefore, the initial definition of a critical size defect was not as «critical» as previously thought [17].J. F. Keating et al. consider a critical size defect to be a bone deficiency longer than 2 cm and involving more than 50 % loss of circumference [18].

In Gustilo Anderson
According to N. Ferreira et al., the critical size defect depends on various variables, including the patientʼs age and condition, anatomical location, and the state of surrounding soft tissues, rather than just its size [19].
In our opinion, the length of the defect is a significant parameter for determining the treatment approach, but it lacks specificity.Firstly, a 3 cm bone defect in the humerus and femur represents substantially different conditions.In the first case, a potential treatment option might involve shortening the segment without significant functional loss, whereas in the case of a 3 cm femur defect, such an approach is usually inappropriate.Secondly, the volume of the bone tissue deficiency is crucial for selecting the defect-filling option, and it varies at the same length of 3 cm on different segments.
Based on the above, the most significant parameter of a bone is the volume of the bone mass deficiency.However, most classifications do regard this specific parameter, which is crucial when considering different treatment options.For example, the comprehensive classification of bone defects published by L. Solomin and T. Slongo in 2022, which is based on the letter-number system of long bone fractures by Muller-AO, also does not consider the volume of bone tissue loss.
Many researchers believe that there is a need for the development of a pragmatic classification system that can be used not only to refine treatment strategies but also to adequately characterize patient cohorts for research purposes.Furthermore, traditional bone defect classification systems are struggling to keep up with modern trends in reconstruction.For example, J. W. May and Jupiter JBʼs classification of post-infection defects of the tibia does not correspond to the induced membrane technique [24].
The distinction between a stable and an unstable cavity defect is essential when making practical decisions regarding the advisability of using additional fixation methods: external immobilization or intramedullary fixation [25].An important consideration when treating fractures with bone defects resulting from combat trauma is the decision to convert the fixation method: replacing an external fixation device with internal constructions [26].
Two-stage treatment of open fractures, especially those of combat origin, is a controversial topic due to the high risk of infectious and purulent complications after using internal constructions, which are likely due to the presence of pathogens in scars, and foreign metal bodies [27,28].Therefore, the search for objective criteria that can help make such an important decision is highly relevant.
S. Zhao et al. [29] in their study by the univariate analysis indentified six risk factors associated with SSI, including Gustilo classification of fracture, EF time, WBC count, CRP level, ESR, and ALB level.Through the multivariate logistic regression analysis, we showed that CRP level, Gustilo fracture classification, and EF time were independently associated with SSI.Among the mentioned predictors, five risk factors were modifiable, and we observed that they played an important predictive role in protecting patients from postoperative infection.
When deciding on the implementation of the second stage, other researchers also mind the laboratory characteristics [30,31].We don't deny the significance of laboratory characteristics in deciding on the fixation method conversion, though, it is necessary to regard other parameters, which are presented in table 2.

Conclusions
The proposed classification, which includes the volume of bone loss, allows the verification of all types of long bone defects.Its use in clinical practice enables the development of optimal and standardized treatment methods for different types of bone defects, aiming to improve outcomes by selecting suitable techniques for their replacement.
Objective parameters for determining the risk of fracture in bone defects allow to choose the method and means for segment stabilization.
The scoring evaluation of the feasibility of transition to an alternative fixation method provides a systematic approach to assess the patientʼs condition and the specific local factors.This assessment aids in determining the potential for a conversion, involving the transition from external fixation to internal osteosynthesis.This approach substantially mitigates complications encountered during this stage of the procedure.

3 5 3 5 5 5 C
sutures, signs left from external fixation apparatus Signs of inflammation in the limb segment 0 Trophic changes in the skin of the limb The degree of inflammatory changes in the area of removed pins (wires) Absent Local inflammatory changes in soft tissues Pin-associated osteomyelitis 0 Injury to major arteries of the segment with signs of segmental ischemia Absent Restoration of blood flow after injury.Partial absence of blood flow (artery ligation) Body temperature during conversion planning 36.5-36.9°С 37.0-37.3°С 37.4-37.7 °С 0 3 -reactive protein level during conversion planning 0-10 mg/1 Less than 50 mg/1 More than 50 mg/1 0 3 5