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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 8  |  Issue : 1  |  Page : 54-62

Universal long bone defect classification


1 Vreden Russian Research Institute of Traumatology and Orthopedics, Ministry of Health of Russia, Saint Petersburg, Russian Federation, Russia
2 Department of Military Traumatology and Orthopedics, S.M. Kirov Military Medical Academy, Saint Petersburg, Russian Federation, Russia
3 Department of Orthopaedic Trauma, Moscow City Clinical Hospital, Moscow, Russian Federation, Russia
4 Department of Orthopaedic Surgery, Limb Lengthening and Complex Reconstruction Service, Hospital for Special Surgery, New York, USA

Date of Submission05-Feb-2022
Date of Decision16-May-2022
Date of Acceptance19-May-2022
Date of Web Publication30-Jun-2022

Correspondence Address:
Gerard A Sheridan
Department of Orthopaedic Surgery, Limb Lengthening and Complex Reconstruction Service, Hospital for Special Surgery, New York
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jllr.jllr_3_22

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  Abstract 


Introduction: Treatment of long bone defects is a challenging problem in orthopedics that requires a robust and comprehensive classification system to guide diagnosis and management. The Universal Long Bone Defect Classification (ULBDC) is an alphanumeric system detailing the size and location of the defect. It is designed to describe the bone defect and indicate the appropriate treatment for both diaphyseal and articular long bones defects. Methods: The location, size, and morphology of the bone defect are the main criteria used in the treatment of both extra-articular and intra-articular bone defects. The proposed classification system utilizes the following nomenclature for both periarticular defects and diaphyseal defects: location (bone and segment) and morphology (type, group, and subgroup). Discussion: The ULBDC is based the same principles of coding as the “gold standard” AO/OTA Fractures Classification system with alpha-numeric coding “from simple to complex.” The choice of treatment method depends on the type, group, and subgroup of the defect as described. The principles of treatment of diaphyseal defects, as well as the principles of treatment of extra-articular fractures, are based on the restoration of the alignment, length, and rotation of the segment. Bone shortening and deformity are considered bone defects because their treatment requires the use of the same principles (osteotomies, bone grafting, bone transport, or combination of these methods) as treating real bone defects. Conclusion: The proposed classification is an attempt to classify all types of long bone defects and its use in clinical practice and research will allow for optimal and standardized treatments for the various types of bone defects to improve the treatment outcomes.

Keywords: Bone defect, classification, diaphysis, periarticular, Universal Long Bone Defect Classification


How to cite this article:
Solomin L, Komarov A, Semenistyy A, Sheridan GA, Rozbruch S R. Universal long bone defect classification. J Limb Lengthen Reconstr 2022;8:54-62

How to cite this URL:
Solomin L, Komarov A, Semenistyy A, Sheridan GA, Rozbruch S R. Universal long bone defect classification. J Limb Lengthen Reconstr [serial online] 2022 [cited 2022 Aug 9];8:54-62. Available from: https://www.jlimblengthrecon.org/text.asp?2022/8/1/54/349418




  Introduction Top


Treatment of long bone defects is a challenging problem in orthopedics that requires a robust and comprehensive classification system to guide diagnosis and management. The development of a widely accepted Universal Long Bone Defect Classification (ULBDC) will enable the international orthopedic community to apply a common classification to a complex problem. This will lead to improved research methodologies when conducting clinical trials, better communication, and documentation between institutions involved with managing these cases and ultimately a more transparent and concise treatment algorithm.

“A classification is useful only if it considers the severity of the bone lesion and serves as a basis for treatment and for evaluation of the results” Maurice E Müller (Müller M. E. et al., 1995). It should be universal and simple to use with a clear and generally accepted nomenclature (Engh GA. 1999; Reichel H. et al. 2002; Mulhall K. J. et al. 2006).

Previously conducted literature reviews have shown that there is still no comprehensive classification of long bone defects that satisfies the above requirements. The ULBDC is an alphanumeric system detailing the size and location of the defect. It is designed to describe the bone defect and indicate the appropriate treatment for both diaphyseal and articular long bones defects.


  General Principles of the Universal Long Bone Defect Classification Top


General characteristics

The location, size, and morphology of the bone defect are the main criteria used in the treatment of both extra-articular and intra-articular bone defects. [Figure 1] demonstrates the proposed nomenclature used to describe bone defects based on two main groupings: location and morphology.
Figure 1: Nomenclature for use in the Universal Long Bone Defect Classification

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Defect location: Bones and segments

The numeric coding of the location corresponds to the coding used in the AO/OTA fracture classification. The numbers 1, 2, 3, and 4 correspond to the humerus, forearm, femur, and lower leg, respectively. Given the presence of two bones in the forearm, the letter R denotes the radius, and the letter U denotes the ulna. Similarly, in the lower leg, the letter T denotes the tibia and the letter F denotes the fibula.

After determining the bone involved, the segment is next identified. Segment 1 corresponds to the proximal periarticular region of the bone. Segment 2 corresponds to the diaphyseal region of the bone. Segment 3 corresponds to the distal periarticular region of the bone [Figure 2].
Figure 2: Numeric coding for bone region involved. Bones – 1: Humerus, 2: Forearm (2U-Ulna: 2R-Radius), 3: Femur, 4: Lower Leg (4T -Tibia, 4F –Fibula), Segments – 1: Proximal periarticular, 2: Diaphyseal, 3: Distal periarticular

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The periarticular segment is defined as per the AO/OTA fracture “square” principle (the side of which is equal to the widest part of the epiphysis of the bone). The diaphyseal segment is then defined as the region between the proximal and distal periarticular segments. After bone segment coding, periarticular bone defects are described in relation to the extent of epiphyseal, metaphyseal, and diaphyseal involvement. This coding is defined using the letters “E,” “M” or “D” [Figure 3] and [Figure 4]. Bone defects relating only to the epiphyseal area are coded with the letter “E.” Metaphyseal defects are coded with letter “M.” Epi-metaphyseal defects are coded with the letters “EM.” A segmental bone defect extending from the epiphysis to the diaphysis (i.e., epi-meta-diaphyseal) is denoted by the letter “ED.”
Figure 3: Nomenclature describing periarticular defects

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Figure 4: The boundaries of periarticular regions in different bone segments

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Defect morphology: Types, groups, and subgroups

After the bone and segment have been identified and classified, the morphology of the bone defect must then be considered. It should first be noted that the treatment approaches vary for both diaphyseal and periarticular bone defects and therefore the principles of dividing these defects into types, groups, and subgroups are also different.

Types

The types of defects are coded using A, B, C, and D according to increasing complexity as shown in [Figure 5]. Type A requires simpler methods of reconstruction. Type B defects are more challenging to manage. Type C and D defects require the most complex reconstructions and, as a rule, have a less favorable prognosis. Amputation levels are determined by the digital localization code.
Figure 5: Defect morphological types

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Groups and subgroups

After the type is determined, long bone defects are then classified into groups (1, 2, 3) and subgroups (.1.,2.,3). Defect Types C2 and C3 are also further classified according to the specifications A, B, or C. The division of defects in the diaphyseal and periarticular regions into types, groups, and subgroups is described in the following paragraphs.


  Diaphyseal Defects Top


Type A groups and subgroups (diaphysis)

The Type A “group” in the diaphysis is the simplest defect types [Figure 6]. The group is determined on the circumference of the bone involved (in thirds) and subgroups are then determined based on the overall defect length which is expressed as a measure in relation to the bone diameter [Figure 6]. The simplest bone defects are those, that require the simplest reconstruction techniques, therefore the Type A1 defects are cortical bone defect <1/3 of bone diameter with preserved bone integrity. Given the deformity and bone shortening require more complex reconstruction techniques they are defined as Type A2. When considering A2 defects, subgroup 1 (2.1) describes a bone deformity that if corrected will leave a residual wedge-shaped defect. Subgroup 2.2 when corrected will leave a rectangular defect and subgroup 2.3 will leave a residual trapezoidal-shaped defect. The cortical bone defects more than 1/3 of bone diameter have a risk of pathologic fracture and therefore defined as Type A3.
Figure 6: Type A diaphyseal bone defects

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Type B groups and subgroups (diaphysis)

Type B defects interrupt the bone integrity (forming multiple bone fragments) with preservation of length due to contact between these bone fragments [Figure 7]. The Type B group is based on the extent of bony contact which is measured in thirds of the diaphyseal width. The Type B subgroup is then determined by the defect length which is measured in cortical diameters [Figure 7].
Figure 7: Type B diaphyseal bone defects

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Type C groups and subgroups (diaphysis)

Type C defects are segmental defects. Type C groups are determined by whether the two fragments have full bone contact (1), limited bone contact (2), or no bone contact (3) [Figure 8].
Figure 8: Type C bone defects

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  Periarticular Defects Top


Type A groups and subgroups (periarticular)

Type A includes all extra-articular defects of the epimetaphyseal region [Figure 9]. Division into groups: (1) extra-articular cancellous defect, (2) extra-articular cortical epimetaphyseal defect, and (3) extra-articular defect with diaphyseal extension.
Figure 9: Type A periarticular defects

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Extra-articular defects of the epimetaphyseal zone are determined by the volume of bone loss and the area of maximum bone loss (S) as a percentage on coronal computed tomography (CT) slices. To identify the spread of the defect toward the diaphysis, the letter designations E, M, D (epiphysis, metaphysis, diaphysis) are used.

Type B groups and subgroups (periarticular)

Type B defects include defects with widespread involvement of the articular surface, but <50% on axial CT scans [Figure 10]. The division into groups is based on the size of the defect (small, medium, large intra-articular) and the subgroups are determined by the location and distribution of the defect. To determine the spread of the defect toward the diaphysis, the letter designations E, M, D (epiphysis, metaphysis, diaphysis) are used.
Figure 10: Type B periarticular defects

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Type C groups and subgroups (periarticular)

The Type C periarticular defects are subtotal or total articular defects involving more than 50% of articular surface. The division of Type C defects into groups is based on the defect extension toward the diaphysis: C1 – epiphyseal defects, C2 – epimetaphyseal defects, and C3 – epimetadiaphyseal defects. The further division into subgroups is based on the presence/absence of articular surface and diastasis. Subtotal bone defects involving <100% articular surface belong to subgroup 1, total articular defects with full bone contact belong to subgroup 2 and total articular defects with defect diastasis are considered as subgroup 3 [Figure 11].
Figure 11: Type C periarticular defects

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Type D groups and subgroups

The Type D defects involve amputation of a limb at the level of proximal joint, diaphysis, or distal joint. The Type D defects are divided into groups depending on the level of amputation. The shorter the stump the more complicated is the exoprosthesis fixation. Therefore, according to principle “from simple to complex” at the same segment in Type D1 amputations, the stump is always longer than in Type D3.

For the proximal segment Type D1 defect is the amputation at the level of metadiaphysis, D2 at the level of metaepiphysis, and D3 is an exarticulation.

For diaphyseal segment Type D1 defect is the defect at the level of distal 1/3, Type D2 at the middle 1/3, and Type D3 at proximal 1/3 of the diaphysis.

For distal segment exarticulation means that the full distal bone end is preserved, therefore D1 defect is disarticulation. Distal D1 defects exist only for distal bones (forearm – 2; lower leg – 4), because disarticulations at the level of proximal and middle joints are coded as 1D3. A distal D2 defect is the amputation at the level of metaepiphysis and D3 at the level of metadiaphysis [Figure 12].
Figure 12: Type D defects – amputations

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Despite the fact that long bone defects are covered in large number of publications, there is still no universally accepted classification to manage them. The newly proposed ULBDC addresses this need.[1],[2],[3] The ULBDC is based on the same principles of coding as the “gold standard” AO/OTA Fractures Classification system with alpha-numeric coding “from simple to complex.” The choice of treatment method depends on the type, group, and subgroup of the defect as described.

The principles of treatment of diaphyseal defects, as well as the principles of treatment of extra-articular fractures, are based on the restoration of the alignment, length, and rotation of the segment. Bone shortening and deformity are considered bone defects because their treatment requires the use of the same principles (osteotomies, bone grafting, bone transport, or combination of these methods) as treating real bone defects.[1],[2],[3],[4]

Type A1 diaphyseal defects usually require conservative treatment and rarely plate augmentation.[5] We propose that the classification should take into account the deformities and shortening of long bones (Type A2), it should be noted so that when they are corrected, a residual wedge-shaped (A2.1), rectangular (A2.2), and trapezoidal-shaped (A2.3) bone defects remains. Type A2 defects are treated in accordance with the principles of deformity correction. Type A3 defects have a high risk of pathologic fracture and therefore the treatment is always surgical-various methods of osteosynthesis with bone grafting, osteotomy, and plate augmentation have been described.[1],[2],[3],[4],[5]

Type B defects have a bone defect with preservation of length. Depending on the defect type, bone grafting or bone substitutes are used/not; compression osteosynthesis, external fixation.[6]

The approaches to the treatment of diaphyseal defects Type C in the upper and lower extremities are different. The restoration of the axis, length, rotation gives a good result. Type C defects: osteosynthesis, the Masquelet technique, bone transport, lengthening, plate augmentation, free/nonfree bone grafting, bone substitutes, and tissue complex transplant.[7],[8],[9]

The treatment of Type A1 defects depends on the size of the defects and its proximity to articular surface. The small metaphyseal defects (A1.1 m) usually have no risk of articular surface collapse. This risk is higher, but still low in epiphyseal defects (A1.1e). The Type A1.1 defects usually do not require any treatment. The large extra-articular defects (A1.3) have the high risk of joint collapse and therefore there is an indication for surgery. The defect may be filled by autologous bone graft or bone cement.[6] The Type A1.2 defects borderline and its usually difficult decision to choose between conservative and surgical treatment. The treatment of extra-articular cortical defects (A2 and A3) depends mostly on the size of the defect. The small defects (A2.1) have usually no risk of pathologic fracture and do not require any treatment. As the size of the defect increases the risk of the fracture increases, therefore the Type A3.3 and are an indication to surgery.[10],[11] If surgery is indicated the A2 and A3 defects are treated by cortical wall augmentation with the plate with or without bone grafting.[12]

The treatment choice of small intra-articular bone defects (B1) mostly depends on the defect location. The defects located on the weight-bearing surface can be treated by arthroscopy, however, the treatment of the vast majority of limited intra-articular defects is conservative.[13]

The B2 intra-articular defects have more severe joint involvement in comparison to Type B1. The treatment of Type B2 defects is surgical in vast majority of cases. The treatment options vary from arthroscopic osteochondroplasty (B1) to total joint replacement or arthrodesis (B3).[14] The defect size and location along with the general condition of the articular cartilage are the most important factors to assess in decision-making process.

The joint preservation is not an option in Type C defects. The treatment options usually vary from a regular total joint arthroplasty (C1.1) to complex reconstructive procedures such as arthrodesis with the subsequent limb lengthening (C2.3) or implantation of megaprosthesis (3.3).[15] The defect location, size, soft tissue condition, and the presence of infection are the most important factors for decision-making process.[16]

For Type D defects the more proximal amputation the less favorable functional prognosis. Historically the treatment of amputations is exoprostethetics, however, the advancement of new osteointegrated exoprostheses is the gamechanger in this field and the use of proposed classification can alleviate the choose of the optimal treatment strategy in the future.[17],[18]

The treatment of periarticular bone defect includes the wide number of surgical techniques such as bone grafting, the Masquelet technique, arthroscopic or open osteochondroplasty, distraction arthroplasty, joint transplantation, partial or total joint replacement, arthrodesis or amputation.[13],[14],[15],[16],[17],[18]

Limitations

The main limitation of this classification system lie in the fact there is a very broad range of potential pathologies that may affect the appendicular skeleton. We have made an attempt to create a very comprehensive classification system that will ultimately capture the vast majority of long bone defects but it may be possible that certain subtypes of defects may fall outside of this classification.


  Conclusion Top


The proposed classification is an attempt to classify all types of long bone defects and its use in clinical practice and research will allow for optimal and standardized treatments for the various types of bone defects to improve the treatment outcomes.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Komarov AV, Semenistyy AA, Sheridan GA, Rozbruch SR, Solomin LN. Acquired long bone defect classifications of the diaphysis: A literature review. J Limb Lengthen Reconstr 2021;7:88-97.  Back to cited text no. 2
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Zellner J, Grechenig S, Pfeifer CG, Krutsch W, Koch M, Welsch G, et al. Clinical and radiological regeneration of large and deep osteochondral defects of the knee by bone augmentation combined with matrix-guided autologous chondrocyte transplantation. Am J Sports Med 2017;45:3069-80.  Back to cited text no. 14
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12]



 

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