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J Orthop Surg Res
J Orthop Surg Res
Journal of Orthopaedic Surgery and Research
1749-799X
BioMed Central London

39294725
5058
10.1186/s13018-024-05058-3
Research Article
Three-dimensional mapping of necrotic lesions for early-stage osteonecrosis of the femoral head
An Wen 1234
Yang Yanjiang 123
He Wei 1235
Li Jiaqi 1234
Chen Wei 809776478@qq.com

1238
Zhang Yingze yzzhang@hebmu.edu.cn

123678
1 https://ror.org/004eknx63 grid.452209.8 0000 0004 1799 0194 Trauma Emergency Center, the Third Hospital of Hebei Medical University, Shijiazhuang, 050051 Hebei People’s Republic of China
2 Orthopaedic Research Institute of Hebei Province, Shijiazhuang, 050051 Hebei People’s Republic of China
3 grid.452209.8 0000 0004 1799 0194 Key Laboratory of Biomechanics of Hebei Province, Shijiazhuang, 050051 Hebei People’s Republic of China
4 grid.256883.2 0000 0004 1760 8442 Department of Orthopaedics, Qinhuangdao First Hospital, Hebei Medical University, Qinhuangdao, 066000 Hebei People’s Republic of China
5 Department of Orthopaedics, Hebei Chest Hospital, Shijiazhuang, 050041 People’s Republic of China
6 NHC Key Laboratory of Intelligent Orthopaedic Equipment, Shijiazhuang, 050051 Hebei People’s Republic of China
7 Hebei Orthopaedic Clinical Research Center, Shijiazhuang, 050051 Hebei People’s Republic of China
8 https://ror.org/04eymdx19 grid.256883.2 0000 0004 1760 8442 Department of Orthopaedics, the 3rd Hospital, Hebei Medical University, NO.139 Ziqiang Road, Shijiazhuang, 050051 People’s Republic of China
19 9 2024
19 9 2024
2024
19 57726 7 2024
5 9 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Background

There is a scarcity of evidence regarding the potential relationship between the size and location of necrotic lesions, which must be understood to provide optimal joint-preserving treatment. The purpose of this study was to characterize the distribution patterns of necrotic lesions of varying sizes in early-stage osteonecrosis of femoral head (ONFH) with the use of three-dimensional mapping.

Methods

We retrospectively evaluated clinical CT images of the hips that were performed in the Third Hospital of Hebei Medical University from January 2018 to December 2022 and collected all CT images diagnosed with stage I and II ONFH. Three-dimensional structures that included both necrotic lesions and normal areas of the femoral heads were reconstructed and divided into eight regions to record their size and location. CT images for all lesions were superimposed onto a standard template, and three-dimensional mapping was created to determine the presence of concentrated areas of lesions.

Results

In a cohort of 143 patients with stage I and II ONFH, a total of 150 hips were reviewed. For lesions with less than 15% of the femoral head volume, necrotic lesions predominantly involve regions I, III, and V, with region I showing concentration. For lesions with volumes ranging from 15 to 30%, necrotic lesions exhibited a wider distribution across regions I, II, III, IV, V, and VII, with significant concentrations in regions I, III, and V. For lesions exceeding 30% of the femoral head volume, the necrotic lesions were extensively distributed across nearly the entire femoral head, with a notable expansion of the concentrated necrotic areas.

Conclusions

The distribution of necrotic lesions varies with lesion size, with smaller lesions primarily concentrated in the anterior and medial regions of the femoral head, particularly in the anterosuperior region, while larger lesions expand to the lateral and inferior regions. These findings enhance existing classification systems and provide crucial insights for guiding hip-preserving surgical planning and approaches.

Keywords

Osteonecrosis of femoral head
Three-dimensional mapping
Three-dimensional distribution
Computed tomography
Major Science and Technology Special Project of Xinjiang Uygur Autonomous RegionNo. 2022A03011 issue-copyright-statement© BioMed Central Ltd., part of Springer Nature 2024
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pmcIntroduction

Osteonecrosis of the femoral head (ONFH) is an escalating global health concern, primarily affecting young males. For younger patients with early-stage ONFH, joint-preserving techniques including core decompression, adjunctive bone grafting, small-diameter drilling, and osteotomies are increasingly employed [1–4]. However, the variability in success rates, ranging from 63.5 to 84% [5–8], may result from the inappropriate depth or position of the decompression procedures [9]. Consequently, precise necrotic lesion localization and measurement are crucial for optimizing surgical outcomes.

Simple visual estimations from traditional radiography provide only a general overview and inaccurate measurements of necrotic lesions, frequently overlooking smaller lesions [10–13]. CT and MR imaging have been shown to exhibit a high degree of consistency with gross specimens in depicting lesion characteristics [14, 15]. However, most investigations have focused primarily on quantifying lesions or localizing them in specific sections. There is a scarce of evidence on the relationship between the size of necrotic lesions and their spatial distribution within the femoral head. Three-dimensional mapping techniques, commonly used to characterize fractures, could enhance our understanding of lesion distribution patterns and inform treatment strategies and surgical approaches.

The purpose of this study was to not only measure the volume of necrotic lesions in various regions but also to characterize their distribution patterns using three-dimensional CT mapping techniques. We hypothesized that early-stage ONFH lesions of similar sizes exhibit consistent distribution patterns.

Methods

Subjects

This study, approved by the Institutional Research Ethics Committee, utilized the Picture Archiving and Communication System (PACS) at the Third Hospital of Hebei Medical University to retrospectively retrieve consecutive CT imaging data from January 2018 to December 2022. Patients diagnosed with osteonecrosis of the femoral head were included, classified as either stage I or II by the 2019 revised version of the Association Research Circulation Osseous staging system. The case records and imaging data were reviewed independently by 3 investigators. Patients under18 years of age or with axial CT images with a slice thickness of > 2 mm were excluded.

Three-dimensional reconstruction

Axial hip CT data were imported into Mimics software (version 21.0; Materialise, Belgium) for initial processing. The proximal femur’s preliminary structure was obtained using segmentation masks and region-growing tools. The necrotic areas were manually segmented at each level in the axial, sagittal, and coronal planes. Three-dimensional models of the proximal femur and necrotic lesions were separately reconstructed in Mimics and exported into 3-matic software (version 13.0; Materialise, Belgium).

Three-dimensional segmentation

In the 3-matic software, we segmented the femoral head into eight regions using three mutually perpendicular planes. The procedure entailed employing the “Wave Brush Marking” technique for surface delineation and identifying the centers of the femoral head and neck to establish the femoral neck axis. Subsequently, coronal and sagittal planes (Plane 1, Plane 2), aligned with the body, were constructed along this axis. A third plane (Plane 3), perpendicular to both coronal and sagittal planes, passed through the femoral head’s center. Another plane (Plane 4), orthogonal to the first two, was positioned at the head-neck junction. The femoral head was segmented from the proximal femur with Plane 4 and divided into eight distinct regions (I-VIII) with planes 1, 2, and 3 (Fig. 1). The total volume of the femoral head, along with the volume of lesion within each region, was recorded in 3-matic software.

Fig. 1 Three-dimensional segmentation

(a) Establish the head-neck axis through the center of the femoral head and femoral neck. (b) Establish planes 1–4 through the femoral head-neck axis, the femoral head center, and the head-neck junction. (c-d) Segment the femoral head into eight distinct regions using three orthogonal planes: anterosuperior (I), anterolateral (II), anteromedial (V), anteroinferior (VI), posterosuperior (III), posterolateral (IV), posteromedial (VII), and posteroinferior (VIII)

Three-dimensional mapping of necrotic lesions

Three-dimensional objects were aligned with a standard template in 3-matic software through a registration process including N points registration, translation, and scaling (Fig. 2). Necrotic lesions were separated from the original femoral head as individual parts and exported to STL format containing three-dimensional coordinates. These files were analyzed in Python using a custom library to extract coordinates and calculate the density of coordinate points, employing a K-Nearest Neighbors (KNN) density estimation method. We build a three-dimensional visual heat map based on the density of coordinate points and define the top 25% as the most concentrated necrotic area.

Fig. 2 Three-dimensional alignment

(a) Landmarks on the standard femoral head template after segmentation. (b) Landmarks on the femoral head to be aligned. (c) Aligned femoral head

Statistical analysis

To determine the distribution patterns of lesions with varying volumes, hips were categorized into groups according to lesion volume percentages at 5% intervals. We calculated the percentage of lesion volume within each region relative to the total femoral head volume. Patient characteristics and lesion volume percentages were summarized using the mean and standard deviation for continuous variables. For statistical comparisons of lesion volumes between adjacent groups, independent sample t-tests or Mann-Whitney U tests were used. Statistical analyses were performed using SPSS 25.0 (IBM, Chicago, IL), with a significance threshold of p < 0.05. The distribution patterns of lesions and the three-dimensional mapping are descriptive in nature.

Result

The baseline characteristics of the participants are presented in Table 1. The study cohort comprised 143 patients, resulting in the examination of 150 hips. Among all patients, 24 patients had unilateral ONFH, and 119 patients had bilateral ONFH, of which 112 patients with bilateral ONFH included only one side because the contralateral side was in stage III or stage IV. In terms of disease staging, 22 hips were classified as stage I and 128 hips as stage II. The cohort was predominantly male, with 114 males and 29 females, and the average age was 44 years, ranging from 18 to 73 years.

Table 1 The Baseline characteristics and demographics of study participants

Variable	Outcome	
Mean age, years (range)	44 (18–73)	
Gender, n (%)		
 Male	114 (79.7%)	
 Female	29 (29.3%)	
ARCO stage, n (%)		
 I	22 (14.7%)	
 II	128 (85.3%)	
Lateral, n (%)		
 Unilateral	24 (16.8%)	
 Bilateral	119 (83.2%)	

In 150 hips, the mean lesion volume constituted 15.07 ± 11.98% of the total femoral head volume, spanning from a minimal 0.25% to a substantial 61.66%. In 135 hips, the largest volume of lesions was predominantly localized in region I, where the mean proportion of lesion volume accounted for 6.93%±3.09% of the femoral head. Besides, regions III and V showed a higher proportion of lesion volume (Table 2).

Table 2 Proportions of lesion volume across different regions of the femoral head

Region	Lesion proportion (Mean ± SD, %)	
I	6.96 ± 3.13%	
II	0.81 ± 1.73%	
III	3.09 ± 2.78%	
IV	0.19 ± 0.74%	
V	2.84 ± 3.20%	
VI	0.49 ± 1.37%	
VII	0.61 ± 1.53%	
VIII	0.08 ± 0.41%	

The hips were categorized into seven groups (Table 3). Comparative analysis of lesion volumes across different groups yielded the following results (Fig. 3). Significant differences in lesion volumes within regions I, III, and V were observed between groups 1 and 2, and between groups 2 and 3. In regions I, II, III, V, and VII, significant differences in lesion volumes were noted between groups 3 and 4, and between groups 4 and 5. For regions II, IV, V, VI, and VII, significant differences in lesion volumes were detected between groups 5 and 6, and between groups 6 and 7, while regions I and III showed no significant differences when comparing these same groups. Region VIII only showed significant differences between groups 6 and 7.

Table 3 Grouping results based on lesion volume

Group	Outcome	Lesions with the largest proportion	
		Region I	Region III	Region V	
1	27	25	1	1	
2	41	37	3	1	
3	24	23	1	0	
4	21	21	0	0	
5	12	11	1	0	
6	8	7	1	0	
7	17	11	0	6	
Total, n (%)	150	135(90%)	7(4.7%)	8(5.3%)	

Fig. 3 Lesion size comparison by groups for regions I-VIII

The sizes of necrotic lesions across eight regions were compared between adjacent groups

Lesion distribution patterns were analyzed using three-dimensional mapping. In groups 1, 2, and 3, lesions involved regions I, II, III, V, and VII (Fig. 4). In group 1, lesions were primarily concentrated in region I, adjacent to the cortical bone. Group 2 showed that the concentrated area of lesions occupied most of region I and extended into regions III and V. In group 3, lesions were still primarily concentrated in region I but also extended partially into regions III and V. For groups 4, 5, and 6, lesions involved regions I, II, III, IV, V, VI, and VII (Fig. 5). In group 4, the concentrated area of lesions nearly occupied the entirety of region I and extended further into regions III and V, reaching the edges of regions II and VII. In group 5, the main concentration of lesions covered all of region I, most of regions III and V, and further extended into regions II and VII. In group 6, the concentrated area of lesions covered all of region I, most of regions III and V, extended into regions II and VII, and reached the boundary of region VI. In group 7, lesions were distributed across all eight regions, while the densest area of lesions nearly covered all of regions I, III, and V, most of regions II and VII, and part of region VI (Fig. 6).

Fig. 4 Three-dimensional mapping of lesions with small volume (< 5%, 5–10%, 10–15%)

Three-dimensional mapping views of the distribution areas of the lesions in each group, including medial(a), anterior (b), posterior (c), and top (d) views

Fig. 5 Three-dimensional mapping of lesions with medium volume (15–20%, 20–25%, 25–30%)

Three-dimensional mapping views of the distribution areas of the lesions in each group, including medial(a), anterior (b), posterior (c), and top (d) views

Fig. 6 Three-dimensional mapping of lesions with large volume (> 30%)

Three-dimensional mapping views of the distribution areas of the lesions in each group, including medial(a), anterior (b), posterior (c), and top (d) views

Discussion

The exploration of the relationship between the size of necrotic lesions and their spatial distribution within the femoral head is a crucial yet insufficiently examined aspect of ONFH research. In this study, necrotic volumes were predominantly localized to the anterosuperior regions in 135 of the 150 examined hips, aligning with prior research that frequently identifies the anterosuperior or anterolateral regions as the most commonly affected areas [15–17]. Nevertheless, the variability in descriptions from previous studies can lead to questions regarding the credibility of these findings. This discrepancy may arise from methodological differences, with some researchers utilizing axial slices of CT or MRI techniques and others employing coronal slices. Additionally, these results are often impacted by factors such as patient positioning and the surgeon’s experience. In this study, we utilized a novel three-dimensional mapping technique, initially developed for complex fractures, to more intuitively and accurately visualize the areas of necrotic lesions and assess their concentration.

This phenomenon, wherein necrosis predominantly affects the anterosuperior region of the femoral head, is often ascribed to the substantial weight-bearing role of this area [18–22]. Furthermore, Zaino and his colleagues examined ten femoral heads using a computer-assisted microscope and found lower bone quality in the anterior hemisphere [23]. They linked this to the significant peak loads resulting from the acetabulum’s continuous oscillation between covering and uncovering this region. Additionally, Bae and his colleagues mapped the contact pressure distribution on the surface of the femoral head using pressure-sensitive film, identifying the highest sensitivity in the anterior area, with subsequent high sensitivity in the superior and inferior areas [24]. In this study, we observed significantly larger lesion volumes in the anterosuperior, anteromedial, and posterosuperior regions and found the concentrated areas of lesions were localized in these regions. These results suggest that the distribution of lesions within the femoral head may align with the surface pressure distribution as described in the study by Bae et al.

Multiple classification systems for osteonecrosis of the femoral head have been developed; however, no universally accepted classification method exists [25]. In previous studies, the University of Pennsylvania classification was considered quantitative but measured lesions at their maximum size, potentially exaggerating the extent of necrosis [11, 26]. Similarly, the classification by the Japanese Investigation Committee, which is based on the central coronal section of T1-weighted images or the anteroposterior x-ray view, may be subject to bias from variations in the selection of mid-coronal images [27]. In our study, lesions involving less than 15% of the femoral head were concentrated in the anterosuperior, anteromedial, and posterosuperior regions. When lesion volume exceeded 15%, the concentrated area could unevenly involve the anterolateral, posteromedial, and other regions. The purpose of this study was not to propose a new classification system. However, the distribution patterns varied significantly with size, prompting a reevaluation of how lesions are classified and suggesting new directions for classification based on detailed lesion size and location.

Femoral head collapse is a critical event in the progression of ONFH. Previous researches demonstrated that hips with lesions in the anterosuperior region are susceptible to collapse, even if the lesions are small or medium-sized [28, 29]. In our study, we similarly observed that smaller lesions tend to concentrate in the anterosuperior region, which requires particular attention during treatment. Core decompression remains an effective strategy for delaying or preventing disease progression by reducing intraosseous hypertension and promoting femoral head repair [30, 31]. Based on our findings, it is recommended that surgeons target the area near the apex of the femoral head during decompression for small to medium-sized lesions. For larger lesions, particularly those involving the anteromedial and posterosuperior regions, the target should shift to areas further from the subchondral bone to ensure the removal of a greater volume of necrotic bone. However, the current range of decompression using a reamer may not adequately cover the dome-shaped areas where necrosis is concentrated. This limitation indicates the need for developing surgical instruments with adjustable tips that can reach specific regions in the future. Despite its benefits, core decompression could carry inherent risks such as femoral neck isthmus injuries and bone defects, which could potentially lead to stress concentration and femoral failure [9, 24, 32, 33]. To address these challenges, various strategies have been developed, such as the use of 3D-printed guide plates and robotic navigation systems to improve the precision of decompression techniques [34, 35]. Zhang and colleagues have also developed a framework for the automatic planning of drilling paths in core decompression surgery [36]. Building on the findings of this study, employing computer-assisted simulations to optimize and guide the placement trajectory for individualized patients may offer a more effective solution.

Finite element analysis (FEA) stands as a crucial instrument in the field of orthopedic research. However, the lack of standardized criteria for simulating various necrotic lesions in FEA studies of ONFH has led to the employment of diverse methods across different studies. For instance, Shi et al. utilized conical shapes centered in the femoral head to represent necrotic lesions, whereas another study depicted early-stage lesions with a necrosis angle of 100° in the mid-coronal and mid-sagittal planes [21, 37]. In contrast, Lutz employed the Kerboul combined necrosis angle of 90° for lesion simulation [38]. This inconsistency might raise concerns about the comparability and reliability of FEA outcomes. Despite the considerable variability in lesion distribution observed, specific patterns emerge in the concentrated areas. According to this study, in smaller lesions, the concentrated area is initially confined to the anterosuperior regions. In contrast, larger lesions expand unevenly into the anteromedial, posterosuperior, and other regions. Building on our findings, future biomechanical studies can achieve more reliable and comparable results across institutions by accurately simulating various necrotic lesions.

There were some limitations to this study. First, this study was conducted at a single center with a relatively small sample size, resulting in varying group sizes that may have influenced the results. Second, CT imaging faces challenges in accurately delineating necrotic lesion boundaries, particularly in the presence of bone marrow edema. Although 3D MRI demonstrates provides superior accuracy in evaluating lesion volume [39], obtaining specialized software and thin-layer images remains a substantial challenge. Additionally, the proposed modeling technique requires time and expertise from orthopedic surgeons. Future studies should incorporate more advanced stages and multi-center data to validate and extend the applicability of these findings, thereby enhancing their utility in preoperative planning.

Conclusion

This study combined lesion size and location to elucidate common distribution patterns of necrotic lesions using three-dimensional mapping techniques. The distribution of necrotic lesions varies with lesion size, with smaller lesions primarily concentrated in the anterior and medial regions of the femoral head, particularly in the anterosuperior region. In larger lesions, the concentrated areas expand to the lateral and inferior regions of the femoral head. These distribution patterns may supplement existing classification systems, enhancing observer consistency in clinical research. Further research is needed to evaluate their reliability and potential to guide hip-preserving surgical planning and approaches.

Acknowledgements

I would like to thank all authors for help and support in the process of data analysis and article writing.

Author contributions

ZY and CW developed the idea. AW and YY wrote an initial draft of the manuscript. AW and LJ were responsible for data collection. AW and YY wrote the final version of the manuscript. All authors read and approved the final manuscript.

Funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. The Major Science and Technology Special Project of Xinjiang Uygur Autonomous Region (Grant No. 2022A03011); Centre Guiding Local Science and Technology Development Fund Project (Science and Technology Innovation Base Project) (Grant No. 236Z7754G).

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

This article does not contain any studies with human participants or animals performed by any of the authors. This study received approval from the Institutional Review Board (IRB) of the Third Hospital of Hebei Medical University. Informed consent was obtained from all individual participants included in the study. All methods were performed in accordance with the Declarations of Helsinki.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Abbreviations

ONFH Osteonecrosis of femoral head

FEA Finite element analysis

CT Computed tomography

MRI Magnetic resonance imaging

PACS Picture Archiving and Communication System

KNN K-nearest neighbors

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Wen An and Yanjiang Yang authors contributed equally to this work.
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