Serial Changes in Graft Diameter Following Anterior Cruciate Ligament Reconstruction Using Allograft

Abstract

Background

To evaluate the serial changes in graft diameter during the 2 years following anterior cruciate ligament (ACL) reconstruction using serial magnetic resonance imaging (MRI).

Methods

This study involved 38 patients (38 knees) who underwent arthroscopic ACL reconstruction and had MRI immediately after surgery, at 1 year, and at 2 years. Graft diameter was measured at the distal, middle, and proximal levels of the intra-articular length, selecting the sagittal MRI slice that optimally showed the graft at each level. Correlation analysis was performed to identify the relationship between the difference of each graft diameter and demographic data and postoperative assessment results.

Results

Post hoc analysis over time showed substantial thickening from the immediate postoperative to the 1-year scan (distal, +3.098 mm; middle, +3.284 mm; proximal, +3.074 mm; all P < 0.001), a modest but significant reduction from 1 to 2 years (distal, −0.749 mm; middle, −0.699 mm; proximal, −0.574 mm; all P < 0.001), and persistent enlargement at 2 years compared with those at baseline (distal, +2.348 mm; middle, +2.586 mm; proximal, +2.499 mm; all P < 0.001). Regarding the correlation analyses, the graft diameter measurements at the proximal, middle, and distal sites across the 3 different time points were not significantly correlated with the postoperative results.

Conclusion

The graft diameter demonstrated a unimodal peak at 1 year postoperatively, followed by a gradual decrease until 2 years; however, it remained thicker at 2 years than immediately after surgery. These changes were not correlated with postoperative patients’ reported outcomes and stability.

Keywords

anterior cruciate ligament graft diameter serial change magnetic resonance image

Introduction

Several factors influence the success of anterior cruciate ligament (ACL) reconstruction.^1
-3 These include modifiable surgical variables such as graft selection, femoral drilling techniques, and graft fixation methods. In addition, non-modifiable biological healing processes, such as graft ligamentization or incorporation, play a crucial role in surgical outcomes. These biological processes undergo serial time-dependent changes, usually referred to as graft healing.^4,5

Magnetic resonance imaging (MRI) remains the only non-invasive and objective tool for observing these temporal changes in vivo.^6,7 Therefore, MRI has been used to evaluate graft changes following ACL reconstruction, primarily focusing on alterations in signal intensity.^8
-11 However, studies on the changes in graft diameter, a parameter closely related to the mechanical properties of the graft, are limited.^12,13 Moreover, the few reports on graft diameter focused on a single postoperative time point, rather than considering serial changes within the same patient over time. In addition to revealing the biological healing phases of the graft, understanding the time-dependent changes in graft diameter following ACL reconstruction has clinical relevance in guiding postoperative rehabilitation protocols.¹⁴ Moreover, few studies have investigated the impact of changes in graft diameter on clinical outcomes or stability.

Therefore, we aimed to evaluate (1) the serial changes in graft diameter during the 2 years following ACL reconstruction using serial MRI and (2) the relationship between changes in graft diameter and postoperative results. It was hypothesized that the diameter of the ACL graft undergoes serial change over time following ACL reconstruction.

Materials and Methods

Study Participants

This study included patients who underwent arthroscopic ACL reconstruction at a single institution between 2015 and 2025. The inclusion criteria were a diagnosis with complete ACL rupture via MRI or arthroscopic examination, a history of ACL reconstruction with the allogenic tibialis anterior tendon, and a >24-month follow-up. The exclusion criteria were a combined meniscus injury requiring meniscectomy or repair, multiple ligament reconstruction, ACL remnant-preservation, revisional ACL reconstruction, and unavailability of radiographic (MRI) or clinical data. A total of 363 patients underwent ACL reconstruction during the study, among whom 305 received allografts. After applying the exclusion criteria, 38 patients (38 knees) were enrolled.

Surgical Technique and Postoperative Management

All procedures were performed by the senior author (D.-H.L.). After detailed counseling regarding the advantages and disadvantages of autografts versus allografts, patients selected their preferred graft. In this study, all surgeries were performed using allografts. Low-dose gamma-irradiated tibialis anterior allografts (Resource Tissue Bank, Seoul, Korea) were used in this series.

Standard arthroscopic portals, including anterolateral, anteromedial, far anteromedial, and superolateral portals, were established. A systematic diagnostic arthroscopy was performed to evaluate the patellofemoral joint, medial compartment, intercondylar notch, and lateral compartment. The femoral tunnel was created through the transanteromedial technique using the far anteromedial portal as the working portal.¹⁵ After the debridement of the torn ACL remnant, the anatomic femoral footprint was identified, and a guide pin was inserted with the knee flexed to 120°. Following the tunnel length measurement, a femoral socket was prepared. The tibial tunnel was subsequently created from the medial tibial cortex to the native ACL footprint using a standard ACL guide.

All grafts were prepared as double-stranded constructs with a uniform diameter of 9 mm. Femoral fixation was achieved with a suspensory device (EndoButton, Smith & Nephew, Andover, MA), while hybrid fixation combining intra-tunnel aperture and extracortical suspensory fixation was performed on the tibial side.¹⁶

Postoperative rehabilitation was standardized. Crutch-assisted partial weightbearing ambulation was started on postoperative day 1, with progression to full weight bearing at 6 weeks. Range of motion exercises commenced on the second postoperative day and were allowed up to 120° of flexion for the first 6 weeks. A functional brace was applied for 6 weeks. Straight-leg raises, quadriceps setting, and ankle pump exercises began on the first postoperative day. Closed-kinetic chain exercises were introduced at week 6, and return to sports was permitted approximately 9 months postoperatively, depending on individual recovery.

Clinical and Radiographic Assessments

Demographic data, including age, sex, and body mass index, were obtained ( Table 1 ). Postoperative outcomes, including KT-2000 arthrometer, Lysholm score,¹⁷ and International Knee Documentation Committee (IKDC) subjective score,¹⁸ were evaluated at 2 years postoperatively. Regarding the KT-2000 arthrometer measurements, the side-to-side differences between the operated and contralateral knees at 30 lb were used for analysis.

Table 1.

Preoperative Demographic Data of the Patients.

Demographic data	Overall (n = 38)
Age (years)	30.7 ± 11.1 (17-60)
Sex: male, female (n)	25, 13
Site of injury: right, left (n) Body mass index (kg/m²)	20, 18 25.4 ± 3.8 (18.7-35.1)

Results reported as mean ± standard deviation (SD).

Conventional MRI with a 1.5-T magnet MRI unit (Magnetom Vision; Siemens, Erlangen, Germany) was used to evaluate the ACL graft status at 3 post-ACL reconstruction time points, namely immediately postoperation, at 1 year, and at 2 years. The following MRI protocols were used: sagittal T2-weighted and proton-density weighted (PDW) fast spin-echo (SE), T1-weighted SE, coronal PDW fast SE, and axial fat-saturated gradient-echo images. The parameters included a repetition time (TR)/echo time (TE) of 2,760 ms/15 ms for PDW images, a TR/TE of 3,900/105 ms for T2-weighted images, a TR/TE of 530/12 ms for T1-weighted images, and a TR/TE/flip angle (FA) of 700 ms/18 ms/20° for gradient-echo images, with 1 echo train length, 3-mm slice thickness, 0.6- to 0.9-mm intervals, a 512 × 512 matrix, a scan time of 4 min and 18 to 23 seconds, and a 16-cm field of view. Because of the patients’ residential location, there were 12 outside MRI studies, which also included T1-, T2-, and PDW-sagittal sequences. All images were reviewed by at least 2 musculoskeletal radiologists in consensus.

The MRI evaluation focused on the width of the ACL graft from the sagittal view. The intra-articular length of the ACL graft was divided into the distal, middle, and proximal sites to analyze the graft dimension. On coronal MRI, the graft trajectory was identified and used to locate the corresponding sagittal planes intersecting the intra-articular tibial aperture, the mid-graft segment visualized on the coronal plane, and the intra-articular femoral aperture. The graft diameter was measured on each of these sagittal images, yielding distal (tibial aperture), middle (mid-segment), and proximal (femoral aperture) diameters ( Fig. 1 ).

Figure 1.

Measurement of graft diameters on the magnetic resonance imaging (MRI) sagittal views. Graft diameters were measured at 3 points (left: proximal, center: middle, right: distal).

All radiographic parameters were measured twice by 2 orthopedic surgeons, with a minimum of a 4-week interval between each measurement, using a picture archiving and communication system (Centricity PACS Viewer; GE Healthcare, Little Chalfont, UK). Intraclass correlation coefficients (ICCs) were used to determine the intra- and inter-observer reliabilities. The inter- and intra-observer ICCs of the graft diameters are presented in Table 2 . All of the ICCs showed good agreement (>0.8).

Table 2.

Intraclass Correlation Coefficients of Inter- and Intra-observer Errors in Assessing Graft Sagittal Diameters on MRI.

Measurements	Interobserver	Intraobserver
Measurements	Interobserver	1	2
Proximal diameter at immediate postoperation	0.887	0.922	0.902
Middle diameter at immediate postoperation	0.854	0.866	0.912
Distal diameter at immediate postoperation	0.864	0.843	0.866
Proximal diameter at 1 year	0.832	0.892	0.887
Middle diameter at 1 year	0.822	0.906	0.91
Distal diameter at 1 year	0.843	0.864	0.924
Proximal diameter at 2 years	0.892	0.924	0.903
Middle diameter at 2 years	0.891	0.836	0.886
Distal diameter at 2 years	0.879	0.918	0.923

Statistical Analysis

An a priori power analysis was performed to determine the sample size using a 2-sided hypothesis test at an alpha level of 0.05 and a power of 0.8. A pilot study of 5 knees revealed that the 32 knees were required to detect a 4-mm difference in the graft diameters from the immediate to the 1-year postoperative period. The current study involved 38 knees, indicating adequate power (0.897) to detect a significant difference between the 2 evaluations.

Repeated-measures analysis of variance was used to evaluate time-dependent changes in ACL graft diameters. This method considered outcome measurements over time and correlated them with successive outcomes. Post hoc Bonferroni tests were used to determine its significant difference at each time point. Pearson’s correlation analysis was performed to identify the relationship between the difference of each graft diameter and demographic data and postoperative assessment results, including KT-2000 arthrometer, Lysholm score, and IKDC subjective score. All data were analyzed using SPSS version 27.0 (IBM, Armonk, NY). Statistical significance was set at P < 0.05.

Results

Among the 38 patients, the mean ACL graft sagittal diameters for the distal, middle, and proximal sites measured 7.35 ± 0.84, 7.48 ± 0.83, and 7.38 ± 0.87 mm on the immediate postoperative MRI, 10.44 ± 1.24, 10.76 ± 1.27, and 10.47 ± 1.13 mm at 1 year, and 9.69 ± 1.53, 10.06 ± 1.53, and 9.88 ± 1.20 mm at 2 years, respectively. In the statistical analyses, mean values differed significantly across time points for all intra-articular locations (all P < 0.001, Table 3 ).

Table 3.

Mean Values of Measured Anterior Cruciate Ligament Graft Sagittal Diameters Differed Significantly Across Time Points for All Intra-Articular Locations.

	Immediate	At 1 year	At 2 years	P-value
Proximal	7.38 ± 0.87^a	10.47 ± 1.13^a	9.88 ± 1.20^a	<0.001
Middle	7.48 ± 0.83^a	10.76 ± 1.27^a	10.06 ± 1.53^a	<0.001
Distal	7.35 ± 0.84^a	10.44 ± 1.24^a	9.69 ± 1.53^a	<0.001

Mean ± standard deviation (SD).

In addition, pairwise comparisons demonstrated substantial thickening from the immediate postoperative to the 1-year scan (distal, +3.098 mm; middle, +3.284 mm; proximal, +3.074 mm; all P < 0.001), a modest but significant reduction from 1 to 2 years (distal, −0.749 mm; middle, −0.699 mm; proximal, −0.574 mm; all P < 0.001), and persistent enlargement at 2 years compared with those at baseline (distal, +2.348 mm; middle, +2.586 mm; proximal, +2.499 mm; all P < 0.001, Table 4 ).

Table 4.

Mean Differences in Graft Sagittal Diameters (Distal, Middle, and Proximal) Among 3 Postoperative Follow-up Periods.

Distal			95% Confidence interval
Distal	Mean difference	Standard error	Lower	Upper	P-value
Immediate vs. 1 year	3.098	0.225	2.534	3.662	<0.001*
Immediate vs. 2 years	2.348	0.284	1.636	3.06	<0.001*
1 year vs. 2 years	–0.749	0.155	–1.139	–0.36	<0.001*
Middle			95% Confidence interval
Middle	Mean difference	Standard error	Lower	Upper	P-value
Immediate vs. 1 year	3.284*	0.238	2.687	3.882	<0.001*
Immediate vs. 2 years	2.586*	0.293	1.850	3.322	<0.001*
1 year vs. 2 years	–0.699*	0.149	–1.073	–0.325	<0.001*
Proximal			95% Confidence interval
Proximal	Mean difference	Standard error	Lower	Upper	P-value
Immediate vs. 1 year	3.074*	0.215	2.535	3.612	<0.001*
Immediate vs. 2 years	2.499*	0.238	1.903	3.096	<0.001*
1 year vs. 2 years	–0.574*	0.124	–0.885	–0.263	<0.001*

Boldface text indicates a parameter that differed significantly between the 2 periods (P < 0.05).

These findings indicate that the graft diameter increased markedly within the first postoperative year and partially regressed by 2 years while remaining higher than the immediate postoperative values at each time point ( Fig. 2 ), demonstrating the graft remodeling process after ACL reconstruction ( Fig. 3 ).

Figure 2.

Mean average graft sagittal diameters at 3 postoperative follow-up periods. The mean graft sagittal diameters were measured immediately, at 1 year, and at 2 years following anterior cruciate ligament (ACL) reconstruction. The results indicated a consistent and significant increase over 1 year postoperatively. In addition, significant increases were observed at each interval: between immediately postoperation and 1 year postoperatively, as well as immediately postoperation and 2 years postoperatively. There was no significant difference between postoperative 1 and 2 years.

Figure 3.

Serial changes in a 23-year-old man after ACL reconstruction (A: proximal, B: middle, C: distal). MRI sagittal view and ACL graft diameter measured on MRI at each point sagittal (1⅓, immediately postoperation; 2⅓, 1 year postoperatively; 3⅓, 2 years postoperatively).

Regarding the correlation analyses, graft diameter differences of proximal, middle, and distal sites among 3 different time points were not significantly correlated with demographic data (age, sex, and body mass index), postoperative KT-2000, Lysholm score, and IKDC subjective score ( Table 5 ).

Table 5.

Pearson Correlation Analysis Between Graft Diameter Difference and Demographic Data Along With Postoperative Data Including KT-2000, Lysholm Score, and IKDC Subjective Score.

		Age30.7 ± 11.1^a		SexM: F, 25: 13^a		Body mass index25.4 ± 3.8^a		KT-20002.55 ± 1.46 mm^a		Lysholm score87.5 ± 10.2^a		IKDC subjective score81.1 ± 11.5^a
		Correlation coefficient	P-value	Correlation coefficient	P-value	Correlation coefficient	P-value	Correlation coefficient	P-value	Correlation coefficient	P-value	Correlation coefficient	P-value
Proximal diameter difference	Immediate to 1 year	0.092	0.581	–0.077	0.645	–0.074	0.661	0.35	0.835	–0.155	0.354	–0.009	0.958
	Immediate to 2 years	0.159	0.342	–0.13	0.436	0.143	0.391	0.006	0.972	–0.137	0.412	0.044	0.792
	1 year to 2 years	0.144	0.387	–0.116	0.488	0.102	0.412	–0.049	0.77	0.005	0.977	0.1	0.55
Middle diameter difference	Immediate to 1 year	0.202	0.225	–0.083	0.622	0.004	0.814	0.041	0.807	–0.196	0.239	–0.137	0.414
	Immediate to 2 years	0.211	0.204	–0.11	0.511	0.194	0.244	–0.091	0.589	–0.136	0.417	–0.104	0.534
	1 year to 2 years	0.092	0.581	–0.084	0.615	0.318	0.152	–0.244	0.14	0.046	0.785	–0.014	0.936
Distal diameter difference	Immediate to 1 year	0.16	0.336	0.01	0.952	0.045	0.79	0.108	0.519	–0.184	0.269	–0.074	0.659
	Immediate to 2 years	0.214	0.197	–0.094	0.575	0.217	0.19	–0.068	0.685	–0.148	0.375	0.093	0.58
	1 year to 2 years	0.159	0.341	–0.186	0.264	0.194	0.244	–0.28	0.18	–0.004	0.981	0.062	0.712

Mean ± standard deviation (SD).

Discussion

The most significant finding of this study was that the graft diameter increased by approximately 40% at 1 year postoperatively (reaching its peak) compared with the value immediately after ACL reconstruction using allograft and gradually decreased over time. However, even at 2 years postoperatively, the graft diameter remained approximately 30% greater than the immediate postoperative size. Graft diameter changes were not influenced by patients’ demographic data and were not correlated with postoperative results.

Although the exact mechanism underlying this phenomenon remains unclear, it may be explained within the time frame of the “graft remodeling” process, during which the intra-articular region of the tendon graft adapts to the new biomechanical environment and gradually transforms to resemble the native ACL.^4,5,19,20 Early postoperation, the middle portion of the graft undergoes inflammation-associated fibroblast necrosis (degenerative phase),^21
-25 followed by host cell invasion and neovascularization into the vacant space, inducing cellular proliferation (proliferation phase).^4,26,27 Subsequently, the collagen fibers within the extracellular matrix realign and increase in diameter, resulting in the progressive acquisition of mechanical properties and structural characteristics similar to those of the native ACL (ligamentization phase).^28,29 Animal models have indicated that this graft remodeling process spans approximately 1 year, with a unimodal peak in graft diameter occurring approximately 6 months postoperatively.⁵ Although the precise duration of this process in humans remains uncertain, previous human models suggest a consensus that graft remodeling requires at least 2 years.³⁰ Assuming that graft diameter, similar to the findings in animal models, exhibits a unimodal peak at the midpoint of the graft remodeling process, and considering that the remodeling period in humans is approximately 2 years; thus, the diameter would peak approximately 1 year postoperatively. Therefore, our observation that the graft diameter was largest at 1 year postoperatively, subsequently decreasing but remaining thicker than that immediately after surgery, may support this inference.

Menghini et al.¹³ evaluated postoperative changes in ACL graft diameter in 33 reconstructed knees using MRI. The ligament cross-sectional area (CSA) of the reconstructed graft was measured with commercial image processing software (Mimics, Materialise, Leuven, Belgium) at 6 months, 1 year, and 2 years postoperatively. Their results demonstrated a unimodal peak pattern, with the CSA being largest at 6 months and subsequently decreasing until 2 years after surgery. Although the timing of the unimodal peak in graft diameter reported in that study differs from that in our findings (6 months vs. 1 year), the overall temporal patterns are similar. In both studies, the ACL graft demonstrated a single unimodal peak during the remodeling process, followed by a gradual decrease in diameter over time. However, Menghini et al.¹³ used combined computer-simulated measurements with Mimics and custom MATLAB scripts (MathWorks). While these tools offer robust capabilities for 3-dimensional reconstruction, segmentation, and quantitative analysis, they have inherent clinical limitations. The process is highly operator-dependent, as manual segmentation and editing require substantial anatomical knowledge and technical expertise, and intra- and inter-observer variability may influence measurement consistency, particularly in borderline or anatomically complex cases.³¹ Furthermore, the workflow is labor-intensive and time-consuming, limiting its practicality in high-throughput clinical environments or large patient cohorts, and integration with standard hospital systems such as PACS or electronic medical record system remains limited, restricting seamless incorporation into routine clinical workflows.³² Moreover, Menghini et al.¹³ did not statistically validate the serial changes in graft diameter, namely the increase to a maximum at 6 months, followed by a decrease at 1 and 2 years postoperatively. In contrast, we directly measured graft diameter on postoperative MRI images, providing a simpler and more cost-effective method than computer-simulated calculations and thus more feasible for clinical application. Furthermore, our analysis demonstrated the serial changes in graft diameter from immediately after surgery to 1 and 2 years postoperatively, supported by statistical testing.

To further evaluate the clinical relevance of our findings, we analyzed the correlation between the serial changes in graft diameter and postoperative clinical outcomes, including the IKDC and Lysholm scores, as well as knee stability measured by the KT-2000 arthrometer. Our analysis revealed no significant correlation between the fluctuations in graft diameter and these functional or stability measures. These results suggest that the observed changes—specifically the unimodal peak at 1 year followed by a gradual decrease—represent the intrinsic biological ligamentization process rather than serving as a predictor of clinical performance. Therefore, the clinical significance of this study lies in confirming that the graft undergoes a specific, time-dependent maturation process for up to 2 years following ACL reconstruction with allografts. Such changes should be interpreted as a normal physiological response during graft remodeling rather than a pathological sign of graft failure or laxity.

In all patients, 9 mm tunnels were created in both the femur and tibia, and a 9 mm graft was prepared for ACL reconstruction. However, the proximal, middle, and distal graft diameters on immediate postoperative MRI were 7.38 mm, 7.48 mm, and 7.35 mm, respectively, which are smaller than the intraoperative 9 mm. This discrepancy is likely attributable to several factors. First, the graft was measured using a sagittal MRI view. Although the optimal view was selected for measurement, a single-plane assessment may not fully reflect the actual 3-dimensional thickness of the graft. Second, Lee et al.³³ observed that even when the tunnel and graft are reconstructed to the same size, the graft may occupy only a portion of the entire tunnel on postoperative MRI. This suggests that the visualized thickness of the ACL graft on MRI can appear thinner after reconstruction than during initial preparation. For these reasons, it is plausible that a 9-mm prepared graft would be measured as smaller than 9 mm on immediate postoperative MRI.

Rehabilitation therapy might be a significant factor influencing graft maturation following ACL reconstruction. Bhullar et al.³⁴ reported in a meta-analysis that variables such as weightbearing status, brace type, range of motion, and initial muscle-strengthening exercises affect tunnel widening; however, their study did not identify any specific rehabilitation method as being superior in preventing such widening. Similar to tunnel widening, we think it is difficult to know which rehabilitation factors are related to graft diameter change. In the present study, crutch-assisted partial weightbearing ambulation was initiated on postoperative day 1, and range of motion exercises commenced on the second postoperative day, allowing up to 120° of flexion for the first 6 weeks. In addition, a functional brace was applied for 6 weeks, and closed-kinetic chain exercises were introduced at week 6. Due to the standardized nature of our protocol, it is difficult to determine from this study whether variations in rehabilitation therapy directly influence graft diameter changes; therefore, further comparative studies on this topic are warranted in the future.

Limitations

This study had some limitations. First, in the present study, we could not obtain MRI images during the 3- to 6-month postoperative period; therefore, changes in graft diameter during the degenerative and early proliferative phases could not be assessed. However, most previous studies have reported that the graft diameter peaks at approximately 1 year postoperatively, and our findings similarly demonstrated a unimodal peak at the 1-year follow-up.^10,12,13 Therefore, it is likely that graft thickness at 3 to 6 months after surgery would have increased compared with that at the immediate postoperative state; however, it would be less than that observed at 1 year. Second, ACL reconstruction in this study was performed using the anteromedial femoral tunnel technique with femoral suspensory fixation and a tibialis anterior allograft. Hence, the findings may not be generalized to all other surgical approaches, fixation methods, or graft choices. Third, this study was conducted as a single-center, single-surgeon series, which may limit the generalizability of the findings to different clinical settings. However, this design allowed for high procedural consistency and minimized potential confounding factors related to variability in surgical technique. Fourth, the graft diameter was measured exclusively using a sagittal MRI cut. Due to the oblique orientation of the reconstructed ACL, it was challenging to visualize and measure the entire graft length in the coronal plane; therefore, coronal measurements were not performed. Consequently, only measuring on a sagittal MRI cut may not fully reflect the 3-dimensional morphology or the complete cross-sectional area of the graft. Nevertheless, we believe that assessment via the sagittal plane is sufficient for monitoring the overall status of the graft. Given the substantial serial changes in diameter observed in this study, it is unlikely that the primary findings would differ significantly from those obtained through 3-dimensional measurements.

Conclusion

Footnotes

ORCID iD

Dae-Hee Lee

Ethical Considerations

The protocol used to evaluate radiographic findings and intraoperative navigation data was approved by our institutional review board (SMC2022-05-056).

Consent for Publication

Patients signed informed consent regarding publishing their data.

Author Contributions

J.-S.Y. contributed to the conception and design, acquisition or analysis of data, interpretation of data, and drafting of the article. S.-S.L. contributed to the interpretation of data, drafting of the article, and critical revision of the article. D-H.L. contributed to the acquisition or analysis of data, conception and design, and revision of the article for important intellectual content. All authors have read and approved the final submitted manuscript.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

The data sets analyzed during the current study are available from the corresponding author upon reasonable request.

Informed Consent

Informed consent was waived due to its retrospective nature.

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