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Optimal measurement method for anterior instability on stress radiographs in anterior cruciate ligament tear: Considering the effect of static anterior tibial subluxation
Optimizing Anterior Instability Measurement in ACL Tears
Han Joo Hyung Conceptualization Investigation Methodology Software Visualization Writing – original draft Writing – review & editing 1
Choi Chong-Hyuk Conceptualization Writing – original draft Writing – review & editing 2 3
Jung Min Conceptualization Writing – original draft Writing – review & editing 2 3
Chung Kwangho Validation Writing – original draft Writing – review & editing 2 4
Kim Sungjun Conceptualization Methodology Project administration Writing – original draft Writing – review & editing 5
Ha Taeho Data curation Formal analysis Writing – original draft Writing – review & editing 3
https://orcid.org/0000-0001-5743-6241
Kim Sung-Hwan Conceptualization Formal analysis Supervision Validation Writing – original draft Writing – review & editing 2 3 *
1 Yonsei University College of Medicine, Seoul, Republic of Korea
2 Arthroscopy and Joint Research Institute, Yonsei University College of Medicine, Seoul, Republic of Korea
3 Department of Orthopedic Surgery, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
4 Department of Orthopedic Surgery, Yongin Severance Hospital, Yonsei University College of Medicine, Yongin, Republic of Korea
5 Department of Radiology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
Badr Ismail Tawfeek Abdelaziz Editor
Menoufia University, EGYPT
Competing Interests: The authors have declared that no competing interests exist.

* E-mail: orthohwan@gmail.com
17 9 2024
2024
19 9 e031042820 2 2024
30 8 2024
© 2024 Han et al
2024
Han et al
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Introduction

Accurate assessment of anterior cruciate ligament (ACL) function is vital for guiding treatment. Nevertheless, the presence of tibial subluxation in the neutral position of a patient with an ACL injury may potentially introduce a confounding factor. This study aims to investigate whether tibial subluxation in the neutral position affects the diagnosis of anterior instability in patients with ACL injuries, potentially impacting the reliability and diagnostic accuracy of stress radiography.

Methods

This study included 88 patients: 30 with acute complete ACL tears (acute group), 28 with chronic complete ACL tears (chronic group), and 30 patients who underwent knee arthroscopic surgery other than ACL reconstruction (control group). Side-to-side differences (SSD) in stress radiography were measured using the Telos load status and the SSD of the gap between the Telos load and unload statuses. Diagnostic accuracy of the two methods was assessed using areas under the receiver operating characteristic curves (AUCs).

Results

The load SSD (5.92 ± 5.28 mm) was higher than the load-unload SSD (4.27 ± 5.99 mm) in the chronic group (P = 0.017). The load SSD demonstrated a significantly higher diagnostic value than that of the load-unload SSD in the combined group (AUC = 0.920 vs. 0.830; P = 0.012) and chronic group (AUC = 0.913 vs. 0.754; P = 0.002). After adjusting the symptoms for radiographic duration from 6 to 3 months in the chronic group, the load SSD exhibited a significantly higher diagnostic value (AUC = 0.902) than that of the load-unload SSD (AUC = 0.740; P < 0.001).

Conclusion

The load SSD provides superior diagnostic accuracy compared to the load-unload SSD in ACL tear cases, where static anterior tibial subluxation may result in false negatives. Although load-unload SSD may have diagnostic value within the first 3 months post-injury, the load SSD method provides a reliable assessment of ACL function for patients beyond this timeframe.

The author(s) received no specific funding for this work. Data AvailabilityAll relevant data are within the manuscript and its Supporting Information files.
Data Availability

All relevant data are within the manuscript and its Supporting Information files.
==== Body
pmcIntroduction

Evaluation of anterior cruciate ligament (ACL) function is crucial in determining the appropriate treatment for ACL injuries [1–5] and plays a significant role in post-treatment management, particularly in determining the patient’s ability to return to their pre-injury activity level [6–8]. While physical examination and patient questionnaires are important for assessing ACL function, there is a need for an objective and quantifiable evaluation tool to ensure more accurate and consistent assessments. Stress radiography using instruments such as Telos and KT-2000 arthrometers has traditionally been employed [9–12], with the recent widespread adoption of the GNRB arthrometer [13, 14].

Among these methods, stress radiography using Telos offers advantages in terms of cost-effectiveness and availability as well as providing a universal and objective assessment of ligamentous knee injuries [15–21]. However, it has some drawbacks, including difficulties in identifying reliable anatomical landmarks and potential errors owing to variations in knee positioning on the Telos device, which can affect the reliability and validity of the measurements [22]. In the measurement of anterior instability using stress radiography, a common approach in clinical practice with the Telos device is to measure the displacement of the tibia under load only [17, 23, 24].

The initial identification of static anterior tibial subluxation following an ACL injury was first proposed by Almekinders et al. [25] This phenomenon refers to the abnormal static alignment between the femur and tibia observed on radiographs taken with the knee extended in individuals with insufficient ACL function [26, 27]. Subsequent investigations have shown that this subluxation cannot be reduced and that the normal relationship between the tibia and femur is not restored even after ACL reconstruction [28]. It has been recognized as a significant concern as it can lead to non-anatomic positioning of the tibial tunnel during ACL reconstruction and potentially impact future clinical outcomes [29, 30].

As mentioned above, static anterior tibial subluxation following ACL injury emphasizes the abnormal association between the tibia and femur in individuals with ACL insufficiency. Consequently, static-predisposed tibial subluxation is believed to be a potential confounding factor in the assessment of anterior instability using stress radiography. This raises concerns regarding the reliability of stress radiography as a diagnostic tool.

Preceding studies have noted the necessity of understanding the anterior translation of both the affected and contralateral joints. Joint laxity and the absolute value of anterior translation in each individual joint can influence side-to-side difference (SSD) measurements, thereby affecting the diagnostic process [31, 32]. Furthermore, the degree of anterior translation correlates with the prognosis of conservative treatment for partial ACL ruptures, as well as influencing surgical outcomes through anterior translation in the contralateral knee [33, 34]. Considering these aspects, the need for a measurement method that considers anterior subluxation in both joints for assessing anterior instability becomes evident.

Therefore, the purpose of this study was to investigate whether static-predisposed tibial subluxation should be considered for the accurate diagnosis of anterior laxity in patients with ACL injury. Specifically, we aimed to compare the diagnostic accuracy of the method we attempted (measuring the difference between the load and unload positions) that reflects tibial subluxation, and the standard method (measuring only the displacement under the load position) to determine the optimal measurement approach for stress radiographs. Additionally, we sought to examine whether there were variations in the diagnostic performance of these two methods based on the chronicity of ACL rupture.

Materials and methods

This retrospective review included 456 patients who underwent arthroscopic knee surgery at a single tertiary center between January 2020 and January 2022. The study protocol was approved by our Institutional Review Board (IRB 2022-1146-001). The need for obtaining informed consent from participants was waived by the IRB due to the nature of the study involving the analysis of anonymized medical records and archived samples.

The medical records and archived samples for this retrospective study were accessed for research purposes on February 1, 2023. This date marks the initiation of data collection and analysis for the current investigation. To uphold the principles of patient confidentiality and privacy, strict measures were implemented to ensure that the authors did not have access to information that could identify individual participants during or after data collection.

The inclusion criteria for this study were as follows: patients aged > 18 years; patients confirmed to have an acute or chronic complete ACL rupture on MRI; patients with greater than grade II instability on the Lachman and pivot shift tests, which indicated the need for ACL reconstruction due to ACL insufficiency; and patients with a complete ACL rupture confirmed intraoperatively during ACL reconstruction using arthroscopy. The exclusion criteria were as follows: previous surgical history of the affected knee; stiff knee or limited range of motion due to pain; requiring revisional ACL reconstruction; radiographic osteoarthritis of Kellgren-Lawrence grade 2 or higher; concomitant injuries to other ligaments in the affected knee; and concomitant meniscal tears involving displaced portions that caused locking symptoms or the door-stopper phenomenon, such as bucket handle or root tears.

Fifty-eight patients underwent ACL reconstruction and were categorized into two groups based on the criteria commonly used in previous studies [35]: the acute group, which included patients who underwent radiographic imaging within 6 months of injury, and the chronic group, which included patients who underwent radiographic imaging > 6 months after injury. The remaining 340 patients underwent surgeries other than ACL reconstruction.

Ultimately, 30 and 28 patients were enrolled in the acute and chronic treatment groups, respectively. A flow diagram of this study is shown in Fig 1. The control group was adjusted using propensity score matching with variables such as age, sex, BMI, and generalized laxity instead of randomization because this study’s retrospective design. There were no significant differences in any of the variables related to patient characteristics (Table 1).

10.1371/journal.pone.0310428.g001 Fig 1 Flow diagram of this study.

ACL, anterior cruciate ligament; MRI, magnetic resonance imaging; ROM, range of motion; BMI, body mass index.

10.1371/journal.pone.0310428.t001 Table 1 Summary of the demographic data between the groups.

	Acute group (n = 30)	Chronic group (n = 28)	Control group	
	Before matching (n = 340)	P value	After matching (n = 28)	P value	
Age, y	32.3 ± 13.8	32.4 ± 12.3	46.3 ± 17.8	<0.001*	32.7 ± 12.2	0.807	
Sex, n (%)				<0.001*		0.467	
Male	27 (90.0%)	22 (78.5%)	189 (55.5%)		25 (89.2%)		
Female	3 (10.0%)	6 (21.4%)	151 (44.5%)		3 (10.7%)		
BMI, kg/m2	24.5 ± 3.2	25.4 ± 4	26.1 ± 3.6	0.032*	25.0 ± 3.1	0.593	
General laxity score	1.5 ± 1.9	1.7 ± 2	0.4 ± 0.9	<0.001*	1.1 ± 1.9	0.335	
*: P < 0.05

Trained and licensed radiographers performed preoperative stress radiographs of both knees using a Telos® device (Telos GmbH® Laubscher, Holstein, Switzerland) at 150 N. The patient was placed in the lateral decubitus position with the knee flexed at approximately 30° (Fig 2A). A pressure plate was positioned at the mid-calf level and counter-bearings were placed at the ankle joint level and approximately 5 cm above the patella. Radiographic measurements were performed using Picture Archiving and Communication System (GE Healthcare, Chicago, IL, USA).

10.1371/journal.pone.0310428.g002 Fig 2 Patient positioning and anterior instability measurement methods.

(a) shows the patient’s position during imaging. The patient was placed in the lateral decubitus position with the knee flexed at approximately 30°. A pressure plate was positioned at the mid-calf level, and counter-bearings were placed at the ankle joint level and approximately 5 cm above the patella. (b) shows the measurement using the load method, and (c) shows the measurement using the load-unload method. Perpendicular lines were drawn tangentially from the reference line to the most posterior contour of the medial femoral condyle (F) and the most posterior contour of the medial tibial plateau (T). The center-to-center method was used.

A reference line parallel to the medial tibial plateau joint line was used to determine the measurements. Perpendicular lines were drawn tangentially from the reference line to the most posterior contour of the medial femoral condyle and the most posterior contour of the medial tibial plateau [36, 37]. For the SSD measurements, we employed the center-to-center measurement method using the bone landmarks described above (Fig 2B and 2C). This involved subtracting the value in the unloaded neutral posture from the value in the loaded condition, which is the load-unload method. For the load method, the SSD was calculated while the knee was loaded. These measurements were repeated with a two-week interval by two different orthopedic surgeons. The SSD grading criteria for subgroup analysis were as follows: grade I, < 5 mm translation; grade II, 5–10 mm translation; and grade III, > 10 mm translation [38]. The diagnostic accuracies of both methods were assessed by calculating the area under the receiver operating characteristic (ROC) curve.

Statistical analysis included the following procedures: continuous variables were analyzed using one-way ANOVA, categorical variables were assessed using Fisher’s exact test, DeLong’s test was employed to compare the two ROC curves, and subgroup analysis of SSD was conducted using paired t-tests, Fisher’s exact tests, and chi-square tests. Statistical significance was set at P < .05. Inter- and intra-observer reliabilities were determined using intraclass correlation coefficients (ICCs).

The sample size for this study was calculated based on previous research with the following conditions: the area under curve (AUC) value of 0.8, a two-tailed α error of 5% and a power (1-β) of 80% was used [39–41]. As a result, a total of 28 patients per group were determined to be the required sample size. All statistical analyses were performed using the R software (version 4.2.1; R Foundation, Vienna, Austria), and data visualization was performed using the ggplot2 package (v3.4.2; Wickham, 2016).

Results

In the chronic group, the load SSD (5.92 ± 5.28 mm) was significantly higher than the load-unload SSD (4.27 ± 5.99 mm) (P = 0.017) (Table 2 and Fig 3). No significant difference was observed in the load SSD (5.86 ± 4.14 mm, -0.67 ± 3.17 mm) and load-unload SSD (5.97 ± 4.16 mm, -0.54 ± 3.96 mm) of the acute and control groups, respectively. Subgroup analyses within each group yielded similar proportions of instability grades. The intra- and inter-observer reliabilities for the radiologic measurements were good to excellent, with an ICC of 0.826 to 0.937.

10.1371/journal.pone.0310428.g003 Fig 3 Box plot of SSD measured using the load and load-unload methods for each group.

In the chronic group, the load SSD was significantly higher than the load-unload SSD. However, no significant difference was observed between the acute and control groups. *: P < 0.05.

10.1371/journal.pone.0310428.t002 Table 2 Side-to-side difference (mean ± standard deviation) and proportion of instability grade between groups.

	Acute Group (n = 30)	Chronic Group (n = 28)	Control Group (n = 28)	
	Load SSD	Load-unload	P value	Load SSD	Load-unload	P value	Load SSD	Load-unload	P value	
SSD (mm)	5.86 ± 4.14	5.97 ± 4.16	0.862	5.92 ± 5.28	4.27 ± 5.99	0.017*	-0.67 ± 3.17	-0.54 ± 3.96	0.863	
Grade I	17 (56.7%)	10 (33.3%)	0.101	17 (60.7%)	18 (64.3%)		27 (96.4%)	27 (96.4%)		
Grade II	8 (26.7%)	16 (53.3%)	6 (21.4%)	6 (21.4%)	0.933	1 (3.6%)	1 (3.6%)	1	
Grade III	5 (16.7%)	4 (13.3%)	5 (17.8%)	4 (14.3%)		0 (0.0%)	0 (0.0%)		
SSD, side-to-side difference

*: P < 0.05

ROC curve analysis was performed for the acute, chronic, and newly formed combined group consisting of both groups, representing the entire ACL rupture patient population. Patients in each group were categorized as cases, whereas those in the control group were designated as controls. The objective of this analysis was to compare the diagnostic performance of load SSD and load-unload SSD as methods for diagnosing cases.

The load SSD (AUC = 0.920) demonstrated a significantly higher diagnostic value than the load-unload SSD (AUC = 0.830; P = 0.012) in the combined group (Fig 4). In the chronic group, the load SSD (AUC = 0.913) exhibited a significantly higher diagnostic value than the load-unload SSD (AUC = 0.754; P = 0.002). However, in the acute group, there was no significant difference between the load SSD (AUC = 0.926) and load-unload SSD (AUC = 0.901) (P = 0.528).

10.1371/journal.pone.0310428.g004 Fig 4 ROC curve analysis performed for the acute, chronic, and combined groups.

The symptom to radiograph duration, which served as the criterion for distinguishing between the acute and chronic groups, was set at 6 months. In the combined group and chronic group, the load SSD exhibited a significantly higher diagnostic value compared to the load-unload SSD. However, no significant difference was observed in the acute group. ROC, receiver operating characteristic; AUC, area under curve; *: P < 0.05.

ROC curve analysis yielded the optimal cutoff values for each group (Table 3). In the combined group, the optimal cutoffs were 5.370 mm for load SSD (specificity:0.893, sensitivity:0.845) and 4.470 mm for load-unload SSD (specificity:0.750, sensitivity:0.828). For the acute group, the optimal cutoffs were 5.612 mm for load SSD (specificity:0.893, sensitivity:0.867) and 4.616 mm for load-unload SSD (specificity:0.929, sensitivity:0.800). In the chronic group, the optimal cutoffs were 5.290 mm for load SSD (specificity:0.893, sensitivity:0.821) and 2.060 mm for the load-unload SSD (specificity:0.750, sensitivity:0.714). Notably, the cutoff value for load SSD remained relatively consistent between 5 and 6 mm between groups, whereas for load-unload SSD, it was 4.6 mm in the acute group and 2.06 mm in the chronic group.

10.1371/journal.pone.0310428.t003 Table 3 Optimal cutoffs and coordinates of the ROC curves.

Group	Method	AUC	P value	Optimal cutoff, mm	Sensitivity, %	Specificity, %	
Combined	Load	0.920	0.012*	5.37	0.845	0.893	
Load-unload	0.830	4.47	0.828	0.75	
Acute	Load	0.926	0.528	5.612	0.867	0.893	
Load-unload	0.901	4.616	0.8	0.929	
Chronic	Load	0.913	0.002*	5.29	0.821	0.893	
Load-unload	0.754	2.06	0.75	0.714	
ROC, receiver operating characteristic; AUC, area under the curve

*: P < 0.05

To assess the diagnostic performance difference, based on the varying cutoff of symptom to radiograph duration, between load and load-unload SSD in the chronic group, we examined the AUC and p-value using the DeLong test for each ROC curve (load and load-unload method) within a range of 7 days to 2 years (Fig 5). Based on the calculated AUC, there was a significant difference in diagnostic accuracy between the two testing methods across the entire range of investigated cutoffs in the chronic group. According to the DeLong test results, the difference in diagnostic accuracy between the two methods was maximized when cutoffs were applied within the range of 90 to 180 days.

10.1371/journal.pone.0310428.g005 Fig 5 AUC and p-value of DeLong test comparing each ROC curve (load and load-unload method applied on the chronic group) on varying symptom to radiograph duration applied to define chronic group, with a range of 7 days to 2 years.

The vertical dashed lines represent the respective cutoffs of 90 days and 180 days, and the horizontal dashed line indicates a p-value of 0.00001. The DeLong test results shows the maximized difference in diagnostic accuracy between the two methods within the symptom to radiograph duration range of 90 to 180 days.

Based on the above results, adjusting the reference interval from 6 to 3 months led to changes in the AUC (Fig 6). In the chronic group, load SSD showed a significantly higher diagnostic value (AUC = 0.902) than the load-unload SSD (AUC = 0.740; P < 0.001). However, in the acute group, no significant difference was observed between load SSD (AUC = 0.939) and load-unload SSD (AUC = 0.926) (P = 0.528). These findings suggest that when the reference interval was set at 3 months, the load SSD exhibited higher diagnostic power and a more pronounced difference in diagnostic performance between the methods, particularly in the chronic group.

10.1371/journal.pone.0310428.g006 Fig 6 ROC curve analysis performed for the adjusted symptom to radiograph duration of 3 months based on the Delong test results above.

In the combined and chronic groups, the load SSD exhibited a significantly higher diagnostic value compared to the load-unload SSD and no significant difference was observed in the acute group. The results exhibited a similar trend to when the symptom to radiograph duration was set at 6 months, but a larger difference in diagnostic performance was observed in the chronic group. ROC, receiver operating characteristic; AUC, area under curve; *: P < 0.05.

Discussion

The diagnostic accuracy of the ACL rupture diagnosis, as indicated by the AUC, revealed that the load SSD (AUC = 0.913) demonstrated a significantly higher diagnostic value than the load–unload SSD (AUC = 0.754; P = 0.002) in the chronic group. In the case of chronic load-unload SSD, the SSD values sometimes appeared negative, which could be attributed to the influence of static anterior tibial subluxation. Because the measurements were based on the midpoints of the lateral and medial femoral condyles and the medial and lateral tibial plateaus on radiography, it is plausible that anterior tibial subluxation in the lateral compartment also affected the measurement values.

Mixed results have been reported regarding the relationship between fixed tibial subluxation and rupture chronicity in patients with ACL. Almekinders et al. [25] were the first to report fixed tibial subluxation, and their subsequent research claimed that osteoarthritic changes in chronically untreated ACL ruptures exacerbate fixed anterior subluxation [42]. However, McDonald et al. [29] conducted a comparison of tibial translation between acute and chronic groups to validate these findings, but no significant difference was found between the two groups. It is worth noting that McDonald et al.’s study defined the chronic group as patients who underwent knee imaging more than 12 months after an ACL tear, which differs from our study’s setting.

High-grade rotatory laxity accompanying ACL rupture results in anterior subluxation of the tibia in both the lateral and medial compartments as well as internal rotation observed on knee imaging [43]. Furthermore, it has been reported that a prolonged time from injury to surgery is a risk factor for high-grade rotatory laxity in chronic patients [44]. The use of radiographs taken in the lateral decubitus position minimizes the influence of gravity, allowing subluxation to persist in this position. Considering the findings of our and previous studies, it can be concluded that this positional adaptation, which is considered a manifestation of rotational instability, may be more pronounced in the chronic group.

The accuracy of the two methods did not differ in the acute group; however, unloading was clearly inaccurate in the chronic group. The cutoff value remained constant between 5 and 6 mm in load SSD, while in the case of load-unload, it was 4.6 mm in the acute group and 2.06 mm in the chronic group, which is a small value that can also be influenced by measurement errors typically reported to be around 1 mm or lower [17, 24]. Moreover, the cutoff value for SSD used in diagnosing ACL rupture is generally reported to be around 4 to 6 mm [1, 23, 45, 46], which differs from the values observed in the chronic group. Therefore, the relatively low diagnostic ability of load-unload SSD observed in the ROC curve, along with the low cutoff value mentioned above, indicates the difficulty of using load-unload SSD for diagnosis. As reported by Almekinders et al., [42] there is a tendency for anterior tibial subluxation in patients with chronic untreated ACL rupture. Static anterior tibial subluxation itself reduces the difference between the load and unload states of the affected knee, which seems to decrease the diagnostic ability of the load-unload method in the chronic group.

In terms of the chronicity of ACL rupture, as mentioned by DeLee et al. [47] there is no specific timeframe for surgical delay, and the physical condition of the patient should be considered rather than a predetermined waiting period when planning the surgical date. Due to this characteristic, the cutoffs used to distinguish between acute and chronic ACL ruptures vary between authors [35]. Some authors use symptom durations such as 6 weeks to 3 months, 6 months, and 12 months or more as cutoffs for chronic ACL ruptures [29, 44, 48–51].

Accordingly, in our study, we initially set the criteria for dividing acute and chronic cases at 6 months. To examine the difference in diagnostic accuracy between the two measurement methods in the chronic group, we conducted AUC and Delong tests by varying the cutoff values. We observed that the difference in diagnostic accuracy between the two methods was maximized when cutoffs were applied within a range of 90 to 180 days. Based on these results, when the reference interval was adjusted to 3 months, load SSD exhibited greater diagnostic power. While there are various criteria for defining chronic ACL rupture from the perspective of diagnosis using stress radiography, this study suggests a symptom duration of 3 months as the cutoff value.

In this study, we compared the method we attempted (measuring the difference between the load and unload positions) that reflects tibial subluxation with the standard method. As mentioned earlier, several other studies have addressed the implications of the anterior translation of both the affected and contralateral joints [31–34]. However, as demonstrated by the results of this study, the reliability of load-unload SSD is diminished in the chronic status. Therefore, careful consideration is necessary when interpreting the findings, and additional supplementary measurements are warranted to address this limitation.

The limitations of this study were as follows. First, the study had a retrospective design. Second, alternative measurement methods for assessing lateral rotational instability were not used. Further studies are needed to determine whether chronic ACL or anterolateral ligament (ALL) injury is the cause of subluxation. Third, this study was retrospective, and the control group consisted of patients who had undergone different types of knee arthroscopic surgery, rather than healthy subjects. It should be noted that not undergoing ACL reconstruction in the control group does not necessarily imply normal ACL function. Although there may have been patients with poor ACL function in the control group, this is unlikely considering the propensity score-matched average age and other demographics. Lastly, although there may have been issues with randomization in the study design, attempts were made to minimize selection bias through propensity score matching in the control group.

In conclusion, the measurement method for anterior instability using load SSD showed superior diagnostic accuracy compared to the load-unload SSD method, which is susceptible to false negatives owing to static anterior tibial subluxation in ACL tear cases. Within the first 3 months after injury, load-unloading may still provide some diagnostic value. However, for patients beyond this timeframe, an accurate assessment of ACL function can be achieved by comparing both sides using only stress radiographs in the loading state.

Supporting information

S1 File Datasets and R code used in this research.

(ZIP)

10.1371/journal.pone.0310428.r001
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Badr Ismail Tawfeek Abdelaziz Academic Editor
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https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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PONE-D-23-39613Optimal Measurement Method for Anterior Instability on Stress Radiographs in Anterior Cruciate Ligament Tear: Considering the Effect of Static Anterior Tibial SubluxationPLOS ONE

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The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: 1.It is possible that ACL injuries may be combined with other conditions, such as knee osteoarthritis and synovitis. It is therefore important to consider whether the patients enrolled in this study were excluded from the disturbances caused by these possible co-morbidities. Were the patients enrolled in this study with ACL confounders excluded?

2.Whether the two measurements mentioned in the paper, "the traditional load-unload method" and "the load method", are routine in clinical practice.

3.This is a retrospective study, the control group of 28 healthy patients was matched to 340 patients who underwent surgical procedures other than ACL reconstruction, did the surgical operations the patients underwent interfere with the results of this study? These patients also underwent the same assessment components as ACL patients, are these measurements also routine in the clinic?

4.This study concludes,“In conclusion, the measurement method for anterior instability using load SSD showed superior diagnostic accuracy compared to the load-unload SSD method, which is susceptible to false negatives owing to static anterior tibial subluxation in ACL tear cases”,does static anterior tibial subluxation also influence the diagnosis of anterior instability in patients with ACL injuries when using the load-unload SSD method?

Reviewer #2: Firstly, I want to congratulate the authors for the efforts to do this article. Althogut there are limitations, it has a good methodology that support its results. However, I have some considerations and suggestions.

Line 27: "...and 28 healthy patients (control group)". However, in Figure 1, I have observed 30 patients in the control group

Line 92: "...486 patients". However, in Figure 1, I have observed 456 patients

Line 121-126: I suggest you include a figure to better visualize the patient's position for the test. This way, it is easier to reproduce your study.

Conclusion

The purpose of the article in the abstract is "to investigate whether tibial subluxation in the neutral position affects

the diagnosis of anterior instability in patients with ACL injuries, potentially impacting the reliability and diagnostic accuracy of stress radiography". I suggest that you include a clearer answer to this question in your discussion and conclusion.

**********

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Reviewer #1: No

Reviewer #2: No

**********

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Attachment Submitted filename: review.docx

10.1371/journal.pone.0310428.r002
Author response to Decision Letter 0
Submission Version1
8 Jul 2024

We are grateful for the effort that the reviewer has put into the review process. Thanks to the detailed comments provided by the reviewer, we were able to advocate our argument for this paper with improved logical progression. Additionally, in terms of format, we were able to revise the entire manuscript to be more concise and clearer, which has allowed us to convey our conclusion more effectively. Our responses to the reviewer are provided below. Thank you again for your valuable feedback.

GENERAL

Reviewer #1:

1. It is possible that ACL injuries may be combined with other conditions, such as knee osteoarthritis and synovitis. It is therefore important to consider whether the patients enrolled in this study were excluded from the disturbances caused by these possible co-morbidities. Were the patients enrolled in this study with ACL confounders excluded?

-> In this study, factors that could act as confounding variables in measuring anterior instability due to ACL rupture—such as previous surgical history of the affected knee, stiff knee or limited range of motion due to pain, concomitant injuries to other ligaments in the affected knee, and concomitant meniscal tears involving displaced portions—were set as the exclusion criteria.

(Revised page #5/lines 106-111)

As suggested by the reviewer, we also considered osteoarthritis as a factor influencing the patient's symptoms and added it to the exclusion criteria, subsequently reviewing the patients again. The reviewer's advice was very helpful in setting the factors that could influence the interpretation of the results, and we are grateful for that.

(Revised page #5/lines 108-109)

2. Whether the two measurements mentioned in the paper, "the traditional load-unload method" and "the load method", are routine in clinical practice.

-> In the measurement of anterior instability using stress radiography, a common approach in clinical practice with the Telos device is to measure the displacement of the tibia under load only, which we have referred to as the “load method" in this study. This method is routine in clinical practice.

However, static-predisposed tibial subluxation is believed to be a potential confounding factor in the assessment of anterior instability using stress radiography. Therefore, in contrast, the “load-unload method" is the method we attempted, which measures the difference between the load and unload positions (page #4/lines 87-90). This method was used to take into account the degree of tibial subluxation. We have revised the introduction to provide a clearer explanation of these two methods.

(Revised page #3/lines 58-61)

(Revised page #6/lines 135)

3.This is a retrospective study, the control group of 28 healthy patients was matched to 340 patients who underwent surgical procedures other than ACL reconstruction, did the surgical operations the patients underwent interfere with the results of this study? These patients also underwent the same assessment components as ACL patients, are these measurements also routine in the clinic?

-> As you pointed out, this study was retrospective, and the control group consisted of patients who had undergone different types of knee arthroscopic surgery rather than healthy subjects. The measurements used in this study were conducted before surgery, so the operations themselves did not interfere with the results. However, the preoperative diagnoses could have influenced the outcomes. Therefore, it should be noted that not undergoing ACL reconstruction in the control group does not necessarily imply normal ACL function.

To minimize differences in ACL function influenced by factors such as average age and other demographics, we performed propensity score matching. Consequently, considering the average age, we believe the concern is minimal. We have added these points to the limitations.

The measurements used in this study are routinely conducted with the same protocol for patients undergoing knee arthroscopic surgery at the institution where this research was carried out. Therefore, we believe there is little concern regarding the differences in measurement methods among patients included in this study, including the control group.

These points are important limitations of the study and should be addressed in future research with new designs. We appreciate the reviewer's comments, which allowed us to add this interpretation to the manuscript. Thank you for your valuable feedback.

(Revised page #10/lines 253-266)

4.This study concludes, “In conclusion, the measurement method for anterior instability using load SSD showed superior diagnostic accuracy compared to the load-unload SSD method, which is susceptible to false negatives owing to static anterior tibial subluxation in ACL tear cases”, does static anterior tibial subluxation also influence the diagnosis of anterior instability in patients with ACL injuries when using the load-unload SSD method?

-> To explain the conclusion of this study, it is crucial to understand how much static anterior tibial subluxation influences the diagnostic ability of the load-unload SSD method. As reported by Almekinders et al.,[1] there is a tendency for anterior tibial subluxation in patients with chronic untreated ACL rupture.

Static anterior tibial subluxation itself reduces the difference between the load and unload states of the affected knee, which seems to decrease the diagnostic ability of the load-unload method in the chronic group. Consequently, while the influence on diagnostic ability for acute injuries is small, static anterior tibial subluxation appears to significantly reduce the diagnostic ability of the load-unload method for chronic injuries.

This point has been added to the discussion, and thanks to the reviewer's comment, we were able to include an important argument to support the conclusion of this study. We appreciate this input.

(Revised page #9/lines 234-235)

Reviewer #2:

Firstly, I want to congratulate the authors for the efforts to do this article. Although there are limitations, it has a good methodology that support its results. However, I have some considerations and suggestions.

Line 27: "...and 28 healthy patients (control group)". However, in Figure 1, I have observed 30 patients in the control group

-> The control group consisted of 30 patients, and the content has been corrected.

(Revised page #2/lines 26-28)

Line 92: "...486 patients". However, in Figure 1, I have observed 456 patients

-> As you pointed out, 456 patients is correct. The content has been corrected in Figure 1.

(Revised Figure 1)

Line 121-126: I suggest you include a figure to better visualize the patient's position for the test. This way, it is easier to reproduce your study.

-> A photo of the actual imaging process has been added to visualize the patient's position for the test.

(Revised Figure 2)

Conclusion
The purpose of the article in the abstract is "to investigate whether tibial subluxation in the neutral position affects
the diagnosis of anterior instability in patients with ACL injuries, potentially impacting the reliability and diagnostic accuracy of stress radiography". I suggest that you include a clearer answer to this question in your discussion and conclusion.

-> As you pointed out, there was a lack of detailed information on how tibial subluxation in the neutral position affects the diagnosis of anterior instability. Almekinders et al.[1] reported that patients with chronic untreated ACL rupture tend to have anterior tibial subluxation. This static anterior tibial subluxation reduces the difference between the load and unload states of the affected knee, which appears to decrease the diagnostic accuracy of the load-unload method in the chronic group. We have added the above content to the discussion to provide a clearer answer on the impact of tibial subluxation.

(Revised page #9/lines 225-230)

The main message of this study was the comparison of the two methods for measuring anterior instability, so this content has been left in the conclusion. Your comments have greatly helped us draw a clear conclusion that aligns with the stated purpose of the paper. Additionally, your detailed feedback allowed us to correct some errors in the manuscript. Thank you for your valuable input.

References

1. Almekinders LC, Pandarinath R, Rahusen FT. Knee stability following anterior cruciate ligament rupture and surgery. The contribution of irreducible tibial subluxation. J Bone Joint Surg Am. 2004;86(5):983-7. doi: 10.2106/00004623-200405000-00014. PubMed PMID: 15118041.

Attachment Submitted filename: loading_laxity_reviewer_answer_0707.docx

10.1371/journal.pone.0310428.r003
Decision Letter 1
Badr Ismail Tawfeek Abdelaziz Academic Editor
© 2024 Ismail Tawfeek Abdelaziz Badr
2024
Ismail Tawfeek Abdelaziz Badr
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submission Version1
13 Aug 2024

PONE-D-23-39613R1Optimal Measurement Method for Anterior Instability on Stress Radiographs in Anterior Cruciate Ligament Tear: Considering the Effect of Static Anterior Tibial SubluxationPLOS ONE

Dear Dr. Kim,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Sep 27 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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Ismail Tawfeek Abdelaziz Badr, M.D.

Academic Editor

PLOS ONE

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Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Comments to the Author

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Reviewer #1: All comments have been addressed

Reviewer #3: (No Response)

Reviewer #4: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: N/A

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #3: This is the second version of this manuscript that was resubmitted after considering the comments of previous 2 Reviewers. The article is about comparing 2 radiological methods for diagnosing the anterior instability in patients with ACL injuries using the Telos device: The load side to side difference (SSD) and the load unload (SSD). The authors found that the load SSD method has a higher diagnostic value specially in chronic cases. They aue this for the static anterior translation occurs in patients with chronic ACL Injuries.

The authors considered all comments of the previous reviewers and modified the article accordingly in a positive way; Yet there are still improvement potential in the article as follows :

• Lines 26-28 (Abstract): the authors included 30 patients in acute group, 28 Patients in the chronic group and 30 patients in the control group. The sum should be 88 not 86 as the authors mentioned.

• Line 90: the authors mentioned that they reviewed 486 patients operated in the their center to choose the included patients, but in the flow chart (Figure 1) they mentioned that the reviewed patients were 456 patients. Please unify this number.

• Line 252: the authors mentioned the abbreviation ALL. Please write it formal because it was not mentioned previously in the . I suppose they mean the anterolateral ligament.

Reviewer #4: Thank you very much for allowing me to review your manuscript. I appreciate the effort you have made performing this study and submitting it to plos one. I think this is appropriate for publishing.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #3: Yes: Ayman F. AbdelKawi

Reviewer #4: No

**********

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While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

10.1371/journal.pone.0310428.r004
Author response to Decision Letter 1
Submission Version2
14 Aug 2024

We are grateful for the effort that the reviewer has put into the review process. Thanks to the detailed comments provided by the reviewer, we were able to correct the remaining typographical errors in this paper and further improve its overall quality. Our responses to the reviewer are provided below. Thank you again for your valuable feedback.

GENERAL

Reviewer #1: (No Response)

Reviewer #3: This is the second version of this manuscript that was resubmitted after considering the comments of previous 2 Reviewers. The article is about comparing 2 radiological methods for diagnosing the anterior instability in patients with ACL injuries using the Telos device: The load side to side difference (SSD) and the load unload (SSD). The authors found that the load SSD method has a higher diagnostic value specially in chronic cases. They aue this for the static anterior translation occurs in patients with chronic ACL Injuries.

The authors considered all comments of the previous reviewers and modified the article accordingly in a positive way; Yet there are still improvement potential in the article as follows :

Lines 26-28 (Abstract): the authors included 30 patients in acute group, 28 Patients in the chronic group and 30 patients in the control group. The sum should be 88 not 86 as the authors mentioned.

-> We have corrected this number to 88.

(Revised page #2/lines 26)

Line 90: the authors mentioned that they reviewed 486 patients operated in the their center to choose the included patients, but in the flow chart (Figure 1) they mentioned that the reviewed patients were 456 patients. Please unify this number.

-> The correct number is 456 patients. We have revised the text accordingly.

(Revised page #4/lines 91)

Line 252: the authors mentioned the abbreviation ALL. Please write it formal because it was not mentioned previously in the . I suppose they mean the anterolateral ligament.

-> We intended to refer to the anterolateral ligament. We have revised the text to include both the full term and the abbreviation.

(Revised page #10/lines 254)

Reviewer #4: Thank you very much for allowing me to review your manuscript. I appreciate the effort you have made performing this study and submitting it to plos one. I think this is appropriate for publishing.

Attachment Submitted filename: loading_laxity_reviewer_answer_0814.docx

10.1371/journal.pone.0310428.r005
Decision Letter 2
Badr Ismail Tawfeek Abdelaziz Academic Editor
© 2024 Ismail Tawfeek Abdelaziz Badr
2024
Ismail Tawfeek Abdelaziz Badr
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submission Version2
2 Sep 2024

Optimal Measurement Method for Anterior Instability on Stress Radiographs in Anterior Cruciate Ligament Tear: Considering the Effect of Static Anterior Tibial Subluxation

PONE-D-23-39613R2

Dear Dr. Kim,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Ismail Tawfeek Abdelaziz Badr, M.D.

Academic Editor

PLOS ONE

**********

10.1371/journal.pone.0310428.r006
Acceptance letter
Badr Ismail Tawfeek Abdelaziz Academic Editor
© 2024 Ismail Tawfeek Abdelaziz Badr
2024
Ismail Tawfeek Abdelaziz Badr
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
5 Sep 2024

PONE-D-23-39613R2

PLOS ONE

Dear Dr. Kim,

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now being handed over to our production team.

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on behalf of

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Academic Editor

PLOS ONE
==== Refs
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2 Kim SH , Jung YB , Song MK , al e. Comparison of double-bundle anterior cruciate ligament (ACL) reconstruction and single-bundle reconstruction with remnant pull-out suture. Knee Surg Sports Traumatol Arthrosc. 2014;22 :2085–93. doi: 10.1007/s00167-013-2619-4 23892438
3 Sundararajan SR , Ramakanth R , Jha AK , Rajasekaran S . Outside-in technique versus inside-out semitendinosus graft harvest technique in ACLR: a randomised control trial. Knee Surg Relat Res. 2022;34 (1 ):16. Epub 20220328. doi: 10.1186/s43019-022-00144-4 ; PubMed Central PMCID: PMC8962090.35346395
4 Chung KS , Kim JH , Kong DH , Park I , Kim JG , Ha JK . An Increasing Trend in the Number of Anterior Cruciate Ligament Reconstruction in Korea: A Nationwide Epidemiologic Study. Clin Orthop Surg. 2022;14 (2 ):220–6. Epub 20211124. doi: 10.4055/cios20276 ; PubMed Central PMCID: PMC9152897.35685966
5 Pontoh LA , Dilogo IH , Kholinne E , Fiolin J , Efar TS . The Role of Lateral Retinacular Release in Preventing Patellofemoral Malalignment in Double-Bundle Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial. Clin Orthop Surg. 2022;14 (3 ):393–400. Epub 20220330. doi: 10.4055/cios20295 ; PubMed Central PMCID: PMC9393287.36061844
6 Meer BLv , Oei EH , Bierma-Zeinstra SM , al e. Are magnetic resonance imaging recovery and laxity improvement possible after anterior cruciate ligament rupture in nonoperative treatment? Arthroscopy. 2014;30 :1092–9. doi: 10.1016/j.arthro.2014.04.098 24951134
7 Schurz M , Tiefenboeck TM , Winnisch M , al e. Clinical and functional outcome of all-inside anterior cruciate ligament reconstruction at a minimum of 2 years’ follow-up. Arthroscopy. 2016;32 :332–7. doi: 10.1016/j.arthro.2015.08.014 26603826
8 Helito CP , da Silva AGM , Guimarães TM , Sobrado MF , Pécora JR , Camanho GL . Functional results of multiple revision anterior cruciate ligament with anterolateral tibial tunnel associated with anterolateral ligament reconstruction. Knee Surg Relat Res. 2022;34 (1 ):24. Epub 20220508. doi: 10.1186/s43019-022-00153-3 ; PubMed Central PMCID: PMC9082885.35527316
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10 Wiertsema SH , van Hooff HJ , Migchelsen LA , Steultjens MP . Reliability of the KT1000 arthrometer and the Lachman test in patients with an ACL rupture. Knee. 2008;15 (2 ):107–10. Epub 20080208. doi: 10.1016/j.knee.2008.01.003 .18261913
11 Hiranaka T , Furuhashi R , Takashiba K , Kodama T , Michishita K , Inui H , et al . Agreement and accuracy of radiographic assessment using a decision aid for medial Oxford partial knee replacement: multicentre study. Knee Surg Relat Res. 2022;34 (1 ):13. Epub 20220314. doi: 10.1186/s43019-022-00140-8 ; PubMed Central PMCID: PMC8919622.35287754
12 Yoon HK , Park SH , Oh HC , Ha JW , Choi H . Combined PCL and PLC Reconstruction Improves Residual Laxity in PCL Injury Patients with Posterolateral Knee Laxity Less Than Grade III. Yonsei Med J. 2023;64 (5 ):313–9. doi: 10.3349/ymj.2022.0487 ; PubMed Central PMCID: PMC10151226.37114634
13 Saravia A , Cabrera S , Molina CR , Pacheco L , Muñoz G . Validity of the Genourob arthrometer in the evaluation of total thickness tears of anterior cruciate ligament. J Orthop. 2020;22 :203–6. Epub 20200326. doi: 10.1016/j.jor.2020.03.041 ; PubMed Central PMCID: PMC7225585.32425418
14 Cojean T , Batailler C , Robert H , Cheze L . GNRB® laximeter with magnetic resonance imaging in clinical practice for complete and partial anterior cruciate ligament tears detection: A prospective diagnostic study with arthroscopic validation on 214 patients. Knee. 2023;42 :373–81. Epub 20230510. doi: 10.1016/j.knee.2023.03.017 .37172464
15 Panisset JC , Ntagiopoulos PG , Saggin PR , Dejour D . A comparison of Telos™ stress radiography versus Rolimeter™ in the diagnosis of different patterns of anterior cruciate ligament tears. Orthop Traumatol Surg Res. 2012;98 (7 ):751–8. Epub 20121011. doi: 10.1016/j.otsr.2012.07.003 .23063311
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