Abstract
Background
As a recently available arthrometer, the Ligs arthrometer has been gradually used in clinical practice to assess knee stability. However, its reliability has not been fully established in this regard. The aim of this study was to assess the intra-rater and inter-rater reliability of the Ligs arthrometer for measuring anterior tibial translation (ATT) and the corresponding side-to-side difference (SSD) in healthy subjects.
Methods
A total of 40 healthy male subjects were recruited for this study between June 2023 and September 2023. Three examiners with different levels of experience tested the subjects with the Ligs arthrometer for ATT and SSD measurements. ATT values for both knees and the corresponding SSD at 90 N, 120 N, and 150 N were recorded for analysis. Statistical significance was determined using Student’s t test or one-way analysis of variance (ANOVA). The intraclass correlation coefficient (ICC) was used to assess the intra-rater and inter-rater reliability of the Ligs arthrometer for ATT and SSD measurements.
Results
No subject asked to stop any test due to pain or discomfort. There was no significant difference among the three examiners in ATT measurements of the subjects’ ipsilateral knees and SSD measurements at the same load (P > 0.05 for all). Furthermore, ATT measurements for the subjects’ left and right knees measured by the same examiner were comparable (P > 0.05 for all). The Ligs arthrometer showed excellent intra-rater reliability (ICCs = 0.930–0.982) for ATT measurements and moderate to good intra-rater reliability (ICCs = 0.705–0.862) for SSD measurements. Similarly, its inter-rater reliability was excellent (ICCs = 0.911–0.930) for ATT measurements, but moderate (ICCs = 0.684–0.737) for SSD measurements.
Conclusion
The Ligs arthrometer had moderate to excellent intra-rater and inter-rater reliability for ATT and SSD measurements in healthy knees. As compared with ATT measurements, SSD measurements showed lower intra-rater and inter-rater reliability at the same load. It is recommended that the tests be performed by the same examiner when using the Ligs arthrometer for SSD measurements.
Keywords: Knee, Anterior cruciate ligament, Arthrometer, Anterior tibial translation, Side-to-side difference
Introduction
The anterior cruciate ligament (ACL) is the primary restraint against anterior tibial translation (ATT), which is vital for maintaining knee joint stability [1]. Orthopaedic surgeons can assess ACL integrity in the injured knee and postoperative knee stability after ACL reconstruction by measuring ATT. Physical examination is the most basic examination method for assessing knee stability, with the anterior drawer test and the Lachman test being commonly used to assess anterior knee stability [2, 3]. However, physical examination results are subjective and qualitative. In addition, these results are susceptible to examiner experience, muscle relaxation, and inherent knee laxity [4–6]. Therefore, classical physical examination has certain limitations in assessing knee stability.
In view of the diverse size, direction, and speed of applied force used by different clinicians during physical examinations, arthrometry has become a supplementary approach for objectively and quantitatively assessing knee stability [7]. In recent decades, a variety of knee arthrometers have been developed to measure ATT before and after surgery. As a reference standard for arthrometry in many studies, the KT-1000 (MEDmetric Corp., San Diego, CA, USA) is the earliest available and most widely used knee arthrometer in clinical practice. However, the reliability of the KT series has been equivocal in the literature, ranging from poor to excellent in healthy knees and ACL-deficient knees [4]. Moreover, the GNRB (Genourob, Laval, France) is a robotic arthrometer widely reported in the past decade, which features a computer-driven motor designed to eliminate the influence of manually applied forces on instrumental measurements. Although the literature generally indicates that the GNRB is more reliable than other devices, its reliability has still been questioned in individual studies [6, 8–12].
The Ligs arthrometer (Innomotion Inc., Shanghai, China) is a recently available arthrometer with digital, convenient, portable, and radiation-free characteristics. Although several studies have reported the application of the Ligs arthrometer in the measurement of ATT and confirmed its validity for the diagnosis of ACL tears, its reliability has not been fully established [13–15]. Given the diversity of testing protocols used in different studies, it is necessary to explore the intra-rater and inter-rater reliability of the Ligs arthrometer to understand the limitations of this device in measuring ATT and to explain the potential differences in the measurements between raters or studies [4].
Consequently, the aim of this study was to assess the intra-rater and inter-rater reliability of the Ligs arthrometer for measuring ATT and the corresponding side-to-side difference (SSD). We hypothesized that ATT measurements would have better intra-rater and inter-rater reliability than SSD measurements when using the Ligs arthrometer in healthy knees.
Materials and methods
This study was conducted in accordance with the Ethics Committee on Biomedical Research, West China Hospital of Sichuan University (No. 2023-279). All subjects signed an informed consent form in which they agreed to participate in the project.
Study participants
We recruited healthy subjects for this study according to the following inclusion criteria: (1) males, (2) aged between 18 and 45 years, and (3) intact ACLs in both knees. Subjects were excluded if they had (1) knee pain during the last three months, (2) generalized joint hypermobility, or (3) a history of knee trauma or surgery [5]. Finally, a total of 40 healthy male subjects were recruited and tested with the Ligs arthrometer between June 2023 and September 2023.
Arthrometer
The Ligs arthrometer is a portable device comprised of an adjustable fixing bracket and a mainframe with built-in load and displacement sensors. The push rod on the mainframe can provide a continuous forward load on the tibia from the rear of the lower leg to measure ATT (Fig. 1). To reduce the influence of soft-tissue effects, the digital sensors collect data on the real-time load and displacement with a sampling rate of 30 Hz and a precision of 1 N and 0.1 mm only when the applied load exceeds 20 N. Moreover, a load–displacement curve is automatically generated on the display screen as an auxiliary reference for the measurement [13, 14].
Fig. 1.
Composition of the Ligs arthrometer, including an adjustable fixing bracket and a mainframe with built-in load and displacement sensors
Examiners
A total of three examiners with different levels of experience performed the study protocol. Examiner 1 was a physical therapist with three years of experience using the Ligs arthrometer. Examiner 2 was a physical therapist with only one year of experience using the device. Examiner 3 was an orthopaedic surgeon with no practical experience in using any arthrometer. Before the study, regardless of their prior experience, all examiners uniformly received standardized training on device introduction, operation protocols, and limb positioning for the Ligs arthrometer. The criterion for passing the training was the successful validation that each examiner could independently complete the measurements on three healthy subjects [9].
Study protocol
Each subject was tested by three examiners on three separate days, and the sequence in which the examiners tested the subjects was randomized using the lottery method. First, the Ligs arthrometer was properly installed according to the manufacturer’s instructions. Next, the subject was positioned on a standard examination table in a lateral position with the knee joint in 30° flexion and neutral rotation. The examiner aligned the center of the push rod with the tibial tubercle and positioned the baffle of the upper fixing bracket to cover the inferior pole of the patella (Fig. 2). Before the test began, the subject was instructed to completely relax the lower limbs, and the condition of the hamstring muscles was checked by the examiner. Then, the examiner gradually applied an anterior load ranging from 0 N to 150 N to the subject with a thruster at a constant speed of 3 N/s, and the loading was stopped when the predefined alarm rang at 150 N. To reduce the risk of bias, the examiner was not allowed to read the collected data on the display screen during the test. The test sequence was the left knee followed by the right knee, and each knee was tested three consecutive times. Between each test, the subject was repositioned to ensure the same test conditions. The ATT for each knee and the corresponding SSD were recorded at 90 N, 120 N, and 150 N. In this study, the SSD was defined as the ATT on the right side minus that on the left side. All the measurements were recorded and calculated by independent analysts who remained blinded to the status of both the examiners and the subjects.
Fig. 2.
Device and subject positioning while using the Ligs arthrometer
Statistical analysis
Data analysis was performed with SPSS 26.0 software (IBM Corp., Armonk, New York, United States). The normality of the data distribution was assessed using the Shapiro‒Wilk test. Data with a normal distribution were analyzed by Student’s t test or one-way analysis of variance (ANOVA). The mean of each examiner’s three measurements for all subjects was calculated for the above analyses. The intraclass correlation coefficient (ICC) was used to assess the intra-rater and inter-rater reliability of the Ligs arthrometer for ATT and SSD measurements. Reliability was considered poor (ICC < 0.5), moderate (0.5 ≤ ICC < 0.75), good (0.75 ≤ ICC < 0.9), or excellent (ICC ≥ 0.9) [16]. The standard error of measurement (SEM) was calculated to assess the precision of the measurements [3, 17, 18]. Moreover, Bland‒Altman analysis was used to assess the agreement of SSD measurements between different examiners. A false positive was defined as an absolute value of the SSD > 3 mm [18]. Differences were considered to be significant at P < 0.05.
Results
The mean age of the subjects was 33.6 ± 5.2 years (range, 23‒42 years), and the mean body mass index (BMI) was 23.9 ± 1.3 kg/m2 (range, 20.4–26.1 kg/m2). No subject asked to stop any test due to pain or discomfort.
ATT and SSD measurements
The ATT and SSD measurements for the three examiners are presented in Table 1. One-way ANOVA revealed no significant differences among the examiners in ATT measurements of the subjects’ ipsilateral knees or in SSD measurements at the same load (Table 1).
Table 1.
Comparisons of ATT and SSD measurements among the examiners
| Examiner 1 | Examiner 2 | Examiner 3 | F | P value | |
|---|---|---|---|---|---|
| 90 N | |||||
| Left knee, mm | 12.59 ± 1.83 | 12.72 ± 2.16 | 12.45 ± 2.39 | 0.158 | 0.854 |
| Right knee, mm | 12.64 ± 1.78 | 12.89 ± 2.03 | 12.58 ± 1.85 | 0.293 | 0.747 |
| SSD, mm | 0.04 ± 0.68 | 0.17 ± 0.93 | 0.13 ± 1.42 | 0.142 | 0.868 |
| 120 N | |||||
| Left knee, mm | 14.60 ± 2.10 | 14.87 ± 2.42 | 14.60 ± 2.61 | 0.171 | 0.843 |
| Right knee, mm | 14.56 ± 2.06 | 14.90 ± 2.30 | 14.59 ± 2.12 | 0.309 | 0.735 |
| SSD, mm | −0.04 ± 0.83 | 0.03 ± 0.97 | −0.01 ± 1.55 | 0.038 | 0.963 |
| 150 N | |||||
| Left knee, mm | 16.15 ± 2.39 | 16.42 ± 2.78 | 16.05 ± 2.85 | 0.202 | 0.817 |
| Right knee, mm | 16.23 ± 2.33 | 16.50 ± 2.52 | 16.15 ± 2.41 | 0.220 | 0.803 |
| SSD, mm | 0.08 ± 0.93 | 0.08 ± 1.16 | 0.10 ± 1.67 | 0.003 | 0.997 |
Data are presented as mean ± standard deviation of three measurements by each examiner
ATT Anterior tibial translation, SSD Side-to-side difference
In addition, the results of ATT measurements for the subjects’ left and right knees measured by the same examiner were comparable at 90 N, 120 N, and 150 N, respectively (Table 2).
Table 2.
Comparisons of ATT measurements between the subjects’ left and right knees measured by the same examiner
| Left knee (mm) | Right knee (mm) | t | P value | |
|---|---|---|---|---|
| 90 N | ||||
| Examiner 1 | 12.59 ± 1.83 | 12.64 ± 1.78 | −0.107 | 0.915 |
| Examiner 2 | 12.72 ± 2.16 | 12.89 ± 2.03 | −0.352 | 0.726 |
| Examiner 3 | 12.45 ± 2.39 | 12.58 ± 1.85 | −0.276 | 0.784 |
| 120 N | ||||
| Examiner 1 | 14.60 ± 2.10 | 14.56 ± 2.06 | 0.082 | 0.935 |
| Examiner 2 | 14.87 ± 2.42 | 14.90 ± 2.30 | −0.062 | 0.951 |
| Examiner 3 | 14.60 ± 2.61 | 14.59 ± 2.12 | 0.023 | 0.981 |
| 150 N | ||||
| Examiner 1 | 16.15 ± 2.39 | 16.23 ± 2.33 | −0.158 | 0.875 |
| Examiner 2 | 16.42 ± 2.78 | 16.50 ± 2.52 | −0.129 | 0.897 |
| Examiner 3 | 16.05 ± 2.85 | 16.15 ± 2.41 | −0.169 | 0.866 |
Data are presented as mean ± standard deviation of each examiner’s three measurements
ATT Anterior tibial translation
Intra-rater reliability
The ICCs for intra-rater reliability are shown in Table 3. The Ligs arthrometer had excellent intra-rater reliability for ATT measurements (ICCs = 0.930–0.982). The two experienced examiners (examiners 1 and 2) showed slightly greater ICCs for intra-rater reliability than the beginner (examiner 3). For SSD measurements, the intra-rater reliability was moderate to good, with the ICCs ranging from 0.705 to 0.862. Specifically, examiner 3 had good intra-rater reliability, while examiners 1 and 2 both had moderate to good intra-rater reliability. However, the two experienced examiners (examiners 1 and 2) showed overall lower SEMs than the beginner (examiner 3) for both ATT and SSD measurements (Table 3).
Table 3.
Intra-rater reliability for ATT and SSD measurements among the examiners
| Left knee | Right knee | SSD | ||||||
|---|---|---|---|---|---|---|---|---|
| ICC (95% CI) | SEM | ICC (95% CI) | SEM | ICC (95% CI) | SEM | |||
| Examiner 1 | ||||||||
| 90 N | 0.982 (0.970–0.990) | 0.167 | 0.980 (0.966–0.988) | 0.162 | 0.811 (0.706–0.887) | 0.066 | ||
| 120 N | 0.975 (0.958–0.986) | 0.192 | 0.963 (0.939–0.979) | 0.189 | 0.740 (0.608–0.842) | 0.083 | ||
| 150 N | 0.978 (0.964–0.988) | 0.218 | 0.977 (0.962–0.987) | 0.214 | 0.819 (0.717–0.892) | 0.090 | ||
| Examiner 2 | ||||||||
| 90 N | 0.966 (0.943–0.981) | 0.198 | 0.949 (0.916–0.971) | 0.187 | 0.705 (0.561–0.818) | 0.094 | ||
| 120 N | 0.971 (0.952–0.984) | 0.221 | 0.965 (0.941–0.980) | 0.211 | 0.757 (0.631–0.853) | 0.097 | ||
| 150 N | 0.973 (0.949–0.984) | 0.254 | 0.957 (0.929–0.976) | 0.232 | 0.735 (0.600-0.838) | 0.116 | ||
| Examiner 3 | ||||||||
| 90 N | 0.954 (0.924–0.974) | 0.220 | 0.930 (0.885–0.960) | 0.172 | 0.837 (0.743–0.904) | 0.137 | ||
| 120 N | 0.961 (0.934–0.978) | 0.240 | 0.942 (0.904–0.967) | 0.197 | 0.842 (0.751–0.907) | 0.149 | ||
| 150 N | 0.970 (0.949–0.983) | 0.261 | 0.950 (0.918–0.972) | 0.223 | 0.862 (0.780–0.919) | 0.159 | ||
ATT Anterior tibial translation, SSD Side-to-side difference, ICC Intraclass correlation coefficient, SEM Standard error of measurement
Inter-rater reliability
The inter-rater reliability for ATT measurements was excellent, with the ICCs between 0.911 and 0.930 at 90 N, 120 N, and 150 N (Table 4). However, the ICCs for SSD measurements ranged from 0.684 to 0.737, indicating only moderate inter-rater reliability in this regard (Table 4). Furthermore, the SEMs for both ATT and SSD measurements among the examiners increased with higher applied loads (Table 4).
Table 4.
Inter-rater reliability for ATT and SSD measurements among the examiners
| Left knee | Right knee | SSD | ||||||
|---|---|---|---|---|---|---|---|---|
| ICC (95% CI) | SEM | ICC (95% CI) | SEM | ICC (95% CI) | SEM | |||
| 90 N | 0.920 (0.866–0.955) | 0.194 | 0.914 (0.854–0.951) | 0.171 | 0.692 (0.480–0.827) | 0.096 | ||
| 120 N | 0.922 (0.868–0.956) | 0.216 | 0.911 (0.850–0.950) | 0.196 | 0.684 (0.467–0.823) | 0.105 | ||
| 150 N | 0.930 (0.882–0.961) | 0.243 | 0.915 (0.856–0.952) | 0.220 | 0.737 (0.555–0.852) | 0.117 | ||
ATT Anterior tibial translation, SSD Side-to-side difference, ICC Intraclass correlation coefficient, SEM Standard error of measurement
Bland‒Altman analysis
The Bland‒Altman plots demonstrated that the majority of SSD measurements for healthy subjects between each pair of examiners fell within the 95% limits of agreement (LoA) at 90 N, 120 N, and 150 N, indicating an overall good agreement (Fig. 3).
Fig. 3.
Bland–Altman plots for the agreement of SSD measurements between each pair of examiners. (A-C) At 90 N. (D-F) At 120 N. (G-I) At 150 N
False positive rate
There were no false positive results for the tests performed by the two experienced examiners (examiners 1 and 2) in healthy subjects. In contrast, the false positive rates for the beginner (examiner 3) were 2.5% (one case) at 90 N, 2.5% (one case) at 120 N, and 7.5% (three cases) at 150 N (Table 5).
Table 5.
False positive rate in healthy subjects among the examiners
| False positive rate (%) | |||
|---|---|---|---|
| 90 N | 120 N | 150 N | |
| Examiner 1 | 0 | 0 | 0 |
| Examiner 2 | 0 | 0 | 0 |
| Examiner 3 | 2.5 | 2.5 | 7.5 |
Discussion
The most important finding of this study was that the intra-rater and inter-rater reliability of the Ligs arthrometer was moderate to excellent for ATT and SSD measurements in healthy knees. Furthermore, SSD measurements showed lower intra-rater and inter-rater reliability than ATT measurements at the same load.
Before the Ligs arthrometer became available, a variety of common knee arthrometers were developed and reported in the literature. Although the KT series has been the most commonly used and studied knee arthrometer since the 1980s, its reliability has long been questioned [19]. Overall, a review by Rohman et al. showed that the KT-1000 had good to excellent intra-rater reliability (ICCs = 0.83–0.97) and poor to excellent inter-rater reliability (ICCs = 0.41–0.92) in healthy knees. Nevertheless, the intra-rater and inter-rater reliability in ACL-deficient knees was more controversial, ranging from poor to excellent (ICCs = 0.47–0.99 and 0.14–0.92, respectively) [4]. In a recent study, Runer et al. further analyzed the reliability of the KT-1000 for different quantitative methods in healthy knees and found that it had good to excellent intra-rater reliability (ICCs = 0.77–0.94) and moderate inter-rater reliability (ICCs = 0.64–0.70) for ATT measurements, while the overall reliability for SSD measurements was inferior to that of ATT measurements, showing poor to moderate intra-rater reliability (ICCs = 0.35–0.77) and poor inter-rater reliability (ICCs = 0.16–0.38) [18].
As a popular robotic arthrometer, the GNRB has been suggested to be more reliable than other devices in several comparative studies, although the methods of reliability assessment used in the studies were not consistent [8–10]. However, few studies have reported different results when the reliability of the GNRB was assessed using the ICC method. On this point, Magdič et al. found that the GNRB had good intra-rater reliability for ATT measurements in healthy subjects, with the ICCs ranging from 0.756 to 0.848 [20]. In another study by Saravia et al., the intra-rater and inter-rater reliability of the GNRB in knees with complete ACL tears and healthy knees was excellent, with all of the ICCs greater than 0.98 [21]. In contrast, the findings of several other studies cast doubt on the reliability of the GNRB. In two separate studies by Vauhnik et al., the GNRB showed poor to moderate intra-rater reliability (ICCs = 0.338–0.786) and poor inter-rater reliability (ICCs = 0.220–0.424) for ATT measurements in healthy subjects [11, 12]. Furthermore, Mouarbes et al. tested 60 healthy knees and argued that the intra-rater reliability of the GNRB was poor for both ATT measurements (ICCs = 0.414–0.486) and SSD measurements (ICCs = 0.210–0.356) [6]. As a result, the reliability of the GNRB remains to be further confirmed in light of the above contradictory results.
In the present study, our results indicated that the intra-rater reliability of the Ligs arthrometer for ATT measurements in healthy subjects was excellent (ICCs = 0.930–0.982) for all examiners. In this regard, the experienced examiners showed slightly greater ICCs than the beginner for ATT measurements, with their SEMs overall lower than those of the latter. Interestingly, the intra-rater reliability for SSD measurements was moderate to good for the experienced examiners (ICCs = 0.705–0.819) and good for the beginner (ICCs = 0.837–0.862), which was inconsistent with the trend found in ATT measurements. Similarly, the study by Runer et al. explained the low ICCs and conflicting results between raters for SSD measurements in healthy subjects, attributing it to several factors, including statistical factors [18]. However, the SEM results still revealed that the experienced examiners had better precision in SSD measurements than the beginner. Overall, although ATT measurements were more reliable than SSD measurements, the Ligs arthrometer showed acceptable intra-rater reliability for both measurement methods.
For the measurements between different examiners, the Ligs arthrometer demonstrated excellent inter-rater reliability for ATT measurements (ICCs = 0.911–0.930) and moderate inter-rater reliability for SSD measurements (ICCs = 0.684–0.737) in healthy subjects, but both were lower than their corresponding intra-rater ICCs. Previous studies also showed that although the intra-rater reliability of various arthrometers, such as the KT-1000, GNRB, Rolimeter, KLT, and Kira, was acceptable, the inter-rater reliability of these devices tended to be inadequate. In particular, the inter-rater reliability for SSD measurements is generally worse than that for ATT measurements [11, 12, 19]. Considering that the quantitative method of the Ligs arthrometer is usually SSD measurements, the reliability of SSD measurements is more important for clinical practice. Consequently, it is recommended that the tests be performed by the same examiner when using the Ligs arthrometer for SSD measurements. Moreover, these findings remind us that caution is also needed when comparing SSD results obtained by different examiners.
With respect to ATT measurements, this study found excellent intra-rater and inter-rater reliability of the Ligs arthrometer (ICCs = 0.930–0.982 and 0.911–0.930, respectively) in healthy subjects, which further confirmed previous findings. Prior to this study, Wu et al. analyzed the reliability of the Ligs arthrometer for ATT measurements in ten healthy subjects and reported excellent intra-rater and inter-rater reliability (ICCs = 0.943 and 0.909, respectively) despite the relatively small sample size [13]. Moreover, a study by Chen et al. described the use of the Ligs arthrometer for quantifying the anterior drawer test in patients with chronic ankle instability and revealed excellent intra-rater and inter-rater reliability (ICCs = 0.963 and 0.949, respectively) [22].
In addition to the reliability of the device, the false positive rate is another important reference index to consider for arthrometers [18]. In this study, neither of the two experienced examiners demonstrated false positive results for SSD measurements in healthy subjects, while the false positive rate of the beginner rose to 7.5% as the applied load increased, indicating a learning curve with the Ligs arthrometer. In view of this, measurements with the Ligs arthrometer should preferably be performed by examiners with experience in using the device. The false positive rates of other arthrometers were also reported in the literature, with the rates of the KT-1000 and Rolimeter ranging from 2% to 5%. The device with the highest false positive rate was the KiRA (34.4%), for which the beginners showed higher false positive rates than the experienced examiners, although the authors speculated that such a high false positive rate may be related to the blocked visual feedback of the device during the test [18, 23, 24].
Generally, the reliability of instrumental measurements in healthy knees can be influenced by several factors, including the type of arthrometer, examiner experience, device positioning, knee flexion angle, lower limb rotation, force application, muscle activity around the knee, and examiner hand dominance [4, 12, 17, 18, 25, 26]. In addition, knee pain, effusion, swelling, and muscle protection can further affect the results of measurements in patients with ACL tears [27, 28]. To avoid examiner-related factors and reduce the effects of lower limb rotation and the contraction of the hamstrings on measurements, robotic arthrometers such as the GNRB were developed to improve the reliability of arthrometers for measuring anterior knee laxity [8, 29]. However, its relatively large size and non-portability limit its wide clinical application to a certain extent, especially in outpatient settings. As a result, some portable arthrometers with their own features have been further developed for clinical use in recent years. These devices were found to have adequate validity and reliability for assessing anterior knee laxity, suggesting that digital and convenient arthrometers have a promising application in the field of instrumental measurements [3, 5, 13–15, 17, 30]. For the Ligs arthrometer, the overall good reliability may be closely associated with several factors. First, the load is applied with a constant direction and constant speed through the push rod, thereby reducing the variations in force and direction caused by manual application. Second, the load and displacement are directly displayed as digital results by the built-in sensors at a sampling frequency of 30 Hz with 0.1 mm precision, which not only improves measurement accuracy but also avoids errors associated with dial use. Nevertheless, compliance with strict operational protocols remains critical for reliable measurements [13, 15].
This study has several limitations. First, due to the lack of validated arthrometers, such as the KT-1000 and GNRB, we cannot directly compare the reliability of the Ligs arthrometer with that of other devices. Second, only male subjects were included for testing to avoid the influence of sex hormone fluctuations during the menstrual cycle on ATT measurements between examiners, which led to selection bias in the study and limited the generalizability of the findings [31–34]. Finally, there was no assessment of the inter-day test-retest reliability since all the tests for the same subject by each examiner were completed on the same day.
Conclusion
The Ligs arthrometer had moderate to excellent intra-rater and inter-rater reliability for ATT and SSD measurements in healthy knees. As compared with ATT measurements, SSD measurements showed lower intra-rater and inter-rater reliability at the same load. It is recommended that the tests be performed by the same examiner when using the Ligs arthrometer for SSD measurements.
Acknowledgements
The authors would like to thank all subjects for their participation in the study.
Abbreviations
- ACL
Anterior cruciate ligament
- ATT
Anterior tibial translation
- SSD
Side-to-side difference
- ANOVA
Analysis of variance
- ICC
Intraclass correlation coefficient
- SEM
Standard error of measurement
- BMI
Body mass index
- LoA
Limits of agreement
Authors’ contributions
Qi Li and Yan Xiong contributed to the study conception and design. Xiaolong Yang, Mingke You, and Zeyu Liu performed the study. Weiting Li and Wenjing Ma collected and analyzed the data. Junqiao Li and Jiayao Zhang wrote the first draft of the manuscript. Jian Li reviewed and edited the manuscript. All authors read and approved the final manuscript.
Funding
This study was supported by the 1.3.5 Project for Disciplines of Excellence of West China Hospital, Sichuan University (ZYGD21005).
Data availability
No datasets were generated or analysed during the current study.
Declarations
Ethics approval and consent to participate
This study was approved by the Ethics Committee on Biomedical Research, West China Hospital of Sichuan University (No. 2023-279). All subjects signed an informed consent form before participating in the study.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Junqiao Li, Jiayao Zhang, and Weiting Li contributed equally to this work.
Contributor Information
Qi Li, Email: liqi_sports@scu.edu.cn.
Yan Xiong, Email: luyibingli@163.com.
Jian Li, Email: hxlijian.china@163.com.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
No datasets were generated or analysed during the current study.