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68 (); 143-148
doi:
10.1016/j.jor.2025.05.064

Reliability of a modified Berger protocol for TKA component rotation using an anatomical tibial component

, , ,
a Department of Orthopaedic Surgery, Deventer Hospital, Deventer, the Netherlands
b Department of Orthopaedic and Trauma Surgery, Deventer Hospital, Deventer, the Netherlands

⁎Corresponding author: Stefan Gelderman. S.gelderman@dz.nl

Received: , Accepted: ,
Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

Abstract

Malrotation in total knee prostheses can cause persistent pain and dissatisfaction. While the Berger protocol is the standard for assessing component rotation, it is unsuitable for anatomically designed tibial components. This study evaluates the inter- and intra-observer reliability of a modified method for anatomical prostheses and its clinical applicability.

In this prospective study, 500 patients underwent postoperative CT scans. Femoral rotation was measured as the angle between the transepicondylar axis and posterior condylar line. Tibial rotation was defined by the angle between a perpendicular axis on the tibial plateau and a line through the tuberosity. Inter- and intra-observer reliability was assessed using the intraclass correlation coefficient (ICC) with a two-way mixed effect model with single measurement/observer and absolute agreement.To determine the clinical applicability, we calculated the percentage of agreement per degree of deviation between observers.

Inter-observer reliability was good for both femoral (ICC 0.752, 95 % CI 0.71–0.79) and tibial (ICC 0.866, 95 % CI 0.84–0.89) measurements. Femoral measurements differed less than 2° in 91.4 % of cases, versus 52.2 % for tibial. Intra-observer reliability was found excellent: femoral (observer 1: ICC 0.941 (95 % CI 0.929–0.950); observer 2: ICC 0.943 (95 % 0.907–0.954)) and tibial (observer 1: ICC 0.941 (95 % CI 0.921–0.956); observer 2: ICC 0.972 (95 % CI 0.960–0.980).

The modified Berger protocol shows high reliability for anatomical tibial components. However, the percentage agreement for the tibial component between and within observers was low and therefore might influence the applicability.

Keywords

Total knee arthroplasty
Malrotation
Measurement protocol
Reliability
1

1 Introduction

Total knee arthroplasty (TKA) is a successful intervention that improves long-lasting functional capabilities in people with end-stage osteoarthritis.1 However, one in five patients is dissatisfied with the post-operative outcome.2–4 A successful TKA depends on many factors, including patient characteristics, implant design, rehabilitation and alignment.5,6 Malrotation has been recognized as a cause for post-operative pain and dissatisfaction.7 When the TKA procedure is performed using the mechanical alignment technique, implementing proper femoral rotation is crucial to achieve normal kinematic function. With this technique, the tibial cut is made perpendicular to the mechanical axis of the tibia, rather than the anatomical, varus, tibial joint line. To enhance function, the distal femur is cut in external rotation. Excessive internal or external rotation can result in instability and anterior knee pain due to altered patellar tracking.8–10

TKA component rotation can be evaluated using computed tomography (CT). Berger et al. (1998) were the first to describe a method for measuring TKA component rotation.11 Their protocol was based on 35 anatomical specimens12 and was then evaluated on 50 patients with total knee replacements.11 This method is still the most used protocol today.13 The Berger protocol defines femoral rotation as the angle between the posterior condylar line (PCL) and the line between the lateral epicondylar prominence and the sulcus of medial epicondyle (surgical transepicondylar axis (sTEA)). Two axes are created for determining the tibial rotation. The first is the tibial component axis (TCA), determined by a line drawn perpendicular to the posterior surface of the tibial component. The second axis runs from the geometric centre of tibial component to the tip of tibial tubercle. The angle between these axes defines the tibial component rotation. The Berger protocol has been proven to have good inter- and intra-observer reliability.14

Currently, new prosthesis designs are used with an anatomical (asymmetric) tibial tray instead of a symmetrical tibial tray. An anatomical tibial tray offers a better bone coverage, less prosthetic overhang and better patient reported outcome scores compared to symmetrical tibial trays.15–17 However, assessing postoperative tibial component rotation becomes more challenging with these designs. Determining the geometric centre is more complex, as it varies with component size. To address this, Benazzo et al. (2019) proposed modifications to the Berger protocol for identifying the geometric centre in asymmetrical tibial trays18

Given the Berger protocol's established use in assessing TKA component rotation, this study determines the inter-observer and intra-observer reliability of rotational measurements for these modifications in asymmetrical tibial components and evaluate its applicability.

2

2 Methods

2.1

2.1 Participants

This study is part of a large prospective, single-centre, observational study.19 In this study, a large cohort of 500 consecutive patients were included and underwent a post-operative CT scan to measure post-operative TKA component rotation to examine the role of rotation in post-operative outcomes. Patients were enrolled between August 2019 and October 2022. All patients with primary knee osteoarthritis (Kellgren Lawrence score 3 or 4) and scheduled for total knee replacement were included. Exclusion criteria included previous distal femoral or proximal tibial fracture resulting in altered anatomy and/or previous osteotomies around the knee.

2.2

2.2 Surgical procedure

Experienced orthopaedic surgeons or residents under their direct supervision performed the TKA. A cemented, posterior stabilised, Persona total knee prosthesis (Zimmer-Biomet, Warsaw, Indiana, USA) was used in all patients. The procedure involved a medial parapatellar approach. The measured resection technique was employed to achieve mechanical alignment. The distal femur was cut using an intramedullary guide. The posterior referencing femoral sizing guide was then applied and was set to 3° or 5° external rotation. An extramedullary guide was used for the tibial cut. Optimal tibial component rotation was assessed based on the tibial tuberosity, anterior tibial crest and proximal tibia coverage.

2.3

2.3 CT evaluation

Patients underwent a low-dose CT 8 weeks post-TKA to assess the femoral and tibial component rotation. A standard metal artefact reduction protocol was used on a Philips Brilliance iCT and Philips IQon spectral CT scanner. Axial CT slices, 1 mm in thickness, were obtained with the investigated knee in maximal extension. The contralateral knee was flexed elevated out of the field of view if necessary.

Femoral component rotation was defined as the angle between the surgical transepicondylar axis and the PCL of the femoral component according the Berger Protocol11 (Fig. 1). This measurement was also performed for the anatomical transepicondylar axis.

Measurement of the surgical transepicondylar axis.
Fig. 1 Measurement of the surgical transepicondylar axis.

Tibial component rotation was measured on multiple axial slices according the modifications of Bennazo et al. (2019) on the Berger protocol.18 The orientation of the tibial component was determined by creating a medial/lateral line connecting both visible step-offs of the tibial plateau (Fig. 2a), with the tibial component axis (TCA) perpendicular to this line. The geometric centre is located on the medial/lateral line at the centre of the insert gap. The TCA and the geometric centre were axially transposed to the axial slice with a clear image of the tibial tuberosity. From the geometric centre, a line was drawn through the tip of the tibial tuberosity (tibial tuberosity axis, TTA) (Fig. 2b). Tibial rotation was represented by the angle between the TCA relative to the TTA. The 18° correction according to the Berger protocol was not applied. This procedure was repeated with the TTA aimed at the medial third of the tibial tuberosity.

A: medial/lateral line connecting both visible step-offs of the tibial plateau; B tibial tuberosity axis.
Fig. 2 A: medial/lateral line connecting both visible step-offs of the tibial plateau; B tibial tuberosity axis.

CT scans were assessed by an experienced orthopaedic surgeon and by an orthopaedic resident, blinded to the clinical data and each other's measurements. For intra-observer reliability, scans were evaluated more than 2 weeks apart.

2.4

2.4 Statistical analysis

The two-way mixed effects model with single measurement and absolute agreement was used to calculate the intra-observer reliability. Intra-observer reliability is defined as the consistency in measurements of the same variable at different time points.20 Inter-observer reliability, the consistency of scores or outcomes measured by different data collectors,21 was calculated using the two-way random effects model with single rater and absolute agreement. Inter-observer and intra-observer intraclass correlation coefficients (ICC) were calculated for the femoral and tibial TKA component separately. ICC estimates and their 95 % confident intervals (CI) were calculated using IBM SPSS statistics version 28.0 (IBM Corp, Armonk, NY, USA. Released 2021). ICC estimates were interpreted accordingly: <0.5 = poor, 0.5–0.75 = moderate, 0.75–0.9 = good and >0.9 as excellent.22 To determine the clinical applicability, we calculated the percentage of agreement per degree of deviation between observers and between two measurements of the same observer for the femoral and tibial rotation. Since even a 2°-6° degrees of internal rotation is considered malrotation.23–26 Power analysis was performed to interpret the findings accurately.27 With an expected intra-observer femoral ICC of 0.85 and 0.85 tibial, and an expected precision of 0.05, 120 scans are needed are needed to provide sufficient power. For the inter-observer reliability, a minimum of 201 CT scans needs to be evaluated, based on an expected ICC 0.80 for femoral and tibial measurements, with an expected precision of 0.05. Rotational values are described with either a negative value representing internal rotation or a positive value representing external rotation.

3

3 Results

3.1

3.1 Inter observer reliability

A total of 490 CT scans of the knee were included in the inter-observer reliability analysis (Table 1). The angle between the PCL and aTEA and between the PCL and sTEA showed good inter-observer reliability with an ICC of 0.783 (95 % CI 0.747–0.815) and 0.756 (95 % CI 0.713–0.794) respectively. Tibial measurement showed also good inter-observer reliability. Specifically, the inter-observer ICC when using the tip of the tibial tubercle as reference showed an ICC of 0.862 (95 % CI 0.833–0.886). When the medial 1/3 of the tibial tubercle was used as a reference, the ICC was 0.866 (95 % CI 0.842–0.887). For femoral measurements (sTEA), 74.9 % of the readings were within a 1° difference and 91.4 % were within a 2° difference. In contrast, for the tibial measurements (tip of tibial tubercle), 52.2 % of the measurements were within a 2° difference and 83.9 % within a 5° difference (Table 2).

Table 1 Intraclass correlation coefficient (ICC) of the inter-observer reliability for femoral and tibial rotational measurements.
ICC (95 % CI) Mean observer 1 (SD) Mean observer 2 (SD)
aTEA 0.782 (0.746–0.815) −2.5 (±2.2) −2.4 (±2.5)
sTEA 0.755 (0.711–0.793) 1.1 (±2.1) 1.4 (±2.3)
Tip of tibial tubercle 0.864 (0.835–0.887) −12.2 (±7.3) −13.0 (±8.1)
Medial 1/3 of tibial tubercle 0.868 (0.844–0.888) −2.7 (±7.3) −2.3 (±8.2)
Table 2 Percentage agreement between observers.
0° difference ≤1° difference ≤2° difference ≤3° difference ≤5° difference
aTEA 33.3 % 75.7 % 92.0 % 96.7 % 99.0 %
sTEA 31.8 % 74.9 % 91.4 % 96.9 % 99.6 %
Tip of tibial tubercle 12.7 % 34.5 % 52.2 % 65.7 % 83.9 %
Medial 1/3 of tibial tubercle 11.8 % 35.5 % 52.0 % 66.1 % 86.7 %
3.2

3.2 Intra-observer reliability

The intra-observer reliability of all four measurements for observer 1 yielded excellent outcomes (Table 3). Observer 1 re-tested 490 scans for the aTEA and sTEA as reference to the PCL, resulting in an ICC of 0.908 (95 % CI 0.890–0.923) for the aTEA and 0.941 (95 % CI 0.929–0.950) for the sTEA. For tibial analysis, 227 scans were re-tested by observer 1, leading to an intra-observer reliability of 0.941 ICC (95 % CI 0.921–0.956) using the tip of tibial tubercle as the reference. Referencing the medial 1/3 of the tibial tubercle resulted in an intra-observer reliability of 0.933 (95 % CI 0.914–0.948) for observer 1.

Table 3 Intraclass correlation coefficient (ICC) of the intra-observer reliability for femoral and tibial rotational measurements.
aTEA (CI 95 %) sTEA (CI 95 %) Tip tibial tubercle (CI 95 %) Medial 1/3 of tibial tubercle (CI 95 %)
Observer 1 0.907 (0.889–0.922) 0.941 (0.929–0.950) 0.941 (0.921–0.956) 0.933 (0.914–0.948)
Observer 2 0.831 (0.763–0.880) 0.935 (0.907–0.954) 0.972 (0.960–0.980) 0.957 (0.940–0.970)

120 scans were re-tested for femoral and tibial rotational measurements by observer 2 in accordance with the power analysis to assess the intra-observer reliability (Table 3). The intra-observer reliability for the aTEA reference was good, with an ICC of 0.831 ICC (95 % CI 0.763–0.880), and for the sTEA reference, it was excellent, with an ICC of 0.935 ICC (95 % CI 0.907–0.954). Tibial measurements also showed excellent intra-observer reliability with an ICC of 0.972 ICC (95 % CI 0.960–0.980) when referencing the rotation at the tip of the tibial tubercle and an ICC of 0.957 (95 % CI 0.940–0.970) when referencing the rotation at the medial 1/3 of the tibial tubercle.

The percentage agreement between the first and second measurements for both observers showed minimal variation (Table 4). Approximately 50 % of femoral measurements had no difference (0°), with nearly all measurements within 2° difference. Tibial measurements exhibited lower agreement, with 15–30 % showing no difference at 0° and about 85 % falling within 2° difference.

Table 4 Percentage agreement test-retest observer 1.
0° difference ≤1° difference ≤2° difference ≤3° difference ≤5° difference
aTEA Observer 1 52.0 % 94.0 % 98.7 % 99.3 % 99.8 %
Observer 2 49.2 % 83.3 % 94.1 % 96.6 % 97.4 %
sTEA Observer 1 55.7 % 98.1 % 99.8 % 100 % 100 %
Observer 2 52.5 % 90.0 % 99.2 % 100 % 100 %
Tip of tibial tubercle Observer 1 22.0 % 58.6 % 85.0 % 93.0 % 96.9 %
Observer 2 29.2 % 65.1 % 82.6 % 90.9 % 98.4 %
Medial 1/3 of tibial tubercle Observer 1 15.9 % 64.4 % 86.9 % 92.2 % 97.4 %
Observer 2 24.2 % 68.4 % 86.7 % 93.4 % 99.2 %
4

4 Discussion

The results of this study demonstrate that with minor modifications to the Berger protocol, reliable and reproducible tibial rotational measurement can be achieved for asymmetrical tibial components. Our findings demonstrated good inter-observer reliability for tibial measurements at the tip and the medial third of the tibial tuberosity. However, for tibial rotation in less than 50 % of the scans, observer measurements varied by less than 2°. Intra-observer reliability for these tibial measurements was excellent for both observers.

Post-operative pain following TKA poses a major challenge in the orthopaedic field. Efforts to reduce the number of dissatisfied patients has led to various innovations, including the development of anatomical tibial components. A systematic review by Zhang et al. (2024) found that anatomical tibial components improve tibial coverage and rotation, reducing underhang without increasing overhang of the component.28 Although significant improvements in clinical outcomes have not yet been demonstrated, anatomical tibial trays are likely the future of knee prosthetics due to their enhanced knee kinematics.29 However, rotational malalignment can still occur. Therefore, reliable measurement of rotational alignment in these new designs is essential.

One previous reliability study was conducted using an anatomical tibia component. Benazzo,18 who made the tibial modifications to the measurement protocol for the Persona knee prosthesis, found excellent inter-observer reliability for femoral and tibial rotational measurement (ICC of 0.97) by examining 60 CT-scans. In our research, we did not find this level of reliability for the femoral measurements. Intra-observer reliability was not assessed by Benazzo.18 Although we found good reliability, the percentage agreement was low, with half of the tibial measurements showing up to 2° difference and 80–85 % falling within 5° difference. Tibial measurements showed much more variance than femoral measurements, with over 90 % of the measurements falling within a 2° difference, compared to 50 % for tibia. This discrepancy is likely due to the fact that femoral and tibial rotational measurements involve different techniques. Even a small change in the tibial tuberosity axis can lead to significant variations, often several degrees. Additionally, tibial anatomy exhibits greater variability than femoral anatomy. Although the ICC shows good to excellent outcomes, its applicability may be limited. In literature, only a few degrees difference between normal tibial rotation (neutral rotation) and malrotation (2° - 6° internal rotation) has been reported.23–26 Due this small difference there is a chance of misclassifying normal rotation as malrotation or vice versa.

The original Berger protocol has been reviewed in several studies, but all using symmetrical tibial components. Three studies reported good tibial inter-observer reliability for tibial measurements with ICC values of 0.670, 0.81 and 0.83.30–32 Van Houten et al. (2018) found excellent inter-observer reliability with an ICC of 0.91, along with excellent intra-observer reliability (ICC of 0.96).33 Saffi et al. (2019) also assessed the intra-observer reliability, yielding an ICC of 0.85.32 Two studies were conducted with regard to the femoral inter-observer reliability. Konigsberg et al. (2014) reported poor femoral inter-observer reliability (ICC of 0.386),30 while Van Houten et al. (2018) found good femoral inter-observer (ICC of 0.80) and good femoral intra-observer reliability (ICC of 0.88) in a small sample size.33 Only Konigsberg et al. (2014) have reported percentage agreement within 5°, with 95.2 % agreement for the femoral component and 69.2 % for the tibial component.

The original Berger protocol was designed for use with a 2D-CT scan. Hirschmann et al. (2011) were the first to introduce the 3D-CT scan in rotational measurement.34 It is suggested that 3D reconstructed images improve the visibility of the anatomical landmarks and therefore have better reliability. The researchers compared the reliability of the 2D-CT with the 3D-CT on femoral rotation. They found poor femoral inter-observer reliability with the 2D-CT (ICC of 0.29), compared to excellent inter-observer reliability using reconstructed 3D images (ICC of 0.91). Two other studies used a 3D reconstruction to determine reliability. Roper et al. (2013) found excellent tibial inter- and intra-observer reliability, reporting ICC values of 0.936 and 0.941, respectively.35 Rasch and colleagues (2013) found good femoral (0.85) and excellent tibial (0.93) inter-observer reliability and with good to excellent femoral intra-observer reliability (CI 0.84 & 0.92), along with good to excellent tibial intra-observer reliability (CI 0.89 & 0.95).36 These findings indicate that 3D reconstructed images leads to better reliability. However, our results demonstrate that 2D-CT can also achieve comparable reliability, particularly in intra-observer reliability. 2D-CT has the advantage of being more generalizable as it is easier to use in daily practice, widely available, and more cost-effective.

This was the first powered study to asses both the inter- and intra-observer reliability of measuring TKA component rotation in an anatomical tibial component. For inter-observer calculations, 490 patients were included, and more than 120 scans were re-evaluated for intra-observer agreement. The tight confidence intervals of the ICCs imply that the sample accurately represented the population, which should make it appropriate for evaluating reliability. However, the high level ICC values for tibial measurements do not align with the low percentage agreement found between and within observers. One explanation for this discrepancy is that ICC calculations take the variance into account.37 Due to the high variance in tibial rotation measurements, the ICC is compensated for this variability. A limitation of this study is that our rotational measurements are recorded as whole numbers, which means that a 1-degree difference can easily occur due to rounding. Secondly, we used a 2D-CT scan instead of 3D-CT technology. While 3D-CT offers higher accuracy due to better visualization of bony landmarks, daily practice typically involves reviewing scans without 3D technology. Our results show that with the most recent CT scanners and an adequate metal artefact reduction protocol, the reliability is not inferior to that of 3D-constructed images and therefore can be used in daily practice.

We believe that the main limitation of assessing TKA component rotation is not the measuring protocol itself, but the use of the patient's own anatomic structures as a reference point. There is large anatomical variance between patients of these anatomical (tibial) landmarks, leading to different normal rotation values among patients, making it difficult to define cut off values for anterior knee pain due to malrotation. This is especially true for tibial rotational measurements, for which many different techniques exist, all with similar results and without clear definitions of malrotation.14

5

5 Conclusion

Minor modifications to the Berger protocol allow for reliable rotational measurements of the TKA components in the Persona knee prosthesis. While our achieved high reliability based on the ICC, the low percentage agreement between and within observers may limit its applicability. Challenges in defining malrotation remain due to the use of anatomical references points.

Ethics, funding, AI and potential conflicts of interest

The Isala Hospital Medical Ethical Committee reviewed and approved this study (reference number NL68333.075.18). The study was conducted in accordance with the Declaration of Helsinki. All patients have consented to participate. None of the authors has had funding that might pose a conflict of interest in connection with the submitted article. During the preparation of this work the author used ChatGPT (Open AI) for grammar check. After using this service, the author reviewed and edited the content as needed and takes full responsibility for the content of the publication.

Credit author statement

Gelderman: Conceptualization, Methodology, Measurements, Formal analysis, Writing original draft. Van Jonbergen: Conceptualization, Measurements, Review Writing, Landman: Methodology, Formal analysis, Review Writing. Kleinlugtenbelt: Conceptualization, Review Writing.

Ethical statement

The Isala Hospital Medical Ethical Committee reviewed and approved this study (reference number NL68333.075.18). The study was conducted in accordance with the Declaration of Helsinki.

Funding statement

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

References

  1. , , , , , . Long-term results in total knee arthroplasty. A meta-analysis of revision rates and functional outcome. Chirurg. 2011 Jul;82(7):618-624.
    [Google Scholar]
  2. , , , , . National joint registry for england and wales. The role of pain and function in determining patient satisfaction after total knee replacement. Data from the national joint registry for england and wales. J Bone Joint Surg Br. 2007 Jul;89(7):893-900.
    [Google Scholar]
  3. , , , , , . Patient satisfaction after total knee arthroplasty: who is satisfied and who is not? Clin Orthop Relat Res. 2010 Jan;468(1):57-63.
    [Google Scholar]
  4. , , , , . Predicting dissatisfaction following total knee replacement: a prospective study of 1217 patients. J Bone Joint Surg Br. 2010 Sep;92(9):1253-1258.
    [Google Scholar]
  5. , , , , , , . Chronic pain after total knee arthroplasty. EFORT Open Rev. 2018 Aug 16;3(8):461-470.
    [Google Scholar]
  6. , , , et al . Improving patient outcomes following total knee arthroplasty: identifying rehabilitation pathways based on modifiable psychological risk and resilience factors. Front Psychol. 2020 May 29;11:1061.
    [Google Scholar]
  7. , , , , , . Effect of rotational alignment on outcome of total knee arthroplasty. Acta Orthop. 2015;86(4):432-439.
    [Google Scholar]
  8. , , , , , , . The influence of malrotation of the femoral component in total knee replacement on the mechanics of patellofemoral contact during gait. J Bone Joint Surg Br. 2010;92-B(5):737-742.
    [Google Scholar]
  9. , , , , , , . Revision total knee arthroplasty for patellar dislocation in patients with malrotated TKA components. Arch Orthop Trauma Surg. 2020 Jun;140(6):777-783.
    [Google Scholar]
  10. , , , , , . Change in tibiofemoral rotational alignment during total knee arthroplasty. J Orthop Sci. 2014 Jul;19(4):571-578.
    [Google Scholar]
  11. , , , , . Malrotation causing patellofemoral complications after total knee arthroplasty. Clin Orthop Relat Res. 1998 Nov;356:144-153.
    [Google Scholar]
  12. , , , , , . Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis. Clin Orthop Relat Res. 1993 Jan;286:40-47.
    [Google Scholar]
  13. , , , . Methods of intra- and post-operative determination of the position of the tibial component during total knee replacement. Int Orthop. 2020 Jan;44(1):119-128.
    [Google Scholar]
  14. , , , . How to assess femoral and tibial component rotation after total knee arthroplasty with computed tomography: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2016 Nov;24(11):3517-3528.
    [Google Scholar]
  15. , , , , , , . Morphometric tibial implant decreases posterior overhang rate and improves clinical outcomes: results of a prospective, matched controlled study. J Arthroplast. 2018 Sep;33(9):2804-2809.
    [Google Scholar]
  16. , , , , , , . Anatomic tibial component design can increase tibial coverage and rotational alignment accuracy: a comparison of six contemporary designs. Knee Surg Sports Traumatol Arthrosc. 2014 Dec;22(12):2911-2923.
    [Google Scholar]
  17. , , . Which tibial tray design achieves maximum coverage and ideal rotation: anatomic, symmetric, or asymmetric? An MRI-based study. J Arthroplast. 2015 Oct;30(10):1839-1841.
    [Google Scholar]
  18. , , , , , , . Computed tomography evaluation of total knee arthroplasty implants position after two different surgical methods of implantation. Int Orthop. 2019 Jan;43(1):139-149.
    [Google Scholar]
  19. , , , , , . Prospective, observational study to evaluate the relation between patient-reported outcomes and component rotation in total knee replacement: protocol for the CRACK study. BMJ Open. 2019 Nov 2;9(11)
    [Google Scholar]
  20. , , , . A primer of inter-rater reliability in clinical measurement studies: pros and pitfalls. J Clin Nurs. 2022 Dec;31(23-24):e39-e42.
    [Google Scholar]
  21. , . Interrater reliability: the kappa statistic. Biochem Med. 2012;22(3):276-282.
    [Google Scholar]
  22. , , . A guideline of selecting and reporting intraclass correlation coefficients for reliability research. J Chiropr Med. 2016 Jun;15(2):155-163.
    [Google Scholar]
  23. , , , , , . Component rotation and anterior knee pain after total knee arthroplasty. Clin Orthop Relat Res. 2001 Nov;392:46-55.
    [Google Scholar]
  24. , , , et al . Component rotational alignment in unexplained painful primary total knee arthroplasty. Knee. 2014 Jan;21(1):272-277.
    [Google Scholar]
  25. , , . Internal rotational error of the tibial component is a major cause of pain after total knee replacement. J Bone Joint Surg Br. 2010 Sep;92(9):1238-1244.
    [Google Scholar]
  26. , , , et al . The benefit of revision knee arthroplasty for component malrotation after primary total knee replacement. Int Orthop. 2012 Dec;36(12):2473-2478.
    [Google Scholar]
  27. , . A web-based sample size calculator for reliability studies. EIMJ. 2018;10(3):67-76.
    [Google Scholar]
  28. , , , et al . Comparison of the coverage and rotation of asymmetrical and symmetrical tibial components: a systematic review and meta-analysis. BMC Musculoskel Disord. 2024 Apr 26;25(1):336.
    [Google Scholar]
  29. , , , et al . How does asymmetric tibial insert affect tibiofemoral kinematics and contact stresses in total knee Arthroplasty? Knee. 2022 Dec;39:185-196.
    [Google Scholar]
  30. , , , , , . Inter- and intraobserver reliability of two-dimensional CT scan for total knee arthroplasty component malrotation. Clin Orthop Relat Res. 2014 Jan;472(1):212-217.
    [Google Scholar]
  31. , , , et al . Reproducibility and precision of CT scans to evaluate tibial component rotation. J Arthroplast. 2017 Aug;32(8):2552-2555.
    [Google Scholar]
  32. , , , , . Measuring tibial component rotation following total knee arthroplasty: what is the best method? J Arthroplast. 2019 Jul;34(7S):S355-S360.
    [Google Scholar]
  33. , , , , . Measurement techniques to determine tibial rotation after total knee arthroplasty are less accurate than we think. Knee. 2018 Aug;25(4):663-668.
    [Google Scholar]
  34. , , , , , , . The position and orientation of total knee replacement components: a comparison of conventional radiographs, transverse 2D-CT slices and 3D-CT reconstruction. J Bone Joint Surg Br. 2011 May;93(5):629-633.
    [Google Scholar]
  35. , , , , , . Analysis of tibial component rotation following total knee arthroplasty using 3D high definition computed tomography. J Arthroplast. 2013 Sep;28(8 Suppl):106-111.
    [Google Scholar]
  36. , , , , , . 4D-SPECT/CT in orthopaedics: a new method of combined quantitative volumetric 3D analysis of SPECT/CT tracer uptake and component position measurements in patients after total knee arthroplasty. Skelet Radiol. 2013 Sep;42(9):1215-1223.
    [Google Scholar]
  37. , , , . Intraclass correlation - a discussion and demonstration of basic features. PLoS One. 2019 Jul 22;14(7)
    [Google Scholar]

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