Is computed tomography an accurate and reliable method for measuring total knee arthroplasty component rotation?

Combined femoral and tibial component total knee arthroplasty device rotation measurement is reliable and predicts clinical outcome

BACKGROUND

The optimal total knee arthroplasty (TKA) rotational alignment and how best to obtain and measure it are debatable. The aim was to analyse the reliability of the Berger femoral, three different tibial and four different combined two-dimensional computer tomography (2D-CT) TKA component rotation measurements, and to ascertain which rotational values best predict a successful clinical outcome.

METHODS

The 2D-CT scans were obtained post-operatively on 60 patients who had TKA. We determined one femoral [Berger's femoral angle (BFA)], three tibial [Berger's tibial angle (BTA), anatomical tibial angle (ATA) and bimalleolar posterior tibial component angle (BM_PTCA)] and four combined [transepicondylar posterior tibial component angle (TE_PTCA), bicondylar posterior tibial component angle (BC_PTCA, transepicondylar bimalleolar angle (TE_BM) and bicondylar bimalleolar angle (BC_BM)] TKA rotation angles. We made all measures in 23 patients twice by three observers and determined inter- and intra-observer agreement using the Bland-Altman plot method. We analysed measures of 55 patients using the area under the ROC curve (AUC) analysis to ascertain the discriminative capacity of BFA, ATA, TE_PTCA and BC_PTCA for predicting a successful clinical outcome according to the Knee Society Score (KSS) threshold.

RESULTS

ATA showed the smaller inter- and intra-observer average of differences (-0.1° and 1.6°, respectively) of the studied methods followed by BFA (-0.9° and 1.4°), TE_PTCA (-2.1° and 2.7°) and BC_PTCA (-0.5° and 1.8°). BFA (-4° to 2.1° and -6.1° to 8.8°) and BC_PTCA (-4.4° to 3.4° and -7.9° to 4.4°) showed the narrower inter- and intra-observer limits of agreement. A TKA device rotation (BC_PTCA) < 0.8° of external rotation (ER) predicted a KSS and KSS knee successful outcome, and < 3.8° ER for KSS functional (AUC = 0.889; 0.907 and 0.764, respectively). BFA and ATA < 0.9° ER and < 3.9° internal rotation (IR) predicted a successful KSS knee outcome (AUC = 0.796 and 0.889, respectively).

CONCLUSION

The ATA tibial component rotation measurement was the most reliable of those studied. BFA, TE_PTCA and BC_PTCA were reliable measures for TKA femoral and combined rotation. The presence of a minimal rotation between the TKA components (BC_PTCA) and a small femoral ER or tibial IR predicted a successful KSS outcome.

LEVEL OF EVIDENCE II

Comparison of Femoral Component Rotation between Robotic-Assisted vs. Soft-Tissue Tensor Total Knee Arthroplasty with Anatomic Implants

Background and Objectives: Total knee arthroplasty (TKA) is the most effective treatment method for end-stage osteoarthritis. One of the most important aspects of this surgery is adequate implant positioning, as it guarantees the desired outcome of restoring limb biomechanics. Surgical technique is being continuously improved along with hardware development. There are two novel devices designed to help establish proper femoral component rotation: soft-tissue tensor and robotic-assisted TKA (RATKA). This study compared the femoral component rotation achieved with the use of three methods: RATKA, soft tissue tensioner and the conventional measured-resection technique, all of them utilizing anatomical design prosthesis components. Materials and Methods: A total of 139 patients diagnosed with end-stage osteoarthritis underwent total knee arthroplasty between December 2020 and June 2021. After the surgery, they were divided into three groups depending on procedure technique and implant type: Persona (Zimmer Biomet) + Fuzion Balancer, RATKA + Journey II BCS or conventional TKA + Persona/Journey. Postoperatively, a computed tomography examination was performed in order to measure femoral component rotation. All three groups were compared independently during statistical analysis. Fisher's exact, Kruskal-Wallis and Dwass-Steel-Crichtlow-Fligner tests were used for particular calculations. Results: Statistically significant differences in femoral component rotation between groups were noticed. However, in terms of values other than 0° in external rotation, no significant variance was revealed. Conclusions: Additional total knee arthroplasty instruments seem to improve the outcomes of the surgery, providing better component positioning than in the conventional measured-resection technique based only on bone landmarks.

Clinical Efficacy of Preoperative CT-Assisted Planning for Primary Total Knee Arthroplasty: A Pilot Randomized Clinical Trial

This study aims to determine the mean posterior condylar angle (PCA) in the included population and its relation to coronal alignment; and to know the clinical importance of the use of preoperative computed tomography (CT) scan in total knee arthroplasty (TKA). We randomized 50 patients with primary knee osteoarthritis into 2 groups. We used CT scan axial images to measure the PCA. In the first group we followed the CT scan plan (group 1), but in the second we did not follow the plan and adjusted rotation to the standard three degrees (group 2). The mean age of the included patients was 63 years. The radiological data of the included patients showed 5 patients with valgus deformity and 45 patients with varus deformity with the mean coronal alignment of 7.5 degrees. CT scan showed the mean PCA of 3.7 degrees (1.3 degrees). The axial knee postoperative X-ray showed the mean patellar tilt angle of 2.1 degrees (0.5 degrees) and 1.9 degrees (0.5 degrees) in groups 1 and 2, respectively. The congruence angle was 4 degrees (2.6 degrees) in group 1 and 5.5 degrees (3.2 degrees) in group 2. The median Knee Society functional score in group 1 was 85 (12), while it was 84 (7.5) in group 2. The median postoperative Western Ontario and McMaster Universities Arthritis Index score in group 1 was 84 (18.6) whereas 80.2 (13.6) in group 2. The median postoperative Bartlett score in group 1 was 30 (5), while it was 30 (6) in group 2. The use of preoperative CT scan did not improve the patient functional scores after TKA.

Failure modes in malrotated total knee replacement

PURPOSE

Achieving normal rotational alignment of both components in total knee arthroplasty (TKA) is essential for improved knee survivorship and function. However, malrotation is a known complication resulting in higher revision rates. Understanding malrotation of the components and its concomitant clinical and functional outcomes are important for early diagnosis and management. The purpose of this study was to evaluate the effect of malrotation on clinical outcomes and failure modes in both single and combined rotational malalignment.

METHODS

From our hospital database of 364 revisions, a cohort of 76 knees with patellar maltracking, stiffness, reduced range of motion and early aseptic failure were reviewed and investigated for component malrotation using computed tomography following Berger protocol. CT findings confirmed component malrotation in 70 of these patients. Investigations included (1) measurement of femoral component malrotation using surgical transepicondylar axis, (2) measurement of tibial component malrotation using anteroposterior axis and (3) measurement of combined component rotational errors.

RESULTS

The correlation of CT analysis and clinical outcomes after primary TKA revealed association of patellar maltracking with femoral internal rotation, pain and instability with tibial internal rotation and knee stiffness in patients with combined component malrotation as the commonest mode of presentation. Our study showed that patients with isolated femoral, tibial and combined malrotation presented at a mean period of 3.4 ± 1.34, 1.7 ± 0.8 and 2.3 ± 0.69 years, respectively, after the index surgery. Post-revision, the mean Knee Society Score and Oxford Knee Score improved from 29.1 to 78.7, and 10.5 to 32.8, respectively, and the mean range of motion improved from 74.9 ± 24.8 to 97.1 ± 12.7 degrees at a mean follow-up of 42 months.

CONCLUSION

Early detection of malrotation in TKA and its management with revision of both components can lead to better clinical and functional outcomes.

LEVEL OF EVIDENCE

III.

Low-Degree Tibial Slope Angle Prevents Component Overhang by Enlarging the Lateral Plateau Surface Area in Total Knee Arthroplasty

This study aimed to investigate whether overhang or underhang around the tibial component that occurs during the placement of tibial baseplates was affected by different slope angles of the tibial plateau and determine the changes in the lateral and medial plateau diameters while changing the slope angle in total knee arthroplasty. Three-dimensional tibia models were reconstructed using the computed tomography scans of 120 tibial dry bones. Tibial plateau slope cuts were performed with 9, 7, 5, 3, and 0 degrees of slope angles 2-mm below the subchondral bone in the deepest point of the medial plateau. Total, lateral, and medial tibial plateau areas and overhang/underhang rates were measured at each cut level. Digital implantations of the asymmetric and symmetric tibial baseplates were made on the tibial plateau with each slope angles. Following the implantations, the slope angle that prevents overhang or underhang at the bone border and the slope angle that has more surface area was identified. A significant increase was noted in the total tibial surface area, lateral plateau surface area, and lateral anteroposterior distance, whereas the slope cut angles were changed from 9 to 0 degrees in both gender groups. It was found that the amount of posteromedial underhang and posterolateral overhang increased in both the asymmetric and symmetric tibial baseplates when the slope angle was changed from 0 to 9 degrees. Although the mediolateral diameter did not change after the proximal tibia cuts at different slope angles, the surface area and anteroposterior diameter of the lateral plateau could change, leading to increased lateral plateau area. Although prosthesis designs are highly compatible with the tibial surface area, it should be noted that the component overhangs, especially beyond the posterolateral edge, it can be prevented by changing the slope cut angle in males and females.

CT measures of femoral and tibial version and rotational position of femoral and tibial components of knee replacements: limitations in reliability and suitability for routine clinical practice

OBJECTIVES

Rotational malalignment of knee replacements as measured on CT is understood to be associated with poor outcomes. The aim of this study is to measure the inter-rater and intra-rater reliability of measures of femoral and tibial version in the native arthritic knee and postoperative TKR component position using CT.

METHODS

Eighty patients underwent CT of the knee before and after total knee replacement. Preoperative femoral and tibial version and component rotation were independently measured by two musculoskeletal radiologists.

RESULTS

Mean differences between and within raters were small (< 1.6°). Maximum 95% limits of agreement for inter-rater and intra-rater comparisons were 8.1° and 7.6° for preoperative femoral version, 9.0° and 7.9° for postoperative femoral rotation, 26.0° and 20.5° for preoperative tibial version, and 24.9° and 23.6° for postoperative tibial rotation respectively. Postoperative ICCs varied from 0.68 to 0.81 (lower 95% CI:0.55-0.72) for both intra- and inter-rater comparisons. Preoperative ICCs were lower: 0.55-0.75 (lower 95% CI:0.40-0.65).

CONCLUSION

The lower 95% confidence level for ICC of version and rotational measurements using the Berger protocol of TKRs on CT are all less than 0.73 and that the normal range of differences between observers is up to 9° for the femoral component and 26° for the tibial component. This suggests that CT measurements derived from the Berger protocol may not be consistent enough for clinical practice.

KEY POINTS

• CT is commonly used to measure the rotational profile of knee replacements in symptomatic patients using the Berger protocol. • The limits of agreement for both femoral and tibial component rotation are wide even for experienced observers. • CT measurements of the rotation of knee arthroplasty are not reliable enough for routine clinical use.

High inter- and intraindividual differences in medial and lateral posterior tibial slope are not reproduced accurately by conventional TKA alignment techniques

PURPOSE

The purpose of this study was to describe the medial and lateral posterior tibial slope (MPTS and LPTS) on 3D-CT in a Caucasian population without osteoarthritis. It was hypothesised that standard TKA alignment techniques would not reproduce the anatomy in a high percentage of native knees.

METHODS

CT scans of 301 knees [male:female = 192:109; mean age 30.1 ([Formula: see text] 6.1)] were analysed retrospectively. Tibial slope was measured medially and laterally in relation to the mechanical axis of the tibia. The proportion of MPTS and LPTS was calculated, corresponding to the "standard PTS" of 3°-7°. The proportion of knees accurately reproduced with the recommended PTS of 0°-3° for PS and 5°-7° for CR TKA were evaluated.

RESULTS

Interindividual mean values of MPTS and LPTS did not differ significantly (mean (range); MPTS: 7.2° ( - 1.0°-19.0°) vs. LPTS: 7.2° ( - 2.4°-17.8°), n.s.). The mean absolute intraindividual difference was 2.9° (0.0°-10.8°). In 40.5% the intraindividual difference between MPTS and LPTS was > 3°. When the standard slope of 3°-7° medial and lateral was considered, only 15% of the knees were covered. The tibial cut for a PS TKA or a CR TKA changes the combined PTS (MPTS + LPTS) in 99.3% and 95.3% of cases, respectively.

CONCLUSION

A high interindividual range of MPTS and LPTS as well as considerable intraindividual differences were shown. When implementing the recommended slope values for PS and CR prostheses, changes in native slope must be accepted. Further research is needed to evaluate the impact of altering a patient's native slope on the clinical outcome.

LEVEL OF EVIDENCE

IV.

The advantages of cone-beam computerised tomography (CT) in pain management following total knee arthroplasty, in comparison with conventional multi-detector CT

BACKGROUND

Revision of total knee arthroplasty (TKA) requires preoperative assessment to identify the causes of failure. Multidetector computerised tomography (MDCT) is a commonly used imaging technique, but is sensitive to certain artifacts, such as metal implants, limiting its use. Cone-beam CT (CBCT) is a new technique dedicated to musculoskeletal imaging that is less sensitive to artifacts and could be utilised in knee implantation surgery. CBCT has not yet been validated for this indication, and we therefore undertook a retrospective assessment of MDCT versus CBCT, comparing: 1) image quality; 2) reproducibility of angle measurements; 3) effectiveness in screening for periprosthetic radiolucency and implant loosening; and 4) radiation dose.

HYPOTHESIS

This study hypothesised that CBCT provides better image quality, angle measurement reproducibility, and screening for radiolucency and implant loosening at lower doses of radiation than MDCT.

PATIENTS AND METHOD

Between October 2017 and March 2018, 28 patients, with a mean age of 61±11.6 years [range, 45-85 years] underwent both MDCT and CBCT for pain following TKA. Two radiologists performed angle measurements on both devices: patellofemoral tilt (PFT), rotation angle of the femoral component (RAFC) and rotation angle of the tibial component (RATC). They also screened for pathological radiolucency and/or implant loosening, and assessed image quality at the various bone/implant interfaces. The mean CT dose index per examination was recorded.

RESULTS

Intraclass correlation coefficients for angles and radiolucency screening on MDCT and on CBCT were respectively good (0.73) and excellent (0.82) for PFT, borderline (0.28) and moderate (0.44) for RAFC, excellent (0.82) and excellent (0.96) for RATC, and moderate (0.45) and excellent (0.84) for radiolucency screening. The inter-observer kappa correlation coefficients for diagnosis of implant loosening and image quality assessment for MDCT and CBCT were respectively moderate (0.45) and excellent (0.93) for tibial loosening and low (0.19) and borderline (0.38) for femoral loosening. The mean image quality at the various interfaces for MDCT and CBCT was respectively 2.2/3 and 2.75/3 at the tibia/tibial implant interface, 1/3 and 2.3/3 at the trochlear region/femoral implant interface, 0.9/3 and 2/3 at the femoral condyle/femoral implant interface, and 1.25/3 and 2.1/3 at the patella/patellar medallion interface. The mean CT dose index was significantly lower, by a factor of 1.24, on CBCT (4.138 mGy) than MDCT (5.125 mGy) (p<00396).

CONCLUSION

The results of the present study revealed added value for CBCT in the etiological work-up for pain following a TKA. It was reliable and reproducible for the rotation measurement and diagnosis of implant loosening, due to enhanced image quality despite a lower radiation dose than conventional MDCT.

LEVEL OF EVIDENCE

III; retrospective comparative study.

A new landmark for measuring tibial component rotation after total knee arthroplasty

BACKGROUND

Existing methods for assessment of total knee arthroplasty (TKA) component rotation on computed tomography (CT) scans are complex, especially in relation to the tibial component. Anecdotal evidence from our practice pointed towards a potential new landmark. The study aims were to check the prevalence of this landmark, define tibial component rotation in relation to it and demonstrate its reliability.

METHODS

Two hundred and eleven CTs undertaken following TKA were reviewed for presence of the landmark. A protocol to measure tibial component rotation in relation to this landmark was developed and the rotation measured using this method and Berger's protocol. Thirty one of the 211 CT scans were measured twice by two observers. Reliability was calculated using the Intraclass Correlation Coefficient (ICC).

RESULTS

The new landmark of a flat area on the lateral cortex of the tibia inferior to the tibial component was identified on all scans. Median tibial component rotation measured using our protocol was 0.0° ± 5.4° and -9.2° ± 5.5° using Berger's protocol. Intra-observer reliability with the new method was excellent (ICCs of 0.899 and 0.871) and inter-observer reliability was good (ICCs of 0.734 and 0.836).

CONCLUSIONS

The new landmark had a very high prevalence and could be used to define tibial component rotation. This measurement of tibial component rotation had acceptable reliability. This landmark has potential for use in the radiological assessment of tibial component rotation following TKA. Further work is required to determine its relationship to anatomical structures and symptoms of tibial component mal-rotation.

Highly variable tibial tubercle-trochlear groove distance (TT-TG) in osteoarthritic knees should be considered when performing TKA

PURPOSE

The tibial tubercle-trochlear groove distance (TT-TG) is an established measurement to assist diagnosis and treatment of patellofemoral instability. However, little is known about the distribution of TT-TG in osteoarthritic knees. The purpose of the current study is to investigate the TT-TG in a large cohort of osteoarthritic knees and to analyse, in particular, the association of knee alignment and TT-TG.

METHODS

Data from 962 consecutive patients [455 male, 507 female; mean age ± SD 70.8 ± 9.3 (37-96)] who had undergone 3D-CT and preoperative knee planning with validated commercial 3D planning software before total knee arthroplasty (TKA) were collected prospectively. The TT-TG, coronal hip knee ankle angle (HKA), femoral anteversion (AVF), external tibial torsion (ETT), and femorotibial rotation (Rot FT) were analysed. Pearson correlations were performed to assess correlations between TT-TG, mechanical axis, and rotational parameters (p < 0.05).

RESULTS

HKA showed a strong correlation with TT-TG (r = 0.488; p < 0.001) with 98 (67.1%) and 45 (30.8%) of valgus knees having respective abnormal and pathological TT-TG values. There were no significant correlations between parameters of rotational alignment (AVF, ETT, Rot FT) and TT-TG. Mean TT-TG was 12.9 ± 5.6 mm, ranging from 0.0 to 33.7 mm. 325 (33.8%) of all patients had abnormal (> 15 mm) and 101 (10.5%) had pathological (> 20 mm) values. A varus alignment was present in 716 (74.4%) of the cases (HKA < - 1.5°), a neutral alignment in 100 (10.4%), and a valgus alignment in 146 (15.2%) (HKA > 1.5°).

CONCLUSION

A wide variation of TT-TG values in osteoarthritic knees was shown by our results. There was a relevant influence of coronal limb alignment on the TT-TG-the more valgus the higher and more pathological the TT-TG. With the aim of having a more personalised TKA, the individual TT-TG should be taken into account to improve the outcome.

LEVEL OF CLINICAL EVIDENCE

III. Retrospective cohort study.

Coronal tibial alignment is linked to femoral rotational asymmetry: Implications for total knee arthroplasty surgery

BACKGROUND

Femoral rotational asymmetry (FRA) is the difference in rotational alignment between the trochlear groove and posterior condyles. We hypothesize that FRA increases as the tibial plateau becomes more varus due to internal rotation of the posterior condyles and external rotation of the trochlear groove to ensure a vertical trochlear groove at 90^o knee flexion.

METHODS

Seventy lower limb Computed Tomography (CT) scans were reviewed by two examiners. Comparisons were made between both the sulcus line (SL) and posterior condylar line (PCL) relative to the surgical epicondylar axis (SEA). Femoral and tibial coronal alignment were measured on CT scanograms and 3D reconstructions. Correlation analysis was performed to identify associations between FRA, SL and PCL and the coronal alignment of the tibia and femur.

RESULTS

The mean FRA was +2.9° (SL externally rotated to PCL) (-2.4° to +7.7°, SD 2.2^o). FRA greater than four degrees occurred in (17/70) 24% of knees. A statistically significant correlation was found between the degree of FRA and proximal tibial varus (MPTA) (R2 = 0.67, p < 0.001). Furthermore, there were significant correlations between the SL and the MPTA (p < 0.001, R² = 0.77) and the PCL and the MPTA (p < 0.001, R² = -0.41).

CONCLUSION

Native femora are frequently rotationally asymmetrical. As the tibial plateau becomes increasingly varus there is an increase in external rotation of the SL and internal rotation of the PCL. The effect is to maintain a more vertical trochlear groove during flexion in the presence of a varus tibia.

Imaging of symptomatic total knee arthroplasty with cone beam computed tomography

BACKGROUND

Computed tomography (CT) can be used to assess the rotational alignment of prosthesis components to identify possible underlying causes of symptomatic total knee arthroplasty (TKA). The use of cone beam computed tomography (CBCT) for the imaging of extremities is relatively new, although it has been widely used in dental imaging.

PURPOSE

To assess the intra- and inter-observer reproducibility of CBCT, as well as to validate CBCT for TKA component and periprosthetic bone diagnostics.

MATERIAL AND METHODS

CBCT scans were performed on 18 patients the day before a scheduled revision TKA, from which the intra- and inter-observer reproducibility were assessed. Component rotation and loosening were evaluated. Perioperative bone defects were classified.

RESULTS

The inter-observer intraclass coefficient correlation (ICC) for femoral component rotation was 0.41 (95% confidence interval [CI] = 0.12-0.69). For the tibial component, the ICC was 0.87 (95% CI = 0.74-0.94). Intra-observer reproducibilities were 0.70 (95% CI = 0.35-0.87) and 0.92 (95% CI = 0.80-0.97), respectively. The sensitivity for tibial component loosening was 97% and the specificity was 85%. The reliability of bone defect classification was only weak to moderate.

CONCLUSION

Two-dimensional (2D) CBCT scanning provides reliable and reproducible data for determining the rotation of femoral and tibial components, while showing minor overestimation of tibial component loosening. CBCT is a promising new tool for the evaluation of symptomatic knee arthroplasty patients, with a substantially lower radiation dose compared to conventional 2D multi-slice CT.

Morphometric Tibial Implant Decreases Posterior Overhang Rate and Improves Clinical Outcomes: Results of a Prospective, Matched Controlled Study

BACKGROUND

Tibial implant's positioning in total knee arthroplasty (TKA) requires a compromise between implant's rotation and bone coverage. We hypothesized that morphometric tibial trays (MTTs) would improve implant positioning and clinical outcomes as compared with symmetrical tibial trays.

METHODS

Thirty-three patients were included prospectively according to the following criteria: age from 18 to 85 years, body mass index <35 kg/m², and posterostabilized cemented TKA performed for primary arthritis. Patients were matched for age, gender, body mass index, and preoperative international knee society (IKS) scoring system and Knee Injury and Osteoarthritis Outcome Score (KOOS) pain score, in a 1:1 fashion with patients from a prospectively collected database receiving a symmetrical tibial tray TKA. Tibial implant's rotation, bone coverage, and the percentage of patients with a posterior overhang (PO) >3 mm were assessed using computerized tomography. The IKS and the KOOS were compared at 3-year follow-up.

RESULTS

Bone coverage (90% vs 88%, P = .07) and rotation (mean difference 0.7 ± 3°; P = .69) were not different between the 2 groups. The percentage of patient with a PO was lower in the morphologic group (2/33 vs 14/33, P = .01, odds ratio = 10.3 [2.12-50.24]). Functional scores were superior in the morphometric group: IKS (mean difference 20 ± 21 points; P = .0005), mainly due to a difference in the IKS pain subscore (mean difference 11 ± 15 points; P = .0002). According to the multivariate analysis, an MTT had a positive, independent effect on IKS pain (P = .006) and KOOS pain subscores (P = .03) at the last follow-up.

CONCLUSION

The use of an MTT in TKA did not modify the tibial implant position in the axial plane; however, it decreased implant's posterior overhang and improved functional scores. The clinical improvement was mainly found on pain scores.

Measurement techniques to determine tibial rotation after total knee arthroplasty are less accurate than we think

BACKGROUND

The present study assessed the inter- and intra-observer reliability of tibial and femoral rotation measures after total knee arthroplasty (TKA), and evaluated the correlation between these measurement techniques and their clinical relevance.

METHODS

Femoral rotation and tibial rotation were determined on 42 2D CT-scans made three-months after TKA. Reliability of the radiological measurements (including Berger's method, the anatomical tibial axis and the tibial tuberosity trochlear-groove) was assessed with 15 randomly selected patients measured twice by three observers. Functional outcomes were scored one-year postoperatively with the KSS, VAS pain, VAS satisfaction, KOOS, and Kujala.

RESULTS

The inter- and intra-observer reliability of the rotational measurements ranged from good to excellent (ICC 0.67-0.98). Tibial rotation measured with the Berger technique was most reliable (ICC inter = 0.91; ICC intra = 0.96). No strong correlations were found between the different rotational measures or the clinical outcomes and rotational outliers.

CONCLUSIONS

Tibial rotation is most reliable measured with the technique described by Berger. There were no strong correlations found between the different tibial rotation measures or between the clinical outcomes and the rotational outliers. Further research is needed to gain more insight into optimal positioning and measuring rotation in TKA for clinical practice.

The type of approach does not influence TKA component position in revision total knee arthroplasty - A clinical study using 3D-CT

BACKGROUND

The influence of the surgical approach on the position of the prosthetic components in revision of total knee arthroplasties (rTKA) is still not clear. This study compared the medial parapatellar approach (MPA) and lateral parapatellar subvastus approach with tibial tubercle osteotomy (LPA).

METHODS

Forty-two consecutive patients underwent rTKA from 2006 to 2016 with either MPA (n=21) or LPA (n=21) because of aseptic loosening, infection, malposition or instability (mean follow-up: 41.5months). Revision TKA component position and leg alignment were assessed on three-dimensional CT (3D-CT) images and compared between groups using a t-test (p<0.05). Rotation of rTKA components graded into internal, neutral or external rotation and rates of postoperative complications and revisions were compared between groups with a chi²-test (p<0.05).

RESULTS

Group MPA and LPA showed no significant differences with respect to the femoral component (coronal: 0.6° vs 0.9°; sagittal: 7.5° vs 7.7°; transversal: 0.4° vs -0.2°), tibial component (coronal: 0.1° vs 0.3°; sagittal: 3.1° vs 1.6°; transversal: 6.9° vs 9.3°) and leg alignment (varus: 0.2° vs 1.1°) (p<0.05). Group LPA showed a non-significant (p=0.25) higher incidence of neutrally (28.6% vs 9.5%) and less internally (23.8% vs 38.1%) rotated tibial components. Rates of complication and revisions did not differ significantly.

CONCLUSIONS

In contrast with primary TKA, the two approaches did not influence postoperative rTKA position. This can be explained with the more extensive approach at rTKA and means that no corrections of the orientation of the components are needed performing either MPA or LPA.

Interobserver and Intraobserver Reliability of Computed Tomography-Based Three-Dimensional Preoperative Planning for Primary Total Knee Arthroplasty

BACKGROUND

Preoperative planning is an important factor for total knee arthroplasty (TKA). The aim of this study is to document the interobserver and intraobserver reliability of computed tomography (CT)-based 3-dimensional (3D) preoperative planning for primary TKA.

METHODS

Twenty knees (10 with osteoarthritis and 10 with rheumatoid arthritis) were studied independently by 6 orthopedic surgeons using a CT-based 3D planning system. The measurements were made twice at more than 3-week intervals without any knowledge of their own previous measurements or those of the others. We assessed the femoral and tibial component sizes and the alignment of the femoral component.

RESULTS

The interobserver and intraobserver agreements for femoral component size were 44.3% and 62.5% with exact size, and increased to 90.7% and 99.2% within one size difference; the intraclass correlation coefficients (ICCs) were 0.919 and 0.936, respectively. The interobserver and intraobserver agreements for tibial component size were 57.0% and 66.7% with exact size, and increased to 87.3% and 90.0% within one size difference; the ICCs were 0.909 and 0.924, respectively. The ICCs for femoral and tibial size were better in rheumatoid arthritis than in osteoarthritis. Interobserver ICC for femoral valgus angle was 0.807, and 0.893 for intraobserver reliability. Interobserver ICC of the femoral external rotation angle was 0.463, and 0.622 for intraobserver reliability.

CONCLUSION

CT-based 3D preoperative planning for primary TKA has clinical implications for predicting appropriate size and alignment of the component in patients with osteoarthritis and rheumatoid arthritis.

Medial parapatellar approach leads to internal rotation of tibial component in total knee arthroplasty

PURPOSE

The purpose of this study was to investigate if the type of approach [medial parapatellar approach (MPA) versus lateral parapatellar approach with tibial tubercle osteotomy (LPA)] influences rotation of femoral and/or tibial component and leg axis in total knee arthroplasty (TKA). It was the hypothesis that MPA leads to an internally rotated tibial TKA component.

METHODS

This study included 200 consecutive patients in whom TKA was performed using either a parapatellar medial (n = 162, MPA) or parapatellar lateral approach with tibial tubercle osteotomy (n = 38, LPA). All patients underwent clinical follow-up, standardized radiographs and computed radiography (CT). TKA components' position and the whole leg axis were assessed on 3D reconstructed CT scans (sagittal, coronal and rotational). Mean values of TKA component position and the whole leg alignment of both groups were compared using a t test. The tibial component was graded as internally rotated (<3° of external rotation (ER)), neutral rotation (equal or between 3° and 6° of ER) and externally rotated (>6° ER). The femoral component was graded as internally rotated [>3° of internal rotation (IR)], neutral rotation (equal or between -3° IR and 3° of ER) and externally rotated (>3° ER).

RESULTS

There was no significant difference in terms of whole leg axis after TKA between both groups (MPA: 0.2° valgus ± 3.4; LPA: 0.0° valgus ± 3.5). Means of tibial component rotation were 2.7° ER ± 6.1 (MPA) and 7.6° ER ± 5.4 (LPA). Patients of group LPA presented a significantly less internally rotated (LPA: 18.4%; MPA: 48.8%) and more externally rotated (LPA: 52.6%; MPA: 22.8%) tibial component (p < 0.001). No significant differences were seen for the femoral component position, tibial valgus/varus and tibial slope.

CONCLUSION

The type of approach (medial versus lateral) significantly influenced tibial TKA component rotation. It appears that a MPA tends to internally rotate the tibial TKA component and a LPA tends to externally rotate the tibial TKA. The anterior cortex should not be used as landmark for tibial TKA component placement when using the lateral approach with tibial tubercle osteotomy.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

No influence of femoral component rotation by the lateral femoral posterior condylar cartilage remnant technique on clinical outcomes in navigation-assisted TKA

PURPOSE

To investigate whether cartilage thickness in the lateral femoral posterior condyle affects the femoral rotation angles on navigation and clinical outcomes of navigation-assisted total knee arthroplasty (TKA).

METHODS

This is a prospective randomized study of navigation-assisted TKA. Fifty cases underwent TKA without removal of the lateral posterior femoral cartilage (Group 1), and 56 cases underwent TKA with removal of the lateral posterior femoral cartilage (Group 2). The femoral rotation was evaluated using CT and compared with navigation values. The angle between the clinical transepicondylar axis and posterior condylar axis measured on CT was defined as the femoral rotation angle on CT. Elevation of the joint line and patellar measurements were also evaluated.

RESULTS

The clinical outcomes were not statistically different in the two groups. The radiographic measurements were not statistically different except femoral rotation angle on navigation. The mean femoral rotation angle of navigation was 4.0° ± 2.2° without cartilage removal and 5.1° ± 2.5° with cartilage removal. The reliability and validity were high between the femoral rotation angle on navigation in the cartilage removal group and that on CT, but there were no differences in clinical outcomes between the two groups.

CONCLUSION

There was little effect of navigation-assisted TKA on radiographic and clinical outcomes, although femoral rotational differences were caused by the lateral femoral posterior condylar cartilage. Although the rotational differences due to cartilage would be within the clinical safety margin, surgeons should consider that difference during TKA.

LEVEL OF EVIDENCE

Lower quality randomized trial (no masking), Level II.

Reproducibility and Precision of CT Scans to Evaluate Tibial Component Rotation

BACKGROUND

Component rotation likely plays a greater role on the survivorship and outcomes of total knee arthroplasties than is currently known. Our goal was to evaluate the precision, interobserver reliability, and intrarater reliability of tibial component rotation as measured by computed tomography (CT) scan, regardless of measurement technique.

METHODS

Three fellowship-trained, academic arthroplasty surgeons independently measured tibial component rotation on CT scans of 62 total knee arthroplasties using their methods of choice. Measurements were repeated at least 2 weeks after the initial measurement. The precision of the measurements was assessed using a formal 8-step protocol as the gold standard. Intraclass correlation coefficients (ICCs) were calculated to evaluate precision, interobserver agreement, and intrarater reliability RESULTS: The interobserver agreement between the 3 surgeons for tibial component rotation was also moderate (ICC = 0.52). The intrarater reliability of tibial rotation was excellent (ICC = 0.81). Comparison of surgeons' measurement to a validated gold standard revealed only moderate precision for tibial component rotation (ICC = 0.64).

CONCLUSION

Practicing surgeons measuring tibial rotation were internally consistent, but failed to demonstrate satisfactory precision and interobserver agreement. We support the adoption of standardized criteria for the measurement of tibial component rotation on CT scans.

The role of cone beam CT in the study of symptomatic total knee arthroplasty (TKA): a 20 cases report

OBJECTIVE

The aims of this study were to evaluate the efficacy of cone beam CT (CBCT) in the study of the patellar tilt angle and rotational alignment of the femoral/tibial component after total knee arthroplasty and to estimate how metallic artefacts impaired detection of periprosthetic bone structures and bordering tendon-muscle structures.

METHODS

20 symptomatic total knee arthroplasties were examined using CBCT by three independent observers. The patellar tilt angle and rotational alignment of femoral and tibial components were measured in relation to the femoral flange, transepicondylar axis and tibial tuberosity, respectively. A four-score scale, ranging from "many metallic artefacts" (the structure cannot be identified) to "no metallic artefacts" (the structure can be perfectly identified), was used to judge every structure.

RESULTS

The patellar tilt angle and rotational alignment of the prosthetic components showed very high intra- and interobserver agreements (intraclass correlation coefficient values 0.895-0.975 and 0.891-0.948, respectively). Bone and tendon-muscle structures cannot be identified in the distal part of the femoral component, whereas they can be well identified in the proximal part of the femoral component and in the proximal/middle third of the tibial stem.

CONCLUSION

CBCT was an effective tool, providing reproducible measurements of the patellar tilt angle and the rotational alignment of the femoral/tibial component. Furthermore, it allowed bone and tendon-muscle structures analysis with little impediments from metal artefacts. Advances in knowledge: CBCT allows easy and accurate measurements on the rotational axial plane, unburdened by image quality impairment due to metal artefacts.