Internal rotation of the tibial component is frequent in stiff total knee arthroplasty

The variability in the external rotation axis of the distal femur: an MRI-based anatomical study

Commonly used total knee arthroplasty (TKA) systems utilising measured resection techniques default to 5°-7° valgus for the distal cut relative to the anatomical axis and 3° external rotation of the femoral component relative to posterior condylar axis (PCA). Rotational errors of the femoral component are associated with pain, patella maltracking and a poorer outcome. We analysed MRI scans from patients undergoing TKA using patient-specific instrumentation to assess coronal and rotational alignment from landmarks identified on the scans. One hundred and eight scans in 59 males and 49 females were studied with age range 35-93 years (mean 67.9 years). We found 91 % of patients had a femoral valgus angle between 5° and 7° (mean angles 5.9°), while only 24 % had an external rotation angle between 2.5° and 3.5° relative to PCA. There was no statistical significance in rotation between males and females although outliers tended to be female. Mean Whiteside's angle was 92.9° (87.8-98). This study highlights the variations in external rotation between patients undergoing TKA using the PCA as a reference for rotation. This may be a contributing factor in implant malalignment and patient dissatisfaction.

Which Tibial Tray Design Achieves Maximum Coverage and Ideal Rotation: Anatomic, Symmetric, or Asymmetric? An MRI-based study

Two goals of tibial tray placement in TKA are to maximize coverage and establish proper rotation. Our purpose was to utilize MRI information obtained as part of PSI planning to determine the impact of tibial tray design on the relationship between coverage and rotation. MR images for 100 consecutive knees were uploaded into PSI software. Preoperative planning software was used to evaluate 3 different tray designs: anatomic, symmetric, and asymmetric. Approximately equally good coverage was achieved with all three trays. However, the anatomic compared to symmetric/asymmetric trays required less malrotation (0.3° vs 3.0/2.4°; P < 0.001), with a higher proportion of cases within 5° of neutral (97% vs 73/77%; P < 0.001). In this study, the anatomic tibia optimized the relationship between coverage and rotation.

Relationship between Tibial Baseplate Design and Rotational Alignment Landmarks in Primary Total Knee Arthroplasty

This study evaluated the influence of modern tibial baseplate designs when using the anterior tibial cortex as a primary rotational landmark for the tibial baseplate in TKA. Eighty patients undergoing TKA were randomized in two groups. Group 1 included 25 females and 15 males receiving a posterior-stabilized (PS) symmetric tibial baseplate while Group 2 included 24 females and 16 males receiving a PS anatomical tibial component. Identical surgical technique, including the use of the surgical transepicondylar femoral axis (sTEA) and the anterior tibial cortex (“Curve-on-Curve”) as rotational alignment landmarks, was used. All patients underwent CT evaluation performed with the knee in full extension. Three observers independently measured the rotational alignment of the tibial component in relation to the sTEA. The rotational alignment of the symmetric baseplate showed an average external rotation of 1.3° (minimum 5°, maximum −1°): 91% of the knees showed 0 ± 3° with respect to the surgical sTEA, being internally rotated in 20%. The rotational alignment of the anatomical baseplate showed an average external rotation of 4.1° (minimum 0.4°, maximum 8.9°): only 47.5% of the knees showed 0 ± 3°, being externally rotated in 100%. The difference between the two groups was statistically significant. This study confirms the reliability of the “Curve-on-Curve” technique as an adequate rotational alignment anatomical landmark in TKA: the use of an asymmetric tibial baseplate might lead to external rotation of the tibial component when this technique is intraoperatively chosen.

Effect of rotational alignment on outcome of total knee arthroplasty

BACKGROUND AND PURPOSE

Poor outcomes have been linked to errors in rotational alignment of total knee arthroplasty components. The aims of this study were to determine the correlation between rotational alignment and outcome, to review the success of revision for malrotated total knee arthroplasty, and to determine whether evidence-based guidelines for malrotated total knee arthroplasty can be proposed.

PATIENTS AND METHODS

We conducted a systematic review including all studies reporting on both rotational alignment and functional outcome. Comparable studies were used in a correlation analysis and results of revision were analyzed separately.

RESULTS

846 studies were identified, 25 of which met the inclusion criteria. From this selection, 11 studies could be included in the correlation analysis. A medium positive correlation (ρ = 0.44, 95% CI: 0.27-0.59) and a large positive correlation (ρ = 0.68, 95% CI: 0.64-0.73) were found between external rotation of the tibial component and the femoral component, respectively, and the Knee Society score. Revision for malrotation gave positive results in all 6 studies in this field.

INTERPRETATION

Medium and large positive correlations were found between tibial and femoral component rotational alignment on the one hand and better functional outcome on the other. Revision of malrotated total knee arthroplasty may be successful. However, a clear cutoff point for revision for malrotated total knee arthroplasty components could not be identified.

Using the anatomical tibial axis for total knee arthroplasty alignment may lead to an internal rotation error

INTRODUCTION

Despite intensive research, current total knee arthroplasty (TKA) designs do not always provide the correct kinematics for the native joint and thus further optimisation is necessary. Several studies support the importance of malrotation of the tibial components in the failure of TKA. We hypothesise that using the anatomical tibial axis (ATA) to align tibial component rotation on the resected tibial surface may lead to an internal rotation error due to relative anterior shift of the lateral articular surface centre compared to the medial one. The aim of this study was to compare the anatomical tibial axis of the physiological tibial joint surface to the resected one.

METHOD

Twenty formalin-fixed cadaveric knees were obtained for study. After computed tomography scanning the data of each specimen were entered into a standardised coordinate system and virtual bone cuts were performed with 6, 8 and 10 mm resection depths. The positions of the articular surface centres were determined at each resection depth.

RESULTS

The lateral articular surface centre had moved anteriorly after the resection by a mean 1.475 mm, while the medial one had not changed significantly. Resecting the tibia at a 6-mm cut and using the transverse tibial axis to align the prosthetic tibial plateau will result in a mean 4.0° (95 % confidence interval, 2.5-5.5°) of internal rotation compared to the uncut tibia.

DISCUSSION

The ATA lies in 6 degrees of external rotation compared to the perpendicular to the posterior tibial condylar axis (PTCA). Graw et al. suggest aligning the tibial component in 10 degrees of external rotation to the latter. Thus, if we accept the above suggestion, the ATA is 4 degrees internally rotated compared to the same line on the resected proximal tibia. These prior studies appear to be in accordance with our findings.

CONCLUSIONS

We conclude that using the ATA on the resected tibial surface may contribute to an internal rotation error.

No demonstrable benefit for coronal alignment outcomes in PSI knee arthroplasty: A systematic review and meta-analysis

AIM

A systematic review and meta-analysis of clinical studies assessing alignment outcomes in patient-specific instrumented (PSI) knee arthroplasty was conducted.

MATERIALS AND METHODS

PRISMA compliant data was extracted from literature databases up to January 2014.

RESULTS

Twenty-six studies met the inclusion criteria, reporting a total of 1792 knees. Twenty-three studies reported alignment outcomes in the coronal plane, 11 in the sagittal plane. In all but three series, MRI was the preoperative imaging modality. Range of mean postoperative alignment (hip-knee-ankle [HKA] angle) was 176.5 to 181.70. The proportion of three degrees of outliers showed an overall mean of 18.6%. In total, fifteen studies compared alignment outcomes between standard and PSI. From these, four studies showed significantly higher accuracy of coronal plane alignment with PSI (HKA angle). Meta-analysis of seven high-quality comparative studies demonstrated no significant increased accuracy in postoperative mechanical axis (HKA angle) with PSI. Subgroup meta-analysis of both femoral and tibial rotation was not feasible due to a low number of inclusive high-quality series.

CONCLUSIONS

PSI knee arthroplasty is shown not to confer increased accuracy in reconstituting the postoperative mechanical axis. Further studies are required to demonstrate both clinical and radiological alignment outcomes in PSI knee arthroplasty with focus upon tibial and femoral rotation.

Higher Rate of Revision in PFC Sigma Primary Total Knee Arthroplasty With Mismatch of Femoro-Tibial Component Sizes

Total knee arthroplasty (TKA) systems permit a degree of femoro-tibial component size mismatch. The effect of mismatched components on revision rates has not been evaluated in a large study. We reviewed 21,906 fixed-bearing PFC Sigma primary TKAs using the Australian Orthopaedic Association National Joint Replacement Registry, dividing patients into three groups: no femoro-tibial size mismatch, tibial component size > femoral component size, and femoral component > tibial component. Revision rates were higher when the femoral size was greater than the tibia, compared to both equal size (HR = 1.20 (1.00, 1.45), P = 0.047) and to tibial size greater than femoral (HR = 1.60 (1.08, 2.37), P = 0.019). Potential mechanisms to explain these findings include edge loading of polyethylene and increased tibial component stresses.

Improved tibial component rotation in TKA using patient-specific instrumentation

INTRODUCTION

Patient-specific instrumentation (PSI) was introduced in an attempt to reduce positional outliers of components in total knee arthroplasty (TKA). It was hypothesized that PSI could help with the positioning of tibial components in optimal rotational alignment.

METHODS

A magnetic resonance imaging (MRI) analysis of 58 patients following TKA was conducted. Of these, 30 operations were performed using PSI and 28 using conventional instrumentation. The rotation of the tibial components was determined in MRI using three different reference lines: a tangent to the dorsal tibial condyles, the tibial epicondylar line, and the tibial tubercle. Deviations >9° were considered outliers. Also internal rotation >1° was considered an outlier. Data were analyzed statistically for positional outliers using the Chi-squared test.

RESULTS

There was excellent inter- and intraobserver reliability with low standard deviations for the determination of tibial component rotation using the tangent to the dorsal condyles and the tibial epicondylar line as reference. Using the dorsal tangent as reference, there were eight components in excessive external rotation (28.6 %) and one component being in relative internal rotation (5.4°) in the conventional group, while there were two components in excessive external rotation in the PSI group (6.7 %). Using the tibial epicondyles as reference, there were seven components in excessive external rotation (21.4 %) and one component being in relative internal rotation (4.4°) in the conventional group; while there were two components in excessive external rotation in the PSI group (6.7 %). These differences were statistically significant (p < 0.05). Measurements based on the tibial tubercle showed poor reproducibility in terms of intra- and interobserver reliability and was of little use in the context of the research question.

DISCUSSION AND CONCLUSION

In this setup, PSI was effective in significantly reducing outliers of optimal rotational tibial component alignment during TKA. Anatomy of the proximal tibia does not deliver clear landmarks that are prominent and consistent. This makes both, MRI analysis as well as cutting jig production and intraoperative placement a challenge.

Inter-observer precision and physiologic variability of mri landmarks used to determine rotational alignment in conventional and patient-specific TKA

Preoperative planning for patient-specific guides (PSGs) in total knee arthroplasty (TKA) requires identification of anatomic landmarks on three-dimensional imaging studies. The aim of this study was to assess the accuracy and precision with which landmarks commonly used to determine rotational alignment in TKA can be identified on magnetic resonance imaging (MRI). Two orthopedic surgeons and two musculoskeletal radiologists independently reviewed a sequential series of 114 MRIs of arthritic knees. The magnitude of interobserver variability was high, suggesting an inherent risk of inconsistency when these landmarks are used in PSG fabrication. Additionally, there was a high degree of physiologic variation among patients, indicating that assuming standard relationships among anatomic landmarks when placing TKA components may lead to rotational malalignment relative to each patient's native anatomy.

Low manipulation prevalence following fast-track total knee arthroplasty

BACKGROUND AND PURPOSE

Postoperative joint stiffness following total knee arthroplasty (TKA) may compromise the outcome and necessitate manipulation. Previous studies have not been in a fast-track setting with optimized pain treatment, early mobilization, and short length of stay (LOS), which may have influenced the prevalence of joint stiffness and subsequent manipulation. We investigated the prevalence of manipulation following fast-track TKA and identified patients at risk of needing manipulation.

PATIENTS AND METHODS

3,145 consecutive unselected elective primary unilateral TKA patients operated in 6 departments with well-defined fast-track settings were included in the study. Demographic data, prevalence, type and timing of manipulation, and preoperative and postoperative ROM were recorded prospectively, ensuring complete 1-year follow-up.

RESULTS

70 manipulations were performed within 1 year (2.2%) at a mean of 4 months after index surgery. Younger age and not using walking aids preoperatively were associated with a higher risk of manipulation. LOS ≤ 4 days (as opposed to a longer LOS) was not associated with an increased risk of manipulation.

INTERPRETATION

The prevalence of manipulation was lower or comparable to that in most published studies following more conventional pathways. Inherent patient demographics were identified as risk factors for manipulation whereas LOS ≤ 4 days was not. Thus, fast-track TKA does not result in increased risk of manipulation-despite a shorter LOS. Optimized pain treatment and early mobilization may contribute to these favorable results that support the use of fast-track.

The problem total knee replacement: systematic, comprehensive and efficient evaluation

There are many reasons why a total knee replacement (TKR) may fail and qualify for revision. Successful revision surgery depends as much on accurate assessment of the problem TKR as it does on revision implant design and surgical technique. Specific modes of failure require specific surgical solutions. Causes of failure are often presented as a list or catalogue, without a system or process for making a decision. In addition, strict definitions and consensus on modes of failure are lacking in published series and registry data. How we approach the problem TKR is an essential but neglected aspect of understanding knee replacement surgery. It must be carried out systematically, comprehensively and efficiently. Eight modes of failure are described: 1) sepsis; 2) extensor discontinuity; 3) stiffness; 4) tibial- femoral instability; 5) patellar tracking; 6) aseptic loosening and osteolysis; 7) periprosthetic fracture and 8) component breakage. A ninth 'category', unexplained pain is an indication for further investigation but not surgery.

Alignment of the tibial component of the unicompartmental knee arthroplasty, assessed in the axial view by CT scan: does it influence the outcome?

BACKGROUND

The ideal position of the unicompartmental knee arthroplasty (UKA) in the axial plane remains undefined the medical literature. The aim of this study was to observe how tibial components are placed in the axial plane and identify whether this could influence the postoperative clinical outcome.

METHODS

A retrospective transversal study of 101 UKA was performed in 88 patients by a single surgeon. Postoperative CT scans were performed at a mean follow-up period of 71 months (36 to 150), and clinical and functional outcomes were assessed by the WOMAC and the KSS scores. Patients were divided several times in two groups depending on a different WOMAC or KSS value each time, and differences in axial angulation were analyzed in every comparison. Distribution of data and influence on outcomes were also analyzed.

RESULTS

The tibial component was positioned with a mean angulation of 11.9° (-1 to 32) of external rotation (ER). A lower angle of ER was observed in all comparisons in the groups with better outcomes. Differences between groups were statistically significant when a good result was defined as a WOMAC score lower than 10.

CONCLUSIONS

Variability in axial positioning (33°) is higher than in other planes due to the free-hand technique. A trend towards better outcomes is observed when the tibial component is placed in a lower angle of ER. Rotational alignment in UKA should be investigated in subsequent studies with larger sample sizes.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Computer-assisted surgery improves rotational positioning of the femoral component but not the tibial component in total knee arthroplasty

PURPOSE

Computer-assisted surgery (CAS) may facilitate better positioning of total knee arthroplasty (TKA) along the coronal and lateral axes; however, there are doubts as to its usefulness in the rotational plane.

METHODS

This is a prospective study of 95 TKAs comparing two groups: the CAS group and the standard equipment group. The series comprises 95 cases. A radiography of the lower limb and computer tomographies (CTs) of the femoral condylar region, the proximal end of the tibia and the ankle were performed to measure rotational angulation. A month after TKA surgery, the radiography and the CTs were repeated to analyze the position of the prosthetic components in the rotational plane.

RESULTS

In the coronal axis, both CAS and mechanical technique improved femoro-tibial alignment, but when there are preexisting deformities ≥4°, CAS obtains better results. A strong correlation (R = 0.94, p = 0.001) was observed between the mean rotational axis measured with CT in the tibial plateau and that measured from the axis of the ankle. The mean initial femoral rotation of the complete series was 6.7° and 2.7° at 1-month follow-up (p < 0.001). In the standard instrumentation group, the femoral rotation went from 6.8° to 2.3°, whereas in the CAS group the femoral rotation went from 6.5° to 3.1° (p = 0.039), which is very close to the ideal 3° angle of external rotation. Tibial rotation changed by 5.28° for the entire patient population, but no differences were found when comparing CAS and standard instrumentation.

CONCLUSION

CAS improves frontal alignment in TKA, especially in the presence of preoperative deformities. In the femoral component, navigation most closely replicated the ideal 3° external rotation of the femoral component, but tibial rotation did not differ when comparing CAS to standard instrumentation.

LEVEL OF EVIDENCE

II.

Malrotated tibial component increases medial collateral ligament tension in total knee arthroplasty

Malrotation of the tibial component can lead to complications after total knee arthroplasty (TKA). Despite reports of internal rotation being associated with more severe pain or stiffness than external rotation, the biomechanical reasons remain largely unknown. We used a computer simulation model and evaluated traction forces in the lateral collateral ligament (LCL) and medial collateral ligament (MCL) with a malrotated tibial component during squatting. We also examined tibiofemoral and patellofemoral contact forces and stresses under similar conditions. A dynamic musculoskeletal knee model was simulated in three different constrained tibial geometries with a prototype component. The testing conditions were changed between 15° external and 15° internal rotation of the tibial component. With internal rotation of the tibial component, the MCL force increased progressively; the LCL force also increased, but only up to less than half of the MCL force values. A higher degree of constraint of the tibial component was associated with greater femoral rotational movement and higher MCL forces. The tibiofemoral and patellofemoral contact forces were not influenced by malrotation of the tibial component, but the contact stresses increased because of decreased contact area. This altered loading condition could cause patient complaints and polyethylene problems after TKA.

Is a "sulcus cut" technique effective for determining the level of distal femoral resection in total knee arthroplasty?

PURPOSE

Determining the level of distal femoral resection is crucial when performing total knee arthroplasty (TKA). However, variations in distal femoral resection are encountered unexpectedly. A "sulcus cut" technique is sometimes used to determine the level of distal femoral resection, but its effectiveness has not been evaluated. The aim of this study was to examine the reliability of the sulcus cut technique using computer simulation for preoperative planning.

METHODS

This study group comprised 40 knees in 34 patients (22 women, 12 men) scheduled for TKA. The preoperative planning software of a computed tomography (CT)-based navigation system was used. We determined the resected level of the femur so that the bone-implant interface of the femoral component was adjusted to the deepest subchondral bone of the trochlear groove in coronal CT images. We then measured each perpendicular distance from the resected surface of the proximal femur to the most distal point of the lateral and medial femoral condyles.

RESULTS

The mean distances of the distal-lateral and distal-medial condylar resections from the femoral sulcus were 7 mm (±1 mm) and 8 mm (±1 mm), respectively. The resection level did not differ significantly between men and women or between different component sizes. There was a slightly positive correlation between the femoral mechanical and anatomical axis angle and the distance of the distal-lateral condylar resection from the femoral sulcus.

CONCLUSIONS

The sulcus cut technique can be used to determine the desirable level of the distal femoral resection in TKA.

LEVEL OF EVIDENCE

Case series, Level IV.

Tibial rotational alignment was significantly improved by use of a CT-navigated control device in total knee arthroplasty

This study compared the accuracy of three methods to set tibial component rotational alignment: (1) conventional method, the anteroposterior (AP) axis was determined by the surgeon using anatomical landmarks; (2) partial-navigation method, the tibia was prepared according to the AP axis using a CT-based navigation system and the component was manually positioned; (3) full-navigation method, the tibial component was positioned and fixed with cement under the control of navigation using a newly developed instrument. The conventional method showed considerable deviation (range, -18.6° to 14.7°), and the partial-navigation method also showed considerable deviation (-11.3° to 8.1°). In contrast, the full-navigation method significantly improved the accuracy of alignment (-2.9° to 2.1°). The tibial component can become malaligned during cement fixation, even after proper bone preparation.

What is the optimal alignment of the tibial and femoral components in knee arthroplasty?

BACKGROUND

Surgeon-dependent factors such as optimal implant alignment are thought to play a significant role in outcome following primary total knee arthroplasty (TKA). Exact definitions and references for optimal alignment are, however, still being debated. This overview of the literature describes different definitions of component alignment following primary TKA for (1) tibiofemoral alignment in the AP plane, (2) tibial and femoral component placement in the AP plane, (3) tibial and femoral component placement in the sagittal plane, and (4) rotational alignment of tibial and femoral components and their role in outcome and implant survival.

METHODS

We performed a literature search for original and review articles on implant positioning following primary TKA. Definitions for coronal, sagittal, and rotational placement of femoral and tibial components were summarized and the influence of positioning on survival and functional outcome was considered.

RESULTS

Many definitions exist when evaluating placement of femoral and tibial components. Implant alignment plays a role in both survival and functional outcome following primary TKA, as component malalignment can lead to increased failure rates, maltracking, and knee pain.

INTERPRETATION

Based on currently available evidence, surgeons should aim for optimal alignment of tibial and femoral components when performing TKA.

Tibial component rotation: The inveterate problem

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.knee.2014.08.010. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Change in tibiofemoral rotational alignment during total knee arthroplasty

BACKGROUND

Rotational mismatch between femoral and tibial components has been recognized as a risk factor of unsuccessful total knee arthroplasty (TKA), but a main cause of rotational mismatch is uncertain. This study aims to evaluate rotational alignment of the knee by measuring both component rotation and version of the knee in TKA.

METHOD

Fifty-one TKAs (mean age 73.7 years) were included in this study. The three dimensional, weight-bearing knee alignment was measured before and after TKA. A transepicondylar axis was referenced to femoral component rotation, and an anteroposterior axis of the tibia (middle of posterior cruciate ligament attachment to medial border of patella tendon attachment) was referenced to tibial component rotation. Knee rotational angle was defined as the angle between these two axes.

RESULT

The mean preoperative knee rotation angle of 9.7° (±8.5°) internal rotation was significantly reduced to 1.8° (±7.3°) external rotation after TKA. Twenty-one of 51 knees (41%) exhibited rotational mismatch (>10°) preoperatively, and this number was reduced to eight knees (16%) post-TKA. The femoral component was rotationally aligned within 5° of neutral in all knees, while rotational alignment of the tibial component showed a high degree of variability (range 20.7° internal rotation to 17.2° external rotation).

CONCLUSION

Rotational malposition of the tibial component was considered to be a main factor of rotational mismatch of the knee after TKA.

The effect of malrotation of tibial component of total knee arthroplasty on tibial insert during high flexion using a finite element analysis

One of the most common errors of total knee arthroplasty procedure is a malrotation of tibial component. The stress on tibial insert is closely related to polyethylene failure. The objective of this study is to analyze the effect of malrotation of tibial component for the stress on tibial insert during high flexion using a finite element analysis. We used Stryker NRG PS for analysis. Three different initial conditions of tibial component including normal, 15° internal malrotation, and 15° external malrotation were analyzed. The tibial insert made from ultra-high-molecular-weight polyethylene was assumed to be elastic-plastic while femoral and tibial metal components were assumed to be rigid. Four nonlinear springs attached to tibial component represented soft tissues around the knee. Vertical load was applied to femoral component which rotated from 0° to 135° while horizontal load along the anterior posterior axis was applied to tibial component during flexion. Maximum equivalent stresses on the surface were analyzed. Internal malrotation caused the highest stress which arose up to 160% of normal position. External malrotation also caused higher stress. Implanting prosthesis in correct position is important for reducing the risk of abnormal wear and failure.

Femoral and tibial component rotation in total knee arthroplasty: methods and consequences

At least four ways have been described to determine femoral component rotation, and three ways to determine tibial component rotation in total knee replacement (TKR). Each method has its advocates and each has an influence on knee kinematics and the ultimate short and long term success of TKR. Of the four femoral component methods, the author prefers rotating the femoral component in flexion to that amount that establishes a stable symmetrical flexion gap. This judgement is made after the soft tissues of the knee have been balanced in extension. Of the three tibial component methods, the author prefers rotating the tibial component into congruency with the established femoral component rotation with the knee is in extension. This yields a rotationally congruent articulation during weight-bearing and should minimise the torsional forces being transferred through a conforming tibial insert, which could lead to wear to the underside of the tibial polyethylene. Rotating platform components will compensate for any mal-rotation, but can still lead to pain if excessive tibial insert rotation causes soft-tissue impingement.

Maximizing tibial coverage is detrimental to proper rotational alignment

BACKGROUND

Traditionally, the placement of the tibial component in total knee arthroplasty (TKA) has focused on maximizing coverage of the tibial surface. However, the degree to which maximal coverage affects correct rotational placement of symmetric and asymmetric tibial components has not been well defined and might represent an implant design issue worthy of further inquiry.

QUESTIONS/PURPOSES

Using four commercially available tibial components (two symmetric, two asymmetric), we sought to determine (1) the overall amount of malrotation that would occur if components were placed for maximal tibial coverage; and (2) whether the asymmetric designs would result in less malrotation than the symmetric designs when placed for maximal coverage in a computer model using CT reconstructions.

METHODS

CT reconstructions of 30 tibial specimens were used to generate three-dimensional tibia reconstructions with attention to the tibial anatomic axis, the tibial tubercle, and the resected tibial surface. Using strict criteria, four commercially available tibial designs (two symmetric, two asymmetric) were placed on the resected tibial surface. The resulting component rotation was examined.

RESULTS

Among all four designs, 70% of all tibial components placed in orientation maximizing fit to resection surface were internally malrotated (average 9°). The asymmetric designs had fewer cases of malrotation (28% and 52% for the two asymmetric designs, 100% and 96% for the two symmetric designs; p < 0.001) and less malrotation on average (2° and 5° for the asymmetric designs, 14° for both symmetric designs; p < 0.001).

CONCLUSIONS

Maximizing tibial coverage resulted in implant malrotation in a large percentage of cases. Given similar amounts of tibial coverage, correct rotational positioning was more likely to occur with the asymmetric designs.

CLINICAL RELEVANCE

Malrotation of components is an important cause of failure in TKA. Priority should be given to correct tibial rotational positioning. This study suggested that it is easier to balance rotation and coverage with asymmetric tibial baseplates; clinical research will need to determine whether the observed difference affects patellar tracking, loosening rates, or the likelihood of revisions after TKA.

Tibial base design and patient morphology affecting tibial coverage and rotational alignment after total knee arthroplasty

PURPOSE

To understand interactions between total knee arthroplasty tibial base design attributes, variations in tibial morphology, and the resulting tibial coverage and rotational alignment.

METHODS

Tibial anthropometric measurements, including aspect ratio (medial-lateral width/anterior-posterior length) and tibial asymmetry, were taken for 14,791 total knee arthroplasty patients and compared with the ability of four different commercial tibial base designs to cover the resected plateau. The anthropometric measurements were also compared with the resulting tibial base rotation, which occurred when rotating the base to maximize coverage.

RESULTS

All four tibial base designs resulted in similar coverage ranging from 80.2 (4.7)% to 83.8 (4.6)%. Mean tibial base rotation when placed to maximize coverage ranged from 3.7 (4.4)° (internal) to 3.8 (4.5)° (external) relative to the medial third of the tibial tubercle. More asymmetric tibiae and tibiae with a lower aspect ratios resulted in increased internal tibial base rotation.

CONCLUSIONS

The four tibial base designs assessed provided similar levels of tibial bone coverage across the patient population, despite different design features. Rotating the tibial base to maximize coverage did not significantly increase the tibial coverage, but induced variability in tibial base alignment. Certain tibial anthropometrics may predispose particular patients to internal tibial base mal-rotation.

Does malrotation of components correlate with patient dissatisfaction following secondary patellar resurfacing?

BACKGROUND

The aim of our study was to identify whether there was any correlation between the outcome of secondary patellar resurfacing and malrotation of either the femoral or tibial component.

METHODS

We identified patients that underwent secondary patellar resurfacing following previous primary total knee arthroplasty (TKA) at a single, large orthopaedic department. Patients were reviewed for range of movement, satisfaction, health status and knee function. CT scanning was performed, assessing rotational alignment of the components.

RESULTS

Twenty-one patients (23 knees) were reviewed. Nine out of 21 (39%) were satisfied while 14 (61%) remained dissatisfied after the secondary patellar resurfacing. There were no complications after the secondary procedure. All knees were internally rotated. The mean femoral internal rotation in the satisfied group was 0.92°, and in the dissatisfied group was 2.88° of internal rotation. In the dissatisfied group eight out of 14 TKAs were in >3° femoral internal rotation compared with only one in nine TKAs in the satisfied group (p<0.05).

CONCLUSIONS

Investigation for malrotation should be considered in patients with post-operative pain, especially anteriorly, causing significant dissatisfaction amongst patients following TKA. This is especially true if the patella has not been primarily resurfaced and secondary resurfacing is being considered. Patients with more than 3(°) of femoral internal rotation undergoing secondary patella resurfacing should be warned of the possibility of a poor outcome. It may well be that if the underlying problem is component malrotation, revision knee replacement may lead to a more satisfactory outcome than secondary resurfacing alone.

LEVEL OF EVIDENCE

Level of Evidence III.

Anatomic tibial component design can increase tibial coverage and rotational alignment accuracy: a comparison of six contemporary designs

PURPOSE

The aim of this study was to comprehensively evaluate contemporary tibial component designs against global tibial anatomy. We hypothesized that anatomically designed tibial components offer increased morphological fit to the resected proximal tibia with increased alignment accuracy compared to symmetric and asymmetric designs.

METHODS

Using a multi-ethnic bone dataset, six contemporary tibial component designs were investigated, including anatomic, asymmetric, and symmetric design types. Investigations included (1) measurement of component conformity to the resected tibia using a comprehensive set of size and shape metrics; (2) assessment of component coverage on the resected tibia while ensuring clinically acceptable levels of rotation and overhang; and (3) evaluation of the incidence and severity of component downsizing due to adherence to rotational alignment and overhang requirements, and the associated compromise in tibial coverage. Differences in coverage were statistically compared across designs and ethnicities, as well as between placements with or without enforcement of proper rotational alignment.

RESULTS

Compared to non-anatomic designs investigated, the anatomic design exhibited better conformity to resected tibial morphology in size and shape, higher tibial coverage (92% compared to 85-87%), more cortical support (posteromedial region), lower incidence of downsizing (3% compared to 39-60%), and less compromise of tibial coverage (0.5% compared to 4-6%) when enforcing proper rotational alignment.

CONCLUSIONS

The anatomic design demonstrated meaningful increase in tibial coverage with accurate rotational alignment compared to symmetric and asymmetric designs, suggesting its potential for less intra-operative compromises and improved performance.

LEVEL OF EVIDENCE

III.

Inter- and intraobserver reliability of two-dimensional CT scan for total knee arthroplasty component malrotation

BACKGROUND

Rotational malalignment of total knee arthroplasty (TKA) has been correlated with patellofemoral maltracking, knee instability, and stiffness. CT is the most accurate method to assess rotational alignment of prosthetic components after TKA, but inter- and intraobserver reliability of CT scans for this use has not been well documented.

QUESTIONS/PURPOSES

The objective of this study was to determine the inter- and intraobserver reliability and the repeatability of the measurement of TKA component rotation using two-dimensional CT scans.

METHODS

Fifty-two CT scans of TKAs being evaluated for revision surgery were measured by three different physicians. An orthopaedic resident and attending measured the same scans twice (more than 2 weeks apart) and a musculoskeletal radiologist measured them once. To assess interobserver reliability, intraclass correlation coefficients (ICCs) with two-way mixed-effects analysis of variance models as well as 95% confidence intervals for each were done. The repeatability coefficient was calculated as well, which is defined as the difference in measurements that include 95% of the values. This indicates the magnitude of variability among measurements in the same scale, which in this study is degrees.

RESULTS

The interobserver ICC measurement for the femoral component was 0.386 (poor), and it was 0.670 (good) for the tibial component. The interobserver ICC for the combined rotation measurements was 0.617 (good). The intraobserver ICC for the femoral component was 0.606 (good), and it was 0.809 (very good) for the tibial component. The intraobserver ICC for combined rotation was 0.751 (good). The intraobserver repeatability coefficient for the femoral component was 0.49°, 10.64° for the tibial component, and 12.29° for combined rotation.

CONCLUSIONS

In this study, the inter- and intraobserver reliability, and the repeatability, of TKA component rotation were variable. This raises concern about whether CT scan is diagnostic in the assessment of component malrotation after TKA.

How frequent is rotational mismatch within 0°±10° in kinematically aligned total knee arthroplasty?

Rotational mismatch of the tibial component on the femoral component within 0°±10° is associated with better function after mechanically aligned total knee arthroplasty (TKA). Kinematically aligned TKA has gained interest; however, the percentage of kinematically aligned TKA within 0°±10° is unknown. The authors prospectively followed all patients who underwent TKA for primary osteoarthritis between December 2011 and April 2012 (194 patients, 195 knees). Each underwent kinematically aligned TKA with manual instruments. Aligning the anteroposterior axis of the tibial component parallel to the line that bisects the oval boundary of the lateral tibial condyle set internal/external rotation. Removing bone from the posterior femoral condyles equal in thickness to the femoral component after correction for cartilage wear set internal/external rotation and anteroposterior translation of the femoral component. Rotational mismatch of the tibial component on the femoral component was determined from a computed tomography scan of the knee. Ninety-seven percent of kinematically aligned TKA with fixed-bearing components had a rotational mismatch within 0°±10° (overall range, -11° to 11°). This percentage was higher and the range narrower than the 85% of TKA within 0°±10° and the -14° to 16° range reported for mechanically aligned TKA. The use of manual instruments to kinematically aligned TKA reliably limited rotational mismatch to within 0°±10°, which has been associated with better function.

Accurate alignment and high function after kinematically aligned TKA performed with generic instruments

PURPOSE

Performing kinematically aligned total knee arthroplasty (TKA) with generic instruments is less costly than patient-specific instrumentation; however, the alignment and function with this new technique are unknown.

METHODS

One hundred and one consecutive patients (101 knees) treated with kinematically aligned TKA, implanted with use of generic instruments, were prospectively followed. The medial collateral ligament was not released. The lateral collateral ligament was released in the 17 % of patients with a fixed valgus deformity. Six measures of alignment were categorized from a scanogram of the extremity, an axial scan of the knee, and an intraoperative measurement. Both the Oxford Knee and WOMAC™ scores were assessed as function. High function was a mean Oxford Knee score >41.

RESULTS

The frequency that patients were categorized as in-range was 93 % for the mechanical alignment of the limb (0° ± 3°), 94 % for the joint line (-3° ± 3°), 57 % for the anatomic axis of the knee (-2.5° ± -7.4° valgus), 4 % for the varus-valgus rotation of the tibial component (≤0° valgus), 98 % for the rotation of the tibial component with respect to the femoral component (0° ± 10°), and 94 % for the intraoperative change in the anterior-posterior distance of the tibia with respect to the femur at 90° of flexion (0 ± 2 mm). The mean OKS score was 42, and WOMAC™ score was 89. For each alignment, the function was the same for patients categorized as an outlier or in-range.

CONCLUSIONS

The authors prefer the use of generic instruments to perform kinematically aligned TKA in place of mechanically aligned TKA because five of six alignments were accurate and because high function was restored regardless of whether patients had an alignment categorized as an outlier or in-range.

LEVEL OF EVIDENCE

IV.

Rotation in total knee arthroplasty: no difference between patient-specific and conventional instrumentation

PURPOSE

It was our hypothesis that patient-specific instrumentation (PSI) can improve the accuracy of the rotational alignment in TKA based on the concept of the system and on the potential to clearly identify pre-operatively during planning the classical anatomical landmarks that serve as references to set-up the rotation both for the femur and tibia.

MATERIALS AND METHODS

In this prospective comparative randomized study, 40 patients (20 in each group) operated in our institution between September 2012 and January 2013 by the 2 senior authors were included. Randomization of patients into one of the two groups was done by the Hospital Informatics Department with the use of a systematic sampling method. All patients received the same cemented high-flex mobile bearing TKA. In the PSI group, implant position was compared to the planed position using previously validated dedicated software. The position of the implants (frontal and sagittal) was compared in the 2 groups on standard X-rays, and the rotational position was analysed on post-operative CT-scan.

RESULTS

90 % of the patients add <2° or mm of difference between the planned position of the implants and the obtained position, except for the tibial rotation where the variations were much higher. Mean HKA was 179° (171-185) in the PSI group with 4 outliers (2 varus: 171° and 172°:184° and 185°) and 178.3° with 2 outliers (171° and 176°) in the control group. No difference was observed between the two groups concerning the frontal and sagittal position of the implants on the ML and AP X-rays. No significant difference of femoral rotation was observed between the two groups with a mean of 0.4° in the PSI group and 0.2° in the control group (p: n.s). Mean tibial rotation was 8° of internal rotation in the PSI group and 15° of internal rotation in the standard group (p: n.s).

CONCLUSION

Based on our results, we were unable to confirm our hypothesis as PSI cannot improve rotation in TKA. More work needs to be done to more clearly define the place of PSI in TKA, to keep on improving the accuracy of the system and to better define the individual targets in TKA in terms of frontal, sagittal and rotational positioning of the implant for each patient.

LEVEL OF EVIDENCE

Prospective comparative randomized study, Level II.

Analysis of tibial component rotation following total knee arthroplasty using 3D high definition computed tomography

Malrotation of the tibial component is associated with poor outcomes after total knee arthroplasty, yet the definition and evaluation of this problem remain controversial. Contributing factors to this controversy include inconsistent and cumbersome methods for measuring rotation, based upon transposed measurements from multiple computed tomography images. We developed and tested the reliability of a new, simple method for measuring tibial component rotation based upon a single, three-dimensional high definition, axial computed tomography image. Sixty individual knees after total knee arthroplasty were evaluated. The intra-reliability and inter-reliability both exceeded 0.9 whether the tibial component was made of titanium, cobalt-chrome or all-polyethylene. Based upon these findings we suggest that this technique be used for evaluating tibial component rotation in future studies.

Customized knee arthroplasty and the role of preoperative imaging

OBJECTIVE

The purpose of this article is to review advances in customized knee arthroplasty, highlighting advances in the use of preoperative imaging for component placement and design.

CONCLUSION

Total knee arthroplasty is a highly successful surgical procedure. Although implant survivorship is generally excellent, failures do occur, and suboptimal component positioning is an important factor in implant failure. Surgical advances have focused on the use of advanced imaging and associated computer-assisted navigation to optimize component positioning.

The stiff total knee arthroplasty: causes and cures

Seven stiff total knee arthroplasties are presented to illustrate the roles of: 1) manipulation under general anesthesia; 2) multiple concurrent diagnoses in addition to stiffness; 3) extra-articular pathology; 4) pain as part of the stiffness triad (pain and limits to flexion or extension); 5) component internal rotation; 6) multifactorial etiology; and 7) surgical exposure in this challenging clinical problem.

Is pain and dissatisfaction after TKA related to early-grade preoperative osteoarthritis?

BACKGROUND

There is growing evidence to suggest many patients experience pain and dissatisfaction after TKA. The relationship between preoperative osteoarthritis (OA) severity and postoperative pain and dissatisfaction after TKA has not been established.

QUESTIONS/PURPOSES

We explored the relationship between early-grade preoperative OA with pain and dissatisfaction after TKA by (1) determining the incidence of early-grade preoperative OA in painful TKAs with no other identifiable abnormality; and (2) comparing this incidence with the incidence of early-grade OA in three other cohorts of patients undergoing TKA.

METHODS

We evaluated all (n = 49) painful TKAs in a 1-year period that had no evidence of loosening, instability, malalignment, infection, or extensor mechanism dysfunction and classified the degree of preoperative OA according to the scale of Kellgren and Lawrence. For comparison, we identified three other cohorts of TKAs from the same center and classified their preoperative grade of OA: Group B (n = 100) was a consecutive series of primary TKAs performed for OA during the same year; Group C (n = 80) were asymptomatic TKAs from 1 to 4 years postoperatively; and Group D (n = 80) were TKAs with some degree of pain at 1 to 4 years postoperatively.

RESULTS

Patients in Group A had a higher incidence of early-grade OA is preoperatively (49%) compared with any of the comparison groups: Group B, 5%; Group C, 6%; and Group D, 10%.

CONCLUSIONS

A high percentage of patients referred for unexplained pain after TKA had early-grade osteoarthritis preoperatively. Patients undergoing TKA for less than Grade 3 or 4 OA should be informed that they may be at higher risk for persistent pain and dissatisfaction.

Design rationale for customized TKA: a new idea or revisiting the past?

Today's most basic and important total knee replacement design concepts arose out of an earlier era in which 2 distinct approaches emerged, functional and anatomic. Functional approaches simplified knee kinetics, were easier to implant, and gained widespread popularity, in part, from their inventory control. Anatomic approaches were an attempt to recreate normal knee motion with low prosthetic contact stress. Historically, however, they became impractical to produce because of the cost of maintaining a wide variety of anatomic knee implants. New customized designs may return the anatomic design to favor due to several key features that borrow anatomic principles developed in the past, and improved with new ideas.

The limits of precision in conventionally instrumented computer-navigated total knee arthroplasty

PURPOSE

Computer-navigated total knee arthroplasty (TKA) improves the accuracy of component implantation. However, the final implant alignment may not match planned alignment. The hypothesis of this study is that although computer navigation improves alignment, imprecision may not be completely eliminated. The aim of the study was to establish the incidence and sources of imprecision during TKA using computer navigation to measure deviations from planned alignment.

METHODS

Computer navigation was used to quantify changes in planned alignment at four steps during 136 TKA's: application of cutting blocks, addition of definitive pin fixation, bone cuts and after prosthesis application. Mean changes in alignment deviation at each step in each plane were measured and the number of significant outliers (>3° from the planned resection plane) were assessed in each plane.

RESULTS

Overall changes in planned alignment were small and non-cumulative between steps but the incidence of outliers (cuts measured as >3° from planned alignment at each step) increased through the steps, with 21.3 % (n = 29) of final implants outlying in the tibial sagittal plane, which was the least precise plane. The highest number of outliers occurred after bone resection and the addition of pins to cutting blocks was also identified as a source of imprecision.

CONCLUSION

Despite improved accuracy of bone resection with computer-navigated TKA, the precision of bone cuts may be affected at several steps of the procedure. Cutting block application, bone resection and prosthesis application may all affect accuracy. Bone cuts should be made with meticulous care, whether navigated or not, and navigated cuts should be checked and corrected, particularly in the tibial sagittal plane.

LEVEL OF EVIDENCE

IV.

MODERN TRENDS IN ORTHOPEDICS: THE KNEE ARTHROPLASTY

Using PubMed the authors analyzed publications dedicated to knee arthroplasty that were published in 2011. The modern trends of knee joint replacement include improvement of implants and instruments; partial knee replacement as alternative to TKA; reducing of surgical trauma due to less-invasive approaches; achieving of deep flexion after TKA; using of computer navigation and individual cutting blocks to make surgery more precise; optimization of rehabilitation process in pre-, intra-and postoperative period; including multimodal pain control; development of complex strategies for prevention of intra- and postoperative complications. In this review the attention was attracted to the most discussed in 2011 subjects: development of new designs and materials of knee implants; navigation, robotics and individualized resection blocks; partial knee replacement; infection, blood loss and venous thromboembolism after TKA; influence of different factors on arthroplasty outcomes, especially components and leg alignment, patella resurfacing, PCL retention or substitution, uncemented fixation, mobility of PE insert, severe pre-op deformities or stiffness, previous intra-articular fractures and tibia or femur osteotomies, soft tissue deficit etc.

Patients with no functional improvement after total knee arthroplasty show different kinematics

PURPOSE

As many as 20 % of all patients following total knee arthroplasty are not satisfied with the result. Rotational alignment is one factor thought to affect clinical outcome. The purpose of this study was to assess relationships between prosthesis rotational alignment, function score and knee kinematics after TKA.

METHODS

In 80 patients a cemented, unconstrained, cruciate-retaining TKA with a rotating platform was implanted. Rotational alignment was measured using CT-scans. Kinematics was assessed using fluoroscopy images.

RESULTS

Seventy-three patients were available for follow-up after two years. Nine patients had more than 10° rotational mismatch between the femoral and tibial component in the postoperative CT scans. These patients showed significantly worse results in the function score. While the normal patients with less than 10° rotational mismatch improved from a mean pre-operative 55 points to a mean 71 points at follow-up, the group with more than 10° mismatch deteriorated from a mean 60 points pre-operatively to a mean 57 points at follow-up. The pattern of motion during passive flexion from approximately 0° to 120° was quite different. While external rotation steadily increased with knee flexion in the normal group, there was internal rotation between 30° and 80° of flexion in the group with more than 10° rotational mismatch.

CONCLUSION

Rotational mismatch between femoral and tibial components exceeding 10° resulted in different kinematics after TKA. It might contribute to worse clinical results observed in those patients and should therefore be avoided.