Femoral Component Malrotation Research Articles

[Translated article] Study of femoral component malrotation as a cause of pain after total knee arthroplasty

IntroductionThe total knee arthroplasty (TKA) has been shown to be a successful and cost-benefit procedure in terms of pain improvement in patient with symptomatic knee osteoarthritis. However, almost a 20% of the patients are not satisfied with the result of the surgery. Material and methodWe have carried out a transversal unicentric cases controls study with clinical cases of the own hospital, obtained by a clinical records revision. A total of 160 patients with a TKA with at least 1 year of follow-up were selected. Demographic variables, functional scales (WOMAC and VAS) and rotation of the femoral component through the analysis of the images obtained by CT scan were collected. ResultsThe total was 133 patients that was divided in two groups. A control group and pain group. The Control group was made up of 70 patients with a mean age of 69.59 years (23 men and 47 women) and the pain group was made up of 63 patients with a mean age of 69.48 years (13 men and 50 women). We didn’t find difference regarding the analysis of the rotation of the femoral component. In addition, we were not found significant differences when applying a stratification by sex. And, the analysis of the malrotation of the femoral component, previously defining limits of value rotation considered as extreme, in any of the case did not show significant differences. ConclusionThe results of the study confirm that malrotation of the femoral component had no influence on the presence of pain at a minimum of one year of follow-up after TKA implantation.

Failure modes in malrotated total knee replacement.

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. 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. 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 ± 0.69years, 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 42months. Early detection of malrotation in TKA and its management with revision of both components can lead to better clinical and functional outcomes. III.

Preoperative rotational assessment of the distal femur with CT may cause femoral component malrotation in TKA

BackgroundBefore total knee arthroplasty (TKA), rotational assessment of the distal femur can be performed using either magnetic resonance imaging (MRI) or computed tomography (CT). Until now, there has been no study comparing the two modalities regarding rotational assessment of the distal femur in the same patients. MethodsWe retrospectively reviewed the preoperative CT and MRI images of 110 knees in 110 patients who underwent TKA. In the axial planes of CT and MRI scan, the posterior condylar axis (PCA), anatomical transepicondylar axis (aTEA), and perpendicular line to anteroposterior axis (pAPA) were identified; the angles between these studied lines were calculated. During TKA, the angles measured on the preoperative CT and MRI were compared with the measurements obtained in the intraoperative field. ResultsThe mean aTEA-PCA angle was 6.2 ± 1.9° with CT and 5.1 ± 1.8° with MRI. The mean pAPA-PCA angle was 4.7 ± 2.1° with CT and 3.5 ± 2.0° with MRI. The mean aTEA-PCA (1.1 ± 1.3°, p = 0.001) and pAPA-PCA (1.2 ± 1.2°, p = 0.012) angles significantly differed between CT and MRI. Intra-operatively, the mean aTEA-PCA angle was 4.7 ± 1.1° and the mean pAPA-PCA angle was 3.2 ± 0.9°. Reliability analysis between the preoperative CT/MRI and the intraoperative measurements gave kappa values of 0.72 for aTEA-PCA and 0.66 for pAPA-PCA with CT, and 0.82 for aTEA-PCA and 0.84 for pAPA-PCA with MRI. ConclusionsPreoperative rotational assessment of the distal femur with CT may cause higher external rotation of femoral component in TKA.

Analysis of Gender Differences in the Rotational Alignment of the Distal Femur in Kinematically Aligned and Mechanically Aligned Total Knee Arthroplasty.

To compare the angle between the external rotation references of the femoral components in the axial plane by gender and lower limb alignment in Korean patients with osteoarthritis (OA). Magnetic resonance (MR) images of 1273 patients were imported into a modeling software and segmented to develop three-dimensional femoral bony and cartilaginous models. The surgical transepicondylar axis (sTEA), posterior condylar axis (PCA), the kinematically aligned axis (KAA), and anteroposterior axis were used as rotational references in the axial plane for mechanically aligned (MA) TKA. The relationship among axes were investigated. Among 1273 patients, 942 were female and 331 were male. According to lower limb alignment, the varus and valgus knee groups comprised 848 and 425 patients, respectively. All measurements, except PCA-sTEA, differed significantly between men and women; all measurements, except PCA-sTEA, did not differ significantly between the varus and valgus knee groups. In elderly Korean patients with OA, rotational alignment of the distal femur showed gender differences, but no differences were seen according to lower limb alignment. The concern for malrotation of femoral components during kinematically aligned TKA is less in Koreans than in Caucasians and relatively less in women than in men. In MA TKA, malrotation of the femoral components can be avoided by setting different rotational alignments for the genders.

Femoral component malrotation is not correlated with poor clinical outcomes after total knee arthroplasty.

Proper rotational alignment of the femoral component is critical for a successful total knee arthroplasty (TKA). The aim of this systematic review was to analyse the available literature to examine the effect of the TKA femoral component malrotation on clinical outcomes and assess a cut-off value for femoral rotation leading to revision surgery. A detailed and systematic search from 1996 to 2019 of the PUBMED, Medline, Cochrane Reviews and Google Scholar databases had been performed using the keyword terms "total knee arthroplasty OR replacement" AND "femoral alignment OR malalignment OR femoral rotation OR malrotation" AND "clinical outcome". We used the methodological index for non-randomized studies (MINORS) to identify scientifically sound articles in a reproducible format. Eleven articles met inclusion criteria. A total of 896 arthroplasties were included in this review; 409 were unexplained painful TKA patients, while 487 were painless TKA patients. The mean age of patients was 67.5 (± 2.1) years. The mean post-operative follow-up delay was 46.8 (± 32.2) months. The mean of MINORS score was 21 points indicating good methodological quality in the included studies. The present review confirms that the malrotation of the femoral component in TKA does not correlate automatically to poor clinical and functional outcome. The clinical relevance of this study was that, to improve accuracy in femoral component rotation, surgeons should consider the anatomical variability of femur in each knee and perform additional measurements pre- and intra-operatively. Taking a more accurate approach will shed light on unanswered questions in unhappy TKA. III.

Prospective, observational study to evaluate the relation between patient-reported outcomes and component rotation in total knee replacement: protocol for the CRACK study

IntroductionTotal knee replacement (TKR) for osteoarthritis results in a satisfactory outcome in the majority of patients, although up to one in five patients may be dissatisfied with the outcome. Persistent...

Femoral Component Malrotation Produces Quadriceps Weakness and Impaired Ambulatory Function following Total Knee Arthroplasty: Results of a Forward-Dynamic Computer Model.

Proper placement of the prosthetic components is believed to be an important factor in successful total knee arthroplasty (TKA). Implant positioning errors have been associated with postoperative pain, suboptimal function, and inferior patient-reported outcome measures. The purpose of this study was to investigate the biomechanical effects of femoral component malrotation on quadriceps function and normal ambulation. For the investigation, publicly available data were used to create a validated forward-dynamic, patient-specific computer model. The incorporated data included medical imaging, gait laboratory measurements, knee loading information, electromyographic data, strength testing, and information from the surgical procedure. The ideal femoral component rotation was set to the surgical transepicondylar axis and walking simulations were subsequently performed with increasing degrees of internal and external rotation of the femoral component. The muscle force outputs were then recorded for the quadriceps musculature as a whole, as well as for the individual constituent muscles. The quadriceps work requirements during walking were then calculated for the different rotational simulations. The highest forces generated by the quadriceps were seen during single-limb stance phase as increasing degrees of femoral internal rotation produced proportional increases in quadriceps force requirements. The individual muscles of the quadriceps displayed different sensitivities to the rotational variations introduced into the simulations with the vastus lateralis showing the greatest changes with rotational positioning. Increasing degrees of internal rotation of femoral component were also seen to demand increasing quadriceps work to support normal ambulation. In conclusion, internal malrotation of the femoral component during TKA produces a mechanically disadvantaged state which is characterized by greater required quadriceps forces (especially the vastus lateralis) and greater quadriceps work to support normal ambulation.

Incidence of Femoral Component Malrotation Using Posterior Condylar Referencing in Total Knee Arthroplasty.

Proper femoral component rotation in total knee arthroplasty (TKA) is important, given the prognostic impact of a poorly positioned component. The purpose of this observational study was to determine the incidence of femoral component malrotation using posterior condylar axis (PCA) referencing. A total of 100 knees in 92 patients with varus gonarthritis of the knee undergoing primary TKA using a standard medial parapatellar approach were evaluated intraoperatively. After distal femoral resection, the standard femoral sizing guide referencing the posterior condylar axis was used to set femoral component rotation. This was then compared with both the transepicondylar (TEA) and trochlear anteroposterior axes (TRAx). Disparites were recorded and corrected in line with the epicondylar axis. Rotational adjustment for addition of further external rotation was made in 13 (13.0%) cases. In seven cases, the medial pin sites were raised between 1 and 3 mm, and in six cases, the lateral pin site was lowered between 1 and 3 mm (based on risk of notching the femoral cortex). It is critical to not rely exclusively on the PCA to confirm rotational positioning of the femoral component as predicted by posterior condylar referencing guides. Intraoperative adjustment and confirmation using the TEA and TRAx occurred in 13% of primary TKA cases, which might have, otherwise, had a significant effect on the clinical outcome.

How coronal alignment affects distal femoral anatomy: an MRI-based comparison of varus and valgus knees

PurposeIn contemporary total knee arthroplasty (TKA), most often, the goal is to align the femoral component to the epicondylar axis (EA). The posterior condylar axis (PCA) is easier to define than the EA, and thus the relationship of PCA to the EA is then used instead to align the femoral component to the EA. However, the relationship of PCA to EA is not constant and has been reported to differ between varus and valgus knees and with increasing deformity. The aim of this large MRI-based study was to evaluate the relationship between PCA and EA with varying coronal deformity especially with increasing valgus deformity.MethodsEA, PCA, AP (Whiteside’s line) and the mechanical axis were obtained from 474 magnetic resonance imaging (MRI) scans used to create patient-specific instrumentation (PSI) for the Biomet Signature (Warsaw, NJ) system.ResultsThe relationship of EA relative to the PCA showed considerable heterogeneity in both varus and valgus groups. In the valgus group, there was statistically greater external rotation (P < 0.05) of the EA from the PCA with a mean of 2.52° (range − 1.9° to 6°) compared to the varus group with a mean of 2.03° (range − 3.9° to 6.9°). This relationship did not significantly change with increasing severity of coronal malalignment.Externally rotating the femoral cutting guide by 3° from the PCA, 11% (42 of 382) of varus knees would lie outside of ± 3° from EA. In valgus knees, externally rotating the femoral cutting block by 3° or 5° from the PCA, 6.5% (6 of 92) and 33.7% (31 of 92) of knees, respectively, would lie outside of ± 3° from EA.ConclusionThe relationship of PCA to EA is heterogeneous and is not altered significantly with increasing valgus coronal deformity. External rotation beyond 3° from PCA in valgus knees may lead to significant femoral component malrotation in a large proportion cases.

No correlation between rotation of femoral components in the transverse plane and clinical outcome after total knee arthroplasty.

It was hypothesized that malrotation of femoral component in total knee arthroplasty (TKA) will significantly impact clinical outcome. Eighty-eight consecutive patients with primary osteoarthritis of the knee were prospectively evaluated. They received a cemented posterior stabilized TKA (NexGen, Zimmer/Biomet® Inc., Warsaw, IN, USA). The femoral component was placed in 3° of external rotation referenced to the posterior condylar line. Postoperatively, a CT scan was performed to evaluate rotation of femoral component in the transverse plane. SF-36, KSS, and WOMAC, as well as their range of motion was assessed prior to surgery, after 6 and 24months. Data are presented as mean and standard deviation (SD), as well as range if applicable. Correlation analysis was performed between the placement of the femoral component in the transverse plane and the clinical outcome. Femoral component placement was on average 0.1° [SD 2.5°, range - 6.5° to + 6.5°] referenced to the surgical transepicondylar line showing a wide range between the two landmarks after surgery. After 6months, WOMAC category 'physical function' correlated significantly with femoral component rotation (r = - 0.28, p = 0.007). After 24months, WOMAC categories 'physical function' and 'pain' correlated significantly with femoral rotation (r = - 0.41, p < 0.001; and r = - 0.33, p = 0.001). No significant correlations were found between femoral component rotation and range of motion (r = 0.04), WOMAC category "stiffness", KSS, as well as SF-36 questionnaires. These reported formally significant correlations were without any clinical relevance. The study showed that there is a significant patients specific femoral component placement in the transverse plane. Internal or external malrotation of the femoral component does not correlate automatically with poor knee function. The lack of correlation between femoral component position and clinical as well as functional outcome underlines complexity and significant individuality of each patient. The surgeon should be aware of the finding and attention should be paid during surgery when significant divergency is seen between the two landmarks. Soft tissue balancing might be very crucial in these specific patients, which needs to be studied in depth in the future. II.

Unexplained pain following total knee arthroplasty: Is rotational malalignment the problem?

BackgroundMalrotation of tibial and femoral components is a potential source of pain following total knee arthroplasty (TKA). This study aimed to 1) compare component rotation in TKA patients with unexplained pain versus a control group with well-functioning TKAs and 2) investigate the relationship between TKA component rotation and pain. MethodsSeventy one patients with unexplained pain after primary TKA were compared to a control cohort of 41 well functioning TKA patients. Both groups underwent post-operative computed tomography (CT) scans to assess component rotation. Findings were compared between the painful and control TKA groups. ResultsWe found no difference in femoral component rotation between the painful and control groups (mean 0.6° vs 1.0° external rotation (ER), p=0.4), and no difference in tibial component rotation (mean 11.2° vs 9.5° internal rotation (IR), p=0.3). Also, there was no difference in combined mal-rotation (tibial+femoral rotation) between the groups (mean 10.5° vs 8.5°IR, p=0.25). Fifty-nine percent of patients in the painful group had tibial component rotation >9°IR vs 49% in the control group. ConclusionIn the largest study yet on component rotation after TKA, we found no difference in the incidence of tibial, femoral, or combined component mal-rotation in painful versus well-functioning TKAs. Tibial component IR relative to the junction of the medial to middle thirds of the tibial tubercle appears to be common in patients with well-functioning TKAs. The significance of slight tibial IR should be interpreted with caution when evaluating the painful TKA.Level III retrospective case–control study.

A computed-tomography-scan-based template to place the femoral component in accurate rotation with respect to the surgical epicondylar axis in total knee arthroplasty

BackgroundFemoral rotational alignment is considered an essential factor for total knee arthroplasty because malrotation of femoral components results in poor outcomes. To obtain proper alignment, we developed a superimposable computed tomography (CT) scan-based template to intraoperatively determine the accurate surgical epicondylar axis (SEA), and evaluated the effectiveness of this CT template. MethodsIn the experimental group (n=55), three serial slices of CT images, including medial and lateral epicondyles, were merged into a single image, and SEA was overlaid. SEA was traced onto an image of an assumed distal femoral resection level; this combined image was then printed out onto a transparent film as a CT template. Following a distal femoral resection in TKA, SEA was duplicated onto the femoral surface. Thereafter, the posterior condyle was resected parallel to this SEA. In the control group (n=53), posterior condyles were resected at three degrees of the external rotation from the posterior condylar line (PCL).A posterior condylar angle (PCA) between PCL of the femoral component and SEA was postoperatively evaluated. Positive values indicated external rotation of the femoral component from the SEA. ResultsIn the experimental group, PCA was 0.01°±1.61°, and three cases were considered as outliers (greater than three degrees or less than −3 degrees). Conversely, in the control group, PCA was 0.10°±2.4°, and 12 cases were considered as outliers. Consequently, dispersion of PCA data was significantly smaller in the experimental group (P=0.004). ConclusionsThe CT template accurately determined intraoperative SEA.

Internal femoral component malrotation in TKA significantly alters tibiofemoral kinematics.

Femoral component malrotation in total knee arthroplasty (TKA) is clinically proven to cause dissatisfaction and impaired function. This study is an attempt to characterize the tibiofemoral kinematics following femoral malrotation in posterior stabilized (PS) TKA. It was hypothesized that internal malrotation would introduce the most pronounced changes. Six fresh-frozen cadaver specimens were mounted in a kinematic rig. Three motion patterns were applied with the native knee and following PS TKA (passive motion, open chain extension, and squatting) while infrared cameras recorded the trajectories of markers attached to femur and tibia. Three different femoral implants were tested: a conventional posterior stabilized component, and adapted components of the same implant with 5° of intrinsic external and internal rotation, respectively. The implantation of the PS TKA resulted in less tibial internal rotation (squat 33-70°, p < 0.05) and the medial femoral condyle shifted posteriorly especially in deep flexion (squat 84-111°, p < 0.05). Internal component malrotation caused internal rotation and abduction of the tibia in flexion (squat 33-111°, p < 0.05), an elevated (squat 43-111°, p < 0.05) and more anterior (passive 61-126°, p < 0.05) located medial femoral condyle and a lateral femoral condyle located more posterior and inferior (squat 73-111°, p < 0.05) than in the neutrally aligned TKA. External component malrotation caused only little changes under passive motion. Under a squat there was less internal rotation and more adduction to the tibia (33-111°, p < 0.05). The medial femoral condyle was moved more posterior (squat 59-97°, p < 0.05), the lateral femoral condyle more superior (squat 54-105°, p < 0.05) than in the neutrally aligned TKA. The greatest differences to the native tibiofemoral kinematics were introduced by internal rotation of the femoral component. Also neutrally and externally rotated femoral components introduce kinematic changes, but to a lesser extent. With respect to the alterations introduced to kinematics internal malrotation should be avoided when performing PS TKA.

Averaging rotational landmarks during total knee arthroplasty reduces component malrotation caused by femoral asymmetry

BackgroundFemoral component malrotation is a common cause of patient dissatisfaction after total knee arthroplasty. The sulcus line (SL) is more accurate than Whiteside’s line as it corrects for variation in the coronal orientation of the groove. The hypothesis is that averaging the SL and posterior condylar axis (PCA) will reduce femoral malrotation.MethodsThe component was inserted at a position between the SL and PCA in 91 patients. An intraoperative photograph was taken showing the landmarks. These were compared to the component position achieved relative to the surgical epicondylar axis (SEA) on a postoperative CT scan. The component position was compared to the position achieved using the individual landmarks.ResultsRelative to the SEA, the final component position was 0.6° (SD 1.4°, range −3.8° to +4.0°), the coronally corrected SL position was −0.7° (SD 2.3°, −5.5° to +4.6°), the PCA position was 0.9° (SD 1.9°, −6.1° to +5.0°). Averaging the landmarks significantly decreased the variance of the component position compared to using the SL and PCA individually. The number of outliers (>3° from SEA) was also significantly less (p < 0.05) for the average position (2/84) when each was compared to the SL (16/84) and PCA (14/84) individually. In 21/84 (25%) of cases, there was more than 4° of divergence between the SL and PCA.ConclusionsAveraging the SL and the PCA decreases femoral component malrotation. Femora are frequently asymmetrical in the axial plane. Referencing posterior condyles alone to set rotation is likely to cause high rates of patellofemoral malalignment.

How to assess femoral and tibial component rotation after total knee arthroplasty with computed tomography: a systematic review.

One of the most important factors leading to revision of total knee arthroplasties (TKA) is malrotation of femoral and/or tibial component. Rotation measurements performed on radiographs are limited and less reliable compared to 2D computed tomography (CT). Nowadays, 2D-CT and 3D-CT can be distinguished in measuring rotation of the TKA components. The aim of this systematic review is to determine the most reliable CT techniques in measuring rotation of the TKA components and to investigate possible cut-off points that can be used in the clinician's decision for a possible revision of the TKA. A search of PubMed, Embase, the Cochrane Central Register of Controlled Trials and Web of Science was performed up to April 2015. Final selections of 12 articles were used in this systematic review. 3D-CT, compared to 2D-CT, is more reliable and shows a high level of intra- and interobserver reliability. Femoral component rotation is measured using the component's posterior condylar line or inner pegs in relation to the epicondylar axis. Five different techniques were used to measure tibial component rotation. The posterior border of the tibial component in relationship to the geometric centre and tibial tubercle was most frequently used. This systematic review shows a strong preference for 3D-CT to determine the component's rotation following a TKA. The literature shows consensus on the reference points of the femoral component. In measurements of the tibial component, various techniques are used with similar results. No clear cut-off point for revision of malrotated TKA components can be stated because of limited evidence. III.

Unexplained Pain Following Total Knee Arthroplasty – Is Rotational Malalignment the Problem?

Objective:Malrotation of both tibial and femoral components has been suggested as a potential source of pain following total knee arthroplasty (TKA). However previous studies have been small, with variable control groups. The aim of this study was to compare component rotational alignment in TKA patients with unexplained pain to a control group with well-functioning TKA.Method:Seventy-one patients presenting with unexplained pain following primary TKA were included in this retrospective, comparative study. Diagnostic work-up included clinical examination, blood tests, x-rays, long-leg films, and CT scan. Patients with an identifiable diagnosis or with initially well-functioning TKAs were excluded. A control group of 41 patients with well-functioning TKAs also underwent CT scans. Femoral component rotation was measured relative to the surgical epicondylar axis, and tibial component rotation relative to the medial third of the tibial tubercle using a previously validated method involving 3D-image reconstruction. Findings were compared between painful and control TKA groups.Results:We found no difference in femoral component rotation between the painful and control groups (mean 0.6° vs 1.0° external rotation (ER), p=0.4), and no difference in tibial component rotation (mean 11.2° vs 9.5° internal rotation(IR), p=0.3). Fifty-nine percent of patients in the painful group had tibial component rotation >9°IR versus 49% in the control group. 6% of patients in the painful group and 2% in the control group had femoral component rotation >3°IR. There was no difference in overall coronal alignment between groups (mean 1.3° varus vs 0.5° varus, p=0.23).Conclusion:In this the largest study yet reported on component rotation in TKA, we found no difference in the incidence of tibial or femoral component malalignment in painful versus well-functioning TKAs. Tibial component IR in particular appears to be a common finding, and its significance when evaluating the painful TKA should be interpreted with caution.

Effect of Rotational Component Alignment on Clinical Outcome 5 to 7 Years After TKA With the Columbus Knee System.

The aim of the study was to examine the effects of rotational component alignment on outcome after total knee arthroplasty (TKA) with a minimum follow-up of 5 years. For this study, 96 patients were available for follow-up at a mean of 5.7 years after TKA. Computed tomography scans were available in 55 patients. Outcome (Oxford Knee Score [KSS], Knee Injury and Osteoarthritis Outcome Score [KOOS], 36-item Short Form Health Survey) was correlated with postoperative femoral and tibial component malrotation or femorotibial rotational alignment mismatch. Results showed that femoral or tibial component malrotation or femorotibial mismatch were present in 15.5%, 38.2%, and 29.1% of patients, respectively. Although femoral componoent malrotation was associated with significantly poorer, KSS and KOOS scores, outcome was comparable for patients with or without tibial component malrotation or femorotibial mismatch. In conclusion, both internal and external rotational femoral malalignment exceeding 3° is associated with significantly poorer subjective and objective outcome 5 to 7 years after TKA. Tibial component malrotation and femorotibial mismatch were more common, but did not significantly compromise outcome. [Orthopedics. 2016; 39(3):S50-S55.].

Combining the Sulcus Line and Posterior Condylar Axis Reduces Femoral Malrotation in Total Knee Arthroplasty

Objectives:Femoral component malrotation is a common cause of patient dissatisfaction after total knee arthroplasty. The Sulcus Line (SL) is formed from multiple points along the floor of the trochlear groove, and has been shown to be more accurate than Whiteside Line. A trochlear alignment guide (TAG) is required to maintain the accuracy of the SL and allow intraoperative comparison of the SL and the posterior condylar axis (PCA). The hypothesis is that averaging these two landmarks will lead to less femoral malrotation.Methods:Surgery was performed in 50 patients using the TAG. The component was inserted at a position between the SL and PCA. An intraoperative photograph was taken of the distal cut surface of the femur showing the pin-holes representing the SL, the PCA and the final component position. These were compared to the component position achieved relative to the surgical epicondylar axis (SEA) on a postoperative CT scan. Comparison was made between the final component position and the position which would have been achieved using either the SL or PCA individually. The theoretical position which could be achieved by averaging the SL and PCA was also calculated.Results:The SEA was identified on CT scan in 46 cases. The component position was 0.7° (SD 1.5°), SL was -0.8° (SD 2.1°), PCA was 1.1° (SD 2.1°), the calculated average position between SL and PCA was 0.1° (SD 1.5°). There was a significant decrease in variance between both the component position and the calculated average when each was compared to the SL and PCA individually. The number of outliers greater than 3° from the SEA was also significantly less (p<0.05) for both the component position (3/46, 6%) and the calculated average position(1/46, 2%) when each was compared to the SL (10/46, 22%) and PCA (11/46, 24%) individually. The rotational alignment of the trochlear and posterior condyles diverged from each other more than 4° in 11/46 (24%).Conclusion:Averaging the SL and the PCA intraoperatively leads to decreased femoral component malrotation compared to the use of either landmark individually.

Referencing the sulcus line of the trochlear groove and removing intraoperative parallax errors improve femoral component rotation in total knee arthroplasty

PurposeFirstly, to assess and compare the accuracy and reproducibility of the sulcus line compared to Whiteside’s line. Secondly, to assess the accuracy of intraoperative techniques for using the rotational alignment of the trochlear groove to set femoral rotation. Thirdly, to assess the reproducibility of a trochlear alignment guide which removes parallax errors that occur when projecting the sulcus line onto the surface of the femur. Finally, to measure the result of combining the geometrically accurate sulcus line and the posterior condylar axis.MethodsThree surgeons measured eight rotational angles on ten cadaveric femora. This included Whiteside’s line, the sulcus line and the techniques in which they can be referenced during surgery.ResultsRelative to the anatomical epicondylar axis, the sulcus line (mean −2.8°, SD 2.0°, range −5.4° to 0.8°) had significantly lower variance (F = 5.16, p = 0.036) than Whiteside’s line (mean −2.0°, SD 3.7°, range −6.0° to 3.4°). The trochlear alignment guide produced the best results of the intraoperative techniques by maintaining the accuracy of the sulcus line and projecting it onto the distal cut surface of the femur without change in rotational angle.ConclusionThe sulcus line is more accurate and reproducible than Whiteside’s line. Removing parallax errors during surgery improves femoral component rotation. The trochlear alignment guide produced accurate results suggesting that it may be beneficial in a clinical setting. Averaging the sulcus line and posterior condylar axis on the cut surface of the femur improved accuracy over the individual landmarks. Femoral component malrotation is a common cause of patient dissatisfaction and revision surgery. By isolating the rotational alignment of the trochlear groove using the sulcus line, and maintaining its accuracy with an intraoperative guide, we can decrease the risk of femoral component malrotation and improve patient outcomes.

Measured Resection Versus Gap Balancing for Total Knee Arthroplasty

The number of TKAs performed in the United States is expected to increase substantially in the next two decades [6]. Additionally, surgeons are performing TKAs in younger and more active patients. While many articles discuss the importance of radiographic alignment, soft-tissue balancing is essential to a successful TKA. There remains great controversy in how surgeons obtain correct alignment and soft-tissue tensioning. Some surgeons utilize a measured resection technique, while other surgeons favor a gap-balancing technique. As such, I have invited two internationally known orthopaedic surgeons to discuss these two approaches, both of which seek to achieve the same general goal — a well-aligned and well-balanced TKA. Bryan D. Springer MD is an attending joint replacement surgeon at the OrthoCarolina Hip and Knee Center in Charlotte, NC, USA, and a member of The Knee Society. Dr. Springer is the recipient of numerous Knee Society Awards, and has extensive experience with the gap-balancing technique. Sebastien Parratte MD, PhD is an attending joint replacement surgeon and assistant professor of orthopedic surgery at the University Hospital of Marseille in Marseille, France. Dr. Parratte likewise has received numerous Knee Society and Hip Society Awards, and has considerable experience with the measured resection technique. Matthew P. Abdel MD:What do you each see as the advantages of the gap-balancing or measured resection techniques, in terms of achieving ligament balance? Bryan D. Springer MD: Instability following TKA remains one of the most common modes of early failure. The gap-balancing technique is based on the progressive release of ligaments to create equal and symmetric flexion and extension gaps. It is imperative that one understands what structures affect extension, flexion, and both in order to create proper balance. One of the fundamental differences between the gap-balancing technique and measured resection technique lies in setting the rotation of the femoral component to achieve a symmetric flexion gap. Measured resection relies on arbitrary bony landmarks (surgical transepicondylar axis, posterior condylar axis, and anteroposterior (AP) axis of the femur) in order to set rotation. While bony landmarks may occasionally provide accurate rotation of the femoral component, one major disadvantage is the surgeon’s inability to accurately and reproducibly find them intraoperatively. Research has suggested there is wide variability in femoral component rotation when using bony landmarks, which leads to asymmetry of the flexion space and condylar lift off (Fig. 1) in flexion [3]. Open in a separate window Fig. 1 This schematic depicts condylar lift off that occurs when there is asymmetry of the flexion space. Published courtesy of Bryan D. Springer MD.