Differences in Trochlear Morphology from Native Using a Femoral Component Interfaced with an Anatomical Patellar Prosthesis in Kinematic Alignment and Mechanical Alignment

Hull, Maury L.; Howell, Stephen M.

doi:10.1055/s-0040-1716413

Cited by 9 publications

(12 citation statements)

References 25 publications

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“…The 2D radiographic findings of the present study, which showed a femoral component with a PTA of 6° valgus did not include the Q-angle in MA TKA simulations, is consistent with 3-D analysis studies that showed that MA TKA does not restore native trochlear morphology [14,22,24]. For example, a study of 45 femoral component designs aligned mechanically in 4116 3-D CT femoral models showed that 41% of the PTA fell out of the range of the native trochlear angle, representing a potential source for biomechanical imbalance, which manufacturers may need to take into account for future implant designs [24].…”

Section: Discussionsupporting

confidence: 89%

Better forgotten joint scores when the angle of the prosthetic trochlea is lateral to the quadriceps vector in kinematically aligned total knee arthroplasty

Howell,

Sappey‐Marinier,

Niesen

et al. 2023

Knee surg. sports traumatol. arthrosc.

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PurposeThe primary aim was to analyze unrestricted kinematic alignment (unKA) total knee arthroplasty (TKA) and determine the frequency of medial deviation of the prosthetic trochlear angle (PTA) of the femoral component relative to the quadriceps vector (QV) that terminates at the anterior inferior iliac spine (AIIS), and whether patients with medial deviation had a worse Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) relative to those with lateral deviation. The secondary aim was to determine the frequency of medial deviation for mechanical alignment (MA) TKA simulations. Methods From a database of a single surgeon, the study extracted de-identified data on 147 patients with a CT scanogram showing the pelvis and AIIS, a limb with an unKA TKA, and a native (i.e., healthy) opposite limb. On the scanogram, an examiner, blinded to the PROMs, measured the PTA-QV angle on the unKA TKA and on the opposite limb simulated MA TKA by drawing the PTA at 6° valgus relative to the femoral mechanical axis and measuring the PTA-QV angle. Results Medial deviation of the PTA occurred in 86% of patients with unKA TKA, and the 126 with medial deviation had a 17/1 point worse median FJS/OKS than the 21 with lateral deviation at a mean follow-up of 47 ± 8 months, respectively (p < 0.0001, p = 0.0053). In addition, 21%, 17%, and 8% of MA TKA had medial deviation after radiographic simulation using reported surgical errors for manual, patient-specific, and robotic instrumentation, respectively. Conclusion In most patients with unKA TKA and a smaller proportion with MA TKA, a PTA of 6° valgus was medial to the QV, which, by excluding the patient's Q-angle, might alter patellofemoral kinematics like an incorrectly oriented trochleoplasty. The 17-point worse FJS in the patients with an unKA TKA and medial deviation of the PTA suggests the surgical target should be to orient the PTA lateral to the QV. Level of evidence IV.

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Section: Discussionsupporting

confidence: 89%

Better forgotten joint scores when the angle of the prosthetic trochlea is lateral to the quadriceps vector in kinematically aligned total knee arthroplasty

Howell,

Sappey‐Marinier,

Niesen

et al. 2023

Knee surg. sports traumatol. arthrosc.

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“…One reason for the low incidence of reoperation for patellofemoral symptoms is that KA with a MA d -FC restores patellofemoral kinematics and contact pressure distribution closer to the native knee than MA with a MA d -FC [ 24 , 25 ]. Another is that the 3-dimensional native trochlear morphology is more closely restored with KA than MA when assessed with a variety of MA d -FC [ 1 , 26 , 27 ].…”

Section: Discussionmentioning

confidence: 99%

The Trochlear Groove of a Femoral Component Designed for Kinematic Alignment Is Lateral to the Quadriceps Line of Force and Better Laterally Covers the Anterior Femoral Resection Than a Mechanical Alignment Design

Sappey‐Marinier

Howell

Nedopil

et al. 2022

JPM

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Background: A concern about kinematically aligned (KA) total knee arthroplasty (TKA) is that it relies on femoral components designed for mechanical alignment (MAd-FC) that could affect patellar tracking, in part, because of a trochlear groove orientation that is typically 6° from vertical. KA sets the femoral component coincident to the patient’s pre-arthritic distal and posterior femoral joint lines and restores the Q-angle, which varies widely. Relative to KA and the native knee, aligning the femoral component with MA changes most distal joint lines and Q-angles, and rotates the posterior joint line externally laterally covering the anterior femoral resection. Whether switching from a MAd- to a KAd-FC with a wider trochlear groove orientation of 20.5° from vertical results in radiographic measures known to promote patellar tracking is unknown. The primary aim was to determine whether a KAd-FC sets the trochlear groove lateral to the quadriceps line of force (QLF), better laterally covers the anterior femoral resection, and reduces lateral patella tilt relative to a MAd-FC. The secondary objective was to determine at six weeks whether the KAd-FC resulted in a higher complication rate, less knee extension and flexion, and lower clinical outcomes. Methods: Between April 2019 and July 2022, two surgeons performed sequential bilateral unrestricted caliper-verified KA TKA with manual instruments on thirty-six patients with a KAd- and MAd-FC in opposite knees. An observer measured the angle between a line best-fit to the deepest valley of the trochlea and a line representing the QLF that indicated the patient’s Q-angle. When the trochlear groove was lateral or medial relative to the QLF, the angle is denoted + or −, and the femoral component included or excluded the patient’s Q-angle, respectively. Software measured the lateral undercoverage of the anterior femoral resection on a Computed Tomography (CT) scan, and the patella tilt angle (PTA) on a skyline radiograph. Complications, knee extension and flexion measurements, Oxford Knee Score, KOOS Jr, and Forgotten Joint Score were recorded pre- and post-operatively (at 6 weeks). A paired Student’s T-test determined the difference between the KA TKAs with a KAd-FC and MAd-FC with a significance set at p < 0.05. Results: The final analysis included thirty-five patients. The 20.5° trochlear groove of the KAd-FC was lateral to the QLF in 100% (15 ± 3°) of TKAs, which was greater than the 69% (1 ± 3°) lateral to the QLF with the 6° trochlear groove of the MAd-FC (p < 0.001). The KAd-FC’s 2 ± 1.9 mm lateral undercoverage of the anterior femoral resection was less than the 4.4 ± 1.5 mm for the MAd-FC (p < 0.001). The PTA, complication rate, knee extension and flexion, and clinical outcome measures did not differ between component designs. Conclusions: The KA TKA with a KAd-FC resulted in a trochlear groove lateral to the QLF that included the Q-angle in all patients, and negligible lateral undercoverage of the anterior femoral resection. These newly described radiographic parameters could be helpful when investigating femoral components designed for KA with the intent of promoting patellofemoral kinematics.

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“…Riviere et al reported a high degree of discrepancy between native and prosthetic trochlear alignment in kinematically aligned TKR, with a more valgus orientation of the latter [25]. In additional studies, this discrepancy was also shown for mechanical alignment [13, 26]; this could be interpreted as an inherent limitation of implant designs. Barink has already proposed a more truly anatomical femoral configuration, with a more medially oriented trochlea [2].…”

Section: Discussionmentioning

confidence: 99%

Mismatch between trochlear coronal alignment of arthritic knees and currently available prosthesis: a morphological analysis of 4116 knees and 45 implant designs

Rosa

Hazratwala

Wilkinson

2022

Knee Surg Sports Traumatol Arthrosc

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Purpose In up to a fifth of total knee replacements (TKR), surgeons are not capable of achieving good clinical and functional results. Despite comprehensive diagnostic workup, an underlying cause is not always identified in these patients. The purpose of this study is to compare native and prosthetic trochlear anatomies, to evaluate a potential source of morphologic mismatch and theoretically, of poor clinical outcomes. Methods Native trochlear angles of 4116 knee CTs from 360 Knee Systems database of arthritic pre-operative TKR patients were evaluated. A semi-automated tridimensional analysis was performed to define the native trochlear angle in the coronal plane (NTA) among other 142 parameters. An active search was conducted to identify currently available TKR models; prosthetic trochlear orientation in the coronal plane (PTA) was extracted from the technical data provided by manufacturers. Results The mean native trochlear angle (NTA) was 1.6° ± 6.6° (valgus) with a range from − 23.8° (varus) to 30.3°(valgus). A valgus NTA was present in 60.6% of the knees and 39.4% of them had a varus NTA. 89 TKR models were identified; trochlear details were available for 45 of them, of which 93% were designed with a valgus orientation of the prosthetic trochlear angle (PTA) and 6.9% showed a neutral (0°) PTA. Varus alignment of PTA was not present in any system. Angular numeric values for PTA were available for 34 models; these ranged from 0° to 15° of valgus, with a median value of 6.18° (SD ± 2.88°). Conclusion This study shows a significant mismatch between native and prosthetic trochlear angles. A relevant proportion of the studied knees (41.45%) fall out of the trochlear angle range of currently available implants; representing a potential source for biomechanical imbalance. While further research is warranted to fully understand the clinical implications of the present study, manufacturers may need to take these findings into account for future implant designs. Level of evidence Level III, retrospective cohort study.

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Differences in Trochlear Morphology from Native Using a Femoral Component Interfaced with an Anatomical Patellar Prosthesis in Kinematic Alignment and Mechanical Alignment

Cited by 9 publications

References 25 publications

Better forgotten joint scores when the angle of the prosthetic trochlea is lateral to the quadriceps vector in kinematically aligned total knee arthroplasty

Better forgotten joint scores when the angle of the prosthetic trochlea is lateral to the quadriceps vector in kinematically aligned total knee arthroplasty

The Trochlear Groove of a Femoral Component Designed for Kinematic Alignment Is Lateral to the Quadriceps Line of Force and Better Laterally Covers the Anterior Femoral Resection Than a Mechanical Alignment Design

Mismatch between trochlear coronal alignment of arthritic knees and currently available prosthesis: a morphological analysis of 4116 knees and 45 implant designs

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