Raising the Joint Line in TKA is Associated With Mid-flexion Laxity: A Study in Cadaver Knees

Although mechanical alignment (MA) has traditionally been considered the gold standard, the optimal alignment strategy for total knee arthroplasty (TKA) is still debated. Kinematic alignment (KA) aims to restore native alignment by respecting the three axes of rotation of the knee and thereby producing knee motion more akin to the native knee. Designer surgeon case series and case control studies have demonstrated excellent subjective and objective clinical outcomes as well as survivorship for KA TKA with up to 10 years follow up, but these results have not been reproduced in high-quality randomized clinical trials. Gait analyses have demonstrated differences in parameters such as knee adduction, extension and external rotation moments, the relevance of which needs further evaluation. Objective improvements in soft tissue balance using KA have not been shown to result in improvements in patient-reported outcomes measures. Technologies that permit accurate reproduction of implant positioning and objective measurement of soft tissue balance, such as robotic-assisted TKA and compartmental pressure sensors, may play an important role in improving our understanding of the optimum alignment strategy and implant position. Cite this article: EFORT Open Rev 2020;5:486-497. DOI: 10.1302/2058-5241.5.190093

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“… 20 Furthermore, an orthogonal distal femoral resection may raise the medial joint line and cause mid-flexion instability. 21 …”

Section: Introductionmentioning

confidence: 99%

Clinical outcomes of kinematic alignment versus mechanical alignment in total knee arthroplasty: a systematic review

2020

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“…The influencing factors on the knee joint biomechanics are difficult to analyse under reproducible conditions for a variety of reasons. Currently, knee joint stability is qualitatively assessed intraoperatively by the surgeon via manual varus-valgus and anterior-posterior stress testing at 0° and 90° knee flexion, while the stability in the mid-flexion range is not quantitatively considered 33 . In addition to intraoperative examinations, knee joint stability can be investigated using computational, experimental, or clinical studies.…”

Section: Discussionmentioning

confidence: 99%

“…During surgery, clinicians are only able to subjectively examine the knee joint by analysing the flexion and extension gap, however, without the capability to quantitatively evaluate neither knee kinematics nor kinetics 33 . Furthermore, in-vitro studies lack the ability to analyse the impact of isolated influencing factors on the overall musculoskeletal dynamics in terms of reproducibility, and most of these studies do not consider the physiological soft tissue response during dynamic activities 33–37 . Such in-vivo measurements are ethically not possible.…”

Section: Introductionmentioning

confidence: 99%

Effect of surgical parameters on the biomechanical behaviour of bicondylar total knee endoprostheses – A robot-assisted test method based on a musculoskeletal model

Kebbach

Grawe

Geier

et al. 2019

Sci Rep

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The complicated interplay of total knee replacement (TKR) positioning and patient-specific soft tissue conditions still causes a considerable number of unsatisfactory outcomes. Therefore, we deployed a robot-assisted test method, in which a six-axis robot moved and loaded a bicondylar cruciate-retaining (CR)-TKR in a virtual lower extremity emulated by a musculoskeletal multibody model. This enabled us to systematically analyse the impact of the posterior cruciate ligament (PCL), tibial slope, and tibial component rotation on TKR function while considering the physical implant components and physiological-like conditions during dynamic motions. The PCL resection yielded a decrease of femoral rollback by 4.5 mm and a reduction of tibiofemoral contact force by 50 N. A reduced tibial slope led to an increase of tibiofemoral contact force by about 170 N and a decrease of femoral rollback up to 1.7 mm. Although a higher tibial slope reduced the contact force, excessive tibial slopes should be avoided to prevent joint instability. Contrary to an external rotation of the tibial component, an internal rotation clearly increased the contact force and lateral femoral rollback. Our data contribute to improved understanding the biomechanics of TKRs and show the capabilities of the robot-assisted test method based on a musculoskeletal multibody model as a preoperative planning tool.

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“…It has been shown that a reduced posterior condylar offset (PCO) and subsequent joint line elevation will result in coronal laxity in the mid-flexion range since the axis for rotation of the knee is proximalized and ventralized ( Fig. 1) [14]. The MCL isometry can only be preserved by fully restoring the medial PCO and the medial joint line height.…”

Section: Aims Of the Flexion First Balancer Techniquementioning

confidence: 99%

Flexion First Balancer: description of new technique in TKA to reproduce joint line and pre-disease mechanical alignment

et al. 2020

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A considerable proportion of patients (19%) are dissatisfied after total knee arthroplasty (TKA). Possible factors contributing to this dissatisfaction are decreased posterior condylar offset (PCO) with subsequent joint line elevation, leading to mid-flexion instability. Secondly, the pre-disease mechanical alignment is changed into a neutral alignment. The Flexion First Balancer was developed to avoid these problems. This technique aims to maintain MCL isometry by restoring medial PCO and medial joint line to its pre-disease level. Also, to reconstruct the pre-disease mechanical alignment by adjusting the distal femoral angle. In this study we provide a detailed technical overview of the Flexion First Balancer technique.

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Raising the Joint Line in TKA is Associated With Mid-flexion Laxity: A Study in Cadaver Knees

Abstract: When recutting the distal and posterior femur and downsizing the femoral component, surgeons should be aware that this action might increase the laxity in mid-flexion, even if the knee is stable at 0° and 90°.

Cited by 89 publications

References 50 publications

Clinical outcomes of kinematic alignment versus mechanical alignment in total knee arthroplasty: a systematic review

Clinical outcomes of kinematic alignment versus mechanical alignment in total knee arthroplasty: a systematic review

Effect of surgical parameters on the biomechanical behaviour of bicondylar total knee endoprostheses – A robot-assisted test method based on a musculoskeletal model

Flexion First Balancer: description of new technique in TKA to reproduce joint line and pre-disease mechanical alignment

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