Revisiting the tibial crest as reference for the mechanical alignment of the tibial component in total knee arthroplasty: a cadaveric study on Caucasian tibiae

Influence of posterior tibial slope on postoperative outcomes after postero-stabilized and condylar-stabilized total knee arthroplasty

PURPOSE

To compare clinical outcomes and surgical times of two different types of total knee arthroplasty(TKA), postero-stabilized(PS) and condylar-stabilized(CS), in relation to posterior tibial slope(PTS) values and the deviation of these values from the surgical technique.

METHODS

168 patients undergoing TKA surgery between 2016 and 2020 met our inclusion criteria. For each case, gender, age at surgery, operating time, type of implant and preoperative PTS(preop-PTS) and postoperative PTS(postop-PTS) measurements were collected; difference(∆PTS) between preop-PTS and postop-PTS was also calculated. Short Form 12 Mental and Physical scores(SF-12 M and P) and functional Knee Society Score(fKSS) were collected preoperatively and at a minimum of 12 months postoperatively. Four subgroups were thus created in relation to PS or CS system and postop-PTS value(≤ 5°and > 5°).

RESULTS

Of the 168 patients, 96 had a PS system and 72 CS system. Performing a CS-TKA took less time than a PS-TKA(p < 0.05). SF-12P showed better results(p < 0.05) in CS-TKA group than PS-TKA, probably because of the younger age of CS-TKA patients(p < 0.05). In the PS > 5° all examined postoperative scores were better(p < 0.05) than PS ≤ 5°, while only fKSS was better(p < 0.05) in CS > 5° than CS ≤ 5°. No significant difference(p > 0.05) in terms of postoperative outcomes between the PS > 5° and CS > 5° was noted, whereas only SF-12P was better in the CS ≤ 5° compared with PS ≤ 5°. Highest values of SF-12 M and fKSS were obtained in the PS ≤ 5°, in which postop-PTS was closer to technique.

CONCLUSION

When performing a PS-TKA, the best result was obtained with a postop-PTS > 5°, but comparable outcomes between the two systems were evident with postop-PTS > 5°. It is crucial to come as close as possible to the indications reported in surgical technique regardless ∆PTS.

Improved angle accuracy of tibial plateau osteotomy for total knee arthroplasty using tibial mechanical axis skin-mapping

Background

The tibial crest is often used as an anatomic landmark for tibial plateau osteotomy (TPO) in total knee arthroplasty (TKA), but it is not very accurate. This study aimed to investigate errors in using the tibial crest as a marker and present a simple approach to improve the angle accuracy of TPO by mapping the tibial mechanical axis (TMA), determined preoperatively, according to the tibial crest on the skin overlying the tibia.

Methods

We evaluated 50 healthy young volunteers and 100 pre-TKA osteoarthritic knees. The middle tibial crest lines (MTCLs) were marked on the shank tibial skin and covered with Kirschner wires. All participants underwent two sets of anteroposterior (AP) standing radiographs of the lower extremity, with the feet in neutral and external rotation positions. The MTCL-TMA angles were measured and compared. The TMA was mapped onto the tibial skin according to the MTCL-TMA angle prior to TKA and used for TPO. Postoperative outcomes were determined by the angle between the vertical tibial component axis (TCA) and the TMA.

Results

The MTCL had no evident relationship with the TMA. A few MTCLs were parallel to the TMA. External rotation of the foot significantly changed the MTCL-TMA relationship. The angle accuracy of the TPO as guided by TMA skin-mapping was 0.83 ± 0.76°. No postoperative errors exceeded 3°.

Conclusion

The MTCL was not equivalent to the TMA. The TPO error can be reduced by preoperatively marking the TMA on the tibial skin according to the MTCL.

Reference Axes for Tibial Component Rotation in Total Knee Arthroplasty: Computed Tomography-Based Study of 1,351 Tibiae

BACKGROUND

Many anatomic landmarks have been described for setting tibial component rotation intraoperatively. There is no consensus as to which axis is best for reducing outliers and preventing malrotation.

METHODS

The SOMA (Stryker Orthopaedic Modeling and Analytics) database (Stryker) was used to identify 1,351 computed tomography (CT) scans of the entire tibia. Several reference axes for the tibia (including the Mayo axis, Akagi line, Insall line, anterior condylar axis [ACA], posterior condylar axis [PCA], lateral tibial cortex [LTC], Cobb axis, tibial crest line [TCL], and transmalleolar axis [TMA]) were constructed according to published guidelines. The Berger method served as the reference standard.

RESULTS

The Mayo method (involving a line connecting the medial and middle one-thirds of the tibial tubercle and the geometric center of the tibia) and the Insall line (involving a line connecting the posterior cruciate ligament [PCL] insertion and the intersection of the middle and medial one-thirds of the tibial tubercle) both had low variability relative to the Berger method (7.8° ± 1.0° and 5.1° ± 2.2°, respectively) and a low likelihood of internal rotation errors (0.7% and 1.8%, respectively). No clinically significant gender-based differences were found (<0.7° for all). The same was true for ethnicity, with the exception of consistently greater tibial intorsion in Asian versus Caucasian individuals (mean difference in TCL position, +4.5° intorsion for Asian individuals; p < 0.001).

CONCLUSIONS

This CT-based study of 1,351 tibiae (which we believe to be the largest study of its kind) showed that the Mayo and Insall methods (both of which reference the medial and middle one-thirds of the tibial tubercle) offer an ideal balance of accuracy, low variability, and a reduced likelihood of internal rotation errors. Setting rotation on the basis of distal landmarks (tibial shaft and beyond) may predispose surgeons to substantial malrotation errors, especially given the differences in tibial torsion found between ethnic groups in this study.

LEVEL OF EVIDENCE

Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Comparison of tibial alignment parameters based on clinically relevant anatomical landmarks : a deep learning radiological analysis

AIMS

Accurate identification of the ankle joint centre is critical for estimating tibial coronal alignment in total knee arthroplasty (TKA). The purpose of the current study was to leverage artificial intelligence (AI) to determine the accuracy and effect of using different radiological anatomical landmarks to quantify mechanical alignment in relation to a traditionally defined radiological ankle centre.

METHODS

Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A sub-cohort of 250 radiographs were annotated for landmarks relevant to knee alignment and used to train a deep learning (U-Net) workflow for angle calculation on the entire database. The radiological ankle centre was defined as the midpoint of the superior talus edge/tibial plafond. Knee alignment (hip-knee-ankle angle) was compared against 1) midpoint of the most prominent malleoli points, 2) midpoint of the soft-tissue overlying malleoli, and 3) midpoint of the soft-tissue sulcus above the malleoli.

RESULTS

A total of 932 bilateral full-limb radiographs (1,864 knees) were measured at a rate of 20.63 seconds/image. The knee alignment using the radiological ankle centre was accurate against ground truth radiologist measurements (inter-class correlation coefficient (ICC) = 0.99 (0.98 to 0.99)). Compared to the radiological ankle centre, the mean midpoint of the malleoli was 2.3 mm (SD 1.3) lateral and 5.2 mm (SD 2.4) distal, shifting alignment by 0.34^o (SD 2.4^o) valgus, whereas the midpoint of the soft-tissue sulcus was 4.69 mm (SD 3.55) lateral and 32.4 mm (SD 12.4) proximal, shifting alignment by 0.65^o (SD 0.55^o) valgus. On the intermalleolar line, measuring a point at 46% (SD 2%) of the intermalleolar width from the medial malleoli (2.38 mm medial adjustment from midpoint) resulted in knee alignment identical to using the radiological ankle centre.

CONCLUSION

The current study leveraged AI to create a consistent and objective model that can estimate patient-specific adjustments necessary for optimal landmark usage in extramedullary and computer-guided navigation for tibial coronal alignment to match radiological planning.Cite this article: Bone Jt Open 2022;3(10):767-776.

Efficacy Analysis of Selection of Distal Reference Point for Tibial Coronal Plane Osteotomy during Total Knee Arthroplasty: A Literature Review

Total knee arthroplasty is an effective treatment for end-stage knee osteoarthritis. The tibial platform osteotomy must take full account of the coronal plane, the sagittal plane, and the rotational alignment of the tibial prosthesis. During surgery, individual differences in the coronal alignment of the tibia need to be taken into account as poor alignment after surgery can lead to rapid wear of the tibial platform, reducing the longevity of the prosthesis and adversely affecting quality of life. Intraoperative tibial osteotomies are often performed using extramedullary alignment. When an extramedullary alignment approach is used, the proximal tibial osteotomy guide is usually placed in the medial third of the tibial tuberosity. There is no consensus on the most reliable anatomical landmarks or axes for achieving distal tibial coronary alignment. Anatomical points or reference axes that are highly reproducible and precise need to be identified. From available data it appears that most surgeons use the extensor hallucis longus tendon, the second metatarsal, and the anterior tibial cortex to determine the distal localization point. However, its accuracy has not been confirmed in clinical and radiographic data, and the alignment concept and preoperative planning for total knee arthroplasty has paid more attention to rotational alignment, but there are few studies on the coronal alignment of the tibia. This article reviews the recent use of the distal tibial coronal osteotomy reference point in total knee arthroplasty. However, due to there being only a small number of studies available, the evidence collected is insufficient to prove that a certain reference axis has obvious advantages and a combination of different reference points is needed to achieve the ideal lower extremity force line angle.