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The influence of component alignment on patellar kinematics in total knee arthroplasty.

Keshmiri A, Maderbacher G, Baier C, Sendtner E, Schaumburger J, Zeman F, Grifka J, Springorum HR - Acta Orthop (2015)

Bottom Line: After TKA, the patellae shifted statistically significantly more laterally between 30° and 60°.Sagittal component alignment, but not rotational component alignment, had a significant influence on patellar kinematics.Combined sagittal component alignment in particular appears to have a major effect on patellar kinematics.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery and.

ABSTRACT

Background and purpose: Postoperative anterior knee pain is one of the most frequent complications after total knee arthroplasty (TKA). Changes in patellar kinematics after TKA relative to the preoperative arthritic knee are not well understood. We compared the patellar kinematics preoperatively with the kinematics after ligament-balanced navigated TKA.

Patients and methods: We measured patellar tracking before and after ligament-balanced TKA in 40 consecutive patients using computer navigation. Furthermore, the influences of different femoral and tibial component alignment on patellar kinematics were analyzed using generalized linear models.

Results: After TKA, the patellae shifted statistically significantly more laterally between 30° and 60°. The lateral tilt increased at 90° of flexion whereas the epicondylar distance decreased between 45° and 75° of flexion. Sagittal component alignment, but not rotational component alignment, had a significant influence on patellar kinematics.

Interpretation: There are major differences in patellar kinematics between the preoperative arthritic knee and the knee after TKA. Combined sagittal component alignment in particular appears to have a major effect on patellar kinematics. Surgeons should be especially aware of altering preoperative sagittal alignment until the possible clinical relevance has been investigated.

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Related in: MedlinePlus

Screenshot of patellar tracking in the arthritic knee (left panel) and after TKA (right panel).
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Figure 2: Screenshot of patellar tracking in the arthritic knee (left panel) and after TKA (right panel).

Mentions: After a midline skin incision, a standard medial parapatellar approach was used. The capsule was marked at standardized locations to ensure later anatomical reconstruction. 2 passive optical reference arrays were secured on the distal medial femur and the proximal medial tibia. The femoral array was attached through an additional 1-cm incision to avoid soft tissue tension during patellar tracking. After referencing the center of the hip by circumduction, the landmarks needed for femorotibial kinematics by the navigation system were digitized. The line connecting the middle of the posterior cruciate ligament to the medial border of the patellar tendon attachment was defined as the tibial a.p. axis according to Akagi et al. (2004). The patellar array was fixed onto the anterior side of the patella by a small screw (Figure 1). A point at the medial, superior, and inferior edge and at the middle of the posterior articular ridge of the patella defined the patella coordinate frame, as recommended by the manufacturer (BrainLab). After anatomical closure of the joint capsule, the natural patellar kinematics and the relative orientation between femur, tibia, and patella were recorded between 30° and 90° of flexion during passive motion (Figure 2). The position of the registered patella coordinate frame relative to the coordinate frame of the femur was calculated by the navigation system during the motion cycle. Both, absolute, and relative values for patellar mediolateral shift (medial: +, lateral: −), axial tilt (medial: −, lateral: +), and coronal rotation (external: −, internal: +) of the patella were collected. In addition, the epicondylar distance describing the line from the previously chosen point at the middle of the posterior articular ridge of the patella perpendicular to the trans-epicondylar line, which is built from the registered femoral epicondyles, was measured during the motion cycle. Figure 2 shows the epicondylar distance before and after TKA was performed, which is represented by green dots in the sagittal view. This distance gives information about the anterior-posterior position of the patella throughout the flexion cycle in relation to the femur. After removal of osteophytes at the medial and lateral compartments, the tibial cut was performed and a double tensiometer inserted at 0° of extension and 90° of flexion with a distraction force of 90 N. In the frontal plane, zero degrees between the femoral and tibial mechanical axis was aimed at. The flexion gap was adapted through bony cuts by the navigation software to achieve ligament balancing. No ligament release was necessary due to well-aligned knees. The femoral component rotation was set by ligament balancing and the rotation of the tibial component was set to the medial third of the tibial tubercle (Berger et al. 1998). A second measurement of patellar kinematics was performed after standardized prosthesis implantation with recommended component placement by the navigation system, as previously published (Bäthis et al. 2006), and with the natural patella without any previously performed surgical patellar intervention. During measurements, the limbs were lifted vertically at the distal femur by the surgeon without touching the tibia, performing 2 repetitions of the motion cycle. Because of missing muscle tone and floppy patellae, values up to 30° of flexion were irregular and were removed from the experimental protocol. Also, definitive femoral component rotation and flexion and tibial component rotation and slope were recorded intraoperatively. The data measured were analyzed using a patellar tracking software application for TKA (Patellar Tracking; BrainLab).


The influence of component alignment on patellar kinematics in total knee arthroplasty.

Keshmiri A, Maderbacher G, Baier C, Sendtner E, Schaumburger J, Zeman F, Grifka J, Springorum HR - Acta Orthop (2015)

Screenshot of patellar tracking in the arthritic knee (left panel) and after TKA (right panel).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4513599&req=5

Figure 2: Screenshot of patellar tracking in the arthritic knee (left panel) and after TKA (right panel).
Mentions: After a midline skin incision, a standard medial parapatellar approach was used. The capsule was marked at standardized locations to ensure later anatomical reconstruction. 2 passive optical reference arrays were secured on the distal medial femur and the proximal medial tibia. The femoral array was attached through an additional 1-cm incision to avoid soft tissue tension during patellar tracking. After referencing the center of the hip by circumduction, the landmarks needed for femorotibial kinematics by the navigation system were digitized. The line connecting the middle of the posterior cruciate ligament to the medial border of the patellar tendon attachment was defined as the tibial a.p. axis according to Akagi et al. (2004). The patellar array was fixed onto the anterior side of the patella by a small screw (Figure 1). A point at the medial, superior, and inferior edge and at the middle of the posterior articular ridge of the patella defined the patella coordinate frame, as recommended by the manufacturer (BrainLab). After anatomical closure of the joint capsule, the natural patellar kinematics and the relative orientation between femur, tibia, and patella were recorded between 30° and 90° of flexion during passive motion (Figure 2). The position of the registered patella coordinate frame relative to the coordinate frame of the femur was calculated by the navigation system during the motion cycle. Both, absolute, and relative values for patellar mediolateral shift (medial: +, lateral: −), axial tilt (medial: −, lateral: +), and coronal rotation (external: −, internal: +) of the patella were collected. In addition, the epicondylar distance describing the line from the previously chosen point at the middle of the posterior articular ridge of the patella perpendicular to the trans-epicondylar line, which is built from the registered femoral epicondyles, was measured during the motion cycle. Figure 2 shows the epicondylar distance before and after TKA was performed, which is represented by green dots in the sagittal view. This distance gives information about the anterior-posterior position of the patella throughout the flexion cycle in relation to the femur. After removal of osteophytes at the medial and lateral compartments, the tibial cut was performed and a double tensiometer inserted at 0° of extension and 90° of flexion with a distraction force of 90 N. In the frontal plane, zero degrees between the femoral and tibial mechanical axis was aimed at. The flexion gap was adapted through bony cuts by the navigation software to achieve ligament balancing. No ligament release was necessary due to well-aligned knees. The femoral component rotation was set by ligament balancing and the rotation of the tibial component was set to the medial third of the tibial tubercle (Berger et al. 1998). A second measurement of patellar kinematics was performed after standardized prosthesis implantation with recommended component placement by the navigation system, as previously published (Bäthis et al. 2006), and with the natural patella without any previously performed surgical patellar intervention. During measurements, the limbs were lifted vertically at the distal femur by the surgeon without touching the tibia, performing 2 repetitions of the motion cycle. Because of missing muscle tone and floppy patellae, values up to 30° of flexion were irregular and were removed from the experimental protocol. Also, definitive femoral component rotation and flexion and tibial component rotation and slope were recorded intraoperatively. The data measured were analyzed using a patellar tracking software application for TKA (Patellar Tracking; BrainLab).

Bottom Line: After TKA, the patellae shifted statistically significantly more laterally between 30° and 60°.Sagittal component alignment, but not rotational component alignment, had a significant influence on patellar kinematics.Combined sagittal component alignment in particular appears to have a major effect on patellar kinematics.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery and.

ABSTRACT

Background and purpose: Postoperative anterior knee pain is one of the most frequent complications after total knee arthroplasty (TKA). Changes in patellar kinematics after TKA relative to the preoperative arthritic knee are not well understood. We compared the patellar kinematics preoperatively with the kinematics after ligament-balanced navigated TKA.

Patients and methods: We measured patellar tracking before and after ligament-balanced TKA in 40 consecutive patients using computer navigation. Furthermore, the influences of different femoral and tibial component alignment on patellar kinematics were analyzed using generalized linear models.

Results: After TKA, the patellae shifted statistically significantly more laterally between 30° and 60°. The lateral tilt increased at 90° of flexion whereas the epicondylar distance decreased between 45° and 75° of flexion. Sagittal component alignment, but not rotational component alignment, had a significant influence on patellar kinematics.

Interpretation: There are major differences in patellar kinematics between the preoperative arthritic knee and the knee after TKA. Combined sagittal component alignment in particular appears to have a major effect on patellar kinematics. Surgeons should be especially aware of altering preoperative sagittal alignment until the possible clinical relevance has been investigated.

Show MeSH
Related in: MedlinePlus