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J Knee Surg 2019; 32(10): 1028-1032
DOI: 10.1055/s-0038-1675422
Original Article
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Evaluation of Femoral–Tibial Flexion Gap in Total Knee Arthroplasty with Everted or Lateralized Patella

Michele Malavolta
1   Knee Department, Paolo Pederzoli Private Hospital, Peschiera del Garda, Verona, Italy
,
Andrea Cochetti
2   University Orthopaedics and Trauma Department, Borgo Trento General Hospital, Verona, Italy
,
Silvio Mezzari
1   Knee Department, Paolo Pederzoli Private Hospital, Peschiera del Garda, Verona, Italy
,
Alberto Residori
1   Knee Department, Paolo Pederzoli Private Hospital, Peschiera del Garda, Verona, Italy
,
Gianpietro Lista
1   Knee Department, Paolo Pederzoli Private Hospital, Peschiera del Garda, Verona, Italy
› Author Affiliations
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Publication History

13 February 2018

16 September 2018

Publication Date:
09 November 2018 (online)

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Abstract

Intraoperative patellar position (eversion, lateralization, or in situ) influences the ligamentous balancing in knee flexion and thereby the correct positioning of the femoral component during total knee arthroplasty. The correct ligament balancing is crucial when, as in our experience, prostheses with medial pivot design are used. It was shown that the flexion gap in the normal knee is not rectangular and that the lateral compartment is significantly slacker than the medial. Therefore, to obtain a correct kinematics of a medial pivot anatomical prosthesis, it is essential to recreate an anatomical flexion gap slacker in the lateral compartment. We conducted a prospective study on a consecutive series of 87 total knee prostheses. The objective of this study is to evaluate the femoral external rotation angle in each patient with everted patella as well as with pure subluxated patella. The purpose of this study is to offer guidance about the optimal femoral rotation angle to achieve best outcomes of a knee replacement. The evaluation was done using an instrument developed by Medacta International (Switzerland) with our direct collaboration (Tensor, Medacta, Switzerland) and standardizing the basic conditions of each patient (knee 90 degrees flexed, medial transquadricipital surgical access, lateral displacement of the patella, tourniquet inflated at 250 mm Hg, spinal anesthesia). Each group was subdivided into subgroups according to gender, preoperative varus or valgus deformity, and patellar height. Our study advises against evaluating the flexion gap with everted patella due to high risk of underestimation of the lateral compartment laxity (differences up to + 3 degrees with pure subluxated patella compared with everted patella).

Keywords

patellar eversion - patellar lateralization - total knee arthroplasty - medial knee stability - lateral knee laxity - knee gap balancing