Minimal effect of patella eversion on ligament balancing in cruciate-retaining total knee arthroplasty.
OBJECTIVE
The effect of patellar eversion on ligament laxity measurements is still unclear. The purpose of this study was to investigate the influence of patellar eversion on medial and lateral ligament laxity measurements performed intra-operatively in total knee arthroplasty (TKA).


METHODS
A total of 49 knees (27 female) with mean age 70 years (42-83) and mean body mass index of 28.5 were operated consecutively with a cruciate-retaining prosthesis. Medial and lateral ligament laxity in extension and in 90° of flexion was measured with the spatula-method intra-operatively after implantation of the prosthetic components with the patella everted and thereafter with the patella repositioned. The corresponding changes in gap height and inclination were calculated.


RESULTS
A statistically significant increase of 0.6 mm (p < 0.001) in ligament laxity (condylar lift-off) laterally in flexion was found with the patella repositioned compared to everted. No differences were found in extension or medially in flexion. Correspondingly, the flexion gap increased by 0.4 mm (p < 0.001) and the flexion gap inclination increased by 0.6° (p = 0.002) when the patella was repositioned.


CONCLUSIONS
Earlier research has shown that ligament laxity must be at least 1-2 mm to cause inferior function after TKA. In the current study, we found that the effect of patellar eversion on ligament laxity measurements is too small to be considered clinically relevant. PROSPECTIVE STUDY EVALUATING THE EFFECT OF PATIENT CHARACTERISTICS: Level II.
Department of Surgery, Innlandet Hospital Trust, Anders Sandvigs Gate 17, 2629, Lillehammer, Norway. eirik.aunan@sykehuset-innlandet.no.
Eirik
http://orcid.org/0000-0002-8337-1776
E
Aunan
Department of Orthopedics, Oslo University Hospital, Postboks 4950, Oslo, Norway.
Thomas
T
Kibsgård
Department of Orthopedics, Oslo University Hospital, Postboks 4950, Oslo, Norway.
Stephan M
SM
Röhrl
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D017885:Collateral Ligaments / Q000503:physiopathology; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D017888:Medial Collateral Ligament, Knee / Q000503:physiopathology*; D008875:Middle Aged; D010329:Patella / Q000503:physiopathology*; D011446:Prospective Studies; D016059:Range of Motion, Articular
Joint instability; Ligament balancing; Patella; Patella eversion; Total knee arthroplasty