title: Comparison between two computer-assisted total knee  arthroplasty: gap-balancing versus measured resection technique.
abstract: Two surgical strategies are possible in total knee arthroplasty (TKA): a measured resection technique, in which bone landmarks are used to guide resections equal to the distal and posterior thickness of the femoral component, or a gap-balancing approach, in which equal collateral ligament tension in flexion and extension is sought before and as a guide to final bone cuts. In this study performed with computer assisted system, we compared the 2 different methods in 126 patients followed prospectively in order to analyze the effect of both the techniques on joint-line (JL) maintenance, axial limb restoration and components position. The gap technique showed a statistical increase in the post-operative value when compared with the measured resection technique, (P = 0.008). When comparing the two groups regarding to the pre-operative deformity, we have found a statistical difference (P = 0.001) in case of moderate pre-operative deformity (less than 10 degrees), and the measured resection technique showed a slight superiority in preserving a joint line more faithful to the pre-operative. We found an ideal alignment for the mechanical axis (180 degrees ± 3 degrees) (95% of cases). In six cases (5%), the mean post-operative value exceeded (varus or valgus) the ideal value by more than 3 degrees. In the frontal plane, a good alignment was observed for both femoral and tibial components without a significant difference between the two techniques. In the sagittal plane was found more alignment variability due to the different implants used and their ideal starting slope, from 7 degrees to 3 degrees. Finally, the surgeon can use the approach with which he has more confidence; however, as the measured resection technique causes less reduction in the post-operative joint-line position, in case of shortening of patellar tendon or patella infera, this technique is preferable.
authors.affiliation: VII Department of Orthopaedic Surgery, Rizzoli Orthopaedic Institute, University of Bologna, Via Pupilli 1, 40136 Bologna, Italy. domenico.tigani@ior.it
authors.forename: Domenico
authors.initials: D
authors.lastname: Tigani
authors.forename: G
authors.initials: G
authors.lastname: Sabbioni
authors.forename: R
authors.initials: R
authors.lastname: Ben Ayad
authors.forename: M
authors.initials: M
authors.lastname: Filanti
authors.forename: N
authors.initials: N
authors.lastname: Rani
authors.forename: N
authors.initials: N
authors.lastname: Del Piccolo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D005260:Female; D005269:Femur / Q000601:surgery; D005500:Follow-Up Studies; D006801:Humans; D007593:Joint Instability / Q000517:prevention & control; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010147:Pain Measurement; D011182:Postoperative Care / Q000379:methods; D011446:Prospective Studies; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology*; D020127:Recovery of Function; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000009:adverse effects / Q000379:methods*; D013977:Tibia / Q000601:surgery; D013997:Time Factors; D016896:Treatment Outcome
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