Abstract
Introduction
By all developments of new technologies on the improvement of the Total Knee implantation, the discussion about the optimum Alignment is in full way. Besides, is to be considered, that Alignment contains not only static, but also dynamic factors and beside the frontal plan also the sagittal plan as well as in particular the rotation in femur and tibia have a great importance for the outcome after TKR. However, beside the bone alignment, the kapsulo-igamentous structures also play an important role for the results after TKR. If a Varus-Malalignment was valid, in the past the „older” literature described it as a big risk factor for pain, less function and durability. However, in the present literature, we discuss more and more about the optimum Alignment during TKR. In particular, newer publications show no interference of the durability with coronar Alignment also outside from 3 °, also the score results and patient's satisfaction seem to deliver no worse results with slight untercorrection of the varus alignment. Some publications described even better score results and Patient satisfaction with slight untercorrection. Condition for it is probably an exact balancing of the extension and flexion gap.
Material and method
With a new developed instruments it was examined with a tibia and extensions-Gap-First-Technique, to what extent a correction of the AMA opposed after digital planning within from 3 ° in distal femur a balancierung of the extension gap could be reached under avoidance of 3° releases with a varusarthritis oft the knee. 103 directly knee arthroplasties following on each other were selected with Varus-OA without exclusion criteria.
Surgical technology
Midvastus-Approach, mostly in LIS technology. Besides, tibial 1–2 ° release and the following resection of the exophytes medial, lateral and intercondylar. External adjustment of the proxima tibia cut, place adjustable (Varus/Valgus, Slope) cutting block, control of the varus-(valgus position and slope after Fixation and if necessary postcorrection of these parameters. Resection of the proximal tibia.
Next intramedullar adjustment of teh ditals femur cut according digital planning and fixation the adjustable/Varus/Valgus) cutting block for the distal femur resection. Insert the the ligament balancer between the promiumal tibia cut and the the dital femur in extension and examination of the parallelism between prox. Tibia and planned distal femur resektion with the same tension medial and lateral. If necessary correction of the cutting block within 3 ° to the achievement of a balanced extension gap, otherwise further releases necessary to create a balanced extension gap.
Distale Femurresektion
Insert the the ligament balancer again between the promimal tibia cut and the the posterior femur condyles in 90° flexion with the same tension medial and lateral. Next step is to transfer the proximal tibia cut on distal Femur to determine femur rotation in gap balance technology. Fixation of the new developed sizing instrumet, final definition of the implant size of the femur according anterior and posterior referencing to avoid undercuts or overstuffing anterior and a reconstructi the posterior offset. Drilling of the admission holes for the 4 in 1 cutting block and at first posterior re section with following resection of posterior exophytes and the possibility of a posterior capsule release. Adapt the extension gap on the flexion gap by means of modular spacer blocks and perhaps necessary postresection oft he distal femur. Now realisation of the remaining femoral cuts with the 4 in 1-cutting block
Results
With 102 of 103 knee prosthesis implantations with Varus-OA a balancing of the extension gap could be realized, outgoing by the presurgical planning with max. 3 ° corrections on the distal femur cut. Only in a 1 case, a 3° release was necessary to achieve a balanced extension gap. The rotation according the posterior condyles with 102 within 3 ° correctable VarusOA lay between 0 and 8 ° with a frequency summit between 4 and 6 °.
Summary
With the described Surgical technology by use a ligament tensioner and new developed instruments the balancing of the extension gap with slight to avarage medial release could be carried out in nearly all cases, so that the rotation could take place in these cases also in Gap-balance technology. Therefore it is possible with this technology beside a bone-saving TKR also sparing the capsulo-ligamtous structures. This thereby still wins on importance, that after newer literature data the kapsulo-ligamentous structures show a more physiological tension, in contrast to the correction to the neutral position, with light untercorrection of the preexistently varus deformity. In a projected prospektiv multicenter study we like to find answers to the questions about constitutional or residual Varus-Alignment after TKR in Varus-OA. Further question is if we can also compiled a sure zone within which an untercorrection is admissible.
