Zusammenfassung
Operationsziel
Implantation einer bikondylären Knieendoprothese in minimalinvasiver Operationstechnik ohne Verletzung des Streckapparats mit der Möglichkeit zur bandspannungsabhängigen Knochenresektion. Nur der Subvastus-Zugang erhält die Integrität des Streckapparats; deshalb Weiterentwicklung zur minimalinvasiven Technik mit kurzer Hautinzision und Lateralisation statt Eversion der Patella. Weichteilbalancierung durch direkten Zugang von ventral.
Indikationen
Leichte und mittelschwere Varusgonarthrosen bis 15° Fehlstellung, leichte oder passiv korrigierbare Valgusgonarthrosen bis 10° Fehlstellung.
Kontraindikationen
Schwere, kontrakte Varusgonarthrosen, mittelschwere und schwere, kontrakte Valgusgonarthrosen, starkes Übergewicht, besonders muskelkräftige Patienten, Durchblutungsstörungen der Haut.
Operationstechnik
Zentraler Hautschnitt vom proximalen Patellapol bis auf die Tuberositas tibiae. Darstellung des medialen Retinakulums und subkutan Lösen des Musculus vastus medialis. Inzision des Retinakulums medial der Patella und subkutan stumpfes Lösen des Musculus vastus medialis vom Septum intermusculare. Lateralisation der Patella und Beugen des Kniegelenks. Tibiaresektion rechtwinklig zum Schaft. Ausrichten des anteroposterioren (a.p.) Resektionsblocks an der ventralen Femurkortikalis und Einstellung der Rotation durch gleichmäßiges Spannen der Kollateralbänder. Nötigenfalls Ausgleich der Bandspannung im Beugespalt durch Releases. Nach a.p. Resektion Fixation des Resektionsblocks für die distale Femurresektion in geplantem Valguswinkel. Nötigenfalls Ausgleich der Bandspannung durch Releases im Streckspalt. Nach distaler Resektion Femurfacettenresektion, Angleichung der posterioren Kondylen und Prothesenimplantation. Prüfung der Stabilität und Beweglichkeit. Wundverschluss.
Weiterbehandlung
Vollbelastung und CPM („continuous passive motion“) bis 90° Beugung bei Toleranz mit Periduralkatheter ab dem 1. postoperativen Tag, Treppensteigen ab dem 7. postoperativen Tag.
Ergebnisse
100 Patienten mit Varusgonarthrose wurden randomisiert über einen parapatellaren oder einen minimalinvasiven Subvastus-Zugang versorgt. Die Röntgenkontrolle zeigte keinen Unterschied in der Präzision oder Wiederherstellung der Beinachse. Minimalinvasiv operierte Patienten hatten postoperativ weniger Schmerzen und erreichten 6 Wochen postoperativ eine größere Flexion von 110° versus 95°. Allerdings traten in dieser Gruppe zwei Wundheilungsstörungen auf. Die Technik ist anspruchsvoll, und die Operationszeit ist verlängert. Langzeitresultate bleiben abzuwarten.
Abstract
Objective
Total knee replacement in minimally invasive technique without any trauma to the extensor apparatus and with soft-tissue-referenced bone resections. Only the subvastus approach preserves the integrity of the extensor apparatus and has therefore been modified to become a minimally invasive technique with a shorter skin incision and lateralization instead of eversion of the patella. Soft-tissue balancing is done through this direct anterior approach.
Indications
Mild to moderate varus osteoarthritis of the knee up to 15° of malalignment, mild and passively correctable valgus osteoarthritis of the knee up to 10° of malalignment.
Contraindications
Severe, contract varus osteoarthritis of the knee, severe and moderate, contract valgus osteoarthritis of the knee, severe obesity, exceptionally muscular patients, decreased skin perfusion.
Surgical Technique
Central skin incision from the superior pole of the patella to the tibial tubercle. Exposure of the medial retinaculum and mobilization of the vastus medialis muscle subcutaneously. Incision of the medial retinaculum and blunt separation of the vastus medialis muscle from the intermuscular septum. Lateralization of the patella and flexion of the knee joint. Resection of the tibia perpendicular to the diaphysis. Adjustment of the anteroposterior (AP) resection block at the level of the anterior femoral cortex and of rotation by applying equal tension to the collateral ligaments. Balancing of soft-tissue tension in flexion gap by release, if necessary. After AP resection fixation of distal resection block in planned valgus angle. Balancing of soft-tissue tension in extension gap by release, if necessary. After distal femur resection facet resection, adaptation of posterior femoral condyles, and implantation of prosthesis. Check on stability and range of motion. Wound closure.
Postoperative Management
Full weight bearing from the 1st postoperative day, CPM (continuous passive motion) with up to 90° flexion with peridural anesthesia as tolerated, stair climbing starting on the 7th postoperative day.
Results
100 patients were randomized to total knee replacement via a parapatellar or subvastus approach. Radiologically, there were no differences in operative precision or leg alignment. Patients treated minimally invasively suffered less pain and achieved a higher flexion of 110° versus 95° 6 weeks postoperatively. However, there were two cases of delayed wound healing in this group. The surgical technique is demanding and the operating time is longer. Long-term results are still missing.
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Halder, A., Beier, A. & Neumann, W. Mini-Subvastus-Zugang bei der Implantation von Knieendoprothesen. Orthop Traumatol 21, 14–24 (2009). https://doi.org/10.1007/s00064-009-1602-1
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DOI: https://doi.org/10.1007/s00064-009-1602-1