Abstract
Management of a knee with valgus deformities has always been considered a major challenge. Total knee arthroplasty requires not only correction of this deformity but also meticulous soft tissue balancing and achievement of a balanced rectangular gap. Bony deformities such as hypoplastic lateral condyle, tibial bone loss, and malaligned/malpositioned patella also need to be addressed. In addition, external rotation of the tibia and adaptive metaphyseal remodeling offers a challenge in obtaining the correct rotational alignment of the components. Various techniques for soft tissue balancing have been described in the literature and use of different implant options reported. These options include use of cruciate retaining, sacrificing, substituting and constrained implants.
Purpose
This presentation describes options to correct a severe valgus deformity (severe being defined as a femorotibial angle of greater than 15 degrees) and their long term results.
Methods
34 women (50 knees) and 19 men (28 knees) aged 39 to 84 (mean 74) years with severe valgus knees underwent primary TKA by a senior surgeon. A valgus knee was defined as one having a preoperative valgus alignment greater than 15 degrees on a standing anteroposterior radiograph. The authors recommend a medial approach to correct the deformity, a minimal medial release and a distal femoral valgus resection of angle of 3 degrees. We recommend a sequential release of the lateral structures starting anteriorly from the attachment of ITB to the Gerdy's tubercle and going all the way back to the posterolaetral corner and capsule. Correctability of the deformity is checked sequentially after each release. After adequate posterolateral release, if the tibial tubercle could be rotated past the mid-coronal plate medially in both flexion and extension, it indicated appropriate soft tissue release and balance. Fine tuning in terms of final piecrusting of the ITB and or popliteus was carried out after using the trial components. Valgus secondary to an extra-articular deformity was treated using the criteria of Wen et al. In our study the majority of severe valgus knees (86%) could be treated by using unconstrained (CR, PS) knee options reserving the constrained knee / rotating hinge options only in cases of posterolateral instability secondary to an inadequate large release or in situations with very lax or incompetent MCL.
Results
The average follow up was 10 years (range 8 to 14 years). The average HSS knee scores improved from 48 points preoperatively (range 32 to 68 points) to 91 points (range 78 to 95 points) postoperatively. The average postoperative range of motion measured with a goniometer was 110 degrees (range 80 to 135 degrees) which was a significant improvement over the preoperative levels (average 65 degrees). None of the patients were clinically unstable in the medioloateral or anteroposterior plane at the time of final follow up. The average preoperative valgus tibiofemoral alignment was 19.6 degrees (range 15 degrees to 45 degrees). Postoperatively the average tibio-femoral alignment was 5 degrees (range 2 degrees to 7 degrees) of valgus. No patient in the study was revised.
Conclusion
Adequate lateral soft tissue release is the key to successful TKA in valgus knees. The choice of implant depends on the severity of the valgus deformity and the extent of soft tissue release needed to obtain a stable knee with balanced flexion and extension gaps. The most minimal constraint needed to achieve stability and balance was used in this study. In our experience the long term results of TKR on severe valgus deformities using minimal constrained knee have been good.
