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This prosthesis is varus-valgus

2. Varus Valgus Instability

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- equal varus and valgus instability

In order to evaluate the extra-articular deformity, the angle formed by the axis of the shaft at both sides of the deformity are measured. If the extra-articular and articular deformities have opposite axis (one in varus and the other in valgus), the resulting axis can be normal. If both deformities are in the same axis they will add up and the correction to make with the bone cuts will be greater. Rotational deformities cannot be properly evaluated with X-Rays, so a CT scan with cuts at the hip and the knee is suggested.

 - permit 2-3o of varus-valgus movement

49 primary total knee-replacements in 48 (6 males, 42 females) patients were performed; 32 through a lateral-parapatellar approach (group L) using an unconstrained-prosthesis and 17 through a medial-parapatellar approach more often requiring a constrained-prosthesis (group M). Mean preoperative valgus angle was 18.5 (range 11-34˚). Patient demographics (p=0.7) and valgus correctability were similar between the two groups.

Creates a net varus or valgus moment

- restricts varus-valgus and translation

Valgus knee deformity is a challenge in total knee arthroplasty (TKA) and it is observed in nearly 10 % of patients undergoing TKA. The valgus deformity is sustained by anatomical variations divided into bone remodelling and soft tissue contraction/elongation. Bone tissue variations consist of lateral cartilage erosion, lateral condylar hypoplasia and metaphyseal femur and tibial plateau remodelling. Soft tissue variations are represented by tightening of lateral structures: lateral collateral ligament, posterolateral capsule, popliteus tendon, hamstring tendons, the lateral head of the gastrocnemius and iliotibial band. Complete pre-operative planning and clinical examination are mandatory to manage bone deformities and soft tissue contractions/elongations and to decide if a higher constrained prosthesis is necessary. Two different approaches have been described to perform TKA in a valgus knee: the anteromedial approach and the anterolateral one. In valgus knee deformity bone cuts can be performed differently in order to correct low-grade deformities and reduce great deformities. There is still debate in the literature on the sequence of lateral soft tissue release to achieve the best alignment without any instability. The aim of this article is to review the anatomical variations underlying a valgus knee, to assess the best pre-operative planning and to evaluate how to choose the grade of constraint of the implant. We will also review the main approaches and surgical techniques both for bone cuts and soft tissue management. Finally, we will report on our experience and technique.

There were 2 complications. A patient with femoral osteomyelitis and poor soft tissue coverage due to previous surgeries developed a deep infection. Currently, this patient has a cement spacer with antibiotics and an expansor to improve the coverage. Another patient with a 20º valgus deformity and a sequel of a distal femoral varus osteotomy developed a medial instability due to insufficiency of the medial collateral ligament, requiring revision to a constrained prosthesis 2 years after the index surgery.

1. Severe varus 15o, intact collaterals

- proximal tibia normally in slight varus of 3o

The option of using a constrained or an unconstrained (PCL retaining) implant for arthroplasty of the moderate to severely valgus knee remains an area of controversy []. Some surgeons consider the valgus knee to be a relative contraindication to implanting an unconstrained prosthesis [].

The valgus knee can present greater challenges of ligament balance in total knee arthroplasty in comparison to varus aligned knees []. Restoration of neutral mechanical axis and correct ligament balance are important factors to reduce incidence of complications relating to instability, loosening, premature wear and patella mal-tracking [-].

In a severe varus deformity, may be best to PS
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  • - or final tibio-femoral angle 2o varus rather than 7o valgus

    No knee exhibited varus-valgus

  • - posterior slope creates varus

    - severe varus knee

  • - in a varus knee the medial joint line is worn

    - normally 3o varus

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The difficult knee: severe varus and valgus[J].

The main disadvantage of the medial approach is that it is more difficult to reach the posterolateral corner during the lateral soft tissue release. For this reason sometimes a tibial tuberosity osteotomy (TTO) is necessary; different complications have been reported with this technique. Besides, patellar vascular damage has been described when a medial parapatellar approach is combined with a lateral release []. Some authors reported that when a medial approach is performed in a valgus knee, the results have been inferior compared to varus deformity [].

- variable varus/valgus stability as well as rotation

We prefer the intramedullary guide if it achieves to cross over the angular deformity. If this is not possible, for example in deformities in the middle third, we recommend to use an extramedullary guide centered on the femoral head. It is important to understand that for varus femoral deformities near the joint, the entry point for the intramedullary guide can be at the articular surface of the lateral condyle and that this condyle will be the most resected. For valgus deformities, the entrance and the greatest resection will be in the medial condyle [4,6] 18,20.

- permit 2-3o of varus-valgus movement

The mechanical axis of the limb is outlined on these images (from the center of the femoral head to the center of the ankle), which should pass through the center of the knee. In patients with a varus deformity (intra or extra articular) the mechanical axis will pass medial to the center of the knee, and if the deformity is in valgus, it will pass laterally.

- restricts varus-valgus and translation

The use of a lateral-parapatellar approach, appropriate soft tissue release, and an unconstrained PCL-preserving implant, yielded in all cases a stable, well aligned knee arthroplasty. This represents a viable alternative to the constrained-prosthesis using a medial-parapatellar approach in patients with moderate and severe genu-valgum.

1. Severe varus 15o, intact collaterals

Figure 5: A, B & C- 35 year old man, with terminal fibular Hemimelia of the left lower limb, homolateral knee osteoarthritis, previous femoral nailing and a 20° varus and 28° sagital antecurvatum tibial deformity, as a sequel of a lengthening treatment. D & E- AP severe knee osteoarthritis, posterior tibial subluxation and Patella baja. F & G- AP and lateral view of the TKA. An osteotomy of the tibial tuberosity was performed.

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