TOTAL KNEE ARTHROPLASTY IN VALGUS DEFORMED KNEE

By

Dr. Laxmikanth. SP.G in M.S. OrthoGandhi Medical College

GENU VALGUM

Causes :

Idiopathic Post traumatic Rickets and Osteomalacia Neoplastic diseases (chondrosarcoma ) Rheumatoid arthritis Osteoarthritis Neuropathic joints Dysplastic bone diseases

TKA in Fixed-valgus deformity knee is difficult and challenging to surgeon.

The correction varus deformity is easier than valgus one.

Factirs that makes TKA in valgus knee difficult are :

ambiguity regarding sequence of ligament release. More chances of patellofemoral maltracking. Common peroneal palsy. More chances of flexion-extension gap mismatch.

In valgus knee, deficient in lateral bone and cartilage leads to adaptive changes occur in following structures,

Contractures and tightening of postero lateral capsule lateral collateral ligament arcuate ligament popliteus tendon iliotibial band lateral intermuscular septum.

PATHOPHYSIOLOGY

Stretching and attenuation of the medial ligaments can occur

Bony deformities:

Femur—The postero lateral femoral condyle is smaller.

Tibia—The tibia is externally rotated, the tibial tubercleis positioned laterally. The lateral plateau :central bone resorption and peripheralosteophyte formation.

Patella—The patella is often subluxed laterally. The lateralfacet is deformed (flattened or concave),with large traction osteophytes , Patella alta.

Ipsilateral hip, ankle and foot to be examined ---- whether they are contributing to knee pathology Alignment of both lower extremities is observed for extra-articular deformities. Stability in coronal and sagital plane should be looked for. To correct large angular deformities bone grafting and modular implants may be needed. Patellofemoral tracking thoroughly examined for any subluxation, mobility. Posterior structures examined for any popliteal cyst etc..

PRE OPERATIVE EVALUATION

RadiographsAP View : Weight bearing AP view superior than supine.

Lateral View :

Patellar height and patellofemoral joint can be visualised.As patella alta common with valgus knee this view is necessary.

Normal :1.02+/- 0.2.Patella alta : (LT/LP 1.2), Patella baja (LT/LP 0.8).

Insall-Salvati Ratio:

Merchant View :Superior than lateral view

Provides the most optimal assessment of,

Patellofemoral alignment Joint space, Articular surfaces.

Standing 52-Inch Cassette(“Three Joint View”) :

Gives information about,

The overall alignment (mechanical axis) of the lower extremity.

To know the degree of varus or valgus alignment at both knees and their relative leg length.

Presence of important extra-articular deformities (with prior trauma ,Paget’s disease)

Implant selection

In young patients --PCL substituting posterior stabilized implant

In elderly low-demand patients ---constrained condylar knee

Cases with bone deficiency---a modular implant with metal augments, offset stems, and variable tibial polyethelene thicknesses may be useful.

SURGICAL TECHNIQUE

Approaches

Bone preparation

Soft tissue balancing

Patellofemoral tracking

Surgical approaches

Skin incision -- anterior midline incision.

For arthrotomy -- medial parapatellar retinacular approach

Disadvantages :

Patellar maltracking is more common. Increased potential for inaccurate flexion-extension gap balancing . Increases external rotation of the tibia Access to the posterolateral corner is more difficult Vascularity to the quadriceps patella tendon (QPT) mechanism and lateral skin is at risk.

Some surgeons prefer lateral approach for valgus kneeAdvantages :

Improved access to the pathologic postero lateral corner

Preserves vascularity because the medial side is untouched; Centralizes the QPT mechanism, which optimizes patella tracking

Not routinely used because Damage to genicular arteries Not familiar with techniques of exposure and closure

Bone preparation:

FEMUR :

Femoral component rotational alignment is important in the valgus knee to attain,

Equal flexion extension gap Normal patellofemoral tracking Joint line level

The intramedullary alignment rod should be slightly medial to the center of the patellar groove.

The cutting guide is set at a 5° valgus angle.

This will align the joint surface perpendicular to the mechanical axisof the femur and parallel to the epicondylar axis.

In some cases resection from the medial side results in minimal or no resection from the lateral side of the distal femur.

For accurate rotational alignment either the APaxis or the epicondylar axis of the femur is used asanatomical reference for resection.

The posterior femoral condyles are unreliable as posterolateral femoral condylar deficiency

The tibial cut should be made at 90+/- 2 degrees to the long axis of the tibial shaft in both the coronal and sagital planes.

Over-resection of the proximal tibia to address a bony defect, and to create a flat surface for the tibial component may damage ligament attachments and may sacrifice excessive amounts of bone.

The medial tibia is referenced and 10 mm of bone is resected.Bony defects can be addressed with cement, bone, or metal augments. The MCL must be protected during resection.

TIBIAL CUT :

SOFT TISSUE RELEASE

The purpose of our release is to provide ligamentous balance with rectangular flexion and extension gaps ,while maintaining lateral side stability of the knee in flexion.

The release can be a full release, partial release, or Z-lengthening

Release is performed in a step-by-step controlled fashion and reassessed with laminar spreaders after each step

At the end of release, The mechanical axis passes through the centre of the knee. The flexion and extension gaps are equal and symmetrical.

The order of release varies among surgeons.

LCL and popliteus tendons, provides lateral stability in both flexion and extension.

IT Baand and posterolateral capsule, provides lateral stability only in extension.

SO, Release in flexion first and then proceed in extension.

Tight in both in Flex and ext

LCL and popliteus release

ITB &Post capsule release

PCL, IMS, Lat gastro release

Tight only in extension

IT Band release

Post capsule release

CONSTRAINED CONDYLAR KNEE

Pie-Crusting Technique

Based on palpation of taut soft tissues followed by their selective release with multiple stabs with 15 no..blade.

Multiple horizontal incisions given from inside to out.

Begin at the level of the joint line and can extend 10 cm proximally. This works like a tensor and allows the lateral tissues to lengthen and slide with some degree of continuity

It is performed only after final implantation of all total knee components, just before wound closure.

MEDIAL LIGAMENT ADVANCEMENT

It should be done when medial ligaments are too lax, after complete release of lateral ligaments

Described by Krackow

Two types Proximal advancement on femur Distal advancement on tibia

Procedure:

Elevation of the femoral origin of the medial collateral ligament.

Proximal advancement using a locking-loop type of suture within the substance of the ligament.

This suture is secured around a screw and washer with a staple placed at desired site on medial epi-condyle.

Finally ,

Patellar maltracking is often associated with a valgusdeformity.

If necessary a lateral retinacular release shouldbe performed.

VALGUS KNEE WITH BONE DEFECT causes:

Arthritis with angular deformityLateral condylar hypoplasiaOsteonecrosis TraumaPost surgical ( HTO, TKA )

TYPES: Contained or cavitary defects ---intact rim of cortical bone surrounding the deficient area. Noncontained or segmental defects ---more peripheral and lack a bony cortical rim.

Treatment options:

Small defects (<5 mm) typically are filled with cement. Contained defects can be filled with impacted cancellous bone graft. Larger noncontained defects can be treated by Structural bone grafts(auto or allografts ) Modular implants Screws with cement or graft.

CEMENT FIXED SCREWS

ALLOGRAFT

MODULAR IMPLANT

AUTOGRAFT FOR TIBIAL BONE DEFECT

AUTOGRAFT FOR FEMORAL BONE DEFECT

THANK YOU