Dear Lin

I have poor experience with TKR and when I perform I prefer valgus 5/6 degree because this is the normal value (average) of knee valgus. If you perform more than 6 degree, the mechanical axis will be changed and the load will be different in each articular surface. Its necessary a preoperative plan to evaluate the normal mechanical axis of both lower limbs (the anatomic characteristic of each person)

Dear Lin

Although there are detailed guidelines about choosing the valgus angle of the distal femoral cut which are based on radiological or navigation investigations, these are not always applicable because of errors , as obtaining and standardization of the images is not always possible in daily practice.

As a general rule patients with more severe varus deformity and short stature and more varus angle of the femoral necks and tighter , unyielding soft tissue need to planned for upper range distal femoral valgus angle.

One should also consider that up to 3 or even 4 degrees outliers in anatomical axis can do well after TKA, if they have achieved a proper soft tissue balance.

In my daily practice of difficult primary knee replacement I feel that soft tissue balance is more important determinant of successful knee arthroplasty , at least in medium term than absolute angles.

You can not achieve a good outcome t with correct anatomical axis , but questionable or poor soft tissue balance.

I use a navigation device. You should try to achieve a valgus angle of 3°. In vaus knees the problem lies on the tibial side. You need at least 10mm resection of the better compartment. Soft tissue balancing is absolute necessary. As severe varus knees often have an extension deficit, i always take the PCL away and mobilise the posterior capsule

I always get a 48 inch standing film and calculate the mechanical axis. It varies from 2 degrees to 8 degrees. I make my femoral cut such that the mechanical axis passes through the center third of the knee.. Arbitrarily selecting a fixed degree for your femoral cut can provide one with the occasional unpleasant surprise of too much varus or valgus

Although soft tissue balancing is considered essential for a successful TKR, bony cuts are also important because these cuts play a significant role for this soft tissue balancing. Ideally a long standing hip to ankle film is necessary for planning. A lesser cut I.e. 3-4 degrees of femoral valgus cut may help to open the medial side by removing more bone from the medial femoral condyle and facilitate the mcl release along with Pcl sacrifice and posteromedial capsular release. I would be very cautious to put more valgus in the distal femur.

A critical issue is to understand where the deformity is, femur, tibia, of in the implant orientation.

A full lenght film is needed and then measurement of the axes of femur, tibia and joint line surfaces.

The objective is to correct the varus with restoration of the femur and tibial mechanical axes such tha the HKA angle is Zero

Which bone to cut and the extend of realignment will depend on the above information.

I agree with Dr. Cooke. I only would add that by the planning and execution of resection of tibia surface the surgeon must have in mind to preserve or restore the stability of the knee. So pay special attention to soft-tissue structures.

Always according to the preoperatively measured, anatomical femur valgus (different for every patient) as you want to restore normal biomechanics for achieving best long-term results.

I would try to use 3º of valgus though it will be difficult to get a proper lateral cut. It a very hard case and you must be very careful quth CPE after your correction. However it is always possible to use navigation to confirm cuts and corrcetion or personal cutting guides that we are using with good results, especially in tough cases like that.

Dear Lin,

you raised a challenging issue for a very complex case (extreme varus knee!!!!). The most important goals in severe varus knee is to restore the mechanical axis of the knee (HKA from 0 to 7° of valgus) preserving the knee balancing, while there are not complete evidences about the possibility to mantain the anatomical axis (leaving the TKR in varus). I perfectly agree with the colleagues who said that you need a pre-operative planning on full length film of the lower limbs; You must check the type of the deformity, not only femoral or tibial but also intra-articular or extra-articular; in fact, in the latter case, an additional osteotomy could be required. if the correction may be obtained only with the intra-articular bony resection, I suggest to don't remove more than 10 mm from the lateral tibial plateau, to check the soft tissue balancing and to release progressively the postero-medial compartment.

Another trick is to undersize the tibial component and remove the excessive bone from the medial side. Generally a good result can be achieved with a PS TKR (i don't like CR TKR because the residual PCL may prevent a complete release of the posterior soft tissues).

Anyway a TKR with a higher constraint should be available in your sugical room.

for more details please read the following publications:

-Meftah M, J Bone Joint Surg Am. 2012 May 16;94(10);

-Mullaji A, J Arthroplasty. 2007 Jun;22(4 Suppl 1):15-9.

-Wang JW, J Bone Joint Surg Am. 2002 Oct;84-A(10):1769-74.

GOOD LUCK

I am sorry, dear Lin. last day I was thinking about a hard valgus deformity instead of the varus knee you were asking. So my answer about lateral cut and PCE.

I agrre with most of the colleagues you need a proper preoperative planning. It os going to be hard to restore mechanical axis. I would rcomend you to make tibial cut under 12 mm and of course I would choose a PS knee replacement. I believe that a careful release of the postetomedial compartmen you will be able to obtain agodd balance and a proper result. If you do not feel confident with the quality of bone after osteotomy a short stem could help you.

Dear Lin

The first question to you is; how much of the varus you described is "fixed"? In other words do you have any flexibility on the medial structures? Also you have to ask; is there any fixed flexion defority? This will determine the height of the insert at the end and the amount of releases that you need to do. Then, how is the deformity of the medial tibial condule, usually the femoral condyle is behaving better. This will determine the possible use of augmentation blocks and possible stem, in the tibia. The femoral cut needs to be at about 5 degrees if you do not use navigation with the entry point of the intramedullary rod to be slightly more lateral than your usual entry so this way you give some more valgus. Your aim is to create a 20mm gap after bone resection (about 10mm from each bone, but this has to judged on the pre-op planning on the xrays and also on the table). Removal of the medial osteophytes and releases of the soft tissues will give you the final correct alignment and I do not think that it will be necessary to do any further osteotomy. It will be better to do the tibial cut first so you could balance your femoral cuts accordingly, if you are confiortable with this approach of the preparation. The use of the components: Posterior stabilising usually is enough but a constraint component may be useful to exist just in case that you will need it. Hope that this will be helpful to you.

In the severe varus, we have to assess what part of the deformity is passively correctable. The remainder of the varus has to be corrected by bony cuts combined with soft tissue release.

Long leg films / CT scanograms can help in preop planning and selecting the appropriate femoral and tibial bony cuts.

I would use a valgus resection of 7 degrees if the resection angle measures 7 or more on the long leg films( usually the femoral shafts show some varus deformity) . However I would use 6 if the femoral mechanical - anatomical angle measures 6. ( In these cases the femoral shaft intramedullary canal is usually straight).

In valgus knees, the lateral femoral condyle can be hypoplastic or the distal femur has a valgus deformity and I would prefer to use resection angle varying from 3 degrees in severe valgus to 5 degrees for mild valgus or aligned knees(no varus or valgus).

I would refrain from using an angle more than 7 as these cases which require 7 or more may actually require more medial soft tissue release to obtain an optimal correction. Also there is a potential of achieving over correction which leads to a valgus lowerlimb alignment

ן would choose the 6 degrees of valgus also

Dear Dr. Lin Po Chun!

Thank you for your question! I normally perform long leg x-rays in weight bearing position to estimate long leg axis and the femoro-machanical axis (normally between 5-7°) before surgery. During the operation i normally choose the preoperatively measured valgus angle to perform the first femur cut. If you are not sure concerning the precise valgus angle (e.g. radiographical measurments results in 6.5°) it is generally recommendet to choose decreased angles in Valgus knees (e.g. 5-6°) and increased angles in varus knees (e.g. 6-7°).

Anyway, to gain a perfectly balanced knee: correct implant position as well as selective ligament release procedures are much more important than the chosen valgus angle at the frontal femur cut (in my opinion).

best regards,

Martin Kaipel .

I agree eintirely with Dr.Kaipel. The frontal stability of the knee is even more important than the valgus angle.If the TKR is not stable when loading the angle will be different.

I never decide arbitrarily the value of cut of 5,6, or 7 degree. I always get a preoperative CT scanogram and calculate the angle between the mechanical and anatomical axis of the femur. This is the amount of valgus that I need to cut in the distal femur. However, in obese patients, I tend to keep the valgus angle never more than 5 degrees otherwise, they find difficulty in walking when the fatty thighs rub against each other during walking.

Dear Lin Po Chun,

In severe varus usually the lateral structures are streched and elongated. If you decide for a perfectly balanced and aligned knee it is thus necessary to completely release the medial structures and the posterior capsule since you need to "elongate the medial collateral elements. If you want to avoid this it is safe to leave the knee unbalanced on the lateral side in the case of a person of a normal weigth. It will be stable after three months but only if the alagnement would be neutral or in slight valgus. The other possibility is to leave some varus but only if the knee is perfectly stable. I agree with dr Gupta in female patients with thick thighs some varus is preferable otherwise they have difficulties with walking. There are no studies showing that limited deviation from perfect alignement is detrimental for the long term survivorship of an artificial knee.

So as it is frequent in medicine you need to deciide what you want basing on all patient caracteristics using medical knowladge as a tool to achieve a good success.

Dear Colleagues

Unbalanced knee is not the teaching if the goal is to have long survivorship of the joint. This is a long standing goal for the good knee function. Big thigh ladies because of other means (difficult exposure may result to varus) but this is not the goal, just it is happening and may be accepted but must not be the norm neither something that will be taught. It is essential to achieve a stable balanced knee at all times and the necessary releases need to be performed. In varus knees medial releases have to be performd and the extend of them is determined by the degree of the deformity. Please review the great teacher and follow them.

Dear All,

Most humbly I want to say that the soft tissue balancing is mandatory in all patients (obese or non obese , males or females)

However, in an obese female I tend to keep the distal vagus cut less than 5 degrees even though the preoperative planning has calculated a higher vagus angle.

I want to reiterate that in no way I accept an asymmetric gap in extension/ flex ion , and in no way the final femoro tibial angle is accepted in varus .

The final femoro tibial angle is always a vagus angle but the angle may be less vagus in obese females than the preoperative calculation.

With regards to all eminent contributors

Dear Ravi

Thanks for the clarification. You are very right. Tibial cuts have to be at 90 degrees and agree that femur can be at 5 degrees as you mentioned. Personally I have changed the 'routine" cut of 7 degrees long time ago to 5 degrees and have no problem at all with the high BMI patients I had not made further reduction< lower than 5 and I ahve no problem with the vastus mediallis which at all times has in these patients some wasting. Thank you very much for the very useful opinion and described technique

Dear

cutting the distal femur 5 degrees in all patients means that 50% of knees are left in varus. For those patients with a large difference between anatomical and mechanical femoral axis (it may be as much as 12 degrees or 0 in extremely valgus hips), the residual varus after a 5 degree cut will be extreeme (12-5= 7) and for sure more than an implant can support in long term. In my opinon deliberate deviation from neutral mechanical axis is appropriate only in some rare indications.

Only in obese females where more valgus results in difficult gait.

Please find attached the publication on the natural distribution of the femoral mechanical anatomic angle in an osteoarthritis population undergoing TKR

Article Natural distribution of the femoral mechanical-anatomical an...