“bone balancing” technique incorporates the positive aspects of both gap balancing and measured resection allowing the surgeon to achieve the planned alignment with the minimal amount of ligament release.
There are two opposing views on the preferred technique for doing a TKR. In “gap balancing” the aim is to achieve a neutral mechanical alignment. This might compromise ligament balance and function but has shown good long term survival rates. In “measured resection” the idea is to restore the natural alignment of the limb without compromising ligament function and thereby improve function. No long-term survival studies are available for this. There is concern that by not achieving a neutral mechanical alignment the long-term survival might be compromised.
We developed a technique, called “bone balancing”, which is a compromise between measured resection and gap balancing. This versatile technique allows the surgeon to intra-operatively decide between an alignment in the range of 3° valgus/varus or avoiding a soft tissue release and accept an alignment outside the range.
Pre-operative long standing A-P X-rays of the lower limbs and varus/valgus A-P stress views are done. Pre-operative planning is done on these views. The pre-operative limb alignment is measured, which gives an indication of the amount of bone resection needed to achieve neutral alignment. In surgery first step is a mechanical neutral tibial cut. The femoral cuts are done off the tibia with a special tool, in a way similar to the technique used in UKR. No intra-medullary instrumentation is used on either the tibia or femur. Intra-operatively it is possible to know what the post-operative alignment would be before making the femoral cuts; if the alignment is acceptable, then no ligament release is indicated. If the alignment fall outside the planned parameters a ligament release is performed till an acceptable alignment is achieved before doing the femoral cuts. Alignment X-rays were repeated post-operatively.
93 TKR’s, that were operated on between January 2015 and June 2016, were followed up. Pre-operative Oxford and Tegner scores were done and were repeated between 6 and 18 months post-operatively; a Forgotten joint score was added.
The preoperative limb alignment was between 15.1° varus and 18.9° valgus with the mean of 3.9° varus alignment. Post-operatively, 75% of the knees had an alignment of between 3° varus and 3° valgus. 25% of the knees fell outside the set parameters; in most of these knees, especially in elderly patients, an intra operative decision was made to rather accept an alignment outside the set parameters instead of doing a soft tissue release.
Before the surgery, mean Oxford score was 26.1 and it improved to 40.4 post-operatively. Tegner score improved from 1.4 pre-operatively to 2.6 post-operatively. The mean Forgotten knee score was 62.9 post-operatively.
We believe that our technique of “bone balancing” incorporates the positive aspects of both gap balancing and measured resection. It allows the surgeon to, intra operatively to decide, between accepting an alignment outside the 3° varus/valgus range or do a soft tissue release to achieve this alignment. It is a versatile technique that can also be used in complicated primary and revision TKR procedures.