Abstract
Post-operative stability in a primary TKA procedure requires surgical skill in establishing symmetric flexion and extension spaces. Many surgeons further utilise techniques associated with “gap balancing” by attending to the dimensional space between the femur and tibia in developing flexion and extension gaps following bone resections and/or soft tissue releases. Questions still arise related to these gaps, in particular whether or not these gaps should be created dimensionally equal to each other by adjusting bone resections. Previous publications on this subject point to the conclusion that they are not dimensionally the same, but have a relationship to the supporting soft tissue in the flexion and extension positions. This study has been designed to investigate this premise.
A soft tissue force sensing device, enabling the surgeon to create accurate balanced posterior femoral condylar resections relative to the soft tissues and the proximal tibia, has been integrated into the current surgical technique to create reliable flexion gap symmetry. To extend the concept of using balanced relative force readings to a more complete gap balancing technique, a preliminary distal femoral resection is made to facilitate mounting the adjustable instrument interfacing with the force sensor. Femoral rotation is adjusted to establish a symmetric flexion space based on balancing the relative force values in the tow femoral-tibial joint compartments. This sensor guided balancing step establishes the desired tibial insert thickness in the reconstructed knee. The final distal femoral bone resection is then made to equate the extension gap to the balanced flexion gap.
Taking the concept of balanced resection to the next level, special angled inserts have been developed to fit onto the sensor and fill the extension space, in efforts to determine and create a balanced extension space.
Data was gathered to relate the relative flexion force value to the resulting relative extension force value to see how this compares in a series of TKA’s.
The results of this data will begin to shed light on the supporting soft tissue conditions when a true balanced resection technique is utilised. The focus of this study is to evaluate the extension forces resulting from this technique to better define a functional relationship between the flexion and extension gaps in the gap balancing technique.
Correspondence should be addressed to Diane Przepiorski at ISTA, PO Box 6564, Auburn, CA 95604, USA. Phone: +1 916-454-9884; Fax: +1 916-454-9882; E-mail: ista@pacbell.net
