Changes in Joint Gap Balances between Intra- and Postoperation in Total Knee Arthroplasty

Abstract

Achieving correct soft tissue balance and preparing equal and rectangular extension and flexion joint gaps are crucial goals of TKA. Intraoperative gap balances would change postoperatively; however, changes in joint gap balances between pre- and postoperation remain unclear. To explore these changes associated with TKA, we prospectively investigated 21 posterior cruciate ligament retaining TKAs for varus knees. Intraoperative extension gap balance (iEGB) was 2.6 ± 2.0° varus versus postoperative extension gap balance (pEGB) of 0.77 ± 1.8° valgus (P < 0.01), while no significant difference between intraoperative flexion gap balance (iFGB) and postoperative flexion gap balance (pFGB) was observed. We also explored correlations between intraoperative and postoperative gap balances but found no significant correlations. These observations indicate that (i) surgeons should avoid excessive release of the medial soft tissue during TKA for varus knees and (ii) intraoperative gap balance may not be necessarily reflected on postoperative gap balance.

Figure 1

Measurements of intraoperative gap balance for the right knee at 0° (extension) and 90° (flexion) with the patella in a reduced position and a constant 40-pound distracting force being applied between the cut surfaces of the distal femur and the proximal tibia.

Figure 2

Postoperative axial radiographs of the left distal femur. Patients sit on a table with their lower legs dependent and a 1.5 kg weight attached to the ankle on the treated side. The angle between the cut lines of the posterior femoral condyles and the proximal tibia represents the flexion gap balance (FGB).

Figure 3

Changes in joint gap balance between intraoperative and postoperative measurements. (a) Intraoperative extension gap balance (iEGB) of 2.6° varus significantly differs from postoperative extension gap balance (pEGB) of 0.77° valgus in neutral position (*P < 0.01). (b) No significant difference is observed between intraoperative flexion gap balance (iFGB) and postoperative flexion gap balance (pFGB) in neutral position.