The Disproportionate Increase of the Intraoperative Flexion and Extension Gap Space after Posterior Cruciate Ligament Resection in Total Knee Arthroplasty

Purpose: Maintaining gap balance is critical for total knee arthroplasty (TKA). This study aimed to elucidate if the extension-flexion gaps would be changed with posterior cruciate ligament (PCL) intact (PI) and PCL resection (PR) during TKA. The flexion gaps were measured using two methods, open-(Fo) and closed-chain position (Fc), based on the definition of kinetic chain position, respectively. Methods: This retrospective study enrolled a total of 33 patients who underwent posterior-stabilized (PS) TKA for symptomatic advanced osteoarthritis of knees. After bone cuts were completed, the extension-flexion gaps before and after PCL resection during TKA were measured using a calibrated tensioning device set at a 100 Nm distraction force. To further differentiate the effect of thigh weight on the 90 degrees flexion gap, two varied methods of examination, either in closed chain (Fc) or open chain (Fo) were performed. Results: The increases in the 90 degrees knee flexion gap after PCL resection were measured by both methods, i.e., Delta Fc (PR-Fc-PI-Fc): 2.04 +/- 2.06 mm, p < 0.001; and mean Delta Fo (PR-Fo-PI-Fo): 1.64 +/- 1.36 mm, p < 0.001. However, there were no differences between Delta Fc and Delta Fo before and after PCL resection. A greater amount of flexion gap was identified in open chain than in closed chain after PCL resection, and the PR-Fo and PR-Fc were 14.36 +/- 3.13 and 11.40 +/- 3.47 (p < 0.001), respectively. Conclusions: The resection of PCL during TKA distinctly increased the flexion gap, but not the extension gap. This disproportionate increase of the gap will cause a gap balance mismatch. The tensioning maneuver in open-chain was more effective to detect the gap differences than in closed-chain before and after PCL resection during TKA.

Automated summary

Maintaining gap balance is crucial for total knee arthroplasty (TKA). This study showed that resecting the posterior cruciate ligament (PCL) during TKA significantly increased the flexion gap but not the extension gap. The tensioning maneuver in open-chain was more effective in detecting gap differences before and after PCL resection.