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

Abstract

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° flexion gap, two varied methods of examination, either in closed chain (Fc) or open chain (Fo) were performed. Results: The increases in the 90° knee flexion gap after PCL resection were measured by both methods, i.e., ΔFc (PR-Fc—PI-Fc): 2.04 ± 2.06 mm, p < 0.001; and mean ΔFo (PR-Fo—PI-Fo): 1.64 ± 1.36 mm, p < 0.001. However, there were no differences between ΔFc and ΔFo 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.

Stress Radiograph Confirmation of Translational Instability After Cruciate-Retaining Total Knee Arthroplasty

“…Then whether through trauma or attrition, the PCL failed leading to an unbalanced flexion gap leading to the observed sagittal plane instability. 9,10 This study has several limitations. First, it was singlecenter study, and the number of participants was small with only 26 participants in total.…”

“…Then whether through trauma or attrition, the PCL failed leading to an unbalanced flexion gap leading to the observed sagittal plane instability. 9 , 10 …”

“…[4][5][6][7] The posterior cruciate ligament (PCL) theoretically helps maintain normal knee kinematics by decreasing posterior translation, which allows the knee to maintain normal femoral rollback, decreases the stress over the femorotibial interface in CR designs, and plays a role in balancing the flexion gap. [8][9][10] Multiple studies have shown either no difference or better survivorship in patients who received CR TKAs compared with posterior stabilized TKA. 4,6,11 A risk with the CR design is the eventual rupture or attenuation of the PCL.…”