The impact of the stretching force of incision on early clinical results after primary total knee arthroplasty (TKA)

Abstract Background：A variety of surgical approaches are used in primary total knee arthroplasty (TKA), including medial parapatellar, sub-vastus, mid-vastus, lateral, and less invasive techniques. Previous studies demonstrated that there existed widely varied degrees of anterior knee soft-tissue stretching in patients undergoing primary TKA. However, the impact of incision stretching on TKA’s results failed to be investigated.Methods：1210 patients accepted primary and unilateral TKA at the authors’ affiliated institutions between Jan. 2011 and Dec. 2015. We recorded and analyzed the following data, including each patient's characteristics, incision stretching index (IS index), perioperative information, and follow-up assessments. By trisecting the IS index, patients were grouped and compared about visual analogue scale (VAS) pain scores as the primary outcome, knee circumference, knee range of motion (ROM), sensory testing, and the strength of quadriceps. Results：1089 patients undergoing primary and unilateral TKA in our two institutions were screened for final analysis, and 121 ones were excluded. The mean IS index was 22.6 (range: 19.7-24.8). VAS pain score, knee circumference, ROM, area of abnormal sensation, and the strength of quadriceps among group IS A, IS B, and IS C were significantly different (P<0.05). With the increase in the IS index, VAS pain score, knee circumference, area of abnormal sensation, and incision problems were significantly increased (P<0.05), while ROM and the strength of quadriceps decreased (P<0.05). Also, no significant difference in PJI and deep vein thrombosis (DVT) among groups was observed (P>0.05). Conclusions： There was a significant impact of incision stretching on clinical outcomes after TKA. Decreased incision stretching, which mainly depended on the length in full extension of the knee, can improve postoperative pain relief, surgical swelling, ROM, sensory disturbance of the knee, and the strength of quadriceps with reduced risk of incision complications.