Application of Modified Pie-crusting Technique in Releasing Medial Tightness During Primary Total Knee Arthroplasty / 中国微创外科杂志

ABSTRACT

Objective To analyze and evaluate the safety and efficacy of modified Pie-crusting ( PC) technique for releasing medial tightness during primary total knee arthroplasty ( TKA) . Methods We completed primary TKA by the same performer with modified PC technique in 30 patients (34 knees) with genu varus from March 2014 to June 2016.By using a special curved scalpel with width limit of 3 mm and depth limit of 5 mm to poke the tension parts , we released the anterion bondle of superficial medial collateral ligament ( sMCL) and posteromedial corner structures ( PMCS) during tension happened in extension , and we released the posterior bondle of sMCL during tension happened in flexion .According to the gap value measured intraoperatively , we divided these cases into three groups extension with flexion tension group ( 10 knees ) , extension tension group ( 13 knees ) , and flexion tension group (11 knees).The difference between medial and lateral gap value no more than 1 mm was defined as gap balance.We calculated the gap balance rate of each group .Series of weighted frontal X-ray were conducted at fixed period to evaluate the varus angle of the knee postoperatively.The range of motion (ROM), HSS scores and WOMAC scores were also recorded at the same time . Results Among the 34 knees , 31 knees reached the medial and lateral gap balance at both extension and flexion .There was a difference of 2 mm in medial and lateral gap value at extension in 1 knee and the same difference at flexion in the other 2 knees.The total postoperative gap balance rate was 91.2%( 31/34 ).The constrained inserts were implanted in 3 cases.No technical-related complications happened after the surgery.After the releasing procedure, the flexion gap value had an increase of 1 mm (range, 1-3mm) in the extension tension group , and the extension gap value had an increase of 1 mm ( range, 1-2 mm) in the flexion tension group, without significant difference (Z=-1.118, P=0.264).The ROM was 83.3°±14.7°preoperatively and 100.7°±14.2° postoperatively (t=-7.714, P=0.000).The median alignment of the knee was 11.5°(range, 7°-32°) preoperatively and 1° (range, 0°-4°) postoperatively (Z=-5.092,P=0.000).The HSS scores were (42.7 ±16.3) points preoperatively and (88.1 ± 9.9) points postoperatively (t=-21.868, P=0.000).The WOMAC scores were (76.2 ±8.2) points preoperatively and (11.4 ± 9.7) points postoperatively (t=31.726, P=0.000).All of them were significantly improved in comparison with those before the surgery. Conclusions Using modified PC technique is safe and effective in medial releasing during primary TKA .Both extension and flexion gap value will be affected by releasing tensed fiber at extension or flexion position .