To investigate the correctable degree and source of varus deformity utilizing the pie-crusting technique in total knee arthroplasty (TKA) of knees with varus deformity, and evaluate its efficacy.

A total of 40 patients with varus knee deformity treated by pie-crusting technique during TKA at the Chifeng Municipal Hospital from November 2018 to June 2020 were retrospectively analysed. The mechanical lateral distal femoral angle(mLDFA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), mechanical axis deviation (MAD) and 180° minus hip-knee-ankle (HKA) angle were measured before operation. The degree and source of deformity, and the restoration of the lower limb force line were assessed. Paired-samples t test and Wilcoxon signed-rank test were conducted to compare changes in the Hospital for Special Surgery (HSS) score, visual analogue scale (VAS) and knee joint range of motion (ROM) before and after surgery.

All the patients subjected to pie-crusting technique treatments in TKA were accompanied by extra-articular varus deformity. The pre-operative mLDFA, MPTA and knee varus angle were (92.7±3.1)°, (74.7±2.6)°and (23.1±3.5)° respectively. The HSS score(t=-93.4), VAS score(Z=5.57), knee ROM(t=-37.1) and MAD(t=64.8) were improved when compared with preoperative ones (all P<0.05).

When the global knee varus angle is less than 29 °, pie-crusting technique can be used in TKA to regain the joint balance and the lower limb mechanical alignment line efficiently and safely; the extra-articular deformities may be corrected intra-articularly.