Purpose: Whether minimally invasive total knee arthroplasty (MIS-TKA) could offer better and faster recovery without the deviation of post-operative prosthesis position and limb alignment is still controversial. This prospective and randomized study was conducted to compare the clinical and radiological outcomes between patients who underwent the mini-subvastus approach of MIS-TKA and those who underwent the medial parapatellar approach of traditional TKA.
Methods: Fifty patients, including 50 knees, who required TKA due to osteoarthritis were randomized to the mini-subvastus group (group I) or the medial parapatellar group (group II). All patients accepted the same method of anaesthesia, equal support therapy and identical rehabilitation exercise after surgery. The evaluation system included operation time, tourniquet time, blood loss, skin incision length in flexion, straight leg raising time, the time of lower limb muscle strength up to grade 4, the time of walking with aid or without aid, the time of walking up and down the stairs, the active flexion angle, range of movement (ROM), the Knee Society Scores (KSS), visual analogue score for pain (VAS), hospital stays and radiographic outcomes.
Results: The mini-subvastus approach offered smaller skin incision length in flexion, but at the cost of operation time (P < 0.001). No significant difference was found in tourniquet time and blood loss. The patients in group I could achieve straight leg raising, the lower limb muscle strength up to grade 4, walking with or without aid, and walking up and down the stairs earlier (P < 0.001). The active flexion angle, ROM, VAS and KSS in group I were superior to those in group II until six months post-operatively (P < 0.001), but the differences was not apparent at 12 months post-operatively. More importantly, there was no significant difference between the two groups on radiological outcomes (P > 0.05).
Conclusions: The mini-subvastus approach could offer faster recovery, less pain and shorter hospital stays without compromising the principles of proper prosthesis position and limb alignment compared with the medial parapatellar approach.
Keywords: Limb alignment; Mini-subvastus; Prosthesis position; Total knee arthroplasty.