Abstract
Introduction:
Proponents of quadriceps-sparing (QS) subvastus approach for total knee arthroplasty (TKA) suggest short-term advantages including better early functional results, less pain and shorter hospital stay. However, because of potentially reduced visibility and exposure, the QS approach may compromise component alignment – an important surgeon-controlled outcome affecting implant longevity. The purpose of this study was to determine if a QS approach resulted in compromised component alignment compared to a medial parapatellar arthrotomy (MPPA), when both were performed with contemporary minimally invasive surgery (MIS) principles including small incision (≤ 15 cm), MIS instrumentation, patellar subluxation without eversion, and in situ bone cuts.
Methods:
This prospective, randomized, double-blinded study enrolled 128 patients with knee osteoarthritis undergoing primary TKA using the same cemented, posterior-stabilized prosthesis. After skin incision, patients were randomized to MPPA (n = 66) or QS technique (n = 62), with all surgeries performed by two fellowship-trained arthroplasty surgeons. Using the Knee Society roentgenographic evaluation system, two reviewers blinded to the surgical approach evaluated post-operative radiographs to measure coronal and sagittal plane alignment using the standing femoral and tibial angles as well as the lateral femoral flexion and tibial angles. Inter-observer agreement was ensured by a secondary review of all x-rays where the two observers differed by more than 1 degree in their measurements of a specific radiograph. Differences in mean angles were evaluated using the general linear model and differences in proportions were evaluated using binary regression. All analyses were conducted with SAS 9.3 on the Windows Ultimate 64-bit operating system.
Results:
Standing and lateral radiographs were available for 63 of 66 patients in the MPPA group and 61 of 62 patients in the QS group. No significant differences were noted in either coronal or sagittal plane component alignment between the two groups and the proportion of patients whose implants were in the normally acceptable range of alignment was not significantly different between the QS and MPPA groups (Table 1). The inter-rater reliability for each of the four radiographic measures was above .90.
Conclusions:
In this prospective, randomized, blinded study, a QS surgical approach did not result in radiographic alignment differences or an increase in TKA component malalignment relative to a MPPA approach, when MIS principles were adhered to in both groups. Of all measurements, the standing tibial angle showed the most outliers in terms of acceptable alignment, with coronal plane tibial component position outside the desired range in 17.5% of patients in the MPPA group and 16.4% of patients in the QS group.
