Comparison of early postoperative rehabilitation outcome following total knee arthroplasty using different surgical approaches and instrumentation

Journal of Orthopaedic Surgery, Apr 2006 by Weinrauch, P, Myers, N, Wilkinson, M, Dodsworth, J, Et al

ABSTRACT

Purpose. To assess early postoperative rehabilitation outcome following computer-assisted total knee arthroplasty (TKA) or standard instrumentation TKA using a medial parapatellar or subvastus approach.

Methods. A prospective controlled trial of 70 consecutive patients undergoing TKA with a low contact stress rotating platform prosthesis was conducted. Patients were randomised to receive surgery with either computer navigation or standard instrumentation. A medial parapatellar or subvastus approach was used according to the surgeons' preference. Outcome measures included preoperative knee function, infra-operative factors, and postoperative rehabilitation.

Results. Duration of surgery was significantly longer when using computer navigation; however, operating time decreased with greater experience. A higher incidence and duration of early postoperative quadriceps dysfunction was associated with computer-assisted TKA through the medial parapatellar approach than through the subvastus approach or TKA performed with standard instrumentation. No patient who received surgery through the subvastus approach had a lag of more than 20 degrees, at 48 hours postoperatively, regardless of the instrumentation used.

Conclusion. Computer-assisted TKA through a medial parapatellar approach was associated with delayed recovery of the quadriceps during early postoperative rehabilitation. This was due to the additional quadriceps dissection required to place the femoral tracking array. The subvastus approach is therefore recommended for computer-assisted TKA.

Key words: arthroplasty, replacement, knee; instrumentation; rehabilitation; surgery, computer-assisted; surgical procedures, operative

INTRODUCTION

Computer-assisted total knee arthroplasty (TKA) provides better reproducibility in implant positioning than standard instrumentation, and may potentially improve the durability of the implant.1-7 Prosthetic malposition has been associated with early failure of TKA; however, the incidence of malposition may be reduced with the use of intra-operative computer navigation systems with or without preoperative computed tomographic scans.4,8-14 Computer-assisted TKA has been demonstrated to result in improved femoral component alignment in rotation and flexion, tibial component posterior slope, and matching of the femoral and tibial components in rotation.15-17 Computer navigation, however, increases surgery cost and operating time. Although gaining popularity, it has not won universal acceptance as presently only surrogate outcome measures demonstrate its advantages.9,15,18

Computer-assisted TKA requires rigid application of tracking arrays as reference points for preparation of bone surfaces and prosthetic implantation by acquisition of data describing the anatomical landmarks and surface topography of the knee joint. Tracking arrays must be rigidly applied to bone in order to reduce instrumentation error associated with movement, and be positioned as not to obstruct the further conduct of surgery, in particular the application of resection blocks and trial prostheses. When performing computer-assisted TKA via a medial parapatellar approach, the attachment pin is drilled into the anteriomedial cortex at the apex of the quadriceps incision or via a separate stab incision. Additional proximal extension of the quadriceps incision is often required for placement of the femoral array into a position suitable to achieve the clearance required to place cutting guides and prosthetic trials. This additional dissection of the extensor is not required when surgery is performed with standard instrumentation.

This study aimed to assess early postoperative rehabilitation following computer-assisted TKA performed via a medial parapatellar or subvastus approach.

MATERIALS AND METHODS

We studied 70 consecutive patients who underwent TKA between November 2002 and November 2003 at the Queen Elizabeth II Jubilee Hospital in Brisbane, Australia. Patients were randomly selected to undergo TKA with computer navigation (CT-free Knee 1.1; BrainLAB, Munich, Germany) or TKA with conventional instrumentation using intramedullary femoral and extramedullary tibial alignment guides. The low contact stress rotating platform prosthesis (DePuy, Johnson & Johnson, Warsaw [IN], US) was used in all patients.

Operating approaches were determined by the surgeons' preference and not randomly assigned. One surgeon used the medial parapatellar approach with application of an arterial tourniquet inflated to 350 mm Hg. The other surgeon used the subvastus approach. No minimally invasive surgical techniques were performed. Patients who underwent computerassisted TKA and had distal femoral and proximal tibial arrays attached using a single bicortical 5.0-mm Schanz pin (without a toothed-nut attachment) predrilled to 3.5 mm. If additional clearance for placement of the femoral array was required, the incision of the superior apex of the quadriceps was extended by approximately 1 to 2 cm. Separate stab incisions for placement of the femoral tracking array were not performed.