A comparision of subvastus and midvastus approaches in minimally invasive

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A Comparison of Subvastus and Midvastus
Approaches in Minimally Invasive
Total Knee Arthroplasty
By Peter M. Bonutti, MD, Michael G. Zywiel, MD, Slif D. Ulrich, MD, D. Alex Stroh, BS,
Thorsten M. Seyler, MD, and Michael A. Mont, MD
Investigation performed at the Bonutti Clinic, Effingham, Illinois, and the Rubin Institute for Advanced Orthopedics, Baltimore, Maryland
Background: Themini-subvastus and the mini-midvastus approaches are among the most common alternatives to the
medial parapatellar approach for total knee arthroplasty. The purpose of this study was to compare the early clinical
outcomes of these two approaches.
Methods: In this prospective, randomized study of fifty-one patients who underwent bilateral total knee arthroplasty,
the mini-subvastus approach was usedin one knee and the mini-midvastus approach, in the contralateral knee. There
were forty-two women and nine men who had a mean age of seventy years at the time of the index arthroplasties, and
they were followed for two years postoperatively. Clinical outcome was assessed and compared with use of the Knee
Society pain and function scores, the straight-leg-raising test, range of motion, andisokinetic strength testing.
Operating time and blood loss for each approach were also compared. In addition, patients were surveyed concerning
which knee they preferred.
Results: Comparisons of postoperative Knee Society scores between both approaches at the time of the two-year
follow-up did not yield a significant difference in outcome. Isokinetic strength testing at twelve weeks postoperativelyrevealed no significant differences in muscle strength, with a mean extensor peak torque-to-body weight ratio of 0.14
Nm/kg for both groups. No significant difference was found with respect to total blood loss, straight-leg-raising test,
range of motion, or patient preference. There was no clinically relevant difference in operative times between the two
Conclusions: Theminimally invasive subvastus and midvastus approaches for total knee arthroplasty were both
associated with excellent short-term clinical results. Some surgeons believe that the subvastus approach completely
avoids damage to the quadriceps mechanism and therefore would be associated with improved muscle function. This
prospective series did not identify a substantive difference between the twoapproaches. We believe that the decision
between these surgical approaches should be based on surgeon preference and experience.
Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.
The standard medial parapatellar approach has consistently
yielded excellent and reproducible results in longterm
studies of total knee arthroplasty1-6.Despite the
success of this approach in providing ample visualization of the
operative field to assist in component alignment and placement,
concerns remain about patient functional outcomes.
Some investigators have reported both short and long-term
deficits in quadriceps muscle function following total knee
arthroplasty using the medial parapatellar approach7,8. These
deficits may bereflected in lower patient satisfaction with this
procedure compared with that reported by surgeons9. Additionally,
disruption of the blood supply as a result of patellar
eversion with this approach has been implicated in worse
Several surgeons have developed alternative surgical
approaches in an attempt to overcome the limitations of these
Disclosure: The authors did not receive anyoutside funding or grants in support of their research for or preparation of this work. One or more of the
authors, or a member of his or her immediate family, received, in any one year, payments or other benefits in excess of $10,000 or a commitment or
agreement to provide such benefits from commercial entities (Stryker, Wright Medical Technology, Joint Active Systems, Inc., Unity Ultrasonic...
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