Background: A vastus-splitting approach for total knee arthroplasty
has been advocated to preserve function of the extensor mechanism and to
decrease the prevalence of lateral release. Critics have claimed that there is
greater blood loss and compromised exposure in large patients who are managed
with this approach. The purpose of the present study was to compare
vastus-splitting and median parapatellar approaches for primary total knee
arthroplasty.
Methods: Forty-two consecutive patients (fifty-one knees) undergoing
primary total knee arthroplasty were randomized to treatment with a median
parapatellar or vastus-splitting approach. The interval of the vastus muscle
split was marked with radiopaque vascular clips. Surgical data, functional
parameters, and preoperative and postoperative electromyograms were
assessed.
Results: Early (six-month) and intermediate-term (five-year)
follow-up showed no differences in functional parameters, tourniquet time, or
the frequency of patellar resurfacing. Significantly more lateral releases (p
< 0.01) and greater blood loss (p = 0.03) occurred in the median
parapatellar group. Nine (43%) of twenty-one knees in the vastus-splitting
group had abnormal electromyographic findings at six months postoperatively,
whereas all patients in the median parapatellar group had normal findings.
Seven knees with abnormal electromyographic findings at six months had normal
findings when restudied at five years; in each of these knees, the vastus
split had been developed bluntly. The other two knees with abnormal findings
at six months had had sharp dissection for the muscle split. Both of these
knees had chronic changes, one with changes indicative of reinnervation and
the other with ongoing denervation, but neither demonstrated functional
compromise.
Conclusions: The vastus-splitting approach offers a viable
alternative to the median parapatellar approach for primary total knee
arthroplasty that reduces the need for lateral retinacular release without
impairment of quadriceps function. Electromyographic abnormalities in the
quadriceps muscle have no functional consequence and most likely represent
reversible neurapraxic injury that may be avoided by blunt dissection in the
vastus medialis muscle.
Level of Evidence: Therapeutic Level I. See Instructions
to Authors for a complete description of levels of evidence.