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.
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.
Early (six-month) and intermediateterm (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.
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.