Background: There is disagreement about whether so-called minimally
invasive approaches result in faster recovery following total knee
arthroplasty. It is also unknown whether patients are exposed to excess risk
during the surgeon's learning curve. We hypothesized that a minimally invasive
quadriceps-sparing approach to total knee arthroplasty would allow earlier
clinical recovery but would require longer operative times and compromise
component alignment during the learning period compared with a traditional
medial parapatellar approach.
Methods: The first 100 minimally invasive total knee arthroplasties
done by a single high-volume arthroplasty surgeon were compared with his
previous fifty procedures performed through a medial parapatellar approach,
with respect to operative times, implant alignment, and clinical outcomes.
Radiographic end points and operative times for the minimally invasive group
were evaluated against increasing surgical experience, in order to
characterize the learning curve.
Results: Overall, the minimally invasive approach took significantly
longer to perform, on the average, than a medial parapatellar approach (86.3
and 78.9 minutes, respectively; p = 0.01); this was the result of especially
long operative times in the first twenty-five patients in the minimally
invasive group (mean, 102.5 minutes). After the first twenty-five minimally
invasive operations, no significant difference in the operative times was
detected between the groups. The first twenty-five minimally invasive
procedures had significantly less patellar resection accuracy (p < 0.001)
and significantly more patellar tilt than the last twenty-five (p = 0.006).
Other end points for implant alignment, including the frequency of
radiographic outliers, were not different between the minimally invasive and
traditional groups. The patients who had the minimally invasive approach
demonstrated significantly better clinical outcomes with respect to the length
of hospital stay (p < 0.0001), need for inpatient rehabilitation after
discharge (p < 0.001), narcotic usage at two and six weeks postoperatively
(p = 0.001 and p = 0.01, respectively), and the need for assistive devices to
walk at two weeks postoperatively (p = 0.025).
Conclusions: A quadriceps-sparing minimally invasive approach seems
to facilitate recovery, but a substantial learning curve (fifty procedures in
the hands of a high-volume arthroplasty surgeon) may be required. If this
experience is typical, the learning curve may be unacceptably long for a
low-volume arthroplasty surgeon.
Level of Evidence: Therapeutic Level III. See
Instructions to Authors for a complete description of levels of evidence.