MINIMAL INCISION TOTAL KNEE ARTHROPLASTY - NEW TECHNIQUE IN
SURGICAL POSITIONING
INTRODUCTION:
Surgical techniques used in performing Total Knee Arthroplasty (TKA) have been
essentially unchanged for over 20 years. The patient is positioned supine and a 20-30 cm
(8-12 inch) incision is made with the leg extended. The patella is then everted and the
knee is flexed with retractors used to expose the arthrotomy site. While this extensive
exposure aides in aligning the knee enhancing visualization of landmarks and allowing
the use of bulky instruments to complete the bone preparation for implants, it imposes
significant trauma to the quadriceps mechanism and soft tissue.
A MIN TKA procedure has been developed utilizing the new Suspended Leg Technique.
The patients leg is placed in a leg holder and flexed over the edge of a surgical table
allowing the weight of the leg to distract the joint and push tissue away. The leg holder
can be adjusted to allow flexion / extension of the hip and further flexion of the knee joint
which results in exposure of the knee through flexion and extension. Sterile draping is
possible and the surgeon can be in a sitting or standing position during the procedure.
MATERIALS AND METHODS:
Twenty consecutive patients were evaluated utilizing the suspended leg approach for
MIN TKA. The patients leg was flexed and suspended over a table. Unique sterile
draping technique and surgical hoods were utilized and an incision was made two times
the patellar length - 6.5-11 cm with the knee in flexion. VMO split was utilized and the
patella was retracted (not everted) laterally using special retractors to expose the joint.
Special downsized instrumentation were used to performed extramedullary tibial
osteotomy and intramedullary femoral instrumentation with an anterior referencing
system.
The knee was sequentially flexed and extended to expose either the tibia or the femur and
allow appropriate releases.
With the leg suspended, enhanced exposure of the posterior joint was obtained and
simplified retraction of the patella laterally was allowed with reduced damage to the
quadriceps mechanism.
Implant trailing and ligament balancing were especially enhanced in flexion allowing
gravity to distract the leg to evaluate true collateral ligament balancing both in flexion /
extension and through rotation. (Note, when the leg is flexed in a traditional leg holder
the posterior femur impacts against the posterior tibia and one does not obtain a true
anatomic ligament balancing).
The patella is then rotated 90 only in full extension to expose the patella for resurfacing.
Then a tricompartmental total knee replacement is cemented in position, patella tracking
and ligament balancing is once again evaluated through range of motion and the knee is
closed in flexion.
Twenty consecutive patients were evaluated utilizing this technique; twelve female, eight
male. Ages ranged from 56-87, weight averaged 210 lbs (110-279 lbs).
Incision length averaged 9 cm in extension or 12 cm in knee flexion (range 9.0-14.0 cm).
Tourniquet time averaged 55 minutes.
RESULTS:
Postoperatively all radiographs showed good alignment in the AP and lateral plains. Two
patients femurs were positioned in slight flexion and one patella was tilted.
Postoperatively all patients had straight leg raise by the second postoperative day and 90
flexion was obtained by 18 of 20 patients by the third postoperative day. Discharge
average was third postoperative day. There were no re-operations and all patients were
satisfied at follow up.
No exclusions were made based on preoperative ROM, contractures, stiffness, or degree
of deformity.
DISCUSSION:
Total Knee Arthroplasty techniques are evolving with minimal incision arthroplasty
posing several potential advantages including: 1) Limited Incision; 2) Reduced Trauma
to the Extensor Mechanism; 3) Improved posterior joint exposure; 4) Enhanced
collateral ligament balancing in flexion.
MIN TKA with the Suspended Leg technique uses the knee in flexion during the bulk of
the procedure through and incision that is two times the patellar length or approximately
9 cm. With the knee in flexion landmarks are easier to expose, the skin is stretched, and
the patella can easily be retracted laterally utilizing a VMO snip of 1 cm. Superior
capsulotomy is simplified and the quadriceps mechanism is elevated rather than released
during the exposure. Sequential flexion or extension of the knee allows exposure of the
joint and progressive relaxation of the retractors, either medially or laterally allows
enhanced exposure as needed to the joint. Elevation of the quadriceps mechanism
permits satisfactory exposure of the anterior joint without extensive damage to the
quadriceps mechanism.
The limited incision technique can be performed with a standard leg holder similar to
arthroscopic knee approach with the hip in slight flexion and novel sterile draping
technique to ensure a mobile sterile field. This approach can be used for Arthroscopy to
Unicompartmental to Total Knee Arthroplasty. It may be considered a universal
positioning for knee surgery. Computer Assisted Navigation may assist in optimizing
alignment and bone cuts.
CONCLUSION:
Although our results are preliminary the suspended leg technique is a viable option for
minimally invasive TKA and further study and evaluation is recommended.