Conventional Alignment System Versus Surgical Navigation System in Total Knee Arthroplasty

Medical records, private office charts, and electronic medical records will be utilized by
the co-investigators to review data on patients who fit the previously stated inclusion
criteria. Demographic data including age, gender, height (cm), and weight (kg) will be
collected. Preoperative, standing anteroposterior hip-to-ankle radiographs will be measured
for the lower extremity mechanical axis, the tibiofemoral anatomic alignment, and the distal
femoral and proximal tibial anatomic angles. Intraoperative time measurements for use of both
the conventional extramedullary alignment guide, and the KneeAlignTM system will be measured
and recorded. The time required to utilize each alignment guide will be measured in seconds,
starting from the time at which the surgeon is handed the alignment guide (KneeAlignTM or
conventional, extramedullary), to the time at which the surgeon is handed the oscillating saw
to make the tibial cut. Of note, no intraoperative alignment measurements are required or
will be recorded for the conventional, extramedullary systems, while intraoperative
alignments reported by the KneeAlignTM system will be recorded when the KneeAlignTM device is
used. In addition, regarding the use of conventional, extramedullary tibial guides, each
surgeon will utilize the guide (regardless of manufacturer) which they currently use most
frequently when performing a total knee arthroplasty. While there may be minimal differences
with regards each of the surgeon's conventional guides, they are all essentially the same
with regards to utilizing an extramedullary rod for alignment of the tibial resection.

Currently, a total knee replacement requires an average tourniquet time of 30-50 minutes
depending on the surgeon. We estimate an approximate increase in total tourniquet time of 5-6
minutes when using the hand-held surgical navigation system.

For each procedure (either KneeAlignTM or conventional, extramedullary guides), after making
the initial cut, if at any point in the procedure the surgeon re-cuts the tibia, they will be
asked a series of questions postoperatively as to why they re-cut the tibia as part of the
data collection. These questions will include:

1. Did you re-cut the tibia because you thought more varus or valgus was required?

2. Did you re-cut the tibia to increase or decrease the posterior slope?

3. Did you re-cut the tibia to increase the amount of bone resected?

4. Were you happy with the overall tibial alignment? Postoperative radiographs will be
obtained as part of each surgeon's postoperative protocol, and will include a standing
anteroposterior hip-to-ankle radiograph and a standing lateral knee-to-ankle radiograph,
from which the lower extremity mechanical axis, the tibiofemoral anatomic alignment, the
tibial component mechanical alignment, and the tibial component posterior slope will be
measured.

This study has the potential to provide significant information regarding the clinical
accuracy and precision of the KneeAlignTM system compared to that of conventional,
extramedullary alignment systems. If mechanical and tibial mechanical alignment is
significantly improved with the use of the KneeAlignTM system, this may encourage surgeons to
utilize this device to improve postoperative alignment in total knee arthroplasty. In
addition, surgeon's may find this type of hand-held system more user-friendly (in contrast to
a large console, computer-assisted surgical system), and this may stimulate future
investigations into similar devices for femoral component alignment, and also total hip
arthroplasty.

Inclusion Criteria:

- a history of osteoarthritis, rheumatoid arthritis, or post-traumatic arthritis

- patients who have been indicated for a primary, posterior-stabilized, total knee
arthroplasty

- patients have had a preoperative standing anteroposterior hip-to-ankle radiograph and
standing lateral knee-to-ankle radiographs

Exclusion Criteria:

- patients with proximal tibial defects requiring either a metal or allograft augment

- inadequate radiographic studies as required by the study protocol

- if they do not receive a total knee arthroplasty, or receive a unicondylar
arthroplasty