POSTER ABSTRACTS - ISAKOS

E-poster #542
Validation of Two Systems of Bone Loss
Measurement in Total Knee Arthroplasty
Revision.
Khaled J. Saleh, Charlottesville, VA, USA
Edward Ranier Santos, Minneapolis, Minnesota
USA
North American Knee Arthroplasty Revision
(NAKAR), Study, Group USA
Kevin James Mulhall, Charlottesville, VA, USA,
Presenter
University of Minnesota, Minneapolis, MN, USA
Background
A key challenge to orthopaedic surgeons in
revision total knee arthroplasty (TKAR) is the
management of bone loss. A valid and reliable
system of measuring bone loss preoperatively
aids in proper planning for revision and permit
meaningful comparison between different series
of patients and treatment methods. The Anderson
Orthopaedic Research Institute (AORI) system
describes three types of defects, depending upon
the ability of the remaining bone to support a
prosthesis. The University of Pennsylvania
(UPenn) assessment system resembles a finite
element grid (200 for the femur and 200 for the
tibia) onto which areas of bone defects that are
seen on antero-posterior and lateral radiographs
can be superimposed. The intraoperative validity
of the AORI and the UPenn systems was
investigated in a large, consecutive series of TKAR
patients.
Methods
Two hundred and ninety consecutive patients with
a failed total knee replacement in need of revision
surgery were prospectively followed in 17 centers.
Based on preoperative anteroposterior and lateral
radiographs, bone loss was assessed using the
AORI and UPenn systems by 31 orthopaedic
surgeons trained in the use of these systems.
These two systems were then used to assess bone
loss intraoperatively. Kappa statistics (categorical
variable test) was used to assess validity of the
AORI classification. Paired t-test (continuous
variable test) results and scatter graphs were
examined to assess validity of the UPenn system.
Results
Among the 290 subjects, 215 (74.1 %) were
assessed to have some degree of bone loss preoperatively
and 222 (76.4 %) intra-operatively.
Using the AORI classification system agreement
between preoperative and intraoperative
classification was moderate for the femur (k =
0.50) and good for the tibia (k = 0.63). For the
UPenn system, the mean number of grids with
bone loss was 31 (2 to 200) for the femur, and 30
for the tibia (1 to144), with resultant mean scores
of 0.137 for both. Intraoperatively, a mean of 34
grids (2 to 200) had bone loss for the femur, and
32 grids (1 to 125) for the tibia. The resultant
mean intraoperative scores were 0.14 and 0.143
for the femur and tibia, respectively. There was no
statistically significant difference between
preoperative and intraoperative scores for the
femur and tibia (p < 0.02).
Conclusions
This study shows a high incidence of bone loss
among patients undergoing TKAR. The results
demonstrated that both the AORI and UPenn
systems are valid tools for assessing the actual
bone loss that will be encountered
intraoperatively, information that will help in the
accurate planning of management of bone loss in
these cases.
E-poster #543
The Influence of Femoral Component Rotation
on the Flexion Gap In Deep Knee Flexion
Myung Chul Lee, Seoul, KOREA,
Sang Cheol Seong, Seoul, KOREA
Chong Bum Chang, Seoul, KOREA, Presenter
Sahnghoon Lee, Seoul, KOREA
Seunghwan Rhee, Seoul, KOREA
Seoul National University Hospital, Seoul, KOREA
Purpose: The aim of this study was to evaluate the
influence of the femoral component rotation on
the status of the flexion space in deep knee
flexion.
Materials and Methods: We performed
preoperative, intraoperative and postoperative
evaluation of the 36 osteoarthritic knees. Using
preoperative and postoperative multi-detector
computed tomography, we measured the angle
among the rotational reference axes and calculate
the actual amount of the femoral component
rotation. Intraoperatively, we measured the
medial and lateral flexion gaps at 90 and 130
degrees of knee flexion. Pearson correlation test
was used to determine whether the amount of
external rotation of femoral component was
associated with the change in the status of the
flexion space as the knee flexed from 90 to 130
degrees.
Results: Through the intraoperative
measurements of the flexion gaps, we found that
the balanced flexion space at 90 degrees became