LIVRE JDG 2010

on varus and valgus stress, respectively

(p=0.11 and p=0.90). Neither group showed

any significant medial joint space width or

lateral joint space width on valgus/varus

stress. The joint space measures did not help to

predict the release procedures (p>0.05). The

opening of the medial compartment space was

not reliable evidence in the evaluation of

varus/valgus stress radiographs to plan medial

release and joint reducibility.

Overall ratios of multiple comparisons bet-

ween the measurements (on varus stress late-

ral/medial joint space width, on valgus stress

medial/lateral joint space width, lateral joint

space width on varus/varus stress, medial joint

space width on valgus/varus stress) of the

varus test to that of the valgus test were found

to show no significant difference between the

groups (p>0.05).

Intra- and inter-observer reliability test by ICC

analysis showed no statistically significant dif-

ference between the independent measure-

ments (ICCintra-observer=0.99, ICCinter-

observer=0.95).

DISCUSSION

The issue that the surgeons are facing during

the TKA is how to analyze the reducibility of

the deformity in the pre-operative phase [28].

A non-reducible varus deformity might have

been the cause of some technical difficulties to

achieve a well-balanced TKA. Identifying the

type of deformity (intra- and extra-articular)

are important to plan the soft-tissue release

procedures during TKA. The long-leg radio-

graphs are useful in the evaluation of deformi-

ties and the alignment of the limb [8-14].

Reducibility of the deformity is most com-

monly assessed by physical examination.

However, the reliability of the physical exami-

nation is poor in the arthritis of the knee [16].

In 1979, Coventry described the principles of

stress radiography [8]. By applying forces

across the knee, the degree of involvement of

each compartment with joint space narrowing

and the laxity of the surrounding structures are

revealed. Extra-articular deformities [13, 14],

secondary restraints [29-31] and specific

aspects of osteoarthritic pathology such as

contracted medial structures and osteophytes

[21] appeared to avoid the varus deformity

reducible on valgus stress.

In the previous studies, the results have been

inconsistent for varus-valgus stress examina-

tion by the stage of osteoarthritis [16-19, 21].

Recent work demonstrated the laxity of the

normal knee by stress radiographs. In exten-

sion, the mean femorotibial separation angle

was found 4.9° in varus stress and 2.4° in val-

gus stress in the normal knee [29]. Regarding

to the results for overall patients in our series,

the lateral laxity was found 6.1° in varus stress

and 0.6° in valgus stress. This comparison

strengthened the knowledge of lateral tissues

were stretched and the medial structures were

tightened during the progress of osteoarthritis.

Although varus/valgus stress radiography

seems to have advantages in the planning of pri-

mary TKA [22-24] compared with physical

examination, the reliability of stress radiogra-

phy has not previously been documented.

Hence, an objective documentation is needed

for the assessment of varus-valgus stress X-rays

to take place in the preoperative plan of TKA

and to figure out its usefulness to the surgery.

The medial osteophytes should be removed

before assessing ligamentous balance in the

coronal plane. These factors place conside-

rable doubt on the validity of the preoperative

stress radiography assessments. In the study of

Pottenger [21], the varus-valgus laxity values

were obtained before and after resecting the

marginal osteophytes during TKA surgery. The

study pointed out that the presence of marginal

osteophytes affects the tension of the liga-

ments and stabilizes osteoarthritic knees to

varus-varus motion. Testing the extended knee

may also have demonstrated the amount of

mediolateral laxity to be less because the pos-

terior capsule and the ligaments resist the

medial compartment opening [31]. Therefore,

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