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J. Bellemans, J. Oosterbosch, J. Truijen
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Recently however, the concept of anatomical
restoration has gained interest amongst knee
surgeons. In this philosophy the natural
anatomy of the knee is restored, by using
patient specific implants that selectively or
completely resurface the eroded or damaged
parts of the knee back to its original anatomic
contours. This approach would not necessarily
restore the alignment to neutral, but rather to
the natural alignment of the knee before the
disease or damage occurred.
A number of patients may indeed exist for
whom neutral mechanical alignment is
abnormal. Patientswith so called “constitutional
varus” knees have since their end of growth
always had varus alignment. Restoring neutral
alignment in these cases would be abnormal for
them, and in fact would almost per definition
require some degree of medial soft tissue
release (fig. 1).
At the same time, anatomic restoration of these
knees would lead to a mechanical alignment in
varus, which could jeopardize the long term
survivorship of the procedure.
The surgeon is therefore confronted with a
strategic dilemma in these patients with
constitutional varus; that is either to opt for
neutral mechanical alignment restoration while
realizing that this is abnormal for that specific
patient, or to opt for anatomic restoration and
accepting varus mechanical alignment.
Unfortunately, until recently no data were
available on the question whether constitutional
varus really exists in the normal population,
and if so in what percentage of healthy
individuals it occurs. Also it was unclear how
these patients could be recognized during
surgery. We therefore performed an interesting
study in order to investigate this [4].
A cohort of 250 asymptomatic adult volunteers
between 20 and 27 years old was recruited, and
all of them underwent full leg standing digital
radiography on which 19 different alignment
parameters were analyzed. The incidence of
constitutional varus alignment was determined
and contributing factors were analyzed using
multivariant prediction models.
Interestingly, as high as 32% of males and 17%
of females had constitutional varus knees with
a natural mechanical alignment ≥ 3° varus [4].
Constitutional varus was associated with
increased sports activity during growth,
increased femoral varus bowing, an increased
femoral neck-shaft angle, and an increased
femoral anatomic-mechanical angle.
The average mechanical hip and knee angle
(HKA) in the male knees was 1.9° varus (SD
2.1) and in the female knees it was 0.8° varus
(SD 2.4) (fig. 2). One hundred sixty five (66%)
of the male knees and 200 (80%) of the female
knees had an HKA between -3° and +3°. Five
(2%) of the male and 7 (2.8%) of the female
knees had an HKA ≥ +3°.
The number of patients with constitutional
varus in our study (32% of males, 17% of
females) may at first sight seem relatively high.
Fig. 1: Patients with constitutional varus knees
have varus alignment since they reached skeletal
maturity. Restoring neutral alignment in these
cases may in fact be abnormal and undesirable,
and would almost per definition require some
degree of medial soft tissue release [4].