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Abstract
High tibial
osteotomy is a modality in the management of early
unicompartmental osteoarthritis which is based on the principle
of redistribution of body weight from the arthritic medial
femorotibial compartment to the healthy lateral one. HTO is
ideally indicated in young, active patients(<60 yrs), with
Unicompartmental involvement whose pain has persisted despite of
adequate trial of conservative treatment. This review article
focuses on various factors that affect the ultimate outcome of
the procedure over a period of time such as age and weight of
the patient, the anatomical alignment achieved, the level of
activity and the duration since surgery. Thus proper selection
of the patient can be done based on these factors to achieve
optimal results.
Keywords: High tibial osteotomy, surgical implications,
osteoarthritis
J.Orthopaedics 2006;3(2)e1
Factors Influencing Results Of High
Tibial Osteotomy: Review Of Literature
High tibial osteotomy was accepted as safe
and effective technique in treatment of osteoarthritis of knee
after the study conducted by Jackson et al[1,2]. Biomechanical
basis behind HTO is that the realignment of varus deformity
reduces stress on the medial compartment of knee joint.
The beneficial effect of tibial osteotomy is due to
redistribution of body weight from the arthrotic medial
femorotibial compartment to healthy lateral compartment . It
also reduces pain by reducing intraosseus hypertension found in
patients of osteoarithitis. Results following HTO are assessed
on various parameters like knee scoring system ( e.g .Hospital
for Special surgery knee scoring method), ability to perform
mild to moderate level of activity, recurrence of
deformity,cosmesis and patient satisfaction.
Conventionally; HTO involves removal of
lateral based wedge from Proximal tibia above the level of
tibial tubercle ; achieving Tibiofemoral angle of 5-14degrees
followed by either internal fixation or immobilization In a
cylinder cast. Most of the studies support utility of HTO in
treating osteoartrotic knee, but several controversial issues
still exist and more longer follow up studies will be required
to clarify such issues. There are various factors that affect
the outcome of a high tibial osteotomy surgery and being well
conversed with them will help surgeon make an informed decision
on which patient to operate.This review article attempts to
focus on various parameters that affect outcome in high tibial
osteotomy for osteoarthritis after extensive literature review.
Factors affecting results of HTO
1. Age of the patient
2. Weight of the patient
3. Severity of arthrosis
4. Surgical implications
5. Duration since surgery
6. Amount of correction achieved
7. Preoperative knee score
1. AGE OF THE PATIENT
Tibial osteotomy is preferred for young ,
active patients (60yrs) to total knee arthroplasty because of
potential to allow strenuous activity. Preservation of bone
stock and intraarticular structures are major advantages of HTO.
Insall etall has reported poor results in patients older than 60
yrs, no matter what degree of correction was achieved[3].
However, some authors have reported favourable results even in
patients more than 60 yrs. Macquet etall, in his studies of knee
osteotomies has reported better and durable results in younger
patients as compared to older age group patients[4] .It seems
that deterioration of articular cartilage at the time of surgery
is a chief determinant of results following HTO and hence to
obtain good results it should be performed during early
osteoarthritic stage that is in younger patients.
2. WEIGHT OF THE PATIENT
In a critical long term study of 87 cases at
Mayo clinic, it was pointed out that if, after one year of
procedure / valgus angulation was 8 degrees or more and if
patient’s weight was 1.32 times ideal weight or less the
likelihood of survival at 5yrs was 95%and after 10yrs was 65%.
However when valgus angulation was less than 8 degrees and
weight was more than 1.32 times ideal body weight, the survival
decreased to 38%at 5yrs and 19% at 10 yrs[5]. Thus patients with
more than 30% body weight can have propensity for poor results.
Perhaps some more studies will be required to clarify this
issue.
3. SEVERITY OF THE DISEASE
PROCESS
There is general consensus that osteotomy
provides best results when done early in patients having mild to
moderate unicompartmental osteoarthritis[4,6]. Patients having
major bone attrition [1 cm],subluxation,patellofemoral arthritis
or secondary lateral arthrosis were reported to have poor
results. Odenberg S in a larger series observed an
increased risk of revision of osteotomy in moderate to severe
preoperative arthritis. Varus deformity of more than 10 degrees
has been associated with poor results [7]
CONTRAINDICATIONS FOR SURGERY ARE
A. Lateral compartment arthrosis
B. Flexion range < 90 degrees
C. Flexion deformity > 15 degrees
D. Lateral tibial subluxation > 1 cm
E. > 20 degrees correction required
4. SURGICAL TECHNIQUE
Most important factor that is related to
continued satisfactory function was surgical accuracy and
appropriate correction of angular deformity[8]. Various surgical
techniques described in literature are
A. COVENTRY’ TECHNIQUE- entails making proximal
plane of osteotomy at least 2 cm distal to the articular surface
of tibia and distal plane of osteotomy depending upon the
correction required ; removal of wedge and closing the wedge.
The osteotomy is fixed securely with 1-2 staples which are
driven anterior to fibula.
B. SLOCUM’S TECHNIUE- involves leaving a thin
posteromedial lip of bone on the proximal tibial fragment .The
required wedge is removed ; osteotomy is closed .Posterior lip
overrides proximal end of distal fragment and gives additional
stability to osteotomy.
C. HTO with JIG-HOFFMANN advocated performing
osteotomy with jig and rigid fixation with L buttress plate
followed by mobilization [ Protocol being immediate CPM and 50%
weight bearing ]
D. MACQUET’ TECHNIQUE- is a barrel
vault osteotomy which used special jigs to make dome osteotomy
allows for adjustability of correction and more accuracy.
E. ILIZAROV METHOD – SCHWARTSMAN
described Ilizarov ring external fixator for HTO with the plane
of osteotomy being distal to the tibial tuberosity so that
adjustments can be made.It provides immediate stability and
permits early weight bearing and knee ROM.
As emphasized by Coventry and supported by
many authors the osteotomy should be performed above tibial
tubercle. He considered good blood supply of this region,
large amount of trabeculae and immediate stability provided by
the muscle pull across osteotomy highly desirable[9]
Insalletall, Harris, Kaustik recommended that
power saw be avoided due to the possibility of thermal necrosis
and subsequent development of nonunion[4]. Internal
fixation in HTO aids in rapid recovery of ROM and number of
complications are also significantly less as described by
Hoffmann. Cast immobilization has therotical disadvantage of
joint stiffness and loss of correction. On the contrary
soft tissue dissection required for internal fixation may impose
problems for revision to total knee arthroplasty.
5. DURATION SINCE SURGERY
There appears to be striking correlation
between duration since surgery and deterioration of results
following HTO in the form of decrease in knee scores , increase
in knee pain ,recurrence of deformity and need for total knee
arthroplast. [ Survival rates been variable in different
series using end point as reccurence of pain or arthroplasty
[6,7,10,11,13]
On an average. survival rates were
- 90- 95% at 1 year
- 80-85% at 5 yrs
- 55-65 %at 10 yrs
It has also being observed that
unsatisfactory results become apparent early after surgery[
usually within 3 yrs].
6. DEGREE OF POSTOPERATIVE
CORRECTION ACHIEVED
The femorotibial angle achieved at the time
of complete bone union after HTO is significant factor
responsible for long term results of HTO. [FTA of 164-168degrees
correlated with good long term results][3] . Overcorrection in
HTO has been found to produce good results but overcorrection [
> 15 degrees of valgus] is cosmetically unappealing and may have
therotical disadvantage of producing early lateral compartment
arthrosis.[12]
7. LEVEL OF ACTIVITY
The preoperative knee score seems to be
principle determinant of post operative level of activity.It has
been usually observed that ability to perform strenuous activity
[such as ability to walk one mile, walk up and down the stairs]
reaches a plateau and then gradually deteriorates with time[8,6]
Table 1: Factors associated with better outcomes in HTO:
| 1.
AGE OF PATIENT < 60YRS |
| 2.
WEIGHT NOT> 30% OF IDEAL BODY WEIGHT |
|
3. MILD-MODERATE UNICOMPARTMENTAL OA |
|
4. OSTEOTOMY ABOVE LEVEL OF TIBIAL TUBERCLE |
|
5. AVOID USE OF POWER SAW |
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6. INTERNAL FIXATION |
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7. ACHIEVING FTA OF 165-170 DEGREES |
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8. GOOD PREOPERATIVE LEVEL OF ACTIVITY |
Conclusion
HTO is an effective modality of management in
unicompartmental Osteoarthritis, but proper patient selection
and appropriate execution of surgical principles is required to
obtain good long term results. The following table tries
to elucidate various factors which seem to influence results in
HTO and should be considered by the operating surgeon before
undertaking the procedure.
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