Clinical Outcomes of the
Townsend Knee Orthosis
Jason M. Jennings, CO
William J. Barringer, MS, CO
Gary S. Trexler, CO
ABSTRACT
Between August 1988 and August 1993,
the Townsend Knee Orthosis (TKO)
was used to treat 47 cases with 49 knee
injuries at the University of Oklahoma.
The injuries were comprised of 12 anterior cruciate ligament- (ACL-) deficient
knees, 26 ACL-reconstructed knees and
11 ACL repairs. There were 20 right
knees and 29 left knees. Ninety-six percent of patients rated their TKOs as effective, and 71 percent continued to wear
their TKOs after two years. The sample
was represented by a nearly 2:1 male to
female ratio, and the average age was 22
years.
Introduction
Orthotic management of the anterior
cruciate ligament- (ACL-) deficient
knee is a controversial topic in the
world of sports medicine. Many studies
have been conducted to determine
which knee orthosis is most effective in
restoring the biomechanics of a deficient human knee (1-6).
To determine which knee orthoses
are effective one must understand the
normal biomechanics and kinematics
of the knee. The knee has been described as having a variable axis for
flexion and extension (FE) and a longitudinal axis for tibial rotation (LA) (7).
The FE axis can be explained by the
geometry of the femoral condyles. Elias
et al. (8) describe the femoral condyles
as having three sections: the patellar
groove, the distal femoral condyle and
the posterior femoral condyle, each
possessing different radii of articular
surface.
Hollister et al. describe the FE axis as
running through the collateral ligament
origins and superior to the intersection
of the cruciate ligaments, and the LA
axis as passing through the insertion of
the anterior cruciate ligament on the
tibial plateau and the insertion of the
posterior cruciate ligament on the femur (7). In full knee extension the FE
axis is located at the center of the radius of the patellar groove. As the tibia
flexes on the femur the FE axis moves
posteriorly across the distal femoral
condyles and stops at the center of the
radius of the posterior femoral
condyles. This posterior translation of
approximately 8 mm of the tibia has
been shown to occur in the first 25 degrees of flexion (9).
Many options are available when
recommending a knee orthosis for the
ACL-deficient knee. Knee orthoses are
either hinge, post and strap, or hinge,
shell and strap with the options of either a single axis, polycentric or cam-bearing type joint. Fisher describes an
effective orthosis as fitting snugly to the
extremity and being fixed with nonelastic straps and rigid shells. Although this
design poses more difficulties for a
comfortable fit, it provides better soft-tissue fixation (10). This is in agreement
with three of the aforementioned comparative studies (3,4,6).
The purpose of this study was to determine outcomes from the patients'
viewpoint of the Townsend Functional
Knee Orthosis (TKO) (see Figure 1
) at
the University of Oklahoma over a
five-year period.
Materials
The TKO is a shell, hinge and strap type
orthosis that is fixed with nonelastic
straps (see Figure 1
). This orthosis'
knee joint uses a cam-bearing type
joint designed to allow the FE axis to
migrate 8 mm posteriorly in the first 25
degrees of knee flexion and then rotate
about a fixed axis. This is the only orthotic knee joint that mimics the
anatomical FE axis of the human knee
as described earlier (10).
Methodology
Between August 1988 and August 1993
the University of Oklahoma Orthotic
Department fit 134 TKOs. The patients
were fit with the TKOs under the following prescription criterion: The knee
must have been ACL deficient, ACL
deficient with other combined instabilities or a surgically repaired or reconstructed ACL. These are the only diagnoses for which this orthosis was recommended.
The data presented in this paper
were obtained by reviewing patients'
charts and attempting to survey each
patient by phone or mail. When contacted by phone, the patients were presented with specific questions from a
prepared list. Patients who could not be
contacted by phone were sent the same
questions by mail (see Table 1
).
Question #10 was somewhat subjective. To ensure all patients understood
the descriptive terminology, noneffective was defined as allowing a new injury to an old injury or allowing an isolated new injury, and effective was defined as allowing the athlete to return
to competitive athletics with the use of
the orthosis without the recurrence of
an injury that required surgical intervention.
A sample of 47 patients with 49 involved knees was obtained. This sample
represents 35 percent of the patients
treated with the TKO at the University
of Oklahoma. The ratio of males to females in the sample was 64 percent
male and 36 percent female. The average age was 22 years, the youngest being 15 and the oldest being 49 years.
Forty-one percent of the sample involved right knees, and 59 percent involved left knees. Fifty-three percent of
the knees had undergone ACL reconstruction, 22 percent had undergone
ACL repair, and 25 percent were still
ACL deficient. Although the majority
of initial injuries were sports-related,
seven were not. These patients were allowed to remain in the study because
they used their orthoses for recreational athletics.
Data
Most injuries had occurred during participation in basketball, softball, soccer
or skiing (see Table 2
).
Twenty-nine percent of the patients
discontinued the use of their orthoses
citing different reasons: 6 percent by
physician orders, 18 percent by self-elimination and 2 percent because the
orthosis was uncomfortable and/or restrictive.
Seventy-one percent of the patients
continued to wear their orthoses
throughout the study. On average,
these patients wore their orthoses two
years. The range was from six months to
four years, six months (see Table 3
).
Eighty percent of the patients reported no problems with their orthoses.
Of the 20 percent who reported problems, 6 percent were with suspension; 6
percent were caused by limb volume
fluctuation; 2 percent were caused by
bent or broken joints; 2 percent of the
patients needed sports sleeves to participate in athletic events; 2 percent reported that the sports sleeves did not
fit; and 2 percent reported that the orthoses needed to provide more mediolateral stability.
Discussion
Many types of knee orthoses have been
used at the University of Oklahoma, including Lenox Hill, ECHO, Analog,
CBI, Ortho Tech, Omni, DonJoy and Townsend . The Townsend
is currently the knee orthosis of choice
for the following reasons: Minimal
maintenance is required; donning/doffing is simple; a comfortable fit is
achieved easily; very few patients have
complaints or problems; knee joints
replicate the FE axis of the knee better
than other knee joints; and the clinical
staff at the University of Oklahoma believe the design to be as good as or better than any other.
The statistics show that 71 percent of
patients involved in this study continued to use their orthosis for an average
of two years. Most of those who discontinued use did so by self-elimination,
not by physician order. Ninety-six percent of patients were able to return to
athletic competition without re-injury
to the affected knee regardless of
whether the ACL had been repaired/
reconstructed.
Two patients indicated that the TKO
was ineffective. The first patient was a
38-year-old female who had participated in competitive athletics since high
school and was still competing, coaching and refereeing indoor soccer. This
patient had suffered an injury to her
ACL playing indoor soccer and had
been fit with a TKO. She was able to
compete in indoor soccer, referee,
coach, scuba dive and participate in
other athletic activities for approximately 18 months after being fit with
the TKO. However, she subsequently
buffered a direct valgus blow to her
knee during a soccer game, which resulted in ACL reconstructive surgery.
She said she had been very pleased
with her orthosis until that point and
Mould have rated it effective if her injury had not recurred. She discontinued
wearing the orthosis after her reconstruction by recommendation of her
physician.
The second patient who rated the
TKO ineffective had undergone ACL
reconstruction and wore the TKO for
approximately two weeks. At that
point, he discontinued use of the orthosis because he did not believe it decreased his pain.
The two most common problems
that occurred with the knee orthosis
were suspension or distal migration
and fluctuating limb volumes that resulted in a compromised fit. Other
problems included bent or broken knee
joints, sports sleeves that did not fit,
needing a sports sleeve to participate
and feeling that the orthosis needed to
provide more mediolateral stability.
When patients experiencing those
problems returned to the University of
Oklahoma, the appropriate modifications were made to the orthosis to remedy the specific problem. When patients failed to report their problems,
however, no modifications could be
made to the orthoses.
Conclusion
These conclusions are based solely on
patients' attitudes toward their TKOs.
This paper has demonstrated the TKO
to be effective clinically, allowing patients to return to athletics with a success rate of 96 percent. It has been
shown that 71 percent of University of
Oklahoma patients fit with the TKO
continue to wear their orthoses for an
average of two years. The majority of
patients who stop wearing their orthoses do so on their own, not by physician order.
It can be concluded that the
Townsend Knee Orthosis has been successful at the University of Oklahoma
in allowing patients to return to athletics. It also can be concluded that, since
most patients return to athletics with-
out a recurring injury, the outcome of
patients treated with the TKO has been
clinically significant.
JASON M. JENNING, CO, graduated from the California State University at Dominuquez Hills orthotic and prosthetic program and has completed his orthotics residency at the University of Oklahoma. He also participated in the prosthetics residency program at the University of Michigan.
WILLIAM J. BARRINGER, MS, CO, is chief of the orthotics section of the Department of Orthopedic Surgery and Rehabilitation at the University of Oklahoma. He is also an associate professor in the College of Medicine.
GARY S. TREXLER, CO, is assistant chief of the orthotics section of the Department of Orthopedic Surgery and Rehabilitation at the University of Oklahoma. He is also assistant clinical professor in the College of Medicine.
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