Comparison of Open Wedge High Tibial Osteotomy versus Unicondylar Knee Replacement for Medial Knee Osteoarthritis
*Walaa El-Din Ahmed El-Nahas, Baseem Choudhry, Mohamad A Imam and Bahaa Kornah
Kings Mill Hospital, Mansfield Road, England
Submission: February 11, 2017; Published: February 23, 2017
*Corresponding author: Kings Mill Hospital, Mansfield Road, Sutton-In-Ashfield, NG17 4JL, Royal Derby Hospital, New Uttoxeter Road, Derby, DE22 3NE, England
How to cite this article: Walaa E-D A E-N, Baseem C, Mohamad A I, Bahaa K. Comparison of Open Wedge High Tibial Osteotomy versus Unicondylar Knee Replacement for Medial Knee Osteoarthritis. Ortho & Rheum Open Access 2017; 5(1): 555651. DOI: 10.19080/OROAJ.2017.05.555651
Introduction: Medial knee osteoarthritis is a source of debilitating pain. Varus malalignment is associated with a 4-fold increase in unicompartmental osteoarthritis. Current non-surgical treatments include patient education, weight loss, analgesics. Two contemporary surgical treatment options for medial knee osteoarthritis are available and each procedure has its merits. These are based on different principles: high tibial osteotomy (OW- HTO) where correction of knee angular deformity with slight valgus overcorrection is the goal and unicondylar knee replacement (UKA) surgery’s aim in replacing damaged articular surface.
Aim: To review clinical outcomes of two matched populations between open wedge high tibial osteotomy (OW-HTO) and unicondylar knee (UKA).
Material and Methods: This was a prospective study of two matched populations at two different centres, employing different techniques for managing medial knee compartment osteoarthritis. The OW-HTO centre had recruited 19 patients over February 2012 to December 2013. The TomoFix® knee osteotomy. The unicondylar knee replacement (UKA) centre had 22 patients over June 2012 to August 2013 and used the Oxford™ partial knee system in these operations.
Conclusion: In conclusion, this study shows that open wedge high tibial osteotomy and unicondylar knee replacements have no significant differences in oxford scores at 6 weeks and 6 months.
Abbreviations:UKA: Medial Unicompartmental Knee Arthroplasty; HTO: High Tibial Valgus Osteotomy; BMI: Body Mass Index; AP Instability: Antero-Posterior Instability; ML Instability: Medio-Lateral Instability; Instability Grading: According to the American Medical Association (grade I = 0-5 mm, grade II = 5-10 mm, grade III = >10 mm, no hard stop); Arthrosis severity: Medial Compartment Arthrosis According To Ahlback Classification; Assuming That Lateral And Patellofemoral Compartments are Intact.
Medial knee osteoarthritis is a source of debilitating pain. Varus malalignment is associated with a 4-fold increase in unicompartmental osteoarthritis independent of BMI, age and sex . Current non-surgical treatments include patient education, weight loss, analgesics, physical therapy and bracing.
Once these conservative options fail or are exhausted, and symptoms persevere then surgical treatments are deliberated.
Two contemporary surgical treatment options for medial knee osteoarthritis are available and each procedure has its merits. These are based on different principles: high tibial osteotomy (OW- HTO) where correction of knee angular deformity with slight valgus overcorrection is the goal and unicondylar knee replacement (UKA) surgery’s aim in replacing damaged articular surface.
UKA is suitable for patients with moderate joint osteoarthritis, traumatic injury, a history of unsuccessful surgical procedures or poor bone density that precludes other types of knee surgery. Patients not eligible for arthroplasty are those with an active or suspected infection in or about the knee joint, have a known sensitivity to device materials, have borne infections or disease that result in an inability to support or fix the new implant to the bone, have inflammatory arthritis, have major deformities
that can affect the knee mechanical axis, have neuromuscular
disorders that may compromise motor control and/or stability,
have any mental neuromuscular disorder, patients who are not
skeletally mature, are obese, have lost a severe amount of bone
from the shin (tibia) or have severe tibial deformities, have
recurring subluxation of the knee joint, have untreated damage
to patellofemoral joint, have untreated damage to the opposite
compartment or the same side of the knee not being replaced by
a device, and/or have instability of the knee ligaments such that
the postoperative stability the UKA would be compromised. The
anterior cruciate ligament (ACL) should be intact.
The indications for an osteotomy are malalignment with
arthrosis, and/or instability, with or without an articular
cartilage procedure. Patients with secondary degenerative
arthritis, a varus knee, and localised medial joint pain are also
candidates for an osteotomy. Total joint replacement outcomes
in the young adult have been less reliable and more complex.
Contraindications for high tibial osteotomy (HTO) are
smokers due to high risk of non-union. HTO should be avoided
in knees that demonstrate larger areas (15 × 15 mm) of
exposed bone on both the tibial and femoral surfaces. Relative
contraindications include body weight greater than 90 kg,
severe patellofemoral symptoms, or patients with abnormal
patella infera or alta since an osteotomy may increase the forces
on articular cartilage in these patients.
A well written review by  summarises indications for
unicondylar knee replacement and high tibial osteotomy well as
presented in table below (Table 1).
This was a prospective study of two matched populations
at two different centres, employing different techniques for
managing medial knee compartment osteoarthritis. These
patients were matched in age, gender, body mass index (BMI),
and failure of conservative treatments. Both of these populations
were pre-operatively assessed and where warranted anaesthetic
review was performed as part of enhanced recovery.
The patients in OW-HTO group had standard long leg films
as part of their preoperative planning where as UKA group had
standard AP, lateral and sky line radiographs. The two centres are
acute service hospitals at two different geographical locations
that are experienced in these techniques, and were blinded
respectively to other centre results. The OW-HTO centre had
recruited 19 patients over February 2012 to December 2013.
The TomoFix® knee osteotomy system using its locking medial
high tibial plate (Synthes Inc., Bettlach, Switzerland) during the
procedure (Figures 1 & 2).
The unicondylar knee replacement (UKA) centre had 22
patients over June 2012 to August 2013 and used the Oxford™
partial knee system in these operations. Majority of patients
had spinal anaesthesia with femoral nerve block and received
3 doses of Cefuroxime. First at induction and then the other
two at 8 hourly intervals. All patients had tourniquet inflated to
300mgHg and were catheterised and then removed the following
morning. All patients received patient controlled analgesia,
which was removed when patients’ pain became manageable.
Patients were discharged when patients were medically fit, able to mobilise safely with crutches, climb stairs as well as flex knee
to 90 degrees.
Both groups of patients were given venous thromboembolism
prophylaxis (Tinzaparin) for 28 days and provided with advice
for immediate complications. These patients were followed up
to 6 months in outpatient clinics and were clinically reviewed
for short term complications, and also given oxford knee score
questionnaires. Oxford knee score is a 12 item questionnaire
over 3 domains. These are corresponding to pain, function and
instability. Each question has 5 choices for answer rated from 1
to 5. Hence the score is given out of 60. 12 is the best outcome
whereas 60 is the worst outcome possible.
The surgery is done with the patient in the supine position
using a tourniquet. Fluoroscopic imaging is used throughout the
surgery. After the patient has received preoperative antibiotics,
the surgical preparation is performed. An incision is made
halfway between the tibial tubercle and the posteromedial
border of the tibia. Dissection is then carried down to the
sartorius fascia. The fascia is incised in line with the fibres of
the pes anserinus tendons, which are then retracted medially,
exposing the superficial medial collateral ligament. A periosteal
elevator is used to retract the MCL medially, exposing the
underlying tibial cortex. The patellar tendon is retracted laterally.
The most superior fibres of the patellar tendon may be released
to improve visualisation of the osteotomy site.
A guide pin is placed under fluoroscopic guidance starting
4 cm distal to the medial tibial plateau and angling 1 cm below
the lateral tibial plateau. Orientation of this pin is marked
to determine the angle of the osteotomy. An oscillating saw
is placed below and parallel to the guide pin to begin the
osteotomy, taking care to only cut the medial and posteromedial
cortex. Thin osteotomes are used to complete the osteotomy
ending approximately 1 cm short of the lateral femoral cortex
to maintain a lateral hinge. Larger osteotomes are then used to
slowly open the osteotomy site. A calibrated osteotome is then
used to open the osteotomy to the desired correction, and then
either locking or non-locking plate can be used according to the
surgeon’s preference (Figure 3).
With knee flexed to 90 degrees the joint was opened via an
anteromedial arthrotomy starting at the medial border of the
patella and ending 3 cm below the tibia plateau. The incision is
deepened through to enter joint capsule and at proximal end the
incision is extended 1-2cm into the vastus medialis. Part of Hoffa’s
pad is excised to allow anterior tibia exposed. ACL is inspected
to ensure the UKA prosthesis is suitable, otherwise TKA was
decided. The osteophytes were resected and the tibial resection
was performed with an oscillating saw under the guidance of
a jig which is positioned according to the physiological tibial
slope. The medial collateral ligament was protected with a
Hohmann retractor. The vertical cut was performed first; then
the horizontal cut is performed. The size of the resected plateau
allowed space for a tibial component and a meniscus implant of
at least 4 mm. The resected plateau serves to determine the size
of the plateau.
With knee flexed at 45 degrees, hole is made into
intramedullary canal of femur with 5mm awl. This is situated
1cm anterior to anteromedial corner of intercondylar notch.
Insert the intramedullary rod until rod pusher is stopped against
the bone. Using femoral drill guide, 4mm drill bit is drilled into
upper hole into bone up to stop and left in place. Once alignments
are confirmed a 6mm drill is then drilled through lower hole in
the guide. Once done all instrumentation from the distal femur is
removed and femoral saw block is inserted into the drilled holes.
At this point any remnants of medial meniscus and osteophytes
from corner of condyle are removed. 0 mm spigot was inserted
into the central drill hole and the distal part of the condyle is
milled. The depth of milling was determined by equalizing
flexion and extension gap.
Extension and flexion gap balancing was controlled with test
inlays. Posterior osteophytes and anterior aspect bone resection
was needed to reduce risk of impingement. Then the tibia
plateau was finally prepared. Here marginal osteophytes were
excised, template is inserted and sizing of component is checked
and altered if necessary. After testing implants the femoral and
tibial components were cemented one stage after preparation of
the bone with a jet lavage (Figure 4).
19 patients were allocated to OW-HTO group and 22 patients
were allocated to UKA group. In OW-HTO group 18 patients had
done unilaterally and one patient had bilateral open wedge
procedures done 1 year apart.
In UKA group, 13 were female and 9 were male and, in OWHTO
group 9 were female and 10 male respectively. In OW- HTO
group 13 patients were aged between 40-50 years where as 5
patients were in UKA group. 7 patients in OW-HTO group and
8 patients were in UKA group were aged between 50-60 years.
The rest were from UKA group, these 9 patients were aged 60-
The average length of stay (LoS) for OW-HTO group was 1.6
days compared to 2.8 days for UKA group.
At 6 week follow up 2/22 patients with UKA had significant
effusion versus one patient with open wedge high tibial
osteotomy, 2/22 patients with UKA compared to 4/20 OW-HTO
patients had significant tenderness. 2 patients complained of
stability problems in UKA group. Neither group had significant
events noted at 6 months.
The mean oxford scores at 6 weeks was 46 for UKA compared
to 44 for OW-HTO. Mean oxford scores at 6 months was 50 for
UKA group versus 48 for OW-HTO group respectively.
The best treatment for OA in a single compartment of the
knee has been the subject of much recent debate. HTO, UKA and
TKA are the typical choices of surgical procedures for treating
this condition. The purpose of surgery is to reduce pain, restore
function and improve quality of life. Both HTO and UKA are less
invasive procedures than TKA, both preserve the bone stock,
and both subsequently allow for normal kinematics by retaining
cruciate ligaments .
Both surgeries have shown satisfactory outcomes and
survival rates at mid- and long-term follow-up  concluded
UKA performed better than CW-HTO. They performed a 20 – 40
month retrospective review of 23 knees after HTO and 21 knees
after UKA. HTO had 100% survivorship at two years while UKA
showed a 91% survival rate at three years. In osteotomy group
there were 9% excellent, 39% good, and 52% poor results. In the
unicompartmental group, there were 48% excellent, 43% good,
and 9% poor results.group.
 performed a similar prospective randomized study on
18 HTO and 22 UKA patients. Patients (from 55 to 70 years of
age) with medial knee arthritis were randomly assigned, and
were examined before surgery, at 3 months, 1 and 5 years after
surgery. Closed wedge osteotomy, postoperatively immobilized
in a whole-leg plaster cast for six weeks) and the UKA used was
BOA score, range of motion, and patient satisfaction were
not different between the groups. Time-distance variables of
gait showed clinically significant differences in favour of the
UKA group at three-months after surgery, but these became
insignificant at one- and five-year follow-up.
At the 2008 AAOS Annual meeting, Dettoni et al. 
presented study of 54 patients with medial opening wedge HTO
(Puddu plate, Anthrex) to 56 patients treated with Accuris UKA
(Smith & Nephew). The Knee Society score and the WOMAC
were evaluated at two to four years of follow-up. The two groups
were comparable in terms of preoperative assessment and
gender, but differed regarding age (mean age 55 years for HTO
and 65 for UKA). Both groups obtained satisfactory results: 93%
good-to-excellent results in the HTO group and 95% in the UKA
group. Although differences were not significant, the UKA group
showed a slightly better knee score (93 points compared to 76 in
the HTO group), while HTO showed a better function score (91
points compared to 84 from the UKA group) [6-11].
In conclusion, this study shows that open wedge high
tibial osteotomy and unicondylar knee replacements have no
significant differences in oxford scores at 6 weeks and 6 months.
Patients should be informed that with open wedge high tibial
osteotomies pain initially is worse but resolve by 6 months.