The body weight applies on the knee through the femoro-tibial mechanical axis of the limb,
it passes across the center of the knee. In case of VARUS deformation, the
mechanical axis is deviated medialy increasing load compression forces on the
medial compartment of the knee, and thus a cartilage lesion leading to medial arthrosis.
High tibial valgus osteotomy realign the varus knee to better distribute forces. There are two major techniques :
- closing wedgeosteotomy that has been the standard procedure for more than 30 years.
This needs removal of a lateral wedge of the tibia associated to a peroneal osteotomy.
- opening wedge osteotomy in recent years with the developpement of strong fixation plates. Ther is an only bonecut that allow to open the tibia like a book, the gap is then filled with autologous ( iliac crest) or allograft or synthetic (Hydroxyapatite) blocs. This technique preserves the proximal tibial anatomy and bone stock allowing easy conversion to total knee arthroplasty, is more precise in correcting the mechanical axis, and avoids lesion of the proximal tibio-fibular joint and peroneal nerve.
HTVO technique of opening wedge :
Patient is positioned supine, and the involved limb and ipsilateral iliac crest are prepared and draped . The procedure carried out under tourniquet. Concurrent arthroscopy is performed as necessary to evaluate the menisci and the status of the articular cartilage.
A vertical incision is made over the pes anserinus insertion halfway between the medial border of the patellar ligament and the posterior margin of the tibia.The sartorial fascia is incised exposing the hamstring Under fluoroscopic control, a guide wire is drilled across the proximal tibia from medial to lateral. The guide is positioned at the level of the superior aspect of the tibial tubercle and oriented obliquely to end approximately 1 cm below the joint line at the lateral tibial cortex. The osteotomy is then performed with an oscillating saw below the guide pin to prevent superior migration and an intra-articular frac ture. The osteotomy is deepened with flexible and rigid osteotomies under fluoroscopic guidance. Once the osteotomy has been nearly completed, the medial opening is created progressively using 2 screwed osteotoms . An alignment guide is used to ensure that the weight-bearing axis is passing through the converted point (62.5% from medial to lateral).
The plate is fixed proximally with 6.5-mm cancellous screws and distally with 4.5-mm
cortical screws. Either iliac crest or allogenic bone grafting or synthetic bloc is inserted
through the opening wedge to prevent delayed or nonunion and fixation failure.
The ideal amount of correction remains a matter of controversy. Overcorrection is recommended by almost all surgeons; valgus correction of >=8° for proximal tibial osteotomy is recommended.
CHECK-UP BEFORE SURGERY
In order to detect vital risk for anesthesiology, and to assess a potential risk
of post-operative complication in a short or long term follow-up, a medical questionnaire
checking list is needed before the operation, to be planed by the surgeon and his team.
Risk factors influencing complications are :
factors increasing risk of infection
- Obesity is associated with a higher risk of infection. Individuals with a body-mass index
(BMI) >35 had a 2.1 times greater risk of infection compared with those with a lower BMI
- patients with osteonecrosis and rheumatoid arthritis had a 2.2 times greater risk of infection compared with those with osteoarthritis.
- previous infection of the joint
- tooth infection : a visit to dentist & panoramic dental X-Ray, and treatment of dental problems are necessary to eliminate a potential risk of infection.
factors increasing risks for medical complications
- American Society of Anesthesiology (ASA)scores > 3 is at risk.
- Previous algo neuro dystrophy may be a recurrent risk.
- Previous deep veinous thrombosis is a predisposing factor to recurrent episode
You will stay 2 to 5 days in the surgical department of orthopaedics.
Internal fixation allows the patient to start immediately rehabilitation exercises and permits a rapid recovery of ROM. Internal fixation is secure enough to avoid any type of bracing.
The knee is mobilised the day after operation, under physiotherapist supervision. Straight leg raising exercises and passive/active mobilisation are encouraged, and the splint is removed at day 2 when active extension of the leg is obtained.
Weight bearing is forbidden during the first 3 weeks, and then authorized under control after X_RAY showing bone healing starting. You will be able to walk without crutches at the end of the 3rd month.
RESULTS AND COMPLICATIONS
Overcorrection to 3° to 10° of valgus produces the best success rates at 10 years following the
osteotomy, but these results tends to deteriorate over time. Progressive osteoarthritis seems to be
the reason for the deterioration of functional outcomes.
Factors associated with an increasing risk of revision of the osteotomy are :
-an older age at the time of the surgery - obesity (morethan 1.32 times the ideal weight) - less constitutional preopera-tive tibial varus (<5°) - advanced femorotibial osteoarthritis ofthe medial compartment with >50% reduction in the jointspace - severe limitation of motion before surgery
Even with a carefull act performed by perfectly trained team, any complications may happen the same as in every surgical act. These are exceptionnal, The list below is not exhaustive.
- Infection is one of the most dreaded complications. The efficacy of prophylactic
measures and risk factors play an important role.
prophylactic mesures: laminar flow, body suits, drains, surgical time (length), the use of preoperative antibiotics. detection and treatment of risk factors :- Obesity, diabetis, pre op treatment of dental or urinary infection.
- Skin necrosis should well controlled with adapted local healthcare . Its prevention is realised with a central skin incision. If not controled, the risk is to transmit an infection to the prosthetic joint. A reoperation is necessary.
- Neuro-algodystrophy : rare ( 1 à 3% ) but impossible to plan ( except in case of previous episode) and difficult to treat.
- un syndrome des loges : may happen in closed wedgeosteotomy technique as the muscle and lateral aponevrosis of the leg are opened.
- delay or non union : rare in this metaphyseal bone area, iIt may break the plate and needs an other operation.
- tibial plateau fracture when opening the osteotomy. It may delay the bone healing.
- Partial peroneal palsy in case of traumatism of the motor branch of the extensor hallucis longus during lateral approach in closing HTVO.
- femoro-cutane nerve palsy when harvesting graft on iliac crest.
- pain at iliac crest harvesting zone.
- hematoma at iliac crest harvesting zone.
- pain on osteosynthsis material some months later : removal is possible at 6 months.
- phlebitis : preventive mesure ( early mobilisation, anti-thrombotic socks, low Weight Molecular Heparin anti-embolic prophylaxis for 6 weeks) and systematic echodoppler control at 7th day allow the risk to be minimize ; in case it happens, an anticoagulation treatment is started and rehabilitation is slowered.
LONG TERM FOLLOW-UP
Long term results of HTVO in terms of knee function, radiographic alignment, and progression of osteoarthrosis are show generaly excellent and good results in 97% of the cases after 2 years, in 85% after 5 years, and only in 60% after 8-10 years. In order to prevent this deterioration in time it is recommanded not overweight to avoid coming of arthrosis desease in lateral compartment, and to delay the Total Knee Arthroplasty indication.
Last updated : 9/12/2007