James Bicos and Robert A. Arciero
DEFINITION
Upper tibial osteotomy (high tibial osteotomy [HTO]) has evolved from a procedure used strictly for treating medial compartment arthrosis of the knee to one that has implications in combination surgeries to address the entire spectrum of knee pathology.
HTO is now used to alter the mechanical alignment of the lower extremity to offload forces through the medial compartment in arthritic knees.
It also can be used to offload forces in cartilage restoration procedures (eg, autologous chondrocyte implantation, meniscal transplants, and osteochondral auto- and allografts).
The subtleties of the HTO can be combined with changes in the sagittal slope of the knee to help correct or aid in treatment of anterior cruciate or posterior cruciate ligament injuries.
Therefore, the indications for an HTO include:
Malalignment plus arthrosis
Malalignment plus instability
Malalignment plus instability plus arthrosis
Malalignment plus cartilage restoration techniques
ANATOMY
The upper tibial location of the osteotomy has certain key anatomic points to consider for a successful result and to avoid injury to the extremity.
On the medial side of the knee, the pes anserine tendons insert on the anteromedial aspect of the tibia. The gracilis and semitendinosus, found on the undersurface of the sartorius fascia, must be preserved. Deep to the tendons, but composing a completely different layer, is the medial collateral ligament (MCL) (deep and superficial layers).
The patellar tendon insertion on the tibial tubercle and its relation to the level of the osteotomy. The osteotomy should be made proximal to the tubercle.
On the lateral side, the common peroneal nerve and its relation to the fibular head. The proximal tibiofibular joint also can be violated in lateral closing wedge osteotomies, leading to arthritic changes in the future.
The posterior neurovascular structures, including the popliteal artery and tibial nerve, must be protected during creation of the posterior aspect of the osteotomy.
The cross-section of the proximal tibia at the location of the osteotomy is not a cylinder, but a triangle. Therefore, the most medial location of the osteotomy is different for the posterior and anterior aspects of the tibia. Because of this, to avoid an inadvertent increase in tibial slope when opening up the osteotomy, the anterior portion of the osteotomy should be opened to one third of the posterior height (FIG 1).
PATHOGENESIS
The biologic basis for performing an HTO can be thought of in regard to its indications.
Arthrosis
Regardless of the cause of the arthritis, whether posttraumatic or primary, medial compartment arthritis continues to be exacerbated when there is mechanical overload of the medial compartment of the knee.
If the mechanical axis of the lower extremity from the hip-knee-ankle films shows that the weight-bearing line falls within the medial compartment, the medial cartilage is overloaded and placed at a risk for further degenerative change.
Instability
Because the osteotomy can alter the orientation of the proximal tibia in two planes (coronal and sagittal), altering the slope of the tibia can aid deficient cruciate ligaments in controlling knee instability.
When the tibial slope is decreased, the tibia is less likely to translate anteriorly, and, therefore, the HTO can aid the patient with an anterior cruciate ligament (ACL) deficiency. When the tibial slope is increased, the tibia is less inclined to translate posteriorly, and thus the HTO can aid the patient with posterior cruciate ligament (PCL) deficiency.
If the status of the ACL is unknown and the tibial slope is unknowingly increased in an ACL-deficient patient, residual instability may worsen due to the biomechanical changes in knee motion.
Cartilage restoration procedures
Because cartilage degeneration necessitating restorative procedures has an associated component of malalignment, placing restored or regenerated cartilage in the knee makes it necessary to off-load the involved compartment to give the new cartilage the best mechanical environment for growth and success.
NATURAL HISTORY
The natural history of medial arthrosis with varus alignment is one of progression and further cartilage degeneration over time. The end result is a spectrum of arthritic change in the knee, from uni- to tricompartmental arthritis.
Performing ACL reconstructions for instability on doubleor triple-varus knees has been shown to have detrimental effects on the ACL graft and higher rates of failure.
Noyes et al17 have recommended addressing both the ligament deficiency and the varus alignment of the extremity, to allow the most biomechanically secure construct and avoid excessive tension on the reconstructed graft.
Cartilage regenerative or restorative procedures (eg, microfracture, autologous chondrocyte implantation, osteochondral autoand allograft transplantation, meniscal transplantation) have a higher rate of failure in the setting of malalignment, because it subjects the newly implanted tissue to mechanical overload.
Studies have shown that limb malalignment is a contraindication to these procedures if not addressed concomitantly in either a staged or concurrent fashion.1–3
FIG 1 • A. The proximal section of the tibia is not a cylinder, but a triangle. This must be kept in mind when making the osteotomy cuts to avoid inadvertently increasing the tibial slope and altering the orientation of the osteotomy. B. Because the tibia is a triangle, an osteotome or wedge placed on one side of the triangle and parallel to the base will not touch the triangle at its most superior aspect. When the wedge is impacted into the triangular tibia, the marking lines should always be more on the posterior tine than on the anterior tine. This will prevent deviations from the preoperative plan in the osteotomy. This should hold true only for a single-plane osteotomy. If one wishes to perform a biplanar osteotomy (ie, change the tibial slope), this must be adjusted accordingly. C. Note the difference in the depth of the anterior and posterior tines.
PATIENT HISTORY AND PHYSICAL FINDINGS
A thorough history should be taken to determine whether the patient's complaints correlate with the ultimate diagnosis. This is especially important when making distinctions regarding pain from arthritis versus pain from instability and when formulating combined treatment options.
The exact location of the pain is determined by asking the patient to point with one finger to its location.
Medial-sided knee pain without radiation and subsequent radiographs showing medial compartment arthritis or narrowing make it possible to form a more definitive conclusion regarding surgical intervention.
Knee pain anteriorly or laterally, for example, does not correlate with varus deformity and medial compartment arthritis, and a different diagnosis must be sought for the patient's pain.
Medial-sided knee pain with radiation from the hip can signify hip arthritis as the cause of the lower extremity pain.
Radiation of the pain distal to the knee and into the foot can signify radiculopathy and a spinal cause of the lower extremity pain.
Further classification of the pain is important, including duration and frequency of symptoms, what aggravates or alleviates the symptoms, and previous injuries to the knee in question.
Does the patient complain of pain only, instability only, or pain plus instability? This distinction is important in the multiply injured knee with chronic ligamentous deficiency and arthritic change.
Pain without instability and radiographs consistent with medial compartment arthritic change can be treated with an osteotomy only.
Instability only with a varus-aligned limb can be treated with a ligamentous reconstruction only when the varus is mild and there is no varus thrust. In the setting of a large varus thrust and significant varus deformity, the ligament reconstruction will fail.
Pain with instability may signify the need to include both a ligamentous reconstruction and an osteotomy, in either a staged or concurrent fashion.
Other conservative treatments have been attempted.
Medial-sided knee pain with varus alignment can respond favorably to heel wedges with lateral posts, which help to offload the medial compartment of the knee by altering the gait mechanics.
Other treatment options include medial unloader braces, which also help to alter the biomechanics of the knee by offloading the medial compartment. Heavy laborers who cannot afford to take time off of work due to job constraints often can get through the work week with the unloader braces and postpone surgical intervention.
Cortisone injections or viscosupplementation are other conservative treatment options for early arthritic change in the knee that can be used as temporizing measures to help relieve acute pain attacks from arthritis.
The physical examination of the varus knee should include:
Investigation of varus thrust when assessing gait
Collateral ligament stability as an indicator of the residual laxity of the knee in the coronal plane
Palpation or ballottement of the patella for effusion, which indicates an intra-articular cause of the symptoms
Systematic palpation of various areas of the knee to localize pain
Assessment of knee range of motion (ROM) to determine goals of surgery: significantly limited ROM may not be caused only by lower extremity varus alignment and may indicate advanced arthritis.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographic evaluation in planning for an HTO is of paramount importance. Routine radiographs to obtain include bilateral anteroposterior (AP) standing, bilateral posteroanterior (PA) 45-degree flexed (ie, skier's view), lateral view of affected knee, and bilateral Merchant views.
The AP standing and PA 45-degree flexed views allow the determination and initial grading of medial or lateral joint space narrowing. Joint space narrowing often can be found at the posterior condylar area and, therefore, may be missed on a routine AP standing knee radiograph.
Flexing the knee to 45 degrees allows a different area of the femoral condyle to be evaluated tangentially by the xray beam and may reveal significant arthritic change (FIG 2A, B).
The lateral view allows initial assessment of the patellofemoral joint and the determination of tibial slope.
The Merchant views complete the patellofemoral joint evaluation and assess the patellofemoral joint for arthritic changes.
Further radiographic evaluation includes a mechanical axis view (hip-knee-ankle). This view makes it possible to determine initial varus and valgus alignment of the bilateral lower extremities and the overall mechanical axis, and to template correction angles for the opening wedge HTO (FIG 2C).
MRI can be useful in younger patients to assess cartilage surfaces and ligament deficiency (eg, the chronic ACL-deficient knee with varus alignment and relatively preserved joint space on radiograph). The extent of cartilage surface damage can be assessed, and meniscal injuries also can be documented.
MRI also can be useful in assessing bone marrow edema and helping to correlate the source of the patient's pain. For example, in the varus knee with medial joint line pain, meniscal symptoms, and 4 mm of medial joint space left, it is difficult to predict whether the patient's pain is coming directly from the meniscal tear or from early arthritic change.
An MRI scan that shows significant bone marrow edema in the medial femoral condyle or tibial plateau indicates that a routine medial meniscectomy should be performed with caution, because the patient's pain actually may be caused by the early arthritic changes and cartilage overload, and symptoms may increase or remain the same.
Bone scanning can also be useful in determining the source of elusive pain in the knee (FIG 2D).
DIFFERENTIAL DIAGNOSIS
Meniscal tear
Osteochondral injury
Bi- or tricompartmental arthritis
ACL, PCL, posterolateral ligament instability
Hip osteoarthritis
Spinal pathology (eg, stenosis, disc herniation)
NONOPERATIVE MANAGEMENT
Nonoperative management for unicompartmental knee arthritis before an osteotomy is needed includes:
Physical therapy and weight loss
Medications (eg, acetaminophen, nonsteroidal antiinflammatory drugs, glucosamine/chondroitin sulfate)
Intra-articular knee injections: eg, corticosteroids, viscosupplementation
Mechanical offloading devices or orthoses (eg, heel wedges with lateral posts, unloader braces). We recommend that a patient fail or find unacceptable all of these nonsurgical modalities before proceeding with an osteotomy procedure. Especially with the unloader braces, a patient may get excellent relief and can either continue the conservative treatment or decide that a formal unloading procedure, such as the HTO, would reliably relieve their pain.
Nonoperative management for instability plus malalignment includes all of the modalities that have been discussed. However, an attempt should be made to distinguish between the patient's complaints of pain, which may signify an underlying arthritic cause of pain, and instability, which, depending on the final alignment values, may need only a ligament reconstruction.
SURGICAL MANAGEMENT
Indications
Varus malalignment with medial compartment arthritis
The ideal patient is physiologically young (less than 55 years old) with an active lifestyle.
Patients should not be excluded solely based on age. Treatment plans may focus on the current and desired Tegner Activity Scores. No study has shown a Tegner Activity Score greater than 4 with total knee arthroplasty or unicompartmental knee arthroplasty.22
FIG 2 • A. AP radiograph of the right knee showing significant narrowing of the medial joint space with flattening of the medial femoral condyle and osteophyte formation. B. PA 45-degree flexed view (ie, Rosenberg view) of the same knee is obtained to show a different tangential view of the condyles. In this view, the patient has cartilage space remaining, but the medial compartment is narrowed. The numbers written in the condyles represent millimeters of joint space. C. Mechanical axis view of the bilateral lower extremities shows severe bilateral varus deformities of the lower extremity. Although the picture is underpenetrated toward the femoral heads, the steps for obtaining the mechanical axis are as follows: (1) Mark the center of the femoral head. (2) Mark the center of the ankle. (3) Draw a straight line between them (ie, the most medial line on the illustration). If the line is medial to the center of the knee, then the patient is in varus. If it is lateral, the patient is in valgus. In this case, the patient is in severe varus. D.Bone scan of the knee, showing increased uptake in the medial compartment of the left knee.
Varus malalignment with instability
Posterolateral instability4,6,17
ACL instability
Varus malalignment with arthritis and instability
The HTO can purposely decrease tibial slope in the sagittal plane and decrease anterior translation in an ACL-deficient knee.
Conversely, the tibial slope in a PCL-deficient knee can be increased to aid in decreasing posterior tibial translation.
Varus malalignment with associated cartilage or meniscal procedures
A favorable mechanical environment for newly transplanted cartilage cells or meniscal transplantation must be created. This includes decreasing the mechanical overload in that compartment via osteotomy.7,11,14,15
Valgus malalignment with lateral compartment arthritis
A distal femoral varus-producing osteotomy usually is performed to avoid producing obliquity of the tibiofemoral joint line with the varus HTO.
Adult osteochondritis dissecans19
Osteonecrosis of the medial femoral condyle in physiologically young individuals
Contraindications
Elderly patients (>60 years old) with low functional demands are better suited for a total knee replacement.
Degeneration of the contralateral knee compartment or loss of lateral compartment meniscus
Loss of knee motion >70 degrees
Patellofemoral degenerative disease that is symptomatic
Pain not consistent with clinical examination (eg, patellofemoral pain with medial compartment osteoarthritis)
Any of the inflammatory arthritides (eg, rheumatoid arthritis)
Preoperative Planning
All imaging studies are reviewed, especially the mechanical axis view, to determine the amount of correction needed for the osteotomy.
The patient and surgeon should discuss the use of auto- or allograft material for bone grafting of the osteotomy site.
If the osteotomy is smaller than 7 degrees, typically no bone graft is needed.
If the osteotomy is larger than 7 degrees, bone graft is needed to fill the defect in opening wedge techniques.
Autograft typically is taken from the iliac crest (ie, tricortical iliac crest graft)
Allograft combines tricortical iliac crest with croutons for medullary packing. Concerns in regard to placing “dead bone” into the osteotomy site have led to recommendations to include osteoconductive or osteoinductive additives (eg, OP-1, DBM) as well.
Intraoperative C-arm fluoroscopy should be available.
Examinations under anesthesia should include assessment of ROM and of varus/valgus stress at 30 degrees and 0 degrees.
Positioning
The patient is placed supine on the operating table (FIG 3).
A lateral post is used during the arthroscopy portion of the procedure and can be lowered during the open osteotomy portion.
FIG 3 • The patient is in the supine position, and the iliac crest area has been marked for draping in order to harvest the iliac crest autograft.
Pre-incision fluoroscopy images should be obtained of the hip and ankle to make sure that the operative bed can accommodate access to these areas. The hip and ankle are needed for intraoperative assessment of the mechanical axis. Depending on the patient's height, the head of the bed may have to be placed at the foot to gain length for the lower extremities.
A tourniquet is placed at the upper thigh area.
Approach
The main approach for the opening wedge HTO is through an anteromedial incision, just distal to the medial joint line and 3 cm medial to the tibial tubercle.
Approaches for the lateral closing wedge are from the anterolateral aspect of the tibia, just anterior to the fibula.
TECHNIQUES
ARTHROSCOPY
A routine diagnostic arthroscopy is performed.
The status of the lateral compartment is confirmed.
If unexpected lateral compartment osteoarthritis or chondral defects are found, off-loading the knee into that compartment may be detrimental to the longterm results of the surgery (TECH FIG 1).
The status of the patellofemoral compartment also is confirmed.
Significant patellofemoral arthritis (especially of the lateral patellar facet and lateral trochlea) can be exacerbated with an HTO. Such arthritis also can be detrimental to the long-term results of the surgery.
Meniscal tears are débrided back to a stable base.
Chondroplasty or marrow stimulation is now performed. If the osteotomy is being performed together with a cartilage restorative procedure (eg, autologous chondrocyte implantation), the osteotomy is performed first and then the restorative cartilage procedures are performed, to minimize any trauma to the newly implanted periosteal covering or injected cartilage cells.
TECH FIG 1 • A. Arthroscopic image of the medial compartment. Note the bone exposed on the medial femoral condyle and tibia. B.Arthroscopic image following use of a microfracture technique. On entering the lateral compartment, an unexpected cartilage lesion was found on the lateral femoral condyle. Offloading the mechanical axis into the lateral compartment that already is degenerated is a contraindication to the procedure.
INITIAL DISSECTION
Proper bony anatomic landmarks are located.
The tibial tubercle, posteromedial tibia, and joint line are clearly identified with a skin marker.
The incision lies 2 to 3 cm posterior to the tibial tubercle and 1 cm distal to the joint line, and extends distally for 5 to 6 cm (TECH FIG 2A).
The incision is taken down through the skin and subcutaneous tissues, revealing the sartorius fascia (TECH FIG 2B).
The superior border of the gracilis hamstring tendon is palpated, and the sartorius fascia is opened along the superior border of the gracilis tendon.
Medially, the pes bursa is released from the medial tibial tubercle in an inverted L fashion.
The pes bursa is carefully elevated distally, taking great care to develop the plane between the bursa and the underlying medial collateral ligament.
Proximally, the retinaculum and layer 1 of the knee are incised to the approximate level of the joint line (TECH FIG 2C).
Anteriorly, the patellar tendon is identified, and a plane posterior to the tendon is identified. A Z-retractor is placed under the tendon to protect it.
Occasionally, the most superior fibers of the patellar tendon attachment to the tibial tubercle must be elevated to avoid inadvertent creation of the osteotomy through the patellar tendon.
Posteriorly, the MCL is dissected subperiosteally using a Cobb elevator, which is taken back toward the posteromedial border of the tibia.
The Cobb elevator is then used to dissect the muscles and tissues from the posterior tibia along the line of the osteotomy. Care must be taken to stay directly on the posterior tibial bone to avoid neurovascular injury.
After adequate posterior dissection, it should be possible to pass a finger bluntly across the posterior tibia. For further protection of the posterior neurovascular structures, a laparotomy sponge is placed across the back of the knee.
Finally, another Z-retractor is placed posteriorly to retract the pes bursa, MCL, and posterior neurovascular structures (TECH FIG 2D, E).
TECH FIG 2 • A. View of the anteromedial knee showing the proper bony landmarks. PMT, posteromedial tibial border; TT, tibial tubercle; arrowhead, joint line; *, level of hamstring tendons. B–E.Dissection from an anteromedial view. B. Overall orientation of incision through subcutaneous fat, down to sartorius fascia. C. Close-up of incision. The sartorius fascia is opened just superior to the gracilis tendon, and the pes bursa is elevated off in an L-type fashion. An incision also is made proximally in the retinaculum. D. This incision reveals the fibers of the medial collateral ligament (MCL), which are then dissected subperiosteally with a Cobb elevator. E.Retractors are placed under the patellar tendon and at the posteromedial tibia.
PLACING GUIDE PINS
Commercially available osteotomy systems provide the necessary instrumentation needed to carry out the procedure. We use the Arthrex instrumentation (Arthrex, Inc., Naples, FL).
Before the osteotomy is performed, an intraoperative mechanical axis view should be obtained, using either the Bovie cord or the alignment rod found in the osteotomy set.
Using fluoroscopy, the alignment rod is placed at the center of the femoral head (TECH FIG 3A) and then at the center of the ankle joint (TECH FIG 3B).
TECH FIG 3 • A. Fluoroscopic image of alignment rod through femoral head. B. Fluoroscopic image of the alignment rod in the center of the ankle. C. The subsequent location of the alignment rod in the knee. This initial mechanical axis must be corrected. It should match with the preoperative planning. D. Initial guide pin from medial to lateral and parallel to the joint line. The pin is placed approximately 1 cm distal to the joint line. E.Osteotomy guide pin assembly over the initial guide pin. The angle of the guide pin assembly is changed so that the guide pins are just superior to the tibial tubercle. Two pins are drilled from medial to lateral along the osteotomy line to intersect the initial guide pin 1 cm from the lateral cortex. F. Fluoroscopic image verifying the two guide pins placed from medial to lateral using the osteotomy guide pin assembly. Note how in this view, which is parallel to the joint surface, the two pins are superimposed on one another, thus verifying that they, too, are parallel to the joint surface. White arrow, guide pin assembly; black arrow, osteotomy guide pins; black arrowhead, initial guide pin.
The subsequent location of the alignment rod in the coronal view of the knee is the intraoperative location of the mechanical axis (TECH FIG 3C).
These radiographs are saved for later comparison.
A guide pin is placed from medial to lateral across the proximal tibia, 1 cm distal to the joint, and parallel to the joint surface.
The tip of the guide pin should be just proximal to the level of the fibula. The location of this guide pin should be verified with fluoroscopy (TECH FIG 3D).
The osteotomy guide pin assembly is then inserted onto the guide pin (TECH FIG 3E). The guide pin assembly acts on the same concept as an ACL tibial aiming guide, placing the subsequent guide pins at the proper angle and oriented to the tip of the previous guide pin placed parallel to the joint line.
A parallel guide sleeve is then inserted onto the osteotomy guide pin assembly.
Not only can the osteotomy guide pin assembly determine the angle of the cut in the coronal plane, but it also has the ability to rotate in the sagittal plane to reproduce the anterior-to-posterior tibial plateau slope accurately. This can be helpful in special situations (eg, PCL or ACL deficiency) in which further alterations in the tibial slope may be necessary (eg, a biplane osteotomy).
The angle of the guide pin assembly in the coronal plane is set so that the guide pins will enter the proximal tibia above the tibial tubercle.
When acceptable, two further guide pins are drilled from medial to lateral along the orientation of the osteotomy cut. Their position is verified with fluoroscopy (TECH FIG 3F).
The parallel guide sleeve, guide pin assembly, and initial guidewire parallel to the joint line are now removed.
CUTTING AND OPENING THE OSTEOTOMY
An optional cutting guide is available for positioning over the guide pins. Either with or without the cutting guide, an oscillating saw is used to make the osteotomy cut.
The saw is always positioned on the inferior surface of the guide pins to avoid inadvertent maltracking of the saw toward the joint surface. The oscillating saw is used to cut the tibial osteotomy to within 1 cm of the lateral cortex.
Fluoroscopy should be used frequently to verify the depth and angle of the osteotomy cut.
Careful attention should be paid when making the posterior and anterior tibial cortex cuts to avoid injury to the posterior neurovascular structures and patellar tendon, respectively.
Thin osteotomes are then used to complete the osteotomy cut to within 1 cm of the lateral cortex (TECH FIG 4A).
To assess whether the osteotomy is ready for distraction, a “valgus bounce test” is performed.
As when assessing a valgus stress to the knee, a gentle valgus stress is applied to the osteotomy. The osteotomy should easily open 4 to 5 mm and “bounce back” to the closed position.
This ensures that adequate posterior and anterior cortical cuts have been made.
An osteotomy wedge is now inserted into the osteotomy cut to gently open the osteotomy to the desired correction.
If it initially is difficult to open the osteotomy and get the wedge in place, three stacked osteotomes can be placed in the osteotomy cut to gently open the osteotomy and provide the initial plastic deformation of the lateral cortex (TECH FIG 4B).
Once the wedge can be inserted into the osteotomy cut, it is gently driven across the osteotomy to the desired correction.
The wedge has laser lines that mark the desired osteotomy opening angle. This angle should be taken from the preoperative templating, and we assume that 1 mm of opening equals 1 degree of correction. Therefore, if your preoperative templating needed an 11-degree correction, the osteotomy guide should be driven to the 11-mm opening laser line. The wedge should be inserted only a few millimeters at a time to allow plastic deformation of the lateral cortex (TECH FIG 4C, D).
Fluoroscopy should be used to assess the status of the lateral cortex and osteotomy progression (TECH FIG 4E).
One should be wary of propagation of the osteotomy to the lateral cortex with disruption of the lateral hinge or propagation of the osteotomy intra-articularly. This can be usually felt by a sudden “give” of the osteotomy wedge on insertion.
The posterior tine of the wedge should be as posterior as possible to avoid an inadvertent increase in tibial slope (TECH FIG 4F).
The proximal tibia is a triangle in cross-section, so the medial starting point of the posterior tine will be more medial to the anterior tine of the wedge.
Because of the triangular shape of the proximal tibia, the millimeter reading of the posterior tine will be greater than that of the anterior tine if the osteotomy is in the proper sagittal plane alignment.
The opening of the anterior half of the osteotomy should be one third the height of the posterior half. This will verify that the tibial slope has not been significantly altered.
TECH FIG 4 • A. Fluoroscopic image showing the thin osteotomes completing the osteotomy cut to within 1 cm of the lateral cortex. Single black arrow, osteotomy guide pins; double black arrows, osteotome; *, posterior retractor protecting the neurovascular structures. B. Stacking the osteotomes in the osteotomy cut to help provide the initial plastic deformation of the lateral cortex. C. An osteotomy wedge impacted into the osteotomy cut. The anterior tine reads 10 mm and the posterior tine reads 11 mm, because the proximal tibia is a triangle, as explained in Figure 1A. The laser lines correspond with the desired osteotomy opening angle. D. Another view of the osteotomy wedge inserted into the osteotomy site. E. Fluoroscopic image showing the osteotomy wedge in place with the guide pins just superior to it. The guide pins are left in place during the opening of the osteotomy to avoid inadvertently propagating the osteotomy. The alignment rod is relied upon to verify the amount of opening of the osteotomy and the change in the mechanical axis. *, osteotomy wedge; black arrow, guide pins; arrowhead, alignment rod. F. The osteotomy wedge handle has been removed, and the posterior tine is seen almost at the level of the posteromedial cortex to avoid the inadvertent increase in tibial slope.
PLATE FIXATION
The handle of the osteotomy wedge can be removed (TECH FIG 5A), leaving the anterior and posterior tines in place.
The proper-sized osteotomy plate is then inserted into the osteotomy site (TECH FIG 5B). To respect the geometry of the tibial slope, it is recommended that the wedge in the plate be sloped from posterior to anterior.
The use of second-generation locking plates is recommended.
Before fixation of the plate, the tines are removed from the osteotomy wedge (TECH FIG 5C).
The plate is secured with two 6.5-mm fully threaded cancellous screws in the proximal fragment. (It is not necessary to use bicortical screws.) The distal fragment is secured with two 4.5-mm bicortical screws.
TECH FIG 5 • A. The handle of the osteotomy wedge is removed, and the wedge trial is placed between the tines to confirm the size of the osteotomy plate to be used.
TECH FIG 5 • B. The osteotomy plate is trialed. In this case, the posterior tine is in place and the anterior tine has been removed. C. Second-generation locking plate in place. The white arrow points to the mark on the plate verifying the slope from anterior to posterior (ie, the trapezoid is larger posterior than anterior).
BONE GRAFTING
Depending on the preference of the surgeon and patient, the osteotomy must be packed with bone graft and the medial cortical margins reinforced with tricortical iliac crest graft.
The graft can be auto- or allograft, but this must be determined in discussion with the patient before the operation.
Autograft Iliac Crest and Bone Grafting
The benefit of autograft iliac crest and bone grafting is that not only are the medial cortical margins of the osteotomy reinforced, but all of the bone graft contains hematopoietic elements and the entire bone formation cascade (TECH FIG 6A).
The difficulty with this technique is that it is necessary to prep out the iliac crest, and some morbidity results from taking the iliac crest. Although the morbidity is minimal, there is the possibility of postoperative infection, seroma, and pain.
Allograft Iliac Crest and Autograft Cancellous Bone Graft
The allograft iliac crest is fashioned into wedges that sit anterior and posterior to the plate.
The tricortical iliac crest helps to restore the medial cortical margins (TECH FIG 6B).
The autologous cancellous bone graft can either be obtained from the iliac crest in the standard fashion, or a harvester from the osteochondral autograft transplantation system (OATS; Arthrex, Inc., Naples, FL) can be used to take two plugs of bone from the distal medial femur to pack into the osteotomy site.
Allograft Iliac Crest and Allograft Cancellous Bone Graft
In this case, we worry about the risk of nonunion with larger osteotomy openings and the amount of bone graft that must be incorporated. Obviously, the larger the correction, the longer it will take for bone graft incorporation.
If the osteotomy is larger than 11 mm, we routinely use either demineralized bone matrix or OP-1 for added osteoinductive benefits.
TECH FIG 6 • A. Iliac crest autograft shaped into wedges to fit into the osteotomy site. B. Final view of the osteotomy with the iliac crest allograft anterior and posterior to the osteotomy plate, helping to restore the medial cortical margins of the osteotomy.
CLOSURE
The pes bursa is reapproximated over the distal portion of the osteotomy plate to its anatomic location with no. 1 Vicryl (TECH FIG 7A).
The horizontal incision in the sartorius fascia also is closed with no. 1 Vicryl, as is the proximal split into the medial retinaculum.
As much coverage of soft tissue over the plate as possible is attempted. In most cases, with careful initial dissection, the plate can be covered completely.
A medium Hemovac drain is then placed in the subcutaneous tissue, and the wound is closed in the standard fashion. A sterile dressing is applied and a CryoCuff device (Aircast, Austin, TX) is used (TECH FIG 7B–D).
The leg is placed into a hinged knee immobilizer, locked in extension.
TECH FIG 7 • A. Closure of the soft tissues over the plate: closure of the pes bursa (solid white line) over the distal portion of the plate to its anatomic location; closure of the incision in the sartorius fascia (square dotted line), just above the gracilis tendon; closure of the superior split in the retinaculum (dotted diamond yellow line), just medial to the patellar tendon. B. Intraoperative final AP radiograph. C,D.Postoperative AP and lateral radiographs.
POSTOPERATIVE CARE
Immediate postoperative care
We admit all of our patients with osteotomies for a one day hospital observation.
A patient-controlled morphine drip is used for the first night; the patient is weaned to medication by mouth the next morning.
The drain is removed the next morning, before the patient is discharged.
Patients are instructed in the immediate use of ankle pumps, straight leg raises, and quadriceps isometric exercises.
Patients are made non-weight bearing with crutches and the hinged knee immobilizer locked in extension at all times, except for knee ROM exercises.
Full knee extension is emphasized. Active ROM is allowed to 90 degrees immediately, with or without the brace. No passive ROM is allowed, to avoid any inadvertent stress on the osteotomy site.
Sequential compression devices are used while in the hospital. Kendall TED anti-embolism knee high stockings (Covidien, Mansfield, MA) and aspirin (650 mg every day) are used for 1 month postoperatively to minimize the risk of deep venous thrombosis.
OUTCOMES
High tibial osteotomy done with proper indications and meticulous technique can lead to consistent, effective reduction of pain and prolongation of knee arthroplasty for up to 7 to 10 years. Factors associated with poor outcomes include undercorrection of the deformity and obesity.
Many articles have been written about HTO outcomes (Table 1).
COMPLICATIONS
Although the HTO can provide many years of pain relief in the physiologically young, arthritic knee, it is not without complications.
As with many surgeries, the learning curve is high, and the surgeon should be prepared for the consequences.
Sprenger and Doerzbacher21 reported a 21% closing wedge HTO complication rate, and Spahn20 reported a 43.6% opening wedge HTO complication rate.
Intraoperative complications
Fracture of the medial or lateral cortex (FIG 4A)
Intra-articular extension of the osteotomy (FIG 4B)
Intra-articular screw placement
Peroneal nerve palsy
Immediate postoperative
Hematoma
Infection
Compartment syndrome
Thromboembolism
Delayed postoperative
Patella baja
Nonunion or delayed union
Hardware failure (FIG 4C)
Collapse with loss of osteotomy correction (FIG 4D–F)
FIG 4 • A. Lateral cortical breach stabilized with a three-hole 1/3 tubular plate. This was placed after the osteotomy had propagated through the lateral wall of the tibia. B. Intra-articular extension of the osteotomy that was not repaired intraoperatively, with subsequent osteotomy collapse and hardware breakage. C. Hardware failure. There is no collapse of the osteotomy, but the distal screws failed secondary to micromotion.
FIG 4 • D–F. Collapse of the osteotomy with loss of correction. D. One-week postoperative image with mechanical axis at lateral tibial spine. E. Four-month postoperative image with significant osteotomy collapse (4 degrees of varus). F. Ten-month postoperative image with final osteotomy collapse into 10 degrees of varus. The patient started off with a 15-degree varus deformity.
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