CHAPTER SYNOPSIS

The goals of osteotomy about the knee are to improve lower extremity alignment, relieve pain, and possibly slow down the progression of arthritis. Osteotomy attempts to alter the forces transmitted across the knee joint to potentially decrease asymmetrical joint wear leading to progressive degenerative joint disease. Distal femoral osteotomy (DFO) is a nonartificial surgical alternative in the treatment of disabling knee arthritis in the young, active patient with lateral tibiofemoral arthrosis.

IMPORTANT POINTS

Indications for distal femoral osteotomy include

• 1
  

  Lateral compartment tibiofemoral arthrosis

  
  
• 2
  

  Valgus deformity (>12 degrees of vargus)

  
  
• 3
  

  Young, active patient

Contraindications for distal femoral osteotomy include

• 1
  

  Rheumatoid arthritis (inflammatory arthropathies)

  
  
• 2
  

  Ligamentous instability

  
  
• 3
  

  Poor range of motion (<90 degrees)

  
  
• 4
  

  Large flexion contractures (>15 degrees)

CLINICAL/SURGICAL PEARLS

• 1
  

  Preoperative planning is central to surgical technique.

  
  
• 2
  

  Fluoroscopy is used to determine alignment throughout the procedure.

  
  
• 3
  

  Preoperatively, a foil template can be constructed to guide the osteotomy.

  
  
• 4
  

  An extensile midline incision is used with a subvastus exposure to the femur.

  
  
• 5
  

  An AO blade plate is used.

  
  
• 6
  

  Intraoperatively, three Steinmann pins are used to approximate the level of osteotomy and guide placement of the blade plate.

  
  
• 7
  

  To approximate alignment, the Bovie cord is passed from center of femoral head to the center of the ankle intraoperatively.

  
  
• 8
  

  Fluoroscopy of the knee should show the Bovie cord traversing approximately at the junction between the medial or most lateral third of the medial compartment and the central third of the medial compartment.

  
  
• 9
  

  During fixation, the blade should be directed from somewhat anteromedial to somewhat posterolateral, allowing it to sit better on the medial femoral condyle.

CLINICAL/SURGICAL PITFALLS

• 1
  

  To minimize risk to the femoral vessels, approximately 1 cm of muscle cuff on the fascia is left close to the femur.

  
  
• 2
  

  The Steinmann pins are to be placed from medial to lateral and drilled all the way through the lateral cortex.

  
  
• 3
  

  During wedge resection, especially when making the second cut, thought must be given to preventing the weight of the leg from inadvertently cracking through residual thin lateral cortex—this can be avoided by the assistant supporting the knee.

  
  
• 4
  

  To prevent laxity of the lateral structures, during wedge resection, the saw is not advanced quite all the way across laterally, but rather the osteotomy is completed with a sharp osteotome.

  
  
• 5
  

  During application of the blade plate, the surgeon should not overcompress as this may lead to a change in the angulation and may also lead to the blade plate pulling through the bone proximally.

  
  
• 6
  

  During blade plate application, the surgeon must ensure that proper rotation of the limb has been maintained.

VIDEO AVAILABLE

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HISTORY/INTRODUCTION/SCOPE OF THE PROBLEM

The goals of osteotomy about the knee are to improve lower extremity alignment, relieve pain, and possibly slow down the progression of arthritis. Osteotomy attempts to alter the forces transmitted across the knee joint to potentially decrease the asymmetrical joint wear, leading to progressive degenerative joint disease. Osteoarthritis of the knee is a common medical condition. In 2001, more than 13.5 million American adults reported having knee joint pain, swelling, and stiffness. Among those with osteoarthritis of the knee, almost half are older than 65 years. Osteoarthritis affects 1% of men and 0.9% of women aged 55 to 64 years and 2% of men and 6.6% of women aged 65 to 74 years.

Numerous published studies in the literature have documented the success of total knee arthroplasty (TKA) for the treatment of osteoarthritis of the knee. Unicompartmental knee arthroplasty is an increasingly popular alternative to both total knee replacement (TKR) and osteotomy; however, patient outcomes following unicompartmental knee arthroplasty have been inconsistent. Currently, the exact indications for unicompartmental knee replacement remain debatable. TKA has become the major surgical treatment for osteoarthritis in the United States today. A 2005 publication about hip and knee arthroplasty in the United Sates revealed primary TKAs increased in frequency from 129,000 in 1990 to 381,000 in 2002, about four times the increase in prevalence of total hip arthroplasty.

Despite the success of TKR, problems with the procedure do exist. Failures due to technical error, wear, loosening, and infection have not yet been eliminated. The overall rate of revision TKAs continues to rise and has been estimated at 5.4 procedures per 100,000 persons per decade. Revision TKR, while more frequent and more successful now than decades ago, remains a large undertaking. Success does not approach that of primary knee replacement and complications are more frequent.

Meanwhile, life expectancy continues to climb and patients are increasingly reluctant to live with disabling arthritic knee pain, leading to larger numbers of patients with more remaining years of life seeking surgical treatment for osteoarthritis of the knee. At a time when TKR continues to demonstrate finite survivorship, there remains a role for a nonartificial surgical alternative in the treatment of disabling knee arthritis.

Normal Alignment

The mechanical axis of the lower extremity is defined as a line passing from the center of the femoral head to the center of the knee to the center of the ankle ( Fig. 3-1 ). In general, it is agreed that this line should pass through the center of the knee in a normal individual. There are several studies that have found an average of 1.3 degrees of varus to the lower extremity, which leads to 60% of the load being transmitted through the medial compartment of the knee during weight bearing.

Normal alignment.

The distal femoral joint line is in 3 degrees of valgus relative to the mechanical axis and the proximal tibial joint line is in 3 degrees of varus. As a consequence, the transverse axis of the knee lies at an angle of 3 degrees from the perpendicular, which allows for the knee joint to be parallel to the ground during gait.

INDICATIONS/CONTRAINDICATIONS

Genu valgum is much less common than genu varum. Predisposing conditions to valgus deformity include post-traumatic arthritis, rheumatoid arthritis, rickets, renal osteodystrophy, overcorrected high tibial valgus osteotomy, and infantile polio. In the valgus knee, the lateral soft-tissue structures are tight, and there is varying degrees of medial laxity and lateral femoral condyle hypoplasia. Treatment may include nonoperative management (nonsteroidal anti-inflammatory drugs, braces, steroid injections, viscosupplementation, and activity modification), osteotomy, unicompartmental knee arthroplasty, and TKA.

TKA has a more predictable course in terms of initial pain relief and longer durability than does knee osteotomy. However, there are concerns regarding the suitability of artificial joints in younger and more active patients specifically in regard to problems with loosening, osteolysis, and the need for multiple future revisions.

Indications for distal femoral osteotomy include lateral compartment tibiofemoral arthosis with valgus deformity in a young, active patient. Patients who have inflammatory states such as rheumatoid arthritis and crystalline arthropathy are usually considered poor candidates for knee osteotomy. There are also concerns involving decreased range of motion, flexion contracture, and ligamentous instability, which need to be assessed preoperatively.

It is generally agreed that the preferred site of osteotomy for genu valgus deformity greater than 12 degrees of valgus is the distal femur. The ideal target for postoperative mechanical axis varies somewhat in the literature. The case has been made for a 0-degree tibiofemoral angle. Phillips and Krackow aim for 4 degrees of mechanical axis varus. Morrey and Edgerton recommended a final mechanical axis that passes slightly medial to the middle of the medial tibial plateau.

SURGICAL TECHNIQUE

The patient is positioned supine on the operating table, with folded sheets rolled under the buttock of the operative side ( Fig. 3-2 ). An image intensification fluoroscope is brought in and tested so that one is confident that the hip and also the knee can be seen without any interference from the table. We use fluoroscopic assessment of the Bovie cord passing from the center of the femoral head to the center of the ankle and check where that crosses the knee to ensure alignment. A tourniquet is used, but it is used as a sterile tourniquet. The draping basically goes from the groin on down so that as much of the extremity as possible is visually apparent and the general appearance of alignment can be assessed.

Surgical technique.

The foil template, used as described later, can be made ahead of time and sterilized, or it can be made on the table. The template is made from one side of the foil envelope in which most surgical knife blades are packaged. A steel Zimmer goniometer can be set to the osteotomy angle and the foil bent along the edges of that goniometer so that the surgeon can cut out and angle a template equal to the angle of the correction.

The surgeon stands to the patient’s opposite side—that is, the left side for a right distal femoral osteotomy. After routine preparation and draping of the patient, a sterile tourniquet is placed and inflated after exsanguination of the limb. A nearly midline, relatively long incision is then made. It is basically a TKR incision extending at least distally to the level of the tibial tubercle. This length is not absolutely necessary, but it does facilitate easier retraction and better appreciation of bony landmarks. The precapsular plane is developed over the knee itself in the medial aspect. This development allows the surgeon to know exactly where he or she is with regard to placement of the blade and provides good confidence that the blade will be in the appropriate bone and not exiting anywhere inappropriately. The knee joint specifically is not opened.

The deep fascia proximal to the patella is incised over the quadriceps tendon and retracted peripherally, medially, and posteriorly as the vastus medialis is separated from this fascia and retracted anteriorly and laterally. This is basically a subvastus exposure. When as much of the vastus medialis as possible has been “shelled-out” of this fascial envelope, a Bovie cord is used to divide the muscle at the inferior proximal aspect, leaving approximately 1 cm of muscle cuff on the fascia, close to the femur. This technique minimizes the risk of injury to the femoral vessels.

The vastus medialis is initially retracted with sharp, relatively shallow, rake retractors or small Myerdings. After enough of the medial femoral metaphysis and diaphysis have been exposed, a longitudinal medial incision into the periosteum is made and, with very careful subperiosteal dissection anteriorly and posteriorly at the level of the osteotomy, the surgeon is then able to place subperiosteal retractors. We typically use malleable retractors 1 cm in width, especially anteriorly, and perhaps a narrow dull-tipped Hohman retractor posteriorly.

The posterior subperiosteal dissection is carried just cephalad to the proximal margin of the femoral condyles and above the origins of the gastrocnemius. This dissection, plus the palpation of the end of the femur deep to the capsule with the knee bent, is the key element that ensures the surgeon of the appropriate level for osteotomy and blade plate placement. Next, the entry point is estimated for the blade plate. This entry is just anterior to the origin of the medial collateral ligament and basically central in a proximal-distal direction with regard to the medial femoral condyle. In the anteroposterior dimension, the entry point is relatively anterior, so that the blade will lie along the shaft. After marking the entry point with cautery, the surgeon can measure back to the osteotomy level (i.e., the distance to the distal cut). The step-off on an AO blade plate is about 2 cm. The cut can actually be 2.5 cm to 2.75 cm from the entry point of the blade. The goal is to maximize the amount of bone between the undersurface of the blade and the osteotomy.

Having marked the entry point for the seating chisel and the level for the distal osteotomy, it is now possible to estimate the location of the proximal osteotomy and then to place the first alignment pin, referred to as pin No. 1. This <SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='18′>1818
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-inch Steinmann pin is placed perpendicular to the shaft of the femur, approximately 1.5 to 2 cm proximal to the anticipated level of the proximal osteotomy. This pin will be used to guide the osteotomy (i.e., the proximal osteotomy), ensuring that the osteotomy is perpendicular to the shaft of the femur. The pin will also be compared with what is described later as pin No. 3, ensuring that when pin No. 1 and pin No. 3 are parallel, the angular correction has been obtained. (Note: When placing all pins, go completely through the lateral cortex.)

Pin No. 2 is placed at the indicated level of the distal osteotomy. The angle between pin No. 2 and pin No. 1 is the one chosen for the osteotomy. This angular relationship is established by using the medial goniometer, which has been locked in the position of the desired correction. The goniometer is held by an assistant so that it is parallel to pin No. 1, and with eyeball alignment pin No. 2 is placed parallel to the other limb of the goniometer. We find this freehand technique more reliable than using drill guides. Drill guides capture the tail end of a Steinmann pin but do not secure the point that enters the bone. Typical wandering of the pin points as they attempt to enter the bone can lead to errors of placement of the pins when the drill guide is removed.

A third pin is placed about 1 cm proximal and anterior to pin No. 2. This position is chosen so as to be out of the way of the seating chisel entry points and the ultimate predicted blade plate position. Pin No. 3 is parallel to pin No. 2.

Pins No. 1 and No. 3 will be used as guides for the saw blade. Again, when the osteotomy is closed, they should be parallel. This position ensures maintenance of rotation, assuming that the pins were put in neutral rotation to the bone and to one another. Also, their parallelism ensures that the angular correction was as planned.

Pin No. 1 is removed. It should be emphasized that each of these Steinmann pins—No. 1, No. 2, and No. 3—is drilled from medial to lateral and indeed is drilled all the way through the lateral cortex. This point, which will become important later, is also important now, as hole No. 2 is used to measure the thickness of the bone at the level of the distal cut using a standard large AO depth gauge. We relocate the plate and seating chisel entry point and place the seating chisel at the entry point parallel to pin No. 3 as seen from anterior to posterior. The seating chisel is impacted 2 to 3 cm and is then removed.

An important feature of this particular technique is that the seating chisel is not used to select the final definitive position of the blade plate but mainly, or only, the entry point. The blade plate will be placed later almost as one would place a staple. This feature of the technique makes it much easier to align the blade plate accurately to the more proximal shaft. An adequately sized piece of distal bone ensures that this technique can be used without questioning the safety of the blade. In other words, it differs from a hip osteotomy in that there is a big distal target.

After the seating chisel is removed, the previously marked distal osteotomy level (i.e., the location occupied by pin No. 2) is identified. This location can be adjusted before starting the distal cut if the seating chisel has changed the expected position. Before starting the distal osteotomy, its location should be clearly drawn on the bone with a skin marking pen or with a cautery. It is usually mad in a straight anteroposterior line, that is, a line that appears perpendicular to the shaft of the femur. After drawing a distal osteotomy line and having measured the thickness of the bone with a standard depth gauge used through the holes for pin No. 2, the foil template is cut corresponding to the thickness of the bone.

What we refer to as the “tail end” of the template is used to mark the starting point for the level of the proximal cut, which is parallel to pin No. 1. The piece of foil cut away should be a triangle congruent to the wedge of bone to be resected. When looking from anterior to posterior at the resected bone wedge, it should represent a triangle congruent to the resected apex angle of the foil.

Before starting the distal osteotomy, pin No. 3 is in place and pins No. 1 and No. 2 are removed. When starting the distal osteotomy and, later, when starting the proximal cut as well, the saw is used to cut into the peripheral cortex along the line drawn, taking care to etch that line but with less attention to having the saw blade parallel to the guide pin, pin No. 3. After the saw has etched the drawn cut line, the blade is adjusted to be parallel to guide pin No. 3 and the saw cut is undertaken. Protecting retractors should be in place, and we usually place a sponge between the posterior retractor and the soft tissues. In addition to trying to effect adequate protection of the soft tissues, care is also taken to attempt not to strip more periosteum than is necessary, ideally nothing more than the periosteum covering the resection wedge. The distal cut is made approximately <SPAN role=presentation tabIndex=0 id=MathJax-Element-2-Frame class=MathJax style="POSITION: relative" data-mathml='23′>2323
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to <SPAN role=presentation tabIndex=0 id=MathJax-Element-3-Frame class=MathJax style="POSITION: relative" data-mathml='34′>3434
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of the way across the femur.

In the case of a large extremity, during wedge resection, especially when making the second cut, thought must be given to preventing the weight of the leg from inadvertently cracking through residual thin lateral cortex. This problem can be avoided by having an assistant support the knee. Although the overall position is one of knee flexion with hip external rotation, it is still possible to support the lateral knee to keep gravity from completing the osteotomy in a way that typically leads to a proximally directed spike on the distal fragment.

After the distal osteotomy has been completed to the desired distance, pin No. 3 is removed. A <SPAN role=presentation tabIndex=0 id=MathJax-Element-4-Frame class=MathJax style="POSITION: relative" data-mathml='764′>764764
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-inch pin is then placed into the holes made for pin No. 1. This selection provides accurate alignment of the pin and instant ease of placement through both bone holes. When starting the proximal cut, care is taken again simply to etch the osteotomy without making certain that the saw blade is parallel to the pin. After the osteotomy has been etched, the saw blade is made parallel to pin No. 1.

After beginning to etch the proximal cut, the tail end of the foil template is brought up to the bone to ascertain that the distance between the distal cut and the proximal cut is as planned. In using the tail end of the foil template to check the width of the base of the wedge, it is important, as shown in the diagram, to keep the proximal and distal edges of this part of the template parallel to the respective pins.

After most of the proximal cut has been made, the surgeon returns alternatively to the distal and back to the proximal osteotomy to complete the wedge resection. It is important to realize that if a saw blade is taken all of the way across the bone and through the lateral cortex, the width of the saw blade itself, the kerf, will create a small lateral defect and laxity of the soft tissues. Therefore, the saw blade is not advanced quite all the way across; rather, the ostoeotmy is completed with a sharp osteotome. The osteotomy is then opened a bit and the saw blade is passed along to smooth off the residual bone without creating a lateral kerf.

Great care must be taken to create flat surfaces that reduce nicely. During trial closure or osteotomy reduction, pins No. 1 and No. 3 are in place. Care is taken to trim the bone and adjust the fit so that the surfaces will be parallel when the osteotomy is well closed. Once the surgeon is confident of this position, an oblique <SPAN role=presentation tabIndex=0 id=MathJax-Element-5-Frame class=MathJax style="POSITION: relative" data-mathml='18′>1818
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-inch Steinmann pin is passed from posteriorly in the distal fragment in a proximal lateral direction to temporarily stabilize the osteotomy. The knee can be extended, the hip internally rotated somewhat, and the extremity basically put back into a neutral position. The fluoroscope is brought in and the overall alignment is checked with the image and the Bovie cord. The Bovie cord is pulled taut in position over the center of the femoral head and is visually positioned over the center of the ankle. Then the fluoroscope is brought over the knee, taking care that the rotation of the C-arm is neutral to the anteroposterior axis of the knee. The point of traverse of the Bovie cord is visualized. The goal is to have it traverse approximately 30% to 40% of the way between the midpoint of the distal femur and the medial edge of the radial femoral condyle. This traverse point approximates the junction between the medial or most lateral third of the medial compartment and the central third of the medial compartment.

When reduction and alignment have been assured, the offset at the osteotomy is inspected. Judging from the measured thickness of the bone taken with the depth gauge through hole No. 2, as well as the radiograph, the length of the blade can be selected. Thus, both parameters for the blade plate, namely blade length and offset, are provided.

The blade plate, grasped with the specific plate-holding instrument, is placed into the previously made seating chisel spot and is adjusted so that the side plate is directed to its proper position along the shaft of the femur. In general, the blade should be directed from somewhat anteromedial to somewhat posterolateral, allowing it to sit better on the medial femoral condyle. If the side plate position is not correct, extract the plate and redirect it slightly. Because the medial bone is relatively soft, this is not difficult to do. This is the point at which we have made blade plating more analogous to staple placement and have eliminated a lot of the problems associated with use of a fully impacted seating chisel. It is generally not necessary to use a plate clamp such as a Verbrug.

Some decision must be made about the amount of compression to be applied. It is important to note two things: (1) overcompression can lead to a change in the angulation, and (2) overcompression of a step-off arrangement can actually lead to the blade plate’s breaking the bone (i.e., pulling through proximally). Note that it is permissible to medialize the shaft slightly, if that is necessary for fitting the best selected blade plate.

Care should be taken before definitive blade plate placement to palpate posteriorly and anteriorly to ensure that rotation has been maintained and that no troublesome step-offs exist. Imaging and the fluoroscope can be used to follow any particular step, but this is rarely necessary once the surgeon has become confident about the location of the blade and is able to feel and see the direction of the osteotomy itself. The wound is closed routinely with suction drainage.