High Tibial Osteotomy

Stephen J. French MD

J. Robert Giffin MD

Peter J. Fowler MD

History of the Technique

High tibial osteotomy (HTO) for knee pain or disability related to arthrosis is a time-tested procedure. It is generally agreed that in the lower limb, arthrosis is frequently associated with malalignment, that the load across the knee joint is a function of alignment, and that changes in the axial alignment of the femur or tibia in either the coronal or sagittal plane will influence the distribution of this load, resulting in abnormal stresses on articular cartilage.¹ It follows that the assessment and correction of alignment, if indicated, must be at the forefront in the treatment algorithm when considering the management of knee arthrosis.

A primary goal of osteotomy, regardless of anatomical site or technique, is to reposition the weight-bearing line so that the load distribution through the knee is normal or as close to normal as possible, minimizing stresses on the affected compartment.²^,³ While “appropriate” postoperative alignment has been studied extensively, there is no clear consensus as to the correction angle when performing an osteotomy in the younger patient with a cartilage defect.⁴^,⁵^,⁶

It has been recently suggested by some that in valgus producing high tibial osteotomy, the weight-bearing line should be relocated from the middle to outer third of the lateral compartment.⁷ We would argue that this amount of correction is excessive, and based on the work of Dugdale et al.,⁸ in the patient with arthrosis, we prefer a weight-bearing line that intersects at a point 62% of the tibial width from the edge of the medial plateau to produce a mechanical axis of 3 degrees to 5 degrees. One should be cautioned against the recommendations of Coventry,⁹ Cass and Bryan,¹⁰ and Rudan and Simurda¹¹ to accept an anatomic valgus of greater than 10 degrees. In the younger patient with malalignment and articular cartilage lesions, an excessively large correction angle may not be required, and repositioning the weight-bearing line to neutral or just beyond, medially or laterally, is sufficient.

Indications and Contraindications

With respect to realignment osteotomy about the knee, Morrey¹² reported that valgus osteotomy can be offered with confidence in those with secondary degenerative arthritis, a varus knee, and localized medial joint pain. The indications for knee osteotomy (Table 52-1), however, are not confined to a deviation in mechanical axis (malalignment) with arthrosis. When knee instability is associated with malalignment, a realignment osteotomy may help restore stability, improve symptoms, and possibly delay the progression of arthrosis.¹³ Sagittal imbalance can be of particular interest in instability, and in these situations the role of the tibial slope must be taken into consideration and addressed when a corrective osteotomy is planned. Malalignment in the setting of any articular cartilage restoration procedure is a clear indication for an osteotomy prior to or in combination with the cartilage restoration or “protection” procedure such as meniscal allograft or anterior cruciate ligament reconstruction.

The treatment options for younger patients with isolated cartilage lesions are unfortunately limited. Consequently, the list of contraindications to knee osteotomy in this group is relatively short. Although a realignment osteotomy through the knee to transfer the load bearing axis away from the lesion may be a viable treatment, severe degeneration in the opposite tibiofemoral compartment and a gross loss of
range of motion will certainly affect the outcome and are relative contraindications. A valgus osteotomy should be avoided in those who have previously undergone a lateral meniscectomy.¹⁴ However, in the very young patient this should be considered only a relative contraindication, and in the case of severe varus alignment, a high tibial osteotomy to correct to a neutral alignment will preserve favorable joint mechanics (Table 52-1 and Table 52-2).

Table 52-1 Indications for Knee Osteotomy

Malalignment and Arthrosis

Malalignment and Instability

Malalignment and Arthrosis and/or Instability

Malalignment and Articular Cartilage Procedure and/or Instability

Surgical Techniques

Alignment is determined by the line extending from the center of the hip to the center of the ankle (i.e., the mechanical axis of the limb).¹⁵ This line typically passes immediately medial to the center of the knee, and by definition, malalignment occurs when this line does not lie close to the center of the knee.¹⁶^,¹⁷ Sagittal plane alignment should also be evaluated by measuring the posterior tibial slope angle (i.e., the angle between a line perpendicular to the mid-diaphysis of the tibia and the posterior inclination of the tibial plateau on a lateral radiograph). The average tibial slope angle has been shown to be 10 ± 3 degrees.¹⁸

Varus Knee

Techniques to realign the varus knee include the classic lateral closing wedge osteotomy, medial opening wedge osteotomy (preferred in most situations by the senior authors), and osteotomy with external fixation.

Table 52-2 Specific Indications for Individual Osteotomy Techniques

	Varus <25°	Varus >25°	Valgus >15°	Increased tibial slope	Decreased tibial slope
Medial opening HTO	X
Lateral closing HTO	X
Medial closing HTO			X
Lateral opening HTO			X
Ex-fix HTO		X		X	X
Anterior closing HTO				X
Anterior opening HTO					X

Lateral Closing Wedge High Tibial Osteotomy

Currently, our only indication for this procedure is a previous lateral closing wedge osteotomy of the contralateral limb. When required, our preferred method for a lateral closing wedge as described by Coventry,³ is performed through an incision made along a line from the lateral epicondyle over the Gerdy tubercle extending distally just lateral to the tibial tubercle. This incision is slightly curved if the knee is flexed at 90 degrees, and straight when the knee is in the extended position (Fig. 52-1A,B). The iliotibial band is identified distally and partially elevated by sharp dissection off the Gerdy tubercle. The common peroneal nerve is identified by palpation posterior to the fibular head. It is not routinely dissected free, however, careful attention to its protection throughout the procedure is required. The fibular head is not routinely osteotomized, but if this is required to close the osteotomy, the proximal tibiofibular joint is released. Soft tissues from the posterior aspect of the tibia are also released. A retractor is placed subperiosteally and posteriorly to protect the neurovascular structures and to facilitate carrying out the osteotomy under direct vision. The upper limb of the osteotomy is made 2 cm below and parallel to the joint line. The appropriate-sized wedge is then marked, cut, and removed, and any remaining posterior cortical bone and medial cancellous bone are removed using bone rongeurs, small curettes, and up-cutting Kerrison rongeurs.

Appropriate wedge size is calculated using a modification of the Noyes method, wherein the wedge removed is measured as the height of the angle subtended by the axes of the femur and tibia from the point of the desired position of the weight-bearing axis in the knee following the corrective osteotomy.¹⁹ The measured length of the proposed osteotomy is transposed to a measure along the axis of the femur, and the distance between the femoral and tibial axis at this point is the width of the wedge to be removed.

The osteotomy is closed with the knee in extension and fixed with one or two stepped staples (Fig. 52-2A,B). Care is taken to ensure that the posterior tibial slope has not been decreased due to failure to complete the osteotomy posteriorly, to remove cortical bone from the osteotomy site, or to adequately release the proximal tibiofibular joint, when required.

Fig. 52-1. Surface anatomy and approach for lateral tibial closing wedge osteotomy. A: Incision made along a line from the lateral epicondyle over the Gerdy tubercle extending distally just lateral to the tibial tubercle. B: This incision is slightly curved if the knee is flexed at 90 degrees and straight when the knee is in the extended position.

Fig. 52-2. A: The osteotomy is closed with the knee in extension and fixed with one or two stepped staples. B: Care is taken to ensure that the posterior tibial slope has not been decreased.

Technical Alternatives and Pitfalls

Technical points to be appreciated include: adequate visualization anteriorly beneath the patellar tendon to confirm osteotomy of the anterior cortex; complete exposure of the posterior tibia; protection of the neurovascular structures
with a curved, blunt retractor placed directly on the bone and for large corrections, adequate exposure, and mobilization of the proximal tibiofibular joint (Table 52-3). The osteotomy is made 2 cm distal to the lateral joint line to ensure that the proximal fragment is sufficiently large to avoid the risk of avascularity and violation of the tibial tubercle.

Table 52-3 Perils and Pitfalls Corrective Osteotomy

	Perils	Pitfalls
All osteotomies	Adequate exposure	Violation of opposite cortex
	Use of intra-op fluoroscopy and guide pins	Making asymmetrical bone cuts in sagittal plane
	Accurate pre-op planning and radiographic evaluation	Opening the osteotomy before the anterior and posterior cortices are osteotomized
High tibial lateral closing	Make osteotomy 2 cm distal to lateral joint line	Decreasing tibial slope inadvertently
High tibial lateral closing	Complete posterior cortical resection in piecemeal fashion with Kerrison rongeurs	Decreasing tibial slope inadvertently
High tibial medial opening	Use oscillating saw to breach cortex only	Suboptimal guide pin positioning
	Make osteotomy below the guide pin	Neglecting the posterior tibial slope when making the osteotomy
	Pay particular attention when securing osteotomy plate

As with all osteotomies of the proximal tibia, there is a tendency to alter the tibial slope if careful attention is not paid to maintain the tibial slope when creating the osteotomy. Fluoroscopy to confirm that the osteotomy has been completed along the anterior and posterior tibial margins and that the medial tibial cortex has been left intact will help avoid an unstable construct. If the medial cortex is breeched, the osteotomy must be considered to be “unstable” and to have a greatly increased risk of nonunion, and plate and screw, rather than staple fixation, is then recommended. As mentioned, completion of the posterior cortical bone
resection with pituitary and Kerrison rongeurs or small bone curettes will minimize risk of damage to the posterior neurovascular structures.

Fig. 52-3. The surgical approach to medial opening wedge HTO is shown. A: The skin incision is centered between the posteromedial border of the tibia and the tibial tubercle and extends distally from the medial joint line. B: The posteromedial border of the tibia is exposed with a blunt retractor placed deep to the superficial MCL. The pes anserinus is left intact.

Medial Opening Wedge High Tibial Osteotomy

Our preferred technique of medial opening wedge high tibial osteotomy is a modification of the technique described by Puddu et al.²⁰ This method allows correction of deformity in all planes and in particular allows planned alterations to tibial slope in the sagittal direction.

The procedure is carried out through a vertical skin incision, which extends 5 cm distally from the medial joint line and is centered between the anterior tubercle and the posteromedial border of the tibia (Fig. 52-3A). The gracilis and semitendinosus tendons and the superficial medial collateral ligament are preserved and retracted medially to expose the posteromedial border of the proximal tibia (Fig. 52-3B). A guide pin is inserted obliquely along a line proximal to the tibial tubercle from approximately 4 cm below the medial joint line in the region of the transition between metaphyseal and diaphyseal cortical bone on radiographs extending to a point 1 cm distal to the lateral joint line.

Figure 52-4 illustrates the opening wedge technique, which is monitored throughout with a mobile, low-dose ionizing radiation fluoroscopy unit. The osteotomy is made below the guide pin using a small oscillating saw to breech the medial, anteromedial, and posteromedial cortices. This is followed by narrow, sharp, thin, flexible osteotomes to a point just 1 cm short of the lateral cortex. Frequent imaging helps prevent violation of the lateral cortex or misdirection of the osteotome. The osteotomy is opened gradually to the desired correction angle first with distracting osteotomes to confirm the mobility of the osteotomy and then a calibrated wedge to the appropriate measured distraction. The distracted osteotomy is then fixed with a 4-hole Puddu plate secured with two 6.5-mm cancellous screws proximally and two 4.5-mm cortical screws distally. Bone grafting is recommended in all opening wedge osteotomies greater than 7.5 mm. Allograft cancellous bone chips or tricortical blocks may be used unless there is an expressed desire by the patient for autograft bone. In our practice osteotomies less than 7.5 mm are rarely grafted.

Fig. 52-4. The use of intraoperative fluoroscopy during medial opening wedge HTO is shown. A: The guide pin is directed toward the tip of the fibular head and from a point 4 cm distal to the medial joint line. Placement should be optimal before proceeding. B: The osteotomy is made below the guide pin. C: The osteotomy is gradually opened to the desired width using a calibrated wedge. D: Fixation is achieved with a 4-hole Puddu plate. Care is taken to avoid intra-articular or intraosteotomy screw placement. E: Here the defect has been filled with tricortical bone graft.

Technical Alternatives and Pitfalls

Dissection of the most superior fibers of the patellar tendon insertion on the tibial tubercle improves exposure and protects the patella tendon when completing the anterior extent of the corticotomy, which must be distal to the patella tendon insertion. The use of a low-dose ionizing radiation fluoroscope throughout the procedure is critical to ensure all of the following: proper guide-pin placement; prevention of lateral cortex violation; avoidance of osteotome misdirection; avoidance of intra-articular screw placement, and adequate sealing of the bone graft and filling of the defect (Table 52-3).

The tip of the fibular head is a helpful reference when aiming the guide pin. The correct obliquity of the osteotomy relies on proper placement of the guide pin. For larger corrections, placement should be more horizontal. Greater obliquity increases the risk of fixation failure but, on the other hand, provides increased depth, which may be appropriate for smaller corrections.

The osteotomy should always be carried out parallel to the joint line in the sagittal plane and below the guide pin to help prevent intra-articular fracture. The use of thick, traditional type osteotomes can apply a greater distraction moment when completing the osteotomy and carries an inherent risk of creating an extra or intra-articular fracture. This is considerably minimized with thin, flexible osteotomies (Fig. 52-5). However, these should be advanced with frequent fluoroscopy checks to avoid misdirection.

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