Unloading the Patellofemoral Joint for Cartilage Lesions

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Chapter 13 Unloading the Patellofemoral Joint for Cartilage Lesions

James Bicos

Introduction

Successful outcomes in patellofemoral cartilage restoration procedures rest on the need to unload the patellofemoral joint. Initial patellofemoral cartilaginous procedures were predisposed to failure because of overload of the patellofemoral compartment or failure to address patellar malalignment. Malalignment is defined as abnormal tilt and or subluxation of the patella,¹ and distal realignment (i.e., tibial tubercle osteotomy) is the most definitive method of either realigning a subluxated/tilted patella or offloading the patellofemoral compartment.

Anteromedialization of the tibial tubercle addresses patellar malalignment, patellar arthritis, or is used in conjunction with cartilage restoration procedures. The original technique, as described by Dr. Fulkerson in 1983,² has been shown in long-term studies to provide long-term relief from instability and patellofemoral pain.³ The idea behind the osteotomy is to alleviate stress from the distal and lateral portions of the patella and trochlea to the proximal and medial patellar articular cartilage.^2,⁴^–⁷ By changing the angle of the osteotomy cut, one can customize the procedure to include more medialization for instability cases or more anteriorization for cartilaginous unloading guidelines. Typically, in most procedures done for cartilage restoration, there is some evidence of patellar malalignment, so a combination of both medialization and anteriorization is chosen.

Indications/Contraindications

Indications for anteromedialization of the tibial tubercle include patellofemoral pain with either lateral or distal patellar arthrosis or lateral subluxation/dislocation of the patella. Other indications include a failed lateral release ⁸ and cartilage restoration procedures that need offloading of the newly regenerated or implanted cartilage cells. The ideal candidate is a patient with lateral patellar tilt (or subluxation) with grade III or IV articular cartilage degeneration localized to the lateral patellar or distal medial patellar facets. Not only should the patient be deemed psychologically mature to undergo the surgical procedure, but he or she should also have failed a course nonoperative management consisting of patellar taping, lateral retinacular mobilization, stretching of the extensor mechanism, bracing, and nonsteroidal anti-inflammatory medication.^1,^2,⁷

Contraindications to the procedure include no malalignment (except in unloading the patellofemoral joint in cartilage procedures), diffuse patellar articular cartilage disease, occult medial subluxation, tilt with no subluxation, mild articular cartilage changes (i.e., grade I or grade II) that would be best treated with an isolated lateral retinacular release, rheumatoid arthritis, bleeding disorders, a history of deep venous thrombosis, and complex regional pain syndrome. Proper patient selection is also important to the success of the procedure, and obesity was found to be the leading cause of tibial metaphyseal fractures or stress fractures in the postoperative period.

The benefits of the osteotomy include a long, flat, oblique cut that maximizes surface area to promote bony healing and allow screw fixation; the angle of the osteotomy cut can be adjusted to allow for more medialization or anteriorization, depending on the goals of the surgery; and the distal taper of the osteotomy minimizes the risk to the tibial metaphyseal bone and decreases the risk of iatrogenic fracture.

Preoperative Planning

Physical Examination

A complete review of the physical examination of the patellofemoral joint is beyond the scope of this chapter, but we will review the pertinent examination points. The exam should begin with a gait evaluation and hip range of motion to assess for increased femoral anteversion, in-toeing, or pes planus that can all predispose the patient to a relative genu valgum of the lower extremity and lead to patellar tilt or subluxation. Increased mobility of the joints is also assessed (elbow, thumb, etc.) because it may predispose the patient to early failure if a soft-tissue only technique is used for patellar stabilization. The skin should also be evaluated for changes associated with complex regional pain syndrome or previous incisions that would alter the standard approach to the tibial tubercle osteotomy. Muscle atrophy should also be assessed as a sign of nerve damage or the need for preoperative physical therapy for strengthening.

Specific tests for the evaluation of the patellofemoral joint include noting patellofemoral crepitance, joint effusion, lower extremity Q-angle, patellar J-sign, lateral retinacular tightness, patellar quadrant mobility, patellar apprehension test, patellar grind test, and stability/pain relief with a lateral to medial force on the patella (i.e., you are simulating holding the patella in an unloaded/reduced position).

Imaging Studies

Imaging studies should start with a complete set of knee x-rays consisting of bilateral anterior-posterior (AP) standing views, bilateral posterior-anterior (PA) 45 degrees; flexed views, a lateral view with the knee in 30 degrees; of knee flexion, and a Merchant view.⁹

The Merchant view is needed rather than the skyline view because as the knee is hyperflexed in the skyline view, the patella is captured by the bony anatomy of the trochlea, and subtle variations of patellar tilt or subluxation are lost at knee angles greater than 30 degrees;.¹

The Merchant view allows the evaluation of patellar tilt (patellofemoral angle of Laurin),¹⁰ trochlear dysplasia, and patellar subluxation (congruence angle)⁹ (Fig. 13-1, A–C). The lateral view allows the evaluation of patellar joint space, trochlear dysplasia, patellar alta/baja, and patellar tilt (Fig. 13-2, A–B). One can also use MRI or CT scans to measure similar angles of patellar subluxation and tilt.^3,¹¹^–¹⁶

FIGURE 13-1 Measuring tilt and subluxation. A, Normal patellofemoral angle of Laurin. Used to measure patellar tilt. The solid line along the lateral patellar facet should open laterally when referenced to the dotted line along the medial and lateral trochlear ridges. B, Abnormal patellofemoral angle of Laurin. Both of the lines are parallel to each other and thus are consistent with lateral patellar tilt. C, Abnormal congruence angle. Used to measure patellar subluxation. Line AB is along the lateral trochlea, and line CB is along the medial trochlea. Line BD is drawn as the bisector of the trochlear groove angle. Finally, line BD’ is drawn from the central trochlea to the central ridge of the patella. Line BD’ should be equal or medial to the bisector line BD. If it is lateral (as in this case), patellar subluxation can be confirmed.

(Reprinted from Operative Techniques in Orthopaedics, vol. 17. issue 4, James Bicos and John P. Fulkerson, Indications and Technique of Distal Tibial Tubercle Anteromedialization, p. 225. Copyright 2007, with permission from Elsevier.)

FIGURE 13-2 Lateral x-ray images showing a normal knee (A) and a knee with lateral tilt (B). A, Arrowhead showing the central patellar ridge, which should not overlap with the medial and lateral patellar facets (arrow line), in a normal knee without patellar tilt. B, Arrowhead showing near superimposition of the central patellar ridge on the lateral patellar facet, in a knee with patellar tilt. Note that the posterior femoral condyles should be superimposed for proper measurements of patellar tilt on the lateral x-ray view.

(Reprinted from Operative Techniques in Orthopaedics, vol. 17, issue 4, James Bicos and John P. Fulkerson, Indications and Technique of Distal Tibial Tubercle Anteromedialization, p. 224. Copyright 2007, with permission from Elsevier.)

Another important measurement for malalignment of the extensor mechanism is the tibial tubercle-trochlear groove (TT-TG) measurement (Fig. 13-3). This relates how far lateral the tibial tubercle is in relation to the central portion of the trochlea.¹⁷ Normal TT-TG values are less than 10 mm, and grossly abnormal values are between 18 to 20 mm. The TT-TG can be easily measured on CT or MRI scans and should be thought of as a guide as to how far to move the tubercle during the osteotomy procedure. The final amount of anteromedialization is based on the intraoperative assessment of patellar stability.

FIGURE 13-3 Tibial tubercle-trochlear groove measurement (TT-TG). A CT scan was obtained and an image through the tibial tubercle was superimposed on an image through the femur. Line 1 is parallel to the posterior femoral condyles. Line 2 is through the highest point of the tibial tubercle and perpendicular to line 1. Line 3 is through the nadir of the trochlear groove and also perpendicular to line 1. The distance between lines 2 and 3 is the TT-TG (labeled as line 4). It equals 1.68 cm, which is on the limits of being abnormal.

Surgical Technique

Holding Area

The patient is identified in the surgical holding area and the correct knee is identified according to the “Sign Your Site” protocol. The patient is given preoperative antibiotics and an exam is carried out showing the patient again the stability of the patella once the realignment is completed.

Any pain blocks can be done at this time by the anesthesia service, although in order to monitor for postoperative function and the possibility of a postoperative compartment syndrome, we do not routinely use nerve blocks for this operation.

Patient Positioning

The patient is brought back to the operating room and placed supine on the operating room table.

After the anesthesia service has secured an airway, a Foley catheter is placed in the standard fashion. The patient is kept supine during the procedure, and a small bump is placed under the ipsilateral hip to avoid the obligate external rotation that occurs in the lower extremity when the patient falls asleep. An exam under anesthesia is documented, looking specifically for knee effusion, passive range of motion, patellar tracking, patellar tilt, and the amount of lateral or medial patellar subluxation.

For the arthroscopy portion of the procedure, we use a lateral post.

A tourniquet is placed at the upper thigh area, and the lower extremity is prepped and draped in the standard fashion. To avoid capturing the quadriceps with tourniquet inflation and thus altering the normal patellar tracking, the knee is hyperflexed for tourniquet inflation.

Arthroscopy

A thorough arthroscopy is performed documenting any cartilaginous defects of the patella or trochlea. One should be acutely aware of defects of the medial or proximal patellar facet or medial trochlea, because this would be a contraindication for the anteromedialization procedure.

Patellar tilt and subluxation should be documented early in knee flexion (i.e., <15–20 degrees) because at greater knee flexion angles the patella is constrained by the trochlear bony anatomy, thus obscuring the patellar tilt and subluxation (Fig. 13-4, A). The other knee compartments are visualized, and any other concomitant arthroscopic surgery is performed at this time (Fig. 13-4, B).

FIGURE 13-4 A, View of patellofemoral joint arthroscopically before tibial tubercle transfer. Note the severe lateral patellar tilt and subluxation. B, View of patellofemoral joint after tibial tubercle transfer with anatomic alignment of the patella on the trochlea.

Incision/Superficial Dissection

The arthroscope is removed but still kept sterile on the field in order to assess the postanteromedialization tibial tracking.

An 8 to 10 cm incision is made incorporating the inferolateral arthroscopy portal proximally and distally extending toward the tibial tubercle. The incision is kept just lateral to the anterior tibial crest to avoid having the incision over the subcutaneous bony skin. In addition, the line of the incision avoids placement of the hardware (tibial fixation screws) directly underneath the skin incision itself (Fig. 13-5). The incision is deepened down to the level of the patellar paratenon and just above the periosteum of the anteromedial tibia.

FIGURE 13-5 View of proposed incision. Note the initials on the knee according to the “Sign Your Site” protocol. The white lines show the arthroscopic portals. The red dotted line shows the tibial crest. The yellow dashed line shows the proposed incision. The incision incorporates the lateral arthroscopic portal and stays just lateral to the tibial crest.

The medial and lateral borders of the patella are identified, in addition to the tibial tubercle and the anterior tibial muscular compartment.

Lateral Release

A subcutaneous skin dissection is made along the lateral retinaculum to the superior border of the patella. Using electrocautery, a lateral retinacular release is performed, taking great care to avoid injury to the cartilage at the lateral trochlea.

The proximal extent of the release is up to but not through the vastus lateralis tendon. Inadvertent sectioning of the vastus lateralis tendon could lead to occult medial instability.

The edges of the lateral release are cauterized to avoid a postoperative hematoma. Distally, the release is taken down to the level of the tibial tubercle, staying lateral to the patellar tendon (Fig. 13-6).

FIGURE 13-6 Open lateral retinacular release. Asterisk marks the lateral retinaculum that has been cut as part of the release. Note that this picture is of a right knee. The other pictures in the labeled figures show a left knee.

Deep Dissection

The medial border of the patellar tendon is identified at the level of the tibial tubercle, and a hemostat is placed behind the patellar tendon. This ensures that the tendon has been freed from the proximal tibia but is still attached to the tibial tubercle (Fig. 13-7). Occasionally there is scar tissue tethering the distal pole of the patella to the fat pad. This should be released, as it could potentially prevent the proper anteromedialization of the patella.

FIGURE 13-7 The medial and lateral borders of the patella have been identified and a hemostat has been placed behind the patellar tendon for retraction purposes. The asterisk marks the anterior muscular compartment. The arrowhead marks the anteromedial tibia. The dotted line marks where the anterior musculature is taken off of the tibial crest.

The anterior tibial muscular compartment is subperiosteally taken off of the lateral border of the tibia using electrocautery, leaving a small cuff of the fascia of the muscular compartment still attached to the tibial crest for later reattachment of the muscle.

The anterior tibial muscle is taken proximally off of Gerdy’s tubercle, and distally it is extended for approximately 4 cm past the tibial tubercle (i.e., enough to fit the osteotomy guide in place).

Posteriorly, the muscle is freed down to the posterolateral tibial border and a special retractor (Tracker AMZ Guide System [TRACKER System] Depuy Mitek, Norwood, Mass.) is used to hold the anterior tibial muscle out of the way (Fig. 13-8).

FIGURE 13-8 The patellar tendon has been skeletonized. The anterior tibial muscular compartment has been taken off of the tibial crest and a wide retractor from the Tracker AMZ Guide System (TRACKER System) set (white arrowhead) is retracting the muscle. The cutting block (asterisk) is positioned on the anteromedial tibia. Note how it is tapered from proximal to distal.

One must be able to see the posteromedial tibial border in order to avoid the inadvertent extension of the osteotomy through the posterior tibial cortex.

The medial border of the patellar tendon attachment onto the tibial tubercle is identified, and starting 2 cm medial from the tibial tubercle crest, a mark is made in the anteromedial tibial periosteum and angled distally and laterally toward the anterior tibial crest.

The osteotomy cut is not only an oblique cut when looking at the tibia in the axial plane, but it also tapers distally toward the tibial crest in the coronal plane (Fig. 13-8).

Osteotomy

The preferred instrument system, the TRACKER System, was developed by Dr. Jack Farr and is a simple, reproducible way of performing the osteotomy.

The TRACKER System cutting block is fashioned on the anteromedial tibial cortex along the line marked on the periosteum. The cutting block should taper from proximal to distal (Fig. 13-8).

The TRACKER System tracker guide is then inserted into the second or third drill hole from the top of the TRACKER System cutting block. The tracker guide helps one to visualize where the osteotomy will exit along the posterolateral tibia (Fig. 13-9). It is imperative that the osteotomy not exit the posterior tibial cortex.

FIGURE 13-9 AMZ Tracker guide is shown positioned in the tibial cutting block (black arrow). The arm of the guide shows where the osteotomy will exit posterolaterally. Using the Tracker guide allows the surgeon to correctly place the slope of the osteotomy.

The angle of the osteotomy cut is now chosen. As previously stated, the steeper the cut, the more anteriorization you will have. Usually the goal is to have the osteotomy exit just anterior to the posterior lateral cortical surface, just before the flare of the metaphysis (Fig. 13-10).

FIGURE 13-10 The proximal tibia in cross section looks like a triangle. The picture depicts the AMX Tracker guide starting on the anteromedial tibia and exiting the posterolateral tibia. Note that if the angle of the osteotomy is too steep, it will emerge through the posterior tibia and predispose the patient to a tibial shaft fracture.

The cutting block is held using two pins that are predrilled. The distal pin should just skirt the anterior tibial cortex to allow for the distal taper of the osteotomy.

A sagittal saw is used to begin the osteotomy cut (Fig. 13-11). The osteotomy is started anteromedially on the tibial cortex, and it exits posterolaterally. As the osteotomy nears the proximal lateral junction between the tibial diaphysis and metaphysis (i.e., metaphyseal flare), care should be taken to avoid penetration of the posterior tibial cortex.

FIGURE 13-11 With the cutting block held in place, a sagittal saw is used to begin the osteotomy cut.

At this area (i.e., under the tibial tubercle), the saw blade cut should be entirely within the bone. The lateral extent of the cut at this proximal location should be just lateral to the tibial tubercle. Distally, the last 1 to 2 mm of tibial crest bone is left intact (hinging on the periosteum) to create a hinge on which to rotate the osteotomy.

The cutting block is now removed and the anteromedial tibial crest cut is carried more proximally with the saw to clear the medial attachment of the patellar tendon on the tibial tubercle. A 1-inch osteotome is used to make a back cut, starting from the most proximal location of the posterolateral tibial cut (i.e., at the metaphyseal/diaphyseal flare) proximally and anteriorly to just above the patellar tendon attachment on the lateral tibial tubercle (Fig. 13-12). A half-inch osteotome is used to make the back cut underneath the patellar tendon from lateral to medial. This should be done just proximal to the patellar tendon.

FIGURE 13-12 View of osteotomy just before anteromedialization. The saw blade is in the sloped oblique cut of the osteotomy. The white arrowhead points to the first osteotomy cut made with the saw blade. The arrow points to the back cut made with the osteotome. This back cut extends from the most proximal location of the posterolateral tibial cut (i.e., arrowhead osteotomy cut), proximally and anteriorly to just above the patellar tendon. What is not visualized is the lateral-to-medial cut under the patellar tendon (marked with a dotted line).

Care should be taken to avoid any distal orientation of this osteotomy cut because this will block the attempted medialization of the tibial tubercle. A 2-inch osteotome is then used along the oblique slope of the osteotomy cut to free it and create an osteoclasis at the distal taper.

Tubercle Fixation

With the osteotomy hinged distally, the proximal portion is anteromedialized along the slope of the osteotomy cut to the desired location. This location depends on your preoperative plan, but typically a 1-cm medialization is created (Fig. 13-13).

FIGURE 13-13 Arrowheads show the amount of anteromedialization of the osteotomy along the sloped plane. This is approximately 1 cm. The dotted line represents the proximal extent of the bony osteotomy under the patellar tendon. The proximal screw is placed approximately 1 cm distal to that point, to avoid splitting the osteotomy fragment. The asterisk represents the location of the second screw placement.

The osteotomy is held in place with two 3.2-mm drill bits placed in an anterior to posterior direction just medial to the tibial crest on the osteotomy and starting 1 cm distal to the attachment of the patellar tendon on the tibial tubercle (Fig. 13-13).

The knee is brought through a range of motion, and one should be able to achieve 90 degrees of knee motion without any undue tension on the osteotomy site.

The arthroscope is now reinserted, and the knee is taken through a range of motion to document the proper patellar tracking and the anatomic lateral to medial engagement of the trochlea. Any medial subluxation of the patella should be corrected by decreasing the medialization of the osteotomy cut and replacing the 3.2-mm drill bits with screws.

A note on the placement of the drill bits for the screws. The purpose of starting 1 cm distal to the patellar tendon attachment on the tibial tubercle is so that if the osteotomy wedge is split when tightening the tibial tubercle screws, one has enough proximal bone on the tibial tubercle to insert another screw for fixation of the proximal fragment. The distal screw should be spaced another 1 cm distal from the proximal screw.

Using proper lag screw technique, two anterior to posterior 4.5-mm fully threaded cortical screws are placed in the proper fashion. They should be countersunk below the anterior tibial cortex of the osteotomy wedge to minimize the postoperative irritation of the hardware on the subcutaneous tissues. Not only should the depth measurement of the screws be made after the countersink bore is done, but the more proximal screw (i.e., the first screw placed) should be downsized 2 mm from its depth gauge reading to allow for the compression of the osteotomy site with the lag screw technique.

For most cartilage restoration procedures, the entire patellofemoral compartment must be adequately visualized. Therefore, at this time, with the osteotomy predrilled, the screws are removed, the distal hinge of the osteotomy is broken and the entire osteotomy wedge/tibial tubercle/patellar tendon complex is retraced proximally.

Once the necessary cartilage procedure is done, the wedge is brought back down to its predetermined location and the screws are reinserted. This minimizes the need for any drilling to be done after the cartilage procedure, which can jeopardize the cartilage repair. While the osteotomy wedge is retracted proximally, it should be wrapped in a moist sponge (Fig. 13-14).

FIGURE 13-14 Figure showing the osteotomy cut retracted proximally.

Closure

With the osteotomy secured, range of motion of the knee is once again checked and the tourniquet is deflated. Meticulous hemostasis is obtained.

Key areas to look for hemorrhage include the anterior tibial muscular compartment or posterolateral tibia (i.e., anterior tibial artery) and the lateral retinacular release (i.e., proximal lateral geniculate artery). The wound is irrigated and a drain is placed deep to the anterior tibial muscular compartment, exiting proximal lateral to the skin incision.

To avoid a compartment syndrome, the anterior tibial musculature is reattached back to the tibial crest with 3 or 4 #1 Vicryl (Ethicon Inc., Somerville, N.J.) sutures. The subcutaneous tissues are reapproximated with a 2-0 Vicryl in an inverted interrupted fashion, and the skin is closed either with staples or a running 3-0 Prolene (Ethicon, Inc.) stitch. A sterile dressing is applied, followed by an elastocompressive dressing from the toe to the upper thigh. A cooling device is then placed on the knee, and a knee immobilizer is secured.

Postoperative Course

I routinely admit the patients for a 23-hour observation stay in the hospital to monitor pain levels and to assess for compartment syndrome. Patients typically do well with an oral pain medication and an intravenous pain medication for breakthrough pain.

The drain is discontinued on postoperative day 1. Physical therapy consists of crutch training, ankle pumps, and quadriceps isometric exercises. The patients are kept nonweight bearing.

The therapist also works on active knee flexion exercises to 90 degrees (or the parameters set intraoperatively) and passive knee extension. Usually for patellofemoral cartilage procedures, knee motion is not started for 6 hours postoperatively and is limited to passive knee flexion of 30 degrees. No straight leg raises are permitted.

Deep venous thrombosis prophylaxis consists of thigh-high compression hose, sequential compression devices to the contralateral extremity, and aspirin 325 mg twice per day for one month.

The patient is discharged on postoperative day 1, assuming he or she has tolerated the oral pain medication and understands the rehab.

Rehabilitation

The rehabilitation protocol can be found in Box 13-1. Important concepts about the rehabilitation protocol can be divided into weight-bearing status and range-of-motion goals.

BOX 13-1 Distal Realignment Rehabilitation

Reprinted from Operative Techniques in Orthopaedics, Vol 17, Issue 4, James Bicos and John P. Fulkerson, Indications and Technique of Distal Tibial Tubercle Anteromedialization, page 228, Copyright 2007, with permission from Elsevier.

____ Weeks 0 to 2

No weight bearing; please use crutches

Knee immobilizer on at all times, except for ROM exercises and hygeine

Remove brace for passive ROM 0 to 90°

Begin quad sets co-contractions immediately in knee immobilizer; ankle ROM

____ Weeks 2 to 6

Start toe touch weight bearing; continue to use crutches

Continue knee immobilizer as above

Remove brace for passive ROM 0 to 90°;

Continue quad sets co-contractions; start abduction/adduction exercises; ankle ROM

____ Weeks 6 to 8

Transition to full weight bearing; may wean off brace/immobilizer

Start AROM to full

Start straight leg raises, partial wall sits no greater than 45 degrees, terminal knee extension with Thera-Band (The Hygenic Corporation, Akron, Ohio); continue previous exercises

____ Weeks 8 to 12

Full weight bearing, no brace

Continue previous exercises as above and start hamstring strengthening, Thera-Band resistance 0 to 45 degrees;, light open chain exercises at 10 weeks

____ Months 3 to 4

Begin treadmill walking at slow pace, progress to balance/proprioception exercises

Initiate sports specific drills

____ Months 4 to 6

Advance close chain strength exercises, focus on single leg strength, progress to normal walking and backward movement

Start light plyometric exercises

AROM, A range of motions; ROM, range of motion.

Except for cartilaginous procedures, which follow different rehabilitation guidelines, the patient should strive to achieve 90 degrees of knee flexion by the first postoperative visit (i.e., 5 to 7 days). Once the he or she reaches the goal of 90 degrees, the patient only has to perform the knee motion once or twice a day to keep up that goal. Active flexion is allowed with passive extension to limit the stress on the osteotomy site.

The patient is kept on strict non-weight-bearing status for the first 2 weeks. Toe-touch weight bearing is then allowed for the next 4 weeks. At the 6-week mark, assuming that the osteotomy shows signs of healing and no migration, the patient progresses to weight-bearing status over the next 2 weeks, so that by 8 weeks postoperatively the patient is at full weight-bearing status. Straight leg raises are started also at this time.

Complications

Complications of anteromedialization of the tibial tubercle can be divided into intraoperative and postoperative groups:

Intraoperative complications include violating the posterior cortex of the tibia with the oscillating saw, making too thick of an osteotomy cut because the cut was not tapered distally on the tibia, splitting the osteotomy with over tensioning of the lag screws, and neurovascular injury to the anterior tibial artery or deep peroneal nerve, which lie just deep to the posterolateral border of the tibia.¹⁸

Postoperative complications include infection, hematoma, compartment syndrome, hardware prominence, migration of the osteotomy, tibial stress fracture, creating a medial patellar subluxation from overzealous release of the lateral retinaculum or over medialization of the osteotomy, patellar baja/alta, arthrofibrosis, and deep venous thrombosis (Fig. 13-15, A–C).

FIGURE 13-15 Complications of tibial tubercle osteotomy. A, Tibial stress fracture in the postoperative period. B, Patellar baja. C, Migration of osteotomy. Arrow shows abnormal location of distal tip of osteotomy.

FIGURE 13-16 A, Bilateral patellar tilt and subluxation seen on Merchant view. B, Close-up view of right knee preosteotomy.

(Reprinted from Operative Techniques in Orthopaedics, vol. 17, issue 4, James Bicos and John P. Fulkerson, Indications and Technique of Distal Tibial Tubercle Anteromedialization, p. 230. Copyright 2007, with permission from Elsevier.)

Illustrative Case

Figure 13-16, (A and B) show a 23-year-old male with a long-standing history of patellar dislocations (>15–20 in each knee) who failed a conservative course of treatment consisting of physical therapy, bracing, and activity modification. Patellar taping helped stabilize his patellae, but this was unacceptable to him as a long-term solution to the dislocations. Preoperative Merchant views show bilateral patellar subluxation and tilt. An intraoperative arthroscopy image is shown in Figure 13-4, A. He subsequently underwent an anteromedialization of the tibial tubercle with anatomic alignment of his patella (Figs. 13-4, B and 13-7, A–D).

FIGURE 13-17 A, Anteroposterior view of right knee post osteotomy. B, Lateral view. C, Merchant view of bilateral knees after right knee tibial tubercle transfer. (d) Close-up of right knee tibial tubercle transfer.

(Reprinted from Operative Techniques in Orthopaedics, vol. 17, issue 4, James Bicos and John P. Fulkerson, Indications and Technique of Distal Tibial Tubercle Anteromedialization, p. 231. Copyright 2007, with permission from Elsevier.)

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