DEFINITION

Trochlear dysplasia is a pathologic condition occurring in approximately 3% of the population but up to 96% of those with recurrent patellar instability.9 The condition is one in which structural abnormalities of the femoral trochlea results in patellar instability.

Trochlear dysplasia is a flattened, shallow or even convex trochlear groove, providing inadequate bony restraint for the patella, and possibly, a “supratrochlear spur” or bump that deflects the patella laterally.8 Depth and morphology of the trochlea is both necessary and sufficient in combination with soft tissue restraints to provide a stable patellofemoral articulation. The aim of surgery is to restore this relationship.10 Currently, sulcus-deepening trochleoplasty as described by David Dejour is for correction of the trochlear

morphology and is one option for addressing high-grade trochlear dysplasia2 in patients presenting with patellar dislocation.

 

 

ANATOMY

 

The normal trochlea has an intricate three dimensional shape located in the anterior aspect of the distal femur. The trochlea is composed of two facets divided by the trochlear sulcus, a longitudinal groove that varies in length and mediolateral position.9

 

The lateral facet is higher than the medial facet (extends further in the anteroposterior [AP] plane) and extends more proximally up the femur.3

 

The normal trochlear sulcus extends proximally from the intercondylar notch until it meets and is level with the anterior cortex of the femur. Distally, the medial and lateral facets extend to the point of becoming the femoral condyles at the sulcus terminalis.

 

The trochlea guides patellar tracking with the opposing patellar surface following the trochlear groove.

 

The medial patellofemoral ligament (MPFL) is an extraarticular ligament that attaches from the patella medial surface to the femur posterosuperior to the medial femoral epicondyle (9.5 mm proximal and 5.0 mm posterior to the center of the medial femoral epicondyle).14 The MPFL is the primary soft tissue restraint to lateral patellar

dislocation.

 

Patellar stability depends on bony and soft tissue architecture. In full extension, soft tissue restraints are dominant. The patella normally engages within the trochlear groove by 30 degrees of flexion. With trochlear dysplasia, the dysmorphic trochlea is unable to guide the patella, resulting in tilt and ultimately dislocation. The dysplastic trochlea also forces the medial retinacular ligaments (ie, the MPFL) to take on a greater role.

 

Trochlear dysplasia describes a trochlear groove, which is shallow or even convex. The abnormal shape of the

trochlea often is accompanied by a superolateral bump or supratrochlear spur best viewed on a lateral x-ray or

computed tomography (CT) scan.6

 

The larger the supratrochlear spur, the greater the reaction force pushing the patella out of the groove.

 

PATHOGENESIS

 

The etiology of trochlear dysplasia remains unclear. It is unknown at this time whether trochlear shape is present throughout one's lifetime or changes over time. Some authors have suggested a genetic origin of trochlear dysplasia.11,12 However, to date, there are no prospective studies looking at trochlear development

and dysplasia.

 

Other authors have suggested a developmental process whereby a lateralized patella due to malalignment or other causes may lead to abnormal development of the trochlear groove.20 Consensus opinion would suggest trochlear dysplasia is a primary abnormality that increases during growth in the setting of malalignment.

 

Patellar dislocation is the result of lack of bony or soft tissue constraint of the patella within the trochlear groove. Recurrent patellar instability often results when soft tissue constraints (ie, MPFL), dynamic muscular constraints, or osseous restraints fail. Patellar instability may be acute or chronic in nature.13

NATURAL HISTORY

 

The overall risk of patients presenting with a history of dislocations for a recurrent dislocation is 50% over a 2-to 5-year period.5

 

Younger patients (younger than 18 years old) and females also tend to have a higher risk of recurrent dislocation.

 

Nonsurgical treatment in patients with underlying anatomic predisposing factors leading to instability has a recurrent dislocation rate near 43% versus a 20% redislocation rate in those patients without predisposing factors.4

 

A combination of other predisposing factors, including increased tibial tuberosity-trochlear groove (TT-TG), patella alta, vastus medialis obliquus (VMO) dysplasia, MPFL attenuation, and rotational malalignment, may also be present in the setting of trochlear dysplasia.2

 

In the setting of trochlear dysplasia, many patients present after having failed prior realignment or soft tissue procedures. This demonstrates the contribution of bony abnormality to recurrent dislocation.13

PATIENT HISTORY AND PHYSICAL FINDINGS

 

 

Trochlear dysplasia should be considered in any patient with a history of recurrent patellar instability. The history of dislocations should be ascertained, including details

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regarding the first dislocation as well as treatment and surgeries to date.

 

History should include evaluation for possible osteochondral injury.

 

It should be ascertained whether the patient is largely concerned about pain or instability. Most patients with recurrent instability from trochlear dysplasia do not experience generalized anterior knee pain between episodes.

 

The type of activities and frequency in which dislocation occurs should be queried.

 

Lower extremity alignment should be noted as well as the presence of an effusion. A thorough knee examination

should be performed.2

 

Several clinical tests have been described that focus on examination of patellar tracking and concomitant patella pathology.

 

 

General active and passive tracking should be evaluated.

 

Tenderness about the medial patella and MPFL insertion should be elicited.19

 

Patellar apprehension—should be evaluated at full extension. A positive test is pathognomonic for patellar instability.

 

Quadrant test—the patella should passively translate between one and two quadrant widths of the patella with the knee extended.

 

Moving patellar apprehension test—involves pushing the patella laterally as the knee is passively brought into flexion.1 Comparison is made to the opposite knee for amount of patellar translation and degree of flexion at which the patella is firmly stable within the trochlear groove.

 

A “J sign” refers to lateral patellar deviation during terminal knee extension as the patella exits the proximal groove and reflects patella alta and/or high-grade trochlear dysplasia.

 

 

 

FIG 1 • Dysplastic trochlea demonstrating a supratrochlear bump on CT imaging (A-C). Supratrochlear spur demonstrated on the lateral view (arrow) (D).

 

 

Patella grind or compression test should be performed to rule out articular degeneration, although this does have a high rate of false positives.

 

Patellar tilt test—the examiner's thumb attempts to flip the lateral edge of the patella upward, slightly off the lateral trochlear facet to horizontal. This is compared to the opposite knee as are all of these tests.

 

No physical examination tests are available specifically for trochlear dysplasia.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Plain radiographs including weight-bearing posteroanterior (PA), true lateral, and axial patellar views at 30 to 45 degrees of flexion should be obtained.2,6,8,9 The lateral radiograph is the key image.

 

Evaluation of the lateral radiograph includes identification of several important features:

 

 

Crossing sign—radiographic line of the trochlear sulcus as it crosses the projection of the femoral condyles. This represents the location at which the deepest part or floor of the trochlear sulcus reaches the same height as the femoral condyles. Hence, at this point, the trochlea is flat and at the same level as the anterior borders of the trochlear facets.

 

In normal knees, the radiographic line representing the base of the trochlear groove merges with the anterior femoral cortex proximally at the end of the groove. However, in dysplastic trochlea, it can be several millimeters in front of the cortex representing the supratrochlear bump.6

 

Supratrochlear spur—a pronounced, superolateral bony bump or projection at the top of the dysplastic trochlea that sits well anterior to the femoral cortex (FIG 1).

 

 

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Double contour sign—represents the hypoplastic medial facet seen in profile compared to the taller lateral facet and even the base of the trochlear groove, as both sit higher or more anterior.

 

Caton-Dechamps ratio can be calculated to evaluate for patella alta and need for distalization of the tibial tubercle. This is the distance from the distal articular surface of the patella to the tibial plateau, divided by the length of the articular surface of the patella.

 

Merchant (axial) views at 45 degrees of flexion allow for general characterization of patellar shape and tilt as well as morphology of the groove, although this does vary with the degree of knee flexion. Knee flexion of 30 degrees is ideally recommended as greater degrees of flexion will underestimate dysplasia.3

 

 

Sulcus angle—from the point of the bottom of the trochlear groove, two lines are drawn connecting to the most superior point of each facet and the subtended angle measured. Normal is typically 138 degrees. A sulcus angle over 145 is indicative of dysplasia. Severely dysplastic trochlea may show very high angles or are unmeasurable (over 180 degrees or convex).

 

 

 

FIG 2 • Classification of trochlear dysplasia. A. Type A is characterized by the crossing sign on the lateral view and by a shallow trochlea on the axial (arrow to distal femur emphasizing no groove). B. Type B demonstrates a crossing sign as well as supratrochlear spur on the lateral view. C. Type C lateral view shows the crossing sign with a double contour sign as well as medial hypoplasia. D. Type D dysplasia shows the crossing sign, double contour, and supratrochlear spur as well as a cliff demonstrating axially due to asymmetry.

 

 

It is important to understand that simply observing a flattened trochlear groove on a Merchant x-ray view is a small part of diagnosing trochlear dysplasia and that evaluation of the supratrochlear bump or spur sitting anterior to the femoral cortex is most important and the feature to which surgical treatment is directed for a groove-deepening procedure.

 

Classification can be based on characteristic morphology using both standard imaging and advanced cross-sectional imaging (CT scan or MRI) as described by Dejour and Le Coultre7 (FIG 2).

 

 

 

Type A: presence of a crossing sign in the true lateral view. The trochlea is shallow but still symmetric and concave, up until the point at which the base of the groove sits

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level with the condyles and “crosses” on the lateral x-ray. The base of the trochlea then is slightly anterior to the femoral cortex at this point representing the bump.

 

Type B: Presence of a crossing sign and supratrochlear spur sitting superolaterally are present. On the axial image, the trochlea is flat or even convex. This type is most amenable to deepening trochleoplasty as the spur is removed and the trochlea is deepened to the level of the femoral cortex.

 

Type C: Crossing sign is present, and a double contour sign is evident on the lateral view representing the hypoplastic medial trochlear facet. No spur is present as the trochlea does not sit far anterior to the femoral cortex. Hence, a deepening trochleoplasty would not be indicated.

 

Type D: The most severe type where a crossing sign, supratrochlear spur, and double contour sign are all present. Axial view demonstrates asymmetry of the facet height, referred to as a cliff pattern, with a clear

difference between the taller lateral and the shorter hypoplastic medial facets.6 This type is amenable to deepening trochleoplasty.

 

Cross-sectional imaging is essential to a thorough assessment of the bony anatomy. CT and MRI allow for global morphology assessment. Evaluation of cartilage and soft tissue structures is one indication for MRI over CT,16 although the bony anatomy can be more easily visualized on CT scan.

 

 

Osteochondral injuries as well as loose bodies are often identified by advanced imaging.

 

Evaluation of medial soft tissue injury, including MPFL attenuation is often identifiable.

 

TT-TG can be calculated to evaluate the need for medialization or an anteromedialization (AMZ) of the tibial tubercle (eg, Fulkerson osteotomy). This is measured as the distance between the center of the trochlear groove and the center of the patella tendon as it inserts on the tibial tubercle (abnormal value on a CT scan is

>20 mm). The measurement is made parallel to a line connecting the posterior femoral condyles on axial MRI or CT images.

 

DIFFERENTIAL DIAGNOSIS

 

 

 

 

 

Extensor mechanism injury MPFL injury Osteochondral injury Patellofemoral arthritis Ligamentous knee injury

NONOPERATIVE MANAGEMENT

 

Trochlear dysplasia treatment depends on patient symptoms combined with severity of dysplasia.

 

Nonoperative care can often be pursued in the setting of type A dysplasia. Additionally, first-time dislocations are often treated without surgery.

 

Immobilization following patellar dislocation episodes is not recommended.

 

Physical therapy focusing on strengthening of patella stabilizing structures, including the VMO, are one option for early care and low-grade dysplasia.

 

Patella stabilizing braces may be worn during sports participation and activities that provoke dislocation, although in more severe trochlear dysplasia, they are unlikely to make a long-term difference.

 

SURGICAL MANAGEMENT

 

Indications for sulcus-deepening trochleoplasty include patients with high-grade trochlear dysplasia with recurrent patella dislocation in the absence of osteoarthritis.6,17,21

 

Type of dysplasia plays an important role in considering the role of surgery. Dysplasia types B and D are most often considered candidates for sulcus-deepening trochleoplasty. These types share a supratrochlear prominence or spur in which the base of the flattened groove sits well in front of the anterior femoral cortex.

Removing this extra bone allows deepening of the base of the groove and recreating a sulcus that sits at the proper depth that is level with the anterior femoral cortex where they meet proximally.

 

Type C is not considered to be amenable to deepening trochleoplasty because there is not a large supratrochlear bump that could be removed to drop the level of the groove to the depth of the anterior femoral cortex. Type C dysplasia is more of a problem with a hypoplastic medial facet and lack of a deep groove and one could consider a lateral facet elevating osteotomy to address this.

 

Type A dysplasia is considered mild, with a minimal bump, such that deepening trochleoplasty is not necessary. Cases with recurrent instability should be evaluated for other tracking abnormalities that may need to be addressed, including patella alta or an elevated TT-TG as well as MPFL deficiency. Procedures to address these problems are generally enough to compensate for a groove that is somewhat shallow with a crossing sign alone. If patella alta is severe (Caton-Deschamps index >1.2), then a distalization of the tibial tubercle will bring the patella further down into the deeper part of the trochlear groove.

 

Correction of associated abnormalities should accompany trochleoplasty for maximal success. Essentially in all cases, this will include an MPFL reconstruction to account for the torn and attenuated medial restraints associated with chronic patellar instability in these patients.

 

Sometimes, in cases of elevated TT-TG distances greater than 20 mm, a tibial tubercle transfer or AMZ osteotomy is also indicated. It is important to note that the deepening trochleoplasty procedure will move the new trochlear groove slightly lateral, thereby reducing the TT-TG and making an AMZ less necessary, especially in borderline cases.

 

A femoral derotational osteotomy or varus producing osteotomy may be indicated for valgus, anteverted femurs, and can compensate to some degree for a dysplastic trochlea. Some authors advocate for this in skeletally immature patients.

 

Other than deepening trochleoplasty, other bony procedures historically have included Albee opening wedge osteotomy, lateral trochlear facet elevation, and rotational trochleoplasty.7 Arthroscopic techniques have also been described.

 

Preoperative Planning

 

Appropriate imaging should be reviewed during surgical planning. Plain radiographs and MRI should be reviewed for the presence of osteochondral fragments as well as loose bodies and soft tissue injuries.

 

The type of trochlear dysplasia and how to address the pathology are essential as previously discussed.

 

Planning for the appropriate amount of bone removal for a deepening trochleoplasty and calculating the amount of movement of the tibial tubercle if an AMZ osteotomy is planned is key.

 

 

 

Positioning

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The patient is positioned supine, and a nonsterile tourniquet is applied to the operative leg. The entire extremity is prepped.

 

Most commonly, we perform the deepening trochleoplasty under general anesthesia with a femoral nerve block for postoperative analgesia. Alternatively, the procedure can be performed under regional anesthesia with patient sedation.

 

Examination under anesthesia should be performed with documentation of patellar displacement and extent of patellar maltracking as well as determination of lateral retinacular tightness. A lateral lengthening or release is seldom necessary.

 

A radiolucent triangle positioner is very helpful during the case.

 

Arthroscopy can initially be performed if chondral abnormalities or loose bodies need to be addressed, although this is not routinely necessary given the arthrotomy planned for the trochleoplasty procedure.

 

Approach

 

A straight midline incision is carried out from the superior patellar margin to the tibiofemoral articulation. The incision is made in 90 degrees of flexion.

 

In extension, medial and lateral full-thickness flaps are developed with preservation of the bursal layer for later closure.

 

An arthrotomy is performed with a fresh scalpel using a midvastus approach. This includes medial retinaculum sharp dissection over the 1 to 2 cm medial border of the patella with blunt dissection of the VMO fibers starting distally at the superomedial pole of the patella, extending approximately 4 cm into the muscle belly.6

Alternatively, a standard medial parapatellar arthrotomy can be used.

 

TECHNIQUES

• Exposure of the Dysplastic Trochlea

   

  After initial arthrotomy, the patella is everted to inspect for any chondral injuries, which can be addressed with various chondral resurfacing procedures as indicated.

   

  Bovie cautery or a scalpel is used to incise the peritrochlear synovium and periosteum. A key elevator or Cobb can be used to elevate the synovial layer for removal. This allows for complete visualization of the anterior femoral cortex and trochlear junction.

   

  The relationship between the anterior femoral cortex and the trochlea is key to determine the amount of deepening needed (TECH FIG 1).

   

  Unless an AMZ or Fulkerson osteotomy is planned, further distal exposure of the tubercle is unnecessary.

   

   

   

  TECH FIG 1 • In the dysplastic femur, the base of the groove sits well anteriorly to the femoral cortex, representing the bump or spur.

• Planning the Future Trochlea

   

  Following full exposure of the trochlea, a new trochlear groove is planned with a sterile marker. It is usually best to dry the trochlea well with a sponge to allow for improved marking ability. The first line drawn is the native groove; then, a second line (the new groove) is marked according to the preoperative TT-TG value. The distance between these two lines at the superior aspect will indicate the mount of proximal realignment or improvement in the TT-TG distance as the groove is lateralized. The goal is to obtain a post-TT-TG value between 10 and 15 mm.

   

  From the notch, two lines are planned at approximately 45-degree angles (although variable depending on patient anatomy) through the condylotrochlear grooves (sulcus terminalis) (TECH FIG 2).

   

  These lines represent the new lateral and medial facet limits.

   

   

   

  TECH FIG 2 • Planned cuts drawn to represent the new trochlear groove. The first line begins at the intercondylar notch and is drawn proximally with two additional lines drawn to represent the sulcus terminalis on either side.

   

   

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• Osteotomy and Removal of the Undersurface of the Trochlea

   

  Access to the undersurface of the trochlea is granted through the osteochondral edge proximally.

   

  Using a sharp straight osteotome, a thin strip of cortical bone is removed around the trochlea to the extent of the lines previously drawn medially and laterally. The strip width that is removed is the height of the bump formed off the anterior femoral cortex and enough to allow access for the burr (TECH FIG 3A,B).

   

  Once access has been gained, cancellous bone is removed from the undersurface of the trochlea using a hand-controlled, highspeed burr. A small, pineapple-tip burr is our preferred technique (TECH FIG 3C).

   

  Prior to beginning burring, it is helpful to mark on the shaft of the burr the length of resection in relationship to the trochlea to avoid penetration of the articular surface anteriorly at the distal aspect of the groove. An alternative is to use a resection guide if available.

   

   

   

  TECH FIG 3 • A,B. A straight osteotome is used to remove a thin shell of cortical bone. A burr is used to remove the underlying cancellous bone (C). The burr may be switched to a drill to allow for deeper insertion for distal resection (D). (continued)

   

   

  Given the limited length of most burr tips when inserted in hand controls, it may be necessary to switch the burr to a drill to allow for deeper insertion for more distal resection as needed (TECH FIG 3D).

   

  Cancellous bone removal must be extended to the notch, including the central portion where the medial and lateral facets converge (TECH FIG 3E).

   

   

  The removed cancellous bone is taken away with irrigation. Bone is removed to allow compression of the osteochondral shell down to the level of the anterior femoral cortex to establish a groove. The remaining shell must be compliant enough to allow a “trampoline” effect. Penetration of the articular cartilage must be avoided, and some remaining bone on the chondral undersurface is critical for viability and healing. An extensive amount of bone removal is not needed to allow shaping of the new trochlea.

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  TECH FIG 3 • (continued) Note the gracilis autograft has already been passed through two short, oblique tunnels in the medial patella for MPFL reconstruction. Once access has been gained, cancellous bone is removed from the undersurface of the trochlea using a handcontrolled, high-speed burr followed by curette with the most bone removed centrally (E). Following trochlear cuts, the new trochlear can be reformed plastically to create the new trochlear groove.

• Cutting the Groove and Obtaining Osteochondral Flap Correction

   

  The surgeon should be ready to mold the flaps to the underlying cancellous bone, which remains in the distal femur.

   

  A no. 20 blade scalpel is used to incise the osteocartilaginous shell along the previously marked new groove. This is done by placing the scalpel on the cartilage and gently tapping on top with a bone tamp placed over the scalpel using a mallet (TECH FIG 4).

   

   

   

  TECH FIG 4 • A. A no. 20 blade scalpel is positioned along the planned trochlear cuts. B. A bone tamp and mallet are used to provide gentle taps to the scalpel.

   

   

   

  The lateral line is next incised in similar manner and the triangular flaps molded with the surgeon's finger to create a deepened central groove. If necessary, the medial line can be cut as well, although the medial side may be plastic enough to bend into the new shape without cutting.

   

• Fixation of the Medial and Lateral Facets

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  The overlying cartilaginous shell is molded to the underlying distal femur cancellous bone (see TECH FIG 3E,F). Various fixation options (TECH FIG 5A-F) to maintain this new position of the formed facets have been described:

   

  Staple fixation is accomplished with a pair of 1-mm diameter Kirschner wires manually bent to a squared “U” shape. One tong is fixed to each side of the groove, with one arm of the staple in the cartilaginous portion of the new facet and the other in the anterior femoral cortex, each oriented longitudinally (see TECH FIG 5A).

   

   

   

  TECH FIG 5 • Intraoperative photo demonstrating K-wire (staple) fixation (A). Postoperative radiographs demonstrating fixation with headless compression screws (B). Fixation can be achieved with an anchor at the base of the new groove adjacent to the intercondylar notch (C) with a pair of no. 1 Vicryl sutures draped across and compressing each shingle creating the new shape as the sutures are attached to two additional anchors at the anterior femoral cortex (D). (continued)

   

   

  Headless compression screws can provide fixation with each fixed perpendicular to and central within the lateral and medial facets of the trochlea (see TECH FIG 5C). These are buried just beneath the articular surface.

   

  Vicryl suture or tape can be used to buttress the overlying cartilage to the underlying cancellous bone without penetration of the new cartilage surface (see TECH FIG 5B,D). This suture construct is fixed at the base of the groove and at the femoral cortex above the new facets using knotless suture anchors to simulate a “cargo net” compressive effect. We typically perform this technique using a pair of no. 2 absorbable Vicryl sutures to each of the top anchors, emanating from a common anchor at the base of the groove.

   

   

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  TECH FIG 5 • (continued) A frontal view of a more severe case with suture fixation (E,F).

• Closure

 

Following completion of the sulcus-deepening portion of the procedure, patellar tracking is testing to ensure adequate tracking throughout flexion.

 

Periosteum and synovial tissue can be sutured to the osteochondral edge or anchored to the staples for additional fixation if desired.

 

Various other procedures depending on patient anatomy can be completed, including MPFL reconstruction, tibial tubercle osteotomy, and open lateral release. We routinely perform an MPFL reconstruction using hamstring autograft. Planning should account for any femoral tunnel used for graft attachment and fixation of the trochleoplasty for potential convergence. Fluoroscopy is helpful for this step.

 

Tight closure of the arthrotomy is accomplished using figureof-eight sutures followed by subcutaneous sutures and skin closure.

 

The lateral retinaculum tightness is evaluated and a release or lengthening is necessary most of the time in those patients with high-grade patellar dislocations.

 

PEARLS AND PITFALLS

A no. 20 blade scalpel is helpful for making trochlear cuts.

The burr can be switched to a drill to increase length for more distal resection of cancellous bone. Cutting of the lateral facet line can aid in molding of the new trochlear facets.

The medial facet can often be plastically molded rather than cut.

Avoid cartilage penetration with the burr to prevent progression of arthritis.

Be sure to address other anatomic factors (MPFL reconstruction, elevated TT-TG with tibial tubercle osteotomy) to avoid recurrent symptoms.

 

 

POSTOPERATIVE CARE

 

Progressive weight bearing to tolerance is allowed following trochleoplasty with crutches for 3 to 6 weeks. If an AMZ tibial tubercle osteotomy is performed, consideration is given to partial weight bearing for 6 weeks until this is healed. If an Elmslie-Trillat procedure is done, then weight bearing is not limited.

 

Range of motion is advanced as tolerated over 6 weeks to full. A hinged knee brace is used initially postoperatively to prevent quad inhibition with discontinuation of the brace as soon as possible. In the setting of an additional tibial tubercle osteotomy, a hinged knee brace is recommended for 30 days. We typically begin with 0 to 60 degrees in a hinged knee brace, advance to 0 to 90 degrees at 2 weeks, and remove the brace by 1 month postoperatively.

 

Continuous passive motion (CPM) following surgery may be helpful to promote cartilage healing and sulcus remodeling to accept the patella shape.

 

 

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Radiographs including AP, lateral, and sunrise views are taken after surgery and 6 weeks postoperatively and then at 6 months when remodeling is complete.

 

Early mobilization is key to prevent quadriceps wasting that compounds instability issues as well as slows recovery.

 

In the case of isolated trochleoplasty, knee motion is encouraged to prevent postoperative arthrofibrosis as well as promote cartilage health and further molding of the patella and trochlear groove.

 

Isometric quadriceps strengthening is avoided until 4 weeks postoperatively, and resistance exercises begin at 6 weeks postoperatively or once healing is apparent on radiographs.

 

OUTCOMES

Sulcus-deepening trochleoplasty has been shown to reliably prevent further patellar dislocations years following surgery.21 Lysholm scores improve significantly in all patients, with 33% of patients reporting

residual symptoms. In a recent series, Ntagiopoulos et al15 reported on 31 trochleoplasties performed at their institution for types B and D trochlear dysplasia. They demonstrated no cases of recurrence or stiffness.15 All patients showed significant improvement in Kujala and International Knee Documentation

Committee (IKDC) scores.

Cartilage viability has been shown to be maintained following trochleoplasty.18 A recent study by Nelitz et al14 highlighted no loss of articular cartilage characteristics on MRI in a series of sulcus-deepening trochleoplasties combined with MPFL reconstruction at 2.5 years following the index procedure.

Additionally, several studies have reported no radiographic evidence of patellofemoral arthritis at midterm

follow-up.15

 

 

COMPLICATIONS

The main concerns during performance of trochleoplasty are damage to articular cartilage outside of the planned trochlear cuts, patellar incongruence, and under- and overcorrection of the groove.

Arthrofibrosis is a potential problem, especially when multiple procedures are combined and if motion is restricted. A manipulation under anesthesia is occasionally required if motion is severely restricted by 45 days postoperatively. However, most of the time, motion will gradually progress with patient rehabilitation. For those patients who are still restricted to less than 90 degrees at 3 months, an arthroscopic lysis of

 

adhesions with manipulation can be performed.

Despite concerns regarding cartilage survival, several studies have demonstrated through MRI and biopsy that cartilage cells remain viable and the flaps heal.

Osteoarthritis may occur in patients with recurrent patellar instability due to chondral injury.

Recurrent instability is rare after sulcus-deepening trochleoplasty, although theoretically, it may occur. As with any large knee surgery, deep venous thrombosis, pulmonary embolus, and infection remain a concern.

 

 

REFERENCES

1. Ahmad CS, McCarthy M, Gomez JA, et al. The moving patellar apprehension test for lateral patellar instability. Am J Sports Med 2009;37(4):791-796.

    

    

2. Bollier M, Fulkerson JP. The role of trochlear dysplasia in patellofemoral instability. J Am Acad Orthop Surg 2011;19(1):8-16.

    

    

3. Brattstroem H. Shape of the intercondylar groove normally and in recurrent dislocation of patella. A clinical and x-ray-anatomical investigation. Acta Orthop Scand Suppl 1964;68(suppl 68):1-148.

    

    

4. Cash JD, Hughston JC. Treatment of acute patellar dislocation. Am J Sports Med 1988;16(3):244-249.

    

    

5. Colvin AC, West RV. Patellar instability. J Bone Joint Surg Am 2008;90(12):2751-2762.

    

    

6. Dejour D, Byn P, Ntagiopoulos PG. The Lyon's sulcus-deepening trochleoplasty in previous unsuccessful patellofemoral surgery. Int Orthop 2013;37(3):433-439.

    

    

7. Dejour D, Le Coultre B. Osteotomies in patello-femoral instabilities. Sports Med Arthrosc 2007;15(1):39-46.

    

    

8. Dejour H, Walch G, Neyret P, et al. Dysplasia of the femoral trochlea [in French]. Rev Chir Orthop Reparatrice Appar Mot 1990;76(1): 45-54.

    

    

9. Dejour H, Walch G, Nove-Josserand L, et al. Factors of patellar instability: an anatomic radiographic study. Knee Surg Sports Traumatol Arthrosc 1994;2(1):19-26.

    

    

10. Feller JA, Amis AA, Andrish JT, et al. Surgical biomechanics of the patellofemoral joint. Arthroscopy 2007;23(5):542-553.

     

     

11. Garron E, Jouve JL, Tardieu C, et al. Anatomic study of the anterior patellar groove in the fetal period [in French]. Rev Chir Orthop Reparatrice Appar Mot 2003;89(5):407-412.

     

     

12. Glard Y, Jouve JL, Garron E, et al. Anatomic study of femoral patellar groove in fetus. J Pediatr Orthop 2005;25(3):305-308.

     

     

13. Jafaril A, Farahmand F, Meghdari A. The effects of trochlear groove geometry on patellofemoral joint

    stability—a computer model study. Proc Inst Mech Eng H 2008;221(1):75-88.

     

     

14. Nelitz M, Dreyhaupt J, Lippacher S. Combined trochleoplasty and medial patellofemoral ligament reconstruction for recurrent patellar dislocations in severe trochlear dysplasia: a minimum 2-year follow-up study. Am J Sports Med 2013;41(5):1005-1012.

     

     

15. Ntagiopoulos PG, Byn P, Dejour D. Midterm results of comprehensive surgical reconstruction including sulcus-deepening trochleoplasty in recurrent patellar dislocations with high-grade trochlear dysplasia. Am J Sports Med 2013;41(5):998-1004.

     

     

16. Pfirrmann CW, Zanetti M, Romero J, et al. Femoral trochlear dysplasia: MR findings. Radiology 2000;216(3):858-864.

     

     

17. Schöttle PB, Fucentese SF, Pfirrmann C, et al. Trochleaplasty for patellar instability due to trochlear dysplasia: a minimum 2-year clinical and radiological follow-up of 19 knees. Acta Orthop 2005;76(5):693-698.

     

     

18. Schöttle PB, Schell H, Duda G, et al. Cartilage viability after trochleoplasty. Knee Surg Sports Traumatol Arthrosc 2007;15(2):161-167.

     

     

19. Steiner TM, Torga-Spak R, Teitge RA. Medial patellofemoral ligament reconstruction in patients with lateral patellar instability and trochlear dysplasia. Am J Sports Med 2006;34(8):1254-1261.

     

     

20. Tardieu C, Dupont JY. The origin of femoral trochlear dysplasia: comparative anatomy, evolution, and growth of the patellofemoral joint [in French]. Rev Chir Orthop Reparatrice Appar Mot 2001;87(4):373-383.

     

     

21. von Knoch F, Böhm T, Burgi ML, et al. Trochleaplasty for recurrent patellar dislocation in association with trochlear dysplasia. A 4- to 14-year follow-up study. J Bone Joint Surg Br 2006;88(10):1331-1335.