Surgical techniques 2022, Dec, 20 | 12:00 am

Proximal Realignment of the Medial Patellofemoral Ligament

  Proximal Realignment of the Medial Patellofemoral Ligament

 

DEFINITION

  • In most cases, patellar dislocation results in injury to the medial retinacular ligaments, including the medial patellofemoral ligament (MPFL), leading to increased lateral patellar mobility.

  • The MPFL is the primary ligamentous restraint against lateral patellar displacement.

Competency of the MPFL is both necessary and sufficient to restore lateral patellar mobility to a normal range9; consequently, surgical treatment should aim for restoration of a functional MPFL.

ANATOMY

  • The main stabilizer of the patella in normal knees is the bony congruence between the patella and trochlear groove.

    • When the trochlear groove is dysplastic, as it is in many patients with patellar instability, the medial retinacular ligaments (ie, the MPFL) take on a greater role.

    • Even in the presence of a normal trochlea, MPFL deficiency can result in symptomatic lateral patellofemoral instability.

  • The patellotibial and patellomeniscal ligament complex play a secondary role in restraining lateral patellar displacement, whereas the medial patellofemoral retinaculum contributes little to patellofemoral stability.

  • The MPFL is an extra-articular ligament that lies in layer 2, between the medial retinaculum superficially and the joint capsule on its deep surface. The vastus medialis obliquus (VMO) tendon lies superficially anteriorly and inserts onto the anterior third of the MPFL.

  • In a recent cadaveric study, the MPFL was moderately or well developed in 17 of 20 (85%) specimens, and poorly developed in 3 of 20 (15%).19

  • The MPFL is about 58 mm long, with a width and thickness of 12 mm and 0.44 mm, respectively, at its midpoint.19

  • The MPFL fans out anteriorly, inserting on the proximal two thirds of the patella.

  • The femoral attachment of the MPFL is posterosuperior to the medial femoral epicondyle and just distal to the adductor

  • If the knee remains flexed, the patella may remain dislocated over the lateral femoral condyle.

  • The history of injury may be unclear, especially if the patella rapidly and spontaneously reduced.

In one cohort of 189 patients, 61% of first-time dislocations occurred during sports activity.2

NATURAL HISTORY

  • Fithian et al8 reported a 17% incidence of redislocation in a cohort of first-time dislocators followed over 2 to 5 years.

  • On the other hand, patients presenting with recurrent patellar instability are much more likely to continue experiencing additional dislocations than patients who present with their first dislocation.

    • The risk of a repeat dislocation in patients presenting with a history of prior patellar dislocation is about 50% over a 2- to 5-year period.8

  • The strongest risk factor for recurrent patellar instability is a history of prior patellar subluxation or dislocation.8

    • Other risk factors include female gender and younger age (less than 18 years old).8,13

    • In one study, girls with open tibial apophyses had the worst prognosis for instability.13

  • It is unclear whether patellar dislocation leads to premature arthritis.

    • Crosby and Insall3 reported that degenerative changes were uncommon after patellar dislocation.

In a more recent study, however, the incidence of degenerative changes was significantly higher at 6- to 26-year follow-up in first-time dislocators treated nonoperatively.11

 

 

 

Quadriceps tendon

 

Adductor magnus tendon

tubercle when the knee is fully extended. The center of the anterior edge of the femoral attachment is located 9.5 mm proximal and 5.0 mm posterior to the center of the medial femoral epicondyle (FIG 1).19

PATHOGENESIS

  • Patellar dislocations usually occur when the foot is planted, the knee is partially flexed, and the body pivots abruptly, resulting in internal rotation of the femur. Patients may or may not have sustained a direct blow.

    Vastus medialis obliquus

     

    Patellar tendon

    Medial patellofemoral ligament

    Superficial medial collateral ligament

  • Patients may report that something “popped out” medially, as the uncovered medial femoral condyle becomes prominent.

The knee usually gives way secondary to pain inhibition of the quadriceps and disruption of the mechanical advantage of the extensor mechanism, and the patient falls down.

426

FIG 1 • Schematic diagram of the medial knee. The medial patellofemoral ligament (MPFL) arises between the adductor tubercle and medial epicondyle, then runs forward just deep to the distal vastus medialis obliquus (VMO) to attach to the superior two thirds of the medial patellar margin.

 

 

 

 

PATIENT HISTORY AND PHYSICAL FINDINGS

  • The patient should be asked about mechanical complaints of locking or catching, because osteochondral loose bodies off the medial patellar facet or lateral trochlea (kissing lesion), impaction fracture of the lateral femoral condyle, or avulsion fragments off the medial patella may result from a patellar dislocation.

  • Physical examination should include:

    • Lateral-medial patellar translation. Increased laxity is signified by more than two quadrants of translation; 10 mm or more of lateral translation; or the absence of an endpoint.

    • Apprehension sign. Inability to fully translate the patella laterally because of patient guarding may lead to a false-negative result.

    • J-sign. The patella abruptly translates laterally as the knee is fully extended, moving in an upside-down “J” pattern.

    • Check-rein sign. A positive test (no endpoint) signifies MPFL laxity (analogous to a Lachman test).

    • Patellar facet palpation. Tenderness may indicate an osteochondral or avulsion injury.

    • Medial retinacular palpation. Tenderness may indicate retinacular injury. A palpable defect may be felt in the retinaculum or even the VMO.

    • Effusion. A tense effusion or hemarthrosis (on aspiration) after an acute dislocation raises suspicion for an osteochondral fracture. MRI or arthroscopy should be considered.

  • The examination also should evaluate associated injuries and rule out differential diagnoses:

    • Anterior cruciate ligament (ACL) injury results from a similar noncontact pivoting mechanism and also leads to an acute effusion. The Lachman test is highly sensitive for an ACL disruption. Pivot shift also may be attempted, but may be difficult to perform on an acutely injured knee. To rule out ACL injury definitively, ligament arthrometry or stress radiography is recommended for all patients presenting with knee injury.

    • If posterior cruciate ligament (PCL) injury is suspected, the patient is checked for normal tibial stepoff with the knee flexed to 90 degrees. A posterior drawer and quadriceps active test also may be done.

    • Medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries result in joint space opening with valgus or varus stresses, respectively. These tests are performed in both full extension and 30 degrees of flexion. Comparison stress radiographs can be useful to control for individual variation.

    • A posterolateral corner (PLC) injury results in 10 degrees or more of external rotation asymmetry (dial test) and a positive posterolateral drawer test.

    • Medial patellar instability can occur following prior lateral retinacular release. Medial patellar instability can be distinguished from lateral instability by the DeLee sign. The patient is placed in the lateral decubitus position with the injured side up. With medial patellar instability, gravity sub-luxates the patella medially. As the knee is flexed, the patella reduces in the trochlea with pain. The DeLee sign is positive if the application of a laterally directed force on the patella (which reduces the patella from its subluxated position) eliminates the pain caused by flexion of the knee.

    • Meniscal tears are indicated by joint line tenderness and also possibly by positive McMurray and Appley’s grind tests.

  • Diagnosis of extensor mechanism disruption should be obvious based on an inability to straight-leg raise and actively extend the knee.

  • Patellofemoral osteoarthritis may be obvious on plain radiographs, but early stages require MR arthrography or arthroscopy for diagnosis.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

  • Recommended plain radiographs include a standing antero-posterior view, a true lateral view with the knee flexed 30 degrees, and a standard axial patellar view at 30 or 45 degrees flexion.

  • On the lateral radiograph, patellar height is measured according to the method of Caton and Deschamps (ie, the ratio between the distance from the lower edge of the patellar articular surface to the upper edge of the tibial plateau and the length of the patellar articular surface).2

    • A ratio of 1.2 or greater indicates patella alta, which predisposes to patellar instability due to late engagement of the patella in the trochlea as the knee flexes.

    • If present, a tibial tubercle osteotomy and distalization may be considered.

  • Trochlear morphology can be assessed on the true lateral radiograph (the posterior borders of both femoral condyles are strictly superimposed).

    • Trochlear dysplasia is evident when the floor of the trochlea crosses the anterior border of both femoral condyles (crossing sign)4 (FIG 2A).

    • Alternatively, the positive trochlear prominence (ie, the sagittal distance between the trochlear groove and the anterior femoral cortex) on the lateral view has been shown to correlate well with trochlear dysplasia4,5 (FIG 2B). A trochlear groove prominence of 3 mm indicates trochlear dysplasia (FIG 2C).

  • The axial patellar view may demonstrate lateral patellar subluxation or even frank dislocation. It may demonstrate medial patellar avulsion fractures, although these may be missed on plain radiographs.

  • Stress radiography has been advocated to demonstrate abnormal patellar mobility.

    • With the knee flexed to 30 degrees, an axial patellar view is taken with a laterally directed force applied to the medial side of the patella.

    • Measurements are made on both the symptomatic and asymptomatic knees.

    • A side-to-side increase of 3.7 mm of lateral translation on the symptomatic side compared to the asymptomatic side is considered abnormal.24

  • MRI identifies osteochondral injuries on the patella and femur, as well as loose bodies, that may be missed on plain radiographs.

    • A tense effusion should be aspirated.

    • Presence of gross hemarthrosis on joint aspiration is an indication for MRI to assess for osteochondral fracture and loose body.

  • The TT–TG offset is the transverse distance between the anterior tibial tuberosity (TT) and the center of the trochlear groove (TG).4

    • It can be measured on axial CT or MRI (FIG 2D).

    • Lateral offsets of 20 mm or more should be corrected with medialization of the tibial tubercle.

 

 

 

 

 

 

 

  1. C D

    Z

    B

     

    A

    C

     

     

    E

     

  2. X Y F

     

 

FIG 2 • A. On a true lateral radiograph, trochlear dysplasia is evident when the floor of the trochlea crosses the anterior borders of both femoral condyles (ie, the “crossing” sign). B. Measurement of the trochlear prominence on the lateral view according to Dejour et al. X and Y are lines tangential to the anterior and posterior cortices of the distal femoral metaphysis, respectively. Line Z crosses the most prominent point of the line of the trochlear groove (point B) and the upper aspect of the posterior border of the condyles. Line

Z crosses the anterior aspect of the lateral condyle (point A) and line X (point C). The distance BC (in mm) is the trochlear prominence. C. Lateral radiograph demonstrating a knee with positive trochlear prominence. Note that the floor of the trochlea lies anterior to the line tangential to the anterior cortex of the distal femur.

D. Measurement of the tibial tuberosity–trochlear groove (TT-TG) offset, the transverse distance between the apex of the anterior tibial tuberosity and the center of the trochlear groove. Measurements are made on superimposed axial CT or MRI images. E,F. MPFL injury appearance on MRI. E. Transverse gradient-echo image of the knee obtained at the level of the insertion of the adductor magnus tendon 3 weeks after lateral patellar dislocation demonstrates a complete tear of the femoral origin of the MPFL, with MPFL fibers retracted anteriorly (solid arrow). Partial injury, with surrounding edema, to the midsubstance of the patellar retinaculum (open arrow) also is seen. F. Transverse gradient-echo image of the knee in a different patient 2 days after lateral patellar dislocation showing partial injury to the femoral origin of the MPFL. The MPFL fibers (solid white arrow) are wavy and show longitudinal split, and there is extensive surrounding edema. A complete tear (open arrow) is seen in the patellar insertion of the medial patellar retinaculum. A large joint effusion with layering (black arrows) is present, consistent with hemarthrosis. Note also the inferior fibers of the VMO (arrowheads).

 

  • MRI also is useful in identifying the location and degree of medial soft tissue injury preoperatively.

MPFL injuries occur commonly in the form of tears near the femoral attachment or avulsions off the femur, but also may occur as midsubstance tears or avulsions off the patella (FIG 2E,F). Injuries to multiple sites in the medial ligamentous stabilizers may occur.5

DIFFERENTIAL DIAGNOSIS

  • Ligament/capsular injury (ACL, PCL, MCL, LCL, PLC)

  • Osteochondral injury

  • Medial patellar dislocation

  • Extensor mechanism disruption

  • Meniscal tear

     

  • Patellofemoral osteoarthritis

Contusion

 

NONOPERATIVE MANAGEMENT

  • Nonoperative treatment usually is indicated for acute, first-time dislocators without associated osteochondral fracture and loose bodies.

    • Randomized prospective studies comparing operative and nonoperative treatment of initial patellar dislocation found no benefit from immediate medial retinacular repair.1,13,14

  • Although there is evidence suggesting that immobilization following patellar dislocation may lower the risk of redislocation, patients often do not accept prolonged cast or splint immobilization. As a result, nonoperative management relies on brace protection during early progressive moblization and functional rehabilitation.

    • After an acute dislocation, patients initially are placed in knee immobilizers for comfort and weight bearing as tolerated.

    • As soon as comfort allows, passive ROM exercises and resisted closed-chain exercises in a patella-stabilizing brace are begun.

    • Patients are allowed to return to stressful activities, including sports, on resolution of the effusion, attainment of a full ROM, and return to at least 80% of their quadriceps strength compared to the noninjured limb.

Patients are encouraged to continue wearing the patella-stabilizing brace during participation in pivoting activities and sports.

 

SURGICAL MANAGEMENT

  • An associated osteochondral fracture and loose body occurs in 3% to 4% of first-time dislocators and is an indication for acute surgical treatment.

    • In this case, primary MPFL repair should be performed after fixation of the osteochondral fracture. Preoperative MRI can help in localizing the site of MPFL injury.

  • Surgical management usually is indicated for any patient with at least two documented patellar dislocations and a physical examination demonstrating excessive lateral patellar laxity.

     

For these recurrent dislocators, MPFL reconstruction should be done.

Preoperative Planning

  • Appropriate imaging studies should be reviewed.

  • Plain radiographs should be reviewed for the presence of trochlear dysplasia (ie, crossing sign and trochlear prominence of 3 mm or more), avulsion fractures, and loose bodies.

    • If signs of trochlear dysplasia are present, an axial CT or MRI scan should be obtained to measure the TT-TG offset. Offset of 20 mm or more should be treated with medialization of the tibial tubercle.

    • If patella alta is present (ie, Caton-Deschamps ratio of 1.2 or greater), then distalization of the tibial tubercle should be considered.

  • MRI scans should be reviewed for the presence of avulsion fractures, osteochondral fractures, and loose bodies.

    • If MPFL repair is to be performed, MRI should be reviewed to identify all locations of MPFL disruption. Failure to identify and treat each location of MPFL disruption may jeopardize the repair.

  • Examination under anesthesia should confirm excessive lateral patellar mobility.

The patella should displace more than 10 mm laterally from the centered position with the knee flexed 30 degrees, and there should be a soft endpoint or no endpoint with the knee extended.

Positioning

  • The patient is positioned supine.

  • If an osteochondral fracture and loose body amenable to reduction and fixation are present, surgery may proceed with an open approach (see Primary MPFL Repair at the Patellar Insertion, in the Techniques section).

If a diagnostic arthroscopy is performed before MPFL reconstruction, then the limb is placed in an adjustable leg holder to adjust knee flexion during the procedure.

Approach

  • The surgical approach depends on whether a primary MPFL repair or reconstruction is to be performed.

  • During MPFL repair, the surgical approach is determined by the location of MPFL and retinacular injury. MPFL injury may be seen as a proximal or distal avulsion, or as a tear near the femoral origin, the midsubstance, or the patellar insertion. Multiple sites of injury may coexist.

     

     

    DIAGNOSTIC ARTHROSCOPY

    TECHNIQUES

    and mobility. ■ Unstable cartilage flaps are débrided.

    PRIMARY MPFL REPAIR AT THE PATELLAR INSERTION

    underlying MPFL. manually reduced in the trochlear groove.

     

    TECHNIQUES

     

    • Standard anterolateral and anteromedial portals are used. ■ Specifically, the patellofemoral compartment is as-

    • A superolateral portal is used to facilitate viewing of the sessed for the severity of articular cartilage injury and patellar articular surface and passive patellar tracking the presence of degenerative changes.

    • Articular cartilage lesions are addressed. ■ Loose bodies are removed.

    • A midline skin incision is made extending from the superior ■ The MPFL is inspected both visually and digitally along its pole of the patella to the midaspect of the patellar tendon. entire length to identify all sites of injury.

    • After dissection through the subcutaneous tissue, the ■ The deep synovial layer (layer 3) can be dissected off superficial medial patellar retinaculum (layer 1) is iden- the deep surface of the ligament to aid in inspection. tified. It is incised and reflected medially, exposing the ■ The knee is then flexed to 30 degrees with the patella

    • Avulsions are repaired with suture anchors.

    • Tears of the substance of the MPFL are repaired with with no. 2 Fiberwire (Arthrex, Naples, FL) in a modified Kessler fashion (TECH FIG 1).10

    • After the repair, proper tensioning is assessed.

      • The knee is taken through a full passive ROM to evaluate patellar tracking, looking for abrupt or gradual deflection of the patella that might indicate either excessive or insufficient medial tightening.

      • With the knee extended, a laterally directed force should reproduce a firm endpoint (“check rein” sign).

      • Patellar mobility is assessed by applying medial and lateral forces of about 5 pounds with the knee flexed to 30 degrees. This should produce 5 to 10 mm of medial and lateral translation, respectively. If lateral displacement is less than 5 mm or more than 10 mm, then the medial repair is retensioned.

  • The wound is closed in layers.

     

    Superficial medial retinaculum

    A

    Medial patellofemoral ligament

     

     

     

     

    Superficial

    B medial retinaculum Medial patellofemoral ligament

     

    TECH FIG 1 • A. Disruption of the medial patellofemoral ligament (MPFL) near its femoral origin. B. For repair at this site, the superficial medial patellar retinaculum (layer 1) is reflected medially, exposing the torn MPFL. With the knee flexed 30 degrees, midsubstance MPFL tears are repaired primarily while avulsions are repaired using suture anchors.

     

    AUGMENTED MEDIAL PATELLOFEMORAL LIGAMENT REPAIR AT ITS FEMORAL ORIGIN

    • The femoral origin of the MPFL may be accessed through an extensile midline skin incision.

      • Alternatively, the origin may be approached through a separate posterior incision centered between the medial epicondyle and the adductor tubercle.

    • The dissection is carried down through the subcutaneous tissue, and the injured medial retinacular tissue is identified.

    • MPFL avulsions off the femur are repaired with suture anchors placed at a point 9 mm proximal and 5 mm

      posterior to the medial epicondyle, just distal to the adductor tubercle.

  • To augment the repair, a 10-mm × 60-mm strip of medial

    retinacular tissue (layer 1) is dissected off the femur, leaving the patellar attachment intact (TECH FIG 2).20

  • This medial retinaculum strip may be placed over the repaired MPFL and anchored into the adductor tubercle using a cancellous screw and either a spiked washer or suture anchor.

     

    A B C

    TECH FIG 2 • Schematic diagram of augmented MPFL repair at its femoral origin. A. Preparation of patellar-based medial retinaculum slip (10 mm × 60 mm). B. Avulsed MPFL repaired to femoral origin. C. Slip of medial retinaculum laid over MPFL and anchored to adductor tubercle with spiked washer and screw. (Redrawn from Nomura E, Inoue M, Osada N. Augmented repair of avulsion-tear type medial patellofemoral ligament injury in acute patellar dislocation. Knee Surg Sports Traumatol Arthrosc 2005;13:346–351.)

     

     

     

    TECHNIQUES

     

    MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION

    Semitendinosus Tendon Graft Harvest and Preparation

    • The sartorial fascia is exposed through a 2- to 3-cm skin incision made 2 cm medial and distal to the medial border of the tibial tubercle (TECH FIG 3).

    • The sartorial fascia is incised in line with the palpable gracilis tendon.

      • Avoid making this incision too deep, to avoid injury to the underlying superficial MCL.

    • Identify and isolate both the gracilis (proximal) and semitendinosus (distal) tendons from their deep aspect, ie, from within the bursal layer.

    • Apply tension to the semitendinosus while freeing it from the crural fascia at the posteromedial corner with tissue scissors.

    • Place stay sutures of no. 0 or 1 absorbable on a tapered needle, and then divide the tendon from the tibial insertion.

    • Once all tendinous slips have been freed, harvest the semitendinosus tendon using a closed (preferred) or open tendon stripper.

    • Baseball stitches are placed on both free ends for later graft passage throught the two patellar tunnels. The remaining free ends are discarded after graft fixation.

    • The graft is prepared on the back table by first sizing the graft to 240 mm, then folding it in half, leaving a doubled graft of 120 mm. The excess is removed.

    • A pullout suture of no. 5 polyester is placed through the loop to be used for pulling the doubled graft into the blind femoral tunnel.

    • A baseball stitch 25 mm in length is placed in the looped end of the graft.

      TECH FIG 3 • Incisions used for MPFL reconstruction at the

      left knee. A. Over the medial patella. B. Over the femoral origin of the MPFL, which lies between the adductor tubercle and the medial epicondyle. C. Over the pes anserinus, which is used to harvest the semitendinosus graft.

       

      Patellar Tunnel Placement

  • A longitudinal incision the length of the patella is made at the junction of the medial and middle thirds of the patella (in line with the medial border of the patellar tendon at the distal patellar pole).

  • The medial 8 to 10 mm of the patella is exposed by subperiosteal dissection with a no. 15 scalpel.

  • The dissection extends medially and dorsally around the patella through layers 1 (longitudinal retinaculum) and 2 (native MPFL), stopping after the transverse fibers of the native MPFL have been cut. The capsule (layer 3) is left intact (TECH FIG 4A).

  • A 4.5-mm drill hole is placed on the medial side of the upper pole of the patella adjacent to the articular margin (TECH FIG 4B).

    • A corresponding drill hole is placed on the anterior surface of the patella approximately 8 mm from the

       

       

      Medial patellofemoral ligament

       

      2 tunnels in patella

       

      Patellar tendon

      Adductor magnus tendon

      1 blind tunnel at femoral attachment

      Medial collateral ligament

       

      A B

       

      TECH FIG 4 • A. Exposure of the medial patella of the right knee. The medial 8 to 10 mm of the patella is exposed by subperiosteal dissection. The native MPFL is dissected off the medial border of the patella, leaving the capsule (layer 3) intact. B. Schematic diagram of the medial knee demonstrating the locations of the two patellar tunnels and the blind femoral tunnel, reproducing the anatomic femoral origin and patellar insertion of the native MPFL.

       

       

       

      TECHNIQUES

       

      medial border (this point corresponds to the lateral edge of the original retinacular dissection).

      • The two drill holes are connected with a curved curette.

    • A second 4.5-mm drill hole is placed on the medial side of the patella at a point two thirds down the length of the patella.

      • Again, a corresponding drill hole is placed on the anterior surface of the patella about 8 mm from the medial border, and the two holes are connected with a curved curette.

    • If the semitendinosus graft is more than 4.5 mm in diameter, the drill holes are enlarged slightly to facilitate graft passage.

    • It is important to avoid placing the distal patellar tunnel distal to the native insertion of the MPFL to avoid constraining the distal pole of the patella.

      Femoral Tunnel Placement and Checking Isometry

    • A skin incision is made just anterior to the palpable ridge connecting the medial femoral epicondyle and the adductor tubercle (see Tech Figs 3 and 4).

      • The knee is flexed slightly to facilitate palpation of this landmark (flexion moves the hamstrings posteriorly away from the medial epicondyle).

      • If the patient is obese and the landmarks are difficult to palpate, a small skin incision is made and palpation is done through the wound to identifty the ridge.

    • The graft may be placed between layers 1 and 2 or between layers 2 and 3 ( joint capsule) (ie, it may lie superficial or deep to the native MPFL).

      • Placing the graft between layers 2 and 3 is preferred, because blind dissection superficial to the native MPFL may disrupt the insertion of the VMO into the anterior portion of the MPFL; in addition, by placing the graft deep to the native MPFL, the latter may be repaired to the graft during wound closure.

      • The graft should not be placed deep to the capsule, because it should remain extra-articular to avoid graft abrasion and facilitate complete healing.

    • Using a long, curved clamp, the selected interval is developed (again, preferably between layers 2 and 3) from the patellar incision anteriorly to the medial femoral epicondyle posteriorly.

    • With the tip of the clamp overlying the ridge between the medial epicondyle and adductor tubercle, layers 1 and 2 are incised using a no.15 blade.

  • The tip of a Beath pin is placed at a point 9 mm proximal and 5 mm posterior to the medial epicondyle; the pin is then passed toward the lateral side of the femur.

  • A loop of no. 5 braided polyethylene suture is passed through the Beath pin, through the dissected retinacular tunnel, then through one of the patellar tunnels.

  • The knee is taken through the ROM to evaluate isometry.

    • If lengthening occurs in flexion, a second Beath pin is placed more distally toward the medial epicondyle. The first pin is left in place to facilitate repositioning while drilling the second Beath pin. The loop of no. 5 suture is passed through the second Beath pin, and the knee is put through ROM again. If isometry is acceptable, then the first Beath pin is removed.

    • If lengthing occurs in extension, a second Beath pin is placed more proximally toward the adductor tubercle. Again, the first pin is left in place to facilitate repositioning while drilling the second Beath pin. The loop of no. 5 suture is passed through the second Beath pin and the knee put through ROM again. If isometry is acceptable, then the first Beath pin is removed.

  • Once the femoral pin site is accepted, a blind tunnel is reamed into the femur the size of the doubled graft. For a semitendinosus graft, this usually is 6 to 7 mm in diameter.

  • The femur is reamed to a depth of at least 20 mm, with a preferred depth of 25 mm.

    Graft Passage and Fixation

  • No. 5 suture is passed through the Beath pin on the looped end of the graft, and the pin then is advanced out the lateral femoral cortex to pass the graft into the femoral tunnel.

  • Fixation to the femur may be achieved reliably with a 20-mm absorbable interference screw.

  • The looped isometry suture, if left in place in the retinacular tunnel, may be used to pass the free ends of the graft through the retinacular interval created previously (TECH FIG 5A,B).

  • The free graft arms are passed individually through their respective patellar tunnels using double 22-gauge stainless steel wire or a curved suture passer.

  • The graft arms enter the medial border of the patella and exit anteriorly (TECH FIG 5C).

  • The free graft arms are then doubled back and sutured on themselves just medial to the patella using two figure 8 mattress sutures of no. 2 nonabsorbable suture on a tapered needle.

     

     

     

    TECH FIG 5 • A. The synthetic isometry suture is in place. After correct placement of the femoral attachment site is confirmed using the isometry suture, the semitendinosus graft has been fixed to the femur using an interference screw.

    B. The isometry suture is used to shuttle

    the graft anteriorly out the medial patellar incision. The graft will then be fixed to

    A B the two patellar tunnels. (continued)

     

     

     

     

     

     

     

    Graft arms are passed through the 2 patellar tunnels and sutured back onto themselves

     

    TECHNIQUES

     

    MPFL graft tunneled between layers 2 and 3 of the medial retinaculum

     

     

    Interference screw in

    C blind femoral tunnel

     

    TECH FIG 5 • (continued) C. Schematic diagram demonstrating fixation of the graft posteriorly into a blind femoral tunnel, and anteriorly to two patellar tunnels. At the patella, each limb of the graft enters into respective medial drill hole, exits the anterior drill hole, then is sutured back to itself medial to the patella.

     

    • Patellar mobility is checked after the first suture is placed. There should be a good endpoint, or checkrein, with the knee in full extension and at 30 degrees of flexion, full knee ROM, and 7 to 9 mm of lateral patellar displacement from the centered position at 30 degrees of flexion.

  • Excess graft is sharply removed.

  • The native MPFL is sutured to the graft, and then the retinaculum is closed over the graft.

  • The wounds are closed in standard fashion.

     

     

    PEARLS AND PITFALLS

    Indications ■ Perform examination under anesthesia to confirm excessive lateral patellar mobility.

    • Perform arthroscopy to stage articular cartilage lesions and rule out preexisting arthritis, a contraindication to MPFL reconstruction.

      Femoral tunnel ■ This is one of the most critical steps in the operation.

      placement ■ Adjust the tunnel placement to ensure appropriate graft behavior during flexion and extension, recreating isometry.

      MPFL graft tensioning ■ Center the patella in the patellar groove and ensure that the MPFL graft is lax throughout a range of motion, becoming tight only when the patella is displaced laterally from its centered position.

    • The patella should enter the trochlea from the lateral side as the knee is flexed.

      Overtightened graft ■ If the patella enters the trochlea from the medial side as the knee is flexed or if there is less than 5 mm resulting in excessive of lateral patellar glide with gentle manual force at 30 degrees of knee flexion, then the graft is medial constraint overtensioned. The sutures should be removed and the graft retensioned.

      Breakage of patellar ■ May occur during preparation of the two patellar tunnels or during passage of an bone bridge oversized graft through a tight patellar tunnel.

    • If this occurs, then drill a second exit hole more laterally on the anterior patellar surface or drill the tunnel transversely across the patella, exiting at the lateral patellar margin.

    • The graft can be secured by tying the sutures over a button or suturing the end of the graft to the soft tissues on the lateral patellar border.

     

     

    POSTOPERATIVE CARE

  • Weight bearing as tolerated is allowed immediately postoperatively in a drop-lock or knee extension brace.

    • Bracing may be continued for up to 6 weeks during am-bulation to prevent falls until quadriceps control is restored.

  • After the soft tissue procedure, passive ROM exercises and resisted closed-chain exercises are begun as soon as possible to restore ROM and quadriceps control.

  • If a tibial tubercle osteotomy is performed, passive ROM using heel slides is begun postoperatively. No active extension is allowed for 6 postoperative weeks. At that time, full active ROM is begun, followed by closed-chain resistance exercises at 3 postoperative months.

  • Patients are allowed to return to stressful activities, including sports, when they attain full ROM and have regained at least 80% of their quadriceps strength compared to the noninjured limb.

  • If at least 90 degrees of flexion is not achieved by 6 postoperative weeks, then the intensity of the therapy program must be increased; manipulation under anesthesia (MUA) may be needed between 9 and 12 postoperative weeks if stiffness does not resolve with therapy alone.

    OUTCOMES

  • In a series of 92 knees treated with MPFL reconstruction, Fithian et al7 reported only 7 failures or reoperations (7.6%) and only one case of frank patellar redislocation (1.1%). Most of the reoperations were for stiffness and were treated successfully with MUA.

  • Schottle et al22 reported 86% good and excellent results at 47 months after MPFL reconstruction using semitendinosus autograft. In their series of 15 MPFL reconstructions, there was one case of bilateral recurrent instability.

  • Steiner et al,23 in a series of 34 patients treated with MPFL reconstruction using a variety of graft sources, reported 91.1% good and excellent results at 66 months and no recurrent dislocations.

  • In series by both Schottle et al22 and Steiner et al,23 the presence of trochlear dysplasia did not affect the outcome of MPFL reconstruction.

  • Nomura and Inoue18 reported on 12 knees after hybrid MPFL reconstruction using semitendinosus graft at a minimum of 3 years follow-up. There were 83% good and excellent results, and no cases of recurrent patellar subluxation or dislocation.

    COMPLICATIONS

  • Stiffness

  • Redislocation

  • Excessive medial patellar constraint resulting in a painful, overconstrained patella6,12,16,17

  • Patellar fracture

Common Peroneal and Lateral Femoral Cutaneous...
Tibial Tubercle Transfer
Proximal Realignment of the Medial Patellofemoral...
Arthroscopic Lateral Release of the Knee
Knee Loss of Motion
Repair of Acute and Chronic Quadriceps Tendon...
Repair of Acute and Chronic Patella Tendon Tears
Management of the Multiple Ligament–Injured Knee
Management of Posterolateral Corner Injuries
Repair of Acute and Chronic Knee Medial Collateral...
Posterior Cruciate Ligament Repair
Posterior Cruciate Ligament Repair
Revision Anterior Cruciate Ligament Repair
Anatomic Double-Bundle Anterior Cruciate Ligament...
Single-Bundle Anterior Cruciate Ligament Repair
Osteochondritis Dissecans and Avascular Necrosis
Allograft Cartilage Transplantation
Autogenous Cartilage Implantation
Osteochondral Autograft “Plug” Transfer
Microfracture Chondroplasty
Meniscal Transplant
Meniscal Repair
Arthroscopic Meniscectomy
Arthroscopic Synovectomy
Knee Arthroscopy: The Basic
Periacetabular Osteotomy
Hamstring
Proximal Hamstring Injury
Athletic Pubalgia
Adductor Longus–Related Groin Pain
Snapping Hip
Hip Arthroscopy: The Basics
Arthroscopy for Soft Tissue Pathology of the Hip
Arthroscopic Treatment of Epicondylitis
Arthroscopic Débridement for Elbow Degenerative...
Arthroscopic Treatment of Elbow Loss of Motion
Arthroscopic Treatment of Valgus Extension...
Arthroscopic Treatment of Chondral Injuries and...
Elbow Arthroscopy: The Basics
Arthroscopic Lateral Release of the Knee
Arthroscopic Débridement and Glenoidplasty for...
Arthroscopic Treatment of Scapulothoracic...
Arthroscopic Capsular Releases for Loss of Motion
Arthroscopic Release of Nerve Entrapment
Repair and Reconstruction of Acromioclavicular...
Acromioclavicular Disorders
Arthroscopic Treatment of Subacromial Impingement
Arthroscopic Treatment of Biceps Tendonopathy
Management of Shoulder Throwing Injuries
Shoulder Arthroscopy: The Basics
Arthroscopic Treatment of Superior Labral (SLAP)...
Arthroscopic Treatment of Multidirectional...
Arthroscopic Treatment of Posterior Shoulder...
Arthroscopic Treatment of Anterior Shoulder...
Arthroscopic Treatment of Anterior Shoulder...
Open Reduction and Internal Fixation of the Distal...
Arthroscopic Treatment of Subscapularis Tears,...
Proximal Hamstring Injury
Revision Total Hip Arthroplasty With Acetabular...
Arthroscopic Treatment of Rotator Cuff Tears
Anterograde Intramedullary Nailing of the Femur
Arthroscopic Acromioclavicular Joint Reduction and...
Chronic Exertional Compartment Syndrome
Repair and Reconstruction of Acromioclavicular...

REFERENCES

  1. Andrade A, Thomas N. Randomized comparison of operative vs. nonoperative treatment following first time patellar dislocation. Presented at the European Society for Sports, Knee and Arthroscopy, Rome, 2002.

  2. Caton J, Deschamps G, Chambat P, et al. Patella infera. Apropos of

    128 cases. Rev Chir Orthop Reparatrice Appar Mot 1982;68: 317–325.

  3. Crosby EB, Insall J. Recurrent dislocation of the patella: relation of treatment of osteoarthritis. J Bone Joint Surg Am 1976;58A:9–13.

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

  5. Elias DA, White LM, Fithian DC. Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella. Radiology 2002;225:736–743.

  6. Elias JJ, Cosgarea AJ. Technical errors during medial patellofemoral ligament reconstruction could overload medial patellofemoral cartilage. Am J Sports Med 2006;34:1478–1485.

  7. Fithian DC, Gupta N. Patellar instability: principals of soft tissue repair and reconstruction. Tech Knee Surg 2006;5:19–26.

  8. Fithian DC, Paxton WE, Stone ML, et al. Epidemiology and natural history of acute patellar dislocation. Am J Sports Med 2004;32: 1114–1121.

  9. Hautamaa PV, Fithian DC, Kaufman KR, et al. Medial soft tissue restraints in lateral patellar instability and repair. Clin Orthop Rel Res 1998;349:174–182.

  10. Kessler I. The grasping technique for tendon repair. Hand 1973;5: 253–255.

  11. Maenpaa H, Lehto MU. Patellofemoral osteoarthritis after patellar dislocation. Clin Orthop Rel Res 1997;339:156–162.

  12. Muneta T, Sekiya I, Tsuchiya M, et al. A technique for reconstruction of the medial patellofemoral ligament. Clin Orthop Rel Res 1999; 359:151–155.

  13. Nikku R, Nietosvaara Y, Aalto K, et al. Operative treatment of primary patellar dislocation does not improve medium-term outcome: a 7-year follow-up report and risk analysis of 127 randomized patients. Acta Orthop 2005;76:699–704.

  14. Nikku R, Nietosvaara Y, Kallio PE, et al. Operative versus closed treatment of primary dislocation of the patella: similar 2-year results in 125 randomized patients. Acta Orthop Scand 1997;68:419–423.

  15. Nomura E, Horiuchi Y, Inoue M. Correlation of MR imaging findings and open exploration of medial patellofemoral ligament injuries in acute patellar dislocations. Knee 2002;9:139–143.

  16. Nomura E, Horiuchi Y, Kihara M. Medial patellofemoral ligament restraint in lateral patellar translation and reconstruction. Knee 2000;7:121–127.

  17. Nomura E, Horiuchi Y, Kihara M. A mid-term follow-up of medial patellofemoral ligament reconstruction using an artificial ligament for recurrent patellar dislocation. Knee 2000;7:211–215.

  18. Nomura E, Inoue M. Hybrid medial patellofemoral ligament reconstruction using the semitendinosus tendon for recurrent patellar dislocation: minimum 3 years’ follow-up. Arthroscopy 2006;22: 787–793.

  19. Nomura E, Inoue M, Osada N. Anatomical analysis of the medial patellofemoral ligament of the knee, especially at the femoral attachment. Knee Surg Sports Traumatol Arthrosc 2005;13:510–515.

  20. Nomura E, Inoue M, Osada N. Augmented repair of avulsion-tear type medial patellofemoral ligament injury in acute patellar dislocation. Knee Surg Sports Traumatol Arthrosc 2005;13:346–351.

  21. Remy F, Chantelot C, Fontaine C, et al. Inter- and intraobserver re-producibility in radiographic diagnosis and classification of femoral trochlear dysplasia. Surg Radiol Anat 1998;20:285–289.

  22. Schottle PB, Fucentese SF, Romero J. Clinical and radiological outcome of medial patellofemoral ligament reconstruciton with a semitendinosus autograft for patella instability. Knee Surg Sports Traumatol Arthrosc 2005;13:516–521.

  23. 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;34:1254–1261.

  24. Teitge RA, Faerber WW, Des Madryl P, et al. Stress radiographs of the patellofemoral joint. J Bone Joint Surg Am 1996;78A:193–203.