DEFINITION

Patellar instability in children and adolescents usually involves an episode of complete dislocation of the patella from the trochlear groove. Occasionally, there can be episodes of patellar subluxation without gross dislocation.

There are two main types of patellar dislocation:

Acute traumatic patellar dislocation in athletic, nonlax individuals Atraumatic dislocations or subluxation secondary to ligamentous laxity

Children between the ages of 10 and 17 years have the highest risk for traumatic and atraumatic patellar dislocation.12 The incidence of primary patellar dislocation in this age group is reported at 29 per 100,000 annually and is more common in females.9

Acute traumatic patellar dislocation is frequently (28% to 39%) associated with articular surface fractures of the patella or of the lateral femoral condyle.3,22

Most traumatic patellar dislocations tear the medial patellofemoral ligament (MPFL), which is the primary restraint to patellar dislocation. This may lead to persistent apprehension or recurrent instability of the patellofemoral joint.

Nonoperative treatment is indicated for patellar dislocation associated with ligamentous laxity and for first-time traumatic patellar dislocation that is not associated with a repairable articular surface injury.

Care must be taken to avoid realignment surgery for patients with patellofemoral pain and no clear evidence of instability.

 

ANATOMY

 

The medial restraints of the patellofemoral joint are made up predominantly of the medial retinaculum and the MPFL. Forty percent to 60% of the resistance to lateral translation is supplied by the MPFL.19 The MPFL provides 50% to 80% of the restraining force to lateral patellar displacement.13

 

Traumatic dislocation of the patella occurs almost exclusively in the lateral direction and often results in a tear of the MPFL at its femur insertion, patellar origin, or in its midsubstance (FIG 1A). The MPFL can tear in multiple sites during a single dislocation.

 

The MPFL is a flat band adjacent to the medial retinaculum that is about 15 mm wide. It extends from the superomedial aspect of the patella, about 10 to 15 mm distal to the superior pole, to the medial epicondylar area, just above and posterior to the origin of the medial collateral ligament, and distal to the adductor

tubercle25 (FIG 1B).

 

During limited-incision surgical approaches, anatomic landmarks are not reliably identified due to small

incisions. Fluoroscopy and isometry is needed to confirm the proper site of MPFL reattachment location (see

TECH FIG 1A,B).

 

Although there is some controversy, most believe that the native MPFL arises from the femur just distal to the growth plate near the medial epicondyle in a skeletally immature patient.12,16,20,32

 

The common finding of a lateral femoral condyle bone bruise at the sulcus terminalis suggests that dislocation usually occurs at 70 to 80 degrees of flexion.29

 

 

 

FIG 1 • A. The MPFL can tear at its patellar origin, its femoral origin, or in its midsubstance. B. The MPFL tethers the medial patella to the medial condyle of the femur. It arises from the superior two-thirds of the medial border of the patella and inserts between the adductor tubercle and medial epicondyle. Its insertion is just distal to the growth plate. C. The entire medial cartilaginous facet of the patella has separated from the underlying bone after a primary traumatic patellar dislocation. (continued)

 

 

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FIG 1 • (continued) D. After patellar dislocation, this patient has an osteochondral fracture of the lateral femoral condyle (arrow). E. Insignificant avulsion fracture off medial patella (arrow), which is pathognomonic for patellar dislocation.

 

 

Traumatic dislocation can cause a serious fracture of the medial patellar facet (FIG 1C) or the lateral femoral condyle (FIG 1D) and can be cartilaginous or osteocartilaginous.

 

Stanitski and Paletta33 found a 71% incidence of osteochondral injury at arthroscopy after patellar dislocation, most of which was radiographically occult.

 

More frequently, there is a less serious nonarticular avulsion fracture of the MPFL off the medial patella. There can be an immediate or delayed appearance of an ossific lesion, which rarely needs removal or reattachment, at the avulsion site off the medial patella (FIG 1E).

 

PATHOGENESIS

 

Noncontact patellar dislocation during sports usually involves lower extremity internal rotation combined with knee valgus on a planted foot (a mechanism very similar to anterior cruciate ligament injury).

 

Less commonly, patellar dislocation is caused by a direct blow on a valgus bent knee that pushes the kneecap laterally.

 

The bony anatomy of the patellofemoral joint may be abnormal with a deficient lateral femoral slope of the trochlear groove, a shallow trochlear groove, patella alta, patellar tilt, or a lateralized and/or hypoplastic tibial tubercle. These factors can increase the risk of dislocation by decreasing the force needed to laterally

translate or dislocate the patella.7

 

The lateral retinaculum may also be tight, characterized by less than 12 mm of medial translation.15

 

The alignment of the lower extremities must also be considered. The quadriceps angle may be greater than average, increasing the lateral translational force.

 

So-called miserable malalignment syndrome may exist, including excessive femoral anteversion with or without increased external tibial torsion.14,15

 

Multiple anatomic factors are theorized to increase the risk of patellar dislocation, such as family history, increased Q angle, femoral intorsion, tibial extorsion, knee valgus, trochlear groove dysplasia, and foot

pronation. Only patella alta is a proven risk factor.2 MPFL reconstruction results are not diminished by patella alta or tibial tuberosity-trochlear groove (TT-TG) distances of up to 25 mm.21

NATURAL HISTORY

 

Patients with an atraumatic presentation of instability or dislocation of the patellofemoral joint have a higher likelihood of repeat instability episodes, despite aggressive physical therapy and bracing.14,15

 

 

A recent study on adolescents with traumatic first-time patellar dislocation reports a 70% recurrence rate.28 Young age was also associated with recurrence, as was a positive family history.9

 

At 6 months after patellar dislocation, only 69% of patients had returned to sports.2

 

At 2 to 5 years of follow-up after patellar dislocation, Fithian and coworkers9 showed no radiographic or scintigraphic evidence of degenerative joint disease.

 

At 6 to 26 years of follow-up after nonoperative treatment for patellar dislocation, 22% of knees showed arthritic changes, compared to 11% of each patient's opposite uninjured knee.17

 

At least 30% to 50% of patients with patellar dislocation will have knee pain more than 2 years after injury, and 69% of athletes will decrease their sports activity.11

 

Young age and skeletal immaturity, especially in females, is associated with worse prognosis.23

 

Patellar dislocation, especially recurrent patellar dislocation, is associated with patellofemoral arthritis in adulthood.34

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patients with an acute traumatic patellar dislocation often present to the emergency room with a history of a noncontact or contact injury to their knee. Many do not recognize the injury as a patellar dislocation.

 

An effusion is usually present after traumatic dislocation but is rarely present after atraumatic dislocations.

 

Like an anterior cruciate ligament injury, it is common to hear or feel a “pop” at the time of injury. If the patella completely dislocates, the athlete may be found to have a deformity of the knee and may be unable to actively extend the knee.

 

Most episodes of patellar dislocation spontaneously reduce in the field.

 

 

If the patella is still dislocated, the emergency physician usually performs a reduction by slowly extending the knee from its flexed position.

 

Patellar dislocation that spontaneously reduces in the field may mimic the history and presentation of an anterior cruciate ligament tear.

 

A thorough examination will include the following:

 

 

Examination for effusion

 

Patellar glide (Patellar stability) test: With the knee flexed 25 to 30 degrees, the patella is gently translated laterally and compared to the opposite knee, which show less

 

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translation. An intact MPFL will usually have a solid end point near the limit of lateral translation. Unfortunately, the patellar stability examination is often unreliable in the awake patient due to extreme

apprehension to lateral translation. In this case, an examination under anesthesia can help confirm the diagnosis when the history and magnetic resonance imaging (MRI) are unclear.

 

Patella apprehension sign: With the knee flexed over a bolster at 25 degrees, the patella is translated laterally. If the patient exhibits apprehension, the test is positive. This is the best test for patellar instability.

 

J sign: Observe and palpate the patella for lateral subluxation during active range of motion. A positive sign occurs when the patella pulls laterally as the knee reaches full extension, tracing the path of an upside-down “J.” This can identify proximal alignment issues.

 

 

Femoral rotation: Average rotation is external rotation greater than or equal to internal motion. Tibial alignment: Average axis is 10 to 15 degrees of external tibial torsion.

 

Patients with obvious genu valgum should have a standing alignment film with their patellas pointing forward. A plumb line drawn between the femoral head center and the center of ankle tibial plafond that passes lateral to the notch may be an indication for a guided growth hemiepiphysiodesis.

 

Assess for generalized hypermobility using the Beighton hypermobility score, which ranges from 0 to 9. One point accrues for each elbow that hyperextends greater than 10 degrees, each little finger that shows greater than 90 degrees extension across the metacarpophalangeal (MCP) joint, each thumb that can touch the volar forearm, each knee that hyperextends greater than 10 degrees, and one point if the patient can bend forward and touch their palms flat on the floor.

 

 

Beighton scores of four or greater may indicate generalized hypermobility.

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Knee radiographs should include the anteroposterior (AP), lateral, and sunrise (or Merchant) views.

 

 

 

 

FIG 2 • A. Osteochondral fragment. Postpatellar dislocation radiographic sunrise view shows a subtle sliver of bone (arrow), which on arthroscopy proved to be a large osteochondral fracture from the lateral condyle that was repaired with screw fixation. B. MPFL tear off from the patella. MRI shows disruption of MPFL off its origin from the patella (arrow), with increased signal on medial patella. C. Lateral femoral condyle bone bruise on MRI scan after a patellar dislocation. There is a subtle break in the articular cartilage (arrow). The location of the bruise provides evidence that the patella usually dislocates with the knee in 70 to 80 degrees of flexion.

 

 

The sunrise or Merchant view requires a patient to flex the knee 30 to 45 degrees, which may be impossible owing to pain at the initial time of presentation in the emergency department. The sunrise view can usually be obtained at the first follow-up visit.

 

Each radiograph is evaluated for fracture or loose fragment necessitating more emergent surgical indications.

 

Plain radiographs can miss 40% of arthroscopically documented chondral or osteochondral lesions. Many reparable osteochondral injuries show only a sliver of bone on one view in the plain radiographic series, which can be easily overlooked (FIG 2A).

 

Because of the high rate of occult articular or osteoarticular injury, we recommend an MRI scan on patients who present with a large traumatic effusion after patellar dislocation.

 

 

The site of MPFL ligament disruption can often be identified on MRI. MRI is reported to be 85% sensitive and 70% accurate30 (FIG 2B). The MPFL is torn or stretched at multiple sites after a patellar dislocation episode in 27% to 46% of cases.8,16

 

MRI after acute traumatic patellar dislocation shows a signature bone contusion pattern (FIG 2C). There was a 100% occurrence of anterior third of the lateral femoral condyle bone bruises and 96% occurrence of

medial patellar bone bruises in one study.27 This bone bruise pattern is distinct from that associated with anterior cruciate ligament tears.

 

DIFFERENTIAL DIAGNOSIS

 

 

Anterior cruciate, medial collateral, lateral collateral, or posterior cruciate ligament tear Meniscal tear

 

 

Knee contusion Osteochondral injury

 

 

Sinding-Larsen-Johansson disease Patellofemoral pain syndrome

NONOPERATIVE MANAGEMENT

 

Some 17% to 70% of adolescent patients will suffer a recurrent patellar dislocation after nonoperative management of their first patellar dislocation.9,28

 

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Nonoperative treatment is appropriate initial treatment for first time dislocators or subluxators who do not have a chondral facture, especially those who have generalized ligamentous laxity or an atraumatic type of presentation.

 

Controversy exists as to the best treatment of first-time dislocators who are ligamentously tight, with or without a traumatic (but usually forceful) event.

 

Some advocate early surgical intervention to repair the MPFL and medial retinaculum, even without fractures or loose body; however, pediatric and adult controlled studies show no advantage of surgical treatment (predominantly medial reef procedures +/- lateral release) over nonsurgical treatment.23,24,28

 

A recent randomized controlled trial of predominantly adults found that MPFL reconstruction gave significantly better outcome than nonoperative treatment.4

 

Nonoperative regimen for an acute traumatic dislocation includes the following:

 

 

Rest, ice, compression, and elevation for acute pain and swelling

 

Anti-inflammatory medications and oral narcotics in the initial phase, if needed

 

Initial knee immobilization for pain followed by early ROM, physical therapy and a patellar stabilizing sleeve starting at about 1-2 weeks after injury.

 

 

In one study, the risk of redislocation is reported as three times higher in patients treated with immediate mobilization versus immobilization with cast or brace.18

 

Weight bearing as tolerated with crutches

 

Early physical therapy with modalities and exercise used to control effusion, restore normal range of motion, and initiate quadriceps activation.

 

A patellar protection program of hip, core, quadriceps, and hamstrings strengthening to provide dynamic stability once symptoms have resolved.

 

 

Bracing, with a lateral patellar restraint type of brace, for return to activity Treatment options for recurrent subluxation should include the following:

 

Bracing with a lateral patellar restraint type of brace

 

Physical therapy: a patellar protection program emphasizing strengthening of the hip flexors, abductors (which are routinely weak in this patient population), and quadriceps in particular.

 

The clinician should emphasize to the patient that therapy requires participation at home as well as at therapy sessions.

 

SURGICAL MANAGEMENT

 

MPFL reconstruction is revolutionizing the functional outcomes and redislocation rates after patellar stabilization surgery in both adults and children4,5,21,35 as compared to the previously mentioned studies showing no benefit to soft tissue repair surgery after first-time dislocation.

 

Operative treatment is indicated for first-time patellar dislocation that fails to reduce concentrically or that involves osteochondral damage necessitating repair or removal of a loose body.

 

Osteochondral or pure chondral lesions larger than 1 cm in diameter should be repaired if surgically possible. Fixation devices should be countersunk 2 to 4 mm beneath the thick cartilage surface.

 

The MPFL can be repaired at the time of surgery for osteochondral lesions in acute dislocations, but the recurrence rate is higher with MPFL repair versus MPFL reconstruction. MPFL reconstruction should not be performed at the time of chondral or osteochondral repair if the fixation devices will need an arthrotomy for future removal. The reconstruction can be staged with implant removal surgery.

 

Operative intervention should not be considered in chronic subluxators unless they prove that instability remains problematic despite a good effort in therapy and bracing over 6 to 12 months.

 

 

Recurrent traumatic patellar dislocation, especially after the patient has complied with a rigorous physical therapy program after the first patellar dislocation, is an indication for surgical stabilization.

 

 

The surgeon should be wary of operative treatment for patients with pain without instability. MPFL reconstruction is not indicated for malalignment, patellofemoral pain, or arthrosis.

 

Lateral release is rarely necessary with repair or reconstruction of the MPFL.

 

Tibial tubercle realignment procedures should be avoided in skeletally immature patients with open growth plates because of the risk of creating iatrogenic genu recurvatum from growth arrest.

 

Patella alta, trochlear dysplasia, and TT-TG axial distance seem to have an insignificant bearing on outcomes after MPFL reconstruction for traumatic patellar instability in children and adolescents, so these are not

contraindications to isolated MPFL surgery.21

 

Preoperative Planning

 

All imaging studies are reviewed for concurrent pathology. MRI scans best determine the size and location of osteochondral fractures and their potential for repair versus removal.

 

Before positioning, an examination of the knee under anesthesia should be performed.

 

 

Test overall knee stability: Lachman, pivot shift, varusvalgus stress test, and AP drawer

 

Test lateral patellar tracking and medial and lateral patellar stability at 45 degrees of knee flexion. Results should be compared with those from the opposite knee.

 

Translation of the patella over 50% of the width of the patella laterally indicates an incompetency of the MPFL (FIG 3).

 

Small metallic or bioabsorbable screws or pins should be available for osteochondral fracture repair.

 

 

 

FIG 3 • Complete dislocation of the patella at the time of surgery.

 

 

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Positioning

 

 

The patient is positioned supine on a table that will allow knee imaging. The operative leg is free with a nonsterile tourniquet on the proximal thigh.

 

A lateral post is used to apply a valgus moment and thus improve visualization of the medial compartment.

 

The table can be kept flat with a 1 L bag of intravenous (IV) fluid taped on the end of the table to allow blocking the knee at about 45-degree flexion during patellar tunnel drilling and during final tensioning (FIG 4). Alternatively, the foot of the table is flexed about 30 to 45 degrees.

 

The opposite leg can be positioned per the surgeon's preference.

 

Approach

 

Some surgeons perform diagnostic arthroscopy in all cases, but this procedure may be eliminated if a preoperative highresolution MRI shows no articular damage of the patella of the lateral femoral condyle. Arthroscopy is indicated when there has been a new traumatic dislocation after the MRI was obtained.

 

 

 

FIG 4 • Operating room position. Patients are positioned supine on a radiolucent operating room table. A bump is placed under the ipsilateral hip to help balance the knee in flexed position so it does not flop medial or lateral. An IV fluid bag is taped to the table to act as a block to hold the knee in about 45 degrees flexion during tensioning of the reconstruction.

 

 

 

FIG 5 • For the modified Insall procedure, first an arthroscopic examination and limited lateral release (arrow) are performed. The surgical incision is centered over the medial aspect of the widest portion of the patella.

 

 

A lateral release is rarely necessary in combination with an MPFL reconstruction and may increase lateral instability.

 

If an arthroscopic lateral release is being perfomed as part of the modified Insall procedure, a 4 to 5 cm limited medial parapatellar approach may be used, centering on the widest portion of the patella (FIG 5).

Subcutaneous flaps can be elevated to allow great mobility of the prepatellar skin to limit the size of the incision.

 

Alternatively, for the modified Insall procedure, and open subcutaneous lateral release can be performed through a 1-cm incision, along with the medial plication-imbrication, or both may be done through a midline incision.

 

If needed, the hamstring semitendinosus graft is harvested through a standard proximal medial tibial approach with a tendon stripper.

 

TECHNIQUES

• Medial Patellofemoral Ligament Reconstruction (Hamstring Autograft)

 

Exposure and Tunnel Creation

 

The semitendinosis or gracilis tendon (single tendon) is harvested using standard technique with a tendon stripper and trimmed if necessary to fit through a 3.5- to 4-mm diameter sizing device.

 

A 3-cm medial patellar longitudinal skin incision is carried down sharply to the anteromedial border of the patella.

 

All medial patellar soft tissue except the joint synovium is sharply elevated of the medial patella, and a tissue plane is developed in the extrasynovial fatty plane under the medial retinaculum, using Metzenbaum or curved tenotomy scissors.

 

This extrasynovial soft tissue tunnel is expanded down toward the medial epicondyle of the femur between layers 2 and 3. A pocket should easily be identified, and the insertion of the native MPFL can be palpated with a finger medially.

 

It is not necessary to enter the joint space.

 

The extra-articular portion of the medial patella face is drilled with a 3.5-mm drill bit about 3 mm posterior to the thick anterior cortex and just superior to the equator of the patella. A 3.5-mm socket is drilled about 10 mm deep transversely from medial to lateral.

 

A 3.5-mm tunnel is then drilled through the anterior cortex that meets up with the deep end of the 10-mm transverse socket, leaving a 10 mm bone bridge in the anterior cortex.

 

No. 0 and no. 1 curettes are used to expand the tunnel up to about 3.5 to 4 mm, especially at the narrow isthmus where the medial and anterior sockets connect. A folded 22-gauge steel wire is placed from medial to lateral through the tunnel and is left as a marker.

Pin Placement

 

A finger is placed back under the medial retinaculum and down to the medial reflection (medial gutter) of the native MPFL, near the medial epicondyle, to estimate placement of a short Beath pin. The pin is positioned over the skin, and fluoroscopy verifies

 

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that the pin is about 4 mm distal to the medial femoral growth plate before the tip is drilled or tapped a few millimeters into the medial femoral condyle.

 

 

 

TECH FIG 1 • A. On the AP fluoroscopy view, the femoral guide pin is placed just distal to the medial femoral growth plate. Because the edge of the growth plate is cupped proximally (arrowheads), the pin trajectory is distal and lateral. B. On the lateral view, the knee is rotated so to obtain a perfect lateral with the posterior condyles superimposed. The femoral pin position (black circle) appears to overlie the growth plate due to the cupping. The pin entry point is halfway between the anterior and posterior condyles, which is slightly anterior to the adult Schöttle point. The patellar tunnel is placed just proximal to the equator of the patella.

 

 

Because of proximal cupping of the medial distal femur growth plate, the Beath pin should be angled slightly distal across the epiphysis (TECH FIG 1A).

 

Placement distal to the growth plate will avoid relative migration of the reconstructed MPFL up the femoral shaft with growth.

 

A cross-table lateral fluoroscopic view is taken with the femoral condyles lined up perfectly. Because of proximal cupping of the edges of the distal femur condyle, the pin tip will project over the growth plate on

the lateral view.21 The pin is usually placed about halfway between the anterior and posterior border of the femoral condyle projections that are perfectly aligned on the lateral view (TECH FIG 1B).

 

This is slightly anterior to “Schöttle point,” as described for adult MPFL surgery.31

 

If the pin is driven all the way across the condyle and out the skin, it will bind on the on the IT band and make isometery and motion testing difficult. A 1-cm incision is made over the pin, stabbing down to the condyle to make a soft tissue tunnel down to the bone.

Isometric Testing

 

Isometry should be pretested before drilling the femoral tunnel. An umbilical tape is looped around the femoral guide pin and then passed under the medial patella retinaculum using a tonsil clamp placed through the anteromedial patellar incision. With the 22-gauge steel wire, the umbilical tape is pulled through the patellar tunnel.

 

The ends of the umbilical tape are then clamped together with the knee at about 45 degrees. With a finger palpating the tension in the umbilical tape, the knee is flexed to 120 degrees and then extended to full hyperextension.

 

If the tape is too tight with hyperextension, the patella will pull medially. The guidewire should be moved slightly anterior, which is the most common correction.

 

If the tape is too tight in flexion, the pin should be moved slightly posterior.

 

About one-third of the time, the pin position needs to be readjusted to optimize isometry.

Graft Placement and Completion

 

Once isometry is acceptable, the thinnest end of the semitendinosus graft is pulled through the patellar tunnel and folded back on itself so it is a doubled graft. Then the two free ends of the tendon are sewn together with a no. 2 nonabsorbable suture using locking Krackow technique so that about 25 mm of tendon will pull into the femoral socket (TECH FIG 2A).

 

The doubled tendon end is sized (usually to 5 to 6 mm in diameter). The femoral socket is drilled to the tendon diameter and about two times the anticipated depth, so as not to “bottom out” in the socket during tensioning.

 

 

 

TECH FIG 2 • A. The hamstring graft is looped through the patellar tunnel, folded back on itself, and then the two free ends are sewn together. The doubled tendon ends are sized, and the femoral guide pin is reamed to the same diameter. The tendon is routed under the soft tissue and out the femoral incision and then drawn back into the femoral socket with the guide pin, which is pulled out laterally. B. Axial view showing the hamstring graft in its final position being looped through the patellar tunnel and the doubled ends fixed into the femoral socket with an interference screw.

 

 

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The tendon graft is then drawn under the medial retinaculum and brought out through the medial soft tissue tunnel surrounding the guide pin. The suture is placed in the guide pin eyelet. The interference screw's guidewire is placed in the socket before pulling the Beath pin across the distal femur and out the lateral side to sink the graft in the femoral socket.

 

Light tension is placed on the tendon at 45 to 60 degrees of flexion, and the knee is fully flexed and extended to allow the graft to seek its level of zero tension.

 

The graft is then fixed with a biocomposite interference screw (same diameter as the tunnel and usually

25 mm long) placed over the previously placed screw guide pin (TECH FIG 2B).

 

Ultimately, the graft should have no tension placed on it but instead should act as a leash that prevents patellar dislocation.

 

Standard closure is performed, and a knee immobilizer is placed.

• Medial Patellofemoral Ligament Reconstruction (Quadriceps Turndown Graft)

   

  The incision in the quadriceps mechanism and retinaculum is kept as extrasynovial as possible, especially directly medial to the patella and distally.

   

  The retinaculum is dissected from the subcutaneous tissue superficially back to the medial intermuscular septum (TECH FIG 3A).

   

  It is then dissected from the synovium deep back to the intermuscular septum.

   

  A puncture hole is made in the retinaculum immediately anterior to the intermuscular septum, superficial to the medial epicondylar insertion of the natural ligament, and immediately distal to the VMO.

   

  The distance from the widest portion of the patella to the planned puncture site is measured.

   

  The medial 6 to 8 mm of full-thickness quadriceps tendon is taken typically as a 50- to 60-mm long graft remaining attached to the superior pole of the patella (TECH FIG 3B).

   

  The graft is subperiosteally reflected distally about 10 to 12 mm from the superior pole of the patella (more distally laterally than medially to allow it to fold over on itself during fixation and tensioning).

   

   

   

  TECH FIG 3 • A. The surgeon dissects deep to the medial retinaculum, posterior to the medial epicondyle and the medial intermuscular septum. B. If the MPFL is to be reconstructed, the surgeon measures the length of graft needed. A full-thickness quadriceps tendon graft 6 to 8 mm wide is obtained, with attachment to the patella maintained at its widest portion. C. The medial retinaculum is punctured at the point marked by placement anterior to the intermuscular septum, distal to the VMO, and superficial to the medial epicondyle. D. The graft is tensioned and secured to the medial retinaculum-intermuscular septum, also at 45 degrees.

   

   

  A nonabsorbable suture is placed in the free end of the graft, with a whipstitch or other graft stitch

  performed with two ends.

   

  The graft is then passed deep to the retinaculum through the puncture hole to the superficial side of the retinaculum (TECH FIG 3C).

   

  The tension is then set via the medial retinaculum suture plication as described earlier before setting the tension of the graft.

   

  At 45 degrees of knee flexion, the graft is then tensioned to allow no more than 25% lateral translation of the patella. (TECH FIG 3D).

   

  The graft is secured into position with no. 1 or 2 nonabsorbable suture placed through the medial intermuscular septum periosteum of the medial epicondyle and the graft and retinaculum at the puncture hole in the retinaculum.

   

  It is further secured by 0 absorbable sutures in the graft and retinaculum, catching the graft superficial and deep to the retinaculum as the free end of the graft is directed back toward the patella.

   

  The suture in the free end of the graft is also used to secure it into position.

   

  Once the graft is secured and imbrication is complete, the knee is flexed to 90 degrees to ensure that no overtightening of the quadriceps mechanism has occurred and that the sutures stay in place.

   

   

  Tracking of the patella is also checked as described earlier.26

   

• Medial Retinaculum Plication (Modified Insall)

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  After dissection of the subcutaneous tissues, a medial parapatellar incision is made, leaving about 2 mm of tendon with the vastus medialis obliquus (VMO) (TECH FIG 4A).

   

  This incision in the tendon and the retinaculum is made from about 3 to 4 cm above the superior pole of the patella distally to 3 to 4 cm distal to the inferior pole of the patella medial to the tendon, leaving enough retinaculum with the tendon to suture to.

   

  The entire depth of the tendon and retinaculum is incised.

   

  The knee is then held in 45 degrees of flexion, and the patella is held in position in the center of the trochlea (TECH FIG 4B).

   

  Three nonabsorbable no. 1 or no. 2 sutures are placed, but not tied, in a horizontal mattress fashion.

   

   

   

  TECH FIG 4 • A. Medial parapatellar incision is made with 2 to 3 mm of quadriceps tendon left attached to the VMO. B. The knee is placed at 45 degrees of flexion, with the patella centered in the femoral groove; set the tension of the medial side by imbricating the medial retinaculum.

   

   

  These are typically placed 25% to 40% across the width of the patella from medial to lateral, imbricating the edge of the tendon of the VMO and the retinaculum distally and laterally.

   

  With the three sutures held tight, the knee is placed through a range of motion, from full extension to 90 degrees of flexion, to check that enough imbrication has been performed.

   

  The sutures are then tied and a 0 absorbable suture is used above and below the imbrication to reinforce the tension set by these sutures.

   

  A running 0 absorbable suture then can be sutured over the imbrication to help reinforce the imbrication as well as lower its profile.

   

  The wound is irrigated and closed in layers.

   

  Absorbable 3-0 or 4-0 monofilament should be used in the skin.10,11

• Galeazzi Procedure (Semitendinosus Tenodesis)

   

  The semitendinosus tendon (posterior and distal to the gracilis) is harvested with an open tendon stripper, and the distal tendon is left attached to the proximal tibia.

   

  The free end of the tendon is secured with a Krackow type of locking stitch of no. 2 nonabsorbable suture.

   

  Through a midline incision, the patella is exposed to allow an oblique 4- to 5-mm drill hole placed from proximal lateral to distal medial in the coronal plane of the patella.

   

  A lateral release is performed about 1 cm lateral to the patella, extending from the proximal tibia to 1 cm above the proximal patella.

   

  The free end of the semitendinosus is passed retrograde up through the oblique tunnel, and the free end is folded back across the anterior surface of the patella periosteum and sutured to the anterior patella or sewn back to itself if its length permits (TECH FIG 5).

   

  The graft should be tensioned and fixed with the knee at 45 to 60 degrees flexion.

   

  A knee immobilizer is placed, and the patient may bear weight as tolerated. Early motion is encouraged.

   

  The Galeazzi procedure was reported to have an 82% redislocation rate and a poor functional outcome on the Kujala and International Knee Documentation Committee (IKDC) scales.10

   

   

   

  TECH FIG 5 • Galeazzi procedure. Semitendinosus is harvested and left attached distally. The free end of the graft is fixed into the oblique patellar tunnel.

   

   

  P.645

• Roux-Goldthwaite Patellar Tendon Hemitransfer

   

  A midline incision about 5 to 6 cm long is taken down to the patellar tendon and the proximal tibia.

   

  A lateral release is performed from about 1 to 2 cm above the proximal pole of the patella, distal to the tibial tubercle.

   

  The patella tendon is split in its midline, and the distal end of the lateral half is released from the proximal tibia insertion without damaging the cartilaginous tibial tubercle.

   

  The free end of the lateral tendon is passed posterior to the medial tendon and brought out and sewn into the soft tissue of the medial proximal tibia, preferably into the insertion of the sartorius muscle (TECH FIG 6).

   

  The hemitransfer is tensioned in 45 to 60 degrees of flexion, with equal tension on both halves of the tendon.

  The knee is immobilized for 4 to 6 weeks.

   

  TECH FIG 6 • Roux-Goldthwaite procedure in which the lateral half of the patella tendon is transferred into the soft tissue of the medial proximal tibia.

   

   

   

   

  PEARLS AND PITFALLS

   

  Indications ▪ Carefully select patients with proven instability.

  • Patients with patellofemoral pain and no instability signs are not good candidates for patellar stabilization.

  • MPFL reconstruction has excellent results in adolescents with recurrent traumatic patellar dislocation.

 

Tension setting

• The surgeon should make sure that the patella translates close to 25% of its width laterally after graft fixation. It should not be rigidly trapped in the trochlear groove.

• This is best done by setting the tension with the knee flexed about 45 degrees.

• Before closure, the knee is taken through the range of motion from 0 to greater than or equal to 120 degrees to ensure good alignment and to make sure that the graft is not under too much tension.

• When placing the interference screw in the femoral tunnel avoid pushing the graft deeper into the tunnel which will cause over-tensioning. Twist the screw in rather than push the screw in.

 

	Quadriceps ▪ Care must be taken not to detach the quadriceps graft from the patella graft completely. management ▪ Dissecting more distally on the lateral aspect of the patellar attachment allows for the graft to lay down on itself. The puncture site is positioned distal to the most inferior aspect of the VMO and immediately anterior to the intermuscular septum. When passing the graft through the puncture hole in the retinaculum, a snap or Kocher clamp is used to hold the stitch in the free end. It is pulled through in line with the graft (the surgeon should push anterior to posterior, not pull posterior to anterior).     Fixation ▪ The quadriceps graft is sutured at the patellar attachment as it folds over itself. problems (quadriceps)     MPFL ▪ The isometry of the femoral guidewire should be checked to avoid patellar reconstruction maltracking before drilling the medial epicondyle tunnel. (hamstring) ▪ The tendon is passed through the patellar tunnel with a Hewson suture passer or a folded 22-gauge steel wire.     Galeazzi ▪ The hamstring tendon is passed retrograde through the patellar tunnel using a procedure Hewson suture passer or a guide pin with an eyelet. The transferred hamstring tendon is tensioned with the knee flexed 30-60 degrees.     Roux- ▪ The surgeon should avoid overtensioning the transferred lateral half of the Goldthwaite patellar tendon to keep adequate tension on the untransferred half. procedure

 

 

POSTOPERATIVE CARE

 

MPFL reconstruction patients are placed in a hinged postoperative knee brace locked in full extension or a knee immobilizer.

 

Weight bearing is as tolerated but is protected with crutches until the patient regains quadriceps control resisted straightleg raise (hamstring graft) or is comfortable to walk with the knee fully extended in a knee brace (quadriceps graft).

 

Physical therapy for range of motion (passive and active assisted) should be started in the first few days to combat arthrofibrosis.

 

During the initial phase of therapy, patellar mobilization, quadriceps activation, straight-leg raises, pain modalities, and edema control are important.

 

 

P.646

 

Range of motion is unrestricted with the hamstring graft technique.

 

 

With the quadriceps turndown graft, knee motion is restricted to 0 to 90 degrees for the first 3 to 4 weeks postoperatively. At 4 weeks, full range of motion is allowed with progressive quadriceps strengthening,

edema control, and pain control, and gait training is initiated.

 

Brace use in community settings is continued until adequate quadriceps strength has returned (about 6 weeks).

 

From 6 to 12 weeks, there is continued progression of quadriceps strengthening and the addition of plyometrics.

 

Functional return to activities starts at 3 to 6 months postoperatively.

 

Galeazzi procedure patients have similar rehabilitation due to solid fixation if the tendon is sewn to itself.

 

Roux-Goldthwaite procedure patients are kept toe-touch weight bearing for 6 weeks postoperatively, owing to the less secure fixation of the transferred tendon into medial proximal tibia soft tissue.

 

 

OUTCOMES

Child and adolescent patellar dislocation, particularly recurrent traumatic dislocation, can often be

improved or cured with reconstructive surgery of the MPFL.21 This is in sharp contrast to the poor functional results of medial imbrication/reef procedures, VMO transfer, and lateral release procedures, all of which usually result in redislocation at a rate equal to nonoperative treatment in adult and pediatric

studies.23,28

Andrish1 suggested that failed MPFL reconstructions associated with trochlear or patellar dysplasia often necessitate a trochleoplasty, tibial tubercle transfer, or both.

Examination of the results of MPFL repairs (not reconstructions), many with suture anchoring into the patella, showed an unacceptably high rate of redislocation.

Paradoxically, lateral release has been shown to increase the tendency for lateral patellar dislocation rather than to relieve lateral tension and let the patella centralize.6

The time-honored Galeazzi procedure has recently been shown to have an 82% redislocation rate and poor overall outcome measured on the IKDC and Kujala scores.10

 

 

COMPLICATIONS

Failure of fixation is typically seen at the time of surgery if knee is tested from 0 to 90 degrees (quadriceps MPFL).

Late fixation failure is uncommon but can happen if flexion beyond 90 degrees is started too soon postoperatively (quadriceps MPFL).

Arthrofibrosis should be treated aggressively with manipulation under anesthesia if greater than 90 degrees of flexion is not obtained by 6 weeks.

Injury to the cutaneous nerves is common, and patients should be warned of this risk. It can be minimized with wellplaced small incisions.

Recurrence is seen in less than 10% of patients after MPFL reconstruction.

Continued pain may occur, especially if not enough or too aggressive of a lateral release was performed, leading to either increased pressure on the patella or medial pressure and instability.

Patellofemoral pain is often unchanged from the preoperative condition. Apprehension sensation is often improved.

 

Patients with severe patellofemoral arthrosis and patellofemoral pain syndrome may not benefit from these procedures.

Skeletally mature patients with patellofemoral arthrosis may benefit from a procedure that moves the tibial tubercle more anterior (Fulkerson osteotomy).

Overtightening of medial soft tissue can result in medial dislocation. This is especially possible if a medial repair is tensioned in full extension or is combined with an extensive lateral release.

Care must be taken to avoid patellar articular cartilage penetration when drilling patella holes, especially with the Galeazzi procedure.

With the Roux-Goldthwaite procedure, there are reports of patellar tendon rupture of the untransferred tendon.

 

 

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