PATELLAR DISLOCATION

PRESENTED BY-DR NAVEEN RATHOR RESIDENT DOCTOR R.N.T. MEDICAL COLLEGE

ANATOMY

-patella is a largest sesamoid bone roughly triangular in shape, with the apex of the patella facing downwards.The apex is the most inferior (lowest)

part of the patella. It is pointed , and gives attachmentto the patellar ligament.

- function of patella :

• 1)primary function is to increase the force production of the quadriceps; acts like a pulley to increase the mechanical action of the quadriceps

• 2)centralizes the divergent muscles of the quadriceps • 3)protects the femur

- Thus improving efficacy of quadriceps contraction- HOW - patella displaces the force vectors of quadriceps and patellar tendons away from the centre of rotation of knee

• In the patella an ossification centre develops between the ages 3–6 years.[1] The patella originates from two centres of ossification which unite when fully formed.

DEVELOPMENT

PATELLAThe upper three-quarters of the patella articulates with the femur and is subdivided into a medial and a lateral facet by

vertical ledge which varies in shape.

Wieberg classification

• Wieberg classify patella on the basis of size of medial and lateral facets-

• Type1-equal medial and lateral facet• Type2-medial facet is slightly smaller• Type3-medial facet is markedly smaller

BLOOD SUPPLYThe patellar network (circulatory anastomosis ) is an intricate network of vessels around and above the patella, and on the contiguous ends of the femur and tibia, forming a superficial and a deep plexus.

•

QUADRICEPS AND OTHER SOFT TISSUE STRUCTURE

• rectus femoris tendon: 8-10 cm in length, triangular in shape with insertion 3-5 cm in width at superior pole patella

• VMO tendon: inserts obliquely at superomedial border of patella,only a few mm in length; primary stabilizer of patella medially against VL

• vastus lateralis: inserts obliquely at superolateral aspect of patella, 2.8 cm in length

• lateral expansion of the vastus lateralis with a superficial and deep layer forms the lateral retinaculum; deep layer is the lateral patellofemoral lig: this is a static guide for the patella; this may decrease medial excursion and increase lateral tracking .

• medial side also has a PF lig, but it is much weaker than the lateral side

PATELLOFEMORAL JOINTThe patellofemoral joint (PFJ) is a complex structure with high functional and biomechanical requirements.

The normal function of this joint is dependent on the congruent relationship of the patella with the trochlear groove.

ARTICULATION

• no contact between the femur and patella in full extension;

• from extension to flexion, the patella: begins laterally and moves medially as the patella enters the trochlear groove and the tibia derotates;

• with flexion, patella enters the trochlear groove from the lateral side

• seats in the trochlea at ~20 degrees; at this point, the congruence and compressive forces provide stability

• from 0-20 degrees, stability comes from soft tissues

PATELLOFEMORAL CONTACT POINTSVariations in area of contact: inf. Surface – first contacts – 20 flexion ⁰Mid-portion – 60 flexion ⁰Superior portion – 90 flexion ⁰Extreme flexion( > 120 ) – only medially & ⁰laterally , quadriceps tendon articulates with trochlea

Patellofemoral Biomechanics

• Joint Reactive Force– In flexion, patella compressed

onto femur creating joint reactive force

-directly related to quadriceps force generation

-increases as the angle of flexion increases

– Stair climbing – 3.5 X BW– Deep bends – 7-8 X BW

The length of the lever arm varies as a function of :• Geometry of trochlea • Varying patellofemoral contact areas • Varying center of rotation of knee (flexion)

PFJ BIOMECHANICSPatellofemoral joint reaction force

WALKING 0.5xBW

STRAIGHT LEG RAISE 0.5xBW 0 DEG

CYCLING: 1.2 × BW

RISING FROM A CHAIR w ARMS: <3 × BW

STAIRS (UP OR DOWN) 3.3xBW 60 DEG

JOGGING & SQUAT–RISE 6xBW at 140 deg

SQUAT–DESCENT 7.6x BW at 140 deg

JUMPING UP TO 12 × BW

Ff

Ft

Fj

PostGrad Orth Deiary Kader

PATELLO FEMORAL INSTABILITY

Static stabilizers1. trochlear groove : primary bony stabilizers: depth, height patellar engagement

2 medial patello femoral ligament (MPFL): primary static soft tissue stabilizer 3 Medial retinaculam Dynamic stabilizerquadriceps (VMO)

CAUSES OF PATELLA INSTABILITY• Soft Tissue Restraints• Medial • MPFL Insufficiency• VMO dysplasia/VL dominance

• Lateral -- ITB, Contracture Lat Ret • Osseous abnormalities• Patella alta/ morphology• Trochlea dysplasia

• Lower limb Malalignment (Torsion or Genu Valgum)

– Fem anteversion, Ext tibia torsion, foot pronation– Increased Q angle or TT:TG distance

• Gait (Valgus thrust, Pelvis core muscles)

• Direct injury-Rare cause Knee flexed, quadriceps relaxed

>> patella forced laterally by direct force.

• Indirect injury-Common cause in athelets

MECHANISM OF INJURY

Sudden, severe contraction of quadriceps muscle

While the knees is stretch in FLEXION VALGUS & EXTERNAL ROTATION

Lateral patellar dislocation. (a) Drawing shows the classic mechanism of injury: fixed tibia, internal femoral

rotation, and quadriceps contraction.

PATTERNS OF DISLOCATION

ACUTE DISLOCATION-Single episode after a significant trauma.Almost always lateral dislocationRECURRENT DISLOCATION-• repeated, occasional dislocation (commonest form).• The dislocations may occur at intervals of weeks or months.HABITUAL DISLOCATION- also known as chronic dislocation• patella which dislocates every time the knee flexes.• in these cases it cannot be held in the reduced position throughout the full range of flexion. i

Recurrent Dislocation

• Second decade • Female preponderance / Athletic males• Initial episode of dislocation• Subsequent episodes of instability • Frequency decreases with Age(Crosby)• The main factor is incompetance of MPFL

Habitual dislocation

• Knees in which patella dislocates laterally each time knee is flexed and returns to midline in extension(Habitual dislocation)

• More severe –patella permanently dislocated –(Permanent dislocation)

PATELLO FEMORAL INSTABILITY

Who tends to recur• Young• Female• Family history• Bilateral• Atraumatic disorders• Anatomic abnormalities patella alta trohlear hypoplasia ↑TT-TG distance ↑ ‘q’ angle quadriceps dysfunction hyper mobility

PATELLO FEMORAL INSTABILITY

Evaluation We evaluate the following features1. Integrity of medial patello femoral ligament2. Height of patella on physical and radiographic

examination3. Length of patellar tendon4. Position of patella in relationship to trochlea

Patella AltaA patella alta, or high-riding patella, is a patella that is too high above the trochlear fossa and occurs when the patellar tendon is too long.

Patella alta is considered a main factor in patellofemoral misalignment because with patella alta, the degree of flexion needs to be higher for the patella to engage in the trochlea, compared with a normal knee.

This problem leads to reduced patellar contact area and decreased bone stability in shallow degrees of flexion.

About 25% of the patients with acute patellar dislocation have a high-riding patella depicted on MR images.

Note, however, that patella alta is a normal anatomic variant that is asymptomatic in most individuals.

Nevertheless, the diagnosis of a high-riding patella is important because it increases the risk of patellar dislocation in conjunction with other factors

Blumensaat's line

NORMAL

TROCHLEAR DYSPLASIA The normal trochlea is located in the anterior aspect of the

distal femur. It is composed of two facets divided by the trochlear sulcus

The lateral facet is the biggest, it extends more proximally than medial facet and is more protuberant in A.P. Aspect

Dysplastic trochleas are shallow, flat or convex These trochleas are not effective in constraining mediolateral

patellar displacement Is defined by a sulcus angle > 140° Trochlear dysplasia has been identified as one of the main

factors contributing to chronic patellofemoral instability.

TROCHLEAR DYSPLASIA

Radiological features

X- ray lateral projection of normal trochlea will typically show the contour of the facets, and posterior to them, the line representing the bottom of the sulcus is visualized and is continues with the intercondylarnotch line

TROCHLEAR DYSPLASIARadiological features

Crossing sign

The radiographic line of trochlear sulcus crosses the projection of the femoral condyles

The crossing point represents the exact location of the deepest point of trochlear sulcus which is about 0.8mm posterior to a line projected from anterior femoral cortex, in dysplastic trochlea it’s an point is 3.2mm forward to same

TROCHLEAR DYSPLASIA

Radiological features

Trochlear spur the supratrochlear spur corresponds to an attempt to contain the lateral

displacement of the patella

TROCHLEAR DYSPLASIA

Radiological features

Double-contour sign represents the hypo plastic medial facet, seen posterior to the lateral facet in

lateral view

TROCHLEAR DYSPLASIA

Classification of trochlear dysplasia

Type A: crossing sign + the trochlea is shallower than normal, but still symmetrical and

concave

Type B: crossing sign + supratrochlear spur +the trochlea is flat or convex in axial view

TROCHLEAR DYSPLASIA

Classification of trochlear dysplasia

Type C: crossing sign + double-contour sign + supratrochlear spur – representing hypoplasia of medial facet and lateral facet convex

Type D: crossing sign + double-contour sign+ supratrochlear spur +clear asymmetry of the height of facets, and referred to as a cliff pattern

Trochlear dyspla

Apprehension test of Fairbank

• Patella pushed laterally in 20-30 deg of flexion

Patellar tilt( Kolowich & Poulos)-in 20 degree knee flexion

-fingers are placed on medial side of patella and thumb on lateral aspect.

Dynamic Patellar Tracking

• Examiner standing in front of seated patient while the patient slowly extend the knee.

• J sign- lateral subluxation as the knee approches full extension.

Active patellar tracking(lateral pull test)

• Should be examined with the knee relaxed in the extended position.

• When the quadriceps muscle tightened ,motion of patella examined

• Normally,the patella should move more superiorly then laterally

Described by sir brattstrom firstly

an angle formed by the line of pull of quadriceps mechanism and that of patellar tendon as they intersect vat the centre of patella.

for measurements patella must be centre on trochlea by flexing the knee 30 degree.

Q- Angle

Q angle(described by sir Brattstrom)

Values vary-male 10-14 deg Female 17 deg > 20 Abn

• Increase in-genu valgum, external tibial torsion increase femoral anteversion• Increase Q angle more chance of Recurrent subluxation

IMAGING OF THE PATELLOFEMORAL JOINT

AP and Lateral Knee x-rayAxial viewMerchant’s viewMRI Axial viewCT Rotational Profile

Merchant’s

Blumensaat's line

NORMAL

Radiology- Insall Salvati Ratio

• T –Length of patellar tendon• P-greatest diagonal length of patella• Average T/P=1.02 SD 0.13(Insall) 1.04SD0.11( Aglietti)

>1.2 Patella Alta,<0.8 Patella infera

MEASURING PATELLA HEIGHT

Caton – Deschamps index =0.6-1.3Ratio between articular facet length of patella and distance between articular facet of patella and anterior corner of superior tibial epiphysis,knee flexed 30 degree.Patella infra-<0.6Patella alta>1.3

PostGrad Orth Deiary Kader

Blackburne-peel ratio-length of articular surface of patella to length measured from articular surfacevof tibia to inferior pole of patella.

-Measurement of patellar heightnormal rangr =0.54-1.06

Distance from Tibial Tubercle to Trochlear Groove(TT-TG)The position of the tibial tubercle is crucial for the inferolateral force vector of the patella. In a normal joint, the tibial tuberosity lies vertically under the femoral sulcus, directing the force vector inferiorly during knee bending.

However, if there is excessive lateralization of the tibial tuberosity, the patella is pulled laterally during flexion.

A tibial tubercle–trochlear groove distance of more than 20 mm is nearly always associated with patellar instability. Values of 15–20 mm are considered borderline, less than 15 mm is considered normal.

However, measurement of the lateral distance between the tibial tubercle and the trochlear groove is less accurate in individuals with severe trochlear dysplasia because no deepest point of the trochlea can be defined.

Image shows a normal distance of 12 mm between the tibial tubercle and the trochlear groove.

Image shows a distance of 22 mm, which is higher than the normal range

Trochlear Depth• Dejour used a true lateral radiograph

with the knee in 20 degree flexion To evaluath trochlear depth. -trochlear depth was defined as the

maximum distance of the trochlear groove from the line connecting the medial and lateral trochlear facets.

< 5MMmm consider pathiological.

Axial views• Various method have been described to taking

axial view.• Knee flexed in range of 20-45 degree.• Shape of patella should be evaluated ,along the

shape of the femoral trochlea and the relationship of patella to femur.

MERCHANTS VIEW

• An xray of knee while it is in 30 degree flexion,with the patellofemoral joint viewed tangentially.

• Show the position of the dorsal surface of patella as it sits in trochlear groove.

• Measurew sulcus angle and congruence angle

Merchants view: tangential axial view of patello femoral joint obtained with knee in 45° of flexion

Sulcus angle normal angle : 140° > 140° : trochlear dysplasia

Congruence Angle normal : -8°to+14° >14° indicates lateral subluxation

Lateral Patello Femoral Angle normal: angle opens laterally abnormal : angle opens medially or lines become parallel

Laurin’s view• Lateral patellofemoral angle is measured • Open laterally in normal knees• Open medially or parallel in recurrent dislocations

CT• Significant advantage– Avoids problems associated with positioning,obesity

etc– Avoid image overlap and distortion

• Look for – sulcus angle, tilt ,congruence and subluxation

• Reference line tangential to posterior condyles more accurate

CT classification of malalignment

• Type 1 -Subluxed with out tilt• Type 2-Subluxed with tilt• Type 3 tilt without Sublux• Type4 normal alignment

MRI SCAN-MR imaging can be used to diagnose prior patellar dislocation on the basis of typical injury patterns.

-In general, deformity or edema of the inferomedial patella and the lateral condyle, in conjunction with MPFL disruption and patellar lateralization, is diagnostic for recent patellar dislocation.

- More than two-thirds of the patients will show chondral or osteochondral lesions of the medial patella.

MPFL injury

Patella pain

Articular Damage

MRI SCAN

MANAGEMENT

CONSERVATIVE

SURGICAL

CONSERVATIVE MX• Non Operative management To be attempted in all patients.• -Goals –Normal flexibility,Balanced quadriceps

strength,Stretching of tight lateral structures

Push back w/o difficulty . Jt aspiration and immobilized in full extension for 3 weeks. >Splint;• If no sign of soft tissue lesion• Retained for 2-3 weeks• Quadriceps strengthening exercise ; 2-3 months.

TREATMENT OF PATELLA INSTABILITYConservative first

Quads strengthening Core stabilityMcConnell TapingInsoles

Quadriceps Training• Most essential component• Strengthening of quads esp. VMO• Isometric and progressive resistive ex. with knee

in extension• With increase in strength,Short arc exercises in

last 300.

McConnell patellar taping

• Indications • With certain knee injuries – such as

patellofemoral pain syndrome where abnormal patella tracking is contributing to the injury.

• To prevent injury or injury aggravation – Patella taping may be beneficial during sports or activities that place the knee (patellofemoral joint) at risk of injury or injury aggravation.

McConnell Medial PatellaTaping with the knee slightly bent, and rolled up towel under the knee.

Start the tape in line with the middle of the knee cap at the outer aspect of the knee. gently push the knee cap towards the inner aspect of the knee.whilst simultaneously using your fingers to pull the skin at the inner aspect of the knee towards the knee cap. Repeat this process 1 – 3 times depending on the amount of support required.

BAREFOOT RUNNING• Barefoot running may reduce patellofemoral joint

stress as a result of reduced joint reaction forces.• Barefoot runners are more likely to use a forefoot

vs a heel strike pattern in the initial loading response, which has been shown to increase ankle eccentric work and simultaneously decrease the loading on the knee joint.

SURGICAL TREATMENT

• Surgery in acute patellar dislocation indicated in-

• 1)osteochondral fracture• 2)loose body formation or joint incongruity• 3)incompetancy of MPFL

• Removal of loose bodies and MPFL repair required in these conditions.

• Recurrent dislocation• Anterior knee pain• Knee swelling• Recurrent haemartheosis

COMPLICATION

MANAGEMENT OF RECURRENT PATELLAR INSTABILITY

Defined as the condition where patellar dislocation had occurred at least twice,

or where patellar instability following initial dislocation

had persisted for more than three months A large number of procedures have been described. No single surgery is universally successful approach is to identify the underlying problem that

cause the patello femoral instability and systemically correct them

MANAGEMENT OF RECURRENT PATELLAR INSTABILITYThe surgical procedures are classified into proximal and distal realingmentIf the operation involves structures at or above the kneecap, it is

called a proximal and If the operation involves structures below the kneecap, it is called a distal realignment.

Proximal Realignment Of Extensor Mechanism 1.Lateral retinacular release 2. Medial plication/ reefing 3. VMO advancement 4.MPFL reconstruction

Distal Realignment Of Extensor Mechanism Medial or antero medial displacement of tibial tuberosity

MEDIAL PATELLO FEMORAL LIGAMENT RECONSTRUCTION

-Medial patello femoral ligament (MPFL) is the primary soft tissue passive restraint to pathologic lateral patellar dislocation, and MPFL is torn when patella dislocates, hence reconstruction of MPFL is done in an attempt to restore its function.

MEDIAL PATELLO FEMORAL LIGAMENT RECONSTRUCTION

indicated in : skeletally mature patient excessive lateral laxity normal trochlea ‘Q’ angle is normal TT-TG distance is < 20mm low grade trochlear dysplasia

Contraindications : skeletally immature

MEDIAL PATELLO FEMORAL LIGAMENT RECONSTRUCTION

Procedure >Graft harvesting and graft preparation

Patellar tunnel preparation

Femoral tunnel preparation

Femoral tunnel graft passage and fixation

Graft passage through patellar tunnel and fixation

Wound closure

Technique – Graft Harvesting-autologus semitendinous hamstring(prefer) or adductor magnus tendon graft used.Make a 3cm incision 3cm medial to the inferior portion of the tibial tuberosity.And harvest the graft.

Technique – Graft Preparationmeasure atleast 16cm of harvested

graft and remove any excess length,place a whip stitch in each

tail of graft

Technique – Patellar Preperation-Make a small incision just superomedial asprct of patella-Junction of Upper1/3rd and lower 2/3rdShould be at thecentre- notviolating ant.Cortex or articularsurface.Tunnel diameter-Minimal to avoidPatellar fracture

FEMORAL TUNNEL PREPARATION-make a 3cm incision in between the adductor tubercle and the

medial epicondyle.-select the site of femoral tunnel approximately 1cm distal and

5mm posterior to adductor tuberccle.

Graft Loop Through Patella

Graft was passed through a Soft Tissue Tunnel between Medial Retinaculum and Joint

Capsule(extrasynovial)

GRAFT FIXATIONGraft Fixed to the Medial Epicondyle of Femur

VID_20160725_182658.mp4

COMPLICATIONS OF MPFL RECONSTRUCTIUON

• 1)RESIDUAL INSTABILITY• 2)PATELLAR FRACTURE• 3)DECREASED ROM OF KNEE JOINT• 4)HAEMARTHROSIS AND WOUND COMPLICATIONS• 5)PATELLOFEMORAL ARTHROSIS• 6)ANTERIOR KNEE PAIN• Now a days due to modification in techniques

complications are very low and it considered as low risk and high rewarding method.

Lateral release >Indication-1)tight lateral structure prevent patellar centering2)lateral patellar pressure syndrome3)Can be done in skeletally immature patients>release to include-1)Lateral retinaculum from distal third of vastus

lateralis2)Lateral patellofemoral ligament3)Lateral patellotibial ligament.

• Can be done open or arthroscopy procedure(now a days arthroscopic release preferred)

• complication-• 1)Extending the release too far can cause medial

subluxation of the patella; in fact.** medial patella subluxation or dislocation is almost

always iatrogenic, secondary to an overzealous lateral release.

• 2)injury to suerolateral geniculate vessel(to prevent this make a superior anterolateral 2cm insion starting just lateral to the proximal pole of patella.

• Results varied,good results in short term(metcalf,Simpson),poorer in long term(Christensen)

Medial repair

• Anatomic and biomechanical studies have indicated that the MPFL and the VMO are the primary restraints to lateral patella translation, particularly early in flexion before full trochlear engagement.

• There are 3 types of primary procedures for medial repair,The techniques include

• (1) plication of the medial patellar retinaculum, (2) anatomic repair of the MPFL, and

• (3), anatomical repair surgery of the VMO.

Technique--make a 4cm incision at the superior pole of

patella,2cm medial and parallel to the medial border of patella extending distally.

-identify the vastus medialis and medial retinaculum,grasp these structure and pull them laterally to assesthe integrity of adductor tubercle attachment site.

-carefully incise the vastus medialis and medial retinaculum along the medial border of patella down to,but not through,the level of synovium.

-using no.2 ethibond suture,advance the medial retinaculum to the medial border of patellausing atleast four mattress suture.

Medial REEFING AND LATERAL RELEASE(NAM AND KARZEL)

• Alters line of pull of quadriceps• Does not alter Q angle or length of patellar

tendon• Can be done in skeletally immature patient.• 2 components –Lateral release + lateral and

distal advancement of medial structures in line of VMO.

DISTAL REALIGNMENT SURGERY

aims to diminish the q angle or TT-TG distance with anteromedialisation of tibial tuberosity and unloads patello femoral articulation .

Indications1. ↑ Q angle or ↑ TT-TG distance > 20mm2. Patellar alta3. Normal patellar glide4. Medial facet arthritisContraindications5. Skeletally immature patients6. incompetent MPFL 7. Diffuse patellar arthritis

ELMSLIE-TRILLAT OPERATION

• The procedure consist of lateral retinacular release,medial retinacular plication, and medial transfer of tibial tuberosity.

• Tibial tuberosity is moved 8-10mm medially and secured with a cancellous screw.

• Usually this method not indicated in atheletes due to high mean load to failure and total energy to failure rates.

• Specially reserved for patients with severe patellofemoral degenerative changes.

TECHNIQUE• Make a 6cm lateral parapatellar

incision approximatelly 1cm lateral to the patellar tendon.

• Perform the lateral release,the release is considered adequate when the patellar articular surface can be everted 90 degree laterally.

• Approach the tibial tubercle through the same incision,using a 2.5cm flat osteotome,raise a flat 6cm long,7mm thick osteoperiosteakl flap

• Rotate the flap medially,cracking the cortex distally,and hold it in place with a k-wire

• -knee is moved through a full passive range of motion to evaluate the patellar tracking.

• if tracking is acceptable,fix it with one or two 4mm cancellous screw

Fullkerson antero-medial tibial tuberosity transfer

>Modification of Elimslie trillat method Routine lateral retinacular release is done An oblique osteotomy is made from anteromedially

close to anterior tibial crest directed in postero lateral direction ,existing at lateral cortex posteriorly

Bone pedicle is displaced in an antero medial direction usually about 10to 15mm of anterization depending on obliquity of osteotomy

• Advantage-• Mechanical studies shows that elimslie-trillat

osteotomy(flat osteotomy)has significantly higher mean load to failure and total energy to failure then the fulkerson techniqur(oblique osteotomy)

Hauser

Fulkerson

DEROTATONAL HIGH TIBIAL OSTEOTOMY

• INDICATIONS-1)Femoral anteversion(thigh foot angle>30

degree)2)External tibial torsiuon3)Tubercle sulcus angle angle more than 10

degree.

MANAGEMENT OF TROCHLEAR DYSPLASIA

Surgical indications

High grade trochlear dysplasia with patellar instability in the absence of patellofemoral osteoarthritis

Type of dysplasia should be identified when deciding the procedure Associated abnormalities including TT-TG distance, patellar alta, patellar tilt

should be identified and rectified MPFL reconstruction is always done

Contra indications

Skeletally immature patients Associated osteoarthritis

MANAGEMENT OF TROCHLEAR DYSPLASIA

Type A dysplasia : medial patellofemoral ligament reconstruction

Type B and D dysplasia : sulcus deepening trochleoplasty with MPFL reconstruction

Type C dysplasia : lateral facet elevation trochleoplasty with MPFL reconstruction

Thank you