patello femoral instability 22

Dr.G.Ramesh M.S(Ortho)

Asst.Professor Dept. of Orthopaedics

Gandhi Medical CollegeSecunderabad

PTELLOFEMORAL INSTABILITY

Dantam

PATELLO FEMORAL INSTABILITY

INTRODUCTION:

patello femoral instability is a common but challenging treatment problem for an orthopaedic surgeon

The patellofemoral joint has a low degree of congruency by nature, hence it is susceptible to dislocation

Dislocation is a result of anatomical abnormalities and/or insufficient soft tissue restraints

Non-surgical approaches have been advocated to treat acute patellar dislocation, while many operative procedures, including proximal soft tissue or distal bony realignment procedures are designed to treat chronic / recurrent patellar dislocations

Addressing the specifics of anatomy, biomechanics, history, physical examination , and radiographic interpretation can shed important light on the treatment options of acute and recurrent patellar dislocations/and subluxations


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

2 medial patello femoral ligament (MPFL): primary static soft tissue stabilizer Dynamic stabilizer quadriceps (VMO)


Biomechanics

stability and normal tracking of the patella with knee flexion requires a complex co ordination of static and dynamic stabilizers. From o° to 30° of

the knee flexion, medial patello femoral ligament and other soft tissue are primary restraints to lateral patellofemoral dislocation. With the greater

knee flexion , the bony confines of the lateral femoral condoyle and trochlear groove captures the patella and patellar stability

PATHOLOGIC ANATOMY OF PATELLAR DISLOCATION

H. dejour classification

Primary instability factors1. Trochlear dysplasia2. Patella alta 3. Patella tilt4. ↑ TT-TG distance(‘q’ angle quantification by CT scan)

Secondary instability factors5. Excessive external femoral rotation / Excessive femoral ante version6. Excessive external tibial rotation7. Genu valgum8. Genu recurvatum ( these underlying pathologies predispose to an acute over load of soft tissue

stabilizers and rupture of MPFL with patellar dislocation following minimal trauma)


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


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


physical examination gait standing alignment ‘Q’ angle J sign laxity rotational malalignment


physical examination gait standing alignment ‘Q’ angle J sign laxity rotational malalignment for males : mean ‘Q’ angle is 10J° for females : mean ’Q’ angle is 15°±5°

↑’q’ angle leads to relative lateral shift of patella ↑’Q’ angle results from ↑ femoral external rotation ↑ external rotation genu valgum tibia vara



observe the movement of the patella during active knee extension, lateral subluxation of the patella as the knee approaches full extension is indicative of j sign positive

positive j sign indicates ↑ lateral force or ↑ ‘q’angle



patellar laxity

patellar translation is assessed by passively moving patella medially and laterally with knee at 0° and 30° of flexion, the amount of translation is quantified in quadrants. Normal glide is one but more than two quadrants indicates laxity


physical examination gait standing alignment ‘Q’ angle J sign laxity rotational malalignment patellar tilt

it is done with knee in full extension normally patella can be tilted so that the lateral edge is well anterior to the medial edge inability to do this indicates lateral retinacular tightness


physical examination gait external tibial torsion standing alignment ‘Q’ angle J sign laxity rotational malalignment

Measured by he relation ship of the transmalleolar axis to the Coronal axis of the proximal tibia, is typically neutral

tibial torsion also may be assessed through measurement of the thigh-foot angle, average values are 5°internal

leads to ↑’Q’ angle and ↑ TT-TG distance


physical examination gait excessive femoral ante version standing alignment ‘Q’ angle J sign laxity rotational malalignmen

measured by hip rotations with the patient in prone position with hips extended and knees at 90°of flexion

Normal range of hip rotations are about 45°. With ↑ femoral antevertion range of I.R. increases and range of E.R. reduced

conditions leads to ↑’q’angle and ↑TT-TG distance


Radiographic evaluation1. long standing weight bearing hip-to-ankle, A.P view

helps in assessing the angular deformity of knee i.e. genu varum and genu valgum


Radiographic evaluation

Lateral view with 30° of knee flexion

Insall-salvati ratio: normal value: 1.0 to 1.2 ↑value indicates: patella alta When patella alta is present ,the patella becomes engaged with greater degrees of

knee flexion , where the patella is not captured and it is at increased risk for instability

..


Radiographic evaluation

Lateral view with 30° of knee flexion

trochlear dysplasia: crossing sign double contour


Radiographic evaluationMerchants 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


CT scan evaluation• Helps in assessing the bony anatomy and architecture of patello femoral joint at different

angles of knee flexion• The protocol includes mid-axial images obtained from 0°to60° of flexion in 10° of increments• Is quantification of ‘q’ angle

TT-TG distance : normal measures are 2to 9 mm borderline measures are 10to 19 mm pathological > 20°

Sulcus angleCongruence angleTrochlear depth


CT scan evaluationThe protocol includes mid-axial images obtained from 0°to60° of flexion in 10° of increments

MANAGEMENT OF PATELLO FEMORAL INSTABILITY

Types of patellar dislocations Acute patellar dislocations Chronic / recurrent patellar dislocations

Acute patellar dislocations Results from high energy transfer, where anatomy of joint is normal Results from internal rotation of femur on a fixed externally rotated tibia Major sequelae of acute patellar dislocation is tear of medial patello

femoral ligament (MPFL) In general most acute dislocations are treated non-operatively unless

associated with an osteochondral injury When surgery is needed MPFL is repaired / reconstructed

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 to treat recurrent patellar dislocations

No single surgery is universally successful in correcting the chronic patellar instability

We need to customize surgery based on the knee problem Our approach is to identify the underlying problem that cause the patello

femoral instability and systemically correct them

MANAGEMENT OF RECURRENT PATELLAR INSTABILITY

The surgical procedures are classified into

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

The procedures like medial plication, vmo advancement, and lateral retinacular release are non anatomic procedures

They don’t address the principle of pathology in recurrent patellar dislocation

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 as a checkrein


Anatomy of medial patellofemoral ligament

MPFL arises from medial surface upper two thirds of patella above equator and inserts into a groove between adductor tubercle and medial epicondyle


Procedure 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 patients where MPFL is normal

MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION

Procedure

Examination under anaesthesia

Hamstring graft preparation

Exposer of MPFL


Procedure

Patellar tunnel preparation

Femoral tunnel preparation

Femoral tunnel graft passage and fixation

Graft passage through patellar tunnel and fixation

Wound closure

DISTAL REALIGNMENT SURGERY

Fullkerson antero-medial tibial tuberosity transfer aims to diminish the q angle or TT-TG distance with medialisation of tibial tuberosity and

unloads patello femoral articulation with anteriorisation of the tubercle

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

Fullkerson antero-medial tibial tuberosity transfer

Procedure Routine lateral retinacular release is done An oblique osteotomy is made from ateromedially close to anterior tibial crest

directed in postero lateral direction ,existing at lateral cortex posteriorly Mitek tracker drill guide with cutting slot is used to define precise osteotomy plane Bone pedicle is displaced in an antero medial direction usually about 12to 17mm

of anterization depending on obliquity of osteotomy

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

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 DYSPLASIA


Crossing sign

The radiographic line of trochlear sulcus crosses he 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


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

displacement of the patella

TROCHLEAR DYSPLASIA


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

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


Type of dysplasia and surgical procedure

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


Procedure: sulcus deepening trochleoplasty by Henrey Dejour

Indicated in type B and D trochlear dysplasia with patellar dislocation It is designed to establish a new trochlear groove of correct length and tilt ,

addressing the root cause of patellar dislocation due to trochlear dysplasia The femoral trochlea is deepened by removing the subchondral trochlear

bone followed by incision, impaction, and fixation of cartilage flare along the trochlear groove


Procedure pre-operative post-operative

MANAGEMENT OF PATELLOFEMORAL INSTABILITY

A management algorithm is proposed for clinical use

CONCLUSION

Patellofemoral instability can be difficult to treat Acute patello femoral dislocations should be treated with immobilization

and rehabilitation. Arthroscopy should be indicated for symptomatic osteochondral injury

In recurrent patellofemoral dislocations, it is important to understand each patients reason for repeated instability.

The reason can be determined through a detailed history, focused physical examination, and radiographic studies including CT scan and MRI

Once determined proximal realignment procedures, distal realignment procedures, trochleoplasty or a combination of above procedures can be tailored to the individual patient and be utilized to correct patellofemoral biomechanics

Thank you