Case 6 Patellar Instability

Case 6

Patellar Instability

What happened ?                          Age at first dislocation ?                     Any Trauma ?

Other joint involved ?

Exposure - Patient standing with exposure upto umbilicus wearing undewear

Look

Alignment of lower Extremity

– Both patella facing forward ?

-At same level ?

                                                 -Any Genu Valgum  ?

Walking

Squatting

Skin normal

Quadriceps muscles wasting

Feel

Temperature

Palpation

-          Sost tissue

-          Deep

Trochlear Groove – tenderness

Patellar Surface

Knee ROM

Special Tests

                        Apprehension test at 30 degree flexion

Patellar Tilt > 20 degree abnormal

Patellar Glide > 2 1/2quadrant abnormal

Patellar Grind +

                                                               

Meaurement – Quadriceps muscle wasting and

Q-angle

Hip -  ROM – External rotation (ER) is more than Internal rotaion (IR) . In case of excess Femoral Anteversion , IR > ER

Thigh foot axis – just check it with eye balling

                

Discussion

X-ray –

1)AP and Lateral View Knee

            Osteochondral fragments

            Patella Baja (Insall Salvati Ration < 0.8 )

Patella  Alta ((Insall Salvati Ration > 1.2 )

(Insall Salvati Ratio – diagonal patellar length / patellar tendon length )

Bluemansat Line – at 30 degrees knee flexion in X-ray lateral film of knee , an imaginary line passing through roof of intercondylar notch . Patella lying above this line is also a Patella Alta.

2) Mechant’s View

            Patellar Tilt < 10 degrees

            Congruence angle -16 to -10

            Trochlear Dysplasia

2) MRI Knee – to see Articular lesion , stat of Medial Patellofemoral Ligament

3) CT Knee – to assess TT-TG distance

Pictures

Xray Knee Lateral View

To see Patellar Tilt Angle                                           

Suculus Angle

Congruence Angle

Page 12

CT – TT – TG distance

Types of Patellar Instabilities

Etiological Factors

1)Bony – Increased Q Angle, Trochlear Dysplasia

2) Malalignment – Excess femoral Anteversion , Tibial Extortion ,Genu Valgum

3)Soft tissue –Weak Vastus Medialis Obliqus , Tight lateral Retinaculum

4)Medial Patellofemoral Ligament Rupture

5)Ligamentous Laxity

Treatment

Depends on     Age ,

 Q – Angle ,

TT-TG (Tibia Tuberosity – Trochlear Groove ) distance

Conservative

1)Cylindrical Cast

2)Soft tissue Procedures

a) Above Patella

Lateral Retinacular Release

VMO Advancement

b)Below Patella

                        Roux-Goldthwait (medialization of lateral one third of patellar tendon )

                        Galeazi (rerouting Semi-tendinosis)

3)Bony

            a)Elmslie-Trillat – Medialization TT

            b)Fulkerson – Medialization and Anteriorization of TT

            c)Hauser – medialization , distal and posterior positioning of TT .

                        (Shortcoming – increases patellofemoral joint reaction force and not done anymore )

            d)Macquet – Anterior transfer –TT

                        High incidence of skin necrosis , compartment syndrome , no effect on         Q angle

               

                       

                             

How this  is Different from Habitual Dislocation of Patella ?

Patella Doesnot dislocate every time knee is flexed.

Cause of Habitual dislocation of Patella

Quadriceps Contracture , Hypoplasia of Patella ,Iliotibial band (ITB) contracture , femoral dysplasia