Case Presentation

Habitual Dislocation of Patella

Dr Sushil SharmaFirst Year MS Orthopaedic Resident

An Interesting Case

Patient Particulars

• Name : Amrita Pun• Age : 21• Sex : F• Address : Salyan-3,Yang• Date of Admission : 2014 July 28

History

• Chief Complaints– Difficulty in walking– Giving way of left knee for past 10 years

• History of Present Illness– Fall injury 10 years back, sustained injury to left

knee following which she had pain in left knee & difficulty in walking. Giving way of left knee.

Clinical Examination• Gait : Normal

• Inspection– No swelling, discoloration, scar

marks– Wasting of left quadriceps

muscle– Position of patella: Centrally

placed (In extension) & laterally dislocated in flexion

– Size of patella : Left appears small than right

– Attitude of leg: B/L varus

Clinical Examination

• Palpation:– No rise in superficial temperature– No superficial & joint line tenderness– No tenderness over patella– Patellar movement restricted medially– No patello femoral tenderness and crepitus

Clinical Examination

• Movement– Range of movement• Flexion

– Left Knee : 0-135– Right Knee : 0-135

• Loss of Extension : Not present• Internal rotation : 10 degree• External rotation : 10 degree

Clinical Examination

• MeasurementLEFT RIGHT

Q angle 25 degree 20 degree

Size of Patella 2.5 X3.5 cm 3 X 4 cm

Thigh Foot Angle 30 30

Clinical Examination - Special Tests

– Apprehension test : Negative

– Patellar grinding test: Negative

– Patellar tracking : Positive J Sign (Lateral subluxation of patella in flexion)

– Patellar glide test: • 1 quadrant medially• 3 quadrant laterally

– Patellar tilt test : Negative

Investigation

• Pre-operative investigation:– CBC (Within normal limit)– Serum Na, Serum K, Serum Urea, Serum

Creatinine (Within normal limit)– Serology : Non reactive– RBS : Normal– Urine RME : Normal

X-Ray B/L Knee AP

• Both leg in varus position

X-Ray B/L Knee Lateral

• Blumensaat line : Lower pole of patella on line with intercondylar notch.

• Insall-Salvati Ratio (N : 1)• Right: 1• Left: 0.8 (patella baja)

X-ray B/L Knee Skyline

• Left patella dislocated laterally out of the trochlear notch

• Left trochlear sulcus shallower than right.

SPECIAL AXIAL VIEWS OF PATELLA

HUGHSTON MERCHANT LAURIN

•Patellar Index : 14 (N: M – 15, F – 17)•Sulcus angle : 120(N : 118)

•Patellofemoral Index: 2.6 (N:1.6)

•Sulcus angle : 145 (N:138)

Management

• Surgical realignment is the treatment of choice.• Principle :– Medialization of Patella– Maintenance of proximal & distal alignment

• Surgery performed– Insall (Suprapatellar realignment) – Roux Goldthwait operation (Infrapatellar soft-tissue

realignment)

Management - Operative• Proximal realignment

• Release of tight lateral patellar retinaculum & vastus lateralis completely

• Plication of medial capsule & patellar retinaculum to strengthen the lax medial structures.

• Vastus medialis obliqus (VMO) was advanced & sutured to lateral border of patella & quadriceps, after locating patella in trochlear notch in 70 degree flexion.

LATERAL

MEDIAL

Management - Operative

Distal realignment

• Lateral third of patellar ligament was released from tibial tubersoity and passed underneath medial portion of patellar tendon & sutured upwards & medially to pes anserinus tendon

LATERAL

MEDIAL

Post Operative

• Above knee posterior slab with knee in 5 degree of flexion was given for first 5 days

• A long-leg hinged knee brace was applied later with the knee in 20° of flexion

• Partial weight bearing with crutches for four weeks was advised, during which the patient was encouraged to do static quadriceps strengthening exercises

• Knee mobilization and full weight bearing was started after four weeks.

Post Operative Results• Position of patella : Centrally placed

& no lateral dislocation on flexion.• Q angle : 20• Range of movement : 0 - 135• Extensor Lag : Not Present

Discussion

Anatomy

Introduction

• Habitual dislocation of the patella is a rare condition among adults, where the patella dislocates during flexion and relocates during extension without pain and swelling unlike the recurrent patellar dislocation.

• Predisposing factors – ligamentous laxity (in women, connective tissue disorder)– contracture of the lateral patellar soft tissues– patella alta– quadriceps contractures– hypoplasia of the lateral femoral condyle– genu valgum

Patho Anatomy

• Q angle– Male (8-10)– Female (15±5)

• Lateral pull : Vastus lateralis, Iliotibial band

• Medial pull : Vastus medialis obliqus (VMO)

• Increased Q angle : Patellar dislocation

Patho Anatomy

• Genu valgum• Increased femoral

anteversion• External tibial torsion• Internal femoral torsion• Tight lateral retinaculum

Types of Patellar DislocationType Dislocation Pain Swelling

Acute Dislocation In response to trauma Present Present

Recurrent Isolated episode in response to trauma Present Present

Habitual Everytime when knee is flexed Absent Absent

Congenital Since birth Absent Absent

Pathology

First episode of traumatic dislocationTear of capsule on medial side of patella

If improper healingPersistent laxity

Recurrent dislocationDamage to contiguous surface of patella & fem.

CondylesFlattening & then further dislocation

Clinical Features

• Symptoms– Feeling of insecurity in knee (Giving way of knee)

• Signs– Patellofemoral crepitus– Postive J sign– Increased Q angle

Management• Proximal realignment – Lateral release – Reconstruction of vastus medialis obliquus

• Distal realignment – partial medialization of the ligamentum patella– Medialization of tibial tuberosity.

• always lateral release is combined with medial augmentation

Typical Procedure

Acknowledgement• Prof Dr S.K. Biswas (HOD, Dept of Orthopaedics)• Asst Prof Dr Niraj Ranjeet• Dr Krishna Sapkota• Dr Pratyunta Raj Onta• Dr Alind Kishore• Dr Pabin Thapa• Dr Upendra Jung Thapa• Dr Manoj Prasad Gupta• Dr Prakash Dware• Department of Anesthesiology• Operation Theatre Staffs

References

• Campbell’s Operative Orthopaedics, 12th Edition

• Apley’s System of Orthopaedics & Fractures, 9th Edition

• Post Graduate Companion in Orthopaedics• Handbook of Fractures, 4th Edition

Thank You

Happy Dashain 2071