patellar anatomy and injury explained extensor mechanism and injury explained

1. Patella Fractures & Extensor
Mechanism Injuries
Dr P. ROHIT RAJ
MBBS MS ORTHO
ASSISTANT PROFESSOR
ORTHOPAEDIC DEPARTMENT
VISHWABHARATHI MEDICAL

2. Patella Fractures & Extensor
Mechanism Injuries

4. Anatomy
• Largest sesamoid bone
• Thick articular
cartilage proximally
• Articular surface
divided into medial
and lateral facets by
longitudinal ridge
• Distal pole
nonarticular

5. Anatomy
• Patellar Retinaculum
– Longitudinal tendinous
fibers
– Patellofemoral
ligaments
• Blood Supply
– Primarily derived from
geniculate arteries

6. Biomechanics
• The patella is a link between the quadriceps
tendon and patella tendon and is subject to
significant forces.
• The patella increases the leverage of the
quadriceps muscle and elevates the
extensor mechanism away from the axis of
rotation of the knee joint.
• The area of contact between the patella and
distal femur varies according to the position
of the knee.

7. Classification
• Allows guidance with
treatment
• Types
– Undisplaced
– Transverse
– Apex
– Comminuted
– Vertical
– Osteochondral
Tip: Vertical fractures may not result in disruption of extensor mechanism

8. Nondisplaced Fractures

10. Transverse fracture
• nondisplaced = medial and lateral
retinaculum usually intact
• Transverse fractures commonly result
in wide fragment separation due to
Strong ligamentous traction

11. Vertical Fractures
• Account for 22% of patella
fractures*
• Typically results from
compression of patella with
flexed knee
• Sometimes only seen on
sunrise view

12. Stellate Fractures
• Result from direct
blow
• 65% of stellate fractures
are displaced
• May have associated
articular damage to
femoral condyles

13. Apex Fractures

14. Osteochondral Fractures

15. Insall-
Salvati ratio,
• The Insall-Salvati ratio or index is the ratio of the patella
tendon length to the length of the patella and is used to
determine patellar height.
• A: patellar tendon length (TL): length of the posterior
surface of the tendon from the lower pole of the patella to
its insertion on the tibia
• B: patellar length (PL): greatest pole-to-pole length
• Insall-Salvati ratio = A/B (or TL/PL)

16. Interpretation
• On plain radiographs:
• patella baja: <0.8
• normal: 0.8-1.2
• patella alta: >1.2

17. Patella alta
• high riding patella, describes a situation
where the position of the patella is
considered high. It may be idiopathic or
may result secondary to a patellar tendon
rupture.

18. Patellar tendon length (6cm) is > 20% than patellar
length (4cm), consistent with a patella alta

19. Patella baja
• Patella baja is an abnormally low lying
patella, which is associated with restricted
range of motion, crepitations, and
retropatellar pain. If longstanding, extensor
dysfunction may ensue with significant
morbidity.

20. patella baja: <0.8

24. Radiographic Evaluation
• AP & Lateral
– Note patella height (baja or alta)
– Note fracture pattern
• Articular step-off, diastasis
• Marginal impaction
• Special views
– Axial or sunrise
• CT Scan
- Occult Fractures
- Complex or Marginal Impaction
Fractures

26. sunrise (skyline) view of the
knee
Normal appearing lateral knee
radiograph in an elderly patient
Sunrise View: Non-displaced
Patellar Fracture of the
same elderly patient with normal
radiographs on the left.

27. Transverse and
displaced patellar
fracture

28.  Non-displaced patellar
fracture.
Comminuted Patellar Fracture

29. Radiographic Evaluation
• Bipartite Patella:
• Don’t get fooled!
– Obtain bilateral views
– Often superolateral corner
(Saupe Classification, 1923)
– Accessory ossification center
– Occurs 1-2% of patients

32. Operative Treatment
• Goals
– Preserve extensor function
– Restore articular congruency
• indicated for displaced fractures and
disruption of the extensor
mechanism.
• Approach
– Longitudinal midline incision
recommended
– Transverse approach alternative (dotted
lines) – potentially higher risk wound
problems, can limit initiation of ROM
– Consider future surgeries!

33. Procedure
Longitudinal
Incision
Clean Fracture
Site
Torn
Retinaculum

34. Procedure
Reduce & Compress Fracture

35. Operative Techniques
• K-wires w/ tension band wiring (TBW)
• Lag-screw fixation
• Cannulated lag-screw with TBW (tension
band screw – TBS)
• Partial patellectomy
• Total Patellectomy

36. Tension Band Wiring
• Transverse, non-comminuted
fractures
• Double Figure-8 wire for equal
compression

37. Tension Band Wiring
• Wire converts anterior distractive
forces to compressive forces at the
articular surface
• Retinacular Injury
– Keep open until the end
– Window to assess articular reduction
– Repair the retinacular injury last

39. Lag-Screw Fixation
• Indicated for vertical
fractures
• Contraindicated for
extensive comminution
and osteopenic bone

40. Example

41. Cannulated Lag-Screw With
Tension Band (TBS)
• Partially threaded
cannulated screws
(4.0mm)
• Wire through screws
and across anterior
patella in figure of
eight tension band
• Make sure tip of
screw remains buried
in bone so it will not
compromise wire

42. Cannulated Lag-Screw With
Tension Band
• More stable construct
– Screws and tension band wire combination
eliminates both possible separation seen at the
fracture site with K wire/TBW and screw
failure due to excessive three point bending

43. Partial Patellectomy
• Indicated for fractures involving
extensive comminution not amenable
to fixation
• Larger fragments repaired with screws
to preserve maximum cartilage
• Smaller fragments excised
– Usually involving the distal pole

45. Total Patellectomy
• Indicated for displaced, comminuted
fractures not amenable to reconstruction
• Bone fragments sharply dissected
• Defect may be repaired through a variety of
techniques

49. Complications
• Knee Stiffness
– Most common
complication
• Infection
– Rare, depends on soft
tissue compromise
• Loss of Fixation
– Hardware failure in up
to 20% of cases
• Osteoarthritis
– May result from
articular damage or
incongruity
• Nonunion < 1% with
surgical repair
• Painful hardware
– Removal required in
approximately 15%

50. Nonunion

51. Loss of Fixation

52. Malunion

53. Extensor Tendon Ruptures
• Adolescent- avulsion tibial tubercle
• Young adult sports-patellar
ligament tear
• Middle age adult -fracture of
patella
• Older people –quadriceps rupture
• Mechanism
– Fall
– Sports “The weekend warrior”
– MVA
– Tendonopathies, Steroids, Renal
Dialysis

55. Quadriceps Tendon Rupture
• Typically occurs in patients > 40 years old
• Usually 0-2 cm above the superior pole
• Level often associated with age
– Rupture occurs at the bone-tendon junction in
majority of patients > 40 years old
– Rupture occurs at midsubstance in majority of
patients < 40 years old

56. Quadriceps Tendon Ruptures
• Risk Factors
– Chronic tendonitis
– Anabolic steroid use
– Local steroid injection
– Inflammatory arthropathy
– Chronic renal failure
– Systemic disease

57. History
• Sensation of a sudden pop while stressing
the extensor mechanism (eccentric load)
• Pain at the site of injury
• Inability to extend the knee
• Difficulty weight-bearing

58. Physical Exam
• Effusion
• Tenderness at the
upper pole
• Palpable defect above
superior pole
• Loss of extension
• With partial tears,
extension will be
intact

60. MRI
• Palpable defect proximal to
superior pole of patella
• If defect present but patient
able to extend the knee then
the extensor retinaculum is
intact
• If no active extension, then
both tendon and retinaculum
completely torn

61. Quadriceps Tendon Rupture
Radiographic Evaluation
• X-ray- AP, Lateral, and
Tangential (Sunrise,
Merchant)
– Distal displacement of
the patella (patella baja)
• MRI
– Useful when diagnosis
is unclear
Treatment
• Nonoperative
– Partial tears and strains
• Operative
– For complete ruptures

62. Nonoperative Treatment
Quadriceps Tendon Rupture
• Reserved for incomplete tears in which
active, full knee extension is preserved
• Immobilize leg in extension for
approximately 4-6 weeks
• Progressive physical therapy required to
regain strength and motion

63. Operative Treatment-muscle-
tendon junction
• Reapproximation of tendon to bone using
nonabsorbable sutures with tears at the
muscle-tendon junction
• Early primary repair of quadriceps tendon
ruptures in recommended

65. Using suture anchor

66. mid substance tear

67. mid substance tear –
acute -Scuderi technique
• The Scuderi technique for repairing acute
tears of the quadri- ceps tendon.
• (A) The torn edges of the quadriceps tendon
are debrided and repaired.
• (B) A triangular flap of the proximal
tendon is developed, folded distally over the
rupture, and sutured in place

69. chronic
Treatment
• Chronic tears may
require a V-Y
advancement of a
retracted quadriceps
tendon (Codivilla V-
Y-plasty Technique)

70. Postoperative Management
• Immediate weight-bearing as tolerated
• Knee immobilizer, Hinged Knee Brace, or
cylinder cast for 5-6 weeks

71. Complications
• Re rupture
• Persistent quadriceps
atrophy/weakness
• Loss of motion
• Infection

72. Patellar Tendon Rupture
• Less common than
quadriceps tendon
rupture
• Associated with
degenerative changes
of the tendon
• Rupture often occurs
at inferior pole
insertion site

73. Patellar Tendon Rupture
• Risk Factors
– Rheumatoid arthritis
– Systemic Lupus
Erythematosus
– Diabetes
– Chronic Renal Failure
– Systemic
Corticosteroid Therapy
– Local Steroid Injection
– Chronic tendonitis

74. History
• Often a report of
forceful quadriceps
contraction against a
flexed knee
• May experience and
audible “pop”
• Inability to weight
bear or extend the
knee

75. Physical Examination
• Palpable defect
• Hemarthrosis
• Painful passive knee
flexion
• Partial or complete
loss of active
extension
• High riding patella on
radiographs (patella
alta)
• Quadriceps atrophy with
chronic injury

77. Radiographic Evaluation
• AP and Lateral X-ray
– Patella alta seen on lateral view
• Patella superior to Blumensaat’s line
• Ultrasonagraphy
– Effective means to confirm diagnosis by determining
continuity of tendon
– Operator and reader dependant
• MRI
– Effective means to assess patellar tendon, especially if
other intraarticular or soft tissue injuries are suspected
– Relatively high cost

78. Patella alta

79. Classification
• No widely accepted means of classification
• Can be categorized by:
– Location of tear
• Proximal insertion most common
– Timing between injury and surgery
• Most important factor for prognosis
• Acute: < 2 weeks
• Chronic: > 2 weeks

81. Nonoperative Treatment of
Patellar Tedon Rupture
• Nonoperative treatment reserved for partial
tears in which patient able to fully extend
knee
• Treatment is immobilization in full
extension for 3-6 weeks

82. Operative Treatment
• Surgical treatment is
required for restoration
of the extensor
mechanism
• Better overall outcome
• Primary repair of the
tendon
• Surgical approach is
through a midline
incision

83. osteotendinous
junction
• For rupture at osteotendinous
junction, tendon reattached to
patella with heavy,
nonabsorbable sutures passed
through drill holes in patella
• Medial and lateral retinacula
repaired with heavy
absorbable suture
• Knee immobilized in
extension for 6 weeks

85. Postoperative Management
• More conservative when compared to early
repair
• Bivalved cylinder cast for 6 weeks; may
start passive range of motion
• Active range of motion is started at 6 weeks

86. Complications
• Knee stiffness
• Persistent extensor weakness
• Rerupture
• Infection
• Patella baja (Insall-Salvati ratio of < 0.8)

87. Thank You!