Updated: 2/25/2017
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TKA in Patella Baja (Infera)

Topic
Review Topic
0
0
Questions
8
0
0
Evidence
10
0
0
Techniques
3
https://upload.orthobullets.com/topic/5018/images/patellabaja sp TO_moved.jpg
https://upload.orthobullets.com/topic/5018/images/insallsal.do.jpg
https://upload.orthobullets.com/topic/5018/images/xr patella baja.jpg
Introduction
  • Patella baja is characterized by lowering of the patella relative to its normal position
    • may be congenital or acquired (this topic)
  • Pathophysiology of acquired patella baja
    • common causes include
      • proximal tibial osteotomy
        • patella baja is the most common complication seen following proximal tibial opening-wedge osteotomy    
        • may be caused by shortening of the patellar tendon during tibial osteotomy or from scarring of the patellar tendon post-operatively
      • tibial tubercle slide or transfer  
      • trauma to the proximal tibia
      • technical error during primary total knee replacement (joint line elevation)
      • ACL reconstruction
  • Associated conditions
    •  total knee arthroplasty
      • patella infera is an important consideration when performing total knee arthroplasty
        • improper technique may cause patella baja
        • special techniques must be utilized when performing TKA in patients with patella baja from congenital or acquired (tibial osteotomy, prior TKA) causes
Presentation
  • Symptoms
    • anterior impingement knee pain
    • knee stiffness
  • Physical exam
    • mechanical block to full flexion 
      •  limited flexion due to patellar impingement on the tibia in extremes of flexion
Imaging
  • Radiographs
    • recommended views
      • AP and lateral views of the knee
      • lateral view of the knee in 30 degrees of flexion
        • used to measure Insall-Salvati ratio
          • measures ratio patellar tendon length to patellar bone length 
          • normal Insall-Salvati is 1:1 between length of the patellar tendon length to patellar bone length
    • findings 
      • lateral view in extension
        • distal positioning of the patella in relation to the trochlear groove 
      • Insall-Salvati ratio of < 0.8 is consistent with patella baja
Treatment
  • Nonoperative
    • activity modifications, physical therapy
      • indications
        • mild symptoms in younger patients
  • Operative
    • total knee replacement
      • indications
        • severe impingement in older patients with osteoarthritis
Techniques
  • Total knee arthroplasty in patient with patella baja
    • methods to address patella infera during TKA
      • place patellar component superiorly
        • indications
          • mild patella baja 
        • technique
          • use a smaller patellar dome placed on superior aspect of patella
          • trim inferior bone to decrease flexion impingement
      •  lower joint line 
        • indications
          • moderate patella baja  
        • technique
          • add distal femoral augmentation  
          • cut more proximal tibia to lower joint line (lower tibial cut)
          • avoid bone cuts that raise the joint line
            • raising the joint line will effectively increase the patella baja deformity 
          • may require revision knee system
      • transfer tibial tubercle to cephalad position
        • indications
          • moderate patella baja 
        • technique
          • technique is difficult due to complexity of a tibial transfer in proximity to a cemented tibial component
        • outcomes
          • unpredictable bone healing leads to variable, and often poor, outcomes
          • patients may be left with extensor lag 
      • patellectomy 
        • indications
          • severe patella baja
        • techniques
          • alters the tension in the anterior knee mechanism
            • therefore recommended to use use a cruciate substituting system
          • consider partial patellectomy in which patella is resected to a width of 10-12mm.
            • lessens impingement & crepitus while maintaining some of the fulcrum of the patella.
 

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Technique Guides (3)
Questions (8)
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(OBQ08.221) A 70-year-old female has persistent anterior knee pain and stiffness 10 months status-post total knee arthroplasty with associated lateral patellar release. Radiographs before and after surgery are shown in Figures A and B respectively. Pre-operatively, her Insall-Savati ratio is 0.95, compared to 0.76 post-operatively. Which of the following is the most likely cause of her radiographic abnormality and pain? Review Topic

QID: 607
FIGURES:
1

Notching of the femur

1%

(35/3289)

2

Excessive resection of the distal femur and lateral release of the patella

57%

(1871/3289)

3

Preoperative patella baja

20%

(646/3289)

4

Excessive release of the patellar ligament from the tibial tubercle

4%

(145/3289)

5

Excessive resection of the proximal tibia

18%

(581/3289)

L 3

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(SAE07HK.58) Figure 35 shows the AP radiograph of a patient who underwent a previous upper tibial osteotomy (UTO). The patient may be at risk for which of the following during total knee arthroplasty (TKA)? Review Topic

QID: 6018
FIGURES:
1

Bone loss

8%

(37/485)

2

Patella alta

21%

(101/485)

3

Myositis ossificans

2%

(11/485)

4

Fracture

25%

(121/485)

5

Instability

44%

(213/485)

L 4

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(SAE07HK.24) What is the most frequent complication of both lateral closing wedge high tibial osteotomy and medial opening wedge osteotomy? Review Topic

QID: 5984
1

Patella baja

71%

(392/554)

2

Fracture

12%

(69/554)

3

Peroneal nerve palsy

5%

(30/554)

4

Compartment syndrome

6%

(35/554)

5

Infection

5%

(25/554)

L 2

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(SAE07HK.13) A 60-year-old patient had the procedure shown in Figure 7 performed 5 years ago. When converting this patient to a total knee arthroplasty (TKA), what patellar problem is commonly encountered intraoperatively? Review Topic

QID: 5973
FIGURES:
1

Fracture

1%

(8/537)

2

Patella baja

76%

(406/537)

3

Patella alta

10%

(53/537)

4

Osteonecrosis

1%

(3/537)

5

Maltracking

12%

(66/537)

L 2

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(SBQ07HK.24) A 25-year-old healthy, active male undergoes lateral closing wedge high tibial osteotomy. Which of the following complaints is most commonly associated with this procedure?





Review Topic

QID: 1609
1

Joint laxity

12%

(598/4888)

2

Infection

1%

(68/4888)

3

Anterior knee pain

62%

(3053/4888)

4

Quadricep weakness

20%

(972/4888)

5

Limb lengthening

3%

(170/4888)

L 4

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(OBQ04.2) A patient who has previously undergone a high tibial osteotomy 10 years prior is scheduled for a total knee arthroplasty (TKA). Which of the following factors is most likely to be present and may complicate the arthroplasty? Review Topic

QID: 113
1

Collateral ligament instability

9%

(261/2765)

2

Patella alta

8%

(220/2765)

3

Patella baja

78%

(2150/2765)

4

Patellar tendon insufficiency

3%

(71/2765)

5

Severe varus deformity

2%

(54/2765)

L 3

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SUBMIT RESPONSE 3
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