dislocation after total hip replacement etiology and management pekka ylinen orton/ invalid...
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Dislocation after Total Hip Replacement
Etiology and management
Pekka YlinenORTON/ Invalid Foundation
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Dislocation
leaves a patient apprehensive tarnishes a surgeons reputation cause extra cost to health care system
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Dislocation
incidence risk factors (patient, surgical, implant) diagnosis principles of treatment case presentations
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Dislocation after THR
overall incidence 2-3% (0,4-11%) in elderly (even 4% if older than 80 y) females ( f:m ~ 2:1) in revision 10-20%
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Dislocation after THR
Patient factors age female gender prior surgery DDH, prior fracture neuromuscular disorders dementia low grade infection alcohol abuse
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Dislocation after THR
Surgical factors component malpositioning offset not restored failure to preserve abductor mechanism
leg length not restored posterior approach
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Risk factors
bilaterality weight leg length difference
suspected:
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Dislocation after THR
Implant factors neck design
- neck cross section- offset- Morse taper length
small head skirted head std. acetabular design vs. elevated cup wall
skirt
poor head-neckratio
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greatest risk within the first few weeks after op. - 60%-80% occur in three months- component malorientation
late instability- 23% after one year, 14 % after 5 years- loss of soft tissue integrity
Dislocation after THR
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Dislocation rate vs. head size and surgical approach
Position 22 mm 28 mm 32 mm
Anterior 2,6% 1,3% 2,1%
Posterior 6,8% 6,0% 3,5%
Woo, Morrey JBJS (Am) 64:1295, 1982
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Dislocation after THR
Rates according to surgeon volume
1-5/year 4,2 % 6-10/year 3,4 % 11-25/year 2,6 % 26-50/year 2,4 % > 50/year 1,5 %
JBJS (Am) 83:1622, 2001
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Surgical approach and THR dislocation
controversial according to literature - quality of orthopaedic literature recarding
THR dislocation is limited
- no prospective studies of sufficient power exist
14 articles fulfilling 5 to 8 inclusion criteria:
- 3,23% for the posterior approach- 0,55% for the direct lateral approach
Clin Orthop 405, 2002
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Treatment
modular component exchange trochanteric advancement bipolar rearthroplasty jumbo femoral heads constrained acetabular components
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For patients who do not have malpositioning of the components or abductor dysfunction increasing neck lenth increasing femoral head size using more lipped and/or reoriented liners
Modular component exchange
be aware about - malposition- impingement
?
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Effectiveness of Modular component exchange*
Author N Follow-up
(years)
Success (%)
Toomey et al. JBJS 2001
13 5,8 77
McGann and WelchJ Arthroplasty 2001
26 3,6 96
Earll et al.J Arthroplasty 2002
29 4,6 69
* without implant malpositioning
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Trochanteric advancement
in monobloc implants without option to increase neck length proximal migration of fractured or ununited trochanter
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Bipolar rearthoplasty
good in gaining stability (~ 80%) bad in functional outcome due to articulation with exposed acetabular bone
JBJS (Am) 82:1132,2001
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Jumbo femoral heads
maximal head to neck ratio minimizes implant impingement 32 mm
- acetabular component size - thickness of the polyethylene
36-38 mm ? tripolar arthroplasty
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Constrained acetabular components
restricted range of motion and impingement thin polyethylene outcome maybe implant dependent? - Osteonics: loosening 2%
dislocations 4% J JBJS (Am) 80:502, 1998
- S-Rom: loosening 4% dislocations 9-29% J Arthroplasty 9:17,325, 1994
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Treatment strategy
Unstable THR
Implant malposition Implant in good position
Revise Impingement Abductor dysfunction
Modular exhangeLipped polyAnterverted polyLateralized poly
laxity non-union incompetent
Longer neckTrochantericadvancement
Refixation Constrained cup
Large head
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Treatment strategy
Pathology Surgical plan
Acetabular malposition
Revision
Rim augmentation
Femoral malposition Revision
Loss of tissue integrity
Trochanteric advancement
Constrained implant
Not defined
Constrained
implant
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First dislocation: treatment strategy
identify the direction of instability determine the cup orientation with C-arc cup orientation acceptable, one-half hip brace for 6 to 8 weeks anterior dislocation: cup in 20° - 30° anteversion, one half hip brace for 6-8 weeks posterior dislocation: cup in retroversion, cup revision
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Cup orientation
direct ap-view:if anterior and posterior rims are coincident the orientation is about 6° in anteversion
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Cup orientation
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Cup orientation
45°
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Cup orientation
the position of C-arcwhen the anterior and posterior rims are coincident shows the cup orientation
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female 60 years, mild right hemiparesis
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C-arc fluoroscope
x-rays (C-arc) vertical X-rays (C-arc) 13° to 15° anteverted
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male, 58 years
trochanteric advancement
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Constrained liner
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Prevention on hip dislocation
identify patient at risk restore femoral head offset larger femoral head restore leg length proper postoperative care
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