1. Dislocation after Total Hip Replacement
Etiology and management
Pekka Ylinen
ORTON/ Invalid Foundation

2. Dislocation leaves a patient apprehensive
tarnishes a surgeons reputation
cause extra cost to health care
system

3. Dislocation incidence risk factors (patient, surgical, implant)
diagnosis
principles of treatment
case presentations

4. 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%

5. Dislocation after THR Patient factors age female gender prior surgery
DDH, prior fracture
neuromuscular disorders
dementia
low grade infection
alcohol abuse

6. Dislocation after THR
Surgical factors
component malpositioning
offset not restored
failure to preserve abductor mechanism
leg length not restored
posterior approach

7. Risk factors
suspected:
bilaterality
weight
leg length difference

8. Dislocation after THR - neck cross section small head 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-neck
ratio

9. Dislocation after THR
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

10. 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

11. Dislocation after THR 11-25/year 2,6 %
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

12. 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

13. Treatment modular component exchange trochanteric advancement
bipolar rearthroplasty
jumbo femoral heads
constrained acetabular components

14. be aware about - malposition ?
Modular component exchange
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
be aware about - malposition
- impingement ?

15. Effectiveness of Modular component exchange*
Author N
Follow-up
(years)
Success (%)
Toomey et al.
JBJS 2001 13
5,8 77
McGann and Welch
J Arthroplasty 2001 26
3,6 96
Earll et al.
J Arthroplasty 2002 29
4,6 69
* without implant malpositioning

16. Trochanteric advancement
in monobloc implants without option to increase neck length
proximal migration of fractured or ununited trochanter

17. Bipolar rearthoplasty
good in gaining stability (~ 80%)
bad in functional outcome due to articulation with exposed acetabular bone
JBJS (Am) 82:1132,2001

18. 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

19. 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

20. Treatment strategy Unstable THR
Implant malposition Implant in good position
Impingement Abductor dysfunction
Revise
laxity non-union incompetent
Modular exhange
Lipped poly
Anterverted poly
Lateralized poly
Longer neck
Trochanteric
advancement
Refixation
Constrained cup
Large head

21. Treatment strategy Pathology Surgical plan Acetabular malposition
Revision
Rim augmentation
Femoral malposition
Loss of tissue integrity
Trochanteric advancement
Constrained implant
Not defined
Constrained
implant

22. 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

23. Cup orientation direct ap-view: if anterior and posterior
rims are coincident
the orientation is about 6°
in anteversion

24. Cup orientation

25. Cup orientation
45°

26. Cup orientation the position of C-arc when the anterior and posterior
rims are coincident shows the
cup orientation

29. female 60 years, mild right hemiparesis

30. C-arc fluoroscope
X-rays (C-arc) 13° to 15° anteverted
x-rays (C-arc) vertical

31. male, 58 years
trochanteric advancement

32. Constrained liner

33. Prevention on hip dislocation
identify patient at risk
restore femoral head offset
larger femoral head
restore leg length
proper postoperative care

34. Thank You for Your attention