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

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

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

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%

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

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

Risk factors suspected: bilaterality weight leg length difference

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

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

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

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

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

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

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 ?

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

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

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

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

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

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

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

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

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

Cup orientation

Cup orientation 45°

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

female 60 years, mild right hemiparesis

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

male, 58 years trochanteric advancement

Constrained liner

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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