Dislocation after total hip arthroplasty
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Dislocation After Total Hip Arthroplasty. Mazloumi MD. Patient Risk F actors. Neuromuscular and cognitive disorders Patient noncompliance Previous hip surgery. Surgical Considerations. Approach S oft-tissue tension C omponent positioning Impingement Head size

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Dislocation After Total Hip Arthroplasty

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Dislocation after total hip arthroplasty

Dislocation After Total Hip Arthroplasty

Mazloumi MD


Patient risk f actors

Patient Risk Factors

  • Neuromuscular and cognitive disorders

  • Patient noncompliance

  • Previous hip surgery


Surgical considerations

Surgical Considerations

  • Approach

  • Soft-tissue tension

  • Component positioning

  • Impingement

  • Head size

  • Acetabularliner profile

  • Surgeon experience


Treatment

Treatment

  • Closed reduction

  • Revision options should target the underlying etiology.

    1- Tensioning or Augmentation of soft tissues

    2- Capsulorrhaphy

    3- Trochanteric advancement

    4- Correction of malpositioned of components

    5- Improving the head – neck ratio


Surgical approach

Surgical Approach

  • 75% to 90% of dislocations are in the posterior direction

  • Dislocation rate was 5.8% after a posterior approach versus 2.3% after an anterolateral approach

    (P < 0.01).

    Woo RY, Morrey BF: Dislocations after total hip arthroplasty. J Bone Joint Surg

    Am 1982;64:1295-1306


Surgical approches

Surgical approches

  • A recent meta-analysis involving 13,203 procedures dislocation rate :

  • 3.23% Posterior approach

  • 2.18% Anterolateral, approach

  • 1.27% Transtrochanteric, approach

  • 0.55% Direct lateral approach.

    Masonis JL, Bourne RB: Surgical approach, abductor function, and total hi arthroplasty dislocation. ClinOrthop2002;405:46-53.


Surgical approach1

Surgical approach

  • Larger heads (32 mm versus 22 and 28 mm)

  • Definitive posterior soft-tissue repair

  • These two influential elements (head size and soft-tissue tension) therefore may reduce or eliminate the disadvantage of the posterior approach with respect to instability.

    Goldstein WM, Gleason TF, Kopplin M, Branson JJ: Prevalence of dislocation after total hip arthroplasty through a posterolateralapproach with partial capsulotomyand capsulorrhaphy. J Bone Joint Surg Am 2001;86:2-7.


Soft tissue tension

Soft-Tissue Tension

  • Meticulous reconstruction of the posterior

    capsule and short external rotators after a posterior approach was shown to reduce dislocation from 4.1% to 0.0% at 1-year followup in a study of 395 patients.

    Pellicci PM, Bostrom M, Poss R: Posterior approach to total hip replacement using enhanced posterior soft tissue repairClinOrthop 1998;355:224-228.


Soft tissue tension1

Soft-Tissue Tension

  • Soft-tissue tension also can be greatly affected by femoral offset

  • Trochanteric nonunion increased the dislocation rate sixfold (17.6% versus 2.8%; P < 0.001).

  • large mismatch between femoral head size and acetabularcomponent size

    (>64 mm cap <26 mm head )


Component positioning

Component Positioning

  • Cup abduction of 40° ± 10° is considered to be the “safe zone” of lower dislocation risk.

  • Cup anteversion should be 20° ± 5°

  • Outside this safe range, dislocation in one study increased fourfold (6.1% versus 1.5%; P < 0.05)

    Lewinnek GE, Lewis JL, Tarr R, Compere CL, Zimmerman JR: Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am 1978;60:217- 220.


Component positioning1

Component Positioning

  • The pelvis of a patient in the decubitus position may be significantly adducted and anteverted relative to the table.

  • Adequate acetabularanteversion may be more critical with a posterior approach because it reduces forces on weakened posterior soft tissues


Impingment

Impingment

  • Impingement occurs when the prosthetic femoral neck impinges against the liner or other sessile object, such as cement, osteophyte, or heterotopic ossification .

  • head-to-neck ratio is important. Components with higher ratios impinge less readily


Impingment1

Impingment


Head size

Head size

  • The improved head-to-neck ratio reduces component impingement and increases ROM.

  • Larger heads are seated deeper within the acetabular liner, requiring greater translation before dislocation “jump distance”


Head size1

Head size

Polyethylene wear increases with larger heads and thinner liners, and wear leads to periprostheticosteolysis and the potential for loosening.


Liner profile

Liner Profile

A, Standard.

B, Elevated rim.

C, Oblique.

D, Lateralized


Surgeon experience

Surgeon Experience

  • In their study of more than 4,000 primary found that surgeons who had performed fewer than 30 procedures had a markedly higher dislocation rate (approximately twofold)

    Hedlundh U, Ahnfelt L, HybbinetteCH, Weckström J, Fredin H: Surgical experience related to dislocations after total hip arthroplasty. J Bone Joint Surg Br 1996;78:206-2


Revision

Revision


Dislocation after total hip arthroplasty

Dislocations within weeks or months

Problems with soft-tissue tension :

1- muscle weakness.

2- inadequate capsular healing and scarring.

3- component malposition.

4- infection.

5- patient noncompliance.

Late dislocations (beyond 1 year)

may suggest :

1- stretching of the soft tissues

2- polyethylene wear.


Salvage procedures

Salvage procedures

  • Constrained cup implantations

  • Dual-mobility hip components

  • Bipolar Femoral Endoprosthesis

  • Soft-tissue grafts

  • Girdlestone resection


Thanks

THANKS

THANKS


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