Edward Tayton, Robert Elliott, Faisal Farooq Butt, William Farrington, Robert Sharp.
Medium term outcome for a constrained acetabular component at a single institution: what is important for success?.
J Ayub Med Coll Abottabad Jan ;31(4):602-7.

Background: The use of constrained Total Hip Replacements (THR) is controversial due to lack of definite indications and potentially high failure rates because of mechanical loosening or component failure. A review was performed to assess a departmental use of a single constrained acetabular component over a ten years period. Methods: Patient demographics, operative indications, complications and patient follow-up were recorded. Post-operative Oxford Hip Scores (OHS) were obtained via a combination of New Zealand Joint Registry interrogation and telephonic questioning. Cup version and inclination angles were obtained from standardised anteroposterior radiographs using established techniques. Results: Forty-four constrained components (in 39 patients) were implanted between 2005 and 2014. The mean age was 78 years with mean ASA 2.7 and mean follow-up 37.2 months (range 13–116). The mean post-operative OHS was 36 (SD 9.25), and there were 4 failures (3 dislocations and 1 peri-prosthetic fracture). The 3 dislocations had either cup ante version (AV) or inclination angles (IA) outside the data set interquartile range (AV 13–24°, IA 40–50°). The cup inclination was significantly lower ( p <0.01) in patients with pain on sitting. At post-operative follow-up, 14/39 patients had died from unrelated causes, with only 1 patient surviving beyond 6 years. Conclusions: Constrained acetabular components offer a solution to hip instability in a difficult group of patients. This study has shown good medium-term outcomes of a single component type in a predominantly frail group of low demand patients. Despite constraint, correct cup placement (particularly inclination) remains important to prevent dislocation or poor reported outcome.

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