1. Constrained Liners in Neurologic and Cognitively Impaired Patients Undergoing Primary Total Hip Arthroplasty P. Hernigou, P. Filippini, A. Poignard, X. Roussignol, C. H. Flouzat-Lachaniette Hôpital Henri Mondor 94010 Creteil (France), University Paris XII University Paris XIIPhilippe.hernigou@wanadoo.fr

2. THA performed in patients with cognitive deficits or neurologic diseases No many series regarding dislocations after THA in neurologic or cognitively impaired patients. Cabanela, Weber /JBJS Am 2000 Historically, braces and hip spica casts were utilized post-operatively or after dislocation. But of course they are not well tolerated in this population.

3. The solution could be a constrained liner, but….. Most of constrained liners are associated with an increased risk of loosening. This risk of loosening is also increased in some neurologic disease as Parkinson disease. Osteolysis may be increased with some constrained liners. Hip surgery in neurologic diseases has other complications than dislocation

4. Between 1999 and 2004, 144 patients with neurologic disease received a constrained liner. 52 consecutive cognitively impaired patients (Alzheimer's, other forms of dementia), 30 patients with decreased muscle tone (e.g. Down's syndrome, Poliomyelitis, Myelomeningocele), 42 patients with increased muscle tone (Parkinson disease, cerebral palsy), 20 patients with stroke (associated with neck fracture on the hemiplegic side)

5. The results were compared with 120 arthroplasties performed for the same diseases between 1988 and 1999 40 consecutive cognitively impaired patients (Alzheimer's, other forms of dementia), 15 patients with decreased muscle tone (e.g. Down's syndrome, Poliomyelitis, Myelomeningocele), 30 Patients Parkinson disease 35 patients with stroke

6. Constrained liner with locking ring Groupe lépine, France

7. Constrained liner with locking ring The principle of retentiveness requires a more enveloping cup than the hemispherical model. The flange in the equatorial plane permits insertion of a split polyethylene ring reinforced by a stainless steel hooping.

8. This ring plays the role of a veritable retentive clip.

9. On crossing the equator of the cup, the head opens the ring,

10. which then closes through simple elasticity

11. Once the head has crossed the ring, it falls below the equatorial plane and the clip is closed against the enveloping part of the cup. So, In most situations the cup is not really a constrained linear. Only in movements at risk for dislocation, the ring is constrained.

12. Less than 30 Newtons (± 6 N) are required to successfully insert the head; however dislocation needs 2153 N (± 32 N). Lever out resistance 2153 ± 32 N Impaction: 30 N (28,3 ± 6N)

13.  End ‑ stage hip arthritis,  Sometimes associated with dysplasia  Osteonecrosis ( corticoids)  Fracture ( stoke and Parkinson)  as well as loss of independence with decreased ambulation. Hip Diseases

14.  All the liners and stem were cemented  Implantation as usual (posterior approach and same position for the cup)  Adductor tenotomy was performed in thirty patients, particularly in patients who have more severe contractures,  All patients were followed for a minimum of 5 years for radiographic evidence of implant failure. Technique

15. 38 patients with one dislocation (31%) 20 patients with recurrent dislocations ( 16%) with revision Risk increased particularly with - Parkinson disease (29%) - stroke (35%) Results in absence of constrained liners (120 patients)

16. At minimum 7 ‑ year follow ‑ up (range 5 ‑ 10 yrs), 3 radiographic failures (dislocations) of the 144 constrained liners (2%), No recurrent dislocation No loosening All patients subjectively exhibited improved ambulation and decreased pain. None of the patients required revision THA. Results with constrained liners (144 liners)

19. Dual mobility Discussion

20. conclusion We conclude that the use of constrained liners in primary THA in cognitively impaired patients or in neurologic patients is an efffective technique to prevent post ‑ operative hip dislocation while achieving good clinical results, and should be considered in this select at risk population.