Introduction: Instability of THR is a problem both for the patient and the surgeon. Its frequency varies from 3 to 20% in multioperated patients. When the cause is known treatment usually gives good results and one way of preventing dislocation is to increase the size of the prosthetic head. The cause for instability is multifactorial and sometimes the patients have predisposing factors: muscular weakness or neurological alterations that determine the need for constrained and bipolar cups.

Materials and methods: Constrained cups capture the prosthetic head preventing dislocation and studies have been published with widely differing results. The bipolar cup introduced by Busquet is based on a metal cup coated with hydroxyapatite that is fixated by means of 2 plots to the ischium and the pubis. The polyethylene insert captures a head of 22.2 or 28 mm. Dislocation, when it takes place, is between the metal cup and the insert, and a force much greater than that needed to dislocate a head of 22.2 or 28 mm in diameter is needed.

Results: In a multi-center study carried out on 238 bipolar cups, Leclerc reports a 3.3 % failure rate. Philippot using 106 bipolar cups, reports no dislocation and a survival of 94.6% at 10 years. Our personal series comprised 75 cases, (54 primary and 21 revisions) with only one episode of dislocation due to significant trauma.

Conclusions: The bipolar cup can be used in primary and revision surgery and is effective in decreasing dislocations in high-risk patients and is our option of choice in patients with neuromuscular alterations or multiple surgeries.

We evaluated long-term follow-up clinically and radiologically of patients with developmental dysplasia of the hip operated between 1956 and 1971 with adductor tenotomy and open reduction of the hip.

Ninety-six patients with developmental dysplasia of the hip were operated between 1956 and 1971. Their ages were from 10 months to 44 months. Eighty-eight patients (88.5%) were girls and 11(11.5%) were boys. There were 58 unilateral cases and 38 bilateral cases for a total of 134 operated hips. The cases with bilateral involvement were operated simultaneously. For all patients, the surgical team used the same technique consisting of open reduction through a Smith Petersen incision together with an adductor tenotomy and lengthening or tenotomy of the Psoas muscle. Postoperative immobilization was a pelvic-toe cast for one month followed by two plaster casts with abduction rod for three to five months. Postoperative follow-up was from 15 years to 44 years, 4 months (mean: 24 years, 4 months).

The clinical outcome evaluated pain, range of motion, limp, muscle strength, and leg length discrepancy. Radiological evaluation included Mose index, acetabular head index, Wiberg’s CE angle, medial articular space, Sharp’s angle, acetabular index of the weight-bearing zone, acetabular depth, radial quotient in unilateral cases, width and shape of teardrop, collodiaphyseal angle, Shenton line, and degenerative changes of the hip.

The results of clinical evaluation were: Excellent – 60 (44.7%), Good – 35 (26.1%), Fair – 26 (19.4%), Poor – 13 (9.7%). Radiological results according to a modified Severin classification were: Class I – 60 (44.7%), Class II – 33 (24.6%), Class III – 31 (23.1%), Class IV – 9 (6.7%), Class V – 1 (0.7%), Class VI – 0 (0%).

Complications were: infections in six hips (4.4%), three (2.2%) being deep ones. Avascular necrosis according to Bucholz and Odgen occurred in 38 hips (28.3%). Four hips (3%) were Type I, 31 hips (23.1%) were Type II, three hips (2.2%) were Type III. Degenerative changes occurred in 29 hips (21.6%) of which seven hips (5.22%) were Grade I, 12 hips (8.95%) were Grade II, and 10 hips (7.46%) were Grade III.

Our conclusions were: 1.) Open reduction of developmental dysplasia of the hip is a valid method in late treatment or failure of orthopaedic treatment. 2.) Clinical results are better than radiological results. 3.) The rate of degeneratives changes increases with long-term follow-up. 4.) The best radiological results are achieved in patients who are younger than one and half year of age at the time of surgery. 5.) There was a significant rate (23.1%) of avascular necrosis Type II according to the Bucholz and Odgen classification, but this can only be realized with long-term follow-up.