Success after surgical treatment of unstable hip prosthesis: 12 years of experience in a Third Level Hospital.

Objetives: Hip arthroplasty instability is one of the most worrisome complications and one of the main indications for revision surgery. We present a retrospective study evaluating the results of revision hip replacement surgery performed for instability.

Material And Methods: Observational, retrospective study from 1/12/2010 to 1/12/2022. Fifty-nine medical records of patients operated for hip dislocation were reviewed. Epidemiological variables and data such as type of dislocation based on Wera classification, cup position based on Lewinnek, type of implants, associated surgical techniques and the results in terms of recurrence of dislocation or reoperation were recorded.

Results: 59 patients: 33 women, 26 men, mean age 77.0 years. Mean follow-up 3.2 years (range 1.6-13.1). Based on Wera: had a single cause 37 cases, 2 causes 19 and 3 causes or more, 3 cases. In 61% of the cases in the series, malposition of the cup played an essential role in the dislocation (type I Wera). In the series, the Lewinnek zone could not be evaluated in 7 cases. For the remaining patients, 30% were within the Lewinnek zone. Only one patient in the series had a history of lumbar instrumentation. Implant used: double mobility (DM) in 17 cases (28.8%) and a constrained system in 38 cases (64.4%). Heads with adaptive cone were used in 2 cases (3%). In 4 cases (6%) a modified Whiteside type plasty was associated. Girdlestone was indicated in 2 cases (3%). Recurrence of dislocation 1 occasion: 18 cases (31%); 2 or more occasions 7 cases (12%). Re-operation 15 cases (25%) range (1-5), main reasons: instability, infection or peri-prosthetic fractures. Probability of success defined as no recurrence: at one year is 80.5%, and at two years is 70.6%, showing no differences between constrained or dual mobility implant.

Comments And Conclusions: Hip prosthesis dislocation is multifactorial in origin, although in most cases in the series the key factor was malposition of the acetabulum. Constrained and DM implants showed similar effectiveness. The results of this study emphasize the need for techniques that allow adequate positioning and orientation of the acetabular component to prevent, in a high percentage of cases, the need for this type of revision surgery.