The Merete BioBall system in hip revision surgery: A systematic review.

BACKGROUND: Modular hip arthroplasty is widely recognized in hip surgery; nevertheless, despite advances in prosthetic design, the incidence of hip revision surgery is increasing. In these procedures, a modular adapter that engages the femoral stem and the modular femoral head could be useful in order to protect the neck-head junction and restore preoperative biomechanics and soft tissue tension when the femoral or acetabular component should be retained. The Merete™ BioBall™ system (Merete Medical, Berlin, Germany) could fill this need. However the literature regarding this device is sparse, therefore we performed a systematic review to analyze: the indications for its use and clinical results and the causes of second revision and survival in hip revision surgery, mainly focus in complications of its use.

MATERIALS AND METHODS: Databases including PubMed and Google Scholar were searched for English-language articles published between 01/01/1999 and 01/04/2017, using search terms related to the system Merete™ BioBall™. Studies that reported the clinical use of the Merete™ BioBall™ system in hip revision surgery were selected. Data related to the indications, characteristics of the implant, clinical results, causes of second revision and survival were gathered.

RESULTS: A total of 14 studies with a level IV evidence were analyzed. Information related to the implant was provided in 194 cases. Isolated acetabular revision was the main indication of implant use (139/194 [71.6%]). The most common combination used was the standard implant (69/110 specified [59.4%]), 3XL length (28/107 specified [26.2%]) with 32mm metal head (58/187 specified [31%]). After a follow-up ranging from 2 to 97 months, there were 16 complications, thirteen (81,2%) were revised, including one neck fracture of the stem (6.25%), two ceramic head fractures (12,5%) and six recurrent dislocations (37,5%). Implant survival was 92.8% at 52.5 months of follow-up in the longest published series. Clinical and functional results were provided in a heterogeneous way.

CONCLUSIONS: There is insufficient evidence to recommend for or contraindicate the use of the Merete™ BioBall™ system. The Isolated acetabular revision was the main indication of implant use. When dislocation is the indication of its use the rate of second revision is high. Some important complications possibly related with the implant design have been reported but as isolated cases. The neck adapter failure or corrosion phenomena have not been reported. Further prospective and controlled trials are needed to assess the use of this type of implant and its survival.

LEVEL OF EVIDENCE: Level III systematic review of case series.