Survival of uncemented acetabular monoblock cups

Abstract

Background and purposeMonoblock acetabular cups represent a subtype of uncemented cups with the polyethylene liner molded into a metal shell, thus eliminating—or at least minimizing—potential backside wear. We hypothesized that the use of mono​block cups could reduce the incidence of osteolysis and aseptic loosening, and thus improve survival compared to modular designs.Patients and methodsWe identified all 210 primary total hip arthroplasty (THA) procedures in the Swedish Hip Arthroplasty Register that used uncemented monoblock cups during the period 1999–2010. Kaplan-Meier and Cox regression analyses with adjustment for age, sex, and other variables were used to calculate survival rates and adjusted hazard ratios (HRs) of the revision risk for any reason. 1,130 modular cups, inserted during the same time period, were used as a control group.ResultsThere was a nearly equal sex distribution in both groups. Median age at the index operation was 47 years in the monoblock group and 56 years in the control group (p < 0.001). The cumulative 5-year survival with any revision as the endpoint was 95% (95% CI: 91–98) for monoblock cups and 97% (CI: 96–98) for modular cups (p = 0.6). The adjusted HR for revision of monoblock cups compared to modular cups was 2 (CI: 0.8–6; p = 0.1). The use of 28-mm prosthesis heads rather than 22-mm heads reduced the risk of cup revision (HR = 0.2, CI: 0.1–0.5; p = 0.001).InterpretationBoth cups showed good medium-term survival rates. There was no statistically significant difference in revision risk between the cup designs. Further review of the current patient population is warranted to determine the long-term durability and risk of revision of monoblock cup designs.

Cemented versus uncemented fixation in total hip replacement: a systematic review and meta-analysis of randomized controlled trials

“…While uncemented stems had a lower revision rate due to loosening they had a higher revision rate due to periprosthetic fracture in the first two postoperative years. Weiss et al 53 on the other hand reviewed the Survival of uncemented acetabular monoblock cups which represent a subtype of uncemented cups with the polyethylene liner molded into the metal shell and compared their survival to the modular designs in 210 hips from the Swedish Hip Arthroplasty Register. They concluded that both cups showed good survival rates at 11 years of follow up.…”

Appraisal of evidence base for introduction of new implants in hip and knee replacement: a systematic review of five widely used device technologies

“…The New Zealand registry reported revision rates per 100 observed component years of in total 10 501 uncemented monoblock cups (MoP and CoP articulations), which varied between 0.23 (95% confidence interval 0.06 to 0.59) and 0.64 (0.45 to 0.88) and which were similar to or slightly better than revision rates with uncemented modular variants (0.64 (0.50 to 0.81) to 0.76 (0.65 to 0.88), n=35 650). The Swedish Hip Registry reported a five year survival of 95% (91 to 98) of all 210 uncemented monoblock cups in the registry, which was similar to the survival of the chosen reference, which consisted of all 1130 most commonly used uncemented metal-backed cup designs implanted during the same period (five year survival 97% (96 to 98)) 25. The Finnish registry reported 100% survival of 136 implanted Morcher uncemented monoblock cups.…”

“…The Swedish Hip Registry reported a five year survival of 95% (91 to 98) of all 210 uncemented monoblock cups in the registry, which was similar to the survival of the chosen reference, which consisted of all 1130 most commonly used uncemented metal-backed cup designs implanted during the same period (five year survival 97% (96 to 98)). 25 The Finnish registry reported 100% survival of 136 implanted Morcher uncemented monoblock cups. One large US single-institutional survival registry (n=9584 total hip replacements, Mayo clinics) reported similar survivorship of in total 634 monoblock cups of three different brands after 4.7 to 8.2 years of follow-up when compared with the reference cup (Harris Galante).…”

An isoelastic monoblock cup versus a modular metal-back cup: a matched-pair analysis of clinical and radiological results using Einzel-Bild-Röntgen-Analyse software

“…The main purported disadvantage of this cup design is the lack of modularity, which rules out isolated liner exchange in cases involving early periprosthetic infections and after extended wear. Furthermore, assessment of proper cup seating due to the missing central screw hole is unfeasible with this cup design [ 26 ]. Coupled with the reasonable outcomes obtained using modular cups, these potential disadvantages of monoblock cups precluded their increased usage [ 21 , 22 ].…”