Early Failure of Metal-on-Metal Large-Diameter Head Total Hip Arthroplasty Revised with a Dual-Mobility Bearing: A Case Report

Clinical usefulness and safety in the early phase after a newly designed rotating-platform total knee arthroplasty: A prospective multicentre cohort study with a 2-year follow up

BACKGROUND

This study aimed to assess the clinical results and safety of a newly designed rotating-platform posterior-stabilised total knee arthroplasty (TKA) in the early postoperative phase, within 2 years of follow up.

METHODS

This prospective, multicentre cohort study included 100 consecutive patients who underwent rotating-platform posterior-stabilised (PS) TKA (Vanguard PSRP). After excluding dropouts, 93 patients were analysed. The objective Knee Society Score (KSS)-2011, subjective KSS-2011, knee range of motion, EuroQol 5 Dimension index, complications, and survival rates were assessed before TKA and at 6 months, 1 year, and 2 years postoperatively. The scores at each time-point were compared, and the survival rate was assessed with revision as the endpoint. To demonstrate non-inferiority, the clinical outcomes of patients who underwent rotating-platform PS TKA were compared with those collected retrospectively from 50 patients who underwent fixed-PS TKA (Vanguard PS), defined as the control group.

RESULTS

All clinical outcomes at the final follow up significantly improved compared with their preoperative values (P < 0.001). The objective KSS-2011 was 90.0 ± 8.2 points, subjective KSS-2011 satisfaction was 30.7 ± 8.6 points, expectation was 10.4 ± 2.1 points, and functional activity was 74.0 ± 18.5 points at 2 years postoperatively. Complications included knee dislocation in one patient and surgical site infection in one patient. The survival rate was 99% at 2 years postoperatively. Clinical outcomes, complications, and survival rates of newly designed TKA were not statistically different compared with the control group.

CONCLUSION

The newly designed rotating-platform PS TKA showed good clinical results and suitable safety during the early postoperative phase in this prospective multicentre cohort study.

Revision of a Monoblock Metal-on-Metal Cup Using a Dual Mobility Component: Is It a Reasonable Option?

Revision of large-diameter, monoblock acetabular components for both hip resurfacing arthroplasty and metal-on-metal (MoM) total hip arthroplasty (THA) is correlated to a high amount of complications. For this reason, performing a limited revision by conversion to a dual mobility (DM) without acetabular component exchange has been proposed in order to limit these complications. Although DM bearing offers an easy solution avoiding the intraoperative and time-associated complications, concern about polyethylene wear and stability remains due to the difference regarding the design, the coverage angle and the clearance of the two implants. In order to evaluate the performance of this new solution with the new material to prevent the possibility of failure it is essential to conduct a review of the literature A qualitative systematic review of the literature has been conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A comprehensive search of PubMed, EMBASE, Google Scholar, and Scopus for English and French articles between January 2000 and October 2019 was performed, with the primary objective of finding articles about dual mobility bearing coupling with large metal-on-metal cup in the case of hip revision procedure. Various combinations of the key words were used in the search strategy. Thirteen articles with DM bearing mated with MoM cup were analyzed. Of the 130 hip revisions selected, with a follow-up from 6 to 53 months, there were a total of 14 with complications (10.77%): four true dislocations (3.08%); six intra-prosthetic dislocations (IPD, 4.6%), two of which presented plastic deformation and polyethylene wear; four other complications (3.08%), included a cup osteolysis, a clicking noise, a superficial infection and a periprosthetic fracture. All the mentioned true dislocations occurred during the first month while IPDs appeared during the first two years from the index revision. In conclusion, according to the literature analyzed, we can stress that the concerns and doubts about mating a DM bearing with large MoM cup cannot be dissolved. It has been pointed out that a DM bearing is not designed for a MoM cup; it is not mechanically tested on MoM cups, which presents different clearance and coverage angles. Predictable complications may occur, such as IPD, polyethylene wear and true dislocation. These complications have been reported at an even higher rate than they were in the eighties, when the first generation of DM implants were of a lower quality of polyethylene and the characteristic of the design was less optimal than modern ones.

No Difference in Force Required for Intraprosthetic Dislocation of Mixed Manufacturer vs Same Manufacturer Dual Mobility Articulations

BACKGROUND

To avoid the morbidity of removing well-fixed implants during revision surgery, the off-label practice of mixing femoral heads with dual mobility (DM) polyethylene liners from different manufacturers is commonly performed. The resistance to intraprosthetic dislocation, when the inner prosthetic head disengages from the polyethylene bearing, between mixed and same manufacturer constructs remains unknown.

METHODS

Between January 2010 and July 2018, 168 DM liners were retrieved. Specimens were excluded for catastrophic wear (n = 14), previously levered-out (n = 17), and cases in legal proceedings (n = 8). Using a validated setup, 129 specimens were uniaxially loaded 100 mm from the femoral head until lever-out failure of the head from the liner. The difference in maximum lever-out force (LOF) was compared for same and mixed manufacturer retrievals (Student t-test). Multivariable regression analysis evaluated the influence of potential confounders (length of implantation, head size, head material, presence of skirt) on LOF.

RESULTS

Ninety-seven same and 32 mixed manufacturer DM constructs were tested. The average LOF for same (272.6 ± 68.7 N) and mixed (299.2 ± 89.0 N) manufacturer specimens was not significantly different (P = .08). An inner head size of 22.2 mm was associated with 184.4-N increase in LOF (P < .001), the presence of a skirt was associated with 63.8-N increase in maximum LOF, and head material (ceramic vs metal) did not influence LOF.

CONCLUSION

We found no difference in the force required to lever-out same and mixed manufacturer inner heads from DM liners, suggesting that mixing manufacturers when placing DM articulations on well-fixed femoral stems should not increase the risk of intraprosthetic instability.

Dual mobility total hip arthroplasty: should everyone get one?

Hip instability following total hip arthroplasty (THA) remains a major challenge and is one of the main causes of revision surgery.

Dual mobility (DM) implants have been introduced to try to overcome this problem. The DM design consists of a small femoral head captive and mobile within a polyethylene liner.

Numerous studies have shown that DM implants reduce the rate of dislocation compared to fixed-bearing inserts.

Early designs for DM implants had problems with wear and intra-prosthetic dislocations, so their use was restricted to limited indications.

The results of the latest generation of DM prostheses demonstrate that these problems have been overcome. Given the results of these studies presented in this review, surgeons may now consider DM THA for a wider patient selection.

Cite this article: EFORT Open Rev 2019;4:541-547. DOI: 10.1302/2058-5241.4.180045

Early intraprosthetic dislocation in dual-mobility implants: a systematic review

BACKGROUND

Dual mobility implants are subject to a specific implant-related complication, intraprosthetic dislocation (IPD), in which the polyethylene liner dissociates from the femoral head. For older generation designs, IPD was attributable to late polyethylene wear and subsequent failure of the head capture mechanism. However, early IPDs have been reportedly affecting contemporary designs.

METHODS

A systematic review of the literature according to the preferred reporting items for systematic reviews and meta-analyses guidelines was performed. A comprehensive search of PubMed, MEDLINE, Embase, and Google Scholar was conducted for English articles between January 1974 and August 2016 using various combinations of the keywords "intraprosthetic dislocation," "dual mobility," "dual-mobility," "tripolar," "double mobility," "double-mobility," "hip," "cup," "socket," and "dislocation."

RESULTS

In all, 16 articles met our inclusion criteria. Fourteen were case reports and 2 were retrospective case series. These included a total of 19 total hip arthroplasties, which were divided into 2 groups: studies dealing with early IPD after attempted closed reduction and those dealing with early IPD with no history of previous attempted closed reduction. Early IPD was reported in 15 patients after a mean follow-up of 3.2 months (2.9 SD) in the first group and in 4 patients after a mean follow-up of 15.1 months (9.9 SD) in the second group.

CONCLUSIONS

Based on the current data, most cases have been preceded by an attempted closed reduction in the setting of outer, large articulation dislocation, perhaps indicating an iatrogenic etiology for early IPD. Recognition of this possible failure mode is essential to its prevention and treatment.

Complete Wear-Through of a Polyethylene Liner and Metal-Backed Acetabular Cup Resulting in a Unique Form of Catastrophic Total Hip Arthroplasty Failure: A Case Report

CASE

We describe a case of total hip arthroplasty failure where a cobalt-chrome femoral head completely wore through the polyethylene liner and the titanium acetabular cup. The patient subsequently underwent revision total hip arthroplasty with acetabular revision and femoral head exchange.

CONCLUSION

This case illustrates the natural history of catastrophic failure in a metal-on-polyethylene total hip arthroplasty design. If recognized earlier, this patient may have been a candidate for isolated liner and head exchange. Additionally, this case represents a unique complication in using mixed metals in total hip arthroplasty, where the harder cobalt-chrome femoral head wore completely through the much softer titanium component.