Uncemented metal-on-metal acetabular component: follow-up of 112 hips for a minimum of 5 years

Complications Are Not Increased With Acetabular Revision of Metal-on-metal Total Hip Arthroplasty

BACKGROUND

Isolated revision of the acetabular component in the setting of total hip arthroplasty has an increased risk of dislocation. With local soft tissue destruction frequently associated with failed metal-on-metal (MoM) bearings, it is presumed that acetabular revision of these hips will have even greater risk of complications. However, no study directly compares the complications of MoM with metal-on-polyethylene (MoP) acetabular revisions.

QUESTIONS/PURPOSES

In the context of a large database analysis, we asked the following questions: (1) Are there differences in early medical or wound complications after isolated acetabular revision of MoM and MoP bearing surfaces? (2) Are there differences in the frequency of dislocation, deep infection, and rerevision based on the bearing surface of the original implant?

METHODS

A review of the 100% Medicare database from 2005 to 2012 was performed using International Classification of Diseases, 9th Revision and Current Procedural Terminology codes. We identified 451 patients with a MoM bearing and 628 patients with a MoP bearing who had an isolated acetabular revision and a minimum followup of 2 years. The incidence, odds ratios, and 95% confidence intervals for early medical or wound complications were calculated using a univariate analysis at 30 days with patient sex and age group-adjusted analysis for blood transfusion. The incidence, odds ratio, and 95% confidence intervals for dislocation, deep infection, and rerevision were calculated using a univariate analysis at 30 day, 90 days, 1 year, and 2 years using a subgroup analysis with the Cochran-Mantel-Haenszel test to adjust for patient gender and age groups.

RESULTS

There were no differences between the MoM and MoP isolated acetabular revisions in the incidence of 30-day local complications. There was a greater risk of transfusion in the MoP group than the MoM group (134 of 451 [30%] versus 230 of 628 [37%]; odds ratio [OR], 0.731; 95% confidence interval [CI], 0.565-0.948; p = 0.018). There were no differences at 2 years between the MoM and MoP acetabular revisions in the incidence of dislocation, infection, or rerevision. When analyzed by patient sex and age group, there were more infections in the age 70 to 79 years MoP group compared with MoM (10 of 451 [5%] versus 29 of 628 [10%]; OR, 4.47; CI, 1.699-11.761; p = 0.001).

CONCLUSIONS

There were high rates of dislocation, infection, and rerevision in both revision cohorts. The rate of dislocation was not greater after acetabular revision of MoM bearings at 2 years. Based on these findings, clinicians should counsel these patients preoperatively about the risks of these complications. Dual-mobility and constrained components have specific advantages and disadvantages in these settings and should be further studied.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Which implant should we use for primary total hip replacement? A systematic review and meta-analysis

BACKGROUND

Many total hip implants are currently available on the market worldwide. We aimed to estimate the probability of revision surgery at ten years for each individual total hip implant and to compare these estimates with the National Institute for Health and Care Excellence (NICE) benchmark.

METHODS

We performed a meta-analysis of cohort studies. The methodological quality was assessed with use of the Assessment of Quality in Lower Limb Arthroplasty (AQUILA) checklist. We searched PubMed, Embase, Web of Science, and the Cochrane Library. Additionally, national joint registries that were full members of the International Society of Arthroplasty Registers (ISAR) were hand searched. Studies in which the authors reported the survival probability for either the acetabular or the femoral component of primary total hip replacements with use of revision for any reason or for aseptic loosening at ten years as the end point, with at least 100 implants at baseline, and in which at least 60% of the patients had primary osteoarthritis were eligible for inclusion.

RESULTS

The search strategy revealed 5513 papers describing survival probabilities for thirty-four types of acetabular components and thirty-two types of femoral components. Eight types of acetabular cups and fifteen types of femoral stems performed better than the NICE benchmark.

CONCLUSIONS

We recommend that surgeons performing a primary total hip replacement use an implant that outperforms the NICE benchmarks.

How have alternative bearings and modularity affected revision rates in total hip arthroplasty?

BACKGROUND

Total hip arthroplasty (THA) continues to be one of the most successful surgical procedures in the medical field. However, over the last two decades, the use of modularity and alternative bearings in THA has become routine. Given the known problems associated with hard-on-hard bearing couples, including taper failures with more modular stem designs, local and systemic effects from metal-on-metal bearings, and fractures with ceramic-on-ceramic bearings, it is not known whether in aggregate the survivorship of these implants is better or worse than the metal-on-polyethylene bearings that they sought to replace.

QUESTIONS/PURPOSES

Have alternative bearings (metal-on-metal and ceramic-on-ceramic) and implant modularity decreased revision rates of primary THAs?

METHODS

In this systematic review of MEDLINE and EMBASE, we used several Boolean search strings for each topic and surveyed national registry data from English-speaking countries. Clinical research (Level IV or higher) with ≥ 5 years of followup was included; retrieval studies and case reports were excluded. We included registry data at ≥ 7 years followup. A total of 32 studies (and five registry reports) on metal-on-metal, 19 studies (and five registry reports) on ceramic-on-ceramic, and 20 studies (and one registry report) on modular stem designs met inclusion criteria and were evaluated in detail. Insufficient data were available on metal-on-ceramic and ceramic-on-metal implants, and monoblock acetabular designs were evaluated in another recent systematic review so these were not evaluated here.

RESULTS

There was no evidence in the literature that alternative bearings (either metal-on-metal or ceramic-on-ceramic) in THA have decreased revision rates. Registry data, however, showed that large head metal-on-metal implants have lower 7- to 10-year survivorship than do standard bearings. In THA, modular exchangeable femoral neck implants had a lower 10-year survival rate in both literature reviews and in registry data compared with combined registry primary THA implant survivorship.

CONCLUSIONS

Despite improvements in implant technology, there is no evidence that alternative bearings or modularity have resulted in decreased THA revision rates after 5 years. In fact, both large head metal-on-metal THA and added modularity may well lower survivorship and should only be used in select cases in which the mission cannot be achieved without it. Based on this experience, followup and/or postmarket surveillance studies should have a duration of at least 5 years before introducing new alternative bearings or modularity on a widespread scale.

Hip resurfacing versus total hip arthroplasty: a systematic review comparing standardized outcomes

BACKGROUND

Metal-on-metal hip resurfacing was developed for younger, active patients as an alternative to THA, but it remains controversial. Study heterogeneity, inconsistent outcome definitions, and unstandardized outcome measures challenge our ability to compare arthroplasty outcomes studies.

QUESTIONS/PURPOSES

We asked how early revisions or reoperations (within 5 years of surgery) and overall revisions, adverse events, and postoperative component malalignment compare among studies of metal-on-metal hip resurfacing with THA among patients with hip osteoarthritis. Secondarily, we compared the revision frequency identified in the systematic review with revisions reported in four major joint replacement registries.

METHODS

We conducted a systematic review of English language studies published after 1996. Adverse events of interest included rates of early failure, time to revision, revision, reoperation, dislocation, infection/sepsis, femoral neck fracture, mortality, and postoperative component alignment. Revision rates were compared with those from four national joint replacement registries. Results were reported as adverse event rates per 1000 person-years stratified by device market status (in use and discontinued). Comparisons between event rates of metal-on-metal hip resurfacing and THA are made using a quasilikelihood generalized linear model. We identified 7421 abstracts, screened and reviewed 384 full-text articles, and included 236. The most common study designs were prospective cohort studies (46.6%; n = 110) and retrospective studies (36%; n = 85). Few randomized controlled trials were included (7.2%; n = 17).

RESULTS

The average time to revision was 3.0 years for metal-on-metal hip resurfacing (95% CI, 2.95-3.1) versus 7.8 for THA (95% CI, 7.2-8.3). For all devices, revisions and reoperations were more frequent with metal-on-metal hip resurfacing than THA based on point estimates and CIs: 10.7 (95% CI, 10.1-11.3) versus 7.1 (95% CI, 6.7-7.6; p = 0.068), and 7.9 (95% CI, 5.4-11.3) versus 1.8 (95% CI, 1.3-2.2; p = 0.084) per 1000 person-years, respectively. This difference was consistent with three of four national joint replacement registries, but overall national joint replacement registries revision rates were lower than those reported in the literature. Dislocations were more frequent with THA than metal-on-metal hip resurfacing: 4.4 (95% CI, 4.2-4.6) versus 0.9 (95% CI, 0.6-1.2; p = 0.008) per 1000 person-years, respectively. Adverse event rates change when discontinued devices were included.

CONCLUSIONS

Revisions and reoperations are more frequent and occur earlier with metal-on-metal hip resurfacing, except when discontinued devices are removed from the analyses. Results from the literature may be misleading without consistent definitions, standardized outcome metrics, and accounting for device market status. This is important when clinicians are assessing and communicating patient risk and when selecting which device is most appropriate for individual patients.

High survival in young patients using a second generation uncemented total hip replacement

Purpose

Whilst excellent long-term results with contemporary uncemented stems have been reported for total hip arthroplasty in young patients, the survival rates for the whole reconstruction are often compromised by high failure rates on the acetabular site due to peri-acetabular osteolysis and accelerated wear.

Methods

In patients 60 years old or younger, we retrospectively reviewed the results at a minimum of ten years of 89 consecutive uncemented total hip replacements in 88 patients using the press-fit Fitmore acetabular component in combination with the CLS Spotorno stem and a 28-mm Metasul metal-on-metal articulation or a 28-mm alumina ceramic on conventional polyethylene bearing. The mean age at the time of surgery was 49 years (range, 25–60). The mean clinical and radiological follow-up was 12 years (range, 10–15).

Results

Six patients (six hips) died and two patients (two hips) were lost to follow-up. Five hips were revised: one for deep infection, one for peri-prosthetic femoral fracture, and one for aseptic stem loosening. In two hips an isolated revision of the acetabular liner was performed (one for recurrent dislocation and one for unexplained pain). No revision was performed for accelerated wear, osteolysis or aseptic loosening of the acetabular shell. We could not detect peri-acetabular osteolysis visible on plain radiographs in those hips evaluated radiographically. The Kaplan-Meier survival with revision for any reason as the endpoint was 94% (95% confidence interval, 86–97) at 12 years.

Conclusions

The survival rates and the radiological outcomes with this implant combination in this young and active patient group are encouraging when compared to the results reported for other uncemented cups in this age group.

Cementless cups do not increase osteolysis risk in metal-on-metal total hip arthroplasty. Apropos of 106 cases

BACKGROUND

Metal-on-metal bearings in total hip arthroplasty (THA) were introduced to reduce the production of wear debris and debris-induced periprosthetic osteolysis. Analysis of various series according to the type of selected acetabular fixation highlights different evolutions: favourable results with uncemented cups contrasting with loosening and radiolucent lines (RLL) evolution for cemented cups.

HYPOTHESIS

Combining metal-on-metal bearings to uncemented cups does not increase the osteolysis risk at a minimum 5 years' follow-up.

MATERIALS AND METHODS

From January 1999 to December 2002, 106 Metasul THAs were implanted in 95 patients using a Hardinge anterolateral approach (40 women and 55 men with an average age of 59.2 years). The cups were of cementless, hydroxyapatite-coated Cedior type (Zimmer) housing a Metasul insert in a polyethylene sandwich. The femoral stem used was the cemented Acora, then the Exafit (Zimmer) type with Metasul 28-mm head mounted on a 8/10 Morse taper. Patients were evaluated clinically using the Postel-Merle-d'Aubigné (PMA) scoring system and radiologically using various markers: cup inclination angle, eventual RLL presence, appearance of osteolysis images, ectopic ossifications and finally, eventual implant migration. In the eventuality of suspected RLL evolution or osteolysis, advanced imaging was performed; joint aspiration liquid and cobalt serum level were studied.

RESULTS

We reviewed 94 prostheses (85 patients) with an average follow-up of 6.4 years (4.3 to 9.3 years, median of 6.3 years). The rate of patient loss from follow-up and death was 12.1%. The PMA score of non-revised patients increased from 11.4+/-1.5 to 17.6+/-0.2 at follow-up. We numbered ten re-operations not attributable to the type of bearings used. Three revisions were directly related to the metal-on-metal bearing: two metallosis due to impingement and one case of hypersensitivity. Cup inclination angle was 45.7+/-5.49 degrees . No implant migration was noted during the follow-up duration. Only one cup undergoing revision presented a substantial osteolysis. On the femoral side, with non-revised implants, we observed 13 cement/bone RLL images around nine femoral stems and six calcar resorptions. The survival rate at more than 6 years was 95.8% (91.8-99.8) for the cups and 94.8% (90.3-99.2) for the femoral stems (95% confidence interval).

DISCUSSION

The present study confirms our hypothesis: with Metasul bearings equipped cementless cups, the rates of aseptic loosening, RLL or acetabular osteolysis are low and remain stable over time, unlike the results observed for Metasul series with polyethylene directly cemented on bone. Specific complications, such as metallosis due to impingement and hypersensitivity, can rarely be encountered. These results encourage us to continue employing metal-on-metal bearings with non-cemented cups in active patients.

LEVEL OF EVIDENCE

Level IV: Therapeutic study.