Friday, December 20, 2013

Failure of the glenoid component in total shoulder joint replacement

Failure of the Glenoid Component in Anatomic Total Shoulder Arthroplasty: A Systematic Review of the English-Language Literature Between 2006 and 2012

Total shoulder arthroplasty is often referred to as the 'gold standard' for the treatment of glenohumeral arthritis; the number of these procedures performed each year is increasing rapidly. Failure of the glenoid component is the most common major long-term complication of this procedure.

The authors conducted a systematic review of the recent literature to search for evidence bearing on two hypotheses: (1) the rate of glenoid component failure is diminishing with time, and (2) certain preoperative and surgical factors are significantly associated with an increased risk of failure of the glenoid component. 27 articles representing 3853 total shoulder arthroplasties met the inclusion criteria.

The analysis of glenoid outcomes after total shoulder arthroplasty was based on the annualized event rates. Use of such a rate (the percentage of shoulders that develop the outcome each year) enables comparison of the outcomes of studies with different durations of follow-up. For example, a 1997 article indicated that 44% of glenoids had loosening at a mean of 12.2 years after surgery, whereas a 2012 article indicated that 26% of glenoids had loosening at a mean of 8.3 years. Even though the prevalences were different, the annualized rates were similar (3.6% and 3.1%, respectively). In the present study:

*Asymptomatic radiolucent lines occurred at a rate of 7.3% per year after the primary shoulder replacement.
*Symptomatic glenoid loosening occurred at 1.2% per year.
*Surgical revision occurred at 0.8% per year.

There was no significant evidence that the rate of symptomatic loosening has diminished over time.

Keeled components had greater rates of asymptomatic radiolucent lines compared with pegged components in side-by-side comparison studies.

Sex, Walch class, and diagnosis were significantly associated with the risk of glenoid component failure. While authors of individual articles proposed various risk factors for glenoid component failure, most of these relationships were not significant in the systematic review.

This study points strongly to the inadequacy of the information on which the treatment of individuals with shoulder arthritis is based. While the study encompassed 3,853 total shoulder arthroplasties done in a six year period, over 22,000 of these procedures are performed each year in the U.S. alone. Thus we have data on only a small percentage of the cases performed. Furthermore, since the majority of total shoulders are performed by surgeons who perform only one or two such cases per year, the reported data are unlikely to reflect the actual state of practice.  Furthermore, the reports that are available often omit key data, such as the preoperative diagnosis, the glenohumeral pathoanatomy (version, biconcavity, posterior humeral subluxation), the surgical technique (e.g. amount of reaming), how glenoid component failure was defined, and whether a revision of a total shoulder pertained to the humeral component, the glenoid component, or other factors. Few of the included studies had a high level of evidence, and few enabled comparison among prosthetic designs and surgical techniques within the same study. 

This study confirms that the problem of glenoid component failure continues unabated. However, existing studies provide little evidence to guide future attempts to curb the rate of this complication. It is suggested that the quality of evidence bearing on glenoid component failure could be substantially improved if future studies of total shoulder arthroplasties adhered to (1) standard definitions of outcome (such as asymptomatic radiolucent lines, symptomatic glenoid loosening, and revision for glenoid loosening), and (2) systematic documentation of potential risk factors (including patient age, sex, diagnosis, rotator cuff status, Walch classification, date of surgery, duration of follow-up, glenoid surface geometry, polyethylene characteristics, type of component fixation, surgical technique, and surgeon total shoulder arthroplasty case volume). In this manner the field of shoulder reconstruction will be able to accumulate the evidence necessary to guide future efforts to improve patient selection, component design, and surgical technique.

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