Complication risk of minimally invasive sacroiliac joint fusion surgery may be higher than previously reported

Minimally invasive sacroiliac joint fusion surgery has been shown to be an effective treatment and potentially cost-saving for sacroiliac joint pain, with low adverse event and reoperation rates, as compared to open surgery. According to the study authors, “possibly as a result of this combination of factors,” the procedure has become a commonly-used technique. Current literature reports over 87% of sacroiliac joint arthrodesis as performed minimally invasively. This “has created the need for reliable data addressing the safety of the procedure,” the authors from Los Angeles, USA, state, noting that “existing literature has largely failed to…address this issue.” Because of the relative novelty of the procedure, the authors speculate that “acquiring a large sample population” has been difficult, with most current literature addressing outcome results via case series.

The Pearl Driver database—cataloguing patient records from US insurer, Humana Incorporated—holds data on 18,620,198 patients “from every major geographic region of the country.” The research team searched the database using International Classification of Disease, Ninth Revision and Current Procedural Terminology codes to distinguish patients who had undergone the minimally invasive procedure. The team specified their search parameters in order to account for changing terminology and pathologies indicated for open procedures, narrowing a population of 508 sacroiliac fusion patients down to 469, once exclusions had been made for neoplasms, pelvic ring trauma and reoperations. Of this patient population, 164 patients were male and 305 were female.

The corresponding records data were evaluated for novel postoperative complications in six categories; postoperative infection, nervous system, pain, urinary tract infection, osteomyelitis and joint derangement. Complication rates were investigated at 90 days and six months postprocedure, with a 30-day point used to evaluate infection rates. Novel lumbar pathology was also investigated as an outcome.

The researchers observed an incidence of 62 complications within the first 90 days (13.2%), and 77 (16.4%) within six months of the procedure. An infection rate of 4.1% (19) was observed within six months. Novel lumbar pathology was found in 3.6% of patients (n=17) at 90 days following the procedure, and in 5.3% (25) at six months, with a 9.1% (15) prevalence among on the male population at this time point.

“The results of our study show higher overall complication rates for minimally invasive sacroiliac joint fusion than have been previously reported,” write the authors. Whilst the team note that their population size is not particularly large, “it is nonetheless significantly bigger than nearly all previously published studies, and as a result has the statistical power that these smaller case series lack.” Whilst the team report that one study (Smith et al, Ann Surg Innov Res, 2013) has previously reported a higher overall complication rate of 18% (114, n=5319), others have reported rates as low as 3.5% (Miller et al, Med Devices (Auckl), 2013).

The observed infection rate, which was comparable to other results in the literature, was highlighted as notably higher than is associated with other minimally invasive procedures. “Minimally invasive sacroiliac joint fusion surgery potentially carries a relatively high risk of postoperative infection,” the authors of this study report. Furthermore, the study “for the first time also demonstrated substantial rates of postoperative complications involving the nervous systems, pain, and urinary tract infections,” with respective rates of 6.2%, 4.1% and 4.9% found for each subtype at six months.

Speculating on reasons for the novel lumbar pathology reported, the authors comment, “previous studies suggest that lumbar fusion can lead to sacroiliac joint degeneration in up to 75% of cases within five years.” “One potential limitation of this finding,” they report, “is that lumbar and sacroiliac joint pains are often difficult to distinguish.” Misdiagnosis, they suggest, may account for some of these findings.

As well as observing higher complication rates, the team observed a stark increase in the incidence of minimally invasive sacroiliac joint fusion procedures performed, particularly in the latter three years of the study data. This spike corresponds with a notable increase in studies of the procedure around this time, as well as “the US Food and Drug Administration approval of multiple minimally invasive sacroiliac fusion devices” at the beginning of 2008. “this notion is further supported”, they state, “by data which show that 92% of the original patient population remained after excluding patients with…indications for open sacroiliac fusion.”

Noting limitations including the potential for missing data as a result of changing billing codes, as well as “some degree of misclassification bias and unmeasured confounding,” the authors conclude that their study was “able to provide a unique analysis of minimally invasive sacroiliac joint fusion complications.” “As more data become available in the long term,” they comment, “adverse events need to be analysed to gain a better understanding of the procedures’ safety.”