Complexity of diagnosis and controversy in treatment make sacroiliac (SI) joint pain a challenging condition to manage. Literature has shown that the SI joint is a legitimate pain generator in patients with low back pain (LBP) although still underappreciated [1]. Some authors have opined that 15-25% patients who presented with LBP had SI joint etiology [2].

The majority of patients with SI joint pain can be treated non operatively. When these treatments fail, some investigators have advocated for SI joint arthrodesis for patients with chronic and debilitating SI joint pain [3]. However, SI joint arthrodesis in the absence of joint destruction from disease process, trauma, or other causes of severe instability remains controversial [4]. SI joint arthrodesis studies exist that report a varying degree of success, most being satisfactory, for treating chronic and debilitating SI joint pain.

Open and percutaneous approaches have been described in literature for SI joint arthrodesis. Studies have shown the benefits of percutaneous approach to be smaller exposure, less blood loss, preservation of the inherent stability of the SI joint, reduced length of hospital stay, and little wound-related morbidity [3, 5-8].

The aim of this study is to independently review the radiographic and surgical results of a new technique of SI fixation. The procedure involves percutaneous placement of triangular titanium implants with a porous plasma spray coating across the SI joint (Figs. 1, 2).

Fig. (1). Porous plasma-coated triangular titanium implants (SI-Bone, San Jose, CA). *

Fig. (2). Postoperative X-ray at 12 months following SI fixation using iFuse (SI-Bone, San Jose, CA) implants.

There were no intraoperative complications. Estimated blood loss was minimal in each case. Every patient was discharged home on post-operative day 1. One patient (3%) required a revision due to nerve root irritation by an implant. Two (6%) developed incisional hematomas that resolved with observation and one developed de novo L5-S1 discitis. At the most recent follow up, 16 (52%) patients reported no pain after the procedure, and 14 (45%) patients reported good to excellent pain relief. All walked full weight-bearing by 16 weeks. 27/31 (87%) patients expressed satisfaction with the procedure. Surgical outcomes are summarized in Table 2 and Fig. (5).

Fig. (5). Graphic representations of outcomes.

26 patients had immediate postoperative imaging reviewed. Of these, 21 (81%) had implants fully within the bone of the ilium and sacrum (Table 3). With the exception of the patient who underwent revision, extra osseous position did not seem to correlate with outcome. 19 patients had imaging available at 6 months after surgery (Table 4). Of these, 18/19 (95%) patients had radiographic evidence of bone ingrowth into at least one side (sacral or iliac) of the implant on CT scan. Bone growth into or across the SI joint was evident in 8/19 (42%) patients although definite bony arthrodesis was not seen. There also was noted to be a lucency around at least one side of an implant in 5/19 (26%) patients. 15 patients had imaging available at one year after surgery (Table 4). 4/15 (27%) patients had continued lucency around at least one implant. None had lucency around all three. Somewhat more bone was seen within the joint when compared to the six month imaging but clear bony arthrodesis remained uncommon. 4/31 (13%) patients were not satisfied with their result although three of them reported good pain relief. Details are given in Table 5.

The SI joint was widely viewed as a potential source of low back pain and dysfunction until 1930’s when the idea that facet arthrosis and lumbar disc disease can cause low back pain arose [9,10]. As this idea gained popularity and acceptance, it seemed to push the SI joint pain and dysfunction theory into obscurity [11]. While SI joint pain and dysfunction remain a controversial and challenging topic, it appears that SI joint may be an underappreciated etiology of low back pain [4]. Currently, it is felt that dysfunctional SI joint is the culprit in 15-25% patients who present with low back pain [2].

The published literature on surgical treatment of chronic painful SI joint dysfunction dates back to early 20^th century. A literature search yielded 11 articles describing open procedure [11-21] and 5 articles describing percutaneous procedure [3, 5-8] for surgically treating chronic SI joint problems. These studies, most of them being a small retrospective case series, reported well to excellent improvement in pain and/or function in 168 out of 211 patients (79.6%). When divided further into open procedure and percutaneous procedure studies, the satisfactory clinical results were 77.2% and 88.6%, respectively. Every open procedure study needed bone graft harvest for SI joint arthrodesis while six out of 11 studies required external immobilization postoperatively. On the other hand, only one out of five percutaneous procedure study required bone graft harvest and external immobilization.

Treating a chronic SI joint dysfunction surgically still remains controversial, but it appears that SI joint arthrodesis or fixation can produce favorable and clinically satisfactory outcome with acceptable rate of complications. Based on the published studies, surgical arthrodesis or fixation is a viable option for patients with chronic debilitating SI joint dysfunction. Because most patients can be managed non operatively, surgical procedures should be considered for a carefully selected group of patients not responding to non operative management [1].

Percutaneous SI fixation using porous plasma-coated triangular titanium implants has not been previously described in literature. This has the advantage of being minimally invasive and potential advantage of not requiring the use of bone graft to achieve long term stabilization. The surgical outcome of this new procedure has been positive in most patients in this study. There were no intraoperative complications. EBL was minimal in each case. Every patient was discharged on post-operative day 1. 27 out of 31 patients reported satisfaction with the procedure. Postoperative pain relief was good, excellent, or complete in 30 out of 31 patients. However, there were 4 postoperative complications in which one patient with L5 nerve root irritation required revision. The other three patients had an uneventful postoperative course despite having infected hematoma and discitis, which was treated appropriately.

It is unclear from the radiographic review whether these patients will go on to develop a bony arthrodesis of the SI joint. Although a significant percentage did show some evidence of bone growth in to the joint, we do not have enough longitudinal radiographic information to know if this process continues. It is also unclear at present whether radiographic evidence of foramenal violation, cortical violation, or lucencies seen on CT scan at 6 and 12 months has an effect on clinical outcome. A much larger sample will be needed to determine this.

In our study, there were 4 patients who were not satisfied with this procedure. They were all female patients with mean age of 55.3 years, and three of them had previous spine surgery. Only one patient was involved in a worker’s compensation case. Postoperatively, two patients were not compliant with non-weight bearing status until the first postoperative clinic visit. One patient was doing well postoperatively until sustaining a fall down a full flight of stairs. After the fall, the preoperative SI pain returned. One of the unsatisfied patient’s postoperative courses was complicated by superficial infected hematoma that required 4 weeks of intravenous antibiotics. This patient reported persistent pain in the lumbosacral junction region although this pain was relieved close to 100% by preoperative CT-guided injection.

The radiographic and surgical outcomes of this new technique of percutaneous SI fixation were independently reviewed. The result of this new novel percutaneous SI fixation using porous plasma-coated triangular titanium implants is promising and compares well with other published clinical studies. SI fixation with this novel implant provides advantageous bony interference fit to decrease motion postoperatively as well as probable bony ingrowth into porous biologically friendly implant surface for long term stability. Literature to date has shown that percutaneous approach to SI fixation or arthrodesis has a higher rate of clinical success, less need for bone harvest, infrequent postoperative immobilization requirement, shorter length of hospital stay, and less wound-related morbidity [3, 5-8].

When patients with chronic disabling SI joint pain fail conservative treatments, we feel that percutaneous SI fixation and/or arthrodesis is an option for a carefully selected group of patients in the hands of meticulous and experienced surgeon. In this study the selection process included; diagnosis of the sacroiliac joint as being a likely pain generator by history, physical examination, imaging and diagnostic intra articular injection as well as lack of response to prolonged non operative measures.

Dr. Kim - No conflicts.

Dr. Glaser - Consultant Depuy Spine $500, Travel Expenses SI bone (after completion of this study) $1000.

Dr. Rudolf Stock ownership $100,000, and paid consultant SI Bone.

The implant discussed in this manuscript is FDA approved for the diagnoses of degenerative sacro-iliitis and sacro-iliac disruption.