Prospective Trial of Sacroiliac Joint Fusion Using 3D-Printed Triangular Titanium Implants: 24-Month Follow-Up

Sacroiliac joint dysfunction: anatomy, pathophysiology, differential diagnosis, and treatment approaches

The sacroiliac joints (SIJ) play a pivotal role in pelvic stability and load transmission. SIJ-related disorders can pose a diagnostic challenge because of complex anatomy, non-specific imaging findings, and overlapping symptomatology with other lower back conditions. Broadly, SIJ pathology can be divided into the following categories: infectious, inflammatory, degenerative, mechanical, traumatic, and neoplastic. On the spectrum of mechanical disorders is the entity of SIJ dysfunction, defined as pain localized to the SIJ due to non-inflammatory causes. This paper aims to enhance the understanding of SIJ dysfunction by exploring SIJ anatomy, pathophysiology, and differential diagnosis for SIJ pain. Etiologies, associations, and diagnostic physical examination maneuvers for SIJ dysfunction are reviewed. We will discuss the role of diagnostic imaging in SIJ dysfunction and propose imaging findings which may indicate the diagnosis. Finally, we will discuss therapeutic strategies to treat SIJ dysfunction. By delving into the complexities of SIJ anatomy and pathophysiology, this paper provides valuable discernment for the diagnosis and management of SIJ-related disorders.

Fixation of the Sacroiliac Joint: A Cadaver-Based Concurrent-Controlled Biomechanical Comparison of Posterior Interposition and Posterolateral Transosseous Techniques

OBJECTIVE

Our study aimed to compare the posterior interposition technique against the posterolateral transosseous technique in the same cadaver specimens.

METHODS

Computer and cadaver models of 2 fixation techniques were developed. The computer model was constructed to analyze bone volume removed during implant placement and the bony surface area available for fusion. The cadaver model included quasi-static multidirectional bending flexibility and dynamic fatigue loading. Relative motions between the sacrum and ilium were measured intact, after joint destabilization, after fixation with direct-posterior and posterolateral techniques, and after 18,500 cycles of fatigue loading. Relative positions between each implant and the sacrum and ilium were measured after fixation and fatigue loading to ascertain the quality of the bone-implant interface. The 2 techniques were randomized to the left and right sacroiliac joints of the same cadavers.

RESULTS

The posterior interposition technique removed less bone volume and facilitated a larger surface area available for bony fusion. Posterior interposition significantly reduced the nutation/counternutation motion of the sacroiliac joint (42% ± 8%) and reduced it more than the posterolateral transosseous technique (14% ± 4%). Upon fatigue loading, the posterior interposition implant maintained the bone-implant interface across all specimens, while the posterolateral transosseous implant migrated or subsided in 20%-50% of specimens.

CONCLUSION

Posterior interposition fixation of the sacroiliac joint reduces joint motion. The amount of fixation from the posterior technique is superior and more durable than the amount of fixation achieved by the posterolateral technique.

Minimally invasive lateral, posterior, and posterolateral sacroiliac joint fusion for low back pain: a systematic review and meta-analysis

OBJECTIVE

This study aimed to evaluate the therapeutic effects of minimally invasive lateral, posterior, and posterolateral sacroiliac joint fusion for low back pain through a meta-analysis.

METHODS

The PubMed, Web of Science, Embase, Cochrane Library, and ClinicalTrials.gov databases were comprehensively searched for studies up to 31 August 2024. Relevant studies using lateral, posterior, and posterolateral approaches were identified. Pooled outcomes and publication bias were assessed. The study was registered with PROSPERO (registration No. CRD42023451047).

RESULTS

A total of 48 studies were included: 32 focused on the lateral approach, 10 on the posterior approach, four on the posterolateral approach, and two compared the lateral and posterolateral approaches. The pooled effect analysis showed statistically significant improvements in the visual analog scale (VAS) scores for all three approaches at 6 and 12 months postoperatively. Although no between-approach comparisons were conducted, the pooled improvements in VAS scores at 6 and 12 months postoperatively were numerically similar across all three approaches, as were the pooled fusion rates. The pooled complication rate for the lateral approach was 9.2%, numerically higher than 1% for the posterior approach. The pooled revision rate for the lateral approach was 2.4%, also numerically higher than 0.6% for the posterior approach.

CONCLUSIONS

Although pain relief and fusion rates were similar across all approaches, the lateral approach might be associated with a higher risk of total complications and revision surgery.

Osseointegration and fixation opportunities of sacroiliac instrumentation: a preclinical evaluation in a large animal model

Background

Implant fixation is often the cornerstone of musculoskeletal surgical procedures performed to provide bony fixation and/or fusion. The aim of this study was to evaluate how different design features and manufacturing methods influence implant osseointegration and mechanical properties associated with fixation in a standardized model in cancellous bone of adult sheep.

Methods

We evaluated the in vivo performance of three titanium alloy implants: (A) iFuse-TORQ implant; (B) Fenestrated Sacroiliac Device; and (C) Standard Cancellous Bone Screw in the cancellous bone of the distal femur and proximal tibia in 8 sheep. Group A was produced using additive manufacturing [three-dimensional (3D) printing] while Groups B and C were made with traditional methods. The vivo responses of the implants at the implant-bone interface were examined using mechanical testing (push out and removal torque), polymethyl methacrylate (PMMA) histology combined with fluorochrome labels and quantitative histomorphometry of bone ongrowth, ingrowth and through growth at 3 and 6 weeks.

Results

New bone formed directly on all groups and no adverse reactions were noted. Osseointegration via ongrowth, ingrowth and through growth was a function of implant design. Implant designs that provide osseointegration via ongrowth, ingrowth and through growth improve implant fixation in torsion. The 3D printed surface in group A was rougher and outperformed traditional manufacturing surfaces of groups B and C in torsion. The porous domains and fenestrations in the design of group A allowed for bone ingrowth and through growth, which accounted for the superior torsional properties.

Conclusions

Implant designs that provide osseointegration via ongrowth, ingrowth and through growth improve implant fixation.

Revision of Failed Sacroiliac Joint Posterior Interpositional Structural Allograft Stabilization with Lateral Porous Titanium Implants: A Multicenter Case Series

Background

Distraction arthrodesis (DA) and stabilization of the sacroiliac (SI) joint by placing standalone structural allograft (SA) into the joint from a posterior trajectory has recently been introduced as a surgical procedure for chronic SI joint pain refractory to non-operative care.

Methods

Retrospective case series of patients with recurrent and/or persistent pain after placement of one or more interpositional/intraarticular standalone SAs between the ilium and sacrum using a posterior procedure to treat SI joint pain/dysfunction. Patients subsequently underwent surgical revision with porous titanium fusion implants using a lateral transfixing procedure. The demographic, clinical, and radiographic features of these cases are described.

Results

Data were available for 37 patients. The average (SD) age was 57 (13) years, 62% were female, and the average BMI was 31 (5.4). On average, two SA implants were placed per joint; 46% of cases were bilateral. At follow-up, two common themes were identified: lucencies around the implants and suboptimal implant position. None of the cases showed radiographic fusion of the SI joint prior to revision. One patient had an inflammatory reaction to the SA. All patients presented for revision due to either continued (49%) or recurrence (51%) of pain. In one revision case, the SA was forced ventrally, resulting in a sacral fracture, which was treated conservatively without sequelae.

Conclusions

The popularity of standalone SA for SI joint stabilization/fusion with a posterior procedure is increasing. This case series demonstrates that clinical failures from this procedure may require surgical revision. The proposed fusion strategy (DA) for these products is unproven in the SI joint, and, therefore, properly conducted prospective randomized clinical trials with long-term clinical and radiographic follow-up are important to establish the safety and efficacy of this approach. In the meantime, the placement of lateral titanium implants appears to be an effective revision strategy.

Minimally Invasive Sacroiliac Fusion-a Review

PURPOSE OF REVIEW

Sacroiliac dysfunction is an important cause of low back pain with significant impact on quality of life and daily activities. Minimally invasive sacroiliac joint fusion (MIS SI fusion) is an effective treatment for patients who failed non-surgical strategies. The purpose of this article is to review the clinical outcomes and complications of this surgical technique.

RECENT FINDINGS

For patients with SI joint dysfunction, MIS SI fusion reduced pain and disability as measured by Visual Analog Scale and Oswestry Index and improved quality of life as measured by Short-Form 36 and EuroQol-5D questionnaires. Satisfaction rates were higher in the SI fusion group when compared to the conservative management. In recent clinical trials, adverse events occurred with a similar rate in the first 6 months for patients assigned in the conservative management versus patients assigned to MIS SI fusion. MIS SI fusion is an effective and safe procedure for patients with sacroiliac dysfunction who failed non-surgical strategies. This procedure provides rapid as well as sustained pain relief, improvement in back function, high patient satisfaction, with low rate of complications.