Hydrogel-Based Strategies for Intervertebral Disc Regeneration: Advances, Challenges and Clinical Prospects.

Millions of people worldwide suffer from low back pain and disability associated with intervertebral disc (IVD) degeneration. IVD degeneration is highly correlated with aging, as the nucleus pulposus (NP) dehydrates and the annulus fibrosus (AF) fissures form, which often results in intervertebral disc herniation or disc space collapse and related clinical symptoms. Currently available options for treating intervertebral disc degeneration are symptoms control with therapy modalities, and/or medication, and/or surgical resection of the IVD with or without spinal fusion. As such, there is an urgent clinical demand for more effective disease-modifying treatments for this ubiquitous disorder, rather than the current paradigms focused only on symptom control. Hydrogels are unique biomaterials that have a variety of distinctive qualities, including (but not limited to) biocompatibility, highly adjustable mechanical characteristics, and most importantly, the capacity to absorb and retain water in a manner like that of native human nucleus pulposus tissue. In recent years, various hydrogels have been investigated in vitro and in vivo for the repair of intervertebral discs, some of which are ready for clinical testing. In this review, we summarize the latest findings and developments in the application of hydrogel technology for the repair and regeneration of intervertebral discs.

The Effects of Preoperative Epidural Steroid Injection on Pseudarthrosis Following Lumbar Fusion: A Retrospective Cohort Study.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The goal of this study is to evaluate the effects of preoperative lumbar epidural steroid injection on the rate of pseudarthrosis following lumbar spine fusion surgery. SUMMARY OF BACKGROUND DATA: Epidural corticosteroids help to reduce nerve root edema and suppress proinflammatory cytokines in patients with radiculopathy. Corticosteroids may inhibit bone formation and reduce bone matrix synthesis rates. Thus, there is concern that corticosteroids may reduce lumbar fusion capability, potentially resulting in increased rates of symptomatic pseudarthrosis. MATERIALS AND METHODS: We identified all patients who underwent 1-level or 2-level lumbar fusion surgery between 2018 and 2022. Patients were categorized into one of 3 groups: no preoperative epidural steroid injection (ESI) history (group 0), preoperative ESI within 90 days of surgery (group 1), or most recent ESI >90 days before surgery (group 2). The primary outcome of this study was pseudarthrosis. Binominal regression analyses were performed to determine the relationships between potential risk factors (sex, age, body mass index, smoking history, diabetes status, history of systemic steroid use, preoperative ESI, perioperative intravenous steroid administration, type of surgery, and postoperative ESI within 6 mo) and the development of postoperative pseudarthrosis. RESULTS: A total of 446 patients were included in this study. Of those, 106 patients (23.7%) did not have a preoperative ESI (group 0), 132 patients (29.5%) had an ESI within 90 days of surgery (group 1), and 208 patients (46.6%) had their most recent ESI >90 days before surgery (group 2). The overall incidence of pseudarthrosis following lumbar fusion was 8.7% (39 of 446). Although the incidence of pseudarthrosis following ESI at any time point was higher than in our control cohort (group 0), this difference was not statistically significant. CONCLUSIONS: This study found no increased risk of postoperative pseudarthrosis in patients who underwent 1-level or 2-level lumbar fusions after preoperative ESI. LEVEL OF EVIDENCE: Level III.

A Calcar Collar Is Protective Against Early Torsional/Spiral Periprosthetic Femoral Fracture: A Paired Cadaveric Biomechanical Analysis.

BACKGROUND: Periprosthetic fracture is a leading reason for readmission following total hip arthroplasty. Most of these fractures occur during the early postoperative period before bone ingrowth. Before ingrowth occurs, the femoral component can rotate relative to the femoral canal, causing a spiral fracture pattern. We sought to evaluate, in a paired cadaver model, whether the torsional load to fracture was higher in collared stems. The hypothesis was that collared stems have greater load to fracture under axial and torsional loads compared with collarless stems. METHODS: Twenty-two cadaveric femora (11 matched pairs) with a mean age of 77 ± 10.2 years (range, 54 to 90 years) were harvested. Following dissection, the femora were evaluated with use of a dual x-ray absorptiometry scanner and T scores were recorded. We utilized a common stem that is available with the same intraosseous geometry with and without a collar. For each pair, 1 femur was implanted with a collared stem and the contralateral femur was implanted with a collarless stem with use of a standard broaching technique. A compressive 68-kg load was applied to simulate body weight during ambulation. A rotational displacement was then applied until fracture occurred. Peak torque prior to fracture was measured with use of a torque meter load cell and data acquisition software. RESULTS: The median torque to fracture was 65.4 Nm for collared stems and 43.1 Nm for uncollared stems (p = 0.0014, Wilcoxon signed-rank test). The median T score was -1.95 (range, -4.1 to -0.15). The median difference in torque to fracture was 29.18 Nm. As expected in each case, the mode of failure was a spiral fracture around the implant. CONCLUSIONS: Collared stems seemed to offer a protective effect in torsional loading in this biomechanical model comparing matched femora. CLINICAL RELEVANCE: These results may translate into a protective effect against early periprosthetic Vancouver B2 femoral fractures that occur before osseous integration has occurred.

Outcomes of Revision Joint Arthroplasty Due to Metal Allergy and Hypersensitivity: A Systematic Review.

BACKGROUND: Lower extremity total joint arthroplasty (TJA) is one of the most successful orthopaedic procedures. However, it is estimated that as many as 10% to 20% of TJAs could fail due to various well-known causes. Furthermore, metal allergy-related complications have recently gained attention as one of the potential causes of failure when the common reasons have been excluded. Reported symptoms from metal allergy can include chronic eczema, joint effusions, joint pain, and limited range of motion. Few studies have explored the outcomes of patients undergoing revisions due to allergic complications. The aim of our study is to quantitatively evaluate the outcomes of revision joint arthroplasty due to metal allergy and hypersensitivity.