Immunoglobulin A Nephropathy in a Patient With Bilateral Metal-on-Metal Hip Arthroplasty.

Immunoglobulin A (IgA) nephropathy in the presence of a metal-on-metal (MoM) hip arthroplasty is a rare condition that requires close monitoring. A 61-year-old male with bilateral hip osteoarthritis underwent resurfacing hip arthroplasty with MoM articulating surfaces. Prior to his four-year postoperative visit, the patient was diagnosed with IgA nephropathy. During this visit, the patient reported clicking in the left resurfacing hip arthroplasty, and serum metal ions were significantly elevated. Consequently, the patient underwent conversion to bilateral ceramic-on-cross-linked polyethylene total hip arthroplasty, which resulted in the restoration of metal ion levels to normal. This case highlights that IgA nephropathy played a critical role in impeding the clearance of metal ions. Routine metal ion counts are warranted in patients with MoM articulating interfaces and a newly diagnosed nephropathy.

Acute Periprosthetic Hip Fractures With Short, Uncemented Femoral Stems.

BACKGROUND: Uncemented femoral stems in hip arthroplasty have shown excellent long-term results, and several systematic studies indicate satisfactory performance of short stems. However, biomechanical and finite element analysis studies have suggested that shorter stems allow greater micromotion, producing greater strain at the implant-bone interface, which potentially increases the risk for periprosthetic fracture (PPF). We sought to assess this risk within our unit. METHODS: Our institution's arthroplasty database was searched for all primary total hip arthroplasties using short femoral stems performed between July 14, 2009 and August 29, 2022. The overall PPF rate and the PPF rate for individual femoral stems were established. Preoperative X-rays for each case were analyzed to characterize individual proximal femoral geometry. A data analysis was performed to identify risk factors for PPF. RESULTS: For the time period assessed, 3,192 short femoral stems were implanted. This included 1,561 of stem A and 1,631 of stem B. Women constituted 55.37% of the cohort. The average patient age was 66 years (range, 22 to 95). The PPF rate was 0.6%, with 19 PPFs identified at a follow-up of 3 months. There was a significantly higher fracture rate in stem A (0.96%) compared to stem B (0.25%) (P ≤ .01). Proximal femoral geometry, age, and sex were not determined to be risk factors for PPF in our cohort. Individual surgeons and surgical approaches appeared to confer no increased risk. There was no significant difference in average stem length, but multivariate analysis identified stem type and stem length as an independent risk factor for PPF. CONCLUSIONS: Our study identified individual stem and stem length as independent risk factors for PPF within our cohort. PPF is a multifactorial issue, and consensus on emerging risk factors such as implant design will hopefully inform decisions that can provide further risk reduction for individual patients.

Cobalt ions induce a cellular senescence secretory phenotype in human synovial fibroblast-like cells that may be an early event in the development of adverse local tissue reactions to hip implants.

Objectives: Total hip arthroplasty is a successful procedure for treating advanced osteoarthritis (OA). Metal bearing surfaces remain one of the most widely implanted prosthesis, however approximately 10% of patients develop adverse local tissue reactions (ALTRs), namely lymphocytic predominant soft tissue reaction with or without necrosis and osteolysis resulting in high revision rates. The mechanism(s) for these reactions remains unclear although T lymphocyte mediated type IV hypersensitivity to cobalt (Co) and chromium (Cr) ions have been described. The purpose of this study was to determine the prolonged effects of Co and Cr metal ions on synovial fibroblasts to better understand the impact of the synovial membrane in the development of ALTRs. Methods: Human synovial fibroblast-like cells were isolated from donors undergoing arthroplasty. DNA content and Alamar blue assay were used to determine cellular viability against exposure to Co and Cr. A beta-galactosidase assay was used to determine the development of cellular senescence. Western blotting and RT-qPCR were employed to determine changes in senescent associated secretory factors, signaling and anti-oxidant enzyme expression. A fluorescent assay was used to measure accumulation of hydrogen peroxide. Results: We demonstrate that prolonged cobalt exposure results in a downregulation of the enzyme catalase resulting in cytosolic accumulation of hydrogen peroxide, decreased Akt activity and cellular senescence. Senescent fibroblasts demonstrated upregulation of proinflammatory cytokines IL-1ß and TNFα in addition to the neurotrophic factor NGF. Conclusion: Our results provide evidence that metal ions induce a senescent associated secretory phenotype in synovial fibroblasts that could contribute to the development of adverse local tissue reactions.

Impact of combined lumbar spine fusion and total hip arthroplasty on spine, pelvis, and hip kinematics during a sit to stand task.

Lumbar fusion is a risk factor for hip dislocation following total hip arthroplasty (THA). The objective was to compare joint/segment angles during sit-stand-sit in participants that had a THA with and without a lumbar fusion. The secondary objective was to compare pain, physical function, disability, and quality of life. This cross-sectional study includes participants that had THA and lumbar fusion (THA-fusion; n = 12) or THA only (THA-only; n = 12). Participants completed sit-stand-sit trials. Joint/segment angles were measured using electromagnetic motion capture. Angle characteristics were determined using principal component analysis. Hierarchical linear models examined relationships between angle characteristics and groups. Pain, physical function, and disability were compared using Mann-Whitney U tests. Upper lumbar spine was more extended during sit-stand-sit in the THA-fusion group (b = 42.41, P = 0.04). The pelvis was more posteriorly and anteriorly tilted during down and end sit-stand-sit phases, respectively, in the THA-fusion group (b = 12.21, P = 0.03). There were no significant associations between group and other angles. THA-fusion group had worse pain, physical function, disability, and quality of life. Although differences in spine joint, pelvis segment, and hip joint angles existed, these findings are unlikely to account for the increased incidence of hip dislocation after total hip arthroplasty in patients that had spine fusion.

Similar complication and readmission rates following simultaneous versus staged bilateral total hip arthroplasty.

PURPOSE: To compare short-term complications and readmission rates, in patients treated with simultaneous versus staged bilateral total hip arthroplasty (THA) within a year from the index procedure. METHODS: We reviewed the charts of patients that underwent simultaneous and staged-within a year-bilateral THA, between 2016 and 2020. Preoperative baseline characteristics were evaluated, while differences in terms of 30-day major and 30-day minor complications and readmission rates were compared between the groups. RESULTS: One-hundred-sixty patients (mean age, 64.3 years; SD, ± 11.7) were identified. Seventy-nine patients were treated with simultaneous (Group A) and eighty-one patients with staged (Group B) THA. There were no differences in baseline characteristic between the two groups (p > 0.050). Group A was more likely to receive general anesthesia (43% vs. 9.9%, p < 0.001) and had longer total operative time (182.8 vs. 128.0 min, p < 0.001). Group A had an overall shorter total length of hospital stay (5.8 vs. 8.6 days, p < 0.001). No differences in transfusion rates (p = 0.229) and no differences in major and minor complications (p > 0.05) were identified. Postoperative visits at the emergency department or readmissions were similar between the two groups (p > 0.050). CONCLUSION: This study shows that similar complication and readmission rates are expected after simultaneous and staged THA. Simultaneous bilateral THA is a safe and effective procedure, that should be considered for patients that present with radiologic and clinical bilateral hip disease.

Inter-segment coordination amplitude and variability during gait in patients with knee osteoarthritis and asymptomatic adults.

BACKGROUND: Inter-segment coordination examines the timing and coupling of multiple body segments and provides a complex understanding of how the neuromuscular system controls the body. Research is required to examine if inter-segment coordination during gait differs between individuals with different knee osteoarthritis (OA) severities and asymptomatic adults. RESEARCH QUESTION: Do inter-segment coordination amplitude and between-trial variability during gait differ between individuals with varying levels of knee OA severity and asymptomatic adults? METHODS: This observational, cross-sectional study included participants with mild/moderate knee OA (n = 38), severe knee OA (n = 24), and asymptomatic adults (n = 51). Participants ambulated overground at self-selected speeds. Data were collected with an eight-camera motion capture system and two force plates. Continuous relative phase (CRP) was used to quantify sagittal plane inter-segment coordination amplitude and between-trial variability for the thigh-shank and shank-foot pairs. Hierarchical linear models examined if CRP variables were related to the group (asymptomatic, mild/moderate OA, severe OA) after accounting for gait speed and gait phase. RESULTS: Thigh-shank CRP amplitude was significantly associated with group variables. The severe OA group had lower CRP amplitudes than both asymptomatic (b=8.57, 95 % confidence interval=2.75-14.38) and mild/moderate OA (b=5.69, 95 % confidence interval=-0.25 to 11.62) groups. Thigh-shank CRP variability was also associated with group. The severe OA group had lower CRP variability than the asymptomatic group (b=0.45, 95 % confidence interval=0.12-0.78); there were no differences between severe and mild/moderate OA groups (p > 0.050). There were no significant associations between any of the shank-foot CRP measures and the groups. SIGNIFICANCE: Lower thigh-shank CRP amplitude and variability in individuals with severe knee OA represents a more rigid motor system. These individuals could be attempting to stabilize their knee in response to a loss of passive stability or in response to pain. They might have difficulty adapting their gait to perturbations.

Indication for total knee arthroplasty based on preoperative functional score: Are we operating earlier?

BACKGROUND: The number of total knee arthroplasty (TKA) procedures performed annually is increasing for reasons not fully explained by population growth and increasing rates of obesity. The purpose of this study was to determine the role of patient functional status as an indication for surgery and to determine if patients are undergoing surgery with a higher level of preoperative function than in the past. METHODS: A systematic review and meta-analysis of the MEDLINE, Embase and Cochrane databases was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Functional status was assessed using the 36-Item Short Form Health Survey's physical component summary (PCS) score. Only primary procedures were included. Articles were screened by 2 independent reviewers, with conflicts resolved with a third reviewer. Meta-regression analysis was performed to determine the effect of time, age and sex on preoperative PCS score. Subgroup analysis was performed to compare results for the United States with those for the rest of the world. RESULTS: A total of 1502 articles were identified, of which 149 were included in the study. Data from 257 independent groups including 57 844 patients recruited from 1991 to 2015 were analyzed. The mean preoperative PCS score was 31.1 (95% confidence interval 30.6-31.7) with a 95% prediction interval of 22.8-39.5. The variance across studies was found to be significant (p < 0.001) with 99.01% true variance. Year of enrolment, age, the percentage of female patients and geographic region did not have any significant effect on preoperative PCS score. CONCLUSION: Patients are undergoing TKA with a level of preoperative function similar to their level of function in the past. Patient age, sex and location did not influence the functional status at which patients were considered to be candidates for surgery.

Outcomes of Ceramic-On-Ceramic Bearing Total Hip Arthroplasty: A Minimum 10-Year Follow-Up Study.

BACKGROUND: Although the fourth generation of ceramics has demonstrated excellent clinical results 5 to 6 years postoperatively, concerns over ceramic fracture and squeaking persist and longer-term follow-up (minimum 10 years) studies are warranted. Our study aimed to evaluate the minimum 10-year clinical outcomes and bearing-specific complications of ceramic-on-ceramic (CoC) total hip arthroplasties. METHODS: We retrospectively evaluated all patients who underwent primary delta CoC total hip arthroplasty in our institution between January 2004 and February 2013. Demographics, surgical techniques, complications, patient-reported outcomes, and radiographic outcomes were collected and analyzed. For continuous variables, the comparison between groups was conducted using a one-way analysis of variance. Of all 235 patients included in the study, 70.5% were women (190 hips). The mean follow-up period was 12 years (range, 10 to 18). The femoral head sizes of 28- mm, 32 mm, and 36 mm were used in 50, 26, and 197 cases, respectively. Mean acetabular inclination and anteversion angles were 39.2 ± 7.1° and 14.9 ± 3.5°. RESULTS: There were 5 hips revised at a mean 4.6 years (range, 0.1 to 7.1). One revision was squeaking-related. Squeaking was also reported by 8 other patients, but did not require revision. Other reasons for revision were early infection in 2 cases, stem loosening in 1 case, and stem fracture in 2 cases. The survival analysis for any causes for revision as an endpoint was 96.7% (95% confidence interval 0.313%-2.57%). CONCLUSION: We report excellent mean 12-year follow-up results regarding the complications and survivorship of the fourth generation CoC bearings.

Osteosarcoma Around a Ceramic-on-Ceramic Total Hip Arthroplasty.

Sarcoma arising at the site of a total hip arthroplasty (THA) is uncommon. We present a case report of a patient diagnosed with an osteosarcoma around a ceramic-on-ceramic THA and a narrative literature review of sarcomas around THA. A search of PubMed MEDLINE was performed from inception. Our case report was included in the analysis. A total of 13 studies were included in the review. We report the first case of a sarcoma around a ceramic-on-ceramic hip implant. All cases in the literature reported poor outcomes with an average time from index THA to diagnosis of 9.3 ± 8.2 years. Sarcomas around THA are extremely rare. Despite the rarity of the diagnosis, osteosarcoma must be considered in the differential diagnosis when investigating a periprosthetic mass.

AOA Critical Issues Symposium: I Have an Idea Now What?

ABSTRACT: The purpose of this symposium was to provide guidance to innovators as they progress from the idea stage to the product development stage,to the issuing of a patent, and to bringing a product or innovation to market. Finding strategic partnerships is a critical component in taking a good idea and turning it into a successful business. Protecting intellectual property through patents and developing an exit strategy are also important parts of making innovation profitable. We strive to empower our colleagues who are pursuing and commercializing ideas to help impact the health-care system at large.

Long-Term Survivorship of Cemented and Uncemented Polyethylene Liner Exchange.

BACKGROUND: Revision surgery is usually required for complications associated with total hip arthroplasty (THA). Significant morbidity can be associated with revision THA and thus some may only revise the liner of the original metal back component if it is found to be well fixed. We compare the long-term survivorship of cemented and uncemented head-liner THA exchange surgeries and possible causes. METHODS: Between 2000 and 2018, we reviewed cases from our arthroplasty database who underwent THA revision for head-liner exchange. We stratified our cohort into 2 groups: cemented and uncemented liners. Patients were followed clinically and radiographically to determine survivorship of the exchanges for both cemented and uncemented liners. Implant survivorship was measured using a competing risk analysis considering death and patients lost to follow-up as competing risks. RESULTS: A total of 84 patients (85 hips) underwent head-liner exchange surgery during the study period (21 cemented and 64 uncemented liners). The mean follow-up time was 6.9 years, with 75.3% and 24.7% of patients having been revised due to non-dislocation and dislocation causes, respectively. Two cemented liners (9.5%) and 11 uncemented liners (17.2%) required revision. The survival analysis of all head-liner revision was 86.4% at 18 years. Survival estimates liner exchanges due to dislocation versus non-dislocation groups were 57.3% versus 82.7% respectively (P = .034). CONCLUSION: The present study shows improved survivorship of head-liner exchanges performed due to non-dislocation etiology compared to dislocation etiology, but no difference in survivorship between cemented and uncemented head-liner exchange. LEVEL OF EVIDENCE: Level III.

Elective Total Hip Arthroplasties in Nonagenarians-Age Does Matter: A National Surgical Quality Improvement Program Study.

BACKGROUND: The aim of this study is to assess the independent effect of age on the risk of postsurgical complications and death in patients undergoing total hip arthroplasty (THA). METHODS: The National Surgical Quality Improvement Program was used to identify all patients aged 65 years and older who underwent primary THA from 2011 to 2017. Study outcomes were minor complications, major life-threatening complications, and 30-day mortality. Predictors of outcomes were identified using bivariate analyses and age was added into the final logistic regression models with stepwise selection. RESULTS: A total of 74,361 patients were included in the analysis. Mean (standard deviation) age was 735 years (6.46), median 72.0 years; 1,119 (1.50%) patients were ≥90 years. Females comprised 60.6% of the patient sample. The incidence of major life-threatening complications, minor complications, and death was 939/74,361 (1.3%), 2,098 (2.8%) and 154 (0.2%) respectively. When added to the final models, age was significantly associated with an increased risk of postoperative complications and mortality. CONCLUSION: Elective THA in relatively healthy nonagenarians should only be considered among patients with disabling osteoarthritis demonstrating a restricted quality of life. Although THA can substantially improve patient wellbeing, our findings suggest that surgeons and patients must consider the impact of age on patient course and outcomes regardless of the presence of comorbidities. LEVEL OF EVIDENCE: Level II, prognostic study.

Patient Functional Status as an Indication for Primary Total Hip Arthroplasty: A Systematic Review and Meta-Analysis.

BACKGROUND: The number of total hip arthroplasties performed per year is increasing for reasons not fully explained by a growing and aging population. The purpose of this study was to determine the role of patient functional status as an indication for surgery and determine if patients are undergoing surgery at a better functional status than in the past. METHODS: A systematic review and meta-analysis of the MEDLINE, EMBASE, and Cochrane databases was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Functional status was assessed using the 36-Item Short-Form Health Survey's Physical Component Summary score. Only primary procedures were included; revisions were excluded. Articles were screened by 2 independent reviewers with conflicts resolved with a third reviewer. Meta-regression analysis was performed to determine the effect of time, patient age, and gender. Subgroup analysis was performed to compare geographic regions. RESULTS: A total of 1504 articles were identified. Data from 172 groups representing 18,644 patients recruited from 1990 to 2013 and identified from 107 articles were included. The mean preoperative Physical Component Summary score was 31.2 (95% confidence interval 30.5-31.9) with a 95% prediction interval of 22.6-39.8. The variance across studies was statistically significant (P = .000) with 97.25% true variance. Year of enrollment, age, and the percentage of females were not found to have any significant effect. There were no differences between countries. CONCLUSION: Patients are undergoing total hip arthroplasty at a similar preoperative physical functional status as in the past. Patient age, gender, and location do not influence the functional status at which patients are indicated for surgery.

Long-Term Outcome of Small Head Metal-On-Metal Total Hip Arthroplasty: A 15-to-22 Year Follow-Up.

BACKGROUND: The Metasul articular interface was a second-generation metal-on-metal (MoM) total hip arthroplasty (THA) that was introduced as a promising interface with improved manufacturing technology, better clearances, and enhanced metal hardness. In December 2001, the manufacturer recalled these implants due to the failure of cup osseointegration. METHODS: Between 1997 and 2004, 168 consecutive primary Metasul THAs were performed in 144 patients. Most patients received a cementless femoral and porous-coated acetabular component with 28 mm head. A competing risk analysis was performed for determination separately for bearing surface-related, recalled bearing failure, and end point revision for any reason. For clinical patient evaluation, we used Harris hip score and University of California at Los Angeles scores. Cobalt and chromium ion level measurement and standard radiographic assessment was performed. RESULTS: Of the 168 THAs, 19 hips were revised at a mean period of 15 years as follows: 12 of them were due to recalled acetabular component, five hips had noninterface-related complication, and two true interface surface failure. The survival distribution function of all hips with revision for any reason was 88.4%, for bearing interface relation 98.8%, and 92.6% for recalled cups. The mean Harris hip score and University of California at Los Angeles scores were 85 and 6, respectively, and the median Co and Cr blood levels were 1.0 and 0.91 µg/L. CONCLUSION: Excluding the recalled components, Metasul articular interface has performed extremely well at a minimum follow-up of 15 years in this relatively young population. There were two interface-related revisions in the entire cohort.

Orthopedic Surgery and Telemedicine in Times of COVID-19 and Beyond: a Review.

PURPOSE OF REVIEW: This review article presents the current knowledge on the use of telemedicine and summarizes the literature highlighting the advantages and limitations of this technology in the field of orthopedic surgery during the COVID-19 pandemic and beyond. RECENT FINDINGS: Orthopedic surgery is the surgical specialty that has seen the highest proportion of its procedures cancelled due to the pandemic. In this context and onward, telemedicine seems to be a reasonable option for the orthopedic surgeon. Multiple studies have described its safety and a similar patient satisfaction compared to in-person consultations. It has a potential to increase productivity and decrease wait times by providing easier access to the clinician and by decreasing travel-associated limitations and costs. Authors have described the possibility to conduct a reliable virtual assessment of the patient range of motion. Some of the limitations to the use of this technology are technological literacy and access to virtual consultation platforms, the inability to conduct a complete physical examination, potential reduction in identification of intimate and child abuse victims, and limited knowledge about the legal implications of this technology. Telemedicine in orthopedic surgery has a potential to increase productivity, reduce costs, and increase the access to healthcare. Identified limitations include risk of misdiagnosis, required technologic literacy, unknown legal implications, and failure to identify victims of abuse. In order to use this technology judiciously, the clinician must take into consideration the patient's condition and his technological literacy and be aware of the advantages and disadvantages.

Unexpected iatrogenic fracture of the femoral neck during subtrochanteric fracture fixation in a patient on bisphosphonate treatment for osteoporosis: Case report.

Osteoporotic patients being treated with bisphosphonates present an interesting dilemma when removing hardware such as dynamic hip screws "DHS". In this paper, we describe the case of a 66-year-old osteoporotic patient who was placed on long term bisphosphonate therapy after sustaining an intertrochanteric hip fracture which was stabilized with a DHS. She presented with a subtrochantric fracture on the ipsilateral side. She was planned for DHS removal and intramedullary nailing. Removal of the dynamic hip screw proved to be difficult, likely due to possible cold welding of the DHS to the barrel of the side plate and sclerotic bone formation around the hardware secondary to the extended bisphosphonate use. The patient had an intra-operative femoral neck fracture while attempting the DHS removal. We had to convert to an unanticipated total hip replacement. Careful considerations should be taken when removing hardware from patients on long term bisphosphonate treatment.

The Influence of Lateral and Posterior Total Hip Arthroplasty Approaches on Muscle Activation and Joint Mechanics During Gait.

BACKGROUND: Lateral and posterior total hip arthroplasty (THA) approaches disrupt muscle function, which could impact gait. The objectives of this study were to compare muscle activation and joint mechanics during gait, and isometric strength between participants after lateral and posterior THA approaches and healthy adults. METHODS: Participants 1 year post-THA from either lateral (n = 21) or posterior (n = 21) approaches, and healthy adults (n = 21) ambulated at self-selected speeds. Surface electromyography, optical motion capture, and force plates measured muscle activation and joint mechanics during gait. A dynamometer measured isometric torque. Gait characteristics and isometric torque were compared using analysis of variance and effect sizes (d). RESULTS: Lateral THA group had higher gluteus medius amplitudes during gait compared to the healthy group (P < .01, d = -0.97). Posterior THA group had higher gluteus maximus amplitudes during loading response (P = .02, d = -0.94) and higher hamstring amplitudes during midstance (P = .02, d = 0.45-1.31) than the healthy group. Both THA groups had decreased hip flexion and adduction angle excursions during gait (d = 0.89-1.14), but increased medial rotation angle excursions (d = -1.06 to -0.91), compared to the healthy group. Lateral THA group had lower isometric hip abduction torque than the healthy group (P = .03, d = 0.74). There was no pelvic drop in the THA groups. CONCLUSION: There were few differences in gait and isometric torque between lateral and posterior THA groups. The elevated muscle activation amplitudes in the lateral and posterior THA groups compared to healthy adults were likely due to muscle weakness. Despite these findings, there was no evidence of pelvic drop.

Injectable Chitosan Hydrogels with Enhanced Mechanical Properties for Nucleus Pulposus Regeneration.

IMPACT STATEMENT: A thermosensitive chitosan-based hydrogel was developed, which mimics the mechanical properties of the human nucleus pulposus (NP) tissue and provides a suitable environment for seeded NP cells to live and produce glycosaminoglycans. This scaffold is injectable through 25G needle and rapidly gels in vivo at body temperature. It has the potential to restore mechanical properties and stimulate biological repair of the degenerated intervertebral disc (IVD). It could therefore be used for the minimally invasive treatment of degenerated IVD, which affects more than one person out of five in the world.

Short Link N promotes disc repair in a rabbit model of disc degeneration.

BACKGROUND: The degeneration of the intervertebral disc (IVD) is characterized by proteolytic degradation of the extracellular matrix, and its repair requires the production of an extracellular matrix with a high proteoglycan-to-collagen ratio characteristic of a nucleus pulposus (NP)-like phenotype in vivo. At the moment, there is no medical treatment to reverse or even retard disc degeneration. The purpose of the present study was to determine if a low dose of short link N (sLN), a recently discovered fragment of the link N peptide, could behave in a manner similar to that of link N in restoring the proteoglycan content and proteoglycan-to-collagen ratio of the disc in a rabbit model of IVD degeneration, as an indication of its potential therapeutic benefit in reversing disc degeneration. METHODS: Adolescent New Zealand white rabbits received an annular puncture with an 18-gauge needle into two noncontiguous discs to induce disc degeneration. Two weeks later, either saline (10 µL) or sLN (25 µg in 10 µL saline) was injected into the center of the NP. The sLN concentration was empirically chosen at a lower molar concentration equivalent to half that of link N (100 µg in 10 µL). The effect on radiographic, biochemical and histologic changes were evaluated. RESULTS: Following needle puncture, disc height decreased by about 25-30% within 2 weeks and maintained this loss for the duration of the 12-week study; a single 25-µg sLN injection at 2 weeks partially restored this loss in disc height. sLN injection led to an increase in glycosaminoglycans (GAG) content 12 weeks post-injection in both the NP and annulus fibrosus (AF). There was a trend towards maintaining control disc collagen-content with sLN supplementation and the GAG-to-collagen ratio in the NP was increased when compared to the saline group. CONCLUSIONS: When administered to the degenerative disc in vivo, sLN injection leads to an increase in proteoglycan content and a trend towards maintaining control disc collagen content in both the NP and AF. This is similar to link N when it is administered to the degenerative disc. Thus, pharmacologically, sLN supplementation could be a novel therapeutic approach for treating disc degeneration.