Effect of Postoperative Analgesic Exposure to the Cannabinoid Receptor Agonist WIN55 on Osteogenic Differentiation and Spinal Fusion in Rats.

BACKGROUND: After spinal surgery and other orthopaedic procedures, most patients receive opioids for pain, leading to potential complications such as pseudarthrosis and opioid abuse associated with long-term use. As an alternative, the endocannabinoid system has been shown to have antinociceptive activity, while contributing to bone homeostasis via the CB1 and CB2 cannabinoid receptors. This study evaluates the impact of the cannabinoid receptor agonist WIN55,212-2 (WIN55) on osteogenic differentiation in vitro as well as bone regeneration and spinal fusion in a preclinical rat model. METHODS: Primary rat bone marrow stromal cells were cultured in standard or osteogenic media and exposed to vehicle alone or WIN55. Runx2 and Alkaline phosphatase (Alpl) were quantified via qPCR (quantitative real-time polymerase chain reaction), followed by assessment of ALP activity and matrix mineralization. For in vivo evaluation, 45 female Sprague Dawley rats (n = 15 per group) underwent L4-L5 posterolateral spinal fusion with bilateral placement of collagen scaffolds preloaded with low-dose rhBMP-2 (recombinant human bone morphogenetic protein-2; 0.5 µg/implant). Postoperatively, rats received the vehicle alone or 0.5 or 2.5 mg/kg WIN55 via daily intraperitoneal injections for 5 days. Bone regeneration and spinal fusion were assessed using radiography, manual palpation-based fusion scoring, microcomputed tomography imaging, and histology. RESULTS: mRNA expression levels of Runx2 and Alp were similar among cells treated with vehicle alone and WIN55. Likewise, exposure to WIN55 did not inhibit ALP activity or bone matrix mineralization. In this animal model, no significant differences were found among groups with regard to mean fusion score, fusion rate, or new bone volume. CONCLUSIONS: WIN55 showed no adverse impact on osteogenic differentiation, bone regeneration, and spinal fusion. This supports that cannabinoid receptor agonists should be further investigated as a potential alternative approach for postoperative analgesia following spinal fusion and other orthopaedic procedures requiring bone-healing. CLINICAL RELEVANCE: The identification of alternative treatments for postoperative pain following orthopaedic surgical procedures is crucial in combating the ongoing opioid abuse crisis. The endocannabinoid system may represent a viable alternative target for addressing orthopaedic postoperative pain.

The Potential Value of Performing Preoperative Urinalysis Prior to Total Knee Arthroplasty.

BACKGROUND: Although the practice of checking a urinalysis prior to elective total knee arthroplasty (TKA) is relatively common, very little has been reported on the association between a preoperative urinary tract infection (UTI) and adverse events in primary TKA. The goal of this study is to investigate the risk of postoperative complication following TKA as it relates to preoperative UTI. METHODS: Patients undergoing TKA were queried in the National Surgical Quality Improvement Program. Morbid events were classified as minor (transfusion, pneumonia, wound dehiscence, UTI, and renal insufficiency) and serious (wound infection, thromboembolic event, renal failure, myocardial infarction, prolonged ventilation, unplanned intubation, sepsis, and death). Risk factors for adverse events were analyzed in both univariate and multivariate fashion. RESULTS: A total of 203,851 patients undergoing TKA met inclusion criteria and 507 patients had a UTI present at time of surgery (UTI PATOS). A propensity matched analysis controlling for age, gender, body mass index, operative year, and American Society of Anesthesiologists score identified 507 patients without a UTI PATOS to serve as the control group. Following adjustment for baseline characteristics, operative year, and American Society of Anesthesiologists score, UTI PATOS was associated with increased risk for serious adverse events (odds ratio [OR] 2.746, 95% confidence interval [CI] 1.546-4.878, P = .0006), occurrence of any morbid event (OR 1.894, 95% CI 1.299-2.761, P = .0009), and reoperation (OR 4, 95% CI 2.592-6.169, P < .0001). CONCLUSION: This study suggests that a UTI present at time of TKA increases the risk of multiple postoperative complications and reoperation.

Differences in Post-Operative Outcome Between Conversion and Primary Total Hip Arthroplasty.

BACKGROUND: The demand for conversion of prior hip surgery to total hip arthroplasty (conversion THA) is likely to increase as a function of increasing US hip fracture burden in addition to its application in managing other conditions. Thus, outcome analysis is warranted to better inform value-based reimbursement schemes in the era of bundled payments. METHODS: Via Current Procedural Terminology codes, the National Surgical Quality Improvement Project data files were queried for all patients who underwent primary THA and conversion of previous hip surgery to THA from 2005 to 2014. To better understand the isolated effect of procedure type on adverse outcomes, primary and conversion cohorts were then propensity-score matched via logistic regression modeling. Comparisons of the study's primary outcomes were drawn between matched cohorts. Statistical significance was defined by a P-value less than or equal to .05. RESULTS: Relative to the primary THA group, the conversion THA group had statistically greater rates of Center Medicare and Medicaid Services (CMS) complications (7.5% vs 4.5%), non-home bound discharge (19.6% vs 14.7%), and longer length of hospital stay. Conversion THA was associated with increased likelihood of CMS complications (odds ratio 1.68, confidence interval 1.39-2.02) and non-home bound discharge (odds ratio 1.41, confidence interval 1.25-1.58). No statistically significant differences in mortality and readmission were detected. CONCLUSION: The elevated risk for CMS-reported complications, increased length of hospital stay, and non-home bound discharge seen in our study of conversion THA indicates that it is dissimilar to elective primary THA and likely warrants consideration for modified treatment within the Comprehensive Care for Joint Replacement structure in a manner similar to THA for fracture.