Opioid Use After Total Knee Replacements

Author's Argument

• Total Knee Replacements (TKRs) serve as the main treatment for knee osteoarthritis (OA)
• Most TKR patients experience post-operative pain
• Initial opioid prescriptions for pain can foster long-term dependence
• The study aims to find possible connections between opioid use and other co-existing health issues

Data Source and Subject Criteria

• Data was sourced from Optum Labs Warehouse, featuring de-identified medical, pharmacy, and lab claim records
• The data included enrollment records for commercially insured and Medicare Advantage recipients
• Insurance coverage is a notable factor due to the legal implications linked to prescribing opioids and the variability in insurance companies' willingness to cover opioid prescriptions
• Some insurances are more willing to prescribe opioids, while others are more selective

Research Design and Variables

• The research used a cohort study design, grouping individuals with shared traits and implementing a retrospective approach
• Exposure variables were categorized by whether the patients had experienced a physical therapy (PT) intervention, either before or after undergoing TKR
• Pre-TKR intervention was identified as having at least one PT code within 90 days before the surgery, whether outpatient or inpatient
• Post-TKR intervention was identified as having at least one PT code within 90 days after the surgery, whether outpatient or inpatient
• Post-TKR treatment was considered complete if no PT codes were updated within 12 weeks after the previous session
• Further definition of post-TKR PT interventions was achieved by identifying the first outpatient PT episode of care (EOC) that started within 90 days of the surgery

Outcome Variable

• Long-term opioid use was the measured outcome, defined as 90 days or more of filled opioid prescriptions during specific assessment periods
• Outcome assessments were conducted both before and after the TKR

Intervention Timing

• Interventions were assessed 12 months after the initial 90 days post-TKR, excluding immediate post-operative opioid usage for recovery
• The 12-month period following the final PT POC marks a phase where normal surgical recovery should occur, reducing the need for opioids

Confounders

• Confounders are factors that influence outcomes but are not accounted for
• The study considered confounders like age, sex, race, ethnicity, obesity, insurance type, geographical location, physical and mental health comorbidities
• Identifying confounders is vital to find other potential reasons for a patient’s opioid use, separate from the TKR itself
• Knowing all the factors for opioid use other than the TKR itself is important for validy
• Co-existing health and mental conditions can significantly influence the outcome measures
• Patients managing additional pain diagnoses, substance abuse, or mental health issues might be more prone to opioid reliance as part of their routine
• Insurance coverage is an important factor, with some insurers more inclined to cover opioids while others may not

Statistical Analysis

• Statistical analyses included data collected from January 1, 1999, to December 31, 2018
• All analyses were performed using SAS, with a statistical significance level set at a 2-sided a level of 0.05
• Researchers incorporated both pre- and post-TKR PT EOCs, which defined long-term opioid use as use during the 12 months after the initial 90 days post-surgery or after the end of the last PT EOC
• The study also distinguished between opioid-experienced (patients who had used opioids before TKR) and opioid-naive (patients who had not used opioids before TKR) individuals

Figure 2 and Table 1

• Figure 2 diagrams the exclusion criteria and resulting participant groups: opioid-naive and opioid-experienced individuals
• Table 1 outlines and compares the characteristics of each group
• Both groups presented similar demographics with mostly female participants
• Participants were gathered mainly from the Midwest and South regions of the U.S
• The spread of insurances was relatively consistent across both groups, minimizing its impact on the study
• The opioid-experienced group generally showed a higher rate of medication use (NSAIDs) and instances of LBP, depression, and general pain

Pre-TKR and Post-TKR PT

• Both opioid-naive and opioid-experienced patients showed a decreased likelihood of long-term opioid use when receiving pre-TKR PT interventions, with an odds ratio (OR) of 0.75 (25% less likely)
• Confidence intervals (CI) excluding 1 indicated significant ORs (opioid-naive CI: 0.6-0.95, opioid-experienced CI: 0.7-0.8)
• Post-TKR PT patients in the opioid-naive group had an OR of 0.89, with a CI including 1 (0.75-1.04), indicating no significant decrease in the risk of developing long-term opioid use
• The opioid-experienced group receiving post-TKR PT had an OR of 0.75, with a CI of 0.7-0.79, suggesting a 25% reduced likelihood of long-term opioid use
• Pre-TKR PT reduces the risk of long-term opioid use for both opioid-naive and opioid-experienced patients
• Post-TKR PT is only significant in reducing the risk of long-term opioid use in the opioid-experienced population.

Post-TKR PT Characteristics

• Opioid-naive patients who received more PT sessions (≥13) showed decreased odds of long-term opioid use (OR=0.82), but the CI included 1 (0.67-1.01), indicating non-significance
• Opioid-experienced patients showed decreased risk in both the ≥13 session group (OR=0.71, 29% less likely) and the 6-12 session group (OR=0.82, 18% less likely)
• More PT sessions correlated with a reduced likelihood of long-term opioid use
• Delaying Post-TKR PT led to increased odds of long-term opioid use, especially at 61-90 days post-surgery for opioid-naive groups (OR=2.15, 2x higher chance) and 61-90 days post-surgery with 32% increase in opioid use
• Starting PT early (<30 days) was most effective in preventing long-term opioid use
• Type of post-TKR PT (active vs. passive) showed no significant difference in either group, indicating this may not be a key factor in preventing long-term opioid use

Sensitivity Analysis

• This analysis tested the quality of results, and validated stability between subgroups.
• More PT sessions (≥13) and early PT (≤30 days) was most impactful in reducing long-term opioid use, with the type of PT having no effect