This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Liposomal Bupivacaine Versus Standard Analgesia in Total Joint Arthroplasty (TJA) (NCT02197273), a randomized na study. The primary outcome is Length of Stay in Hospital (Days).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02197273 |
| Phase | NA |
| Condition | Osteoarthritis, Knee, Osteoarthritis, Hip, Osteoarthritis, Shoulder |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 211 |
| Arms in the primary outcome | 2 |
| Lead sponsor | OhioHealth |
| Results posted | Yes |
2. Clinical Question
Population
The trial concerns people undergoing total joint arthroplasty for osteoarthritis of the knee, hip, or shoulder. The registry records enrollment of 211. The posted arm results concern total hip and total knee arthroplasty; further information about how the shoulder condition was represented in the treatment groups is not reported in the registry record.
Intervention
The intervention is liposomal bupivacaine added to standard-of-care analgesia. The registry describes an amount of 266 mg in its hip and knee descriptions. Full treatment details, including a complete description of the standard-care protocols, are not reported in the registry record.
Comparator
The comparator is standard-of-care analgesia without the listed addition of liposomal bupivacaine. The registry describes standard-care components for hip and knee arthroplasty, but the complete protocols are not reported in the registry record.
Primary question
The primary question is whether the groups differed in length of hospital stay, measured in days, after total joint arthroplasty. The reported summary is the median and full range for each arm, with a Wilcoxon (Mann-Whitney) comparison.
The registry frames the study as an evaluation of pain management after joint replacement. Hospital stay is the primary outcome, while the listed secondary outcomes concern time to postoperative rescue opioids and pain-related readmission or emergency department visits. These outcomes address related but distinct aspects of postoperative care: length of stay reflects time in hospital, rescue opioid timing reflects additional pain treatment, and return visits reflect care after discharge. They should not be treated as interchangeable measures of pain.
The clinical question is narrower than whether one regimen is generally better for every patient or procedure. The posted results describe the enrolled trial groups and the outcomes recorded in the registry. They do not establish how the findings apply to other settings, other analgesia protocols, or people outside the trial population.
3. Trial Design
The registry identifies NCT02197273 as a completed, randomized, single-masked, parallel-group study sponsored by OhioHealth. Its title concerns liposomal bupivacaine versus standard analgesia in total joint arthroplasty. The registry lists enrollment of 211. The study began in 2014-07, and primary completion was recorded in 2015-09.
Participants were assigned to standard-of-care analgesia or liposomal bupivacaine in addition to standard-of-care analgesia. The available arm results label the groups “Standard of Care Analgesia” and “Liposomal Bupivacaine.” The registry describes an added 266 mg of liposomal bupivacaine in its hip and knee intervention descriptions. The full protocol details are not reported in the registry record, and the masking description does not identify which people involved in the trial were masked.
The conditions listed are osteoarthritis of the knee, hip, and shoulder. The posted treatment descriptions refer to total hip arthroplasty and total knee arthroplasty. How the shoulder condition relates to the treatment descriptions and posted arm results is not reported in the registry record. The registry lists phase as NA.
The primary outcome is length of stay in hospital, reported as a median in days with a full range. The timeframe says participants were followed for the duration of their hospital stay, described as an expected average of 3 days. The registry also lists time to postoperative rescue opioids and readmission or emergency department visit due to pain control within 30 days. Numeric results are posted for the pain-related return-visit outcome, but not for time to rescue opioids.
The registry record does not report the rationale for the enrollment target, a detailed statistical analysis plan, interim analyses, or the analysis population. Those omissions limit what can be inferred about planning and conduct beyond the design features and results explicitly recorded.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: Patients were randomized in a one to one fashion to one of two study groups within each surgical group. 10 patients were excluded after enrollment due to dual enrollment in another study, changes in anesthesia plan or improper dose of study drug. These 10 patients were not included in the analysis.
Overall Study
| Stage | Standard of Care Analgesia | Liposomal Bupivacaine |
|---|---|---|
| STARTED | 107 | 104 |
| COMPLETED | 107 | 104 |
| NOT COMPLETED | 0 | 0 |
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Standard of Care Analgesia | Liposomal Bupivacaine | Total |
|---|---|---|---|---|
| Participants analysed | 107 | 104 | 211 | |
| Age, Continuous | years | 66.5 (SD 8.4) | 65.9 (SD 9.1) | 66.3 (SD 8.6) |
| Sex: Female, Male: Female | Participants | 57 | 61 | 118 |
| Sex: Female, Male: Male | Participants | 50 | 43 | 93 |
6. Primary Endpoint
The registry lists the primary outcome as Length of Stay in Hospital (Days), measured over Participants were followed for the duration of hospital stay, an expected average of 3 days.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Full Range |
| Unit | days |
| Endpoint classification | Time-to-Event Analysis |
The primary endpoint is length of stay in hospital, measured in days. The registry reports the median and full range for each treatment group. Median length of stay was 2 days in both groups. The full range was 1 to 7 days with standard-of-care analgesia and 1 to 3 days with liposomal bupivacaine.
Length of stay is a practical measure of hospital use after surgery. As a general statistical point, it can reflect many influences beyond pain management, including recovery, discharge practices, and care arrangements. It is therefore not a direct measure of pain intensity or analgesic use. The registry does not report a pain score as the primary endpoint.
The trial’s recorded timeframe is the duration of hospital stay, with an expected average of 3 days. The endpoint’s median gives a measure of the middle of the observed distribution, while the full range describes its minimum and maximum values. A range does not show how observations are distributed between those endpoints. The registry does not provide additional distributional summaries or a confidence interval for the difference between groups.
The primary analysis used a Wilcoxon (Mann-Whitney) test. This test compares the distributions of observations between groups; it is not, by itself, a direct estimate of the difference between the group medians. The reported p-value therefore addresses a group comparison, while the posted medians and ranges describe each group separately.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The median hospital stay was 2 days in each arm. The observed ranges differed: 1 to 7 days for standard-of-care analgesia and 1 to 3 days for liposomal bupivacaine. The registry reports a Wilcoxon (Mann-Whitney) p-value of 0.764 for the primary comparison. This is not evidence of a clear difference in the recorded distributions, but it does not establish that the treatments are equivalent.
The group medians alone provide limited information about the full outcome distributions. In particular, equal medians do not imply that every feature of the groups’ stay durations was the same. The ranges give some information about observed extremes, but do not show how often stays of different lengths occurred. A confidence interval for a treatment contrast is not reported in the registry record, so the precision of an estimated group difference cannot be assessed from an interval.
The comparison should be read in light of the endpoint: hospital stay is a measure of time in hospital, not a direct measure of pain. It may be influenced by clinical and organizational factors. The registry’s expected average duration of 3 days is a timeframe description, not an observed group average or a treatment effect.
The posted results also include a pain-related readmission or emergency department outcome within 30 days after discharge. The reported counts are 2 participants in the standard-care arm and 4 in the liposomal bupivacaine arm. The recalculated unadjusted risk difference is 0.020, with a 95% confidence interval from -0.025 to 0.065, and an unadjusted p-value of 0.388. Because the interval includes zero, the estimate is compatible with outcomes ranging from a lower risk in the liposomal bupivacaine group to a higher risk. This secondary result is imprecise and should not be read as a definitive difference.
The registry lists time to postoperative rescue opioids as a secondary outcome, but numeric results are not reported in the registry record. Consequently, that outcome cannot contribute to a comparison of the overall pattern of pain-related findings. The available outcomes address different parts of postoperative care, and the primary result does not substitute for missing secondary results.
These findings describe the posted trial results. They do not demonstrate that the treatments are clinically equivalent, nor do they establish that either approach improves or worsens pain management. The registry record does not provide enough information to assess the clinical importance of a particular difference in hospital stay or return visits.
9. Statistical Methods Explained
The primary endpoint is summarized using the median and full range. The median is the middle value when observations are ordered. It is less affected by unusually long or short stays than the arithmetic mean. The full range reports the smallest and largest observed values, but does not indicate the frequency of values within that span. These summaries make it possible to see the group medians and observed extremes, but they do not provide a direct estimate with uncertainty for the treatment contrast.
What does the Wilcoxon (Mann-Whitney) test compare?
The registry names a Wilcoxon (Mann-Whitney) test for the primary outcome and reports p = 0.764. As a general statistical explanation, this rank-based method compares the relative ordering of observations from the groups. It does not require the outcome to be normally distributed in the way a conventional comparison of means often does. Its result is not automatically a test of equality of medians: a median-focused interpretation requires assumptions about the shapes of the group distributions. The registry does not report those distributional details or a confidence interval for the primary contrast.
A p-value describes how incompatible the observed data are with a specified null model, under the assumptions of the test. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. A p-value of 0.764 does not establish equivalence or prove that the groups have identical outcomes. Assessing equivalence would require a prespecified margin and an analysis designed for that purpose; such information is not reported in the registry record.
How should the secondary binary outcome be read?
For pain-related readmission or emergency department visits within 30 days, the registry reports participant counts by group and a sponsor analysis using Fisher Exact. The recalculated unadjusted comparison expresses the absolute difference as a risk difference: the estimated risk in the liposomal bupivacaine group minus the estimated risk in the standard-care group. The posted estimate is 0.020, with a 95% confidence interval from -0.025 to 0.065. The interval gives a range of values compatible with the data and the calculation’s assumptions. Because it spans zero, it does not rule out no absolute difference.
The recalculated unadjusted p-value is 0.388. A confidence interval and a p-value answer related but distinct questions: the interval displays uncertainty around an estimated effect, while the p-value assesses compatibility with a null hypothesis. Neither conveys whether an effect would be clinically important. The estimate is based on a small number of recorded events, so the interval is wide relative to the point estimate. This is a general reason that rare binary outcomes can be estimated imprecisely even when their counts are reported clearly.
Fisher Exact is a method for comparing categorical outcomes, particularly useful when event counts are sparse. It calculates a test result from the observed counts under its null model. The registry’s sponsor-reported analysis gives a value of 0.486 and p = 0.656. The recalculated unadjusted comparison uses a different calculation and reports p = 0.388; the methods and estimates should not be conflated. These are unadjusted results, and the registry does not report a multiplicity adjustment for the family of outcomes.
What do the planning illustrations mean?
The planning calculations are illustrations based on the observed secondary effect, not the trial’s own design justification. The stated assumptions are a two-sided significance level of 0.05, equal allocation, and a normal approximation. Different rows consider planning for 100%, 75%, and 50% of the observed effect, with participants per arm for 80% power and participants per arm for 90% power. These are hypothetical planning quantities, not observed power and not evidence about the probability that the trial detected an effect. The registry record does not report the trial’s own sample-size justification or assumptions.
As a general statistical principle, planning illustrations depend on the assumed effect and analysis model. A smaller target effect generally requires a larger planned sample to detect it under otherwise unchanged assumptions. Because the observed effect is uncertain, basing a future design on it alone may be misleading; the illustrations are best treated as scenarios rather than recommendations.
Why do missing results matter?
Although time to postoperative rescue opioids is listed as a secondary outcome, numeric results are not reported in the registry record. Without those results, readers cannot evaluate the treatment-group contrast, its uncertainty, or its relationship to hospital stay and return visits. The analysis population, handling of missing observations, and any covariate adjustment are also not reported in the registry record. These details matter because the interpretation of a trial comparison depends not only on the summary numbers but also on who was included and how incomplete observations were handled.
10. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| Wilcoxon (Mann-Whitney) | not reported | 0.764 |
For the primary endpoint, the registry reports the sponsor’s Wilcoxon (Mann-Whitney) comparison with p = 0.764. The posted medians are 2 days in both groups, with ranges of 1 to 7 days for standard-of-care analgesia and 1 to 3 days for liposomal bupivacaine. No recalculated primary effect estimate or confidence interval is reported, so the sponsor’s test is the available inferential result for this endpoint.
For pain-related readmission or emergency department visits, the sponsor reports a Fisher Exact analysis with value 0.486 and p = 0.656. The unadjusted recalculation reports a risk difference of 0.020, a 95% confidence interval from -0.025 to 0.065, and p = 0.388. The recalculation uses an unadjusted comparison based on the posted counts; it is not the same result as the sponsor’s Fisher Exact test. The figures should therefore be interpreted with their methods attached rather than treated as interchangeable estimates.
The registry does not flag a discrepancy between the sponsor’s result and the recalculation. The sponsor’s primary analysis remains the reported inferential analysis for length of stay; the recalculation adds a different summary for the secondary binary outcome. Neither result establishes equivalence, and the registry record does not report the analysis plan needed to determine whether these analyses were prespecified.
11. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary endpoint and secondary outcomes, but a multiplicity strategy is not reported in the registry record. When several outcomes are tested, the chance of at least one apparently unusual result can increase if each test is interpreted at the same threshold without adjustment. As a general statistical point, an analysis plan may control this issue by defining a hierarchy, adjusting thresholds, or distinguishing confirmatory from exploratory analyses. The registry does not say whether any such approach was used.
Missing outcome information also limits interpretation. Time to postoperative rescue opioids is listed, but numeric results are not reported in the registry record. The record does not describe missing-data amounts, reasons for missingness, imputation, or sensitivity analyses. Without those details, the completeness and robustness of the outcome analyses cannot be assessed.
The registry reports group-level results and named tests, but the analysis population is not reported in the registry record. It is therefore unclear from the record whether analyses included all randomized participants, only participants with recorded outcomes, or another defined population. The record also does not report whether the analysis adjusted for baseline variables or other covariates. These omissions do not invalidate the posted summaries, but they constrain conclusions about how the results were generated and how broadly they represent the randomized comparison.
For the primary endpoint, a confidence interval for a treatment contrast is not reported. The medians and ranges describe the groups, while the p-value gives a test result; together they do not quantify uncertainty around a specific effect estimate. The trial’s sample-size justification and any interim analyses are not reported in the registry record. Those details cannot be inferred from the enrollment or the observed findings.
As a general matter, absence of a reported multiplicity plan, missing-data approach, or analysis population is not proof that those procedures were absent. It means the registry record does not allow readers to verify them. Interpretations should stay close to the posted results and acknowledge that the available record leaves these design and analysis details unresolved.
12. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Standard of Care Analgesia | 0 | 107 | 0.0% |
| Liposomal Bupivacaine | 0 | 104 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Standard of Care Analgesia | 0 of 107 |
| Liposomal Bupivacaine | 2 of 104 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Standard of Care Analgesia | Liposomal Bupivacaine |
|---|---|---|---|
| knee pain | Musculoskeletal and connective tissue disorders | 0 of 107 | 2 of 104 |
The registry records 0 serious adverse events among 107 participants at risk in the standard-of-care group and 0 among 104 participants at risk in the liposomal bupivacaine group. It lists no serious adverse event terms. These figures describe serious adverse events recorded in the registry; they do not establish that serious harms cannot occur or that the groups have identical safety profiles.
For other adverse events, the registry records 0 among 107 participants at risk in the standard-care group and 2 among 104 participants at risk in the liposomal bupivacaine group. Death counts are not reported in the registry record. No further detail about the nature, timing, severity, or relatedness of these other events is available in the record.
As a general statistical point, a lack of recorded events in a trial does not demonstrate absence of risk. Event counts are descriptive, and the registry does not provide a comparative safety analysis or uncertainty intervals for these figures. They should be read as the adverse-event information recorded, not as a complete safety assessment.
13. What the Result Does, and Does Not, Mean
The primary result describes a comparison of hospital length of stay in this randomized trial. The median was 2 days in each arm, the observed ranges were 1 to 7 days and 1 to 3 days, and the reported Wilcoxon (Mann-Whitney) p-value was 0.764. These results do not show a clear difference in the recorded primary outcome, but they do not prove that the treatments are equivalent or that their effects are identical.
A non-significant test result is not evidence that an effect is exactly zero. The registry does not report a confidence interval for the primary treatment contrast, so the precision of a possible difference cannot be judged directly. The medians and ranges alone cannot show the shape of the distributions or identify a clinically important threshold. The registry record does not report such a threshold.
The primary endpoint measures hospital stay rather than pain directly. It should not be used as a substitute for pain scores or opioid use. The secondary outcome for time to rescue opioids has no numeric results reported in the registry record. The pain-related return-visit outcome has a small number of events and an imprecise recalculated estimate. Together, these registry entries mean that the available registry results offer only a partial picture of postoperative pain-related care.
The findings also do not establish the effects of the regimens in every type of joint arthroplasty or in settings beyond the trial. Although the registry lists knee, hip, and shoulder osteoarthritis, the posted treatment descriptions refer to hip and knee procedures, and the relationship to shoulder procedures is not reported in the registry record. Details about the analysis population and the full analysis plan are also unavailable.
Accordingly, the result is best understood as a description of the outcomes recorded in this trial, with a primary comparison that did not identify a clear difference in hospital stay. It is not proof of no effect, not a demonstration of equivalence, and not a general conclusion about the effectiveness or safety of either regimen.
14. Why This Trial Matters Statistically
This trial is statistically useful because it illustrates the difference between a group summary and an estimate of treatment effect. The primary outcome has equal reported medians, but the ranges differ and the registry reports a rank-based comparison. Readers need all of these pieces to understand what was observed, while also recognizing that none alone supplies a complete description of the outcome distributions.
It also shows why a p-value should not be treated as a measure of effect size or certainty. The primary p-value does not establish equivalence, and the registry does not report a confidence interval for the primary contrast. For the secondary binary outcome, the recalculated risk difference is paired with an interval that conveys substantial uncertainty. These are different kinds of information and answer different questions.
The record also makes the distinction between sponsor-reported analyses and unadjusted recalculations important. The sponsor used Fisher Exact for the return-visit outcome, while the recalculation reports a risk difference and a different unadjusted p-value. Careful interpretation keeps each result connected to its method rather than selecting a single number without context.
Finally, incomplete reporting has statistical consequences. The missing numeric rescue-opioid results, unavailable analysis population, and absent multiplicity description constrain what can be concluded across outcomes. These gaps do not determine what the unreported results would have been. They show why registry reporting should include estimates, uncertainty, outcome completeness, and analysis details alongside test results.
15. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
Several limitations specific to this trial follow from the registry record. The primary outcome is hospital length of stay, which is not a direct pain measure. The record reports medians and ranges but does not provide a confidence interval for a treatment contrast or additional information about the distribution of stays. This limits assessment of the magnitude and precision of any primary difference.
The outcome information is incomplete. Time to postoperative rescue opioids is listed as a secondary endpoint, but numeric results are not reported in the registry record. The record does not report how missing outcome data were handled, the analysis population, covariate adjustment, or a multiplicity approach. These absences make it difficult to evaluate the completeness and prespecification of the analyses.
The pain-related return-visit outcome has few recorded events, and the recalculated interval is broad and spans no difference. The sponsor’s Fisher Exact result and the unadjusted recalculation are based on different methods; their p-values should not be combined or treated as if they answer an identical calculation.
The registry lists osteoarthritis of the knee, hip, and shoulder, while the treatment descriptions available for the arms refer to hip and knee arthroplasty. The application of the described protocols to shoulder procedures is not reported in the registry record. The full standard-care protocols are also not reported. In addition, the registry’s single-masking label does not specify who was masked.
The enrollment rationale, sample-size justification, interim analyses, and detailed statistical plan are not reported in the registry record. These limits concern what can be verified from the record; they do not establish that a particular procedure was or was not carried out.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: Liposomal Bupivacaine Versus Standard Analgesia in Total Joint Arthroplasty (TJA) — NCT02197273.
- Registry record last updated 2016-10-21; status last verified 2016-08.
- Results first posted 2016-10-21.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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19. Record Summary
NCT02197273 is a completed, randomized, single-masked, parallel-group trial sponsored by OhioHealth. The registry records enrollment of 211, a start date of 2014-07, and primary completion in 2015-09. It compares standard-of-care analgesia with liposomal bupivacaine added to standard care after total joint arthroplasty.
The primary endpoint is hospital length of stay. Median stay was 2 days in each group, with ranges of 1 to 7 days and 1 to 3 days; the reported Wilcoxon (Mann-Whitney) p-value is 0.764. The registry also lists time to postoperative rescue opioids and pain-related readmission or emergency department visits within 30 days. Numeric results for rescue-opioid timing are not reported in the registry record. The return-visit outcome has posted counts and sponsor-reported Fisher Exact results. The registry does not report the analysis population, multiplicity approach, or detailed statistical plan.