Minimally Invasive Surgery of the Hip Versus Standard Approach: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Minimally Invasive Surgery of the Hip Versus Standard Approach (NCT00261040), a randomized na study. The primary outcome is Clinical Outcomes.

2. Clinical Question

This is a comparison of two procedures within a randomized, parallel-group study, rather than a comparison with no surgery. The main statistical question is whether the observed difference in average hospital stay is sufficiently precise to distinguish a difference between approaches from the range of values compatible with sampling variation. The secondary outcomes broaden the picture to hip function, mobility, operating time, and estimated blood loss. The registry record does not report detailed participant characteristics, eligibility criteria, or the exact postoperative assessment schedule beyond the timeframes listed for outcomes. Those omissions limit how fully the clinical question and the group comparability can be assessed from the record alone.

3. Trial Design

The registry describes a completed, randomized, parallel study sponsored by the Ottawa Hospital Research Institute. Enrollment was 40. Participants were assigned to minimally invasive surgery or standard surgery. The record identifies the study as single-masked, but does not say which people involved in the study were masked or how masking was maintained. The phase is listed as not applicable.

The two approaches differed in incision size and the way the hip replacement was performed through the incision. The minimally invasive arm used a shorter incision and special instruments; the standard arm used a longer incision. The study's stated purpose was to compare hospital length of stay and postoperative outcomes. The registry identifies length of stay as the primary outcome, with Harris Hip Score, change in Timed Get-up-and-Go Test, operating time, and estimated blood loss as secondary outcomes. Estimated blood loss is listed among the secondary outcomes, but a corresponding result is not included in the posted secondary results.

The registry lists a start date of 2003-06 and a primary completion date of 2010-12. It does not report the original protocol's sample-size assumptions, the planned analysis population, the randomization procedure, or the statistical analysis plan. The posted primary outcome summaries include 18 participants in the minimally invasive arm and 19 in the standard arm. The secondary outcome summaries use 20 participants in each arm. The record does not explain why the counts differ across outcomes or how missing observations were handled. These summaries should therefore be read as outcome-specific data, not as a complete account of participant flow or analysis populations.

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: Patient recruitment occurred at the Ottawa Hospital (General Campus) by one of two co-investigator surgeons trained in MIS of the hip. Randomization occurred on the day of surgery in order to minimize the potential number of dropouts.

Overall Study

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.

6. Primary Endpoint

The registry lists the primary outcome as Clinical Outcomes, measured over 24 months.

The primary endpoint is hospital length of stay, expressed in days. It measures the time a participant remains in hospital after the hip replacement. As a measure, length of stay can reflect the course of immediate postoperative care and is relevant to hospital resource use. It is not, on its own, a complete measure of recovery, hip function, or later health.

The registry reports the endpoint as a mean with a standard deviation and gives a timeframe of 24 months. The record does not explain the connection between that timeframe and the measurement of hospital stay, which is ordinarily recorded around the hospitalization itself. It also does not define the starting and ending points used to determine the stay, or describe how transfers, readmissions, or discharge arrangements were treated. These details are not reported in the registry record.

For interpretation, the primary comparison is the difference in mean length of stay between the minimally invasive and standard arms. A negative difference means the posted mean is lower in the minimally invasive arm; it does not by itself establish that the approaches differ in the population. The confidence interval is important because it describes the range of differences compatible with the summary data under the calculation used. The posted interval includes no difference and also permits differences in either direction. The endpoint is therefore best understood alongside its precision and the limitations of the registry's description, rather than as a standalone verdict about postoperative recovery.

7. Results Posted in the Registry

• Minimally Invasive Surgery (MIS): mean 5.39 versus 5.74 on control; difference -0.35 (95% CI -1.43 to 0.73), standardized effect d = -0.21; z-test p = 0.527.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Harris Hip Score

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Minimally Invasive Surgery (MIS): mean 90.40 versus 90.30 on control; difference 0.10 (95% CI -6.64 to 6.85), standardized effect d = 0.01; z-test p = 0.976.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Minimally Invasive Surgery (MIS) and the control. The interval gives the range of effects that remain compatible with the data.

Change in Timed Get-up-and-Go Test (TUG)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Minimally Invasive Surgery (MIS): mean 11.01 versus 12.03 on control; difference -1.02 (95% CI -3.47 to 1.43), standardized effect d = -0.26; z-test p = 0.415.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Minimally Invasive Surgery (MIS) and the control. The interval gives the range of effects that remain compatible with the data.

Operating Time Duration

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Minimally Invasive Surgery (MIS): mean 95.20 versus 87.70 on control; difference 7.50 (95% CI -6.93 to 21.93), standardized effect d = 0.32; z-test p = 0.308.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Minimally Invasive Surgery (MIS) and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes span patient-reported or clinical hip function, mobility, and operating time. Across the posted summaries, the estimated differences are modest relative to the uncertainty, and each confidence interval includes zero. The signs of the estimates are not all in the same direction: some are lower in the minimally invasive arm and operating time is higher. Taken together, the outcomes do not show a consistent pattern of clear separation between approaches.

The secondary results complement the primary length-of-stay comparison by covering different aspects of the perioperative and postoperative course. Harris Hip Score addresses hip status at 24 months, the Timed Get-up-and-Go measure records mobility performance at 3 months, and operating time reflects the day of surgery. These outcomes do not measure the same construct as hospital stay, so similarity or difference in one does not determine the result for another. Estimated blood loss is named as a secondary outcome, but a result for it is not reported in the registry record.

The secondary comparisons are unadjusted and the record does not report a plan for controlling multiplicity. When several outcomes are tested, interpreting each result as if it were the only planned comparison can overstate the strength of evidence. The registry also does not state which secondary outcomes, if any, were designated as confirmatory or how their analyses were prioritized. For those reasons, these findings carry less weight than a prespecified primary analysis and are best treated as descriptive supporting evidence.

The pattern should not be summarized as proof that the approaches produce identical outcomes. The intervals allow a range of possible differences, and the clinical relevance of that range cannot be judged without thresholds that are not reported. The secondary outcomes add context, but they do not resolve the uncertainty around the primary endpoint or substitute for a complete analysis plan.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Harris Hip Score
• Change in Timed Get-up-and-Go Test (TUG)
• Operating Time Duration
• Estimated Blood Loss

9. Statistical Interpretation

10. Statistical Methods Explained

The comparison concerns means of continuous outcomes. A mean describes the average observed value within an arm, while the standard deviation describes variation among participants around that average. These summaries help describe each group, but do not by themselves show how certain the between-group contrast is. The confidence interval and the underlying group sizes are needed to assess that uncertainty.

How should the mean difference be read?

The posted contrast is calculated as the minimally invasive mean minus the standard-surgery mean. A value below zero therefore indicates a lower observed mean in the minimally invasive arm, while a value above zero indicates a higher observed mean. For length of stay, the recalculated estimate is -0.35 days. This is a difference between group averages, not the change experienced by each individual participant. It also does not adjust for other characteristics or account for any factors beyond the posted summary statistics.

The reported comparison values are simple, unadjusted recalculations from the posted arm summaries. They should not be confused with a full model-based analysis of individual participant data. No sponsor-reported analyses are listed for the primary or posted secondary outcomes. Since no discrepancy is flagged, there is no stated conflict between these recalculations and a sponsor analysis; if such a conflict were present, the sponsor's own analysis would take precedence.

What does a confidence interval communicate?

A confidence interval describes the precision of an estimated difference under the assumptions of the method used. In general, a wider interval means the estimate is less precise, while a narrower interval means it is more precise. When an interval includes zero for a difference in means, the data do not distinguish the observed estimate from no difference at the confidence level used for that interval. This does not establish that the true difference is zero. Nor does it establish equivalence, which requires a prespecified margin and a suitable analysis.

The registry does not state a clinically important threshold for any of the outcomes. That means the numerical range in an interval cannot be classified from the record as clinically unimportant or important. Clinical interpretation would require a justified threshold and relevant context, neither of which is reported in the registry record.

Why are the p-values unadjusted?

The posted p-values are labelled unadjusted. A p-value describes how compatible the data are with a specified null model, under the assumptions of the calculation; it is not the probability that the null hypothesis is true. The primary unadjusted p-value is 0.527. The secondary comparisons also have unadjusted p-values, but testing multiple outcomes raises the chance of finding an apparently unusual result by chance when all null hypotheses are true. No multiplicity strategy is reported, so the secondary p-values should not be interpreted as confirmatory evidence.

The record does not report the exact test or model used by the trial investigators, whether any covariates were planned, or whether there were interim analyses. Those methods cannot be inferred from the summary results. The posted comparisons are therefore best understood as unadjusted summaries, not as a reconstruction of the trial's original analysis plan.

What role does variation play?

Standard deviations describe how dispersed individual observations are within each arm. Greater participant-to-participant variation makes a mean difference harder to estimate precisely when group sizes are otherwise similar. The standard deviations listed for the outcomes are substantial relative to some of the observed differences, and the small outcome-specific group counts contribute to uncertainty. This is one reason the confidence intervals are important: they combine information about the estimate and its variability rather than focusing only on the two means.

For outcomes such as time to an event or binary outcomes, other methods may be needed. The posted primary and secondary comparisons are continuous measures and use means. Adverse-event counts are descriptive and are not interpreted through the continuous-outcome mean-difference method.

What can and cannot be inferred?

Random assignment is intended, in general, to make groups comparable in expectation and reduce confounding by baseline characteristics. The registry identifies randomization, but does not describe the sequence-generation or allocation-concealment methods. The record also does not report participant characteristics, analysis populations, or missing-data handling. Thus, the design label alone cannot establish how well these protections were implemented or whether all randomized participants contributed to each outcome.

The outcome-specific recalculations are useful for describing the posted means and their uncertainty. They cannot recover details absent from the registry record, such as an adjusted analysis, a prespecified testing hierarchy, or the reasons participants may be absent from a particular outcome summary. Interpretation should keep the distinction between a descriptive estimate and a complete trial analysis clear.

11. Confidence Intervals and Precision

For the primary endpoint, the estimated mean difference was -0.35 days, with a confidence interval from -1.434 days to a positive upper bound. Because the interval includes zero, the posted summary does not precisely establish the direction of a difference. It is compatible with no difference as well as with a range of effects on either side of zero. The unadjusted p-value of 0.527 likewise does not indicate a clear departure from the no-difference model, but it is not a measure of the probability that the approaches are the same.

Confidence intervals are useful because they show uncertainty around the estimate rather than presenting the point estimate alone. A point estimate can look specific even when the data allow a broad range of underlying differences. Here, the primary interval includes values that could represent a shorter or a longer mean stay in the minimally invasive arm. The registry record does not identify a threshold for clinical importance, so the interval cannot be divided into clinically negligible and clinically meaningful ranges on the basis of the posted information.

The primary outcome summary includes 18 participants in the minimally invasive arm and 19 in the standard arm, while total enrollment was 40. The record does not explain the difference between enrollment and the outcome-specific counts. It also does not state how missing outcome data were handled. The limited counts and absent missing-data description restrict the conclusions that can be drawn about precision and potential bias.

The secondary confidence intervals also include zero, with varying widths across outcomes. Their precision should be considered in light of their outcome-specific group counts and variability. None of these intervals establishes equivalence. A more precise estimate would require adequate information and a prespecified clinical margin if the aim were to demonstrate that any difference is small enough to be unimportant.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total participants across both arms. They are illustrative calculations based on the observed effect, not the trial's original design assumptions. The listed assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The planning scenarios use 100%, 75%, or 50% of the observed effect as the effect to detect. The original sample-size justification and assumptions are not reported in the registry record.

The 80% power column gives the estimated number of participants per arm for a design with an 80% chance of detecting the chosen effect under the stated planning assumptions, if that effect is the true one and the model assumptions hold. The 90% power column gives the corresponding per-arm requirement for a design with a 90% chance under those same assumptions. These are forward-looking planning quantities, not characteristics of the completed trial.

Smaller effects are harder to distinguish from random variation and therefore require more participants under otherwise similar assumptions. The planning estimates increase as the assumed effect is reduced from the full observed effect to a smaller fraction. In this study, the observed primary estimate is small relative to its uncertainty, so sample-size illustrations based directly on it should be read cautiously. They do not establish what effect the trial was originally designed to detect, because that design information is not reported.

This is not observed power. Observed power calculated from a study's estimated effect largely restates the result and its uncertainty; it does not provide an independent explanation for the findings. The planning figures are better used to understand how assumed effect size and desired power shape future sample-size requirements than to grade the completed trial.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -0.350; pooled standard deviation σ = 1.673.
2. n = 2 × (1.96 + 0.842)² × 1.673² / -0.350² = 358.6, rounded up to 359 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -0.350000000000001                      # observed difference in means
sigma <- 1.67285597535643                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(261040)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 359 (80% power), 481 (90% power)
 75% of observed effect: n per arm = 638 (80% power), 854 (90% power)
 50% of observed effect: n per arm = 1,435 (80% power), 1,921 (90% power)
power.t.test: 359.6 
Simulated power at n = 359 per arm: 0.801 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists several outcomes, including a primary endpoint and multiple secondary measures. The number of outcomes creates a multiplicity issue: when many statistical comparisons are made, the chance of at least one apparently notable result can rise even if there is no true effect on any outcome. A prespecified hierarchy, adjustment procedure, or clear distinction between confirmatory and exploratory outcomes can help readers interpret a family of tests. None is reported in the registry record.

The available secondary p-values are unadjusted. That does not make them incorrect as individual calculations, but it means they do not account for the broader set of outcome comparisons. The record does not report whether multiplicity was considered in the original protocol or analysis plan. In the absence of such information, the secondary findings should be read cautiously and should not be elevated to definitive evidence based on isolated p-values.

Missing-data handling is also not reported. The primary outcome summaries include 18 participants in the minimally invasive arm and 19 in the standard arm; the secondary summaries report 20 in each arm. Enrollment was 40, but the record does not give participant flow by outcome, reasons for missing observations, or the method used to handle incomplete data. It is therefore not possible to determine from the record whether the analyses followed intention-to-treat, per-protocol, or another population definition, or whether the missingness could have influenced the estimates.

The registry does not describe interim analyses, stopping rules, covariate adjustment, or sensitivity analyses. These omissions do not show that such methods were absent from the full study materials; they mean that they are not reported in the registry record. Without these details, the posted unadjusted summaries offer a limited account of statistical methods and do not support a full assessment of the analysis's prespecification or robustness.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: patient mortality (5.0%), myocardial infarction (5.0%).

The registry reports serious adverse events for 2 of 20 participants at risk in the minimally invasive arm and 0 of 20 in the standard arm. Other adverse events were reported for 0 of 20 and 1 of 20, respectively. These are descriptive counts. The record does not provide event-level descriptions, timing, severity details beyond the serious classification, or an assessment of whether an event was related to the procedure.

The serious adverse event terms listed include Patient mortality at 5.0% and Myocardial Infarction at 5.0%. The record does not link those terms to an arm or provide enough detail to reconcile them with the group counts. The deaths field is not reported in the registry record. A listed mortality term should therefore not be treated as a confirmed arm-specific death count on the basis of this information alone.

With limited group counts and sparse event descriptions, these figures cannot establish a comparative safety profile. They also should not be interpreted as showing that events did or did not occur beyond what the registry explicitly records.

16. What the Result Does, and Does Not, Mean

The posted results estimate differences between the two randomized groups for hospital length of stay and several postoperative outcomes. The primary estimate favors a shorter mean stay in the minimally invasive arm by direction, but its confidence interval includes zero and extends to values on either side. The secondary estimates are also uncertain. These data do not establish that one approach is superior, and they do not establish that the approaches are equivalent.

Failure to identify a clear difference is not proof that no difference exists. The confidence intervals describe a range of values compatible with the posted summaries under the calculation used. A result can be uncertain because of limited information, outcome variability, missing observations, or other factors; the registry record does not provide enough detail to identify the contribution of each. Nor does a point estimate alone determine whether an effect would matter to patients or clinicians. The record does not state clinically important thresholds for the outcomes.

The study addresses one specific comparison in hip replacement: a minimally invasive incision and technique versus a standard approach. Its results should not automatically be generalized to other surgical techniques, settings, patient groups, or care practices. Detailed eligibility criteria and participant characteristics are not reported, limiting assessment of how closely the enrolled group represents other populations.

The safety counts are similarly limited. They describe events recorded in the registry but do not provide sufficient detail to establish causation, timing, or a reliable difference between approaches. The registry's sparse reporting of analysis methods and participant flow also limits assessment of bias and robustness.

In short, the registry offers estimates rather than a conclusive answer. The most defensible interpretation is that the available summaries do not show a precise separation between approaches on the reported measures. They cannot rule out potentially relevant differences, demonstrate equivalence, or replace a complete analysis with prespecified methods and fuller outcome reporting.

17. Why This Trial Matters Statistically

This trial is statistically instructive because its point estimates are easy to overread. The primary mean difference is negative, which indicates a lower observed average length of stay for the minimally invasive arm, but the confidence interval includes zero. Reading only the direction of the estimate would ignore the uncertainty; reading a non-significant p-value as proof of no effect would make the opposite mistake. The interval and the design context are both essential.

The record also illustrates the distinction between enrollment and outcome-specific counts. The primary and secondary summaries use different numbers of participants, and the registry does not explain why. Without participant flow and missing-data methods, readers cannot determine whether the differences reflect missing observations, outcome availability, or another reason. Reporting those details is important because incomplete data can affect both precision and the validity of a comparison.

Another statistical issue is the presence of multiple outcomes. The secondary measures address different aspects of care and can provide useful context, but unadjusted comparisons across several measures need cautious interpretation. A clear plan identifying the primary contrast, the role of secondary outcomes, and any multiplicity approach would make the strength of evidence easier to judge.

Finally, the sample-size illustrations show why planning depends on an assumed effect and a desired power level. They do not explain the original design, which is not reported, and they are not a retrospective measure of the trial's success. Overall, the record demonstrates the value of distinguishing estimates, uncertainty, analysis choices, and clinical importance rather than reducing a trial to a single p-value.

18. 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 trial-specific reporting gaps limit interpretation. The registry identifies the study as single-masked but does not state who was masked. It does not describe the randomization sequence or allocation concealment, so the implementation of those design features cannot be assessed from the record.

The participant information is sparse. Detailed eligibility criteria, baseline characteristics, screened and excluded participants, and participant flow are not reported. Enrollment was 40, while outcome summaries use differing group counts. The record does not explain the difference or report missing-data handling, analysis populations, or sensitivity analyses. These omissions prevent a full appraisal of whether the posted comparisons include all randomized participants and whether incomplete outcomes could have affected results.

The primary outcome is described as hospital length of stay with a timeframe of 24 months, but the record does not explain that timing or define how the stay was measured. It does not report a clinically important difference for length of stay or the secondary measures. The secondary list includes estimated blood loss, but a corresponding result is absent from the posted outcome summaries.

Statistical reporting is also limited. No sponsor-reported analyses are listed, and the registry does not state the original sample-size justification, analysis plan, adjustment strategy, multiplicity procedure, or whether interim analyses occurred. The displayed comparisons are unadjusted recalculations from summary statistics, which cannot account for participant-level factors or recover missing methodological details.

Safety reporting lacks event-level detail and does not explain the listed serious adverse event terms or their relation to the group counts. These limitations mean the record supports a cautious reading of the reported estimates, not a comprehensive judgment of the trial's conduct or all of its outcomes.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Minimally Invasive Surgery of the Hip Versus Standard Approach — NCT00261040.
• Registry record last updated 2020-03-27; status last verified 2020-03.
• Results first posted 2020-03-27.
• 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.

22. Record Summary

The registry record describes a completed randomized, parallel-group study sponsored by the Ottawa Hospital Research Institute, with enrollment of 40. It compared minimally invasive hip replacement with the standard surgical approach. The primary outcome was hospital length of stay in days, listed with a 24-month timeframe. Secondary outcomes included Harris Hip Score, change in Timed Get-up-and-Go Test, operating time, and estimated blood loss.

The posted primary comparison is an unadjusted recalculation from outcome summaries. Its estimated mean difference is -0.35 days, and its confidence interval includes zero. The secondary comparisons also have intervals that include zero. The record does not report sponsor analyses, original sample-size assumptions, missing-data methods, analysis populations, or a multiplicity plan. Serious and other adverse-event counts are posted, but event details are limited. These results describe the available registry summaries and leave important uncertainties about analysis and reporting.