In Vivo Kinematics for Subjects With Smith & Nephew Journey II BCS TKA, Journey II CR TKA, Or Journey II XR TKA: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for In Vivo Kinematics for Subjects With Smith & Nephew Journey II BCS TKA, Journey II CR TKA, Or Journey II XR TKA (NCT04612036), a registered phase not stated study. The primary outcome is Medial AP Translations, in mm.

2. Clinical Question

This is a comparison of measurements among implant groups, not a randomized comparison according to the registry record. Allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. Accordingly, the clinical question is descriptive and comparative: what kinematic and vibroarthrography measurements were recorded for subjects in each arm, and how do those measurements compare?

The primary endpoint focuses on movement of the medial femoral condyle across the range of motion during a deep knee bend. The registry defines positive translation as anterior sliding from full extension to maximum flexion and negative translation as posterior rollback. The record does not report the endpoint means, standard deviations, or between-arm estimates, so the magnitude or direction of observed differences cannot be described from the registry record.

3. Trial Design

The study is titled as a multicenter investigation of in vivo kinematics in subjects implanted with Journey II BCS, CR, or XR total knee arthroplasty. Its stated objective also includes comparison of vibroarthrography signals. The sponsor is The University of Tennessee, Knoxville. The registry lists enrollment of 60 and the status as completed. The recorded study start is 2020-10-22, and primary completion is recorded as 2022-05-16.

Three device arms are described. The BCS arm includes subjects whose ACL and PCL were both resected. In the CR arm, the ACL was resected and the PCL retained. In the XR arm, both the ACL and PCL were retained. These descriptions identify differences in the retained ligaments alongside the implant designs, which matters when interpreting comparisons: observed group differences cannot be attributed to implant design alone on the basis of this record.

The registry explicitly indicates that this is not a randomized comparison and that allocation is not stated. It also cautions that the arms are not a like-for-like control comparison. Details about how participants entered each arm, whether groups were formed consecutively, and whether any factors were used to adjust comparisons are not reported in the registry record. The protocol's sample-size justification and any interim analyses are not reported in the registry record.

The primary endpoint is a continuous measure, reported as a mean with standard deviation, assessed at least 6 months postoperative. The record lists 4 outcome measures and 0 analyses. It does not provide a detailed analysis plan or numerical primary endpoint results. Thus, the registry identifies the study question, arms, and endpoint definition, but not the statistical evidence needed to quantify differences among the groups.

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.

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 Medial AP Translations, in mm, measured over At least 6 months postoperative.

The primary endpoint is medial anterior-posterior translation, in millimeters, of the medial femoral condyle during a deep knee bend. The measurement reflects the participant's range of motion throughout the activity. The registry defines positive values as anterior sliding from full extension to maximum flexion, and negative values as posterior rollback over that movement. The timeframe is at least 6 months postoperative.

This continuous measure describes movement along a specific direction during a specified activity. In general, kinematic measurements can characterize how joint components move during a task; they do not by themselves establish how a participant feels or functions in daily life. The direction convention is important because a positive and a negative mean represent different directions of movement, not simply different magnitudes of the same direction.

The registry specifies that the endpoint is summarized by a mean and standard deviation. The mean describes the group's average translation, while the standard deviation describes spread among measurements. These summaries answer different questions: a mean alone does not show how variable individual measurements are, and a standard deviation alone does not show the group's average direction or magnitude.

Numerical means and standard deviations for the endpoint are not reported in the registry record. Nor are confidence intervals or between-arm estimates reported. Therefore, the endpoint definition can be interpreted, but the observed movement and the precision of any comparison cannot be assessed from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary outcome as a continuous measure summarized by a mean and standard deviation. A continuous outcome can take values along a measurement scale rather than being restricted to a category. Here, the scale is millimeters of medial femoral condyle anterior-posterior translation during a deep knee bend. The mean is the arithmetic average within a group; the standard deviation describes how dispersed the measurements are around that average. Neither summary is reported numerically for the primary endpoint in the registry record.

What does a mean describe?

A mean provides a concise description of the group's central measurement. Its interpretation depends on the measurement definition and sign convention. In this study, a positive value represents anterior sliding from full extension to maximum flexion, while a negative value represents posterior rollback. Thus the sign communicates direction. A mean close to zero, if one were reported, could reflect measurements near zero or a mixture of positive and negative measurements; the mean alone would not distinguish those patterns. This is a general statistical point, not a claim about the study's observed values.

Why report a standard deviation?

The standard deviation gives information about variation among the observations. Two groups can have similar means but different spreads, or similar spreads but different means. For that reason, a mean and standard deviation are complementary descriptive statistics. The standard deviation is not a confidence interval: it describes variation among measurements, whereas a confidence interval describes uncertainty about an estimated quantity, such as a group mean or difference in means. Confidence intervals for the primary endpoint are not reported in the registry record.

What would a group comparison estimate?

A comparison of group means would describe the difference between the average measurements in two arms. In general, an unadjusted comparison uses the observed group summaries without accounting for other characteristics, while an adjusted comparison attempts to account for specified factors. The registry record does not report the numerical group means, a between-arm estimate, or whether any adjusted comparison was performed. The comparison method and its assumptions are not reported in the registry record, so the actual analysis cannot be reconstructed from the endpoint description alone.

Confidence intervals are useful because they present a range of values compatible with the data and the analysis assumptions. They convey precision as well as direction and magnitude, whereas a p-value alone does not show the size of an effect. This is general statistical guidance. Neither confidence intervals nor p-values for the primary comparison are reported in the registry record, so no interval-based or hypothesis-test interpretation is possible.

How should the study arms affect interpretation?

The registry indicates that this is not a randomized comparison and that allocation is not stated. Randomization, in general, is intended to make treatment groups comparable with respect to both measured and unmeasured characteristics on average. Without a randomized allocation described in the record, a group comparison can be affected by differences in who entered each arm or by other factors. The arm descriptions also distinguish groups by ligament retention or resection. Consequently, an observed difference would not automatically represent an isolated implant-design effect. The registry does not report adjustment methods or enough information to assess the comparability of the groups.

The registry's sample-size assumptions describe a planning illustration based on an observed effect. They specify a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is expressed as a stated fraction of the observed effect. These are assumptions for illustration, not a report of the study's own design justification, and the protocol's sample-size justification is not reported in the registry record. Such calculations describe hypothetical future planning under their assumptions; they are not observed power and do not change the uncertainty in an already observed estimate. The observed effect used for the illustration is not numerically reported in the registry record.

In general, a normal approximation is a method for estimating the sampling behavior of a statistic under specified conditions. Its suitability depends on features such as the data distribution and sample size, neither of which can be assessed fully without the underlying observations and analysis details. No diagnostic checks, distributional assessments, or alternative analysis methods are reported in the registry record. Because the primary outcome is continuous and the record gives only a mean-and-standard-deviation summary format, it is not possible to determine whether the analysis used a particular parametric method or how its assumptions were evaluated.

Over-dispersion is a general concern when observed variability exceeds what a statistical model assumes; when present, it can make uncertainty estimates too small if not accounted for. That concept is most directly relevant to models whose variance assumptions may be inadequate. The registry does not report a model or evidence of over-dispersion for this continuous endpoint, so it should not be presumed to have occurred. More broadly, the absence of analysis details means that no specific model, variance correction, or inferential procedure can be attributed to this study.

The registry lists 4 outcome measures and 0 analyses. The count of outcomes does not disclose which comparisons were planned, whether multiple outcomes were tested together, or whether any adjustment was made for multiple testing. Those details are not reported in the registry record. The statistical methods that were actually applied, including the handling of missing values and the analysis populations, are also not reported. The endpoint description therefore supports an explanation of what the measurement means, but not a reconstruction or evaluation of the actual statistical analysis.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Journey II Bi-Cruciate Stabilized", "Journey II Cruciate Retaining", "Journey II Bi-Cruciate Retaining")
n   <- c(25, 25, 10)
m   <- c(-6.9, -0.2, -4.4)
sp  <- c(2.8, 4.3, 3.8)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Journey II Bi-Cruciate Stabilized  25  -6.900  2.800  -8.056  -5.744
CARM  Journey II Cruciate Retaining  25  -0.200  4.300  -1.975  1.575
CARM  Journey II Bi-Cruciate Retaining  10  -4.400  3.800  -7.118  -1.682

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures and 0 analyses. Multiple outcomes can raise a multiplicity issue when several hypotheses are tested: the chance of at least one apparently unusual result can increase as the number of tests increases. In general, an analysis plan may specify one primary comparison, designate secondary outcomes, or use an adjustment for multiple testing. The registry record does not report whether any such approach was specified or used. The count of outcomes alone does not establish that all outcomes were tested or that an adjustment was needed.

The primary endpoint is identified as medial AP translation, but its numerical group results and inferential statistics are not reported in the registry record. The stated objective also includes vibroarthrography signals, and their numerical results and analysis methods are not reported. The record does not report which outcome comparisons were prespecified, how outcomes were prioritized, or how any multiplicity was handled.

Missing-data methods are not reported in the registry record. There is no description of the amount or pattern of missing outcome measurements, whether measurements were excluded, or whether imputation or another method was used. The analysis population is also not reported. It is therefore not possible to determine which participants contributed to each outcome or whether the analysis included all enrolled subjects with available measurements.

These omissions limit interpretation of both precision and representativeness. A group summary based on only a subset of enrolled subjects may not characterize all enrolled subjects in the same way, and missingness can matter if it is related to measured outcomes. These are general considerations, not claims that missing observations occurred in this study. The registry does not provide enough detail to assess these questions or to judge the robustness of any outcome analysis.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The registry reports adverse-event figures separately for the BCS, CR, and XR groups. For serious adverse events, the listed numbers affected are 0 in each group. For other adverse events, the listed numbers affected are also 0 in each group. Deaths are listed as 0 in each group. The registry gives the numbers at risk for these entries as 25 for BCS, 25 for CR, and 10 for XR.

These entries describe what the registry reports; they do not establish that no adverse events occurred outside the registry's reporting period or reporting scope. The record does not provide further details about event definitions, surveillance procedures, or follow-up duration for safety reporting. It also does not provide event-level descriptions because no top serious adverse-event terms are listed.

Zero reported affected is not a comparison of safety between devices, and the group entries should not be read as proof of equal safety. The groups are not described as randomized or like-for-like controls, and allocation is not stated. The registry's figures should therefore be read narrowly as the recorded adverse-event counts for these groups, with the limitations of the available reporting information.

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

The registry record identifies a study of in vivo kinematics and vibroarthrography signals among subjects with three Journey II knee arthroplasty designs. It defines the primary endpoint as medial femoral condyle anterior-posterior translation during a deep knee bend, at least 6 months postoperative. It also supplies a sign convention: positive values indicate anterior sliding, while negative values indicate posterior rollback.

Those details clarify what the study set out to measure, but they do not show the observed primary outcome. Means, standard deviations, between-arm estimates, confidence intervals, and p-values are not reported in the registry record. The direction and size of any differences, as well as their precision, cannot be determined. The record lists 4 outcome measures and 0 analyses, so the numerical evidence needed to interpret the stated objective is not available in the registry record.

The study's group structure also limits causal interpretation. The record says allocation is not stated and identifies the comparison as nonrandomized, with arms that are not like-for-like controls. The arm descriptions differ in ACL and PCL retention or resection. Even if numerical differences were available, an observed association between arm and kinematic measurement would not, by itself, establish that the implant design caused the difference.

The safety entries report 0 serious adverse events, 0 other adverse events, and 0 deaths for each group. These are registry entries, not evidence of equivalence or proof that no events occurred beyond the recorded scope. Further details about safety definitions and surveillance are not reported in the registry record.

In general, a study's endpoint definition, observed estimates, uncertainty, analysis methods, and design all contribute to interpretation. Here, the definition and design cautions are available, while numerical outcome results and analysis details are not. The record therefore supports an account of the research question and its limits, but not a conclusion about which design had greater translation or whether any difference was statistically or clinically important.

14. Why This Trial Matters Statistically

This study is statistically notable because it compares a defined biomechanical measurement across groups with different ligament-retention descriptions. The primary endpoint is not an abstract score: it is medial femoral condyle translation in a specified direction during a deep knee bend. The registry's sign convention makes clear why both direction and magnitude matter when describing a mean.

The record also illustrates why study design matters when interpreting group comparisons. It identifies the study as nonrandomized, says allocation is not stated, and cautions that the arms are not like-for-like controls. In general, differences between groups may reflect characteristics associated with group membership as well as any difference related to the implant. This is especially relevant when the arm descriptions themselves distinguish which cruciate ligaments were retained or resected.

A second statistical issue is the gap between an outcome definition and an analyzable result. The registry names 4 outcome measures but reports 0 analyses, and it does not provide primary endpoint means, standard deviations, or comparative estimates. Without those results, readers cannot judge the observed magnitude, variability, or precision. A clear endpoint is valuable, but it cannot substitute for the numerical results and analysis information needed to assess evidence.

Finally, the sample-size assumptions described for planning illustrations should be distinguished from a justification of the completed study's design. They refer to an observed effect and specified calculation assumptions, but the numerical observed effect and the protocol's sample-size justification are not reported in the registry record. This distinction helps prevent a planning exercise from being mistaken for evidence about the result or its certainty.

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.

The principal limitation for statistical interpretation is that numerical outcome results are not reported in the registry record. The record does not give primary endpoint means or standard deviations, between-arm estimates, confidence intervals, or p-values. As a result, the direction, magnitude, variability, and precision of the primary comparison cannot be evaluated from the posted results.

The design also restricts interpretation. The registry describes the study as nonrandomized, states that allocation is not reported, and cautions that the arms are not like-for-like controls. The groups differ in their ligament-retention descriptions, so an association between group and measured kinematics would not isolate an implant-design effect. Methods for adjusting for differences between groups are not reported in the registry record.

Additional analysis details are absent. The record lists 4 outcome measures and 0 analyses, but does not state which comparisons were conducted, how multiplicity was addressed, or how missing measurements were handled. The analysis population is not reported. Distributional assessments, model details, and other checks of statistical assumptions are likewise not reported in the registry record.

The stated sample-size assumptions concern a planning illustration based on an observed effect, but the numerical effect used is not reported. The registry's protocol-level sample-size justification is not reported either. Finally, details about safety-event definitions, surveillance, and reporting scope are not given. These limits mean the record can describe the endpoint, arms, and recorded safety counts, but it cannot support a detailed assessment of treatment effects, statistical uncertainty, or the completeness of outcome and safety reporting.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: In Vivo Kinematics for Subjects With Smith & Nephew Journey II BCS TKA, Journey II CR TKA, Or Journey II XR TKA — NCT04612036.
• Registry record last updated 2023-11-29; status last verified 2023-02.
• Results first posted 2023-11-29.
• 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.

19. Record Summary

The registry describes a completed multicenter study of in vivo kinematics and vibroarthrography signals in subjects implanted with Journey II BCS, CR, or XR total knee arthroplasty. The sponsor is The University of Tennessee, Knoxville. Enrollment is listed as 60, with a recorded start of 2020-10-22 and primary completion of 2022-05-16.

The primary endpoint is medial femoral condyle anterior-posterior translation during a deep knee bend, measured at least 6 months postoperative and summarized as a mean with standard deviation. Positive values indicate anterior sliding; negative values indicate posterior rollback.

The registry identifies the comparison as nonrandomized, with allocation not stated and arms that are not like-for-like controls. It lists 4 outcome measures and 0 analyses. Numerical primary outcome results and detailed analysis methods are not reported in the registry record. Adverse-event entries list 0 serious adverse events, 0 other adverse events, and 0 deaths in each group.