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 Effectiveness of Minimally Invasive Total Knee Replacement in Improving Rehabilitation and Function (NCT00710840), a randomized phase 2 study. The primary outcome is Quadriceps Muscle Force.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00710840 |
| Phase | Phase 2 |
| Condition | Osteoarthritis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 44 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Colorado, Denver |
| Results posted | Yes |
2. Clinical Question
Population
People with osteoarthritis undergoing total knee arthroplasty. The registry record lists an enrollment of 44 and describes quadriceps muscle force measured before surgery and after surgery. It does not report further eligibility criteria or the characteristics of participants at enrollment.
Intervention
Minimally invasive total knee arthroplasty, identified in the record as TKA Min. The record names the procedure but does not provide a detailed description of the surgical technique or the care received alongside the procedure.
Comparator
Traditional total knee arthroplasty. The registry record does not give further detail about how the traditional procedure was performed or whether other aspects of care were standardized between the arms.
Primary question
The trial set out to compare quadriceps muscle force between the two procedure groups. Force was measured in Nm/kg before surgery and at 4 weeks and 12 weeks after surgery. The stated purpose was to examine whether the procedures differed in muscle strength and rehabilitation-related function. The registry record does not report the group means, variability, or a statistical comparison for this endpoint, so the magnitude and precision of any difference cannot be assessed from that record.
3. Trial Design
The registry describes a randomized, parallel-group Phase 2 study of minimally invasive and traditional total knee arthroplasty for osteoarthritis. The trial status is completed. The listed enrollment is 44. The sponsor is the University of Colorado, Denver. The registry dates the study start to 2008-06 and primary completion to 2011-02.
Random allocation is intended to make the treatment groups comparable on average at the start of a study. It does not guarantee that every measured or unmeasured characteristic will be balanced in a particular trial. The registry record does not report the randomization sequence method, allocation concealment procedures, or whether any stratification was used.
The design is parallel: participants were assigned to a procedure group, rather than crossing between procedures. Masking is listed as none. This means the registry does not describe the study as masked; it does not establish which people involved in care, outcome measurement, or analysis knew each assignment. Further details about assessor masking are not reported in the registry record.
The arm descriptions are blank. The record names the procedures but does not describe the surgical protocols, rehabilitation schedules, or other care that might affect recovery. It also does not report the inclusion and exclusion criteria or participant characteristics. These omissions limit how fully the enrolled population and the contrast between the procedures can be characterized.
Quadriceps muscle force is the primary outcome. Functional performance on a 6 Minute Walk and a Stair Climb Test is listed among the secondary outcomes. The record identifies four outcome measures and four analyses, but does not provide their estimates or the methods used for those analyses. The design information establishes what was planned to be compared; it does not establish what the results were.
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
| Stage | TKA Min | TKA Traditional |
|---|---|---|
| STARTED | 22 | 22 |
| COMPLETED | 22 | 19 |
| NOT COMPLETED | 0 | 3 |
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 | TKA Min | TKA Traditional | Total |
|---|---|---|---|---|
| Participants analysed | 22 | 22 | 44 | |
| Age, Continuous | years | 64.6 (SD 8.5) | 64.0 (SD 8.4) | 64.3 (SD 8.4) |
| Sex: Female, Male: Female | Participants | 12 | 10 | 22 |
| Sex: Female, Male: Male | Participants | 10 | 12 | 22 |
| Region of Enrollment: United States | participants | 22 | 22 | 44 |
| BMI | kg\m^2 | 30.5 (SD 5.6) | 31.3 (SD 5.1) | 30.9 (SD 5.4) |
6. Primary Endpoint
The registry lists the primary outcome as Quadriceps Muscle Force, measured over Measured pre-operatively; post-surgery at 4 weeks and 12 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | Nm/kg |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is quadriceps muscle force, reported as a mean with standard deviation and measured in Nm/kg. It was assessed before surgery and at 4 weeks and 12 weeks after surgery. Expressing force relative to body mass can support comparisons across people of different body sizes, while force itself provides a measure of quadriceps muscle strength.
Quadriceps strength is relevant to rehabilitation and function after knee replacement because the muscles around the knee contribute to movement and physical tasks. It is therefore a plausible outcome for a study asking whether a surgical approach is associated with different functional recovery. This rationale explains why the endpoint may be useful; it does not establish that force is a complete measure of recovery or that a change in force necessarily corresponds to a meaningful change in daily life.
The repeated measurement schedule permits assessment at different recovery stages, including a pre-operative measurement for context. However, the registry record does not report the observed means or standard deviations at any measurement time, nor does it specify whether the primary comparison focused on a particular follow-up time, change from baseline, or an overall trajectory. No endpoint effect estimate or confidence interval is reported in the registry record. The outcome definition is available, but its numerical result and precision cannot be interpreted from the record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The record identifies the comparison of interest and the primary measurement, but it does not report the quadriceps muscle force results. In particular, group means, standard deviations, the treatment-effect estimate, its confidence interval, and a p-value are not reported in the registry record. It is therefore not possible to describe the direction, magnitude, or statistical precision of the primary comparison from the recorded information. The trial's completion status does not substitute for an outcome result.
The primary endpoint was measured before surgery and at 4 weeks and 12 weeks after surgery. Those time points could support descriptions of the course of recovery, but without values and a stated analysis the record does not show how force changed over time or whether the groups differed at any assessment. It also does not clarify whether the comparison was adjusted for baseline force or whether repeated measurements were modeled jointly.
The registry lists the 6 Minute Walk distance and Stair Climb Test as secondary outcomes. Their results are not reported in the registry record. The record's mention of these measures indicates that functional performance was part of the outcome plan, but does not establish the findings for either measure. The registry lists four outcome measures and four analyses, without enough detail to determine the relationship between each measure and analysis.
For adverse events, the registry lists serious events affecting 1 participant in the TKA Min arm and 0 in the TKA Traditional arm, with 22 at risk in each arm. For other adverse events, it lists 10 affected in TKA Min and 22 in TKA Traditional, again with 22 at risk in each arm. These are recorded counts, not estimates of a causal treatment effect. The record lists Pulmonary Embolus at 4.5% among the top serious terms. Deaths are not reported in the registry record. These safety entries do not fill the gap in the primary efficacy outcome reporting.
Overall, the registry supports a description of the trial's design, scheduled assessments, and recorded adverse-event figures. It does not support a conclusion about which procedure produced greater quadriceps force or better functional performance. Any interpretation of efficacy would require outcome estimates and their uncertainty, along with a clear account of the analysis population and methods.
9. Statistical Methods Explained
What does a mean and standard deviation describe?
The primary measure is continuous, meaning it can take a range of numerical values rather than belonging only to a set of categories. A group mean describes the central level of the measurements. The standard deviation describes how dispersed individual measurements are around that mean. A mean on its own does not show whether participants had similar measurements or widely varying measurements; the standard deviation adds information about that spread.
These descriptive summaries are not themselves a comparison between randomized groups. To estimate a treatment contrast, an analysis must specify which measurements are being compared and how participant-level information is used. The registry record identifies the outcome summary as a mean with standard deviation, but does not report the means, standard deviations, or a treatment contrast. It also does not describe the statistical model used.
How might repeated measurements be analyzed?
Quadriceps force was scheduled for measurement before surgery and at 4 weeks and 12 weeks after surgery. Measurements from the same participant are related: a person's later force measurement is likely to carry information about that person's earlier measurement. A method that treats every measurement as independent can misrepresent that relationship. General approaches for repeated measurements account for within-person correlation and can estimate differences between groups over time.
There is more than one valid way to formulate such an analysis. An investigator could compare groups at a prespecified follow-up, model change from baseline, or estimate group patterns across time. These approaches answer related but not identical questions and can depend on assumptions about the measurements and missing observations. The registry record does not report which approach was used, whether baseline values were included as a covariate, or how the time pattern was modeled. No one approach should be attributed to the trial without that information.
What does randomization contribute?
Randomization is a design method for assigning participants to treatment groups by chance. Its purpose is to reduce systematic differences in prognostic factors at assignment, supporting a fair comparison. Randomization does not remove the need to describe the actual groups, account for missing data, or state how participants were analyzed. The record labels the trial randomized, but does not report its sequence-generation or concealment procedures. Consequently, the general strengths of randomized allocation should not be confused with evidence about the details of implementation in this study.
What would uncertainty measures tell readers?
A confidence interval is a range of values compatible with an estimate under the assumptions of the analysis. It conveys precision: a narrower interval indicates a more precise estimate than a wider interval. It also helps readers judge which effect sizes remain plausible, not merely whether a test crosses a chosen significance threshold. A p-value addresses the compatibility of data with a specified null model; it is not the probability that a treatment works or that the null hypothesis is true.
The registry record does not report a confidence interval or p-value for quadriceps force. There is therefore no basis for describing the estimate's precision or statistical significance. General explanations of these measures cannot replace the absent trial-specific results.
Why do analysis assumptions matter?
Statistical methods rely on assumptions about how measurements vary and how observations relate to one another. For continuous outcomes, analysts may consider the distribution of values, the pattern of residual variation, and whether observations are independent or clustered. Over-dispersion is a general concern when observed variability is greater than a model allows; if it is ignored, uncertainty can be understated. The record does not indicate whether over-dispersion was relevant to these continuous measurements or how model assumptions were assessed.
More broadly, a treatment estimate is interpretable only in relation to the population analyzed, the outcome definition, the time point, and the model. Randomized assignment is not a description of the analysis population. The registry record does not report whether analyses followed assignment regardless of treatment received, whether participants with missing measurements were included, or whether any adjusted analyses were performed. Because outcome estimates and analysis details are absent, a recalculation from summary statistics is not possible.
10. Multiplicity, Missing Data and Analysis Populations
The study includes a primary outcome measured at multiple times, along with secondary functional outcomes. Testing several outcomes or time points can increase the chance of obtaining at least one apparently notable result by chance when each is assessed separately. General strategies include prespecifying a primary comparison, adjusting for multiple tests, or interpreting secondary analyses as exploratory. The registry record does not report a multiplicity-control plan, a hierarchy among the outcomes, or whether any interim analyses were conducted. The primary outcome has several time points and is not reduced in the record to a single comparison.
Missing-data handling also affects interpretation. If outcome measurements are unavailable for some participants, the analyzed results may depend on why they are missing and on the method used to address them. The registry record does not report the number of participants contributing primary outcome data at each time, reasons for missing measurements, imputation methods, or sensitivity analyses. It therefore does not show whether missingness could have influenced the estimates.
The analysis population is not reported in the registry record. The record does not specify whether participants were analyzed according to randomized assignment, according to procedure received, or under another definition. Nor does it describe exclusions from analysis. Without these details and without the outcome results, readers cannot determine how closely the analysis preserved the randomized comparison or how robust the findings were to alternative assumptions.
11. 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 |
|---|---|---|---|
| TKA Min | 1 | 22 | 4.5% |
| TKA Traditional | 0 | 22 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| TKA Min | 10 of 22 |
| TKA Traditional | 22 of 22 |
Most frequent serious adverse event terms
| Event term | Organ system | TKA Min | TKA Traditional |
|---|---|---|---|
| Pulmonary Embolus | Respiratory, thoracic and mediastinal disorders | 1 of 22 | 0 of 22 |
Most frequent non-serious adverse event terms
| Event term | Organ system | TKA Min | TKA Traditional |
|---|---|---|---|
| Hematoma\Excessive Bleeding | Blood and lymphatic system disorders | 2 of 22 | 6 of 22 |
| Surgical Malalignment | Surgical and medical procedures | 4 of 22 | 4 of 22 |
| Femoral Notching | Surgical and medical procedures | 2 of 22 | 2 of 22 |
| Retained Cement | Surgical and medical procedures | 1 of 22 | 2 of 22 |
| Cellulitis | Skin and subcutaneous tissue disorders | 0 of 22 | 2 of 22 |
| Heterotopic Ossification | Surgical and medical procedures | 0 of 22 | 1 of 22 |
| Retained Drill Bit | Surgical and medical procedures | 0 of 22 | 1 of 22 |
| Intra-Operative Fracture | Surgical and medical procedures | 0 of 22 | 1 of 22 |
| Poor Bone Quality | General disorders | 0 of 22 | 1 of 22 |
| Urinary Tract Infection | Infections and infestations | 0 of 22 | 1 of 22 |
Serious events with the highest arm-level rate: pulmonary embolus (4.5%).
The registry lists serious adverse events for each arm, with 22 participants at risk in each. It records 1 participant affected in the TKA Min arm and 0 in the TKA Traditional arm. For other adverse events, the record lists 10 affected in TKA Min and 22 in TKA Traditional. These figures describe what was entered in the registry; they do not by themselves establish that a procedure caused an event or that the observed difference would persist in another study.
The record identifies Pulmonary Embolus at 4.5% among the top serious terms. It does not provide enough detail in this entry to interpret the event's timing, clinical course, or relationship to the procedure. Deaths are not reported in the registry record; the absence of a numerical death entry should not be read as a confirmed count of zero.
Adverse-event counts are distinct from the primary muscle-force outcome and do not answer the trial's main comparative question. The registry entry does not describe event-collection procedures, definitions, follow-up completeness, or statistical comparisons for safety. These limitations matter when interpreting small-group safety summaries.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, parallel-group Phase 2 trial compared minimally invasive with traditional total knee arthroplasty and planned to assess quadriceps muscle force before surgery and after surgery. It also identifies functional performance measures and records adverse-event figures. These details describe the question and some aspects of the study conduct, not the treatment effect.
The principal limit is that the primary outcome estimates are not reported in the registry record. Without group means, standard deviations, a defined comparison, and an uncertainty interval, readers cannot determine whether the observed data favored either procedure, how large any difference was, or how precisely it was estimated. The same limitation applies to the listed secondary functional outcomes, whose results are also not reported in the registry record.
The design label of randomized supports the general rationale for comparing groups, but does not establish that allocation was concealed, that outcome assessment was masked, or that all participants were analyzed as assigned. Masking is listed as none, and the record does not clarify assessor masking. Missing-data methods, analysis populations, and multiplicity handling are not reported in the registry record.
The safety counts should be read as registry entries rather than causal conclusions. They do not establish comparative safety, and the serious-event figures do not resolve the absent efficacy results. Likewise, trial completion indicates status, not that the planned question was answered in a way that can be evaluated from this record.
Accordingly, the registry information supports a careful account of the design and reporting gaps, but not a claim that one surgical approach is better or worse. The statistical meaning of the trial's primary result remains undetermined from the registry record.
13. Why This Trial Matters Statistically
This trial is statistically relevant because it illustrates the distinction between a clearly stated research question and a result that can be evaluated. The registry identifies a randomized comparison, a primary continuous measure, and scheduled assessment times. Those elements help define what an analysis would need to estimate. Yet without reported means, variability, treatment contrasts, or uncertainty intervals, readers cannot assess the evidence for the primary question.
The repeated assessments also highlight the importance of specifying the estimand: the particular treatment contrast the analysis is intended to estimate. A comparison at 4 weeks, a comparison at 12 weeks, and a summary of change over time can represent different questions. The registry record does not specify which comparison was primary in the analysis. That omission matters because the interpretation of a result depends on its time point and method, not only on the outcome's name.
The record also makes clear why statistical significance, clinical relevance, and precision are separate considerations. A p-value alone would not convey the size of an effect or its practical importance, while an effect estimate without an interval would leave its precision unclear. In this case, neither is reported for the primary outcome, so those distinctions cannot be applied to a trial-specific finding.
Finally, the presence of safety counts and secondary outcomes does not substitute for reporting the planned primary outcome. Transparent outcome estimates, analysis methods, and missing-data information are necessary for independent statistical appraisal. The registry record offers some design and safety details, while leaving those central interpretive elements unreported.
14. 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 registry record contains limited information about eligibility, participant characteristics, and the procedures used in each arm. Arm descriptions are blank, and the surgical techniques and accompanying rehabilitation are not detailed. This makes it difficult to determine how the intervention contrast was implemented or how broadly the enrolled group can be characterized.
Although randomization is recorded, the method for generating and concealing allocation is not reported in the registry record. Masking is listed as none, but the record does not clarify whether outcome assessors or analysts were masked. This is relevant because expectations and knowledge of treatment assignment can influence the measurement or reporting of outcomes.
The primary outcome results are absent, including values at the scheduled assessments and the statistical comparison. Results for the listed secondary functional measures are also not reported in the registry record. The record does not describe the analysis model, the target comparison across time, adjustment for baseline measurement, or the handling of repeated observations.
Information about missing measurements, reasons for loss to follow-up, analysis populations, and sensitivity analyses is not reported in the registry record. The multiplicity plan and any interim analyses are also not reported. These gaps prevent assessment of the robustness and precision of any outcome finding. The safety entries lack further detail about event definitions, ascertainment, timing, and analysis. Together, these limitations mean that the registry supports description of the trial's scope, but not a complete statistical appraisal of its results.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Effectiveness of Minimally Invasive Total Knee Replacement in Improving Rehabilitation and Function — NCT00710840.
- Registry record last updated 2015-06-10; status last verified 2015-03.
- Results first posted 2015-05-15.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The record describes a completed, randomized, parallel-group Phase 2 trial sponsored by the University of Colorado, Denver, comparing minimally invasive and traditional total knee arthroplasty in people with osteoarthritis. Enrollment is listed as 44. The study start is recorded as 2008-06, with primary completion in 2011-02.
The primary outcome was quadriceps muscle force in Nm/kg, summarized by mean and standard deviation and scheduled before surgery and at 4 weeks and 12 weeks after surgery. The 6 Minute Walk distance and Stair Climb Test are listed as secondary outcomes. The registry record does not report the primary or secondary outcome estimates, statistical comparisons, or analysis methods in sufficient detail to interpret efficacy.
Safety entries list serious and other adverse events by arm. The registry also lists Pulmonary Embolus at 4.5% among the top serious terms. Deaths are not reported in the registry record.