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 A Study on M2a Magnum Total Hip Arthroplasty (NCT01010763), a randomized na study. The primary outcome is Range of Motion.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01010763 |
| Phase | NA |
| Condition | Degenerative Joint Disease, Avascular Necrosis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 184 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Zimmer Biomet |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns people undergoing total hip arthroplasty in the setting of degenerative joint disease or avascular necrosis. The registry record does not report further eligibility details in the information available for the primary outcome. At the one-year range-of-motion assessment, outcome counts are reported separately for the two device groups.
Intervention
The M2a Magnum group received total hip arthroplasty using the M2a Magnum large metal articulation. The description characterizes it as a metal-on-metal articulation with a large ball. The intervention is listed as a device.
Comparator
The comparison group received total hip arthroplasty using the M2a Taper Acetabular System. Its description includes a titanium outer shell, a cobalt chromium metallic liner, and a cobalt chromium modular femoral head. The registry record identifies the study as randomized and parallel-group, but does not report further details about how allocation was carried out.
Primary question
The posted primary outcome asks what hip flexion angle, in degrees, was observed at one year after surgery in each group. The reported group means are 109.2 for M2a Magnum and 110.2 for M2a Taper. These are descriptive results, not a reported adjusted or unadjusted estimate of the difference between groups. A confidence interval, p-value, and formal comparative analysis are not reported in the registry record. The posted results therefore describe the observed angles but do not establish the precision of a between-group contrast.
3. Trial Design
The study is titled as a prospective, controlled, multicenter study of M2a Magnum total hip arthroplasty. Its registry design is randomized, with a parallel-group model and no masking. The two groups are M2a Magnum and M2a Taper. The record lists total hip arthroplasty as the device intervention and describes distinct implant configurations for the groups. No further detail about the randomization procedure, allocation concealment, or conduct across centers is reported in the registry record.
The registry lists enrollment of 184 participants and marks the study as completed. The start is recorded as 2009-11, and the primary completion date is 2017-02-28. The phase is listed as NA. Zimmer Biomet is identified as the sponsor. The brief study description identifies investigation of metal-ion release and renal function as a purpose. The primary outcome reported in the results, however, is range of motion: hip flexion angle at one year postoperatively.
The primary outcome results list 94 participants for M2a Magnum and 80 for M2a Taper. Those outcome counts do not account for every participant in the listed enrollment, and the registry record does not explain the difference. The outcome description says that 2 patients in the M2a Magnum group and 4 patients in the M2a Taper group failed to obtain range-of-motion data at the one-year follow-up visit. The registry does not state whether these are the only reasons that the outcome counts differ from enrollment, nor does it describe an analysis population for the posted means.
Randomization supports a planned comparison between the device groups, but design labels alone do not show how fully the randomized groups were represented in a particular outcome analysis. The record does not report a statistical analysis plan, the intended handling of missing measurements, or details of the sample-size justification. The available outcome results should therefore be read as descriptive group summaries rather than as a complete account of the planned randomized comparison.
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: Four patients withdrer before randomization.
Overall Study
| Stage | M2a Magnum | M2a Taper |
|---|---|---|
| STARTED | 96 | 84 |
| COMPLETED | 61 | 54 |
| NOT COMPLETED | 35 | 30 |
Analysis population for the primary outcome, as defined in the registry: 2 patients in M2a Magnum group and 4 patients in M2a Taper group were failed to obtain Range of Motion data at 1 year follow-up visit.
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 | M2a Magnum | M2a Taper | Total |
|---|---|---|---|---|
| Participants analysed | 96 | 84 | 180 | |
| Age, Continuous | years | 65 (39 to 86) | 67 (41 to 98) | 66 (39 to 98) |
| Sex: Female, Male: Female | Participants | 72 | 61 | 133 |
| Sex: Female, Male: Male | Participants | 24 | 23 | 47 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 96 | 84 | 180 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): White | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: Japan | participants | 96 | 84 | 180 |
| Harris Hip Score | units on a scale | 52.3 (3 to 79) | 51.2 (22 to 82) | 51.7 (3 to 82) |
| EQ-5D | units on a scale | 0.620 (-0.109 to 1.000) | 0.647 (0.049 to 1.000) | 0.633 (-0.109 to 1.000) |
| UCLA Activity Score | units on a scale | 3.1 (1 to 6) | 3.0 (2 to 6) | 3.0 (1 to 6) |
6. Primary Endpoint
The registry lists the primary outcome as Range of Motion, measured over 1 year.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Full Range |
| Unit | degrees |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is range of motion, specified as hip flexion angle at one year after surgery and measured in degrees. Hip flexion is one component of hip movement. A group summary of this measure describes the typical angle reached by participants with recorded results, while its range indicates the lowest and highest reported values. The registry reports a mean of 109.2 for M2a Magnum and a mean of 110.2 for M2a Taper. The full range is reported as 70.0 to 130.0 in each group.
Range of motion is used as a functional measurement: it quantifies movement at the hip rather than measuring metal-ion release, renal function, or implant survival. That makes it a distinct outcome from the study purposes described in the brief summary and from the secondary outcomes listed in the record. The one-year time point defines when the measurement was intended to characterize postoperative hip flexion. The registry does not report the measurement protocol, assessor training, or whether assessors knew the assigned device.
These summaries do not by themselves show how much individual participants varied around their group means. Although the full range is reported, a standard deviation, standard error, or confidence interval is not. Nor does the record post a formal estimate of the between-group difference for this endpoint. Consequently, the group means are useful for describing the observed values, but are insufficient on their own to determine the precision of a comparative effect or to assess whether any observed difference could plausibly reflect sampling variation.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry reports mean hip flexion angles at one year of 109.2 in the M2a Magnum group and 110.2 in the M2a Taper group. Both groups have a reported full range from 70.0 to 130.0. The outcome description notes that 2 patients in the M2a Magnum group and 4 patients in the M2a Taper group did not obtain range-of-motion data at the one-year visit. These figures describe the posted outcome; they do not indicate why each measurement was unavailable or how missing results were handled in the analysis.
The record does not report a formal between-group estimate, confidence interval, or p-value for the primary outcome. It also does not report a standard deviation or another measure of dispersion around the mean. The shared reported range gives information about the endpoints of observed values, but it cannot replace a measure of how observations are distributed within that range. Without an uncertainty estimate for the contrast, the precision of any apparent difference between the group means cannot be judged from the registry results alone.
The study is labeled randomized, which identifies the intended basis for comparing the groups. However, a randomized design label does not supply the missing endpoint analysis details. The registry record does not state whether the posted means come from an intention-to-treat population, a subset with observed measurements, or another analysis population. It also does not explain how the difference between overall enrollment and the outcome counts arose. Those omissions matter when interpreting summaries at a particular follow-up time.
Other outcomes are listed, including metal-ion outcomes, UCLA Activity Score, radiographic assessment, and Harris Hip Score. The record lists 10 posted secondary outcomes and 11 outcome measures overall, but the registry information does not give corresponding comparative estimates in the registry record for interpretation. The repeated listing of metal-ion outcomes also means the reader should not treat the different measures as a single result. No analysis linking these outcomes to the primary range-of-motion endpoint is reported.
The safety results are counts of participants with serious or other adverse events in each group, accompanied by separate numbers at risk. They are descriptive safety summaries and are not a substitute for a formal comparative safety analysis. No adjusted or unadjusted statistical comparison of adverse events is reported. The interpretation of both efficacy-related outcomes and safety counts is therefore limited to the posted descriptions and summaries; the registry does not establish the precision of between-group differences.
Planning illustrations based on the observed effect, when included, should be read as hypothetical sample-size calculations under stated assumptions. They are not evidence of the trial's original design justification and are not observed power. The registry does not report the original sample-size rationale. The illustrations cannot resolve the absence of a posted confidence interval or formal primary-outcome comparison, and they should not be interpreted as additional trial results.
9. Statistical Methods Explained
What does a group mean describe? The mean is the arithmetic average of the recorded measurements in a group. In general, a mean gives a compact description of the center of a distribution, but does not show its shape or how widely individual measurements vary. Here the posted means are 109.2 for M2a Magnum and 110.2 for M2a Taper, in degrees. Those values summarize the measurements included in each reported group result; the registry record does not explain the analysis population in further detail.
What does the reported range add? A range identifies the lowest and highest observed values included in the summary. The registry reports a full range from 70.0 to 130.0 in each group. In general, the range is sensitive to the values at the extremes and does not describe how many observations lie near either endpoint or near the mean. It is not equivalent to a standard deviation or a confidence interval. The record does not report a standard deviation, standard error, or other measure of dispersion for the primary endpoint.
Why is a comparative estimate useful? In general, a randomized two-group study is designed to compare outcomes between groups. A direct estimate of the difference would describe the observed contrast, while an uncertainty interval would indicate the range of values compatible with the data under the analysis assumptions. A confidence interval is not a guarantee that the true value lies within its limits; it is a statistical procedure with a defined long-run coverage property when its assumptions hold. No confidence interval or formal between-group estimate for hip flexion is reported in the registry record. The two group means alone do not supply that missing uncertainty information.
What can a p-value answer? In general, a p-value measures how unusual data at least as incompatible with a specified null hypothesis would be under the assumptions of a statistical model. It does not measure the size or importance of an effect, and it does not give the probability that a null hypothesis is true. A p-value is not reported for the primary endpoint. Without a reported test, model, or analysis details, there is no basis for describing the primary result as statistically significant or not statistically significant.
Why does dispersion matter? General statistical interpretation depends not only on group means but also on variation and the amount of information available. Greater variation can make a group contrast less precise, whereas less variation can make it more precise, all else being equal. The full observed range does not provide enough information to recover that variation. In this record, the group sizes for the endpoint are reported, but the within-group dispersion needed for many conventional comparisons is not. No new comparative uncertainty estimate can be inferred from the posted summaries alone.
How should missing outcome values be considered? The registry states that 2 patients in M2a Magnum and 4 patients in M2a Taper failed to obtain range-of-motion data at the one-year follow-up visit. General methods for missing data distinguish between the fact that an observation is absent and the assumptions used to handle it. The reason for missingness can affect interpretation, particularly if availability is related to the outcome or differs systematically across groups. The record does not report reasons beyond failure to obtain the measurement, the method used to handle missing values, or a sensitivity analysis. It is therefore not possible to determine from the posted information whether the reported means reflect a specific missing-data method.
What does randomization contribute? General statistical reasoning treats random allocation as a way to make the groups comparable on average with respect to factors that might influence outcomes. In a particular study, that benefit depends on how randomization was implemented and on how participants are followed and analyzed. The registry labels the study randomized, but does not report the allocation procedure or the analysis population for the one-year endpoint. Those details should not be inferred from the design label. The study is also described as having no masking; the record does not state whether outcome assessors were masked separately from participants or clinical staff.
How should planning calculations be read? The sample-size illustrations use the observed effect as a planning input, with a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. They consider detecting a stated fraction of the observed effect. Such calculations are hypothetical planning exercises: they do not describe the trial's original sample-size rationale, which is not reported in the registry record. They are not observed power, and they do not change what the trial actually measured or the uncertainty that is reported. A calculation based on an observed effect can also depend strongly on the effect chosen as its input, so it should not be treated as independent confirmation of the result.
Why can secondary outcomes raise multiplicity concerns? General statistical methods recognize that testing many outcomes can increase the chance of at least one apparently notable result arising by chance when each test is considered separately. Approaches to multiplicity may adjust significance thresholds, define a hierarchy, or distinguish primary from exploratory outcomes. The registry lists multiple secondary outcomes, but a multiplicity strategy, testing hierarchy, and secondary-outcome analysis plan are not reported in the registry record. It would therefore be inappropriate to assume that the results were adjusted, or that each outcome was intended to support a separate confirmatory claim.
The record lists no posted analyses for the outcomes in the information available. It does not report a model specification, covariate adjustment, inferential test, or confidence-interval method for the primary result. This absence does not show that no analyses were conducted; it means those details are not reported in the registry record. Statistical interpretation should stay with the posted descriptive summaries and make the missing inferential details explicit.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists multiple secondary outcomes, including metal-ion outcomes, UCLA Activity Score, radiographic assessment, and Harris Hip Score. Metal Ion appears repeatedly in the secondary-outcome list. The record lists 10 posted secondary outcomes and 11 outcome measures overall. Multiple outcomes can create a multiplicity issue: in general, when many hypotheses are tested, the chance of at least one result appearing notable by chance can rise unless the analysis plan accounts for the set of tests. A multiplicity adjustment, outcome hierarchy, or other strategy is not reported in the registry record. No conclusion about whether secondary-outcome tests were adjusted is therefore justified.
For the primary range-of-motion endpoint, the record states that 2 patients in the M2a Magnum group and 4 patients in the M2a Taper group did not obtain data at the one-year follow-up visit. It does not report the reasons for those unavailable measurements beyond that statement, how missing values were handled, or whether sensitivity analyses were conducted. In general, missing-data methods rely on assumptions about why values are absent; those assumptions cannot be assessed from counts alone.
The outcome results list 94 participants in M2a Magnum and 80 in M2a Taper. The registry record does not explain how these endpoint counts relate to the listed enrollment of 184 or specify an analysis population such as all randomized participants or only those with measured outcomes. It also does not report whether participants were analyzed according to assigned group. These population and missing-data details limit interpretation of the group summaries and the generalizability of the one-year result.
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 |
|---|---|---|---|
| M2a Magnum | 1 | 96 | 1.0% |
| M2a Taper | 1 | 84 | 1.2% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| M2a Magnum | 0 of 96 |
| M2a Taper | 3 of 84 |
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 |
|---|---|
| M2a Magnum | 2 of 96 |
| M2a Taper | 3 of 84 |
Most frequent serious adverse event terms
| Event term | Organ system | M2a Magnum | M2a Taper |
|---|---|---|---|
| Revision due to Adverse Reaction to Metal Debris | Musculoskeletal and connective tissue disorders | 1 of 96 | 0 of 84 |
| Femoral Epicondyle Fracture | Musculoskeletal and connective tissue disorders | 0 of 96 | 1 of 84 |
Most frequent non-serious adverse event terms
| Event term | Organ system | M2a Magnum | M2a Taper |
|---|---|---|---|
| Dislocation | Musculoskeletal and connective tissue disorders | 0 of 96 | 3 of 84 |
| Cerebral Infarction | Vascular disorders | 1 of 96 | 0 of 84 |
| Intra-operative fracture | Surgical and medical procedures | 1 of 96 | 0 of 84 |
Serious events with the highest arm-level rate: femoral epicondyle fracture (1.2%), revision due to adverse reaction to metal debris (1.0%).
The registry reports serious adverse event counts and other adverse event counts separately for each group, with separate numbers at risk. For M2a Magnum, 1 of 96 participants at risk had a serious adverse event, and 2 of 96 had other adverse events. For M2a Taper, 1 of 84 participants at risk had a serious adverse event, and 3 of 84 had other adverse events. The reported death counts are 0 for M2a Magnum and 3 for M2a Taper.
These are descriptive counts. Serious and other adverse events are distinct categories in the record, and the counts should not be combined or interpreted as rates without a defined analysis. A participant count also does not show the number, timing, duration, or relatedness of all events. The registry does not report a comparative statistical analysis, an assessment of causality, or further context for the deaths in the information available for these results.
The record also lists Femoral Epicondyle Fracture at 1.2% and Revision due to Adverse Reaction to Metal Debris at 1.0% among the top serious terms. These entries should be read as registry-reported terms and percentages, not as a complete description of every safety event. Differences in the at-risk counts and the absence of inferential analysis mean the figures alone do not establish a between-group safety effect.
12. What the Result Does, and Does Not, Mean
The primary outcome results describe hip flexion at one year after total hip arthroplasty in the two randomized groups. The means are 109.2 for M2a Magnum and 110.2 for M2a Taper, and the reported full range is 70.0 to 130.0 for both groups. These are descriptive summaries of the posted outcome. They do not, on their own, quantify a precise difference between the devices.
The registry record does not report a confidence interval, p-value, formal comparative estimate, or within-group standard deviation for the primary outcome. Consequently, the numerical separation between the reported means cannot be evaluated for statistical uncertainty from this record. A shared range does not establish that the distributions are the same, and the means do not reveal how individual measurements were distributed. The record also does not describe an analysis population or the method used to address missing measurements.
The study's randomized design is relevant to its intended comparison, but the registry description is not enough to reconstruct the full analysis. No conclusion about the original sample-size justification, interim analyses, or statistical plan can be drawn because these are not reported in the registry record. Planning illustrations based on an observed effect are not a substitute for the original rationale and are not observed power.
The safety counts likewise offer a descriptive account rather than a formal comparison. The reported numbers at risk and adverse-event counts can be read as posted, but they do not establish whether a difference between groups is meaningful or attributable to the device. Event definitions, timing, relatedness, and inferential methods are not fully reported in the information available.
Thus, the registry supports a narrow reading: it records group summaries for hip flexion at one year and descriptive safety counts for the two device groups. It does not provide enough inferential or analysis detail to determine the precision of comparative effects, nor to make broader claims about outcomes beyond those summaries.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of the difference between a randomized design and a fully reported comparative result. Random allocation creates a framework for comparing the M2a Magnum and M2a Taper groups, but interpretation still depends on the outcome analysis, its uncertainty, and the population included. The registry reports group means and ranges for hip flexion at one year, while a confidence interval, p-value, and formal contrast are not reported in the registry record.
The endpoint also illustrates why summaries need to be read together. Means describe group centers; ranges describe observed extremes. Neither alone shows the shape of the outcome distribution or the precision of the between-group comparison. The lack of reported standard deviations or other dispersion measures means the reader cannot assess within-group variability from the primary results. The listed missing one-year measurements add a further question about how the reported means were formed, which the registry does not answer.
Multiplicity is another statistical consideration. The record lists a range of secondary outcomes, while a strategy for controlling or interpreting multiple analyses is not reported. This matters because different outcomes answer different questions and testing many outcomes can complicate interpretation when no hierarchy or adjustment is stated.
Finally, the record distinguishes participant counts for the primary outcome from overall enrollment and provides separate at-risk counts for safety summaries. Keeping these denominators and outcome definitions distinct is essential. This trial therefore underscores that design labels, endpoint summaries, safety counts, and planning calculations each answer different statistical questions; none should be treated as a replacement for missing details about the analysis or uncertainty.
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 principal limitation for interpreting the primary result is the lack of a reported comparative analysis. The registry gives group means and full ranges for hip flexion, but does not report a between-group estimate, confidence interval, p-value, or measure of within-group dispersion. The reported means can be described, but their comparative precision cannot be evaluated from these summaries alone.
The one-year outcome has missing measurements: 2 patients in M2a Magnum and 4 patients in M2a Taper failed to obtain range-of-motion data at follow-up. The registry record does not give further reasons, explain the handling of these values, or report sensitivity analyses. The outcome counts of 94 and 80 are not reconciled with the listed enrollment of 184. The analysis population and the relationship between enrollment and available outcome data are not reported in the registry record.
Important design and measurement details are also absent. Although the study is labeled randomized and unmasked, the allocation procedure, concealment, measurement protocol, and assessor masking are not reported in the information available. The record does not describe the original sample-size justification, statistical analysis plan, interim analyses, or multiplicity approach. These gaps limit assessment of whether the reported summaries reflect prespecified methods and how the multiple outcomes were intended to be interpreted.
Safety information is presented as counts, with some serious event terms and percentages. The registry does not report a formal comparative safety analysis or additional context about event timing, relatedness, or the deaths. These limitations do not invalidate the posted descriptive data; they define what can and cannot be concluded from the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Study on M2a Magnum Total Hip Arthroplasty — NCT01010763.
- Registry record last updated 2019-06-21; status last verified 2019-03.
- Results first posted 2019-06-21.
- 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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18. Record Summary
The registry record describes a completed, prospective, controlled, multicenter, randomized parallel-group study with no masking, sponsored by Zimmer Biomet. It lists enrollment of 184 and compares M2a Magnum with M2a Taper total hip arthroplasty. The primary outcome is hip flexion angle at one year, reported as means of 109.2 and 110.2, respectively, with a full range from 70.0 to 130.0 in each group.
The record notes unavailable one-year range-of-motion data for 2 M2a Magnum patients and 4 M2a Taper patients. It also lists adverse-event counts and multiple secondary outcomes. A formal comparative estimate and its uncertainty for the primary outcome, the analysis population, missing-data methods, multiplicity strategy, and original sample-size rationale are not reported in the registry record. The posted figures therefore support descriptive interpretation, with substantial limits on inferential conclusions.