Avenir Müller Hip Stem Post Market Surveillance Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Avenir Müller Hip Stem Post Market Surveillance Study (NCT04079127), a registered phase not stated study. The primary outcome is Evaluation of Pain and Functional Performance Determined by the Harris Hip Score.

2. Clinical Question

3. Trial Design

This is a multicentre, non-comparative, retrospective post-market surveillance study of the Avenir Müller Hip Stem. Its stated purpose was to collect clinical outcomes data as part of post-market follow-up and to confirm the device’s safety and performance. Zimmer Biomet is listed as the sponsor. The record lists enrollment of 150 and gives the study status as completed.

The recorded study start is 2010-01-09 and the primary completion date is 2019-06-29. These dates describe the registry record; they do not establish when each participant received the device or when each outcome was measured. The primary outcome timeframe is specified as 10 years, but participant-level timing and follow-up completeness are not reported in the registry record.

The study population is described as patients with severe hip pain and disability who needed total hip arthroplasty. The intervention description refers to patients who met inclusion and exclusion criteria to receive the Avenir Müller stem. The listed conditions include several causes of hip disease or injury. Eligibility details beyond that description are not reported in the registry record.

The primary outcome was evaluation of pain and functional performance using the Harris Hip Score. The secondary outcomes were confirmation of safety based on complications and implant survivorship. The record lists three outcome measures, but it does not provide results for the primary endpoint or detailed results for the secondary outcomes in the information available for this analysis.

Because the study is non-comparative, it does not provide a randomized or concurrent control comparison. Allocation is not stated. A single-arm surveillance design can describe outcomes recorded among patients receiving a device, but it cannot by itself separate device-related effects from other explanations for those outcomes. The registry record does not report a statistical analysis plan, the analysis populations, or the number of participants with outcome data.

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

Analysis population for the primary outcome, as defined in the registry: The HHS values are within the interval 0-100 points and the higher the score is, the better the outcome is for the individuals. The results are interpreted with the following ratings: \<70 points = poor result; 70-79 points = fair, 80-89 points = good, and 90-100 points = excellent. Number Of Unilateral Patients: 68; Number Of Bilateral Patients:7. Here, the data at 10 year post surgery of 75 patients (82 hips) were available for analysis.

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 Evaluation of Pain and Functional Performance Determined by the Harris Hip Score, measured over 10 years.

The primary endpoint is the Harris Hip Score, used to evaluate pain and functional performance at 10 years. It is completed by the surgeon with the patient and covers pain, function, absence of deformity, and range of motion. Pain includes severity, effects on activities, and need for pain medication. Function includes daily activities and gait, such as stair use, sitting, limp, walking distance, and support needed. Deformity and range of motion cover specified features of hip position, movement, and limb length.

The score has 10 items and a maximum of 100 points, with a higher score indicating a better outcome. The pain item contributes 0-44 points, the seven function items contribute 0-47 points, the deformity item contributes 4 points, and the two range-of-motion items contribute 5 points. The record describes ratings as poor below 70 points, fair at 70-79, good at 80-89, and excellent at 90-100.

As a patient-focused clinical measure, the score combines symptoms and functional ability rather than measuring implant status alone. It can therefore describe more than one aspect of the patient’s hip-related outcome. However, the record does not report the observed score, the number of scores available at the stated timeframe, or how incomplete assessments were handled. The endpoint’s purpose and scoring are described, but its results cannot be evaluated from the registry information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a continuous primary endpoint summarized as a mean and standard deviation. It does not report statistical analysis results for that endpoint. The concepts below explain what those summaries and common planning methods mean in general; they should not be mistaken for analyses reported for this study.

What does a mean describe?

For a continuous measure such as the Harris Hip Score, the mean is the arithmetic average across the observations included in an analysis. It gives a compact description of the group’s central score. A mean alone does not show whether most participants had similar scores or whether scores varied widely. It also does not reveal the score distribution’s shape or the presence of unusually high or low observations.

What does the standard deviation describe?

The standard deviation describes how spread out individual measurements are around the mean. A relatively larger standard deviation indicates more variation among the measured scores, while a smaller one indicates that scores are more concentrated around the average. This is a general explanation, not a characterization of the study’s observed variability: no standard deviation is reported in the registry record.

How would a confidence interval be read?

In general, a confidence interval gives a range of values compatible with the data and the method used to calculate it. Its width conveys precision: a narrower interval indicates a more precise estimate under the method’s assumptions, while a wider interval indicates greater uncertainty. A confidence interval is not reported for the primary endpoint in the registry record. Without one, the precision of any mean score cannot be judged from the posted information.

What is not available about the endpoint analysis?

The registry record does not report a statistical analysis plan, the number of participants included in the primary analysis, the number with measurements at 10 years, or how missing scores were treated. It does not state whether the primary analysis used only a single assessment or compared scores across multiple assessments. It also does not describe covariate adjustment, assumptions checks, or a method for handling repeated measurements. These details should not be inferred from the endpoint description.

How should planning illustrations be understood?

The record describes sample-size illustrations based on a stated fraction of an observed effect. These are planning exercises, not observed outcomes and not the study’s own design justification. The described assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustrations are hypothetical even though this study is non-comparative. The registry record does not report the sample-size values for those illustrations or the effect estimate on which they depend.

In general, power is the probability that a specified statistical procedure detects an effect of a chosen size when that effect is present, under the assumptions used for planning. A planning calculation therefore depends on the target effect, variability, significance level, allocation and analysis method. It does not describe the probability that a completed study’s result is correct. Nor does it replace an observed effect estimate with its uncertainty. The listed planning assumptions should not be read as evidence that the study enrolled two arms or used a two-arm analysis.

The record notes that non-time-to-event planning illustrations are expressed as participants per arm, while time-to-event illustrations use a total number of events under the Schoenfeld method. This is a general distinction between planning approaches: continuous outcomes are commonly planned using participant counts, whereas time-to-event analyses can be driven by the number of events. No time-to-event analysis result is reported for this study, and the record does not provide a sample-size justification for its completed surveillance study.

Why does over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a statistical model expects. When a method assumes less variability than the data actually contain, standard errors can be understated and confidence intervals can be too narrow. The Harris Hip Score is specified as a continuous outcome summarized with a mean and standard deviation, but the registry record does not report an over-dispersion assessment or indicate that one was needed. This concept therefore provides general statistical context rather than a finding about this study.

The record lists three outcome measures and no analyses. That absence means there are no posted inferential statistics to interpret for the primary endpoint in the information. The registered endpoint and descriptive methods can be explained, but conclusions about estimates, statistical significance, or precision require results that are not reported in the registry record.

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("Patients Suffering From Severe Hip Pain and Disabi")
n   <- c(75)
m   <- c(90.9)
sp  <- c(11.7)
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  Patients Suffering From Severe Hip Pain and Disabi  75  90.900  11.700  88.208  93.592

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary outcome and two secondary outcomes: confirmation of safety based on complications and implant survivorship. It also states that there are three outcome measures, but does not provide a multiplicity strategy or describe how statistical testing across outcomes was handled. Whether tests were adjusted, ordered hierarchically, or treated as descriptive is not reported in the registry record.

Multiplicity is a general statistical concern when several hypotheses are tested. As the number of tests increases, the chance of at least one apparently positive result can increase if each test is interpreted on its own. Methods to address this can include adjusting significance thresholds or defining a prespecified testing sequence. These are general options, not methods known to have been used in this study. Because no outcome analyses are reported, the effect of multiplicity on the study’s conclusions cannot be assessed.

Missing-data methods and analysis populations are also not reported in the registry record. The entry does not state how many participants had a Harris Hip Score at 10 years, how many were included in each outcome analysis, whether follow-up differed across outcomes, or how unavailable measurements were handled. It does not describe whether an analysis used all enrolled participants, only participants with recorded outcomes, or another defined group. Enrollment of 150 does not establish the number with evaluable outcome data.

These omissions matter because follow-up data may be incomplete and the reason for missingness can affect interpretation. In general, an analysis restricted to participants with recorded scores may differ from one that accounts for missing outcomes, particularly if the availability of scores is related to participants’ health or follow-up. No missingness pattern or sensitivity analysis is reported. The direction or size of any potential impact cannot be inferred from the registry information.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: fracture of femoral shaft (0.7%), bascule implant cotyl (0.7%), post traumatic pain on acetabular (0.7%), cup pain after trauma (0.7%), deep infection (>6 weeks (0.7%).

The registry lists 141 participants at risk for serious adverse events and 17 participants affected. For other adverse events, it lists 141 at risk and 14 affected. It also reports 3 deaths. These are registry counts; the record does not provide a comparative analysis or establish that the events or deaths were caused by the implant.

The listed serious event terms each have a reported frequency of 0.7%: Fracture of Femoral Shaft, Bascule Implant cotyl, Post traumatic Pain on acetabular, Cup pain after Trauma, Deep Infection (>6 Weeks, and Cardiac Arrhythmia. The record does not clarify whether these terms refer to distinct participants, whether individuals could contribute more than one event, or how the listed terms relate to the total affected count. The counts should therefore be read as reported safety summaries, not as a complete event-level account.

The at-risk denominator is useful context for the affected counts, but the registry record does not describe the timing or duration of individual safety follow-up. It also does not report whether all participants had the same observation period or whether any events were considered related to the device. The 3 deaths should not be attributed to the stem on the basis of the posted figures. They are a recorded count, with cause and relationship not reported in the registry record.

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

The registry record describes a completed, retrospective post-market surveillance study with a primary goal of evaluating pain and functional performance using the Harris Hip Score. It also identifies complications and implant survivorship as secondary outcomes. These details clarify what the study was intended to assess, but the primary score result and detailed secondary outcome results are not reported in the registry record.

Accordingly, the posted information does not give an estimate of average Harris Hip Score at 10 years, its variability, or the precision of an estimate. It does not show how participants’ scores were distributed across the poor, fair, good and excellent categories. It also does not provide an analysis of score change or a comparison with another device or treatment. The presence of a defined endpoint is not itself evidence of a particular outcome.

The safety counts indicate that adverse events and deaths were recorded among participants at risk. Counts alone do not establish the cause of an event, the risk attributable to the implant, or how the observed safety profile compares with another option. Such interpretations would require information and analyses not reported in the registry record, including relevant follow-up details and, for comparative claims, an appropriate comparator.

This was a non-comparative study, so it cannot directly estimate a difference between the Avenir Müller Hip Stem and another intervention. Even if a group’s outcome estimate were available, a single-group result would need to be interpreted in light of participant characteristics, follow-up, missing data and other influences. Those data and analyses are not reported in the registry record.

The study is therefore informative about the surveillance question that was registered and the outcomes the investigators intended to assess. The posted information is not sufficient to determine the magnitude or precision of the primary clinical outcome, to attribute adverse events to the device, or to establish comparative performance. No claim that the device works or does not work follows from the information reported.

14. Why This Trial Matters Statistically

Post-market surveillance addresses questions about device outcomes after a device is in clinical use. This study’s stated objective was to collect clinical outcomes data for the Avenir Müller Hip Stem and confirm safety and performance. Its registry entry therefore illustrates how a surveillance study can define a clinical endpoint and safety outcomes while using a non-comparative design.

The Harris Hip Score is multidimensional: it includes pain and function as well as deformity and range of motion. That makes the endpoint broader than a single symptom measure, but also means that a summary score can conceal variation among its component domains. The record describes the score’s content and ratings. It does not report the score distribution or domain-level outcomes, so those aspects cannot be examined statistically from the posted results.

The design is important to interpretation. A non-comparative study can record outcomes and adverse events among recipients, but it does not provide a like-for-like control group. This distinction prevents a descriptive surveillance result from being treated as an estimate of comparative benefit or harm. The registry record also leaves important analytical details unreported, including missing-data handling, analysis populations and multiplicity methods.

There is a further practical lesson in the difference between a registered endpoint and a reported result. The primary endpoint and timeframe are specified, yet the mean and standard deviation are absent from the posted information. Without those estimates and measures of uncertainty, readers cannot assess the size or precision of the outcome. Clear reporting of both the endpoint and its results is needed for a quantitative statistical interpretation.

The record’s safety counts offer another reason to distinguish description from inference. An affected count is useful context, but attribution and comparative risk require more than a count alone. Taken together, the design and reporting make this study a useful example of why study purpose, outcome definitions, analyses and uncertainty all matter when interpreting clinical surveillance evidence.

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 interpreting this registry entry is that the primary endpoint result is not reported. Although the Harris Hip Score, its summary type and its 10-year timeframe are specified, no mean or standard deviation is posted. The number of participants with a score at that timeframe is also not reported in the registry record. This prevents assessment of the observed outcome and its precision.

The non-comparative design limits conclusions about relative performance. No comparator is described, and the record does not state an allocation method. The study therefore does not supply a like-for-like control comparison. The posted information cannot show how outcomes compare with another device, and it cannot isolate the implant’s contribution to observed outcomes from other influences.

The retrospective design is identified, but the registry record does not describe the source or completeness of the clinical records, the detailed eligibility criteria, or the participant-level follow-up schedule. It does not report the number of participants with outcome measurements, missing-data patterns, or methods for handling missing scores. These gaps make it difficult to judge representativeness and follow-up completeness.

Analysis details are also limited. The record lists three outcome measures and no analyses, and it does not report an analysis plan, confidence intervals, p-values, multiplicity procedures, or analysis populations. The safety record provides counts and selected serious event terms, but does not report event timing, causality assessments, or a comparative safety analysis. The relationship of the reported deaths to the device is not stated.

Finally, the registered description of the Harris Hip Score explains what the measure captures, but there are no posted score distributions or domain-level results. The study’s completed status and stated surveillance purpose do not resolve these reporting limitations. Conclusions about the size, precision, or comparative meaning of the outcomes cannot be drawn from the registry information alone.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Avenir Müller Hip Stem Post Market Surveillance Study — NCT04079127.
• Registry record last updated 2021-05-14; status last verified 2021-04.
• Results first posted 2020-06-23.
• 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 record describes a completed, multicentre, retrospective, non-comparative post-market surveillance study of the Avenir Müller Hip Stem, sponsored by Zimmer Biomet. It lists enrollment of 150, a study start of 2010-01-09, and primary completion on 2019-06-29. The stated purpose was to collect clinical outcomes data and confirm safety and performance.

The primary outcome was the Harris Hip Score for pain and functional performance at 10 years, summarized as a mean with standard deviation. Secondary outcomes concerned complications and implant survivorship. The record lists 141 participants at risk for serious adverse events, 17 affected, 14 affected by other adverse events among 141 at risk, and 3 deaths.

The registry record does not report the primary outcome estimate, its variability, confidence intervals, p-values, or analysis populations. It also does not report missing-data methods, a multiplicity strategy, or a comparator. The posted information therefore describes the study design, intended outcomes and some safety counts, but does not permit quantitative interpretation of the primary result or comparative conclusions.