Restoration® Modular Revision Hip System Post Market Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Restoration® Modular Revision Hip System Post Market Study (NCT00962013), a na na study. The primary outcome is Stem Survivorship (%).

2. Clinical Question

3. Trial Design

This is a prospective, open-label evaluation of the Restoration® Modular Revision Hip System. The registry record identifies it as a post-market study and classifies its model as single-group. All subjects were enrolled into one arm and received the system to replace the femoral portion of a failed previous implant. There is no randomized or concurrent control group described, and allocation is listed as NA. Masking is listed as NONE.

The registry record lists enrollment as 137 and status as completed. The recorded study start is 2004-01, and primary completion is 2011-12. These dates describe the record’s study timeline; they do not establish how long each participant was followed. The primary endpoint is defined at 5 years, and its stated population includes participants with 5 year follow-up evaluations or participants who had a stem revision before reaching 5 years. The number meeting this endpoint population is not reported in the registry record.

The primary outcome is stem survivorship, expressed as a percentage, with failure defined as stem revision for any cause. The record also lists Radiographic Stability, Harris Hip Score, SF-36 Health Status Survey: Role - Physical, and Post-surgery Femoral Crack/Fracture and Subsidence Rate as secondary outcomes. It records 6 outcome measures and 4 analyses, but those counts alone do not describe the analysis methods or show which results were reported.

The sponsor is Stryker Orthopaedics. Because all enrolled subjects received the same system, the study is suited to reporting outcomes within the treated group, subject to the quality and completeness of follow-up and outcome reporting. It does not provide a like-for-like control comparison. The protocol details, eligibility criteria, sample-size justification, and statistical analysis plan are not reported in the registry record.

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: 137/139 participants/hips enrolled and 17/17 participants/hips censored=120/122 participants/hips started

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Participants with 5 year follow-up evaluations or participant had a stem revision before they reached 5 years.

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.

Population: Includes participants who received the Restoration® Modular Hip System and were not censored from analysis.

6. Primary Endpoint

The registry lists the primary outcome as Stem Survivorship (%), measured over 5 years.

The primary endpoint is stem survivorship (%) at 5 years. The registry record defines failure as revision of the stem for any cause. In general, a survivorship endpoint describes the proportion of an eligible group whose device has not met the specified failure definition by the stated follow-up time. Here, the event is stem revision, not every complication, radiographic change, or additional procedure.

This endpoint is used to address the study’s stated purpose of evaluating femoral stem survivorship after replacement of the femoral portion of a failed previous implant. It focuses on whether the stem remains unrevised, regardless of the reason for revision. That definition is important: it gives the endpoint a specific, observable event, while leaving other clinical experiences to be captured through separate outcomes.

The endpoint population is defined as participants with 5 year follow-up evaluations or participants who had a stem revision before they reached 5 years. This wording identifies how early revisions are included in the primary-outcome population, but it does not report the number of participants assessed, the follow-up completeness, or how other loss to follow-up was handled. The registry record specifies a 90% confidence interval for the percentage. Neither the survivorship estimate nor its interval is reported in the registry record, so the observed endpoint value and its precision cannot be evaluated from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies stem survivorship as a percentage at 5 years and specifies a 90% confidence interval. It does not report the estimate, interval limits, or the statistical procedure used to produce them. The method cannot be inferred from the endpoint label alone. In particular, the record does not state whether the analysis used a time-to-event estimator, a fixed-time calculation, or another approach.

What does a survivorship endpoint represent?

In general, survivorship analysis follows an outcome over time and treats a defined event as failure. For this study, the specified event is stem revision for any cause. The endpoint’s time horizon is 5 years. If a time-to-event approach is used, participants with different follow-up durations and participants who do not experience the event during observed follow-up may require explicit handling. The registry record does not report the estimator, censoring rules, assumptions, or details of follow-up used for the primary analysis. It is therefore not possible to determine from the posted information how these features were incorporated.

The primary population description says participants qualified through a 5 year follow-up evaluation or through a stem revision before reaching 5 years. That description indicates that an early revision counts as an endpoint event rather than requiring a participant to complete the full follow-up period. It does not explain how participants without a 5 year evaluation and without a recorded revision were treated, or whether any other rules were used to define evaluability. Those details are not reported in the registry record.

What does the confidence interval add?

In general, a confidence interval expresses statistical uncertainty around an estimated quantity. It is not a guarantee that the true value lies within the observed limits, nor is it a substitute for the estimate itself. Its interpretation depends on the analysis method and the data available. The registry specifies a 90% confidence interval, but gives neither the limits nor the calculation method. As a result, readers cannot assess whether the interval is narrow or wide, or how much uncertainty surrounds the primary estimate.

The term percentage also requires a defined denominator and analysis population. The registry describes the population criteria but does not report the size of that population or a denominator for the primary estimate. Enrollment is listed as 137, but that is not stated to be the primary analysis denominator. The adverse-event risk group of 120 is also not identified as the primary analysis population. These counts should not be substituted for the missing endpoint denominator.

What can the study design estimate?

In general, a single-group study can estimate outcomes within the group observed, provided the outcome data and analysis are appropriately defined and reported. It cannot directly estimate a contrast against a concurrent control group when no such group is present. This study is recorded as single-group, with all subjects receiving the device. Thus, any reported survivorship value would describe the study group and would not be a randomized comparison or a controlled estimate of relative performance.

The registry record lists the study as prospective and open-label. Prospective follow-up can establish that outcomes were intended to be collected after enrollment, but it does not by itself establish complete follow-up or eliminate measurement and reporting limitations. Open-label describes the absence of masking; the record does not give further detail about outcome assessment procedures. It is not possible to infer whether specific analyses were blinded or independently adjudicated.

How should planning illustrations be distinguished from trial design?

Sample-size calculations based on an observed effect are planning illustrations, not evidence about the power achieved by this completed study. The described illustration assumptions use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. The assumptions also distinguish total event counts for time-to-event calculations from participants per arm for other calculations. These are hypothetical planning conventions and do not describe the actual single-group design, which has no two-arm allocation.

The registry record does not report a sample-size justification for the original study. It also does not provide a numerical observed primary effect from which a reader could evaluate an effect-based illustration. Planning outputs, where available, should therefore not be read as observed results, as an account of the original design, or as observed power. The study’s enrollment entry is not a substitute for a reported rationale or analysis plan.

What analysis details remain unknown?

The record lists 6 outcome measures and 4 analyses, but does not give enough detail to reconstruct the statistical methods. The primary analysis model, confidence-interval procedure, missing-data strategy, analysis population size, and any sensitivity analyses are not reported in the registry record. Nor is there a stated threshold against which the survivorship estimate was to be judged. Without these details and without the numerical primary result, readers cannot independently assess the estimate, its uncertainty, or the robustness of the analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary outcome and several secondary outcomes, including Radiographic Stability, Harris Hip Score, SF-36 Health Status Survey: Role - Physical, and Post-surgery Femoral Crack/Fracture and Subsidence Rate. It records 6 outcome measures and 4 analyses. However, the multiplicity strategy is not reported in the registry record. The record does not say whether adjustments were planned for assessing multiple outcomes, how outcomes were prioritized beyond the primary designation, or whether any analyses were exploratory.

In general, evaluating multiple outcomes can increase the chance of finding an apparently notable result by chance if each is treated as a separate confirmatory test. A prespecified analysis strategy can clarify which findings are intended to support confirmatory conclusions and how uncertainty should be interpreted across outcomes. The posted information does not describe such a strategy, and the numerical results for the primary and secondary outcomes are not reported in the registry record. It is therefore not possible to evaluate the effects of multiplicity on interpretation.

Missing-data methods are also not reported in the registry record. The primary population definition includes participants with 5 year follow-up evaluations or participants with a stem revision before they reached 5 years, but does not explain how other incomplete follow-up was handled. The number included in the primary analysis, the reasons for missing outcome information, and any imputation or sensitivity methods are not reported. The enrollment count cannot be assumed to be the primary analysis population.

The registry record does not describe a broader analysis population definition, such as rules for inclusion or exclusion from each outcome analysis. Its primary-outcome population wording is the available endpoint-specific description. Without details about missing observations, follow-up, analysis populations, and multiplicity, the potential impact of selective availability or multiple testing cannot be assessed from the posted information.

11. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: operative site musculoskeletal and connective tissue disorders (14.2%), non-operative site cardiac disorders (7.5%), non-operative site gastrointestinal disorders (6.7%), non-operative site infections and infestations (6.7%), non-operative site musculoskeletal and connective tissue disorders (5.8%).

The safety summary lists 44 affected among 120 at risk for serious adverse events in the Restoration® Modular group. It also lists 44 affected among 120 at risk for other adverse events. These are registry-record counts for the two categories; they are not measures of stem survivorship and should not be interpreted as such. The record does not explain how the risk groups relate to the enrollment count.

The most frequently listed serious-event terms include Operative Site Musculoskeletal and Connective Tissue Disorders at 14.2%, Non-operative Site Cardiac Disorders at 7.5%, Non-operative Site Gastrointestinal Disorders at 6.7%, Non-operative Site Infections and Infestations at 6.7%, Non-operative Site Musculoskeletal and Connective Tissue Disorders at 5.8%, and Operative Site Infections or Infestations at 5.0%. These percentages are the term-specific figures recorded; their denominators and any overlap between categories are not reported in the registry record. They should not be added together or treated as mutually exclusive categories.

These summaries do not establish whether an event was caused by the device, and they do not provide event timing or a comparative safety estimate. Deaths are not reported in the registry record. The figures describe the recorded adverse-event information, not a controlled assessment of risk relative to another treatment.

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

The record establishes that a prospective, open-label, single-group post-market study was conducted to evaluate femoral stem survivorship at 5 years. It defines failure as stem revision for any cause and specifies a 90% confidence interval for the primary percentage. This information clarifies the intended endpoint, but the numerical survivorship result and confidence interval are not reported in the registry record.

Without the primary estimate, it is not possible to describe the observed percentage of stems without revision or how precisely it was estimated. The stated purpose of demonstrating survivorship is not itself evidence that a particular outcome was observed. The registry record also does not report the methods used to calculate the estimate, the primary analysis population size, or how incomplete follow-up was handled. These omissions prevent a full appraisal of the endpoint analysis.

The study’s single-group design means there is no concurrent comparator. Even if a within-group survivorship result were available, it would not establish how outcomes compare with another implant or care strategy. Nor would it establish that any observed outcome was caused solely by the device. The record’s open-label status and lack of reported analysis details further limit assessment of how outcomes were measured and analyzed.

The adverse-event summary offers descriptive safety information, including affected counts and serious-event term percentages, but it cannot answer the primary survivorship question. Likewise, the secondary outcomes listed in the registry do not provide evidence of functional or radiographic results when their numerical findings are not reported. Distinct outcome types should be interpreted on their own definitions and not substituted for one another.

Accordingly, the registry record supports an account of the study’s design, its intended endpoint, and the adverse-event entries that were recorded. It does not support a quantitative conclusion about 5-year stem survivorship, the precision of that result, or comparative performance. Those limits concern what can be concluded from the posted registry information, rather than a claim that the study did or did not observe favorable outcomes.

13. Why This Trial Matters Statistically

This study illustrates why a clearly defined endpoint and a reported result are both necessary for statistical interpretation. The registry defines stem failure as revision for any cause and sets the assessment at 5 years. That definition gives the primary question a concrete event and follow-up horizon. But without the survivorship estimate, its confidence interval, and the analysis population, readers cannot quantify the outcome or assess its precision.

The single-group design also illustrates the distinction between describing outcomes and estimating comparative effects. A study can report what happened among participants who received a device, but a comparison requires an appropriate comparator and design. Here, all subjects received the Restoration® Modular Revision Hip System. The data therefore cannot directly answer how outcomes would differ under another device or treatment.

The record further demonstrates that endpoint labels do not reveal the analysis method. A percentage at a specified time may require decisions about follow-up and participants without complete evaluations. The record’s primary population description addresses participants with 5 year evaluations and those with a stem revision before reaching 5 years, while other follow-up handling is not described. Statistical transparency about these rules is needed to understand the reported estimate.

Finally, safety summaries, secondary outcome names, and sample-size planning concepts address different questions. Serious adverse-event counts do not substitute for survivorship, and listed outcomes do not constitute reported findings. Planning illustrations do not describe observed power or the original study’s design. Keeping these distinctions clear helps prevent a registry entry’s design information from being mistaken for evidence about the magnitude, precision, or comparative meaning of an outcome.

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 most consequential limitation in the registry record is the absence of the numerical primary endpoint result and its 90% confidence interval. Without those values, observed stem survivorship and its precision cannot be assessed. The primary analysis denominator and the number meeting the stated endpoint population are also not reported.

The single-group design has no concurrent comparator, so it cannot support a direct comparative estimate. The study is open-label, and the registry record does not describe outcome-assessment procedures, independent adjudication, or safeguards against measurement influence. The design and reporting details do not establish that any observed outcome is attributable to the device alone.

Follow-up and missing-data handling are not described in sufficient detail. Although the primary population definition includes 5 year evaluations or revision before that point, the record does not explain how other participants without complete follow-up were handled, why the adverse-event risk group differs from the enrollment entry, or whether any sensitivity analyses were conducted. These points limit assessment of completeness and potential selection effects.

The record does not report the statistical analysis plan, primary estimation method, confidence-interval procedure, multiplicity approach, or original sample-size justification. It lists secondary outcomes and analysis counts, but does not report their numerical results or how analyses were prioritized. Detailed eligibility criteria, participant characteristics, and event timing are also not reported in the registry record. Together, these omissions constrain evaluation of generalizability, analytic robustness, and the context of the safety summaries.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Restoration® Modular Revision Hip System Post Market Study — NCT00962013.
• Registry record last updated 2017-03-29; status last verified 2017-02.
• Results first posted 2014-08-15.
• 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.

18. Record Summary

The completed study is listed as a prospective, open-label, single-group post-market evaluation of the Restoration® Modular Revision Hip System, sponsored by Stryker Orthopaedics. Enrollment is listed as 137; the recorded study start is 2004-01 and primary completion is 2011-12.

The primary outcome is stem survivorship (%) at 5 years, with stem revision for any cause defined as failure and a 90% confidence interval specified. The numerical primary result and interval are not reported in the registry record. The record lists secondary outcomes, 6 outcome measures, and 4 analyses, but does not report their numerical findings or the statistical analysis plan.

Safety entries include 44 affected among 120 at risk for serious adverse events and 44 affected among 120 at risk for other adverse events. Several serious-event terms are listed with percentages. The record has no comparator group, and deaths are not reported in the registry record. The available information describes the study question and design but does not permit a quantitative assessment of the primary survivorship result.