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 Robotic Arm Assisted Total Knee Arthroplasty (NCT02058069), a na na study. The primary outcome is Intra-Operative Complications.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02058069 |
| Phase | NA |
| Condition | Osteoarthritis, Rheumatoid Arthritis, Post-traumatic Arthritis |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 100 |
| Arms in the primary outcome | n/a |
| Lead sponsor | MAKO Surgical Corp. |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns people undergoing total knee arthroplasty for osteoarthritis, rheumatoid arthritis, or post-traumatic arthritis. The registry lists an enrollment of 100. The primary outcome specifies that participants are counted as knees, so the unit of assessment is described as participants = knees. The registry record does not report further eligibility criteria or participant characteristics in the information available for this study.
Intervention
The intervention is robotic arm assisted total knee arthroplasty using the Robotic Arm Interactive Orthopedic System (RIO) Total Knee Arthroplasty Application. The study objective is to assess the safety and effectiveness of that application. The registry describes a single-group study; it does not report a separate treatment arm or a control intervention.
Comparator
There is no randomized or concurrent control group described. The study therefore does not provide a like-for-like comparison between robotic arm assisted surgery and another procedure or approach. The secondary outcomes include pre-operative to post-operative radiographic assessment, but a within-participant assessment over time is not the same as a comparison against a control group.
Primary question
The primary question is whether standardized complications are identified by the surgeon during the operation. The stated endpoint is the number of intra-operative complications, assessed after the procedure is complete while the participant remains in the operating room. The brief summary also describes short-term follow-up as part of the overall primary objective, but the primary outcome entry specifies intra-operative assessment. The registry record does not report the observed primary endpoint result.
3. Trial Design
This is a completed, single-group device study of robotic arm assisted total knee arthroplasty. The registry lists an enrollment of 100 and identifies the intervention as the Robotic Arm Interactive Orthopedic System Total Knee Arthroplasty Application. Allocation is listed as NA, masking as NONE, and the model as SINGLE GROUP. These entries describe a study without a randomized allocation or a masking arrangement; they do not establish how every aspect of clinical care was organized.
The registry lists a start of 2014-02 and primary completion of 2015-01. It describes the study as multi-center and says it was to be conducted with approval from and in compliance with the Western Institutional Review Board. The listed status is COMPLETED. These record details do not, by themselves, establish whether every planned assessment was completed or how participants were followed.
The stated overall objective is to assess safety and effectiveness. The primary objective concerns surgeon assessment of standardized total knee arthroplasty complications intra-operatively and at short-term follow-up. The secondary objective concerns radiographic assessment of post-operative limb alignment, while the supporting objective concerns patient assessment of post-operative function and satisfaction. The listed secondary outcomes include change in radiographic limb alignment from pre-operative to 3 months post-operative and the number of participants with limb alignment difference <4.38 degrees.
Because the study has no control group, the design can describe outcomes observed among participants receiving the intervention but cannot provide a randomized estimate of its effect relative to another approach. The registry record does not report a protocol-level statistical analysis plan, detailed eligibility criteria, or the basis for the enrollment target.
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 | Robotic Assisted Total Knee Arthroplasty |
|---|---|
| STARTED | 100 |
| COMPLETED | 89 |
| NOT COMPLETED | 11 |
Reasons for not completing this period:
| Reason | Robotic Assisted Total Knee Arthroplasty |
|---|---|
| Exclusion due to implant size | 5 |
| Withdrawal by Subject | 6 |
Analysis population for the primary outcome, as defined in the registry: participants = knees.
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 | Robotic Assisted Total Knee Arthroplasty |
|---|---|---|
| Participants analysed | 89 | |
| Age, Continuous | years | 65.78 (SD 8.49) |
| Sex: Female, Male: Female | Participants | 49 |
| Sex: Female, Male: Male | Participants | 40 |
6. Primary Endpoint
The registry lists the primary outcome as Intra-Operative Complications, measured over Subject will be assessed for these complications intra-operatively. The assessment occurs after the surgeon has completed the surgical procedure, but while the subject is still in the operating room with the surgeon..
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | intra-operative complications |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the number of intra-operative complications. The surgeon assesses standardized complications after completing the surgical procedure, while the participant remains in the operating room. The complications listed are blood loss, vascular injury, MCL injury, periprosthetic fracture, extensor mechanism disruption, patellofemoral dislocation, tibiofemoral dislocation, neurological impairment, and instability. The registry describes the assessment as based on standardized total knee arthroplasty complications.
A complication count is a safety-oriented outcome: it records whether specified events were identified during the procedure. Such an endpoint is useful for describing what occurred in the study group, but its interpretation depends on consistent definitions, observation, and reporting. The registry record does not report the primary endpoint result, individual complication counts, or the method used to combine or summarize the listed complications.
The outcome entry states that participants are knees. This matters because the analysis unit should match the unit contributing outcome information; the record does not provide additional details about how multiple knees, if any, were handled. The brief summary mentions short-term follow-up within the primary objective, whereas the primary endpoint’s timeframe specifies intra-operative assessment. A follow-up complication result is not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a completed, single-group study and identifies intra-operative complications as the primary endpoint. It does not report the observed primary endpoint result. Consequently, the record does not support a numerical description of how many participants experienced those complications, which complication types were observed, or how precisely the complication frequency was estimated. The absence of a result in the record should not be interpreted as a result of zero complications.
The record lists 6 outcome measures and 3 analyses, but it does not report the outcome estimates or the analysis details needed to interpret them. The secondary outcome names identify planned topics: radiographic change in limb alignment from pre-operative to 3 months post-operative, and participants with limb alignment difference <4.38 degrees. Their results are not reported in the registry record. The supporting objective on post-operative function and satisfaction is described in the brief summary, but corresponding results are not reported in the registry record.
The available safety information lists 9 serious adverse events among 100 at risk and 0 other adverse events among 100 at risk in the robotic assisted total knee arthroplasty group. The registry also lists arthrofibrosis at 4.0%, adhesions at 4.0%, and pulmonary embolism at 1.0% among the top serious terms. These entries describe reported safety events; they do not replace the missing result for the primary intra-operative endpoint. The deaths field is not reported in the registry record, so it cannot be interpreted as zero deaths.
In general, a confidence interval expresses the range of estimates compatible with the data under the specified statistical method and assumptions. No confidence interval for the primary endpoint is reported in the registry record. Without an estimate and its precision, readers cannot judge how uncertain the primary result would be, even if a point estimate were available.
The absence of a control group also limits interpretation. Outcomes recorded in a single group cannot establish how those outcomes compare with outcomes under another surgical approach. The study description supports a report of what was assessed and the safety entries that are present, but not a causal claim that the intervention changed the risk of complications, alignment, function, or satisfaction.
9. Statistical Methods Explained
What does a single-group design allow?
General: A single-group study observes outcomes among participants who receive the intervention, without a concurrent comparison group. It can describe event counts and other measured outcomes in that group. It cannot separate an intervention-related effect from other explanations, such as participant characteristics, clinical practice, or changes over time. This is why descriptive findings from such a design should not be read as a randomized comparison.
For this study, the registry identifies a single-group model, allocation listed as NA, and masking listed as NONE. Those entries are consistent with interpreting the study as a description of outcomes following robotic arm assisted total knee arthroplasty rather than as a randomized treatment comparison. The registry record does not report a comparator group or an adjusted causal analysis.
How should a count endpoint be understood?
General: A count endpoint records the number of events observed under a defined assessment process. It is important to distinguish the number of events from the number of participants who experienced at least one event. One participant can potentially experience more than one event, so those quantities need not be identical. The registry’s primary outcome is described as the number of intra-operative complications and says participants = knees, but the record does not report the observed count or clarify whether results would be presented as event counts, participants with events, or both.
The complication list sets the clinical scope of the endpoint: blood loss, vascular injury, MCL injury, periprosthetic fracture, extensor mechanism disruption, patellofemoral dislocation, tibiofemoral dislocation, neurological impairment, and instability. Consistent definitions and ascertainment matter because variation in how events are recognized or recorded can affect a count. The registry describes standardized complications but does not report operational definitions, adjudication procedures, or the handling of overlapping events.
Why do analysis details matter?
General: Statistical methods should match the outcome type and study design. Counts may be summarized descriptively, and uncertainty can be expressed with an interval estimate. When counts vary more than a simple model expects, over-dispersion can make standard errors too small if it is ignored. The choice of method should therefore be informed by the data structure, event frequency, and analysis plan rather than assumed from the outcome label alone.
The registry record does not report the statistical method for the primary count, an interval estimate, a hypothesis test, or an adjustment strategy. It also does not report whether the analysis was prespecified or how any deviations from an intended analysis were handled. The listed number of analyses does not reveal their purpose or their assumptions.
What do planning illustrations represent?
General: A sample-size calculation estimates how many participants would be needed under stated assumptions to detect a specified effect with a chosen error rate and power. It is a planning exercise, not evidence that an effect was observed. A calculation based on an observed effect is especially dependent on that estimate, and its result should be treated as an illustration rather than as a design justification unless the registry identifies it as the original planning method.
The registry record describes planning illustrations based on a stated fraction of an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that time-to-event illustrations use total events and other illustrations use participants per arm. These are planning illustrations, not observed power and not evidence of a trial design with two arms. The record does not report the trial’s own sample-size justification. The observed effect used for those illustrations is not reported in the registry record.
How should uncertainty be read?
General: A point estimate alone does not show how much uncertainty surrounds an outcome. A confidence interval conveys sampling uncertainty conditional on a statistical model and its assumptions; it does not account automatically for biases, outcome misclassification, incomplete follow-up, or limitations of study design. A p-value, when reported, addresses compatibility with a specified null model and does not by itself measure clinical importance or the probability that a hypothesis is true.
No primary endpoint estimate, confidence interval, or p-value is reported in the registry record. Accordingly, readers cannot assess the precision or statistical compatibility of the primary result from this record. The registry lists outcome and analysis counts, but those counts do not supply the missing estimates or methods.
10. Multiplicity, Missing Data and Analysis Populations
The study description identifies a primary objective, a secondary objective, and a supporting objective. It also lists 6 outcome measures and 3 analyses. When a study examines multiple outcomes or performs multiple tests, the chance of at least one apparently unusual result can increase if each test is interpreted separately. General approaches to multiplicity include identifying a primary outcome in advance, using a hierarchical testing sequence, or adjusting inference across a defined family of tests. Which approach is appropriate depends on the research questions and analysis plan.
The registry record does not report a multiplicity strategy, the prespecified hierarchy among all outcomes, or whether analyses were adjusted for multiple testing. It also does not report which outcomes were included in each analysis. The stated primary objective includes surgeon assessment of complications intra-operatively and at short-term follow-up, while the primary outcome entry specifies intra-operative complications; the analysis of any short-term follow-up endpoint is not reported in the registry record.
Missing-data methods and analysis populations are also not reported in the registry record. The record does not explain how incomplete assessments, withdrawals, or unavailable radiographs were handled, nor does it specify whether analyses included all enrolled participants or a subset. These omissions matter because exclusions and missing measurements can affect both the estimated outcome and its uncertainty. The listed enrollment of 100 is not enough to determine the number contributing to each endpoint.
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 |
|---|---|---|---|
| Robotic Assisted Total Knee Arthroplasty | 9 | 100 | 9.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Robotic Assisted Total Knee Arthroplasty | 0 of 100 |
Most frequent serious adverse event terms
| Event term | Organ system | Robotic Assisted Total Knee Arthroplasty |
|---|---|---|
| Arthrofibrosis | Musculoskeletal and connective tissue disorders | 4 of 100 |
| Adhesions | Musculoskeletal and connective tissue disorders | 4 of 100 |
| Pulmonary Embolism | Vascular disorders | 1 of 100 |
Serious events with the highest arm-level rate: arthrofibrosis (4.0%), adhesions (4.0%), pulmonary embolism (1.0%).
The registry lists 9 serious adverse events among 100 at risk in the robotic assisted total knee arthroplasty group. It lists 0 other adverse events among 100 at risk. The top serious adverse event terms are arthrofibrosis at 4.0%, adhesions at 4.0%, and pulmonary embolism at 1.0%. These figures should be read as registry safety entries, not as a comparison between treatment groups, because the study is described as single-group and has no control arm.
Serious adverse events and the primary intra-operative complication endpoint are distinct reporting categories in the record. The serious adverse event entries do not tell readers how many of the standardized intra-operative complications occurred. Nor do the listed top terms establish that other serious events did not occur; they identify the terms reported as top serious events. The registry record does not report event-level detail, timing for these serious events, or how many participants experienced more than one event.
The deaths field is not reported in the registry record. It should not be read as a count of zero. General: Safety counts are descriptive and their interpretation depends on event definitions, follow-up duration, and completeness of reporting. The registry record does not provide enough detail to assess those aspects fully.
12. What the Result Does, and Does Not, Mean
The record establishes the study’s purpose, design, intervention, endpoint description, and some safety reporting. It describes a completed single-group study of robotic arm assisted total knee arthroplasty, with intra-operative complications as the primary endpoint and post-operative limb alignment among the secondary outcomes. It also lists serious adverse event information for the intervention group.
It does not report the result of the primary endpoint. It therefore does not establish how often the listed intra-operative complications occurred or how precisely that frequency was estimated. Secondary outcome results for radiographic alignment are not reported in the registry record, and the supporting objective concerning function and satisfaction is not accompanied by results in the registry record. The listed serious adverse event figures do not fill these gaps or answer the primary endpoint question.
Because the study has no control group, any reported outcomes would describe the participants observed in this study, not the difference attributable to the intervention compared with another approach. General: Establishing a causal treatment effect usually requires a comparison that can address differences between groups, through randomization or carefully justified methods. No such comparison is described in this record.
The record also does not report the statistical analysis plan, confidence intervals, missing-data procedures, analysis populations, or multiplicity handling. Without those details, readers cannot fully evaluate precision, risk of bias from incomplete observations, or how multiple outcomes were interpreted. A completed status does not itself show that all planned outcomes are available in the registry record.
The defensible interpretation is therefore limited: the registry documents what the study intended to assess and includes certain adverse-event entries, but it does not provide the primary efficacy or complication outcome results needed for a fuller statistical interpretation. No conclusion about comparative effectiveness can be drawn from this single-group record.
13. Why This Trial Matters Statistically
This study is statistically instructive because its design and endpoint make the distinction between describing outcomes and estimating comparative effects especially important. A single-group study can record complications and radiographic outcomes after a procedure, but without a comparator it cannot directly estimate how those outcomes differ from another approach. Readers should keep the study’s descriptive scope in view when interpreting any event counts.
The primary endpoint is a count of standardized intra-operative complications, while the study objectives also refer to short-term follow-up, radiographic alignment, function, and satisfaction. These are different outcome domains and may require different summaries and analysis methods. A clear distinction between the stated objective and the primary outcome’s specified timeframe is important for deciding which question a particular result answers.
The record also illustrates why outcome results and statistical methods must be considered together. An event count without a denominator, estimate, or measure of uncertainty can be difficult to interpret. A point estimate with an interval can communicate precision, while a clear account of outcome definitions and analysis populations helps readers understand what was counted. Those primary endpoint results and methods are not reported in the registry record.
Finally, planning calculations should not be confused with observed evidence. The record characterizes its sample-size illustrations as planning exercises based on an observed effect and stated assumptions. Such calculations do not establish that the study was designed around those assumptions, and they are not observed power. The registry does not report the trial’s own sample-size justification. These distinctions help separate design, analysis, and interpretation rather than treating them as interchangeable.
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 does not report the primary intra-operative complication result, limiting direct interpretation of the central outcome. It also does not provide the result of the radiographic secondary outcomes or the patient-reported supporting objective. Although certain adverse event figures are listed, the record does not include the detail needed to relate those events to the primary endpoint or to assess their timing and follow-up context.
The single-group design has no concurrent control comparison. This prevents a like-for-like estimate of outcomes under robotic arm assisted surgery versus another procedure. Allocation is listed as NA and masking as NONE, but the record does not provide further detail about outcome ascertainment or potential influences on the surgeon’s assessment.
The statistical methods are not reported in the registry record. In particular, the record does not specify how the primary count was summarized, whether uncertainty was quantified, which analysis populations were used, or how missing outcome data were handled. Multiplicity procedures and a trial-specific sample-size justification are also not reported. The record’s description of planning illustrations does not replace a trial design rationale.
Some basic information needed to evaluate applicability is absent from the registry record, including detailed eligibility criteria and participant characteristics. The record lists an enrollment of 100, but does not state how many participants contributed data to each outcome. The deaths field is not reported in the registry record and cannot be treated as a zero count. These limits mean that the available entries support only a partial reading of the study’s intended questions and reported safety information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Robotic Arm Assisted Total Knee Arthroplasty — NCT02058069.
- Registry record last updated 2017-04-18; status last verified 2017-03.
- Results first posted 2016-02-12.
- 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, single-group device study of robotic arm assisted total knee arthroplasty, with enrollment listed as 100. The primary endpoint is the number of standardized intra-operative complications assessed by the surgeon after the procedure. Secondary objectives concern post-operative limb alignment, and the supporting objective concerns patient function and satisfaction.
The primary endpoint result and the listed secondary outcome results are not reported in the registry record. Safety entries list 9 serious adverse events among 100 at risk and 0 other adverse events among 100 at risk; deaths are not reported in the registry record. The study has no control group, and its statistical analysis details, missing-data procedures, multiplicity handling, and trial-specific sample-size justification are not reported in the registry record. The record therefore supports a description of the study design and available safety entries, but not a comparative treatment-effect conclusion.