Time Driven Activity Based Costing (TDABC): How To Accurately Measure the True Costs of Surgical Pathways

Understanding the true cost of surgical care is a major priority for hospitals that are continuing to deal with rising accountability, tighter margins, and value-based payment programs (e.g. CMS TEAM). However, claims data alone cannot capture what it actually costs a hospital to deliver a procedure. It only reflects what was billed and paid, not the resources consumed.

This is where Time-Driven Activity-Based Costing (TDABC) offers an advantage. TDABC provides a clear, practical way to measure care delivery costs at the level of individual steps in a surgical pathway. Unlike traditional costing models, it helps clinical and administrative leaders see how time, staffing, and process variation shape financial performance.

This guide explains how TDABC works, why it is well-suited to surgical care, and how hospitals can use it to improve accuracy, reduce waste, and support high-value clinical decision-making.

Why Surgical Pathways Need a Better Costing Method

If you speak with OR directors, perioperative nursing, or service line leaders, you'll often hear a similar story:

"We know variation is there. We can feel it in the workflow. But we can't quantify it in a way that supports change."

That's because hospitals routinely rely on cost accounting systems that were not built to measure care at the pathway or procedure level. And these legacy systems often rely on:

• Department-level averages
• Historical allocation formulas
• Charges as a proxy for cost

The problem is, these methods mask variation within surgical lines. For example, two total knee arthroplasties may have identical charges and similar reimbursement, but the underlying costs may differ significantly depending on:

• Time in the OR
• Case staffing
• Surgical technique
• Supply use
• PACU duration
• Post-operative care
• Post-acute utilization

And without a clear view into these differences, leaders are left guessing where true cost variation comes from.

TDABC solves this gap by measuring costs at the ground level: the activities and time required for care.

What Is Time Driven Activity Based Costing (TDABC)?

Time-Driven Activity-Based Costing is a method created by Kaplan and Anderson at Harvard Business School to simplify and modernize activity-based costing. It focuses on two inputs that every hospital already understands intuitively:

1. The cost of each resource per unit of time

Every clinician, space, piece of equipment, and supply has a cost for the minutes it is in use. TDABC calculates this by assigning a "capacity cost rate." This makes it possible to compare the financial impact of activities based on time spent.

2. The time required to complete each step in the pathway

This includes pre-op evaluation, room setup, anesthesia induction, operative time, PACU recovery, therapy assessment, and all subsequent care.

Once you multiply time by the cost per minute, you get the actual cost of each step. Adding those steps together gives you the cost of the full care episode.

The method is straightforward. But the insight it produces is often eye-opening for teams that have long worked without this level of clarity.

Why TDABC Fits Surgical Care Naturally

Surgical care is built around sequences of highly coordinated tasks. Even small shifts in timing or staffing echo through the entire pathway. TDABC captures this reality in a way clinicians immediately recognize.

Time drives everything in surgery

OR minutes shape case cost, throughput, and access. PACU minutes shape staffing and bed availability. Length of stay influences downstream demand and post-acute use.

Because time is so central, TDABC provides a realistic picture of how both clinical and operational factors influence performance.

Resources are predictable

Surgical pathways involve reproducible activities staffed by interdisciplinary teams. Mapping who does what, and for how long, is far easier than many hospital leaders expect once the right people are in the room.

Surgeon variation becomes visible in a constructive way

Instead of broad comparisons, TDABC highlights where and why performance differs. This creates a more supportive environment for clinical conversations because the insights are grounded in actual workflow data, not assumptions.

The method aligns with the needs of value-based programs

CMS TEAM, BPCI Advanced, CJR, and commercial bundles require hospitals to understand their internal cost structure. Claims data alone cannot explain why some patients cost more or how variation emerges. TDABC fills that gap.

How TDABC Works Across a Surgical Pathway

Hospitals applying TDABC typically follow a process that brings clinicians, finance, and operations together. The approach is collaborative rather than technical, which helps build trust and alignment early.

1. Map the journey from first touchpoint to final follow-up

Teams outline what happens from pre-op assessment to post-operative recovery. These conversations often bring immediate clarity, as clinicians describe the reality of workflow variation that financial systems cannot capture.

2. Identify the resources that make each step possible

Rather than thinking at a department level, TDABC looks at the specific people, tools, and spaces required for each activity. Clinicians appreciate this because it finally reflects the complexity of their work.

3. Assign a cost per minute to each resource

This step transforms abstract staffing and equipment costs into something far more useful: the financial impact of time.

4. Measure how long each step takes

Hospitals typically combine EHR time stamps, OR records, direct observation, and clinician input. The goal isn't perfection. It's accuracy sufficient to reveal patterns.

5. Calculate the cost of each activity

Multiplying time by cost per minute shows the real financial footprint of a step in care. For many teams, this is the moment when insights begin to emerge.

6. Assemble activity costs into a full episode view

Instead of a departmental snapshot, leaders now see a patient's entire surgical journey. This unified view helps both clinical and financial leaders speak the same language.

The process is structured, but it also humanizes cost data by tying it directly to the real work clinicians perform every day.

What TDABC Helps Hospitals See More Clearly

Once hospitals begin using TDABC, they quickly notice patterns that traditional systems have never captured clearly.

Variation in operative time and workflow

Two surgeons may perform the same procedure with similar outcomes, yet differ by 30 minutes or more in the OR. TDABC quantifies the financial impact of this variation and allows teams to discuss it constructively.

Supply choices sometimes matter less than expected

Hospitals often assume devices drive most cost differences. TDABC often reveals that staffing time, room setup, or PACU recovery have a larger influence.

Small inefficiencies create measurable ripple effects

A delay in room turnover or inconsistent handoff workflow may add costs that no department sees on its own. TDABC captures these hidden dynamics.

Outpatient vs. inpatient pathways show predictable differences

With TDABC, hospitals can better model which patients are appropriate for outpatient settings and how to structure staffing accordingly.

Care variation is often correctable

Many cost differences arise from processes that evolved organically rather than intentionally. TDABC reveals opportunities to streamline care without compromising clinical judgment.

These insights give clinicians and leaders a shared understanding of where change will have the most meaningful impact.

4 Major Ways TDABC Supports Clinical, Operational, and Financial Decisions

TDABC can help teams move beyond general improvement goals and focus on steps that meaningfully influence cost and patient experience. It clarifies where variation is helpful, where it is neutral, and where it may unintentionally create inefficiency.

1. Better forecasting for staffing and capacity

Time-based data helps hospitals model scenarios with far more precision:

• How staffing models influence cost per case
• How changes in block scheduling affect throughput
• How process improvements reduce bottlenecks

This supports OR leadership, nursing, therapy, and bed management.

2. Stronger performance in value-based care programs

When hospitals understand their internal episode costs, they are better equipped to:

• Identify high-leverage opportunities
• Reduce variation
• Improve coordination
• Support effective gainsharing models

TDABC gives teams a clearer picture of what actually drives performance.

3. More thoughtful supply chain decisions

Instead of focusing solely on unit price, hospitals can evaluate vendor choices in the context of the entire episode. For example, a slightly more expensive implant may reduce operative time or eliminate an additional step in the workflow, creating overall savings.

4. Better alignment between finance and frontline teams

Perhaps the most meaningful benefit is that TDABC helps clinical teams and administrators speak the same language. Cost is no longer something abstract. It becomes tied to the work people perform every day.

Common Concerns and How Hospitals Can Navigate Them

Barrier 1: "The Method Seems Too Complex"

While it may feel complex at first, TDABC is far simpler than activity-based costing or cost-to-charge methodologies. Modern analytics platforms automate most of the calculations. Start with one procedure line (example: total knee arthroplasty), then expand.

Barrier 2: "We Don't Have Enough Accurate Time Data"

Perfect data is not required. Reasonable estimates produce strong insights. Use a combination of EHR time stamps, OR logs, and observational studies for validation.

Barrier 3: "Clinicians Won't Engage"

Most clinicians appreciate seeing where workflow variation exists when the insights are presented respectfully and rooted in data accuracy. Involve clinical leaders early in pathway mapping.

Barrier 4: "We're Not Sure How to Maintain the Model Long Term"

TDABC does not require constant recalibration. Updates happen when staffing, supply, or process changes occur. Review annually or after key operational shifts. This is also where utilizing 3rd party partners that have the experience and tools to help you maintain your tracking long term can be invaluable.

Practical Advice for Teams Getting Started with Time Driven Activity Based Costing

Hospitals are most successful when they view TDABC as a shared project rather than a finance-led initiative. Early wins come from:

• Starting with a high-volume procedure
• Creating a cross-functional team
• Speaking with frontline staff to validate time assumptions
• Prioritizing clear, simple visual outputs
• Focusing on insights rather than perfection
• Sharing early findings to build momentum

These steps help organizations generate value quickly and build momentum for broader adoption.

Final Thoughts: TDABC Provides A More Accurate, Practical Way to Measure Surgical Costs

Time-Driven Activity-Based Costing gives hospitals a straightforward and reliable way to understand the true cost of surgical pathways. Instead of relying on outdated allocation formulas, it measures cost through two variables that are easy to track: time and resource rates.

The result is a detailed, pathway-level understanding of cost drivers that supports:

• Better clinical pathways
• Improved OR efficiency
• Smarter staffing
• Effective supply chain strategy
• Stronger performance in value-based programs
• Clearer communication between finance and clinical teams

As hospitals prepare for increasing financial accountability, TDABC provides the accuracy and transparency needed to navigate the next decade of surgical care.