Medical Device Link.

Orthopedics

Total knee replacement is one of the most common surgical procedures in the United States, with more than 540,000 knee-replacement surgeries performed in 2006.1 Refined through three decades of experience, knee replacements initially went through a period of rapid evolution in the first decade after introduction and then settled into a fairly standard procedure for a broad group of patients. Today, older patients with debilitating knee pain will typically be offered a total knee replacement that functions similarly to the one they might have received as far back as 20 years ago.

Yet the traditional, off-the-shelf approach to treating knee osteoarthritis still has clinical drawbacks that leave an equal number of patients, particularly early intervention patients, without an attractive option. In addition, patient satisfaction with total knee replacement has tended to lag behind surgeon satisfaction. Patients are unhappy because of the difficultly in replicating natural knee kinematics using an off-the-shelf prosthesis that is not designed for the individual patient. Moreover, the build-to-stock model results in unnecessary investment that must be borne by both hospitals and manufacturers.

This article explains how advances in technology allows a patient-specific, just-in-time (JIT) approach to knee replacement to take the orthopedics industry through a new cycle of development. This model, based on personalized knee implants and surgical tools designed using advanced imaging and CAD technology, has the potential to improve outcomes for patients and surgeons and to improve operating efficiencies for hospitals. It also creates opportunities for manufacturers to take advantage of capital-efficient technologies that would not be suitable for the traditional mass-inventory model.

CT scans create a digital 3-D image of the knee. A personalized implant, as well as surgical instruments, can be designed using automated software and design rules.

In the existing model, orthopedics companies produce and hospitals stock hundreds of millions of dollars of variously shaped and sized implants and surgical tools. Surgeons choose an implant from this inventory, working with a limited range of sizes, to best match the implant to the patient. The mismatch between a limited array of implant sizes and the much greater variations found among patients necessitates surgical remodeling of the knee to fit the patient to the implant and also compromises on knee kinematics.

The mass-inventory model uses a large armament of cutting and measurement guides, provided as loaner instrumentation by manufacturers to hospitals at a substantial cost, to perform the surgeries. The necessary removal of sometimes-healthy tissue can slow patients’ recovery and limit their options for future surgery. Furthermore, the extensive metal instruments used for the implant procedure require transport, sterilization, and stocking before and after each surgery, saddling hospitals with the costs associated with managing this inventory. Each of these issues can be addressed to substantial degree by designing, manufacturing, and delivering patient-specific implants and disposable surgical tools on demand. One study, for example, found that current commercial tibial designs for unicompartmental knee replacement typically use only 67% of the cortical bone to support the implant due to the limited range of standard shapes.2

Technology Enables an Innovation Curve

Through manufacturing redesign, companies can employ rapid prototyping technologies, such as fused deposition modeling or laser sintering, that are ideally suited for cost-effective small-run production of implants and instruments.

Recent advances in information and manufacturing technology have made this custom, JIT approach feasible for orthopedics. ConforMIS, for example, was founded in 2004 to develop such a model. The process starts by using a magnetic resonance imaging or computer tomography scan to create a digital 3-D image of the individual patient’s knee. Using software automation and design rules created by a scientific advisory board, a personalized knee implant as well as surgical instruments are designed and manufactured. The system is delivered in a small, one-way package. Every component of the system is either implanted in the patient or discarded.

Because all components of the system are made for one-time use, this patient-specific approach to orthopedics creates many opportunities for business model innovation. Three examples of reconstructing the business model include rethinking design, rethinking manufacturing, and rethinking the customer supply chain.

Rethinking Design

Traditional orthopedic implants use measurements or scans from a sampling of patients or cadavers to guide the design process. Although the sample size varies, the principle approach uses sample averages to set the parameters of the design objectives, often neglecting potential variations and dispersion from the average.3 Some attempts to fine-tune the approach have incorporated race and gender as variables, but these designs still rely on averages.4,5

By combining cross-sectional imaging data and information processing technology, a new approach uses automation software to dedicate a design to an individual patient rather than to an average of patient sizes. Proprietary software, loaded with proven design algorithms, now processes full implant designs within a matter of seconds, eliminating the design time and cost disadvantage of custom implants. In fact, the use of electronic design files creates opportunities for efficiency throughout the entire manufacturing process.

Rethinking Manufacturing

When it comes to manufacturing, the traditional method has been to invest in production runs scaled to create medium to large stock inventories of both implant components and their associated surgical tools. A large manufacturer, for example, typically invests more than $150 million each year to create instruments with an average depreciation period of three to five years, depending on the life cycle of the implant system. The traditional manufacturing model focuses on process standardization for longer production runs.

By moving to a patient-specific approach, a host of technologies can be introduced that have been developed in the direct digital manufacturing area over the last decade. Through manufacturing redesign, rapid prototyping technologies such as fused deposition modeling, laser sintering, or direct metal laser sintering are employed. These techniques are ideally suited for cost-effective small-run production of implants and instruments.

Technologies completely unsuitable for orthopedics using traditional approaches become suitable and cost-competitive in a patient-specific approach. For example, rather than amortizing the cost of a $15,000–$20,000 metal instrument set, direct digital manufacturing uses inexpensive engineered materials to enable single-use instrument sets at a radically reduced cost per surgery. Indeed, lower inventory carrying costs and the opportunity to introduce rapid product iterations without replacing field inventory helps turn JIT production into a competitive advantage.

Rethinking the Customer Supply Chain

Hospitals typically do not have a full accounting of the costs they incur in their relationships with orthopedic manufacturers. It is likely that a full and complete activity-based cost analysis would demonstrate that hundreds of dollars in central supply costs are incurred for every knee replacement. And substantial opportunities for reengineering the work flow would exist if a critical mass of consigned or loaner inventory were no longer available.

A fully patient-specific approach encompassing both the implant and instrumentation allows for radically simplified logistics and work flow. The full system is shipped to the hospital in a one-way tray. At the hospital, transport and setup involve unpacking the single tray in one small area, and then disposing of all components after surgery. Tear down and disposal consumes far less time, sterilizer usage, and central supply personnel. For the manufacturer, the entire set of activities required for inventory tracking and management at the customer site is completely eliminated.

Patient-specific approaches have allowed a move to a new business model. This model presents an innovation curve in orthopedics with expansive possibilities. This revolution will quickly have the entire industry talking about patient-specific systems as the next key developments in the industry.

Philip Licari is chief operating officer of ConforMIS Inc. (Burlington, MA).