There can be a lot of reasons to change a device and as long as it doesn't effect he safety, efficacy or performance of the device, there shouldn't be too much of a hassle to change it. Reasons to change a device can be a little as rotating the image of the logo on a device to make it more aesthetically pleasing or it could be an actual change to the device to make the efficacy better.In order to accomplish these changes you will have to supplment the PMA or offer a special 510k to the FDA.

Usually change has a driving factor which comes mainly in the three, not mutually exclusive, flavors; necessity, efficiency, and profitability. In the first situation, change is unavoidable because the product at the moment is either out of spec, fails to meet a required standard, or has a change in risk(usually an increase) that is too great for governing agencies to accept such as carcinogenic debris from wear of certain materials or previously unknown side effects of particles in the body from "bioresorbable" products or their components. for the second case, improving the cost effectiveness of the product after it has been launched based on new information. This can be changes in the manufacturing process, the density of the material, the amount of coating, and other variables that were initially set high but are now understood to be excessive or unnecessary. In the third category, you can have improvements to existing products to either meet a different customer base, be more appealing to the current base by improving performance, or simply launching an alternative product such as a high end and economy version of a device.
Depending on the nature of the change and how great an impact the change have on the chemistry and performance of the product as well the driving force that initiated the change, only a 510K or supplementing the PMA as PSM34 said. If it is however driven by necessity, the product may end up changing classes.

Change control is a systematic approach to managing all changes made to a product or system. The purpose is to ensure that no unnecessary changes are made, that all changes are documented, that services are not unnecessarily disrupted and that resources are used efficiently.
The change control process is usually conducted as a sequence of steps proceeding from the submission of a change request.
Documenting the change request,Formal assessment,Planning,Designing and testing,Implementation and review,Final assessment

Change control is a procedure for ensuring that changes to any product within scope of quality management system are planned, approved and implemented in a controlled manner maintaining safety and efficacy of the product. The company have to decide they will go for letter-to-file or a special PMA/510(K) supplement. Letter-to-file remains internal in the company while PMA/510(K) depends on regulatory path of original devices. The company should do analysis and testing that whether the change have could have impact on device safety and efficacy. After the analysis and testing are done results should be packed in letter -to -file or send to FDA The control changes reduces the defects and increases the end user satisfaction . The major factors that cause change in a medical device are due to labelling, engineering and technology , performance

For the company that I work for they implement new devices in order to make the work of technicians easier and ensure quality. One such device is one meant to cut tissue into predetermined shapes with very little human input. The device is not used often however because those who created it did not take into account the size of the room that it is meant to be used in not big enough for the device. In this case, the driving force for the change is the unwillingness of the intended user which is something that I believe is the most important thing because if the person who it is meant for doesn't want to use it then it is a bad device. To fix it we need to go to change control procedure to either make it smaller or more attractive for the intended user which is a much more abstract concept

There are many reasons why a certain product or process will require changes during its life cycle. One example could be cost. To attain certain tight tolerances, material purity, or other favorable physical characteristics, companies may have to pay a lot more money. If it is able to be determined that the acceptability criteria can be changed to allow for cheaper parts, then that may be a logical choice. Other times, product failure or complaints can result in immediate corrective and preventive action which could result in changes to a certain design feature. This is to ensure the safety and success of the product in the future. Whether mandatory or preferential, all changes will need to go through a formal Change Order procedure which Engineers will have to submit. This usually consists of what the change is, why it was changed, and how it could affect the functional performance or risk level of that product. Sometimes it may even go to an in-depth design review which will have certain department representatives attending the meeting so they all agree that there will be no unintended repercussions in the form of violating quality standards or regulatory rules.

Change control is another well-know concept that focuses on managing change to prevent unintended consequences. The regulations provide for change control primarily through the assigned responsibilities of the quality control unit. Certain major manufacturing changes (e.g., changes that alter specifications, a critical product attribute) might require regulatory filings and prior regulatory approval. Effective change control activities (e.g., quality planning and control of revisions to specifications, process parameters, procedures) are key components of any quality system. There are regulatory guidances that explain changes and in these guidances change is discussed in terms of creating a regulatory environment that encourages change towards continual improvement. This means a manufacturer is empowered to make changes subject to the regulations based on the variability of materials used in manufacturing and process improvements resulting from knowledge gained during a product’s lifecycle. Based on my 13+ years of experience, I believe it is practically impossible to avoid changes during product development and post market. Therefore, the better the change is documented (evaluation against the basis and documented tests to ensure any implemented risk control measures do not introduce new unforeseen risks, etc.) the better the project team will be able to handle the change at hand.

Changing control in project management ensure that each change proposed during a project is adequately defined, reviewed and approved before implementation. The change control process helps avoid unnecessary changes that might disrupt services and also ensures the efficient use of resources. Project change control processes is the process of reviewing all change requests, approving changes and managing changes to the deliverables.

The concept controlling changes in projects expresses the approaches used by those in charge of business to change the status of project and the achievements of workers to a better condition through following a set of basic steps necessary for that, which include the use of modern technological technologies or modification of management style or work systems, The project change process is one of the organizational processes that aim to ensure success in those projects and achieve many benefits associated with the business objectives in projects. The importance of change in projects is to achieve the benefit from all the resources and capabilities of projects available in Control the work system and direct the efforts of workers to achieve the maximum benefit

Change Control is implemented as part of the Monitoring & Controlling process of a project, and occurs throughout the entirety of the project. It basically entails measuring the current state of the project against the baseline that was established during the planning phase, and documenting that data, which is the "change" from baseline. Changes can occur in practically any aspect of a project, including Design Control documents, since they are intended to be living documents that evolve over time. Factors that may necessitate a change to a Design Control document include the completion of a verification or validation test, overlooked errors in documentation, or updates to company-wide SOPs or legal regulations. Then changes are initiated by a Change Request, which is a formal way of proposing which changes need to be made, usually in writing. A member from the project team will then markup the currently issued document with the changes, and review this draft with the team and the Project Manager. If they are all in agreement, then the document is submitted into the Change Control System, where its final approval and release is documented and can be traced back for future reference.

In addition to the various steps for controlling changes, as mentioned in the previous posts, various types of changes exist, which may influence which steps to take. Different types of changes include: non-essential design change (NDC), design change number (DCN), and engineering change order (ECO). NDC usually occurs when the product is still in the design controls phase and is not very far along the project, such that only one document is changed. DCN occurs very close to the end of the project, where the changes made are more major, such as those to the Bill of Materials or other manufacturing documents. The ECO occurs when the device is already on the market, but due to user variables unaccounted for (such as the product being unable to fit in a room, as mentioned in @nakimw's case), changes need to be made, which could be a project in itself. After identifying the type of change that needs to be implemented, various steps are taken, including the design review meetings, which is an essential part of change controls, since the project team needs to approve of the changes to move onto the next stage. 

Change control is a systematic approach of managing changes to a product or a system. The change control process is usually conducted as a sequence of steps in submission of change request. Change control is to enable project teams to modify the scope of the project using specified policies. A change request is a documentation for requesting an actual change. It is a formal process of proposing things that needs to be made, usually by means of writing.

Factors the causes changes are :

Business needs changed.

Business benefits changed.

Proper planning was not done.

Planning suffered a lack of stakeholder engagement.

Gold-Plating (scope inflation, scope creep).

Realized Risk

Project Resourcing Changes.

Project Funding Changes.

Project Schedule Changes.

A Corrective Action needs to occur

Change control is something that will happen in all projects even with the most successful companies. It enables the project team to made changes to the project scope and that change will affect the project time and cost. Fist of all, the change request should be defined, and the output is a change request Document which should have the actual request, reason for the request, and estimation for completion time. After that, the request must be discussed with the team, and then to get the approval or denied.

There are a lot of different factors that would affect the project, Internal or external of the organization, problems with Time estimation for tasks, Cost estimation, Risks, or even clients or stockholders requests.