Custom Knee Replacement
Custom knee replacements are an option for the vast majority of patients who are candidates for a normal type of knee replacement.
The indications for custom knee replacement are no different than the indications for a total knee replacement of a normal type – the patient must have symptoms relating to underlying osteoarthritis that has been radiographically demonstrated and confirmed with physical examination.
Custom knee replacement is a breakthrough in the treatment of arthritis, and can be particularly useful for patients who have previously undergone knee replacement surgery. A custom knee replacement is designed using computer-aided design and built from metal shapes that precisely fit the patient’s joint morphology. This technique allows surgeons to tailor the prosthesis to each person’s specific anatomy.
Knee arthritis symptoms
Symptoms from knee arthritis must be sufficiently debilitating and frequent to warrant surgical intervention and ideally, the patient should also have attempted to control these symptoms with the nonsurgical interventions and treatments for osteoarthritis before proceeding to surgery.
Custom Knee Replacement Materials and Equipment
The way custom knee replacements differ from normal knee replacements are that a scan is necessary of the knee prior to the surgery being performed. The scan is completed in the same way as any other CT or MRI scan. This scan is then sent off to the custom knee replacement manufacturer who will then likely construct computer-based 3D model of the knee joint. They will then make calculations as to exactly where cuts need to be made in the bone, so that the arthritis is cut out of the knee in its entirety whilst leaving as much of the patient’s own healthy bone behind as possible.
Based on these scans and calculations, the company then creates custom cutting guides for the surgeon to use during the procedure as well as matching these custom cutting guides to the inner surface of the knee replacement component.
These cutting guides are prepared alongside the normal instruments for a total knee arthroplasty and when the time comes for the patient to have surgery, the surgeon uses the custom cutting guides instead of the stock cutting guides that he or she would, otherwise, have used in a normal knee replacement. This essentially means that the patient has a customized or patient-specific surgery that matches their own unique knee anatomy.
Custom Knee Replacement Treatment Options
As previously mentioned, patients will ideally have had osteoarthritis previously diagnosed and attempted some form of nonsurgical management of their arthritis before reaching the stage of requiring a knee replacement. The four main strategies for management an arthritic knee without surgery are anti-inflammatory medications (if the patient can tolerate taking these), physical therapy, bracing and intra articular knee injections of corticosteroid or in some cases hyaluronic acid analogs.
Not all patients will respond favorably to all nonsurgical managements and some patients will be so far along in the knee arthritis process at the time of diagnosis that even if they work to try nonsurgical managements of their arthritis, it is unlikely that they will be successful. For a definitive opinion on how severe patient’s arthritis is, they should first consult with an appropriate medical professional or orthopedic surgeon and they can be advised as to what stage of the arthritic process their knee is currently in and whether they would be candidates to trial nonsurgical management or whether surgery is likely the only option left for them.
Who is a good candidate of Custom Knee Replacement Surgery?
The patients who have reached a stage in their arthritis where their symptoms are frequent and so severe that they have become quite debilitated by their arthritis (and have also failed nonsurgical management strategies) are considered good candidates for any kind of knee replacement. The vast majority of these patients will be candidates for custom knee replacement surgery as the only contraindication to performing a custom knee replacement would be if there is significantly abnormal anatomy or major deformity that precludes the use of primary arthroplasty components.
This is likely to be a very small subset of patients and if you feel that you may be a candidate for a custom knee replacement surgery, consulting with one of our orthopedic surgeons is the best option to have a full assessment and appraisal as to whether you would be a good candidate or, if you are indeed one of the small subset of patients that are unable to have a custom knee replacement.
Custom Knee Replacement Surgery Procedure
Custom knee replacement surgery is almost identical to any other type of knee replacement surgery that uses non-custom components. The only difference in the entire process is that rather than the stock cutting guides that the implant companies prepare for use in normal total knee arthroplasties, the cutting guides are instead built in a custom fashion to the patient’s native knee anatomy. As a result, they are made of 3D-printed plastic and not metal.
The images above show 3D printed customized total knee components along with 3D printed bone models. The customized components allow accurate bone cuts and ensure snugly fit implants which are not subjected to undue stress on movement. The accurate bone cuts also aid in preserving bone.
They are usually disposable and the process of placing the custom guides in the appropriate position is slightly different than it would be for a normal total knee cutting guide which is usually made of metal and has to be manually placed into what the surgeon estimates to be the appropriate position for the cutting guide. This is essentially the only step that is any different from a normal total knee replacement and as such, the surgical dissection, tissue disruption and subsequent overall recovery would be largely the same (although there are numerous reports that custom knee replacement surgery patients recover quicker than non-custom knee replacement patients).
Custom Knee Replacement Surgery Success Rate
Custom knee replacement surgery is still, at its core, knee replacement surgery and as such has demonstrated broadly similar success rates to normal total knee arthroplasty. There are some studies published that suggest patients with custom knee replacements function biomechanically much more closely to their presurgery knee biomechanics and as such seem to recover slightly quicker than other knee replacement patients, but this is still controversial and some surgeons argue as to whether this difference is clinically significant.
In any case, at the very least, custom knee replacement surgery approaches between 85% and 90% success rate with around 5% to 10% of patients experiencing the same sort of symptoms preoperatively as they did postoperatively and a small subset of patients (usually less than 5%) reporting that their knee is worse after surgery.
Custom Knee Replacement Surgery Risks
The risks of custom knee replacement surgery are broadly similar to the risks of any knee replacement surgery, as the anesthetic that you will receive for the surgery will likely be the same and the procedure generally lasts about as long as the normal knee replacement would also. As previously mentioned, tissue dissection and surgical approach will likely be the same and, as such, the risks of having such surgery are identical to the risks of having a non-custom knee replacement surgery. These include periprosthetic infection, neurovascular injury, heart attack, blood clot, stroke, intraoperative fracture and postoperative knee stiffness.
Custom Knee Replacement Recovery and Timeframe
The immediate postoperative recovery from a custom knee replacement will involve the same process of performing exercises with the physical therapist and being assisted with ambulation in order to allow the patient to be up and walking as soon as possible after surgery. Once the patient has demonstrated a degree of independence with mobilization and is able to ascend 2 to 3 steps unassisted, this is usually the final physiotherapy goal prior to discharge. The knee will experience soreness and this will be controlled with opioid and non-opioid analgesics.
The primary goal in the early postoperative period is to work on range of motion exercises and there are a great number of these that you can perform. Your physical therapist will advise you on the best exercises for you specifically. It is also important to work on quadriceps strengthening and overall gait training too.
By around 3 to 6 months post surgery, most patients have achieved recovery to their approximate baseline, although some patients, particularly patients who are more elderly, may take a little longer than this and this is perfectly normal.
Custom Knee Replacement Exercises that help
Although physical therapists tend to tailor the treatment regimens to the individual patient based on their lifestyle and their immediate home environment, there are a series of exercises that most patients can perform that improve range of motion as well as quad strength and overall gait quality. Straight leg raises will improve quad strength without working on range of motion and assisted knee flexion with a blanket around the heel in bed is one of the first exercises that your physical therapy will likely have you perform and can be continued into the recovery process indefinitely.
Later on in the recovery process being able to sit on a stationary bicycle and use the nonoperative leg to help propel the pedals around is an excellent exercise that helps to work on the range of motion in the operative leg without putting too much strain across the knee. It is also an excellent exercise for general cardiovascular health and can be continued well after the patient has fully recovered from the knee replacement surgery.
Custom Knee Replacement Exercises to Avoid
Generally, we advise that the patient to avoid exercises that put a great deal of strain across the knee or to work too heavily on the quadriceps too early on the process. A good example of this would be resisted leg extension exercises particularly on gym weight machines. These put a great deal of strain across the patellofemoral joint and will also cause tension on the arthrotomy closure, which in the early postoperative period should be avoided.
Resisted or heavy barbell squatting should also be avoided as for the same reasons. Squatting can be a very good way to recovery from a knee replacement surgery, but usually beginning with bodyweight squats and usually using a wall to aid in the squatting motion is a good place to start. Once strength has been gained back in the knee through other exercises then resisted squats with barbells can be begun should the patient be very keen on pursuing this particular exercises, but we would not recommend performing heavy resisted squats until at least 6 months after the surgery.
Custom Knee Replacement Surgery Cost
For the most part, custom knee arthroplasty is more expensive than standard non-custom knee arthroplasty. This is for a number of reasons; the extra scan required for the process of 3D printing the custom cutting guides, and the process of manufacturing the guides themselves. However, there are a number of insurance plans that will cover, at the very least, part of the cost of a custom total knee arthroplasty. If you are unsure if this is the case, you can either talk to your plan provider directly or come and see one of our orthopedic surgeons in consultation who will be able to discuss the options with you and work with you to achieve a desirable solution if custom knee replacement is something that you are very knee on pursuing.
Custom total knee arthroplasty is available for the vast majority of patients who are candidates for a knee replacement surgery and although the benefit of these is controversial amongst many orthopedic surgeons, there is some research to suggest that it is beneficial and there is also plenty of research to suggest that custom knee replacement patients knees perform biomechanically more similarly to what we would consider “normal” knee biomechanics.
If custom knee arthroplasty is something that you are interested in pursuing, come and see one of our orthopedic surgeons as we will be to able to discuss your options with you and we will be happy to provide you with the information necessary to make a decision as to whether you wish to pursue custom knee arthroplasty or indeed whether you wish to proceed knee replacement at all.
I am fellowship trained in joint replacement surgery, metabolic bone disorders, sports medicine and trauma. I specialize in total hip and knee replacements, and I have personally written most of the content on this page.
You can see my full CV at my profile page.