‘No correct answer’ exists to guide patella resurfacing decision
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Opinions on performing patella resurfacing during total knee arthroplasty differ worldwide, with registries showing about 90%, 72% and 3% of orthopedic surgeons resurface the patella in the United States, Australia and Sweden, respectively.
This differing of opinion and utilization among knee surgeons has been spurred partly by registry data and patient-reported outcome studies which show mixed results regarding whether resurfacing the patella is beneficial to patients. Jay R. Lieberman, MD, professor and chair of the department of orthopedic surgery at Keck School of Medicine of USC and orthopedic surgeon at Keck Medicine of USC, said studies often include a variety of implants and the patients may have different diagnoses. Also, frequently, those studies do not use the best patient-related outcome measures.
Source: Forge Collaborative 2020.
“The results with resurfacing or not resurfacing are different if a posterior-stabilized, posterior cruciate-retaining or cruciate-sacrificing TKA is used,” Lieberman told Orthopedics Today. “Patients with a resurfaced patella can have knee pain. The reason for this knee pain may include maltracking, overstuffing of the patella, changes in posterior condylar offset or lack of joint line restoration. It is often multifactorial, which is why it may be hard to determine the source of the pain.”
The variability in research results has led orthopedic surgeons to form three surgical camps: those who resurface the patella all the time, those who resurface it some of the time and those who never resurface the patella during TKA.
“[Patella resurfacing is] like a religion in terms of some people resurface everybody, some people resurface hardly anybody and some people do it in and out of what the kneecap looks like during surgery,” Keith R. Berend, MD, senior partner at Joint Implant Surgeons Orthopedics and president and CEO of White Fence Surgical Suites, said. “But there has been no key article that says this is exactly how you need to do it.”
Possible complications
Those surgeons in the unresurfaced patella camp argue that an advantage of not resurfacing is that patients have no risk of potential implant complications, according to Lieberman.
Although complications associated with patella resurfacing are rare, Nicholas J. Giori, MD, PhD, said complications can be devastating.
“It is not that this happens commonly, but the complications, particularly of periprosthetic fracture of the patella, are absolutely devastating because you cannot just fix it. You have to do an extensor mechanism reconstruction,” Giori, of VA Palo Alto Health Care System and Stanford University, told Orthopedics Today. “Even though the complications are rare, if they do happen, ... it makes you take pause and ask if you should have done this to start with when some of the literature is not that strong.”
In addition to possible periprosthetic fracture, other complications of patella resurfacing include loosening, oblique resection, which can be associated with maltracking, and osteonecrosis, according to Lieberman. He said overstuffing the knee can occur when the patella is under-resected and it can impact range of motion, while over-resection of the patella can increase a patient’s risk of fracture.
“Depending on how you perform the patella resurfacing, you can have lateral facet pain where the lateral facet is rubbing against the metal implant. This may be associated with an oblique resection of the patella,” Lieberman said.
Greater knee pain, more revisions
Although an unresurfaced patella may not lead to problematic postoperative complications, sources who spoke with Orthopedics Today said the literature has shown a higher rate of reoperation among patients with an unresurfaced patella, usually due to postoperative anterior knee pain.
“If a person who has a knee replacement and has pain shows up at the office of a surgeon who routinely replaces the patella, then that surgeon is likely to say [that] is the source of the problem. They did not get the patella resurfaced and so he is going to take the patient back to resurface the patella,” Giori said.
However, there will always be a certain percentage of patients who underwent TKA and have postoperative pain, he said, and the literature is unclear regarding the benefit of patella resurfacing on reducing pain.
Differences in knee pain
Despite literature that suggests there is reduced knee pain when the patella is resurfaced during TKA, Ryan M. Nunley, MD, associate professor in the department of orthopedic surgery at Washington University in St. Louis, said some research has shown no difference in anterior knee pain incidence when revision surgery for patella resurfacing.
“In patients who have anterior knee pain when the patella is not resurfaced, there is a higher incidence of those patients going on to have a patella resurfaced,” Nunley told Orthopedics Today. “But when looking at the outcomes once they get the patella resurfaced, it does not seem to make any benefit in terms of their anterior knee pain and, therefore, it becomes an extra surgery without a huge benefit.”
Patella-friendly implants
Implants are another factor to consider in deciding whether to resurface the patella during TKA, according to Berend, who is a member of the Orthopedics Today Editorial Board.
Continued advances in implant designs that yield components that are more patella-friendly have resulted in some controversy among orthopedic surgeons regarding whether the patella should be resurfaced, according to Lieberman.
“The modern implants are more patella-friendly and so now surgeons are looking at this differently and noting good tracking of the patella without resurfacing,” Lieberman said.
Although TKA implants historically focused on femur and tibia, replacement and did not resurface the patella, Nunley said design of the patellar button helped track the patella within the knee implant and increased the rate of patella resurfacing throughout the United States.
Earlier patellar component designs that had one large central peg also started to be replaced by components with three all-polyethylene pegs, which lowered the risk of periprosthetic fractures associated with one-peg designs, according to Giori.
Advancements in technology
Within the past 2 decades, implants began to appear that had a more accurate trochlear groove anatomy, which is important for successful long-term survivorship and outcomes in conjunction with accuracy of alignment and rotation and limited use of lateral release, Berend said. In addition, modern implants with a femoral component specifically designed with a patella that is both friendly to the native patella and accepting of a resurfaced patella, such as the Klassic Knee System (Total Joint Orthopedics Inc.), may reduce complications, such as patella clunk syndrome, he said.
“The [Total Joint Orthopedics] TJO Klassic Knee, to me, is interesting because it has a universal femur which is considered to be old school, but it has a novel trochlear design where it has two trochlear-groove anatomy, right and left,” Berend said. “When positioned correctly, it is just as friendly for a resurfaced kneecap, maybe even friendlier, because it has a universal femur. So, I think that is a novel approach to the patellofemoral joint.”
Despite such advances in the development of more patella-friendly implants, Mark J. Spangehl, MD, orthopedic surgeon at Mayo Clinic Arizona, said technological advancements related to femoral and tibial components, such as robotic-assisted surgery, are lacking for patella resurfacing, which is still performed manually.
“There is not any big technology that is helping us with the patella,” Spangehl told Orthopedics Today. “You just have to follow basic good principles and that is to measure your thickness, carefully resect it, do not over-resect, do not under-resect, do not overstuff the patellofemoral joint, use your implant position appropriately and then you will hopefully minimize the complications that are related to resurfacing.”
Appropriate surgical technique
In addition to choosing an appropriate implant, Spangehl said reducing complications in patella resurfacing is also dependent on the surgical technique.
“You do not want to over-resect the patella and leave the patella too thin, or you do not want to under-resect the patella and leave it too thick,” Spangehl said.
He noted surgeons can choose to perform patella resurfacing with either an inlay technique, which involves reaming into the native patella and leaving the perimeter and the rest of the patella untouched, or an onlay technique, which involves removing the articular surface across the patella and measuring for the appropriately sized patella implant which is fixed to the top of the patella.
“In either technique, you have to make sure that you do not have bone peripherally that could impinge against the femoral component. You want to contour the patella appropriately,” Spangehl said.
Complications also can be avoided if surgeons release the tourniquet when assessing patellar tracking at the end of the operation, Berend said.
“Having the tourniquet up severely changes patellar tracking and increases the chance that you need to do a lateral release, which is arguable whether it has long-term sequelae, but you want to avoid it if you can,” Berend told Orthopedics Today.
Patient selection
While Giori noted available data are not strong enough to indicate which patients should or should not undergo patella resurfacing, Lieberman, who is a member of the Orthopedics Today Editorial Board, said there are certain indications for patella resurfacing on which orthopedic surgeons generally agree.
“Patients with inflammatory arthritis, patella subluxation and, most would agree, patients with significant erosion of the patella should be resurfaced,” Lieberman said.
However, surgeons should probably consider not resurfacing a patella that is less than 20 mm thick, he said.
“When the patella is thin, you should not resurface it because there is potential risk for fracture,” he said.
Berend said he does not resurface the patella among patients who are being operatively converted from a partial knee replacement to a total knee replacement due to a risk of lateral ulcer, lateral fissure or cartilage loss in the lateral compartment if they have a normal kneecap.
“Assuming that the kneecap was relatively normal ... and I am converting intraoperatively from a partial to a total, I will not resurface those knees,” Berend said.
A surgeon’s decision to not to resurface the patella may also be based on ease and accuracy of the procedure, he said.
Nunley said young patients should not undergo patella resurfacing because of the likelihood they may need to undergo added procedures in the future to replace the implant.
Resurfacing the patella is controversial in patients with a high BMI and poor bone quality, Lieberman said.
“Some [surgeons] believe morbidly obese patients should not be resurfaced, particularly if they are younger,” he said. “Also, a relative indication for non-resurfacing or selective resurfacing might be a patient with an elevated BMI, particularly if they are young and active. A young patient may wear out the patella cartilage over time.”
‘No correct answer’
With many unknowns surrounding patella resurfacing, more studies are needed to determine which patients are the best candidates for non-resurfacing or resurfacing of the patella during TKA, Lieberman said. Multicentered randomized trials that use and study results with the same implant may help guide surgeons in their decision-making process in this regard, he said.
“But that would just tell you the results of that particular implant. It may not be true for other implants even with a similar design,” Lieberman said.
In general, Lieberman said there is no correct answer when it comes to resurfacing the patella. Giori said young surgeons just beginning in practice should continue to perform what they learned in training until they feel confident enough and have justification for changing their practice.
Surgeons should also be aware of and consider what the standard of care is within their community in regard to patella resurfacing, according to Lieberman.
“If your community predominantly resurfaces and you are going to be a non-resurfacer, that may put you in some difficult situations if patients require a revision,” Lieberman said. “In general, just like you discuss the type of knee replacement you are putting in, it is probably best to discuss the issue of patella resurfacing with the patient.”
Know your technique
Orthopedic surgeons who choose to resurface the patella should be well versed in whatever resurfacing technique they decide to use, according to Berend. They should be familiar with the implant, femoral component and its trochlear anatomy, as well as whether the components are friendly or unfriendly for patella resurfacing, he said.
According to Spangehl, orthopedic surgeons who choose to resurface the patella should take their time carrying out the procedure.
“Measure the patella beforehand, be careful not to over-resect, be careful not to overstuff the patella and, if you are deciding whether or not to resurface, it is probably best to do what is done mostly in your community,” Spangehl said.
For surgeons who wish to change from always resurfacing the patella to selectively resurfacing it, Nunley said they should treat the decision in the same way that surgeons who transition from performing posterior to anterior THA do: cherry-pick the best and easiest patients until they are comfortable enough to expand their indications.
“[Surgeons] selectively do anterior approach total hips but, for complicated cases or revisions, they still use posterior,” Nunley said. “Some surgeons, as they migrated, they went to everything anterior, but most surgeons still find that there are some cases that are too complex, they want to do posterior instead of anterior. [This is similar] for the patella.”
He said surgeons who do not resurface the patella should still treat and respect the patella.
“The patella needs some attention and, for me, the data and the literature support doing a denervation,” during which the nerve supply to the patella is disrupted, Nunley said. “I do a lateral facetectomy in all patients,” he said.
‘Stick to your decision’
Regardless of any preference for resurfacing the patella or not resurfacing it, surgeons should know how to perform a resurfacing in the event it needs to be done during TKA, Lieberman said.
Nunley encouraged orthopedic surgeons to keep an open mind on the topic of patella resurfacing.
“Before [you are] critical of another surgeon who does not resurface the patella, [you] should read the literature and understand that anterior knee pain is equal and common between the two techniques,” he said.
Overall, surgeons should stick to their decision of resurfacing or non-resurfacing, which will lead to better operative results in the long term, according to Berend.
“If you are a non-resurfacer, do not resurface. If you are a resurfacer, resurface everyone. If you are selective, use a standardized criteria to make that decision,” he said.
- References:
- The American Joint Replacement Registry Annual Report. Available at: www.aaos.org/registries/publications/ajrr-annual-report/. Accessed April 12, 2021.
- The Australian Orthopaedic Association National Joint Replacement Registry Annual Report 2020. Available at: https://aoanjrr.sahmri.com/annual-reports-2020. Accessed April 12, 2021.
- The Swedish Knee Arthroplasty Register Annual Report. Available at: http://myknee.se/en/publications/annual-reports. Accessed April 12, 2021.
- Verhaar JAN. Always resurfacing the patella in TKR is no longer a reasonable practice. Available at: www.healio.com/news/orthopedics/20180314/always-resurfacing-the-patella-in-tkr-is-no-longer-a-reasonable-practice. Accessed April 12, 2021.
- For more information:
- Keith R. Berend, MD, can be reached at 7277 Smith’s Mill Rd., #200, New Albany, OH 43054; email: berendkr@jisortho.com.
- Nicholas J. Giori, MD, PhD, can be reached at 3801 Miranda Ave., MC 112, Palo Alto, CA 94304; email: ngiori@stanford.edu.
- Jay R. Lieberman, MD, can be reached at 1520 San Pablo St., Suite 2000, Los Angeles, CA 90033; email: gabriella.robison@med.usc.edu.
- Ryan M. Nunley, MD, can be reached at 1044 North Mason Rd., Suite 110, Creve Coeur, MO 63141; email: jdryden@wustl.edu.
- Mark J. Spangehl, MD, can be reached at 5777 E. Mayo Blvd., Phoenix, AZ 85054; email: mcveigh.jim@mayo.edu.
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