OCS Field Guide: A PT Podcast

Total Knee Arthroplasty CPG

August 08, 2021 David Smelser and Austin Kercheville Season 1 Episode 20
OCS Field Guide: A PT Podcast
Total Knee Arthroplasty CPG
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Hello, everyone. Welcome back to OCS Field Guide. We’ve been on a break since the 2021 cycle ended, and we appreciate your patience as we’ve prepared for the 2022 cycle. We won’t waste valuable study time telling you everything we’ve been up to during this hiatus, but we do want to make you aware of one notable development: we are now MedBridge affiliates, which means that we can offer you $175 off a MedBridge subscription with the code FIELDGUIDE. This is the maximum discount available—you won’t find a better discount anywhere else. Now every OCS prep course has its strengths and weaknesses, and the MedBridge prep course is no exception. And we always recommend using multiple sources for OCS prep. But if you’re planning to sign up for MedBridge—either for their OCS material or for their con ed courses, you can use promo code FIELDGUIDE (with no spaces) for $175 off.

But enough about that. Let’s jump right back into OCS prep.

Today we’re covering the 2020 total knee arthroplasty CPG produced by the APTA. This is the first clinical practice guideline published directly by the APTA, which means you won’t find it on the orthopedic section’s website. It also means that the CPG looks and works a little differently than the orthopedic section CPGs. It took me a little getting used to, but I really like the way this CPG makes its recommendations. For the sake of your valuable time, I’ll just explain the gist of the new recommendation system so that the rest of this episode will make sense.

In the orthopedic section CPGs that we are used to, recommendations are made on an A through F scale based solely on strength of evidence. So that means a very well studied intervention that only provides moderate benefit at high cost to the patient or PT would be ranked higher than a slightly less studied intervention that has demonstrated tremendous benefit at low cost. This system values strength of evidence higher than potential cost or benefit. This new APTA CPG tries to fix that problem. Instead of A through F, this CPG uses a diamond rating system, where four diamonds represents a strong recommendation, three diamonds represents a moderately strong recommendation, two represents a weak recommendation, and one diamond represents best practice or theoretical or foundational evidence. These rankings are a combination of the strength of evidence and the authors’ judgment about the cost-benefit ratio of the recommendation. So a “strong” recommendation means there is “a high level of certainty of moderate-to-substantial benefit, harm, or cost, or a moderate level of certainty for substantial benefit, harm, or cost.” For the sake of time, I won’t read the definitions for each recommendation level, but you can see how this system takes into account both the amount of evidence and the amount of potential benefit or harm of an intervention. So as we get into this CPG, you won’t hear me talking about “A-level,” “B-level,” or, “C-level” recommendations. Instead I’ll be talking about strong, moderate, weak, and best practice recommendations.

By way of introduction, the CPG clarifies that these recommendations apply to primary TKA for knee OA, not revisions or partial arthroplasties or TKA following trauma or for RA. So keep that in mind as we go through these recommendations. The recommendations are roughly organized by interventions first, then prognosis, then PT settings and roles, and finally outcomes.

So first, the CPG covers preoperative exercise programs. It makes a moderate recommendation in favor of preoperative exercise programs, stating, “Physical therapists should design preoperative exercise programs and teach patients…to implement strengthening and flexibility exercises.” This recommendation is based on 6 studies which showed that preoperative physical therapy led to shorter inpatient stays, decreased pain,  improved function, improved flexion and extension, and improved quadriceps, hamstrings, and hip abduction strength from 1 to 3 months out after surgery. Basically, if it was measurable, it was better in the groups that had preoperative therapy or exercise programs. So to reiterate, we have a moderate recommendation that says, ““Physical therapists should design preoperative exercise programs and teach patients…to implement strengthening and flexibility exercises.”

Next, we have a “best practice” recommendation for preoperative education. This is the lowest level of recommendation due to lack of evidence. We have one study of moderate quality that showed preoperative education decreased inpatient stay and medical expenses. So the CPG reads, “It is the consensus of the work group that physical therapists or other team members should provide preoperative education of patients undergoing TKA, including, at a minimum, patient expectations during hospitalization and factors influencing discharge planning and disposition, postoperative rehabilitation program, safe transferring techniques, use of assistive devices, and fall prevention.” I’m sure we have all worked with postoperative patients who were surprised to find out after their surgery that they had to do physical therapy or that the recovery would take longer than just the 4-6 weeks that the MD wrote on the prescription. That’s obviously not ideal. So again, the CPG says that education should include, at a minimum, patient expectations during hospitalization, factors influencing discharge planning, postoperative rehabilitation program, safe transferring techniques, use of assistive devices, and fall prevention.

Next, we have a moderate-level recommendation against continuous passive movement devices, or CPMs. It reads, “Physical therapists should NOT use CPMs for patients who have undergone primary, uncomplicated TKA.” The manuscript admits that three lower quality studies favored CPM use, but many higher quality studies and meta-analyses all demonstrated nonsignificant results. Combined with the cost of using a CPM and the potential for prolonged bed rest as patients use the CPM, we have a pretty good argument against CPMs. The authors admit that there may be some patients who could maybe benefit somewhat in exactly the right circumstances from using a CPM, but we don’t have data to show who those patients might be. So for uncomplicated TKAs, we have a moderate strength recommendation to ditch the CPM.

Next is cryotherapy. The CPG makes a moderate-strength recommendation for cryotherapy, saying, “Physical therapists should teach and encourage use of cryotherapy for early postoperative pain management for patients who have undergone TKA.” The studies cited examined standard cold packs, ethyl chloride spray, and continuous-flow cooling devices, and every form of cryotherapy examined significantly decreased pain. I want to point out here that there was one meta-analysis comparing standard cold packs to other cryotherapy devices, and they found no difference between them. So whatever your patient prefers and whatever is most cost-effective appears to be fine based on the evidence we have available.

I will also draw attention to the section under this recommendation called, “Intentional vagueness.” This section explains what we don’t know yet and cannot make specific recommendations on. Here, the authors write, “There was not sufficient evidence to provide a prescriptive time frame for the application after surgery. In addition, there was insufficient evidence to identify how many days postsurgery cryotherapy should be continued.” So based on this CPG, we have a recommendation for using cryotherapy for a vague time period soon after surgery, but you shouldn’t necessarily be memorizing specific timeframes for cryotherapy use in this population. That means the OCS exam is less likely to ask about specifics there.

Moving on, next is physical activity. This is a best practice recommendation, which reads, “It is the consensus of the work group that physical therapists should develop an early mobility plan and teach patients who have undergone TKA regarding the importance of early mobility and appropriate progression of physical activity, based on safety, functional tolerance, and physiological response.” If you’re like me, you kind of wonder why that recommendation even needed to be made. But this recommendation is based on a study that showed that 42% of participants who had TKAs did not meet healthy standards for physical activity 1 year following following their surgery. In contrast, those who engage in specific exercise regiments like aquatics, Pilates, or tai chi and those who engage in resistance exercise demonstrate better function, balance, gait—all the stuff we’d expect. And the authors note that there is a dose-response relationship between exercise intensity and gait function. So we need to help our patients get active early after surgery, and we need to help them set goals to engage in a healthy level of physical activity even after discharge.

Next we have a strong recommendation for motor function training. This is the only “strong” recommendation in this CPG. It reads, "Physical therapists should include motor function training (e.g., balance, walking, movement symmetry) for patients who have undergone TKA.” The studies behind this recommendation examined dynamic balance training, robot-assisted gait training, movement training with visual biofeedback for weight bearing symmetry, and motor functional training. It’s no surprise that these interventions improved balance, gait, and function. There is no direct comparison to show one is superior to another, so right now, any of these interventions are recommended, and any of them would be appropriate answers to an OCS exam question looking for an intervention to improve balance, gait, and function in this population .

Our next recommendation is a funny one. We have a best practice recommendation for postoperative knee ROM exercises. We have no research comparing a ROM exercise group to a control group that received a TKA but no ROM exercises, and we don’t really expect ever to have a study like that. We know knee ROM is critical to function following TKA, so it would be unethical to design a study like that. So our recommendation in favor of knee ROM exercises is based on group consensus.

Our next recommendation is a “weak” recommendation for immediate postoperative knee flexion during rest to reduce blood loss and swelling. The CPG says, “To reduce immediate postoperative blood loss and swelling in the first 7 days after surgery, physical therapists or other team members may teach patients to position the operated knee in some degree of flexion (30°–90°) while resting.” This may be one of the more controversial recommendations in this guideline—especially If you don’t pay attention to the discussion. This is based on five studies that examined blood loss and knee girth within the first week after surgery. Each study had a group that was positioned in full knee extension and a group that was positioned—presumably supine—in some degree of hip flexion and some degree of knee flexion (between 30 and 90 degrees, depending on the study). Four out of five studies favored the knee flexion group for reduced swelling and blood loss, and the fifth study found no difference. In the studies that also examined ROM, only flexion was measured. These found either no difference in flexion ROM or a small difference favoring the knee flexion group.

There are three things I want to point out. First, most of these studies were only positioning patients in slight knee flexion for the first 6 to 48 hours after surgery. And in the studies that positioned patients in flexion for longer than 48 hours, none of them lasted longer than 7 days. So we’re talking about the very acute and immediate subacute phase here. Second, the studies were unclear on how long each day the knee was kept in slight flexion, so we don’t have enough evidence for clear dosing parameters. And third, since none of the studies examined knee extension ROM, we need to recognize that we don’t know whether this recommendation will put someone at risk of contracture limiting full knee extension. It’s because of these unknowns and potential risk that the CPG decided to make this a “weak” recommendation. So here’s the take-home message for the clinic and for the OCS exam: if a patient is in the very acute phase—meaning less than 1 week out from surgery—and he or she is having problems with postoperative blood loss or swelling, then some amount of time spent supine with the hip and knee in some amount of flexion will help with those symptoms. Other than that, I think we need to be careful about the effect that constant rest in knee flexion might have on knee extension ROM.

Okay, moving on. Next we have a moderately strong recommendation for neuromuscular electrical stimulation. It reads, “Physical therapists should use NMES for patients who have undergone TKA to improve quadriceps strength, gait performance, performance-based outcomes, and patient-reported outcomes.” The studies cited here showed no difference in knee ROM, but improved quadriceps and hamstring strength, walking, stair climbing, and patient-reported outcomes for up to 1 year after surgery in the group that received NMES. The authors note that earlier NMES—as early as post-op day 2—and more frequent NMES (up to 5-7 times daily) with longer cumulative time at the maximum tolerated intensity led to improved outcomes. They state that NMES should be used for a minimum of 3 weeks, and it is most likely to benefit those with quadriceps activation deficits. So again, this is something that is going to be most useful very soon after surgery, and it should be applied early, often, and at the highest tolerable intensity for a minimum of 3 weeks for best results.

Our last intervention recommendation is a moderate strength recommendation in favor of high intensity strength training. It reads, “Physical therapists should design, implement, teach, and progress patients who have undergone TKA in high-intensity strength training and exercise programs during the early postacute period (i.e., within 7 days after surgery) to improve function, strength, and ROM.” They note that high intensity exercise that is initiated as soon as 72 hours after surgery is safe and demonstrated improved functional mobility and knee ROM compared to historical controls. However, they also point out that if there are large muscle activation deficits, then patients not experience true muscle overload with high intensity training. Fortunately the previous recommendation for NMES gives us some guidance on how to address muscle activation deficits.

Alright, that wraps up interventions. Next, the CPG offers a moderate strength recommendation for the following prognostic factors. Higher BMI, depression, and greater number of comorbidities are all associated with worse postoperative outcomes. Preoperative ROM is positively associated with postoperative ROM, but it has little to no effect on function or quality of life. Preoperative physical function is positively associated with postoperative physical function—meaning those who were less functional before surgery will still be less functional after surgery compared to those who were higher functioning before surgery and remain higher functioning afterward. Preoperative strength is positively associated with postoperative physical function—which is another good argument for preoperative physical therapy to improve strength prior to surgery. We have mixed evidence on how age and sex affect prognosis, with men perhaps having slightly lower function and less ROM and women perhaps having slightly more pain and longer rehabilitation. Finally, current evidence says diabetes has no prognostic effect on outcomes.

The CPG also makes a separate “best practice” recommendation suggesting that active tobacco use and lack of patient support (such as family support) are also likely negative prognostic factors. However, there’s no strong evidence to back up this consensus statement at the moment—only foundational evidence from other studies on tobacco use and lack of support.

As we get toward the end of the CPG, the authors make a few broad recommendations about the roles of PTs and what PT should look like following TKA.

There is a moderate strength recommendation in favor of supervised physical therapy compared to home-based unsupervised exercise. Now, in my region of Atlanta, there has been a trend amongst several orthopedic surgeons of sending joint replacement patients home after surgery with only a video-based home exercise program and no supervised physical therapy. This decision is justified by a small study that was performed here that—in my opinion—has some significant data problems and conflicts of interest. So contrary to that practice, the CPG cites two randomized controlled studies that both show that more frequent physical therapist supervision led to better self-reported outcomes, mobility scores, and balance. So if you ask some surgeons, PT isn’t important, but if you ask the PT Journal, PT is important. Go figure.

We also get a weak recommendation that says either group-based therapy or individualized therapy can be used following TKA. The evidence is murky, but right now group therapy has been shown to be non-inferior to individualized therapy following TKA. Since the evidence isn’t clear enough to make a firm recommendation, they CPG says that either is fine.

Next we have a moderate-strength recommendation on timing the initiation of physical therapy. The recommendation states that physical therapist management should start within 24 hours of surgery and prior to discharge. When patients get ambulating sooner after surgery, they get better faster. Of course this is talking about inpatient TKAs. The new trend is to perform joint replacements as outpatient procedures, and the CPG acknowledges that, but it points out that we don’t have data on that group yet, so we don’t know exactly when PT should start for that group. But odds are, sooner is better.

Our second to last recommendation is a moderate strength recommendation that says physical therapists “should be involved in giving the care team feedback on discharge planning, patient functional status, assistance equipment, and services needed to support a safe discharge from the acute care setting.” In other words, inpatient PTs should be involved in all the discharge planning things that inpatient PTs were taught to do in PT school. It seems like this is something that wouldn’t need to be said, but I know there are some hospitals out there who do not want PTs involved in discharge planning and explicitly forbid them from making recommendations, so I guess it’s a good thing this is in a published paper somewhere. A lot of this information about discharge planning is not super important for the OCS exam, but there are a couple parts I’m going to point out. A very large study with over 100k patients found that referrals to inpatient rehab facilities did not influence 6 month reductions of complications, nor did it lead to functional differences at 2 years when compared to discharge home. Another study showed that fewer days between hospital discharge and initiation of outpatient PT predicted improvement in patient-reported pain and outcomes. Now we all know there are patients who do need inpatient rehab. But on average, discharge home is no worse, and the sooner patients start outpatient PT, the better they do. So since 10% of the OCS exam is the broad category of “orthopedic physical therapy and practice,” I could see an item writer ask a question about discharge planning for this population. So remember: on average, discharge home is just as good as discharge to inpatient, and the sooner patients start outpatient PT, the better.

Finally, we have a best practice recommendation for outcome measures that says PTs should use the Knee Injury Osteoarthritis Outcomes Survey Joint Replacement (or KOOS JR) and the 30-second sit-to-stand test and the TUG test as outcome measures. This CPG doesn’t mention any cutoff values, and since this is just a best practice recommendation, I won’t spend time on those here. However, I will point out that the KOOS JR is slightly different from the more familiar KOOS, so maybe if you got a question on a TKA patient where you had to pick an outcome measure, you might be thrown off by that. The APTA recommends the KOOS JR since it is more specific to knee replacements.

That was a lot, because this is a long CPG. So let’s summarize the recommendations and run through a practice question before we sign off for today.

I’ll summarize the recommendations from strongest to weakest.

  • We have a strong recommendation for motor function training, meaning balance, walking, or movement symmetry training. This is the only strong recommendation.
  • We have a moderate recommendation for a PT-designed preoperative exercise program (or pre-hab) focused on strength and flexibility.
  • We have a moderate recommendation against using CPM devices.
  • We have a moderate recommendation for cryotherapy, which could include ice packs, ethyl chloride sprays, or continuous flow cooling devices.
  • We have a moderate recommendation for NMES—especially for those with quad activation deficits—and the recommendation is for NMES early, often, and at maximum tolerated intensity.
  • We have a moderate recommendation for high intensity resistance exercises as soon as 72 hours after surgery.
  • We have a moderate recommendation to consider the specific prognostic factors mentioned before. In particular, BMI, depression, and number of comorbidities were most closely connected to worse outcomes.
  • We have a moderate recommendation in favor of supervised PT over unsupervised exercise.
  • We have a moderate strength recommendation in favor of initiating PT within 24 hours after surgery.
  • We have a moderate strength recommendation that says PTs should help with discharge planning in acute care.
  • Now the weak recommendations. We have a weak recommendation that says the knee could rest in slight flexion to reduce blood loss and swelling in the acute and immediate subacute phase after surgery.
  • We have a weak recommendation that says group therapy or individualized therapy are both viable rehab options.
  • And finally, the best-practice consensus statements. We have consensus that preoperative education is helpful.
  • We have consensus that PTs should promote early mobility after a TKA and continue to promote healthy physical activity beyond discharge.
  • We have consensus that post-operative knee ROM exercises are good and important.
  • We have consensus that active tobacco use and poor environmental support are negative prognostic factors.
  • And we have consensus from the workgroup that PTs should use the KOOS JR, the 30-second sit-to-stand, and the TUG as outcome measures.

Now for our practice question.

A patient presents to an outpatient physical therapy clinic 4 days after a L TKA. His BP is 128/82. He is using a straight cane for safety but he says that he previously ambulated without an assistive device. Girth measurements at the inferior pole of the patella are 45 cm on the L and 44 cm on the right. His seated L knee PROM is 85 degrees flexion and 5 degrees from full extension. His seated L knee AROM is 80 degrees flexion and 13 degrees from full extension. His NPRS is currently 3/10. Which of the following interventions would be most indicated by this patient presentation?

A. Educate the patient to rest supine with knee slightly flexed
B. Initiate high intensity exercises
C. Initiate high intensity NMES to L quadriceps
D. Apply continuous flow cooling device.

The correct answer here is C, initiate high intensity NMES to L quadriceps. You’ll notice that all of these options are in line with the CPG’s recommendations, but C is the best based on the CPG’s discussion of those recommendations. Yes, the patient could rest supine with his knee slightly flexed to reduce swelling and blood loss, but his girth measurements are WNL and his BP is normal. High-intensity exercises are completely appropriate as early as 72 hours after surgery. However, the CPG noted that patients with muscle activation deficits may not benefit as much from high intensity exercise. The patient’s greatest impairment right now is quadriceps muscle activation, as you can see a clear extensor lag in the 8-degree difference between his active and passive knee extension ROM. This leads us to the correct answer, C, which has been shown to improve quadriceps strength and is most likely to benefit those with muscle activation impairments. Finally, D, the cooling device is appropriate for pain management, but the patient’s pain is relatively low right now.

You can see how this question could be modified to make other options correct. If there was no extensor lag, high-intensity exercise might be the best answer. Or if there was significant swelling and bruising, perhaps resting with the knee slightly flexed would be appropriate. Or if the other findings were relatively normal but the patient’s pain was high, cryotherapy might be the best option. You have to look at the patient presentation to guide your answer choice.

That wraps up the TKA CPG. Thanks for joining us as OCS Field Guide makes its return. Until next time, study hard and good luck.

Recommendation Differences in the APTA CPG
Broad PT Recommendations
Recommendation Summary
Practice Question