Putting prehab to the test highlights inconsistencies

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The growing popularity of prehabilitation contrasts with mixed findings in the lower extremity literature: Specifically, the approach seems to be more effective in patients undergoing anterior cruciate ligament (ACL) reconstruction than those undergoing hip or knee replacement.

By Cary Groner

In recent years, lower extremity practitioners have been instrumental in developing “prehabilitation” regimens that aim to strengthen patients in advance of orthopedic surgeries, with the goal of making for a quicker and better recovery.

Papers describing outcomes have reported decidedly mixed results, however; in the lower extremity literature, specifically, prehab seems to be far more effective in patients undergoing anterior cruciate ligament (ACL) reconstruction than those undergoing hip or knee replacement. Increasingly, it appears that prehab’s success—or lack thereof—depends on a number of variables that include the type of surgery performed and several aspects of the patient’s profile.

Moreover, as the Center for Medicare & Medicaid Services (CMS) continues to phase in its Comprehensive Care for Joint Replacement (CJR) reimbursement model,¹ which includes financial penalties for exceeding a bundled payment, hospital administrators will be increasingly motivated to identify aspects of care that contribute to efficient recovery and to eliminate those that don’t. Even before prehab is factored in, expenses associated with joint replacement procedures are high, according to CMS; Medicare patients received 400,000 hip or knee replacements in 2014, and per-procedure costs ranged from $16,500 to $33,000 across geographic areas.²

If clinicians want to promote prehab, then, they’re going to have to justify it both therapeutically and in terms of cost efficiency.

Prehab and joint replacements

As previously described in LER, clinicians in several therapeutic settings have tested prehab approaches for total knee replacements (TKAs) and total hip replacements (THAs).^3-5 The strengthening that usually accompanies a prehab regimen should theoretically offer benefits to these patients given that they almost always have painful osteoarthritis, which discourages exercise and leads to a concomitant loss of muscle tone. Nevertheless, the findings reported by these authors are typical of those found by others: the programs improve preoperative functional status, muscle strength, and related goals, but their effects rarely carry over postsurgically. These conclusions have been borne out in other papers by those same researchers, including a 2012 article in Physical Medicine & Rehabilitation reporting that, while a prehab intervention led to significant increases in quadriceps strength and walking speed before TKA, there were no benefits 12 weeks after the surgery.⁶

Jonathan Chang, MD, a clinical associate professor of orthopedics at the University of Southern California in Los Angeles, explained some of the challenges associated with prehab in such patients.

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“For some of them, trying to do that kind of program is too painful,” Chang said. “That’s why you’re planning the surgery, after all—things have deteriorated enough that it’s the only hope. If you can get compliance with a prehab regimen you’ll show improvement in strength, but does that translate into better postop success? It would make sense, but we’re not really finding that. As a big advocate of exercise, it’s hard for me to accept, but it has to be a consideration. It may be that the hit you get from the operation is sufficient that it knocks everybody back to baseline.”

To be fair, some researchers have reported positive postoperative results from prehab, but they are not usually long-lasting. In one case, Thai investigators reported decreased pain, as well as improved quadriceps strength and quality of life (QOL), in the short term after TKA.⁷ In another, researchers in Spain found that preoperative strengthening shortened postoperative length of stay and led to faster recovery.⁸ And a 2014 study from Italy found that a prehab program led to better knee ROM just after surgery, though the advantage had vanished by six weeks out.⁹

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These votes of confidence are far outweighed by the studies that have found little or no postoperative benefit from prehab for TKA and THA patients, however. For example, a 2004 Canadian study found prehab did not alter functional recovery or QOL after TKA.¹⁰ A 2008 study in Clinical Rehabilitation reported that preoperative PT did not improve impairment or QOL after surgery in THA patients.¹¹ A 2014 paper found that eight weeks of prehab offered no additional benefits (over surgery alone) three months postoperatively.¹² A 2015 article from Switzerland, similarly, found no difference three months postoperatively between prehab and control patients.¹³ A literature review of 13 studies that same year found no significant postsurgical benefits in function, QOL, or pain in THA patients, though it did note prehab may have reduced use of postoperative rehabilitation.¹⁴ Finally, a 2016 article in BMJ Open reported that, whereas prehab may have slightly improved early postsurgical pain and function, the effects remained too small and short-term to be clinically important, and had no effect on key outcomes such as length of stay, QOL, and costs.¹⁵

Seeking better evidence

In one of the LER articles already mentioned, Claire Robbins, PT, DPT, coordinator of arthroplasty research at New England Baptist Hospital in Boston, described the comprehensive prehab model that had been instituted there for TKA and THA patients, including “evaluation, education, and therapeutic exercise designed to meet the functional, psychological, and social needs of patients undergoing joint replacement surgery.”⁴ She noted the program had helped modify patients’ expectations of recovery and had decreased length of stay; moreover, in a separate article, she reported that in one patient subset—those who were obese—prehab exercises improved postop functional mobility and increased the rate of immediate home discharge (to 54%, vs 46% of those who didn’t exercise preoperatively).¹⁶

When LER spoke to Robbins for this article, however, she acknowledged that in the general population, evidence for clinically significant advantages of prehab isn’t yet available.

“I wish I could say we’ve documented positive clinical outcomes, but I don’t think the physical therapy profession is totally on board yet in recording those and reporting them back to the surgeon,” she said. “We have to start collecting that data—find out, for example, why some patients are more likely to come back within thirty days for manipulation of the knee. Then you know how to better gear your prehab and patient education.”

Regarding the CMS reimbursement program, Robbins hopes it will spur improved prehab approaches and accountability.

“It’s going to prompt facilities to look at their standards of care, how they are approaching this type of surgery, what can be done better,” she said. “We need to establish a clinical pathway so that we get the best results. If prehab is part of that—if it looks like we have this group that did prehab and they didn’t get readmitted within thirty days as often—then let’s keep it. It’s going to become hugely important going forward.”

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A different story with ACL repair

If it’s challenging to make a case for the strength of prehab’s positive effects in patients undergoing total joint replacements, the job becomes easier when it comes to those having ACL reconstruction. Studies dating back more than a decade have delineated the postoperative advantages of prehab in these patients.

For example, a 2003 Australian paper reported a significant correlation between quadriceps strength and functional stability both before and after ACL repair.¹⁷ In 2013, Irish investigators reported that a six-week preoperative exercise program led to postoperative improvements in knee function, such as in the single-leg hop test.¹⁸  Another paper that year, from the University of Delaware in Newark, found that preoperative quadriceps strength in patients given prehab predicted self-reported function six months after ACL reconstruction.¹⁹ In 2015, Korean researchers reported that four weeks of prehab had positive effects three months postreconstruction, particularly in extensor strength deficits.²⁰ And a 2015 study in the British Journal of Sports Medicine found that Norwegian patients who received prehab had superior outcomes two years postoperatively versus those who had normal care—for example, 86% to 94% were within the normative range of the five Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales, versus 51% to 76% of those who did not receive prehab.²¹

Some of the benefits of prehab in ACL patients may have to do with the demographics of the population, according to Jonathan Chang.

“Most people—not all, but most—who have ACL reconstructions have them due to sports injuries,” he said. “They’re younger, they’re used to working out, and there are fewer of the comorbidities and BMI [body mass index] issues that afflict older OA patients.”

Claire Robbins agreed.

“The ACL is such a small structure, but it takes such great stress, that prehab conditioning is really important,” she said. “The patients are in a protected period postop, their weightbearing and range of motion are limited, and after six weeks there’s a huge decrease in strength and function. But, if those muscles are prepared preoperatively for that, if they’re stronger and better able to handle that decline, I think it makes a difference.”

Describing the advantages of prehab in these patients can become convoluted, given the complexities of the related physiology. For example, experts have long suspected that quadriceps activation failure—a neural inability to fully contract the muscle despite the absence of structural damage to it—contributes to the weakness that follows ACL reconstruction. However, until recently no one had studied the impact of preoperative activation on postoperative quadriceps function.

In 2016, however, researchers at the University of Michigan reported that preoperative activation was not associated with postoperative strength, in fact; rather, preop activation was related to postop activation, and preop strength to postop strength. The authors concluded therapeutic approaches should target both activation and strength for the most complete improvements after surgery.²²

The paper’s lead author, Lindsey Lepley, PhD, ATC, told LER that prehab in ACL patients is beneficial, in her experience.

“It improves postoperative functional performance in things like hop testing and agility measures that people use as return-to-sport criteria,” said Lepley, now an assistant professor of kinesiology at the University of Connecticut in Storrs. “It also seems to be beneficial from a self-reported outcomes perspective. Another compelling argument for preoperative rehabilitation is that it’s not that big of a time investment; emerging evidence²¹ indicates that ten treatments over five weeks is beneficial.”

Underlying neural factors

Lepley and her colleagues have focused particularly on the role of neural function in these patients and have done their best to tease out which aspects of prehab affect postsurgical outcomes.

“We’re looking at some of the factors underlying poor quadriceps muscle strength after ACL reconstruction, and we’re seeing that neural activity—someone’s ability to fire their muscle on their own, to volitionally activate it—is also related to how well they can do that before surgery,” she said. “Opening up the joint capsule to surgically repair the ACL is another neurological insult to the joint, compounding the neuromuscular deficits associated with the injury itself. That, in turn, could compromise the direct relationship between preoperative activation and postoperative strength.”

Understanding this doesn’t necessarily elucidate the underlying causes, Lepley acknowledged.

“Neural alterations at a variety of levels could be contributing to a depressed neural environment after ACL surgery,” she said. “For example, someone could have altered information coming in from the joint, or descending cortical inhibition, or alterations at the interneuron level that could contribute to the inability to activate the muscle well. After ACL injury and reconstruction, all of these pathways could be involved.”

Further complicating assessment, Lepley said, is that distinct pathways may be implicated before and after the reconstruction surgery.

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“There could be different mediators affecting the patient’s ability to volitionally fire their quadriceps preoperatively than postoperatively,” she said.

As for how this relates to prehabilitation regimens, Lepley pointed out that good neurological activity contributes to strength, and to the patient’s performance on agility tests.

“You may need to approach prehab the way you would postoperative care, acknowledging that there’s a depressed neural environment,” she said. “The clinician’s goal should be to identify interventions that can promote someone’s ability to fire their muscles on their own, because this underlying neurological factor is going to either help promote rehabilitation or delay it even more.”

To that end, Lepley supports prehab neuromuscular training regimens that include perturbation, such as the one developed at the University of Delaware, which have been shown to improve gait symmetry prior to ACL reconstruction.²³

“You can achieve those perturbations through balance or rocker-board activities, and of course we want to reinstitute range of motion, minimize joint effusion, improve force production, and get good quadriceps strength overall,” she said. “Ideally, we think patients should have ninety percent of their strength on their ACL-reconstructed limb, compared to the uninjured side, before they return to sport, and maybe those guidelines should be imposed before someone undergoes ACL surgery.”²¹

Neuromuscular training

Investigators at the University of Delaware have investigated preoperative neuromuscular training in ACL patients, in fact, and found that it significantly improved outcomes two years after surgery.²⁴ The study compared 150 patients from the Delaware-Oslo Cohort (DOC) to 150 from the Multicenter Orthopaedic Outcomes Network (MOON) cohort, who did not have extended prehab. At two years, those who had participated in the Delaware regimen of progressive strengthening and neuromuscular training had significantly better scores on two knee outcome scales (IKDC and KOOS), and significantly more had returned to preinjury sports than in the MOON group (72% vs 63% respectively).

Lead author Mathew Failla, PT, PhD, now an assistant professor of physical therapy at the University of Vermont in Burlington, told LER that currently, the typical requirement for someone about to undergo an ACL reconstruction is that the knee be “quiet”—that is, that there be an absence of swelling, a return of visible quadriceps contraction, and full range of motion.

“We wanted to know whether that was good enough,” Failla said. “So with the study we compared the two cohorts and saw that the one that underwent the additional preoperative rehab ended up having better postoperative outcomes at two years.”

Although neuromuscular training targeted specifically for an ACL-deficient population was part of the study regimen for the Delaware cohort, he continued, the researchers don’t yet know to what extent it contributed to the functional gains.

“We put them through ten sessions that included neuromuscular or perturbation training—a combination of high-level balance exercises and neuromuscular control exercises,” he explained. “We still don’t know if it was the neuromuscular training itself that led to those improved outcomes or the entire package. We’ve just begun to scratch the surface of prehab; we don’t know what the ideal program is, and it’s likely to be specific to certain populations or pathologies. As more prospective research is completed, we should be able to design targeted programs both pre- and postoperatively to maximize those outcomes.”

Failla believes future therapeutic approaches will most likely balance the best of new and old.

“Historically, we’ve had a bias that what happens after surgery is most important,” he said. “Now we’re seeing that there is a potential to influence outcomes based on the status of the patient entering surgery. Even so, we don’t want to get too fancy with treatments and technologies. Our evidence so far takes us back to the basics of a sound program that addresses strength, range of motion, and dynamic control of movement. It’s a challenging program that’s continually reassessed to make sure gains are being made. It’s not sexy, but it’s evidence-based, and so far it’s withstood the test of time.”

Cary Groner is a freelance writer based in the San Francisco Bay Area.

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