Sports Medicine Research: In the Lab & In the Field: Single-Leg Hop Predicts Success After ACL Surgery (Sports Med Res)
Wednesday, October 31, 2012

Single-Leg Hop Predicts Success After ACL Surgery

Single-Legged Hop Tests and Predictors of Self-Reported Knee Functional After Anterior Cruciate Ligament Reconstruction: The Delaware-Oslo ACL Cohort Study

Logerstedt D, Grindem H, Lynch A, Eitzen I, Engebresten L, Risberg MA, Axe MJ, & Snyder-Mackler L. American Journal of Sports Medicine. 2012; 40:12348-2356. doi 10.1177/0363546512457551

Anterior cruciate ligament (ACL) reconstruction is performed regularly with relatively favorable results.  However, there remains a lack of evidence to predict who will have favorable outcomes and who may have problems after surgery.  Therefore, purpose of this prospective cohort study was to assess the effectiveness single-legged hop tests to predict self-reported knee function 1-year post ACL reconstruction.  One hundred twenty patients (mean age = 26) received ACL reconstruction surgery and followed the same pre- and post-operative rehabilitation programs.  Patients performed 4 single-legged hop tests (i.e., single hop, crossover hop, triple hop, and 6-m timed hop) at the end of pre-operative rehabilitation and at 6 months post-surgery. Patients also completed the IKDC 2000 (knee outcome survey) 1-year post surgery.  Only 84% of the patients completed the preoperative hop testing due to various reasons (e.g., meniscal injuries, missed appointments, quadriceps weakness/poor dynamic stability).  There were no significant differences found in IKDC scores between those who did or did not perform the pre-operative hop tests.  Among the 79 patients that completed the pre-operative hop tests and 1-year knee outcome survey the authors found that none of the preoperative hop tests could conclusively predict function 1-year post ACL reconstruction.  However, among the 85 patients that completed the 6-month post-surgery hop tests and 1-year knee outcome surveys the authors discovered that all of the hop tests successfully predicted self-reported knee function. They noted that the crossover hop and 6-m timed hop indexes were the most accurate at identifying patients who would or would not have normal knee function at 1 year.

Clinically, it appears that the single-legged hop tests performed at 6-months are accurate predictors of self-reported outcomes 1-year post-surgery.  However, we are still lacking a tool to assess and potentially identify patients that will likely have favorable surgical outcomes prior to their having the surgery done.  While the study controlled for rehabilitation, it contained a variety of graft types.  It would be interesting to see if there were any differences among graft types with some sub-analyses.  Furthermore, it may be interesting to see if there are certain exercises that could be provided if someone performed poorly at a 6-month assessment.  While the results seem favorable, there is still room for more investigation to verify these results and to explore pre-surgery predictors, as well as to evaluate what we can do for the patients that are not performing well on hop tests at 6 months post-surgery.  Have you seen other clinical measures that seem to predict favorable (or even not favorable) function after an ACL reconstruction?

Written by: Nicole Cattano 
Reviewed by: Jeffrey Driban

Related Posts:
Logerstedt, D., Grindem, H., Lynch, A., Eitzen, I., Engebretsen, L., Risberg, M., Axe, M., & Snyder-Mackler, L. (2012). Single-Legged Hop Tests as Predictors of Self-Reported Knee Function After Anterior Cruciate Ligament Reconstruction: The Delaware-Oslo ACL Cohort Study The American Journal of Sports Medicine, 40 (10), 2348-2356 DOI: 10.1177/0363546512457551

17 comments:

Anonymous said...

I agree that more research in this area would be very beneficial to the functional outcomes of ACL reconstruction surgery. In my experience in the rehabilitation setting, I have used a simple single leg squat in the assessment of post op function throughout the duration of a patients rehab and found it to be a great tool. It is a less stressful movement than the hopping tests that allows me to evaluate a patients dynamic movement patterns. I think incorporating a more sport specific movement such as the hopping tests mentioned in this study could help me to further evaluate the function of ACL patients during the duration of their rehab. Hopefully more research in this area will be available in the near future.

Nicole Cattano said...

I think its great that you use a SL squat in the assessment. Do you have the leg extended behind the patient, or suspended in front of the patient as they conduct a SL squat?

I think some of the hopping may be sport dependent, and definitely agree that sport specific movements are critical. I think it is great that you are utilizing some of these concepts clinically. Thank you for sharing, and if you are willing to share more information about what you look at or do, I think it would be a great thing for some of us to hear to potentially add to our own clinical skills set.

Dave Logerstedt said...

Thank you taking the time to review our article. We feel that the hop tests provide a good prognosis of future knee function. I have a couple comments. You refer to the IKDC2000 as knee outcome survey. Did you mean to say that it is a knee questionnaire because there is a Knee Outcome Survey (ADLS and Sports)? IKDC2000 and KOS are two similar but separate questionnaires.

In regards to the graft type, we had to address with comment with the reviewers and found no differences in graft types related to clinic site that might influence the hop performance.

We are in fact proposing funds to answer the question of neuromuscular training to address those who perform poorly at 6 months. We are very excited about answering that question.

Others have found that pre-operative quadriceps strength is a predictor of knee function after surgery. Others have found that meniscal or chondral injuries can influence outcomes. We are attempting to develop a large-scale practice-based clinical network in order to answer many of these question.

Nicole Cattano said...

Dr. Logerstedt- Thank you so much for your comment. I apologize for my lack of clarity in referencing the IKDC. I should have better articulated the use of the two separate, but similar, questionnaires to look at knee outcome measures. The IKDC does a great job in looking at knee symptoms and ADLs, where the knee outcome survey looked more specifically at sports and ADLs. Knee Outcomes is an area of research that has many options, and I do think it is important for readers to understand the instruments chosen and what they investigate.

It is very exciting that your group is in the process of looking into training for the poor-performers at the 6 month mark. I think that this will have a large clinical application.

Regarding graft type-has your group encountered any differences with the double versus single bundle techniques?

Dave Logerstedt said...

Your group is not working at double vs single bundle. Jay Irrgang at Pittsburgh has a randomized prospective study to investigate those differences.

Nicole Cattano said...

Dr. Logerstedt-Thank you for your response. And thank you for your work in this area. It is very exciting and I look forward to the next research article from your group.

Natalie said...

I've always been taught that pre-surgery quad strength was a good predictor of successful post-surgery outcomes, and that using a "prehab" program before surgery was a good way to help attenuate atrophy. However, I haven't had much experience with it myself. Has anyone used prehab for ACL surgery and seen positive results? Or conversely, has anyone not used prehab and noticed worse outcomes?

Nate said...

This type of research is the next step in providing better care for our patients. Being able to use clinically applicable tests to predict outcomes in patients is a huge finding. The next step would be to specifically understand why the people with poor single leg hop tests also had worse self-reported outcomes to begin to develop targeted interventions. Is it a direct correlation where if you work on single leg hop the patient would have a better outcome? My guess is it is more complicated that that and a poor single leg hop represents a combination of decreased quadriceps function, decreased balance, fear or re-injury, etc. It will be interesting to see how other measures that we can take as clinicians can be used as predictors of patients outcomes

Nicole Cattano said...

Natalie-where I work, we do emphasize the prehab that you mention, and I think it definitely helps with our post surgical results. Research like this may help inform our pre-surgery dehabs as well as our post-surgery rehabs.

Nate brings up a really good point regarding the possible confounding poor performance on the SL hop. I think this emphasizes the importance of an all encompassing rehab program. But by performing the SL hop, we may actually address some of the deficits in quad control, proprioception, and mental aspects such as fear. Has anyone had any luck with using the SL hop as part of the rehab process?

Kate said...

It is always exciting to get new information in regards to predicting how our athletes will do in the future. However, I am normally telling my athletes that they will be back on the field in 6 months. Is there any way we can use these tests to predict earlier function recovery? And as Nate said we also need to ask why people who performed poorly on the hop tests had worse results in a year. Do they all present with quad weakness etc? That will help us answer the question of if they fail the hop test, how can we rehab them to help them still regain full function in a year?

Natalie-I also prehab before ACL surgeries and sometimes it works and sometimes it doesn't. I get athletes to full quad strength and at least 90 degrees of flexion and full extension but some do great and some have poor results. I think pain level during prehab is a good indicator. If patients can do the prehab but constantly complain of pain during exercises they often have a slow recovery after surgery.

Nicole Cattano said...

Kate-I think you make a great point about prehab being a good indicator of tolerance and work ethic post-surgery.

My only concern is that if we are returning athletes to play too soon. ACL survival techniques have advanved so much that healing time has been significantly decreases kver yhe years. Back to Nate's earlier point, are the athletes even me tay lrepared for RTP? Furthermore, post ACL outcomes long-term appear to have an increased risk for OA development, which seems not to be linked to time to RTP.

I really like the idea of utilizing these or similar tests to modify the rehab to optimize outcomes. Has anyone had any trials or success with this?

William T. said...

In my short experience with ACLr patients I haven’t utilized a single leg hop more so a single leg eccentric step down and a single leg squat (with knee flexed/hip extended) knee touch to a box. I picked that up from viewing a few ACL webinars by Kevin Wilk regarding current ACL research techniques. These tests are used within rehab early on but also can be used later on to view progression. The athlete is to maintain consistent linear alignment of the knee in relation to the hip and first ray of the foot. The purpose is to help with neuromuscular control and stability while helping educate, or re-educate rather, correct biomechanics. Having the athlete perform the SL tasks in front of a mirror helps them be conscious and aware of whether they are performing the tasks correctly as well providing live feedback. I think the use of these exercises, or tests, help the athlete as well as the clinician determine where they are in the rehabilitation process and what needs to be assessed/monitored more closely. I understand that 6 months is the viewed RTP time frame however I think the approach needs to be more task oriented rather than time so that the athlete can continue to set goals and their sights on proving to themselves as well as to us that they are ready to move to the next level. In addition to the SL step down and SL squat to box I’ve also used a SL RDL test which incorporates the same purpose as the aforementioned tests in focusing on the knee mechanics but also the hip and ankle.

Nicole Cattano said...

I think those are great exercises to use. Are there certain things that you are looking for when the athlete is performing these exercises as potential indictors for exercise modification? For example, if the knee collapses into Valgus are there other exercises you would do to help this or do you find that correcting form of this exercise corrects the strengthening issues?

Chip W. said...

As Natalie said, my understanding is that pre-op quad strength is the best predictor of outcomes after surgery. Using a single leg hop test makes sense, as it addresses multiple issues(patient fear, quad eccentric function, NM control, etc). I'll have to keep this in mind next time I have an ACL-R patient, and may give it a try on an ACL/MCL/PCL/mensicus patient I have who is struggling to progress in her rehab. On a side note, I've found that pain during a single leg hop is a good indicator of a stress fractures and use it with cross country runners.

Nicole Cattano said...

That's very interesting Chip. When executing the single leg hop, which type do you do? Do you do one for distance, for height, or something else?

Thanks for sharing.

Ros Cooke said...

Hi
I am very intrested to read all your comments inn this area. Also a little suprised that hop tetsing is not routniely done. As natalie points out the test porvides us with alot more information than a controlled SL Squat motion. We also know that the mechanis behind ACL is complex and in non contact mutliple forces in mucltiple planes are contributing factors. Within a sporting context the presence of multiple stimuli and ques means that a test that requires the patient to react and land with good postion and control may be the most relaisitc and indicator of their fucntion in real time. Although saying that I do feel that if they fail on a closed sskill precietd movement test such as hop or SL squat they are likely to fail at something more complicated. Within the setting I work in I have rotuinely used hop test to assess limb symmetry index prinicaply single, triple and cross over versions. I also no look at the Myer tuck jump to analyse repeated high intensity movement like they will experience in any sport.

Nicole Cattano said...

Ros-thanks for your comment. I'm not familiar with utilizing the Myer tuck jump. Is this a specific protocol using the tuck jump? I feel that there are many hop tests out there and it becomes a question of which ones do we find used most clinically.

What hop tests are clinicians regularly using? Like Natalie, I think the SL squat tells us alot about eccentric confirm, but agree with Ros that we need more functional/sporting like tasks. Is there a single best test or do we think they may be short dependent?

Great comments!

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