Be Careful Reading Abstracts! ALIF Study

The Study | The Blunders | The Results | The Discussion >

Duggal N, Dickman CA, et al. "Anterior Lumbar Interbody Fusion for Treatment of Failed Back Surgery Syndrome: An Outcome Analysis." Neurosurgery 2004; 54:636-644

READING ABSTRACTS DOES NOT ALWAYS GIVE YOU THE FULL STORY! I’m supposed to be taking some time-off for some well-deserved R&R, but after I received an e-mail from Dr. XXXXX claiming that a new investigation confirms that ALIF is the "wonder treatment" for failed spinal surgery, I had to take a brief hiatus from my sabbatical to further investigate these claims.

Rant: This is a perfect example of why you should not read the abstract alone. I mean by reading the abstract of this investigation, it would seem that anterior lumbar interbody fusion (ALIF) is a great treatment for failed back syndrome. However, if you read the entire manuscript, you will soon learn there are some serious problems within study. In acknowledgment, the author states,“It is possible that our results overestimate the potential benefit of ALIF for FBSS (failed back surgery syndrome) because of the subjective nature of the selection process, the small sample size, and the relatively short follow-up period.”

The Study:

The cohort for this study consisted of 30 patients that had all previously underwent spinal surgery that had failed to alleviate there pain. They were all diagnosed with the dreaded "Failed Back Surgery Syndrome" (FBSS). All of the members of this group were examined, x-rayed, and completed to subjective assessment tools. This was a very selective group! That is, patients of whom suffered signs of neuropathic pain ( i.e., allodynia, causalgia, hyperalgesia, or progressive tactile hypersensitivity); recurrent disc herniation; and/or stenosis were excluded from the investigation.

Of that tiny cohort, three sub-groups were formed: the Degenerative Disc Disease group, the Postsurgical spondylolisthesis group, and the Pseudoarthrosis (failure to fuse) group.

Then, all of the patients underwent an Anterior Lumbar Interbody Fusion (ALIF) as performed by the senior author- Dr. Dickman. In this style of fusion, all the delicate posterior neural structures were not disturbed during the procedure, for they approach the spine from the front.

The Assessment Tools: The root of this investigations woes.

The most important part of any investigation, in my humble opinion,is the method by which the patient-improvement, or lack there of of, is measured following the procedure. Some of the standard methods for assessing the efficacy of a procedure's efficacy are as follows: 1) has the patient return to work? 2) has the patient been able to stop/reduce there medication intake? 3) would the patient choose to repeat the procedure knowing what he knows now? and 4) have the patient's VAS and Oswestry improved?

The biggest design problem of this investigation--aside from the small study cohort (33 patients); the relatively short follow-up period (one year); and the exclusion of so many diagnoses (i.e., cherry picking syndrome)--was the method used for assessing the pre-surgery and post-surgery level of patient pain and disability. More specifically, neither the 'Oswestry Disability Index' nor the 'Visual Analog Scale' (two of the best outcome assessment tools known to mankind) were used in this investigation. Instead, the team used a bizarre outcome assessment tools--one that I have never seen before. These name-less assessment tools, simply called "assessment forms", required the patient to select one of five categories that would best describe their level of pain and dysfunction one year statusafter the ALIF was performed. More specifically, here they are:

Some Criticism: my biggest beefs with regard to the functional disability assessment tool is the walking components and a wheelchair component (frankly I'm not sure what the wheelchair component has to do with anything – none of these patients were in a wheelchair). If they would've taken this out, things would've been better. I mean, in order to be considered a success in this outcome study, the patient had a reach a category two. This means that the patient has the ability to walk just over half a mile (4-5 blocks). In my book (and I'm sure in most of the lay population's book) that is not a success.

note that the criteria for a near total disability (category 4) is the inability to walk more than one to two blocks. This is where most of the patients were categorized prior to surgery. In order to be considered a "success" in this outcome study, the patient had to improve two categories. Note that a category 2, which is where most of the patients ended up one year after surgery, was described as "being able to walk 5 or 6 blocks! In my humble opinion that is barely any walking improvement at all, yet was considered a success! You mean to tell me that the ability to walk 5 to 6 blocks, which isn't even a mile, is considered a success and a very low level disability! You see my problem with this tool.

The Results: Seems to good to be True.

Leg Pain: According to the researchers, 94% of the patients had level 4 or 5 leg pain prior to surgery. After the surgery the authors claimed that “...more than 80% of patients achieved our definition of successful outcome [with respect to leg pain]." Therefore by extrapolation it appears that 82% achieved an UNBELIEVABLE RESULT, in that they recovered to the point of having "no compromise in activities" and only had "occasional pain" in the leg (level 2 or better)! Apparently they could do anything they wanted: swim, play tennis, hike, bike, etc! UNBELIEVABLE. Where do I sign up! More explicitly, 15% of the patients improved to the #2 level (Slight: occasional pain, no compromise in activities.), and 67% of the patients had NO leg pain or were able to completely ignore the leg pain. So, 82% of the patients basically completely recovered from their post-surgical leg pain.!

Back Pain: Yet another amazing result! 76% of the cohort (patient group) recovered at least to the point of having "no compromise in activities" and only had "occasional pain" in the back (level 2 of lower)!

Functional Outcome: The functional outcome, although still unbelievable in my book, was not nearly as spectacular: 67% of the patients obtained a “successful” outcome, i.e., 22 of the 33 patient improved from a category #4 to a category #2. This means that the patient could go from walking only 1 or 2 blocks to a 5 or 6 blocks. NOT very impressive in my book... 8 blocks is a mile, so they still can't even walk a mile yet they were deemed a success. (I'm playing the devils advocate here)

Employment: Ah, they did add one of my favorite assessment categories; one that is very unforgiving in terms of proving the efficacy of a tested procedure:   Unfortunately, 0% of the patients who had been unable to work prior to the surgery were able to return to any form of work. How can that be!   Supposedly, 82% of the cohort recovered from their leg pain and 76% recovered from their low back pain, yet none could return to work? Granted some of these patients may have had no motivation to return to work, i.e., retired and collecting disability, but this result still raises a 'red-flag' in my book.

There was also a 11% complication rate: One torn small iliac vein that resulted in an 800 ml blood loss and forced the patient into a transfusion; one attack of atrial fibrillation, one development of respiratory insufficiency, and two Interbody cage displacements.

In all fairness to these researchers, they did fess-up to the inadequacies of this investigation, but not in the abstract.   They stated the following: “It is possible that our results overestimate the potential benefit of ALIF for FBSS because of the subjective nature of the selection process, the small sample size, and the relatively short follow-up period.”

Discussion:

The only reason I have even bothered to posted this investigation is to demonstrate how DANGEROUS it can be to only read 'investigation abstracts'. Since most layperson's will not pay $30.00 for a full version of an investigation paper, the whole truth of an outcome may go unlearned. I believe it is the responsibility of the authors to include any data compromising factors within the abstract, in order to avoid the distribution of false and misleading information to the public--which frankly this investigation did (in my humble opinion).

In this investigation, Dr. Dickman and company touted that fusion, from the anterior approach, offered a statistically very favorable alternative to suffering with significant chronic back and leg pain, i.e. there is an 80% chance that you will have a "favorable" outcome, you will have "no compromise to activities" and you will suffer only have "occasional pain."

Unfortunately, their investigation was fatally flawed by the outcome instruments that were used (discussed above). The only viable outcome measure, in my opinion, we can rely on in this investigation was the number of patients who recovered enough to be able to return to some form of work. And that number was 0%. This of course completely flyies in the face of the touted 80% success rate of ALIF and demonstrated that fusion treatment for Failed Back Surgery Syndrome is certainly no panacea.

I have learned the hard way that there is no 'magic bullet' for killing off chronic back and leg pain. Fusion surgery is a risk and should ONLY be performed as a last ditch effort. I'm afraid 'mother nature' and 'grandfather time' are all us chronic pain sufferers have going for us--at least at the time of this writing (11/28/04). Don't get me wrong, fusion has it place for the treatment for chronic back and leg pain, and it occasionally (empirically 33% of the time) can indeed yield a wonderful outcome... but the numbers touted in this investigation were absolutely ridiculous!