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Morgan-Hough CVJ, et al. (2003) "Primary and revision lumbar discectomy: A 16-Year review from one center" J Bone Surg [Br] 2003;85-B:871-4

This was a large study of 531 patients that focused on disc protrusion patients that underwent a standard discectomy.   In fact 64% of the patients in this study had surgically confirmed disc protrusions (aka: contained herniation) in which the outer layers of the anulus fibrosus had NOT completely ruptured and the nuclear fragments were contained within the bulging disc.   I might add that this is the only study I've come across that has focused on the disc protrusion patient, rather than the disc extrusion patient.   The results showed an 8% surgical failure rate which is about in the middle range of all studies on this subject.   The surprising thing was that 80% of the revision surgery patients came from the disc protrusion group!   The only disappointing thing about this study was it did not assess the success rates or subjective outcomes of these any of these patients. There was also some question in my mind as to why every patient with a protrusion got the same anulotomy?   We have learned from the work of Carragee et al. 2002, that there are two types of protrusions, each requiring a different surgical technique. (Click 'here' to read Carragee's most excellent paper.)

Here's the study:

Five hundred and fifty three (553) patients underwent a discectomy with partial laminectomy in some cases, by the same surgeon between 1986 and 2001.   All patients had failed at least six weeks of physical therapy for radicular symptoms in the lower extremities and were suffering with intractable sciatica.   All had signs of nerve root entrapment which matched with imaging studies; myelogram, CT and/or MRI.   Only L4 or L5 disc herniation (or prolapses as they call it on the other side of the pond) were allowed in the study.   Cauda equina cases were excluded.   (This was probably due to the fact that these central herniations (which often cause cauda equina) do not do well with discectomy.)

Surgically, a standard discectomy was performed, with a minimal laminectomy if needed.   If the disc was not extruded, the protrusion was removed via a "square annulectomy made with a number 15 blade".  

Break Down of Disc Conditions:

The type and number of "prolapses" (aka: herniation) were noted during surgery and classified into one of these three categories:

•  Protrusion (341 - 64%): This was described as a focal bulging of the anulus without a complete disruption.   No nuclear material was seen outside of the intact anulus.

•  Extrusion (87 - 16%):   Now, herniated nuclear material was seen extending through the torn anulus of the disc, but this extension of nuclear material was still connected to the disc and had not broken loose.

•  Sequestration (103 - 19%): Now, the herniated nuclear material was NOT found to be attached to the disc at all.   The fragment of nuclear material had broken loose and was in the epidural space unattached from the disc.

The case files were reviewed at an average of 7 years post primary surgery.   The range was from 1 year to 16.5 years.

A total of 22 patients were lost or excluded leaving 531 patients for the study.   This was an excellent retention rate of 96%.


There were Forty two of the 531 patients (7.9%) whom needed a second surgery because of a worsening of the sciatica condition. The causes for revision surgery were as follows: 32 patients (6%) had recurrent disc herniation, 6 patients (1.1%) had scar tissue (epidural fibrosis), and 4 patients (0.8%) had a mixture of recurrent herniation and scar tissue. (see result table)   

Of the 42 revision surgeries: 34 were from the protrusion group (81%), 2 were from the extrusion group (4.8%), and 6 were from the sequestration group (14%).    

Result Table:

  *Surgical Failure Reasons:

Number of patients

% of total group (531)




Total Revisions surgeries:



*Recurrent disc herniation:



*Epidural Fibrosis (scar tissue):



*Fibrosis & recurrent herniation:






Which Discs Needed Revision Surgery?


% of Disc Type (42)




Protrusions (aka: Contained herniation)






Extrusions (aka: uncontained herniation)




Of all three types of herniation, the occurrence rate was slightly higher at the L5 disc, as compared to the L4 disc; approximately 60% at L5 and 40% at L4.   The L5 disc was more than twice as likely to need revision surgery, compared to that of the L4 level.

Also of interest was the degree of the 'straight leg raise test'.   The protrusion group had a much higher or non-restricted 'straight leg raise test' (SLR) than did the extrusion and/or sequestration group.   The protrusion group also had a much higher rate of a 'non-positive neurological examination; i.e., 35% of the protrusion group had NO neurological deficit on per-surgery examination, compared to 22% of the extrusion group, and sequestration group.

Interestingly there was an 8.7% 'complication rate' (surgical mistake or accident) from the first surgery.   The number one cause (63%) was from an accidental perforation of the dura of the cauda equina, which resulted in a cerebral spinal fluid leak.   Bladder infection was the number 2 complication (11%).

Final Conclusion:

The bottom line of this paper was that patients with disc protrusions had a 2 to 3 time great need for revision surgery because of recurrent sciatica, as compared with the extrusion and sequestration group.   The authors warned that extended conservative care, including multiple epidural injections, should be tried for as long as possible in suspected disc-protrusion-patients because the greater possibility for recurrent sciatica following the primary surgery.    

The author's theory as to why there was such a high 'surgical revision rate' was as follows: "We suggest that this surprising finding (the high surgical revision rate in the protrusion group) could be explained on the basis that a protrusion represents the beginning of a process of serial fragmentation of disc material, whereas extrusion and sequestration are an end-stage of this process."   I have always heard of this line of thinking but still have found no research on it.   Just speculation, but sure could have some merit.

The authors warn the following: "Even though surgical treatment (via discectomy) yields a satisfactory resolution of symptoms more quickly (than conservative care), the consequences of surgery (for the disc protrusion patient), in terms of complications, must be carefully considered." (76,77,78)   The results of revision surgery are less predictable (than a primary surgery) and the incidence of complications increased."

ChiroGeek' Comments:

My only question why was there a need for a rather massive "anulotomy" in every disc protrusion (contained herniation) patient?   This seems to be a different technique that what Carragee described for the treatment of contained herniations.   Remember that according to Dr. Carragee, who is the head of Stanford's Orthopedic Spinal Surgical Unit, there are two types of contained herniations; the type called the "Fragment-Contained Herniation" did well with surgery and did not need the anulotomy; the type called the "No-Fragment Contained Herniation" did terrible with discectomy and required the anulotomy. (Review Carragee's paper here)

My surgeon, who uses the same technique as Carragee, explained this surgical finding the same way to me personally.   IF there was not a fragment ready to pop out or to be debrided then the last resort was the dreaded anulotomy / anulotomy, which is know not to have a very low success rate.   I'm sure that there's an answer.   Maybe Morgan-Hough just didn't get as detailed about the surgical procedure as Carragee did.


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