Adjacent Vertebral Body Fracture following Vertebroplasty with Polymethylmethracrylate and Calcium Phosphate Cement: A Biomechanical Evaluation of the Cadaveric Spine

S. Nouda, M.D., et. al, Department of Orthopaedic Surgery,
Osaka Medical College, Osaka, Japan

The authors presented a biomechanical study using human cadaveric thoracolumbar spinal columns with the purpose of comparing the effect of treatment by vertebroplasty with polymethylmethacrylate cement and vertebroplasty with calcium phosphate cement in the creation of adjacent vertebral body fracture following vertebroplasty.  They found that new vertebral fractures occurred in the vertebrae adjacent to augmented vertebrae in the P group (polymethylmethacrylate) and in the augmented vertebrae in the C group (calcium phosphate).  The difference in the fracture  site may be because of a difference in strength between the two bone filling materials. Therefore, the strength of bone-filling materials is considered a risk factor in developing adjacent vertebral body fracture after vertebroplasty.  There were different failure rates, however, of the spinal column following vertebroplasty with each group.  The authors state that calcium phosphate cement may be superior to PMMA as a bone filling material because although vertebrae augmented at CPC are subject to collapse, they are gradually replaced by new bone and subsequently obtain adequate compressive strength and stiffness  leading to bone union with a lower risk of inducing new adjacent vertebral body fracture in PMMA, which is a very strong material for the human body to adapt to it. 

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Furor Over Vertebroplasty Demonstrates the Importance of Timely Research

page 124

The furor over the pros and cons of vertebroplasty continues to grow. The authors point out that this is a reminder of the importance of performing early high-quality research on new technologies before they become widely disseminated and entrenched in the marketplace.  They reviewed a recent report in The Back Letter and the New England Journal of Medicine in August 2009 which concluded that vertebroplasty is no better than a sham procedure in the treatment of osteoporotic compression fractures.  They note that vertebroplasty proponents argue that the benefits of vertebroplasty are indisputable and that further rigorous clinical trials are not necessary. They note that thousands of practitioners have received training in vertebroplasty techniques and augmentation procedures such as vertebroplasty and kyphoplasty have become popular offerings of clinics and hospitals across the country. 

The authors state that their group had advocated 3 years of vertebroplasty be subjected to randomized controlled trial evaluation. They note that there is a balance that needs to be struck between rigorous evaluation and innovation and that technologies  may be too entrenched to evaluate. They expressed their belief that we have erred on the side of being too late. They conclude that a future vertebroplasty would likely be settled by payers who will weigh the merits of the positive observational status of vertebroplasty against those of two sham-controlled randomized trials and other  high-quality clinical trials that might emerge in the near future.   They point out that Medicare underwrites the majority of vertebroplasties in the U.S. However, the centers for Medicare and Medicaid have not yet indicated their intentions regarding this issue. 

They refer to additional papers from the New England Journal of Medicine 2009, including studies by Buchbinder and Kalmes, noting that osteoporotic vertebral fractures are not the only indication for vertebroplasty and it is widely used in cancer-related vertebral fractures.  They report that 1/3 of their patients suffered from myeloma. 

Long-Term Opioid Therapy for Injured Workers No Panacea. 

The authors report studies from the Clinical Journal of Pain 2009 and Clinical Journal of Pain 2008 and include authors Franklin and Von Korff, and note that a new study  from the State of Washington suggests that opioids have become a common treatment for workers with compensable back pain and that most Workers Compensation patients with back pain who opt for opioids take them only for the short term, as their acute back problems subside when back in the workforce. They point out that for those who opt for longer-term therapy, opioid use appears to be problematic. In this study, the majority of workers  who chose to take opioids over the long term failed to make significant long-term recovery in terms of pain and function.  They reported a study of 883 Workers Compensation patients in which 42% of these claimants with back pain were prescribed an opioid, usually at the first visit. However, they note that the research suggests that most workers who file a compensation claim for low back problems make a fairly speedy recovery and return to work.  Only 16% of the injured workers in their study took opioids for the entire 12 months of the study. 

They found that opioids were clearly not a panacea for a majority of those who chose long-term therapy and only 26.9% of those with long-term opioid prescriptions had a significant improvement in pain with findings of at least a 30% decrease in pain.  They noted that only 15.9% reported a significant gain in physical function with at least a 30% improvement in the Roland Morris disability questionnaire scores. 

Higher dosages were not associated with clinical improvement and reached potentially dangerous levels in some cases, and provided documentation  is commonly lacking, according to the authors.  This and other studies suggest that a small minority of individuals using opioids for low back pain who make the leap from short to long term use deserve careful study and management, according to Franklin, et. al. 

They found that subjects who had a high daily intake with opioids, greater than a 40 mg morphine equivalent dose, in the first few months of treatment, had a six-fold increase in the odds of going on to long-term opioid therapy compared to those taking smaller doses. 

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Lasers & Spine Surgery: A Review

Jack Stern, M.D., Ph.D., F.A.C.S.,
White Plains, NY,
Spineline, September-October 2009, 17-20

The author notes that when focused on a point, a laser can cauterize deeply as it cuts, reducing surgical trauma caused by a scalpel, and can vaporize the surface of a tissue. In spinal surgery, the laser has been most widely applied to discectomy. The general concept of laser-assisted discectomy evolved from the development of percutaneous techniques. The author notes there are no reported prospective controlled studies reporting percutaneous laser discectomy.  Inclusion criteria  were based on the presence of a documented non-sequestered disc herniation in patients with radicular pain corresponding to the level of disc involvement.  Exclusion criteria have included a previous surgery to the level of the disc to be treated, as well as an absence of spinal stenosis, facet impingement, lateral recess stenosis, advanced degenerative disc disease, or spondylolisthesis.   The author also notes that patients with active litigation in Workers Compensation claims have also been considered in the exclusion criteria.  The author made reference to a series with 21-26 month follow-up reported by Choy noting that 78.4% of patients rated good to fair relief of pain and of failures, 21.6% had subsequent open surgical treatment.  There were other series to which reference was made, including Yeung reporting 81% rate of good or excellent results, and Sherk noting no difference between treated and control groups and analysis of response to pain questionnaire in the presence of physical signs. 

References were made to other series by Ohnmeiss, who had reviewed 204 patients who had undergone laser disc decompression by a nonspecified number of surgeons at 3 different centers and only 41 of these patients were found to fit the inclusion criteria utilized by Choy.  They found, however, 70.7% successful results. 

Ohnmeiss was quoted as reporting that laser disc decompression was considered appropriate for a type of disc which does not correspond to conservative measurements and is not serious enough to undergo surgery. 

A series by Ahn was cited in which 81.4% of patients had good or fair outcomes and in this series lasers in percutaneous  lumbar discectomy for recurrent disc herniations had been applied through posterolateral approach and not through the original incision, thereby avoiding possible complications of operating through a scarred area. 

There were several other series cited, including those by Jako and Cselik, noting the need for stereotactic computer assisted identification systems in that the accuracy was reported as better than 2% when tracking instruments from pre-acquired formatted CT reconstructed images, and tracking of instruments from pre-acquired CT with reconstructive images reduce overall radiation exposure by limiting the need for continuous intraoperative C-arm fluoroscopy. 

An additional reference was made to Ahan, who utilized a side-firing laser for posterolateral percutaneous foraminotomy, utilizing laser and endoscopic forceps to undergo hypertrophy of the superior facet and L5-S1 foraminal or exit zone stenosis. 

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The Value of Routinely Performing a Bone Biopsy during Percutaneous Vertebroplasty in Treatment of Osteoporotic Vertebral Compression Fractures

Sander, Paul, Jan, Mui, et. al.
Department of Orthopaedic Surgery & Radiology,
Leiden University Medical Center, Leiden, The Netherlands.
Spine, vol. 34, no. 22, pp. 2395-2399

The authors reported a retrospective histological evaluation of biopsies obtained during percutaneous vertebroplasty procedures as treatment for presumed osteoporotic vertebral compression fractures.  Their objective was to determine the rat of unsuspected malignancy in bone biopsies of patients undergoing PVP for osteoporotic vertebral compression fractures. 

The authors note that most vertebral compression fractures which resulted from minimal to no trauma have osteoporosis as their underlying disease, and the diagnosis of osteoporosis is based on clinical and radiologic findings. They also point out that even in patients with proven osteoporosis, it is not always the true cause of the fractures.  They reviewed the literature which revealed that outcomes of bone biopsies obtained during vertebroplasty have been described in inconsistent percentages of unexplained malignancy. 

This research team reviewed 78 biopsies from 78 patients, 18 male and 60 female, with a mean age of 73 years. They found that in 3 patients, 3.8% of all biopsies, previously undiagnosed malignancies, two multiple myeloma stage II-A, and one chondrosarcoma, grade I, were found.  They concluded that obtaining bone biopsies during PVP does not lead to increased morbidity and can verify the pathologic process underlying the vertebral compression fracture.  They concluded that since this study demonstrated an unsuspected malignancy rate of 3.8%, they recommend routinely obtaining a vertebral bone biopsy, preferably using a biopsy needle, with a diameter larger than 14 gauge. 

The authors note that vertebral compression fractures are a common cause of pain and disability and that 20-30% of these fractures are refractive to conservative treatment and become chronically painful.  They further note that minimally invasive techniques such as percutaneous vertebroplasty are increasingly used for the treatment of chronic treatment in disability caused by osteoporotic vertebral compression fractures. They found that this procedure has been found to provide a reasonably safe and effective means of pain control, reducing disability and enhancing return to function. 

They again note that the diagnosis of osteoporosis is based on clinical and radiologic findings and should include a DEXA examination.  They state that these studies, however, do not always reveal the true cause of these fractures. 

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“Predominant Leg Pain is Associated with Better Surgical Outcomes in Degenerative Spondylolisthesis & Spinal Stenosis”

Adam Pearson, M.D., et. al
Spine Journal 8 (2008, 1S-191S)

Proceedings of the 23rd Annual Meeting of
the North American Spine Society,
October 15-18, 2008.

The authors compared baseline characteristics and surgical and non-operative outcomes in degenerative spondylolisthesis and spinal stenosis patients stratified by location predominant leg pain v. back pain. They studied 591 patients with DS and 615 patients with SPS.  The outcome measures utilized were in SF-36 bodily pain (BP) and physical function (PF) scores, Oswestry Disability Index (ODI), and Stenosis Bothersomeness Index (SBI).  All of these patients had neurogenic claudication and/or radicular symptoms.  They found that overall, surgery resulted in better outcomes compared to non-operative treatment for all patients regardless of pain location. However, predominant leg pain patients improved more with surgery than predominant back pain patients. 

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 “Why Lumbar Artificial Disc Replacements Fail:
Home Run or Strikeout?”

Kenneth Bettine, M.D., et. al
Spine Journal 8 (2008, 1S-191S)

Proceedings of the 23rd Annual Meeting of
the North American Spine Society,
October 15-18, 2008.

The authors studied 3 different designs, including the Maverick, Charite, and Kineflex.  This study was part of an FDA IDE study performed at one level, either L4-5 or L5-S1.  Overall, clinical failures occurred in 26%, or 2,491 patients at 2-year follow-up. Clinical failure was 28% in the Maverick, 39% in the Charite, and 14% in the Kineflex.  They found that the type of design made a difference.  They felt that different failure rates between surgeons was due to poor patient selection and not to technical skill.  Causes of failure included facet pathology in 46% of failure patients, implant complications occurring in 6% of the total patients and 25% of the failure patients.  There was a 29% failure rate in patients with unrelated orthopaedic or medical pathology and/or disability or narcotic issues.  They noted that only 5 patients went from a success to failure after 3 months.  One was an infection in one year, 4 patients developed additional pathology unrelated to their surgery, and 1 patient went from a failure to a success after a facet rhizotomy one year after the procedure.  They also noted that 74% of patients after artificial disc replacement met with clinical success after a 2-year follow-up, and the clinical success v. failure rate did not change from the 3-month follow-up in 85 of the 91 patients, or 93%.  Failure can be determined early with respect to facet pain, implant complications and unrelated pathology or disability/narcotic issues.  They stated that in addition to patient selection being very important, implant type also appears to impact clinical success.  They further concluded that patients with a BMI over 34, multiple orthopaedic and/or medical pathologies, facet pain, or disability/narcotic issues have a higher failure rate with this procedure. 

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“An Analysis of Risk Factors of
Adjacent Segment Degeneration After
Fusion Using Pedicle Screws for
Degenerative Lumbar Disease”

Jae Chule Lee, et. al
Spine Journal 8 (2008, 1S-191S)

Proceedings of the 23rd Annual Meeting of
the North American Spine Society,
October 15-18, 2008.

They studied 55 patients who underwent instrumented lumbar fusion utilizing pedicle screws and had degenerative lumbar disease. They studied patients post fusion for over 5 years. They reported 38.2%, or 21 patients, developed  adjacent segment disease.  18 of these patients had upper adjacent segment degeneration, including retrolisthesis in  14 patients,  marked reduction of disc height in  7, hypermobility in 7, and listhesis in 1, respectively, whereas 4 patients had lower adjacent segment disease with reduction of disc height in 2 patients, listhesis in 1, or retrolisthesis in 1. One patient had both upper and lower problems. 

They found no statistically significant  relationship between radiographic adjacent segment disease and gender, age, lifestyle, fusion method, number of fused segments, or pre-existing adjacent disc degeneration on MR or on pre- and postop lumbar lordosis.  A significant risk factor they observed was the finding of less than 10º of segmental lordosis in the fused segments on the postoperative radiographs. They stated that this loss of the lordotic curve with the fused segments placed the patient at risk by 5.8 times.  They noted that there was no statistically significant relationship between adjacent segment disease and the clinical result. There was only 14% or 3 patients requiring revision surgery due to significant symptoms. They recommend restoring segmental lordosis in the fused segments greater than 10º at the time of surgery to decrease the risk for this problem.

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“Two-Year Clinical Outcome of Cervical Artificial
Disc Compared to Anterior Cervical Discectomy & Fusion: A Prospective Randomized Study”

Joseph Marzluff, et. al
Spine Journal 8 (2008, 1S-191S)

Proceedings of the 23rd Annual Meeting of
the North American Spine Society,
October 15-18, 2008.

The SECURE-C cervical artificial disc was used with respect to this study.  They note that this is an investigational device. In 82 patients, 47% male and 53% female, with an age range of 18 to 60 years, the average age was 43.7 years for  the cervical artificial disc, and 45.7 years for the anterior cervical discectomy and fusion.  They concluded that the SECURE-C cervical arthroplasty results in significant improvement in pain and function in patients with symptomatic cervical disc disease, similar to anterior cervical discectomy and fusion. Initial data indicate that cervical arthropasty appears promising, but additional follow-up data are needed to determine the long-term safety and efficacy of this treatment. 

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“Extreme Lateral Interbody Fusion (XLIF)
in the Morbidly Obese”

William D. Rodgers, et. al
Spine Journal 8 (2008, 1S-191S)

Proceedings of the 23rd Annual Meeting of
the North American Spine Society,
October 15-18, 2008.

The authors studied the safety and utility of the XLIF technique in treating morbidly obese patients.  They state that the XLIF is performed in the lateral decubitus position, minimizing the difficulty of the pannus as it falls away from the exposure.  Their series included 150 patients with a BMI of over 30 who were considered obese, and 43 of those patients were morbidly obese with a BMI of over 38.  The heaviest patient in their series weighed 375 pounds, and the largest BMI was 57.4.  Of the morbidly obese patients, the BMI was an average of 42.9.  The age ranges were from  31 to 78 years, with an average of 54 years. 

They described the XLIF approach as using 2 small skin incisions and  with blunt dissection  through the retroperitoneal space, traversing the psoas, and they note that protection was provided of the lumbosacral plexus with the utilization of automated dynamic nerve proximity monitoring.  They used a large expandable 3-blade retractor, which afforded good exposure and which would allow the surgeons to perform a discectomy and complete anterior column stabilization utilizing a large load-bearing implant.  They conclude by stating that the extreme lateral interbody fusion technique offers even morbidly obese patients the advantages of minimally invasive surgery without added complication for patient or surgeon.  They reported the usefulness and safety of this technique in treating obese patients.  They stated that the outcomes were similar to non-obese patients.

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The Results of The Prospective, Randomized, Controlled Multicenter Food and Drug Administration Investigational Device Exemption Study of the ProDisc-C Total Disc Replacement Versus Anterior Discectomy and Fusion with a Treatment of One-Level Symptomatic Cervical Disc Disease.
Murrey, Janssen et al
The Spine Journal (April 2009, volume 9, #4, 275-286)

This was a multicenter study involving 13 different sites and 209 patients were randomized and treated, 106 with anterior cervical discectomy and fusion and 103 with the ProDisc-C.  This was a prospective randomized controlled clinical trial. 

The most common treated level was C5-6, utilizing the ProDisc-C for 56.3% and utilizing the fusion for 57.5%.  They noted that NDI and SF-36 scores were significantly less compared with presurgery scores at all follow-up visits for both treatment groups.  They stated that neck pain intensity and frequency and arm pain intensity and frequency were statistically lower at all follow-up time points compared with preoperative levels, but were not different between treatments.  The authors stated that neurologic success was achieved at 24 months in 90.9% of ProDisc-C and 88% of fusion patients.  They note that results show that at 24 months postoperatively, 84.4% of ProDisc-C patients achieved a more than or equal to 4° of motion or maintain motion relative to preoperative baseline at the operated level. 

They also reported that there was a statistically significant difference in the number of secondary surgeries with 8.5% of fusion patients requiring re-operation, revision or supplemental fixation within the 24-month postop period compared with 1.8% of the ProDisc-C patients.  They stated that at 24 months, there was a statistically significant difference in medication usage with 89.9% of ProDisc-C patients not on strong narcotics or muscle relaxants compared with 81.5% of fusion patients. 

The authors concluded that the results of this clinical trial demonstrated that ProDisc-C is a safe and effective surgical treatment for patients with disabling cervical radiculopathy with one-level disease.  By all primary and secondary measures evaluated, the clinical outcomes after ProDisc-C implantation were either equivalent or superior to those clinical outcomes after fusion. 

They stated that in general, the ProDisc-C patients maintained motion in all planes at the operative level averaging 9.36° as reported in most other cervical total disc replacement in clinical trials, a small percentage of ProDisc-C patients developed motion relevant heterotopic ossification.  Three did go on to fuse at the operative level, however, these patients achieved successful clinical outcomes for pain and disability relief. 

The authors further pointed out that heterotopic ossification is a well-documented complication of large joint arthroplasty especially hip arthroplasty, and has been successfully controlled with short-term use of NSAIDS in cervical total disc replacement.  They noted that the NSAIDS was not required in this study and was not routinely used by the investigators.  They stated that most notably in this series, nine patients were radiographic failures in the anterior cervical discectomy and fusion group leading to a fusion rate of 90.2%.  To the best of their knowledge this was the largest prospective series of this type.  They noted a consensus among surgeons that anterior cervical discectomy and fusion is highly successful.  They also further opined that this study has questioned that  to some extent with regards to secondary surgery required, medication usage and lower than anticipated fusion rates.  Their final conclusion was that the ProDisc-C total disc replacement is a viable surgical option for patients with symptomatic cervical disc disease, and it was shown to have significant benefits in comparison to anterior cervical discectomy and fusion.

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Pregnancy After Anterior Spinal Surgery: Fertility, Cesarean-Section Rate and The Use of Neuraxial Anesthesia
Lavelle, Demers et al
The Spine Journal (January 9, 2009, 271-274)

This was a retrospective survey of 67 female patients of childbearing age who had undergone anterior spinal surgery.  Nineteen of these patients had tried to become pregnant after their anterior spinal surgery.  All patients who reported that they tried to become pregnant were successful in having a child.  Seven of the 19 women had children who were born by a cesarean section (37%).  Only two patients received an epidural as analgesia for the delivery.  The cesarean section rate appeared high, but was found to be consistent with current obstetrical trends.  Anesthesiologists appear less inclined to offer neuraxial anesthesia to a population which has undergone anterior spinal surgery.

The authors note that sympathetic nerves innervate the uterus and could also be damaged by anterior spinal surgery. One possible complication of this would be an increased rate of cesarean sections.  They note that the use of spinal or epidural analgesia and anesthesia is also controversial in a patient with a history of previous spinal surgery.  The patient may be at an increased risk for difficulties in identifying the epidural space, increased attempts for insertion of an epidural catheter and an increased chance for vascular or unintentional dural puncture. 

The women surveyed who had undergone anterior spinal surgery, had preoperative diagnoses of fracture, spondylolisthesis, degenerative disease, scoliosis, and tumor/infection.  The vast majority, 43 of the 67 had the surgery performed for scoliosis. 

The authors noted that there was no difference in the pregnancy rate for patients undergoing either an isolated anterior spinal surgery or a combined anterior and posterior spinal surgery.  They also noted that the method of delivery did not appear influenced by the region of the spine that was exposed via the anterior approach.  Of the 19 patients who gave birth, only two patients had received epidural analgesia for their delivery.  Both of these patients did not have a posterior spinal fusion.  Three patients had previous vaginal deliveries and two of those patients reported repeated vaginal deliveries after their spinal surgery. 

The authors found that 37% of the patients who underwent anterior spinal surgery and became pregnant subsequently received a cesarean section. 

The authors noted that with respect to anterior spinal surgery, the hypogastric plexus is at risk and for men this can result in a retrograde ejaculation.  For women, it is noted that the hypogastric plexus is involved in pain mediation to the uterus. 

The authors note that the rate of cesarean section in the United States is currently 29.1% of all total births which is a 40% increase since 1996.  They note that the rate for cesarean section in this study was higher than the national average, but also it was more likely that the increased rate was also attributable to current medical trends regarding cesarean sections in general.  They noted that 75% of the fracture patients had delivered by cesarean section. The authors point out that a displaced pelvic fracture is the injury most often attributed to a posttraumatic increased C-section rate and sexual dysfunction.  They did note that all patients were neurologically intact.  They also observed that anterior spinal surgery and scoliosis patients had no detrimental effect on fertility and did not result in higher than average rate of cesarean section. 

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Abstract: Current article

A minimally invasive device for Lumbar Spinal Stenosis, familiar to members of the American Back Society as Drs Zuckerman and Hsu presented the scientific basis and development at annual meetings, has been released as the X Stop.

Lumbar spinal stenosis presents with pain in the legs in the standing position and limitation in walking even short distances and is treated conservatively with physiotherapy, analgesics, NSAIDs and epidural steroid injections for generally 6 months. In cases of failure of conservative treatment, surgical treatment is considered which is customarily and a laminectomy with or without fusion, which may involve bone autograft and pedicle screw instrumentation.

This article provides two year follow up on 175 patients with spinal stenosis with neurogenic intermittent claudication, average 69.4 years, 108 males and 67 females. These patients improved on all parameters (p<0.001) with the VAS reduced from 61.2% to 39.0% at 6 weeks and the Oswestry disability index from 32.6% pre operatively to 22.7% at 6 weeks and 20.3% at 24 months. The device was removed in 8 and a decompression performed without compromise of final procedure.

These results are consistent with reports of the FDA index studies and confirmatory of the effectiveness of the device. Customary decompression was reserved for “massive stenosis” or continuous claudication, but the procedure is a safe and effective less invasive alternative in selected patients.

Reference: Two-year results of interspinous spacer (X-Stop) implantation in 175 patients with neurologic intermittent claudication due to lumbar spinal stenosis 
Johannes Kuchta Rolf Sobottke Peer Eysel Patrick Simons  
Eur Spine J  Published online: Thursday, April 23, 2009

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Transoral Kyphoplasty for Tumors of C2
R. Sinighelia, U. Nena, D. Fabris Monterumici
Proceedings of Ear Pin Federation of National Association of Orthopedics and Chromatology Eighth Congress, May 11-15, 2007 Florence Italy

The authors described a new surgical technique, the transoral kyphoplasty and presented three clinical cases where this procedure was performed for tumors of C2.  The authors found this to be a safe, quick and effective treatment in reducing pain and avoiding vertebral collapse in patients with tumors in C2 not responding to nonoperative treatment.  the authors found the transoral route to be the most straightforward percutaneous access to the C2 body.  They found that the transoral kyphoplasty would avoid major surgical procedures, and while maintaining normal cervical spine anatomy and avoiding fusion or fixation of the cervical spine. 

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Cervical Disc Arthroplasty Compared
With Arthrodesis for the Treatment of Myelopathy
Riew, Jacob et al
J. Bone Joint Surg Am 2008; 90:2354-64

The authors compared the results of cervical disc arthroplasty for the treatment of myelopathy, with arthrodesis (fusion) and found that patients in both the arthroplasty and the arthrodesis groups had improvement following surgery.  They found that improvement was similar between the groups with no worsening myelopathy in the arthroplasty group.  While the findings at two years postoperatively suggested arthroplasty is equivalent to arthrodesis for the treatment of cervical myelopathy for a single-level abnormality localized in the disc space, this study did not evaluate the treatment of retrovertebral compression which occurs in association with ossification of the posterior longitudinal ligament. 

They utilize the Prestige ST and Bryan disc replacements (Medronic) and the inclusion criteria they utilized included myelopathy and spondylosis or disc herniation at a single level from C3-C7. 

They studied 199 patients in this study and 53% underwent arthroplasty whereas 47% underwent arthrodesis.  They utilized the neck disability index, Short Form-36 scores and specific arm and neck pain scores improved significantly from baseline at all time points. 

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Corrective Osteotomies in Spine Surgery
Gill, Levin et al
J Bone Joint Surg Am 2008; 90:2509-20

The authors note that spinal deformities can result in increased thoracic kyphosis or loss of lumbar lordosis, leading to imbalance of the sagittal plane.  These deformities can be functionally and psychologically debilitating. They further noted that the Smith-Petersen Osteotomy can achieve approximately 10% of correction of the sagittal plane in each spinal level at which it is performed.  They recognize that this osteotomy is beneficial for patients who have a degenerative balance in the sagittal plane. 

The authors further present that pedicle subtraction osteotomy can achieve approximately 30 to 40° of correction to the sagittal plane in each spinal level at which it is performed.  It is the preferred osteotomy for patients with ankylosing spondylitis who have an imbalance of spine in sagittal plane.  The cervical extension osteotomies performed in the cervical spine at the cervical and thoracic junction in patients who have a cervical flexion deformity that impedes their ability to look straight ahead while walking or who have difficulty swallowing. 

The vertebral column resection is used when the imbalance is severe enough that the other osteotomies cannot correct the deformity, especially in patients who have a combined sagittal and coronal spinal imbalance.

Neurologic problems whether transient or permanent are often the most commonly encountered complications following these procedures.  Recent results have shown a high patient satisfaction rate and good functional outcome after spinal osteotomies done to treat a variety of disorders. 

The authors conclude that corrective osteotomies are used to treat sagittal and coronal imbalances of the spine in patients with a variety of deformities, and was important to be able to recognize the type and underlying cause of the deformity so that the most appropriate osteotomy could be chosen.  They state that the Smith-Petersen osteotomy is relatively simple compared to the other osteotomies and could typically be used to treat type-I deformities.  Also, curves that have a relatively smooth kyphosis instead of a sharp angular kyphosis can be treated with a Smith-Petersen osteotomy.  Multiple Smith-Petersen osteotomies can be used to achieve the necessary amount of correction.

They further add that pedicle subtraction osteotomies are typically used in patients with greater imbalances in the sagittal plane in the spine and when a minimum of 30° of flexion is needed.  Vertebral column resections are reserved for deformities such as those in both the sagittal and the coronal plane that are not amenable to treatment with either a Smith-Petersen osteotomy or pedicle subtraction osteotomy or a combination of the two.  The authors find that cervical extension osteotomy is performed in patients with a history of ankylosing spondylitis, but it is specifically used to correct the horizontal plane by directing the visuals field forward.  As the level of complexity of the osteotomy increases so does the potential for complications. 

Posterior Lumbar Interbody Fusion
for Adult Isthmic Spondylolisthesis
A Comparison of Fusion
with One or Two Cages
Suh, Park, et al
JBJS volume 90-B #10, October 2008, 1352-1356

The authors studied 100 patients with low-grade isthmic spondylolisthesis who were randomized to receive a single-level and instrumented posterior lumbar interbody fusion with either one or two cages.  The minimum follow-up was two years.  47 patients received one cage and 44 patients received two cages.  They found no significant difference between the two groups in terms of postoperative pain, Oswestry disability score, clinical results, complication rate, percentage of post-operative slip, or posterior fusion rate.  Their results suggested that an instrumented posterior lumbar interbody fusion performed with either one or two cages in addition to a bone graft around the cage has a low rate of complication and a high fusion rate.  The clinical outcomes were good in most cases regardless of whether one or two cages were used. 

In addition, the authors pointed out another significant point regarding this study was that it has been widely thought that it is difficult to achieve a satisfactory fusion for the posterior approach alone because of the lack of graft bed, as only the transverse processes in the lateral aspects of the facet joints are available.  They noted a large gap between the fusion elements which results from anterior vertebral displacement and a lack of stability from the incompetent disc.  They stated that posterior lumbar interbody fusion allows reconstruction of the anterior support and a circumferential fusion may be achieved through a single posterior approach if a posterior lumbar interbody fusion is combined with a posterolateral fusion thereby stabilizing both columns. 

They found that the advantages include support of the anterior column, removal of the degenerated disc, indirect foraminal decompression, restoration on a normal sagittal contour and a reduction in the degree of slip by ligamentotaxis and improvement in spinal biomechanics.  Consequently, interbody fusion is considered by many to be the treatment of choice for degenerative disorders of the lumbar spine. 

They state that posterior lumbar interbody fusion using bilateral interbody cages has been the standard treatment.  However, only a single cage can be placed at the time of surgery for technical reasons such as large epidural vessels which cause bleeding, narrow disc space, nerve root anomalies that blocked access to the disc space or difficulty in retracting the nerve roots because of epidural scarring from previous surgery.  They stated that it was unclear whether a single cage provides acceptable balance, strength and rate of fusion. 

They pointed out that despite a large number of publications on the subject there is little scientific support for a posterior lumbar interbody fusion as a method of fusion.  They stated that there were few studies comparing the outcomes of a posterior lumbar interbody fusion using one or two cages in a well-defined population in patients with isthmic spondylolisthesis. 

They noted that the disadvantages of the two-cage procedure are the increased risk of excessive epidural bleeding and prolonged or excessive dural retraction.  They noted the study of Elias et al, who found a 15% incidence of dural tear and postoperative radiculopathy in 67 patients who had undergone an instrumented fusion using bilateral titanium threaded cages.  They noted that these complications included radiculopathy, epidural fibrosis, arachnoiditis and recurrent disc herniation.  They noted one patient had suffered a permanent motor deficit with sexual dysfunction. 

The authors reported no significant difference in additional stability and stiffness between a transforaminal lumbar interbody fusion with a single cage and a posterior lumbar interbody fusion with two cages.  They found that a unilateral cage and unilateral pedicle screw produced similar stability to a unilateral cage of bilateral pedicle screws in a porcine model. They found that a unilateral cage is as stable as bilateral cages in the human cadaver.  They stated that the position of the cage did not adversely affect the stability of the construct.