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Transforaminal Lumbar Interbody Fusion:
Topic Started: 20 Jun 2007, 04:06 PM (1,458 Views)
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Transforaminal Lumbar Interbody Fusion: A Retrospective Study of Long-term Pain Relief and Fusion Outcomes

By Cody A. Chastain, BS; Jason C. Eck, DO, MS; Scott D. Hodges, DO; S. Craig Humphreys, MD; Peggy Levi, RN
ORTHOPEDICS 2007; 30:389
May 2007

No long-term studies exist on the effectiveness of transforaminal lumbar interbody fusion. This study sought to determine postoperative pain, disability, and fusion status of transforaminal lumbar interbody fusion patients after >4 years to establish long-term outcomes. A retrospective analysis of 42 patients with minimum 4-year follow-up was conducted. Patients completed visual analog pain scale (VAS) and Oswestry functional capacity evaluation pre- and postoperatively. Statistically significant improvement was noted in VAS and Oswestry functional capacity evaluation scores. Transforaminal lumbar interbody fusion is effective in alleviating intractable back pain over an extended time period. Solid radiographic fusion is unnecessary for clinically successful outcomes.

Spinal fusion has evolved since 1911 when Albee1 reported the first posterior fusion. After this initial attempt, various methods have improved the approach to the spine and refined the methodology used when removing intervertebral disks and fusing the spinal column. Interbody fusion techniques have been developed to achieve solid spinal fusion while maintaining normal disc height.

Posterior lumbar interbody fusion was first introduced by Cloward2,3 and later revised by Lin.4 The interbody fusion immediately produces a biomechanically stable construct.5,6 Posterior lumbar interbody fusion also avoids the risks associated with the anterior approach to the lumbar spine. Unfortunately, posterior lumbar interbody fusion is limited to fusions from L3-S1 due to the high risk of damage to the conus medullaris and cauda equina from retraction above these levels.

Modifications of the posterior lumbar interbody fusion technique have recently culminated in Harms et al?s7 development of a unilateral, transforaminal approach to the spinal column. This has resulted in the widespread use of transforaminal lumbar interbody fusion as a treatment for lumbar instability and intractable lower back pain.8

The transforaminal lumbar interbody fusion procedure has numerous advantages over the surgery it has tended to replace. Posterior lumbar interbody fusion was the first to allow physicians to stabilize spinal instability and relieve nerve compression in a single surgery.9 This surgery, however, has multiple complications including excessive bleeding, nerve damage, and harm to the dura. Nerve root retraction and close proximity to the dura is unnecessary in the transforaminal lumbar interbody fusion procedure because the transforaminal approach does not interfere with the nerve exiting the vertebral column through the intervertebral foramen, essentially eliminating all nerve irritation and damage from normal surgery complications.10,11 This surgery also provides a full 360? vertebral surface in order to achieve arthrodesis across the intervertebral space.8,12 Humphreys et al13 noted that since the contralateral laminar surface of the vertebra is preserved in the transforaminal lumbar interbody fusion procedure, an increased surface area may be used for new bone to grow and bridge the gap left by the removed intervertebral disk.13 They also found that blood loss was significantly lower in two-level lumbar fusions when a transforaminal lumbar interbody fusion procedure was used instead of a posterior lumbar interbody fusion.

Harms? approach was first used by other orthopedic surgeons in late 1998 and early 1999, and only recently has it been possible to determine the long-term effects of the transforaminal lumbar interbody fusion procedure.

The aim of this retrospective study was to examine the long-term effects of transforaminal lumbar interbody fusion in a random patient population with a minimum 4-year follow-up. Each participant?s current pain levels and perceived disabilities were used to examine the extent of recovery a patient and their physician can expect when using transforaminal lumbar interbody fusion to treat diskogenic back pain. Complications associated with these surgeries were noted to quantify the risk involved with transforaminal lumbar interbody fusion.

Radiographic information was obtained to determine the successful fusion rate of this surgery; however, the role of spinal fusion in back pain relief is ambiguous at best. Postoperative pain can be present both in patients that exhibit spinal fusion and in those that do not exhibit fusion. Adjacent level degeneration often plagues patients years after spinal fusion because of the increased stress put on the flexible segments next to the fusion.14 This study aimed to evaluate the fusion status of the targeted vertebral levels in study patients as well as compare the levels of postoperative pain in patients who show spinal fusion and those who do not. Finally, the study aimed to evaluate the success of transforaminal lumbar interbody fusion from the perspective of the patients themselves.

Materials and Methods
Potential patients had several inclusion criteria to meet. They must have been at least 4 years postoperatively. They must have had no <3 consecutive lumbar levels fused during the transforaminal lumbar interbody fusion procedure. Operative levels were determined preoperatively by magnetic resonance imaging and diskogram. All patients received iliac crest autograft with interbody cage. No other bone extenders or bone morphogenic proteins were used. The surgery must have been their first transforaminal lumbar interbody fusion procedure. Furthermore, the patients must have sought medical treatment for pain relief by other methods including analgesics and physical therapy before choosing surgery. The surgical procedure was confirmed by both the attending surgeon and by the hospital operation report. Patients were contacted by mail and phone for invitation to participate in the study. Patients were seen between April and October 2003.

During the patient?s visit, three questionnaires were completed. The first was a general and spine-specific health survey, concerning topics such as chronic health problems, the types of treatment sought before choosing spinal fusion, and whether litigation was involved in the original injury. The Oswestry functional capacity evaluation then was completed by the patient, providing the patient?s perspective of their back pain?s effect on their daily activities. This index often is used to quantify the patient?s perceived pain on a percentage disability scale.15 The final questionnaire was a visual analog pain index, indicating the pain level on a visual analog scale (VAS) between 0 and 10. The Oswestry Pain Index and the VAS were compared to scores obtained by the patients prior to their surgery and statistically analyzed using a paired t test to identify any significant differences. In addition, three radiographs were taken at each visit. An independent radiologist determined the fusion status of each patient and evaluated the group?s fusion rate as a whole using flexion, extension, and anteroposterior radiographs. Radiographs had to have <5? of motion on dynamic views and the presence of bony bridging between adjacent vertebrae. If radiolucent lines were visible, the patient was considered not to have a fusion.

The study was comprised of 19 men and 23 women. Mean patient age was 52 years (range: 35-66 years). A statistically significant improvement of mean pre- and postoperative VAS scores from 6.3 to 3.9 (P<.001) occurred. The maximum improvement reported was a 10 point drop in pain. The Figure illustrates the changes in observed pain in patients based on the original pain reported. A statistically significant improvement in Oswestry functional capacity evaluation scores from 40.5% to 30.0% (P<.001) also was noted. The maximum improvement was a 44% drop in perceived disability. Of the 40 patients working preoperatively, 33 (82.5%) patients returned to work. Twenty-three (69.7%) of those returned to the same job.

Thirteen (31.0%) of the 42 patients who underwent spinal fusion had complications related to their transforaminal lumbar interbody fusion. Six (14.3%) patients had complete or partial hardware removal postoperatively. Two (4.8%) patients had additional surgery to relieve their pain. Five (11.9%) patients experienced complications such as postoperative superficial infection, hardware loosening, and/or numbness. No deep infection or injury to the neurovascular structures occurred.

Of the 42 study patients, 3 radiographs were not evaluated because of poor film quality. Of the remaining 39 patients, 25 (64.1%) patients had fusion observed in their targeted vertebral segments. Thirteen (33.3%) patients did not demonstrate fusion; however, no motion >5? was seen across the vertebral space because of the hardware support. One (2.6%) patient demonstrated movement in the operative levels.

This study aimed to evaluate whether solid fusion across the vertebral space is necessary for pain relief. The two major radiological groups, patients with fusion and those with no fusion and no movement, exhibited different levels of postoperative pain. Patients with fusion recorded an average pain level one point below the average pain level for those patients with no fusion and no movement (3.3 versus 4.3), but the difference was not statistically significant. The average disability scores provided by the Oswestry Pain Index for the two groups were similar (27.5 versus 29.2) also with no significant difference.

Of 42 patients, 36 (85.7%) indicated that they would have surgery again, 4 (9.5%) would not choose the surgery again, and 2 (4.8%) had some reservations about the procedure or the recovery involved.

As indicated by the results, the average patient had a moderate improvement in both pain relief and perceived physical disability; however, these statistics somewhat minimize the overall improvement shown by the average patient. Many patients made tremendous improvements in pain relief and perceived physical disability. However, some patients made no progress or perceived their pain as worse than before their surgery. This small group of patients minimized the pain relief and the improvement in perceived physical disability shown by the group as a whole, lowering the overall averages to a 2.4 point drop in perceived pain and to a 10.5% improvement in physical disability.

The Figure illustrates that this surgery is most effective for treating patients with higher pain levels. Patients with higher initial pain levels showed more improvement than those who exhibited lower pain levels and elected to have surgery. Physicians should note that patients who exhibit higher levels of pain are good candidates for this particular surgery. Physicians whose patients perceive their pain at levels <5 on a 0-10 scale should consider that there may not be a large improvement in these patients? pain; postoperative pain may be greater than the original pain in these patients.

Figure: Levels of perceived pain before and after transforaminal interbody lumbar fusion for each initial pain level. All patients reporting a certain pain level before surgery were compiled into a single group based on their preoperative pain level. Their pain levels post-transforaminal interbody lumbar fusion were averaged and recorded to establish the degree of improvement for each level of preoperative pain. The value above each column indicates the number of patients in each group.

Several possible explanations exist for why a number of patients did not improve with the transforaminal lumbar interbody fusion surgery. First, many patients had health conditions that are detrimental to full spine and nerve recovery. Several patients had chronic health conditions such as diabetes and Morton?s neuroma. Some patients had other back surgeries prior to transforaminal lumbar interbody fusion. Many of these patients acknowledged that they could not distinguish between some of their chronic medical problems and their perceived back pain. Second, nine of the transforaminal lumbar interbody fusion patients currently smoked, and an additional 11 smoked for a long time prior to the study. Nicotine is known to disrupt the microvasculature and inhibit subsequent bone remodeling needed for fusion to occur.16,17 Third, 10 patients had litigation related to the original incident for which they were receiving transforaminal lumbar interbody fusion as a treatment for pain. Patients involved with litigation have been reported to recover slower and improve less than patients who are not involved in litigation concerning their injury.18

A large number of patients (31.0%) experienced complications related to their transforaminal lumbar interbody fusion. Many of these complications (ie, postoperative wound infection) can be attributed to the invasive nature of the surgery and the length of wound exposure (approximately three hours in an average case). Two cases of nerve irritation and numbness were reported as postoperative complications, but these cases should not be considered complications of the transforaminal lumbar interbody fusion surgery. One patient reported that numbness in the left leg was not relieved by the surgery and one patient reported that the surgery coincided with numbness and loss of feeling in his right arm, although he did not have any cervical trauma or procedures that coincided with his transforaminal lumbar interbody fusion. No other cases of nerve irritation were reported, emphasizing one of the positive aspects of the transforaminal approach of this surgery.

It should be noted that although a large number of patients experienced complications, the majority of these patients would have chosen the surgery again, despite the recovery and postoperative problems they experienced.

Of the 39 patients evaluated radiographically, 14 (35.9%) patients showed no fusion in their targeted vertebral levels. This rate of pseudoarthrosis is higher than other recent publications on fusion rates for transforaminal lumbar interbody fusion. One possible explanation for this is the criteria chosen in this study to define fusion. Patients had to have <5? of motion on dynamic radiographs as well as solid bridging bone between adjacent vertebrae. Patients with radiolucent lines were considered not fused. This fusion criteria was more strict than that used in many previous studies that have reported fusion rates of 89%-100%.19,20 Twenty-five (64.1%) of 39 patients were considered to have a solid fusion based on our criteria. Another 13 (33.3%) of 39 patients had <5? of motion, but were not considered fused due to the presence of radiolucent lines. If fusion criteria were based solely on having <5? of motion 38 (97.4%) of 39 patients would have been graded as fused. Additionally, both smoking and chronic health problems could impair bone arthrodesis just as they could limit improvement in pain and perceived physical disability.

The current data demonstrate no significant difference between patients who undergo fusion and those who do not in terms of pain or disability scores. Ideally, transforaminal lumbar interbody fusion would lead to all targeted vertebral levels achieving solid fusion; however, physicians can expect that patients without solid fusion can still achieve improvements in pain and disability. Fusion is not necessary for a positive surgical outcome. Furthermore, of the 39 evaluated patients, only 1 patient exhibited motion in any targeted vertebral level. This data supports the use of transforaminal lumbar interbody fusion as a method to stabilize the spine.

Transforaminal lumbar interbody fusion is an effective method for controlling intractable back pain, especially in patients who exhibit high pain levels. Most patients show an improvement in both their pain levels and in their perceived physical disability over a long-term period. Furthermore, the vast majority of patients who elected to have the surgery felt the risk, recovery time, and potential complications involved were well worth the relief provided by the surgery. This study illustrates that transforaminal lumbar interbody fusion can provide long-term pain relief. The positive long-term effects of this surgery confirm its status as an acceptable option for treating intractable back pain.

What is already known on this topic
Posterior lumbar interbody fusion allows for 3608 fusion of the spine, but is limited to L3-S1.
Transforaminal lumbar interbody fusion has good short-term results with significantly less blood loss and risk to neurovascular structures than posterior lumbar interbody fusion.

What this article adds
Transforaminal lumbar interbody fusion provides good long-term pain relief for patients with moderate to severe back pain.
Solid radiographic fusion is not necessary for clinically successful outcomes

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