Salvador A. Brau

Mini-open approach to the spine for anterior lumbar interbody fusion: description of the procedure, results and complications

BACKGROUND CONTEXT Since the introduction of threaded devices in the mid-1990s, anterior lumbar interbody fusion (ALIF) has become a staple in the armamentarium of the spine surgeon. The procedure, however, is heavily dependent on the ability of the approach surgeon to provide exposure quickly and safely in view of a reported incidence of vascular injury as high as 15% and 2.3% incidence of retrograde ejaculation. PURPOSE This study describes a mini-open approach to the lumbar spine and discusses the results and the complications seen. STUDY DESIGN/SETTING The study was designed to evaluate patients for possible complications of the approach while they were in the hospital undergoing ALIF. They were also followed for 6 months after the operation. PATIENT SAMPLE A total of 686 approaches to the lumbar spine performed on 684 patients between August 1997 and December 2000 were reviewed concurrently and retrospectively. OUTCOME MEASURES All complications of the approach were reported. These included vascular injury, retrograde ejaculation, deep vein thrombosis (DVT), pulmonary emboli, infection, wound disruption/hernia, ileus, hematoma, myocardial infarction, stroke, peripheral ischemia, rectus muscle paralysis, aborted cases and death. METHODS The patients were observed in the perioperative period and for 6 months postoperatively to determine the occurrence of complications related to the approach. The data collected included age, weight, gender, levels approached, time of completion of the approach, size of incision and complications. RESULTS There were six arterial injuries (0.8%), six venous injuries (0.8%) and one instance of retrograde ejaculation (0.1%). In addition, there were seven cases that developed DVT (two ileofemoral and five calf-popliteal, 1.0%), four cases of ileus lasting more than 3 days (0.6%), three wound infections above the fascia (0.4%), two hernias and two compartment syndromes. There was one myocardial infarction and one death. No rectus muscle paralysis occurred. CONCLUSIONS This experience suggests that a well-planned small incision that preserves the musculature can be performed quickly and safely to allow the spine surgeon adequate access to the anterior lumbar spine. The learning curve, however, can be high even for experienced surgeons.

Nerve monitoring changes related to iliac artery compression during anterior lumbar spine surgery

BACKGROUND CONTEXT There are no studies in the literature that correlate compression of the iliac vessels resulting in obstruction of blood flow with changes in nerve monitoring parameters during anterior lumbar surgery. PURPOSE To determine whether there is significant compression of the iliac vessels that can cause temporary nerve root ischemia or limb ischemia that could be responsible for loss of somatosensory evoked potentials (SSEP) while retractors are in place for exposure during anterior lumbar interbody fusion (ALIF). SETTING Patients coming to the operating room for ALIF from levels L2-L3 to L5-S1 would be studied for nerve monitoring changes during the procedure with particular attention to the intervals just before placement of a retractor, while the retractor was in place and immediately after removal of the retractor. PATIENT SAMPLE Forty-five consecutive patients were studied for changes in SSEP and oxygen saturation (SaO(2)) while undergoing ALIF. OUTCOME MEASURES Patients were considered to have lost saturation if the SaO(2) decreased to below 90%. Patients were considered to have abnormal SSEP with any increase in latency and decrease in amplitude. METHODS SSEP and SaO(2) were monitored continuously and simultaneously before exposure of the disc spaces, during exposure with retractors in place and after removal of the retractors. RESULTS Thirteen of 23 patients with exposure at L4-L5 had both loss of SSEP signals and loss of SaO(2) with exposure. All 13 patients had return to normal saturation and recovery of the SSEP signals within 15 minutes of removal of the retractors. Both of these are significant correlations (p<.001). CONCLUSION This study showed that the majority (57%) of patients undergoing ALIF at the L4-L5 level are subject to compression of the left iliac vessels enough to cause desaturation distally as measured by pulse oxymetry. This vascular compromise, as well as the return to normal saturation, correlates with changes noted in SSEP soon after both deployment and removal of the retractors used for exposure. The mechanism appears to be a transient ischemic response. Failure of the SSEP signals to recover may be diagnostic of left iliac artery thrombosis.

Bilateral implantation of low-profile interbody fusion cages: subsidence, lordosis, and fusion analysis

BACKGROUND CONTEXT The use of interbody fusion cages as a treatment for degenerative disc disease has become widespread. Low-profile cages have been developed to allow a closer fit when implanting bilateral cages in patients with smaller vertebral bodies. Some surgeons feel the open design also allows better bone contact and visualization. This is particularly true when two low-profile cages are used adjacent to one another. Because of the open design of low-profile interbody fusion cages, there has been concern regarding such issues as subsidence, lordosis and fusion rates. PURPOSE This retrospective review of paired bilateral reduced profile interbody fusion cages was completed to assess changes in subsidence, lordosis and fusion. As a secondary goal, patient outcomes were measured to determine overall health since surgery and the patients satisfaction with the spine surgery, in an attempt to assess the effect of the outcome variables cited supra. STUDY DESIGN This was a retrospective evaluation of patients who underwent anterior lumbar interbody fusion with low-profile interbody fusion cages. PATIENT SAMPLE Seventy-one consecutive patients who underwent bilateral implantation of low-profile interbody fusion cages were evaluated. OUTCOME MEASURES A patient self-evaluation, which included a Short Form (SF)-36 and questions regarding patient satisfaction were administered to patients who were at least 1 year postoperative. Subsidence and lordosis measurements were completed. Fusion was assessed by the operating surgeon. METHODS Low-profile interbody fusion cages (BAK/Proximity, Centerpulse Spine-Tech, Inc., Minneapolis, MN) were implanted bilaterally in at least one level from L3-L4 to L5-S1. Most patients had degenerative disc disease with leg and back pain that was not responsive to conservative treatment and demonstrated segmental instability or collapse. A small percentage of patients had either a degenerative spondylolisthesis (7.0%) or an isthmic spondylolisthesis (4.2%). Autograft harvested from the iliac crest was used in all cases. Demographic, surgical and follow-up data were retrospectively collected from patient charts. A clinical outcome questionnaire that included an SF-36 as well as questions regarding patient satisfaction was either mailed to each patient who was at least 1 year postsurgery or given to patients to complete at their 1-year visit. Patients were routinely followed radiographically before surgery, immediately after surgery and at 3, 6, 12 and 24 months after surgery. Fusion was assessed by the operating surgeon using lateral radiographs often in conjunction with a thin-slice computed tomography (CT) scan. Criteria for a successful fusion were lack of motion, anterior bridging bone and lack of lucencies on flexion/extension X-rays and/or contiguous bone through the cage using a thin-cut sagittal CT scan. Lateral X-rays on each patient were also measured for subsidence and lordosis changes. RESULTS A total of 71 patients (45 men, 26 women) with a mean age of 43.4 years (range, 25 to 74) were evaluated. Thirty-six percent of the patients were smokers, and 96% were workers compensation patients. Thirty-two percent of the patients had previous lumbar surgery. A total of 100 operative levels were evaluated. There were 45 one-level, 23 two-level and three three-level cases. Forty-nine percent were level L5-S1, 43% were L4-L5 and 8% were L3-L4. The mean duration of symptoms was 31.5 months. Mean surgical time, mean blood loss and mean hospital stay were 139 minutes, 186 cc and 3.34 days, respectively. There were no intraoperative or postoperative complications attributable to the construct and no cases of cage migration or collapse. Patients who were at least 1-year postsurgery and had follow-up X-rays or had undergone a CT scan at this time point were evaluated for fusion status. Sixty-three patients were assessed for fusion. Fifty-four (86%) of these patients were determined to have a solid fusion. Mean time to fusion was 10 months. Fusion was assessed as solid only if all operative levels were fully fused. Mean subsidence of the anterior region was 1.97 mm, whereas the mean subsidence of the posterior region was 0.82 mm. Lordosis was unchanged at all surgical levels with mean lordosis in L3-L4 decreasing only slightly from 13 degrees before surgery to 12 degrees after surgery. L4-L5 and L5-S1 showed only slight increases in lordosis changing from 17 to 18 degrees at L4-L5 and from 17 to 19 degrees at L5-S1. These changes were not statistically significant. The clinical outcome questionnaires had a return rate of 68%. Of the 48 patients who completed the questionnaire, 75% responded that they were happy with the surgical results and would definitely recommend the surgery to a friend. Sixty-seven percent agreed that surgery met their expectations or that surgery improved their condition enough that they would go through it again for the same outcome. The results of the SF-36 portion of the survey revealed that the physical and mental composite scores were within normal range of the US population that has experienced back pain or sciatica. CONCLUSION Bilateral implantation of low-profile cages in this patient population led to satisfactory outcomes. Subsidence and changes in lordosis were minimal. Fusion rates were good, especially for one-level cases. Patient satisfaction was relatively high, considering the population consisted of 96% workers compensation cases. With proper surgical technique, bilateral low-profile cages can be used effectively to treat patients with degenerative disc disease.

Access Strategies for Revision in Anterior Lumbar Surgery

Study Design. Sixty-two consecutive patients undergoing anterior lumbar revision surgery from February 2000 to September 2007 were evaluated for approach strategies and complications. Objective. To determine the incidence of complications in these patients and to make recommendations on future revisions based on the results obtained. Summary of Background Data. Only 2 articles exist in the literature that address this situation and they have widely varying results in a small number of patients. This larger series may help give more certainty to the expectations for complications in patients undergoing revision anterior lumbar surgery. Methods. A concurrent database was maintained on these 62 consecutive patients. Preoperative strategies were evaluated and complications were tabulated as they occurred and later analyzed to arrive at recommendations for future similar cases. Results. Twenty-three patients had the same level revised and 39 patients had adjacent levels operated on. There were 3 venous injuries (4.8%), 3 arterial injuries (4.8%), and 1 ureteral injury (1.6%). All 3 arterial injuries occurred while approaching L3–L4 after L4 to S1 prior fusion or disc replacement. All 3 venous injuries and the ureteral injury occurred while approaching a previously operated level or levels. Six of these patients had the injuries repaired and the procedures completed with full recovery. One L5–S1 revision had the procedure aborted after a venous injury. There were no deaths. Conclusion. Although the incidence of complications in revisions is much greater than for index cases, the actual percentage of venous, arterial, and ureteral complications is certainly acceptable for patients who must have this type of surgery. Only very experienced access surgeons should attempt revision surgery.