Adhesion Improvement of Solvent-Free Pressure-Sensitive Adhesives by Semi-IPN Using Polyurethanes and Acrylic Polymers.

To improve the peel strength and holding time of polypropylene glycol (PPG)-based pressure-sensitive adhesives (PSAs), a semi-interpenetrating polymer network (semi-IPN) was prepared using acrylic polymers. In addition, to prevent air pollution due to volatile organic compound emissions and avoid the degradation of physical properties due to a residual solvent, the PPG-based semi-IPN PSAs were fabricated by an eco-friendly solvent-free method using an acrylic monomer instead of an organic solvent. PPG-based semi-IPN PSAs with different hard segment contents (2.9-17.2%) were synthesized; their holding time was found to depend on the hard segment contents. The peel strength was improved because of the formation of the semi-IPN structure. Moreover, the high degree of hard domain formation in the semi-IPN PSA, derived from the increase in the hard segment content using a chain extender, resulted in a holding time improvement. We believe that the as-prepared PSAs can be used in various applications that require high creep resistance.

Transdural Nerve Rootlet Entrapment in the Intervertebral Disc Space through Minimal Dural Tear : Report of 4 Cases.

Four patients underwent lumbar surgery. In all four patients, the dura was minimally torn during the operation. However, none exhibited signs of postoperative cerebrospinal fluid leakage. In each case, a few days after the operation, the patient suddenly experienced severe recurring pain in the leg. Repeat magnetic resonance imaging showed transdural nerve rootlets entrapped in the intervertebral disc space. On exploration, ventral dural tears and transdural nerve rootlet entrapment were confirmed. Midline durotomy, herniated rootlet repositioning, and ventral dural tear repair were performed, and patients' symptoms improved after rootlet repositioning. Even with minimal dural tearing, nerve rootlets may become entrapped, resulting in severe recurring symptoms. Therefore, the dural tear must be identified and repaired during the first operation.

Changes in the cross-sectional area of multifidus and psoas in unilateral sciatica caused by lumbar disc herniation.

OBJECTIVE: To quantitatively evaluate the asymmetry of the multifidus and psoas muscles in unilateral sciatica caused by lumbar disc herniation using magnetic resonance imaging (MRI). METHODS: Seventy-six patients who underwent open microdiscectomy for unilateral L5 radiculopathy caused by disc herniation at the L4-5 level were enrolled, of which 39 patients (51.3%) had a symptom duration of 1 month or less (group A), and 37 (48.7%) had a symptom duration of 3 months or more (group B). The cross-sectional areas (CSAs) of the multifidus and psoas muscles were measured at the mid-portion of the L4-5 disc level on axial MRI, and compared between the diseased and normal sides in each group. RESULTS: The mean symptom duration was 0.6±0.4 months and 5.4±2.7 months for groups A and B, respectively (p<0.001). There were no differences in the demographics between the 2 groups. There was a significant difference in the CSA of the multifidus muscle between the diseased and normal sides (p<0.01) in group B. In contrast, no significant multifidus muscle asymmetry was found in group A. The CSA of the psoas muscle was not affected by disc herniation in either group. CONCLUSION: The CSA of the multifidus muscle was reduced by lumbar disc herniation when symptom duration was 3 months or more.

Carbon dioxide (CO2) laser-assisted microdiscectomy for extraforaminal lumbar disc herniation at the L5-S1 level.

OBJECTIVE: The purpose of this study was to analyze the surgical outcomes of carbon dioxide (CO(2)) laser-assisted microdiscectomy for extraforaminal lumbar disc herniations (EFLDH) at the L5-S1 level. BACKGROUND DATA: Microdiscectomy via the lateral transmuscular route is beneficial for treating EFLDH at the L5-S1 level. However, this technique may not effectively remove concomitant foraminal lumbar disc herniation (FLDH), resulting in persistent leg pain and a necessity for revision surgery. CO(2) laser-assisted microdiscectomy could be an effective alternative, as it enables effective decompression of EFLDH as well as of the accompanying FLDH, despite a narrow operative window. METHODS: Thirty-one consecutive patients with EFLDH at the L5-S1 level who underwent CO(2) laser-assisted microdiscectomy via the lateral transmuscular route were prospectively enrolled. Clinical outcomes were assessed 1 year after surgery by using the visual analogue scale (VAS) scores, Oswestry Disability Index (ODI), and patient's subjective satisfaction rate. RESULTS: Of the 31 patients, 10 were male and 21 were female, with a mean age at surgery of 62.2 years. All patients showed improvement in leg pain immediately after surgery. Transient dysesthesia developed in one patient. Of the 28 patients (90.3%) followed for a 1-year period, the mean VAS for back pain and leg pain, as well as the mean ODI, decreased significantly from 5.2, 8.3, and 60.7% to 2.6, 1.8, and 18.1%, respectively. The mean subjective satisfaction rate was 75.7%. Clinical success was observed in 27 patients (96.4%), and reherniation occurred in one patient (3.6%). No patient underwent reoperation for reherniation or segmental instability. CONCLUSIONS: CO(2) laser-assisted microdiscectomy for EFLDH at the L5-S1 level showed satisfactory surgical results at the 1-year follow-up.

Postoperative spinal epidural hematoma after microscopic lumbar decompression: a prospective magnetic resonance imaging study in 89 patients.

STUDY DESIGN: A prospective case series. OBJECTIVE: To prospectively analyze the incidence, characteristics, clinical outcomes, and risk factors of postoperative spinal epidural hematoma (SEH) after microscopic lumbar decompression using magnetic resonance imaging (MRI). SUMMARY OF BACKGROUND DATA: Studies prospectively focusing on postoperative SEH after microscopic lumbar decompression alone are rare. METHODS: Eighty-nine patients who underwent microscopic lumbar decompressive surgery for herniated disc and/or stenosis between January 2007 and June 2007 were prospectively followed. Decompression was carried out using unilateral or bilateral laminotomy in all patients. Postoperative MRI was taken at 24 hours after surgery in all patients. Using operative report, chart, and MRI, the incidence, characteristics, and risk factors of postoperative SEH were evaluated. Clinical outcomes were evaluated 2 years after surgery using Visual Analogue Scale score and Oswestry Disability Index. RESULTS: Postoperative SEH developed in 13 patients (14.6%). There were 5 males and 8 females. The mean age of these patients was 57.1 years. Postoperative SEH occurred at the index level in 6 cases, and at the index level with extension toward non-decompressed adjacent levels in 7 cases. Eleven patients were asymptomatic and 2 patients complained of leg pain and/or mild weakness. No patients underwent revision surgery owing to postoperative SEH. There was no significant difference in improvements of Visual Analogue Scale and ODI scores, and clinical success rate between patients with and without SEH. Patient's age 50 years old or more was the only significant risk factor for the development of postoperative SEH (P=0.024; odds ratio=5.12). CONCLUSIONS: The incidence of postoperative SEH after microscopic lumbar decompressive surgery was 14.6%. Postoperative SEH did not delay clinical improvements. Age 50 years old or more was strongly associated with the development of postoperative SEH.

Asymptomatic Cervical or Thoracic Lesions in Elderly Patients who Have Undergone Decompressive Lumbar Surgery for Stenosis.

STUDY DESIGN: A retrospective study. PURPOSE: To evaluate the prevalence and risk factors of asymptomatic cervical or thoracic lesions in elderly patients who have undergone surgery for lumbar spinal stenosis. OVERVIEW OF LITERATURE: Concurrent multiple spinal lesions have been reported in many studies with a varied prevalence, and described the characteristics of the disease and its treatment options. However, the cervical or thoracic lesions without apparent symptoms in patients with symptomatic lumbar stenosis had not been evaluated. METHODS: A total of 101 elderly patients (aged 65 or more), who had undergone surgery for lumbar spinal stenosis from January 2005 to December 2005, were enrolled in this study. All patients underwent lumbar magnetic resonance imaging (MRI) along with T2-weighted cervical and thoracic sagittal MRI prior to surgery. The concurrent cervical or thoracic lesions were classified according to the disease entity, and the severity of the lesions was graded from grade 0 (no lesion) to grade 4 (any lesion compressing the cord with a signal change). The prevalence of concurrent cervical and thoracic lesions was then analyzed. In addition, the risk factors for the development of concurrent lesions were evaluated, and the risk factors affecting the severity of the concurrent lesion were analyzed individually. RESULTS: Seventy-seven (76.2%) and 30 (29.7%) patients had a concurrent cervical and thoracic lesion, respectively. Twenty-six patients (25.7%) had both a cervical and thoracic lesion. There was a positive correlation between the symptom duration of lumbar stenosis and the prevalence of both cervical (p = 0.044) and thoracic (p = 0.022) lesions. CONCLUSIONS: The incidence of asymptomatic cervical or thoracic lesions is apparently high in elderly patients who have undergone surgery for lumbar spinal stenosis, particularly in those with longer symptom duration. This highlights the need for a preoperative evaluation of the cervical and thoracic spine in these patients.

Two-level anterior lumbar interbody fusion with percutaneous pedicle screw fixation: a minimum 3-year follow-up study.

The clinical and radiological outcomes of two-level anterior lumbar interbody fusion (ALIF) with percutaneous pedicle screw fixation (PSF) were evaluated in 24 consecutive patients who underwent two-level ALIF with percutaneous PSF for segmental instability and were followed up for more than 3 years. Clinical outcomes were assessed using a visual analogue scale (VAS) score and the Oswestry Disability Index (ODI). Sagittal alignment, bone union, and adjacent segment degeneration (ASD) were assessed using radiography and magnetic resonance imaging. The mean age of the patients at the time of operation was 56.3 years (range 39-70 years). Minor complications occurred in 2 patients in the perioperative period. At a mean follow-up duration of 39.4 months (range 36-42 months), VAS scores for back pain and leg pain, and ODI score decreased significantly (from 6.5, 6.8, and 46.9% to 3.0, 1.9, and 16.3%, respectively). Clinical success was achieved in 22 of the 24 patients. The mean segmental lordosis, whole lumbar lordosis, and sacral tilt significantly increased after surgery (from 25.1 degrees , 39.2 degrees , and 32.6 degrees to 32.9 degrees , 44.5 degrees , and 36.6 degrees , respectively). Solid fusion was achieved in 21 patients. ASD was found in 8 of the 24 patients. No patient underwent revision surgery due to nonunion or ASD. Two-level ALIF with percutaneous PSF yielded satisfactory clinical and radiological outcomes and could be a useful alternative to posterior fusion surgery.

Anterior bone cement augmentation in anterior lumbar interbody fusion and percutaneous pedicle screw fixation in patients with osteoporosis.

OBJECT: The purpose of the present study was to evaluate the efficacy of anterior polymethylmethacrylate (PMMA) cement augmentation in instrumented anterior lumbar interbody fusion (ALIF) for patients with osteoporosis. METHODS: Sixty-two patients with osteoporosis who had undergone single-level instrumented ALIF for spondylolisthesis and were followed for more than 2 years were included in the study. The patients were divided into 2 groups: instrumented ALIF alone (Group I) and instrumented ALIF with anterior PMMA augmentation (Group II). Sixty-one patients were interviewed to evaluate the clinical results, and plain radiographs and 3D CT scans were obtained at the last follow-up in 46 patients. RESULTS: The mean degree of cage subsidence was significantly higher in Group I (19.6%) than in Group II (5.2%) (p = 0.001). The mean decrease of vertebral body height at the index level was also significantly higher in Group I (10.7%) than in Group II (3.9%) (p = 0.001). No significant intergroup differences were observed in the incidence of radiographic adjacent-segment degeneration (ASD) or in terms of pain and functional improvement. The incidences of clinical ASD (23% in Group I and 10% in Group II) were not significantly different. There was 1 case of nonunion and 3 cases of screw migration in Group I, but none resulted in implant failure. CONCLUSIONS: Anterior PMMA augmentation during instrumented ALIF in patients with osteoporosis was useful to prevent cage subsidence and vertebral body collapse. In addition, PMMA augmentation did not increase the nonunion rate and incidence of ASD.

L2 radicular compression caused by a foraminal extradural gas pseudocyst.

Gas pseudocysts are a rare cause of lumbar radiculopathy and most symptomatic gas pseudocysts are found within the confines of the spinal canal. A gas pseudocyst in the foramen causing lumbar radiculopathy is very rare. We present a case of a 67-year-old woman suffering from severe pain in the right leg. Computed tomography and magnetic resonance imaging revealed a gas pseudocyst compressing the L2 root at the right L2-3 foramen. The patient underwent cyst excision using the lateral transmuscular approach and her leg pain was improved after the operation.

Adjacent segment disease after interbody fusion and pedicle screw fixations for isolated L4-L5 spondylolisthesis: a minimum five-year follow-up.

STUDY DESIGN: A retrospective study. OBJECTIVE: The purpose of this study are (1) to analyze prevalence of clinical and radiologic adjacent segment diseases (ASD), (2) to find precipitating factor of clinical ASD in each isthmic and degenerative spondylolisthesis groups, and (3) to compare clinical and radiologic change in isthmic and degenerative spondylolisthesis. SUMMARY OF BACKGROUND DATA: There is no clinical report regarding the use of magnetic resonance imaging (MRI) for evaluating ASD in patient who underwent 360° fusion with single-level spondylolisthesis with healthy adjacent segment. METHODS: A total of 69 patients who underwent instrumented single-level interbody fusion at the L4-L5 level and showed no definitive degenerated disc in adjacent segments on preoperative MRI and plain radiographs were evaluated at more than 5 years after surgery. The patients were divided into 2 groups: group I was isthmic spondylolisthesis patients and group II was degenerative spondylolisthesis patients. The radiologic ASD was diagnosed by plain radiographs and MRI. Clinical ASD is defined as symptomatic spinal stenosis, intractable back pain, and subsequent sagittal or coronal imbalance with accompanying radiographic changes. Symptomatic spinal stenosis was defined as stenosis diagnosed by MRI and combined with neurologic claudication. RESULTS: The prevalence of radiologic ASD on group I and group II was 72.7% and 84.0%, respectively. About 7 (15.9%) patients showed clinical ASD in group I and 6 (24.0%) patients showed clinical ASD in group II. MRI showed significant reliability for diagnosis of clinical ASD. Compared with patients with asymptomatic ASD, patients with clinical ASD showed significantly less postoperative lordotic angle at the L4-L5 level (i.e., less than 20°) in both groups. CONCLUSION: Maintaining postoperative L4-L5 segmental lordotic angle at about 20° or more is important for prevention of clinical ASD in single-level 360° fusion operation. MRI is reliable method for diagnosing clinical ASD.

Computed tomography fluoroscopy-guided selective nerve root block for acute cervical disc herniation.

OBJECTIVE: To analyze the clinical outcomes of computed tomography (CT) fluoroscopy-guided selective nerve root block (SNRB) for severe arm pain caused by acute cervical disc herniation. METHODS: The authors analyzed the data obtained from 25 consecutive patients who underwent CT fluoroscopy-guided SNRB for severe arm pain, i.e., a visual analogue scale (VAS) score of 8 points or more, caused by acute soft cervical disc herniation. Patients with chronic arm pain, motor weakness, and/or hard disc herniation were excluded. RESULTS: The series comprised 19 men and 6 women whose mean age was 48.1 years (range 35-72 years). The mean symptom duration was 17.5 days (range 4-56 days) and the treated level was at C5-6 in 13 patients, C6-7 in 9, and both C5-6 and C6-7 in 3. Twenty-three patients underwent SNRB in 1 session and 2 underwent the procedure in 2 sessions. No complications related to the procedures occurred. At a mean follow-up duration of 11.5 months (range 6-22 months), the mean VAS score and NDI significantly improved from 9 and 58.2 to 3.4 and 28.1, respectively. Eighteen out of 25 patients (72%) showed successful clinical results. Seven patients (28%) did not improve after the procedure, and 5 of these 7 underwent subsequent anterior cervical discectomy and fusion. CONCLUSION: CT fluoroscopy-guided SNRB may play a role as a primary conservative treatment for severe arm pain caused by acute cervical disc herniation.

Cervicothoracic spinal epidural hematoma after anterior cervical spinal surgery.

The purpose of this case report is to describe a rare case of a cervicothoracic spinal epidural hematoma (SEH) after anterior cervical spine surgery. A 60-year-old man complained of severe neck and arm pain 4 hours after anterior cervical discectomy and fusion at the C5-6 level. Magnetic resonance imaging revealed a postoperative SEH extending from C1 to T4. Direct hemostasis and drainage of loculated hematoma at the C5-6 level completely improved the patient's condition. When a patient complains of severe neck and/or arm pain after anterior cervical spinal surgery, though rare, the possibility of a postoperative SEH extending to non-decompressed, adjacent levels should be considered as with our case.

Radiologically documented adjacent-segment degeneration after cervical arthroplasty: characteristics and review of cases.

BACKGROUND: The authors retrospectively studied the incidence and characteristics of radiologically documented adjacent-segment degeneration after single-level diskectomy and subsequent cervical arthroplasty using the Bryan (Medtronic Sofamor Danek; Memphis, TN) disk prosthesis. METHODS: Seventy-two patients with single-level arthroplasty using the Bryan cervical disk prosthesis were evaluated. Radiological evidence of adjacent-disk disease included new formation or enlargement of anterior osteophyte, new or increasing ALL calcification, or narrowing of disk space documented on serial plain radiographs. We reported the characteristics of adjacent-segment degeneration and reviewed all of the cases. RESULTS: Among the 72 patients, 9 patients (12.5%) showed radiological evidence of adjacent-segment degeneration. The mean age was 43.3 years old, with a male-female ratio 1:3. The mean follow-up period was 24.2 (12.1-35.9) months. The mean period of onset was 16.3 months. Upper-segment degeneration was documented in 4 cases (3 new osteophyte, 1 enlargement of osteophyte), whereas lower-segment degeneration was noted in 5 cases (1 new osteophyte, 3 enlargement of osteophyte, 1 decreased disk height). Among the degenerated cases, 4 cases (44.4%) also showed various degrees of HO. CONCLUSIONS: The rate of adjacent-segment degeneration was higher than that observed in previous studies. Adjacent-segment degeneration documented a tendency toward HO. A longer follow-up period is necessary to investigate and document the different types of degeneration seen at levels adjacent to artificial Bryan cervical disk prostheses.

Effect of anthropometric features on the severity of lumbar disk herniation.

Normal standing body height, body weight, and body mass index were measured in 256 patients with severe lumbar disk herniation who underwent surgery and compared with those of matched controls with mild lumbar disk herniation who showed improvement of symptoms after conservative treatment. Statistical analysis was performed using the paired sample t test and analysis of covariance test. Body weight and body mass index were significantly higher in women with severe lumbar disk herniation than in those with mild lumbar disk herniation (p=0.01 and p=0.01, respectively), but not in men. Standing body height showed no significant difference between patients with severe and mild lumbar disk herniations in both sex groups. Differences in body weight and body mass index may be key factors distinguishing the development of severe lumbar disk herniation from that of mild lumbar disk herniation in women.

Effects of facet tropism and disk degeneration on far lateral lumbar disk herniation: comparison with posterolateral lumbar disk herniation.

Differences in facet tropism and disk degeneration were investigated as key factors distinguishing the development of far lateral lumbar disk herniation from that of posterolateral lumbar disk herniation in 46 patients with far lateral lumbar disk herniation individually matched with 46 patients with posterolateral lumbar disk herniation. Preoperative standing body height, body weight, and body mass index were compared. Facet tropism was measured using computed tomography and disk degeneration was evaluated using magnetic resonance imaging. Mean body mass index showed a significant difference between patients with the far lateral and posterolateral lumbar disk herniation (24.9 +/- 2.7 vs. 23.7 +/- 2.3 kg/m(2), p = 0.04). However, no significant differences were found in standing body height and body weight, facet tropism, or disk degeneration between two groups. Neither facet tropism nor disk degeneration are involved in distinguishing the development of far lateral lumbar disk herniation from that of posterolateral lumbar disk herniation.

Comparison of percutaneous endoscopic lumbar discectomy and open lumbar microdiscectomy for recurrent disc herniation.

OBJECTIVE: The purpose of this study was to compare clinical and radiological outcomes of percutaneous endoscopic lumbar discectomy (PELD) and open lumbar microdiscectomy (OLM) for recurrent disc herniation. METHODS: Fifty-four patients, who underwent surgery, either PELD (25 patients) or repeated OLM (29 patients), due to recurrent disc herniation at L4-5 level, were divided into two groups according to the surgical methods. Excluded were patients with sequestrated disc, calcified disc, severe neurological deficit, or instability. Clinical outcomes were assessed using Visual Analogue Scale (VAS) score and Oswestry Disability Index (ODI). Radiological variables were assessed using plain radiography and/or magnetic resonance imaging. RESULTS: Mean operating time and hospital stay were significantly shorter in PELD group (45.8 minutes and 0.9 day, respectively) than OLM group (73.8 minutes and 3.8 days, respectively) (p < 0.001). Complications occurred in 4% in PELD group and 10.3% in OLM group in the perioperative period. At a mean follow-up duration of 34.2 months, the mean improvements of back pain, leg pain, and functional improvement were 4.0, 5.5, and 40.9% for PELD group and 2.3, 5.1, and 45.0% for OLM group, respectively. Second recurrence occurred in 4% after PELD and 10.3% after OLM. Disc height did not change after PELD, but significantly decreased after OLM (p = 0.0001). Neither sagittal rotation angle nor volume of multifidus muscle changed significantly in both groups. CONCLUSION: Both PELD and repeated OLM showed favorable outcomes for recurrent disc herniation, but PELD had advantages in terms of shorter operating time, hospital stay, and disc height preservation.

Microdecompression for extraforaminal L5-s1 disc herniation; the significance of concomitant foraminal disc herniation for postoperative leg pain.

OBJECTIVE: To analyze the relationship of concomitant foraminal lumbar disc herniation (FLDH) with postoperative leg pain after microdecompression for extraforaminal lumbar disc herniation (EFLDH) at the L5-S1 level. METHODS: Sixty-five patients who underwent microdecompression for symptomatic EFLDH at the L5-S1 level were enrolled. According to the severity of accompanying FLDH, EFLDH was classified into four categories (Class I : no FLDH; Class II : mild to moderate FLDH confined within a lateral foraminal zone; Class III : severe FLDH extending to a medial foraminal zone; Class IV : Class III with intracanalicular disc herniation). The incidence of postoperative leg pain, dysesthesia, analgesic medication, epidural block, and requirement for revision surgery due to leg pain were evaluated and compared at three months after initial surgery. RESULTS: The incidences of postoperative leg pain and dysesthesia were 36.9% and 26.1%, respectively. Pain medication and epidural block was performed on 40% and 41.5%, respectively. Revision surgery was recommended in six patients (9.2%) due to persistent leg pain. The incidences of leg pain, dysesthesia, and requirement for epidural block were higher in Class III/IV, compared with Class I/II. The incidence of requirement for analgesic medication was significantly higher in Class III/IV, compared with Class I/II (p=0.02, odds ratio=9.82). All patients who required revision surgery due to persistent leg pain were included in Class III/IV. CONCLUSION: Concomitant FLDH seems related to postoperative residual leg pain after microdecompression for EFLDH at the L5-S1 level.

Extraforaminal lumbar synovial cyst causing sudden foot drop: case report.

A 52-year-old female presented with extraforaminal lumbar synovial cyst at the L4-5 level causing sudden foot drop on the right. Computed tomography, magnetic resonance (MR) imaging, and coronal MR myelography source images identified the cystic mass in the extraforaminal zone. The patient underwent microdecompression via a lateral transmuscular route, and the extraforaminal cyst compressing L4 ganglion was successfully removed. The histological diagnosis was synovial cyst. This unique case of surgically proven extraforaminal lumbar synovial cyst causing sudden foot drop indicates that extraforaminal synovial cyst should be included in the differential diagnosis of patients presenting with sudden foot drop.

Single-level instrumented mini-open transforaminal lumbar interbody fusion in elderly patients.

OBJECT: The purpose of this study was to analyze the surgical outcomes in cases involving elderly patients who underwent single-level instrumented mini-open transforaminal lumbar interbody fusion (TLIF). METHODS: The authors performed a retrospective review of 27 consecutive cases involving elderly patients (> or = 65 years of age) who underwent single-level instrumented mini-open TLIF and were followed up for at least 3 years. Degenerative spondylolisthesis was diagnosed in 16 patients, stenosis with instability in 8, and lytic spondylolisthesis in 3. All cases were Grade I or II based on the American Society of Anesthesiologists' classification system. Clinical outcomes were assessed using a visual analog scale, the Oswestry Disability Index, and patients' subjective satisfaction. Sagittal balance, bone union, and adjacent segment degeneration (ASD) were assessed using plain radiography and 3D CT. RESULTS: The mean age of patients at the time of surgery was 69.3 years (range 65-80 years). Minor complications occurred in 2 patients (7.4%) in the perioperative period. At a mean follow-up duration of 38.6 months (range 36-42 months), clinical success was achieved in 88.9% of cases. The mean segmental lordosis and sacral tilt significantly increased after surgery (from 11.9 and 33.5 degrees to 13.9 and 37.2 degrees , p = 0.024 and p = 0.001, respectively). Solid fusion was achieved in 77.8% of the patients. Adjacent segment deterioration was found in 44.4% of the patients. No patients underwent revision surgery due to nonunion or ASD. The development of ASD was significantly related to postoperative sacral tilt (p = 0.006). CONCLUSIONS: Single-level instrumented mini-open TLIF yielded good clinical and radiological outcomes with a low complication rate in elderly patients.

Learning curve for percutaneous endoscopic lumbar discectomy.

Percutaneous endoscopic lumbar discectomy (PELD) is one of the surgical options for soft lumbar disk herniation, but the learning curve is perceived to be steep. The first 51 PELD cases performed for single-level intracanalicular lumbar disk herniation causing radiculopathy by the same surgeon were prospectively studied. The patients were divided into 3 groups of 17 patients, and the PELD learning curve was assessed by evaluating operating time, failure rate, complication rate, and 1-year reherniation rate. One-year clinical success rate was assessed by telephone interviews. The herniated disk was successfully removed by PELD in 47 patients. Four patients required subsequent open discectomy due to PELD failure. There were 2 minor complications. One year after surgery, clinical success was achieved in 42 of the 47 patients in whom PELD was initially successful, and reherniation developed in 5 patients. A significant reduction in operating time was observed after 17 patients had been treated (p = 0.0004). No significant differences were observed in terms of either failure rate or complication rate between the 3 groups. No significant differences were observed in terms of either the clinical success rate or the reherniation rate at 1 year after surgery. The PELD learning curve seems to be stable and acceptable with proper pre-PELD training.