Calcium Pyrophosphate Deposit Disease of Cervical Spine Mimicking Ossification of the Yellow Ligament / 대한정형외과학회잡지

Calcium pyrophosphate deposition disease is deposited mainly in the knee joint or the cartilage of the wrist joint and rarely in the spine, but the transverse ligament invasion of the atlas is most common. A patient with gait disturbance showed spinal cord compression caused by thickening of the yellow ligament of the subaxial cervical spine. This paper reported two cases of calcium pyrophosphate deposition disease associated with Crown dens syndrome on a computed tomography scan of the atlantoaxial joint.

Adhesive Arachnoiditis of the Lumbar Spine after Endoscopic Discectomy - A Case Report -

Objective@#We present a rare case of adhesive arachnoiditis that occurred after percutaneous endoscopic discectomy.Summary of Literature Review: Adhesive arachnoiditis can be caused by infection, trauma, surgery, and other iatrogenic injuries.Material and Methods: A 60-year-old man presented with acute onset of lower back pain, radiating to the right leg. His symptoms had developed 10 days previously without any trauma. He had a history of L4-5 percutaneous endoscopic discectomy 10 months ago. There was no evidence of infection in an examination of cerebrospinal fluid obtained from a spinal tap. However, magnetic resonance imaging showed peridural fibrosis, clumping of the nerve roots of the cauda equina with the pia mater, and dural enhancement at the L4-5 level. @*Results@#His symptoms disappeared after steroid pulse therapy. @*Conclusions@#Even minimally invasive surgery, such as endoscopic discectomy, can lead to adhesive arachnoiditis of the lumbar spine.

Results of Decompression Alone in Patients with Lumbar Spinal Stenosis and Degenerative Spondylolisthesis: A Minimum 5-Year Follow-up

Background@#Surgical treatment consisting of decompression and fusion is generally known to produce good clinical results for lumbar spinal stenosis with degenerative spondylolisthesis. However, the clinical outcome of decompression alone, without fusion, remains unclear, and long-term follow-up results are scarce. This study aimed to retrospectively analyze the 5-year clinical results of decompression only in patients with lumbar spinal stenosis and degenerative spondylolisthesis. @*Methods@#Among the patients diagnosed as having lumbar spinal stenosis with degenerative spondylolisthesis, 36 patients who underwent decompression without fusion and were followed up for minimum 5 years were included in this study. The average follow-up period was 7.2 years, and the mean age of patients was 63.2 years. Visual analog scale (VAS) score and Oswestry disability index (ODI) were investigated pre- and postoperatively, and also radiologic displacement and instability were measured. In addition, patients who needed fusion or redecompression at the decompression site postoperatively were also investigated. @*Results@#VAS score and ODI improved from an average of 7.8 points and 57 points preoperatively, respectively, to 1.4 points and 19 points at 5 years postoperatively, respectively. The degree of radiologic displacement increased from an average of 5.1 mm preoperatively to 6.4 mm at the final follow-up. Radiological instability was detected in five patients. Two patients (9.5%) required fusion. @*Conclusions@#The long-term follow-up results revealed that satisfactory clinical outcomes were obtained with decompression alone, without fusion, for patients with lumbar spinal stenosis and degenerative spondylolisthesis.

Multiple Fractures in Thoracic Vertebrae after Epilepsy / 대한정형외과학회잡지

The musculoskeletal system can be damaged by massive contractions of the muscles in the case of systemic attacks by epilepsy. Several studies or case reports of multiple thoracic vertebrae fractures following generalized seizures without underlying diseases or falls have been reported, but there are few domestic studies or case reports. This paper reports the case of a 42-year-old male patient without any specific underlying disease, who was diagnosed with multiple fractures of the thoracic vertebrae caused by generalized myoclonic epilepsy during sleep.

Comparison of the Clinical Outcomes of an Ultrasound-Guided and C-Arm Guided Cervical Nerve Root Block / 대한정형외과학회잡지

PURPOSE@#This paper compares the clinical outcomes of patients who were treated with a cervical nerve block by ultrasound and C-arm and reports the complication.@*MATERIALS AND METHODS@#A total of 97 patients were treated with an ultrasound-guided nerve root block from May 1, 2015 to February 8, 2018. On the other hand, 94 patients were treated with a C-arm guided nerve root block. The consequences of the cervical pain and the radiating pain before and after the procedures were reviewed using the verbal numeric rating scale (VNRS). In addition, the complications related to the procedures from the daily notes from the chart were inspected.@*RESULTS@#Sixty-six cases out of 97 cases of ultrasound-guided nerve root block were enrolled in the study. The average age of the patients was 57 years, including 41 males and 25 females. Seventy seven out of 94 cases by a C-arm guided root block were included in the study. The average age of the patients was 55 years, including 40 males and 37 females. Before the nerve root block, the mean numeric rating pain scale (NRS) of the cervical pain in ultrasound-guided block decreased from 5.4 points to 2.7 points at three weeks and 1.4 points at six weeks (p=0.0023, p<0.001), and 3.1 points in the C-arm (p<0.001, p<0.001) at three weeks and 1.5 points at six weeks (p<0.001, p<0.001). In the case of radiating pain, the mean NRS in the ultrasound-guided nerve root block group improved from 6.3 points after the procedure to 2.8 points at three weeks and 1.5 points at six weeks (p<0.001, p<0.001). In the C-arm guided nerve root block group, the NRS improved from 7.4 points after the procedure to 3.3 points at three weeks and 1.9 points at six weeks. In the case of complications, Horner's syndrome and propriospinal myoclonus were observed in one case of C-arm guided block group.@*CONCLUSION@#The clinical results of the patients who underwent ultrasound-guided cervical nerve root block were not significantly different from those who underwent a C-arm guided cervical nerve root block.

Use of an Epidural Steroid Sponge for Postoperative Pain Control in Lumbar Discectomy

STUDY DESIGN: Retrospective study. OBJECTIVES: This study was conducted to evaluate the effects of using an epidural steroid sponge for postoperative pain control in lumbar discectomy. SUMMARY OF LITERATURE REVIEW: There are many methods to control postoperative pain after lumbar discectomy, including opioid analgesics, epidural catheters, and epidural steroid Gelfoam sponges. MATERIALS AND METHODS: A total of 72 patients who underwent surgery between March 2011 and February 2014 were enrolled. Their average age was 54 years (range, 24–82 years). In group A (35 patients), Gelfoam was inserted after being soaked with a solution of 2% lidocaine (400 mg/20 mL; 1 vial) and dexamethasone (5 mg/mL; 1 ampoule). In group B (37 patients), it was inserted after soaking with normal saline. Postoperative pain was assessed by visual analogue scale (VAS) scores. Pain above 5 points was controlled by a narcotic analgesic agent, and the duration and number of postoperative interventions, the period of time before walking after the operation, and the period until the date of discharge after surgery were assessed and compared. The Mann-Whitney U test was used as a nonparametric method. P-values less than 0.05 were considered to indicate statistical significance. RESULTS: In group A, 15 patients did not require analgesics on the day of surgery. In 20 patients, no analgesics were needed on postoperative day (POD) 1. In group B, 8 patients on the day of surgery and 13 patients on POD 1 did not require analgesics. In group A, 26 patients were able to walk on the day of surgery, and all patients were able to walk on POD 1. In group B, 19 patients was able to walk on the day of surgery and all patients were able to walk on POD 1. The mean number of hospital days before discharge was 6.3 in group A and 8.2 in group B. CONCLUSIONS: By continuously releasing low doses of steroids into the epidural space, this technique provided satisfactory results for postoperative pain control.

Use of an Epidural Steroid Sponge for Postoperative Pain Control in Lumbar Discectomy

OBJECTIVES@#This study was conducted to evaluate the effects of using an epidural steroid sponge for postoperative pain control in lumbar discectomy.SUMMARY OF LITERATURE REVIEW: There are many methods to control postoperative pain after lumbar discectomy, including opioid analgesics, epidural catheters, and epidural steroid Gelfoam sponges.@*MATERIALS AND METHODS@#A total of 72 patients who underwent surgery between March 2011 and February 2014 were enrolled. Their average age was 54 years (range, 24–82 years). In group A (35 patients), Gelfoam was inserted after being soaked with a solution of 2% lidocaine (400 mg/20 mL; 1 vial) and dexamethasone (5 mg/mL; 1 ampoule). In group B (37 patients), it was inserted after soaking with normal saline. Postoperative pain was assessed by visual analogue scale (VAS) scores. Pain above 5 points was controlled by a narcotic analgesic agent, and the duration and number of postoperative interventions, the period of time before walking after the operation, and the period until the date of discharge after surgery were assessed and compared. The Mann-Whitney U test was used as a nonparametric method. P-values less than 0.05 were considered to indicate statistical significance.@*RESULTS@#In group A, 15 patients did not require analgesics on the day of surgery. In 20 patients, no analgesics were needed on postoperative day (POD) 1. In group B, 8 patients on the day of surgery and 13 patients on POD 1 did not require analgesics. In group A, 26 patients were able to walk on the day of surgery, and all patients were able to walk on POD 1. In group B, 19 patients was able to walk on the day of surgery and all patients were able to walk on POD 1. The mean number of hospital days before discharge was 6.3 in group A and 8.2 in group B.@*CONCLUSIONS@#By continuously releasing low doses of steroids into the epidural space, this technique provided satisfactory results for postoperative pain control.

Corrigendum: The Usefulness of Selective Nerve Root Block for Failed Back Surgery Syndrome / 대한정형외과학회잡지

There are some errors in the published article. The authors would like to make corrections in the original version of the article.

Erratum: Radiological Results of the Double-Balloon Inflation Technique during Kyphoplasty

Correction of funding statement.

Radiological Results of the Double-Balloon Inflation Technique during Kyphoplasty

STUDY DESIGN: Retrospective case-control study. OBJECTIVES: We analyzed the radiological results of the double-balloon inflation technique in terms of its ability to reduce cement leakage, to increase bone cement bonding, and to promote anterior column height recovery. SUMMARY OF LITERATURE REVIEW: Various methods, such as the egg-shell technique, have been proposed to prevent leakage of cement during kyphoplasty in cases of osteoporotic compression fracture. MATERIALS AND METHODS: This study analyzed 18 patients diagnosed with osteoporotic compression fracture of the lumbar spine who underwent the double-balloon inflation technique after April 2015, and 30 consecutive patients with the same diagnosis who were treated using the conventional method prior to April 2015. We analyzed the radiological results on immediate postoperative simple X-rays in the anteroposterior and lateral views, 6-week postoperative lateral X-rays, and 6-month postoperative lateral X-rays to detect changes in anterior vertebral height and the cement leakage rate. RESULTS: The average anterior vertebral height increased by 7.58 mm in the double-balloon inflation group, and by 5.8 mm in the conventional group on the immediate postoperative radiographs (p=0.044). On average, a decrease of 3.08 mm was observed at 6 weeks postoperatively in the double-balloon inflation group, in contrast to a decrease of 4.68 mm in the conventional group (p=0.149). At the 6-month postoperative follow-up, an average decrease of 1.45 mm was found in the double-balloon inflation technique group, while a decrease of 1.40 mm was found in the conventional group (p=0.9110). The cement leakage rate was 22% in the double-balloon inflation group and 27% in the conventional group (p=0.730). CONCLUSIONS: Compared to the conventional method, the double-balloon inflation technique can be done more safely, and also promotes a greater recovery of anterior vertebral height.

Erratum: Radiological Results of the Double-Balloon Inflation Technique during Kyphoplasty

Correction of funding statement.

Radiological Results of the Double-Balloon Inflation Technique during Kyphoplasty

OBJECTIVES@#We analyzed the radiological results of the double-balloon inflation technique in terms of its ability to reduce cement leakage, to increase bone cement bonding, and to promote anterior column height recovery.SUMMARY OF LITERATURE REVIEW: Various methods, such as the egg-shell technique, have been proposed to prevent leakage of cement during kyphoplasty in cases of osteoporotic compression fracture.@*MATERIALS AND METHODS@#This study analyzed 18 patients diagnosed with osteoporotic compression fracture of the lumbar spine who underwent the double-balloon inflation technique after April 2015, and 30 consecutive patients with the same diagnosis who were treated using the conventional method prior to April 2015. We analyzed the radiological results on immediate postoperative simple X-rays in the anteroposterior and lateral views, 6-week postoperative lateral X-rays, and 6-month postoperative lateral X-rays to detect changes in anterior vertebral height and the cement leakage rate.@*RESULTS@#The average anterior vertebral height increased by 7.58 mm in the double-balloon inflation group, and by 5.8 mm in the conventional group on the immediate postoperative radiographs (p=0.044). On average, a decrease of 3.08 mm was observed at 6 weeks postoperatively in the double-balloon inflation group, in contrast to a decrease of 4.68 mm in the conventional group (p=0.149). At the 6-month postoperative follow-up, an average decrease of 1.45 mm was found in the double-balloon inflation technique group, while a decrease of 1.40 mm was found in the conventional group (p=0.9110). The cement leakage rate was 22% in the double-balloon inflation group and 27% in the conventional group (p=0.730).@*CONCLUSIONS@#Compared to the conventional method, the double-balloon inflation technique can be done more safely, and also promotes a greater recovery of anterior vertebral height.

The Usefulness of Selective Nerve Root Block for Failed Back Surgery Syndrome / 대한정형외과학회잡지

PURPOSE: To retrospectively evaluate the improvement of symptoms and diagnosis using selective nerve root block (SNRB) for radiating pain after spine surgery. MATERIALS AND METHODS: From October 2012 to October 2013, 112 patients with failed back surgery syndrome (41 male and 71 female, with the mean age of 62.4 years and range of 35 to 78 years), who were admitted and underwent SNRB, were included. All patients were followed-up for more than 12 months. Three groups were classified: Group 1 included patients with no improvement or aggravation of symptoms, group 2 included those with improvement of radiating pain, and group 3 included those with recurrence of radiating. RESULTS: Among the 112 patients, there were 15 patients in group 1, 59 patients in group 2, and 38 patients in group 3. Laminectomy was the highest surgical procedure, inducing failed back surgery syndrome. In group 2, the occurrence of failed back surgery syndrome was higher in case that radiating pain was complained more than 1 year before the first surgery. There is statistically significant symptom improvement in accordance with the visual analogue scale and Korean version of Oswestry disability index on every group after SNRB (p<0.05). CONCLUSION: It is considered that SNRB is expected to improve the symptoms and to find the cause of symptoms as a diagnostic value even after spine surgery.

Relative Risk of Operation between Lumbar Far Lateral Disc Herniation and Posterolateral Disc Herniation: A Retrospective Cohort Study / 대한정형외과학회잡지

PURPOSE: We reported relative risk of operation between patients who were diagnosed with lumbar far lateral disc herniation and posterolateral disc herniation after transforaminal epidural block. MATERIALS AND METHODS: A retrospective cohort study was performed on 295 patients (131 male and 164 female) who underwent transforaminal epidural block for unilateral radiculopathy caused by lumbar intervertebral disc herniation. Among these 295 patients, 34 patients were diagnosed with far lateral disc herniation and 261 patients with posterolateral disc herniation. The median follow-up period was 23.9 months, with an average age of 55.7 years. RESULTS: Fifty-one patients underwent surgical treatment. Among them, 38 patients had posterolateral disc herniation and 13 patients had far lateral disc herniation. Patients with far lateral disc herniation, when compared with posterolateral disc herniation, had a relative risk of operation of 2.67 (1.59-4.48, 95% confidence interval) with statistical significance (p=0.0002). At the final follow-up, the average visual analogue scale (VAS) score for radicular pain in the surgical and non-surgical groups was 0.69 and 1.50, respectively; the average Korean-Oswestry Disability Questionnaire (K-ODI) score was 11.7 and 9.6, respectively. The difference of average VAS score showed a statistical significance (p=0.035), however, that of K-ODI showed no statistical significance (p=0.266). CONCLUSION: In the case of far lateral disc herniation, the relative risk of surgery after transforaminal epidural block was 2.67, which is higher than that of posterolateral disc herniation. Therefore, we should consider surgical treatment more aggressively.

Clinical Outcomes of a Zero Profile Implant for Single-Level Anterior Cervical Discectomy and Fusion

STUDY DESIGN: A retrospective study. OBJECTIVES: To evaluate and compare the clinical results of a zero profile implant with a conventional stand-alone cage. SUMMARY OF LITERATURE REVIEW: A new zero-profile interbody fusion implant named Zero-P was developed in order to avoid plate-related complications. MATERIALS AND METHODS: Twenty-three patients with cervical degenerative disc disease were enrolled. Twelve of these were implanted with a stand-alone cage, and 11 patients received a Zero-P. The mean follow-up time was 16.7 months, ranging from 12 to 34 months. Intraoperative parameters, clinical outcomes (Korean Neck Pain Disability Index [K-NDI], visual analog scale [VAS] score for neck/arm pain), dysphagia scores, and device-related complications were recorded. RESULTS: At the 6-week, 3-month, 6-month, and 12-month follow up, the K-NDI and VAS scores significantly improved in both groups. Dysphagia scores in both groups have no significant differences (p>0.05). However, the cage subsidence rate was significantly higher in the stand-alone cage group (p<0.05). CONCLUSIONS: Clinical outcomes of ACDF with the Zero-P were satisfactory. The incidence of cage subsidence was lower than with the conventional stand-alone cage.

Usefulness of Anterior Cervical Interbody Fusion Using Locally Harvested Bone: Minimum 5-Year Follow-Up / 대한정형외과학회잡지

PURPOSE: The purpose of this study is to determine the usefulness of locally harvested autobone as a filling material for fusion. MATERIALS AND METHODS: Retrospective study was conducted for 21 patients diagnosed as cervical disc herniation with cervical myelopathy or radiculopathy who underwent anterior cervical fusion using locally harvested autobone and polyetheretherketone solis cage from June 2006 to September 2009, with a follow-up period of longer than 5 years. Radiologic outcomes were evaluated by the rate of bone union, the change of intervertebral height, and the subsidence of the cage. RESULTS: In clinical results, visual analogue scale score was 5.8±0.71/7.7±0.78 at preoperative, 1.6±0.58/2.3±0.97 at 1-year follow-up, 1.8±0.81/2.7±1.28 at 5-year follow-up, and neck disability index score was 34.3±6.2 in preoperative stage, 6.25±3.21 at 1-year follow-up, and 6.51±4.05 at 5-year follow-up. Radiologically intervertebral height was reduced from average 6.31±0.93 mm in 1-year follow-up to average 6.22±0.85 mm in 5-year follow-up. Subsidence of cage was average 1.28±0.41 mm at 1-year follow-up and average 1.31±0.43 mm at 5-year follow-up, with no statistically significant difference (p>0.05). Average subsidence of cage in these cases was 3.25 mm. In postoperative complication, screw breakage occurred in 1 case, screw pull out occurred in 1 case, and there was no postoperative infection. CONCLUSION: Using locally harvested autobone as filling material for fusion resulted in outstanding bone union and improvement of clinical results. In long term follow-up, there was no significant difference in union rate and complication incidence. Therefore use of locally harvested autobone as a filling material for fusion is considered an effective method.

Effectiveness of Selective Nerve Root Block on the Need for Surgical Treatment of Patients with Cervical Radicular Pain: A Minimum 5 Years Follow-Up / 대한정형외과학회잡지

PURPOSE: The purpose of this study is to assess the 5-year outcome of patients considering surgery for complaint of cervical and radiating pain treated by selective nerve root block (SNRB). MATERIALS AND METHODS: Between January 2001 and December 2007, 39 cases were selected from patients who underwent SNRB before the operation and were followed-up for more than five years. The mean follow-up period was 64.3 months and the mean age was 57.7 years. The patients were divided into the operation group and the only cervical SNRB group. The groups were compared for gender, age, duration, disease, single or multi-level, and root compression rate on magnetic resonance imaging. The clinical results were analyzed using the neck disability index (NDI) and the visual analogue scale (VAS) score. RESULTS: Among the 39 cases scheduled for the operation, 20 cases (51.3%) did not proceed to the operation and 13 cases among them were treated with additional conservative treatment. The average VAS score for the operation group and the cervical SNRB group was 8.1 points and 7.5 points at the preoperative state and the pre-injection state. After surgical treatment and cervical nerve root block, the scores were 3.0 points for all. The NDI for the operation group was 11.3 points at the last follow-up. The NDI for the cervical nerve root block group was 13.6 at the last follow-up. There was no significant difference between the two groups. Shorter duration and younger age tended to show a higher operation rate. At the last follow-up, 7 cases (17.9%) after cervical SNRB had persistent symptom relief without other treatment. CONCLUSION: Cervical SNRB is considered an effective treatment for patients with cervical disease with radiating pain and who are scheduled for an operation.

Clinical Outcomes of Coccygectomy for Chronic Coccygodynia

STUDY DESIGN: Retrospective study. OBJECTIVES: To confirm the clinical outcomes of coccygectomy for intractable chronic coccygodynia. SUMMARY OF LITERATURE REVIEW: Coccygectomy has been reported to be one of the good options for the failure of conservative treatment. MATERIALS AND METHODS: A retrospective review was conducted, including nine patients who underwent coccygectomy for intractable chronic coccygodynia. RESULTS: Improvements in the mean visual analogue scale (VAS) scores, from 5.6 to 2.1, were observed. As for patient satisfaction, there were four cases with excellent outcomes, three with good outcomes, one with a fair outcome, and only one with a poor outcome. Surgical complications, such as wound infection, did not occur in any of the cases. CONCLUSIONS: Irrespective of the causes, coccygectomy for chronic coccygodynia, for which nonsurgical management, including cushions, nonsteroidal anti-inflammatory drugs, and corticosteroid injections, has no effect, is considered a useful method because it brings definite pain relief and leads to high patient satisfaction.

Digital Pulse Oximetry for the Screeing of Lower Extremity Arterial Disease

STUDY DESIGN: Retrospective study. OBJECTIVES: The aim of the study was to investigate the usefulness of a handheld digital pulse oximetry in the detection of lower extremity arterial disease. SUMMARY OF LITERATURE REVIEW: Pulse oximetry is a well-established method for noninvasive evaluation of arterial oxygenation. MATERIALS AND METHODS: A Retrospective study was performed in 45 patients with lower extremity arterial disease. We compared the accuracy of a handheld digital pulse oximetry and the ankle brachial index (ABI). Digital pulse oximetry was conducted for 42 patients with 84 limbs to measure the SaO2 of their index fingers and big toes in supine position. The ABI was defined as abnormal if it was less than 0.9. Pulse oximetry of big toes was defined as abnormal if the SPO2 was less than 96% or it was more than 2% lower than that of the index finger. RESULTS: Digital pulse oximetry had a sensitivity of 47%(95% CI, 34-60%) and specificity of 86%(95% CI, 64-96%). ABI had a sensitivity of 49%(95% CI, 34-64%) and specificity of 95%(95% CI, 72-99%). Positive predictive values were 91%(95% CI, 74-98%) for digital pulse oximetry and 96%(95% CI, 77-99%) for ABI. Negative predictive values were 37%(95% CI, 24-51%) for digitial pulse oximetry and 43%(95% CI, 25-72%) for ABI. In 22 cases with acute ischemicwere the sensitivity 73%, the specifity 100%, the positive predictive value 100% and the negative predictive value 79%. CONCLUSIONS: Handheld digital pulse oximetry of the big toes seems as accurate as ABI to detect lower extremity arterial diseases. The combination of both will help to distinguish low extremity arterial disease and spinal radiculopathy.

Usefulness of Anterior Cervical Interbody Fusion Using Locally Harvested Bone: Locally Harvested Bone Versus Autogenous Iliac Bone / 대한정형외과학회잡지

PURPOSE: The purpose of this study is to evaluate the usefulness of locally harvested bone in anterior cervical interbody fusion. MATERIALS AND METHODS: A retrospective review was conducted, including 31 patients who underwent anterior cervical interbody fusion using a polyetheretherketone (PEEK) cage and anterior plate fixation. We randomly divided the patients into two groups, local bone group and iliac bone group. In 15 patients of the local bone group, the cage was filled with locally harvested bone, and in another 16 patients of the iliac bone group, the cage was filled with autogenous iliac bone. RESULTS: Improvements in mean visual analogue scale (VAS) scores, from 5.8 and 7.7 to 1.6 and 2.3 for neck pain and arm pain, respectively, were observed in cases using locally harvested bone, while the improvements were from 5.7 and 7.2 to 1.4 and 2.2, respectively, in those using autogenous iliac bone grafts. However, no significant differences in mean VAS and neck disability index were observed between the two groups at the last follow up (p>0.05). Radiologic union was achieved at 14.0+/-2.50 weeks in the local bone group, and at 12.62+/-1.58 weeks in the iliac bone group. However, no significant difference was observed between the two groups (p=0.076). CONCLUSION: Utilization of locally harvested bone for packing in a PEEK cage for anterior cervical interbody fusion is considered a useful method because it gives satisfactory clinical results for retention of bone union and lordosis angles.