H. Michael Mayer

Bio: H. Michael Mayer is an academic researcher from Paracelsus Private Medical University of Salzburg. The author has contributed to research in topics: Lumbar & Oswestry Disability Index. The author has an hindex of 13, co-authored 34 publications receiving 1052 citations.

Heterotopic ossification in total cervical artificial disc replacement.

Abstract: Study design Prospective clinical study enrolled in 2 centers (Munich and Liberec) as part of a prospective European multicenter study with ProDisc C (Synthes Inc., Paoli, PA). Objectives The first goal of the study was to evaluate the rate of heterotopic ossifications identified with plain radiograph following total cervical disc replacement (TCDR). The second goal was to show whether segmental motion can be preserved, and whether TCDR can provide improvement of the patient's ability to perform activities of daily living as well as a decrease of pain. Summary of background data Only a few reports about the radiologic outcome after TCDR are published so far. Heterotopic ossification is a well-known phenomenon after total hip arthroplasty. The rate of heterotopic ossification following TCDR is unclear. Methods The radiographs of 54 patients (in total, 77 implanted prostheses) were analyzed 1 year after TCDR with a ProDisc C prosthesis. We classified the heterotopic ossification in 5 grades according to a recently published classification system for lumbar total disc replacement. For clinical parameters, the visual analog scale and the Neck Disability Index were evaluated preoperatively and 1 year postoperatively. The Student t test and Wilcoxon test were used for statistical analysis. Results In 26 treated segments (33.8%), no heterotopic ossification was detectable. Grade 1 ossifications were present in 6 levels (7.8%). A total of 30 segments (39.0%) showed grade 2 ossifications. Heterotopic ossifications that led to restrictions of the range of motion were present in 8 cases (10.4%). One year postoperatively, 7 cases (9.1%) had a spontaneous fusion of the treated segment. The clinical parameters improved significantly and were similar to previous reports about TCDR. Conclusions Only 33.8% of the patients did not show any signs of heterotopic ossification, and the rate of spontaneous fusion after TCDR 1 year after surgery was unexpectedly high. There were 49.4% of the patients with grade 2-3 ossification, which lets us suspect an even higher rate of spontaneous fusion after long-term follow-ups. Motion preservation after TCDR is only guaranteed if spontaneous fusion can be prevented. Thus, mobility of the implanted segments needs to be further studied.

Clinical results of total lumbar disc replacement with ProDisc II: three-year results for different indications.

Abstract: STUDY DESIGN Prospective study analyzing midterm clinical results of total lumbar disc replacement (ProDisc II) for different indications OBJECTIVES To assess functional outcome after total lumbar disc replacement (TDR) treated for varying indications SUMMARY OF BACKGROUND DATA Despite its frequent use and increasing popularity, indications and contraindications for TDR have not been defined precisely at this stage and remain a matter of debate, leading to disc replacement procedures in a variety of pathologies that have not yet been evaluated and compared separately METHODS Patients meeting inclusion criteria were evaluated prospectively according to Visual Analogue Scale (VAS), Oswestry Questionnaire, SF-36, and numerous clinical parameters Indications included degenerative disc disease (DDD), DDD with accompanying soft disc herniation (nucleus pulposus prolapse, NPP), osteochondrosis following previous discectomy, and DDD with presence of Modic changes Postoperative improvement was recorded and analyzed for influence of preoperative diagnosis RESULTS Overall, 92 patients from four groups with a mean follow-up of 342 months (minimum, 24 months) achieved significant and maintained improvement from preoperative levels (P < 0001) Patients with DDD + NPP achieved results significantly better than patients from the other groups (P < 005) Presence of Modic changes or previous discectomy did not influence outcome negatively Improvement was achieved for both monosegmental and bisegmental disc replacements (P < 005), nevertheless with significantly inferior results for bisegmental interventions at 12- and 24-month follow-up and considerably higher complication rate While older patients were still highly satisfied with postoperative outcome, better functional outcome was observed in younger patients CONCLUSION Present data suggest beneficial clinical results of TDR for treatment of DDD in a highly selected group of patients Better functional outcome was obtained in younger patients under 40 years of age and patients with degenerative disc disease in association with disc herniation Multilevel disc replacement had significantly higher complication rate and inferior outcome Results are significantly dependent on preoperative diagnosis and patient selection, number of replaced segments, and age of the patient at the time of operation Because of significantly varying outcomes, indications for disc replacement must be defined precisely

Total lumbar disc replacement: different results for different levels.

Abstract: STUDY DESIGN Prospective study analyzing midterm clinical results of total lumbar disc replacement (TDR) with ProDisc II performed at different lumbar motion segments. OBJECTIVES To assess the influence of the disc level and number of discs replaced following TDR on postoperative outcome. SUMMARY OF BACKGROUND DATA Multisegmental disc replacement procedures belong to the so-called "off-label" indications for disc replacement, which still lack evidence of noninferiority when compared with fusion procedures. Results from uncontrolled clinical trials regarding monosegmental versus multisegmental disc replacements are contradictory. METHODS The influence of the level and the number of lumbar discs replaced on postoperative outcome was analyzed prospectively according to Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and numerous clinical parameters. Post-TDR pain patterns were analyzed with fluoroscopically guided spine infiltrations. RESULTS A total of 99 patients from 3 treatment groups with a mean follow-up of 25.8 months (range, 12.1-57.5 months) achieved significant improvement of preoperative VAS and ODI levels (P < 0.05). Best results and highest patient satisfaction rates (90.9%) were achieved in patients with monosegmental TDR at L4-L5 (n = 22). Results deteriorated when monosegmental TDR was performed at the lumbosacral junction (n = 57) with a tendency toward statistical significance at 24-month follow-up (P = 0.07). Postoperative outcome was significantly inferior following bisegmental disc replacements at L4-L5 + L5-S1 (n = 20) with a considerably higher complication rate when compared with monosegmental TDR procedures. Fluoroscopically guided spine infiltrations confirmed that the incidence of postoperative pain from posterior joint structures was 9.1% (n = 2) for L4-L5 TDR, 28.1% (n = 16) following L5-S1, and 60.0% (n = 12) for bisegmental-TDR at L4-L5 + L5-S1, respectively. CONCLUSION The level and the number of lumbar disc replacements influence postoperative outcome significantly. Satisfactory outcome was achieved for monosegmental L4-L5 and L5-S1 disc replacement procedures with best results achieved following TDR at L4-L5. For bisegmental TDR, complication rates are significantly higher and inferior postoperative results are to be expected. The incidence of postoperative pain originating from facet and/or iliosacral joints is currently underestimated and will require further investigation.

The Oblique Anterolateral Approach to the Lumbar Spine Provides Access to the Lumbar Spine With Few Early Complications

Abstract: Background During the last 20 years several less-invasive anterior approaches to the lumbar spine have become standard, including the extreme lateral transpsoas approach. Although it is associated with a lower risk of vascular injury compared with anterior midline approaches, neuromonitoring is considered mandatory to avoid neurologic complications. Interestingly, despite neuromonitoring, the reported risk of neurologic deficits with the extreme lateral transpsoas approach is greater than observed with other anterior approaches. An alternative lateral, oblique, psoas-sparing approach, recently named the oblique lumbar interbody fusion, uses the anatomic pathway between the abdominal vessels anteriorly and the lumbar plexus laterally to decrease the risk of neurologic and vascular injury; however, as yet, little on this new approach has been reported.

Histological analysis of surgical lumbar intervertebral disc tissue provides evidence for an association between disc degeneration and increased body mass index

Abstract: Although histopathological grading systems for disc degeneration are frequently used in research, they are not yet integrated into daily care routine pathology of surgical samples. Therefore, data on histopathological changes in surgically excised disc material and their correlation to clinical parameters such as age, gender or body mass index (BMI) is limited to date. The current study was designed to correlate major physico-clinical parameters from a population of orthopaedic spine center patients (gender, age and BMI) with a quantitative histologic degeneration score (HDS). Excised lumbar disc material from 854 patients (529 men/325 women/mean age 56 (15-96) yrs.) was graded based on a previously validated histologic degeneration score (HDS) in a cohort of surgical disc samples that had been obtained for the treatment of either disc herniation or discogenic back pain. Cases with obvious inflammation, tumor formation or congenital disc pathology were excluded. The degree of histological changes was correlated with sex, age and BMI. The HDS (0-15 points) showed significantly higher values in the nucleus pulposus (NP) than in the annulus fibrosus (AF) (Mean: NP 11.45/AF 7.87), with a significantly higher frequency of histomorphological alterations in men in comparison to women. Furthermore, the HDS revealed a positive significant correlation between the BMI and the extent of histological changes. No statistical age relation of the degenerative lesions was seen. This study demonstrated that histological disc alterations in surgical specimens can be graded in a reliable manner based on a quantitative histologic degeneration score (HDS). Increased BMI was identified as a positive risk factor for the development of symptomatic, clinically significant disc degeneration.

Intervertebral disc repair by autologous mesenchymal bone marrow cells: a pilot study.

Abstract: Background. Degenerative disc disease may cause severe low-back pain, a large public health problem with significant economicandlifequalityimpact.Chroniccasesoftenrequiresurgery,whichmayleadtobiomechanicalproblemsand accelerated degeneration of the adjacent segments. Cell-based therapies may circumvent these problems and have exhibitedencouragingresultsinvitroandinanimalstudies.Wedesignedapilotstudytoassessfeasibilityandsafetyand to obtain early indications on efficacy of treatment with mesenchymal stem cells (MSC) in humans. Methods. Ten patients with chronic back pain diagnosed with lumbar disc degeneration with intact annulus fibrosus were treated with autologous expanded bone marrow MSC injected into the nucleus pulposus area. Clinical evolution wasfollowedfor1yearandincludedevaluationofbackpain,disability,andqualityoflife.Magneticresonanceimaging measurements of disc height and fluid content were also performed. Results. Feasibility and safety were confirmed and strong indications of clinical efficacy identified. Patients exhibited rapid improvement of pain and disability (85% of maximum in 3 months) that approached 71% of optimal efficacy. This outcome compares favorably with the results of other procedures such as spinal fusion or total disc replacement. Although disc height was not recovered, water content was significantly elevated at 12 months. Conclusions. MSC therapy may be a valid alternative treatment for chronic back pain caused by degenerative disc disease. Advantages over current gold standards include simpler and more conservative intervention without surgery, preservation of normal biomechanics, and same or better pain relief.

Complications of artificial disc replacement: a report of 27 patients with the SB Charité disc.

Abstract: Disc prosthesis surgery is rapidly becoming an option in treating patients with symptomatic degenerative disc disease. Only short-term and midterm results are described in the literature. Most operated patients belong to the age group of 30-50 years. In these active patients, complications can be expected to increase with longer follow-up, similar to total joint replacements in the extremities. Reported here is a series of 27 patients from another institution, who presented with unsatisfactory results or complications after SB Charite disc replacement. The objective of this work was to describe the possible short- and long-term unsatisfactory results of disc prosthesis surgery. Twenty-seven patients were seen in a tertiary university referral center with persisting back and leg complaints after having received a Charite disc prosthesis. All patients were operated on in a neighboring hospital. Most patients were operated on at the L4-L5 and /or the L5-S1 vertebral levels. The patients were evaluated with plain radiography, some with flexion-extension x-rays, and most of them with computed tomography scans. The group consisted of 15 women and 12 men. Their mean age was 40 years (range 30-67 years) at the time of operation. The patients presented to us a mean of 53 months (range 11-127 months) following disc replacement surgery. In two patients, an early removal of a prosthesis was required and in two patients a late removal. In 11 patients, a second spinal reconstructive salvage procedure was performed. Mean follow-up for 26 patients with mid- and long-term evaluation was 91 months (range 15-157 months). Early complications were the following: In one patient, an anterior luxation of the prosthesis after 1 week necessitated removal and cage insertion, which failed to unite. In another patient with prostheses at L4-L5 and L5-S1, the prosthesis at L5-S1 dislocated anteriorly after 3 months and was removed after 12 months. Abdominal wall hematoma occurred in four cases. Retrograde ejaculation with loss of libido was seen in one case and erection weakness in another case. A temporary benefit was experienced by 12 patients, while 14 patients reported no benefit at all. Main causes of persistent complaints were degeneration at another level in 14, subsidence of the prosthesis in 16, and facet joint arthrosis in 11. A combination of pathologies was often present. Slow anterior migration was present in two cases, with compression on the iliac vessels in one case. Polyethylene wear was obvious in one patient 12 years after operation. In eight cases, posterior fusion with pedicle screws was required. In two cases, the prosthesis was removed and the segment was circumferentially fused. These procedures resulted in suboptimal long-term results. In this relatively small group of patients operated on with a Charite disc prosthesis, most problems arose from degeneration of other lumbar discs, facet joint arthrosis at the same or other levels, and subsidence of the prosthesis. It is to be expected that many more patients will be seen with late problems some years after this operation as the survivorship will decrease with time.

Spondylolisthesis 의 手術治驗例

Abstract: Objectives 1. List the types of spondylolisthesis described by Wiltse, and fully describe the types seen in children and adolescents 2. Describe commonly used radiographic parameters used to quantitate the severity of spondylolisthesis 3. Discuss the etiology of spondylolisthesis 4. Discuss the risk of progression of a child or adolescent with spondylolisthesis, and factors which contribute a higher risk of progression 5. Discuss factors related to symptoms in patients with spondylolisthesis 6. Describe physical findings associated with mild and severe spondylolisthesis 7. Discuss indications for surgery for spondylolisthesis, including specific procedures useful for both mild and severe slippage

Clinical and radiographic analysis of an artificial cervical disc: 7-year follow-up from the Prestige prospective randomized controlled clinical trial: Clinical article.

Abstract: Object The authors assess the long-term safety and efficacy of cervical disc replacement with the Prestige Cervical Disc in a prospective, randomized, multicenter trial at 7 years of follow-up. Methods At 31 investigational sites, 541 patients with single-level cervical disc disease with radiculopathy were randomized to 1 of 2 treatment groups: 276 investigational group patients underwent anterior cervical discectomy and arthroplasty with the Prestige disc, and 265 control group patients underwent anterior cervical discectomy and fusion. Clinical outcomes included Neck Disability Index, the 36-Item Short-Form Health Survey, and neck and arm pain scores. Radiographs were assessed for angle of motion and fusion. Clinical and radiographic outcomes were evaluated preoperatively, intraoperatively, and at 1.5, 3, 6, 12, 24, 36, 60, and 84 months. Results Of the 541 patients treated, 395 patients (73%; 212 investigational and 183 control patients) completed 7 years of clinical follow-up. Significant improvements...

Artificial intervertebral disc

Abstract: An artificial intervertebral disc includes housing members including spaced inner surfaces facing each other and oppositely facing outer surfaces for engaging spaced apart vertebral surfaces. Bearing surfaces extend from each of the inner surfaces for engaging each other while allowing for low friction and compression resistant movement of the housing members relative to each other while under compression. Load sharing pads are disposed between the inner surfaces and about at least a portion of the bearing surfaces for sharing absorption compressive loads with the bearing surfaces while limiting the relative movement of the housing members.