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Biomedical subjects

H Michael Mayer

Publications and source records attributed to H Michael Mayer.

9 recordsLinked to original sources
PubMed2007

Total lumbar disc replacement in athletes: clinical results, return to sport and athletic performance.

Despite the increasing popularity of total lumbar disc replacement (TDR) in predominantly young and active patients, no previous study has addressed possibilities, limitations and potential risks regarding athletic performance following TDR. Mechanical concerns remain and the implant's resilience as regards its load-bearing capacity during sporting activities is unknown. Thirty-nine athletic patients fulfilled the inclusion criteria for this study. These patients participated in a large variety of different types of sport. Significant and lasting pain-relief was attained following TDR with a mean follow-up of 26.3 months (range 9-50.7 months; FU rate 97.4%). Sporting activity was resumed within the first 3 months (38.5%) to 6 months (30.7%) with peak performance being reached after 5.2 months. Thirty-seven patients (94.9%) achieved resumption of sporting activity. Athletic performance improved significantly in 33 patients (84.6%). Minor subsidence was observed in 13 patients (30%) within the first 3 months with no further implant migration thereafter in 12 patients. Participation in all types of sport recorded in this study was accessible for a high rate of patients up to the level of professional athletes as well as those participating in extreme sports. Preoperative participation in sport proved to be a strong positive predictor for highly satisfactory postoperative outcome following TDR. In a selected group of patients, however, preoperative inability to participate in sporting activities did not impair postoperative physical activity. Due to the young age of the patients and significant load increase exerted during athletic activities, persisting concerns regarding the future behaviour of the implant remain and will require longer follow-up, modified investigation techniques and larger patient cohorts.

Adult↗
PubMed2006

Heterotopic ossification in total cervical artificial disc replacement.

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.

Cervical Vertebrae↗
PubMed2006

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

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 34.2 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 < 0.05). Presence of Modic changes or previous discectomy did not influence outcome negatively. Improvement was achieved for both monosegmental and bisegmental disc replacements (P < 0.05), 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.

Adult↗
PubMed2005

An immunohistochemical study of the tissue bridging adult spondylolytic defects--the presence and significance of fibrocartilaginous entheses.

UNLABELLED: Introduction Spondylolytic spondylolisthesis is an osseous discontinuity of the vertebral arch that predominantly affects the fifth lumbar vertebra. Biomechanical factors are closely related to the condition. An immunohistochemical investigation of lysis-zone tissue obtained from patients with isthmic spondylolisthesis was performed to determine the molecular composition of the lysis-zone tissue and enable interpretation of the mechanical demands to which the tissue is subject. METHODS: During surgery, the tissue filling the spondylytic defects was removed from 13 patients. Twelve spondylolistheses were at the L5/S1 level with slippage being less than Meyerding grade II. Samples were methanol fixed, decalcified and cryosectioned. Sections were labelled with a panel of monoclonal antibodies directed against collagens, glycosaminoglycans and proteoglycans. RESULTS: The lysis-zone tissue had an ordered collagenous structure with distinct fibrocartilaginous entheses at both ends. Typically, these had zones of calcified and uncalcified fibrocartilage labelling strongly for type II collagen and aggrecan. Labelling was also detected around bony spurs that extended from the enthesis into the lysis-zone. The entheses also labelled for types I, III and VI collagens, chondroitin four and six sulfate, keratan and dermatan sulfate, link protein, versican and tenascin. CONCLUSIONS: Although the gap filled by the lysis tissue is a pathological feature, the tissue itself has hallmarks of a normal ligament-i.e. fibrocartilaginous entheses at either end of an ordered collagenous fibre structure. The fibrocartilage is believed to dissipate stress concentration at the hard/soft tissue boundary. The widespread occurrence of molecules typical of cartilage in the attachment of the lysis tissue, suggests that compressive and shear forces are present to which the enthesis is adapted, in addition to the expected tensile forces across the spondylolysis. Such a combination of tensile, shear and compressive forces must operate whenever there is any opening or closing of the spondylolytic gap.

Adult↗
PubMed2005

Marfan syndrome: what internists and pediatric or adult cardiologists need to know.

Marfan syndrome (MFS) is one of the most frequent connective tissue disorders, showing striking pleiotropism and clinical variability. There is autosomal dominant inheritance with complete penetrance but variable expression. Approximately 25% of MFS patients have no family history of the syndrome and represent sporadic cases due to new mutations. This hazardous condition is often associated with premature cardiovascular death unless surveillance and management are optimized. The fibrillin gene (FBN1) encodes the structure of the connective tissue protein fibrillin. MFS is caused by mutations in the fibrillin gene, located on chromosome 15 at locus 15q21. Fibrillin abnormalities reduce the structural integrity of different body systems, primarily involving the heart valves, blood vessels, lungs, bones, tendons, ligaments, cartilages, eyes, skin, spinal dura and the CNS. Patients with MFS are likely to have too little fibrillin within these structures, resulting in clinically relevant problems. For example, in the aortic wall, deficient fibrillin may trigger progressive aortic ectasia and may result in aortic dissection.

Adult↗
PubMed2002

Non-fusion technology in degenerative lumbar spinal disorders: facts, questions, challenges.

Although surgical fusion of the painful degenerating functional spinal unit (FSU) of the lumbar spine has always been a matter of debate, it has become a gold-standard procedure for all cases that lack an alternative treatment. However, a detailed and honest review of the clinical data reveals a considerable number of undesired side effects, complications and poor outcomes. The continuous search for alternative surgical treatment modalities has led to the development of numerous ideas for surgical reconstruction of the anterior and/or posterior column. The term "spine arthroplasty" summarises all procedures that have the goal of restoring function. This article describes the principles of the most current surgical techniques and implants, it points out potential challenges and poses a number of questions that need evidence-based answers before the incorporation of these innovations into surgical routine can be justified.

Humans↗
PubMed2002

Microsurgical anterior approaches to the lumbar spine for interbody fusion and total disc replacement.

OBJECTIVE: Anterior approaches to the lumbar spine for the treatment of various degenerative or postoperative abnormalities associated with low back pain have always been a matter of debate. They are known to be associated with considerable surgical trauma, high postoperative morbidity, and, occasionally, unacceptably high complication rates. In 1997, we inaugurated two new microsurgical modifications of conventional anterior approach techniques, which have been applied in anterior lumbar interbody fusion and more recently in total disc replacement. This article describes the results of microsurgical anterior interbody fusion in a consecutive series of 171 patients as well as preliminary results of these techniques for total disc replacement in 26 patients. METHODS: The approaches are performed with the use of a surgical microscope. Lumbar segments L2-L5 are exposed through a lateral retroperitoneal approach. L5-S1 can be reached through a midline retroperitoneal or transperitoneal approach. Both approaches can be performed through a limited skin incision of 4 cm. RESULTS: An independent observer evaluated results of anterior lumbar interbody fusion in 171 patients during a 2-year follow-up period. The clinical follow-up demonstrated low perioperative and postoperative morbidity with an average blood loss of less than 100 ml at the fusion site. Pseudoarthrosis rates were less than 5%, and clinical results, as evaluated in accordance with the scoring system developed by Prolo et al., did not differ significantly from conventional open techniques. Total disc replacement through a microsurgical anterior approach seems to be a promising alternative to fusion procedures with even less intraoperative and perioperative morbidity. CONCLUSION: Microsurgical anterior approaches to the lumbar spine provide a reasonable surgical alternative to conventional approaches for anterior interbody fusion and total disc replacement.

Adolescent↗