Stefan Glasmacher

Revision characteristics of cement-augmented, cannulated-fenestrated pedicle screws in the osteoporotic vertebral body: a biomechanical in vitro investigation. Technical note.

In generalized osteoporosis, instrumentation with cement-augmented pedicle screws is an amplification of the therapeutic spectrum. Early clinical results are promising for both solid and cannulated screws; however, there are concerns regarding the revision characteristics of these screws, especially for the cannulated-fenestrated type with its continuous cement interconnection from the core of the screw to surrounding bone tissue. In a human cadaver model, bone mineral density (BMD) was assessed radiographically. Spinal levels T9-L4 were instrumented left unilaterally, transpedicularly by using cannulated-fenestrated pedicle screws with the dimensions 6.5 x 45 mm. Polymethylmethacrylate cement (1.5 ml) was injected through the screws into each vertebra. After polymerization of the cement, the extraction torque was recorded. For both implantation and explantation of the screws, a fluoroscope was used to guarantee correct screw and cement positioning and to observe possible co-movements-that is, any movement of the cement mass within the vertebral body upon removal of the screw. For comparison, the extraction torque of same-dimension pedicle screws was recorded in a nonosteoporotic, non-cement-augmented instrumentation. The BMD was 0.60 g/cm2, a level that corresponds to a severe grade of osteoporosis. For removal of the screws, the median and mean extraction torques were 34 and 49 +/- 44 Ncm, respectively. No co-movements of the cement mass occurred within the vertebral body. In the nonosteoporotic control, BMD was 1.38 g/cm2. The median and mean extraction torques were 123 and 124 +/- 12 Ncm, respectively. Thus, the revision characteristics of cement-augmented, cannulated-fenestrated pedicle screws are not problematic, even in cases of severe osteoporosis. The winglike cement interconnection between the screw core and surrounding bone tissue is fragile enough to break off in the event of an extraction torque and to release the screw. There is no proof to support the theoretical fear that while trying to remove a screw, the composite of screw and cement would not break but instead would rotate as a whole in the osteoporotic vertebral body.

Die gekreuzte Schraubenosteosynthese proximaler Humerusfrakturen

ZusammenfassungIm Zeitraum zwischen 4/1997 und 10/1999 wurden 31 Patienten mit dislozierten proximalen Humerusfrakturen mit einer gekreuzten Schraubenosteosynthese operativ versorgt. Bei diesem Operationsverfahren werden 2–3 Kleinfragmentschrauben über einen deltoidopektoralen Zugang vom Schaftfragment aus überkreuzend ventral und dorsal im Humeruskopf platziert. Bei den 2-Segmentfrakturen wird zusätzlich eine Zuggurtung angelegt, bei den 3-Segmentfrakturen das Tub. majus zusätzlich mit 2 Schrauben fixiert. 21 Patienten (14 w, 7 m, Altersmedian 62 Jahre, 18–86) konnten nach einem medianen Follow-up von 18 Monaten (10–29) klinisch und radiologisch nachuntersucht werden. Dabei handelte es sich um 10 2-Segment- und 11 3-Segmentfrakturen. Die Ergebnisse im Constant-Score ergaben bei 15 Frakturen sehr gute und gute Ergebnisse, in 3 Fällen befriedigende und bei 3 Patienten schlechte Ergebnisse (1-mal 2-Segment-, 2-mal 3-Segmentfrakturen). Die Komplikationsrate lag bei 29% (3 Patienten mit frühzeitiger Schraubenentfernung wegen Kopfperforation, 2 mit sekundärer Prothesenimplantation bei Humeruskopfnekrose und 1 mit Redislokation der Fraktur). Die gekreuzte Schraubenosteosynthese stellt eine Alternative bei der Versorgung dislozierter proximaler Humerusfrakturen dar und ermöglicht eine frühfunktionelle Nachbehandlung.AbstractBetween March 1997 and October 1999 thirty-one patients with displaced proximal humeral fractures were treated with crossed screw osteosynthesis. Insertion of the screws was realized by using a deltoideo-pectoral approach placing the screws anteriorly and posteriorly in a crossed manner from the distal fragment into the humeral head. Additionally, in all two-part-fractures a tension band was applied. In all three-part-fractures, the greater tuberosity was reattached by additional screws. In 21 patients (14 female, 7 male, median age 62 years, 18–86) a clinical and radiological follow-up (median 18 months, 10–29) was obtained. Fractures were classified as two-part-fractures in 10 patients and as three-part-fractures in 11 patients. According to the Constant-Score, “excellent” and “good” results were achieved in 15 patients, “moderate” results were found in 3 patients. However, in 3 patients results were only “poor” (1 two-part-, 2 three-part-fractures). The complication rate was 29% (premature hardware removal due to head perforation in 3 cases; humeral head necrosis necessitating prosthetic replacement in 2 patients; secondary displacement in 1 case). Crossed screw osteosynthesis represents an justified alternative in the surgical treatment of displaced proximal humeral fractures permitting early functional therapy.

Arthroscopic-Assisted Simultaneous Reconstruction of the Posterior Cruciate Ligament and the Lateral Collateral Ligament Using Hamstrings and Absorbable Screws

Arthroscopic-assisted simultaneous reconstruction of the posterior cruciate ligament (PCL) and the lateral collateral ligament (LCL) using hamstring tendon grafts is described. The femoral tunnel is drilled through an incision over the medial femoral condyle and the tibial tunnel through the same skin incision used for harvesting the tendon graft. PCL reconstruction is performed using a 4-strand hamstring tendon graft and absorbable screw fixation. The tendon of the semitendinosus muscle of the uninvolved knee is used as a lateral loop for LCL reconstruction. After pulling the transplant through the fibular head, femoral fixation of the loop is made with an absorbable screw.

Navigationsgestützte Rekonstruktion der vorderen Säule bei Verletzungen im Brustwirbel- und thorakolumbalen Übergangsbereich

BACKGROUND In anterior reconstruction of the unstable thoracolumbar spine, discectomy and corpectomy are technically demanding steps requiring maximal surgical precision. This study investigated the feasibility of computer-aided guidance for discectomy and corpectomy. It also analysed the precision, advantages, and disadvantages of the procedure. PATIENTS AND METHODS Vertebral body fractures of the non-osteoporotic thoracolumbar spine addressed by discectomy/corpectomy and subsequent implant interposition (cage, tricortical strut graft) for anterior reconstruction were included. All surgical steps were done under endoscopic assistance. In the trial group, discectomy and corpectomy were performed with computer-aided guidance; in the control group, no computer navigation was used. The time required for surgery was noted. To assess surgical precision, decentralization of the implant in the frontal plane was measured in postoperative x-rays and computed tomography. Additionally, parallel alignment of vertebral body end plates with the implant was evaluated. RESULTS The trial group (TG) consisted of 16 patients, and the control group (CG) of 10 patients. Fractures were localized between T10 and L1 in TG, and between T9 and L1 in CG. Operating time was significantly shorter in CG: 104+/-28 min compared with 229+/-64 min in TG (p<0.0005). In contrast, data on surgical precision showed no statistically significant differences between the 2 groups for either decentralization or parallel endplate alignment of implants. Remarkably, for CG we noted 2 cases of cage subsidence into an adjacent end plate, whereas for TG this was noted in only 1 case. However, this difference was not statistically significant. CONCLUSION Computer-aided guidance for anterior reconstruction of the thoracolumbar spine is a technically feasible option that may help in performing discectomy and corpectomy. However, this technique significantly prolongs the operating time. There were no differences in the precision of implant positioning between the groups. However, during discectomy the use of computer navigation may possibly add to the protection of adjacent end plates.

[Computer-aided discectomy and corpectomy in anterior reconstruction of the injured thoracolumbar spine. A prospective, controlled clinical trial].

BACKGROUND In anterior reconstruction of the unstable thoracolumbar spine, discectomy and corpectomy are technically demanding steps requiring maximal surgical precision. This study investigated the feasibility of computer-aided guidance for discectomy and corpectomy. It also analysed the precision, advantages, and disadvantages of the procedure. PATIENTS AND METHODS Vertebral body fractures of the non-osteoporotic thoracolumbar spine addressed by discectomy/corpectomy and subsequent implant interposition (cage, tricortical strut graft) for anterior reconstruction were included. All surgical steps were done under endoscopic assistance. In the trial group, discectomy and corpectomy were performed with computer-aided guidance; in the control group, no computer navigation was used. The time required for surgery was noted. To assess surgical precision, decentralization of the implant in the frontal plane was measured in postoperative x-rays and computed tomography. Additionally, parallel alignment of vertebral body end plates with the implant was evaluated. RESULTS The trial group (TG) consisted of 16 patients, and the control group (CG) of 10 patients. Fractures were localized between T10 and L1 in TG, and between T9 and L1 in CG. Operating time was significantly shorter in CG: 104+/-28 min compared with 229+/-64 min in TG (p<0.0005). In contrast, data on surgical precision showed no statistically significant differences between the 2 groups for either decentralization or parallel endplate alignment of implants. Remarkably, for CG we noted 2 cases of cage subsidence into an adjacent end plate, whereas for TG this was noted in only 1 case. However, this difference was not statistically significant. CONCLUSION Computer-aided guidance for anterior reconstruction of the thoracolumbar spine is a technically feasible option that may help in performing discectomy and corpectomy. However, this technique significantly prolongs the operating time. There were no differences in the precision of implant positioning between the groups. However, during discectomy the use of computer navigation may possibly add to the protection of adjacent end plates.

Skeletal Muscle Expression of the Adhesion-GPCR CD97: CD97 Deletion Induces an Abnormal Structure of the Sarcoplasmatic Reticulum but Does Not Impair Skeletal Muscle Function

CD97 is a widely expressed adhesion class G-protein-coupled receptor (aGPCR). Here, we investigated the presence of CD97 in normal and malignant human skeletal muscle as well as the ultrastructural and functional consequences of CD97 deficiency in mice. In normal human skeletal muscle, CD97 was expressed at the peripheral sarcolemma of all myofibers, as revealed by immunostaining of tissue sections and surface labeling of single myocytes using flow cytometry. In muscle cross-sections, an intracellular polygonal, honeycomb-like CD97-staining pattern, typical for molecules located in the T-tubule or sarcoplasmatic reticulum (SR), was additionally found. CD97 co-localized with SR Ca2+-ATPase (SERCA), a constituent of the longitudinal SR, but not with the receptors for dihydropyridine (DHPR) or ryanodine (RYR), located in the T-tubule and terminal SR, respectively. Intracellular expression of CD97 was higher in slow-twitch compared to most fast-twitch myofibers. In rhabdomyosarcomas, CD97 was strongly upregulated and in part more N-glycosylated compared to normal skeletal muscle. All tumors were strongly CD97-positive, independent of the underlying histological subtype, suggesting high sensitivity of CD97 for this tumor. Ultrastructural analysis of murine skeletal myofibers confirmed the location of CD97 in the SR. CD97 knock-out mice had a dilated SR, resulting in a partial increase in triad diameter yet not affecting the T-tubule, sarcomeric, and mitochondrial structure. Despite these obvious ultrastructural changes, intracellular Ca2+ release from single myofibers, force generation and fatigability of isolated soleus muscles, and wheel-running capacity of mice were not affected by the lack of CD97. We conclude that CD97 is located in the SR and at the peripheral sarcolemma of human and murine skeletal muscle, where its absence affects the structure of the SR without impairing skeletal muscle function.

The influence of distraction force on the intradiscal pressure gradient in the bridged lumbar spine: a biomechanical investigation using a calf model.

Study Design. A biomechanical calf cadaver study. Objective. The purpose of this study was to determine the intradiscal pressure gradient of bridged healthy intervertebral segments in correlation with intraoperative distraction force. Summary of Background Data. Bisegmental dorsal stabilization and anatomic reduction is a common treatment option for incomplete burst fractures of the lumbar spine. However, it remains unknown to what extent bridging and intraoperative distraction compromises an intact intervertebral disc. Methods. The L2–L3 intervertebral disc level was evaluated in 6 freshly frozen calf cadaver spines. Pressure measurements were obtained with the spine uninstrumented, after dorsal segmental instrumentation from L1 to L3, and after distraction with 400 N and 800 N. Pressure gradient measurements were accomplished with a balloon pressure sensor placed within the nucleus pulposus of the L2–L3 intervertebral disc. Pressure data were recorded by computer data acquisition. Flexion, extension, and lateral bending moments were applied continuously by a testing machine up to a load moment of 7.5 N·m. The pressure gradients were compared with respect to the effects of added instrumentation and distraction. Results. After segmental bridging the mean pressure gradients were significantly reduced in all movement directions (P < 0.001). However, after dorsal stabilization a continuously rising intervertebral disc pressure was recordable. In contrast, no relevant additional reduction of the intradiscal pressure gradient was detectable after applying distraction forces of 400 N or 800 N. Conclusion. In a calf model, a distraction force of up to 800 N leads to no additional reduction of the pressure gradient of bridged healthy lumbar segments under flexion and extension moments. Level of Evidence: N/A

Indikation und Grenzen der minimal-invasiven Stabilisierung der metastatisch befallenen Wirbelsäule

ZusammenfassungDie Zahl der Patienten mit symptomatischer Metastasierung nimmt von Jahr zu Jahr zu. Gerade Metastasen in der Wirbelsäule führen immer zu einer unterschiedlich ausgeprägten Schmerzsymptomatik, die meist durch adäquate konservative Maßnahmen nicht ausreichend zu therapieren ist. Im klinischen Alltag ist der behandelnde Chirurg mit Instabilitäten, pathologischen Frakturen und neurologischen Funktionsausfällen konfrontiert, wobei eine meist notwendig operative Therapie mehr und mehr eine Herausforderung darstellt. Die operative Vorgehensweise hat sich in den letzten Jahren deutlich gewandelt. Sie ist patientenindividualisiert, die Implantatwahl und -technik dem Zustand des Patienten und dem Fortschreiten der Grunderkrankung angepasst. Das primäre Ziel der operativen Behandlung spinaler Metastasen muss unter palliativen Gesichtspunkten eine ausreichende Schmerzreduktion mit Wiedererlangung der Mobilität des Patienten sein, in Kombination mit der Vermeidung neurologischer Defizite, hervorgerufen durch progrediente Osteolysen. Zwei minimal-invasive Stabilisierungsverfahren kommen prinzipiell in Betracht. Unter bestimmten Voraussetzungen kann eine alleinige Wirbelkörperaugmentation im Sinne einer Kyphoplastie/Vertebroplastie ausreichend sein, dem gegenüber steht die Möglichkeit der kurz- oder langstreckigen perkutanen dorsalen Stabilisierung in Verbindung mit einer selektiven Schnitterweiterung zur Dekompression der nervalen Strukturen. Diese perkutanen Operationsverfahren haben bereits einen großen Stellenwert bei der operativen Versorgung von Wirbelsäulenmetastasen. Vorteile sind die weniger traumatisierenden Eingriffe für den Patienten mit weit fortgeschrittener Tumorerkrankung und reduziertem Allgemeinzustand. Ein geringer intraoperativer Blutverlust bedeutet weniger Operationsstress für den Patienten, kleinere Operationszugänge führen zu einer schnelleren Mobilisierung und effektiver Schmerzlinderung. Patienten sind insgesamt kürzer hospitalisiert und werden frühzeitig zur weiteren adjuvanten Therapie oder in das häusliche Umfeld entlassen.AbstractThe number of patients with symptomatic metastases increases from year to year. Especially spinal metastases often lead to severe pain which often cannot be treated adequately by conservative treatment. Surgeons are confronted with the risk of instability, pathological fractures and neurological failure and the surgical treatment necessary in most cases is nowadays becoming an even greater challenge. The surgical procedure has changed considerably in recent years. The therapy is patient-individualized, the selection of implants and technology is adapted to the physical condition of the patient and the progression of the underlying disease. The main targets of the surgical treatment of spinal metastases have to be sufficient pain reduction with restoration of mobility as well as with the prevention of neurological deficits caused by progressive osteolysis. There are two minimally invasive stabilization procedures which can basically be applied. Under certain circumstances a single kyphoplasty/vertebroplasty procedure can be sufficient, in contrast to the possibility of short or long percutaneous posterior stabilization in combination with selective decompression of neural structures. These percutaneous surgical procedures currently have an important place in the surgical treatment of spinal metastases. The advantages are a less traumatic intervention for patients with advanced malignant diseases and poor general condition. Low intraoperative loss of blood means less intraoperative stress for the patient and minor surgical approaches lead to rapid mobilization and effective pain relief. As a result the hospital stay is shorter, adjuvant therapy can be started earlier and patients can be discharged sooner.The number of patients with symptomatic metastases increases from year to year. Especially spinal metastases often lead to severe pain which often cannot be treated adequately by conservative treatment. Surgeons are confronted with the risk of instability, pathological fractures and neurological failure and the surgical treatment necessary in most cases is nowadays becoming an even greater challenge. The surgical procedure has changed considerably in recent years. The therapy is patient-individualized, the selection of implants and technology is adapted to the physical condition of the patient and the progression of the underlying disease. The main targets of the surgical treatment of spinal metastases have to be sufficient pain reduction with restoration of mobility as well as with the prevention of neurological deficits caused by progressive osteolysis. There are two minimally invasive stabilization procedures which can basically be applied. Under certain circumstances a single kyphoplasty/vertebroplasty procedure can be sufficient, in contrast to the possibility of short or long percutaneous posterior stabilization in combination with selective decompression of neural structures. These percutaneous surgical procedures currently have an important place in the surgical treatment of spinal metastases. The advantages are a less traumatic intervention for patients with advanced malignant diseases and poor general condition. Low intraoperative loss of blood means less intraoperative stress for the patient and minor surgical approaches lead to rapid mobilization and effective pain relief. As a result the hospital stay is shorter, adjuvant therapy can be started earlier and patients can be discharged sooner.

Indications and limitations of minimally invasive stabilization of metastatic spinal disease

ZusammenfassungDie Zahl der Patienten mit symptomatischer Metastasierung nimmt von Jahr zu Jahr zu. Gerade Metastasen in der Wirbelsäule führen immer zu einer unterschiedlich ausgeprägten Schmerzsymptomatik, die meist durch adäquate konservative Maßnahmen nicht ausreichend zu therapieren ist. Im klinischen Alltag ist der behandelnde Chirurg mit Instabilitäten, pathologischen Frakturen und neurologischen Funktionsausfällen konfrontiert, wobei eine meist notwendig operative Therapie mehr und mehr eine Herausforderung darstellt. Die operative Vorgehensweise hat sich in den letzten Jahren deutlich gewandelt. Sie ist patientenindividualisiert, die Implantatwahl und -technik dem Zustand des Patienten und dem Fortschreiten der Grunderkrankung angepasst. Das primäre Ziel der operativen Behandlung spinaler Metastasen muss unter palliativen Gesichtspunkten eine ausreichende Schmerzreduktion mit Wiedererlangung der Mobilität des Patienten sein, in Kombination mit der Vermeidung neurologischer Defizite, hervorgerufen durch progrediente Osteolysen. Zwei minimal-invasive Stabilisierungsverfahren kommen prinzipiell in Betracht. Unter bestimmten Voraussetzungen kann eine alleinige Wirbelkörperaugmentation im Sinne einer Kyphoplastie/Vertebroplastie ausreichend sein, dem gegenüber steht die Möglichkeit der kurz- oder langstreckigen perkutanen dorsalen Stabilisierung in Verbindung mit einer selektiven Schnitterweiterung zur Dekompression der nervalen Strukturen. Diese perkutanen Operationsverfahren haben bereits einen großen Stellenwert bei der operativen Versorgung von Wirbelsäulenmetastasen. Vorteile sind die weniger traumatisierenden Eingriffe für den Patienten mit weit fortgeschrittener Tumorerkrankung und reduziertem Allgemeinzustand. Ein geringer intraoperativer Blutverlust bedeutet weniger Operationsstress für den Patienten, kleinere Operationszugänge führen zu einer schnelleren Mobilisierung und effektiver Schmerzlinderung. Patienten sind insgesamt kürzer hospitalisiert und werden frühzeitig zur weiteren adjuvanten Therapie oder in das häusliche Umfeld entlassen.AbstractThe number of patients with symptomatic metastases increases from year to year. Especially spinal metastases often lead to severe pain which often cannot be treated adequately by conservative treatment. Surgeons are confronted with the risk of instability, pathological fractures and neurological failure and the surgical treatment necessary in most cases is nowadays becoming an even greater challenge. The surgical procedure has changed considerably in recent years. The therapy is patient-individualized, the selection of implants and technology is adapted to the physical condition of the patient and the progression of the underlying disease. The main targets of the surgical treatment of spinal metastases have to be sufficient pain reduction with restoration of mobility as well as with the prevention of neurological deficits caused by progressive osteolysis. There are two minimally invasive stabilization procedures which can basically be applied. Under certain circumstances a single kyphoplasty/vertebroplasty procedure can be sufficient, in contrast to the possibility of short or long percutaneous posterior stabilization in combination with selective decompression of neural structures. These percutaneous surgical procedures currently have an important place in the surgical treatment of spinal metastases. The advantages are a less traumatic intervention for patients with advanced malignant diseases and poor general condition. Low intraoperative loss of blood means less intraoperative stress for the patient and minor surgical approaches lead to rapid mobilization and effective pain relief. As a result the hospital stay is shorter, adjuvant therapy can be started earlier and patients can be discharged sooner.The number of patients with symptomatic metastases increases from year to year. Especially spinal metastases often lead to severe pain which often cannot be treated adequately by conservative treatment. Surgeons are confronted with the risk of instability, pathological fractures and neurological failure and the surgical treatment necessary in most cases is nowadays becoming an even greater challenge. The surgical procedure has changed considerably in recent years. The therapy is patient-individualized, the selection of implants and technology is adapted to the physical condition of the patient and the progression of the underlying disease. The main targets of the surgical treatment of spinal metastases have to be sufficient pain reduction with restoration of mobility as well as with the prevention of neurological deficits caused by progressive osteolysis. There are two minimally invasive stabilization procedures which can basically be applied. Under certain circumstances a single kyphoplasty/vertebroplasty procedure can be sufficient, in contrast to the possibility of short or long percutaneous posterior stabilization in combination with selective decompression of neural structures. These percutaneous surgical procedures currently have an important place in the surgical treatment of spinal metastases. The advantages are a less traumatic intervention for patients with advanced malignant diseases and poor general condition. Low intraoperative loss of blood means less intraoperative stress for the patient and minor surgical approaches lead to rapid mobilization and effective pain relief. As a result the hospital stay is shorter, adjuvant therapy can be started earlier and patients can be discharged sooner.

Verletzungen der oberen Halswirbelsäule

Rund 30% aller Halswirbelsäulenverletzungen entfallen auf die obere Halswirbelsäule, wobei mit steigendem Lebensalter die Frakturen des zweiten Halswirbelkörpers prozentual zunehmen: Bezogen auf alle Verletzungen der Halswirbelsäule finden sich bei den unter 60-Jährigen zu 21% Frakturen des zweiten Halswirbelkörpers, bei den 60- bis 75-Jährigen zu 28% und bei den über 75-Jährigen zu 54% [1]. Auch die Art der Verletzung ist altersabhängig: Bei jüngeren Patienten dominieren aufgrund der guten Knochenqualität die ligamentären Läsionen, bei älteren überwiegen die knöchernen Verletzungen.