Cement-augmented Screw Research Articles

PS5-1 Biomechanical evaluation on the pull-out strength of an improved cement-augmented dynamic hip screw(PS5: Poster Short Presentation V,Poster Session)

PS5-1 Biomechanical evaluation on the pull-out strength of an improved cement-augmented dynamic hip screw(PS5: Poster Short Presentation V,Poster Session)

Is polymethyl methacrylate a viable option for salvaging lateral mass screw failure in the subaxial cervical spine?

Study Design Biomechanical analysis of lateral mass screw pullout strength. Objective We compare the pullout strength of our bone cement–revised lateral mass screw with the standard lateral mass screw. Methods In cadaveric cervical spines, we simulated lateral mass screw “cutouts” unilaterally from C3 to C7. We salvaged fixation in the cutout side with polymethyl methacrylate (PMMA) or Cortoss cement (Orthovita, Malvern, Pennsylvania, United States), allowed the cement to harden, and then drilled and placed lateral mass screws back into the cement-augmented lateral masses. On the contralateral side, we placed standard lateral mass screws into the native, or normal lateral, masses and then compared pullout strength of the cement-augmented side to the standard lateral mass screw. For pullout testing, each augmentation group was fixed to a servohydraulic load frame and a specially designed pullout fixture was attached to each lateral mass screw head. Results Quick-mix PMMA-salvaged lateral mass screws required greater force to fail when compared with native lateral mass screws. Cortoss cement and PMMA standard-mix cement-augmented screws demonstrated less strength of fixation when compared with control-side lateral mass screws. Attempts at a second round of cement salvage of the same lateral masses led to more variations in load to failure, but quick-mix PMMA again demonstrated greater load to failure when compared with the nonaugmented control lateral mass screws. Conclusion Quick-mix PMMA cement revision equips the spinal surgeon with a much needed salvage option for a failed lateral mass screw in the subaxial cervical spine.

Percutaneous dorsal instrumentation for thoracolumbar extension-distraction fractures in patients with ankylosing spinal disorders: a case series

Background contextThoracolumbar extension-distraction fractures are rare injuries mainly restricted to patients suffering from ankylosing spinal disorders. The most appropriate surgical treatment of these unstable spinal injuries remains to be clarified. PurposeTo report on a cohort of 10 patients treated with closed reduction and percutaneous dorsal instrumentation. Study designCase series. Patient sampleTen consecutive patients with ankylosing spinal disorders and thoracolumbar extension-distraction fractures (Type B3 according to the AOSpine Thoracolumbar Spine Injury Classification System). Outcome measuresPostoperative reduction, alignment, and implant position were analyzed by computed tomography. Loss of reduction was assessed on lateral radiographs by using the Cobb technique. Ambulation ability and pain were assessed at follow-up. MethodsMinimally invasive dorsal percutaneous instrumentation was performed in 10 consecutive patients (3 men, 7 women) with a mean age of 81.5 (range 72–90) years between May 2010 and December 2012. The mean postoperative follow-up time was 7.9 (range 4–28) months. ResultsAll 10 patients were treated with closed reduction and dorsal instrumentation; in no case was conversion to an open approach required. The mean operation time was 60.2 (range 32–135) minutes. None of the patients presented neurologic deficits. Cement-augmented screws were implanted in two cases. Sufficient radiographic correction was achieved in all patients; no case of loss of reduction was noted at final follow-up. In one case, complete hardware removal was performed 9 months after the index operation because of persistent back pain at the level of the implant. One patient died of postoperative inferior vena cava obstruction. At discharge, all patients were able to ambulate without the need for crutches or opioid analgesics. At final follow-up, all patients ambulated with full weight bearing; four patients reported persistent back pain. ConclusionsIn fragile patients with ankylosing spinal disorders and thoracolumbar extension-distraction fractures, closed reduction and percutaneous dorsal instrumentation provide a satisfying midterm functional outcome while minimizing perioperative risks compared with conventional dorsoventral procedures.

Percutaneous Cement-Augmented Screws Fixation in the Fractures of the Aging Spine: Is It the Solution?

Introduction. Management of elderly patients with thoracolumbar fractures is still challenging due to frequent osteoporosis and risk of screws pull-out. The aim of this study was to evaluate results of a percutaneous-only procedure to treat these fragile patients using cement-augmented screws. Methods. 12 patients diagnosed with a thoracolumbar fracture associated with an important loss of bone stock were included in this prospective study. Surgical procedure included systematically a percutaneous osteosynthesis using cemented fenestrated screws. When necessary, additional anterior support was performed using a kyphoplasty procedure. Clinical and radiographic evaluations were performed using CT scan. Results. On the whole series, 15 fractures were diagnosed and 96 cemented screws were inserted. The difference between the pre- and postoperative vertebral kyphosis was statistically significant (12.9° versus 4.4°, P = 0.0006). No extrapedicular screw was reported and one patient was diagnosed with a cement-related pulmonary embolism. During follow-up period, no infectious complications, implant failures, or pull-out screws were noticed. Discussion. Aging spine is becoming an increasing public health issue. Management of these patients requires specific attention due to the augmented risk of complications. Using percutaneous-only screws fixation with cemented screw provides satisfactory results. A rigorous technique is mandatory in order to achieve best outcomes.

Radiofrequenzkyphoplastie in Kombination mit posteriorer Fixierung zur Behandlung von Wirbelsäulenfrakturen

Radiofrequency kyphoplasty is an advancement of the balloon kyphoplasty and offers comparable results with a shorter operation time and a lower risk of cement leakage. This prospective study investigates the outcome of radiofrequency kyphoplasty in combination with posterior fixation by a cement-augmented screw system. Accordingly, statistical analyses of the treatment data were performed. 19 patients (mean age: 74.5 ± 7.2 years) with osteoporotic vertebral burst fractures were included in the study. All of them required a surgical intervention for treating the fracture. Thereby, the vertebrae were augmented by radiofrequency kyphoplasty and a posterior fixation by cement-augmentable screws was performed. To evaluate the effectiveness and safety of the procedure, pain was measured with the visual analog scale (VAS) and functional impairment was analysed by measuring the Oswestry disability index (ODI). Furthermore, a radiographic analysis of the anterior and medial height of the vertebrae and the degree of kyphosis were undertaken. All data were recorded preoperatively, 3 to 4 days postoperatively, 3 months postoperatively and 6 months postoperatively and any additionally occurring cement leakage was documented. The treatment showed a significant reduction of pain and improvement of the functional impairment at the 3 to 4 days postoperative evaluation (pVAS < 0.001, pODI < 0.001). The further follow-ups demonstrated an ongoing improvement of the VAS and ODI from each measurement to the next (pVAS_post-3 M < 0.001, pVAS_3 M-6 M = 0.17, pODI_post-3 M < 0.001, pODI_3 M-6 M = 0.004). The height of the vertebrae was significantly improved after the surgery (p_anterior < 0.001, p_medial < 0.001) and reduced slightly from follow-up to follow-up, but still remained higher than the preoperative value. The degree of kyphosis was also significantly improved after the surgery (p < 0.001), whereby a significant deterioration was shown at the following examinations (p_post-3 M = 0.023, p_3 M-6 M = 0.016). But even as the height decreased the degree of kyphosis was still improved in relation to the preoperative values. During the surgery cement leakage occurred in 3 cases (15.79 %). Radiofrequency kyphoplasty is a safe and effective procedure for the treatment of vertebral compression fractures in combination with the use of posterior fixation by cement-augmentable screws with an acceptable rate of cement leakage.

Komplikationsanalyse von spinalen Eingriffen bei adulten zentralen Bewegungsstörungen und Skoliosen

Adult central movement disorders, malpostures, and scolioses can have their cause in various neurological underlying diseases such as Morbus Parkinson, Pisa syndrome, or segmental dystonia. Important clinical characteristics are marked postural distortions such as camptocormia (bent spine) or laterocollis. In cases of these adult scolioses, surgical spine treatment puts high demands on the surgeon. Surgery in Parkinson's disease, for example, is associated with serious surgery-specific as well as general complications. The more rarely occurring Pisa syndrome is an entity primarily requiring medical therapy. A series of ten case reports of patients with Morbus Parkinson and Pisa syndrome who underwent spinal surgery is presented and discussed. From these reports, treatment recommendations have been derived and complemented by references from the literature. An extensive MEDLINE search was performed for this purpose. In patients suffering from Parkinson's disease, even minor surgical interventions can lead to instability of whole spine segments or even the entire spine. Implant loosening, adjacent segment instability, general perioperative complications, and progressive malposture due to disease progress can bring forth disastrous treatment courses. Spinal fixation should be performed long-segmented in combination with ventral stabilisation. Due to osteoporosis, pedicle screw cement augmentation is recommended in this collective. If the diagnosis of Pisa syndrome is established, an optimised preoperative preparation should be initiated in close cooperation with neurologists. In many cases medical therapy is sufficient and surgical interventions can be avoided.

The impact of a distal expansion mechanism added to a standard pedicle screw on pullout resistance. A biomechanical study

Background contextSpinal deformity surgery in elderly patients is associated with an increased risk of implant loosening due to failure at the screw-bone interface. Several techniques can be used to increase the screw anchorage characteristics. Cement-augmented screw fixation was shown to be the most efficient method; however, this technique is associated with a risk of complications related to vertebral cement deposition and leakage. Hence, there is a need to further elaborate the alternative screw augmenting techniques to reduce the indications for bone cement. PurposeTo analyze surgical alternatives to cement augmentation, the present study sought to quantify the impact of a distal expansion mechanism added to a standard pedicle screw on an axial pullout resistance. Study designA biomechanical laboratory study on the uniaxial pullout resistance of a standard pedicle screw versus a customized pedicle screw with a distal expansion mechanism. MethodsA total of 40 vertebrae from seven fresh-frozen human specimens were harvested and subjected to a computed tomography scanning and an analysis of the bone mineral density (BMD). The vertebrae were instrumented with a standard 6.0-mm pedicle screw and a modified 6.0-mm pedicle screw with a distal expansion mechanism added. The actual working length of both screws inside the vertebrae was identical. The distal expansion mechanism made up one-fifth of the shaft length. The accuracy of the screw insertion was assessed using biplanar radiographs and by inspection. Analysis of resistance to pullout was performed by a coaxial alignment of the pedicle screws and attachment to an electromechanical testing machine. The pullout rate was 5 mm/min, and the load-displacement curve was recorded until the force of the pullout resistance peaked. The peak load-to-failure was measured in Newtons and reported as the ultimate failure load. With each test, the mode of failure was noted and analyzed descriptively. ResultsA total of 17 vertebrae with matched pairs of standard and expansion pedicle screws were eligible for the final statistical analysis. The BMD of the vertebrae tested was 0.67±0.19 g/cm³. The screw length was 50 mm, and the actual working length of both screws was 40.3±4.2 mm. The ultimate failure load of the standard screw was 773.8±529.4 N and that of the expansion screw was 910.3±488.3 N. Statistical analysis revealed a strong trend toward an increased failure load with the expansion screw (p=.06). The mean increase of the ultimate failure load was 136.5±350.4 N. Abrupt vertebral fracture at the vertebral body-pedicle junction and the pedicle occurred seven times with the expansion screw and only five times with the standard screw (p=.16). ConclusionsOur study indicates that adding a distal expansion mechanism to a standard pedicle screw increases the failure load by one-fifth. Modern expansion screws might offer an intermediate solution for the augmentation of screw-rod constructs in osteoporotic bone while reducing the need for cement-augmented screws and avoiding the related risks.

Die Behandlung osteoporotischer Wirbelkörperfrakturen mit augmentierter Instrumentation

Reduction and stabilization of osteoporotic vertebral body fractures using posterior short-segment instrumentation. Cement augmentation of the pedicle screws in order to improve the screw’s holding power in osteoporotic bone and to reduce postoperative loss of reduction. Quick and painless postoperative mobilization without further bracing. Burst fractures (type A3 according to Magerl). Posttraumatic kyphosis following osteoporotic vertebral body fractures. Revision surgery after screw loosening. Type B and C fractures according to Magerl. Osteoporotic fractures which are suitable for nonoperative treatment or percutaneous cement augmentation techniques (vertebroplasty, kyphoplasty). Vertebral body fractures in patients with good bone quality. Insertion of pedicle screws in a typical manner. If perforated screws are used, cement application under fluoroscopic control via the central perforation of the screws. If pedicle screws without perforation are used, application of the cement using a Kyphoplasty technique and insertion of the screws. After hardening of the cement, completion of the instrumentation. Mobilization starting on the first day after surgery. Avoidance of heavy lifting and manual labor for 3 months. Implant removal only if it is necessary due to complications. Between July 2008 and December 2009, 10 patients with osteoporotic vertebral body fractures of the thoracic and lumbar spine were treated with cement-augmented posterior instrumentation. The mean age was 65.8 years (range 35–94 years). There were six type A (2 A1 and 4 A3 lesions) and four type B lesions (1 B1, 1 B2, and 2 B3 lesions) according to Magerl. Indications for cement augmentation of the pedicle screws were the patients’ age (4 patients), osteoporosis with t scores < − 2.5 (2 patients), poor intraoperative screw hold (2 patients), and revision surgery after loosening of pedicle screws (2 patients). Cement leakage was observed in 5 patients with no further clinical relevance. Loosening of cement augmented pedicle screws occurred in 1 patient with a consecutive loss of reduction of 10°. There was no need to remove any of the cement-augmented screws in the first 24 months.

Clinical efficacy of bone cement augmented screw fixation for the severe osteoporotic spine.

ObjectiveTranspedicular instrumentation of the osteoporotic spine is a challenge for the spine surgeon due to the probability of screw loosening and the potential possibility of nonunion. The purpose of this study was to evaluate the clinical efficacy of bone cement augmented screw fixation in patients with severe osteoporosis.MethodsBetween February 2004 and August 2007, 250 patients with severe osteoporosis (T-score on BMD < -3.0) that had screw fixation were included in this study. The patients were divided into two groups (Group I: 157 patients that underwent bone cement augmented screw fixation that had a variety of spine spinal diseases including fractures, and Group II: 93 patients with severe osteoporosis that had screw fixation without bone cement augmentation). The imaging and clinical features were analyzed, including bone cement augmented levels, fusion rate and related complications. The visual analog scale (VAS), Oswestry disability questionnaire (ODI) and modified MacNab's criteria were used for the assessment of pain and functional capacity.ResultsIn both groups, a significant improvement in the VAS and ODI was achieved. 146 out of 157 patients (93%) in Group I and 83 out of 93 patients (90%) in Group II were graded as an excellent or good result according to the modified MacNab's criteria. None of the patients experienced serious complications. However, there were two cases with neurological deterioration as a result of bone cement extravasation in Group I. For Group II, there were five cases of screw loosening that required re-operation for bone cement augmentation.ConclusionWhether bone cement augmentation was performed or not, it was possible to achieve satisfactory results in patients with severe osteoporosis. However, if used carefully, bone cement augmented transpedicular screwing can reduce screw loosening and pullout in patients with severe osteoporosis.

A case of posterior element fracture in Kummell's disease

Kummell's disease is a rare, delayed posttraumatic collapse of a vertebral body that can occur several months or even years after an osteoporotic compression fracture. However, there are few reports of posterior element fractures associated with Kummell's disease. A 72-year-old man who had sustained an L1 osteoporotic compression fracture 14 months prior was admitted to our institution with incapacitating back pain. Plain radiographs showed progressive collapse of the L1 vertebral body and severe kyphosis at the thoracolumbar junction. Magnetic resonance imaging revealed a posterior element fracture as well as osteonecrosis of the L1 vertebral body. An L1 percutaneous vertebroplasty was performed, followed by bone cement-augmented screw fixation to maintain stability and correct the kyphotic deformity. After surgery, pain relief was immediate, and the patient was able to walk unassisted. This case illustrates that continuous axial distraction stress caused by aggravated kyphosis secondary to Kummell's disease may result in posterior element fractures. Our discussion concludes with a literature review.

Bone Cement Augmented Screw Fixation for Severe Osteoporotic Spine: Large Series of Clinical Application

Objective: The purpose of this study was to evaluate the clinical efficacy of bone cement augmented screw fixation for the patients accompanying severe osteoporosis. Methods: Between February 2004 and August 2007, 157 patients with various spinal diseases including fractures accompanying severe osteoporosis underwent a bone cement augmented screw fixation (947 levels). About 4.8cc of polymethylmethacrylate was injected into the each vertebral body through transpedicular route. We divided the patients into two groups (Group I: Posterior fusion for compression/burst fractures or idiopathic scoliosis, Group Ⅱ: Interbody fusion for various spinal diseases). Imaging and clinical features were analyzed, including bone cement augmented levels, fusion rate, clinical outcome and complications. The visual analog scale (VAS), Oswestry disability questionnaire and modified MacNab’s criteria were used for the assessment of pain and functional capacity. Results: In both groups, a significant improvement in VAS and Oswestry disability questionnaire was achieved. 146 out of 157 patients (93%) were graded as excellent or good result according to the modified MacNab’s criteria. None of the patients experienced operative death, screw pullout or cut-up. However, there were two cases of neurologic deterioration as a result of bone cement extravasation. Conclusion: Bone cement augmented transpedicular screwing can reduce the possibility of screw loosening and pullout in patients with severe osteoporosis.

Revision of Cannulated and Perforated Cement-Augmented Pedicle Screws

Biomechanical investigation of primary and revised cement-augmented pedicle screws in comparison with unaugmented screws. To evaluate revision of cannulated pedicle screws and investigate cement-augmented and nonaugmented screws biomechanically, testing the torque of primary screws and axial pullout force of revised screws in cadaver vertebrae. Cement augmentation increases the pullout force and stability of pedicle screws in vertebrae with low bone mineral density, but surgeons are concerned about complications during revision. Bone mineral density was measured using quantitative computed tomography (CT) in 23 osteoporotic thoracolumbar junction vertebrae from human cadavers. Cannulated pedicle screws, augmented with bone cement (on right) or unaugmented (left), were inserted into each vertebra. After CT control, extraction torque was measured and the pedicles were reinstrumented with larger-diameter screws. The right screws were augmented again, with another CT control, before pullout testing. Mean vertebral bone density was 52.6 mg/cm. No major screw malpositioning was observed on primary CTs. Cement leakage was observed anterolaterally and into the spinal canal. Mean maximal torque in augmented screws (1.2 Nm, SD: 0.6) differed significantly from nonaugmented screws (0.8 Nm, SD: 0.6). Screw removal did not lead to vertebral destruction. No relevant changes due to positioning or leakage were observed on CT after revision procedures compared with primary findings. Maximal pullout force in revised augmented screws (713.2 N, SD: 254.6) differed significantly compared with nonaugmented screws (554.0 N, SD: 296.5). Bone damage was observed in several vertebrae during pullout force testing in augmented screws. Revision of cement-augmented pedicle screws was feasible without bone destruction, and larger-diameter screws can be used in revision procedures. The pullout force after revision was significantly better in cement-augmented screws. During pullout testing, the cement-bone interface broke before the screw-cement interface in several vertebrae, fracturing the pedicles.

Development of a technique for cement augmentation of nailed tibiotalocalcaneal arthrodesis constructs

Background Tibiotalocalcaneal arthrodesis with a retrograde nail is an established procedure. Many patients considered for this arthrodesis have poor bone stock, which may make it difficult to obtain construct stability. This study was undertaken to determine whether stability could be enhanced by the cement augmentation of the calcaneal locking screws. Methods A cannulated and perforated screw, and a technique for cement augmentation via this screw, were developed. Eight pairs of human cadaver bones were instrumented with a retrograde intramedullary device (Expert Hindfoot Arthrodesis Nail, Synthes AG, Solothurn, Switzerland). Within each pair, one specimen was randomized to have the nail interlocked in the calcaneus with two conventional screws; while the other specimen was similarly instrumented with the use of two cement-augmented screws. The bone mineral density was determined. In quasi-static tests, the neutral zone and the range of motion of the constructs were determined. Subsequently the specimens were tested in dorsiflexion/plantar flexion until failure occurred. The neutral zone and the range of motion of the constructs were determined every 200 cycles. Findings Augmentation resulted in significantly greater stiffness and a significantly smaller range of motion in the quasi-static dorsiflexion/plantar flexion test, and in a significantly smaller neutral zone in all quasi-static tests. With cyclic loading, the number of cycles to failure was significantly larger in the augmented group. In both groups, bone mineral density was significantly correlated with the number of cycles to failure. Two augmented screws broke. Interpretation Cement augmentation confers significant mechanical benefit in hindfoot arthrodesis and therefore can be used as a salvage procedure. Further development should be performed to validate the concept.

Revision of failed pedicle screws using hydroxyapatite cement. A biomechanical analysis.

The biomechanical influence of in situ setting hydroxyapatite cement was examined for use in pedicle screw revision surgery. Pull-out testing of control and pedicle screws augmented with hydroxyapatite cement was performed in human cadaver vertebrae. To determine the immediate effect of using hydroxyapatite cement to augment revision pedicle screws after failure of the primary pedicle screw fixation. The potential problems associated with using polymethylmethacrylate to augment revision pedicular instrumentation have prompted the search for other solutions. The introduction of resorbable hydroxyapatite pastes may have provided new biocompatible solutions for pedicle screw revision. Ten human cadaver vertebrae were instrumented with 6.0-mm pedicle screws in each pedicle. The screws were loaded to failure in axial tension (pull-out). The failed pedicles then were instrumented with 7.0-mm pedicle screws, either augmented with hydroxyapatite cement or nonaugmented, which also were loaded to failure. Finally, the nonaugmented 7.0-mm screw hole was reinstrumented with a hydroxyapatite cement-augmented, 7.0-mm pedicle screw and loaded to failure. The pull-out strength of the 7.0-mm, hydroxyapatite cement-augmented screws was 325% (P = 2.9 x 10(-5)) of that of the 6.0-mm control screws, whereas the strength of the 7.0-mm nonaugmented screws was only 73% (P = 2.0 x 10(-2)) of that of the 6.0-mm control screws. The 7.0-mm screws augmented with hydroxyapatite cement also were able to salvage 7.0-mm pull-out sites to 384% (P = 6.9E-5) of the pull-out strength of the 7.0-mm nonaugmented screws. Hydroxyapatite cement may be a mechanically viable alternative to polymethyl methacrylate for augmenting revision pedicular instrumentation and should be considered for future experimental, animal, and clinical testing.