Screw Purchase Research Articles

Cement-augmented anterior odontoid screw fixation for osteoporotic type II odontoid fractures in elderly patients: prospective evaluation of 11 patients.

Osteoporosis is considered to be a relative contraindication for anterior screw fixation of odontoid fractures because of reduced screw purchase. In the presence of osteoporosis, the most frequent mode of implant failure is via cut-out through the anterior wall of C2. Under in vitro conditions, cement-augmented odontoid screws show significant biomechanical advantages as compared to non-augmented screws. Against this background, we present our prospectively collected data on cement-augmented anterior screw fixation of osteoporotic odontoid fractures in elderly patients. 11 patients (8 female, 3 male, median age 83 years, range 73-89 years) with an isolated, osteoporotic type II odontoid fracture were treated. After closed reduction and standard anterior approach to the C2/3 level, a self-tapping, short-threaded 3.5-mm lag screw was placed. High-viscosity polymethylmethacrylate cement was injected via a cannulated Jamshidi needle into the base of the C2 vertebral body around the screw shaft and the screw was further tightened. Thin slice CT reconstructions for follow-up evaluation were done consistently postop and 12 months after surgery. Anatomic fracture reposition was achieved in all patients. Cement application was uneventful and well controllable. Cement leakage towards the fracture gap was not detectable. There were no major perioperative complications and no early revision surgeries. After 1 year, thin slice CT with three-dimensional reconstruction demonstrated solid osseous healing of the odontoid fracture in 8 out of 10 patients. Additional cement augmentation for anterior odontoid fracture repair is technically easy and safe. In elderly people with osteoporotic odontoid fractures, the procedure seems to be a useful supplementary option.

Bicortical screw fixation provides superior biomechanical stability but devastating failure modes in periprosthetic femur fracture care using locking plates.

The incidence of periprosthetic fractures is inevitably increasing. Sufficient stabilisation and proper screw placement next to large-volume implants remains difficult. Modern locking plates allow polyaxial, thus bicortical, screw placement around a prosthetic stem. This study analysed the biomechanical properties of different screw configurations in a locking plate construct of a periprosthetic femoral fracture model. A total of 20 Sawbones were used to stabilise a Vancouver-B1 femoral fracture with a locking plate using either four monocortical screws or three bicortical screws for proximal fixation. These were loaded with an increasing axial compression until failure. Bicortical screw purchase was significantly superior to monocortical regarding load to failure (1,510N ± 284N versus 2,350N ± 212N, p < 0.001) and maximal number of cycles (6803 ± 760 versus 4041 ± 923, p < 0.001). However, the mode of failure in the bicortical group was a severe comminuted fracture pattern as opposed to the monocortical group in which a pull-out of the screws without further damage to the bone was observed. Bicortical screw placement enhances the primary stability in treating periprosthetic femoral fractures. Notably, the mode of failure may limit the salvage options in case of revision surgery.

A New Entry Point and Trajectory for Iliac Bolt Fixation in Patients Undergoing Long Fusion to the Sacrum

Introduction Osteotomy of the posterior superior iliac spine for preparation of traditional iliac screw entry point exposes the cancellous bone of the inner ilium and causes loss of circumferential cortical starting point which may compromise biomechanical stability. For this reason, traditional iliac screws may not provide the desired primary stability especially in osteopenic and osteoporotic patients. We describe a new free-hand technique with a starting point located at the posterior inferior iliac spine (PIIS), which does not require any decortication for entry and courses very close to the rigid subcortical bone over sciatic notch while providing a low profile fixation and easier connection with S1 screw. The aim of this study is to evaluate the result of this new iliac bolt fixation technique. Patients and Methods A total of 26 patients (21 F and 5 M) having lumbopelvic fixation with the new technique were reviewed. The new entry point is located at the midpoint of PIIS. Lateral cortex of distal iliac wing is exposed subperiosteally and sciatic notch was palpated for safe trajectory. Screw trajectory is intended to be parallel to the outer cortex of ilium, passing 1 to 1.5 cm above the sciatic notch. PIIS provides a rigid circumferential cortical starting point for entrance and trajectory through thick cortical iliac bone over sciatic notch which provides very strong screw purchase even in osteopenic and osteoporotic spine. New entry point also enables easier connection to S1 screw. Free-hand technique eliminates radiation exposure. Pre-op, post-op, and follow-up X-rays were reviewed for the radiological data. Results Mean age was 63.6 years (range, 19–84 years) and mean follow-up was 14 months (range, 12–18 months). Mean screw length was 93.46 mm (range, 80–110 mm). Screw diameters were 8.5 mm in 22 patients and 7.5 mm in 4 patients. Lumbosacral fusion was achieved in all the cases. There were no neurovascular injuries related to the sciatic nerve and gluteal artery during screw placement. There were no implant failures or screw breakage at end of final follow-up. Conclusion This new technique seems to be a viable option in patients undergoing fusion to the sacrum for iliac bolt fixation. PIIS provides a circumferential cortical starting point and low profile fixation with stronger screw purchase especially in osteoporotic patients.

Reduction in Fluoroscopy Time, Radiation Dosage, and Complications Using an Innovative Guide Wire for Percutaneous Pedicle Screws

Introduction Despite the benefits of minimally invasive spine surgery (MIS), inherent risks to the patient and surgeon exist. Numerous studies demonstrate increased radiation exposure with MIS secondary to the need for increased fluoroscopy, thereby increasing the risk of cataracts and malignancy. Additionally, inadvertent advancement of standard guide wires through the vertebral body can occur, placing vital ventral structures at risk. This study evaluates the benefit of utilizing a novel split-tip guide wire for percutaneous pedicle screw placement. Methods A total of 30 consecutive cases of MIS transforaminal lumbar interbody fusion (TLIF) at L5–S1 were retrospectively evaluated. Group 1: Standard straight guide wire, 15 patients; group 2: split-tip guide wire, 15 patients. Except for the type of guide wire utilized, the same operative technique was used in each case, including bicortical S1 screw fixation. Total fluoroscopy time, radiation dosage, operative time, and complications were evaluated. Technique: (1) S1 pedicles are cannulated with standard Jamshidi needles. (2) Y-wires are placed through Jamshidi needles. (3) A cannulated Steffee probe cannulates the distal sacral promontory over the Y-wire. (4) The Steffee probe is retracted 50% and Y-wire is repositioned (Y-wire design prevents inadvertent advancement through sacral promontory). (5) The proximal S1 pedicle can be tapped over the Y-wire (not required). (6) Cannulated pedicle screws are placed over the Y-wire, engaging the distal sacral promontory for bicortical S1 purchase. Results Mean total fluoroscopy time per case for group 1 was 231.1 seconds versus 154.2 seconds for group 2 ( p = 0.017). Mean radiation dosage for group 1 was 16.22 versus 8.69 rads in group 2 ( p &lt; 0.001). There was no significant difference in operative time ( p = 0.18). Inadvertent advancement of two S1 guide wires occurred in two different patients in group 1. Postoperative abdominal CT scans with contrast were negative. Conclusion Utilizing a split-tip guide wire for percutaneous pedicle screw placement significantly decreased fluoroscopy time by 33% and radiation dosage by 46%. Cannulating the sacral promontory allows for bicortical S1 screw purchase, but removes the mechanical stop preventing inadvertent guidewire advancement. The split-tip guidewire may prevent wire advancement and decreases the need for fluoroscopic surveillance. This, in turn, reduces the risk of injury to structures ventral to the spine, while reducing the exposure to harmful radiation.

Pedicle screw placement in the lumbar spine: effect of trajectory and screw design on acute biomechanical purchase.

OBJECT Low bone mineral density in patients undergoing lumbar spinal surgery with screws is an especially difficult challenge because poor bone quality can severely compromise the maximum achievable purchase of the screws. A relatively new technique, the cortical bone screw trajectory, utilizes a medialized trajectory in the caudocephalad direction to engage a greater amount of cortical bone within the pars interarticularis and pedicle. The objectives of this cadaveric biomechanical study were to 1) evaluate a cortical screw system and compare its mechanical performance to the traditional pedicle screw system; 2) determine differences in bone quality associated with the cortical screw trajectory versus the normal pedicle screw insertion technique; 3) determine the cortical wall breach rate with both the cortical and traditional screw trajectories; and 4) determine the performance of the traditional screw in the cortical screw trajectory. METHODS Fourteen fresh frozen human lumbar spine sections (L1-5) were used in this study (mean age 57 ± 19 years). The experimental plan involved drilling and tapping screw holes for 2 trajectories under navigation (a traditional pedicle screw and a cortical screw) in both high-and low-quality vertebrae, measuring the bone quality associated with these trajectories, placing screws in the trajectories, and evaluating the competence of the screw purchase via 2 mechanical tests (pullout and toggle). The 3 experimental variants were 1) traditional pedicle screws placed in the traditional pedicle screw trajectory, 2) traditional pedicle screws placed in the cortical screw trajectory, and 3) cortical screws placed in the cortical screw trajectory. RESULTS A statistically significant increase in bone quality was observed for the cortical trajectories with a cortical screw (42%; p < 0.001) and traditional pedicle screw (48%; p < 0.001) when compared to the traditional trajectory with a traditional pedicle screw within the high-quality bone group. These significant differences were also found in the lowquality bone cohort. All mechanical parameter comparisons (screw type and trajectory) between high-quality and lowquality samples were significant (p < 0.01), and these data were all linearly correlated (r ≥ 0.65) to bone mineral density. Not all mechanical parameters determined from pullout and toggle testing were statistically significant between the 3 screw/trajectory combinations. The incidence of cortical wall breach with the cortical or traditional pedicle screw trajectories was not significantly different. CONCLUSIONS The data demonstrated that the cortical trajectory provides denser bone that allows for utilization of smaller screws to obtain mechanical purchase that is equivalent to long pedicle screws placed in traditional pedicle screw trajectories for both normal- and low-quality bone. Overall, this biomechanical study in cadavers provides evidence that the cortical screw trajectory represents a good option to obtain fixation for the lumbar spine with low-quality bone.

A Survey on Cortical Bone Trajectory for Spinal Fusions

There have been a number of developments in screw design and implantation techniques over recent years, including proposal of an alternative trajectory entitled as cortical bone trajectory (CBT). Cortical bone trajectory has been investigated in recent medical treatments as an alternative for screw fixation aimed at increasing purchase of pedicle screws in higher density bone. CBT screw insertion follows a lateral path in the transverse plane and caudocephalad path in the sagittal plane. This technique has been advocated because it is reportedly less invasive, improves screw−bone purchase and reduces neurovascular injury. Furthermore CBT pedicle screw fixation provides stabilization to multilevel lumbar segment with low-grade spondylolisthesis comparable to the standard trajectory pedicle screw construct. However, these claims have not been supported by robust clinical evidence. Recent investigations focus on evaluations of CBT as a pioneer method.

C1 lateral mass screw placement in occipitalization with atlantoaxial dislocation and basilar invagination: a report of 146 cases.

Retrospective study of 146 patients with the diagnosis of occipitalization, atlantoaxial dislocation (AAD) and basilar invagination, using a novel surgical treatment strategy. To introduce a novel fixation and reduction technique. Atlas occipitalization associated with basilar invagination often result in fixed AAD that need reduction and occipitocervical fixation. The widely used occipitocervical fixation with suboccipital screws has several limitations such as the poor screw purchase in maldevelopment of the occipital bone, limited area available for implants in previous suboccipital craniectomy. The placement of occipitalized C1 lateral mass screw is an alternative option. From June 2007 to June 2013, 146 patients of occipitalized atlas with fixed AAD and basilar invagination, underwent fixation and reduction via C1 lateral mass and C2 pars/pedicle screw. A total of 143 patients achieved the follow-up in the range from 6 months to 4 years (average, 30 mo). Neurological improvement was seen in all the 143 patients, with the averaged Japanese Orthopedic Association scores increasing from 11.6 to 15.5. Radiographical evaluation showed that solid bony fusion was achieved in all patients, and complete reduction was attained in 95 patients, and partial reduction (>60%) in 40 patients, and no effective reduction in 8 patients who had additional transoral decompression. Magnetic resonance imaging demonstrated that the ventral cervicomedullary compression was relieved in all patients. Although technically demanding, the C1 lateral mass placement in occipitalization is very useful in the rescue situation where more conventional stabilization alternatives are not technically possible, or as routine occipitocervical stabilization. It provides firm stabilization offering an optimum situation for bony fusion, and meanwhile the effective reduction of fixed AAD and basilar invagination. An extremely high fusion rate can be expected with minimal complications and minimal postoperative immobilization with this technique.

Can high-friction intraannular material increase screw pullout strength in osteoporotic bone?

Osteoporotic bone brings unique challenges to orthopaedic surgery, including a higher likelihood of problematic screw stripping in cancellous bone. Currently, there are limited options to satisfactorily repair stripped screws. Additionally, nonstripped screws hold with less purchase in osteoporotic bone. This study attempts to answer the following questions: (1) Does high-friction intraannular (HFIA) augmentation increase pullout strength in osteoporotic and in severely osteoporotic bone; and (2) can HFIA repair stripped bone thread in osteoporotic and severely osteoporotic bone? We measured screw pullout strength using a synthetic bone model in three groups: (1) predrilled nonstripped control holes as controls; (2) predrilled nonstripped augmented with HFIA; and (3) predrilled stripped holes repaired with HFIA. We tested this in osteoporotic and severely osteoporotic synthetic bone for a total of six test groups. We measured screw pullout force using an electromechanical tensile-testing machine comparing pullout force between the test groups and controls. HFIA augmentation did not increase pullout force compared with the control group in the osteoporotic bone model (489 ± 175 versus 607 ± 76, respectively; effect size = 0.94 [95% confidence interval {CI}, -1.75 to 0.08], p = 0.06). However, in severely osteoporotic cancellous bone that was augmented, the HFIA material generated more pullout force than the control (51 ± 18 versus 35 ± 16, respectively; effect size = 0.94 [95% CI, -0.02 to 1.82], p = 0.05). In stripped holes, HFIA partially restored pullout strength but remained weaker than controls in both osteoporotic and severely osteoporotic bone models (osteoporotic: 320 ± 59 versus 607 ± 76, respectively; effect size = -4.28 [95% CI, -5.57 to -2.51], p < 0.001; severely osteoporotic: 21 ± 8 versus 35 ± 16, respectively; effect size = -1.13 [95% CI, -2.0 to 0.12], p = 0.027). HFIA effectively augmented severely osteoporotic bone for screw purchase, but this effect was not seen for osteoporotic bone. In a model simulating both osteoporotic and severely osteoporotic bone, we found that HFIA can be used to repair stripped screw holes, but the resulting construct remains weaker than nonstripped controls. The HFIA material looks promising as a potential solution to stripped screws in osteoporotic bone. However, this material has yet to be tested in human bone. Furthermore, the fine mesh material could be damaged by autoclaving and could break off in vivo causing unknown tissue reactions. We recommend additional testing in a living animal model to better understand how living bone will react to the HFIA material.

Teriparatide increases the insertional torque of pedicle screws during fusion surgery in patients with postmenopausal osteoporosis.

The object of this study was to examine the efficacy of preoperative teriparatide treatment for increasing the insertional torque of pedicle screws during fusion surgery in postmenopausal women with osteoporosis. Fusion surgery for the thoracic and/or lumbar spine was performed in 29 postmenopausal women with osteoporosis aged 65-82 years (mean 72.2 years). The patients were divided into 2 groups based on whether they were treated with teriparatide (n = 13) or not (n = 16) before the surgery. In the teriparatide-treated group, patients received preoperative teriparatide therapy as either a daily (20 μg/day, n = 7) or a weekly (56.5 μg/week, n = 6) injection for a mean of 61.4 days and a minimum of 31 days. During surgery, the insertional torque was measured in 212 screws inserted from T-7 to L-5 and compared between the 2 groups. The correlation between the insertional torque and the duration of preoperative teriparatide treatment was also investigated. The mean insertional torque value in the teriparatide group was 1.28 ± 0.42 Nm, which was significantly higher than in the control group (1.08 ± 0.52 Nm, p < 0.01). There was no significant difference between the daily and the weekly teriparatide groups with respect to mean insertional torque value (1.34 ± 0.50 Nm and 1.18 ± 0.43 Nm, respectively, p = 0.07). There was negligible correlation between insertional torque and duration of preoperative teriparatide treatment (r(2) = 0.05, p < 0.01). Teriparatide injections beginning at least 1 month prior to surgery were effective in increasing the insertional torque of pedicle screws during surgery in patients with postmenopausal osteoporosis. Preoperative teriparatide treatment might be an option for maximizing the purchase of the pedicle screws to the bone at the time of fusion surgery.

Surgical treatment of scoliosis in osteogenesis imperfecta with cement-augmented pedicle screw instrumentation.

A retrospective study. To report the early postoperative results of scoliosis surgery in osteogenesis imperfecta (OI) patients utilizing all pedicle screw constructs and present a novel cementing technique to increase pedicle screw purchase in the osteoporotic OI spine. Scoliosis surgery utilizing hooks and wire systems have high complication rates in OI. Pedicle screw fixation systems have the biomechanical advantage of 3-column fixation, and cement augmentation of pedicle screws provides additional pull-out strength in the osteoporotic OI spine. The clinical and radiologic results of 10 consecutive OI patients treated with all pedicle screw instrumentation and fusion were retrospectively reviewed. The radiologic data included preoperative and postoperative major curve measurements: major curve Cobb angle, global coronal balance (GCB), apical vertebral translation (AVT), and the lowest instrumented vertebral (LIV) tilt. Operative findings included blood loss, surgery time, and additional procedures. All patients received intravenous pamidronate therapy preoperatively to increase bone mineral density. Ten patients with OI were operated on between 2005 and 2009. Seven had cement-augmented pedicle screw insertion at the proximal and distal foundations. The mean hospital stay was 10±7.5 days (range, 4-27 d) and the average follow-up period was 25.7±13.1 months (range, 14-50 mo). Mean preoperative and postoperative major Cobb angles were 83.7±23.8 and 40.3±14.6 degrees, respectively (48% correction; P<0.05). Mean preoperative and postoperative GCB deviations were 26.7±18.6 and 14.1±13.3 mm, respectively (P=0.097). Mean preoperative and postoperative AVTs were 69.3±29.1 and 29±12.2 mm, respectively (P<0.05). Preoperative and postoperative LIV tilts were 18.5±8.9 and 5.2±3.9 degrees, respectively (P<0.05). At the latest follow-up, the mean major curve Cobb angle was 37.7±13.1 degrees, the GCB deviation was 13.8±5.1 mm, the AVT was 31.7±13.3 mm, and the LIV tilt was 11.3±8.8 degrees. There was no difference between the early postoperative and the latest follow-up major curve Cobb angle, GCB deviation, AVT, or LIV tilt, indicating maintenance of correction. The mean blood loss was 23,75 mL (range, 800-45,00 mL). The mean operative time was 375.4 minutes (range, 262-491 min). The mean postoperative Scoliosis Research Society-22 patient-based outcome scores were 4.6±0.7 (out of 5). There were no instrumentation failures or permanent neurological deficits in this series. Pedicle screw instrumentation in OI scoliosis is safe and effective. Cement augmentation in these patients may help to increase the pedicle pull-out strength and decrease the screw failure rates, especially at the proximal and the distal ends of instrumentation.

Cortical bone trajectory for lumbosacral fixation: penetrating S-1 endplate screw technique: technical note.

A cortical bone trajectory (CBT) is a new pedicle screw trajectory that maximizes the thread contact with cortical bone surface, providing enhanced screw purchase. Despite the increased use of the CBT in the lumbar spine, little is known about the insertion technique for the sacral CBT. The aim of this study was to introduce a novel sacral pedicle screw trajectory. This trajectory engages with denser bone maximally by the screw penetrating the S-1 superior endplate through a more medial entry point than the traditional technique, and also has safety advantages, with the protrusion of the screw tip into the intervertebral disc space carrying no risk of neurovascular injury. In this study, the CT scans of 50 adults were studied for morphometric measurement of the new trajectory. The entry point was supposed to be the junction of the center of the superior articular process of S-1 and approximately 3 mm inferior to the most inferior border of the inferior articular process of L-5. The direction was straight forward in the axial plane without convergence, angulated cranially in the sagittal plane penetrating the middle of the sacral endplate. The cephalad angle to the sacral endplate, length of trajectory, and safety of the trajectory were investigated. Next, the insertional torque of pedicle screws using this technique was measured intraoperatively in 19 patients and compared with the traditional technique. The mean cephalad angle in these 50 patients was 30.7° ± 5.1°, and the mean length of trajectory was 31.5 ± 3.5 mm. The CT analysis revealed that the penetrating S-1 endplate technique did not cause any neurovascular injury anteriorly in any case. The new technique demonstrated an average of 141% higher insertional torque than the traditional monocortical technique. The penetrating S-1 endplate technique through the medial entry point is suitable for the connection of lumbar CBT, has revealed favorable stability for lumbosacral fixation, and has reduced the potential risk of neurovascular injuries.

Correction of Lower Extremity Angular Deformities in Skeletal Dysplasia With Hemiepiphysiodesis

Lower extremity angular deformities are common in children with skeletal dysplasia and can be treated with various surgical options. Both acute correction by osteotomy with internal fixation and gradual correction by external fixation have been used with acceptable results. Recently, the Guided Growth concept using temporary hemiepiphysiodesis for correction of angular deformities in the growing child has been proposed. This study presents the results of temporary hemiepiphysiodesis using eight-Plates and medial malleolus transphyseal screws in children with skeletal dysplasia with lower extremity angular deformities. Twenty-nine patients (50 lower extremities) with skeletal dysplasia of different types were treated for varus or valgus deformities at 2 centers. The mean age at the time of hemiepiphysiodesis was 10±2.9 years. A total of 66 eight-Plates and 12 medial malleolus screws were used. The average follow-up time between the index surgery and the latest follow-up with the eight-Plate in was 25±13.4 months. Erect long-standing anteroposterior and lateral view radiographs were obtained for deformity planning before the procedure. Angular deformities on radiograph were evaluated by mechanical axis deviation, mechanical lateral distal femoral angle, medial proximal tibial angle, and lateral distal tibial angle. Mechanical axis deviation was also expressed as a percentage to one half of the width of the tibial plateau, and the magnitude of the deformity was classified by determining the zones through which the mechanical axis of the lower extremity passed. Four zones were determined on both the medial and lateral side of the knee and the zones were labeled 1, 2, 3, and 4, corresponding to the severity of the deformity. A positive value was assigned for valgus alignment and a negative for varus alignment. Patients were analyzed in valgus and varus groups. There was correction in 34 of 38 valgus legs and 7 of 12 varus legs. In the valgus group, the mean preoperative and postoperative mechanical lateral distal femoral angles were 82.1±3.7 and 91.1±4.9 degrees, respectively (P<0.001). The mean preoperative and postoperative medial proximal tibial angles were 98.5±8 and 87.8±7.1 degrees, respectively (P<0.001). Six patients with bilateral ankle valgus deformities (12 ankles) underwent single-screw medial malleolus hemiepiphysiodesis. The mean preoperative and postoperative lateral distal tibial angles were 73.9±8.7 and 86.1±6.8 degrees, respectively (P<0.001). The numbers of plates in each anatomic location were not enough to make statistical conclusions in varus legs. Four patients in the valgus group and 3 patients in the varus group did not benefit from the procedure. Mechanical axes were in zone 2 or over in 94% of the legs preoperatively, whereas postoperatively, only 23% of the legs had mechanical axes in zone 2 or over in varus and valgus groups. Growth modulation with an eight-Plate is a relatively simple surgery and has low risk of mechanical failure or physeal damage. It can be performed in very young patients, which is an important advantage in skeletal dysplasia. Screw purchase is reliable even in the abnormal epiphysis and metaphysis. Our results show that Guided Growth using eight-Plates in skeletal dysplasia is safe and effective. Level IV.

Internal Splinting with a Balloon-Shaped Allogenic Cancellous Bone Graft for Proximal Humerus Comminuted Fracture

Background/Purpose: Mechanical support of the inferomedial region of the proximal humerus is important for maintaining fracture reduction in comminuted fracture of the proximal humerus. We use the balloon shape of allograft cancellous bone to provide medial column support and summarize the result. Patients and methods: We included 25 patients (12 men and 13 women with a mean age of 55 years) with 3-and 4-part humerus fractures, who underwent internal splinting from July 2008 to September 2012, in our study. We used a T-plate with internal splinting (balloon shaped allogenic cancellous bone) to fix the proximal humerus fracture. Radiographs were periodically checked half, 1, 2, 4, 6, 12 and 24 months months after surgery. The shoulder function was evaluated with Constant-Murley score one year after surgery. Results: Eighteen (72%) of humerus fractures healed after 12 months. The following complications were observed:2 case of screws pull out (8%), 1 case of nonunion (4%), 2 cases of avascular necrosis (8%), and 2 cases of varus collapse (8%). There were no cases of infection or nerve injury. The median Constant-Murley score at one year was 70 points. Discussion and conclusion: Medial support is important to provide stability after proximal humerus fractures.. We used a balloon-shaped allogenic cancellous bone graft to provide (1) a more balanced medial support, (2) material for screw purchase, and (3) a biologic effect for bone healing. It should be another treatment option for patients with comminuted proximal humerus fractures.

A Surgical Method for Determining Proper Screw Length in ACDF.

ObjectiveWe describe a surgical tool that uses the distractor pin as a reference for determining proper screw length in ACDF. It is critical that screw purchase depth be as deep as possible without violating or penetrating the posterior cortical wall, which ensures strong pull out strength.MethodsWe enrolled 81 adult patients who underwent ACDF using an anterior cervical plate from 2010 to 2012. Patients were categorized into Groups A (42 patients: retractor pin used as a reference for screw length) and B (39 patients: control group). Intraoperative lateral x-rays were taken after screwing the retractor pin to confirm the approaching vertebral level. The ratio of retractor pin length to body anteroposterior (A-P) diameter was measured as a reference. Proper screw length was determined by comparison to the reference.ResultsThe average distance from screw tip to posterior wall was 3.0±1.4mm in Group A and 4.1±2.3mm in Group B. The ratio of screw length to body sagittal diameter was 86.2±5.7% in Group A and 80.8±9.0% in Group B. Screw length to body sagittal diameter ratios higher than 4/5 occurred in 33 patients (90%) in Group A and 23 patients (59%) in Group B. No cases violated the posterior cortical wall.ConclusionWe introduce a useful surgical method for determining proper screw length in ACDF using the ratio of retractor pin length to body A-P diameter as a reference. This method allows for deeper screw purchase depth without violation of the posterior cortical wall.

Biomechanical measurements of cortical screw purchase in five types of human and artificial humeri

Humerus shaft fracture fixation is largely dependent on cortical screw purchase in host bone. Only 2 prior studies assessed cortical screw purchase in human humeral shafts, but were of very limited scope and did not fully assess humerus material properties. Also, no studies evaluated the human dried or artificial humeri both commercially available from Sawbones. Vashon, WA, USA. Therefore, present authors measured cortical screw purchase in human fresh-frozen (FF) (n=19), human embalmed (EM) (n=18), human dried (DR) (n=14), artificial “normal” (AN) (n=13), and artificial “osteoporotic” (AO) (n=13) humeri. Each humerus had 2 bicortical screws of 3.5-mm diameter inserted 20mm apart through the shaft's anterior and posterior cortices. Absolute force, displacement, and energy for screw-bone interface failure were measured by screw pullout tests, afterwhich data were normalized by total surface area engaged at the screw-bone interface. For absolute force, AN humeri reached a higher load than EM (p=0.001) and AO (p<0.001) humeri, whilst AN humeri achieved lower normalized force than DR humeri (p=0.018). For absolute displacement, AO humeri achieved a lower level than FF humeri (p=0.013), whilst for normalized displacement AN humeri had lower levels than all other groups (p≤0.005) and AO humeri had lower values than EM humeri (p=0.029). For absolute and normalized energy, there were no statistical differences (p≥0.066). Human bone mineral density (BMD) ranged from 0.7 to 1.8g/cm2 and was linearly correlated to screw pullout parameters in 14 of 18 cases (R=0.61 to 0.96), whilst humerus age was not. Consequently, it is recommended that human fresh-frozen, human embalmed, and human dried humeri can be used interchangeably for cortical screw purchase, since they were statistically equivalent for all comparisons. However, artificial humeri were involved in all statistical differences observed and, thus, may not replicate cortical screw purchase in human humeri. To date, this is the most comprehensive study on cortical screw purchase in human and artificial humeral shafts.

Assessment of Pedicle Bone Strength in the Lumbar Spine Using a “Smart” Ball Tip Probe

Preoperative assessment of bone mineral density (BMD) via dual X-ray absorptiometry (DEXA) has been shown to help determine the need for screw augmentation, particularly in the pedicle. However, patients frequently present without preoperative DEXA scans, especially in trauma situations. We developed a “smart” probe for intra-operative assessment of local bone strength in the pedicle. A standard ball tip probe was instrumented with an in-line load cell and was used to test the bone strength of fresh-frozen human cadaveric lumbar spine. Local bone crush strength was assessed using the probe at five locations within the centrum and the pedicle. The contralateral pedicle was outfitted with a standard pedicle screw and insertion torque and pull-out force of the screw were measured. Correlation was found between PS-centrum (probe strength-centrum) and screw pull-out strength (adj. R2 = 0.42). A stepwise linear regression revealed that when considering BMD, insertion torque, and PS-centrum, pull-out strength could be predicted based on PS-centrum and insertion torque (adj. R2 = 0.51, p &lt; 0.01, Fisher test). The results suggest that use of the new probe may be a more quantitative measurement of screw purchase when DEXA is unavailable, such as in spinal trauma cases. Furthermore, when used in conjunction with DEXA, the “smart” ball tip probe may improve assessment of the strength of pedicle screw purchase.

Cement-augmented anterior screw fixation of Type II odontoid fractures in elderly patients with osteoporosis

Background contextClosed reduction and internal fixation by an anterior approach is an established option for operative treatment of displaced Type II odontoid fractures. In elderly patients, however, inadequate screw purchase in osteoporotic bone can result in severe procedure-related complications. PurposeTo improve the stability of odontoid fracture screw fixation in the elderly using a new technique that includes injection of polymethylmethacrylat (PMMA) cement into the C2 body. Study designRetrospective review of hospital and outpatient records as well as radiographs of elderly patients treated in a university hospital department of orthopedic surgery. Patient sampleTwenty-four elderly patients (8 males and 16 females; mean age, 81 years; range, 62–98 years) with Type II fractures of the dens. Outcome measuresComplications, cement leakage (symptomatic/asymptomatic), operation time, loss of reduction, pseudarthrosis and revision surgery, patient complaints, return to normal activities, and signs of neurologic complications were all documented. MethodsAfter closed reduction and anterior approach to the inferior border of C2, a guide wire is advanced to the tip of the odontoid under biplanar fluoroscopic control. Before the insertion of one cannulated, self-drilling, short thread screws, a 12 gauge Yamshidi cannula is inserted from anterior and 1 to 3 mL of high-viscosity PMMA cement is injected into the anteroinferior portion of the C2 body. During polymerization of the cement, the screws are further inserted using a lag-screw compression technique. The cervical spine then is immobilized with a soft collar for 8 weeks postoperatively. ResultsAnatomical reduction of the dens was achieved in all 24 patients. Mean operative time was 64 minutes (40–90 minutes). Early loss of reduction occurred in three patients, but revision surgery was indicated in only one patient 2 days after primary surgery. One patient died within the first eight postoperative weeks, one within 3 months after surgery. In five patients, asymptomatic cement leakage was observed (into the C1–C2 joint in three patients, into the fracture in two). Conventional radiologic follow-up at 2 and 6 months confirmed anatomical healing in 16 of the19 patients with complete follow-up. In two patients, the fractures healed in slight dorsal angulation; one patient developed a asymptomatic pseudarthrosis. All patients were able to resume their pretrauma level of activity. ConclusionsCement augmentation of the screw in Type II odontoid fractures in elderly patients is technically feasible in a clinical setting with a low complication rate. This technique may improve screw purchase, especially in the osteoporotic C2 body.

Morphometric Measurement of Cortical Bone Trajectory for Lumbar Pedicle Screw Insertion Using Computed Tomography

A morphometric measurement of cortical bone trajectory (CBT) for the lumbar pedicle screw insertion using computed tomography (CT). The aim of this study was to conduct a detailed morphometric measurement of the CBT. The CBT is a novel lumbar pedicle screw trajectory, which follows a caudocephalad path sagittally and a laterally directed path in the transverse plane. The advantage associated with this modified technique is increased cortical bone contact, providing an enhanced screw purchase. However, little is known about the possible screw size or detailed direction of the trajectory. The CT scans of 100 adults who underwent examination for spinal problems were studied. A total of 470 lumbar vertebrae excluding spondylosis, malformation, and tumor were observed. In this trajectory, the starting point was supposed to be the junction of the center of the superior articular process and 1 mm inferior to the inferior border of the transverse process. The CT images were analyzed using 3-dimensional reconstruction software. The diameter, length, lateral angle to the vertebral sagittal plane, and cephalad angle to the vertebral horizontal plane of the trajectory were measured. The mean diameter gradually increased from L1 to L5 (from 6.2 mm at L1 to 8.4 mm at L5). The mean length from L1 to L5 were 36.8, 38.2, 39.3, 39.8, and 38.3 mm, respectively. The lateral angle from L1 to L5 were 8.6, 8.5, 9.1, 9.1, and 8.8 degrees, respectively. The cephalad angle from L1 to L5 were 26.2, 25.5, 26.2, 26.0, and 25.8 degrees, respectively. The morphology of the pedicle, such as shape and pedicle axis angle, differed over the lumbar levels, our measurements demonstrated similar data excluding the diameter of the trajectory. There were no significant differences between each level of the lateral and cephalad angles.

Biomechanical Comparison of 4 Different Lateral Plate Constructs for Distal Fibula Fractures

Displaced lateral malleolar fractures are often treated with reduction and surgical stabilization. However, there has not been a comprehensive laboratory comparison to determine the most appropriate device for treating these patients. This study subjected a range of contemporary lateral fibular plates to a series of mechanical tests designed to reveal performance differences. Forty fresh frozen lower extremities were divided into 4 groups. A Weber B distal fibula fracture was simulated with an osteotomy and stabilized using 1 of 4 plate systems: a standard Synthes one-third tubular plate with interfragmentary lag screw, a Synthes LCP locking plate with lag screw, an Orthohelix MaxLock Extreme low-profile locking plate with lag screw, or a TriMed Sidewinder nonlocking plate. Controlled monotonic bending and cyclic torsional loading were applied and bending stiffness, torsional stiffness, and fracture site motion were quantified. Resistance to cyclic torsional loading was determined by quantifying the number of loads withstood before excessive rotation occurred. Correlation between bone mineral density and each of the mechanical measures was determined. There was no difference in angulation or bending stiffness between plates. All plates except the LCP showed greater lateral deflection than in the other bending directions. Bending stiffness was lowest in lateral distal fragment deflection for all 4 plates. There was a positive correlation between bone mineral density and bending stiffness for all plate types. There was no difference in fracture site rotation between plate types in internal or external torsion, but internal rotation of the distal fragment consistently exceeded external rotation. Torsional stiffness in external rotation exceeded stiffness in internal rotation in nearly all specimens. LCP plates performed relatively poorly under cyclic torsion. Significant differences in plate performance were not demonstrated. The effects of bone quality variability and differences in interfragmentary screw purchase resulted in data dispersion that confounded absolute ranking of plate performance. Identification of an optimal lateral fibular plating system has the potential to improve the clinical outcome of malleolar fracture fixation, particularly when patient conditions are unfavorable.

Reduction of Lumbar Spondylolisthesis, Surgical Technique and Clinical Outcome.

Background Data: Reduction of the slipped vertebrae as a part of surgical approach is now attempted. In the current literature, the studies have paid attention to the surgical reduction of the slippage or in situ spinal fixationtechnique. These studies have a lack of comparison between these variable techniques. Purpose: To define the role and benefits of reduction and stabilization of lumbar spondylolisthesis. Study Design: A retrospective clinical case study.Patients and Methods: 24 patients with low grade isthmic lumbar spondylolisthesis between January 2008 and June 2010 were enrolled for this study. Patients were treated by slip reduction, interbody fusion with or without cage and internal pedicle screw fixation. All patients had back pain and radicular pain for at least one year pre-operatively. All patients were examined by plain radiographs, CT scan and MRI. Oswestry Disability Index (ODI) was used for pre and post-operative clinical assessment in all cases. Radiological assessment for bony fusion was done using plain radiography and CT scan. All patients were followed up both clinically and radiologically for at least one and half years. Results: The overall rate of neurological improvement after our procedures was 91%. Radicular pain improved earlier than back pain. Slip was reduced and satisfactory screw purchase was proved in all patients. Reported fusion rate was 92%. Operative and postoperative complications occurred in five patients but were minor and cured.Conclusion: Reduction of lumbar spondylolisthesis improved the clinical manifestations, increased the fusion rate and speed the return to normal or near normal life activities. (2013ESJ044)