Comparison of the fixation ability of headless compression screws and locking plate for metacarpal shaft transverse fracture

Metacarpal shaft fractures are common hand fractures. Although bone plates possess strong fixation ability, they have several limitations. The use of headless compression screws for fracture repair has been reported, but their fixation ability has not been understood clearly.This study aimed to compare the fixation ability of locked plate with that of headless compression screw for metacarpal fracture repair.A total of 14 artificial metacarpal bones (Sawbones, Vashon, WA, USA) were subjected to transverse metacarpal shaft fractures and divided into 2 groups. The first group of bones was fixed using locked plates (LP group), whereas the second group was fixed using headless compression screws (HC group). A material testing machine was used to perform cantilever bending tests, whereby maximum fracture force and stiffness were measured. The fixation methods were compared by conducting a Mann-Whitney U test.The maximum fracture force of the HC group (285.6 ± 57.3 N, median + interquartile range) was significantly higher than that of the LP group (227.8 ± 37.5 N; P < .05). The median of the HC group was 25.4% greater. However, no significant difference in stiffness (P > .05) was observed between the HC (65.2 ± 24.6 N/mm) and LP (61.7 ± 19.7 N/mm) groups.Headless compression screws exhibited greater fixability than did locked plates, particularly in its resistance to maximum fracture force.

Fractured coracoid process with acromioclavicular joint dislocation: A case report

RATIONALE

Coracoid processes (CPs) fracture with acromioclavicular (AC) joint dislocation are extremely rare. This combined injury has brought many challenges to surgeons, and the mechanism underlying the injury is still not fully understood. There is no clear consensus on its treatment.

PATIENT CONCERNS

Here, we describe a CP fracture with AC joint dislocation in a middle-aged manual worker.

DIAGNOSIS

Radiographs showed a fracture of the base of the CP and a third-degree AC joint separation.

INTERVENTIONS

The patient was treated surgically with open reduction and internal fixation of the AC joint by LCP clavicle hook plate, and the CP was fixed with a 3.5 mm diameter cannulated screw.

OUTCOMES

Three months after the operation, shoulder function was completely restored, and the affected shoulder had full mobility with no tenderness. Plain film radiography showed anatomical indications of the healing of these combined injuries.

LESSONS

Although AC joint dislocation with CP fractures is extremely rare in adults, it is important to remind and remember that this possibility exists. In unclear cases, special radiographic films and CT are necessary. Surgical treatment of AC joint dislocation with CP fractures can provide solid stability and restore normal shoulder function with an excellent prognosis.

Distal third femoral shaft fractures in school-aged children: A comparative study of elastic stable intramedullary nail and external fixator

Internal fixation such as elastic stable intramedullary(ESIN) nail and submuscular plate (SMP) is gaining popularity for femoral shaft fractures in school-aged children. However, external fixation (ExFix) might be a valuable option for the distal third femoral shaft fractures, where the fracture heals rapidly, but it is crucial to avoid angular malunion. This study aims to compare the clinical outcomes, postoperative complications of distal third femoral shaft fractures in school-aged children treated by ESIN versus ExFix.Patients aged 5 to 11 years with distal third femoral shaft fractures treated at our institute from January 2014 to January 2016 were included and categorized into ESIN (n = 33) and ExFix (n = 38) group. The preoperative data, including baseline information of the patients, radiographic parameters, and type of surgical procedure, were collected from the hospital database, and postoperative data, including complications, were collected during the follow-up visit.In all, 33 patients (average, 8.0 ± 2.1 years, male 20, female 13) in the ESIN group and 38 patients (average, 8.3 ± 2.3 years, male 23, female 15) in the ExFix group were included in this study. There was significantly less operative time for the ExFix group (45.4 ± 7.8 min) as compared to the ESIN group (57.8 ± 11.3 min) (P < .01), reduced estimated blood loss (EBL) in the ExFix group (9.9 ± 3.5) as compared to the ESIN group (16.4 ± 6.5) (P < .01). As for the frequency of fluoroscopy, there was a significant difference between the ExFix group (13.9 ± 2.4) and the ESIN group (15.5 ± 3.2) (P = .02). The rate of major complications was not significantly different between the 2 groups (P = .19). The rate of implant irritation was significantly higher in the ExFix group (28/38, 73.7%) than the ESIN group (12/33, 36.4%) (P < .01). The rate of surgical site infection (SSI) is significantly higher in the ExFix group (18/38, 47.4%)) than the ESIN group (1/33, 3%) (P < .01). The rate of scar concern was significantly higher in the ExFix (9/38, 23.7%) than the ESIN (2/33, 6.1%), (P = .04). According to the Flynn scoring system, 30(90.9%) patients in the ESIN group and 24(89.5%) patients in the ExFix group were rated as excellent. None of the patients had poor outcomes.Both ESIN and ExFix produced satisfactory outcomes in distal third femoral shaft fractures. ExFix remains a viable choice for selected cases, especially in resource-challenged and austere settings.

Comparison of two reinforcement rings for primary total hip arthroplasty addressing displaced acetabular fractures: a biomechanical analysis

INTRODUCTION

Aim of this study was to biomechanically compare two different acetabular cup fixation constructs in terms of fracture fixation for displaced acetabular fractures involving the anterior column with hemitransverse fracture under partial and full weight-bearing conditions.

METHODS

Two different reinforcement rings designed as cages for primary THA were biomechanically tested in terms of managing a complex acetabular fracture. Single-leg stance cyclic loading was performed to assess fracture gap movement and fragment rotation. Twelve hemi pelvis Sawbones were divided into two groups: primary THA with acetabulum roof reinforcement plate (ARRP) (n = 6) and primary THA with Burch-Schneider reinforcement cage (BSRC) (n = 6).

RESULTS

During loading under partial weight-bearing (250 N) fracture gap movement tended to be larger in the BSRC group as compared to the ARRP group. Under full weight-bearing conditions, the ARRP showed 60% significantly less motion (p = 0.035) of the os ilium to os ischii gap compared to BSRC. Fracture gap movements between the os ilium and spina iliaca fragments were significantly reduced by 76% (p = 0.048) for ARRP in contrast to BSRC. The ARRP group also demonstrated significantly less movement in the fracture gaps os ischii to quadrilateral plate (62% reduction, p = 0.009) and quadrilateral plate to spina iliaca (87% reduction, p < 0.001). Significantly less rotational movement of the quadrilateral plate to the os ilium was exhibited by the ARRP group (p = 0.015).

CONCLUSIONS

The presented acetabulum roof-reinforcement plate (ARRP) provides stable conditions at the acetabular component with adequate stabilization of a displaced acetabular fracture.

Distal Radius Allograft Reconstruction Utilizing a Step-Cut Technique After En Bloc Tumor Resection

Background: En bloc resection of the distal radius is a common treatment for advanced and recurrent giant cell tumors and less commonly for sarcoma. Various reconstructive options exist, including ulnar transposition, osteoarticular autograft and allograft, and allograft arthrodesis. We present a technique of reconstruction using a distal radius bulk allograft with a step-cut to allow for precise restoration of proper length and to promote bony union. Methods: Preoperative templating is performed with affected and contralateral radiographs to assess the size of the expected bony defect, location of the step-cut, and the optimal size of the distal radius allograft required. A standard dorsal approach to the distal radius is utilized, and the tumor is resected. A proximal row carpectomy is performed, and the plate/allograft construct is applied to the remaining host bone. Iliac crest bone graft is harvested and introduced at the graft-bone interface and radiocarpal arthrodesis sites. Results: We have previously reported outstanding union rates with the step-cut technique compared with a standard transverse cut. Conclusions: The technique described provides reproducible union and stabilization of the wrist and forearm with adequate function following en bloc resection of the distal radius for tumor.

Successful management of lower limb nonunion using locking plates and bone graft with retention of intramedullary nail

This study aims to investigate the clinical effect of the combined an additional locking plate with bone graft based on retaining the original intramedullary nail for the treatment of lower limb nonunion.From June 2008 to December 2012, 39 patients were admitted and treated, who developed non-infectious bone nonunion after intramedullary nail fixation for long bone fracture in the lower limb. Additional locking plate and autogenous iliac bone grafting were performed for these patients, in which the original intramedullary nail was retained. Follow-ups were performed once at postoperative months 1, 2, 3, 6, and 12, and every year onwards. During these follow-ups, imaging and clinical function examinations were performed, in order to observe callus growth and the fractured limb functions.All patients have been followed-up, in which the duration of these follow-ups ranged between 8 and 24 months. All patients gained bony union within 6 to 11 months, and the healing rate was 100%. Radiographic healing time ranged between 8 and 15 months. Full weight-bearing time ranged between 2 and 10 months. According to Harris hip scores and Hospital for Special Surgery (HSS) Knee joint scores, 17 cases were excellent, 2 cases were good, and 1 case was acceptable; with an excellent and good rate of 95.00%. According to HHS score for the knee, 15 cases were excellent, 3 cases were good, and 1 case was acceptable; with an excellent and good rate of 94.74%.The combined treatment of the additional blocking plate with bone grafting based on retaining the original intramedullary nail for bone nonunion could effectively eliminate lateral and rotatory instability of the fractured ends. This surgical method had a short operation time, high healing rate and other advantages.

Retrospective evaluation of perioperative and short term clinical outcomes in appendicular long bone skeleton fractures repaired via the string of pearls (SOP) locking plate system

BACKGROUND

Internal plate fixation and, more recently, locking plate fixation are commonly used in the repair of fractures in small animal surgery. This retrospective study reviewed the use of the String of Pearls locking plate system in the fixation/repair of appendicular long bone skeleton fractures in 31 small animal veterinary patients (33 fractures).

RESULTS

Major complications necessitating revision surgery occurred in 7/33 (21%), with implant failure as the inciting cause in all cases. Variables corresponding to an unsuccessful outcome were evaluated, and a correlation was found with plates placed in a bridging manner (placed without rigid anatomic reconstruction, p = 0.02) and length of follow-up (p = 0.01).

CONCLUSIONS

The SOP plating system can be used in the repair of appendicular longbone skeletal fractures, however, the authors propose that adjunct fixation, such as intramedullary pin, double plating, or external coaptation would likely improve results and should be considered imperative in cases in which anatomic reconstruction is either not desirable or achievable.

Osteosynthesis with Locking Plate for Proximal Humerus Fracture

Background Approximately 5% of all fractures consists of proximal humeral fractures. In the elderly population, most of these fractures are related to osteoporosis. Internal fixation has led to unpredictable results, especially in patients with osteopenic bone and those with comminuted fractures. Objective To evaluate functional outcome and complications following proximal humerus fracture fixation using locking plate. Method This prospective observational study was conducted at Nepal Medical College and Teaching Hospital from February 2014 to June 2015. We reviewed 35 patients with proximal humerus fractures, who underwent open reduction and internal fixation with locking plate.Functional outcome was evaluated according to the ConstantMurley shoulder assessment. Result Fracture union was achieved in all cases with the mean time to union being 14.6 weeks (11-24 weeks). At the final follow up the mean constant murley score was 73.6 (48-94). There was total 8(22.85%) cases who developed complication. Conclusion Internal fixation with the locking plate for proximal humerus fractures provides stable construct with better functional outcome as it allows early shoulder mobilization.

Evaluation of Anterolateral Plating of Distal Third Tibial Fractures

Background Distal one-third tibial fractures with or without articular involvement can be difficult to manage. Variety of treatment methods have been suggested for these injuries, including conservative treatment, external fixation with or without limited internal fixation, intramedullary nailing, plate fixation (medial or anterolateral) and more recently minimally invasive plate osteosynthesis (MIPO). All of these techniques have advantages and disadvantages. None of these techniques can be considered the "gold standard" for these injuries. Objective The objective of this prospective study was to evaluate the results of anterolateral plating of these fractures. Method Forty-five fractures of distal third of tibia were treated with open reduction and internal fixation with anterolateral tibial plate from December 2011 to December 2016. All the patients were followed up at least for nine months for the study. Radiological union was finally assessed in nine months. Result All the fractures united within nine months of plating without angulation in sagittal or coronal plane. One patient (2%) had limb length shortening of more than one cm. Full range of motion of ankle and knee joint was achieved compared to the normal side by nine months follow up. 17 (38%) patients developed marginal skin necrosis. Three (7%) patients developed superficial wound infection. These complications were seen more in patients in whom posterior below knee slab was used for pre-operative splintage (as compared to calcaneal traction). Conclusion Hence distal one-third tibial fractures with or without articular involvement can be treated with anterolateral tibial plate.

Prototype of a Silicon Nitride Ceramic-Based Miniplate Osteofixation System for the Midface

OBJECTIVE: The favorable properties of silicon nitride (Si3N4) ceramics, such as high mean strength level and fracture toughness, suggest biomedical use as an implant material. Minor reservations about the biocompatibility of Si3N4 ceramics were cleared up by previous in vitro and in vivo investigations.

STUDY DESIGN AND SETTING: A Si3N4 prototype mini-fixation system was manufactured and implanted for osteosynthesis of artificial frontal bone defects in 3 minipigs. After 3 months, histological sections, computed tomography (CT) scans, and magnetic resonance imaging (MRI) scans were obtained. Finite element modeling (FEM) was used to simulate stresses and strains on Si3N4 miniplates and screws to calculate survival probabilities.

RESULTS: Si3N4 miniplates and screws showed satisfying intraoperative workability. There was no implant loss, displacement, or fracture. Bone healing was complete in all animals. The formation of new bone was observed in direct contact to the implants. The implants showed no artifacts on CT and MRI scanning. FEM simulation confirmed the mechanical reliability of the screws, whereas simulated plate geometries regarding pullout forces at maximum load showed limited safety in a bending situation.

CONCLUSIONS: Si3N4 ceramics show a good biocompatibility outcome both in vitro and in vivo. In ENT surgery, this ceramic may serve as a biomaterial for osteosynthesis (eg, of the midface including reconstruction the floor of the orbit and the skull base). To our knowledge, this is the first introduction of a ceramic-based miniplate-osteofixation system. Advantages compared with titanium are no risk of implantation to bone with mucosal attachment, no need for explantation, and no interference with radiologic imaging. Disadvantages include the impossibility of individual bending of the miniplates.

Impact of screw location and endplate preparation on pullout strength for anterior plates and integrated fixation cages

BACKGROUND CONTEXT

Numerous integrated fixation cages (IFCs) have recently been introduced to the market with "zero-profile" designs that incorporate screw fixation through the vertebral endplate. It is unclear whether differences in bone quality and quantity in this insertion location may affect fixation compared with screws used in traditional anterior plate (AP) fixation. Moreover, endplate preparation for IFC implantation may affect fixation strength.

PURPOSE

This study aimed to compare pullout strength of screws used in IFCs with screws used for AP implantations.

STUDY DESIGN

A biomechanical cadaveric study.

METHODS

T12 and L1 vertebrae from 13 human cadaver spines were prepared for pullout testing. End plates in T12 vertebrae were scraped according to surgical practice for fusion procedures. Conversely, endplates in L1 vertebrae were kept intact (unscraped). Integrated fixation cage screws were implanted at a 45° angle into the endplate and AP screws were implanted horizontally into the same vertebral body. Pullout testing was performed on all screws, and peak pullout force (PPF) and work were compared between groups to determine fixation strength. In addition, micro-CT imaging was used to assess bone quantity and quality parameters such as trabecular bone volume fraction, endplate and anterior cortex thickness at screw insertion location, endplate mineralization, and anterior cortex mineralization.

RESULTS

Peak pullout force for IFC screws (176±68 N) with scraped endplates was similar (p=.26) to AP screws (192±84 N). However, PPF for IFC screws (231±75 N) with unscraped endplates was significantly greater (p<.01) than AP screws (176±50 N). Peak pullout force for IFC screws with scraped endplates was significantly lower (p=.03) than IFC screws with unscraped endplates. Scraped endplates group (0.17±0.05 mm) were thinner (p=.05) than unscraped endplates (0.21±0.06 mm) by approximately 40 µ on average.

CONCLUSIONS

These data indicate that IFC and AP screws exhibited similar fixation behavior when the endplate is prepared according to common surgical practices. However, endplate scraping reduces endplate thickness by 20% on average, resulting in a decrease in fixation strength when compared with the unscraped endplates and provides bounds for IFC screw fixation strength.

Clinical comparative analysis on unstable pelvic fractures in the treatment with percutaneous sacroiliac screws and sacroiliac joint anterior plate fixation

OBJECTIVE

To investigate clinical efficacy of unstable pelvic fractures in the treatment with percutaneous sacroiliac screws and sacroiliac joint anterior plate fixation.

PATIENTS AND METHODS

64 patients with unstable pelvic fractures were selected in the hospital from January 2008 to June 2011, and were randomly divided into two groups.(32 patients with sacroiliac anterior plate fixation as the control group, and another 32 patients with percutaneous sacroiliac screw internal fixation as the observation group). The perioperative period clinical indicators, postoperative Matta score, postoperative Majeed function score of all patients were compared and analyzed.

RESULTS

The operation time, intraoperative blood loss, wound total length, postoperative fever time, duration of hospitalization in the observation group were significantly less than those in the control group. The complication rate (3.1%) in the observation group was lower than that in the control group (21.9%). The rate of Matta score excellent (96.9%) in the observation group was higher than that in the control group (81.2%) after the treatment. The rate of Majeed function score excellent (93.8%) in the observation group was significantly higher than that in the control group (75%) after the treatment.

CONCLUSIONS

Percutaneous sacroiliac screw internal fixation in the treatment of unstable pelvic fractures has less injury, less bleeding, less pain and rapid recovery which is a safe and effective minimally invasive operation method. The clinical curative effect of percutaneous sacroiliac screw internal fixation is better than anterior plate fixation for the treatment of sacroiliac joint. The full preparation before the surgery and patients with positive can substantially reduce the occurrence of complications rate.

Biomechanical comparison of the Locking Compression superior anterior clavicle plate with seven and ten hole reconstruction plates in midshaft clavicle fracture stabilisation

PURPOSE

The purpose of this study was to characterise the biomechanical properties of the seven hole superior anterior clavicle LCP (locking compression plate) and to compare these with the properties of commonly applied implants used for the stabilisation of clavicular midshaft fractures such as the locking 7- and ten hole reconstruction plate.

METHODS

Twenty-four synthetic clavicles were used. A transverse midshaft fracture was induced. The clavicles were fixed with angle stable clavicle LCPs, seven hole and ten hole reconstruction plates (n = 8 each). Twenty cycles of axial compression and torsion were performed for each sample, which was followed by 1,000 cycles of three point bending and ultimately bending to failure. Axial, torsional and cantilever bending stiffness were calculated from the data recorded.

RESULTS

The clavicle LCP showed the highest overall stiffness compared to the seven and ten hole reconstruction plate. Significantly higher stiffness values were found for axial compression and external rotation. In the load-to-failure tests, the ten hole reconstruction plate especially showed early signs of plastic deformation, which might account for early plate insufficiency so frequently observed clinically.

CONCLUSION

The results indicate that the clavicle LCP, as compared to the reconstruction plates, leads to superior biomechanical stability in the treatment of midshaft clavicle fractures.

Biomechanical analysis of a new expandable vertebral body replacement combined with a new polyaxial antero-lateral plate and/or pedicle screws and rods

PURPOSE

Restoration of the anterior spinal profile and regular load-bearing is the main goal treating anterior spinal defects in case of fracture. Over the past years, development and clinical usage of cages for vertebral body replacement have increased rapidly. For an enhanced stabilization of rotationally unstable fractures, additional antero-lateral implants are common. The purpose of this study was the evaluation of the biomechanical behaviour of a recently modified, in situ distractible vertebral body replacement (VBR) combined with a newly developed antero-lateral polyaxial plate and/or pedicle screws and rods using a full corpectomy model as fracture simulation.

METHODS

Twelve human spinal specimens (Th12-L4) were tested in a six-degree-of-freedom spine tester applying pure moments of 7.5 Nm to evaluate the stiffness of three different test instrumentations using a total corpectomy L2 model: (1) VBR+antero-lateral plate; (2) VBR, antero-lateral plate+pedicle screws and rods and (3) VBR+pedicle screws and rods.

RESULTS

In the presented total corpectomy defect model, only the combined antero-posterior instrumentation (VBR, antero-lateral plate+pedicle screws and rods) could achieve higher stiffness in all three-movement planes than the intact specimen. In axial rotation, neither isolated anterior instrumentation (VBR+antero-lateral plate) nor isolated posterior instrumentation (VBR+pedicle screws and rods) could stabilize the total corpectomy compared to the intact state.

CONCLUSIONS

For rotationally unstable vertebral body fractures, only combined antero-posterior instrumentation could significantly decrease the range of motion (ROM) in all motion planes compared to the intact state.

Hemiarthroplasty versus angle-stable locking compression plate osteosynthesis in the treatment of three- and four-part fractures of the proximal humerus in the elderly: design of a randomized controlled trial

BACKGROUND

The optimal surgical management of dislocated three- and four-part fractures of the proximal humerus in elderly patients remains unclear. Most used techniques are hemiarthroplasty and angle-stable locking compression plate osteosynthesis. In the current literature there is no evidence available presenting superior results between hemiarthroplasty and angle-stable locking compression plate osteosynthesis in terms of speed of recovery, pain, patient satisfaction, functional outcome, quality of life or complications.

METHODS/DESIGN

A randomized controlled multicenter trial will be conducted. Patients older than 60 years of age with a dislocated three- or four-part fracture of the proximal humerus as diagnosed by X-rays and CT-scans will be included. Exclusion criteria are a fracture older than 14 days, multiple comorbidity, multitrauma, a pathological fracture, previous surgery on the injured shoulder, severely deranged function caused by a previous disease, "head-split" proximal humerus fracture and unwillingness or inability to follow instructions. Participants will be randomized between surgical treatment with hemiarthroplasty and angle-stable locking compression plate osteosynthesis. Measurements will take place preoperatively and 3 months, 6 months, 9 months, 12 months and 24 months postoperatively. Primary outcome measure is speed of recovery of functional capacity of the affected upper limb using the Disabilities of Arm, Shoulder and Hand score (DASH). Secondary outcome measures are pain, patient satisfaction, shoulder function, quality of life, radiological evaluation and complications. Data will be analyzed on an intention-to-treat basis, using univariate and multivariate analyses.

DISCUSSION

Both hemiarthroplasty and angle-stable locking compression plate osteosynthesis are used in the current treatment of dislocated three-and four-part fractures of the proximal humerus. There is a lack of level-1 studies comparing these two most-used surgical treatment options. This randomized controlled multicenter trial has been designed to determine which surgical treatment option provides the fastest recovery of functional capacity of the affected upper limb, and will provide better outcomes in pain, satisfaction, shoulder function, quality of life, radiological evaluation and complications.

TRIAL REGISTRATION NUMBER

The trial is registered in the Netherlands Trial Registry (NTR2461).

[The radical minimal access thoracoplasty by funnel chest in adults]

A new technique of radical thoracoplasty, performed with a small size incision, using the sternocostal complex fixation with nitinol plates with shape memory and the surgical toolkit required for the purpose, has been successfully introduced. 23 patients underwent surgery using the technique. Tree patients had early postoperative complications: 2 cases of exudative pleurisy and 1 case of bronchitis aggravation. Good cosmetic results was achieved in all operated patients. The mechanical ground of the technique is based on the use of the effective force of the sternum traction and the pressure of the plate on the tissues below. The main advantage of the method is avoidance of the transverse sternotomy.

Vertebral reconstruction using the telescopic plate spacer-thoracolumbar (TPS-TL) device

STUDY DESIGN

Retrospective study of surgical technique and outcome.

OBJECTIVE

The authors conducted a study to evaluate the ability of the TPS-TL (telescopic plate spacer-thoracolumbar) implant to correct kyphotic deformity and restore vertebral body height after vertebrectomy in the thoracolumbar spine.

SUMMARY OF BACKGROUND DATA

TPS-TL is a novel vertebral body replacement device that consists of an expandable cage with an integrated plate component for transvertebral screw fixation.

METHODS

This is a retrospective study of 20 patients who underwent anterior column reconstruction with TPS-TL after a 1 or 2 level thoracolumbar vertebrectomy. Preoperative and postoperative sagittal alignment and vertebral body heights were radiologically analyzed in all patients. The mean follow-up was 14 months.

RESULTS

Preoperative and postoperative Cobb angles were measured to assess sagittal alignment. The average preoperative Cobb angle was 16.0 + or - 7 degrees. This was reduced to 9.8 + or - 10 degrees at the final follow-up (P<0.001). Percent of ideal vertebral body height was used to assess postoperative restoration of vertebral body height. This value was obtained by creating a ratio of the height of the effected vertebral levels to the height of the adjacent normal vertebral bodies. The mean percent of ideal vertebral body height improved from a preoperative value from 86.2 + or - 2% to 93.1 + or - 6% at the final follow-up (P<0.001).

CONCLUSIONS

The TPS-TL implant is effective in restoring vertebral body height and correcting kyphotic deformity after thoracolumbar vertebrectomy.

Comparison of ventral corpectomy and plate-screw-instrumented fusion with dorsal laminectomy and rod-screw-instrumented fusion for treatment of at least two vertebral-level spondylotic cervical myelopathy

The objective of the article is to verify the hypothesis that the dorsal multilevel laminectomy and rod-screw-instrumented fusion (DLF) for multilevel spondylotic cervical myelopathy (MSCM) is less strenuous for patients, and less prone to perioperative complications, than ventral multilevel corpectomy and plate-screw-instrumented fusion (VCF), while clinical outcome is comparable. One hundred and three successive patients were treated for at least two vertebral-level MSCM, 42 of them by VCF and 61 by DLF. The two patients groups were retrospectively compared. VCF patients were slightly younger than DLF patients (62.5 +/- 10.61 years versus 66 +/- 12.4 years, P = 0.012). In VCF patients, a median of 2 (2-3) corpectomies and in DLF patients a median of 3 (2-5) laminectomies were performed. In VCF patients, surgery lasted longer than in DLF patients (229 +/- 60 min versus 183 +/- 46 min, P < or = 0.001). Between the VCF and the DLF patients groups, no significant difference was found in perioperative complications (e.g. hardware failure rates of 16.7% in VCF and of 6.6% in the DLF patients) and mortality rates. The postoperative outcome, as assessed by the postoperative change of the Nurick scores, the change of neck pain, the patients' satisfaction, and the change of the subaxial Cobb angle of the spine did not differ between the two patients groups. However, when comparing the postoperative Nurick scores directly, VCF patients fared somewhat better than DLF patients [median of 2 (0-5) versus 3 (1-5), P = 0.003]. The hypothesized advantages of DLF over VCF in the surgical treatment of at least two vertebral-level MSCM could not be confirmed in this retrospective study. A prospective randomized study is warranted to clarify this issue.

Biomechanical testing of unstable humeral shaft fracture plating

This study compared the biomechanical performance of 4.5-mm limited-contact dynamic compression plates (DCPs) and 3.5-mm locking compression plates (LCPs) for the fixation of unstable humeral shaft fractures. Composite humeri were divided into two groups: 3.5-mm LCPs and 4.5-mm DCPs. Osteotomy gaps of 5 mm, simulating diaphyseal comminution, were created. Stiffness tests were performed in anterior-posterior (AP) bending, medial-lateral (ML) bending, torsion, and axial compression. Results showed that while construct stiffnesses in ML bending and torsional loading are significantly higher for the 4.5 DCP group (p < .05), no statistically significant differences were observed in AP bending or axial compression. Fatigue characteristics under cyclic AP bending conditions were also evaluated, although no failures occurred. Data from the literature suggest that stiffness results for the LCP constructs perhaps afford sufficient fixation strength capable of supporting the physiologic loads most commonly applied during postoperative rehabilitation. However, results indicate that the DCP construct is mechanically advantageous for stabilizing diaphyseal comminuted fractures.

Complications during and after surgery of the lower cervical spine by isolated anterior approach with CSLP implant

BACKGROUND

The merits of different operative approaches in the management of spinal injury is debated. The aim of this study was to assess, retrospectively, the outcome of treatment of injuries of the lower cervical spine by an anterior approach, in terms of fusion rate and complications.

MATERIALS AND METHODS

Between 1995 and 2004, 270 patients with an injury of the lower cervical spine were operated on by an anterior approach in our hospital. There were 67 females and 203 males. Using the Aebi and Nazarian classification, 22% of patients had a type A injury, 23% of patients had a type B injury and 55% of patients had a type C injury. All had an anterior approach with monocortical stabilisation using a cervical spine locking plate [Synthes].

RESULTS

Radiological evidence of fusion was found in all but one patient at 6 months. Complications occurred in a small proportion of the series. Recurrent laryngeal nerve injury was noted in seven patients, an abscess in the wound in one patient, a haematoma requiring re-operation for evacuation in two patients. The cervical locking plate broke in one patient and this patient went on to develop a pseudoarthrosis from failure to fuse. In another patient there was release of the plate osteosynthesis.

CONCLUSIONS

Treatment of the injured lower cervical spine by an anterior operation and plate fixation was successful in achieving bone fusion in almost every patient and was followed by a complication in only a small proportion of our series. Similar results in other reports indicate that this approach is a safe and effective procedure.

Mechanical properties of 18 different AO bone plates and the clamp-rod internal fixation system tested on a gap model construct

OBJECTIVE

To compare the stiffness and strength of AO bone plates (DCP, LC-DCP, VCP, RCP, and LP) and the Clamp-Rod Internal Fixation System (CRIF).

STUDY DESIGN

In vitro.

SAMPLE SIZE

12 individual implants of 18 plate dimensions and four sizes of CRIF, each corresponding to 2.0, 2.4/2.7, 3.5, or 4.5 mm screw sizes.

METHODS

Implant-constructs of each plate and CRIF were created using Canevasit rods as a bone substitute in an unstable gap fracture model. Six implant-constructs of each type were tested under single cycle four-point bending loading, and six were tested under single cycle torsional loading until permanent plastic deformation occurred.

RESULTS

Torsional stiffness and yield load of the DCP were always significantly greater than the CRIF within the same group. Bending properties of the 2.0 DCP were not significantly different to the 2.0 CRIF. The 2.7 DCP had significantly higher bending values than the 2.7 CRIF. The bending stiffness of the 3.5 DCP and 4.5 DCP was significantly less than their CRIF counterparts. While the bending yield load of the 3.5 DCP was significantly greater than the 3.5 CRIF, the bending yield load of the 4.5 DCP was significantly less than the 4.5 CRIF.

CONCLUSION

A weakness was found in the torsional resistance of the CRIF constructs compared to the DCP constructs.

CLINICAL SIGNIFICANCE

Bone holding power and applied screw torque should be considered when using the CRIF system in clinical application.

Use of resorbable implants for symptomatic cervical spondylosis: experience on 16 consecutive patients

AIM

The aim of this study was to evaluate the results of a consecutive series of 16 patients affected by degenerative cervical spondylosis and operated on by anterior cervical discectomy and fusion (ACFD) by means of anterior bioresorbable plate and screws. Further, the authors compared the results in these patients with a series of 13 patients also affected by degenerative cervical spondylosis in whom arthrodesis was obtained by means of cages without plates.\

METHODS

The series included 8 males and 8 females aging from 37 to 69 years, operated from June 2003 to September 2004. They showed signs of cervical myelopathy, radiculopathy or both. The ACDF was performed with the insertion of dense cancellous allograft and application of anterior bioresorbable plate and screws (group A). The group B series included 9 males and 4 females aging from 50 to 77 years, all affected by the same pathology of group A patients and operated on in the same period of time. In these cases the ACDF was followed by the insertion of cages without anterior plates.

RESULTS

The retrospective analysis of our series showed lack of soft tissue reaction, with safeguarding of the vertebral body and disc space height. The degree of alignment of the cervical spine was also preserved, with a good rate of fusion and a good clinical outcome in both series of patients.

CONCLUSION

The use of a cervical plate increase stability and rate of fusion when added to the interbody device; while the use of a metallic plate may be responsible for several shortcomings, a resorbable plate may overcome these problems.

Complication avoidance in 116 dynamic-plated single-level anterior corpectomy and fusion

Complications arising over a 6-year interval after 116 single-level anterior corpectomy/fusions (ACF) using iliac crest autograft and dynamic ABC plates were sequentially evaluated. Patients averaged 45 years of age (52 females and 64 males). Preoperative magnetic resonance and computed tomography studies documented adjacent 2-level disease/retrovertebral extension. Single level ACF (eg, C5-C7) used iliac crest autograft and dynamic ABC plates (Aesculap, Tuttlingen, Germany). Patients underwent dynamic x-ray and 2D-computed tomography evaluations 3, 4.5, 6, and up to 12 months postoperatively until fusion was documented by 2 independent radiologists. Patient were followed an average of 3.2 years (minimum 1 y). Three patients undergoing surgery in the first year of the study exhibited plate/graft extrusion (1 to 3 wk) or pseudarthroses (2 to 6 mo); subsequent improvements in surgical technique eliminated these complications in the last 5 years of the study. Inadequate bracing (4 mo on average) over the first 2 years was presumed responsible for 2-delayed strut fractures requiring secondary surgery (6 mo, and 2 y/Lupus/steroids) and 5 managed nonsurgically had 3 to 6 months of additional bracing. The routine addition of 6 weeks of cervicothoracic orthoses bracing in the latter 4 years of the study eliminated these strut fractures. Of interest, only 1 patient developed symptomatic adjacent level disease requiring a laminectomy (C6, C7) and posterior fusion (C2-T2) 5 years later. Complications observed in the first 2 years of a study involving 116 single-level dynamic-plated ACF were largely eliminated by introducing more prolonged bracing and improved surgical techniques for the study's last 4 years.

Screw pull-out force is dependent on screw orientation in an anterior cervical plate construct

Two common justifications for orienting cervical screws in an angled direction is to increase pull-out strength and to allow use of longer screws. This concept is widely taught and has guided implant design. Fixed versus variable angle systems may offer strength advantages. The purpose of our study is to test the influence of screw orientation and plate design on the maximum screw pull-out load. Variable and fixed angle 4.0 x 15 mm and 4.0 x 13 mm self-tapping screws were used to affix a Medtronic Atlantis cervical plate to polyurethane foam bone samples (density 0.160/cm). This synthetic product is a model of osteoporotic cancellous bone. The fixed angle screws can only be placed at 12 degrees convergent to the midline and 12 degrees in the cephalad/caudal ("12 degrees up and in") direction. Three groups were tested: (1) all fixed angle screws, (2) variable angle, all screws 12 degrees up and in, (3) variable angle, all screws 90 degrees to the plate. Plate constructs were pulled off with an Instron DynaMight 8841 servohydrolic machine measuring for maximum screw pull-out force. There was no difference between group 1, fixed angle (288.4 +/- 37.7 N) (mean +/- SD) and 2, variable angle group (297.7 +/- 41.31 N P< or =0.73). There was a significant increase in maximum pull-out force to failure for the construct with all screws at 90 degrees (415.2+/-17.4 N) compared with all screws 12 degrees "up and in" (297.4 +/- 41.3 N, P< or =0.0016). Group 3 done with 13 mm screws, showed a trend toward better pull-out strength, compared to group 2 w/15 mm screws (345.2 +/- 20.5 vs. 297.4 +/- 41.3, P< or =0.06). In this plate pull-out model, screw orientation influences maximum force to failure. When all 4 screws are 90 degrees to the plate the construct has the greatest ability to resist pullout. Fixed angle designs show no advantage over variable angle. These findings are contrary to current teaching.

Bicortical screw fixation of distal fibula fractures with a lateral plate: an anatomic and biomechanical study of a new technique

One of the potential drawbacks of lateral plating of distal fibula fractures is less than satisfactory fixation of unicortical screws commonly placed in the distal fragment to avoid implant penetration of the ankle joint. This study examines the anatomy of the distal fibula, proposes new techniques for bicortical screw fixation and radiographic evaluation of screw placement, and compares pullout strength of unicortical versus bicortical screws in this area. Sixteen pairs of human cadaver feet were used in this study. It was found that a large percentage of the surface area of the distal fibula is nonarticular and that the distal fibula could be divided into 3 zones with distinct anatomic features. Zone I is defined as the distal most 1.5 cm of the fibula, zone II is the next 1 cm of fibula proximal to zone I, and zone III is defined as the fibula above the ankle joint, starting at just over 2.5 cm proximal to the tip of the fibula. We determined a safe corridor for bicortical screw placement by means of a lateral plate in each zone. An improved radiographic view is described for confirmation of extraarticular screw placement. Screw pullout testing was performed on 8 pairs of fresh-frozen human cadaver fibulas. In both zone I and zone II, the bicortical screw fixation was significantly stronger than the unicortical screw fixation. In zone I, the average pullout strength for the bicortical screw fixation was 2.3 times higher than the unicortical screw fixation. In zone II, the average pullout strength for the bicortical screw fixation was 3.3 times higher than the unicortical screw fixation. This study shows that not only is bicortical screw placement in the distal fibula technically feasible, but it is also biomechanically stronger than unicortical placement in this area.

Correlation of cervical endplate strength with CT measured subchondral bone density

Cervical interbody device subsidence can result in screw breakage, plate dislodgement, and/or kyphosis. Preoperative bone density measurement may be helpful in predicting the complications associated with anterior cervical surgery. This is especially important when a motion preserving device is implanted given the detrimental effect of subsidence on the postoperative segmental motion following disc replacement. To evaluate the structural properties of the cervical endplate and examine the correlation with CT measured trabecular bone density. Eight fresh human cadaver cervical spines (C2-T1) were CT scanned and the average trabecular bone densities of the vertebral bodies (C3-C7) were measured. Each endplate surface was biomechanically tested for regional yield load and stiffness using an indentation test method. Overall average density of the cervical vertebral body trabecular bone was 270 +/- 74 mg/cm3. There was no significant difference between levels. The yield load and stiffness from the indentation test of the endplate averaged 139 +/- 99 N and 156 +/- 52 N/mm across all cervical levels, endplate surfaces, and regional locations. The posterior aspect of the endplate had significantly higher yield load and stiffness in comparison to the anterior aspect and the lateral aspect had significantly higher yield load in comparison to the midline aspect. There was a significant correlation between the average yield load and stiffness of the cervical endplate and the trabecular bone density on regression analysis. Although there are significant regional variations in the endplate structural properties, the average of the endplate yield loads and stiffnesses correlated with the trabecular bone density. Given the morbidity associated with subsidence of interbody devices, a reliable and predictive method of measuring endplate strength in the cervical spine is required. Bone density measures may be used preoperatively to assist in the prediction of the strength of the vertebral endplate. A threshold density measure has yet to be established where the probability of endplate fracture outweighs the benefit of anterior cervical procedure.

New rod-plate anterior instrumentation for thoracolumbar/lumbar scoliosis: biomechanical evaluation compared with dual-rod and single-rod with structural interbody support

STUDY DESIGN

A new rod-plate anterior implant was designed to provide plate fixation at the cephalad and caudal-end segments of a 5-level anterior spine construct. Biomechanical testing was performed on calf spines instrumented with 5-segment anterior scoliosis constructs. OBJECTIVES.: To analyze the initial and post-fatigue biomechanical performance of the new implant, and compare it to an anterior dual-rod construct and a single-rod construct with interbody cages.

SUMMARY OF BACKGROUND DATA

Using single-rod anterior instrumentation for thoracolumbar and lumbar scoliosis, an unacceptable incidence of loss of correction, segmental kyphosis, and pseudarthrosis has been reported. Inadequate construct stiffness due to early postoperative bone-screw interface failure, especially at cephalad and caudal-end vertebrae, has been implicated as the cause of these complications.

METHODS

Thirty calf spines were instrumented over 5 segments with: (1) single-rod augmented with rod-plate implants, (2) dual-rod construct, and (3) single-rod with titanium mesh cages. Stiffness in flexion-extension and lateral bending modes was determined initially and post-cyclical loading by measuring segmental range of motion (ROM). Post-fatigue screw pullout tests were also performed.

RESULTS

In lateral bending, the caudal-end segmental ROM for rod-plate construct was 54% less than single-rod with cages construct (P < 0.05), with no difference between rod-plate and dual-rod constructs. In flexion-extension, the rod-plate construct showed 45% to 91% (initial test) and 84% to 90% (post-fatigue) less ROM than the single-rod with cages construct (P < 0.001). Again, there was no difference between rod-plate and dual-rod constructs at the cephalad and caudal-end segments. Post-fatigue screw pullout strengths of the rod-plate construct were significantly greater than those of the dual-rod and single-rod with cages constructs (P < 0.05).

CONCLUSIONS

The rod-plate construct was significantly stiffer and provided greater stability of bone-screw interface than the single-rod with cages construct. It achieved similar stiffness and improved bone-screw interface stability compared to dual-rod construct.

An In Vitro Biomechanical Comparison Between Prototype Tapered Shaft Cortical Bone Screws and AO Cortical Bone Screws for an Equine Metacarpal Dynamic Compression Plate Fixation of Osteotomized Equine Third Metacarpal Bones

OBJECTIVES

To compare biomechanical properties of a prototype 5.5 mm tapered shaft cortical screw (TSS) and 5.5 mm AO cortical screw for an equine third metacarpal dynamic compression plate (EM-DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones.

STUDY DESIGN

Paired in vitro biomechanical testing of cadaveric equine MC3 with a mid-diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation.

ANIMAL POPULATION

Adult equine cadaveric MC3 bones (n=12 pairs).

METHODS

Twelve pairs of equine MC3 were divided into 3 groups (4 pairs each) for (1) 4-point bending single cycle to failure testing, (2) 4-point bending cyclic fatigue testing, and (3) torsional single cycle to failure testing. An EM-DCP (10-hole, 4.5 mm) was applied to the dorsal surface of each, mid-diaphyseal osteotomized, MC3 pair. For each MC3 bone pair, 1 was randomly chosen to have the EM-DCP secured with four 5.5 mm TSS (2 screws proximal and distal to the osteotomy; TSS construct), two 5.5 mm AO cortical screws (most proximal and distal holes in the plate) and four 4.5 mm AO cortical screws in the remaining holes. The control construct (AO construct) had four 5.5 mm AO cortical screws to secure the EM-DCP in the 2 holes proximal and distal to the osteotomy in the contralateral bone from each pair. The remaining holes of the EM-DCP were filled with two 5.5 mm AO cortical screws (most proximal and distal holes in the plate) and four 4.5 mm AO cortical screws. All plates and screws were applied using standard AO/ASIF techniques. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05.

RESULTS

Mean 4-point bending yield load, yield bending moment, bending composite rigidity, failure load and failure bending moment of the TSS construct were significantly greater (P<.00004 for yield and P<.00001 for failure loads) than those of the AO construct. Mean cycles to failure in 4-point bending of the TSS construct was significantly greater (P<.0002) than that of the AO construct. The mean yield load and composite rigidity in torsion of the TSS construct were significantly greater (P<.0039 and P<.00003, respectively) than that of the AO construct.

CONCLUSION

The TSS construct provides increased stability in both static overload testing and cyclic fatigue testing.

CLINICAL RELEVANCE

The results of this in vitro study support the conclusion that the EM-DCP fixation using the prototype 5.5 mm TSS is biomechanically superior to the EM-DCP fixation using 5.5 mm AO cortical screws for the stabilization of osteotomized equine MC3.

Fatigue Analysis of Plates Used for Fracture Stabilization in Small Dogs and Cats

OBJECTIVE

To evaluate the fatigue life of stacked and single, veterinary cuttable plates (VCP) and small, limited contact, dynamic compression plates (LC-DCP).

STUDY DESIGN

In vitro biomechanical study.

METHODS

Fracture models (constructs; n = 8) were assembled for each of 6 groups all with 8-hole plates: 2.0 mm LC-DCP; 2.4 mm LC-DCP; single 1.5/2.0 mm VCP; stacked 1.5/2.0 mm VCP; single 2.0/2.7 mm VCP; and stacked 2.0/2.7 mm VCP. Plate(s) were secured to 2 polyvinylchloride pipe lengths, mounted in a testing system with a custom jig, and subjected to axial loading (10-100 N) for 1,000,000 cycles at 10 Hz or until failure. Differences in number of cycles to failure among groups were compared. Failure mode was determined.

RESULTS

All LC-DCP and single VCP constructs failed before 1,000,000 cycles. Stacked 2.0/2.7 mm VCP constructs withstood 1,000,000 cycles without failure. ANOVA and Fisher's least significant difference tests demonstrated significantly more cycles to failure for the stacked 1.5/2.0 mm VCP and stacked 2.0/2.7 mm VCP compared with the single 1.5/2.0 mm VCP, single 2.0/2.7 mm VCP, 2.0 mm LC-DCP, or 2.4 mm LC-DCP. Constructs that failed did so through a screw hole adjacent to the gap.

CONCLUSION

Stacked VCP constructs have greater fatigue lives than comparably sized LC-DCP or single VCP constructs. Plates with 2.4 mm screws were not significantly different from the comparable construct with 2.0 mm screws.

CLINICAL RELEVANCE

Although these data reveal that stacked VCP create a superior construct with respect to cyclic fatigue, surgeons must decide whether this is a clinical advantage on a case-by-case basis.

Surgical treatment of spondylodiscitis in the cervical spine: a minimum 2-year follow-up

Cervical spine spondylodiscitis is a rare, but serious manifestation of spinal infection. We present a retrospective study of 20 consecutive patients between 01/1994 and 12/1999 treated because of cervical spondylodiscitis. Mean age at the time of treatment was 59.7 (range 34-81) years, nine of them female. In all cases, diagnosis had been established with a delay. All patients in this series underwent surgery such as radical debridement, decompression if necessary, autologous bone grafting and instrumentation. Surgery was indicated if a neurological deficit, symptoms of sepsis, epidural abscess formation with consecutive stenosis, instability or severe deformity were present. Postoperative antibiotic therapy was carried out for 8-12 weeks. Follow-up examinations were performed a mean of 37 (range 24-63) months after surgery. Healing of the inflammation was confirmed in all cases by laboratory, clinical and radiological parameters. Spondylodesis was controlled radiologically and could be achieved in all cases. One case showed a 15 degrees kyphotic angle in the proximal adjacent segment. Spontaneous bony bridging of the proximal adjacent segment was observed in one patient. In the other cases the adjacent segments radiologically showed neither fusion nor infection related changes. Preoperative neurological deficits improved in all cases. Residual neurological deficits persisted in three of eight cases. The results indicate that spondylodiscitis in cervical spine should be treated early and aggressive to avoid local and systemic complications.

Eyebrow Surgery: The Supraciliary Craniotomy: Technical Note

OBJECTIVE:

Many approaches have been recommended for the surgical treatment of anterior and middle cranial fossa lesions. The frontobasal approach and its many modifications have been proposed and developed for such situated lesions. An alternative approach is the frontolateral craniotomy through a supraciliary skin incision.

METHODS:

This minimally invasive technique, a 2.5 × 3.0 cm craniotomy, just above the eyebrow through a supraciliary incision, is a simple but elegant modification of the traditional approach to the anterior cranial fossa.

RESULTS:

A step-by-step description of the approach is offered in this report to facilitate a clear understanding of the lesions treatable with this minimally invasive technique.

CONCLUSION:

The supraciliary frontolateral keyhole craniotomy is a minimally invasive cosmetic approach that provides excellent exposure to a variety of intracranial lesions. This approach cannot be used for all intracranial pathologies, but is recommended for many anterior and middle cranial fossa lesions.

Comparison of the biomechanical stability of dense cancellous allograft with tricortical iliac autograft and fibular allograft for cervical interbody fusion

Several choices are available for cervical interbody fusion after anterior cervical discectomy. A recent option is dense cancellous allograft (CS) which is characterized by an open-matrix structure that may promote vascularization and cellular penetration during early osseous integration. However, the biomechanical stability of CS should be comparable to that of the tricortical iliac autograft (AG) and fibular allograft (FA) to be an acceptable alternative to these materials. The purpose of this study was to compare the initial biomechanical stability of CS to that of AG and FA in a one-level anterior cervical discectomy and interbody fusion (ACDF) model. Twelve human cervical spines (C3-T1) were loaded in six modes of motion and evaluated under three conditions: (1) intact, (2) after ACDF using CS, AG, and FA in alternating sequences, and (3) after ACDF with anterior plating. Three reflective markers were placed on the adjacent vertebral bodies. Intervertebral motion was measured with a video-based motion-capture system (MacReflex, Qualisys, Sweden). Torques were applied to a maximum of 2.0 N m. The range-of-motion and neutral-zone values measured in each loading mode were compared. No graft material displayed significant differences in biomechanical stability in any of the tested loading modes, suggesting that the initial stability of CS is comparable to that of AG and FA. Anterior cervical plating significantly increased biomechanical stability in all modes.

Biomechanical analysis of posterior fixation techniques in a 360 degrees arthrodesis model

STUDY DESIGN

A biomechanical study to assess the ability of posterior fixation techniques to stabilize a functional spine unit (FSU) after insertion of an anterior load-sharing device.

OBJECTIVE

The objective of this study is to compare various posterior fixation techniques in combination with an anterior load-sharing implant.

SUMMARY OF BACKGROUND DATA

Pedicle screws and translaminar facet screws have been shown to improve the stiffness of an FSU in combination with an anterior load-sharing device. No published studies, to our knowledge, have compared translaminar facet screw fixation versus bilateral and unilateral pedicle screw fixation used with an anterior load-sharing device.

METHODS

Ten cadaveric FSUs were potted using methylmethacrylate and attached to a spine simulator mounted to an MTS Mini-Bionix testing machine. The simulator was configured to control compressive loading, axial torque, flexion, extension, and lateral bending. Each specimen was tested in the intact state and following the application of each of four stabilization techniques: custom cage alone, cage plus translaminar facet screw fixation, cage plus unilateral pedicle screw and plate fixation, and cage plus bilateral pedicle screw and rod fixation with transverse coupling. Compressive stiffness and total range of motion (ROM) between +/-8 Nm of torque were extracted from the raw data.

RESULTS

Each fixation method decreased ROM in torsion, flexion-extension, and lateral bending compared with the intact state. Unilateral pedicle fixation offered less stability than either of the other posterior fixations in all modes of testing except axial loading, where it was equivalent. Translaminar facet screw fixation was equivalent to bilateral pedicle screws in all modes tested.

CONCLUSIONS

Using a load-sharing interbody implant, translaminar facet screws are equivalent to bilateral pedicle screws in resisting motion in all three planes. Translaminar facet screws and bilateral pedicle screws offer greater stabilization in all three planes compared with unilateral pedicle screws and a single plate.

Sarcoma of the proximal portion of the tibia in a dog 5.5 years after tibial plateau leveling osteotomy

Osseous neoplasia was identified in the proximal portion of the tibia and distal portion of the femur in an 11.75-year-old spayed female German Shepherd Dog. A tibial plateau leveling osteotomy, followed by application of a metal plate, had been performed on the affected limb 5.5 years earlier. Areas of osteolysis and periosteal proliferation were seen radiographically, with an intense area of osteolysis directly beneath the metal plate. Histologically, the tumor was identified as a poorly differentiated sarcoma. Extracellular and intracellular debris was seen histologically, and energy-dispersive x-ray analysis confirmed that this debris was metallic. On visual examination, areas of the underside of the metal plate that had been in contact with bone had a dull, roughened appearance, and scanning electron microscopy of these areas revealed multiple corrosion pits. The plate was strongly magnetic, suggesting that it contained ferrite, and metallographic examination of the plate revealed substantial differences in the chemical makeup of various parts of the plate. Microstructure analysis revealed that the plate consisted of an austenite matrix with a large fraction of ferrite. The plate was determined to be a cast 316L stainless steel implant, but it did not meet American Society for Testing Materials standards for implant-grade materials. The possibility that implant corrosion might have played a role in tumor development is of concern; however, a definitive association was not established.

Comparison of stiffness and failure load of two cervical spine fixation techniques in an in vitro human model

OBJECTIVE

Recently, an unpaired threaded cage has been introduced as a fusion device for the cervical spine. No biomechanical comparison of a stand-alone single interbody threaded cage to a standard plated Smith-Robinson construct has been reported. Accordingly, an in vitro biomechanical comparison of a single threaded cylindrical interbody fusion cage versus a plated Smith-Robinson cervical discectomy and fusion construct was conducted to establish whether a single cylindrical interbody cage in the cervical spine would perform mechanically as well as a plated structural interbody graft.

METHODS

Six fresh-frozen human cadaveric cervical spines were used for biomechanical testing. Flexion-extension and load-to-failure testing were performed on two single-level discectomy and interbody fusion constructs from each specimen.

RESULTS

Initial range of motion (ROM) was significantly greater for the specimens implanted with a cage than specimens implanted with a structural graft and plate (9.1 degrees +/- 3.7 degrees vs 5.8 degrees +/- 2.4 degrees ; P = 0.040). Initial stiffness in flexion in caged specimens was significantly less than in plated specimens (0.7 +/- 0.3 vs 0.9 +/- 0.3 Nm/ degrees ; P = 0.028). Cage specimens also failed at a significantly lower load than plated specimens (9.8 +/- 3.5 vs 15.8 +/- 4.1 Nm; P = 0.0104).

CONCLUSIONS

This study demonstrates that a plated Smith-Robinson cervical discectomy and fusion construct provides greater stiffness and failure load and reduced ROM across operated levels than a single interbody cage construct. Although clinical success may not directly correlate with biomechanical data, these results raise concern regarding the use of a single threaded interbody cage as a stand-alone device for cervical interbody fusion.

Biomechanical comparison of transarticular facet screws to lateral mass plates in two-level instrumentations of the cervical spine

STUDY DESIGN

In vitro biomechanical comparison of transarticular facet screws to lateral mass plates in two level instrumentations of the cervical spine.

OBJECTIVE

Lateral mass plates are costly, and screw placement is difficult. Facet screws have never been tested as an alternative in the cervical spine. This biomechanical study compared cervical transarticular facet screws to lateral mass plates in two-level instrumentations of human cadaveric cervical spines.

SUMMARY OF BACKGROUND DATA

Translaminar facet screws have been shown to have similar biomechanical performance to pedicle screw fixation in the lumbar spine, especially in flexion. They have proven to be fast, safe, and effective, with authors reporting 94% to 100% fusion rates in single-level lumbar fusions. However, a biomechanical comparison of transarticular facet screws to lateral mass plates in cervical spine instrumentations has not been reported.

METHODS

Thirteen human cadaveric cervical motion segments (C2-C4, C5-C7) were tested before and after instrumentation, with either transarticular facet screws or lateral mass plates, in flexion, extension, lateral bending, and torsion. Specimens were subjected to six cycles under a load of 2 Nm.

RESULTS

Both fixation systems significantly reduced range of motion (ROM) and increased stiffness compared with the intact state in flexion, extension, lateral bending, and torsion. There were also no significant differences between the facet screws and plates in any of the four directions. To compare the two systems, ROM of each was analyzed relative to the uninstrumented state. Flexion was 0.26 (or 26% of the intact state) for the transarticular facet screws versus 0.20 for the lateral mass plates (P = 0.34), extension was 0.10 versus 0.07 (P = 0.43), lateral bending was 0.17 versus 0.15 (P = 0.52), and torque was 0.25 versus 0.38 (P = 0.12). Load to failure testing failed to indicate any differences between the two methods of fixation because all the specimens failed elsewhere.

CONCLUSION

This study proves that transarticular facet screws and lateral mass plates are equivalent in two-level instrumentations of the cervical spine. This is the first biomechanical study to test transarticular facet screws in this context.

Anterior correction of cervical spine lordosis using an adjustable depth tap: technical note

OBJECTIVE

In cases of multilevel anterior cervical spine decompression where intervening vertebral bodies need to be incorporated into the anterior plate construct, it may be difficult to apply the plate flush against the entire anterior cortical surface of the spine segment. Some have suggested using the levering property of bicortical screws to "pull" the body against the plate. Others have recommended contouring the anterior cervical plate with a plate bender. The objective of this work was to describe a novel technique using the adjustable depth tap provided in the Atlantis plating system for achieving cervical spine alignment against the lordotic plate after multilevel anterior decompression.

METHODS

We describe an illustrative case of a 14-year-old girl with complex cervical spine fractures after trauma. We used the 4.0-mm adjustable depth tap in the Atlantis plating system to lever the C4 body against the premachined lordotic plate.

RESULTS

Cervical lordosis and anterior cervical plate placement were accomplished after multilevel anterior cervical decompression with the use of an adjustable depth tap.

CONCLUSIONS

Bicortical screw placement and plate bending have drawbacks in trying to apply the anterior cervical plate firmly to the anterior surface of the cervical spine. We describe a new and safe technique of using an adjustable depth tap for achieving that same goal without any obvious drawbacks.

Anterior-Only Stabilization of Three-Column Thoracolumbar Injuries

OBJECTIVE

The optimal treatment of "unstable" thoracolumbar injuries remains controversial. Studies have shown the advantages of direct anterior decompression of thoracolumbar injuries along with supplemental posterior instrumentation as a combined or staged procedure. Others have also shown success in decompression as a single-stage anterior procedure, largely limited to two-column (anterior and middle) injuries. A retrospective review of all available clinical and radiographic data was used to classify unstable three-column thoracolumbar fractures according to the Association for the Study of Internal Fixation (AO) classification system. This was conducted to evaluate the efficacy of stand-alone anterior decompression and reconstruction of unstable three-column thoracolumbar injuries, utilizing current-generation anterior spinal instrumentation.

METHODS

Between 1992 and 1998, 40 patients underwent anterior decompression and two-segment anteriorly instrumented reconstruction for three-column thoracolumbar fractures. Retrospective review of all available clinical and radiographic data was used to classify these unstable injuries according to the AO classification system, evaluating for neurologic changes, spinal canal compromise, preoperative and postoperative segmental angulation, and arthrodesis rate.

RESULTS

According to the AO classification system, there were 24 (60%) type B1.2, 10 (25%) type B2.3, 5 (12.5%) type C1.3, and 1 (2.5%) type C2.1 three-column injuries. Preoperative canal compromise averaged 68.5% and vertebral height loss averaged 44.5%. There were no cases of neurologic deterioration, and 30 (91%) patients with incomplete neurologic deficits improved by at least one modified Frankel grade. Mean preoperative segmental kyphosis of 22.7 degrees was improved to an early mean of 7.4 degrees (P < 0.0001). At latest follow-up, angulation had increased by an average 2.1 degrees but maintained significant improvement from preoperative measurements (P < 0.0001). There was one early construct failure due to technical error. Thirty-seven of the remaining patients (95%) went on to apparently stable arthrodesis.

CONCLUSIONS

Current types of anterior spinal instrumentation and reconstruction techniques can allow some types of unstable three-column thoracolumbar injuries to be treated in an anterior stand-alone fashion. This allows direct anterior decompression of neural elements, improvement in segmental angulation, and acceptable rates of arthrodesis without the need for supplemental posterior instrumentation.

Treatment of complex tibial plateau fractures using the less invasive stabilization system plate: clinical experience and a laboratory comparison with double plating

BACKGROUND

Bicondylar tibial plateau fractures are complex injuries, historically associated with high complication rates. The purpose of this study was: 1) to evaluate the clinical use L.I.S.S plating system for stabilization of bicondylar tibial plateau fractures. 2) To compare the biomechanics of this plating system with a double plate construct.

METHODS AND MATERIALS

Thirty-eight patients who sustained a complex tibial plateau fracture (OTA type 41C) at one of three level-one trauma centers were stabilized using the Less Invasive Stabilization System (L.I.S.S.). The cohort of patients was evaluated clinically and radiographically for outcomes at a mean 15 months. In phase 2 of this study a model of a bicondylar tibial plateau fractures was made in six matched pairs of embalmed, human tibia and randomized to fixation with either a L.I.S.S plate or a standard double plate construct. The tibias were then subjected to an axial cyclic load of 500N for 10 cycles (3Hz) to approximate 2 months in vivo and displacements measured.

RESULTS

Thirty-six of /38 (95%) patients united at 4 months after surgery with no loss of fixation nor infection. Two patients underwent prophylactic autogenous bone grafting for bone loss and united by 3 months postgrafting. Significant loss of knee range of motion (<90) was seen in five patients.Biomechanically, no differences in permanent inferior displacement of the medial fragment were found in initial axial loading and after 10 cycles between the two plate constructs. However, when loaded to 500N the L.I.S.S plate construct demonstrated almost twice the displacement of the medial fragment compared with the dual plate construct. No specimen lost fixation during cycling.

CONCLUSION

The L.I.S.S plating system provides stable fixation of complex bicondylar tibial plateau fractures allowing early range of knee motion with favorable clinical results.

A retrospective review of cervical corpectomy: indications, complications and outcome

BACKGROUND

Cervical corpectomy is a common spinal surgery procedure used to decompress the spinal cord in numerous degenerative, traumatic and neoplastic conditions. The aim of this study was to investigate the indications, complications and outcomes in past cervical corpectomy cases at one centre.

METHOD

72 patients who underwent cervical corpectomy between February 1992 and June 2001 were retrospectively investigated.

FINDINGS

The indications for this operation were degenerative spondylitic disease (26 cases; 36.1%), trauma (18 cases; 25%), tumour (11 cases; 15.3%), infection (10 cases; 13.9%), and ossification of the posterior longitudinal ligament (7 cases; 9.7%). Thirty-seven patients (51.4%) underwent one-level corpectomy, and 35 (48.6%) underwent two-level corpectomy. Autografts were used in 13 cases (18.1%) and allografts were used in 59 cases (81.9%). Anterior plate-screw fixation was performed in all cases. There were 31 postoperative complications in 15 (20.8%) patients. Twelve of the complications were surgical, 5 were graft-related, 7 were plating-related, and 7 were medical. Solid bony fusion was achieved in 65 (92.9%) of the 70 surviving patients. The mean follow-up time was 23.4 months. An overall favourable outcome was achieved in 88% of cases.

CONCLUSION

The outcomes in this series indicate that cervical corpectomy is an effective method for treating traumatic lesions, degenerative disease, tumours and infectious processes involving the anterior and middle portions of the cervical spine.

New material for Nuss procedure

The Nuss procedure for pectus excavatum repair has been considered an acceptable method in terms of its decreased invasiveness and excellent cosmetic results. Although a steel bar is usually used for elevating the sternum, we used a titanium alloy plate for pectus excavatum repair for the first time. The characteristics of this plate are that 1) it comes out translucently on X-rays, 2) MRI examination is possible because titanium will not be magnetized, and 3) it is possible to go through the security checkpoint at the airport without setting off the metal detector. Furthermore, the titanium alloy is highly elastic, which reduces complications such as dislocation, and it excels in the conformity to organization. Patients who have received the Nuss operation are forced to somewhat limit their daily life for two or three years until the bar is removed. A plate made from titanium alloy resolves this problem because of its material and it is thought to be an ideal candidate for elevating the sternum during the Nuss operation.

Reconstruction of a large post-traumatic cranial defect with a customized titanium plaque

The treatment of serious cranial defects has always been a fascinating and controversial issue for craniofacial surgeons and in the last years many solutions have been proposed. One of the most effective method is a personalized titanium plaque prepared by processing anatomical data obtained with a CAT of the patient. A case of wide cranial defect on the left fronto-parietal region in a 56-year-old man treated with a personalized titanium plaque obtained by processing the data of a spiral CAT of the skull is described. No complications were observed in the postoperative course and follow-up after 6 moths showed that the patient was in good general condition.

Distractive flexion injuries of the subaxial cervical spine treated with anterior plate alone

The clinical and radiographic effect of anterior plate fixation alone was evaluated in 36 consecutive patients with distractive flexion (DF) injuries in the lower cervical spine. Mean follow-up time was 15 months. The aim of the present study was to determine whether anterior plate fixation alone provides sufficient stability when treating DF injuries in the cervical spine. Solid union was seen in 6 of 6 patients with stage 1 injury and in 15 of 17 patients with stage 2 injury. In the patients with stage 3 injury, 7 of 13 of the anterior fixations failed. These failures occurred mainly among the patients with severe neurologic injuries. We believe these findings substantiate the use of anterior plate alone for DF injuries at stage 1 and 2 but disqualify anterior plate fixation alone for DF injuries at stage 3, with neurologic injury present.

Stability analysis of craniovertebral junction fixation techniques

BACKGROUND

Craniovertebral arthrodesis in the upper cervical spine is challenging because of the high degree of mobility afforded by this region. A novel method for achieving atlantoaxial fixation with use of polyaxial screws inserted bilaterally into the lateral masses of C1 and transpedicularly into C2 with longitudinal rod connection has recently been introduced. The question remains as to whether this technique provides adequate stability when extended cephalad to include the occiput. The purpose of this study was to determine the primary stability afforded by this novel construct and compare its stability with the current standard of bilateral longitudinal plates combined with C1-C2 transarticular screws.

METHODS

We used ten fresh-frozen human cadaveric cervical spines (C0-C4). Pure moment loads were applied to the occiput, and C4 was constrained during the testing protocol. We evaluated four conditions: (1) intact, (2) destabilized by means of complete odontoidectomy, (3) stabilization with longitudinal plates with C1-C2 transarticular screw fixation, and (4) stabilization with a posterior rod system with C1 lateral mass screws and C2 pedicle screws. Rigid-body three-dimensional rotations were detected by stereophotogrammetry by means of a three-camera system with use of marker triads. The range of motion data (C0-C2) for each fixation scenario was calculated, and a statistical analysis was performed.

RESULTS

Destabilization of the specimen significantly increased C0-C2 motion in both flexion-extension and lateral bending (p < 0.05). Both fixation constructs significantly reduced motion in the destabilized spine by over 90% for all motions tested (p < 0.05). No significant differences were detected between the two constructs in any of the three rotational planes.

CONCLUSIONS

Both hardware systems provide equivalent construct stability in the immediate postoperative period when it is critical for the eventual success of a craniovertebral arthrodesis. On the basis of this work, we believe that the decision to use either construct should be determined by clinical rather than biomechanical concerns.