Additional Screw Research Articles

Arthrodesis of the Lisfranc Joint Complex With a New Multidirectional Locking Plate

Lisfranc injuries generally have a poor prognosis with considerable potential for long-term disability. Currently, the recommended treatment of Lisfranc injuries is open reduction and internal fixation (ORIF), as closed reduction and plaster immobilization alone often leads to a painful loss of function of the medial arch of the foot. Furthermore, there are studies that propose primary arthrodesis as a treatment option for complex fractures. In addition, the necessity for arthrodesis not only arises from posttraumatic etiology but also from primary degenerative arthritis. For metatarsal cuneiform arthrodesis, screw fixation is the traditional fixation method. However, plate fixation is becoming increasingly common. In December 2007, a novel multidirectional locking plate was introduced in our hospital (wing-plate). Through October 2010, a total of 14 patients underwent a metatarsal cuneiform arthrodesis of the medial arch of the affected Lisfranc joints. In some cases, an additional fusion of the middle Lisfranc joint (Tarso metatarsal II and III) with a 3.5-mm lag screw was performed by placing the screw from medial to lateral for a fixation of the base of metatarsal I and II. Clinical and radiologic follow-up was possible for 11 of the 14 patients. The average follow-up was 16 months (6 to 39 mo). The etiology of the 11 metatarsal cuneiform arthrodesis patients was posttraumatic in 4 cases, whereas it was performed primary in 1 case and secondary in 3 cases, and degenerative in 7 cases. Union was reported in 91% (10 of 11) patients with a mean time to union of 143 days. Mean American Orthopaedic Foot and Ankle Society midfoot score was 85.64, with a reduction in the visual analog scale score from 8.36 preoperatively to 1.82 postoperatively. The patient with the documented nonunion had an American Orthopaedic Foot and Ankle Society midfoot score of 91 and a reduction in the visual analog scale score from 10 preoperatively to 0 postoperatively, showing that nonunion may not correlate with poor function or pain. These promising clinical midterm results show that the APTUS titanium wing-plate, combined with or without additional lag screws, offers a good option for Lisfranc arthrodesis in posttraumatic and degenerative arthritis.

Anterior Interosseous Nerve Palsy after Supracondylar Fracture of Humerus in Adult. Case report

We present a case of anterior interosseous nerve palsy after a supracondylar fracture of the humerus in a 24-year-old woman. The patient was diagnosed and treated in two hospitals where the impairment of function of the hand indicating nerve damage was not noticed during a standard examination. An open reduction of the fracture with internal fixation using LCP plates and additional screws was performed, ultimately producing a good therapeutic outcome. Anterior interosseous nerve palsy was detected after 14 days during the first follow-up visit. The decision was made to institute conservative treatment. Full functional recovery was achieved after approximately 8 months. We believe that injuries of this type are more common but can be easily overlooked in the course of an imprecise physical examination. The Introduction of improved algorithms for the clinical examination of patients with similar fractures should be considered for the patient's good and on account of possible legal aspects of a failure to establish a correct diagnosis.

The Treatment of Intertrochanteric Fractures of the Femur with Endovis Nail

BACKGROUND The incidence of fractures in the trochanteric area has risen with the increasing numbers of elderly persons with osteoporosis. The imperative goals of treatment are early mobilization by means of stable fixation using as minimally invasive a procedure as possible. Nowadays, there is an increasing interest in intramedullary nailing, especially for unstable intertrochanteric fractures. The aim of the present paper is to assess the efficacy of closed intramedullary osteosynthesis with the Endovis® proximal femoral nail in the treatment of peritrochanteric fractures to solve the problems associated with the use of intramedullary fixation devices. MATERIAL AND METHODS The authors describe their experience with 87 stable and unstable proximal extra-capsular femoral fractures treated with the Endovis femoral nail from July 2007 to March 2009. The results were evaluated clinically, functionally and radiographically during the 1st, 3th, 6th and 12th months post-op. Pre-injury activity and functional levels were recorded using the modified Harris hip score and V.A.S. score. RESULTS Postoperative radiographs showed a near-anatomical fracture reduction in 85% of patients. Three were the cases of cut-out, one case of valgus and two cases of shortening of the operated leg (<1 cm). The Harris Hip Score increased between the thirtieth and ninetieth postoperative day, accompanied by a significant decrease in pain symptoms and functional limitation. CONCLUSION 1. The application of an intramedullary nail provides primary stability of the fracture. 2. The Endovis nail constitutes a powerful synthesis for stable and unstable fractures of the trochanteric region, in which is difficult to reconstruct appropriate continuity between the medial and posterior cortical layers. 3.The good mechanical stability of the nail allows rapid mobilization and early functional recovery. 4. The presence of an additional anti-rotational screw and the free sliding mechanism of the lag screw may increase rotational stability of cervico-cephalic fragments and decrease overload on the femoral head.

Pure percutaneous pedicle screw fixation without arthrodesis of 32 thoraco-lumbar fractures: clinical and radiological outcome with 36-month follow-up

To evaluate the outcome of pure percutaneous fixation of unstable single level fractures at the thoraco-lumbar junction (A1 to B2 Magerl/AO Spine). Neurological intact patients were included in a 2-year prospective study (follow-up 36 months). Two groups were considered: the group in which additional short bilateral screws in the fractured vertebra were placed was called lordorizing screw group (LSG), the other was called non lordorizing screw group (nLSG). Clinical outcome was evaluated using the SF-36, the Oswestry disability index and the recovery time needed to go back work. The following radiological parameters were also evaluated on the follow-up exams: the Mid-Sagittal Index, the Cobb's angle and the Sagittal Index. In the LSG, the correction values of MSI, Cobb's angle and SI were statistically significantly higher than in nLSG. When feasible we recommend a pure percutaneous short segment pedicle screw fixation adding a lordorizing screw.

Seismic performances of RC columns reinforced with screw ribbed reinforcements connected by mechanical splice

Various types of reinforcement splicing methods have been developed and implemented in reinforced concrete construction projects for achieving the continuity of reinforcements. Due to the complicated reinforcement arrangements and the difficulties in securing bar spacing, the traditional lap splicing method, which has been widely used in reinforced concrete constructions, often shows low constructability and difficulties in quality control. Also, lap spliced regions are likely to be over-reinforced, which may not be desirable in seismic design. On the other hand, mechanical splicing methods can offer simple and clear arrangements of reinforcement. In order to utilize the couplers for the ribbed-deformed bars, however, additional screw processing at the ends of reinforcing bars is typically required, which often lead to performance degradations of reinforced concrete members due to the lack of workmanship in screw processing or in adjusting the length of reinforcing bars. On the contrary, the use of screw-ribbed reinforcements can easily solve these issues on the mechanical splicing methods, because it does not require the screw process on the bar. In this study, the mechanical coupler suitable for the screw-ribbed reinforcements has been developed, in which any gap between the reinforcements and sleeve device can be removed by grouting high-flow inorganic mortar. This study presents the uniaxial tension tests on the screw-ribbed reinforcement with the mechanical sleeve devices and the cyclic loading tests on RC columns with the developed coupler. The test results show that the mechanical sleeve connection developed in this study has an excellent splicing performance, and that it is applicable to reinforced concrete columns with a proper confinement by hoop reinforcement.

Fracture risk and initial fixation of a cementless glenoid implant: The effect of numbers and types of screws

The initial fixation of an anatomical cementless glenoid component, provided by different numbers and types of screws, and the risk of bone fracture were evaluated by estimating the bone-implant interface micromotions and the principal strains around the prosthesis. Four different fixation configurations using locking or compression screws were tested. Estimation of the micromotions at the bone-implant interface was performed both experimentally, using an in vitro model, and computationally, using a numerical model. Principal bone strains were estimated using the numerical model. Subject variability was included by modelling two different bone qualities (healthy and rheumatoid bone). For the fixation configurations that used two screws, experimental and modelling results found that the micromotions at the bone-implant interface did not change with screw type. However, screw type had a significant effect on fixation when only one screw was used; in this case, a locking screw resulted in less micromotion at the bone-implant interface compared with the compression screw. Bone strains were predicted by the numerical model, and strains were found to be independent of the screw type; however, the predicted strain levels calculated in rheumatoid bone were larger than the strain levels that may cause bone damage for most considered arm positions. Predicted bone strain in healthy bone did not reach this level. While proper initial component fixation that allows biological fixation can be achieved by using additional screws, the risk of bone failure around the screws must be considered, especially in cases of weak bone.

Is there a role for intramedullary nails in the treatment of simple pilon fractures? Rationale and preliminary results

IntroductionCertain patients with pilon fractures present with significant soft-tissue swelling or with a poor soft-tissue envelope typically not amenable to definitive fixation in the early time period. The objective of this study was to review the treatment of simple intra-articular fractures of the tibial plafond (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) type 43C1–C2) via intramedullary nailing (IMN) with the assessment of clinical and radiographic results and any associated complications. Materials and methodsRetrospective clinical and radiological reviews of 31 patients sustaining AO/OTA type 43C distal tibial fractures treated with IMN were evaluated. Our main outcome measurement included achievable alignment in the immediate postoperative period and at the time of union along with complications or need for secondary procedures within the first year of follow-up. ResultsSeven patients were lost to follow-up. All the remaining patients achieved bony union at a mean union time of 14.1±4.9 weeks with no evidence of malunion or malrotation. All patients were at full-weight-bearing status at 1-year follow-up. Complications were notable for one delayed union, one non-union, one patient with superficial wound drainage, two with deep infection, one with symptomatic hardware and one with deep vein thrombosis. ConclusionSimple articular fractures of the tibial plafond (AO/OTA type 43C) treated via IMN can achieve excellent alignment and union rates with proper patient selection and surgical indication. One should not hesitate to use additional bone screws or plating options to help achieve better anatomic reduction. However, larger, prospective randomised trials comparing plating versus nailing, in experienced hands, are needed to completely delineate the utility of this treatment modality.

Minimally invasive reconstruction of lateral tibial plateau fractures using the jail technique: a biomechanical study

BackgroundThis study described a novel, minimally invasive reconstruction technique of lateral tibial plateau fractures using a three-screw jail technique and compared it to a conventional two-screw osteosynthesis technique. The benefit of an additional screw implanted in the proximal tibia from the anterior at an angle of 90° below the conventional two-screw reconstruction after lateral tibial plateau fracture was evaluated. This new method was called the jail technique.MethodsThe two reconstruction techniques were tested using a porcine model (n = 40). Fracture was simulated using a defined osteotomy of the lateral tibial plateau. Load-to-failure and multiple cyclic loading tests were conducted using a material testing machine. Twenty tibias were used for each reconstruction technique, ten of which were loaded in a load-to-failure protocol and ten cyclically loaded (5000 times) between 200 and 1000 N using a ramp protocol. Displacement, stiffness and yield load were determined from the resulting load displacement curve. Failure was macroscopically documented.ResultsIn the load-to-failure testing, the jail technique showed a significantly higher mean maximum load (2275.9 N) in comparison to the conventional reconstruction (1796.5 N, p < 0.001). The trend for better outcomes for the novel technique in terms of stiffness and yield load did not reach statistical significance (p > 0.05). In cyclic testing, the jail technique also showed better trends in displacement that were not statistically significant. Failure modes showed a tendency of screws cutting through the bone (cut-out) in the conventional reconstruction. No cut-out but a bending of the lag screws at the site of the additional third screw was observed in the jail technique.ConclusionsThe results of this study indicate that the jail and the conventional technique have seemingly similar biomechanical properties. This suggests that the jail technique may be a feasible alternative to conventional screw osteosynthesis in the minimally invasive reconstruction of lateral tibial plateau fractures. A potential advantage of the jail technique is the prevention of screw cut-outs through the cancellous bone.

Locking versus standard screw fixation for acetabular cups: is there a difference?

Total hip replacement has been established as a valid treatment option for displaced subcapital fractures. However, insufficient primary fixation may be the reason for early loosening in these osteoporotic patients. Primary fixation of the cup is usually achieved by press-fit fixation that can be enhanced using screws. Locking the screws into their respective cups may seem to improve the primary fixation of the construct, as locked plates proved superior fixation for osteoporotic fractures. The study consisted of three groups: in each group, three cups were fixed into blocks of foam bone using press-fit technique. In the first group, no additional screws were used, in the second group two standard screws were inserted, while in the third group two acetabular screws were cemented into the cup to simulate locked screw fixation. Load was applied onto the rim of the acetabular component to cause shearing between the cup and the block. Cup fixation was examined by a loading machine that acquired load versus displacement. The stiffness (load vs. displacement) was calculated. Screws, either locked or non-locked, enhanced cup fixation by 26% (p value <0.01). No significant changes were found between the locking and non-locking screws groups. These experimental results indicate that acetabular screws enhance primary cup fixation. This may become significant in conditions where the acetabular bone stock is suboptimal, such as when performing total hip arthroplasty after displaced subcapital fractures. However, there is no superiority for locked screws over standard screw fixation.

Minimally invasive plate osteosynthesis for humeral shaft fracture: a reproducible technique with the assistance of an external fixator

Minimally invasive plate osteosynthesis (MIPO) has become a popular option for treatment of humeral shaft fractures. However, indirect reduction might risk unpromising results, with mal-alignment/mal-union or nonunion. The purpose of this study was to describe a reproducible MIPO technique that used an external fixator during the procedure as a tool for reduction and maintenance, and to assess the outcomes in patients with humeral shaft fracture. Of 31 consecutive cases of humeral shaft fracture in 30 patients, 29 were included in this study. There were seven simple (type A) and 22 comminuted (type B or C) fractures. After the insertion of one Schanz pin on each proximal and distal humerus, a provisional reduction was achieved by connecting the pins with a monolateral external fixator. The MIPO procedure was then performed over the anterior aspect of the humerus. To evaluate the efficacy of the provisional reduction by external fixator, coronal and sagittal alignments were assessed. We also assessed bony and functional results, including complications, from this technique. There was no case of mal-union >10°, and mean angulation was 1.3° (range 0°-9°) in the coronal plane and 1.2° (range 0°-8°) in the sagittal plane. Twenty-eight of 29 fractures were united, including three delayed unions, with a mean union time of 19.1 weeks (range 12.3-38.4 weeks) and a mean follow-up of 20.8 months (range 13.5-31.0 months). There was one hypertrophic nonunion that healed after fixing with two additional screws. Except one patient with associated injury in the elbow, all patients recovered to pre-injury joint motion. There were two cases of postoperative radial nerve palsy that both recovered completely. We attributed them to manipulation, and not to the Schanz pins or plate fixation. Surgical treatment of humeral shaft fractures with external fixator-assisted reduction and MIPO resulted in excellent reductions and high union rates.

Comparative study on curative effect of internal fixations with three dual plates for type C fractures of distal humerus

Objective To compare three different internal fixations using dual plates in treatment of type C distal humerus fractures.Methods A total of 59 patients with type C distal humerus fractures fixed with dual plates between January 2004 and December 2008 were enrolled in the study,including 34 patients managed by perpendicular dual plate internal fixation (Group A),14 patients by dorsal dual plate internal fixation (Group B),and 11 patients by parallel dual plate internal fixation (Group C).Functional outcomes of injured elbow joints were assessed using Mayo elbow performance score (MEPS).Fisher' s exact probability,chi-square test and variance analysis were used to compare the perioperative variables among groups.Results The patients were followed up for average 28 months (range,12-55 months),which showed that all fractures were smoothly healed with satisfactory curative effects in each group.There were no significant differences with respect to functional outcomes among three groups.The patients with surgery difficulty in Group C were more than those in other two groups.Besides,an additional intercondylar screw was always required in Groups A and B,but rarely in Group C.Conclusions All internal fixations with three dual plates are effective in management of type C distal humeral fractures.The location of plates is determined by experiences of orthopedic surgeons and specific fracture type. Key words: Humeral fractures ; Fracture fixation, internal; Treatment outcome

Commentary: Intramedullary Nailing Supplemented with Poller Screws for Proximal Tibial Fractures

is challenging owing to the relatively high chance of displacement during nail insertion. The stability of the proximal fixation is inferior because of the wider diameter of the intramedullary canal in the metaphysis. This has led to the use of Poller screws for additional blocking during intramedullary fixation of proximal or distal tibial fractures.1 The effects of Poller screw is two-fold. First, fracture reduction is better maintained during nail insertion, which reduces the chance of malunion. Second, the stability achieved by additional Poller screws enables quicker fracture union. Stability can be further enhanced by modifying nail design and locking options,2 such as increasing the number of locking screws inserted into the metaphyseal fragment, and using angularly stable locking screws that diminish the amount of nail wobble in the screw hole.3 Commentary: Intramedullary nailing supplemented with Poller screws for proximal tibial fractures

Biomechanical comparison of intramedullar versus extramedullar stabilization of intra-articular tibial plateau fractures

Fractures of the proximal tibia occur very often and are a great challenge for trauma surgeons to stabilize. Although locked nails were developed to stabilize these fractures, this technique has not been sufficiently investigated. The purpose of this study was to biomechanically assess the stability of locked intramedullary nailing compared to locked plating. 16 fresh frozen human cadaveric tibiae were osteotomized in the meta-diaphyseal intersection with an osteotomy gap of 10 mm and a single osteotomy through the medial epicondyle to simulate a 41-C.2 fracture. Stabilization was performed with an angle stable locked Targon-TX nail (n = 8) and two additional canulated screws. The other testing group (n = 8) was treated with two canulated screws and a five-hole LCP-PLT. The bones were tested in a cyclic testing protocol with increasing loads under compression and a load sharing of 60 % through the medial tibial plateau and 40 % to the lateral side. Stiffness and fracture gap movement were measured and failure mode was assessed. No significant differences were found between the two implants regarding load until failure. The stiffness of the intramedullary nailing group (927 N/mm) was statistically significantly higher than the stiffness of the plating group (564 N/mm). No differences were found for fracture gap movement in the z-axis. However, differences were found for dislocation of the proximal-lateral and proximal-medial fragments, with absolute values of 0.099 mm in the plate group and 0.66 mm in the nailing group at 800 N. Prior to failure, fracture gap movement was 0.22 mm for the plating group and 1.66 mm for the nailing group, a difference that was also statistically significantly different. The nailing group failed by screw cut-out while the plating group failed by screw breakage. Nailing of proximal tibia fractures leads to a stiffer implant-bone construct than plating. Since no adverse effects were found after nailing it seems to be a good alternative to plating for intra-articular proximal tibia fractures, especially in patients with soft tissue problems.

The use of beta-tricalcium phosphate and bone marrow aspirate as a bone graft substitute in posterior lumbar interbody fusion

Due to the disadvantages of iliac crest bone and the poor bone quality of autograft gained from decompression surgery, alternative filling materials for posterior lumbar interbody fusion cages have been developed. β-Tricalcium phosphate is widely used in cages. However, data regarding the fusion rate of β-TCP assessed by computer tomography are currently not available. A prospective clinical trial involving 34 patients (56.7 years) was performed: 26 patients were treated with single-level, five patients double-level and three patients triple-level PLIF filled with β-TCP and bone marrow aspirate perfusion, and additional posterior pedicle screw fixation. Fusion was assessed by CT and X-rays 1 year after surgery using a validated fusion scale published previously. Functional status was evaluated with the visual analogue scale and the Oswestry Disability Index before and 1 year after surgery. Forty-five levels in 34 patients were evaluated by CT and X-ray with a follow-up period of at least 1 year. Clinically, the average ODI and VAS for leg and back scores improved significantly (P < 0.001). CT assessment revealed solid fusion in 12 levels (26.67%) and indeterminate fusion in 15 levels (34.09%). Inadequate fusion (non-union) was detected in 17 levels (38.63%). The technique of PLIF using β-TCP yielded a good clinical outcome 1 year after surgery, however, a high rate of pseudoarthrosis was found in this series therefore, we do not recommend β-TCP as a bone graft substitute using the PLIF technique.

A cementless, elastic press-fit socket with and without screws

Background The acetabular component has remained the weakest link in hip arthroplasty regarding achievement of long-term survival. Primary fixation is a prerequisite for long-term performance. For this reason, we investigated the stability of a unique cementless titanium-coated elastic monoblock socket and the influence of supplementary screw fixation.Patient and methods During 2006–2008, we performed a randomized controlled trial on 37 patients (mean age 63 years (SD 7), 22 females) in whom we implanted a cementless press-fit socket. The socket was implanted with additional screw fixation (group A, n = 19) and without additional screw fixation (group B, n = 18). Using radiostereometric analysis with a 2-year follow-up, we determined the stability of the socket. Clinically relevant migration was defined as > 1 mm translation and > 2º rotation. Clinical scores were determined.Results The sockets without screw fixation showed a statistically significantly higher proximal translation compared to the socket with additional screw fixation. However, this higher migration was below the clinically relevant threshold. The numbers of migratory sockets were not significantly different between groups. After the 2-year follow-up, there were no clinically relevant differences between groups A and B regarding the clinical scores. 1 patient dropped out of the study. In the others, no sockets were revised.Interpretation We found that additional screw fixation is not necessary to achieve stability of the cementless press-fit elastic RM socket. We saw no postoperative benefit or clinical effect of additional screw fixation.

Paper 274: Tibial Fixation in Posterior Cruciate Ligament Reconstruction: A Biomechanical Comparison Study between Biodegradable Interference Screw and Biodegradable Cross Pin

The purpose of this study was to compare ultimate tensile load, stiffness and slippage after cyclic loading of biodegradable interference screw and biodegradable cross pin for tibial fixation in posterior cruciate ligament reconstruction. Biomechanical testing of 2 different fixation techniques was performed by use of human cadaver tibia and Achilles tendon. Two independent testing sessions were examined. The A session compared biodegradable interference screw and cross pin for Achilles bone block (10 x 30 mm). The B session compared hybrid fixation of soft tissue with the use of cancellous screw-washer in each group. The tibia-graft fixation compex was cyclically loaded between 50 N and 250 N at 1 Hz for 1000 cycles. After cycling, the amount of graft slippage was determined by measuring the change in grip to grip distance. The complex was then loaded to failure at 1mm/s, and ultimate tensile strength, stiffness, and mode of failure were determined. In session A, cross pin fixation group resulted in a significantly higher ultimate tensile strength (917.80 ± 102.4 vs 514.58 ± 148.4, p<0.01), significantly higher stiffness (302.3 ± 52.9 vs 193.5 ± 12.1, p < 0.05), and significantly less slippage (3.75 ± 1.0 mm vs 5.66 ± 0.6, p<0.001) than interference screw fixation group. In session B, cross pin fixation with additional screw group resulted in a significantly higher ultimate tensile strength (1023.75 ± 94.4 vs 816.81 ± 115.3, p<0.01), significantly higher stiffness (341.5 ± 64.9 vs 223.5 ± 38.1, p < 0.05), and less slippage (13.70 ± 1.3 mm vs 12.75 ± 1.0, p>0.05) than interference screw fixation with additional screw group. The failure mode of cross pin fixation group was pin breakage in all specimens. The failure mode of interference screw fixation group was pullout of the graft in all specimens. Our study showed that cross pin tibial fixation both bone block and soft tissue in posterior cruciate ligament reconstruction is stronger than interference screw with respect to ultimate tensile strength, stiffness, and slippage.

Paper 163: The Clinical Result and Incidence of Tunnel Widening in Hamstring ACL Patients is Not Influenced by an Additional Femoral Interference Screw. A Prospective and Randomized One Year Follow-up Study with 73 Patients

Paper 163: The Clinical Result and Incidence of Tunnel Widening in Hamstring ACL Patients is Not Influenced by an Additional Femoral Interference Screw. A Prospective and Randomized One Year Follow-up Study with 73 Patients

Biomechanical efficacy of monoaxial or polyaxial pedicle screw and additional screw insertion at the level of fracture, in lumbar burst fracture: An experimental study

Background:Use of a pedicle screw at the level of fracture, also known as an intermediate screw, has been shown to improve clinical results in managing lumbar fracture, but there is a paucity of biomechanical studies to support the claim. The aim of this study was to evaluate the effect of adding intermediate pedicle screws at the level of a fracture on the stiffness of a short-segment pedicle fixation using monoaxial or polyaxial screws and to compare the strength of monoaxial and polyaxial screws in the calf spine fracture model.Materials and Methods:Flexibility of 12 fresh-frozen calf lumbar spine specimens was evaluated in all planes. An unstable burst fracture model was created at the level of L3 by the pre-injury and dropped-mass technique. The specimens were randomly divided into monoaxial pedicle screw (MPS) and polyaxial pedicle screw (PPS) groups. Flexibility was retested without and with intermediate screws (MPSi and PPSi) placed at the level of fracture in addition to standard screws placed at L2 and L4.Results:The addition of intermediate screws significantly increased the stability of the constructs, as measured by a decreased range of motion (ROM) in flexion, extension, and lateral bending in both MPS and PPS groups (P < 0.05). There was neither any significant difference in the ROM in the spines of the two groups before injury, nor a difference in the ROM between the MPSi and PPSi groups (P > 0.05), but there was a significant difference between MPS and PPS in flexion and extension in the short-segment fixation group (P < 0.05).Conclusions:The addition of intermediate screws at the level of a burst fracture significantly increased the stability of short-segment pedicle screw fixation in both the MPS and PPS groups. However, in short-segment fixation group, monoaxial pedicle screw exhibited more stability in flexion and extension than the polyaxial pedicle screw.

Combined corpectomy in the treatment of multilevel cervical spondylotic myelopathy and ossified posterior longitudinal ligament

Objective To evaluate effect of combined corpeetomy for multilevel cervical spondylotic myelopathy (CSM) and ossified posterior longitudinal ligament (OPLL).Methods Fifteen patients with CSM or OPLL,including 9 males and 6 females,were treated with combined corpectomy which is characterized by C4 and C6 corpectomy,excision of osteophyma,protruded disc and/or ossified posterior longitudinal ligament on basis of preservation of C5 vertebral body,structural bone grafting in C3-5 and C5-7,and anterior cervical plate fixation at C3,C5,and C7.The clinical results were evaluated with Japanese Orthopaedic Association (JOA) score.X-rays and CT scans were taken to evaluate vertebral fusion,and MRI was used to access spinal canal decompression and condition of spinal cord.Results All patients were followed up for 9 to 42 months (average,26.7 months).Bony fusion was achieved in all 15 patients.The JOA score improved from preoperative 13.44±2.81 to postoperative 16.16±2.19 (P=0.0354).The cervical lordosis improved from preoperative 1.16°±11.74° to immediately postoperative 14.36°±7.85° (P=0.00217),and 12.92°+6.17° at the final follow-up (P=0.00292).The complications included temporary hoarseness in 2 cases,dysphagia in 1 case.Conclusion The combined corpectomy for treating CSM and OPLL can obtain reliable and satisfactory results.In operation,the preservation of C5 vertebral body can provide an additional screw anchoring force and strengthen stahility. Key words: Cervical spondylosis; Ossification of posterior longitudinal ligament; Spinal cord compression; Spinal fusion

Screw- versus plate-fixation strength of acetabular anterior column fractures

The standard for operative treatment of acetabular fractures is open reduction and plate fixation. Recently, screw fixation-only methods through less invasive approaches are reported, but biomechanical data are missing. Questions posed in this study are (1) is the static fixation strength of different screw types equivalent to the standard plate fixation for anterior column fractures of the acetabulum? and (2) does the placement of an additional screw in the infra-acetabular corridor increase the fixation strength independent of the used implant? Three groups of different screws (group II, titanium; group III, stainless steel; and group IV, biodegradable Poly-L-Lactid) were compared with the standard plate fixation (group I) in Synbone pelves with custom-made anterior column fractures. Six pelvises per group were axial loaded with six cycles of 800 N, twice with and without an additional placed infra-acetabular screw. The fixation strength of titanium screws was equivalent to the standard plate fixation. The stainless steel and Poly-L-Lactid screw fixation strengths were equivalent to each other but inferior to the aforementioned. The additional placement of an infra-acetabular screw significantly increased the fracture fixation strength, independent of the used implant. Screw fixation is a promising alternative approach for the stabilization of noncomminuted acetabular fractures of the anterior column with equivalent fixation strength to the standard plate fixation. The additional placement of an infra-acetabular screw significantly increases the fracture fixation independent of the used implant and should be considered for acetabular fractures with separation of both columns. Therapeutic study, level IV.