Cannulated Lag Screws Research Articles

Femoral neck osteosynthesis using interfragmentary compression or position screw in synthetic bones. What are the mechanical differences?

We aim to compare interfragmentary compression with the position osteosynthesis in the fixation of different femoral neck fractures (FN)in synthetic bones subjected to vertical load. Forty-two synthetic femurs were subjected to neck fractures and separated into 3 groups according to the Pauwels classification: Pauwels I had 6 units (PI); Pauwels II, 24 units, with and without comminution (PII); and Pauwels III, 12 units, with and without comminution (PIII). After, they were fixed with 2 different ways: three 7, 0mm cannulated lag screws (CSs) versus three 6, 5mm solid fully threaded screws (SSs). Screws positioning was oriented by the Pauwels classification: inverted triangle or crossed screws. All specimens were submitted to vertical loading until failure. The average force was 79.4 ± 22.6Kgf. The greatest one was recorded in model 1 (135.6Kgf), and the lowest in model 41 (39.6Kgf). CSs and SSs had similar resistance until failure (p = 0.2). PI showed heightened resistance and PIII showed a worse response (p < 0,01). CSs had better performance in PIII (p = 0.048). Comminution and screws orientation caused no difference on peak force (p = 0.918 and p = 0.340, respectively). In synthetic bones, the resistance of a femoral neck fracture osteosynthesis using a 7, 0mm cannulated lag screw or 6, 5mm solid fully threaded screw are similar. There was no loss of efficiency with comminution in the femoral neck. Osteosynthesis resistance decreased with the verticalization of the fracture line and, in the more vertical ones, interfragmentary compression with CSs was more resistant than positional osteosynthesis with SSs.

Computed tomography-guided cannulated lag screw placement for treatment of ununited anconeal process: surgical technique, clinical outcome, and radiographic healing in 7 dogs.

A novel technique and outcomes for correction of ununited anconeal process (UAP) via CT-guided cannulated lag screw placement in 7 canine patients is described. Cases of canine patients (7 patients/8 elbows) diagnosed with UAP that subsequently underwent CT-guided cannulated lag screw placement were retrospectively evaluated. Pre- and postoperative exam findings (lameness and pain on range of motion) are presented. Preoperative radiographs and postoperative radiographs at 2 time points (approximately 8 weeks postoperatively and at the time of the most recent imaging; mean, 221 days; range, 85 to 828 days) were scored for degree of arthrosis and postoperative radiographs were evaluated for radiographic union. Complications were reported and stratified by severity and time postoperatively. Minor perioperative (0 to 3 months postoperatively) complications included seroma formation (n = 1) and major perioperative complications involved development of surgical site infections (2), with 2 patients requiring implant removal in the perioperative period (44 and 82 days postoperatively). All patients achieved radiographic union, defined as partial or complete bridging of the anconeal process to the ulna within the study period (mean radiographic follow-up time 221 days postoperatively; range, 85 to 828 days; 5/8 joints partial bridging, 3/8 joints complete bridging) and pre- versus postoperative elbow arthrosis scores remained static in all patients. The case outcomes described support the use of CT-guided cannulated lag screw placement as a feasible option for treatment of UAP.

Biomechanics of internal fixation in Hoffa fractures – A comparison of four different constructs

ObjectiveCompare the biomechanical effectiveness of four different bone-implant constructs in preventing fracture displacement under axial loading. MethodsTwenty artificial femora had a standardized coronally oriented fracture of the lateral femoral condyle, representing a Hoffa fracture classified as a Letenneur type I. Four different fixation constructs were applied to the synthetic bones for biomechanical testing. The constructs consisted of a posterolateral (PL) buttressing locking plate in conjunction with two cannulated lag screws inserted from posterior to anterior (PA) – Group 1; Two cannulated screws inserted from anterior to posterior (AP) without plating– Group 2; A posterolateral (PL) buttressing locking plate in isolation – Group 3; and a combination of two lag screws from anterior to posterior (AP) in addition to a horizontal one-third tubular locking plate – Group 4. An axial load was applied to the fracture site with a constant displacement speed of 20 mm/min, and the test was interrupted when a secondary displacement was detected determining a fixation failure. We recorded the maximum applied force and the maximum fracture displacement values. ResultsGroup 1 demonstrated the highest overall bone-implant axial stiffness with the lowest secondary displacement under loading. Groups 3 and 4 showed equivalent mechanical behavior. Group 2 presented the lowest mechanical stiffness to axial loading. The combination of the one-third tubular locking plate with anterior-to-posterior lag screws (Group 4) resulted in 302 % increase in fixation stiffness when compared to anterior-to-posterior lag screws only (Group 2). ConclusionsThis study confirms the mechanical superiority of having a plate applied parallel to the main fracture plane in the setting of coronally oriented femoral condyle fractures. The addition of a horizontal plate, perpendicular to the main fracture plane, significantly increased the resistance to shearing forces at the fracture site when compared to constructs adopting just cannulated screws. Level of evidenceBiomechanical study

Finite element comparative analysis of three different internal fixation methods in the treatment of Pauwels type III femoral neck fractures

BackgroundComparison of 4 cannulated lag screws (3 inverted triangular cannulated screws + anti-rotating screws;4 CLS), dynamic hip screws + derotational screws (DHS + DS), and femoral neck fixation system (FNS) in the treatment of Biomechanical properties of middle-aged Pauwels type III femoral neck fractures.MethodsThe femur CT data of a healthy young volunteer was selected and imported into Mimics software to construct a three-dimensional model of a normal femur. Pauwels type III femoral neck fractures were simulated according to the 70° fracture line. Use Geomagic and SolidWorks software to optimize and build CLS, DHS + DS, and FNS fracture internal fixation models. Finally, Ansys software was used to analyze the stress distribution, peak value, and maximum displacement of the proximal fracture fragment and internal fixation; the displacement distribution, and peak value of the fracture surface at the fracture end.Results① The stress peaks of the proximal fracture fragments in the three groups were concentrated near the femoral calcar. The peak stress of the FNS group was the largest, and the DHS + DS group was the smallest. ②The displacement of the fracture fragments was all located at the top of the femur. The peak displacement of the FNS group was the largest, and the DHS + DS group was the smallest. ③ The internal fixation stress of the three groups is concentrated in the middle part of the device. The stress distribution of the first two groups of models is more uniform than that of FNS. The peak stress of FNS is the largest and the CLS is the smallest. ④ The internal fixed displacements are all located at the top of the model. The peak displacement of the CLS is the largest, and the DHS + DS is the smallest. ⑤ The displacement of the fracture surface is in the upper part of the fractured end. The peak displacement of the FNS group was the largest, and the DHS + DS group was the smallest.ConclusionCompared with the other two internal fixation methods, dynamic hip screw + derotational screw (DHS + DS) showed good biomechanical stability. When Pauwels type III femoral neck fracture occurs in young adults, DHS + DS can be given priority as the preferred treatment for this type of fracture.

EVALUATION OF FUNCTIONAL OUTCOME OF MODIFIED TENSION BAND WIRING AT 6 MONTHS IN ISOLATED OLECRANON FRACTURES IN ADULTS

Introduction: Fractures of the olecranon account for 8 - 10 % of all fractures around the elbow joint . An uncomplicated fracture of the olecranon is considered to be a common injury. Incidence in adult population is approximately 11.5% per 1 64 100000 population .Younger individuals suffer fracture olecranon due to high energy trauma and older individuals due to simple fall . When displaced, open reduction and internal xation is usually required to obtain anatomical realignment of the articular surface and restore normal elbow function. The xation should be stable, allow active elbow exion and extension and promote union of the fracture. There are other modalities of xation of isolated olecranon fractures, such as olecranon hook plate and cannulated lag screws as well but tension band wiring is less costly and operative complications are less in non comminuted olecranon fractures. Material and methods: This prospective observational study was done over a period of 2 years on transverse and oblique fractures of olecranon. Results: the outcome of our study was favorable in support of tension band wiring in transverse and oblique fracture of olecranon in respect to union rate, early initiation of physiotherapy and nal range of motion. Conclusion: By this method post-operative immobilization in POP is greatly minimized. Thereby avoiding fracture disease.Because of rigid xation between the fracture fragments, early active and functional movements can be given to the patient reducing the chances of joint stiffness. Early initiation of physiotherapy program within 2 – 3 weeks induces compression between the fragments. This compression hastens fracture healing. Because of early union of fracture, patient is back to work earlier

Technique Tip: Correcting Malalignment of the Talus Using a Pin-Based Distracter During Arthroscopic Ankle Arthrodesis

It is technical demanding work to perform arthroscopic ankle arthrodesis to treat end-stage ankle osteoarthritis with excessive talar tilt. This article aimed to provide an effective technique tip for the treatment of Takakura stage 3b ankle osteoarthritis with a talar tilt angle more than 15 degrees under arthroscopy. A conventional anterior arthroscopic approach is used. After arthroscopic examination and debridement, one pin which is parallel to the distal tibial surface is inserted into the tibial side of the ankle, the other pin which is parallel to the talar dome surface is inserted into the talar side of the ankle, both at the coronal plane. Then a distracter is used in the medial side to open the interspace of the tibiotalar joint and correct the talar tilt through the 2 pins, under which circumstance the tibiotalar joint surface can be well prepared. Next an anti-distracter is used in the lateral side to close the tibiotalar interspace and correct the talar tilt through the 2 pins, in which condition 3 fully threaded cannulated lag screws can be inserted through guide pins in a cross pattern to fix the ankle joint. We used the pin-based distracter to open and close tibiotalar interspace, correct the talar tilt and maintain a good mechanical axis for fusion, and the outcomes were good.

Treatment of Intracapsular Femoral Neck Fracture with Multiple Cannulated Lag Screws and Minimal Capsulotomy

Background: Intracapsular femoral neck fracture (ICFNF) was and still is a challenge for orthopedic surgeons; and among few accepted methods of treatment, the most widely used is multiple cannulated lag screws (CLS); but still there are some controversies in the accepted time lapse for operation and age limit of the patients. Objective: treatment of choice for (ICFNF) in wide variety age groups, and after different times since the fracture happened. Patients and Methods: from (Dec. 2014-Sep. 2017) 23 patients with (ICFNF) were selected from those admitted to the orthopedic surgery department in Azadi Teaching Hospital Kirkuk. The time lapse before the surgery ranged from 1/2-6 days; the patient's ages ranged from 14-62years. All were treated by fixation with multiple (CLS) and minimal capsulotomy. The outcomes studied monthly both clinically and radiologically in duration from 8 to 20 months. Results: Fourteen cases (61%) were rated as excellent, six cases (26%) as good, two cases (9 %) as fair, and one case (4%) was rated as poor; according to the pain, limp and range orded in four cases (17%) in the form of superficial infection in one case, malunion in two and both in the other. Conclusion: This method can be used successfully in treating (ICFNF) in wide age groups and even after a delay of up to 6 days.

Management of Vertical Sternal Fracture Nonunion in Elite-Level Athletes.

Background:Sternal fractures are rare, and they can be treated nonoperatively. Vertical sternal fractures have rarely been reported.Purpose:To describe the management and surgical treatment of a series of elite-level athletes who presented with symptomatic nonunions of a vertical sternal fracture.Study Design:Case series; Level of evidence, 4.Methods:Patients with an established symptomatic nonunion of a vertical sternal fracture, as diagnosed by computed tomography (CT) or magnetic resonance imaging (MRI), underwent open reduction and internal fixation using autologous bone graft and cannulated lag screws. The patients were assessed preoperatively and at the final follow-up using the Rockwood sternoclavicular joint (SCJ) score; Constant score; and shortened version of the Disabilities of the Arm, Shoulder and Hand (QuickDASH) scores. Bony union was confirmed on postoperative CT scan.Results:Five patients (4 men and 1 woman) were included; all were national- or international-level athletes (rugby, judo, show-jumping, and MotoGP). The mean age at surgery was 23.4 years (range, 19-27 years), the mean time from injury to referral was 13.6 months (range, 10-17 months), and the mean time from injury to surgery was 15.8 months (range, 11-20 months). The mean follow-up was 99.4 months (range, 25-168 months). There was a significant improvement after surgery in the mean Rockwood SCJ score (from 12.6 to 14.8 [P < .05]), Constant score (from 84 to 96.4 [P < .05]; 80% met the minimal clinically important difference [MCID] of 10.4 points), and QuickDASH (from 6.8 to 0.98 [P < .05]; 0% met the MCID of 15.9 points). Four of the patients were able to return to sport at their preinjury level, and 1 patient retired for nonmedical reasons. All of the fractures had united on the postoperative CT scan. There were no postoperative complications.Conclusion:Vertical fractures of the sternum are very rare and tend to behave clinically like an avulsion fracture injury to the capsuloligamentous structure of the inferior SCJ. The requirement of advanced imaging to diagnose this injury means that the actual incidence and natural history are not known. For high-demand athletes, early identification, surgical reduction, and fixation are likely to achieve the best outcome.

Mechanical Effects of Lag Screw Retightening in a Simulated Hindfoot Arthrodesis Model.

Background:Nonunion following hindfoot arthrodesis may be caused by failure to maintain compression at the arthrodesis site. The ability of lag screws, commonly used in arthrodesis, to maintain compression in hindfoot bones has not been well characterized. The aim of this work was to quantify the stress relaxation response of hindfoot bone with initial and repeated compression with a lag screw.Methods:Ten sets of 25-mm-diameter bone cylinders were cut from the talus and calcaneus in fresh-thawed cadaveric feet. A load cell was compressed between cylinders with an 8.0-mm partially threaded cannulated lag screw simulating arthrodesis. For 7 sets, screws were tightened by 3 quarter-turns, rested for 3 minutes, retightened 1 quarter-turn, and rested for 30 minutes. Three sets served as controls in which screws were not retightened.Results:Maximum compression after initial screw tightening and retightening averaged 275 and 337 N (P = .07), respectively. Compression 3 minutes after initial screw tightening and retightening averaged 199 and 278 N (P = .027), respectively. The compression recorded 3 minutes after screw retightening was an average of 40% higher than that recorded 3 minutes after initial tightening. The average compression 30 minutes after screw retightening was 255 N, a compression loss of 25% from the average maximum compression after retightening. Eighty percent of this compression loss happened in an average of 5.5 minutes.Conclusion:Hindfoot bones exhibit compression loss over time during simulated arthrodesis. Compression maintenance in bone is improved with screw retightening. Further work is needed to understand the mechanism of action and determine optimum time for recompression.Clinical Relevance:Retightening lag screws before wound closure may improve compression at the arthrodesis site and thereby decrease the chance of nonunion.Level of Evidence:N/A, laboratory experiment.

Does Lag Screw Retightening Improve Compression in Hindfoot Arthrodesis?

Category:Hindfoot; Ankle; Ankle ArthritisIntroduction/Purpose:Non-union and delayed union are common complications following hindfoot arthrodesis. The failure to obtain and maintain compression at the arthrodesis site may be a causative factor. Partially threaded cannulated ‘lag’ screws are commonly used for fixation in hindfoot arthrodesis; however, the ability of these screws to maintain compression in the hindfoot bones has not been well-characterized. The goals of this work were to: 1) quantify the stress relaxation response of hindfoot bones when compressed with a lag screw, particularly compression change upon screw retightening, and 2) compare the results to prior studies on stress relaxation in direct bone compression.Methods:12 pairs of calcaneus, talus and tibia bone cylinders, 25mm in diameter, were cut with a keyhole saw from fresh thawed cadaveric feet. The bone cylinders were prepared for simulated arthrodesis by removing the cartilage and flattening the subchondral surface with an oscillating saw. A Futek LTH 300 donut load cell and two metal washers were sandwiched between the two bone cylinders. An 8.0mm partially threaded cannulated lag screw (Smith and Nephew) was placed from the posterior- inferior aspect of the calcaneus cylinder to the anterior-superior aspect of the talus cylinder to simulate subtalar arthrodesis, or from the superior aspect of the tibia cylinder to the inferior aspect of the talus cylinder. Compression was recorded continuously as the screws were tightened by three-quarters of a turn and left untouched for 3 minutes. Recording continued as the screws were retightened one quarter-turn and then left untouched for 30 additional minutes.Results:Both initial and subsequent compression with a lag screw demonstrated a stress relaxation pattern, with increased maximum compression and slowed decay upon retightening. Maximum compression after three quarter-turns and retightening averaged 284 N and 351 N, respectively (n=12; t=-2.55; p=0.0136). Time to decay to 80% of maximum compression after three quarter-turns and retightening averaged 34 and 528 (n=9; t=-2.59; p=0.0159) seconds, respectively, compared to 21 seconds for direct compression. Compression loss 30 minutes after retightening averaged 25.5% (SD=8.8%), compared to 34.3% for direct compression.Conclusion:The maximum compression attained following retightening was significantly greater than the maximum compression attained after initial tightening. The time required to reach 80% of maximum compression was significantly longer after subsequent compared to initial maximum compression. These findings suggest that screw retightening before surgical wound closure may slow compression loss, which could increase the likelihood of successful arthrodesis. Lag screw compression resulted in a lower percent compression loss and loss rate compared to direct compression, which was previously used to describe bone viscoelasticity.

Arthroscopic osteosynthesis of capitellum fractures: Feasibility study and clinical study on 2 cases

BackgroundThe current management of displaced capitellum fractures is traditionally surgical. Most authors perform open reduction and internal fixation. The working hypothesis was that closed reduction and internal fixation of capitellum fractures is achievable by arthroscopy. MethodsWe carried out a cadaveric study on six fresh frozen elbows. We performed two Bryan and Morrey type I fractures of the capitellum, three type II and one type IV using a 15 mm osteotome. Fracture reduction was performed under arthroscopy using a probe hook and an aiming femoral instrument set. Fixation with a lag screw was performed under arthroscopy and radioscopic control. We reviewed, two patients who had been operated on for a type I and type II capitellum fracture and osteosynthesized under arthroscopy with a 7.5 years follow-up. ResultsIn our cadaveric study, we obtained anatomical reduction and stable osteosynthesis in four cases. We had two failures (2 type II fractures) due to a fracture of the fragment during screwing. In our clinical study, range of motion was very satisfactory with only a 5° extension deficit. The x-rays did not reveal any signs of osteoarthritis or periarticular ossification. One patient had minimal signs of osteonecrosis. ConclusionsArthroscopic osteosynthesis of capitellum fractures is feasible and reproducible. We recommend cannulated lag screws for Bryan and Morrey type I and IV fractures and adjustable lock pins for type II fractures. We have shown that this technique gives good results on two patients with a 7.5-year follow-up. Level of evidenceIV.

Cement augmentation of odontoid peg fractures: the effect of cement volume and distribution on construct stiffness.

The cement augmentation of a conventional anterior screw fixation in type II odontoid process fractures for elderly patients significantly increased stiffness and load to failure under anterior-posterior load in comparison with non-augmented fixation. The amount and quality of bone cement are usually taken ad hoc in clinical practise. In this study, we wanted to clarify the role of bone cement amount and its quality to the stiffness of odontoid and vertebrae body junction. Finite-element method was used to achieve different scenarios of cement augmentation. For all models, an initial stiffness was calculated. Model (1) the intact vertebrae were virtually potted into a polymethylmethacrylate base via the posterior vertebral arches. A V-shaped punch was used for loading the odontoid in an anterior-posterior direction. (2) The odontoid fracture type IIa (Anderson-D'Alonzo classification) was achieved by virtual transverse osteotomy. Anterior screw fixation was virtually performed by putting self-drilling titanium alloy 3.5mm diameter anterior cannulated lag screw with a 12mm thread into the inspected vertebrae. A V-shaped punch was used for loading the odontoid in an anterior-posterior direction. The vertebrae body was assumed to be non-cemented and cemented with different volume. The mean cement volume was lowest for body base filling with 0.47 ± 0.03ml. The standard body filling corresponds to 0.95 ± 0.15ml. The largest volume corresponds to 1.62 ± 0.12ml in the presence of cement leakage. The initial stiffness of the intact C2 vertebrae was taken as the reference value. The mean initial stiffness for non-porous cement (E = 3000MPa) increased linearly (R2 = 0.98). The lowest stiffness (123.3 ± 5.8N/mm) was measured in the intact C2 vertebrae. However, the highest stiffness (165.2 ± 5.2N/mm) was measured when cement leakage out of the odontoid peg occurred. The mean initial stiffness of the base-only cemented group was 147.2 ± 8.4N/mm compared with 157.9 ± 6.6N/mm for the base and body cemented group. This difference was statistically significant (p < 0.0061). The mean initial stiffness for porous cement (E = 500MPa) remains constant. Therefore, there is no difference between cemented and non-cemented junction. This difference was not statistically significant (p < 0.18). The present study showed that the low porous cement was able to significantly influence the stiffness of the augmented odontoid screw fixation in vitro, although further in vivo clinical studies should be undertaken. Our results suggest that only a small amount of non-porous cement is needed to restore stiffness at least to its pre-fracture level and this can be achieved with the injection of 0.7-1.2ml of cement. These slides can be retrieved under Electronic Supplementary Material.

Patella fractures treated with cannulated lag screws and fiberwire® have a high union rate and low rate of implant removal

ObjectivesThe purpose of this study is to report the results of open reduction internal fixation of patella fractures (OTA 34 A-C) using cannulated lag screws and FiberWire® (Arthrex, Naples, FL, USA) with regard to union and symptomatic implant removal. DesignRetrospective review of prospectively collected database. SettingUrban Level 1 trauma center and Level 2 trauma center MethodsAll displaced intra-articular patella fractures (OTA 34 A-C) treated with ORIF by cannulated lag screws and FiberWire® tension band/cerclage between January 1, 2009 and August 1, 2018. Three hundred and eighty seven consecutive patients were identified. Fifty fractures were included in the final analysis. Main Outcome MeasurementAll patients were followed to clinical and radiographic union. Nonunion was defined as lack of clinical and radiographic union, fracture displacement, and/or return to OR for revision surgery. Rate of symptomatic implant removal was recorded. ResultsAverage age was 57.7 years (range 21–86). Average follow up was 20.6 months (range 6–98 months). Average time to clinical and radiographic union was 3.1 months (range 3–7 months). Four fractures were open. There was a 96% (48/50) rate of primary union, with one patients requiring revision surgery to achieve union, and one developing an asymptomatic radiographic nonunion. The rate of symptomatic implant removal was 8% (4/50). Only 1 of the 4 was operated for a prominent suture knot, and the remaining 3 were for prominent screw removal. Knee range of motion averaged 0.37° extension to 119° flexion (range, 0–150°). ConclusionPatella fractures can be treated with cannulated lag screws and FiberWire® with a high rate of primary union (96%) and a low rate of symptomatic implant removal (8%). The implant removal rate compares favorably with alternative constructs, with an equivalent rate of fracture union.

A study on outcome of tibial plateau fractures (TPF) at a tertiary care hospital

The head of the tibia is sometimes obliquely broken; and if it be fractured into the knee joint the treatment which it requires is similar to that which is necessary in the oblique fracture of the condyle of the Os femoris; i.e., Firstly, the straight position of the limb, because the femur preserves the proper adaptation of the fractured tibia by forming a splint to its upper portion, and keeping the articular surfaces in apposition. Secondly, a roller, to press one part of the broken surface against the other. Thirdly, a splint of pasteboard, to assist in the preservation of that pressure and fourthly, early passive motion to prevent ankylosis. All surgeries were performed under either spiral or lumbar plexus block with Sciatic nerve block. Tourniquet was not used in any of the patients. Patient was positioned supine on the fracture table. Traction was given along the axis of the limb, fracture reduced by closed manipulation with the help of C arm. Condyles were fixed with 6 mm cannulated lag screws and olive wires. Most of the patients were followed up for a period of 23 months. The longest follow up was 24 months and the shortest was 3 months. Average duration of follow up was 16.3 months. The maximum flexion achieved was 150 deg [2 patients] and minimum was 90 deg [4 patients] and 7 patients had a flexion of 135 deg. The average flexion achieved was 118.25 deg.

Guidance for the Treatment of Femoral Neck Fracture with Precise Minimally Invasive Internal Fixation Based on the Orthopaedic Surgery Robot Positioning System.

Femoral neck fractures are among the most common fractures in orthopaedics. There are many surgical methods for the treatment of femoral neck fracture. Percutaneous cannulated lag screw fixation for the treatment of femoral neck fractures is favored by orthopaedic doctors because of its characteristics of being minimally invasive, with less bleeding and firm fixation. However, traditional freehand screw placement is limited by many factors, and the screw malposition rate is very high, which directly leads to the reduction of its biomechanical stability, and even leads to the ischemic necrosis of the femoral head caused by damage to blood vessels. In addition, excessive attempts to drill holes can damage cancellous bone and affect the screw's holding force, which reduces the stability of internal fixation and increases the risk of failure. At the same time, too much radiation exposure to medical personnel and patients also causes great damage to the body. Robot‐assisted orthopaedic surgery combines the mechanical “eye” (an infrared ray tracking device) and the mechanical “hand” (six degrees of freedom mechanical arm), and through the process of preoperative planning, intraoperative assistance in screw placement, and postoperative confirmation, provides a more minimally invasive and precise treatment method for this kind of surgery, and significantly reduces radiation exposure. This guide uses the TiRobot system as an example to describe the robot surgery in detail, aiming at standardizing the application of robots in orthopaedic surgery.

Biomechanical comparison of Kangli hollow screws with sliding compression locking plate system and conventional cannulated lag screws for fixation of type Pauwels III femoral neck fracture

Objective To compare the biomechanical performance of Kangli hollow screws with sliding compression locking plate system (KHS) and conventional cannulated lag screws for fixation of type Pauwels III femoral neck fracture. Methods 7 cadaveric femurs were selected, vertical fractures (Pauwels III fracture, at 70° to the horizontal) were artificially conducted in these cadaveric proximal femurs by an orthopaedic surgeon and fixed by KHS screws with plate system or conventional cannulated lag screws. Samples were positioned at 75° of the femoral shaft to the horizontal, embedded in the mould and fixed in the experimental console. Optical sensors were set at the femoral neck around the osteotomy line. Then the loading were input in the vertical, horizontal lateral direction and rotating direction around the femoral neck axis, the maximal and minimal values between the fractured fragments and the corresponding values of the loading were recorded. The values of stiffness in three directions were calculated and compared. The CT data of the left femur of a 25 year-old healthy male volunteer was input into the corresponding software and vertical femoral neck fracture model was generated. Two finite element analysis models were obtained after the fracture being fixed using these two different implants, and the Von Mises stress distribution on the femur, implants and the interface between the fractured fragments and the relative motion between the fractured fragments were compared. Results In the vertical, horizontal lateral direction and rotating direction around the femoral neck axis, the stiffness of the KHS were 3 904±1 148 N/mm, 4 324±1 234 N/mm and 11.45±4.95 N·m/° respectively, higher than those of the CSs method with the values of 3 020±1 150 N/mm, 3 020±854 N/mm and 6.53±4.83 N·m/° respectively. The differences between the two groups were statistically significant (t=2.7194, 4.7694 and 2.9424; P=0.0347, 0.0050 and 0.0423). In the finite element analysis test, the maximal Von Mises stress values distributing on the femur and the screws in the KHS group were 40.1 MPa and 126.4 MPa, and those in the CSs group were 98.1 MPa and 145.5 MPa respectively, and both values of the former were lower than the latter. But the Von Mises stress value on the interface between the fractured fragments in the KHS group was 14.37 MPa, which was much higher than that in the CSs groupwhich was 9.39 MPa. The gap at the fracture site of the CSs fixation model was dramatically larger than that of KHS fixation model. Conclusion The KHS screws and plate system could provide better immobilization effect for vertical femoral neck fracture compared to the cannulated lag screws. The risk of the screws failure was lower and the fracture union would be easier to obtained by the fixation of KHS screws with plate system. Key words: Femoral neck fractures; Fracture fixation, internal; Biomechanics; Finite element analysis

Análise comparativa do tratamento de fraturas basocervicais de fêmur com CCS, DHS e PFN em adultos jovens

ObjectiveTo the best of the authors’ knowledge, no studies in the literature have compared the clinical outcome of the three most common implants used to treat basicervical fractures of the femoral neck in young adults, i.e. CCS, DHS, and PFN. The present study attempts to fill the void in the literature and reach a conclusion regarding the usefulness of these implants in these fractures. MethodsThis was a prospective interventional study including 90 patients with basicervical fracture of the neck of femur treated randomly with cancellous cannulated lag screws or dynamic hip screw, with a derotation screw or short PFN. ResultsMean time for fracture union was 14.4, 13.9, and 13.5 weeks and union rate was 93.2%, 100%, and 100% in groups 1, 2, and 3, respectively. The mean Harris Hip Score at the final follow up was similar among all the groups, i.e. 79.4, 82.2, and 81.9 in CCS, DHS, and PFN groups, respectively. The highest proportion of good to excellent results was noted in the DHS group, i.e. 83.3%, whereas it was 73.6% and 80% in the CCS and PFN groups, respectively. ConclusionMultiple cancellous screws do not provide a sufficiently stable construct during fracture healing. PFN, although associated with lesser implant failures than CCS, have a higher incidence of technical errors. DHS provides sufficient stability in well‐reduced basicervical fractures in young adults; it is associated with highest fracture union rates and best functional outcome out of the three implants at final follow‐up.

A Single Lateral Rectus Abdominis Approach for the Surgical Treatment of Complicated Acetabular Fractures: A Clinical Evaluation Study of 59 Patients.

BackgroundThis study aimed to evaluate outcome following a single lateral rectus abdominis surgical approach for complicated acetabular fractures, involving anterior and posterior columns.Material/MethodsFrom January 2012 to March 2016, 59 patients, including 36 anterior column hemitransverse fractures, 18 two-column fractures, and five T-type complicated acetabular fractures, were treated with a single lateral rectus abdominis approach and fixed by plates and cannulated lag screws. Anterior column fractures were fixed with 3.5 mm reconstruction plates; posterior column fractures were fixed with 6.5 mm cannulated lag screws. The quality of surgical reduction (using the Matta criteria), functional outcome (using the modified Merle d’Aubigné and Postel scoring system), and postoperative complications were assessed with 24-month follow-up.ResultsFifty-nine patients (mean age, 45 years; range, 18–64 years) including 39 men and 20 women underwent surgery. Mean intraoperative blood loss was 514.6 ml (range, 150–830 ml) and mean operating time was 86.3 min (range, 42–145 min). Anatomical reduction was good in 40 cases (67.8%), fair in 15 cases (25.4%), and poor in four cases (6.8%). The modified Merle d’Aubigné score was excellent in 39 cases (66.1%), good in 14 cases (23.7%), fair in five cases (8.5%), and poor in one case (1.7%). At follow-up, there were five cases of peritoneal damage, eight cases of obturator nerve dysfunction, and four cases of postoperative traumatic arthritis.ConclusionsThe single lateral rectus abdominis surgical approach for the treatment of complicated acetabular fractures was minimally invasive with good anatomical exposure and good outcomes.

Plate Alone Versus Plate and Lag Screw for Lapidus Arthrodesis: A Biomechanical Comparison of Compression.

Background. Arthrodesis of the first tarsal metatarsal joint can be accomplished in many ways. The compressive force attained between various constructs remains unclear. This study compares compression achieved through a locking/compression Lapidus plate both with and without the addition of a lag screw. Methods: A dorsal medial Lapidus/locking compression plate (Total Compression Plate System, OrthoPro, Salt Lake City, UT, now Wright Medical) was applied to one cadaveric limb, while the same plate with the addition of a 4.0-mm cannulated lag screw was applied to the contralateral limb for a total of 5 matched pairs of cadaveric specimens. Compressive force was recorded over time and compared between the constructs using a compression sensor (8" FlexiForce Resistive Force Sensor, Phidgets Inc, Calgary, Alberta, Canada). Results: Compression was maintained for 45.4 minutes in the plate only construct, and 317 minutes with the addition of the lag screw (P = .010). The mean time to 50% peak compression for the plate only construct was 4.90 minutes compared with 15.11 minutes for plate with lag screw construct (P = .012). Conclusion: The addition of a lag screw is recommended for extending the length of compression and possibly reducing nonweightbearing time and the risk of nonunion. Levels of Evidence: Level V.

Comparative analysis of treatment of basicervical femur fractures in young adults with CCS, DHS, and PFN

ObjectiveTo the best of the authors’ knowledge, no studies in the literature have compared the clinical outcome of the three most common implants used to treat basicervical fractures of the femoral neck in young adults, i.e. CCS, DHS, and PFN. The present study attempts to fill the void in the literature and reach a conclusion regarding the usefulness of these implants in these fractures. MethodsThis was a prospective interventional study including 90 patients with basicervical fracture of the neck of femur treated randomly with cancellous cannulated lag screws or dynamic hip screw, with a derotation screw or short PFN. ResultsMean time for fracture union was 14.4, 13.9, and 13.5 weeks and union rate was 93.2%, 100%, and 100% in groups 1, 2, and 3, respectively. The mean Harris Hip Score at the final follow up was similar among all the groups, i.e. 79.4, 82.2, and 81.9 in CCS, DHS, and PFN groups, respectively. The highest proportion of good to excellent results was noted in the DHS group, i.e. 83.3%, whereas it was 73.6% and 80% in the CCS and PFN groups, respectively. ConclusionMultiple cancellous screws do not provide a sufficiently stable construct during fracture healing. PFN, although associated with lesser implant failures than CCS, have a higher incidence of technical errors. DHS provides sufficient stability in well-reduced basicervical fractures in young adults; it is associated with highest fracture union rates and best functional outcome out of the three implants at final follow-up.