Comparative biomechanical performance of two configurations of screw constructs and types used to stabilize different sites of unstable Pauwels type II femoral neck fractures: A finite element analysis.

BACKGROUND: A smaller dimension of the femoral neck in the Asian population may have difficulty placing inverted triangle multiple screws configuration for treatment. Posterior triangle configuration, which is suitable in limited space of the femoral neck, is a promising alternative treatment approach. This study aimed to investigate the biomechanical performance of inverted and posterior triangles of multiple screws fixation configuration for both cannulated and standard solid-core screws in stabilizing Pauwels type II femoral neck fracture sub-capital, mid-cervical, and basilar regions using Finite Element (FE) method. METHODS: A 3D femur model was created for Pauwels type II femoral neck fractures. The fracture sites were in the mid-cervical, sub-capital, and basilar regions, with a spacing of 7 mm between adjacent fracture lines. Both cannulated and solid-core screws were configured in the inverted and posterior triangle patterns. The applied physiological loads to the FE models included muscle and hip contact forces. Equivalent von Mises (EQV) stresses were used to monitor fixation strength whereas elastic strain of each configuration indicated the degree of stability of a fracture site. RESULTS: EQV stress on the screws for posterior and inverted triangle configuration ranged from 212.1 to 290.2 MPa, and 224.4-314.8 MPa, respectively. The EQV stress the posterior triangle configuration was lower than the inverted triangle configuration by 5.5-10.8%. The stress exhibited on the screw was greatest when the fracture site was at basilar regions, 1.1-1.3 times greater than fracture in sub-capital region. Elastic strain at fractures retained by cannulated screw was greater than solid-core screw with maximum difference of 68 microstrains. Cannulated screw provided less stability than the solid-core screw. CONCLUSIONS: The screws used in the posterior triangle configuration exhibits lower screw stress in all fracture regions of the femoral neck. The solid-core screw shows superior biomechanical properties compared with cannulated screw with lower EQV stress and better fracture stability. Posterior triangle configuration is considered an alternative treatment of choice for the patient with a small dimension of the femoral neck.

3D CAD/reverse engineering technique for assessment of Thai morphology: Proximal femur and acetabulum.

PURPOSE: To assess morphological parameters of proximal femur and acetabulum in Thai population with three-dimensional measurement technique, and to analysis of collateral side symmetric, gender difference, and correlation between morphometric parameters. METHODS: Investigation was performed in 240 femurs. All three-dimensional femur models were acquitted from 64-slice spiral CT scanner. Morphometric parameters under consideration included acetabular diameter, femoral head diameter, shaft isthmus location, intramedullary canal diameter, diaphyseal diameter, femoral head height, femoral neck isthmus, femoral neck length, neck shaft angle, bow angle, and anteversion angle. All parameters were measured based on functions and least-square regression function in CAD software. Obtained measured data were then used for analysis of collateral side symmetric, gender difference, correlation between morphometric parameters, and compared with other populations. RESULTS: Female had a smaller dimension compared with male in most of the parameters. No significant difference was observed between left and right femurs. High correlation pairs of morphometric parameters included femoral head diameter-acetabular diameter, femoral head diameter-neck isthmus diameter, femoral head diameter-diaphyseal diameter at shaft isthmus level, acetabular diameter-neck isthmus diameter, neck isthmus diameter-diaphyseal diameter at shaft isthmus level, and acetabular diameter-diaphyseal diameter at shaft isthmus level. Some morphometric parameters of Thai are smaller than other Caucasian, and some Asian nation, i.e. femoral head diameter, femoral neck length, and femoral head height. CONCLUSIONS: This study provides essential morphometric data for various orthopedic implant designs relating to proximal femur region.

Biomechanical performance of retrograde nail for supracondylar fractures stabilization.

The study compared the biomechanical performance of retrograde nail used to stabilize supracondylar fracture (three different levels) by means of finite element analysis. Three different nail lengths (200, 260, and 300 mm) of stainless steel and titanium nails were under consideration. Intact femur model was reconstructed from Digital Imaging and Communications in Medicine images of Thai cadaveric femur scanned by computed tomography spiral scanner, whereas geometry of retrograde nail was reconstructed with the data obtained from three-dimensional laser scanner. The retrograde nail was virtually attached to the femur before nodes and elements were generated for finite element model. The finite element models were analyzed in two stages, the early stage of fracture healing and the stage after fracture healing. The finding indicated that purchasing proximal locking screw in the bowing region of the femur may be at risk due to the high stresses at the implant and bone. There were no differences in stress level, elastic strain at a fracture gap, and bone stress between stainless steel and titanium implant. Since the intramedullary canal requires reaming to accommodate the retrograde nail, the length of retrograde nail should be as long as necessary. However, in case that the retrograde nail can be accommodated into the intramedullary canal without reaming, the longer retrograde nail can be used.

Breakage of a Lag Screw of Cephalomedullary Nail: A Technique of Removal.

A broken lag screw of the cephalomedullary nail is a rare condition. Removal of the retained lag screw from the femoral head is also very challenging. This article describes a surgical technique and the modified instrument that was available in the operating room for removing the broken implant by closed technique.

Radiation exposure in fluoroscopy of the shoulder: a comparison between mini and conventional C-arm image intensifier.

OBJECTIVE: To compare the radiation exposure of the primary surgeon while using the conventional c-arm and mini c-arm fluoroscopy at the shoulder MATERIAL AND METHOD: Twelve shoulders of six fresh cadavers were used to simulate this experimental study. Radiation exposure of the primary surgeon was measured at the head and neck region. The average radiation dose was measured using both the conventional c-arm and mini c-arm, then the findings were compared. RESULTS: Mean radiation energy of the conventional c-arm was significantly lower than the mini c-arm at 59.39 ± 1.43 kV and 70.58 ± 4.01 kV respectively (p < 0.001). Dose rates to which the primary surgeon was exposed from the conventional c-arm and the mini c-arm were 81.46 ± 30.37 µSv/hour and 87.54 ± 43.69 µSv/hour, respectively. However, the difference was not statistically significant (p = 0.875). CONCLUSION: There is no difference in the level of radiation safety for the primary surgeon when using the conventional c-arm vs. the mini c-arm for a fluoroscopic-assisted shoulder procedure. Therefore, selection of the methodology should be based on equipment availability and clinical considerations.

Lateral condylar prominence, post corrective osteotomy of cubitus varus: a study using three-dimensional reverse engineering technique.

Lateral condylar prominence is a common problem after corrective osteotomy of the cubitus varus, which is believed to result from unequal opposing cut surfaces of lateral-based wedge osteotomy using a medial hinge. This study investigated this issue using a 3-dimensional CT data set consisting of images of the deformed elbow and the normal elbow of a patient with cubitus varus deformity who was scheduled for corrective osteotomy A CT scan was performed with 3mm slice thickness and a reconstruction was done with 1mm interpolated slice thickness on both the left and right humerus. The CT-data set was then manipulated using reverse engineering software. Three-dimensional models of both the deformed and normal humeri were studied. Several locations or levels of medial hinge placement, each with 4-degree-tilt wedge osteotomy cut options, were then virtually performed and evaluated. The degree of correction was determined from the varus angle plus the normal carrying angle of the normal side. From the study, it was found that the degree of lateral condylar prominence is directly proportional to the distance of placement of the medial hinge above the joint. Differences in the lengths of the osteotomy surfaces have no effect on condylar prominence; only the step-off phenomenon affects condylar prominence. According to our findings, placement of the medial hinge close to the joint with a 10-degree distal osteotomy cut just above the olecranon fossa will result in optimal minimization of condylar prominence or the step-off phenomenon.

Optional entry point for retrograde femoral nailing: an anatomical study using the reverse engineering method.

OBJECTIVE: To investigate the optimal entry point for retrograde femoral nailing using medical imaging and reverse engineering technologies. MATERIAL AND METHOD: One hundred and eight adult cadaveric femurs were scanned using a computed tomography (CT) scanner. To obtain three-dimensional models, medical imaging and reverse engineering technologies were used. The insertion assessment was performed using computer aided design (CAD) software. The curve representing the mid-line in the intramedullary canal in the mid-shaft region was approximated using regression analysis. The curve was extended tangentially toward the femoral condyle, where the intersection between the curve and the condylar surface is the insertion site. The location of the insertion site was determined using the center of the anterior most of the intercodylar notch as a reference point. The measured distances were presented in medial-lateral and anterior-posterior perspectives from the reference point. RESULTS: Average insertion site for Thai population was 0.56 mm lateral to and 12.67 mm medial to the anterior most of the intercondylar notch. The distance measured from intercondylar notch to the insertion site in the anterior-posterior direction was not significantly different between males and females; however a significant difference in the insertion site was found in medial-lateral directions. CONCLUSION: The insertion site can be clinically approximated lying on the anterior-posterior axis, since the distance from the anterior-posterior axis to the insertion site is relatively small. The insertion site for the Thai population was found to be 12 mm anterior to the center of the anterior most of the intercondylar notch.

Prevention of excessive medialisation of trochanteric fracture by a buttress screw: a novel method and finite element analysis.

This paper proposes a novel method of using an antero-posterior buttress screw at the distal fragment just below the fracture site in conjunction with the sliding hip screw (SHS) to resist excessive femoral medialisation. A virtual assessment of the effectiveness of this new method was performed using the finite element analysis. The results indicate that the use ofa sliding hip screw (SHS) combined with a buttress screw can help resistfemoral medialisation better than using an SHS with no buttress screw. The von Mises equivalent stress (EQ ) was found to be in a safe range, which indicates increased integrity of the lateral wall with the addition of the buttress screw.

Removal of a broken cannulated femoral nail: a novel retrograde impaction technique.

This report presents a surgical technique to remove a broken cannulated nail from the femur. A Harrington rod was modified for retrograde impaction of the retained fragment. The broken implant was finally removed without complication. This particular procedure was safe, simple, and promising.

Heterotopic ossification after closed femoral nailing.

BACKGROUND: Heterotopic ossification is defined as pathological bone formation in soft tissue, it usually occurs postoperatively and varies in amount from faint to massive ossification, which are frequently asymptomatic. The cause of heterotopic ossification is unknown, but it occurs more commonly after the procedure, in which considerable bone and soft tissue are dissected extensively. The heterotopic ossification in the abductor region of the hip following closed femoral nailing has rarely been documented. OBJECTIVE: To assess the prevalence and type of heterotopic ossification after closed antegrade femoral nailing. MATERIAL AND METHOD: A retrospective study was performed in patients who underwent closed antegrade femoral nailing. The occurrence of heterotopic bone was assessed by reviewing of the series of the follow-up films in this group of patients with sufficient duration of at least after 6 months post-operation. The size and extent of the heterotopic ossification were measured and graded according to Brumback classification. RESULTS: From 100 patients who were completely followed-up. There were 54 cases (54%) presented with heterotopic ossification. The heterotopic ossification are classified as grade I in 16 cases (16%), grade II in 13 cases (13%), grade III in 24 cases (24%) and grade IV in 1 case (1%). There was a significant different between the prevelence of heterotopic ossification in patients with trochnateric fractures when compared to patients with femoral shaft fractures (p-value < 0.05).

Tourniquet pain: calf versus ankle tourniquet.

The tourniquet pain during 30 minutes after the application of calf tourniquet and ankle tourniquet were assessed and compared in 63 healthy volunteers, 32 males and 31 females whose ages ranged from 21-36 (average, 24) years. The visual analogue pain score assessed at 0, 1, 3, 5, 10, 20, 30 minutes of adequate tourniquet pressure application and after removal of the tourniquet at 0, 5 and 30 minutes were recorded. The results revealed significant less visual analogue pain scores with the ankle tourniquet group (range, 0-4.4 mmHg) than the calf tourniquet group (range, 0-6.7 mmHg) at all time-points of evaluations and the tourniquet pain was also diminished faster in the ankle tourniquet group after the tourniquet was removed. It was also found a significant higher minimal tourniquet pressure required for the vascular occlusion distal to the tourniquet sites detected by a pulse oximeter in the ankle tourniquet group (mean, 310.8 +/- 40.8 mmHg) than the calf tourniquet group (mean, 272.5 +/- 36.9 mmHg, p = 0.024). The present study supports the use of ankle tourniquet to minimize tourniquet pain for foot surgery.

Mismatch analysis of humeral nailing: antegrade versus retrograde insertion.

BACKGROUND: Closed humeral nailing is now considered an alternative treatment for humeral-shaft fracture. The nail can be inserted with either the antegrade or retrograde method. We investigated and compared the problem of geometric mismatch of the humeral nail to the humerus between the two methods of insertion. METHODS: The study was performed using virtual simulation based on computed tomography (CT) data of 76 Thai cadaveric humeri and the commonly used Russell-Taylor humeral nail 8 mm in diameter and 220 mm long. Mismatch of the nail to the intact humerus was analyzed and compared between the antegrade and retrograde nailing approaches. RESULTS: The results showed: (1) the diameter of the medullary canal averaged 7.9-13.8 mm; (2) the minimal reaming diameter to accommodate virtual nail insertion averaged 8.8-14.8 mm for the antegrade and 8.8-29.3 mm for the retrograde approach; (3) the minimal reaming thickness of the inner cortex averaged 0.1-1.5 mm for the antegrade and 0.1-9.9 mm for the retrograde approach; (4) the percentages of cortical bone removed prior to nail insertion were 3.8-107.1% and 3.8-1,287.6% for the antegrade and retrograde approaches, respectively; (5) the eccentricity of the nail-medullary canal center were 0.4-3.4 and 0.4-10.6 mm for the antegrade and retrograde approaches, respectively. CONCLUSIONS: Less mismatching occurred with antegrade nailing than with the retrograde approach. Retrograde nailing requires excessive reaming at the distal part of the humerus to accommodate nail insertion. This may create bone weakness and the risk of supracondylar fracture.

Geometric mismatch analysis of retrograde nail in the Asian femur.

The geometric mismatch analysis of the retrograde nail was performed in 108 Asian cadaveric adult femora. The insertion was done virtually based on a three-dimensional geometric model derived from computed tomographic images. The investigation was performed at eight levels located at 120, 140, 160, 180, 200, 220 and 240 mm above the condylar surface. The evaluation of each level included: (1) the diameter of the intramedullary canal, (2) the percentage of area filled by the nail in the unreamed intramedullary canal, (3) the minimal reamer diameter that required enlargement of the canal to accommodate retrograde nail insertion, (4) the minimal inner cortical reaming thickness that needed to be removed, (5) the percentage of the cortical bone area that needed to be removed prior to nail insertion and (6) the deviation of the nail center from the center of the intramedullary canal. The result showed significant mismatch of the nail to most of the study specimens (94 femora, 87%), which the intramedullary canal needed extensive reaming to accommodate the nail insertion. This may lead to a high possibility of clinical complications. Redesign for proper shape and size of retrograde nail should be considered for the use in Asian population.

Three-dimensional morphometric study of the Thai proximal humerus: cadaveric study.

Seventy-six cadaveric humeri were investigated to study the three-dimensional morphometric data based on CT data. The present study was an advanced method to determine the 3D proximal humeral parameters for both intra and extra geometries through the utilization of medical imaging and reverse engineering techniques. The following parameters were calculated for each humerus and then compared with the 3D Caucasian data such as diameter of humeral head, articular surface thickness, inclination angle, retroversion angle, medial offset, posterior offset, curve length, radius of curvature, and mediolateral angle. It was found that the Thai humeral parameters were smaller than Caucasian except the retroversion angle and posterior offset. This data could be further used to develop a proper design of shoulder arthroplasty for Thai patients.

Three dimensional transient multifield analysis of a piezoelectric micropump for drug delivery system for treatment of hemodynamic dysfunctions.

In this paper, we present design of a transdermal drug delivery system for treatment of cardiovascular or hemodynamic disorders such as hypertension. The system comprises of integrated control electronics and microelectromechanical system devices such as micropump, micro blood pressure sensor and microneedle array. The objective is to overcome the limitations of oral therapy such as variable absorption profile and the need for frequent dosing, by fabricating a safe, reliable and cost effective transdermal drug delivery system to dispense various pharmacological agents through the skin for treatment of hemodynamic dysfunction such as hypertension. Moreover, design optimization of a piezoelectrically actuated valveless micropump is presented for the drug delivery system. Because of the complexity in analysis of piezoelectric micropump, which involves structural and fluid field couplings in a complicated geometrical arrangement, finite element (FE) numerical simulation rather than an analytical system has been used. The behavior of the piezoelectric actuator with biocompatible polydimethylsiloxane membrane is first studied by conducting piezoelectric analysis. Then the performance of the valveless micropump is analyzed by building a three dimensional electric-solid-fluid model of the micropump. The effect of geometrical dimensions on micropump characteristics and efficiency of nozzle/diffuser elements of a valveless micropump is investigated in the transient analysis using multiple code coupling method. The deformation results of the membrane using multifield code coupling analysis are in good agreement with analytical as well as results of single code coupling analysis of a piezoelectric micropump. The analysis predicts that to enhance the performance of the micropump, diffuser geometrical dimensions such as diffuser length, diffuser neck width and diffuser angle need to be optimized. Micropump flow rate is not strongly affected at low excitation frequencies from 10 to 200 Hz. The excitation voltage is the more dominant factor that affects the flow rate of the micropump as compared with the excitation frequency. However, at extremely high excitation frequencies beyond 8,000 Hz, the flow rate drops as the membrane exhibits multiple bending peaks which is not desirable for fluid flow. Following the extensive numerical analysis, actual fabrication and performance characterization of the micropump is presented. The performance of the micropump is characterized in terms of piezoelectric actuator deflection and micropump flow rate at different operational parameters. The set of multifield simulations and experimental measurement of deflection and flow rate at varying voltage and excitation frequency is a significant advance in the study of the electric-solid-fluid coupled field effects as it allows transient, three dimensional piezoelectric and fluid analysis of the micropump thereby facilitating a more realistic multifield analysis. The results of the present study will also help to conduct relevant strength duration tests of integrated drug delivery device with micropump and microneedle array in future.

3D geometrical assessment of femoral curvature: a reverse engineering technique.

OBJECTIVE: Investigate the 2D/3D geometry of femoral curvature and femoral length using the advanced technique of computerized tomography combined with reverse engineering techniques. MATERIAL AND METHOD: The present study was performed using reverse engineering technique based on CT data of 99 cadaveric femora. The femur was divided into three segments, proximal, mid-shaft, and distal regions by defining 35% and 65% of the femoral total length as a boundary of each region. The intramedullary canal in the mid-shaft region was mainly extracted to determine the set of circular center, which could consequence to approximate the 3D femoral radius of curvature using the 3D least square best fit. The 3D femoral curvature was then projected into A-P and M-L directions to investigate the correlation of 2D/3D femoral curvature as normal radiographic images. RESULTS: It was found that the average 3D Thai femoral curvature was 895.46-mm (SD = 238.06) and the average femoral total length is 421.96-mm (SD = 27.61). In addition, the 2D femoral curvature derived from sagittal radiographic image can be used to determine the 3D femoral curvature with this equation: R3D = RSagittal + 3.67 with r = 0.987. CONCLUSION: This described technique is a non-destructive method that can effectively assess the internal/ external 3D geometric data of the femur The obtained data is useful to develop a proper design of prosthesis that required inserting into the intramedullary canal. From the present study, it can be concluded that the 2DSagittal femoral curvature derived from standard radiographic image can be represented for the 3D femoral curvature.

Musculoskeletal trauma service in Thailand.

Trauma is becoming a leading cause of death in most of the low-income and middle-income countries worldwide. The growing number of motor vehicles far surpasses the development and upkeep of the road and highway networks, traffic laws, and driver training and licensing. In Thailand, road traffic injuries have become the second leading cause of death and morbidity overall since 1990. The lack of improvement to existing roadways, implementation of traffic safety and ridership laws including seatbelt regulations, and poor emergency medical assistance support systems all contribute to these statistics. An insufficient number and inequitable distribution of healthcare professionals is also a national problem, especially at the district level. Prehospital care of trauma patients remains insufficient and improvements at the national level are suggested.

Technique of closed unlocked femoral nailing using ultrasound guidance.

We report a method of closed femoral nailing, without locking, using only ultrasound guidance from the beginning to end of the operation. The method was evaluated as a prospective study in 150 cases of unilateral femoral mid-shaft fracture that underwent surgery within 1 week. There were 132 males and 18 females aged from 16 to 70 years (mean 26). The interval from injury to operation averaged 2.3 days (range 1-7). Twenty-seven cases had Winquist I comminution and 123 cases had no comminution. In 145 cases (97%), we were successful using this method, with an average operation time of 35.8 min (range 30-50). In five cases, we had to change to using fluoroscopic control. Of these, in one case the fracture could not be reduced under ultrasound monitoring, one had nail incarceration, in one there was breakage of the flexible reamer and in two cases we were unable to pass the guide-wire across the fracture within 10 min. Ultrasound is readily available in most hospitals and can be used as an alternative method for monitoring the fracture alignment in closed unlocked femoral nailing.

Radiation scattering to the primary surgeon during closed locked femoral nailing.

A prospective study of the radiation exposure to the primary surgeon during closed static locked femoral nailing was performed in 50 cases. There were 44 males and 6 females whose ages ranged from 15 to 70 years (average, 32). The degree of fracture comminution was classified by Winquist. The cases included 1 Winquist (WQ)1, 9 WQ2, 27 WQ3 and 13 WQ4. The Grosse-Kempf femoral nail was used in 40 cases and the AO interlocking femoral nail was used in 10 cases. The C-arm image intensifier model Phillip BV212 and BV 300 were used during the present study. The average operation time was 52 minutes (range, 30 to 120). The fluoroscopic time for the entire procedure average 132 seconds (range, 23 to 366). The radiation exposure to the primary surgeon ranged from 2 to 231 micro-Sv with an average of 30 micro-Sv per procedure. From the present study, it was found that radiation scattered to the primary surgeon during current practice for closed static femoral nailing using the recent model of C-arm image intensifier was minimal and far below the permissible dose. It was also found that the group using the C-arm model BV 300 (n = 16) had significant lesser fluoroscopic time and less radiation scattering to the primary surgeon than the group with model BV 212 (n = 34).

Neglected dislocation of the elbow.

We retrospectively review the intermediate-term to long-term results of 24 patients treated after late open reduction of neglected posterior elbow dislocation in terms of the elbow, particularly noting joint mobility. The mean interval from injury to operation was 7.9 months (range, 1-60 months). The posterior approach with V-Y muscleplasty was used in most patients with 2 to 3 weeks postoperative immobilization. The average preoperative arc of elbow flexion was from 17 degrees with an average maximum flexion of 27 degrees (range, 5-60 degrees ) and an average flexion contracture of 10 degrees (range, 0-30 degrees ). The mean followup was 48.3 months (range, 12-132 months). At the time of final followup, the average arc of elbow flexion was 82 degrees with an average of maximum flexion of 122 degrees (range, 90-150 degrees) and an average flexion contracture of 40 degrees (range, 0-75 degrees). There was no correlation between the postoperative arc of elbow motion and preoperative parameters including patient age, preoperative arc of elbow motion, or duration of untreated dislocation.