Calcar Screws Research Articles

Correlation of radiological parameters with functional outcomes post fixation with proximal humerus locking plates.

Proximal humerus fractures account for 4-5% of all fractures in adults and affect females more than males. With the advent of special locking plates, the treatment trend has shifted more towards a surgical approach. These methods have produced good results but very high complications rates have been reported in the literature. This study was undertaken to analyse the radiological parameters which reflect towards a favourable long term functional outcome in order to advance the surgical fixation skills for managing fractures of the proximal part of the humerus. 83 study participants with proximal humerus fracture fixed using proximal humerus locking plates were retrospectively analysed. The radiological parameters studied were neck shaft angle, head shaft angle, head diameter, head height, greater tuberosity to articular surface distance and reduction of the medial hinge with or without placement of calcar screw. The functional parameters assessed were the Constant Murley Score and range of movements of the shoulder joint. The patients were not followed further for the purpose of the study. The mean Constant Murley Score for the participants was 80.75 ± 8.09 (range 60-90). The participants with good to excellent CM Score had a significantly higher neck shaft angle (107.47 ± 9.74 v/s 124.16 ± 10.68) and (-0.28 ± 0.85 v/s 2.37 ± 2.28), head shaft angle (23.09 ± 4.82 v/s 31.76 ± 7.76), head diameter (40.08 ± 8.63 v/s 45.15 ± 4.73), head height (18.77 ± 1.96 v/s 20.69 ± 2.76) and greater tuberosity to articular surface distance (-0.28±0.85 v/s 2.37±2.28) as compared to the patients with satisfactory and worse CM Score. The patients with a higher neck shaft angle and a maintained subacromial space had a better range of shoulder abduction. A higher rate of valgus collapse was seen with an inadequate medial hinge reduction. The radiological parameters which can predict towards a good functional outcome are a higher neck shaft angle and head shaft angle, a larger head diameter and head height, a superior position of the greater tuberosity in relation to the articular surface and a good medial hinge reduction.

Impact of augmentation strategy variations on the mechanical characteristics of patients with osteoporotic proximal humerus fractures with medial column instability.

Low bone density and lack of medial support are the two most important factors affecting the stability of locking plate fixation for osteoporotic proximal humeral fractures (PHFs). This study aimed to compare the biomechanical characteristics of PHILOS locking plates combined with calcar screws, bone cement, fibular allografts, and medial locking plate support strategies for treating osteoporotic PHFs with medial column instability. A three-part osteoporotic PHF (AO 11-B3.2) model with metaphyseal loss was generated using 40 synthetic humeri and fixed via four distinct medial support strategies. All models were mechanically tested to quantify the mechanical characteristics. Subsequently, finite element models were created for each biomechanical test case. The stress distribution and displacement of the four different fixation structures were analyzed using finite element analysis. The results demonstrated that the PHILOS locking plate combined with the medial locking plate, exhibited the greatest stability when subjected to axial, shear, and torsional loading. Furthermore, the PHILOS locking plate combined with bone cement showed structural stability similar to that of the PHILOS locking plate combined with fibular allograft but with lower stress levels on the fracture surface. In conclusion, the PLP-MLP fixation structure showed superior biomechanical properties under axial, shear, and torsional loading compared to other medial support methods. Repairing the medial support when treating osteoporotic PHFs with medial column instability can enhance the mechanical stability of the fracture end in both the short and long term.

Primary Arthrodesis with Retrograde Hindfoot Nail for Elderly Patients with Tibia Pilon Fractures and Psychiatric Illness.

Management of tibial pilon fracture in elderly patients with psychiatric illness remains challenging for orthopedic doctors because of patients' poor bone quality and inability for self-care. This study aimed to ascertain the viability and reliability of primary arthrodesis by using retrograde hindfoot nail for these difficult cases. We retrospectively reviewed eight elderly consecutive patients (age older than 65 years) with tibial pilon fractures and psychiatric illness from January of 2012 to December of 2019 in our institute. Primary tibiotalocalcaneal arthrodesis with retrograde hindfoot nail was used as a definitive procedure. The bone union time, wound complication rate, ankle alignment, necessity for narcotic agents, and ambulation status were evaluated. The average length of follow-up was 22.25 months (range, 15-36 months). Additional bone grafting surgery was performed for one patient because of fusion-site nonunion 6 months postoperatively. Another patient required debridement and removal of posterior calcaneal screw because of implant prominence and local infection. Osseous union with angular deformity less than 10° was achieved in all patients finally. The average bone union time was 6.6 months (range, 4-12 months). In terms of walking ability, six patients were capable of outdoor ambulation (classes 2 and 3). Two patients required oral pain medication at the final visit. The current study involved only a small number of patients, and two of the eight cases encountered undesired complications (one local infection and one bone nonunion); however, we believe that our method may serve as a valuable alternative for the treatment of tibial pilon fractures in elderly patients with psychiatric illness, considering the specificity of this fragile population.

Pre-operative virtual three-dimensional planning for proximal humerus fractures: A proof-of-concept study.

To (1) evaluate surgeon agreement on plating features (position and screw length) in virtual 3D planning software, (2) describe outcomes (fracture reduction, plate position, malpositioning of calcar screws and screw lengths) of plate fixations planned with routine pre-operative assessment (2D- and 3D CT imaging) and those planned with dedicated virtual 3D software of the same proximal humerus fracture. Fourteen proximal humerus fractures were retrospectively reduced and fixed with virtual planning software by eight attending orthopaedic surgeons and compared to the true surgical fixation with post-operative computed tomography (CT) scans. Reduction differences were quantified using CT micromotion analysis. Intraclass correlation for screw lengths was 0.97 (95% CI: 0.96-0.98) and 0.90 (95% CI: 0.79-0.96) for plate position. Mean difference in total fracture rotation of the head between the virtual and conventional group was 22.0°. Plate position in the virtual planning group was 3.2 mm more proximal. There were no differences in inferomedial quadrant calcar screw positioning and, apart from the superior posterior converging screw, no significant differences in screw lengths. Reproducibility on plate position and screw length with virtual planning software is adequate. Apart from fracture reduction, virtual planning yielded similar plate positions, screw malpositioning rates and lengths compared to routine pre-operative assessment.

Correct positioning of the calcar screw leads to superior results in proximal humerus fractures treated with carbon-fibre-reinforced polyetheretherketone plate osteosynthesis with polyaxial locking screws

BackgroundPlate osteosynthesis with implants made of carbon-fibre-reinforced polyetheretherketone (CFR-PEEK) has recently been introduced for the treatment of fractures of the proximal humerus (PHFs). The advantages of the CFR-PEEK plate are considered to be its radiolucency, its favourable modulus of elasticity, and the polyaxial placement of the screws with high variability of the angle. The primary aim of this study is to investigate the influence of calcar screw positioning on the complication and revision rates after CFR-PEEK plating of PHFs. The secondary aim is to assess its influence on functional outcome.Material and methodsPatients were identified retrospectively. Minimum follow-up was 12 months. The cohort was divided into two groups depending on the distance of the calcar screw to the calcar (group I: < 12 mm, group II: ≥ 12 mm). The range of motion (ROM), Subjective Shoulder Value Score (SSV) and Constant–Murley Score (CS) were analysed at follow-up examination. Subjective complaints, complications (e.g. humeral head necrosis, varus dislocation) and the revision rate were evaluated.Results51 patients (33 female, 18 male) with an average age of 68.6 years were included after a period of 26.6 months (group I: 32 patients, group II: 19 patients). Apart from the gender distribution, no significant differences were seen in the patient characteristics. The outcome scores showed significantly better clinical results in group I: SSV 83.4 vs 71.2, p = 0.007; CS 79.1 vs 67.8, p = 0.013. Complications were seen less frequently in group I (18.8 % vs 47.4 %, p = 0.030).ConclusionThis study shows that the positioning of the calcar screw is relevant for CFR-PEEK plate osteosynthesis in PHFs with a good reduction of the fracture. Optimal positioning of the calcar screw close to the calcar (< 12 mm) is associated with a lower rate of complications, resulting in significantly superior functional outcomes.Level of evidence: III, retrospective cohort study

Dynamic biomechanical investigation of a novel sulcus bicipitalis plate in combination with a conventional locking plate for the treatment of complex proximal humerus fractures

BackgroundComplex proximal humerus fractures place high demands on osteosynthetic treatment. In some cases, double plating has already been used to increase primary stability of the osteosynthesis. This approach was advanced in the present study by developing an additive plate for the sulcus bicipitalis. To demonstrate the superior primary stability of the newly developed plate osteosynthesis, a biomechanical comparison against a conventional locking plate with an additional calcar screw was performed. MethodsTen pairs of cadaveric humeri were treated proximally with a locking plate (PENTA plate small fragment, INTERCUS). Each had a two-part fracture model with a fracture gap of 10 mm. All right humeri were treated with an additive novel plate that extends along the bicipital sulcus and encircles the lesser tuberosity proximally. First, the specimens were loaded sinusoidally at 250 N in 20° abduction for 5000 cycles. Afterwards quasi-static loading until failure was applied. FindingsThe movement at the fracture gap due to the cyclic loading occurred mainly as rotation around the z-axis, corresponding to a tilt medially and distally. The double plate osteosynthesis reduces the rotation by approximately 39%. For all load cycles observed, except 5000 cycles, medial and distal rotation of the head was significantly reduced by the double plate. The failure loads showed no significant differences between the groups. InterpretationIn the tested scenario under cyclic loading, the novel double plate osteosynthesis showed a significant superiority of primary stability over the conventional treatment with one locking plate. Furthermore, the study showed the advantages of cyclic load application over quasi-static load application until failure.

Treatment of Sanders typeⅡto Ⅲ calcaneal fractures with percutaneous reduction and minimally invasive calcaneal screw fixation

To investigate clinical effect of percutaneous reduction combined with internal fixation of calcaneal nail in treating Sanders typeⅡto Ⅲ calcaneal fractures. From July 2017 to August 2019, clinical data of 98 patients with Sanders typeⅡto Ⅲ calcaneal fractures treated were retrospectively analyzed, and divided into observation group and control group according to different surgical methods. In observation group, there were 35 males and 21 females, aged from 23 to 58 years old with an average of (34.50±7.81) years old;29 patients with Sanders typeⅡand 27 patients with Sanders type Ⅲ;30 patients on the left side and 26 patients on the right side;the time from fracture to operation ranged from 1 to 4 days with an average of (3.45±0.54) days;and treated with percutaneous reduction combined with internal fixation of calcaneal nail system. In control group, there were 25 males and 17 females, aged from 25 to 60 years old with an average of (35.27±7.64) years old;23 patients with Sanders type Ⅱ and 19 patients with Sanders type Ⅲ;24 patients on the left side and 18 patients on the right side;the time from fracture to operation ranged from 2 to 5 days with an average of (3.42±0.62) days;and treated with open reduction and internal fixation. Operation time, blood loss, hospital stay, fracture healing time, and postoperative visual analogue scale (VAS) at 1 day, preoperative and postoperative American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, Böhler angle, Gissane angle and calcaneus width, and postoperative complications were compared between two groups. All patients were followed up from 13 to 18 months with an average of (15.6±2.2) months. There were significant differences in operation time, blood loss, hospital stay, fracture healing time and postoperative VAS at 1 day between two groups (P<0.05). There was statistical difference in postoperative AOFAS score at 12 months between two groups (P<0.05), and AOFAS score at 12 months after operation was higher than that before operation (P<0.05). According to AOFAS score, 21 patients got excellent result, 30 good and 5 moderate in observation group, and 10 excellent, 22 good, 7 moderate and 3 poor in control group, which had statistical difference between two groups (P<0.05). Postoperative Böhler angle, Gissane angle and calcaneus width at 6 months were better than that before operation between two groups(P<0.05). One patient in observation and 20 patients in control group occurred skin numbness after operation, and 14 patients occurred skin necrosis in control group, there were obvious difference between two groups(P<0.01). Compared with open reduction and internal fixation, percutaneous reduction combined with internal fixation system in treating Sanders typeⅡto Ⅲ calcaneal fractures is feasible for fracture repair without waiting for foot deswelling, which could accurately restore normal shape and position of the fractured heel bone, completely eliminate fracture malunion, and reduce postoperative complications. Therefore, it could shorten operation time, hospital stay, fracture healing time, reduce amount of blood loss, promote postoperative recovery, and less complications, high safety, which could be used as a choice of orthopedic surgery for foot and ankle trauma.

Functional results of deltoid split minimally invasive osteosynthesis for neer type 3 proximal humerus fractures

We aimed to evaluate the short-term functional and radiological outcomes of the minimally invasive fixation of three-part proximal humerus fractures without using calcar screws. Twenty patients were treated with the minimally invasive approach using locking plate-screws. The relationship between the cephalo-diaphyseal angles and the functional outcomes were evaluated. The mean follow-up time were 22.7 months. The mean Constant-Murley score of the patients was 83.7. The modified Constant-Murley score was excellent in 16 and good in four patients. A statistically significant difference was detected between cephalo-diaphyseal angles. Osteosynthesis with minimally invasive plate-screw and deltoid splitting application is encouraging with its satisfactory results in three-part fractures of the humerus; however, the total complication rate of 35% should not be ignored. In addition, in order to prevent a significant varus collapse and angular loss, the fracture subgroups should be studied in detail and additional measures should be taken based on the fracture type.

Comparison of effective factors in loss of reduction after locking plate-screw treatment in humerus proximal fractures.

In proximal humerus fractures, loss of reduction can occur following surgical fixation. The factors that affect loss of reduction in cases treated with locking plates as well as their relationship with the degree of loss of reduction were investigated in this study. The study included 48 patients who underwent surgical treatment with a locking plate for a displaced proximal humerus fracture and experienced loss of reduction during follow-up. According to the degree of reduction loss, patients were divided into two groups as low grade and severe loss of reduction. The following parameters were investigated: Head-neck angle, loss of head height, degree of medial support displacement, screw penetration, implant-to-screw ratio, graft use, calcar screw application for medial sup-port, delayed union/nonunion, arthrosis, and avascular necrosis findings. In the early period, in Group I (n=27) and Group II (n=21) patients, the mean head-neck angle was 133°±9.9° (118°-141°) and 131°±11.2° (114°-143°), the distance between the head-plate end points was 8.08±2.8 mm and 11.5±3.1 mm, and the displace-ment between the medial support fracture fragment was 1.19±0.9 mm and 1.69±1.8 mm, respectively. Furthermore, in the late period, the mean head-neck angle was 120°±11.8° (106°-136°) and 112°±13.1° (98°-120°), the distance between the head-plate end points was 5.6±3.2 mm and 6.3±3.3 mm, and the displacement between the medial support fracture fragment was 2.79±1.9 mm and was 6.79±1.9 mm in Group I and Group II patients, respectively. While there was a significant relationship between the amount of medial displacement and changes in neck-shaft angle (p=0.0313) and humeral head height (p=0.0272), there was no significant relationship between the groups in terms of screw ratios, fracture type, and age. Many factors influence loss of reduction in proximal humerus fractures after surgical treatment with a locking plate. Supporting the medial region is particularly critical for maintaining reduction in the post-operative period. Furthermore, a relationship was revealed between the amount of medial displacement and the values of head-neck angle and head height.

How to improve the biomechanical stability of endosteal augmentation for proximal humerus fracture with osteopenia? A cadaveric study

BackgroundEndosteal augmentation enhances the stability of osteoporotic proximal humeral fracture fixation, but the optimal configuration is unknown. The purpose of this study was to compare the biomechanical properties of different lengths of fibula with or without calcar screw in osteoporotic proximal humeral fracture. MethodsThree-part proximal humeral fractures with osteopenia were created on 20 pairs of fresh-frozen humeri specimens and allocated to four groups: (1) locking plate with a 6-cm fibular strut allograft, (2) locking plate with a 6-cm fibular strut allograft and additional calcar screws, (3) locking plate with a 12-cm fibular strut allograft，and (4) locking plate with a 12-cm fibular strut allograft and additional calcar screws. Specimens were loaded to simulate the force at 25° abduction. Thereafter, an axial stiffness test and a compound cyclic load to failure test were applied. Structural stiffness, number of cycles loaded to failure and relative displacement values for 5000 cycles at predetermined measurement points were recorded using a testing machine and a synchronized 3D video tracking system. FindingsIn terms of initial stiffness, number of cycles loaded to failure, and relative displacement values, the groups with 12-cm fibular strut showed obvious improvement compared to the groups with 6-cm fibular strut irrespective of the influence of calcar screw implementation. Further, the groups implemented with calcar screws also showed promising biomechanical stability irrespective of fibular length. InterpretationLateral locking plate with longer endosteal fibular augmentation and calcar screw can significantly improve biomechanical stability for elderly proximal humeral fractures with posteromedial comminution.

Influence of neck shaft angle of humerus in prosthesis design

BackgroundA better understanding of the proximal humerus is essential for anatomical reconstruction of the glenohumeral joint during prosthetic replacement. The neck-shaft angle is critical for correct calcar screw positioning when fixing a proximal humeral fracture with a locking plate. It's essential for exact implant placement and treatment of any soft-tissue or bone pathology. Improper implants cause discomfort and post-operative complications, therefore understanding the humeral neck shaft angle is fundamental in the design and manufacturing of prostheses. This study looked into the necessity regional data of the humeral neck shaft angle (NSA) and its importance in shoulder prosthesis manufacturing. MethodThis cross-sectional investigation was conducted on 300 dry cadaveric humeri of unknown gender and age that were free of damage or deformity. The Goniometer was used to measure the neck shaft angle. The data was analysed using SPSS software. The standard deviation and mean were calculated. The statistical difference between the right and left humeri was assessed using the students' t' test. ObservationsThe NSA of the humerus was 131.265.82° on average. The NSA mean values were substantially higher on the right side. A statistically significant difference between the right and left humeri was revealed by a P value of 0.001. ConclusionSuccess of the shoulder arthroplasty demands anatomical reconstruction of the normal neck-shaft angle of the humerus. Racial variations in the morphometry of the neck-shaft angle needs to be considered in prosthesis design.

Using the Greater Tuberosity as a Reference for Placement of Proximal Humerus Plates Leads to a High Rate of Calcar Screw Malposition.

Achieving calcar fixation is critical to minimize the failure of proximal humerus fractures repaired with proximal humeral locking plates (PHLPs). Many operative technique manuals reference the greater tuberosity (GT) for plate placement. The objective of this study was to examine the accuracy of calcar screw placement when PHLPs were placed based on distance from the GT. Twenty cadaveric specimens were acquired representing a height distribution across the US population. Thirteen different PHLPs were applied. A drill bit was placed through the designated calcar screw hole and measured on radiographs, with the inferior 25% of the head representing an ideal placement. Three hundred fifty constructs were studied. In 28% of the specimens, the calcar screw was misplaced. In 20% of the specimens, it was too low, whereas in 8%, it was too high. The calcar screw missed low in 30% of patients shorter than 5 feet, 5.5 inches versus 8% of taller patients ( P = 0.007). It missed high in 13% of taller patients versus 2% of shorter patients ( P = 0.056). Calcar screws in variable-angle plates missed 0% of the time, whereas those in fixed-angle plates missed 36% of the time ( P = 0.003). Placement of PHLPs based on distance from the GT results in unacceptable position of the calcar screw 28% of the time and up to 36% in fixed-angle plates. This could be further compounded if the GT is malreduced. Current technique guide recommendations result in an unacceptably high rate of calcar screw malposition.

Effect of Calcar Screw in Locking Compression Plate System for Osteoporotic Proximal Humerus Fracture: A Finite Element Analysis Study.

This study proposes a finite element analysis (FEA) model for complex fractures at the osteoporotic proximal humerus and investigates the relevance of using a calcar screw in surgical treatments using this model. Two types of three-dimensional (3D) fracture models of patients with osteoporotic humerus were constructed reflecting the mechanical properties of the osteoporotic humerus, such as the Young's modulus and Poisson's ratio, and two load conditions mimicking the clinical environment were applied for simulation. Using the 3D models and the conditions, the FEA software calculated the concentration and distribution of stresses developing in the humerus, locking compression plate (LCP), and screws. Then, we evaluated and predicted the fixed state of a LCP system depending on whether the maximum stress value exceeded tensile strength. When axial force was applied, insertion of the calcar screw led to significant reduction of stress applied on screws in the fracture model having a medial gap by approximately 61%, from 913.20 MPa to 351.84 MPa. Based on the results, it was clearly confirmed that using of calcar screws improved the stability of a three-part fractures and simultaneously reinforced medial support.

Well-Performing Locking Plate Fixation with Calcar Screws Technique in Three-Part Proximal Humorous Fracture: Educational Corner

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Three-dimensional finite element analysis of exo-cortical placement of humeral calcar screw for reconstruction of medial column stability

To explore the biomechanical stability of the medial column reconstructed with the exo-cortical placement of humeral calcar screw by three-dimensional finite element analysis. A 70-year-old female volunteer was selected for CT scan of the proximal humerus, and a wedge osteotomy was performed 5 mm medially inferior to the humeral head to form a three-dimensional finite element model of a 5 mm defect in the medial cortex. Then, the proximal humeral locking plate (PHILOS) was placed. According to distribution of 2 calcar screws, the study were divided into 3 groups: group A, in which 2 calcar screws were inserted into the lower quadrant of the humeral head in the normal direction for supporting the humeral head; group B, in which 1 calcar screw was inserted outside the cortex below the humeral head, and the other was inserted into the humeral head in the normal direction; group C, in which 2 calcar screws were inserted outside the cortex below the humeral head. The models were loaded with axial, shear, and rotational loadings, and the biomechanical stability of the 3 groups was compared by evaluating the peak von mises stress (PVMS) of the proximal humerus and the internal fixator, proximal humeral displacement, neck-shaft angle changes, and the rotational stability of the proximal humerus. Seven cases of proximal humeral fractures with comminuted medial cortex were retrospectively analyzed between January 2017 and December 2020. Locking proximal humeral plate surgery was performed, and one (5 cases) or two (2 cases) calcar screws were inserted into the inferior cortex of the humeral head during the operation, and the effectiveness was observed. Under axial and shear force, the PVMS of the proximal humerus in group B and group C was greater than that in group A, the PVMS of the internal fixator in group B and group C was less than that in group A, while the PVMS of the proximal humerus and internal fixator between group B and group C were similar. The displacement of the proximal humerus and the neck-shaft angle change among the 3 groups were similar under axial and shear force, respectively. Under the rotational torque, compared with group A, the rotation angle of humerus in group B and group C increased slightly, and the rotation stability decreased slightly. All the 7 patients were followed up 6-12 months. All the fractures healed, and the healing time was 8-14 weeks, with an average of 10.9 weeks; the neck-shaft angle changes (the difference between the last follow-up and the immediate postoperative neck-shaft angle) was (1.30±0.42)°, and the Constant score of shoulder joint function was 87.4±4.2; there was no complication such as humeral head varus collapse and screw penetrating the articular surface. For proximal humeral fractures with comminuted medial cortex, exo-cortical placement of 1 or 2 humeral calcar screw of the locking plate outside the inferior cortex of the humeral head can also effectively reconstruct medial column stability, providing an alternative approach for clinical practice.

Predictive Indicators for Complications of Proximal Humerus Fractures Treated with Locking Plate or Intramedullary Nail Fixation.

ObjectiveThe purpose of this study was to evaluate the best placement of calcar screws in proximal humerus fracture surgeries.MethodsThis retrospective cohort study included clinical and radiographic outcomes of 98 patients treated with proximal humerus fracture surgeries between January 2017 and June 2020. Demographic data of patients were obtained from medical records. The surgical and radiographic results were also collected: operation time, blood loss, time to surgery, fibular allograft, disruption of medial region hinge, Neer classification, and recovery of medial support. Patients were allocated into two groups: the locking plate group (n = 65) and the intramedullary nail group (n = 33). In this study, we proposed new predictive indicators, named horizontal ratio (HR) and vertical ratio (VR), to quantify the placement of calcar screws in these two groups. A receiver operating characteristic (ROC) analysis was conducted to display the accuracy of these indicators. Shoulder activity, visual scale analog (VAS) score, and Constant score were performed to evaluate postoperative clinical outcomes at 1 year follow‐up.ResultsIn the multivariate logistic regression analysis, only time to surgery and effective medial support were considered statistically significant factors of postoperative complications (p < 0.05). Significant differences were observed between medial support and postoperative complications both in the locking plate group and the intramedullary nail group (p < 0.05). Only the vertical ratio of locking plate (VRLP) was a statistically significant predictor of postoperative complications (p < 0.05). The area under curve was calculated to assess the predictive value of VRLP, which came to 0.84. In addition, a ROC analysis found quantifiable thresholds of the VR was 0.1713 as measures to avoid postoperative complications in the locking plate fixation.ConclusionIn locking plate fixation, the incidence of postoperative complications increased significantly when the VR of calcar screws greater than 0.1713, which was beneficial to surgeons to place calcar screws.

Should cannulated screws be removed after a femoral neck fracture has healed, and how? A finite element analysis of the femur before and after cannulated screw removal.

The removal of three inverted triangular parallel cannulated screws after the femoral neck fracture healing is sometimes accompanied by osteonecrosis of the femoral head (ONFH) or its refracture. The purpose of this study was to determine the biomechanical changes of the femur before and after the screw removal using a finite element analysis. The CT data of the femurs were obtained from a 69-year-old healthy female to establish the femur models. The established finite element models consisted of N, C, and R groups: N group, the normal femur; C group (to simulate the femoral neck fracture healing after the internal fixation), the normal femur with three inverted triangular parallel cannulated screws (C1) or with two upper parallel screws (C2). For the R1 or R2 groups, the screws in the model of the C1 or C2 individuals were gradually removed in seven or three types of different screw combinations, respectively. The stresses and displacements of the femur were determined. (1) Compared with the N group, a uniform stress distribution was stopped by the addition of three screws in the C1 group; in contrast, all screw removals resulted in the stress concentration on the screw holes and the disappearance of stress shielding. Moreover, the average stress of the femoral head in C1 group increased by 37.85%, while that of the femoral neck decreased by 23.03%. (2) Compared with the C1 group, while only the lowest femoral calcar screw was removed, there was a similar stress distribution in the proximal femur, and the average stress of the femoral head increased only by 0.35% although that of the femoral neck increased by 63.62%; however, removal by any other means resulted in a significant stress concentration in the proximal femur and a significant increase in the average stresses of the femoral head and neck (5.96-40.95% and 12.82-75.46%, respectively). (3) Compared with the N or C1 group, there was a significant stress concentration on the screws and its surrounding proximal femur in the C2 group. (4) Compared with the C2 group, the simultaneous removal of two upper screws not only did not cause a significant stress concentration on the proximal femur but also significantly reduced the average stresses of the femoral head and neck by 87.49% and 65.51% respectively. On the contrary, the gradual removal of two screws caused a significant stress concentration on the screw and its surrounding proximal femur although the average stresses of the femoral head and neck decreased by 88.79-89.06% and 67.00-67.22%, respectively. (5) Compared with the N group, the average displacements of the femoral head and neck in the C1 group increased only by 3.12% and 3.37%, respectively. Additionally, compared with the C1 group, while three, two, or one screw was simultaneously removed, the average displacements of the femoral head and neck only fluctuated - 5.51-1.65% and 1.78-9.03%, respectively. Residual internal fixation after femoral neck fracture healing may lead to stress concentration on screws and stress shielding around screws. The first removal of the lowest femoral calcar screw and then the second removal of two upper residual screws have a minimum effect on the stress concentration on the proximal femur and the average stress on the femoral head. The incorrect screw removal and resulting femoral load may well be closely related to occurrence in ONFH or its refracture.

The effect of long calcar screws on the primary stability of 3-part, varus impacted proximal humeral fractures compared to short calcar screws: a real fracture simulation study

BackgroundComplex proximal humeral fracture ranks among the most common fracture types, especially in elderly patients. In locked plate fixation of proximal humerus fractures, the calcar is deciding for screws providing further medial column support. To date, the biomechanical effect of the length of these calcar screws is not well known. The purpose of this study was to analyze the effect of long calcar screws on fresh frozen prefractured cadaveric specimens.MethodsIn the present biomechanical study, 8 pairs of cadaveric proximal humeri were fractured identically using a custom-made fracture simulator. ORIF was performed using a locking plate (PHILOS; Fa. Synthes). The specimens were tested in a biomechanical setup under increased axial load without any calcar screws installed, with short calcar screws and long calcar screws installed. Strain gages (4-wire-120 Ohm, Fa. Vishay) mounted on the locking plate were used to evaluate the fixation strain and to give an estimate for primary stability..ResultsThe measured strain of the locking plate without calcar screws (804,64 µm/m) at maximum load (200 N) was significantly higher than with short (619,07 µm/m; p = 0.02) or long calcar screws (527,31 µm/m; p = 0.007). Additionally, strain with short calcar screws was noticeably higher in comparison to long calcar screws (619,07 µm/m vs. 527,31 µm/m; p = 0.03).ConclusionUse of calcar screws improves the stability of realistically impacted 3-part varus humeral fractures. Long calcar screws that are positioned as close as possible to the joint provide further primary stability compared to short calcar screws.Level of evidenceBasic science study.

Optimization of Locking Plate Screw Angle Used to Treat Two-Part Proximal Humerus Fractures to Maintain Fracture Stability

Proximal humerus fractures increase with the aging of the population. Due to the high failure rates of surgical treatments such as open reduction and internal fixation (ORIF), biomechanical studies seek to optimize the treatments and intervening factors to improve the quality of life of people undergoing these treatments. The aim of the present study was to determine the optimal insertion angle configuration of screws used in a two-part proximal humerus fracture-locking plate osteosynthesis treatment based on finite element analysis (FEA). A series of 3D models of PHILOS locking plates with different screw insertion angle configurations were designed using a matrix system for screw angulation. The locking plate models were evaluated in a two-part proximal humerus fracture with surgical neck fracture under bending and compressive loading conditions using FEA and statistically analyzed using a design of experiments (DOE). The optimal screw insertion angle setting showed an improvement in relation to the interfragmentary strain value of the fracture. Moreover, calcar screws were the most significant feature in fracture stability throughout the tests, followed by the divergence of the most proximal screws and the proximal–distal alignment of the locking plate.

How can medial support for proximal humeral fractures be achieved when positioning of regular calcar screws is challenging? Slotting and off-axis fixation strategies.

Achieving medial support for proximal humeral fractures (PHFs) by regular calcar screw positioning is challenging when the humeral head is small or locking plates are placed distally, as there are unable inserted calcar screws into the humeral head. We aimed to investigate the suitability of the 2 strategies, slotting calcar screw (SCS) and off-axis calcar screw (OCS), to achieve medial support for PHFs. Regular calcar screw (RCS), SCS, OCS, and noncalcar screw (NCS) were tested via mechanical experiments and finite element analysis (FEA), using synthetic bones for biomechanical comparisons. All PHFs treated in our hospital from March 2017 to March 2019 were reviewed. The patients were divided into 3 groups based on the calcar screw fixation: RCS, SCS, and OCS. The postoperative varus collapse (neck-shaft angle changed to less than 120°) and Disabilities of the Arm, Shoulder and Hand (DASH) scores were recorded. The properties of RCS, SCS, and OCS against the torsion and varus force were superior to those of NCS, whereas the stiffness of SCS, OCS, and RCS were similar. FEA predicted lower peri-screw strains in the OCS and SCS than in the RCS, indicating a lower risk of cut-out. Patients (n = 125; 75 female, 50 male) aged 55.9 ± 13.0 years were evaluated. Compared with the RCS (5/55), varus collapse incidences were not significantly higher following SCS (0/29, P = .094) or OCS (3/41, P = .756), and neither were DASH scores (P = .867 and .736, respectively). This study is a preliminary study demonstrating that the SCS and OCS fixation strategies could be useful alternatives when regular calcar fixation is not possible using the plate at hand.