Intramedullary Diameter Research Articles

Morphometry of the proximal humerus and the relationship to global offset

BackgroundPrevious research has consistently identified the medial and posterior offset of the native humeral head in relation to the intramedullary canal. These anatomic parameters and others such as humeral head and intramedullary diameter provide valuable insight for prosthesis development. However, it is critical to understand the relationship of morphometry to the native center of rotation. Our objective was to use 3-dimensional analysis to demonstrate the native morphometry of the proximal humerus and those relationships to global offset. MethodsFourteen cadaveric humeri were manually measured then digitally analyzed following 3-dimensional scanning. Pearson’s r was used to determine the relationship between variables. ResultsThe mean digital humeral head diameter (Hdd) was 46.5 (± 4.67) mm and the mean manual humeral head diameter was 46.8 (± 4.42) mm. The mean global offset (GO) was 6.36 (± 2.21) mm, and the mean best fit sphere diameter was 46.5 (± 4.63) mm. Pearson’s r = 0.58 (95% confidence interval 0.07-0.84, P = .021) for GO and Hdd which indicates a moderate correlation. Pearson’s r = 0.96 (95% confidence interval 0.89-0.99, P < .001) for Hdd and manual humeral head diameter which indicates a strong correlation. DiscussionNative GO demonstrated a moderately positive correlation to humeral head diameter. The manual measurement of head diameter was strongly correlated to the 3-dimensional software value which reinforces the importance of intraoperative measurement. These data contribute to further understanding of shoulder morphometry which is integral to prosthesis design which impacts postoperative function and complications.

Indian Hand Anthropometry: Computer Tomography-Based Morphometric Analysis of Metacarpal.

Introduction Metacarpal fractures are common and have various treatment options, but understanding their morphometry is crucial for optimizing fixation techniques and reducing complications. Accurate assessment of metacarpal anatomy is challenging in conventional radiographs but feasible with computed tomography (CT) scans, which offer precise views. This study aimed to provide accurate anatomical data on metacarpals within an Indian population using CT scans and to compare the results with existing literature. The findings have implications for surgical procedures, including plating, pinning, and intramedullary screw fixation. Materials and Methods This retrospective analysis utilized CT scans of 100 hands, including 50 males and 50 females, from two hospitals in India. Inclusion criteria included complete metacarpal visualization with a slice thickness of 0.6 mm, while exclusion criteria involved trauma, deformity, or underlying pathologies. Various parameters of all metacarpals were measured using RadiAnt DICOM Viewer 2021.1, providing accurate anteroposterior and lateral views. Results Male and female cohorts had mean ages of 38.58 ± 12.02 and 43.60 ± 13.61 years, respectively. The study showed good to excellent reliability in measurements. The 2nd metacarpal was consistently the longest, and the general length pattern was 3rd > 4th > 5th > 1st metacarpal in both genders. Men generally had larger metacarpal dimensions than women, except for intramedullary diameter, which showed minimal sex-related differences. Notably, the medullary cavity's narrowest part was at the 4th metacarpal, and the thumb had the widest intramedullary diameter. Conclusion This study provides valuable anatomical reference data for metacarpals in an Indian population, aiding in optimizing surgical techniques for metacarpal fractures. The 2nd metacarpal consistently stood out as the longest, and men generally had larger metacarpal dimensions than women. These insights into anatomical variations can inform clinical decisions and stimulate further research in this field. However, a larger and more diverse sample would enhance the study's representativeness.

Imaging risk factors for predicting postoperative complications of intramedullary nailing for tibial fracture

ObjectiveThe objective of this study was to analyze the ratio of fracture site diameter to tibial isthmus diameter (TFI ratio) as a predictor of postoperative complications, including malunion and delayed union, after tibial intramedullary nailing for middle and lower tibial fractures.MethodsData were collected from all adult patients older than 20 years of age who underwent tibial intramedullary nailing for middle and lower tibial fractures between January 2015 and January 2023 and were followed up for at least 1 year. Diabetes history, smoking history, fracture type, injury mechanism, surgical method, surgical approach, diameter of the medullary cavity at the fracture site, and diameter of the tibial isthmus were recorded. Logistic regression analysis was used to determine the variables affecting the occurrence of complications. The TFI ratio was used to calculate the sensitivity and specificity of the parameters, and ROC curves were generated to establish TFI ratio thresholds for predicting complications.ResultsA total of 123 patients with middle and lower tibial fractures were treated with intramedullary nails. The mean age of the patients was 43.72 years (range, 21–81 years); 89 were males, and 34 were females. Univariate logistic regression analysis showed that fracture type, open reduction surgery, superior patellar approach, and TFI ratio were significantly correlated with postoperative complications after intramedullary nailing of a tibial fracture. Multivariate logistic regression analysis showed that the TFI ratio was an independent risk factor for complications (P = 0.001*). By using the TFI ratio as a predictor of complications, an ROC curve was generated to establish a threshold. The ROC curve showed that a TFI ratio ≥ 1.31 had a sensitivity of 0.89, a specificity of 0.71, and an area under the ROC curve of 0.82 for predicting complications.ConclusionsThe results of this study suggest that a wider intramedullary diameter and a shorter fixed length at the fracture site are associated with a higher incidence of complications after tibial intramedullary nailing. The TFI ratio may be used as a reliable parameter for predicting complications after such surgery. In patients with a high TFI ratio (≥ 1.31), additional reduction and fixation techniques may be needed to obtain and maintain fracture reduction.

Computed Tomography-Based Humeral Templating for Uncemented Elbow Arthroplasty.

Intramedullary (IM) screw insertion into the distal humerus provides fixation for a novel, uncemented elbow arthroplasty. A multitude of screw sizes is required to accommodate variable humeral morphology. The goal of this study was to use computed tomography (CT) for IM screw sizing and to validate this templating by inserting screws into three-dimensionally (3D) printed models. Computed tomography humerus scans for 30 patients were reformatted in the plane of the distal IM canal. Screw size was templated by measuring the canal diameter at 3 locations corresponding to the lengths of the screws being tested. Interrater and intrarater reliabilities of the measurements were assessed. Three-dimensional models of 5 humeri were printed, and IM screws were placed to achieve a secure endosteal fit. We identified combinations of body components and IM screw length and diameter for all patients to seat this uncemented elbow arthroplasty. The measurements and screw width determinations were reliable. Canal diameter correlated with age but was unrelated to sex. Screws were inserted into five 3D-printed models which matched the templates and demonstrated mechanical and radiographic evidence of secure fit. This study characterizes distal humerus anatomy in the context of IM screw fixation. Humerus CT scans of 30 patients were able to be templated, and validation via implantation of IM screws into 3D models was successful. Computed tomography templating will allow surgeons to predict the optimal screw size prior to implantation. A broad range of screw lengths and diameters is critical for implantation of this novel elbow arthroplasty.

A Novel Radiological Classification System of the Proximal Humerus.

Different anatomical variants have been reported for the proximal and distal femur. Given this context, the goal of our study was to answer the following question: Can we also identify different anatomical variants of the proximal humerus?Two hundred anteroposterior (AP) radiographs of the proximal humerus with an equal gender distribution and equal laterality per gender were reviewed. The metaphyseal diameter of the proximal humerus at the level of the anatomical neck (X) and the intramedullary diameter at 10cm from the apex of the greater tuberosity (Y) were measured. A new ratio was established, based on both measurements (Y/X). Radiographs showed different anatomical variants: type A: Y/X<0.3, type B: Y/X=0.3-0.4, type C: Y/X>0.4. Two observers reviewed the AP radiographs independently and blindly in 2 different sessions.Three different anatomical groups (A, B and C) were identified based on the 25th and 75th percentiles. A higher percentage of type C was observed among females and a higher percentage of type A among males. A high inter-observer reliability was noted, with a Cronbach's alpha of 0.97 (ICC 0.96-0.98). The intra-observer reliability for observer 1 had a Cronbach's alpha of 0.98.A novel radiological classification of the proximal humerus has been established based on 3 different anatomical types (A, B and C). Further studies are needed to establish whether the novel classification system can be used as an indicator for aseptic loosening of cemented or cementless total shoulder arthroplasty.

Multiplanar analysis of proximal humerus anatomy of patients with rotator cuff arthropathy and relevance to reverse shoulder press-fit stems

Short stems have become increasingly popular in reverse shoulder arthroplasty (RSA) due to their ability to preserve bone stock for revision surgery. However, short stems may be more at risk for malalignment or loosening, and commercially available stems have varied designs. The purpose of this study was to perform a multiplanar analysis of proximal humerus anatomy in patients with rotator cuff arthropathy to better define canal geometry and identify differences based on sex. A retrospective review was performed of a consecutive series of patients undergoing RSA for rotator cuff arthropathy. A total of 117 patients were identified with preoperative computed tomography scans. Measurements were undertaken following multiplanar reconstruction of the computed tomography scans. Measured parameters included the following: transition point (TP), anteroposterior (AP) and mediolateral (ML) distances, intramedullary (IM) and bone diameter, and cortical thickness. The TP was defined as the distance from the periosteal border of the greater tuberosity to the level of the IM canal where the endosteal borders became parallel. Measurements started at the metaphysis, and then proceeded 25 and 50 mm distal to the metaphysis followed by 10 mm increments thereafter. Each level was compared to the level above with t tests in the overall cohort and separately by sex. Height was correlated to ML-AP difference and IM diameter with Pearson correlation coefficient. Potential stem sizes that extended 50, 60, 70, and 80 mm from the metaphysis were analyzed to record the percentage of patients in whom the stem would reach past the TP. The mean TP for all patients was 55.6±7.4 mm (37.5-78.4) from the greater tuberosity, 53.3±6.6 mm (37.5-67.0) in females and 58.1±7.5 mm (41.9-78.4) in males. ML and AP distances and IM diameter became consistent at level 3 (mean, 83 mm distal to the greater tuberosity) in the overall cohort and in both sexes. Height positively correlated with IM diameter. Males had significantly larger IM diameters compared to females at all levels. Cortical thickness remained relatively consistent throughout the proximal humerus. A stem length of 70 mm would extend past the TP in 98% of patients. Humeral implants in RSA with a stem of at least 70 mm in length would extend distally past the TP in the majority of cases regardless of sex. At this point, the canal's area remains consistent which would facilitate diaphyseal fixation if required.

The Optimum Size of K-Wires for Fifth Metacarpal Neck Fractures: Double 1.6 mm K-Wires Antegrade Intramedullary Nailing Technique

Objective: Previous researches did not pay significant attention to the 5th metacarpal’s intramedullary diameter. This research aims to determine the optimal K-wires for 5th metacarpal neck fractures based on the narrowest part of 5th metacarpal. Methods: We retrospectively studied 31 patients with fifth metacarpal neck fractures. All patients underwent Intramedullary (IM) nailing surgery with two 1.6 mm K-wires. The narrowest part of the fifth metacarpal was measured preoperatively based on CT scan. Quick-DASH was assigned to be the primary outcome, pain, satisfaction, motor function and complications were also recorded. Results: Well reductions were observed in all patients. QuickDASH sore was median 0 with the range of 0-32, pain score was median 0 with the range of 0-2, VAS satisfaction was median 5 with the range of 3-5 at the endpoint. Grip strength, metacarpophalangeal joint and total active motion were improved immediately after operation. Two patients remained persistent paresthesia, and three patients experienced persistent pain at the endpoint with the VAS score of 1, 2, 2. Conclusion: The use of double 1.6 mm K-wires antegrade intramedullary nailing could be an optimum option for patients with fifth metacarpal neck fractures.

Comparison of Results Based on the Number of Kirschner Wires of Different Diameters in Antegrade Intramedullary Fixation of Fifth Metacarpal Neck Fractures

Purpose: The purpose of this study was to compare the clinical and radiological results of patients with fifth metacarpal neck fractures using different sizes and numbers of Kirschner wires (K-wire).Methods: A single institutional retrospective review identified 67 patients with a fifth metacarpal neck fracture between January 2015 and July 2020. The minimum follow-up time was 6 months and they were all treated within 6.4 days of the initial injury. Either one K-wire (1.6 mm), two K-wires (1.1 mm), or three K-wires (0.9 mm) was used. We analyzed the bone union period, and K-wire removal period, duration of surgery, total active motion, intramedullary diameter, pre/postoperative shortening, and pre/postoperative angulation clinically. We used a Method of Shortening Stipulated to measure shortening and the Medullary Canal-lateral view method for angulation. The intramedullary diameter was measured in the mid-shaft of the fifth metacarpal bone in the coronal view. Total active motion was measured at the time of follow-up in our outpatient department.Results: Clinical and radiological parameters showed no statistically significant differences. Even though it did not present a statistical significance, the absolute mean duration of surgery was the shortest in a single K-wire group. Conclusion: The clinical and radiological outcomes of surgery were comparable regardless of the number of K-wires inserted. However, we could look forward to gaining potential benefit from shortened operation time in a single K-wire group. Since stable fixation can be obtained even if one K-wire is used, inserting one thick K-wire into the intramedullary canal can be an alternative according to the surgeon’s preference.

"Ratio of fracture site diameter to isthmus femoral canal diameter" as a predictor of complication following treatment of infra-isthmal femoral shaft fracture with antegrade intramedullary nailing.

Fixation of infra-isthmus femoral shaft fracture using antegrade intramedullary (IM) nailing is difficult and is associated with a high complication rate. This study aimed to identify risk factors for complications following this procedure. The ratio of the fracture site diameter to the diameter of the femoral intramedullary canal of the isthmus (FI ratio) was evaluated as a novel parameter to predict complication. Patients who underwent antegrade IM nailing for infra-isthmus femoral shaft fracture between January 2008 and December 2018 and had a minimum of 12 months of follow-up were retrospectively reviewed. The primary outcome was occurrence of complication, including non-union, mal-alignment, fixation failure, or progressive loss of reduction. Logistic regression analysis was performed to identify risk factors of complication. The sensitivity and specificity of FI ratio as a predictor of complication was calculated. A receiver operating characteristic (ROC) curve was generated to establish an FI ratio threshold to predict occurrence of complication following antegrade IM nailing. Sixty-five patients with a mean age of 47.1 years were included. Using univariate logistic regression analysis, comminuted fracture pattern (p=0.026), distance from screws to fracture site (< 3cm) (p=0.002), and higher FI ratio (p=0.001) were associated with complication. Using multivariate logistic regression analysis, FI ratio was identified as an independent risk factor for complication following antegrade IM nailing (p=0.038). ROC curve indicated that FI ratio ≥ 2 had sensitivity and specificity of 0.72 and 0.72, respectively, in predicting complication. Our study indicates that wider intramedullary diameter at the fracture site was associated with higher complication rate following antegrade IM nailing in distal infra-isthmal femoral fractures. The FI ratio could be a reliable predictor of complication after antegrade IM nailing for such fracture, and alternative strategies should be considered for patients with higher FI ratio (≥ 2).

An Anatomical Study of Metacarpal Morphology Utilizing CT Scans: Evaluating Parameters for Antegrade Intramedullary Compression Screw Fixation of Metacarpal Fractures

This study evaluated metacarpal morphology for antegrade placement of intramedullary headless compression screws (IMHCS) for metacarpal fracture fixation. We analyzed 100 hand computed tomography scans to quantify cortical thickness, intramedullary diameter, and metacarpal lengths. In addition, dorsal or ulnar overhang of the metacarpals over their respective carpal bones was measured. We also predicted optimal entry points for guidewire placement at the metacarpal head. The ring finger metacarpal had the narrowest medullary canal width (coronal, 2.8 mm; sagittal, 3.5 mm). Not counting the thumb, the little finger metacarpal had the widest midshaft medullary width of 4.1 mm in the coronal plane and the middle metacarpal was widest in the sagittal plane with canal width of 3.9 mm. On average, there was maximal dorsal overhang at the base of the middle metacarpal (4.2 mm) and maximal ulnar overhang at the base of the small metacarpal (3.9 mm). The optimal entry point for guidewire placement over each metacarpal head was approximately 3.5 to 3.8 mm volar to the dorsal cortex. Minimum IMHCS diameters of 3.5 mm for the ring and 4.0 mm for the index, middle and little fingers are necessary to achieve interference fit within the medullary canal. Minimum screw lengths of 38 mm would be needed to ensure 6 mm fixation past the midshaft of the metacarpals. Antegrade IMHCS for fixation of proximal metacarpal fractures may be most feasible with thumb, middle, and little finger metacarpals because there was larger dorsal or ulnar overhang to allow screw placement without violating the carpometacarpal joints. Our analysis provides a reference guide for intramedullary screw sizes for each metacarpal of the hand to achieve interference fit with fracture fixation. Furthermore, the dorsal and ulnar overhangs of the metacarpal bases suggest the practicality of antegrade IMHCS fixation.

Total Hip Arthroplasty in Patients With Osteopetrosis

BackgroundOsteopetrosis is an inherited bone disease associated with high risk of osteoarthritis and fracture non-union, which can lead to total hip arthroplasty (THA). Bone quality and morphology are altered in these patients, and there are limited data on results of THA in these patients. The goals of this study were to describe implant survivorship, clinical outcomes, radiographic results, and complications in patients with osteopetrosis undergoing primary THA. MethodsWe identified 7 patients (9 hips) with osteopetrosis who underwent primary THA between 1970 and 2017 utilizing our total joint registry. The mean age at index THA was 48 years and included two males and five females. The mean follow-up was 8 years. ResultsThe 10-year survivorship free from any revision or implant removal was 89%, with 1 revision and 1 resection arthroplasty secondary to periprosthetic femoral fractures. The 10-year survivorship free from any reoperation was 42%, with 4 additional reoperations (2 ORIFs for periprosthetic femoral fractures, 1 sciatic nerve palsy lysis of adhesions, 1 hematoma evacuation). Harris hip scores significantly increased at 5 years (P = .04). Five hips had an intraoperative acetabular fracture, and 1 had an intraoperative femur fracture. All postoperative femoral fractures occurred in patients with intramedullary diameter less than 5 mm at a level 10 cm distal to the lesser trochanter. ConclusionPrimary THA in patients with osteopetrosis is associated with good 10-year implant survivorship (89%), but a very high reoperation (58%) and periprosthetic femoral fracture rate (44%). Femoral fractures appear associated with smaller intramedullary diameters.

Metacarpal Bony Dimensions Related to Headless Compression Screw Sizes

Introduction The purpose of this study is to determine the radiographic dimensions of the finger metacarpals and to compare these measurements with headless compression screws commonly used for fracture fixation.Materials and Methods We analyzed computed tomography (CT) scans of the index, long, ring, and small metacarpal bones and measured the metacarpal length, distance from the isthmus to the metacarpal head, and intramedullary diameter of the isthmus. Metacarpals with previous fractures or hardware were excluded. We compared these dimensions with the size of several commercially available headless screws used for intramedullary fixation.Results A total of 223 metacarpals from 57 patients were analyzed. The index metacarpal was the longest, averaging 67.6 mm in length. The mean distance from the most distal aspect of the metacarpal head to the isthmus was 40.3, 39.5, 34.4, and 31 mm for the index, long, ring, and small metacarpals, respectively. The narrowest diameter of the isthmus was a mean of 2.6, 2.7, 2.3, and 3 mm for the index, long, ring, and small metacarpals, respectively. Of 33 commercially available screws, only 27% percent reached the isthmus of the index metacarpal followed by 42, 48, and 58% in the long, ring, and small metacarpals, respectively.Conclusion The index and long metacarpals are at a particular risk of screw mismatch given their relatively long lengths and narrow isthmus diameters.

A computed tomography study of the fibula: morphology, morphometry, intramedullary anatomy, application prospects on intramedullary nailing.

The intramedullary percutaneous pinning in fractures of the lateral malleolus is a technique of osteosynthesis that can reduce complications of ORIF. Our study describes the morphology and the morphometry of the fibula, in particular intramedullary, so as to specify the best fibular nail features. We conducted a retrospective study on CT acquisitions of fibulae in vivo. We studied total length, and the distal malleolar angle. Regarding intramedullary morphology, six axial study levels were defined. Each level was assigned a morphometric classification (oval, triangular, quadrangular or irregular), and a measure of the diameter of the cavity. The distance between the smaller diameter and the malleolar tip was investigated. We included 50 patients for 97 fibulae. The average age was 66.5years. The irregular morphology type was the most frequently found. The average length was 370.5mm (SD = 18.1; CI 95% [366.9; 374.1]), the average distal malleolar angle was 163.5° (SD = 3.7; CI 95% [162.7; 164.2]). The average minimal intramedullary diameter at malleolus level was 3.2mm (SD = 1.2; CI 95% [3.0; 3.5]), with a minimum size reaching 95.8mm (SD = 13.8; CI 95% [93.0; 98.5]) of the malleolar tip. The analysis of morphological parameters of the fibula, in particular the lateral malleolus and intramedullary morphology is necessary for the design of a morpho-adapted nail. Interpersonal variability must be taken into account by the implant industry to offer nails of suited lengths and diameters.

Intramedullary Screw Fixation and Relevant Diameter of the Proximal Phalanges of the Foot

Category: Midfoot/Forefoot Introduction/Purpose: The average intramedullary diameter of the proximal phalanges of the foot has not been well documented in the literature. This dimension has important implications for surgical fixation devices, such as intramedullary screws. By design, intramedullary fixation devices rely on endosteal fit to provide stability. The precise intramedullary diameter is not readily identifiable on plain radiographs. A better understanding of the average diameter of the proximal phalanges of the foot can assist surgeons in surgical planning and appropriate screw diameter selection to provide more satisfactory patient outcomes. Methods: Twenty below-knee cadaveric specimens were dissected to expose each proximal phalanx. A sagittal saw was used to transect the diaphysis at its narrowest portion. The dorsal to plantar and medial to lateral diameters were measured using a digital manometer. Results: The average diameter dorsal to plantar for each digit was 6.25 ± 2.24 mm, 3.61 ± 1.25 mm, 2.94 ± 0.70 mm, 2.72 ± 0.77 mm, and 2.48 ± 0.80 mm, respectively. The average diameter medial to lateral for each digit was 7.83 ± 2.13 mm, 3.08 ± 0.93 mm, 2.47 ± 0.74 mm, 2.33 ± 0.73 mm, and 2.62 ± 0.69 mm, respectively. The overall average diameter for toes one through five was 7.04 ± 1.95 mm, 3.35 ± 1.04 mm, 2.71 ± 0.66 mm, 2.52 ± 0.71 mm, and 2.55 ± 0.63 mm, respectively. Conclusion: Understanding the intramedullary diameters of the proximal phalanges of the foot is a valuable tool when utilizing intramedullary surgical stabilization. The hallux proximal phalanx demonstrated the largest, and most variable, diameter, which could make selection intramedullary fixation difficult. In addition, the hallux proximal phalanx may lend itself better to 2 smaller fixation devices rather than one larger one. The lesser phalanges demonstrated smaller diameters more consistently, which is more amenable to a single smaller (2.5 mm) intramedullary device. This data can provide surgeons with an expected intramedullary diameter during surgical planning.

Morphological differences of proximal femoral medullary cavity in elderly patients and its effect on proximal femoral nail fixation

Objective To investigate the morphological differences of proximal femoral medullary cavity in elderly patients with intertrochanteric fracture and its effect on the treatment efficacy of proximal femoral nail antirotation (PFNA). Methods A retrospective case series study was conducted on the clinical data of 112 elderly patients with intertrochanteric fracture of the femur from December 2012 to January 2017, including the preoperative and postoperative hip joints orthotopic X ray (including the proximal femur), lateral X ray, and pelvic orthotopic X ray films. The proximal femoral canal flare index (CFI) and the metaphyseal canal flare index (MCFI) were measured. The proportion of patients with different types of medullary cavity and the gender difference were analyzed according to Dorr typing. The fractures were classified according to the modified Evans classification. Operation time, fracture reduction quality, tip apex distance (TAD), incidence of intraoperative split fracture around the rotors, postoperative fracture reduction loss rate, weight bearing time, and fracture healing time were recorded. Results The proximal femoral canal flare index (CFI) was significantly correlated with the intramedullary diameter above the lesser trochanter, the inner diameter of the affected side medullary cavity isthmus, and metaphyseal canal flare index (MCFI) (P 0.05). In this group, the medullary cavity of proximal femur was classified by Dorr: the proportion of funnel type, normal type, and chimney type was 5.4% (6/112), 73.2% (82/112), and 21.4% (24/112), respectively. There was no significant difference in the modified Evans fracture stability among different morphological types of the proximal femoral medullary cavity. The difference of weight bearing time between normal group and chimney group was statistically significant [normal type: (21.4±16.9)d, chimney type: (45.5±11.2)d](P 0.05). Conclusions The occurrence and development of osteoporosis can cause significant changes in the morphology of proximal femoral medullary cavity, mainly manifesting as the gradual increase of the proportion of chimney type. The efficacy of PFNA in treatment of the intertrochanteric fracture is satisfactory. However, the risk of intraoperative cleavage fracture and postoperative reduction loss should be taken seriously. Key words: Hip fractures; Fracture fixation, intramedullary; Anatomy; Histology; Aged

The effect of intramedullary pin size and plate working length on plate strain in locking compression plate-rod constructs under axial load.

To investigate the effect of intramedullary pin size and plate working length on plate strain in locking compression plate-rod constructs. A synthetic bone model with a 40 mm fracture gap was used. Locking compression plates with monocortical locking screws were tested with no pin (LCP-Mono) and intramedullary pins of 20% (LCPR-20), 30% (LCPR-30) and 40% (LCPR-40) of intramedullary diameter. Two screws per fragment modelled a long (8-hole) and short (4-hole) plate working length. Strain responses to axial compression were recorded at six regions of the plate via three-dimensional digital image correlation. The addition of a pin of any size provided a significant decrease in plate strain. For the long working length, LCPR-30 and LCPR-40 had significantly lower strain than the LCPR-20, and plate strain was significantly higher adjacent to the screw closest to the fracture site. For the short working length, there was no significant difference in strain across any LCPR constructs or at any region of the plate. Plate strain was significantly lower for the short working length compared to the long working length for the LCP-Mono and LCPR-20 constructs, but not for the LCPR-30 and LCPR-40 constructs. The increase in plate strain encountered with a long working length can be overcome by the use of a pin of 30-40% intramedullary diameter. Where placement of a large diameter pin is not possible, screws should be placed as close to the fracture gap as possible to minimize plate strain and distribute it more evenly over the plate.

Distal Normograde Intramedullary Pin and Locking Plate Placement in the Canine Humerus: A Cadaveric Study.

To identify a repeatable anatomic landmark for pin insertion and to describe the technique for placement of a distal normograde intramedullary (IM) pin of approximately 35% of the IM diameter using this approach combined with a locking compression plate (LCP) on the medial aspect of the canine humerus. Ex vivo anatomic study. Canine cadavers (n=10 Greyhounds). An anatomic landmark for pin insertion was identified based on three-dimensional reconstructions of previous elbow computed tomography studies and cadaveric dissection of the medial aspect of the humeral condyle. Bilateral distal normograde IM pin and LCP placement were performed and confirmed radiographically and by disarticulation and sagittal sectioning. The anatomic landmark for pin insertion was consistently identified in each specimen using the technique described. Distal normograde insertion of a 3.5 mm IM pin was possible in Greyhound cadaveric humeri at the described location in conjunction with a 3.5 mm LCP with fixed angle, locked screws. A monocortical locking screw was required to avoid interference with the IM pin in 28 of 60 of the 3 proximal screw holes. No pin interference was encountered in any of the distal screw holes. The anatomic landmark and technique described in our study enabled repeatable successful placement of a distal normograde IM pin of approximately 35% of the IM diameter combined with an LCP on the medial aspect of the canine humerus. This technique may be useful for locking plate-rod fixation of distal humeral diaphyseal fractures.

Novel modification of second generation intramedullary PMMA cementing technique for narrow upper and lower extremity canals.

It is very difficult to cement intramedullary canals smaller than 10mm with standard commercially available cement syringes due to mismatch in canal and syringe diameters. This is often encountered in children and in the upper limb. We describe a simple method of cementing, using cement gun with size-matched plastic endotracheal tube (ET). The medullary canal is prepared and the size determined. ET with outer diameter 0.5-1mm smaller than the canal diameter is chosen. The standard cementing syringe nozzle is cut at the middle and fitted to Portex(®) tube with the adaptor connector, which comes with the ET. The plastic ET is cut to an appropriate length depending on canal length to be cemented. The nozzle is fitted to the syringe and cementing done in the usual way. We applied this new modification in the method to cement narrow canals of ulna, humerus, tibia and femur. The method has proven to be consistently reliable and useful in cases of cementing stems into bones with narrow intramedullary diameters. Apart from femur and tibia in children, humerus and ulna in adults were also cemented. The cement mantle by this technique is uniform and uninterrupted. Special care should be taken to fit the connector properly to the syringe nozzle and to hold it firmly while cementing. In our experience, this new technique has proven to be very useful, easy to use, reproducible and effective in cementing narrow canals.

The effect of intramedullary pin size and monocortical screw configuration on locking compression plate-rod constructs in an in vitro fracture gap model.

To investigate the effect of intramedullary pin size in combination with various monocortical screw configurations on locking compression plate-rod constructs. A synthetic bone model with a 40 mm fracture gap was used. Locking compression plates with monocortical locking screws were tested with no pin (LCP-Mono) and intramedullary pins of 20% (LCPR-20), 30% (LCPR-30) and 40% (LCPR-40) of intramedullary diameter. Locking compression plates with bicortical screws (LCP-Bi) were also tested. Screw configurations with two or three screws per fragment modelled long (8-hole), intermediate (6-hole), and short (4-hole) plate working lengths. Responses to axial compression, biplanar four-point bending and axial load-to-failure were recorded. LCP-Bi were not significantly different from LCP-Mono control for any of the outcome variables. In bending, LCPR-20 were not significantly different from LCP-Bi and LCP-Mono. The LCPR-30 were stiffer than LCPR-20 and the controls. The LCPR-40 constructs were stiffer than all other constructs. The addition of an intramedullary pin of any size provided a significant increase in axial stiffness and load to failure. This effect was incremental with increasing intramedullary pin diameter. As plate working length decreased there was a significant increase in stiffness across all constructs. A pin of any size increases resistance to axial loads whereas a pin of at least 30% intramedullary diameter is required to increase bending stiffness. Short plate working lengths provide maximum stiffness. However, the overwhelming effect of intramedullary pin size obviates the effect of changing working length on construct stiffness.

The morphometric parameters of the proximal radius of Chinese adults

Objective To measure and study the morphometric parameters of the proximal radius, and to provide the references for further anatomical design of the radial head prosthesis. Methods The MRIs of 24 male and 24 female adult patients with lateral epicondylitis were reviewed. The following parameters were measured from the axial, sagittal, and coronal images: (1)maximum and minimum diameters of the radial head (Rmax and Rmin), (2) radial head height (H1), (3) radial neck height (Hn), (4) maximum and minimum intramedullary diameters at the narrowest level of the radial neck (Dmax and Dmin), and (5) depth of the radial head surface (Dep). Statistical analysis (SPSS16.0) was performed to analyze the relationship among individual morphometric data. Results The maximum radial head diameter (Pmax) and the minimum radial head diameter (Rmin) were (23.1±5.3) mm and (21.8±5.0) mm respectively. The radial head height (H1) and radial neck height (Hn) were (11.3±2.3) mm and (11.8±4.8) mm on average. The maximum intramedullary diameter at the narrowest level of the radial neck(Dmax)and the minimum intramedullary diameter at the narrowest level of the radial neck(Dmin)averaged (10.6±2.7)mm and (9.0±2.5) mm. The depth of the radial head surface was (2.1±0.6) mm on average.Rmax and Rmin of male were (25.1±4.2) mm and (23.7±4.0) mm respectively, H1and Hn(11.9±1.9) mm and (12.2±3.9) mm respectively, Dmax and Dmin (11.1±2.5) mm and (9.6±2.2) mm respectively. The depth of the articular surface was (2.2±0.6)mm. In female, Rmax and Rmin, were (21.1±2.3) mm and (19.9±2.2) mm respectively, H1 and Hn (10.7±1.9) mm and (11.5±6) mm respectively, Dmax and Dmin (10.0±2.6) mm and (8.4±2.3) mm respectively, and the depth of the articular surface was (2.0±0.6) mm. There were statistically significant differences between male and female radial head dimensions(P<0.05). Rmax and Rmin had a correlation of Rmin= 0.95 x Rmax; and there was a correlation between Dmax and Dmin with the formula Dmin=0.85×Dmax(P<0.05). The correlations between Rmax and Dmax, Rmax and H1, Rmax and Hn were more dispersed. Conclusion The radial head has an ellipse shape. The commercially available radial head prostheses can not precisely replicate normal anatomy.Modular implant system slmuld be considered. Key words: Radius; Prosthesis; Research design; Nuclear magnetic resonance