Intramedullary Canal Research Articles

Understanding the variability of the proximal femoral canal: A computational modeling study.

Statistical shape modeling (SSM) offers the potential to describe the morphological differences in similar shapes using a compact number of variables. Its application in orthopedics is rapidly growing. In this study, an SSM of the intramedullary canal of the proximal femur was built, with the aim to better understanding the complexity of its shape which may, in turn, enhance the preoperative planning of total hip arthroplasty (THA). This includes the prediction of the prosthetic femoral version (PFV) which is known to be highly variable amongst patients who have undergone THA. The model was built on three dimensional (3D) models of 64 femoral canals which were generated from pelvic computed tomography images including the proximal femur in the field of view. Principal component analysis (PCA) was performed on the mean shape derived from the model and each segmented canal. Five prominent modes of variations representing approximately 84% of the total 3D variations in the population of shapes were found to capture variability in size, proximal torsion, intramedullary femoral anteversion, varus/valgus orientation, and distal femoral shaft twist/torsion, respectively. It was established that the intramedullary femoral canal is highly variable in its size, shape, and orientation between different subjects. PCA-driven SSM is beneficial for identifying patterns and extracting valuable features of the femoral canal.

No differences in clinical and radiographic outcomes between standard offset and high offset short cementless stems.

To compare clinical and radiographic outcomes of total hip arthroplasty (THA) using standard offset versus high offset short cementless stems. We reviewed a consecutive series of 204 primary THAs performed over 5years using a short cementless collared stem. At a minimum follow-up of 2years, 6 patients had deceased, 6 were not evaluated radiographically and, 2 were lost to follow-up. This left a final cohort of 190 hips, of which 72 had received a standard offset stem and 118 had received a high offset stem. Outcomes collected included: Oxford hip score (OHS), forgotten joint score (FJS), canalfill ratio (CFR),canal-bone ratio (CBR), stem subsidence (≥ 3mm), stem misalignment (> 5°), radiolucent lines (≥ 2mm), cortical hypertrophy, and calcar modifications. There were no significant differences in postoperative clinical and radiographic outcomes between the standard offset and high offset groups, except for incidence of stems in varus (6% vs 17%; p = 0.001). Multivariable analyses revealed that OHS was significantly worse for patients of greater age (β = 0.1; p = 0.001), higher BMI (β = 0.2; p = 0.018), or with inflammatory arthropathy (β = 4.7; p = 0.005); while FJS was significantly worse for patients with higher BMI (β = -0.7; p = 0.003); and cortical hypertrophy was significantly associated with CBR (OR > 100; p = 0.008). There were little to no differences in clinical or radiographic outcomes of THA performed using standard offset versus high offset short cementless stems. Although high offset stems are more frequently aligned in varus, while cortical hypertrophy occurs in wider intramedullary canals.

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.

Elbow hemiarthroplasty for coronal shear fractures of the distal humerus

The aim of the operation is to replace the articular surface of the distal humerus in cases of nonreconstructible fractures of the distal humerus. Active patients with high functional requirements, in whom weight limitation of total elbow arthroplasty should be avoided. Contraindications include fractures with irreconstructible epicondyles and/or irreconstructible collateral ligaments, as well as ulnohumeral, or radiohumeral osteoarthritis. Following subcutaneous anterior transposition of the ulnar nerve, surgical dislocation of the elbow joint is achieved through aparatricipital approach with release of the soft tissue structures from the humerus. After resection of the trochlea, the intramedullary canal of the humerus is prepared using rasps in order to implant the hemiprosthesis with retrograde cementing. Finally, the medial and lateral collateral ligaments as well as the flexors and extensors are repaired. Early functional rehabilitation in ahinged elbow orthosis while avoiding varus/valgus stress after wound healing is completed. Between 2018 and 2022, 18patients with coronal shear fractures were treated with elbow hemiarthroplasty. The mean Mayo Elbow Performance Score (MEPS) was 79 (70-95) after amean follow-up of 12months. The mean range of motion was 99° (70-130°) in extension-flexion and 162° (90-180°) in pronation-supination.

Biomechanical validation of novel polyurethane-resin synthetic osteoporotic femoral bones in axial compression, four-point bending and torsion

In addition to human donor bones, bone models made of synthetic materials are the gold standard substitutes for biomechanical testing of osteosyntheses. However, commercially available artificial bone models are not able to adequately reproduce the mechanical properties of human bone, especially not human osteoporotic bone.To overcome this issue, new types of polyurethane-based synthetic osteoporotic bone models have been developed. Its base materials for the cancellous bone portion and for the cortical portion have already been morphologically and mechanically validated against human bone. Thus, the aim of this study was to combine the two validated base materials for the two bone components to produce femur models with real human geometry, one with a hollow intramedullary canal and one with an intramedullary canal filled with synthetic cancellous bone, and mechanically validate them in comparison to fresh frozen human bone.These custom-made synthetic bone models were fabricated from a computer-tomography data set in a 2-step casting process to achieve not only the real geometry but also realistic cortical thicknesses of the femur. The synthetic bones were tested for axial compression, four-point bending in two planes, and torsion and validated against human osteoporotic bone.The results showed that the mechanical properties of the polyurethane-based synthetic bone models with hollow intramedullary canals are in the range of those of the human osteoporotic femur. Both, the femur models with the hollow and spongy-bone-filled intramedullary canal, showed no substantial differences in bending stiffness and axial compression stiffness compared to human osteoporotic bone. Torsional stiffnesses were slightly higher but within the range of human osteoporotic femurs.Concluding, this study shows that the innovative polyurethane-based femur models are comparable to human bones in terms of bending, axial compression, and torsional stiffness.

Osteotomy Site Venting Enhances Femoral Bone Consolidation With Magnetic Intramedullary Lengthening Nails.

Magnetic intramedullary lengthening nailing has demonstrated benefits over external fixation devices for femoral bone lengthening. These include avoiding uncomfortable external fixation and associated pin site infections, scarring, and inhibition of muscle or joint function. Despite this, little has changed in the field of biologically enhanced bone regeneration. Venting the femoral intramedullary canal at the osteotomy site before reaming creates egress for bone marrow during reaming. The reamings that are extruded from vent holes may function as a prepositioned bone graft at the distraction gap. The relationship between venting and the consolidation of regenerating bone remains unclear. (1) Do bone marrow reamings extruded through venting holes enhance the quality of bone regeneration and improve healing indices and consolidation times? (2) Is venting associated with a higher proportion of complications than nonventing? We performed a retrospective study of femoral lengthening performed at one hospital from December 2012 to February 2022 using a magnetic intramedullary lengthening nail with or without venting at the osteotomy site before reaming. This was a generally sequential series, in which the study groups were assembled as follows: Venting was performed between July 2012 and August 2016 and again from November 2021 onward. Nonventing was used between October 2016 and October 2021 because the senior author opted to create drill holes after the reaming procedure to avoid commitment to the osteotomy level before completing the reaming procedure. Outcomes were evaluated based on bone healing time, time to achieve full weightbearing, and complications. Sixty-one femoral lengthening procedures were studied (in 33 male and 28 female patients); two patients were excluded because of implant breakage. The mean age was 17 ± 5 years. The mean amount of lengthening was 55 ± 13 mm in the venting group and 48 ± 16 mm in the nonventing group (mean difference 7 ± 21 [95% CI 2 to 12]; p = 0.07). The healing index was defined as the time (in days) required for three cortices to bridge with new bone formation divided by the length (in cm) lengthened during the clinical protocol. This index signifies the bone formation rate achieved under the specific conditions of the protocol. Full weightbearing was allowed upon bridging the regenerated gap on three sides. Consolidation time was defined as the total number of days from the completion of the lengthening phase until adequate bone union (all three cortices healed) was achieved and full weightbearing was permitted. This time frame represents the entire healing process after the lengthening is complete divided by the amount of lengthening achieved (in cm). Patient follow-up was conducted meticulously at our institution, and we adhered to a precise schedule, occurring every 2 weeks during the distraction phase and every 4 weeks during the consolidation phase. There were no instances of loss to follow-up. Every patient completed the treatment successfully, reaching the specified milestones of weightbearing and achieving three cortexes of bone bridging. The mean healing index time in the venting group was faster than that in the nonventing group (21 ± 6 days/cm versus 31 ± 22 days/cm, mean difference 10 ± 23 [95% CI 4 to 16]; p = 0.02). The mean consolidation time was faster in the venting group than the nonventing group (10 ± 6 days/cm versus 20 ± 22 days/cm; mean difference 10 ± 23 [95% CI 4 to 15]; p = 0.02). No medical complications such as deep vein thrombosis or fat or pulmonary embolism were seen. Two patients had lengthy delays in regenerate union, both of whom were in the nonventing group (healing indexes were 74 and 62 days/cm; consolidation time was 52 and 40 days/cm). Femoral lengthening with a magnetic intramedullary lengthening nail healed more quickly with prereaming venting than with nonventing, and it allowed earlier full weightbearing without any major associated complications. Future studies should evaluate whether there is a correlation between the number of venting holes and improvement in the healing index and consolidation time. Level III, therapeutic study.

Promising osteoplastic materials and surgical technologies in reconstructive treatment of patients with bone nonunion and defects

Introduction Some progress has been made in the development of innovative implantation materials for osteoplastic surgery. However, the problem of bone defect management still remains relevant due to the continued high prevalence of injuries resulting from road accidents, catatrauma, man-made disasters and military operations.The purpose of the work was to analyze the relevant literature and to identify options for solving the problems of bone nonunion and defect management using materials developed on the principles of orthobiology and surgical technologies based on autologous repair.Materials and methods The search for sources was carried out with the ConnectedPapers analytical tool and the capabilities of the eLibrary electronic library using keywords and without restrictions on publication date.Results and discussion Recent publications contain information about the effectiveness of the combination of Masquelet technology and Ilizarov bone transport in patients with acquired and congenital defects, including in the conditions of active purulent infection. According to the literature, a promising autologous bone plastic material is the contents of the bone marrow cavity, containing osteogenic growth factors and bone morphogenetic proteins. Biomaterial is collected using the Reamer-Irrigator-Aspirator system (RIA) from the intramedullary canal of the femur or tibia. Currently, the effectiveness of bone morphogenetic proteins rhBMP-2 and rhBMP-7 in the restorative treatment of patients with bone defects and nonunion of various etiologies has actually been proven. The use of bone morphogenetic proteins has been introduced into foreign treatment protocols. Recent positive results of a combination of surgical technologies have proposed the combined use of the Ilizarov and Masquelet technologies, supplemented by PRP therapy. The basis for the expected effect from the combination of surgical technologies and orthobiological materials are the results of preclinical studies of the osteogenic potential of PRP therapy.Conclusion There are grounds for studying the clinical effect of the combined use of surgical technologies based on autologous reparative processes and materials developed on the principles of orthobiology. It is necessary and advisable to clinically implement the use of bone morphogenetic proteins rhBMP-2 and rhBMP-7 in the reconstructive treatment of patients with bone defects and nonunion of various etiologies. Multicenter clinical studies of a high level of evidence are needed to determine the effectiveness of PRP therapy in the reconstructive treatment of patients with bone nonunion and defects.

The feasibility of a novel 3D-Printed patient specific cutting guide for extended trochanteric osteotomies

BackgroundThe extended trochanteric osteotomy (ETO) is a surgical technique utilized to expose the intramedullary canal of the proximal femur, protect the soft tissues and promote reliable healing. However, imprecise execution of the osteotomy can lead to fracture, soft tissue injury, non-union, and unnecessary morbidity. We developed a technique to create patient specific, 3D-printed cutting guides to aid in accurate positioning of the ETO and improve osteotomy quality and outcomes.MethodsPatient specific cutting guides were created based on CT scans using Synopysis Simpleware ScanIP and Solidworks. Custom 3D printed cutting guides were tested on synthetic femurs with foam cortical shells and on cadaveric femurs. To confirm accuracy of the osteotomies, dimensions of the performed osteotomies were compared to the virtually planned osteotomies.ResultsUse of the patient specific ETO cutting guides resulted in successful osteotomies, exposing the femoral canal and the femoral stem both in synthetic sawbone and cadaveric testing. In cadaveric testing, the guides allowed for osteotomies without fracture and cuts made using the guide were accurate within 6 percent error from the virtually planned osteotomy.ConclusionThe 3D-printed patient specific cutting guides used to aid in ETOs proved to be accurate. Through the iterative development of cutting guides, we found that a simple design was key to a reliable and accurate guide. While future clinical trials in human subjects are needed, we believe our custom 3D printed cutting guide design to be effective at aiding in performing ETOs for revision total hip arthroplasty surgeries.

Robotic arm-assisted total knee arthroplasty in a patient with osteopetrosis: a case report and review of literature.

Osteopetrosis, a rare condition arising from osteoclast dysfunction, is characterised by increased bony density and obliteration of the intramedullary canal. While total knee arthroplasty (TKA) is preferred for osteoarthritic patients with osteopetrosis, inherent disease characteristics pose surgical challenges. This article presents a patient with osteopetrosis treated with robotic arm-assisted TKA (RA-TKA). This approach provided precise bone resection, obviates the need for intramedullary guides, minimizes saw disposal, and reduces surgical duration, with satisfactory short-term outcomes. RA-TKA may be an effective treatment for osteoarthritis in patients with osteopetrosis.

Mesenchymal stem cells enhance targeted bone growth from injectable hydrogels with BMP-2 peptides.

Osteoporosis is the most common chronic metabolic bone disease, and the prevalence of osteoporotic fractures is rapidly increasing with the aging population. While bisphosphonates can reduce bone loss and risk of fracture, these drugs are systemic, rely on long-term use, and patient compliance is low. Recombinant human bone morphogenetic protein-2 (BMP-2) is an FDA-approved protein that can offer a more targeted therapeutic than systemic treatments. DWIVA is a peptide sequence corresponding to the wrist epitope of BMP-2, and DWIVA-functionalized hydrogels feature osteoinductive propertiesin vitro and in vivo. This study reports that self-forming DWIVA-functionalized hydrogels injected into the intramedullary canal of rat femurs induce a local increase in trabecular bone in as little as 2 weeks. Increases in bone volume, trabecular thickness, and trabeculae count from DWIVA-laden hydrogels persist for at least 4 weeks, and the inclusion of mesenchymal stem cells (MSCs) significantly enhances the development of mineralized bone. Histological analysis of decalcified femurs also shows that hydrogel injections containing DWIVA peptide and MSCs stimulate unmineralized bone tissue formation and induce an increased count of osteoblasts and osteoclasts at the injection site after 4 weeks. Overall, the MSC-laden DWIVApeptide-functionalized hydrogels presented rapidly induce targeted bone formation and have the potential to form nascent bone within bones in jeopardy of an osteoporotic fracture such as the femur.

Outcomes and Complications of Intramedullary Metacarpal Fixation.

Metacarpal fractures are common orthopedic injuries with potentially debilitating outcomes. Ideal surgical treatment remains a topic of debate, with intramedullary fixation becoming popular as a technique to allow for earlier mobilization with few reported complications. The aim of this study was to report observed outcomes and complications of intramedullary metacarpal fixation using the ExsoMed INnate metacarpal nail. A retrospective chart review of 37 patients with 44 metacarpals treated with the ExsoMed INnate between July 2020 and December 2021 by a single fellowship-trained hand surgeon at a single level 1 trauma center was performed. Variables recorded included both patient and injury demographics, surgical complications, and postoperative outcomes. We also measured metacarpal isthmus diameter of the second to fifth metacarpals on all patients to determine the intramedullary canal diameter to assist in implant size selection. Average follow-up was 5.84 weeks with average time to radiographic healing of 5.5 weeks, and time to full activity 6.32 weeks. The mean postsurgical active total arc of motion was 250°, while passive total arc of motion was 259.74°. A total of 10 complications (22%) were identified, including 4 bent screws which occurred as a result of a punching event postoperatively. Intramedullary fixation of metacarpal fractures using the ExsoMed INnate metacarpal nail has shown to preserve range of motion and quick return to full activity, with a low rate of major complications. Our study highlights the potential major complication of the bent intramedullary screw and its association with an initial punching mechanism.

Use of a Low Profile Ultra-High Molecular Weight Polyethylene Diaphyseal Humeral Cement Restrictor in Shoulder Arthroplasty.

When implanting a cemented humeral stem, a reliable method to prevent inappropriate extension and enable pressurization of cement in the intramedullary canal is required. The aim was to assess the outcomes of a dedicated humeral diaphyseal cement restrictor. In total 218 shoulders (207 patients) were included in the study, all of whom underwent a cemented total shoulder arthroplasty and a retrospective review was performed. The primary outcomes of interest were device stability in the medullary canal, successful occlusion of the canal, cement extrusion and quality of cement mantle. The majority of the cohort was female (63.3%) males and the average patient age was 71.7 years (SD 8.45). In 81.7% the device was deemed to be stable in the medullary canal. The device was significantly more stable in primary (84.2%) compared to revision cases (64.3%, p = 0.02). In 69.7% Barrack grade A mantle quality was achieved, this was higher in primary cases (74.2%) compared to revision cases (39.3%) (p = 0.00006). We noted excellent cementation outcomes using a cement restrictor specifically designed for the diaphyseal humerus anatomy. However, this humeral specific restrictor was noted to be more stable in primary as compared to revision cases.

Design and In Vitro Validation of an Orthopaedic Drill Guide for Femoral Stem Revision in Total Hip Arthroplasty.

Cemented total hip arthroplasty (THA) demonstrates superior survival rates compared to uncemented procedures. Nevertheless, most younger patients opt for uncemented THA, as removing well-fixed bone cement in the femur during revisions is complex, particularly the distal cement plug. This removal procedure often increases the risk of femoral fracture or perforation, haemorrhage and weakening bone due to poor drill control and positioning. Aim of this study was to design a novel drill guide to improve drill positioning. A novel orthopaedic drill guide was developed, featuring a compliant centralizer activated by a drill guide actuator. Bone models were prepared to assess centralizing performance. Three conditions were tested: drilling without guidance, guided drilling with centralizer activation held, and guided drilling with centralizer activation released. Deviations from the bone centre were measured at the entry and exit point of the drill. In the centralizing performance test, the drill guide significantly reduced drill hole deviations in both entry and exit points compared to the control ([Formula: see text]). The absolute deviation on the exit side of the cement plug was 10.59mm (SD 1.56) for the 'No drill guide' condition, 3.02mm (SD 2.09) for 'Drill guide - hold' and 2.12mm (SD 1.71) for 'Drill guide - release'. The compliant drill guide centralizer significantly lowered the risk of cortical bone perforation during intramedullary canal drilling in the bone models due to better control of the cement drill position. Clinical and Translational Impact Statement: The drill guide potentially reduces perioperative risks in cemented femoral stem revision. Future research should identify optimal scenarios for its application.

How to manage blocked intramedullary canal while reaming during hip arthroplasty

Blockage of femoral canal while doing hemiarthroplasty is rare finding. Before inserting the femoral stem trial we should manage this blockage adequately to prevent iatrogenic fracture. Herein, we present a case of fracture neck of femur right in a 79-year-old male who presented with history of right hip pain and later was diagnosed with neck of femur fracture subcapital type that was treated with cementless hemiarthroplasty. In conclusion, if the canal is blocked, start with small diameter (K-wire), then insert guide wire and then reaming over it to open the blocked canal, do not hammer directly to prevent iatrogenic fracture. Go sequentially to open the blockage. First open the marrow then insert trial stem.

Anthropometric measurements of the foot cannot predict the screw diameter for fifth metatarsal fractures intramedullary fixation

PurposeThe present study aimed to evaluate the accuracy of anthropometric foot measurements in predicting the diameter of the intramedullary screw for fifth metatarsal fracture fixation. Secondary aim was to identify whether the fifth metatarsal intramedullary canal diameter is correlated to the fifth metatarsal length and the foot dimensions.MethodsIn 29 cadaveric feet, the maximum length of the plantar surface of the foot (PL) and the perimeter of the foot at the level of the fifth metatarsal base (PBFM) were measured using a measuring tape. Subsequently, the fifth metatarsal was excised. Using Computed Tomography scan, the metatarsal length (FML), and the horizontal (HDI) and vertical diameter (VDI) at the isthmus level were measured. The HDI values were grouped in 5 mm increments to correspond to the recommended screw diameter (RSD) for intramedullary fixation. A univariate linear regression analysis considered RSD and HDI as the dependent variables and FML, PL, PBFM as the independent variables. A multivariate regression analysis was performed to examine the predictive value of the two anthropometric measurements. A p-value < 0.05 was considered statistically significant.ResultsAll six univariate analyses revealed that the dependent variable was significantly correlated with the independent variable. However, the multivariate regression models showed that the anthropometric measurements were not significantly correlated with the RSD and HDI.ConclusionThe current study found an association between the fifth metatarsal intramedullary canal diameter and the fifth metatarsal length and foot anthropometric dimensions. However, the anthropometric measurements of the foot presented a low predictive value for the decision of an intramedullary screw diameter in the treatment of fractures of the base of the fifth metatarsal.

Does medullary diameter to stem width ratio and stem length affect outcomes of revision total knee arthroplasties? A case series.

This study aimed to investigate the relationship between the ratio of stem size to intramedullary canal diameter, stem length, and functional outcome in revision total knee arthroplasty (RTKA) procedures, which remains largely unexplored in the current literature. A single surgeon series of RTKA procedures performed between October 2014 and November 2022 were included in this case series, and data were analyzed retrospectively. A total of 32 patients (27 females, 5 males; mean age: 73.2±8.1 years; range, 52 to 88 years) were identified, with a minimum follow-up period of five months and a maximum of eight years. Filtering the patients based on >24 month follow-up, we were left with 13 patients aged between 65 and 88 (mean 74.9±6.9) years. The latest X-rays of patients were analyzed, and the ratio of intramedullary canal diameter to stem width was calculated for both femur and tibia in both anteroposterior and lateral planes. Household income, preoperative C-reactive protein, erythrocyte sedimentation rate, comorbidities, body mass index, and implant dimensions were also recorded. Postoperative Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Short Form-12 (SF-12) scores, and range of motion (ROM) measurements were used to evaluate functional outcome. A moderate negative relationship between the tibial canal fill ratio (CFR) in anteroposterior views and ROM of the patients was noted. Additionally, a significant positive correlation was found between SF-12 physical score and CFR in lateral view. A moderate level of correlation between femoral CFR in anteroposterior views was also established. Due to insufficient data, joint ROM data did not show normal distribution. Therefore, a cutoff value indicating the relationship between the stem size and knee ROM could not be calculated using receiver operating characteristic analysis. Multiple regression analysis did not yield significant results, suggesting that hypothesized predictor variables were not sufficient to predict the variation in functional scores. Otherwise, no clear statistical importance or correlation between functional scores, such as WOMAC or SF-12, and CFR was found. In conclusion, the findings suggest that other factors, such as other patient characteristics, surgical techniques, or implant designs, may have a more substantial impact on the functional outcomes in RTKA patients.

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.

Bullet Fragment Retrieval During Intramedullary Nailing: A Report of 2 Cases.

Two young adult patients, 22 and 27 years, who sustained ballistic long bone fractures, presented for incarcerated, retained metallic fragments in the medullary canal, which blocked fixation. Owing to the presence and location of the fragments, each case required a bullectomy (removal of the metallic fragment) before intramedullary nail fixation because the projectile impeded the appropriate insertion of the intramedullary rod and, in one case, induced fracture malalignment. Attempts at removal using conventional tools did not provide adequate length or grasp of the retained projectile, necessitating the use of the novel technique. The Babcock Laparoscopic Endopath is an easy-to-use, ubiquitous tool that facilitates the removal of content within the intramedullary canal, including metallic or bony fragments. There is limited literature describing accessible, cost-effective techniques for the removal of intramedullary retained metallic foreign fragments when it is unremovable through conventional means. This article reports on a novel, minimally invasive technique for bullet removal from the intramedullary canal of the femur and tibia using the Babcock Laparoscopic Endopath, a tool typically used by urologists. Both patients were followed for at least 8 weeks postoperatively with no complications secondary to the procedure. The article describes the technique and advantages of using this readily available tool that is both flexible enough to navigate through the intramedullary canals as well as rigid enough to obtain and manipulate metallic objects.

The effect of humeral head positioning and incomplete backside contact on bone stresses following total shoulder arthroplasty with a short humeral stem.

The use of uncemented humeral stems in total shoulder arthroplasty (TSA) is known to be associated with stress shielding. This may be decreased with smaller stems that are well-aligned and do not fill the intramedullary canal; however, the effect of humeral head positioning and incomplete head backside contact has not yet been investigated. The purpose of this study was to quantify the effect of changes in humeral head position and incomplete head backside contact on bone stresses and expected bone response following reconstruction. Three-dimensional finite element models of 8 cadaveric humeri were generated, which were then virtually reconstructed with a short-stem implant. An optimally sized humeral head was then positioned in both a superolateral and inferomedial position for each specimen that was in full contact with the humeral resection plane. Additionally, for the inferomedial position, 2 incomplete humeral head backside contact conditions were simulated whereby contact was defined between only the superior or inferior half of the backside of the humeral head and the resection plane. Trabecular properties were assigned based on computed tomography attenuation and cortical bone was applied uniform properties. Loads representing 45° and 75° of abduction were then applied, and the resulting differentials in bone stress versus the corresponding intact state and the expected time-zero bone response were determined and compared. The superolateral position reduced resorbing potential in the lateral cortex and increased resorbing potential in the lateral trabecular bone, while the inferomedial position produced the same effects but in the medial quadrant. For the inferomedial position, full backside contact with the resection plane was best in terms of changes in bone stress and expected bone response, although a small region of the medial cortex did experience no load transfer. The implant-bone load transfer of the inferior contact condition was concentrated at the midline of the backside of the humeral head, leaving the medial aspect largely unloaded as a result of the lack of lateral backside support. This study shows that inferomedial humeral head positioning loads the medial cortex at the cost of unloading the medial trabecular bone, with the same occurring for the superolateral position except that the lateral cortex is loaded at the cost of unloading the lateral trabecular bone. Inferomedial positioned heads also were predisposed to humeral head lift-off from the medial cortex, which may increase the risk of calcar stress shielding. For the inferomedial head position, full contact between the implant and resection plane was preferable.

Preliminary Results and a Treatment Algorithm for Osteomyelitis of the Distal Tibia and Talus

Category: Hindfoot; Ankle Introduction/Purpose: Management of hindfoot osteomyelitis involves eradication of infection, deformity correction, and bony stabilization in the setting of bone loss and poor bone quality. This case series of 20 patients presents a two-stage technique: debridement, deformity correction, joint surface preparation, intramedullary reaming with antibiotic-impregnated polymethyl methacrylate rod and ring external fixation, followed by a second stage of external fixator removal and exchange of antibiotic rod for definitive hindfoot fusion rod. The purpose of the study is to highlight techniques and preliminary results that can improve the success of obtaining stable fixation, remission of infection and ultimately fusion. Techniques highlighted are ring fixator placement, antibiotic rod formulation, intramedullary canal preparation, rod exchange and use of blocking screws to enhance compression and axial loading of the fusion. Methods: Twenty patients were treated with this two-stage protocol. The most common indication was post-traumatic osteomyelitis followed by neuropathic (Charcot) joint. All were treated with an initial debridement of nonviable tissue including osteomyelitic bone. The tibiotalar and talocalcaneal joint surfaces were prepared for fusion at the initial debridement. Provisional stabilization and compression were obtained using a ring external fixator for patients without rotational stability. The polymethyl methacrylate-antibiotic impregnated rod (PMMA with gentamycin and vancomycin) was introduced through the calcaneus, talus, and the intramedullary space of the tibia. The patients were kept in the fixator until the skin was healed and all incisions were dry. At this point, the fixator was removed, and the antibiotic rod was exchanged for the definitive hindfoot fusion rod. Results: Cultures were positive for Staphylococcal or Streptococcal species in 60% of cases, Fingeoldia magna 10%, Cutibacterium Acnes 2%, and Gram-negative organisms in 30%. On average patients spent 80 days in the fixator while wounds were healing, and were receiving systemic antibiotics. One patient died while in the frame. There have been no amputations in the series. Of the patients that have completed the protocol, all have gone on to either bony fusion or stable fibrous union. All are able to walk unaided and 25% used an AFO to control and protect the foot and equalize leg length. Secondary procedures are described. Conclusion: This technique of staged fusion for hindfoot osteomyelitis offers the following advantages. The first stage involves thorough debridement and deformity correction. Oftentimes, there is extensive scarring, and the soft tissue envelope is not conducive to internal fixation. This technique allows the soft tissues to heal before placing the definitive internal fixation. It also allows for graduated compression at the fusion site with the ring fixator. The antibiotic rod not only delivers high concentration of local antibiotics, but it prevents deformity recurrence during the compression phase. The definitive rod provides support of pathologic bone and maintains deformity correction.