Introduction:. Total shoulder arthroplasty (TSA) is the current standard treatment for severe osteoarthritis of the glenohumeral joint [1]. Often, severe arthritis is associated with abnormal glenoid version or excessive posterior wear [2]. Reaming to correct more than 15° of retroversion back to neutral is not ideal as it may remove an excessive amount of the outer cortical support and medialize the glenoid component [3]. Two recent glenoid components with posterior augments—wedged and stepped—have been designed to address excessive posterior wear and to allow glenoid component neutralization. Hypothetically, these augmented glenoid designs lessen the complications associated with using a standard glenoid component in cases of shoulder osteoarthritis with excessive posterior wear. We set out to determine which implant type (standard, stepped, or wedged) corrects retroversion while removing the least amount of bone in glenoids with posterior erosion. Methods:. Serial shoulder CT scans were obtained from 121 patients before total shoulder arthroplasty. These were then classified using the Walch Classification. We produced 3D models of the scapula from CT scans for 10 subjects that were classified as B2 using the software MIMICS (Materialise, Belgium). Each of these 10 glenoid subjects were then virtually implanted with standard, stepped, and wedged glenoid components (Fig 1). The volume of surgical bone removed and maximum reaming depth were calculated for each design and for each subject. In addition, the area of the backside of the glenoid in contact with cancellous versus cortical bone was calculated for each glenoid design and for each subject (Fig 2). ANOVA testing was performed. Results:. Arthritic bone loss in shoulder specimens was always posteroinferior, and the worn portion or neoglenoid made up an average of 68 ± 11% in the shoulder specimens. Mean surgical bone volume removed (2857 ± 1618 mm. 3. ) was least for the wedged component when compared to stepped (4307 ± 1485 mm. 3. , p=.0003) and conventional (5385 ± 2348 mm. 3. , p=.0003) designs. Maximum bone depth removed for the wedge (4.5 ± 2.3 mm) was less than the stepped (7.6 ± 1.4 mm, p=.00003) and conventional (9.7 ± 2.7 mm, p=.00001). The mean percentage of the implant's back surface supported by cancellous bone was 17.0% for the conventional, 6.1% for the stepped (p=.009), and 3.1% for the wedged (p=.0001). Discussion:. Both wedged and stepped components were able to correct glenoid version to neutral and required less bone removal, required less reaming depth, and were supported by more cortical bone than the standard implant. The wedged component was significantly better in these three categories than the stepped implant. There may be a mismatch between the usual patterns of wear that occurs in B2 glenoids where neoglenoid comprises (68 ± 11%) vs. the stepped implant's 50%. A stepped implant that matches the usual B2 glenoid may correct version while removing less bone than the current design

Patients receiving reverse total shoulder arthroplasty (RTSA) often have osseous erosions because of glenohumeral arthritis, leading to increased surgical complexity. Glenoid implant fixation is a primary predictor of the success of RTSA and affects micromotion at the bone-implant interface. Augmented implants which incorporate specific geometry to address superior erosion are currently available, but the clinical outcomes of these implants are still considered short-term. The objective of this study was to investigate micromotion at the glenoid-baseplate interface for a standard, 3 mm and 6 mm lateralized baseplates, half-wedge, and full-wedge baseplates. It was hypothesized that the mechanism of load distribution from the baseplate to the glenoid will differ between implants, and these varying mechanisms will affect overall baseplate micromotion. Clinical CT scans of seven shoulders (mean age 69 years, 10°-19° glenoid inclinations) that were classified as having E2-type glenoid erosions were used to generate 3D scapula models using MIMICS image processing software (Materialise, Belgium) with a 0.75 mm mesh size. Each scapula was then repeatedly virtually reconstructed with the five implant types (standard,3mm,6mm lateralized, and half/full wedge; Fig.1) positioned in neutral version and inclination with full backside contact. The reconstructed scapulae were then imported into ABAQUS (SIMULIA, U.S.) finite element software and loads were applied simulating 15°,30°,45°,60°,75°, and 90° of abduction based on published instrumented in-vivo implant data. The micromotion normal and tangential to the bone surface, and effective load transfer area were recorded for each implant and abduction angle. A repeated measures ANOVA was used to perform statistical analysis. Maximum normal micromotion was found to be significantly less when using the standard baseplate (5±4 μm), as opposed to the full-wedge (16±7 μm, p=0.004), 3 mm lateralized (10±6 μm, p=0.017), and 6 mm lateralized (16±8 μm, p=0.007) baseplates (Fig.2). The half-wedge baseplate (11±7 μm) also produced significantly less micromotion than the full-wedge (p=0.003), and the 3 mm lateralized produced less micromotion than the full wedge (p=0.026) and 6 mm lateralized (p=0.003). Similarly, maximum tangential micromotion was found to be significantly less when using the standard baseplate (7±4 μm), as opposed to the half-wedge (12±5 μm, p=0.014), 3 mm lateralized (10±5 μm, p=0.003), and 6 mm lateralized (13±6 μm, p=0.003) baseplates (Fig.2). The full wedge (11±3 μm), half-wedge, and 3 mm lateralized baseplate also produced significantly less micromotion than the 6 mm lateralized (p=0.027, p=012, p=0.02, respectively). Both normal and tangential micromotion were highest at the 30° and 45° abduction angles (Fig.2). The effective load transfer area (ELTA) was lowest for the full wedge, followed by the half wedge, 6mm, 3mm, and standard baseplates (Fig.3) and increased with abduction angle. Glenoid baseplates with reduced lateralization and flat backside geometries resulted in the best outcomes with regards to normal and tangential micromotion. However, these types of implants are not always feasible due to the required amount of bone removal, and medialization of the bone-implant interface. Future work should study the acceptable levels of bone removal for patients with E-type glenoid erosion and the corresponding best implant selections for such cases. For any figures or tables, please contact the authors directly

Glenoid replacement is a manual bone removal procedure that can be difficult for surgeons to perform. Surgical robotics have been utilized successfully in hip and knee orthopaedic procedures but there are no systems currently available in the shoulder. These robots tend to have low adoption rates by surgeons due to high costs, disruption of surgical workflow and added complexity. As well, these systems typically use optical tracking which needs a constant line-of-sight which is not conducive to a crowded operating room. The purpose of this work was developing and testing a surgical robotic system for glenoid replacement. The new surgical system utilizes flexible components that tether a Stewart Platform robot to the patient through a patient specific 3D printed mount. As the robot moves relative to the bone, reaction loads from the flexible components bending are measured by a load cell allowing the robot to “feel” its way around. As well, a small bone burring tool was attached to the robot to facilitate the necessary bone removal. The surgical system was tested against a fellowship-trained surgeon performing standard surgical techniques. Both the robot and the surgeon performed glenoid replacement on two different scapula analogs: standard anatomy and posterior glenoid edge wear referred to as a Walch B2. Six of each scapula model was tested by the robot and the surgeon. The surgeon created a pre-operative plan for both scapula analogs as a target for both methodologies. CT scans of the post-operative cemented implants were compared to the pre-operative target and implant position and orientation errors were measured. For the standard shoulder analogs the net implant position and orientation errors were 1.47 ± 0.48 mm and 2.57 ± 2.30° for the robot and 1.61 ± 0.29 mm and 5.04 ± 1.92° for the surgeon respectively. For the B2 shoulders, the net implant position and orientation errors were 2.16 ± 0.36 mm and 2.89 ± 0.88° for the robot and 3.01 ± 0.42 mm and 4.54 ± 1.49° for the surgeon respectively. The new tracking system was shown to be able to match or outperform the surgeon in most metrics. The surgeon tended to have difficulty gauging the depth needed as well as the face rotation of the implant. This was not surprising as the reaming tool used by the surgeon obscures the view of the anatomy and the spherical cutter hinders the ability to index the tool. The robot utilized only one surgical tool, the bone burr, precluding the need for multiple instruments used by the surgeon to prepare the glenoid bone bed. The force-space navigation method can be generalized to other joints, however, further work is needed to validate the system using cadaveric specimens

Abstract. Extended Trochanteric Osteotomy (ETO) improves surgical exposure and aids femoral stem and bone cement removal in Revision Total Hip Replacement (RTHR) surgery. The aim of this study was to identify healing rates and complications of ETO in RTHR. Methods. From 2012 to 2019 we identified patients who underwent ETO for RTHR. Data collected demographics, BMI, diabetes, anticoagulants, indication for ETO, surgical approach, length of ETO and complications. Descriptive analysis of patient demographics, multiple linear regression analysis was performed to assess ETO complications. Results. There were 63 patients with an average age of 69 years. Indications for ETO were aseptic loosening (30), infection (15), periprosthetic fracture (9), recurrent dislocation (5), broken implant (4). There were 44 cemented and 19 uncemented femoral stem that underwent ETO. Average time from index surgery was 12 years (less than a year to 38 years). All procedures were through posterolateral approach and all ETO were stabilised with cables. Average length of ETO was 12.5cm. BMI varied from 18 to 37. There were 5 diabetics and 16 on anticoagulants. All but one ETO went on to unite. Other complications included infection, dislocations, lateral thigh pain and significant limp. Discussion. Fixation of ETO can be with either wires or cables or plate with cables/screws. Advantages of cables are no irritation over greater trochanter, no disruption of gluteus medius/vastus lateralis continuity, reproducible tension in cables and use of torque limiter minimises loss of tension in cables

Superiorly eroded glenoids in cuff tear arthropathy represent a surgical challenge for reconstruction. The bone loss orientation and severity may influence glenoid component fixation. This computed-tomography study quantifies both the degree of erosion and orientation in superiorly eroded Favard E2 glenoids. We hypothesized that the erosion in E2 glenoids does not occur purely superiorly, rather, it is oriented in a predictable posterosuperior orientation with a largely semicircular line of erosion. Three-dimensional reconstructions of 40 shoulders with E2 glenoids (28 female, 12 male patients) at a mean age of 74 years (range, 56–88 years) were created from computed-tomography images. Point coordinates were extracted from each construct to analyze the morphologic structure. The anatomical location of the supra- and infraglenoid tubercle guided the creation of a superoinferior axis, against which the orientation angle of the erosion was measured. The direction and, thus, orientation of erosion was calculated as a vector. By placing ten point coordinates along the line of erosion and creating a circle of best fit, the radius of the circle was placed orthogonally against a chord that resulted by connecting the two outermost points along the line of erosion. To quantify the extent of curvature of the line of erosion between the paleo- and neoglenoid, the length of the radius of the circle of best fit was calculated. Individual values were compared against the mean of circle radii. The area of bony erosion (neoglenoid), was calculated as a percentage of the total glenoid area (neoglenoid + paleoglenoid). The severity of the erosion was categorized as mild (0% to 33%), moderate (34% to 66%), and severe erosion (>66%). The mean orientation angle between the vector of bony erosion and the superoinferior axis of the glenoid was 47° ± 17° (range, 14° – 74°) located in the posterosuperior quadrant of the glenoid, resulting in the average erosion being directed between the 10 and 11 o'clock position (right shoulder). In 63% of E2 cases, the line of erosion separating the paleo- and neoglenoids was more curved than the average of all bony erosions in the cohort. The mean surface area of the neoglenoid was 636 ± 247 mm2(range, 233 – 1,333 mm2) and of the paleoglenoid 311 ± 165 mm2(range, 123 – 820 mm2), revealing that, on average, the neoglenoids consume 67% of the total glenoid surface. The extent of erosion of the total cohort was subdivided into one mild (2%), 14 moderate (35%) and 25 severe (62%) cases. Using a clock-face for orientation, the average orientation of type E2 glenoid defects was directed between the 10 and 11 o'clock position in a right shoulder, corresponding to the posterosuperior glenoid quadrant. Surgeons managing patients with E2 type glenoids should be aware that a superiorly described glenoid erosion is oriented in the posterosuperior quadrant on the glenoid clock-face when viewed intra-operatively. Additionally, the line of erosion in 63% of E2 glenoids is substantially curved, having a significant effect on bone removal techniques when using commercially available augments for defect reconstruction

INTRODUCTION. Preoperative planning software for reverse total shoulder arthroplasty (RTSA) allows surgeons to virtually perform a reconstruction based off 3D models generated from CT scans of the glenohumeral joint. While anatomical studies have defined the range of normal values for glenoid version and inclination, there is no clear consensus on glenoid component selection and position for RTSA. The purpose of this study was to examine the distribution of chosen glenoid implant as a function of glenoid wear severity, and to evaluate the inter-surgeon variability of optimal glenoid component placement in RTSA. METHODS. CT scans from 45 patients with glenohumeral arthritis were planned by 8 fellowship trained shoulder arthroplasty specialists using a 3D preoperative planning software, planning each case for optimal implant selection and placement. The software provided four glenoid baseplate implant types: a standard non-augmented component, an 8° posterior augment wedged component, a 10° superior augment wedged component, and a combined 8° posterior and 10° superior wedged augment component. The software interface allowed the surgeons to control version, inclination, rotation, depth, anterior-posterior and superior-inferior position of the glenoid components in 1mm and 1° increments, which were recorded and compared for final implant position in each case. RESULTS. Two cases were excluded due to extreme deformity and consensus that a feasible RTSA may not be possible. For resultant implant version, a bimodal distribution was observed with a local maxima occurring at 0°, and a bell-shaped distribution at −5° of version. Upon individual surgeon analysis, it was revealed that certain surgeons had a preference to correct to 0 degrees, whereas others were more accepting of residual version. As well, the surgeons accepting residual retroversion removed less bone on average per implant type than the surgeons who aimed to correct to 0°. For resultant implant inclination, surgeons consistently tried to plan for 0 degrees of inclination. CONCLUSION. This study indicates that while there was limited consensus on the optimal reconstruction in any one case, there appear to be thresholds of retroversion and inclination that favor the use of augmented glenoid components based on frequency of selection. Our results indicate a wide variability in terms of what experienced shoulder surgeons consider to be an optimal reconstruction despite the common goal of attempting to restore anatomy, maximize implant fixation in bone and minimize bone removal. High frequency of augmented glenoid component use raises questions about how much retroversion and inclination is optimal and whether this technology allows surgeons to potentially focus more on a quantitative reconstruction relative to the Friedman axis versus a qualitative implant placement relative to what may be normal anatomy for a patient

BACKGROUND. Total hip revision surgery in cases with previous multiple reconstructive procedures is a challenging treatment due to difficulties in treatment huge bone defects with standard revision prosthetic combinations. A new specially made production system in Electron-Beam Melting (EBM) technology based on a precise analysis of patients' preoperative CT scans has been developed. METHODS. Objectives of design customization in difficult cases are to correctly evaluate patient's anatomy, to plan a surgical procedure and to obtain an optimal fixation to a poor bone stock. The 3D Printing (EBM) technology permits to create an extremely flexible patient matching implant and instrument, with material performances not viable with standard manufacturing process. Dedicated visual 3D tools and instrumentations improve implants congruency according to preoperative plan. Primary stability is enhanced and tailored on patient's anatomy by means of press-fit, iliac stems and the high friction performances of Trabecular Titanium matrix. The use of bone screws and their position is designed to enhance primary stability, even in critical bone conditions, avoiding implant stress shielding and allowing bone integration. 4 cases (2 men and 2 women) of acetabular customized implants were performed. Mean age at surgery was 51.5 years (range 25–72). Patients were reviewed clinically and radiographically at follow-up. RESULTS. No signs of miss-match between intraoperative bone conditions and pre-operative planning were observed. No additional bone grafts or further native bone removal were needed. Biomechanical parameters were restored by using internal modularity (i.e. face-changers / angled spacers). Face-changers allow to correct coverage and anteversion of the acetabular system. Incompatibility or impingement between the stems and new acetabular component was not observed and stem revision was performed in one case. On-table stability proved excellent and no intraoperative complications were observed. All patients underwent an immediate mobilization with full weight-bearing. Mean Harris Hip Score increased significantly from 13.9 (range 6.9–20.6) preoperatively to 75.8 (range 53.9–94) at last follow-up (mean 17.5, range: 10–33), showing an improvement in terms of both pain relief, function and joint mobility. Radiographically neither signs of instability, migration nor tilting were observed. No case of dislocation nor infection were recorded. CONCLUSION. A detailed anatomical reconstruction, in-depth preoperative planning, custom-implant design, high performance of the 3D-printing technology, system modularity and patient-specific surgical tools permitted an effective restoration of the biomechanical joint parameters in these complex revision cases. The optimal primary stability of the implants promoted an early osseointegration with the remaining bone stock. Further studies shall be necessary to assess the performance of these Implants at long-term follow-up

Aims. The aim of this study was to optimize screw hole placement in an acetabulum cup implant to improve secondary initial fixation by identifying the region of thickest acetabulum bone. The “scratch fit” of modern acetabular cup implants with highly porous coatings is often adequate for initial fixation in primary total hip arthroplasty. Initial fixation must limit micromotion to acceptable levels to facilitate osseointegration and long term cup stability. Secondary initial fixation can be required in cases with poor bone quality or bone loss and is commonly achieved with bone screws and a cup implant with multiple screw holes. To provide maximum secondary initial fixation, the cup screw holes should be positioned to allow access to the limited region of thick pelvic bone. Patients and Methods. Through a partnership with Materialise, a statistical shape model of the pelvis was created utilizing 80 CT scans (36 female, 44 male). To limit the effect of variation outside the area of cup implant fixation, the shape model includes only the inferior pelvis (cut off at the greater sciatic notch and above the anterior inferior iliac spine). A virtual implantation protocol was developed which creates instances of the pelvis shape model that accurately simulate the intraoperative reaming of the acetabulum to accept the cup implant. First a sphere is best fit to the native acetabulum and the diameter is rounded to the nearest whole millimeter. The diameter of the best fit sphere is increased by 1mm to simulate bone removal during the spherical reaming procedure. The sphere is translated medially and superiorly such that it is tangent to the teardrop and removes 2mm of superior acetabulum. The sphere is used to perform a Boolean subtraction from the shape model to create a virtually reamed pelvis shape model. The Materialise 3-Matic software was used to perform a thickness analysis of the prepared shape models. The output of the thickness analysis is displayed as a color “heat map” where green represents thin bone and red is thick bone. The region of thickest bone was identified and used to drive ideal screw hole placement in the cup implant to access this region. Results. The analysis finds there is a limited arc of thick bone in the acetabulum that begins superiorly and extends posterior-inferior that accounts for only about 15% of total reamed surface area. Maximum screw purchase is provided when screw holes in the cup implant are placed over this limited region of thick bone. The thickest bone, located superiorly, facilitates the placement of a long bone screw up the iliac column and the posterior-inferior region of thick bone facilitates the placement of additional posterior screws. Conclusion. The shape model development, virtual implantation protocol, and heat map thickness analysis allowed the placement of bone screw holes directly over the limited region of thick pelvic bone. This allows maximum screw purchase which is important in achieving adequate secondary initial fixation with bone screws. Disclaimer. Author is an engineer employed by DJO Surgical who funded this study

Total hip replacement is one of the standard procedures in orthopedic surgery. Due to various reasons revision surgery (RTHR) has to be performed. In case of the revision of a cemented prosthesis stem, the bone cement has to be removed from the femoral cavity. Conventionally the cement removal is done manually using a hammer, chisel or burr under X-ray control, causing a considerable radiation exposure for patient and the surgeon. Furthermore the risk of undesirable bone damage is high due to bad sight and access conditions, leading to complications and prolongation of the intervention. Different approaches addressing the mentioned problems were proposed, but did not achieve acceptance in clinical practice due to disadvantages concerning process controllability. Another possibility is to use a robot guided milling tool. However, to be able to control it typically a 3D reconstruction of the cement volume to be removed is necessary. Existing approaches use computed tomography based measurements combined with previously implanted markers, fluoroscopy or ultrasound based measurements, all requiring additional process steps prior to the surgery or to the actual cement removal. The ICOS project (Impedance Controlled Surgical Instrumentation, Chair of Medical Engineering, RWTH Aachen University) investigates the approach of electrical impedance controlled, robot assisted bone cement removal, based on real time cement detection during the removal process without radiation exposure or the necessity of prior imaging or marker implanting steps. Therefore the electrical impedance is measured between the milling head mounted on the surgical mini-robot MINARO and one or more electrodes attached to the skin of the patient's thigh. An impedance variation mainly results from decreasing thickness of bone cement near the milling head contact point due to material removal. Hence the proposed method does not generate a 3D volume allowing for a milling path generation prior to the process. It requires a strategy for real time path generation using only the limited local information. Up to now, only the differentiation between bone cement and bone, and thus the cement-bone interface breakthrough, is reliably detectable. To efficiently use this information for the tool path generation, generic a-priori knowledge of the bone cement shape after removal of the prosthesis stem is used. The concept for impedance controlled milling has been verified in first lab trials. For impedance measurements during the cement removal process the robots milling tool has been modified to achieve electrical insulation of the milling head. A strategy for online adaptive robot path planning has been implemented and tested in a Matlab/Simulink based process simulation. For all data sets a cement removal rate of about 90% with a bone removal of approximately 3% was achieved. These results confirm that it is generally possible to use only the limited local information for automated cement removal. Future work aims for a practical evaluation of the algorithm using real impedance measurement values. This work has been funded by the German Ministry for Education and Research (BMBF) in the framework of the ICOS project under grant No. BMBF 13EZ1005

INTRODUCTION. Most total knees today are CR or PS, with lateral and medial condyles similar in shape. There is excellent durability, but a shortfall in functional outcomes compared with normals, evidenced by abnormal contact points and gait kinematics, and paradoxical sliding. However unicondylar, medial pivot, or bicruciate retaining, are preferred by patients, ascribed to AP stability or retention of anatomic structures (Pritchett; Zuiderbaan). Recently, Guided Motion knees have been shown to more closely reproduce anatomic kinematics (Walker; Willing; Amiri; Lin; Zumbrunn). As a design approach we proposed Design Criteria: reproduce the function of each anatomic stabilizing structure with bearing surfaces on the lateral and medial sides and intercondylar; resected cruciates because this is surgically preferred; avoid a cam-post because of central femur bone removal, soft tissue entrapment, noises, and damage (Pritchett; Nunley). Our hypothesis was that these criteria could produce a Guided Motion design with normal kinematics. METHODS & MATERIALS. Numerous studies on stability and laxity showed the ACL was essential to controlling posterior femoral displacement on the tibia whether the knee was loaded or unloaded. Under load, the anterior upwards slope of the medial tibial plateau prevented anterior displacement (Griffen; Freeman; Pinskerova; Reynolds). The posterior cruciate and the downward lateral tibial slope produced lateral rollback in flexion. The Replica Guided Motion knee had 3 bearings (Fig 1). The lateral side was shallow and sloped posteriorly, with a posterior lip to prevent excess displacement. The medial anterior tibial and femoral slopes were increased as in the anatomic knee. In the intercondylar region, a saddle bearing replaced ACL function by controlling posterior femoral displacement. For testing, a typical PS design was used as comparison. A Knee Test Machine (Fig 2) flexed the knee, and applied axial compression, shear and torque to represent a range of functions. Bone shapes were reproduced by 3D printing and collaterals by elastomeric bands. Motion was recorded with a digital camera, and Geomagic to process data. RESULTS. The kinematics of normal knees was the benchmark (Arno). The results for neutral path of motion, and the AP laxity about the neutral path, are shown (Fig 3). The PS showed symmetric motion, with anterior medial sliding and excessive constraint in low and high flexion. For the Replica, the medial condyle remained almost constant, but the lateral side rolled posteriorly with flexion, less than normal to prevent damage to the posterior lateral tibial plastic. The lateral side had similar anterior laxity to anatomic, but more than anatomic in late flexion. Based on 10 parameter motion scoring, the Replica was closer to normal than the PS, 82% cf 51%. DISCUSSION. Functional outcomes after TKA are less than normal, TKA design being a likely factor. The approach shown here is intended to reproduce more anatomic kinematics of neutral path of motion and laxity. Such a Replica Guided Motion knee, based on an anatomic structure/stability approach, could reproduce close to normal kinematics even without the cruciates or a cam-post. This may result in improved functional outcomes, and a closer feeling of a normal knee. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

The well-fixed cemented femoral stem and surrounding cement can be challenging to remove. Success requires evaluation of the quality of the cement mantle (interface lucency), position of the stem, extent of cement below the tip of the stem and skill with the specialised instruments and techniques needed to remove the stem and cement without perforating the femur. Smooth surfaced stems can usually be easily removed from the surrounding cement mantle with a variety of stem extractors that attach to the trunnion or an extraction hole on the implant. Roughened stems can be freed from the surrounding cement mantle with osteotomes or a narrow high speed burr and then extracted with the above instruments. Following this, the well-fixed cement mantle needs to be removed. Adequate exposure and visualization of the cement column is essential to remove the well-fixed cement without damage to the bone in the femur. This is important since fixation of a revision femoral component typically requires at least 4 cm of contact with supportive cortical bone, which can be difficult to obtain if the femur is perforated or if the isthmus damaged. Proximally, cement in the metaphyseal region can be thinned with a high speed burr, then split radially and removed piecemeal. It is essential to remember that both osteotomes and high speed burrs will cut thru bone easier than cement and use of these instruments poses a substantial risk of unintended bone removal and perforation of the femur if done improperly. These instruments should, as a result, be used under direct vision. Removal of more distal cement in the femur typically requires use of an extended femoral osteotomy (ETO) to allow for adequate access to the well-fixed cement in the bowed femoral canal. An ETO also facilitates more efficient removal of cement in the proximal femur. The ETO should be carefully planned so that it is distal enough to allow for access to the end of the cement column and still allow for stable fixation of a new implant. Too short of an ETO increases the risk of femoral perforation since the straight cement removal instruments cannot negotiate the bowed femoral canal to access the end of the cement column without risk of perforation. An ETO that is too distal makes cement removal easier, but may not allow for sufficient fixation of a new revision femoral stem. Cement below the level of the ETO cannot be directly visualised and specialised instruments are necessary to safely remove this distal cement. Radiofrequency cement removal devices use high frequency (ultrasonic) radio waves to melt the cement within the canal. Although cement removal with these devices is time consuming and tedious, they do substantially reduce the chances of femoral perforation. These devices can, however, generate considerable heat locally and can result in thermal injury to the bone and surrounding tissues. Once the distal end of the cement mantle is penetrated, backbiting or hooked curettes can be use to remove any remaining cement from within the canal. It is important that all cement be removed from the femur since reamers used for preparation of the distal canal will be deflected by any retained cement, which could result in eccentric reaming and inadvertent perforation of the femur and make fixation of a new implant very challenging. An intra-operative x-ray can be very helpful to insure that all cement has been removed before reaming is initiated. One should always plan for a possible femoral perforation and have cortical strut grafts and a stem available that will safely bypass the end of the cement column and the previous cement restrictor

Distal femoral fractures in elderly patient occurred with lower energy injury due to preexisting osteoporosis. Gonarthrosis is frequently accompanied in these patients, and which is difficult to treatment and hard to restore function. Traditionally, the fractures in osteoarthritic knee are treated by open reduction and internal fixation (ORIF) and total knee arthroplasty (TKA) for osteoarthritis is considered after bone union of the prior fractures. However two-stage procedure makes some problems when TKA is performed following long immobilization, previous scar, implant removal, prolonged hospital stay, and increased cost. Several authors have reported acceptable results of primary TKA with concomitant ORIF using long stem with hinged, constrained type or posterior stabilized prosthesis, but which generally need substantial bone removal for notch preparation and is disadvantageous for the fractured extremity. We report 5 patients who were treated with primary TKA with concomitant ORIF for osteoarthritic knee accompanied by distal femoral fracture using ADVANCE Medial Pivot knee (Wright Medical, Arlington, TN) in which prosthesis stem extension can be used without notch cutting. All patents were women with mean age of 79 (69–87 years). There was 1 case of medial femoral condylar fracture, 2 cases of supracondylar fractures and 2 cases of supracondylar/intercondylar femoral fractures. Fracture is well reduced in all cases and well united. The range of motion was good (mean 1–112, flexion contracture 0–5, maximal flexion 90–130) at mean follow-up of 12.6 months (range, 5–33 months). We believe that one-stage primary TKA using medial pivot knee is a reasonable alternative treatment for osteoarthritic knees accompanied by distal femoral fractures if a surgeon is experienced in fracture management and arthroplasty

The well-fixed cemented femoral stem and surrounding cement can be challenging to remove. Success requires evaluation of the quality of the cement mantle (interface lucency), position of the stem, extent of cement below the tip of the stem and skill with the specialised instruments and techniques needed to remove the stem and cement without perforating the femur. Smooth surfaced stems can usually be easily removed from the surrounding cement mantle with a variety of stem extractors that attach to the trunnion or an extraction hole on the implant. Roughened stems can be freed from the surrounding cement mantle with osteotomes or a narrow high speed burr and then extracted with the above instruments. Following this, the well fixed cement mantle needs to be removed. Adequate exposure and visualization of the cement column is essential to remove the well-fixed cement without damage to the bone in the femur. This is important since fixation of a revision femoral component typically requires at least 4cm of contact with supportive cortical bone, which can be difficult to obtain if the femur is perforated or if the isthmus damaged. Proximally, cement in the metaphyseal region can be thinned with a high speed burr, then split radially and removed piecemeal. It is essential to remember that both osteotomes and high speed burrs will cut thru bone easier than cement and use of these instruments poses a substantial risk of unintended bone removal and perforation of the femur if done improperly. These instruments should, as a result, be used under direct vision. Removal of more distal cement in the femur typically requires use of an extended femoral osteotomy (ETO) to allow for adequate access to the well-fixed cement in the bowed femoral canal. An ETO also facilitates more efficient removal of cement in the proximal femur. The ETO should be carefully planned so that it is distal enough to allow for access to the end of the cement column and still allow for stable fixation of a new implant. Too short of an ETO increases the risk of femoral perforation since the straight cement removal instruments cannot negotiate the bowed femoral canal to access the end of the cement column without risk of perforation. An ETO that is too distal makes cement removal easier, but may not allow for sufficient fixation of a new revision femoral stem. Cement below the level of the ETO cannot be directly visualised and specialised instruments are necessary to safely remove this distal cement. Radiofrequency cement removal devices (OSCAR) use high frequency (ultrasonic) radio waves to melt the cement within the canal. Although cement removal with these devices is time consuming and tedious, they do substantially reduce the chances of femoral perforation. These devices can, however, generate considerable heat locally and can result in thermal injury to the bone and surrounding tissues. Once the distal end of the cement mantle is penetrated, backbiting or hooked curettes can be used to remove any remaining cement from within the canal. It is important that all cement be removed from the femur since reamers used for preparation of the distal canal will be deflected by any retained cement, which could result in eccentric reaming and inadvertent perforation of the femur and make fixation of a new implant very challenging. An intraoperative x-ray can be very helpful to insure that all cement has been removed before reaming is initiated

Introduction:. Acetabular revision Jumbo cups are used in revision hip surgeries to allow for large bone to implant contact and stability. However, jumbo cups may also result in hip center elevation and instability. They may also protrude through anterior wall leading to ilopsoas tendinitis. Methods:. The study was conducted using two methods:. Computer simulation study. 265 pelvic CT scans consisting of 158 males and 107 females were converted to virtual 3-dimensional bones. The average native acetabular diameter was 52.0 mm, SD = 4.0 mm (males in 52.4 mm, SD = 2.8 mm and 46.4 mm, SD = 2.6 mm in females). Images were analyzed by custom CT analytical software (SOMA™ V.3.2). 1. and over-sized reaming was simulated. Four distinct points, located in and around the acetabular margins, were used to determine the reamer sphere. Points 1, 2, 3 were located at the inferior and inferior-medial acetabular margins, and Point 4 was located superiorly and posteriorly in the acetabulum to simulate a bony defect in this location, Point 4 was placed at 10%, 20%, 30%, 40%, 50% and 60% of the distance from the superior – posterior margin of the acetabular rim to the sciatic notch to simulate bony defects of increasing size. (Figure 1). Radiographical study. Retrospective chart review of patient records for all cementless acetabular revisions utilizing jumbo cups between January 1, 1998 and March 30, 2012 at UCFS (98 patients with 57 men, 41 women). Jumbo cups: ≥66 mm in males; <62 mm in females. Reaming was directed inferiorly to the level of the obturator foramen to place the inferior edge of the jumbo cup at the inferior acetabulum. To determine the vertical position of the hip center, a circle was first made around both the jumbo and the contralateral acetabular surfaces using Phillips iSite PACS software. The center of this circle was assumed to correspond to the “hip center”. The height of the hip center was estimated by measuring the height of a perpendicular line arising from the interteardrop line (TL) and ending at the hip center. Results:. The computer simulation and radiographic analysis deomonstrated similar results. The computer simulation predicted that the hip center shifted superiorly and anteriorly as the reamer size increased. The hip center shifted 0.27 mm superiorly and 0.02 mm anteriorly for every millimeter in diameter increased for the reaming. (Figure 2) Anterior column bone removal was increased 0.86 mm for every 1 mm of reamer size increase. (Figure 3). Results of radiographical study is shown in Table bellow:. Discussion:. Use of a jumbo cup in revision THA results in elevation of the hip center. Therefore a longer femoral head may be needed to compensate for hip center elevation when a jumbo cup is used. Reaming for a jumbo cup can also result in loss of anterior bone stock and protrusion of the cup anteriorly which may cause iliopsoas tendonitis

Digital templating was used in 50 patients who underwent THA using Merge Ortho software, Cedara. Clinical examination was performed first, to measure leg lengths and account for pelvic obliquity and flexion deformity. Good quality digital radiographs were obtained with anteroposterior and lateral views extending beyond the tip of the femoral component and the cement restrictor. A coin was placed on the ASIS to help in determining radiological magnification. Digital radiographs were saved in DICOM format and imported to EndoMap software system. A 6-step technique was used for templating as follows:. Radiographic assessment; looking at the quality of bone, amount of bone stock, dysplasia, osteophytes, and other abnormalities. Correction of magnification; following the specific instructions of the software, by measuring the diameter of the coin on the digital radiograph. 3. Measuring leg length discrepancy; the software system automatically calculated the leg length discrepancy, even in the presence of pelvic obliquity (Figure1). 4. Templating acetabular component; the desired cup was selected from the implant library after identifying important landmarks. The size and position was modified to fit the acetabulum and to restore the center of rotation of the hip, considering minimal bone removal and sufficient bone coverage laterally. Templating femoral component; the size and position of the desired stem was adjusted to fit the femoral canal, different offsets were compared to find the best match for the patient's original offset. Correction of leg length discrepancy and measuring length of neck resection; the height of the femoral stem was adjusted to correct any leg length discrepancy by placing the center of the head above the center of the cup by the same length of discrepancy. Then the level of the neck resection was marked at the level of the stem collar and the femoral neck cut was measured by a digital ruler from the tip of the lesser trochanter to the mark of neck resection. In case of leg length discrepancy, the height of the femoral neck cut was adjusted accordingly to compensate for the leg length discrepancy. For example, if the affected leg is 20 mm short, place the centre of the head 20 mm above the centre of the cup. Intraoperatively, the surgeon performed the femoral neck osteotomy at the level determined by preoperative templating. Postoperatively, the leg length was measured and compared to the preoperative leg length. Preoperatively, the leg length discrepancy ranged from 5 to 30 mm. In all cases, the leg was short on the side of THR (ipsilateral). Leg length discrepancy was adjusted in all THR cases. Postoperatively, the accuracy of the correction was found to be within 5 millimeters i.e. less than 5mm of shortening or lengthening). Intraoperatively, the level of femoral neck cut ranged from 1 to 44 mm. Digital templating is useful in adjusting leg length discrepancy. In addition, there were other benefits such as predication of femoral and acetabular implant sizes, restoration of normal hip centre, and optimization of femoral offset