Introduction. Instability continues to be the number one reason for revision in primary total hip arthroplasty (THA). Commonly, impingement precedes dislocation, inducing a levering out the prosthetic head from the liner. Impingement can be prosthetic, bony or soft tissue, depending on component positioning and anatomy. The aim of this virtual study was to investigate whether bony or prosthetic impingement occurred first in well positioned THAs, with the hip placed in deep flexion and hyperextension. Methods. Twenty-three patients requiring THA were planned for a TriFit/Trinity ceramic-on-poly cementless construct using the OPS. TM. dynamic planning software (Corin, UK). The cups were sized to best fit the anatomy, medialised to sit on the acetabular fossa and orientated at 45° inclination and 25° anteversion when standing. Femoral components and head lengths were then positioned to reproduce the native anteversion and match the contralateral leg length and offset. The planned constructs were flexed and internally rotated until anterior impingement occurred in deep flexion [Fig. 1]. The type (bony or prosthetic), and location, of impingement was then recorded. Similarly, the hips were extended and externally rotated until posterior impingement occurred, and the type and location of impingement recorded [Fig. 2]. Patients with minimal pre-operative osteophyte were selected as a best-case scenario for bony impingement. Results. 6/23 (26%) patients were planned with only a 32mm articulation (<50mm cup size), with the remaining 17 patients all planned with both 32mm and 36mm articulations (≥50mm cup size). Anterior impingement was 26% prosthetic and 74% bony with the 32mm articulations, and 100% bony with the 36mm articulations. Bony impingement in deep flexion was exclusively anterior neck on anterior inferior iliac spine. Posterior impingement was 57% prosthetic and 43% bony with the 32mm articulations, and 41% prosthetic and 59% bony with the 36mm articulations. Bony impingement in hyperextension was exclusively lesser trochanter (LT) on ischium. Of the patients planned with both 32mm and 36mm articulations, there was a 14% increase in prosthetic impingement when a 32mm head was planned (35% and 21% respectively). Discussion. Impingement in THA usually precedes dislocation and should be avoided with appropriate component positioning. We found that in hyperextension, prosthetic and bony impingement were equally common. In deep flexion, impingement was almost exclusively bony. Further studies should investigate the effects of stem version, cup orientation, liner design, cup depth, native offset and retained osteophytes on the type of impingement in THA. For any figures or tables, please contact the authors directly

Aims. Traumatic central cord syndrome (CCS) typically follows a hyperextension injury and results in a motor impairment affecting the upper limbs more than the lower limbs, with occasional sensory impairment and urinary retention seen. Current evidence on mortality and long-term outcomes is limited. The primary aim of this study is to assess the five-year mortality of CCS, and to determine any difference in mortality between management groups or age. Patients and Methods. Patients ≥18 years with traumatic CCS between January 2012 and December 2017 in Wales were identified. Patient demographics and injury, management and outcome data was collected. Statistical analysis was performed to assess mortality and between group differences. Results. 65 patients were identified (66.2% male, mean age 63.9 years). At five-years follow-up, 32.3% (n=21) of CCS patients were dead. 6 (9.2%) patients had died within 31 days of their injury. 69.2% (n=45) of patients were managed conservatively and there was no significant difference (p=0.062) in age between conservatively and surgically managed patients. Kaplan-Meier analysis revealed no significant difference in mortality between patients managed conservatively compared to those managed surgically (log rank test, p=0.819). However, there was a significant difference (p=0.001) in mortality between the different age groups (<50 years vs 50–70 years vs >70 years). At five-years follow up, 55.6% of the patient group aged >70 years at time of injury were dead. Respiratory failure was the most common cause of death (n=9, 42.9%). Conclusion. Almost one third of patients with traumatic CCS in Wales were dead at five years following their injury. Management type did not significantly affect mortality, however age at time of injury did. Further work assessing the long-term functional outcomes of surviving patients is needed, to allow more reliable prognostic information and functional recovery predictions to be given

Introduction. Genu recurvatum deformities are unusual before total knee arthroplasty (TKA), occurring in less than 1% of patients. The purpose of this study is to evaluate the clinical and radiographic results of primary TKA in patients that had recurvatum deformities before surgery. Patients and Methods. The inclusion criteria was to have recurvatum deformity over 10 degrees on lateral standing X-ray view. We retrospectively reviewed 22 knees with pre-operative recurvatum deformities, and the incident was 1.0% of all TKAs at our hospital. The etiology of the arthritis was osteoarthritis in 21 knees, of which 3 knees were neuropathic disease, and rheumatoid arthritis in 1 knee. There were 6 men and 16 women, and the average age was 73.3 years (range, 53 to 83 years) at the time of operation. The average follow-up period was 15 months (range, 3 to 81 months). We performed to use medial parapatellar approach and bone cutting was done by measured resection technique. The surgical knacks were resection of less distal femur and proximal tibia bone to make extension gap tightly, additionally decrease the tibial posterior slope. Posterior-stabilizer (PS) implants (NexGen LPS: Zimmer, Bisurface KU4+: JMM) were used in 20 knees and constrained implants (NexGen RH knee: Zimmer, Endo-Model Hinge Knee: Link) were in 2 knees with neuropathic joints. Results. The averaged Knee Society Knee and Function score improved from 33.1 points to 94.1 points, and 28.0 points to 60.5 points at the time of the last follow-up. The femorotibial angle changed from averaged 183.4 degrees (range, 162 to 195 degrees) preoperatively to averaged 173.3 degrees (range, 170 to 177 degrees). Preoperative hyperextension was averaged 18.2 degrees (range, 10 to 40 degrees). Intraoperatively, the hyperextension deformity was corrected in all cases. The tibial posterior slope was averaged 1.7 degrees (range, −2.7 to 6 degrees). The final hyperextension improved averaged 6.9 degrees (range, −1.7 to 26.6 degrees), all but one knee were corrected. One case treated with a standard PS type, who was associated with neuropathic disease, had a recurrence of recurvatum deformity and required revision surgery. Discussion. Recurvatum may be associated with a severe osseous deformity, capsular or ligamentous laxity, and neuromuscular disease. Surgical solutions may be to use a standard PS prosthesis with a slight underresection of the bone edge, and decrease tibial posterior slope. An alternative solution is to use a rotating-hinge prosthesis with less than antigravity quadriceps strength for neuromuscular disease

Introduction. Genu recurvatum is a deformity rarely seen in patients receiving total knee arthroplasty. This deformity is defined as hyperextension of the knee greater than 5°. The incidence of recurvatum has been cited in the literature as less than 1%. Purpose. The purpose of this study was to report data on 1510 consecutive total knee replacements (TKR) with navigation to demonstrate that the incidence of genu recurvatum is higher than what is cited in the literature. Methods. This is a retrospective review that was approved by our health science institutional review board. We reviewed resting, intra-operative alignment of 206 navigated total knee arthroplasty cases with recurvatum. This is data from 4 surgeons who are lower extremity joint replacement physicians. The range of motion (ROM) is measured and recorded by the attending physician during routine physical examination of the lower extremity. Demographic data was used to describe the patient group. The data will include pre-operative, intra-operative and post-operative ROM. The intra-operative data will be captured by the navigation system, this sytem is accurate to 1° and 1mm. The post-operative ROM will be obtained from an office visit. We are interested in the post-operative ROM to demonstrate correction of the recurvatum. Results. One thousand five hundred and ten primary TKR were reviewed for this study. Two hundred and six patients (13.6%) had genu recurvatum as measured by the navigation computer. The range of recurvatum was 0.5–30°; mean 5 degrees (STD 4.3°). Sixty six patients had >5 degrees of recurvatum (4.4%). Only 2 patients had recurvatum recorded on their pre-operative office visit. These 2 patients did not have extreme recurvatum, 3° and a few degrees on walking respectively. No patient had recurvatum at the 4 year visit (visit range 3 months – to 4 years). The primary diagnosis for the group was osteoarthritis, 92 %. All cases of recurvatum were treated with under resection of the femur and correction of the coronal plane. All cases were corrected intraoperatively. Conclusion. Etiology of recurvatum can be due to bony insufficiency at the anterior tibia, insufficiency at both femoral condyles or laxity of the posterior capsule and ligaments. During surgery this can be addressed by under resection of the femur and undersizing the femoral component to increase the flex space, or soft tissue tightening can be implemented. Our surgical technique aimed to balance hyperextension with reduction of the distal femoral cut. Coronal balance is also important in the management of hyperextension. Current total knee designs lack the extension cam effect and make sagital balancing critical. Recurvatum is difficult to correct after total knee arthroplasty and this issue is important to address at the time of primary surgery. The use of a navigation system helped us appreciate a deformity that is not easily detected during routine examination. This study found that genu recurvatum in patients receiving TKR is significantly higher than what is reported in the literature. This finding has important implications for the management of a small percentage but nonetheless significant number of patients. This deformity is not appreciated in the clinical setting during routine examination

Introduction. Severe angular deformities in total knee arthroplasty require specific attention to bone resections and soft tissue balancing. This can add technical complexity and time, with some authors reporting an increase of approximately 20 minutes in mean surgery time when managing large deformities with conventional instrumentation [1]. We evaluate the utility of computer-navigation with imageless BoneMorphing® and Apex Robotic Technology, or A.R.T.® for managing large deformities in TKA. BoneMorphing® allows for real-time visualization of virtual bone resection contours, limb alignment and soft-tissue balance during TKA. A.R.T. permits accurate cutting and recutting of the distal femur in 1 mm increments. We asked what effects do severe pre-operative deformities have on post-operative alignment and surgery time in comparison to knees with only mild deformities when using this system. Methods. This was a retrospective cohort study of 128 consecutive A.R.T. TKA's performed by a single surgeon (mean age: 71 y/o [range 53–93], BMI: 31.1 [20–44.3], 48 males). Patients were stratified into three groups according to their pre-operative coronal plane deformity: Neutral or mild deformity <10° (baseline group); Severe varus ≥10°; and Severe valgus ≥10°; and according to the degree of flexion contracture: Neutral or mild flexion from −5° hyperextension to 10° flexion (baseline group); Hyperextension ≤−5°, and Severe flexion ≥10°. The degree of deformity and final postoperative alignment achieved was measured using computer navigation in all patients and analyzed using multivariate regression. The APEX CR/Ultra Knee System (OMNIlife Science, Inc.) was used in all cases. Results. Pre-operative coronal alignment ranged from 27° varus to 22° valgus (figure 1). Postoperative alignment across all patients ranged from 2° valgus to 3.5° varus (figure 2), and from 4° flexion to −4° hyperextension. Effect of deformity on alignment accuracy. Mean post-operative alignment was 1.4° varus in the control group, 0.4° varus in the severe valgus group (p=0.004), and 1.8° varus in the severe varus group (p=0.111). Preoperative flexion, obesity, and gender had no significant effect on alignment accuracy or final extension. Tourniquet time. Mean tourniquet time for the control group was 48.8 minutes [95% CI: 45.3–52.4] (figure 3). Severe varus knees took 4.8 min longer (p=0.006), while valgus knees took 2.9 min longer (p=0.260). Flexion contractures ≥10° and ≥15° increased tourniquet time by 3.8 min (p=0.152) and 10 min (p=0.033), respectively. Tourniquet time was slightly longer in obese patients by 3.2 min (p = 0.048) and was 6.3 min shorter for females than males (p<0.001). Conclusions. We have shown that in one surgeon's hands severe coronal deformities and flexion contractures can be consistently corrected to within 3–4° of neutral when using A.R.T. This is achieved by assessing the pre-resection kinematics, formulating a virtual plan, and executing and validating in real time that plan's execution. The additional time required for managing these more difficult cases using this technology was typically less than 5 minutes, which demonstrates the effectiveness of real-time navigation and robotics for TKA

Introduction. The large diameter mobile polyethylene liner of the dual mobility implant provides increased resistance to hip dislocation. However, a problem specific to the dual mobility system is intra-prosthetic dislocation (IPD), secondary to loss of the retentive rim, causing the inner head to dissociate from the polyethylene liner. We hypothesized that impingement of the polyethylene liner with the surrounding soft-tissue inhibits liner motion, thereby facilitating load transfer from the femoral neck to the liner and leading to loss of retentive rim over time. This mechanism of soft-tissue impingement with the liner was evaluated via cadaver experiments, and retrievals were used to assess polyethylene rim damage. Methods. Total hip arthroplasty was performed on 10 cadaver hips using 3D printed dual mobility components. A metal wire was sutured to the posterior surface (underside) of the iliopsoas, and metal wires were embedded into grooves on the outer surface of the liner and inner head to identify these structures under fluoroscopy. Tension was applied to the iliopsoas to move the femur from maximum hyperextension to 90° of flexion for the purpose of visualizing the iliopsoas and capsule interaction with the mobile liner. The interaction of the mobile liner with the iliopsoas was studied using fluoroscopy and direct visual observation. Fifteen retrieved dual mobility liners were assessed for rim edge and rim chamfer damage. Rim edge damage was defined as any evidence of contact, and rim chamfer damage was classified into six categories: impact ribs on the chamfer surface, loss of machining marks, scratching or pitting, rim deformation causing a raised lip, a rounded rim edge, or embedded metal debris. Results. Manipulation of the cadaver specimens through full range of motion showed liner impingement with the iliopsoas tendon in low flexion angles, which impeded liner motion. At high flexion angles (beyond 30°), the iliopsoas tendon moved away from the liner and impingement was not observed. The fluoroscopy tests using the embedded metal wires confirmed what was observed during manual manipulation of the specimen. When observing the hip during maximum hyperextension, 0°, 15°, and 30° of flexion, there was obvious tenting of the iliopsoas. All retrieved components showed damage on the rim and the chamfer surface. The most common damage seen was scratching/ pitting. There was no association between presence of damage and time in vivo controlling for age and Body Mass Index (p≥0.255). Discussion. The cadaver studies showed that the mobile liner motion could be impeded by impingement with the iliopsoas tendon and hip capsule. Visual and fluoroscopic observation showed impingement of iliopsoas and hip capsule with the distal portion of the mobile liner, particularly during low flexion angles. All retrieved liners showed damage despite their limited time in vivo and despite being retrieved for reasons other than IPD. This suggests that soft-tissue impingement may inhibit liner motion routinely in vivo, resulting in load transfer from the femoral neck on to the rim of the liner. This may be an important mechanism for IPD

Introduction. Post cam is useful to realize the intrinsic stability of a posterior-stabilized (PS) knee prosthesis replaced for a case with the severe degeneration. Some retrieval studies reveal the ultrahigh molecular weight polyethylene (UHMWPE) deformation or severe failure of the tibial post of PS knee. Strength of the tibial post of available design is obviously insufficient to prevent the severe deformation. The large size post might, however, shorten the range of knee motion. Therefore, minimally required size of the post should be clarified for polyethylene inserts. In the present study, we performed finite element (FE) analysis assumed the mechanical conditions of a tibial post in a PS knee and aimed to design criterion of a post of polyethylene insert of a knee prosthesis. Method. The shape of three commercially available knee prostheses, product A, B, and C was referred as PS knee prosthesis. The contour of the metallic femoral component and the UHMWPE insert were digitized by a computed tomography apparatus. Three dimensional finite elements were generated by modeling software (Simpleware, Ltd. UK) as four-node tetrahedral elements. In FE analysis, we used LS-DYNA ver.971 (Livemore Software Technology Corp. USA) as the software and Endeaver Pro-4500 (EPSON Corp. Japan) as the hardware. These bottoms of the tibial insert were fully constrained. The value of 30MPa was defined as yield stress of UHMWPE. 500N posterior load was applied to each femoral component at 10 degree hyperextension. Then, 1000N anterior load at 120 degree flexion, after tibial insert was located 10 degree internal rotation (Fig. 1). These loads were assumed to realize the two types of tibial post impingement under several kinds of knee motions. The distributed values of von Mises stress and plastic strain on the tibial post were shown as the results of the analysis. Results. At the 10 degree hyperextension, these maximum values of von Mises stress were 24.5, 3.23, 27.09MPa on anterior aspect of tibial post of the product A, B, and C, respectively (Fig. 2). These plastic strains were 0.045, 0.001, 0.064. At the 120 degree flexion, these maximum values of von Mises stress were 33.67, 4.53, 27.03MPa on posterior aspect of the product A, B, and C, respectively (Fig. 3). These plastic strains were 0.28, 0.004, 0.061. The stress of product A was higher than yield stress of UHMWPE. The strain was obviously higher than that of product B and C. Discussion. Our results showed that plastic deformation may occur in the posterior aspect of a tibial post by impingement during common exercises like climbing up, or squatting. In the femoro-tibial articulation, the true-stress decreases with increase in load because the compressive deformation can widen the contact area on the UHMWPE. The true-stress in the tibial post, however, increases with increase in load because bending and tensile deformation reduces the section area. Therefore, the design criterion including the post size must be revised the safety coefficient which realizes that the generated stress in the tibial post is sufficiently lower than the yield stress of UHMWPE

Introduction. Post cam structure, which is the main structure of posterior-stabilized design (PS), is useful to realize the intrinsic stability of a knee prosthesis replaced for a case with the severe degeneration. A large size post might, however, shorten the range of knee motion. On the other hand, retrieval studies sometimes reveal the ultrahigh molecular weight polyethylene (UHMWPE) deformation or severe failure of the tibial post of PS knee. Strength of a tibial post of available design is obviously insufficient to prevent the severe deformation. Therefore, minimally required size of the post should be clarified for polyethylene inserts. In the present study, we performed finite element (FE) analysis assumed the mechanical conditions of a tibial post in a PS knee and aimed to design criterion of a post of polyethylene insert of a knee prosthesis. Method. The shape of one commercially available knee prosthesis was referred as a posterior-stabilized knee prosthesis. The contour of the metallic femoral component was traced and digitized by hand. The contour of the UHMWPE insert was digitized by a micro computed tomography apparatus. Three dimensional finite elements were generated by a modeling software (Simpleware, Ltd. UK) as total 83000 four-noded tetrahedral elements. The bottom of the tibial insert was fully constrained. Load on femoral component was assumed to realize the tibial post impingement under several kinds of knee motions. Posterior load 100 N or 500N at the 10 degree hyperextension, anterior load 500N or 1000N during 120 degree flexion were applied (Fig. 1). The software of FE analysis was LS-DYNA ver.971 (Livemore Software Technology Corp. USA). The hardware was Endeaver Pro-4500 (EPSON Corp. Japan). The distributed values of von Mises stress and plastic strain of the tibial post were shown as the results of the analysis. Results. At the 10 degree hyperextension, the maximum values of von Mises stress and plastic strain of anterior aspect of tibial post were 26.0 MPa, 0.054 at posterior load 100 N., 35.3 MPa, 0.383 at posterior load 500N, respectively (Fig. 2). At 120 degree flexion, these values of posterior aspect of tibial post were 27.6 MPa, 0.086 at anterior load 500 N, 32.1 MPa, 0.208 at anterior load 1000N, respectively (Fig. 3). Plastic deformation has occurred on the contact area, as shown in Fig. 2, 3. Discussion. Our results showed that large plastic deformation may occur in the anterior or the posterior aspect of a tibial post by impingement during common exercises like running, climbing up, or squatting. In the femoro-tibial articulation, the true-stress decreases with increase in load because the compressive deformation can widen the contact area on the UHMWPE. The true-stress in the tibial post, however, increases with increase in load because bending and tensile deformation reduces the section area. Therefore, the design criterion of tibial post of PS knee prosthesis including the size of the post must be revised the safety coefficient that realize the sufficiently lower stress generated in the tibial post than the yield stress of UHMWPE

Introduction. Coronal misalignment of the lower limbs is closely related to the onset and progression of osteoarthritis. In cases of severe genu varus or valgus, evaluating this alignment can assist in choosing specific surgical strategies. Furthermore, restoring satisfactory alignment after total knee replacement promotes longevity of the implant and better functional results. Knee coronal alignment is typically evaluated with the Hip-Knee-Ankle (HKA) angle. It is generally measured on standing AP long-leg radiographs (LLR). However, patient positioning influences the accuracy of this 2D measurement. A new 3D method to measure coronal lower limb alignment using low-dose EOS images has recently been developed and validated. The goal of this study was to evaluate the relevance of this technique when determining knee coronal alignment in a referral population, and more specifically to evaluate how the HKA angle measured with this 3D method differs from conventional 2D methods. Materials and methods. 70 patients (140 lower extremities) were studied for 2D and 3D lower limb alignment measurements. Each patient received AP monoplane and biplane acquisition of their entire lower extremities on the EOS system according the classical protocols for LLR. For each patient, the HKA angle was measured on this AP X-ray with a 2D viewer. The biplane acquisition was used to perform stereoradiographic 3D modeling. Valgus angulation was considered positive, varus angulation negative. Student's T-test was used to determine if there was a bias in the HKA angle measurement between these two methods and to assess the effect of flexion/hyperextension, femoral rotation and tibial rotation on the 2D measurements. One operator did measurements 2 times. Results. The average total dose for both acquisitions was 0.75mGy (± 0.11mGy). The 2D and 3D measurements are reported in table 1. Intraoperator reliability was >0,99 for all measurements. In the whole series, 2D–3D HKA differences were >2° in 34% of cases, >3° in 22% of cases, >5° in 9% of cases and >10° in 3% of cases >10°. We compared 2D and 3D measurements according to the degree of flessum/recurvatum (> or <5° and > or <10°). The results are reported in table 2. The statistical analysis of parameters influencing 2D/3D measurements is reported in table 3. Discussion and conclusion. The HKA angle is typically assessed from 2D long-leg radiographs. However, several studies highlighted that 2D assessment of this angle may be affected by patient's positioning. Radtke showed that lower limb rotation during imaging significantly affected measurements of coronal plane knee alignment. Brouwer showed that axial rotation had an even greater effect on the apparent limb alignment on AP radiographs when the knee was flexed. This last finding is particularly relevant as many lower extremities present some amount of flexion or hyperextension, especially in aging subjects. This low dose biplanar EOS acquisitions provide a more accurate evaluation of coronal alignment compared to 2D, eliminating bias due to wrong knee positioning. This study points out the interest of EOS in outliers patients and opens new perspectives for preoperative planning and postoperative control of deformity correction or knee joint replacement

Introduction. The assessment of leg length is essential for planning the correction of deformities and for the compensation of length discrepancy, especially after hip or knee arthroplasty. CT scan measures the “anatomical” lengths but does not evaluate the “functional” length experienced by the patients in standing position. Functional length integrates frontal orientation, flexion or hyperextension. EOS system provides simultaneously AP and lateral measures in standing position and thus provides anatomical and functional evaluations of the lower limb lengths. The objective of this study was to measure 2D and 3D anatomical and functional lengths, to verify whether these measures are different and to evaluate the parameters significantly influencing these potential differences. Material and Methods. 70 patients without previous surgery of the lower limbs (140 lower extremities) were evaluated on EOS images obtained in bipodal standing position according to a previously described protocol. We used the following definitions:. anatomical femoral length between the center of the femoral head (A) and center of the trochlea (B). anatomical tibial length between the center tibial spine (intercondylar eminence) (C) and the center of the ankle joint (D). functional length is AD. global anatomical length is AB + CD. Other parameters measured are HKA, HKS, femoral and tibial mechanical angles (FMA, TMA), angles of flexion or hyperextension of the knee, femoral and tibial torsion, femoro-tibial torsion in the knee, and cumulative torsional index (CTI). All 2D et3D measures were evaluated and compared for their repeatability. Results. Regarding repeatability, an ICC> 0.95 was found for all measurements except for the tibial mechanical angle (0.91 for 2D, 3D 0.92 for 3D). We observed 54/140 lower limbs with Flessum/Recurvatum angles (FRA) >10°. 2D results (mean, SD) were. 41,8mm(2,9) for femoral anatomical length. 36,1mm(2,8) for tibial anatomical length. 78,0mm(5,4) for global anatomical length. 78,5 mm(5,5) for functional length. 7,4°(12,0) for Flessum/Recurvatum angle. −1,5°(6,4) for HKA. 4,9°(2,0) for HKS. 92,1°(3,4) for FMA. 87,1°(3,4) for TMA. 3D results (mean, SD) were. 42,4mm (2,8) for femoral anatomical length. 36,6mm (2,8) for tibial anatomical length. 79,0mm (5,4) for global anatomical length. 78,9mm (5,5) for functional length. 7,2°(12,0) for Flessum/Recurvatum angle. −1,0°(5,9) for HKA. 4,9°(1,5) for HKS. 92,7°(2,7) for FMA. 87,9°(3,9) for TMA. The 2D/3D measurements of functional lengths were statistically significant (p <0.0001. Student's test). For anatomical lengths. 2D/3D measurements were also statistically significant (p <0.0001. Student's test for femoral tibial and global anatomical lengths). Some parameters significantly influenced 2D/3D differences:. for the global anatomical length: FRA P<0,0001, TMA P=0,0173, HKA P=0,0259 and femoro-tibial torsion P=0,0026. for the functional length FRA P=0,0065. Discussion and conclusion. EOS imaging allows to accurately assess the anatomical and functional length experienced by the patient. These new data open new perspectives for planning length or axis corrections and for an optimized evaluation in some medico legal issues after joint replacement or posttraumatic sequelae. This study points out the importance of 3D measurements in outliers cases (varus or valgus cases, flessum or recurvatum of the knee)

Introduction. Aseptic loosening is one of the highest causes for revision in total knee arthroplasty (TKA). With growing interest in anatomically aligned (AA) TKA, it is important to understand if this surgical technique affects cemented tibial fixation any differently than mechanical alignment (MA). Previous studies have shown that lipid/marrow infiltration (LMI) during implantation may significantly reduce fixation of tibial implants to bone analogs [1]. This study aims to investigate the effect of surgical alignment on fixation failure load after physiological loading. Methods. Alignment specific physiological loading was determined using telemetric tibial implant data from Orthoload [2] and applying it to a validated finite element lower limb model developed by the University of Denver [3]. Two high demand activities were selected for the loading section of this study: step down (SD) and deep knee bend (DKB). Using the lower limb model, hip and ankle external boundary conditions were applied to the ATTUNE. ®. knee system for both MA and AA techniques. The 6 degree of freedom kinetics and kinematics for each activity were then extracted from the model for each alignment type. Mechanical alignment (MA) was considered to be neutral alignment (0° Hip Knee Ankle Angle (HKA), 0° Joint Line (JL)) and AA was chosen to be 3° varus HKA, 5° JL. It is important not to exceed the limits of safety when using AA as such it is noted that DePuy Synthes recommends staying within 3º varus HKA and 3º JL. The use of 5º JL was used in this study to account for surgical variation [Depuy-Synthes surgical technique DSUS/JRC/0617/2179]. Following a similar method described by Maag et al [1] ATTUNE tibial implants were cemented into a bone analog with 2 mL of bone marrow in the distal cavity and an additional reservoir of lipid adjacent to the posterior edge of the implant. Tibial implant constructs were then subjected to intra-operative ROM/stability evaluation, followed by a hyperextension activity until 15 minutes of cement curing time, and finally 3 additional ROM/stability evaluations were performed using an AMTI VIVO simulator. The alignment specific loading parameters were then applied to the tibial implants using an AMTI VIVO simulator. Each sample was subjected to 50,000 DKB cycles and 120,000 SD cycles at 0.8 Hz in series; approximating 2 years of physiological activity. After physiological loading the samples were tested for fixation failure load by axial pull off. Results. Following alignment specific physiological loading the average fixation pull-off load for MA was 3289 ± 400 N and for AA was 3378 ± 133 N (Figure 1). There was no statistically significant difference fixation failure load by axial pull-off between the two alignment types (p=0.740). Conclusion. This study indicated that anatomic alignment, as defined with the alignment limits of this study, does not adversely affect the fixation failure load of ATTUNE tibial implants. For any figures or tables, please contact the authors directly

Introduction. Limb-length discrepancy (LLD) is a common postoperative complication after total hip arthroplasty (THA). This study focuses on the correlation between patients’ perception of LLD after THA and the anatomical and functional leg length, pelvic and knee alignments and foot height. Previous publications have explored this topic in patients without significant spinal pathology or previous spine or lower extremity surgery. The objective of this work is to verify if the results are the same in case of stiff or fused spine. Methods. 170 patients with stiff spine (less than 10° L1-S1 lordosis variation between standing and sitting) were evaluated minimum 1 year after unilateral primary THA implantation using EOS® images in standing position (46/170 had previous lumbar fusion). We excluded cases with previous lower limbs surgery or frontal and sagittal spinal imbalance. 3D measures were performed to evaluate femoral and tibial length, femoral offset, pelvic obliquity, hip-knee-ankle angle (HKA), knee flexion/hyperextension angle, tibial and femoral rotation. Axial pelvic rotation was measured as the angle between the line through the centers of the hips and the EOS x-ray beam source. The distance between middle of the tibial plafond and the ground was used to investigate the height of the foot. For data with normal distribution, paired Student's t-test and independent sample t-test were used for analysis. Univariate logistic regression was used to determine the correlation between the perception of limb length discrepancy and different variables. Multiple logistic regression was used to investigate the correlation between the patient perception of LLD and variables found significant in the univariate analysis. Significance level was set at 0.05. Results. Anatomical femoral length correlated with patients’ perception of LLD but other variables were significant (the height of the foot, sagittal and frontal knee alignment, pelvic obliquity and pelvic rotation more than 10°). Interestingly some factors induced an unexpected perception of LLD despite a non-significant femoral length discrepancy less than 1cm (pelvic rotation and obliquity, height of the foot). Conclusions. LLD is a multifactorial problem. This study showed that the anatomical femoral length as the factor that can be modified with THA technique or choice of prosthesis is not the only important factor. A comprehensive clinical and radiological evaluation is necessary preoperatively to investigate spinal stiffness, pelvic obliquity and rotation, sagittal and coronal knee alignment and foot deformity in these patients. Our study has limitations as we do not have preoperative EOS measurements for all patients. We cannot assess changes in leg length as a result of THA. We also did not investigate the degree of any foot deformities as flat foot deformity may potentially affect the patients perception of the leg length. Instead, we measured the distance between the medial malleolus and ground that can reflect the foot arch height. More cases must be included to evaluate the potential influence of pelvis anatomy and functional orientation (pelvic incidence, sacral slope and pelvic tilt) but this study points out that spinal stiffness significantly decreases the LLD tolerance previously reported in patients without degenerative stiffness or fusion

Aims. The aims of this prospective study were to determine the effect of osteophyte excision on deformity correction and soft- tissue gap balance in varus knees undergoing total knee arthroplasty (TKA). Patients and Methods. Limb deformity in coronal (varus) and sagittal (flexion) planes, medial and lateral gap distances in maximum knee extension and 90° knee flexion and maximum knee flexion were recorded before and after excision of medial femoral and tibial osteophytes using computer navigation in 164 patients who underwent 221 computer-assisted, cemented, cruciate- substituting TKAs. Results. Mean varus and flexion deformities of 4.5°±3° (0.5° to 30° varus) and 4.9°±5.9° (−15° hyperextension to 30° flexion) reduced significantly (p<0.0001) to mean varus deformity of 1°±2.3° and mean flexion deformity of 2.7°±4.2° after excision of medial femoral and tibial osteophytes. The mean medio-lateral (ML) soft-tissue gap difference in maximum knee extension and 90°knee flexion of 2.7±3.6mm and 0.7±2.6mm reduced significantly (p<0.0001) to mean ML soft-tissue gap difference of 0.7±2.5mm in maximum knee extension and 0.1±1.9mm in 90°knee flexion. The mean maximum knee flexion (122.8°±8.4°) increased significantly to mean maximum knee flexion of (125°±8°). Conclusion. Excision of medial femoral and tibial osteophytes during TKA in varus knees significantly improves varus and flexion deformities, mediolateral soft-tissue gap imbalance in maximum extension and in 90°knee flexion and maximum knee flexion. Clinical Relevance. Excision of medial femoral and tibial osteophytes can be a useful, initial step towards achieving deformity correction and gap balance without having to resort to soft-tissue release during TKA in varus knees

The patterns of nerve and associated skeletal injury were reviewed in 84 patients referred to the brachial plexus service who had damage predominantly to the infraclavicular brachial plexus and its branches. Patients fell into four categories: 1. Anterior glenohumeral dislocation (46 cases); 2. ‘Occult’ shoulder dislocation or scapular fracture (17 cases); 3. Humeral neck fracture (11 cases); 4. Arm hyperextension (9 cases). The axillary (38/46) and ulnar (36/46) nerves were most commonly injured as a result of glenohumeral dislocation. The axillary nerve was ruptured in only 2 patients who had suffered high energy trauma. Ulnar nerve recovery was often incomplete. ‘Occult’ dislocation refers to patients who had no recorded shoulder dislocation but the history was suggestive that dislocation had occurred with spontaneous reduction. These patients and those with scapular fractures had a similar pattern of nerve involvement to those with known dislocation, but the axillary nerve was ruptured in 11 of 17 cases. In cases of humeral neck fracture, nerve injury resulted from medial displacement of the humeral shaft. Surgery was performed in 7 cases to reduce and fix the fracture. Arm hyperextension cases were characterised by injury to the musculocutaneous nerve, with the nerve being ruptured in 8 of 9. Five had humeral shaft fracture or elbow dislocation. There was variable involvement of the median and radial nerves, with the ulnar nerve being least affected. Most cases of infraclavicular brachial plexus injury associated with shoulder dislocation can be managed without operation. Early nerve exploration and repair should be considered for:. Axillary nerve palsy without recorded shoulder dislocation or in association with fracture of the scapula. Musculocutaneous nerve palsy with median and/or radial nerve palsy. Urgent operation is necessary for nerve injury resulting from fracture of the humeral neck to relieve ongoing pressure on the nerves

Peri-prosthetic fractures above a TKA are becoming increasingly more common, and typically occur at the junction of the anterior flange of the femoral component and the osteopenic metaphyseal distal femur. In the vast majority of cases, the TKA is well fixed and has been functioning well prior to fracture. For fractures above well-fixed components, internal fixation is preferred. Fixation options include retrograde nailing or lateral plating. Nails are typically considered in arthroplasties that allow intercondylar access (“open box PS” or CR implants) and have sufficient length of the distal fragment to allow multiple locking screws to be used. This situation is rare, as most distal fragments are quite short. If a nail is chosen, use of a long nail is preferred, since it allows the additional fixation and alignment that diaphyseal fill affords. Short nails should be discouraged since they can “toggle” in the meta-diaphysis and do not engage the diaphysis to improve coronal alignment. Plates can be used with any implant type and any length of distal fragment. The challenge with either fixation strategy is obtaining stable fixation of the distal fragment while maintaining length, alignment, and rotation. Fixation opportunities in the distal fragment can be limited due to obstacles caused by femoral component lugs, boxes, stems, cement mantles, and areas of stress shielding or osteolysis. Modern lateral locked plates can be inserted in a biologically friendly submuscular extra-periosteal fashion. The goal of fixation is to obtain as many long locked screws in the distal fragment as possible. High union rates have been reported with modern locked plating and nailing techniques, however, biplanar fluoroscopic vigilance is required to prevent malalignments, typically valgus, distraction, and distal fragment hyperextension. For certain fractures, distal femoral replacement (DFR) is a wise choice. The author reserves DFR for situations where internal fixation is likely to fail (severe distal osteolysis, severe osteopenia) or for cases where it has already failed (nonunion). Obviously, if the implant is loose, revision is indicated, and typically the distal bone loss is so severe that a distal femoral replacement is indicated. The author prefers cemented constructs and routinely adds antibiotics to the cement mixture. Careful attention to posterior dissection of the distal fragment is recommended to avoid neurovascular injury. Cementing the femoral component in the proper amount of external rotation is important to allow central patellar tracking. The available literature demonstrates excellent functional results with these reconstructions, however, complications are not uncommon. Infection and extensor mechanism complications are the most frequent complications and are best avoided. In summary, ORIF remains the treatment of choice for these fractures, however, for cases where ORIF is likely to fail, or has failed, DFR remains a predictable salvage option

The extent of soft-tissue release and the exact structures that need to be released to correct deformity and balance the knee has been a controversial subject in primary total knee arthroplasty. Asian patients often present late and consequently may have profound deformities due to significant bone loss and contractures on the concave side, and stretching of the collateral ligament on the convex side. Extra-articular deformities may aggravate the situation further and make correction of these deformities and restoration of ‘balance’ more arduous. These considerations do not apply if a hinged prosthesis is used, as may be warranted in an elderly, low-demand patient. However, in active, younger patients, it may be best to avoid use of excess constraint by balancing the soft-tissues and using the least constrained implant. Releasing collateral ligaments during TKA has unintended consequences such as the creation of significant mediolateral instability and a flexion gap which exceeds the extension gap; both of these may require a constrained prosthesis to achieve stability. We will show that soft-tissue balance can be achieved even in cases of severe varus, valgus, flexion and hyperextension deformities without collateral ligament release. The steps are: 1) Determining pre-operatively whether deformity is predominantly intra-articular or extra-articular, 2) Individualizing the valgus resection angle and bony resection depth, 3) Meticulous removal of osteophytes, 4) Reduction osteotomy, posteromedial capsule resection, sliding medial or lateral condylar osteotomy, extra-articular corrective osteotomy, 5) Compensating for bone loss, 6)Only rarely deploying a more constrained device. Case examples will be presented to illustrate the entire spectrum of varus deformities

INTRODUCTION. Tibiofemoral contact at the base of the articular surface spine in posterior-stabilized total knee arthroplasty (TKA) implants can lead to spine fracture [1]. Revision TKA implants also have an articular surface spine to provide sufficient constraint when soft tissues are compromised. While some revision TKA designs have metal reinforcement in the articular surface spine, others rely solely on a polyethylene spine. This study used finite element analysis (FEA) to study the effect of metal reinforcement on stresses in the spine when subjected to posteriorly directed loading. METHODS. Two clinically successful Zimmer Biomet revision TKA designs were selected; NexGen LCCK with metal reinforcement and all-poly Vanguard SSK. The largest sizes were selected. FEA models consisted of the polyethylene articular surface and a CoCr femoral component; LCCK also included a CoCr metal reinforcement in the spine. A 7° and 0° tibial slope, as well as 3° and 0.7° femoral hyperextension, were used for the LCCK and SSK, respectively. A posteriorly directed load was applied to the spine through the femoral component (Figure 1). The base of the articular surface was constrained. The articular surfaces for both designs are made from different polyethylene materials. However, for the purpose of this study, to isolate the effect of material differences on stresses, both were modeled using conventional GUR1050 nonlinear polyethylene material properties. Femoral component and metal reinforcement were modeled using linear elastic CoCr properties. Additionally, the LCCK was reanalyzed by replacing the metal reinforcement component with polyethylene material, in order to isolate the effect of metal reinforcement for an otherwise equivalent design. Frictional sliding contact was modeled between the spine and femoral/metal reinforcement components. Nonlinear static analyses were performed using Ansys version 17 software and peak von mises stresses in the spine were compared. RESULTS. Peak von mises stresses were predicted towards the base of the anterior aspect of the spine in both designs (Figure 2). In LCCK, the high stresses were also predicted on the medial and lateral edges of the anterior spine, matching the tibiofemoral contact (Figure 3). The LCCK with metal reinforcement design predicted 14% and 31% lower stress than LCCK and SSK all-poly designs. DISCUSSION. Clinical reports of spine fracture in TKA highlight the need for further understanding of the biomechanics of spine loading. Here, through comparison of two clinically successful devices, the effect of multiple design factors was quantified. Inclusion of metal reinforcement in the spine, as well as differences in the conforming geometry between the femoral component and the articular surface, resulted in a 31% decrease in polyethylene stress for the LCCK as compared to the all-poly SSK; of which only 16% was attributed to the metal reinforcement. Further improvements to articular surface design, as well as polyethylene material advances, have the potential to result in all-poly designs with strength characteristics equivalent to or exceeding those of designs with metal reinforcement

Introduction. Aseptic loosening of total knee replacements is a leading cause for revision. It is known that micromotion has an influence on the loosening of cemented implants though it is not yet well understood what the effect of repeated physiological loading has on the micromotion between implants and cement mantle. This study aims to investigate effect of physiological loading on the stability of tibial implants previously subjected to simulated intra-operative lipid/marrow infiltration. Methods. Three commercially available fixed bearing tibial implant designs were investigated in this study: ATTUNE. ®. , PFC SIGMA. ®. CoCr, ATTUNE. ®. S+. The implant designs were first prepared using a LMI implantation process. Following the method described by Maag et al tibial implants were cemented in a bone analog with 2 mL of bone marrow in the distal cavity and an additional reservoir of lipid adjacent to the posterior edge of the implant. The samples were subjected to intra- operative range of motion (ROM)/stability evaluation using an AMTI VIVO simulator, then a hyperextension activity until 15 minutes of cement cure time, and finally 3 additional ROM/stability evaluations were performed. Implant specific physiological loading was determined using telemetric tibial implant data from Orthoload and applying it to a validated FE lower limb model developed by the University of Denver. Two high demand activities were selected for the loading section of this study: step down (SD) and deep knee bend (DKB). Using the above model, 6 degree of freedom kinetics and kinematics for each activity was determined for each posterior stabilized implant design. Prior to loading, the 3-D motion between tibial implant and bone analog (micromotion) was measured using an ARAMIS Digital Image Correlation (DIC) system. Measurement was taken during the simulated DKB at 0.25Hz using an AMTI VIVO simulator while the DIC system captured images at a frame rate of 10Hz. The GOM software calculated the distance between reference point markers applied to the posterior implant and foam bone. A Matlab program calculated maximum micromotion within each DKB cycle and averaged that value across five cycles. The implant specific loading parameters were then applied to the three tibial implant designs. Using an AMTI VIVO simulator each sample was subjected to 50,000 DKB and 120,000 SD cycles at 0.8Hz in series; equating to approximately 2 years of physiological activity. Following loading, micromotion was measured using the same method as above. Results. Initial micomotion measurements during DKB activity for ATTUNE. ®. , PFC SIGMA. ®. CoCr, ATTUNE. ®. S+ were 155µm, 246µm, and 104µm, respectively, and following physiological loading were 159µm, 264µm, and 112µm, respectively. While there was statistical significance between the micromotion of implant designs (p<0.05), there was no significance between before and after loading. Conclusion. This study shows there is no significant change in micromotion after approximately 2 years of physiological loading. However, there is a significant difference in micromotion between implant designs

INTRODUCTION. Porous metal bone fillers are frequently used to manage bony defects encountered in revision total knee arthroplasty (rTKA). Compared to structural graft, porous metal bone fillers have shown significantly lower loosening and failure rates potentially due to osseointegration and increased material strength [1]. The strength of porous metal bone fillers used in lower extremities is frequently assessed using compression/shear/torsion test methods, adapted from spine standards. However, these basic methods may lack clinical relevance, and do not provide any insight on the relationship between patient activity and anticipated prosthesis performance. The goal of this study was to evaluate the response of bone fillers under different activities of daily living, in order to define physiologically relevant worst case biomechanics for component evaluation. METHODS. A bone filler tibial augment is shown in Figure 1. A test construct for tibial augments (half-block each for medial and lateral sides) is shown in Figure 2, along with compatible rTKA components. An additional void in the bone was filled using bone cement. Loading was applied through the tibiofemoral contact patches created on polyethylene tibial insert. Loading was used for two activities of daily living; walking and deep knee bend [2–3]. During walking, the tibiofemoral contact patch on the anterior tibial post gets loaded due to femoral hyperextension with 1.2xbody weight (BW), whereas the medial and lateral condyles get loaded with 3xBW compressive load. For deep knee bend, only the condyles get loaded with 4.34xBW. Compared to walking, 45% higher compressive load magnitude in deep knee bend located further posterior was anticipated to create a larger bending moment and induce higher stress on the half augments. A finite element analysis (FEA) was performed by modeling this test construct with a medium size tibial augment. All components were modeled using linear elastic material properties. All interfaces, including the augment-bone interface (representing full bony ingrowth construct) were modeled using bonded contact. The inferior surface of the bone analogue was constrained. Linear static analyses were performed and peak von mises stress predicted in the tibial augments was compared between activities. RESULTS. Deep knee bend resulted in 31% higher stresses in the tibial augments than for walking. High von mises stresses were mostly predicted at the superior/posterior aspect of the internal side of the augment and in the corners of the cutouts. Figure 3 presents the von mises stresses in the tibial augments for both loading scenarios. DISCUSSION. This study revealed that the 45% increased posterior compressive load associated with deep knee bend is a more significant factor than the moment applied to the post during walking gait for a hyperextended knee, when considering the stress in bone filler augments in revision TKA. The stress in the augments can depend on multiple factors and the proposed FEA method can be used to compare stresses in different porous material bone fillers to determine worst case for assessing its strength

Total knee arthroplasty has been the main treatment method among advanced osteoarthritis (OA) patients. The main post-operative evaluation considers the level of pain, stability and range of motion (ROM). The knee flexion level is one of the most important categories in the total knee arthroplasty patient's satisfaction in Asian countries due to consistent habits of floor-sitting, squating, kneeling and cross legged sitting. In this study, we discovered that the posterior capsular release enabled the further flexion angles by 14 degrees compared to the average ROM without posterior release group. Our objective was to increase the ROM using the conventional total knee arthroplasty by the posterior capsular release. Posterior capsular release is being used in order to manage the flexion contraction. Although the high flexion method extends the contact area during flexion by extending the posterior condyle by 2mm, the main problem has been the early femoral loosening. We searched for the method to get the deep knee flexion with the conventional knee prosthesis. 122 OA patients with less than preoperative 130 flexion that underwent conventional TKAs using Nexgen from January, 2014 to September, 2016 were reviewed. Posterior femoral osteophytes were removed as much as possible, but 74 cases were performed posterior capsular release, while 48 cases were not performed. After checking postoperative ROM after 6 months of operation, we compared 74 knees with a posterior capsular release and 48 knees without posterior capsular release. As a result, the average ROM in the posterior capsular release group was 132 degrees, but the average ROM without posterior release group is 118 degrees. No postoperative hyperextension was found when the adequate size of polyethylene (PE) thickness was utilized. Hence, the conventional TKA with a posterior capsular release showed satisfactory clinical outcomes in the deep knee flexion of Asians