Introduction and Objective. Zone 2 flexor tendon injuries are still one of the challenges for hand surgeons. It is not always possible to achieve perfect results in hand functions after these injuries. There is no consensus in the literature regarding the treatment of zone 2 flexor tendon injuries, tendon repair and surgical technique to be applied to the A2 pulley. The narrow fibro-osseous canal structure in zone 2 can cause adhesions and loss of motion due to the increase in tendon volume due to surgical repair. Different surgical techniques have been defined to prevent this situation. In our study, in the treatment of zone 2 flexor tendon injuries; Among the surgical techniques to be performed in addition to FDP tendon repair; We aimed to compare the biomechanical results of single FDS slip repair, A2 pulley release and two different pulley plasty methods (Kapandji and V-Y pulley plasty). Materials and Methods. In our study, 12 human upper extremity cadavers preserved with modified Larssen solution (MLS) and amputated at the mid ½ level of the arm were used. A total of 36 fingers (second, third and the fourth fingers were used for each cadaver) were divided into four groups and 9 fingers were used for each group. With the finger fully flexed, the FDS and FDP tendons were cut right in the middle of the A2 pulley and repaired with the cruciate four-strand technique. The surgical techniques described above were applied to the groups. Photographs of fingers with different loads (50 – 700 gr) were taken before and after the application. Proximal interphalangeal (PIP) joint angle, PIP joint maximum flexion angle and bowstring distance were measured. The gliding coefficient was calculated by applying the PIP joint angle to the single-phase exponential association equation. Results. Gliding coefficient after repair increased by %21.46 ± 44.41, %62.71 ± 116.9, %26.8 ± 35.35 and %20.39 ± 28.78 in single FDS slip repair, A2 pulley release, V-Y pulley plasty and Kapandji plasty respectively. The gliding coefficient increased significantly in all groups after surgical applications (p<0.05). PIP joint maximum flexion angle decreased by %3.17 ± 7.92, %12.82 ± 10.94, %8.33 ± 3.29 and %7.35 ± 5.02 in single FDS slip repair, A2 pulley release, V-Y pulley plasty and Kapandji plasty respectively. PIP joint maximum flexion angle decreased significantly after surgery in all groups (p<0.05). However, there was no statistically significant difference between surgical techniques for gliding coefficient and PIP joint maximum flexion angle. Bowstring distance between single FDS slip repair, kapandji pulley plasty and V-Y pulley plasty showed no significant difference in most loads (p>0.05). Bowstring distance was significantly increased in the A2 pulley release group compared to the other three groups (p<0.05). Conclusion. Digital motion was negatively affected after flexor tendon repair. Similar results were found in terms of gliding coefficient and maximum flexion angle among different surgical methods. As single FDS slipe repair preserves the anatomical structure of the A2 pulley therefore we prefer it as an ideal method for zone 2 flexor tendon repair. However, resection of FDS slip may jeopardizes nutrition to the flexor digitorum profundus tendon which weakens the repair site. Therefore the results must be confirmed by an in vivo study before a clinical recommendation can be made. Keywords: Flexor tendon; injury; pulley plasty; cadaver;

Mechanical alignment (MA) in total knee arthroplasty (TKA), although considered the gold standard, reportedly has up to 25% of patients expressing post-operative dissatisfaction. Biomechanical outcomes following kinematic alignment (KA) in TKA, developed to restore native joint alignment, remain unclear. Without a clear consensus for the optimal alignment strategy during TKA, the purpose of this study was to conduct a paired biomechanical comparison of MA and KA in TKA by experimentally quantifying joint laxity and medial collateral ligament (MCL) strain. 14 bilateral native fresh-frozen cadaveric lower limbs underwent medially-stabilised TKA (GMK Sphere, Medacta, Switzerland) using computed CT-based subject-specific guides, with KA and MA performed on left and right legs, respectively. Each specimen was subjected to sensor-controlled mediolateral laxity tests. A handheld force sensor (Mark-10, USA) was used to generate an abduction-adduction moment of 10Nm at the knee at fixed flexion angles (0°, 30°, 60°, 90°). A digital image correlation system was used to compute the strain on the superficial medial collateral ligament. A six-camera optical motion capture system (Vicon MX+, UK) was used to acquire kinematics using a pre-defined CT-based anatomical coordinate system. A linear mixed model and Tukey's posthoc test were performed to compare native, KA and MA conditions (p<0.05). Unlike MA, medial joint laxity in KA was similar to the native condition; however, no significant difference was found at any flexion angle (p>0.08). Likewise, KA was comparable with the native condition for lateral joint laxity, except at 30°, and no statistical difference was observed. Although joint laxity in MA seemed lower than the native condition, this difference was significant only for 30° flexion (p=0.01). Both KA and MA exhibited smaller MCL strain at 0° and 30°; however, all conditions were similar at 60° and 90°. Medial and lateral joint laxity seemed to have been restored better following KA than MA; however, KA did not outperform MA in MCL strain, especially after mid-flexion. Although this study provides only preliminary indications regarding the optimal alignment strategy to restore native kinematics following TKA, further research in postoperative joint biomechanics for load bearing conditions is warranted

Total knee replacement (TKR) design aims to restore normal kinematics with emphasis on flexion range. The survivorship of a TKR is dependent on the kinematics in six-degrees-of-freedom (6-DoF). Stepping up, such as stair ascent is a kinematically demanding activity after TKR. The debate about design choice has not yet been informed by 6-DoF in vivo kinematics. This prospective randomised controlled trial (RCT) compared kneeling kinematics in three TKR designs. 68 participants were randomised to receive either cruciate retaining (CR-FB), rotating platform (CR-RP) or posterior stabilised (PS-FB) prostheses. Image quality was sufficient for 49 of these patients to be included in the final analysis following a minimum 1-year follow-up. Patients completed a step-up task while being imaged using single-plane fluoroscopy. Femoral and tibial computer-aided design (CAD) models for each of the TKR designs were registered to the fluoroscopic images using bespoke software OrthoVis to generate six-degree-of-freedom kinematics. Differences in kinematics between designs were compared as a function of flexion. There were no differences in terminal extension between the groups. The CR-FB was further posterior and the CR-RP was more externally rotated at terminal extension compared to the other designs. Furthermore, the CR-FB designs was more posteriorly positioned at each flexion angle compared to both other designs. Additionally, the CR-RP design had more external femoral rotation throughout flexion when compared with both fixed bearing designs. However, there were no differences in total rotation for either step-up or down. Visually, it appears there was substantial variability between participants in each group, indicating unique patient-specific movement patterns. While use of a specific implant design does influence some kinematic parameters, the overall patterns are similar. Furthermore, there is high variability indicating patient-specific kinematic patterns. At a group level, none of these designs appear to provide markedly different step-up kinematic patterns. This is important for patient expectations following surgery. Future work should aim to better understand the unique patient variability

Poor soft tissue balance in total knee arthroplasty (TKA) is one of the most primary causes of dissatisfaction and reduced joint longevity, which are associated with postoperative instability and early implant failure. 1. Therefore, surgical techniques, including mechanical instruments and 3-D guided navigation systems, in TKA aim to achieve optimum soft tissue balancing in the knee to improve postoperative outcome. 2. Patella-in-Place balancing (PIPB) is a novel technique which aims to restore native collateral ligament behaviour by preserving the original state without any release. Moreover, reduction of the joint laxity compensates for the loss of the visco-elastic properties of the cartilage and meniscus. Following its clinical success, we aimed to evaluate the impact of the PIPB technique on collateral ligament strain and laxity behaviour, with the hypothesis that PIPB would restore strains in the collateral ligaments. 3. . Eight fresh-frozen cadaveric legs were obtained (KU Leuven, Belgium, H019 2015-11-04) and CT images were acquired while rigid marker frames were affixed into the femur, and tibia for testing. After carefully removing the soft tissues around the knee joint, while preserving the joint capsule, ligaments, and tendons, digital extensometers (MTS, Minnesota, USA) were attached along the length of the superficial medial collateral ligament (MCL) and lateral collateral ligament (LCL). A handheld digital dynamometer (Mark-10, Copiague, USA) was used to apply an abduction or adduction moment of 10 Nm at fixed knee flexion angles of 0°, 30°, 60° and 90°. A motion capture system (Vicon Motion Systems, UK) was used to record the trajectories of the rigid marker frames while synchronized strain data was collected for MCL/LCL. All motion protocols were applied following TKA was performed using PIPB with a cruciate retaining implant (Stryker Triathlon, MI, USA). Furthermore, tibiofemoral kinematics were calculated. 4. and combined with the strain data. Postoperative tibial varus/valgus stresses and collateral ligament strains were compared to the native condition using the Wilcoxon Signed-Rank Test (p<0.05). Postoperative tibial valgus laxity was lower than the native condition for all flexion angles. Moreover, tibial valgus of TKA was significantly different than the native condition, except for 0° (p=0.32). Although, tibial varus laxity of TKA was lower than the native at all angles, significant difference was only found at 0° (p=0.03) and 90° (p=0.02). No significant differences were observed in postoperative collateral ligament strains, as compared to the native condition, for all flexion angles, except for MCL strain at 30° (p=0.02) and 60° (p=0.01). Results from this experimental study supported our hypotheses, barring MCL strain in mid-flexion, which might be associated with the implant design. Restored collateral ligament strains with reduced joint laxity, demonstrated by the PIPB technique in TKA in vitro, could potentially restore natural joint kinematics, thereby improving patient outcomes. In conclusion, to further prove the success of PIPB, further biomechanical studies are required to evaluate the success rate of PIPB technique in different implant designs

Differences at motor control strategies to provide dynamic balance in various tasks in diabetic polyneuropatic (DPN) patients due to losing the lower extremity somatosensory information were reported in the literature. It has been stated that dynamics of center of mass (CoM) is controlled by center of pressure (CoP) during human upright standing and active daily movements. Indeed analyzing kinematic trajectories of joints unveil motor control strategies stabilizing CoM. Nevertheless, we hypothesized that imbalance disorders/CoM destabilization observed at DPN patients due to lack of tactile information about the base of support cannot be explained only by looking at joint kinematics, rather functional foot usage is proposed to be an important counterpart at controlling CoM. In this study, we included 14 DPN patients, who are diagnosed through clinical examination and electroneuromyography, and age matched 14 healthy subjects (HS) to identify control strategies in functional reach test (FRT). After measuring participants’ foot arch index (FAI) by a custom-made archmeter, they were tested by using a force plate, motion analysis system, surface electromyography and pressure pad, all working in synchronous during FRT. We analyzed data to determine effect of structural and functional foot pathologies due to neuropathy on patient performance and postural control estimating FAI, reach length (FR), FR to height (H) ratio (FR/H; normalized FR with respect to height), displacement of CoM and CoP in anteroposterior direction only, moment arm (MA, defined as the difference between CoP and CoM at the end of FRT), ankle, knee and hip joint angles computed at the sagittal plane for both extremities. Kinematic metrics included initial and final joint angles, defined with respect to start and end of reaching respectively. Further difference in the final and initial joint angles was defined as Δ. FAI was founded significantly lower in DPN patients (DPN: 0.3404; HS: 0.3643, p= <0.05). The patients’ FR, FR/H and absolute MA and displacement of CoM were significantly shorter than the control group (p= <0.05). Displacement of CoP between the two groups were not significant. Further we observed that CoM was lacking CoP in DPN patients (mean MA: +0.88 cm), while leading CoP in HS (mean MA: −1.59 cm) at the end of FRT. All initial angles were similar in two groups, however in DPN patients final right and left hip flexion angle (p=0.016 and p=0.028 respectively) and left ankle plantar flexion angle (p=0.04) were smaller than HS significantly. DPN patients had significantly less (p=0.029) hip flexion (mean at right hip angle, Δ=25.0°) compared to HS (Δ=33.53°) and ankle plantar flexion (DPN mean at right ankle angle, Δ=6.42°, HS mean Δ=9.07°; p=0.05). The results suggest that movement of both hip and ankle joints was limited simultaneously in DPN patients causing lack of CoM with respect to CoP at the end of reaching with significantly lower FAI. These results lead to the fact that cutaneous and joint somatosensory information from foot and ankle along with the structure of foot arch may play an important role in maintaining dynamic balance and performance of environmental context. In further studies, we expect to show that difference at control strategies in DPN patients due to restricted functional foot usage might be a good predictor of how neuropathy evolves to change biomechanical aspects of biped erect posture

Abstract. Introduction. Recent reports show that spinopelvic mobility influences outcome following total hip arthroplasty. This scoping review investigates the relationship between spinopelvic parameters (SPPs) and symptomatic femoroacetabular impingement (FAI). Methods. A systematic search of EMBASE, PubMed and Cochrane for literature related to SPPs and FAI was undertaken as per PRISMA guidelines. Clinical outcome studies and prospective/retrospective studies investigating the role of SPPs in symptomatic FAI were included. Review articles, case reports and book chapters were excluded. Information extracted pertained to symptomatic cam deformities, pelvic tilt, acetabular version, biomechanics of dynamic movements and radiological FAI signs. Results. The search identified 42 papers for final analysis out of 1168 articles investigating the link between SPPs and pathological processes characteristic of FAI. Only one (2.4%) study was of level 1 evidence, five (11.9%) studies) were level 2, 17 (40.5%) were level 3 and 19 (45.2%) were level 4. Three studies associated FAI pathology with a greater pelvic incidence (PI), while four associated it with a smaller PI. Anterior pelvic tilt was associated with radiographic overcoverage parameters of FAI. In dynamic movements, decreased posterior pelvic tilt was a common feature in symptomatic FAI patients at increased hip flexion angles. FAI patients additionally demonstrated reduced sagittal pelvic ROM during dynamic hip flexion. Six studies found kinematic links between sagittal spinopelvic movement and sagittal and transverse plane hip movements. Conclusions. Our study shows that spinopelvic parameters can influence radiological and clinical manifestations of FAI, with pelvic incidence, acetabular version and muscular imbalances being aetiologically implicated. These factors may be amenable to non-surgical therapy. Individual spinopelvic mechanics may predispose to the development of FAI. If FAI pathoanatomy already exists, sagittal pelvic parameters can influence whether FAI symptoms develop and is an area of further research interest

The aim is to investigate if there is a relation between patellar height and knee flexion angle. For this purpose we retrospectively evaluated the radiographs of 500 knees presented for a variety of reasons. We measure knee flexion angle using a computer-generated goniometer. Patellar height was determined using computer generated measurement for the selected ratios, namely, the Insall–Salvati (I/S), Caton–Deschamps (C/D) and Blackburne–Peel (B/P) indices and Modified I/S Ratio. A search of an NHS hospital database was made to identify the knee x rays for patients who were below the age of forty. A senior knee surgeon (DC) supervised three trainee trauma and orthopaedics doctors (HA, JM, ES) working on this research. Measurements were made on the Insall–Salvati (I/S), Caton–Deschamps (C/D) and Blackburne–Peel (B/P) indices and Modified I/S Ratio. The team leader then categorised the experimental measurement of patients’ knee flexion angle into three groups. This categorisation was according to the extent of knee flexion. The angles were specifically, 10.1 to 20, 20.1 to 30, and 30.1 to 40 degrees of knee flexion. Out of the five-hundred at the start of the investigation, four hundred and eighteen patients were excluded because they had had either an operation on the knee or traumatic fracture that was treated conservatively

Despite high success rates following total knee arthroplasty (TKA), knee kinematics are altered following TKA. Additionally, many patients report that their reconstructed knee does not feel ‘normal’ [1], potentially due to the absence of the anterior cruciate ligament (ACL), an important knee stabilizer and proprioceptive mechanism. ACL-retaining implants have been introduced with the aim of replicating native knee kinematics, however, there has yet to be a detailed comparison between knee kinematics in the native knee and one reconstructed with an ACL-retaining implant. Six fresh-frozen right legs (77±10 yr, 5 male) were mounted in a kinematic rig and subjected to squatting (40°-105°) motions. The vertical positon of the hip was manipulated with a linear actuator to induce knee flexion while the quadriceps were loaded with an actuator to maintain a vertical load of 90 N at the ankle [2]. Medial/lateral hamstring forces were applied with 50 N load springs. During testing, an infrared camera system recorded the trajectories of spherical markers rigidly attached to the femur and tibia. Two trials were performed per specimen. Following testing on the native knee, specimens were implanted with an ACL-retaining TKA (Vanguard XP, Zimmer Biomet) and all trials were repeated. Three inlay thicknesses were tested to simulate optimal balancing as well as over- (1 mm thicker) and understuffing (1 mm thinner) relative to the optimal thickness. Pre-operative computed tomography scans allowed identification of bony landmarks and marker orientation, which were used define anatomically relevant coordinate systems. The recorded marker trajectories were transformed to anatomical translations/rotations and resampled at increments of 1° of knee flexion. Translations of the medial and lateral femoral condyle centers were scaled to maximum anterior-posterior (AP) width of the medial and lateral tibial plateau, respectively. For all kinematics, statistical analysis between knee conditions was conducted using repeated measures ANOVA in increments of 10° knee flexion. Internal rotation of the tibia was significantly lower (p<0.05) for the three reconstructed conditions relative to the native knee at flexion angles of 60° and below. No significant differences in tibial rotation were observed between the balanced, overstuffed, or understuffed conditions. The varus orientation was not significantly influenced by implantation, regardless of inlay thickness, for all flexion angles. At 40° flexion, the AP position of the femoral medial condyle was significantly more anterior for the native knee relative to the balanced and understuffed conditions. This finding was not significant for the other flexion angles. No significant differences were found for the lateral condyle center AP position at any flexion angle. Preservation of the cruciate ligaments during total knee arthroplasty may allow better physiologic representation of knee kinematics. The implants tested in this study were able to replicate kinematics of the native knee, except for tibial rotation and AP position of the medial femoral condyle in early knee flexion. Interestingly, the impact of inlay thickness was generally small, suggesting some tolerance in the choice of inlay thickness

Abstract. Objectives. Catastrophic neck injuries in rugby tackling are rare (2 per 100,000 players per year) with 38% of these injuries occurring in the tackle. The aim of this study was to determine the primary mechanism of cervical spine injury during rugby tackling and to highlight the effect of tackling technique on intervertebral joint loads. Methods. In vivo and in vitro experimental data were integrated to generate realistic computer simulations representative of misdirected tackles. MRI images were used to inform the creation of a musculoskeletal model. In vivo kinematics and neck muscle excitations were collected during lab-based staged tackling of the player. Impact forces were collected in vitro using an instrumented anthropometric test device during experimental simulations of rugby collisions. Experimental kinematics and muscle excitations were prescribed to the model and impact forces applied to seven skull locations (three cranial and four lateral). To examine the effects of technique on intervertebral joint loads the model's neck angle was altered in steps of 5° about each rotational axis resulting in a total of 1,623 experimentally informed simulations of misdirected tackles. Results. Neck flexion angles and cranial impact locations had the largest effects on maximal compression, anterior shear and flexion moment loads. During posterior cranial impacts compression forces and flexion moments increased from 1500 to 3200 N and 30 to 60 Nm respectively between neck angles of 30° extension and 30° flexion. This was more evident at the C5-C6 and C6-C7 joints. Anterior shear loads remained stable throughout neck angle ranges however during anterior impacts they were directed posteriorly when the neck was flexed. Conclusions. The combination of estimated joint loads in the lower cervical spine support buckling as the primary injury mechanism of anterior bilateral facet dislocations observed in misdirected rugby tackles and highlights the importance of adopting a correct tackling technique. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

During TKA surgery, the usual goal is to achieve equal balancing between the lateral and medial side, which can be achieved by ligament releases or “pie crusting”. However little is known regarding a relationship between the balancing forces on the medial and lateral plateaus during TKA surgery, and the varus and valgus and rotational laxities when the TKA components are inserted. It seems preferable that the laxity after TKA is the same as for the normal intact knee. Hence the first aim of this study was to compare the laxity envelope of a native knee, with the same knee after TKA surgery. The second aim was to examine the relationship between the Varus-Valgus (VV) laxity and the contact forces on the tibial plateau. A special rig that reproduced surgical conditions and fit onto an operating table was designed (Verstraete et al. 2015). The rig allows application of a constant varus/valgus moment, and an internal-external (IE) torque. A series of heel push tests under these loading conditions were performed on 12 non-arthritic half semibodies hip-to-toe cadaveric specimens. Five were used for method development. To measure laxities, the flexion angle, the VV and the IE angle were measured using a navigation system. After testing the native knee, a TKA was performed using the Journey II BCS implant, the navigation assuring correct alignments. Soft tissue balancing was achieved by measuring compressive forces on the lateral and medial condyles with an instrumented tibial trial (Orthosensor, Dania Beach, Florida). At completion of the procedure, the laxity tests were repeated for VV and IE rotation and the contact forces on the tibial plateau were recorded, for the full range of flexion. The average of the varus-valgus and the IE laxity envelope is plotted for the native (yellow), the TKA (pink) and the overlap between the two (orange). The average for six specimens of the contact force ratio (medial/medial+lateral force) during the varus and valgus test is plotted as a function of the laxity for each flexion angle. The Journey II implant replicated the VV laxity of the native knee except for up to 3 degrees more valgus in high flexion. For the IE, the TKA was equal in internal rotation, but up to 5 degrees more constrained in varus in mid range. Plotting contact force ratio against VV laxity, as expected during the varus test the forces were clustered in a 0.85–0.95 ratio, implying predominant medial force with likely lateral lift-off. For the valgus test, the force ratio is more spread out, with all the values below 0.6. This could be due to the different stiffness of the MCL and LCL ligaments which are stressed during the VV test. During both tests the laxity increases progressively with flexion angle. Evidently the geometry knee reproduces more lateral laxity at higher flexion as in the anatomic situation

Abstract. Objectives. The need for gender specific knee arthroplasty is debated. This research aimed to establish whether gender differences in patellar tendon moment arm (PTMA), a composite measure that characterises function of both the patellofemoral and tibiofemoral joints, are a consequence of knee size or other variation. Methods. PTMA about the instantaneous helical axis was calculated from positional data acquired using optical tracking. First, data post-processing was optimised, comparing four smoothing techniques (raw, Butterworth filtered, generalised cross-validation cubic spline interpolated and combined filtered/interpolated) using a fabricated knee. Then PTMA was measured during open-chain extension for N=24 (11 female) fresh-frozen cadaveric knees, with physiologically based loading and extension rates (420°/s) applied. Gender differences in PTMA were assessed before and after accounting for knee size with epicondylar width. Results. Combined smoothing enabled sub-mm accuracy (root-mean-squared (RMS) error 0.16mm, max error 0.47mm), whereas large errors were measured for raw (RMS 3.61mm, max 23.71mm), filtered-only (RMS 1.19mm, max 7.38mm) and interpolated-only (RMS 0.68mm, max 1.80mm) techniques. Before scaling, average PTMA throughout knee flexion was 46mm and mean, maximum, and minimum absolute values of PTMA were larger in males (mean differences >8mm, p<0.001), as were the PTMAs at terminal extension and flexion, and the change in PTMA from peak to terminal extension (differences >4mm, p<0.05). After scaling, the PTMA in deep flexion and the change in PTMA from peak to terminal extension were still larger in male knees (differences >2mm, p<0.05). The flexion angle of peak PTMA, unaffected by scaling, was closer to terminal extension for female knee (female 15°, male 29°, p<0.05). Conclusion. Gender differences in PTMA were identified both before and after accounting for knee size, with implications for gender-specific arthroplasty and musculoskeletal models. The developed measurement framework could also be applied in vivo for accurate measurement of the PTMA. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. OBJECTIVES. Although surgical periacetabular osteotomy (PAO) for hip dysplasia aims to optimise acetabular coverage and restore hip function, it is unclear how surgery affects capsular mechanics and joint stability. The purpose was to examine how the reoriented acetabular coverage affects capsular mechanics and joint stability in dysplastic hips. METHODS. Twelve cadaveric dysplastic hips (n = 12) were denuded to the capsule and mounted onto a robotic tester. The robot positioned each hip in multiple flexion angles (Extension, Neutral 0°, Flexion 30°, Flexion 60°, Flexion 90°) and performed internal-external rotations and abduction-adduction to 5 Nm in each rotational or planar direction. Each hip underwent a PAO, preserving the capsule, and was retested postoperatively in the robot. Paired sample t-tests compared the range of motion before and after PAO surgery (CI = 95%). RESULTS. Pre-operatively, the dysplastic hips demonstrated large ranges of internal-external rotations and abduction-adduction motions throughout all flexion positions. Post-operatively, the PAO slackenend the anterosuperior capsule and tightened the inferior capsule. This increased external rotation in Flexion 60° and Flexion 90° (∆. ER. = +16 and +23%) but provided lateral coverage to decrease internal rotation at Flexion 90° (∆. IR. = –15%). The PAO also reduced abduction throughout, but increased adduction in Neutral 0°, Flexion 30°, and Flexion 60° (∆. ADD. = +34, +30%, +29% respectively). CONCLUSIONS. The PAO provided crucial osseous structural coverage to the femoral head, decreasing hypermobility and adverse loading at extreme hip flexion-extension. However, it also slackened the anterosuperior capsule and increased adduction and external rotation, which may lead to ischiofemoral impingement and adductor irritations. Capsular instability may be secondary to acetabular undercoverage, thus capsular alteration may be warranted for larger corrections or rotational osteotomies. To preserve native hip and delay joint degeneration, it is crucial to preserve capsule and elucidate amount of reorientation needed without causing iatrogenic instability. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Objectives. Implant loosening remains a common cause of total ankle replacement (TAR) revision, and has been associated with wear-mediated osteolysis. Limited pre-clinical studies for TARs have been reported and the variety of experiment settings make it difficult to compare wear rates. Factors such as simulator control mechanism; whether pneumatic or electromechanical, may influence the integrity of the simulator outputs with respect to input profiles. This study compares the wear of a TAR, tested in electromechanical and pneumatic experimental simulators under identical input conditions. Methods. Twelve medium BOX® (MatOrtho Ltd) TARs (n=6 for each simulator) were tested in an electromechanical and pneumatic knee simulator (Simulation Solutions, UK) for 3 million cycles (Mc). Standard ‘Leeds’ displacement-controlled inputs were used. Kinematic performance was investigated by comparing the output profiles against the maximum demanded input values. The lubricant used was 25% new-born calf serum and wear was determined gravimetrically. Results. There was no significant difference (P=0.66) in wear rate between simulators (electromechanical = 15.96 ± 6.37mm. 3. /Mc; pneumatic = 14.51 ± 5.27mm. 3. /Mc). The electromechanical simulator (3157.06 ± 1.52N) achieved the maximum load (3150N), but the pneumatic simulator was unable to attain the demand (2542.34 ± 86.52N). Maximum AP displacement from the electromechanical simulator was 3.27 ± 0.07mm (3.1mm input), compared to 3.62 ± 0.95mm from the pneumatic simulator. Internal/external rotation angle was 7.97° ± 0.00 (8° input) and 7.24° ± 0.12 from the electromechanical and pneumatic simulators respectively. Both simulators achieved the demanded flexion angle (±15°). Conclusions. The outputs from the electromechanical simulator followed the input profiles more closely than the pneumatic simulator. Despite these differences, there was no significant influence on wear rate. The variation in kinematics between simulators was not sufficient to significantly change the tribological conditions of the TAR. The authors recommend the use of electromechanical simulators for future studies where more demanding and adverse conditions may be applied. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Abstract. OBJECTIVES. Cam femoroacetabular impingement (FAI – femoral head-neck deformity) and developmental dysplasia of the hip (DDH – insufficient acetabular coverage) constitute a large portion of adverse hip loading and early degeneration. Spinopelvic anatomy may play a role in hip stability thus we examined which anatomical relationships can best predict range of motion (ROM). METHODS. Twenty-four cadaveric hips with cam FAI or DDH (12:12) were CT imaged and measured for multiple femoral (alpha angles, head-neck offset, neck angles, version), acetabular (centre-edge angle, inclination, version), and spinopelvic features (pelvic incidence). The hips were denuded to the capsule and mounted onto a robotic tester. The robot positioned each hip in multiple flexion angles (Extension, Neutral 0°, Flexion 30°, Flexion 60°, Flexion 90°); and performed internal-external rotations to 5 Nm in each position. Independent t-tests compared the anatomical parameters and ROM between FAI and DDH (CI = 95%). Multiple linear regressions determined which anatomical parameters could predict ROM. RESULTS. The FAI group demonstrated restricted ROM in deep hip flexion, with DDH showing higher ROM in Flexion 30° (+20%, p = 0.03), 60° (+31%, p = 0.001), and 90° (+36%, p = 0.001). In Neutral 0° and Flexion 30°, femoral neck and version angles together predicted ROM (R. 2. = 60%, 58% respectively); whereas in Flexion 60°, pelvic incidence and femoral neck angle predicted ROM (R. 2. = 77%). In Flexion 90°, pelvic incidence and radial alpha angle together predicted ROM (R. 2. = 81%), where pelvic incidence alone accounted for 63% of this variance. CONCLUSIONS. Pelvic incidence is essential to predict hip ROM. Although a cam deformity or acetabular undercoverage can elevate risks of labral tears and progressive joint degeneration, they may not be primary indicators of restrictive hip impingement or dysplastic instability. Better delineating additional spinopelvic characteristics can formulate early diagnostic tools and improve opportunities for nonsurgical management. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Shortening of patellar tendon after total knee arthroplasty (TKA) was previously reported by several studies. Its etiology still remains controversial. Patellar tendon shortening, a direct cause of patella baja, has a dramatic negative impact in terms of clinical outcomes after TKA. Main objective of this study is to assess the feasibility of utilizing a different technique with Ultrasound that is easy to use, cost-effective and able to eliminate the problem of differential magnification occurring in other techniques which count on standard x-rays and to establish the correlation between clinical outcomes and changes in patellar tendon length and thickness after TKA. The study was designed as prospective cohort and, after a minimum of 4-year-follow up period, 47 knees of 24 patients who had undergone primary TKA without patellar resurfacing were included in the study. All patients were scored with Kujala and HSS scores and all patellar tendons were evaluated with USG regarding their length and thickness. We used conventional grey-scale ultrasound imaging (US) to determine any changes in patellar tendon morphology. All cases were evaluated by the same radiologist. The patellar tendon was examined with the knee in 30° flexion. The flexion angle helped to stretch the extensor mechanism and avoid anisotropy (concavity) of the patellar tendon. The transducer was placed along the long axis of the tendon. The patellar tendon was initially examined in the longitudinal plane in order to measure the total length. Then, total length was divided into three parts and sagittal thickness was calculated at the proximal, median, and distal thirds of the patellar tendon. Both the length and thickness of the tendon were measured before surgery and at the 4th year of follow-up. Of the 47 knees that were included in our study, the mean pre-operative and postoperative length of the patellar tendon was 40.78±6.15 mm and 35.93±4.52 mm. Our results suggested significant shortening of the patellar tendon after primary TKA surgery (p<0.05). Intergroup analysis suggested that reduced sagittal thickness in the proximal third of the tendon was more strongly correlated with an increase in functional outcomes (p<0.05). Our results suggested no significant difference in clinical outcome scores between patients with increased or decreased length of the patellar tendon after TKA (p>0.05). We suggest that determining morphologic changes in sagittal thickness as well as length is important in explaining some of the ambiguous causes of anterior knee pain and impaired clinical outcomes after TKA. More accurate documentation of morphologic changes in the patellar tendon after TKA will certainly help to develop new techniques by surgeons or avoid some existing routines that may harm the tendon. USG is a feasible method for evaluating patellar tendon morphology after TKA but more future studies are needed

Physiological kinematics is very difficult to restore after total knee arthroplasty (TKA). A new model of medial stabilized (MS) TKA prosthesis has a high spherical congruence of the internal compartment, which guarantees anteroposterior (AP) stability associated with a flat surface of the insert in the lateral compartment, that allows a greater AP translation of the external condyle during knee flexion. The aim of our study is to evaluate, by dynamic radiostereometric analysis (RSA), the knee in vivo kinematics after the implantation of a MS prosthesis during sit to stand and lunge movements. To describe the in vivo kinematics of the knee after MS Fixed Bearing TKA (GMK Sphere (TM) Medacta International AG, Castel San Pietro, Switzerland) using Model Based dynamic RSA. A cohort of 18 patients (72.1 ± 7.4 years old) was evaluated by dynamic RSA 9 months after TKA. The kinematic evaluation was carried out using the dynamic RSA tool (BI-STAND DRX 2), developed at our Institute, during the execution of sit to stand and lunge movements. The kinematic data were processed using the Grood and Suntay decomposition and the Low Point method. The patients performed two motor tasks: a sit-to-stand and a lunge. Data were related to the flexion angle versus internal-external, varus-valgus rotations and antero-posterior translations of the femur with respect to the tibia. During the sit to stand, the kinematic analysis showed the presence of a medial pivot, with a significantly greater (p=0.0216) anterior translation of the lateral condyle (3.9 ± 0.8 mm) than the medial one (1.6 ± 0.8 mm) associated with a femoral internal rotation (4.5 ± 0.9 deg). During the lunge, in the flexion phase, the lateral condyle showed a larger posterior translation than the medial one (6.2 ± 0.8 mm vs 5.3 ± 0.8 mm) associated with a femoral external rotation (3.1 ± 0.9 deg). In the extension phase, there is a larger anterior translation of the lateral condyle than the medial one (5.8 ± 0.8 mm vs 4.6 ± 0.8 mm) associated with femoral internal rotation (6.2 ± 0.9 deg). Analysing individual kinematics, we also found a negative correlation between clinical scores and VV laxity during sit to stand (R= −0.61) and that the higher femoral extra-rotation, the poorer clinical scores (R= 0.65). The finding of outliers in the VV and IE rotations analysis highlights the importance of a correct soft tissue balancing in order to allow the prosthetic design to manifest its innovative features

Introduction. A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). During DS, the hip flexion angle approximates the functional range of hip motion. In some hip morphologies this femoroacetabular conflict has been shown to occur as early as 80° of hip flexion. So far in-vivo HJRF measurements have been limited to instrumented hip implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). Clearly, young adults have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since hip loading data on this subgroup of the population is lacking and performing invasive measurements would be unfeasible, this study aimed to report a personalised numerical model solution based on inverse dynamics to calculate realistic in silico HJRF values during DS. M&M. Fifty athletic males (18–25 years old) were prospectively recruited for motion and morphological analysis. DS motion capture (MoCap) acquisitions and MRI scans of the lower extremities with gait lab marker positions were obtained. The AnyBody Modelling System (v6.1.1) was used to implement a novel personalisation workflow of the AnyMoCap template model. Bone geometries, semi-automatically segmented from MRI, and corresponding markers were incorporated into the template human model by an automated nonlinear morphing. Furthermore, a state-of-the-art TLEM 2.0 dataset, included in the Anybody Managed Model Repository (v2.0), was used in the template model. The subject-specific MoCap trials were processed to compute squat motion by resolving an overdeterminate kinematics problem. Inverse dynamics analyses were carried out to compute muscle and joint reaction forces in the entire body. Resulting hip joint loads were validated with measured in-vivo data from Knee bend trials in the OrthoLoad library. Additionally, anterior pelvic tilt, hip and knee joint angles were computed. Results. A preliminary set of results (20 out of 50 subjects) was analysed. The average HJRF was 3.42 times bodyweight at the peak of DS (95% confidence interval: 2.99 – 3.85%BW). Maximal hip and knee flexion angles were 113° (109.7°–116.8°) and 116° (109.4 – 123.0°) respectively. The anterior pelvic tilt demonstrated a biphasic profile with peak value of 33° (28.1° – 38.4°). Discussion. A non-invasive and highly personalised alternative for determining hip loading was presented. Consistently higher HJR forces during DS in young adults were demonstrated as opposed to the Orthoload dataset. Similarly, knee and hip flexion angles were much higher, which could support the increase in HJRF. We can conclude that DS hip kinetics in young adults clearly differ from the typical total hip arthroplasty population

The study aimed to compare trochlear profiles in recent total knee arthroplasty (TKA) models and to determine whether they feature improvements compared to their predecessors. The hypothesis was that recent TKA models have more anatomic trochlear compartments and would display no signs of trochlear dysplasia. The authors analyzed the geometry of the 6 following TKA models using engineering software: PFC and Attune (DePuy), NexGen and Persona (Zimmer), Noetos and KneeTec (Tornier). The mediolateral trochlear profiles were plotted at various flexion angles (0°, 15°, 30° and 45°) to deduce the sulcus angle. Analysis of sulcus angles reveals general convergence of recent designs towards anatomic values. At 0° of flexion, sulcus angles of recent implant models were between 156.0–157.4°, while those of previous generation models between 154.5–165.5°. At 30° of flexion, sulcus angles of recent models also lie within 145.7–148.6°, but those of previous models are between 149.5–152.0°. All three manufacturers deepened their trochlear profile at 30° of flexion in recent models compared to earlier designs. Sulcus angles converge towards anatomic values but still exceed radiologic signs of dysplasia by 2–5°. Recent TKA designs have more anatomic trochlear geometries than earlier TKA models by the same manufacturers, but trochlear compartments still exceed radiologic signs of trochlear dysplasia by 2° to 5°. The hypothesis that recent TKA models display no signs of trochlear dysplasia is therefore refuted. Surgeons should be aware of design limitations to optimize choice of implant and extensor mechanisms alignment. Level of evidence: IV geometric implant analysis

Posterolateral rotatory instability (PLRI) is the most common type of elbow instability. It is caused by an insufficiency of the lateral ligamentous complex, which consists mainly of the radial collateral ligament (RCL) and the lateral ulnar collateral ligament (LUCL). Investigate the influence of serial sectioning of the lateral ligamentous complex on elbow stability in a cadaveric model of PLRI. Kinematics of six fresh frozen cadaveric elbow specimens were measured by digitizing anatomical marks with a Microscribe 3DLX digitizing system (Revware Inc, Raleigh, NC). Each specimen was tested under four conditions: Intact, LUCL tear, LUCL and RCL tear, and complete Tear (LUCL, RCL and capsule tear). Each specimen was tested in 30°, 60° and 90° elbow flexion angles. Varus- laxity was measured in supination, pronation, and neutral forearm rotation positions and total forearm rotation was measured with 0.3 Nm of torque. Statistical significant differences between the conditions were detected using a two-way ANOVA with Tukey's post-hoc test. The radial head dislocated in all specimens in LUCL and RCL tear and Comp but not in LUCL tear. Total forearm ROM did not increase form intact to LUCL tear (p>0.05) but significantly increased in LUCL and RCL tear (p=0.0002) and complete tear (p<0.0001) in all flexion angles. Additionally, ROM in LUCL tear significantly differed from LUCL and RCL tear and complete tear (p=0.0027 and p=0.0002). A similar trend was seen with the varus angle. While there was a significant difference when the intact condition was compared to both the LUCLand RCL tear and complete tear conditions (p<0.0001 and p<0.0001), there was no difference between the intact and LUCL tear conditions. LUCL tear alone is not sufficient to cause instability and increase ROM and varus angle, meanwhile the increase of ROM and varus angle with additional capsular tear was not significant compared to LUCL and RCL tear. The increase of ROM after LUCL and RCL tear is an unknown symptom of PLRI

Summary Statement. ACL reconstruction using a quadriceps tendon autograft was quantitatively evaluated using a robotic testing system. Biomechanical results on joint stability and graft function support its use as an alternative to the hamstrings. Introduction. Recently, a number of surgeons have chosen the quadriceps tendon (QT) autograft as an alternative autograft over the hamstrings tendon for ACL reconstruction because its bone-to-bone healing on one side, large size, and preservation of lateral and rotatory knee function could lead to fewer post-operative complications. However, there have been little or no biomechanical studies that quantitatively evaluate knee function after reconstruction using a QT autograft. Therefore, the objective of this study was to assess the function of a reconstructed knee with a QT autograft and compare the results with a quadrupled semitendinosus and gracilis (QSTG) tendon autograft on the same knee. Methods. Ten human cadaveric knees (57.4 ± 4.2 years of age) were tested using a robotic/UFS testing system in 4 knee states: intact, ACL-deficient, and after ACL reconstruction with both QT and QSTG autografts. Reconstructions were performed in randomised order using posterolateral femoral tunnel placement. The knee kinematics in each state were measured at 5 flexion angles (full extension, 15°, 30°, 60°, and 90°) under 3 externally applied loading conditions: (1) 134 N anterior tibial load (ATL), (2) 134 N ATL with 200 N axial compression, and combined rotatory (CR) load of 10 Nm valgus and 5 Nm internal tibial torque (at 15° and 30°). Based on the established procedure, knee kinematics and in-situ forces were obtained using the principle of superposition. A repeated measures ANOVA was used to compare anterior tibial translation (ATT) and in-situ forces between the knee states at each flexion angle, with a Bonferroni post-hoc analysis. Results. Under the ATL, the ATT was found to be restored to within 1.1 mm of the intact knee for both reconstructions (P > 0.05). The in-situ forces in the grafts were also not significantly different from those in the intact ACL except in deep flexion (P < 0.05 at 90° for both grafts). With added axial compression, both reconstructions could still restore the ATT to within 2.4 mm of the intact joint at all flexion angles, and the in-situ forces in both grafts were within 25 N of the intact ACL at 15°, 30°, and 60° (P > 0.05). Under the CR load, knee kinematics and in-situ forces in the grafts were not significantly different from the intact ACL at any tested angle (P > 0.05). Further, no significant differences could be detected between the reconstructions under any experimental condition (P > 0.05). Discussion/Conclusion. ACL reconstruction with a QT autograft was found to restore knee function close to levels of the intact knee and similar to those reconstructed with a QSTG autograft. These results support clinical findings suggesting the QT autograft as a viable alternative for ACL reconstruction