Distraction Force Research Articles

Use of Bio-integrative Screws for Fixation of Lisfranc Instability; Pros and Cons from Surgeons' Point of View in a Cadaver Study.

Majority of Lisfranc fracture-dislocations require anatomic reduction and rigid internal fixation to prevent debilitating sequelae. Current methods include solid screws and flexible fixations which have been in use for many years. Biointegrative screw is a newer option that has not yet been thoroughly investigated for its effectiveness for Lisfranc injuries. The ligaments of the Lisfranc complex were resected in eight lower-leg cadaveric specimens. This was done by eight foot and ankle surgeons individually. Distraction forces were applied from opposite sides at the joint to replicate weight bearing conditions. Three methods of fixation - flexible fixation, metal, and biointegrative screws- were evaluated. The diastasis and area at the level of the ligament were measured at four conditions (replicated injury and each type of fixation) in neutral and distraction conditions using fluoroscopy images. The Wilcoxon test and Kruskal Wallis test were used for comparison. P value <0.05 was considered statistically significant. The diastasis value for the transected ligament scenario (2.47 ± 0.51 mm) was greater than those after all three fixation methods without distraction (2.02 ± 0.5 for flexible fixation, 1.72 ± 0.63 mm for metal screw fixation and 1.67 ± 0.77 mm for biointegrative screw fixation). The transected ligament diastasis was also greater than that for metal screw (1.61 ± 1.31mm) and biointegrative screws (1.69 ± 0.64 mm) with distraction (p<0.001). The area at the level of the ligament showed higher values for transected ligament (32.7 ± 13.08 mm2) than the three fixatives (30.75 ± 7.42 mm2 for flexible fixation, 30.75 ± 17.13 mm2 for metal screw fixation and 29.53 ± 9.15 mm2 for biointegrative screw fixation; p<0.05). Metal screws, flexible fixation and biointegrative screws showed comparable effectiveness intra-op, in the correction of diastasis created as a consequence of Lisfranc injury.

Quantification of the passive behavior of the glenohumeral joint: A biomechanical study

Shoulder stabilization and arthroplasty procedures aim to restore the complex motion innate to the glenohumeral joint relying on proper tensioning of the surrounding soft-tissues at the time of surgery. Joint instability remains a leading cause for revisions of these procedures necessitating a deeper understanding of the passive constraint of the intact glenohumeral joint. The current literature lacks comprehensive analysis of the passive glenohumeral joint in all degrees-of-freedom (DOF). The objective of the present study is to better understand this complex joint by quantifying the passive laxity of the glenohumeral joint in multiple DOFs over a range of motion. Sixteen fresh-frozen cadaveric shoulders were tested in the intact state using a robotic simulator capable of six-DOF motion. The limits of range of motion was quantified in separate laxity tests applying a ± 2 Nm internal-external (IE) torque, ±20 N anterior-posterior (AP) force, ±20 N superior-inferior (SI) force and a 44 N distraction force at six levels of glenohumeral abduction. Overall, glenohumeral joint laxity was greatest between 15° and 45° of abduction except for SI translation which increased with abduction. IE rotation and AP translation were dominated by external rotation and anterior translation, respectively. Although early abduction and late abduction produced similar laxities, the increase in laxity in the mid abduction range indicates it is important to assess the shoulder joint throughout the range of motion and not just at these two end points. The presented laxity data establishes a baseline for intact shoulder laxity over a range of motion in multiple DOFs under known loading conditions.

Lateral Laxity in Flexion Influences Patient-Reported Outcome After Total Knee Arthroplasty

IntroductionSlight lateral laxity exists in normal knee especially in flexion. The lateral laxity in flexion has possibility to affect the outcome after total knee arthroplasty (TKA).PurposeThe purpose of this study was to determine how intraoperative laxity in flexion affects patient-reported outcome after total knee arthroplasty.MethodsWe retrospectively analysed 98 knees with osteoarthritis that underwent total knee arthroplasty. After bone resection, ligament imbalance and joint component gaps were measured using an offset-type tensor while applying a 40-lb joint distraction force at 0° and 90° of knee flexion. The lateral laxity in flexion was determined by subtracting polyethylene insert thickness from the lateral gap at 90°. All patients were divided into three groups: ≤ 2 mm (A), 2–5 mm (B), and > 5 mm (C). One year after surgery, patients were asked to fill out questionnaires using the new Knee Society Score after examination outside the consultation room.ResultsThe mean intraoperative lateral laxities at 90° were − 0.2 ± 2.1 mm, 3.5 ± 0.7 mm, and 6.7 ± 1.9 mm in groups A, B, and C, respectively. The symptom score of group C was significantly lower than those of groups A or B. There were no significant differences in terms of satisfaction or the expectation and activity scores among all groups. There were no significant differences in terms of alignment after total knee arthroplasty among all groups.ConclusionsExcessive lateral laxity possibly resulted in worse patient-reported outcomes. However, slight lateral laxity of 2–5 mm might have no effect on patient-reported outcome and this slight varus imbalance could be acceptable. Altogether, our findings would lead to avoidance of excessive medial release in soft tissue balancing.

Two-pin Posterior Tuberosity to Medial Wall Reduction Technique in Calcaneal Fracture Using Sinus Tarsi Approach

Introduction: The purpose of this study was to describe a novel technique in the surgical treatment of displaced intra-articular calcaneal fractures using 2 Schanz pins to reduce the posterior tuberosity to the medial wall (constant fragment) and correcting the varus malalignment while using the sinus tarsi approach. Materials and Methods: Twelve patients with calcaneal fractures Sanders type 2 and 3 underwent surgical fixation using this technique at our center from January 2021 to September 2021. One Schanz pin was inserted into the constant fragment and another one was inserted into the posterior tuberosity from lateral to medial. By holding the 2 pins the fracture fragments were first disengaged by applying a distraction force. The heel was then brought out of varus by a combination of maneuvres. The posterior calcaneal tuberosity pin was pushed medially and then the 2 pins were held together with one hand. The ankle was then dorsiflexed to lock the reduction. Harris heel views were taken to ensure reduction. Results: The mean Bohler angle improved from 7.5 degrees preoperatively to 29 degrees postoperatively. The mean Visual Analog Scale was 2.3 out of 10 at 6 months’ follow-up. None of the patients had wound complications, sural nerve neuropraxia, or revision surgery due to malreduction. Discussion: The 2-pin posterior tuberosity to medial wall reduction technique in calcaneal fractures using the sinus tarsi approach is a useful maneuver that can be used by orthopedic surgeons to correct the varus malalignment which is a frequent problem in calcaneal fracture fixation.

Opposing Flanks vs Parallel Flanks – the Influence of Headless Screw Design on Compression and Pull- Out Resistance

Category: Basic Sciences/Biologics; Basic Sciences/Biologics Introduction/Purpose: Screws generate and maintain compression against distracting forces when performing osteotomy or fusion surgery. Headless screws with opposing flank angles (OFA) between the threads of the head and shaft are purported to achieve better compression. The purpose of this study was to compare OFA designs against traditional parallel flank angle (PFA) headless screws and headed screws to determine differences in compression and pull-out resistance (POR). Methods: In this biomechanical in-vitro study, four screw designs were compared: headless screws with OFA (Screw_A and Screw_B), headless screws with PFA (Screw_C), and headed screws (Screw_D). All screws were 4.0x50mm partially threaded cannulated screws. Screw_B had a 1.4mm shorter head length and 0.5mm narrower head thread diameter than Screw_A and Screw_C, which were similar. A custom apparatus was designed for measuring compression and POR. Osteotomies were created on synthetic bone blocks (density 0.32g/cm3) simulating cancellous bone. Screws were inserted perpendicular to osteotomies in accordance with manufacturer guidance and maximum compression recorded. Increasing distracting forces were then applied to the blocks until the screws pulled out. For each screw type, five screws were tested. Results: There was no significant difference in maximum compression between screw designs: Screw_A=38.7N±14.2N, Screw_B=48.7N±15.6N, Screw_C=51.9N±36.4N, Screw_D=32.0N±9.2N; p=0.921. When assessing POR, all screws failed at the head-bone interface (screw heads subsided into block). Pull-out forces significantly differed between all groups: Screw_A=466N±29.0N, Screw_B=310N±22.0N, Screw_C=399N±46.0N, Screw_D=183N±12.9N; p&lt; 0.001 (ANOVA). Screw_Ahad the highest POR but the other OFA design (Screw_B) had significantly lower POR. Conclusion: Screw design, whether headless (OFA or PFA) or headed did not appear to influence compression generated. However, headed screws had significantly lower POR than headless designs. Within headless designs, OFA may increase POR, but other screw head features (number / diameter of threads) had an apparently greater influence than flank angle.

Successful use of dual-plate fixation to treat a canine comminuted scapula fracture

A 9-month-old, female, cross-breed dog was presented for management of a left-sided, traumatic, closed, comminuted scapula fracture that had occurred 8 days prior to presentation. Following a computed tomography scan, the fracture was stabilised via open reduction and internal fixation with a 2.7 mm 12-hole locking compression plate (DePuy Synthes, West Chester, PA) along the cranial aspect of the scapular spine. Intraoperatively, a gap was opening along the fracture line on the caudal aspect of the scapular body during shoulder extension, likely due to the large muscular distraction forces. A 2.7 mm 6-hole semitubular plate was placed on the caudal aspect of the lateral body of the scapula and secured using four cortical screws, which successfully prevented gap formation. At the time of discharge, the dog was able to bear weight on the operated left thoracic limb with a moderate lameness. At 9 weeks postoperatively, a computed tomography scan showed complete healing of the scapula fracture. At 1 year postoperatively, her owner reports no signs of lameness, stiffness or pain. In this case, dual-plate fixation allowed early return to weight bearing, successful healing by 9 weeks postoperatively and return to full function at 1 year postoperatively.

Timing Of Peak Shoulder Distraction Force Between Pitch Types Across A Simulated Softball Game

Timing Of Peak Shoulder Distraction Force Between Pitch Types Across A Simulated Softball Game

During Postless Hip Arthroscopy, Male Patients, High Body Mass Index, Low Beighton Scores, and Limited Range of Motion Require High Traction Force

To determine the effects of demographic and anatomic factors on traction force required during postless hip arthroscopy. A prospectively collected database was retrospectively analyzed on patients undergoing hip arthroscopy by the senior author, including patient sex, age, body mass index (BMI), Beighton Hypermobility Score, hip range of motion in clinic and under anesthesia, hip dysplasia, acetabular version, and femoral version. All patients underwent postless hip arthroscopy under general anesthesia. At the initiation of hip arthroscopy, the traction force required to distract the hip joint was measured before and following interportal capsulotomy. Multiple regression analysis was performed to determine the effects of demographic and anatomic factors on measured distraction force. In total, 352 hips (114 male, 238 female) were included with a mean age of 32.6 years and a mean BMI of 24.1 kg/m2. Mean initial traction force was 109 lbs and decreased to 94.3 lbs following capsulotomy (P < .0001). The starting traction force was significantly greater in male patients (P < .001), patients with a lack of hypermobility (Beighton Hypermobility Score of 0-2) (P= .026), and in patients with lower abduction (P < .001), lower internal rotation (P= .002), and lower external rotation (P= .012) on multiple regression analysis. When performing a subanalysis divided by sex, male patients with elevated BMI required significantly greater starting traction force (P= .014). Lateral center edge angle, sourcil angle, and the presence of hip dysplasia did not demonstrate a significant correlation with traction force. Male patients, patients with reduced preoperative hip range of motion, patients with a lack of joint hypermobility, and male patients with an elevated BMI require greater initial traction force during postless hip arthroscopy. Level IV, retrospective case series.

Lateral joint tightness in flexion following cementless mobile-bearing total knee arthroplasty decreases patient-reported outcome measures and postoperative range of motion

PurposeThe purpose of this study was to clarify the association between clinical outcomes and the flexion joint gap following rotating concave–convex (Vanguard ROCC) total knee arthroplasty (TKA). MethodsThis consecutive retrospective series included 55 knees that underwent ROCC TKA. All the surgical procedures were performed using a spacer-based gap-balancing technique. To evaluate the medial and lateral flexion gaps, axial radiographs of the distal femur were obtained using the epicondylar view with a distraction force to the lower leg at 6 months postoperatively. Lateral joint tightness was defined as the lateral gap being greater than the medial gap. To evaluate clinical outcomes, patients were asked to complete patient-reported outcome measures (PROMs) questionnaires preoperatively and during at least 1 year of follow-up postoperatively. ResultsThe median follow-up duration was 24.0 months. Overall, 16.0% of patients had postoperative lateral joint tightness in flexion. The postoperative range of motion and PROMs were lower in patients with lateral joint tightness than in those with a balanced flexion gap or lateral joint laxity. No serious complications, including bearing dislocations, occurred during the observation period. ConclusionLateral joint tightness in flexion following ROCC TKA decreases PROMs and postoperative range of motion. Level of evidence4.

A Dynamic Ankle Orthosis Reduces Tibial Compressive Force and Increases Ankle Motion Compared to a Walking Boot.

Tibial bone stress injuries are a common overuse injury among runners and military cadets. Current treatment involves wearing an orthopedic walking boot for three to twelve weeks, which limits ankle motion and leads to lower limb muscle atrophy. A Dynamic Ankle Orthosis (DAO) was designed that provides a distractive force that offloads in-shoe vertical force and retains sagittal ankle motion during walking. It remains unclear how tibial compressive force is altered by the DAO. This study compared tibial compressive force and ankle motion during walking between the DAO and an orthopedic walking boot. Twenty young adults walked on an instrumented treadmill at 1.0 m/s in two brace conditions: DAO and walking boot. 3D kinematic, ground reaction forces, and in-shoe vertical force data were collected to calculate peak tibial compressive force. Paired t-tests and Cohen's d effect sizes were used to assess mean differences between conditions. Peak tibial compressive force (p = 0.023; d = 0.5) and Achilles tendon force (p = 0.017; d = 0.5) were moderately lower in the DAO compared to the walking boot. Sagittal ankle excursion was 54.9% greater in the DAO compared to the walking boot (p = 0.05; d = 3.1). The findings from this study indicated that the DAO moderately reduced tibial compressive force and Achilles tendon force and allowed more sagittal ankle excursion during treadmill walking compared to an orthopedic walking boot.

Comparison of Peak Shoulder Distraction Forces Between Pain and Pain-Free Youth Baseball Pitchers.

Increased shoulder distraction force during a baseball pitch may make a pitcher susceptible to rotator cuff or glenohumeral labral injuries. A precursor to a pitching injury may be pain experienced in the throwing arm. To (1) compare peak shoulder distraction (PSD) forces in youth baseball pitchers with and without upper extremity pain when throwing a fastball and (2) assess if PSD forces across trials differ between pain and pain-free groups. Controlled laboratory study. A total of 38 male baseball pitchers aged 11 to 18 years were separated into a pain-free group (n = 19; mean age, 13.2 ± 1.7 years; mean height, 163.9 ± 13.5 cm; mean weight, 57.4 ± 13.5 kg) and a pain group (n = 19; mean age, 13.3 ± 1.8 years; mean height, 164.9 ± 12.5 cm; mean weight, 56.7 ± 14.0 kg). Pitchers in the pain group indicated that they experienced pain in their upper extremity while throwing a baseball. Pitching mechanical data from 3 fastballs per pitcher were recorded with an electromagnetic tracking system and motion capture software. The mean PSD (mPSD) was calculated as the mean PSD of 3 pitches per pitcher, the trial with the highest recorded PSD was determined as the maximum-effort PSD (PSDmax), and the PSD range (rPSD) was defined as the difference of the PSD force of the trial with the highest PSD and the lowest PSD for each pitcher. The PSD force was normalized to the pitcher's body weight (%BW). Pitch velocity was also recorded. The mPSD force was 114%BW ± 36%BW for the pain group and 89%BW ± 21%BW for the pain-free group. Pitchers in the pain group exhibited a significantly higher PSDmax force (t30.548 = 2.894; P = .007) and mPSD force (t29.231 = 2.709; P = .009) compared with those in the pain-free group. There were no significant between-group differences in the rPSD force or pitch velocity. The normalized PSDmax force was higher in pitchers who experienced pain while throwing fastballs compared with pitchers who were pain-free while throwing. Baseball pitchers who experience pain in their throwing arm are likely to have higher shoulder distraction forces. Improvement in pitching biomechanics and corrective exercises may assist in the mitigation of pain while pitching.

Increasing soft tissue depth is associated with stalling of magnetically controlled growing rods

Magnetically controlled growing rods (MCGR) represent the most used implant for the treatment of early onset scoliosis (EOS). These implants lengthen through the application of a remote magnetic field but distraction force generation has been negatively correlated with increasing soft tissue depth. Given the high rate of MCGR stalling, we proposed to investigate the impact of preoperative soft tissue depth on the rate of MCGR stalling at a minimum of 2 years following implantation. A single-center, retrospective review of prospectively enrolled children with EOS treated with MCGR was performed. Children were included if they had a minimum of 2-years follow-up after implantation and underwent advanced spinal imaging (MRI or CT) preoperatively within a year of implantation. The primary outcome was the development of MCGR stall. Additional measures included radiographic deformity parameters and gain in MCGR actuator length. About 55 patients were identified with 18 having preoperative advanced imaging allowing tissue depth measurement (Mean 5.99 ± 1.9 years, 83.3% female, mean Cobb 68.6 ± 13.8°). At a mean follow-up of 46.1 ± 11.9 months, 7 patients (38.9%) experienced stalling. MCGR stalling was associated with increased preoperative soft tissue depth (21.5 ± 4.4 mm vs. 16.5 ± 4.1 mm; p=.025) and increased BMI (16.3 ± 1.6 vs. 14.5 ± 0.9; p=.007). Greater preoperative soft tissue depth and BMI were associated with the development of MCGR stalling. This data supports previous studies showing that the distraction capacity of MCGR diminishes with increased soft tissue depth. Further research is needed to validate these findings and their implications on the indications for MCGR implantation.

Hip Arthroscopy in Adolescents Through an Extra-Capsular Approach

Hip arthroscopic treatment for femoroacetabular impingement syndrome and labral tears is the gold standard in the adult and adolescent population, as we all know the most common surgical approach to the hip is entering the central compartment with fluoroscopy and with continuous distraction. A periportal capsulotomy in traction must be done to have visibility and instrument maneuverability. These maneuvers avoid scuffing the femoral head cartilage. In adolescents, extreme care must be taken in hip distraction, as the force used can cause iatrogenic neurovascular lesions, avascular necrosis, and lacerations of the genitals and foot/ankle. Experienced surgeons around the world have developed an extracapsular approach to the hip with smaller capsulotomies with a low complication rate. This approach to the hip has brought attention in the adolescent population because it is more secure and simple. Less force of distraction is needed because the capsulotomy is done first. This surgical technique allows observation of the cam morphology while entering to the hip without distraction. We describe an extracapsular approach as an option to treat femoral acetabular impingement syndrome and labral tears in the pediatric and adolescent population.

Treatment outcomes of applying external fixator on distal radius fractures: a randomized clinical trial to compare between two directions of force exertion in parallel to radius shaft and perpendicular to the distal radius articular surface

BackgroundExternal fixation has been one of the conventional managements of unstable distal radius fracture. The main aim of this paper is to compare two methods of applying distractive force along the radius shaft versus perpendicular to the distal radius articular surface.DesignSixty patients with unstable distal radius fracture were included in present clinical trial and randomized in two groups, using block randomization method. In group A (first arm), distraction force was exerted parallel to the radius shaft. In group B (second arm), the external fixator was adjusted based on radial and palmar tilt of the mean population healthy wrist so that distraction was exerted perpendicular to the wrist articular surface.MethodsRadiological and clinical parameters were evaluated in both groups of patients pre-operatively, immediately after surgery, and 6 weeks post-operatively. We also followed up patients clinically at 12 weeks after surgery. Patient-Rated Wrist Evaluation (PRWE), Mayo wrist score, and Quick Disabilities of the Arm, Shoulder and Hand (DASH) questionnaires were used in order to assess patients’ clinical and functional states.ResultsThe method used in group B resulted in better improvement of palmar tilt both immediately (P = 0.007) and at 6 weeks follow up (P = 0.013) post-operatively in comparison with patients in group A. Radius height and radial inclination were also better restored when using the proposed modified method (P = 0.001 and < 0.001, respectively). There was no difference in any of clinical results (range of motion, grip strength, PRWE, Mayo, and DASH scores) between two groups of study, 12 weeks after surgery.ConclusionApplying distractive force perpendicular to the distal radius articular surface seems to improve some radiological outcomes, probably due to better reduction maintenance, when compared with the technique of applying distraction force along distal radius shaft axis.Level of EvidenceLevel I (clinical trial study).Trial registrationThis study is registered at Iranian Registry of Clinical Trials (IRCT) with approval code of IRCT20200313046759N1.

Comparison of Internal and External Distraction in Frontofacial Monobloc Advancement: A Three-Dimensional Quantification.

Crouzon syndrome is characterized by complex craniosynostosis and midfacial hypoplasia. Where frontofacial monobloc advancement (FFMBA) is indicated, the method of distraction used to achieve advancement holds an element of equipoise. This two-center retrospective cohort study quantifies the movements produced by internal or external distraction methods used for FFMBA. Using shape analysis, this study evaluates whether the different distraction forces cause plastic deformity of the frontofacial segment, producing distinct morphologic outcomes. Patients with Crouzon syndrome who underwent FFMBA with internal distraction [Hôpital Necker-Enfants Malades (Paris, France)] or external distraction [Great Ormond Street Hospital for Children (London, United Kingdom)] were compared. Digital Imaging and Communications in Medicine files of preoperative and postoperative computed tomographic scans were converted to three-dimensional bone meshes and skeletal movements were assessed using nonrigid iterative closest point registration. Displacements were visualized using color maps and statistical analysis of the vectors was undertaken. Fifty-one patients met the strict inclusion criteria. Twenty-five underwent FFMBA with external distraction and 26 with internal distraction. External distraction provides a preferential midfacial advancement, whereas internal distractors produce a more positive movement at the lateral orbital rim. This confers good orbital protection but does not advance the central midface to the same extent. Vector analysis confirmed this to be statistically significant ( P < 0.01). Morphologic changes resulting from monobloc surgery differ depending on the distraction technique used. Although the relative merits of internal and external distraction still stand, it may be that external distraction is more suited to addressing the midfacial biconcavity seen in syndromic craniosynostosis. Therapeutic, III.

Automated continuous distraction osteogenesis system for limb lengthening and reconstruction

Distraction osteogenesis (DO) is a classical surgical technique for limb lengthening and reconstruction (LLR). Most existing DO devices for LLR are operated manually, and the accurate DO process is user dependant, which could affect new bone formation. Recently, automated devices have been introduced for continuous DO processes to aid in tissue healing. To the best of our knowledge, few automated continuous distraction osteogenesis (ACDO) devices have focused on DO surgery for the long bones of the extremities and monitoring of their status during the surgical process. This study presents a novel ACDO device, which is driven by a deceleration stepper motor for further reduction in total mass and amplification in distraction force, including a precise and programmable man–machine-interaction system to allow surgeons to control and monitor the treatment remotely. The mechanical device was verified to be capable of generating a continuous and controllable distraction force and rate. The proposed man–machine-interaction system possesses the functions of customizing and following up on treatment plan by clinicians, including setting the DO process, measuring and displaying parameters, and uploading DO information to the data cloud. During electromechanical system simulation and prototype experiments, the performance of the proposed system was consistent with the setting DO parameters and treatment plan.

Ligament Tension and Balance before and after Robotic-Assisted Total Knee Arthroplasty - Dynamic Changes with Increasing Applied Force.

The optimal force applied during ligament balancing in total knee arthroplasty (TKA) is not well understood. We quantified the effect of increasing distraction force on medial and lateral gaps throughout the range of knee motion, both prior to and after femoral resections in tibial-first gap-balancing TKA. Twenty-five consecutive knees in 21 patients underwent robotic-assisted TKA. The posterior cruciate ligament was resected, and the tibia was cut neutral to the mechanical axis. A digital ligament tensioning tool recorded gaps and applied equal mediolateral loads of 70 N (baseline), 90 N, and 110 N from 90 degrees to full extension. A gap-balancing algorithm planned the femoral implant position to achieve a balanced knee throughout flexion. After femoral resections, gap measurements were repeated under the same conditions. Paired t-tests identified gap differences between load levels, medial/lateral compartments, and flexion angle. Gaps increased from 0 to 20 degrees in flexion, then remain consistent through 90 degrees of flexion. Baseline medial gap was significantly smaller than lateral gap throughout flexion (p <0.05). Increasing load had a larger effect on the lateral versus medial gaps (p <0.05) and on flexion versus extension gaps. Increasing distraction force resulted in non-linear and asymmetric gap changes mediolaterally and from flexion to extension. Digital ligament tensioning devices can give better understanding of the relationship between joint distraction, ligament tension, and knee stiffness throughout the range of flexion. This can aid in informed surgical decision making and optimal soft tissue tensioning during TKA.

Posterior cruciate ligament resection under minimum medial collateral ligament release changes tibial internal rotation, joint center gap, and varus ligament balance on joint distraction force at flexion in total knee arthroplasty

BackgroundThe purpose of this study was to assess the effect of posterior cruciate ligament resection under minimum medial collateral ligament release on the joint center gap, varus ligament balance, and the rotational change of the femur and tibia. MethodsThis study included 75 knees with varus osteoarthritis that underwent total knee arthroplasty. After minimum medial collateral ligament releases and bone resection of the distal femur and proximal tibia, the joint center gap and varus ligament balance were measured before and after posterior cruciate ligament resection using a digital tensor with a joint distraction force of 89, 133, 178 N. The rotational changes under a distraction force of 200 N were captured using a navigation system. FindingsThe joint center gap and varus ligament balance at 90° and 120° of flexion significantly increased after posterior cruciate ligament resection with distraction forces of 89 N (90°: 0.4 mm / 0.9° and 120°: 0.5 mm / 0.8°), 133 N (90°: 0.9 mm / 1.3° and 120°: 0.9 mm / 1.1°), 178 N (90°: 1.5 mm / 1.9° and 120°: 1.5 mm / 1.5°). Tibial internal rotation significantly increased after posterior cruciate ligament resection at 90° (1.9°) and 120° (2.2°). InterpretationJoint distraction forces after posterior cruciate ligament resection increased the tibial internal rotation, joint center gap, and varus ligament balance at flexion. These findings indicate that posterior cruciate ligament resection should increase the lateral gap more than the medial gap due to tibial internal rotation at flexion. (245 words).

The flexion–extension gap is predictive of patient-reported outcome measures after cruciate-retaining total knee arthroplasty

BackgroundWe aimed to evaluate the association between the flexion–extension gap difference and patient-reported outcome measures after total knee arthroplasty (TKA). MethodsThis was a retrospective case–control study of 60 cruciate-retaining single-radius TKAs. Soft tissue balancing was measured using an offset seesaw tensioner and centre-type digital knee balancer under joint distraction forces of 20–50 lbf and 1.5 times body mass index (1.5 BMI). At the last follow up of 2.0–6.5 (mean, 4.5) years postoperatively, patients were asked if they perceived their knee joint as ‘natural’ (26 knees) or ‘artificial’ (34 knees). Age, sex, and the flexion–extension gap were compared between the two groups. A receiver operating characteristic curve was used to determine cut-off values of variables predictive of a natural joint perception. ResultsNatural joint perception was associated with a greater flexion–extension gap difference under a distraction force of 1.5 BMI (P = 0.016), higher knee function (Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, P = 0.019), and quality of life (EuroQol 5-Dimension, P = 0.029). A gap difference of 0.95 mm under 1.5 BMI distraction predicted a natural joint perception post-TKA (sensitivity, 97.1%; specificity, 88.5%). Using a gap threshold of 1.0 mm under a 1.5 BMI distraction force yielded significant between-group differences in postoperative flexion (P = 0.040), satisfaction (P = 0.043), knee joint function (P < 0.001), quality of life (P = 0.032), and posterior femoral condylar offset (P = 0.037) ConclusionA flexion–extension gap difference ≥1.0 mm under a distraction force of 1.5 BMI predicted superior outcomes, including patient satisfaction, after cruciate-retaining TKA. It was suggested that posterior femoral condylar offset could influence this finding.

On the forces of driver distraction: Explainable predictions for the visual demand of in-vehicle touchscreen interactions

With modern infotainment systems, drivers are increasingly tempted to engage in secondary tasks while driving. Since distracted driving is already one of the main causes of fatal accidents, in-vehicle touchscreens must be as little distracting as possible. To ensure that these systems are safe to use, they undergo elaborate and expensive empirical testing, requiring fully functional prototypes. Thus, early-stage methods informing designers about the implication their design may have on driver distraction are of great value. This paper presents a machine learning method that, based on anticipated usage scenarios, predicts the visual demand of in-vehicle touchscreen interactions and provides local and global explanations of the factors influencing drivers’ visual attention allocation. The approach is based on large-scale natural driving data continuously collected from production line vehicles and employs the SHapley Additive exPlanation (SHAP) method to provide explanations leveraging informed design decisions. Our approach is more accurate than related work and identifies interactions during which long glances occur with 68% accuracy and predicts the total glance duration with a mean error of 2.4s. Our explanations replicate the results of various recent studies and provide fast and easily accessible insights into the effect of UI elements, driving automation, and vehicle speed on driver distraction. The system can not only help designers to evaluate current designs but also help them to better anticipate and understand the implications their design decisions might have on future designs.