To investigate and compare the biomechanical characteristics of Bipedicular versus Unipedicular Vertebroplasty in cadaveric vertebra. Cadaveric single level vertebra were used to evaluate Bipedicular versus Unipedicular Vertebroplasty as an intervention for vertebral compression fractures. Cadaveric vertebra were assigned to two arms: Arm A simulated a wedge fracture followed by bipedicular cement augmentation; Arm B simulated a wedge fracture followed by unipedicular cement augmentation. Micro-CT imaging was performed to assess vertebral dimension, cement fill volumes and bone mineral density. All augmented specimens were then compressed under a static eccentric flexion load to failure. Pre and post augmentation failure load and stiffness were used to compare the two groups. Results suggest, when compared with actual failure strength, that the product of bone mineral density and endplate surface area gave a good prediction of failure strength for specimens in both arms. The mean cement volume fill of augmented vertebral bodies was 22.8% ± 7.21%. The bipedicular group showed a reduction in stiffness but an increase in post augmentation failure load of 1.09. The unipedicular group also showed a reduction in stiffness but showed a much greater increase in post augmentation failure load of 1.68. Preliminary data from this study suggests there is a significant reduction in stiffness following both bipedicular and unipedicular vertebroplasty. There is a significant increase in failure load post augmentation in the unipedicular group

Hip joint biomechanics can be altered by abnormal morphology of the acetabulum and/or femur. This may affect load distribution and contact stresses on the articular surfaces, hence, leading to damage and degradation of the tissue. Experimental hip joint simulators have been used to assess tribology of total hip replacements and recently methods further developed to assess the natural hip joint mechanics. The aim of this study was to evaluate articular surfaces of human cadaveric joints following prolonged experimental simulation under a standard gait cycle.

Four cadaveric male right hips (mean age = 62 years) were dissected, the joint disarticulated and capsule removed. The acetabulum and femoral head were mounted in an anatomical hip simulator (Simulation Solutions, UK). A simplified twin peak gait cycle (peak load of 3kN) was applied. Hips were submerged in Ringers solution (0.04% sodium azide) and testing conducted at 1 Hertz for 32 hours (115,200 cycles). Soft tissue degradation was recorded using photogrammetry at intervals throughout testing.

All four hips were successfully tested. Prior to simulation, two samples exhibited articular surface degradation and one had a minor scalpel cut and a small area of cartilage delamination. The pre-simulation damage got slightly worse as the simulation continued but no new areas of damage were detected upon inspection. The samples without surface degradation, showed no damage during testing and the labral sealing effect was more obvious in these samples.

The fact that no new areas of damage were detected after long simulations, indicates that the loading conditions and positioning of the sample were appropriate, so the simulation can be used as a control to compare mechanical degradation of the natural hip when provoked abnormal conditions or labral tissue repairs are simulated.

The clinical success of osteochondral autografts is heavily reliant on their mechanical stability, as grafts which protrude above or subside below the native cartilage can have a negative effect on the tribological properties of the joint [1]. Furthermore, high insertion forces have previously been shown to reduce chondrocyte viability [2]. Commercial grafting kits may include a dilation tool to increase the diameter of the recipient site prior to insertion. The aim of this study was to evaluate the influence of dilation on the primary stability of autografts.

Six human cadaveric femurs were studied. For each femur, four 8.5 × 8mm autografts were harvested from the trochlear groove and implanted into the femoral condyles using a Smith & Nephew Osteochondral grafting kit. Two grafts were implanted into dilated recipient sites (n=12) and two were implanted with no dilation (n=12). Insertion force was measured by partially inserting the graft and applying a load at a rate of 1 mm/min, until the graft was flush with the surrounding cartilage. Push-in force was measured by applying the same load, until the graft had subsided 4mm below congruency. Significance was taken as (p<0.05).

Average maximum insertion force of dilated grafts was significantly lower (p<0.001) than their non-dilated equivalent [28.2N & 176.7N respectively]. There was no significant difference between average maximum push-in force between the dilated and non-dilated groups [1062.8N & 1204.2N respectively].

This study demonstrated that significantly less force is required to insert dilated autografts, potentially minimising loss of chondrocyte viability. However, once inserted, the force required to displace the grafts below congruency remained similar, indicating a similar degree of graft stability between both groups.

Early mobilisation following Anterior Cruciate Ligament(ACL) reconstruction surgery is indicated for optimum results for accelerated rehabilitation. However, the graft used in reconstruction is at it’s weakest during the early post-operative period and can be prone to slipping. Aim: This study compared two types of graft, bone-patellar tendon-bone (BPTB) and soft tissue tendon, with the hypothesis that BPTB grafts would lead to less slippage under cyclical loading conditi ons. Materials & Method: A comparative biomechanical study was carried out using sixteen proximal tibiae of calves, aged 20–26 weeks and carrying out ACL reconstruction, 8 constructs with human Cadaveric BPTB and another 8 with calves’ extensor tendons. An interference screw measured 9 x 25mm was used to fix graft tissue in the transosseous tunnel. The specimens were tested in material-testing machine using Merlin software. The constructs were subjected to cyclical loading. A load cycle of 0-150-0N was applied at a crosshead speed of 100mm/min, approximately 80 load cycles per minute simulating the forces applied in post-operative mobilisation. The crosshead position was noted at peak load at 1, 100, 300, and 1000 cycles. Results: The value of the graft slippage found in the soft tissue tendon model was 1.83 ± 0.54 and that of bone tissue (BPTB) model was 0.76 ±0.29. Creep value showed no statistical significance. There was significantly less slippage when using BPTB-to-bone fixation than with soft tissue tendon-to bone fixation (p< 0.005). Clinical relevance: BPTB grafts are more likely to resist the return of anterior-posterior laxity in the immediate post-operative period, prior to graft fixation by tissue healing. BPTB grafts should be used when accelerated rehabilitation is required

Introduction. Patient-specific cutting guides entered into clinical practice few years ago, first introduced in total knee replacement and recently also for other joint replacements. Advantages claimed are improving accuracy and repeatability in implant placement. New patient-specific guides to perform an accurate femoral neck resection and provide a precise alignment reference for acetabular reaming in total hip arthroplasty (THA) were recently developed by Medacta International: MyHip Technology. To date femoral guides can be designed for both anterior and posterior approaches, whereas acetabular guides are available only for posterior approach. Evaluation of the repeatability and reproducibility of MyHip guides placement on cadavers is performed using a navigation system. Accuracy of femoral MyHip guides is evaluated also through one author's clinical experience (RP). Materials and Methods. During each cadaveric session one body (2 hips) was available. A pre-operative CT scan has been obtained and used in order to create the 3D bone model of the pelvis and proximal femurs. Afterwards, a surgical planning for THA has been performed for each case, and, once it was approved by the surgeons, the designed patient-specific blocks were made. Intraobserver and interobserver agreement in positioning the guides was assessed getting measures of femoral head resection height (mm), femoral head plane inclination/anteversion (°) and acetabular reaming axis orientation (°). 9 surgeons, through 2 cadaveric sessions, positioned each guide, removed it and re-positioned it 5 times alternatively. The system is judged as accurate if all measures differ less than 3mm and 5°for lengths and angles respectively from the average among all the acquisitions. Clinical experience includes 68 THA which were performed between March 2014 and April 2015. Anterior femoral MyHip guides were used for the femoral head resection, while the acetabular side was prepared using the standard metal instrumentation for minimally invasive anterior approach. Intra-operative complications, as well post-operative leg length difference and implant positioning are assessed. Results. During cadaveric sessions, all measures taken meet the acceptance criteria with the exception of two measures, which are −5,98° and −5,57°, in femoral head plane anteversion and inclination respectively with femoral anterior guides. Looking at intraobserver variation, MyHip Femoral anterior guide positioning average deviation was between −0.91 mm and 1.44 mm (resection height), −1.25° and 1.41° (anteversion), and −0.85° and 0.82° (inclination); MyHip Femoral posterior guide positioning average deviation was between −0.47 mm and 0.67 mm (resection height), −1.33° and 1.50° (anteversion), −0.66° and 1.50° (inclination); MyHip Acetabular posterior guide had an average z-axis deviation from the mean value between −0.91° and 0.91°. All surgeries were successfully performed. The surgeon feels a good fitting and stability of the guide during each surgery. A preliminary analysis suggests optimal outcomes in terms of accurate prosthetic component positioning and reduction of occurrence of leg length inequality. Conclusion. Cadaveric sessions show intraobserver and intraobserver agreement, demonstrating reproducibility and repeatability in placement of MyHip patient specific cutting guides. Clinical experience confirms the advantages claimed by this technique, suggesting a possible reduction of complications usually linked to implant malpositioning, such as wear, impingement, risk of luxation

Tightrope fixation is known method for reconstructing acromioclavicular joint and the presence of good bone stock around the two drillholes is the most important determining factor for preventing failure. Aim. Arthroscopic-assisted tightrope stabilisation involve drilling clavicle and coracoids in a straight line. This leads to eccentric drillholes with inadequate bone around it. Open tightrope fixation involves drilling holes under direct vision, independently and leading to centric hole with adequate bone around it. Our study assesses the hypothesis of tightrope fixation in relation to location of drillholes using CT-scan and cadaveric models for arthroscopic and open technique for ACJ fixation. Methods. CT-scans of 20 shoulders performed. Special software used to draw straight line from distal end of clavicle to coracoid. Bone volume around coracoid drillhole was calculated. Cadaveric shoulder specimens were dissected. The arthroscopic technique was performed under vision by drilling both clavicle and base of coracoid holes in one direction. Same specimens were used for open technique. Base of coracoid crossectioned and volume calculated. Results. 40 shoulders were included(20 cadaveric specimens&20 CT). Bone stock was adequate in both techniques. Variable angle for insertion of drillholes using arthroscopic technique were needed depending on shape of shoulder. Conclusion. Tightrope allows nonrigid anatomic fixation of acromioclavicular joint. Published studies showed high rate of fixation failure with tightrope system but with patient satisfaction and high functional results. Our study showed adequate bone stock around coracoid in both open and arthroscopic technique. Mode of failure remains unclear and we recommend further biomechanical studies to assess failure factors

The purpose of this study was to develop a quality appraisal tool for the assessment of laboratory basic science biomechanical studies.

Materials andScore development comprised of the following phases: item identification/development, item reduction, content/face/criterion validity, weighting, test-retest reliability and internal consistency. For item identification/development, the panel was asked to independently list criteria and factors they considered important for cadaver study and generate items that should be used to appraise cadaver study quality. For content validity, the content validity ratio (CVR) was calculated. The minimum accepted content validity index (CVI) was set to 0.85. For weighting, equal weight for each item was 6.7% [15 items]. Based on these figures the panel was asked to either upscale or downscale the weight for each item ensuring that the final sum for all items was 100%. Face validity was assessed by each panel member using a Likert scale from 1–7. Strong face validity was defined as a mean score of >5. Test-retest reliability was assessed using 10 randomly selected studies. Criterion validity was assessed using the QUACS scale as standard. Internal consistency was assessed using Cronbach's alpha.

Five items reached a CVI of 1 and 10 items a CVI of 0.875. For weighting five items reached a final weight of 10% and ten items 5%. The mean score for face validity was 5.6. Test-retest reliability ranged from 0.78–1.00 with 9 items reaching a perfect score. Criterion validity was 0.76 and considered to be strong. Cronbach's alpha was calculated to be 0.71 indicating acceptable internal consistency.

The new proposed quality score for basic science studies consists of 15 items and has been shown to be reliable, valid and of acceptable internal consistency. It is suggested that this score should be utilised when assessing basic science studies.

Novel immersive virtual reality (IVR) technologies are revolutionizing medical education. Virtual anatomy education using head-mounted displays allows users to interact with virtual anatomical objects, move within the virtual rooms, and interact with other virtual users. While IVR has been shown to be more effective than textbook learning and 3D computer models presented in 2D screens, the effectiveness of IVR compared to cadaveric models in anatomy education is currently unknown. In this study, we aim to compare the effectiveness of IVR with direct cadaveric bone models in teaching upper and lower limb anatomy for first-year medical students.

A randomized, double-blind crossover non-inferiority trial was conducted. Participants were first-year medical students from a single University. Exclusion criteria included students who undertook prior undergraduate or graduate degrees in anatomy. In the first stage of the study, students were randomized in a 1:1 ratio to IVR or cadaveric bone groups studying upper limb skeletal anatomy. All students were then crossed over and used cadaveric bone or IVR to study lower limb skeletal anatomy. All students in both groups completed a pre-and post-intervention knowledge test. The educational content was based on the University of Toronto Medical Anatomy Curriculum. The Oculus Quest 2 Headsets (Meta Technologies) and PrecisionOS Anatomy application (PrecisionOS Technology) were utilized for the virtual reality component. The primary endpoint of the study was student performance on the pre-and post-intervention knowledge tests. We hypothesized that student performance in the IVR groups would be comparable to the cadaveric bone group.

50 first-year medical students met inclusion criteria and were computer randomized (1:1 ratio) to IVR and cadaveric bone group for upper limb skeletal anatomy education. Forty-six students attended the study, 21 completed the upper limb modules, and 19 completed the lower limb modules. Among all students, average score on the pre-intervention knowledge test was 14.6% (Standard Deviation (SD)=18.2%) and 25.0% (SD=17%) for upper and lower limbs, respectively. Percentage increase in students’ scores between pre-and post-intervention knowledge test, in the upper limb for IVR, was 15 % and 16.7% for cadaveric bones (p = 0. 2861), and for the lower limb score increase was 22.6% in the IVR and 22.5% in the cadaveric bone group (p = 0.9356).

In this non-inferiority crossover randomized controlled trial, we found no significant difference between student performance in knowledge tests after using IVR or cadaveric bones. Immersive virtual reality and cadaveric bones were equally effective in skeletal anatomy education. Going forward, with advances in VR technologies and anatomy applications, we can expect to see further improvements in the effectiveness of these technologies in anatomy and surgical education. These findings have implications for medical schools having challenges in acquiring cadavers and cadaveric parts.

Novel immersive virtual reality (IVR) technologies are revolutionizing medical education. Virtual anatomy education using head-mounted displays allows users to interact with virtual anatomical objects, move within the virtual rooms, and interact with other virtual users. While IVR has been shown to be more effective than textbook learning and 3D computer models presented in 2D screens, the effectiveness of IVR compared to cadaveric models in anatomy education is currently unknown. In this study, we aim to compare the effectiveness of IVR with direct cadaveric bone models in teaching upper and lower limb anatomy for first-year medical students.

A randomized, double-blind crossover non-inferiority trial was conducted. Participants were first-year medical students from a single University. Exclusion criteria included students who undertook prior undergraduate or graduate degrees in anatomy. In the first stage of the study, students were randomized in a 1:1 ratio to IVR or cadaveric bone groups studying upper limb skeletal anatomy. All students were then crossed over and used cadaveric bone or IVR to study lower limb skeletal anatomy. All students in both groups completed a pre-and post-intervention knowledge test. The educational content was based on the University of Toronto Medical Anatomy Curriculum. The Oculus Quest 2 Headsets (Meta Technologies) and PrecisionOS Anatomy application (PrecisionOS Technology) were utilized for the virtual reality component. The primary endpoint of the study was student performance on the pre-and post-intervention knowledge tests. We hypothesized that student performance in the IVR groups would be comparable to the cadaveric bone group.

50 first-year medical students met inclusion criteria and were computer randomized (1:1 ratio) to IVR and cadaveric bone group for upper limb skeletal anatomy education. Forty-six students attended the study, 21 completed the upper limb modules, and 19 completed the lower limb modules. Among all students, average score on the pre-intervention knowledge test was 14.6% (Standard Deviation (SD)=18.2%) and 25.0% (SD=17%) for upper and lower limbs, respectively. Percentage increase in students’ scores between pre-and post-intervention knowledge test, in the upper limb for IVR, was 15 % and 16.7% for cadaveric bones (p = 0. 2861), and for the lower limb score increase was 22.6% in the IVR and 22.5% in the cadaveric bone group (p = 0.9356).

In this non-inferiority crossover randomized controlled trial, we found no significant difference between student performance in knowledge tests after using IVR or cadaveric bones. Immersive virtual reality and cadaveric bones were equally effective in skeletal anatomy education. Going forward, with advances in VR technologies and anatomy applications, we can expect to see further improvements in the effectiveness of these technologies in anatomy and surgical education. These findings have implications for medical schools having challenges in acquiring cadavers and cadaveric parts.

Orthopaedic training sessions, vital for surgeons to understand post-operative joint function, are primarily based on passive and subjective joint assessment. However, cadaveric knee simulators, commonly used in orthopaedic research,¹ could potentially benefit surgical training by providing quantitative joint assessment for active functional motions. The integration of cadaveric simulators in orthopaedic training was explored with recipients of the European Knee Society Arthroplasty Travelling Fellowship visiting our institution in 2018 and 2019. The aim of the study was to introduce the fellows to the knee joint simulator to quantify the surgeon-specific impact of total knee arthroplasty (TKA) on the dynamic joint behaviour, thereby identifying potential correlations between surgical competence and post-operative biomechanical parameters.

Eight fellows were assigned a fresh-frozen lower limb each to plan and perform posterior-stabilised TKA using MRI-based patient-specific instrumentation. Surgical competence was adjudged using the Objective Structured Assessment of Technical Skills (OSATS) adapted for TKA.² All fellows participated in the in vitro specimen testing on a validated knee simulator,³ which included motor tasks – passive flexion (0°-120°) and active squatting (35°-100°) – and varus-valgus laxity tests, in both the native and post-operative conditions. Tibiofemoral kinematics were recorded with an optical motion capture system and compared between native and post-operative conditions using a linear mixed model (p<0.05). The Pearson correlation test was used to assess the relationship between the OSATS scores for each surgeon and post-operative joint kinematics of the corresponding specimen (p<0.05).

OSATS scores ranged from 79.6% to 100% (mean=93.1, SD=7.7). A negative correlation was observed between surgical competence and change in post-operative tibial kinematics over the entire range of motion during passive flexion – OSATS score vs. change in tibial abduction (r=−0.87; p=0.003), OSATS score vs. change in tibial rotation (r=−0.76; p=0.02). When compared to the native condition, post-operative tibial internal rotation was higher during passive flexion (p<0.05), but lower during squatting (p<0.033). Post-operative joint stiffness was greater in extension than in flexion, without any correlation with surgical competence.

Although trained at different institutions, all fellows followed certain standard intraoperative guidelines during TKA, such as achieving neutral tibial abduction and avoiding internal tibial rotation,⁴ albeit at a static knee flexion angle. However, post-operative joint kinematics for dynamic motions revealed a strong correlation with surgical competence, i.e. kinematic variability over the range of passive flexion post-TKA was lower for more skilful surgeons. Moreover, actively loaded motions exhibited stark differences in post-operative kinematics as compared to those observed in passive motions. In vitro testing on the knee simulator also introduced the fellows to new quantitative parameters for post-operative joint assessment.

In conclusion, the inclusion of cadaveric simulators replicating functional joint motions could help quantify training paradigms, thereby enhancing traditional orthopaedic training, as was also the unanimous opinion of all participating fellows in their positive feedback.

Introduction

In daily clinical practice, progression of spinal fusion is typically monitored during clinical follow-up using conventional radiography and Computed Tomography scans. However, recent research has demonstrated the potential of implant load monitoring to assess posterolateral spinal fusion in an in-vivo sheep model. The question arises to whether such a strain sensing system could be used to monitor bone fusion following lumbar interbody fusion surgery, where the intervertebral space is supported by a cage. Therefore, the aim of this study was to test human cadaveric lumbar spines in two states: after a transforaminal lumbar interbody fusion (TLIF) procedure combined with a pedicle-screw-rod-construct (PSR) and subsequently after simulating bone fusion. The study hypothesized that the load on the posterior instrumentation decreases as the segment stiffens due to simulated fusion.

Understanding the long-term effects of total knee arthroplasty (TKA) on joint kinematics is vital to assess the success of the implant design and surgical procedure. However, while in vitro cadaveric studies quantifying post-operative biomechanics primarily reflect joint behaviour immediately after surgery,¹in vivo studies comprising of follow-up TKA patients often reflect joint behaviour a few months after surgery.² Therefore, the aim of this cadaveric study was to explore the long-term effects of TKA on tibiofemoral kinematics of a donor specimen, who had already undergone bilateral TKA, and compare them to post-operative kinematics reported in the literature.

Two fresh-frozen lower limbs from a single donor (male, age: 83yr, ht: 1.83m, wt: 86kg), who had undergone bilateral TKA (Genesis II, Smith&Nephew, Memphis, USA) 19 years prior to his demise, were obtained following ethical approval from the KU Leuven institutional board. The specimens were imaged using computed tomography (CT) and tested in a validated knee simulator³ replicating active squatting and varus-valgus laxity tests. Tibiofemoral kinematics were recorded using an optical motion capture system and compared to various studies in the literature using the same implant – experimental studies based on cadaveric specimens (CAD)^1,4 and an artificial specimen (ART)⁵, and a computational study (COM)⁶.

Maximum tibial abduction during laxity tests for the left leg (3.54°) was comparable to CAD (3.30°), while the right leg exhibited much larger joint laxity (8.52°). Both specimens exhibited valgus throughout squatting (left=2.03±0.57°, right=5.81±0.19°), with the change in tibial abduction over the range of flexion (left=1.89°, right=0.64°) comparable to literature (CAD=1.28°, COM=2.43°). The left leg was externally rotated (8.00±0.69°), while the right leg internally rotated (−15.35±1.50°), throughout squatting, with the change in tibial rotation over the range of flexion (left=2.61°, right=4.79°) comparable to literature (CAD=5.52°, COM=4.15°). Change in the femoral anteroposterior translation over the range of flexion during squatting for both specimens (left=14.88mm, right=6.76mm) was also comparable to literature (ART=13.40mm, COM=20.20mm).

Although TKA was reportedly performed at the same time on both legs of the donor by the same surgeon, there was a stark difference in their post-operative joint kinematics. A larger extent of intraoperative collateral ligament release could be one of the potential reasons for higher post-operative joint laxity in the right leg. Relative changes in post-operative tibiofemoral kinematics over the range of squatting were similar to those reported in the literature. However, differences between absolute magnitudes of joint kinematics obtained in this study and findings from the literature could be attributed to different surgeons performing TKA, with presumable variations in alignment techniques and/or patient specific instrumentation, and the slightly dissimilar ranges of knee flexion during squatting.

In conclusion, long-term kinematic effects of TKA quantified using in vitro testing were largely similar to the immediate post-operative kinematics reported in the literature; however, variation in the behaviour of two legs from the same donor suggested that intraoperative surgical alterations might have a greater effect on joint kinematics over time.

Unstable distal tibia fractures are challenging injuries requiring surgical treatment. Intramedullary nails are frequently used; however, distal fragment fixation problems may arise, leading to delayed healing, malunion or nonunion. Recently, a novel angle-stable locking nail design has been developed that maintains the principle of relative construct stability, but introduces improvements expected to reduce nail toggling, screw migration and secondary loss of reduction, without the requirement for additional intraoperative procedures.

The aim of this study was to investigate the biomechanical competence of a novel angle-stable intramedullary nail concept for treatment of unstable distal tibia fractures, compared to a conventional nail in a human cadaveric model under dynamic loading.

Ten pairs of fresh-frozen human cadaveric tibiae with a simulated AO/OTA 42-A3.1 fracture were assigned to 2 groups for reamed intramedullary nailing using either a conventional (non-angle-stable) Expert Tibia Nail with 3 distal screws (Group 1) or the novel Tibia Nail Advanced system with 2 distal angle-stable locking low-profile screws (Group 2). The specimens were biomechanically tested under conditions including quasi-static and progressively increasing combined cyclic axial and torsional loading in internal rotation until failure of the bone-implant construct, with monitoring by means of motion tracking.

Initial axial construct stiffness, although being higher in Group 2, did not significantly differ between the 2 nail systems, p=0.29. In contrast, initial torsional construct stiffness was significantly higher in Group 2 compared to Group 1, p=0.04. Initial nail toggling of the distal tibia fragment in varus and flexion was lower in Group 2 compared to Group 1, being significant in flexion, p=0.91 and p=0.03, respectively. After 5000 cycles, interfragmentary movements in terms of varus, flexion, internal rotation, axial displacement and shear displacement at the fracture site were all lower in Group 2 compared to Group 1, with flexion and shear displacement being significant, p=0.14, p=0.04, p=0.25, p=0.11 and p=0.04, respectively. Cycles to failure until both interfragmentary 5° varus and 5° flexion were significantly higher in Group 2 compared to Group 1, p=0.04.

From a biomechanical perspective, the novel angle-stable intramedullary nail concept has the potential of achieving a higher initial axial and torsional relative stability and maintaining it with a better resistance towards loss of reduction under dynamic loading, while reducing the number of distal locking screws, compared to conventional locking in intramedullary nailed unstable distal tibia fractures.

Introduction

Supraspinatus and infraspinatus tears (Massive Rotator Cuff Tear- MRCT) cause compensatory activation of the teres minor (TM) and subscapularis (SubS) to maintain humeral head alignment. This study measures force changes in TM and SubS using a dynamic shoulder testing setup. We hypothesize that combining superior capsule reconstruction (SCR) and lower trapezius tendon (LTT) transfer will correct rotator cuff forces.

Rotator cuff tears are the most common cause of shoulder disability, affecting 10% of the population under 60 and 40% of those aged 70 and above. Massive irreparable rotator cuff tears account for 30% of all tears and their management continues to be an orthopaedic challenge. Traditional surgical techniques, that is, tendon transfers are performed to restore shoulder motion, however, they result in varying outcomes of stability and complications. Superior capsular reconstruction (SCR) is a novel technique that has shown promise in restoring shoulder function, albeit in limited studies. To date, there has been no biomechanical comparison between these techniques. This study aims to compare three surgical techniques (SCR, latissimus dorsi tendon transfer and lower trapezius tendon transfer) for irreparable rotator cuff tears with respect to intact cuff control using a clinically relevant biomechanical outcome of rotational motion.

Eight fresh-frozen shoulder specimens with intact rotator cuffs were tested. After dissection of subcutaneous tissue and muscles, each specimen was mounted on a custom shoulder testing apparatus and physiologic loads were applied using a pulley setup. Under 2.2 Nm torque loading maximum internal and external rotation was measured at 0 and 60 degrees of glenohumeral abduction. Repeat testing was conducted after the creation of the cuff tear and subsequent to the three repair techniques. Repeated measures analysis with paired t-test comparisons using Sidak correction was performed to compare the rotational range of motion following each repair technique with respect to each specimen's intact control. P-values of 0.05 were considered significant.

At 0° abduction, internal rotation increased after the tear (intact: 39.6 ± 13.6° vs. tear: 80.5 ± 47.7°, p=0.019). Internal rotation was higher following SCR (52.7 ± 12.9°, intact - SCR 95% CI: −25.28°,-0.95°, p=0.034), trapezius transfer (74.2 ± 25.3°, intact – trapezius transfer: 95% CI: −71.1°, 1.81°, p=0.064), and latissimus transfer (83.5 ± 52.1°, intact – latissimus transfer: 95% CI: −118.3°, 30.5°, p=0.400) than in intact controls. However, internal rotation post SCR yielded the narrowest estimate range close to intact controls. At 60° abduction, internal rotation increased after the tear (intact: 38.7 ± 14.4° vs. tear: 49.5 ± 13°, p=0.005). Internal rotation post SCR did not differ significantly from intact controls (SCR: 49.3 ± 10.1°, intact – SCR: 95% CI: −28°, 6.91°, p=0.38). Trapezius transfer showed a trend toward significantly higher internal rotation (65.7 ± 21.1°, intact – trapezius transfer: 95% CI: −55.7°, 1.7°, p=0.067), while latissimus transfer yielded widely variable rotation angle (65.7 ± 38°, intact – latissimus transfer: 95% CI: −85.9°, 31.9°, p=0.68). There were no significant differences in external rotation for any technique at 0° or 60° abduction.

Preliminary evaluation in this cadaveric biomechanical study provides positive evidence in support of use of SCR as a less morbid surgical option than tendon transfers. The cadaveric nature of this study limits the understanding of the motion to post-operative timepoint and the results herein are relevant for otherwise normal shoulders only. Further clinical evaluation is warranted to understand the long-term outcomes related to shoulder function and stability post SCR.

Anatomic studies have demonstrated that bipolar glenoid and humeral bone loss have a cumulative impact on shoulder instability, and that these defects may engage in functional positions depending on their size, location, and orientation, potentially resulting in failure of stabilisation procedures. Determining which lesions pose a risk for engagement remains a challenge, with Itoi's 3DCT based glenoid track method and arthroscopic assessment being the accepted approaches at this time. The purpose of this study was to investigate the interaction of humeral and glenoid bone defects on shoulder engagement in a cadaveric model. Two alternative approaches to predicting engagement were evaluated; 1) CT scanning the shoulder in abduction and external rotation 2) measurement of Bankart lesion width and a novel parameter, the intact anterior articular angle (IAAA), on conventional 2D multi-plane reformats.

Hill-Sachs and Bony Bankart defects of varying size were created in 12 cadaveric upper limbs, producing 45 bipolar defect combinations. The shoulders were assessed for engagement using cone beam CT in various positions of function, from 30 to 90 degrees of both abduction and external rotation. The humeral and glenoid defects were characterised by measurement of their size, location, and orientation. The abduction external rotation scan and 2D IAAA approaches were compared to the glenoid track method for predicting engagement.

Engagement was predicted by Itoi's glenoid track method in 24 of 45 specimens (53%). The abduction external rotation CT scan performed at 60 degrees of glenohumeral abduction (corresponding to 90 degrees of abduction relative to the trunk) and 90 degrees of external rotation predicted engagement accurately in 43 of 45 specimens (96%), with sensitivity and specificity of 92% and 100% respectively. A logistic model based on Bankart width and IAAA provided a prediction accuracy of 89% with sensitivity and specificity of 91% and 87%. Inter-rater agreement was excellent (Kappa = 1) for classification of engagement on the abduction external rotation CT, and good (intraclass correlation = 0.73) for measurement of IAAA.

Bipolar lesions at risk for engagement can be identified using an abduction external rotation CT scan at 60 degrees of glenohumeral abduction and 90 degrees of external rotation, or by performing 2D measurements of Bankart width and IAAA on conventional CT multi-plane reformats. This information will be useful for peri-operative decision making around surgical techniques for shoulder stabilisation in the setting of bipolar bone defects.

PURPOSE

To validate the efficacy and accuracy of a novel patient specific guide (PSG) and instrumentation system that enables minimally invasive (MI) short stemmed total shoulder arthroplasty (TSA).

INTRODUCTION

As computer navigated surgery continues to progress to the forefront of orthopedic care, the application of a navigated total shoulder arthroplasty has yet to appear. However, the accuracy of these systems is debated, as well as the dilemma of placing an accurate tool in an inaccurate hand. Often times a system's accuracy is claimed or validated based on postoperative imaging, but the true positioning is difficult to verify. In this study, a navigation system was used to preoperatively plan, guide, and implant surrogate shoulder glenoid implants and fiducials in nine cadaveric shoulders. A novel method to validate the position of these implants and accuracy of the system was performed using pre and post operative high resolution CT scans, in conjunction with barium sulfate impregnated PEEK surrogate implants.

Modular un-cemented acetabular components are used in over 50% of UK hip replacements. Mal-seating of hard liners has been reported as a cause of failure which may be a result of errors in assembly, but also could be affected by deformation of the acetabular shell on insertion. Little information exists on in vivo shell deformation. Previous work has confirmed the importance of shell diameter and thickness upon shell behaviour, but mostly using single measurements in models or cold cadavers.

Exploration of deformation and its relaxation over the first twenty minutes after implantation of eight generic metal cups at body temperature.

Using a previously validated cadaveric model at controlled physiological temperature with standardised surgical technique, we tested the null hypothesis that there was no consistency for time dependent or directional change in deformation for a standard metal shell inserted under controlled conditions into the hip joint. Eight custom made titanium alloy (TiAl6V4) cups were implanted into 4 cadavers (8 hips). Time dependent cup deformation was determined using the previously validated ATOS Triple Scan III (ATOS) optical measurement system. The pattern of change in the shape of the surgically implanted cup was measured at 3 time points after insertion.

We found consistency for quantitative and directional deformation of the shells. There was consistency for relaxation of the deformation with time. Immediate mean change in cup radius was 104μm (sd 32, range 67–153) relaxing to mean 96 μm (sd 32, range 63–150) after 10 minutes and mean 92 μm (sd 28, range 66–138) after 20 minutes.

This work shows the time dependent deformation and relaxation of acetabular titanium shells and may aid determining the optimal time for insertion of the inner liner at surgery.