One-fourth of all ankle trauma involve injury to the syndesmotic ankle complex, which may lead to syndesmotic instability and/or posttraumatic ankle osteoarthritis in the long term if left untreated. The diagnosis of these injuries still poses a deceitful challenge, as MRI scans lack physiologic weightbearing and plain weightbearing radiographs are subject to beam rotation and lack 3D information. Weightbearing cone-beam CT (WBCT) overcomes these challenges by imaging both ankles during bipedal stance, but ongoingdebate remains whether these should be taken under weightbearing conditions and/or during application of external rotation stress. The aim of this study is study therefore to compare both conditions in the assessment of syndesmotic ankle injuries using WBCT imaging combined with 3D measurement techniques.

In this retrospective study, 21 patients with an acute ankle injury were analyzed using a WBCT. Patients with confirmed syndesmotic ligament injury on MRI were included, while fracture associated syndesmotic injuries were excluded. WBCT imaging was performed in weightbearing and combined weightbearing-external rotation. In the latter, the patient was asked to internally rotate the shin until pain (VAS>8/10) or a maximal range of motion was encountered. 3D models were developed from the CT slices, whereafter. The following 3D measurements were calculated using a custom-made Matlab® script; Anterior tibiofibular distance (AFTD), Alpha angle, posterior Tibiofibular distance (PFTD) and Talar rotation (TR) in comparison to the contralateral non-injured ankle.

The difference in neutral-stressed Alpha angle and AFTD were significant between patients with a syndesmotic ankle lesion and contralateral control (P=0.046 and P=0.039, respectively). There was no significant difference in neutral-stressed PFTD and TR angle.

Combined weightbearing-external rotation during CT scanning revealed an increased AFTD in patients with syndesmotic ligament injuries. Based on this study, application of external rotation during WBCT scans could enhance the diagnostic accuracy of subtle syndesmotic instability.

Intra-articular cartilage pressure distribution in the knee joint is critical in the understanding of osteoarthritis. Combining personalized statistical modeling of the morphological characteristics with discrete element modeling enables patient-specific predictions of the pressure on the tibial plateau. However, modeling of the meniscus during gait is complicated by the dynamic nature of the structure. Nevertheless, the position of the meniscus has a substantial impact on intra-articular stress distribution. Therefore, the focus of this presentation will be on how modeling of meniscal movement during knee flexion improves insight in general meniscal kinematics for the use in tibiofemoral stress distribution calculations.

Several emerging reports suggest an important involvement of the hindfoot alignment in the outcome of knee osteotomy. At present, studies lack a comprehensive overview. Therefore, we aimed to systematically review all biomechanical and clinical studies investigating the role of the hindfoot alignment in the setting of osteotomies around the knee.

A systematic literature search was conducted on multiple databases combining “knee osteotomy” and “hindfoot/ankle alignment” search terms. Articles were screened and included according to the PRISMA guidelines. A quality assessment was conducted using the Quality Appraisal for Cadaveric Studies (QUACS) - and modified methodologic index for non-randomized studies (MINORS) scales.

Three cadaveric, fourteen retrospective cohort and two case-control studies were eligible for review. Biomechanical hindfoot characteristics were positively affected (n=4), except in rigid subtalar joint (n=1) or talar tilt (n=1) deformity. Patient symptoms and/or radiographic alignment at the level of the hindfoot did also improve after knee osteotomy (n=13), except in case of a small pre-operative lateral distal tibia- and hip knee ankle (HKA) angulation or in case of a large HKA correction (>14.5°). Additionally, a pre-existent hindfoot deformity (>15.9°) was associated with undercorrection of lower limb alignment following knee osteotomy. The mean QUACS score was 61.3% (range: 46–69%) and mean MINORS score was 9.2 out of 16 (range 6–12) for non-comparative and 16.5 out of 24 (range 15–18) for comparative studies.

Osteotomies performed to correct knee deformity have also an impact on biomechanical and clinical outcomes of the hindfoot. In general, these are reported to be beneficial, but several parameters were identified that are associated with newly onset – or deterioration of hindfoot symptoms following knee osteotomy. Further prospective studies are warranted to assess how diagnostic and therapeutic algorithms based on the identified criteria could be implemented to optimize the overall outcome of knee osteotomy.

Remark: Aline Van Oevelen and Arne Burssens contributed equally to this work

The incisura fibularis (IF) provides intrinsic stability to the ankle joint complex by interlocking the distal tibia and fibula. Despite a high frequency of ligamentous ankle injuries, scant attention has been given to the morphology of the IF morphology incisura fibularis in the onset and development of these lesions. Therefore, we systematically reviewed the relation between ligamentous ankle disorders and the morphometrics of the IF.

A systematic literature search was conducted on following databases: PubMed, Embase and Web of Science. Search terms consisted of ‘ankle trauma’, ‘ankle injury’, ‘ankle sprain’, ‘ankle fracture’, ‘tibiofibular’, ‘fibular notch’, ‘fibular incisura’, ‘incisura fibularis’, ‘morphometric analysis’, ‘ankle syndesmosis’, ‘syndesmotic stability’. The evaluation instrument developed by Hawker et al. was used to assess the quality of the selected studies. This protocol was performed according to the PRISMA guidelines and is registered on PROSPERO (CRD42021282862).

Nineteen studies were included and consisted of prospective cohort (n=1), retrospective comparative (n=10), and observational (n=8) study design. Comparative studies have found certain morphological characteristics in patients with ankle instability. Several studies (n=5) have correlated a shallow IF depth with a higher incidence of ankle injury. A significant difference has also been found concerning the incisura height and angle (n=3): a shorter incisura and more obtuse angle have been noted in patients with ankle sprains. The mean Hawker score was 28 out of 36 (range=24-31).

A shallower IF is associated with ligamentous ankle lesions and might be due to a lower osseous resistance against tibiofibular displacement. However, these results should be interpreted in light of moderate methodological quality and should always be correlated with clinical findings. Further prospective studies are needed to further assess the relation between the incisura morphometrics and ligamentous disorders of the ankle joint.

Keywords: ankle instability, ankle injury, incisura fibularis, fibular notch, tibiofibular morphometrics, ankle syndesmosis

Abstract

Introduction and Objective

The human body is designed to walk in an efficient way. As energy can be stored in elastic structures, it is no surprise that the strongest elastic structure of the human body, the iliofemoral ligament (IFL), is located in the lower limb. Numerous popular surgical hip interventions, however, affect the structural integrity of the hip capsule and there is a growing evidence that surgical repair of the capsule improves the surgical outcome. Though, the exact contribution of the iliofemoral ligament in energy efficient hip function remains unelucidated. Therefore, the objective of this study was to evaluate the influence of the IFL on energy efficient ambulation.

Introduction and Objective

Forced external rotation is hypothesized as the key mechanism of syndesmotic ankle injuries. This complex trauma pattern ruptures the syndesmotic ligaments and induces a three-dimensional deviation from the normal distal tibiofibular joint configuration. However, current diagnostic imaging modalities are impeded by a two-dimensional assessment, without taking into account ligamentous stabilizers. Therefore, our aim is two-fold: (1) to construct an articulated statistical shape model of the normal ankle with inclusion of ligamentous morphometry and (2) to apply this model in the assessment of a clinical cohort of patients with syndesmotic ankle injuries.

Syndesmotic ankle injuries are present in one fourth of all ankle trauma and may lead to chronic syndesmotic instability as well as posttraumatic ankle osteoarthritis. The main challenge remains distinguishing them from other types of ankle trauma. Currently, the patient's injured and non-injured ankles are compared using plain radiographs to determine pathology. However, these try to quantify 3D displacement using 2D measurements techniques and it is unknown to what extent the 3D configuration of the normal ankle syndesmosis is symmetrical.

We aimed to assess the 3D symmetry of the normal ankle syndesmosis between the right and left side in a non- and weightbearing CT.

In this retrospective comparative cohort study, patients with a bilateral non-weightbearing CT (NWBCT; N=28; Mean age=44, SD=17.4) and weight-bearing CT (WBCT; N=33; Mean age=48 years; SD=16.3) were analyzed. Consecutive patients were included between January 2016 and December 2018 when having a bilateral non-weightbearing or weightbearing CT of the foot and ankle. Exclusion criteria were the presence of hindfoot pathology and age less than 18 years or greather than 75 years. CT images were segmented to obtain 3D models. Computer Aided Design (CAD) operations were used to fit the left ankle on top of the right ankle. The outermost point of the apex of the lateral malleolus (AML), anterior tubercle (ATF) and posterior tubercle (PTF) were computed. The difference in the coordinates attached to these anatomical landmarks of the left distal fibula in the ankle syndesmosis with respect to right were used to quantify symmetry. A Cartesian coordinate system was defined based on the tibia to obtain the direction of differences in all six degrees of freedom. Statistical analysis was performed using the Mann-Whitney U test to allow comparison between measurements from a NWBCT and WBCT. Reference values were determined for each 3D measurement in a NWBCT and WBCT based on their 2SD. The highest difference in translation could be detected in the anterior-posterior direction (Mean AP_NWBCT= −0.01mm; 2SD=3.43/Mean AP_WBCT=−0.1mm; 2SD=2.3) and amongst rotations in the external direction (Mean AP_NWBCT=−0.3°; 2SD=6.7/Mean AP_WBCT=-0,2°; 2SD=5.2). None of these differences were statistically significant in the normal ankle syndesmosis when obtained from a NWBCT compared to a WBCT (P>0.05).

This study provides references values concerning the 3D symmetry of the normal ankle syndesmosis in weightbearing and non-weightbearing CT-scans. These novel data contribute relevantly to previous 2D radiographic quantifications. In clinical practice they will aid in distinguishing if a patient with a syndesmotic ankle lesion differs from normal variance in syndesmotic ankle symmetry.

High ankle sprains (HAS) cause subtle lesions in the syndesmotic ligaments of the distal tibiofibular joint (DTFJ). Current intrinsic anatomical parameters of the DTFJ are determined based on 2D imaging and uncertainty remains whether they differ in a HAS patients. The aim of this study is therefore two-fold: radiographic parameters will be determined in 3D and compared in a healthy vs sprained group. Ten patients with a mean age of 42,56 (SD = 15,38) that sustained a HAS and twenty-five control subjects with a mean age of 47,44 (SD = 6,55) were retrospectively included. The slices obtained from CT analysis were segmented to have a 3D reconstruction. The following DTFJ anatomical parameters were computed using CAD software: incisura width, incisura depth, incisura length, incisura angle, and incisura-tibia ratio. The mean incisura depth in the sprained group was 3,93mm (SD = 0,80) compared to 4,76 mm (SD = 1,09) in the control group, which showed a significant difference (P < 0.05). The mean incisura length in the group of patients with HAS was 30,81 mm (SD = 3,17) compared to 36,10mm (SD = 5,27) in the control group which showed a significant difference (P < 0.05). The other DTFJ anatomical parameters showed no significant difference. This study shows a significant difference in both incisura depth and incisura length between HAS patients and control subjects. These parameters could be used to identify potential anatomical intrinsic risk factors in sustaining a HAS.

Introduction

A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). As a closed chain exercise, it has great value in rehabilitation and muscle strengthening of hip and knee. During DS, the hip flexion angle approximates the functional range of hip motion risking femoroacetabular impingement in some morphologies. In-vivo HJRF measurements have been limited to instrumented implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). On the other hand, total hip arthroplasty is being increasingly performed in a younger and higher demanding patient population. These patients clearly have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since measurements of HJRF with instrumented prostheses in healthy subjects would be ethically unfeasible, this study aims to report a personalised numerical solution based on inverse dynamics to calculate realistic in-silico HJRF values during DS.

Hip arthroscopy is a rapidly expanding technique that has a steep learning curve. Simulation may have a role in helping trainees overcome this. However there is as yet no validated hip arthroscopy simulator. This study aimed to test the construct validity of a virtual reality hip arthroscopy simulator.

Nineteen orthopaedic surgeons performed a simulated arthroscopic examination of a healthy hip joint in the supine position. Surgeons were categorized as either expert (those who had performed 250 hip arthroscopies or more) or novice (those who had performed fewer than this). Twenty-one targets were visualized within joint; nine via the anterior portal, nine via the anterolateral and three via the posterolateral. This was followed by a task testing basic probe examination of the joint in which a series of eight targets were probed via the anterolateral portal. Each surgeon's performance was evaluated by the simulator using a set of pre-defined metrics including task duration, number of soft tissue & bone collisions, and distance travelled by instruments. No repeat attempts at the tasks were permitted. Construct validity was then evaluated by comparing novice and expert group performance metrics over the two tasks using the Mann–Whitney test, with a p value of less than 0.05 considered significant.

On the visualization task, the expert group outperformed the novice group on time taken (P=0.0003), number of collisions with soft tissue (P=0.001), number of collisions with bone (P=0.002) and distance travelled by the arthroscope (P=0.02). On the probe examination, the two groups differed only in the time taken to complete the task (P=0.025).

Increased experience in hip arthroscopy was reflected by significantly better performance on the VR simulator across two tasks, supporting its construct validity.

This study validates a virtual reality hip arthroscopy simulator and supports its potential for developing basic arthroscopic skills.

The aim of this study was to determine the accuracy of registration and the precision of the resection volume in navigated hip arthroscopy for cam-type femoroacetabular impingement, using imageless and image-based registration. A virtual cam lesion was defined in 12 paired cadaver hips and randomly assigned to either imageless or image-based (three-dimensional (3D) fluoroscopy) navigated arthroscopic head–neck osteochondroplasty. The accuracy of patient–image registration for both protocols was evaluated and post-operative imaging was performed to evaluate the accuracy of the surgical resection. We found that the estimated accuracy of imageless registration in the arthroscopic setting was poor, with a mean error of 5.6 mm (standard deviation (sd) 4.08; 95% confidence interval (CI) 4.14 to 7.19). Because of the significant mismatch between the actual position of the probe during surgery and the position of that probe as displayed on the navigation platform screen, navigated femoral osteochondroplasty was physically impossible. The estimated accuracy of image-based registration by means of 3D fluoroscopy had a mean error of 0.8 mm (sd 0.51; 95% CI 0.56 to 0.94). In terms of the volume of bony resection, a mean of 17% (sd 11; -6% to 28%) more bone was resected than with the virtual plan (p = 0.02). The resection was a mean of 1 mm deeper (sd 0.7; -0.3 to 1.6) larger than on the original virtual plan (p = 0.02).

In conclusion, given the limited femoral surface that can be reached and digitised during arthroscopy of the hip, imageless registration is inaccurate and does not allow for reliable surgical navigation. However, image-based registration does acceptably allow for guided femoral osteochondroplasty in the arthroscopic management of femoroacetabular impingement.

We report a long term experience on massive rotator cuff tears treated by the means of a nonresorbable transosseously fixed patch combined with a subacromial decompression

From December 1996 until August 2002, a total of 41 patients were treated with a synthetic interposition graft and subacromial decompression. All patients had a preoperative ultrasound evidence of a primary massive full-thickness tear that was thought to be irreparable by simple suture. All patients were evaluated pre- and postoperatively using the Constant and Murley score, DASH questionnaire, Simple Shoulder Test, VAS scale for pain, ultrasound and plain radiographs.

The patients consisted of 23 men and 18 women aged 51–80 years (mean 67 years). We had a lost of follow up of 6 patients. One patient had a total shoulder arthroplasty at 7.7 years and one patient had a redo with a new synthetic graft at 9.6 years. They were followed up for a mean of 7.2 years. Their mean preoperative Constant and Murley score improved from 25.7 preoperatively to 69.6. Similar improvements were seen with the DASH score (56.6 to 23.3), SST (1.2 to 7.9) and VAS scale (75.4 to 14.1)

Anatomically, the repair resulted in mean acromio-humeral interval of 6.6 mm. Ultrasound showed a further degeneration of the rotator cuff with tears posteriorly from the interposition graft. In 67.7% of all patients the graft was continuous present. Histology – obtained from one patient scheduled for a reversed shoulder arthroplasty- showed partial ingrowth of peri-tendinous tissue.

Despite ongoing degeneration of the cuff in nearly half our population, restoring a massive rotator cuff defect with a synthetic interposition graft and subacromial decompression can give significant and lasting pain relief with a significant improvement of ADL, range of motion and strength.

Role of ultrasonography in shoulder pathology: Consistency with clinical and operative findings K. W. Chan, G. G. McLeod Department of Trauma and Orthopaedic Surgery, Perth Royal Infirmary, Perth PH1 1NX, United Kingdom.

Shoulder disorders are common and main causes of shoulder pain with/without functional deficit include adhesive capsulitis (frozen shoulder), impingement syndrome and rotator cuff pathology. The sensitivity and specificity of ultrasonography have been reported as 80% and 100% respectively in the literature. We carried out a retrospective case note review of patients that underwent ultrasonography of shoulder, comparing the radiological findings with clinical diagnosis and operative findings. 58 patients, 36 male and 22 female attended the orthopaedic outpatient clinic with painful shoulder and underwent ultrasonography of shoulder during the period of study. Mean age of patients is 55 (range 28 to 78 years old). 33 patients had ultrasonography of right shoulder, 20 patients had ultrasonography of left shoulder while 5 patients had ultrasonography of both shoulders. 79% (50/63) of the ultrasonography findings were consistent with clinical diagnosis. 17 patients had normal findings on ultrasonography and were discharged fully. 25 patients with clinical and radiological diagnosis of biceps tendon tear, calcifying tendinosis and partial/full thickness rotator cuff tear were treated conservatively. 19% (4/21) of patients with diagnosis of calcifying tendinosis had decompression surgery. 38% (8/21) of patients with diagnosis of partial/full thickness rotator cuff tear had decompression surgery + rotator cuff repair. The degree of rotator cuff tear in operative findings for 6 out of 8 patients (75%) that underwent decompression surgery +/− rotator cuff repair were consistent with ultrasonography findings. 4 patients had inconclusive ultrasonography findings and had magnetic resonance imaging to further confirm the pathology. We conclude that ultrasonography should be used as the first line of investigation in aiding the clinical diagnosis and management of shoulder disorders as it is non-invasive and cost effective. The sensitivity of ultrasonography in detecting shoulder pathology is 75% from this study.

The concept of non-anatomic reversed arthroplasty is becoming increasingly popular. The design medializes and stabilizes the center of rotation, and lowers the humerus relative to the acromion, and lengthens the deltoid muscle up to 18%. Such a surgically created global distraction of muscles is likely to affect nervous structures. When nerves are stretched up to 5–10%, axonal transport and nerve conduction starts to be impaired. At 8% of elongation, venous blood flow starts to diminish and at 15% all circulation in and out of the nerve is obstructed. [1] To understand nerve dynamics following reversed arthroplasty, we investigated nerve strain and excursion in a cadaver model.

In a formalin-embalmed female cadaver specimen, the brachial plexus en peripheral upper limb nerves were carefully dissected and injected with an iodine containing contrast medium. At the same time 1.2 mm-diameter leaded markers were implanted at topographically crucial via points for later enhanced recognition on CT reconstructions. After the first session of CT scanning a plastic replica of the Delta reversed shoulder prosthesis® was surgically placed followed by re-injection of the plexus with the same solution. The preoperative and the postoperative specimen were studied using a helical CT scan with a 0,5 mm slice increment. The Mimics® (Materialise NV, Belgium) software package was used for visualization and segmentation of CT images and 3D rendering of the brachial plexus and peripheral nerves.

After surgery, there was an average increase in nerve strain below physiologically relevant amplitudes. In a few local segments of the brachial plexus an increase in nerve strain exceeding 5–10 % was calculated. The largest increase in strain (up to 19%) was observed in a segment of the medial cord. These results suggest there might be a clinically relevant increase in nerve strain following reversed shoulder arthroplasty.

Physiological studies have revealed that the central nervous system controls groups of muscle fibers in a very efficient manner. Within a single skeletal muscle, the central nervous system independently controls individual muscle segments to produce a particular motor outcome. Mechanomyographic studies on the deltoid muscle have revealed that the deltoid muscle, commonly described as having three anatomical segments, is composed of at least seven functional muscle segments, which all have the potential to be at an important level independently coordinated by the central nervous system.[1] In this study we tried to anatomically describe and quantify these different functional segments within the deltoid muscle, based on the branching out pattern of the axillary nerve.

Forty-four deltoids of 22 embalmed adult cadavers, were analyzed. The axillary nerve was carefully dissected together with his anterior and posterior branch upon invasion into the muscle. According to the pattern of fiber distribution and their fascial embalmment, we then carefully splitted the deltoid muscle into different portions each being innervated by a major branch of the axillary nerve. The position and volume of each segment in relation to the whole muscle was derived.

In 3 cases the axillary nerve branched out in 8 major divisions. In 22 out of 44 cases (50%), the axillary nerve branched out in 7 principal parts. A branching out pattern of 6 major divisions occurred in 14 out of 44 cases. Finally we found a division in 5 major branches in 5 of the specimens. In general, both posterior and anterior peripheral segments seemed to have the largest volume. In nearly all (93%) cases, the central segments were smaller in weight and volume compared to the more peripheral segments.

Based on the innervation pattern of the deltoid muscle a segmentation in 5 up to 8 major segments seem to be found. This confirms from anatomical point of view earlier reports of functional differentiation within the deltoid muscle.

Biomechanical models have been successfully applied to screen potential risk factors for injuries and to plan and evaluate the effects of orthopedic surgical procedures.[1] These models have made apparent the feasibility and necessity for the generation of subject specific models that are aimed at custom clinical applications. In order to develop such models a methods needs to be developed that allows accurate geometrical visualization and reconstruction of position and characteristics of bone and soft tissues, including neurovascular structures.[2] In this study, we present our approach to obtain both bony as soft tissue features necessary for upper limb modeling from computer tomography alone. As a case study the techniques were applied in a non-anatomic shoulder reconstruction.

In order to determine the muscles of the shoulder girdle, ultrathin flexible metallic markers were sutured from origin to insertion according to the fiber directions in all muscles involved in shoulder movement on a total of ten different cadaver shoulders. The plexus brachialis and upper limb nerves were dissected and injected with a iodium contrast containing mixture. A Ct multi-slice image reconstruction was performed from occiput to the hip joint. The software package Mimics® (Materialise NV, Heverlee, Belgium) was used to segment and reconstruct the different anatomical models that included bone, muscle features, nerves and vascular structures. A clustering method algorithm, was used to filter interruptions of the different masks, scattering rustle and small irregularities due to the different contrasting markers used. Vascular tissue could be reconstructed and segmented as air filled structures. We were able to accurately reconstruct nerve tissue in an highly complex configuration such as the plexus brachialis.

Analysis of the representations showed that the different morphologic parameters were within the normal anatomical ranges and that our method is suitable to create complete anatomical models based on Ct-imaging alone.