Lateral Femoral Epicondyle Research Articles

Poster 200: High Prevalence of Abnormal Imaging Findings in Clinically Asymptomatic Siblings Of JOCD Patients On 3T Knee MRI

Objectives:Endochondral ossification is a skeletal developmental process in children by which the embryonic cartilaginous model of bones undergoes gradual ossification over time until skeletal maturity is reached. Juvenile Osteochondritis Dissecans (JOCD) is a developmental disease characterized by focal areas of chondronecrosis within the epiphyseal cartilage and subsequent delay of the ossification front. JOCD lesions can become loose bodies and lead to premature Osteoarthritis. The etiology of JOCD is not yet well understood, however, there is mounting evidence of a genetic predisposition. Recently, positive familial history, including familial OCD and a genome-wide association study in humans identified genetic loci related to juvenile OCD. In this longitudinal pilot study, we examined siblings of JOCD patients utilizing clinical 3T MRI data to evaluate morphological integrity of the epiphyseal cartilage and the advancing ossification front in the distal femoral condyles in bilateral knees. We hypothesized that asymptomatic, clinically “silent” JOCD lesions could be detected in young siblings of patients affected by JOCD.Methods:In this longitudinal study, 44 MRI datasets from seven skeletally immature participants with no clinical symptoms (7 siblings of JOCD patients; 3 females; 12 bilateral knees; average age at first visit=8.7 years; range=6-10 years) were evaluated. This study was approved by the institutional review board and informed consent was obtained. All images were acquired at 3T MRI system with a 1Tx/15Rx knee coil. Sagittal PD-weighted TSE images without fat suppression (TR/TE = 3900/40 ms, resolution = 0.36x0.36 mm2, scanning time = 1min:49s) and with fat suppression (TR/TE = 3530/40 ms, resolution = 0.36x0.36 mm2, scanning time = 3min:46s) were acquired bilaterally at first visit and at multiple MRI follow-up studies ranging from 6-21 months. The images were reviewed by an experienced musculoskeletal radiologist using the following MRI criteria: (i) integrity of the ossification front; (ii) presence/absence of bone marrow edema; (iii) intact/disrupted secondary physis; and (iv) T2 hyperintensity in epiphyseal cartilage.Results:Five of seven participants (71%) met at least one of the MRI criteria defining a JOCD lesion. Six of the seven participants (86%) had an irregular ossification front at the distal aspect of the medial and/or lateral femoral epicondyles, focal areas of T2 hyperintensities in the epiphyseal cartilage, and a disrupted secondary physis. Of the 13 imaged knees, two knees (both lateral and medial epicondyle) from the same participant and two knees (only lateral epicondyle) had no abnormal MRI findings (= 6 normal epicondyles). Abnormal findings in the medial and lateral epicondyles of the remaining bilateral knees resolved over time in 11 epicondyles (Fig. 1), whereas in the remaining 9 epicondyles the abnormal findings persisted or progressed (Fig. 2).Conclusions:The most important finding of this pilot study is the high prevalence (6 out of 7, 86%) of morphological changes during skeletal development in this group of first-degree relatives of JOCD patients. Furthermore, 71% (5 out of 6) of participants met the imaging criteria for early JOCD lesions at least at one time point during the study without developing any clinical symptoms. There is mounting evidence of a genetic contribution to the etiology of JOCD. In the literature, so called ossification variants are considered morphological variants of bone shape with an overall prevalence of 12% and are believed to resolve naturally over time. While 55% of the epicondyles with abnormalities in the ossification front in our cohort resolved over time on MRI, during the course of this study – typically 8-21 months, the remaining 45% did not resolve or occurred at the last imaging time point with associated marrow edema and needed clinical surveillance. A high incidence of MRI abnormalities in the ossification front, epiphyseal cartilage and secondary physis in a clinically asymptomatic study group of first degree relatives of patients with JOCD supports the hypothesis a) that there is a strong genetic predisposition for this disease, b) clinically “silent” initial stages of the disease could be overlooked, challenging the common current understanding of normal physiologic “ossification variants”.Figure 1.Sagittal PD-weighted TSE w/o fat-suppression (FS) of the lateral femoral condyle in a 10-year-old boy. The follow-up studies demonstrate complete resolution of the irregular ossification front (arrowhead), absence of bone marrow edema.Figure 2.Sagittal PD-weighted TSE w/o fat-suppression (FS) of the lateral femoral condyle in a 10-year-old boy. The baseline study demonstrates a focal T2-hyperintense lesion (arrow) and a delayed ossification front with associated bone marrow edema (*) meeting the MR imaging criteria for an early JOCD lesion. The asymptomatic sibling was clinically surveilled and subsequent follow-up studies demonstrated resolution of the MR imaging findings.

Intraobserver Assessment of Shear Wave Elastography in Tensor Fasciae Latae and Gluteus Maximus Muscle: The Importance of the Hip Abductor Muscles in Runners Knee Compared to Healthy Controls.

Background: Iliotibial band syndrome (ITBS) represents one of the most common running related injuries. The pathophysiology is postulated to be caused by excessive ITB tension, impingement and irritation of soft tissues at the lateral femoral epicondyle. However, direct evidence has yet to be found and the multifactorial etiology is under discussion. The purpose was to evaluate stiffness of ITB, gluteus maximus (GM) and tensor fasciae latae (TFL) muscles using shear wave elastography (SWE). Methods: In 14 patients with clinically verified ITBS and 14 healthy controls, three SWE measurements each of ITB, GM and TFL in both legs was performed to determine measurement reliability and between-group and -leg differences. Results: The mean value of ITB was 12.8 m/s with ICC of 0.76, whereas the values measured in the GM were 3.02 m/s with an ICC of 0.87. No statistically significant difference in controls compared to patients were found (p = 0.62). The mean value of TFL was 5.42 m/s in healthy participants, compared to 3.89 m/s patients with an ICC of 0.98 (p = 0.002). Conclusion: Although SWE showed no difference in ITB stiffness, significant differences for TFL muscle stiffness in runner’s knee was found, suggesting that the hip abductor muscles might play a bigger role in the pathophysiology of ITBS. We aimed to implement baseline values for stiffness assessments and prove reliability for further prospective studies of SWE in runner’s knee.

Anterolateral ligament of the knee—Cadaver study in a Caucasian population

IntroductionDespite the recognized importance of the anterolateral ligament (ALL) in rotational stability of the knee, some studies still deny its role and even its existence. We studied the prevalence of the ALL in a Caucasian population, as well as its characteristics and anatomical relationships. Materials and methodsThe study was performed on 20 knees from 10 embalmed cadavers. A lateral approach, as described by Steven Claes, was used and the relations of the ALL with the lateral epicondyle, lateral inferior genicular artery, lateral meniscus, Gerdy's tubercle and fibular head were recorded. Its length and its width were also measured. ResultsThe ALL was identified in 16 knees. Its origin was at a distance inferior to 1mm posterior and proximal to the lateral femoral epicondyle and insertion within a mean distance of 2.1±0.6mm from de tibial articular surface, 20.6±1.3mm from the Gerdy's tubercle and 20.3±1.2mm from the fibular head. In all cases ALL presented mutual fibers with the lateral meniscus. The length was 35.8±4.6mm and the width was 4.2±1.3/4.9±1.0/6.5±1.5mm at its proximal, middle and distal third, respectively. No difference was found between gender and the dimensions of the ligament. ConclusionsThe ALL was found in 80% of the knees. Its origin is closely related to the lateral collateral ligament and its insertion is halfway between the fibular head and the Gerdy's tubercle. In all cases, we verified the connection between ALL and the lateral meniscus.

High Rates of Damage to the Medial Patellofemoral Ligament, Lateral Trochlea, and Patellar Crest After Acute Patellar Dislocation: Magnetic Resonance Imaging Analysis

The primary outcome of interest of this study was to determine the frequency, location, and extent of chondral injuries and medial patellofemoral ligament (MPFL) tears, along with the rate of loose bodies, in the knee after acute primary patellar dislocation. The secondary outcome of interest was to conduct a multivariate analysis to investigate whether the presence of pathoanatomic abnormalities, including structural differences in the knees of the patients, is associated with the features of the lesions. Patients who underwent magnetic resonance imaging after primary acute patellar dislocation were identified from our institutional databases. We analyzed a total of 175 magnetic resonance imaging scans of patients aged between 14 and 25 years who were eligible for inclusion. Chondral damage to the medial facet of the patella was present in 36 patients; patellar crest, 78 patients; and lateral patellar facet, 28 patients. One patient presented with chondral defects in the medial trochlear facet, whereas 118 patients showed chondral defects in the lateral trochlear facet. Loose bodies were present in 142 patients. A total of 161 patients (92%) showed MPFL damage. The patellar portion was affected in 119 patients. Of the patients, 28 showed a partially damaged MPFL (<50%), 42 showed MPFL damage greater than 50%, and 49 presented with a complete tear of the MPFL. MPFL lesions were observed on the femoral side in 42 patients. Fourteen patients presented with an avulsion fracture on the patellar side; 28 patients, on the femoral side. The MPFL was injured in 92% of 175 patients after a first-time acute patellar dislocation. Chondral damage was most frequent at the patellar crest, followed by the lateral femoral epicondyle. No association was found between patella alta, the sulcus angle, the Q angle, the tibial tubercle-trochlear groove distance, trochlear and patellar dysplasia, and soft-tissue damage. Level IV, retrospective cohort study.

Kinematic Analysis During Straight Line Free Swimming in Horses: Part 2 - Hindlimbs.

BackgroundSwimming is used for rehabilitation and conditioning purposes in equine sports medicine. We described the swimming kinematics of the equine forelimbs in Part 1. The aim of Part 2 is to assess stifle, tarsus, and hind fetlock joints kinematics in swimming horses. The objectives were 1- to calculate and compare joint angles during swimming against passive mobilizations (PM), 2- to determine joints angular velocities during a swimming stride cycle.MethodsEleven elite endurance horses were used to swim in a 100-meter straight pool. Underwater (swimming) and overground PM videos were recorded from the horses' left side. Joint markers were applied on the lateral hoof wall, lateral metatarsal epicondyle, lateral aspect of the talus, lateral femoral epicondyle, and great trochanter of the femur. As a reference, maximal fetlock, tarsus, and stifle flexion/extension angles were determined during PM overground. Differences between angle extrema, angular velocities, and range of motion (ROM) were statistically compared.ResultsThe tarsus ROM was similar during PM and swimming. The stifle and fetlock ROM were greater during PM, although the stifle flexion was greater during swimming. The stifle and tarsus had the greatest hindlimb angular velocity during the swimming cycle. Greater angular velocities were observed during the retraction phase for all the hindlimb joints.ConclusionA short retraction phase with great angular velocity for the joints of interest characterized the swimming pattern observed. Swimming may be beneficial in horses when an increased ROM of the tarsus and stifle or a reduced fetlock extension is indicated for rehabilitation purposes.

The Modified Lemaire Procedure

Background: Anterolateral rotatory instability (ALRI) may be one reasons why anterior cruciate ligament (ACL) reconstructions fail. An additional reconstruction of the anterolateral structures reduces the graft rupture rate by 50%. The modified Lemaire procedure is one of the lateral extra-articular tenodeses (LET) to restrain ALRI. The purpose of the present video is to describe this technique in detail. Indications: According to the international anterolateral complex consensus group indications may include revision ACL reconstruction, high grade pivot shift, generalized ligamentous laxity, like genu recurvatum, and young patients returning to pivoting activities. However, clinical evidence to recommend specific indications is still missing. Technique description: A 7 to 10 mm wide strip of the iliotibial tract, attached to Gerdy tubercle is shuttled deep to the lateral collateral ligament and is then attached proximal to the lateral femoral epicondyle. The biomechanical principle behind this is to place the graft posterior to the transverse axis of rotation through the entire range of motion. This posterior pull will restrain internal rotation and the anterior subluxation of the lateral tibial plateau. Results: Newer comparative studies show a reduced graft rupture rate and higher rate of returning to preinjury level, when adding an anterolateral extra-articular reconstruction to the ACL reconstruction at 2 years follow-up. At long-term follow-up there was also a trend toward decreased graft rupture rate. However, one must be aware of the possible increased risk of lateral compartment osteoarthritis. Conclusion: The modified Lemaire procedure is an easy-to-use addon to the ACL reconstruction, which can effectively reduce graft failure rate.

Evaluation of Hip Frontal Plane Flexibility and Strength in Male Sprinter Runners With Unilateral Patellofemoral Arthropathy: A Case-Control Study

Background and Objectives: Patellofemoral Arthropathy (PFA) is the most common knee disorder in runners and various factors can lead to the development of its symptoms. It has been proposed that frontal plane motions of the hip and knee can raise the dynamic quadriceps angle during functional tasks. The aim of this study was to evaluate frontal plane acting hip muscle flexibility and strength differences in male sprinter runners with unilateral PFA. Methods: A total of 38 male runners complaining of peripatellar pain or showing positive unilateral patellar grind test, assigned to the normal and sound legs, and 20 matched control groups were compared in this case-control study. Participants’ hip abductor and adductor muscles strength and their flexibility were evaluated through a hand-held dynamometer and 2D motion analysis tracker software. To measure the strength, participants were positioned side-lying position, performing abduction and adduction, while a dynamometer was placed on the lateral and medial femoral epicondyle. Active and passive abduction and adduction range of motion were recorded via a camera in the supine position and the film was analyzed by the software. Results: Abductor muscle strength and abduction-to-adduction ratio on the involved side were significantly lower than the uninvolved side (P=0.029, P=0.008, d=-0.388, d=-0.459), while greater adduction and lower abduction to adduction ratio were found in the control group (P&lt;0.001, F=3.599). Also, lesser passive abduction and active adduction range of motion were found in the control group on both sides (P&lt;0.001, F=2.792, F=8.979). Conclusion: Strength changes of the involved side compared with uninvolved side and less flexible side, but more probably inhibited and stronger adductors in the control group may suggest impaired muscular interaction based on frontal plane muscles torque/length curve function in unilateral PFA. Changes in the strength of the involved side compared to the healthy side and the adductor muscles with more flexibility and strength but more inhibited by the abductor’s muscles in the control group could indicate.

Femoral Positioning of the Anterolateral Ligament Graft With and Without Ultrasound Location of the Lateral Epicondyle

Background: In anterior cruciate ligament (ACL) reconstruction with anterolateral ligament (ALL) reconstruction, precise positioning of the ALL graft on the femur and tibia is key to achieve rotational control. The lateral femoral epicondyle is often used as a reference point for positioning of the ALL graft and can be located by palpation or with ultrasound guidance. Purpose: To compare the ALL graft positioning on the femoral side between an ultrasound-guided technique and a palpation technique for the location of the lateral epicondyle. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 120 patients receiving a primary combined ACL and ALL reconstruction between June and December 2019 were included. The location of the lateral epicondyle was determined by palpation in the palpation group (n = 60) and with preoperative ultrasound guidance in the ultrasound group (n = 60). Groups were comparable in age, sex, body mass index (BMI), and operated side. The planned positioning of the femoral ALL graft was proximal and posterior to the lateral epicondyle. The effective positioning of the femoral ALL graft was evaluated on postoperative lateral radiographs. The primary outcome was location of the graft in a 10-mm quadrant posterior and proximal to the lateral epicondyle. Results were analyzed in 2 subgroups according to BMI. Results: All 60 anterolateral grafts (100%) in the ultrasound group were positioned in a 10-mm quadrant posterior and proximal to the lateral epicondyle, as opposed to 52 (87%) in the palpation group (P = .006). Errors in graft positioning with palpation occurred in overweight patients (BMI >25) as well as nonoverweight patients (P = .3). Conclusion: Femoral positioning of the ALL graft posterior and proximal to the lateral epicondyle is more reproducible with ultrasound guidance when compared with palpation alone, regardless of BMI.

Appropriate determination of the surgical transepicondylar axis can be achieved following distal femur resection in navigation-assisted total knee arthroplasty

BackgroundMany surgeons have determined the surgical transepicondylar axis (sTEA) after distal femur resection in total knee arthroplasty (TKA). However, in most navigation systems, the registration of the sTEA precedes the distal femur resection. This sequential difference can influence the accuracy of intraoperative determination for sTEA when considering the proximal location of the anatomical references for sTEA and the arthritic environment. We compared the accuracy and precision in determinations of the sTEA between before and after distal femur resection during navigation-assisted TKA.MethodsNinety TKAs with Attune posterior-stabilized prostheses were performed under imageless navigation. The sTEA was registered before distal femur resection, then reassessed and adjusted after distal resection. The femoral component was implanted finally according to the sTEA determined after distal femur resection. Computed tomography (CT) was performed postoperatively to analyze the true sTEA (the line connecting the tip of the lateral femoral epicondyle to the lowest point of the medial femoral epicondylar sulcus on axial CT images) and femoral component rotation (FCR) axis. The FCR angle after distal femur resection (FCRA-aR) was defined as the angle between the FCR axis and true sTEA on CT images. The FCR angle before distal resection (FCRA-bR) could be presumed to be the value of FCRA-aR minus the difference between the intraoperatively determined sTEAs before and after distal resection as indicated by the navigation system. It was considered that the FCRA-bR or FCRA-aR represented the differences between the sTEA determined before or after distal femur resection and the true sTEA, respectively.ResultsThe FCRA-bR was −1.3 ± 2.4° and FCRA-aR was 0.3 ± 1.7° (p < 0.001). The range of FCRA-bR was from −6.6° to 4.1° and that of FCRA-aR was from −2.7° to 3.3°. The proportion of appropriate FCRA (≤ ±3°) was significantly higher after distal femur resection than that before resection (91.1% versus 70%; p < 0.001).ConclusionsThe FCR was more appropriate when the sTEA was determined after distal femur resection than before resection in navigation-assisted TKA. The reassessment and adjusted registration of sTEA after distal femur resection could improve the rotational alignment of the femoral component in navigation-assisted TKA.Level of evidenceIV.

EIF2α-ATF4 Pathway Activated by a Change in the Calcium Environment Participates in BCP-Mediated Bone Regeneration.

Biphasic calcium phosphate (BCP) ceramic is a classic bone void filler and a common basis of new materials for bone defect repair. However, the specific mechanism of BCP in osteogenesis has not been fully elucidated. Endoplasmic reticulum stress (ERs) and the subsequent PERK-eIF2α-ATF4 pathway can be activated by various factors, including trauma and intracellular calcium changes, and therefore worth exploring as a potential mechanism in BCP-mediated bone repair. Herein, a rat lateral femoral epicondyle defect model in vivo and a simulated BCP-mediated calcium environment in vitro were constructed for the analysis of BCP-related osteogenesis and the activation of ERs and the eIF2α-ATF4 pathway. An inhibitor of eIF2α dephosphorylation (salubrinal) was also used to explore the effect of the eIF2α-ATF4 pathway on BCP-mediated bone regeneration. The results showed that the ERs and eIF2α-ATF4 pathway activation were observed during 4 weeks of bone repair, with a rapid but brief increase immediately after artificial defect surgery and a re-increase after 4 weeks with the resorption of BCP materials. Mild ERs and the activated eIF2α induced by the calcium changes mediated by BCP regulated the expression of osteogenic-related proteins and had an important role during the defect repair. In conclusion, the eIF2α-ATF4 pathway activated by a change in the calcium environment participates in BCP-mediated bone regeneration. eIF2α-ATF4 and ERs could provide new directions for further studies on new materials in bone tissue engineering.

High Rate of Initially Overlooked Kaplan Fiber Complex Injuries in Patients With Isolated Anterior Cruciate Ligament Injury

Background: Injuries to the Kaplan fiber complex (KFC) are not routinely assessed for in the anterior cruciate ligament (ACL)-deficient knee during preoperative magnetic resonance imaging (MRI). As injuries to the KFC lead to anterolateral rotatory instability (ALRI) in the ACL-deficient knee, preoperative detection of these injuries on MRI scans may help surgeons to individualize treatment and improve outcomes, as well as to reduce failure rates. Purpose: To retrospectively determine the rate of initially overlooked KFC injuries on routine MRI in knees with isolated primary ACL deficiency. Study Design: Case series; Level of evidence, 4. Methods: Patients who underwent isolated ACL reconstruction between August 2013 and December 2019 were identified. No patient had had Kaplan fiber (KF) injury identified on the initial reading of the MRI scan or at the time of surgery. Preoperative knee MRI scans (minimum 1.5 T) were reviewed and injuries to the proximal and distal KFs were recorded by 3 independent reviewers. KF length and distance to nearby anatomic landmarks (the lateral joint line and the lateral femoral epicondyle) were measured. Additional radiological findings, including bleeding, lateral femoral notch sign, and bone marrow edema (BME), were identified to detect correlations with KFC injury. Results: The intact KFC could reliably be identified by all 3 reviewers (85.9% agreement; Kappa, 0.716). Also, 53% to 56% of the patients with initially diagnosed isolated ACL ruptures showed initially overlooked injuries to the KFC. Injuries to the distal KFs were more frequent (48.1%, 53.8%, and 43.3% by the first, second, and third reviewers, respectively) than injuries to the proximal KFs (35.6%, 47.1%, and 45.2% by the first, second, and third reviewers, respectively). Bleeding in the lateral supracondylar region was associated with KFC injuries (P = .023). Additionally, there was a positive correlation between distal KF injuries and lateral tibial plateau BME (P = .035), but no associations were found with the lateral femoral notch sign or other patterns of BME, including pivot-shift BME. Conclusion: KF integrity and injury can be reliably detected on routine knee MRI scans. Also, 53% to 56% of the patients presenting with initially diagnosed isolated ACL ruptures had concomitant injuries to the KFC. This is of clinical relevance, as ACL injuries diagnosed by current routine MRI examination protocols may come with a high number of occult or hidden KFC injuries. As injuries to the KFC contribute to persistent ALRI, which may influence ACL graft failure or reoperation rates, significant improvements in preoperative diagnostic imaging are required to determine the exact injury pattern and to assist in surgical decision making.

Defining the popliteal fossa by bony landmarks and mapping of the courses of the neurovascular structures for application in popliteal fossa surgery.

Surgical access to the posterior knee poses a high-risk for neurovascular damage. The study aimed to define the popliteal fossa by reliable bony landmarks and comprehensively mapping the neurovascular structures for application in posterior knee surgery. Forty-five (20 male, 25 female) embalmed adult cadaveric knees were included. The position of the small saphenous vein (SSV), medial cutaneous sural nerve (MCSN) and lateral cutaneous sural nerv (LCSN), tibial nerve (TN) and common fibular nerve (CFN) nerves, and popliteal vein (PV) and popliteal artery (PA) were determined in relation to either medial (MFE) or lateral (LFE) femoral epicondyles, medial (MTC) and lateral (LTC) tibial condyles and the midpoint between the MFE and MTC and LFEF and LTC. The distance between the MFE and the PA, PV, TN, MCSN, and SSV was 38.4±12.1 mm, 38.4±12.9 mm, 39.4±10.2 mm, 39.2±14.0 mm and 37.6±12.5 mm respectively for males and 34.6±4.9 mm, 32.8±5.6 mm and 38.0±8.1 mm 38.8±10.1 mm and 37.9±8.2 mm respectively for females. The distance between LFE and the CFN and LCSN was 13.4±8.2 mm and 24.9±7.3 mm respectively for males and 8.4±9.1 mm and 18.4±10.4 mm respectively in females. This study defined the popliteal fossa by reliable bony landmarks and provided a comprehensive map of the neurovascular structures and will help to avoid injuries to the important neurovascular structures.

The anatomy of Kaplan fibers.

Kaplan fibers (KF) have been described as connections between the iliotibial band and the distal femur. They are divided into two distinct structures, proximal (PKF) and distal (DKF) fibers, which may participate in the control of the rotatory knee stability. Their anatomical characteristics have not been investigated completely, in particular with respect to reconstruction procedures. The aim was to determine their anatomical characteristics and their morphological variation. Twenty-one nonpaired fresh frozen human cadaveric knees (from whole leg) were used for the analysis of PKF and DKF through an anterolateral approach. The anatomical relationships between the adjacent anterolateral structures were reported and anatomical characteristics of PKF and DKF (thickness, width and length) measured at 50° knee flexion under different rotational conditions (neutral: NR, Internal at 5Nm: IR applied with a dynamometric torque rig). Bony ridges of PKF and DKF were measured. PKF and DKF and their respective bony ridges were individually identified in all knees studied (n = 21). The PKF and DKF were proximal and posterior to the lateral femoral epicondyle, respective distances 49.20 ± 7.38 and 27.54 ± 7.69mm. DKF were thicker (p < 0.001), wider (p < 0.001) and longer (p < 0.001) than the PKF, regardless of the tibial rotation applied. Tensioning of KF was achieved in IR with a decrease in thickness and width, alongside fiber lengthening (p < 0.001). PKF and DKF are distinct and constant anatomical structures of the lateral compartment of the knee, whose anatomical characteristics and their tensioning in IR presume a function of controlling rotational knee stability.

The determination of safe zones for arthroscopic portal placement into the posterior knee by mapping the courses of neurovascular structures in relation to bony landmarks.

Minimally invasive surgery in the posterior knee is high risk for iatrogenic injury to popliteal neurovascularneurovasculature structures. This study aimed to use reliable landmarks to define safe zones for arthroscopic portal placement into the posterior knee. Distances were measured between bony landmarks and neurovascular structures within the popliteal fossa using 45 formalin-embalmed cadavers: small saphenous vein (SSV), medial (MCSN) and lateral (LCSN) cutaneous sural nerves, tibial nerve (TN), common fibular nerve (CFN), popliteal vein (PV) and artery (PA). The structures were measured in relation to medial (MEF) and lateral (LEF) femoral epicondyle, medial (MCT) and lateral (LCT) tibial condyle and the midpoint between the landmarks. The mean distance (mm) between MEF and structures was, male and female, respectively: SSV 37.6 + 12.5, 37.9 + 8.2; MCSN 39.2 + 14, 38.8 + 10.1; TN 39.4 + 10.2, 38.0 + 8.1; PV 38.4 + 12.9, 32.8 + 5.6; PA 38.4 + 12.1, 34.6 + 4.9. At midpoint and MCT all structures medialized between 5 and 28%. The mean distance between LEF and structures was, male and female, respectively: CFN 13.4 + 8.2, 8.4 + 9.1; LCSN 24.9 + 7.3, 18.4 + 10.4. At midpoint and LCT the CFN lateralized by 37-42% and the LCSN medialized by 8-9%. Results suggest posteromedial portal placement can be safely established < 20mm from the medial femoral epicondyle, tibial condyle or the midpoint between the two landmarks. Posterolateral portal placement is of higher risk, and entry point is 18mm from the lateral femoral epicondyle, tibial condyle or the midpoint between the two landmarks in males and 12mm in females. These landmarks will allow safe portal placement in 99% of cases.

The effect of simulated marker misplacement on the interpretation of inter-limb differences during a change of direction task

The objective assessment of biomechanical asymmetries during movement tasks is used to monitor rehabilitation following anterior cruciate ligament reconstruction (ACLR). Marker placement is an important source of methodological variability within human motion analysis. It is currently unclear how marker placement error effects the interpretation of biomechanical asymmetries throughout post ACLR rehabilitation. The aim of this investigation was to determine the effect of random marker placement variation on the interpretation of inter-limb differences during a change of direction (CoD) task. Forty-seven participants 9 months post-ACLR and fifty uninjured controls completed a 90° CoD task on both limbs. Inter-limb differences in kinematic and kinetic metrics during the CoD stance phase were calculated for both groups using the Vicon Plug-in Gait model, and ACLR subjects were classified as having ‘normal’ or ‘abnormal’ inter-limb differences relative to the control group. Simulated random marker displacements based on published marker placement error ranges were then repeatedly applied to the lateral thigh, femoral epicondyle and tibia markers. ACLR inter-limb differences were recalculated each time, allowing the estimation of 95% confidence intervals and minimal identifiable between-session changes. ACLR subjects were also reclassified relative to the control group after each simulation and the percentage of participants to change classification was calculated. Marker displacements caused large deviations in inter-limb difference measures in several variables including hip rotation angle, knee abduction angle and knee abduction moment, thus limiting the ability to identify participants with large inter-limb differences relative to a control group. These findings highlight the challenges in using marker-based biomechanical models to conduct objective assessments of inter-limb differences during CoD tasks.

ILIOTIBIAL BAND SYNDROME IN CYCLING: A COMBINED EXPERIMENTAL-SIMULATION APPROACH FOR ASSESSING THE EFFECT OF SADDLE SETBACK.

Despite abundant literature, the treatment of iliotibial band syndrome (ITBS) in cyclists remains complicated as it lacks evidence-based recommendations. The aim of this study was to develop a musculoskeletal modelling approach that investigates three potential biomechanical determinants of ITBS (strain, strain rate and compression force) and to use this approach to investigate the effect of saddle setback. Cross-sectional. An existing 3D lower-body musculoskeletal model was adapted to cycling and to the computation of three putative pathomechanisms responsible for ITBS: ITB strain, ITB strain rate, and compression force between ITB and the lateral femoral epicondyle (LFE). Lower limb kinematics recorded from ten well-trained healthy cyclists served as input data of the model. Cyclists pedalled at a steady state (90rpm and 200W) on an ergometer, and three different saddle setback conditions were tested. The theoretical combined influence of hip and knee joint angles on ITBS was investigated and analysed through the lens of individual pedalling technique. ITB-LFE compression force was the only parameter significantly affected by saddle setback and supports the hypothesis that compression force is likely to be a determinant factor in ITBS etiology. Furthermore, results showed that ITB-LFE compression force increases in individuals whose pedalling technique exacerbates hip extension-adduction and/or knee extension-internal rotation. This approach has the potential to be advantageously implemented as an additional tool to help diagnose/correct potentially harmful sport techniques and optimize equipment setup/design. 3b.

Unique myological changes associated with ossified fabellae: a femorofabellar ligament and systematic review of the double-headed popliteus.

IntroductionThe fabella is a sesamoid bone embedded in the tendon of the lateral head of the gastrocnemius. It is the only bone in the human body to increase in prevalence in the last 100 years. As the fabella can serve as an origin/insertion for muscles, tendons, and/or ligaments (e.g., the oblique popliteal and fabellofibular ligaments), temporal changes in fabella prevalence could lead to temporal changes in “standard” knee anatomy. The aim of this study was to investigate unique myological changes to the posterolateral corner knee associated with ossified fabella presence and perform a systematic review to contextualize our results.MethodsThirty-three fresh frozen cadaveric knees were considered. As the knees were all used for previous experimentation, the knees were in variable levels of preservation. Those with adequate preservation were used to determine ossified fabella presence/absence. When ossified fabellae were present, unique myologies associated with the fabella were recorded. A systematic review was performed on the double-headed popliteus to investigate possible correlations between this anatomical variant and the fabella.ResultsOf the 33 knees, 30 preserved enough soft tissue to determine fabella presence/absence: 16/30 knees had fabellae (five cartilaginous and 11 ossified). Eight of the eleven knees with ossified fabellae retained enough soft tissue to investigate the posterolateral knee anatomy. Of these, 4/8 exhibited unique myological changes. One knee had a double-headed popliteus muscle where one head originated from the medial side of a large, bulbous fabella. A systematic review revealed double-headed popliteus muscles are rare, but individuals are 3.7 times more likely to have a fabella if they have a double-headed popliteus. Another knee had a large, thick ligament stretching from the lateral edge of the fabella to the inferoposterior edge of the lateral femoral epicondyle, deep to the lateral collateral ligament (LCL) and near the popliteal sulcus. We found no mention of such a ligament in the literature and refer to it here as the “femorofabellar ligament”. In all four knees, the plantaris and lateral gastrocnemius appeared to share a common tendinous origin, and the fabella was located at/near the junction of these muscles. In the case of the double-headed popliteus, the fabella clearly served as an origin for the plantaris.ConclusionsDespite being found in an average of 36.80% of human knees, most standard anatomical models fail to account for the fabella and/or the unique myological changes associated with fabella presence. Although our sample is small, these data highlight aspects of human biological variability generally not considered when creating generalized anatomical models. Further work is needed to identify additional changes associated with ossified fabellae and the functional consequences of omitting these changes from models.

Extended approach to the lateral tibial plateau with central meniscal subluxation in fracture repair: feasibility and first clinical and radiographic results

PurposeAnatomic reduction in tibial plateau fractures remains to be demanding. For further visualisation of and approach to the joint surface an extended lateral approach using a lateral femoral epicondyle osteotomy and subluxation of the lateral meniscus was recently described. First clinical and radiographic mid-term results of this technique are presented in this feasibility study.MethodTen complex tibial plateau fractures treated with extended lateral approach and lateral meniscal subluxation were prospectively analysed. Clinical and radiographic results were objectified according to the Rasmussen scores.ResultsAfter a median follow-up of 8.6 (IQR 4.3) months good to excellent clinical and radiographic results were noted. The clinical Rasmussen Score showed a median of 25 (IQR 2.8) and radiographic a median of 17 (IQR 2.0) points.ConclusionGood to excellent clinical and radiological scores were obtained after using an extended lateral approach with lateral femoral epicondyle osteotomy and central meniscus subluxation. No approach specific complications could be observed.

Anterolateral ligament in pediatric knees: A radiographic study

Background: The anterolateral ligament (ALL) is a true well-defined ligament in the knee first described in 1879 by Segond. After the work of Claes et al., several studies were conducted about biomechanics and its role in stability of the knee. The anatomical existence of the ALL has been studied by and various radiographic diagnostic modalities and in cadavers. It originates from lateral femoral epicondyle and is inserted between Gerdy’s tubercle and the fibular head. There has been controversy about the existence of ALL in pediatric patients. The aim of this work was to confirm the presence of ALL in pediatric patients by using MRI. Materials and Methods: We reviewed the knee MRI scans of 100 pediatric patients (ages between one and 12 yr) who had no knee injury or congenital deformity and had been evaluated by an expert radiologist. Results: The ALL was detected in 90% of the pediatric patients with the use of MRI. Conclusions: The main finding of this study was that ALL can be seen in pediatric patients using MRI. Despite numerous studies, additional research is needed to further define the role of the ALL in knee function. Level of Evidence: Level IV.

Microstructural and Mechanical Properties of the Anterolateral Ligament (ALL) of the Knee

Objectives:The anterolateral ligament (ALL) of the knee has recently emerged as a potential contributor to rotational stability of the knee, with growing interest in ALL reconstruction as a supplement to anterior cruciate ligament reconstruction. The prevalence of the ALL in the knee has varied in anatomic dissection and imaging studies, raising questions about its importance as a knee stabilizer. The purpose of this study was to assess the microstructural and mechanical properties of the anterolateral knee, to better understand the ALL structure compared to the surrounding anterolateral capsule (ALC) and lateral collateral ligament (LCL). A polarized light imaging technique was used to quantify collagen fiber alignment simultaneously with measurement of tensile mechanical properties. Our primary hypothesis was that there is no difference in the microstructural and mechanical properties between the ALL and ALC. Our secondary hypothesis was that the properties of the LCL are different from the ALL and ALC.Methods:Twenty-five knee specimens from sixteen donors (five males, eleven females; mean age 45.6 +/- 6.4; age range 35-59 years; mean BMI 26.5 +/- 8.4) were obtained as determined by a priori power analysis. The anatomic technique to dissect the anterolateral knee structures was performed as described previously. Three tissue samples (LCL, ALL, and ALC) were harvested (Fig. 1). The ALL was taken as a quadrilateral piece of tissue starting posterior/proximal from the lateral femoral epicondyle and ending at the lateral border of Gerdy’s tubercle. During gross dissection, the knee was assessed for the presence or absence of a distinct visible and palpable structure within the area defined as the ALL. Harvested samples were thinned to approximately 1-mm thick using a freezing-stage sliding microtome. Cross-sectional area was measured using a 3D laser scanning system. Four 0.8-mm diameter aluminum beads were attached to the sample surface to enable strain measurement. Mechanical testing was performed with preconditioning followed by both a stress-relaxation test and a quasi-static ramp to failure. Microstructural analysis was performed using transmitted circularly-polarized incident light and a high-resolution, division-of-focal-plane polarization camera. The average degree of linear polarization (AVG DoLP; i.e., mean strength of collagen alignment) and standard deviation of the angle of polarization (STD AoP; i.e., degree of variation in collagen angle orientation) were calculated for the region of interest of each sample. Statistical analysis was performed using Kruskal-Wallis test (assuming nonparametric data) with Dunn’s correction for multiple comparisons.Results:Mechanical analysis of elastic moduli for the toe- and linear-region of the stress-strain curves showed no difference between the ALL and ALC but were significantly higher for the LCL (p<0.0001; Fig. 2). Microstructural analysis of the ALL and ALC during quasi-static ramp to failure showed no difference in AVG DoLP and STD AoP values at all strain levels (Fig. 3). Larger DoLP values (i.e., stronger collagen fiber alignment) were observed for the LCL than both the ALL and ALC (p<0.0001). Larger STD AoP values (i.e., more variation in collagen orientation) were observed for the ALL and ALC compared to the LCL (p<0.0001; Fig. 3). When looking at correlations between mechanical and microstructural properties (Fig. 4), we found clustering of the LCL data points at high linear modulus and AVG DoLP while the ALL and ALC data points were clustered together. Similarly, we found clustering of the LCL at high linear modulus and low STD AoP while the ALL and ALC were clustered together. Only three of 25 knee specimens (12%) were observed to have a distinct, ligamentous structure in the region of the ALL. Interestingly, these distinct ALL samples (outlined in black on figures) showed relatively larger elastic moduli, higher AVG DoLP, and lower STD AoP (i.e., uniform and organized collagen alignment) across the stress-strain curve compared to samples harvested from knees without a distinct ALL. The distinct ALL tissues were also seen clustered near the LCL data points in the correlation plots.Conclusions:Overall, there were no differences in the mechanical and microstructural properties between the ALL and ALC, while the LCL demonstrated different properties compared to both the ALL and ALC. Both the ALC and ALL show significantly weaker collagen fiber alignment and more variation in the direction of collagen fiber alignment compared to the LCL. These findings suggest that the ALL has similar properties to capsule (i.e., ALC). However, when a distinct ALL was present at dissection (12%), the data indicates stronger and more uniform collagen alignment suggestive of more ligament-type qualities. Further research is needed to more precisely define the prevalence and properties of distinct ALLs in the knee.