Understanding a mass in the paraspinal region: an anatomical approach.

The paraspinal region encompasses all tissues around the spine. The regional anatomy is complex and includes the paraspinal muscles, spinal nerves, sympathetic chains, Batson's venous plexus and a rich arterial network. A wide variety of pathologies can occur in the paraspinal region, originating either from paraspinal soft tissues or the vertebral column. The most common paraspinal benign neoplasms include lipomas, fibroblastic tumours and benign peripheral nerve sheath tumours. Tumour-like masses such as haematomas, extramedullary haematopoiesis or abscesses should be considered in patients with suggestive medical histories. Malignant neoplasms are less frequent than benign processes and include liposarcomas and undifferentiated sarcomas. Secondary and primary spinal tumours may present as midline expansile soft tissue masses invading the adjacent paraspinal region. Knowledge of the anatomy of the paraspinal region is of major importance since it allows understanding of the complex locoregional tumour spread that can occur via many adipose corridors, haematogenous pathways and direct contact. Paraspinal tumours can extend into other anatomical regions, such as the retroperitoneum, pleura, posterior mediastinum, intercostal space or extradural neural axis compartment. Imaging plays a crucial role in formulating a hypothesis regarding the aetiology of the mass and tumour staging, which informs preoperative planning. Understanding the complex relationship between the different elements and the imaging features of common paraspinal masses is fundamental to achieving a correct diagnosis and adequate patient management. This review gives an overview of the anatomy of the paraspinal region and describes imaging features of the main tumours and tumour-like lesions that occur in the region.

The interosseous tuberosities of the forearm exist from 1-year-old: a pediatric radiological study describing the ages of appearance of the different forearm reliefs.

PURPOSE: Interosseous tuberosities have been described in adults on the radial and ulnar sides. However, their presence at birth and their development during growth is still unknown. The objective of this work is to establish the age of onset of this tuberosity among a cohort of children aged 1-year-old or older. METHODS: All anterior-posterior and lateral radiographs performed in our hospital during a consecutive period of 6 months were retrospectively analyzed. Exclusion criteria were: presence of a fracture, a tumor, an age higher than 16 years, radiograph not performed strictly from the front with supination or from the side. On the anterior-posterior radiograph, the presence of the following structures was sought: radial interosseous tuberosity and determination of its length and width; the appearance of the epiphyseal nucleus of the radial head, of the bicipital tuberosity, and of the distal epiphysis. On the lateral views, the presence of the following structures was sought: ulnar interosseous tuberosity and determination of its length and width; the appearance of the olecranon epiphyseal nucleus, and the distal epiphysis. RESULTS: Over the review period, anterior-posterior and lateral radiographs were performed on 368 consecutive children. Finally, 179 patients were included in the radiographic analysis. The radial and ulnar interosseous tuberosities and bicipital tuberosity were present in all cases, from 1-year-old. Only the distal radial epiphysis began to appear at the age of one year, the others ossifying progressively during growth. CONCLUSION: Tuberositas interossea ulnarii and radii exists, are present from 1-year-old and continue to develop during growth.

Chronic elbow instability in adults: The why, when and how of ligament reconstruction.

Chronic elbow instability in adults mainly consists of valgus instability and posterolateral instability. They most often occur because of ligament damage following elbow dislocation but can also occur due to repeated microtrauma. The aim of ligament stabilization surgery is always the same: recreate the anatomy and function of the original ligament. Extensive knowledge of the elbow's anatomical structures and biomechanics is crucial to understanding why the elbow is unstable and how to treat it. In this review, we will explain how elbow instability develops, what types of grafts are available and which reconstruction techniques can be used for posterolateral or valgus instability. LEVEL OF EVIDENCE: 3.

Biomechanical assessment of the central band of the interosseous membrane using shear wave elastography: reliability and reproducibility.

The interosseous membrane of the forearm is an essential structure for the stability of the forearm skeleton, the most important part being the central band. The purpose of this study was to determine if shear wave elastography, a non-invasive ultrasound technique, can be used to measure shear wave speed in the central band and quantify stiffness. Fifteen healthy adult subjects were included (30 forearms). The participants forearms were positioned on an articulated plate, with their hand in neutral, pronated and then supinated positions of 30°, 60° and 90°. The shear wave speed was highest in 90° pronation (4.4 m/s (SD 0.3)) and 90° supination (4.4 m/s (SD 0.27)) indicating maximum stiffness in these positions. Its minimum value was in the neutral position, and either in 30° pronation or supination (3.5 m/s (SD 0.3)). Intra- and interobserver agreement was excellent, regardless of probe positioning or forearm mobilization. This study presents a reliable shear wave elastography measurement protocol to describe the physiological function of the central band of the interosseous membrane in healthy adults.Level of evidence: IV.

Complex Posterior Glenohumeral Instability Case Management.

A 21-year-old male patient suffering from insidious shoulder instability from neurogenic and structural attenuation of shoulder stabilizer, due to old minor cerebrovascular accident, presented with a two-year history of repetitive shoulder dislocation, operated by fixing the biceps tendon to its insertion on the superior labrum, correction of the glenoid version and reattaching the subscapular tendon along with a new technique for stabilization of the shoulder replicating the coracohumeral ligament with a ligament advanced reinforcement system (LARS) transplant. Following structured physical therapy, our patient returned to normal daily activities at 15 months.

Subscapularis minor-does it exist?

INTRODUCTION: It has been well established that the subscapularis is divided in two different parts with a tendinous insertion at its superior two-thirds and a muscular attachment on its inferior third. The objective of this cadaveric study was to follow the muscular insertion of the subscapularis medially in order to determine the origin of this inferior muscle insertion and whether a subscapularis minor can be individualized MATERIALS AND METHODS: Twenty-six shoulders from thirteen fresh-frozen cadaveric specimens (5 males and 8 females; mean age, 74.4 years) were dissected in our anatomy lab. The humeral insertion of the subscapularis was then analyzed, and the inferior muscular part of the insertion was identified. The muscle fibers were followed medially until their scapular origin which was recorded as line drawings and photographs. We measured the dimensions of both the humeral insertion and of the scapular origin of the fibers going to the muscular portion. RESULTS: In all cases, the fibres going to the tendinous portion and those going to the muscular portion of the insertion had a different orientation. The fibres going to the muscular portion of the humeral insertion did not originate from the subscapularis fossa but on the glenoid neck and in a depression at the infero-lateral part of the scapular pillar. The mean length of the superior tendinous portion of the humeral insertion was 3.42 cm (± 0.43 cm); the mean length of the inferior muscular portion of the humeral insertion was 1.88 cm (± 0.80 cm). The mean length of the scapular origin in the depression at the infero-lateral part of the scapular pillar of the fibres going to the muscular portion of the humeral insertion was 3.7 cm (± 0.17 cm). CONCLUSION: The fibres of the subscapularis do not all originate from the subscapularis fossa. An additional origin exists at the inferior part of the glenoid neck and in a depression at the infero-lateral part of the scapular pillar. The fibers which originate at this location all insert on the humerus at the muscular portion of the subscapularis humeral insertion. This portion however does not seem to correspond to the so-called subscapularis minor which has been previously described.

Arthroscopic proximal carpal row replacement by semitendinosus and gracilis graft (CArpus Row Plasty Using the Semitendinosus: CARPUS procedure). An anatomical study of 16 cases.

INTRODUCTION: Post-traumatic lesions of the carpus (scapholunate rupture, scaphoid non-union) frequently evolve into disabling osteoarthritis (scapholunate advanced collapse or scaphoid non-union advanced collapse: SLAC or SNAC wrist). Proximal row carpectomy (PRC) is a reliable option but with poorer prognosis in case of osteoarthritis of the distal radius or capitate head. In such situations, radiocarpal arthrodesis may be necessary, sacrificing wrist motion. To circumvent this limitation, we propose a new procedure consisting in arthroscopic PRC and replacing the proximal row by tendon graft. METHODS: This was a study on 16 cadaver specimens. A scapholunate pin was introduced via an approach into the anatomical snuffbox and used as a guide for a cannulated drill bit (9mm) to create a tunnel through the proximal row. The arthroscope and a reamer were introduced into the tunnel via its radial and ulnar ends. PRC was performed under arthroscopic control. The gracilis and semitendinosus tendons were harvested and folded so as to obtain a graft with the same length and diameter as the proximal row. The graft was threaded through the radial approach and fixed to the capsule. RESULTS: Mean procedure time was 68min. There was no pre- to postoperative difference in joint motion or carpal height. On radiocinematography, the graft was stable between the radius and the second row of the carpus. The radial and ulnar sensory branches, median nerve and radial artery were intact at end of procedure. DISCUSSION: This technique could be a solution in SLAC or SNAC wrist with osteoarthritis of the capitate head or radial glenoid. It also conserves carpal height. Being arthroscopic, the procedure avoids the major edema observed after a dorsal approach of the carpus, and also ensures graft stability, since the radiocarpal ligaments are conserved. Harvesting from a second anatomical site and the in vivo fate of the transplant are two issues that need to be discussed. CONCLUSION: This anatomical study paves the way for clinical experimentation. LEVEL OF EVIDENCE: IV.

Decompression of the suprascapular nerve at the suprascapular notch under combined arthroscopic and ultrasound guidance.

Decompression of the suprascapular nerve (SSNe) at the suprascapular notch (SSNo) is usually performed with an arthroscopic procedure. This technique is well described but locating the nerve is complex because it is deeply buried and surrounded by soft tissue. We propose to combine ultrasound and arthroscopy (US-arthroscopy) to facilitate nerve localization, exposure and release. The main objective of this study was to assess the feasibility of this technique. This is an experimental, cadaveric study, carried out on ten shoulders. The first step of our technique is to locate the SSNo using an ultrasound scanner. Then an arthroscope is introduced under ultrasound control to the SSNo. A second portal is then created to dissect the pedicle and perform the ligament release. Ultrasound identification of the SSNo, endoscopic dissection and decompression of the nerve were achieved in 100% of cases. Ultrasound identification of the SSNo took an average of 3 min (± 4) while dissection and endoscopic release time took an average of 8 min (± 5). Ultrasound is an extremely powerful tool for non-invasive localization of nerves through soft tissues, but it is limited by the fact that tissue visualization is limited to the ultrasound slice plane, which is two-dimensional. On the other hand, arthroscopy (extra-articular) allows three-dimensional control of the surgical steps performed, but the locating of the nerve involves significant tissue detachment and a risk of damaging the nerve with the dissection. The combination of the two (US-arthroscopy) offers the possibility of combining the advantages of both techniques.

The ulnar interosseous tuberosity exists: a radiological and descriptive cadaveric study.

PURPOSE: The anatomy of the ulna seems to have already been described exhaustively, particularly at its extremities, but very little in its middle third. We report the existence of an interosseous tuberosity on the interosseous border of the ulnar shaft that we have named the "tuberositas interossea ulnarii" (TIU). METHODS: First, we analyzed all side view X-rays of the forearm in neutral rotation, as well as forearm CT scans carried out during a 1-year period in our hospital. On these radiographic examinations, we evaluated the presence or absence of the TIU, its length, the thickness of the interosseous cortex at its level, above and below compared with anterior, posterior, and lateral bone cortices. In the second part of the study, we dissected cadaveric forearms to determine which ligaments and muscles were attached to it. RESULTS: A total of 91 standard forearm radiographs and 13 CT scans were analyzed. In all cases, the ulnar interosseous tuberosity was present. The mean tuberosity length was 107.5 mm (± 18.2), without any significant gender influence. It corresponded to a thickening (6.9 mm then 4.6 mm above and 3.9 mm below; p < 0.0001) of the ulnar interosseous cortex. Then, ten anatomic subjects (six females, four males) were dissected. We observed that this tuberosity served as an attachment for the central band of the interosseous membrane, for the deep flexor and extensor muscles for the long fingers, and for the abductor pollicis longus muscle's inner attachment. CONCLUSION: Tuberositas interossea ulnarii exists besides the tuberositas interossea radii, corresponds to thickening of the cortex and may play a role in the stability of the forearm and the function of the long fingers.

Use of Gracile and semi-tendinosus tendons (GRAST) for the reconstruction of irreparable rotator cuff tears.

BACKGROUND: Irreparable rotator cuff tears are common and difficult to treat. Techniques for "filling the loss of substance" require fixation to the rotator cuff stump (tendon augmentation) or to the glenoid (superior capsular reconstruction), which are complicated by the narrow working zone of the subacromial space. The main objective of this study was to determine whether a braided graft of gracilis (GR) and semitendinosus (ST) could fill a loss of tendon substance from an irreparable rupture of the supra- and infraspinatus, by fixing the graft to the greater tuberosity and the spine of the scapula. METHODS: This was a cadaveric study with the use of ten specimens. The GRA and ST tendons were harvested, braided and reinforced with suture. An experimental tear of the supraspinatus (SS) and upper infraspinatus (IS) retracted at the glenoid was made. The GRAST transplant was positioned over the tear. The transplant was attached to the greater tuberosity by two anchors and then attached to the medial third of the scapular spine by trans-osseous stitching. The percentage of filling obtained was then measured and passive mobility of the shoulder was assessed. We proceeded to the same technique under arthroscopy for a 73 years old patient whom we treated for a painful shoulder with irreparable cuff tear. We inserted a GRAST graft using arthroscopy. RESULTS: The Braided-GRAST allowed a 100% filling of the loss of tendon substance. Mobility was complete in all cases. CONCLUSION: This technique simplifies the medial fixation and restores the musculo-tendinous chain where current grafting techniques only fill a tendinous defect. The transplant could have a subacromial "spacer" effect and lower the humeral head. The donor site morbidity and the fate of the transplant in-vivo are two limits to be discussed. This anatomical study paves the way for clinical experimentation.

The interosseous tuberosity of radius: a descriptive radiological and cadaveric anatomical study.

PURPOSE: The radius is described with a single tuberosity: the radial tuberosity. However, we hypothesize that there is a second tuberosity on the interosseous border of the radius: which we propose to call the interosseous tuberosity - Tuberositas interossea radii - (IT). METHODS: First, we analyzed all anteroposterior radiographs of the forearm (48 females, 54 males; 62 lefts and 40 rights) as well as CT scans (6 females, 7 males; 5 lefts and 8 rights) carried out during one year in our hospital. We evaluated the presence of IT, its length, thickness of the interosseous cortex at IT level, above and below compared with anterior, posterior and lateral bone cortices. In the second part of the study, we dissected cadaveric forearms to determine which ligaments and muscles were attaches on the IT. RESULTS: A total of 102 standard forearm radiographs and 13 CT-scans were analyzed. In all cases, an IT was present. The mean tuberosity length was 93.9 mm (+ / - 15.8), which corresponds to 37% (+ / - 5) of total radial length. IT corresponds to a significant thickening (7.6 mm than 4.2 mm and 4.3 mm below; p < 0.0001) of radial interosseous cortex. A total of 10 forearms were dissected. In all cases, we observed that IT served as an attachment for central band of interosseous membrane and for all extrinsic muscles of the thumb with the exception of the extensor pollicis longus. CONCLUSION: Tuberositas interossea radii exists, corresponds to a cortex thickening and may play a role in the stability of the forearm and the function of the thumb.

Stabilization of the radial head with the palmaris longus or the gracilis tendon: an anatomical feasibility study.

PURPOSE: The proximal radioulnar joint (PRUJ) and the radiocapitellar joint may be destabilized after trauma. Different techniques for stabilization of PRUJ have been proposed, but none of them can stabilize the radiocapitellar joint at the same time. We propose a ligamentoplasty to stabilize the radial head at these two joints by reconstructing the radial head annular ligament and the lateral collateral ulnar ligament (LCUL) with a single graft (palmaris longus or gracilis tendon of the knee). METHODS: Fifteen cadaveric upper limbs were used to compare the stabilization obtained by performing our ligamentoplasty with the palmaris longus or the gracilis tendon. For each technique, the stabilization obtained was evaluated by measuring the displacement of the radial head in the anterior, lateral and posterior directions when a force of 1 N was applied in maximum supination, neutral rotation and maximum pronation. We also evaluated whether this technique could damage the ulnar nerve or the posterior interosseous nerve by dissecting them and whether it could limit the range of rotation of the forearm. RESULTS: Our ligamentoplasty enables to restore PRUJ stability equivalent to the intact ligament condition. The palmaris longus was inconstant (13/15) and too short to allow concomitant reconstruction of the LCUL (except in one case). No nerve damage was found during the dissection, and the range of rotation of the forearm was not limited by the ligamentoplasty. We also report a clinical case with an excellent result and without complications. CONCLUSION: This ligamentoplasty we have described makes it possible to stabilize the radial head with respect to the radial notch of the ulna and with respect to the capitellum of the humerus. The gracilis tendon is more suitable than the palmaris longus because of its constant presence and length. A clinical series is now necessary to better evaluate this technique.

The paraspinal muscle-tendon system: Its paradoxical anatomy.

Anatomy of the muscle-tendon system is an important component to musculoskeletal models. In particular, the cross-sectional area of belly (mCSA) and tendon (tCSA) provides information about the maximum force that a muscle may exert. The ratio of mCSA to tCSA (rCSA) demonstrates how muscle force is related to the ability to resist/transmit the force to bone. Previous anatomical studies of the lumbar paraspinal muscles (LPM) showed that their bellies have large mCSA suggesting that they are powerful muscles. Surprisingly, surgical experience shows that the tendons of the LPM are among the thinnest tendons of the body. We therefore hypothesized that traditional biomechanics of the LPM and the rCSA do not correspond for LPM. In 10 fresh-frozen old cadavers, we measured the mCSA, tCSA and rCSA of the LPM (multifidus and the erector spinae, i.e. the longissimus and the iliocostalis); then, we compared these data with those of one of the weakest muscles in the body, i.e. the extensor digitorum communis (EDC) chosen because it shares some common anatomical features with the LPM, in particular with the erector spinae. For instance, the EDC has a polyarticular course and presents long and thin effector tendons. Among the LPM, the longissimus has the greatest mean ACSA with 10.42 cm2 compared with 9.16 cm2 for the iliocostalis and 0.24 cm2 for the multifidus. Mean ACSA of the EDC was almost ten times smaller than those of erector spinae. Regarding the mean tCSA, the EDC was the largest one with 11.48 mm2 compared with 2.69 mm2 and 1.43 mm2 for the longissimus, 5.74 mm2 and 2.38 mm2for the iliocostalis and 5.28 mm2 and 4.96 mm2 for the multifidus. Mean rCSAs of the erector spinae were extremely small, ranged from 1/156 for the spinal attachment of the iliocostalis to 1/739 for the rib attachment of the longissimus that suggests that tendons are an unsuitable size to transmit the force to bone. Mean rCSA of the multifidus and the EDC were in the same range with rCSA = 1/5 and rCSA = 1/9 respectively. The rCSA of the multifidus was substantial, but its ACSA (1cm2) corresponds to low-power muscles. This paradoxical anatomy compels us to consider the biomechanics of the LPM in a different way from that of the classical "chord-like model", i.e. the muscle belly creates a force that is applied to a bone piece through a tendon. The LPM have large contractile mass in a semi-rigid compartment inside which the pressure may increase. This result strengthens the hypothesis that high pressure and intrinsic stiffness of the LPM create two stiff bodies, closely attached to the spine thus ensuring its stabilization.

Posture-related stiffness mapping of paraspinal muscles.

The paraspinal compartment acts as a bone-muscle composite beam of the spine. The elastic properties of the paraspinal muscles play a critical role in spine stabilization. These properties depend on the subjects' posture, and they may be drastically altered by low back pain. Supersonic shear wave elastography can be used to provide quantitative stiffness maps (elastograms), which characterize the elastic properties of the probed tissue. The aim of this study was to challenge shear wave elastography sensitivity to postural stiffness changes in healthy paraspinal muscles. The stiffness of the main paraspinal muscles (longissimus, iliocostalis, multifidus) was measured by shear wave elastography at the lumbosacral level (L3 and S1) for six static postures performed by volunteers. Passive postures (rest, passive flexion, passive extension) were performed in a first shear wave elastography session, and active postures (upright, bending forward, bending backward) with rest posture for reference were performed in a second session. Measurements were repeated three times for each posture. Sixteen healthy young adults were enrolled in the study. Non-parametric paired tests, multiple analyses of covariance, and intra-class correlations were implemented for analysis. Shear wave elastography showed good to excellent reliability, except in the multifidus at S1, during bending forward, and in the multifidus at L3, during bending backward. Yet, during bending forward, only poor quality was recorded for nine volunteers in the longissimus. Significant intra- and inter-muscular changes were observed with posture. Stiffness significantly increased for the upright position and bending forward with respect to the reference values recorded in passive postures. In conclusion, shear wave elastography allows reliable assessment of the stiffness of the paraspinal muscles except in the multifidus at S1 and longissimus, during bending forward, and in the multifidus at L3, during bending backward. It reveals a different biomechanical behaviour for the multifidus, the longissimus, and the iliocostalis.

Influence of thoracolumbar fascia stretching on lumbar back muscle stiffness: A supersonic shear wave elastography approach.

The lumbar paraspinal muscle compartment (PMC) is a stabilizing system of the spine whose efficiency depends on its elastic properties, which may be quantifiable by supersonic shear wave elastography (SWE). The thoracolumbar fascia (TLF) encapsulates the lumbar paraspinal muscles (LPM) and creates a PMC. Tensioning of the TLF via the stretching of the latissimus dorsi is supposed to increase stiffness within the PMC. The aims of this study were (1) to test the reliability of SWE in the multifidus and the erector spinae (ES) in prone and sited position; (2) to investigate the role of the tensioning of the pTLF, via stretching of the latissimus dorsi (LD), on LPM stiffness. Stiffness of ES and multifidus was measured using SWE at L3-L4 in procubitus and seated position in 15 participants. Stretching of LD was performed with arm elevation. Parametric paired tests, multiple analyses of variance, and intraclass correlation were used for statistical analysis. Reliability estimates were fair to excellent. Reliability was greater in ES than the multifidus, greater in seated position than during rest. Stiffness was greater in the ES than in multifidus, and in seated position than at rest. Tensioning of the TLF via LD stretching did not generate significant LPM stiffness changes. SWE is a reliable tool for assessing stiffness in the LPM. Reliability of SWE protocols is improved during seated position. Tensioning of the TLF via LD stretching did not influence LPM stiffness. Clin. Anat. 32:73-80, 2019. © 2018 Wiley Periodicals, Inc.

Organization of the fascia and aponeurosis in the lumbar paraspinal compartment.

PURPOSE: The thoracolumbar fascia (TLF) and the erector spinae aponeurosis (ESA) play significant roles in the biomechanics of the spine and could be a source of low back pain. Attachment, collagen fiber direction, size and biomechanical properties of the TLF have been well documented. However, questions remain about the attachment of the TLF and ESA in relation to adjoining tissues in the lumbosacral region. Moreover, quantitative data in relation to the ESA have rarely been examined. The aim of this study was to further investigate the anatomical features of the TLF and ESA and to determine the attachments and sliding areas of the paraspinal compartment through dissection. MATERIALS AND METHODS: In 10 fresh cadavers (6 females, 4 males, mean age: 77 ± 10 years), we determined (1) the gross anatomy of the ESA and the TLF (attachments and sliding areas) and (2) the structure of the ESA and the TLF (thickness, width, orientation of collagen fibers). The pennation angle between the axis of the ES muscle fibers and the axis of the collagen fibers of the ESA were also measured. RESULTS: The TLF is an irregular dense connective tissue with a mean thickness of 0.95 mm. The distance between the spinous processes line and the site where the neurovascular bundles pierced the TLF, depending on the vertebral level, ranged from 29 mm at L1 to 75 mm at L3. The ESA constituted a band of regular longitudinally oriented connective fibers (mean thickness: 1.85 mm). Muscles fibers of the ES were strongly diagonally attached to the ESA (mean pennation angle 8° for the iliocostalis and 14° for the longissimus). To a lesser extent, the superficial multifidi were attached to the ESA at the lumbar level close to the midline and at the sacral level. CONCLUSION: The ESA, at twice the thickness of the pTLF, was the thickest dense connective tissue of the paraspinal compartment. The ESA and the TLF circumscribed subcompartments and sliding areas between the TFL and the lumbar paraspinal muscles, between the ES and the multifidus, and between the longissimus and the iliocostalis.

Magnetic resonance elastography of the lumbar back muscles: A preliminary study.

Back pain is associated with increased lumbar paraspinal muscle (LPM) stiffness identified by manual palpation and strain elastography. Recently, magnetic resonance elastography (MRE) has allowed the stiffness of muscle to be characterized noninvasively in vivo, providing quantitative 3D stiffness maps (elastograms). The aim of this study was to characterize the stiffness (shear modulus, SM) of the LPM (multifidus and erector spinae) using MRE. MRE of the lumbar region was performed on seven adults in supine position. MRE was acquired in three muscular states: relaxed with outstretched legs, stretched with passive pelvis flexion, and contracted with outstretched legs and tightened trunk muscles. The mean SM was measured within a region of interest manually defined in the multifidus, erector spinae, and the entire paraspinal compartment. The intermuscular difference and the effects of stretching and contraction were assessed by ANOVA and t-tests. At rest, the mean SM of the paraspinal compartment was 1.6 ± 0.2 kPa. It increased significantly with stretching to 1.65 ± 0.3 kPa, and with contraction to 2.0 ± 0.7 kPa. Irrespective of muscular state, the erector spinae was significantly stiffer than the multifidus. The multifidus underwent proportionally higher stiffness changes from rest to contraction and stretching. MRE can be used to measure the stiffness of the LPM in different muscular states. We hypothesize that, irrespective of posture, the erector spinae behaves as semi-rigid beam, and ensures permanent stiffness of the spine. The multifidus behaves as an adaptable muscle that provides segmental flexibility to the spine and tunes the spine stiffness. Clin. Anat. 31:514-520, 2018. © 2018 Wiley Periodicals, Inc.

De novo generation in an in vivo rat model and biomechanical characterization of autologous transplants for ligament and tendon reconstruction.

BACKGROUND: Surgical reconstruction of ligaments and tendons is frequently required in clinical practice. The commonly used autografts, allografts, or synthetic transplants present limitations in terms of availability, biocompatibility, cost, and mechanical properties that tissue bioengineering aims to overcome. It classically combines an exogenous extracellular matrix with cells, but this approach remains complex and expensive. Using a rat model, we tested a new bioengineering strategy for the in vivo and de novo generation of autologous grafts without the addition of extracellular matrix or cells, and analyzed their biomechanical and structural properties. METHODS: A silicone perforated tubular implant (PTI) was designed and implanted in the spine of male Wistar rats to generate neo-transplants. The tensile load to failure, stiffness, Young modulus, and ultrastructure of the generated tissue were determined at 6 and 12weeks after surgery. The feasibility of using the transplant that was generated in the spine as an autograft for reconstruction of medial collateral ligaments (MCL) and Achilles tendons was also tested. FINDINGS: Use of the PTI resulted in de novo transplant generation. Their median load to failure and Young modulus increased between 6 and 12weeks (respectively 12N vs 34N and 48MPa vs 178MPa). At 12weeks, the neo-transplants exhibited collagen bundles (mainly type III) parallel to their longitudinal axis and elongated fibroblasts. Six weeks after their transfer to replace the MCL or the Achilles tendon, the transplants were still present, with their ends healed at their insertion point. INTERPRETATION: This animal study is a first step in the design and validation of a new bioengineering strategy to develop autologous transplants for ligament and tendon reconstructions.