Impact of Sacroiliac Interosseous Ligament Tension and Laxity on the Biomechanics of the Lumbar Spine: A Finite Element Study.

OBJECTIVE: To investigate the influence of sacroiliac interosseous ligament tension and laxity on the biomechanics of the lumbar spine. METHODS: A static analysis of a three-dimensional finite element model of the Lumbar-Pelvic is conducted to verify the model's effectiveness. Adjusting the sacroiliac ligament's elasticity modulus under a 10Nm lumbar flexion/extension moment, it simulates ligament tension/laxity to calculate vertebrae displacements, intervertebral disc stress and deformation, nucleus pulposus pressure, facet joint force, and ligament stress. RESULTS: With the elastic modulus of the sacroiliac ligament changing by +50%, -50%, and -90%, the angular displacement of vertebra 3 in forward flexion changes by +1.64%, -4.84%, and -42.3%, and the line displacements change by +5.7%, -16.4%, and -144.9%, respectively; and the angular displacements in backward extension change by +0.2%, -0.6%, -5.9% and the line displacements change by +5.5%, -14.3%, and -125.8%. However, the angular displacement and center distance between adjacent vertebrae do not change, leading to no change in the maximum stress of the intervertebral disc and the maximum pressure in the nucleus pulposus. Flexion and extension directly affect the deformation and stress magnitude and distribution in the lumbar spine. CONCLUSIONS: While sacroiliac interosseous ligament laxity and tension have little effect on disc deformation and stress, and nucleus pulposus pressure, they reduce the stability of the lumbar-sacral vertebrae. In a forward flexion state, the lumbar ligaments bear a large load and are prone to laxity, thereby increasing the risk of lumbar injury.

Outcomes of a Modified Arthroscopic-assisted Reconstruction Technique for Lateral Ankle Instability / Resultados de uma técnica modificada de reconstrução assistida por artroscopia para instabilidade lateral do tornozelo

Abstract Objective The present study assesses the results of a minimally invasive surgical technique for acute and chronic ankle instability management. Methods The present case series study retrospectively evaluated 40 patients undergoing arthroscopic-assisted percutaneous ankle ligament reconstruction from 2013 to 2019. Results The present study included 17 males and 23 females with an average age of 38.3 years old. Postintervention follow-up using American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot scores identified improvement of > 30 points in function and pain control. The most frequently occurring associated injuries were osteochondral (35%). No patient required reintervention or had infection during follow-up. Conclusion The technique in the present study is easy and achieves satisfactory results for function and pain control. Level of Evidence IV.

Resumo Objetivo O presente estudo avalia os resultados de uma técnica cirúrgica minimamente invasiva para o manejo da instabilidade aguda e crônica do tornozelo. Métodos O presente estudo de uma série de casos avaliou retrospectivamente 40 pacientes submetidos à reconstrução percutânea assistida por artroscopia do ligamento do tornozelo entre 2013 e 2019. Resultados O estudo incluiu 17 homens e 23 mulheres com idade média de 38,3 anos. O acompanhamento pós-intervenção utilizou a pontuação American Orthopaedic Foot and Ankle Society (AOFAS, na sigla em inglês). As pontuações do tornozelo-retropé identificaram melhora > 30 pontos na função e no controle da dor. As lesões associadas mais frequentes foram as osteocondrais (35%). Nenhum paciente precisou de reintervenção ou teve infecção durante o acompanhamento. Conclusão A técnica do presente estudo é fácil e consegue resultados satisfatórios para a função e o controle da dor. Nível de Evidência IV.

Carpometacarpal Ligament Reconstruction, Surgical Technique and Outcomes.

Basal thumb arthritis is a common condition with the earliest stage described as a period of ligament laxity and joint instability, without radiographic signs of arthritis. The condition is usually managed conservatively but a number of individuals can present with persistence of symptoms. We would like to describe our preferred technique for the management carpometacarpal ligament instability and laxity. This technique utilizes a slip of the flexor carpi radialis tendon and offers reconstruction of the intermetacarpal, dorsoradial and anterior oblique ligaments in an anatomic fashion using standard instruments available. The author has performed this technique in 33 patients over a course of 10 years and long-term outcomes of these cases are presented in this paper.

Lateral tenodesis procedures increase lateral compartment pressures more than anterolateral ligament reconstruction, when performed in combination with ACL reconstruction: a pilot biomechanical study.

OBJECTIVES: Given the common occurrence of residual laxity and re-injury post anterior cruciate ligament reconstruction (ACLR), additional anterolateral procedures are increasingly used in combination with an ACLR. Despite the perception that there is a risk of over-constraining the lateral tibiofemoral (LTF) compartment, potentially leading to osteoarthritis, assessment on their effect on intra-articular compartment pressures is still lacking. Our objective was therefore, through a pilot biomechanical study, to compare LTF contact pressures after the most commonly used anterolateral procedures. METHODS: A controlled laboratory pilot study was performed using 4 fresh-frozen cadaveric whole lower limbs. Through 0° to 90° of flexion, LTF contact pressures were measured with a Tekscan sensor, located under the lateral meniscus. Knee kinematics were obtained in 3 conditions of rotation (NR: neutral, ER: external and IR: internal rotation) to record the position of the knees for each loading condition. A Motion Analysis system with a coordinate system based on CT scans 3D bone modelling was used. After an ACLR, defined as the reference baseline, 5 anterolateral procedures were compared: anterolateral ligament reconstruction (ALLR), modified Ellison, deep Lemaire, superficial Lemaire and modified MacIntosh procedures. The last 3 procedures were randomised. For each procedure, the graft was fixed in NR at 30° of flexion and with a tension of 20 N. RESULTS: Compared with isolated ACLR, addition of either ALLR or modified Ellison procedure did not increased the overall LTF contact pressure (all p>0.05) through the full range of flexion for the IR condition. Conversely, deep Lemaire, superficial Lemaire and modified MacIntosh procedure (all p<0.05) did increase the overall LTF contact pressure compared with ACLR in IR. No significant difference was observed in ER and NR conditions. CONCLUSION: This pilot study, comparing the main anterolateral procedures, revealed that addition of either ALLR or modified Ellison procedure did not change the overall contact pressure in the LTF compartment through 0° to 90° of knee flexion. In contrast, the deep and superficial Lemaire, and modified MacIntosh procedures significantly increased overall LTF contact pressures when the knee was internally rotated.

Different anterolateral procedures have variable impact on knee kinematics and stability when performed in combination with anterior cruciate ligament reconstruction.

OBJECTIVE: The optimal anterolateral procedure to control anterolateral rotational laxity of the knee is still unknown. The objective was to compare the ability of five anterolateral procedures performed in combination with anterior cruciate ligament reconstruction (ACLR) to restore native knee kinematics in the setting of a deficient anterior cruciate ligament (ACL) and anterolateral structures. METHODS: A controlled laboratory study was performed using 10 fresh-frozen cadaveric whole lower limbs with intact iliotibial band. Kinematics from 0° to 90° of flexion were recorded using a motion analysis three-dimensional (3D) optoelectronic system, allowing assessment of internal rotation (IR) and anteroposterior (AP) tibial translation at 30° and 90° of flexion. Joint centres and bony landmarks were calculated from 3D bone models obtained from CT scans. Intact knee kinematics were assessed initially, followed by sequential section of the ACL and anterolateral structures (anterolateral ligament, anterolateral capsule and Kaplan fibres). After ACLR, five anterolateral procedures were performed consecutively on the same knee: ALLR, modified Ellison, deep Lemaire, superficial Lemaire and modified MacIntosh. The last three procedures were randomised. For each procedure, the graft was fixed in neutral rotation at 30° of flexion and with a tension of 20 N. RESULTS: Isolated ACLR did not restore normal overall knee kinematics in a combined ACL plus anterolateral-deficient knee, leaving a residual tibial rotational laxity (p=0.034). Only the ALLR (p=0.661) and modified Ellison procedure (p=0.641) restored overall IR kinematics to the normal intact state. Superficial and deep Lemaire and modified MacIntosh tenodeses overconstrained IR, leading to shifted and different kinematics compared with the intact condition (p=0.004, p=0.001 and p=0.045, respectively). Compared with ACLR state, addition of an anterolateral procedure did not induce any additional control on AP translation at 30° and 90° of flexion (all p>0.05), except for the superficial Lemaire procedure at 90° (p=0.032). CONCLUSION: In biomechanical in vitro setting, a comparison of five anterolateral procedures revealed that addition of either ALLR or modified Ellison procedure restored overall native knee kinematics in a combined ACL plus anterolateral-deficient knee. Superficial and deep Lemaire and modified MacIntosh tenodeses achieved excellent rotational control but overconstrained IR, leading to a change from intact knee kinematics. LEVEL OF EVIDENCE: The level-of-evidence statement does not apply for this laboratory experiments study.

Isolated medial patellofemoral ligament reconstruction for recurrent patellofemoral instability: analysis of outcomes and risk factors.

BACKGROUND: The medial patellofemoral ligament (MPFL) is always damaged after patellar dislocation. In selected patients, MPFL reconstruction is necessary to restore a correct patellar tracking. Despite the large number of different techniques reported to reconstruct the MPFL, there is no consensus concerning the optimal procedure, and debates is still ongoing. The present study analysed the results after isolated MPFL reconstruction in patients with patellofemoral instability. Furthermore, a subgroup analysis of patients presenting pathoanatomical risk factors was made. METHODS: In November 2020, the main electronic databases were accessed. All articles reporting the results of primary isolated MPFL reconstruction for recurrent patellofemoral instability were considered for inclusion. Only articles reporting a minimum 12-month follow-up were eligible. RESULTS: Data from a total of 1777 knees were collected. The mean age of the patients involved was 22.8 ± 3.4 years. The mean follow-up was 40.7 ± 25.8 months. Overall, the range of motion (+ 27.74; P < 0.0001) and all the other scores of interests improved at last follow-up: Kujala (+ 12.76; P = 0.0003), Lysholm (+ 15.69; P < 0.0001), Tegner score (+ 2.86; P = 0.006). Seventy-three of 1780 patients (4.1%) showed a positive apprehension test. Thirty of 1765 patients (1.7%) experienced re-dislocations, while 56 of 1778 patients (3.2%) showed persisting joint instability. Twenty-five of 1786 patients (1.4%) underwent revision surgeries. CONCLUSION: Isolated MPFL reconstruction for recurrent patellofemoral instability provides reliable surgical outcomes. Patients with pathoanatomical predisposing factors reported worse surgical outcomes.

Deep deltoid ligament injury is related to rotational instability of the ankle joint: a biomechanical study.

PURPOSE: In the athletic population, the prevalence of isolated syndesmotic lesions is high. To detect potential instability of the ankle is crucial to define those lesions in need of surgical management. The aim was to define how the extent of tibio-fibular syndesmotic ligament injury influences the overall stability of the ankle joint in a cadaver model. METHODS: Twenty fresh-frozen through knee cadaveric leg specimens were subjected to different simulated syndesmotic ligament lesions. In Group 1 (n = 10), the order of ligament sectioning was: anterior tibio-fibular ligament (ATFL), superficial deltoid ligament (SDL), deep deltoid ligament (DDL), posterior tibio-fibular ligament (PTFL), and progressive sectioning at 10, 50 and 100 mm of the distal interosseous membrane (IOM). In Group 2 (n = 10), the sequence was: ATFL, PITFL, 10 and then 50 mm of the distal IOM, SDL, DDL, and 100 mm of the distal IOM. Diastasis of 4 mm in the coronal or sagittal plane and external rotation of the ankle greater than 20° were considered indicative of instability. RESULTS: Both coronal and sagittal diastasis exceeded 4 mm with injury patterns characterized by IOM lesions extending beyond 5 cm. External rotation of the ankle exceeded 20° with injury patterns characterized by a DDL lesion. CONCLUSION: Coronal and sagittal plane diastases of the tibio-fibular syndesmosis are particularly affected by sequential lesions involving the IOM, whereas increased external rotation of the ankle most depends on DDL. The identification of the specific syndesmotic and deltoid ligament injuries is crucial to understanding which lesions need operative management. The knowledge of which pattern of tibio-fibular syndesmotic ligament injury influences the ankle joint stability is crucial in defining which lesions need for surgical management.

Isolated MPTL reconstruction fails to restore lateral patellar stability when compared to MPFL reconstruction.

PURPOSE: To biomechanically evaluate MPTL reconstruction and compare it with two techniques for MPFL reconstruction in regard to changes in patellofemoral contact pressures and restoration of patellar stability. METHODS: This is an experimental laboratory study in eight human cadaveric knees. None had patellofemoral cartilage lesions or trochlear dysplasia as evaluated by conventional radiographs and MRI examinations. The specimens were secured in a testing apparatus, and the quadriceps was tensioned in line with the femoral shaft. Contact pressures were measured using the TekScan sensor at 30°, 60° and 90°. The sensor was placed in the patellofemoral joint through a proximal approach between femoral shaft and quadriceps tendon to not violate the medial and lateral patellofemoral complex. TekScan data were analysed to determine mean contact pressures on the medial and lateral patellar facets. Patellar lateral displacement was evaluated with the knee positioned at 30° of flexion and 9 N of quadriceps load, then a lateral force of 22 N was applied. The same protocol was used for each condition: native, medial patellofemoral complex lesion, medial patellofemoral ligament reconstruction (MPFL-R) using gracilis tendon, MPFL-R using quadriceps tendon transfer, and medial patellotibial ligament reconstruction (MPTL-R) using patellar tendon transfer. RESULTS: No statistical differences were found for mean and peak contact pressures, medial or lateral, among all three techniques. However, while both techniques of MPFL-R were able to restore the medial restraint, MPTL-R failed to restore resistance to lateral patellar translation to the native state (mean lateralization of the patella [mm]: native: 9.4; lesion: 22; gracilis MPFL-R: 8.1; quadriceps MPFL-R: 11.3; MPTL-R: 23.4 (p < 0.001). CONCLUSION: MPTL-R and both techniques for MPFL-R did not increase patellofemoral contact pressures; however, MPTL-R failed to provide a sufficient restraint against lateral patellar translation lateral translation in 30° of flexion. It, therefore, cannot be recommended as an isolated procedure for the treatment of patellar instability.

Arthroscopic coronal plane syndesmotic instability has been over-diagnosed.

PURPOSE: Ankle arthroscopy is widely used for diagnosis of syndesmotic instability, especially in subtle cases. To date, no published article has systematically reviewed the literature in aggregate to understand which instability values should be used intraoperatively. The primary aim was to systematically review the amount of tibiofibular displacement that correlates with syndesmotic instability after a high ankle sprain. A secondary aim is to assess the quality of such research. METHODS: Systematic searches of EMBASE (Ovid) and MEDLINE via PubMed, CINAHL, Web of Science, and Google Scholar were used. INCLUSION CRITERIA: studies that arthroscopically evaluated the fibular displacement at various stages of syndesmotic ligament injury. Two reviewers independently extracted data and assessed methodological quality using the Anatomical Quality Assessment (AQUA) Tool and methodological index for non-randomized studies (MINORS). RESULTS: Eight cadaveric studies and three clinical studies were included for review. All studies reported displacement in the coronal plane, four studies reported in the sagittal plane, and one reported findings in the rotational plane. Four cadaveric studies had a similar experimental set up and the weighted mean associated with instability in the coronal plane could be calculated and was 2.9 mm at the anterior portion of the distal tibiofibular joint and 3.4 mm at the posterior portion. Syndesmotic instability in the sagittal plane is less extensively studied, however available data from a cadaveric study suggests thresholds of 2.2 mm of posterior fibular translation when performing an anterior to posterior hook test and 2.6 mm of anterior fibular translation when performing a posterior to anterior hook test. CONCLUSIONS: The results have concluded that the commonly used 2.0 mm threshold value of distal tibiofibular diastasis may lead to overtreatment of syndesmotic instability, and that using threshold values of 2.9 mm measured at the anterior portion of the incisura and 3.4 mm at the posterior portion may represent better cut off values. Given the ready availability of 3 mm probes among standard arthroscopic instrumentation, at the very least surgeons should use 3 mm in lieu of 2 mm probes intraoperatively. LEVEL OF EVIDENCE: IV.

A constrained-condylar fixed-bearing total knee arthroplasty is stabilised by the medial soft tissues.

PURPOSE: Revision constrained-condylar total knee arthroplasty (CCK-TKA) is often used to provide additional mechanical constraint after failure of a primary TKA. However, it is unknown how much this translates to a reliance on soft-tissue support. The aim of this study was therefore to compare the laxity of a native knee to the CCK-TKA implanted state and quantify how medial soft-tissues stabilise the knee following CCK-TKA. METHODS: Ten intact cadaveric knees were tested in a robotic system at 0°, 30°, 60° and 90° flexion with ± 90  N anterior-posterior force, ± 8 Nm varus-valgus and ± 5 Nm internal-external torques. A fixed-bearing CCK-TKA was implanted and the laxity tests were repeated with the soft tissues intact and after sequential cutting. The deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) were sequentially transected and the percentage contributions of each structure to restraining the applied loads were calculated. RESULTS: Implanting a CCK-TKA did not alter anterior-posterior laxity from that of the original native knee, but it significantly decreased internal-external and varus-valgus rotational laxity (p < 0.05). Post CCK-TKA, the sMCL restrained 34% of the tibial displacing load in anterior drawer, 16% in internal rotation, 17% in external rotation and 53% in valgus, across the flexion angles tested. The dMCL restrained 11% of the valgus rotation moment. CONCLUSIONS: With a fully-competent sMCL in-vitro, a fixed-bearing CCK-TKA knee provided more rotational constraint than the native knee. The robotic test data showed that both the soft-tissues and the semi-constrained implant restrained rotational knee laxity. Therefore, in clinical practice, a fixed-bearing CCK-TKA knee could be indicated for use in a knee with lax, less-competent medial soft tissues. LEVEL OF EVIDENCE: Controlled laboratory study.

A four-step approach improves long-term functional outcomes in patients suffering from chronic ankle instability: a retrospective study with a follow-up of 7-16 years.

PURPOSE: The aim of the present study was to assess the long-term outcomes of the treatment of chronic ankle instability (CAI) with a four-step protocol. METHODS: Fifty-four patients with isolated anterior talo-fibular ligament (ATFL) lesion suffering from CAI who underwent surgical treatment between 2000 and 2009 were assessed. All the patients underwent a four-step protocol including synovectomy, debridement of ATFL lesion borders, capsular shrinkage, and 21-day immobilization and nonweightbearing. Median age at surgery was 31.6 years (18-48). Patients were examined preoperatively and at follow-up. Clinical assessment included the American Orthopaedic Foot and Ankle Society (AOFAS) ankle and hindfoot scoring system, Karlsson-Peterson score, Tegner activity level, and objective examination comprehending range of motion (ROM) and manual laxity tests. RESULTS: AOFAS (preoperative, 64.8; postoperative, 92.4; p < 0.001) and Karlsson-Peterson score (preoperative, 62.5; postoperative, 88.8; p < 0.001) significantly improved after a median 11 years follow-up (7-16 years). Similarly median Tegner activity level significantly increased at follow-up compared to pre-operatory status (6.0 and 4.0 respectively, p < 0.001). Objective examination documented a statistically significant improvement in terms of ankle stability compared to pre-operative manual laxity tests, with negative anterior drawer test observed in 48 (88.9%) patients (p < 0.001). Sagittal ROM was full in 50 patients (92%). Nine patients had subsequent ankle sprains (15.6%), two patients required further surgery, while seven were treated conservatively. No major complications were reported. CONCLUSION: Satisfying subjective and objective clinical outcomes in selected patients with isolated ATFL lesion suffering from CAI were reported with a treatment protocol including arthroscopic synovectomy, debridement of ATFL remnants, capsular shrinkage, and immobilization. These findings are of clinical relevance because they provide a suitable minimally invasive method for the treatment of mild to moderate ankle instability. LEVEL OF EVIDENCE: Level IV.

Evolving evidence in the treatment of primary and recurrent posterior cruciate ligament injuries, part 1: anatomy, biomechanics and diagnostics.

The posterior cruciate ligament (PCL) represents an intra-articular structure composed of two distinct bundles. Considering the anterior and posterior meniscofemoral ligaments, a total of four ligamentous fibre bundles of the posterior knee complex act synergistically to restrain posterior and rotatory tibial loads. Injury mechanisms associated with high-energy trauma and accompanying injury patterns may complicate the diagnostic evaluation and accuracy. Therefore, a thorough and systematic diagnostic workup is necessary to assess the severity of the PCL injury and to initiate an appropriate treatment approach. Since structural damage to the PCL occurs in more than one third of trauma patients experiencing acute knee injury with hemarthrosis, background knowledge for management of PCL injuries is important. In Part 1 of the evidence-based update on management of primary and recurrent PCL injuries, the anatomical, biomechanical, and diagnostic principles are presented. This paper aims to convey the anatomical and biomechanical knowledge needed for accurate diagnosis to facilitate subsequent decision-making in the treatment of PCL injuries.Level of evidence V.

The Importance of the Deep Deltoid Ligament Repair in Treating Supination-External Rotation Stage IV Ankle Fracture: A Comparative Retrospective Cohort Study.

BACKGROUND: The necessity of the deep deltoid ligament repair in the treatment of supination-external rotation (SER) ankle stage IV fracture with deltoid ligament rupture is highly debated. We conducted this retrospective research aimed at exploring the curative effect of the deep deltoid ligament repair in treating SER fracture. METHODS: Sixty-three patients with closed SER stage IV fractures received open reduction and internal fixation (ORIF), using either deep deltoid ligament repair (the DDLR group, 31 patients) or nondeep deltoid ligament repair (the NDDLR group, 32 patients). The radiographic parameters examined include the talocrural angle (TA), fibular length (FL), tibiomedial malleolar angle (TMMA), medial clear space (MCS), and tibiofibular clear space (TFCS). The functional performance parameters examined in the study were visual analog scale (VAS) pain score, American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot scales, and range of motion of bilateral ankles (RMBA). Complications, including bone nonunion, infection, and fragment displacement, were also recorded and compared. RESULTS: Similar basic characteristics were found in both cohorts. All patients completed follow-up ranging from 12 to 22 months (mean time: 12.41 ± 4.21 months). The DDLR group had significantly reduced VAS score (p < 0.05), with markedly increased RMBA (p < 0.05) compared to the NDDLR group. The two cohorts showed similar follow-up performance at 3 months (p > 0.05), 6 months (p > 0.05), and 12 months (p > 0.05), in terms of parameters including TA, FL, TMMA, MCS, TCS, and AOFAS ankle-hindfoot scales. CONCLUSION: Although similar radiographic performances were achieved in both cohorts, the DDLR group displayed enhanced functional outcome postsurgery, indicating that DDLR may be a better potential for the treatment of SER stage IV fracture with deltoid ligament rupture.

[Etiology, pathogenesis, clinical features, diagnostics and conservative treatment of adult flatfoot]. / Ätiologie, Pathogenese, Klinik, Diagnostik und konservative Therapie des adulten erworbenen Plattfußes.

BACKGROUND: On average, one in six adults is affected by an acquired flatfoot. This foot deformity is characterized by its progression of stages and in 10% of cases causes complaints that require treatment. Untreated, the loss of walking ability may result in the final stage. Correct staging is crucial to being able to offer a specific course of therapy including a wide spectrum of conservative and operative treatments. MATERIAL AND METHODS: This review is based on pertinent publications retrieved from a selective search in PubMed and Medline and on the authors' clinical experience. DIAGNOSTICS: The loss of function of static (spring ligament complex) and dynamic (tibialis posterior tendon) stabilizers causes the characteristic deformity with loss of the medial arch, hind foot valgus and forefoot abduction. In the late stage, severe secondary osteoarthritis in upper and lower ankle joints occurs and impedes walking ability. The essential physical examination is supplemented by weight-bearing dorsoplantar and lateral radiographs, which provide further information about axial malalignment (Meary's angle, Kite's angle). The long axis hind foot view allows analysis of the hindfoot valgus. MRI provides further information about the integrity of the tibialis posterior tendon, spring ligament complex and cartilage damage. THERAPY: The therapy aims to reduce pain, regain function and avoid development of secondary osteoarthritis and degenerative tendon disorders. Progress of the deformity should be stopped. Therefore, the main aspects of the deformity-loss of medial arch, hindfoot valgus and forefoot abduction should be addressed and corrected. In the acute phase, tendovaginitis of the tibialis posterior tendon can be treated sufficiently by anti-inflammatory measures, relieving mechanical loads on the tendon and muscle and physiotherapy.

Chronic Distal Radioulnar Joint Instability.

The distal radioulnar joint is inherently unstable, relying primarily on ligaments for stability. Disruption of the joint-stabilizing structures can occur in isolation or concomitantly with osseous trauma. Instability can result from dislocations, fractures, ligament injuries, or malunions. Untreated instability alters wrist and forearm kinematics, leading to pain, weakness, and possibly arthritis. In chronic instability, the native ligaments may not be reparable, necessitating a reconstructive procedure.

Length-change patterns of the medial collateral ligament and posterior oblique ligament in relation to their function and surgery.

PURPOSE: To define the length-change patterns of the superficial medial collateral ligament (sMCL), deep MCL (dMCL), and posterior oblique ligament (POL) across knee flexion and with applied anterior and rotational loads, and to relate these findings to their functions in knee stability and to surgical repair or reconstruction. METHODS: Ten cadaveric knees were mounted in a kinematics rig with loaded quadriceps, ITB, and hamstrings. Length changes of the anterior and posterior fibres of the sMCL, dMCL, and POL were recorded from 0° to 100° flexion by use of a linear displacement transducer and normalised to lengths at 0° flexion. Measurements were repeated with no external load, 90 N anterior draw force, and 5 Nm internal and 5 Nm external rotation torque applied. RESULTS: The anterior sMCL lengthened with flexion (p < 0.01) and further lengthened by external rotation (p < 0.001). The posterior sMCL slackened with flexion (p < 0.001), but was lengthened by internal rotation (p < 0.05). External rotation lengthened the anterior dMCL fibres by 10% throughout flexion (p < 0.001). sMCL release allowed the dMCL to become taut with valgus rotation (p < 0.001). The anterior and posterior POL fibres slackened with flexion (p < 0.001), but were elongated by internal rotation (p < 0.001). CONCLUSION: The structures of the medial ligament complex react differently to knee flexion and applied loads. Structures attaching posterior to the medial epicondyle are taut in extension, whereas the anterior sMCL, attaching anterior to the epicondyle, is tensioned during flexion. The anterior dMCL is elongated by external rotation. These data offer the basis for MCL repair and reconstruction techniques regarding graft positioning and tensioning.

Biomechanical analysis of simultaneous distal and proximal radio-ulnar joint instability.

BACKGROUND: Simultaneous dislocation of the proximal and distal radio-ulnar joints without bony injuries has been reported, but the mechanism remains unclear. We investigated concurrent proximal and distal radio-ulnar joint instability after sequential sectioning of the annular ligament, triangular fibrocartilage complex, and quadrate ligament. METHODS: We performed this biomechanical study with six fresh-frozen cadaveric upper extremities. Proximal and distal radio-ulnar joint displacement was measured using an electromagnetic tracking device during passive mobility testing with anterior, lateral, and posterior loads on the radial head with pronation, supination, and neutral rotation. Measurements were statistically analyzed using the generalized linear mixed model. FINDINGS: Proximal radio-ulnar joint instability was significantly greater after sectioning of the annular (lateral: 1.4%, P < .05; posterior: 0.7%, P < .05) and quadrate (lateral: 43.7%, P < .05; posterior: 29.5%, P < .05) ligament. Distal radio-ulnar joint instability was significantly greater in every sequential stage (final stage: anterior: 24.1%, P < .05; lateral 21.0%, P < .05; posterior: 31.3%, P < .05). Finally, significant simultaneous instability of the joints was observed after sectioning of the annular ligament, triangular fibrocartilage complex, and quadrate ligament, and neutral rotation potentially induced gross instability. INTERPRETATION: Our ligament injury model induced simultaneous proximal and distal radio-ulnar joint instability without bony or interosseous membrane injury, probably induced by severe soft tissue injury. Proximal radio-ulnar joint instability may influence distal radio-ulnar joint instability from pivoting of the interosseous membrane. Our findings will help surgeons evaluate the magnitude of soft tissue injury and plan surgery for patients with simultaneous proximal and distal radio-ulnar joint instability.

Kinetic dysfunction of the wrist with chronic scapholunate dissociation. A cadaver study.

BACKGROUND: Most laboratory studies investigating scapholunate dissociations are based on normal cadaver arms with serially sectioned ligaments. It is assumed that the kinetic behavior of a ligament-sectioned wrist is similar to a scapholunate dissociation. We tested five cadaver wrists with real injuries. The goal of this research was to evaluate the biomechanical behavior of scapholunate advanced collapse wrists compared to an experimental group with simulated injuries. METHODS: Using a magnetic 6-degree of freedom motion tracking device, changes in scaphoid alignment induced by isometric loading 5 wrist motor tendons in two groups of specimens were monitored. Twelve fresh cadaver wrists in which scapholunate injury was simulated by sectioning the scapholunate ligament were compared to 5 arms with chronic scapholunate dissociation. FINDINGS: The behavior of the scaphoid is the same in both groups, but the magnitude of displacement is greater in chronic scapholunate dissociation wrists, although not statistically significant. The extensor carpi ulnaris is the only muscle that provokes scaphoid pronation; all other muscles induce its supination. INTERPRETATION: Different factors may play a role in the amount of scaphoid rotation observed in wrists with chronic scapholunate dissociation. Ligament sectioning alone in the experimental setup can only partially replicate the behavior of real scapholunate dissociations. The extensor carpi ulnaris has a major role in destabilizing scapholunate advanced collapse wrists; therefore, isometric contraction of this muscle should be avoided in the conservative treatment. The experimental setup designed is useful to evaluate the biomechanical behavior of the carpus under traction load.

Strain pattern of each ligamentous band of the superficial deltoid ligament: a cadaver study.

BACKGROUND: There are few reports on the detailed biomechanics of the deltoid ligament, and no studies have measured the biomechanics of each ligamentous band because of the difficulty in inserting sensors into the narrow ligaments. This study aimed to measure the strain pattern of the deltoid ligament bands directly using a Miniaturization Ligament Performance Probe (MLPP) system. METHODS: The MLPP was sutured into the ligamentous bands of the deltoid ligament in 6 fresh-frozen lower extremity cadaveric specimens. The strain was measured using a round metal disk (clock) fixed on the plantar aspect of the foot. The ankle was manually moved from 15° dorsiflexion to 30° plantar flexion, and a 1.2-N-m force was applied to the ankle and subtalar joint complex. Then the clock was rotated every 30° to measure the strain of each ligamentous band at each endpoint. RESULTS: The tibionavicular ligament (TNL) began to tense at 10° plantar flexion, and the tension becomes stronger as the angle increased; the TNL worked most effectively in plantar flex-abduction. The tibiospring ligament (TSL) began to tense gradually at 15° plantar flexion, and the tension became stronger as the angle increased. The TSL worked most effectively in abduction. The tibiocalcaneal ligament (TCL) began to tense gradually at 0° dorsiflexion, and the tension became stronger as the angle increased. The TCL worked most effectively in pronation (dorsiflexion-abduction). The superficial posterior tibiotalar ligament (SPTTL) began to tense gradually at 0° dorsiflexion, and the tension became stronger as the angle increased, with the SPTTL working most effectively in dorsiflexion. CONCLUSION: Our results show the biomechanical function of the superficial deltoid ligament and may contribute to determining which ligament is damaged during assessment in the clinical setting.

Effects of joint capsular release on range of motion in patients with frozen shoulder.

BACKGROUND: A thickened joint capsule is believed to be one of the most specific manifestations of and the primary restraint against range of motion (ROM) in frozen shoulders. The purpose of this study was to evaluate the relationship among ROMs under general anesthesia before surgery and the effects of each joint capsular release on ROM. METHODS: ROM was measured using a goniometer with scapular fixation. Arthroscopic pan-capsular release was performed with the patient in the beach-chair position in the following order: (1) rotator interval, (2) coracohumeral ligament, (3) superior capsule, (4) middle glenohumeral ligament, (5) anterior inferior glenohumeral ligament, and (6) posterior inferior glenohumeral ligament. ROMs in forward flexion (FF), lateral elevation (LE), external rotation with the arm at the side (ER1), external rotation at 90° of LE (ER2), internal rotation at 90° of LE (IR2), horizontal flexion, external rotation at 90° of FF (ER3), and internal rotation at 90° of FF (IR3) were evaluated before and after each release. RESULTS: A total of 32 consecutive shoulders were included. After each capsular release, the ROM recovered; the final ROM was significantly greater on the affected side than on the unaffected side. Significant correlations were found between FF and LE, FF and ER1, ER1 and ER2, ER1 and ER3, ER2 and ER3, and IR2 and IR3 on both sides, regardless of surgery. CONCLUSION: Each segment of the joint capsule affected ROM in all directions, supporting the need for whole-joint capsular release; ROM was significantly greater on the affected side than on the unaffected side after surgery.