Lateral Portal Research Articles

Novel gain-of-function mutants identify a critical region within CFTR membrane-spanning domain 2 controlling cAMP-dependent and ATP-independent channel activation

CFTR is an anion channel that has evolved from the mold of an ABC transporter. It possesses specific structural features, including a lateral portal between the cytoplasmic extensions of its transmembrane helices TM4 and TM6. This TM4-TM6 portal is lined by basic residues attracting anions from the cytosol towards the intracellular vestibule. Even though a symmetric, open portal is not observed at the level of the TM10/TM12 interface, basic amino acids are also present at this level, exposed to solvent in the vicinity of the regulatory R region, whose phosphorylation enables channel activation. Here, using all-atom molecular dynamics simulations in combination with functional and biochemical assays, we investigate the importance of these basic amino acids (R1158 and R1030), and of a neighboring aromatic amino acid (W846) in the regulation of CFTR activity. Results indicate that mutation of these amino acids globally increased channel activity and enabled channel opening by potentiators without the need to elevate cAMP levels. These effects (i) were observed even when the binding site of the potentiator VX-770 was mutated, revealing a probable independent mechanism, and (ii) were additive to one gain-of-function mutant within the selectivity filter. Taken together, our results indicate that the region of the membrane-spanning domain 2 (MSD2), symmetric to the lateral portal located between MSD1 TM4 and TM6, is a novel critical actor of CFTR regulation.

Clinical Outcomes for Arthroscopic Anterior Talofibular Ligament Repair After Suture Anchor Insertion Through the Anterolateral Portal vs the Lateral Accessory Portal.

Two types of suture anchor insertion pathways (anterolateral portal vs lateral accessory portal) are used in arthroscopic anterior talofibular ligament (ATFL) repair. However, it is not clear which one is the better choice. This study aims to compare the clinical outcomes of these 2 suture anchor insertion pathways when performing arthroscopic ATFL lasso-loop repair for the treatment of chronic lateral ankle instability (CLAI). From 2019 to 2021, patients with CLAI who underwent arthroscopic ATFL lasso-loop repair were retrospectively reviewed and divided into the anterolateral portal (ALP) group and the lateral accessory portal (LAP) group. A 1:1 propensity score matching was used to control confounding factors based on age, sex, body mass index, follow-up duration, preoperative visual analog scale (VAS) score, and Tegner score (ALP group, n = 26; LAP group, n = 26). Karlsson score, VAS score, Tegner score, operation time, anterior drawer test results, patient symptoms, and magnetic resonance (MR) evaluation of ATFL quality were used to describe the outcomes. The patient characteristics and follow-up durations were similar between the 2 groups. After a mean follow-up duration of 28.8 ± 2.3 months, the ALP group had significantly better Karlsson score, VAS score, and Tegner score improvement than the LAP group, with fewer symptoms. Seven patients in the LAP group still had a feeling of ankle instability, and 3 of them exhibited ankle laxity. In this study, we found that inserting the suture anchor through the anterolateral portal was associated with better outcomes compared to that through the lateral accessory portal when performing arthroscopic ATFL lasso-loop repair for CLAI patients. The improvement was greater for pain relief and function and was associated with a lower frequency of subjective ankle instability.

Screw placement through a higher medial portal provides better initial stability in arthroscopic ACL tibial avulsion fracture fixation: a finite element analysis

ObjectiveThe objective of this study was to investigate the initial stability of different screw placements in arthroscopic anterior cruciate ligament (ACL) tibial avulsion fracture fixation.MethodsA three-dimensional knee model at 90° flexion was utilized to simulate type III ACL tibial avulsion fracture and arthroscopic screw fixation through different portals, namely the central transpatellar tendon portal (CTP), anterolateral portal (ALP), anteromedial portal (AMP), lateral parapatellar portal (LPP), medial parapatellar portal (MPP), lateral suprapatellar portal (LSP), medial suprapatellar portal (MSP). A shear force of 450 N was applied to the finite element models at 30° flexion to simulate the failure condition. The displacement of the bony fragment and the volume of the bone above 25,000 µ-strain (damaged bone volume) were calculated around the screw path.ResultsWhen the screw was implanted through CTP, the displacement of the bony fragment reached the maximum displacement which was 1.10 mm and the maximum damaged bone volume around the screw path was 148.70 mm3. On the other hand, the minimum displacement of the bony fragment was 0.45 mm when the screw was implanted through LSP and MSP. The minimum damaged bone volume was 14.54 mm3 around the screw path when the screw was implanted through MSP.ConclusionScrews implanted through a higher medial portal generated less displacement of the bony fragment and a minimum detrimental strain around the screw path. The findings are clinically relevant as they provide biomechanical evidence on optimizing screw placement in arthroscopic ACL tibial avulsion fracture fixation.

Proximal lateral insertion portal of an intra-articular arthroscopic stifle lever: A cadaveric study.

To (1) Describe the proximal lateral insertion portal for the placement of an intra-articular distraction lever. (2) Assess for associated damage with the insertion of the lever and (3) evaluate the impact of duration of lever use on articular cartilage damage. Ex vivo canine cadaveric experimental study. Paired canine stifles from seven cadavers (14 stifles from dogs weighing >20 kg). A separate 0.5 cm proximal lateral portal was established adjacent to the lateral scope portal. A standard Ventura stifle thrust lever (VSTL) was inserted without removing the arthroscope. In Group A, the VSTL was placed in distraction for 5 min while in Group B the VSTL was placed for 10 min. The stifle joints were disarticulated and evaluated for associated damage to the long digital extensor tendon and iatrogenic articular cartilage injury (IACI) via India ink assay. No damage to the long digital extensor tendon was noted in any of the specimens during dissection. Superficial IACI was present in all specimens. There were no differences between groups when assessing for overall IACI. A proximal lateral portal and insertion of a standard VSTL can be performed without removing the arthroscope. The use of a proximal lateral lever portal without repositioning the arthroscope was repeatable without damaging the long digital extensor tendon. A duration of up to 10 min in which the thrust lever was engaged did not result in increased visual cartilage damage.

Optimizing Femoral Tunnel Placement in ACL Reconstruction: Effect of a 70-degree Arthroscope and Portal Position

Purpose: The aim of this study was to assess the accuracy of femoral tunnel placement for anterior cruciate ligament reconstruction (ACLR) using either an accessory medial portal or a 70-degree arthroscope compared with the standard 2-portal technique. Methods: A computerized 3D model of the femur was obtained with 4 reference points marked around the LFC. Using the simulator, 2 surgeons marked 5 consecutive femoral tunnel points with a 30-degree arthroscope in the lateral portal (30AL), then with a 30-degree arthroscope in an accessory medial portal (30AM), and next with a 70-degree arthroscope in the lateral portal (70AL). This was repeated after one week. Subjects then marked their target femoral tunnel positions (T) on the free femur sawbone model. After each episode, the distances from the marked tunnel point to the 4 reference points (d1, d2, d3, d4) were measured. After mapping to the 3D femur model, the co-ordinates of each marked tunnel position were determined. The distance (r) from T was calculated for each episode. Results: The median value of r was 1.27 mm(SE 0.15 mm) using 30AL, 0.54 mm (SE 0.12 mm) using the 30AM portal, and 0.20 mm (SE 0.047 mm) with 70AL. r was significantly smaller with 70AL (P<0.0001). The difference in r between 30AM and 30AL was also statistically significant (P=0.019). Conclusions: A 70-degree arthroscope in the lateral portal allows greater accuracy in femoral tunnel placement compared with a 30-degree arthroscope in either the lateral or an accessory medial portal.

Arthroscopic Biceps Tenodesis With Interference Screw Fixation: A Technique Video

Background: Management of long head of the biceps tendon (LHBT) pathology is accomplished through a biceps tenotomy or tenodesis. While both modalities provide beneficial outcomes, a biceps tenodesis may confer improved cosmesis, functional outcomes, and decreased muscle cramping postoperatively. Many procedural considerations are undertaken prior to a tenodesis, such as the surgical approach and fixation device. While similar clinical outcomes are achieved between an open subpectoral and arthroscopic suprapectoral biceps tenodesis (ASPBT) with interference screw (IS) fixation, the latter technique offers a minimally invasive modality. Indications: The primary indications for an ASPBT include superior labrum anterior posterior (SLAP) tears, LHBT tears, biceps instability, bicipital tunnel disease, biceps pulley lesions, and biceps tenosynovitis. Contraindications to the arthroscopic approach include a distal lesion of the biceps tendon below the pectoralis major tendon (PMT). The IS may be used to create a biomechanically stiffer construct. Technique Description: With the arthroscope in the lateral portal, the distal aspect of the bicipital groove proximal to the superior border of the PMT is identified and opened. The LHBT is subsequently mobilized and released. An anterosuperolateral portal is localized with a spinal needle positioned perpendicular to the bicipital tunnel, 1.5 cm proximal to the superior border of the PMT. The biceps is then removed ex vivo and whip-stitches are sewn beginning 1 cm proximal to the myotendinous junction of the LHBT. After firmly associating the LHBT with the tip of the IS, a guidewire is placed 1.5 cm superior to the superior border of the PMT, perpendicular to the humerus, and a reamer is used to prepare a 6-, 7-, or 8-mm diameter socket. The tendon is inserted through the accessory portal into the tunnel, followed by screw fixation. Suture tails are tied with 5 alternating half hitches, each secured via an arthroscopic knot pusher. Results: ASPBT with IS fixation provides significant pain relief, improves range of motion (ROM), and enhances quality of life. Discussion: ASPBT with IS fixation provides significant improvements in patient-reported and functional outcomes and thus can be an acceptable treatment for LHBT pathology. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Microwave Ablation of the Pig Growth Plate: Proof of Concept for Minimally Invasive Epiphysiodesis.

Different surgical methods for epiphysiodesis of limb length discrepancy (LLD) have been described. Although these methods are variably effective, they are associated with morbidity (pain and limp) and potential complications. Microwave ablation is a less-invasive opportunity to halt growth by selectively destroying the growth plate via thermal energy to treat LLD in children. In this proof-of-concept study using an in vivo pig model, we asked: (1) What is the durability of response 2 to 4 months after microwave ablation of the tibial growth plate as measured by length and angulation of the tibia via a CT scan? (2) Was articular cartilage maintained as measured by standard histologic staining for articular cartilage viability? To develop an in vivo protocol for microwave ablation, we placed microwave antennas adjacent to the proximal tibia growth plate in the cadaveric hindlimbs of 18 3-month-old pigs. To determine the suitable time, we varied ablation from 90 to 270 seconds at 65-W power settings. After sectioning the tibia, we visually assessed for discoloration (implying growth plate destruction) that included the central growth plate but did not encroach into the epiphysis in a manner that could disrupt the articular surface. Using this information, we then performed microwave ablation on three live female pigs (3.5 to 4 months old) to evaluate physiologic changes and durability of response. A postprocedure MRI was performed to ensure the intervention led to spatial growth plate alterations similar to that seen in cadavers. This was followed by serial CT, which was used to assess the potential effect on local bone and growth until the animals were euthanized 2 to 4 months after the procedure. We analyzed LLD, angular deformity, and bony deformity using CT scans of both tibias. The visibility of articular cartilage was compared with that of the contralateral tibia via standard histologic staining, and growth rates of the proximal tibial growth plate were compared via fluorochrome labeling. Eighteen cadaveric specimens showed ablation zones across the growth plate without visual damage to the articular surface. The three live pigs did not exhibit changes in gait or require notable pain medication after the procedure. Each animal demonstrated growth plate destruction, expected limb shortening (0.8, 1.2, and 1.5 cm), and bony cavitation around the growth plate. Slight valgus bone angulation (4º, 5º, and 12º) compared with the control tibia was noted. No qualitatively observable articular cartilage damage was encountered from the histologic comparison with the contralateral tibia for articular cartilage thickness and cellular morphology. A microwave antenna placed into a pig's proximal tibia growth plate can slow the growth of the tibia without apparent pain and alteration of gait and function. Further investigation and refinement of our animal model is ongoing and includes shorter ablation times and comparison of dynamic ablation (moving the antennae during the ablation) as well as static ablation of the tibia from a medial and lateral portal. These refinements and planned comparison with standard mechanical growth arrest in our pig model may lead to a similar approach to ablate growth plates in children with LLD.

Arthroscopic-Assisted Core Decompression of Humeral Head Osteonecrosis With Bone Marrow Aspirate Concentrate Augmentation

Background: The proximal humerus is the second-most common anatomic site for osteonecrosis, a condition of disrupted blood supply leading to death of bone tissue, with resultant shoulder pain and dysfunction. Core decompression is a viable joint-preserving surgical intervention that aims to improve local blood supply and restore bone health prior to bony collapse. Indications: Humeral head osteonecrosis has numerous underlying causes, most commonly the sequelae of prior trauma, chronic use of systemic corticosteroids, sickle cell disease, and alcohol abuse. Core decompression may be indicated in the early, pre-collapse stages of osteonecrosis, whereas more advanced stages of disease are commonly indicated for joint reconstruction procedures, such as bone grafting or arthroplasty. Technique Description: With the patient in the beach chair position, bone marrow aspirate concentrate (BMAC) is harvested through a percutaneous incision along the anterolateral proximal humerus. While viewing through a standard posterior portal, a transtibial anterior cruciate ligament (ACL) guide is placed through an anterior portal at a site on the humeral head surface, centered at the area of greatest humeral head bone edema as identified on preoperative magnetic resonance imaging. A guide pin is placed through a lateral portal within the ACL guide, to the subchondral bone. A 7.0-mm reamer is applied over the guidewire, followed by administration of demineralized bone matrix soaked in BMAC into the reamed channel within the proximal humerus. Results: In patients with early stages of humeral head osteonecrosis, core decompression confers superior clinical outcomes with reduced rates of subsequent surgical procedures compared with nonoperative treatment. Core decompression has shown to reduce the radiographic progression of osteonecrosis. Further research is necessary to determine the additional clinical benefits of augmentation with orthobiologic agents, such as BMAC. Conclusion: Arthroscopic-assisted core decompression is a valuable, minimally invasive surgical treatment for early-stage proximal humerus osteonecrosis. Adjunctive treatment with BMAC and demineralized bone matrix may enhance clinical outcomes. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Arthroscopic Long Digital Extensor Tenodesis: Technique and Outcome in a Dog

AbstractAvulsion of the long digital extensor (LDE) tendon is an uncommon cause of pelvic limb lameness in the dog. Surgical exploration is recommended with reattachment of the tendon and the avulsed fragment of bone using a small screw in lag fashion. In more chronic cases, the bone fragment can be removed, and the tendon attached by suture or staple to the proximolateral tibia. Arthroscopic tenodesis of the LDE has not been previously reported in the literature. A 6-year-old male neutered Labrador Retriever was presented for evaluation of a left pelvic limb lameness that was localized to the stifle. Avulsion of the LDE tendon was diagnosed based on palpation and radiographs. Arthroscopic assessment of the joint was performed. The origin of the LDE was freed with the use of a mechanical 3.0-mm shaver and an arthroscopic punch. The freed end was then exteriorized from the lateral portal and mineralized tissue removed. The tendon end was captured using no. 2 braided suture loop using a SpeedWhip technique. A 4.75-mm SwiveLock® polyetheretherketone anchor was utilized to fasten the tendon in the proximal groove of the LDE. The dog returned to dock diving by 16 weeks postsurgery at the preinjury level of performance and remained free of lameness at 30 months postoperatively. Arthroscopic long digital tendon tenodesis is a feasible surgical option in canine patients.

Anchorless Transosseous Rotator Cuff Repair: A Technical Note

Background: Transosseous rotator cuff repair provides robust fixation and broad footprint compression without the risk of foreign body reaction that may be seen with suture anchors. We present our technique for anchorless transosseous repair using a modern device to efficiently create bone tunnels and assist in suture passage. Indications: Tears of the supraspinatus tendon, with or without extension to the infraspinatus, in patients with acute or chronic tears, with good bone quality, and who fail appropriate nonoperative management. Technique: The beach-chair position with an articulating arm holder is preferred for this procedure. A glenohumeral diagnostic arthroscopy is performed, and intra-articular pathology is addressed as needed. The arthroscope is brought into the subacromial space, and a lateral viewing portal is established. A thorough bursectomy with or without acromioplasty is performed to attain visualization of the cuff. After the tear is identified, the tendon edges are debrided. It is critical to determine the tear pattern, the reduction maneuvers necessary, and the number of bone tunnels that are warranted. The desired location of the bone tunnel is marked with a pilot hole. The device is positioned over the pilot hole and a power drill is advanced through the lateral cortex. The device assists in creating a bone tunnel through the greater tuberosity and passes a nitinol loop through the tunnel. The loop is retrieved by the device and is brought to the lateral portal. Sutures are loaded into the loop and are brought through the bone tunnel. The sutures are then passed through the tendon using a curved retrograde suture passer in simple fashion and are tied to secure the tendon to the footprint. For larger tears, 2 or 3 tunnels may be used to widen the area for footprint compression. The specific configuration used will depend on the tear size, pattern, and surgeon preference. Results: Arthroscopic transosseous repairs have yielded promising results. Healing rates are comparable to anchor-based techniques, with the benefit of avoiding foreign bodies at the footprint. Discussion: Anchorless transosseous rotator cuff repair may be reproducibly performed with the use of a modern device for bone tunnel creation and suture passage. However, this technique should be used with caution in patients with osteoporosis or poor bone quality due to theoretical concerns of greater tuberosity fracture or suture pullout through the tunnels. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Minimally invasive subtalar joint and talonavicular joint preparation for hindfoot arthrodesis: A Cadaveric study evaluating structures at risk

Minimally invasive surgery (MIS) is growing in popularity due to smaller incisions, faster recovery times with less post-operative pain, and measurable decreases in morbidity. Our center performed an MIS hindfoot joint preparation about the talonavicular and subtalar joints and defined structures at risk in order to make this procedure more reproducible. Using ten fresh frozen cadaver limbs, we created a medial and lateral portal for talonavicular joint (TN) access, and an additional portal for subtalar joint (STJ) access to prepare the subtalar joint. After denuding the aforementioned joints of cartilage, the specimens were dissected to identify nearby anatomical structures. We documented the position of the peroneal sheath and sural nerve relative to the STJ portal, and the position of the dorsalis pedis artery (DP), medial dorsal cutaneous nerve (MDCN), extensor hallucis longus (EHL), extensor digitorum longus (EDL), tibialis anterior (TA), and tibialis posterior (TP) tendons relative to the TN portals. The average distance of the sural nerve and the peroneal sheath from the STJ portal was 34.21 mm and 14.12 mm respectively. The average distance of the DP, MDCN, and deep peroneal nerve from the medial and lateral TN portals were 13.31 mm, 11.54 mm, and 17.14 respectively. No neurovascular structures were transected throughout joint preparation. To our knowledge this is the first study looking into structures at risk for this specific procedure.

Landmarks for a Minimally Invasive Approach for Haglund's Deformity: A Cadaveric Study.

Haglund's deformity is a posterosuperior calcaneal prominence often associated with a painful bursa and insertional Achilles tendinopathy. Endoscopic debridement has been previously described; however, the aim of this cadaveric study is to describe landmarks of a minimally invasive surgical (MIS) approach to Haglund's deformity. Twelve specimens were dissected to identify medial and lateral portals for minimally invasive burr placement and anchor placement. A standard ruler was used to measure the distance in millimeters from the medial and lateral neurovascular structures in relation to medial and lateral portals. A separate 7-cm longitudinal incision posterior to the lateral malleolus and a separate 7-cm longitudinal incision posterior to the medial malleolus were made to identify at-risk neurovascular structures. The average distance from the sural nerve to the lateral portal was 25.7 mm (23-26). The mean distance from the lateral calcaneal branch of the sural nerve to lateral portal was 11.4 mm (10-12). The mean distance from the tibial nerve to the medial portal was 35.3 mm (35-36). Both the medial and lateral incisions were 9.3 mm from the calcaneal tuberosity. The results indicate that the MIS approach to Haglund's deformity resection can be performed reliably without neurovascular compromise. Level IV.

Clinical outcomes of arthroscopic lateral ligament repair using a knotless anchor for chronic lateral ankle instability

Background/objectiveArthroscopic lateral ligament repair (ALLR) for chronic lateral ankle instability (CLAI) has been improving with technical innovations. However, there is a lack of information regarding mid- and/or long-term clinical outcomes after the introduction of ALLR. This study aimed to report mid-term clinical outcomes of ALLR with a knotless anchor. MethodsThirty-two patients (11 men and 21 women; mean age, 28 ± 14 years) who underwent ALLR with a knotless anchor from December 2015 to October 2020 were included. The mean follow-up period was 31 ± 11 months. The Japanese Society for Surgery of the Foot (JSSF) ankle-hindfoot scale and the Self-Administered Foot Evaluation Questionnaire (SAFE-Q) were used for clinical evaluation preoperatively and at the 2-year follow-up. Surgical complications, particularly knot irritation, were also examined. ResultsThe JSSF scale scores were significantly improved, from 71.3 ± 13.1 preoperatively to 96.6 ± 5.1 postoperatively (P < 0.05), and the SAFE-Q showed similar improvement in all subscales (P < 0.05). One case had a complication of persistent pain around the lateral portal (3.1%). ConclusionALLR using a knotless anchor provided satisfactory clinical outcomes over 2 years, and no major complications, such as knot irritation, were observed. Case seriesLevel of Evidence, 4.

Feasibility of feline coxofemoral arthroscopy using a supratrochanteric lateral portal: A cadaveric study.

To evaluate the feasibility of feline diagnostic coxofemoral arthroscopy. Ex vivo feline cadaveric descriptive study. Seven feline cadavers (14 hips). Gross dissection of two feline hips was performed to evaluate anatomic landmarks, guide arthroscopic portal development, and determine optimal limb positioning. A 1.9 mm, 0° arthroscope, inserted through a supratrochanteric lateral portal, was used to assess intraarticular structures in 12 feline cadaver hips. Arthroscopy was followed by gross dissection of periarticular soft tissues. Relative portal locations and damage to periarticular structures were recorded. Hips were disarticulated, and an India ink assay was performed to assess whether there was iatrogenic cartilage injury (ICI). Scope insertion was achieved in all hips. Articular cartilage of the femoral head and acetabulum, round ligament, joint capsule, transverse acetabular ligament, and dorsal acetabular rim were identified arthroscopically in all hips. Probe insertion and intra-articular structure palpation was achieved in all hips. Scope and instrument portals resulted in minimal periarticular muscle trauma. No sciatic nerve damage was detected. Minor partial thickness ICI was observed in all hips at the site of scope insertion. Focal full thickness ICI was noted in one hip. Arthroscopy of the feline coxofemoral joint allowed visual and probe evaluation of intra-articular structures without evidence of major periarticular neurovascular trauma. Iatrogenic cartilage injury occurred in all hips but severity of lesions was considered mild. Coxofemoral arthroscopy is feasible in cats and can be utilized as a diagnostic tool for minimally invasive joint evaluation.

Rotator Cuff Repair With a Novel Interpositional Allograft Augmentation

Background: Nearly half a million rotator cuff repairs are performed annually in the United States. Rotator cuff healing occurs at the interface between the tendon and greater tuberosity, known as the enthesis. Given that a significant number of rotator cuff tears do not heal following surgical repair, multiple adjunctive strategies have been devised to improve the structural integrity of the repaired construct. Recently, a biphasic, demineralized allograft bone implant has been developed to improve enthesis healing. Indications: Relative indications for use of tissue augmentation include greater tuberosity osteopenia, revision rotator cuff surgery, attenuated rotator cuff tissue quality, and massive rotator cuff tears. Relative contraindications include a history of infection and recent immunosuppression. Technique Description: Following preparation of the footprint with an arthroscopic burr, two triple-loaded PEEK suture anchors were placed along the medial aspect of the greater tuberosity. Sutures were then passed through the rotator cuff tendon in a horizontal mattress configuration, and each pair of suture limbs were tied along the medial row. To aid in arthroscopic passage, the biphasic graft is folded longitudinally and clamped with a curved hemostat. The graft is loaded into an arthroscopic cannula and both are delivered simultaneously through a lateral arthroscopic portal. Two 18-gauge spinal needles are placed percutaneously to fix the allograft in the desired position. Subsequently, double-row transosseous-equivalent rotator cuff repair with standard techniques is done, which provides sufficient stability to the graft. Discussion: In a series of 192 patients who underwent arthroscopic rotator cuff repair augmented with a similar bioinductive collagen implant, patients demonstrated significant improvement in patient-reported outcomes at 1 year postoperatively. Moreover, a meta analysis published in 2022 demonstrated a significantly reduced retear rate among patch-augmented rotator cuff repairs as compared to isolated rotator cuff repairs. Conclusion: Tissue augmentation can be performed efficiently and reproducibly to promote biologic healing of arthroscopic rotator cuff repairs. The specific biphasic cancellous allograft presented in this video may be a viable treatment adjunct in the setting of deficient greater tuberosity bone stock, revision cases, or impaired native enthesis healing; however, further research is needed to assess clinical outcomes associated with its use. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Molecular dynamics study of Cl− permeation through cystic fibrosis transmembrane conductance regulator (CFTR)

The recent elucidation of atomistic structures of Cl− channel CFTR provides opportunities for understanding the molecular basis of cystic fibrosis. Despite having been activated through phosphorylation and provided with ATP ligands, several near-atomistic cryo-EM structures of CFTR are in a closed state, as inferred from the lack of a continuous passage through a hydrophobic bottleneck region located in the extracellular portion of the pore. Here, we present repeated, microsecond-long molecular dynamics simulations of human CFTR solvated in a lipid bilayer and aqueous NaCl. At equilibrium, Cl− ions enter the channel through a lateral intracellular portal and bind to two distinct cationic sites inside the channel pore but do not traverse the narrow, de-wetted bottleneck. Simulations conducted in the presence of a strong hyperpolarizing electric field led to spontaneous Cl− translocation events through the bottleneck region of the channel, suggesting that the protein relaxed to a functionally open state. Conformational changes of small magnitude involving transmembrane helices 1 and 6 preceded ion permeation through diverging exit routes at the extracellular end of the pore. The pore bottleneck undergoes wetting prior to Cl− translocation, suggesting that it acts as a hydrophobic gate. Although permeating Cl− ions remain mostly hydrated, partial dehydration occurs at the binding sites and in the bottleneck. The observed Cl− pathway is largely consistent with the loci of mutations that alter channel conductance, anion binding, and ion selectivity, supporting the model of the open state of CFTR obtained in the present study.

Endoscopic Technique to Remove Endobutton After Anterior Cruciate Ligament Reconstruction.

Suture button-based femoral cortical suspension constructs of anterior cruciate ligament grafts may facilitate fast and secure fixation. The necessity of Endobutton removal is controversial. Many current surgical techniques do not allow direct visualization of the Endobutton(s), making it challenging to remove; the buttons are fully flipped without soft tissue interposition between the Endobutton and femur. This Technical Note demonstrates endoscopic removal of Endobuttons through the lateral femoral portal. This technique allows direct visualization facilitating easier hardware removal while harnessing the advantages of a less-invasive procedure.

Arthroscopic Double-Row Rotator Cuff Repair With Box Configuration

Background: Arthroscopic transosseous-equivalent (TOE) techniques may offer additional advantages, including a more efficient surgery with a self-reinforcing construct with equivalent clinical results to medial knotted TOE repair for rotator cuff tears (RCTs). Indications: An arthroscopic knotless double-row (DR) rotator cuff repair (RCR) using FiberTak RC anchors for medial row fixation with box configuration may be an appropriate construct for operatively indicated small-to-moderate full-thickness RCTs. Technique: Our modified technique uses TOE repair principles to address RCTs too small for traditional 4.75-mm anchors using medial row fixation and too large to apply a single medial to lateral anchor repair. The patient is placed in a beach chair position. In addition to standard anterior and posterior portals, a lower lateral working portal and a higher posterolateral viewing portal are made. Subsequent to supraspinatus footprint visualization/preparation, two 2.6-mm FiberTak RC anchors each loaded with 1 LabralTape and 1 FiberWire are placed medially. The 4 sets of sutures for one anchor are placed through the rotator cuff tendon together in 1 spot and the process is repeated for the second anchor. One FiberWire from each anchor is then tied extracorporeally and then a double pulley technique is used to compress the medial aspect of the repair at the footprint in a box configuration. Finally, 1 limb of LabralTape from each of the medial anchors along with the corresponding FiberWire is secured through 2 lateral-row 4.75-mm anchors anteriorly and posteriorly to restore the lateral footprint and secure the rotator cuff in TOE box configuration. This modified technique can provide anatomical compression of the rotator cuff tendon at the footprint with additional medial compression achieved by the box configuration while taking advantage of knotless fixation. Results: Postoperatively, a sling is worn for 4 weeks, passive range of motion (ROM) is initiated at 2 weeks, active ROM is begun at 6 weeks, and strengthening at 3 months. Patients may return to full unrestricted activities around 5 to 6 months. Discussion/Conclusion: A modified arthroscopic DR RCR with box configuration is an excellent treatment option for patients with small-to-moderate full-thickness RCT who fail conservative treatment. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Arthroscopic Superior Capsular Reconstruction

Background: Limited options exist for young patients with massive, irreparable rotator cuff tears. While several treatment options exist, superior capsular reconstruction (SCR) was developed to restore glenohumeral joint stability by preventing superior humeral head migration during glenohumeral motion. Indications: Arthroscopic SCR is indicated in young patients with a massive, irreparable rotator cuff tear. Patients require a functioning deltoid muscle with minimal to no glenohumeral joint arthritis. In addition, patients should have Hamada grade 2 or less and should have an intact or repairable subscapularis tendon. Technique Description: The patient is positioned in the beach chair position. Standard anterior, posterior, and mid-lateral portals are established. An accessory posterior-superior lateral portal is used for visualization. Three 3.0 mm knotless anchors are placed in the glenoid through lateral percutaneous incisions. Two 4.75 mm anchors are placed adjacent to the humeral articular cartilage for medial row fixation. The graft dimensions are measured using the distance between the anchors. The graft is prepared using a gown card as a template with 5 mm added to the medial, posterior, and anterior graft dimensions, and 10 mm added to the lateral dimension. Sutures are passed through the graft in an inverted horizontal mattress for the glenoid anchors to diminish friction and allow appropriate suture passage through the knotless mechanism of the anchor. The graft is then shuttled into the joint through a lateral PassPort button cannula. Two lateral row anchors are used to secure the lateral graft on the humerus. Native rotator cuff tissue is repaired to the graft using sutures from the medial row anchors as well as free SutureTape. Results: Outcomes following SCR have demonstrated improvements in clinical outcomes and shoulder range of motion. Similar outcomes have been identified between the use of allograft and autograft. Patients generally are able to return to light recreational activities and work. Discussion/Conclusion: Arthroscopic SCR yields favorable results in the setting of a massive, irreparable rotator cuff tear. Meticulous surgical technique is needed to avoid intraoperative surgical complications. The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Tips and tricks for maximising access to the middle cranial fossa using the superior lateral orbital portal.

Transorbital endoscopic approaches are becoming increasingly popular for skull base pathologies; the superior lateral orbital portal is one such approach to the middle cranial fossa. This paper provides a technical description that maximises the surgical portal and minimises morbidity. A superior lid crease incision is made extending laterally and the orbital rim is exposed. A subperiosteal dissection of the lateral and superior orbit is performed, with elevation of periosteum off Whitnall's tubercle, ligation of the recurrent branch of the middle meningeal artery, and identification of the superior orbital fissure. The lacrimal keyhole is then drilled away. The middle cranial fossa is accessed by drilling posterior to the orbital rim to expose: the temporalis muscle anterior-laterally, the dura of the temporal lobe posterior-laterally, the anterior cranial fossa superiorly and the periorbita medially. These surgical steps can maximise the surgical portal and minimise morbidity, with avoidance of injury to surrounding structures.