Baseball Stitch Research Articles

Choice of suture technique may mitigate figure-of-8 deformity in slide tracheoplasty

ObjectivesTo demonstrate varying degrees of immediate postoperative figure of 8 deformity following three different methods of tracheal suturing. Study designComparative ex-vivo study. MethodsA fresh, unfixed rabbit trachea was harvested and bisected at its midpoint. The posterior membranous trachea was excised from both segments to mimic the anatomy of complete tracheal rings following longitudinal release. A slide tracheoplasty was performed on the same tracheal segments as an internal control, using three different methods of closure: simple running, running horizontal mattress, and a modified baseball stitch. Endoscopic and external photographs were taken immediately following repair to document the effect of closure technique on external and endoluminal anatomy. ResultsA simple running closure, in which traveling occurs between needle passes, showed the greatest degree of postoperative figure of 8 deformity. A running horizontal mattress suture closure showed less deformity and a modified running closure, in which traveling occurs within needle passes, showed the least deformity. ConclusionsOur study suggests that a minor modification of standard running closure techniques may help limit the common figure-of-8 deformity often noted following slide tracheoplasty. Lay SummaryFigure of-8 deformity is a problem that can occur when repairing a narrow trachea referred to as tracheal stenosis. This deformity may be prevented using particular suture techniques which may decrease the likelihood that the trachea becomes blocked again following repair.

Comparative Study of Biomechanical Properties between Needled Suture and Needleless Suture in Multi-Strand Tendon Graft Model

Objective: To compare the biomechanical properties of the Chinese finger (CF) suture, a needleless suture technique, with the baseball stitch (BS) suture, a needled suture technique, in a multi-strand model by using a 4-strand tendon model. Additionally, the BS was compared with the serial rolling hitch (RH), a locking needleless suture technique. Materials and Methods: 4-strand grafts, made from two 20-cm fresh porcine toe extensors, were used in all three groups. After the grafts were sutured, pretension was applied with a load of 100-N distraction force for five minutes. After the tendon elongation was measured before and after the pretension, the distraction force was continued until the constructed graft failed. Stress-strain relationship graphs were recorded by universal testing machine (UTM), distributing to the calculation of percentage on tendon elongation, stiffness, and load-to-failure. Results: The BS had significantly higher load of failure than the CF (p=0.001) but no significant difference when compared with the RH. Comparing between BS, CF, and RH, there were no significant difference in stiffness and percentage of tendon elongation. In modes of failure, there was evidence of knot slipping in CF in six of six cases and graft strangulation in RH in four of six cases. Conclusion: Multi-strand model BS, a needled suture, had a higher load to failure than CF, a needleless suture. Moreover, needleless sutures had serious modes of failure, which were knot slipping and strangulation of graft by the suture material. Therefore, needleless suture technique for multi-strand tendon graft preparation was not recommended. Keywords: Tendon preparation; Multi-Strand; Needled suture; Needleless suture; Chinese finger; Baseball stitch; Rolling Hitch; Biomechanical study; Graft elongation; Load to failure

Sock Laparoscopy: Very Low-Fidelity Simulation to Develop Advanced Skills

Study Objective Demonstrate the construction and use of very low-fidelity simulation to practice advanced laparoscopic skills in gynecologic surgery. Design Educational demonstration using affordable materials and a basic laparoscopic box trainer. Setting N/A Patients or Participants N/A Interventions N/A Measurements and Main Results N/A Conclusion Laparoscopic surgical training is an important aspect of OB/GYN residency and successful completion of the Fundamentals of Laparoscopic Surgery is now required. A laparoscopic box trainer provides a platform for practicing basic and advanced laparoscopic skills. Very low-fidelity models can be quickly created using inexpensive material to simulate more advanced skills such as vaginal cuff closure, cystotomy repair, myomectomy closure with baseball stitch of the serosa, bowel serosa repair, ovarian cystectomy, and peritoneal biopsy.

Suturing Techniques during Robotic-Assisted Myomectomy

Study Objective To help novice surgeons master robotic suturing techniques using side-by-side views of the surgical instruments and field as well as the surgeon's hands at the console during robotic-assisted myomectomy. Design Compilation of recorded video segments showing the suturing of various myometrial defects with simultaneous views of the surgeon's hands during robotic-assisted myomectomy. Setting A tertiary care hospital. Patients or Participants A total of four patients were selected to demonstrate different suture techniques after removal of leiomyoma of different sizes and locations within the uterus. Interventions Deep myometrial defects are standardly closed in three layers starting with a deep running stitch, followed by an imbricating layer, and lastly with a baseball stitch closure of the uterine serosa utilizing a unidirectional barbed suture. We demonstrate different tips and tricks for proper ergonomic placement of the hands at the console, needle handling and camera angling that can be employed, depending on the location and orientation of the hysterotomy site. The intra-abdominal surgical views are shown alongside the view of the surgeon's hands at the console. Measurements and Main Results N/A Conclusion By offering a side-by-side view of the surgical instruments and the hand orientation of the surgeon at the console, it provides an additional perspective for a surgical learner that is otherwise not achievable in the intraoperative setting for robotic surgeries. We hope that this video can serve as a helpful resource to surgeons, instructors, and trainees for suturing techniques during robotic-assisted myomectomies.

Trajectory-based VMAT for cranial targets with delivery at shortened SAD.

Trajectory-based volumetric modulated arc therapy (tr-VMAT) treatment plans enable the option for noncoplanar delivery yielding steeper dose gradients and increased sparing of critical structures compared to conventional treatment plans. The addition of translational couch motion to shorten the effective source-to-axis distance (SAD) may result in improved delivery precision and an increased effective dose rate. In this work, tr-VMAT treatment plans using a noncoplanar "baseball stitch" trajectory were implemented, applied to patients presented with cranial targets, and compared to the clinical treatment plans. A treatment planning workflow was implemented: (a) beamlet doses were calculated for control points defined along a baseball stitch trajectory using a collapsed-cone convolution-superposition algorithm; (b) VMAT treatment plans were optimized using the column generation approach; (c) a final dose distribution was calculated in Varian Eclipse using the analytical anisotropic algorithm by importing the optimized treatment plan parameters. Tr-VMAT plans were optimized for ten patients presented with cranial targets at both standard and shortened SAD, and compared to the clinical treatment plans through isodose distributions, dose-volume histograms, and dosimetric indices. The control point specifications of the optimized tr-VMAT plans were used to estimate the delivery time. The optimized tr-VMAT plans with both shortened and standard SAD delivery yielded a comparable plan quality to the clinical treatment plans. A statistically significant benefit was observed for dose gradient index and monitor unit efficiency for shortened SAD tr-VMAT plans, while improved target volume conformity was observed for the clinical treatment plan (P≤0.05). A clear dosimetric benefit was not demonstrated between tr-VMAT delivery at shortened SAD compared to standard SAD, but shortened SAD delivery yielded a fraction size-dependent reduction in the estimated delivery time. The implementation of "baseball stitch" tr-VMAT treatment plans to patients presented with cranial targets demonstrated comparable plan quality to clinical treatment plans. The delivery at shortened SAD produced a fraction size-dependent decrease in estimated delivery time.

Biomechanical comparison of the use of different surgical suture techniques for continuous loop tendon grafts preparation

We introduce a new approach for a continuous loop tendon-graft preparation, benchmarking it against established graft preparation techniques widely used in conjunction with non-adjustable interference screw fixation. A four-strand bovine tendon graft was prepared using the following graft preparation techniques: standard graft using the baseball stitch technique (M-tech group); continuous loop graft using the GraftLinkTM technique (Arthrex-tech group); continuous loop graft using the Kessler anastomosis technique (Kessler-tech group); and continuous loop graft using a Double-Z anastomosis technique (Double Z-tech group). Each group of eight specimens underwent cyclic loading followed by a load-to-failure test. The M–technique yielded a smaller graft diameter (8.4 ± 0.5 mm) compared to the statistically equivalent diameters of the three continuous loop techniques (8.9 ± 0.6 mm of Arthrex-tech group, 9.1 ± 0.4 mm of Kessler-tech group and 9.2 ± 0.6 mm of Double Z-Tech group). The continuous loop grafts formed by the Double Z-Technique showed outstanding performance among the tested techniques in terms of ultimate failure load (982 ± 121 N) and cyclic elongation (3.7 ± 1.0 mm). There was no significant difference between the four groups in cyclic stiffness. Of the assessed techniques, the Arthrex technique resulted in the lowest ultimate elongation (2.0 ± 0.7 mm), followed by the Double Z-tech (4.5 ± 1.8 mm), the M-tech (5.2 ± 3.9 mm), and the Kessler-tech (5.3 ± 2.4 mm). The Arthrex-tech group (5.98 ± 0.38 min) displayed the shortest graft preparation time, followed by the M-Tech (7.94 ± 0.58 min), Kessler-tech (9.03 ± 0.39 min) and Double Z-Tech (13.29 ± 1.14 min). Double Z-Tech can improve the construct of continuous loop tendon graft with regard to mechanical performance.

1736 Novel Approach to Repair of Laparoscopic Cystotomy

Video Objective This video aims to demonstrate an interesting incidental cystotomy created laparoscopically during a total hysterectomy, demonstrate best practices for repair techniques, and review relevant anatomy. Setting Our patient is a 47 year old G7P3223 with a prior surgical history of 4 cesarean sections, who presents for total laparoscopic hysterectomy and bilateral salpingectomy as definitive treatment for abnormal uterine bleeding (AUB) due to leiomyomas. The surgery takes place at a large tertiary medical center. During creation of the colpotomy, a through and through anterior cystotomy and a partial thickness posterior cystotomy is incidentally created. Illustrations of relevant anatomy demonstrate how the colpotomy is created and which areas of the bladder need to be repaired. Interventions The extent of the cystotomy is assessed by guiding the laparoscope into the bladder via the cystotomy. The ureteric orifices are found to be intact bilaterally. The repair is then performed laparoscopically. First, the partial thickness posterior cystotomy is repaired in two layers. The first layer is a running non-locking stitch that is started in an inside-to-out followed by an outside-to-in fashion, allowing the knot to be buried below the mucosa. The second layer is an imbricating baseball stitch burying the mucosal layers. Next, the anterior full thickness cystotomy is repaired in two running non-locking layers burying all knots outside the bladder to prevent a nidus for stone formation and other complications. The bladder is backfilled to assure a water tight seal and the hysterectomy is continued. Conclusion Our video demonstrates an interesting cystotomy that involves both the anterior and posterior walls of the bladder and evaluation of the trigone from the abdominal side. It summarizes and illustrates best practices for bladder injury repair laparoscopically and relevant anatomy. Finally, it reviews necessary intraoperative care after repair, including retrograde filling of the bladder and cystoscopy, and postoperative care.

Soft Tissue Fixation Strategies of Human Quadriceps Tendon Grafts: A Biomechanical Study

To evaluate the effects of different stitching methods and suture diameters on the graft fixation of soft tissue human quadriceps tendon grafts for anterior cruciate ligament (ACL) reconstruction. The Krackow locking stitch (K), whipstitch (W), and baseball stitch (B) were combined with either a 2× no. 2 (#2) or a 1× no. 5 (#5) braided composite suture for graft fixation of 36 human quadriceps tendons in 6 groups. Biomechanical testing was performed using a cyclic protocol with loads between 0 and 100N. The maximum load until failure, cyclic elongation, and failure mode were recorded. The highest mean maximum load to failure was observed in the 2 Krackow stitch groups. The K#2 group had significantly higher load to failure values compared with those of the W#2 and B#2 groups (K#2, 553 ± 82N vs W#2, 392 ± 107N, P= .0349; K#2 vs B#2 366 ± 118N, P= .0129). The mean cyclic elongation was lowest in the Krackow groups (K#2, 10.59 ± 2.63mm; K#5, 13.66 ± 2.3mm). The regular failure mode was the rupture of the suture for the Krackow stitch (8 of 12) and suture pullout for the whipstitch (11 of 12) and baseball stitch groups (12 of 12). The double Krackow stitch with no. 2 braided composite suture exhibits a high maximum load to failure combined with a low amount of elongation in a biomechanical study for human quadriceps tendon soft tissue graft fixation. Unlike the whipstitch and the baseball stitch, it can solidly prevent suture pullout. A safe soft tissue graft fixation technique is especially important for quadriceps tendon grafts with their laminar anatomical structure and physiologically varying diameter. Unlike other grafts for ACL replacement, it fully relies on the soft tissue suture fixation to resist the pullout force.

IFT04. Dermabond and Tegaderm, a Better Surgical Incision Dressing

Surgical site infections are a common source of morbidity with vascular surgery incisions, especially in the groin. Single institution case series’ have widely varying, but high incidences of groin wound infection after open lower extremity revascularization. We developed and validate a new dressing using n (Ethibond) and Tegaderm for vascular surgery incisions that could simplify and reduce postoperative surgical site infections. This is a retrospective study of 99 consecutive patients who received open lower extremity revascularization by a single surgeon between January 2008 and December 2015 at a single tertiary medical center. In all the incisions, the subcutaneous tissues were closed in a running fashion using 3-0 or 4-0 Vicryl suture. The skin was closed with a running baseball stitch using 4-0 Monocryl suture on a P3 needle. No adhesions or other instruments were used. Dermabond was then applied generously to the wound and the surrounding skin, extending it to the boundaries of the selected Tegaderm. A Tegaderm is then applied while the Dermabond was still wet, so the entirety of the Tegaderm seals to the wound and surrounding skin (Figs 1 and 2). The dressing remained in place until it auto-detached or was taken off at the postoperative 2-week follow-up. The primary end point was the presence of a surgical site infection, dehiscence, or another complication such as hematoma, lymphocele, or seroma. A linear regression model was used to identify any statistical significance and trends. Of 99 patients, 94 met inclusion criteria. Average age was 66 years, 55 of the 94 patients were male, 11 of the 94 were obese (body mass index of >30), 67 of the 94 were active smokers, 27 of the 94 had diabetes mellitus (insulin dependent and noninsulin dependent). Operative factors we examined were the presence of an active infection being treated at the time of surgery (17 of 94), whether the operation was done emergently (0 of 94), and whether a nonautogenous conduit was used (8 of 94). Of the 99 patients, none had signs of infection superficial or deep, dehiscence, or evidence of nonhealing. Moisture accumulation under the Tegaderm requiring removal in only eight patients, and all healed normally thereafter with daily dry dressing changes. Gluing a Tegaderm to an incision using Dermabond is a novel and easy to perform dressing that reduces wound infection, increases patient comfort, avoids dressing changes, and allows visualization of the wound.Fig 2View Large Image Figure ViewerDownload Hi-res image Download (PPT)

No difference in the graft shift between a round and a rounded rectangular femoral tunnel for anterior cruciate ligament reconstruction: an experimental study.

We developed a novel technique of creating a rounded rectangular femoral bone tunnel for anatomical, single-bundle, autologous hamstring tendon anterior cruciate ligament (ACL) reconstruction. Although this tunnel has many advantages, its non-circular shape has raised concerns regarding excessive graft shift within the bone tunnel. This study aimed to compare the graft shift between round and rounded rectangular tunnels using a graft diameter tester for simulating the femoral bone tunnel. Seven semitendinosus tendon grafts harvested from fresh-frozen cadavers were prepared by removing all excess soft tissue. The two ends of a double-fold hamstring tendon were sutured using a baseball stitch and then looped over a TightRope (Arthrex Co., Ltd., Naples, Florida, USA) to make a fourfold graft. The diameter of the graft was standardized to 8mm using a round graft diameter tester. A round and an original rounded rectangular graft diameter tester were used for simulating the respective femoral bone tunnels. The graft was inserted into the tunnel, with the TightRope positioned on the outside of the tunnel. The distal end of the graft was tensioned to 40N at an angle of 75° to reproduce the most severe graft bending angle. Digital photographs of the tunnel aperture taken at each simulated tunnel and the range of graft shift in the simulated tunnel were analyzed by ImageJ software. Statistical analyses were performed using the Tukey test. P < 0.05 was considered to be significant. There were no significant differences between the round and the rounded rectangular tunnel groups (P > 0.05) in terms of graft shift, gap area, and graft shift ratio. In a simulated ACL reconstruction, there is no difference in the graft shift between a round and a rounded rectangular bone tunnel.

289 - Combined Hysteroscopic and Laparoscopic Repair of Isthmocele

Combined Hysteroscopic and Laparoscopic Repair of Isthmocele presents a rare case of isthmocele diagnosed after cesarean section scar ectopic pregnancy treated successfully with methotrexate and uterine artery embolisation. Patient was advised against future pregnancies. After MRI and SIS confirmation, video demonstrates combined hysteroscopic approach - transillumination and laparoscopic excision and repair of the isthmocele. We also emphasize the importance of different techniques for decreasing blood loss - tourniquet and vasopressin administration. Defect was repaired with multilayer closure, including final imbricating baseball stitch technique.Following the repair, hysteroscopy was repeated demonstrating resolution of the defect.

Biomechanical Investigation of Different Preparation Techniques of Tripled Soft Tissue ACL Grafts

Aims and Objectives:The purpose was to investigate biomechanical properties of different preparation techniques of tripled soft tissue ACL grafts to avoid early mechanical graft failure. It was hypothesized that 1) a graft with a quadrupled femoral portion results in higher load to failure and stiffness compared to a uniformly tripled graft, and 2) a Krackow stitch technique is superior to both baseball stitch and whipstitch technique.Materials and Methods:Forty-eight bovine flexor tendons (eight per group) with a final graft length of 8 cm were used for the present study and randomly assigned to the two graft configuration groups: A) quadrupled femoral portion with a tripled tibial portion, and B) uniformly tripled soft tissue graft. Within the two groups, three different stitching techniques were applied: 1) Whipstitch technique, 2) Krackow stitch, and 3) Baseball stitch. After preconditioning, the grafts were cyclically loaded for 1000 cycles between 50 and 200 N (1 Hz) with consecutive load to failure testing using a constant elongation of 30 mm/min. During biomechnical testing, graft elongation was evaluated with an optical tracking system. For statistical analysis a two-way analysis of variance with a post-hoc Holm-Sidak test was performed. To evaluate the failure mode the Fisher’s exact test was used. The significance level was set at p #CHR: lesslike# 0.05.Results:Considering load to failure, quadrupling the femoral portion of the graft significantly increased the load to failure (p = 0.003) while varying the stitching technique had no influence (p = 0.998). Additionally, graft elongation was lower in group A, but difference was not significant (p = 0.058). Lowest graft elongation was observed when a Krackow stitch was applied, followed by the baseball stitch, and the whipstitch technique (p = 0.035). In group A, all the constructs (graft including sutures) failed at the suture, whereas in group B the failure mode was a slippage of the free femoral graft strand in seven of eight grafts (p = 0.005).Conclusion:When using tripled ACL soft tissue grafts in combination with an extracortical fixation device, the femoral portion should be quadrupled whereas the stitching technique does not have a significant influence on the biomechanical properties. To achieve a higher load to failure with less graft elongation at time zero, the free femoral strand of the tendon graft should be wrapped around the femoral graft tendon loop. This could reduce early graft failure due to slippage of the third free femoral graft strand.

An ex-vivo quantitative assessment to determine the optimal aortotomy closure technique.

BackgroundAfter performing an aortotomy, there are a variety of techniques utilized for suture closure. There is no published data comparing the efficacy of various suture techniques. The goal of this study is to provide an ex-vivo quantitative assessment of resistance to leakage and dehiscence for three aortotomy closure techniques.Materials and methodsAn ex-vivo model was developed utilizing explanted porcine aorta. Aortotomies were closed using one of three techniques: 1) single layer baseball stitch 2) double layer baseball stitch 3) horizontal mattress stitch with a top layer baseball stitch. The aorta was pressurized with saline using an apparatus which captured all leaked fluid. The intra-aortic pressure was adjusted over 8 increments from 110 to 375 mmHg. Leakage rates were determined at each pressure level. Ten aortotomies were performed for each technique, resulting in 240 calculated leakage rates.ResultsAt all pressures, the horizontal mattress group was measured to have significantly less leakage when compared to single or double layer baseball stitch closures (p < 0.005). There was a trend towards a lower leakage rate in the double layer baseball compared to the single layer baseball stitch. However, this difference is statistically significant only at 300 and 335 mmHg. There were no instances of rupture.ConclusionThis study provides the first quantitative comparison of three commonly used aortotomy closure techniques. The running horizontal mattress stitch combined with a baseball stitch provides the greatest resistance to leakage at all pressures. This technique may be superior in clinical scenarios with challenging hemostasis.

207 An In-Vitro Quantitative Assessment of Hemostasis After Three Commonly Used Aortotomy Closure Techniques

After performing aortic valve surgery, there are varying techniques used in clinical practice to close the aortotomy. Although these techniques are used successfully by surgeons every day, there is no published data comparing the efficacy of the techniques. The goal of this study is to provide a quantitative assessment of three commonly used aortotomy closure techniques. An in-vitro model was developed to utilize explanted porcine thoracic aorta. Aortotomies were performed and re-approximated by a single surgeon using one of the three closure techniques: 1) single-layer running baseball stitch 2) double-layer running baseball stitch 3) running horizontal mattress stitch combined with a baseball stitch. The aorta was pressurized with saline in a purpose-built apparatus which captured all leaked fluid for measurement of the leakage rate over time. The intra-aortic pressure was adjusted over 8 increments from 110 mmHg to supra-physiologic levels at 375 mmHg. Leakage rates were measured at each incremental pressure level and compared to previously measured baseline values. Eighteen trials were performed, with six trials in each of the three groups. At all pressures, the horizontal mattress group was measured to have significantly less leakage when compared to single or double baseball stitch closure (p < 0.05). The double layer baseball stitch shows a trend towards decreased leakage compared to the single layer closure. This porcine model provides the first quantitative comparison of three commonly used aortotomy closure techniques. The running horizontal mattress stitch combined with a baseball stitch provides the greatest resistance to leakage throughout the normal, hypertensive, and supra-physiologic aortic pressures. This evidence suggests that this closure technique may provide superior hemostasis and resistance to rupture in the perioperative period.

Biomechanical Properties of Porcine Flexor Tendon Fixation With Varying Throws and Stitch Methods

Background: The well-known suture technique configurations used for hamstring tendon autograft preparation in anterior cruciate ligament (ACL) reconstruction are the Krackow locking stitch and nonlocking stitch, such as a baseball stitch and a whipstitch. However, there are few data in the literature regarding biomechanical comparisons of suture techniques. Purpose: The purpose of this study was to determine the properties of several current techniques of tendon graft suture employed in ACL reconstruction. Study Design: Controlled laboratory study. Methods: Forty-two fresh-frozen porcine flexor digitorum tendons were used. Three stitch configurations (Krackow stitch [group K], baseball stitch [group B], and whipstitch [group W]) were assessed with varying suture throws (6 throws, group×6; 10 throws, group×10) using No. 5 Ethibond sutures. Each group was tested at 1500 loading cycles between 50 and 200 N. After loading cycles, the surviving tendons underwent a load-to-failure test. Results: During the loading cycles, 3 of 7 specimens in group B×6 and all specimens in group W×6 failed by suture pullout. Four of 7 specimens in group B×10 and all specimens in group W×10 showed partial tearing of the tendon. Elongation of group B×10 and group W×10 showed significantly greater elongation than other groups (P < .05). Maximum loads at failure showed significant differences between group K and the other groups (K×6, 436 ± 52 N; K×10, 419 ± 34 N; P < .05). Most specimens failed by rupture of the suture thread in group K. Pullout of the suture from the tendon was observed most in groups B and W. Conclusion: The Krackow stitch was superior to other stitch methods. There was, however, no significant effect of the number of throws on the holding strength. Clinical Relevance: The Krackow stitch could prevent suture slippage by a locking mechanism. The whipstitch is not suitable for clinical application even with an increased number of throws.

Clinical Applications of Suturing in Parallel and Perpendicular Planes

Laparoscopic suturing is a complex task that requires many hours of practice and experience to perform proficiently. This video will highlight some clinical applications of suturing using parallel and perpendicular planes in a systematic and geometric approach. This video will demontrate vaginal cuff closure techniques using extra-corporeal and intra-corporeal knot tying. We will also present a myomectomy closure with emphasis on intra-corporeal knot tying, running suturing and suture managment as well as a laparoscopic techhnique for a baseball stitch closure.

Arthroscopic Coracoclavicular Ligament Reconstruction Utilizing Biologic and Suture Fixation: One to Two Year Results (SS-40)

Arthroscopic Coracoclavicular Ligament Reconstruction Utilizing Biologic and Suture Fixation: One to Two Year Results (SS-40)

Arthroscopic Coracoclavicular Ligament Reconstruction Using Biologic and Suture Fixation

Presented in this report is a modified arthroscopic approach to acromioclavicular joint reconstruction via suture and allograft fixation. An arthroscopic approach is used to expose the base of the coracoid by use of electrocautery. After an open distal clavicle excision is performed, clavicular and coracoid tunnels are created under arthroscopic visualization as previously described by Wolf and Pennington. The myotendinous end of a semitendinosus allograft is sutured to a Spider plate (Kinetikos Medical, San Diego, CA). The tendinous end of the graft is prepared with a running baseball stitch. A Nitinol wire with a loop end (Arthrex, Naples, FL) is used to pass 2 free FiberTape sutures (Arthrex) and the leading sutures from the tendinous end of the graft through the clavicular and coracoid tunnels, exiting out the anterior portal. One of the FiberTape sutures is retrieved with a grasper and passed over the anterior aspect of the distal clavicle. The second FiberTape suture and the allograft are passed over the distal end of the resected clavicle. While the acromioclavicular joint is held reduced, the FiberTape sutures are tied to the plate and the allograft is tensioned medially until the plate is embedded against the superior surface of the clavicle. The tendinous end of the graft is secured to the superior surface of the clavicle with a Bio-tenodesis screw (Arthrex) medial to the clavicular tunnel.

Propagation of an MHD Shock in the Vicinity of a Magnetic Neutral Sheet

The acceleration of solar cosmic rays in association with certain solar flares is known to be highly correlated with the propagation of an MHD shock through the solar corona (Svestka, 1976). The spatial structure of the sources of solar cosmic rays will be determined by those regions of the corona which are accessible to the flare-induced shock. The regions to which the flare shock is permitted to propagate are determined by the large scale magnetic field structure in the corona. McIntosh (1972, 1979) has demonstrated that quiescent filaments form a single continuous feature (a “baseball stitch”) around the surface of the sun. It is known that helmet streamers overlie quiescent filaments (Pneuman, 1975), and these helmet streamers contain large magnetic neutral sheets which are oriented essentially radially. Hence the magnetic field structure in the low solar corona is characterized by a large-scale radial neutral sheet which weaves around the entire sun following the “baseball stitch”. There is therefore a high probability that as a shock propagates away from a flare, it will eventually encounter this large neutral sheet.