Meniscus Repair and Replacement.

The importance of preserving the function of the meniscus is seen with renewed interest. There has been an evolution of arthroscopic meniscus repair from inside-out, outside-in, meniscal fixators, to all-inside suturing techniques. Tear patterns once ignored or thought to be irreparable, such as root tears and horizontal cleavage tears, have recently been undergoing repair with promising results. Newer techniques have also recently allowed surgeons to address postmeniscectomy knee pain. Replacing lost tissue with scaffolds or replacing the meniscus with an allograft helps restore function and reduce degenerative changes.

Acute choke zone effects: Lessons from radioactive and fluorescent microspheres in a pig model muscle flap.

BACKGROUND: Choke vessels dilate and contract to regulate blood flow between adjacent arterial angiosomes. In skin flap surgery, when arterial inflow to an angiosome is ligated, choke vessels allow blood supply from an adjacent angiosome. In muscle flap surgery, the vascular anatomy is analogous to skin flaps; however, while it is established that the choke vessels will fully dilate irreversibly after two to three days, no study has yet analyzed the acute changes in each vascular region immediately following ligation of one pedicle. OBJECTIVE: To establish whether the choke vessels open or close immediately following ligation of a pedicle, and how this change affects blood flow in the adjacent proximal and distal vascular regions. METHODS: Radioactive and fluorescent microspheres in a pig model were used to study the regional intramuscular blood flow in each anatomical zone of a rectus abdominis flap. Blood flow measurements for each zone were calculated relative to the entire muscle at preligation, ligation and various times (15 min to 90 min) postligation. RESULTS: There was no statistically significant difference in blood flow across choke zones as a result of ligation. This signifies that the choke vessels do not significantly dilate to produce a statistically significant measureable change in blood flow. CONCLUSIONS: Given these results and previous literature findings, the anatomical presence of choke vessels in a muscle is the strongest determining factor for acute flap viability in surgery.

HISTORIQUE: Les vaisseaux anastomotiques se dilatent et se contractent pour réguler le débit sanguin entre les angiosomes artériels adjacents. Dans le cadre d'une chirurgie par lambeau cutané, lors de la ligature du débit artériel vers un angiosome, les vaisseaux anastomotiques assurent un débit sanguin en provenance d'un angiosome adjacent. L'anatomie vasculaire est alors analogue aux lambeaux cutanés. Cependant, bien qu'il soit établi que les vaisseaux anastomotiques se dilatent pleinement et de manière irréversible au bout de deux ou trois jours, aucune étude n'a encore analysé les changements aigus de chaque région vasculaire immédiatement après la ligature d'un pédicule. OBJECTIF: Établir si les vaisseaux anastomotiques s'ouvrent ou se ferment immédiatement après la ligature d'un pédicule et examiner l'effet de ce changement sur le débit sanguin des régions proximales et distales adjacentes. MÉTHODOLOGIE: Les chercheurs ont utilisé les microsphères radioactives et fluorescentes d'un porc pour étudier le débit sanguin intramusculaire régional de chaque zone anatomique d'un lambeau du grand droit. Ils ont mesuré le débit sanguin de chaque zone par rapport au muscle entier avant la ligature, au moment de la ligature et à divers moments (de 15 à 90 minutes) après la ligature. RÉSULTATS: Il n'y avait pas de différence statistiquement significative du débit sanguin dans les diverses zones anastomotiques après une ligature. Ainsi, les vaisseaux anastomotiques ne se dilatent pas au point de produire un changement du débit sanguin pouvant être mesuré de manière statistiquement significative. CONCLUSIONS: Compte tenu de ces résultats et des conclusions de publications scientifiques, la présence anatomique de vaisseaux anastomotiques dans un muscle est le principal déterminant de viabilité aiguë d'un lambeau lors d'une chirurgie.

Improving residency training in arthroscopic knee surgery with use of a virtual-reality simulator. A randomized blinded study.

BACKGROUND: There is a paucity of articles in the surgical literature demonstrating transfer validity (transfer of training). The purpose of this study was to assess whether skills learned on the ArthroSim virtual-reality arthroscopic knee simulator transferred to greater skill levels in the operating room. METHODS: Postgraduate year-3 orthopaedic residents were randomized into simulator-trained and control groups at seven academic institutions. The experimental group trained on the simulator, performing a knee diagnostic arthroscopy procedure to a predetermined proficiency level based on the average proficiency of five community-based orthopaedic surgeons performing the same procedure on the simulator. The residents in the control group continued their institution-specific orthopaedic education and training. Both groups then performed a diagnostic knee arthroscopy procedure on a live patient. Video recordings of the arthroscopic surgery were analyzed by five pairs of expert arthroscopic surgeons blinded to the identity of the residents. A proprietary global rating scale and a procedural checklist, which included visualization and probing scales, were used for rating. RESULTS: Forty-eight (89%) of the fifty-four postgraduate year-3 residents from seven academic institutions completed the study. The simulator-trained group averaged eleven hours of training on the simulator to reach proficiency. The simulator-trained group performed significantly better when rated according to our procedural checklist (p = 0.031), including probing skills (p = 0.016) but not visualization skills (p = 0.34), compared with the control group. The procedural checklist weighted probing skills double the weight of visualization skills. The global rating scale failed to reach significance (p = 0.061) because of one extreme outlier. The duration of the procedure was not significant. This lack of a significant difference seemed to be related to the fact that residents in the control group were less thorough, which shortened their time to completion of the arthroscopic procedure. CONCLUSIONS: We have demonstrated transfer validity (transfer of training) that residents trained to proficiency on a high-fidelity realistic virtual-reality arthroscopic knee simulator showed a greater skill level in the operating room compared with the control group. CLINICAL RELEVANCE: We believe that the results of our study will stimulate residency program directors to incorporate surgical simulation into the core curriculum of their residency programs.

Evaluation of skill level between trainees and community orthopaedic surgeons using a virtual reality arthroscopic knee simulator.

BACKGROUND: Several virtual reality simulators have been developed to assist orthopaedic surgeons in acquiring the skills necessary to perform arthroscopic surgery. The purpose of this study was to assess the construct validity of the ArthroSim virtual reality arthroscopy simulator by evaluating whether skills acquired through increased experience in the operating room lead to improved performance on the simulator. METHODS: Using the simulator, six postgraduate year-1 orthopaedic residents were compared with six postgraduate year-5 residents and with six community-based orthopaedic surgeons when performing diagnostic arthroscopy. The time to perform the procedure was recorded. To ensure that subjects did not sacrifice the quality of the procedure to complete the task in a shorter time, the simulator was programmed to provide a completeness score that indicated whether the surgeon accurately performed all of the steps of diagnostic arthroscopy in the correct sequence. RESULTS: The mean time to perform the procedure by each group was 610 seconds for community-based orthopaedic surgeons, 745 seconds for postgraduate year-5 residents, and 1028 seconds for postgraduate year-1 residents. Both the postgraduate year-5 residents and the community-based orthopaedic surgeons performed the procedure in significantly less time (p = 0.006) than the postgraduate year-1 residents. There was a trend toward significance (p = 0.055) in time to complete the procedure when the postgraduate year-5 residents were compared with the community-based orthopaedic surgeons. The mean level of completeness as assigned by the simulator for each group was 85% for the community-based orthopaedic surgeons, 79% for the postgraduate year-5 residents, and 71% for the postgraduate year-1 residents. As expected, these differences were not significant, indicating that the three groups had achieved an acceptable level of consistency in their performance of the procedure. CONCLUSIONS: Higher levels of surgeon experience resulted in improved efficiency when performing diagnostic knee arthroscopy on the simulator. Further validation studies utilizing the simulator are currently under way and the additional simulated tasks of arthroscopic meniscectomy, meniscal repair, microfracture, and loose body removal are being developed.

Virtual reality in orthopaedics: is it a reality?

BACKGROUND: Virtual reality (VR) simulation has been a requirement for airline and military pilots for decades and is only now being integrated into surgical training programs. Thus far, orthopaedic training programs have been slow to adopt VR training. QUESTIONS/PURPOSES: We therefore asked (1) how VR has worked for other surgical specialties; (2) what VR solutions are available for orthopaedics; and (3) should VR simulation become part of the orthopaedic curriculum? METHODS: An informal literature review was performed, searching for orthopaedically-oriented VR surgical simulators and comparing this to the number of programs available for general surgery teaching programs. An in-depth review of a VR simulator for knee arthroscopy is also presented. WHERE ARE WE NOW?: The number of papers specific to orthopaedics and VR is limited. VR is used effectively in other specialties, especially general surgery. VR simulators are readily available for shoulder and knee arthroscopy but not as well incorporated into training curricula. WHERE DO WE NEED TO GO?: VR technology is available today for training programs. Integration of VR into the orthopaedic curriculum will save time in the OR, reduce operative errors, and improve the resident's overall educational experience. The public will expect their surgeons to train on these simulators. HOW DO WE GET THERE?: Orthopaedic training programs should take advantage of the commercially available VR simulators for orthopaedic procedures and incorporate them into their training curricula. This effort could be led by the American Academy of Orthopaedic Surgeons (AAOS) and the American Board of Orthopaedic Surgery (ABOS), two of the primary sponsors of a major study in the effectiveness of VR simulators for knee arthroscopy.

An autologous cartilage tissue implant NeoCart for treatment of grade III chondral injury to the distal femur: prospective clinical safety trial at 2 years.

BACKGROUND: The healing potential of damaged articular cartilage is limited. The NeoCart is a tissue-engineered collagen matrix seeded with autogenous chondrocytes designed for the repair of hyaline articular cartilage. HYPOTHESIS: The NeoCart implant is well tolerated in the human knee. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Eight patients (treatment group) with full-thickness cartilage injury were treated with the NeoCart and evaluated prospectively. Autogenous chondrocytes provided by arthroscopic biopsy were seeded into a 3-dimensional type I collagen scaffold. The seeded scaffold was subjected to a tissue-engineering protocol including treatment with a bioreactor. Implantation of the prepared cartilage tissue patch was performed via miniarthrotomy and secured with a collagen bioadhesive. Evaluations through 24 months postoperatively included the subjective International Knee Documentation Committee questionnaire, visual analog scale, range of motion, and cartilage-sensitive magnetic resonance imaging (MRI), including quantitative T2 mapping. RESULTS: Pain scores after NeoCart implantation were significantly lower than baseline at 12 and 24 months after the procedure (P < .05). Improved function and motion were also noted at 24 months. Six patients had 67% to 100% defect fill at 24 months with MRI evaluation. One patient had moderate (33%-66%) defect fill, and another patient had poor (less than 33%) defect fill. Partial stratification of T2 values was observed for 2 patients at 12 months and 4 patients at 24 months. No patients experienced arthrofibrosis or implant hypertrophy. CONCLUSION: Pain was significantly reduced 12 and 24 months after NeoCart treatment. Trends toward improved function and motion were observed 24 months after implantation. The MRI indicated implant stability and peripheral integration, defect fill without overgrowth, progressive maturation, and more organized cartilage formation.

Asphyxial games or "the choking game": a potentially fatal risk behaviour.

OBJECTIVES: To determine the prevalence of knowledge about and participation in asphyxial games, sometimes called "the choking game", and how best to raise awareness of this risk-taking behaviour and provide preventive education. DESIGN: Questionnaire; collaborative research model; lay advocacy group/university researchers. SETTING: 8 middle and high schools in Texas (six) and Ontario (two). A recent death from playing the choking game had occurred in one Texas school, and two other fatalities had occurred within the state. SUBJECTS: Students in grades 4-12, aged 9-18 years. INTERVENTION: None. OUTCOME MEASURES: None. RESULTS: Of 2762 surveys distributed, 2504 (90.7%) were completed. The mean (SD) age of the responders was 13.7 (2.2) years. 68% of children had heard about the game, 45% knew somebody who played it, and 6.6% had tried it, 93.9% of those with someone else. Forty percent of children perceived no risk. Information that playing the game could result in death or brain damage was reported as most likely to influence behaviour. The most respected source of a preventive education message was parents for pre-adolescents (43%) or victim/victim's family (36%) for older adolescents. CONCLUSIONS: Knowledge of and participation in self-asphyxial behaviour is not unusual among schoolchildren. The age of the child probably determines the best source (parents or victim/victim's family) of preventive education.

All-inside meniscus repair: a systematic review.

All-inside meniscus repairs are becoming more common with the invention of meniscal arrows, darts, screws, staples, and other suture devices. With the rising popularity of these new all-inside meniscal repair devices, it is necessary to assess the effectiveness of various all-inside surgical interventions used in the treatment of meniscal tears. We performed an evidence based review of the outcomes of all-inside meniscus repair devices. Seventy-seven percent of identified studies were case series; 10% were retrospective comparative studies; 6.5% were prospective comparative studies; and 6.5% were prospective randomized studies. The failure rates ranged from 0 to 43.5%. We found no substantial differences in the failure rates among various meniscus devices. We also found no substantial differences in failure rates with length of followup. Given the paucity of randomized controlled studies comparing different all-inside meniscal repairs, no definite conclusions can be made regarding the difference in clinical outcomes of various all-inside meniscal repair devices.

A second paradigm for gene activation in bacteria.

Control of gene expression is key to development and adaptation. Using purified transcription components from bacteria, we employ structural and functional studies in an integrative manner to elaborate a detailed description of an obligatory step, the accessing of the DNA template, in gene expression. Our work focuses on a specialized molecular machinery that utilizes ATP hydrolysis to initiate DNA opening and permits a description of how the events triggered by ATP hydrolysis within a transcriptional activator can lead to DNA opening and transcription. The bacterial EBPs (enhancer binding proteins) that belong to the AAA(+) (ATPases associated with various cellular activities) protein family remodel the RNAP (RNA polymerase) holoenzyme containing the sigma(54) factor and convert the initial, transcriptionally silent promoter complex into a transcriptionally proficient open complex using transactions that reflect the use of ATP hydrolysis to establish different functional states of the EBP. A molecular switch within the model EBP we study [called PspF (phage shock protein F)] is evident, and functions to control the exposure of a solvent-accessible flexible loop that engages directly with the initial RNAP promoter complex. The sigma(54) factor then controls the conformational changes in the RNAP required to form the open promoter complex.

Mercury in soils, lakes, and fish in Voyageurs National Park (Minnesota): importance of atmospheric deposition and ecosystem factors.

Concentrations of methylmercury in game fish from many interior lakes in Voyageurs National Park (MN, U.S.A.) substantially exceed criteria for the protection of human health. We assessed the importance of atmospheric and geologic sources of mercuryto interior lakes and watersheds within the Park and identified ecosystem factors associated with variation in methylmercury contamination of lacustrine food webs. Geologic sources of mercury were small, based on analyses of underlying bedrock and C-horizon soils, and nearly all mercury in the 0- and A-horizon soils was derived from atmospheric deposition. Analyses of dated sediment cores from five lakes showed that most (63% +/- 13%) of the mercury accumulated in lake sediments during the 1900s was from anthropogenic sources. Contamination of food webs was assessed by analysis of whole, 1-year-old yellow perch (Perca flavescens), a regionally important prey fish. The concentrations of total mercury in yellow perch and of methylmercury in lake water varied substantially among lakes, reflecting the influence of ecosystem processes and variables that affect the microbial production and abundance of methylmercury. Models developed with the information-theoretic approach (Akaike Information Criteria) identified lake water pH, dissolved sulfate, and total organic carbon (an indicator of wetland influence) as factors influencing methylmercury concentrations in lake water and fish. We conclude that nearly all of the mercury in fish in this seemingly pristine

Report of a group developing a virtual reality simulator for arthroscopic surgery of the knee joint.

Apprenticeship training of surgical skills is time consuming and can lead to surgical errors. Our group is developing an arthroscopic virtual reality knee simulator for training orthopaedic residents in arthroscopic surgery before live-patient operating room experience. The simulator displays realistic human knee anatomy derived from the Visible Human Dataset developed by the National Library of Medicine and incorporates active force-feedback haptic technology. Our premise is that postgraduate year 2 residents completing a formal virtual education program who are trained to reach a proficiency standard in the techniques and protocol for an arthroscopic knee examination will complete a diagnostic arthroscopy on an actual patient in less time with greater accuracy, less iteration of movement of the arthroscope, and less damage to the patient's tissue compared with residents in the control group learning and practicing the arthroscopic knee examination procedures through the residency program's established education and training program. The validation study, done at eight orthopaedic residency programs, will commence in early 2006 and will take one year to complete. We anticipate that proficiency obtained on the simulator will transfer to surgical skills in the operating room.

Extensor mechanism disruption after contralateral middle third patellar tendon harvest for anterior cruciate ligament revision reconstruction.

The contralateral central third patellar tendon autograft is a reliable graft choice for revision, and recently, for primary reconstruction of the anterior cruciate ligament (ACL). We report 2 complications including a lateral third tibial tuberosity fracture and a distal patellar tendon avulsion with contralateral patellar tendon autograft with disruption of the extensor mechanism of the donor knee. A patient sustained a lateral tibial tuberosity fracture of the donor knee and underwent open reduction and internal fixation. At 1-year follow-up, she had no extensor lag and full range of motion. Another patient sustained a distal patellar tendon avulsion of the donor knee and underwent primary repair. Three years postoperatively, she had a full range of motion and no extensor lag. Although contralateral middle third patellar tendon autograft for primary and revision ACL reconstruction is established in the literature, extensor mechanism complications can occur. Technical considerations are important to avoid weakening the remaining patellar tendon insertion. Postoperative nerve blocks or local anesthetics may alter pain feedback for regulation of weight bearing and contribute to overload of the donor knee.

Nucleotide-dependent interactions between a fork junction-RNA polymerase complex and an AAA+ transcriptional activator protein.

Enhancer-dependent transcriptional activators that act upon the sigma54 bacterial RNA polymerase holoenzyme belong to the extensive AAA+ superfamily of mechanochemical ATPases. Formation and collapse of the transition state for ATP hydrolysis engenders direct interactions between AAA+ activators and the sigma54 factor, required for RNA polymerase isomerization. A DNA fork junction structure present within closed complexes serves as a nucleation point for the DNA melting seen in open promoter complexes and restricts spontaneous activator-independent RNA polymerase isomerization. We now provide physical evidence showing that the ADP.AlF(x) bound form of the AAA+ domain of the transcriptional activator protein PspF changes interactions between sigma54-RNA polymerase and a DNA fork junction structure present in the closed promoter complex. The results suggest that one functional state of the nucleotide-bound activator serves to alter DNA binding by sigma54 and sigma54-RNA polymerase and appears to drive events that precede DNA opening. Clear evidence for a DNA-interacting activity in the AAA+ domain of PspF was obtained, suggesting that PspF may make a direct contact to the DNA component of a basal promoter complex to promote changes in sigma54-RNA polymerase-DNA interactions that favour open complex formation. We also provide evidence for two distinct closed promoter complexes with differing stabilities.

Mechanochemical ATPases and transcriptional activation.

Transcriptional activator proteins that act upon the sigma54-containing form of the bacterial RNA polymerase belong to the extensive AAA+ superfamily of ATPases, members of which are found in all three kingdoms of life and function in diverse cellular processes, often via chaperone-like activities. Formation and collapse of the transition state of ATP for hydrolysis appears to engender the interaction of the activator proteins with sigma54 and leads to the protein structural transitions needed for RNA polymerase to isomerize and engage with the DNA template strand. The common oligomeric structures of AAA+ proteins and the creation of the active site for ATP hydrolysis between protomers suggest that the critical changes in protomer structure required for productive interactions with sigma54-holoenzyme occur as a consequence of sensing the state of the gamma-phosphate of ATP. Depending upon the form of nucleotide bound, different functional states of the activator are created that have distinct substrate and chaperone-like binding activities. In particular, interprotomer ATP interactions rely upon the use of an arginine finger, a situation reminiscent of GTPase-activating proteins.