Common Repair Techniques Research Articles

Posterior Horn Lateral Meniscal Root Repair Via Double-Tunnel Transtibial Pullout With Meniscocapsular Release

Background: Lateral meniscal root tears often occur in the acute setting in concert with anterior cruciate ligament (ACL) tears. Severe changes in tibiofemoral biomechanics and joint degeneration are encountered when these injuries are either unrecognized or are treated with meniscectomy; therefore, meniscal root surgical repair is now preferred for longer-term benefits. The most common repair techniques include side-to-side and transtibial pull-out repair, which may be performed via single or double transtibial tunnel techniques. Indications: The primary indication for lateral meniscal root repair with double transtibial tunnels is suspicion for a lateral meniscal root tear based upon injury mechanism, physical examination findings, magnetic resonance imaging findings, and confirmation with diagnostic arthroscopy. Technique Description: The root attachment site is decorticated. Adhesions that cause lateral meniscal root retraction are arthroscopically released. Two separate transtibial tunnels are drilled 5 mm apart from the anterolateral tibia, entering the anterolateral tibia distal to Gerdy’s tubercle and entering the joint at the decorticated lateral root attachment site. Two suture tapes are passed through the torn lateral meniscal root in a vertical mattress configuration and shuttled with a passing suture through the tibial tunnels. The suture tapes are tied over a surgical button on the anterolateral tibia with the knee flexed to approximately 90° while the repair is viewed arthroscopically. Results: Lateral meniscal root repairs are safe and have very low reoperation rates. It has been reported that the transtibial pullout repair technique of the lateral meniscus significantly decreases lateral meniscus extrusion compared with other repair techniques in patients with combined ACL reconstruction. Zhuo et al also reported significantly improved postoperative clinical outcomes compared with the preoperative state in patients who underwent pullout repair for posterior lateral meniscal root avulsion tears. Discussion/Conclusion: The biomechanical and clinical evidence supports concomitant lateral meniscal root repair in the setting of concurrent ACL injury, and no studies to date have demonstrated a clear harm associated with this procedure. In addition, failure to repair the lateral meniscal root places supraphysiologic loads on the ACL graft and may increase the risk of graft failure. 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.

Decision Support System for Optimum Repair Technique of Concrete Bridges Girders in Egypt

Nowadays, value engineering (VE) has become an essential application in many fields, especially structural engineering. Bridges normally experience local damages throughout their service life, whether due to natural hazards, accidents, or harsh environmental conditions. These damages can compromise the integrity of the structure based on their severity. This paper aims to develop a decision support system (DSS) that selects the most optimal repair technique for girders of concrete bridges, considering different factors such as financial, technical, and logistical factors. The proposed DSS is developed by integrating the analytical hierarchy process (AHP) and VE to specify the optimum repair technique. Furthermore, the most common repair techniques are considered in this research, such as repairing using Steel plates, sheets of glass fiber reinforced polymers (GFRPs), laminates of carbon fiber reinforced polymers (CFRPs), external pre-stressing cables, and concrete jackets. The developed (DSS) was presented graphically as a map for the optimum repairing technique for certain (span, span/depth) combinations. Finally, the DSS was verified using collected case studies from the literature and showed good matching within the considered range of girder’s dimensions.

Higher Rates of Mensical Repair and Rim Preservation in Younger Patients with Discoid Lateral Menisci

Background:Management of discoid meniscus in pediatric patients requires understanding of the presentation, associated risks, and appropriate techniques. Surgical treatment consists of saucerization, meniscus repair, meniscocapular stabilization, and, periodically, subtotal meniscectomy. The type of meniscal treatment is commonly determined during arthroscopy. Thus, surgeons, patients, and their parents/guardians must be prepared for a variety of surgical options.Hypothesis/Purpose:To compare intraoperative arthroscopic findings and treatment of discoid meniscus across pediatric age groups in a large multicenter quality improvement registry.Methods:A multi-center quality improvement registry (16 institutions, 26 surgeons) monitoring the safety of discoid meniscus surgery was reviewed. Audit processes using CPT codes were designed to ensure that all consecutive cases from 2018-2020 were prospectively entered on patients <19 years old into a HIPAA-compliant electronic platform. Patients were grouped into five groups based on age at time of surgery (<7, 7-10, 11-13, 14-16, >16). Demographic characteristics, discoid type, presence and type of tear, peripheral rim instability, repair technique, and partial meniscectomy/debridement beyond saucerization were reviewed. Chi-Square or Fisher’s exact tests were used for categorical comparisons and a Kruskal-Wallis test for continuous comparisons.Results:274 patients were identified (mean age 12.4 years, range 3-18; 47.3% females). Complete discoid meniscus and peripheral rim instability were found to be more prevalent in younger age groups (Table 1). Peripheral rim instability was noted in 55.5% of cases, most commonly in the posterior horn (24.8%). While a focal region of instability was most common, the youngest age group was more likely to have either multifocal instability or no instability. Repair was conducted more commonly in the younger cohorts, with a significant decrease in repair percentage (p=0.008) per age group. All-inside was the most common repair technique in all age groups. Partial meniscectomy/debridement beyond saucerization occurred more frequently in older age groups than younger age groups (p=.0002), including 38.4% of cases in the oldest age group (Table 2).Conclusion:Younger patients experienced a greater incidence of complete discoid menisci and meniscus repair in this age group and was more likely to have more than one area of rim instability. However, when meniscal resection beyond a saucerization was required, this was more likely to occur in older patients.Table 1.Age-Related Comparison of Discoid Meniscal Presentation and TreatmentTable 2.Incidence of Additional Meniscal Resection Beyond Saucerization

STANDARDIZATION OF ARTIFICIAL CHORDAL LENGTH FOR POSTERIOR LEAFLET PROLAPSE: A SIMPLIFIED APPROACH FOR MULTIPLE SCENARIOS

<h3>BACKGROUND</h3> While leaflet resection is the most common repair technique for primary mitral regurgitation (MR), there has been a growing interest towards the use of artificial chords for the repair of primary MR. Neo-chord sizing is paramount to the effectiveness of this technique; inappropriate lengths can result in restriction or residual prolapse of the diseased segments. In previous reports, sizing was typically performed on the arrested heart either by visual inspection or with a caliper. Herein, we report our initial experience with a standardized length for multi-loop neo-chord for posterior leaflet (PL) prolapse based on a pre-operative measurement. <h3>METHODS AND RESULTS</h3> Between October 2017 and October 2020, 18 patients who underwent mitral valve (MV) repair for MR due to PL prolapse were included in the study. Pre-operative transesophageal echocardiogram (TEE) was used to determine the optimal neo-chordae length, which was the distance between the papillary muscle tip and desired coaptation point: consistently, 16mm was the optimal neo-chordae length regardless of the affected PL segment. Multi-loop neo-chords were prepared prior to incision. The procedure was performed minimally invasively in 6 patients. Pre-measured 16 mm neo-chords were used to treat prolapsing segments either at the level of P1 (28%), P2 (39%) or P2-P3 (33%). An incomplete semi-rigid band was implanted in all cases. Post-procedural TEE was performed to confirm MV competency. The mean age was 65±13 years and majority were male (74%). Patients either exhibited moderate-severe (11%) or severe (89%) MR. The mean aortic cross-clamp time was 101±17 min. The mean ICU and hospital length of stay were 2±1 and 7±5 days, respectively. No patient required conversion to MV replacement. There was no in-hospital mortality. None exhibited systolic anterior leaflet motion, residual MR greater than grade 2, or mitral stenosis. The mean post-procedural coaptation length was 11±3 mm. At discharge, the mean transmitral gradient and left ventricular ejection fraction were 3±1 mmHg and 61±7%, respectively. <h3>CONCLUSION</h3> Our results show that a standard neo-chord length of 16mm can sufficiently correct MR arising from PL prolapse, while avoiding SAM of the anterior leaflet and mitral stenosis and irrespective of the affected segment. However, long-term outcomes are warranted to validate the durability of this approach.

Surgical repair of ischemic mitral regurgitation: one ring does not fit all.

The review summarizes the key parameters that can aid in determining the optimal treatment of ischemic mitral regurgitation (IMR). Left ventricular (LV) and mitral valve (MV) parameters are important for surgical planning and risk stratification in IMR. Although LV dimensions is one of the main parameters used in the guidelines, volumes more accurately depict LV remodelling. Furthermore, wall motion abnormalities and wall motion score index can also be useful for surgical planning in treatment of IMR. Viability is best measured with cardiac magnetic resonance, but it is not feasible in certain centres. In contrast, measurement of strain with echocardiography is an emerging and feasible tool for estimating viability. MV leaflet tethering and pattern measured with echocardiography are also useful for MV surgery. Anterior leaflet excursion angle can identify patients in whom undersized ring annuloplasty is potentially unsuitable. Treatment of IMR relies on accurate parameters that can determine the optimal surgical approach. In some patients, lack of viable myocardium suggests inadequacy of revascularization and thus, an adjunctive left ventricular reconstruction may be necessary. Degree and pattern of MV leaflet tethering can indicate whether ring annuloplasty, which is the most common repair technique, is sufficient or an adjunctive sub-valvular intervention is beneficial.

Bicuspid Aortic Valve Repair: The Art of Objective Valve Analysis

In this issue of The Annals of Thoracic Surgery, the Mayo Clinic group1 report their experience and outcomes with repair of bicuspid aortic valve for aortic regurgitation. The series included 113 patients with at least moderate aortic regurgitation over 23 years. The most common repair technique was subcommissural annuloplasty (SCA) (94%) with or without raphe excision (55%). Over a median follow-up of 5.6 years 25 valves required reoperation, although in one-fifth of these cases the valves were replaced “prophylactically” at the time of a redo for other causes.

Endoscopic Mitral Repair for Degenerative Mitral Regurgitation: Effect of Disease Complexity on Short- and Mid-term Outcomes

BackgroundWe set out to compare in a prospective cohort study the mid-term clinical and echocardiographic outcomes of mini-mitral repair for simple (posterior prolapse) vs complex regurgitation (anterior/bileaflet prolapse). MethodsA total of 245 consecutive patients underwent mini-mitral repair for severe degenerative mitral regurgitation through a right, endoscopic approach (n = 145 simple, n = 100 complex). The most common repair technique was annuloplasty + artificial chordae (84%, n = 121 for simple vs 88%, n = 88 for complex, P = 0.3). Patients were prospectively followed for a maximal duration of 9 years. Patients’ characteristics were well balanced between groups. ResultsThe 30-day/in-hospital mortality was similar (0%, n = 0 simple vs 1%, n = 1 complex, P = 0.2). Both groups had similar rates of early postoperative complications: myocardial infarction (1.4%, n = 2 vs 0%, n = 0, P = 0.2), neurologic complications (1.4%, n = 2 vs 0%, n = 0, P = 0.2), reoperation for bleeding (0.7%, n = 1 vs 3%, n = 3, P = 0.2), intensive care unit length of stay (1 interquartile range, 1-1 days vs 1 interquartile range, 1-1 days, P = 0.7). Late survival (88% for simple vs 92% for complex, P = 0.4) was similar between groups. Cumulative incidence of late reoperation at 6 years is 0% for both groups (subdistribution hazard ratio = 1, P = 1). There was no difference in recurrent mitral regurgitation greater than 2+ at each year after surgery up to 6 years postoperatively. ConclusionMitral repair using an endoscopic, minimally invasive approach yields excellent mid-term outcomes regardless of disease complexity.

Bacteria encapsulation using synthesized polyurea for self-healing of cement paste

Cracks in concrete increase permeability and exacerbate the detrimental effects of weathering and potential chemical attacks. Common repair techniques involve the use of sealant agents or utilization of biotechnology methods that can self-heal the cracks. In this study, a polyurea polymer because of its adaptable mechanical properties needed for encapsulation (e.g. moisture barrier and spore immobilisation) and its fast curing reaction is proposed as a potential suitable shield and carrier for Bacillus pseudofirmus to produce calcium carbonate (CaCO3) crystal.Synthesis and encapsulation of the bacteria in the polyurea were performed using in-situ polymerization. Chemical characterization and microstructural analysis of the produced polyurea capsules show that the Bacillus pseudofirmus bacterial spores and nutrition were successfully encapsulated without affecting its chemical structure. The bacterial growth further was confirmed by integration of several morphological analyses. The polyurea microcapsules carrying the bacteria were well-mixed in a cement paste. The hardened specimens were cracked using a three-point bending apparatus to artificially trigger the healing effect of the bacteria capsules. The morphology and chemical characterization confirmed precipitation of calcium carbonate around the cracked zone. Polyurea encapsulation was found to be a practical approach to protect bacteria included in cementitious material for the purpose of self-healing.

Current Trends Among US Surgeons in the Identification, Treatment, and Time of Repair for Medial Meniscal Ramp Lesions at the Time of ACL Surgery.

Background:Given the potential hidden nature of medial meniscal ramp lesions and the controversy regarding treatment, it is important to understand the current trends regarding the identification and treatment strategies of meniscal ramp lesions by the leading surgeons and educators in the field of sports medicine.Purpose:To better understand the current trends in orthopaedic surgery regarding arthroscopic identification and treatment of medial meniscal ramp lesions at the time of anterior cruciate ligament (ACL) surgery.Study Design:Cross-sectional study.Methods:An electronic questionnaire was sent in a blinded fashion to 91 directors of orthopaedic sports medicine fellowship training programs in the United States. Participants’ email addresses were obtained through the American Orthopaedic Society for Sports Medicine directory of current fellowship program directors. Inclusion criteria were only those surgeons who currently performed ACL reconstruction surgery. Exclusion criteria were those surgeons who did not perform ACL reconstruction or who chose to opt out of the survey.Results:Overall, 19 surgeons opted out of the survey; 36 responded from the remaining 72 surveys (50%). The majority (n = 31, 86%) reported routinely checking for a medial meniscal ramp lesion via inspection of the posteromedial meniscocapsular junction during an ACL reconstruction. The most common repair technique cited was all-inside (n = 24, 66.7%), followed by inside-out (n = 8, 22.2%). Three (8%) surgeons indicated that they did not repair meniscal ramp lesions. Regarding surgical treatment (repair vs no treatment), the majority reported using the extent of the tear (89%; partial vs full thickness) and the stability of the tear upon probing (81%) as the main criteria for intraoperative decision making. Nineteen (52.8%) surgeons required a mean time of <15 minutes for meniscal ramp repair; 16 surgeons (44.4%), 15 to 30 minutes; and 1 surgeon (2.8%), 30 to 45 minutes.Conclusion:This study provides insight regarding meniscal ramp tear identification, treatment, and repair strategies from the fellowship directors of sports medicine orthopaedic surgery in the United States. Such information may be useful for current orthopaedic surgeons to advance their practice according to the current trends surrounding ACL reconstruction and medial meniscal ramp repair.

Determining postoperative outcomes after cleft palate repair: A systematic review and meta-analysis

BackgroundA lack of high-level evidence exists on the outcomes of different cleft palate repair techniques. A critical appreciation for the complication rates of common repair techniques is paramount to optimize cleft palate care. MethodsA literature search was conducted for articles on the measurement of fistula and velopharyngeal insufficiency (VPI) rates following cleft palate repair. Study quality was determined using validated scales. The heterogeneity between studies was evaluated using the I2 statistic. Random-effect model analysis and forest plots were used to report pooled relative risks (RRs) with 95% confidence intervals for treatment effect. P-values of 0.05 were considered statistically significant. ResultsOf 2386 studies retrieved, 852 underwent screening and 227 met inclusion criteria (130 studies (57%) on fistulas and 122 studies (54%) on VPI). Meta-analyses were performed using 32 studies. The Furlow technique was associated with less postoperative fistulae than the von Langenbeck and Veau/Wardill/Kilner techniques (RR = 0.56 [0.39–0.79], p < 0.01 and RR = 0.25 [0.12–0.52], p < 0.01, respectively). One-stage repair was associated with less fistulae compared to two-stage repair (RR = 0.42 [0.19–0.96], p = 0.04). The Furlow repair was also associated with a less VPI than the Bardach palatoplasty (RR = 0.41 [0.23, 0.71], p < 0.01), and the one-stage repair was associated with a reduction in VPI rates compared to two-stage repair (RR = 0.55 [0.32, 0.95], p = 0.03). ConclusionThe Furlow repair is associated with less risk of fistula formation than the von Langenbeck and Veau/Wardill/Kilner techniques and less VPI compared to the Bardach repair. One-stage repair is associated with less risk of fistula formation and VPI than two-stage repair.

Simple versus complex degenerative mitral valve disease

ObjectivesAt a center where surgeons favor mitral valve (MV) repair for all subsets of leaflet prolapse, we compared results of patients undergoing repair for simple versus complex degenerative MV disease. MethodsFrom January 1985 to January 2016, 6153 patients underwent primary isolated MV repair for degenerative disease, 3101 patients underwent primary isolated MV repair for simple disease (posterior prolapse), and 3052 patients underwent primary isolated MV repair for complex disease (anterior or bileaflet prolapse), based on preoperative echocardiographic images. Logistic regression analysis was used to generate propensity scores for risk-adjusted comparisons (n = 2065 matched pairs). Durability was assessed by longitudinal recurrence of mitral regurgitation and reoperation. ResultsCompared with patients with simple disease, those undergoing repair of complex pathology were more likely to be younger and female (both P values < .0001) but with similar symptoms (P = .3). The most common repair technique was ring/band annuloplasty (3055/99% simple vs 3000/98% complex; P = .5), followed by leaflet resection (2802/90% simple vs 2249/74% complex; P < .0001). Among propensity-matched patients, recurrence of severe mitral regurgitation 10 years after repair was 6.2% for simple pathology versus 11% for complex pathology (P = .007), reoperation at 18 years was 6.3% for simple pathology versus 11% for complex pathology, and 20-year survival was 62% for simple pathology versus 61% for complex pathology (P = .6). ConclusionsEarly surgical intervention has become more common in patients with degenerative MV disease, regardless of valve prolapse complexity or symptom status. Valve repair was associated with similarly low operative risk and time-related survival but less durability in complex disease. Lifelong annual echocardiographic surveillance after MV repair is recommended, particularly in patients with complex disease.

Preoperative Ultrasonographic Prediction of Hamstring Tendon Diameter for Anterior Cruciate Ligament Repair.

The incidence of anterior cruciate ligament (ACL) injuries is rising every year. The autologous hamstring tendon graft, using semitendinosus tendon (SMT) and gracilis tendon (GR), is a common repair technique in the management of ACL injuries due to its multiple advantages. Using a final graft with a minimum diameter of 8 mm is necessary to avoid graft failure. The aim of this study was to find a correlation between preoperative ultrasound (USG) measurement of the SMT and GR tendon diameters (SMTd and GRd) and their actual diameters measured during the grafting procedure. In the present study, 33 male patients aged between 16 and 43 years with ACL injury that required grafting were enrolled. Before the grafting procedure, we sonographically measured the SMTd, GRd, and calculated the hamstring tendon diameter (SMTd + GRd) as the sum of these two. During surgery, we obtained the SMTd, GRd, and SMTd + GRd; we also obtained the length of both tendons and the final graft diameter (FGd). We then compared the obtained values. Mean age was 25.6 ± 7.9 years in our study population. The mean SMTd, GRd, and SMTd + GRd obtained by USG versus transoperatively were 4.9 versus 4.7 mm, 4.3 versus 3.8 mm, and 9.3 versus 8.6 mm, respectively. The mean of FGd was 8.4 mm and the mean length of both tendons was 14.2 cm. The GRd obtained by USG positively correlated with SMTd, SMT tendon length, GRd, and SMTd + GRd (r = 0.460, 0.404, 0.411, and 0.508, respectively). USG-obtained GRd predicts a final tendon diameter < 8 mm (high risk of failure) with a sensitivity, specificity, positive predictive value, and negative predictive value of 100, 54, 28 and 100%, respectively, using 4.5 mm as cutoff. Of all obtained grafts, 85% were deemed adequate (≥ 8 mm) using transoperative measurement, while 91% were ≥ 8 mm using USG measurement. The USG measurement of hamstring tendons is a useful method to predict their transoperative diameter. GRd obtained by USG is the best predictor of transoperative GRd and SMTd + GRd.

Causes of Flexor Tendon Repair Failures in Two Common Repair Techniques: A Cadaver Study.

Flexor tendon repair failures have primarily been attributed to either core suture rupture or core suture pull out. Recent studies have suggested that knot unravelling may also cause failure of a tendon repair. The aim of this study was to investigate the causes of core suture failure in two types of common flexor tendon repairs. Twenty four cadaver tendons were divided into three groups of eight. Each group tested a specific flexor tendon repair. The repairs tested included an Adelaide repair using 4/0 Ethibond (Ethicon), an Adelaide repair using 4/0 Fiberwire (Arthrex) and the Tsai repair with 4/0 Fiberloop (Arthrex). The repaired tendons were pull-tested to failure. The mechanism of failure, maximum tensile strength and 2 mm gap force were recorded. The predominant mode of failure was by the knot unravelling. This occurred in 50-88% of the tendon repairs. The sequence of failure was initiated with gapping at the repair site followed by failure of the epitendinous suture. Next the core suture knot unravels. Once the knot unravels, the suture thread slips out of the tendon resulting in the repair failure. Failures due to knot slippage occurred at a lower maximum tensile strength in Ethibond and Fiberloop sutures than failure due to core rupture or pull out. However, given the small number of tendons tested, this result was not significant. This study has clearly demonstrated one of the main causes of flexor tendon repair failure in two common repair techniques is knot unravelling.

Simplifying Forehead Reconstruction: A Review of More Than 200 Cases.

The forehead is a unique facial region with distinct boundaries and variability in shape from patient to patient. When reconstructing the forehead, it is critical to take into account the regional boundaries as their distortion may result in noticeable facial asymmetry. We propose subdividing the forehead into newly defined zones and put forth a rational algorithm for forehead repair based on these divisions. We retrospectively reviewed a single surgeon's (F. H. S.) experience with Mohs excision and immediate reconstruction of the forehead over a 3-year period. A total of 227 consecutive post-Mohs forehead reconstructions were identified, and the reconstructive technique for a given defect size and location and postoperative complications were recorded. The average patient age was 69 years and 114 (50%) patients were female. Reconstructive techniques varied based on defect size and location within the five distinct forehead zones. Primary closure was the favored technique when appropriate, with variation in orientation based on forehead zone. Modified Burow's advancement flap was the most commonly utilized reconstruction for defects of midlateral forehead and suprabrow area, accounting for 51.7 and 62.5% of repairs, respectively. Other techniques included A-to-T flaps, rotation flaps, and full-thickness skin grafting. Using our defined zones, most common repair techniques, and final outcomes, a reconstructive algorithm for post-Mohs excisions on the forehead was derived. Consideration of the five distinct forehead zones and application of an algorithm to guide technique selection for post-Mohs forehead defect repair can lead to consistent results.

The use of parchment to reinforce split wooden bookboards, with preliminary observations into the effects of RH cycling on these repairs

Abstract Split wooden boards are a common problem in early book bindings, and treatment can be complicated by the need to disturb original components as little as possible. A technique used to reinforce or rejoin fully or partially split wooden boards using parchment has been evaluated. A reinforcing parchment strip has sometimes been employed to treat cracks in wooden musical instruments and examples of reinforcing strip repairs to wooden bookboards have also been observed. The books considered in this article presented an opportunity to use this technique and make observations about its merits. With favourable results but some questions, the authors undertook a systematic study of this method, considering and comparing several options for re‐joining split wooden boards. Samples of some common repair techniques were made and subjected to relative humidity cycling to compare how each method might withstand extreme RH fluctuations at a constant temperature. The response of reinforcing strip repairs to RH c...

Tensile forces on sutures in the human lateral knee meniscus

Tensile strength is the most often reported parameter in biomechanical investigations of meniscal repair techniques. However, the magnitude of the tensile forces that actually occur on repaired lesions is not clear. The purpose of this study was to investigate if tensile forces occur on repaired lateral meniscal lesions, which could exceed the failure strength of common repair techniques. In human knees (n = 6), vertical-longitudinal lesions 25 mm in length were created in the posterior horn of the lateral meniscus at a distance of 3 mm from the meniscosynovial junction and the popliteal hiatus. A braided steel wire, resembling a vertical suture, was inserted into the meniscal tissue and fitted with a force transducer. The knees were mounted in an apparatus, which simulated weight bearing and non-weight bearing conditions. Repeated measurements were conducted with both internal and external rotation at flexion angles of 0 degrees , 30 degrees , 60 degrees , 90 degrees and 120 degrees . Weight loading alone caused no tension on the suture. Combined flexion and rotation generated mean forces between 0.5 and 4.1 N. No significant effect of the flexion angle or direction of rotation was found. If a minimum strength of 10 N was assumed for the common meniscal repair techniques, the tensile forces were well below this limit under all circumstances (P < 0.001). These data indicate that, within the range of motion investigated, no significant tensile forces occur on longitudinal lateral lesions. Forces other than tension and biological factors are of greater importance for the healing. Therefore, the assessment of repair techniques should not be based on alone the ability to resist high distraction forces.

The Repair of Magnesium Rotorcraft Components by Cold Spray

The U.S. Army and Navy have experienced significant corrosion problems with magnesium alloys that are used to fabricate aircraft components. The most severe of these are associated with large and expensive transmission and gearbox housings for rotorcraft, which have to be removed prematurely because of corrosion, adversely affecting fleet readiness and safety. Many of the parts cannot be reclaimed because there is not an existing technology that can restore them adequately for service. The replacement of these parts is very expensive ranging in the millions of dollars every year. One common repair technique, used for some of those parts that can be salvaged, involves the use of aluminum shims, which are adhesively bonded over areas where the corrosion has been ground down and dimensional restoration is required. The U.S. Army Research Laboratory (ARL) Center for Cold Spray has developed a cold spray process to reclaim magnesium components that shows significant improvement over existing methods and is in the process of qualification for use on rotorcraft. The cold spray repair has been shown to have superior performance in the tests conducted to date, is inexpensive, can be incorporated into production, and has been modified for field repair, making it a feasible alternative over competing technologies. The work presented in this chapter represents the first two years of a three-year effort, which will result in the establishment of a demonstration cold spray facility at the Naval Air Depot at Cherry Point, North Carolina (NADEP-CP) where the overhaul and repair of Navy rotorcraft is accomplished. The program involved the participation of all branches of the U.S. Department of Defense, major U.S. helicopter companies, academia and international participation.