Aman Gupta

Normalization of Glenohumeral Articular Contact Pressures After Latarjet or Iliac Crest Bone-Grafting

BACKGROUND Multiple bone-grafting procedures have been described for patients with glenoid bone loss and shoulder instability. The purpose of this study was to investigate the alterations in glenohumeral contact pressure associated with the placement and orientation of Latarjet or iliac crest bone graft augmentation and to compare the amount of glenoid bone reconstruction with two coracoid face orientations. METHODS Twelve fresh-frozen cadaver shoulders were tested in static positions of humeral abduction (30 degrees , 60 degrees , and 60 degrees with 90 degrees of external rotation) with a 440-N compressive load. Glenohumeral contact pressure and area were determined sequentially for (1) the intact glenoid; (2) a glenoid with an anterior bone defect involving 15% or 30% of the glenoid surface area; (3) a 30% glenoid defect treated with a Latarjet or iliac crest bone graft placed 2 mm proud, placed flush, or recessed 2 mm in relation to the level of the glenoid; and (4) a Latarjet bone block placed flush and oriented with either the lateral (Latarjet-LAT) or the inferior (Latarjet-INF) surface of the coracoid as the glenoid face. The amount of glenoid bone reconstructed was compared between the Latarjet-LAT and Latarjet-INF conditions. RESULTS Bone grafts in the flush position restored the mean peak contact pressure to 116% of normal when the iliac crest bone graft was used (p < 0.03 compared with the pressure with the 30% defect), 120% when the Latarjet-INF bone block was used (p < 0.03), and 137% when the Latarjet-LAT bone block was used (p < 0.04). Use of the Latarjet-LAT bone block resulted in mean peak pressures that were significantly higher than those associated with the iliac crest bone graft (p < 0.02) or the Latarjet-INF bone block (p < 0.03) at 60 degrees of abduction and 90 degrees of external rotation. With the bone grafts placed in a proud position, peak contact pressure increased to 250% of normal (p < 0.01) in the anteroinferior quadrant and there was a concomitant increase in the posterosuperior glenoid pressure to 200% of normal (p < 0.02), indicating a shift posteriorly. Peak contact pressures of bone grafts placed in a recessed position revealed high edge-loading. Augmentation with the Latarjet-LAT bone block led to restoration of the glenoid articular contact surface from the 30% defect state to a 5% defect state. Augmentation of the 30% glenoid defect with the Latarjet-INF bone block resulted in complete restoration to the intact glenoid articular surface area. CONCLUSIONS Glenohumeral contact pressure is optimally restored with a flush iliac crest bone graft or with a flush Latarjet bone block with the inferior aspect of the coracoid becoming the glenoid surface. Bone grafts placed in a proud position not only increase the peak pressure anteroinferiorly, but also shift the articular contact pressure to the posterosuperior quadrant. Glenoid bone augmentation with a Latarjet bone block with the inferior aspect of the coracoid as the glenoid surface resulted in complete restoration of the 30% anterior glenoid defect to the intact state. These findings indicate the clinical utility of a flush iliac crest bone graft and utilization of the inferior surface of the coracoid as the glenoid face for glenoid bone augmentation with a Latarjet graft.

Biomechanical Evaluation of Transosseous Rotator Cuff Repair Do Anchors Really Matter

Background: Suture anchor fixation has become the preferred method for arthroscopic repairs of rotator cuff tears. Recently, newer arthroscopic repair techniques including transosseous-equivalent repairs with anchors or arthroscopic transosseous suture passage have been developed. Purpose: To compare the initial biomechanical performance including ultimate load to failure and localized cyclic elongation between transosseous-equivalent repair with anchors (TOE), traditional transosseous repair with a curved bone tunnel (TO), and an arthroscopic transosseous repair technique utilizing a simple (AT) or X-box suture configuration (ATX). Study Design: Controlled laboratory study. Methods: Twenty-eight human cadaveric shoulders were dissected to create an isolated supraspinatus tear and randomized into 1 of 4 repair groups (TOE, TO, AT, ATX). Tensile testing was conducted to simulate the anatomic position of the supraspinatus with the arm in 60° of abduction and involved an initial preload, cyclic loading, and pull to failure. Localized elongation during testing was measured using optical tracking. Data were statistically assessed using analysis of variance with a Tukey post hoc test for multiple comparisons. Results: The TOE repair demonstrated a significantly higher mean ± SD failure load (558.4 ± 122.9 N) compared with the TO (325.3 ± 79.9 N), AT (291.7 ± 57.9 N), and ATX (388.5 ± 92.6 N) repairs (P < .05). There was also a significantly larger amount of first-cycle excursion in the AT group (8.19 ± 1.85 mm) compared with the TOE group (5.10 ± 0.89 mm). There was no significant difference between repair groups in stiffness during maximum load to failure or in normalized cyclic elongation. Failure modes were as follows: TOE, tendon (n = 4) and bone (n = 3); TO, suture (n = 6) and bone (n = 1); AT, tendon (n = 2) and bone (n = 3) and suture (n = 1); ATX, tendon (n = 7). Conclusion: This study demonstrates that anchorless repair techniques using transosseous sutures result in significantly lower failure loads than a repair model utilizing anchors in a TOE construct. Clinical Relevance: Suture anchor repair appears to offer superior biomechanical properties to transosseous repairs regardless of tunnel or suture configuration.

Biomechanical Evaluation of Bioabsorbable versus Metallic Screws for Posterior Cruciate Ligament Inlay Graft Fixation: A Comparative Study

Background Although a tibial inlay technique for posterior cruciate ligament reconstruction is advantageous, metallic screw fixation of the bone block is required. This may pose problems for future surgery (eg, osteotomies, total knee replacement). Hypothesis There is no significant difference in the biomechanical integrity of bone block fixation using stainless steel versus bioabsorbable screw fixation of the tibial inlay graft in posterior cruciate ligament reconstruction. Study Design Controlled laboratory study. Methods Fourteen human cadaveric knees were randomized to receive either stainless steel or bioabsorbable screw fixation of a bone—patellar tendon—bone graft. Cyclic tensile testing of each construct was performed, followed by a load-to-failure test. Digital video digitization was used to optically determine tendon graft deformation. Results Cyclic creep deformation showed no significant difference between the 2 groups (P = .8). The failure load (stainless steel, 461 ± 231 N; bioabsorbable, 638 ± 492 N; P = .7) and linear stiffness (stainless steel, 116 ± 22 N/mm, bioabsorbable, 106 ± 44 N/mm; P = .6) also showed no significant difference between the 2 groups. Optically measured graft deformation was not significant for distal (P = .7) and midsubstance (P = .8) regions, while proximal deformation was significantly higher for bioabsorbable fixation (P = .02). All samples failed at the tibial insertion site with the tibial bone block fracturing at the screws. Conclusion Bioabsorbable screw fixation using a tibial inlay technique does not compromise the strength and stiffness characteristics afforded by metallic fixation. From a biomechanical perspective, bioabsorbable screws are a viable alternative to metal in the context of tibial inlay reconstruction. Clinical Relevance Use of bioabsorbable fixation can potentially eliminate future hardware problems after posterior cruciate ligament reconstruction using a tibial inlay technique.

Usefulness of the direct agglutination test in the early detection of subclinical Leishmania donovani infection: a community-based study

Abstract The value of a direct agglutination test (DAT) in the detection of subclinical infections with Leishmania donovani has recently been investigated in the Indian state of Bihar, after the sensitivity and specificity of the test had been determined. When used to screen sera from 108 parasitologically confirmed cases of visceral leishmaniasis, 50 patients with active, non-leishmanial infection, and 641 healthy controls living close to, or distant from, an endemic area, the test was found to be 91.7% sensitive and 100% specific if a titre of 1 : 800 was used as the threshold for seropositivity. During a longitudinal clinical study in a rural, VL-endemic area of the Indian state of Bihar, the test was used, with 1 : 800 set as the threshold titre, to determine the baseline prevalence of infection with L. donovani among villagers who, though showing no symptoms of VL, had recently been febrile for at least 2 weeks. The 234 subjects of this study were either VL-case contacts [i.e. members of households in which there were active or cured VL cases (N=78)] or the members of control households with no cases or history of the disease (N=156). The results of DAT at the start of the study indicated that 49 (20.9%) of the subjects — 29 (37.2%) of the VL-case contacts and 20 (12.8%) of the other subjects — were seropositive and therefore probably had subclinical infections with L. donovani. During the subsequent 9 months of follow-up, however, only eight of the subjects found seropositive at the start of the study — seven (24.1%) of the seropositive case contacts but only one (5.0%) of the other seropositives — developed symptomatic VL, all by month 6 of the follow-up. Compared with their neighbours, therefore, individuals who shared households with active or cured cases of VL appeared at greater risk not only of L. donovani infection (indicating focal transmission) but also of developing symptomatic disease once infected. Curiously, among the seropositive case contacts, those from the households that harboured active cases of VL at the baseline survey were less likely to develop symptomatic VL during the 9 months of follow-up than those from households that harboured only cured cases (18.8% v. 30.8%). The wide-spread use of DAT could allow the detection and early treatment of latent L. donovani infections and so contribute to the elimination of VL, at least as a public-health problem, from India.

Tibial Fixation of Anterior Cruciate Ligament Allograft Tendons Comparison of 1-, 2-, and 4-Stranded Constructs

Background In sum, 1-, 2-, and 4-stranded allografts are used for soft tissue anterior cruciate ligament reconstruction; however, the fixation properties of fixation devices are not well assessed. Hypothesis There are no differences in the biomechanical characteristics of 1 (Achilles)-, 2 (posterior tibialis)-, and 4 (semitendinosus)-stranded allograft tibial fixation. Study Design Controlled laboratory study. Methods Sixty-three fresh-frozen porcine tibiae were used to evaluate the fixation of 1-, 2-, and 4-stranded human tendon allografts (Achilles, posterior tibialis, and semitendinosus) with 3 fixation devices (Delta, Intrafix, and Calaxo screws). With use of a materials testing system, each graft was subjected to 500 cycles of loading (50-250 N, 0.75 mm/sec) to determine displacement and cyclic stiffness, followed by a monotonic failure test (20 mm/min) to determine maximum load and pullout stiffness. Results For each graft type, there were no significant biomechanical differences between fixation devices. However, the 1-stranded graft (Achilles) construct demonstrated significantly higher mean displacement (3.17 ± 1.62 mm), lower cyclical stiffness (156 ± 25 N/mm), lower load to failure (479 ± 87 N), and lower pullout stiffness (140 ± 28 N/mm). In comparison with the 2-stranded graft (posterior tibialis), the 4-stranded graft (semitendinosus) exhibited lower displacement (0.86 ± 0.44 to 1.12 ± 0.51 mm) and higher ultimate failure load (832 ± 255 to 656 ± 168 N). Numerous differences in fixation properties were noted when comparing a device to each of the 3 grafts. Conclusion The 1-stranded allograft demonstrated inferior biomechanical tibial fixation properties when compared with 2 (posterior tibialis)- and 4 (semitendinosus)-stranded allograft constructs for all fixation devices tested. Clinical Relevance This study demonstrated that not all tibial fixation devices are designed to adequately accommodate different types of anterior cruciate ligament allografts. Biomechanical evidence suggests that caution is warranted when using an Achilles allograft fixated solely with an interference device.

Removal of bacterial and yeast contamination from Leishmania promastigote cultures, by agar plating

It has recently been estimated that 12 million people in 88 countries have some form of leishmaniasis, that between 2 million to 3 million new cases of the disease occur each year, and that about 350 million people are at risk of leishmanial infection (Hermoso et al., 2003). Worryingly, there have been marked increases in the incidence and geographical distribution of human leishmaniasis over the last decade, attributed mostly to the urbanization of rural or semi-rural areas and to the immunosuppression caused by HIV (Habtemariam, 2003). Those attempting to isolate Leishmania strains in vitro frequently face the problem of the contamination of cultures by various species of bacteria and yeasts (Sundar and Rai, 2002), especially when working under field conditions and/or with samples from animal reservoirs or the sandfly vectors (Schnur and Jacobson, 1987). Although there have been revolutionary developments in the field of molecular biology, allowing very small samples to be investigated in detail, much research on the genus Leishmania still depends on the availability of large numbers of the parasites with no contaminating bacteria or yeasts (Visvesvara and Garcia, 2002). Antimicrobial compounds are often added to the medium used for Leishmania cultures, to kill any bacteria and/or yeasts (Kimber et al., 1981; Berman et al., 1984; Yayon et al., 1984), but this practice may not be entirely beneficial. The antimicrobial agents may kill or inhibit the multiplication of certain parasite genotypes (Schnur and Jacobson, 1987) or certain genotypes of the contaminating organisms (Pawlik and Barylak, 1979; Barylak et al., 1982; Lockhart, 1998; Smith and Coast, 2002), leading to the selection of particular subpopulations of the parasites, or of microorganisms that can no longer be controlled with the antibiotics. Some antimicrobial agents are known to have strong antileishmanial activity (Brajtburg and Bolard, 1996; Gangneux et al., 1996; Ali et al., 1997), and antifungal agents such as 5-fluorocytosine may be mutagenic (Oliver and Williamson, 1977; Lockhart, 1998). In the many resource-poor areas where leishmaniasis is endemic, the antimicrobial agents frequently used to clear contamination elsewhere may simply be too expensive. In addition, the complete removal of contamination from leishmanial cultures by the addition of antimicrobial agents may require so many subcultures into fresh medium (Schnur and Jacobson, 1987) that the procedure becomes very laborious and time-consuming. The aim of the present study was to see if a simple agar-plating technique could be used to decontaminate mock isolates of Leishmania (containing yeasts, bacteria and L. donovani promastigotes, in varying numbers and ratios) without the use of any antimicrobial agents. The parasites used were isolated, on NNNmedium, from several cases of visceral leishmaniasis who had been admitted to the inpatient ward at the Rajendra Memorial Research Institute of Medical Sciences, in Patna, India. Each culture found positive for promastigotes was maintained by weekly subculture. A positive culture found to be contaminated with bacteria and another found to contain yeasts were each inoculated onto three plates of blood agar [10%, v/v, defibrinated rabbit blood in commercial Annals of Tropical Medicine & Parasitology, Vol. 99, No. 6, 617–621 (2005)

Long-term preservation of Leishmania donovani promastigotes on blood-agar slants

Isolates of Leishmania are maintained in vitro, often as cultures in liquid medium that require regular (often weekly) passage, or in vivo, usually by passage in Syrian hamsters or mice (Neal, 1984; Schnur and Jacobson, 1987). The methods employed are often labour-intensive, costly and timeconsuming (Ihalamulla et al., 2004), and frequent sub-culture increases the risk that cultures will become contaminated with bacteria or fungi. Although the long-term maintenance of isolates by lyophilization (Iusupov et al., 1976) or cryopreservation (Callow and Farrant, 1973; Raether and Seidenath, 1972, 1977; Miyake et al., 2004) is possible, in the developing countries where leishmaniasis is endemic there are few institutions that have the necessary facilities and supplies. Fortunately, there is a simple method that can be used to maintain the promastigotes of Leishmania donovani, and perhaps other Leishmania species, in culture for at least 7 months without a single sub-passage. This method, which is based on the maintenance of the parasites on blood-agar slants, with no overlay, in a refrigerator, has been developed and evaluated at the Rajendra Memorial Research Institute of Medical Sciences (RMRIMS), in Patna, India. For the evaluation, splenic aspirates from three cases of visceral leishmaniasis who had been admitted to the inpatient ward at the RMRIMS were cultured on NNN medium (Muniaraj et al., 2005). After primary isolation, which was successful for all three cases, the promastigotes were transferred to tubes of fresh NNN medium overlain with Locke’s solution, and incubated at 24¡1uC for 1 week (i.e. until the cultures were in early log phase). The promastigotes in the overlay from each culture were then counted, in a haemocytometer, so that sufficient Locke’s solution could be added to give 2610 promastigotes/ml. Each culture was then used to inoculate 72 screw-cap tubes — 36 that each contained a blood-agar slant [5% (v/v) defibrinated rabbit blood in Blood Agar Base No. 2 (HiMedia laboratories, Mumbai, India) at pH 8, with 15 mg gentamycin/ml] and, as controls, 36 tubes that each contained NNN medium with an overlay of Locke’s solution. Each slant was inoculated by zigzag streaking with 10 ml culture in an inoculation loop. The same volume of culture was added to the overlay in each tube of NNN. All 216 tubes were then incubated at 24¡1uC for 8 days, when promastigote colonies were visible on all the slants, as milky-white, raised, mucoid patches. The caps of the tubes were then sealed tightly before the tubes were placed in zip-lock polythene bags (with three tubes of each isolate/bag) and then transferred to a refrigerator at 7–8uC. At monthly intervals thereafter, 18 tubes — three of each isolate on agar slants and three of each isolate on NNN medium — were removed from the refrigerator so that the viability of the parasites in these tubes could be checked. Viability was investigated by adding 1 ml Locke’s solution to each tube, incubating the tubes at 24¡1uC, and checking the overlay, under a light microscope, after 3 h of incubation and then daily until motile promastigotes had been observed. The parasites in a tube were assumed to be non-viable if no motile parasites had been seen after checking for 25 days. Annals of Tropical Medicine & Parasitology, Vol. 100, No. 2, 173–175 (2006)