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Akbar Nawab

Publications and source records attributed to Akbar Nawab.

13 recordsLinked to original sources
PubMed2006

Bioabsorbable screw divergence angle, not tunnel preparation method influences soft tissue tendon graft-bone tunnel fixation in healthy bone.

Bone tunnel fixation of a soft tissue tendon graft is the weak link immediately following ACL reconstruction. This biomechanical study evaluated the influence of extraction drilled or step dilated bone tunnels and bioabsorbable screw divergence on soft tissue tendon graft fixation. From an initial group of 50 available specimens, similar apparent bone mineral density porcine tibiae (1.2 +/- 0.24 g/cm2) were divided into two groups of ten specimens each. Group 1 (extraction drilled) received 9 mm diameter tunnels. Group 2 (step dilated) received 7 mm diameter tunnels that were dilated to 9 mm. Grafts were secured in tunnels using 10 mm diameter, 35 mm long tapered screws. After high resolution CT scanning to evaluate screw divergence, constructs were pretensioned on a servo hydraulic device between 10 and 50 N for 10 cycles, and isometric pretensioned at 50 N for 1 min, prior to 500 sub-maximal loading cycles (50-200 N) and load to failure testing at 20 mm/min. Wilcoxon Signed Rank tests and Mann-Whitney U-tests were used to evaluate group differences. Coefficient of determination values (r2) were calculated to further delineate statistically significant relationships. Tunnel preparation method did not display statistically significant effects on insertion torque, displacement during cyclic testing, relative stiffness during cyclic testing, load at failure, stiffness during load to failure testing or displacement during load to failure testing. Screw divergence < 15 degrees produced lower displacement and greater relative stiffness during cyclic testing and greater load at failure and stiffness during load to failure testing. Screw divergence angle displayed moderate relationships with construct displacement during cyclic testing (r2 = 0.54), stiffness during load to failure testing (r2 = 0.60), and load at failure (r2 = 0.41). Tunnel dilation does not enhance soft tissue tendon graft fixation strength in healthy bone. Bioabsorbable screw divergence of > or = 15 degrees significantly reduces soft tissue tendon graft-bone tunnel fixation.

Absorbable Implants↗
PubMed2006

A biomechanical comparison of the FasT-Fix meniscal repair suture system and the RapidLoc device in cadaver meniscus.

PURPOSE: This biomechanical study compared the fixation characteristics of horizontally or vertically implanted FasT-Fix devices (Smith & Nephew, Endoscopy Division, Andover, MA) consisting of two 5-mm PLLA suture T-bar anchors with a pretied self-sliding knot (No. 0 nonabsorbable, USP, braided polyester suture material) and the RapidLoc device (Mitek Surgical Products, Westwood, MA) consisting of a PLLA T-bar anchor or "backstop," a connecting suture (No. 2 nonbiodegradable Ethibond; Ethicon, Somerville, NJ), and a PLLA grommet, for repairing posterior third lesions in human menisci. TYPE OF STUDY: Controlled laboratory biomechanical study. METHODS: After repair of a vertical longitudinal meniscus lesion with either vertically or horizontally implanted FasT-Fix devices or RapidLoc devices, 3 groups of 6 specimens underwent cyclic loading (5 mm/minute, cycling between 5 and 50 N at 1 Hz for 500 cycles) before load to failure testing on a servo hydraulic device. One-way analysis of variance and Tukey HSD post hoc tests were used to evaluate group differences (P < .05). RESULTS: The vertical FasT-Fix device group (3.2 +/- 0.49 mm) had less displacement after cyclic testing than either the horizontal FasT-Fix (4.4 +/- 0.73 mm, P = .003) or the RapidLoc (4.6 +/- 0.22 mm, P = .002) device groups. The vertical FasT-Fix device group had greater stiffness during cyclic testing (14.4 +/- 2.1 N/mm) than the horizontal FasT-Fix (10.4 +/- 1.6 N/mm, P = .0001) or the RapidLoc (9.7 +/- 0.44 N/mm, P = .0001) device groups. During load to failure testing, the vertical FasT-Fix group (125.3 +/- 39 N) had 28% greater strength than the horizontal FasT-Fix device group (89.7 +/- 14 N, P = .02) and 30% greater strength than the RapidLoc device group (87.1 +/- 13 N, P = .028), whereas displacement and stiffness did not show statistically significant group differences. CONCLUSIONS: The vertical FasT-Fix group had superior biomechanical characteristics for meniscal fixation during cyclic and load to failure testing compared with horizontal FasT-Fix or RapidLoc devices. CLINICAL RELEVANCE: Although the RapidLoc devices provided fixation characteristics comparable to horizontally implanted FasT-Fix devices, vertically implanted FasT-Fix devices may provide superior all-inside fixation.

Absorbable Implants↗
PubMed2005

Comparison of volumetric bone mineral density in the tibial region of interest for ACL reconstruction.

Adequate tibial bone mineral density (BMD) is essential to soft tissue graft fixation during anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare volumetric bone plug density measurements at the tibial region of interest for ACL reconstruction using a standardized immersion technique and Archimedes' principle. Cancellous bone cores were harvested from the proximal, middle, and distal metaphyseal regions of the lateral tibia and from the standard tibial tunnel location used for ACL reconstruction of 18 cadaveric specimens. Proximal tibial cores displayed 32.6% greater BMD than middle tibial cores and 31.8% greater BMD than distal tibial cores, but did not differ from the BMD of the tibial tunnel cores. Correlational analysis confirmed that the cancellous BMD in the tibial tunnel related to the cancellous BMD of the proximal and distal lateral tibial metaphysis. In conjunction with its adjacent cortical bone, the cancellous BMD of the region used for standard tibial tunnel placement provides an effective foundation for ACL graft fixation. In tibia with poor BMD, bicortical fixation that incorporates cortical bone from the distal tibial tunnel region is recommended.

Aged↗
PubMed2005

Biomechanical comparison of the bioabsorbable RetroScrew system, BioScrew XtraLok with stress equalization tensioner, and 35-mm Delta Screws for tibialis anterior graft-tibial tunnel fixation in porcine tibiae.

BACKGROUND: Achieving effective soft tissue graft-tibial tunnel fixation remains problematic. HYPOTHESIS: No differences would exist for tibialis anterior graft-tibial tunnel fixation when comparing the RetroScrew System (20-mm retrograde screw, 17-mm antegrade screw), the 35-mm tapered Delta Screw (manual tensioning), and the 35-mm BioScrew XtraLok (applied using an instrumented tensioner). STUDY DESIGN: Controlled laboratory study. METHODS: Porcine tibiae (apparent bone mineral density, 1.3 g/cm(2)) and human tendon allografts were divided into 3 matched groups of 6 specimens each before cyclic (500 cycles, 50-250 N, 1 Hz) and load-to-failure (20 mm/min) tests. RESULTS: The BioScrew XtraLok (210.9 +/- 54.9 N/mm) and the 35-mm Delta Screw (224.3 +/- 43.7 N/mm) displayed superior stiffness to the RetroScrew System (114.1 +/- 23.3 N/mm) (P = .0004) during cyclic testing. The BioScrew XtraLok (1.0 +/- 0.2 mm) and the Delta Screw (0.9 +/- 0.2 mm) also displayed less displacement during cyclic testing than the RetroScrew System (1.8 +/- 0.5 mm) (P = .001). During load-to-failure testing, the BioScrew XtraLok withstood greater loads (1436.3 +/- 331.3 N) (P = .001) and displayed greater stiffness (323.6 +/- 56.8 N/mm) (P = .002) than the 35-mm Delta Screw (load, 1042.2 +/- 214.4 N; stiffness, 257.2 +/- 22.2 N/mm) and the RetroScrew System (load, 778.7 +/- 177.5 N; stiffness, 204.4 +/- 52.9 N/mm). CONCLUSION: The BioScrew XtraLok with instrumented tensioning displayed superior fixation to the RetroScrew System and the 35-mm Delta Screw applied with manual tensioning. CLINICAL RELEVANCE: The BioScrew XtraLok may provide superior soft tissue graft-tibial tunnel fixation. Further in vitro studies using human tissue and in vivo clinical studies are needed.

Absorbable Implants↗
PubMed2005

Salvage rotator cuff repair using a biotenodesis screw.

Rotator cuff tear fixation can be difficult when humeral head bone stock is poor as a result of osteopenia or osteoporosis. This technical note describes biotenodesis screw use to achieve effective fixation after 2 previous attempts at implanting suture anchors failed.

Bone Screws↗
PubMed2004

Posterolateral corner reconstruction using a hamstring allograft and a bioabsorbable tenodesis screw: description of a new surgical technique.

Capsuloligamentous posterolateral corner knee joint deficiencies cause increased anterior cruciate ligament forces during internal knee rotation and increased posterior cruciate ligament forces during external knee rotation. Undiagnosed posterolateral corner knee joint injury in combination with anterior cruciate ligament or posterior cruciate ligament injury can lead to failure of anterior cruciate ligament or posterior cruciate ligament reconstruction. The purpose of this technical note is to present a new posterolateral corner reconstruction technique for treating patients with chronic capsuloligamentous posterolateral corner deficiency. The technique uses a bioabsorbable tenodesis screw and a hamstring allograft to reconstruct the popliteofibular and lateral collateral ligaments.

Absorbable Implants↗
PubMed2004

Tendon graft fixation in ACL reconstruction: in vitro evaluation of bioabsorbable tenodesis screw.

BACKGROUND: Conventional ACL reconstruction requires sufficient tibial bone quality for secure graft fixation. We evaluated the mechanical characteristics of a supplemental tenodesis screw in cadaveric specimens. MATERIAL AND METHODS: One group of 7 specimens from 7-paired tibiae was randomly assigned to undergo tibialis anterior tendon graft-bone tunnel fixation with a bioabsorbable interference screw, using conventional ACL reconstruction techniques. The other group of 7 specimens underwent the same procedure supplemented with a bioabsorbable tenodesis screw. All specimens were subjected to pullout testing on a servo hydraulic device. RESULTS: Specimens in the supplemental fixation group had double the load to failure (tenodesis = 467 (SD 184) N, control group = 223 (SD 66) N, p = 0.02) and were also one-third stiffer (tenodesis = 31 (SD 13) N/mm, control group = 21 (SD 6) N/mm, p = 0.03) than the specimens in the conventional fixation group. INTERPRETATION: Supplemental bioabsorbable tenodesis screw fixation may be advantageous for primary reconstruction in patients with low tibial bone mineral density or during revision procedures. By providing secure soft tissue graft-tibia fixation during the early phase after ACL reconstruction, supplemental tenodesis fixation may enable patients to participate safely in more intense, early rehabilitation.

Absorbable Implants↗
PubMed2004

[Soft tissue tendon graft fixation in the tibial tunnel with a bioabsorbable screw-EndoPearl combination in tibiae of low bone mineral density: a biomechanical study].

OBJECTIVES: This biomechanical study evaluated soft tissue tendon graft fixation in the tibial tunnel using a bioabsorbable interference screw with or without supplemental EndoPearl device. METHODS: Ten bovine tibiae were stripped of all soft tissues and bone tunnels 7 mm in diameter were drilled with dilation to 9 mm. Tibialis anterior allografts were fixed with a screw (10 mm in diameter, 30 mm in length) in five tibiae of high bone mineral density (1.36 g/cm2), and with a screw-EndoPearl combination in five tibiae of low bone mineral density (0.84 g/cm2). The specimens were cycled 10 times from 10 to 50 N, and 500 times from 50 to 200 N in a servo hydraulic test device prior to ultimate load-at-failure testing at a rate of 20 mm/min. RESULTS: No statistically significant differences were found between the two fixation groups with respect to displacement and stiffness during cyclic testing, and with respect to load at failure, displacement, and stiffness during load-to-failure testing (p>0.05). CONCLUSION: The finding of similar results in both fixation groups with respect to displacement and stiffness during cyclic testing and during load-to-failure testing suggests that a screw-EndoPearl combination in tibiae of low bone mineral density may be helpful in the prevention of graft slippage.

Absorbable Implants↗
PubMed2003

Determination of organochlorine pesticides in agricultural soil with special reference to gamma-HCH degradation by Pseudomonas strains.

Soil samples were taken from different agricultural fields and analyzed for organochlorine pesticide residues by gas chromatography. The analysis indicated that the soil samples contained some common organochlorine pesticides DDT, DDD, DDE, HCH and Aldrin. gamma-HCH was detected as 47.35 ppb whereas the concentrations of alpha-HCH, beta-HCH, p('),p(')-DDE, o('),p(')-DDT were 38.81, 1.79, 7.10 and 13.30 ppb, respectively, in the same soil. Two Pseudomonas strains isolated from agricultural soil were found to possess gamma-hexachlorocyclohexane degrading ability when the isolates were grown in a mineral salt medium containing gamma-HCH as the sole source of carbon and a number of metabolites were produced and detected by the gas chromatography. These bacterial isolates were further tested for carbohydrate and amino acid utilization as well as for their susceptibility against 10 commonly used antibiotics namely amoxycillin, chloramphenicol, cloxacillin, doxycycline, methicillin, nalidixic acid, neomycin, nitrofurantoin, streptomycin and tetracycline. Both the isolates were also screened for plasmid DNA and found to harbour a single plasmid.

Agriculture↗
PubMed2002

Second generation intramedullary nailing of subtrochanteric femur fractures: a biomechanical study of fracture site motion.

OBJECTIVES: To compare fracture site motion between different second-generation intramedullary nails used to fix subtrochanteric fractures of the proximal femur with and without femoral neck fractures. DESIGN: Nondestructive mechanical testing of four types of femoral intramedullary nails was undertaken to evaluate fracture site motion using a model that simulated single-leg and double-leg stance. METHODS: Three types of reconstruction nails (the Russell-Taylor Delta [Smith & Nephew, Memphis, TN], the Uniflex [Biomet, Warsaw, IN], Alta CFX [Howmedica-Osteonics, Rutherford, NJ]) and the Long Gamma nail (Howmedica-Osteonics, Rutherford, NJ), each measuring 11 x 380 mm, were inserted in fiberglass composite femurs. Four fracture patterns were studied (transverse subtrochanteric, subtrochanteric with posteromedial wedge comminution, subtrochanteric with one-centimeter gap, and a one-centimeter gap with a subcapital neck fracture). Single-and double-leg stance loading was simulated using a servohydraulic load frame (MTS, Eden Prairie, MN). Two-way analysis of variance and post hoc t tests were used to determine any statistically significant differences between groups. RESULTS: In single-leg stance there were significant differences in coronal plane rotation, shear, and axial translation across the subtrochanteric fracture site between the different nail types and the different fracture patterns (p < 0.001). In double-leg stance there were significant differences in coronal plane rotation and femoral head vertical motion between the different nail types and the different fracture patterns (p < 0.001), and there were significant differences in shear and axial translation between the different fracture patterns (p < 0.001) but not the different nail types (p > 0.05). CONCLUSIONS: For simple, well-reduced fractures the choice of implant is not critical. As fracture severity increased (comminution, gap, and combined neck fracture), the choice of implant, particularly with reference to proximal nail dimensions and implant materials, was a significant factor in reducing fracture site motion. Therefore, our laboratory data suggest that when subtrochanteric fractures are unstable (e.g., comminution, segmental bone loss) and early weight bearing is desirable, the choice of implant is critical and should be restricted to implants that allow minimal fracture site motion (Long Gamma and Russell-Taylor).

Biomechanical Phenomena↗
PubMedDate not supplied

Reconstruction of neglected Achilles' tendon defect with peroneus brevis tendon allograft: a case report.

This case report describes the use of a peroneus brevis allograft to reconstruct a neglected Achilles' tendon injury in a 75-year-old woman. She had difficulty walking, had stiffness, and was unable to perform a heel raise from a single-leg standing position. Magnetic resonance imaging confirmed a 6.8-cm wide defect 13 months after the initial injury. Surgical repair of the neglected rupture was performed using 4 strands of peroneus brevis allograft to bridge the defect. Early weight bearing and rehabilitation was allowed. At follow-up clinical examination 14 months postoperation, the patient could perform 15 full-range standing heel raises on the involved side versus 22 on the noninvolved side. Maximum calf circumference was 30.7 cm in the operated leg versus 33 cm at the noninvolved side. At 24 months postoperation the patient could perform 16 full-range standing heel raises on the injured leg versus 24 on the normal leg (33% deficit). The maximum calf circumference improved to 31 cm on the injured side compared with 34 cm on the noninvolved side (9% deficit). The AOFAS Ankle-Hindfoot Clinical Rating System score improved from 55 just before operation to 96 at 14 months postoperatively. The score further improved to 100 at the 2-year follow-up examination. The patient was playing recreational doubles tennis 1 to 2 times per week without symptoms.

Achilles Tendon↗