Biomedical subjects

Moheb S Moneim

Publications and source records attributed to Moheb S Moneim.

8 recordsLinked to original sources

PubMed2006

Two potential causes of EPL rupture after distal radius volar plate fixation.

Rupture of the extensor pollicis longus tendon can occur after volar plate fixation of dorsally comminuted distal radius fractures. We attempted to identify the etiology of extensor pollicis longus tendon injury after volar plate fixation of the distal radius and potential solutions to this problem. After describing two case reports, we examine six cadaveric specimens and retrospectively review 10 selected patients to evaluate possible technique refinements to minimize damage to the extensor pollicis longus tendon during volar plating of the distal radius. We identify specific screw holes in three commercially available volar distal radius plates that direct the drill bit or prominent screw tips into the third extensor compartment. In addition, after reduction and plate fixation, bone fragments or dorsal gapping may predispose the extensor pollicis longus tendon to injury. We recommend either using shorter screw lengths or leaving the implicated plate holes unfilled. In addition, we suggest consideration of an open assessment of the third extensor compartment, if indicated, as performed through a small dorsal incision ulnar to Lister's tubercle.

Adult↗

PubMed2005

Dynamic effects of joint-leveling procedure on pressure at the distal radioulnar joint.

PURPOSE: Wrist joint-leveling procedures for decompression of the radiocarpal and ulnocarpal joints are accompanied by the risk for subsequent disorders of the adjacent distal radioulnar joint (DRUJ). This study evaluated the dynamic change of the pressure pattern at the DRUJ after joint-leveling procedures. METHODS: Thirteen fresh-frozen adult cadaveric upper extremities were used. A segment of the radius was excised at its midshaft to allow lengthening and shortening via a mini external fixator attachment. Dynamic pressure sensors were inserted into the DRUJ and the ulnocarpal joint. Axial loads were applied to the extensor carpi radialis brevis, extensor carpi radialis longus, extensor carpi ulnaris, flexor carpi radialis, and flexor carpi ulnaris for a total of 89 N with or without 30 N of radioulnar loading. The dynamic pressure distribution for full range of forearm rotation was recorded from 6 mm of radial shortening to 6 mm of radial lengthening in increments of 1 mm. RESULTS: The peak pressures at the DRUJ before the joint-leveling procedures averaged 3.3 MPa without radioulnar loading and 5.0 MPa with radioulnar loading. The peak pressures with axial and radioulnar loading increased 85% at 6 mm of lengthening and only 8% at 6 mm of shortening. The peak pressures at the DRUJ for radial lengthening of 4 mm or more were significantly greater than that of the original length. Pressure at the ulnocarpal joint increased in proportion to the amount of radial shortening and decreased with radial lengthening. CONCLUSIONS: Radial lengthening but not radial shortening significantly increases the peak pressure at the DRUJ.

Adult↗

PubMed2004

Smart intramedullary rod for correction of pediatric bone deformity: a preliminary study.

We were interested in determining if a smart intramedullary rod made of nitinol shape-memory alloy is capable of correcting deformed immature long bones. Because of limitations in our study design the process was reversed in that we examined the smart rod's ability to create a deformity rather than to correct one. Smart rods of different lengths and diameters were heat-treated to resume a radius of curvature of 30 to 110 mm. The low and high temperature phases of the smart rods were set, respectively, at 0 degrees C to 4 degrees C and 36 degrees C to 38 degrees C. The preshaped smart intramedullary rods were implanted in the cooled martensite phase in the medullary canal of the tibia in eight rabbits, where they restored their austenite form, causing a continuous bending force. On a weekly basis anteroposterior and lateral radiographs of the surgically treated tibia and the contralateral tibia were obtained for comparison. Rabbits were euthanized 6 weeks after surgery and computed tomography scans of both tibias were used for image analysis. Smart rods with a larger radius of curvature showed only minimal signs of remodeling; however, rods with a radius of curvature of 50 and 70 mm generated enough force history to create bone remodeling and deformation. The amount of bone deformation was highly magnified when unicortical corticotomy on the tension side was done. Based on this preliminary study the technology of the smart intramedullary rod may provide a valuable alternative method to correct pediatric skeletal deformities.

Alloys↗

PubMed2003

Vascularized bone graft for scaphoid nonunion.

The management of recalcitrant nonunion of the scaphoid can be frustrating. Recent understanding of the vascular anatomy of the distal radius has helped in the management of these problems. Vascularized bone grafting for scaphoid nonunion has improved the union rates. Consequently, familiarity with this procedure is an important tool for any surgeon who treats scaphoid nonunion. Although there are numerous publications discussing both the vascular anatomy of the distal radius and the scaphoid, little is written about the surgical technique. This study reviews the literature on scaphoid nonunion and outlines the authors' experience with this procedure.

Journal Article↗

PubMed2002

Flexor tendon repair using shape memory alloy suture: a biomechanical evaluation.

The purpose of the current study was to test in vitro a new shape memory alloy suture for flexor tendon repair. Forty fresh-frozen human anatomic flexor superficialis and profundus tendons were divided and repaired via the cruciate four-strand technique using one of two suture materials (the shape memory alloy suture and the 4-0 Ethibond suture). The forces required to cause a 1, 2, and 3 mm gap, ultimate load to failure, and repair stiffness were compared. Twenty specimens of each suture material also were tensile tested for load to failure, tensile strength, and elongation at failure. The shape memory alloy suture had a significantly higher mean resistance force to 1, 2, and 3 mm gap formation than the 4-0 Ethibond suture (47 N versus 31 N, 51 N versus 36 N, and 57 N versus 41 N, respectively). The shape memory alloy suture repair was 40% stronger than the 4-0 Ethibond suture (61.9 +/- 8.8 N versus 44.3 +/- 10.6 N). Repair with the shape memory alloy suture was significantly stiffer than repair with the 4-0 Ethibond suture (8.1 +/- 1.0 N/mm versus 6.1 +/- 0.9 N/mm). The load to failure and tensile strength of the shape memory alloy suture were significantly higher than that of the 4-0 Ethibond suture. The values of elongation for the two materials were not significantly different. The results of the current study suggest that the shape memory alloy suture may be superior to the 4-0 Ethibond suture in resisting gap formation in the range of forces generated in the early rehabilitation protocol and may be the future material of choice for tendon repairs.

Alloys↗

PubMed2002

A study of ulnar collateral ligament of the thumb metacarpophalangeal joint.

The current study examined the biomechanical properties of intact and repaired ulnar collateral ligaments of the metacarpophalangeal joint of the thumb to determine a safe rehabilitation protocol after repair. In the first part of the study mechanical properties of the ligament were examined and the induced stress and strain were determined during simulated pinch and grip. In the second part of the study the strength and limitations of ulnar collateral ligament repair using a mini-Mitek bone suture anchor was determined. The biomechanical study was done on 16 fresh-frozen thumbs from male cadavers. Failure load, maximum stress, and Young's modulus of intact ulnar collateral ligament were 294.3 +/- 28.2 N, 11.4 +/- 1.2 MPa, and 37.3 +/- 5.1 MPa, respectively. There was no significant correlation between the low grip force and the ligament strain. There was, however, a significant correlation between the pinch force and the ligament strain. The failure load and joint rigidity of intact ulnar collateral ligaments were significantly higher (3.1 and 2.3 times, respectively) than the mini-Mitek repaired ligaments. The current study suggests that pinch activity during the rehabilitative process after repair or reattachment of the ulnar collateral ligament should be eliminated. Repaired ligaments with mini-Mitek bone suture anchors may be able to do a moderate range of motion during postoperative rehabilitation; however, additional in vivo studies are necessary before any clinical recommendation is made.

Aged↗

PubMedDate not supplied

Thumb amputations from team roping.

BACKGROUND: Thumb injuries during team roping have elements of both avulsion and crush, resulting in a poor prognosis for replantation success. PURPOSE: To review 19 cases of thumb amputation from team roping at our institution since 1983. STUDY DESIGN: Retrospective cohort study. METHODS: Cases were included in the study only if a microvascular repair of artery and vein was needed for the thumb to survive. Vein grafts were used to span the damaged vessel segment. Of the 19 thumb amputation cases, 15 attempts were made to replant the thumb. In the remaining four cases, patients had bone shortening and primary closure. The force of injury was calculated based on mechanism. RESULTS: Of the 15 attempts at replantation, only 5 (33%) were successful, despite meticulous technique. One patient subsequently had an emergency toe-to-thumb transfer after an unsuccessful replant, and the remaining nine underwent amputation. Nine of the 10 patients with failed replants had poor flow intraoperatively. In the group of patients younger than 15, the success was 3 of 5 (60%) and in the group 15 years or older the success was 2 of 10 attempts (20%.) Follow-up was available in 13 of the 15 cases of replanted thumbs. CONCLUSIONS: All patients were subjectively satisfied with their results, and all patients with successful replants and seven patients with no thumb returned to rodeo. Biomechanical analysis showed a huge amount of force and pressure, several times larger than that of ring avulsion injury, results when a steer pulls on the thumb.

Adolescent↗

PubMedDate not supplied

Long-term follow-up of surgical release of the A(1) pulley in childhood trigger thumb.

Trigger thumb is an uncommon problem in infants and children. The authors reexamined 21 patients (30 thumbs) who underwent a release procedure, with an average follow-up of 181.3 months (15.1 years). Twenty-three percent of patients had a loss of interphalangeal motion and 17.6% had metacarpal phalangeal hyperextension, and this was unrelated to age at the time of surgery. There was no recurrence of triggering or nodules and no functional deficit. All seven patients who had a longitudinal incision had concerns about their scar appearance. It is the authors' belief that a transverse skin incision and surgical release of the A(1) pulley for trigger thumb in children is a successful procedure even when done after age 3, but interphalangeal motion loss and metacarpal phalangeal hyperextension may occur in the long term.

Child, Preschool↗