Search

Parachordoma, or myoepithelioma, is a very rare tumor histologically resembling chordoma but occurring in the nonaxial soft tissues. It typically has an indolent nature, with occasional late recurrence and even rare metastases. Review of existing literature reveals a male predilection, with the tumor typically occurring in the fourth decade of life in the lower extremity. It typically is managed with wide resection. We report the case of a 60-year-old woman with a right distal upper arm parachordoma treated with wide resection of the tumor.

Purpose To compare the mechanical behavior of a novel internal tendon repair device with commonly used 2-strand and 4-strand repair techniques for zone II flexor tendon lacerations. Methods Thirty cadaveric flexor digitorum profundus tendons were randomized to 1 of 3 core sutures: (1) cruciate locked 4-strand technique, (2) modified Kessler 2-strand core suture technique, or (3) Teno Fix multifilament wire tendon repair device. Each repair was tested in the load control setting on a Instron controller coupled to an MTS materials testing machine load frame by using an incremental cyclic linear loading protocol. A differential variable reluctance transducer was used to record displacement across the repair site. Cyclic force (n-cycles) to 1-mm gap and repair failure was recorded using serial digital photography. Results There was no significant difference in differential variable reluctance transducer displacement between the cruciate, modified Kessler, and Teno Fix repairs. The cruciate repair had greater resistance to visual 1-mm repair-site gap formation and repair-site failure when compared with the Kessler and Teno Fix repairs. No significant difference was found between the modified Kessler repair and the Teno Fix repair. In all specimens, the epitenon suture failed before the core suture. Repair failure occurred by suture rupture in the 7 cruciate specimens that failed, with evidence of gap formation before failure. Seven of 10 modified Kessler repairs failed by suture rupture. All of the Teno Fix repairs failed by pullout of the metal anchor. Conclusions The Teno Fix repair system did not confer a mechanical advantage over the locked cruciate or modified Kessler suture techniques for zone II lacerations in cadaveric flexor tendons during cyclic loading in a linear testing model. This information may help to define safe boundaries for postoperative rehabilitation when using this internal tendon repair device.

The purpose of this study was to examine how a natural knee responds to the inputs of a total knee replacement testing standard developed by the International Organization for Standardization (ISO). This load control standard prescribes forces to be used for wear testing of knee replacements independent of implant size or design. A parallel ISO standard provides wear testing inputs that are displacement based instead of force based. Eight fresh frozen cadaveric knees were potted and tested in a 6 degree of freedom knee simulator using the load-control standard. The resulting displacements during load-control testing were compared to the prescribed displacements of the ISO displacement standard. At half the tibial torque prescribed by the load standard there was three times more average internal tibial rotation (20.3 degrees) than is prescribed by the displacement standard (5.7 degrees). The AP motion resulting from load testing was much different than is specified by the displacement standard. All eight knees had anterior tibial translation with respect to the femur during swing phase while the displacement standard specifies posterior tibial displacement. The variation in these motions among knees and their difference from the ISO displacement standard may be one factor that explains why wear results of total knee replacements based on ISO load or displacement testing frequently do not agree with each other or with clinical retrievals.

Parachordoma, or myoepithelioma, is a very rare tumor histologically resembling chordoma but occurring in the nonaxial soft tissues. It typically has an indolent nature, with occasional late recurrence and even rare metastases. Review of existing literature reveals a male predilection, with the tumor typically occurring in the fourth decade of life in the lower extremity. It typically is managed with wide resection. We report the case of a 60-year-old woman with a right distal upper arm parachordoma treated with wide resection of the tumor.

The pumping of fluid and polyethylene wear debris from the joint space to the retroacetabular bone is implicated in the pathogenesis of osteolysis. Three possible mechanisms for this pumping: pressure gradients, diaphragm pumping, and piston pumping were studied in vitro in a laboratory model. The simulated activities of rising from a chair and climbing stairs produced high—pressure gradients and high angles of loading that could pump fluid through the apical hole to the retroacetabular bone. A noncongruent liner acted as a diaphragm pump, producing pressures 6 times higher than that seen with a congruent liner. Pistoning motion of the liner produced pressures 8 times higher than when no pistoning occurs. These pumping mechanisms could be mitigated by the use of acetabular components without holes.

Background: The suture configurations in arthroscopic rotator cuff repairs have been limited to simple and horizontal stitches. Recent objective evaluations have demonstrated high failure rates of arthroscopic repairs of rotator cuff tears. A novel stitch for arthroscopic repair of the rotator cuff, the massive cuff stitch, was developed to increase the strength of the suture-tendon interface. The goal of this study was to determine the biomechanical properties of the massive cuff stitch and to compare it with other stitches commonly used for rotator cuff repair. Methods: Eight pairs of sheep infraspinatus tendons were harvested and split in half to yield a set of four tendon specimens from each animal. Four stitch configurations (simple, horizontal, massive cuff, and modified Mason-Allen) were randomized and biomechanically tested in each set of tendon specimens. Each specimen was first cyclically loaded on an MTS uniaxial load frame under force control from 5 to 30 N at 0.25 Hz for twenty cycles. Each specimen was then loaded to failure under displacement control at a rate of 1 mm/sec. Cyclic elongation, peak-to-peak displacement, ultimate tensile load, and stiffness were measured with use of an optical motion analysis system and load-cell output. The type of failure (suture breakage or pull-out) was also recorded. A repeated-measures analysis of variance was performed on the results, with the alpha level of significance set at p < 0.05. Results: There was no difference in cyclic elongation or peak-to-peak displacement among the four stitches. Ultimate tensile load was significantly higher (p < 0.05) for the massive cuff stitch (233 ± 40 N) and the modified Mason-Allen stitch (246 ± 40 N) than it was for either the simple stitch (72 ± 18 N) or the horizontal stitch (77 ± 15 N). There was no significant difference in the ultimate load between the massive cuff and modified Mason-Allen stitches. There was also no difference in stiffness among the four stitches. The simple and horizontal stitches failed by tissue pull-out, whereas the massive cuff and Mason-Allen stitches failed by a mixture of suture breakage and pull-out. Conclusions: The massive cuff stitch provides strength comparable with that of the modified Mason-Allen stitch commonly used in open rotator cuff repair. The ultimate tensile load before failure of the massive cuff stitch was significantly higher (p < 0.05) than that of the simple and horizontal stitches. Clinical Relevance: The massive cuff stitch may be a promising alternative for arthroscopic repairs of rotator cuff tendons.