Staple leg profile influence on pullout strength: a biomechanical study.

Bone staples have widespread applicability in orthopaedic surgery. Their use, however, is limited by inconsistent quality of fixation. Prior studies have shown potential for improvement in the reliability of staple fixation through a change in the design of the staple legs. To identify a superior leg cross section profile, pullout strength of 5 different newly designed staple leg cross sections were evaluated in fresh frozen human cadaveric bones before and after toggle loading. The tests were repeated in a synthetic bone model with variable but consistent densities. The curvilinear square profile had the highest pullout strength in both the cadaveric and synthetic bone, followed in descending order by square, circular, and triangular profiles. Controlling for density, the pullout strength of the curvilinear square profile was 8% higher than the square profile and 34% higher than the circular profile. The triangular profiles had the least resistance to pullout force before and after cyclic loading. The curvilinear square may be the best profile for the cross section of the staple leg for maximum pullout strength and may expand the clinical use of staples in bone fixation.

Internal fixation of oblique metacarpal fractures. A biomechanical evaluation by impact loading.

Internal fixation of oblique metacarpal fractures was studied in a cadaver model by impact loading. One hundred twenty fresh-frozen human metacarpals underwent compressive and bending impacts after oblique osteotomy and internal fixation. Dorsal plating with lag screws, 2 dorsal lag screws (2-screws), crossed Kirschner wire tension band (crossed K-wire), 5 stacked intramedullary Kirschner wire (5-rod), and paired intramedullary Kirschner wire (2-rod) were used. The failure occurred within 6 msec in the compressive impact and was almost immediate in the bending impact. The dorsal plate and the intramedullary rod fixations were the strongest and were not significantly different from the intact specimens in compressive impact; they were, however, 19% weaker in bending impact. The 2-screws was the weakest fixation in this group. This fixation was 59% weaker in compressive impact and 47% weaker in bending impact compared with the dorsal plating.

Heterotopic ossification.

Heterotopic ossification is a well-recognized condition frequently encountered by the orthopedic surgeon. Although typically asymptomatic, heterotopic ossification can be a complication of extreme severity. This article is a review of literature and attempts to clarify the definition, and delineates the etiology, incidence, risk factors, and current modes of prophylaxis and treatment of various types of heterotopic ossification.

Mechanics of retrograde nail versus plate fixation for supracondylar femur fractures.

Two common types of internal fixations for the supracondylar femur fractures--the retrograde intramedullary nail and the 95 degrees sideplate and screw--were mechanically tested in synthetic composite femur bones to determine the quantitative differences in their inherent rigidity. The medial and lateral femoral condyles were separated by a sagittal osteotomy, and a standardized medial segmental shaft defect was created at the distal shaft. The osteotomized specimens were stabilized using one of the two implants and were tested in different modes of loading. The bending stiffness of both constructs were not significantly different in varus compression, medial bending (pure varus), and bending in flexion. The plate and screw implant was three times stiffer in lateral bending (pure valgus) and 1.2 times stiffer in valgus compression than the retrograde supracondylar nail (p < 0.01). The torsional stiffness of the plate and screw implant was significantly higher, 1.6 times that of the nail. Clinically, the most important and common cause of implant failure is varus loadings due to loss of medial cortical contact. Although the retrograde nail was less rigid in other physiologically less critical modes of loading, it had a rigidity comparable to that of the plate in varus loading. Therefore, a supracondylar nail may be considered a mechanically possible alternative to plate fixation.

Cystic degeneration and calcification of muscle: late sequelae of compartment syndrome.

Cystic degeneration and calcification of the leg are uncommon late sequelae of compartment syndrome. Previously reported cases have all involved the anterior compartment of the leg. We present a 68-year-old man with a mass in the superficial posterior compartment of the leg who presented 37 years after the initial trauma and ischemic myonecrosis. MRI was useful in establishing the diagnosis and early surgical intervention. The mass was excised and closed primarily over a drain. Patient was followed up for 29 months, and there were no secondary infections, chronic sinus formation, or recurrences. Based on our experience and the available literature review, we recommend considering either excision and primary closure, or repeated needle aspiration of the mass. Packing the wound and delayed closure may lead to secondary infection, chronic sinus formation, and lower limb amputation as potential complications.

The reduction clamp: a simple device for closed reduction during intramedullary nailing.

Reduction of femoral shaft fractures prior to passing the guide pin during intramedullary fixation may be a challenging problem, especially in delayed reductions or obese patients. We describe a simple and useful instrument for obtaining and maintaining reduction for closed intramedullary fixation. It provides a three-point fixation that may be locked into position to maintain the reduction. The surgeon is not required to hold the device in position while passing the guide pin, the reamer, or the nail. It frees the surgeon's hands, minimizes the need for an assistant, and reduces harmful x-ray exposure to the hands.