Kevin J. Pugh

Modified Tibial Nails for Treating Distal Tibia Fractures

Objective: To determine the biomechanical consequences of cutting one centimeter off the tip of a tibial nail when treating distal tibia fractures with intramedullary nails. Design: Randomized laboratory investigation using matched pairs of cadaveric tibias with osteotomies made to resemble distal tibia fractures extending to four and five centimeters from the tibiotalar joints. Intervention: The smaller (four‐centimeter) distal tibias were stabilized using ten‐millimeter diameter tibial nails that had been modified by removing the distal one centimeter of the nail. The five‐centimeter distal tibias were stabilized with standard ten‐millimeter diameter tibial nails. Each tibia was tested in elastic compression, rotation, and compression‐bending on a servohydraulic materials testing machine. Main Outcome Measurements: Stiffness was calculated for each type of loading to compare stability of the modified nail construct to that of the standard nail construct. Results: Four‐centimeter distal tibia fragments stabilized with modified nails have comparable stiffness in compression and in torsion to five‐centimeter distal tibia fragments stabilized with standard tibial nails. The stiffness in compression‐bending was surprisingly low in both groups and differed by only 3.7 percent. Conclusions: Removal of one centimeter from the tip of a tibial nail allows placement of two distal interlocking screws in tibial fractures located four centimeters from the tibiotalar joint. The fixation strength achieved is comparable to that of standard intramedullary nailing of tibial fractures located five centimeters from the tibiotalar joint using two distal interlocking screws. Fixation strength with these distal fractures, however, is not strong enough to resist moderate compression‐bending loads. Thus, patients with distal tibia fractures treated with intramedullary nailing must follow weight‐bearing restrictions until significant fracture healing occurs to prevent coronal plane malalignment of the fracture.

Effect of Acute Reamed Versus Unreamed Intramedullary Nailing on Compartment Pressure When Treating Closed Tibial Shaft Fractures : A Randomized Prospective Study

OBJECTIVE To compare anterior and deep posterior compartment pressures during reamed and unreamed intramedullary nailing of displaced, closed tibial shaft fractures. DESIGN Randomized prospective study. SETTING University Hospital/Level I trauma center. PATIENTS Forty-eight adults with forty-nine fractures treated with intramedullary nailing within three days of injury. INTERVENTION After intraoperative placement of compartment pressure monitors, the tibia fractures were treated by either unreamed intramedullary nailing or reamed intramedullary nailing. A fracture table and skeletal traction were not used in any of these procedures. MAIN OUTCOME MEASUREMENTS Compartment pressures and deltaP ([diastolic blood pressure] - [compartment pressure]) were measured immediately preoperatively, intraoperatively, and for twenty-four hours postoperatively. RESULTS Compartment syndrome did not occur in any patient. Peak average pressures were obtained during reaming in the reamed group (30.0 millimeters of mercury anterior compartment, 34.7 millimeters of mercury deep posterior compartment) and during nail insertion in the unreamed group (33.9 millimeters of mercury anterior compartment, 35.2 millimeters of mercury deep posterior compartment). The average pressures quickly returned to less than thirty millimeters of mercury and remained there for the duration of the study. The deep posterior compartment pressures were lower in the reamed group than in the unreamed group at ten, twelve, fourteen, sixteen, eighteen, twenty, twenty-two, and twenty-four hours postoperatively (p < 0.05 at each of these times. A statistically significant difference between anterior compartment pressures could not be shown with the numbers available. The deltaP values were greater than thirty millimeters of mercury at all times after nail insertion in both the reamed and unreamed groups. CONCLUSION These data support acute (within three days of injury) reamed intramedullary nailing of closed, displaced tibial shaft fractures without the use of a fracture table.

The biomechanics of hybrid external fixation

OBJECTIVE The objective of this study was to ascertain which factors determine the rigidity of a hybrid external fixation frame in a tibial periarticular fracture model. DESIGN Laboratory investigation using a polyvinylchloride pipe periarticular tibia fracture model. SETTING Simulated periarticular tibia fractures were created in a tibia model. Instrumented specimens were tested in a biomaterials testing system. INTERVENTION Groups of simulated periarticular tibia fractures were stabilized with one of nine different external fixation constructs with components from one manufacturer. MAIN OUTCOME MEASUREMENTS Elastic stiffness was measured for each specimen in compression, torsion, flexion bending, extension bending, and varus and valgus bending. RESULTS The four-ring Ilizarov fixator was the stiffest in all modes of testing. There was a trend toward increasing stiffness with an increasing number of rings. Fixators constructed with multiple levels of fixation in the periarticular fragment were stiffer in all modes of testing. The additional spacing between wires gained by the use of a single thick carbon ring or the use of a drop wire three centimeters from a single ring did not increase stiffness in this model. Frame modifications intended to augment the bar-to-ring connection did not increase stiffness. The use of rings mounted with half-pins instead of a unilateral bar mounted with half-pins for diaphyseal fixation increased the stiffness of the frame only in torsional testing. CONCLUSIONS Although the ideal stiffness of an external fixator is unknown, our results show that the addition of more than one level of fixation in the periarticular fragment increases the stiffness of hybrid external fixators in this periarticular tibia fracture model. Augmentation of the ring-to-bar connection did not significantly affect the stiffness of the frame.

A mechanical comparison of subtrochanteric femur fracture fixation.

OBJECTIVE To determine whether the mechanical properties of first-generation interlocking femoral nails are different from those of second-generation interlocking femoral nails in a subtrochanteric femur fracture model. DESIGN Randomized laboratory investigation using a synthetic subtrochanteric femur fracture model. SETTING Simulated stable and unstable fractures were created at three levels in the subtrochanteric region of synthetic femora. Instrumented specimens were tested elastically in a biomaterials testing system. INTERVENTION Synthetic femora were instrumented with either a statically locked first-generation femoral nail or a statically locked second-generation femoral nail. MAIN OUTCOME MEASUREMENTS Elastic stiffness for both the stable and unstable fracture groups was measured in both compression and torsion. Unstable fracture specimens were tested to failure in compression, and load to failure was measured. RESULTS Throughout the subtrochanteric region, second-generation femoral nail constructs were consistently stiffer in compression and torsion than were statically locked first-generation femoral nail constructs. In general, second-generation constructs also withstood larger loads to failure in the unstable fracture model. CONCLUSIONS Second-generation nails provided significantly enhanced mechanical stiffness compared with first-generation femoral nails when used to treat both stable and unstable subtrochanteric femur fractures. Although these results were obtained by using a well-controlled, mechanically consistent model, clinical validation of an increased incidence of fracture unions or of decreased time to union is required before we can recommend that second-generation nails be used routinely to treat subtrochantenic femur fractures.

Comparative biomechanics of hybrid external fixation

OBJECTIVE To compare the elastic stiffness, in several loading modes, of commercially available hybrid external fixation systems. DESIGN Laboratory investigation using a polyvinylchloride pipe periarticular tibia fracture model. SETTING Simulated periarticular fractures were created in an in vitro tibia fracture model. Instrumented specimens and intact controls were elastically tested in a biomaterials testing system. INTERVENTION Groups of simulated periarticular tibia fractures were stabilized with one of six different hybrid external fixator designs. MAIN OUTCOME MEASUREMENTS Elastic stiffness of each specimen was measured in compression, torsion, flexion bending, extension bending, and varus/valgus bending. RESULTS Fixators with multiple levels of fixation in the periarticular fragment, regardless of design, were stiffer than those with one level. Specifically, the EBI Ring Connector fixator was stiffer than all others in all modes of testing. The Ace, Synthes, Smith & Nephew Richards, and How medica fixators were mechanically similar. The Zimmer Torus fixator was the least stiff fixator tested. CONCLUSIONS Fixators with multiple levels of fixation in the periarticular fragment, regardless of design, were stiffer than those with one level. The choice of which hybrid external fixator to use should be made based not only on stiffness but also on ease of clinical application, patient comfort, customer support from the manufacturer, and cost. Clinical investigation of the efficacy of each of these devices is warranted.

Musculoskeletal Trauma in Tobacco Farming

The incidence of musculoskeletal injury sustained during tobacco farming has been poorly documented. Using the trauma registry for all farm-related injuries occurring during a 16-month period, hospital charts, radiographs, and clinic charts were reviewed to identify those patients sustaining tobacco farming-related injury. Twenty-three of 24 persons who sustained a farm-related injury during the study period were injured while farming tobacco. Seventeen (74%) were injured in falls from vented tobacco-drying barns, and 18 (75%) sustained skeletal injury. Extreme heat, humidity, and poor barn design and maintenance contribute to the incidence of falling. These injuries, largely underreported, may be substantially reduced by improvements in barn design and construction.

Case Report: Irreducible Fracture Dislocation of the Knee

A unique case of an irreducible fracture dislocation of the knee is reported. A review of the literature revealed no previously reported cases of fracture dislocation of the distal femur not amenable to closed reduction.