Biomechanical evaluation of impaction fractures of the femoral head.

OBJECTIVES: To measure the effect of an impaction fracture of the femoral head on load transmission in the hip joint. DESIGN: We measured the contact areas and pressure between the acetabulum and femoral head of cadaveric pelves in four different conditions: intact, with an operatively created one-square-centimeter defect in the superior femoral head, with a two-square-centimeter defect, and with a four-square-centimeter defect. All defects were uniformly three millimeters deep. SETTING: Hips were loaded in a simulated single-limb stance. Pressure and area measurements were made with Fuji pressure-sensitive film. SPECIMENS: Seven hip joints in seven whole pelves were tested. MAIN OUTCOME MEASUREMENTS: Contact area, load, and mean and maximum pressures were measured. RESULTS: Peripheral loading was seen in the intact acetabulum. This was not disrupted after impaction fractures of any size. A significant increase in mean maximum pressures in the superior acetabulum was seen with two-square-centimeter and four-square-centimeter defects. CONCLUSIONS: In contrast to prior biomechanical studies of acetabular fractures, our investigation revealed that disruption of the peripheral distribution of load does not occur with impaction fractures of the femoral head. Clinical series indicate that impaction injuries to the femoral head are associated with a poor prognosis. Previous biomechanical data on acetabular fracture patterns associated with a poor prognosis have shown increases in mean and peak pressures in the superior acetabulum. This was seen with two-square-centimeter and four-square-centimeter impaction injuries. Other factors, such as wear of the articular cartilage during joint motion or associated microscopic damage to the remainder of the joint surface at the time of injury, may also contribute to the rapid joint deterioration seen in these injuries. Further study is indicated.

Posterolateral approach for tibial pilon fractures: a report of two cases.

Open reduction and internal fixation (ORIF) of displaced tibial pilon fractures can lead to a high percentage of good and excellent functional results, but has also been associated with a meaningful incidence of wound breakdown and infection. The use of the posterolateral approach to the distal tibia for ORIF of tibial pilon fractures is presented. This may be used instead of the standard anteromedial incision in certain fracture configurations. The flexor hallucis longus muscle coverage overlying the plate fixation of the tibia and ability to fix both the tibia and fibula through the same incision may decrease the risk of deep infection and wound complications in these injuries frequently associated with marked soft tissue trauma.

Biomechanical consequences of anterior column fracture of the acetabulum.

OBJECTIVES: To measure biomechanical consequences of a high anterior column acetabular fracture. DESIGN: A benchtop biomechanical model using quasi-static loading of the hip joint in a simulated single-leg stance. Pressure-sensitive prescale (Fuji) film was used to determine hip joint loading parameters. PARTICIPANTS: Six cadaveric hemipelvi with one hip tested in each specimen. Three right and three left hips were tested. INTERVENTION: Creation of an anterior column fracture with anatomic reduction and fixation, followed by gap malreduction/fixation, and subsequently step malreduction/fixation. MAIN OUTCOME MEASUREMENTS: Contact pressure, contact area, and load distribution throughout the hip joint in each experimental condition. RESULTS: There were significant increases in load (p<0.01) and peak pressures (p<0.01) in the superior acetabular region after gap malreduction and in peak contact pressures after step malreduction (p<0.01) as compared with the intact acetabulum. Anatomic reduction was not associated with increased mean or peak contact pressures (in any region). CONCLUSIONS: Both step and gap malreductions of a high anterior column fracture resulted in significantly increased peak contact pressures in the superior acetabular region. These biomechanical data cannot be directly extrapolated to clinical applications, but these data suggest that anatomic reduction of anterior column fracture affords the best opportunity to restore contact pressures, contact area, and load distribution within the hip to levels similar to those seen in the intact acetabulum.

Outcomes following repair of quadriceps tendon ruptures.

OBJECTIVES: The purpose of this study was to examine critically the outcomes of patients sustaining a quadriceps tendon rupture and to compare outcomes in patients with bilateral simultaneous ruptures versus a unilateral rupture. DESIGN: Retrospective review. SETTING: Patients were treated at a Level I trauma center. PATIENTS/PARTICIPANTS: Fifty-one quadriceps tendon ruptures in thirty-nine patients were evaluated. A mean four-year follow-up (range 13 to 204 months) was available for forty-eight tendon ruptures. INTERVENTIONS: All patients except one were treated with operative repair of the quadriceps tendon rupture(s). MAIN OUTCOME MEASUREMENTS: Patients were assessed by physical examination, Lysholm and Tegner scores, a functional questionnaire, quadriceps isokinetic testing, and radiographs. RESULTS: A statistically greater number of patients in the bilateral simultaneous rupture group had a systemic illness associated with tendon rupture (p = 0.014). This result did not adversely affect outcome as compared with patients with unilateral ruptures. Mean range of motion was 123 degrees in injured knees. Eighty-four percent of working patients returned to their previous occupations. More than half the patients, however, in general the most active, could no longer participate in their preinjury recreational activities. Fifty-three percent of unilateral rupture patients had persistent quadriceps strength deficits (>20 percent) in the injured extremity. Both quadriceps and hamstring isokinetic testing correlated significantly with Lysholm and Tegner scores. CONCLUSIONS: Most patients with bilateral simultaneous and unilateral tendon repairs can expect a good range of motion and return to their previous occupation, but many have persistent weakness and difficulty returning to higher level sporting activities.

Biomechanical evaluation of a low anterior wall fracture: correlation with the CT subchondral arc.

OBJECTIVE: To measure the effect of a simulated low anterior wall fracture of the acetabulum on load transmission in the hip joint. DESIGN: We measured the contact areas and pressure between the acetabulum and the femoral head of cadaveric pelves in three different conditions: intact, with an operatively created fracture of the anterior wall, and after anatomic reduction and internal fixation of the fracture. SETTING: Hips were loaded in simulated single-limb stance. Pressure and area measurements were made with Fuji pressure-sensitive film. SPECIMENS: Seven hip joints in seven whole pelves were tested. INTERVENTION: Anterior wall fractures were anatomically reduced and fixed. MAIN OUTCOME MEASUREMENTS: Contact area, load, and mean and maximum pressures were measured. RESULTS: Anterior wall fractures in our specimens entered the hip joint an average of 9.7 millimeters from the vertex of the acetabulum, corresponding to a 45-degree roof arc measurement. Peripheral loading seen in the intact acetabulum was disrupted after fracture. The loading pattern was not restored to preinjury levels with anatomic reduction and fixation. There was no significant change in the contact area (p = 0.43), force (p = 0.06), or mean (p = 0.57) or maximum (p = 0.20) pressures in the superior aspect of the acetabulum after creation of the anterior wall fracture. CONCLUSIONS: These results differ from those of previous studies with posterior wall acetabulum fractures, where significant increases in force and mean and maximum pressures were noted in the superior acetabulum after fracture. The lack of significant increases in superior acetabular pressures is discussed in relation to the mean computed tomographic subchondral arc of approximately ten millimeters in our specimens.

The role of the acetabular labrum and the transverse acetabular ligament in load transmission in the hip.

We performed a biomechanical study of seventeen hip joints in the pelves of nine cadavera in order to assess the role that the acetabular labrum and the transverse acetabular ligament play in load transmission. The distribution of contact area and pressure between the acetabulum and the femoral head was measured with the hip in four different conditions: intact (seventeen hips), after removal of the transverse acetabular ligament (eight hips), after removal of the entire labrum (nine hips), and after removal of both the transverse acetabular ligament and the labrum (seventeen hips). The hip joint was loaded in simulated single-limb stance, and the measurements were made with use of pressure-sensitive film. A peripheral distribution of load was seen in the intact acetabula. This pattern was altered only minimally after removal of the transverse acetabular ligament or the labrum, or both. When both of these structures were removed, the only significant change was a decrease in the maximum pressure in the posterior aspect of the acetabulum (p = 0.02). No significant changes were detected with regard to the contact area, load, mean pressure, or maximum pressure in the anterior or superior aspect of the acetabulum under any testing condition.

The use of cold therapy after anterior cruciate ligament reconstruction. A prospective, randomized study and literature review.

We performed a randomized, prospective study to assess the effectiveness of postoperative cold therapy in patients who had anterior cruciate ligament reconstructions. Drain output, length of hospital stay, range of motion, and use of pain medication were all assessed. Patients were randomized into one of four groups after surgery. Group 1 patients had a cooling pad applied to the knee postoperatively and set at a temperature of 40 degrees to 50 degrees F, Group 2 had the cooling pad set at 70 degrees to 80 degrees F, Group 3 received ice packs, and Group 4 received no cold therapy of any kind. The skin temperatures in Groups 1 and 3 were significantly lower than the skin temperatures in Groups 2 and 4 (P < 0.001). The length of hospital stay, range of motion at discharge, use of oral and intramuscular pain medicine, and drain output were not significantly different between groups. No complications related to the type of cold therapy were seen in any group. Thus, both ice packs and cooling pads significantly decreased knee temperature, but we found no objective benefits in the early postoperative course due to this decrease in temperature.

Magnetic resonance imaging in the diagnosis of localized pigmented villonodular synovitis of the ankle: a case report.

The use of magnetic resonance imaging (MRI) in pigmented villonodular synovitis (PVS) has been well described in the literature. MRI has been used predominantly with diffuse PVS lesions. We recently had a patient with an unusual case of localized PVS of the ankle with bone and cartilage destruction. Preoperative MRI was useful in the diagnosis of localized PVS and in the planning for surgery. MRI in a patient with this lesion had not been documented previously, but should be considered whenever PVS, either diffuse or localized PVS, is suspected.