Faculty Bibliography

We report a case of chondromyxoid fibroma of the ala of the sacrum: its presentation, diagnosis, treatment, and resolution. Although this tumor is admittedly rare, our case demonstrates the need for careful evaluation of pack pain in an adolescent.

Seventeen patients who sustained severe trauma resulting in dislocation or fracture-dislocation of the elbow were treated using osseous suture anchors to repair the soft-tissue constraints of the elbow. In 15 of these patients, the medial collateral ligament and flexor-pronator origin were repaired. Ten patients underwent repair of the lateral collateral ligament using anchors. Five patients were also treated with a hinged external fixator. All of the elbows were rendered grossly unstable by the injury; all of the patients had stable elbows at follow-up. Elbow flexion averaged 127 degrees; an average 19 degrees extension loss was noted. The arc of forearm rotation averaged 156 degrees. The aggressive approach detailed in this report is applicable only to severe injuries to the elbow, not routine dislocations. These cases demonstrate the reliability of the osseous suture anchor in the operative treatment of massive trauma to the elbow.

A 74-year-old male involved in a pedestrian-automobile collision sustained a comminuted supracondylar-diaphyseal femur fracture. The fracture was stabilized by retrograde intramedullary fixation with a Synthes unreamed tibial nail. Knee motion reached 0 degree-120 degrees by the sixth postoperative day and the fracture healed within twelve weeks. Twelve months after his injury, his knee motion was symmetric to his uninjured side and he had resumed full preinjury activities, including martial arts training. Although antegrade intramedullary nailing remains the treatment of choice for fractures of the femur, this case highlights the usefulness of retrograde nailing and demonstrates the adjunctive application of an existing implant, the tibial nail, in certain special trauma situations.

The influences of heterogeneity, anisotropy and geometric irregularity on the unrestrained, linearly elastic torsional response of long bones are assessed. Longitudinal geometric variations contribute insignificantly to the torsional response for typical long bone geometries. Anisotropy, heterogeneity and transverse geometric irregularity significantly influence the torsional response. A procedure is discussed which uses an approximate means to characterize both heterogeneity and anisotropy in predicting the torsional response. The accuracy of circular and elliptical annulus models of the bone cross-sectional geometry are assessed by comparing the stress predictions of these simple models to those of finite element models of the bone geometry.

A technique is established which allows an effective torsional shear modulus to be determined for long bones, while remaining nondestructive to whole bone specimens. Strain gages are bonded to the diaphysis of the bone. Strains are then recorded under pure torsional loads. Theoretical stress predictions are combined with experimental strain recordings to arrive at a modulus value. Shear modulus calculations for four canine radii are reported using theoretical stress predictions from circular, elliptical and finite element models of the transverse bone geometry. The effective shear modulus, obtained from an average of the shear moduli determined at strain gage locations, serves to average the heterogeneous shear modulus distribution over the cross section. The shear modulus obtained is that associated with the "circumferential" direction in transverse planes.