Wayne J. Daum

Heterotopic ossification and other perioperative complications of acetabular fractures.

Summary Thirty-eight operatively treated fractures of the acetabulum were evaluated retrospectively for perioperative complications. Functionally significant heterotopic ossification (Brooker class III or IV) developed in 23% of those patients who did not receive adequate prophylactic irradiation or indo-methacin. Irradiation and indomethacin were effective in the prevention of severe heterotopic ossification. The development of severe heterotopic ossification (class III or IV) was associated with increased time from injury to operation. We concluded that prophylaxis against heterotopic ossification is warranted to decrease the incidence of this potentially preventable complication in patients who incur significant time delays prior to surgery. Other significant complications included avascular necrosis (26%), infection (13%), and neural injury (16%). Avascular necrosis developed in one patient who did not have a documented dislocation.

Can simple radiographs be predictive of total hip dislocation

The usefulness of angles measured on standardized radiographs to determine acetabular position and predict dislocation after primary total hip arthroplasty (THA) was reviewed retrospectively. Seventy-four patients (97 primary THAs) were reviewed. All patients underwent a standardized protocol of postoperative radiographs which included an anteroposterior view of the pelvis and a cross-table lateral radiograph of the hip. Two angles were measured to define acetabular position: the abduction angle was measured on the anteroposterior radiograph and the version angle was measured on the cross-table lateral radiograph. The values for these angles were compared in a group of known dislocating THAs (7 hips) and a control group of stable THAs (90 hips). These radiographic measurements were also assessed for their reproducibility. The values for the abduction and version angles were not significantly different between the two groups. The values for abduction and version angles for a given hip, from one examination to another, were reproducible. Neither the abduction nor the version angle was a predictor of dislocation.

Pull-Out Strengths of Bone Screws at Various Sites About the Pelvis—A Preliminary Study

The pull-out strength of both cortical and cancellous screws from bone at various sites about cadaveric pelves was examined. No significant differences were seen between cortical or cancellous screws at similar sites with the possible exception of the sacroiliac joint. Pull-out strengths were best correlated to the depth of bone at a particular screw hole. For practical purposes, the strongest sites are in the thick buttress of bone along the iliopubic column.

Correlation of MRI images with histology in avascular necrosis in the hip. A preliminary study.

The role of MRI in identifying the tissue level changes in the femoral head was investigated in five patients diagnosed as having avascular necrosis by radiology, scintigraphy, and MRI (0.35 Telsa). Radiographic scoring by the Ficat and Arlet system showed one hip with stage I, one stage II, two stage III, and one stage IV changes. The histologic features of core biopsy specimens obtained during decompression of the femoral heads were compared to the preoperative T1 and mixed T1/T2-weighted MR images. The cores varied with respect to their distance from the subchondral bone (7-23 mm) and length (19-45 mm). At the subchondral end of the core tract, low T1-weighted images corresponded to marrow fibrosis (5 cases) and in three of five cases to increased trabecular bone volume (TBV = 44-50%). Subjacent areas of diffusely decreased MR signal corresponded to marrow fibrosis and necrosis, with a relatively normal TBV (17-28%). The distal ends of the core tracts showed normal fatty marrow and a normal MR signal. The observations affirm that the MR signal intensity is largely reduced as a function of marrow degeneration and loss of fat content, but the signal is not predictive of particular histotypic morphologic patterns.

Removal of the acetabular component minimizing destruction of the bone bed

Removal of a well-fixed acetabular component can be difficult and may produce destruction of the acetabular bone bed. The authors describe a technique for removal of such a component with minimal bone destruction that involves the use of an offset punch and breaking the fixation interface in tension. This technique obviates the need for prying at the interface and fracturing the bone bed.

Comparison of Cortical and Cancellous Screw Pull-out Strengths about the Posterior Column and Sacroiliac Joint

This study addresses the comparative pull-out strengths of cortical (4.5 mm) and fully threaded cancellous (6.5 mm) bone screws from sites about the pelvis commonly used in the fixation of posterior column acetabular fractures and sacroiliac (SI) disruptions. These sites include one from lateral to medial through the posterior column, two from posterolateral to anteromedial across the SI joint, one vertically through the sacral ala, and one vertically through the iliopubic column (see Fig. 1A and B). Statistical analysis showed no significant difference in the force required for pull-out failure of the cortical versus the cancellous screws at any of the sites tested.

Radiostrontium clearance and bone formation in response to simulated internal screw fixation

Changes in radiostrontium clearance (SrC) and bone formation (tetracycline labeling) were observed in the femurs of skeletally mature dogs following the various operative steps involved in bone screw fixation. Drilling, but not periosteal stripping, produced a small but statistically significant increase in SrC and endosteal bone formation in the distal third of the bone. Strontium clearance values equivalent to those produced by drilling alone were recorded after screw fixation at low or high torque (5 versus 20 inch pounds), as well as by the insertion of loosely fitting stainless steel implants. Bone formation (equals the percentage tetracycline-labeled trabec-ular bone surfaces) was increased by 30% when SrC values exceeded 3.5 ml/100 g bone/min, and the relationship was linear when SrC values ranged between 1.0 and 7.0 ml/100 g bone/min. The changes in SrC and bone formation one-week after bone screw application are primarily those associated with a response to local trauma caused by drilling.

Traumatic posterior acetabular defects reconstructed with iliac crest autograft : a report of two cases

In two cases of posterior wall acetabular fracture, the fracture fragment was too comminuted to be fixed per primam. A full-thickness iliac crest autograft was used as initial reconstruction in these two cases. Although the reconstruction was not anatomic, one of the two patients is functioning with only minimum symptoms at five years. Incorporation of the autograft has been documented in both cases. Although the procedure may not accurately reproduce the anatomy of the hip joint, it will appropriately supplement viable acetabular bone structure.

Subcapital fracture of the hip following an intertrochanteric fracture. A case report and literature review.

A 42-year-old alcoholic man who had a normal femoral head histologically incurred a subcapital fracture four months after surgical treatment of an intertrochanteric fracture of the same hip. Subcapital fracture of the hip following intertrochanteric fracture is an unusual occurrence, with possibly as few as 11 cases documented in the literature. Affected persons are usually elderly females with severe osteoporosis. Though unusual, the fracture is obvious and not difficult to treat.

Effect of fixation devices on radiostrontium clearance in the intact canine femur.

Femoral metaphyseal/diaphyseal blood flow was studied by 85Sr clearance in unfractured segments of dog femurs following compression plating and various control procedures (drilling with and without application of screws). The animals were tested as early as seven days and as late as two months after surgery. The only statistically significant change in strontium clearance (SrC) was an increase produced by the application of stainless-steel bone screws, with or without plates. The presence or absence of compression had no consistent effect on changes in the rate of SrC. During the period of study, no changes in bone mineralization, haversian porosity, or cortical bone thickness accompanied the SrC alterations.