Faculty Bibliography

BACKGROUND: A comminuted, intra-articular distal femur fracture was surgically treated by the authors with a locked, double-plating technique because fixation stability could not be initially achieved by using a standard double-plating technique. The purpose of this study was to determine biomechanically whether a locked double-plate construct would enhance fixation stability compared with a nonlocked double-plate construct. METHODS: Six matched pairs of mildly osteopenic femurs were selected and all had a reproducible intra-articular fracture pattern created. Each pair underwent fixation with either a double-plating construct or a locked, double-plating construct that was randomly assigned. The instrumented femurs were then mechanically tested in several loading modes to determine fixation stability. After initial testing, specimens were cyclically loaded and retested for stability. RESULTS: The locked, double-plating construct provided significantly greater fixation stability than the standard double-plating construct in precycling and postcycling biomechanical testing. CONCLUSION: The technique described is particularly applicable for severely comminuted fractures of the distal femur and fractures in osteopenic bone with poor screw purchase. It offers a simple alternative for enhancing fixation stability, which avoids the potential complications of methylmethacrylate-enhanced screw fixation

The one-bone forearm procedure can be a successful salvage option for forearm stability in selected patients and is indicated if instability and bone loss are irreparable by other means. We report a case of a dysfunctional arm secondary to radical debridement of the ulna after osteomyelitis treated successfully with a one-bone forearm procedure and followed up for 8 years

No studies have demonstrated a direct relationship between pregnancy and rib fracture. A case of spontaneous rib fracture in the third trimester presents the opportunity to examine factors unique to pregnancy that may predispose the patient to stress fractures of the lower ribs. A 28-year old woman in week 31 of her pregnancy presented with the chief complaint of acute onset of right upper quadrant pain. A chest radiograph demonstrated a minimally displaced fracture of the right 10th rib. During pregnancy, the enlarging uterus causes certain opposing muscular forces to act on the ribs, making them more susceptible to fracture after minimal trauma or after repeated stresses such as a chronic cough

High rates of aseptic loosening have been reported for microstructured hydroxyapatite-coated acetabular components. A macrostructured component surface (arc-deposition) not only improves resistance to shear forces experienced by the acetabular component and increases initial stability, but also provides channels for bone ingrowth. The purpose of this investigation was to radiographically compare a series of grit-blasted (microstructured) and arc-deposited (macrostructured) hydroxyapatite-coated acetabular components. A minimum 4-year retrospective radiographic analysis of acetabular components was performed on a total of 50 total hip arthroplasties. At 4 years, arc-deposited components were associated with fewer radiolucent lines in all Charnley zones, particularly Charnley zone III. While the 4-year results for arc-deposited hydroxyapatite acetabular components are superior to their microstructured predecessors, long-term results are still unknown

Patellofemoral complications, instability, and tibial polyethylene wear after total knee arthroplasty (TKA) resulting from malrotation of the tibial or femoral components (or both) may be difficult to diagnose based on physical examination and standard knee radiographs. The preoperative assessment of implant rotational alignment is critical in planning treatment because the femoral or tibial component (or both) may need to be revised if malpositioned. The purpose of this study was to ascertain the accuracy of computed tomography (CT) scan for determining rotational alignment of femoral and tibial components in TKA. TKA components were inserted in human cadaver specimens at neutral and 5 degrees of external or internal rotation. For each position, the amount of rotation, determined from digital photographs, was compared with CT scan. The correlation coefficient between these two values averaged 0.87, which was significant at P < .05. The CT scan protocol described in this study can be applied clinically to patients with patellofemoral complaints to confirm or rule out the presence of component malrotation

BACKGROUND: Treatment of thromboembolism with intravenous heparin therapy in the early postoperative period after total joint arthroplasty has been associated with a high rate of complications. The purpose of the present study was to compare the rate of bleeding complications in a group of patients who required intravenous heparin therapy for the treatment of thromboembolism after total hip or knee arthroplasty with the rate in a control group of patients who received only prophylactic anticoagulation. METHODS: The postoperative courses of forty-four consecutive patients who were managed with intravenous administration of heparin and oral administration of warfarin for the treatment of a thromboembolic event following unilateral total hip or knee arthroplasty were compared with those of a control group of 376 consecutive patients who had these same procedures but did not have a thromboembolic complication. The patients in the control group were managed with prophylactic anticoagulation with use of enoxaparin. Sixty-eight percent (thirty) of the forty-four patients in the heparin group received the initial dose of heparin on or before the fourth postoperative day, and 82 percent (thirty-six) received an initial bolus of 5000 units of heparin at the initiation of therapy. RESULTS: The rate of bleeding complications was 9 percent (four of forty-four) in the heparin group, compared with 6 percent (twenty-three of 376) in the control group (p = 0.44). The mean transfusion requirement in the heparin group (1.8 units of packed red blood cells) was significantly greater than that in the control group (0.8 unit) (p < 0.0001). Three of the four patients who had a bleeding complication while receiving heparin and warfarin had coagulation parameters that were substantially higher than recommended levels. The mean duration of hospitalization in the heparin group (fifteen days) was significantly longer than that in the control group (seven days) (p < 0.0001). CONCLUSIONS: The results of the present study suggest that the use of intravenous heparin therapy for the treatment of thromboembolism in the early postoperative period after total joint arthroplasty is associated with a rate of bleeding complications that is similar to that associated with the use of prophylactic anticoagulation with use of enoxaparin alone. One should expect an increased transfusion requirement and a longer duration of hospitalization for patients who require intravenous heparin therapy for the treatment of a thromboembolic event

A biomechanical cadaver study was performed to compare the strength and stability of three cannulated cancellous lag screws with a sliding hip screw for fixation of a vertically oriented fracture of the femoral neck (Pauwels Type III). Using eight matched pairs of human cadaveric femurs, vertically oriented femoral neck osteotomies were created, reduced, and randomized to one of the two fixation methods. The constructs were tested with incremental axial loading from 100 N to 1200 N and cyclical loading at 1000 N for 10,000 cycles; fracture displacements and ultimate load to failure were determined. The specimens stabilized using a sliding hip screw showed less inferior femoral head displacement, less shearing displacement at the osteotomy site, and a much greater load to failure than did those stabilized with multiple cancellous lag screws. These results support the use of a sliding hip screw for treatment of vertically oriented fractures of the femoral neck.

STUDY DESIGN: A biomechanical study comparing two materials for augmentation of osteoporotic vertebral bodies and vertebral bodies after compression fracture. OBJECTIVES: To compare an injected, biodegradable calcium phosphate bone substitute with injected polymethylmethacrylate bone cement for strengthening osteoporotic vertebral bodies and improving the integrity of vertebral compression fractures. SUMMARY OF BACKGROUND DATA: Injection of polymethylmethacrylate bone cement into fractured vertebral bodies has been used clinically. However, there is concern about thermal damage to the neural elements during polymerization of the polymethylmethacrylate bone cement as well as its negative effects on bone remodeling. Biodegradable calcium phosphate bone substitutes have been studied for enhancement of fixation in fractured vertebrae. METHODS: Forty fresh osteoporotic thoracolumbar vertebrae were used for two separate parts of this study: 1) injection into osteoporotic vertebrae: intact control (n = 8), calcium phosphate (n = 8), and polymethylmethacrylate bone cement (n = 8) groups. Each specimen then was loaded in anterior compression until failure; 2) injection into postfractured vertebrae: calcium phosphate (n = 8) and polymethylmethacrylate bone cement (n = 8) groups. Before and after injection, the specimens were radiographed in the lateral projection to determine changes in vertebral body height and then loaded to failure in anterior bending. RESULTS: For intact osteoporotic vertebrae, the average fracture strength was 527 +/- 43 N (stiffness, 84 +/- 11 N/mm), 1063 +/- 127 N (stiffness, 157 +/- 21 N/mm) for the group injected with calcium phosphate, and 1036 +/- 100 N (stiffness, 156 +/- 8 N/mm) for the group injected with polymethylmethacrylate bone cement. The fracture strength and stiffness in the calcium phosphate bone substitute group and those in the polymethylmethacrylate bone cement group were similar and significantly stronger than those in intact control group (P < 0.05). For the compression fracture study, anterior vertebral height was increased 58.5 +/- 4.6% in the group injected with calcium phosphate and 58.0 +/- 6.5% in the group injected with polymethylmethacrylate bone cement as compared with preinjection fracture heights. No significant difference between the two groups was found in anterior vertebral height, fracture strength, or stiffness. CONCLUSION: This study demonstrated that the injection of a biodegradable calcium phosphate bone substitute to strengthen osteoporotic vertebral bodies or improve vertebral compression fractures might provide an alternative to the use of polymethylmethacrylate bone cement