Lumbar spinal fusion using recombinant human bone morphogenetic protein in the canine. A comparison of three dosages and two carriers.

STUDY DESIGN: A randomized, prospective and controlled animal study. OBJECTIVE: To evaluate lumbar spinal fusion using recombinant human bone morphogenetic protein 2 in a canine model. SUMMARY OF BACKGROUND DATA: Spinal fusion using autogenous bone grafting is associated with donor site morbidity and a nonunion rate of 5% to 35%. The use of recombinant human bone morphogenetic protein 2 as a bone graft substitute would eliminate donor site morbidity and perhaps augment the rate of successful fusion. METHODS: Mature beagles underwent bilateral paraspinal exposure at L4-L5, followed by transverse process decortication and randomization into one of six groups using differing doses of recombinant human bone morphogenetic protein 2 implanted using either a Type I collagen carrier or a polylactic acid carrier. Two control groups were used: one group without recombinant human bone morphogenetic protein 2 and another group using autogenous rib graft alone. RESULTS: Groups treated with recombinant human bone morphogenetic protein 2 demonstrated complete fusion in all animals. Animals treated with collagen carrier alone (no recombinant human bone morphogenetic protein 2) demonstrated complete absence of fusion. Successful fusion occurred in one of three canines in the autogenous bone graft group. Fusion masses in the recombinant human bone morphogenetic protein 2 treatment groups were significantly larger in size at 3 months than in the autogenous bone graft group. The collagen carrier was more biocompatible and biodegradable because residual polylactic acid carrier was seen with adjacent multinucleated giant cells. There was no evidence of spinal canal or nerve root encroachment in the recombinant human bone morphogenetic protein 2 treatment groups. CONCLUSIONS: The use of recombinant human bone morphogenetic protein 2 implanted using a Type I collagen carrier resulted in 100% fusion without adverse effects.

Safety of recombinant human bone morphogenetic protein-2 after spinal laminectomy in the dog.

STUDY DESIGN: This was a randomized, blinded trial of the safety of the application of recombinant human bone morphogenetic protein (rhBMP)-2 or autologous bone graft onto a laminectomy defect of the dog in the presence or absence of a dural membrane puncture. OBJECTIVE: To test the safety of rhBMP-2 in an application in which direct contact of the material with neural tissue occurs. SUMMARY OF BACKGROUND DATA: Application of rhBMP-2 in laboratory animals stimulates local bone formation to effect spinal fusion and healing of segmental bone defects. The use of rhBMP-2 as a bone graft substitute in spinal fusion would eliminate donor site morbidity and may augment the rate of successful fusion. Because rhBMP-2 may unintentionally come in contact with neural tissue, the consequences of such a safety issue must be addressed in an animal model before human trials. METHODS: Twenty skeletally mature beagles underwent spinal exposure followed by bilateral laminectomy at L5. In half of the dogs, a puncture wound was made to the dura with the expression of cerebrospinal fluid at the site of the puncture. In randomly selected animals, the exposed dural elements received either autologous bone graft with the bone removed from the laminectomy site or an implant of the rhBMP-2 device. The animals was observed for 12 weeks with periodic clinical examinations and monthly computed tomographic scans. RESULTS: There was no clinical, radiographic, or histologic evidence of neurologic abnormalities in these animals. The rhBMP-2 stimulated bone growth in the laminectomy defect and came into direct contact with the dural membrane. There was no evidence of abnormal mineralization within the thecal sac or in the spinal cord itself. CONCLUSIONS: The rhBMP-2 implant stimulated bone formation in the laminectomy site. Neither autologous bone, rhBMP-2, nor the dural puncture had deleterious consequences for the animals.

Unicompartmental arthroplasty: a long-term follow-up study.

Seventy-three consecutive unicompartmental knee arthroplasties (UKAs) using a Marmor-style non-metal-backed cemented tibial component were performed from 1975 to 1990. Sixty-seven knees (58 patients) were evaluated with minimum 5-year follow-up (mean, 9.7 years; range, 5-20 years). Knee rating and patient function were assessed using the updated Knee Society scoring system. Survivorship was 91% at 5 years, 84% at 10 years, and 79% at 15 years. The mean knee rating for surviving implants was 91 (range, 48-100), and mean functional score was 77 (range, 5-100). Survivorship and functional outcome were not affected by body habitus, age, gender, or tibial component thickness. UKA offers long-term relief of symptoms and excellent knee function in a high percentage of carefully selected patients with single compartment gonarthrosis.

Does bacteremia occur during high pressure lavage of contaminated wounds?

The risk of bacteremia secondary to high pressure lavage of contaminated wounds was assessed. Twenty canines were divided randomly into four treatment groups. A 10-cm incision was made over the left shoulder of each dog. The deltoideus muscle was disrupted and traumatized. Groups A and B (n = 8) had wound contamination with 1.4 x 10(9) Staphylococcus aureus followed 75 minutes later by high pressure lavage or bulb syringe irrigation, respectively. Groups C and D (n = 2) had no contamination, followed by the same treatment. Bacterial counts were obtained before and after wound irrigation. Blood cultures were obtained before, during, and 15 minutes after irrigation. Positive control cultures were obtained during injection of bacteria into the antecubital vein. A detectable bacteremia did not occur during or after high pressure lavage or bulb syringe irrigation of acute contaminated wounds but did occur in 18 of 20 positive controls. Bacterial levels were reduced by an average of 70% +/- 10% by high pressure lavage and 44% +/- 50% by bulb irrigation. Reduction of wound bacteria was achieved more consistently with high pressure lavage than with bulb syringe irrigation.

Effects of surgical approaches for acetabular fractures with associated gluteal vascular injury.

OBJECTIVES: To examine the viability of the abductor muscles following extensile exposures to the acetabulum in the presence of superior gluteal artery (SGA) or vein (SGV) injury. DESIGN: In vivo animal study. INTERVENTION: Twenty-two dogs underwent either an extensile or combined two-incision acetabular approach; either the SGA, the SGV, or no vessel was ligated. MAIN OUTCOME MEASUREMENTS: Blood flow to the affected gluteal region was evaluated by angiography, laser Doppler flowmetry, and fluorescent microspheres, and histologic and wet weight analyses were performed on the abductor muscles. RESULTS: Complete ischemic necrosis of the abductor muscles did not occur in any specimen; however, there were statistically significant reductions in immediate postoperative gluteal muscle perfusion (-47 percent, p < 0.01), loss of abductor muscle mass (-41 percent, p < 0.001), and histologic evidence of moderate to severe necrosis in five of seven specimens with extensile exposures and SGA ligation (p = 0.01). Extensile exposure and SGV ligation also caused a significant loss of muscle mass (-25 percent, p < 0.02), with moderate to severe necrosis occurring in four of seven specimens (p < 0.04). Dogs with SGA ligation undergoing the two-incision approach had no significant changes in muscle mass (-3 percent) or perfusion. Moderate to severe necrosis occurred in only one of four specimens. CONCLUSIONS: This study fails to support the hypothesis that extensile approaches to complex acetabular fractures eliminate abductor collateral circulation when performed in the presence of SGA injury.

Iatrogenic posterior interosseous nerve injury: is transosseous static locked nailing of the radius feasible?

To assess the risk of injury to the posterior interosseous nerve (PIN) in transosseous locked nailing of the radius, the relationship of the PIN to the surgical zone was studied in five pairs of fresh frozen adult cadaver arms. A static locked intramedullary nail was inserted in each radius using the recommended surgical technique. A formal dissection of the radial nerve and its branches was then performed to document the relationship of the PIN to the radial head in neutral, pronation, and supination also was measured. In no specimens was the PIN injured by the screw insertion. However, in two specimens (right and left arm of the same donor) the PIN was 1 mm and 2 mm, respectively, from the screw insertion site. The average shortest distance from the PIN to the screw was 11.3 mm. As measured along the mid-shaft of the radius, the average distance from the radial head to the PIN was 36.2 mm in 90 degrees supination, 46.7 mm in neutral, and 56.9 mm in 90 degrees pronation. Transosseous static locked nailing of the radius is feasible, but the surgeon and patient must be aware of the risk of possible injury to the PIN. To minimize this risk, we suggest that the proximal locking screw should be inserted from a direct lateral entry at < 30 mm from the radial head with the forearm in neutral rotation.

Treatment of single compartment osteoarthritis of the knee using modular arthroplasty: a review of the literature and presentation of 29 cases.

Twenty-nine knees with degenerative arthritis, generally confined to a single weightbearing compartment, were treated by modular arthroplasty. A mean followup of 20 months at formal evaluation and 30 months at time of reporting revealed satisfactory results in 89%. Anticipated complications of loosening, deterioration of the opposite compartment or patella, progressive lucent lines by x-ray, particle arthritis, or instability have been rare. Loss of knee stability or infection, requiring bracing or arthrodesis, has not occurred. One case of thrombophlebitis occurred and responded to anticoagulant treatment. We have revised two knees, both successfully. Technical problems of high tibial osteotomy are reviewed and compared to reported results with uni-arthroplasty in an effort to balance the generally negative attitude held by many surgeons concerning modular replacement of a single compartment of the knee.