James R. Urbaniak

Effect of increased compartment pressure on the microcirculation of skeletal muscle.

To determine the changes in capillary perfusion, which occur with elevated tissue pressure, and to highlight the relationship between systemic blood pressure and compartment pressure, we designed an experiment that allowed direct observation of the microcirculation of skeletal muscle under normal and increased compartment pressures. In each of 10 anesthetized rats, the cremaster muscle was exposed and suspended in a transparent pressure chamber. In vivo videomicroscopy was then performed and blood pressure was monitored via left carotid artery cannulation. Two sets of data for each animal were obtained: ΔP (mean arterial pressure − compartment pressure) at which the muscle capillary blood flow was completely arrested, and the number of capillaries per 10,000 square micrometers of skeletal muscle with blood flowing at compartment pressures of 0, 15, 30, 45, and 60 mm Hg. Capillary blood flow stopped at a ΔP of 25.5 mm Hg ± 14.3 SD. We found that capillary blood flow, as measured by the number of capillaries with blood flow per 10,000 square micrometers, decreased significantly (P< 0.05) as compartment pressure reached 15, 30, 45, and 60 mm Hg, when compared to 0 mm Hg; there was no vessel collapse at these pressures. These data show that increasing compartment pressure reduces the number of perfused capillaries per unit area, and that there is complete cessation of muscle capillary blood flow when the compartment pressure is within about 25 mm Hg of the mean arterial pressure.

Functional effects of lymphotoxin on crushed peripheral nerve

The effect of lymphotoxin (LT) on the functional recovery of crushed peripheral nerves was studied. Using a specially designed compression device, a 5 mm segment of the right sciatic nerve of rats was subjected to a 100 g crush load with a 2 hr duration. The rats in the experimental and control groups received two doses of LT (20 μg/kg each) or the same volume of saline, respectively, administered intraperitoneously 24 hr and 1 hr before the procedure. Walking track tests and histologic examinations were performed at intervals up to 56 days after the crush. Motor functional recovery in the LT pretreated group started at day 7 while the crushed limb in the control group remained totally dysfunctional. The sciatic functional index improved faster in the LT group than in the control group during the second week after the crush and reached a significant difference (P < 0.05) at day 18. Subsequently, both groups had a similar evolution. Histologic results paralleled the functional findings. In conclusion, LT can promote motor functional recovery of crushed rat peripheral nerve in the early stage of regeneration.

Free Vascularized Fibular Grafting for treatment of osteonecrosis of the femoral head secondary to hip dislocation.

Traumatic dislocation of the hip results in osteonecrosis of the femoral head (ONFH) or avascular necrosis (AVN) in ∼40% of patients. This high‐energy event causes an ischemic insult to the femoral head that may lead to ONFH. Here, we investigate use of Free‐Vascularized Fibular Grafting (FVFG) in patients with ONFH after traumatic hip dislocation. Thirty‐five patients with FVFG for this indication were reviewed (average follow‐up 3.3 years, range 1–21). We reviewed patient injury statistics, demographics, preoperative radiographs, pre‐ and postoperative Harris Hip scores, complications, and rate of conversion to total hip arthroplasty (THA). The majority (81%) of our patients were young males (22 years) with ONFH diagnosed an average of 2 years after injury. The average preoperative Harris Hip score was 64.9 which improved by over 10 points to 76.1 at 1‐year follow‐up. Seven of 35 patients required conversion to THA at an average of 45 (13–86) months postoperation. After a maximum follow up of 21 years, the remainder of the patients retained their native hips and Harris Hip scores tended to show improved hip function.

Donor sites for pedicled skeletal grafts of the hand, wrist, and forearm.

Pedicled bone and periosteal grafts provide successful reconstruction of skeletal problems of the distal radius, wrist, and hand. The purpose of this study was to evaluate the available alternatives and to propose the most suitable skeletal grafts for the reconstruction of the distal radius, and the carpal and hand bones. The alternative donor sites (dorsal and palmar distal radius, and metacarpals), their pedicles, and the potential coverage area in relation to specific wrist and hand pathology were determined in the cadaveric dissections. In the clinical setting, 75 pedicled grafts were used for the treatment of scaphoid nonunions (62 cases), lunate necrosis (8 cases), reconstruction of the metacarpal defects (2 cases), and wrist fusions (3 cases). All alternatives have the advantage of a single approach that may be performed under tourniquet control, from the same team. Among the available alternatives, surgeons familiarity plays the most important role for the final selection of the graft.