The influence of oral L-arginine on fracture healing: an animal study.

BACKGROUND: The known biological activities of nitric oxide suggest a role in bone healing. We hypothesized that L-arginine, a source of nitric oxide, expedites the healing process of stabilized diaphyseal defects. TYPE OF STUDY: Prospective blinded animal study. METHODS: Using a guinea-pig model, a 7 mm diaphyseal and periosteal defect was produced in the right femur and splinted intramedullary with a 1.4 mm K-wire. The guinea pigs (n = 44) were treated orally in three parallel groups: two treatment groups received high doses of L-arginine (one group for 2 weeks and the other for 4 weeks) and a control group received vehicle only. After four weeks, all animals were killed and both femora explanted. Radiological, histological, histomorphometric and mechanical evaluation was performed blinded. RESULTS: Radiographs showed significantly more healing in the treatment groups (2 weeks, 10/15; 4 weeks, 11/15) than in the control group (3/14). The mechanical energy necessary for femur failure was significantly higher in the 4-week treatment group than in the control group (P < 0.05). Histology and histomorphometry showed significantly increased coverage of nonvascularized bone fragments with newly formed bone in the treatment groups (P < or = 0.05). The contralateral uninjured femora did not show significant differences between groups. CONCLUSIONS: Oral L-arginine expedites healing in stabilized diaphyseal defects in guinea pigs without detrimentally affecting uninjured counterparts.

Measuring the pressure pattern of the joint surface in the uninjured knee.

PURPOSE: Testing an applicable intraoperative system for measuring surface pressure in knee joints, simulating as accurately as possible operating theatre conditions. TYPE OF STUDY: Cadaver study. METHODS: Pressure probes were introduced into the knee joints medially and laterally (K 6900 quad probes) in five cadavers, providing real-time data with computerized data recording (K-scan system, manuf. Tekscan Inc., South Boston, MA). The initial position of the knee was flexed and hanging, as in a leg holder. In simulation of usual operating theatre procedures, the knee was manually extended to 0 degrees and again brought to hanging position. The data are given as relative-pressure values and should serve as the basis for intraoperative use. During arthroscopy, absolute-pressure values would then be influenced by the pressure of the arthroscopy pump. RESULTS: In 90 degrees flexion the average pressure ratio between the medial and lateral joint compartments was initially 1:1.5. When the leg was brought to full extension the pressure in the medial compartment increased, giving a pressure ratio of 1:1 at about 15 degrees and 1.8:1 at full extension. When bringing the leg back again to 90 degrees a similar pressure ratio curve was recorded. CONCLUSIONS: The pressure relationship between the medial and lateral knee compartments could be recorded and was found reproducible in simulated operating-theatre conditions. The measurement of joint surface pressure during implantation of an anterior cruciate ligament graft could provide data for individual intraoperative quality control, thus improving surgical results.