The effect of intermittent pneumatic compression on fracture healing.

OBJECTIVES: Continuously increased venous pressure has been shown to enhance bone growth, stimulate fracture healing, and prevent bone loss, but also causes soft-tissue breakdown as a result of chronic edema. This study was designed to test the hypothesis that intermittently increased venous pressure improves fracture healing without injuring soft tissue. DESIGN: An ostectomy was created in the right radius of 30 skeletally mature male beagles. On postoperative day 7, a pneumatic cuff was placed around the forelimb of each dog. In experimental animals (n = 13), the cuff compressed for 5 minutes followed by no compression for 2.5 minutes. This cycle was repeated 100 times per day for 8 weeks. Control animals (n = 15) wore a nonfunctional cuff. Fracture healing was assessed with dual-energy x-ray absorptiometry, histologic analysis, and biomechanical testing. RESULTS: No soft-tissue complications were noted. Bone mineral content at the ostectomy increased significantly more in the experimental group than in the control group (P < 0.05). Histology revealed that the bone defects in the experimental group were significantly more healed than those in the control group (P < 0.005). No differences were noted between groups in the biomechanical properties of the healing bones. CONCLUSIONS: Intermittently increased venous pressure proximal to a bone defect seems to enhance the formation of new bone without soft-tissue complications. These findings can potentially be applied to the clinical treatment of "difficult to heal" fractures. Further work is necessary to determine the most effective ratio of the presence and absence of pneumatic compression.

The mechanical properties of the human hip capsule ligaments.

The human hip capsule is adapted to facilitate upright posture, joint stability, and ambulation, yet it routinely is excised in hip surgery without a full understanding of its mechanical contributions. The objective of this study was to provide information about the mechanical properties of the ligaments that form the hip capsule. Cadaver bone-ligament-bone specimens of the iliofemoral, ischiofemoral, and femoral arcuate ligaments were tested to failure in tension. The hip capsule was found to be an inhomogeneous structure and should be recognized as being composed of discrete constituent ligaments. The anterior ligaments, consisting of the 2 arms of the iliofemoral ligament, were much stronger than the posterior ischiofemoral ligament, withstanding greater force at failure and exhibiting greater stiffness. Knowledge of the anatomy and mechanical properties of the capsule may help the hip surgeon choose an appropriate surgical approach or repair strategy.