The popliteofibular ligament. An anatomical study of the posterolateral corner of the knee.

We designed an experimental study to prove the existence of the popliteofibular ligament (PFL) and to define its role in providing static stability of the knee. We also examined the contribution of the lateral collateral ligament (LCL). We found this ligament to be present in all eight human cadaver knees examined. These specimens were mounted on a specially designed rig and subjected to posterior, varus and external rotational forces. We used the technique of selective sectioning of ligaments and measured the displacement with a constant force applied, before and after its division. We recorded the displacement in primary posterior translation, coupled external rotation, primary varus angulation and primary external rotation. Statistical analysis using the standard error of the mean by plotting 95% confidence intervals, was used to evaluate the results. The PFL had a significant role in preventing excessive posterior translation and varus angulation, and in restricting excessive primary and coupled external rotation. Isolated section of the belly of popliteus did not cause significant posterolateral instability of the knee. The LCL was also seen to act as a primary restraint against varus angulation and secondary restraint against external rotation and posterior displacement. Our findings showed that in knees with isolated disruption of the PFL stability was restored when it was reconstructed. However in knees in which the LCL was also disrupted, isolated reconstruction of the PFL did not restore stability.

Allograft bone transplantation: a Sheffield experience.

There has been an increase in demand for allograft bone in recent years. This type of bone provides an excellent material to fill in bony defects, but could be associated with an incidence of infection. Any newly established tissue bank has to meet the very stringent criteria to process and store bone and maintain a donor and recipient database to avoid transmission of infection. The Sheffield Tissue Bank has been functioning since 1989 and until 1993 has provided bone allografts to 220 patients; these have been used mainly to reconstruct defects at revision hip and knee arthroplasty and for scoliosis surgery. There have been no cases of disease transmission and the rate of infection has been reduced by strict screening protocols. This paper outlines our experience, problems and success with human bone banking.

A robot trace maker: modeling the fossil evidence of early invertebrate behavior.

The study of trace fossils, the fossilized remains of animal behavior, reveals interesting parallels with recent research in behavior-based robotics. This article reports robot simulations of the meandering foraging trails left by early invertebrates that demonstrate that such trails can be generated by mechanisms similar to those used for robot wall-following. We conclude with the suggestion that the capacity for intelligent behavior shown by many behavior-based robots is similar to that of animals of the late Precambrian and early Cambrian periods approximately 530 to 565 million years ago.

Biochemical properties of cortical allograft bone using a new method of bone strength measurement. A comparison of fresh, fresh-frozen and irradiated bone.

There have been conflicting reports on the effects of gamma irradiation on the material properties of cortical allograft bone. To investigate changes which result from the method of preparation, test samples must be produced with similar mechanical properties to minimise variations other than those resulting from treatment. We describe a new method for the comparative measurement of bone strength using standard bone samples. We used 233 samples from six cadavers to study the effects of irradiation at a standard dose (28 kGy) alone and combined with deep freezing. We also investigated the effects of varying the dose from 6.8 to 60 kGy (n = 132). None of the treatments had any effect on the elastic behaviour of the samples, but there was a reduction in strength to 64% of control values (p < 0.01) after irradiation with 28 kGy. There was also a dose-dependent reduction in strength and in the ability of the samples to absorb work before failure. We suggest that irradiation may cause an alteration in the bone matrix of allograft bone, but provided it is used in situations in which loading is within its elastic region, then failure should not occur.

A new method of comparative bone strength measurement.

Most investigations of the material properties of bone have been concerned with the measurement of absolute values for various mechanical parameters. It can be necessary, however, to produce test samples with similar mechanical properties in order to assess the effect on these properties of particular treatments. Absolute values for these properties may not be as important as any changes observed. We describe here a new method whereby many bone test samples with very similar mechanical properties can be produced. If the femoral shaft at the diaphysis is cut in transverse section, it is possible to produce many similar shaped rings of bone. We compared the material properties of 48 ring samples with 65 beam specimens. Both were tested in three-point bending. Global estimates of coefficient of variation (CV) for each parameter were used to assess similarity within each group. All the rings had very similar ash weights (1.98%), thicknesses (1.97%), and diameters (< 0.01%). Values of load/deflection of the rings were more similar than the values of Young's modulus (E) for the beams (7.06 versus 9.9%), and the maximum loads sustainable by the rings were more similar than the bending strengths of the beams (5.7 versus 13.6%). The energy absorbed by the ring samples were more consistent than the beams (14.31 versus 34.41%). We suggest that there is improved similarity in mechanical characteristics within groups of samples produced in this manner than with more conventional sample configurations.