Anatomy of the proximal tibiofibular joint and interosseous membrane, and their contributions to joint kinematics in below-knee amputations.

A result of below-knee amputations (BKAs) is abnormal motion that occurs about the proximal tibiofibular joint (PTFJ). While it is known that joint morphology may play a role in joint kinematics, this is not well understood with respect to the PTFJ. Therefore, the purposes of this study were: (i) to characterize the anatomy of the PTFJ and statistically analyze the relationships within the joint; and (ii) to determine the relationships between the PTFJ characteristics and the degree of movement of the fibula in BKAs. The PTFJ was characterized in 40 embalmed specimens disarticulated at the knee, and amputated through the mid-tibia and fibula. Four metrics were measured: inclination angle (angle at which the fibula articulates with the tibia); tibial and fibular articular surface areas; articular surface concavity and shape. The specimens were mechanically tested by applying a load through the biceps femoris tendon, and the degree of motion about the tibiofibular joint was measured. Regression analyses were performed to determine the relationships between the different PTFJ characteristics and the magnitude of fibular abduction. Finally, Pearson correlation analyses were performed on inclination angle and surface area vs. fibular kinematics. The inclination angle measured on the fibula was significantly greater than that measured on the tibia. This difference may be attributed to differences in concavity of the tibial and fibular surfaces. Surface area measured on the tibia and fibula was not statistically different. The inclination angle was not statistically correlated to surface area. However, when correlating fibular kinematics in BKAs, inclination angle was positively correlated to the degree of fibular abduction, whereas surface area was negatively correlated. The characteristics of the PTFJ dictate the amount of fibular movement, specifically, fibular abduction in BKAs. Predicting BKA complications based on PTFJ characteristics can lead to recommendations in treatment.

In vitro biomechanical evaluation of fibular movement in below knee amputations.

BACKGROUND: In below knee amputations, the remaining fibula may be subjected to abnormal forces resulting in problematic tibia-fibular movement. The purpose of the current work was to examine the effect of amputation length and interosseous membrane integrity on fibular movement when subjected to unopposed biceps femoris muscle tension. METHODS: Forty embalmed cadaveric specimens were subjected to a below knee amputation with fibular lengths of 5cm and 10cm. A subset of specimens (n=20) was further modified by sectioning the interosseous membrane. The tibias were mounted in a material testing machine and the biceps femoris was sutured to the actuator. Position-controlled tensile cyclic loading was applied (initial displacement of 4mm for 100 cycles at 0.5Hz with increments of 2mm up to 20mm) to the biceps femoris. The kinematics of the fibula with respect to the tibia was analyzed for three degrees of freedom: abduction, flexion and rotation. FINDINGS: There was no interaction between below knee amputation length and interosseous membrane integrity on the degree of abduction, flexion, and rotation. However, below knee amputations with a sectioned interosseous membrane are abducted to a significantly greater degree than intact interosseous membrane below knee amputations. Furthermore, although embalmed specimens were tested here, embalming was consistent across specimens and it is unlikely that this confounded the findings. INTERPRETATION: Understanding the cause of fibular abduction in below knee amputation will lead to recommendations for preventive surgical and rehabilitative measures.

Relative risk and odds ratio data are still portrayed with inappropriate scales in the medical literature.

OBJECTIVE: To determine the frequency of inappropriate use of arithmetic scales to present relative risk (RR) and odds ratio (OR) data in figures among a group of high-profile general medical journals. STUDY DESIGN AND SETTING: Articles presenting RR or OR data in figures and published in one of five journals during 2002-2003 and 2007-2008 were evaluated to determine the type of scale used with the figures. Logarithmic and reciprocal (inverse) scales were identified as appropriate, whereas arithmetic scales were deemed inappropriate. If an article included one or more inappropriate figures, it was counted once as an incorrect publication. RESULTS: Fifty-two percent (53 of 101) of the articles with a graphical presentation of RR or OR data had used an inappropriate scale in 2002-2003 and 25% (58 of 231) in the time period 2007-2008. Although all five journals showed some improvement over the 5-year interval, there continued to be a problem with inappropriate presentations occurring with one in four articles. CONCLUSION: Given the perpetuation of this problem, it may be time for the International Committee of Medical Journal Editors to address this issue by requiring that figures portraying ratio data use only logarithmic or reciprocal scales.