[Medial tibial pain in runners]

Local bone deformation at two predominant sites for stress fractures of the tibia: an in vivo study

Local bone deformation was registered at two predominant injury sites for tibial stress fractures in a healthy female volunteer. Two instrumented strain gauge staples were inserted under local anesthesia to the anterior middiaphysis (AM) and to the posteromedial part of the distal tibia (PD). Calibration and reliability of the instrumented staple system have previously been demonstrated in vitro. Concomitant ground reaction forces were registered with a Kistler force plate. Studying peak values, it was shown that during a voluntary 30-cm forward jump, PD deformation was greater during forefoot landing (2700-4200 microstrain) than during a heel strike landing (1200-1900 microstrain) and also compared with the concomitant AM deformation under both above testing conditions (1300-1900 microstrain). The stance phase during walking resulted in PD deformation of 950 microstrain, whereas the concomitant AM deformation was 334 microstrain. The greatest AM deformation (mean, 2128 microstrain) was registered during ground contact after a voluntary vertical drop from a height of 45 cm, concomitant with a PD deformation of 436 microstrain. These data are the first to show different local deformations at various sites of the tibia in vivo. The PD deformation was larger than previously noted from other parts of the tibia, whereas the middiaphysis data are consistent with other reports. The results may support the clinical assumption of different etiologies for stress fractures at these predominant sites.

The reliability and validity of an instrumented staple system for in vivo measurement of local bone deformation. An in vitro study

We recently presented a pilot study using an instrumented staple system for measuring in vivo local deformation on tibia. Methodological development has now proceeded in vitro. Consecutively, we performed 1. a sheep bone micrometer study, 2. a sheep bone four-point bending test and 3. a pig bone four-point and three-point bending test. This was done in order to secure a standardized application of the staple, to analyze the interaction of the bone and the staple and to secure calibration and the reliability of the system to be used in vivo. With reference to the above studies: 1. There was a linear relationship (r = 0.998) between the applied deformation of the bone and the measured deformation of the staple. ICC values ranged from 0.866 to 0.997. 2. An excellent intra-test reliability as well as linearity between staple measures and surface strain on the bone was observed (r = 0.998). 3. The slope of regression lines (k) was min 7.2 and max 9.4. The results from this test are used for calibration of the instrumented staple. Great variations were found between tension and compression measurements. However, within each test the SD was negligible. We suggest that the instrumented staple system may be calibrated in vitro and validly used for in vivo measurement of local bone deformation.

A study of intrinsic factors in patients with stress fractures of the tibia

We aimed to study intrinsic factors in 29 consecutive patients with well-documented unilateral stress fractures of the tibia. Anthropometry, range of motion, isokinetic plantar flexor muscle performance, and gait pattern were analyzed. The uninjured leg served as the control. A reference group of 30 uninjured subjects was compared regarding gait pattern. Anterior stress fractures of the tibia (N = 10) were localized in the push-off/ landing leg in 9/10 athletes, but were similarly distributed between legs in posteromedial injuries (N = 19). Ten (30%) of the stress fracture subjects had bilateral high foot arches, similar to those found in the reference group. There were no other systematic differences in anthropometry, range of motion, gait pattern, or isokinetic plantar flexor muscle peak torque and endurance between injured and uninjured legs. No other differences were found between anterior and posteromedial stress fractures. We conclude that anterior stress fractures of the tibia occur mainly in the push-off/landing leg in athletes. Within the limitations of our protocol, no registered intrinsic factor was found to be directly associated with the occurrence of a stress fracture of the tibia.

Overuse injuries of the lower extremity in runners

The purpose of this article is to review the literature on overuse injuries of the lower extremity in runners and to discuss briefly today's knowledge concerning etiology, diagnosis and treatment. Running is a natural entity in many sports and a majority of runners will sustain one or more overuse injuries throughout the career, in most cases affecting the lower extremity. A runner may be regarded as an athlete who regularly runs as the predominant physical activity. From that point, we should subdivide the definition "runner" considering the character of different sports or recreational activities performed. Overuse injuries are often described merely from symptoms, including several different etiological and pathoanatomic correlates covering a variety of ailments. The clinical approach should be focused on a thorough history and physical examination. Analysis of possible injury mechanisms, correction of associated extrinsic and intrinsic factors and advice on alternative training should be given. A knowledge of specific demands from the type of running performed is necessary to evaluate the symptoms presented. Overuse etiology has to be considered multifactorial with a yet unsolved exact pathophysiology needing further research. The definition of a "runner", of "running" and of "overuse injury" should be established and agreed upon. This review attempts to draw attention to the huge multidisciplinary work that has to be done to better understand the mechanisms causing an overuse injury in a runner and to define diagnoses on a scientific base, whether or not excentric or intrinsic factors predispose or trigger.

The plantar flexor muscle attachments on the tibia. A cadaver study

Thirty-six tibiae from 11 female and 7 male cadavers were dissected. Anatomical and histological examinations of the plantar flexor muscle origins at the posteromedial border of the tibia were performed. Many individual variations in the type and size of muscle origin were observed. Muscle fibers and/or connective tissue in different proportions attached the muscle to the periosteum or directly to the cortical bone. The length of the attachments varied greatly and there was a considerable overlap of the muscles in some individuals. The attachments of the flexor digitorum longus overlapped the tibialis posterior and the flexor digitorum longus muscle was overlapped by the soleus muscle. In two cases the soleus muscle did not attach to the tibia at all. Our findings may shed some light on the question as to why some athletes sustain posteromedial tibial stress fractures and others develop shin splits or other posteromedial injuries from similar precipitating activity.