Sagittal plane bending moments acting on the lower leg during  running.
Haris Phuah A, Schache AG, Crossley KM, Wrigley TV, Creaby MW.

Centre for Health, Exercise & Sports Medicine, University of  Melbourne, Victoria, Australia; School of Medicine, University of Melbourne,  Victoria, Australia.
Sagittal bending moments acting on the lower leg during running may play a  role in tibial stress fracture development. The purpose of this study was to  evaluate these moments at nine equidistant points along the length of the lower  leg (10% point-90% point) during running. Kinematic and ground reaction force  data were collected for 20 male runners, who each performed 10 running trials.  Inverse dynamics and musculoskeletal modelling techniques were used to estimate  sagittal bending moments due to reaction forces and muscle contraction. The  muscle moment was typically positive during stance, except at the most proximal  location (10% point) on the lower leg. The reaction moment was predominantly  negative throughout stance and greater in magnitude than the muscle moment.  Hence, the net sagittal bending moment acting on the lower leg was principally  negative (indicating tensile loads on the posterior tibia). Peak moments  typically occurred around mid-stance, and were greater in magnitude at the  distal, compared with proximal, lower leg. For example, the peak reaction moment  at the most distal point was -9.61+/-2.07%Bw.Ht., and -2.73+/-1.18%Bw.Ht. at the  most proximal point.
These data suggest that tensile loads on the posterior  tibia are likely to be higher toward the distal end of the bone. This finding  may explain the higher incidence of stress fracture in the distal aspect of the  tibia, observed by some authors. Stress fracture susceptibility will also be  influenced by bone strength and this should also be accounted for in future  studies.

Microdamage Repair and Remodeling Requires Mechanical  Loading.
Waldorff EI, Christenson KB, Cooney LA, Goldstein SA.

Abstract Bone remodeling is necessary in order to avoid microdamage  accumulation, which could lead to whole bone failure. Previous studies have  shown that this bone repair mechanism is triggered by osteocyte apoptosis.  Through the use of a rodent hindlimb suspension model and tibial 4-point bending  model the effects of disuse on microdamage remodeling was examined. At day 0,  male rats were assigned to one of three groups: Weight-bearing (WB), hindlimb  suspension (HS) or hindlimb suspension with daily intermittent weight bearing  following damage inducing loading (HW). Within each group, the rats were further  divided into subgroups, corresponding to three sacrifice time points (day 14 (WB  and HS only), 18 or 35). At day 14, animals were anesthetized and their left  tibia underwent cyclic 4-point bending in order to produce fatigue-induced  microdamage. At sacrifice tibiae were examined using 3D microCT, flow cytometry,  and histological and immunohistochemical stains. The results indicate that only  the WB and HW group had a significant increase in intra-cortical TRAP positive  resorption pits following damage induction, which was paralleled by a  significant decrease in microdamage over time in combination with a shift in the  osteoclast lineage due to a decrease in monocytes. These results demonstrate  that osteocyte apoptosis may be insufficient for repair of microdamage without  the stimulation provided through physiological loading. In addition this could  potentially have clinical implications for the current therapeutic paradigm for  treating stress fractures, where extended non-weight bearing is employed.

Effects of stride length and running mileage on a probabilistic  stress fracture model.
Edwards WB, Taylor D, Rudolphi TJ, Gillette JC, Derrick TR.
Department of Kinesiology, Iowa State University, Ames, IA  50011-1160, USA.

The fatigue life of bone is inversely related to strain magnitude. Decreasing  stride length is a potential mechanism of strain reduction during running. If  stride length is decreased, the number of loading cycles will increase for a  given mileage. It is unclear if increased loading cycles are detrimental to  skeletal health despite reductions in strain. PURPOSE: To determine the effects  of stride length and running mileage on the probability of tibial stress  fracture. METHODS: Ten male subjects ran overground at their preferred running  velocity during two conditions: preferred stride length and 10% reduction in  preferred stride length. Force platform and kinematic data were collected  concurrently. A combination of experimental and musculoskeletal modeling  techniques was used to determine joint contact forces acting on the distal  tibia. Peak instantaneous joint contact forces served as inputs to a finite  element model to estimate tibial strains during stance. Stress fracture  probability for stride length conditions and three running mileages (3, 5, and 7  miles x d(-1)) were determined using a probabilistic model of bone damage,  repair, and adaptation. Differences in stress fracture probability were compared  between conditions using a 2 x 3 repeated-measures ANOVA. RESULTS: The main  effects of stride length (P = 0.017) and running mileage (P = 0.001) were  significant. Reducing stride length decreased the probability of stress fracture  by 3% to 6%. Increasing running mileage increased the probability of stress  fracture by 4% to 10%. CONCLUSIONS: Results suggest that strain magnitude plays  a more important role in stress fracture development than the total number of  loading cycles. Runners wishing to decrease their probability for tibial stress  fracture may benefit from a 10% reduction in stride length.

Medial tibial stress syndrome: evidence-based prevention.
Craig DI.

Department of Physical Thereapy and Athletic Training, Northern Arizona University, Flagstaff, AZ 86011-5094, USA.

REFERENCE: Thacker SB, Gilchrist J, Stroup DF, Kimsey CD. The prevention of shin splints in sports: a systematic review of literature. Med Sci Sports Exerc. 2002;34(1):32-40. CLINICAL QUESTION: Among physically active individuals, which medial tibial stress syndrome (MTSS) prevention methods are most effective to decrease injury rates? DATA SOURCES: Studies were identified by searching MEDLINE (1966-2000), Current Contents (1996-2000), Biomedical Collection (1993-1999), and Dissertation Abstracts. Reference lists of identified studies were searched manually until no further studies were identified. Experts in the field were contacted, including first authors of randomized controlled trials addressing prevention of MTSS. The Cochrane Collaboration (early stage of Cochrane Database of Systematic Reviews) was contacted. STUDY SELECTION: Inclusion criteria included randomized controlled trials or clinical trials comparing different MTSS prevention methods with control groups. Excluded were studies that did not provide primary research data or that addressed treatment and rehabilitation rather than prevention of incident MTSS. DATA EXTRACTION: A total of 199 citations were identified. Of these, 4 studies compared prevention methods for MTSS. Three reviewers independently scored the 4 studies. Reviewers were blinded to the authors' names and affiliations but not the results. Each study was evaluated independently for methodologic quality using a 100-point checklist. Final scores were averages of the 3 reviewers' scores. MAIN RESULTS: Prevention methods studied were shock-absorbent insoles, foam heel pads, Achilles tendon stretching, footwear, and graduated running programs. No statistically significant results were noted for any of the prevention methods. Median quality scores ranged from 29 to 47, revealing flaws in design, control for bias, and statistical methods. CONCLUSIONS: No current evidence supports any single prevention method for MTSS. The most promising outcomes support the use of shock-absorbing insoles. Well-designed and controlled trials are critically needed to decrease the incidence of this common injury.

Medial tibial stress syndrome: a critical review.
Moen MH, Tol JL, Weir A, Steunebrink M, De Winter TC.

Department of Sports Medicine of the University Medical Centre Utrecht and Rijnland Hospital, Leiderdorp, the Netherlands.

Medial tibial stress syndrome (MTSS) is one of the most common leg injuries in athletes and soldiers. The incidence of MTSS is reported as being between 4% and 35% in military personnel and athletes. The name given to this condition refers to pain on the posteromedial tibial border during exercise, with pain on palpation of the tibia over a length of at least 5 cm. Histological studies fail to provide evidence that MTSS is caused by periostitis as a result of traction. It is caused by bony resorption that outpaces bone formation of the tibial cortex. Evidence for this overloaded adaptation of the cortex is found in several studies describing MTSS findings on bone scan, magnetic resonance imaging (MRI), high-resolution computed tomography (CT) scan and dual energy x-ray absorptiometry. The diagnosis is made based on physical examination, although only one study has been conducted on this subject. Additional imaging such as bone, CT and MRI scans has been well studied but is of limited value. The prevalence of abnormal findings in asymptomatic subjects means that results should be interpreted with caution. Excessive pronation of the foot while standing and female sex were found to be intrinsic risk factors in multiple prospective studies. Other intrinsic risk factors found in single prospective studies are higher body mass index, greater internal and external ranges of hip motion, and calf girth. Previous history of MTSS was shown to be an extrinsic risk factor. The treatment of MTSS has been examined in three randomized controlled studies. In these studies rest is equal to any intervention. The use of neoprene or semi-rigid orthotics may help prevent MTSS, as evidenced by two large prospective studies.


Athletes with exercise-related pain at the medial side of the lower leg
Hartgens F, Hoogeveen AR, Brink PR.

Maastricht Universitair Medisch Centrum, capaciteitsgroep Algemene Chirurgie, Polikliniek Sportgeneeskunde, Postbus 5800, 6202 AZ Maastricht.

Two patients were diagnosed with exercise-related pain at the medial side of the lower leg. The first patient, an 18-year-old woman who had expanded her athletic activities extensively, had developed pain at the inner side of the distal third portion of the left lower leg. She showed over-pronation of the ankle during running. A 3-phase bone scintigram revealed diffuse uptake of the tracer covering a large portion of the medial tibia margin. Based on this evidence, a diagnosis of periostalgia was made. She recovered after a period of relative calf massages and used insoles. The second patient was a 28-year-old male endurance runner who developed pain at the medial shin after intensifying his training regimen. The periods without pain during running became increasingly shorter, and the medial side of the lower leg became sore and tense. Intracompartmental pressure measurements indicated exercise-related posterior deep compartment syndrome of the calf. The patient recovered after fasciotomy. In athletes, exercise-related symptoms of the medial side of the lower leg can be usually attributed to the tibial periosteum or tendons of the deep calfmusculature, tibial stress reaction or fracture, or a compartment syndrome of the deep calf. Surgery is indicated for chronic compartment syndrome, but conservative therapy provides favourable outcomes in the other types of disorders. The optimal conservative therapeutic approach is unknown, but it is advisable to temporary reduce symptom-provoking athletic activity and modify any risk factors present. Ankle over-pronation during running is considered a very relevant intrinsic risk factor.

Current developments concerning medial tibial stress syndrome.
Craig DI.

Department of Physical Therapy and Athletic Training, Northern Arizona University, Flagstaff, AZ 86011-5094, USA.

Medial tibial stress syndrome (MTSS) is one of the most common lower leg injuries in athletes who run. Studies have reported MTSS to occur in 4% to 20% of this population. It can be defined as an overuse injury that creates pain over an area covering the distal to middle third of the posteriomedial tibial border, which occurs during exercise and creates cyclic loading. Differential diagnosis includes ischemic disorders and stress fractures. Although the pathology of this injury is understood, the etiology is less agreed upon. This makes it difficult for clinicians to diagnose and treat this common injury. The purpose of this article is to present health care practitioners with the most current information regarding MTSS so they can better diagnose and treat this common injury. To this end, a literature review was conducted, with the most current results presented. The areas of etiological theories, imaging techniques, and treatment options for MTSS were searched. Five of the most prevalent etiological theories are presented with supporting evidence. Of the imaging tools available to the clinician, magnetic resonance imaging (MRI) and bone scintigraphy have comparable specificity and sensitivity. Clinicians should first make the clinical diagnosis of MTSS, however, because of high percentages of positive MRI scans in asymptomatic patients. There have been few randomized controlled trials investigating treatment options for athletes with MTSS. Those that have been performed rendered no significant findings, leading researchers to conclude that rest is equal to or better than other treatment options. Given the evidence, treatment suggestions for practitioners caring for athletes with MTSS are provided