Methodologic issues in clinical trials for prevention or risk reduction in osteoarthritis.

The design and execution of prevention trials for OA have methodological issues that are distinct from trials designed to impact prevalent disease. Disease definitions and their precise and sensitive measurement, identification of high-risk populations, the nature of the intervention (pharmaceutical, nutraceutical, behavioral) and its potential pleiotropic impacts on other organ systems are critical to consider. Because prevention trials may be prolonged, close attention to concomitant life changes and co-morbidities, adherence and participant retention in the trial is of primary importance, as is recognition of the potential for "preventive misconception" and "behavioral disinhibition" to affect the ability of the trial to show an effect of the intervention under study. None of these potential pitfalls precludes a successful and scientifically rigorous process and outcome. As technology improves the means to measure and predict the OA process and its clinical consequences, it will be increasingly possible to screen individuals for high-risk phenotypes, combining clinical factors with information from imaging, genetic, metabolic and other biomarkers and to impact this high-risk condition to avoid or delay OA both structurally and symptomatically.

A biomechanical model of the foot: the role of muscles, tendons, and ligaments.

A biomechanical model of the foot is developed and analyzed to determine the distribution of support under the metatarsal heads, the tension in the plantar aponeurosis, and the bending moment at each of the joints of the foot. This model is an extension of our earlier work to include the role of muscles, tendons, and ligaments. Two cases are presented: in the first the center of gravity of the body is over the mid foot, and in the second, the center of gravity is anterior, over the metatarsals, and no support is provided by the heel. The model shows the extent to which the muscles reduce the force in the supporting ligaments at each of the joints and decrease the tension in the plantar aponeurosis, and that this effect is more pronounced when the center of gravity of the body is moved forward.

Medial displacement calcaneal osteotomy reduces the excess forces in the medial longitudinal arch of the flat foot.

OBJECTIVE: The hypothesis tested was that the increased load on the medial arch of the flat foot can be reduced through a medial displacement calcaneal osteotomy. DESIGN: A three-dimensional, biomechanical, multisegment model was used in conjunction with experimental data from the literature. BACKGROUND: Biomechanical models have been used to study the plantar fascia, medial arch height, subtalar motion and distribution of forces in the foot. METHODS: Responses of a normal foot, a flat foot and a flat foot with a medial displacement calcaneal osteotomy to an applied load of 683 Newtons were analyzed, and the distribution of support among the metatarsal heads and moment about various joints were computed. RESULTS: Compared to the normal foot, our flat foot model shifts the distribution of support from the lateral to the medial side, decreasing support provided by the fifth metatarsal from 11% to 1% of the total load, increasing support provided by the first metatarsal from 12% to 22% and increasing the moment about the talo-navicular joint from 20 to 28 Newton-meters. A ten millimeter medial displacement calcaneal osteotomy shifts support back toward the lateral side, with 11% provided by the fifth metatarsal and 13% by the first metatarsal. The moment at the talo-navicular joint decreases to eighteen Newton-meters. CONCLUSION: Our analysis indicates that a ten millimeter medial displacement calcaneal osteotomy in a flat foot model decreases the load on the medial arch.

Subtalar pronation--relationship to the medial longitudinal arch loading in the normal foot.

A three-dimensional biomechanical model was used to calculate the mechanical response of the foot to a load of 683 Newtons with the subtalar joint in the neutral position, at five degrees of pronation, and at five degrees of supination. Pronation causes the forefoot to evert, increasing the load borne by the first metatarsal. This results in a 47% increase in the moment about the talonavicular joint and a 58% increase in the moment about the navicular-medial cuneiform joint. Subtalar joint supination causes the forefoot to invert and results in a 55% increase in the moment about the calcaneal-cuboid joint.

Effect of varying arch height with and without the plantar fascia on the mechanical properties of the foot.

A biomechanical model was used to calculate the mechanical properties of the foot at a load of 683 newtons, while changing arch height with and without the plantar fascia. An increase in arch height from 20 mm to 60 mm decreased predicted vertical displacement of the foot from 11.8 mm to 5.5 mm with the plantar fascia intact and from 13.5 mm to 7.5 mm without the plantar fascia. The amount of horizontal elongation decreased from 8.6 mm to 8.4 mm with the plantar fascia and increased from 9.8 mm to 11.7 mm without. A 60-mm arch height yielded a 40% increase in horizontal elongation and a 36% increase in vertical displacement when the plantar fascia was cut, whereas a 20-mm arch height yielded a 13% increase in horizontal elongation and a 14% increase in vertical displacement. A change in arch height from 20 mm to 60 mm increased stiffness of the foot with and without the plantar fascia.

Thigh muscle size and strength after anterior cruciate ligament reconstruction and rehabilitation.

It is the hypothesis of the senior author (GAA) that high circumference measurements are not an accurate reflection of thigh muscle cross-sectional area or muscle strength after standard rehabilitation following anterior cruciate ligament reconstruction. Likewise, normal quadriceps femoris strength is not achieved in these patients despite aggressive rehabilitation. The purpose of our study was to quantify thigh muscle size and strength and correlate thigh circumference, muscle cross-sectional area by magnetic resonance imaging (MRI), and isokinetic strength in our patients. Thirty-three patients with anterior cruciate ligament repair utilizing autografts of iliotibial band (N = 28), semitendinosus autograft (N = 3), and bone-patellar tendon-bone autograft (N = 2) were retrospectively evaluated 48.7 +/- 6.91 months after surgery. We compared involved operated extremities with uninjured, uninvolved contralateral extremities, measuring thigh circumference, isokinetic peak torque, and cross-sectional area by MRI. We found a significant 1.8% decrease in thigh circumference, a 10% decrease in average quadriceps torque, and a 8.6% decrease in quadriceps cross-sectional area by MRI in the involved extremities compared with the uninvolved extremities. A positive correlation between MRI cross-sectional area, quadriceps, and hamstring peak torque was recorded in involved and uninvolved extremities. A positive correlation between thigh circumference, quadriceps, and hamstring peak torque was found in uninvolved extremities but not in operated extremities. The authors concluded that thigh circumference underestimates atrophy and is not correlated with cross-sectional thigh muscle area by MRI or strength in operated extremities. Persistent quadriceps weakness and decreased cross-sectional area at 49 months postsurgery and rehabilitation continue to challenge our efforts. The pathophysiology of the decrease in thigh muscle size and quadriceps femoris strength is discussed.

Effect of cutting the plantar fascia on mechanical properties of the foot.

A biomechanical model was used to calculate the loadbearing characteristics of the plantar fascia and to determine the effect of cutting the plantar fascia on the stiffness of the foot. With a load of 683 N applied to the foot, the model predicted a 17% increase in vertical displacement and a 15% increase in horizontal elongation when the plantar fascia was cut, compared with the corresponding value when the plantar fascia was intact. Plantar fasciotomy, although clinically satisfactory in cases of recalcitrant heel pain, decreases the stiffness of the foot and creates a less rigid and more deformable arch. The biomechanical model described can help to evaluate the possible outcome of such a procedure.

Reemployment of patients with surgical salvage of open, high-energy tibial fractures: an outcome study.

Between January 1, 1988, and December 31, 1990, 36 patients with 37 type III high-energy open tibial shaft fractures were treated at Lehigh Valley Hospital. Patients with primary amputations were excluded. All patients with high-energy open tibial fractures with an intact posterior tibial nerve, protective sensations of the plantar surface of the foot, and warm ischemia time of less than 6 hours were considered salvageable. A retrospective review of the charts was completed. Twenty-eight patients with 29 fractures were interviewed for work status, an average of 39 months after treatment. Twenty-five patients with 25 fractures were working at the time of the accident. Three patients with four fractures were not working at the time of the accident. Nineteen of 25 patients (76%) returned to work. Sixteen of 25 patients (64%) returned to work at a similar level of manual labor. The average delay between injury and return to work was 11 months (range, 3-18 months). Two of the 36 patients (5.5%) required secondary amputations. Twenty-five of 28 patients (89%) interviewed reported one or more subjective complaints. The two amputees reported no subjective complaints.

Biomechanical study of stress in the fifth metatarsal.

OBJECTIVE: The stress throughout the fifth metatarsal was determined under various loading conditions, in order to better understand the causes of fractures to this bone. DESIGN: A mathematical approach was taken, in which the stresses were analysed using the methods of beam theory. BACKGROUND: Finite element analysis has frequently been used to determine the stress in bones. Beam theory provides an easier method for determining the force and moment resultant in any cross-section. The distribution of stress throughout the cross-section can then be found by solving certain partial differential equations defined on the cross-sections. METHODS: Cross-sections of the bone were obtained by slicing a mould, into which the bone was placed, at numerous intervals along its length. Analytic expressions describing each cross-section were obtained by fitting a Fourier series to a sequence of points along the boundary. RESULTS: The maximum stress found in the fifth metatarsal resulted from an oblique load, and had a magnitude less than would occur in a subject during normal walking. CONCLUSIONS: Since the magnitude of the stress is submaximal, this study lends theoretical support to the clinical observation that the diaphyseal fracture is indeed a stress fracture. RELEVANCE: Our analysis adds a biomechanical rationale to the pathomechanics of diaphyseal stress fractures of the fifth metatarsal. It suggests that inversion during repetitive activities may predispose the foot to fractures at a predictable location.

Transverse proximal diaphysial fracture of the fifth metatarsal: a review of 12 cases.

A review of 12 cases of transverse proximal diaphysial fractures 3.0 cm distal from the fifth metatarsal tuberosity with a 2-year follow-up is presented. Six cases treated with percutaneous pinning, cast, and partial weightbearing with crutches and six cases treated with cast, partial weightbearing, and crutches are analyzed by classification, age, and average time to union. The healing times were the same in both groups.

Intraarticular pressures in a gravity-fed arthroscopy fluid delivery system.

Seven consecutive patients undergoing arthroscopic surgery in a gravity-fed fluid delivery system were studied. The average minimum adequate intraarticular pressure (MAIP) was 55 mm Hg. The height of a saline bag above the knee necessary to achieve this average MAIP was 75 cm. There was a positive correlation between diastolic blood pressure and the minimum adequate intraarticular pressure in this study. There was no positive correlation between systolic blood pressure and the MAIP.

Significance of lumbosacral list and low-back pain. A controlled radiographic study.

A prospective study of 43 patients with low-back pain was performed to determine if there exists 1) a significant correlation between lumbosacral list and low-back pain, 2) a significant difference between measured list in patients pretreatment and posttreatment, and/or 3) a significant difference in results obtained using two different measuring techniques. All patients had standing antero-posterior radiographs. The radiographs were analyzed for lumbosacral list using two measurement methods. The results indicated that there was no significant correlation between lumbosacral list and low-back pain and no significant change in measured list in individuals pretreatment and posttreatment. There was a significant difference between the two methods described above. The intercristal line (ICL) method proved most precise.

The foot as a shock absorber.

A mathematical analysis of the deformation of the foot is developed to determine the role that stretch of ligaments and tendons plays in absorbing shock following impact. Our analysis is based on an anatomical biomechanical model that includes each of the bones of the foot. We calculate the time course of the deflection of the joints and the elongation of the ligaments and tendons and determine the ground reaction force acting on the heel. Quasi-linear viscoelastic theory is used for soft tissue constitutive relationships. With biomechanical data selected from the literature, we obtain a vertical force impact peak of 8000 N, occurring at 16 ms following heel strike. This is of higher magnitude and shorter duration than is found experimentally, as is to be expected, since we did not include the heel pad in our model and we assumed that the impact surface was ideally rigid.

An application of beam theory to determine the stress and deformation of long bones.

We present a generalized beam theory in which deformation and load are determined simultaneously, in order to analyze statically indeterminant problems involving long bones. We regard a long bone as a beam curved in three dimensions for which the cross-sectional properties vary continuously along its length. The theory is used to determine the force, moment, deflection and twist along the fifth metatarsal when it is subjected to both a pointwise and a distributed load.

Restoration of the foot using the radial forearm flap.

Large foot defects unsuitable for reconstruction by local foot flaps are most expediently salvaged with distant free-tissue transfers. Although muscle flaps are preferred for infected wounds, coverage of the clean or acute foot deformity may be better achieved with the innervated radial forearm fasciocutaneous flap. This almost ideal donor site has been used by us for all traumatic foot defects requiring free flaps during the previous year. Our results document that in the 5 available clinical examples, restoration of normal foot contour, durability during ambulation, and an excellent aesthetic appearance were achieved.

A biomechanical model of the foot.

The foot is modeled as a statically indeterminate structure supporting its load at the heads of the five metatarsals and the tuberosity of the calcaneous. The distribution of support is determined through an analysis of the deformations caused in the structure as a result of the forces at these locations. The analysis includes the effect of the plantar aponeurosis and takes into account the deformation of the metatarsals and bending of the joints. A parametric study is presented to illustrate the behavior of the solution under a broad range of conditions.

Amelioration of oxygen-induced osteoporosis in the in vitro fetal rat tibia with a capacitively coupled electrical field.

Near-term fetal rat tibiae were grown in M.E.M. Eagle/NCTC 135/15% newborn calf serum in 5% carbon dioxide and 5, 10, 21, 35, 60, and 90% oxygen for 3, 7, 10, and 14 days. Linear growth of the explants, as measured from macrophotographs of the explants at day zero and each of the days above, was greatest in the lower oxygen concentrations and least in the higher oxygen concentrations. Breaking strengths of the tibial diaphyses were significantly reduced in those explants grown in 60 and 90% oxygen. When the fetal rat tibiae were grown in 60% oxygen for 7 days and were subjected to a capacitively coupled electrical signal (sine wave, 60 kHz, 10 V peak-to-peak output signal; current density and field in the culture dish calculated to be 5.2 microA/cm2 and 0.32 mV/cm, respectively), the breaking strengths and middiaphyseal widths were statistically significantly greater than control tibiae grown in 60% oxygen alone. It is concluded that an appropriate capacitively coupled electrical field can inhibit an oxygen-induced osteoporosis in an in vitro mammalian long bone model.

Prognostic value of exercise EKG testing in asymptomatic normotensive subjects. A prospective matched study.

We prospectively studied 135 asymptomatic normotensive subjects with exercise-induced ST ischemic depression of 1 mm or more and compared them with 379 controls. At least two controls with negative responses on the exercise electrocardiographic (EKG) test were selected for each case and were matched for age, sex, work, community, and coronary-risk-factors index. The end points considered were the following coronary events: angina pectoris, myocardial infarction, and sudden death. After a median follow-up period of 6.0 years for the cases and 6.4 years for the controls, the relative risk was 5.55 (95 per cent confidence limits, 2.75 to 11.22). Coronary events occurred significantly earlier in the cases than in the controls. Our data also suggest that the exercise EKG response is a particularly good prognostic indicator for myocardial infarction. In addition, our analysis has confirmed the predictive roles of age, smoking, blood pressure, and the coronary-risk-factors index and suggests that the exercise EKG response is an additional independent risk indicator for coronary events.

Proximal diaphyseal fractures of the fifth metatarsal (Jones' fracture): two cases treated by cross-pinning with review of 106 cases.

Two young males with proximal diaphyseal fractures of the fifth metatarsal (Jones' fractures), one acute and one with delayed union, have been presented and healed with percutaneous cross-pinning, shortleg casting, and partial weightbearing. Both healed without complications in 7 and 11 weeks, respectively. Both were followed for more than 2 years. In the acute Jones' fracture the treatment of choice is a nonweightbearing shortleg cast for 8 weeks. In the symptomatic nondisplaced delayed union the author favors percutaneous cross-pinning, shortleg cast, and partial weightbearing. Intramedullary screw fixation is an alternative. In the patient with symptomatic nonunion, bone grafting is the treatment of choice. Asymptomatic patients with radiographically unhealed fractures require no treatment. One hundred six cases of the Jones' fracture are reviewed.

Patellar tendon rupture with underlying systemic disease.

Two patients with patellar tendon rupture and underlying systemic disease are described. One had systemic lupus erythematosus and the other had chronic renal failure and secondary hyperparathyroidism. There have been 13 other cases of patellar tendon rupture in patients with systemic disease reported in the literature and they are reviewed. Patellar tendon rupture has occurred spontaneously in more than one-half of the cases and has been associated with rupture of the contralateral extensor tendon mechanism in 87%. Although patellar tendon rupture almost always occurs at the tendinous insertion, on a rare occasion (as in one case described in this report), the tear may involve the main substance of the tendon, which is the part of the tendon with the greatest tensile strength. The relation between systemic disease and patellar tendon rupture is discussed and the clinical and radiographic findings are described.