Wayne H. Akeson

The carpal tunnel syndrome. A study of carpal canal pressures.

We measured intracarpal canal pressures with the wick catheter in fifteen patients with carpal tunnel syndrome and in twelve control subjects. The mean pressure in the carpal canal was elevated significantly in the patients. When the wrist was in neutral position, the mean pressure was thirty-two millimeters of mercury. With 90 degrees of wrist flexion the pressure increased to ninety-four millimeters of mercury, while with 90 degrees of wrist extension the mean pressure was 110 millimeters of mercury. The pressure in the control subjects with the wrist in neutral position was 2.5 millimeters of mercury; with wrist flexion the pressure rose to thirty-one millimeters of mercury, and with wrist extension it increased to thirty millimeters of mercury. Carpal tunnel release brought about an immediate and sustained reduction in pressure.

The effect of prolonged physical training on the properties of long bone: a study of Wolff's Law.

UNLABELLED Five one-year-old immature swine were subjected to twelve months of exercise training. Four matched swine with no training served as controls. After they were killed, four-millimeter-wide strips of bone taken from the anterior, medial, posterior, and lateral quadrants of the central femoral diaphysis were subjected to four-point bending tests to failure. It was found that although exercise did not change the mechanical properties of the cortical bone, it resulted in significant increases in the averaged femoral cross-sectional properties: 17 per cent in cortical thickness, 23 per cent in cortical cross-sectional area, and 21 per cent and 27 per cent in maximum and minimum area moments of inertia, respectively. These changes were due primarily to reduction in the diameter of the medullary canal. The analyses of bone composition showed that the bone density and biochemical contents of the control and exercised animals were similar, but the total volume and the dry, ash, and calcium weights of the exercised bone were significantly higher. These combined results suggest that prolonged exercise has a significant effect on the quantity of the bone, but not on its quality. CLINICAL RELEVANCE It has long been recognized that stress deprivation from immobilization in plaster casts results in profound bone atrophy, and it is generally accepted that a minimum level of activity is necessary for homeostasis of bone. These results show that exercise at a level comparable to that prescribed in running fitness programs for humans (65 to 80 per cent of maximum heart rate) can not only maintain homeostasis, but produce actual hypertrophy of bone. This work further suggests the importance of graduated, prolonged, supervised rehabilitation programs in overcoming osteoporotic states.

Acute compartment syndromes: diagnosis and treatment with the aid of the wick catheter.

Intracompartmental pressures were measured by the wick catheter technique in sixty-five compartments of twenty-seven patients who were clinically suspected of having acute compartment syndromes. A pressure of thirty millimeters of mercury or more was used as an indication for decompressive fasciotomy. The range of normal pressure was from zero to eight millimeters of mercury. Eleven of these patients were diagnosed as actually having compartment syndromes and in these patients, twenty-seven compartments were decompressed. Only two patients had significant sequelae. In the sixteen patients (thirty-eight compartments) whose pressures remained less than thirty millimeters of mercury, fasciotomy was withheld and compartment syndrome sequelae did not develop in any patient. Intraoperatively the wick catheter was used continuously in eight patients to document the effectiveness of decompression. Fasciotomy consistently restored pressures to normal except in the buttock and deltoid compartments, where epimysiotomy was required to supplement the fasciotomy. Continuous intraoperative monitoring of pressure by the wick catheter technique allowed us to select the few cases in which primary closure of wounds was appropriate and to decide which patients were best treated with secondary closure.

Mechanical properties of tendons and ligaments. II. The relationships of immobilization and exercise on tissue remodeling.

The primary goal of this investigation is to study whether soft tissue homeostatic responses secondary to decrease or increase in physiological stress levels and range of motion are a change of mechanical properties or a change of mass, or both. Two experimental animal studies are presented. One is a stress and motion deprivation study by immobilization of a rabbit knee, and the other is an increase in stress and motion study by running exercise of the miniature swine. The findings are that changes in stress and motion significantly altered the tissue properties as well as mass in the case of ligaments and digital extensor tendons. Whereas, no significant changes in properties and mass were detected for the digital flexor tendons. Possible mechanisms of the difference in tissue responses to stress and motion are discussed, and nonlinear relationships between stress and tissue remodeling are suggested.

The biomechanical and morphological changes in the medial collateral ligament of the rabbit after immobilization and remobilization.

The effects of immobilization and remobilization on the biomechanical and morphological properties of the femur-medial collateral ligament-tibia complex and each of its components were investigated in the rabbit. Specimens that had been obtained after periods of unilateral immobilization of the knee and remobilization were evaluated for structural properties. In addition, the mechanical properties of the substance of the medial collateral ligament and the histological characteristics of both the substance of the ligament and its sites of insertion were evaluated. After immobilization, there were significant reductions in the ultimate load and energy-absorbing capabilities of the bone-ligament complex, and an increased number of failures occurred by tibial avulsion. The tissue of the medial collateral ligament also became less stiff as a result of immobilization. Histologically, the femoral and tibial insertion sites showed increased osteoclastic activity, resorption of bone, and disruption of the normal attachment of the bone to the ligament. With remobilization, the ultimate load and energy-absorbing capabilities of the bone-ligament complex improved but did not return to normal. Failure by tibial avulsion became less frequent, and the stress-strain characteristics of the medial collateral ligament returned to normal. Histologically, the sites of insertion of the ligament also showed evidence of recovery.

The wick catheter technique for measurement of intramuscular pressure. A new research and clinical tool

The wick catheter technique was developed in 1968 for measurement of subcutaneous pressure and has been modified for easy intramuscular insertion and continuous recording of interstitial fluid pressure in animals and humans. Studies in dogs of the anterolateral compartment of the leg in simulation of the compartment syndrome showed the technique to be accurate and reproducible. The wick catheter technique is capable of important clinical applications in the diagnosis and treatment of acute and chronic compartment syndromes.

Articular cartilage transplantation. Clinical results in the knee.

Between December 1983 and August 1991, 55 consecutive patients (55 knees) who underwent articular cartilage transplantation to their damaged knees were enrolled in the study. Average followup was 75 months (range, 11-147 months). Eight-two percent were younger than 45 years of age. Patients were evaluated through an 18-point scale, with 6 points each allocated to pain, range of motion, and function. An excellent knee was pain free, had full range of motion, and permitted unlimited activity. A good knee allowed full time employment and moderate activity. Eleven of 15 (73%) allografts transplanted 10 or more years ago were still good or excellent at the time of last followup. Overall, 45 of 55 (76%) knees that received the transplants were rated good or excellent. Specifically, 36 of 43 (84%) patients with unipolar transplants regained normal use of their resurfaced knee. The results after bipolar resurfacing were less encouraging, with only six of 12 (50%) knees rated good or excellent. The described technique of osteochondral shell allograft resurfacing of the knee capitalize on the different healing potentials of bone and cartilage by transplanting the viable articular cartilage organ in its entirety along with just enough of the underlying bone to allow for graft incorporation through creeping substitution. The results support the use of fresh osteochondral shell allograft transplantation for the treatment of large, full thickness articular cartilage defects to the medial or lateral femoral condyles and to the patella.

Flexor tendon healing and restoration of the gliding surface. An ultrastructural study in dogs.

Healing canine flexor tendons were treated with either total immobilization and were studied by light, scanning, and transmission electron microscopy at ten, twenty-one , and forty-two days. The immobilized tendons healed by ingrowth of connective tissue from the digital sheath and cellular proliferation of the endotenon. The ingrowth of reparative tissue from the digital sheath overwhelmed the epitenon response. At the ultrastructural level, collagen resorption was prominent whereas protein synthesis was limited. This was observed at all study-intervals. In contrast, the mobilized tendons healed by proliferation and migration of cells from the epitenon. Ingrowth of reparative tissue from the tendon sheath was notably lacking in this group. The epitenon cells exhibited greater cellular activity and collagen production at each interval compared with cells of the immobilized repairs.

Resurfacing of the knee with fresh osteochondral allograft

Fifty-nine fresh osteochondral allografts were consecutively transplanted into the knees of fifty-eight patients. The preoperative diagnoses were chondromalacia or degenerative arthritis of the patella, osteochondritis dissecans, a traumatic defect or osteonecrosis of the femoral condyle, a painful healed depressed fracture or traumatic defect of the tibial plateau, and unicompartmental traumatic arthritis of the knee. All of the patients had disabling pain after the failure of previous attempts to correct the problem surgically. Thirty-nine patients (forty knees) were available for follow-up at two to ten years after the allograft was transplanted. Nine transplants (22.5 per cent) failed and thirty-one (77.5 per cent) were successful. The result was rated excellent after thirteen of the successful transplants, good after fourteen, and fair after four. Transplantation of a fresh osteochondral allograft proved to be a satisfactory intermediate procedure for the treatment of the disabling conditions, except unicompartmental traumatic arthritis, in the young patients in this series. For the patients who had unicompartmental traumatic arthritis, the rate of success was only 30 per cent.

The Importance of Controlled Passive Mobilization on Flexor Tendon Healing: A Biomechanical Study

The effects of controlled passive motion on primary tendon repair were studied using the canine forepaw flexor apparatus as experimental model. The animals were divided into seven groups based on duration(3 to 12 weeks post repair) and mode of immobilization and partial mobilization. The repaired tendons were subjected to biomechanical evaluation of their gliding function and tensile strength characteristics. The results showed positive effects of controlled passive motion on tendon repair. The rate of tendon repair was significantly improved over those animals that were continuously immobilized. At 12 weeks, the repaired flexors from the motion group had regained over one-third of the ultimate tensile load as compared to their contralateral intact controls. Of equal importance is that these repaired tendons maintained good gliding function within the sheath during the repair process. The gliding function of these tendons was also significantly better than those subjected to continuous immobilization.