The effects of non-weight-bearing and limited motion on the tensile properties of the meniscus.

Recent clinical studies have suggested that many of the complications of prolonged immobilization after knee surgery can be prevented by permitting early motion while minimizing loading of healing tissues. The purpose of this study was to determine the effects of such a regimen on the tensile properties of the meniscus. The right knee of 10 skeletally mature sheep received a sham operation after which the hindlimb was placed in a harness that prevented weight bearing while permitting limited knee motion. The left knee served as the nonoperated control. Twelve weeks after surgery, paired specimens from the medial meniscus of each limb were tested in tension with the load parallel to the circumferentially oriented collagen fibers. No significant differences in the modulus, tensile strength, and ultimate strain between treated and control medial menisci were identified. Our data thus suggest that preventing weight bearing while permitting even limited motion of the knee will prevent any detrimental effect on the tensile properties of the meniscus in the circumferential direction.

Effects of an in-substance conduit with injection of a blood clot on tears in the avascular region of the meniscus.

The purpose of this study was to test the hypothesis that healing of a stable tear in the avascular region of the meniscus occurs when a horizontal conduit, extending from the periphery to the defect, is filled with an exogenous fibrin clot. In 6 sheep a full-thickness laceration was made in the lateral meniscus, and autologous blood clot was then injected into the conduit. Three animals in the control group received identical meniscal tears but no additional treatment. Casting and a harness prevented weight-bearing and maintained the knee in a flexed position. Twelve weeks after the operation histologic examination revealed only partial healing in one animal. In both the experimental and control groups increased numbers of dividing chondrocytes on either side of the tear were seen. We conclude that an in-substance conduit in combination with the injection of a blood clot is not sufficient to facilitate complete healing of a tear within the avascular region of the lateral meniscus of the sheep when the knee is immobilized only with a harness.

Effects of abrasion therapy on tears in the avascular region of sheep menisci.

This study was designed to test the hypothesis that abrasion of the parameniscal synovium aids healing of a stable tear in the avascular region of the meniscus in a sheep model. In six sheep, a 5-7-mm longitudinal full-thickness tear was made in the avascular inner half of the anterior part of the lateral meniscus. The parameniscal synovium was abraded superiorly and inferiorly from the meniscus periphery to the lesion. Three animals in a control group received identical meniscal tears but no abrasion treatment. A harness prevented weight bearing and maintained the knee fully flexed after surgery. Twelve weeks after the operation, no healing was seen in any tears. Histologic examination revealed in both groups increased numbers of dividing chondrocytes on either side of the tear. In the test group, several layers of fibroblasts, which appeared in two menisci to derive from the upper meniscal surface, were seen covering both cut surfaces of the tear. It is concluded that the distance from the periphery to the defect is too far for abrasion therapy to stimulate sufficient cellular ingrowth to facilitate repair of tears in the avascular region of the meniscus.

Experimental models to promote healing of tears in the avascular segment of canine knee menisci.

Longitudinal tears were created in canine lateral menisci and techniques were applied to induce healing by removal of a core of tissue from the periphery of the meniscus to the tear or by implantation of a vascularized synovial flap into the tear. The meniscal tears did not heal in knees that were not immobilized, and they healed poorly and sporadically in knees that were immobilized in a cast but bore some weight. However, a higher percentage of tears that were treated by the core-removal or synovial-flap technique healed when the knee was firmly immobilized and weight-bearing was prevented by the use of an external skeletal fixator across the joint for eight to twelve weeks. Neovascularization and access to a source of reparative cells appear to be important in the healing process.

Intraarticular pressure during continuous passive motion of the human knee.

Intraarticular pressure (IAP) was continuously monitored during continuous passive motion (CPM) of five normal and 11 abnormal human knees using a new fiberoptic, transducer-tipped Camino catheter. IAP varied in a consistent hysteresis pattern in the normal knees, with subatmospheric pressures recorded at intermediate angles of joint flexion. A similar pattern was recorded in the abnormal knees without cruciate ligament pathology, whereas considerable variability was noted in the knees with cruciate ligament abnormality. IAP was lower in the extension to flexion than in the flexion to extension portion of the CPM cycle, providing evidence of intraarticular fluid flow during portions of the CPM cycle. IAP changes were consistent with "physiologic compartmentation" within the knee at extremes of joint position. Capsular viscoelastic changes and/or synovial fluid volume changes were observed during CPM. The therapeutic mechanism of continuous passive motion may be related to cyclic variation of the intraarticular pressure.

Kappa Delta Award paper. Tissue fluid pressures: from basic research tools to clinical applications.

The two basic research tools developed to measure tissue fluid pressure (wick catheter) and osmotic pressure (colloid osmometer) have undergone extensive validation and refinement over the past 20 years. Using these techniques, basic science investigations were undertaken of edema in Amazon reptiles, pressure-volume relations in animals and plants, adaptive physiology of Antarctic penguins and fishes, edema in spawning salmon, tissue fluid balance in humans under normal conditions and during simulated weightlessness, and orthostatic adaptation in a mammal with high and variable blood pressures--the giraffe. Following and sometimes paralleling this basic research have been several clinical applications related to use of our colloid osmometer and wick technique. Applications of the osmometer have included insights into (a) reduced osmotic pressure of sickle-cell hemoglobin with deoxygenation and (b) reduced swelling pressure of human nucleus pulposus with hydration or certain enzymes. Clinical uses of the wick technique have included (a) improvement of diagnosis and treatment of acute and chronic compartment syndromes, (b) elucidation of tissue pressure thresholds for neuromuscular dysfunction, and (c) development of a better tourniquet design for orthopaedics. This article demonstrates that basic research tools open up areas of basic, applied, and clinical research.

Regional nutrition and cellularity of the meniscus. Implications for tear and repair.

The knee menisci are relatively avascular and must rely to a large degree on synovial sources of nutrition. Lack of nutrition may lead to degenerative changes and may inhibit any potential repair capabilities of the menisci. Continuous passive motion applied to the knee stimulates greater activity and/or transport of nutrients to the meniscal fibrochondrocytes. However, in an avascular model, solutes within the synovial fluid are lost by their convective transport from the joint. Regional differences in transport of a low molecular weight nutrient like sodium sulphate exist such that cells in the central core region of the meniscus are poorly supplied with nutrients by the synovial fluid and/or are less active. These conditions may be the cause of a relatively high incidence of degenerative changes in the central core region.

Differential response of the dog quadriceps muscle to external skeletal fixation of the knee.

The change in muscle fiber size and fiber percentage was studied in three heads of the dog quadriceps following 10 weeks of immobilization using an external skeletal fixator. Muscle biopsy morphometric analysis revealed that muscle fiber atrophy was greatest for the vastus medialis and least for the rectus femoris. The atrophic response for type 1 fibers was, in order from most to least atrophied: VM greater than VL greater than RF, whereas for type 2 fibers the corresponding order was VM = VL greater than RF. An increase in connective tissue was also observed for all muscles. These results are discussed in terms of skeletal muscle architecture, initial fiber-type distribution, and level of use. As a result, predictions are made as to the muscles that are most vulnerable to disuse atrophy, namely the postural muscles that contain a relatively large proportion of slow muscle fibers and cross a single joint. Conversely, those that are least susceptible to atrophy are those that are not used as postural muscles, that cross multiple joints, and that are predominantly composed of fast muscle fibers.

Increased transsynovial transport with continuous passive motion.

Thirteen freshly killed immature rabbits were used to study the effect of continuous passive motion (CPM) on regional nutritional pathways of the medial and lateral menisci and the transport of a solute from synovial fluid to the patellar tendon. A bolus of 35SO4 was injected into each knee joint cavity. The right knee underwent CPM for 1 h, whereas the left knee was immobilized (rest extremity). Both knees were then rapidly resected and immediately frozen. The medial and lateral menisci were removed and sectioned into anterior, middle, and posterior thirds for Group 1 animals; in Group 2 animals a portion of patellar tendon was harvested. Radioactivity as counts per minute per milligram of tissue was counted in a scintillation counter. The posterior portion of the lateral meniscus in the rest extremity had significantly higher uptake than the extremity that underwent CPM (p less than 0.001). In the extremity at rest, the posterior third of the lateral meniscus had a significantly higher uptake than that of the middle third (p = 0.04). In Group 2 rabbits, the patellar tendon of the knee undergoing CPM had significantly higher uptake as compared with the patellar tendon of the knee at rest (p = 0.02). These results indicate that diffusion from synovial fluid to meniscal cells is an important mechanism of transport for low-molecular-weight nutrients such as sulfate; CPM does not facilitate this mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutrition of the anterior cruciate ligament. Effects of continuous passive motion.

Twelve freshly killed mature male rabbits were used to study the effects of continuous passive motion (CPM) on regional and overall nonvascular nutritional pathways of the anterior cruciate ligament (ACL). One hundred fifty microcuries of 35sulphate was injected intraarticularly into each knee joint. The right knee underwent CPM for 1 hour, while the left knee remained immobilized. Both knee joints were then isolated and immediately frozen. The ACLs were removed while still mostly frozen, and sectioned into anterior, middle, and posterior thirds for the six rabbits in Group 1, and proximal, middle, and distal thirds for the six rabbits in Group 2. In addition, quadriceps tendon samples were harvested from each limb of three rabbits. After appropriate processing, all samples were counted in a scintillation counter, and counts per minute per milligram of tissue were calculated. There was significantly higher uptake in rest extremity ACLs compared to CPM extremity ACLs (P = 0.0001). No significant difference was demonstrated in regional uptake comparing respective thirds of the ACL in either Group 1 or Group 2. Quadriceps tendon uptake trended higher in the limbs exposed to CPM compared to those maintained at rest (P = 0.14). The ACL uses diffusion as a primary nutrient pathway. CPM does not increase nutrient uptake by the ACL in this avascular model, but CPM may facilitate transport of metabolites out of the joint. No regional differences in uptake within the ACL occurred in either group.

Extensive spinal osteophytosis as a risk factor for heterotopic bone formation after total hip arthroplasty.

Observations on 54 patients present circumstantial evidence of a relationship between an underlying spinal ossifying diathesis and the heterotopic bone formation following total hip arthroplasty. This relationship should be investigated in a larger patient population to determine whether a spine-hip diathesis exists and could account for some patients with this complication. If it can be statistically substantiated, spinal roentgenograms may provide a preoperative screening procedure for the identification of "a population at risk" of heterotopic bone formation who might benefit from a prophylactic medical regimen.

Pseudomasses in the suprapatellar pouch at arthrography.

An arthrographic appearance, confidently diagnosed as synovial chrondromatosis, showed no abnormality at surgery. This experience prompted further investigation which led to the conclusion that a normal variant of the suprapatellar pouch may be confused with synovial masses. Single or multiple pseudomasses in this region may relate to the presence of an embryonic remnant of the synovial folds, the plicae synovialis. If the finding is looked for, with careful arthrographic technique and palpation under fluoroscopic control, along with correlation with the clinical findings, unnecessary arthrotomy may be avoided.

The Hill-Sachs lesion. An experimental study.

The Hill-Sachs lesion is an important indication of previous anterior shoulder dislocation. We created Hill-Sachs lesions by using cadaveric humeri. Roentgenographs of these cadaveric humeri in the standard projections were then taken. Under fluoroscopy, new projections of the cadaveric humeri were obtained. In a clinical study, 15 patients (14 men and 1 woman; age range, 23 to 63 years; mean, 30 years) with known recurrent anterior shoulder dislocations were evaluated by using standard and new roentgenographic projections. On the basis of the cadaveric and clinical studies, the optimal methods for detecting Hill-Sachs lesions include the following three roentgenograms: anteroposterior view of the glenohumeral joint with the humerus in 45 degrees internal rotation, the notch (Stryker) view, and the modified Didiee view.

The treatment of cervical spine metastasis from the prostate with a Halo cast.

Three patients with adenocarcinoma of the prostate and metastasis to the cervical spine required stabilization to prevent neurologic impairment. In each instance, a Halo cast was used. This method of stabilization is easily applied and well suited for patients with shortened life expectancy. It allows protection of the cord while chemotherapy and radiation are administered.

Internal fixation plates after fifty-six years of implantation: report of a case.

Lane plates removed and examined after 56 years in the femur of a 77-year-old man were markedly corroded. There was no loss of tensile strength, but other structural properties were altered and inflammation may have been locally induced by leaching of metal ions from the steel alloy.

Proximal tibiofibular joint: anatomic-pathologic-radiographic correlation.

An anatomic-pathologic-radiographic study of the proximal tibiofibular joint was undertaken. This synovial articulation between the proximal tibia and fibula may communicate with the knee joint in 10% of adults. Radiography of the normal proximal tibiofibular articulation outlines a consistent relationship between the proximal portions of the tibia and fibula. Disruption of this normal relationship is indicative of anterolateral or posteromedial subluxation or dislocation. Articular disorders of this joint include reheumatoid arthritis and septic arthritis. In the latter, initial alterations of the knee joint may subsequently extend to involve the proximal tibiofibular joint, illustrating the potential communication between these two articulations.