David R. McAllister

Gait Pattern in the Early Recovery Period after Stroke

The gait patterns of eighteen patients who had had a single infarct due to obstruction of the middle cerebral artery were evaluated within one week after the patients had resumed independent walking and before a gait rehabilitation program had been initiated. Gait was analyzed with use of motion analysis, force-plate recordings, and dynamic surface electromyographic studies of the muscles of the lower extremities. The patterns of motion of the lower extremity on the hemiplegic side had a stronger association with the clinical severity of muscle weakness than with the degree of spasticity, balance control, or phasic muscle activity. There was a delay in the initiation of flexion of the hip during the pre-swing phase, and flexion of the hip and knee as well as dorsiflexion of the ankle progressed only slightly during the swing phase. During the stance phase, there was decreased extension of the hip that was related to decreased muscle effort and a coupling between flexion of the knee and dorsiflexion of the ankle. The abnormal patterns of motion altered the velocity, the length of the stride, the cadence, and all phases of the gait cycle. The duration of the pre-swing phase was prolonged for the patients who had the slowest gait velocities. There also were abnormal movements of the upper extremity, the trunk, the pelvis, and the lower extremity on the unaffected side in an effort to compensate for the decreased velocity on the hemiplegic side. As velocity improved, these abnormal movements decreased. Therefore, the goal of therapy should be to improve muscle strength and coordination on the hemiplegic side, especially during the pre-swing phase.

A biomechanical comparison of posterior cruciate ligament reconstruction techniques.

Most posterior cruciate ligament reconstruction techniques use both tibial and femoral bone tunnels for graft placement. Because of the acute angle the graft must make to gain entrance into the tibial tunnel, abnormal stresses are placed on the graft that could lead to graft failure. An alternative technique for posterior cruciate ligament reconstruction involves placement of the bone plug from the graft anatomically on the back of the tibia (inlay), preventing formation of an acute angle at the tibial attachment site. We used six pairs of human cadaver knees to compare the biomechanical properties of these two techniques. One knee from each pair underwent tunnel reconstruction while the other knee underwent inlay reconstruction. There was significantly less anterior-posterior laxity in the inlay group when compared with the tunnel group from 30° to 90° of knee flexion and after repetitive loading at 90° of knee flexion. Evaluation of the grafts revealed evidence of mechanical degradation in the tunnel group but not in the inlay group. The inlay technique resulted in less posterior translation with less graft degradation than did the tunnel technique for posterior cruciate ligament reconstruction.

Increased adenosine concentration in blood from ischemic myocardium by AICA riboside. Effects on flow, granulocytes, and injury.

Morbidity and mortality from acute coronary artery occlusion may be reduced if local myocardial adenosine concentration is augmented because 1) coronary collateral blood flow during ischemia increases with adenosine infusion, and 2) granulocytes that accumulate in the microcirculation during ischemia are, to a large extent, inhibited by adenosine from generating superoxide anion free radicals, from adhering to vascular endothelium, and from damaging endothelial cells in culture. Using a cultured lymphoblast model system, we found that 5-amino-4-imidazole carboxamide (AICA) riboside enhanced adenosine accumulation during ATP catabolism. Therefore, AICA riboside pretreatment was used in canine myocardium to selectively increase adenosine concentration in the ischemic area during 1 hour of ischemia. At 5 minutes of ischemia, endocardial flow to ischemic myocardium in saline-treated and AICA riboside-treated dogs was 0.06 +/- 0.03 and 0.34 +/- 0.11 ml/min/g, respectively (p less than 0.01); flow to nonischemic myocardium was not affected. Ventricular tachycardia and premature ventricular depolarizations were significantly attenuated in the AICA riboside-treated dogs. Blood pressure and heart rate were not affected by AICA riboside. In venous blood from ischemic tissue, adenosine increased from undetectable levels (less than 0.01 microM) to 0.22 +/- 0.08 microM in saline and 1.79 +/- 0.06 microM in AICA riboside-treated dogs, respectively (p less than 0.001). Coronary vein inosine concentrations were greater in saline than in AICA riboside-treated dogs. In separate in vitro studies, AICA riboside did not alter the removal rate of adenosine from canine blood. Indium-labeled granulocyte accumulation was significantly less in ischemic myocardium in AICA riboside-treated compared with saline-treated dogs. In addition, adenosine, but not AICA riboside, inhibited in vitro canine granulocyte superoxide production. We conclude that AICA riboside given before myocardial ischemia augments adenosine concentration, decreases arrhythmias, decreases granulocyte accumulation, and improves collateral flow to ischemic myocardium. One of the beneficial mechanisms could be an increased production of adenosine rather than inosine from ATP catabolism that causes vasodilation and inhibition of granulocytes. We propose a new hypothesis regarding regulation of the inflammatory reaction to ischemia in the microcirculation. Adenosine, in addition to its vasodilator action, is an anti-injury autacoid that links ATP catabolism to inhibition of granulocyte adherence, microvascular obstruction, and superoxide anion formation.

Outcomes of Postoperative Septic Arthritis After Anterior Cruciate Ligament Reconstruction

Background: Septic arthritis is a rare but potentially devastating complication of anterior cruciate ligament (ACL) reconstruction surgery. Several studies, including one by this group, have reported short- and medium-term outcomes, but to our knowledge there are no long-term follow-up studies. Hypothesis: Postoperative septic arthritis after ACL reconstruction surgery will lead to diminished long-term outcomes compared with surgery without infectious complications, likely related to the development of arthritis. Study Design: Case series; Level of evidence, 4. Methods: Four of 831 consecutive patients undergoing arthroscopically guided ACL reconstruction surgeries performed by 1 surgeon were previously reported on by this group at an average follow-up of 36 months. These same patients were contacted and reevaluated. Each patient underwent a physical examination, functional testing, and subjective evaluations with the SF-36, Lysholm, International Knee Documentation Committee (IKDC), and Tegner activity scale scores. Plain film radiographs and magnetic resonance imaging (MRI) scans were analyzed by 2 musculoskeletal radiologists. Results: Average follow-up time for this study was 17.9 years, and average age was 44.3 years. No other injuries or surgeries had occurred from the time of the previous study. Each patient had a decline in SF-36, Lysholm, and IKDC score, and the average Tegner score was unchanged. Average vertical hop test performance and Biodex dynamometry were both improved. The average side-to-side displacement measured via the KT-1000 arthrometer was increased. Radiographic and MRI studies revealed progression of arthritis in all patients and ACL graft rupture in 1 patient. Conclusion: Patients who develop septic arthritis as a complication of ACL reconstruction surgery have diminished long-term subjective, functional, and radiographic outcomes compared with historical reports of uncomplicated cases, likely related to pain from advanced arthritis. As compared with their own earlier follow-up, these patients had declines in pain-related subjective measures but remained stable or improved in both functional testing and activity-related subjective scales.

Allograft Update: The Current Status of Tissue Regulation, Procurement, Processing, and Sterilization

Allografts are commonly used during sports medicine surgical procedures in the United States, and their frequency of use is increasing. Based on surgeon reports, it is estimated that more than 60 000 allografts were used in knee surgeries by members of the American Orthopaedic Society for Sports Medicine in 2005. In the United States, there are governmental agencies and other regulatory bodies involved in the oversight of tissue banks. In 2005, the Food and Drug Administration finalized its requirements for current good tissue practice and has mandated new rules regarding the “manufacture” of allogenic tissue. In response to well-publicized infections associated with the implantation of allograft tissue, some tissue banks have developed methods to sterilize allograft tissue. Although many surgeons have significant concerns about the safety of allografts, the majority believe that sterilized allografts are safe but that the sterilization process negatively affects tissue biology and biomechanics. However, most know very little about the principles of sterilization and the proprietary processes currently used in tissue banking. This article will review the current status of allograft tissue regulation, procurement, processing, and sterilization in the United States.

Cyclic Loading of Posterior Cruciate Ligament Replacements Fixed with Tibial Tunnel and Tibial Inlay Methods

Background: The optimal method of replacement of the posterior cruciate ligament with a bone-patellar tendon-bone graft is not known. The purpose of this study was to compare the mechanical responses to cyclic loading tests of bone-patellar tendon-bone allograft replacements fixed to the tibia with one of two methods: a tibial tunnel or a tibial inlay technique. Methods: The proximal ends of sixty-two posterior cruciate graft replacements, thirty-one fixed with the tibial tunnel technique and thirty-one fixed with the tibial inlay technique in cadaver knees, were subjected to 2000 cycles of tensile force of 50 to 300 N with the angle of pull at 45° to the tibial plateau. The central 10 mm of the medial and lateral halves of previously fresh-frozen bone-patellar tendon-bone preparations from cadaver knees were used as the grafts. Two pairs of tibiae were used for testing; the two types of fixation and the medial and lateral halves of the patellar tendons were distributed between the tibial pairs. Graft thickness was measured at the point of highest anticipated tissue deformation and at two additional locations at distances from these points. The total change in graft length after cyclic loading at an applied force level of 200 N was recorded. Elongation of the graft during loading cycles between 20 and 200 N of applied tensile force was also measured. A repeated-measures analysis of variance was used to compare all measurements between the inlay and tunnel techniques, and between the medial and lateral halves of the graft used for the inlay method. Results: Ten of the thirty-one grafts that had been passed through a tibial tunnel failed at the acute angle before 2000 cycles of testing could be completed; all thirty-one grafts that had been fixed to the tibia with use of the inlay method survived the testing intact. Evaluation of the twenty-one graft pairs that survived testing after both fixation techniques revealed that the grafts that had been fixed with the inlay method had significantly less thinning at all three measurement sites at the completion of testing; the mean reduction of thickness was 40.6% (at the acute angle) in the grafts fixed with the tunnel method and 12.5% (adjacent to the bone block) in those fixed with the inlay method. After 2000 cycles, the mean lengths of the grafts fixed with the inlay and tunnel methods increased 5.9 and 9.8 mm, respectively; 38% of this increase occurred during the first six loading cycles. After both methods of fixation, the mean graft elongation during a loading cycle decreased approximately 50% from cycle 1 to cycle 2000, resulting in an effectively stiffer graft construct. There was no significant difference in any measured parameter between medial and lateral graft halves. Conclusions: These tests showed that the inlay technique of posterior cruciate ligament replacement was superior to the tunnel technique with respect to graft failure, graft thinning, and permanent increase in graft length. Clinical Relevance: Grafts replacing the posterior cruciate ligament are subjected to repetitive mechanical loading, and our results demonstrated that, with either the tunnel or the inlay fixation technique, the graft undergoes thinning and permanent length changes at the load levels used in these tests. These permanent length changes could be reduced substantially if the graft were cyclically preconditioned in situ before final pretensioning and fixation. The marked thinning of graft tissue at the acute angle and the permanent length changes of the tunnel grafts that did not fail may explain the increased posterior laxity observed in many patients who have undergone posterior cruciate replacement with use of the tunnel technique. The inlay technique of fixation significantly reduced these degradative effects. Regardless of the type of fixation to the tibia, there appears to be no advantage to using either the medial or the lateral half of a bone-patellar tendon-bone allograft preparation.

Effects of Applied Quadriceps and Hamstrings Muscle Loads on Forces in the Anterior and Posterior Cruciate Ligaments

Background Muscle contraction can subject healing knee ligament grafts to high loads. Purpose To directly measure the effects of quadriceps and hamstrings muscle loads on forces in the anterior cruciate ligaments and posterior cruciate ligaments. Study Design Controlled laboratory study. Methods Thirteen cadaveric knee specimens had load cells installed to record resultant forces in both anterior and posterior cruciate ligaments under 5 loading conditions. Cruciate force measurements were repeated with a 100-N load applied to the quadriceps tendon and again with a combined 50-N biceps load and 50-N semimembranosus-semitendinosus load. Results Applied quadriceps loads resulted in mean changes in anterior cruciate ligament and posterior cruciate ligament forces that were less than 20 N for all loading conditions. Hamstrings load significantly increased mean posterior cruciate ligament force between 30° and 105° of flexion with 100 N of applied posterior tibial force. Conclusions At the muscle force levels used in this study, the hamstrings were more effective than the quadriceps in altering cruciate force levels, especially near 90° of flexion, where they have an excellent mechanical advantage for controlling anterior-posterior tibial translation. Clinical Relevance Isolated hamstrings activity generally had little or no effect on anterior cruciate ligament forces but significantly increased forces in the posterior cruciate ligament beyond approximately 30° of flexion.

Anterior-Posterior and Rotatory Stability of Single and Double-Bundle Anterior Cruciate Ligament Reconstructions

BACKGROUND Some surgeons presently reconstruct both the anteromedial and posterolateral bundles of the anterior cruciate ligament. The purposes of this study were to measure the abilities of single-bundle and anatomic double-bundle reconstructions to restore anteroposterior laxities and rotational kinematics to intact knee levels and to compare graft forces in reconstructed knees with forces in the native anterior cruciate ligament for the same loading conditions. METHODS Native anterior cruciate ligament force and tibial rotations were recorded during passive knee extension tests with and without applied tibial loads. The anteromedial and posterolateral bundles were reconstructed with patellar tendon tissue sized to fit tightly within 7-mm femoral tunnels. Testing was repeated with the anteromedial graft alone (single bundle), tensioned to restore anteroposterior laxity at 30 degrees of flexion, and with double-bundle grafts. For double-bundle reconstructions, the anteromedial graft was first tensioned as above and then the posterolateral graft was tensioned with use of one of four protocols: posterolateral tension = anteromedial tension at 10 degrees (DB1), posterolateral tension = anteromedial tension at 30 degrees (DB2), posterolateral tension = (anteromedial tension + 30 N) at 10 degrees (DB3), and posterolateral tension = (anteromedial tension + 30 N) at 30 degrees (DB4). RESULTS The posterolateral graft underwent a greater length change than the anteromedial graft between 0 degrees and 90 degrees . This difference in elongation patterns produced high forces in the posterolateral graft at 0 degrees when both grafts were tensioned and fixed at 30 degrees . The mean laxities for single-bundle reconstructions were within 1.1 mm of those of the intact knee between 0 degrees and 90 degrees ; the mean graft force at 0 degrees was 76 N. The mean laxities for DB4 reconstructions were from 0.9 to 2.8 mm less than those of the intact knee, and the mean graft force at 0 degrees was 264 N. Coupled internal tibial rotations from valgus moment were normal with the single-bundle graft. Internal rotations from tibial torque were approximately 2 degrees to 4 degrees greater than normal with a single-bundle graft. DB3 and DB4 reconstructions overcorrected the coupled tibial rotations from valgus moment and restored tibial rotations from internal torque to normal from 0 degrees to 45 degrees . The graft forces from tibial torque and valgus moment were normal with the single-bundle graft. The mean double-bundle graft forces at 0 degrees were 57 N to 143 N and 34 N to 171 N greater than normal for internal torque and valgus moment, respectively. CONCLUSIONS The single-bundle reconstruction produced graft forces, knee laxities, and coupled tibial rotations that were closest to normal. Adding a posterolateral graft to an anteromedial graft tended to reduce laxities and tibial rotations, but the reductions were accompanied by markedly higher forces in the posterolateral graft near 0 degrees that occasionally caused it to fail during tests with internal torque or anterior tibial force.

A Biomechanical Comparison of Tibial Inlay and Tibial Tunnel Posterior Cruciate Ligament Reconstruction Techniques Graft Pretension and Knee Laxity

Background Most posterior cruciate ligament reconstruction techniques use a tibial bone tunnel, which results in an acute bend in the graft as it passes over the posterior portion of the tibial plateau. Hypothesis The tibial inlay technique will result in lower graft pretensions, less laxity, and less stretch-out after cyclic loading. Study Design Controlled laboratory study. Methods Graft pretensions necessary to restore normal laxity at 90° of knee flexion (laxity match pretension) and anteroposterior laxities at five knee flexion angles were recorded in 12 fresh-frozen knee specimens with bone-patellar tendon-bone posterior cruciate ligament graft reconstructions using both techniques and two femoral tunnel positions. Results When the graft was placed in a central femoral tunnel, the tibial tunnel reconstruction required an average 15.6 N greater laxity match pretension than the tibial inlay reconstruction. There were no significant differences in mean knee laxities between the tibial tunnel and tibial inlay techniques at any knee flexion angle; both reconstruction techniques restored mean knee laxity to within 1.6 mm of intact knee values over the entire flexion range. Conclusions There was no important advantage of one technique over the other with respect to the biomechanical parameters measured.

Quality of life assessment in elite collegiate athletes

The objectives of this study were to establish baseline Medical Outcomes Study Short Form Health Survey (SF-36) data for Division I collegiate athletes and to determine the effects of injury severity and training time. All participating athletes (N = 562) at a major university were evaluated with the SF-36. Regression analysis was performed to identify predictive factors. When the men without injury were compared with a previously established norm group, there was a significant increase in the role emotional score. In the women without injury there were significant increases in mental component summary, physical function, role emotional, mental health, and vitality scores when compared with the norm group. Serious injury was a predictor of lower scores in all domains, whereas minimal injury was predictive of lower physical component summary, role physical, bodily pain, social function, and general health scores. Increased training time was predictive of higher mental component summary, role physical, vitality, and general health scores. Elite collegiate athletes scored differently from previously established age-matched norms, and injury was a strong predictor of lower scores.