Bone marrow mesenchymal stem cells in a hyaluronan scaffold for treatment of an osteochondral defect in a rabbit model

The purpose of this study was to evaluate the efficiency of using mesenchymal stem cells (MSC) in a hyaluronan scaffold for repair of an osteochondral defect in rabbit knee. Bone marrow was harvested from the posterior iliac crest in 11 New Zealand White rabbits. MSC were isolated and cultured in autologous serum for 28 days and transferred to a hyaluronan scaffold 24 h prior to implantation. A 4 mm diameter and 1.5 mm deep defect was created in the medial femoral condyle of both knees and the scaffold with MSC was implanted in one knee while an empty scaffold was implanted in the contra-lateral knee. After 24 weeks the rabbits were killed and histological sections were subjected to semiquantitative and quantitative evaluation by observers blinded regarding treatment modality. High degree of filling was obtained, but there was no statistically significant difference between the two treatments. However, there was a tendency for a better quality of repair in the MSC treated knees. No hypertrophy was observed by either method. MSC in a hyaluronan scaffold may be a promising treatment approach, but further studies are needed to determine the best combination of scaffold and cells.

Contralateral tendon rupture risk is increased in individuals with a previous Achilles tendon rupture

The purpose of this study was to examine the outcome after surgery for an acute Achilles tendon rupture. In particular, we wanted to study whether persons who have suffered an Achilles tendon rupture are at greater risk of a contralateral tendon rupture. From September 1990 to April 1997, 168 acute Achilles tendon ruptures in 26 women and 142 men were treated operatively. In August 1998 (median: 4.2 years post injury), 154 of these patients (92%) responded to a follow-up questionnaire. Local symptoms (pain, decreased strength and/or reduced range of motion) were reported pre injury by 25% of the patients; at follow-up this had increased to 52%. Ten patients (6%) experienced a rupture on the contralateral side during the follow-up period (OR: 176 [70-282] vs. the expected rate based on the general population risk of this injury, P<0.001). Thus, this study suggests that patients with an Achilles tendon rupture are at significantly increased risk of a contralateral tendon rupture, as well. Also, as many as half of the patients suffered from post-injury problems at long-term follow-up.

Effects of sectioning the posterolateral structures on knee kinematics and in situ forces in the posterior cruciate ligament

The objective of this study was to determine the effects of sectioning the posterolateral structures (PLS) on knee kinematics and in situ forces in the posterior cruciate ligament (PCL) in response to external and simulated muscle loads. Ten human cadaveric knees were tested using a robotic/universal force-moment sensor testing system. The knees were subjected to three loading conditions: (a) 134-N posterior tibial load, (b) 5-Nm external tibial torque, and (c) isolated hamstring load (40 N biceps/40 N semimembranosus). The knee kinematics and in situ forces in the PCL for the intact and PLS-deficient knee conditions were determined at full extension, 30 degrees, 60 degrees, 90 degrees, and 120 degrees of knee flexion. Under posterior tibial loading posterior tibial translation with PLS deficiency increased significantly at all flexion angles by 5.5+/-1.5 mm to 0.8+/-1.2 mm at full extension and 90 degrees, respectively. The corresponding in situ forces in the PCL increased by 17-19 N at full extension and 30 degrees of knee flexion. Under the external tibial torque, external tibial rotation increased significantly with PLS deficiency by 15.1+/-1.6 degrees at 30 degrees of flexion to 7.7+/-3.5 degrees at 90 degrees, with the in situ forces in the PCL increasing by 15-90 N. The largest increase occurred at 60 degrees to 120 degrees of knee flexion, representing forces two to six times of those in the intact knee. Under the simulated hamstring load, posterior tibial translation and external tibial and varus rotations also increased significantly at all knee flexion angles with PLS deficiency, but this was not so for the in situ forces in the PCL. Our data suggest that injuries to the PLS put the PCL and other soft tissue structures at increased risk of injury due to increased knee motion and the elevated in situ forces in the PCL.

In situ forces in the human posterior cruciate ligament in response to muscle loads: a cadaveric study

The objectives of this study were to determine the effects of hamstrings and quadriceps muscle loads on knee kinematics and in situ forces in the posterior cruciate ligament of the knee and to evaluate how the effects of these muscle loads change with knee flexion. Nine human cadaveric knees were studied with a robotic manipulator/universal force-moment sensor testing system. The knees were subjected to an isolated hamstrings load (40 N to both the biceps and the semimembranosus), a combined hamstrings and quadriceps load (the hamstrings load and a 200-N quadriceps load), and an isolated quadriceps load of 200 N. Each load was applied with the knee at full extension and at 30, 60, 90, and 120 degrees of flexion. Without muscle loads, in situ forces in the posterior cruciate ligament were small, ranging from 6+/-5 N at 30 degrees of flexion to 15+/-3 N at 90 degrees. Under an isolated hamstrings load, the in situ force in the posterior cruciate ligament increased significantly throughout all angles of knee flexion, from 13+/-6 N at full extension to 86+/-19 N at 90 degrees. A posterior tibial translation ranging from 1.3+/-0.6 to 2.5+/-0.5 mm was also observed from full extension to 30 degrees of flexion under the hamstrings load. With a combined hamstrings and quadriceps load, tibial translation was 2.2+/-0.7 mm posteriorly at 120 degrees of flexion ut was as high as 4.6+/-1.7 mm anteriorly at 30 degrees. The in situ force in the posterior cruciate ligament decreased significantly under this loading condition compared with under an isolated hamstrings load, ranging from 6+/-7 to 58+/-13 N from 30 to 120 degrees of flexion. With an isolated quadriceps load of 200 N, the in situ forces in the posterior cruciate ligament ranged from 4+/-3 N at 60 degrees of flexion to 34+/-12 N at 120 degrees. Our findings support the notion that, compared with an isolated hamstrings load, combined hamstrings and quadriceps loads significantly reduce the in situ force in the posterior cruciate ligament. These data are in direct contrast to those for the anterior cruciate ligament. Furthermore, we have demonstrated that the effects of muscle loads depend significantly on the angle of knee flexion.

[Ankle arthroscopy--indications, findings and results]

Thirty-six consecutive ankle arthroscopies from 1991 to 1996 were reviewed. Indications for arthroscopy were loose bodies, osteochondritis dissecans, and post traumatic and degenerative ankle joints. Thirty patients were re-examined 5-60 months postoperatively (median follow-up 12 months). Among twelve patients with an ankle fracture, a loose body was arthroscopically removed from eight patients while the remaining four patients were treated with local synovectomy. Of these twelve patients, nine had no symptoms at follow-up. Of eight patients with initial ankle sprain, four had no symptoms after removal of soft tissue lesions. Of five patients with osteochondritis dissecans treated by drilling through the fragment into the subchondral bone or, alternatively, removal of small pieces, two had no symptoms at follow-up. Five patients with degenerative joint disease had no improvement after arthroscopical debridement. Ankle arthroscopy seems to provide an effective treatment of loose bodies and soft tissue impingement, but the results are not convincing in osteochondritis dissecans and are poor in degenerative ankle joint disease.

Intermittent sub-ambient interstitial hydrostatic pressure as a potential mechanical stimulator for chondrocyte metabolism

OBJECTIVE

Experimental findings have suggested that the metabolic activities of articular cartilage can be influenced by mechanical stimuli. Our mathematical analysis predicted that cyclic compressive loading may create periods of intermittent sub-ambient hydrostatic pressure within the cartilage extracellular matrix. Based on this mathematical analysis, the present study was aimed to investigate whether the intermittent sub-ambient hydrostatic pressure, created in the cartilage extracellular matrix during cyclic compression, has a stimulative effect on the biosynthesis of chondrocytes.

METHOD

In order to test this hypothesis, the present study developed a custom-designed sub-ambient pressure generator to subject a monolayer culture of chondrocytes to an intermittent sub-ambient pressure. Using this pressure generator, the monolayer chondrocyte culture system was analyzed for 35S-sulfate and 3H-proline incorporation rates for biosynthesis of proteoglycan and collagenous/noncollagenous protein molecules, respectively. Northern analyses for aggrecan and type II collagen mRNAs were also performed.

RESULTS

It was found that the intermittent sub-ambient pressure produced a 40% increase in proteoglycan and a 17% increase in non-collagenous protein synthesis during the pressurization period (P < 0.05). The collagenous protein synthesis was not affected by the intermittent sub-ambient pressure regimen used in this study. After the intermittent sub-ambient pressurization, the metabolic activities of the chondrocytes returned to normal (control level). The intermittent sub-ambient pressure also produced an increase in the mRNA signals for aggrecan. Therefore, we conclude that intermittent sub-ambient pressure may be one of the potential mechanical stimulators of chondrocytes in articular cartilage during dynamic compression.

[Primary suture of the posterior cruciate ligament]

23 acute midsubstance ruptures of the posterior cruciate ligament were treated by primary suture. 20 patients returned for follow-up. Four of them had an isolated rupture of the PCL. The remaining 16 patients had sustained combined injuries to ligaments, including eight total ruptures of the anterior cruciate ligament. All ruptured ligaments were sutured. At follow-up (median = 5.5, range 3-10 years) median knee score according to Lysholm was 81 (range 53-100). Five were rated excellent, six good, three fair and six poor. KT-1000 arthrometer measurements revealed a posterior instability of between 5 and 10 mm in five patients and below 5 mm in 14 patients. Thus, in most patients, some instability remained in spite of operative treatment.