A cryo-jaw designed for in vitro tensile testing of the healing Achilles tendons in rats.

We present a simple but very secure non-compressive clamping device for in vitro tensile testing of the Achilles tendon in rats. Biomechanical studies were performed on 178 native and injured specimens without any registration of slippage out of the clamp. The average tensile strength of the native rat Achilles tendon was determined to be 48 N (+/-11 N) and its displacement to failure averaged 0.8 mm (+/-0.2 mm). The mean values for tensile strength within the injured tendons increased with time and were above the native tendon values from week 2 and later. Correspondingly, the displacement to failure decreased with time.

Comparison of cobalt chromium, ceramic and pyrocarbon hemiprosthesis in a rabbit model: Ceramic leads to more cartilage damage than cobalt chromium.

Cartilage wear after hemiarthroplasty remains a problem in orthopedic surgery. The main cause of cartilage wear, apart from incongruency of the joint partners, is generally considered to be the tribology of the material surfaces. This study evaluates in 27 rabbits the degree of cartilage wear of the tibia plateau after hemiarthroplasty with proximal interphalangeal prostheses made of three different materials [cobalt chromium (CoCr), pyrocarbon (PyCa), and ceramic (Cer)]. Three months after hemiarthroplasty, the articulating tibial cartilage was histomorphologically examined and degenerative damage was graded using the modified Mankin score. The mechanical capacity of the cartilage was assessed by stress relaxation testing. The biomechanical properties of the cartilage were significantly superior in the CoCr group as compared with the Cer group (p < 0.03), indicating less damage to the articulating cartilage surface. The Mankin score showed significantly lower values in the CoCr compared with Cer group (p = 0.011), whereas no differences were found between PyCa and CoCr or PyCa and Cer. In contrast to earlier reports, in this hemiarthroplasty model, the CoCr alloy showed less cartilage damage than a ceramic surface. Further, in vivo experiments are necessary to elucidate the controversial issue of the most suitable material for hemiarthroplasty.

Osseointegration and mechanical stability of pyrocarbon and titanium hand implants in a load-bearing in vivo model for small joint arthroplasty.

PURPOSE: To test the mechanical stability and histologic osseointegration under load-bearing conditions of 2 different materials, pyrocarbon (Py) and titanium (Ti), in a rabbit model. METHODS: Proximal interphalangeal implants (9 Ti, 8 Py) were placed into rabbit knees and the animals were killed after 3 months. Subsidence was assessed by monthly x-rays. Mechanical stability was measured with a nondestructive pullout test. Implant osseointegration was evaluated by an analysis of the relative implant-calcified bone contact surface on microradiographs and by a histomorphometric analysis of the percentage of bone and connective tissue contact with the implant surface. Histologic examination included assessment of bone apposition on the basis of fluorochromes. RESULTS: Subsidence was found in all 8 Py implants but in none of the Ti group. All 9 Ti implants were mechanically stable; all 8 Py implants were loose. A significantly higher implant-bone contact was found for the Ti group compared with the Py group. Bone apposition increased with time and was highest for the Ti implants 6 weeks after implantation. CONCLUSIONS: In the rabbit model osseointegration of implants was highly dependent on the material. A reliable osseointegration was found for Ti implants. For Py implants no osseointegration or implant stability was achieved. For use of small joints of the hand we therefore recommend Ti-based implants.

Adenovirus-mediated gene transfer of growth and differentiation factor-5 into tenocytes and the healing rat Achilles tendon.

Growth and differentiation factor-5 (GDF-5) is known to induce tendon tissue and stimulate tendon healing. The hypothesis was that adenoviral GDF-5 transfer leads to transitory transgene expression and improves Achilles tendon healing. In vitro experiments were first performed with rat tenocytes. Transgene expression was evaluated by RT-PCR, Western blotting and GDF-5-ELISA. In vivo virus dosage and transgene expression were examined by a marker gene transfer (LacZ and luciferase). In the main experiment in 131 rats, adenovirus particles (3 x 10(10)) were injected into transected Achilles tendons. The time course of GDF-5 mRNA expression was assessed by real-time RT-PCR. Histology and biomechanical testing were used to evaluate tendon healing and tensile strength. In vitro GDF-5 was secreted with a maximum after 2 weeks (330 ng GDF-5/10(6) cells per 24 hr). In vivo GDF-5 transgene expression showed a maximum at 4 weeks. At 8 weeks, GDF-5 specimens were thicker (p<0.05) with a trend to higher strength (p=0,064). Histology showed greater cartilage formation in type II collagen stains than in controls. Injection of adenovirus particles successfully can deliver the GDF-5 gene in healing tendons and leads to thicker tendon regenerates after 8 weeks. This technique might become a new approach for nonsurgical treatment of tendon injuries.

Vascularized os pisiform for reinforcement of the lunate in Kienböck's Disease: an average of 12 years of follow-up study.

PURPOSE: Little is known about the long-term results of vascularized bone transplantation for Kienböck's disease. This retrospective study investigated the long-term results of vascularized pisiform transfer. METHODS: We reviewed 23 patients to analyze results after vascularized pisiform transposition to a cored-out lunate for Lichtman stages II and III. Patients with ulnar-minus variance received additional radial shortening. RESULTS: Pain improved in 20 of 23 patients. Range of motion increased significantly relative to preoperative values but was only 80% that of opposite side. Grip power was 84% of the contralateral hand. At follow-up evaluation the mean Disabilities of the Arm, Shoulder, and Hand questionnaire score was 15.3 +/- 17.9 and the mean Cooney score was 82.4 +/- 10.0. Radiologically, out of 20 patients with preoperative x-rays Lichtman stage was unchanged in 11, improved in 3, and progressed in 6 patients. No patient showed radiologic signs of arthritis before surgery. At follow-up evaluation osteoarthritis was found in 7 of 22 patients. The majority of degenerative changes were of low grade and were seen at the radiocarpal joint. CONCLUSIONS: The results show high patient satisfaction and good function after vascularized bone transplantation for Kienböck's disease. In the long term vascularized pisiform transfer prevented lunate collapse in 16 of 22 patients.

Occurrence of carpal osteoarthritis after treatment of scaphoid nonunion with bone graft and herbert screw: a long-term follow-up study.

PURPOSE: To determine the occurrence, progression, and clinical results of osteoarthritis (OA) after bone grafting and Herbert screw fixation for scaphoid nonunion. METHODS: Fifty patients were reviewed (mean follow-up period, 12.0 +/- 1.6 y) to analyze degenerative changes of the wrist after use of Herbert screws for scaphoid nonunion. RESULTS: Radiologic signs of OA were observed in 15 of 50 patients before surgery and in 23 of 50 after 10 years or more. The majority of degenerative changes were low grade. No OA at follow-up evaluation was seen in 27 of 35 patients with no preoperative degenerative changes. In 6 of 8 patients with OA its occurrence was either subsequent to concomitant injury, occurred after incorrect scaphoid reconstruction, or was caused by persistent nonunion. Of 15 wrists with OA at the time of surgery 9 remained unchanged and 6 increased in severity. Healing of nonunion was achieved in 42 of 50. Range of motion, however, was reduced to 88% of that of the opposite hand. At follow-up evaluation the mean Disabilities of the Arm, Shoulder, and Hand score was 9 +/- 13 and the mean Cooney score was 80 +/- 10. CONCLUSIONS: The results show high patient satisfaction and good function after healing of scaphoid nonunion. In the long term correct anatomic reconstruction of the nonarthritic carpus with a Herbert screw prevents onset of OA in most patients.

Lunate resection and vascularized Os pisiform transfer in Kienböck's Disease: an average of 10 years of follow-up study after Saffar's procedure.

PURPOSE: To investigate the long-term results of lunate replacement by vascularized bone transfer in advanced Kienböck's disease. METHODS: Twenty-one patients were reviewed (mean follow-up period +/- SD, 9.9 +/- 3.5 y) to analyze results after lunate replacement by vascularized pisiform transposition (Saffar's procedure) for Lichtman stages III and IV. RESULTS: Pain was improved in 16 of 21 patients but range of motion did not improve after surgery. Range of motion was reduced to 68% and grip power to 80% of that of the opposite hand. At follow-up evaluation the mean score on the Disabilities of the Arm, Shoulder, and Hand Questionnaire was 22.3 +/- 17.9 and the mean Cooney score was 75.4 +/- 13.2. Radiologically, Lichtman stage persisted in 8, improved in 1, progressed in 8, and could not be evaluated in 3 patients. Two patients had radiologic signs of arthritis before surgery. At follow-up examination osteoarthritis was found in 50% of patients. The majority of degenerative changes were associated with carpal collapse. CONCLUSIONS: The replacement of the lunate by vascularized pisiform transposition maintained preoperative ranges of motion. At follow-up examination both patient satisfaction and wrist function were high. In the long term, however, Saffar's procedure can restore alignment of the carpus only partly and also results in osteoarthritis in half of all patients.