An in vitro study of cartilage-meniscus tribology to understand the changes caused by a meniscus implant.

Active lifestyles increase the risk of meniscal injury. A permanent meniscus implant of polycarbonate urethane (PCU) is a promising treatment to postpone/prevent total knee arthroplasty. Study of the changes in articular cartilage tribology in the presence of PCU is essential in developing the optimum meniscus implant. Therefore, a cartilage-meniscus reciprocating, sliding model was developed in vitro, mimicking the stance and swing phases of the gait cycle. The meniscus was further replaced with PCU and surface-modified PCUs (with C18 chains, mono-functional polydimethylsiloxane groups and mono-functional polytetrafluoroethylene groups) to study the changes. The coefficient of friction (COF) was calculated, and cartilage wear was determined and quantified histologically. The cartilage-meniscus sliding resulted in low COF during both stance and swing (0.01< COF <0.12) and low wear of cartilage (scores <1). The cartilage-PCU sliding, during stance, revealed similar low COFs. But during swing, the COFs were high (average ∼1, maximum 1.6), indicating a breakdown in interstitial fluid pressurization lubrication and non-effective activation of the boundary lubrication. This may lead to wear of cartilage in long term. However, under the tested conditions the wear of cartilage against PCUs was not higher than its wear against meniscus, and the cartilage was occasionally damaged. The COF decreased with increasing the contact pressure (as-per a power equation) up to 1MPa. The changes in the surface modification of PCU did not affect PCU's tribological performance.

Focal knee resurfacing and effects of surgical precision on opposing cartilage. A pilot study on 12 sheep.

BACKGROUND: Full thickness cartilage lesions (ICRS grade 3-4) and focal lesions of degenerative origin may progress to osteoarthritis (OA). Such focal lesions can be treated by metallic implants. We hypothesized that such treatment results in opposing surface cartilage damage that correlates with implant position (height) relative to the adjacent cartilage surface. This relationship was investigated using a sheep animal model. METHODS: Both medial femoral condyles of 12 sheep were operated. The implants, were inserted in the weight-bearing surface at different heights relative to the surrounding cartilage. Euthanasia was performed at 6 or 12 weeks. After retrieval, implant height was analyzed using laser scanning. Damage to the opposing tibial cartilage was evaluated macroscopically and microscopically according to the modified Mankin score. RESULTS: Twenty-two knees were available for evaluation and showed cartilage lesions ranging from severe damage (Mankin stage 11) to almost pristine conditions (Mankin stage 1). There was a strong correlation between implant height and cartilage damage. Standard deviation from the aimed implant height was 0.47 mm. CONCLUSIONS: Our results showed significant surgical imprecision and protruding implants imposed severe cartilage damage. We therefore suggest implants should be placed recessed (approx. 0.5 mm) below the surrounding cartilage in this animal model. These results encourage further studies of metallic implants yet the utmost precision regarding position is required.

Cemented total knee replacement in 24 dogs: surgical technique, clinical results, and complications.

OBJECTIVE: To characterize the performance of cemented total knee replacement (TKR) in dogs. STUDY DESIGN: Preclinical research study. ANIMALS: Skeletally mature, male Hounds (25-30 kg; n=24) with no preexisting joint pathology. METHODS: Dogs had unilateral cemented TKR and were evaluated at 6, 12, 26, or 52 weeks (6 dogs/time point) by radiography, bone density analysis, visual gait assessment, and direct measurement of thigh circumference and stifle joint range of motion as indicators of functional recovery. At study end, the stability of the cemented tibial component was determined by destructive mechanical testing. RESULTS: Joint stability was excellent in 16 dogs (67%) and good in 8 dogs. None of the tibial components had evidence of migration or periprosthetic osteolysis whereas 1 femoral component was loose at 52 weeks. There was an early and significant decrease in tibial bone density, likely because of disuse of the operated limb. Dogs returned to full activity by 12 weeks. The tibial cement-bone interface maintained its strength over 52 weeks. CONCLUSIONS: Cement provides stable fixation of the tibial component in canine TKR. CLINICAL RELEVANCE: Cemented TKR yields adequate clinical function and stifle joint excursion in the dog. Clinical studies are needed to determine the long-term fate of cemented TKR implants, to assess the influence of implant design on implant fixation and wear, and to obtain objective functional data.

Canine total knee replacement: surgical technique and one-year outcome.

OBJECTIVE: To describe a surgical technique for total knee replacement (TKR) in dogs with severe osteoarthritis (OA) and report 1-year outcome. STUDY DESIGN: Prospective clinical case study. ANIMALS: Dogs (n=6) with severe stifle OA. METHODS: Preoperative and postoperative evaluations were compared after 6 dogs had TKR. Data gathered included radiographs, goniometric measures of passive range of motion, ground reaction forces, and girth measurements of the thigh before surgery and at 6 weeks, 3 months, 6 months, and 1 year. RESULTS: Stifle extension and excursion angles were significantly improved by 3 months after TKR. Mean peak vertical force and impulse were significantly improved by 6 months. CONCLUSIONS: TKR is a viable treatment option for dogs with severe stifle OA. CLINICAL RELEVANCE: With continued refinement of surgical technique, instrumentation, and implants, TKR could become a reliable treatment for dogs with disabling, painful nonseptic stifle OA.

[Viscosity determination of synovial fluids from the canine hip and elbow joint as well as the human knee joint]. / Ermittlung der Viskosität von Synovialflüssigkeiten aus dem caninen Ellenbogen- und Hüftgelenk sowie dem humanen Kniegelenk.

The development of pathological changes in both human and canine hip joints is mainly caused by a lack of synovial fluid lubrication. This results in an increased joint abrasion. Even after implantation of joint prosthesis, inadequate lubrication can lead to abrasion in the tribological pair. This can finally result in aseptic loosening of the prosthesis. In spite of the enormous number of studies that have been performed on human, only little knowledge about the tribological properties of the joints in dogs is available in the literature. For this reason the viscosities of synovial fluid, derived from physiological and pathologically changed canine elbow joints were measured. The viscosities were determined by the use of a cone-plate viscometer at different temperatures and shear rates. The obtained values were compared with the viscosity values of pathologically changed synovial fluids from human knee joints as well as with pathological samples from the canine hip joint. The results show that the viscosity values vary within a series of measurements and are inversely proportional to the temperature of the sample and the shear rate. The differences between the average viscosities of canine and human synovial fluids taken from pathologically changed joints are below 4% (22.5 s(-1) at theta1 = 25 degrees C). The findings of this study are being implemented in a FE-Model for the computation of actual forces in the hip joint during different movements. This would represent a contribution to an improved prosthetic treatment of canine and human hips.

Custom total knee replacement in a dog with femoral condylar bone loss.

OBJECTIVE: To report surgical planning, technique, and outcome of custom total knee replacement (TKR) performed to manage a medial femoral condylar nonunion in a dog. STUDY DESIGN: Clinical case report. ANIMAL: A 3-year-old, 20 kg Karelian Bear Hound. METHODS: Computed tomographic scan of the left pelvic limb was used to build a stereolithography model of the distal portion of the femur. The model was used to create a custom augment to replace the missing medial femoral condyle and a custom stem for intramedullary condylar cemented fixation. The augment and stem were adapted to femoral and tibial components already available. The model was used to rehearse the surgery and then the custom prosthesis was implanted. RESULTS: Weight bearing returned 8 hours after surgery and improved thereafter. Joint alignment was normal and prosthetic joint motion was 60-165 degrees postoperatively. The dog resumed moose hunting 3 months after surgery. Peak vertical force and impulse of the operated limb measured 17 months after surgery were 65% and 47% of the normal, contralateral limb. CONCLUSION: Based on short-term follow-up, cemented canine TKR was successfully achieved for management of a severely abnormal stifle joint. CLINICAL RELEVANCE: With further refinement and development of commercially available prostheses, TKR should be possible for canine patients.

Total joint replacement in the dog.

Total joint replacement has evolved over the past 50 years from a concept that was first attempted in people suffering from osteoarthritis to a commonly applied practice in veterinary medicine. Although many questions have been answered, several controversies still exist, with many implant and technical options being explored. Currently, total hip and elbow replacement are commercially available options viable for use in dogs. These options are detailed in this article. Joint replacement for other canine joints (ie, knee, hock, shoulder) that develop osteoarthritis likely will be developed in the near future.

Filamentous carbon fiber prosthesis for cranial cruciate ligament replacement in the dog--a pilot study.

Cranial cruciate ligament replacement by filamentous carbon fiber was studied in 4 dogs. Incomplete ligament formation occurred. The prosthesis did not cause any adverse gross or histologic reaction in the joints, but failed to induce complete ligament formation because of breakage.