Lars Linder

Cancellous impaction grafting in the human femur: Histological and radiographic observations in 6 autopsy femurs and 8 biopsies

6 whole postmortem femurs and 8 femoral biopsies were studied histologically, 3 months to 8 years after cancellous impaction grafting with a cemented stem for aseptic loosening. All stems were stable. Radiographs showed cortical healing in 5 cases, trabecular remodelling in 1, and trabecular incorporation in 9. There was a radiolucent line in 1 case. The histology varied. There was always a viable cortical shell around the grafted area. 1 patient showed complete bony restitution. The others still had varying amounts of remaining graft in the neo-medullary cavity, even after 8 years. The graft particles were usually embedded in dense fibrous tissue, thus forming a supporting composite tissue capable of carrying load. There was no time-dependent deterioration in the histological appearance. Radiographically, cortical healing and trabecular remodeling corresponded to viable bone. The lack of a radiolucent line said little about the viability of the tissue closest to the cement. The radiographs did not detect thin soft tissue membranes. Radiographic criteria used to assess primary total joint replacement do not necessarily apply to impaction grafting, and radiographic changes should be interpreted cautiously, especially as regards tissue viability.

Localized bone resorption in the femur in mechanical failure of cemented total hip arthroplasties.

In 70 total hip arthroplasties exchanged because of mechanical loosening of the stem prosthesis, localized bone resorption or scalloping was found in 33 cases. In 19 of the 33 cases the process started at the level of the tip of the stem, which in 15 cases was found to be in direct contact with cortical bone as observed in the radiographs obtained immediately after the primary surgery. In 37 failures without scalloping this metal-to-bone contact was less common. It is concluded that localized bone resorption may occur as a result of mechanical stress and in the absence of deep infection. It is also suggested that the phenomenon might be avoided by proper cementing technique and centering of the tip of the stem, perhaps with the help of a centering device.

Tibio-talocalcaneal arthrodesis as a primary proce dure using a retrograde intramedullary nail : A retrospective study of 26 patients with rheumatoid arthritis

Background Arthrodesis of the ankle joint using screws or external fixation is often a demanding procedure, notably in patients with rheumatoid arthritis. We investigated whether tibio-talocalcaneal arthrodesis with the use of an intramedullary nail is a safe and simple procedure. Patients and methods We retrospectively reviewed 25 ankles (25 patients) at median 3 (1–7) years after tibio-talocalcaneal arthrodesis because of rheumatoid arthritis. All had been operated on by retrograde insertion of a retrograde nail. 5 types of nail had been used. Complications, functional outcome scores, and patient satisfaction were determined and the radiographs evaluated for healing. Results All but 1 ankle had a radiographically healed arthrodesis. We recorded 3 deep infections, all healed—in 2 cases after extraction of the nail—and the arthrodesis healed in all 3 patients. The average functional scores at follow-up were high, considering that the patients suffered from rheumatoid arthritis. 23 patients were satisfied with the outcome. We found a correlation between the functional scores and the general activity of the disease expressed as a Health Assessment Questionnaire score. Interpretation In patients with rheumatoid arthritis, tibio-talocalcaneal arthrodesis with a retrograde intra-medullary nail results in a high rate of healing, a high rate of patient satisfaction, and relatively few complications.BACKGROUND Arthrodesis of the ankle joint using screws or external fixation is often a demanding procedure, notably in patients with rheumatoid arthritis. We investigated whether tibio-talocalcaneal arthrodesis with the use of an intramedullary nail is a safe and simple procedure. PATIENTS AND METHODS We retrospectively reviewed 25 ankles (25 patients) at median 3 (1-7) years after tibio-talocalcaneal arthrodesis because of rheumatoid arthritis. All had been operated on by retrograde insertion of a retrograde nail. 5 types of nail had been used. Complications, functional outcome scores, and patient satisfaction were determined and the radiographs evaluated for healing. RESULTS All but 1 ankle had a radiographically healed arthrodesis. We recorded 3 deep infections, all healed--in 2 cases after extraction of the nail--and the arthrodesis healed in all 3 patients. The average functional scores at follow-up were high, considering that the patients suffered from rheumatoid arthritis. 23 patients were satisfied with the outcome. We found a correlation between the functional scores and the general activity of the disease expressed as a Health Assessment Questionnaire score. INTERPRETATION In patients with rheumatoid arthritis, tibio-talocalcaneal arthrodesis with a retrograde intra-medullary nail results in a high rate of healing, a high rate of patient satisfaction, and relatively few complications.

Osseointegration of metallic implants: I. Light microscopy in the rabbit

Thirty-eight adult albino rabbits received one implant of pure titanium and one implant of another, test, material in each tibia. The test materials were titanium-aluminum-vanadium alloy, chrome-cobalt alloy, and stainless steel. Observation times were 4 months and 11 months. Light microscopy of the interface revealed a direct contact between bone and implant surface (osseointegration) in 73 of the 76 cases. The exceptions were two implants of pure titanium and one of stainless steel. Thus, given identical healing conditions, the modern implant metals were accepted by the bone in the same way. It is suggested that osseointegration should be regarded not as an exclusive reaction to a specific implant material, but as the expression of a nonspecific and basic healing potential in bone.

Tissue Reactin to Methyl Methacrylate Monomer: A Comparative Study in the Rabbit's Ear on the Toxicity of Methyl Methacrylate Monomer of Varying Composition

The aim of the present investigation was to evaluate if a bone cement monomer with a high concentration of accelerator (N,N-dimethyl-p-toluidine) is more toxic than a methyl methacrylate monomer, free from accelerator. 1) No difference in the acute local toxicity between CMW, Simplex-P and pure methyl methacrylate monomer was seen. 2) By gas chromatography. N,N-dimethyl-p-toluidine was shown to be water soluble to a small extent. Any bone cement monomer in current use can be fully dissolved in saline to a concentration of about 1 per cent.

Implant stability, histology, RSA and wear–more critical questions are needed: A view point

I discuss the radiostereometry (RSA) of prosthetic micromovement from clinical and histological viewpoints. Even in non-migrators there is a wide variety of interfaces with various resistances to trigger factors, such as mechanical forces and sequels of wear. I suggest that the various forms of bone resorption seen with conventional radiography are caused by such trigger factors and that their anatomical appearance is determined by the structure of the interface obtained at surgery.

High-resolution microscopy of the implant-tissue interface

A method is described which permits study of the interface of tissue and bulk implant at the light and electron microscopic level. It is based on epoxy embedding of implant and surrounding tissue with subsequent separation of implant and plastic. The separation takes place at the interface between tissue and implant; neither cells nor matrix are disturbed.

Hip revision using the Exeter stem, impacted morselized allograft bone and cement: A consecutive 5-year radiostereometric and radiographic study in 15 hips

Background Impaction grafting in hip revision surgery is widely used but studies with mid- and long-term follow-up are scarce.Patients, methods and results A 5-year radiostereometric (RSA) follow-up of 15 hip revisions with the Exeter stem, morselized impacted allograft bone and cement revealed that 3 stems had not migrated between 2 and 5 years after revision, 11 stems had migrated to a minor degree in at least 1 direction, and 1 stem was loose according to RSA but without any radiographic signs of loosening or pain. The pain score was comparable to primary arthroplasties.Interpretation From a 5-year perspective, first-time hip revisions for aseptic loosening with impacted morselized allograft bone and cement appear to yield good clinical results, although stem migration continues to a minor degree 2 years after revision.

Ultrastructure of the bone-cement and the bone-metal interface

A review is given of the methods used to demonstrate the bone-implant interface by transmission electron microscopy (TEM). Neither method is yet refined enough to permit demonstration without artifacts of the contact between implant, cells, and organic and inorganic matrix. Published studies on certain metallic implants and bone cement demonstrate a direct contact between bone matrix and implant, without a continuous interposed layer of cells. The 1000 nm closest to the implant surface show a variable structure, the interpretation of which is unknown. The degree of mineralization within this distance of the implant has not yet been adequately studied. Without completely reliable analytic methods and comparable implantation protocols, the gradation of implant biocompatibility, based on the TEM appearance of the interface, should be performed with great caution.

Microvascular Response to Locally Injected Collagenase: An Experimental Investigation in Hamsters and Rabbits

Collagenase was injected into the ears of rabbits and the cheek-pouches of hamsters. The acute and long-term microvascular effects were studied by vital microscopy and microangiography. The enzyme was injected at three different concentrations: 120 units/ml, 600 units/ml and 3,000 units/ml. The medium (600 units/ml) and high (3,000 units/ml) concentrations induced effects on the microcirculation such as blood flow impairment and microbleedings. The magnitude of these effects was related to the concentration of the enzyme. Generally, these microvascular effects were of low magnitude as compared with other substances tested using the same experimental models.