Tord Röstlund

Osseointegration of titanium implants.

Forty-eight screws, six double cylindrical implants and six T-plates were inserted into the tibia or femur of 6 dogs. Two titanium screws were inserted into the proximal tibia of 5 patients to anchor a titanium mould. The implants were removed en bloc with adjacent bone tissue after 3 to 14 months. They were sectioned using a technique that allowed analysis of the intact tissue-to-metal specimens. Osseointegration, defined as a direct bone-to-implant contact without interposed soft tissue, was confirmed in all screw-shaped implants while the cylindres had only partial bone contact as did the T-plates. We conclude that osseointegrated implants may be applicable in joint reconstruction for arthrosis or rheumatoid arthritis.

Implant fixation improved by close fit Cylindrical implant – bone interface studied in rabbits

Cylindric titanium implants of three different diameters were inserted and stabilized in a 3.7-mm burr hole in the rabbit tibia. The purpose of the study was to investigate the interfacial reaction to screw- and cylinder-shaped implants, and to determine if there is a critical gap at the insertion between bone and implant that prevents direct cortical bone apposition on the implant. The study indicated that this critical gap approached zero.

Wear of ion-implanted pure titanium against UHMWPE

Six specimens were manufactured from commercially pure titanium (grade IV) to resemble femoral head prostheses, and five of them ion implanted to increase the wear properties. Together with three cobalt-chrome controls they were run for one million cycles on a 10-station joint simulator. For the first time both the polymer and metallic wear were quantified in the same study. The purpose of the investigation was to estimate the potential for using commercially pure titanium as a bearing surface against ultrahigh-molecular-weight polyethylene for total joint application. It was concluded that the wear properties of titanium were improved by ion implantation, and that these positive effects could probably be enhanced with development of a better polishing technique, and by finding methods of extending the penetration depth of the nitrogen ions.

Denervation of the Wrist Joint - An Alternative in Conditions of Chronic Pain

Nine patients with chronic pain in the wrist secondary to lunatomalacia and non-union of the scaphoid bone were treated by denervation of the wrist joint. This operation was first presented by Wilhelm in 1966. We have been using a modified technique. The purpose of the operation is to achieve relief of pain by selective neurotomy without impairment of hand function and with preservation of wrist mobility. Eight patients were considerably improved; one was not helped at all. No appreciable progression of the pathological changes have occurred radiographically during the period of follow-up. We find our results encouraging and the method worth trying.

Morphometrical studies of human femoral condyles.

Thirty-six cadaver knees were examined by various morphometrical methods in order to obtain mathematical and graphical data concerning the geometry of the lower end of the femora. It was found that the paramedian sagittal curves represented magnifications of a certain curvature pattern specific to the medial and the lateral femoral condyle. These curves could be expressed mathematically for each condyle. Furthermore, we found dimensional as well as geometrical intervariations between the different size groups in the knee sample. This could serve as an argument for preferring a different design for medial and lateral condyle components in knee prostheses.

Stepwise introduction of a bone-conserving osseointegrated hip arthroplasty using RSA and a randomized study: I. Preliminary investigations—52 patients followed for 3 years

Background We developed a total hip system using osseointegration guidelines, a metaphyseal-loading proximal femoral replacement in the retained neck and a dual-geometry titanium shell in the acetabulum. Patients and methods A randomized controlled clinical trial was undertaken in 52 patients (53 hips), using the cemented Spectron stem and cementless Harris-Galante II cup as control implants (24 patients in experimental group, 29 control patients). Clinical measures of Harris Hip Score (HHS), pain score and radiostereometric analysis (RSA) at regular intervals for up to three years were used to monitor progress. Results No statistically significant differences were found in HHS and pain score; the stability of the cementless experimental implant was also comparable to that of the cemented controls by RSA. 3 revisions were required for migration in the experimental group and 1 was required for component dislocation in the control group. Interpretation Our findings indicate the practicality of osseointegration of titanium implants, but suggest that current performance is inadequate for clinical introduction. However, the stable fixation achieved in the retained neck in the majority of patients is indicative of osseointegration. This finding will encourage technical and design improvements for enhancement of clinical osseointegration and should also encourage further study. Periprosthetic osteolysis might be avoided by the establishment and maintenance of direct implant-bone connection: “osseointegration”.

Wear of Titanium 6–4 Alloy in Laboratory Tests and in Retrieved Human Joint Replacements

During the period from 1975 to 1985, a variety of joint replacement prostheses were introduced clinically that included a bearing surface of titanium-6% alumi-num-4% vanadium alloy (Ti-6A1-4V) articulating against an acetabular component of ultra-high molecular weight (UHMW) polyethylene. Hip prostheses included the STH, the DF-80, the Six Ti-28 and the Six Ti-32 (Zimmer, Inc. Warsaw, IN), the Stanmore (Zimmer GB), the ES-30 (Biomet, Inc., Warsaw, IN) and the APR (Intermedics, Inc., Austin, TX). Titanium alloy knee prostheses included the Miller/Galante (Zimmer) and the Natural Knee (Intermedics). The suitability of this combination of bearing materials was initially questioned because, in some laboratory wear tests, titanium alloy underwent severe abrasive-corrosive wear, characterized by extensive scoring of the metal surface and the release of large amounts of finely divided metallic particles that blackened the opposing polymer and the lubricant [1-8].

Evaluation of wear in an all-polymer total knee replacement. Part 1: Laboratory testing of polyethylene on polyacetal bearing surfaces

The friction and wear characteristics of a prototype, all-polymer hip prosthesis were evaluated using a multi-station hip-joint simulator. The components consisted of 41 mm diameter polyacetal copolymer balls in combination with acetabular cups of UHMW polyethylene, and were compared to the conventional combination of cobalt-chromium alloy balls against UHMW polyethylene cups. The all-polymer combination exhibited about 20% lower friction and 39% lower wear of the polyethylene cups. The total volume of polymer wear from the all-polymer combination (i.e. including the wear of the polyacetal ball) was 23% less than the volume of polyethylene wear from the metal-polymer components. The appearance of the worn surfaces of the polyethylene cups in the scanning electron microscope were similar for the two combinations of materials, and the surfaces of the polyacetal balls showed only mild wear. Formaldehyde, a product of the degradation of polyacetal, was present in traces in some samples of lubricant from the test chambers with polyacetal balls. In this laboratory model, the friction and wear properties of a polyacetal copolymer ball in combination with an UHMW polyethylene demonstrated good potential for clinical application.

MIS techniques in orthopedics

Minimally invasive technique in orthopedics is an evolving field and is gaining a great deal of interest among surgeons, and perhaps even more among patients. This concept started in the early 1990s when Repicci introduced the technique for unicompartmental knee replacement, where a significantly less invasive surgical procedure resulted in less postoperative morbidity and faster rehabilitation. Different techniques and modifications of instruments followed for the hip and for total knee replacements, and today most manufacturers offer these options. Now, Springer has released this book, MIS Techniques in Orthopedics, edited by three renowned surgeons in the field, in an attempt to introduce, summarize and evaluate the MIS technique. The result is a mixture of different procedures and the quality is quite variable. One of the main problems is the definition of what MIS really stands for. The fact that the skin incision is made a few centimetres shorter can hardly be the criterion that qualifies a surgical procedure as an MIS technique. Some of the chapters in this book have difficulties in recognizing this. The book covers, in four sections, the shoulder, the elbow, the hip and the knee. The MIS technique has already been used for the hip and knee for quite a while, and most interested surgeons are already familiar with the concept, whereas the MIS technique for the shoulder and elbow may be less well known. The fifth section covers computer-guided hip and knee surgery. The first section consists of 6 chapters, 4 on shoulder surgery and 2 on elbow surgery. The chapter on the Bankart procedure is a comprehensive description of shoulder instability, physical examination and surgical treatment. Except for the positioning and length of the skin incision, however, the MIS technique does not differ much from the standard procedure. Also, the description of MCL repair in the elbow is mainly a modification of a ligamentous repair, but is otherwise the same surgical procedure as before. This shows the difficulty of trying to define the difference between MIS and standard technique. The chapter on mini-open rotator cuff repair is well written. Percutaneous pinning of valgus impacted proximal four-part humeral fractures is also nicely presented and easy to follow. The most difficult step is the right fracture selection, and there will always be a possible need to invoke open surgery. Finally, the MIS technique for shoulder joint replacements is also discussed. One important indication for a smaller incision seems to be cosmetic, but at the same time replacement of the shoulder most often includes meticulous soft tissue release and balancing. These goals cannot easily be combined. This technique is still at the developmental stage and the clinical need for it still has to be proven. The section on hips describes mainly 4 approaches with the MIS technique. The surgical procedures are extremely detailed and may be useful to the experienced surgeon. One problem is the rapid advancement in this field; procedures are developed but go out of fashion quite quickly. The two-incision approach, for example, which has given excellent results in the hands of Berger, the master of this technique, has not been successful in the hands of others. Quite a number of complications have been encountered and the technique has been abandoned in most centers, at least in Europe. The anterior approach in the supine position, as originally described by Judet in 1947, is interesting to read from a historical point of view. It will probably not become a widely used technique, though, because of the unfamiliarity with the patient positioning and the need for a special, expensive operating table. The parts dealing with the knee consist of 5 chapters on unicondylar prostheses and 5 on total knee MIS techniques in orthopedics Giles R Scuderi, Alfred J Tria, Jr., Richard A Berger (editors), 438 pages, Springer Verlag 2006 ISBN 0-387-24210-4