[Low-Carbon Metal-on-Metal Articulations for Hip Arthroplasties--Evaluation of Wear and Histology after 11 to 17 Years]. / Verschleißtechnische Analysen und histologische Befunde bei Low-Carbon-Metall-Metall-Artikulationen des Hüftgelenks nach 11 bis 17 Jahren.

BACKGROUND: High-carbon (HC) alloys for hip arthroplasties were preferred to low-carbon (LC) alloys for a long time because of their structurally hard carbide content. We opted for an LC alloy in 1994, because we expected it to be subject to less wear on account of its more homogeneous structure. Prompted by early complications not seen with ceramic-on-polyethylene mating surfaces, LC metal-on-metal articulations were, however, given up by us in early 1999. A series of implants retrieved after 11 to 17 years was now studied to establish the actual amount of wear. Potential tissue reactions associated with hypersensitivity were also evaluated histologically and correlated with the measured wear and the amount of metal particles in capsular tissue. PATIENTS AND METHODS: Ten patients with LC metal-on-metal hip implants were the subjects of analyses after a mean follow-up time of 13.9 years. They underwent revision surgery because of osteolysis, cup loosening without dislocation, late infection in 1 patient and pain. The implant positions at the time of retrieval were the same as on the postoperative radiographs. Wear was determined in keeping with ISO 14242-2 and by SEM. In addition, periprosthetic tissue including the joint capsule and interface membranes were obtained for histological analysis. The amount of metal particles and the extent of lymphocyte infiltration were determined with the method described by Willert et al. Tissue alterations were evaluated histologically for signs of ALVAL using the method of Campbell et al. and correlated with the amount of wear and metal particles. RESULTS: The mean maximum linear wear rate was found to be 1.6 (1.0-2.1) µm/year. Our data also showed a mean rate of 0.32 mm³/year (range, 0.22-0.47 mm³/year). This is equivalent to an annual metal release of 2.7 (1.9-3.9) mg/year. No corrosion or corrosion products were present on the ball heads and their taper. All mating surfaces studied by SEM showed signs of abrasion. Sporadically, additional abrasions in the submicrometer range were detected on the ball head surfaces. These were caused by corundum particles detached from the blasted implant surfaces and interpreted as third-body wear below the level of quantification. Signs of impingement were absent. Histologically, metal wear particles of variable amount were detected in all cases. In 4 of them solid corrosion products were present in the tissue. The ALVAL scores were 5 to 10 (moderate to high), but did not correlate with the measured wear and the amount of metal particles. CONCLUSION: The wear of LC articulations found after years of implant survival was very low. In fact, it was lower than the data reported for HC articulations and would permit implants to function for decades in engineering terms. However, their survival is limited by tissue alterations associated with hypersensitivity. These tissue alterations may contribute to implant loosening as also reported for HC articulations. They are apparently not related to the actual amount of wear and may reflect adaptive immunological processes.

[Bony ongrowth on the surface of HA-coated femoral implants: an x-ray analysis]. / Die Ausbildung von Knochengewebe an der Oberfläche von hydroxylapatitbeschichteten Prothesenschäften: eine radiologische Analyse.

BACKGROUND: To facilitate implant osseointegration in the early postoperative period, coating of the implant surfaces with osseoconductive materials, e.g. hydroxyapatite (HA), is being increasingly recommended. It apparently reduces the rate of radiolucent lines and even improves the osseointegration of implants less well suited for cementless anchorage. We analysed HA-coated stems to find out whether newly formed bone adherent to the implant surface such as seen on explanted stems is also seen on radiographs and whether it follows a specific morphological pattern. We also wanted to know whether newly formed peri-implant bone extends over the entire length of the HA-coating, at which point in time it is seen radiographically and whether it expands within the first few years post implantation by radiological evidence. PATIENTS AND METHOD: Radiographs of 40 unselected patients after primary total hip arthroplasty (THR), 14 males and 26 females, aged 44.4 to 86.7 years at the time of THR, with a mean age of 67.3 years were available for analysis. Monitor-guided a.-p. and axial views of the stems were obtained in the early postoperative period up to 6 weeks post THR, at a mean follow-up time of 1.3 (1.0 to 1.8) years and 3.0 (1.9 to 3.7) years. Tapered straight stems with a rectangular cross-section made of a wrought Ti6AI7Nb alloy with an HA coating in the proximal third were used. RESULTS: A.-p. views: At one year there were no signs suggesting an increased ongrowth of bone. At 3 years, on average, delicate bony appositions were seen on the implant surfaces in position 1 in three stems, in one of them also in position 7. These looked like a sclerotic zone lacking a sharp demarcation and were in direct contact with the implants without any bone-to-implant gaps. Axial views: At about one year two stems showed delicate bony appositions parallel to the implant surface in the proximal part in positions 8 and 9 as well as 13 and 14. Named "miniscleroses" by us, these structures were confined to the length of the HA coating. At three years these miniscleroses were clearly visible around 11 stems (more than 25 %). Those already seen at one year were much better defined at three years, but still confined to the HA-coated part of the stem. Some of them were poorly demarcated from the adjacent bone and medullary canal and some showed smooth demarcations. The density of the bony ongrowths was either homogeneous or increased from the medullary space or adjacent bone towards the implant surface. All of them were adherent to the implant surface. While not related to the peri-implant cortical bone, they were in contact with trabecular structures. After a mean follow-up time of one year radiolucent lines were seen around four stems in positions 1, 7 and 8. These were up to 1 mm in size around two stems and 2 mm or more in the other two. At 3 years all of the visible radiolucencies had disappeared except for one measuring 1 mm in position 8. CONCLUSIONS: The structures we found radiographically apparently reflect newly formed bone along the entire HA-coated implant surface. Most of them were located in positions 8, 9 and 13, 14. They provide visible evidence of osseointegration at osseoconductive surfaces. As they apparently did not have any contact with the peri-implant bone, they appear to be compatible with the bilateral osteogenesis according to Osborn. The effects of the rapid bony ongrowth on HA-coated surfaces and the striking absence of radiolucencies on the long-term outcome are still speculative. But the structures seen may be taken as a sign of improved implant stability by rapid osseointegration and of early sealing of the medullary canal. As a result, wear particles of the articulating surfaces are barred from spreading to the medullary cavity of the femur. This alone argues in favour of using coated implants throughout. However, more studies are needed to shed light on these issues.

Accuracy of navigation-assisted acetabular component positioning studied by computed tomography measurements: methods and results.

The postoperative position of the acetabular component is key for the outcome of total hip arthroplasty. Various aids have been developed to support the surgeon during implant placement. In a prospective study involving 4 centers, the computer-recorded cup alignment of 37 hip systems at the end of navigation-assisted surgery was compared with the cup angles measured on postoperative computerized tomograms. This comparison showed an average difference of 3.5 degrees (SD, 4.4 degrees ) for inclination and 6.5 degrees (SD, 7.3 degrees ) for anteversion angles. The differences in inclination correlated with the thickness of the soft tissue overlying the anterior superior iliac spine (r = 0.44; P = .007), whereas the differences in anteversion showed a correlation with the thickness of the soft tissue overlying the pubic tubercles (r = 0.52; P = .001). In centers experienced in the use of navigational tools, deviations were smaller than in units with little experience in their use.

[Bilateral hip joint replacement as a one-stage or two-stage procedure for dysplastic coxarthritis: a comparative analysis of 30 patients]. / Ein- und zweizeitiger bilateraler Hüftgelenksersatz bei Dysplasiecoxarthrosen: eine vergleichende Analyse von 30 Patienten.

AIM: Dysplastic coxarthritis usually occurs earlier than primary coxarthritis. As a rule dysplastic coxarthritis mostly affects young and active individuals. Bilateral coxarthritis may lead to severe impairment requiring surgical replacement of both hip joints, as the patients are frequently dissatisfied with the substitution of one joint alone. METHOD: In a retrospective study, 15 patients with bilateral hip dysplasia who had received total endoprostheses in both hip joints in a one-stage procedure (group A) were compared to 15 patients with bilateral dysplasia who had been operated on bilaterally in two stages (group B). Group B was subdivided into B1 (first side) and B2 (second side). All dysplasias were classified according to Hartofilakidis and Crowe. RESULTS: On the first postoperative day, group A experienced a mean drop of 33.9% in haemoglobin values, group B1 a mean drop of 25.1% and group B2 a mean drop of 26.3%. Patients of groups A/B1/B2 received on average 1.7/1.1/1.3 units of autologous blood and 1.2/0.1/0.3 units of foreign blood, respectively. Both groups experienced an improvement in their quality of life due to marked improvements in their Harris Hip Score and UCLA Score. Group A had no higher rate of complications. CONCLUSION: Although the single-stage procedure involved greater effort in terms of physiotherapy, patients preferred bilateral implantation of total hip endoprosthesis in a single surgical session because they needed to undergo the process of operation, mobilisation and rehabilitation only once.

Morphometric examination of straight, tapered titanium stems: a retrieval study.

Cementless straight, tapered rectangular cross section titanium stems have been used by the senior author since 1979. Thirty-four stems retrieved postmortem, after between 10 days and 15.2 years in situ, were studied morphometrically and histologically. Nineteen stems were first generation (1979-1986), with an incomplete sagittal taper and a mean surface roughness of 1 microm (Ra 1.23 +/- 0.3 microm); 15 stems were second generation after 1986, with a full biplane taper and a mean surface roughness of 4 microm (Ra 4.14 +/- 0.36 microm). Implant surface bony coverage was determined morphometrically in 10 segments of the stems, and expressed as a bone implant contact index. Histologically, there were no differences between implants with different levels of roughness. Morphometrically, the first-generation stems showed significant differences in coverage (distal > proximal); second-generation stems had a more uniform pattern. Stems retrieved early after arthroplasty had a mean bone implant contact index of 10%. The mean bone implant contact index showed attainment of maximum coverage by 5 years after arthroplasty, without additional apposition or loss thereafter. Patients younger than 65 years at arthroplasty had similar bone implant contact indices to patients 65 years or older; coverage in the six patients 80 years of age at retrieval did not differ from the rates in the other patients. Morphometry was able to provide objective evidence of design change effects. No differences in coverage were found in terms of times in situ, patient age at arthroplasty and at retrieval, and degree of stem surface roughness.

Are allergic reactions to skin clips associated with delayed wound healing?

BACKGROUND: Metal skin clips are used in surgery. They may contain metals that might cause allergic reactions and delayed wound healing. METHODS: The metal composition of 18 different surgical clamps was examined. The allergy status of 184 patients was determined by patch tests and was correlated with the clinical outcome of wound healing after application of skin clips. RESULTS: Skin clips contained chromium, nickel, molybdenum, cobalt, and titanium in concentrations high enough to cause allergic reactions. Eighteen percent of the men and 23% of the women were sensitive to nickel and 16% of the men to chromium. We found a positive correlation between the grade of nickel allergy and the reaction to the skin clips. CONCLUSIONS: Our study suggests that allergic reactions and delayed wound healing can be caused by the use of surgical skin clips. Therefore skin clips are not recommended for patients with a history of contact dermatitis to metals and/or atopy.

Short term prophylaxis against heterotopic bone after cementless hip replacement.

The aim of the current study was to reveal whether 7 days of indomethacin treatment sufficiently prevents heterotopic ossification after cementless total hip arthroplasty. One group received indomethacin for 14 days (n = 102), and the second for 7 days (n = 99) after cementless total hip arthroplasty. At followup 1 year postoperatively, the average Harris Hip Score was 91 points in the 14-day treatment group and 89 points in the 7-day treatment group. The incidence of heterotopic ossification as outlined by Brooker was similar in both groups. Ninety-six patients in the 14-day treatment group had heterotopic ossification Grades 0 or 1, and 6 patients had Grade II heterotopic ossification; whereas in the 7-day treatment group, 95 patients had Grades 0 or 1 heterotopic ossification and 4 patients had Grade II ossification. None of the patients had Grades III or IV heterotopic ossification. In the 14-day treatment group, headache, dizziness, or gastritic disorders develop in 10 patients, and in the 7-day treatment group, 7 patients had these effects. This study shows that treatment with 100 mg indomethacin daily for 7 days is not significantly different than 14 days of treatment for the prevention of formation of severe heterotopic ossification after cementless hip arthroplasty.

Musculus sartorius bicaudatus.

While dissecting 88 lower limbs, a distal division of the sartorius muscle was detected in one of the specimens. The larger posteromedial portion was found to take a normal course to the so-called superficial pes anserinus. The thinner anterolateral portion attached to the medial meniscus anteromedially. The smaller anterolateral part approached the medial meniscus anteromedially, pushing the synovial membrane into the joint. Its meniscal attachment ensures that the medial meniscus is stabilized in its primary position during bending and external rotation in the knee joint, thus preventing its herniation or injury during sudden extension. The accessory part of the sartorius muscle thus acts as a protector of the medial meniscus.

[Cement-free Zweymüller hip system. Results of a 5-year follow-up study]. / Das zementfreie Zweymüller Hüft-System. Ergebnisse einer 5-Jahres-Nachuntersuchung.

85 patients with 96 cementless pressfit hip implants were followed over a period of at least 5 years postoperatively. Average Harris score was 87.5 points. One socket had to be exchanged because of aseptic loosening. Additionally, 5 implants developed radiolucent lines, only one of them totally around the socket. In no case an exchange of the stem was necessary; one stem initially sank by 4 mm axially but was stable at the last follow-up investigation. Only one patient personally is dissatisfied with the outcome of the operation. In no case, implant specific complications such as breakage of the implant, breakage or crack of the stem, or shattering of the pelvic girdle by acetabular-screwing could be observed.

[Is high-density polyethylene suitable as an implant material in cement-free anchoring of hip endoprostheses? A histomorphologic study of an explanted polyethylene screw-in acetabula]. / Ist hochdichtes Polyäthylen als Implantatmaterial zur zementfreien Verankerung von Hüftendoprothesen geeignet? Eine histomorphologische Untersuchung an explantierten Polyäthylenschraubpfannen.

Firmly attached screw-in polyethylene acetabula which had been implanted for between 16 and 54 months were explanted after autopsies and subjected to macroscopic, radiologic and histologic examination. Metaplasias were seen around the threads and on the floor of the acetabulum. Their tendency to ossify represents an attempt at secondary stabilization. Due to the low stability of the polyethylene this causes increased wear on the floor of the acetabulum. The small defects in the polyethylene found in the threads, resembling damage done by mice, may be a sign of biodegradation. In view of the tissue reactions pointed out, the material stability of the polyethylene needs to be improved or implantation must be restricted to a very limited range of indications.

Biologic fixation of a press-fit titanium hip joint endoprosthesis.

The rectangular cross section of a straight-stem prosthesis makes a primary stable, rotation-safe fixation possible that is independent of the individual form of the femur. Due to the curvature of the femur, a three-dimensional large-area anchorage is achieved along the entire prosthesis length in the corticalis as well as in the spongiosa. The titanium-aluminum-niobium alloy is extremely biocompatible and enables the fast ongrowth of newly formed osseous tissue to act as secondary stabilization. Pathohistologic examinations on the prostheses of deceased patients show that this osseointegration leads to a complete osseous ingrowth of the implant. The average surface roughness of 3-5 microns, with which the entire prosthesis length is structured, supports this osseointegration. This microroughness is, therefore, totally sufficient for the primary and secondary stabilization of the implant. The osseous fixation of the prosthesis over the entire stem length guarantees a physiologic and functional load transmission to the surrounding femoral bone, thus avoiding stress shielding. The combination of a ceramic ball head with a polyethylene cup results in less wear than is the case with the customary metal-polyethylene combination and, thus, prolongs the life span of artificial hip joints. Good results in the future can only be expected in osseointegrated implants with minimal wear of the synthetic material.

[5- to 10-year results of an acetabulum with ceramic pegs for cement-free bone implantation. Material and analysis of design]. / 5-10-Jahresergebnisse mit einer Füsschenpfanne aus Keramik zur knochenzementfreien Implantation. Material und Designanalyse.

The authors report on the follow-up results of a hemispherical acetabular cup with small pegs, which is designed for cementless implantation in human beings. At an average time of 89 months after implantation, these results reveal a high percentage of 60% loosenings and seam formations of more than 2 mm which could constitute the basis for subsequent loosening. An analysis of these failures attributes the cause to material-engineering as well as design problems associated with the bone pathology. A ceramic cup of this shape is apparently unsuitable for osteointegration. It would appear that the design favours tilting movements and, due to its high E-module, it is unable to compensate for the relative movements of the pelvis.

[Computerized tomography analysis of cement-free total hip endoprostheses]. / Computertomographische Analyse zementfreier Hüfttotalendoprothesen.

16 patients with total hip endoprosthesis were investigated by high resolution computed tomography (CT) to analyse possible advantages of CT over conventional radiography. The quality of the examinations was good only in pure titanium systems: examinations of chromium-molybdenum alloys were severely deteriorated by strike artifacts. Positioning of implants is well defined in radiographs; CT provides better visualisation of the relation between implant and cortical bone. Evaluation of the contact of the shaft to the femoral corticalis is difficult in radiographs but facilitated in axial scans. Determination of relevance of CT analysis of total hip endoprosthesis remains subject to a future long-term follow-up study.

Reactions of surrounding tissue to the cementless hip implant Ti-6Al-4V after an implantation period of several years. Autopsy studies in three cases.

Three femoral endoprosthetic stems implanted without cement, made of Ti-6Al-4V alloy, with implantation periods of between 2 and 4 years were examined histologically in the form of undecalcified thin ground sections after having been split into segments and embedded in plastic. During the implantation period total osseointegration in the metadiaphyseal region takes place, while in the proximal area reaction forms with direct contact between metal and bone on the one hand and with an interposed membrane of connective tissue and adjacent secondary bony shell on the other must be distinguished. The osseointegration of the stem is the result of a primary healing of the bone and is due to the biocompatibility of the metal alloy and to the primary stability obtained by the press-fit method.

[Epicondylitis humeri radialis with special reference to the Wilhelm operation]. / Die Epicondylitis humeri radialis unter besonderer Berücksichtigung der Operation nach Wilhelm.

48 cases of epicondylitis humeroradialis were treated by means of an operation described by Wilhelm at the Orthopaedic Department of the University of Vienna between 1975 and 1979. They received a POP back slab for the upper arm for one week. Average time required to reach a pain-free state was three months (minimum two weeks, maximum six months). The follow-up examination at least five years later, taking clinical and subjective parameters into consideration, showed very good the satisfactory results in 93.2% and non-satisfactory results in the remaining 6.6% of cases.

[Analysis and results following replacement surgery of loose, cemented hip endoprostheses]. / Analyse und Ergebnisse nach Austauschoperation von gelockerten zementierten Hüftendoprothesen.

Between 1971 and May 1981 2380 Total Hip Replacements were performed at the Orthopedic Clinic of the University of Vienna. In 145 patients (6,1%) a revision arthroplasty had to be done, because of loosening of the prostheses. 10 of these patients had to be reoperated once more because of a second failure. All together 76% of the patients were either very or almost content with the result of the operation. Considering only patients with one revision arthroplasty we saw 87% good and very good results. The average hip movement was 93 degrees in flexion, 20 degrees in abduction and 24 degrees in adduction. They had a fairly good walking capacity and have not been reduced in their daily work. The revision arthroplasty of a loosened total hip replacement can be advised to the patients, even though the second operation is larger and of higher risk to the patients than the first one.

Tissue reactions to titanium endoprostheses. Autopsy studies in four cases.

Four cementless prosthetic hip implants of Ti-6Al-4V-alloy with and without longitudinal grooves and Al2O2 ceramic ball heads, with implant periods of 3, 4, 5, and 10 months, were sectioned and examined histologically in undecalcified thin ground sections. Especially on the medial and lateral sides of the prostheses, there was direct bone-to-metal contact without interposed connective tissue, spreading to the dorsal and ventral areas of the prosthesis shaft, which was considered osseointegration. This is based mainly on the technique of implantation with primary stability in the cortical bone by press-fit and on the bioinertness of the titanium alloy. Ungrooved prosthesis areas seem to favor bone growth at the shaft. The secondary bone ring, occurring on the dorsal and ventral areas of the prosthesis, with evidence of further bone remodeling with the passage of time, indicates that osseointegration is a dynamic process that continues to improve prosthetic stability.