Femoral neck retention in hip arthroplasty. A cadaver study of mechanical effects

The compression forces on the medial cortex of the femoral neck were measured in 6 cadaver specimens using pressure-sensitive film. A hip prosthesis was loaded in an Instron machine comparing the situation with retained versus resected neck. The results indicate that retaining the neck can be mechanically valuable.

The mechanical properties of cement and loosening of the femoral component of hip replacements

Mechanical and biomechanical testing of a new bone cement suggests that improved load transfer to the proximal femur could be achieved with the combination of a cement having a lower modulus, a greater ductility and a lower creep resistance than polymethylmethacrylate and a suitably shaped femoral component.

Presence of macrophages at the bone-cement interface of stable hip arthroplasty components

The bone cement interface of four clinically stable hip-joint prosthetic components was examined histologically for the presence of macrophages using routine staining and a histochemical technique for acid phosphatase. Macrophages were found in the absence of wear debris in all four cases. Because these cells are capable of bone resorption, their presence at a well-fixed interface must give cause for concern.

Resurfacing arthroplasty. Femoral head viability

Although obvious theoretic advantages accrue from resurfacing arthroplasty of the hip, the indications for the procedure are controversial because the failure rate is high and loosening is unacceptably frequent. To determine the role of osteonecrosis in these failures, the viability of bone within the femoral head was determined by histologic examination of bone inside 25 failed femoral resurfacing components. The bone was substantially alive throughout the femoral head in 23 of 25 cases (92%). In two cases, the bone of the femoral head was dead. Both of these hips had clinically failed because of femoral neck fracture. This histologic evaluation indicates that bone death is not an inevitable consequence of femoral head resurfacing and the use of polymethylmethacrylate fixation.

[Cementless fixation in endoprosthetics]

Prostheses have been fixed to the skeleton with polymethylmethacrylate for some 30 years. Many of these prostheses have failed with time, and failure has been blamed on the use of polymethylmethacrylate. Methods of fixing endoprostheses without cement have been developed in recent years. It is argued in this paper that the most important precondition for fixation is stable press-fit of the implant. Other methods of supplementary fixation, such as porous ingrowth, have been developed. However, there is little evidence to suggest that this ingrowth improves the immediate clinical result, if it occurs at all.

The relationship of neck orientation to the shape of the proximal femur

Neck angles and various dimensions measured from 70 normal cadaver femora and from clinical radiographs of 120 normal hips were analyzed. The neck-shaft angle and the inclination of the medial trabecular system varied over a range of approximately 35 degrees. The location of the femoral head center in relation to the femoral shaft and to the trochanters was related to neck orientation. As the neck became vertical, horizontal offset of the head center from the shaft decreased and its vertical level relative to that of the trochanter increased. The abductor muscle lever arm was measured with two methods. Values obtained when assuming that the joint resultant force follows the medial trabeculae demonstrated the closest relationship to the distance from head center to body midline. The normal shape of the proximal femur is variable, and variations in the absence of intrinsic bone disease appear to reflect adaptation to physiologic variations in the line of action of muscle forces.

Total prosthetic replacement of ankylosed knees

Total knee arthroplasty is reliable for achieving pain relief, increasing range of motion, maintaining stability, and improving walking ability. In this study, the results in knees with a preoperative range of motion of 0 were reviewed to determine whether an ankylosed knee can be replaced successfully. In eight of nine knees, the results with regard to pain, stability, and walking ability were good at follow-up evaluations greater than 2 years after operation. Range of motion was also improved in all knees but was still limited. Motion achieved was in a physiologic arc with all knees having full, or nearly full, extension.

British contribution to knee arthroplasty

British surgeons and engineers contributed various types of knee prostheses, including hinged, unconstrained, and semiconstrained prostheses, in the development of total knee arthroplasty. Methods of implant fixation, the place of stems, pegs, the use of special instrumentation, and alignment procedures ensure both intrinsic and extrinsic prosthetic stability.

Knee arthroplasty at the London Hospital. 1975-1984

In the past ten years, three related prostheses (Freeman-Swanson, ICLH, Freeman-Samuelson) have been used at the London Hospital. The new findings reported in this article are the result of cementless fixation of the ICLH prosthesis has not deteriorated with time; the patellofemoral complications and postoperative limitation of movement seen with the ICLH prosthesis has been resolved by the Freeman-Samuelson design; and cementless press-fit fixation of all three components of the Freeman-Samuelson design resulted in a 1.6% (tibial) revision rate in the first four years.

The management of infected total knee replacements

A review of patients with an infected resurfacing prosthesis is presented. Eight patients with a loose infected prosthesis were treated by a one-stage exchange arthroplasty; six others with a well-fixed infected prosthesis were treated by drainage and antibiotics. All eight treated by exchange arthroplasty remained free of infection as did five of those treated by drainage. In four of these last five patients, the prosthesis was inserted without cement; the possible role of polymethylmethacrylate in the persistence of infection is discussed.

Total ankle arthroplasty. A long-term review of the London Hospital experience

We report a retrospective study of 62 total ankle arthroplasties performed between 1972 and 1981. Forty-one of these have been reviewed clinically after an average follow-up of five and a half years; only 13 can be described as satisfactory. The complications encountered in all 62 arthroplasties are detailed, the most significant being superficial wound healing problems, talar collapse, and loosening of the components; 13 prosthetic joints have already been removed and arthrodesis attempted. The management of the complications is discussed. In view of the high complication rate and the generally poor long-term clinical results, we recommend arthrodesis as the treatment of choice for the painful stiff arthritic ankle, regardless of the underlying pathological process.

Cementless acetabular replacement using a pegged polyethylene prosthesis

Acetabular replacement without cement using three types of pegged polyethylene prostheses was begun as a prospective trial by Morscher (August 1977). Ring (June 1979), and Freeman (January 1980); 1878 hips have been replaced using this technique and are reviewed. Follow-up averaged 2 years (range: 6 months-6 years). Successful pain relief and satisfactory walking ability were present in 97% and adequate flexion in 90%. Radiographic review showed the consistent development of a stable, uniform sclerotic line adjacent to the prosthesis. No component migration could be documented. Ten hips have been revised for obvious femoral loosening, and two acetabula showed slight motion during revision for femoral failure and were revised. Deep infection (0.37%) occurred only in patients not receiving perioperative antibiotics and not operated upon in unidirectional filtered air-flow enclosures. Postmortem histological evaluation of eight hips showed a thin fibrous membrane separating the prosthesis from viable bone. These results are preliminary, but nevertheless at least as good as those in any large series of cemented acetabula with the same follow-up. The advantages of this technique are its reproducible results, low complication rate, limited invasion of the skeleton, and easy revision should failure occur.

Stemmed revision arthroplasty for aseptic loosening of total knee replacement

Fifty-three failed knee replacements were revised using minimally constrained implants with smooth uncemented intramedullary stems and metal-backed tibial components. Polymethylmethacrylate was used only to replace lost bone near the surface of the implant. Excluding four knees which had serious postoperative complications, 91% had successful relief of pain, 84% had over 90 degrees of movement and 80% could walk for more than 30 minutes. Review of the radiographs showed that there were no progressive lucencies at the interface between bone and cement, and no subsidence of components or changes in alignment. At the uncemented stem-to-bone interface, thin white lines developed near the metal, and their significance is discussed. This revision technique is an effective treatment for aseptic failure of primary total knee arthroplasty.

Freeman-Samuelson total arthroplasty of the knee

Experience with cementless fixation over the last six years indicates that the technique offers greater opportunities for bone conservation. Thus, when cement is used, and especially if it is forced into the skeleton under pressure, the amount of bone incorporated into the implant is considerable. Conversely, if no cement is used, grafting techniques to fill defects are becoming increasingly routine, so that today no bone may be removed from the replaced knee or hip--all fragments that are excised are repositioned as grafts in defects. Thus, cementless fixation meets the fundamental orthopedic maxim of the conservation of bone stock. Given that an implant can be fixed with satisfactory clinical results without cement and without bone ingrowth, it becomes difficult to demonstrate a clinical advantage for the latter. Nevertheless, bone ingrowth is possible both experimentally and (with less confidence) in man. Thus, it is clearly a technique that should be evaluated. However, it is not, in the senior author's view, a technique that should as yet be generally used. Hopefully, investigations of this problem will take place in a restrained scientific way rather than by the current method, which is in response to the dictates of fashion and commerce.

The composition of normal and osteoarthritic articular cartilage from human knee joints. With special reference to unicompartmental replacement and osteotomy of the knee

The articular cartilage from nineteen osteoarthritic and fourteen normal control adult human knee joints was analyzed for changes in water content, proteoglycan composition and structure, glycosaminoglycan synthesis rates, and cell content. We found no significant differences between visually intact cartilage from osteoarthritic knee joints and cartilage from control joints for any of the parameters studied. In osteoarthritic specimens in which the cartilage surface was not intact the biochemical changes depended on the degree of fibrillation. Surface-fibrillated specimens had a higher water content in the surface layers but no change in the content or synthesis rate of glycosaminoglycan. Deeply fibrillated cartilage, however, had an increased water content through its full depth, and there was a decrease in both the rate of synthesis and the content of glycosaminoglycans.

CLINICAL RELEVANCE

The results of this study suggest that degenerative changes in osteoarthritic knees are focal in origin and that corrective osteotomy or unicompartmental joint replacement might be rational procedures for knees in which the cartilage in all of one compartment is visually intact.

Revision of failed hip resurfacing

Resurfacing arthroplasty of the hip is a relatively recent innovation that has theoretic advantages in certain instances. One alleged advantage is "revisability." At the London Hospital 28 resurfaced hips that were converted to stemmed hip arthroplasties have been reviewed. Follow-up periods averaged 2.8 years (range, 1-9 years). Almost 90% of these hips were functioning satisfactorily at the time of review. The data suggest that the result of revising a resurfaced hip may be predictably better than that of revising a stemmed hip arthroplasty.

ICLH surface replacement of the hip. An analysis of the first 10 years

Clinical experience of the ICLH method of resurfacing the hip now spans 10 years. The first 36 arthroplasties, performed between 1972 and 1974, have been previously reported. This review covers in detail 204 such arthroplasties performed between 1975 and 1979 using a standard operative technique and prosthesis; these hips were consecutive and entirely unselected. Follow-up averaged 3.2 years (range two to six years). Successful hips are comparable to hips successfully replaced with stemmed prostheses. The rates of perioperative complications and failure due to infection, ectopic ossification, fracture of the femoral neck, and dislocation are favourably comparable to rates reported for stemmed total hip arthroplasties. The rate of aseptic loosening (17 per cent) greatly exceeded that found for stemmed total hip arthroplasties. Errors of patient selection, operative technique and prosthetic design have been identified. It is concluded that, although resurfacing arthroplasty of the hip may be an appealing procedure with theoretical advantages in certain instances, patient selection is essential, operative technique is demanding and changes in the design of the prosthesis are required. The procedure is still in evolution and therefore it should not yet be generally employed.

Why not resurface the patella?

The results of resurfacing or not resurfacing the articular cartilage of the patella were reviewed in 71 knees--47 with rheumatoid arthritis and 24 with osteoarthritis--which had been replaced with the ICLH prosthesis. Two rheumatoid and osteoporotic patellae developed transverse fractures with separation and were excluded from the review. The results showed that resurfacing the patella greatly reduced peripatellar pain with no counter-balancing disadvantage.

Implant arthroplasty in the adult hindfoot

In patients with mild to moderate valgus deformity and localized pain due to lateral impingement, the subtalar implant has been effective in controlling position and relieving localized pain. When used in conjunction with a talonavicular resurfacing prosthesis in the absence of talonavicular subluxation, the implant has been effective in relieving pain and maintaining the foot in a normal or nearly normal position. In feet with valgus deformity and talonavicular subluxation, both the subtalar implant and the talonavicular prosthesis with a built-in stop must be used. Use of these implants requires that the foot be supple and correctable to at least neutral position at surgery. The valgus hindfoot with a subluxated but otherwise normal talonavicular joint presents a greater problem. In this condition correction can be maintained only if the subtalar implant is used in conjunction with the modified talonavicular joint with a built-in stop. External supports in the shoe have not been routinely used in all patients after operation for a variety of reasons (mostly nonmedical). It may be advisable in patients who have had correction of a deformity to continue to use some sort of support in the shoe for most ambulation. Arthroplasty early in the disease course, before severe deformities develop, may prevent progression of the disorder, but more experience is necessary to validate clinical impressions.

Cementless fixation of prosthetic components in total arthroplasty of the knee and hip

An appropriately designed implant can be fixed without cement to accurately prepared bone surfaces so as to give results comparable with those of cemented fixation in the short term. The unchanging appearance of the roentgenograms suggests that these results may be maintained in the long term. If these conclusions are valid, polymethylmethacrylate (PMMA) may be thought of as an optional alternative in joint arthroplasty. Thus, theoretically, inert materials, e.g., carbon, can be directly interfaced with the skeleton. Since the authors have achieved interlock with viable bone without relying on bony ingrowth, these materials need not be porous. It is strongly suspected (but as yet unsupported by data) that adequate fixation can be obtained without relying even on the authors' relatively unsophisticated finned peg, provided that (1) the overall shape of the implant achieves interlock on the gross scale, with acceptably low shear stresses at the interface; and (2) the surgical technique achieves a correctly positioned implant applied to accurately cut bone surfaces. However, if for any reason accurate bone cuts can not be achieved, the authors advocate use of PMMA as a valuable fixation agent.

Replacement of the knee in rheumatoid arthritis using the Imperial College London Hospital prosthesis (ICLH) 1977-1979

The Imperial College London Hospital (ICLH) technique and prosthesis for the total replacement of the knee was evolved over the period 1968 to 1977. The results now reported were obtained at The London Hospital on rheumatoid knees operated upon in the period 1977 to 1979. These knees were reviewed and the results published with a one to 2 year follow-up in 1981. In the present paper this review has been extended to 3 to 5 years. We find that in successfully replaced knees the quality of the clinical result has remained unchanged over the extended period of review. Certain further complications have been encountered which are described. These complications have led us to the conclusion that whereas we previously accepted post-operative alignments between one and 10 degrees of valgus, we should now adjust these limits. We now regard a knee having anything less than 5 degrees of valgus post-operatively as having been incorrectly replaced. The limits of valgus can perhaps be extended to 15 degrees. Experience over the period 1977 to 1980 suggested the possibility of further improvements in both the operative technique and the prosthesis. Accordingly the ICLH prosthesis has now been modified. The modified prosthesis (the Freeman-Samuelson prosthesis) is described in this paper but results with it are not reported.