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Thirty-six consecutive total knee arthroplasties with hydroxyapatite (HA)-coated femoral components were prospectively followed up according to a standardised protocol for a mean period of 10 years (range, 7-11 years). Clinical and radiologic examination was performed at each follow-up evaluation. One patient (1 knee) was lost to follow up at 7 years, and 4 other patients (6 knees) died. Radiographs were studied for signs of loosening and presence of lucencies. Survival analysis was performed using a life table with revision as the criterion for failure. Two knees (1 patient) were revised because of aseptic loosening. The tibial component of one other knee was revised because of osteolysis in the medial tibial condyle. In the remaining knees, no radiologic evidence of loosening was seen. The survival of the femoral component at a mean follow-up time of 7 years, when 31.5 knees were at risk, was 94% with revision for femoral aseptic loosening as the end point. At 10 years, when 24 knees were at risk, the survival remained 94%.

The histologic findings from 2 total knee arthroplasties (TKAs) in 1 patient who died 5 years after surgery are reported. Cement was placed under the tibial and femoral metal backs but not around the stems. All components were securely fixed. "Reactive lines," present around the tips of the stems on radiography, were seen to contain thin, soft connective tissue without debris or macrophages. The histologic features of a reactive line are described., (Copyright 2003, Elsevier Science (USA). All rights reserved.)

The outcome at 10 years is reported of a prospective study of 2 cohorts of total knee arthroplasties treated with (center A) or without (center B) patellar replacement. The same tibiofemoral components were used in all knees. The cohorts were demographically similar. A total of 124 patellae were treated by replacement, and 143 were treated without replacement. The clinical outcome and the patellofemoral revision rates were the same in the 2 cohorts: 1 patient required analgesia for anterior knee pain after replacement, and 1 without replacement required patellar replacement for pain. In the replaced group, patellofemoral survival on a best-case scenario was 100% at 10 years; on a worst-case scenario, 96%. One of the unreplaced patellae had been resurfaced for pain by 10 years. In view of the satisfactory and similar outcomes with and without replacement, we suggest that an appropriate design for the prosthetic trochlea, rather than the replacement or otherwise of the patella, is the main determinant of patellofemoral outcome in total knee arthroplasty. Patella replacement may be optional. Desirable trochlea design features are described.

A total of 207 tibial components in total knee arthroplasty (TKA) have been reviewed at a maximum of 10 years after replacement. Twelve knees developed aseptic femoral loosening and were reviewed separately from the remaining 195. All tibial components were fixed with cement confined to the proximal surface of the implant combined with an uncemented stem. In the 195 TKAs with well-fixed femoral components and (presumably) low wear, 15% of tibiae developed early-onset, nonprogressive partial radiolucent lines (RLLs), typically in relation to preoperative sclerosis. Tibial component vertical migration was measured in 36 components: no migration was detected over the course of 5 years whether or not an RLL was present. There was no case of tibial osteolysis, no tibial component was revised for aseptic loosening, and no implant was radiologically loose. In 12 knees, the femoral component loosened with subsidence exposing peripheral bone that caused severe HDP wear. Tibial RLLs were present in 9, and osteolysis was present in 11 (although the tibial component was actually loose in only 1). This material has been used to study 1) the natural history of RLLs in cemented TKA and 2) the outcome of using cement confined to the proximal part of the tibial interface. We conclude that in low-wear prostheses RLLs are due to a failure to inject cement into sclerotic bone. Such lines are nonprogressive and do not affect fixation. In the presence of severe wear, however, they may provide a portal for the entry of debris into the interface causing progression of the RLL and lysis. Proximal cement plus an uncemented stem furnishes adequate tibial fixation, provided that the HDP wear rate is low.

We have prospectively studied 63 total knee replacements (TKR) in which the femoral component was polyacetal, and 138 TKRs in which the femoral component was conventional cobalt chrome. The tibial and patellar components were of ultrahigh molecular weight polyethylene (UHMWPE). Patients were followed-up for at least 10 years. In the polyacetal group, a number of patients have died or have been revised, for reasons unrelated to the presence of polyacetal. There were no instances of femoral component fracture, nor failure by wear. One postmortem specimen, retrieved at 9 years after surgery, showed no measurable polyacetal wear and negligible HDP wear. The histology of tissue in contact with polyacetal was indistinguishable from that adjacent to polymethyl methacrylate and UHMWPE in the same knee. We believe that polyacetal could be used for the femoral component of a TKR and that a further trial should be undertaken.

To obtain information about the bone scintigraphic appearance of a hydroxyapatite (HA)-coated proximal femoral implant, this examination was performed on 24 patients with a clinically and radiologically successful femoral implant in hip arthroplasty. The prosthesis had a proximal HA coating for supplementary fixation. The patients' mean age was 50.3 years (range, 28-65 years) at operation. The interval from the operation to the scintigraphy ranged from 6 months to 5.5 years (mean, 2.2 years). Scintigraphy was performed using 99mTc-medronic acid. Quantitative counts were recorded in 4 zones: 3 along the length of the implant (trochanteric region with HA coating, midprosthesis, and distal tip) and 1 below the prosthesis. The results were expressed as ratios using the nonoperated femur as a control value. The results demonstrated that the mean activities in all 4 zones were increased relative to the untreated side. The highest activity was observed in the region around the prosthetic tip, with an elevation of 46% above the control value. This activity showed a significant decline over time. The counts recorded in the trochanteric region, where the implant was coated with HA, were 20% above the control value and similar to those seen in its adjacent noncoated midprosthetic region. In the trochanteric region, however, the activity did not show a decline over the follow-up period.

In a prospective study the accuracy of a new radiographic method, Matched Indicators for Radiographic Assessment (MIRA), used to assess tibial component migration in total knee arthroplasty was evaluated. Radiopaque markers were placed in the tibial component and the tibial metaphysis in a standardized way so that four vertical distances could be measured on standard radiographs. Subsidence during the first postoperative year was measured both with this new method and with roentgen stereophotogrammetric analysis in 27 Freeman-Samuelson total knee arthroplasties. The error of measurement of MIRA was determined using the known error of roentgen stereophotogrammetric analysis. The new method was found to be promising with an accuracy of 1 mm, and the correlation between MIRA and roentgen stereophotogrammetric analysis was high when subsidence exceeded this value. Therefore, subsidence of clinical importance should be detected with MIRA. The method is simple and well suited for routine follow-up examination of large patient materials.

This report outlines an exposure to the hip using one curved skin incision, permitting retention of the femoral neck, and allowing access to both the anterior and posterior aspects of the hip, the whole of the proximal femur, and the circumference of the acetabulum. This approach is useful in revision surgery. The anterior abductors are mobilized using partial sharp release. A review of postoperative abductor function is presented, demonstrating satisfactory function after partial sharp release.

A canine implant study was performed to assess whether hydroxyapatite (HA) could induce bone to close gaps at the bone-prosthesis junction. Titanium alloy (TiAlV) plates with varying grooves cut into them (1, 2, and 3 mm deep) and identical on both sides were sprayed on one side with HA and left as bare metal on the other. These were then implanted into the distal femora of dogs that were killed 4 and 8 weeks afterwards. Specimens were analyzed using optical microscopy and microradiography. Results show that the presence of HA induces bone to grow almost completely down the deepest groove by 8 weeks. In the 1- and 2-mm grooves at 4 weeks the depth of penetration of bone into the grooves was greater on the HA coated side (but the actual volume of bone in the grooves was greater on the TiAlV side because the bone present was more dense). We conclude that the presence of HA induces bone to close relatively large gaps. Although bone does not grow all the way into uncoated defects there can be more bone here in the short term. This feature of HA may be of great value in hip implant fixation.

The results are presented of 92 double-cup arthroplasties modified in light of previously published experience. The review period lasted up to 7 years after operation. Eighty-six had a metal femoral component and six had a ceramic femoral component. Forty metal femoral cups were matched with a cemented acetabulum, while with 46 the acetabular implant was cementless. The overall revision rate for the metal femoral cups was 23.3%, and a further 31.8% demonstrated radiological signs suggestive of loosening. There was no difference between the cemented and uncemented cups in terms of revision rates or clinical results. The clinical results of those hips that have not yet loosened were excellent. A histological study showed that femoral lossening was associated with an erosive cellular response. Surface arthroplasty of the hip with current materials should be abandoned.

The authors report seven cases of unconstrained knee arthroplasty with excision of both cruciate ligaments, after previous patellectomy. Six of these seven cases were completely painfree and function was satisfactory in all cases. The reasons for previously reported pain and instability after total unconstrained knee arthroplasty with excision of the cruciate ligaments and a previous patellectomy are discussed.

Three methods of tibial component fixation without cement (as part of TKA) have been used at the London Hospital. All three methods have used the same polyethylene component fixed with two HDP (Day) pegs. A metal-back without a stem was added to the HDP in group 1. Group 2 consisted of an HDP-only component. In group 3 a stem was added to the metal-back used in group 1. Radiological comparison showed the fixation of the polyethylene component with metal back but no stem to be inadequate; the component tilted into varus more frequently than the other configurations. It is suggested that failure was due to the increased rigidity of the metal-backed component (as compared with the HDP only) and that the rigidity (and the resultant tendency to rock) can be offset by a stem. It is concluded that rigid (ie, metallic) tibial components should have a stem.

Radiological measurements of downward femoral component migration are reported for 203 hips in the first 2 years following total hip arthroplasty. The femora differed with respect to the retention of the femoral neck--in 167 it was retained and in 36 it was damaged--and to the use of cement--142 hips were press-fits and 61 were cemented. Multivariate analysis demonstrated that both retention of the neck and the use of cement retarded migration (ie, increased stability) of the femoral component (P = .0003 and .0037, respectively).

Some desirable design features of the patellofemoral joint in a total knee arthroplasty condylar prosthesis are proposed. These are that the femoral element should be grooved, have a high anterior flange, and be circular as viewed from the side. The groove should be about 5 mm deep and have relatively vertical walls. The patellar component should have a saddle-shaped articular surface matching the femur and should be countersunk into the patella. The components should be placed so as to position the joint automatically. Results with such a design are reported; loosening, wear, dislocation, and fracture have been rare. Osteolysis of the patella has not been seen after 9 years, so that the cementless press-fit fixation of an H.D.P. patellar prosthesis to date seems safe and efficacious.

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.

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.

The arguments for resection of the (anterior and) posterior cruciate ligament(s), as a step in total knee arthroplasty, are reviewed on the basis of the authors' personal experience and the work of others published in the literature.