Richard D. Mulroy

The effect of improved cementing techniques on component loosening in total hip replacement. An 11-year radiographic review

Improved cementing techniques have been shown to decrease the rate of aseptic loosening of femoral components of cemented total hip replacements at five to seven years. We now report our results in 105 hips in 93 patients at 10 to 12.7 years (mean 11.2). The improved techniques included use of a medullary plug, a cement gun, a doughy mix of Simplex P and a collared stem of chrome cobalt. Only three femoral components had definitely loosened, none were probably loose and 24 were graded as possibly loose. In contrast, the incidence of radiographic loosening on the acetabular side was 42%. Improved cementing techniques have produced a marked reduction in the rate of aseptic loosening of the femoral component, but the incidence of acetabular loosening is unchanged.

Failure of acetabular autogenous grafts in total hip arthroplasty. Increasing incidence: a follow-up note.

We reported previously on the application of an autogenous femoral-head graft to the acetabulum during total hip arthroplasty for compensation of marked osseous deficiency in patients who had arthritis secondary to severe congenital dysplasia or dislocation of the hip. An average of seven years postoperatively, the graft seemed to have been a successful adjunct to the arthroplasty. Five years later, to assess our long-term results, we reviewed the findings in the same forty-six hips (thirty-seven patients) that we had studied previously. An average of 11.8 years after the total replacement and use of the autogenous femoral-head graft, nine hips (20 per cent) needed a second operation because the acetabular fixation had failed. Two had had a resection arthroplasty and seven, a complex revision. In one additional hip, a resection arthroplasty was done for infection that had developed after operative reattachment of the greater trochanter. In twelve of the remaining thirty-six hips, there was definite radiographic evidence of acetabular loosening. Thus, the total incidence of loosening of the acetabular component was 46 per cent (twenty-one hips). The average time from the index operation to the first definite radiographic evidence that the fixation had failed was 6.4 years (range, 2.9 to 12.7 years). While we recognize that application of a bulk autogenous graft to the acetabulum is useful when the acetabular bone stock is extremely deficient, we no longer recommend the use of bulk corticocancellous autogenous grafts in other situations.

The histology of the radiolucent line

The radiographic and histological features of radiolucent areas at the cement-bone interface were correlated in 15 specimens retrieved at post-mortem from patients who had undergone cemented total hip arthroplasty, two weeks to 15 years prior to death. All but one of the components were securely fixed, as demonstrated by direct measurements of micromotion. Extensive radiolucencies were present in all but one case. In 11 of the 14 specimens with radiolucencies, histological examination showed that the radiolucent areas represented regions of osteoporosis and bone remodelling. The remodelling changes were characterised by osteoporosis, cancellisation and thinning of the endosteal cortex, and osteopenia of the trabecular bone. In two specimens the appearance of radiolucency was found to be due to fibrous tissue at the cement-bone interface and in one specimen there was a mixed picture of osteolysis and fibrosis. The study demonstrates that radiolucent lines can occur with well-fixed components and that they may commonly represent osteoporosis rather than the presence of a fibrous membrane at the cement-bone interface.

Intraoperative measurement of rotational stability of femoral components of total hip arthroplasty

High out-of-plane forces acting on the hip joint can produce important rotational micromotion of the femoral component. This micromotion at the prosthesis interface may be detrimental to the stability of the implant. In cementless femoral implants this could prevent bone ingrowth, and in the cemented component this could cause generation of particulate debris, lysis, and loosening. The introduction of the torque wrench micrometer for assessment of intraoperative femoral component stability can quantify the initial stability of primary cementless femoral components and critically evaluate the stability (at either the initial or revision arthroplasty) of both cemented and cementless femoral components. It allows the surgeon to produce a known torque in the direction and magnitude of the out-of-plane forces that load the hip in vivo.

Iatrogenic Disease in General Practice: Its Incidence and Effects

A years survey of iatrogenic disease in general practice showed that one consultation in every 40 was the result of iatrogenic disease. Iatrogenic disease may affect the doctor/patient relationship, often leading the doctor to feel guilty or the patient to become aggressive.

Prophylaxis for heterotopic bone formation after total hip arthroplasty using low-dose radiation in high-risk patients.

Fifteen consecutive total hip arthroplasties (THAs) in 14 patients considered at risk for developing significant heterotopic ossification (HO) were treated postoperatively with 7.5 Gy of external beam radiation in three fractions. Eight hips in eight of the patients (Group I) had developed previous Brooker Class III or IV HO after THA and were radiated after having excision of HO in conjunction with a revision THA. Three additional hips in three patients (Group II) were radiated after primary THA, because they developed significant HO on the contralateral hip after a previous THA. The remaining four hips in three patients (Group III) were radiated after primary THA because they had bilateral hypertrophic arthritis. Precision shielding was employed to minimize the volume of tissue in the radiation field and to protect the bone-implant interface around porous-coated components and the trochanteric osteotomy sites. Of the eight hips in which Class III or IV bone was excised during revision THA (Group I), no new bone formed in five hips and in the other three hips, only Class I bone formed. No heterotopic bone formed in the remaining seven hips of Groups II and III. All six trochanteric osteotomies healed. There were no wound healing problems. There were no significant radiolucencies around any of the components and there was no radiographic evidence of implant instability. This regimen using 7.5 Gy over three fractions minimizes the radiobiologic impact, whereas the use of precision shielding minimizes the total volume of tissue treated. This regimen is an effective means of preventing significant HO after THA in high-risk patients while minimizing radiation exposure.

Bone ingrowth into a low-modulus composite plastic porous-coated canine femoral component

Bone ingrowth into low-modulus canine femoral components made of composite plastics and porous coated with titanium fiber mesh was evaluated and compared to that found in femoral components of the same design made of titanium alloy and porous coated with titanium fiber mesh. Both types of components demonstrated extensive bone ingrowth into the porous coatings at 6 weeks and there were no differences in the histologic appearance of the tissue ingrowth in the two groups. The amount of bone that grew into the porous surface, the areal density of bone within the available pore space, and the extent of the prosthesis periphery with bone ingrowth were not significantly varied in the two different components. The results of this study show that adequate fixation of low-modulus composite femoral components porous coated with titanium fiber mesh by bone ingrowth can occur and that further investigation of these materials for femoral components may be warranted.

Technique to detect migration of femoral components of total hip arthroplasties on conventional radiographs

Critical to the evaluation of patients with painful total hip arthroplasties and to the assessment of the efficacy of fixation of new prosthetic designs and/or new insertion techniques is the ability to detect migration of the femoral components. The authors present a simple and effective technique using plain radiography that can detect migration of 1 mm with a high degree of accuracy.

Insertion of a prosthetic hip into a total hip allograft. Case report

We describe a patient in whom a total hip replacement had failed and who subsequently fractured her proximal femur. The prosthetic hip and the surrounding bone were excised and replaced by a matched pair of allograft components. She obtained seven years of pain free hip function before the graft showed radiographic signs of failure; it was then replaced by a new prosthetic hip.