When fracture of an extensively porous-coated femoral component occurs, its removal at revision total hip arthroplasty (THA) may require a femoral osteotomy and the use of a trephine. The remaining cortical bone after using the trephine may develop thermally induced necrosis. A retrospective review identified 11 fractured, well-fixed, uncemented, extensively porous-coated femoral components requiring removal using a trephine with a minimum of two years of follow-up. . The mean time to failure was 4.6 years (1.7 to 9.1, standard deviation (. sd. ) 2.3). These were revised using a larger extensively porous coated component, fluted tapered modular component, a proximally coated modular component, or a proximal femoral replacement. The mean clinical follow-up after revision THA was 4.9 years (2 to 22, . sd. 3.1). The mean diameter of the femoral component increased from 12.7 mm (. sd. 1.9) to 16.2 mm (. sd. 3.4; p >  0.001). Two revision components had radiographic evidence of subsidence that remained radiographically stable at final follow-up. The most common post-operative complication was instability affecting six patients (54.5%) on at least one occasion. . A total of four patients (36.4%) required further revision: three for instability and one for fracture of the revision component. There was no statistically significant difference in the mean Harris hip score before implant fracture (82.4; . sd. 18.3) and after trephine removal and revision THA (81.2; . sd. 14.8, p = 0.918). . These findings suggest that removal of a fractured, well-fixed, uncemented, extensively porous-coated femoral component using a trephine does not compromise subsequent fixation at revision THA and the patient’s pre-operative level of function can be restored. However, the loss of proximal bone stock before revision may be associated with a high rate of dislocation post-operatively. Cite this article: Bone Joint J 2015;97-B:1192–6

Aims

We previously reported the long-term results of the cementless Duraloc-Profile total hip arthroplasty (THA) system in a 12- to 15-year follow-up study. In this paper, we provide an update on the clinical and radiological results of a previously reported cohort of patients at 23 to 26 years´ follow-up.

Between January 1984 and January 1986, 131 porous-coated anatomic total hip replacements were performed in 119 consecutive patients. Of these, 100 patients (110 hips) who were alive at a minimum of 18 years after replacement were included in the study. The mean age of the patients at surgery was 48.4 years and that of surviving patients at the latest follow-up was 67.8 years. The mean duration of the clinical and radiological follow-up was 19.4 years (18 to 20). The mean Harris hip score initially improved from 55 points before to 95 points at two years after operation, but subsequently decreased to 91 points after six years, 87 points after 11.2 years, and 85 points after 19.4 years. At the final follow-up, 23 hips (18%) of the entire cohort and 21% of survivors had undergone revision because of loosening or osteolysis of the acetabular component and eight hips (6%) of the entire cohort and 7% of survivors for loosening or osteolysis of the femoral component. Only four femoral components (4%) were revised for isolated aseptic loosening without osteolysis and two (2%) for recurrent dislocation. On the basis of these long-term results, the porous-coated anatomic femoral component survived for a minimum of 18 years after operation while the acetabular component was less durable. The findings identify the principles of uncemented joint replacement which can be applied to current practice

We assessed the outcome of patients with Vancouver type B2 and B3 periprosthetic fractures treated with femoral revision using an uncemented extensively porous-coated implant. A retrospective clinical and radiographic assessment of 22 patients with a mean follow-up of 33.7 months was performed. The mean time from the index procedure to fracture was 10.8 years. There were 17 patients with a satisfactory result. Complications in four patients included subsidence in two, deep sepsis in one, and delayed union in one. Concomitant acetabular revision was required in 19 patients. Uncemented extensively porous-coated femoral stems incorporate distally allowing stable fixation. We found good early survival rates and a low incidence of nonunion using this implant

Revision surgery of the hip was performed on 114 hips using an extensively porous-coated femoral component. Of these, 95 hips (94 patients) had a mean follow-up of 10.2 years (5 to 17). No cortical struts were used and the cortical index and the femoral cortical width were measured at different levels. There were two revisions for aseptic loosening. Survivorship at 12 years for all causes of failure was 96.9% (95% confidence interval 93.5 to 100) in the best-case scenario. Fibrous or unstable fixation was associated with major bone defects. The cortical index (p = 0.045) and the lateral cortical thickness (p = 0.008) decreased at the proximal level over time while the medial cortex increased (p = 0.001) at the proximal and distal levels. An increase in the proximal medial cortex was found in patients with an extended transtrochanteric osteotomy (p = 0.026) and in those with components shorter than 25 cm (p = 0.008). The use of the extensively porous-coated femoral component can provide a solution for difficult cases in revision surgery. Radiological bony ingrowth is common. Although without clinical relevance at the end of follow-up, the thickness of the medial femoral cortex often increased while that of the lateral cortex decreased. In cases in which a shorter component was used and in those undertaken using an extended trochanteric osteotomy, there was a greater increase in thickness of the femoral cortex over time

We studied the results of total hip arthroplasty (THA) using AML porous-coated femoral components at a mean follow-up of 11 years in a non-selected, consecutive series of patients with rheumatoid arthritis. We reviewed 64 patients with 82 primary THAs using these components. There were seven men (8 hips) and 57 women (74 hips) with a mean age of 55.1 years (24 to 80) at the time of surgery. Nine patients (11 hips) died before the two-year follow-up. Of the remaining 71 hips, only one stem was revised for aseptic loosening. Survivorship for the stems was 98.1% (95% confidence interval (CI) 94.5 to 100.0) at ten years, using a life-table analysis, with revision for any reason as an endpoint. Of the 70 unrevised stems, 66 (94%) had bony ingrowth, while four (6%) were radiologically loose at the most recent follow-up (mean 11.4 years). Our study shows the excellent long-term results which can be achieved with porous-coated femoral components in patients with rheumatoid arthritis

The measurement of bone mineral density in defined areas around metal implants has improved with the development of dual-energy X-ray absorptiometry. We used this technique to compare the bone mineral density adjacent to metal cementless femoral implants with that of identical regions of bone in normal proximal femora. We studied the anteroposterior views only of 72 femora which contained total hip implants and 34 non-operated femora. We compared the regional bone mineral density of bone adjacent to proximally porous-coated and distally porous-coated implants of one design, to measure the relative differences in the remodelling changes induced by different amounts of porous coating. We also measured differences in bone density with time and with variations in implant size (and therefore stiffness). The greatest decrease in bone mineral density (34.8%) occurred in the most proximal 1 cm of the medial femoral cortex around relatively stiff, extensively porous-coated implants. The next most severe decrease (20% to 25%) was in the next most proximal 6 cm of the medial femoral cortex. Small, progressive decreases in bone mineral density continued for five to seven years after implantation

We reviewed a consecutive series of 241 uncemented, porous-coated anatomic (PCA) hip replacements at an average follow-up of five years (2 to 9). Of these, 32 had failed (13%), 26 at the acetabular component (11%) and six at the femoral component (2%). Acetabular failure was associated with local osteolysis and excessive polyethylene wear in 20 cases: in these histological examination showed giant macrophages incorporating numerous particles of high-density polyethylene. The femoral failures were related to a poor intramedullary fit with subsequent subsidence. Using the recommendation for revision as the end point, the cumulative survival rate for prostheses was 91% at six years (95% CI +/- 6%), 73% (+/- 11%) at seven years, and 57% (+/- 20%) at eight years. The result of uncemented PCA hip replacement is satisfactory up to six years, but then increasing failure of the acetabular component appears to be due to polyethylene wear, leading to osteolysis, loosening and component migration. At first, failure is often asymptomatic; routine follow-up of uncemented hip replacement is essential, especially after five years

We reviewed 134 primary noncemented porous-coated total hip replacements in 125 patients: 64 were DePuy AML prostheses, 20 were Howmedica PCA and 50 were Implant Technology LSF. The prostheses had been in situ for an average of 36 months, 40 months and 24 months respectively. The average pre-operative Harris hip scores were 38.2 for AML, 33.2 for PCA, and 41.0 for the LSF prostheses. The average postoperative scores were 80.7 for AML, 83.8 for the PCA, and 91.5 for LSF. Thigh or groin pain associated with the prosthesis was present in 30% of AML, 30% PCA and 8% of the LSF cases. The clinical and radiographic review showed better early results with the LSF prostheses than the others; this seemed to be related to the implant design, which provided improved initial stability and more physiological transfer of load

We report the incidence of osteolysis in the femur, tibia, and patella of 44 consecutive patients (60 knees) who were followed for more than seven years after cementless knee arthroplasty with a Porous-Coated Anatomic prosthesis. The average age of the patients was 56.5 years (17 to 73); the operative diagnosis was osteoarthritis (33 knees), rheumatoid arthritis (17), tuberculous arthritis (7) and post-traumatic arthritis (3). All patellae were resurfaced. No femoral or tibial component was loose at the final follow-up examination. Thirty patellar components were loose of which six had been revised. Radiographs revealed osteolysis in 90% of the tibial plateaux and in 80% of the 30 intact patellar prostheses. No osteolysis was seen around any femoral component. In 50 knees (83%) the average wear of the polyethylene liner was 2.5 mm in the medial compartment and 1.7 mm in the lateral compartment. Four of 60 knees (6.7%) were revised for complete wear of the polyethylene liner of the tibial component. Fixation of the tibial and patellar components without cement fails to seal the interface between bone and prosthesis and allows the migration of polyethylene particulate debris which causes osteolysis

The causes of mechanical failure of five noncemented porous-coated components were studied. There were two cobalt-chromium alloy and three titanium alloy implants which fractured after 12 to 48 months. The implants included one acetabular component, and one femoral condylar, one patellar and two tibial components. Examination of the fractured surfaces revealed fatigue to be the mechanism of failure in all cases. The porous coating and the processes required for its fabrication had resulted in weakening and reduction of substrate thickness. Additional factors were stress concentration due to limited, localised bone ingrowth, and some features of the design of the implants

In 44 consecutive patients, 60 porous-coated anatomic total knee (PCA) prostheses with a porous-coated central tibial stem were implanted without using cement. The clinical results and bony remodelling have been assessed after five years' follow-up. The average Hospital for Special Surgery knee score was 33.1 before operation and 95.7 at the latest follow-up, while the average range of movement improved from 63 degrees to 123 degrees. No subsidence or migration of the components was seen. A radiodense line appeared around the components at six months to one year after the operation and became more dense with time. There was no evidence of bone resorption related to stress-shielding in the tibial plateau

We studied 108 patients (116 hips) who were followed for a minimum of six years (73 to 89 months) after primary total hip arthroplasty using an uncemented porous-coated anatomic hip. The average age of the patients at operation was 48.4 years, and the diagnosis was avascular necrosis of the femoral head in 46 hips, neglected femoral neck fracture in 27, osteoarthritis secondary to childhood pyogenic arthritis in 24 and to childhood tuberculous arthritis in five, and miscellaneous in 14. The average preoperative Harris hip score was 55, which improved to 91 at latest follow-up. All patients with loose femoral components or disabling thigh pain had received prostheses which were undersized in the coronal or the sagittal plane, or in both. No patient with a satisfactory fit in both coronal and sagittal planes had loosening of the femoral component or disabling thigh pain. Three acetabular components showed aseptic loosening and 20 showed excessive wear (5 to 11 mm) of the polyethylene liner. Excessive wear was related to young age, but not to body-weight, gender, primary diagnosis, hip score, or range of hip movement. There was a high incidence of osteolysis (38 of 116 hips, 33%). We recommend careful preoperative planning, with the use of a contemporary cemented technique when a satisfactory fit cannot be obtained. The high incidence of excessive wear and of osteolysis needs further investigation

Total hip replacement using porous-coated cobalt-chrome femoral implants designed for biological fixation has been evaluated in 307 patients after two years and in 89 patients after five years. Histological study of 11 retrieved specimens showed bone ingrowth in nine and fibrous tissue fixation in two. Fixation by bone ingrowth occurred in 93% of the cases in which a press fit of the stem at the isthmus was achieved, but in only 69% of those without a press fit. The clinical results at two years were excellent. The incidence of pain and limp was much lower when there was either a press fit of the stem or radiographic evidence of bone ingrowth. Factors such as age, sex, and the disease process did not influence the clinical results. Most cases showed only slight resorptive remodelling of the upper femur, but in a few cases with a larger, more rigid stem, more extensive bone loss occurred. The results after five years showed no deterioration with time. Fixation by the ingrowth of bone or of fibrous tissue both appeared to be stable, but bone ingrowth gave better clinical results

We retrospectively reviewed, ten years after surgery, 100 consecutive total hip replacements in which the Duraloc 300 cup had been used. Post-operative radiographs were analysed for placement of the cup and interface gaps and follow-up radiographs for lucent lines, osteolysis, wear and migration.

All the components were found to be stable with no evidence of loosening. The mean rate of wear was 0.12 mm/year. Three hips developed acetabular osteolysis at the level of the apex hole. Two have successfully undergone bone grafting without removal of the implants and one patient is awaiting surgery. The Duraloc 300 cup has a survival of 100% at ten years with no aseptic loosening and a low incidence of pelvic osteolysis.

We reviewed 111 hemispherical Duraloc series-500 acetabular components with a minimum follow-up of 12 years. The mean clinical and radiological follow-up was 13.4 years (12 to 15). A Profile hydroxyapatite-coated anatomical femoral component was used in each case. Six patients had a late dislocation, for whom the polyethylene liner was exchanged. Each acetabular component was well fixed and all femoral components showed signs of bone ingrowth. The mean rate of femoral head penetration was 0.10 mm/year (0.021 to 0.481). The probability of not developing femoral cortical hypertrophy and proximal osteopenia by 12 years was 80.2% (95% confidence interval, 72.7 to 87.6) and 77.5% (95% confidence interval, 69.7 to 85.2), respectively. Despite these good clinical results, further follow-up is needed to determine whether these prostheses will loosen with time.

We designed an in vivo study to determine if the superimposition of a microtexture on the surface of sintered titanium beads affected the extent of bone ingrowth. Cylindrical titanium intramedullary implants were coated with titanium beads to form a porous finish using commercial sintering techniques. A control group of implants was left in the as-sintered condition. The test group was etched in a boiling acidic solution to create an irregular surface over the entire porous coating. Six experimental dogs underwent simultaneous bilateral femoral intramedullary implantation of a control implant and an acid etched implant. At 12 weeks, the implants were harvested in situ and the femora processed for undecalcified, histological examination. Eight transverse serial sections for each implant were analysed by backscattered electron microscopy and the extent of bone ingrowth was quantified by computer-aided image analysis. The extent of bone ingrowth into the control implants was 15.8% while the extent of bone ingrowth into the etched implants was 25.3%, a difference of 60% that was statistically significant.

These results are consistent with other research that documents the positive effect of microtextured surfaces on bone formation at an implant surface. The acid etching process developed for this study represents a simple method for enhancing the potential of commonly available porous coatings for biological fixation.

Ten uncemented total hip replacements were performed in 1975 using an implant in which the cobalt-chrome femoral stem was coated to give a porous surface. In all but one case a high-density polyethylene head was used. The radiological changes in the upper femoral shafts were assessed between three and nine years later. Seven showed extensive stress-relieving changes, loss of calcar, stress fractures at the root of the lesser trochanter with subsequent detachment, and osteoporosis followed by avulsion of the greater trochanter. In these seven patients the lower part of the stem appeared to be soundly embedded, although in only one was there evidence of bony incorporation. It is suggested that if the fixation of a fully coated implant of this sort remains sound, gross atrophy of the upper femoral shaft develops after five years. This atrophy, associated with an implant which can be removed only at the expense of further bone destruction, presents substantial problems if revision is needed.

We investigated the implant-bone interface around one design of femoral stem, proximally coated with either a plasma-sprayed porous coating (plain porous) or a hydroxyapatite porous coating (porous HA), or which had been grit-blasted (Interlok). Of 165 patients implanted with a Bimetric hip hemiarthroplasty (Biomet, Bridgend, UK) specimens were retrieved from 58 at post-mortem.

We estimated ingrowth and attachment of bone to the surface of the implant in 21 of these, eight plain porous, seven porous HA and six Interlok, using image analysis and light morphometric techniques. The amount of HA coating was also quantified.

There was significantly more ingrowth (p = 0.012) and attachment of bone (p > 0.05) to the porous HA surface (mean bone ingrowth 29.093 ± 2.019%; mean bone attachment 37.287 ± 2.489%) than to the plain porous surface (mean bone ingrowth 21.762 ± 2.068%; mean bone attachment 18.9411 ± 1.971%). There was no significant difference in attachment between the plain porous and Interlok surfaces. Bone grew more evenly over the surface of the HA coating whereas on the porous surface, bone ingrowth and attachment occurred more on the distal and medial parts of the coated surface. No significant differences in the volume of HA were found with the passage of time.

This study shows that HA coating increases the amount of ingrowth and attachment of bone and leads to a more even distribution of bone over the surface of the implant. This may have implications in reducing stress shielding and limiting osteolysis induced by wear particles.