Viability of the acetabular bone bed at revision surgery following cemented primary arthroplasty

Histological evaluation of acetabular bone quality during revision hip arthroplasty

PURPOSE

Aim of this study was to evaluate acetabular bone vitality during revision hip arthroplasty and to compare the bone quality between revision and primary acetabular arthroplasty.

METHODS

During primary and revision total hip arthroplasty surgeries, biopsies were taken from the acetabulum after reaming. The samples (osteochondral cylinders of approximately ⩽1 cm long and 3 mm thickness), after removing the mineral component, were cut longitudinally with a thickness section of 5 µm and colored with hematoxylin-eosin dichromic dye and then evaluated histologically by optical microscopy with 40× magnification. Preoperative radiographs were evaluated.

RESULTS

According to inclusion and exclusion criteria, 14 patients formed the revision group patients (mean age: 67.9 years, average time before revision 8.8 years, SD ± 7.06) and 5 patients formed the control primary group (mean age: 61.4 years). The bone quality of the revision group was generally poorer than the primary group, while similar vitality and bone quality has been found between septic and aseptic group. Variables such as age, gender and BMI did not significantly contribute to define bone quality classes.

CONCLUSIONS

The study confirms the differences in quality and bone vitality between cases and controls and the necessity to find strategies to improve the osteointegrative processes in revision arthroplasties.

Acetabular reconstruction using fresh frozen bone allograft

The success of total hip arthroplasty has led to a move toward operating on a wider and younger population. All implants have a finite useful life, and bone loss is associated with all major causes of failure. The use bone allograft, either morselized or structural has the aim of reconstituting the bone stock. We retrospectively reviewed the clinical and radiological results of 72 acetabular reconstructions both primary and revision, done at our institute between May 1999 and October 2004 with a minimum follow-up of one year. The Harris Hip Score (HHS) was calculated and follow-up radiographs were evaluated for graft incorporation; evidence of loosening and migration. Preoperatively 28 acetabular defects were type III (AAOS), 18 were type II, 16 were type I and 10 were type IV. 60 reconstructions were done using cementless acetabular prostheses, and the remaining twelve had cemented implants. Patients were followed up for an average of 30.69 months (range 12 - 64 months). The mean preoperative HHS was 36.13 points which improved to a mean of 81.6 points (range 61 to 91) at final follow-up. None of the patients required reoperation. Dislocation was the commonest complication (8 hips). Short and medium term results were encouraging with the use of this technique.

The role of stainless steel wire mesh and cement in bone allograft incorporation in impaction grafting technique: an experimental study in rabbits

Cages of flexible stainless steel wire mesh were filled with impacted morcellized cancellous allograft. Bone defects were created in both tibial metaphyseal regions of 10 adult white New Zealand rabbits. The base of both defects was plugged with a small amount of bone cement. The cages were implanted in the right tibia while the left tibia was filled with impacted bone allograft. Histologic and histomorphometric evaluation of the retrieved specimens at 3 months showed a statistically significant difference in active bone formation parameters between the 2 groups. Active bone formation was more prominent away from the bone cement. The biological process of bone graft incorporation in the "impaction grafting" technique seems to be adversely affected by stainless steel wire mesh and in areas adjacent to bone cement.

Factors associated with excessive migration in bone impaction hip revision surgery: a radiostereometric analysis study

A prospective radiostereometric analysis (RSA) study of 18 patients with cemented revision hip surgery and impaction grafting with an Exeter stem was done with a follow-up of 2 years for all patients. All factors that could influence migration (ie, micromotion) of the stem were analyzed with a repeated measurements analysis of variance. Two groups could be identified: a stable group and a continuous migrating group. Two factors significantly influenced micromotion during the follow-up measurements. The first factor was the Paprosky classification (the bigger the defect, the higher the micromotion). The second factor was cement mantle defects in > or =1 Gruen zones. The migrating hip stems had more Gruen zones with cement mantle defects (45%) compared with the stable prostheses (21%). The effect of the first factor on micromotion was limited and probably clinically less relevant. Because the cement mantle defects found in this study were caused by poor instrumentation, the second factor stresses the importance of good instrumentation, which is essential to make this technically demanding technique effective in creating a stable stem-allograft construct in the defective femoral canal.

Incorporation of morselized bone grafts: a study of 24 acetabular biopsy specimens

Animal studies have shown almost complete incorporation of impacted morselized bone grafts. To determine whether this also is true in humans, 24 acetabular bone biopsy specimens from 21 hips of 20 patients were examined. Biopsy specimens were obtained 3 months to 15 years after acetabular reconstruction in primary and revision total hip arthroplasties in combination with a cemented cup. Histologic examination showed rapid revascularization of the graft, directly followed by osteoclastic resorption and woven bone formation on the graft remnants. New bone also was formed on fibrin accumulations or without any scaffold in the fibrous stroma tissue that had invaded the graft. Thereafter the mixture of graft, new bone, and fibrin was remodeled completely into a new trabecular structure, with normal lamellar bone and only scarce remnants of graft material. Localized areas of nonincorporated bone graft surrounded by fibrous tissue remained, irrespective of the followup period. Large nonincorporated fragments of cartilage also were found, particularly in cases in which femoral head bone chips were produced by a bone mill. In general, impacted trabecular bone chips incorporate by a mechanism that is similar to that previously observed in animal studies. In some patients, however, areas of nonincorporated bone graft remained and long-term alterations were found, probably related to the loosening process.

Effect of load on the early incorporation of impacted morsellized allografts

Impacted morsellized bone grafts are clinically successful to restore bony defects after failed total hip arthroplasties. The incorporation process seems to be dependent on the location where the reconstruction is performed, which suggests that load could play a role. In this study, we hypothesised that, as in fracture healing, physiological loading has a stimulatory effect on the process of early bone graft incorporation. To test this hypothesis we created a standardised defect in the distal femur of twelve goats. Allograft bone chips were impacted into the defect and a subcutaneous pressure implant was screwed in. With this implant the graft can be loaded under controlled circumstances. Six goats were subjected to a daily loading regime of 3 MPa, the other six were non-loaded. After five weeks the bone mineral density was measured with peripheral quantitative computer tomography. Thereafter, routine histology and histomorphometry were carried out. Bone mineral density was not affected by load. Histology revealed microscopic evidence of bone graft incorporation, which proceeded in a similar way in both loaded and non-loaded specimens. New bone was formed free in the stroma or on graft remnants after osteoclastic resorption of the graft. Only the area of active incorporating bone graft was higher under load. In conclusion, the formation of a new bony structure was not affected by load after five weeks. However, load resulted in a larger area of active graft incorporation at this early stage. Possibly biological and immunological factors govern the early incorporation process independent of the local loading regime.

Revision arthroplasty of the acetabulum with restoration of bone stock

Bone defects on the acetabular side are defined as contained (cavitary) and uncontained (segmental). Contained (cavitary) defects can be treated by morselized allograft bone with an uncemented cup if contact can be made with 50% host bone. If contact cannot be made with 50% host bone, the author prefers to use a ring and a cemented cup. Defining success as a stable implant, no additional surgery, and improvement in hip score of at least 20 points, the success rate was 90% in 51 hips in 51 patients at an average followup of 7 years. Segmental defects involving between 30% and 50% of the acetabulum are treated by minor column allografts (shelf graft), and a cemented or an uncemented cup. In 29 hips in 28 patients with an average followup of 7 years the success rate was 86%. Segmental defects involving more than 50% of the acetabulum are treated by major column allografts. These grafts are fixed by cancellous screws and protected by a reconstruction ring that extends from ilium to ischium. In 33 hips in 32 patients with an average followup of 7 years, the success rate was 76%.