Impaction technique and graft treatment in revisions of the femoral component: laboratory studies and clinical validation

Uncemented Cups and Impaction Bone Grafting for Acetabular Bone Loss in Revision Hip Arthroplasty: A Review of Rationale, Indications, and Outcomes

Total hip arthroplasty (THA) is increasingly performed in young patients and the number of revisions is estimated to rise over time. Acetabular osteolysis and bone loss are frequently encountered during revision and may be classified and treated in different ways. Impaction bone grafting (IBG) with morselized allograft offers a viable option. IBG was introduced over 40 years ago in combination with cemented cups, and is also used with uncemented cups. The impacted bone chips act as a void filler to restore bone stock; once incorporated they are substituted by host bone. Surgery entails assessment of the defect, acetabular preparation, preparation of the morselized graft, impaction of the graft, and cup implantation. Satisfactory medium- and long-term results have now been reported in most studies. With the advent of high-porosity cups, indications have been extended, enhancing the potential of IBG, in which primary stability of the cup to the host bone is essential for a successful procedure. Synthetic bone substitutes have also been used in combination with allogenic grafts and may extend the original technique for which long-term studies are warranted.

A 3- to 18-Year Follow-Up of Revision Total Hip Arthroplasty With Impacted Bone Allografts and Cemented Lubinus SP II Stem. Clinical, Radiographic, and Survivorship Analysis With Comparison to the Literature

BACKGROUND

We present the first medium- to long-term follow-up of revision total hip arthroplasty using impaction bone grafting (IBG) combined with the matte and collared Lubinus SP II stem for cases of severe osteolysis and stem loosening.

METHODS

Sixty-nine femoral revisions were identified for 67 patients consecutively operated with revision femoral arthroplasty using IBG and a cemented Lubinus SP II stem. The mean age was 69 years (standard deviation, 9.9). We retrospectively analyzed 68 cases (1 was lost to follow-up). At the time of the revision surgery, all had substantial femoral bone loss. Fifteen of the revisions were performed due to deep infection. The patients were analyzed by clinical score and radiography.

RESULTS

At follow-up, 4 femoral components (6%) had been rerevised or assessed as failure. Of these 4, 3 were assessed as mechanical failure, and 1 for dislocation; none was for infection. Three cups (4%) had been revised for dislocation; 1 of these also had a stem exchange. Three cases (4%) had been reoperated for a periprosthetic fracture in distal femur without stem exchange. Radiologic results were excellent and the clinical Merle d'Aubignè-Postel score had improved from a mean of 12.2 preoperatively to 17.5 at follow-up.

CONCLUSION

IBG combined with the Lubinus SP II stem is safe and results in a low rate of periprosthetic fractures and dislocations. The medium- to long-term clinical result was excellent, with regeneration of living bone in the femur.

Femoral Component Revision Using a 2nd Generation Modular Femoral Implant

The purpose of this prospective multicenter study was to evaluate results of 122 revision THAs using a 2nd generation modular femoral implant in 120 patients. Majority of cases had significant femoral bone loss. HHS improved from a pre-operative mean score of 46 to 88 points, and SF-36 scores improved from 31 to 44 points at 2- to 5-year follow-up. There were 18 cases of intraoperative fractures of which 10 were femur shaft, 7 trochanteric, and 1 acetabular. Dislocation incidence was 9% and overall survivorship at 5 years was 97%. Use of modular femoral implants provides versatility and simplification to restore stability, limb length and offset in patients undergoing femoral component revision, Additional steps need to be undertaken to minimize incidence of fracture and dislocation.

Impaction bone grafting for periprosthetic fractures around a total hip arthroplasty

The incidence of periprosthetic fractures has been reported to be between 1 and 20.9% and appears to be on the rise. Fractures that occur around the femoral stem, particularly when the stem is loose or there is a loss of bone stock pose a technical challenge. These are rare injuries and there is considerable debate regarding their optimal treatment. Reconstruction with large segment endoprosthetic replacement is an acceptable solution for elderly patients who have limited functional demands and where the prosthesis is expected to outlive the patient. The younger patient poses a much greater challenge, the bone must be reconstituted and the femoral canal geometry must sufficiently restored to allow the stable insertion of a prosthesis. There are very few techniques that exist in this scenario. One such technique is impaction bone grafting and revision to a long smooth tapered cemented stem. This allows the restoration of bone stock and the stable insertion of a prosthesis. The aim of this article is to discuss the theory behind impaction bone grafting, the technical aspects and challenges of this technique, including fracture reduction methods, and to appraise all the literature available on impaction bone grafting for periprosthetic fractures.

Adherence of hip and knee arthroplasty studies to RSA standardization guidelines. A systematic review

BACKGROUND AND PURPOSE

Guidelines for standardization of radiostereometry (RSA) of implants were published in 2005 to facilitate comparison of outcomes between various research groups. In this systematic review, we determined how well studies have adhered to these guidelines.

METHODS

We carried out a literature search to identify all articles published between January 2000 and December 2011 that used RSA in the evaluation of hip or knee prosthesis migration. 2 investigators independently evaluated each of the studies for adherence to the 13 individual guideline items. Since some of the 13 points included more than 1 criterion, studies were assessed on whether each point was fully met, partially met, or not met.

RESULTS

153 studies that met our inclusion criteria were identified. 61 of these were published before the guidelines were introduced (2000-2005) and 92 after the guidelines were introduced (2006-2011). The methodological quality of RSA studies clearly improved from 2000 to 2011. None of the studies fully met all 13 guidelines. Nearly half (43) of the studies published after the guidelines demonstrated a high methodological quality and adhered at least partially to 10 of the 13 guidelines, whereas less than one-fifth (11) of the studies published before the guidelines had the same methodological quality. Commonly unaddressed guideline items were related to imaging methodology, determination of precision from double examinations, and also mean error of rigid-body fitting and condition number cutoff levels.

INTERPRETATION

The guidelines have improved methodological reporting in RSA studies, but adherence to these guidelines is still relatively low. There is a need to update and clarify the guidelines for clinical hip and knee arthroplasty RSA studies.

Age-dependent fracture risk in hip revisions with radial impaction grafting technique: a 5-10 year medium-term follow-up study

Radial impaction grafting (RIG) potentially improves the durability and reliability of cementing the femoral components in revision total hip arthroplasty (THA). In this multicenter, prospective study, 88 revision THAs (87 patients) with RIG technique were performed. The average follow-up time was 7.0 years (range, 5.0-10.2). There were 14 femur fractures: 2 intraoperative, 5 within 3 months after surgery, and 7 later in the postoperative stage (range, 5-84 months). Sixteen patients were lost to follow-up and 20 died without stem re-revision. None of the patients have been re-revised for any reason during follow-up. Age was observed to be a significant factor for determining fracture risk. In conclusion, RIG can be considered a reliable surgical technique, especially for younger patients.

What is the long-term survival of impaction allografting of the femur?

BACKGROUND

Revision hip surgery of the femur for patients with substantial bone loss is challenging. We previously reported 41 patients (44 hips) treated with femoral impaction grafting followed for a minimum of 2 years. The survivorship, using femoral reoperation for symptomatic aseptic loosening as the end point, was 97% at 8 years. However, data on longer term survival are crucial to adequately compare this surgical technique with other types of revision hip arthroplasty procedures.

QUESTIONS/PURPOSES

We therefore asked what the survivorship of impaction bone grafting was at longer followup, if the severity of bone loss was associated with failure, and finally, if longer length stems had improved survival compared with shorter stems.

METHODS

Between 1993 and 2002, 78 femoral revisions were performed in 71 patients using impaction grafting. The average age of the patients was 67 years (range, 33–84 years). Sixty-nine of the 71 patients were available for followup evaluation. We obtained Harris hip scores preoperatively and postoperatively. Radiographs were measured for radiolucent lines. Patients were followed a minimum of 2 years (average, 10.6 years; range, 2-19 years).

RESULTS

Survival of the femoral component without revision for any cause was 93% (confidence interval [CI], 83%–97%) and for aseptic loosening was 98% (CI, 87%–100%) at 19 years. Neither severity of bone loss nor the length of the stem predicted failure.

CONCLUSIONS

Impaction bone grafting has a high survival of 93% at the 19-year followup for patients with severe bone loss of their femur.

Optimizing the fat and water content of impaction bone allograft

Fresh morselized impacted bone graft usually fails due to shear forces. The presence of fat, water, and marrow particles act as interparticle lubricants, reducing the interlocking of particles and allowing the graft to move more freely. Furthermore, the presence of this incompressible fluid damps and resists compressive forces during impaction, preventing the graft particles from moving into a closer formation. We believe there exists an ideal concentration of fat and water that will maximize resistance to shear forces. We performed mechanical shear testing in vitro on morselized human femoral heads, varying the amount of fat and water to determine their optimum concentrations. Level of fat and water were determined that increased strength by 36% over unaltered bone graft. This is most closely approximated in an operating room by washing and subsequently squeezing the bone graft. Optimizing the fat and water content of bone graft produces a stronger graft that is more resistant to shear stresses, protecting the surgical construct until bone growth can occur.

Revision total hip arthroplasty using a modular femoral implant in Paprosky type III and IV femoral bone loss

The purpose of this study was to compare results of patients with Paprosky type I and II femoral defects vs type IIIA, IIIB, and IV defects in patients undergoing revision hip arthroplasty. There were 64 patients in the group with type I and II defects with an average age of 68 years. There were 52 patients with Paprosky type IIIA, IIIB, and IV defects with an average age of 67 years. There were 8 intraoperative fractures in the type III and IV group, whereas there were 9 in the type I and II group. There were no differences between the 2 groups with respect to subsidence, loosening, dislocation, infection, and medical complications. Survivorship for the whole group was 96.9% at 5 years. Modular femoral implants provide several intraoperative options to restore leg length, offset, and stability despite femoral defects. We did not realize a higher failure rate in patients with type III or IV defects.

A customised collared polished stem may reduce the complication rate of impaction grafting in revision hip surgery: a 12-year follow-up study

We describe the results of 81 consecutive revision total hip replacements with impaction grafting in 79 patients using a collared polished chrome-cobalt stem, customised in length according to the extent of distal bone loss. Our hypothesis was that the features of this stem would reduce the rate of femoral fracture and subsidence of the stem. The mean follow-up was 12 years (8 to 15). No intra-operative fracture or significant subsidence occurred. Only one patient suffered a post-operative diaphyseal fracture, which was associated with a fall. All but one femur showed incorporation of the graft. No revision for aseptic loosening was recorded. The rate of survival of the femoral component at 12 years, using further femoral revision as the endpoint, was 100% (95% confidence interval (CI) 95.9 to 100), and at nine years using re-operation for any reason as the endpoint, was 94.6% (95% CI 92.0 to 97.2). These results suggest that a customised cemented polished stem individually adapted to the extent of bone loss and with a collar may reduce subsidence and the rate of fracture while maintaining the durability of the fixation.

Review article: Treatments for bone loss in revision total knee arthroplasty

Bone deficiency hinders implant alignment and stabilisation of the bone-implant interface in revision total knee arthroplasty (TKA). Treatments for bone defects include bone cement, bone cement with screw reinforcement, metal augments, impaction bone grafts, structural allografts, and tantalum, depending on the location and size of the defects. Small defects are usually treated with cement, cement plus screws, or impaction allograft bone. Large defects are repaired with structural allografts or metal augments. Recent developments involve the use of highly porous osteoconductive tantalum. We reviewed the pros and cons of each method for bone defect management in revision TKA.

Reduced femoral component subsidence with improved impaction grafting at revision hip arthroplasty

BACKGROUND

Despite stem subsidence being a major complication of femoral impaction bone grafting in cemented revision hip arthroplasty, few studies have distinguished subsidence at the prosthesis-cement interface from that at the cement-bone interface. It is unknown how technique developments intended to improve the procedure influence stability of the stem.

QUESTIONS/PURPOSES

We used a sensitive technique to measure subsidence of a cemented polished collarless double-taper stem at each interface after femoral impaction grafting and compared subsidence, radiographic loosening, complications, and reoperations over three series of hips defined by technique developments.

PATIENTS AND METHODS

Three series were defined: Series 1 (n = 23, irradiated allograft), Series 2 (n = 12, double-washed, size-profiled graft, nonirradiated bone, long stems as required), and Series 3 (n = 21, modular tamps). Stem subsidence was analyzed with Ein Bild Röntgen Analyse software. Radiographic loosening, complications, and reoperations were also determined.

RESULTS

The median subsidence at 12 months for Series 1, 2, and 3 were 2.1, 0.5, and 0.7 mm at the prosthesis-cement interface and 1.3, 0.1, and 0.1 mm at the cement-bone interface. There were two postoperative Vancouver B periprosthetic fractures in Series 1, four hips were revised for loosening in Series 1, and there were no fractures or loosening in Series 2 and 3 at minimum 2 years' followup. There were no surviving hips radiographically classified as possibly or probably loose.

CONCLUSIONS

Evolution in techniques of femoral impaction grafting in this study were associated with reduced subsidence of the stem at both the prosthesis-cement interface and cement-bone interface when compared to the original series. Concurrent with reduced stem subsidence was the absence of periprosthetic fracture, radiographic loosening, and complications requiring rerevision.

The threshold force required for femoral impaction grafting in revision hip surgery

BACKGROUND AND PURPOSE

Femoral impaction grafting requires vigorous impaction to obtain adequate stability without risk of fracture, but the force of impaction has not been determined. We determined this threshold force in a preliminary study using animal femurs.

METHODS

Adult sow femurs were used because of their morphological similarity to human femurs in revision hip arthroplasty. 35 sow femurs were impacted with morselized bone chips and an increasing force was applied until the femur fractured. This allowed a threshold force to be established. 5 other femurs were impacted to this force and an Exeter stem was cemented into the neomedullary canal. A 28-mm Exeter head was attached and loaded by direct contact with a hydraulic testing machine. Axial cyclic loading was performed and the position sensor of the hydraulic testing machine measured the prosthetic head subsidence.

RESULTS

29 tests were completed successfully. The threshold force was found to be 4 kN. There was no statistically significant correlation between the load at fracture and the cortex-to-canal ratio or the bone mineral density. Following impaction with a maximum force of 4 kN, the average axial subsidence was 0.28 mm.

INTERPRETATION

We achieved a stable construct without fracture. Further studies using human cadaveric femurs should be done to determine the threshold force required for femoral impaction grafting in revision hip surgery.

Medium term results of revision total hip replacement using radial impaction grafting and a collared textured stem

Massive bone loss is a problem frequently encountered during revision hip surgery. Several ways of addressing the bone loss in proximal femur have been described with varying results. We present our results with the use of a radial impaction grafting technique and a collared textured component. 107 consecutive cases of Revision Total Hip Arthroplasty, who underwent radial impaction grafting and had a textured collared implant inserted for femoral deficiencies were assessed. The average follow up was seven years and four months (3 to 11 years). All the patients experienced a significant improvement in the clinical scores. Oxford Hip scores improved from an average of 41.2 (30 - 56) to 19.3 (12 - 32). Harris Hip scores improved from an average of 40.8 (28 - 65) to 83.4 (60 - 99). There were no cases of subsidence at follow up. Using revision for any cause as the end point the survivorship at an average of 88.8 months was 93.8%. Three revisions were performed for deep infection within the first year. There were three cases of peri-prosthetic fractures distal to the tip of standard length stems at an average of 8.4 months after surgery. We recommend the use of morsellised allografts with radial impaction grafting and textured, collared stems for selected cases with Paprosky type II and type III femoral defects. We also recommend use of long stems bypassing the tip of the previous implant with impaction grafting to avoid peri-prosthetic fractures.

Impaction bone grafting in revision hip surgery: past, present and future

Joint replacement surgery can have excellent clinical results. However, as the number of patients undergoing surgery increases, the number of failed joint replacements is set to rise. One of the greatest challenges for the revision surgeon is the restoration of bone stock. This article focuses upon revision hip surgery, with particular reference to the scope of the problem; historical and current solutions to bone loss in the femur and acetabulum; the clinical results following revision surgery; and the basic science behind impaction bone grafting, before ending with possible future directions for improving the restoration of bone stock.

Factors influencing the stability of stems fixed with impaction graft in vitro

Mechanical stability of the stem is believed to be an important factor in successful impaction grafting in revision THA. We asked whether particle size, femoral bone deficiencies, stem design, graft composition, and impaction technique influenced the initial stability of the stem in vitro using model femora and human bone particles. Bone particles made with a reciprocating blade-type bone mill contained larger particles with a broader size distribution than those made by a rotating drum-type bone mill and had higher stiffness on compression testing. The stiffness on torsional testing decreased as the degree of proximal-medial segmental deficiencies increased. The stiffness and maximum torque in a stem with a rectangular cross section and wide anteroposterior surface were higher in torsional tests. Adding hydroxyapatite granules to the bone particles increased the torsional stability. To facilitate compact bone particles, we developed a spacer between the guidewire and modified femoral packers. This spacer facilitated compacting bone particles from the middle up to the proximal and the technique increased the amount of impacted bone particles at the middle of the stem and also improved the initial stability of the stem. Stem design and degree of deficiencies influenced stiffness in the torsional test and the addition of hydroxyapatite granules enhanced torsional stiffness.

Impaction grafting in association with the Charnley-Kerboull cemented femoral component

We describe 129 consecutive revision total hip replacements using a Charnley-Kerboull femoral component of standard length with impaction allografting. The mean follow-up was 8.2 years (2 to 16). Additionally, extramedullary reinforcement was performed using struts of cortical allograft in 49 hips and cerclage wires in 30.

There was one intra-operative fracture of the femur but none later. Two femoral components subsided by 5 mm and 8 mm respectively, and were considered to be radiological failures. No further revision of a femoral component was required. The rate of survival of the femoral component at nine years, using radiological failure as the endpoint, was 98%. Our study showed that impaction grafting in association with a Charnley-Kerboull femoral component has a low rate of subsidence. Reconstruction of deficiencies of distal bone with struts of cortical allograft appeared to be an efficient way of preventing postoperative femoral fracture for up to 16 years.

Subsidence of the stem after impaction bone grafting for revision hip replacement using irradiated bone

Loss of bone stock is a major problem in revision surgery of the hip. Impaction bone grafting of the femur is frequently used when dealing with deficient bone stock. In this retrospective study a consecutive series of 68 patients (69 hips) who had revision of a hip replacement with femoral impaction grafting were reviewed. Irradiated bone allograft was used in all hips. Radiological measurement of subsidence of the stem, incorporation of the graft and remodelling was carried out and showed incorporation of the graft in 26 of 69 hips (38%). However, there was no evidence of trabecular remodelling. Moderate subsidence of 5 mm to 10 mm occurred in ten hips (14.5%), and massive subsidence of > 10 mm in five (7.2%). The results of this study are less favourable than those of others describing studies of revision of the femoral stem using impaction bone grafting. The absence of the characteristic changes of graft remodelling noted in other series raises the question as to whether irradiated bone graft may be a significant factor influencing the post-operative outcome.

Strain imparted during impaction grafting may contribute to bony incorporation: an in vitro study of the release of bmp-7 from allograft

In order to investigate the osteoinductive properties of allograft used in impaction grafting and the effect of strain during impaction on these properties, we designed an in vitro experiment to measure strain-related release of bone morphogenetic protein-7 (BMP-7) from fresh-frozen femoral head allograft. A total of 40 10 mm cubes of cancellous bone were cut from ten samples of fresh-frozen femoral head. The marrow was removed from the cubes and the baseline concentrations of BMP-7 were measured. Specimens from each femoral head were allocated to four groups and subjected to different compressive strains with a material testing machine, after which BMP-7 activity was reassessed. It was present in all groups. There was a linear increase of 102.1 pg/g (95% confidence interval 68.6 to 135.6) BMP-7 for each 10% increase in strain. At 80% strain the mean concentration of BMP-7 released (830.3 pg/g bone) was approximately four times that released at 20% strain. Activity of BMP-7 in fresh-frozen allograft has not previously been demonstrated. This study shows that the freezing and storage of femoral heads allows some maintenance of biological activity, and that impaction grafting provides a source of osteoinductive bone for remodelling. We have shown that BMP-7 is released from fresh-frozen femoral head cancellous bone in proportion to the strain applied to the bone. This suggests that the impaction process itself may contribute to the biological process of remodelling and bony incorporation.

[Modified Exeter technique in revision hip surgery]

PURPOSE OF THE STUDY

The Exeter technique opened new perspectives for the treatment of femoral bone stock loss in revision hip arthroplasty. Implant migration in the cement sheath is, however, a frequent finding. According to the promoters of the technique, this would favor transformation of the allograft into living bone. For others it is a worrisome problem since it alters the heterogeneous cement sheath, leading to loosening and final surgical revision, with an incidence up to 20%. We propose an analysis of the mid-term results of the modified Exeter technique with the objective of cementing the distal part of the implant directly into the recipient bone in order to achieve satisfactory primary stability. The purpose of this work was to analyze the consequences of this method on the long-term evolution of the allograft.

MATERIAL AND METHODS

After preparing the femur, a specific gun is filled with allograph dough obtained from frozen femoral heads fragmented with an acetabular reamer. The Mersilene mesh enables the deposit of a tube of graft material at the desired level. The implant is sealed after impaction of the graft to enable direct distal cementing in contact with the recipient bone. Partial weight bearing is allowed as early as the fifth day and increased progressively to complete weight bearing at three months. Forty-five patients (46 hips) were treated between June 1996 and January 2002. Six patients were not retained for analysis due to insufficient follow-up. For three patients, graft outcome could not be properly assessed due to a major complication. In addition, two patients died and one was lost to follow-up. In all 39 patients (40 hips) were analyzed at mean follow-up of 84 months (range 48-110). There were no cases of revision for femoral loosening. Femoral bone loss was mainly moderate to severe type II and III hips (Sofcot classification) but limited in height (no grade IV in the Endo-Klinik classification).

RESULTS

Clinical outcome was excellent in 13 hips, good in 16, fair in nine and poor in two (Postel-Merle-d'Aubigné score). Defective distal cementing with implant migration (less than 5 mm) was noted in four cases followed by secondary stabilization. Transformation of the allograft occurred in 36 cases, associated with corticalization of the recipient bone in 14.

CONCLUSION

This technique is reproducible since primary stability was obtained in 90% of hips, without hindering transformation of the allograft. The results, which are sustained over time, are the same as with the princeps technique and no radiographic evidence of stress shielding could be found.

Cement penetration and primary stability of the femoral component after impaction allografting

This study explored the relationship between the initial stability of the femoral component and penetration of cement into the graft bed following impaction allografting.

Impaction allografting was carried out in human cadaveric femurs. In one group the cement was pressurised conventionally but in the other it was not pressurised. Migration and micromotion of the implant were measured under simulated walking loads. The specimens were then cross-sectioned and penetration of the cement measured.

Around the distal half of the implant we found approximately 70% and 40% of contact of the cement with the endosteum in the pressure and no-pressure groups, respectively. The distal migration/micromotion, and valgus/varus migration were significantly higher in the no-pressure group than in that subjected to pressure. These motion components correlated negatively with the mean area of cement and its contact with the endosteum.

The presence of cement at the endosteum appears to play an important role in the initial stability of the implant following impaction allografting.

Vibration-assisted bone-graft compaction in impaction bone grafting of the femur

The complications of impaction bone grafting in revision hip replacement includes fracture of the femur and subsidence of the prosthesis. In this in vitro study we aimed to investigate whether the use of vibration, combined with a perforated tamp during the compaction of morsellised allograft would reduce peak loads and hoop strains in the femur as a surrogate marker of the risk of fracture and whether it would also improve graft compaction and prosthetic stability.

We found that the peak loads and hoop strains transmitted to the femoral cortex during graft compaction and subsidence of the stem in subsequent mechanical testing were reduced. This innovative technique has the potential to reduce the risk of intra-operative fracture and to improve graft compaction and therefore prosthetic stability.

Stereolithographic models for biomechanical testing

Variable properties and limited availability are pitfalls in using cadaveric bones for implant stability tests. Artificial bones avoid these, but tailoring them to specific studies may be difficult. Stereolithography (SLA) techniques produce tailor-made bones with realistic geometries, but their lower Young's modulus might affect outcomes. We investigated whether implant stability and cortical strains with SLA made bones match those with stiffer artificial bones and, if not, whether a thicker cortex to compensate the lower modulus gives a better match. Tibial trays were cemented in place and cyclically loaded while determining cortical strain and tray migration. Permanent and cyclic migration of trays in both types of SLA model (range: 13-28 and 58-85 mum) was within the range of those in composite models (range: 4-62 and 51-105 microm). Strains more distally were approximately inversely proportional to the material stiffness and cortical thickness of the tibiae. We conclude this first study provides a strong indication for SLA tibiae as a valid model for the biomechanical assessment of new techniques in knee surgery and compare favourably with previously utilised models.

Five-year follow-up of socket movements and loosening after revision with impacted morselized allograft bone and cement: a radiostereometric and radiographic analysis

In 1999, we reported on the 2-year results of a series of 21 first-time socket revisions using impacted morselized allograft bone. Seven still migrated between 1.5 and 2 years. Seventeen remained for the current 5-year follow-up. No socket had been rerevised. Five sockets showed signs of radiographic loosening. These 5 cases also exhibited radiographic signs of allograft resorption as well as high rates of socket migration and rotation as measured by radiostereometric analysis. Of the 6 remaining sockets that had migrated between 1.5 and 2 years, 3 stabilized and 3 were among those with signs of radiographic loosening. Fifteen patients (15 hips) revealed pain reduction at the 5-year follow-up. Three had slight pain on walking that disappeared immediately at rest (pain score 4). All the others revealed either no pain (pain score 6) or slight pain that disappeared with activity (pain score 5). No pattern of early socket migration according to radiostereometric analysis could be identified, predicting later socket migration or loosening. The rate of cases with signs of radiographic loosening (29%, 5/17) was comparable to that reported by the Nijmegen group but the follow-up was shorter in the current study. The rate of cases with signs of radiographic loosening was comparable to both conventionally cemented socket revisions and cementless revisions. The future will show if further sockets loosen and if the loose sockets up to date will end up in rerevisions.

Reconstruction of femoral defects in revision hip surgery: risk of fracture and stem migration after impaction bone grafting

The use of impaction bone grafting during revision arthroplasty of the hip in the presence of cortical defects has a high risk of post-operative fracture. Our laboratory study addressed the effect of extramedullary augmentation and length of femoral stem on the initial stability of the prosthesis and the risk of fracture. Cortical defects in plastic femora were repaired using either surgical mesh without extramedullary augmentation, mesh with a strut graft or mesh with a plate. After bone impaction, standard or long-stem Exeter prostheses were inserted, which were tested by cyclical loading while measuring defect strain and migration of the stem. Compared with standard stems without extramedullary augmentation, defect strains were 31% lower with longer stems, 43% lower with a plate and 50% lower with a strut graft. Combining extramedullary augmentation with a long stem showed little additional benefit (p = 0.67). The type of repair did not affect the initial stability. Our results support the use of impaction bone grafting and extramedullary augmentation of diaphyseal defects after mesh containment.

Factors affecting the cohesion of impaction bone graft

The role of bone-graft extenders in impaction revision surgery is becoming increasingly important. Tricalcium phosphate and hydroxyapatite have been shown to be both biocompatible and osteoconductive, yet many surgeons remain reluctant to use them. The difficulty in handling bone-graft extenders can be partly alleviated by using porous particles and adding clotted blood. In an in vitro model we measured the cohesive properties of various impaction graft mixes. Several factors were evaluated including the use of pure bone graft compared with mixes with extender, washing the bone and the addition of clotted blood. Our findings showed that pure allograft bone particles had significantly higher cohesion than when mixed with extender (p < 0.001). Washing had no effect on cohesion. The addition of clotted blood significantly increased the cohesion of both pure bone (p < 0.019) and mixes with pure bone and with porous graft extender (p < 0.044).

Impaction allografting for massive femoral defects in revision hip arthroplasty using collared textured stems

We present a prospective study of impaction grafting using collared textured stems in femurs with massive defects (defined as requiring >150 cm(3) of cancellous allograft). Eighteen hips were followed for a minimum of 2 years. Average Harris hip scores increased from 50 preoperatively to 83 at most recent follow-up. Seventeen hips were functioning well at the time of most recent follow-up and exhibited no stem subsidence or aseptic loosening. One hip was associated with visible subsidence and required further revision. Single-photon emission computed tomography analyses performed at an average of 37 months indicated active graft reorganization in all cases studied. Impaction allografting with collared textured stems for massive defects demonstrates good intermediate-term clinical results and may be a useful alternative to allograft stem composites and megaprostheses.

Reprise fémorale par tige cimentée et greffe morcelée compactée: analyse de la migration fémorale

PURPOSE OF THE STUDY

If the bone loss is significant, revision total hip arthroplasty can be most difficult. We present a series of 30 patients with major loss of bone stock treated with the X-change (Exeter) technique for revision total hip arthroplasty.

MATERIAL AND METHODS

This prospective consecutive series included 30 reconstructions performed between 1996 and 2001. Compacted grafts with cryopreserved bone were used. Mean follow-up was 42 months (range 24-80). According to the SOFCOT classification, bone loss was stage II in one patient, stage III in 14 and stage IV in 15. The technique described by Gie, Linder and Ling was rigorously applied: smooth stem, no force on the Merckel, cement in the impacted allograft, filling of femoral bone defects. Reinforcement with plates, mesh, or wire was used as necessary to bridge cortical defects. The Postel-Merle-d'Aubigné (PMA) score was used to assess clinical outcome. Digital x-rays were obtained before and after surgery and at last follow-up to assess implant position (vertical migration and frontal deviation), changes in bone stock, and the Pierchon classification. Thirty patients were seen at two years follow-up. Two patients were lost to follow-up after two years. Material had to be removed in two patients because of mechanical intolerance. There was one postoperative fracture at six months. One patient died more than two years after implantation. The PMA score improved from 11 to 17 at last follow-up. Radiographic results showed mean 7.3 mm stem migration and mean 2 degrees frontal deviation which were not correlated with clinical presentation. The Pierchon classification revealed 20 situations of corticalization and eight of trabeculation. Factors affecting migration were modalities of graft preparation and time to first weight bearing. Migration was unchanged after twelve months.

DISCUSSION AND CONCLUSION

The functional and radiographic results remained satisfactory in light of the initial bone loss. Implant migration did not affect outcome. We have modified the surgical technique in line with these results, particularly concerning preparation of the impacted bone graft. This technique has the advantage of filling bone defects and avoiding therapeutic escalation.

Larger bone graft size and washing of bone grafts prior to impaction enhances the initial stability of cemented cups: experiments using a synthetic acetabular model

BACKGROUND

Bone defects after failed total hip arthroplasty can be reconstructed with impacted morselized bone grafts and a cemented cup. On the acetabular side, the effects on initial cup stability of washing bone grafts prior to impaction and bone graft size remain unclear. Related to these variables, cement penetration and inter-particle shear resistance have been suggested to be critical factors to ensure initial cup stability.

METHODS

Using a synthetic acetabular model, we studied the effects of (1) washing bone grafts prior to impaction, and (2) bone graft size on the initial stability of cemented cups. In addition, cement penetration was measured using CT scans.

RESULTS

Reconstructions with large, washed bone grafts provided the highest stability during mechanical compression and in a lever-out situation. Washing of the bone grafts had a positive effect on initial cup stability, but the size of the bone grafts appeared to be more important. Cement penetration was affected by bone graft size but not by washing.

INTERPRETATION

From a mechanical standpoint, large bone grafts that have been washed prior to impaction may be preferable in order to obtain optimal cup stability using the bone impaction grafting technique.

Mixing bone graft with OP-1 does not improve cup or stem fixation in revision surgery of the hip: 5-year follow-up of 10 acetabular and 11 femoral study cases and 40 control cases

BACKGROUND

Bone morphogenetic proteins (BMPs) have the potential to improve incorporation of allograft bone in revision surgery. This could result in improved fixation and graft incorporation.

PATIENTS AND METHODS

We evaluated the effect of mixing OP-1 (BMP-7) with morselized allograft in hip revisions. In a case-control study, 20 acetabular revisions (10 in the study group, 10 controls) and 41 femoral revisions (11 in study group, 30 controls) were done using impaction allografting. The migration of the cups and stems was studied with radiostereometric analysis (RSA) for up to 5 years. Changes of bone mineral density around the femoral component were measured with dual energy X-ray adsorptiometry for 2 years. Bone remodeling and the extent of radiolucent lines were evaluated on conventional radiographs after 5 years. The clinical results were documented using Harris hip score.

RESULTS

In the cup study, there was no significant difference in implant migration between the study and control groups. 4 sockets in the study group were classified as radiographically loose after 5 years and 2 of them were revised after 5 years. After 2 years, the stems in the study group showed slightly increased posterior tilt (0.3 degrees , p = 0.03). 1 stem in the study group loosened and was revised during the third year of observation.

INTERPRETATION

The sample size and study design in our evaluation did not allow any firm conclusions. Absence of any trend to improved fixation and early revisions in the study group prompted us to stop recruitment to this study.

Modified Exeter technique in revision hip surgery: does distal fixation of the stem affect allograft transformation?

Promising results have made the Exeter technique a valuable alternative in hip replacement revision. However, even with this technique, subsidence remains a difficult problem because it may lead to additional revision if it is not mild and self-limited. We propose a technical modification that achieves primary stability by cementing the distal portion of the stem directly to the host bone. We conducted a prospective study on 45 hips. After an average of 46 (range, 18-72) months of follow-up monitoring, no hips required or underwent revision for aseptic loosening of the prosthesis. Four stems subsided <5 mm. In each case, distal cementation was only fair, so implant strength was decreased. Allograft transformation occurred in 36 hips and was associated with host bone remodeling in 11. This technical modification appears to be reliable, as satisfactory distal cementation was achieved in 41 hips (91%), and the modification did not interfere with allograft transformation.

Femoral revision with impaction grafting and a collarless, polished, tapered stem

Femoral impaction allografting has been done with and without variations of the original description. The purpose of this study was to review Harris hip scores, radiographs, and complications in patients in whom we used the original technique without significant modifications. Preoperative and postoperative hip scores and radiographic data were available at a mean of 4.7 years for 43 of 44 hips that had femoral component impaction allografting with a collarless, polished, tapered stem. Bone stock was classified according to the Endo-Klinik classification. Survivorship, using femoral reoperation for symptomatic aseptic loosening as the end point, was 97%. The mean Harris hip score improved from 45 to 90 with pain improved in all. Subsidence 4 mm and greater occurred in only two hips, but neither has been revised. One hip was revised for mechanical loosening after a fall on the surgically treated extremity 6 years after surgery. Complications included three intraoperative fractures, one femoral fracture recognized postoperatively, one trochanteric nonunion, and one dislocation. Femoral component revision with impaction allografting and a collarless, polished, tapered stem was reproducible and improved Harris hip scores in patients with aseptic femoral component loosening and bone loss at a mean of 4.7 years after surgery.

The use of OP-1 in femoral impaction grafting in a sheep model

The aim of this pilot study was to examine bone graft incorporation in femurs impacted with allograft bone alone (control group) or with allograft containing the bone morphogenetic protein OP-1 (BMP-7) (OP-1 group) in a sheep model of cemented hemiarthroplasty. Two sheep in each group were sacrificed at 6, 18 and 26 weeks. Successful bone graft incorporation was evident in both groups by six weeks but in the OP-1 group, there had been more extensive resorption of the graft. There was one case of excessive stem subsidence in the OP-1 group at six weeks. By 18 weeks, there was remodelling and trabeculation of the new bone in the OP-1 group, but this appeared less advanced in the control group. By 26 weeks, there was remodelling of bone in the graft bed. The results of this small study suggest that OP-1 promotes initial graft resorption, thus hastening bone graft incorporation and remodelling in femoral impaction grafting. The one case of stem subsidence may be associated with the early resorption seen in the OP-1 group and reinforces the need for further studies, examining dose response and using precise measures of stem movement, before this BMP is used in femoral impaction grafting at revision hip arthroplasty.

Impaction allografting for femoral component revision: clinical update

The technique of cancellous impaction allografting with cement aims to reconstitute a bone-deficient proximal femur while also gaining stable fixation of the femoral prosthesis. Some reports of this technique imply it is a system, requiring not just an exacting surgical method, but also a particular implant design, the polished, double-tapered stem. Other series consider it a surgical technique, and have varied the femoral component design, the method of graft delivery, and other elements of the procedure. Our review evaluates the current literature, with the goal of beginning to ascertain whether published results suggest impaction grafting must be considered a system, requiring a particular stem design, or simply another means to achieve femoral reconstruction in the revision setting. The conclusive answer will require randomized, controlled clinical trials to evaluate particular elements of the procedure, and these studies have yet to be done. However, investigators have shown similarly good short-term to intermediate-term results with various femoral stems at numerous centers. Currently, femoral impaction allografting, whether as a system using particular implant designs or as a surgical technique, is an accepted alternative for revision of a failed femoral component, particularly when bone-stock deficiency is present.

Impacted cancellous graft plus cement in hip revision

Revision of the femoral component is difficult in the presence of large cavitary defects of the femur. Impaction cancellous grafting used in conjunction with a cemented prosthesis has been recommended as a means of restoring bone stock while providing excellent and durable clinical results. Fifty-seven consecutive femoral revisions were done between 1993 and 1997 in 54 patients (24 men and 30 women) using the impaction grafting technique and a collarless, tapered, polished stem. Strut allografts were used for femoral reinforcement in 40 hips. No patient was lost to followup. One patient had an infection develop and had a resection arthroplasty. Three patients died of causes unrelated to the hip. After 6.3 years the clinical results were excellent. Radiographic evaluation showed no evidence of loosening in any of the 53 surviving hips. Subsidence of 1 to 3 mm was seen in 40 hips and subsidence of 4 to 6 mm was seen in two hips. Cancellous remodeling was observed in 42 hips. The most common complications were postoperative femoral fractures. All six fractures occurred at the distal end of the prosthesis, were not associated with prosthetic loosening, and were treated successfully with open reduction and internal fixation without prosthetic revision. These satisfactory results and the limited subsidence observed in our patients radiographs could be explained by the careful attention to the technical details of the procedure. However, even with the generous use of strut graft augmentation, postoperative femoral fractures remain our most serious complication.

Cancellous and cortical morselized allograft in revision total hip replacement: A biomechanical study of implant stability

To restore femoral intramedullary bone stock loss in revision surgery of failed total hip arthroplasties, impacted morselized cancellous allograft is recommended. This study investigated the mechanical properties of both impacted cortical (group A) and cancellous (group B) morselized bone graft for reconstruction of femoral bones. Ten matched pairs of fresh frozen human femora were prepared by over-reaming to create a smooth-walled cortical shell. Each pair had one cortical and one cancellous impacted morselized allograft and cement. Stem subsidence was evaluated by a cyclic axial load, which was applied by a servohydraulic test. The stem subsidence was measured for initial subsidence (subsidence at the first 1000 cycles), the total axial subsidence (subsidence at the end of cycles under load) and the final axial subsidence (subsidence after the unloading phase). Torque test was measured by torsional loads through the prosthetic femoral heads. Total axial subsidence was significantly higher in group B (mean: 1.32+/-0.32 mm) compared to group A (mean: 0.94+/-0.26 mm) (P<0.01). There was no significant difference between the two groups in terms of initial subsidence (P=0.09) and final axial subsidence. The mean maximum torque before failure was 39.5+/-22.2 N-m for the cortical morselized allograft and 32.5+/-18.1N-m for cancellous. We concluded that impacted morselized cortical bone graft used for reconstruction of contained femoral bone loss in revision hip arthroplasty, may reduce the stem subsidence. Further animal experimentation for mechanical and histological evaluation of in vivo application is warranted.

Rinsing morselized allografts improves bone and tissue ingrowth

Bone defects in revision hip surgery can be reconstructed with impacted morselized bone grafts. Rinsing these trabecular allografts may enhance graft incorporation by washing out immunogenic factors present in blood, marrow, and fat. However, it has been proposed that impaction of the graft releases biologically active factors, which can provide sufficient activity to stimulate new bone formation. Rinsing before impaction could enhance bone allograft incorporation, but rinsing after impaction could diminish the incorporation process of impacted bone graft. To study the effect of rinsing and impaction of morselized bone grafts on bone ingrowth, a bone chamber study was done in goats. Autografts and allografts were divided into three treatment groups: (A) impacted; (B) rinsed and impacted; and (C) rinsed, impacted, rinsed, and impacted again. Ten goats received three bone chambers in each proximal tibia. The chambers were filled with either allograft or autograft, yielding six different implants per goat. After 6 weeks, histologic analyses were done and bone and tissue ingrowth were measured. New bone and total tissue ingrowth were higher in autografts than in allografts, especially in the nonrinsed group. With rinsing, total tissue ingrowth increased in the allograft group to approach that of autografts. Rinsing after impaction did not additionally alter bone ingrowth. The current findings show that incorporation of allografts can be improved by rinsing the grafts before impaction.

Femoral impaction grafting in revision hip arthroplasty with irradiated bone

We evaluated the results of femoral impaction grafting with the Exeter stem (Stryker Howmedica Osteonics, Newbury, UK) and irradiated bone-graft. We followed 57 hips for an average of 27 months. Endo-Klinik grading showed 8 grade 1, 22 grade 2, and 27 grade 3 hips. Radiographic analysis revealed cortical repair in 34% and graft incorporation in 39% but no evidence of trabecular remodeling. Moderate subsidence (5-10 mm) occurred in 7 patients (12.5%), and massive subsidence (>10 mm) occurred in 4 patients (7%). Complications included 6 dislocations, 3 periprosthetic fractures, and 2 stem revisions. Impaction grafting with the Exeter system produces satisfactory results for most patients, but a few hips perform poorly, and the reasons for this are unclear. We have concerns about irradiated bone-graft because the characteristic changes of graft remodeling are not seen.

Impaction grafting: doing it right

Impaction grafting has emerged as a useful technique in the armamentarium of the revision total hip arthroplasty surgeon. The original technique proposed by Ling has been associated with complications, including femoral shaft fractures, recurrent dislocations, and uncontrolled component subsidence. Modifications in that technique seem to be associated with a reduction in complications. The radial impaction grafting technique permits the use of revision femoral components with variable stem lengths, neck lengths, and neck offsets. The technique seeks to improve the quality of bone impaction and reduce the incidence of subsidence. Initial results have been encouraging.