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

Management of Severe Bone Defects in Femoral Revision following Total Hip Arthroplasty

Treatment of femoral bone defects continues to be a challenge in revision total hip arthroplasty (THA); therefore, meticulous preoperative evaluation of patients and surgical planning are required. This review provides a concise synopsis of the etiology, classification, treatment strategy, and prosthesis selection in relation to femoral bone loss in revision THA. A search of literature was conducted for identification of research articles related to classification of bone loss, management of femoral revision, and comparison of different types of stems. Findings of a thorough review of the included articles were as follows: (1) the Paprosky classification system is used most often when defining femoral bone loss, (2) a primary-length fully coated monoblock femoral component is recommended for treatment of types I or II bone defects, (3) use of an extensively porouscoated stem and a modular fluted tapered stem is recommended for management of types III or IV bone defects, and (4) use of an impaction grafting technique is another option for improvement of bone stock, and allograft prosthesis composite and proximal femoral replacement can be applied by experienced surgeons, in selected cases, as a final salvage solution. Stems with a tapered design are gradually replacing components with a cylindrical design as the first choice for femoral revision; however, further confirmation regarding the advantages and disadvantages of modular and nonmodular stems will be required through conduct of higher-level comparative studies.

Decellularised human bone allograft from different anatomical sites as a basis for functionally stratified repair material for bone defects

Tissue engineered bone solutions aim to overcome the limitations of autologous and allogeneic grafts. Decellularised tissues are produced by washing cellular components from human or animal tissue to produce an immunologically safe and biocompatible scaffold, capable of integration following implantation. A decellularisation procedure utilising low concentration sodium dodecyl sulphate (0.1% w/v) was applied to trabecular bone from human femoral heads (FH) and tibial plateaus (TP). Biological (histology, DNA quantification), biomechanical (compression testing) and structural (μCT) comparisons were made between decellularised and unprocessed cellular tissue. Total DNA levels of decellularised FH and TP bone were below 50 ng mg^-1 dry tissue weight and nuclear material was removed. No differences were found between cellular and decellularised bone, from each anatomical region, for all the biomechanical and structural parameters investigated. Differences were found between cellular FH and TP and between decellularised FH and TP. Decellularised FH had a higher ultimate compressive stress, Young's modulus and 0.2% proof stress than decellularised TP (p = 0.001, 0.002, 0.001, Mann Whitney U test, MWU). The mineral density of cellular and decellularised TP bone was significantly greater than cellular and decellularised FH bone respectively (cellular: p = 0.001, decellularised: p < 0.001, MWU). The bone volume fraction and trabecular thickness of cellular and decellularised FH bone were significantly greater than cellular and decellularised TP bone respectively (cellular: p = 0.001, 0.005; decellularised: p < 0.001, <0.001, MWU). Characterisation of decellularised trabecular bone from different anatomical regions offers the possibility of product stratification, allowing selection of biomechanical properties to match particular anatomical regions undergoing bone graft procedures.

The storage of skull bone flaps for autologous cranioplasty: literature review

The use of autologous bone flap for cranioplasty after decompressive craniectomy is a widely used strategy that allows alleviating health expenses. When the patient has recovered from the primary insult, the cranioplasty restores protection and cosmesis, recovering fluid dynamics and improving neurological status. During this time, the bone flap must be stored, but there is a lack of standardization of tissue banking practices for this aim. In this work, we have reviewed the literature on tissue processing and storage practices. Most of the published articles are focused from a strictly clinical and surgical point of view, paying less attention to issues related to tissue manipulation. When bone resorption is avoided and the risk of infection is controlled, the autograft represents the most efficient choice, with the lowest risk of complication. Otherwise, depending on the degree of involvement, the patient may have to undergo new surgery, assuming further risks and higher healthcare costs. Therefore, tissue banks must implement protocols to provide products with the highest possible clinical effectiveness, without compromising safety. With a centralised management of tissue banking practices there may be a more uniform approach, thus facilitating the standardization of procedures and guidelines.

Clinical and radiological survivorship of the Thackray cross plate with rim reinforcement ring for cemented acetabular revision

INTRODUCTION

Acetabular component revision surgery can be a challenging task due to the encountered bone defects. Both cemented and uncemented techniques are described. We report on the survivorship of the Thackray cross plate with rim reinforcement ring for cemented acetabular revision.

PATIENTS AND METHODS

This is a retrospective case series of all patients treated with the implant with a minimum follow-up of 2 years. Acetabular defects were characterized according to the Paprosky classification. Data on potential risk factors for failure of the construct as well as the Oxford Hip Score (OHS) were collected. Kaplan-Meier survival analysis with radiographic aseptic loosening or revision for aseptic loosening as the end point was performed.

RESULTS

From 2000 to 2017, 35 revisions in 18 male and 17 female patients with an average age of 72 years were included. Bone allograft was used in 26 cases and additional implants (medial or supero-lateral mesh) in 13. Seven patients have deceased and the fate of all revisions is known. At an average clinical follow-up of 9.7 (2.6 to 19.6) years, there were no further re-revisions for construct failure. Five hips have demonstrated radiological evidence of aseptic loosening. Radiologically loose components were associated with more severe grades of acetabular bone defects (Paprosky Type 3) (60% vs 3%, p = 0.006). Kaplan-Meier survival analysis demonstrates 79.8% overall survivorship at 7 years. Survivorship for Type 2 defects was significantly higher compared to Type 3 (90% vs 0% at 7 years, Logrank test p = 0.002, Cox proportional hazards p = 0.03). The final median OHS was 38 (12-48) and was not affected by component loosening.

CONCLUSION

This is a cost-effective device that protects the underlying bone graft (81% complete remodeling) and prevents subsidence of the cemented cup (2 mm on average). It should be used with caution in high-grade defects and perhaps not advised.

[Allogeneic bone transplantation in hip revision surgery : Indications and potential for reconstruction]

The increasing number of people having joint replacements will lead to increasing numbers of revision operations. The transplantation of allogeneic bones might reconstruct bone defects and improve long-term anchorage of the implant. A sufficient primary stability of the implanted construct is necessary to achieve osseous incorporation as well as tight contact between the implanted allogeneic and host bones. Transplantation of bone can contribute to downgrading acetabular defects and so avoid bigger reinforcement implants. An improvement of bone stock due to reconstruction of femoral bony defects might also reduce the size of the stem necessary since the indication might be limited in case of extensive bone defects. According to good longterm results of modular revision stems the Impaction-Bone-Grafting has not yet generally been established.

[Influence of thermodisinfection on impaction of cancellous bone : An in vitro model of femoral impaction bone grafting]

BACKGROUND

The reconstruction of bony defects during endoprosthesis revision surgery using "impaction bone grafting" leads to the possibility of a longstanding osseous integration to achieve good clinical results. Native allogeneic cancellous bone is often used for the procedure. This study examines the influence of thermodisinfection on the impaction behaviour of cancellous bone of different geometries and on the cement distribution.

METHODS

The cancellous bone was obtained from the femoral heads of 7‑month old pigs. One half of the head was thermodisinfected while the other remained native. Bone chips with sizes of 3-5, 5-8 and 8-10 mm were produced. The impaction was performed in a cylinder model with an internal diameter of 30 mm and with standardized impaction force using an impactor with a weight of 1450 g. The best particle combination was used for the subsequent computer tomography examination of the cement distribution and the contact surface to the bone in different parts of the shaft in seven investigations. For statistic measurements two-dimensional variance analysis including repetitions of measurement and Bonferroni correction, the LSD post-hoc-zest and the Mann Whitney U Test were used. The error probability was set at α = 5%. The SPSS® for Windows software was used for the statistical analysis.

RESULTS

The distribution of the cancellous and compacted bone also along the shaft revealed no significant difference between thermodisinfected and native cancellous bone at different levels (p > 0.05). Impacted native cancellous bone showed less inclusion of air, which resulted in a better distribution of density compared with thermodisinfected bone overall (p < 0.001). In the distal shaft area the cement volume was significantly larger in conjunction with the native bone. The overall area of cement penetration appeared to be significantly larger for native cancellous bone (p < 0.001).

CONCLUSIONS

The impaction of thermodisinfected and native cancellous bone showed greater deformation of the processed bone without any significant difference in the maximum density reached at different levels. Cement volume and cement penetration were pronounced proximally in native and processed cancellous bone. The cement distribution was significantly more distal for the native bone. Distally, the stabilization of the shaft appears to be increasingly dependent on the density of the impacted spongiosa, while proximally, the penetration of the cement into cancellous bone seems to correlate with porosity.

Locally administered bisphosphonate in hip stem revisions using the bone impaction grafting technique: a randomised, placebo-controlled study with DXA and five-year RSA follow-up

BACKGROUND:

Bisphosphonates have previously been shown to increase the density of impacted graft bone. In the present study we hypothesise that bisphosphonates also reduce early stem subsidence. We examined the effect of locally applied bisphosphonate to allografts on prosthetic micromotion and bone density in femoral stem revision with impaction grafting.

METHODS:

37 patients were randomised to either clodronate or saline as local adjunct to the morsellised allograft bone. 24 patients were finally analysed per protocol and evaluated by dual-energy x-ray absorptiometry (DXA) during the first year and with radiostereometric analysis (RSA) for 5 years.

RESULTS:

There were no significant differences neither in bone density, nor in migratory behaviour between the groups. The femoral stems had subsided 3.6 mm in both groups (p = 0.99) at 5 years and there was no difference as measured over time with mixed models analysis. The clinical outcome was good in both groups.

CONCLUSION:

Clodronate as a local addendum to allograft bone in hip revision did not increase bone density or reduce micromotion of the implant.

Platelet concentrate as an additive to bone allografts: a laboratory study using an uniaxial compression test

Chemical cleaning procedures of allografts are destroying viable bone cells and denaturing osteoconductive and osteoinductive proteins present in the graft. The aim of the study was to investigate the mechanical differences of chemical cleaned allografts by adding blood, clotted blood; platelet concentrate and platelet gel using a uniaxial compression test. The allografts were chemically cleaned, dried and standardized according to their grain size distribution. Uniaxial compression test was carried out for the four groups before and after compacting the allografts. No statistically significant difference was found between native allografts, allografts mixed with blood, clotted blood, platelet concentrate and platelet concentrate gel regarding their yield limit after compaction. The authors recommend to chemical clean allografts for large defects, optimize their grain size distribution and add platelet concentrate or platelet rich plasma for enhancing as well primary stability as well bone ingrowth.

A 2- to 16-Year Clinical Follow-Up of Revision Total Hip Arthroplasty Using a New Acetabular Implant Combined With Impacted Bone Allografts and a Cemented Cup

BACKGROUND

Treatment of acetabular bone loss with impaction bone grafting (IBG) at revision total hip arthroplasty is highly dependent on mechanical stability and graft compression for clinical success. Here, we describe a new technique to further compress and stabilize the acetabular graft bed with a thin, perforated titanium shell.

METHODS

We retrospectively analyzed 170 cases of acetabular revision arthroplasty 7 years (standard deviation 2.8) after IBG combined with a graft-compressing titanium shell implant. The patients were reviewed by clinical score and radiography. Three patients were lost to follow-up. The medical journals of the 33 deceased cases were reviewed for any reoperation. Of the 170 cases, 74 had a cavitary acetabular bone defect, 93 had combined segmental and cavitary bone defects, and 3 had a pelvic dissociation. Bone graft incorporation was assessed and correction of the hip center of rotation was calculated.

RESULTS

Five cases (3%) were reoperated for mechanical loosening. One more was assessed as loose but asymptomatic and was not planned for revision. There were 3 reoperations for recurrent dislocation, 2 for deep infection and 1 for technical error. Reoperation for any reason, as the end point of survivorship, showed a survival rate of 92% after 10 years. Hip score according to Merle, d'Aubigne, and Postel increased from 10.8 (preoperatively) to 16.4 at follow-up. The clinical and radiological results were excellent.

CONCLUSION

IBG combined with the compressing shell results in excellent results for this challenging condition.

The Influence of Liquids on the Mechanical Properties of Allografts in Bone Impaction Grafting

Allografts are used to compensate for bone defects resulting from revision surgery, tumor surgery, and reconstructive bone surgery. Although it is well known that the reduction of fat content of allografts increases mechanical properties, the content of liquids with a known grain size distribution has not been assessed so far. The aim of the study was to compare the mechanical properties of dried allografts (DA) with allografts mixed with a saline solution (ASS) and with allografts mixed with blood (AB) having a similar grain size distribution. Fresh-frozen morselized bone chips were cleaned chemically, sieved, and reassembled in specific portions with a known grain size distribution. A uniaxial compression was used to assess the yield limit, initial density, density at yield limit, and flowability of the three groups before and after compaction with a fall hammer apparatus. No statistically significant difference could be found for the yield limit between DA and ASS (p = 0.339) and between ASS and AB (p = 0.554). DA showed a statistically significant higher yield limit than AB (p = 0.022). Excluding the effect of the grain size distribution on the mechanical properties, it was shown that allografts have a lower yield limit when lipids are present. The liquid content of allografts seems to play an inferior role as no statistically significant difference could be found between DA and ASS. It is suggested, in accordance with other studies, to chemically clean allografts before implantation to reduce the contamination risk and the fat content.

Femoral impaction bone grafting in revision hip arthroplasty

Aims

Femoral impaction bone grafting was first developed in 1987 using morselised cancellous bone graft impacted into the femoral canal in combination with a cemented, tapered, polished stem. We describe the evolution of this technique and instrumentation since that time.

Patients and Methods

Between 1987 and 2005, 705 revision total hip arthroplasties (56 bilateral) were performed with femoral impaction grafting using a cemented femoral stem. All surviving patients were prospectively followed for a mean of 14.7 years (9.8 to 28.3) with no loss to follow-up. By the time of the final review, 404 patients had died.

Results

There were 76 further revisions (10.8%) involving the stem; seven for aseptic loosening, 23 for periprosthetic fracture, 24 for infection, one for malposition, one for fracture of the stem and 19 cement-in-cement exchanges of the stem during acetabular revision. The 20-year survival rate for the entire series was 98.8% (95% confidence interval (CI) 97.8 to 99.8) with aseptic loosening as the endpoint, and 87.7% (95% CI 82.8 to 92.6) for revision for any reason. Survival improved with the evolution of the technique, although this was not statistically significant due to the overall low rate of further revision.

Conclusion

This is the largest series of revision total hip arthroplasties with femoral impaction grafting, and the results support the continued use of this technique. Cite this article: Bone Joint J 2016;98-B:1611–19.

THA revisions using impaction allografting with mesh is durable for medial but not lateral acetabular defects

BACKGROUND

Most acetabular revisions are managed with cementless hemispherical or elliptical metal implants relying on bone ingrowth. Nonetheless, loss of acetabular bone stock and inability to achieve secure component fixation represent challenges in the setting of revision total hip arthroplasty. Impaction bone grafting (IBG) using allograft represents one option for treatment of this problem. However, cup migration and bone graft resorption are limitations when IBG is used for large segmental defects, and the precise role of IBG as well as the use of mesh (and the kinds of defects for which mesh does not work well) in this setting remains unknown.

QUESTIONS/PURPOSES

We therefore evaluated patients undergoing acetabular revision surgery using IBG and a cemented cup in large bone defects to determine (1) the frequency with which the hip center could be restored in hips with Paprosky 3A and 3B defects and in hips with or without the use of metallic mesh during surgery; (2) survivorship of IBG acetabular-revision reconstructions in patients with severe Paprosky 3A and 3B defects; and (3) risk factors for failure of the reconstruction, including the use of mesh and defect severity (3A versus 3B).

METHODS

Between 1997 and 2009, we performed 226 acetabular revisions using IBG. During that time, indications for using IBG in this setting included Paprosky 3A and 3B defects without pelvic discontinuity. Of these, 204 (90.2%) were available for followup at a minimum of 5 years (mean, 10 years; range, 5-17 years). There were 100 hips with an intraoperative bone defect of Paprosky 3A and 104 with a 3B. Medial or rim acetabular uncontained defects were treated with medial and/or lateral metallic mesh in 142 hips. We determined the postoperative radiological cup position and acetabular reconstruction of the hip center according to Ranawat in both groups. We assessed the appearance of cup loosening and the possible risk factors with regression analysis.

RESULTS

Mean postoperative acetabular abduction angle and vertical, horizontal, and hip rotation center distances improved (p < 0.001 in all parameters). Nine hips showed radiological loosening in the group with bone defect 3A and 16 in Group 3B. The survival rate for loosening at 15 years was 83% (95% confidence interval [CI], 71%-95%) for Group 3A and 73% (95% CI, 60%-84%) for Group 3B (p = 0.04). The survivorship for loosening when using mesh or not at 15 years was: no mesh 89% (95% CI, 74%-99%), medial mesh 85% (95% CI, 72%-97%), lateral mesh 80% (95% CI, 67%-91%), and medial and lateral meshes 54% (95% CI, 31%-76%) (p = 0.008). After controlling the most relevant confounding variables we found that the most important factor associated with loosening was lateral mesh use (p = 0.008; hazard ratio, 2.942; 95% CI, 1.328-6.516).

CONCLUSIONS

IBG provides an improvement in reconstruction of the hip rotation center in acetabular revision surgery. Although results are good for contained or medial large defects, hips with a rim or lateral segmental defect may need other options for reconstruction of these challenging surgeries.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Optimized demineralization of human cancellous bone by application of a vacuum

Human demineralized bone matrix derived from cortical bone is used by surgeons due to its ability to promote bone formation. There is also a need for shaped demineralized bone matrices made from cancellous bone, where the properties of the material allow its insertion into defects, therefore acting as a void filler and scaffold onto which new bone can form. In this study, we report that demineralized bone sponges were prepared by dissecting and cutting knee bone into cancellous bone cubes of 1 cm(3) . These cubes were then taken through a series of warm water washes, some with sonication, centrifugation, and two decontamination chemical washes. The cubes were optimally demineralized into sponges with 0.5N hydrochloric acid under vacuum with constant pH measurement. Demineralization was confirmed by quantitative measurement of calcium and qualitatively by compression. The sponges were freeze dried before terminal sterilisation with a target dose of 25 kGy gamma radiation whilst frozen. Samples of the sponges were histologically examined for calcium and collagen and also tested for osteoinductivity. Data showed well defined collagen staining in the sponges, with little residual calcium. Sponges from two out of three donors demonstrated osteoinductivity when implanted into the muscle of an athymic mouse.

Local treatment of a bone graft by soaking in zoledronic acid inhibits bone resorption and bone formation. A bone chamber study in rats

Background

Bone grafts are frequently used in orthopaedic surgery. Graft remodelling is advantageous but can occur too quickly, and premature bone resorption might lead to decreased mechanical integrity of the graft. Bisphosphonates delay osteoclastic bone resorption but may also impair formation of new bone. We hypothesize that these effects are dose dependent. In the present study we evaluate different ways of applying bisphosphonates locally to the graft in a bone chamber model, and compare that with systemic treatment.

Methods

Cancellous bone grafts were placed in titanium chambers and implanted in the tibia of 50 male rats, randomly divided into five groups. The first group served as negative control and the grafts were rinsed in saline before implantation. In the second and third groups, the grafts were soaked in a zoledronic acid solution (0.5 mg/ml) for 5 seconds and 10 minutes respectively before being rinsed in saline. In the fourth group, 8 μL of zoledronic acid solution (0.5 mg/ml) was pipetted onto the freeze-dried grafts without rinsing. The fifth group served as positive control and the rats were given zoledronic acid (0.1 mg/kg) systemically as a single injection two weeks after surgery. The grafts were harvested at 6 weeks and analysed with histomorphometry, evaluating the ingrowth distance of new bone into the graft as an equivalent to the anabolic osteoblast effect and the amount (bone volume/total volume; BV/TV) of remaining bone in the remodelled graft as equivalent to the catabolic osteoclast effect.

Results

In all chambers, almost the entire graft had been revascularized but only partly remodelled at harvest. The ingrowth distance of new bone into the graft was lower in grafts soaked in zoledronic acid for 10 minutes compared to control (p = 0.007). In all groups receiving zoledronic acid, the BV/TV was higher compared to control.

Conclusions

This study found a strong inhibitory effect on bone resorption by bisphosphonates but also a limited inhibition of the ingrowth of new bone. Local treatment at surgery resulted in stronger inhibition of both resorption and bone formation compared to systemic treatment.

The extent of the bone defect affects the outcome of femoral reconstruction in revision surgery with impacted bone grafting: a five- to 17-year follow-up study

We report the results of 79 patients (81 hips) who underwent impaction grafting at revision hip replacement using the Exeter femoral stem. Their mean age was 64 years (31 to 83). According to the Endoklinik classification, 20 hips had a type 2 bone defect, 40 had type 3, and 21 had type 4. The mean follow-up for unrevised stems was 10.4 years (5 to 17). There were 12 re-operations due to intra- and post-operative fractures, infection (one hip) and aseptic loosening (one hip). All re-operations affected type 3 (6 hips) and 4 (6 hips) bone defects. The survival rate for re-operation for any cause was 100% for type 2, 81.2% (95% confidence interval (CI) 67.1 to 95.3) for type 3, and 70.8% (95% CI 51.1 to 90.5) for type 4 defects at 14 years. The survival rate with further revision for aseptic loosening as the end point was 98.6% (95% CI 95.8 to 100). The final clinical score was higher for patients with type 2 bone defects than type 4 regarding pain, function and range of movement. Limp was most frequent in the type 4 group (p < 0.001). The mean subsidence of the stem was 2.3 mm (SD 3.7) for hips with a type 2 defect, 4.3 mm (SD 7.2) for type 3 and 9.6 mm (SD 10.8) for type 4 (p = 0.022). The impacted bone grafting technique has good clinical results in femoral revision. However, major bone defects affect clinical outcome and also result in more operative complications.

Impaction bone grafting

In revision total hip replacement, bone loss can be managed by impacting porous bone chips. In order to guarantee sufficient mechanical strength, the bone chips have to be compacted. The aim of this study was to determine in an in vitro simulation whether the use of a pneumatic hammer leads to higher primary stability than manual impaction. Bone mass characteristics were measured by force and distance variation of a penetrating punch, which was lowered into a plastic cup filled with bone chips. From these measurements bulk density, contact stiffness, impaction hardness and penetration resistance were calculated for different durations of impaction.

We found that the pneumatic method reached higher values of impaction hardness, contact stiffness and bulk density suggesting an increase in stability of the implant. No significant differences were found between the two different methods concerning the penetration resistance. The pneumatic method might reduce the risk of fracture in vivo, as force peaks are smaller and applied for a shorter period. Results from manual impaction showed higher variability and depend much on the experience of the surgeon. The pneumatic hammer is a suitable tool to standardise the impaction process.

Bone metabolism analyzed by PET and DXA following revision THA using a distally fixed stem. A pilot study

In a pilot study we analyzed bone remodeling using ¹⁸F-PET (positron emission tomography) scanning or DXA (dual-energy x-ray absorptiometry) in 3 patient groups, one with a loose femoral stem and 2 after revision using a modular stem (MP). In loose implants (group 1), bone formation activity compared to the contralateral healthy femur was 261 %. In the proximal part of the femur bone formation was increased by 253 % one week after revision (group 2) and did not normalize within 1 year. In the distal region it decreased to normal after one year. In the second revision group DXA showed decreased bone mineral density at 6 and 24 months (group 3). The PET technique provided evidence of bone healing despite osteolysis and prosthetic loosening which continued after revision. Decreasing BMD after revision in the third group is multifactorial, but suggests that despite intensive bone formation resorption was still higher.

The survival and fate of acetabular reconstruction with impaction grafting for large defects

BACKGROUND

Impaction bone grafting has been used for acetabular reconstruction in revision surgery. However, most series do not establish differences in survival in revisions with differing severity of bone loss.

QUESTIONS/PURPOSES

We therefore determined (1) the survival rate for rerevision associated with varying degrees of bone loss; (2) the frequency with which bone graft resorption occurred; and (3) whether the reconstruction restored the anatomic center of rotation of the hip.

METHODS

We retrospectively reviewed 165 patients (181 hips) who underwent rerevision for major bone loss. Using the classification of Paprosky et al. 98 hips had a Grade 3A defect and 83 a Grade 3B. We determined survival rates for revision and graft resorption. Cup position was determined measuring vertical and horizontal positions and the distance from the center of the prosthetic femoral head to the normal center of rotation of the hip in both groups according to Ranawat. The minimum followup until rerevision or the latest evaluation was 0.3 years months (mean, 7.5 years; range, 0.3-17.7 years).

RESULTS

The survival rate for revision at 8 years was 84% (95% confidence interval: 61-100) for Grade 3A and 82% (95% confidence interval: 68-100) for Grade 3B. Twelve hips were rerevised. Seventeen grafts showed bone resorption. Acetabular cup position was anatomically restored in both Grades 3A and 3B.

CONCLUSIONS

The midterm results for impacted bone allograft and cemented all-polyethylene cups were similar in both Grade 3A and Grade 3B hips. Acetabular reconstruction allows anatomic positioning of the cups and is associated with a low rate of rerevision.

Obliterative airway remodelling in transplanted and non-transplanted lungs

Obliterative airway remodelling is a morphological sequence in a variety of pulmonary diseases. Notably, bronchiolitis obliterans represents one of the key complications of lung transplantation, induced by (immigrating) myofibroblasts. A comparative expression analysis of obliterative airway remodelling in transplanted and non-transplanted patients has not been reported so far. Obliterated and unremodelled airways from explanted lungs (n = 19) from patients suffering from chronic allograft dysfunction, infection, graft-versus-host disease and toxic exposure were isolated by laser-assisted microdissection. Airways from lung allografts harvested shortly before and after transplantation (n = 4) as well as fibroblastic foci from lungs with interstitial pulmonary fibrosis (n = 4) served as references. Pre-amplified cDNA was analysed by quantitative real-time RT-PCR for expression of fibrosis, inflammation and apoptosis-associated genes. Composition of infiltrating cells and protein expression were assessed by conventional histology and immunohistochemistry. Bronchiolitis obliterans in transplanted patients showed a significant increase of BMP-7 expression (p = 0.0141 compared with controls), while TGF-beta1 and FGF-2 as well as BMP-4 and BMP-7 were up-regulated in fibroblastic foci in interstitial pulmonary fibrosis (p < 0.0424 compared with controls). Regarding other fibrosis-associated genes (BMP-6, SMAD-3, CASP-3 and CASP-9, FASLG, NF-KB1, IL-1 and IL-2) as well as cellularity and cellular composition, no significant differences between obliterative airway remodelling in transplanted and non-transplanted patients could be shown. Obliterative airway remodelling in lung allografts and in non-transplanted patients share many morphological and genetic traits. BMPs, especially BMP-7, warrant further investigation as possible markers for the aggravation of airway remodelling.

A sliding stem in revision total knee arthroplasty provides stability and reduces stress shielding

BACKGROUND AND PURPOSE

In the reconstruction of unicondylar femoral bone defects with morselized bone grafts in revision total knee arthroplasty, a stem extension appears to be critical to obtain adequate mechanical stability. Whether stability is still assured by this reconstruction technique in bicondylar defects has not been assessed. The disadvantage of relatively stiff stem extensions is that bone resorption is promoted due to stress shielding. We therefore designed a stem that would permit axial sliding movements of the articulating part relative to the intramedullary stem.

METHODS

This stem was used in the reconstruction with impaction bone grafting (IBG) of 5 synthetic distal femora with a bicondylar defect. A cyclically axial load was applied to the prosthetic condyles to assess the stability of the reconstruction. Radiostereometry was used to determine the migrations of the femoral component with a rigidly connected stem, a sliding stem, and no stem extension.

RESULTS

We found a stable reconstruction of the bicondylar femoral defects with IBG in the case of a rigidly connected stem. After disconnecting the stem, the femoral component showed substantially more migrations. With a sliding stem, rotational migrations were similar to those of a rigidly connected stem. However, the sliding stem allowed proximal migration of the condylar component, thereby compressing the IBG.

INTERPRETATION

The presence of a functional stem extension is important for the stability of a bicondylar reconstruction. A sliding stem provides adequate stability, while stress shielding is reduced because compressive contact forces are still transmitted to the distal femoral bone.

Impaction bone grafting for acetabular reconstruction: mean 5.5-year results in Japanese patients

INTRODUCTION

We performed a retrospective outcome study on 23 consecutive acetabular reconstructions involving impaction bone grafting in Japanese patients.

METHOD

Two hips had cavitary defects, and 21 hips had combined segmental and cavitary defects. The mid-term follow-up was performed at a mean of 5.5 years postoperatively. The mean Merle d'Aubigné and Postel hip score had improved from 11.5 to 15.7 points at the final follow-up. Two hips showed migration at 30 months after surgery, and one of these was a candidate for re-revision due to symptomatic cup migration.

RESULTS

The Kaplan-Meier survival rate of the cup, with loosening and re-operation as the end points, was 91.3 and 95.7% at 5 years, respectively.

CONCLUSION

Acetabular impaction bone grafting is a reproducible technique in which surgeons should strictly follow the recommended technical procedure.

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.

Bone healing of severe acetabular defects after revision arthroplasty

BACKGROUND AND PURPOSE

Healing of acetabular bone grafts may be difficult to assess in conventional radiographs. We used PET to analyze healing of morselized bone allografts, impacted in large osteolytic acetabular defects at revision arthroplasty.

PATIENTS AND METHODS

7 cases had a cup revision because of loosening, with repair of a segmental defect using a perforated, wide and thin plate. The osteolytic acetabulum was impacted with morselized bone allograft before cementing a polyethylene cup. [(18)F]-fluoride PET scans were used to monitor bone healing inside the graft bed 1 week, 4 weeks, and 12 months after surgery. The contralateral pelvic bone above the acetabulum was used as reference. A second group of 4 cases was analyzed for bone-forming activity in the state of mechanical loosening of an acetabular component of a THA.

RESULTS

Preoperatively, the uptake was raised by 64% compared to the reference. 1 week after surgery it was increased by 77% in segmental regions, while the uptake was at the reference level in cavitary regions. After 4 months the uptake was increased by 91% in cavitary regions and by 117% in segmental regions. 1 year after surgery, the increase in uptake was 20% in both regions. All implants were stable on radiographs.

INTERPRETATION

We found PET to be a sensitive and useful method for evaluation of the spatial and temporal development of bone formation.