Impaction bone grafting in revision hip surgery. A high incidence of complications

Short uncemented femoral component for hip revision: prognosis and risk factors associated with failure

Background

The application of short femoral stems is partially restricted in revision surgery. This study will demonstrate the therapeutic effect and unsuitable situation for short stem revision.

Methods

Demographic characteristics of all patients were recorded in detail (Table 1). Anteroposterior view radiographic examinations of proximal femur are necessary before and after the operation for patients. The primary outcome of interest was the survival rate of the femoral stem at the final follow-up. Risk factors for failure were also investigated. The secondary outcomes of interest included the Harris hip score, excellent to good rate and incidence of complications. The Mann–Whitney U test was performed for comparisons between continuous variables. The chi-square test was performed for comparisons between categorical variables. Cox regression analysis was used to assess the association between potential risk factors and the failure of revision surgery.

Results

A total of 381 patients with short stems were retrospectively reviewed. There were 188 males and 193 females. The average age and body mass index before revision surgery were 58.85 ± 13.46 years and 23.72 ± 3.40 kg/m², respectively. The mid-term survival rate of the short femoral component was 94.23%. The prognosis and complications of patients between the two groups were compared. There was no significant difference between the two groups in the Harris score, complication incidence or survival rate of the femoral component. The strongest risk factor in this study was intraoperative periprosthetic femoral fracture during revision surgery (HR = 5.477, 95% CI = 2.156–13.913).

Conclusion

Three risk factors for failure were identified: ageing, osteoporosis and intraoperative periprosthetic femoral fracture during revision surgery. Therefore, a short femoral stem should be implanted in patients with these risk factors with additional caution.

Uncemented or cemented stems in first-time revision total hip replacement? An observational study of 867 patients including assessment of femoral bone defect size

Background and purpose - Uncemented stems are gradually replacing cemented stems in hip revision surgery. We compared the risk of re-revision between uncemented and cemented revision stems and assessed whether the different fixation methods are used in similar femoral bone defects.Patients and methods - 867 patients operated on with uncemented or cemented stems in first-time hip revision surgery due to aseptic loosening performed 2006-2016 were identified in the Swedish Hip Arthroplasty Register. Preoperative femoral bone defect size was assessed on radiographs of all patients. Cox regression models were fitted to estimate the adjusted risk of re-revision during different postoperative time periods. Re-revision of any component for any reason, and stem re-revision, as well as risk of cause-specific re-revision was estimated.Results - Most patients in both fixation groups had Paprosky class IIIA femoral bone defects prior to surgery, but there were more severe bone defects in the cemented group. The adjusted risk of re-revision of any component for any reason was higher in patients with uncemented compared with those with cemented revision stems during the first 3 years after index surgery (hazard ratio [HR] 4, 95% confidence interval [CI] 2-9). From the 4th year onward, the risk of re-revision of any component for any reason was similar (HR 0.5, CI 0.2-1.4). Uncemented revision stems conferred a higher risk of dislocation compared with cemented stems (HR 5, CI 1.2-23) during the first 3 years.Interpretation - Although not predominantly used in more complex femoral defects, uncemented revision stem fixation confers a slightly higher risk of re-revision during the first years, but this risk is attenuated after longer follow-up.

Effects of femoral bone defect morphology on initial polished tapered stem stability in massive defect model: a biomechanical study

Background

Good outcomes have been reported in revision total hip replacement with massive segmental defects using impaction bone grafting with circumferential metal meshes. However, the morphology of defects that require a mesh is poorly defined. The purpose of this study was to evaluate the effects of a variety of segmental defects on load transmission to the proximal femur under both axial and rotational loads.

Methods

Initial stability of the Exeter stem was investigated in a composite bone model using three medial bone defect morphologies: Long (length 5 cm × width 2 cm), Short (2.5 cm × 2 cm), Square (3.2 cm × 3.2 cm), Square with mesh (3.2 cm × 3.2 cm defect covered with metal mesh), and with no defect as control. Specimens (5 per group) were axially loaded and internally rotated up to 20° or to failure. Strain distributions of the femora were measured using a strain gauge.

Results

All Square group specimens failed while rotation was increasing. In the other four groups, failure was not observed in any specimens. Mean torsional stiffness in the Long (4.4 ± 0.3 Nm/deg.) and Square groups (4.3 ± 0.3 Nm/deg.) was significantly smaller than in the Control group (4.8 ± 0.3 Nm/deg.). In the medio-cranial region, the magnitude of the maximum principal strain in the Square group (1176.4 ± 100.9) was significantly the largest (Control, 373.2 ± 129.5, p < 0.001; Long, 883.7 ± 153.3, p = 0.027; Short, 434.5 ± 196.8, p < 0.001; Square with mesh, 256.9 ± 100.8, p < 0.001). Torsional stiffness, and both maximum and minimum principal strains in the Short group showed no difference compared to the Control group in any region.

Conclusions

Bone defect morphology greatly affected initial stem stability and load transmission. If defect morphology is not wide and the distal end is above the lower end of the lesser trochanter, it may be acceptable to fill the bone defect region with bone cement. However, this procedure is not acceptable for defects extending distally below the lower end of the lesser trochanter or defects 3 cm or more in width.

Successful Outcomes Using Interlocking Prostheses for Periprosthetic Fractures with Loose Femoral Components

Periprosthetic femoral fractures with implant loosening are difficult to treat, especially when accompanied by severe bone loss. We report here the treatment outcomes of 4 patients (1 man, 3 women; age range 69-86 years) with periprosthetic femoral fractures and implant loosening after bipolar hemiarthroplasty. Fractures were classified according to the Vancouver classification as type B2 and B3, with adequate or compromised bone stock, respectively. One patient was initially treated conservatively but symptoms due to implant loosening persisted and revision surgery was required. All patients underwent revision using a long-stem cementless implant with interlocking screws as well as a cancellous allograft to augment the bone stock. At final follow-up (mean, 25 months), all patients had stable implant fixation, bony union of the fracture, and marked recovery of the proximal femoral bone stock through allograft use. This revision procedure achieved implant fixation and fracture healing with reconstitution of the femur even in the short term and even in cases with severe bone deficiency.

Prevalence and risk factors for intra-operative periprosthetic fractures in one thousand eight hundred and seventy two patients undergoing total hip arthroplasty: a cross-sectional study

PURPOSE

The purpose of this study was to identify the frequency and type of intra-operative periprosthetic fractures and to describe risk factors in a single tertiary, public hospital, so that these events could be prevented, even among less experienced surgeons.

METHODS

This is a cross-sectional study, based on medical records and imaging exams from the archives of a public, tertiary hospital, from April 1998 to October 2013. All consecutive patients submitted to total hip arthroplasty (THA) in the study period were evaluated, excluding unipolar or bipolar arthroplasty, surgery for the osteosynthesis of periprosthetic fractures, surgical procedure to clean infection site without component substitution and not arthroplastic surgery. Data were analyzed with chi-squared test and multivariate Cox regression.

RESULTS

In the study period, 1,872 THA (1,728 patients) were performed and analyzed, with 144 bilateral cases. In 173 cases, patients had undergone surgical procedures other than THA previously, and in only 260 the surgery consisted of revision THA. There were only two cases of resection THA. Among all patients 101 intra-operative periprosthetic fractures occurred. The univariate analysis revealed a significantly higher risk of intra-operative fractures in female patients, aged more than 65 years, with indication of primary THA and the presence of a previous hip surgery. It indicated also that revision surgeries were associated with a 2.8-fold higher risk of intra-operative fracture, 2.18-fold risk in a previously operated hip and 3.9-fold in cases of resection THA or revision surgery in two stages.

CONCLUSIONS

Intraoperative periprosthetic fracture is a rare event, and it is associated with revision type surgery and THA in a previously operated hip.

Management of severe femoral bone loss in revision total hip arthroplasty

Femoral bone loss is a complex problem in revision total hip arthroplasty. The Paprosky classification is used when determining the degree and location of bone loss. Meticulous operative planning is essential where severe bone loss is a concern. One must correctly identify the bone loss pattern, safely remove the existing components, and proceed with the proper reconstruction technique based on the pattern of bone loss. This article discusses the etiology and classification of bone loss, clinical and radiographic evaluation, components of effective preoperative planning, and clinical results of various treatment options with a focus on more severe bone loss patterns.

The use of Gamma-irradiated proximal femoral allografts for bone stock reconstruction in complex revision hip arthroplasty

We have followed a consecutive series of 49 revision hip arthroplasties, performed for severe femoral bone loss using Gamma-irradiated anatomic-specific proximal femoral allografts longer than five centimetres. The patients were followed for a median 10.2 years, with a five year minimum follow-up. The median preoperative Harris Hip Score (HHS) improved from 42 points to 77 points postoperatively. In four hips the femoral component was further revised for non-union of the allograft and aseptic failure. In one hip the allograft and the femoral component were removed because of infection. In one hip the allograft and the femoral component were re-revised for host step-cut fracture. Junctional-union was observed in 44/49 hips. By defining success as an increase of HHS by 20 points or more, a stable implant and no need for any subsequent re-operations related to the allograft and /or the implant, a success rate of 76% was observed. Kaplan-Meier survivorship analysis predicted 79% rate of survival at 10 years and 75% rate of survival at 17 years, with the need for further revision of the allograft and/or implant as the end point. Three hips underwent re-attachment of the greater trochanter for trochanteric escape. Asymptomatic non-union of the greater trochanter was noticed in another three hips. Moderate allograft resorption was observed in four hips. Two fractures of the host step-cut occurred. There were four dislocations. Good long-term results with the use of large anatomic-specific femoral allografts justify their continued use in cases of revision hip arthroplasty complicated with severe femoral bone loss.

Long term results with the interlocking uncemented long stem in revision hip arthroplasty: a mean 15-year follow-up

Stem fixation is difficult to achieve in severe proximal bone loss in revision hip surgery. In this study, we sought to present the results of distally-locked stem with screws (HUCKESTEP HIP stem) in 21 revision hips with mean follow-up period of 15 years. The preoperative mean Japanese Orthopaedic Association hip score had improved from 54 to 75 points. Further revisions were required for 2 stems, in one because of infection and the other because of screws fracture and subsidence. With removal of the stem for any reason as an end-point, the cumulative survival at 15 years was 90.4%. While this study had small number, the use of this interlocking stem for revision hips with extensive proximal bone defects provided satisfactory 15-year clinical and radiographic results.

Proximal femoral reconstruction with impaction bone grafting and circumferential metal mesh

INTRODUCTION

Impaction bone grafting (IBG) using a circumferential metal mesh is one of the options that allow restoration of the femoral bone stock and stability of the implant in revision hip arthroplasty. Here we examine the clinical and radiographic outcome of this procedure using a cemented stem, including experimental analysis of the initial stability of mesh-grafted bone-cemented stem complexes.

METHODS

We retrospectively reviewed six hips (six patients) that had undergone femoral revisions with a circumferential metal mesh, impacted bone allografts, and a cemented stem. The mean follow-up period was 3.9 years (range 2.4-4.8 years). Hip joint function was evaluated using the Japanese Orthopaedic Association hip score, and radiographic changes were determined from radiographs. The initial resistance of mesh-grafted bone-cemented stem complexes to axial and rotational force was measured in a composite bone model with various segmental losses of the proximal femur.

RESULTS

The hip score improved from 50 (range 10-84) preoperatively to a mean of 74 (range 67-88) at the final follow-up. The overall implant survival rate was 100 % at five years when radiological loosening or revision for any reason was used as the endpoint. No stem subsided more than 3 mm vertically within one year after implantation. Computed tomography showed reconstitution of the femoral canal in a metal mesh. In mechanical analyses, there was no relationship between IBG reconstruction rates under axial compression and stem subsidence or failure load. In contrast, under rotational load, the rotation angles of the stem to the stainless steel mesh were strongly affected by the IBG reconstruction rate.

CONCLUSIONS

The short-term results show good outcomes for reconstruction of proximal bone loss with IBG and a circumferential mesh. The procedure should be applied in cases where the circumferential proximal bone loss is less than half the length of the implanted stem.

The management of femoral bone stock in THA revision: indications and techniques

Following the increasing number of total hip arthroplasties, the amount of hip revision procedures continue to rise. Careful patient selection and bone loss evaluation is crucial for a correct management of femoral revision procedures. The key point in femoral revision is to obtain a reliable primary stability of the stem, with the least invasive implant as possible, to preserve and if possible to restore the bone stock. In this article we present the indications and the techniques for the femoral revisions most commonly used in Europe, referring to the evidence in the literature and our personal experiences.

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.

Experience of structural onlay allografts for the treatment of bone deficiency in revision total hip arthroplasty

Background and Aims:

Loss of femoral bone stock in elective revision total hip arthroplasty poses unique and substantial challenges. Structural onlay allografts may provide mechanical stability for the cementless revision prosthesis and increase bone stock.

Material and methods:

At least one cortical onlay allograft was used in 40 elective total hip arthroplasty revisions (40 patients) to reconstruct femoral bone defects. The operations were performed between January 1999 and August 2010 in the Turku University Hospital, Finland. The mean follow-up time was 52 months (range: 12–125 months).

Results:

The allografts were incorporated into the bone tissue in 37 of 40 (92.5%) patients. Cementless revision stems healed in 36 of 40 (90.0%) patients, but these patients were not exactly the same patients whose allografts were successfully incorporated. One or more surgical complications were experienced by 14 of 40 (35.0%) patients during follow-up. In all, 4 of 40 (10.0%) patients (all women) had hip infections during follow-up. Of the 7 patients with rheumatoid arthritis, 4 (57.1%) had at least one complication.

Conclusions:

The use of the cortical onlay allografts provides a feasible option for restoring the integrity of the proximal femur in revision total hip arthroplasty, but the complication rate is high, particularly in female patients with rheumatoid arthritis.

Impaction grafting in the femur in cementless modular revision total hip arthroplasty: a descriptive outcome analysis of 243 cases with the MRP-TITAN revision implant

Background

We present a descriptive and retrospective analysis of revision total hip arthroplasties (THA) using the MRP-TITAN stem (Peter Brehm, Weisendorf, GER) with distal diaphyseal fixation and metaphyseal defect augmentation. Our hypothesis was that the metaphyseal defect augmentation (Impaction Bone Grafting) improves the stem survival.

Methods

We retrospectively analyzed the aggregated and anonymized data of 243 femoral stem revisions. 68 patients with 70 implants (28.8%) received an allograft augmentation for metaphyseal defects; 165 patients with 173 implants (71.2%) did not, and served as controls. The mean follow-up was 4.4 ± 1.8 years (range, 2.1–9.6 years). There were no significant differences (p > 0.05) between the study and control group regarding age, body mass index (BMI), femoral defects (types I-III as described by Paprosky), and preoperative Harris Hip Score (HHS). Postoperative clinical function was evaluated using the HHS. Postoperative radiologic examination evaluated implant stability, axial implant migration, signs of implant loosening, periprosthetic radiolucencies, as well as bone regeneration and resorption.

Results

There were comparable rates of intraoperative and postoperative complications in the study and control groups (p > 0.05). Clinical function, expressed as the increase in the postoperative HHS over the preoperative score, showed significantly greater improvement in the group with Impaction Bone Grafting (35.6 ± 14.3 vs. 30.8 ± 15.8; p ≤ 0.05). The study group showed better outcome especially for larger defects (types II C and III as described by Paprosky) and stem diameters ≥ 17 mm. The two groups did not show significant differences in the rate of aseptic loosening (1.4% vs. 2.9%) and the rate of revisions (8.6% vs. 11%). The Kaplan-Meier survival for the MRP-TITAN stem in both groups together was 93.8% after 8.8 years. [Study group 95.7% after 8.54 years ; control group 93.1% after 8.7 years]. Radiologic evaluation showed no significant change in axial implant migration (4.3% vs. 9.3%; p = 0.19) but a significant reduction in proximal stress shielding (5.7% vs. 17.9%; p < 0.05) in the study group. Periprosthetic radiolucencies were detected in 5.7% of the study group and in 9.8% of the control group (p = 0.30). Radiolucencies in the proximal zones 1 and 7 according to Gruen occurred significantly more often in the control group without allograft augmentation (p ≤ 0.05).

Conclusion

We present the largest analysis of the impaction grafting technique in combination with cementless distal diaphyseal stem fixation published so far. Our data provides initial evidence of improved bone regeneration after graft augmentation of metaphyseal bone defects. The data suggests that proximal metaphyseal graft augmentation is beneficial for large metaphyseal bone defects (Paprosky types IIC and III) and stem diameters of 17 mm and above. Due to the limitations of a retrospective and descriptive study the level of evidence remains low and prospective trials should be conducted.

[What can be done when hip prostheses fail? : New trends in revision endoprosthetics]

Revision surgery after total hip arthroplasty is increasing steadily in numbers. These procedures demand high performance from both the treating surgeon as well as the implants used. Novel developments from basic research and industrial partners extend the possibilities for treating affected patients. This article gives an overview of the state of the art in revision hip arthroplasty: new techniques and trends are outlined and presented.

Midterm results of femoral impaction bone grafting with an allograft combined with hydroxyapatite in revision total hip arthroplasty

The purpose of this study was to evaluate the outcome of femoral impaction bone grafting with an allograft combined with hydroxyapatite (HA). Fifty-four consecutive femoral reconstructions that were performed with the use of frozen morselized allografts and HA were followed up retrospectively. The average follow-up period was 92 months. A femoral head and HA were mixed and used as allograft. The average Merle d'Aubigné clinical score improved from 8.9 preoperatively to 13.1 points postoperatively. Stem subsidence was seen in 26 hips; however, it was not progressive after 1 year postoperatively. Cortical repair was detected at an average of 7 months postoperatively. Impaction bone grafting with an allograft combined with HA provided favorable results, with bone remodeling and less subsidence.

Femoral impaction grafting in revision total hip arthroplasty: a follow-up of 540 hips

Between 1987 and 1999, 540 revision total hip arthroplasties in 487 patients were performed at our institution using the femoral impaction grafting technique with a cemented femoral stem. All patients were prospectively followed up for 2 to 15 years postoperatively with no loss to follow-up. A total of 494 hips remained successfully in situ at an average of 6.7 years. The 10-year survival rate was 98.0% (95% confidence interval, 96.2-99.8) with aseptic loosening as the end point and 84.2% (95% confidence interval, 78.5-89.9) for reoperation for any reason. Indication for surgery and the use of any kind of reinforcement significantly influenced outcome (P < .001). This is the largest known series of revision THA with femoral impaction grafting, and the results support continued use of this technique.

Defining the impaction frequency and threshold force required for femoral impaction grafting in revision hip arthroplasty. A human cadaveric mechanical study

BACKGROUND AND PURPOSE

The two most common complications of femoral impaction bone grafting are femoral fracture and massive implant subsidence. We investigated fracture forces and implant subsidence rates in embalmed human femurs undergoing impaction grafting. The study consisted of two arms, the first examining the force at which femoral fracture occurs in the embalmed human femur, and the second examining whether significant graft implant/subsidence occurs following impaction at a set force at two different impaction frequencies.

METHODS

Using a standardized impaction grafting technique with modifications, an initial group of 17 femurs underwent complete destructive impaction testing, allowing sequentially increased, controlled impaction forces to be applied until femoral fracture occurred. A second group of 8 femurs underwent impaction bone grafting at constant force, at an impaction frequency of 1 Hz or 10 Hz. An Exeter stem was cemented into the neomedullary canals. These constructs underwent subsidence testing simulating the first 2 months of postoperative weight bearing.

RESULTS

No femurs fractured below an impaction force of 0.5 kN. 15/17 of the femurs fractured at or above 1.6 kN of applied force. In the second group of 8 femurs, all of which underwent femoral impaction grafting at 1.6 kN, there was no correlation between implant subsidence and frequency of impaction. Average subsidence was 3.2 (1-9) mm.

INTERPRETATION

It is possible to calculate a force below which no fracture occurs in the embalmed human femur undergoing impaction grafting. Higher impaction frequency at constant force did not reduce rates of implant subsidence in this experiment.

Chronology of the radiographic appearances of the calcium sulphate-calcium phosphate synthetic bone graft composite following resection of bone tumours--a preliminary study of the normal post-operative appearances

OBJECTIVE

To describe the normal chronological radiographic appearances of the calcium sulphate-calcium phosphate (CaSO(4)/CaPO(4)) synthetic graft material following bone tumour resection during the processes of graft resorption and new bone incorporation into the post-resection defect.

MATERIALS AND METHODS

Retrospective review of our oncology database identified patients who had undergone serial radiographic assessment after treatment with the CaSO(4)/CaPO(4) synthetic graft following bone tumour resection. Post-operative radiographs were assessed for (1) partial resorption of graft material with partial ingrowth of new bone at the graft site and (2) complete resorption of graft material with complete incorporation of new bone into the graft site. The pattern of resorption of graft material was also documented. Any radiographic evidence of complication was recorded. Radiographs were also divided into groups according to their interval from surgery to establish a pattern of time-related changes.

RESULTS

A total of 11 patients were identified from our database. Partial resorption of graft material/partial ingrowth of new bone was seen in nine patients, initially observed at a mean of 1.4 months from surgery. Resorption commenced peripherally with gradual inward progression in 100% (9 of 9) of cases. Complete resorption of graft/complete new bone incorporation at the graft site was seen in 89% (8 of 9) of cases followed up for more than 5 months after surgery. The other patient developed recurrence of tumour at 14 months, before complete incorporation was demonstrated. The mean time to complete incorporation of new bone was 5 months. Two patients have, to date, been followed up at 2 and 3 months respectively with a pattern of peripheral graft resorption observed so far in both cases. Ten of 13 (77%) radiographs performed 1-3 months after surgery demonstrated peripheral resorption of graft material with partial osseous ingrowth into the defect. Seven of eight (88%) radiographs performed 6-12 months after surgery demonstrated complete new bone incorporation at the graft site with graft material completely resorbed. Ten of 11 (91%) radiographs performed 1 year after surgery demonstrated complete new bone incorporation, the other examination demonstrating recurrence.

CONCLUSION

Our preliminary observations suggest a characteristic, time-related radiographic pattern during the processes of CaSO(4)/CaPO(4) bone graft resorption and complete new bone incorporation. This pattern can be directly related to processes that occur at the molecular level. Radiographic findings that are not in keeping with this may merit closer follow-up.

Incidence of deep infection in aseptic revision THA using vancomycin-impregnated impacted bone allograft

The addition of antibiotic to cement is a frequent practice in aseptic revision hip surgery There is concern about adding vancomycin to cement due to potential effects on mechanical properties and prolonged elution of subtherapeutic levels antibiotic. Bone allografts can store and provide high levels of vancomycin to surrounding tissues. We analyzed the incidence of infection after one-stage aseptic revision hip reconstruction utilizing acetabular and/or femoral vancomycin-impregnated impacted bone allograft and a THA fixed with cement containing no antibiotic. We hypothesized that the infection rate may be similar to that reported in the literature following traditional impaction grafting using antibiotic loaded cement. Seventy five consecutive patients (80 hips) with a preoperative Merle D'Aubigné and Postel functional score averaging 4.8 points were followed up for a mean of 36 months (range 24 - 59 months). The incidence of infection was 1.25% (CI 95%=96.26-100%). A deep infection (thought to be haematognous in origin) occurred in 1 patient 2 years after the index surgery. The average postoperative Merle D´Aubigne score was 16.2 points. The last radiographic evaluation demonstrated a less than 5 mm acetabular migration and a less than 5 mm femoral subsidence in all cases. Vancomycin-supplemented allografts restored bone stock and provided sound fixation with a low incidence of infection. This incidence of deep sepsis is similar to that reported with antibiotic-loaded PMMA but without the reported mechanical and pharmacological disadvantages.

An alternative solution to achieve primary stability in cementless revision hip arthroplasty for femur ectasia

BACKGROUND/PURPOSE

Revision total hip arthroplasty is technically demanding, especially when treating a large defective femur. The aim of this study was to evaluate the clinical results of cementless total hip arthroplasty revision in patients with advanced femoral bony defects.

METHODS

By using the canaloplasty technique, which osteotomized the proximal femur to reduce the width of canal, 12 patients were enrolled and underwent revision operation. Patients were evaluated by radiographic examination and Harris hip score before and after the index procedures.

RESULTS

The average length of follow-up was 38.7 months. All the osteotomies united at a mean of 5.3 months. Structural allografts were used on six patients to augment the thinned cortices. A total of 11 femoral components (91%) achieved and maintained stability at the last follow-up. One patient was complicated with early stem subsidence and another with deep infection. Both patients were treated successfully without late sequelae. The mean Harris hip score improved from 37.2 to 75.0 after the operation (p < 0.05).

CONCLUSION

The canaloplasty technique could be an alternative solution to help revision surgery in some younger patients with advanced femoral defects.

Outcome after femoral revision using the restoration cone/conical femoral revision stem

Despite improvements in implant technology and surgical technique, failure of total hip arthroplasty (THA) remains a persistent problem. This article reports clinical outcomes at a mean follow-up of 42 months using the Restoration cone/conical modular femoral revision stem (Stryker, Newbury, United Kingdom). A prospective cohort study was performed of 46 consecutive patients who underwent revision THA between January 2004 and June 2007. Patients were reviewed pre- and postoperatively at regular intervals for clinical and radiological assessment. Forty-six patients (17 men, 29 women) with a mean age of 72 years (range, 44-93 years) were observed for a mean of 42 months (range, 28-66 months). Indications for surgery included aseptic loosening/osteolysis (38/46 [83%]), periprosthetic fracture (4/46 [9%]), and infection (4/46 [8%]). Median time from index procedure was 16 years (range, 1-26 years). No patient was lost to follow-up. Two patients (4%) with well-fixed asymptomatic stems died during follow-up. Three patients (7%) sustained an early postoperative dislocation. One patient sustained a periprosthetic fracture after a fall. This was treated by osteosynthesis, and stem revision was not required. Mean Oxford Hip Score improved from 42 points (range, 24-57 points) to 28 points (range, 18-51 points) at 3-month follow-up (P=.003). Median stem subsidence was 1.0 mm (standard error of the mean, ±1.7 mm; range, 0-7mm) at last follow-up. No patient developed loosening or osteolysis around the stem. The Restoration femoral revision system has favorable clinical and radiological outcomes at a mean follow-up of 42 months.

Revision total hip arthroplasty with femoral impaction bone grafting

PURPOSE

To report the radiological and clinical results of revision total hip arthroplasty (THA) with femoral impaction bone grafting (IBG).

METHODS

4 men and 9 women (15 hips) aged 38 to 84 years underwent revision THA with femoral IBG using Elite plus stems for aseptic loosening or infection.

RESULTS

The mean follow-up duration was 7.7 years. The Harris hip score improved from 61.7 to 83.7. There was no pain in 11 hips and slight pain in 4. The mean subsidence was 5.7 mm. The mean change of alignment was 1.2 degrees. There was no radiological evidence of stem loosening. One stem was revised due to a peri-prosthetic fracture. Cortical healing was noted in 11 hips, and trabecular incorporation in 10.

CONCLUSION

Although intra- and post-operative complications were not uncommon, femoral IBG is a safe procedure in carefully selected patients and offers good medium-term results.

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.

Distal interlocking screws with a modular revision stem for revision total hip arthroplasty in severe bone defects

A prospective study of 15 patients was designed to examine whether the modular cementless revision stem (Revitan curved; Zimmer GmbH, Winterthur, Switzerland) is suitable for stem revisions with a defective isthmus when distal interlocking screws are also used for fixation. During a follow-up period of 35.4 +/- 11.4 months (24-70 months), there was one stem loosening with screw breakage in a case of a stem that was too thin. According to Engh et al, bony ingrowth fixation of the stem occurred in 12 cases and stable fibrous fixation in 2 cases. The Harris Hip Score rose continuously from 44.7 +/- 12.9 points preoperatively to 75 +/- 10 points at 24 months. This concept of additional stem fixation with distal interlocking screws represents a useful treatment option for revision arthroplasty in rare cases of a defective isthmus.

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.

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.

Neck fracture femoral heads for impaction bone graftingEvolution of stiffness and compactness during impaction of osteo-arthrotic and neck-fracture femoral heads

BACKGROUND

The need for safe bone allografts is increasing and preservation of femoral heads from patients being operated on with hip arthroplasty should be encouraged. However, should we preserve femoral heads from patients operated on for neck fracture as tissue mechanical quality may not be satisfactory?

MATERIAL AND METHODS

We compared the evolution of stiffness and compactness of fresh-frozen morselized bone obtained from osteoarthrotic femoral heads and those from neck fractures. Both materials were also compared after freeze-drying and irradiation. We used 6 osteoarthrotic and 6 neck-fracture femoral heads to prepare 4 batches of morselized bone. 18 samples from each batch were impacted in a contained cylinder. Frozen bone grafts were tested after thawing at room temperature for 2 hours and freeze-dried grafts were tested after 30 minutes of rehydration.

RESULTS

The stiffness of fresh-frozen neck fracture bone was lower than that of fresh-frozen osteoarthrotic bone at 150 impactions. The stiffness of freeze-dried irradiated bone was higher than that of the fresh-frozen bone and did not differ between osteoarthrotic and neck-fracture bone.

INTERPRETATION

Solvent-treated freeze-dried bone from femoral heads procured during arthroplasty for sub-capital hip fractures represents a valuable source of material for allografts, addressing concerns regarding serological testing, medical history and bone quality.

Impaction bone grafting with freeze-dried irradiated bone. Part II. Changes in stiffness and compactness of morselized graftsExperiments in cadavers

In the technique of impaction bone grafting, implant stability depends on the mechanical properties of the impacted morselized grafts. Although the procedure is usually performed with fresh-frozen femoral heads, there is still some concern about their supply and safety. Bone processing is a potential solution, but the mechanical properties of this material during and after impaction need to be determined. We used 6 osteoarthrotic femoral heads to prepare two paired batches of morselized bone. One batch was morselized and frozen. The other batch was chemically treated, morselized, freeze-dried and then gamma-irradiated. We impacted 18 samples from each batch in a contained cylinder. Freeze-dried bone grafts were tested after 30 minutes of rehydration. The changes in the compactness and stiffness of the material were monitored during the impaction. The compaction of the freeze-dried bone was faster than that of their fresh-frozen control. The maximal stiffness reached by both materials was the same (55 MPa), but the freeze-dried grafts required three to four times fewer impactions to achieve that stiffness. After 3, 10 and 50 impactions the freeze-dried bone was stiffer than the fresh-frozen bone. As it is easier to impact, the freeze-dried bone may be mechanically more efficient than the fresh-frozen bone in surgical conditions. Moreover, the processed bone meets the highest safety standards, as regards the risk of disease transmission.

Intraoperative periprosthetic fractures during total hip arthroplasty. Evaluation and management

Intraoperative periprosthetic fractures are becoming more common given the increased prevalence of revision total hip arthroplasty and increased use of cementless fixation. Risk factors for intraoperative periprosthetic fractures include the use of minimally invasive techniques; the use of press-fit cementless stems; revision operations, especially when a long cementless stem is used or when a short stem with impaction allografting is used; female sex; metabolic bone disease; bone diseases leading to altered morphology such as Paget disease; and technical errors at the time of the operation. Appropriate treatment of intraoperative periprosthetic fractures does not compromise the long-term results of total hip arthroplasty unless the bone damage precludes stable fixation of the implant.

[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.

The use of long cemented stems for femoral impaction grafting in revision total hip arthroplasty

BACKGROUND

Following revision total hip arthroplasty involving femoral impaction grafting, fractures usually have occurred distal to a standard-length stem in an area of weakened bone that was left inadequately supported. The purpose of the present study was to determine whether the use of a long stem decreases the rate of femoral fracture after revision hip surgery. We hypothesized that the use of a long-stem femoral component would decrease the risk of these fractures.

METHODS

From 1991 to 2000, 567 revision total hip arthroplasties were performed with use of femoral impaction grafting. Of these, forty-two procedures in forty patients (average age, 73.8 years) were performed with use of a stem that was > or = 220 mm in length. The average number of previous revisions was 1.85. Thirty-four of the forty hips with preoperative radiographs had preoperative bone loss that was classified as grade III or IV according to the Endo-Klinik system. Major complications were recorded, and survival analysis was performed.

RESULTS

No patient was lost to follow-up. Sixteen patients (sixteen hips) died at an average of fifty-two months postoperatively. The average duration of clinical follow-up for the hips in which the implant survived for more than forty-eight months was 7.5 years. The rate of major postoperative complications was 29%. Two postoperative femoral fractures occurred. Six patients (six hips) required a femoral reoperation. The survival rate with revision hip surgery as the end point was 90% at both five and ten years. The rate of survival with any failure as the end point was 82% at five years and 64% at ten years.

CONCLUSIONS

The use of a long stem for femoral impaction grafting did not completely resolve the problem of postoperative fractures in these patients with substantial loss of bone stock undergoing revision hip surgery. Poor bone stock, technical errors, and other patient-related factors continue to account for the high postoperative fracture rate.

Impaction grafting for femoral component revision in a goat model using washed morselized cancellous allograft

To determine whether washing morselized cancellous bone allograft in impaction grafting for revision hip arthroplasty would improve mechanical and biologic performance, left hip hemiarthroplasty with a collarless stem cemented into impacted morselized cancellous bone was performed in 22 goats. Washed allograft was used in the experimental group, and standard allograft was used in the control group. One of 11 experimental and 4 of 11 control implants were observed to be loose at 8 weeks. Washing allowed significantly more morselized cancellous bone to be placed in the experimental group compared to the control group (7.7+/-1.9 and 6.2+/-2.0 g, respectively, P<.05). Significantly less in vivo subsidence over the 8-week study period also was demonstrated in the experimental group compared to the control group (0.4+/-0.4 and 2.2+/-2.3 mm, respectively, P<.05). Angular motion during cyclic +/-1.5 Nm loading demonstrated significant differences between the 2 groups at time zero (2.67 degrees +/-1.02 degrees for the control group and 1.98 degrees +/-0.47 degrees for the experimental group, P<.05) and at 8 weeks (2.40 degrees +/-0.38 degrees for the control group and 1.74 degrees +/-0.55 degrees for the experimental group, P<.05). Histology showed little difference between the 2 groups, but there was a trend toward less inflammation in the experimental group.

The effect of preoperative planning and impaction grafting surgical technique on intraoperative and postoperative complication rate for femoral revision patients with moderate to severe bone loss mean 4.7-year results

This study reports the results of 41 revision hips, implanted by a single surgeon using impaction grafting (mean follow-up, 4.7 years). All hips had Paprosky scores of III or IV. Harris hip scores improved from 43 to 82. There was 1 intraoperative and 2 postoperative fractures. A single stem was revised during the study. Radiographic review showed the 40 unrevised stems to be stable, and graft incorporation was seen in at least 1 zone in 100% of the femurs. There was no stem subsidence greater than 2.5 mm. The results of this study demonstrate that preoperative planning and a surgical technique, which emphasizes femoral support and vigorous impaction grafting, resulted in an acceptable incidence of complications.

Good results with an uncemented proximally HA-coated stem in hip revision surgery: 62 hips followed for 2-13 years

BACKGROUND AND PURPOSE

Proximal bone loss due to stress-shielding is a matter of concern after uncemented femoral hip revision. We have used short, proximally hydroxyapatite-coated prostheses in revision since 1989, and we now report the results.

METHODS

60 patients (62 hips) were revised because of aseptic loosening. Bone defects prior to revision were mostly of type II according to the Gustilo-Pasternak and Endo-Klinik classifications. Follow-up time was 73 (24-161) months. 9 patients had died before follow-up; 8 of these still had the stem in place. Clinical assessment was performed with the Harris hip score. Radiographs were evaluated for bone defects at revision, postoperative stem fixation, and periprosthetic bone remodeling.

RESULTS

Mean Harris hip score was 75 (30-100) points. There was no stem loosening or progressive subsidence. 8 patients had mild to moderate thigh pain. Osteolysis, present at revision, had diminished, partially or completely, in four-fifths of the hips at follow-up. 4 hips had required re-revision due to fracture or dislocation. The 6-year prosthesis survival rate was 95% (95% CI: 0.83-0.98).

INTERPRETATION

Uncemented revision with a short, proximally hydroxyapatite-coated prosthesis is a reliable procedure with encouraging results in the medium term if bone defects at revision are moderate.

Fixation and bone remodeling around a low stiffness stem in revision surgery

Femoral stems with reduced stiffness have the potential of decreasing stress shielding and could be an alternative in revision surgery when restoration of bone stock is required. We retrospectively reviewed 38 patients (40 stems) with a central core of cobalt-chromium surrounded by a polymer and an outer titanium mesh layer containing a proximal coating of hydroxyapatite/tricalcium phosphate; 30 of the 38 patients (32 hips) had a minimum 2-year followup. We impacted morselized allograft around the stem in 28 of 32 revisions. Repeated radiostereometric examinations showed medial, distal, and posterior migration (median, 0.21 mm, 0.17 mm, and 0.96 mm, respectively) of the femoral head center for up to 6 months followed by stabilization. Measurements of bone mineral density in the seven Gruen zones at 6 months revealed either a decrease (down to a median of 3%), no change, or a slight increase (up to 5%) followed by a further increase up to 2 years in three of the regions (2, 3, and 5). Conventional radiography at 2 years demonstrated graft remodeling and incomplete radiolucent lines in 19 hips, mainly in Regions 1 and 7. Two hips were reoperated on as a result of dislocation, but none of the stems had been revised.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Reconstruction of bone defects with impacted allograft in femoral stem revision surgery

A retrospective clinical review was done on 54 revision hip patients. Radiological analysis examined the Gross and AAOS classifications, stem position, cement mantles, allograft and evolution (subsidence, resorption and remodelling). The Harris Hip score was used for clinical assessment. We used bone bank allograft and a polished non-collared stem LD. The follow-up period was 60.5 months (19.4-152.4), and the average age 68.5 (range: 22-85). There were 21 females and 33 males. The surgical approach was: lateral (5.56%) posterior (91.4%); trochanteric osteotomy: 25.9%; associated acetabular revision: 59.3%; previous operations: 1.9. The preoperative Harris score was 35 (28-40) and rose to 81 (50-99) postoperatively. The stem alignment was neutral (44.44%), varus (38.89%) and valgus (16.67%). The femur/stem diameter relationship was 1.8 (1.2-2.7). There were no changes in stem alignment in 94.4%. An adequate cement mantle was: proximal zone (61.1%), medium zone (27.8%) and distal zone (16.7%). The rate of any subsidence was 38.9% (progressive: 12.96%). The rate of complications was 40.7% and included periprosthetic fracture: 14.8%; superficial infection: 1.9%; deep late infection: 1.9%; dislocation: 3.7%; heterotopic ossification: 13%. The rate of new stem revision was 16.6%. The clinical and radiological success rate was 77.78%. A greater incidence of revisions has been found in stem malalignment, progressive subsidence, a Harris increase of <20 points, allograft resorption, small diameter stems and inadequate cement mantle. We recommend hard impaction and a cement mantle of at least 2 mm. Non-progressive subsidence does not increase stem loosening. The technique has been useful in recovering bone stock in a severely defective femur and achieves a stable reconstruction. The level of evidence was therapeutic study level III-2 (retrospective cohort study; see the instructions to the authors for a complete description of the levels of evidence).

Extensively porous-coated stems for femoral revision: a choice for all seasons

We reviewed the outcome of 905 femoral revisions performed at our institution between June 1980 and August 2006 using extensively porous-coated, cylindrical stems. A total of 20 femoral rerevisions were identified, including 12 for aseptic loosening, 4 for infection, 3 for stem fracture, and 1 in conjunction with a periprosthetic femur fracture. All stem rerevisions occurred within the first 10 years after surgery. Kaplan-Meier survivorship, using stem rerevision for any reason as an end point, was 97.5% +/- 1.3% (95% confidence intervals) at 5 years, declined to 95.9% +/- 1.9% at 10 years, and remained constant thereafter. With long-term follow-up, extensively porous-coated, cylindrical stems used for femoral revision continue to demonstrate excellent survivorship.

Initial stability of circumferential meshes with impacted bone allografts for massive femoral defects

When the proximal femur is absent due to a failed femoral stem in total hip arthroplasty, impacted bone grafts contained within circumferential meshes could be an alternative reconstructive method. The purpose of this study was to analyse the initial resistance to axial and rotational forces in a fresh frozen bovine model with complete loss of the proximal femur reconstructed with a circumferential metal mesh, impacted bone allografts and a long cemented stem. Four bovine femurs with a complete proximal bone defect were reconstructed with a circumferential mesh, impacted bone grafts and a cemented stem. The results were compared with four intact femurs using the same implant. Under axial load, subsidence was observed at an average of 617 kg in the experimental group, and a cortical fracture occured at 1335 kg in the control group. Under rotational load, experimental femurs failed at an average of 79 kg and the control femurs fractured at 260 kg. This model provided 50% of the resistance to axial load and 30% of the resistance to rotational load compared to an intact femur, which is enough to resist physiological load. This stability encourages the use of circumferential meshes, impacted bone allografts and cemented stems in revision hip surgery with massive bone loss.

Reinforcement of deficient femur with inlay strut grafts in revision hip arthroplasty: a small series

Failure of the femoral component due to severe loss of femoral bone is an important long-term complication of total hip arthroplasty. We treated four patients with a type IV femoral defect (Paprosky classification) because of aseptic and septic loosening. To enhance bone stock and create a stable prosthetic reconstruction we used femoral allografts as inlay strut grafts alone or combined with onlay strut grafts and impaction grafting. At a mean follow-up of 11 years all four patients presented good or excellent results with Harris Hip Score between 86 and 95 points. Radiologically, no migration of the stems were found and the struts showed signs of incorporation. Inlay strut grafts are a reliable method for bone reconstruction of deficient femoral bone stock in failed total hip replacement.

The bovine bone protein lyophilisate Colloss improves fixation of allografted implants--an experimental study in dogs

BACKGROUND

Impacted morselized bone allograft is a well-established way of giving joint arthroplasties additional support in situations where there is insufficient bone stock. For long-term survival of the implant, early implant fixation is important. We hypothesized that Col-loss, a bone protein lyophilisate, might improve early implant fixation of allografted implants.

METHOD

We inserted 4 porous-coated Ti implants in the distal femurs of 16 dogs. All implants were surrounded by a 2.5-mm gap, which was impacted with morselized allograft with or without Colloss. In each dog, the implants were treated with no Collos or low-, middle- or high-dose (0, 10, 20 and 40 mg) Colloss per cm3 allograft. The observation time was 4 weeks.

RESULTS

Mechanical implant fixation was improved for all 3 groups with Colloss-treated implants (p < 0.05). The best anchorage was seen in the middle-dose group, where fixation was improved by 100%. We saw a dramatic reduction in fibrous tissue on the surface of the Colloss-treated implants (p < 0.001). The Colloss groups showed increased ongrowth of new bone (p < 0.01) and accelerated gap remodeling (p < 0.05).

INTERPRETATION

Colloss can improve early osseointegration and fixation of allografted implants.

In vitro monitoring of hoop strains during impaction grafting of the femur

A test was designed to monitor hoop strains around the proximal femur during impaction grafting. Four electrical resistance strain gauges were attached to Sawbone femurs just below the level of the lesser trochanter. Experimentation with these femoral models included the use of a device called an "impactometer", which delivered controllable impaction energies. Test material used was ovine morsellised bone graft prepared from sheep femoral condyles. Instruments used were "X-change" revision instruments from the Exeter hip system. Maximum strains occurred at the medial and lateral cortices and there were lesser strains on anterior and posterior cortices. These findings raise questions about the quality of impaction anterior and posterior to the femoral stem. At the medial and lateral gauges significant differences in levels of strain were recorded at the three different levels of impaction. An individual hoop strain was found to have three components: peak, rapid drop and slow drop. The strain level did not drop back to the starting point at the end of the drop phase but dropped only halfway back to the starting level. This resulted in a rise in strain levels in a stepladder pattern. Strains continued to rise significantly when the impaction process was continued beyond the endpoint of impaction. Early recognition of the endpoint of impaction can save the weak femoral bone from unnecessary high levels of hoop strain.

Bone substitution in revision hip replacement

The aim of this retrospective study was to report the preliminary results of femoral peri-prosthetic bone defect reconstruction with a synthetic bone substitute. Twenty-one revisions of the femoral component in 20 patients were evaluated. The mean age at operation was 65.7 years (range, 30 to 79 years). Preoperative femoral deficiencies were rated grade II in 7 cases and grade III in 14 cases according to the SOFCOT classification. None was rated grade IV. Femoral revision was indicated for loosening in 18 hips (including 8 septic cases), femoral osteolysis (1 hip), persistent pain (1 hip) and recurrent dislocation (1 hip). Once the loose prosthesis had been removed, calcium phosphate ceramic (CPC) granules (14 cases) or ceramic granules + cancellous allograft (5 cases) or autograft (2) were firmly impacted in the femoral canal. The stem was standard and always cemented using modern cementing technique. At a mean follow-up of 36 months (range, 14 to 76 months), 90% of the hips were rated good or very good according to the Merle d'Aubigné score. Two diaphyseal femoral fractures occurred and later united. Two hips required re-revision (aseptic loosening; septic recurrence). The absence of radiological osteolysis in 17 cases suggested direct bonding between ceramic granules and bone. Stem subsidence occurred in two cases and was limited (5 and 8 mm). Femoral bone reconstruction using impacted CPC or CPC in conjunction with bone graft in revision hip replacement commonly provided restoration of the bone stock in the short to mid-term. Further long-term studies will be necessary to support this conclusion.

Reconstruction fémorale par céramique de phosphate de calcium macroporeuse impactée au cours des reprises d’arthroplastie de hanche

PURPOSE OF THE STUDY

Management of bone stock loss remains one of the most challenging problems for revision hip surgery. The aim of this retrospective study was to report the preliminary results of peri-prosthetic femoral defect reconstruction with impacted granules of calcium phosphate ceramic.

MATERIAL AND METHODS

Fourteen hips in 13 patients (3 men and 10 women) were evaluated. Age at surgery ranged from 30 to 79 years (mean 66.1 years). All revised devices had been cemented. Femoral revision was indicated for loosening in eleven hips (including six septic cases), femoral osteolysis (one hip), persistent pain (one hip), and recurrent dislocation (one hip). On the preoperative radiological evaluation, bone defects were assessed as SOFCOT grade II in seven case, and grade III in fourteen. None was rated grade IV. Once the loose prosthesis had been removed, bone graft or ceramic granules (14 cases) were firmly impacted in the femoral canal. The stem was standard and always cemented using modern cementing technique.

RESULTS

At a mean follow-up of 34 +/- 15 months (range 14-76 months), eleven of fourteen hips were rated good or very good according to the Postel-Merle-d'Aubigné score. One diaphyseal femoral fracture occurred and later united. Two hips required re-revision (one aseptic femoral loosening, one septic recurrence). Direct bonding between synthetic graft and bone was observed on standard radiographs in eleven cases. Stem subsidence occurred in two cases and was limited (mean 4.5 mm).

DISCUSSION

Femoral bone reconstruction using impacted calcium phosphate ceramic in revision hip arthroplasty provided encouraging results in the short to mid term. Femoral stock restoration was achieved in the great majority. No adverse effect related to the use of a synthetic graft was noted. Further long-term evaluation is required before wider application.

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.

Cement flow during impaction allografting: a finite element analysis

Cement intrusion into cancellous or impacted bone is not well understood. We adopted an engineering mechanics approach to predict the effect of surgical variables on the cement intrusion into impacted cancellous bone, used for the revision of failed total hip replacement with the impaction allografting technique. Specifically, a three-dimensional finite element model was used to determine the effects of cement viscosity, the magnitude and duration of pressurization, and the distribution of the porosity along the femur on cement intrusion. The overall averaged mean intrusion depth difference between the finite element model prediction and the cadaveric measurements was 1.1mm. The depth of penetration increased with higher pressurization pressure, duration of pressurization, and earlier stem insertion (lower viscosity), but maintained a similar profile. The distribution of the porosity along the femur determined the intrusion profile. Cement viscosity, the applied pressure or the duration of the pressurization can be adjusted to limit the cement volume injected into the medullary canal and therefore prevent the cement from reaching the endosteal surface.

Factors affecting stiffness properties in impacted morsellized bone used in revision hip surgery: An experimentalin vitro study

When revising loosened joint prosthesis, impacted morsellized bone is frequently used as organic scaffolding. We studied the relative influence that different bone particle size, impaction energy, and liquid content had on impacted bone stiffness. Bovine bone was morsellized in a bone mill by three grinding drums to produce bone with different chip size distribution. Next, portions of bone chips of controlled sizes were produced by a five-leveled sieve. Layer by layer of bone are constructed into pellets by our experimental impaction method. This method allows us to vary one independent factor at a time in a controlled manner while keeping the other factors constant. Stiffness for all bone pellets were measured during impaction and loading. In earlier studies, we focused on how impaction force, number of impaction strokes, and bone liquid contents influence mechanical behavior. Here, we compare the outcome of all studies using general linear models. All five factors significantly contribute to stiffness of impacted morsellized bone. Changing bone moisture has major, while increasing the number of impaction strokes beyond five per layer has minor effect. Low water content is the main contributor to highest load stiffness. Optimal stability of impacted morsellized bone is achieved with dried and well-graded particles. The number of heavy impaction strokes can be restricted.

Biological and mechanical changes of the bone graft-cement interface after impaction allografting

In impaction allografting, the host bone interface may consist of morsellized allograft alone or as a composite with bone cement. The objective of this study was to investigate the temporal changes in the interface for these two materials in a rat bone chamber model. To simulate the impaired endosteal circulation after impaction allografting, bone chambers were tightened bilaterally to the endosteal surfaces of proximal tibiae of mature rats and filled with pure allograft or cement/allograft composite. The cement/allograft composite-host bone interface strength was significantly higher at 3 weeks and was higher than the allograft construct failure strength. Limited allograft, but extensive periosteal remodeling, was observed at 3 weeks which resulted in a significantly increased cortical porosity and cortical thickness. The allograft porosity decreased significantly at 6 weeks indicating extensive remodeling of the allograft bone. Little or no remodeling of the allograft particles in the cement was found. At 6 weeks a new medullary canal was formed, and the endosteal cortex was partially absorbed. Endosteal absorption resulting in medullary canal widening in revision THR may be responsible for clinically unstable stems after impaction allografting.

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.