A three-dimensional method for evaluating changes in acetabular osteolytic lesions in response to treatment

The morphological variation of acetabular defects in revision total hip arthroplasty-A statistical shape modeling approach

Classification and evaluation of acetabular defects remain challenging and are primarily based on qualitative classification methods. That is because quantitative techniques describing variations of acetabular defects and accompanying bone loss volume are not available. This study introduces a new method based on statistical shape models (SSMs) to quantitively describe acetabular defects. This method is then applied to 87 acetabular defects to objectively describe the variations in acetabular defects typically encountered during revision total hip arthroplasty. The absolute bone loss volume, relative bone loss volume, and relative bone loss surface area with respect to the SSM-based pre-diseased anatomy were used to quantify the acetabular bone defects in different segments of the acetabular surface. The absolute bone loss volume of the average defect shape was equal to 37.0 cm³ . The first three principal modes, accounting for 62% of the total shape variation, were found to represent variations in acetabular defect morphology. The first, second, and third principal modes described, respectively, the size of the bone defects, the difference between superomedially and superolaterally migrated defects, and the degree of involvement of the posterior or anterior column. The developed SSM and the introduced approach could be used to create automated and unbiased classification methods based on quantitative data. Moreover, the proposed model and the underlying data provide the basis for a quantitative design approach where the shape and size of new acetabular implants are determined according to clinical variation present in acetabular defects.

Quantitative assessment of acetabular bone defects: A study of 50 computed tomography data sets

Objectives

Acetabular bone defect quantification and classification is still challenging. The objectives of this study were to suggest and define parameters for the quantification of acetabular bone defects, to analyze 50 bone defects and to present the results and correlations between the defined parameters.

Methods

The analysis was based on CT-data of pelvises with acetabular bone defects and their reconstruction via a statistical shape model. Based on this data, bone volume loss and new bone formation were analyzed in four sectors (cranial roof, anterior column, posterior column, and medial wall). In addition, ovality of the acetabulum, lateral center-edge angle, implant migration, and presence of wall defects were analyzed and correlations between the different parameters were assessed.

Results

Bone volume loss was found in all sectors and was multidirectional in most cases. Highest relative bone volume loss was found in the medial wall with median and [25, 75]—percentile values of 72.8 [50.6, 95.0] %. Ovality, given as the length to width ratio of the acetabulum, was 1.3 [1.1, 1.4] with a maximum of 2.0, which indicated an oval shape of the defect acetabulum. Lateral center-edge angle was 30.4° [21.5°, 40.4°], which indicated a wide range of roof coverage in the defect acetabulum. Total implant migration was 25.3 [14.8, 32.7] mm, whereby cranial was the most common direction. 49/50 cases showed a wall defect in at least one sector. It was observed that implant migration in cranial direction was associated with relative bone volume loss in cranial roof (R = 0.74) and ovality (R = 0.67).

Conclusion

Within this study, 50 pelvises with acetabular bone defects were successfully analyzed using six parameters. This could provide the basis for a novel classification concept which would represent a quantitative, objective, unambiguous, and reproducible classification approach for acetabular bone defects.

Isolated Acetabular Liner Exchange for Polyethylene Wear and Osteolysis with Well-Fixed Metal Shell

Background

The isolated liner and head exchange procedure has been an established treatment method for polyethylene wear and osteolysis when the acetabular component remains well fixed. In this study, the mid-term results of this procedure were evaluated retrospectively.

Methods

Among the consecutive patients operated on from September 1995, two patients (three hips) were excluded because of inadequate follow-up, and the results of remaining 34 patients (34 hips) were evaluated. There were 20 men and 14 women with a mean age of 49 years. A conventional polyethylene liner was used in 26 cases and a highly cross-linked polyethylene liner was used in eight cases. In three cases, the liner was cemented in a metal shell because a compatible liner could not be used.

Results

After a follow-up of 5 to 20.2 years, re-revision surgery was necessary in 10 cases (29.4%): in eight for wear and osteolysis at 55 to 101 months after liner exchange and in two for acetabular loosening at 1 and 1.5 years after liner exchange. Re-revision surgery included all component revision (four cases), cup revision (four cases), and liner exchange (two cases). In all re-revision cases, a conventional polyethylene liner was used initially. There was no failure in the cases in which a highly cross-linked polyethylene liner was used.

Conclusions

The results of this study suggest that isolated acetabular liner exchange is a reasonable option for wear and osteolysis when the metal shell is well fixed. More promising long-term results are expected with the use of highly cross-linked polyethylene liners.

Outcome of 4 Surgical Treatments for Wear and Osteolysis of Cementless Acetabular Components

BACKGROUND

Loosening and periprosthetic osteolysis are some of the most common long-term complications after hip arthroplasty. The decision-making process and surgical treatment options are controversial.

METHODS

We retrospectively reviewed 96 acetabular revisions (91 patients) performed between 2002 and 2012, with a minimum of 2 years of follow-up and a mean of 5.7 years of follow-up. Clinical outcome was assessed using the Harris Hip Score. The size and location of osteolytic lesions were evaluated using the preoperative radiographs; healing of the defects was categorized using a standardized protocol.

RESULTS

Thirty-three (34.4%) hips had isolated liner exchanges (ILEs), 10 (10.4%) hips had cemented liners into well-fixed shells (CLS), 45 (46.9%) hips had full acetabular revisions (FARs), and 8 (8.3%) hips had revision with a roof ring/antiprotrusio cage (RWC). All procedures showed significant improvement in Harris Hip Score after revision (P ≤ .001). Fifteen patients had moderate residual pain (pain score ≤20): 8 (24%) ILE, 3 (30%) CLS, and 4 (9%) FAR. Complete bone defect healing after grafting was lower with acetabular component retention procedures (ILE and CLS; 27%) compared with full acetabular component revision procedures (FAR and RWC; 57%). Fifteen patients underwent reoperation: 3 ILE, 1 CLS, 8 FAR, and 3 RWC.

CONCLUSION

Acetabular component retention demonstrates a low risk of reoperation; however, residual pain and limited potential for bone graft incorporation are a concern. FAR is technically challenging and may have an elevated risk of reoperation; however, higher degrees of bone graft incorporation and satisfactory clinical outcome can be expected.

Isolated Head and Liner Exchange in Revision Hip Arthroplasty

As the number of primary total hip arthroplasties increases, so does the burden of revision procedures. The decision to revise well-fixed components in the setting of polyethylene wear and osteolysis is controversial. Modular head and liner exchange offers the advantages of reduced invasiveness, faster recovery, and bone preservation. These advantages come at the expense of higher rates of revision surgery for instability. Using the native locking mechanism for securing the new liner is preferred; however, cementing a liner into a well-fixed acetabular component is a practical alternative. The use of bone allograft or bone graft substitute for areas of osteolysis is controversial. In the setting of osteolysis, outcomes associated with the use of highly cross-linked polyethylene liners have been better than those associated with the use of conventional polyethylene; therefore, thinner liners and larger femoral heads can be used and reduce the risk of instability.

Influence of clinical and radiological variables on the extent and distribution of periprosthetic osteolysis in total hip arthroplasty with a hydroxyapatite-coated multiple-hole acetabular component: a magnetic resonance imaging study

Polyethylene wear-induced osteolysis constitutes the most severe long-term complication of total hip arthroplasties (THA). Our aim was to assess through MRI the severity and growth pattern of osteolysis, as well as the influence clinical-radiographic variables exert. We analyzed 75 THA with an average evolution time of 13.67years. The implant was a titanium alloy, non-cemented, multiple-hole model with hydroxyapatite coating. Osteolysis was found with a peripheral pattern in 48 and a central pattern in 6; in 52 cases it was continuous, and in 4, isolated. Out of 118 screws, 20 exhibited lysis. There was a proportional correlation between osteolysis severity and wear rate with age, physical activity and acetabular abduction, as well as an association between said variables and peripheral and continuous patterns.

The variability of the volume of os coxae and linear pelvic morphometry. Considerations for total hip arthroplasty

This study investigated the variability of os coxae's volume and linear morphometry in 50 dry adult bones. There was a wide variability, with coefficients of variation exceeding 30%, of the bones' volumes (mean 142 ml, range 80 to 300 ml) and distances between the acetabular rim and the horizontal plane through the sciatic notch (mean 10.6 mm, range -7 to 19 mm). The smallest width of the ilium ranged between 3 and 9 mm at a level between 1.5 and 4 cm above the acetabulum. The volume of os coxae correlated with the acetabular diameter (r = 0.79), the height of os coxae (r = 0.88) and antero-posterior length of the ilium at mid-acetabular level (r = 0.70). Knowledge of the variability of os coxae may be useful during preoperative planning in primary and revision hip arthroplasty.

Cemented liner exchange with bone grafting halts the progression of periacetabular osteolysis

The aims of this were to examine the effect of acetabular liner exchange and intra-operative bone grafting surgery on peri-prosthetic osteolysis. Seven patients with well-fixed Harris-Galante-1 acetabular components received cemented exchange liners for worn liners associated with pre-operatively CT-quantified osteolysis. During surgery, accessible osteolytic lesions were debrided and bone-grafted. Except for one patient with recurrent dislocation and acetabular component revision, the other patients had CT scans at a median of 4 months and at approximately 4 years after surgery. None of the pre-operative lesions increased in volume during the post-operative reporting period and no new lesions were detected. These results show that cemented liner exchange surgery can halt the progression of osteolysis and that bone grafting has the potential to restore bone.

Impaction grafting of the acetabulum with ceramic bone graft substitute: high survivorship in 43 patients with a mean follow-up period of 4 years

BACKGROUND AND PURPOSE

Loss of bone stock remains a challenge in revision hip surgery. Grafting with allograft is well established, but there are problems with availability, cost, infection, antigenicity, reproducibility, and stability of the created construct. BoneSave is a biphasic porous ceramic consisting of sintered 80% tricalcium phosphate and 20% hydroxyapatite. In vitro and in vivo studies, including its use mixed with allograft, have shown good results in impaction grafting. This is the first reported series of its use alone in impaction grafting of the acetabulum.

METHODS

We conducted a retrospective review of a cohort of 43 consecutive patients undergoing impaction grafting of contained acetabular defects by multiple surgeons at a single centre. All patients received uncemented acetabular components. They were followed up radiographically, together with self-reported satisfaction scale (SAPS), Oxford hip score (OHS), and Short-Form 12 (SF12) health survey. Kaplan-Meier survivorship analysis was performed with revision of the acetabular component, revision of any part of the construct, and reoperation as endpoints.

RESULTS

The fate of all cases was known. Mean follow-up was 4 years. 5 patients died during follow-up, with their constructs in situ. The survivorship of the acetabular component was 98% (95% CI: 85-100) at 7 years. 1 acetabular component was revised for infection and there was 1 radiographic acetabular failure. The median OHS was 36 (6-48), the median SF12 PCS was 36 (14-57), the median SAPS was 75 (0-100), and the median SF12 MCS was 50 (23-64). The graft material had incorporated in all 3 zones of the acetabulum in 33 out of 37 cases with complete radiographic follow-up.

INTERPRETATION

Medium-term results show that BoneSave alone is a reliable material for impaction grafting of contained defects in the acetabulum at revision surgery.

Bone graft substitutes in hip revision surgery: a comprehensive overview

INTRODUCTION

Total hip replacement is increasingly used to treat diseased and damaged joints. With time, some joint replacements may require revision, mainly because of instability and mechanical loosening, and this is of particularly significance to younger patients. A major problem in revision surgery is the loss of bone stock and the consequent difficulty in reconstructing a stable joint. Loss of bone stock has been widely treated using bone autografts and allografts but supplies are limited. Use of bone graft substitutes in combination with, or as a substitute for, human bone is a possible alternative.

AIM

To identify empirical studies of bone graft substitutes in hip revision surgery.

METHODS

Systematic review based on Cochrane and MOOSE methods. We searched MEDLINE and EMBASE to December 2010 with terms relating to hip replacement and bone graft substitutes, and checked key citations in ISI Web of Science and reference lists. We considered all human studies irrespective of study design.

RESULTS

Searches identified 397 articles. Screening of abstracts and full text articles identified 7 studies reporting outcomes of bone-graft substitute combined with autograft or allograft, and 6 studies reporting outcomes of bone graft substitute exclusively. One economic evaluation compared costs of femoral head banking with costs of bone graft substitutes. No randomised controlled trials evaluating bone graft substitute effectiveness were identified. Studies generally included small numbers of patients with a follow up too short to assess outcomes relating to implant survival. However, excepting those based on glass ceramic, ceramic bone graft substitutes show promise as an alternative to use of exclusive autograft or allograft. In the case of calcium phosphate ceramic bone graft substitute, potential cost savings were evident.

CONCLUSION

With increased allograft shortage, bone graft substitutes will be required in hip revision surgery. However, appropriately designed randomised controlled trials are required to compare use of existing and new bone graft substitutes with established practice. As well as prosthesis related outcomes, studies should explore the patient experience of revision hip replacement with bone graft substitute material.