Chapter 89 Acetabular Reconstruction. In an attempt to better define these defects, classification systems are used. Each has its own advantages and disadvantages. Over the past decade, improvements in technology and surgical technique have made acetabular revision more successful and straightforward.
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The incidence of THA revision has increased substantially during the last decade and is projected to nearly double by [ 8 , 9 ]. Aseptic loosening and osteolysis continue to be major challenges in hip reconstruction surgery; planning surgical treatments for these conditions requires accurate preoperative characterizations of the bone loss caused by these conditions, as preoperative planning is essential to ensure the appropriate equipment and prostheses are available.
Many different classification schemes have been proposed to describe the extent of periacetabular bone loss in revision THA including those proposed by Paprosky et al. These classification schemes differ in that some aim to simplify classification to improve communication and reproducibility [ 3 , 5 , 7 , 12 ], whereas others seek to provide detailed anatomic information for defect-specific preoperative planning [ 2 , 6 , 7 , 11 , 13 ].
Other fundamental differences include the presence or absence of standard anatomic landmarks compared with pure volumetric bone loss independent of the structures affected and the focus on bone stock remaining in contrast to bone stock required for revision [ 7 ]. Described in , the Paprosky classification is a commonly used system for classifying acetabular bone loss in revision THA Fig.
J Arthroplasty. Given the complexity of revision THA, the Paprosky system identifies which acetabular supporting structures are deficient for the purposes of predicting the biologic augments and synthetic components that will be needed at the time of surgery. This classification is anatomically oriented and assesses specific osseous structures for deficiency, rather then being geared toward generalized volumetric bone loss, which is the basis of several other systems [ 3 , 5 , 12 ].
Based on the structures predicted to be deficient, and the degree of hip center migration, Paprosky et al. More recently short-, mid-, and long-term results of revision THAs using implants selected to treat specific acetabular deficiency patterns have become available [ 15 , 16 , 18 ]. The classification system is based on the integrity of the teardrop, hip center, Kohler line, and ischium [ 11 ].
The original classification included preoperative and intraoperative evaluations of failed THA acetabular components and the associated surrounding osseous support [ 11 ]. The Paprosky classification is based on the amount of hip center migration and the integrity of four acetabular supporting structures as evaluated on preoperative AP radiographs of the pelvis [ 11 , 14 ] Fig.
The Paprosky classification is divided into three types with increasingly severe degrees of bone loss; Types 2 and 3 are further divided into subtypes Fig. Type 1 defects have minimal focal bone loss with maintenance of the hemispheric shape of the acetabulum. The supporting structures, including the acetabular walls and columns, are all intact and with no hip center component migration. Type 2 defects have moderate bone loss, deficient walls but intact acetabular columns, and less then 2 cm of hip center migration.
Type 2 defects are further subdivided into A, B, and C based on defect location and resultant direction of component migration. Type 2A defects have global cavitation of the acetabulum with direct superior hip center migration; sufficiently intact superior dome and teardrop prevent concomitant lateral or medial displacement, respectively.
Type 2B defects are characterized by a deficient superior dome, allowing for superior and lateral component migration owing to the lack of a lateral stabilizing buttress, normally provided by the lateral margin of the superior dome.
Type 2C defects have a deficient medial wall teardrop causing direct medial migration of the hip center; the superior dome is intact, preventing vertical displacement. Type 3 defects have extensive global erosion of the acetabulum with attenuation or destruction of all supporting structures and greater than 2 cm of hip center migration; these defects can be associated with pelvic discontinuity.
Type 3A defects have moderate-to-severe destruction of the acetabular walls and posterior column, rendering these structures nonsupportive. Although the original description denotes hip center migration as more or less than 2 cm [ 11 ], a more recent publication liberalizes this migration to less than or greater than 3 cm [ 14 ]. Validity refers to how closely the preoperative radiographic classification predicted the actual defect found at the time of surgery.
Most of the time the values were between 0. The source of this heterogeneity is likely multifactorial and includes the loosely defined and relatively subjective categories of mild, moderate, and severe used by the Paprosky system, the partial obstruction of acetabular features by the radiopaque cup on routine radiographs, and potential discrepancies in the measurement of hip center migration between reviewers which is a major differentiating feature between Types 1 and 2 defects.
These findings suggest that regardless of surgeon experience level, the Paprosky classification is unlikely to achieve excellent intraobserver reliability. One study compared the Paprosky classification with other classification systems [ 12 ]. There have been fewer studies on the degree to which the classification actually reflects surgical findings validity.
However, there was no correlation for the posterior acetabular wall or ischial defects; this was believed to be the result of the radiopaque acetabular cup obscuring these features on standard AP radiographs of the pelvis.
Yu et al. Paprosky et al. In another study, Gozzard et al. Intraobserver and interobserver reliabilities have been shown to be highly variable, but generally achieve only fair to moderate agreement [ 1 , 4 , 12 , 19 ]. Five years after the original study, Campbell et al. Additionally, it is worth remembering that the English-language literature on reliability and validity for the Paprosky system, while reasonably large for evaluations of a classification scheme, is still based on the findings of only 18 orthopaedists and hips [ 1 , 4 , 12 , 19 ].
Additionally, when developing their original classification, Paprosky et al. The original Paprosky classification is based on analysis of AP radiographs of the pelvis and therefore attempts to classify complex three-dimensional structures using a two-dimensional image.
Smaller areas of lysis may not be seen well on radiographs alone and certain structures such as the ischium may be obscured by the radiopaque cup making accurate determinations of defect size difficult.
CT is used increasingly in preoperative planning; however, we are unaware of a classification system that incorporates this modality. Finally, femoral bone stock also must be considered because a successful outcome depends on appropriate management of both sides of the hip. To this end, Della Valle and Paprosky proposed a classification system for femoral bone loss [ 17 ], which was intended to be used in conjunction with the acetabular classification.
The development of a reliable, valid, and universally accepted classification for acetabular bone loss in revision THA continues to problematic. Despite its limitations, the Paprosky classification has many advantages including its widespread familiarity, simplicity of use, the availability of routine perioperative radiographs, and reasonable reliability and validity. Furthermore, given the Paprosky classification can be used to predict implant needs, this system is being used in an increasing number of studies to report midterm and long-term outcomes for revision THA with acetabular bone loss [ 15 , 16 , 18 ].
Although agreement is limited, the Paprosky classification performs as well as or better than other acetabular classification schemes. This suggests that, despite its shortcomings, it is one of the best options available to help surgeons anticipate and plan for findings at the time of revision surgery. Furthermore, one study showed that it has increased reliability with dedicated teaching [ 19 ], suggesting that the classification may be more reliable when surgeons are specifically trained in its use.
National Center for Biotechnology Information , U. Clin Orthop Relat Res. Published online Aug Jessica J. Telleria , MD and Albert O. Gee , MD. Albert O. Author information Article notes Copyright and License information Disclaimer. Telleria, Email: ude. Corresponding author. Received Jun 23; Accepted Aug This article has been cited by other articles in PMC.
History The incidence of THA revision has increased substantially during the last decade and is projected to nearly double by [ 8 , 9 ]. Open in a separate window. Purpose Given the complexity of revision THA, the Paprosky system identifies which acetabular supporting structures are deficient for the purposes of predicting the biologic augments and synthetic components that will be needed at the time of surgery.
Description The original classification included preoperative and intraoperative evaluations of failed THA acetabular components and the associated surrounding osseous support [ 11 ].
Limitations Intraobserver and interobserver reliabilities have been shown to be highly variable, but generally achieve only fair to moderate agreement [ 1 , 4 , 12 , 19 ].
Conclusions and Uses The development of a reliable, valid, and universally accepted classification for acetabular bone loss in revision THA continues to problematic. References 1.
Reliability of acetabular bone defect classification systems in revision total hip arthroplasty. Periprosthetic bone loss of the acetabulum: classification and management. Orthop Clin North Am. Results of cementless revision for failed cemented total hip arthroplasty. A comparison of the reliability and validity of bone stock loss classification systems used for revision hip surgery. Bone grafts in hip replacement surgery: the pelvic side.
Revision total hip arthroplasty with titanium ingrowth prosthesis and bone grafting for failed cemented femoral component loosening. Grading acetabular defects: the need for a universal and valid system.
Prevalence of primary and revision total hip and knee arthroplasty in the United States from through J Bone Joint Surg Am. Projections of primary and revision hip and knee arthroplasty in the United States from to The measurement of observer agreement for categorical data. Acetabular defect classification and surgical reconstruction in revision arthroplasty: a 6-year follow-up evaluation. A comparison of the validity and reliability of established bone stock loss classification systems and the proposal of a novel classification system.
Hip Int. Development, test reliability and validation of a classification for revision hip arthroplasty. J Orthop Res. Acetabular bone loss in revision total hip arthroplasty: evaluation and management. J Am Acad Orthop Surg. The use of a trabecular metal acetabular component and trabecular metal augment for severe acetabular defects.
Acetabular revision using a trabecular metal acetabular component for severe acetabular bone loss associated with a pelvic discontinuity. Classification and an algorithmic approach to the reconstruction of femoral deficiency in revision total hip arthroplasty. Porous-ingrowth revision acetabular implants secured with peripheral screws: a minimum twelve-year follow-up. Validity and reliability of the Paprosky acetabular defect classification.
Classifications Used in Total Hip Arthroplasty
Bone loss from 9am-5pm around rim, superomedial cup migration. Average 3. Thank you for rating! Please vote below and help us build the most advanced adaptive learning platform in medicine.
Total hip arthroplasty is one of the most successful operation to be done and is definitely a rewarding procedure for both the surgeon and the patient. Ever since 3 days of low friction arthroplasty by Sir John Charnley, there has been considerable interest in improvement in the knowledge of surgical techniques and hip biomechanics. Over the past two decades there has been an exponential increase in total hip replacements. Therefore strategies to simplify the procedure and classifications to encounter difficulties in treatment plans were devised. It is imperative for consultants and trainees to be aware of these classifications systems which are helpful in pre op, intra op and postop planning.
Classifications In Brief: Paprosky Classification of Acetabular Bone Loss