This outline reviews many of the classification schemes that aid in treatment decisions in revision total hip arthroplasty.
AAOS Femoral Deficiency Classification
D'Antonio J, McCarthy JC, Bargar WL, et al. Classification of femoral abnormalities in total hip arthroplasty. Clin Orthop 1993; 296:133-139.
- Type I- segmental defects
- Type II- cavitary defects (loss of cancellous bone without loss cortex)
- Type III- combined defects
- Type IV- femoral malalignment (angular or rotational)
- Type V- femoral stenosis (critical narrowing or obliteration)
- Type VI- femoral discontinuity (fracture with/without implant)
Paprosky Femoral Deficiency Classification
Della Valle CJ, Paprosky WG. Classification and an algorithmic approach to the reconstruction of femoral deficiency in revision total hip arthroplasty. JBJS 2003; 85-A Suppl. 4: 1-6.
- Type I: Minimal loss of metaphyseal cancellous bone. Intact diaphysis. Consider cemented vs. cementless fixation.
- Type II: Extensive loss of metaphyseal cancellous bone. Intact diaphysis. Loss of cancellous bone makes cemented fixation more suspect, consider uncemented fixation (e.g. fully porous coated stem)
- Type III-A: The metaphysis is not supportive. There remains greater than 4 cm of bone in the diaphysis to allow for a scratch fit. Consider uncemented fixation with a fully porous-coated stem vs. a modular tapered stem.
- Type III-B: The metaphysis is not supportive. There remains less than 4 cm of bone in the diaphysis to allow for a scratch fit. Due to short segment of cylindrical bone to support a fully-porous coated stem, the failure rate is high with such a device (50% in one study by the senior author). Consider a modular tapered stem.
- Type IV: Wide open canal without any appreciable isthmus to support an uncemented stem. Consider impaction grafting if the proximal tube is intact +/- an intact calcar. Other alternatives would include an APC or a modular tumor megaprosthesis.
Paprosky WG, Sporer SM. Revision total hip arthroplasty: The limits of fully coated stems. CORR 2003; 417: 203-209.
- This study looked at patients with Type IIIB and Type IV femoral deficiencies revised with 9C/10-inch Solution stems vs. modular, fluted, tapered stems vs. impaction grafting.
- Again noted was the higher failure rate with fully-coated stems in the bad deficiencies.
- They recommend NOT using a Solution in Type IIIB deficiencies at > 19mm diameter, and never in Type IV.
Chiang PF, et al. Osteolysis of the pelvis. Evaluation and treatment. CORR 2003, 417: 164-174.
- Cemented sockets
- Tends to be linear at cement-bone interface
- Lesional treatment not really an option
- Operate when the socket is loose (usually revise to uncemented socket)
- Uncemented sockets
- Tends to be expansile (ballooning), often at screw holes
- Look for areas of radiolucency, often well-circumscribed, without bony trabeculae
- OR Indications: loose socket, progressive lysis +/- pain, poly fracture/catastrophic bearing surface failure, (? eccentric poly wear- relative indication)
- OR Options:
- Lesional treatment (liner exchange +/- grafting) if the socket is well-fixed and- with a proven track record, positioned appropriately, and allows for poly of sufficient thickness
- If socket is fixed, but does not meet above; or if the socket is loose, treat with revision and bone grafting
AAOS Acetabular Deficiency Classification
Berry DJ, et al. Pelvic discontinuity . . . JBJS 1999; 81-A: 1692-1702.
D'Antonio JA, et al. Classification and management of acetabular deformities in total hip arthroplasty. CORR 1989; 243: 126-137.
- Type I: Segmental
- Type II: Cavitary
- Type III: Combined
- Type IV: Pelvic discontinuity
- Type IVa- Mild segmental loss or cavitary only loss
- Type IVb- Moderate-severe segmental loss or combined bone loss
- Type IVc- Associated with prior pelvic irradiation
- Type V: Hip arthrodesis -
Paprosky Acetabular Deficiency Classification
- Paprosky WG, Perona PG, Lawrence JM. Acetabular defect classification and surgical reconstruction in revision arthroplasty. A six year follow-up evaluation. J Arthroplasty 1994; vol. 9.
- Sporer SM, O'Rourke M, Chong P, Paprosky WG. The use of structural distal femoral allografts for acetabular reconstruction. Average ten-year follow-up. JBJS 2005: 87-A: 760-5.
- Nehme A, Lewallen DG, Hanssen AD. Modular porous metal augments for treatment of severe acetabular bone loss during revision hip arthroplasty. CORR 2004; 429: 201-208.
Similar to his femoral defect classification, this system attempts to stratify the degree of host bone loss in order to estimate the ability to achieve stable cementless fixation for any given bone loss pattern.
Four landmarks require evaluation:
- Femoral head center- as measured from Hilgenreiner's line (horizontal line connecting the inferior aspects of the teardrops or the superior margins of the obturator foramina). Note any superior displacement greater than 3 cm and if the displacement tends to go medial or lateral.
- Ischial osteolysis- as measured from Hilgenreiner's line inferiorly to the edge of the osteolytic lesion in the ischium. Greater than 1.5 cm of bone loss represents 20-25% loss of the acetabular bone stock, primarily posterior column and posterior wall loss.
- Tear Drop- Loss of the radiographic tear drop indicates damage to the medial wall as well as the inferior portions of the columns (mostlikey anterior column). ~ 10-15% host bone loss.
- Kohler's line- breakthrough medial to this line (the ilioischial line) represents medial wall destruction and likely damage to the midportion of the columns.
- Migration relative to this line can be graded as follows:
- Grade 1- the socket remains lateral to the line
- Grade 2- the socket has migrated to, not through, the line
- Grade 3- the socket has migrated medially into the pelvis
Type 1- there is an intact rim with little or no migration superior or medial. The teardrop and ischium are intact. 90% of host bone is available
- Treat with an uncemented hemisphere (with screws) and possibly cancellous bone grafting to small defects.
Type 2A- Increase in superomedial bone destruction but superior rim remains intact. The cup migrates superior and medially ("up and in"). By definition, cup migration in type 2 defects is less than 2 cm. Greater than 70% host bone contact with cup. Anterior/posterior columns are intact. Trial cup is stable.
- Treat with an uncemented hemisphere (with screws) and cancellous bone grafting to defects.
Type 2B- Characterized by increased destruction of the superior rim (small superolateral segmental rim defect of less than 1/3 rim circumference). The cup migrates superolaterally ("up and out") less than 2 cm. The dome remains supportive and lysis in the teardrop/ischium is minimal. Greater than 70% host bone contact with cup. Anterior/posterior columns are intact. Trial cup is stable.
- Treat with an uncemented hemisphere (with screws) and cancellous bone grafting to any contained defects. There may be a role in some cases for a small structural bone graft superolateral to the segmental defect. However, as a rule this graft would be to restore bone stock because it would be a Type 3 if the bone graft was required for implant stability.
Type 2C- Obliteration of teardrop due to localized destruction of medial wall with migration medial to Kohler's line. Minimal ischial osteolysis. The dome remains supportive. This is the case with an intact rim but no medial wall. Greater than 70% host bone contact with cup. Anterior/posterior columns are intact. Trial cup is stable.
- Treat with an uncemented hemisphere (with screws) and cancellous bone grafting to defects. Consider the use of a "medial wafer" structural bone graft.
Type 3A- significant superior dome destruction with greater than 2cm superolateral migration ("up and out"). The medial wall is intact, but there is moderate ischial and teardrop lysis. 40-60% of host bone available for ingrowth. There is usually adequate host bone for ingrowth, but the cup requires some form of augmentation to achieve implant stability.
- Treat with an uncemented cup with screws and . . .
- A structural bone graft- femoral head, figure 7
- A modular prosthetic graft- e.g. TM wedges
- A bilobed implant- e.g. a "double bubble"
- Place the cup into the high hip center
- Use a cage- in the very old/inactive (rarely used)
Type 3B- Significant superior dome destruction with greater than 2cm superomedial migration ("up and in"). Kohler's line is broken. There is complete obliteration of the teardrop, severe ischial lysis and potentially a pelvic discontinuity. There is less than 40% host bone available for ingrowth and the rim defect is greater than ½ the rim circumference.
- Treatment follows two main principles:
- Establish initial implant stability
- Attempt to achieve biological fixation where possible
- Structural allograft and uncemented cup with screws +/- plate the column
- Cup-cage construct
- Place large TM shell against host bone, then place a cage inside this shell and attach to remaining host bone. Cement a liner.
- Structural allograft + cage + cemented cup
- Cage + cemented cup
- Avoid using constrained liners
Include Gross Classification and Algorithm from University of Toronto. Very simple and useful. I will upload a presentation outlining the classification shortly. (CV)