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.
Key points
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Femoral bone loss is a complicated problem requiring meticulous preoperative patient evaluation and surgical planning.
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The Paprosky classification system is most commonly used to define femoral bone loss.
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The Paprosky system is based on the location of femoral bone loss, degree of residual proximal femoral bone stock, and the amount of residual isthmus available for diaphyseal fixation.
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More severe bone loss patterns have variable amounts of diaphysis remaining.
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Diaphyseal engaging stems are successful when used with adequate isthmic bone stock. Severe loss of isthmic bone typically requires a cemented option or a megaprosthesis.
Background
Total hip arthroplasty (THA) has been shown to be an extremely effective procedure for the treatment of end-stage arthritis of the hip. Long-term follow-up continues to demonstrate favorable clinical outcomes and as a result, younger, more active patients are being considered candidates for surgery.
Based on the current state of affairs, Kurtz and colleagues have extrapolated the need for THA to increase by more than 170% by 2030. Inherent to this increased utilization of THA is an associated burden of revision surgical procedures. As patient life expectancy continues to increase, THA prostheses are being asked to exhibit improved longevity, which may in turn result in more severe bone loss surrounding the femoral component at the time of revision.
The treatment of femoral bone loss in the setting of revision THA is a challenging problem. This article addresses the etiology of femoral bone loss, associated classification systems, clinical and radiographic patient evaluation, components of effective preoperative planning, and clinical results of various treatment options.
Background
Total hip arthroplasty (THA) has been shown to be an extremely effective procedure for the treatment of end-stage arthritis of the hip. Long-term follow-up continues to demonstrate favorable clinical outcomes and as a result, younger, more active patients are being considered candidates for surgery.
Based on the current state of affairs, Kurtz and colleagues have extrapolated the need for THA to increase by more than 170% by 2030. Inherent to this increased utilization of THA is an associated burden of revision surgical procedures. As patient life expectancy continues to increase, THA prostheses are being asked to exhibit improved longevity, which may in turn result in more severe bone loss surrounding the femoral component at the time of revision.
The treatment of femoral bone loss in the setting of revision THA is a challenging problem. This article addresses the etiology of femoral bone loss, associated classification systems, clinical and radiographic patient evaluation, components of effective preoperative planning, and clinical results of various treatment options.
Etiology of femoral bone loss
Femoral bone loss may result from osteolysis, stress shielding, periprosthetic infection, periprosthetic fracture, aseptic femoral loosening, iatrogenic bone loss during component removal, and metastatic lesions. Regardless of etiology, the pattern of bone loss as well as the degree of residual fixation of the femoral component must be defined preoperatively to determine the appropriate treatment at the time of revision.
Femoral bone loss classifications
The femoral bone loss classification system proposed by the American Academy of Orthopedic Surgeons is based on the presence of segmental, cavitary, or combined bone defects. As has been described previously, the classification system by the American Academy of Orthopedic Surgeons is organized in a simple manner; however, its practical application with regard to the type of treatment that should be used is limited.
We advocate the use of the classification system described by Paprosky, which is based on the location of femoral bone loss (metaphyseal or diaphyseal), degree of residual proximal femoral bone stock (ie, amount of cancellous bone loss), and the amount of residual isthmus available for diaphyseal fixation. The Paprosky classification system defines 4 different types of femoral bone loss. In type I defects, there is minimal metaphyseal bone loss and the diaphysis is intact. This type of defect is typically not associated with proximal femoral retroversion or varus femoral remodeling ( Fig. 1 ). Type II defects, the most commonly encountered pattern, exhibit extensive metaphyseal bone loss with an intact diaphysis. There is a greater degree of proximal femoral remodeling compared with type I femoral defects ( Fig. 2 ).
This article focuses on the treatment of more severe bone loss patterns about the femur, specifically types III and IV defects. Type III defects exhibit extensive metaphyseal bone loss with some degree of bone loss within the diaphysis. Type III defects are subdivided into types IIIA and IIIB defects. In IIIA defects, there is greater than 4 cm of diaphyseal isthmus remaining, whereas in IIIB defects, there is less than 4 cm of diaphyseal isthmus remaining for femoral component fixation. Theses defects are associated typically with significant proximal femoral remodeling ( Fig. 3 ). In type IV defects, there is extensive metadiaphyseal bone loss with complete femoral canal ectasia. The femoral diaphysis is unsupportive and owing to this severe degree of bone loss, there is minimal proximal femoral remodeling ( Fig. 4 ).
Radiographic and clinical patient evaluation
Preoperative Planning: Imaging Options
Plain radiographs, including an anteroposterior view of the pelvis and anteroposterior and frog-leg lateral views of the femur (ensuring that the entire length of the existing femoral stem is visible) are usually sufficient to identify the location and severity of femoral bone loss. If there is any concern for femoral deformity (ie, prior ipsilateral total knee arthroplasty, history of infection or congenital deformity, previous femoral fracture) full-length x-rays of the femur can be helpful. Preoperative CT could be obtained to better define the location and severity of femoral bone loss as an adjunct to plain radiographs.
Preoperative Planning: Clinical Patient Evaluation
A thorough preoperative patient assessment is critical before femoral component revision. The patient history must document the location, type, character, duration, temporal nature, and exacerbating and remitting factors (ie, activity-related symptoms) of the pain. In addition, a history of all prior procedures and perioperative complications should be recorded.
The lack of a pain-free interval after primary THA prompts questioning of the surgical indication or may indicate low-grade sepsis. A diagnosis of deep infection must be ruled out before revision surgery. An erythrocyte sedimentation rate (normal <20 mg/dL) and C-reactive protein (<10 mg/dL) should always be obtained preoperatively and, if elevated, a preoperative hip aspiration should be performed. Synovial fluid obtained from the hip aspiration should routinely be sent for cell count analysis (including differential) and cultures (aerobic and anaerobic). The surgeon must consider the presence of an infection if there are more than 1700 white blood cells in the sample and a differential of greater than 65% segmented neutrophils, if the aspiration is performed outside of the immediate postoperative period.
A detailed physical examination includes an assessment of the patient’s general health, the lumbosacral spine, contralateral limb, and thorough examination of the affected hip and lower extremity. Assessment of previous incisions about the hip may govern the planned operative approach. A detailed motor, sensory, and vascular examination must also be performed. The patient’s gait should be evaluated for the presence of painful ambulation (antalgic gait) and presence of compensatory gait patterns (ie, Trendelenburg gait). Leg lengths should also be evaluated to address appropriately a discrepancy at the time of femoral revision.
Preoperative Planning: Formulating a Detailed Operative Plan
A comprehensive preoperative plan is important for every case; however; it is critical for revision THA where femoral bone loss is present. Several alternate operative plans must be constructed to address adequately unforeseen scenarios encountered during the procedure. Obtaining previous operative reports allows for a better understanding of the components in place and prior operative events.
We recommend the formulation of a detailed, written preoperative plan, which should be distributed to the entire surgical team ( Table 1 ). The process of creating this preoperative plan is an extremely effective exercise and allows the surgeon to preemptively prepare for possible intraoperative complications. Sending the plan to the entire surgical team (eg, scrub technician, circulating nurse, anesthesia team, and manufacturing company representatives) minimizes the time spent intraoperatively waiting for instruments and implants ( Box 1 ). In addition, identifying items that may be required for addressing potential complications should be set aside preoperatively and made available when needed.
Patient position : Lateral decubitus
Table : Radiolucent Jackson table
Positioners : Mizuoki hip positioners
C-arm
Bovie setting : 60/60
Cell saver
Epinephrine soaked sponges
Retractors/special equipment :
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Self-retainer ×2
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Hibbs retractor ×2
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Anaerobic and aerobic culture tissue ×2 specimen cups
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60 mL of 0.25% Marcaine with epinephrine
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30 mL of 0.25% Marcaine without epinephrine
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Charnley retractor – shallow blades
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2 proximal femoral elevators (Dark and Stormy)
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#5 Ethibond sutures × 5 + free needles × 2
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#2, #4 and #7 ZIMMER acetabular retractors
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Footed impactor, curved curettes, curved osteotomes, bone tamp, and Cobb elevator
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Broad flat osteotome set
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Ball spike pusher
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Anspach – Pencil tip burr
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Microsagittal saw
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DEPUY Moreland cement removal set
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BIOMET Ultradrive for cement removal (have available but do not open)
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BIOMET Arcos STS stem (190/250 mm length) (have available but do not open)
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ZIMMER Continuum shell trial liners (50/36) neutral and elevated lip
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ZIMMER SL revision femoral stem (length 190 and 265 available)
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ZIMMER long-stem CPT (length 240) (have available but do not open)
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SYNTHES distal femoral locking plate with locking attachment outrigger
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SYNTHES cable plate attachments (have available but do not open)
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5 Dall miles cables
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16 gauge cardiac wire (have available but do not open)
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Fibular allograft strut graft (have available but do not open)
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Large cement restrictor (have available but do not open)
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Preoperative Antibiotics: Ancef 2 g IV + Vancomycin 1 g IV.
Abbreviation: IV, intravenous.
a Includes the circulating nurse, scrub technician, and manufacturing representatives.
In the academic setting, complex revision cases are often thought of as possessing little educational value, especially for junior residents or residents who do not plan to pursue a fellowship in adult reconstruction. However, detailed preoperative plans present a road map for the case and allow even novice residents to be engaged in the operative procedure ( Box 2 ).
Surgical Approach : Extensile posterolateral approach
- 1.
Posterior incision
- 2.
Clearly identify fascia (1 cm in anterior and posterior direction)
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Fascial incision with curved Mayo scissors
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Define plane between the underlying g. maximus and deep g. medius
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Split g. maximus and place Charnley retractor with shallow blades
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Identify the posterior border of the vastus lateralis → find the g. maximus expansion on the femur
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Use the bovie to transect the g. max insertion (full thickness)
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Follow posterior border of the vastus lateralis proximally into a posterior capsular approach
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Extend the approach proximally over the border of the acetabulum and over the posterior ilium after the posterior border of the gluteus medius
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Tag the posterior capsule with #5 Ethibond suture on backhand x 3
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Send pseudocapsule tissue for final microbiology × 2 specimen cups
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Place a Hibbs retractor deep to the g. medius and remove scar tissue anterior to the femoral neck
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Dislocate the hip once adequate scar tissue has been removed and remove the femoral head
Femoral component removal:
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Place 2 Dark and Stormy retractors for femoral exposure
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Clear the shoulder of the prosthesis
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Release the anterior capsular tether to the proximal femur
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Remove the cemented CPT stem → should tap out of the cement
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Extend incision distally to identify the allograft
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Remove the first 2 cables and the allograft
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Use the microsaggital saw to perform an ETO of the proximal femoral fracture fragment
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Osteotomy length – make osteotomy at level of second wire
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Broad osteotomes to open the osteotomy
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Use the Anspach pencil tip burr to disrupt the cement–prosthesis interface
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Remove the remainder of the cement within the proximal femur
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May need BIOMET Ultradrive to remove cement under direct visualization
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Use the 4.5-mm cement drill to penetrate the distal cement plug if needed
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Use the larger cement drills to drill a larger hole in the cement plug if needed
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Use back scrapers to try and remove the cement plug and all remaining cement
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Debride the canal thoroughly
Acetabular component removal:
- 1.
Obtain circumferential exposure of the acetabulum
- 2.
Place #2 and #7 retractors in place for acetabular exposure
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Remove the liner – size 4.5 mm Synthes screw for liner removal
- 4.
Insert a new a 50/36 trial liner
Femoral reconstruction:
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Hand ream using the conical ZIMMER SL revision tapered reamers → ream under Fluoro
- 6.
Place a trial stem → most likely 265 mm in length → check intra-op fluoro
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Check hip stability with trial
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If sizing of the stem is acceptable, then open the real stem and complete reconstruction
- 9.
3–4 cables for ETO fixation
Distal femoral plating:
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Make an incision distally for insertion of a distal femoral locking plate
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Place a K-wire distally
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Achieve plate balance and place a K-wire proximally distal to the stem
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Place a screw distally in the metaphysis
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Place a screw as proximal as possible
- 6.
Place additional screws for fixation
- 7.
Place cables through the proximal incision around the plate and the distal part of the stem
- 8.
Obtain final C-arm images and final flat plate x-rays on the table before complete wound closure
Wound closure:
- 9.
Size 10 flat JP drain × 1 deep to the fascia → ( deep drain distal )
- 10.
#1 Vicryl × 2 for fascia closure
- 11.
Size 10 flat JP drain × 1 superficial to the fascia → ( superficial drain superior )
- 12.
#1 Vicryl for deep closure and 2-0 Vicryl for dermal closure
- 13.
2-0 Nylon suture for the skin – horizontal mattress formation
- 14.
Sterile size 14-inch and 10-inch Aquacel dressings
Postoperative management:
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TDWB right LE
- 2.
Posterior hip precautions
- 3.
No active abduction × 6 weeks
- 4.
Abduction brace (patient has been called and asked to bring brace from home)
- 5.
ASA 325 mg PO BID × 6 weeks
- 6.
Ancef 1 g q8 hours until intra-op cultures are final
- 7.
Drains to be left in until low output – less than 15 mL/shift
Abbreviations: ASA, aspirin; ETO, extended trochanteric osteotomy; LE, lower extremity; PO, orally; TDWB, touch down weight bearing.
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