Revision Hip Arthroplasty Case Title: Revision of Paprosky IIIB Defect with Massive Bone Loss

Case Title: Revision

of Paprosky IIIB Defect with Massive Bone Loss

 

 

Demographics

 

Age: 68 years old Sex: Female BMI: 32

 

Relevant Past Medical History

 

Principal pathologies: Rheumatoid arthritis, non-insulin-dependent diabetes mellitus, MI, DVT, CVA, HTN, HLD, GI bleed, SCFE, left TKA

infection status post two-stage reimplantation.

Previous surgical procedures: IVC filter, SCFE pinning, removal of SCFE hardware.

Medication: Coumadin, Nexium, glipizide, gabapentin, leflunomide, atorvastatin, hydrochlo-rothiazide, metoprolol, verapamil, lisinopril.

History of presenting complaint: This is the case of a patient with a history of slipped capital femoral epiphysis that initially had a left total hip arthroplasty in 1985 at the age of 39 for degenerative joint disease and acetabular protrusio secondary to rheumatoid arthritis. This total hip replacement functioned well for 25 years until it was revised in 2010 for aseptic loosening of the acetabular shell. At the time of her first revision in 2010, she was found to have a Paprosky type IIC defect, and this was revised with bone grafting and placement of a large cup with six screws and an eccentric liner, while the femoral component was left in place. In 2013, she presented to the clinic with left hip pain and mechanical failure of the acetabular component. Radiographs and CT scan revealed a Paprosky type IIIB defect of the acetabulum with a >3 cm superior migration of the hip centre, ischial osteolysis, and violation of Kohler’s line with obliteration of the teardrop (Fig. 19.7).

 

Clinical Examination

 

Symptoms: Groin pain, feeling of instability of the hip.

Range of motion: Limited exam secondary to hip pain.

Specific tests: ESR: 63 mm/h; CRP: 1.24 mg/dL; hip aspiration was performed revealing a negative gram stain; no growth from cultures, 108 WBCs and 55% PMNs.

Main disability: Ambulatory dysfunction.

Neurovascular evaluation: Sensation and motor intact distally. Palpable pulses distally.

 

Preoperative Radiological Assessment/Imaging (Figs. 19.7, 19.8, and 19.9)

 

 

Fig. 19.7 Paprosky type IIIB defect with a failed acetabular cup. The horizontal line is the superior obturator line. From this, the level of superior migration and ischial osteolysis can be measured. The ischial involvement is greater than 15 mm indicating severe osteolysis. Kohler’s line has been disrupted, and there is severe lysis of the teardrop. Although difficult to measure because the cup has failed, superior migration of the center of rotation of the femoral head is greater than

3 cm

 

 

 

Fig. 19.8 3D CT

reconstruction

 

 

 

 

 

Fig. 19.9 Custom implant design

3D reconstructions of the pelvis were obtained for evaluation of the defect and custom implant design. The 3D CT and 3D printed models further highlight characteristics of the IIIB defect seen on X-ray. The medial wall of the acetabulum has been violated, and the anterior column is deficient. There is also an erosion of bone superiorly into the ilium as well as ischial bone erosion.

Three-dimensional models were used to create a custom triflange implant that can anchor to the ilium, ischium, and pubis to bridge the defect. This type of implant is especially useful in pelvic discontinuity.

 

Preoperative Planning

 

Diagnosis: Aseptic failure of revision total hip arthroplasty with Paprosky type IIIB acetabular defect (Fig. 19.7).

Possible treatment options: Cementless jumbo cup, cementless jumbo cup with augments, cup-cage construct, custom triflange cage.

Chosen treatment method: Custom triflange cage.

Selection of implants if applicable and rational: Custom triflange cage was chosen to provide maximum stability of the construct given the severe bone loss (Figs. 19.8 and 19.9).

Expected difficulties: Pelvis could convert to pelvic discontinuity during reaming. Custom cage may not fit well if there are intraoperative changes to anatomy or further progression of bone loss preoperatively.

Strategies to overcome difficulties: Must have equipment (pelvic reconstruction hardware) ready to treat discontinuity should this occur. If the custom implant does not fit, convert to acetabular porous metal augments that can be used to provide support for a cementless cup against host bone.

Templating: Radiographs and CT were used for pre-op planning and templating. A 3D printed pelvis model can be very useful for templating implants as the three-dimensional nature of the defect makes templating from images alone difficult. A 3D model was used to design the custom implant and to develop a backup construct (Figs. 19.8, 19.9 and 19.10).

 

Surgical Note

 

Patient’s position: Supine on a regular table.

Type of anesthesia: Spinal.

Surgical approach: Direct lateral.

Main steps: A modified anterolateral gluteus medius splitting approach was made to the left hip. There was no overt evidence of infection seen. The femoral component was exposed. The

 

 

 

 

Fig. 19.10 The final implant used had been templated as a backup preoperatively. A 3D printed model was generated from the CT and was then reamed for placement of the jumbo cup with augment. The augment fills the superior defect while the jumbo cup fills in the medial and inferior defects

 

femoral head component was disimpacted and removed. The femoral stem was checked and noted to be in good position and stable and therefore, it was maintained. Attention was then turned to the acetabular component, which was grossly loose. There was a massive amount of bone loss encountered, and a Paprosky type IIIB defect was confirmed. An attempt was made to insert the custom cage; however, there was not a proper fit, and this was abandoned. The remaining acetabulum was reamed to accept a size 78 mm jumbo porous metal shell. The superior acetabular defect was augmented with an augment measuring 50 × 10 mm with two screws providing fixation. The acetabulum was then bone grafted with a combination of cancellous allograft and demineralized bone matrix. The acetabular cup was

 

impacted into place, and three screws were utilized for supplemental fixation. The interface between the acetabular component and the augment was then cemented. A 36, 0-degree liner was utilized. Trial and final reduction of the hip revealed excellent leg length, stability, and range of motion. The incision was copiously irrigated at multiple points during the case and the incision was closed in layers (Fig. 19.11).

Reconstruction techniques: Reamers were used to reshape the pelvis for the jumbo revision porous metal cup. Augments were utilized and screws for acetabular fixation. A custom cage was attempted but was aborted because it did not fit.

 

Intraoperative Challenges

 

Challenges and solutions: The custom cage implant did not fit well. This was anticipated, and jumbo cups with augments were available. A good fit was achieved using a jumbo cup with screws for augmentation and a superior augment.

Thorough description of decision-making, including the reason for the final decision: The fit of the custom implant was inadequate due to continued bone loss since the CT that it was based upon had been taken. Both cages and augments were available as a backup. Because a 3D pelvis had been constructed to design the custom implant, this was also used to develop a backup construct consisting of a cementless jumbo cup and porous metal augment (Fig. 19.10). After reaming the model to size the cup and fitting the appropriate size and shape augment, the construct appeared to be stable. The final implant was chosen for this IIIB defect case and was based upon this preoperative “practice” run.

Postoperative Radiographs

(Fig. 19.11)

 

 

 

 

Fig. 19.11 AP of left hip post-op with jumbo cup and augment. Note that one broken screw was retained from the prior surgery

 

Postoperative Management

 

Chemoprophylaxis and anticoagulant treatment period: Perioperative antibiotics including vancomycin and cephalexin. The patient was on Coumadin preoperatively for a history of a thromboembolic disease, and this was restarted postoperatively.

Gait/limb loading until full loading: The patient was limited to toe-touch weight bearing (10% of body weight on the reconstructed side) for twelve weeks with hip precautions for six weeks.

 

Follow-Up and Complications

 

The revision became infected one month postoperatively and returned to the operating room for irrigation and debridement, removal of all hardware including the femoral components, and antibiotic spacer placement. The spacer was eventually replaced with another jumbo cup, and the femur had to be revised to a revision modular stem. This became infected, and the patient underwent irrigation and debridement and is now on chronic antibiotic suppression.

 

Discussion

 

Advantages of the applied method: The advantages of large porous metal cups are that they are technically straightforward, and once ingrown they provide a stable construct that will be anchored to both columns. They also maximize contact with host bone, reduce the need for bone grafting, and help normalize the hip center of rotation. Porous metal augments facilitate the fixation of the cementless cup when there is not enough circumferential bone. These augments are an alternative to traditional allograft reconstruction of severe acetabular bone loss.

Disadvantages of the method: The disadvantages of using large cups are that they may not have an adequate initial fixation in massive bone loss cases and may not become osseointegrated. If there is a pelvic discontinuity, this technique may not work unless a distraction technique is utilized.

Alternative evidence-based techniques for the case: Custom triflange components can help with fixation and bridging of defects, especially if there is a concern for discontinuity, but have the disadvantage of a potential mismatch between the implant and the bone stock found intraoperatively. This was the case here, as there was an additional bone loss from the time the CT scan was obtained and the surgical reconstruction.

Modular cup, cage constructs, and cup-cage constructs have also been described. These provide extra modularity and more points of fixation, but have the disadvantage of requiring multiple interfaces, may require cement, and pose their own unique technical challenges.

Why is the chosen technique better for this case? In this case, the custom implant did not fit, but a jumbo cup and augment had good fixation after reaming and screw fixation with augments. Indications and contraindications for your technique: The indications for jumbo cup with augment use are Paprosky type II and III defects that can be reamed to create a circumferential socket, with the aid of augments, that will provide adequate fixation for the hemispherical cup. If a good press fit cannot be obtained intraoperatively with the cup alone, augments or a cage should be used to aid fixation. In cases of pelvic discontinuity, alternative techniques must be added, for example, plating of the fracture or

expansion osteotomy of the discontinuity.

Learning curve and how to manage complications: One advantage of jumbo cup use is that the technique is straightforward and similar to the placement of a standard cup.

Level of evidence concerning the superiority of this method against others: Most evidence for the use of jumbo cups or custom implants are level IV studies [32–34]