Background:
Knee arthrodesis for recurrent periprosthetic knee infection is a limb salvage procedure that simultaneously provides a stable limb for weight-bearing and effective eradication of the chronic infection. Knee arthrodesis is a final resort for limb salvage that is appropriate for patients with multiple recurrent revisions for infection, a history of failed 2-stage exchanges, medical comorbidities, and an inability to tolerate multiple additional procedures. Another important consideration is whether the patient has a poor soft-tissue envelope that leaves knee arthrodesis as the only viable option. The procedure is a definitive surgery to eliminate return trips to the operating room.
Description:
This technique involves knee arthrodesis using a long intramedullary rod inserted proximally through the piriformis fossa that spans the entire medullary canal of the femur and the tibia. Before insertion, the surgeon may elect to create a long antibiotic cement-coated intramedullary rod. The rod is locked proximally and distally. An alternative method for large bone defects (>6 cm) at the level of the knee is to create intercalary antibiotic-impregnated cement spacers.
Alternatives:
Alternative surgical treatments for this problem include above-the-knee amputation or resection arthroplasty, neither of which provides a functional limb for weight-bearing. The most common alternative methods for knee arthrodesis include external fixation using circular or biplanar frames, as well as short intramedullary modular rods.
Rationale:
Knee arthrodesis using a long intramedullary rod is a very effective and efficient method of fusion. With recurrent periprosthetic knee infections, metaphyseal bone loss is common and short knee-fusion rods may not provide adequate stability. Long rods for knee arthrodesis use the diaphysis for stability and have the additional advantage of being easily accessible for removal in the event of a recurrent infection with a well-healed fusion. Long intramedullary rods also provide the additional advantages of immediate weight-bearing. Immediate weight-bearing on the affected limb is critical because often these patients have been unable to bear weight preoperatively secondary to pain and infection. External fixation techniques are effective but come with pin-site problems. Pin-site problems are amplified in patients with obesity who have large soft-tissue envelopes, and the long intramedullary rod avoids pin problems in such patients. Antibiotic cement coating of the long intramedullary rod also provides local antibiotic delivery.
Introductory Statement
Knee arthrodesis for recurrent or failed periprosthetic knee infection and/or a nonreconstructible extensor mechanism deficit after total knee arthroplasty (TKA) is a limb salvage procedure that simultaneously provides a stable limb for weight-bearing with the additional benefit of effective eradication of a chronic infection.
Indications & Contraindications
Indications
Recurrent periprosthetic knee infection
Failed TKA
Nonreconstructible extensor mechanism deficit after TKA
Contraindications
Ipsilateral total hip arthroplasty
Ipsilateral total ankle arthroplasty
Deformed canals precluding intramedullary rod insertion
Retained implants in the tibia and femur that would make rod passage impossible
Step-by-Step Description of Procedure
Step 1: Preoperative Planning and Patient Presentation (Video 1)
Perform a laboratory assessment, complete history, and a physical examination; make and review femoral and tibial radiographs; measure remaining bone available as well as the diameter of the canal; and determine the extent of bone loss.
Perform a laboratory assessment and a complete history and physical examination to document any clinical signs of infection as well as elevated C-reactive protein level and erythrocyte sedimentation rate (ESR).
Make and review femoral and tibial radiographs with magnification markers (Figs. 1-A and 1-B). Full-length standing anteroposterior and lateral radiographs are the most helpful.
Measure the remaining bone available and the diameter of the canal, which allows the surgeon to determine the diameter of the intramedullary rod. Diameter sizes that are available are 10 mm (custom), 11.5 mm, and 13 mm. Available rod lengths range from 55 to 90 cm.
Determine the extent of the bone loss on the basis of the size of the components. If >6 cm of bone loss is anticipated, alternative measures to deal with this gap other than acute compression must be considered carefully. Alternative options include stacked intercalary spacer blocks (described below) or double-level bone transport over the rod.
Figs. 1-A and 1-B Preoperative full-length standing anteroposterior (Fig. 1-A) and lateral (Fig. 1-B) radiographs. In addition to review, these radiographs are used to make sure that there is no additional hardware in the canals that would obstruct the insertion of a rod. (Reproduced, with permission, from: Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Fig. 1-A.
Fig. 1-B.
Video 1.
Preoperative planning and patient presentation. After multiple revision procedures, the patient had an infection at the site of the right TKA with a draining wound. There was a large gap at the level of the knee. The plan was to insert an antibiotic cement-coated long intramedullary rod with antibiotic cement-coated spacer blocks at the level of the knee. This surgical plan preserves limb length and allows immediate weight-bearing. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Step 2: Patient Positioning (Figs. 2-A, 2-B, and 2-C, Video 2)
Position the patient on a radiolucent operating table in the supine position with a bump (2 blankets taped together with a height of 9 to 10 cm) under the sacrum to elevate the pelvis but keep it level.
Shift the bump under the pelvis slightly to the contralateral side to allow the ipsilateral buttock adipose tissue to hang free. This allows access to the piriformis fossa. A foot bump at the level of the calf is needed to flex the knee when removing implants.
Forward flex the ipsilateral shoulder to 90° and internally rotate the shoulder. Tape the arm across the chest with the elbow at 90°. Place egg crate padding or blankets under the forearm to maintain the elbow at 90°. Remove the arm board from the operatively treated side to keep it out of the way of the rod insertion. When the arm is taped across the chest, it must be placed so that the elbow is flexed to only 90°. This usually requires some foam padding to be placed under the forearm prior to taping, to prevent ulnar nerve palsy.
The contralateral leg should be well padded and taped to the bed. This is critical for preventing the contralateral leg from falling off the bed with aggressive adduction of the involved limb during rod insertion.
Once the patient is positioned, adduct the leg to check that access to the piriformis fossa is unimpeded and that the C-arm can image the insertion point at the piriformis fossa as well.
Ensure that there is nothing that obstructs the ability to adduct the leg. Make sure that the insertion device will have access to the insertion point. There should be nothing next to the ipsilateral flank to block this—including the safety strap or air warming device. These can be positioned more proximally.
Figs. 2-A, 2-B, and 2-C Positioning of the patient. (Reproduced, with permission, from: Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Fig. 2-A.
Close-up photograph of the patient’s hip region on the operating-room table shows the proper positioning of the bump. The bump is placed flat under the pelvis with the soft tissue of the lateral aspect of the buttocks hanging over the 2-blanket bump to allow access to the rod insertion point (piriformis fossa).
Fig. 2-B.
Figs. 2-B and 2-C Photographs show the patient positioned on the operating-room table. Note that the ipsilateral arm is taped across the chest to allow unobstructed rod insertion. The foot bump shown in the photograph is optional.
Fig. 2-C.
Video 2.
The patient is positioned on a radiolucent operating table in a supine position with a bump (height of 9 to 10 cm) under the sacrum to elevate the pelvis while allowing the ipsilateral buttock adipose tissue to hang free over the side of the operating table. A foot bump can be placed at the level of the calf. The contralateral leg should be well padded and taped to the bed. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Step 3: Drape Out the Limb, Apply a Tourniquet, and Set up the Mayo Stand to Perform the “Dirty” Portion of the Case
Carefully drape out and prepare the entire limb, including the foot; place a sterile tourniquet on the proximal aspect of the thigh; and then set up the Mayo stand for the debridement instruments.
Place the drape posteriorly as close to the gluteal cleft as possible, keeping the soft-tissue lateral mass of the buttock sterile and hanging freely over the bump.
Place the proximal drape proximal to the level of the iliac crest or higher.
Inflate the tourniquet to 350 to 400 mm Hg (depending on the diameter of the thigh).
Confine all debridement instruments to the Mayo stand.
Ensure that the back tables remain sterile for the clean reconstructive portion of the procedure.
Step 4: Mark the Location of the Incision on the Skin (Videos 3-A and 3-B) and Make a Transverse or Longitudinal Incision
Under fluoroscopic guidance, use a sterile surgical skin marker to mark the location of the incision on the knee, which can be either transverse (Video 3-A) or longitudinal (Video 3-B), and make the incision to allow for exposure of the knee joint, debridement, and optional patellar excision.
Use a transverse incision to allow compression and shortening of the limb, excision of excess skin, and ease of closure. It also prevents potential wound-healing problems since the transverse incision is positioned at 90° to the previous incision(s). If the patient has a good soft-tissue envelope and is a potential candidate for TKA in the future, this incision is contraindicated and the patellar tendon is preserved.
Use a longitudinal incision when the gap is >6 cm and fill the gap with spacer blocks.
Place the incision to allow access to the tibial and femoral components in order to easily remove all components.
For the transverse incision, place the incision at the level of the polyethylene portion of the component and mark this on the anteroposterior and lateral radiographs. The lateral mark is usually at a slightly different level than the anteroposterior mark. It is the practice of the author typically to use the level of the lateral mark for the transverse incision.
Make the longitudinal incision in a standard fashion as if performing a TKA.
For a permanent fusion, consider excising the patella to improve the debridement. This also helps with closure.
Make a full-thickness incision down to the components. For a transverse incision, transect the patellar tendon. For a longitudinal incision, perform a parapatellar arthrotomy (Video 4).
Flex the knee joint and widen the incision to obtain full access to the tibia and femur. Once the knee joint is flexed up, remove the polyethylene component.
Optional: Excise the patella. The patella can be used for autogenous bone graft if it is healthy and not necrotic.
Video 3-A.
The transverse incision. The location of the incision is marked at the level of the knee. The transverse incision is made and allows for full exposure of the knee joint and debridement. The patellar tendon is transected. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Video 3-B.
The longitudinal incision is marked on the skin. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Video 4.
The longitudinal incision is made and a parapatellar arthrotomy is performed. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Step 5: Remove the Tibial Component (Video 5) and the Femoral Component (Video 6)
Remove the baseplate, the cement on the tibial surface, and necrotic bone using a high-speed saw and burr and then remove the femoral component, cement, and necrotic bone using a Gigli saw, oscillating saw, and a burr.
Expose the tibial baseplate. Pass a high-speed saw between the baseplate and the cement interface. This usually works well for the anterior and medial interfaces; the lateral interface may be slightly more difficult to access.
After the saw has passed completely around the baseplate, use a tamp to remove the baseplate.
Remove any remaining cement from the tibial surface and open the tibial canal using a high-speed burr.
Remove necrotic bone using the burr until a healthy bone surface is obtained.
Remove the proximal and anterior interfaces of the femoral component using a Gigli saw. For the distal and posterior interfaces, use a small oscillating saw.
Utilize a tamp on the anterior flange to remove the femoral component.
Remove any remaining cement with a high-speed burr.
Remove necrotic bone using the burr until a healthy bone surface is obtained.
Use the burr to open up the femoral canal.
Video 5.
Remove the tibial component. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Video 6.
Remove the femoral component. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Step 6: Synovectomy, Posterior Capsular Release, and Gap Assessment (Video 7)
Complete the synovectomy and the posterior capsular release and assess the gap.
Perform a complete and total synovectomy using a scalpel and a hydroscalpel.
Remove necrotic soft tissue.
Subperiosteally strip the posterior capsule on the femur and tibia to allow for compression of the tibia and the femur.
Measure the gap between the femur and tibia.
Note that defects of ≤6 cm are not associated with vascular compromise.
Note also that a critical defect size is >6 cm. Compression of >6 cm is contraindicated because it will promote vessel kinking and ischemia.
Video 7.
Complete the synovectomy and the posterior capsular release. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Step 7: Manage the Bone Gap
If the bone gap is ≤6 cm, ensure there is at least 50% apposition of the bone ends, and if the bone gap is >6 cm, plan to use intercalary spacers.
Manually check the bone ends to see if they can be approximated and evaluate the bone contact area.
Ensure that at least 50% of the bone is able to be approximated for the fusion. Usually, the surgeon can achieve bone contact with the posterior bone ends (typically there is anterior bone loss).
If the bone gap is ≤6 cm and 50% apposition cannot be achieved, use a saw or high-speed burr to achieve better bone contact for the fusion. This step is critical because bone contact is essential for fusion, but any additional bone removal can excessively shorten the limb.
If the gap is >6 cm, use intercalary spacers.
Step 8: Evaluate the Canals, Ream the Tibia (Video 8), and Ream the Femur (Video 9)
Determine whether the canals are infected or clean, sequentially ream the tibia to 14 mm, sequentially ream the femur to 16 mm in a retrograde fashion, and then perform femoral and tibial irrigation.
If the canals are pristine and have not been violated by the infection around the total joint replacement, then irrigate with 6 L of saline solution. Reprepare and redrape the leg.
If the canals are infected, perform the reaming during the debridement portion of the procedure. Confine all instruments to 1 Mayo stand. Ream to clean the canals and then irrigate. Change all gowns and gloves and remove the Mayo stand with the contaminated instruments. Use new instruments for the remainder of the procedure.
Under fluoroscopic guidance and with the aid of a guide rod, ream the tibial canal to 14 mm. Reaming to this diameter allows for rod insertion without incarceration of the antibiotic cement-coated intramedullary rod.
If the canal is sclerotic, use a drill bit with a 4.8-mm length to open up the canal under fluoroscopic guidance.
If the femoral canal is sclerotic, a drill bit (4.8-mm length) can be used under fluoroscopic guidance to open the femoral canal.
Adduct the leg (this will allow the guidewire to be accessed through a proximal incision).
Insert the guidewire into the distal femoral canal.
Drive the guidewire through the femoral canal and out the proximal piriformis fossa using a mallet and T-handle chuck.
Once the guidewire has exited the femoral canal, make a proximal incision to retrieve the guidewire proximally. This incision will serve as the insertion point for the intramedullary rod.
Place a Kocher clamp on the exposed guidewire that was pulled out of the proximal incision.
Sequentially ream the femoral canal to 16 mm in a retrograde fashion. Reaming to this diameter allows for rod insertion without incarceration of the antibiotic-cement coated intramedullary rod.
Following the sequential reaming, perform femoral and tibial irrigation with 6 L of saline solution.
Video 8.
Ream the tibia sequentially to 14 mm. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Video 9.
Ream the femur sequentially to 16 mm in a retrograde fashion. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Step 9A: Standard Method to Select the Knee Intramedullary Rod for Direct Osseous Apposition (Bone Gap of ≤6 cm) (Figs. 3-A and 3-B, Video 10)
Determine the femoral and tibial lengths and select the length and diameter of the knee intramedullary rod.
Measure the femoral length from the piriformis fossa to the end of the femur distally. To determine the femoral length, advance a guide rod under fluoroscopic guidance from the distal aspect to the proximal aspect of the femur until the tip of the rod is at the piriformis fossa. Attach a Kocher clamp to the guide rod at the end of the distal end of the femur and then remove the rod. Measure the length of the guide rod from the Kocher clamp to the tip of the rod to determine the femoral length.
Measure the tibial length from the tibial plateau to the tibial plafond. To determine the tibial length, advance the guide rod under fluoroscopic guidance from the proximal part to the distal part of the tibia until the tip of the rod is at the tibial plafond. Attach the Kocher clamp to the guide rod at the proximal portion of the tibial plateau and then remove the guide rod. Measure the length of the guide rod from the Kocher clamp to the tip of the rod.
Add the femoral and tibial lengths together to determine the length of the long intramedullary rod. Do not include the length of the gap at the knee region.
Select the length of the intramedullary rod. Intramedullary rods are made in increments of 5 cm of length (e.g., 60, 65, 70, 75, and 80 cm) and range from 55 to 90 cm. When choosing the length, be sure to account for some compression at the bone ends. If this compression is not considered, the surgeon will insert a rod that is too long. Note that if the rod is too long, the surgeon will have to remove the long rod and then insert a new rod that is 5 cm shorter. For example, if the femoral plus tibial lengths total 71 cm (without considering compression), then the surgeon should select a 65-cm or 70-cm rod depending on the amount compression that the surgeon anticipates. This decision should depend on the quality of bone (e.g., osteoporotic bone) and/or the anticipated amount of invagination of the femur into the tibia.
Select the diameter of the knee intramedullary rod. Rods are available in 11.5 mm and 13 mm; however, a custom diameter of 10 mm can be ordered. Consider a 11.5-mm or 13-mm diameter if a patient has a body mass index of >40 kg/m2. Consider the 10-mm diameter if the tibial and/or femoral canals are narrow.
Video 10.
Standard method to measure femoral and tibial lengths and select the intramedullary rod for direct osseous apposition (bone gap of ≤6 cm). See also Figures 3-A and 3-B. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Figs. 3-A and 3-B The standard method to select the intramedullary rod length for direct osseous apposition (a bone gap of ≤6 cm). (Reproduced, with permission, from: Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore. Copyright 2020.)
Fig. 3-A.
The first 3 steps in selecting the length of the intramedullary rod.
Fig. 3-B.
The next 3 steps in selecting the intramedullary rod length.
Step 9B: Alternate Method to Select the Intramedullary Rod and the Intercalary Spacers (Bone Gap of >6 cm) (Video 11)
Determine the length between the piriformis fossa and the tibial plafond, determine the diameter of the canal, and select the length and diameter of the intramedullary rod and the height of the spacers.
To determine the length of the intramedullary rod, obtain fluoroscopic views to confirm the location of the piriformis fossa and the tibial plafond and mark each location on the skin. Use a ruler and a skin marker to measure from the piriformis fossa to the tibial plafond.
To determine the rod diameter, measure the width of the femoral isthmus. Clamp a surgical instrument to a ruler at the 0-cm mark and another to the ruler at the 1-cm mark. Obtain a fluoroscopic view of the ruler with the 2 clamps over the femoral isthmus to determine the width of the canal.
To determine the height of the intercalary spacers, obtain fluoroscopic views at the level of the knee. Mark the location of the distal end of the femur and the location of proximal end of the tibia using a skin marker. Use a ruler to measure from the distal end of the femur to the proximal end of the tibia to determine the bone gap. Select appropriately sized spacer blocks to allow for 1 cm of shortening, which will allow the fused leg to clear the ground.
Select the length of the intramedullary rod. Intramedullary rods are made in increments of 5 cm of length (e.g., 60, 65, 70, 75, and 80 cm) and range from 55 to 90 cm.
Select the diameter of the intramedullary rod. Rods are available in 11.5 mm and 13 mm; however, a custom diameter of 10 mm can be ordered. Consider a 11.5-mm or 13-mm diameter if a patient has a body mass index of >40 kg/m2. Consider the 10-mm diameter if the tibial and/or femoral canals are narrow.
Video 11.
Alternate method to select the intramedullary rod and the intercalary spacers (bone gap of >6 cm). (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Step 10: Optional: Create an Antibiotic Cement-Coated Intramedullary Rod (with or without Cannulation) and Intercalary Spacers Made from Antibiotic-Impregnated Cement
Create an antibiotic cement-coated long intramedullary rod with optional rod cannulation and optional intercalary spacers made from antibiotic-impregnated cement (Video 12).
Note that this step will take approximately 15 to 20 minutes to allow the antibiotic cement to cure. If you know the size of the rod before the procedure, the antibiotic cement-coated rod can be created prior to the start of the case or simultaneously during the previous steps in the operation if you have a reliable first assistant.
Use a silicone tube (12.5-mm diameter) to create the rod.
Add antibiotics to the cement. Use 1 g of vancomycin and 3.6 g of tobramycin per bag. Add extra monomer to make the wet cement very thin. Perform this part very carefully. The cement mixture must be of a very thin viscosity to keep the silicone tube from excessively dilating during the insertion of the rod into the tube.
Pump the silicone tube full of cement and then insert the rod. Do not let the cement and the rod dilate the tube excessively. Overfilling the silicone tube will make the diameter of the rod too large and will result in rod incarceration. To prevent this complication, the tibial and femoral canals were reamed in previous steps to 14 mm and 16 mm, respectively.
Optional: The cement rod can be cannulated by using a long guide rod to remove cement from the center portion of the intramedullary nail before it is cured.
Optional: If the surgeon does not plan to unite the bone ends, spacer blocks can be created using prefabricated molds and antibiotic cement.
Allow the rod to cure and then cut the tube off.
Video 12.
The surgeon has the option of creating an antibiotic cement-coated intramedullary rod (with or without cannulation). If the bone gap is >6 cm, the surgeon may also choose to make intercalary spacers from antibiotic-impregnated cement. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Step 11: Rod Insertion (Figs. 4-A and 4-B, Video 13) and Closing the Incision
Insert the rod from the piriformis fossa to the distal end of the tibia, lock the rod proximally, compress the bone ends by loading the foot and tapping the insertion handle after the proximal locking screw has been inserted, examine the arthrodesis site with the aid of fluoroscopy to make sure that maximal compression of the bone ends or spacer blocks has been achieved, lock the rod distally (Figs. 4-A and 4-B), and then close the transverse incision at the level of the knee in 2 layers.
Start proximally by adducting the leg and placing the rod with the attached insertion device (locking screw guide arm) into the piriformis fossa. Be careful not to abduct the limb until the insertion device is removed as this can fracture the femoral neck.
If using spacers, a long guide rod is helpful (Video 13). Insert the rod into the knee arthrodesis site and then manually guide the rod into the proximal part of the tibia to ensure that it is centered in the bone correctly. Once the rod is in the canal, drive it into the distal end of the tibia by hitting the insertion handle.
Note: Check the rotation of the limb during the insertion of the rod into the proximal end of the tibia as doing so is critical to prevent excessive internal or external rotation. Simultaneously adduct the leg and position the foot perpendicular to the floor. Ensure that the foot remains perpendicular to the floor during insertion to prevent malrotation of the lower limb. Another rotational guide can be the incision at the knee. This incision should line up if the rotation of the limb was acceptable preoperatively. Do not try to rotate the tibia after the rod is fully inserted.
As the rod is inserted, load the foot so that there is compression at the arthrodesis site.
After the rod is completely inserted, lock it proximally and then use the mallet on the insertion device to compress the arthrodesis site while loading the foot.
After the knee joint is compressed with excellent bone apposition (confirmed via fluoroscopic and direct visualization), remove the insertion device and then abduct the limb. If the surgeon does not remove the insertion device before abducting the limb, the femoral neck may fracture.
Insert the distal interlocking screws using the “perfect circle” fluoroscopic technique. If an antibiotic cement-coated intramedullary rod has been inserted, it is not difficult to drill through the cement. However, screws with a capture device are needed because the screws can be stripped as they are inserted through the hardened cement inside the rod.
Insert antibiotic absorbable beads for local antibiotic delivery into the wound.
Optional: Insert bone morphogenetic protein-2 to promote union at the arthrodesis site because the bone ends have been traumatized by infection and the joint replacement.
Place a drain if there is a concern for hematoma.
Close the transverse incision at the level of the knee in 2 layers using 1.0 polydioxanone (PDS) and then 2.0 PDS monofilament sutures.
Figs. 4-A and 4-B Intraoperative fluoroscopic views show osseous apposition. The nail is locked proximally. The foot is loaded and held as the rod is hit to compress the gap. (Reproduced, with permission, from: Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Fig. 4-A.
Distracted.
Fig. 4-B.
Compressed.
Video 13.
The long intramedullary rod is inserted. A guide rod is helpful when inserting spacers at the level of the knee. (Used with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Step 12: Postoperative Care
Instruct the patient to bear weight on the limb as tolerated on postoperative day 1.
Advise the patient to wear thigh-high, compression stockings or a long ACE wrap (3M) to prevent venous stasis and improve wound-healing.
Administer venous thromboembolism prophylaxis for 6 weeks.
Obtain full-length standing anteroposterior and lateral radiographs at 6 weeks, 3 months, and 6 months.
Consider supplemental bone graft and plate fixation if the knee arthrodesis has not healed, there are signs of screw lucency at the tibial-screw interface, and the patient has persistent pain with weight-bearing (Fig. 5). In such cases, the lucency is most likely secondary to motion.
Fig. 5.
Fluoroscopic anteroposterior view shows the wire indicating the location of a severe case of screw lucency in the distal end of the tibia, consistent with a nonunited knee arthrodesis. (Reproduced, with permission, from: Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
Results
Balato et al.1, in a meta-analysis involving 18 studies on knee arthrodesis conducted with long fusion rods for the treatment of infection at the site of TKAs, found that 84% (65) of the 77 patients included in the studies were free of infection and 83% (64 patients) achieved union at an average (and standard deviation) of 5.62 ± 1.6 months. This meta-analysis, which did not include any long antibiotic-coated rods, showed an increased rate of reinfection compared with external fixation techniques for knee arthrodesis. However, the study did show that the rate of major complications following intramedullary arthrodesis was lower than that after external fixation techniques for knee arthrodesis. The pooled rate of reoperation was similar in both groups, however, demonstrating the challenge of fusing the knee after an infection at the site of a TKA.
The results of using long antibiotic-coated rods to achieve knee arthrodesis were previously published in 20142. Thirty-six procedures were performed, with a successful limb salvage rate of 91.6%. Additional surgical procedures were required for nonunion or recurrent infection in 43% of the patients. All patients were able to bear weight following treatment and maintained their ability to walk. Published results for amputation after infection at the site of a TKA have documented that a large percentage of these patients were nonambulators3-5. Patients with knee arthrodesis have an ambulatory advantage compared with the patients who have had an amputation3-8.
Pitfalls & Challenges
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Challenges
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Narrow canals might not have a wide enough diameter to accommodate the antibiotic-cement coating on the long rod.
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Large defects (>6 cm) may require different bone loss management (i.e., spacer block, gradual compression, and bone transport).
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In patients with a body mass index of >40 kg/m2, accessing the starting point for the antegrade intramedullary rod can be challenging.
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Delayed bone-healing at the knee arthrodesis site can occur secondary to the substantial flexion-extension force transmitted across the knee joint as well as the bone ends that have been repeatedly exposed and devascularized with multiple surgical procedures.
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Pitfalls
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Underreaming the canals
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Not achieving good bone contact and compression
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Abducting the leg with the insertion handle still attached, potentially fracturing the proximal part of the femur
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Allowing the limb to become rotated internally or externally during rod insertion
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Failing to remove all of the necrotic tissue until a healthy bone surface is obtained
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Acknowledgments
Note: The author thanks Amanda E. Chase, MA, Alvien Lee, and Joy Marlowe, MA, for their invaluable assistance with the manuscript, videos, and illustrations.
Published outcomes of this procedure can be found at: BMC Musculoskelet Disord. 2018 Oct 10;19(1):361.
Investigation performed at the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, Baltimore, Maryland
Disclosure: The author indicated that no external funding was received for any aspect of this work. On the Disclosure of Potential Conflicts of Interest form, which is provided with the online version of the article, the author checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work and “yes” to indicate that the author had other relationships or activities that could be perceived to influence, or have the potential to influence, what was written in this work (http://links.lww.com/JBJSEST/A299).
References
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