Infected total hip arthroplasty (THA) is catastrophic, but it is treatable with a high degree of success. Two-stage revision with an antibiotic-loaded cement spacer is the most widely accepted method of treatment, and considered by some to be the best method; however, single-stage treatment currently is used widely, and is gaining acceptance. Although antibiotic-loaded cement is considered to be important for antibiotic delivery after surgery, cementless revision is equally successful with one- or two-stage procedures.

Delivery of antibiotics with depot methods, such as cement or bone graft impregnated with antibiotics, is considered to be effective, but the antibiotic levels rapidly deteriorate after the first three days, leaving the cement itself vulnerable to colonization by resistant organisms. Nephrotoxicity is not common, but it does occur, and necessitates removal of the cement. This can be catastrophic if the implants are fixed with antibiotic-impregnated cement.

Success rates of THA revision for infection can be as high as 98%, but this rate is dependent on the organism. Failure rates of 20% are the norm for resistant organisms such as methicillin-resistant Staphylococcus aureus, The cost of this failure rate is huge. Failure probably is due to the low concentration of antibiotics in the operative site. Antibiotic infusion into the operative site achieves concentrations that are hundreds of times higher than can be achieved with any other technique and has the additional advantage of being able to be discontinued in the case of renal or auditory damage. Limited personal experience suggests that the failure rate of revision total hip with resistant organisms is significantly lower with intra-articular delivery than with other currently available methods.

Between January 2002 and July 2013, 9 patients (9 hips) presented with late-onset acute infections in cementless THA with bone-ingrown implants. These patients were all more than 2 years from their original surgery and had acute symptoms of infection for 4 to 9 days. Two were the author's patients and 7 were referred from another institution. None had symptoms until the onset of their infection, and none had postoperative wound complications, fever, or prolonged pain suggestive of a chronic process. All were treated with debridement and head/liner exchange, followed by catheter infusion of intraarticular antibiotics. All remained free of signs of infection at a mean follow-up of 74 months (range, 62–121 months). This sequential series of successful treatment of late-onset infection of osteointegrated total hip replacement suggests that this is a highly effective method. It has the advantages of being a single-stage procedure, and of avoiding the catastrophic surgical procedure of removing fully osteointegrated total hip replacements.

Complete or nearly complete disruption of the attachment of the gluteus is seen in 10–20% of cases at the time of THA. Special attention is needed to identify the lesion at the time of surgery because the avulsion often is visible only after a thickened hypertrophic trochanteric bursa is removed. From 1/1/09 to 12/31/13, 525 primary hip replacements were performed by a single surgeon. After all total hip components were implanted, the greater trochanteric bursa was removed, and the gluteus medius and minimus attachments to the greater trochanter were visualised and palpated. Ninety-five hips (95 patients) were found to have damage to the muscle attachments to bone. Fifty-four hips had mild damage consisting of splits in the tendon, but no frank avulsion of abductor tendon from their bone attachments. None of these cases had severe atrophy of the abductor muscles, but all had partial fatty infiltration. All hips with this mild lesion had repair of the tendons with #5 Ticron sutures to repair the tendon bundles together, and drill holes through bone to anchor the repair to the greater trochanter. Forty-one hips had severe damage with complete or nearly complete avulsion of the gluteus medius and minimus muscles from their attachments to the greater trochanter. Thirty-five of these hips had partial fatty infiltration of the abductor muscles, but all responded to electrical stimulation. The surface of the greater trochanter was denuded of soft tissue with a rongeur, the muscles were repaired with five-seven #5 Ticron mattress sutures passed through drill holes in the greater trochanter, and a gluteus maximus flap was transferred to the posterior third of the greater trochanter and sutured under the vastus lateralis. Six hips had complete detachment of the gluteus medius and minimus muscles, severe atrophy of the muscles, and poor response of the muscles to electrical stimulation. The gluteus medius and minimus muscles were sutured to the greater trochanter, and gluteus maximus flap was transferred as in the group with functioning gluteus medius and minimus muscles. Postoperatively, patients were instructed to protect the hip for 8 weeks, then abductor exercises were started.

The normal hips all had negative Trendelenburg tests at 2 and 5 years postoperative with mild lateral hip pain reported by 11 patients at 2 years, and 12 patients at 5 years. In the group of 54 with mild abductor tendon damage that were treated with simple repair, positive Trendelenburg test was found in 5 hips at 2 years and in 8 hips at 5 years. Lateral hip pain was reported in 7 hips at 2 years, and in 22 at 5 years. In the group of 35 hips with severe avulsion but good muscle tissue, who underwent repair with gluteus maximus flap transfer, all had good abduction against gravity and negative Trendelenburg tests at 2 and 5 years postoperative, and none had lateral hip pain. Of the 6 hips with complete avulsion and poor muscle who underwent abductor muscle repair and gluteus maximus flap transfer, all had weak abduction against gravity, mildly positive Trendelenburg sign, and mild lateral hip pain at 2 and 5 years postoperative. Abductor avulsion is uncommon but not rare, and is detected during THA only by direct examination of the tendon and removal of the trochanteric bursa. Simple repair of mild abductor tendon damage did not prevent progressive abductor weakness in some hips; and the increase in number of patients with lateral hip pain from 2 to 5 years suggests progressive deterioration. Augmentation of the repair with a gluteus maximus flap appears to provide a stable reconstruction of the abductor muscles, and seemed to restore abductor function in the hips with functioning muscles.

When dealing with a flexion contracture, a surgeon first should consider all potential causes, specifically ligament contracture and osteophytes. Then consider the size of the femoral component and its position proximal to distal and also the posterior slope of the tibial component.

Most knee flexion contractures are caused by osteophytes and tight ligaments, and once these problems are corrected, no further work needs to be done on the knee. So when the bone surface cuts are made, in general, little compensation is done in terms of positioning the femoral component proximal or distal, or in terms of sloping the tibial component (beyond the normal 3–4 degrees posterior slope), before the ligaments or osteophytes are managed. If the deep medial collateral ligament (MCL) and posterior portion of the superficial MCL are tight, a flexion contracture will almost always be present after the bone surfaces are finished. Once this is corrected with proper ligament releases and removal of osteophytes, then ligament balance and flexion contracture should be reassessed. In the very few cases that still have a flexion contracture, posterior capsule release should be done. Once this is finished, releasing the capsule from both the femur and the medial aspect of the tibia, then ligament balance is reassessed again. If flexion contracture still remains (<10% of cases), then the distal surface of the femur is resected another 4–6 mm, trial components are inserted, and flexion contracture is evaluated. If more bony resection is needed, then changing tibial slope from 4 degrees posterior slope to 0 degrees slope is another step that can be done to remove bone from extension space of the knee finally to achieve full extension. Virtually all flexion contractures, except those with severe contracture resulting from hamstring tightness, can be corrected with this method.

In the valgus knee with flexion contracture, similar management is used. Knees that will not extend and remain tight on the lateral side usually are corrected with release of the posterior capsule and posterior portion of the iliotibial band. Just as on the lateral side, bone resection from the distal femur can be performed as a final effort to achieve full extension of the knee.

It is worth reiterating that almost all flexion contractures are caused by ligament imbalance, and that over-resection of the distal femur at the start of these cases can easily result in hyperextension that is difficult to manage once ligaments have been balanced.

Stems are a crucial part of implant stabilization in revision total knee arthroplasty. In most cases the metaphyseal bone is deficient, and stabilization in the diaphyseal cortical bone is necessary to keep the implant tightly fixed to bone and to prevent tilt and micromotion. While sleeves and cones can be effective in revision total joint arthroplasty, they are technically difficult and may lead to major bone loss in cases of loosening or infection, especially if the stem is cemented past the cone. A much more conservative method is to ream the diaphysis to the least depth possible to achieve tight circumferential fixation, and to apply porous augments to the undersurface of the tibial tray or inner surface of the femoral component to allow them to bottom out against the bone surface and apply compressive load. If a robust, strong taper, stem and component combination is used, rim contact on only one side is necessary to achieve rigid permanent fixation.

Porous and non-porous stems are available. The non-porous stems should have a spline surface that engages the diaphyseal bone and achieves rigid initial fixation but does not provide long-term axillary support. In that way the porous rim-engaging surface can bear compressive load and finally unload the stem and taper junction.

Correctly designed stems do not stress relieve unless they are porous-coated. In situations where metaphyseal bone is not available, porous-coated stems that link to hinge prostheses are a very important part of the armamentarium in complex revision arthroplasty.

Use of stems requires experience and special technique. Slight underreaming and initial scratch fit are necessary techniques. This does not result in tight fixation every time because split of the cortex does occasionally occur. In most cases these splits do not need to be repaired, but when there is a question, an intra-operative x ray should be taken and the surgeon should be prepared to repair the fracture.

Stems are an essential part of revision total knee arthroplasty. A tightly fit stem in the diaphysis is necessary for fixation when metaphyseal bone is deficient. No amount of cement pressed into the deficient metaphyseal bone will substitute for rigid stem fixation..

Prevention and treatment of total joint infection is closely related to biofilm formation and concentration of antibiotics achieved in the area around the implants. Most total joint infections are caused by bacteria that enter the wound at the time of the operation. These bacteria can attach to surfaces and rapidly form biofilm that is highly resistant to antibiotics. Prophylactic antibiotics given intravenously achieve concentration of local antibiotics in the knee in response to intravenous antibiotics about 1/3 of that achieved in the serum, and the level is transient. This may be enough to treat the planktonic form of the bacteria, but far from enough to treat the biofilm. The concentration of antibiotics in the joint fluid achieved with antibiotics applied locally during surgery is 1000 times higher, and can be maintained throughout the procedure. High concentration persists in drainage fluid for 24 hours after surgery. Studies done with use of local antibiotics in spinal implant surgery indicate a major reduction in the rate of infection, and cost analysis shows remarkable monetary benefit to this effect.

Infected total joints benefit especially from direct application of antibiotics to the local area. The safety and efficacy of this protocol was evaluated in patients undergoing primary or revision TKA by measuring joint and serum levels of vancomycin following IV administration (as a prophylactic) and IA administration (as a treatment for infected TKA), and comparing the levels with each method. Therapeutic levels of vancomycin were present in the knee following IV or IA administration, but much higher levels were possible with IA administration (avg. of 6.8 and 9,242 µg/mL). Vancomycin achieved therapeutic levels in the synovial fluid of the knee with IV administration, but clearance from the knee was rapid, suggesting that the synovial fluid concentration may be sub-therapeutic for hours before the next IV dose is given. In contrast, IA delivery of vancomycin resulted in peak levels that were thousands of times higher, and trough levels remained therapeutic for 24 hours in both the joint space and in the serum (minimum trough levels of 8.4 and 4.2 µg/mL, respectively). The elimination constant (half-life) of IA-administered vancomycin was 3.1 hours.

Directly infusing antibiotics into the infected area maintains a high local concentration level while minimizing systemic toxicity. This method avoids the use of antibiotic-loaded cement and the potential for growth of antibiotic-resistant strains of bacteria. These findings support single-stage revision in cases treated with cementless revision and IA antibiotics.

Preventing and treating infection in orthopaedic implant surgery requires achieving concentrations that are above the minimal biofilm eradication concentration. This can be achieved only with direct application.

Alignment of total joint replacement in the valgus knee can be done readily with intramedullary alignment and hand-held instruments. Intramedullary alignment instruments usually are used for the femoral resection. The distal femoral surfaces are resected at a valgus angle of 5 degrees. A medialised entry point is advised because the distal femur curves toward valgus in the valgus knee, and the distal surface of the medial femoral condyle is used as reference for distal femoral resection. In the valgus knee, the anteroposterior axis is especially important as a reliable landmark for rotational alignment of the femoral surface cuts because the posterior femoral condyles are in valgus malalignment, and are unreliable for alignment. Rotational alignment of the distal femoral cutting guide is adjusted to resect the anterior and posterior surfaces perpendicular to the anteroposterior axis of the femur. In the valgus knee this almost always results in much greater resection from the medial than from the lateral condyle. Intramedullary alignment instruments are used to resect the proximal tibial surface perpendicular to its long axis. Like the femoral resection, resection of the proximal tibial surface is based on the height of the intact medial bone surface.

After correction of the deformity, ligament adjustment is almost always necessary in the valgus knee. Stability is assessed first in flexion by holding the knee at 90 degrees and maximally internally rotating the extremity to stress the medial side of the knee, then maximally externally rotating the extremity to evaluate the lateral side of the knee. Medial opening greater than 4mm, and lateral opening greater than 5mm, is considered abnormally lax, and a very tight lateral side that does not open at all with varus stress is considered to be abnormally tight. Stability is assessed in full extension by applying varus and valgus stress to the knees. Medial opening greater than 2mm is considered to be abnormally lax, and a very tight lateral side that does not open at all with varus stress is considered to be too tight.

Release of tight structures should be done in a conservative manner. In some cases, direct release from bone attachment is best (popliteus tendon); in others, release with pie-crusting technique is safe and effective. In knees that are too tight laterally in flexion, but not in extension, the LCL is released in continuity with the periosteum and synovial attachments to the bone. When this lateral tightness is associated with internal rotational contracture, the popliteus tendon attachment to the femur is also released. The iliotibial band and lateral posterior capsule should not be released in this situation because they provide lateral stability only in extension.

The only structures that provide passive stability in flexion are the LCL and the popliteus tendon complex, so knees that are tight laterally in flexion and extension have popliteus tendon or LCL release (or both). Stability is tested after adjusting tibial thickness to restore ligament tightness on the lateral side of the knee. Additional releases are done only as necessary to achieve ligament balance. Any remaining lateral ligament tightness usually occurs in the extended position only, and is addressed by releasing the iliotibial band first, then the lateral posterior capsule, if needed. The iliotibial band is approached subcutaneously and released extrasynovially, leaving its proximal and distal ends attached to the synovial membrane. In knees initially too tight laterally in extension, but not in flexion, the LCL and popliteus tendon are left intact, and the iliotibial band is released. If this does not loosen the knee enough laterally, the lateral posterior capsule is released. The LCL and popliteus tendon rarely, if ever, are released in this type of knee.

Finally, the tibial component thickness is adjusted to achieve proper balance between the medial and lateral sides of the knee. Anteroposterior stability and femoral rollback are assessed, and posterior cruciate substitution is done, if necessary, to achieve acceptable posterior stability.

Prevention and treatment of total joint infection is closely related to biofilm formation and concentration of antibiotics achieved in the area around the implants. Most total joint infections are caused by bacteria that enter the wound at the time of the operation. These bacteria can attach to surfaces and rapidly form biofilm that is highly resistant to antibiotics. Prophylactic antibiotics given intravenously achieve concentration of local antibiotics in the knee in response to intravenous antibiotics about 1/3 of that achieved in the serum, and the level is transient. This may be enough to treat the planktonic form of the bacteria, but far from enough to treat the biofilm. The concentration of antibiotics in the joint fluid achieved with antibiotics applied locally during surgery is 1000 times higher, and can be maintained throughout the procedure. High concentration persists in drainage fluid for 24 hours after surgery. Studies done with use of local antibiotics in spinal implant surgery indicate a major reduction in the rate of infection, and cost analysis shows remarkable monetary benefit to this effect.

Infected total joints benefit especially from direct application of antibiotics to the local area. The safety and efficacy of this protocol was evaluated in patients undergoing primary or revision TKA by measuring joint and serum levels of vancomycin following IV administration (as a prophylactic) and IA administration (as a treatment for infected TKA), and comparing the levels with each method. Therapeutic levels of vancomycin were present in the knee following IV or IA administration, but much higher levels were possible with IA administration (average of 6.8 and 9,242µg/mL, respectively). Vancomycin achieved therapeutic levels in the synovial fluid of the knee with IV administration, but clearance from the knee was rapid, suggesting that the synovial fluid concentration may be sub-therapeutic for hours before the next IV dose is given. In contrast, IA delivery of vancomycin resulted in peak levels that were thousands of times higher, and trough levels remained therapeutic for 24 hours in both the joint space and in the serum (minimum trough levels of 8.4 and 4.2µg/mL, respectively). The elimination constant (half-life) of IA-administered vancomycin was 3.1 hours.

Directly infusing antibiotics into the infected area maintains a high local concentration level while minimizing systemic toxicity. This method avoids the use of antibiotic-loaded cement and the potential for growth of antibiotic-resistant strains of bacteria. These findings support single-stage revision in cases treated with cementless revision and IA antibiotics.

Preventing and treating infection in orthopaedic implant surgery requires achieving concentrations that are above the minimal biofilm eradication concentration. This can be achieved only with direct application.

Avulsion of the abductor muscles of the hip may cause severe limp and pain. Limited literature is available on treatment approaches for this problem, and each has shortcomings. This study describes a muscle transfer technique to treat complete irreparable avulsion of the hip abductor muscles and tendons.

Ten adult cadaver specimens were dissected to determine nerve and blood supply point of entry in the gluteus maximus and tensor fascia lata (TFL) and evaluate the feasibility and safety of transferring these muscles to substitute for the gluteus medius and minimus. In this technique, the anterior portion of the gluteus maximus and the entire TFL are mobilised and transferred to the greater trochanter such that the muscle fiber direction of the transferred muscles closely matches that of the gluteus medius and minimus. Five patients (five hips) were treated for primary irreparable disruption of the hip abductor muscles using this technique between January 2008 and April 2011. All patients had severe or moderate pain, severe abductor limp, and positive Trendelenburg sign. Patients were evaluated for pain and function at a mean of 28 months (range, 18–60 months) after surgery.

All patients could actively abduct 3 months post-operatively. At 1 year post-operatively, three patients had no hip pain, two had mild pain that did not limit their activity, three had no limp, and one had mild limp. One patient fell, fractured his greater trochanter, and has persistent limp and abduction weakness.

The anterior portion of the gluteus maximus and the TFL can be transferred to the greater trochanter to substitute for abductor deficiency. In this small series, the surgical procedure was reproducible and effective; further studies with more patients and longer follow-up are needed to confirm this.

Infection is one of the most devastating complications following total joint arthroplasty. Treatment is difficult, often requiring multiple surgical procedures, prolonged hospitalization, and long-term intravenous (IV) antibiotic therapy. Failure rates are high for resistant organisms and mixed-flora infections, and antibiotic-loaded cement spacers deliver antibiotics for only a few days and can harbor resistant bacteria on the surface. We have adopted a direct-exchange method with antibiotics infused directly into the joint using Hickman catheters to achieve extremely high levels of intraarticular (IA) antibiotics for six weeks. Hickman catheters have a fibrous cuff that allows soft-tissue ingrowth and seals the surface of the tube to prevent contamination of the joint by tracking along the catheter. Two catheters are inserted to ensure that at least one will be functional for six weeks.

The safety and efficacy of this protocol was evaluated in patients undergoing primary or revision TKA by measuring joint and serum levels of vancomycin following IV administration (as a prophylactic) and IA administration (as a treatment for infected TKA), and comparing the levels with each method. Therapeutic levels of vancomycin were present in the knee following IV or IA administration, but much higher levels were possible with IA administration (avg. of 6.8 and 9,242 µg/mL). Vancomycin achieved therapeutic levels in the synovial fluid of the knee with IV administration, but clearance from the knee was rapid, suggesting that the synovial fluid concentration may be sub-therapeutic for hours before the next IV dose is given. In contrast, IA delivery of vancomycin resulted in peak levels that were many orders of magnitude higher, and trough levels remained therapeutic for 24 hours in both the joint space and in the serum (minimum trough levels of 8.4 and 4.2 µg/mL, respectively). The elimination constant (half-life) of IA-administered vancomycin was 3.1 hours.

This protocol was used in 18 knees (18 patients) with methicillin-resistant Staphylococcus aureus treated between January 2001 and January 2007 with one-stage revision that included débridement, uncemented revision of total knee components, and IA infusion of 500 mg vancomycin via Hickman catheter once or twice daily for 6 weeks. No IV antibiotics were used after the first 24 hours. Serum vancomycin levels were monitored to maintain levels between 3 and 10 µg/mL. Mean serum vancomycin peak concentration was 6 ± 2 µg/mL and the mean serum vancomycin trough concentration was 3 ± 1 µg/mL at 2 weeks post-operative. Knee synovial fluid peak and trough vancomycin levels were measured in two knees. Synovial fluid peak concentrations were 10,233 µg/mL and 20,167 µg/mL and trough concentrations were 724 µg/mL and 543 µg/mL, respectively. Minimum follow-up was 27 months (range, 27–75 months). Mean followup was 62 months, (range, 27–96 months). At 2-year follow-up, mean Knee Society score was 83 ± 9. No radiographic evidence of implant migration has occurred. One knee reinfected with MRSA and was reoperated at 5 months. A necrotic bone segment was found, the knee was debrided and revised, and the antibiotic infusion protocol was readministered. The knee remained free of infection at 42 months post-operatively.

Directly infusing antibiotics into the infected area maintains a high local concentration level while minimizing systemic toxicity. This method avoids the use of antibiotic-loaded cement and the potential for growth of antibiotic-resistant strains of bacteria. These findings support single-stage revision in cases treated with cementless revision and IA antibiotics.

Critical review of the literature fails to make a convincing case for use of cement in TKA. Many studies demonstrate clinical, mechanical, and biological failure when cement is used for fixation. Work by Ryd et al. has shown that initial migration within the first few months diminished rapidly after the first 6 months with virtually no additional movement for years after. They also suggested that cemented components do not remain rigidly fixed to bone long-term, but loosen enough to move 0.2 to 1 mm at the bone-cement interface with provocative testing. Although bone-ingrowth tibial components migrate slightly more initially than cemented ones do, they stabilise and do not sink progressively. Screw fixation adds rigidity, but does not seem to improve results. Rigidity of initial fixation is the most important feature after alignment to ensure pain-free function after arthroplasty, and can be achieved with press-fit techniques in TKA. Several early reports of bone-ingrowth TKA had inferior results because the tibial component had no stem, peg, or screw fixation, leading to implant migration and loosening. An effective stem has been shown to greatly improve tibial component fixation. The cut upper surface of the prepared tibia has areas that are too weak to withstand the forces that are applied to the surface, and failure in compression is likely unless fixation is augmented. An effective stem also reduces the shear and tensile loads at the bone-prosthesis interface. The effectiveness of compression or compaction of the tibial cancellous bone with an appropriately sized tibial metaphyseal stem has been shown, and probably was a major factor in the long-term success of fixation in our series.

Clinical results of TKA with osteointegration techniques for fixation of the femoral and tibial components in our series are comparable with the best series reported with cemented fixation. Many recent studies show significant advantages of osteointegration over cement fixation in TKA. Fixation of implants with PMMA pressed into cancellous bone eventually loosens, and fixation of a metal component to bone cement also is tenuous in most cases. Cement is disappearing rapidly from use in total hip, ankle, and shoulder arthroplasty, and soon will be replaced with osteointegration technique in the knee.

Perhaps the most appealing aspect of bone-ingrowth TKA is bone preservation. The ease of revisability because of good bone was encouraging in the components that wore, loosened, or became infected in the current series of TKA. These knees are functioning as well as knees with primary TKA. Should these knees develop additional problems, progressive destruction of bone is unlikely to occur, even if repeated revision is necessary.

Performance and durability of total knee arthroplasty is optimised when bone surfaces are prepared with the knee in neutral varus-valgus alignment in the anteroposterior (AP) plane. For the femur, this means resecting the surface perpendicular to the mechanical axis of the femur, which passes through the center of the femoral head and center of the knee. Because the center of the femoral head is not a reliable landmark during the operation, the distal femoral surface can be resected at 5 degrees valgus to the long axis of the femur using an intramedullary (IM) alignment rod to establish the position of the femur's long axis. The IM rod also provides the landmark for alignment of the femoral component in the flexion-extension position. Tibial alignment is established by cutting the upper surface of the tibia perpendicular to the long axis. An extramedullary (EM) rod easily can span the distance between the centers of the tibial surface at the knee and ankle to establish a reference for upper tibial surface resection via the long axis of the tibia. In cases with femoral deformity or bone disease that prevents use of an IM rod as a landmark for the long axis of the femur, plain film radiographs can be used along with intraoperative measurements and hand-held tools that are readily available in the standard total knee instrument set.

Using an AP radiograph taken to include the femoral head and knee: 1.) Mark the centers of the femoral head and knee. 2.) Draw a line to connect the centerpoints. 3.) Mark the high points of the medial and lateral femoral condylar joint surfaces. 4.) Draw a line perpendicular to the mechanical axis that crosses the mark on the high point of the most prominent femoral condyle. This marks the position and alignment of the femoral implant surface. 5.) To measure the distal thickness of the femoral component and adding 10% to account for magnification of the radiograph, mark two points proximal to the two high points of the condyles and draw a line perpendicular through these two points to mark the resection line for the distal femoral surfaces. Less than the thickness of the implant will be resected from the least prominent condyle. 6.) Measure the thickness of bone to be resected and the distance between the bone surface and distal surface line. This distance represents the space between the distal femoral cutting guide and the joint surface of the deficient condyle. 7.) Insert a threaded pin into the bone surface with the measured distance protruding from the surface to set this position. 8.) Seat the distal femoral cutting guide against the protruding pin on the low side and against the surface of the femur on the high side. This aligns the distal femoral cutting guide perpendicular to the mechanical axis of the femur. 9.) Draw the AP axis from the center of the intercondylar notch posteriorly to the deepest point of the patellar groove, and use the combined cutting guide to finish the femur. 10.) Make the anterior, posterior, and bevel cuts perpendicular to the AP axis. 11.) Finally, align the tibial surface, with an IM or EM rod, to resect perpendicular to the long axis of the tibia in the AP plane and sloped 4 degrees posteriorly in the lateral plane. 12.) Once the bone surfaces are resected at the proper angle, insert the trials or spacer blocks and finish the arthroplasty with release of tight ligaments.

Infected total hip arthroplasty (THA) is catastrophic, but it is treatable with a high degree of success. Two-stage revision with antibiotic-loaded cement spacer is the most widely accepted method of treatment, and considered by some to be the best method; however, single-stage treatment currently is used widely, and is gaining acceptance. Although antibiotic-loaded cement is considered to be important for antibiotic delivery after surgery, cementless revision is equally successful with one- or two-stage procedures.

Delivery of antibiotics with depot methods, such as cement or bone graft impregnated with antibiotics, is considered to be very effective, but the antibiotic levels rapidly deteriorate after the first three days, leaving the cement itself vulnerable to colonization by resistant organisms. Nephrotoxicity is not common, but it does occur, and necessitates removal of the cement. This can be catastrophic if the implants are fixed with antibiotic-impregnated cement.

Success rates of THA revision for infection can be as high as 98%, but this rate is dependent on the organism. Failure rates of 20% are the norm for resistant organisms such as methicillin-resistant Staphylococcus aureus. The cost of this failure rate is huge. Failure probably is due to the low concentration of antibiotics in the operative site. Antibiotic infusion into the operative site achieves concentrations that are hundreds of times higher than can be achieved with any other technique and has the additional advantage of being able to be discontinued in the case of renal or otic damage. Limited personal experience suggests that the failure rate of revision total hip with resistant organisms is significantly lower with intra-articular delivery than with other currently available methods.

Performance and durability of total knee arthroplasty is optimised when bone surfaces are prepared with the knee in neutral varus-valgus alignment in the anteroposterior (AP) plane. For the femur, this means resecting the surface perpendicular to the mechanical axis of the femur, which passes through the center of the femoral head and center of the knee. Because the center of the femoral head is not a reliable landmark during the operation, the distal femoral surface can be resected at 5 degrees valgus to the long axis of the femur using an intramedullary (IM) alignment rod to establish the position of the femur's long axis. The IM rod also provides the landmark for alignment of the femoral component in the flexion-extension position. Tibial alignment is established by cutting the upper surface of the tibia perpendicular to the long axis. An IM rod is not necessary for alignment since the ankle is accessible for reference. An extramedullary (EM) rod easily can span the distance between the centers of the tibial surface at the knee and ankle to establish a reference for upper tibial surface resection via the long axis of the tibia. In cases with femoral deformity or bone disease that prevents use of an IM rod as a landmark for the long axis of the femur, computer-assisted alignment can be helpful to establish the mechanical axis of the femur and to determine the level of resection of the femoral surface to create a plane that is perpendicular to the mechanical axis of the femur and positioned to place the joint surface at the correct level. Whereas this can be done with CT scan or MRI imaging and robotic instrumentation, the cost in time and money is substantial. Rather, plane film radiographs can be used along with intra-operative measurements and hand-held tools that are readily available in the standard total knee instrument set.

Using an AP radiograph taken to include the femoral head and knee: Mark the centers of the femoral head and knee. Draw a line to connect the centerpoints. Mark the high points of the medial and lateral femoral condylar joint surfaces. Draw a line perpendicular to the mechanical axis that crosses the mark on the high point of the most prominent femoral condyle. This line marks the position and alignment of the femoral implant surface. Next, measure the distal thickness of the femoral component and add 10% to account for magnification of the radiograph. Draw a parallel line this distance proximal to the femoral surface line. This is the femoral resection line. Less than the thickness of the implant will be resected from the least prominent condyle. On the low side, measure the thickness of bone to be resected and the distance between the bone surface and distal surface line. Insert a threaded pin into the bone surface with the measured distance protruding from the surface to set this position. Seat the distal femoral cutting guide against the protruding pin and against the surface of the femur on the high side. Resect with the cutting guide fixed perpendicular to the long axis of the femur. This resects the thickness of the implant from the prominent side and resects the prescribed amount from the low side to set the distal cut perpendicular to the mechanical axis of the femur. Draw the AP axis from the center of the intercondylar notch posteriorly to the deepest point of the patellar groove, and use the combined cutting guide to finish the femur. Make the anterior, posterior, and bevel cuts perpendicular to the AP axis. Finally, align the tibial surface, with an IM or EM rod, to resect perpendicular to the long axis of the tibia in the AP plane and sloped 4 degrees posteriorly in the lateral plane. Once the bone surfaces are resected at the proper angle, insert the trials or spacer blocks and finish the arthroplasty with release of tight ligaments.

Infection is still a major problem in implant surgery. Most infections are caused by bacteria that enter the wound at the time of the operation. Although prophylactic antibiotics given intravenously have been shown to be effective if given during the correct time frame, the concentration of local antibiotics in the knee in response to intravenous antibiotics is about 1/3 that achieved in the serum, and the level is transient. The concentration of antibiotics in the joint fluid achieved with antibiotics applied locally during surgery is 1000 times higher, and can be maintained throughout the procedure. High concentration persists in drainage fluid for 24 hours after surgery.

Studies done with use of local antibiotics in spinal implant surgery indicate a major reduction in the rate of infection, and cost analysis shows a remarkable monetary benefit to this effect.

Local antibiotic irrigation during implant surgery is inexpensive, easy, and effective.

Implants without diaphyseal-fixed stems

The femoral component is removed first. Whether the implants are fixed with cement or osteointegration, the principles are the same. The interface between the metal implant and bone or cement is freed using both osteotome and saw. All interfaces are cut loose before the implant is driven off with either a hand-held driver and hammer or slap-hammer. Driving off the femoral component before it has been completely loosened removes excessive amounts of bone or causes major condylar fracture.

The polyethylene component is removed next, and then the tibial component. If the tibial component has no metaphyseal stem, the interfaces are separated directly with osteotome and saw until the tibial component is completely loose. If the tibial component has a metaphyseal stem, it usually requires a direct approach to the stem through a tibial osteotomy to loosen the stem from the cement mantle or bone attachment. If a tibial tubercle osteotomy is used to expose the knee, direct access can be obtained through the osteotomy to expose the attached interfaces. Several cuts with the osteotome will loosen the cement from the stem and allow the tibial component to be lifted from the tibial surface. Special care is taken to ensure that the posterior portion of the tibial surface is completely loosened from the bone before final removal is done. Driving tools and slap-hammers almost never are needed on the tibial component without a diaphyseal stem.

Two big problems exist with the all-polyethylene cemented tibial component—the polyethylene and the cement. The polyethylene is too weak and flexible to bear tibial load, so it deforms and loosens. Isoelastic material has never worked, and it never will. The interface stresses are too high when two flexible structures are poorly bonded and heavily loaded. Critical review of the literature fails to make a convincing case for use of cement in TKA. Many studies demonstrate clinical, mechanical, and biological failure when cement is used for fixation. Work by Ryd et al. has shown that initial migration within the first few months diminished rapidly after the first 6 months with virtually no additional movement for years after. They also found that cemented components do not remain rigidly fixed to bone long-term, but loosen enough to move 0.2 to 2.1 mm at the bone-cement interface with provocative testing. Although bone-ingrowth tibial components migrate slightly more initially than cemented ones do, they stabilise and do not sink progressively. Screw fixation adds rigidity, but does not seem to improve results. Rigidity of initial fixation is the most important feature after alignment to ensure pain-free function after arthroplasty, and can be achieved with press-fit techniques in TKA. Several early reports of bone-ingrowth TKA had inferior results because the tibial component had no stem, peg, or screw fixation, leading to implant migration and loosening. An effective stem has been shown to greatly improve tibial component fixation. The cut upper surface of the prepared tibia has areas that are too weak to withstand the forces that are applied to the surface, and failure in compression is likely unless fixation is augmented. An effective stem also reduces the shear and tensile loads at the bone-prosthesis interface. The effectiveness of compression or compaction of the tibial cancellous bone with an appropriately sized tibial metaphyseal stem has been shown, and probably was a major factor in the long-term success of fixation in our series.

Clinical results of TKA with osteointegration techniques for fixation of the femoral and tibial components in our series are comparable with the best series reported with cemented fixation. Many recent studies show significant advantages of osteointegration over cement fixation in TKA. Fixation of implants with PMMA pressed into cancellous bone eventually loosens, and fixation of a metal component to bone cement also is tenuous in most cases. Cement is disappearing rapidly from use in total hip, ankle, and shoulder arthroplasty, and soon will be replaced with osteointegration technique in the knee. Perhaps the most appealing aspect of bone-ingrowth TKA is bone preservation. The ease of revisability because of good bone was encouraging in the components that wore, loosened, or became infected in the current series of TKA. These knees are functioning as well as knees with primary TKA. Should these knees develop additional problems, progressive destruction of bone is unlikely to occur, even if repeated revision is necessary.

Infected total hip arthroplasty (THA) is catastrophic, but it is treatable with a high degree of success. Two-stage revision with an antibiotic-loaded cement spacer is the most widely accepted method of treatment, and considered by some to be the best method; however, single-stage treatment currently is used widely, and is gaining acceptance. Although antibiotic-loaded cement is considered to be important for antibiotic delivery after surgery, cementless revision is equally successful with one- or two-stage procedures.

Delivery of antibiotics with depot methods, such as cement or bone graft impregnated with antibiotics, is considered to be very effective, but the antibiotic levels rapidly deteriorate after the first three days, leaving the cement itself vulnerable to colonization by resistant organisms. Nephrotoxicity is not common, but it does occur, and necessitates removal of the cement. This can be catastrophic if the implants are fixed with antibiotic-impregnated cement.

Success rates of THA revision for infection can be as high as 98%, but this rate is dependent on the organism. Failure rates of 20% are the norm for resistant organisms such as methicillin-resistant Staphylococcus aureus. The cost of this failure rate is huge. Failure probably is due to the low concentration of antibiotics in the operative site. Antibiotic infusion into the operative site achieves concentrations that are hundreds of times higher than can be achieved with any other technique, and has the additional advantage of being able to be discontinued in the case of renal or otic damage. Limited personal experience suggests that the failure rate of revision total hip with resistant organisms is significantly lower with intra-articular delivery than with other currently available methods.

Total knee arthroplasty causes unresolved pain and swelling in about 10% of patients despite good alignment, ligament balance, and fixation. Metal sensitivity becomes more common in total knee patients as time passes, wear continues to be a clinically relevant issue, loosening increases in frequency with time, and infection continues to plague implant surgery. Ceramic bearing surfaces address all of these issues. New technologies make possible stronger, more flexible ceramic materials, and one ceramic in particular (magnesia-stabilised zirconia) is especially interesting because of its ability to accept a commercially pure titanium porous coating. These materials do not release metal debris or ions, wear is reduced by a factor of three, and biofilm formation is reduced by a factor of three or more when compared with cobalt-chromium.

After clearing regulatory requirements, this new ceramic technology is likely to advance our solutions to many of the most important clinical problems in knee arthroplasty.

Infection is still a major problem in implant surgery. Most infections are caused by bacteria that enter the wound at the time of the operation. Although prophylactic antibiotics given intravenously have been shown to be effective if given during the correct time frame, the concentration of local antibiotics in the knee in response to intravenous antibiotics is about 1/3 that achieved in the serum, and the level is transient. The concentration of antibiotics in the joint fluid achieved with antibiotics applied locally during surgery is 1000 times higher, and can be maintained throughout the procedure. High concentration persists in drainage fluid for 24 hours after surgery.

Studies done with use of local antibiotics in spinal implant surgery indicate a major reduction in the rate of infection, and costs analysis shows a remarkable monetary benefit to this effect.

Local antibiotic irrigation during implant surgery is inexpensive, easy, and effective.

Revision of the total hip femoral component in the presence of significant bone loss requires a variety of implants as well as fixation devices and bone substitute materials.

Rule 1: Fix the implant into the best remaining bone.

A variety of stem shapes and sizes are needed to fill the bone cylinder. Stem modularity is helpful to fashion a good fit, but every taper junction is a liability as a potential source of metal debris and a weak spot in the stem. Rather, fully porous-coated titanium femoral components with a tapered stem design are safe, convenient, and reasonably inexpensive.

Rule 2: Reconstruct the bone to accept a rigidly fixed intramedullary stem.

Cables, strut allograft, plates, and screws are needed to support the remaining bone.

Rule 3: Manage the bone so that it is still viable after the implant is inserted.

As much intraosseous and extraosseous blood supply as possible should be maintained, so broaching rather than extensive reaming is the best choice for maintaining bone viability.

Rarely more exotic procedures such as reduction osteotomy must be done to achieve rigid fixation of implants.

Infection is still a major problem in implant surgery. Most infections are caused by bacteria that enter the wound at the time of the operation. Although prophylactic antibiotics given intravenously have been shown to be effective if given during the correct time frame, the concentration of local antibiotics in the knee in response to intravenous antibiotics is about 1/3 that achieved in the serum, and the level is transient. The concentration of antibiotics in the joint fluid achieved with antibiotics applied locally during surgery is 1000 times higher, and can be maintained throughout the procedure. High concentration persists in drainage fluid for 24 hours after surgery.

Studies done with use of local antibiotics in spinal implant surgery indicate a major reduction in the rate of infection, and costs analysis shows a remarkable monetary benefit to this effect.

Local antibiotic irrigation during implant surgery is inexpensive, easy, and effective.

Loss of the abductor portions of the gluteus medius and gluteus minimus muscles due to total hip arthroplasty (THA) causes severe limp and often instability. To minimise the risk of limp and instability the anterior half of the gluteus maximus was transferred to the greater trochanter and sutured under the vastus lateralis. A separate posterior flap was transferred under the primary flap to substitute for the gluteus minimus and capsule. To ensure tight repair, the flaps were attached and tensioned in abduction.

The technique was performed in 11 patients (11 hips) with complete loss of abductor attachment; the procedure was performed in 9 patients during THA and in 2 later as a secondary procedure. Pre-operatively, all patients had abductor lurch, positive Trendelenburg sign, and no abduction of the hip against gravity. The follow up ranged from 16 to 42 months.

Post-operatively, 9 patients had strong abduction of the hip against gravity, no abductor lurch, and negative Trendelenburg sign. One patient had weak abduction against gravity, negative Trendelenburg sign, and slight abductor lurch. One patient failed to achieve strong abduction, had severe limp after 6 months of protection and physical therapy, and was lost to follow up.

Gluteus maximus transfer can restore abductor function in THA, but it is technically demanding and requires careful, prolonged rehabilitation.

Total knee arthroplasty causes unresolved pain and swelling in about 10% of patients despite good alignment, ligament balance, and fixation. Metal sensitivity becomes more common in total knee patients as time passes, wear continues to be a clinically relevant issue, loosening increases in frequency with time, and infection continues to plague implant surgery. Ceramic bearing surfaces address all of these issues. New technologies make possible stronger, more flexible ceramic materials, and one ceramic in particular (magnesia-stabilised zirconia) is especially interesting because of its ability to accept a commercially pure titanium porous coating. These materials do not release metal debris or ions, wear is reduced by a factor of three, and biofilm formation is reduced by a factor of three or more when compared with cobalt-chromium.

After clearing regulatory requirements, this new ceramic technology is likely to advance our solutions to many of the most important clinical problems in knee arthroplasty.

Infection is one of the most devastating complications following total joint arthroplasty. Treatment is difficult, often requiring multiple surgical procedures, prolonged hospitalisation, and long-term intravenous (IV) antibiotic therapy. Failure rates are high for resistant organisms and mixed-flora infections, and antibiotic-loaded cement spacers deliver antibiotics for only a few days and can harbor resistant bacteria on the surface. We have adopted a direct-exchange method with antibiotics infused directly into the joint using Hickman catheters to achieve extremely high levels of intraarticular (IA) antibiotics for six weeks. Hickman catheters have a fibrous cuff that allows soft-tissue ingrowth and seals the surface of the tube to prevent contamination of the joint by tracking along the catheter. Two catheters are inserted to ensure that at least one will be functional for six weeks.

The safety and efficacy of this protocol was evaluated in patients undergoing primary or revision TKA by measuring joint and serum levels of vancomycin following IV administration (as a prophylactic) and IA administration (as a treatment for infected TKA), and comparing the levels with each method. Therapeutic levels of vancomycin were present in the knee following IV or IA administration, but much higher levels were possible with IA administration (avg. of 6.8 and 9,242 µg/mL). Vancomycin achieved therapeutic levels in the synovial fluid of the knee with IV administration, but clearance from the knee was rapid, suggesting that the synovial fluid concentration may be sub-therapeutic for hours before the next IV dose is given. In contrast, IA delivery of vancomycin resulted in peak levels that were many orders of magnitude higher, and trough levels remained therapeutic for 24 hours in both the joint space and in the serum (minimum trough levels of 8.4 and 4.2 µg/mL, respectively). The elimination constant (half-life) of IA-administered vancomycin was 3.1 hours.

This protocol was used in 18 knees (18 patients) with methicillin-resistant Staphylococcus aureus treated between January 2001 and January 2007 with one-stage revision that included debridement, uncemented revision of total knee components, and IA infusion of 500 mg vancomycin via Hickman catheter once or twice daily for 6 weeks. No IV antibiotics were used after the first 24 hours. Serum vancomycin levels were monitored to maintain levels between 3 and 10 µg/mL. Mean serum vancomycin peak concentration was 6±2 µg/mL and the mean serum vancomycin trough concentration was 3±1 µg/mL at 2 weeks postoperative. Knee synovial fluid peak and trough vancomycin levels were measured in two knees. Synovial fluid peak concentrations were 10,233 µg/mL and 20,167 µg/mL and trough concentrations were 724 µg/mL and 543µg/mL, respectively. Minimum follow-up was 27 months (range, 27–75 months). Mean followup was 62 months, (range, 27–96 months). At 2-year follow-up, mean Knee Society score was 83±9. No radiographic evidence of implant migration has occurred. One knee reinfected with MRSA and was reoperated at 5 months. A necrotic bone segment was found, the knee was debrided and revised, and the antibiotic infusion protocol was readministered. The knee remained free of infection at 42 months postoperatively.

Directly infusing antibiotics into the infected area maintains a high local concentration level while minimising systemic toxicity. This method avoids the use of antibiotic-loaded cement and the potential for growth of antibiotic-resistant strains of bacteria. These findings support single-stage revision in cases treated with cementless revision and IA antibiotics.

Fixation of the femoral component in total hip arthroplasty is a surgical challenge in the best of circumstances. Achieving immediate fixation without breaking the femur is a challenge, even to highly skilled and experienced arthroplasty surgeons. Surgical procedures are available that offer cosmetic benefit or a slightly quicker recovery, but accepting this compromise for fixation should be avoided.

The mechanical environment of the femoral component is challenging. The implant is exposed to offset loading in two planes, which results in substantial bending stress and rotational loads in the frontal plane as well as bending stress and torsional loads in the sagittal plane. The proximal femur is built to transmit load through the surface fibers, not the central cavity, so efforts to change it to a centrally loaded structure are fraught with difficulty. The entire structure should be used. The least reliable material is the cancellous bone in the intertrochanteric metaphysis and the most effective is the cancellous bone of the femoral neck and cortical bone of the upper diaphysis. For best fixation of the femoral component, the cortical bone of the upper metaphysis should be contacted, and the diaphyseal cortical bone actually should be grooved by the femoral stem during insertion.

Approach to the hip is important in fixation of the femoral component. Approaches that require femoral neck resection and use of a short stem are especially treacherous. The posterior approach is attractive because it encourages preservation of the femoral neck, and it provides straight access to the medullary canal of the femur while protecting the abductor muscles.

Static axial load in the extended position is most readily resisted by the femoral component. Distal cortical contact is very important to prevent toggle. Torsional loads generated from offset loading of the femoral head in flexion and with front-to-back acceleration generated loads during rapid gait are the most challenging in securing fixation of the implant. Ideal conditions include preservation of the femoral neck, engagement of a rectangular stem in a rectangular cavity, and mechanical lock into grooves in the diaphyseal cortical bone. If all these conditions are met, femoral component fixation can be achieved every time without damaging the abductor muscle group, and with minimal danger of femoral fracture.

A posterior approach with femoral neck preservation and a rectangular shaped femoral component with diaphyseal engaging stem is safe surgery and good mechanics. The anterior approach with femoral neck sacrifice and round, short stems is unsafe surgery and bad mechanics.

The cornerstone to proper ligament balancing in TKR is correct varus and valgus alignment in flexion and extension. For alignment in the extended position, fixed anatomic landmarks such as the intramedullary canal of the femur and long axis of the tibia are accepted. When the joint surface is resected at an angle of 5 degrees to 7 degrees valgus to the medullary canal of the femur and perpendicular to the long axis of the tibia, the joint surfaces are perpendicular to the mechanical axis of the lower extremity, and roughly parallel to the epicondylar axis. In the flexed position, anatomic landmarks are equally important for varus-valgus alignment. Incorrect varus-valgus alignment in flexion not only malaligns the long axes of the femur and tibia, but also incorrectly positions the patellar groove both in flexion and extension.

Finding suitable landmarks for varus-valgus alignment has led to efforts to use the posterior femoral condyles, epicondylar axis, and anteroposterior (AP) axis of the femur. The posterior femoral condyles provide excellent rotational alignment landmarks if the femoral joint surface has not been worn or otherwise distorted by developmental abnormalities or the arthritic process. However, as with the distal surfaces, the posterior femoral condylar surfaces sometimes are damaged or hypoplastic (more commonly in the valgus than in the varus knee) and cannot serve as reliable anatomic guides for alignment. The epicondylar axis is anatomically inconsistent and in all cases other than revision total knee arthroplasty with severe bone loss, is unreliable for varus-valgus alignment in flexion just as it is in extension. The AP axis, defined by the lateral border of the posterior cruciate ligament posteriorly and the deepest part of the patellar groove anteriorly, is highly consistent, and always lies within the median sagittal plane that bisects the lower extremity, passing through the hip, knee, and ankle. When the articular surfaces are resected perpendicular to the AP axis, they are perpendicular to the AP plane, and the extremity can function normally in this plane throughout the arc of flexion.

The cornerstone to correct ligament balancing is correct varus and valgus alignment in flexion and extension. For alignment in the extended position, fixed anatomic landmarks such as the intramedullary canal of the femur and long axis of the tibia are accepted. When the joint surface is resected at an angle of 5° to 7° valgus to the medullary canal of the femur and perpendicular to the long axis of the tibia, the joint surfaces are perpendicular to the mechanical axis of the lower extremity, and roughly parallel to the epicondylar axis. In the flexed position, anatomic landmarks are equally important for varus-valgus alignment. Incorrect varus-valgus alignment in flexion not only malaligns the long axes of the femur and tibia, but also incorrectly positions the patellar groove both in flexion and extension.

Finding suitable landmarks for varus-valgus alignment has led to efforts to use the posterior femoral condyles, epicondylar axis, and anteroposterior (AP) axis of the femur. The posterior femoral condyles often are not reliable rotational alignment landmarks because the femoral joint surface has been worn or otherwise distorted by developmental abnormalities or the arthritic process. As with the distal surfaces, the posterior femoral condylar surfaces sometimes are damaged or hypoplastic (more commonly in the valgus than in the varus knee) and cannot serve as reliable anatomic guides for alignment. The epicondylar axis is anatomically inconsistent and in all cases other than revision total knee arthroplasty with severe bone loss, is unreliable for varus-valgus alignment in flexion just as it is in extension. The AP axis, defined by the centre of the intercondylar notch posteriorly and the deepest part of the patellar groove anteriorly, is highly consistent, and always lies within the median sagittal plane that bisects the lower extremity, passing through the hip, knee, and ankle. When the articular surfaces are resected perpendicular to the AP axis, they are perpendicular to the AP plane, and the extremity can function normally in this plane throughout the arc of flexion. Once the knee is set up in correct alignment, ligament balancing can be done with simple procedures based on basic anatomy. Anterior structures tighten in flexion, and posterior structures tighten in extension. Release of tight structures in a controlled fashion completes the aligned and balanced knee.

Infection is one of the most devastating complications following total joint arthroplasty. Treatment is difficult, often requiring multiple surgical procedures, prolonged hospitalisation, and long-term intravenous (IV) antibiotic therapy. Failure rates are high for resistant organisms and mixed-flora infections, and antibiotic-loaded cement spacers deliver antibiotics for only a few days and can harbor resistant bacteria on the surface. We have adopted a direct-exchange method with antibiotics infused directly into the joint using Hickman catheters to achieve extremely high levels of intra-articular (IA) antibiotics for six weeks. Hickman catheters have a fibrous cuff that allows soft-tissue ingrowth and seals the surface of the tube to prevent contamination of the joint by tracking along the catheter. Two catheters are inserted to ensure that at least one will be functional for six weeks.

The safety and efficacy of this protocol was evaluated in patients undergoing primary or revision TKA by measuring joint and serum levels of vancomycin following IV administration (as a prophylactic) and IA administration (as a treatment for infected TKA), and comparing the levels with each method. Therapeutic levels of vancomycin were present in the knee following IV or IA administration, but much higher levels were possible with IA administration. Vancomycin achieved therapeutic levels in the synovial fluid of the knee with IV administration, but clearance from the knee was rapid, suggesting that the synovial fluid concentration may be sub-therapeutic for hours before the next IV dose is given. In contrast, IA delivery of vancomycin resulted in peak levels that were many orders of magnitude higher, and trough levels remained therapeutic for 24 hours in both the joint space and in the serum (trough levels of 8.4 and 4.2 μg/mL, respectively). The elimination constant (half-life) of IA-administered vancomycin was determined to be 3.06 hours.

This protocol was used in 18 knees (18 patients) with methicillin-resistant Staphylococcus aureus treated between January 2001 and January 2007 with one-stage revision that included debridement, uncemented revision of total knee components, and IA infusion of 500 mg vancomycin via Hickman catheter once or twice daily for 6 weeks. No IV antibiotics were used after the first 24 hours. Serum vancomycin levels were monitored to maintain levels between 3 and 10 μg/mL. Mean serum vancomycin peak concentration was 6±2 μg/mL and the mean serum vancomycin trough concentration was 3±1 μg/mL at 2 weeks post-operative. Knee synovial fluid peak and trough vancomycin levels were measured in two knees. Synovial fluid peak concentrations were 10,233 μg/mL and 20,167 μg/mL and trough concentrations were 724 μg/mL and 543μg/mL, respectively. Minimum follow-up was 27 months (range, 27–75 months). Mean follow-up was 62 months, (range, 27–96 months). At 2-year follow-up, mean Knee Society score was 83±9. No radiographic evidence of implant migration has occurred. One knee reinfected with MRSA and was reoperated at 5 months. A necrotic bone segment was found, the knee was debrided and revised, and the antibiotic infusion protocol was readministered. The knee remained free of infection at 42 months post-operatively.

Directly infusing antibiotics into the infected area maintains a high local concentration level while minimising systemic toxicity. This method avoids the use of antibiotic-loaded cement and the potential for growth of antibiotic-resistant strains of bacteria. These findings support single-stage revision in cases treated with cementless revision and IA antibiotics.

Loss of the quadriceps tendon, patella, and patellar tendon leaves a major anterior defect that is difficult to close and compromises knee extension strength. Gastrocnemius muscle transfer does not sufficiently cover such major defects. A new surgical procedure is described that transfers the vastus medialis or the vastus lateralis and their tibial attachments, or both muscles and their distal expansions to cover major deficiencies in the anterior knee.

Nine cadaver knee specimens were dissected to ensure that the blood and nerve supply of the muscles would remain intact in the flap transfer. Eight clinical cases were done between 2005 and 2009. Four knees had vastus medialis transfer, two knees required vastus medialis and vastus lateralis transfer, two knees required transfer of the vastus medialis and medial gastrocnemius muscles, and two knees required transfer of both the medial gastrocnemius and medial half of the soleus muscle to close the knee and to secure distal attachment of the vastus transfer.

All patients achieved closure of the knee joint without synovial leaks by 10 days post-operatively. Mean flexion contracture at last follow-up was 3° (range, 0–7°). Mean extension lag was 22° (range, 5–65°). Extension lag was less in those cases that included gastrocnemius or soleus muscle transfer. None of the flaps developed necrosis.

The vastus medialis and vastus lateralis muscles are effective as muscle transfers about the knee.

Introduction

Resistant organisms are difficult to eradicate in infected total knee arthroplasty, and treatment of methicillin-resistant Staphylococcus aureus (MRSA) is especially challenging. Whereas most surgeons use antibiotic-impregnated cement during revision to treat infection, the delivery of the drug in adequate doses is limited in penetration and duration. This study presents the 2- to 8-year prospective results of one-stage revision and intraarticular antibiotic infusion protocol used to treat MRSA.

Introduction

Recent clinical studies found no apparent reduction in wear using yttria-stabilized zirconia (Y-TZP) instead of cobalt chromium alloy femoral heads bearing against cross-linked UHMWPE. The purpose of this study was to compare the surface topography of retrieved Y-TZP and magnesia-stabilized zirconia (Mg-PSZ) femoral heads and evaluate the influence of time in vivo. The increase in average roughness (Ra, Sa) of Y-TZP due to phase transformation in vivo is well documented, while Mg-PSZ does not roughen or undergo phase transformation in vivo. However, the effects of phase transformation on the polarity (skewness, Ssk) of the surface of retrieved ZrO₂ heads has not been reported. We hypothesized that phase transformation associated with the increased roughness of Y-TZP would influence skewness and thus the wear potential of the heads.

Instrumentation is advocated for implantation of a unicompartmental total knee replacement because:

Intramedullary instrumentation in the femur and tibia provides highly reliable alignment of the implants and extremities.

Resection of the peripheral rim of the tibia doesn’t compromise primary fixation or later revision.

Results of a laboratory study published in 1992 revealed that intramedullary instrumentation accurately and reliably restored the knee to correct alignment and kinematics. In five adult human cadaveric lower extremities, anteroposterior radiographs were used to evaluate valgus angle and position of the center of the knee relative to the mechanical axis of the lower extremity. Intramedullary instrumentation returned the knee to normal alignment in all cases. The greatest valgus angle change was 3°, and the position of the center of the knee relative to the mechanical axis was not significantly altered. In five fresh-frozen adult knee specimens, kinematics were evaluated and found to follow the predicted pattern of normal stability in extension. Slightly less varusvalgus laxity was seen at 30°, 45°, and 60°.

A review of results obtained with unicompartmental total knee replacement reveals that excellent alignment and long-term fixation have been achieved and maintained over the past 10 years.

Ligament balancing is an integral part of total knee arthroplasty and is highly dependent on correct alignment of the knee in flexion and extension. The technique proposed begins with correct alignment of the articular surfaces of the femur both in flexion and extension so that the joint surfaces are perpendicular to the anteroposterior plane of the lower extremity. This is done separately on the femur and tibia in extension and flexion, irrespective of ligament contracture or stretching. Once alignment, sizing, and positioning of the implants are correct, the ligaments can be assessed. Only ligaments that are tight need to be released, thus minimising trauma and maximising stability of the knee.

Varus Knee: Knees that are tight medially only in flexion should first have the anterior portion of the medial collateral ligament (MCL) released, leaving the posterior oblique portion intact to provide stability in flexion and extension. Knees that are tight only in extension first should have release of the posterior oblique fibres of the MCL, and release of the posterior capsule if medial contracture persists in extension. This leaves the anterior portion of the MCL intact to stabilise the knee. Major destabilisation of the knee may occur if the posterior cruciate ligament (PCL) is released after full release of the MCL, release of posterior oblique fibres of the MCL, and posterior capsule release.

Valgus Knee: Knees that are tight laterally in flexion and extension first have release of the lateral collateral ligament (LCL) and popliteus tendon for tightness in flexion, then the iliotibial (IT) band and the lateral posterior capsule for any tightness in extension. For knees that are tight laterally only in extension, only the IT band and the lateral posterior capsule should be released. For knees that are tight laterally only in flexion, the LCL is released first, then the popliteus tendon. If all static lateral stability structures require release, the biceps femoris muscle, gastrocnemius muscle, and deep fascia can support the knee until capsular healing occurs.

Block allografts traditionally have been used for massive bone deficiencies, but their complication rates are high, and the destructive effects of allograft rejection can limit their long-term success. Large segments of allograft also heal slowly, are never replaced by new bone, and weaken as the ossification and vascularisation front proceeds. In contrast, morselised allograft has proven structurally reliable for both small and large defects while supporting new bone formation. Morsels that are 1 cm in diameter maintain their integrity long enough to act as a substrate for new bone formation. Morsels less than 0.5 to 1 cm in diameter tend to be resorbed while those larger than 1 cm incorporate slowly, if ever, and tend to collapse.

Rejection can be a major problem with allograft because marrow is immunogenic. However, marrow elements can be thoroughly removed from morselised allograft to prevent the inflammatory response and loss of graft and to capitalise on the osteoconductive potential of the demineralised bone and autologous marrow. The allograft acts as scaffolding for new bone growth, and although it is not osteoinductive, demineralised bone (mildly osteoinductive) and bone marrow aspirate (highly osteoinductive) can be added to the allograft to enhance bone formation. The surrounding bone structure supplies most of the osteoinductive activity because metaphyseal bone has a rich blood supply and maintains the capacity to heal even after repeated failed arthroplasty.

Grafting preparation and placement: Fresh-frozen cancellous allograft in morsels measuring 0.5 to 1 cm in diameter is soaked for five to ten minutes in normal saline solution that contains polymyxin 500,000 units, bacitracin 50,000 units, and cephazolin 1 g/l. The fluid is removed and 10 cm3 of powdered demineralised cancellous bone is added to each 30 cm3 of the cancellous morsels. Bone fragments and diaphyseal reamings are added to improve the osteoinductive potential. This mixture is packed into the bone defects, then the implants are impacted so as to seat on the remnant of viable bone while compacting the morselised bone graft.