Fifteen-year survivorship studies demonstrate that total knee replacement have excellent survivorship, with reports of 85 to 97%. However, excellent survivorship does not equate to excellent patient reported outcomes. Noble et al. reported that 14% of their patients were dissatisfied with their outcome with more than half expressing problems with routine activities of daily living. There is also a difference in the patient's subjective assessment of outcome and the surgeon's objective assessment. Dickstein et al. reported that a third of total knee patients were dissatisfied, even though the surgeons felt that their results were excellent. Most of the patients who report lower outcome scores due so because their expectations are not being fulfilled by the total knee replacement surgery.

Perhaps this dissatisfaction is a result of subtle soft tissue imbalance that we have difficulty in assessing intraoperatively and postoperatively. Soft tissue balancing techniques still rely on subjective feel for appropriate ligamentous tension by the surgeon. Surgical experience and case volume play a major role in each surgeon's relative skill in balancing the knee properly.

New technology of “smart trials” with embedded microelectronics and accelerometers, used in the knee with the medial retinaculum closed, can provide dynamic, intra-operative feedback regarding knee quantitative compartment pressures and component tracking. After all bone cuts are made using the surgeon's preferred techniques, trial components with the sensored tibial trial are inserted and the knee is taken through a passive range of motion. After visualizing the resultant compartment pressures and tracking data on a graphical interface, the surgeon can decide whether to perform a soft tissue balance or a minor bone recuts. If soft tissue balancing is chosen, pressure data can indicate where to perform the release and allow the surgeon to assess the pressure changes as titrated soft tissue releases are performed.

A multi-center study using smart trials has demonstrated dramatically better outcomes out to three years.

Total knee arthroplasty (TKA) is currently one of the most common elective surgical procedures in the United States. The increase in the proportion of younger patients in receipt of surgery, in concert with a dramatic rise in the incidence of obesity, has contributed to the on-going, exponential increase in the number of arthroplasties performed annually. Despite materials advances for implants, the U.S. revision burden has remained static for the last decade. According to the 2013 CMS MEDPAR file the typical CMS reimbursement falls far short of costs incurred by the hospital, resulting in an average net loss of revenue of $9,539; and over 90% of hospitals lose money for every revision case performed. Today, approximately 5% of all primaries performed will result in an early revision (< 3 years). In order to understand ways with which to mitigate the incidence of early revision due to mechanical complications, a multicentric group of sensor-assisted patients was follow-up out to 3 years.

In this study, 278 sensor-assisted patients were followed out to 3 years. The intraoperative devices used in this study contain microsensors and a processing unit. Kinetic and center of load location data are projected, in real-time, to a screen. Because of the wireless nature of the intraoperative sensors, the patella can be reduced, and kinematic data can be evaluated through the range of motion. For each patient, the soft-tissue envelope was balanced to within a mediolateral differential of 15 lbf., through the ROM, as per the suggestion of previously reported literature. The average patient profile indicates: age = 69.7 years, BMI = 30.4, gender distribution = 36% male/64% female. Any adverse event within the 3-year follow-up interval was captured.

By 3 years, 1 patient in this population has required revision surgeon due to mechanical complicatons. Overall adverse events included: pain in hip (3), pain in contralateral knee (2), wound drainage (3), DVT (1), death (1), stiffness in operative knee (2), infection (3), global pain (2), back pain (2).

Based on the average reported number of early revisions that occur in the U.S. (5% of primaries), it was anticipated for this patient group to require approximately 13 revisions by the 3-year follow-up interval. Using 2013 CMS MEDPAR data, these 13 revisions would have resulted in $124,007 cost-to-hospital. However, only 1 revision (0.4%) was observered, therefore $114,468 in additional costs were spared for the aggregate of participating hospitals. This data suggests that the incorporation of kinetic sensors in TKA may assist the surgeon in achieving soft-tissue balance and thereby avoiding adverse mechanical complications that require surgical intervention.

Total knee arthroplasty (TKA) patients are consistently reported to be less satisfied than total hip arthroplasty (THA) patients. A patient's perception of success of his/her own total knee is dictated by their levels of post-operative pain and function, and many return to follow-up visits with inexplicable pain and stiffness that contradict favorable radiographic results. Several of these chief complaints that contribute to dissatisfaction are associated with soft-tissue imbalance. Therefore, in an effort to thoroughly understand the post-operative impact of soft-tissue balance on satisfaction, a multicenter study was conducted to evaluate the satisfaction outcomes of quantifiably balanced patients.

In this study, 102 sensor-assisted patients were followed out to 3 years. The intraoperative devices used in this study project kinetic loading (lbf.) and center of load location data, in real-time, to a screen. Because of the wireless nature of the intraoperative sensors, the patella can be reduced, and kinematic data can be evaluated through the range of motion. The target balance window that was used in this study has been previously reported in literature and includes: 1) a mediolateral differential of 15 lbf., through the ROM, and 2) Sagittal plane stability as determined by a posterior drawer analysis. A robust, face-validated satisfaction survey was administered at 3-year follow-up and included 7 questions with answers on a 5-point Likert scale.

At 3 years, post-operatively, 97.2% of this patient group reported being “satisfied” to “very satisfied” with their procedure, in comparison to the 81% average TKA satisfaction reported in literature (df = 11). The comparative literature included annual satisfaction intervals from 1 to 5 years (n = 33,775) which is comparable to the interval reported in this patient group. The sensor-assisted patient group exhibited a 16% increase in the proportion of satisfaction over what is currently reported in the comparative literature (p = 0.001).

Despite the success rate of TKA, unfavorable patient-reported satisfaction continues to present a problem for operative recipients and surgeons. Because satisfaction is dependent upon several variables – including pain, function, and activity levels – the satisfaction survey used in this study represents a more accurate account of patient perception than many traditional surveys. It was shown that sensor-balanced TKA patients exhibited a 16% increase in the proportion of those reporting being “satisfied” to “very satisfied”, over the average satisfaction reported in literature. Allowing the surgeon to quantitatively balance the soft-tissue envelope, dynamically, has continued to a significant decrease in the proportion of dissatisfaction.

Use of a short femoral stem for total hip replacement is not a new idea. Morrey first reported on the results of the Mayo Conservative Stem (Zimmer) in 1989. A short femoral stem can also be soft tissue conserving by allowing for a curved insertion track avoiding the abductor attachments. These concepts have made use of a short femoral stem attractive for use in less invasive total hip surgical approaches. The goal of a short femoral stem is to be bone conserving and provide preferential stress transfer to the proximal femur. This may make the short stem desirable for most total hips regardless of surgical approach.

The proximal femur has considerable variability in shape, canal size, and offset. This makes a single geometry short stem potentially unstable in some anatomic variants without having a longer stem to resist varus bending moments or obtain diaphyseal stability. The Fitmore Stem (Zimmer) has addressed these anatomic variants by having three different shaped stems with different offsets.

The presenter has implanted over 1,000 short stems, using them for both standard and less invasive surgical approaches. There is a learning curve when using these short stems. Initially some stems were undersized and inserted in some varus. Thirty-four percent of the first 100 short stems inserted had measurable subsidence. However, all stabilised with no further subsidence. Rarely, subsidence now occurs with attention to preoperative planning for size and improved surgical technique. The surgical technique for insertion of this short stem is different from a conventional length total hip stem. The canal is broached along a curved track with a posterior and lateral moment applied to the broach. Use of the largest size broach that doesn't sink with moderate impaction forces is necessary to maximally contact the medial and lateral proximal cortices to lessen stem subsidence.

Four of over 1,000 stems have been revised for postoperative peri-prosthetic fracture after falls. Two stems were revised for late infection but were not clinically loose. No stems have been revised for aseptic loosening.

Fifteen-year survivorship studies demonstrate that total knee replacements have excellent survivorship, with reports of 85 to 97%. However, excellent survivorship does not equate to excellent patient reported outcomes. Noble et al reported that 14% of their patients were dissatisfied with their outcome with more than half expressing problems with routine activities of daily living. There is also a difference in the patient's subjective assessment of outcome and the surgeon's objective assessment. Dickstein et al reported that a third of total knee patients were dissatisfied, even though the surgeons felt that their results were excellent. Most of the patients who report lower outcome scores due so because their expectations are not being fulfilled by the total knee replacement surgery.

Perhaps this dissatisfaction is a result of subtle soft tissue imbalance that we have difficulty in assessing intraoperatively and postoperatively. Soft tissue balancing techniques still rely on subjective feel for appropriate ligamentous tension by the surgeon. Surgical experience and case volume play a major role in each surgeon's relative skill in balancing the knee properly.

New technology of “smart trials” with embedded microelectronics and accelerometers, used in the knee with the medial retinaculum closed, can provide dynamic, intraoperative feedback regarding knee and component alignment along with quantitative compartment pressures and component tracking. After all bone cuts are made using the surgeon's preferred techniques, trial components with the sensored tibial trial are inserted and the knee is taken through a passive range of motion. After visualizing the resultant compartment pressures and tracking data on a graphical interface, the surgeon can decide whether to perform a soft tissue balance or minor bone recuts. If soft tissue balancing is performed, the surgeon can assess the pressure changes as titrated soft tissue releases are performed.

A multicenter study using smart trials has demonstrated dramatically better outcomes at six months and one year.

A study by Harris reported a 40% incidence of femoral and acetabular dysplasia in routine idiopathic osteoarthritic patients. Due to pediatric screening in the United States, today most cases are minimally dysplastic requiring little modification from standard total hip surgical techniques. As the degree of dysplasia increases numerous anatomic distortions are present. These include high hip centers, relative acetabular retroversion, soft bone in the true acetabular area, increased femoral neck anteversion and relative posteriorly positioned greater trochanters, metaphyseal/diaphyseal size mismatch, and small femoral canals. Total hip replacements for these patients have known higher risks for earlier loosening, dislocation, and neurovascular injuries.

Use of medialised small uncemented acetabular components placed in the anatomic acetabulum, modular uncemented femoral components, and diaphyseal rotational and shortening osteotomies has become a preferred method of treatment. In 2007, we reported our experience with this technique in 23 cases utilizing a subtrochanteric femoral osteotomy with a 5–14 year follow-up. There were 4 Crowe I, 3 Crowe II, 5 Crowe III, and 11 Crowe IV cases. All osteotomies healed. There were no femoral components revised. In most cases, small (mean 46 mm) hemispherical components were used without bulk allografts in all but 5 early cases. One acetabular component was revised for a recalled component. 3 acetabular liners were revised for wear (2 were very small cups with 4.7 mm poly thickness). Four patients sustained dislocations, with 2 closed and 2 open reductions. There were no neurovascular injuries.

The Crowe classification is commonly used to preoperatively classify the degree of dysplasia. However, there are large variations in these anatomic distortions within each class, so it is difficult to preoperatively plan the acetabular component size needed and if one will need to do shortening and/or rotational osteotomy. So the surgeon needs to be prepared for these cases with smaller acetabular components and be prepared to perform a femoral osteotomy.

Total knee replacements (TKRs) are being more commonly performed in active younger and obese patients. Fifteen year survivorship studies demonstrate that cemented total knee replacements have excellent survivorship, with reports of 85% to 97%. However, inferior survivorship occurs in younger patients and obese patients who would be expected to place increased stress on the bone cement interfaces. Cementless fixation for total knee replacement has not gained widespread utilization due to the plethora of poor results reported in early series. These poor results do not reflect that cementless fixation is not obtainable, since an almost universal acceptance of cementless fixation for total hip replacement has shown. A Cochrane database study of total knees with roentgen stereophotogrammetric analysis (RSA) demonstrated that the risk of future aseptic loosening should be 50% less with cementless fixation. The poor initial results with cementless total knee replacement have occurred due to poor implant designs such as cobalt chrome porous interfaces, poor initial tibial component fixation, lack of continuous porous coating, poor polyethylene, and use of metal-backed patellae.

I have used cementless fixation for total knee replacements for young, active, and heavy patients since 1986 when durability over 20 years is desirable. My series of over 1,000 cementless TKRs represents about 20% of the total knees I have performed from 1986 to 2015. I have seen failures in my series due to the initial use of metal-backed patellae with thin polyethylene and use of screws and femoral and tibial components which provide access to the metaphyseal bone for polyethylene wear debris. Overall failures were still significantly low due to the use of highly porous titanium surfaces on the tibial and femoral components. Isolated aseptic loosening only occurred on one tibial component in my entire series. With the advent of utilizing implants with continuous porous surfaces and highly cross-linked polyethylene, and elimination of use of metal-backed patellae and tibial screws, I have only had one revision due to aseptic loosening or osteolysis in the last 760 cases performed since 2002.

Almost 50% of total knees are now performed on patients under the age of 65. A 55-year-old patient has a 30-year life expectancy. Modern total knee replacement design has made biological fixation predictable for young and heavy patients. Because it is a biological interface, it should respond better than cement to the increased stresses that will be applied over many years by our younger, more active and heavier total knee population.

Fifteen-year survivorship studies demonstrate that total knee replacements have excellent survivorship, with reports of 85% to 97%. However, excellent survivorship does not equate to excellent patient reported outcomes. Noble et al reported that 14% of their patients were dissatisfied with their outcome with more than half expressing problems with routine activities of daily living. There is also a difference in the patient's subjective assessment of outcome and the surgeon's objective assessment. Dickstein et al reported that a third of total knee patients were dissatisfied, even though the surgeons felt that their results were excellent. Most of the patients who report lower outcome scores due so because their expectations are not being fulfilled by the total knee replacement surgery.

Perhaps this dissatisfaction is a result of subtle soft tissue imbalance that we have difficulty in assessing intra-operatively and post-operatively. Soft tissue balancing techniques still rely on subjective feel for appropriate ligamentous tension by the surgeon. Surgical experience and case volume play a major role in each surgeon's relative skill in balancing the knee properly.

New technology of “smart trials” with embedded microelectronics and accelerometers, used in the knee with the medial retinaculum closed, can provide dynamic, intra-operative feedback regarding knee quantitative compartment pressures and component tracking. After all bone cuts are made using the surgeon's preferred techniques, trial components with the sensored tibial trial are inserted and the knee is taken through a passive range of motion. After visualizing the resultant compartment pressures and tracking data on a graphical interface, the surgeon can decide whether to perform a soft tissue balance or minor bone recuts. If soft tissue balancing is chosen, pressure data can indicate where to perform the release and allow the surgeon to assess the pressure changes as titrated soft tissue releases are performed.

A multi-center study using smart trials has demonstrated dramatically better outcomes at six months and one year.

Use of a short femoral stem for total hip replacement is not a new idea. Morrey first reported on the results of the Mayo Conservative Stem (Zimmer) in 1989. A short femoral stem can also be soft tissue conserving by allowing for a curved insertion track avoiding the abductor attachments. These concepts have made use of a short femoral stem attractive for use in less invasive total hip surgical approaches. The goal of a short femoral stem is to be bone conserving and provide preferential stress transfer to the proximal femur. This may make the short stem desirable for most total hips regardless of surgical approach.

The proximal femur has considerable variability in shape, canal size, and offset. This makes a single geometry short stem potentially unstable in some anatomic variants without having a longer stem to resist varus bending moments or obtain diaphyseal stability. The Fitmore Stem (Zimmer) has addressed these anatomic variants by having three different shaped stems with different offsets.

The presenter has implanted over 1,000 short stems, using them for both standard and less invasive surgical approaches, and in all bone types. There is a learning curve when using these short stems. Initially some stems were undersized and inserted in some varus. Thirty-four percent of the first 100 short stems inserted had measurable subsidence. However, all stabilised with no further subsidence. Rarely, subsidence now occurs with attention to pre-operative planning for size and improved surgical technique. The surgical technique for insertion of this short stem is different from a conventional length total hip stem. The canal is broached along a curved track with a posterior and lateral moment applied to the broach. Use of the largest size broach that doesn't sink with moderate impaction forces is necessary to maximally contact the medial and lateral proximal cortices to lessen stem subsidence.

Four of over 1,000 stems have been revised for post-operative peri-prosthetic fracture after falls. Two stems were revised for late infection but were not clinically loose. No stems have been revised for aseptic loosening.

Introduction

Preoperative templating of femoral and tibial components can assist in choosing the appropriate implant size prior to TKA. While weight bearing long limb roentograms have been shown to provide benefit to the surgeon in assessing alignment, disease state, and previous pathology or trauma, their accuracy in size prediction is continually debated due to scaling factors and rotated views. Further, they represent a static time point, accounting for boney anatomy only. A perceived benefit of robotic-assisted surgery is the ability to pre-operatively select component sizes with greater accuracy based on 3D information, however, to allow for flexibility in refining based on additional data only available at the time of surgery.

Introduction

Total knee arthroplasty (TKA) using conventional instrumentation has been shown to be a safe and effective way of treating end stage osteoarthritis by restoring function and alleviating pain. As robotic technology is developed to assist surgeons with intra-operative decision making such as joint balancing and component positioning, the safety of these advancements must be established. Furthermore, functional recovery and clinical outcomes should achieve comparable results to the gold standard of conventional instrumentation TKA.

Introduction

Total knee arthroplasty (TKA) is a well established treatment option for patients with end stage osteoarthritis. Conventional TKA with manual instruments has been shown to be a cost effective and time efficient surgery. While robotic-assisted operative systems have been shown to have benefits in surgical accuracy, they have also been reported to have longer surgical times. The purpose of this work was to determine surgical time and learning curve for a novel robotic-assisted TKA platform.

The goals of any rehabilitation protocol should be to control pain, improve ambulation, maximise range of motion, develop muscle strength, and provide emotional support. Over 85% of TKA patients will recover knee function regardless of which rehabilitation protocol is adopted but the process can be facilitated by proper pain control, physical therapy, and emotional support. The remaining 15% of patients will have difficulty obtaining proper knee function secondary to significant pain, limited pre-operative motion, and/or the development of arthrofibrosis. This subset will require a special, individualised rehabilitation program, which may involve prolonged oral analgesia, continued physical therapy, more diagnostic studies and occasionally manipulation. Controlling pain is the mainstay of any treatment plan. The program described herein has been used at Ranawat Orthopaedics over the last 10 years in more than 2000 TKAs.

Several methods of treatment are available in the revision of loose acetabular components associated with significant bone loss. Jumbo cups are the preferred treatment for large acetabular defects with segmental and cavitary defects. By definition, a jumbo cup has a minimum diameter of 62 mm in women, 66 mm in men, or is greater than 10 mm larger than the normal contralateral acetabulum. They are easier to use and less expensive than cages, bulk supporting allografts, or custom cups. Proper technique is for bone to be moved, not removed. The acetabulum is reamed larger to gain more host-bone surface area. The acetabulum should then accommodate the large shell and maximise the shell host-bone contact for long-term biological fixation. The preferred shell is one with high porosity to maximise the potential area for bone ingrowth when less bone contact is present. At least 50% host-bone to shell contact is ideal but not mandatory. The larger surface area of a jumbo cup provides more opportunity for bone ingrowth. Therefore having an initially stable cup is more important than the amount of host-bone contact. Jumbo cups are only contraindicated in acetabulae that lack the superior lateral acetabulum and the posterior column. In that situation, fortunately uncommon, a cup/ cage reconstruction is used.

We reported a retrospective review of 690 acetabular revisions performed from 1986–2005. Jumbo cups were used in 196 (28%) of all the acetabular revisions and greater than 95% of the cases with large defects. This is the largest series or revisions with jumbo cups reported. Significant bony deficiencies were present; 68% were Paprosky type II and 25% were Paprosky type III. The average follow-up for the jumbo cups was ten years. Five revisions and two resection arthroplasties were performed for failure. The probability of survival of the jumbo cups was 98% at four years and 96% at 16 years.

Porous jumbo cup acetabular revision with supplemental screw fixation provides good to excellent intermediate- and long-term outcomes.

Preoperative planning in revision total knee replacement is important to simplify the surgery for the implant representative, operating room personnel and the surgeon. In revision knee arthroplasty, many implant options can be considered. This includes cemented and cementless primary and revision tibial and femoral components, with posterior cruciate retention or resection, and either with no constraint, varus/valgus constraint, or with rotating hinge bearings. One may also need femoral and tibial spacers, metaphyseal augments, or bulk allograft. It is important to preoperatively determine which of these implants you may need. If you schedule a revision total knee and ask the implant representative to “bring everything you've got, just in case,” they will have to bring a delivery van full of instruments and implants.

Ideally, the least constraint needed should be used. This requires determination of the status of the collateral ligaments preoperatively. If there is instability present, use physical examination with confirmation from radiographs. Predict the constraint needed and have the next level as a back-up. Substitution for the posterior cruciate ligament is usually needed for most revisions.

Intraoperative determination of the joint line position is difficult due to lack of anatomic landmarks. Having intact collateral ligaments with an appropriate anatomic joint line position will usually negates the need for increased implant constraint. Radiographically, one can determine the appropriate joint line position relative to the existing femoral component to simplify the surgery.

Preoperative review of radiographs should determine the amount and location of bone loss. This will help determine if having cementless and/or primary components available can be eliminated. Larger defects may warrant having metallic augments or bulk graft present. Determine if bony deficiencies will mandate use of stems. Most revision knee implants can be conservatively cemented with diaphyseal engaging press-fit stems.

Occasionally, one may not need to revise all components, so the surgeon needs to be familiar with the implants they are revising. Consider having some or all compatible components available.

Excellent preoperative planning will minimises the need to bring in an excessive number of instruments and implants. It will help assure that the patient has a stable revision knee and simplify the surgery for all participants.

The mean age of patients with osteonecrosis reported in series in our literature is 38 to 53. Thus, performing a total hip replacement on a patient who would need a procedure to last 40–45 years is a concern. Patients with osteonecrosis of the hip require some type of surgical treatment. Without treatment, a large majority of femoral heads in patients even with Ficat stage I osteonecrosis will collapse or become symptomatic. A common scenario is a patient who first presents to the orthopaedic surgeon with severe arthritis secondary to osteonecrosis in one hip and a normal appearing radiograph on the asymptomatic contralateral side. Performing a total hip on the severe arthritic hip is usually not debated. A MRI will commonly show Ficat stage I osteonecrosis on the asymptomatic contralateral hip. Some method of core decompression is a reasonable choice if it is non-steroid induced, small more medially positioned lesion, but not for other Ficat stage 1 lesions or those with more advanced stages. The problem is convincing the patient to have anything done when they are asymptomatic. Because results with total hip replacement for patients with osteonecrosis of the hip have significantly improved, most patients with a symptomatic hip prefer arthroplasty as treatment. Arthroplasty has become the predominant surgical treatment for osteonecrosis of the hip in the United States. 88% of procedures performed on 6,400 patients with osteonecrosis in 2008 reported in the Nationwide Inpatient Sample Database of the hip were total hip replacements. From 16 years earlier, the number of procedures performed had almost doubled and the percentage use of arthroplasty as the performed treatment had increased by 13%. I expect both numbers will continue to increase.

Fifteen-year survivorship studies demonstrate that total knee replacement have excellent survivorship, with reports of 85 to 97%. However, excellent survivorship does not equate to excellent patient reported outcomes. Noble et al reported that 14% of their patients were dissatisfied with their outcome with more than half expressing problems with routine activities of daily living. There is also a difference in the patient's subjective assessment of outcome and the surgeon's objective assessment. Dickstein et al reported that a third of total knee patients were dissatisfied, even though the surgeons felt that their results were excellent. Most of the patients who report lower outcome scores due so because their expectations are not being fulfilled by the total knee replacement surgery.

Perhaps this dissatisfaction is a result of subtle soft tissue imbalance that we have difficulty in assessing intraoperatively and postoperatively. Soft tissue balancing techniques still rely on subjective feel for appropriate ligamentous tension by the surgeon. Surgical experience and case volume play a major role in each surgeon's relative skill in balancing the knee properly.

New technology of “smart trials” with embedded microelectronics and accelerometers, used in the knee with the medial retinaculum closed, can provide dynamic, intraoperative feedback regarding knee and component alignment along with quantitative compartment pressures and component tracking. After visualising the resultant data on a graphical interface, the surgeon can decide whether to perform a soft tissue balance or redo the bone cuts. If soft tissue balancing is performed, the surgeon can assess the pressures effect of sequential soft tissue releases performed to balance the knee.

A multi-center study using smart trials has demonstrated dramatically better outcomes at six months and one year.

Pre-operative planning in revision total knee replacement is important to simplify the surgery for the implant representative, operating room personnel and the surgeon. In revision knee arthroplasty, many implant options can be considered. This includes cemented and cementless primary and revision tibial and femoral components, with posterior cruciate retention or resection, and either with no constraint, varus/valgus constraint, or with rotating hinge bearings. One may also need femoral and tibial spacers, metaphyseal augments, or bulk allograft. It is important to pre-operatively determine which of these implants you may need. If you schedule a revision total knee and ask the implant representative to “bring everything you've got, just in case,” they will have to bring a delivery van full of instruments and implants.

Ideally, the least constraint needed should be used. This requires determination of the status of the collateral ligaments pre-operatively. If there is instability present, use physical examination with confirmation from radiographs. Predict the constraint needed and have the next level as a back-up. Substitution for the posterior cruciate ligament is usually needed for most revisions.

Intra-operative determination of the joint line position is difficult due to lack of anatomic landmarks. Having intact collateral ligaments with an appropriate anatomic joint line position will usually negate the need for increased implant constraint. Radiographically, one can determine the appropriate joint line position relative to the existing femoral component to simplify the surgery.

Pre-operative review of radiographs should determine the amount and location of bone loss. This will help determine if having cementless and/or primary components available can be eliminated. Larger defects may warrant having metallic augments or bulk graft present. Determine if bony deficiencies will mandate use of stems. Most revision knee implants can be conservatively cemented with diaphyseal engaging press-fit stems.

Occasionally, one may not need to revise all components, so the surgeon needs to be familiar with the implants they are revising. Consider having some or all compatible components available.

Excellent pre-operative planning will minimise the need to bring in an excessive number of instruments and implants. It will help assure that the patient has a stable revision knee and simplify the surgery for all participants.

Fifteen-year survivorship studies demonstrate that total knee replacement has excellent survivorship, with reports of 85 to 97%. However, excellent survivorship does not equate to excellent patient reported outcomes. Noble et al. reported that 14% of their patients were dissatisfied with their outcome with more than half expressing problems with routine activities of daily living. There is also a difference in the patient's subjective assessment of outcome and the surgeon's objective assessment. Dickstein et al. reported that a third of total knee patients were dissatisfied, even though the surgeons felt that their results were excellent. Most of the patients who report lower outcome scores do so because their expectations are not being fulfilled by the total knee replacement surgery.

Perhaps this dissatisfaction is a result of subtle soft tissue imbalance that we have difficulty in assessing intra- and post-operatively. Soft tissue balancing techniques still rely on subjective feel for appropriate ligamentous tension by the surgeon. Surgical experience and case volume play a major role in each surgeon's relative skill in balancing the knee properly.

New technology of “smart trials” with embedded microelectronics, used in the knee with the medial retinaculum closed, can provide dynamic, intra-operative feedback regarding quantitative compartment pressures and component tracking. While visualising a graphical interface, the surgeon can assess the effect of sequential soft tissue releases performed to balance the knee. These smart trials also have embedded accelerometers used to confirm that one is balancing a properly aligned knee and to provide the option of doing small bony corrections rather than soft tissue releases to obtain balance.

A multi-center study using smart trials is demonstrating dramatically better outcomes.

The mean age of patients with osteonecrosis reported in series in our literature is 38 to 53. Thus, performing a total hip replacement on a patient who would need a procedure to last 40–45 years is a concern. Patients with osteonecrosis of the hip require some type of surgical treatment. Without treatment, a large majority of femoral heads in patients even with Ficat stage I osteonecrosis will collapse or become symptomatic. A common scenario is a patient who first presents to the orthopaedic surgeon with severe arthritis secondary to osteonecrosis in one hip and a normal appearing radiograph on the asymptomatic contralateral side. Performing a total hip on the severe arthritic hip is usually not debated. A MRI will commonly show Ficat stage I osteonecrosis on the asymptomatic contralateral hip. Some method of core decompression is a reasonable choice if it is non-steroid induced, small more medially positioned lesion, but not for other Ficat stage 1 lesions or those with more advanced stages. The problem is convincing the patient to have anything done when they are asymptomatic. Because results with total hip replacement for patients with osteonecrosis of the hip have significantly improved, most patients with a symptomatic hip prefer arthroplasty as treatment. Arthroplasty has become the predominant surgical treatment for osteonecrosis of the hip in the United States. Eighty-eight percent of procedures performed on 6,400 patients with osteonecrosis in 2008 reported in the Nationwide Inpatient Sample Database of the hip were total hip replacements. From 16 years earlier, the number of procedures performed had almost doubled and the percentage use of arthroplasty as the performed treatment had increased by 13%. I expect both numbers will continue to increase.