Introduction

Cardiac events have been found to occur with increased frequency in total joint arthroplasty (TJA) patients >65 y/o without known coronary artery disease (CAD). Avoidance of readmissions for cardiac events is paramount with bundled payment programs. It has been thought that many of these patients may have undiagnosed CAD because of sedentary life styles brought on by chronic osteoarthritis.

The purpose of this study is to assess with Coronary Computed Tomographic Angiography (CCTA) the prevalence and severity of CAD in patients >65 y/o for elective TJA.

Background

In surgeon controlled bundled payment and service models, the goal is to reduce cost but preserve quality. The surgeon not only takes on risk for the surgery, but all costs during 90 days after the procedure. If savings are achieved over a previous target price, the surgeon can receive a monetary bonus. The surgeon is placed in a position to optimize the patients preoperatively to minimize expensive postoperative readmissions in a high risk population. Traditionally, surgeons request that primary care providers medically clear the patient for surgery with cardiology consultation at their discretion, and without dictating specific testing. Our participation in the Bundled Payments for Care Improvement (BPCI) program for total hip and knee replacement surgeries since 1/1/15 has demonstrated a significant number of patients having costly readmissions for cardiac events.

Background

Use of a robotic tool to perform surgery introduces a risk of unexpected soft tissue damage due to the uncommon tactile feedback for the surgeon. Early experience with robotics in total hip and knee replacement surgery reported having to abort the procedure in 18–34 percent of cases due to inability to complete preoperative planning, hardware and soft tissue issues, registration issues, as well as concerns over actual and potential soft tissue damage. These can result in significant morbidity to the patient, negating all the desired advantages of precision and reproducibility with robotic assisted surgery. The risk of soft tissue damage can be mitigated by haptic software prohibiting the cutting tip from striking vital soft tissues and by the surgeon making sure there is a clear workspace path for the cutting tool. This robotic total knee system with a semi-active haptic guided technique was approved by the FDA on 8/5/2015 and commercialized in August of 2016. Two year clinical results have not been reported to date.

Background

Intraoperative balancing of total knee arthroplasty (TKA) can be accomplished by either more prevalent but less predictable soft tissue releases, implant realignment through adjustments of bone resection or a combination of both. Robotic TKA allows for quantifiable precision performing bone resections for implant realignment within acceptable final component and limb alignments.

Introduction

Robotic TKA allows for quantifiable precision performing bone resections for implant realignment within acceptable final component and limb alignments. One of the early steps in this robotic technique is after initial exposure and removal of medial and lateral osteophytes, a “pose-capture” is performed with varus and valgus stress applied to the knee in near full extension and 90° of flexion to assess gaps. Component alignment adjustments can be made on the preoperative plan to balance the gaps. At this point in the procedure any posterior osteophytes will still be present, which could after removal change the flexion and extension gaps by 1–3mm. This must be taken into consideration, or changes in component alignment could result in over-correction of gaps can occur.

Introduction

In total knee arthroplasty (TKA), component realignment with bone-based surgical correction (BBSC) can provide soft tissue balance and avoid the unpredictability of soft tissue releases (STR) and potential for more post-operative pain. Robotic-assisted TKA enhances the ability to accurately control bone resection and implant position. The purpose of this study was to identify preoperative and intraoperative predictors for soft tissue release where maximum use of component realignment was desired.

Total knee replacements 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%. Cemented knee arthroplasties are doomed to failure due to loss of cement-bone interlock over time. Inferior survivorship occurs in younger patients and obese patients who would be expected to place increased stress on the bone-cement interfaces. Roentgen stereophotogrammetric analysis (RSA) studies have indicated that cementless fixation should perform better than cemented fixation. However, cementless fixation for total knee replacement has not gained widespread utilization due to the plethora of poor results reported in early series. 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 stability, 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 1,300 cementless TKAs represents about 20% of the 6,500 total knees I have performed from 1986 to 2017. I have seen initial failures in my series due to the use of metal-backed patellae with thin polyethylene, older generation polyethylene, and use of screws with the tibial components which provide access to the metaphyseal bone for polyethylene wear debris. Overall implant fixation failures were still significantly low due to the use of a highly porous titanium surface on both the tibial and femoral components. With the advent of utilizing implants with continuous porous surfaces and highly crosslinked 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 1,071 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 survivorships 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. Total knee imbalance with either too tight or loose soft tissues account for up to 54% of revisions in one series. This may account for many of the 20% unsatisfactory total knee arthroplasty outcomes.

Soft tissue balancing technique is more like an art. The surgeon relies on subjective feel for appropriate ligamentous tension. 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 quantitative compartment pressures and component tracking. After all bone cuts are made using the surgeon's preferred techniques, trial components with the sensor 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, imbalance situations such as a too tight MCL or ITB, an incompetent or too tight PCL, or malrotated femoral or tibial component can be identified. A decision can be made as to whether to recut the bone to realign components, do a soft tissue release, or a combination of both. Soft tissue releases can be titrated while observing equalizing compartment pressures.

Sensor feedback improves soft tissue balancing. More balanced compartments occur using a sensor trial than with standard soft tissue balancing technique blinded to sensor information. A multicenter three year study has shown that having the medial and lateral compartments in flexion and extension balanced within 15 pounds provides better outcomes. Patients with quantitatively balanced TKA with <15lbf mediolateral load differential have better forgotten knee scores at six weeks and six months. Use of smart trials is a new approach to total knee replacement surgery allowing fine tune balancing and takes soft tissue balancing from art to science.

Anterior surgical approaches for total hip arthroplasty (THA) have increased popularity due to expected faster recovery and less pain. However, the direct anterior approach (Heuter approach which has been popularised by Matta) has been associated with a higher rate of early revisions than other approaches due to femoral component loosening and fractures. It is also noted to have a long learning curve and other unique complications like anterior femoral cutaneous and femoral nerve injuries. Most surgeons performing this approach will require the use of an expensive special operating table. An alternative to the direct anterior approach is the anterior-based muscle-sparing approach. It is also known as the modified Watson-Jones approach, anterolateral muscle-sparing approach, minimally invasive anterolateral approach and the Röttinger approach. With this technique, the hip joint is approached through the muscle interval between the tensor fascia lata and the gluteal muscles, as opposed to the direct anterior approach which is between the sartorius and rectus femoris and the tensor fascia lata. This approach places the femoral nerve at less risk for injury. I perform this technique in the lateral decubitus position, but it can also be performed in the supine position. An inexpensive home-made laminated L-shaped board is clamped on end of table allowing the ipsilateral leg to extend, adduct, and externally rotate during the femoral preparation.

This approach for THA has been reported to produce excellent results. One study reports a complication rate of 0.6% femoral fracture rate and 0.4% revision rate for femoral stem loosening. In a prospective randomised trial looking at the learning curve with new approach, the anterior-based muscle-sparing anterior approach had lower complications than a direct anterior approach. The complications and mean operative time with this approach are reported to be no different than a direct lateral approach. Since this surgical approach is not through an internervous interval, a concern is that this may result in a permanent functional defect as result of injury to the superior gluteal nerve. At a median follow-up of 9.3 months, a MRI study showed 42% of patients with this approach had fat replacement of the tensor fascia lata, which is thought to be irreversible. The clinical significance remains unclear, and inconsequential in my experience. A comparison MRI study showed that there was more damage and atrophy to the gluteus medius muscle with a direct lateral approach at 3 and 12 months. My anecdotal experience is that there is faster recovery and less early pain with this approach.

A study of the first 57 patients I performed showed significantly less pain and faster recovery in the first six weeks in patients performed with the anterior-based muscle-sparing approach when compared to a matched cohort of THA patients performed with a direct lateral approach. From 2004 to 2017, I have performed 1308 total hip replacements with the anterior-based muscle sparing approach. Alternatively, I will use the direct lateral approach for patients with stiff hips with significant flexion and/or external rotation contractures where I anticipate difficulty with femoral exposure, osteoporotic femurs due to increased risk of intraoperative trochanteric fractures, previously operated hips with scarring or retained hardware, and Crowe III-IV dysplastic hips when there may be a need for a femoral shortening or derotational osteotomy. Complications have been very infrequent. This approach is a viable alternative to the direct anterior approach for patients desiring a fast recovery. The anterior-based muscle-sparing approach is the approach that I currently use for all outpatient total hip surgeries.

Stems provide short- and long-term stability to the femoral and tibial components. Poorer epiphyseal and metaphyseal bone quality will require sharing or offloading the femoral and tibial component interfaces with a stem. One needs to use stem technique most appropriate for each individual case because of variable anatomy and bone loss situations. The conflict with trying to obtain stability via the stem is that most stems are cylindrical but femoral and tibial metaphyseal/diaphyseal areas are conical in shape. Viable stem options include fully cemented short and long stems, uncemented long stems, offset uncemented stems, and a hybrid application of a cemented proximal end of longer uncemented diaphyseal engaging stems.

Stems are not without their risk. The more the load is transferred to the cortex, the greater the risk of proximal interface stress shielding. A long uncemented stem has similar stress shielding as a short cemented stem. Long diaphyseal engaging stems that are cemented or uncemented have the potential to have end of stem pain, especially if more diaphyseal reaming is done to obtain greater cortical contact. A conical shaped long stem can provide more stability than a long cylindrical stem and avoid diaphyseal reaming. Use of long stems may create difficulty in placement of the tibial and femoral components in an optimal position. If the femoral or tibial components do not allow an offset stem insertion, using a long offset stem or short cemented stem is preferred. The amount of metaphyseal bone loss will drive the choice of stem used. Short cemented stems will not have good stability in poor metaphyseal bone without getting the cement out to the cortex. Long cemented stems provide satisfactory survivorship, however, most surgeons avoid cementing long stems due to the difficulty of removal, if a subsequent revision is required. If the metaphyseal bone is excellent, use of a short cemented stem or long uncemented stem can be expected to have good results. Long fully uncemented stems must have independent stability to be effective, or should be proximally cemented as a hybrid technique. Cases with AOI type IIb and III tibial and femoral defects are best managed with use of metaphyseal cones with short cemented stems or long hybrid straight or offset stems. Some studies also suggest that if the cone is very stable, no stem may be required.

My preference is to use a short cemented stem or hybrid conical stem in patients with good metaphyseal bone. If significant metaphyseal bone loss is present, I will use a porous cone with either a short cemented stem, hybrid cylindrical or offset stem depending on the primary stability of the cone and whether the femoral or tibial component can be placed in an optimal position in patients with good metaphyseal bone.

Background

The Bundled Payments for Care Improvement (BPCI) was developed by the US Center for Medicare and Medicaid (CMS) to evaluate a payment and service delivery model to reduce cost but preserve quality. 90 day postoperative expenditures are reconciled against a target price, allowing for a monetary bonus to the provider if savings were achieved. The surgeon is placed in a position to optimize the patients preoperatively to minimize expensive postoperative cardiovascular readmissions in a high risk population. Traditionally, surgeons request that primary care providers medically clear the patient for surgery with or without additional cardiology consultation, without dictating specific testing. Typical screening includes an EKG, occasionally an echocardiogram and nuclear stress test, and rarely a cardiac catheterization. Our participation in the BPCI program for total hip and knee replacement surgeries since 1/1/15 has demonstrated a significant number of patients having readmissions for cardiac events.

Background

Intraoperative balancing can be accomplished by either more prevalent but less predictable soft tissue releases, implant realignment through adjustments of bone resection or a combination of both. There is no published study directly comparing these methods.

Background

Use of a robotic tool to perform surgery introduces a risk of unexpected soft tissue damage due to the lack of tactile feedback for the surgeon. Early experience with robotics in total hip and knee replacement surgery reported having to abort the procedure in 18–34 percent of cases due to inability to complete preoperative planning, hardware and soft tissue issues, registration issues, as well as concerns over actual and potential soft tissue damage. These damages to the soft tissues resulted in significant morbidity to the patient, negating all the desired advantages of precision and reproducibility with robotic assisted surgery. The risk of soft tissue damage can be mitigated by haptic software prohibiting the cutting tip from striking vital soft tissues and by the surgeon making sure there is a clear workspace path for the cutting tool. This robotic total knee system with a semi-active haptic guided technique was approved by the FDA on 8/5/2015 and commercialized in August of 2016. One year clinical results have not been reported to date.

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 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-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 sensor 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 if compartment loading differences are greater than 15 pounds 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 out to three years.

Pre-operative planning in revision total knee replacement is important to simplify the surgery for the implant representative, operating room personnel and the surgeon.

Revision knee arthroplasty is performed for many different reasons and of variable complexity. Many implant options can be considered including cemented and cementless primary and stemmed 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 truck full of instruments and implants.

The first step of pre-operative planning is to determine how much implant constraint will be needed. Survivorship of revision total knees with modern varus/valgus constrained or rotating hinge implants are not that unacceptable. Ideally to enhance longevity, the least constraint needed should be used. This requires determination of the status of the ligaments. Varus and valgus stress is applied to the knee in near full extension, mid-flexion, and ninety degrees of flexion. If instability of the knee is noted, then radiographs are reviewed to determine if component malposition or malalignment is the reason for the collateral ligament laxity. If radiographs don't show a reason, then have additional constraint available in case the knee can't be balanced with proper component position and ligament balancing. In cases other than simple revisions, the posterior cruciate ligament is usually inadequate or needs to be resected to balance the knee. Substitution for the posterior cruciate ligament is usually needed for most revisions

The second step of pre-operative planning is to review radiographs to determine the amount and location of any bone loss. Osteolysis induced bone loss is usually worse than seen on plain radiographs. If unsure, a CT scan can be of help. The presence of significant bone loss contraindicates the use of primary components and mandates the need for stemmed implants. Larger defects may warrant having metallic augments or bulk graft present. Most revision knee implants can be conservatively metaphyseal cemented with diaphyseal engaging press-fit stems.

The third step of pre-operative planning is to be familiar with what implants are present. Occasionally, one may not need to revise components that are stable and well aligned. Having compatible components available may simplify the surgery

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

Introduction & Aims

The traditional method of soft-tissue balancing during TKA is subjective in nature, and stiffness and instability are common indications for revision, suggesting that TKA balancing by subjective assessment is suboptimal. This study examines the intraoperative mediolateral loads measured with a nanosensor-enabled tibial insert trial and the sequential balancing steps used to achieve quantitative balance. Data obtained from a prospective multicenter study was assessed to determine the effect of targeted ligament release on intra-articular loading, and to understand which types of releases are necessary to achieve quantified ligament balance.

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 out to three years.

Robotic arm-assisted total knee replacement is performed as a semi-active system in which haptic guidance is used to precisely position and align components. This is based on pre-operative planning based on CT imaging and can be modified as needed throughout the procedure. This technology, as shown with unicompartmental arthroplasty, is more accurate than conventional and even computer navigated instrumentation and will decrease variability. The knee can be planned to a neutral mechanical alignment. Intra-operatively, the computer will demonstrate compartment gap measurements to assist with soft tissue balancing.

Alternatively, limb and component alignment can be accurately adjusted several degrees off the neutral axis to balance the knee and avoid or minimise soft tissue releases. This allows a more constitutional alignment within the alignment parameters accepted by the surgeon. This technique was utilised commonly in the first 60 robotic total knee replacements performed.

We will now have the ability to collect accurate component positioning, alignment, and soft tissue balance data that can be correlated to outcomes of total knee replacements.

Removing well-fixed components can be difficult. It can be required in instances of infection, malalignment, instability and polyethylene wear. Success requires patience, skill and the use of correct instruments. Using too much force or haste will result is excessive bone loss and a more difficult reconstruction. One's goal should be to save bone and save time. The surgeon must be familiar with the implants to know if any special techniques will be required to deal with modularity of the tibial polyethylene, surface coatings and geometry of pegs and stems. The usual steps are to remove the tibial liner if modular, followed by removal of the femoral component, then tibial component. Thin osteotomes are used to loosen the cement prosthesis or bone prosthesis interfaces to be able to remove the implants and not lose bone in the process. Removal of cement mantles around long-stemmed femoral and tibial components can be facilitated by femoral cortical window osteotomies and tibial crest osteotomies.

Acetabular protrusio occurs from migration of the femoral head medial to Kohler's line. This occurs in inflammatory arthritis, osteoarthritis with coxa vara deformities, previous acetabular fracture, and in metabolic bone diseases such as osteomalacia, Paget's disease, Marfan's syndrome, and osteogenesis imperfecta. Total hip replacement in this situation is difficult due to the requirement to place the acetabular component opening at the level of the normal rim or the patient will be at risk for component-on-component or bone-on-bone impingement, resulting in dislocation or component loosening. The deficient medial wall doesn't resist cup subsidence and the deficient peripheral rim may provide poor initial cup stability.

Many management options have been described including using cement, bulk bone graft, and particulate graft to support the cup medially, and use of a reinforcement ring cage to provide better rim support. Gates reported on a series of 36 primary total hip replacements with acetabular protrusio treated with cemented cups and medial particulate autograft with a mean follow-up of 12.8 years with 6 definitively loose, 3 probably loose, and 22 possibly loose. The technique that provides initial porous cup stability and potential for long-term biological fixation is preferred. Mullaji and Shetty reported 90% good and excellent results and no loosening or migration at a mean 4.2 years in 30 primary total hips with acetabular protrusio treated with oversized porous cups for rim support and medial particulate bone grafting. Forty percent of their cases had protrusio greater than 15 mm medial to Kohler's line. Hansen and Ries also reported no revisions using this same technique in 19 revision total hips with an average follow-up of 2.8 years. However, they emphasised that this technique should only be used if the peripheral rim is intact, and if inadequate, to use a reconstruction cage. In revision total hips with large medial acetabular defects this is more likely to be the case. However, use of a reconstruction cage doesn't provide biological fixation. Ilyas reported a 15.1% loosening rate using cages for revisions with medial defects at a follow-up of 6 years.

I have alternatively used a porous protrusio shell when rim support is poor and the medial defect is greater than 10 mm. The technique is to perform a cylindrical peripheral ream and a medial hemispherical ream. This provides greater host bone to shell contact for stability and greater biological fixation, and fills much of the medial defect. I used this technique in 43 cases with an average follow-up of 3.7 years. There were no revisions, no apparent cup migrations, and no progressive component bone radiolucencies. For primary total hips with protrusio, when good rim support can be achieved with a few millimeters of peripheral over-ream, a standard porous cup and medial particulate autografting is preferred. However, in many primary cases with greater than 10 mm of protrusio, the peripheral rim may be significantly stress shielded and thus, may have poor rim support unless the rim is significantly over-reamed. Because of my excellent results using protrusio shells in revision cases, I will consider also using a protrusio shell in primary total hips in elderly patients with >10 mm of protrusio. I have experience in 10 primary cases with an average follow-up of 4.1 years. One failed for infection. The other 9 have been successful with no apparent cup migration and no progressive component bone radiolucencies.

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.

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.

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.

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.

In a study by Dickstein, one-third of total knee patients were not satisfied even though they were all thought to have had successful results by their orthopaedic surgeons. Noble and Conditt's study showed 14% of patients dissatisfied with their outcome with more than half expressing problems with routine activities of daily living. This occurs despite improvements in instrumentation to obtain proper alignment and implants with excellent kinematics and wear characteristics. Perhaps this dissatisfaction is a result of subtle soft tissue imbalance. Soft tissue imbalance can result in almost a third of early TKR revisions. 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, intraoperative 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 imbedded 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 at six months.

Total hip replacement for developmental hip dysplasia is challenging. The anatomical deformities on the acetabular and femoral sides are difficult to predict. The Crowe classification is usually used to describe these cases – however, it is not a very helpful tool for pre-operative planning. Small acetabular components, acetabular augments, and modular femoral components should be available for all cases. Regardless of the Crowe classification, the surgeon must be prepared to perform a femoral osteotomy for shortening, or to correct rotation, and/or angulation.

Cite this article: Bone Joint J 2013;95-B, Supple A:31–6.

Most orthopaedic surgeons believe that total knee replacement has superb patient outcomes. Long-term results are excellent, with one study showing 15 year survivorship of 97%. However, our objective assessments of our patients' results are greater than patients' subjective assessments. In a study by Dickstein of total knee patients, one-third were not satisfied even though they were all thought to have had successful results by their orthopaedic surgeons. Noble and Conditt's study showed 14% of patients dissatisfied with their outcome with more than half expressing problems with routine activities of daily living. We are puzzled by this patient dissatisfaction since radiographs usually show normal component alignment and positioning. Perhaps some of these patients have subtle soft tissue imbalance and kinematic maltracking.

Excellent aligned bone cuts can be expected with modern instrumentation, especially if patient specific cutting instruments or computer navigation are used. However, inadequate instrumentation exists for soft tissue balancing. It is usually based on feel and visual estimation. Soft tissue balancing techniques are difficult to teach and perform by a less experienced surgeon.

Smart trials with load bearing and alignment sensors, which can be used with the medial retinaculum closed, will demonstrate the total knee kinematics and quantify soft tissue balance. Graduated soft tissue balancing can be performed while visualising changes in compartment loads. Studies are ongoing with smart trials to establish evidence-based clinical algorithms for soft tissue balancing and document the effects of these techniques on patient satisfaction and long-term outcome.

A study by Harris reported a 40% incidence of femoral and acetabular dysplasia in routine idiopathic osteoarthritic patients. Fortunately most are minimally dysplastic requiring little modification from standard total hip surgical techniques. However, as the degree of dysplasia increases numerous anatomic distortions are present. These include high hip centres, 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 the standard method of treatment. In 2007, we reported our experience with this technique in 23 cases utilising 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. 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). 4 patients sustained dislocations, with 2 closed and 2 open reductions. There were no neurovascular injuries.

The Crowe classification is commonly used to pre-operatively classify the degree of dysplasia. However, there are large variations in these anatomic distortions within each class, so it is difficult to pre-operatively plan the acetabular component size needed and if one will need to do shortening and/or rotational osteotomy. So the surgeon needs to bring their entire bag of tricks and tools for these surgeries.

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 or bulk allograft. It is important to pre-operatively determine which of these implants you may need. If I ask my implant representative to “bring everything you've got, just in case,” I will get 23 pans of instruments, 24 bins of implants composed of 347 boxes of sterile implants, and chaos for everyone.

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.

Most revision knee implants can be conservatively cemented with diaphyseal engaging press-fit stems. Most importantly, pre-operative physical examination and radiographs are used to determine the status of the collateral ligaments, so that the appropriate constrained implants will be available at surgery. Radiographs will also show the amount and location of bone loss. This will determine if revision type implants, spacers or bone graft will be needed. Radiographically, one can determine the appropriate joint line position relative to the existing femoral component to simplify the surgery. Excellent pre-operative 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.

Smart trials are total knee tibial trial liners with load bearing and alignment sensors that will graphically show quantitative compartment load-bearing forces and component track patterns. These values will demonstrate asymmetrical ligament balancing and misalignments with the medial retinaculum temporarily closed. Currently surgeons use feel and visual estimation of imbalance to assess soft-tissue balancing and tracking with the medial retinaculum open, which results in lower medial compartment loads and a wider anteroposterior tibial tracking pattern. The sensor trial will aid the total knee replacement surgeon in performing soft-tissue balancing by providing quantitative visual feedback of changes in forces while performing the releases incrementally. Initial experience using a smart tibial trial is presented.

The use of short stems has become more popular with the increased interest in less invasive approaches for total hip arthroplasty. The curved broaches and stem can be inserted along a curved track to avoid the abductor attachments. Short stems have the potential of being more bone conserving by allowing for higher neck retention, maintenance of the medial greater trochanter, and preferential stress transfer to the proximal femur.

An initial experience with 500 new short stems (Fitmore, Zimmer Orthopedics) stems used for total hip arthroplasty is reported. No stems have been revised for aseptic loosening.

Frequently surgeons performing total knee replacements are faced with the dilemma of whether to notch the anterior cortex or overhang the medial and/or lateral cortices when implanting the femoral component. This is almost always seen in female patients. There is also a higher incidence of patellar alignment problems in female patients post total knee replacement. A unique 3D to 3D matching study of 202 cadaveric femurs has demonstrated a significant difference in the average comparable shapes of male versus female distal femoral anatomy. For the same AP dimension, female distal femurs are more than 5mm narrower. Also the angle formed between the anterior condyles and the posterior condyles are significantly different with the female being more trapezoidal in shape.

Most existing total knee femoral component designs follow the ratio similar to that found in the average male distal femur. Options for management of this gender variability have been either utilizing instrumentation that references the anterior cortex to avoid notching or placing additional flexion on the distal femoral cut to allow downsizing. Both techniques are potentially problematic. Total knee implants systems are now utilizing this anthropomorphic data to redesign for separate male and female femoral components taking into consideration the relatively narrower female distal condylar width, lower medial anterior femoral condyle, and greater patellofemoral Q-angle.

Minimally invasive arthroplasty surgery has the potential advantage of accelerating recovery. The short-term advantages should not compromise the excellent long-term results that can be obtained with total knee replacement surgery via traditional surgical technique.

A study was performed to ascertain that MIS TKR was safe, especially in one’s early experience. The first 50 MIS surgeries performed by the author via a subv-astus surgical approach through a shorter incision were compared to a matched set of total knees performed with a standard rectus femoris splitting approach with a standard skin incision. No changes were made in anesthesia or rehabilitation protocols to determine the difference as result of the change in surgical technique only. The femoral and tibial bone cuts were performed in a conventional fashion from the front with specially designed smaller instruments. The average skin incision was 12cm in the MIS group and 21cm in the non-MIS group.The average tourniquet time wa 9 minutes longer in the MIS group, but the total surgery time was the same due to a shorter time for wound closure. Range of motion was the same. Pain levels were slightly less for the MIS group for the first 3 days. Rehabilitation was faster for the MIS group in terms of distance walking and advancement to a cane. There were no wound complications, infections or component malposition problems in either group.

MIS total knee replacement appears to be no worse than conventional total knee replacement through a muscle splitting wide skin exposure. The potential short-term advantage of faster rehabilitation and slightly less pain makes it an attactive technique for many total knee patients.