Introduction

Surface sensor technology provides useful information about the status of an individual's health and been available for many years, but has not been widely adopted by orthopaedic surgeons. However, its usage may be become more prominent as COVID-19 has created a shift towards telemedicine. This study reports the use of a joint specific surface sensor to remotely monitor the recovery of patients who underwent knee replacement surgery prior to the enforced stay-at-home social distancing necessitated by the COVID-19 pandemic.

Background

Total hip replacement is a highly successful procedure, yet access to arthroplasty is limited in many developing nations. In response, organizations in the United States have conducted service trips to provide international arthroplasty care to underserved populations. Little outcomes data are currently available related to these trips. We aimed to assess patient outcomes following total hip arthroplasty performed on a surgical mission trip.

Cementless femoral stems of many designs now provide dependable long-term fixation and excellent, near normal function in patients of all ages, sexes and level of activity. However, a number of issues related to cementless stem fixation could be further improved: Optimization of load transfer to proximal femur to minimise fracture risk and maximise bone preservation; Elimination of proximal-distal mismatch concerns, including bowed femurs; Facilitation of femoral stem insertion, especially for Anterior and MIS exposures; Facilitation of revision with implants capable of providing durable fixation for active patients.

The potential benefits of short stem femoral THA implants include: Ease of insertion; Reproducibility of insertion; Avoidance of issues related to proximal-distal anatomic mismatch or variations in proximal femoral diaphyseal anatomy (e.g. femoral bowing); Facilitation of MIS surgical approaches, especially anterior exposures; Optimization of proximal femoral load transfer with consequent maximization of proximal bone preservation.

The purpose of this presentation is to describe the design rationale and characteristics of short (< 120 mm) uncemented primary THA femoral stems and to evaluate the clinical and radiographic results of short stems.

Outcome results extending beyond 10 years support the proposition that short stems of appropriate design provide dependable long-term fixation and equivalent clinical results to those currently achievable with cementless stems of conventional length in patients of all ages, sexes and level of activity.

The number of Americans over the age of 80 is increasing at a faster rate than that of the 65–80 population. The cohort age 85–94 years had the fastest rate of growth from 2000–2010. The number of Americans older than 95 years grew at approximately 26% during the same period. This rapid growth has been associated with an increasing incidence of osteoarthritis of the hip and knee in this population. This surge in the growth rate of the elderly population has coincided with an increasing demand for primary and revision total joint arthroplasty. Surgeons need to be prepared to perform safely and appropriately these procedures in this rapidly growing segment of the population. Surgeons need to be aware of the 1) clinical outcomes that can be expected when total joint procedures are performed in this group of patients; 2) the morbidity and mortality associated with the performance of these procedures; and 3) the relative cost effectiveness of these interventions.

Clinical outcomes of TJA in this population are generally good. Pain and satisfaction scores are similar to those of younger patients. Although pre-operative pain and functional impairment scores are higher pre-operatively in elderly patients, these improve significantly following TJA. However, functional outcome scores decline noticeably after 5 years, reflecting the impact of coexistent comorbidities. The continued need for assistive devices is greater in this age group than in younger total joint patients. The risk of falls, a particular issue of concern in this age group, is reduced after total hip and knee surgery.

The rate of complications, including mortality, following TJA in this age group is greater than in the 65–79-year-old group. The use of hospitalists to co-manage peri-operative care is particularly important in this age group. The increased rate of complications is associated with longer lengths of stay. However, the length of stay for this age group after primary total joint replacement is decreasing significantly; reflecting the widespread streamlining of peri-operative care that is being incentivised and implemented nationwide. The use of extended care facilities is also greater in this age group.

The performance of revision TJA in this age group is particularly challenging. The rates of revision in elderly patients are anticipated to rise significantly in coming years. Although revision TJA is associated with significant pain relief and patient satisfaction, it is accompanied by mortality and complication rates that are substantially greater than those in younger age groups.

Introduction

Three anatomic landmarks are typically used to estimate proper femoral component rotation in total knee arthroplasty: the transepicondylar axis (TEA), Whiteside's line, and the posterior condylar axis (PCA). Previous studies have shown that the presence of tibia vara may be accompanied by a hyperplastic posteromedial femoral condyle, which affects the relationship between the PCA and the TEA. The purpose of this study was to determine the relationship of tibia vara with the PCA.

Introduction

Current techniques in total knee arthroplasty aim to restore the coronal mechanical axis to neutral. Preoperative planning has historically been based on long-leg standing films (LLSF) which allow surgeons to plan bony resection and soft tissue releases. However, LSSF can be prone to error if malrotated. Recently, patient-specific guides (PSG) utilizing supine magnetic resonance imaging (sMRI) have become an accepted technique for preoperative planning. In this study we sought to compare the degree of coronal deformity using LLSF and sMRI.

Introduction

Given the association of osteoarthritis with obesity, the typical patient requiring total knee arthroplasty (TKA) is often obese. Obesity has been shown to negatively influence outcomes following TKA, as it is associated with increased perioperative complications and poorer clinical and functional outcomes. Achieving proper limb alignment can be more difficult in the obese patient, potentially requiring a longer operation compared to non-obese patients. Patient specific instrumentation (PSI), a technique that utilizes MR- or CT-based customized guides for intraoperative cutting block placement, may offer a more efficient alternative to manual instruments for the obese patient. We hypothesize that the additional information provided by a preoperative MRI or CT may allow surgeons to achieve better alignment in less time compared to manual instrumentation. The purpose of this study was to assess whether PSI offers an improved operation length or limb alignment compared to manual instruments for nonmorbidly and morbidly obese patients.

As an increasing number of young, active, large patients are becoming candidates for total hip replacements, there is an increasingly urgent need to identify arthroplasties that will be durable, highly functional and amenable to possible future successful revision. In an era when cemented femoral stems were the primary implant option, the concept of a surface replacement was attractive and, perhaps, appropriate. However, cementless femoral stems of many designs now provide dependable long-term fixation and excellent, near normal function in patients of all ages, sex and level of activity.

However, a number of issues related to cementless stem fixation could be further improved: Optimization of load transfer to proximal femur to minimise fracture risk and maximise bone preservation; Elimination of proximal-distal mismatch concerns, including bowed femurs; Facilitation of femoral stem insertion, especially with MIS THA exposures; Facilitation of revision with implants capable of providing durable fixation for active patients.

The potential benefits of short stem femoral THA implants include: Ease of insertion; Reproducibility of insertion; Avoidance of issues related to proximal-distal anatomic mismatch or variations in proximal femoral diaphyseal anatomy (e.g. femoral bowing); Facilitation of MIS surgical approaches, especially anterior exposures; Optimization of proximal femoral load transfer with consequent maximization of proximal bone preservation.

The purpose of this presentation is to describe the design rationale and characteristics of short (< 115 mm) uncemented primary THA femoral stem, to evaluate the clinical and radiographic results of short stems and to discuss the possible drawbacks specific to the use of short stems.

There are many reasons that the surgically inclined orthopaedic surgeon should be responsible for the medical management of osteoarthritis of the knee. These include: 1) The non-operative treatment of OA is often highly effective for all stages of the disease; 2) A non-operative treatment program is the best preparation for a successful surgical outcome; and 3) Patients appreciate a surgeon's interest in their overall care and are likely to return if surgery is needed; 4) Medicare and many insurance companies are refusing to pay for a TJA until many months of conservative management has been administered.

There are many potential causes of pain in an arthritic knee. These include intra-articular (e.g. degenerative meniscal tears, loose bodies, synovitis) and extra-articular (tendonitis, e.g. ilio-tibial band syndrome, bursitis, muscle overload syndromes and referred pain) sites. The potential sources of pain in an arthritic knee produce a wide range of symptoms that are not necessarily correlated with objective measurements (e.g. x-rays, MRI). Moreover, the natural history of an arthritic knee is unpredictable and variable.

The treatment of the young, arthritic knee patient of all stages requires a systematic and consistent non-surgical approach. This approach includes the use of: 1) analgesics/anti-inflammatory agents; 2) activity modification; 3) alternative therapies; 4) exercise; 5) injections/lavage. The response to each form of non-surgical treatment is unpredictable at each stage (Kellgren 1–4) of OA. The placebo effect of each form of treatment, including the physician-patient interaction, is 50–60% in patients with mild-moderate OA.

The components of a non-operative treatment program include: 1) Education-emphasizing the importance of the patient taking charge of his/her care; 2) Appropriate activity/life style modifications-emphasizing the importance of remaining active while avoiding activities that aggravate symptoms (e.g. running to biking); 3) Medications-oral, topical, intra-articular; 4) Physical therapy. There are extensive data to support each of these interventions. The AAOS has issued guidelines based upon a review of the literature-based effectiveness of conservative interventions.

The goal of tibial tray placement in total knee arthroplasty (TKA) is to maximise tibial surface coverage while maintaining proper rotation. Maximising tibial surface coverage without component overhang reduces the risk of tibial subsidence. Proper tibial rotation avoids excess risk of patellar maltracking, knee instability, inappropriate tibial loading, and ligament imbalance. Different tibial tray designs offer varying potential in optimising the relationship between tibial surface coverage and rotation. Patient specific instrumentation (PSI) generates customised guides from an MRI- or CT-based preoperative plan for use in TKA. The purpose of the present study was to utilise MRI information, obtained as part of the PSI planning process, to determine, for anatomic, symmetric, and asymmetric tibial tray designs, (1) which tibial tray design achieves maximum coverage, (2) the impact of maximising coverage on rotation, and (3) the impact of establishing neutral rotation on coverage.

MR images for 100 consecutive patients were uploaded into Materialise™ PSI software that was used to evaluate characteristics of tibial component placement. Tibial component rotation and surface coverage was analysed using the preoperative planning software. Anatomic (Persona™), symmetric (NexGen™), and asymmetric (Natural-Knee II™) designs from a single manufacturer (Zimmer™) were evaluated to assess the relationship of tibial coverage and tibial rotation. Tibial surface coverage, defined as the proportion of tibial surface area covered by a given implant, was measured using Adobe Photoshop™ software. Rotation was calculated with respect to the tibial AP axis, which was defined as the line connecting the medial third of the tibial tuberosity and the PCL insertion.

When tibial surface coverage was maximised, the anatomic tray compared to the symmetric/asymmetric trays showed significantly higher surface coverage (82.1% vs 80.4/80.1%; p<0.01), significantly less deviation from the AP axis (0.3° vs 3.0/2.4°; p<0.01), and a significantly higher proportion of cases within 5° of the AP axis (97% vs 73/77%). When constraining rotation to the AP axis, the anatomic tray showed significantly higher surface coverage compared to the symmetric/asymmetric trays (80.8% vs 76.3/75.8%; p<0.01). No significant differences were found between symmetric and asymmetric trays.

We found that the anatomic tibial tray resulted in significantly higher tibial coverage with significantly less deviation from the AP axis compared to the symmetric and asymmetric trays. When rotation was constrained to the AP axis, the anatomic tray resulted in significantly higher tibial coverage than the symmetric and asymmetric trays. Tibial rotation is recognised as an important factor in the success of a total knee replacement. Maximising coverage with the least compromise in rotation is the goal for tibial tray design. In this study, the anatomic tibia seemed to optimise the relationship between tibial surface coverage and rotation. This study additionally illustrates the way by which advanced preoperative planning tools (ie. MRI/computer reconstructions) allow us to obtain valuable information with regard to implant design.

As an increasing number of young, active, large patients are becoming candidates for total hip replacements, there is an increasingly urgent need to identify arthroplasties that will be durable, highly functional and amenable to possible future successful revision. In an era when cemented femoral stems were the primary implant option, the concept of a surface replacement was attractive and, perhaps, appropriate. However, cementless femoral stems of many designs now provide dependable long-term fixation and excellent, near normal function in patients of all ages, sex and level of activity.

However, a number of issues related to cementless stem fixation could be further improved: Optimisation of load transfer to proximal femur to minimise fracture risk and maximise bone preservation; Elimination of proximal-distal mismatch concerns, including bowed femurs; Facilitation of femoral stem insertion, especially with MIS THA exposures; Facilitation of revision with implants capable of providing durable fixation for active patients

The potential benefits of short stem femoral THA implants include: Ease of insertion; Reproducibility of insertion; Avoidance of issues related to proximal-distal anatomic mismatch or variations in proximal femoral diaphyseal anatomy (e.g. femoral bowing); Facilitation of MIS surgical approaches, especially anterior exposures; Optimisation of proximal femoral load transfer with consequent maximisation of proximal bone preservation.

The purpose of this presentation is to describe the design rationale and characteristics of short (< 115mm) uncemented primary THA femoral stem, to evaluate the clinical and radiographic results of short stems and to discuss the possible drawbacks specific to the use of short stems.

The incidence of clinically significant (Brooker stage 3–4) heterotopic ossification (HO) after THA is 3–7%. Risk factors include male gender, old age, a history of HO, Paget's disease, post-traumatic arthritis, osteonecrosis and rheumatoid arthritis. Prophylaxis for high-risk patients consists of 1) radiotherapy given as one dose of 7–8 Gy either pre-operatively (<4 hours) or post-operatively (within 72 hours) or 2) NSAIDS. Treatment of clinically significant HO includes intensive physiotherapy during the maturation phase of the disease and surgical excision in conjunction with a combination of radiotherapy and indomethacin once the HO has matured. Less invasive surgical approaches may be associated with a reduced incidence of HO.

In the early days of total hip arthroplasty, the discussion of surgical approaches centered on issues related to obtaining optimum exposure for accurate insertion and fixation of implants and appropriate restoration of hip kinematics. More recently, attention has been directed to those aspects of exposure that appear to be associated with rapid recovery, shorter lengths of stay, less pain and minimal gait disturbance. The role of less invasive (“MIS”) exposures in achieving these outcomes has been sharply and extensively debated. Currently, the Direct Anterior Approach is being used by an increasing number of surgeons to address these outcomes. The purpose of this presentation is to discuss the relationship of total hip surgical approaches to peri-operative morbidity, rate of functional recovery, length of hospital stay and ultimate lower extremity function.

Many factors affect the quality and rate of recovery from THA surgery. These include: 1) patient characteristics; 2) implant type; 3) surgical exposure and technique; and 4) peri-operative management. Numerous reports suggest that patient selection and effective peri-operative management have the greatest impact on the rate of recovery. The quality of the arthroplasty outcome is related to the accuracy with which the procedure is performed, regardless of the surgical approach used. Available evidence strongly suggests that the quality of the surgical technique used to perform a THA is a much more important determinant of outcome than the surgical approach used.

Stiffness after a TKA might be said to be present when reasonable functions of daily living cannot be performed or can only be performed with difficulty or pain. This will certainly be true if flexion is less than 75 degrees and/or there is a 15-degree lack of full extension. The purpose of this presentation is to discuss the causes of a stiff TKA, consider the aspects of surgical technique that are associated with the occurrence of stiffness, present post-surgical management that impacts on the development of stiffness and summarise the results of the surgical treatment of a stiff TKA.

Pre-operative stiffness is strongly correlated with post-operative limitation of motion. Therefore, pre-surgical measures to optimise motion should be carried out. These include appropriate physical therapy, adequate pain management and a discussion with the patient of the issues likely to affect post-operative range of motion. It is particularly important to discuss with the patient appropriate expectations with regard to the likely range of motion that will be achieved following TKA surgery.

There are a number of steps that can be taken during the performance of a TKA that have an impact on range of motion. Osteophytes must be removed. Correctly sized implants must be used to avoid over-stuffing the tibio-femoral and patello-femoral compartments. Mal-positioning implants and the extremity can adversely affect range of motion. Inadequate bone resection will also lead to a reduced range of motion. Improper soft tissue balancing in both flexion and extension may be associated with post-surgical stiffness.

Post-operative management must include adequate pain management as well as appropriate rehabilitation. Close post-surgical surveillance will help identify those patients likely to achieve unsatisfactory range of motion. Manipulation of appropriate patients within the first 6 weeks following surgery is usually associated with a satisfactory final range of motion.

When persistent stiffness occurs, an attempt must be made to identifying possible causes, including component mal-alignment or mal-rotation, component mis-sizing or mis-positioning and inadequate soft tissue balancing. The surgical treatment of a stiff total knee include: 1) arthroscopic debridement and manipulation; 2) arthrotomy with debridement; and 3) single or complete component revision. Although surgical intervention often results in improved range of motion, the results are variable and somewhat limited.

Introduction

Patient specific instrumentation (PSI) is an innovative technology in total knee arthroplasty (TKA). With the use of a preoperative MRI or CT scan, custom guide blocks are individually manufactured for each patient. Contrary to other TKA technologies such as computer-assisted surgery, PSI utilises measured resection technique rather than a primarily ligament balancing technique. This has the potential to negatively affect the operating surgeon's ability to achieve optimal soft tissue balancing, which is especially critical in patients with severe lower extremity malalignment. Despite early research suggesting that PSI is accurate, has a low learning curve, and can reduce operating room time, it remains unclear whether a surgeon using PSI can achieve optimal soft tissue balancing using a measured resection technique. The purpose of this study is to evaluate the efficacy of PSI in patients with severe preoperative limb alignment deformities.

Femoral components used in total hip arthroplasty (THA) rely on good initial fixation determined by implant design, femoral morphology, and surgical technique. A higher rate of varus alignment may be of specific concern with short stem implants. Varus placement in uncemented femoral components has been proven not to be detrimental to clinical function; though long-term bone remodeling secondary to varus placement remains unknown. The goal of this study was to compare the clinical and radiographic outcomes in patients who underwent THA with one of two uncemented short stem metaphyseal engaging implants at minimum two-year follow-up.

A review of 105 patients (average age 65 years; BMI 29 kg/m²) who underwent a total of 109 primary THAs using the ABG II short stem femoral implant (Stryker, Mahwah, NJ), and 160 hips in 149 patients (average age 70 years; BMI 28 kg/m²) who underwent primary THA using the Citation stem (Stryker, Mahwah, NJ). The same surgeon (SDS) performed all surgeries through a less invasive posterolateral approach. Pre-operative and post-operative Harris Hips Scores (HHS) and WOMAC scores were collected. Digital radiograph analysis was performed including measuring the stem alignment relative to the femoral shaft. A stem placed with greater than 5 degrees of varus was considered to be in varus.

There was no significant difference in demographics (age, gender or BMI) or pre-operative HHS and WOMAC scores between the two groups. Follow-up HHS was 90 (range 63–100) and 94 (range 70–100) for the ABG II and Citation groups, respectively. Follow-up WOMAC scores were 10 (range 0–24) and 6 (range 0–43) for the ABG II and Citation groups, respectively. There was no statistically significant difference in any of the scores between the two groups (p>0.05).

When looking at AP radiographs for postoperative intramedullary alignment, none of the ABG II implants were placed in varus (>5°), while a small number (4.9%) of Citation implants were implanted in varus alignment. No significant difference was observed in the alignment between the two groups (p>0.05). Average post-op alignment with the ABG was 1.10° (range −4.7–4.9°) and 0.88° (range −4.5–8.9°) with the Citation.

The clinical results associated with the use of these stems in patients of all ages and bone types have been identical to those achieved by uncemented stems of standard length. Both implants in this study had excellent clinical and functional results in primary THA after a minimum 24-month follow up. In addition, postoperative radiographic analysis demonstrated that these stems can be reliably and reproducibly placed in neutral alignment despite their short length. The lateral flare on the Citation implant led to a greater number of implants in varus alignment, potentially affecting offset and leg-length, yet the relative increased incidence compared to the ABG II was not significant. Further research is needed in designing implants that optimize proximal femoral contact while maintaining alignment and overall hip kinematics.

The incidence of clinically significant (Brooker stage 3–4) heterotopic ossification (HO) after THA is 3–7%. Risk factors include male gender, old age, a history of HO, Paget's disease, post-traumatic arthritis, osteonecrosis and rheumatoid arthritis. Prophylaxis for high-risk patients consists of 1) radiotherapy given as one dose of 7–8 Gy either pre-operatively (< 4 hours) or post-operatively (within 72 hours) or 2) NSAIDS. Treatment of clinically significant HO includes intensive physiotherapy during the maturation phase of the disease and surgical excision in conjunction with a combination of radiotherapy and indomethacin once the HO has matured. Less invasive surgical approaches may be associated with a reduced incidence of HO.

As an increasing number of young, active large patients become candidates for total hip replacements, there is an increasingly urgent need to identify arthroplasties that will be durable, highly functional and amenable to possible future successful revision. In an era when cemented femoral stems were the primary implant option, the concept of a surface replacement was attractive and, perhaps, appropriate. However, cementless femoral stems of many designs now provide dependable long term fixation and excellent, near normal function.

However, a number of issues related to cementless stem fixation could be further improved: –

Optimisation of load transfer to proximal femur to minimize fracture risk and maximize bone preservation

The potential benefits of short stem femoral THA implants include: –

Ease of insertion

However, a number of potential drawbacks may be associated with the use of cementless short stems: –

Initial and durable fixation may be highly sensitive to implant design and surface treatment.

At this time, it is important to realize that not all short stem implants are equal. In view of the reliability of a large number of uncemented femoral stems of conventional length, surgeons should base their use of specific short stems upon clinical evidence of their safety and durability.

Navigation has been felt to play a role in a number of THA issues. These issues include: 1) Instability-Dislocation; 2) Leg Length discrepancy; 3) Impingement and its impact on range of motion and wear; 3) gait mechanics; and 4) less invasive surgery. Navigation requires that anatomic landmarks be accurately identified. This can be done using images obtained either pre-operatively or intra-operatively (image-based navigation) or using intra-operative techniques for registering the relevant bony anatomy (image-free). The suggested advantages of imaged-based navigation are that is potentially very accurate, makes registering bone landmarks relatively easy and provides information about relevant anatomic landmarks that are not visible during surgery. The disadvantages of image-based navigation are that the acquisition of pre-operative imaging may be inconvenient or cumbersome, the imaging may be associated with increased radiation exposure, the imaging may be associated with additional costs and the pre-operative planning carried out on the imaging may be elaborate and time consuming. The advantages of image-free navigation are that no special pre-operative planning is required, no special imaging is necessary and the intra-operative workflow is consistent with the routine performance of a THA. However, image free registration techniques may be unreliable or inaccurate and the information obtained with image-free registration techniques is limited.

When surgeons proficient in the technique perform image free navigation, positioning of the acetabular component is more accurate and consistent than that achieved using manual techniques. However, this increased accuracy has not been associated with a reduction in hip dislocations and has not had a measurable impact on short-term clinical outcomes. However, navigation is an accurate measurement tool that can be used to validate other computer-based technologies (e.g. patient specific guides). Navigation is also essential to the performance of robotic hip surgery. It is in this latter capacity that navigation may prove most useful to the hip surgeon.

Custom instrumentation in TKA utilises pre-operative imaging to generate a customised guide for cutting block placement. The surgeon is able to modify the plan using three-dimensional software. Although this technology is increasingly gaining acceptance, there is a paucity of clinical data supporting it.

One hundred and eleven patients underwent primary TKA using the Zimmer Patient-Specific Instrumentation (PSI) system, in 28 of the cases surgical navigation was used to validate the PSI-generated cuts. Alignment measurements included long-leg alignment and biplanar distal femoral and proximal tibial cuts. Further measurements evaluated femoral implant placement in the AP plane, femoral component rotation, measured bone resection and implant sizing accuracy.

The mean final limb alignment as recorded by computer-assisted surgical (CAS) tools was 0.3° of varus. Only two limbs were malaligned by greater than 3°. The femoral component had a mean alignment of 0.3° of valgus and 4.5° of flexion (PSI plan 3° flexion). The predicted femoral size was accurate in 89% of cases and the anterior femoral cut was congruent with the anterior cortex in 92% of cases. The PSI-directed femoral component rotation was consistent with the surgeon's perceived rotation in 95% of cases. The posterior condylar bone resection had a mean difference of < 1mm from the predicted resection.

The tibial component had a mean alignment of 0.5° of varus and 8.5° of posterior slope (PSI plan 7° posterior slope). The only statistically significant deviation in alignment was the increased tibial slope (p = 0.046). The tibial component size was accurately predicted in 66% of cases.

Custom instrumentation in total knee arthroplasty accurately achieved implant and limb alignment in our study. The plan was more reproducible on the femoral slide. The overestimation of tibial slope and tibial sizing incongruity were related to some of the reference points for the software. A potential benefit of this technology is improved mid-flexion stability by accurately determining femoral component size, placement, and rotation. Further studies will need to be conducted to determine the efficiency and cost-effectiveness of this technology.