Introduction

Component position and overall limb alignment following total knee arthroplasty (TKA) have been shown to influence prosthetic survivorship and clinical outcomes. Robotic-assisted (RA) total knee arthroplasty has demonstrated improved accuracy to plan in cadaver studies compared to conventionally instrumented (manual) TKA, but less clinical evidence has been reported.

The objective of this study was to compare the three-dimensional accuracy to plan of RATKA with manual TKA for overall limb alignment and component position.

Introduction

The purpose of this study is to compare total and rate of caloric energy expenditure between conventional and robotic-arm assisted total knee arthroplasty (TKA) between a high volume “veteran” surgeon (HV) and a lower volume, less experienced surgeon (LV).

Traditional risk factors for post-operative neuropathy include learning curve of surgical approach, DDH, and significant leg lengthening (>1 inch). Despite these risk factors, the most common scenario of a neuropathy is in a routine THA, by an experienced surgeon, for osteoarthritis, with no leg lengthening.

Post-operative hematoma can lead to nerve compression, albeit rarely. The usual clinical presentation is of an acute event, with a previously intact nerve, sometime within the first days of surgery. Once diagnosed, immediate surgical decompression should be performed.

Sciatic neuropathy is the most common, regardless of surgical approach, but the posterior approach poses the highest risk. Routine gluteus maximus tendon release may help to reduce the risk. When seen in the PACU, our approach is to immediately perform CT imaging to evaluate nerve integrity or to check on acetabular screw position. If no underlying cause is identified, the patient will be managed conservatively with foot orthotics and monitored for recovery.

Femoral nerve palsy (FNP) can result in significant initial disability. Fortunately most patients recover function (although it can take over 18 months). In the early post-operative period it is often diagnosed after a patient complains of the leg giving away while attempting to walk. A knee brace will assist the patient with mobilization while the nerve recovers. The highest incidence of FNP is described for the direct lateral approach.

Superior gluteal nerve (SGN) palsy is related to the direct lateral approach and may be avoided if the gluteus medius split is made within the safe zone (<5 centimeters from the tip of the greater trochanter). While early post-operative limp is common after the direct lateral approach, the true reported incidence of SGN palsy is low. Few studies showed that the persistent positive Trendelenburg test and limp is not exclusively related to the SGN damage and therefore the clinical effect of the SGN damage remains controversial.

Lateral femoral cutaneous nerve can be affected during the direct anterior hip approach. One study suggests the presence of peri-incisional numbness in over 80% of patients. This is akin to numbness seen lateral to the incision after TKA. The incidence of meralgia paresthetica is extremely low (<1%).

Modern modular revision stems employ tapered conical (TCR) distal stems designed for immediate axial and rotational stability with subsequent osseo-integration of the stem. Modular proximal segments allow the surgeon to achieve bone contact proximally with eventual ingrowth that protects the modular junction. The independent sizing of the proximal body and distal stem allows for each portion to obtain intimate bony contact and gives the surgeon the ability precisely control the femoral head center of rotation, offset, version, leg length, and overall stability.

The most important advantage of modular revision stems is versatility - the ability to manage ALL levels of femoral bone loss (present before revision or created during revision). Used routinely, this allows the surgeon to quickly gain familiarity with the techniques and instruments for preparation and implantation and subsequently master the use for all variety of situations. This also allows the operating room staff to become comfortable with the instrumentation and components. Additionally, the ability to use the stem in all bone loss situations eliminates intra-operative shuffle (changes in the surgical plan resulting in more instruments being opened), as bone loss can be significantly under-estimated pre-operatively or may change intra-operatively. Furthermore, distal fixation can be obtained simply and reliably. Paprosky 1 femoral defects can be treated with a primary-type stem for the most part. All other femoral defects can be treated with a TCR stem. Fully porous coated stems also work for many revisions but why have two different revision stem choices available when the TCR stems work for ALL defects?

The most critical advantage is the ability to separate completely the critical task of fixation from other important tasks of restoring offset, leg length, and stability. Once fixation is secured, the surgeon can concentrate on hip stability and on optimization of hip mechanics (leg length and offset). The ability to do this allows the surgeon to maximise patient functionality post-operatively. Modular tapered stems have TWO specific advantages over monolithic stems in this important surgical task. The proximal body size and length can be adjusted AFTER stem insertion if the stem goes deeper than the trial. Further, proximal/distal bone size mismatch can be accommodated. The surgeon can control the diameter of the proximal body to ensure proper bony apposition independent of distal fitting needs. If the surgeon believes that proximal bone ingrowth is important to facilitate proximal bone remodeling, modular TCR stems can more easily accomplish this.

The most under-appreciated advantage is the straightforward instrumentation system that makes the operation easier for the staff and the surgeon, while enhancing the operating room efficiency and reducing cost. Also, although the implant itself may result in more cost, most modular systems allow for a decrease in inventory requirements, which make up the cost differential.

One theoretical disadvantage of modular revision stems is modular junction fracture, which can happen if the junction itself is not protected by bone. Ensuring proximal bone support can minimise this problem. Once porous ingrowth occurs proximally, the risk of junction fracture is eliminated. Even NON-modular stems fracture when proximal bone support is missing. Another theoretical issue is modular junction corrosion but this not a clinical one, since both components are titanium. One can also fail to connect properly the two parts during surgery.

Despite the best of technique, when faced with a sub-capital or per-trochanteric fracture, inevitably there are failures of proximal fixation. These situations provide unique challenges for the reconstructive surgeon.

While there are specific issues related to either sub-capital or per-trochanteric fractures, there also are many commonalities. The causes of failure are nonunion, malunion, failure of fixation or avascular necrosis. In all cases, it is imperative to rule out infection. Since the surgery is now elective, the patient's medical status must be optimised prior to the intervention.

Basic surgical principles apply to both fracture types. Use the old incision (if possible) and choose an approach that can be extensile. Of course, the old hardware needs to be removed – this task can be quite frustrating, so good preparation and patience is imperative. Retrieve old operative notes to identify the type of hardware so that any special tools needed are available. Hardware can be intra-osseous in location and excavation of the hardware may require bone osteotomy. These patients are at higher risk of post-operative dislocation, so absolute hip stability must be achieved and confirmed in the OR. Bigger heads and dual mobility options improve stability provided that the components are properly positioned and offset and leg length are restored.

Subcapital fractures provide certain specific issues related to stem choice. While, my bias is towards THA because of better chance of complete pain relief, especially in community ambulators, certainly bipolar arthroplasties can be a satisfactory solution. Stem fixation can be either cemented or cementless.

For per-trochanteric fractures in younger patients, repeat osteosynthesis should be considered if the femoral head is viable. Bone deformity – trochanteric overhang, shaft offset – may necessitate an osteotomy as part of the reconstruction. While proximal fixation primary type stems are often possible, distal fixation revision stems may be required. Any bone defects related to screw holes should be bypassed by the femoral component.

Despite the best of technique when faced with a sub-capital or per-trochanteric fracture, inevitably there are failures of proximal fixation. These situations provide unique challenges for the reconstructive surgeon.

While there are specific issues related to either sub-capital or per-trochanteric fractures, there also are many commonalities. The causes of failure are nonunion, malunion, failure of fixation or avascular necrosis. In all cases, it is imperative to rule out infection. Since the surgery is now elective, the patient's medical status must be optimised prior to the intervention. Basic surgical principles apply to both fracture types. Use the old incision (if possible) and choose an approach that can be extensile. Of course, the old hardware needs to be removed – this task can be quite frustrating, so good preparation and patience is imperative. Retrieve old OP notes to identify the type of hardware so that any special tools needed are available. Hardware can be intra-osseous in location and excavation of the hardware may require bone osteotomy. These patients are at higher risk of postoperative dislocation, so absolute hip stability must be achieved and confirmed in the OR. Bigger heads and dual mobility options improve stability provided that the components are properly positioned and offset and leg length are restored.

Subcapital fractures provide certain specific issues related to stem choice. While, my bias is towards total hip arthroplasty because of better chance of complete pain relief, especially in community ambulators, certainly bipolar arthroplasties can be a satisfactory solution. Stem fixation can be either cemented or cementless.

For per-trochanteric fractures in younger patients, repeat osteosynthesis should be considered if the femoral head is viable. Bone deformity – trochanteric overhang, shaft offset – may necessitate an osteotomy as part of the reconstruction. While proximal fixation primary type stems are often possible, distal fixation revision stems may be required. Any bone defects related to screw holes should be bypassed by the femoral component.

My goal for every patient undergoing THA is to achieve a perfect result. At the very least this includes no pain at any time, normal range of motion, normal functionality and a minimal chance of a second operation. Both the Posterolateral Approach (PLA) and the Direct Anterior Approach (DAA) have the capability of achieving these important goals.

However, when you dive deeper into the goal of a “perfect” THA, some differences between the approaches become apparent. These include less muscle damage, faster recovery, and no restrictions at any time with the DAA as opposed to the PLA. Also there is some evidence of better wound healing (Poehling) and less chance of thromboembolic disease with the DAA (Stryker).

The PLA violates all posterior structures of the hip joint, and specifically also goes through the gluteus maximus muscle. Done properly, the DAA spares all the gluteal muscles, and all of the posterior muscles about the hip. Bergin, who demonstrated lower levels of creatine kinase using the DAA vs PLA, has provided evidence of lower muscle damage.

Faster recovery patterns have been well documented after DAA (Christen, Taunton). Part of this may be related to not needing hip precautions after DAA, while PLA patients are restricted in certain activities and positions in the postoperative period, because of the violation of the posterior capsule. Not having any restrictions enhances patient confidence, and patients tend to do more activities sooner with less reluctance and a subsequent faster recovery.

It is my belief that DAA problems (outside the learning curve) are related to the dependence upon special tables and fluoroscopy, as opposed to proper exposure, to perform a DAA. If you don't test hip stability in the OR, you will miss subtle impingement that can lead to postoperative dislocation. If you depend upon fluoroscopy to guide acetabular reaming (without proper exposure), you run the risk of over-reaming or asymmetric reaming with dire consequences. If you don't measure leg length directly, but rely on fluoroscopic measurements, you run the risk of inadvertent leg lengthening.

Revision hip surgery is about simplification. As such, a single revision stem makes sense. The most important advantage of Tapered Conical Revision (TCR) stem is versatility - managing ALL levels of femoral bone loss (present before revision or created during revision). The surgeon and team quickly gain familiarity with the techniques and instruments for preparation and implantation and subsequently master its use for a variety of situations. This ability to use the stem in a variety of bone loss situations eliminates intraoperative shuffle (changes in the surgical plan resulting in more instruments being opened), as bone loss can be significantly underestimated preoperatively or may change intraoperatively. Furthermore, distal fixation can be obtained simply and reliably.

Paprosky 1 femoral defects can be treated with a primary-type stem for the most part. All other femoral defects can be treated with a TCR stem. Fully porous coated stems also work for many revisions but why have two different revision stem choices available when the TCR stems work for ALL defects?

TCR stems can be modular or monolithic but there are common keys to success. First and foremost, proper exposure is essential to assess bone defects and to safely prepare the femur. An extended osteotomy is often useful. Reaming distally to prepare a cone for fixation of the conical stem is a critical requirement to prevent subsidence (true for all revision stems). Restoration of hip mechanics (offset, leg length and stability) is fundamental to the clinical result. TCR stems have instrumentation and techniques that ensure this happens, since all this occurs AFTER distal stability is achieved.

Modular TCR versions have some advantages. The proximal body size and length can be adjusted AFTER stem insertion if the stem goes deeper than the trial. Any proximal/distal bone size mismatch can be accommodated. If the surgeon believes that proximal bone ingrowth is important to facilitate proximal bone remodeling, modular TCR stems can more easily accomplish this. Further, proximal bone contact and osseointegration will protect the modular junction from stress and possible risk of fracture.

Monolithic TCR versions also have some advantages. Modular junction mechanical integrity cannot accommodate smaller bone sizes. Shorter stem lengths are not available in modular versions, and shorter TCR stems are an option in many revision cases. The possibility of modular junction corrosion is eliminated and fracture of the stem at that junction, of course, is not possible. The monolithic stem option is less expensive as well.

Consider Modular TCR stems in your learning curve, if you feel proximal bone osseointegration is important and if proximal/distal size mismatch is present. Consider Monolithic TCR stems after your learning curve to reduce cost, when a short stem works, and if a small stem is needed.

Both Modular and Monolithic stems can be used for ALL cases with equal quality of result.

Dual mobility (DM) cups have 2 points of articulation – between the shell and the polyethylene (external bearing) and between the polyethylene and the femoral head (internal bearing). Primary motion occurs at the inner bearing while the outer bearing moves only in cases of extreme range of motion.

Dislocation is a top reason for revision surgery and a major cost burden on society. Instability is also a significant problem after revision THA. While a variety of factors are important in hip stability, DM cups provide the safety of larger femoral heads in virtually all patients. These larger heads increase jump distance (the distance the femoral must travel before dislocation occurs) and they also increase ROM before impingement occurs.

ROM and impingement are competing with each in primary THA. Especially in the flexible female with small bone structure, their increased ROM significantly increases the risk of impingement during physiologic activities. While not necessarily leading to dislocation, subluxation can occur resulting in pain. Further, ongoing impingement reduces the longevity of the PE. The ability to increase head size and head-neck ration with the DM cups in these patients is both an immediate and long-term advantage.

PE thickness still can compromise the integrity of the liner. DM cups have thicker PE, especially in the smaller size cups than standard PE inserts. Even with the dual articulation, PE wear in DM cups are less, or at worst, equivalent to standard cups while at the same time providing adequate PE thickness for PE integrity and longevity.

The most important advantage of modular revision stems is versatility - managing ALL levels of femoral bone loss (present before revision or created during revision). The surgeon quickly gains familiarity with the techniques and instruments for preparation and implantation and subsequently masters its use for all variety of situations. This allows the operating room staff to become comfortable with the instrumentation and components. This ability to use the stem in a variety of bone loss situations eliminates intraoperative shuffle (changes in the surgical plan resulting in more instruments being opened), as bone loss can be significantly under-estimated preoperatively or may change intraoperatively. Furthermore, distal fixation can be obtained simply and reliably.

The most critical advantage is the ability to separate completely the critical task of fixation from other important tasks of restoring offset, leg length, and stability. Once fixation is secured, the surgeon can concentrate on hip stability and on optimization of hip mechanics (leg length and offset). This allows the surgeon to maximise patient functionality postoperatively. Additionally, the surgeon can control the diameter of the proximal body to ensure proper bony apposition, especially if an extended trochanteric osteotomy was made to obtain femoral exposure.

The most under-appreciated advantage is the straightforward instrumentation that makes the operation easier for the staff and the surgeon, while enhancing the operating room efficiency and reducing cost. Also, although the implant itself may result in more cost, most modular systems allow for a decrease in inventory requirements, which make up the cost differential.

INTRODUCTION

While standard instrumentation tries to reproduce mechanical axes based on mechanical alignment guides, a new “shape matching” system derives its plan from kinematic measurements using pre-operative MRIs. The current study aimed to compare the resultant alignment in a matched pair cadaveric study between the Shape Match and a standard mechanical system.

In minimally invasive direct anterior total hip arthroplasty double offset broach handles are used, in order to facilitate the preparation of the femoral canal. The maximum value of the main force peak and the impulse of two types of double offset broach handles (A European version, B American version) were compared to a single offset broach handle (S). Results have demonstrated that the highest values of the main force peak and force impulse were found in the single offset broach handle. Broach handle A had higher impulse values and lower maximum force values compared to broach handle B. In double offset broach handles less energy is transmitted to the tip. Broach handle A has a lower force peak than B and therefore a reduced risk of bone fracture.