Keywords

10.1 Introduction

The goals of total knee arthroplasty (TKA) are to relieve the pain of end-stage arthrosis, restore mobility and improve a patient’s quality of life. This should be done with the least trauma to the patient and should produce a result that is sustained over the longer term. Although decades of research and development have produced implants that are modelled on native anatomy and provide excellent outcomes, the artificial joint is still not able to completely reproduce the function of a native knee joint. Achieving the optimal result from any particular implant is reliant on precise surgical technique and optimised perioperative care. Many advances in surgical technique have been introduced in the last decade, leading to improved outcomes, and the purpose of this chapter is to describe the basic concepts of surgical technique in TKA, including an evidence-based analysis of newer techniques and their utility in improving the outcomes of this surgery.

10.2 Preparation and Patient Setup

On the day of surgery the patient should be identified by the surgeon and the correct side confirmed and marked. All relevant imaging should be displayed in the operating room. Preoperative shaving and prepping with antiseptic such as iodine prior to entry to the operating room is the author’s preference, although the option of shaving and antiseptic washing in the operative room is an acceptable alternative and largely depends on surgeon preference. A urinary catheter is usually inserted, particularly if spinal anesthesia is used, and the catheter is placed away from the surgical field.

The knee is positioned at approximately 90° of flexion with a foot support and a side support adjacent to the proximal thigh, such that the leg is stable in this position without additional support. Operating lights should be then focussed on the operative field as light handles carry a risk of contamination and are best avoided. If computer navigation is used, this is then activated and appropriately positioned (Fig. 10.1).

Fig. 10.1
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Positioning the patient and application of isolation drapes

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10.2.1 Anesthesia

The author’s preference for the majority of patients undergoing TKA is spinal anesthesia with accompanying sedation. Patients will usually request varying levels of sedation from very light to full general anesthesia, and this can be prescribed individually. Spinal anesthesia has a number of advantages: hypotensive effect that reduces intraoperative bleeding, particularly if the surgery is undertaken without tourniquet; postoperative analgesia effect that usually results in minimal or no pain for approximately 24 h which is reassuring for patients and facilitates ongoing pain management; protection against deep venous thrombosis (DVT); and less nausea due to avoidance of general anesthesia [1].

Periarticular local anaesthetic injections have been shown in a number of studies to provide a significant benefit in management of postoperative pain and have become a routine for most TKA surgeons [2]. Various “cocktails” have been described, with the author’s preference being use of 100 ml of 0.2 % ropivacaine, admixed with adrenaline and ketorolac, injected evenly throughout the knee joint capsule intraoperatively. Peripheral nerve blocks have also been used extensively in TKA surgery. Whilst there is no doubt that these blocks may provide excellent ancillary analgesia, there is a significant risk of complications with these techniques. Although uncommon, neuralgia post nerve block can lead to persistent pain postoperatively, sometimes indefinitely. The author has published separate studies about complications of femoral nerve blocks for knee surgery and comparative studies of femoral nerve blocks versus intra-articular injection of local anaesthetic, with the ultimate conclusion that the potential benefit of nerve block over intra-articular injection is marginal and not enough to justify the risk of nerve block, which was therefore discontinued [3].

10.2.2 Use of Tourniquets

Use of pneumatic tourniquet has become a routine in lower limb surgery, but in recent times it is used less in TKA by many surgeons, including this author. Avoidance of tourniquet results in less postoperative pain, improved postoperative quadriceps recovery and reduced thrombosis [4]. The potential disadvantage of this approach is increased intraoperative bleeding, with greater difficulty in visualisation. There may also be compromise of cementing technique if the field cannot be adequately dried. Maintenance of relative hypotension during the procedure, particularly facilitated by spinal anaesthetic, significantly reduces bleeding and negates these potential issues. This obviously requires a good understanding from the anaesthetist, but if done properly can result in a relatively dry surgical field, with less overall blood loss. A meta-analysis of over 800 citations concluded that tourniquet usage in TKA does not have a statistically significant advantage [4]. The author’s practice is therefore to not use a tourniquet in the presence of good hypotensive anesthesia. A tourniquet can be applied to the thigh and just inflated in cases of excessive intraoperative bleeding, but if adequate hypotensive anesthesia is achieved, then the need for this is rare.

10.2.3 Surgical Prep, Draping and Antibiotic Cover

Perioperative infection has become relatively rare in joint replacement, due to careful aseptic technique, improved operating room conditions and judicious use of perioperative antibiotics. Prepping and draping is an important preliminary step in avoidance of infection and should be performed carefully under supervision of the operating surgeon. The author’s preference is to use an iodine with alcohol formulation for prepping and to apply this to the entire leg including the foot. Draping is then completed, including a stocking to cover the leg, an adhesive U-drape to exclude the proximal region and an extremity drape to cover the entire field. The operative site is then exposed by cutting the stocking in the midline, and an iodine-impregnated adhesive sheet is then applied over the area (Fig. 10.1).

10.3 Surgical Approaches

10.3.1 Skin Incision

The skin incision for TKA should allow easy access to the chosen deep approaches, be extensile and, where appropriate and possible, incorporate previous incisions. A sound understanding of the blood supply of the skin around the knee joint is important and should be respected. The saphenous and lateral descending geniculate arteries are the main supply to the medial aspect of the knee [5, 6]. If more than one previous incision is present and possible to use, the more lateral one is less likely to cause skin breakdown. If previous scars are present from many years earlier, and are inappropriate for incorporation into a new incision, then an assumption can be made that a new midline incision can be safely used.

The anterior midline incision is the gold standard as it provides access to the medial and lateral aspects of the knee. It is usually centred over the medial edge of the patella, for the more common medial parapatellar arthrotomy and over the lateral margin of the patella and patellar tendon if a lateral arthrotomy is planned. This incision is extensile and lets the surgeon perform the conventional approaches. Healing rates and tensile strengths of the subsequent scars are theoretically improved if incisions are parallel to the Langer’s lines, and a more curved incision may achieve this [6]. The length of the skin incision will vary depending on the patient and surgeon and should allow clear exposure of the deep approach, without undue tension on skin edges. It is important to elevate full-thickness flaps to maintain adequate vascularity, and flaps should only be elevated sufficient to expose the deep approach. The arthrotomy is usually offset from the skin incision to avoid a direct pathway for communication with the external environment.

10.3.2 Medial Parapatellar Arthrotomy

This is the most commonly used approach for TKA and is an excellent extensile approach that can be used in virtually all primary knee arthroplasty. Following the skin incision, the arthrotomy will divide extensor mechanism, capsule and synovium in one layer and will usually begin approximately 5 cm proximal to the superior pole of the patella, leaving a 5–10 mm cuff of tendon attached to the vastus medialis obliquus (VMO) and distally around the medial edge of the patella and patellar tendon to the level of the tibial tubercle. A small cuff of retinaculum should be left on the patella, and paratenon on the tendon, for later closure. A transverse pen marking can be made at the level of the patella prior to the arthrotomy to guide later closure. The fat pad is partially excised, sufficient for exposure, and the anterior horns of both menisci divided. A release of the anterior part of the medial collateral ligament (MCL) attachment is then done sufficient to expose the tibial plateau to the level of likely resection. The patella is then either everted or simply dislocated laterally. Studies comparing patellar eversion to dislocation without eversion have suggested that the latter approach results in reduced postoperative pain and improved quadriceps recovery. Excision of fat and synovium immediately proximal to the trochlea is done sufficient to expose the site of anterior resection. If necessary, improved exposure can be achieved by extending the medial release, particularly in cases of fixed varus deformity, or by extending the quadriceps incision proximally.

10.3.3 Subvastus Approach

This approach is considered by proponents to be more “biological” than the medial parapatellar arthrotomy as it does not violate the quadriceps tendon and lifts the vastus medialis muscle as a whole. The skin incision is the standard midline, and the inferior border of the vastus medialis obliquus is then identified. The arthrotomy begins by incising the fascial sheath along this border from the patella medially to the intermuscular septum. The incision then continues distally along the medial patellar retinaculum along the medial border of the patella and along the medial patellar tendon to the tubercle. The vastus medialis is then peeled off the intermuscular septum, and the capsule of the suprapatellar pouch is then incised proximally to gain access to the joint and dislocate the patella.

This approach has the added advantages of preserving vascularity and causing less pain postoperatively although it may be more difficult to visualise the surgical field, particularly in larger patients or in cases of significant deformity, for whom this approach would therefore usually be unsuitable [7, 8]. Patients who have limited motion, severe flexion contracture, severe valgus alignment, patella baja or obese are not good candidates for this approach. Although this approach is technically more demanding, in appropriate patients it has been shown to have faster functional recovery, less postoperative pain and better knee flexion than the medial parapatellar approach [9, 10].

10.3.4 Lateral Parapatellar Approach

The lateral approach is for many surgeons the preferred choice in valgus deformities. It affords an excellent exposure of lateral structures that may require release for deformity correction and also preserves the medial ligament. It is particularly useful in cases of severe fixed valgus deformity, with lateral patellar subluxation. Potential difficulties include posteromedial exposure and a tendency to excessively externally rotate the tibial component. The skin incision is anterior longitudinal, just lateral to the midline and centred over the lateral margin of the patella. The arthrotomy begins proximally in the quadriceps tendon 5–10 mm medial to the vastus lateralis, from approximately 5 cm proximal to the patella distally around the lateral margin of the patella to the lateral edge of the tibial tubercle. The fat pad is partially excised for exposure, but it is beneficial to preserve as much fat pad as possible as this will assist in closing the defect lateral to the patellar tendon at the end of the procedure. The patella is dislocated medially, and the iliotibial band and lateral capsule can be released under direct vision as necessary for deformity correction.

10.3.5 Approaches That Pass Through the Quadriceps

10.3.5.1 Midvastus Approach

The benefits of the midvastus approach are that it violates less of the extensor mechanism whilst still providing a good surgical exposure [11]. The distal part of the arthrotomy is the same as the medial parapatellar approach, whereas proximally the arthrotomy extends through the centre of the VMO parallel to and splitting the muscle fibres. The capsule and synovium are then split longitudinally to the proximal limit of the suprapatellar pouch. The traditional midvastus approach extends the muscle split to the intermuscular septum, whereas a “mini-midvastus” extending just 2–3 cm into the muscle has been popularised as a minimally invasive approach. The theoretical advantage of this approach is that it preserves the lateral half of the VMO attachment, whilst still providing a good exposure for most cases. The main limitation is its non-extensile nature and therefore should be avoided in cases for which a difficult exposure is predicted.

10.3.5.2 Quadriceps Sparing Minimally Invasive Approach

Another variant popularised as a minimally invasive approach in recent years, this approach essentially involves a medial parapatellar arthrotomy extending distally from the superior pole of the patella and not extending proximally into the quadriceps tendon. This approach was particularly promoted by companies with side-cutting instruments to be used from a medial direction. It uses a short skin incision and was endorsed by a small number of authors [12]. The exposure obtained is not as good as with a standard arthrotomy and should be used with caution only in straightforward cases. As with other “minimally invasive” approaches, there is little evidence of any sustained improvement in outcome over standard approaches.

10.3.6 Extended Approaches

10.3.6.1 Quadriceps Snip

This extension is a simple addition to a standard medial parapatellar arthrotomy, allowing improved exposure particularly in knees that are stiff and difficult to visualise with the standard approach [13]. Having performed a standard medial arthrotomy and assessed the need for additional exposure, a 45° oblique incision is made in the proximal quadriceps tendon towards the vastus lateralis. This incision relieves tension on the extensor mechanism and tibial tubercle [13]. Another, more aggressive approach is the Coonse–Adams quadriceps turndown which involves a standard medial arthrotomy, with the incision in the quadriceps then taken distally and laterally from its proximal limit, distally to the lateral margin of the patella. This then allows complete displacement of the patella and excellent exposure, but is rarely used due to the high risk of patellar avascular necrosis [14].

10.3.6.2 Tibial Tubercle Osteotomy

This extended approach allows excellent exposure in knees that are particularly stiff and difficult to expose without undue tension on the patellar tendon attachment. It is also useful in revision arthroplasty to gain access to the medullary cavity for cement removal. Using an oscillating saw and osteotomes from the medial side, the tubercle is elevated from the tibia preserving the lateral periosteal hinge. The osteotomy is trapezoidal and approximately 5 cm long and tapered distally towards the anterior cortex [15]. Refixation of the tubercle is most commonly done with cerclage wires through or around the tubercle and secured through the posteromedial cortex.

10.4 Bony Cuts

The amount of bone resected to accommodate the prosthesis usually corresponds to the thickness of the component being implanted, otherwise known as “matched resection” in which the thickness of the resection is “matched” to the thickness of the implant. This thickness is implant specific with minor variations between implants. There are five standard femoral cuts in all prosthetic designs.

10.4.1 Distal Femoral Cut (Fig. 10.2)

Fig. 10.2
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Distal femoral resection equivalent to the thickness of the component (matched resection)

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For most implants this corresponds to 8–10 mm from the less affected surface. For example, in a varus knee the less affected side is lateral, and this serves as a guide to the correct joint line. This cut selectively influences the extension gap, and the amount resected can be adjusted depending on the surgeon’s desire to influence extension. In most cases a matched resection is performed, but additional resection may be considered in cases of fixed flexion deformity, particularly in cases with unrestricted flexion such that a preoperative flexion–extension imbalance is evident. Increased resection will raise the joint line, with implications for ligament balancing and patellar height.

10.4.2 Posterior Femoral Cut (Fig. 10.3)

Fig. 10.3
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The anterior, posterior and chamfer resections

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This cut selectively influences the flexion gap. In most cases, a matched resection is indicated to restore posterior offset whilst avoiding overstuffing the flexion gap and restricting flexion. Increased resection can be considered in cases of relative flexion tightness, particularly after checking balancing after initial standard cuts, but excessive resection should be avoided as this will lead to flexion instability.

10.4.3 Anterior Femoral Cut (Fig. 10.3)

This cut will directly influence the anterior compartment and associated patellofemoral joint. In general the proximal limit of the cut should be flush with the anterior cortex of the femur, and whilst it is often not possible to perform a perfectly matched resection with this cut, care should be taken to remove at least as much bone as will be replaced by the prosthesis.

10.4.4 Anterior and Posterior Chamfer Cuts (Fig. 10.3)

These cuts do not directly affect bony gaps and will vary between different prosthetic geometries.

10.4.5 Tibial Cut

This cut equally affects flexion and extension gaps. The depth of the cut is usually 8–10 mm, but will be varied depending on implant thickness and patient factors. In particular, if the knee has equivalent significant restriction in extension and flexion, increased tibial resection will be beneficial in restoring range of motion.

10.5 Sizing of the Femoral Component

Selection of femoral component size is one of the more critical aspects of success with knee arthroplasty. Oversizing the component can result in pain and stiffness, whereas undersizing most commonly results in flexion instability. Implants are “off the shelf”, and although many companies now have a wide range of sizes, due to the variability in femoral anatomy, it is not usually possible to obtain an exact match, and therefore the surgeon’s judgement is critical to making the most appropriate selection.

The sizing of the femoral component is conventionally done in the anteroposterior plane, although assessment of prosthetic width to avoid any medial or lateral overhang is also important. Anterior or posterior referencing for sizing can be used, although experienced arthroplasty surgeons will have an appreciation of both concepts and use this knowledge to achieve the optimal prosthetic size and fit.

10.5.1 Anterior Referencing System

This concept prioritises the anterior cut using a point on the anterior femoral surface as a reference, in order to achieve a flush cut but avoid femoral notching; thus, the posterior resection is variable. If the assessment is between sizes, the smaller one is selected to avoid overstuffing the posterior space. This has the potential effect of a larger posterior resection, with a larger flexion gap and possible flexion instability.

10.5.2 Posterior Referencing System

This concept prioritises a matched resection posteriorly to restore posterior offset and avoid flexion instability. The posterior femoral condyles are the reference, and if between sizes the traditional recommendation is to choose the larger size in order to avoid femoral notching anteriorly. In practice however, in most cases it is usually possible to downsize and accept a small femoral notch anterolaterally. This is unlikely to increase risk of periprosthetic fracture and achieve the goals of restoring posterior offset without overstuffing anteriorly.

10.6 Concept of Gaps

Understanding the concept of flexion and extension gaps is fundamental to achieving the critical goal of a well-balanced knee arthroplasty. The extension gap refers to the gap between the distal femoral cut and tibial cut in extension, and the flexion gap is between the posterior femoral cut and the tibial cut, usually assessed at 90° of flexion. The goal is to have “balanced gaps”, i.e. equal tension in medial and lateral compartments in full extension and 90°. This is classically measured with spacer blocks (Fig. 10.4), but some systems will have a more dynamic method such as tensiometers, or this can also be measured throughout the range of motion with some navigation systems.

Fig. 10.4
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Gap balancing – a spacer block is placed between the posterior femur and the tibia at 90° – of knee flexion. This should be balanced coronally and matched to the gap between the distal femur and the tibia in full extension

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10.7 Surgical Technique: Gap Balancing Versus Matched Resection

There are two commonly used approaches to achieve the goal of a well-balanced knee arthroplasty: gap balancing and matched or measured resection. Which technique is used largely relates to surgeon preference and implant type. Both techniques can achieve good results, and there is no evidence to strongly favour one over the other. Most experienced surgeons will understand both techniques, and whichever technique is chosen it is therefore critical to understand the principles of the technique, as well as the potential limitations.

10.7.1 Gap Balancing

The primary principle of this technique is balancing flexion and extension gaps, with prosthetic alignment, particularly positioning of the femoral component secondary. After osteophyte excision the tibial cut is performed first, and referencing for positioning of the femoral cutting block is then taken from the tibial cut and directed by ligament tension. Having completed the posterior femoral cut, the resultant flexion gap is assessed. The knee is then brought into extension and the distal femoral cut completed at a depth to match the previously measured flexion gap. Having done this, the gaps are usually well balanced, and femoral finishing cuts are completed. Potential limitations of this technique are that it relies on the integrity of the collateral ligaments and an accurate tibial cut, as minor alterations in the tibial cuts could affect femoral component rotation and joint line. This should not be a significant problem for surgeons who have a good understanding of appropriate femoral component rotation and how to assess this intraoperatively.

10.7.2 Matched (Measured) Resection

The primary principle of this technique is reproduction of femoral anatomy, and ligament balancing is then done secondarily. Restoring joint line and posterior offset is felt to be critical to outcome, and this therefore dictates the bony cuts. This technique usually begins with standard femoral resection to match the thickness of the implant, followed by a standard tibial cut. The gap balancing is then assessed secondarily with spacer blocks or tensiometers (Fig. 10.4). Coronal plane imbalances are addressed with appropriate ligament releases and any residual flexion–extension imbalances addressed with further bony resection. The end goal is a knee that resembles original anatomy as much as possible whilst still being well balanced. The main potential drawback of this technique is that proper identification of bony landmarks is crucial for the resection, although in experienced hands this should not be a concern [16, 17].

10.8 Tibial Component Sizing and Positioning

Tibial component sizing and positioning requires a clear exposure of the entire cut surface and cortical rim and a clear understanding of optimal tibial rotation as described later in this chapter. The goal is to choose the tibial size that when appropriately rotated provides maximal coverage, with minimal underhang and preferably avoiding overhang. Symmetrical components will tend to provide less coverage than more anatomical asymmetric components, although this has not been shown to confer any significant clinical difference [18]. Ideally the prosthesis should rest on the cortical rim for the majority of its perimeter. Underhang is generally preferable to overhang and can therefore be accepted in small areas, although care should be taken in patients with marked osteopenia or in cementless components that require cortical support.

10.9 Optimal Alignment of the Knee

Malalignment is a well-described cause of early prosthetic failure, and therefore all available measures should be taken to make this part of the procedure as accurate as possible [19]. Use of computer navigation and other technologies will be covered in other chapters of this book, but in summary navigation is well established as more accurate for coronal and sagittal alignment with no demonstrable benefit for component rotation. Navigation also allows “real-time” assessment of each cut and the final alignment. Whether navigation or manual instrumentation is used, it is important to understand the assumptions and limitations inherent with any chosen instrumentation system. Extra-articular deformities also effect the final alignment and must be accurately measured with appropriate preoperative imaging to allow appropriate intraoperative adjustments to be predicted.

Alignment in all three planes needs to be carefully considered. The distal femoral cut will determine coronal and sagittal alignment, with ideal coronal alignment usually perpendicular to the mechanical axis and ideal sagittal alignment less clear but usually between 0° and 5° flexed with respect to mechanical axis. If not using navigation, intramedullary systems and extramedullary rods parallel to the femoral shaft or aimed towards the femoral head are used for femoral component placement. If the femoral shaft is used as the reference, it is usually assumed that this is approximately 5–7° valgus relative to the mechanical axis.

Tibial alignment in both sagittal and coronal planes is also determined by the proximal resection. Navigation or intramedullary or extramedullary instrumentation is used to perform the resection perpendicular to the mechanical axis of the tibia in the coronal plane. In the sagittal plane, the degree of posterior slope is dictated by design of the chosen prosthesis and is usually in the range of 0–5°.

Axial plane alignment is referred to as component rotation. Rotation of both femoral and tibial components, and the congruence between them, is critical to a good outcome, with errors in component rotation, a common cause of poor outcomes and patient dissatisfaction [19].

Femoral component rotation will have implications for patellar tracking and the balancing of the flexion space. In gap balancing techniques femoral rotation will be determined by the tibial cut and ligament tension, whereas in matched resection it will be determined from anatomical landmarks (Fig. 10.5). In practice surgeons using either technique should appreciate the anatomy and the effect of the chosen alignment on balancing. Rather than relying on one landmark only, it is best to assess all available landmarks to achieve the best possible alignment. Anatomical landmarks most commonly used include:

Fig. 10.5
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Femoral axial alignment axes. (A) AP axis; (B) trans-epicondylar axis; (C) posterior femoral condylar axis

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  1. 1.

    Whiteside’s line anteroposterior (AP) axis of the femoral sulcus: the femoral component should be perpendicular to this line. This may be less reliable in patients with a valgus deformity and trochlear dysplasia [20, 21].

  2. 2.

    Posterior femoral condyles: the femoral component should be on average 3° externally rotated to this line. There can be a large variability in posterior condylar anatomy, and therefore this technique should usually be used in combination with other landmarks [22, 23].

  3. 3.

    Trans-epicondylar axis: although not universally agreed upon, this is felt to best represent the rotational axis of the femur, and therefore the femoral component should be placed parallel to this [6, 24].

Tibial component rotation will impact upon patellar tracking, tibiofemoral congruence and rotation of the patient’s foot. The primary axis on the tibial cut surface is a line from the centre of the PCL attachment to the junction of the medial and middle third of the patellar tendon attachment [25]. Once aligned to this axis, the congruence with the femoral component can be checked in extension and flexion and the position of the foot in extension. Excessive external rotation will lead to intoeing postoperatively. Once these checks are completed, the rotation is confirmed and marked. Other described landmarks are the posterior condylar line of the tibia [26], the mid-sulcus of the tibial spine [27, 28] and the transcondylar line of the tibia [29, 30]. These landmarks may be affected by osteophyte formation and bone loss and should be used with caution.

10.9.1 Patellar Component Placement

Whether or not a patella is resurfaced depends largely on disease pattern and surgeon preference. The two main techniques are inlay reaming for an inset component or a saw cut for an onlay component. Avoiding complications requires familiarity with the system and careful technique. General principles are to avoid “overstuffing”, to produce a resurfaced patella that is either the same thickness or slightly thinner than the original patella and to align the patella so that it tracks centrally throughout the range of motion. Positioning of the component should place the apex of the dome in line with the original median ridge of the patella, which is medial to the centre of the cut surface. Patellar tracking should be assessed prior to closure, with tourniquet deflated, navigation pins removed and a single suture in the medial retinaculum. If the medial facet is not seated on the medial femoral condyle in flexion, a soft tissue release is required. The iliotibial band should be palpated and if tight should be released. If this does not improve tracking, then progressive release of the lateral retinaculum is performed until the medial facet of the patella is well seated. Complete retinacular release is uncommon.

10.10 Ligament Balancing

Knowledge of the anatomy of the ligaments around the knee, their function and their tension in different positions is critical to planning appropriate ligament releases when balancing a knee arthroplasty. In knees without fixed deformities, ligament releases are not usually necessary other than for exposure. In cases of fixed coronal deformity or fixed flexion deformity, releases are usually required. These can usually be predicted based on the deformity, but are reassessed at the time of gap balancing and again after trial component placement. The findings then dictate the stepwise progression of ligament release and reassessment as outlined in the figures below (Figs. 10.6 and 10.7). These algorithms provide a general plan for sequential releases, but should be individualised for each case depending on surgeon judgement. Popliteus tendon release should be reserved for cases of severe fixed valgus deformity only, as it is a musculotendinous unit with some inherent elasticity, and a recent study has demonstrated functional benefits of popliteus preservation [31, 32]

Fig. 10.6
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Suggested algorithm for ligament balancing in a varus knee33

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Fig. 10.7
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Suggested algorithm for ligament balancing in a valgus knee33

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10.11 Use of Wound Drainage

The use of drains in TKA has evolved from being a routine practice to less common currently and determined by individual surgeon preference [33]. There have been few studies showing an increase in allogenic transfusion in patients in whom drains are not used as compared to those in which it is used [34], whereas most studies have shown no benefit in routine wound drainage. The increased cost, as well as the pain and inconvenience for the patient associated with a drain, would not seem justified [34, 35]. Avoidance of tourniquet usage, combined with efficient haemostasis, also decreases the need for drainage, and the author does not use wound drainage for TKA.

10.12 Antifibrinolytic Agents

Tranexamic acid has been routinely used in other surgical specialties, and in recent times its benefit in decreasing swelling, blood loss and the requirement for blood transfusion in knee arthroplasty has been established. A number of controlled trials, as well as a Cochrane review that included 21 articles on the use of tranexamic acid, have confirmed its efficacy [36]. The benefits have been shown with both intravenous and intra-articular use, and it is the author’s practice to administer an intravenous dose with induction of anesthesia and an intra-articular injection after extensor mechanism closure and prior to skin closure. The intravenous dose is omitted in patients with a history of thromboembolic disease.

10.13 Wound Closure

Predictable wound healing is critical to the outcome of knee arthroplasty, particularly for avoidance of infection [37]. The importance of a good cosmetic outcome to the patient’s satisfaction should also not be underestimated. Many variations of closure technique exist depending on surgeon preference, with the important universal goals being to obtain a watertight closure of the joint capsule to avoid postoperative wound ooze, a durable extensor mechanism repair that can withstand the rigours of postoperative rehabilitation and a good cosmetic closure of the superficial layers. The wound is conventionally closed in three layers: extensor mechanism, subcutaneous fat and skin. The extensor mechanism is first closed with intermittent heavy sutures in the parapatellar region in extension, beginning at the level of the previous pen mark made prior to arthrotomy. It is then oversewn along its length with the knee in flexion. The fat layer is closed with deep intermittent sutures to close any dead space, and then with a continuous suture, after which the skin closure is completed. The author’s preference is a subcuticular suture using a barbed resorbable suture, reinforced with fibrin glue and steristrips placed longitudinally.

10.14 Simultaneous Bilateral TKA

Not uncommonly, patients will present with bilateral symptomatic knee arthrosis requiring arthroplasty, and surgeons and patients need to choose between either having the surgeries as a staged procedure or as a simultaneous procedure. The definition of “simultaneous” is variable in the literature, but the senior author’s definition is to perform the procedures sequentially under the same anaesthetic. Some surgeons will prefer doing staged procedures, due to the commonly held perception of increased morbidity and mortality, with some support from earlier literature. However, more recent literature would suggest that there is no increased risk with this approach, except possibly for a slightly increased risk of blood transfusion. Particularly, when compared to the cumulative risks of two separate procedures, the simultaneous procedure may even be a safer option for patients. Additional factors have probably contributed to the decreased risk, including avoidance of tourniquets and the use of computer navigation which negates the need for intramedullary instrumentation and resultant fat emboli. From a patient’s perspective, the convenience of having one less operation is appealing, including the reduced overall time in hospital and rehabilitation and reduced cost [38].

Previous studies have demonstrated lower morbidity, and few others have refuted this [39–52]. The incidence of deep vein thrombosis (DVT) has been shown to be less if not same as that of a staged procedure [48]. Pulmonary thromboembolism does not have an increased incidence in bilateral simultaneous procedures barring one study [41]. The satisfaction rates are uniformly high in most previously done studies. Jenny et al. in 2013 showed that 65 % patients would undergo the surgery again and 57 % would recommend it to a friend, whereas Leonard et al. showed that 95 % of patients would choose getting a bilateral simultaneous knee replacement done again [53, 54].

10.15 Minimally Invasive TKA (Fig. 10.8)

Fig. 10.8
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Minimally invasive TKA

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The concept of minimally invasive knee arthroplasty has been popularised in recent years, but due to the failure to demonstrate a consistent benefit across several studies and a higher complication rate, this has not become a routine practice. Several studies have shown better improvement in early postoperative rehabilitation but the same as a conventional TKA after 6 months [55]. There have been at least three meta-analyses and one systematic review. Smith et al. in their meta-analysis showed superior function with minimally invasive surgery (MIS) and no added complications, whereas Cheng et al. showed better recovery but delayed wound healing and increased incidence of infections in the MIS groups [55, 56].

This concept has however introduced some advances in technique and instrumentation that have been widely adopted. The surgical approaches that have been popularised have been described earlier, but the principles can apply to any chosen approach and essentially involve careful soft tissue handling, and using as large an exposure as necessary to perform the procedure safely, but avoiding any excessive or unnecessary soft tissue dissection and damage. Specific retractors and smaller instrumentation (Figs. 10.8 and 10.9) facilitate safe use of a smaller exposure. Retractors are used in a symbiotic manner, relaxing them alternately according to the area that is being addressed. The knee can be extended to expose the anterior areas and flexed to expose the posterior areas. Capsular releases are done superior and inferior to the patella on exposure. The patella is not everted, with the benefits previously described, and the tibia and femur are carefully cut in situ, avoiding joint dislocation. Clearly the size of implants and the need for adequate safe exposure will always dictate a minimum required exposure, but whilst no benefit occurs from having a small skin incision, many of the principles introduced with minimally invasive arthroplasty have provided some benefits to surgeons and patients.

Fig. 10.9
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MIS (minimally invasive surgery) principles have led to smaller, more anatomical cutting guides and instruments. Here, a modern cutting block on the left is compared to an older style cutting block on the right

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10.16 Conclusions

Total Knee Arthroplasty has become a routine, and very successful surgical procedure. Key elements in achieving success include knowledge of the various techniques to obtain adequate exposure, as well as a thorough understanding of the principles of knee arthroplasty, particularly the skills and techniques required to obtain an accurately aligned, stable, and well balanced knee arthroplasty. In addition to appropriate patient selection and postoperative rehabilitation, these are the critical factors to achieving success with this procedure.