Introduction                       

Total hip replacement (THR) is widely considered as one of the most successful orthopedic procedures in terms of quality of life and cost-effectiveness, and has been rightly termed as the ‘operation of the (20th) century’.1 Preoperative planning is the first and most important step in performing a successful THR. The goals of preoperative planning are to restore the hip biomechanics (center of rotation, offset and limb length), and to anticipate and minimize the risks and complications in terms of component malpositioning, impingement, dislocation and fixation failure.2,3 Many of these factors are under the control of the surgeon; thus, a thorough preoperative plan may mitigate the likelihood of failure. Preoperative planning also help shortening the learning curve for the surgeon, especially with newer implant, newer procedure or newer approach.3 It is important to consider the entire patient rather than just the hip and the planning consists of numerous crucial steps even before a surgeon decides about type of prosthesis, fixation, bone grafts and other accessories. It includes a thorough history, physical examination, appropriate laboratory work-up and radiologic examination-

—all towards an accurate diagnosis and its successful treatment.

 

Preoperative Planning in Primary Total Hip Replacement

 

History     and     Physical     Examination              

Establishing an accurate diagnosis is the first step in successful planning for a THR and starts with a detailed patient’s history, review of systems, and physical examination.

It should be kept in mind that a wide spectrum of musculoskeletal and non-musculoskeletal diseases can present with a chief complaint of hip pain and thus determination of the patient’s source of symptoms is important.4 Detailed questioning is done to clarify the symptoms— location, intensity, character, onset, duration, severity, alleviating and aggravating factors, and associated symptoms. A history of childhood or adolescent hip disease, previous hip surgery, hip trauma, risk factors for avascular necrosis, history of inflammatory arthritis, the current medical problems and medications should also be determined. Review of systems is equally important as detailed below. A history of remote infection or prior failed or painful hip surgery needs additional work-up including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and hip aspiration. Such patients may also need frozen sections during surgery and thus coordination with pathology department may be needed. Whenever necessary, it is prudent to retrieve the previous operative notes, implant details and the pathologic results. If a patient has a well-functioning THR on contralateral side, types and sizes of the prosthesis should be sought with an aim to reproduce the results. Bone defects

 

 

 

 

Total Hip Arthroplasty

 

Figure 3.1: (A) AP and (B) False Profile radiographs of the left hip showing a deformed proximal femur with coxa vara and brevia (history of Perthes disease).

(C) Because of the deformed proximal femoral anatomy, this patient was treated with modular S-ROM (DePuy, Warsaw, IN) prosthesis with a ‘dial-in’ anteversion

 

like cortical thinning or screw holes from previous implants may necessitate longer stemmed implants to avoid stress risers, with or without strut allografts.

Physical examination includes patient’s general condition and body habitus. In general, large muscular males and obese patients are more likely to lead to difficulty with exposure.3 Posture and gait pattern are observed. In-toeing may indicate excessive femoral anteversion. This may be further suggested by increased internal rotation (usually > 70°)5 with limited external rotation at the hip, and can be confirmed with a computed tomography (CT) scan. A deformed proximal femur with excessive anteversion (e.g. dysplasia) or retroversion (SCFE; slipped capital femoral epiphysis) can alter the choice of implant (especially with uncemented system, where there is no substantial control of the anteversion). In these cases, ‘dial-in’ modular implants may be more advantageous (Fig. 3.1).3,6-8 Derotation and/or shortening osteotomy may rarely be indicated in extreme cases of complex anatomy. Hip abductor function is assessed by Trendelenburg test and side lying abduction strength testing.3 In cases with weak abductors, the surgeon should try to at least maintain, if not try to increase, the femoral offset to aid the abductor lever arm. Primary stability is of utmost importance in these cases, and rarely, a primary constrained liner may be considered.3,6-8 While assessing range of motion, it is important to steady the pelvis to appreciate the end point and forced motion of the pelvis through the hip. Similarly it is important to differentiate the motion from the spine. Deformities and contractures should be noted. A substantial adduction contracture may necessitate a percutaneous adductor tenotomy prior to the THR.3 Various clinical tests have been described for assessing the range of motion, contractures, intra-articular and/or labral pathology but are beyond the scope of this review.4.5 It is also important to evaluate the previous surgical scars as well as the current neurovascular status of the limb.

Functional and real limb length discrepancy (LLD) should be distinguished and quantified.3-9 It is important to correlate this with patient’s own feeling of limb length, clinical and radiographic measurements. A functional discrepancy may be secondary to a variety of causes such as an abduction contracture at the hip or a spinal deformity, which can cause a pelvic obliquity. Suprapelvic obliquity, in association with scoliosis or degenerative disease of the lumbosacral spine, persists in the seated position. Conversely, pelvic and infrapelvic obliquity resolves with sitting. Functional length is measured from xiphisternum (preferably) or umbilicus to the medial malleolus. True length is measured from the anterior superior iliac spine to the medial malleolus and reflects the actual length of the extremity. It is important to square the pelvis or put the limbs in symmetrical fashion before measurement. Quite often it is a combination of the two discrepancies where a small true LLD leads to a large functional LLD. The block test is considered the most accurate clinical measurement.5,10 Rarely a scanogram or a computed tomography (CT) scan may be necessary. However, inPreoperative Planning in Primary Total Hip Replacement

 

severe deformities and contractures, even these may not be accurate. Occasionally, it may be necessary to measure the thigh and/or leg compartment separately to assess the correct LLD and its source. Certain conditions may predispose to postoperative LLD and include coxa vara, dysplastic hips, protrusio, flexion contractures, fixed pelvic tilts, spinal deformities, neuromuscular disorders, hypermobile joints, short stature and preoperative longer limb.11 The patient should be counseled that the goal of the surgery is to attempt to equalize the true length and not necessarily the functional length.

Examination of other joints, especially the spine, contralateral hip and ipsilateral knee is critical for comprehensive evaluation of the contributing factors. This is most important for inflammatory arthropathies. In polyarticular disease, the most symptomatic joint is addressed first, with some exceptions. Hip pathology should be addressed first in patients with both hip and knee problems.3,7,12 It is difficult to do a knee surgery with a stiff hip. Several muscles cross both the hip and the knee, and thus a THR may affect the direction or pull of the muscles across the knee. THR can also change the center of rotation, which will impact the alignment and stability of a knee replacement. Internal rotation of the femur can impact the patellar tracking. Performing a THR first also helps in rehabilitation and avoids confusion of a referred pain at the knee. If diseases of upper limb preclude postoperative rehabilitation, these should be addressed before the lower limb.

In patients with substantial involvement of the contralateral hip to the point that postoperative rehabilitation will be compromised, bilateral surgery should be considered if other factors are favorable.3,13 Patients with excessive spine lordosis and/or pelvic tilt have a different orientation of the acetabulum in the erect position (compared to intraoperative lateral position) that may impact the prosthetic acetabular orientation. Placing the cup in more anteverted position has been recommended in these patients.3,6-8,12 Similarly, the cup may need to be relatively adducted on the higher side in cases of fixed pelvic tilt and vice versa. Patients with ankylosed spine need careful positioning and manipulation to avoid neural injuries during the surgery. Moreover they may have preexisting restrictive cardio-respiratory disease. Anesthesia, both general and regional, may be quite challenging in these patients.14

 

PREOPERATIVE MEDICAL EVALUATION

The preoperative medical evaluation of these patients follows the basic principles of preoperative assessment of patients undergoing anesthesia and non-cardiac surgery. This has been described previously14,15 and is beyond the scope of this chapter. Patients indicated for THR are frequently elderly and have associated medical comorbidities, requiring evaluation, and occasionally, treatment and medical optimization before surgery. Any potential source of infection (including dental and urinary) should be looked for. Cardiopulmonary and peripheral neurovascular status need special emphasis. Patient’s ambulatory and functional status should also be evaluated. Immobilized patients may have a higher risk of perioperative thromboembolic events. High-risk patients may need preoperative inferior vena cava filter.

 

PREOPERATIVE AUTOLOGOUS BLOOD DONATION

Preoperative autologous blood donation (PAD) represents an attractive alternative to allogeneic blood transfusion. This process gained popularity in the 1980s and 1990s because of the public fear of transfusion related diseases, especially human immunodeficiency virus (HIV). Although still a routine in some centers, improvement in blood safety, evolving hypotensive anesthetic techniques, increasing health care cost and lack of evidence-based medicine has made it difficult to justify the routine use of PAD in recent times.16,17 In a randomized study, Billote et al18 found that PAD was of no benefit in patients undergoing primary THR with hemoglobin > 12 g/dl. It has been shown that preoperative hemoglobin/hematocrit levels are important tools in determining perioperative blood transfusion, with patients less than 13 g/dl being at greatest risk.19 Thus PAD may be avoided in patients who have minimal risk of requiringTotal Hip Arthroplasty

 

transfusion but may be considered in conjunction with erythropoietin alpha in patients with anticipated major blood loss (e.g. bilateral THR, revisions).20

 

Indications       and       Contraindications              

Sir John Charnley commented “When total hip becomes a true science, there ought to be no need for a chapter on how to select patients, because then all hip disorders will be treated by total hip replacement.”21 As predicted, evolving technology, improved understanding and the long-term success of THR has engendered increased confidence in its durability and has led to expanded indications. Although pain remains the primary indication for surgery, disability and reduced function associated with painful and stiff hip are increasingly seen as indications for THR. The surgery is usually indicated when the surgeon and the patient have exhausted all other non-surgical options. The usual etiology is either primary arthritis or secondary causes like dysplasia, trauma, avascular necrosis, impingement, epiphyseolysis/Perthes disease, SCFE and inflammatory arthritis. Absolute contraindications include active local and/or systemic infection. Other things to consider are medical comorbidities, immune status, functional status, age, bone stock, renal function, metal allergy, neuromuscular disorders and patient compliance.3,6-8

 

Informed   Consent   and   Decision   Making           

It is essential that the surgeon and the patient align their goals and incentives. The patient must understand that surgery is the only remaining option to improve function. The process may, not unexpectedly, be detailed and laborious. Quite often the discussion is focused on the different alternative bearings and fixation options that are currently available.22 There should be a proper discussion and documentation of the known risks and complications, not only with a THR but also due to patients’ other comorbidities. Realistic expectations of the patients should be thoroughly discussed.

 

Preoperative        Patient        Education               

The initial communication of the surgeon’s office with the patient is vital in establishing the patients’ confidence in both the surgeon’s skill and the care the patient will receive. The best methods for building trust and confidence are friendly open communication and thorough education. Preoperative education should include as much information regarding the surgery as the patient desires and the discussion should include the entire perioperative events and the expected outcomes. Apart from one on one discussion, other methods include pamphlets, audio and video materials, testimonials from other patients and participation in a preoperative class.23

The preoperative class is one of the best methods available to educate the patients and their families because it provides ample information about the anticipated perioperative events (e.g. hospitalization, surgery, anesthesia, deep vein thrombosis prophylaxis, dislocation precautions, driving status and postoperative recovery and rehabilitation) and thus, relieves the element of surprise and/or fear of the unknown.23 The preoperative class should ideally be conducted by a person who is knowledgeable, confident and pleasant. The class also provides opportunity to meet other members of the team like the nurses and physical therapists. The class provides a forum for extensive questioning and answering, many of which arise after the initial visit to the surgeon. Moreover, the patients feel more comfortable when they interact with other patients with similar problems in the similar environment.

 

FUNCTIONAL OUTCOMES

In view of the importance now placed on ‘outcomes’ rather than the ‘results’, it may be worthwhile to teach and have the patients complete a validated self-assessment evaluationPreoperative Planning in Primary Total Hip Replacement

 

form for pain and function.24 Innovations in imaging and gait analysis have also allowed better pre- and postoperative assessment of functional outcomes.25-29

 

Imaging                      Studies                     

Obtaining appropriate and consistent radiographs forms the first step in radiologic evaluation.3,8 We prefer to have five radiographs as a routine for preoperative evaluation: a weight bearing low antero-posterior (AP) view of the pelvis with the proximal one-third of the femur, an AP view of the affected hip, a false profile view of the hip (Figs 3.1B and 3.2B), and AP and lateral views of the lumbo-sacral spine.11,22 It is important to obtain the AP view of the pelvis with the hips internally rotated about 10-15° to estimate the offset accurately. If stiffness of the joint prevents appropriate views, the patient may be allowed to rotate.30 With external rotation, intertrochanteric area appears narrower, the femoral offset smaller, the neck more valgus, and the lesser trochanter more prominent and vice versa.3,7,31 Pelvic rotation is suggested by the absence of superimposition of the center of the sacrum and coccyx on the pubic symphysis and a symmetry of the obturator foramina. In the presence of hyperlordosis at the spine (primary or due to hip flexion contracture), the AP view of the pelvis resembles an inlet view, and the acetabular landmarks may not be accurately visualized. Specific parameters assessed include the lateral center-edge angle, anterior center-edge angle, acetabular inclination and version, the sphericity of the femoral head, the head-neck offset, alignment and morphology of the proximal femur, height of the greater trochanter, osteophytes and bony defects.22 Adjunctive imaging studies are sometimes needed to evaluate and define the etiology of symptoms, and may include full length femur films, Judet views, CT scan and/or a magnetic resonance imaging (MRI). Sometimes, a scano gram may be needed if the LLD is due to extraarticular causes distally in the extremity (e.g. malunited fractures).

The radiographs should also be assessed for general bone disease process that may

 

 

make surgery or recovery difficult. Hypertrophic osteoarthritis, prominent lumbar syndesmo-phytes of diffuse idiopathic skeletal hyperostosis, or previous heterotopic ossification should alert the surgeon to consider prophylaxis for heterotopic ossification.3,7,31 Osteomalcia and osteoporosis may increase the risk of periprosthetic fractures, both during and after surgery. Bone quality may be classified based on several indices and can help guide the selection of technique and prosthesis.32-34 Patients with deformed and/or sclerotic bones (e.g. Paget’s disease, sickle cell and osteopetrosis) may need special instrumentations like high speed burrs, guide wires, sharper reamers and intraoperative fluoroscopy (Fig. 3.2).3,7,31

 

Figure 3.2: (A) AP and (B) False Profile radiographs of the right hip in a patient with a SC type of sickle cell disease showing sclerotic bones with avascular necrosis and hypertrophic type of arthritis. Note the obliterated medullary canal (black arrows). (C) This patient was treated modular S-ROM (Depuy, Warsaw, IN) prosthesis which needed reaming (rather than broaching) over a guide wire under fluoroscopic guidance. In spite of anticipating the higher risk, there was a perforation in the cortex, necessitating circlage wires. Again note the obliteration of the medullary canal beyond the reamings (white arrow)

Preoperative                  Templating                  

Total Hip Arthroplasty

 

Preoperative templating greatly facilitates the accomplishment of surgical goals of restoration of hip biomechanics in terms of the center of rotation, the offset and the limb length.35 It also allows the surgeon to choose appropriate implants and anticipate the need for special devices, allografts, or a different surgical approach. Sizing of prosthesis may also reduce the inventory and surgical time and thus the cost. Della Valle et al30 estimated that by already having + 1 size of the implant in the operating room, about 6.6 hours of operating time could be saved for every 100 THR. Templating also helps in anticipating intraoperative difficulties and formulating an alternate plan.35

 

IDENTIFICATIONS OF LANDMARKS AND MEASUREMENTS

The first step is to identify bilateral teardrops base, proximal edge and most medial part of the lesser trochanter (LT), tip of the greater trochanter (GT), center of the femoral head (CFH), subchondral bone at the acetabulum and the calcar (Fig. 3.3).3,7,11,22,30,31,35 These landmarks are easily identifiable intraoperatively and thus help correlating the preoperative information during the actual surgery. The tear drop is the most consistent landmark on the AP view of the pelvis.36 LLD is measured off the inter-teardrop line to a fixed point on the LT (often the most medial point). Alternatively, a line drawn between the inferior aspect of both ischium, most distal aspect of the sacroiliac joint, inferior aspect of obturator foramen or the superior margin of both greater trochanters may also be used as a reference.30,37 In addition, the distance from the proximal edge of the LT to the CFH, the distance and relation of the tip of the GT to the CFH (offset) are also measured and attempt is made to reproduce these parameters during surgery. Because of the inconsistency in defining the tip of GT, some surgeons use the saddle of the neck (Fig. 3.3; junction of the femoral neck and GT,

 

 

 

Figure 3.3: AP radiograph of the pelvis and bilateral hips showing the identification of landmarks required before templating. T and T1: teardrop, AB: interteardrop line, CD and EF: vertical lines at teardrops, G and H: center of the femoral heads, I and K: proximal part of lesser trochanter, J and L: medial most part of lesser trochanter, and, M and N: superolateral subchondral bone at the acetabulum. OJ and PL represent the distance between the interteardrop line and medial most part of lesser trochanter and PL – OJ = limb length discrepancy. GI and HK represent the distance between the center of femoral head and the proximal lesser trochanter, and are correlated intraoperatively for limb length assessment. GQ and HR are distances from the center of the femoral head to the saddle of the neck, and represent the femoral offset. This is also correlated intraoperatively for reproducing the femoral offset. The red arrow points a large cyst which may need curetting and bone grafting during surgery. The radiographs are scaled for magnification using standard sized markers (black star on the viewer’s left)usually at the piriformis fossa) as a landmark, especially with minimal invasive techniques.38 It is crucial to consider the effect of magnification (10-20% depending on the distance of the film and the built of the patient) during these measurements, and use of a magnification marker is strongly recommended to minimize error (Fig. 3.3).

 

TEMPLATING OF IMPLANTS

The next step is to template the implants. In cases of a unilateral hip disease, the goal is to match the opposite leg in terms of limb length and offset. If the patient has a contralateral well-functioning THR, the goal should be to match it. All the preoperative sizes which are templated should be noted and correlated with the operative findings. A marked discrepancy between the templated size and the actual size may indicate component malpositioning, mal-sizing, or an intraoperative fracture.3,7,31

 

Acetabular Side

The acetabulum is first templated for the approximate component size, position and to find out its effect on the center of rotation (COR). The acetabular template is placed just lateral to the lateral edge of the tear drop at a 40–45 degrees angle, with the inferior margin approximating the teardrop base, and the medial border approximating the lateral cortex of the teardrop (Figs 3.4 and 3.5). In the contained acetabulum, complete superolateral coverage of the cup with minimal removal of the supportive subchondral bone is desired. However, in reality there usually is some superolateral uncovering and this should be measured and correlated during surgery (Fig. 3.4). A 2 mm cement mantle thickness may be allowed for cemented cups. With the cup template in place, the COR of the cup (and of the THR) is marked (Fig. 3.4). In most cases, this will restore the anatomic COR. The COR should be compared with the contralateral COR by measuring the horizontal and vertical distance of the COR from a vertical line at the tear drop and the inter-tear drop line respectively (Fig. 3.6). The LLD can then be added to the COR to determine the prosthetic CFH. The presence of intra-osseous cysts to be curetted and grafted before cup implantation, and peripheral osteophytes to be removed after cup insertion, may be boldly marked to remind the surgeon in the operating room (Figs 3.3 and 3.7). Superolateral osteophytes can occasionally be used to provide supplemental coverage and thus, may be retained (Figs 3.1, 3.2 and 3.7).

 

 

 

 

Preoperative Planning in Primary Total Hip Replacement

 

Figure 3.4: The acetabular template is placed just lateral to the lateral edge of the teardrop at a 40–45 degrees angle, with the inferior margin approximating the teardrop base, and the medial border approximating the lateral cortex of the teardrop, with minimal removal of the subchondral bone superolaterally. The center of rotation (star) is marked. The superolateral uncovering of the cup (U) is also measured and correlated intraoperatively. Less coverage may denote an abducted and/ or more medialized cup and vice versa. In this case a size 56 uncemented cup seems appropriate

 

Total Hip Arthroplasty

 

Figure 3.5: Templating should also be done on the false profile view. The anteroposterior diameter of the acetabulum may be the determining factor in sizing the cup. In this view (same case as in Fig. 3.4), a size 54 uncemented cup seems more appropriate. Intraoperatively, a size 54 cup was implanted in this case

 

 

 

Figure 3.6: The center of rotation (COR) should be compared with the contralateral COR by measuring the horizontal (H) and vertical (V) distance of the COR (star) from a vertical line at the teardrop and the interteardrop line respectively

 

 

 

Figure 3.7: Peripheral osteophytes, to be removed after cup insertion, may be boldly marked (arrows) to remind the surgeon. Superolateral osteophytes can occasionally be used to provide supplemental coverage and thus, may be retained if not impinging

 

Preoperative Planning in Primary Total Hip Replacement

 

Figure 3.8: In cases with protrusion, careful reaming is warranted as bone is also softer usually. Relative lateralization of the cup will be needed to restore the biomechanics and minimize impingement

 

Protrusio acetabuli, defined as medial migration of the head beyond the ilio-ischial line (Kohler’s line), may be present in inflammatory arthritis, osteoporosis, metabolic bone disease and post trauma cases. Careful reaming is warranted in these cases as usually bone is also softer. Relative lateralization of the cup will be needed to restore the biomechanics and minimize impingement (Fig. 3.8).3,7,31 Peripheral rim contact with supplementary screw fixation is desirable in these cases for primary stability. In most cases, bone graft from the femoral head would be sufficient, but severe cases may need structural allografts or cages. If lateralization increases the leg length, a shortened neck with a low neck cut may be needed. Moreover, asymmetric correction may have cosmetic implications, especially in females. In contrast, in cases of dysplastic hips with less supero-lateral covering, over-medialization with or without superior placement of a smaller size cup may be necessary (Figs 3.1 and 3.3). A relative vertical cup with offset liner in superior position is another option.3,7,31 Structural grafts with metal augments may be necessary in some cases. Similarly in cases of hypertrophic osteoarthritis, it is important to adequately ream the medial osteophytes and medialize the cup with adequate superolateral coverage (Fig. 3.2).3,7,31

 

Femoral Side

Provided that the socket would reproduce the normal COR and there is no substantial deformity on the normal side, the templating should also be done on the normal side for comparative assessment. Templating of the femoral canal is done to determine the type and size of the component to be selected, its position relative to the LT, the level of the neck osteotomy, the width of the remaining calcar and the selection of the neck length to reproduce both leg length and femoral offset. The template is aligned along the anatomical axis of the femur, centering within the intramedullary canal in an AP film, and is gradually raised or lowered until one of the potential head positions is directly over or at least level with the proposed COR (Fig. 3.9). The height and medialization of the center of the prosthetic head is then compared with the COR of the templated cup, and adjustments are then made to compensate for limb length and offset. Depending on the type of implant, the size that adequately filled the metaphysis (for proximally coated) or the diaphysis (for extensively coated) of the femur is selected. For cemented stems, an allowance of 2-3 mm for the cemented mantle is taken into consideration. Once finalized, the neck cut is marked and

 

 

Total Hip Arthroplasty

 

Figure 3.9: Templating of the femoral canal is done to determine the type and size of the component to be selected, its position relative to the lesser trochanter, the level of the neck osteotomy (NC), the width of the remaining calcar (C) and the selection of the neck length (red and blue stars) to reproduce both leg length and femoral offset. The required offset may be increased by using a higher offset or dual offset prosthesis (the red stars showing the different neck lengths at a higher offset than the standard offset as represented by the blue stars). The limb length discrepancy (L) that will be corrected after reduction is the difference between the center of femoral head (green star) and the center of the cup (yellow star). Similarly the medial placement of the femoral head relative to the cup head will increase the abductor lever arm after reduction. In this case (inset), a size 5 femur with a standard offset, 0 neck length and 36 head were implanted (as planned)

 

 

 

measured from the LT (Fig. 3.9). Similarly the distance from the LT to the prosthetic head center is also measured. If the COR has been placed higher than normal, this distance needs to be increased to compensate for LLD. The width of the calcar, medial to the stem at the level of the neck cut is also measured (Fig. 3.9). This allows intraoperative assessment of the stem alignment in the frontal plane. If a shorter distance is observed with the rasp in place, malalignment in varus is suspected, and valgus is suspected when the distance is more. A neutral or slight valgus alignment is desirable during surgery. Lateral radiographs may be templated now to reassess the size and to see if stem tip is impinging (Fig. 3.10). If stem tip impinges, options include changing the entry point in the AP plane, using an anatomic stem, or using a smaller cemented stem.3,6,31

 

Figure 3.10: Lateral radiographs are templated to reassess the size and to see if the stem tip is impinging because of the mismatch in the bow of the bone and the prosthesis

 

Preoperative Planning in Primary Total Hip Replacement

 

Figure 3.11: Cases with coxa vara may need a lower neck cut (white arrow) with a longer neck size (black arrow), or a higher offset (Inset: the implant on the left has a lesser neck shaft angle and thus a higher offset) or dual offset prosthesis to reproduce the biomechanics and avoid limb lengthening. Sometimes less medialization (blue arrow) is required due to limitations in increasing the offset with the available prosthesis and to minimize impingement

 

 

 

Figure 3.12: In contrast to coxa vara, cases with coxa valga may need a longer neck cut (arrows) and shorter neck length

 

Expected offset can be estimated from the CFH. If it is medial to the COR, the offset would increase and vice versa. Although increased offset aids abductor mechanism, adds stability, minimizes impingement, over correction should be avoided as it can lead to asymmetry, trochanteric prominence and bursitis.3,6,31 Reduced offset decreases the abductor force, increases limp, increases joint reaction force and may lead to higher rates of wear.3,6,31 A longer neck cut, longer prosthetic neck and/or seating the component proud will also increase the offset. On the other hand, sometimes an increased offset prosthesis may be required. Coxa vara cases are at increased risk for limb lengthening without restoring the offset. 3,6,31 Options include lowering the neck cut and using a longer neck or using a higher offset (less neck shaft angle) or dual offset prosthesis (Fig. 3.11). The opposite holds true for valgus hips (Fig. 3.12). Similarly in cases of short neck (coxa brevia, e.g. in Perthes disease), a shorter neck cut with a shorter neck length is required (Fig. 3.1).3,6,31 In doubtful cases, it is better to cut the neck longer and then adjust later on after trial reduction.

ACCURACY OF TEMPLATING

Total Hip Arthroplasty

 

Based on preoperative templating, Eggli et al35 could plan the correct type of prosthesis in 98% of the cases in a series of 100 consecutive primary THR; the agreement between planned and actually used component was 92% for the femur and 90% for the acetabulum, the mean LLD was 0.2+0.1 cm and more than 80% of the intraoperative difficulties had been anticipated. Similarly in another study by Della Valle et al,30 the acetabular component size was predicted exactly in 116 (83%) of 139 THR and the femoral component size was predicted exactly in 108 THR (78%). The accuracy was 99% (138 THA) for both components, when considering +1 size. In 75 THR (45%), the COR was within 2 mm of horizontal and vertical distance from the plan, and in 127 (91%) THA, it was within 4 mm. In 81 THA with a normal contralateral hip or a stable THR, the average limb-length discrepancy was 1.3 mm (–6 to +10, SD 3.44). The implants used in both these studies were cemented or hybrid.

The accuracy has been lower for uncemented implants. The likely reason for this could be due to under-reaming, the use of press-fit implants and the fear of intraoperative fracture with larger implants. In a study on 109 uncemented primary THR, Unnanuntana et al39 demonstrated 42.2% accuracy of acetabular size (increased to 93% with +2 sizes) and 68.8% for femoral size (increased to 98% with +1 sizes). Having a contralateral THR increased the accuracy for the femoral component (80%) but not for the cup. In a review of 75 primary uncemented THR, Tripuraneni et al37 found that the common errors in execution of preoperative templating were excessive limb lengthening and increased offset, primarily due to error in the cup placement. They also found that LLD measurement was more reproducible with inter-obturator line, rather than inter teardrop or inter-ischial lines.

 

DIGITAL TEMPLATING

With the shifting trend towards electronic ‘picture archiving and communication systems’ (PACs), several soft digital templating softwares are currently available and provide intuitive image analysis and manipulation tools to perform critical preoperative measurements, offset, LLD, and implant selection and placement.40-47 The surgeon can select from a collection of templates (different designs from different manufacturer) and electronically overlay them on digital radiographs, which are scaled for magnification (Fig. 3.13). The surgeon can then perform the necessary measurements critical to the templating and preoperative planning

 

 

 

Figure 3.13: AP radiograph of the pelvis and bilateral hips showing the choice and planning of prosthesis placement using a TraumaCad software (Voyant Health, Columbia, MD). In this particular patient, a size 46 RB uncemented cup (Biomet, Warsaw, IN) and a size 7/115 Echo Bimetric uncemented stem with standard offset (Biomet, Warsaw, IN) are being digitally planned. The radiographs are scaled for magnification using standard sized markersdigitally. The process is fast, efficient, cost-effective and provides a permanent, archived record of the templating process.40 Levine et al41 found exact sizing accuracy of digital templating in 73.1% of cups and 44.1% of the femoral component in 96 THRs (mostly uncemented). The accuracy increased to 98.3% and 88% respectively when +1 size was considered, and to 100% with +2 sizes.

Preoperative Planning in Primary Total Hip Replacement

 

However, studies comparing digital templating to standard overlay templating have shown inconsistent results. Using digital templating in 40 uncemented THR, Gamble et al43 found the sizing accuracy (within +1) to be 85% for femoral stem and 80% for the cup. Using onlay templating, the accuracy was same for the femur but was worse (60%) for the cup. In contrast, in a study on 64 hybrid THRs, Della Valle et al42 found that analog templating was more accurate than digital templating, particularly with cup sizing and LT to head measurement (useful for limb length assessment). In a large prospective study, The et al44 reported that digital templating of a THR was less frequently correct (cemented cup and stem: 72% and 79%; uncemented cup and stem: 52% and 66% respectively) than analog planning (cemented cup and stem: 73% and 89%; uncemented cup and stem: 64% and 52% respectively) when considering +1 size. Accuracy was further decreased when templating was done by someone other than the surgeon. However in a later study of 210 randomized THRs (majority cemented), the same group45 concluded that the digital preoperative plans were more accurate in planning the cup (p = 0.04) and scored higher on the postoperative radiologic assessment of cemented cup (p = .03) and femoral component (p = 0.01). These inconsistent results may be due to errors in magnification,46 use of different softwares at different phases of development, combining cemented and uncemented implants, and different levels of experience of the person doing the templating. Descamps et al47 found a relation between the magnification factor and the weight of the patient. They have suggested a correction formula, which improves the accuracy of sizing (+1) to 98%.

Computer-assisted two and three-dimensional preoperative planning for THR has also

been investigated and found to be comparable to the manual method, thereby allowing the surgeon to simulate various stem designs easily.25,26 Research is also ongoing on the combination of robotic technology and CT in preoperative planning.27 Irrespective of the methodology chosen, the surgeon should use the input from preoperative templating and correlate it with intraoperative visual and tactile cues to choose and correctly position the components.

Choice of Surgical Approach

 

Choosing an appropriate surgical approach is a critical aspect of preoperative planning. Although most primary THRs can be done through the same approach based on the surgeon’s training, experience and level of comfort, certain approaches may have added benefit based on the information gathered during the preoperative evaluation.3,7,31 A history of previous hip surgery is an important consideration in planning the incision. Although not possible all the time, it’s usually safer to incorporate the previous incision as the part of new incision. This is also useful if prior hardware needs to be removed, e.g. a posterior approach for removal of a posterior acetabular wall hardware. Narrow skin flaps should be avoided. If it is necessary to cross the previous incision, acute angulations should be avoided. Young muscular and/or obese patients may need longer incisions and deeper retractors. In noncompliant patients, patients with neuromuscular disorders, patients with substantial flexion and/or adduction contractures, it may be preferable to avoid a posterior approach to reduce the risk of postoperative dislocations.3,6,31 In addition, using a larger size head and avoiding prosthesis with thicker trunions (or skirts) that may cause impingement, may be beneficial in these cases. Similarly the use of a transtrochanteric approach with/without in situ neck osteotomy may be considered in cases of stiff and/or ankylosed hips. The surgical approach may also be governed by the anatomy of the patient, especially if there are areas of bony deficiencies that might need reconstruction, e.g. an anterior based approach for cases with substantial anterior acetabular deficiency.Anesthesia and Pain Control

 

Total Hip Arthroplasty

 

A detailed discussion of the anesthesia and perioperative pain control is beyond the scope of this review and has been described before.14,48-51 Positive trends have been shown for hypotensive regional anesthesia compared with general anesthesia, especially in terms of lower incidence of complication. Apart from lowering the blood loss and preventing deep vein thrombosis, postoperative epidural analgesia provides excellent pain relief after THR and allows early painless range of motion and weight bearing, enhancing overall patient satisfaction. Multimodal anesthesia and analgesia, which focuses on avoidance of parenteral narcotics has accelerated rehabilitation with significant drop in postoperative complications.

 

Conclusion

 

It has been rightly commented “Each procedure should be performed three times by the surgeon: the first time in one’s head when seeing the patient for the initial consultation, the second while meticulously planning all the details of the surgery preoperatively, and the third when executing the final plan.” 6 Preoperative planning is one of the most crucial steps to the success of THR. It may be prudent to conference all cases with the surgical team before the surgery. Information gathered from history, physical examination and radiographic templating provides important input during the actual surgical procedure and postoperative period and minimizes surprises. It guides the selection of appropriate surgical approach, appropriate implants and need for special tools or bone grafts. If substantial intraoperative deviation from the preoperative surgical plan occurs, explanation should be sought. Following a rational preoperative protocol with attention to detail will more likely lead to consistent and reproducible results.

 

Acknowledgment

 

We thank Dr Jose A Rodriguez MD for providing Figures 3.3 to 3.6 and 3.9 to 3.10. We thank Dr Ajit J Deshmukh MD for his help with photography. We also thank Dr Edward Y Cheng MD and Dr Rameshkumar Periyasamy MD for providing Figure 3.13.

 

References

 

1. Learmonth ID, Young C, Rorabeck C. The operation of the century: total hip replacement. Lancet 2007;370(9597):1508-19.

2. Barrack RL, Burnett SJ. Preoperative planning for revision total hip arthroplasty. J Bone Joint Surg Am 2005;87(12):2800-11.

3. Barrack RL, Stephen R, Burnett J. Preoperative planning. The adult hip. Callaghan JJ, Rosenberg AG, Rubash HE (Eds). 2nd ed, Lippincott Williams and Wilkins, Philadelphia, PA, 2007.pp.884-910.

4. Clohisy JC, Keeney JA, Schoenecker PL. Preliminary assessment and treatment guidelines for hip disorders in young adults. Clin Orthop Relat Res 2005;441:168-79.

5. Hoppenfeld S. Physical examination of the spine and extremities. New York: Appleton-century-Crofts; 1976.

6. De Beer J. Preoperative planning for primary total hip arthroplasty. In: Hozack W, Parvizi J, Bender B (Eds). Surgical treatment of hip arthritis: reconstruction, replacement, revision surgery. 1st ed, Saunders Elsevier, Philadelphia, PA, 2009.pp.93-8.

7. Blackley HR, Howell GE, Rorabeck CH. Planning and management of the difficult primary hip replacement: preoperative planning and technical considerations. Instr Course Lect 2000;49: 3-11.

8. Della Valle AG, Padgett DE, Salvati EA. Preoperative planning for primary total hip arthroplasty. J Am Acad Orthop Surg 2005;13(7):455-62.

9. Ranawat CS, Rodriguez JA. Functional leg-length inequality following total hip arthroplasty. J Arthroplasty 1997;12(4):359-64.