Leg-Length Discrepancy After Total Hip Arthroplasty Abstract Leg-length discrepancy after total hip arthroplasty can pose a substantial problem for the orthopaedic surgeon. Such discrepancy has been associated with complications including nerve palsy, low back pain, and abnormal gait. Careful preoperative measurement and assessment, as well as preoperative and postoperative patient education, are important factors in achieving an acceptable result. However, after total hip arthroplasty, equal leg length should not be guaranteed. Rather, the patient should be given a realistic assessment of what can reasonably be expected. T he objectives of total hip arthro- plasty (THA) include pain relief, improved mobility and stability of the hip, normal mechanics of the hip joint, and, when possible, equality of leg length. In general, obtaining pain relief and improving stability take precedence over restoring equal leg length. However, leg lengthening may be required to provide a stable hip joint after reconstruction arthro- plasty. Data published by the Joint Com- mission on Accreditation of Health- care Organizations (JCAHO) provide an account of the types of medical errors that occur in hospitals in the United States. 1 In his presidential address to the American Academy of Orthopaedic Surgeons, James Hern- don, MD, remarked on the 19 major events described by the JCAHO that deserve watchfulness; 6 are relevant to orthopaedic surgery. 2 Included among these are patient falls and leg- length issues; the latter account for 4.7% of medical errors. Leg-length discrepancy after THA has been associated with compli- cations including sciatic, femoral, and peroneal nerve palsy; low back pain; 3-5 and abnormal gait. 6-10 Al- though not quantified as a problem in most series of hip arthroplasties, low back pain in some cases may be related to increased limb length of the operated side. 11 A shoe lift is not always well accepted as an alterna- tive. 12 Many patients are annoyed by leg- length discrepancy; patient edu- cation is important in preventing dissatisfaction. Patient dissatisfac- tion with leg-length discrepancy af- ter THA is the most common reason for litigation against orthopaedic surgeons. 12,13 Nerve injury is the most serious complication associated with leg- length inequality. 14 In a review of 23 THAs complicated by peroneal and sciatic nerve palsy, Edwards et al 15 noted an average lengthening of 2.7 cm (range, 1.9 to 3.7 cm) for perone- al palsy and 4.4 cm (range, 4.0 to 5.1 cm) for sciatic palsy. In a case report describing acute sciatic and femoral neuritis following THA, Mihalko et al 7 described a patient who, follow- ing a leg lengthening of 2.5 cm, re- ported pain without motor or senso- ry deficit; the patient also had abnormal electromyography and nerve conduction velocities. Pritchett 16 reported on 19 patients who had severe neurologic deficit and persistent dysesthetic pain fol- Charles R. Clark, MD Herbert D. Huddleston, MD Eugene P. Schoch III, MD Bert J. Thomas, MD Dr. Clark is the Dr. Michael Bonfiglio Professor, Department of Orthopaedic Surgery, University of Iowa Hospitals, Iowa City, IA. Dr. Huddleston is in private practice at Huddleston Hip and Knee Institute, Tarzana, CA. Dr. Schoch is in private practice, Austin, TX. Dr. Thomas is Professor of Orthopaedic Surgery, David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, CA. Neither Dr. Huddleston nor the department with which he is affiliated has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article. Drs. Clark and Thomas or the departments with which they are affiliated have received research or institutional support from DePuy. Dr. Thomas or the department with which he is affiliated has received nonincome support (such as equipment or services), commercially derived honoraria, or other non-research–related funding (such as paid travel) from DePuy. Drs. Clark and Schoch or the departments with which they are affiliated serve as consultants to or are employees of DePuy. Reprint requests: Dr. Clark, University of Iowa Hospitals, 200 Hawkins Drive, 01075 JPP, Iowa City, IA 52242. J Am Acad Orthop Surg 2006;14: 38-45 Copyright 2006 by the American Academy of Orthopaedic Surgeons. 38 Journal of the American Academy of Orthopaedic Surgeons lowing THAs in which limb length- ening of 1.3 to 4.1 cm was per- formed. After evaluating factors that influence nerve repair, Smith 17 con- cluded that nerve lengthening of as much as 15% to 20% of the resting length was safe. However, for hip ar- throplasty, the specific degree of length that can be gained without risking nerve palsy remains unde- fined. Although surgeons generally agree that progressively greater lengthening is associated with great- er risk to the nerve, no consensus ex- ists regarding a safe threshold for lengthening. Some sciatic nerve problems that occur in the presence of leg-length inequality are not directly related to the leg lengthen- ing. Most patients with minor leg- length discrepancy after THA have few symptoms, and most patients with moderate leg- length discrepan- cy have readily manageable symp- toms. However, a minority of pa- tients, mostly those with marked limb-length discrepancy, may have substantial disability as a result of pain or functional impairment. 18 Common symptoms include pain, paresthesias, and instability of gait. Gurney et al 19 evaluated the ef- fects of an artificial limb-length dis- crepancy on gait economy and low- er extremity muscle activity in older adults. They found that with 2 to 4 cm of limb-length discrepancy, there was a significant (P < 0.0005) in- crease in oxygen consumption. With 3 and 4 cm of limb-length discrepan- cy, there was a significant (P = 0.001 and P < 0.005, respectively) increase in heart rate and significant (P = 0.001 and P < 0.005, respectively) quadriceps activity in the longer limb. With a 4-cm limb-length dis- crepancy, there was a significant (P < 0.003) increase in plantar flexor ac- tivity in the shorter limb. The au- thors concluded that in older adults, limb-length discrepancy of between 2 and 3 cm is the critical point with regard to the effects on most physi- ologic parameters. Elderly patients with substantial pulmonary, cardiac, or neuromuscular disease may have difficulty walking with a limb- length discrepancy as small as 2 cm. Bhave et al 20 reported that a limb- length discrepancy creates an asym- metry in the ground reaction force and that surgical lengthening of the short limb to within 1 cm of the con- tralateral limb reduced the asymme- try to less than a significant level. Vink and Huson 21 reported a notable increase in the electromyographic activity of the erector spinae mus- cles only when the leg-length dis- crepancy was ≥3 cm. To prevent postoperative leg- length discrepancy and its attendant problems, it is important to under- stand the various components of leg- length assessment related to THA, including preoperative planning, in- traoperative measurement, and post- operative management. With mini- mally invasive techniques and smaller incisions, the need for accu- rate placement of implants is height- ened. Computer-assisted surgery may play a role in accurately deter- mining such placement. Preoperative Planning Patient History The patient’s perceived leg-length discrepancy is a ver y important as- pect of the preoperative history. It is useful to ask patients specifically whether their legs feel equal and whether they use a shoe lift. A pa- tient’s legs often are of unequal length before surgery. Ranawat and Rodriguez 22 noted a high prevalence of asymptomatic leg-length inequal- ity in the general population. Muscle contracture frequently is a cause of apparent discrepancy. A history of scoliosis, poliomyelitis, develop- mental dysplasia of the hip, degener- ative disk disease of the lumbar or thoracic spine, or lumbar surgery, in- cluding spinal fusion, is important and may have an effect on leg length and the subsequent development of symptoms. Physical Examination An abduction, adduction, or flex- ion contracture should be assessed and quantified because of the poten- tial influence on perceived length. A flexion contracture can lead to over- estimating shor tening, and an ad- duction contracture can increase perceived length. 23 Next, the pelvis should be leveled by placing a series of blocks under the shorter limb. Fi- nally, the true and apparent limb lengths are measured. 3 The true limb length is deter- mined by measuring the length of the femur and implants. The appar- ent limb length is determined by adding the effect of soft-tissue con- tractures and pelvic obliquity. Most discrepancies are a combination of true and apparent differences. Be- cause functional limb length is the result of a complex interaction of the lengths of bones, implants, soft- tissue contractures, and pelvic obliq- uities, no single measure adequately conveys all of this information. The apparent leg length can be measured from the umbilicus to the medial malleolus. This technique provides a simple measure of the functional length; however, it does not assess the effect of soft-tissue contractures and pelvic obliquity. This measurement also can be influ- enced by the position of the limb and the pelvis. The true leg length is measured from the anterior superior iliac spine to the medial malleolus. This is arguably the most reliable clinical measure of limb length; however, the technique requires pre- cise identification of landmarks, which may be difficult, particularly in obese individuals. True leg-length measurement also is subject to vari- ation because of changes in the posi- tion of limbs and pelvis and because of soft-tissue contractures. 24 The physical examination should include an assessment of spinal de- formity and iliac crest symmetry. True leg-length differences may re- sult in a compensatory scoliosis, which may be resolved by placing an Charles R. Clark, MD, et al Volume 14, Number 1, January 2006 39 appropriate lift beneath the shorter limb. Conversely, when contrac- tures of the hip and knee cause a fixed pelvic obliquity, placing a lift beneath the shorter limb will not re- solve the pelvic obliquity. Balancing by using wooden blocks provides easy assessment of functional leg- length discrepancy in a reproducible fashion; however, this method does not adequately separate the effects of soft-tissue contractures and fixed pelvic obliquity. Of particular concern is the pa- tient who presents with a leg-length discrepancy in which one leg is per- ceived to be longer than the other al- though the actual leg lengths are equal. Common causes of such a per- ceived “long leg” include scoliosis, fixed pelvic tilt, and contralateral leg deformity . Less commonly seen is an abduction contracture in which the true leg lengths are equal even though the apparent leg length is longer on the side of the contracture. Patient Education and Informed Consent How a patient reacts to perceived leg-length inequality is associated with his or her discussion with the surgeon, who can reassure the patient that most inequalities have little im- portance. 3 Patients retain little preop- erative information about risks and expectations, no matter how carefully presented preoperatively; they re- member more of the information pro- vided about potential benefits. 25 During the preoperative discus- sion, the surgeon should establish the expectation that equal leg lengths is not a guarantee after surgery. Chronic shortening and tis- sue scarring may make residual shortening unavoidable at surgery. Conversely, some individuals with excessive laxity may require length- ening to ensure adequate hip stabil- ity. However, studies have reported that, even after appropriate patient education was provided and consent given, approximately one half of pa- tients with lengthened legs did not recall that this possibility had been communicated to them. 25,26 Ad- ditionally, patients whose affected side is longer preoperatively should be warned that further lengthening may occur as a result of surgery and that deliberate shortening may not be feasible. Radiographic Assessment Preoperative radiographs are help- ful in assessing true leg-length dis- crepancy; included should be an an- teroposterior view of the pelvis with both femurs internally rotated ap- proximately 20° (Figure 1). External rotation of the hip, which often oc- curs in association with degenera- tion, gives the false appearance of de- creased femoral offset. This false appearance can contribute to under- estimating the offset and neck length required to restore hip stabil- ity and optimal biomechanics. An appropriately rotated hip shows the anterior and posterior aspects of the greater trochanter to be in align- ment and does not show the entire lesser trochanter in profile. In patients with unilateral disease, the anteropos- terior pelvic view should have appro- priate rotation on the contralateral side. When an external rotation con- tracture prevents appropriate internal rotation in the supine position, plac- ing the patient prone may correct the radiographic appearance. Determining radiographic leg length can be difficult in a patient undergoing revision THA, particu- larly when significant metaphyseal and/or diaphyseal bony deficiency exists as a result of the previous ar- throplasty. Attempts should be made to identify radiographic land- marks on the deficient side that can be identified at surgery and used in- traoperatively to help reapproximate the appropriate leg length. 27,28 Preoperative Templating Templating is useful for predict- ing limb lengths. With acrylic tem- Figure 1 As an estimate of leg-length discrepancy radiographically, a reference line is drawn through the bottom of the obturator foramina. On each side, the distance from the lesser trochanter landmark to the reference line is measured. The difference between the two is the radiographic leg-length discrepancy. The tip of the greater trochanter may be used as an alternative reference mark in conjunction with the lines through the obturator foramina. Leg-Length Discrepancy After Total Hip Arthroplasty 40 Journal of the American Academy of Orthopaedic Surgeons plates, the surgeon is able to predict the approximate change in limb length by noting the relationship of various implant landmarks, such as the hip center and its relationship to fixed bony landmarks (eg, the tear drop, the lesser trochanter). The sur- geon also can note how these land- marks change with acetabular and femoral implants of various size. The templates are designed to fit the internally rotated anteroposteri- or view of the femur. Ideally the ip- silateral side, when available, should be templated first to determine the potential correct sizes for both the acetabular and femoral components. It is important to remember that ra- diographs typically are magnified up to 20%. Acetabular Templating Preoperative acetabular templating is performed with the following goals in mind. First, the acetabular shell should make bone contact at the sub- chondral plate. The lateral opening should approximate 40° ± 5°. 29,30 Fi- nally, in most cases, the tear drop should coincide with the infe- romedial corner of the acetabular component. Placing the acetabular template in this position establishes the new center of rotation of the THA (Figure 2). Placement of the acetabu- lar component as close as possible to the templated position is important because doing so defines the hip cen- ter and directly influences leg length. Femoral Templating When templating the femoral side of the acetabular socket, there are three main goals: optimally size the femoral component, maintain offset, and optimize limb lengths. With appropriately aligned, internal- ly rotated femoral views, the sur- geon should be able to determine whether an adequate offset can be achieved with the implants being considered. One method to create a larger offset is to make a lower neck cut and use a longer neck. Another strategy to obtain a larger offset is the use of lateralized femoral com- ponents. The advantage of using lat- eralized femoral components is that offset can more readily be restored without lengthening the limb. Trochanteric advancement can improve soft-tissue tension without increasing leg length. Disadvantages to using this method, however, in- clude the risk of trochanteric bursi- tis, nonunion, increased operating time, and the potential need for tension-band wire removal. The use of templates is the first step in obtaining acceptable clinical results with regard to leg length. 31-33 However, such use should be com- bined with a reliable intraoperative method to obtain optimal length. Intraoperative Leg- Length Measurement Application of Preoperative Templating Intraoperatively Because determining limb length intraoperatively relies on identifying anatomic landmarks, patient posi- tioning is important to ensure prop- er orientation of these landmarks. Before draping, with the patient in the position that will be evaluated intraoperatively, the baseline limb length is assessed with respect to the contralateral limb. It is also helpful to check that landmarks on the con- tralateral extremity can be palpat- ed intraoperatively through the drapes. The accuracy of preoperative fem- oral templating relates in part to the location of landmarks from which to measure the level of the femoral neck resection during surgery. Al- though the lesser trochanter is com- monly used, its sloping superior sur- face blends with the inferior femoral neck and therefore may not always provide a definitive landmark, either on radiographs or intraoperatively. In a series of 100 consecutive hip sur- geries in which the authors mea- sured from the lesser trochanter and used digitized radiographs and a spe- cial software program, Eggli et al 31 found that the actual to the planned Figure 2 Using the anteroposterior radiograph, the template is positioned 35° to 45° to the inter–tear drop or interischial line, so that the inferomedial aspect of the cup abuts the teardrop and the superior-lateral cup is not excessively uncovered. Charles R. Clark, MD, et al Volume 14, Number 1, January 2006 41 level of neck resection varied by as much as 7 mm. Woolson and Harris 32 measured from the top of the femoral head to the level of the neck resection, a practical method when the femoral head is not deformed and the pre- operative leg-length difference is minimal. Woolson et al 33 used this technique and radiographically de- termined postoperative leg-length discrepancy for a consecutive series of 351 patients (408 hips) who under- went bilateral or unilateral primary THA. Ninety-seven percent of the patients had a postoperative leg- length discrepancy of <1 cm. The av- erage discrepancy for these patients was 1 mm. Knight and Atwater 34 conducted a prospective study of 110 consecutive primary THAs in which surgeons re- corded the preoperative plan that was used to determine implant size; im- plant sizing was correctly predicted from the plan for 62% of acetabular cups (69 of 110) and for 78% of ce- mented stems (43 of 55); how- ever, correct sizing was predicted from the plan in only 42% of cementless stems (23 of 55). Surgeons stray from the template plan for cases in which implants of different size or offset are used, the femoral neck resection is not made where intended preoperatively, the neck cut is modified to provide bet- ter implant fit, or a tight press-fit femoral component fails to fully seat. A further variable is the diffi- culty of predicting the actual superi- or and medial extent of acetabular reaming. Intraoperative Radiographs An intraoperative radiograph can be taken with trial components in place and radiographic landmarks measured, as in revision surgery templating. When possible, both hips should be clearly visible on the film. However, metallic patient po- sitioners that can obscure landmarks may need to be removed during film exposure, making intraoperative magnification hard to assess and ac- curate positioning difficult. Intraoperative Measurements As noted, proper patient position- ing and identification of baseline landmarks are important. The great- er trochanter may be used as an in- traoperative landmark for leg-length measurement. 35 However, the center of the femoral head does not always coincide with the superior tip of the greater trochanter. 36 Several intraoperative methods to measure for implants use one or more reference pins driven into the pelvis. Measurements are made from the pin to a mark on the greater tro- chanter. The leg should be placed in the same position during each mea- surement. Mihalko et al 7 used a method in which a large unicortical fragment screw is placed above the superior rim of the acetabulum. The screw- driver is placed in the hex-headed screw; as the baseline limb length, the distance is measured from the shaft of the screwdriver to a mark made with the cautery at the vastus tubercle on the lateral aspect of the greater trochanter. After the implan- tation of the prosthetic trial compo- nents, a check is made to ensure the appropriate limb length. McGee and Scott 37 used a method in which a Steinmann pin is driven into the pelvis 1.5 to 2 cm superior to the acetabulum and bent into a U. A mark is made at the point where the free end of the U contacts the greater trochanter. T he pin is swiveled out of the operative field and returned dur- ing measurements, with each mea- surement obtained with the legs in a reproducible position. Restoring the mark to the tip of the pin restores the preoperative length, and suitable ad- justments are then made from that reference point. The tip of the pin is used to reference hip offset. Because a standard Steinmann pin may be too short in obese pa- tients, other measuring pins have been recommended. 38,39 One option is to use two Steinmann pins, one in the pelvis and the other in the great- er trochanter. The distance between the two is measured before dislocat- ing the hip and during trial measure- ments. However, a trochanteric pin, which is removed and replaced in its track during measurements, may be unreliable. 38 A variety of measuring calipers has been described in which one end articulates with a pin, pins, or spikes anchored into the pelvis, while a sty- lus at the other end references off a mark on the greater trochanter. 40 Another device combines a spirit level with the two-pin method to eliminate variations in the abduc- tion/adduction position of the leg during measurements. Bose 41 report- ed its use in 117 operations; by using the device, the leg was lengthened >12 mm in 5% of hips, compared with 31% lengthening without the device. Other devices also can measure offset with the use of a vertical cal- iper. In the lateral decubitus posi- tion, the horizontal distance be- tween the tip of the stylus and the marked point on the femur repre- sents the change in leg length, whereas the vertical distance be- tween the tip of the stylus and the lateral surface of the greater tro- chanter represents the change in hip offset. A removable caliper decreas- es the risk of bending or dislodging the pin. The pin should not be used to retract the wound edge or the ab- ductor muscles because doing so may cause it to bend or dislodge from soft bone. Finally, a separate skin stab incision may be required. The accuracy of all of the meth- ods that measure from pins anchored in the pelvis to a point on the great- er trochanter may be affected by the inherent variability of the leg posi- tion when measurements are made. Because bending a pin or dislodging it from osteoporotic bone will com- promise measurements, an intraop- erative radiograph of the pelvis with Leg-Length Discrepancy After Total Hip Arthroplasty 42 Journal of the American Academy of Orthopaedic Surgeons the trial components in place still may be necessary. Variation caused by changes in leg position can be lessened by creating a rigid cradle for the operated leg. 39 Performed following reduction of trial implants, the so-called “shuck” test, described by Charnley, 42 is af- fected by many factors that make it unreliable for leg-length mea- surement. 43-45 However, the test can provide some sense of hip stability, and it may influence the surgeon’s decision on the desired final leg length. The use of a stable pelvic refer- ence, combined with a method for accurately positioning the leg during measurements, provides the surgeon with a practical method for measur- ing leg length during hip arthroplas- ty. Such a method helps the surgeon select implants that provide optimal fit and allows him or her to stray from the preoperative plan, confi- dently using femoral neck and sock- et modularity to adjust the final leg length. Postoperative Assessment and Treatment Options Perception of leg-length inequality is common after the surgical proce- dure. 40 Functional but transient ine- quality was found to occur in 14 of 100 patients in one study. Persistent functional limb-length inequality (FLLI) is far less common and is found most often in patients who are short of stature or who already have some degeneration of the spine. 22 Perceived Inequality of Leg Lengths Pain is the most obvious and fre- quent symptom associated with a perceived postoperative FLLI: low back pain may be associated with an overlengthened leg; impaired abduc- tor function and possibly hip disloca- tion may occur with shortening. 3 Of- ten a patient’s legs were of unequal length before the surgery, and it is important to document this baseline measurement preoperatively. FLLI af- ter THA also may result from a pre- existing degenerative process in the lumbar spine that is producing scoli- osis and pelvic obliquity. 22 Postoperative Assessment A careful physical examination that includes a neurovascular assess- ment is important. Determination of FLLI should be delayed until rehabilitation/recovery has pla- teaued, typically 3 to 6 months after surgery. Preoperative and postoperative clinical measurement of the legs is important; radiographic measure- ments may provide further helpful information. Orthoroentgenography, commonly known as a “scano- gram,” may provide a clear measure- ment of true leg-length inequality. 46 In some cases, a computed tomogra- phy scanogram may give the most accurate assessment of leg lengths, particularly in patients with a flex- ion deformity of the knee. In addi- tion, computed tomography delivers only 20% of the radiation needed for orthoroentgenography. 46 Perhaps most useful is simple but thorough questioning and observa- tion of the patient. How does the leg feel when standing? How does the leg feel when using the walker? Is there pain in the lower back, iliac crest, groin, or abductors? Is the gait awkward? Do these problems seem attributable, at least in part, to leg- length discrepancy? Treatment Nonsurgical management of a perceived or true leg-length inequal- ity can take several forms. The most expedient initial treatment is the in- sertion of a shoe lift for the leg that seems to be shorter; thickness of up to three-eighths of an inch can be in- serted without altering the shoe it- self. In a study by Edeen et al, 26 24% of patients required a shoe lift after THA. A shoe lift also may alleviate some low back pain. Friberg 11 de- scribed a series of more than one thousand cases in which simply pro- viding an adequate shoe lift to cor- rect leg-length inequality resulted in permanent and mostly complete al- leviation of symptoms. However, one should be some- what cautious regarding the early use of a shoe lift because such use may prevent soft-tissue contractures or pelvic obliquity from “relaxing” and perhaps resolving. Therefore, when a lift is used, the surgeon may choose to compensate only for the actual or perceived length discrepan- cy. Similarly, in most cases, it is de- sirable to delay the use of a lift for approximately 6 months postopera- tively to determine whether the per- ceived leg-length discrepancy will resolve. Equally important is the perspec- tive assumed by the physical thera- pist. A positive attitude toward the outcome of therapy by the therapist may make a difference in the pa- tient’s accommodation of a different sensation. Such a sensation may be felt even when the legs are anatom- ically the same length after surgery. Most patients experience gradual (over approximately 6 months) im- provement with therapy that stretches soft tissue and relieves pel- vic obliquity. 22 Assurance from the therapist that the leg will work well with adequate stretching and manip- ulation may affect eventual out- come. As with any change in the body, the “tincture of time” may be all that is necessary for satisfactory functioning. For example, of the 100 patients reviewed by Ranawat and Rodriguez, 22 14 had pelvic obliquity and FLLI 1 month after surgery, but by 6 months postoperatively, all of these symptoms had subsided with the use of physical therapy. Like- wise, in a study by Abraham and Di- mon, 3 perceived postoperative ine- quality was most common in patients with preoperative discrep- ancies in leg length and usually re- solved with time. Charles R. Clark, MD, et al Volume 14, Number 1, January 2006 43 Surgical options are available when nonsurgical management fails to produce the desired effects. Possi- ble indications for surgical manage- ment include severe hip or back pain, hip instability, paresthesias, and foot drop that the surgeon deter- mines may be improved by reducing the leg-length discrepancy. 18 Simple soft-tissue release may relieve symp- toms associated with a minor degree of inequality. 22 For the small subset of patients who have a leg that is too short, a modular head can be changed to increase leg length; how- ever, the increase in length usually is small. For shortening >2 cm, revi- sion to a femoral component with a longer base neck length (eg, a calcar replacement prosthesis) may be con- sidered. More commonly, patients find the leg length to be too long after THA. Femoral shortening can be accom- plished by exchanging a modular head for a shorter one, although this can lead to instability and may only mar- ginally decrease the length. Treat- ment by shortening may improve motor impairment after lengthening. Pritchett 16 described motor improve- ment in 7 of 11 patients who had re- vision shortening of from 0.5 to 3.6 cm. He noted that when painful neu- rologic symptoms accompany leg lengthening after THA, revision hip surgery may be helpful although pa- tients should be informed that the rate of success is far from uniform. When shortening is done, it may be necessary either to exchange the fem- oral component for one with an in- creased offset, use a larger femoral head, or perform a trochanteric os- teotomy to achieve stability. A fur- ther option is use of a constrained ac- etabular liner . If the hip is stable and functions well but the leg is still too long, shortening can be accomplished by a distal femoral osteotomy. All sur- gical options should be undertaken with caution because of the unpre- dictability of symptom improvement and the risk of creating new problems (eg, hip instability). Finally, when hip disease exists in the contralateral hip and contralater- al arthroplasty is contemplated, it may be reasonable to use a shoe lift and other nonsurgical management until the time of the second opera- tion, when the leg lengths can be ap- proximated. In the future, it is likely that ad- vances in technology will lead to greater precision and accuracy in the management of leg length. 47 With the advent of navigation/image- guided surgery technologies, correc- tion of limb-length inequality may be dramatically enhanced. Registra- tion of three-dimensional bony anat- omy, coupled with real-time track- ing during surgery, may allow the surgeon to accurately balance limb length to within 1 or 2 mm of the contralateral side, based on preoper- ative measurement and planning. Current image-guided systems use computed tomography scans, fluoro- scopic imaging, or point matching/ surface registration with optical scanners and morphing technology to provide anatomic referencing for the femur and pelvis at the time of surgery. The relative position of these bony structures can then be tracked in real time as implant ad- justments (eg, cup position and placement, femoral implant posi- tion, offset, femoral head diameter, neck length) are made that affect limb length. Finally, the surgeon can evaluate limb length, range of mo- tion, hip stability, and possible im- pingement of components or ana- tomic structures before closure to ensure optimal clinical outcome. Summary Careful preoperative measurement and assessment, as well as preopera- tive and postoperative education of the patient, are important factors in gaining an acceptable result with re- gard to leg lengths after THA. Equal- izing perceived or actual leg length should not be guaranteed. The pa- tient should be given a realistic ex- pectation of what may be likely after surgery; the preoperative and postop- erative visits during which this in- formation is conveyed can be quite important to the eventual outcome. Ideally, the surgeon’s communica- tion with the physical therapist should go beyond written orders; a surgeon’s attitude and positive ex- pectations may well be adopted by the therapist and passed on to the pa- tient. Only in rare circumstances in which nonsurgical measures—in- cluding education, recovery time, physical therapy, and shoe lifts—fail to bring satisfactory resolution should surgical intervention be con- sidered for leg-length inequality. 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