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Two-Incision Hip Replacement in the Morbidly Obese Patient
Two-Incision Hip Replacement in the Morbidly Obese Patient Dana C. Mears, MD, PhD,* Simon C. Mears, MD, PhD,† and Jacques E. Chelly, MD, PhD, MBA‡ Hip replacement in the morbidly obese patient is fraught with medical, anesthetic, and surgical difficulties. The two-incision technique affords several advantages by providing: 1) a minimally invasive hip replacement in the morbidly obese patient; 2) radiographically controlled orientations for the correct placements of the acetabular and femoral implants; and 3) possibly fewer surgical risk factors via a markedly decreased incision size, allowing rapid return of independent activities. Meticulous medical care and rapid mobilization help to decrease the potential for postoperative complications. We describe total hip replacement in the morbidly obese patient with the use of the two-incision technique. Semin Arthro 18:272-279 © 2007 Elsevier Inc. All rights reserved. KEYWORDS two-incision technique, morbidly obese, hip replacement, postoperative complications, minimally invasive
T
he World Health Organization1 has defined obesity as a body mass index (BMI) between 30 and 40, morbid obesity as a BMI between 40 and 50, and superobesity as a BMI ⬎ 50. Morbid obesity is a problem of epidemic proportions in the United States, currently affecting 5% of the population.2 Comorbidities associated with morbid obesity include hypertension, diabetes mellitus type II, coronary artery disease, stroke, obstructive sleep apnea, and difficult airway access. Compared with the normal population, this subgroup possesses an enhanced incidence of severe degenerative arthritis of the hip and knee,3,4 with a corresponding increase in the need for total joint arthroplasty. Many orthopedic surgeons refuse to perform a total hip replacement in a morbidly obese individual,5 perhaps because this procedure in a morbidly obese patient is associated with multiple challenges in terms of completion of the surgical procedure, medical management, and the potential for numerous complications. Although most surgeons use conventional surgical approaches for virtually all of their arthro-
*Greater Pittsburgh Orthopedic Associates, Pittsburgh, PA. †Department of Orthopaedic Surgery, The Johns Hopkins University/Johns Hopkins Bayview Medical Center, Baltimore, MD. ‡Departments of Anesthesiology and Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA. Address reprint requests to Simon C. Mears, MD, PhD, c/o Elaine P. Henze, BJ, ELS, Department of Orthopaedic Surgery, Johns Hopkins Bayview Medical Center, 4940 Eastern Avenue, A672, Baltimore, MD 212242780. E-mail: [email protected]
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1045-4527/07/$-see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1053/j.sart.2007.09.011
plastic procedures, the large size of the morbidly obese patient complicates the procedure with respect to positioning on the operating table, retraction of the soft tissues, and accurate alignment of the implants. Reported results of total hip replacement in the obese patient vary. Some studies have indicated increased blood loss and infection rates,6,7 whereas others have described no increase in the overall complications.8,9 When the results of total hip replacement are evaluated for morbidly obese patients, the incidence of complications is increased10 with respect to a higher risk for deep wound infection, thromboembolic problems, and pulmonary complications, including a predisposition for sleep apnea. Overall, the potential risk for a postoperative dislocation is increased by the difficulty of positioning the patient accurately and stably and documenting rigorously the optimal intraoperative alignment of the components. In the presence of a thick layer of subcutaneous fat, postoperative fat necrosis represents a predisposition to postoperative wound infection. The use of a minimally invasive approach (such as the two-incision approach) for total hip replacement has not been reported for the morbidly obese patient, but the results of using this approach in other selected population groups have been published.11-13 The two-incision approach addresses several key technical issues by the placement of the femoral and acetabular components through two small incisions, each of which is optimally situated to align the components correctly. If a conventional single incision is used,
Hip replacement in the morbidly obese
Figure 1 A comparison of a standard incision for a morbidly obese incision and two small incisions as used with the minimally invasive technique. In the latter instance, each incision is made along the axis of the center of the acetabulum or the femoral canal. For a standard approach, the cutaneous incision and deep dissection extend the full length of the two small incisions.
the thick subcutaneous layer of fat prohibits the placement of each of the components at the correct orientation unless a greatly enlarged incision is used (Fig 1). This review outlines the use of the two-incision approach for total hip replacement in the morbidly obese patient by addressing the presurgical evaluation, surgical procedure, anesthesia protocol, postoperative pain management, therapy regimen, and management of potential postoperative complications.
Preoperative Clinical Evaluation At the time of an initial clinical presentation, the clinician obtains a conventional history, physical examination, and radiographic assessment, including an inquiry about previous attempts at weight reduction, such as dietary measures and aerobic exercise regimens. Occasionally, a patient acknowledges a commitment for a renewed effort to lose substantial weight before the arthroplasty and subsequently returns to the clinic having lost that substantial weight. More typically, however, such weight reduction attempts are unsuccessful, in part secondary to the sedentary lifestyle engendered by the large body habitus and the severe hip pain provoked by all attempted activity.14,15 Surgical methods of weight reduction are reviewed with the patient. Depending on the patient’s interest and the presence of potential complicating factors, a referral to a bariatric surgeon is made. Bariatric surgery may allow a patient to achieve substantial weight loss and a reversal of the comorbidities of morbid obesity.16,17 If the patient plans to consider seriously both total hip arthroplasty and a gastric bypass procedure, he/she is encouraged to undergo the bypass first. Successful results for subsequent total hip arthroplasty have been reported.18 An enquiry of the medical history focuses on the potential concomitant medical conditions for which the morbidly obese patient is susceptible, including diabetes mellitus, hypertension, venous insufficiency in the lower extremities, and sleep apnea. If such medical evaluations have not been obtained previously, the patient is encouraged to undergo these relevant assessments. Overall, sleep apnea is underdi-
273 agnosed in obese patients, notably one who is about to undergo a total joint replacement.19 In view of the high likelihood for this condition, a routine questionnaire should be instituted20 to help determine which patients should be evaluated formally for sleep apnea. Before the hip surgery, a patient with sleep apnea is fitted with an appropriate continuous positive airway pressure device. As part of the physical examination of the hip, the presence and size of the panniculus and the diameter of the proximal thigh are documented. Ultimately, even for an experienced hip surgeon who is knowledgeable with the two-incision technique, the most limiting factor is the diameter of the thigh compared with the length of the lower extremity. For example, a short patient with a large thigh has insufficient adduction of the involved hip to permit effective preparation of the femoral canal. Usually, a BMI ⬎ 50 is a reasonable guideline for potentially difficult access to the femoral canal, meriting consideration of an alternative surgical approach. Conventional preoperative radiographs of the pelvis and hips are obtained. Radiographic features representing contraindications for the use of the two-incision technique include dysplasia with a high hip center, a marked proximal femoral deformity, and, occasionally, posterior acetabular hardware. The radiographic assessment includes an anteroposterior view of the pelvis and anteroposterior and lateral views of the hip to determine the anticipated type, size, and position of the cementless implants. In the morbidly obese patient, magnification errors routinely accompany the increased distance between the hip joint and the radiographic film cassette, culminating in an undersizing of the implants. If the radiographic quality of the hip joint is markedly impaired by the adjacent adipose tissue, a computed tomography scan merits consideration to permit identification of any complicating radiographic features. After completion of the clinical examination, the clinician reviews with the patient the recommendation for the type of surgical procedure and discusses the therapeutic alternatives, surgical risks, and potential for intra- and postoperative complications.
Anesthesia Preoperative Period Optimal postoperative pain control is needed to enable a patient to optimize his/her functional objectives, including independent gait, independent transfers, and discharge to home. This objective is best achieved with a multimodal approach, including the use of a regional anesthetic technique and a COX-2 inhibitor, pregabalin, and oral opioid administered as needed. After an appropriate preoperative assessment and before surgery, a lumbar plexus block is administered to facilitate the placement of a perineural catheter along with a parasacral sciatic nerve block. Catheter placement may be difficult in the morbidly obese patient and requires technical skill by the anesthesiologist. With the patient in the lateral position, a combination of lumber plexus block and a parasacral sciatic block is performed. The lumbar plexus
D.C. Mears, S.C. Mears, and J.E. Chelly
274 block is monitored by quadriceps muscular contractions via the femoral nerve. The parasacral sciatic block is assessed by repetitive inversion of the foot or a dorsiflexion of the foot and extension of the toes via the common peroneal nerve, eversion, or plantarflexion of the foot and toes via the tibial nerve.
Intraoperative Period Anesthesia for minimally invasive hip surgery can be provided with general or regional anesthesia to supplement the lumbar plexus and sciatic nerve blocks administered via the indwelling catheters. The anesthetic requirement is minimized by the presence of the nerve blocks and ketamine, an N-methyl-D-aspartic acid receptor blocker. Although we prefer a spinal technique, alternative anesthetic techniques are acceptable if the patient can be mobilized within a few hours after the surgical procedure. Many anesthesiologists prefer to use general anesthesia as a means of controlling the airway in a morbidly obese patient who is undergoing ambulatory surgery. The use of propofol for induction and maintenance is preferred21 for optimizing the patient’s recovery and minimizing the risk of postoperative nausea and vomiting. Whatever technique of general anesthesia is used, positive pressure ventilation, along with the minimal administration of opioids and a reversal agent, is favored for such a patient. A spinal and/or epidural technique represents a suitable alternative. With the recent introduction of a pencil-point needle, the frequency of postdural puncture headache after spinal anesthesia has decreased considerably, notably in older patients who are particularly likely to undergo a total hip replacement.22 With the “minidose” bupivacaine–fentanyl spinal technique, the duration of the spinal anesthetic can be adjusted to coincide with the expected duration of the surgery.23 Although the epidural technique is an alternative method for anesthesia and postoperative analgesia, epidural catheter removal is required before the patient is discharged,
whereas a nerve block infusion can be continued at home, which is a considerable asset. To prevent hypothermia and excessive cooling of the patient in the operating room, a “Bear Hugger” or alternative hot-air blower is used in conjunction with the application of a blood warmer for all infused fluids. To optimize recovery of the patient and to minimize the risk of an orthostatic episode, a high volume of replacement fluid is essential. This volume is based on the weight of the patient and the estimated surgical blood loss. Typically, intravenous fluid replacement includes the use of 2500 to 3000 mL of crystalloid and 500 to 1000 mL of colloid solutions.
Surgical Technique Under a suitable spinal or general anesthetic, the patient is placed in a supine position on a radiolucent operating table (Jupiter Operating Table, Trumpf Inc, Charleston, SC) or a similar model that permits an independent hyperextension of the right or left hip and lower extremity. The supine position greatly simplifies the documentation of the pelvic alignment for positioning of the acetabular cup. An inflatable pad is inserted and inflated under the operative hip. A large and pendulant panniculus is taped toward the contralateral side to displace the overlying adipose tissue, which otherwise would impede access to the front of the hip joint (Fig 2). A special padded anchoring strap is placed around the contralateral thigh to secure the patient to the operating table. The ipsilateral upper extremity is placed overhead and suspended from a specialized holding frame. The tension on the axilla is assessed to ensure that the risk of a traction injury to the brachial plexus is minimized. The patient is prepared and draped in a conventional way so that the surgical field extends proximally superior and medial to the umbilicus and distally to include the entire ipsilateral lower extremity. A 12or 15-inch image intensifier is used to identify the critical
Figure 2 This patient is a morbidly obese (height, 5 feet, 2 inches; weight, 285 pounds) 67-year-old woman. (A) Because the panniculus is overlying the anterior incision site, an inflatable pad is used under the operative hip, which facilitates skin preparation, draping, and the initial acetabular approach. (B) Broad tape is used to displace the panniculus away from the groin. (Color version of figure is available online.)
Hip replacement in the morbidly obese landmarks of the hip so that the symphysis also can be observed in the radiographic field. Using an anteroposterior view of the hip joint, the intertrochanteric ridge of the proximal femur is identified. A marker pen is used to draw a 7-cm line overlying the intertrochanteric ridge. This line represents the conventional site for the anterior incision on a patient of normal weight. For each additional 100 pounds of weight, the incision is displaced inferiorly and laterally by 2 cm along a line parallel to the intertrochanteric line. The incision is extended sharply to the deep fascia. The interval between the tensor fascia lata and the sartorius muscles is identified by palpation. Especially in an obese patient, this proper interval is confirmed by palpation of the anterior superior iliac spine. If an interval medial to the anterior superior iliac spine is developed inadvertently, it represents a hazardous position between the sartorius and the iliopsoas. When a retractor is placed erroneously around the iliopsoas, the associated femoral nerve and its branches are highly vulnerable to a traction injury. This error is more likely to occur in a morbidly obese patient than in a patient of normal weight. Likewise, an excessively lateral interval between the tensor and glutei muscles can be entered inadvertently, which greatly hampers a proper approach to the acetabulum. The interval between the tensor and sartorius muscles is developed with finger dissection continuing below the sartorius and the direct head of rectus femoris to the precapsular fat. Frequently, anomalous patterns of vessels are encountered, including superficial and deep branches or a T-type branch. The latter ascends the capsule along the lateral margin of the rectus femoris toward the acetabular rim. The relevant vessels are clamped, cauterized, and divided. Then, the capsule is divided with electrocautery along the axis of the femoral neck. Supplementary releases in the capsule are made along the acetabular rim and the intertrochanteric line. A variable sized portion of the anterior capsule is removed to augment the view of the underlying hip joint. The appropriate site on the femoral neck for a standard femoral osteotomy is marked with fluoroscopy at the site predicted with preoperative templating. The neck is divided with a reciprocal saw, and a second parallel division is made through the equator of the femoral head. The neck fragment is removed by impalement with a Schanz screw. The head fragment is grasped with a uterine clamp and the ligamentum teres is transected with a special cutting tool. The labrum and all intraarticular soft tissue are removed. The acetabulum is reamed with a hemispherical reamer that is connected to an angled drive shaft. After reaming, a cementless acetabular component is impacted in place with an angled insertional tool. To confirm the appropriate depth, positioning, and sizing of the reamed concavity and the position of the acetabular cup, fluoroscopic images are taken at strategic stages and compared with visual observations. Before the insertion of the cup, the pad under the hip is deflated so that the cup is positioned in the truly supine patient. The alignment of the symphysis is used to confirm the proper orientation of the pelvis and to ensure that the abduction angle of the impacted cup is 45°. To ensure that the placement of the acetabular
275 component is at 20 to 25° of anteversion, four assessments are used. 1) Placement of the guide on the implant parallel to the floor provides an abduction angle of 25°. 2) The fluoroscopic image of the cup is used to assess the anteversion of the cup. 3) Fluoroscopic images of the cup are taken after the impaction to ensure that the separation of the driver from the cup does not culminate in a movement of the cup with a loss of the optimal alignment. Subsequently, two screws are used to anchor the cup. 4) Fluoroscopic imaging is repeated to ensure that the insertion of an eccentrically positioned screw does not provoke a shift in the position of the cup. A polyethylene liner then is locked into the cup. To prepare the femur, the contralateral hip initially is hyperextended by an adjustment of the lower segment of the table that underlies that extremity. The underlying hip is hyperextended sufficiently so that the operative hip is in 10 to 20° of hyperextension. When a patient’s thigh girth is greater than that of an individual of normal weight, a correspondingly greater degree of hyperextension of the contralateral hip is needed to achieve the desired position of the operative limb. The operative limb is placed over the contralateral limb to provide adduction of the operative hip joint. The operative limb is positioned in a “figure-four” position, with external rotation and adduction of the hip. Just as for an individual of normal weight, three hip retractors are inserted: one around the base of the medial femoral neck, one below the tubercle of the greater trochanter, and one around the front of the greater trochanter (which retracts the hip abductor muscles). To augment the visualization in a morbidly obese patient, a fourth retractor may be placed on the anterolateral rim of the acetabulum, immediately superior to the cup. This retraction permits a direct view of the osteotomized femoral neck. A special angled box chisel is used to create a slot in the femoral neck, along the axis of the anticipated femoral stem. The capsule at the base of the lateral neck is excised sharply. With lengthy scissors, a division is made in the hip capsule above the insertion of the piriformis tendon. Deep to the capsule, the scissors are bluntly spread to create a “tunnel” through the gluteus maximus. Subsequently, the tunnel is used for the insertion of the femoral stem. Lines are drawn on the anterior and lateral axes of the thigh that extend proximally to the lateral aspect of the iliac crest. A second 4-cm incision is made along the axis of the first incision at approximately the intersection of these two lines. This incision is made approximately 10 cm below the iliac crest and is continued sharply below the deep fascia. Curved scissors are used to create a tunnel through the superficial portion of the gluteus maximus, to connect with the previous capsular incision. Three dilating tools are used to enlarge the tunnel gently (Fig 3A and B). A ball-ended guide wire is inserted through the second incision and advanced into the femoral canal. Cannulated flexible reamers are used in incremental sizes until substantial contact or chatter on the bony surface is felt. Solid reamers are used incrementally under fluoroscopy to reaffirm the proper depth and diameter of the reamed canal. An 8-inch extension rod is attached to each reamer to create a tool sufficiently long to pass through the thick soft-tissue
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Figure 3 The tools for femoral preparation in this 62-year-old morbidly obese woman (height, 5 feet 7 inches; weight, 305 pounds). (A and B) During the preparation of the second incision, after a blunt preparation of a tunnel through the gluteus maximus and extending through the previously prepared capsular incision, rectal dilators are used to enlarge the tunnel gently. (C and D) An 8-inch extension is attached to the reamer for reaming the femoral canal. (Color version of figure is available online.)
envelop (Fig 3C and D). Two sequential sizes of rasps are used to complete the preparation of the canal. The last rasp corresponds to the size of the largest solid reamer and the cementless stem itself. The proper axial alignment and fit and fill of the rasp are confirmed with fluoroscopy. For the morbidly obese patient, a fully coated or Epoch stem (Zimmer Inc, Warsaw, IN) is impacted progressively until fully seated. During the rasping or stem insertion, the progress and proper rotation of the depth of the rasp or stem is visualized directly through the anterior incision. Fluoroscopy is used to reconfirm the appropriate axial alignment of the rasp or stem and of the fit and fill of the stem in the canal. The operating table is readjusted to restore the contralateral hip to a neutral position. Through the anterior incision, a trial femoral head component is applied to the femoral neck. To facilitate the application of the trial and definitive heads in a morbidly obese individual, the split table under the ipsilateral lower extremity is adjusted to provide 20° of hyperextension of the operative hip. With this maneuver, accompanied by the application of a bone hook around the trunnion of the femoral stem, the trunnion is brought closer to the entrance of the incision. The hip is reduced to assess the proper stability of the hip and tension of the soft tissues. Both hips are imaged fluoroscopically to assess limb-length equality. Once the proper limb length is confirmed, the hip is dislocated for a replacement of the trial head by a definitive
metallic or ceramic head. During the removal of the trial head, care is taken to minimize the risk of losing it within the incision by placing a finger underneath the trial head. Although the hip capsule can be closed, we have not found that somewhat tedious step to be helpful. A small suction drain is inserted, the wounds are irrigated, and the deep fascia, subcutaneous tissues, and skin are closed in a routine fashion with resorbable sutures.
Postoperative Care After surgery, the patient is transferred to a postoperative recovery unit where vital signs and oxygen saturation are monitored. When the patient is stable, he/she is transferred to a unit with a monitored bed. Pain is controlled by the continuous lumbar plexus block and administration of celecoxib and pregabalin. The catheters are removed on the second day after surgery. An aggressive postoperative therapy regimen is critical to mobilize the morbidly obese patient rapidly and to decrease the potential for postoperative complications, such as atelectasis, pneumonia, and venous stasis. After the initial recovery period, the patient is assisted by a therapist to transfer from the bed to a chair and to a standing position. In view of the potential for postural hypotension and a complaint of lightheadedness, the initial transfer of a morbidly obese individ-
Hip replacement in the morbidly obese ual is supervised by a therapist and an aid. Once the patient tolerates an erect position, gait training with the use of an appropriately large walker is initiated, along with independent transfers. As the therapy sessions progress, an assessment of the optimal walking aid follows, potentially including the use of a cane. If necessary, the patient is taught to climb stairs. Typically, on day 2, the morbidly obese patient is discharged home. Routine postoperative follow-up assessments are undertaken at 1, 6, 12, and 24 months after surgery.
Postoperative Complications Related to Anesthesia and Pain Management In a morbidly obese patient, excessive sedation from opioids may culminate in obstructive apnea, respiratory arrest, or cardiac arrest. The use of a continuous peripheral nerve block serves to lessen the reliance on opioids and to decrease the potential for excessive sedation. A lumbar plexus block can be associated with several potential complications. 1) A grand mal seizure, which is an infrequent complication, may occur after the inadvertent intravascular dissemination of ropivacaine. The administration of 2 mg of midazolam intravenously provides a rapid resolution of the seizure. 2) A lack of infusion of the local anesthetic solution may occur if the catheter becomes dislodged or the pump has a mechanical or an electrical failure. A secure taping of the catheter to the patient is critical for minimizing the risk of premature dislodgement or leakage. 3) The catheter may be positioned incorrectly and thus fail to provide pain relief. The institution of nursing protocol for serial evaluations of the lumbar plexus block ensures recognition of the problem so an alternative therapy can be initiated.
Wound Infection In the morbidly obese patient, the anterior incision is particularly vulnerable to breakdown or dehiscence. Generally, the posterior wound heals without difficulty. In the morbidly obese patient, coverage of the anterior wound by the overhanging panniculus creates a warm and moist environment that promotes the onset of a superficial wound infection. Because of this protuberant abdomen, a morbidly obese patient cannot visualize the anterior incision wound. Therefore, in the early postoperative period, the patient is likely to ignore incisional drainage or even dehiscence. As a supplementary problem, most obese patients are embarrassed to request assistance for dressing changes and other forms of wound care. If a superficial wound infection ensues, it prolongs the time required for complete healing of the incision and can lead to a deep wound infection, thereby jeopardizing the viability of the arthroplasty. To minimize the potential for these problems, several strategies have been adopted. A resorbable suture (eg, 4.0 Monocryl; Ethicon, Somerville, NJ) is used for the cutaneous closure, along with a skin glue (eg, Indermil; Syneture, Norwalk, CT) or tissue adhesive. The
277 skin glue functions as a sealant for the incision. The use of alternative materials, such as nonresorbable sutures or staples, is less satisfactory in this potentially moist environment. The placement of a dry dressing over the incision is needed to insulate it from the overlying panniculus. Until the anterior incision is healed completely, the dry dressing is changed twice per day to maintain a dry barrier interface.
Venous Insufficiency A morbidly obese patient has an elevated intraabdominal pressure, which culminates secondarily in an elevation of the iliofemoral venous pressure.24 Over the long term, an increased iliofemoral venous pressure promotes venous stasis, edema, and venous stasis ulceration. Serial postoperative assessments of the lower legs and calves are performed to identify features of secondary cellulitis or ulceration so that prompt and aggressive treatment with antibiotics and compressive dressings can be initiated.
Thrombosis/Embolism Morbid obesity is a major risk factor for deep venous thrombosis and pulmonary embolism.25 The latter complication is one of the most common causes of death for the morbidly obese patient after gastric bypass surgery.26 A contributing factor to deep venous thrombosis is the elevation of venous pressures and venous insufficiency. After surgery, a morbidly obese patient is managed aggressively with mechanical and chemical prophylaxis. In view of the large lower leg circumference in such a patient, the use of thromboembolism-deterrent stockings may be difficult or impossible. Generally, thigh stockings cannot be used without creating marked indentations in the skin. Usually, a pair of fitted and sized calf stockings can be used without difficulty. Meticulous observation by the nursing staff is required to avoid binding of the skin from the edge of an ill-fitting stocking. In view of the difficulty in obtaining properly fitted sequential compressive devices, the use of foot pumps is preferred. Chemical prophylaxis with warfarin or low-molecular-weight heparin is used for at least 1 month after surgery.
Pulmonary Issues A morbidly obese patient is vulnerable to diverse pulmonary complications, such as atelectasis and pneumonia. Early mobilization of the patient is crucial to minimize this risk. Satisfactory pain management is instrumental in enabling a postoperative patient to sit, transfer, and ambulate, and thereby to optimize his/her pulmonary function. The aggressive use of an incentive spirometer facilitates pulmonary toilet.
Diabetes Mellitus A morbidly obese patient is predisposed to diabetes mellitus and to prediabetes.27 An elevated perioperative glucose level appears to increase the risk of a postoperative wound infection.28 Before, during, and after surgery, the blood glucose level is monitored carefully by assessments undertaken at 6-h intervals. If an elevation of the blood glucose level is con-
278 firmed, a sliding scale of insulin is used. The use of insulin in the preoperative period may be necessary, even for a patient who is not diabetic.
Cardiovascular Issues Morbid obesity predisposes a patient to hypertension, dyslipidemia, and cardiovascular disease.2 This collection of comorbidites is termed the metabolic syndrome.29 In the early postoperative period for such patients, an attempt is made to maintain blood pressure to minimize the risk of cardiac ischemia. A complaint of chest pain is evaluated promptly with electrocardiography and troponin testing to rule out myocardial infarction.
Sleep Apnea Sleep apnea occurs in approximately 24% of individuals with a BMI ⬎ 40.30 After total joint replacement, sleep apnea is a risk factor for perioperative mortality.31,32 On the first night after surgery, hypoxemia frequently ensues from the typical application of opioids for pain management. A hypoxemic patient is susceptible to cardiac arrhythmia, ischemia, and respiratory distress, all of which may be associated with fatal consequences. Overall, sleep apnea is underdiagnosed in obese patients, notably in those undergoing total joint replacements.19 To minimize such complications, a morbidly obese patient with sleep apnea is encouraged to bring his/her continuous positive airway pressure machine to the hospital for use after surgery. For the first postoperative evening, continuous pulse oximetry monitoring is undertaken.33
Conclusion The two-incision approach to hip replacement in the morbidly obese patient affords several advantages, including excellent exposure, the correct angles for facilitating implant placement, and rapid mobilization and recovery. Careful attention to detail is required for an optimal outcome in such a challenging patient. The protocol includes a preoperative examination to identify the typical comorbidites of morbid obesity, an anesthetic routine to facilitate the recovery, and a postoperative plan to minimize complications.
References 1. World Health Organization: Obesity: Preventing and managing the global epidemic. Report of a WHO consultation. World Health Organ Tech Rep Ser 894:vii-xii, 1-253, 2000 2. Hensrud DD, Klein S: Extreme obesity: A new medical crisis in the United States. Mayo Clin Proc 81:S5-S10, 2006 3. Wendelboe AM, Hegmann KT, Biggs JJ, et al: Relationships between body mass indices and surgical replacements of knee and hip joints. Am J Prev Med 25:290-295, 2003 4. Flugsrud GB, Nordsletten L, Espehaug B, et al: The impact of body mass index on later total hip arthroplasty for primary osteoarthritis: A cohort study in 1.2 million persons. Arthritis Rheum 54:802-807, 2006 5. Naik G: Surgeons’ weighty dilemma: Wary of extra risk, work, some doctors won’t replace knees, hips of obese patients. Wall St J (East Ed). February 28:B1, 2006
D.C. Mears, S.C. Mears, and J.E. Chelly 6. Namba RS, Paxton L, Fithian DC, et al: Obesity and perioperative morbidity in total hip and total knee arthroplasty patients. J Arthroplasty 20:46-50, 2005 7. Bowditch MG, Villar RN: Do obese patients bleed more? A prospective study of blood loss at total hip replacement. Ann R Coll Surg Engl 81:198-200, 1999 8. Ibrahim T, Hobson S, Beiri A, et al: No influence of body mass index on early outcome following total hip arthroplasty. Int Orthop 29:359-361, 2005 9. Soballe K, Christensen F, Luxhoj T: Hip replacement in obese patients. Acta Orthop Scand 58:223-225, 1987 10. Lehman DE, Capello WN, Feinberg JR: Total hip arthroplasty without cement in obese patients: A minimum two-year clinical and radiographic follow-up study. J Bone Joint Surg Am 76:854-862, 1994 11. Bal BS, Haltom D, Aleto T, et al: Early complications of primary total hip replacement performed with a two-incision minimally invasive technique. J Bone Joint Surg Am 87:2432-2438, 2005 12. Berger RA: Total hip arthroplasty using the minimally invasive twoincision approach. Clin Orthop Relat Res 417:232-241, 2003 13. Berry DJ, Berger RA, Callaghan JJ, et al: Minimally invasive total hip arthroplasty: Development, early results, and a critical analysis. J Bone Joint Surg Am 85:2235-2246, 2003 14. Aderinto J, Brenkel IJ, Chan P: Weight change following total hip replacement: A comparison of obese and non-obese patients. Surgeon 3:269-272, 305, 2005 15. Heisel C, Silva M, dela Rosa MA, et al: The effects of lower-extremity total joint replacement for arthritis on obesity. Orthopedics 28:157159, 2005 16. Buchwald H, Avidor Y, Braunwald E, et al: Bariatric surgery: A systematic review and meta-analysis. J Am Med Assoc 292:1724-1737, 2004 17. Kushner RF, Noble CA: Long-term outcome of bariatric surgery: An interim analysis. Mayo Clin Proc 81:S46-S51, 2006 18. Parvizi J, Trousdale RT, Sarr MG: Total joint arthroplasty in patients surgically treated for morbid obesity. J Arthroplasty 15:1003-1008, 2000 19. Harrison MM, Childs A, Carson PE: Incidence of undiagnosed sleep apnea in patients scheduled for elective total joint arthroplasty. J Arthroplasty 18:1044-1047, 2003 20. Netzer NC, Stoohs RA, Netzer CM, et al: Using the Berlin Questionnaire to identify patients at risk for the sleep apnea syndrome. Ann Intern Med 131:485-491, 1999 21. Apfel CC, Korttila K, Abdalla M, et al: A factorial trial of six interventions for the prevention of postoperative nausea and vomiting. N Engl J Med 350:2441-2451, 2004 22. Tsen LC, Hepner DL: Needles used for spinal anesthesia. Expert Rev Med Devices 3:499-508, 2006 23. Ben-David B, Frankel R, Arzumonov T, et al: Minidose bupivacaine– fentanyl spinal anesthesia for surgical repair of hip fracture in the aged. Anesthesiology 92:6-10, 2000 24. Arfvidsson B, Eklof B, Balfour J: Iliofemoral venous pressure correlates with intraabdominal pressure in morbidly obese patients. Vasc Endovascular Surg 39:505-509, 2005 25. Mantilla CB, Horlocker TT, Schroeder DR, et al: Risk factors for clinically relevant pulmonary embolism and deep venous thrombosis in patients undergoing primary hip or knee arthroplasty. Anesthesiology 99:552-560, 2003 26. Abou-Nukta F, Alkhoury F, Arroyo K, et al: Clinical pulmonary embolus after gastric bypass surgery. Surg Obes Relat Dis 2:24-28, 2006 27. Sugerman HJ, Wolfe LG, Sica DA, et al: Diabetes and hypertension in severe obesity and effects of gastric bypass-induced weight loss. Ann Surg 237:751-756, disc 757-758, 2003 28. Pomposelli JJ, Baxter JK III, Babineau TJ, et al: Early postoperative glucose control predicts nosocomial infection rate in diabetic patients. J Parenter Enteral Nutr 22:77-81, 1998 29. Eckel RH, Grundy SM, Zimmet PZ: The metabolic syndrome. Lancet 365:1415-1428, 2005 30. Scott SK, Rabito FA, Price PD, et al: Comorbidity among the morbidly obese: A comparative study of 2002 U.S. hospital patient discharges. Surg Obes Relat Dis 2:105-111, 2006
Hip replacement in the morbidly obese 31. Gupta RM, Parvizi J, Hanssen AD, et al: Postoperative complications in patients with obstructive sleep apnea syndrome undergoing hip or knee replacement: A case-control study. Mayo Clin Proc 76:897-905, 2001 32. Parikh SN, Stuchin SA, Maca C, et al: Sleep apnea syndrome in patients undergoing total joint arthroplasty. J Arthroplasty 17:635-642, 2002
279 33. Gross JB, Bachenberg KL, Benumof JL, et al: Practice guidelines for the perioperative management of patients with obstructive sleep apnea: A report by the American Society of Anesthesiologists Task Force on Perioperative Management of patients with obstructive sleep apnea. Anesthesiology 104:1081-1093, 2006
T
he World Health Organization1 has defined obesity as a body mass index (BMI) between 30 and 40, morbid obesity as a BMI between 40 and 50, and superobesity as a BMI ⬎ 50. Morbid obesity is a problem of epidemic proportions in the United States, currently affecting 5% of the population.2 Comorbidities associated with morbid obesity include hypertension, diabetes mellitus type II, coronary artery disease, stroke, obstructive sleep apnea, and difficult airway access. Compared with the normal population, this subgroup possesses an enhanced incidence of severe degenerative arthritis of the hip and knee,3,4 with a corresponding increase in the need for total joint arthroplasty. Many orthopedic surgeons refuse to perform a total hip replacement in a morbidly obese individual,5 perhaps because this procedure in a morbidly obese patient is associated with multiple challenges in terms of completion of the surgical procedure, medical management, and the potential for numerous complications. Although most surgeons use conventional surgical approaches for virtually all of their arthro-
*Greater Pittsburgh Orthopedic Associates, Pittsburgh, PA. †Department of Orthopaedic Surgery, The Johns Hopkins University/Johns Hopkins Bayview Medical Center, Baltimore, MD. ‡Departments of Anesthesiology and Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA. Address reprint requests to Simon C. Mears, MD, PhD, c/o Elaine P. Henze, BJ, ELS, Department of Orthopaedic Surgery, Johns Hopkins Bayview Medical Center, 4940 Eastern Avenue, A672, Baltimore, MD 212242780. E-mail: [email protected]
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plastic procedures, the large size of the morbidly obese patient complicates the procedure with respect to positioning on the operating table, retraction of the soft tissues, and accurate alignment of the implants. Reported results of total hip replacement in the obese patient vary. Some studies have indicated increased blood loss and infection rates,6,7 whereas others have described no increase in the overall complications.8,9 When the results of total hip replacement are evaluated for morbidly obese patients, the incidence of complications is increased10 with respect to a higher risk for deep wound infection, thromboembolic problems, and pulmonary complications, including a predisposition for sleep apnea. Overall, the potential risk for a postoperative dislocation is increased by the difficulty of positioning the patient accurately and stably and documenting rigorously the optimal intraoperative alignment of the components. In the presence of a thick layer of subcutaneous fat, postoperative fat necrosis represents a predisposition to postoperative wound infection. The use of a minimally invasive approach (such as the two-incision approach) for total hip replacement has not been reported for the morbidly obese patient, but the results of using this approach in other selected population groups have been published.11-13 The two-incision approach addresses several key technical issues by the placement of the femoral and acetabular components through two small incisions, each of which is optimally situated to align the components correctly. If a conventional single incision is used,
Hip replacement in the morbidly obese
Figure 1 A comparison of a standard incision for a morbidly obese incision and two small incisions as used with the minimally invasive technique. In the latter instance, each incision is made along the axis of the center of the acetabulum or the femoral canal. For a standard approach, the cutaneous incision and deep dissection extend the full length of the two small incisions.
the thick subcutaneous layer of fat prohibits the placement of each of the components at the correct orientation unless a greatly enlarged incision is used (Fig 1). This review outlines the use of the two-incision approach for total hip replacement in the morbidly obese patient by addressing the presurgical evaluation, surgical procedure, anesthesia protocol, postoperative pain management, therapy regimen, and management of potential postoperative complications.
Preoperative Clinical Evaluation At the time of an initial clinical presentation, the clinician obtains a conventional history, physical examination, and radiographic assessment, including an inquiry about previous attempts at weight reduction, such as dietary measures and aerobic exercise regimens. Occasionally, a patient acknowledges a commitment for a renewed effort to lose substantial weight before the arthroplasty and subsequently returns to the clinic having lost that substantial weight. More typically, however, such weight reduction attempts are unsuccessful, in part secondary to the sedentary lifestyle engendered by the large body habitus and the severe hip pain provoked by all attempted activity.14,15 Surgical methods of weight reduction are reviewed with the patient. Depending on the patient’s interest and the presence of potential complicating factors, a referral to a bariatric surgeon is made. Bariatric surgery may allow a patient to achieve substantial weight loss and a reversal of the comorbidities of morbid obesity.16,17 If the patient plans to consider seriously both total hip arthroplasty and a gastric bypass procedure, he/she is encouraged to undergo the bypass first. Successful results for subsequent total hip arthroplasty have been reported.18 An enquiry of the medical history focuses on the potential concomitant medical conditions for which the morbidly obese patient is susceptible, including diabetes mellitus, hypertension, venous insufficiency in the lower extremities, and sleep apnea. If such medical evaluations have not been obtained previously, the patient is encouraged to undergo these relevant assessments. Overall, sleep apnea is underdi-
273 agnosed in obese patients, notably one who is about to undergo a total joint replacement.19 In view of the high likelihood for this condition, a routine questionnaire should be instituted20 to help determine which patients should be evaluated formally for sleep apnea. Before the hip surgery, a patient with sleep apnea is fitted with an appropriate continuous positive airway pressure device. As part of the physical examination of the hip, the presence and size of the panniculus and the diameter of the proximal thigh are documented. Ultimately, even for an experienced hip surgeon who is knowledgeable with the two-incision technique, the most limiting factor is the diameter of the thigh compared with the length of the lower extremity. For example, a short patient with a large thigh has insufficient adduction of the involved hip to permit effective preparation of the femoral canal. Usually, a BMI ⬎ 50 is a reasonable guideline for potentially difficult access to the femoral canal, meriting consideration of an alternative surgical approach. Conventional preoperative radiographs of the pelvis and hips are obtained. Radiographic features representing contraindications for the use of the two-incision technique include dysplasia with a high hip center, a marked proximal femoral deformity, and, occasionally, posterior acetabular hardware. The radiographic assessment includes an anteroposterior view of the pelvis and anteroposterior and lateral views of the hip to determine the anticipated type, size, and position of the cementless implants. In the morbidly obese patient, magnification errors routinely accompany the increased distance between the hip joint and the radiographic film cassette, culminating in an undersizing of the implants. If the radiographic quality of the hip joint is markedly impaired by the adjacent adipose tissue, a computed tomography scan merits consideration to permit identification of any complicating radiographic features. After completion of the clinical examination, the clinician reviews with the patient the recommendation for the type of surgical procedure and discusses the therapeutic alternatives, surgical risks, and potential for intra- and postoperative complications.
Anesthesia Preoperative Period Optimal postoperative pain control is needed to enable a patient to optimize his/her functional objectives, including independent gait, independent transfers, and discharge to home. This objective is best achieved with a multimodal approach, including the use of a regional anesthetic technique and a COX-2 inhibitor, pregabalin, and oral opioid administered as needed. After an appropriate preoperative assessment and before surgery, a lumbar plexus block is administered to facilitate the placement of a perineural catheter along with a parasacral sciatic nerve block. Catheter placement may be difficult in the morbidly obese patient and requires technical skill by the anesthesiologist. With the patient in the lateral position, a combination of lumber plexus block and a parasacral sciatic block is performed. The lumbar plexus
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274 block is monitored by quadriceps muscular contractions via the femoral nerve. The parasacral sciatic block is assessed by repetitive inversion of the foot or a dorsiflexion of the foot and extension of the toes via the common peroneal nerve, eversion, or plantarflexion of the foot and toes via the tibial nerve.
Intraoperative Period Anesthesia for minimally invasive hip surgery can be provided with general or regional anesthesia to supplement the lumbar plexus and sciatic nerve blocks administered via the indwelling catheters. The anesthetic requirement is minimized by the presence of the nerve blocks and ketamine, an N-methyl-D-aspartic acid receptor blocker. Although we prefer a spinal technique, alternative anesthetic techniques are acceptable if the patient can be mobilized within a few hours after the surgical procedure. Many anesthesiologists prefer to use general anesthesia as a means of controlling the airway in a morbidly obese patient who is undergoing ambulatory surgery. The use of propofol for induction and maintenance is preferred21 for optimizing the patient’s recovery and minimizing the risk of postoperative nausea and vomiting. Whatever technique of general anesthesia is used, positive pressure ventilation, along with the minimal administration of opioids and a reversal agent, is favored for such a patient. A spinal and/or epidural technique represents a suitable alternative. With the recent introduction of a pencil-point needle, the frequency of postdural puncture headache after spinal anesthesia has decreased considerably, notably in older patients who are particularly likely to undergo a total hip replacement.22 With the “minidose” bupivacaine–fentanyl spinal technique, the duration of the spinal anesthetic can be adjusted to coincide with the expected duration of the surgery.23 Although the epidural technique is an alternative method for anesthesia and postoperative analgesia, epidural catheter removal is required before the patient is discharged,
whereas a nerve block infusion can be continued at home, which is a considerable asset. To prevent hypothermia and excessive cooling of the patient in the operating room, a “Bear Hugger” or alternative hot-air blower is used in conjunction with the application of a blood warmer for all infused fluids. To optimize recovery of the patient and to minimize the risk of an orthostatic episode, a high volume of replacement fluid is essential. This volume is based on the weight of the patient and the estimated surgical blood loss. Typically, intravenous fluid replacement includes the use of 2500 to 3000 mL of crystalloid and 500 to 1000 mL of colloid solutions.
Surgical Technique Under a suitable spinal or general anesthetic, the patient is placed in a supine position on a radiolucent operating table (Jupiter Operating Table, Trumpf Inc, Charleston, SC) or a similar model that permits an independent hyperextension of the right or left hip and lower extremity. The supine position greatly simplifies the documentation of the pelvic alignment for positioning of the acetabular cup. An inflatable pad is inserted and inflated under the operative hip. A large and pendulant panniculus is taped toward the contralateral side to displace the overlying adipose tissue, which otherwise would impede access to the front of the hip joint (Fig 2). A special padded anchoring strap is placed around the contralateral thigh to secure the patient to the operating table. The ipsilateral upper extremity is placed overhead and suspended from a specialized holding frame. The tension on the axilla is assessed to ensure that the risk of a traction injury to the brachial plexus is minimized. The patient is prepared and draped in a conventional way so that the surgical field extends proximally superior and medial to the umbilicus and distally to include the entire ipsilateral lower extremity. A 12or 15-inch image intensifier is used to identify the critical
Figure 2 This patient is a morbidly obese (height, 5 feet, 2 inches; weight, 285 pounds) 67-year-old woman. (A) Because the panniculus is overlying the anterior incision site, an inflatable pad is used under the operative hip, which facilitates skin preparation, draping, and the initial acetabular approach. (B) Broad tape is used to displace the panniculus away from the groin. (Color version of figure is available online.)
Hip replacement in the morbidly obese landmarks of the hip so that the symphysis also can be observed in the radiographic field. Using an anteroposterior view of the hip joint, the intertrochanteric ridge of the proximal femur is identified. A marker pen is used to draw a 7-cm line overlying the intertrochanteric ridge. This line represents the conventional site for the anterior incision on a patient of normal weight. For each additional 100 pounds of weight, the incision is displaced inferiorly and laterally by 2 cm along a line parallel to the intertrochanteric line. The incision is extended sharply to the deep fascia. The interval between the tensor fascia lata and the sartorius muscles is identified by palpation. Especially in an obese patient, this proper interval is confirmed by palpation of the anterior superior iliac spine. If an interval medial to the anterior superior iliac spine is developed inadvertently, it represents a hazardous position between the sartorius and the iliopsoas. When a retractor is placed erroneously around the iliopsoas, the associated femoral nerve and its branches are highly vulnerable to a traction injury. This error is more likely to occur in a morbidly obese patient than in a patient of normal weight. Likewise, an excessively lateral interval between the tensor and glutei muscles can be entered inadvertently, which greatly hampers a proper approach to the acetabulum. The interval between the tensor and sartorius muscles is developed with finger dissection continuing below the sartorius and the direct head of rectus femoris to the precapsular fat. Frequently, anomalous patterns of vessels are encountered, including superficial and deep branches or a T-type branch. The latter ascends the capsule along the lateral margin of the rectus femoris toward the acetabular rim. The relevant vessels are clamped, cauterized, and divided. Then, the capsule is divided with electrocautery along the axis of the femoral neck. Supplementary releases in the capsule are made along the acetabular rim and the intertrochanteric line. A variable sized portion of the anterior capsule is removed to augment the view of the underlying hip joint. The appropriate site on the femoral neck for a standard femoral osteotomy is marked with fluoroscopy at the site predicted with preoperative templating. The neck is divided with a reciprocal saw, and a second parallel division is made through the equator of the femoral head. The neck fragment is removed by impalement with a Schanz screw. The head fragment is grasped with a uterine clamp and the ligamentum teres is transected with a special cutting tool. The labrum and all intraarticular soft tissue are removed. The acetabulum is reamed with a hemispherical reamer that is connected to an angled drive shaft. After reaming, a cementless acetabular component is impacted in place with an angled insertional tool. To confirm the appropriate depth, positioning, and sizing of the reamed concavity and the position of the acetabular cup, fluoroscopic images are taken at strategic stages and compared with visual observations. Before the insertion of the cup, the pad under the hip is deflated so that the cup is positioned in the truly supine patient. The alignment of the symphysis is used to confirm the proper orientation of the pelvis and to ensure that the abduction angle of the impacted cup is 45°. To ensure that the placement of the acetabular
275 component is at 20 to 25° of anteversion, four assessments are used. 1) Placement of the guide on the implant parallel to the floor provides an abduction angle of 25°. 2) The fluoroscopic image of the cup is used to assess the anteversion of the cup. 3) Fluoroscopic images of the cup are taken after the impaction to ensure that the separation of the driver from the cup does not culminate in a movement of the cup with a loss of the optimal alignment. Subsequently, two screws are used to anchor the cup. 4) Fluoroscopic imaging is repeated to ensure that the insertion of an eccentrically positioned screw does not provoke a shift in the position of the cup. A polyethylene liner then is locked into the cup. To prepare the femur, the contralateral hip initially is hyperextended by an adjustment of the lower segment of the table that underlies that extremity. The underlying hip is hyperextended sufficiently so that the operative hip is in 10 to 20° of hyperextension. When a patient’s thigh girth is greater than that of an individual of normal weight, a correspondingly greater degree of hyperextension of the contralateral hip is needed to achieve the desired position of the operative limb. The operative limb is placed over the contralateral limb to provide adduction of the operative hip joint. The operative limb is positioned in a “figure-four” position, with external rotation and adduction of the hip. Just as for an individual of normal weight, three hip retractors are inserted: one around the base of the medial femoral neck, one below the tubercle of the greater trochanter, and one around the front of the greater trochanter (which retracts the hip abductor muscles). To augment the visualization in a morbidly obese patient, a fourth retractor may be placed on the anterolateral rim of the acetabulum, immediately superior to the cup. This retraction permits a direct view of the osteotomized femoral neck. A special angled box chisel is used to create a slot in the femoral neck, along the axis of the anticipated femoral stem. The capsule at the base of the lateral neck is excised sharply. With lengthy scissors, a division is made in the hip capsule above the insertion of the piriformis tendon. Deep to the capsule, the scissors are bluntly spread to create a “tunnel” through the gluteus maximus. Subsequently, the tunnel is used for the insertion of the femoral stem. Lines are drawn on the anterior and lateral axes of the thigh that extend proximally to the lateral aspect of the iliac crest. A second 4-cm incision is made along the axis of the first incision at approximately the intersection of these two lines. This incision is made approximately 10 cm below the iliac crest and is continued sharply below the deep fascia. Curved scissors are used to create a tunnel through the superficial portion of the gluteus maximus, to connect with the previous capsular incision. Three dilating tools are used to enlarge the tunnel gently (Fig 3A and B). A ball-ended guide wire is inserted through the second incision and advanced into the femoral canal. Cannulated flexible reamers are used in incremental sizes until substantial contact or chatter on the bony surface is felt. Solid reamers are used incrementally under fluoroscopy to reaffirm the proper depth and diameter of the reamed canal. An 8-inch extension rod is attached to each reamer to create a tool sufficiently long to pass through the thick soft-tissue
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Figure 3 The tools for femoral preparation in this 62-year-old morbidly obese woman (height, 5 feet 7 inches; weight, 305 pounds). (A and B) During the preparation of the second incision, after a blunt preparation of a tunnel through the gluteus maximus and extending through the previously prepared capsular incision, rectal dilators are used to enlarge the tunnel gently. (C and D) An 8-inch extension is attached to the reamer for reaming the femoral canal. (Color version of figure is available online.)
envelop (Fig 3C and D). Two sequential sizes of rasps are used to complete the preparation of the canal. The last rasp corresponds to the size of the largest solid reamer and the cementless stem itself. The proper axial alignment and fit and fill of the rasp are confirmed with fluoroscopy. For the morbidly obese patient, a fully coated or Epoch stem (Zimmer Inc, Warsaw, IN) is impacted progressively until fully seated. During the rasping or stem insertion, the progress and proper rotation of the depth of the rasp or stem is visualized directly through the anterior incision. Fluoroscopy is used to reconfirm the appropriate axial alignment of the rasp or stem and of the fit and fill of the stem in the canal. The operating table is readjusted to restore the contralateral hip to a neutral position. Through the anterior incision, a trial femoral head component is applied to the femoral neck. To facilitate the application of the trial and definitive heads in a morbidly obese individual, the split table under the ipsilateral lower extremity is adjusted to provide 20° of hyperextension of the operative hip. With this maneuver, accompanied by the application of a bone hook around the trunnion of the femoral stem, the trunnion is brought closer to the entrance of the incision. The hip is reduced to assess the proper stability of the hip and tension of the soft tissues. Both hips are imaged fluoroscopically to assess limb-length equality. Once the proper limb length is confirmed, the hip is dislocated for a replacement of the trial head by a definitive
metallic or ceramic head. During the removal of the trial head, care is taken to minimize the risk of losing it within the incision by placing a finger underneath the trial head. Although the hip capsule can be closed, we have not found that somewhat tedious step to be helpful. A small suction drain is inserted, the wounds are irrigated, and the deep fascia, subcutaneous tissues, and skin are closed in a routine fashion with resorbable sutures.
Postoperative Care After surgery, the patient is transferred to a postoperative recovery unit where vital signs and oxygen saturation are monitored. When the patient is stable, he/she is transferred to a unit with a monitored bed. Pain is controlled by the continuous lumbar plexus block and administration of celecoxib and pregabalin. The catheters are removed on the second day after surgery. An aggressive postoperative therapy regimen is critical to mobilize the morbidly obese patient rapidly and to decrease the potential for postoperative complications, such as atelectasis, pneumonia, and venous stasis. After the initial recovery period, the patient is assisted by a therapist to transfer from the bed to a chair and to a standing position. In view of the potential for postural hypotension and a complaint of lightheadedness, the initial transfer of a morbidly obese individ-
Hip replacement in the morbidly obese ual is supervised by a therapist and an aid. Once the patient tolerates an erect position, gait training with the use of an appropriately large walker is initiated, along with independent transfers. As the therapy sessions progress, an assessment of the optimal walking aid follows, potentially including the use of a cane. If necessary, the patient is taught to climb stairs. Typically, on day 2, the morbidly obese patient is discharged home. Routine postoperative follow-up assessments are undertaken at 1, 6, 12, and 24 months after surgery.
Postoperative Complications Related to Anesthesia and Pain Management In a morbidly obese patient, excessive sedation from opioids may culminate in obstructive apnea, respiratory arrest, or cardiac arrest. The use of a continuous peripheral nerve block serves to lessen the reliance on opioids and to decrease the potential for excessive sedation. A lumbar plexus block can be associated with several potential complications. 1) A grand mal seizure, which is an infrequent complication, may occur after the inadvertent intravascular dissemination of ropivacaine. The administration of 2 mg of midazolam intravenously provides a rapid resolution of the seizure. 2) A lack of infusion of the local anesthetic solution may occur if the catheter becomes dislodged or the pump has a mechanical or an electrical failure. A secure taping of the catheter to the patient is critical for minimizing the risk of premature dislodgement or leakage. 3) The catheter may be positioned incorrectly and thus fail to provide pain relief. The institution of nursing protocol for serial evaluations of the lumbar plexus block ensures recognition of the problem so an alternative therapy can be initiated.
Wound Infection In the morbidly obese patient, the anterior incision is particularly vulnerable to breakdown or dehiscence. Generally, the posterior wound heals without difficulty. In the morbidly obese patient, coverage of the anterior wound by the overhanging panniculus creates a warm and moist environment that promotes the onset of a superficial wound infection. Because of this protuberant abdomen, a morbidly obese patient cannot visualize the anterior incision wound. Therefore, in the early postoperative period, the patient is likely to ignore incisional drainage or even dehiscence. As a supplementary problem, most obese patients are embarrassed to request assistance for dressing changes and other forms of wound care. If a superficial wound infection ensues, it prolongs the time required for complete healing of the incision and can lead to a deep wound infection, thereby jeopardizing the viability of the arthroplasty. To minimize the potential for these problems, several strategies have been adopted. A resorbable suture (eg, 4.0 Monocryl; Ethicon, Somerville, NJ) is used for the cutaneous closure, along with a skin glue (eg, Indermil; Syneture, Norwalk, CT) or tissue adhesive. The
277 skin glue functions as a sealant for the incision. The use of alternative materials, such as nonresorbable sutures or staples, is less satisfactory in this potentially moist environment. The placement of a dry dressing over the incision is needed to insulate it from the overlying panniculus. Until the anterior incision is healed completely, the dry dressing is changed twice per day to maintain a dry barrier interface.
Venous Insufficiency A morbidly obese patient has an elevated intraabdominal pressure, which culminates secondarily in an elevation of the iliofemoral venous pressure.24 Over the long term, an increased iliofemoral venous pressure promotes venous stasis, edema, and venous stasis ulceration. Serial postoperative assessments of the lower legs and calves are performed to identify features of secondary cellulitis or ulceration so that prompt and aggressive treatment with antibiotics and compressive dressings can be initiated.
Thrombosis/Embolism Morbid obesity is a major risk factor for deep venous thrombosis and pulmonary embolism.25 The latter complication is one of the most common causes of death for the morbidly obese patient after gastric bypass surgery.26 A contributing factor to deep venous thrombosis is the elevation of venous pressures and venous insufficiency. After surgery, a morbidly obese patient is managed aggressively with mechanical and chemical prophylaxis. In view of the large lower leg circumference in such a patient, the use of thromboembolism-deterrent stockings may be difficult or impossible. Generally, thigh stockings cannot be used without creating marked indentations in the skin. Usually, a pair of fitted and sized calf stockings can be used without difficulty. Meticulous observation by the nursing staff is required to avoid binding of the skin from the edge of an ill-fitting stocking. In view of the difficulty in obtaining properly fitted sequential compressive devices, the use of foot pumps is preferred. Chemical prophylaxis with warfarin or low-molecular-weight heparin is used for at least 1 month after surgery.
Pulmonary Issues A morbidly obese patient is vulnerable to diverse pulmonary complications, such as atelectasis and pneumonia. Early mobilization of the patient is crucial to minimize this risk. Satisfactory pain management is instrumental in enabling a postoperative patient to sit, transfer, and ambulate, and thereby to optimize his/her pulmonary function. The aggressive use of an incentive spirometer facilitates pulmonary toilet.
Diabetes Mellitus A morbidly obese patient is predisposed to diabetes mellitus and to prediabetes.27 An elevated perioperative glucose level appears to increase the risk of a postoperative wound infection.28 Before, during, and after surgery, the blood glucose level is monitored carefully by assessments undertaken at 6-h intervals. If an elevation of the blood glucose level is con-
278 firmed, a sliding scale of insulin is used. The use of insulin in the preoperative period may be necessary, even for a patient who is not diabetic.
Cardiovascular Issues Morbid obesity predisposes a patient to hypertension, dyslipidemia, and cardiovascular disease.2 This collection of comorbidites is termed the metabolic syndrome.29 In the early postoperative period for such patients, an attempt is made to maintain blood pressure to minimize the risk of cardiac ischemia. A complaint of chest pain is evaluated promptly with electrocardiography and troponin testing to rule out myocardial infarction.
Sleep Apnea Sleep apnea occurs in approximately 24% of individuals with a BMI ⬎ 40.30 After total joint replacement, sleep apnea is a risk factor for perioperative mortality.31,32 On the first night after surgery, hypoxemia frequently ensues from the typical application of opioids for pain management. A hypoxemic patient is susceptible to cardiac arrhythmia, ischemia, and respiratory distress, all of which may be associated with fatal consequences. Overall, sleep apnea is underdiagnosed in obese patients, notably in those undergoing total joint replacements.19 To minimize such complications, a morbidly obese patient with sleep apnea is encouraged to bring his/her continuous positive airway pressure machine to the hospital for use after surgery. For the first postoperative evening, continuous pulse oximetry monitoring is undertaken.33
Conclusion The two-incision approach to hip replacement in the morbidly obese patient affords several advantages, including excellent exposure, the correct angles for facilitating implant placement, and rapid mobilization and recovery. Careful attention to detail is required for an optimal outcome in such a challenging patient. The protocol includes a preoperative examination to identify the typical comorbidites of morbid obesity, an anesthetic routine to facilitate the recovery, and a postoperative plan to minimize complications.
References 1. World Health Organization: Obesity: Preventing and managing the global epidemic. Report of a WHO consultation. World Health Organ Tech Rep Ser 894:vii-xii, 1-253, 2000 2. Hensrud DD, Klein S: Extreme obesity: A new medical crisis in the United States. Mayo Clin Proc 81:S5-S10, 2006 3. Wendelboe AM, Hegmann KT, Biggs JJ, et al: Relationships between body mass indices and surgical replacements of knee and hip joints. Am J Prev Med 25:290-295, 2003 4. Flugsrud GB, Nordsletten L, Espehaug B, et al: The impact of body mass index on later total hip arthroplasty for primary osteoarthritis: A cohort study in 1.2 million persons. Arthritis Rheum 54:802-807, 2006 5. Naik G: Surgeons’ weighty dilemma: Wary of extra risk, work, some doctors won’t replace knees, hips of obese patients. Wall St J (East Ed). February 28:B1, 2006
D.C. Mears, S.C. Mears, and J.E. Chelly 6. Namba RS, Paxton L, Fithian DC, et al: Obesity and perioperative morbidity in total hip and total knee arthroplasty patients. J Arthroplasty 20:46-50, 2005 7. Bowditch MG, Villar RN: Do obese patients bleed more? A prospective study of blood loss at total hip replacement. Ann R Coll Surg Engl 81:198-200, 1999 8. Ibrahim T, Hobson S, Beiri A, et al: No influence of body mass index on early outcome following total hip arthroplasty. Int Orthop 29:359-361, 2005 9. Soballe K, Christensen F, Luxhoj T: Hip replacement in obese patients. Acta Orthop Scand 58:223-225, 1987 10. Lehman DE, Capello WN, Feinberg JR: Total hip arthroplasty without cement in obese patients: A minimum two-year clinical and radiographic follow-up study. J Bone Joint Surg Am 76:854-862, 1994 11. Bal BS, Haltom D, Aleto T, et al: Early complications of primary total hip replacement performed with a two-incision minimally invasive technique. J Bone Joint Surg Am 87:2432-2438, 2005 12. Berger RA: Total hip arthroplasty using the minimally invasive twoincision approach. Clin Orthop Relat Res 417:232-241, 2003 13. Berry DJ, Berger RA, Callaghan JJ, et al: Minimally invasive total hip arthroplasty: Development, early results, and a critical analysis. J Bone Joint Surg Am 85:2235-2246, 2003 14. Aderinto J, Brenkel IJ, Chan P: Weight change following total hip replacement: A comparison of obese and non-obese patients. Surgeon 3:269-272, 305, 2005 15. Heisel C, Silva M, dela Rosa MA, et al: The effects of lower-extremity total joint replacement for arthritis on obesity. Orthopedics 28:157159, 2005 16. Buchwald H, Avidor Y, Braunwald E, et al: Bariatric surgery: A systematic review and meta-analysis. J Am Med Assoc 292:1724-1737, 2004 17. Kushner RF, Noble CA: Long-term outcome of bariatric surgery: An interim analysis. Mayo Clin Proc 81:S46-S51, 2006 18. Parvizi J, Trousdale RT, Sarr MG: Total joint arthroplasty in patients surgically treated for morbid obesity. J Arthroplasty 15:1003-1008, 2000 19. Harrison MM, Childs A, Carson PE: Incidence of undiagnosed sleep apnea in patients scheduled for elective total joint arthroplasty. J Arthroplasty 18:1044-1047, 2003 20. Netzer NC, Stoohs RA, Netzer CM, et al: Using the Berlin Questionnaire to identify patients at risk for the sleep apnea syndrome. Ann Intern Med 131:485-491, 1999 21. Apfel CC, Korttila K, Abdalla M, et al: A factorial trial of six interventions for the prevention of postoperative nausea and vomiting. N Engl J Med 350:2441-2451, 2004 22. Tsen LC, Hepner DL: Needles used for spinal anesthesia. Expert Rev Med Devices 3:499-508, 2006 23. Ben-David B, Frankel R, Arzumonov T, et al: Minidose bupivacaine– fentanyl spinal anesthesia for surgical repair of hip fracture in the aged. Anesthesiology 92:6-10, 2000 24. Arfvidsson B, Eklof B, Balfour J: Iliofemoral venous pressure correlates with intraabdominal pressure in morbidly obese patients. Vasc Endovascular Surg 39:505-509, 2005 25. Mantilla CB, Horlocker TT, Schroeder DR, et al: Risk factors for clinically relevant pulmonary embolism and deep venous thrombosis in patients undergoing primary hip or knee arthroplasty. Anesthesiology 99:552-560, 2003 26. Abou-Nukta F, Alkhoury F, Arroyo K, et al: Clinical pulmonary embolus after gastric bypass surgery. Surg Obes Relat Dis 2:24-28, 2006 27. Sugerman HJ, Wolfe LG, Sica DA, et al: Diabetes and hypertension in severe obesity and effects of gastric bypass-induced weight loss. Ann Surg 237:751-756, disc 757-758, 2003 28. Pomposelli JJ, Baxter JK III, Babineau TJ, et al: Early postoperative glucose control predicts nosocomial infection rate in diabetic patients. J Parenter Enteral Nutr 22:77-81, 1998 29. Eckel RH, Grundy SM, Zimmet PZ: The metabolic syndrome. Lancet 365:1415-1428, 2005 30. Scott SK, Rabito FA, Price PD, et al: Comorbidity among the morbidly obese: A comparative study of 2002 U.S. hospital patient discharges. Surg Obes Relat Dis 2:105-111, 2006
Hip replacement in the morbidly obese 31. Gupta RM, Parvizi J, Hanssen AD, et al: Postoperative complications in patients with obstructive sleep apnea syndrome undergoing hip or knee replacement: A case-control study. Mayo Clin Proc 76:897-905, 2001 32. Parikh SN, Stuchin SA, Maca C, et al: Sleep apnea syndrome in patients undergoing total joint arthroplasty. J Arthroplasty 17:635-642, 2002
279 33. Gross JB, Bachenberg KL, Benumof JL, et al: Practice guidelines for the perioperative management of patients with obstructive sleep apnea: A report by the American Society of Anesthesiologists Task Force on Perioperative Management of patients with obstructive sleep apnea. Anesthesiology 104:1081-1093, 2006