Essentials of Orthopedic Surgery, third edition / 11-The Hip and Femur

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lation therapy. The efficacy of these medicines for pain relief will probably be similar to that noted with traditional NSAI medications. However, their safety is currently being investigated as they may be associated with an increase in cardiac disease.

Intraarticular corticosteroid injections are helpful for the treatment of an acute exacerbation in pain. Intraarticular injections are more beneficial in the treatment of shoulder and knee and knee pathology compared to the hip. They have not been as widely utilized for arthritis of the hip, in part because of the difficulty ensuring the injection is in fact intraarticular. Fluoroscopy is helpful in confirming proper placement of the needle. Injection of the hip with local anesthetic can be helpful in differentiating referred back pain from intraarticular hip pathology. Also, there are patients who have a strong referred pain from the hip to the knee; in these patients, an intraarticular hip injection will relieve the knee pain and confirm its site of origin. However, injections are limited in their ability to provide longterm relief of symptoms. Corticosteroid injection for arthritis should not be done more than three times per year. If the patient requires morefrequent injections for pain control, other therapeutic measures or surgery should be considered. Repeated injection of the joint is not indicated because this will result in acceleration of articular cartilage degeneration and increase the risks of complications such as infection.

Physical therapy can be beneficial in reducing pain and improving range of motion for osteoarthritis involving the knee or shoulder; however, limited benefit has been found for the treatment of osteoarthritis involving the hip. If this modality is to be utilized it should be done early in the course of osteoarthritis. As the arthritis progresses, therapy will only serve to exacerbate an already painful joint. However, all patients should be encouraged to maintain aerobic fitness to maintain their joint function as well as their general health. Activities such as swimming and cycling have minimal repetitive impact and are excellent for aerobic fitness. Activities such as running and racquet sports can further damage an arthritic joint and should be discouraged in a patient with hip arthritis. As the arthritis progresses the patient is able to do less and less and becomes more sedentary. As this occurs, the symptoms also will increase in severity.

Assistive devices including crutches, cane, and a walker can be quite effective in the relief of stress across the joint surface with ambulation in patients with osteoarthritis involving the lower extremities. A cane used in the contralateral hand of a patient with isolated hip arthritis can reduce the joint reaction force by as much as 30%. However, the use of these devices is associated with a significant change in a patient’s perception of themselves and their global health status. So, although this modality can be helpful in relieving symptoms and maintaining mobility, it will commonly meet resistance from the patient.

Modification of activities is one of the most significant aspects in the nonoperative management of arthritis, which includes modification in a

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patient’s activities of daily living and self-care. Modification of car-parking and obtaining devices to assist in putting on shoes and socks, for example, can be very helpful for patients with limitations caused by hip arthritis. Reduction in certain activities such as running or racquet sports can improve the joint symptoms. However, this change will result in a gradual progressive decrease in the patient’s quality of life. The level of social interaction and activities in which the patient can comfortably participate can become markedly reduced. Modification of activities should also address patients who are overweight. Reduction in weight can significantly improve a patient’s symptoms, increase their mobility, and improve their global health status. In addition, reduction in weight will reduce the stress placed upon the joint replacement if they require surgery.

The nonoperative management of a patient with osteoarthritis involves all the aforementioned therapies. However, as the arthritis progresses, pain and limitation of activities continue to increase. When the patient fails to achieve acceptable symptomatic relief with the nonoperative regimen, joint replacement should be discussed. No significant change in the complexity of the surgery or outcome will be noted in patients with hip arthritis who delay operative intervention with nonoperative treatment. Therefore, the timing of the surgical intervention is based entirely upon the patients and their pain and limitations.

Surgical Management

Most hip pathology can be managed with one of several options: these include arthroscopy, osteotomy, arthrodesis, and arthroplasty (hemiarthroplasty or total hip arthroplasty). Each option has specific indications and contraindications, discussed in the next few sections.

Arthroscopy

Hip arthroscopy is in its infancy compared to this technique in the knee. The indications for hip arthroscopy are to remove loose bodies from the hip joint, to address acetabular labral pathology, and to identify articular cartilage defects. The technique requires the use of special equipment because of the more extensive soft tissue envelope around the hip compared to the knee. The soft tissue envelope also limits the mobility of the arthroscope within the hip. In addition, the hip capsule is quite thick and the articular space quite small. Frequently traction is required to gain visualization of the hip joint. The portals must be opened with care to avoid injury to the neurovascular structures surrounding the hip. These issues have significantly slowed the widespread use of this technique in practice today.

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Arthrotomy

Arthrotomy involves surgical opening of the hip joint. Many of the indications for hip arthroscopy are also indications for hip arthrotomy, such as removal of loose bodies and addressing acetabular labral lesions. However, hip arthrotomy can also address the drainage of hip sepsis and hip synovectomy. The hip joint can be exposed and opened from either the anterior aspect or the posterior aspect. Anterior approaches are more commonly utilized as this approach is less likely to injure the blood supply to the femoral head, which arises from the medial femoral circumflex vessels along the posterior intertrochanteric line.

The hip joint is then opened usually from the acetabular edge with care taken to preserve the acetabular labrum. If the labrum is torn it can either be excised or repaired, depending upon the condition and nature of the tear. Traction may need to be applied to the leg to allow inspection of the hip joint. Any loose bodies or fragments can be removed. If the indication for arthrotomy is synovectomy, it may be necessary to open the hip both from the posterior as well as the anterior aspect. This requirement does increase the risk of postoperative avascular necrosis; however, the synovium of the hip cannot be removed from a single approach.

Osteotomy

Osteotomy involves redirecting the articular surface to move damaged cartilage from the weight-bearing areas of the joint and place a lessdamaged area of the articular surface in the weight-bearing area of the hip joint (see Fig. 11-10). Osteotomy can also reduce joint forces by realigning the bone of the pelvis or proximal femur to yield a larger area of contact to distribute the force of weight-bearing. During osteotomy, the bone of the pelvis or femur is transected, redirected, and then fixed rigidly. If the arthritis is localized to only one region of a joint, by performing an osteotomy the damaged cartilage can be moved away from the weight-bearing area, and undamaged articular surfaces are transferred into the high-stress area. The result is reduced pain and prolongation of the functional life of the patient’s native joint. Prerequisites for an osteotomy are that the patient has an adequate range of motion of the joint, that the joint is stable, and that the articular damage involves only a limited area of the joint. If extensive arthritis or an inflammatory arthritis is present, an osteotomy will not be successful.

In properly selected patients, hip osteotomies can have a success of greater than 80% at 8 to 10 years follow-up. For young patients with focal articular damage, osteotomy can provide an acceptable result and allow them to retain their own hip joint; this can delay or possibly eliminate the need for replacement with artificial materials, which can wear or become loose. Acetabular osteotomy for developmental dysplasia of the hip can

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FIGURE 11-11. Anteroposterior radiograph of a 26-year-old female 6 months after a left pelvic osteotomy was performed to deepen her acetabulum and improve coverage of the femoral head. Her primary diagnosis was developmental dysplasia of the hip, which left her with a shallow left acetabulum.

make subsequent total hip arthroplasty easier by redirecting the acetabular bone stock and providing better coverage for an acetabular component (Fig. 11-11). However, osteotomy of the proximal femur can make a future hip replacement more difficult by altering the anatomy of the proximal femur; this may require an additional osteotomy to reconstruct the femur at the time of total hip replacement.

Arthrodesis

Arthrodesis involves the fusion of the proximal femur to the pelvis, which can provide a strong, stable, painless lower extremity. The patient can return even to heavy labor without the risk of loosening or damage to the arthrodesis. Arthrodesis is indicated in patients who are young with unilateral hip disease with no symptoms or disease involving the lumbar spine, contralateral hip, or ipsilateral knee. Patients with an inflammatory arthritis or nontraumatic AVN are relatively contraindicated for arthrodesis, as these diseases are frequently bilateral. Several studies of the long-term results of arthrodesis have found good results lasting greater than 20 years.

However, the hip is stiff, and after 15 to 20 years the arthrodesis can result in low back pain and pain in the ipsilateral knee. Several reports have noted between 50% and 60% of patients complaining of pain in the back or knee at 25 to 50 years follow-up. If the pain is severe, the fusion

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can be taken down surgically and a total hip replacement performed. The outcome of this surgery depends upon the functional status of the hip abductor muscles. If the surgical arthrodesis involved the removal of the insertion or origin of the hip abductors, the patient will have an increased rate of dislocation, pain, and limp after conversion to total hip replacement. These complications can be minimized if the technique used for the arthrodesis spares the hip abductor muscles. The return to a mobile hip can relieve the patient’s low back pain; however, they may experience pain in the hip that they did not have with the arthrodesis.

Hip Replacement Surgery

Total hip replacement (THR) is a common operation today. Approximately 250,000 replacements are performed each year. The primary goal of hip replacement is to relieve pain, which can be accomplished in more than 95% of patients. The results of THR can last approximately 15 years or more. In fact, one study found that more than 90% of THRs survived a minimum of 30 years.

In total hip replacement, both the socket (acetabulum) and the ball (femoral head) are replaced with metal and plastic parts. The socket is replaced with either a plastic cup cemented onto the bone or by a metal shell impacted into the prepared acetabular space with a removable liner (Fig. 11-12). The ball is replaced by a metal ball attached to a stem that goes inside the canal of the femur. Two principal types of implants are used

FIGURE 11-12. Total hip arthroplasty with the acetabular component press-fit onto the pelvis and the femoral component inserted into the femoral canal, with the femoral head articulating with the acetabular polyethylene liner.

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today: those inserted with bone cement and those inserted without cement and designed to allow bone to grow onto or into a porous metal surface. Both techniques have excellent long-term follow-up data supporting their effectiveness.

The principal advantage of utilizing bone cement is that immediate rigid fixation is obtained. The bone does not need to respond to the implant to obtain fixation. In patients with an average age of 65 years, excellent survival of 30 years or greater has been noted. The patients can fully weightbear immediately after the surgery, which facilitates their rehabilitation. In addition, the implants are simpler to manufacture and are correspondingly less expensive. Noncemented fixation requires the bone to respond to the implant to provide rigid long-term fixation. The implant has a surface that allows the bone to grow into or onto to stabilize the implant. Many surgeons keep the patient on restricted weight-bearing for the first 6 weeks postoperatively to allow for bone ingrowth. If the bone does stabilize the implant as the bone remodels over time, rigid fixation should be maintained over the long term.

Noncemented fixation is compromised by the presence of thigh pain, which is a mechanical pain that occurs over the anterior thigh. It is mechanical in nature, increasing with weight-bearing and usually relieved by rest. Usually thigh pain can be controlled with NSAIDs or mild narcotic analgesics. In a small number of patients, 1% to 2%, the pain can be severe. In these cases stem revision is indicated. Thigh pain is present in 5% to 15% of patients. Thigh pain is not uniformly associated with loosening of the stem. Thigh pain usually peaks by 6 months postoperatively, but it can persist for up to 18 to 24 months. In a small number of patients, it can persist indefinitely. Thigh pain is only rarely seen in cemented fixation and is usually associated with loosening.

Total hip arthroplasty is performed from either an anterior, posterior, transtrochanteric, or minimally invasive (MIS) approach. The transtrochanteric approach utilizes an osteotomy of the greater trochanter to mobilize the abductors to gain access to the hip joint; this has the advantage providing excellent exposure by lifting the abductors superiorly, allowing visualization of both the anterior and posterior column of the acetabulum. In addition, advancing the trochanter distally to tighten the abductors and reduce the risk of postoperative dislocation can increase the stability of the total hip. However, historically there has been a trochanteric osteotomy nonunion rate of 5% to 15%. Trochanteric nonunion will result in a persistent limp and an increased rate of hip dislocation postoperatively. The transtrochanteric approach is currently used primarily for revision procedures where additional exposure is required.

The posterior approaches are the most commonly used for total hip replacement. The dissection is carried posterior to the trochanter. The short external rotators are divided and a posterior capsule is opened; this creates a defect in the posterior capsule. The hip is dislocated posteriorly

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by flexion, adduction, and internal rotation. The posterior approach provides an excellent extensile exposure to the pelvis, hip, and femur. In addition, the gluteus medius and minimus are preserved, optimizing the function of the hip abductors postoperatively. However, postoperatively the patients are most at risk for a posterior dislocation with flexion, adduction, and external rotation. The rate of instability after a posterior approach is 2% to 5% in primary total hip replacement.

Anterior approaches to the hip are also commonly employed for total hip replacement. These approaches enter the hip from in front of the greater trochanter by detaching a portion of the gluteus medius and minimus. The anterior capsule is then opened. The hip is extended, adducted, and externally rotated to dislocate the femoral head and the arthroplasty completed. This approach can yield extensile exposure proximally and distally; this leaves the posterior capsule intact, protecting the patient from a posterior dislocation. The rate of instability is 1% to 2% in most series. Thus, the rate of instability is less with the anterior approach compared to the posterior approach. However, by detaching a portion of the gluteus medius from the trochanter, the muscle is weakened, which can lead to a greater incidence of limp and pain in the postoperative period. Further, if the repair of the detached gluteus medius pulls off the trochanter, the patient may be left with a persistent Trendelenburg limp.

Currently there is a great deal of interest in minimally invasive approaches for hip replacement; these can be done from either a single incision of 4 inches or less or from two 2-inch incisions. Also, there are minimally invasive anterior and posterior approaches. The single-incision approaches are an evolution of what we have done in the past. The two-incision MIS approach requires the use of fluoroscopy for implant placement. Because the surgeon cannot fully visualize the femur during implantation, the excess cement cannot be adequately removed after cementing a stem in place. Thus, the surgeon is limited to the use of noncemented implants with a two-incision MIS approach. The two-incision approaches are new and need additional research to demonstrate safety and durability.

All approaches can provide good exposure and a successful arthroplasty. However, there is a trade-off in terms of stability and function. The posterior approach does not violate the abductors and has a low incidence of limp postoperatively. However, the posterior capsule is opened and the rate of instability is increased, whereas the anterior approaches leave the posterior capsule intact with a correspondingly lower rate of instability. The abductor mechanism is partially detached and repaired, which may leave the abductors weak and yield an increased rate of limp postoperatively.

The patient is mobilized to a chair the day of surgery and begins physical therapy. If the femoral component is cemented, the patient may fully weight-bear on the operative leg immediately. If porous ingrowth fixation is utilized, some surgeons allow only restricted weight-bearing for 6 weeks to allow for bone ingrowth. The best exercise in the postoperative period

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is walking. With a posterior approach, hip abduction exercises may be done as well. However, if an anterior approach was utilized, the active abduction exercises may be delayed to allow the gluteus medius repair to heal.

Patients need to be careful not to flex the hip beyond 90 degrees and to keep their legs abducted and neutrally rotated for the first 6 weeks to prevent the femoral head from dislocating out of the acetabular component. The rate of instability and the position of greatest instability vary with the approach used for the arthroplasty. With anterior approaches, the greatest instability is with extension and external rotation. The patients usually report a dislocation occurring while they are standing and pivoting or while they are supine in bed with the legs adducted and the feet externally rotated. In contrast, posterior instability occurs when the hip is in a flexed, adducted, and internally rotated position. Patients report instability when they are getting out of a chair, off the toilet, or out of an automobile. The rate of dislocation is greatest in the first 6 weeks postoperatively. If a dislocation does occur with in the first 6 weeks, the rate of recurrent instability is approximately 30%, with the majority having a single event. However, if the first dislocation occurs after the first 6 months, the rate of recurrent instability increases to 60%, with the majority of patients having recurrent instability that often requires revision surgery to address the problem.

The treatment of a dislocated hip is to first reduce the hip, usually with conscious sedation; occasionally a general anesthetic may be required. The patient is placed into a brace for a period of 6 weeks. The patients can weight-bear as tolerated. If the patient does have recurrent instability, revision may be necessary. Before revision, it is helpful to determine the precise position of the components. Plain radiography can accurately determine the vertical inclination of the component; however, it is the degree of anterior rotation of the component that is a greater factor in instability after total hip replacement. Accurate assessment of the anterior rotation of the component can be best assessed by the use of CT imaging. If CT scan imaging cuts are also taken through the femoral condyles, the rotation of both the femoral and acetabular components can be determined. This information is important to aid in identifying the cause of the recurrent instability and to plan appropriate reconstructive surgery to correct the problem.

Aseptic loosening of the implant from bone occurs at a low rate with modern techniques. A recent study reviewed the minimum 20-year follow up of patients after cemented total hip arthroplasty revealed approximately 90% of patients had retained their original implant until they had died or reached their minimum 20-year follow-up evaluation. Revision surgery had been performed on 15% of the surviving patients; 11% of the revisions were for aseptic loosening. The rate of loosening of the femoral component was found to be 3% and 10% for the acetabular component in the surviving patients; 85% of the patients who survived a minimum of 20 years had

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retained their initial implants. Another study demonstrated the rate of femoral loosening is greater in the first 5 years and that the rate decreases after 5 years. Acetabular loosening, however, was noted to increase over time when cemented components were used. A rate of cemented acetabular revision or radiographic loosening was noted to be approximately 50% at more than 10 years. The use of modern cementing techniques has decreased the rate of early failure of cemented stems. Modern techniques, however, have not resulted in any significant change in the rate of acetabular loosening.

The survival of cemented implants in patients less than 50 years of age is less than that noted in older patients, most likely related to the higher demands and higher activity level in this younger group of patients. In an attempt to reduce the rate of aseptic loosening after THR, surgeons have tried to achieve implant fixation directly to bone; this can be achieved through the use of porous surfaces made of small beads or wires sintered onto the base stem. If this surface is closely approximated to bone and essentially no motion occurs at the interface, bone trabeculae will interdigitate into the porous surface and secure the implant. The rate of early loosening of the porous ingrowth femoral implants is comparable in most series to cemented stems. The rate of loosening appears to vary with the stem design for the porous ingrowth devices. Therefore, data should be analyzed individually for each implant. Porous ingrowth hemispherical acetabular components, however, appear to have a lower rate of loosening compared to cemented acetabular components. Although fixation of the metal shell to bone was maintained, some early designs developed problems with the interface between the polyethylene liner and the metal shell. Motion and wear would occur at this interface as well as the articulating interface, leading to the development of wear debris and failure of the metal-polyethylene liner and the need for revision surgery. In addition, the importance of high-quality, thick polyethylene liners for the noncemented acetabular components was not appreciated early, which resulted in a number of patients having early failure because of wear-through or fragmentation of the polyethylene liners (Fig. 11-13). The current recommendations are for a polyethylene thickness of at least 8 mm.

Modern liner shell interfaces should be conforming, with the polyethylene liner supported by the metal shell across the entire nonarticulating surface. The liner should not bear stress on the rim only but be uniformly supported. Most designs limit the holes in the metal shell. The holes in the shell can provide a direct conduit for wear debris to the implant–bone interface. This debris can lead to an osteolytic reaction and subsequent loosening of the acetabular shell. Early designs had many holes in the metal shell for the use of ancillary fixation screws to fix the shell to bone before bone ingrowth. Currently, most surgeons press-fit the metal shell on the bone by underreaming the acetabular bed and then inserting a slightly larger metal shell into the acetabular bed; this can provide an excellent

FIGURE 11-13. (A) Anteroposterior radiograph of the left hip of a 52-year-old man 5 years after a noncemented total hip arthroplasty demonstrates a markedly eccentric position of the femoral head within the acetabular component. (B) Photograph of retrieved acetabular component and femoral head of this patient. The polyethylene is fragmented and was found displaced within the shell, allowing the femoral head to articulate with the metal acetabular shell.

A

B