ESSENTIALS OF DIAGNOSIS
Pain deep in the groin on the affected side.
Degeneration of joint cartilage.
Loss of active and passive range of motion in severe OA.
In the United States, the prevalence of OA will grow as the number of persons over age 65 years doubles to more than 70 million by 2030. Cartilage loss and OA symptoms are preceded by damage to the collagen-proteoglycan matrix. The etiology of OA is often multifactorial, including previous trauma, prior high-impact activities, genetic factors, obesity, and rheumatologic or metabolic conditions. Femoroacetabular impingement, which affects younger active patients, is considered an early development of hip OA.
OA usually causes pain in the affected joint with loading of the joint or at the extremes of motion. Mechanical symptoms—such as swelling, grinding, catching, and locking—suggest internal derangement, which is indicated by damaged cartilage or bone fragments that affect the smooth range of motion expected at an articular joint. Pain can also produce the sensation of “buckling” or “giving way” due to muscle inhibition. As the joint degeneration becomes more advanced, the patient loses active range of motion and may lose passive range of motion as well.
Patients complain of pain deep in the groin on the affected side and have problems with weight-bearing activities such as walking, climbing stairs, and getting up from a chair. They may limp and develop a lurch during their gait, leaning toward the unaffected side as they walk to reduce pressure on the arthritic hip. The most specific findings to identify hip osteoarthritis were squat causing posterior pain (sensitivity, 24%; specificity, 96%; LR, 6.1 [95% CI, 1.3–29]), groin pain on passive abduction or adduction (sensitivity, 33%; specificity, 94%; LR, 5.7 [95% CI, 1.6–20]), abductor weakness (sensitivity, 44%; specificity, 90%; LR, 4.5 [95% CI, 2.4–8.4]), and decreased passive hip adduction (sensitivity, 80%; specificity, 81%; LR, 4.2 [95% CI, 3.0–6.0]) or less passive internal rotation (sensitivity, 66%; specificity, 79%; LR, 3.2 [95% CI, 1.7–6.0]) compared with the contralateral leg. The presence of normal passive hip adduction was most useful for suggesting the absence of OA (LR–, 0.25 [95% CI, 0.11–0.54]).
An anterior-posterior weight-bearing radiograph of the pelvis with a lateral view of the symptomatic hip are preferred views for evaluation of hip OA. Joint space narrowing and sclerosis suggest early OA. Findings of femoroacetabular impingement are commonly reported on radiograph reports with arthritic changes and anatomic variations involving the acetabulum and femoral head neck junction. After age 35, MRI of the hips already show labral changes in almost 70% of asymptomatic patients. Osteophytes near the femoral head or acetabulum and subchondral bone cysts (advanced Kellgren and Lawrence grade), superior or (supero) lateral femoral head migration, and subchondral sclerosis suggest the patient will more likely progress to total hip replacement. However, not all patients with radiographic hip OA have hip or groin pain; the converse is also true. Radiographs have low sensitivity for hip pain (sensitivity 36.7%, specificity 90.5%, positive predictive value 6.0%, and negative predictive value 98.9%).
Changes in the articular cartilage are irreversible. Therefore, a cure for the diseased joint is not possible, although symptoms or structural issues can be managed to try to maintain activity level. Conservative treatment for patients with OA includes activity modification, proper footwear, therapeutic exercises, weight loss, and use of assistive devices (such as a cane). A 2014 randomized study found that physical therapy did not lead to greater improvement in pain or function compared with sham treatment in patients with hip OA. In a large cohort, running significantly reduced OA and hip replacement risk possibly since running is associated with lower BMI. Analgesics may be effective in some cases. Corticosteroid injections can be considered for short-term relief of pain; however, hip injections are best performed under fluoroscopic, ultrasound, or CT guidance to ensure accurate injection in the joint.
Joint replacement surgeries are effective and cost-effective for patients with significant symptoms and functional limitations, providing improvements in pain, function, and quality of life. Various surgical techniques and computer-assisted navigation during operation continue to be investigated. A review of nine randomized controlled trials concluded that a direct anterior approach for hip replacement was associated with a shorter incision, lower blood loss, lower pain scores, and earlier functional recovery. However, there was no significant difference in complication rates between groups for the direct anterior or posterior approaches. There has not been clear clinical benefit of minimally invasive surgery compared to the standard invasive surgery, except for less total blood loss, shorter duration of surgery, and a shorter length of hospital stay.
Hip resurfacing surgery is a newer joint replacement technique. Rather than use a traditional artificial joint implant of the whole neck and femur, only the femoral head is removed and replaced. Evidence to date suggests that hip resurfacing is comparable to total hip replacement and is a viable alternative for younger patients. The cumulative survival rate of this implant at 10 years is estimated to be 94%. Concerns following resurfacing surgery include the risk of femoral neck fracture and collapse of the head. In a systematic review of national databases, the average time to revision was 3.0 years for metal-on-metal hip resurfacing versus 7.8 years for total hip arthroplasty. Dislocations were more frequent with total hip arthroplasty than metal-on-metal hip resurfacing: 4.4 vs 0.9 per 1000 person-years, respectively.
Guidelines recommend prophylaxis for venous thromboembolic disease for a minimum of 14 days after arthroplasty of the hip or knee using warfarin, low-molecular-weight heparin, fondaparinux, aspirin, rivaroxaban, dabigatran, apixaban, or portable mechanical compression (see Table 14–14).
Patients with sufficient disability, limited benefit from conservative therapy, and evidence of severe OA on imaging can be referred for joint replacement surgery.
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