How Should Surgeons Manage Symptoms of Psoas Tendinitis after THA?
Dr. Michael Taunton answers ICJR’s questions about the diagnosis, causes, and treatment options for patients who present with groin pain following total hip arthroplasty.
ICJR: How do you diagnose psoas tendinitis after total hip arthroplasty (THA)? What are the key history, physical exam, and radiographic findings that suggest psoas tendinitis?
Michael J. Taunton, MD: The iliopsoas muscle originates from the transverse processes of the 12th thoracic vertebrae through the 5th lumbar vertebrae. The musculotendinous portion crosses the anterior acetabulum over the anterior column. The tendon inserts on the lesser trochanter. The muscle is innervated by branches of the femoral nerve and serves in hip flexion.
Patients experiencing psoas tendinitis after THA typically present with groin pain with activity. The onset of this pain may occur immediately after surgery or in a delayed fashion. The symptoms typically develop with resisted hip flexion activities, such as ascending stairs, getting up out of a chair, and getting in and out of automobiles. Patients who exercise excessively after THA, especially soon after surgery, may also experience groin pain. [1-3]
On physical exam, patients have pain with resisted hip flexion or, in some cases, passive hyperextension. There is occasionally a “snap” or a “catch” as the leg is extended. The hip is typically painless throughout the remainder of passive range of motion. Patients may also have tenderness when palpated on the anterior aspect of the hip. Neurologic findings, such as numbness or weakness in other muscle groups, are atypical, and if present, suggest that other diagnoses should be investigated.
Hip radiographs should be scrutinized carefully. I usually obtain an anteroposterior (AP) pelvis, an AP proximal femur, and a cross-table lateral for all pre- and postoperative hips. On the AP pelvis, the positioning and placement of the acetabular component should be evaluated. The clinician should measure how lateral the cup is to Kohler’s line. An excessively lateral acetabular component may be more likely to impinge on the psoas tendon. A more vertically abducted cup (>45°) may do the same. The cross-table lateral radiograph is the most sensitive image for detecting acetabular component causes for psoas tendonitis. Evaluate the amount of anteversion on the acetabular component, as well as how proud the acetabular component is relative to the anterior wall of the acetabulum.
ICJR: What are the acetabular and femoral causes of psoas tendinitis?
Dr. Taunton: The most common acetabular cause of psoas tendonitis is the under-anteversion of the acetabular component. A combination of an under-anteverted, more-abducted (>45°), and lateralized acetabular component is the most common technical error adding to the incidence of psoas tendinitis. An overly large acetabular component, as well as acetabular screws that perforate the medial wall in the course of the iliopsoas, may also attribute to psoas pain.
On the femoral side, a component that is exposed on the proximal medial aspect of the femoral implant may rub on the tendon. For example, a femoral component with a collar that protrudes medially to the calcar may catch on the tendon. In addition, large femoral heads, which have become a popular means of enhancing stability, may act as a major pully. In the early range of motion (0° to 30°), there is maximal tension on the muscle that may lead to abrasion. Femoral heads with a sharp cut-off on the edge of the sphere may be a greater risk. It is important to remember, however, that a loose femoral implant may closely mimic psoas tendinitis.
ICJR: What are the treatment options for psoas tendinitis, and how do you determine which patients are candidates for which treatments?
Dr. Taunton: Treatment depends on when the pain occurs: early or later. I usually advise patients who develop groin pain and psoas tendinitis in the first 8 to 12 weeks after surgery to dramatically decrease activity, including going up and down stairs, walking up and down hills, and doing exercises such as deep squats or resistance training. Mothers carrying young children are especially at risk for developing psoas tendinitis. I typically combine this recommendation with the use of anti-inflammatory drugs and a gait aid, either a crutch or a cane. Patients are encouraged to extend the affected limb and use their arms to push up or lower down when they are getting in or out of a chair.
After rest and a course of anti-inflammatory drugs, these patients often benefit from gentle physical therapy focused on strengthening and mild stretching and range of motion. Overexuberance by the physical therapist may contribute to the problem.
In patients who develop psoas tendinitis later than 12 weeks, I also recommend reduction in activity and use of anti-inflammatory drugs. However, I am quicker to go to an iliopsoas tendon sheath injection and physical therapy in these patients. I also do a work-up to rule out infection and metal reaction, and if either is present, additional treatment may be recommended.
If non-operative measures fail, some patients may benefit from operative intervention. Typically, all patients I am considering for operative intervention have had a diagnostic or therapeutic injection to the psoas tendon to confirm the source of pain. It is important to instruct the physician who is performing the injection to inject at the level of the acetabular component, as many inject at the level of the lesser trochanter.
Research performed by my colleagues at Mayo Clinic found that an acetabular component with more than 8 mm of cup exposed relative to the anterior wall responds best to component revision. Cups with less than 8 mm of exposure anteriorly may respond just as well to arthroscopic fractional lengthening at the level of the acetabular component.
A few tenants should be followed when performing an acetabular revision for psoas tendonitis. Careful extraction of the existing acetabular component with an explantation system will lead to less bone loss. The goal is for the acetabular component to be as small as possible. I may stay at the exact same size or go even smaller and then translate the component medially and superiorly, especially if the initial malposition involved a large, lateralized component.
When anteverting the acetabular component, make sure that the anterior rim of the component is completely buried on the anterior wall. It is also important to remove any remaining anterior osteophytes or sharp edges.
I will then perform a fractional lengthening of the psoas tendon at the level of the component at the musculotendinous portion of the psoas. This does not lead to a decrease in hip flexion strength. 
ICJR: What outcomes are typically seen with non-operative versus operative treatment?
Dr. Taunton: In the Mayo Clinic series,  only 50% of patients treated non-operatively had resolution of their groin pain. If the prominence of the acetabular component was greater than 8 mm anteriorly, 92% experienced relief of groin pain with component revision, compared with only 12% if treated with a psoas tendon release. If the prominence was less than 8 mm, 100% experienced relief with an arthroscopic psoas tendon release.
Based on the data, we typically examine and assess patients as above. Initial non-operative treatment is employed,  and if the patient continues to have pain, an injection may be done to confirm the diagnosis. If non-operative care fails, patients with less than 8 mm of anterior component prominence are counseled for treatment with an arthroscopic release at the level of the acetabular component. Patients with a prominence greater than 8 mm are counseled for treatment with an acetabular component revision.
Michael J. Taunton, MD, is a board-certified orthopaedic surgeon specializing in hip and knee reconstructive surgery at Mayo Clinic, Rochester, Minnesota.
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