INTRODUCTION

Hip and spine syndrome is a condition in which patients experience hip, buttock, and groin pain that concomitantly originates from pathology involving both the spine and the hip. Symptoms of lumbar spondylosis, stenosis, radiculopathy, and facet arthropathy can cause referral of pain to the groin and anterior thigh. Underlying hip pathology may also present with groin and anterior thigh pain. This leads to the clinical dilemma of determining if the patient’s symptoms originate from the hip, spine, or both. Patients may be misdiagnosed with primary hip pathology leading to ineffective management including total joint arthroplasty. They may also be misdiagnosed with lumbar stenosis as the etiology of their lower limb pain and undergo an unnecessary spinal surgery. Difficulty arises when trying to determine the major source of pathology contributing to the patient’s pain and disability. Consequently, clinicians must evaluate both the hip and the spine as possible sources of lower limb pain and weakness.

Lower extremity symptoms can stem from spinal nerve root irritation or compression, particularly at the L3 or L4 nerve roots, which can lead to weakness of the hip flexors and quadriceps, as well as sensory deficits over the anterior thigh. This type of pain will typically have a dermatomal pattern.

Lumbar stenosis is a common source of lower limb pain. Approximately 1.2 million people in the United States have back and leg pain that is related to spinal stenosis.¹ If lumbar stenosis is the underlying pathology, patients commonly present with complaints of leg pain brought on by standing, walking, or with lumbar extension that increases the lordosis of the spine. They may describe what is termed neurogenic claudication, pain that radiates to the lower extremities and worsens with walking and improves with forward flexion. Severe neurologic symptoms are typically rare.²

Facet arthropathy can cause low back pain with occasional radiation to the buttock, posterior thigh, or knee that worsens with lumbar extension. Pain relief with partial spinal flexion is common.³ Studies carried out by Schwarzer et al. estimate that 15–40% of chronic low back pain is related to facet joint pathology.^4,5 In the absence of coexisting pathology, a detailed neurologic examination should be normal.

Biomechanical dysfunction such as muscle imbalance secondary to weakness or flexor contractures of the hip can be the cause of low back pain. An abnormality of the hip joint causes abnormal curvature of the sagittal alignment of the spine and can induce low back or lower limb pain.⁶ Matsuyama et al. examined the total spinal sagittal alignment in patients with bilateral congenital hip dislocations and found that the most common clinical symptom of the lumbar hyperlordosis found in these patients was low back pain and not lower limb pain.⁷ Additionally, patients with painful hips from synovitis or chronic inflammatory states may develop a biomechanical dysfunction with secondary effects to the spine.

Osteoarthritis of the hip can present in a similar fashion. In general, osteoarthritis has been radiographically reported in more than 80% of individuals older than 55 years.⁸ Radiographic evidence of osteoarthritis of the hip has been reported in 12% of patients over the age of 80.⁹ Osteoarthritis of the spine, hip, or both may result in significant impairment and disability and therefore correct diagnosis is essential for approaching the optimal treatment plan.

Patients with acetabular labral tears often describe ‘deep’ discomfort, most commonly in the anterior groin but occasionally directly lateral, just proximal to the trochanter or deep within the buttocks. Patients may or may not remember a provoking cause of the hip pain. The general complaint is usually discrete episodes of sharp hip pain triggered by pivoting or twisting.¹⁰ Lage et al. reported the incidence of idiopathic and degenerative acetabular labral tears to be 27.1% and 48.6%, respectively.¹¹

Vascular disease is a widely reported phenomenon. It is estimated that up to 12% of the population older than 66 years of age has peripheral vascular disease.¹² In many ways, the symptomatology of vascular disease mimics that of hip and lumbar spine pathology. Intermittent claudication secondary to peripheral arterial disease has been commonly described as a pain felt in the calf of the leg. It is brought on by walking, relieved by rest, and described as ‘heaviness,’ ‘cramping,’ or ‘tiredness in the legs.’¹³ Less frequently, patients may complain of pain in the thigh, buttock, groin, or lower back without associated calf pain as can be seen with common iliac artery obstruction.¹⁴ The presence of these symptoms is sometimes coupled with numbness in the foot which results from ischemia of peripheral nerves. The least appreciated symptom associated with severe vascular disease is rest pain.¹⁵ It may be intermittent or continuous in nature and it is not made worse with exercise. It characteristically occurs at night when the affected limb is elevated and cardiac output and blood pressure fall. Rest pain is typically relieved when the patient gets up and walks as perfusion improves.^16,17

TYPES

‘Simple hip spine syndrome’ occurs when the pain generator is easily determined to be coming from either the hip or the spine exclusively.⁶ Once the appropriate treatment is instituted, the patient should then have significant relief.

‘Complex hip spine syndrome’ is not as clearly differentiated when both the hip and the spine are contributing to a patient’s discomfort.⁶ Further differential testing including a comprehensive physical examination as well as other radiologic or interventional diagnostic procedures must be done to find the major structure involved.

In ‘secondary hip spine syndrome,’ the hip and spine are not distinct entities, and dysfunction with one causes abnormalities with the other. This syndrome can arise from hip flexor contractures placing the spine in excessive hyperlordosis by forward rotation of the pelvis. This increased curvature affects the facet joints, with slippage of the posterior facet joint increasing foraminal stenosis and creating nerve root impingement. Concomitant nerve root involvement with hip osteoarthritis can worsen an already weak hip.⁶ Difficulty arises when determining the greater offender and the ultimate treatment course.

CLINICAL PRESENTATION

The etiology of hip, groin, or lower limb pain can be delineated by a comprehensive physical examination with or without supplemental testing, including imaging and minimally invasive diagnostic studies. Patients must undergo a detailed history and physical examination to establish an appropriate diagnosis and treatment plan. Non-specific diagnoses will lead to poorly directed treatment plans and may compromise patient outcomes. The considerable overlap of referred and radicular pain patterns complicates one’s ability to make a clear diagnosis with any appreciable degree of certainty. This is further confounded with vague symptoms and an incomplete history, which can often be the case. Therefore, a thorough physical examination of a patient with hip, groin, or anterior thigh pain should include an in-depth evaluation of the neurological, musculoskeletal, and vascular systems.

The assessment of strength must be performed in a sequential manner, evaluating muscle groups innervated by different peripheral nerves and nerve roots. The strength examination should include the assessment of hip flexors (L1–3), quadriceps (L2–4), tibialis anterior (L4–5), extensor hallucis longus and hip abductors (L5), and the gastrocnemius/soleus complex (S1). Johnsson reported on 163 cases of lumbar spinal stenosis and found that extensor hallicus longus and peroneal paresis were the most common signs.² L4 nerve root irritation may lead to a diminished patella reflex and can create pain that typically radiates to the anterior knee and not necessarily below the knee. The straight leg raise, sitting root, and femoral nerve stretch tests provide evidence of nerve root irritation. Lower limb symmetry should be carefully assessed, as asymmetric muscle bulk and the presence of muscle fasciculations portend a neurologic component. Asymmetric muscle strength is often subtle in patients with radiculopathies. Single-leg partial squats and single-leg standing heel raises can assess the functional strength of the quadriceps and calf muscles, respectively.

Examination of bilateral hip joints is essential. Time should be spent assessing the hip and its function, specifically with passive range of motion and strength testing. Asymmetric decreased range of motion is commonly found in arthritic hips. Pain reproduction with decreased internal rotation of the hip suggests underlying hip osteoarthritis. Patients will typically have decreased hip extension secondary to tight or contracted hip flexors, limited internal and external rotation, and weakness of the quadriceps. Ely’s test can be performed to evaluate for a hip flexion contracture. With the patient prone, the knee is fully flexed. By pushing the heel towards the buttocks, the rectus femoris is stretched, causing the hip to flex and the buttock to rise. Functional testing of the hip abductor strength should be performed with the patient standing on one leg to evaluate for the presence of a Trendelenburg sign. Manual muscle testing of the hip abductors should be performed to elicit subtle differences in muscle strength, which would imply a neurologic component and a probable spinal source of pathology.

Anterior acetabular labral tears may be detected by moving the hip from a position of full flexion, external rotation, and abduction to a position of extension, internal rotation, and adduction. Conversely, moving the hip from a position of full flexion, adduction, and internal rotation to a position of extension, abduction, and external rotation allows detection of posterior labral tears.¹⁸ Hase and Ueo reported that all patients with acetabular labral tears had pain with axial compression upon a 90° flexed and slightly adducted hip.¹⁹

Identification of peripheral vascular disease requires blood pressure recordings taken in both limbs, pulses checked on each side, and bruits auscultated for over the major peripheral arteries of both the upper and lower limbs.²⁰ Absence of hair growth on the dorsum of the foot and toes, particularly when it was formerly present, suggests arterial insufficiency.²¹ Femoral pulses should be palpated and timed with the radial pulses. Other pulses can be assessed and compared in the same manner. Temperature gradients in each limb ought to be assessed. The palm of the hand should be used moving across the limb in a proximal to distal fashion. A cold foot with warm knees is characteristic of popliteal arterial obstruction.¹⁴ Simply reporting whether a pulse is present, reduced, absent, or aneurysmal in nature provides less subjectivity than using scales composed of too many gradations. Limb color should be evaluated with the limbs elevated, then with the limbs hanging off the edge of the examination table. A healthy, elevated limb will show mild blanching, whereas an elevated ischemic limb will appear appreciably paler.²² As the limbs are brought into a gravity-dependent position, the ischemic limb will appear redder. Severe ischemic disease will result in dependent rubor. The proximal extent of the rubor is directly related to the severity of the arterial insufficiency.²³ Of note, rubor is typically seen in patients with rest pain.¹⁴ Assessment of the vascular system after exercise will regularly give rise to an unsuspected diagnosis in patients where there is doubt about the presence or absence of peripheral arterial disease. A poorly perfused limb after exercise will be much paler, with collapsed veins. The patient can exercise the legs by actively dorsiflexing and plantarflexing for 30–60 seconds.²¹

DIAGNOSTIC AIDS

Imaging should begin with plain radiographs that encompass the lumbosacral spine and bilateral hips, looking for degenerative disease or severe arthritis. For further evaluation of the spine, a magnetic resonance imaging (MRI) or computed tomography-myelogram should be performed for better localization of pathology affecting the nerve roots and spinal canal.

Plain radiographs have generally been utilized to assess the presence of severe hip osteoarthritis. Plain radiographs in patients with only acetabular labral pathology are typically negative. While arthroscopy is the gold standard for diagnosing acetabular labral tears, MRI arthrography is currently the most sensitive nonsurgical test. MRI alone appears to be less sensitive than arthrography alone for diagnosing acetabular labral tears. Hase and Ueo demonstrated an accurate diagnosis of acetabular labral tears in 37% of their patients tested using arthrography alone. However, they were unable to confirm a tear in any of their patients examined with MRI alone. Arthroscopy was used as the definitive measure to confirm their findings.¹⁹ Petersilge et al. found complete correlation between MRI arthrography and arthroscopy in diagnosing acetabular labral tears.²⁴

Electromyography can aid in localizing peripheral neurologic pathology. This becomes particularly beneficial in differentiating between a lumbar radiculopathy versus a lower limb compression neuropathy.

Employing minimally invasive diagnostic procedures including epidural nerve root or hip joint injections has proven to be invaluable in assessing the involvement of each area to the patient’s diagnosis. A minimally invasive fluoroscopically guided injection to the hip joint or nerve root can easily and safely be performed with diagnostic and therapeutic benefit. Following the procedure, the patient should be taken through those activities that would normally reproduce or exacerbate their symptoms. A careful assessment of the patient’s response will assist in identifying the area of inciting pathology. Kleiner et al. described the identification of the hip as the source of pain in 88% of cases after injection of 10 mL of bupivacaine HCl to the hip joint.²⁵ If no relief is provided with a hip injection, a closer look should be given to the spine. There are several diagnostic blocks that can be performed to the spine to evaluate and treat the pain etiology. Lumbar facet and medial branch blocks or epidural injections via interlaminar, transforaminal, or caudal approaches can be done. If there is significant relief, the spine is the likely contributor of the pain.

When the hip and spine diseases are interrelated, as in ‘secondary’ hip spine syndrome, correction of the hip pathology may amend the symptoms resulting from the lumbar spine. In the setting of ‘complex’ hip spine syndrome where pathology from the hip and spine are both believed to be contributing to pain generation and both areas warrant surgery, hip arthroplasty should probably be considered first. Patient outcomes after this particular surgery tend to be encouraging. Occasionally, the improved gait and longer walking distances after hip arthroplasty can exacerbate spinal pathology. This silent lumbar pathology can become symptomatic, requiring surgery as well. If, on the other hand, hip surgery was performed and the patient still had no relief of their pain, the lumbar spine should then undergo a thorough evaluation.

Infrequently, low back and lower limb symptoms may be the result of an occult process. Kleiner et al. reported on 12 cases of misdiagnosis. Ten patients were initially diagnosed with having an L3 and/or L4 or S1 radiculopathy. Two patients were referred with an initial diagnosis of sciatic neuropathy. All patients had failed various therapeutic measures aimed at correcting their initial diagnoses, including two patients who underwent laminectomies without resolution of their symptoms. Further investigation uncovered occult malignancies in nine patients. A hematoma, an aneurysm of the obturator artery, and a neurilemmoma of the sciatic nerve were discovered in the remaining three. The authors note that the most useful means of identifying the correct diagnosis was computed tomography or MRI of the abdomen and pelvis.²⁵

SUMMARY

Lumbar spine pathology can create symptoms that mimic those generated by hip joint disease and vice versa. Moreover, pathology of the hip joint and lumbar spine can coexist as well. The impediment to successful treatment has been differentiating the severity each pathologic entity may contribute to the patient’s disability. A detailed, systematic, and exhaustive diagnostic approach may be necessary, as each pathologic process may mandate a separate treatment paradigm. Failure to identify the correct site of disease can result in misdiagnosis of the source of pain, and consequently result in misguided treatment. Unfortunately, many of these patients are identified after the fact when the expected result of treatment is not realized. When faced with hip spine syndrome, a detailed physical examination accompanied by proper diagnostic interventional procedures will usually discern the source. This may spare patients further delay in the correct treatment and speed the process to improved function.

Many different pathologies or combination of pathologies can affect the hip and spine as mentioned above. We pointed out some of the diagnoses more commonly identified as the etiologies of pain in the population of patients afflicted with hip spine syndrome. The different diagnoses discussed above are not intended to be exhaustive. Of course, patients can have more discrete and less-known hip and spine diagnoses creating their symptoms. It was our goal to impart the importance of examining the lumbar spine even though the hip may seem so clearly the source of the patient’s disability and vice versa. As well, it is vital to consider pathology stemming from areas outside the neurologic and musculoskeletal systems.