SACROILIAC JOINT SYNDROME (SIJS) is an extraspinal. Sacroiliac Joint Pain Referral Zones

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1 334 Sacroiliac Joint Pain Referral Zones Curtis W. Slipman, MD, Howard B. Jackson, MD, Jason S. Lipetz, MD, Kwai T. Chan, MD, David Lenrow, MD, Edward J. Vresilovic, MD, PhD ABSTRACT. Slipman CW, Jackson HB, Lipetz JS, Chan KT, Lenrow D, Vresilovic EJ. Sacroiliac joint pain referral zones. Arch Phys Med Rehabil 2000;81: Objective: To determine the patterns of pain referral from the sacroiliac joint. Study Design: Retrospective. Participants/Methods: Fifty consecutive patients who satisfied clinical criteria and demonstrated a positive diagnostic response to a fluoroscopically guided sacroiliac joint injection were included. Each patient s preinjection pain description was used to determine areas of pain referral, and 18 potential pain-referral zones were established. Outcome Measures: Observed areas of pain referral. Results: Eighteen men (36.0%) and 32 women (64.0%) were included with a mean age of 42.5 years (range, 20 to 75 yrs) and a mean symptom duration of 18.2 months (range, 1 to 72 mo). Forty-seven patients (94.0%) described buttock pain, and 36 patients (72.0%) described lower lumbar pain. Groin pain was described in 7 patients (14.0%). Twenty-five patients (50.0%) described associated lower-extremity pain. Fourteen patients (28.0%) described leg pain distal to the knee, and 6 patients (14.0%) reported foot pain. Eighteen patterns of pain referral were observed. A statistically significant relationship was identified between pain location and age, with younger patients more likely to describe pain distal to the knee. Conclusions: Pain referral from the sacroiliac joint does not appear to be limited to the lumbar region and buttock. The variable patterns of pain referral observed may arise for several reasons, including the joint s complex innervation, sclerotomal pain referral, irritation of adjacent structures, and varying locations of injury with the sacroiliac joint. Key Words: Low back pain; Sacroiliac joint syndrome; Sacroiliac joint block by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation SACROILIAC JOINT SYNDROME (SIJS) is an extraspinal cause of low-back and lower-extremity pain that can present in a myriad of ways. The constellation of symptoms attributed to SIJS includes pain referral to numerous anatomic regions. Specific pain referral zones reported include the posterior superior iliac spine (PSIS), 1 lower lumbar region, 2-12 buttock, 3,4,6,12-18 groin and medial thigh, 8,13,15,18 posterior thigh, 13,14,19-23 lower abdomen, 6,14,24 calf, and foot. 18 From the Department of Rehabilitation Medicine (Drs. Slipman, Jackson, Lipetz, Chan, Lenrow) and the Department of Orthopaedic Surgery (Dr. Vresilovic), Hospital of the University of Pennsylvania, Philadelphia, PA. Submitted for publication June 15, Accepted in revised form August 10, No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Curtis W. Slipman, MD, Director, The Penn Spine Center, Ground Floor White Building, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation /00/ $3.00/0 There are several potential explanations for the apparent varied pain complaints presenting in SIJS. The sacroiliac joint s variable innervation has been previously described and may result in complex symptom referral Varying sclerotomal 28,29 pain referral patterns may also arise from injury to distinct locations in the sacroiliac joint. 30 Additionally, the piriformis muscle, situated in close proximity to the sacroiliac joint, may be affected by intrinsic joint pathology, resulting in pain of muscular origin and/or associated sciatic nerve irritation. 12 Previous descriptions of sacroiliac joint pain referral zones have been based upon a diagnosis of SIJS established through history and physical-examination findings. Using provocative intra-articular injections, the pain referral patterns of the sacroiliac joint in asymptomatic individuals has been demonstrated. 1 Patterns of pain referral, encompassing the entire lower limb, have also been described in symptomatic individuals responding to intra-articular diagnostic injections. 24 It was the purpose of this retrospective study to further investigate and characterize the pain referral patterns of patients with SIJS who demonstrated a positive response to a fluoroscopically guided diagnostic sacroiliac joint injection. METHODS Fifty consecutive patients satisfying inclusion criteria were included. Patients eligible for inclusion were referred to our Spine Center with complaints of low-back or buttock pain regardless of associated hip or leg symptoms. Physical examination had to demonstrate a positive response to a minimum of 3 widely accepted maneuvers typically used to diagnose SIJS. Two of the 3 positive responses had to include 2 specific stress maneuvers: Patrick s test, and pain with pressure application to the sacroiliac ligaments at the sacral sulcus while in the prone position. Other maneuvers we performed, which are believed to be indicative of SIJS, were shear test, Gaenslen s maneuver, and Yeoman maneuver. Patients with a history of spondylarthropathy, urethritis, peripheral arthritis, psoriasis, inflammatory bowel disease, pain associated with early-morning stiffness that resolved with exercise, positive root tension signs, or a neuromuscular deficit were excluded. Patients with electrodiagnostic evidence of an acute lumbosacral radiculopathy or peripheral neuropathy or radiographic evidence of spondylolisthesis or lumbar instability were similarly excluded. Patients who satisfied inclusion criteria and were not previously enrolled in a physical-therapy program began a regimen consisting of lumbar spine stabilization techniques, upper- and lower-extremity conditioning, and enhancement of soft tissue pliability. Those who failed to improve following at least 4 weeks of the above regimen and still met our inclusion criteria underwent a fluoroscopically guided diagnostic sacroiliac joint block (SIJB). Approximately 15 minutes before this procedure, a preinjection pain drawing and visual analogue scale (VAS) rating was completed. Each pain drawing and VAS was administered by a trained nurse or medical technician.

2 SACROILIAC JOINT PAIN, Slipman 335 Injection Technique Fluoroscopically guided diagnostic sacroiliac joint injections were performed using the technique of Hendrix and coworkers. 31 While all injections were performed with fluoroscopic guidance, slight modifications were incorporated, because a rotating myelogram table was used in place of a C-arm. During each injection, blood pressure and pulse were recorded in 3-minute cycles. Patients were prepped and draped in the usual sterile manner. A skin weal was raised with 1% xylocaine at the needle insertion site. A 3.5-in 22-gauge needle was used for thin or moderate-sized patients, and a 5-in needle was used for larger patients. The needle was advanced in a medial-to-lateral direction to achieve joint entry at the medial aspect of the medial or posterior joint line. After infusing 0.5cc of Iohexola 300mg/mL into the most caudal aspect of the sacroiliac joint and establishing proper needle position, 2cc of 2% lidocaine hydrochloride was injected. Within 30 minutes of the SIJB, each patient completed a postinjection VAS supervised by a trained nurse or medical technician. Immediately preceding completion of this VAS, the patient was required to assume any position or perform any maneuver that typically provoked low-back pain. A minimum reduction of 80% in the VAS rating was required to be considered a positive response. Those patients demonstrating a positive diagnostic response were included in the study. Data Collection All data collection and analysis was performed by an independent reviewer. Initial data recorded included the patients age, sex, and symptom duration before treatment. Each patient s prediagnostic injection pain description as recorded by their examiner was used to determine areas of pain referral. Pain referral zones were first categorized into 9 primary anatomic regions: upper lumbar, lower lumbar, buttock, groin, abdomen, thigh, lower leg, ankle, and foot. The upper lumbar region was defined as that lumbar area above the level of the iliac crests. The lower lumbar region was defined as that lumbar area above the posterior superior iliac spines extending superiorly to the level of the iliac crests. Upper lumbar, lower lumbar, and buttock complaints were further categorized as ipsilateral, bilateral, and midline. Through a further anatomic division of the thigh, lower leg, and foot, a total of 18 potential pain referral zones were established. The thigh and lower leg were anatomically subdivided into anterior, posterior, medial, and lateral regions. The foot was similarly subdivided into dorsal, plantar, medial, and lateral regions. Statistics Relationships between patient age, sex, symptom duration, and pain distribution were investigated with the use of t tests and chi-squared tests. RESULTS Fifty consecutive patients were included in the study. The mean age of the patient population was 42.5 years (range, 20 to 75 yrs). Eighteen males (36.0%) and 32 females (64.0%) were included. The mean symptom duration before diagnostic injection was 18.2 months (range, 1 to 72 mo). Eighteen patients (36.0%) demonstrated a positive diagnostic injection response bilaterally, and 32 (64.0%) demonstrated unilateral involvement. Patients with bilateral involvement generally demonstrated symmetric pain complaints, and pain referral zones in these individuals were therefore not described independently for each side of involvement. The frequency of pain referral to the lumbar, buttock, groin, and abdominal areas is summarized in table 1. Only 3 patients (6.0%) demonstrated upper lumbar pain. In 2 individuals, this pain was reported ipsilateral to the side of sacroiliac joint involvement, and the other reported more midline upper lumbar pain. Thirty-six patients (72.0%) described lower lumbar pain. Except for 1 patient, bilateral lower lumbar pain was described only in those individuals demonstrating a positive diagnostic injection response bilaterally. In 3 patients, the lower lumbar pain was midline in location, and in 2 cases, this was associated with a unilateral positive diagnostic injection response. Forty-seven patients (94.0%) reported buttock pain. Bilateral buttock pain was described only in those individuals demonstrating a positive diagnostic injection response bilaterally. One individual demonstrating a positive bilateral diagnostic injection response described asymmetric buttock involvement, with right-sided buttock pain only. Seven patients (14.0%) reported groin pain. Abdominal pain was observed in 1 patient (2.0%) in the study group. The frequency of pain referral to the lower extremity is summarized in table 2. Overall, 25 patients (50.0%) reported associated lower-extremity pain. Twenty-four patients (48.0%) described thigh pain, with complaints most commonly localized to the posterior or lateral thigh. One individual demonstrating a positive bilateral diagnostic injection response described asymmetric thigh involvement, with right-sided posterior thigh pain only. Overall, 18 patterns of pain referral were observed. These are listed in order of decreasing frequency of presentation in table 3. No significant relationship between patient sex or symptom duration and the presence of pain in any anatomic region was identified. Statistically significant relationships were identified between patient age and the presence of pain distal to the knee, and these are described in table 4. DISCUSSION Our findings demonstrate that SIJS may involve pain referral to various sites not limited to the lower lumbar region and buttock. Fortin and colleagues 1 previously described pain referral zones resulting from provocative intra-articular injections. A common area of resultant pain was located over the PSIS, extending 10cm caudally and 3cm laterally. In our study, no attempt was made to provoke symptoms during injection. Rather, patients pain referral regions were recorded after establishing a diagnosis of SIJS through physical-examination findings and a positive response to an intra-articular diagnostic injection. Several previous studies have attempted to describe sacroiliac joint pain referral zones with a diagnosis of SIJS established by history and physical-examination findings alone. 2-14,19-23 Subsequent to those reports, it has been demonstrated that historical and clinical features have proven unreliable in the diagnosis of sacroiliac joint pain. The sacroiliac joint is mobile, albeit limited to only a few millimeters of glide and 3 of rotation, 33,34 but physical-exam maneuvers employed to detect Table 1: Frequency of Pain Referral to the Lumbar, Buttock, Groin, and Abdominal Regions Anatomic Region Percentage of Patients With Pain Upper lumbar 6 Lower lumbar 72 Buttock 94 Groin 14 Abdomen 2

3 336 SACROILIAC JOINT PAIN, Slipman Table 2: Frequency of Pain Referral to the Lower Extremity Anatomic Region Percentage of Patients With Pain Thigh 48 Posterior 30 Lateral 20 Anterior 10 Lower leg 28 Posterior 18 Lateral 12 Anterior 10 Ankle 14 Foot 12 Lateral 8 Plantar 4 Dorsal 4 motion abnormalities have demonstrated poor intertester and intratester reliability. 9,35 Additionally, it has been demonstrated that motion-abnormality testing may be positive in 20% of patients who are asymptomatic. 36 Diagnostic intra-articular injections were first described in 1938, 37 with the use of fluoroscopic guidance introduced in The detection of joint motion abnormalities, 36 response to pain provocation tests, 24,39,40 and historical features 18,24 have all correlated poorly with the response to fluoroscopically guided intra-articular diagnostic injections, which have arisen as the gold standard for diagnosing sacroiliac joint pain. It was the purpose of this article to describe pain referral zones of the sacroiliac joint with a diagnosis of SIJS established by a fluoroscopically guided diagnostic injection, and not through less reliable physical-examination and historical findings. Variable and diffuse patterns of pain referral were observed in our patient population. The majority of patients reported pain involving the lower lumbar region and buttocks, 72.0% and 94.0%, respectively. Groin pain was described by 14.0% of the patient population. Table 3: Eighteen Observed Patterns of Sacroiliac Pain Referral in Order of Decreasing Frequency Pattern of Pain Referral Percent of Patients Lower lumbar and buttock 30 Buttock alone 12 Lower lumbar, buttock, and thigh 10 Lower lumbar, buttock, thigh, and leg 10 Lower lumbar alone 6 Buttock and thigh 4 Buttock, groin, and thigh 4 Buttock, thigh, leg, ankle, and foot 4 Buttock and leg 2 Lower lumbar, buttock, and groin 2 Buttock, groin, thigh, leg, ankle, and foot 2 Lower lumbar, buttock, thigh, leg, and ankle 2 Lower lumbar, buttock, abdomen, and thigh 2 Lower lumbar, buttock, thigh, leg, ankle, and foot 2 Lower lumbar, buttock, groin, thigh, leg, and foot 2 Upper lumbar, lower lumbar, buttock, thigh, and leg 2 Upper lumbar, lower lumbar, buttock, groin, and thigh 2 Upper lumbar, lower lumbar, buttock, groin, thigh, leg, ankle, and foot 2 Table 4: Relationship Between Patient Age and Pain Distribution to the Leg, Ankle, and Foot Number of Patients Pain Mean Age (yrs) Leg 44 Absent 43.7 ( 11.7) 6 Present 30.5 ( 10.1) p.0118 Ankle 44 Absent 43.4 ( 12.2) 6 Present 32.8 ( 8.7) p.0468 Foot 36 Absent 44.3 ( 11.8) 14 Present 36.6 ( 12.4) p.0477 While the most commonly observed pattern of pain distribution was that involving the buttock and lower lumbar region alone, observed in 30.0% of the patient population, associated symptoms were not confined to a proximal distribution. Lowerextremity pain complaints were common, reported in 50.0% of patients. Pain complaints in the lower leg and as distal as the foot were reported in 28.0% and 12.0%, respectively. The clinical significance of the increased frequency of distal pain complaints in younger patients remains questionable. This may represent a pure mathematical construct, because multiple analyses were performed in an attempt to identify relationships between patient characteristics and pain distribution. If true, this finding would suggest that older patients with distal extremity pain, such as that associated with lumbar spinal stenosis and neurogenic claudication, should be less often confused with pain secondary to SIJS. The diffuseness of the sacroiliac joint pain referral zones may arise for several reasons: (1) the joint s innervation is highly variable and complex; (2) pain may be referred in a sclerotomal fashion; (3) adjacent structures may be affected by intrinsic joint pathology and become active nociceptors; and (4) pain referral patterns may be dependent on the distinct locations of injury in the sacroiliac joint. It remains unclear precisely how the anterior and posterior aspects of the sacroiliac joint are innervated. 27 The anterior portion of the sacroiliac joint likely receives innervation from the posterior rami of the L2-S2 roots. The contributions from these root levels are highly variable and may differ in the 2 joints of a given individual. 24,32 Additional innervation to the anterior joint may arise directly from the obturator nerve, superior gluteal nerve, and lumbosacral trunk. 32,41,42 The posterior portion of the joint is innervated by the posterior rami of L4-S3, 32 with a particular contribution from S1 and S An additional autonomic component of the joint s innervation further increases the complexity of its neural supply and likely adds to the variability of pain referral patterns. 41 A sclerotome has been defined as the ventral and medial portion of the embryonic somite. The cells in this portion of the somite evolve to form the vertebral column, while the dorsolateral cells form the musculature of the trunk and extremity. 44 When an osseous or ligamentous structure of the vertebral column, such as the sacroiliac joint, is injured, it may refer pain along its path of embryonic growth. This has been referred to as sclerotomal pain referral. 28,29 The resultant pain referral patterns may be quite complex, involving local and distal sites in the lower extremity. 30 The piriformis muscle is situated in close proximity to the

4 SACROILIAC JOINT PAIN, Slipman 337 sacroiliac joint. It originates from the ventrolateral aspect of the sacrum and inserts into the greater trochanter. As a result of this intimate spatial relationship, any injury to or pathology affecting the sacroiliac joint may result in a reflex spasm of the piriformis. The sciatic nerve, which passes immediately beneath or traverses through the piriformis, may become irritated from a resultant compressive syndrome. 12,45 This sequence of events may manifest as buttock and lower-extremity complaints. With sacroiliac joint injury, varying structural and biomechanical insults may ensue. Due to the joint s complex innervation, different patterns of pain referral may arise depending on the distinct areas of joint injury. 24 Unmyelinated synovial nerve endings can refer pain in a pattern dependent on the portion of synovium injured. 32 A fifth potential explanation for the varying pain referral patterns observed may be a limitation of the study design. Only a single diagnostic injection was used for patient selection. The false-positive rate of uncontrolled injections has been reported to be 38%. 46 Up to one third of patients may have demonstrated a false-positive response to the diagnostic injection secondary to placebo effect alone. 47,48 The effect of including these potential false positives in our study remains an issue. The purpose of this study was to investigate pain referral patterns in patients with SIJS diagnosed by a single diagnostic block. 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