Review of the aetiology, diagnosis and management of sacroiliac joint disorders
Stephan Grech and Bob Chatterjee discuss the complex condition of sacroiliac joint pathology and how to manage it
The sacroiliac joint (SIJ) has a complex anatomical structure which is prone to a whole spectrum of structural and mechanical disorders. Pathology of the SIJ is commonly overlooked, particularly in busy out-patient departments, as the presentation is protean and often non-specific. It is often masked by other more common pathologies, such as low back pain and facet joint disease.
It is therefore crucial that the orthopaedic surgeon is familiar with the pathologies affecting the sacroiliac joints and includes these in his differential diagnosis. It is also important that he understands the biomechanics involved in this complex joint as this helps to understand the pathological processes involved.
Anatomy
The SIJ is a stress-relieving joint that serves as a buffer between the lumbosacral and hip joints [1]. It has all the defining characteristics of a proper joint: the bony segments are the wedge-shaped sacrum and the two iliac bones; the sacrum can be regarded as the keystone stabilising the bony pelvis; and the joint contains a small amount of synovial fluid.
The articular surfaces are very irregular which confers a degree of stability. The cartilaginous surfaces permit limited amount of movements. Joint stability is further accentuated by the thick arrangement of ligaments. This ligamentous complex can be divided into a number of defined ligaments, namely the interosseous sacroiliac ligament, the posterior and anterior ligaments, the sacrotuberous, sacrospinous and iliolumbar ligaments.
The SIJ is somewhat unique in its muscular envelope. It is enveloped by a substantial number of large muscle groups, namely the hamstrings, gluteal muscles, quadratus lumborum, erector spinae and the abdominal obliques. All these cross the SIJ without actually providing the driving force for SIJ movement. They are, however, responsible for movement in the adjacent hip or the lumbar spine.
Innervation to the joint is still somewhat debatable but the general belief is that it receives a posterior innervation from the lateral branches of the posterior rami of L4 – S3 and anteriorly from the L2 – L3 segments [2]. This supports the fact that SIJ pathology shows a highly variable pain pattern, although the classic pain localises to the buttock and posterior thigh.
Movement is a restricted range of a special type of joint movement known as nutation and counter-nutation. This is limited to 1–2 degrees in males and 2–4 degrees in females [3]. Nutation means a nodding type of movement. It results in anterior rotation, where the sacral promontory moves inferiorly and anteriorly. In counter-nutation, the opposite movements occur.
Aetiology of SIJ disorders
Causes of SIJ dysfunction may be divided into two broad categories: traumatic and atraumatic. The former might be anything from a broad spectrum of injuries, ranging from a high-energy motor vehicle accident to a simple fall on the buttock. Repetitive micro trauma caused by lifting and twisting movements has also been identified as a possible causative factor.
The atraumatic spectrum is even vaster. Pregnancy and inflammatory arthropathies could cause SIJ dysfunction as part of a more generalised process. Any factor responsible for altered biomechanics of the whole body is a recognised causative factor. These include leg length discrepancy, joint replacements and scoliosis. Iatrogenic causes include adjacent segment phenomena seen most frequently after lumbar/lumbosacral fusion and iliac crest bone graft.
Clinical diagnosis
Diagnosing SIJ pathology is challenging due to the multitude of different presentations. This disorder spans a vast age range, pain patterns, pain-causing activities and presenting complaints. Females are twice as likely to develop SIJ dysfunction, and the literature is rich in evidence of SIJ in concurrence with other pathologies (Tables 1 and 2).
Diagnosis is based on four major criteria:
Positive patient history
Evaluation of lumbar spine and hip joints
Positive SIJ pain provocative tests
Positive SIJ infiltration
Positive patient history
The typical pain pattern is sharp stabbing pain in the buttock. The diagnostic pain patterns are divided into primary and secondary. Primary areas are described as pain radiating to the posterior superior iliac spine and below the L5 dermatome. Secondary patterns are ill-defined pain over the groin, postero-lateral thigh and calf areas.
Patients usually complain of disturbed sleep patterns in view of an inability to find a comfortable position in bed. The pain typically gets worse with sitting or prolonged standing, worsening from sitting to standing. It is not infrequent to note an abnormal gait pattern with increasing difficulties encountered in climbing up and down stairs.
Evaluation of lumbar spine and hip joints
The Fortin test is a simple diagnostic test which is subjective and patient directed. The patient is asked to localise the point of worse pain. The cut-off level is the fifth lumbar vertebra. Pain above this point indicates a lumbar spine culprit; below L5 suggests the SIJ as the primary cause.
Various lumbar spine conditions can overlap and mask SIJ pathology. These include static/structural conditions as well as dynamic ones. Disc prolapse, annular tear, degenerative disc disease, nerve root compression, lumbar spine stenosis and facetic pain can all mimic SIJ-related pain. This is the rationale behind a full lumbar spine examination in all patients presenting with a similar pain pattern. Sembrano showed that up to 25 per cent of low back pain patients have significant pain coming from their hip and/or SI joints [4]. Fortin et al. concluded that discogenic pain may account for at least part of the pain and discomfort associated with these conditions. The fact that sciatica may be associated with SIJ dysfunction has merit. The authors propose that the role of the pain neurotransmitter, substance P, may account for sciatic symptoms in patients with SIJ dysfunction [5].
The hip joint is well known for referred pain. Conditions such as avascular necrosis, degenerative joint disease, labral tears and femoral acetabular impingement might well overlap with SIJ pathology. Special tests such as the hip quadrant scour test can be employed to help clinch the proper diagnosis [6].
SIJ examination
Clues pointing towards primary SIJ pathology are tenderness over the PSIS and the sacral sulcus, pain with palpation of the dorsal ligament, tenderness over the pubic symphysis, antalgic gait, difficulty in performing single leg stance and painful, limited active straight leg raising. There are five sacroiliac provocation tests which have been proven to yield a high degree of sensitivity and specificity, as shown by Laslett et al. [7], Szadek et al. [8] and Van der Wurff et al. [9]. These are detailed below in Figure 1 and in table 3.
- Distraction: The patient is in the lateral position with the examiner positioned behind him/her with both hands over the lateral aspect of the pelvis. Downward pressure is applied through the anterior portion of the ilium, spreading the SI joints.
- Thigh thrust: The patient is supine and the hip is flexed to 90 degrees and the knee is bent. The tester then applies a posterior shearing force to the SIJ through the femur. Avoid excessively adducting during this exam.
- Compression: The patient lies supine and pressure is applied to spread the ASIS.
- FABER: The patient is supine with the foot of the involved side crossed over the opposite thigh and the leg resting in the full external rotation. One hand is placed on the opposite ASIS and the other hand on the medial aspect of the flexed knee. Overpressure at the knees and the ASIS is applied.
- Gaenslen’s manoeuvre: The patient is supine, lying close to the side of the table. The examiner allows the near leg to hang over the side edge of the table. The patient is asked to actively flex the other leg to his/her chest and hold. The examiner stabilises the patient and applies pressure to the near leg, forcing it into hyperextension.
The distraction (1) and the thigh thrust (2) tests have the highest sensitivity out of all five tests.
Radiological investigations have to be used judiciously as an adjunct to clinical examination. There is a whole array of different modalities ranging from plain radiography to MR and SPECT CT scanning. The clinician has to balance the radiation dose risk vs the expected benefit when choosing the correct investigation. The same also holds when ordering laboratory tests.
Positive SIJ infiltration
SIJ infiltration is a well-known procedure that must be used judiciously. When should one consider proceeding with the intervention? There are three major steps. First, the patient’s history must be strongly indicative of SIJ pathology with lumbar spine and hip aetiology excluded. There must be at least three positive provocative tests, with one being either the compression or the thigh thrust test [10]. The injections can be used bimodally: as a diagnostic tool or as part of the treatment plan.
Treatment options
As always in the medical field the treatment options are varied and multiple. Manchikanti et al. came up with guidelines for treatment of chronic spinal pain and SIJ pain [11]. The common practice is that the first line of treatment should be non-operative. This is usually undertaken by prescribing non-steroidal anti-inflammatory drugs as the first line medication. These are usually followed by six to eight weeks of physiotherapy in order to build the core musculature as well as the big muscle groups surrounding the SIJ. This helps to stabilise the joint and prevent excessive movement which reduces the painful stimulus. This regime is quite helpful and successful as the initial management plan for SIJ disorders. Some patients who for some reason cannot stick to the above treatment protocol, find relief by using external supports in the form of sacroiliac belts.
SIJ injections are the next step if all the above fails to provide pain relief. The skin is marked over the correct area under fluoroscopic or CT guidance, and prepped using the standard surgical technique. The area is anaesthetised using Lignocaine at 1–2 per cent strength. A 22 gauge spinal needle is advanced toward the target. ‘Articular slide’ is encountered by the needle tip after piercing the SIJ capsule and a distinct pop is felt as the joint is penetrated. Around 0.25ml of contrast medium is injected, noting the superior spread of the dye in the SIJ space. Standard AP and lateral views are obtained to confirm the needle position when using fluoroscopy. Up to 2.5ml of a mixture of local anaesthetic and steroid are injected. Symptom intensity is compared pre- and post-injection using the standard visual analogue scale (VAS). A positive clinical response is when the patient reports a 50–75 per cent reduction in pain during the first two hours (anaesthetic phase). This is a powerful indicator of the SIJ as the primary pain generator. Less than 50 per cent pain reduction on the VAS indicates a non-significant clinical response. No pain relief points more towards other pathologies as the primary cause of pain, even though SIJ pathology cannot be excluded altogether.
Surgery is the last option for recalcitrant pain when all non-surgical options have been burnt out. In basic terms, the aim is to achieve fusion of the sacroiliac joint. This can be achieved using a multitude of different implants and techniques. The trend nowadays is more towards minimally invasive surgery. As surgeons, we start to consider offering surgery only when the patient meets a set of very strict indications. These include: relative certainty that the SIJ is the primary pain generator; pain that is not responsive to conservative (non-surgical) measures with significant physical limitations; and no major contraindication for surgery.
A thorough pre-operative assessment must be undertaken. Apart from the routine investigations that need to be performed prior to every surgery, there are specific issues that need to be addressed. The treating physician must keep in mind the normal anatomical differences in the pelvic bony architecture between males and females (Table 4). The internal bony architecture of the sacrum shows specific patterns. The trabecular bony density is highest in the area adjacent to the endplates, in the sacral body and in the area of the pedicle as shown by Peretz [12]. Cancellous bone mineral density is lowest in the sacrum just medial to the SIJ [13].
These factors might require special investigations such as DEXA or CT scans pre-operatively. This might help guide the surgeon as to the direction of the implant insertion during the surgery itself. A poor result on DEXA scans could incite anti-osteoporotic treatment prior to surgery in order to try to increase the bone mineral density, thus increasing the possibility of a successful implant hold.
Regarding the post-operative treatment plan, there are a number of general issues that need to be tackled. These include instructions such as partial weight-bearing regimes. These depend on both patient factors (including bone mineral density) and also the type of implant used. Under the guidance of a physiotherapist, heel toe gait with normal foot progression is advocated. It is usually not contemplated fusing the contralateral side before 6–8 weeks post-operative recovery.
The effectiveness and safety of minimally invasive techniques vs the traditional screw fixation methods have been extensively reported in the literature. Two recent papers [14,15] carrying level three evidence, show very encouraging results in favour of minimally invasive techniques. Smith et al. concluded that patients who underwent either open surgery (OS) or minimally invasive SIJ fusion showed postoperative improvements in pain score. Compared with OS patients, patients who underwent minimally invasive SIJ fusion had significantly greater pain relief and more favourable perioperative surgical measures [14].
Duhon et al. [15] concluded that minimally invasive SIJ fusion using iFuse Implant system® is safe. Mid-term follow-up indicates a high rate of improvement in pain and function with high rates of patient satisfaction.
Conclusion
SIJ pathology is a very complex condition, riddled with pitfalls and difficulties in clinching the proper diagnosis. It is very commonly associated with low back pain and should be kept in mind by the treating clinician. Treatment should always be targeted towards avoiding surgery. Fusion is the last resort, with minimally invasive techniques using biologic fixation techniques regarded as the gold standard.
References
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