Surgeons should educate each other on the hip-spine connection
Hip and spine surgeons should collaborate to diagnose, treat patients with hip-spine pathology
The belief that the spine moves independently of the pelvis and hip has been disproved in recent years as researchers repeatedly identified important connections between the alignment of the spinal column and the position of the pelvis. As a result, the treatment of patients with hip-spine pathology is now headed in a new direction, according to orthopedic surgeons interviewed for this Cover Story.
“We have known for a long time that the spine is obviously connected to the sacrum, which is part of the pelvis, and the position of the spine can affect the position of the pelvis,” Geoffrey Westrich, MD, professor of clinical orthopedic surgery and director of research, adult reconstruction and joint replacement service at Hospital for Special Surgery, told Orthopedics Today. “That is critically important when it comes to total hip replacement because any change in the position of the pelvis, regardless of what it is from, can affect the orientation of the hip replacement.”
Lack of mobility or function caused by osteoarthritis of the spine or degenerative spine conditions has been shown to increase the stress and functional challenges of the hip joint, according to Asheesh Bedi, MD, who is chief of sports medicine at University of Michigan.
The relationship between spinal sagittal alignment and the pelvis is often assessed by parameters, such as pelvic incidence, and certainly the change in the orientatiFon of the pelvis can affect the mechanics of the hip joints, he said.
“Correspondingly, restricted range of motion at the hip can increase strain patterns in the [sacroiliac] SI joint, pubic symphysis and even in the lumbosacral spine, as all of these are part of the same kinetic chain,” Bedi, an Orthopedics Today Editorial Board Member, said.
Some posterior pain conditions that are hip-generated were previously attributed to a problem with the spine, Dean K. Matsuda, MD, CEO of Premier Hip Arthroscopy, said. These include ischiofemoral impingement, deep gluteal syndrome and proximal hamstring tendinopathy. Published studies reported buttock pain in 71% of patients with hip pathology and low back pain in 23% of patients with nonarthritic hips and femoroacetabular impingement (FAI), Matsuda said.
The complexity of the hip-spine connection is such that the diagnosis and treatment of patients who present with hip and spine pathology may be difficult, sources said.
“We are trying to educate surgeons on a better understanding of how involved the spine is, making sure that surgeons identify patients before they are doing a hip replacement, making sure they ask if [patients] have had a spine fusion or arthritis of their spine or spinal stenosis,” Westrich said.
A careful history and assessment of both the hip and the spine in patients who present with hip and spine pathology can provide insights for distinguishing symptoms that may be more related to the spine from symptoms that are more related to the hip, according to Bedi.
Robert S. Bray Jr., MD, said hip surgeons should perform a cursory spine exam of patients to check for muscle strength, muscle weakness, reflexes, neurologic parameters and mechanical movement of the spine.
“If I ever operated on [a patient’s] spine for anything, at least on my chart, there is a hip exam,” Bray, CEO of DISC Sports and Spine Center, said. “I have at least rotated their hip and seen if they have catches or pulls or limited range of motion or pain in the groin.”
According to Matsuda, a positive flexion/adduction/internal rotation or FADIR test is helpful in differentiating a hip from a spine source with decreased internal rotation 14-times more likely to be a problem that is generated by the hip rather than the spine. Although the flexion/abduction/external rotation test or FABER test “may be positive with hip or SI joint pathology, it is still useful as differentiation can be achieved via SI compression testing and palpation,” he said.
The femoral nerve stretch test may also be helpful in diagnosing radiculopathies high in the lumbar spine, which may masquerade as groin or hip pain, Matsuda, who is an Orthopedics Today Editorial Board member, said.
“Epidural and/or selective transforaminal nerve root injections may be beneficial as diagnostic tools, but because intra-articular hip injections have high sensitivity and specificity, and are arguably easier, safer and quicker for patients, the latter is my preferred choice,” Matsuda said.
Imaging types, modalities
In the past decade, surgeons have become more aware of the effect the position of the pelvis has on the angles of the acetabular component of a THA prosthesis, Robert L. Barrack, MD, professor of orthopedic surgery at Washington University School of Medicine, noted.
He told Orthopedics Today, “When [patients] change positions [their] pelvis changes positions and that affects the angles of the acetabular component. When an average patient [stands, their] pelvis flexes forward and the cup angle changes and when they sit, the pelvis extends.”
Recognition of this interplay between pelvic position and acetabular cup angle has changed the way imaging is performed in patients who present with both hip and spine pathology.
“For 30 or 40 years, most hip surgeons in the U.S. typically did ... all their pre- and postoperative X-rays with the patient supine, lying flat on their back,” Barrack said. “That is not where problems occur. Most dislocations occur when a patient is seated or leaning forward, and it was not that obvious to surgeons that the pelvis rotated so much between the supine position and the standing and seated position.”
“If [a patient has] advanced arthritis of the lower lumbar spine, particularly if they have had surgical fusion of the lower lumbar spine, then we get lateral X-rays of the spine and pelvis seated and standing to see how the pelvis is moving,” he said. “You can also have the patient lean forward somewhat when they are sitting because that is the highest risk position [of dislocation] to see what is happening with the pelvic rotation and the interaction with the femur.”
Kern Singh, MD, who is co-director of the Minimally Invasive Spine Institute at Rush University Medical Center, said orthopedic surgeons should get a weight-bearing radiograph that includes both the pelvis and the lumbar spine.
When surgeons evaluate the spine, they should order plain X-rays with flexion/extension views which can depict significant slippages in the spine or other pathology, according to Bray, who noted MRI and CT scans can also provide insight into the proper diagnosis.
“The MR shows us the soft tissue but, an incredible number of times, CT with reconstruction shows us the degree of the degenerative disease, calcification of the foramen and measures the height of the foramen,” Bray said.
He said single-positron emission CT (SPECT) scans, in addition to a CT scan, can be useful in identifying degenerative or bony disease and used for treating complex issues.
“[Surgeons] take data [from the SPECT scan] and merge it onto a CT scan. If there is an area of inflamed bone, it will show up as a red spot,” Bray said.
Order of treatment
Once the underlying pathology has been identified, surgeons decide whether to treat the hip pathology or spine pathology first.
“It is always critical to identify which is the predominant source of symptoms and complaint for the patient,” Bedi said. “Oftentimes, this may help you prioritize the order and sequence of treatment or even avoid treatment of degenerative spine findings that are often present on imaging, but the patient is asymptomatic.”
If the symptoms are equal, patients should undergo spine surgery first since anti coagulation is not used, Singh said.
“[Patients] could theoretically have their hip surgery done quickly after back surgery, where if [they] have a hip replacement or even a knee replacement, then [they] have to be on blood thinners and it makes it challenging, if not impossible, to do the back surgery,” he said.
As the hip affects the motion of the spine, Bray generally has his patients undergo hip surgery first.
“When the hip is restricted in its range of motion and limited, the antalgic gait that is created puts a huge stress on the lumbar spine,” Bray said. “When people cannot move their hip ... they twist their spine so much to compensate that I have seen many patients with concomitant problems where, if you fix their hip, their back settles down with conservative care, physical therapy and a block.”
However, sources noted that patients with neurologic deficits who are at risk of losing function and patients with symptomatic spine deformity should undergo spine surgery first.
“If someone has advanced spine disease that is affecting the position of the pelvis and it is going to change a lot when they have spine surgery then, in that particular case, it is occasionally advantageous to do the spine first because then you could plan your hip surgery based on the position that the pelvis is in based on the spine surgery having been done,” Barrack said.
Bray said dynamic stabilization systems used in patients who have lumbar spine pathology and have degenerative facets can cause more pain in the lower back or hip. Therefore, when performing spinal fusion, he said the less segments fused the better.
“You can always do more and fuse more segments, but I am of the opinion that in the spine often fusing less is better,” Bray said.
Published research has also shown that patients with a spine fusion or advanced arthritis have a higher THA dislocation rate, according to Barrack.
“If you have either had a spinal fusion or bad arthritis in your back, it impacts the ability of your pelvis to rotate and there are dislocation rates in patients who have extensive spinal disease or spine fusions that can be several times higher, can be 6%, 8% or 10%,” Barrack said.
In patients undergoing THA who either already underwent spine fusion or who have additional spinal stenosis and neurologic symptoms, Westrich recommends surgeons use a dual-mobility construct which, he said, has been found to yield a more stable construct in patients at high risk for instability.
A study published in The Bone and Joint Journal by Christopher W. Jones, FAOrthA, FRACS, PhD, MBBS(Hons), BEng(Hons), BCom, and colleagues showed a 0.66% dislocation rate among 151 patients at high risk for instability who underwent THA with dual-mobility constructs.
“[Dual mobility cups] essentially allow a greater diameter of the polyethylene head, so what becomes larger is the jump distance and that is the distance that the hip would have to move before it could dislocate,” Westrich said.
The hip-spine connection has impactful relevance in nonarthritic hip conditions, such as FAI and dysplasia, Matsuda said. It “presents an exciting new frontier in hip preservation. Functional alteration in pelvic position from a myriad of spinal conditions causes obligatory changes in acetabular orientation and FA dynamic, which can significantly influence decisions regarding possible acetabuloplasty, femoroplasty or periacetabular osteotomy,” he said.
Collaboration among surgeons
In a medical specialty such as orthopedic surgery, in which surgeons tend to focus on and subspecialize in a given area of expertise, the hip-spine connection is an area in which it is critical for surgeons to expand their vantage point and maintain a broader expertise, Bedi said.
“It is not possible to adequately and appropriately treat patients without an understanding of both the hip and the spine disciplines, if you are working in this area,” he said.
Appropriately diagnosing a patient who presents with both hip and spine pathology may depend heavily on hip and spine surgeons working together, according to Singh.
“In a patient who has an involved spine, I would always have them see a spine surgeon in addition to seeing me, and the two of us would discuss what the priorities are prior to embarking on surgery,” Westrich said.
In addition to hip and spine surgeons working together, Matsuda said orthopedic surgeons should also collaborate with radiologists.
“A well-trained and partnered musculoskeletal radiologist can help to reliably guide and assess the appropriate imaging studies both to make specific measurements, but also to evaluate for any and all potential sources of pain, including occult pathology,” Bedi said.
Pain management specialists are also key members of the multidisciplinary team that helps diagnose and treat patients with hip/spine pathology, he said.
“These colleagues can not only evaluate gait and overall mechanics, but can perform image-guided injections, which can be critical to differentiate between primary hip and lumbosacral pathology,” according to Bedi.
Research into overall alignment
Despite the progress that has been made in understanding how the hip and spine impact one another, Singh said more research is needed on how the overall alignment of a patient is affected by hip and spine pathology.
“That is even more complex because there are more motion segments, but we are realizing that you cannot just look at one body part and then ignore its effect on the overall alignment of the patient,” Singh said.
Bedi said it is still unknown how physical therapy and muscular strengthening impact the ability to change sagittal alignment, posture, pelvic tilt and obliquity, as well as how outcomes are impacted by nonoperative management with conditioning and rehabilitation.
He said a rapidly evolving area is how component position for THA may be affected by the variability in lumbosacral alignment and lordosis as well as pelvic obliquity and tilt.
“I think much of the navigation and robot-assisted technologies that are evolving will focus on this area to help us perform, not the same surgery in every patient, but the right surgery for each patient,” Bedi said.
As more research on treatment modalities for the hip-spine connectionis done, Barrack said it mus be proven “that by using functional imaging and changing the cup position and the type of implant” outcomes can be improved.
“Intuitively we think it should, but then proving that you are having an impact, that is going to be the next big research question,” Barrack said. – by Casey Tingle
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- Jones CW, et al. Bone Joint J. 2019;doi:10.1302/0301-620X.101B1.BJJ-2018-0506.R1.
- Redmond JM, et al. Arthroscopy. 2014;doi:10.1016/j.arthro.2014.02.033.
- Rowan FE, et al. J Arthroplasty. 2018;doi:10.1016/j.arth.2018.01.047.
- For more information:
- Robert Barrack, MD, can be reached at 14532 S. Outer Forty Drive, Suite 210, Chesterfield, MO 63017; email: firstname.lastname@example.org.
- Asheesh Bedi, MD, can be reached at 24 Frank Lloyd Wright Drive, Lobby A, Ann Arbor, MI 45106; email: email@example.com.
- Robert S. Bray Jr., MD, can be reached at 3501 Jamboree Road, Suite 1250, Newport Beach, CA 92660; email: firstname.lastname@example.org.
- Dean K. Matsuda, MD, can be reached at 13160 Mindanao Way, #300, Marina Del Rey, CA 90292; email: email@example.com.
- Kern Singh, MD, can be reached at 1611 W. Harrison St., Suite 400, Chicago, IL 60612; email: firstname.lastname@example.org.
- Geoffrey H. Westrich, MD, can be reached at 535 East 70th St., 3rd Floor, New York, NY 10021; email: email@example.com.
Disclosures: Barrack reports he designs implants for Stryker and receives research funding from EOS Imaging. Matsuda reports he is a paid consultant for Zimmer Biomet and receives royalties for intellectual property from Smith & Nephew, ArthroCare and Zimmer Biomet. Westrich reports he consults for and receives research support from Stryker. Bedi, Bray and Singh report no relevant financial disclosures.
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