OPLL — Ossification of the Posterior Longitudinal Ligament

A condition guide by Mr Mohammed Madi, Consultant Orthopaedic & Spinal Surgeon.

OPLL stands for ossification of the posterior longitudinal ligament. It describes a process in which a ligament running down the back of the vertebral bodies, inside the spinal canal, gradually turns to bone. As it thickens, it can narrow the canal and press on the spinal cord or nerves, most often in the neck. Two ideas are worth holding on to from the start. First, OPLL is very often silent — found by chance on a scan and causing no symptoms at all, and in many people it never causes trouble. Second, where it does press on the cord, the symptoms and the decisions can be important, and a particular risk is sudden deterioration after even a minor fall, so it deserves to be understood and, where needed, watched.

A series of ligaments hold the spine together. One of them, the posterior longitudinal ligament, runs as a continuous band down the back of the vertebral bodies, immediately in front of the spinal cord. In OPLL, this normally soft, flexible ligament gradually ossifies — it turns to bone — and thickens. Because it sits directly in front of the cord, an enlarging ossified ligament can narrow the spinal canal and press on the cord, producing a condition called myelopathy, or on the nerve roots, producing radiculopathy. It is most common in the neck, but it can also occur in the chest and lower back, and it sometimes accompanies a related stiffening condition called DISH.

In plain terms: OPLL is when a ligament at the back of the vertebrae slowly turns to bone. It is often harmless and silent, but if it grows enough to press on the spinal cord it can cause problems with the hands, balance and walking.

OPLL is much more common in people of East Asian background — for example, it is found on scans in a few per cent of adults in Japanese studies — than in people of white European background, where it is less common. It affects men about twice as often as women, and tends to come to attention in middle age and later life, typically from the fifties onwards. Importantly, most OPLL that is detected on a scan never causes symptoms; the proportion of people who develop symptoms severe enough to need treatment is far smaller than the proportion who simply have the finding. It is associated with the stiffening condition DISH, with diabetes, and with a tendency to run in families.

The exact cause is not fully understood, and OPLL is best thought of as the result of several factors acting together. There is a genuine genetic predisposition — it clusters in families, and several genes have been implicated. There are metabolic associations, particularly with diabetes and impaired handling of blood sugar, and with being overweight. Mechanical stress on the ligament is thought to play a part, and it tends to occur alongside other conditions in which ligaments and tendons ossify, such as DISH. In many people the ossified mass slowly enlarges over the years.

OPLL is described on scans by its shape and extent. There are four classic patterns: continuous (a single band of bone spanning several vertebrae), segmental (separate deposits behind individual vertebrae), mixed (a combination), and localised. The continuous and mixed types tend to be associated with more narrowing of the canal. Surgeons also use a measure of how much of the canal the ossified mass occupies, and a planning concept called the K-line — an imaginary line drawn on a side-on X-ray of the neck. Whether the ossified ligament stays behind that line, or extends across it, helps predict whether decompressing the cord from the back of the neck will be enough, or whether it is typically tackled from the front. These details matter mainly for planning any surgery.

Many people with OPLL have no symptoms at all, and it is found incidentally. When it does cause symptoms, the most important is cervical myelopathy — pressure on the spinal cord in the neck. This typically shows itself as clumsy or numb hands and a loss of fine finger skills, so that buttons, handwriting or picking up small objects become difficult; as problems with balance and an unsteady or heavy-legged way of walking; and, in more advanced cases, as disturbance of bladder or bowel control. There may also be radiculopathy — pain, numbness or weakness in an arm from pressure on a nerve root — and neck pain or stiffness. The usual course is a gradual change over time, but there is one particularly important pattern to be aware of, described next.

Seek prompt assessment for progressive myelopathy — worsening hand function, balance or walking — and for any disturbance of bladder or bowel control. Above all, urgent assessment is warranted for assessment for sudden neurological deterioration after a fall or a minor injury: because the cord may already be compressed and the spine stiffened, even a low-energy knock, particularly one that forces the neck backwards, can cause a sudden spinal cord injury. New weakness, numbness or difficulty using the hands or legs after even a minor fall should never be ignored.

An ordinary X-ray may show the ossified ligament and is useful for the overall alignment of the neck and for drawing the K-line. The single most useful test, however, is a CT scan, which shows the ossified ligament in fine detail — its extent, its type, how much of the canal it occupies, and whether it has involved the lining of the cord — all of which are essential for planning treatment. An MRI scan is the best way to see the spinal cord itself, to show whether it is being compressed, and to detect any change in the cord signal that indicates it has been affected. In practice a CT and an MRI are usually used together, both to make the diagnosis and to plan any surgery.

This is reassuring for most people. Many with OPLL remain free of symptoms for years, and most OPLL found on a scan never causes myelopathy. The ossified mass does tend to enlarge slowly over time in a proportion of people, particularly younger patients and the continuous and mixed types, but enlargement does not necessarily mean symptoms will follow. In long-term studies of people who had OPLL but no myelopathy to begin with, only a minority — around one in six — went on to develop myelopathy over many years, and most remained free of it. The likelihood of developing problems relates chiefly to how much the canal is narrowed and the cord compressed, to movement of the neck, and to injury.

For OPLL that is causing no symptoms, or only mild and non-progressive ones, the right approach is usually observation and monitoring, since most never deteriorate. An important part of conservative care is advice about avoiding falls and high-risk activities, because of the danger of a sudden cord injury if the neck is forced backwards. Neck pain is managed in the usual conservative ways, with attention to posture and gentle exercise, and caution is advised about forceful neck manipulation when the canal is narrowed. It is important to be clear that no medicine dissolves the ossified ligament; conservative care manages symptoms and monitors the situation.

Surgery is considered when there is significant or progressive myelopathy — that is, real and worsening pressure on the spinal cord. The aim of surgery is to take the pressure off the cord, halt the deterioration and, where possible, improve function; it does not remove the underlying tendency to ossify. There are two broad approaches. From the back of the neck, the canal can be enlarged — by laminoplasty (reshaping the bony arch to give the cord more room) or laminectomy, sometimes with a fusion — which lets the cord drift backwards away from the ossified ligament; this is often chosen for disease over several levels and where the alignment is favourable. From the front of the neck, the ossified ligament can be removed more directly, which is used where it is very thick, where the neck is bent forward, or where the K-line is unfavourable; this is a more direct decompression but is technically demanding and carries a higher chance of a tear in the lining of the cord, because OPLL often sticks to or breaks through that lining. The choice depends on the number of levels, the alignment of the neck, the K-line, the size of the ossified mass and individual factors. Risks include a temporary weakness of a shoulder muscle (C5 palsy), a tear in the lining of the cord, incomplete decompression, and continued growth of any remaining ossified ligament. In well-selected patients, results are generally good for halting deterioration and improving myelopathy, though established cord damage may not fully recover — which is why it is best not to leave significant myelopathy too long.

For most people with OPLL the outlook is good, because most never develop significant problems and can simply be monitored. Where myelopathy does develop and surgery is needed, the results in carefully selected patients are generally favourable for halting deterioration and improving function, particularly when treated before the cord has been damaged for a long time. The keys throughout are to interpret the scans alongside the symptoms, to give sensible advice about avoiding falls, and to act in good time if myelopathy develops.

"The ossified ligament can be dissolved with medicine." No — there is no drug that reverses the ossification; treatment, when needed, is surgical decompression of the cord.

"If it's not causing trouble now, it can be completely ignored." Most cases stay stable, but OPLL can progress and a minor fall can be dangerous, so monitoring and fall-precautions matter.

"Surgery cures it completely." Surgery decompresses the cord and prevents deterioration; any remaining ossified ligament can still grow, and recovery of existing symptoms is variable.

"A bit of clumsiness in the hands is just age." In someone with OPLL, new clumsiness, numbness or unsteadiness can signal cord involvement and deserves assessment.

"A minor fall is nothing to worry about." With a cord that is already compressed, even a low-energy fall can cause a serious, sudden injury.

OPLL is the gradual turning-to-bone of a ligament at the back of the vertebrae, most often in the neck, where it can narrow the canal and press on the spinal cord. It is far more common in East Asian populations and is frequently silent, found by chance and never causing trouble in many people. When it does cause myelopathy — clumsy hands, unsteadiness, walking and balance problems — it deserves careful assessment, with CT to show the bone and MRI to show the cord. Most people are simply monitored, with advice to avoid falls; surgery, from the back or front of the neck depending on the anatomy, is reserved for significant or progressive myelopathy and aims to protect the cord. The warning signs are progressive hand, balance or bladder and bowel symptoms, and any sudden deterioration after even a minor fall.

This page is for general education only and is not a substitute for individual medical advice. Seek prompt review if a patient develop clumsy or numb hands, unsteadiness when walking, or any disturbance of bladder or bowel control, and urgent assessment is warranted for assessment for any sudden neurological change after a fall or minor injury.

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• —Boody BS, Lendner M, Vaccaro AR. Ossification of the Posterior Longitudinal Ligament in the Cervical Spine: A Review. International Orthopaedics. 2019.
• —Stapleton CJ, et al. Ossification of the Posterior Longitudinal Ligament: Pathophysiology, Diagnosis, and Management. 2022.
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• —Fujiyoshi T, Yamazaki M, Kawabe J, et al. A new concept for making decisions regarding the surgical approach for cervical ossification of the posterior longitudinal ligament: the K-line. Spine. 2008;33(26):E990–E993.
• —Fujimori T, Le H, Hu SS, et al. Epidemiology of symptomatic ossification of the posterior longitudinal ligament: a nationwide registry survey. Journal of Spine Surgery. 2016.
• —Mori K, et al. Prevalence and progression of radiographic OPLL: a 3-year follow-up of the ROAD study. 2013.
• —Tetreault L, Nakashima H, Kato S, et al. A Systematic Review of Classification Systems for Cervical Ossification of the Posterior Longitudinal Ligament. Global Spine Journal. 2019.
• —Nishida N, et al. Molecular Pathophysiology of Ossification of the Posterior Longitudinal Ligament. International Journal of Molecular Sciences. 2019.
• —Matsunaga S, Sakou T. Ossification of the posterior longitudinal ligament of the cervical spine: natural history and long-term outcomes. 2012.
• —Wu JC, et al. Risk of acute spinal cord injury after minor trauma in patients with cervical stenosis including OPLL. 2015.

This information is for general patient education and is not a substitute for an individual consultation. Always seek personalised advice from a qualified spinal specialist.