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Hyperlaxity of the vertebral segment can favour the early degenerative process of the disc causing a minor resistance to the excessive stress
Alessandro Landi MD PhD
Demo Eugenio Dugoni MD
Cristina Mancarella MD
Roberto Delfini MD PhD
Department of Neurology and Psychiatry, Division of Neurosurgery,
Policlinico Umberto I,
‘Sapienza’ University of Rome, Italy
When the range of movement of a joint exceeds the norm for that individual, considering age, sex, and ethnic background it is defined as a hypermobile joint. The first cause of hypermobility is ligamentous laxity.1 This disorder seems determined by the fibrous protein genes, the ones that encode collagen, elastin, and fibrillin. Hypermobility that is not associated with systemic disease occurs in 4–13% of the population. The incidence diminishes as one ages, and it also appears to be related to sex and race.2,3
Most commonly, the initial symptom of a hypermobile patient is joint pain, which may affect one or multiple joints and may be generalised or symmetric. The diagnosis is one of exclusion but some tests help physicians to make a diagnosis. The Beighton score (Table 1) is essential for diagnosis. It is a measure of generalised joint laxity in five manoeuvres.4 When hypermobility is associated to symptoms such as scoliosis, pes planus, genu valgum, lordosis, varicose veins, rectal or uterine prolapse, or may have a history of recurrent dislocations, it is correct to talk about benign joint hypermobility syndrome (BJHS).2,5 This is a connective tissue disorder in which musculoskeletal symptoms occur in absence of systemic rheumatologic disease.
The spinal motor unit is characterised by a complex bone and discoligamentous system, which confers movements in all directions; for this characteristic the spinal motor unit is defined as an articular joint, for which the most important structures are the intervertebral disc and the articular masses. Our hypothesis is that the spinal motor unit should be involved in the hypermobility and consequently the hyperlaxity of the vertebral segment and can favour the early degenerative process of the disc causing a ‘minor resistentia’ to the excessive stress.
This study is a prospective analysis of 100 consecutive patients younger than 40 years, in which we want to assess the possibility of: (1) a correlation between hypermobility and disc herniation in patients younger than 40; (2) a correlation between hypermobility and recurrent disc herniation; (3) the role of physiotherapy to prevent degenerative disc disease in patients with hypermobility.
Materials and methods
From January 2008 to January 2011, 100 consecutive patients younger than 40, affected by lumbar disc herniation were assessed in the Department of Neurosurgery of the University of Rome ‘Sapienza’. The diagnosis of disc herniation was based on patient history (lower back, leg, or lower back/leg pain, numbness, tingling, paraesthesia, etc), clinical examination, conventional radiography, magnetic resonance imaging (MRI) and neurophysiological exams. Inclusion criteria were healthy young people aged less than 40 years without any acute or chronic disease, without any specific musculoskeletal complaints and with failing of drug and physical therapy.
Laboratory tests as blood cell count, erythrocyte sedimentation rate, rheumatoid factor, antinuclear antibody test, serum immunoglobulin levels (IgG, IgM, IgA) and serum complement (C3, C4, CH90) were used to exclude systemic diseases. One patient was excluded being positive for Marfan syndrome. For the diagnosis of hypermobility, the Beighton score was used. This score consist of five simple manoeuvres as explained in Table 1. The maximum score was nine, and a score of more than four was defined as hypermobility. One point was given for each positive result on each side. All the patients were calculated, then the Brighton criteria (Table 2) was used to diagnose the BJHS.6 The Brighton criteria use the previous score in conjunction with other symptoms. BJHS was diagnosed in the presence of either two major criteria, one major and two minor criteria, or four minor criteria. The criteria are described in Table 2. Out of the 100 patients, 40 resulted in being affected by hypermobility and one by BJHS. All patients underwent surgical treatment by microdiscectomy. All patients were assessed at 1, 3, 12 and 24 months follow-up by clinical examination and, at 12 and 24 months, by dynamic X-rays to evaluate an eventual instability of the metamere involved. Dermal ultrastructural studies were performed in all the patients with hypermobility.
Results: 100 patients (60 female and 40 male) were included in the study, 40 of them were positive for a diagnosis of hypermobility and one of them for BJHS. The mean age was 29.7 years (range: 17–40 years), of which, 25 were women and 15 men. The results of the Beighton score in the 40 positive (Table 3) patients were: four in one case, five in four cases, six in ten cases, seven in 15 cases, eight in eight cases and nine in two cases. All the patients underwent microdiscectomy and only two of them showed recurrence after two years follow-up. None of them showed instability at 12 and 24 months X-rays control. All of them are symptoms free. Dermal ultrastructural studies showed the presence of flowerlike collagen fibrils, elastic fibre abnormalities consisting of increased osmiophilic structures.
Joint laxity is maximal at birth, declining progressively during adult life. Women are generally more lax jointed than men and there is wide ethnic variation. Epidemiological studies have shown that hypermobility is seen in up to 10% of individuals in Western populations.1 In our study, we analysed only one selected subpopulation consisting of young patients with lumbar disc herniation. In this group, the incidence of hypermobility was higher than general population (40% versus 10%).
That is why we hypothesised a correlation between disc herniation and hypermobility. In the presence of symptoms (musculoskeletal, varicose veins, rectal or uterine prolapse etc.) associated to joint hypermobility, it is possible to talk about ‘hypermobility syndrome’. With its favourable prognosis by comparison with other more serious heritable disorders of connective tissue, this syndrome was named benign joint hypermobility syndrome. BJHS is a connective tissue disorder, characterised by joint pain, which may affect one or multiple joints in absence of systemic rheumatologic disease. This syndrome is clinically different from other disorders that cause local joint hypermobility and generalised joint laxity, such Marfan syndrome, Ehlers-Danlos syndrome and osteogenesis imperfecta.
Notwithstanding, lately Hermanns-Lê et al. reported the concept that BJHS may represent a mild variant of Ehlers-Danlos syndrome hypermobile type (EDSH).7 The BJHS is thought to have an autosomal dominant pattern. The syndrome appears to be due to an abnormality in genes that encode collagen, elastin and fibrillin and even dermal ultrastructural.3,8–13 Mutations in the fibrillin gene have also been identified in families with BJHS but molecular abnormalities remain often undisclosed. Moreover, the recent literature reports that benign joint hypermobility syndrome is a multisystem disorder with features that overlap with Marfan syndrome, Ehlers-Danlos syndrome, and osteogenesis imperfecta.9–14 This abnormality in the collagen structure leads to laxity of the joints, increased fragility of the connective tissue, and decreased proprioception, thereby resulting in a predisposition to joint degeneration and soft tissue injuries.15–17
Correlation between hypermobility and disc herniation
Disc degeneration associated to lower back pain (LBP) is one of the world’s most debilitating conditions, presenting with substantial socioeconomic and healthcare consequences.14,18 LBP can lead to reduced physical activity, lost wages, diminished quality of life, and psychological distress. Disc degeneration is multifaceted, traditionally attributed to age, mechanical loading, gender, trauma, obesity and other factors impairing disc nutrition. Hypermobility increases the risk of disc herniation. The hyperlaxity of the vertebral segment corresponds to an increased lumbar ROM that seems to favour the early degenerative process of the disc caused by an high exposure and a ‘minor resistencia’ to the excessive stress.19
The intervertebral disc consists in the central nucleus pulposus (that is, a fibrogelatinous mass composed of 80–90% water, collagen, and a mucopolysaccharide matrix); and the peripheral annulus fibrosus (formed by the concentric alternating lamellae of obliquely oriented collagenous fibres). The main function of the intervertebral discs is shock absorption and primarily, the annulus acts as a shock absorber, not the nucleus, which is predominantly viscous elastic (and incompressible).
When an axial load occurs, the increased force on the incompressible nucleus pushes on the annulus and stretches its fibres. If the fibres break, then a herniated nucleus pulposus occurs. Logically, the annulus fibrosus is more likely to become disrupted in areas where it is thinner or has less reinforcement.20 Our hypothesis is that the function of shock absorption of the intervertebral disc in patients affected by hypermobility is more stressed, simultaneously the annulus fibrosus is more fragile because of the connective alterations; these features lead to an earlier degeneration of the intervertebral disc.21
Correlation between hypermobiliy and recurrence
Our hypothesis was that there was a correlation between hypermobility and recurrence of disc herniation but our results refuted this hypothesis. In fact, only two patients affected by hypermobility had recurrence. We obtained the same result in the group of patients negative for hypermobility. There are two reasons:
– The hypermobility accelerates the degenerative cascade of the disc in young people but doesn’t influence the evolution of the degenerative process once it is started;
– The surgical procedure causes damage to the disc which predisposes all patients to recurrence whether or not they are affected by hypermobility.
Role of rehabilitation
The literature suggests that physiotherapy may improve clinical outcomes for young people but it remains unknown whether a target or physiotherapy intervention program is superior. The proprioceptive deficits in people with hypermobility are fundamental for the prescription of exercises. For this reason, we started a rehabilitation programme selected to improve proprioception.22–24
Role of surgery: In patients with joint laxity, disc degeneration that causes the development of disc herniation, places the vertebral spine to a greater risk of developing segmental instability. In these cases, surgical herniectomy alone may not be definitive since the discectomy weakens an already unstable vertebral body further. In these cases, it is appropriate to perform a minimally invasive fusion of the vertebral body involved as completion of the procedure. The current minimally invasive techniques include the use of interspinous anchors (such as ASPEN, AXLE etc.), or the use of devices for joint arthrodesis (such as Facet Wedge etc.). These devices allow the execution of a minimally invasive arthrodesis associated to the discectomy, which in patients with hyperlaxity prevents the development of spondylolisthesis.
Interspinous Anchor (ASPEN, AXLE etc.):25 These devices have previously been described; their aim is interspinous bone fusion, a surgical technique already described many years ago. The main function of interspinous anchors is to block the hypermotion through an interspinous bone fusion. In this way they could stop the degeneration and immobilise the metamere. Theoretically the surgeon, with the insertion of those devices, should obtain a stabilisation of the metamere with a really minimally invasive surgical approach, avoiding the use of screws and rods (Figure 1).
Surgical technique: These devices could be implanted by a minimally invasive approach: through a very short median skin incision (extended from the upper spinous process to the lower spinous process) of about 3–4cm, the surgeon must expose the upper and lower lamina of one side of the metamere. Using a specific instrumentation the device must be implanted between spinous processes using a technique similar to the one used for the insertion of a classic interspinous spacers. After radiological intraoperative check, the device must be blocked in the position desired. After this, in the interspinous space, using a specific instrument, a cruentation of the bone must be performed and bone chips could be inserted. The mean time of the surgical intervention is 40 minutes and the blood loss is extremely poor. It is important to underline that a TLIF technique could be added to this devices with the aim of obtaining a 360° fusion with only a monolateral minimally invasive approach.
Interarticular Fusion (Facet Wedge):26 this device has as main purpose to make a fusion of the joint complex, by cruentation and the inclusion within the articular rime of the device which is then attached to the vertebrae with screws. The advantage of this device is the possibility of his insertion by minimally invasive percutaneous approach. It is possible to obtain a better metameric fusion than the one given by interspinous anchor because of the block of the rotatory instability of the articular facets (Figure 2).
Surgical technique: The device can be inserted either with percutaneous approach or with the open one. It has to be positioned within the joint space, which is previously cruentate with appropriate tools, and finally fixed to the vertebrae with small screws. This device allows then the fusion of the joint and the block of the movement. The only thing to point out is the fact that the slope articular masses, if too acute, can prevent the insertion of the device with a percutaneous approach at L4-L5 and L5-S1 in relation to the presence of the iliac crest.
Even though a poor sample group limited the study, it demonstrated a higher incidence of hypermobility in young people with disc herniation than in the general population. This data let us put in correlation the risk of disc herniation and hypermobility in young people. We suggest that all young people under 40 years should be tested for this disorder and if positive should be directed to rehabilitation.