It is often difficult to be precise about exactly why an athlete is complaining of low-back pain, a common complaint which accounts for some 10% of all sports injuries. Diagnoses may be non-specific, investigations unhelpful and treatment approaches often inconsistent. There is, however, one group in whom a clear diagnosis can often be made and effective treatment offered: namely, adolescent athletes with extension-provoked low-back pain.

History

A 17-year-old professional football goalkeeper complained of low-back pain when he extended his lumbar spine. What had started as a mild ache after training and playing six weeks before had progressed to the stage where his back was aching the whole time. He had never suffered from low-back pain before and could not identify a clear precipitant for his pain, which was fairly well localised to his lower lumbar spine, with no significant radiation. He had taken ibuprofen after training on a number of occasions, which had helped, but he now felt that his performance in both training and games was being compromised.

Examination

The physiotherapist and I examined him jointly and found a marked lumbar lordosis - inward curvature of the spine - with pain on single-legged hyperextension (where the athlete stands on one leg and leans backwards). We felt his rectus abdominis muscle was long and weak and his transversus and posterior glutei mediae were weak. His psoas, rectus femoris muscle and hamstrings appeared to be tight and weak. He was locally tender to palpation at the L4 vertebral level and slightly to the right.
Important negative findings included full and pain-free lumbar flexion, a negative sciatic slump test and normal lower limb neurology.

Differential diagnosis

We felt that possible causes of his pain might be:

• stress fracture of the posterior vertebral elements - ie spondylolysis or stress fracture of the pedicle;
• facet joint pathology;
• lumbar disc pathology;
• sacro-iliac joint dysfunction.

Spondylolysis may be defined as a defect in the pars interarticularis of the vertebral arch and is reported in some 4% of the general population. Such a defect may occur asymptomatically or in association with low-back pain, particularly in adolescent athletes. Isthmic (Type 2) spondylolysis represents the primary pathology in this adolescent group. It is generally thought that these pars lesions represent a stress response/ stress fracture from repetitive mechanical stress, particularly hyperextension.

Investigation

While we suspected a symptomatic lesion of the pars interarticularis as a cause of our goalkeeper's pain, visualising the lesion was an essential part of confirming the diagnosis. Plain X-rays have long been recognised as an important diagnostic tool in such cases. The defect is seen as a lucency on plain radiographs but may require multiple X-ray views and a significant radiation exposure. In longer-standing cases, the typical 'Scotty dog' appearance of a pars defect may be seen on the 45¡ oblique X-ray. In cases with recent onset of pain, plain X-rays may well not demonstrate the fracture.
The limited sensitivity of plain X-rays and the difficulty in attributing symptomatology to a lesion seen on plain X-rays has led to the increasing use of Single Photon Emission Computerised Tomography (SPECT) scanning. SPECT scanning is a form of radionucleotide imaging (bone scan) and has been shown to be more sensitive for identifying pars lesions than plain radiography in a number of studies. The SPECT scan will demonstrate a focal area of increased uptake at the site of the lesion and is therefore also able to differentiate between a metabolically active or 'hot' lesion and an inactive lesion.

One needs to be aware that SPECT imaging, although sensitive, is not necessarily highly specific, and that Computerised Tomography (CT) or Magnetic Resonance Imaging (MRI) scanning may be required in some patients to fully clarify the diagnosis. CT is recognised to be more sensitive than plain X-rays and more specific than SPECT in this condition. In addition it can define the morphology of the bony defect clearly, and many feel that it is complementary to SPECT. The role of MRI in this range of imaging techniques is the subject of much debate at present, but it offers a number of theoretical advantages, not least the lack of ionising radiation and its ability to identify other potential pathologies in the lumbar spine. It is important to recognise that there have been no direct comparisons of the above imaging techniques as they relate to clinical outcome.

Notwithstanding this lack of consensus, we organised plain X-rays (AP, lateral and obliques of the lumbar spine), which were normal. We proceeded to a SPECT scan, which showed significantly increased uptake in the posterior elements of L4 on the right. This confirmed our clinical suspicion of a 'hot' posterior element lesion but told us nothing about the morphology of the lesion. A CT scan at this level (L4) showed a relatively recent fracture through the right pars interarticularis of L4. This illustrates well the complementary roles the three investigations can play.

Treatment

As with the imaging process, there is considerable variation in the recommended treatment for these fractures. There are no large scale randomised controlled trials published in the literature. Almost all clinicians agree on the need to restrict athletic activity, especially hyperextension, and to correct the muscle imbalances seen around the low back and pelvis, but a number of published trials have used and advocate rigid anti-lordotic braces for periods of up to six months. It seems clear that lesions detected earlier are associated with much higher healing rates and that this is particularly true for unilateral lesions. Pars defects can be subdivided into early, progressive and terminal stages. The early stages are characterised by focal bony absorption or a hairline defect on CT. In the progressive stage, the defect is wider and small fragments may be present. In the terminal stage, there is sclerosis at the fracture site.

While it is reasonable to expect bony union (healing) in almost all of the early stage lesions, this is the exception in terminal stage lesions. Bony healing has been shown to occur with rigid, soft and no bracing, and excellent clinical outcomes can also be achieved in the absence of fracture healing, although it is desirable to aim for healing wherever possible. This published variation in outcomes makes it very difficult to define the role of bracing, but my feeling is that it is not mandatory in the adolescent athlete with an early unilateral lesion and precludes the core/abdominal stability work that is essential in preventing recurrence.

The place of surgery is also a matter for some debate. The current consensus is that it should be reserved for athletes who fail to respond to conservative treatment, but a detailed critique is beyond the scope of this case report.

Once we were sure of the diagnosis, and following discussion with the coaching staff, our player was removed from playing and training. We were optimistic that, in view of his short history of pain (six weeks) and the favourable CT appearance, we would see bony union with appropriate treatment and restriction of activity. We felt that his excessive lordosis and sub-optimal core stability were significant predisposing factors to this injury and that if we could correct these we would reduce the chance of the problem recurring when he returned to sport. We attempted to maintain his aerobic and anaerobic fitness on a stationary cycle, and planned a fairly intensive 10-week cycling programme for him. The lumbar flexion (and avoidance of extension) required in stationary cycling meant that there was minimal risk of compromising fracture healing. He worked each day with the physiotherapist on an intensive progressive pain-free core stability programme.

By 10 weeks he reported no discomfort on single-legged hyperextension and he started to run on the treadmill. At 12 weeks a repeat CT scan showed excellent fracture healing and he returned to first team play at 16 weeks. He has reported no problems since.

Key points

We believe that significant pars pathology is seen in approximately 50% of all athletes under 18 who complain of extension-related low-back pain of six weeks duration. Appropriate imaging and a clear understanding of the roles of the imaging techniques should enable the diagnosis to be confirmed. Early detection of these lesions is associated with a very favourable outcome. Of all the elements of a conservative treatment programme, the importance of devoting real attention to developing effective core stability cannot be overestimated. Despite increasing awareness of this particular problem, young athletes are still presenting late with terminal lesions that may be very difficult to heal.

Simon Kemp