Research Review By Gary Maguire©

Date Posted:

May 2010

Study Title:

Low-Energy Extracorporeal Shock Wave Therapy as a Treatment for Medial Tibial Stress Syndrome

Authors:

Rompe J et al.

Author's Affiliations:

OrthoTrauma Evaluation Center, Mainz, Germany.

Publication Information:

American Journal of Sports Medicine 2010; 38(1):125-132.

Background Information:

“Shin splints” is a colloquial term that patients use when referring to pain and discomfort in the leg from repetitive running on hard surfaces or forcible excessive use of the foot flexors. This condition accounts for 6% to 16% of all running injuries and is responsible for as much as 50% of all lower leg injuries reported in select populations.

A more contemporary term for “shin splints” is Medial Tibial Stress Syndrome (MTSS), which is a repetitive strain condition that leads to pain in the posteromedial aspect of the distal two thirds of the tibia.

It should be noted that a diagnosis of MTSS must be differentiated specifically from chronic exertional compartment syndrome and tibial stress fracture, both of which can share some symptoms with MTSS. On physical examination, those with MTSS will have palpable tenderness over a 4-6 cm area at the posteromedial margin of the middle to distal third of the tibia. Ankle range of motion testing should not elicit pain. Passive stretching of the soleus, heel raises and unilateral hopping may elicit symptoms. Vascular and neurologic examinations are normal with MTSS.

Non-surgical treatment of MTSS typically consists of activity modification (rest), icing, nonsteroidal anti-inflammatory medications, stretching and strengthening and biomechanical assessment for things like over-pronation (which is often associated with this condition). Surgery is very rarely performed for MTSS and is only suggested as an option for very severe cases of shin splints/MTSS, with uncertainty surrounding its overall effectiveness.

Extracorporeal Shock Wave Therapy (ESWT or SWT) has been utilized since the late 1980s for various musculoskeletal disorders (e.g. Achilles tendinopathy, shoulder calcific tendinitis, and epicondylitis). Due to favorable outcomes when utilizing SWT for other forms of insertional enthesopathies this study was set up to determine whether low energy SWT is a safe and effective management modality for chronic MTSS.

Pertinent Results:

Subjects in this study were all runners or involved in running sports (soccer). MTSS was defined as follows in this study:
  1. pain located on the medial border of the tibia during running or marching,
  2. insidious onset of pain unrelated to any traumatic event, and
  3. pain on palpation of the medial tibial border not localized to one spot.

Findings:
  • At 1 and 4 months after baseline, success rates (return to preferred sport) for SWT vs. control were 30% vs. 13% and 64% vs. 30% (P < 0.001)
  • At 15 months from baseline, 40 of the 47 (76%) subjects receiving SWT were able to return to their preferred sport compared to 22 of the 47 (47%) control subjects.
  • Time to return to sport was variable and ranged from 6 weeks for some soccer players to 6 months for some runners.
  • The use of prescription pain medication (naproxen or paracetamol) was allowed but considered as failure. Fourteen of 17 SWT subjects who failed in the treatment group and 30 of 33 who failed in the control group requested these named analgesics
  • There were 10 minor complications – 8 subjects had pain during SWT treatment and 2 had temporary reddening of the skin – none were considered severe

Clinical Application & Conclusions:

The pathophysiology of MTSS remains unclear, although it is thought to be a traction enthesiopathy that occurs with some degree of periostitis (hence the need to differentiate from an early or existing tibial stress fracture).

Histologically, biopsy specimens reveal an inflammatory process with vasculitis that is consistent with periostitis. Although the soleus muscle may be the major contributing factor of MTSS, the flexor digitorum longus muscle and deep crural fascia also contribute to it, based on their sites of origin along the medial aspect of the tibia (2).

Proposed risk factors for developing MTSS are increased foot pronation, increased muscular strength of the plantar flexors, and increased varus tendency of the forefoot, hindfoot or both. An abrupt increase in training intensity, inadequate calcium intake, hard or inclined running surfaces, inadequate shoes and previous injuries are also theorized to contribute but lack supporting evidence.

The diagnosis and management of MTSS remains unclear, however the initial approach is always conservative/non-surgical. The authors were only able to identify 1 uncontrolled pilot study on SWT for MTSS (3). What this study adds is a successful evaluation of the effects of SWT on a consecutive series of subjects with MTSS who had not responded to at least 3 nonoperative forms of management. This was strongly measured against a well-matched control group with detailed home management guidelines.

The positive outcome was that 76% of the successfully treated subjects improved at 15 months from baseline compared to 47% in the control group without significant complications or requiring additional SWT.

The main consideration from a patient’s perspective regarding SWT remains the cost which is high compared to other treatment options. In this study however, subjects had not succeeded with other treatment interventions, in which case SWT may be the “next step”.

Study Methods:

Again, MTSS was defined as follows in this study:
  1. pain located on the medial border of the tibia during running or marching,
  2. insidious onset of pain unrelated to any traumatic event, and
  3. pain on palpation of the medial tibial border not localized to one spot.

Inclusion Criteria:

Subjects were included if they had an established diagnosis of unilateral chronic MTSS for at least 6 months before treatment and had failed at least 3 forms of traditional non-operative measures for a minimum of 3 months. Radiographs of the affected tibia including the knee and ankle joints were performed to rule out tumor, osteoarthritis, or fracture. Ambiguous subjects received 3-phase bone scintigraphy and/or MRI.

Exclusion criteria:
Those with extertional compartment syndrome, bilateral MTSS, rheumatoid and polyarthritis, local infection, pregnancy, tumors, bleeding disorders, ankle osteoarthritis, osteophytes and prior knee or ankle surgery were excluded from this study.

Initially 127 subjects were selected with 49 of the 127 subjects electing to receive SWT treatment in combination with a home training program. Final analysis consisted of 47 subjects (28 female/19 male, mean age 41, range 18-56 yrs). The average duration of the MTSS in subjects was 15 months, representing a chronic patient population.

Treatment consisted of rest, ice and rehabilitation exercises 2x/day for 12 weeks. SWT was performed at weeks 2, 3 and 4 after start of the home training program.

The control group consisted of 78 subjects and 47 of those subjects (26 female/21 male, mean age 43, range 18-54 yrs) made their decision in favor of the home training program. These were considered the best match of age and gender for comparison to the treatment group. Unintentional bias and blinding the decision process for either group selection was accounted for. The control group received the same home management program.

All the subjects in both groups were running athletes, had the time and inclination to pursue an intensive training regime and were all at risk for overuse injuries. The home rehabilitation exercise program was well detailed and specific with all exercises (calf stretch sitting and standing, active range of motion, anterior compartment stretch, and Thera-band exercises for resisted dorsiflexion, plantar flexion, inversion and eversion. Toe raises in sitting/standing, and heel raises were also performed).

All SWT treatments were performed by the senior author (J.D.R.) utilizing the same radial shock wave device (Swiss DolorClast). Shock waves are produced with this device with a projectile in a handpiece accelerated by a pressurized air source which strikes a 15-mm diameter metal applicator (1). Shock wave energy is transmitted to the skin via ultrasound gel. These waves are then dispersed radially from the application site to the surrounding tissues.

Each subject was treated lying supine and received 3 low-energy treatments in weekly intervals (2000 shocks applied at a pressure of 2.5 bars which is equal to an energy flux density of approximately 200mJ/mm sq.)

SWT application focused on the tenderness area for clinical focusing and treated in a circumferential pattern starting at the maximum point of pain (average size of treated area was 2-4cm wide to 4-8cm long). Immediate weight bearing was allowed and no ambulatory aids, immobilization or other co-intervention were used.

Outcome Measures:
  • Due to no disease-specific questionnaires available for MTSS outcome measures pain severity and recovery were chosen as primary outcome measures. This consisted of measurement of degree of recovery at 4 months compared with baseline utilizing a 6-point Likert scale (“completely recovered” to “much worse”). Successful treatment was recorded as either “completely recovered” or “much improved” versus failure as “somewhat improved”, “same”, “worse” or “much worse”.
  • Secondary outcome measurements were degree of recovery at 1 and 15 months utilizing the Likert scale. The use of a pain scale measuring severity of pain over the past week was also applied with a numeric rating scale (0 = no pain, 10 = very severe pain) at 1, 4 and 15 months from baseline.
  • Sports activities were compared to pre-symptom levels, type of sports, hours of exercise/week and the exercise surface.
Statistical analyses were performed using the GraphPad Instant version 3.0 for Windows. Clinical relevance consisted of a difference of 25% in success rate between groups on the Likert scale. Sample size loss was 10% in follow up with a type I error rate of 0.05 and a power of 0.8. Assumption was a success rate of 30% in the traditional nonoperative treatment forms, and a success rate of 60% in the more SWT group leaving a calculated 40 subject per each group rate.

After 6 weeks from baseline all subjects were allowed progressive return to sports/recreational activity and advanced as symptoms dissipated. Each subject was progressed on a case-by-case basis.

Study Strengths / Weaknesses:

This retrospective cohort study had a clear hypothesis, used functional outcomes and provided some foundation for further follow up research as to the benefits of successfully treating this difficulty musculoskeletal problem with SWT.

The authors did point out some weaknesses with some inherent limitations that required consideration. There was no randomization and there was no placebo arm to the investigation (this was a restrospective cohort study). The length of follow up was also only 15 months from baseline but positive treatment outcomes were noted within this timeframe.

Additional References:

  1. Gerdesmeyer L et al. Radial extracorporeal shock wave therapy is safe and effective in the treatment of chronic recalcitrant plantar fasciitis: results of a confirmatory randomized placebo-controlled multicenter study. Am J Sports Med 2008: 36: 2100-2109.
  2. Beck BR. et al. Tibial stress injuries: an aetiological review for the purposes of guiding management. Sports Med 1998; 26: 265-279.
  3. Lohrer H et al. Results of radial shockwave treatment of sports-induced diseases (achillodynia, patella tip syndrome and tibialis anterior syndrome). In: Gerdesmeyer L et al eds. Extracorporeal Shockwave Therapy. Towson, MD: Data Trace Publishing Company; 2007: 161-176..