**4.1. Target volume definition in LD‐EBRT**

Traditionally target volume definition has been quite large. Field sizes of 12 × 17cm were treated, including the entire dorsal and middle foot, and not just the calcaneus [37, 82] (**Figure 3A**).

**Figure 3.** Field definitions in LD‐EBRT of a painful plantar heel spur/fasciitis. (A) traditional field definition including the entire dorsal and middle foot. (B) In randomized trials and large prospective series commonly used field definition encompassing the entire calcaneus, including insertion of the plantar fascia and the Achilles tendon. (C) Proposed small field definition for localized painful plantar fasciitis/plantar spur, encompassing only the painful area with 2 cm margins extending into the neighboring areas (calcaneus, fascia, fat pad).

In the recent randomized trials and prospective observational studies target volume defini‐ tion was more restricted and confined to the calcaneus (**Figure 3B**). "The target volume con‐ sisted of the calcaneus and the region of the plantar aponeurosis" [26]. "The ventral margin is corresponding to the ventral surface of the calcaneus, the plantar and dorsal margins are surrounding the soft‐tissue border, and the cranial margin is below the ankle" [30]. "Target volume is the calcaneus, normally with a field size of 6 cm × 8 cm" [32]. "The calcaneus and the plantar aponeurosis were included in the target volume" [25].

In a German national survey 2001 on LD‐EBRT of painful heel spurs the target volume defini‐ tion "large" (dorsal and middle foot) vs. "small" (entire calcaneus) was not correlated with treatment outcome [83]. Consequently, very large field definitions should be regarded as obsolete.

However, as the pathophysiological cause of calcaneodynia is thought to be a localized inflammatory process (see Section 1), it is questionable, whether the entire calcaneus has to be irradiated (as long as there are not a plantar as well as a painful dorsal spurs). There are some clinical data that support a further restriction of target volume definition.

Field sizes have been given in the study by Miszczyk et al. on 327 patients treated with X‐ray beams [39]. Target volume was "… the insertion of the plantar fascia with a cal‐ caneal spur and a reasonable margin. The field size varied from 27 to 150 cm<sup>2</sup> (mean 47 cm2 )." However, although not explicitly stated, no correlation was found between field size and duration of pain relief after LD‐EBRT. Treatment efficacy in itself was apparently not investigated.

In the above‐mentioned series of 285 heels Hermann et al. analyzed treatment efficacy in dependence of field sizes, too [38]. The mean field size was 74 cm<sup>2</sup> . No correlation between field size (smaller vs. larger than 74 cm<sup>2</sup> ) with treatment efficacy was found. Further analyses of small fields (< 6 × 6 cm), medium‐sized fields (36–64 cm<sup>2</sup> ) and larger fields revealed no significant differences.

This is why it seems to suffice to encompass the painful region with 2 cm margins extending into the neighboring areas (calcaneus, fascia, fat pad; **Figure 3C**). However, this recommen‐ dation is deducted from pathophysiological considerations and the above‐mentioned case series. A randomized trial is necessary to proof clinical equivalence of a field definition "entire calcaneus" (**Figure 3B**) vs. "insertion of the plantar fascia" (**Figure 3C**).

### **4.2. Fractionation of LD‐EBRT**

in Germany to suffer from cancer was 50.7% (25.9% to die from malignancy), in women 42.8%

By limiting the application of LD‐EBRT treatment to patients > 30 years of age, an exposure of

Traditionally target volume definition has been quite large. Field sizes of 12 × 17cm were treated, including the entire dorsal and middle foot, and not just the calcaneus [37, 82] (**Figure 3A**).

**Figure 3.** Field definitions in LD‐EBRT of a painful plantar heel spur/fasciitis. (A) traditional field definition including the entire dorsal and middle foot. (B) In randomized trials and large prospective series commonly used field definition encompassing the entire calcaneus, including insertion of the plantar fascia and the Achilles tendon. (C) Proposed small field definition for localized painful plantar fasciitis/plantar spur, encompassing only the painful area with 2 cm margins

extending into the neighboring areas (calcaneus, fascia, fat pad).

**4. Future perspectives: Definition of questions in further randomized** 

the juvenile "relatively higher risk" patient population is avoided.

and 20.2% respectively [62].

160 Radiotherapy

**trials and future research**

**4.1. Target volume definition in LD‐EBRT**

The optimal fractionation schedule has not been elucidated yet. All randomized trial used twice weekly treatments. Only one experimental arm was scheduled three times a week [25]. In a National Survey in Germany with 146 answering institutions, about 45% applied two fractions and 37.5% three fractions weekly [83].

Interestingly, in the landmark study by von Pannewitz a fractionation schedule of only once per week was established [34]. Until now, there is no proof of a higher efficacy applying LD‐ EBRT twice or three times per week.

In radiotherapy of another benign disease (endocrine orbitopathy) a 1 Gy per week over 20 weeks schedule was more effective than the standard schedules (10 × 2 Gy or 10 × 1 Gy every working day) [84]. Although other immunological mechanisms cause endocrine orbitopathy in comparison with plantar fasciitis, there is sufficient clinical evidence to test in a random‐ ized trial different fractionation schedules (twice a week vs. once a week, possibly thrice a week).

#### **4.3. Comparison of LD‐EBRT with other therapies**

Other therapies than LD‐EBRT have been applied in painful heel spur. In the following, just a rough overview can be given.

Different kinds of insoles and foot orthoses have been developed. The goal was to reduce plantar contact pressure and to distribute the pressure uniformly over the whole rearfoot [63]. Magnetic insoles do not seem to provide additional benefit [64]. As a short‐term treatment, low‐Dye taping techniques are often used. However, in a randomized trial only a modest improvement in 'first‐step' pain was seen in comparison with sham‐intervention [65].

Manual stretching is often recommended. A systematic review of six studies found only sta‐ tistically significant differences in comparison with the control in one study combining calf muscle and plantar fascia stretches [66].

Several trials have investigated acupuncture. A systematic review from 2010 showed (limited) evidence for the effectiveness [67]. A randomized trial published in 2014 recruited 84 patients [68]. The authors concluded, that "dry needling provided statistically significant reductions in plantar heel pain, but the magnitude of this effect should be considered against the fre‐ quency of minor transitory adverse events."

Ultrasound therapy has led to questionable results [69], but a randomized trial on cryo‐ultra‐ sound with about 100 patients published in 2014 showed good effectiveness [70].

Low‐level laser light (635 nm), given twice a week for a total of six applications, reduced in a ran‐ domized trial VAS scores significantly after 8 weeks in comparison with placebo [71]. However, the study comprised of just 69 patients; other similar studies have not been reported so far.

Extracorporeal shock waves are widely applied. Three metaanalyses comprising at least five randomized trials found significant short‐term pain relief and improved functional outcomes for this therapeutic option [72–74]. Another study compared the analgesic efficacy of ultra‐ sound and shock wave therapy in 47 patients [75]. The results suggested that the shock wave therapy had greater analgesic efficacy.

Another basic approach is the oral administration of nonsteroidal anti‐inflammatory drugs (NSAID) to achieve a symptomatic relief. Injections into the painful area are also recommended. A recent review summarized ten randomized trials on corticosteroid injections into the plantar fascia [76]. A significant effect of the steroids on the pain has been shown. However, it was usually short‐term, lasting 4–12 weeks in duration. No advantage of ultrasound‐guided injec‐ tion techniques in comparison with palpation guidance was found, and no superiority of one type of corticosteroid over another was seen. A longer lasting pain relief has been suggested by a small randomized trial of botulinum toxin injections [77]. Another option is the injec‐ tion of autologous platelet‐rich plasma. A recent review identified three randomized trials, all showing promising results [78]. However, a very small trial challenged this method of plasma preparation, as the same clinical effectivity was observed after the injection of whole blood [79].

Different surgical approaches have been developed. Releases of the plantar fascia are done, in some studies combined with a spur resection [80]. Due to a probably faster recovery after surgery with comparable functional results endoscopic procedures are recommended nowa‐ days [81]. Surgery is usually indicated after failure of conservative therapies as the ultimate "salvage‐therapy."

There is only a limited amount of studies randomizing patients between LD‐EBRT and the above‐mentioned alternative therapies.

Canyilmaz et al. randomized 123 patients between LD‐EBRT (6 × 1 Gy, three times a week) and 1 ml injection of 40 mg methylprednisolone and 0.5 ml 60 mg 1% lidocaine under the guidance of palpation [85]. After 3 and 6 months, VAS values and CS‐scores were compared between both groups. After 3 months, the results in the radiotherapy arm were significantly superior compared with those after injections.

To corroborate these findings, similar studies should be conducted. Furthermore, more stud‐ ies randomizing LD‐EBRT against other therapies (e.g. extracorporeal shock waves) are needed. A minimum size of 50 patients per treatment arm should be assured to gain more statistically relevant results. Recruiting patients without prior excessive other therapies for these studies would be optimal.

The goal must be an evidence‐based algorithm defining the therapeutic sequence of the dif‐ ferent conservative treatment modalities for plantar fasciitis.
