Objectives. Inflammation of the retrocalcaneal bursa (RB) is a common clinical problem, particularly in professional athletes. RB inflammation is often treated with corticosteroid injections however a number of reports suggest an increased risk of Achilles tendon (AT) rupture. The aim of this cadaveric study was to describe the anatomical connections of the RB and to investigate whether it is possible for fluid to move from the RB into AT tissue. Methods. A total of 20 fresh-frozen AT specimens were used. In ten specimens, ink was injected into the RB. The remaining ten specimens were split into two groups to be injected with radiological contrast medium into the RB either with or without ultrasonography guidance (USG). Results. In specimens injected with ink, diffusion outside the RB was observed with staining of the anterior portion of the AT. In eight contrast-injected specimens (five USG, three non-USG), a similar localised diffusion pattern was observed, with the contrast identified superiorly and anteriorly. In two contrast-injected specimens (non-USG), the diffusion pattern was more extensive. Conclusion. This study confirmed the existence of connections between the RB and the AT, especially rich in the anteroinferior portion of the tendon, which should be considered a weak zone for substances injected into the RB. We hypothesise that this part of the AT might be most vulnerable to rupture after corticosteroid injections. Cite this article: P. A. Pękala, B. M. Henry, J. R. Pękala, K. Piska, K. A. Tomaszewski. The Achilles tendon and the retrocalcaneal bursa: An anatomical and radiological study. Bone Joint Res 2017;6:446–451. DOI:10.1302/2046-3758.67.BJR-2016-0340.R1

Introduction:. The insertion footprint of the different muscles tendon fascicles of the Achilles Tendon on the calcanium tuberosity has not been described before. Method:. Twelve fresh frozen leg specimens were dissected to identify the different Achilles Tendon fascicles insertion footprint on the calcaneum in relation to their corresponding muscles. Further ten embalmed cadaveric leg specimens were examined to confirm an observation on the retrocalcaneal bursa. Results:. The superficial part of the AT insertion is made by tendon fascicles from the medial head of the gastrocnemius muscle which insert over the entire width of the inferior facet of the calcaneal tuberosity. In three specimens, this insertion had continuity with the plantar fascia in the form of periostium. The deep part of the TA insertion is made of fascicles from the soleus tendon which insert on the medial aspect of the middle facet of the calcaneal tuberosity while the lateral head of the gastrocnemius tendon fascicles insert on the lateral aspect of the middle facet of the calcaneal tuberosity. A bicameral retrocalcaneal bursa was present in 68% of examined legs. Conclusion:. This new observation and description of the Achilles insertion footprint and the retrocalcaneal bursa may allow a detailed understanding of the function of each muscular part of the gastrosoleous complex. This has potential significant clinical relevance in the treatment of Achilles pathologies around its insertion

Insertional Achilles tendonitis is an inflammatory disorder affecting mainly active young patients. The etiology is multifactorial and include the combination of anatomical and biomechanical characteristics. One fifth of the tendon injuries in athletes are insertional complaints which includes bursitis and insertion tendinitis.The complex of the insertion of the Achilles tendon includes three main components of fibrocartilage sesamoid, periosteum and enthesis. A conservative regime is recommended as the first line of treatment. In case of failure a surgical decompression of the posterior margin of the calcaneum is indicated. Nine cadaveric legs were used for the experiment. The leg was mounted on an MTS machine and was axially loaded 360 N. The foot was attached to a plate which enabled dorsal and plantar flexion. The Achilles was sutured twice in an Ethibond No. 5 using the Krakow technique in order to anchor the tendon to an actuator. A thin pressure sensor plate (Teckscan) was inserted into the retrocalcaneal bursa to measure the force, pressure and contact area of the Achilles to the calcaneus in various positions of the foot. The conditions included 90 degrees of the foot, 15 and 30 degrees of dorsiflexion while the tension that was applied on the Achilles was 0, 200 N and 300 N. After resection of the posterior surface of the calcaneus in a 20 degrees inclination. The mean peak force, pressure and area did not change in Achilles tensioning while the foot was in 90 degrees and were close to zero. In 15 degrees of dorsiflexion there was increase in the mean peak force, pressure and area when the Achilles was tensed to 200 and 300 Newton. Larger increase in these parameters was achieved by further dorsiflexion of the foot to 30 degrees. After resection of the posterior margin of the calcaneus in an angle of 20 degrees the mean peak force, pressure and area dropped close to zero and remained almost unchanged during the various conditions of the experiment. Dorsiflexion and tension of the Achilles tendon increases the mean peak force, pressure and area in the Achilles retrocalcaneal bursa. These data may explain the mechanism for insertional Achilles tendinosis. Resection of the posterior surface of the calcaneus in 20 degrees efficiently decompresses the retrocalcaneal bursa in various angles of the foot and in various tensions of the Achilles

Introduction. Kager's fat pad (KFP) is located in Kager's triangle between the Achilles tendon (AT), the superior cortex of the calcaneus and Flexor Hallucis Longus (FHL) muscle & tendon. Although the biomechanical functions of KFP are not yet fully understood, a number of studies suggested that KFP performs important biomechanical roles including assisting in the dynamic lubrication of the AT subtendinous area, protection of AT vascular supply, and load and stress distribution within the retrocalcaneal bursa space. Similar to the knee meniscus, KFP has become under increasing investigations since strong indications were found that it serves more than just a space filler. Both KFP and the knee meniscus are anchored to their surrounding tissues via fibrous attachments, they can be found in encapsulated (or ‘air tight’) regions, lined by synovial membranes, and they both slide within their motion ranges. The protruding wedge (PW) of KFP was observed to slide in and out of the retrocalcaneal bursal space during ankle plantarflexion and dorsiflexion, respectively. In-vitro studies of KFP suggest that it reduces the load by 39%, which is similar to that of the knee meniscus (30%-70% of the load applied on the knee joint). This study investigated the in-vivo load bearing functionality of KFP. Materials and Methods. The ankles of 5 volunteers (3 males, 2 females, Age 20-28, BMI 21-26) were scanned using a 0.2T MRI scanner at ankle plantarflexion and neutral positions. The ankles of 2 of those volunteers were later scanned using a 3T MRI scanner for higher accuracy. The areas and volumes of KFP were measured using Reconstruct¯ 3D modelling software. The hind foot of the volunteers were scanned using dynamic ultrasound to measure in-vivo real time shape changes of PW. Results. The cross sectional area of KFP in the AT midline saggital plane increased on average by 10% when ankles were changed from neutral to plantarflexion positions. The volume of KFP showed less variation than cross sectional areas (3.9% variation in volume). Previous studies showed the cross sectional area of the knee meniscus changes by 9.8% during loading, or flexing the knee by 90°, and its volume was reduced by 3.5%-5.9% (medial and lateral menisci respectively). Ultrasound imaging showed that PW's thickness decreased during dorsiflexion compared to plantarflexion by an average of 1mm and a hysteresis was found between the location of PW's tip and the insertion angle of AT, suggesting the fibrous tip of PW bears load during dorsiflexion. Discussions and conclusions. The similarities in results between the knee meniscus (literature review) and KFP supports hypotheses that KFP assists in reducing the load applied at the AT enthesis organ. Furthermore, histological studies showed a fibrosis is evident at the tip of PW, which is thought to be developed as a result of resisting external loading. This also supports speculations that KFP removal is likely to reduce lubrication, pressure distribution, load bearing, and consequently, increasing the tear and wear level within AT enthesis