Paratenon preserving repair of the midsubstance acute Achilles tendon rupture: a systematic review and meta-analysis with best- and worst-case analyses for rerupture rates.

INTRODUCTION: Paratenon preserving techniques to facilitate acute Achilles tendon rupture repair (AATR) functions by maintaining vascularity and biology for optimal healing response. Therefore, the purpose is to evaluate the outcomes following paratenon preserving repair of the midsubstance AATR. The hypothesis was that paratenon-preserving techniques demonstrate high return to play rates and low complication rates for the repair of the midsubstance AATR. MATERIALS AND METHODS: A systematic review of the PubMed, Embase, and the Cochrane Library databases was performed by two authors using specific search terms and eligibility criteria. The assessment of the evidence was two-fold: level and quality of evidence. A meta-analysis of proportions for the various complication rates was performed using the restricted maximum likelihood method following the Freeman-Tukey double-arcsine transformation. Fixed effects models were employed if I2 < 25% (low heterogeneity), and random effects models were employed if I2 ≥ 25% (moderate to high heterogeneity). RESULTS: The pooled return to play rate was 90.3%. The pooled rerupture rate as reported was 0.9% (best-case scenario 0.8% and worst-case scenario 6.8%). No meaningful subgroup analysis for rerupture rates could be performed based on the meta-regression. The pooled complication rate other than reruptures was 4.8%. The pooled infection rates were 0.3%, DVT rates were 1.6%, and sural nerve injury rates were 0.3%. CONCLUSIONS: Paratenon preserving techniques that are minimally invasive in nature demonstrated safe and favorable outcomes with high return to play rates and low complication rates for the repair of the midsubstance AATR.

High-resolution ultrasound of the paratenon of the Achilles calcaneal tendon: anatomical study and description of the paratendinous injection technique.

PURPOSE: The aim of this study is to determine if ultrasound (US) allows a precise assessment of the paratenon (PT) of the Achilles calcaneal tendon (AT), and to anatomically describe the US-guided paratendinous injection technique. METHODS: This study was initially conducted on eight cadaveric specimens using high-resolution ultrasound (HRUS) to examine the PT appearance, thickness, and its relationships with the AT, plantaris tendon (PLT), Kager's fat pad (KFP), sural nerve (SN), and fascia cruris (FC). US-guided paratendinous injection of China ink was performed in all specimens, followed by anatomical dissection to assess injectate distribution. Then, HRUS study of the PT was carried out bilaterally in twenty asymptomatic volunteers (40 legs). Two musculoskeletal radiologists recorded all data in consensus except PT thickness in volunteers which was recorded independently in order to calculate intra and inter-observer reliability. RESULTS: The PT was consistently identified with HRUS along its entire course in both cadaveric specimens (8/8) and volunteers (40/40). The mean PT thickness was 0.54 mm in cadavers and 0.39 mm in vivo, without any correlation with the AT thickness. Intra- and inter observer reliability were respectively excellent and good for PT thickness. All eight (100%) ex vivo China ink injections were accurate, demonstrating a circumferential distribution of the injectate between the PT and the AT, associated with an anterior spread to the KFP. CONCLUSION: HRUS allows visualization of the PT along its entire length, and assessment of its relationships to adjacent structures. US-guided paratendinous injections can accurately and safely deliver injectates in the paratendinous sheath.

Anatomical Structures Responsible for CTEV Relapse after Ponseti Treatment.

Relapse of deformity after a successful Ponseti treatment remains a problem for the management of clubfoot. An untreated varus heel position and restricted dorsal flexion of the ankle are the main features of recurrences. We analyze the anatomical structures responsible for these recurrences. Materials and methods: During 5 years, 52 children with CTEV (Congenital Talipes Equino Varus) were treated with casts according to the Ponseti method, with a mean number of 7 casts. Closed percutaneous tenotomy was performed in 28 infants. Children were followed monthly and treated with the continuous use of a molded cast. We had 9 children with relapsed clubfeet. During the standing and walking phase, they had a fixed deformity with a varus position of the heel and dorsal flexion of the ankle <10 d. They were surgically treated with the posterolateral approach. Results: In all patients, we found a severe thickening of the paratenon of the Achilles in the medial side, with adhesions with the subcutaneous tissue. The achilles after the previous tenotomy was completely regenerated. The achilles was medially displaced. Conclusions: A severe thickening of the paratenon of the achilles and adhesions with the subcutaneous tissue are anatomical structures in fixed relapsed cases of clubfoot. We treated our patients with an appropriate surgical release.

Anatomical study of paratenons and fascia lata connections in the posteromedial knee region.

INTRODUCTION: In the last decade, fascia research increased significantly in various aspects such as anatomical and biomechanical features related to epimuscular force transmission. METHODS: The present anatomic study focuses on macroscopic observations of the potential gracilis and semitendinosus paratenons, as well as fascial surroundings connections in the posteromedial knee region on 17 lower-limbs dissections. RESULTS: The gracilis and semitendinosus expansions and paratenons were observed in all specimen and further connections with the fascia lata and crural fascia were demonstrated. Contrary to the previously described expansions connected to the tendons, we observed that the expansions were the edges of the paratenon tunnel and that the paratenon structure surrounded the overall muscle. Both paratenons of gracilis and semitendinosus were connected to the crural fascia and, respectively, to the sartorius fascia (part of the fascia lata), to the semimembranosus and the fascia lata. Furthermore, numerous connections between the fascia lata and the neighboring structures in the posteromedial knee region are described. DISCUSSION-CONCLUSION: The present study describes for the first time gracilis and semitendinosus paratenons and other surrounding fascial connections. Such macroscopic observations may represent a new basis for further characterization of the myofascial pathway of epimuscular force transmission in the knee region.

Paratenon of the cruciate ligaments of the knee: a macroscopic and histological study of human foetuses.

BACKGROUND: The paratenon is a sheath-like connective tissue that allows the tendon to move with minimal friction. The careful removal of the paratenon along the cruciate ligaments is a critical step of knee surgery. Thus, orthopaedic surgeons and interventional radiologists consider the paratenon as a basic anatomical tissue along a ligament, not along a tendon. MATERIALS AND METHODS: We performed macroscopic and histological observations of cruciate ligament-associated paratenons in 43 human foetuses. RESULTS: This tissue usually had a thick armour-like appearance that was distant from the infrapatellar fat pad. The anterior cruciate ligament, rather than the posterior ligament, was deeply embedded in the paratenon. The paratenon contained abundant arteries and veins and, at and near the crossing between the cruciate ligaments, had a well-developed venous plexus. Notably, there were abundant fused veins in the paratenon venous plexus, and prenatal knee movements (especially rotation) seemed to restrict its blood supply, leading to the development of a large cavity by way of advancing fusion of veins in the degenerating plexus. This unique manner of cavitation likely expanded the joint cavity. CONCLUSIONS: Differences in knee movements in utero seemed to cause differences in the thickness of the paratenon among foetuses. New-borns might have limited knee flexion due to a mass-effect of the thick paratenon around the cruciate ligaments. A slight twisting or rotation at the knee may help to release the knee, because it can break the foetal paratenon and accelerate cavitation.

Gracilis and semitendinosus moment arm decreased by fascial tissue release after hamstring harvesting surgery: a key parameter to understand the peak torque obtained to a shallow angle of the knee.

PURPOSE: Semitendinosus and gracilis muscles whose tendons are used in surgical reconstruction of the anterior cruciate ligament maintain their contractile ability, but the peak torque angle of hamstring muscles shifted to a shallow angle postoperatively. The goal was to quantify the influence of the myofascial structures on instantaneous moment arms of knee muscles to attempt explaining the above-mentioned post-surgical observations. METHODS: Hamstring harvesting procedures were performed by a senior orthopaedic surgeon on seven lower limbs from fresh-frozen specimens. Femoro-tibial kinematics and tendons excursion were simultaneously recorded at each step of the surgery. RESULTS: No significant difference was demonstrated for instantaneous moment arm of gracilis during anterior cruciate ligament surgery (84% of the maximum intact values; P ≥ 0.05). The first significant semitendinosus moment arm decrease was observed after tendon harvesting (61% of the maximum intact values; p ≤ 0.005). After hamstring harvesting, the maximum and minimum moment arm (both gracilis and semi tendinosus) shifted to a shallow angle and 90°, respectively. CONCLUSION: Moment arm modifications by paratenons and the loose connective tissue release are essential to understand the peak torque obtained to a shallow angle. LEVEL OF EVIDENCE: Basic science study, biomechanics.

Full thickness open tear of the tendoachilles - Functional outcomes following a stable, single stage repair.

OBJECTIVE: Open injuries of the Tendoachilles present a challenge to the treating surgeon. Although, common in our setting, there is a paucity of literature regarding management of the same. The purpose of this retrospective study was to analyse the functional outcomes following debridement and primary repair of open tears of the Tendoachilles. MATERIALS AND METHODS: Patients with open tears of the tendoachilles, between January 2012 to January 2017. After obtaining demographic data, including mechanism of injury, all patients were managed by adequate debridement and primary repair, by Pennington's modification of Kessler's technique in a single sitting, paratenon closed circumferentially, plantaris reinforcement used when end to end repair couldn't be achieved. Below knee cast for 2 months. Weight bearing started at three months. Statistical analysis using paired t-test for calf circumference, ankle range of motion comparing with uninjured limb. Functional outcome assessment by AOFAS hindfoot score and Achilles tendon rupture score. RESULTS: 23 male patients, mean age 35, were analysed. Field injury was the most common mechanism, with slip in Indian lavatory pans accounting for four patients. Average time to surgery from injury was 22 hours. Plantaris reinforcement in one case. No case of wound dehiscence, scar adherence, tendon rerupture or infection. One patient had serous discharge at three weeks which settled with oral antibiotics. 21 patients performed single heel raise. There was no significant difference in calf circumference and ankle range of motion compared to uninjured limb. Mean AOFAS score was 92, mean Achilles tendon rupture score 77. CONCLUSION: Though open injuries of the tendoachilles is fraught with complications, early debridement, adequate repair of the tendon edges with circumferential closure of the paratenon, yields adequate functional outcomes with minimal complications.

Ligaments of the os trigonum: an anatomical study.

PURPOSE: The aim of the study was to examine the ligaments of the os trigonum. METHODS: The ankle joint magnetic resonance imaging (MRI) of 104 patients with the os trigonum (experimental group) and 104 patients without the os trigonum (control group) were re-reviewed. The connections of the os trigonum and posterior talofibular ligament (PTFL), the fibulotalocalcaneal ligament (FTCL), the paratenon of the Achilles tendon, the posterior talocalcaneal ligament (PTCL), the osteofibrous tunnel of the flexor hallucis longus (OF-FHL) and the flexor retinaculum (FR) were studied. RESULTS: The os trigonum is connected to structures. The posterior part of the PTFL inserted on the os trigonum in 85.6% of patients, whereas in all patients in the control group, the posterior part of the PTFL inserted on the posterior talar process (p < 0.05). The connection of the PTCL was seen in 94.2% of patients in the experimental group, while it was seen in 90.4% of patients in the control group (p > 0.05). The connection to the FTCL in the experimental group was 89.4%, while in the control group, it was 91.3% (p > 0.05). The communication with the paratenon was seen more often in the control group compared to that in the experimental group (31.7% vs. 63.8%, p < 0.001). The FTCL was prolonged medially into the FR in 85.6% of patients in the experimental group and in 87.5% of patients in the control group (p > 0.05). The flexor hallucis longus (FHL) run at the level of articulation between the os trigonum 63.5% and the posterior process of the talus 25% and less often on the os trigonum 11.5%. CONCLUSION: The os trigonum is connected with all posterior ankle structures and more connections than previously reported.

Characterization of the structure, vascularity, and stem/progenitor cell populations in porcine Achilles tendon (PAT).

This study aimed to characterize porcine Achilles tendon (PAT) in terms of its structural components, vascularity, and resident tendon cells. We found that PAT is composed of a paratenon sheath, a core of fascicles, and an endotenon/interfascicular matrix (IFM) that encases the fascicle bundles. We analyzed each of these three tendon components structurally using tissue sections and by isolating cells from each component and analyzing in vitro. Many blood vessel-like tissues were present in the paratenon and IFM but not in fascicles, and the vessels in the paratenon and IFM appeared to be inter-connected. Cells isolated from the paratenon and IFM displayed characteristics of vascular stem/progenitor cells expressing the markers CD105, CD31, with α-smooth muscle actin (α-SMA) localized surrounding blood vessels. The isolated cells from paratenon and IFM also harbored abundant stem/progenitor cells as evidenced by their ability to form colonies and express stem cell markers including CD73 and CD146. Furthermore, we demonstrate that both paratenon and IFM-isolated cells were capable of undergoing multi-differentiation. In addition, both paratenon and IFM cells expressed elastin, osteocalcin, tubulin polymerization promoting protein (TPPP), and collagen IV, whereas fascicle cells expressed none of these markers, except collagen I. The neurotransmitter substance P (SP) was also found in the paratenon and IFM-localized surrounding blood vessels. The findings of this study will help us to better understand the vascular and cellular mechanisms of tendon homeostasis, injury, healing, and regeneration.

Diffuse-Type Giant Cell Tumor of the Paratenon of Achilles Tendon Requiring Reconstruction Using Bilateral Autografts: A Case Report.

Although a diffuse-type giant cell tumor is a rare benign lesion, when it develops it tends to localize to the tendons of the hand and foot. In this study, we report the case of a 41-year-old male patient who was diagnosed with diffuse-type paratenon giant cell tumor involving the Achilles tendon. The duration of the bilateral tumors was 8 years. He visited first affiliated Hospital of Wenzhou Medical University for medical attention. Both his Achilles tendons required removal. The reconstructed Achilles tendon was replaced using tissue derived from the knee and foot. Postoperatively, the patient recovered well and regained full range of motion in the ankle. The use of autografts may shorten patients' recovery period.

Platelet-Rich Plasma Promotes Migration, Proliferation, and the Gene Expression of Scleraxis and Vascular Endothelial Growth Factor in Paratenon-Derived Cells In Vitro.

BACKGROUND:: Platelet-rich plasma (PRP) is a treatment option for tendon injury because of its effective tendon-healing properties. At the early stage of tendon repair, paratenon-derived cells (PDCs) are thought to play a more important role than tendon proper-derived cells (TDCs). However, there has been no study investigating the effects of PRP on PDCs. HYPOTHESIS:: PRP promotes the migration, proliferation, and differentiation of PDCs in vitro. STUDY DESIGN:: Controlled laboratory study. METHODS:: TDCs and PDCs were isolated from the tendon proper and paratenon of rat Achilles tendons and were cultured to the third passage. PRP was prepared from the rats using the double-spin method. Third-passage TDCs and PDCs were cultured in Dulbecco's modified Eagle medium with 2% fetal bovine serum (control group) or 2% fetal bovine serum plus 5% PRP (PRP group), and cell migration, proliferation, and differentiation were evaluated. The relative mRNA expression levels of scleraxis (Scx), tenomodulin (Tnmd), collagen type I alpha 1 (Col1a1), collagen type III alpha 1 (Col3a1), and vascular endothelial growth factor A (VEGF) were examined by quantitative real-time reverse transcription polymerase chain reaction. RESULTS:: The cell migration rate was significantly higher in the PDCs of the PRP group than in the control group (1.4-fold increase; P = 0.02). Cell proliferation was significantly higher in the PDCs of the PRP group (2.2-fold increase; P < 0.01). In the PDCs, the gene expression levels of Scx, Col1a1, and VEGF were significantly increased by PRP (Scx: 2.0-fold increase, P = 0.01; Col1a1: 5.3-fold increase, P = 0.01; VEGF: 7.8-fold increase, P = 0.01), but the gene expression level of Tnmd, a factor for tendon maturation, was significantly reduced by PRP (0.11-fold decrease; P = 0.02). CONCLUSION:: In vitro PRP promoted migration, proliferation, and tenogenic differentiation with the upregulation of Scx in PDCs. PRP also upregulated the expression of the angiogenic marker VEGF. CLINICAL RELEVANCE:: Our results suggest that PRP treatment in vitro may enhance the tendon-healing properties of PDCs at the initial stage of tendon repair.

Response of the Injured Tendon to Growth Factors in the Presence or Absence of the Paratenon.

BACKGROUND: The paratenon is important for Achilles tendon healing. There is much interest in the use of exogenous growth factors (GFs) as potential agents for accelerating the healing of damaged Achilles tendons. PURPOSE/HYPOTHESIS: The present study used a rat model to study the responses of the injured Achilles tendon to GFs in the presence or absence of the paratenon. The hypothesis was that responses of the injured tendon to GFs would be lower in the absence of a paratenon. STUDY DESIGN: Controlled laboratory study. METHODS: A 4-mm defect was created in the right Achilles tendon of 60 skeletally mature rats, which were treated with a validated combination of GFs (bFGF, BMP-12, and TGF-ß1). Animals were randomly assigned to the intact paratenon (IP) group or resected paratenon (RP) group. Healing was studied anatomically, mechanically, and histologically after 1, 2, and 4 weeks. RESULTS: IP tendons showed improved healing compared with RP tendons. IP tendons were significantly stronger (32.2 N and 48.9 N, respectively) than RP tendons (20.1 N and 31.1 N, respectively) after 1 and 2 weeks. IP tendons did not elongate as much as RP tendons and had greater cross-sectional areas (18.0 mm2, 14.4 mm2, and 16.4 mm2, respectively) after 1, 2, and 4 weeks compared with RP tendons (10.5 mm2, 8.4 mm2, and 11.9 mm2, respectively). On histology, earlier collagen deposition and parallel orientation of fibrils were found for IP tendons. CONCLUSION: The paratenon is essential for efficient Achilles tendon healing. Healing with GFs in this Achilles tendon defect model was superior in the presence of the paratenon. CLINICAL RELEVANCE: Biological approaches to tendon engineering using GFs are in vogue and have been shown to improve healing of the rat Achilles tendon, most likely by inducing progenitor cells located within the paratenon. Clinically, resection or incision of the paratenon has been proposed for wound closure. Our data demonstrate the fundamental importance of the paratenon, which therefore should be preserved during Achilles tendon repair, especially if augmented with products such as platelet-rich plasma or autologous conditioned serum that are rich in GFs.

Open Re-rupture of the Achilles Tendon Following Minimally Invasive Repair: A Case Report.

In this report, we describe a rare complication of an open re-rupture of the Achilles tendon following a minimally invasive Achilles tendon repair on a healthy 29-year-old active male. The reinjury happened 19 weeks following the primary surgical repair of a spontaneous rupture, performed by minimally invasive technique with the help of a jig using partially absorbable sutures and four locking stitches. The wound of the open re-rupture was transverse, in a perpendicular orientation relative to the longitudinal approach used in the index procedure. Increased scar tissue formation, the absence of an adequate layer of paratenon overlying the primary tendon repair, and foreign-body reaction to the suture may have been involved in the occurrence of this unusual complication in the surgical treatment of Achilles tendon rupture.

The Role of the Paratenon in Achilles Tendon Healing: A Study in Rats.

BACKGROUND: The role of the paratenon in tendon healing is unknown. The present study compares healing in the presence or absence of the paratenon in an Achilles tendon defect model in rats. HYPOTHESIS: Resection of the paratenon impairs tendon healing. STUDY DESIGN: Controlled laboratory study. METHODS: Sixty skeletally mature Sprague Dawley rats were randomly assigned to either a resected paratenon (RP) group or an intact paratenon (IP) group. In all animals, a 4-mm portion of the Achilles tendon was resected in the midsubstance. In the RP group, the paratenon was resected completely. In the IP group, the paratenon was opened longitudinally and closed again after the tendon defect had been created. One, 2, and 4 weeks after surgery, 7 animals per group were tested biomechanically and 3 animals per group examined histologically. RESULTS: The recovery of mechanical strength was much more rapid in IP tendons. Tear resistance was significantly increased for IP tendons (41.3 ± 8.8 N and 47.3 ± 14.1 N, respectively) compared with RP tendons (19.3 ± 9.1 N and 33.2 ± 6.4 N, respectively) after 1 and 2 weeks. The cross-sectional area was larger in the IP group after 1 and 2 weeks (8.2 ± 2.3 mm2 and 11.3 ± 3.1 mm2 vs 5.0 ± 2.4 mm2 and 5.9 ± 2.0 mm2, respectively) compared with the RP group. Tendon stiffness was greater in the IP group after 1 week (10.4 ± 1.9 N/mm vs 4.5 ± 1.6 N/mm, respectively) compared with the RP group. In comparison, normal contralateral tendons had a maximal tear resistance of 56.6 ± 7.2 N, a cross-sectional area of 3.6 ± 0.7 mm2, and stiffness of 17.3 ± 3.8 N/mm. Hematoxylin and eosin staining revealed slightly delayed healing of RP tendons. Early collagen formation was seen in the IP group already after 1 week, whereas in the RP group, this only occurred after 2 weeks. After 4 weeks, the IP tendons showed more collagen crimp formation than the RP tendons. CONCLUSION: An intact paratenon promotes healing of the Achilles tendon. CLINICAL RELEVANCE: Although incision or resection of the paratenon has been advocated when repairing injured or degenerative tendons, our data suggest that the integrity of the paratenon should be preserved.

Peritenolysis and Debridement for Main Body (Mid-Portion) Achilles Tendinopathy in Athletic Patients: Results of 107 Procedures.

Achilles tendinopathy in the main body (mid-portion) of the tendon is a common pathologic finding among active and athletic populations and can be debilitating without proper and adequate treatment. Numerous surgical approaches for this common pathologic finding have been reported, with variable outcomes. We evaluated the surgical outcomes of peritenolysis and debridement of main body Achilles tendinopathy among athletic populations using the return to activity (RTA) and decreased desired activity (DDA) as our primary outcome measures. A total of 100 patients underwent 107 procedures by the senior author (A.S.) from January 2001 through December 2015 met the inclusion criteria, 65 (65%) of whom were runners. The mean follow-up duration was 106.6 ± 55.5 months from the index procedure, and the mean interval necessary to RTA for the entire group was 10.9 ± 5.3 weeks. The average RTA after debridement was 14.1 ± 5.2 weeks and after peritenolysis was 7.3 ± 2.0 weeks (p = .00001). Of the 100 patients, 3 (3%) had experienced a DDA at the last follow-up visit. With >97% of the patients able to return to their desired activities, we have concluded that peritenolysis and debridement are favorable surgical techniques for main body Achilles tendinopathy.

Relative motion between the flexor digitorum superficialis tendon and paratenon in zone V increases with wrist flexion angle.

Carpal tunnel syndrome is characterized by non-inflammatory fibrosis of the subsynovial connective tissue (SSCT), a paratenon-like structure inside the carpal tunnel. This pathology suggests repetitive and/or excessive shear forces are involved in injury development. We assessed relative motion between the flexor digitorum superficialis (FDS) tendon and adjacent paratenon in Zone V using colour Doppler imaging as 16 healthy participants completed three long finger movements (metacarpophalangeal joint flexion, proximal and distal interphalangeal joint flexion, full finger flexion) in three wrist postures (30° extension, 0°, 30° flexion). While the type of finger movement did not affect tendon-paratenon relative motion, we found a significant main effect of wrist posture (p < 0.001). Relative displacement between the FDS tendon and paratenon (as a percentage of tendon displacement) increased from 27.2% (95%CI = 24.8-29.5%) in 30° wrist extension to 39.9% (95%CI = 37.3-42.4%) in 30° wrist flexion. Optical motion capture confirmed that wrist posture did not affect metacarpophalangeal joint range of motion (p = 0.265) or proximal interphalangeal joint range of motion (p = 0.582). These results indicate that relative motion increased due to paratenon strain when the wrist was flexed. While our findings agree with previous cadaveric research in wrist flexion, we found that relative displacement decreased in 30° wrist extension (compared to 0°). These results differ from cadaveric research, possibly due to challenges maintaining anatomic fidelity of the viscoelastic paratenon tissue in vitro. Overall, our study suggests a greater susceptibility to shear injury during repetitive finger movements, particularly when the wrist is flexed. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1248-1255, 2016.

Isolated schwannoma attached to the paratenon of semitendinosus muscle.

Schwannomas are benign tumors arising from the peripheral nerves with a Schwann cell sheath. Schwannomas can be found in almost every region, but are usually associated with cranial, spinal, sympathetic and peripheral nerves. Schwannoma in lower extremity is relatively common and most are associated with sciatic nerve, peroneal nerve and tibial nerve. However, schwannoma arising in the tendon or paratenon is extremely rare. We report a rare case of a 25-year-old male patient with a schwannoma originating from the paratenon of semitendinosus muscle without evidences of any neurologic symptoms. The clinical history, plain radiographs, magnetic resonance imaging, and pathologic findings of the reported patient have been reviewed. The tumor was fully excised by dissecting a tendon sheath of semitendinosus muscle.

Plantar fascia anatomy and its relationship with Achilles tendon and paratenon.

Although the plantar fascia (PF) has been studied quite well from a biomechanical viewpoint, its microscopic properties have been overlooked: nothing is known about its content of elastic fibers, the features of the extracellular matrix or the extent of innervation. From a functional and clinical standpoint, the PF is often correlated with the triceps surae muscle, but the anatomical grounds for this link are not clear. The aim of this work was to focus on the PF macroscopic and microscopic properties and study how Achilles tendon diseases might affect it. Twelve feet from unembalmed human cadavers were dissected to isolate the PF. Specimens from each PF were tested with various histological and immunohistochemical stains. In a second stage, 52 magnetic resonance images (MRI) obtained from patients complaining of aspecific ankle or foot pain were analyzed, dividing the cases into two groups based on the presence or absence of signs of degeneration and/or inflammation of the Achilles tendon. The thickness of PF and paratenon was assessed in the two groups and statistical analyses were conducted. The PF is a tissue firmly joined to plantar muscles and skin. Analyzing its possible connections to the sural structures showed that this fascia is more closely connected to the paratenon of Achilles tendon than to the Achilles tendon, through the periosteum of the heel. The PF extended medially and laterally, continuing into the deep fasciae enveloping the abductor hallucis and abductor digiti minimi muscles, respectively. The PF was rich in hyaluronan, probably produced by fibroblastic-like cells described as 'fasciacytes'. Nerve endings and Pacini and Ruffini corpuscles were present, particularly in the medial and lateral portions, and on the surface of the muscles, suggesting a role for the PF in the proprioception of foot. In the radiological study, 27 of the 52 MRI showed signs of Achilles tendon inflammation and/or degeneration, and the PF was 3.43 ± 0.48 mm thick (99%CI and SD = 0.95), as opposed to 2.09 ± 0.24 mm (99%CI, SD = 0.47) in the patients in which the MRI revealed no Achilles tendon diseases; this difference in thickness of 1.29 ± 0.57 mm (99%CI) was statistically significant (P < 0.001). In the group of 27/52 patients with tendinopathies, the PF was more than 4.5 mm thick in 5, i.e. they exceeded the threshold for a diagnosis of plantar fasciitis. None of the other 25/52 paitents had a PF more than 4 mm thick. There was a statistically significant correlation between the thicknesses of the PF and the paratenon. These findings suggest that the plantar fascia has a role not only in supporting the longitudinal arch of the foot, but also in its proprioception and peripheral motor coordination. Its relationship with the paratenon of the Achilles tendon is consistent with the idea of triceps surae structures being involved in the PF pathology, so their rehabilitation can be considered appropriate. Finally, the high concentration of hyaluronan in the PF points to the feasibility of using hyaluronan injections in the fascia to treat plantar fasciitis.