Therapeutic approach with platelet lysate and ozone therapy for partial gastrocnemius tendon rupture in a horse - case reportABSTRACT
Lesions of the gastrocnemius muscle and tendon often require prolonged recovery periods and carry a guarded prognosis. The goal of treating tendinous injuries is to restore morphology and function. The combination of biological therapies with ozone therapy appears promising by modifying the lesions microenvironment and promoting faster, more controlled, and organized tissue repair. This case report describes intralesional allogeneic platelet lysate combined with perilesional subcutaneous ozone for gastrocnemius tendon rupture. A two-year-old male Mangalarga Marchador horse presented with reciprocal apparatus dysfunction and loss of function of the pelvic limb, diagnosed by ultrasonography with a partial gastrocnemius tendon rupture. The treatment included limb immobilization, serial intralesional injections of pooled allogeneic platelet lysate, and subcutaneous ozone applications around the lesion. Within a short period, limb stabilization, improved weight-bearing capacity, and high-quality tendon repair were observed, confirmed by imaging and clinical evaluation. These findings suggest that biological therapies, like platelet lysate, which improve tissue condition and stimulate regeneration, combined with ozone therapy, which modulates inflammation, may be effective adjuvant strategies in tendon injury treatment, accelerating healing. This case demonstrates the effectiveness of a multimodal therapeutic approach in promoting tendon repair and restoring functionality, highlighting the potential of combining regenerative and modulatory therapies to enhance clinical outcomes in equine tendon injuries.
Keywords:
regenerative medicine; platelet-derived therapy; ozone therapy; tendinous lesion; horses
RESUMO
Lesões do músculo gastrocnêmio e seu tendão frequentemente exigem longos períodos de recuperação e prognóstico reservado. O objetivo do tratamento das lesões tendíneas é restaurar morfologia e função do tecido afetado. A combinação de terapias biológicas com ozonioterapia apresenta potencial terapêutico ao modificar o microambiente da lesão e promover reparo mais rápido, controlado e organizado. Este relato descreve o uso de lisado plaquetário alogênico intralesional associado à aplicação subcutânea de ozônio ao redor da lesão em ruptura do tendão gastrocnêmio. Um cavalo macho Mangalarga Marchador de dois anos apresentou disfunção do aparelho recíproco e perda de função no membro pélvico, diagnosticado por ultrassonografia com ruptura parcial do tendão gastrocnêmio. O tratamento incluiu imobilização do membro, injeções intralesionais seriadas de lisado plaquetário alogênico em pool e aplicações subcutâneas de ozônio ao redor da lesão. Em curto período, observaram-se estabilização do membro afetado, melhora na sustentação de peso e reparo tendíneo de alta qualidade, confirmados por exames de imagem e avaliação clínica. Esses achados sugerem que terapias biológicas, como lisado plaquetário, que melhoram condições teciduais e estimulam regeneração, associadas à ozonioterapia, que modula o ambiente inflamatório, podem representar estratégias adjuvantes eficazes no tratamento de lesões tendíneas, acelerando o processo de cicatrização. Este caso demonstra a efetividade de abordagem multimodal na promoção da reparação tendínea e da restauração da funcionalidade.
Palavras chaves:
medicina regenerativa; terapia derivada de plaquetas; ozonioterapia; lesão tendínea; cavalos
INTRODUCTION
The gastrocnemius muscle is a component of the caudal aspect of the reciprocal apparatus and functions synchronously as a flexor of the femoropatellar joint and as an extensor of the tarsus (Jesty et al., 2005; Sato et al., 2014; Martens, 2019). Injuries to the gastrocnemius muscle or tendon most frequently occur at the musculotendinous junction or near its insertion on the calcaneal tuberosity. However, avulsion of the gastrocnemius muscle from the supracondylar tuberosities of the femur may also occur (Shoemaker et al., 1991; Swor et al., 2001). Clinical signs vary according to the degree of dysfunction of the reciprocal apparatus. In cases of partial rupture, the animal typically presents with acute onset severe lameness, accompanied by varying degrees of soft tissue edema, distal dropping of the tarsus, or gait abnormalities characterized by lateral rotation of the calcaneus and medial rotation of the hoof. (Toppin and Lori, 2006; Martens, 2019). In cases of complete rupture, the animal may become unable to bear weight on the affected limb, resulting in tarsal collapse and hyperextension of the femoropatellar joint (Jesty et al., 2005; Martens, 2019). As the gastrocnemius is a key caudal component of the reciprocal apparatus, animals may become unable to rise, depending on the severity of the lesion (Jesty et al., 2005).
The cornerstone of treatment involves rest and immobilization of the affected limb. However, this frequently results in fibrotic scar tissue formation, and the prognosis remains guarded, both regarding survival and the potential return to athletic activity (Lescun et al., 1998; Swor et al., 2001; Jesty et al., 2005; Toppin and Lori, 2006; Sato et al., 2014).
In general, the available interventions are predominantly conservative, including the use of non-steroidal anti-inflammatory drugs and corticosteroids, which generally provide only symptomatic relief. In more severe cases, surgical treatment may be indicated, although outcomes are often limited. Tendon healing is inherently slow and inefficient because of the low vascularization and reduced regenerative capacity. Even when repair occurs, the resulting tissue is generally biomechanically weaker, favoring the recurrence of injuries (Klatte-Schulz et al., 2018; Ortved, 2018).
In recent years, there has been growing interest in therapies aimed at improving the regenerative environment of injured tissue and controlling pain, with the goal of achieving more effective outcomes (Chen et al., 2018; Markazi et al., 2022). Regenerative medicine seeks to restore tissue quality and functionality. Among its approaches, blood-derived products stand out, with their therapeutic action based on the secretome of blood cells (Ribitsch et al., 2021). One such product is platelet lysate (PL), an acellular supernatant derived from platelet-rich plasma (PRP), whose therapeutic effects are mediated by the release of multiple bioactive growth factors (Schulz et al., 2018; Markazi et al., 2022). Ozone therapy, in turn, is used across various medical specialties and involves the administration of medicinal ozone at therapeutic concentrations, promoting immunomodulatory, anti-inflammatory, antimicrobial, analgesic, and other clinical benefits (Bocci, 2006; Sagai and Bocci, 2011; Schwartz and Martínez Sanchéz, 2012; Basile and Baccarin, 2022).
The present case report aims to describe the outcomes of intralesional platelet lysate application combined with perilesional subcutaneous ozone administration in the treatment of gastrocnemius tendon rupture in a horse.
CASE REPORT
A two-year-old male Mangalarga Marchador horse, weighing 330kg, was presented for evaluation of acute-onset lameness following a fall 10 days prior, with no favorable response to anti-inflammatory treatment. The horse showed functional impairment of the left pelvic limb, with instability and distal displacement of the tarsus, which appeared semi-flexed, along with semi-extension of the femoropatellar joint. Increased local temperature and swelling were observed proximal to the tarsal joint, in the region of the common calcaneal tendon (Figure 1A). A small superficial wound was observed in the swollen region, with no apparent communication with the tendon sheath. No significant abnormalities were identified in laboratory testing. Additional physical findings included tachycardia (52 bpm) and tachypnea (28 breaths/minute). Radiographic examination of the femoropatellar joint, tibia, tarsus, metatarsus, and metatarsophalangeal joint revealed no bone abnormalities. In this case, the ultrasonographic findings were as follows: Figure 2A - longitudinal evaluation of the gastrocnemius tendon shows a distinct area of fibrillar discontinuity, characterized by interruption of the normal parallel architecture of the hyperechoic collagen fibers; Figure 2B - the gastrocnemius tendon presents a significant increase in volume, with irregular margins and heterogeneous echotexture. A diffuse decrease in echogenicity was observed, consistent with intratendinous edema. There are also scattered punctate hyperechoic areas, possibly related to the onset of tissue repair, corresponding to the initial deposition of immature collagen and structural reorganization; Figure 2C - the gastrocnemius tendon shows a reduction in volume compared to the previous examination, indicating decreased edema. The echotexture appears more homogeneous, with progressive reorganization of collagen fibers arranged in a partially parallel pattern and exhibiting elongated linear echoes.
To prevent further damage to the tendon and allow for proper healing, rigid immobilization of the limb was performed under general inhalation anesthesia. The horse was sedated with detomidine (10 µg/kg IV), anesthesia was induced with ketamine (2.5 mg/kg IV) and diazepam (0.08 mg/kg IV) and maintained with isoflurane. The limb was immobilized using synthetic orthopedic plaster, extending from the hoof to the proximal portion of the tibia. Assisted anesthetic recovery occurred without complications. Following immobilization, the horse was able to partially bear weight on the left pelvic limb. Multimodal analgesia included administration of phenylbutazone (4.4 mg/kg IV SID), dipyrone (12.5 mg/kg IV BID), morphine (0.1 mg/kg IM TID), and ketamine (0.6 mg/kg PO TID) during the first 15 days of hospitalization. To improve the lesion environment and promote faster and higher-quality healing, intralesional platelet lysate applications and perilesional subcutaneous ozone injections were performed. Three intralesional infiltrations of pooled allogeneic platelet lysate (40mL), prepared using a platelet-rich plasma protocol validated for the species (Seidel et al., 2019) with a 5-fold platelet enrichment compared to baseline, were performed at intervals of 10 to 14 days. Perilesional subcutaneous ozone applications (totaling 20mL at 10mg/L concentration, with 4 mL per injection site) were administered weekly for 5 weeks, with evident improvement in analgesia following each treatment. The first application was given on the day of hospital admission, immediately prior to rigid immobilization. This treatment was combined with physiotherapy, including controlled therapeutic exercises (neck and core muscle stretching, proprioception pathways), as well as active and passive limb mobilization. After four days, due to poor tolerance of the rigid immobilization and worsening discomfort, it was decided to replace it with a caudal splint, which remained in place for seven days before being substituted by a Robert-Jones bandage. The animal developed pressure sores caused by the synthetic cast on the craniodistal portion of the tibia and the calcaneus, which were successfully treated using a pericardial membrane. The Robert-Jones bandage was discontinued twenty-five days after the initial immobilization, as limb stability, improved weight-bearing, and increased flexion capacity of the tarsal and femoropatellar joints were observed.
Ultrasonographic examination revealed improvement in edema, more homogeneous echotexture, and process of organization of collagen fibers, being partially parallel and with elongated linear echoes. The animal was discharged after 38 days of hospitalization, with recommendations to continue the physiotherapy exercises performed during the stay. The affected limb showed restoration of function and symmetry between the pelvic limbs (Figure 1B).
Images illustrating the clinical progression of the right hindlimb posture in a horse diagnosed with gastrocnemius tendon rupture. (A) Condition of the animal upon hospital admission, showing distal dropping of the tarsus characteristic of this lesion; (B) Condition of the animal at the end of treatment.
Longitudinal ultrasonographic images of the gastrocnemius tendon at three different time points during clinical follow-up: (A) Initial examination showing a marked area of fiber disruption and intratendinous hematoma. (B) Fifteen days after the first evaluation, showing early fiber reorganization and reduction of the anechoic area. (C) Thirty days after the first evaluation, demonstrating improved collagen fiber alignment and decreased lesion size. Images were obtained using different presets, which may account for variations in echogenicity between time points.
DISCUSSION
The most common cause of gastrocnemius muscle or tendon rupture is a forceful active contraction occurring simultaneously with forced passive extension. For this reason, a fall with the limb extended beneath the body is one of the primary causes of injury to the caudal components of the reciprocal apparatus, as occurred in the present case (Lescun et al., 1998; Toppin and Lori, 2006).
In cases of gastrocnemius tendon rupture, clinical examination is essential for diagnosis, as the patient’s clinical presentation provides key diagnostic clues. In the present case report, the animal exhibited acute and severe lameness accompanied by soft tissue swelling on the caudal aspect of the limb immediately proximal to the tarsus and tarsal rotation, characterized by lateral deviation of the calcaneus and medial rotation of the hoof. These clinical findings were consistent with gastrocnemius tendon rupture.
Complementary imaging tests are also crucial. Radiographic examinations aid in diagnosis, as they identify associated fractures, which are often caused by trauma (Tull, 2009), and need to be ruled out, potentially altering therapeutic decisions. Ultrasonography allows detailed soft tissue evaluation and identification of the lesion, typically identified by discontinuity of tendon fibers, provides the location and extent of the injury. Ultrasound is essential in clinical decision-making based on findings. In cases of ruptures, defining the extent of the injury is essential. Since the lesion was partial rather than complete, amenable to surgical repair, infiltration should be considered the treatment of choice, as the fibers are distant enough to prevent spontaneous repair, which would likely represent a prolonged healing process, as cited in the literature. It also helps to define the prognosis, which in this case is considered reserved, although the ultrasound allowed us to determine that it was a partial rupture, thus having better chances when compared to cases of total rupture, in addition to enabling monitoring of the progress of the treatment (Toppin and Lori, 2006).
The goal of treatment is to restore weight-bearing on the affected limb, prevent hyperflexion of the tarsus, and minimize the distance required for the formation of a fibrous scar tissue bridge. Various techniques have been described, but all involve movement restriction (Toppin and Lori, 2006). For this reason, one of the main pillars of the treatment applied was movement restriction combined with limb immobilization, which allowed for reduced load on the injured tendon, approximation of the torn fibers, and prevention of lesion worsening. Continuous weight-bearing on an immobilized affected limb can exacerbate the injury and lead to complete rupture of the affected tissues (Shoemaker et al., 1991). One of the main complications associated with external immobilization is pressure concentration within the cast, which often results in severe pressure sores on the proximal tibia and calcaneus. This was the primary complication in the case, prompting the replacement of the cast with a caudal splint on the fourth day. Additionally, this type of support allows access to the limb, enabling the administration of platelet lysate and ozone therapies in this case. Despite this complication, the benefits of rigid immobilization outweigh the risks associated with pressure sore development (Lescun et al., 1998). Other complications reported in the literature include the development of flexural deformities (Lescun et al., 1998; Toppin and Lori, 2006), contralateral limb laminitis (Toppin and Lori, 2006), vascular damage and hemorrhage (Shoemaker et al., 1991; Jesty et al., 2005; Sato et al., 2014), and formation of hematomas, fibrosis, and calcification (Lescun et al., 1998; Swor et al., 2001; Jesty et al., 2005; Sato et al., 2014).
Among the available regenerative medicine approaches, intralesional application of PL was chosen due to its advantages over PRP, such as exhibiting similar concentrations of therapeutic components, including growth factors (GFs); demonstrating stability during storage, being acellular, and having previously demonstrated biosafety (Klatte Schulz et al., 2018; Fonseca et al., 2021; Markazi et al., 2022). In this report, an allogeneic PL pool derived from selected donors was used, allowing for the same product to be applied throughout the entire treatment and minimizing the possibility of unwanted inflammatory reactions. In a comparative analysis between different platelet lysates, allogeneic PL showed better results compared to autologous PL, although the exact differences between the two products were not fully identified; allogeneic PL had higher concentrations of growth factors than the autologous PL (Klatte Schulz et al., 2018). However, studies on PL remain scarce, mostly involving human subjects or in vitro experiments, and results regarding the use of PL in tendon injuries remain controversial. In an in vitro study, human tenocytes cultured with increasing concentrations of PL showed improved proliferation and migration compared to the control group in a dose-dependent manner (Fonseca et al., 2021), whereas the in vitro study by Klatte Schulz et al. (2018) did not find any clear positive stimulatory effect of different platelet lysates on tendon cell biology. In the present case, rapid and organized tissue repair was observed, without evidence of excessive fibrotic scar tissue formation.
Alongside the use of PL, ozone therapy was also applied through subcutaneous perilesional injections due to its effect on modulating the inflammatory environment via controlled acute oxidative stress (Vendruscolo et al., 2018; Anzolin and Bertol, 2018). Ozone therapy also exerts amplifying effects on cellular antioxidant mechanisms, optimizes immune function, stimulates tissue repair and angiogenesis, and is effective in pain management (Basile and Baccarin, 2022). Studies have evaluated the potential of ozone therapy in the treatment of tendinopathies and suggest that ozone applications are comparable to corticosteroid injections in relieving symptoms. (Jeyaraman et al., 2024).
Kizilkaya et al. (2018) assessed the efficacy of ozone application in Achilles tendon injuries in rats and observed fibroblast proliferation, tissue remodeling, and significantly higher load and tension values compared to the control group, which exhibited a more severe degree of inflammation. Gurger et al. (2021) compared the effect of PRP combined with ozone therapy on rotator cuff tendon healing in rabbits and observed a statistically significant increase in biomechanical strength and improved collagen fiber organization compared to other groups evaluated. In the present case, marked analgesic improvement was observed following ozone applications, reinforcing the potential of this therapy in inflammation modulation and pain control.
The prognosis for horses with rupture of the caudal component of the reciprocal apparatus is guarded, being better in partial ruptures and poor in complete ruptures. Age, weight, and temperament are factors that impact the outcome, with young, lightweight horses showing a better prognosis (Toppin and Lori, 2006; Reeves and Trotter, 1991). In the present case, the horse had a partial rupture of the gastrocnemius tendon, was young, had low weight, and a good temperament, all of which contributed to a better prognosis and positive outcome. The prognosis for athletic career is often compromised by inadequate tissue reorganization and a high rate of re-injury, which was also minimized using regenerative medicine that favored tissue repair and reduced fibrotic tissue formation.
CONCLUSION
The therapeutic approach adopted in the present case promoted high-quality tissue repair and complete restoration of function in the affected limb within a shorter timeframe than that generally reported in the literature. The observed functional recovery and restoration of limb symmetry emphasize that, when combined with strict immobilization, platelet lysate and ozone therapy may represent effective adjunctive therapies for improving tendon healing quality and clinical outcomes in equine patients. This case highlights the importance of a multimodal therapeutic approach, representing a promising and effective strategy for the clinical management of tendinopathies.
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ETHICAL ASPECTS
This research was not submitted to the Ethics Committee on Animal Use however, the necessary consent forms were signed to authorize and carry out the treatment in accordance with institutional policies.
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DATA AVAILABILITY STATEMENT
The research data are available within the article itself.
The research data are available within the article itself.
