Introduction

Muscle hernias are abnormal protrusions of muscle through a fascial weakness or acquired fascial defect, with the lower leg being the most commonly involved extremity. Findings of lower limb muscle herniation typically involve the anterior compartment muscles, with the tibialis anterior muscle being the most commonly documented. Symptomatic lower leg muscle hernias, while rarely encountered in surgical practice, have previously been documented with varying presentations, chiefly soft tissue mass(es) and mass effects, pain, weakness, and chronic exertional compartment syndrome. Current literature is mixed on the modalities of imaging for diagnosis, where the choice of dynamic ultrasound versus magnetic resonance imaging (MRI) remains a debated topic. While most symptomatic presentations respond successfully to conservative treatment, recently published case reports on refractory lower leg muscle hernia highlight the need for surgery, with no consensus on the type of surgical technique (fasciotomy, anatomical repair, mesh repair). We performed a systematic review of published literature on lower leg muscle hernias to highlight patient demographics, presentations, diagnostic investigations, treatment methods, and functional outcomes. Additionally, we included a rare case of symptomatic bilateral, bicompartmental lower leg muscle hernia in a young male cross-country runner, managed in our institution with surgical repair into the cases available for systematic review

Material and Methods

A systematic review was performed according to PRISMA guidelines. Electronic searches were performed on PubMed, MedLine, and EMBASE to identify all relevant studies that reported on lower leg muscle herniation (Level I-IV). The following search terms (last performed on 30 September 2019) were combined using Boolean operators for PubMed: (muscle hernia OR muscular hernia) AND (leg OR lower limb) NOT (lumbar OR disc). Bibliographies of included studies and review articles identified were also hand-searched for additional eligible articles. Conference abstracts and unpublished data were considered to limit publication bias (only if sufficient results were available to conduct meaningful analyses). One patient with lower leg herniation that was treated in the authors’ institution was also included in the data analysis. Cadaveric studies, and studies describing muscle herniation in other anatomical regions, were excluded. This process was repeated twice independently. Each study’s data was then retrieved individually for patient demographics, injury characteristics, nerve involvement, investigations, management and functional or clinical outcomes.

Results

Case Report

A 14-year-old male cross-country runner presented with a 3-month history of bilateral lateral leg pain exclusively occurring during running activities, localised to 10cm above the lateral malleolus bilaterally. Concomitantly, he also noted localised swelling at the lateral aspect of the bilateral lower legs that corresponded to the area of the pain. The pain and swelling were noted to be similar since its onset, with no worsening prior to his presentation. The patient denied any associated weakness or numbness, preceding trauma or injuries, infective symptoms, and personal or family history of malignancies. Clinical examination revealed bilateral localised swellings. Two swellings were present over the right lower limb: Each located 10cm and 13cm above the lateral malleolus respectively, and were 2cm and 1cm in diameter respectively (Figure 1). A similar 1cm soft, hemispherical, nontender swelling was noted over the left lower limb, located 10cm above the lateral malleolus. All masses were noted to be soft, hemispherical, non-tender, attached to the underlying muscles, more prominent on ankle dorsiflexion, not attached to the overlying skin and subcutaneous tissue, and had no overlying skin changes. Examination of the bilateral lower limbs were otherwise normal. The clinical impression was therefore possible bilateral muscle herniation. Ultrasound of the lower limbs then revealed bilateral lower limb swellings consistent with muscle herniations. The patient was then managed with a trial of nonsurgical management, including activity modification and antiinflammatories. However, the patient returned in 3 months with persistence of pain symptoms despite conservative management and was therefore keen for surgical intervention. Subsequently, the patient underwent surgical repair of bilateral calf hernia defects. The surgery was performed under general anaesthesia with the patient in supine position. A longitudinal incision was made directly over the swellings. Careful subcutaneous dissection was performed to identify the herniated muscle. The herniated muscles were noted to involve both the anterior and lateral compartments bilaterally. On further exploration of the fascial defect, it was noted that the proximal herniation occurred at the point where the perforating vessels were traversing through the fascia (Figure 2A, 3A) while the distal herniation occurred at the point where the superficial peroneal nerves were exiting through the fascia bilaterally (Figure 2B, 3B). For the proximal herniation, the perforating vessels were ligated, and the muscle herniation was then reduced by closing the fascial defect over the herniated muscle. For the distal herniation, careful dissection was performed to release the exiting nerve and the muscle herniation was reduced by closing the fascial defect over the herniated muscle with 1-0 Prolene sutures, with sufficient portal for the nerve to exit the fascia without strangulation (Figure 4A, 4B). Irrigation and wound closure were then performed. Following the surgery, the patient was monitored post-operatively and discharged well on the same day. He was allowed full weightbearing but advised to start his athletic activities of running only 3 weeks after the surgery. The patient was then reviewed in clinic post-operatively at regular intervals. 10 weeks following the surgery, the patient reported to have returned to full athletic activities including running, with no more recurrence of pain or swelling. There were no intraoperative or post-operative complications noted during the follow-up visits. The patient was followed-up until 1 year post-operatively and was noted to be doing well. The patient as well as his legal guardians consented for his data to be submitted for publication.

Figure 1: Proximal and distal points of muscle swellings in the right lower leg with incisions marked by skin marker. A single mass similar in size and site to the distal muscle swelling on the right leg was found on the contralateral leg.

Figure 2: Intraoperative photos showing proximal anterior compartment muscle herniation (A) and distal lateral compartment herniation (B) in the left leg. M, Medial; L, Lateral; S, Superior; I, Inferior.