Unusual variant of distal biceps femoris muscle associated with common peroneal entrapment neuropathy: A cadaveric case report

The Association between Anatomical Variants of Musculoskeletal Structures and Nerve Compressions of the Lower Limb: A Systematic Review and Meta-Analysis

Objective: The aim of this study was to describe the main anatomical variants and morphofunctional alterations in the lower limb that compress surrounding nervous structures in the gluteal region, thigh region, and leg and foot region. Methods: We searched the Medline, Scopus, Web of Science, Google Scholar, CINAHL, and LILACS databases from their inception up to October 2023. An assurance tool for anatomical studies (AQUA) was used to evaluate methodological quality, and the Joanna Briggs Institute assessment tool for case reports was also used. Forest plots were generated to assess the prevalence of variants of the gluteal region, thigh, and leg. Results: According to the forest plot of the gluteal region, the prevalence was 0.18 (0.14-0.23), with a heterogeneity of 93.52%. For the thigh region, the forest plot presented a prevalence of 0.10 (0.03-0.17) and a heterogeneity of 91.18%. The forest plot of the leg region was based on seven studies, which presented a prevalence of 0.01 (0.01-0.01) and a heterogeneity of 96.18%. Conclusions: This review and meta-analysis showed that, in studies that analyzed nerve compressions, the prevalence was low in the thigh and leg regions, while in the gluteal region, it was slightly higher. This is mainly due to the PM region and its different variants. We believe that it is important to analyze all the variant regions defined in this study and that surgeons treating the lower limb should be attentive to these possible scenarios so that they can anticipate possible surgical situations and thus avoid surgical complications.

An Update on Peroneal Nerve Entrapment and Neuropathy

Peroneal neuropathy is the most common compressive neuropathy of the lower extremity. It should be included in the differential diagnosis for patients presenting with foot drop, the pain of the lower extremity, or numbness of the lower extremity. Symptoms of peroneal neuropathy may occur due to compression of the common peroneal nerve (CPN), superficial peroneal nerve (SPN), or deep peroneal nerve (DPN), each with different clinical presentations. The CPN is most commonly compressed by the bony prominence of the fibula, the SPN most commonly entrapped as it exits the lateral compartment of the leg, and the DPN as it crosses underneath the extensor retinaculum. Accurate and timely diagnosis of any peroneal neuropathy is important to avoid progression of nerve injury and permanent nerve damage. The diagnosis is often made with physical exam findings of decreased strength, altered sensation, and gait abnormalities. Motor nerve conduction studies, electromyography studies, and diagnostic nerve blocks can also assist in diagnosis and prognosis. First-line treatments include removing anything that may be causing external compression, providing stability to unstable joints, and reducing inflammation. Although many peroneal nerve entrapments will resolve with observation and activity modification, surgical treatment is often required when entrapment is refractory to these conservative management strategies. Recently, additional options including microsurgical decompression and percutaneous peripheral nerve stimulation have been reported; however, large studies reporting outcomes are lacking.

A Cadaveric Study of the Distal Biceps Femoris Muscle in relation to the Normal and Variant Course of the Common Peroneal Nerve: A Possible Cause of Common Peroneal Entrapment Neuropathy

The most frequent mononeuropathy in the lower extremity has been reported as the common peroneal nerve entrapment neuropathy (CPNe) around the head and neck of the fibula, although the mechanism of the neuropathy in this area cannot be fully explained. Therefore, the aim of this cadaveric study was to evaluate the relationship between morphologic variations of the distal biceps femoris muscle (BFM) and the course of the common peroneal nerve (CPN) and to investigate the incidence and morphological characteristics of anatomical variations in the BFM associated with CPNe. The popliteal region and the thigh were dissected in 115 formalin-fixed lower limbs. We evaluated consensus for (1) normal anatomy of the distal BFM, (2) anatomic variations of this muscle, and (3) the relationship of the muscle to the CPN. Measurements of the distal extents of the short and long heads of the BFM from insertion (fibular head) were performed. Two anatomic patterns were seen. First, in 93 knees (80.8%), the CPN ran obliquely along the lateral side of the BFM and then superficial to the lateral head of the gastrocnemius muscle. Second, in 22 cases (19.2%), the CPN coursed within a tunnel between the biceps femoris and lateral head of the gastrocnemius muscle (LGCM). There was a positive correlation between the distal extents of the short heads of the biceps femoris muscle (SHBFM) and the presence of the tunnel. The “popliteal intermuscular tunnel” in which the CPN travels can be produced between the more distal extension variant of the SHBFM and the LGCM. This anatomical variation of BFM may have a clinical significance as an entrapment area of the CPN in the patients in which the mechanism of CPNe around the fibula head and neck is not understood.