Combined common peroneal and tibial nerve injury after knee dislocation: one injury or two? An MRI-clinical correlation

Abstract

<jats:sec> <jats:title>OBJECT</jats:title> <jats:p>Knee dislocations are often accompanied by stretch injuries to the common peroneal nerve (CPN). A small subset of these injuries also affect the tibial nerve. The mechanism of this combined pattern could be a single longitudinal stretch injury of the CPN extending to the sciatic bifurcation (and tibial division) or separate injuries of both the CPN and tibial nerve, either at the level of the tibiofemoral joint or distally at the soleal sling and fibular neck. The authors reviewed cases involving patients with knee dislocations with CPN and tibial nerve injuries to determine the localization of the combined injury and correlation between degree of MRI appearance and clinical severity of nerve injury.</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>Three groups of cases were reviewed. Group 1 consisted of knee dislocations with clinical evidence of nerve injury (n = 28, including 19 cases of complete CPN injury); Group 2 consisted of knee dislocations without clinical evidence of nerve injury (n = 19); and Group 3 consisted of cases of minor knee trauma but without knee dislocation (n = 14). All patients had an MRI study of the knee performed within 3 months of injury. MRI appearance of tibial and common peroneal nerve injury was scored by 2 independent radiologists in 3 zones (Zone I, sciatic bifurcation; Zone II, knee joint; and Zone III, soleal sling and fibular neck) on a severity scale of 1–4. Injury signal was scored as diffuse or focal for each nerve in each of the 3 zones. A clinical score was also calculated based on Medical Research Council scores for strength in the tibial and peroneal nerve distributions, combined with electrophysiological data, when available, and correlated with the MRI injury score.</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>Nearly all of the nerve segments visualized in Groups 1 and 2 demonstrated some degree of injury on MRI (95%), compared with 12% of nerve segments in Group 3. MRI nerve injury scores were significantly more severe in Group 1 relative to Group 2 (2.06 vs 1.24, p &lt; 0.001) and Group 2 relative to Group 3 (1.24 vs 0.13, p &lt; 0.001). In both groups of patients with knee dislocations (Groups 1 and 2), the MRI nerve injury score was significantly higher for CPN than tibial nerve (2.72 vs 1.40 for Group 1, p &lt; 0.001; 1.39 vs 1.09 for Group 2, p &lt; 0.05). The clinical injury score had a significantly strong correlation with the MRI injury score for the CPN (r = 0.75, p &lt; 0.001), but not for the tibial nerve (r = 0.07, p = 0.83).</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>MRI is highly sensitive in detecting subclinical nerve injury. In knee dislocation, clinical tibial nerve injury is always associated with simultaneous CPN injury, but tibial nerve function is never worse than peroneal nerve function. The point of maximum injury can occur in any of 3 zones.</jats:p></jats:sec>

Magnetic resonance imaging for common peroneal nerve injury in trauma patients: Are routine knee sequences adequate for prediction of outcome?

“…In the Reddy et al ., clinical injury score strongly correlation with the MRI injury score for CPN ( r = 0.75, P < 0.001). Reddy used axial fat‐suppressed T2 weighted images that may have been more sensitive to abnormal T2 signal.…”

“…Sensitivity of 54.5% for CPN injury on adequate scans was lower than expected. This is likely because axial PD images are not as sensitive for abnormal neural T2 signal as fat‐suppressed T2 weighted images used in other studies . Recent work on the brachial plexus has shown the value of T2 weighted imaging for nerve injury, specifically using what is called MR neurography or 3D SPACE short tau inversion recovery (STIR) sequences .…”

“…Current literature suggests MRI has a role in determining severity of CPN damage . Nevertheless, no study has followed long‐term clinical outcome based on MRI findings.…”

Neurologic Assessment and Management of the Multiple Ligament Injured Knee: A Review and Synthesis of Current Evidence

“…MRI can, in some cases, assist in determining location of injury, presence of a compressive hematoma or scar tissue, axonotmesis versus neurotmesis, and determining gap length between two ends of a severed nerve. However, while many agree that MRI can provide some helpful information in the setting of neurological injury for these patients, 8,21,22 conventional MRI likely does not provide more accurate information than ultrasound evaluation. 19 A 2019 study by Tran et al 23 examined the ability of routinely sequenced MRIs to evaluate the CPN and predict outcome in patients following knee dislocation.…”

New and unusual causes of foot drop

“…These include diseases affecting the central nervous system, trauma, diseases affecting the peripheral nervous system and diseases or trauma affecting the muscle and tendon. Many reasons have been reported such as ganglion cyst in the proximal tibiofibular joint [3], motor cortex contusion [4], long-term lead intoxication [5], tight application of compression bandage [6,7], after lateral decubitus position [8] following dislocation reduction after total hip arthroplasty and gluteal haematoma [9,10], a complication of disc surgery [11], peripheral nerve entrapment [12,13], poorly administered injections (14], sciatic nerve pressure, piriformis syndrome [15], knee dislocations [16], following spinal and spinoepidural anaesthesia [17], paraspinal abscess [18], myopathies [19], neuropathic demyelinisation, hereditary neuropathies [20], popliteal artery aneurism [21], stroke [22,23], neuromuscular diseases [24,25], degenerative lumbar spinal diseases [26], gluteal compartment syndrome [27], decompression in burns [28], parasitic diseases such as neuro schistomiasis [29], after lower extremity compartment syndrome [30], and after total knee prosthesis [31].…”