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

OBJECT 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. METHODS 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. RESULTS 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 < 0.001) and Group 2 relative to Group 3 (1.24 vs 0.13, p < 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 < 0.001; 1.39 vs 1.09 for Group 2, p < 0.05). The clinical injury score had a significantly strong correlation with the MRI injury score for the CPN (r = 0.75, p < 0.001), but not for the tibial nerve (r = 0.07, p = 0.83). CONCLUSIONS 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.

Peroneal nerve decompression: institutional review and meta-analysis to identify prognostic associations with favorable and unfavorable surgical outcomes.

OBJECTIVEA common cause of peroneal neuropathy is compression near the fibular head. Studies demonstrate excellent outcomes after decompression but include few cases (range 15-60 patients). Consequently, attempts to define predictors of good outcomes are limited. Here, the authors combine their institutional outcomes with those in the literature to identify predictors of good outcomes after peroneal nerve decompression.METHODSThe authors searched their institutional electronic medical records to identify all peroneal nerve decompressions performed in the period between December 1, 2012, and September 30, 2016, and created an IRB-approved database. They also conducted a MEDLINE and literature search to identify articles discussing surgical decompression. All data were combined by meta-analysis to identify the factors associated with a favorable outcome, which was defined as improvement in preoperative symptoms. Patients were analyzed in the aggregate and by presentation (pain, paresthesias, weakness, foot drop). The factors evaluated included age, sex, body mass index, diabetes, smoking status, previous knee or lumbar spine surgery, preoperative symptom duration, and etiology. A meta-analysis was completed for any factor evaluated in at least three data sets.RESULTSTwenty-one institutional cases had sufficient data for review. The follow-up among this group was long: median 29 months, range 12-52 months. On aggregate analysis of the data, only diabetes was significantly associated with unfavorable outcomes after decompression (p = 0.05). A trend toward worse outcomes was seen in smokers presenting with pain (p = 0.06). Outcomes were not affected by presentation.An additional 115 cases in the literature had extractable data for meta-analysis, and other associations were seen. Preoperative symptom duration longer than 12 months was associated with unfavorable outcomes (OR 0.23, 95% CI 0.08-0.65). Patients presenting with paresthesias or hypesthesia demonstrated a trend toward more unfavorable outcomes when operated on more than 6 months after symptom onset (OR 0.37, 95% CI 0.13-1.06). Even after the meta-analysis, outcomes did not vary with an advanced age (OR 0.70, 95% CI 0.24-1.98) or with patient sex (OR 1.13, 95% CI 0.42-3.06).CONCLUSIONSThe authors provide their institutional data in combination with published data regarding outcomes after peroneal nerve decompression. Outcomes are typically favorable and generally unaffected by the type of symptoms preoperatively, especially if the patient is nondiabetic and preoperative symptom duration is less than 12 months. Patients with paresthesias may benefit from surgery within 6 months after onset. Smoking may adversely affect surgical outcomes. Finally, an advanced age does not adversely affect outcomes, and older patients should be considered for surgery.

Clinical outcome after decompression of intraneural peroneal ganglion cyst and its morphologic correlation to postoperative nerve ultrasound.

OBJECTIVE: Intraneural ganglion cysts are rare and benign mucinous lesions that affect peripheral nerves, most frequently the common peroneal nerve (CPN). The precise pathophysiological mechanisms of intraneural ganglion cyst development remain unclear. A well-established theory suggests the spread of mucinous fluid along the articular branch of the peroneal nerve as the underlying mechanism. Clinical outcome following decompression of intraneural ganglion cysts has been demonstrated to be excellent. The aim of this study was to evaluate the correlation between clinical outcome and ultrasound-detected morphological nerve features following decompression of intraneural ganglion cysts of the CPN. METHODS: Data were retrospectively analyzed from 20 patients who underwent common peroneal nerve ganglion cyst decompression surgery at the Universität Ulm/Günzburg Neurosurgery Department between October 2003 and October 2017. Postoperative clinical outcome was evaluated by assessment of the muscular strength of the anterior tibial muscle, the extensor hallucis longus muscle, and the peroneus muscle according to the Medical Research Council grading system. Hypesthesia was measured by sensation testing. In all patients, postoperative morphological assessment of the peroneal nerve was conducted between October 2016 and October 2017 using the iU22 Philips Medical ultrasound system at the last routine follow-up appointment. Finally, the correlations between morphological changes in nerve ultrasound and postoperative clinical outcomes were evaluated. RESULTS: During the postoperative ultrasound scan an intraneural hypoechogenic ring structure located at the medial side of the peroneal nerve was detected in 15 (75%) of 20 patients, 14 of whom demonstrated an improvement in motor function. A regular intraneural fasicular structure was identified in 3 patients (15%), who also reported recovery. In 1 patient, a recurrent cyst was detected, and 1 patient showed intraneural fibrosis for which recovery did not occur in the year following the procedure. Two patients (10%) developed neuropathic pain that could not be explained by nerve ultrasound findings. CONCLUSIONS: The results of this study demonstrate significant recovery from preoperative weakness after decompression of intraneural ganglion cysts of the CPN. A favorable clinical outcome was highly correlated with an intraneural hypoechogenic ring-shaped structure on the medial side of the CPN identified during a follow-up postoperative ultrasound scan. These study results indicate the potential benefit of ultrasound scanning as a prognostic tool following decompression procedures for intraneural ganglion cysts of the CPN.

Choosing the target wisely: partial tibial nerve transfer to extensor digitorum motor branches with simultaneous posterior tibial tendon transfer. Could this be a way to improve functional outcome and gait biomechanics?

OBJECTIVE: The objective of this study was clinical assessment of the reduction of pathological motor phenomena with the recovery of long toe extensors, and evaluation of functional outcome with simultaneous nerve and tendon transfer in cases of common peroneal nerve (CPN) injuries. METHODS: Seven male patients (mean age 26.4 years) received a partial tibial nerve transfer to the extensor hallucis longus muscle (MEHL) and extensor digitorum longus muscle (MEDL) motor branches, after a mean of 2.7 months following a traction-type injury to the CPN. Tibialis posterior muscle (MTP) tendon transfer through the interosseous route was performed on the same day. The follow-up period included a clinical neurological examination, a modified Stanmore System questionnaire (MSSQ), electromyographic examination of the interference pattern, and a video-based analysis of the gait biomechanics in the 3rd and 12th months. Video analysis of the gait investigated the presence or reduction of "stair-climbing maneuver" (SCM), foot slap (FS), and foot stability during the gait cycle. RESULTS: The average range of active dorsiflexion in the 3rd month was 0.85°. SCM accompanied walking in 6 patients (86%). FS accompanied walking in 3 patients (43%) and 3 patients (43%) avoided FS by planting the entire foot on the ground. All patients required orthopedic support (shoe inserts) to compensate for mediolateral foot instability. The average MSSQ score was 80.4 points. The average duration for the effective recovery of function (≥ 4 points on the Medical Research Council grading system) of long toe extensors was 11.2 months. The average range of active dorsiflexion in the 12th month increased to 4.4°. A reduction of FS was observed in 5 patients (71%). Excessive foot eversion was reduced in 4 patients (57%). Another 3 patients (43%) required no specific orthopedic shoe inserts. Reduction of pathological motor phenomena with recovery of the long toe extensors resulted in an increase of functional outcome. The average MSSQ score after 12 months was 92.4 points. CONCLUSIONS: Partial tibial nerve transfer to the motor branches of the extensor hallucis longus and the long toe extensors along with the simultaneous tibialis posterior tendon transfer produce the reduction of FS and bring mediolateral stability to the foot, i.e., improved gait biomechanics. The reduction of pathological motor phenomena at the time of recovery of the long toe extensors is reflected in an increase in patients' functional perception of the injured lower extremity during daily walking.