Ulnar Neuropathy Following Distal Humerus Fracture Fixation




Ulnar nerve dysfunction is a well-recognized phenomenon following distal humerus fractures. Its fixed anatomic position predisposes the nerve to injury. Injury can occur at the time of injury, during closed-fracture manipulation, intraoperatively during fracture fixation (when it is routinely identified), or during fracture healing. Intraoperative management varies widely and can include in situ decompression or anterior transposition. This article reviews the literature and presents 24 patient cases. A 38% incidence of late ulnar neuropathy following open reduction and internal fixation is identified. There is no statistical difference between an in situ release and all anterior transpositions, except for submuscular.








  • Ulnar nerve injury can occur at the time of injury, during closed fracture manipulation, intraoperatively during fracture fixation, or during fracture healing.



  • The authors recommend vigilance in ulnar nerve management during fixation of distal humerus fractures and routine disclosure to patients preoperatively concerning the high potential for postoperative ulnar neuropathy.



  • Based on the best available evidence, the authors cannot recommend in situ release versus anterior transposition of the ulnar nerve intraoperatively. However, an anterior transposition in a subcutaneous fashion is recommended if increased tension on the ulnar nerve and/or direct hardware contact is noted intraoperatively following fracture fixation.



Key Points


Introduction


Ulnar nerve dysfunction following distal humerus fractures is a well-recognized phenomenon. Its fixed anatomic position behind the medial epicondyle of the distal humerus predisposes the nerve to potential injury. Ulnar nerve injury can occur at the time of injury, during closed fracture manipulation, intraoperatively during open reduction internal fixation (ORIF), or during fracture healing and recovery. During ORIF of distal humerus fractures, the ulnar nerve is routinely identified; however, intraoperative management varies widely. Some surgeons only perform in situ decompression, others prefer routine transposition in all cases, whereas others transpose the nerve only for specific indications related to preoperative nerve deficits, implant position, or to facilitate intraoperative nerve manipulation. To better understand ulnar nerve dysfunction following operative management of distal humerus fractures, the authors evaluated the ulnar nerve function of patients treated with ORIF of distal humerus fractures over a 5-year period. We hypothesized that the (1) incidence of late ulnar nerve dysfunction following ORIF is higher than previously reported in the literature and (2) that the type of intraoperative nerve management does not significantly affect ulnar nerve dysfunction.




Patients and methods


After appropriate institutional review board approval was obtained, a retrospective chart review was performed of all patients aged 18 years and older that underwent ORIF for a distal humerus fracture, between 2004 and 2008 at a level I urban academic medical center. Patients were excluded if they had a preinjury history of ulnar nerve dysfunction. The minimum postoperative follow-up period was 6 months. A total of 24 patients were identified. Medical records and radiographs were reviewed in each case. Mechanism of injury, time to surgery, intraoperative fracture management, implants, intraoperative ulnar nerve management, perioperative ulnar nerve function, and late postoperative ulnar nerve function determined by McGowan stages were recorded. Fractures were classified in accordance with the AO (Arbeitsgemeinschaft für Osteosynthesefragen) classification system and the Gustilo and Anderson classification system for open fractures. The patient’s associated musculoskeletal injuries were also noted. Preoperative neurovascular examination of the affected upper extremity was documented in all cases except in three cases in which the patient was uncooperative or unresponsive.


Surgical approaches were divided into two types: either with or without olecranon osteotomy. During surgery, the ulnar nerve was routinely identified and protected in all cases. Ulnar nerve management was divided into three types: (1) in situ release, (2) subcutaneous anterior transposition, and (3) submuscular anterior transposition. Postoperatively, patients were treated with a posterior splint for approximately 2 weeks or less, followed by progressive range of motion. The classification for symptom occurrence was based on the time frames suggested by Shin and Ring and included preoperative (injury induced), postoperative (within 2 weeks of operation), and subacute (occurrence after an asymptomatic 2 weeks of follow-up).


At final follow-up, McGowan staging was performed to assess severity of ulnar nerve dysfunction. Grade I was defined as minimal lesions with no detectable motor weakness of the ulnar intrinsics and paresthesia in the ulnar nerve distribution with only slight blunting of sensation. Grade II was defined as intermediate lesions with weak interossei and muscle wasting as well as blunting of sensibility. Grade III was defined as a severe lesion with interossei paralysis and the marked hypoesthesia. This classification system is based on ulnar neuritis occurring after all causes with significant time for muscle atrophy. During follow-up of our patients, late complications and secondary procedures were also recorded.




Patients and methods


After appropriate institutional review board approval was obtained, a retrospective chart review was performed of all patients aged 18 years and older that underwent ORIF for a distal humerus fracture, between 2004 and 2008 at a level I urban academic medical center. Patients were excluded if they had a preinjury history of ulnar nerve dysfunction. The minimum postoperative follow-up period was 6 months. A total of 24 patients were identified. Medical records and radiographs were reviewed in each case. Mechanism of injury, time to surgery, intraoperative fracture management, implants, intraoperative ulnar nerve management, perioperative ulnar nerve function, and late postoperative ulnar nerve function determined by McGowan stages were recorded. Fractures were classified in accordance with the AO (Arbeitsgemeinschaft für Osteosynthesefragen) classification system and the Gustilo and Anderson classification system for open fractures. The patient’s associated musculoskeletal injuries were also noted. Preoperative neurovascular examination of the affected upper extremity was documented in all cases except in three cases in which the patient was uncooperative or unresponsive.


Surgical approaches were divided into two types: either with or without olecranon osteotomy. During surgery, the ulnar nerve was routinely identified and protected in all cases. Ulnar nerve management was divided into three types: (1) in situ release, (2) subcutaneous anterior transposition, and (3) submuscular anterior transposition. Postoperatively, patients were treated with a posterior splint for approximately 2 weeks or less, followed by progressive range of motion. The classification for symptom occurrence was based on the time frames suggested by Shin and Ring and included preoperative (injury induced), postoperative (within 2 weeks of operation), and subacute (occurrence after an asymptomatic 2 weeks of follow-up).


At final follow-up, McGowan staging was performed to assess severity of ulnar nerve dysfunction. Grade I was defined as minimal lesions with no detectable motor weakness of the ulnar intrinsics and paresthesia in the ulnar nerve distribution with only slight blunting of sensation. Grade II was defined as intermediate lesions with weak interossei and muscle wasting as well as blunting of sensibility. Grade III was defined as a severe lesion with interossei paralysis and the marked hypoesthesia. This classification system is based on ulnar neuritis occurring after all causes with significant time for muscle atrophy. During follow-up of our patients, late complications and secondary procedures were also recorded.




Results


A total of 31 patients had distal humerus fractures during the specified study period. However, 24 patients met the inclusion criteria. There were 9 women and 15 men. The average age was 46 (range 21–78). The average follow-up period was 13 months (range 6–26). The fractures were classified as seven AO type A (two A2 and five A3), two AO type B (all B1), and 15 AO type C (five C1, seven C2, and three C3). All patients underwent ORIF with plates and screws through a triceps-sparing approach, with 42% also requiring an olecranon osteotomy. The mechanisms of injury included: fall on the outstretched arm (12, including four open-fracture cases), motor vehicle accidents (three total, including one open-fracture case), and gunshot fractures (eight total). A total of 20% (five out of 24) of the patients had preoperative neuropathy, with 12% (three out of 24) involving the radial nerve and only 8% (two out of 24) with ulnar neuropathies.


Intraoperative ulnar nerve management included 50% in situ release and 50% anterior transposition (one submuscular and 11 subcutaneous). At final follow-up, 38% (nine) patients had a persistent ulnar neuropathy. McGowan stages included 56% stage 1 and 44% stage 2. There were no cases of McGowan stage 3. Only two patients complained of preoperative ulnar paresthesias and both went on to have persistent ulnar neuropathy at final follow-up (one type 1 and one type 2). No patients with AO type B fractures developed late neuropathy, whereas three AO type A (all A3) and six AO type C (three C1, two C2, and one C1) did develop late neuropathy. Among the patients with persistent ulnar neuropathy at final follow-up, 44% (four) had undergone an in situ release and 56% (five) had undergone an anterior transposition. This difference was not statistically significant ( P >.05). Among the patients with persistent ulnar neuropathy at final follow-up, 44% (four) had undergone ORIF without and 56% (five) had undergone ORIF with olecranon osteotomy. This was not statistically different ( P >.05). In terms of implant, all fractures were treated with dual-column locking plates (one direct medial plate and one posterolateral plate) except for three cases treated with a single posterolateral locking plate. Late ulnar neuropathy was identified in 38% of dual-column plated fractures versus 33% of posterolateral-plated fractures. This was not statistically different ( P >.05).


Among the McGowan stage 1 patients, 40% had an olecranon osteotomy and 40% were AO type A versus 60% were AO type C fractures. Among the McGowan stage 2 patients, 75% had an olecranon osteotomy and 25% were AO type A versus 75% were AO type C. All four McGowan stage 2 and one McGowan stage 1 patient ultimately required a second surgery involving removal of hardware and ulnar nerve neurolysis. All five patients had the second procedure performed at least 6 months after the index surgery. Among the cases without late ulnar neuropathy 20% (three out of 15) also underwent removal of hardware and joint release for painful hardware and/or elbow stiffness.


Discussion


We identified a 38% incidence of late ulnar neuropathy following ORIF of a distal humerus fracture, supporting our first hypothesis. This was most common in AO type C, followed by AO type A injuries. There were no cases of AO type B injuries resulting in late ulnar nerve dysfunction. The presence of a preoperative history of ulnar nerve paresthesias led to a 100% incidence of late symptoms. In no case was there a McGowan stage 3 finding, but 56% were type 1 and 44% were type 2. All type 2 injuries ultimately required a second surgery to address ulnar nerve function. There was no statistical significance difference as to the development of late ulnar neuropathy and the surgical exposure, but there was a trend toward olecranon osteotomy. Supporting our second hypothesis, there was no statistical significance difference in general between the use of an in situ release versus transpositions and the development of late ulnar neuropathy, except for the single case using a submuscular transposition that ultimately led to late symptoms.


Ulnar Neuropathy Incidence


Nerve injuries, especially involving the ulnar nerve, are considered to be more often associated with severe fracture patterns. High-energy fractures dissipate their forces through the soft tissue and can also result in greater bone displacement. This can result in both direct and indirect nerve injury at the time of fracture. The incidence of ulnar neuropathy following distal humerus fracture fixation is variable. Occurrence presenting in the immediate postoperative period ranges from the low values of 0% to 6.6% to higher values of 10.1% to 21%. Most of these reported postoperative neuropathies resolve with late ulnar neuropathy incidences ranging only from 0% to 3.3% but they have been documented at higher ranges of 11.7% to 16%.


Helfet and Schmeling retrospectively reviewed their experience with bicondylar intraarticular distal humerus fractures and identified, among other complications, a 7% incidence of late ulnar neuropathy but it was unclear from their series whether these were early or late neuropathies. More recently, Vazquez and colleagues retrospectively examined 69 distal humerus fractures (both AO type A and C) without preoperative ulnar nerve symptoms to determine the incidence of late ulnar nerve dysfunction at a minimum of 12-months postoperatively. They identified an incidence of 10.1% immediately postoperatively and 16% at final follow-up. Also, using McGowan staging, they identified that 57% were grade I and 43% were grade II and, similar to our series, no development of grade III stages. They also did not identify any specific risk factors for the development of late ulnar neuropathy. Moreover, Ruan and colleagues retrospectively examined 117 consecutive AO type C distal humerus fractures at two centers to evaluate late ulnar nerve dysfunction and found that no patients without preoperative ulnar nerve symptoms developed late symptoms, whereas, among the 29 patients with preoperative ulnar nerve symptoms, there were 31% that continued to demonstrate late ulnar nerve symptoms.


Ulnar Nerve Management


There are inherent advantages and disadvantages to either releasing the ulnar nerve in situ or transposing it. In situ release affords surgical simplicity, decreased nerve handling, avoiding devascularization of the nerve, and iatrogenic traction injury. However, it maintains the nerve in close proximity to hardware in the cubital tunnel and tensioned around the medial epicondyle, in which case the native anatomy may also be altered. Transposition avoids contact of the nerve from fracture inflammation, callous formation, periarticular fibrosis, and soft tissue edema, as well as decreasing its tension along its path. However, transposition requires increased nerve handling, potential devascularization, traction injury, and late compressive neuropathy from inadequate decompression of soft tissue restraints.


Numerous recommendations have been made regarding when to transpose the ulnar nerve in distal humerus fracture management. An article reviewing distal humerus fractures from 1985 to 2003 advised transposition in those fractures with preoperative ulnar nerve symptoms, or when internal fixation requires extension over the medial epicondyle. One investigator used indications of preoperative palsy, possible implant irritation, or intraoperative traction. There continues to be no clear consensus as to when an ulnar nerve is transposed during surgery. The investigators’ terminology in their decisions to transpose include “if hardware came to lie in the ulnar groove,” “if during elbow flexion, ulnar nerve was noted to impinge on hardware,” or “the ulnar nerve was mobilized if necessary to prevent iatrogenic damage.” Some investigators prefer to routinely transpose the ulnar nerve in all intrarticular distal humerus fractures, whereas some investigators transpose without citing particular reasoning and, in some cases, the investigators make no mention of their ulnar nerve management.


The controversy is apparent when comparing studies analyzing similar fractures. The surgeons involved in the type C distal humerus fracture study by Athwal and colleagues preferred to routinely anteriorly transpose the ulnar nerve in all cases with subcutaneous placement in 98%. Six patients (19%) had preoperative ulnar nerve injuries. Similar to our transposition results, five patients (16%) had postoperative neuropathies (four ulnar and one radial sensory). The symptoms of three out of these five patients resolved at a mean of 4.5 months. The study did not specifically comment on the outcome of the preoperative neuropathic patients but did question whether the routine anterior transposition contributed to the increased incidence of postoperative ulnar neuropathy. However, another study by Luegmair and colleagues with all type C fractures only transposed the nerve in two patients (12%). They reported only one (6%) of their 17 patients with preoperative ulnar symptoms and two (12%) postoperative ulnar neuropathies in patients without nerve transposition. Of note, the percentages of postoperative neuropathies is similar without transposition as reported by Luegmair and colleagues and with transposition, in both the results of our study and Athwal and colleagues’ study. Results, or without transposition as reported by Luegmair and colleagues.


Other studies seem to favor anterior transposition of the ulnar nerve for both prevention and treatment of neuropathy. Gofton and colleagues conducted another study analyzing type C fractures by assessed sensorimotor ulnar nerve outcomes with the 28-item Patient-Rated Ulnar Nerve Evaluation. Preoperatively, six patients (26%) had ulnar neuropathy. The investigators did not define the time frame for resolution but reported four of six patients’ neuropathies resolving quickly. The other two preoperative neuropathies were categorized as subjective complaints after not finding any functional or objective deficits. Only one patient (4.3%) developed neuropathy after surgery, which could be classified as subacute or postoperative depending on the specific time-frame of symptom presentation. The investigators credit the low rate of objective ulnar neuropathy to routine transposition. Kinik and colleagues also routinely transposed the ulnar nerve in their patients and had similar postoperative results. Three patients (6.5%) had ulnar neurapraxia caused initially by the fracture, whereas only two patients (4.3%) developed postoperative neuropathy. After transposition, the preoperative symptoms resolved and one of the two postoperative neuropathies improved during follow-up. One study by Wang and colleagues, who performed anterior transposition during fixation of type C fractures, found none of their 20 patients developed postoperative or delayed ulnar neuropathies after adequate follow-up. Their results could be credited to small study group or other variables. No mention was made concerning the incidence of any preoperative symptoms.


In contrast, Robinson and colleagues did not primarily transpose the ulnar nerve during treatment of distal humerus fractures—even with preoperative symptoms. Eight of their 320 patients (2.5%) had preoperative ulnar symptoms. One went on to have symptoms 3-months postinjury and treatment. Postoperatively, six patients (1.9%) developed ulnar neurapraxia and the investigators associated the palsy with surgical treatment of type C fractures. All but two palsies recovered postoperatively over 6 to 10 weeks. An additional study, in which transposition was not routinely performed in all but two patients, also found good ulnar nerve recovery. Although it is not known which patients received the primary transpositions, it can be assumed that only the two postoperative neuropathic (11.7%) patients were not primarily transposed because they underwent additional ulnar nerve surgeries to treat their symptoms. Therefore, both studies had a small percentage of patients develop postoperative neuropathy without transposing the nerve.


In other studies, some investigators transposed the ulnar nerve based on simple criteria and produced favorable results. Two age-demographic studies of distal humerus fractures by Huang and colleagues transposed the nerve with indications of preoperative palsy, possible implant irritation, and/or intraoperative traction of the nerve. In their study of elderly patients, they transposed the nerve based on their indications in 4.5%, 22.7%, and 4.5% of the patients. In their larger study of all adult ages, they transposed the nerve in 5.0%, 12.5%, and 7.5% of patients based on their indications. Overall, only one patient (5.3%) from their study of elderly patients and two patients (5%) from their study of adult patients developed a postoperative neuropathy. Ultimately, all patients with neuropathies resolved within 3 months. A group of surgeons in one study mobilized the ulnar nerve, if necessary, to prevent iatrogenic damage, although they did not give specific criteria. Their rate of postoperative ulnar neurapraxia was 17%; however, all patients had resolved during follow-up.


The ulnar nerve can also be managed with in situ decompression. In a study by Russell and colleagues, the surgeon initially performed what was described as an in-situ release of the ulnar nerve and would transpose the nerve only if during elbow flexion the nerve impinged on the hardware or subluxed. A total of seven patients (29%) had transpositions. Only one patient with transposition developed postoperative ulnar neuropathy, but symptoms resolved within 3 months. However, three patients (12.5%) without transposition postoperatively developed what the investigators called ulnar neuritis and attributed the results to the plating around the medial epicondyle.


A recent study by Ruan and colleagues compared in situ decompression versus anterior subfascial (intramuscular) transposition of the ulnar nerve. The investigators chose a subfascial location because of its vascular bed as well as its decreased vulnerability to irritation and scarring when compared with submuscular alternatives. The 29 patients with preoperative ulnar symptoms (24.8%) were randomized to receive either ulnar nerve procedure. The Bishop rating system was used to classify ulnar nerve function. In the transposition group, 80% of the patients recovered completely, whereas the remaining 20% recovered partially. The in situ group had 57% of patients with complete recovery and 43% with only partial recovery. Furthermore, their rating system determined excellent and good results in 86.7% of the transposition group versus 57.1% of the in situ group. The results of this study advocate subfascial transposition over in situ release. Interestingly, the subfascial transposition was also performed on patients without preoperative symptoms and found no incidence of postoperative or delayed ulnar neuropathy.

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Oct 6, 2017 | Posted by in ORTHOPEDIC | Comments Off on Ulnar Neuropathy Following Distal Humerus Fracture Fixation
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