Summary Isolated ulnar shaft fractures are rare fractures of the forearm caused by either direct blow to the forearm ("nightstick" fracture) or indirect trauma (fall). Diagnosis can be made primarily by physical exam and plain radiographs. Minimally displaced (< 50% displacement and < 10° of angulation) are often treated nonsurgically, while treatment has historically been surgical open reduction and internal fixation with compression plating for displaced fractures. Epidemiology Incidence rare < 1% of upper extremity fractures Demographics highest incidence in men between age 10 and 20 women over age of 60 Etiology Pathophysiology mechanism of injury direct trauma direct blow to forearm ("nightstick" fracture) indirect trauma motor vehicle accidents falls from height axial load applied to the forearm through the hand Associated conditions bisphosphonate-related seen as isolated, transverse proximal one-third ulnar fractures appear similar to the more commonly known atypical subtrochanteric fracture transverse, minimal/no comminution, posterior cortical thickening elbow and DRUJ injuries Monteggia fractures Essex-Lopresti injuries compartment syndrome evaluate compartment pressures if concern for compartment syndrome Anatomy Osteology axis of rotation of forearm runs through radial head (proximal) and ulna fovea (distal) distal radius effectively rotates around the distal ulna in prono-supination the ulna and radius form a functional unit; mal-angulation of ulna fractures can lead to limitation of forearm rotation Ligaments Interosseous membrane (IOM) occupies the space between the radius and ulna permits rotation of the radius around the ulna comprised of 5 ligaments central band is key portion of IOM to be reconstructed accessory band distal oblique bundle proximal oblique cord dorsal oblique accessory cord Classification Descriptive closed versus open location comminuted, segmental, multi-fragmented displacement angulation rotational alignment OTA Classification OTA classification Type A Simple fracture Spiral (A1) Oblique (A2) Transverse (A3) Type B Wedge fracture Intact (B2) Fragmentary (B3) Type C Multifragmentary fracture Intact segmental (C2) Fragmentary (C3) Presentation Symptoms pain and swelling loss of forearm and hand function Physical exam inspection gross deformity open injuries check for tense forearm compartments neurovascular exam assess radial and ulnar pulses document median, radial, and ulnar nerve function provocative tests pain with passive stretch of fingers alert to impending or present compartment syndrome Imaging Radiographs recommended views AP and lateral views of the forearm additional views oblique forearm views for further fracture definition ipsilateral AP and lateral of the wrist and elbow to evaluate for associated fractures or dislocation radial head must be aligned with the capitulum on all views Treatment Nonoperative cast or brace immobilization, soft compression dressing indications isolated nondisplaced or distal 2/3 ulna shaft fx (nightstick fx) with < 50% displacement and < 10° of angulation modality bracing functional fracture brace casting Muenster cast with good interosseous mold soft compression dressings allowing immediate mobilization outcomes union rates > 92% if above criteria met similar union and functional outcomes with casting and bracing/soft compression dressings Operative external fixation indications severe soft tissue injury (Gustilo IIIB) ORIF indications displaced distal 2/3 isolated ulna fractures proximal 1/3 isolated ulna fractures Gustilo I, II, and IIIa open fractures may be treated with primary ORIF outcomes goal is for cortical opposition, compression, and restoration of forearm anatomy ORIF with bone grafting indications open fractures with significant bone loss (bone grafting often performed in a delayed fashion) nonunions outcomes use of autograft is critical to achieve fracture union technique cancellous autograft indications ulnar fractures with significant bone loss vascularized fibula grafts indications can be used for large defects and have a lower rate of infection Masquelet technique indications utilized in cases of non-union or open fractures with significant bone loss IM nailing indications poor soft-tissue integrity outcomes recent studies have shown similar union rates compared to ORIF for isolated ulnar shaft fractures Techniques Cast or brace immobilization, soft compression dressing technique cast/brace may extend just above elbow to control forearm rotation, however, randomized studies have shown no difference in outcomes between above elbow and below elbow immobilization monitor very closely (~1 week) for displacement should be worn for at least 6 weeks Some authors have advocated for immediate mobilization as tolerated External fixation technique 2nd and 3rd metacarpal shaft can both be utilized for distal pin placement pin diameter should not exceed 4 mm ORIF approach subcutaneous approach to ulna shaft technique 3.5 mm DCP plate (AO technique) is standard 4.5 plates no longer used due to increased rate of re-fracture following removal compression mode preferred when the fracture allows to achieve anatomic primary bony healing to minimize strain, six cortices proximal and distal to fracture should be engaged locked plates are increasingly indicated over conventional plates in osteoporotic bone bridge plating may be used in extensively comminuted fractures interfragmentary lag screws (2.0 or 2.7 screws) if necessary open fractures irrigation and debridement should be performed to remove any contaminated tissue or bony fragments without soft tissue attachments postoperative care early ROM unless there is an injury to proximal or distal joint should be managed with a period of non-weight bearing due to risk of secondary displacement of the fracture generally 6 weeks ORIF with bone grafting technique bone graft options cancellous autograft iliac crest, proxmial tibia, reamer-irrigator-aspirator (RIA) vascularized fibula grafts Masquelet technique ("induced-membrane" technique) can also be utilized in cases of non-union or open fractures with significant bone loss 2 stage technique 1st stage: I&D, cement spacer and temporizing fixation 2nd stage: placement of bone graft into "induced membrane" and definitive fixation Studies show optimal time frame for bone grafting to be 4-6 weeks after placement of cement spacer IM nailing approach inserted through the posterior olecranon technique may use a small incision at fracture site to facilitate passing of nail Complications Infection incidence 3% incidence with ORIF risk factors open fractures Compartment syndrome incidence up to 15% depending on mechanism and fracture characteristics risk factors high energy crush injury open fractures low velocity GSWs vascular injuries coagulopathies (DIC) Nonunion incidence < 5% after compression plating up to 12% in extensively comminuted fractures treated with bridge plating risk factors extensive comminution poorly applied plate fixation treatment atrophic nonunions can be treated with 3.5 mm plates and autogenous cancellous bone grafting Infection and atrophic nonunions can also be treated with the Masquelet technique Hypertrophic nonunions treated with debridement and compression plating Malunion risk factors direct correlation between restoration of radial bow and functional outcome Neurovascular injury risk factors PIN injury with Monteggia fxs Type III open fxs treatment observe for three months to see if nerve function returns explore if no return of function after 3 months Refracture incidence up to 10% with early hardware removal risk factors removing plate too early plates should not be removed < 1 year from implantation large plates (4.5 mm) comminuted fractures persistent radiographic lucency treatment wear functional forearm brace for 6 weeks and protect activity for 3 months after plate removal Prognosis For minimally displaced and angulated fractures (< 50% displacement and < 10° of angulation), nonoperative management has equivalent clinical outcomes to surgical treatment.