Simultaneous induction of vasculature and neuronal network formation on a chip reveals a dynamic interrelationship between cell types.

BACKGROUND: Neuronal networks receive and deliver information to regulate bodily functions while the vascular network provides oxygen, nutrients, and signaling molecules to tissues. Neurovascular interactions are vital for both tissue development and maintaining homeostasis in adulthood; these two network systems align and reciprocally communicate with one another. Although communication between network systems has been acknowledged, the lack of relevant in vitro models has hindered research at the mechanistic level. For example, the current used in vitro neurovascular models are typically established to be short-term (≤ 7 days) culture models, and they miss the supporting vascular mural cells. METHODS: In this study, we utilized human induced pluripotent stem cell (hiPSC) -derived neurons, fluorescence tagged human umbilical vein endothelial cells (HUVECs), and either human bone marrow or adipose stem/stromal cells (BMSCs or ASCs) as the mural cell types to create a novel 3D neurovascular network-on-a-chip model. Collagen 1-fibrin matrix was used to establish long-term (≥ 14 days) 3D cell culture in a perfusable microphysiological environment. RESULTS: Aprotinin-supplemented endothelial cell growth medium-2 (EGM-2) supported the simultaneous formation of neuronal networks, vascular structures, mural cell differentiation, and the stability of the 3D matrix. The formed neuronal and vascular networks were morphologically and functionally characterized. Neuronal networks supported vasculature formation based on direct cell contacts and by dramatically increasing the secretion of angiogenesis-related factors in multicultures in contrast to cocultures without neurons. Both utilized mural cell types supported the formation of neurovascular networks; however, the BMSCs seemed to boost neurovascular networks to greater extent. CONCLUSIONS: Overall, our study provides a novel human neurovascular network model that is applicable for creating in vivo-like tissue models with intrinsic neurovascular interactions. The 3D neurovascular network model on chip forms an initial platform for the development of vascularized and innervated organ-on-chip and further body-on-chip concepts and offers the possibility for mechanistic studies on neurovascular communication both under healthy and in disease conditions. Video Abstract.

Heat Shock Protein 27 Is Involved in the Bioactive Glass Induced Osteogenic Response of Human Mesenchymal Stem Cells.

Bioactive glass (BaG) materials are increasingly used in clinics, but their regulatory mechanisms on osteogenic differentiation remain understudied. In this study, we elucidated the currently unknown role of the p38 MAPK downstream target heat shock protein 27 (HSP27), in the osteogenic commitment of human mesenchymal stem cells (hMSCs), derived from adipose tissue (hASCs) and bone marrow (hBMSCs). Osteogenesis was induced with ionic extract of an experimental BaG in osteogenic medium (OM). Our results showed that BaG OM induced fast osteogenesis of hASCs and hBMSCs, demonstrated by enhanced alkaline phosphatase (ALP) activity, production of extracellular matrix protein collagen type I, and matrix mineralization. BaG OM stimulated early and transient activation of p38/HSP27 signaling by phosphorylation in hMSCs. Inhibition of HSP27 phosphorylation with SB202190 reduced the ALP activity, mineralization, and collagen type I production induced by BaG OM. Furthermore, the reduced pHSP27 protein by SB202190 corresponded to a reduced F-actin intensity of hMSCs. The phosphorylation of HSP27 allowed its co-localization with the cytoskeleton. In terminally differentiated cells, however, pHSP27 was found diffusely in the cytoplasm. This study provides the first evidence that HSP27 is involved in hMSC osteogenesis induced with the ionic dissolution products of BaG. Our results indicate that HSP27 phosphorylation plays a role in the osteogenic commitment of hMSCs, possibly through the interaction with the cytoskeleton.

Growth Response and Differentiation of Bone Marrow-Derived Mesenchymal Stem/Stromal Cells in the Presence of Novel Multiple Myeloma Drug Melflufen.

Mesenchymal stem/stromal cells (MSCs) are self-renewing and multipotent progenitors, which constitute the main cellular compartment of the bone marrow stroma. Because MSCs have an important role in the pathogenesis of multiple myeloma, it is essential to know if novel drugs target MSCs. Melflufen is a novel anticancer peptide-drug conjugate compound for patients with relapsed refractory multiple myeloma. Here, we studied the cytotoxicity of melflufen, melphalan and doxorubicin in healthy human bone marrow-derived MSCs (BMSCs) and how these drugs affect BMSC proliferation. We established co-cultures of BMSCs with MM.1S myeloma cells to see if BMSCs increase or decrease the cytotoxicity of melflufen, melphalan, bortezomib and doxorubicin. We evaluated how the drugs affect BMSC differentiation into adipocytes and osteoblasts and the BMSC-supported formation of vascular networks. Our results showed that BMSCs were more sensitive to melflufen than to melphalan. The cytotoxicity of melflufen in myeloma cells was not affected by the co-culture with BMSCs, as was the case for melphalan, bortezomib and doxorubicin. Adipogenesis, osteogenesis and BMSC-mediated angiogenesis were all affected by melflufen. Melphalan and doxorubicin affected BMSC differentiation in similar ways. The effects on adipogenesis and osteogenesis were not solely because of effects on proliferation, seen from the differential expression of differentiation markers normalized by cell number. Overall, our results indicate that melflufen has a significant impact on BMSCs, which could possibly affect therapy outcome.

Vasculogenic Potency of Bone Marrow- and Adipose Tissue-Derived Mesenchymal Stem/Stromal Cells Results in Differing Vascular Network Phenotypes in a Microfluidic Chip.

The vasculature is an essential, physiological element in virtually all human tissues. Formation of perfusable vasculature is therefore crucial for reliable tissue modeling. Three-dimensional vascular networks can be formed through the co-culture of endothelial cells (ECs) with stromal cells embedded in hydrogel. Mesenchymal stem/stromal cells (MSCs) derived from bone marrow (BMSCs) and adipose tissue (ASCs) are an attractive choice as stromal cells due to their natural perivascular localization and ability to support formation of mature and stable microvessels in vitro. So far, BMSCs and ASCs have been compared as vasculature-supporting cells in static cultures. In this study, BMSCs and ASCs were co-cultured with endothelial cells in a fibrin hydrogel in a perfusable microfluidic chip. We demonstrated that using MSCs of different origin resulted in vascular networks with distinct phenotypes. Both types of MSCs supported formation of mature and interconnected microvascular networks-on-a-chip. However, BMSCs induced formation of fully perfusable microvasculature with larger vessel area and length whereas ASCs resulted in partially perfusable microvascular networks. Immunostainings revealed that BMSCs outperformed ASCs in pericytic characteristics. Moreover, co-culture with BMSCs resulted in significantly higher expression levels of endothelial and pericyte-specific genes, as well as genes involved in vasculature maturation. Overall, our study provides valuable knowledge on the properties of MSCs as vasculature-supporting cells and highlights the importance of choosing the application-specific stromal cell source for vascularized organotypic models.

Does the shoe-lace technique aid direct closure of fasciotomy wounds after acute compartment syndrome of the lower leg? A retrospective case-control study.

BACKGROUND AND OBJECTIVE: Tibia fractures are relatively common injuries that are accompanied with acute compartment syndrome in approximately 2% to 20% of cases. Although the shoe-lace technique, where vessel loops are threaded in a crisscross fashion and tightened daily, has been widely used, no studies have compared the shoe-lace technique with the conventional one. The aim of this study was to compare the shoe-lace technique with the conventional technique. METHODS: We identified 359 consecutive patients with intramedullary nailed tibia fracture and complete medical records including outpatient data between April 2007 and April 2015 from electronic patient database of our institute. The use of the shoe-lace technique was compared to conventional one (in which wounds were first left open with moist dressings). Main outcome measurement is direct closure of fasciotomy wounds. RESULTS: From 359 consecutive patients with intramedullary nailed tibia fracture, fasciotomy was performed on 68 (19%) patients. Of these, the shoe-lace technique was used in 47 (69%) patients while in 21 (31%) patients, the shoe-lace technique was not applied. Side-to-side approximation was successful in 36 patients (77%) in the shoe-lace+ group and 7 patients (33%) in the shoe-lace- group (p = 0.002). CONCLUSIONS: The main finding of our comparative study was that the shoe-lace technique seems to ease direct closure of lower leg fasciotomy wounds, and thus reduces the frequency of free skin grafts. Our finding needs to be confirmed in a high-quality randomized controlled trial.

Modified Harrington's procedure for periacetabular metastases in 89 cases: a reliable method for cancer patients with good functional outcome, especially with long expected survival.

Background and purpose - The pelvis is the 3rd most common site of skeletal metastases. In some cases, periacetabular lesions require palliative surgical management. We investigated functional outcome, complications, and implant and patient survival after a modified Harrington's procedure.Patients and methods - This retrospective cohort study included 89 cases of surgically treated periacetabular metastases. All patients were treated with the modified Harrington's procedure including a restoration ring. Lesions were classified according to Harrington. Functional outcome was assessed by Harris Hip Score (HHS) and Oxford Hip Score (OHS). Postoperative complications, and implant and patient survival are reported.Results - The overall postoperative functional outcome was good to fair (OHS 37 and HHS 76). Sex, age, survival > 6 and 12 months, and diagnosis of the primary tumor affected functional outcome. Overall implant survival was 96% (95% Cl 88-100) at 1 year, 2 years, and 5 years; only 1 acetabular implant required revision. Median patient survival was 8 months (0-125). 10/89 patients had postoperative complications: 6 major complications, leading to revision surgery, and 4 minor complications.Interpretation - Our modified Harrington's procedure with a restoration ring to achieve stable fixation, constrained acetabular cup to prevent dislocation, and antegrade iliac screws to prevent cranial protrusion is a reliable reconstruction for periacetabular metastases and results in a good functional outcome in patients with prolonged survival. A standardized procedure and low complication rate encourage the use of this method for all Harrington class defects.

Revision rate of reconstructions in surgically treated diaphyseal metastases of bone.

INTRODUCTION: Skeletal metastases can weaken the bone, necessitating surgery, and surgical treatment options vary. The aim of this study was to investigate the revision rate of reconstructions in surgically treated diaphyseal skeletal metastases. MATERIALS AND METHODS: Between 2000 and 2018 at Helsinki and Tampere university hospitals in Finland, a total of 164 cases with diaphyseal skeletal metastases were identified from a prospectively maintained database. Tumor location was humerus, femur, and tibia in 106 (65%), 53 (32%), and 5 (3.0%) cases, respectively. A total of 82 (50%) cases were treated with intramedullary nailing (IMN), 73 (45%) with IMN and cementation, and 9 (5%) with another technique. RESULTS: In the upper extremity, implant survival (IS) was 96.4% at 1, 2, and 5 years; in the lower extremity, it was 83.8%, 69.1%, and 57.6% at 1, 2, and 5 years, respectively. Lower extremity IS for impending lesions was 100% at 1, 2, and 5 years, and in cases operated for true pathologic fracture, it was 71.6%, 42.9%, and 21.5% at 1, 2, and 5 years, respectively. In IMN cases without cement, the complication rate was 16% (13/82) when compared to 6% (4/73) in IMN cases with cementation. DISCUSSION: We would advocate for early intervention in patients with metastatic bone disease affecting the femur rather that watchful waiting with the risk for fracture and the need for urgent intervention. However, this choice must be balanced against the underlying risk of surgical intervention in a potentially fragile population with often limited prognoses.

Total hip arthroplasty, combined with a reinforcement ring and posterior column plating for acetabular fractures in elderly patients: good outcome in 34 patients.

Background and purpose - Low-energy acetabulum fractures are uncommon, and mostly occur in elderly patients. Determining the optimal operative treatment for such fractures is challenging. Here we investigated whether acutely performed total hip arthroplasty plus posterior column plating (THA) reduced complications and reoperations compared with open reduction and internal fixation (ORIF) in elderly patients with acetabular fractures. Patients and methods - We retrospectively reviewed the records of 59 patients, > 55 years of age, with complex acetabular fractures, caused by low-energy trauma, treated between January 2008 and September 2017. Of these patients, 34 underwent acute THA, and 25 ORIF alone. Patient and implant survival were compared between groups using Kaplan-Meier survival analysis and Cox multiple regression. Functional outcomes assessed by Oxford Hip Score (OHS) were compared between the THA patients and those 9 ORIF patients who underwent secondary THA due to posttraumatic hip osteoarthritis (OA) during follow-up. Results - Overall patient survival was 90% (95% CI 82-98) at 12 months, and 64% (CI 47-81) at 5 years. Of 25 ORIF patients, 9 required secondary THA due to posttraumatic OA. Large fragments on the weight-bearing acetabular dome upon imaging predicted ORIF failure and secondary THA. The acute THA group and secondary THA group had similar 12-month OHS. Interpretation - Acute THA including a reinforcement ring resulted in fewer reoperations than ORIF alone in elderly patients with acetabular fractures. These findings support acute THA as first-line treatment for complex acetabular fractures in elderly patients.

Clinical results and quality of life after reconstruction following sacrectomy for primary bone malignancy.

BACKGROUND: Sacrectomy is a rare and demanding surgical procedure that results in major soft tissue defects and spinopelvic discontinuity. No consensus is available on the optimal reconstruction algorithm. Therefore, the present study evaluated the results of sacrectomy reconstruction and its impact on patients' quality of life (QOL). METHODS: A retrospective chart review was conducted for 21 patients who underwent sacrectomy for a primary bone tumour. Patients were divided into groups based on the timing of reconstruction as follows: no reconstruction, immediate reconstruction or delayed reconstruction. QOL was measured using the EQ-5D instrument before and after surgery in patients treated in the intensive care unit. RESULTS: The mean patient age was 57 (range 22-81) years. The most common reconstruction was gluteal muscle flap (n = 9) and gluteal fasciocutaneous flap (n = 4). Four patients required free-tissue transfer, three latissimus dorsi flaps and one vascular fibula bone transfer. No free flap losses were noted. The need for unplanned re-operations did not differ between groups (p = 0.397), and no significant differences were found for pre- and post-operative QOL or any of its dimensions. DISCUSSION: Free flap surgery is reliable for reconstructing the largest sacrectomy defects. Even in the most complex cases, surgery can be safely staged, and final reconstruction can be carried out within 1 week of resection surgery without increasing peri­operative complications. Sacrectomy does not have an immoderate effect on the measured QOL.

Tibia Adamantinoma Resection and Reconstruction with a Custom-Made Total Tibia Endoprosthesis: A Case Report with 8-Year Follow-Up.

This case study describes a total tibia resection and reconstruction with a custom-made endoprosthetic replacement (EPR) and a long-term, 8-year follow-up. The patient underwent a total tibia adamantinoma resection in 2009. Reconstruction was performed with a custom-made total tibia EPR, where both the knee joint and ankle joint were reconstructed. Two muscle flaps, latissimus dorsi free flap and a pedicled medial gastrocnemius flap, were used for soft tissue reconstruction. The patient returned to normal life as a kindergarten teacher, without complications for eight years. This case demonstrated the importance of successful multidisciplinary teamwork in close collaboration with industry. In our best knowledge, no over 2 years of follow-up of total tibia replacement reports have been published.

High blood metal ion levels in 19 of 22 patients with metal-on-metal hinge knee replacements.

Background and purpose - There has been increasing alarm regarding metal-on-metal (MoM) joint replacements leading to elevated levels of metal ions and adverse reactions to metal debris (ARMDs). There is little information available concerning the prevalence of and risk factors for these adverse reactions, except with MoM hip joint replacements. We determined the levels of metal ions in blood and the rate of revision due to ARMDs in patients treated with MoM hinge total knee arthroplasty (TKA). Patients and methods - 22 patients with TKAs and MoM hinge connecting mechanisms were studied for whole-blood chromium and cobalt levels at 6 months, 1 year, and/or ≥2 years after surgery. Possible ARMDs were investigated by MRI. 12 patients with TKAs and metal-on-polyethylene (MoP) connecting mechanisms served as controls. Results - The cobalt levels were over 5 ppb in 19 of the 22 patients in the MoM group and in 1 of the 12 patients in the MoP group. The chromium levels were over 5 ppb in 11 of the 22 patients in the MoM group and in none of the 12 patients in the MoP group. Pseudotumors were operated in 4 of the 22 patients in the MoM group and in none of the patients in the MoP group. Interpretation - Our results clearly show that the MoM hinge TKA carries a high risk of increased levels of systemic metal ions and also local ARMD, leading to complicated knee revisions. We therefore discourage the use of MoM hinge TKA.

Primary flap reconstruction of tissue defects after sarcoma surgery enables curative treatment with acceptable functional results: a 7-year review.

BACKGROUND: Sarcomas, a heterogeneous group of tumors, are challenging to treat and require multidisciplinary cooperation and planning. We analyzed the efficacy of flap reconstruction in patients with bone and soft tissue sarcoma. METHODS: Patient charts and operative records were retrospectively reviewed from January 2006 through October 2013 to identify sarcoma patient characteristics, postoperative complications, revisions, recurrences, and survival. Pedicled and/or free flap reconstruction was performed in 109 patients. Flap selection was based on defect size, and exposure of anatomically critical structures or major orthopedic implants. RESULTS: Of 109 patients, 71 (65.1 %) were men, and mean age was 56.4 years. Tumors most frequently located in a lower extremity (38.7 %). Primary sarcomas comprised 79.2 % and recurrences occurred in 18.9 %. Wide resection was performed for 65.7 %, and there were 10 planned amputations combined with flap reconstruction. A total of 111 tumors received 128 flaps: 76 pedicled flaps, 42 free flaps, and 5 combined (10 total) pedicled + free-flaps. The success rate was 94 % for the pedicled flap group, 97 % for the free-flap group, and 100 % for the pedicle + free-flap group. Of 35 patients, 5 developed deep prosthetic infections. Only one amputation due to disease progression was performed. Satisfactory functional outcome was achieved in 69 %. Survival rate during a mean (standard deviation) 3(2) year follow-up was 83.5 %. CONCLUSIONS: Primary flap reconstruction after sarcoma surgery satisfies oncologic goals. Large tumors in difficult areas can be removed and complete tumor resection achieved. Our findings indicate a high survival rate after sarcoma surgery utilizing flap reconstruction and a low recurrence rate.

An unusual case of clear cell chondrosarcoma with very late recurrence and lung metastases, 29 years after primary surgery.

Clear cell chondrosarcoma is a rare bone neoplasm with low-grade clinical course and the potential to metastasize to the skeleton and lungs. The aim of this report is to present a case that is extremely rare, but in accordance with the literature where the clear cell chondrosarcoma reportedly has a tendency for late metastases. In our patient the primary surgery was intralesional, since it was mistakenly interpreted as a benign tumour in the early 80s. The local recurrence and lung metastases occurred, however, 29 years after the initial treatment. The local recurrence was resected with wide margins, no additional surgery or oncological treatments were given, and two and half years postoperatively patient is doing well and there is no progression in the disease. In conclusion, it is important to have a long follow-up to the clear cell chondrosarcoma patients even for decades or lifelong, because the malignancy tends to metastasize or recur after an extended period. The course of metastasized disease may be unusually slow, so relatively aggressive treatment in metastasized and recurring cases is justified.

Effect of immobilization, off-loading and zoledronic acid on bone mineral density in patients with acute Charcot neuroarthropathy: a prospective randomized trial.

BACKGROUND: Bisphosphonates are commonly used as an adjuvant in the management of acute Charcot neuroarthropathy (CNA), although the clinical efficacy of the treatment is controversial. The aim of the present study is to investigate the effect of immobilization and zoledronic acid on bone mineral density (BMD) changes during the treatment of acute CNA. METHODS: Thirty-five patients with acute midfoot CNA were randomly assigned to treatment with either zolendronic acid or placebo. BMD of the lumbar spine and both hips was measured at baseline and after six months of treatment. RESULTS: Comparison between BMD at presentation and at 6 months demonstrated a significant fall in BMD in the placebo group at the CNA-affected femoral neck (-3.2%, p=0.016) and in the CNA-free hip (-1.2%, p=0.026). Conversely, a significant rise in BMD was observed in the zolendronic acid group at all measured areas of the CNA-free hip. DISCUSSION AND CONCLUSIONS: Immobilization and off-loading does not lead to marked disuse osteoporosis in patients with acute CNA after 6 months of treatment. Treatment with zoledronic acid led to a statistically significant increase in hip BMD compared to placebo.

The effect of zoledronic acid on the clinical resolution of Charcot neuroarthropathy: a pilot randomized controlled trial.

OBJECTIVE: To investigate the clinical efficacy of zoledronic acid in patients with diabetes and acute Charcot neuroarthropathy. RESEARCH DESIGN AND METHODS: Thirty-nine consecutive patients were randomly assigned to placebo or three intravenous infusions of 4 mg zoledronic acid. The primary outcome was clinical resolution of acute Charcot neuroarthropathy determined by total immobilization time (casting plus orthosis). RESULTS: At baseline, there was no significant difference between the randomly assigned groups with respect to Charcot disease activity or other baseline values. In the zoledronic acid group, the median time for total immobilization was 27 weeks (range 10-62), and in the placebo group it was 20 weeks (20-52) (P=0.02). CONCLUSIONS: Zoledronic acid had no beneficial effect on the clinical resolution of acute Charcot neuroarthropathy in terms of total immobilization time. It is possible that it may prolong the time to clinical resolution of Charcot neuroarthropathy.

Treatment of pathological humerus shaft fractures with intramedullary nails with or without cement fixation.

INTRODUCTION: Bone metastasis is a severe complication for patients with cancer. Not only does it cause intractable pain and other clinical problems such as fracture after trivial injury, it also signifies that the malignant process is incurable. Since life expectancy of metastasised cancer patients has improved due to advanced oncological treatment but is still limited, appropriate surgical intervention has increased. METHOD: This is a retrospective control study of 21 patients who underwent cemented intramedullary nailing for pathological fractures in the humeral shaft between 2005 and 2009 as compared to a historical control group of 19 patients that underwent locked intramedullary nailing for pathological fractures in the humeral shaft between 1999 and 2004. Four major outcomes were assessed, namely, pain relief, use of analgesics, recovery of function and rate of complication. RESULTS: Patients treated with cemented intramedullary nailing had better pain relief, less use of analgesics and better functional restoration immediately after surgical procedure when compared to the patients without cement fixing. The rate of complication did not differ between these two groups. CONCLUSION: Since surgery for metastases does not prolong life but improves the quality of life, the aim towards a short postoperative rehabilitation time is recommended. Cement fixation gives immediate stabilisation to the fracture site and thus allows less pain but full range of motion from the first postoperative day.

Long-term outcome and quality of life in patients with Charcot foot.

BACKGROUND: There is only sparse scientific data about the long-term effects of the Charcot foot on patients' lives and the clinical outcome. This study evaluates the long-term effects of diabetic Charcot foot. METHODS: A cross-sectional follow-up study of consecutive series of patients with Charcot foot referred to the University Hospital Diabetic Foot and Ankle Clinic between 1991 and 2002. RESULTS: Forty-one patients were referred with Charcot foot between 1991 and 2002. After an average follow-up of 8 years their overall mortality rate was 29% (12/41) and 29 patients (30 Charcot feet) have been followed more than 5 years. Sixty-seven percent of Charcot feet suffered at least one episode of ulceration and 50% (15/30) of affected feet had surgical treatment resulting in 29 operations. Simple exostectomy was successful in 62% of cases. The need for surgical management increased markedly 4 years after the diagnosis. Correct diagnosis within 3 months resulted in better functional outcome (AOFAS) and walking distance (p=0.006 and p=0.008, respectively). Lower SF-36 component scores in physical functioning, social functioning and general health perceptions were found when the study population was compared to the general population and chronically ill control subjects. CONCLUSIONS: Diabetic Charcot foot decreases patient's physical functioning and general health but does not usually affect mental health. Surgical management is often required with an increase 4 years post-diagnosis. A delay of diagnosis of more than 3 months was found to adversely affect the quality of life and functional outcome.

Management of cervical stab wounds in low volume trauma centres: systematic physical examination and low threshold for adjunctive studies, or surgical exploration.

INTRODUCTION: In Nordic countries penetrating neck injuries (PNIs) are infrequent and management has traditionally been guided by surgeons' preferences. Some form of selective non-operative approach is currently practised in most urban trauma centres. OBJECTIVE: To examine demographic features and treatment outcome of non-ballistic penetrating neck injuries in southern Finland and provide management guidelines for centres with low volume of penetrating neck trauma. MATERIALS AND METHODS: Retrospective analysis of 85 platysma penetrating neck injuries in two southern Finland hospitals (Helsinki University Central Hospital, HUCH and Tampere University Hospital, TaUH) was carried out using the ICD-10 based hospital databases to identify PNI-patients. RESULTS: The incidence of admitted patients with penetrating neck injuries was 1.3/100000/year. Fifty-two (61%) injuries were caused by random acts of violence, 28 (38%) were self-inflicted and 5 (6%) were accidents. Of all 85 patients, 52 (61%) underwent operative exploration with a negative exploration rate of 65%. Hard signs for vascular or aerodigestive trauma were present in 23 (27%) patients and all of these were operated with a negative exploration rate of 30%. Two patients had no hard signs on physical examination but were operatively explored and significant injuries were found in both patients. The hospital mortality rate was 0% and the overall complication rate for operated patients was 7.7%. CONCLUSIONS: Trauma centres managing PNIs infrequently should have an individually tailored management protocol for penetrating neck injury patients. If mandatory exploration is not practised, a systematic physical examination should be the mainstay of diagnostic work up but the threshold for adjunctive studies should be low. Although not evident by the current data, protocol-based management could be useful in decreasing treatment variation and enhancing residency training.