Sustainability studies in orthopaedic surgery: The carbon footprint of anterior cruciate ligament reconstruction depends on graft choice.

PURPOSE: Environmental sustainability in medicine is a growing concern. Determining the carbon footprint of medical procedures may aid in selecting a less impactful technique moving forward. The purpose of this study was to understand the environmental impact of different anterior cruciate ligament reconstruction techniques, for which there is no consensus in terms of optimal graft. METHODS: A life cycle analysis of different anterior cruciate ligament reconstruction techniques was performed. These included quadrupled semitendinosus graft, bone-patellar tendon-bone graft, iliotibial band augmented with gracilis graft, doubled semitendinosus and doubled gracilis graft, and quadriceps tendon graft. All procedures were systematically paired with a lateral extra-articular procedure. The study was conducted in a specialised centre using surgeon preference cards, with the help of a dedicated organisation for calculation according to the ISO 14044 standard. The primary outcome measure was the carbon footprint of each of the five techniques. Secondary outcomes included other environmental impact indicators, including human carcinogenic toxicity and mineral resource scarcity, among others, based on the ReCiPe 2016 midpoint guideline. The analysis had three scopes, each encompassing varying numbers of processes: graft implantation, full procedure, and entire environmental impact, from medical prescription to patient discharge. Results were reported as percentage increases compared to the graft technique with the lowest environmental impact. RESULTS: It was demonstrated that the surgical procedure itself accounted for <40% of the life cycle, with arthroscopy being 88% of surgery's GHG emissions, and scrubbing and draping contributing 39% to the carbon footprint. The iliotibial band augmented with gracilis tendon technique had the lowest carbon footprint (0.199 Kg Co2 eq), and the least impact in most categories at all scopes of the life cycle analysis. Using this technique as a reference, in terms of graft implantation, it was determined that extensor mechanism grafts had the highest carbon footprint (300% higher than the reference). Greater scopes showed a similar trend, with percentage differences decreasing significantly, reaching 1-3% when considering the entire environmental impact for most categories. Nevertheless, among the aforementioned factors of the ReCiPe 2016 guidelines, the semitendinosus graft paried with a lateral extra-articular procedure displayed greater difference in human carcinogenic toxicity and mineral resource scarcity (6% and 10% respectively) compared to the reference. The individual processes with the highest impact were also highlighted. CONCLUSIONS: In the institution where the study was conducted, the studied iliotibial band graft option was found to have the lowest environmental impact. Such analyses of standardised procedures can be replicated in individual institutions in order to determine their environmental impact. Identification of procedures with comparable results and differing environmental consequences may influence the future decision-making process. LEVEL OF EVIDENCE: Level II, prospective cohort study.

The impact of bone graft type used to fill bone defects in patients undergoing ACL reconstruction with bone-patellar tendon-bone (BPTB) autograft on kneeling, anterior knee pain and knee functional outcomes.

PURPOSE: Multiple different materials are used for filling bone defects following bone-patellar tendon-bone (BPTB) graft ACL reconstruction surgery. The theoretical objective being to minimize kneeling pain, improve clinical outcomes and reduce anterior knee pain following surgery. The impact of these materials is assessed in this study. METHODS: A prospective monocentric cohort study was conducted from January 2018 to March 2020. There were 128 skeletally mature athletic patients who underwent ACL reconstruction using the same arthroscopic-assisted BPTB technique, with a minimum follow-up of two years identified in our database. After obtaining approval from the local ethics committee, 102 patients were included in the study. Patients were divided into three groups based on type of bone substitute. The Bioactive glass 45S5 ceramic Glassbone™ (GB), collagen and hydroxyapatite bone void filler in sponge form Collapat® II (CP), and treated human bone graft Osteopure®(OP) bone substitutes were used according to availability. Clinical evaluation of patients at follow-up was performed using the WebSurvey software. A questionnaire completed in the 2nd post-operative year included three items: The ability to kneel, the presence of donor site pain, and the palpation of a defect. Another assessment tool included the IKDC subjective score and Lysholm score. These two tools were completed by patients preoperatively, and postoperatively on three occasions (6 months, 1 year, and 2 years). RESULTS: A total of 102 patients were included in this study. In terms of Kneeling pain, the percentage of GB and CP patients' who kneel with ease were much higher than that of OP patients (77.78%, 76.5% vs 65.6%, respectively). All three groups experienced an important increase in IKDC and Lysholm scores. There was no difference in anterior knee pain between the groups. CONCLUSION: The use of Glassbone® and Collapat II® bone substitutes reduced the incidence of kneeling pain compared to Osteopure®. There was no influence of the bone substitute type on the functional outcome of the knee or on the anterior knee pain at two years of follow.

A new self-assessment tool following shoulder stabilization surgery, the auto-Walch and auto-Rowe questionnaires.

PURPOSE: Patient-reported outcome measures (PROMS) are increasingly used for patient evaluation, as well as for scientific research. Few are used for practical purposes in the clinical setting, and few are reliable enough to allow proper feedback to physicians. Two of the most commonly used assessment tools in shoulder instability are the Walch-Duplay and the Rowe scores. The aim of this study was to evaluate the validity of self-administered versions of the Walch-Duplay and Rowe scores following shoulder stabilization procedure. METHODS: Between the months of May and December 2021, all patients who were followed in one of six institutions for shoulder instability were included. Patients were required to anonymously fill a self-administered version of Walch-Duplay and Rowe score. The classic scores were measured by the surgeon. Correlations between self-assessment and physician-assessment were then recorded. RESULTS: A total of 106 patients were evaluated during the study period. Using the Spearman coefficient for correlation, a strong correlation (r > 0.5) was found between the results of the self-administered questionnaire and the surgeon-measured score. The difference between surgeon- and patient-administered questionnaires was non-significant. CONCLUSION: The self-administered version of the Walch-Duplay and Rowe questionnaires can reliably be used in the clinical setting for post-operative follow-up of patients undergoing shoulder stabilization procedures. LEVEL OF EVIDENCE: Level II.

Posterior tibial slope (PTS) ≥ 10 degrees is a risk factor for further anterior cruciate ligament (ACL) injury; BMI is not.

PURPOSE: This case-control study aimed to assess the influence of BMI and PTS on subsequent ACL injury affecting either ACL graft or the native ACL of the contralateral knee after primary ACL reconstruction. METHODS: A retrospective case-control study was performed using a cohort of patients who underwent arthroscopic ACL reconstruction between 2010 and 2020 using the same surgical procedure: Hamstring tendon autograft. The study group (group I) included all the patients (n = 94) during this period who sustained a subsequent ACL injury. The control group (group II) consisted of 94 patients randomly selected (matched Group I in terms of sex, age, and ACL graft) who did not sustain any further ACL injury. PTS was measured by two blinded surgeons on lateral knee view radiographs of the operated knee after primary ACL. BMI in kg/m2 was measured during the preoperative anesthesia consultation. Exclusion criteria were: non-true or rotated lateral knee radiographs of the operated knee post-ACLR, associated knee ligament injury requiring surgical management, iterative knee surgeries, open growth plate, and related fracture. RESULTS: The mean posterior tibial slope in group I was 7.5° ± 2.9, and 7.2° ± 2.0 in group II. A PTS angle cutoff was set at 10 degrees. The rate of patients showing a PTS ≥ 10° was significantly higher in group I compared to group II (p < 0.01). Patients with PTS ≥ 10° were 5.7 times more likely to sustain a subsequent ACL injury, (OR: 5.7 95% CI[1.858-17.486]). The Average BMI in group I was 24.5 ± 3.7 kg.m-2 compared to group II which was 23.3 ± 3.0 kg.m-2. There were no significant differences in any of the four BMI categories between both groups (p value 0.289). A series of BMI cut-offs were also analyzed at 23 to30 kg/m2, and there was no significant difference between both groups. CONCLUSIONS: A posterior tibial slope equal to or above 10 degrees measured on lateral knee radiographs was associated with 5.7 times higher risk of ACL graft rupture or contralateral native ACL injury; however, BMI was not.

Gangrenous Cholecystitis as a Potential Complication of COVID-19: A Case Report.

While primarily a respiratory disease, COVID-19 can affect several organ systems and has been recently linked to cases of acalculous cholecystitis. We present a previously healthy elderly patient who presented to the emergency department with sepsis and was found to have COVID-19 after initially testing negative on PCR, along with suspected concomitant acalculous gangrenous cholecystitis. The patient passed away before any surgical intervention could be made. This case aims to discuss the potential relationship between acalculous cholecystitis and COVID-19.

Development of a new aerosol barrier mask for mitigation of spread of SARS-CoV-2 and other infectious pathogens.

The COVID-19 pandemic has caused huge impact on public health and significantly changed our lifestyle. This is due to the fast airborne oro-nasal transmission of SARS-CoV-2 from the infected individuals. The generation of liquid aerosolized particles occurs when the COVID-19 patients speak, sing, cough, sneeze, or simply breathe. We have developed a novel aerosol barrier mask (ABM) to mitigate the spread of SARS-CoV-2 and other infectious pathogens. This Aerosol Barrier Mask is designed for preventing SARS-CoV-2 transmission while transporting patients within hospital facilities. This mask can constrain aerosol and droplet particles and trap them in a biofilter, while the patient is normally breathing and administrated with medical oxygen. The system can be characterized as an oxygen delivery and mitigation mask which has no unfiltered exhaled air dispersion. The mask helps to prevent the spread of SARS-CoV-2, and potentially other infectious respiratory pathogens and protects everyone in general, especially healthcare professionals.

Self-contained system for mitigation of contaminated aerosol sources of SARS-CoV-2.

Contaminated aerosols and micro droplets are easily generated by infected hosts through sneezing, coughing, speaking and breathing1-3 and harm humans' health and the global economy. While most of the efforts are usually targeted towards protecting individuals from getting infected,4 eliminating transmissions from infection sources is also important to prevent disease transmission. Supportive therapies for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2) pneumonia such as oxygen supplementation, nebulizers and non-invasive mechanical ventilation all carry an increased risk for viral transmission via aerosol to healthcare workers.5-9 In this work, we study the efficacy of five methods for self-containing aerosols emitted from infected subjects undergoing nebulization therapies with a diverse spectrum on oxygen delivery therapies. The work includes five study cases: Case I: Use of a Full-Face Mask with biofilter in bilevel positive airway pressure device (BPAP) therapy, Case II: Use of surgical mask in High Flow Nasal Cannula (HFNC) therapy, Case III: Use of a modified silicone disposable mask in a HFNC therapy, Case IV: Use of a modified silicone disposable mask with a regular nebulizer and normal breathing, Case V: Use of a mitigation box with biofilter in a Non-Invasive Positive Pressure Ventilator (NIPPV). We demonstrate that while cases I, III and IV showed efficacies of 98-100%; cases II and V, which are the most commonly used, resulted with significantly lower efficacies of 10-24% to mitigate the dispersion of nebulization aerosols. Therefore, implementing cases I, III and IV in health care facilities may help battle the contaminations and infections via aerosol transmission during a pandemic.

Bilateral femoral shaft fracture in polytrauma patients: Can intramedullary nailing be done on an emergency basis?

INTRODUCTION: Whether damage control orthopedics (DCO) or early total care (ETC) is the best way to treat polytrauma patients who have suffered a bilateral femoral shaft fracture remains unanswered. The aim of this study was to evaluate the morbidity of bilateral femur fractures treated by simultaneous intramedullary (IM) nailing according to ETC principles. MATERIALS AND METHODS: This retrospective single-centre study included all polytrauma patients who had suffered a femoral shaft fracture and were treated at our level I trauma centre. Demographic data, associated lesions, injury severity score (ISS) and occurrence of acute respiratory distress syndrome (ARDS) were collected prospectively in our trauma database. Unilateral fractures (UF) were compared to bilateral fractures (BF). The risk of ARDS was evaluated by multivariate logistic regression. RESULTS: Between 2010 and 2019, 176 UF (88%) and 25 BF (12%) were included. Patients with BF had a higher ISS (36 vs. 25, p<0.001) and more brain injuries (44% vs. 15%, p=0.001) than patients with a UF. More blood transfusions were done in BF than UF (4.0 vs. 1.6 units, p=0.002). The incidence of ARDS was higher in BF patients than UF (36% vs. 4%) with longer stay in intensive care (18 vs. 12 days, p=0.02) and in the hospital (32 vs. 23 days, p=0.006). There were no deaths in either group. The risk of ARDS was correlated to ISS, but not to bilaterality. DISCUSSION: Studies on DCO and ETC report similar mortality and ARDS rates for BF. ISS appears to determine the postoperative morbidity irrespective of how the patients are managed. In contrast with DCO, perioperative intensive care has a predominant role in ETC, allowing early definitive fixation of fractures, even in severely injured patients. CONCLUSION: Bilateral femoral shaft fractures are a sign of severe trauma leading to high postoperative morbidity. The patient is likely to have concomitant severe injuries. Simultaneous ECM can be done emergently providing appropriate perioperative intensive care management. LEVEL OF EVIDENCE: IV; retrospective study.

Development of a new Aerosol Barrier Mask for mitigation of spread of SARS-CoV-2 and other infectious pathogens.

The COVID-19 pandemic has caused huge impact on public health and significantly changed our lifestyle. This is due to the fast airborne oro-nasal transmission of SARS-CoV-2 from the infected individuals. The generation of liquid aerosolized particles occurs when the COVID-19 patients speak, sing, cough, sneeze, or simply breathe. We have developed a novel aerosol barrier mask (ABM) to mitigate the spread of SARS-CoV-2 and other infectious pathogens. This Aerosol Barrier Mask is designed for preventing SARS-CoV-2 transmission while transporting patients within hospital facilities. This mask can constrain aerosol and droplet particles and trap them in a biofilter, while the patient is normally breathing and administrated with medical oxygen. The system can be characterized as an oxygen delivery and mitigation mask which has no unfiltered exhaled air dispersion. The mask helps to prevent the spread of SARS-CoV-2, and potentially other infectious respiratory pathogens and protects everyone in general, especially healthcare professionals.

A novel vertical flow assay for point of care measurement of iron from whole blood.

Disorders in iron metabolism are endemic globally, affecting more than several hundred million individuals and often resulting in increased rates of mortality or general deterioration of quality of life. To both prevent and monitor treatment of iron related disorders, we present a point of care medical device which leverages a simple smartphone camera to measure total iron concentration from a finger-prick sample. The system consists of a smartphone and an in-house developed app, a 3D printed sensing chamber and a vertical flow membrane-based sensor strip designed to accommodate 50 µl of whole blood, filter out the cellular components and carry out a colorimetric chelation reaction producing a colour change which is detected by our smartphone device. The app's accuracy and precision were assessed via comparison of the mobile app's RGB output to a reference imaging software, ImageJ for the same colorimetric sensing strip. Correlation plots resulted in slopes of 0.99 and coefficient of determination (R2 = 0.99). The device was determined to have a signal to noise ratio >40 and a mean bias of 2% which both indicate high analytical accuracy and precision (in terms of RGB measurement). The smartphone device's iron concentration readout was then studied using an extensively validated laboratory developed test (LDT) for iron detection, which is an optimized spectrophotometry-based technique (this is considered the gold standard for iron quantification among LDTs). In comparison of the smartphone-based technique with the gold standard LDT, a calibration slope of 0.0004 au µg-1 dL-1, a correlation plot with slope of 1.09 and coefficient of determination (R2) of 0.96 and a mean bias of 5.3%, our device can accurately measure iron levels in blood. With detection times of five minutes, fingerpick sample and sensor cost less than 10 cents, the device shows great promise in being developed as the first ever commercial device for iron quantification in blood.

Cortical versus cancellous screws in treating medial malleolar fractures: A systematic review of comparative clinical and biomechanical studies.

STUDY DESIGN: Systematic review of comparative studies. BACKGROUND: Partially threaded (PT) cancellous screws are a common method to fix medial malleolar fractures but with reported complications due to the hardware. Fully threaded (FT) screws have been advanced as an alternative yielding similar union results with less implant-related complications. OBJECTIVES: The aim of this study is to systematically collate comparative clinical and biomechanical evidence on the effectiveness and complications of the PT versus FT screw constructs in the treatment of medial malleolar fractures. RESULTS: Based on 7 studies (8 subgroups), similar weighted healing rates were found from pooling 3 clinical studies with the time to heal outcome significantly shorter following FT compared to FT screws. Complication rates in the form of screw loosening (1.97% vs. 13.4%, p = 0.008) and screw removal surgery (0% vs. 15.7%, p < 0.0001) were significantly higher after using PT screws. The five biomechanical studies demonstrated that FT screw constructs had significantly superior properties than the PT constructs and that for all outcomes. CONCLUSION: Fully threaded screws seem to offer significantly better clinical and biomechanical outcomes when compared to the partially threaded screws in treating medial malleolar fractures. The use of headless FT screws could contribute to reduce the implant-related complications. LEVEL OF EVIDENCE: Therapy, level 3.

Adenoma Detection before and after the age of 50: a retrospective analysis of Lebanese outpatients.

BACKGROUND AND AIM: Colorectal cancer (CRC) has an increased impact on the Lebanese population's morbidity and mortality. This study evaluated the situation of adenoma detection in an outpatient clinic in Lebanon. PATIENTS AND METHODS: 918 patients underwent colonoscopy over a period of 24 months by a qualified physician. Biopsy results were divided into normal versus abnormal colonic tissue, which was further subdivided into number of polyps and cancer. RESULTS: Out of 918 individuals included, 82 cases of Crohn's colitis (8.93%) and 22 cases of ulcerative colitis (2.39%) were identified. A total of 42 cases of CRC (4.58%) and 188 cases of adenomatous polyps (20.48%) were identified. The data show that age >50 years and male gender significantly correlate with increased incidence of precancerous and cancerous polyps. Further exploring the results by age groups and gender, detection of adenomatous polyps in women aged 40-49 (8.33%) was significantly different from their female counterparts aged ≥50 years old (25.26%) (p<0.01). However, no statistical difference between detection of adenomas was found between men aged 40-49 (33.33%) and their male counterparts aged ≥50 years old (37.5%) (p=0.6). CONCLUSION: Within the limitations of this study, the incidence of CRC and adenomatous polyps falls in the high range compared with international studies. Furthermore, symptomatic male patients aged 40-49 appear to exhibit detection rates of adenomas similar to their counterparts aged ≥50 years old. Subjects younger than 50 years underwent diagnostic rather than screening colonoscopy, which introduces some selection bias. Nevertheless, these findings can serve as a basis for further studies.

Calcaneus Metastasis from Follicular Thyroid Carcinoma 12 Years after Total Thyroidectomy.

We report the case of a sixty-eight-year-old female patient who presented for left ankle pain; X-rays and MRI showed a benign calcaneal cyst, found to be delayed distant metastasis from primary papillary thyroid carcinoma. Patient required surgical excision of the cyst. Results of histological examination showed metastatic papillary thyroid carcinoma. The patient underwent total thyroidectomy 12 years prior to presentation, with the same pathology. Postoperatively, she was treated with radioactive iodine. At 10-year follow-up post calcaneal mass excision, she was found to have a right proximal tibial mass and found to be recurrent with the same pathology. This case reports a rare condition that will be taken into consideration in bone metastasis with thyroid cancer.

Aortic Root Reconstruction with a New Dacron Graft Featuring Prefabricated Coronary Side Branches: Lessons Learned from the Cabrol Procedure.

BACKGROUND: Coronary button reimplantation can represent a technical challenge of aortic root reconstruction that can be associated with significant morbidity and mortality. With the goal of simplifying coronary reimplantation and reducing the incidence of related complications, we designed a new Dacron graft with prefabricated coronary branches to minimize coronary artery mobilization and prevent the potential mechanical complications of reattachment to the body of the graft. METHODS: Between June 2010 and May 2012, we implanted the graft in eight patients (six males, two females) ranging in age from 42-68 years (mean, 54 years). Six procedures were modified Bentall reconstructions, and two procedures were valve-sparing root replacements using the reimplantation technique. RESULTS: There were no complications and no morbidity or mortality related to coronary reattachment. All patients were alive and doing well at a mean follow-up of 26 months (range, 17-38 months). At an extended mean follow-up of 42 months (range, 25-56 months), one patient died of stroke-related complications. No radiologic or clinical evidence of impairment of coronary perfusion was identified in any patient. CONCLUSIONS: The use of this new graft model may simplify the technique of root reconstruction and potentially lower the incidence of mechanical complications related to coronary button reimplantation.

Technique of aortic root reconstruction using a new model of Dacron graft with prefabricated coronary branches.

Aortic root reconstruction is a demanding surgical procedure still associated with a significant morbidity. Arguably, the most demanding aspect of the operation is reestablishing continuity between the prosthetic graft replacing the aortic root and the coronary arteries. With the objective of simplifying the possible challenges of coronary reimplantation, we designed a new model of aortic root graft with prefabricated coronary branches. We used this technique in 8 patients (6 males, 2 females; mean age, 54 years). There were 6 modified Bentall procedures and 2 valve-sparing root replacements with the "reimplantation" technique. There was no mortality or morbidity related to the use of this new prosthetic graft. Our purpose was to report in detail the technique of aortic root reconstruction using this new graft with prefabricated coronary branches. The use of this graft may simplify the procedure and offer a valuable tool for aortic root reconstruction in cases where the reimplantation of the coronary buttons may represent a technical challenge.

Comparative study of bronchial artery revascularization in lung transplantation.

OBJECTIVE: Restoring dual blood supply to transplanted lungs by bronchial artery revascularization (BAR) remains controversial. We compared outcomes after lung transplantation performed with and without BAR. METHODS: From December 2007 to July 2010, 283 patients underwent transplantation; 187 were 18 years or older, without previous or concomitant cardiac surgery. Of these patients, 27 underwent BAR in a pilot study to test success, safety, effectiveness, and teachability. A propensity score was generated to match BAR patients and 54 routine non-BAR patients. Follow-up was 1.3 ± 0.68 years. RESULTS: BAR was angiographically successful in 26 (96%) of 27 patients. BAR and non-BAR patients had similar skin-to-skin time (P = .07) and postoperative hospital stays (P = .2), but more reoperations for bleeding (P = .002). Tracheostomy was performed in 9 (33%) of 27 BAR and 10 (19%) of 54 non-BAR patients (P = .2, log-rank). One BAR (3.7%) and 4 non-BAR (7.4%) patients required extracorporeal membrane oxygenation (P = .7). Airway ischemia was observed in 1 BAR (3.7%) versus 12 non-BAR (22%) patients (P = .03); anastomotic intervention was required in no BAR versus 8 non-BAR (15%) patients (P = .04). Hospital mortality was 1 of 27 versus 2 of 54 (P = .9). BAR patients had lower early biopsy tissue rejection grades (P = .008) and fewer pulmonary (P < .04) and bloodstream (P < .02) infections. Forced 1-second expiratory volume was similar (P > .2); 3 BAR versus 9 non-BAR patients developed bronchiolitis obliterans syndrome (BOS) (P = .14, log-rank). During follow-up, 4 BAR and 8 non-BAR patients died (P = .6, log-rank). CONCLUSIONS: BAR is safe, with comparable early outcomes. Benefits of BAR include reduced airway ischemia and complications, lower biopsy tissue grades, fewer infections, and delay of BOS. A multicenter study is needed to establish these benefits.

Computed tomography findings in a patient with fungal aortitis: acute aortic syndrome secondary to fusariosis.

Fusarium is a mould widely distributed in soil and water which causes various diseases in plants and occasionally in animals. The Fusarium species cause a broad spectrum of infections in humans, of which, the degree of severity is largely determined by the immune-status of the host, occurring in the most severe and invasive forms in immunocompromised individuals. Skin infections, sinusitis and pneumonia are the most common human manifestations of the disease. In patients with severe immunodeficiency, the disease can become invasive and disseminated causing fungemia. We report a case of an immunocompromised patient presenting with acute chest pain secondary to complicated Fusarium aortitis.

Comparison of the perinatal morbidity and mortality of the presenting twin and its co-twin.

OBJECTIVE: To compare the perinatal outcome of the presenting twin to its co-twin. STUDY DESIGN: All live nonanomalous twin gestations delivered at >25 weeks' gestation between 1984 and 1994 (N=461) were identified. Twin A was compared to twin B regarding the following variables: presentation, Apgar score (AS) <4 at 1 minute, AS <7 at 5 minutes, birth weight, gender, traumatic delivery, meconium-stained amniotic fluid, cord prolapse, need for mechanical ventilation, intraventricular hemorrhage, respiratory distress syndrome, sepsis, seizures, perinatal mortality, and length of nursery stay. RESULTS: Except for differences in presentation, the perinatal outcome was similar in both twins regarding variables studied. This continued to hold true after subdividing according to mode of delivery, when infants with birth weight < or = 1500 g were considered separately, and when vaginally delivered cephalic twin A was compared to the noncephalic co-twin. However, differences in some outcome variables became evident when pregnancies with only one affected member were analyzed separately. CONCLUSIONS: When all twin pairs are considered, the outcome of the second-born twin is similar to that of the first-born regardless of the mode of delivery, presentation, or birth weight < or = 1500 g. If only those twin pairs with one affected and one unaffected twin are considered, it becomes apparent that the presenting twin is at increased risk for infection-related morbidities whereas the co-twin is at risk for other complications.