Biomechanical parameters of the golf swing associated with lower back pain: A systematic review.

Low back pain (LBP) is the most common injury in golfers of all abilities. The primary aim of this review was to improve understanding of human golf swing biomechanics associated with LBP. A systematic review using the PRISMA guidelines was performed. Nine studies satisfying inclusion criteria and dually reporting golf swing biomechanics and LBP were identified. Human golf swing biomechanics potentially associated with LBP include: reduced lumbar flexion velocity; reduced transition phase length; reduced lumbar torsional load; earlier onset of erector spinae contraction; increased lumbar lateral flexion velocity; reduced or greater erector spinae activity; and earlier onset of external oblique contraction. These potential associations were undermined by a very limited and conflicting quality of evidence, study designs which introduced a severe potential for bias and a lack of prospective study design. There is no conclusive evidence to support the commonly held belief that LBP is associated with "poor" golf swing technique. The potential associations identified should be further investigated by prospective studies of robust design, recruiting participants of both sexes and dexterities. Once firm associations have been identified, further research is required to establish how this knowledge can be best integrated into injury prevention and rehabilitation.

LBP has the highest incidence of any injury in elite, sub-elite and recreational golfers, causing a significant burden of injury worldwide.There is very limited and conflicting evidence that some human biomechanical factors in the golf swing may be associated with LBP.Prospective studies investigating the full movement pattern are required in order to improve understanding of the potential relationship between the biomechanics of the golf swing and LBP.

The forgotten joint score-12 is a valid and responsive outcome tool for measuring success following hip arthroscopy for femoroacetabular impingement syndrome.

PURPOSE: The forgotten joint score-12 (FJS-12) is an outcome questionnaire designed to evaluate joint awareness. The responsiveness and validity of the English language version of the FJS-12 in patients undergoing hip arthroscopy for femoroacetabular impingement (FAI) is not known. METHODS: Consecutive patients undergoing hip arthroscopy for a diagnosis of FAI were prospectively followed up over a 1 year period. Patients completed preoperative and postoperative FJS-12, EuroQol 5 Dimension (EQ-5D-5L), and the 12-item international hip outcome tool (iHOT-12). We evaluated construct validity with Spearman correlation coefficients for the FJS-12, and responsiveness by way of effect size and ceiling effects. RESULTS: Forty-six patients underwent hip arthroscopy, of which 42 (91%) completed post-operative PROMs at 1 year follow-up. Construct validity was strong with the iHOT-12 (r = 0.87) and also the EQ-5D-5L (r = 0.83). The median postoperative FJS score was 50.2 (IQR 64). The mean change in score for the FJS-12 was 31 points (SD 31) (p < 0.001), with an effect size (Cohen's d) of 1.16. Preoperatively, three patients scored the lowest possible value resulting in a floor effect of 7.1%. Similarly, only three patients (7.1%) scored the best possible score post-operatively. CONCLUSION: This is the first evaluation of the joint awareness concept in the English language version of the FJS-12 following hip arthroscopy for FAI. The FJS-12 is a valid and responsive tool for the assessment of this cohort of patients. LEVEL OF EVIDENCE: II.

Golfers are physically more active and have greater health associated quality of life than non-golfers following lower limb arthroplasty.

Background: The health benefits of physical activity are well recognised. This study assessed whether golfers were more physically active after lower limb arthroplasty when compared to those that did not play golf (primary outcome). In addition pre and postoperative changes in health-associated quality of life (HAQoL) and joint specific outcomes between golfers and none golfers were assessed (secondary outcomes). Methods: There were 304 patients [THA (n = 155) or TKA (n = 149)] prospectively registered during a 4-month period undergoing lower limb arthroplasty. The mean age was 70.0 (range 37-92, standard deviation 10.2) years and included 188 (61%) females and 120 (39%) males. They completed pre and postoperative questionnaires assessing recreational activity, physical activity, HAQoL (EuroQol [EQ]), joint specific health (Oxford scores), and satisfaction. Results: Golfers (n = 33, 10.9%) were more likely to achieve longer than 3 hours of moderate activity during a week (48.5% vs 38.0%, odds ratio (OR) 3.4, p = 0.045) and achieved their recommended activity level (96.8% vs 77.7%, OR 8.6, p = 0.015) compared to non-golfers following arthroplasty. Postoperative EQ5D (p = 0.034) and EQVAS (p = 0.019) were significantly greater in golfers. The joint specific Oxford hip score was greater in golfers compared to non-golfers (mean difference 5.6, p = 0.022), however no difference was observed in the Oxford knee score following TKA (p = 0.495). Conclusion: Golfers were more likely to achieve their weekly recommended level of physical activity and had a greater HAQoL relative to those that did not play golf following lower limb arthroplasty. More specifically after THA golfers also had a greater postoperative joint specific outcome, but no such advantage was observed in those following TKA. Evidence Level: Level II, diagnostic study.

Traumatic anterior shoulder instability in the athlete.

Anterior glenohumeral dislocation is common among athletes and may progress to recurrent instability. The pathoanatomy of instability and specific needs of each individual should be considered to prevent unnecessary absence from sport. Traditionally, primary dislocations have been managed with immobilization followed by rehabilitation exercises and a return to sporting activity. However, arthroscopic stabilization and external rotation bracing are increasingly used to prevent recurrent instability. In addition to the typical capsulolabral disruptions seen following a primary dislocation, patients with recurrent instability often have coexistent osseous injury to the humeral head and glenoid. In patients without significant bone loss, open soft-tissue stabilizations have long been considered the 'gold standard treatment' for recurrent instability, but with advances in technology, arthroscopic procedures have gained popularity. However, enthusiasm for arthroscopic repair has not been supported with evidence, and there is currently no consensus for treatment. In patients with greater bone loss, soft-tissue stabilization alone is insufficient to treat recurrent instability and open repair or bone augmentation should be considered. We explore the recent advances in epidemiology, classification, pathoanatomy and clinical assessment of young athletes with anterior shoulder instability, and compare the relative merits and outcomes of the different forms of treatment.

Cracking the code: the accuracy of coding shoulder procedures and the repercussions.

BACKGROUND: Coding of patients' diagnosis and surgical procedures is subject to error levels of up to 40% with consequences on distribution of resources and financial recompense. Our aim was to explore and address reasons behind coding errors of shoulder diagnosis and surgical procedures and to evaluate a potential solution. METHODS: A retrospective review of 100 patients who had undergone surgery was carried out. Coding errors were identified and the reasons explored. A coding proforma was designed to address these errors and was prospectively evaluated for 100 patients. The financial implications were also considered. RESULTS: Retrospective analysis revealed the correct primary diagnosis was assigned in 54 patients (54%) had an entirely correct diagnosis, and only 7 (7%) patients had a correct procedure code assigned. Coders identified indistinct clinical notes and poor clarity of procedure codes as reasons for errors. The proforma was significantly more likely to assign the correct diagnosis (odds ratio 18.2, p < 0.0001) and the correct procedure code (odds ratio 310.0, p < 0.0001). Using the proforma resulted in a £28,562 increase in revenue for the 100 patients evaluated relative to the income generated from the coding department. CONCLUSION: High error levels for coding are due to misinterpretation of notes and ambiguity of procedure codes. This can be addressed by allowing surgeons to assign the diagnosis and procedure using a simplified list that is passed directly to coding.

Preoperative morbidity and joint awareness while awaiting hip arthroscopy for femoroacetabular impingement.

PURPOSE: The Forgotten Joint Score (FJS-12) is a valid tool in the evaluation of patients undergoing hip arthroscopy, assessing the unique concept of joint awareness in the setting of a patient's hip pathology. The preoperative burden on patients' mental wellbeing of impaired joint function or symptoms is well established. The purpose of this study was to determine patients' awareness of their hip joint whilst awaiting hip arthroscopy for femoroacetabular impingement, to explore any association between joint awareness and mental health status, and to determine whether this relates to time spent waiting for arthroscopy preoperatively. METHODS: A prospective database of patients undergoing hip arthroscopy between January 2018 and November 2020 was analysed. All patients with a diagnosis of femoroacetabular impingement (FAI) undergoing arthroscopic treatment were included. Questionnaires included the FJS-12, twelve item international hip outcome tool (iHOT-12), EuroQol 5D-5L (EQ-5D-5L) and the Tegner activity score. Pearson's correlation coefficient was used to assess relationships between continuous variables. RESULTS: Preoperative functional outcomes were completed by 81 patients (97.5%) prior to undergoing hip arthroscopy. Median preoperative FJS-12 score was 16.67 (IQR 8.33 - 29.68). Forty-four patients reported any level of anxiety/depression preoperatively (54.3%). Preoperative FJS-12 showed a significant negative correlation with worsening mental health status (r = - 0.359, p <  0.001), and a significant positive correlation with EQ-5D-5L (r = 0.445, p <  0.001). The duration of symptoms or time on the waiting list did not correlate with increased joint awareness or worsened mental health. CONCLUSION: Joint awareness is high when awaiting hip arthroscopy for FAI. Increasing levels of joint awareness correlate with poorer mental health status and poorer quality of life measures, however these parameters do not seem to be associated with increased duration of symptoms prior to surgery or time on the waiting list for surgery.

Sporting participation following the operative management of chondral defects of the knee at mid-term follow up: a systematic review and meta-analysis.

PURPOSE: The purpose of this study was to perform a systematic review of the reparticipation in sport at mid-term follow up in athletes who underwent biologic treatment of chondral defects in the knee and compare the rates amongst different biologic procedures. METHODS: A search of PubMed/Medline and Embase was performed in May 2020 in keeping with Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. The criteria for inclusion were observational, published research articles studying the outcomes and rates of participation in sport following biologic treatments of the knee with a minimum mean/median follow up of 5 years. Interventions included microfracture, osteochondral autograft transfer (OAT), autologous chondrocyte implantation (ACI), matrix-induced autologous chondrocyte implantation (MACI), osteochondral allograft, or platelet rich plasma (PRP) and peripheral blood stem cells (PBSC). A random effects model of head-to-head evidence was used to determine rates of sporting participation following each intervention. RESULTS: There were twenty-nine studies which met the inclusion criteria with a total of 1276 patients (67% male, 33% female). The mean age was 32.8 years (13-69, SD 5.7) and the mean follow up was 89 months (SD 42.4). The number of studies reporting OAT was 8 (27.6%), ACI was 6 (20.7%), MACI was 7 (24.1%), microfracture was 5 (17.2%), osteochondral allograft was 4 (13.8%), and one study (3.4%) reported on PRP and PBSC. The overall return to any level of sport was 80%, with 58.6% returning to preinjury levels. PRP and PBSC (100%) and OAT (84.4%) had the highest rates of sporting participation, followed by allograft (83.9%) and ACI (80.7%). The lowest rates of participation were seen following MACI (74%) and microfracture (64.2%). CONCLUSIONS: High rates of re-participation in sport are sustained for at least 5 years following biologic intervention for chondral injuries in the knee. Where possible, OAT should be considered as the treatment of choice when prolonged participation in sport is a priority for patients. However, MACI may achieve the highest probability of returning to the same pre-injury sporting level. LEVEL OF EVIDENCE: IV.

Classification systems for platelet-rich plasma.

There is good scientific rationale to support the use of growth factors to promote musculoskeletal tissue regeneration. However, the clinical effectiveness of platelet-rich plasma (PRP) and other blood-derived products has yet to be proven. Characterization and reporting of PRP preparation protocols utilized in clinical trials for the treatment of musculoskeletal disease is highly inconsistent, and the majority of studies do not provide sufficient information to allow the protocols to be reproduced. Furthermore, the reporting of blood-derived products in orthopaedics is limited by the multiple PRP classification systems available, which makes comparison of results between studies challenging. Several attempts have been made to characterize and classify PRP; however, no consensus has been reached, and there is lack of a comprehensive and validated classification. In this annotation, we outline existing systems used to classify preparations of PRP, highlighting their advantages and limitations. There remains a need for standardized universal nomenclature to describe biological therapies, as well as a comprehensive and reproducible classification system for autologous blood-derived products. Cite this article: Bone Joint J 2019;101-B:891-896.

Revision anterior cruciate ligament reconstruction: timing of surgery and the incidence of meniscal tears and degenerative change.

We reviewed 87 patients who underwent revision reconstruction of the anterior cruciate ligament. The incidence of meniscal tears and degenerative change was assessed and related to the interval between failure of the primary graft and revision reconstruction. Patients were divided into two groups: early revision surgery within six months of graft failure, and delayed revision. Degenerative change was scored using the French Society of Arthroscopy system. There was a significantly higher incidence of articular cartilage degeneration in the delayed group (Mann-Whitney U-test, 53.2% vs 24%, p < 0.01). No patient in the early group had advanced degenerative change, compared to 9.2% of patients in the delayed group. There was no significant difference (Mann-Whitney U-test, p = 0.3) in the incidence of meniscal tears between the two groups. We conclude that revision reconstruction should be carried out within six months of primary graft failure, in order to minimise the risk of degenerative change.

The Influence of Shortening on Clinical Outcome in Healed Displaced Midshaft Clavicular Fractures After Nonoperative Treatment.

BACKGROUND: We aimed to evaluate the effect of clavicular shortening, measured with 3-dimensional computed tomography (3DCT), on functional outcomes and satisfaction in patients with healed displaced midshaft clavicular fractures up to 1 year following injury. METHODS: The data used in this study were collected as part of a multicenter, prospective randomized controlled trial of open reduction and plate fixation compared with nonoperative treatment for acute, displaced midshaft clavicular factures. Patients who were randomized to nonoperative treatment and had healed by 1 year were included in the present study. Clavicular shortening relative to the uninjured, contralateral clavicle was measured on 3DCT. Outcome analysis was conducted at 6 weeks, 3 months, 6 months, and 1 year following injury and included the Disabilities of the Arm, Shoulder and Hand (DASH), Constant, and Short Form-12 (SF-12) scores and patient satisfaction. RESULTS: In the original trial, 105 patients were randomized to nonoperative treatment. Thirteen patients were lost to follow-up, leaving 92 patients, and an additional 16 (17%) developed nonunion and were excluded from the present study. Of the remaining 76 patients, 48 who had a 3DCT scan that included the whole length of both clavicles were included in the present study. The shortening of the injured clavicles, relative to the contralateral side, was a mean (and standard deviation) of 11.3 ± 7.6 mm, with a mean proportional shortening of 8%. Proportional shortening did not significantly correlate with the DASH (p ≥ 0.42), Constant (p ≥ 0.32), or SF-12 (p ≥ 0.08) scores at any point during follow-up. There was no significant difference in the mean DASH or Constant scores at any follow-up time point when the cutoff for shortening was defined as 1 cm (p ≥ 0.11) or as 2 cm (p ≥ 0.35). There was no significant difference in clavicular shortening between satisfied and unsatisfied patients (p ≥ 0.49). CONCLUSIONS: The present study demonstrated no association between shortening and functional outcome or satisfaction in patients with healed displaced midshaft clavicular fractures up to 1 year following injury. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

αv integrins on mesenchymal cells regulate skeletal and cardiac muscle fibrosis.

Mesenchymal cells expressing platelet-derived growth factor receptor beta (PDGFRß) are known to be important in fibrosis of organs such as the liver and kidney. Here we show that PDGFRß+ cells contribute to skeletal muscle and cardiac fibrosis via a mechanism that depends on αv integrins. Mice in which αv integrin is depleted in PDGFRß+ cells are protected from cardiotoxin and laceration-induced skeletal muscle fibrosis and angiotensin II-induced cardiac fibrosis. In addition, a small-molecule inhibitor of αv integrins attenuates fibrosis, even when pre-established, in both skeletal and cardiac muscle, and improves skeletal muscle function. αv integrin blockade also reduces TGFß activation in primary human skeletal muscle and cardiac PDGFRß+ cells, suggesting that αv integrin inhibitors may be effective for the treatment and prevention of a broad range of muscle fibroses.

Adipose derived pericytes rescue fractures from a failure of healing--non-union.

Atrophic non-union is attributed to biological failure of the fracture repair process. It occurs in up to 10% of fractures, results in significant morbidity to patients, and treatment often requires complex reconstructive procedures. We tested the ability of human bone derived marrow mesenchymal stem cells (MSC), and human adipose derived pericytes (the native ancestor of the MSC) delivered percutaneously to the fracture gap to prevent the formation of atrophic non-union in a rat model. At eight weeks, 80% of animals in the cell treatment groups showed evidence of bone healing compared to only 14% of those in the control group. Radiographic parameters showed significant improvement over the eight-week period in the cell treatment groups, and histology confirmed bone bridges at the fracture gap in the both treatment groups. The quality of bone produced and its biomechanical properties were significantly enhanced in both treatment groups. The results from this study demonstrate that MSC and pericytes have significant bone regeneration potential in an atrophic non-union model. These cells may have a role in the prevention of atrophic non-union and could enable a paradigm shift in the treatment of fractures at high risk of failing to heal and developing non-union.

Infrapatellar Fat Pad: An Alternative Source of Adipose-Derived Mesenchymal Stem Cells.

Introduction. The Infrapatellar fat pad (IPFP) represents an emerging alternative source of adipose-derived mesenchymal stem cells (ASCs). We compared the characteristics and differentiation capacity of ASCs isolated from IPFP and SC. Materials and Methods. ASCs were harvested from either IPFP or SC. IPFPs were collected from patients undergoing total knee arthroplasty (TKA), whereas subcutaneous tissues were collected from patients undergoing lipoaspiration. Immunophenotypes of surface antigens were evaluated. Their ability to form colony-forming units (CFUs) and their differentiation potential were determined. The ASCs karyotype was evaluated. Results. There was no difference in the number of CFUs and size of CFUs between IPFP and SC sources. ASCs isolated from both sources had a normal karyotype. The mesenchymal stem cells (MSCs) markers on flow cytometry was equivalent. IPFP-ASCs demonstrated significantly higher expression of SOX-9 and RUNX-2 over ASCs isolated from SC (6.19 ± 5.56-, 0.47 ± 0.62-fold; p value = 0.047, and 17.33 ± 10.80-, 1.56 ± 1.31-fold; p value = 0.030, resp.). Discussion and Conclusion. CFU assay of IPFP-ASCs and SC-ASCs harvested by lipoaspiration technique was equivalent. The expression of key chondrogenic and osteogenic genes was increased in cells isolated from IPFP. IPFP should be considered a high quality alternative source of ASCs.

Prospective purification of perivascular presumptive mesenchymal stem cells from human adipose tissue: process optimization and cell population metrics across a large cohort of diverse demographics.

BACKGROUND: Adipose tissue is an attractive source of mesenchymal stem cells (MSC) as it is largely dispensable and readily accessible through minimally invasive procedures such as liposuction. Until recently MSC could only be isolated in a process involving ex-vivo culture and their in-vivo identity, location and frequency remained elusive. We have documented that pericytes (CD45-, CD146+, and CD34-) and adventitial cells (CD45-, CD146-, CD34+) (collectively termed perivascular stem cells or PSC) represent native ancestors of the MSC, and can be prospectively purified using fluorescence activated cell sorting (FACS). In this study we describe an optimized protocol that aims to deliver pure, viable and consistent yields of PSC from adipose tissue. We analysed the frequency of PSC within adipose tissue, and the effect of patient and procedure based variables on this yield. METHODS: Within this twin centre study we analysed the adipose tissue of n = 131 donors using flow cytometry to determine the frequency of PSC and correlate this with demographic and processing data such as age, sex, BMI and cold storage time of the tissue. RESULTS: The mean number of stromal vascular fraction (SVF) cells from 100 ml of lipoaspirate was 34.4 million. Within the SVF, mean cell viability was 83 %, with 31.6 % of cells being haematopoietic (CD45+). Adventitial cells and pericytes represented 33.0 % and 8 % of SVF cells respectively. Therefore, a 200 ml lipoaspirate would theoretically yield 23.2 million viable prospectively purified PSC - sufficient for many reconstructive and regenerative applications. Minimal changes were observed in respect to age, sex and BMI suggesting universal potential application. CONCLUSIONS: Adipose tissue contains two anatomically and phenotypically discreet populations of MSC precursors - adventitial cells and pericytes - together referred to as perivascular stem cells (PSC). More than 9 million PSC per 100 ml of lipoaspirate can be rapidly purified to homogeneity using flow cytometry in clinically relevant numbers potentially circumventing the need for purification and expansion by culture prior to clinical use. The number and viability of PSC are minimally affected by patient age, sex, BMI or the storage time of the tissue, but the quality and consistency of yield can be significantly influenced by procedure based variables.

How evidence based is the management of two common sports injuries in a sports injury clinic?

OBJECTIVES: To examine the diagnosis and management of adults attending a sports injury clinic, to establish to what extent the management of the two most common injuries treated at this clinic is evidence based, and to explore factors that affect management. METHODS: A retrospective examination of 100 random case notes extracted age, sex, sport, type and site of injury, treatment, and outcome. Systematic literature reviews examined the extent and quality of scientific evidence for the management of the two most commonly presenting injuries. A clinical attachment period and practitioner interviews allowed recognition of factors impinging on management decisions. RESULTS: Patellofemoral pain syndrome (PFPS; 10% of all injuries) and Achilles tendinopathy (6% of all injuries) were the most commonly presenting injuries. The mean (SD) number of treatments used for PFPS was 2.8 (0.9). The mean number of treatments used for Achilles tendinopathy was 3.7 (1.0). Clinicians reported that personal experience formed the basis of management plans in 44% of PFPS cases and 59% of Achilles tendinopathy cases, and that primary research evidence only accounted for 24% of management plans in PFPS and 14% in Achilles tendinopathy. Practitioners were unaware of literature supporting over 50% of the treatment modalities they used. However, clinicians were often using evidence based treatments, unaware of the supporting research data. CONCLUSIONS: This study highlights a lack of evidence base, a lack of knowledge of the research evidence, and a lack of management based on the current evidence that is available for these conditions. Practitioners practised evidence based medicine in under 50% of cases.

Recent insights into the identity of mesenchymal stem cells: Implications for orthopaedic applications.

The ability of mesenchymal stem cells (MSCs) to differentiate in vitro into chondrocytes, osteocytes and myocytes holds great promise for tissue engineering. Skeletal defects are emerging as key targets for treatment using MSCs due to the high responsiveness of bone to interventions in animal models. Interest in MSCs has further expanded in recognition of their ability to release growth factors and to adjust immune responses. Despite their increasing application in clinical trials, the origin and role of MSCs in the development, repair and regeneration of organs have remained unclear. Until recently, MSCs could only be isolated in a process that requires culture in a laboratory; these cells were being used for tissue engineering without understanding their native location and function. MSCs isolated in this indirect way have been used in clinical trials and remain the reference standard cellular substrate for musculoskeletal engineering. The therapeutic use of autologous MSCs is currently limited by the need for ex vivo expansion and by heterogeneity within MSC preparations. The recent discovery that the walls of blood vessels harbour native precursors of MSCs has led to their prospective identification and isolation. MSCs may therefore now be purified from dispensable tissues such as lipo-aspirate and returned for clinical use in sufficient quantity, negating the requirement for ex vivo expansion and a second surgical procedure. In this annotation we provide an update on the recent developments in the understanding of the identity of MSCs within tissues and outline how this may affect their use in orthopaedic surgery in the future.

Ethical, legal and practical issues of establishing an adipose stem cell bank for research.

Access to human tissue is critical to medical research, however the laws and regulations surrounding gaining ethical and legal access to tissue are often poorly understood. Recently, there has been a huge increase in the interest surrounding the therapeutic application of adipose tissue, and adipose-derived stem cells. To facilitate our own research interests and possibly assist our local colleagues and collaborators, we established a Research Tissue Bank (RTB) to collect, store and distribute human adipose tissue derived cells with all the appropriate ethical approval for subsequent downstream research. Here we examine the legal, ethical and practical issues relating to the banking of adipose tissue for research in the UK, and discuss relevant international guidelines and policies. We also share our experiences of establishing an RTB including the necessary infrastructure and the submission of an application to a Research Ethics Committee (REC).

Risk factors for nonunion after nonoperative treatment of displaced midshaft fractures of the clavicle.

BACKGROUND: Identification of patients at higher risk of nonunion after diaphyseal clavicular fractures is desirable to improve patient counseling and enable targeted surgical treatment. METHODS: Seventy-nine percent (941 of 1196) of diaphyseal clavicular fractures were followed to union or nonunion. Demographic, injury, and radiographic characteristics associated with nonunion were determined with use of bivariate and multivariate statistical analyses. RESULTS: In patients who were eighteen years of age or older, 125 (13.3%) of the fractures had clinical and radiographic evidence of nonunion. Factors significantly associated with nonunion on bivariate analysis were sex, smoking status, overall fracture displacement, overlap, translation, and comminution. The factors that maintained significance on multivariate analysis were smoking (odds ratio, 3.76), comminution (odds ratio, 1.75), and fracture displacement (odds ratio, 1.17). If all displaced midshaft fractures were managed operatively, 7.5 procedures would need to be undertaken to prevent a single nonunion. If only fractures with a predicted probability of ≥40% were managed operatively, the number of patients managed operatively to prevent a single nonunion would fall to 1.7. CONCLUSIONS: Thirteen percent of displaced diaphyseal fractures in patients who were at least eighteen years of age did not heal. Smoking was the strongest risk factor, and smoking cessation should be an integral part of treatment. The probability of nonunion in a particular individual can be estimated with use of a statistical model based on known risk factors. This information can be useful when counseling the patient even though nonunion remains difficult to predict accurately in that individual. The number who would need to be treated to prevent a single nonunion can be reduced by identifying those at higher risk.