Are displaced distal clavicle fractures associated with inferior clinical outcomes following nonoperative management? A systematic review.

BACKGROUND: Management of displaced distal clavicle fractures remains a topic of discussion because of notoriously high nonunion rates, but there is little documented in the literature as to what effect this may have on patient-reported function. The aim of this systematic review was to look at nonoperative management following displaced distal clavicle fractures to determine union rates, complications, and patient-reported outcome measures. METHODS: A review of the online databases MEDLINE and Embase was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Clinical studies that included a cohort of nonoperatively managed displaced distal clavicle fractures and reported on union rate, complications, and patient-reported functional scores were included. RESULTS: Eleven studies were eligible for inclusion (2 randomized controlled trials, 1 prospective noncomparative cohort study, 5 retrospective comparative cohort studies, and 3 case series) with a total of 779 patients included in this review. Average union rate was 63.2% (22.2%-94.4%) in nonoperatively managed patients, compared with 96.3% (87.9%-100%) in operatively managed patients. The Constant-Murley score and Disabilities of the Arm, Shoulder, and Hand questionnaire were the most frequently used outcome measure tools. No study demonstrated any significant difference in any outcome measure when comparing nonoperative with operative treatment. Complication rate (including nonunion) in nonoperatively managed patients was 45.1%, with 11.1% requiring delayed surgery. Average complication rate in the operatively managed groups was 41.2%, with 40.1% requiring a second operation. CONCLUSION: Nonoperative management of displaced distal clavicle fractures results in higher nonunion rates, but shoulder function remains excellent, and risk of complications and delayed surgery are low. Decision making must take into account patient factors and expectations to provide high-quality, individualized care.

Graft Healing Is More Important Than Graft Technique: Superior Capsular Reconstruction Versus Bridging Grafts-A Prospective Randomized Controlled Trial.

PURPOSE: To compare superior capsular reconstruction (SCR) versus bridging graft (BG) for massive irreparable rotator cuff tears (RCTs). METHODS: A prospective double-blind randomized study was conducted to compare SCR versus BG for massive irreparable RCTs. Fifty patients (mean age: 60.2 ± 6.0 years) with chronic tears (mean duration of symptoms: 5 ± 5.2 years) were intraoperatively randomized following partial repair to SCR or BG using human dermal allograft. All patients underwent standardized rehabilitation and were followed at 3, 6, 12, and 24 months clinically and radiographically. Magnetic resonance imaging were obtained at 12 months to determine graft integrity. RESULTS: At 2 years, 46 patients were available for follow-up. Mean American Shoulder and Elbow Surgeons (ASES), Western Ontario Rotator Cuff (WORC), and Quick Disabilities of the Arm, Shoulder and Hand scores were 74.8 ± 23.9, 66.0 ± 28.3, and 24.7 ± 26.1 for the SCR group, and 77.9 ± 19.9, 69.5 ± 24.5, and 25.0 ± 19.1 for the BG group, respectively, with no significant difference between groups. Magnetic resonance imaging demonstrated 18 of 24 (75%) in the SCR group and 14 of 22 (64%) in the BG group were intact at 12 months (P = .53). Patients with intact grafts compared with those with retorn grafts, whether SCR or BG, had greater ASES and WORC scores at 24 months (ASES 81.0 ± 18.7 vs 65.7 ± 24.4, P = .021 and WORC 72.3 ± 24.6 vs 53.7 ± 26.7, P = .04) and greater acromiohumeral intervals on radiographs at all follow-up time points. CONCLUSIONS: When performing arthroscopic reconstruction using human dermal allograft for an irreparable RCT, whether the proximal edge of the graft is attached on the glenoid bone or to the torn tendon does not significantly change short-term clinical and radiographic outcomes. LEVEL OF EVIDENCE: I, therapeutic.

Glenohumeral arthrodesis for recurrent types II and III shoulder instability.

BACKGROUND: This study reports the clinical outcome after glenohumeral arthrodesis for recurrent type II (atraumatic structural) and type III (muscle patterning nonstructural disorder) shoulder instability. METHODS: A retrospective review was conducted at a single facility. Eight consecutive patients (7 women and 1 man) with recurrent shoulder instability underwent arthrodesis and were monitored for a mean of 57 months (range, 24-123 months). Mean age at the time of surgery was 47 years (range, 21-73 years). RESULTS: Bony union was achieved in all patients at a mean time to fusion of 3 months (range, 1-11 months). No complications, such as routine removal of the metalwork or loosening, were noted. No residual perceived glenohumeral instability was reported, and no patient developed scapulothoracic instability or painful scapular dyskinesis. The mean Oxford Shoulder Instability Score improved from 8 preoperatively (range, 0-19) to 32 postoperatively (range, 16-41; P = .001). This was accompanied by an increase in the mean subjective shoulder value, which improved from 22 (range, 0-50) preoperatively to 73 (range, 50-100) postoperatively (P = .004). CONCLUSION: In our series, glenohumeral arthrodesis was associated with no complications and was able to reduce pain, eliminate instability, and improve functional outcome. It should therefore be considered in this patient population.

The effectiveness of demineralized cortical bone matrix in a chronic rotator cuff tear model.

BACKGROUND: The purpose of this study was to assess the effect of demineralized bone matrix (DBM) on rotator cuff tendon-bone healing. The hypothesis was that compared with a commercially available dermal matrix scaffold, DBM would result in a higher bone mineral density and regenerate a morphologically superior enthesis in a rat model of chronic rotator cuff degeneration. METHODS: Eighteen female Wistar rats underwent unilateral detachment of the supraspinatus tendon. Three weeks later, tendon repair was carried out in animals randomized into 3 groups: group 1 animals were repaired with DBM (n = 6); group 2 received augmentation with the dermal scaffold (n = 6); and group 3 (controls) underwent nonaugmented tendon-bone repair (n = 6). Specimens were retrieved at 6 weeks postoperatively for histologic analysis and evaluation of bone mineral density. RESULTS: No failures of tendon-bone healing were noted throughout the study. All groups demonstrated closure of the tendon-bone gap with a fibrocartilaginous interface. Dermal collagen specimens exhibited a disorganized structure with significantly more abnormal collagen fiber arrangement and cellularity than in the DBM-based repairs. Nonaugmented repairs exhibited a significantly higher bone mineral density than in DBM and the dermal collagen specimens and were not significantly different from control limbs that were not operated on. CONCLUSION: The application of DBM to a rat model of chronic rotator cuff degeneration did not improve the composition of the healing enthesis compared with nonaugmented controls and a commercially available scaffold. However, perhaps the most important finding of this study was that the control group demonstrated a similar outcome to augmented repairs.

Management of recurrent shoulder instability in patients with epilepsy.

Epileptic seizures can cause dislocation of the shoulder. Recurrent instability is common and occurs soon after the first dislocation. Significant bone loss from the humeral head and glenoid is thought to be responsible for this, and therefore the majority of surgical approaches focus on bone augmentation of the glenohumeral joint. Understanding of the current management strategies and the anatomic lesions associated with seizure-related shoulder instability will guide clinical decision-making. The purpose of this article was to review the pathoanatomy, treatment options, and clinical outcomes of seizure-related shoulder instability.

The management of recurrent shoulder instability in patients with epilepsy: a 15-year experience.

BACKGROUND: The purpose of this study was to review our experience with recurrent shoulder instability in epileptic patients and to discuss factors influencing its management. METHODS: A retrospective review was conducted at a single facility. All patients with epilepsy and recurrent shoulder instability were included for study. RESULTS: A consecutive series of 33 patients with 49 unstable shoulders presented during a 15-year period. Mean age at the time of the index dislocation was 20 years (range, 9-31). There were 24 patients with 36 anteriorly unstable shoulders, 6 patients with 8 posteriorly unstable shoulders, and 3 patients with 5 multidirectionally unstable shoulders. A large Hill-Sachs lesion was present in 21 shoulders. Glenoid bone loss was seen in 11 cases and involved >25% of the anterior-inferior margin in 6 cases and >50% in 2 cases. Thirty-six shoulders in 31 patients underwent surgery. Ongoing postoperative instability was found in 61% (22 of 36 shoulders) of the anterior group, 38% (3 of 8 shoulders) of the posterior group, and 40% (2 of 5 shoulders) of the multidirectional group. Skeletal reconstruction was found to be associated with a significantly lower rate of recurrence compared with an isolated soft tissue repair (P = .004). Glenohumeral arthrosis was found in 17 patients (22 shoulders) a mean of 12 years (range, 5-20) after the index dislocation. CONCLUSION: The presence of bone loss and degenerative changes are the principal factors affecting the specific surgical strategy employed to treat shoulder instability in patients with epilepsy.

Two cases of sternoclavicular joint replacement arthroplasty: A case report. A novel prosthesis and surgical technique for recalcitrant instability, arthropathy of the sternoclavicular joint with medial clavicular bone loss.

Instability arthropathy of the sternoclavicular joint is most commonly managed by rehabilitation, injection, and either arthroscopic or open debridement with or without interposition arthroplasty. When these options fail to achieve symptom relief, excision arthroplasty is an option. This is associated with a risk of persistent instability and incomplete pain relief. We describe two cases in which custom sternoclavicular joint replacement was performed for painful insufficiency of scapular suspension. Although the prostheses remained secure in both cases, the first case was complicated by persistent instability due to insufficient reconstruction of the intrinsic sternoclavicular capsular ligaments. This was recognised and corrected for in the second case, in which stability of the sternoclavicular joint replacement has been noted on more than a 5-year review. We conclude that sternoclavicular joint replacement is an option for patients in whom instability arthropathy remains an intrusive problem in daily life after other conventional treatments have not controlled symptoms. Stability of the joint remains a concern. We offer one method of achieving stability through an iterative design process including the ability to reconstruct the intrinsic capsular ligaments around the articulation.

Arthroscopic superior capsular reconstruction with dermal allograft for primary and recurrent rotator cuff tears.

Background: The aim of this study was to compare the clinical outcomes and retear rate of arthroscopic superior capsular reconstruction (SCR) with dermal allograft following structural failure of a previous rotator cuff repair, with a cohort of primary SCRs. Methods: This was a retrospective comparative study with a study group comprising 22 patients who were followed up at a minimum of 24 (mean, 41; range, 27-65) months after SCR with dermal allograft performed for structural failure of a previous rotator cuff repair. The control group included 13 patients who previously underwent a primary SCR using dermal allograft and were followed up for 24 months. Clinical outcome measures comprised range of motion, the American Shoulder and Elbow Surgeons score, and the Western Ontario Rotator Cuff (WORC) Index. Radiological outcomes included the acromiohumeral interval and graft integrity on magnetic resonance imaging at one year. Logistic regression was used to determine whether SCR being undertaken as either a primary or revision procedure influenced functional outcomes or retear rate. Results: The mean age at the time of surgery was 58 (range, 39-74) years for the study group and 60 (range, 48-70) years for the control group. Forward flexion improved from a mean of 117° (range, 7°-180°) preoperatively to 140° (range, 45°-170°) postoperatively (P = .11), and external rotation increased from a mean of 31° (range, 0°-70°) preoperatively to 36° (range, 0°-60°) postoperatively (P = .23). The American Shoulder and Elbow Surgeons score improved (P = 0) from a mean of 38 (range, 12-68) to 73 (range, 17-95), and the WORC Index improved (P = 0) from a mean of 29 (range, 7-58) to 59 (range, 30-97). Following SCR, there was no significant change in the acromiohumeral interval. The graft was intact in 42% of cases on magnetic resonance imaging and none of the retears underwent further surgery. Compared to revision SCR, primary SCR resulted in a significant improvement in forward flexion (P = .001), external rotation (P = 0), and WORC Index (P = .019). Logistic regression demonstrated that SCR performed as a revision procedure was associated with a higher retear rate (P = .006) and worse forward flexion (P = .009) and external rotation (P = .008). Conclusion: SCR using human dermal allograft following structural failure of a previous rotator cuff repair can lead to an improvement in clinical outcomes but the results are inferior to primary procedures.

Management of the failed rotator cuff repair.

Rotator cuff repair is increasingly being performed, and this is likely to continue to given the ageing population. An improvement in functional outcome can be achieved, with the best results noted in those tendons that go on to heal. Failure of repair following surgery can be associated with debilitating symptoms that are not always amenable to non-operative measures, so further surgery may be indicated for these patients. Several operative strategies have been described, but careful evaluation is required to determine the most suitable option. This review describes the decision-making strategies and treatment options available during management of a failed rotator cuff repair.

Optimal Management of Partial Thickness Rotator Cuff Tears: Clinical Considerations and Practical Management.

Partial thickness rotator cuff tears have been diagnosed with increased frequency due to heightened awareness and an improvement in diagnostic modalities. When >50% of the tendon thickness has ruptured, intra-tendinous strain of the residual tendon increases. Surgery is generally confined to patients who have failed non-operative measures and have persistent symptoms. The rationale for repairing partial thickness tears lies in their limited self-healing capacity, and propensity to enlarge over time and progress to a full thickness defect. Although tear debridement and acromioplasty can improve pain and function, tear progression can occur, in addition to worse results being noted in bursal-sided defects. Several surgical strategies have been recommended but there is a lack of evidence to advocate one form of treatment over another. The aim of this narrative review is to discuss the treatment options for partial thickness tears of the rotator cuff.

Isolated Bioinductive Arthroscopic Repair of Partial-Thickness Rotator Cuff Tears Using a Resorbable Collagen Implant.

Over 300,000 rotator cuff repairs are performed annually in the United States, where the annual financial burden of managing shoulder pain has been estimated to be $3 billion. Despite advances in surgical techniques, retear rates range from 39% to 94%4. Partial-thickness tears are approximately twice as common as full-thickness tears and can lead to considerable pain and loss of function. Although some partial-thickness tears can be treated nonoperatively, spontaneous healing is unlikely when >50% of the bursal/articular-sided tendon thickness is involved, and thus nonoperative treatment would be unsuccessful1-4. Regeneten (Smith & Nephew) is a bioinductive type-1 collagen implant that can be utilized to repair a partial-thickness rotator cuff tear without formal tendon-bone reattachment. Because this implant does not require tendon-bone reattachment, treatment does not typically entail prolonged rehabilitation. At 2 years postoperatively, this implant has been shown to significantly improve functional outcomes and tendon thickness without any serious adverse events4. Description: A diagnostic arthroscopy is performed via a posterior viewing portal, paying particular attention to the insertion of the posterosuperior rotator cuff onto the humeral head. The subacromial space is entered posteriorly and visualized. With use of electrocautery through a lateral portal, all soft tissue is cleared from the undersurface of the acromion and from the superficial rotator cuff. The coracoacromial ligament is released from the underside of the acromion, and an acromioplasty is performed if indicated. The partial-thickness rotator cuff tear is visualized and examined for tissue quality, tear area, and residual tendon thickness. The size of the tear is measured, and an appropriate implant size is chosen. The lateral portal is enlarged so that the graft can be inserted and unfolded with use of a specialized delivery guide. The implant is centered over the tear, ensuring that it covers as much of the lateral footprint as possible. To complete the procedure, the implant is secured to the tendon with use of soft-tissue staples and to the lateral osseous footprint with use of bone staples. Alternatives: First-line treatment is often nonoperative and entails activity modification, pharmacological therapies, and targeted physiotherapy directed toward strengthening parascapular muscles and the remaining rotator cuff. Surgical treatment is considered for persistent symptoms. Conventional operative strategies include subacromial decompression, rotator cuff debridement, in situ repair, and conversion to a full-thickness defect and repair. Rationale: Partial-thickness tears substantially increase intratendinous strain. This increased strain leads to further tissue degeneration and tear enlargement5, likely influencing the high rate of tear propagation observed with nonoperative treatment and nonanatomic operative treatment, such as subacromial decompression. Isolated bioinductive repair of partial-thickness tears with use of a resorbable collagen implant does not involve tendon excision or repair of the tendon to the bone, which can sometimes be challenging. This technique offers a simple solution to a complex problem and has the benefit of an accelerated rehabilitation program compared with formal rotator cuff repair. Accordingly, patient satisfaction with the procedure is high, making this treatment an appealing option4. Expected Outcomes: Short and midterm results following isolated bioinductive repair of partial-thickness tears demonstrate that it is a safe procedure associated with a reduction in pain, increased range of motion, and improvement in functional outcomes. Patients should be counselled regarding the safety of a resorbable collagen patch and its potential to promote healing and improve symptoms4-6. Important Tips: If the tear is articular, it should be marked with a needle so that the graft can be centered over the tear within the subacromial space.When positioning the implant, ensure that it covers the defect and the lateral footprint.Position the cannulas so that they allow the staples to enter the tissue perpendicular to the tendon and osseous footprint.To prevent tearing of the patch, do not depress the staples with excessive force. Acronyms and Abbreviations: MRI = magnetic resonance imagingPEEK = polyetheretherketoneVAS = visual analogue scaleASES = American Shoulder and Elbow Surgeons Shoulder Score.

Arthroscopic revision rotator cuff repair of large and massive retears using an interpositional bridging dermal allograft.

Background: The purpose of this study was to report the clinical outcomes and retear rate following arthroscopic interpositional bridging dermal allograft for revision rotator cuff repair of large and massive retears. Methods: Twenty-three patients were retrospectively reviewed at a minimum follow-up of 24 (mean, 47; range, 24-77) months after revision rotator cuff repair using an interpositional bridging dermal allograft. There were 17 males and 6 females with a mean age of 56 (range, 40-74) years. Clinical outcomes were assessed using range of motion, the American Shoulder and Elbow Surgeons score and Western Ontario Rotator Cuff Index. Graft integrity was assessed at 12-months using magnetic resonance imaging. Results: The interval between the primary rotator cuff repair and interpositional bridging graft was a mean of 82 (range, 7-192) months. Forward flexion improved from a mean of 145° (range, 60-180°) preoperatively to 152° (range, 135-170°) postoperatively (P = .3561). There was a decrease in external rotation from a mean of 50° (range, 20-80°) preoperatively to 37° (range, 0-45°) postoperatively (P = .0021). The American Shoulder and Elbow Surgeons score improved (P = .0196) from a mean of 50 (range, 10-88) to 69 (range, 22-97), and the Western Ontario Rotator Cuff index improved (P = .0008) from a mean of 34 (range, 3-90) to 57 (range, 14-93). The graft was intact in 39% of patients. No patients underwent further surgery. Conclusion: Interpositional bridging grafting for revision rotator cuff repair of large and massive retears leads to a significant improvement in functional outcome but is associated with a high retear rate.

Arthroscopic Anterior Glenoid Reconstruction Using a Distal Tibial Allograft Positioned With an Intra-Articular Guide and Secured With Double-Button Fixation.

Recurrent shoulder instability and its role in bone loss from the anterior glenoid is well recognized throughout the literature. This technique paper presents an all-arthroscopic technique that uses distal tibial allograft and double-button suture fixation to address anterior recurrent shoulder instability. With the patient in the lateral decubitus position, we use the posterior portal to position the double-barrel drill guide tangential to the face of the glenoid, while viewing through the anterosuperolateral portal. We then use the "bullets," which are made through two percutaneous posterior skin incisions of the double-barreled drill. This guide ensures parallel drill tunnels are created 5 mm medial to the glenoid articular surface and 1 cm apart, minimizing risk to the suprascapular nerve caused by a straying medial. We prepare a bone block from allograft distal tibia and place two drill holes to match those drilled in the glenoid vault. The allograft is then shuttled arthroscopically using looped passing wires. Once the final position is confirmed, a tensiometer is used to tension the graft in place. We then reattach the labrum to the native glenoid rim. Our technique creates a reproducible, anatomic, glenoid surface reconstruction for anterior glenoid bone loss in recurrent instability.

Day case shoulder arthroplasty: needed now more than ever.

The demand for total shoulder arthroplasty has grown over the years and is set to continue in a similar trend because of the ageing population. Following a global reduction in elective orthopaedic treatment and an exponential rise in surgical waiting times, innovative strategies are desperately needed to mitigate against the harmful effects of delaying vital operations on both patients and the wider society. Day case shoulder arthroplasty is a safe alternative to a traditional inpatient approach, with evidence supporting substantial cost savings, improved outcomes and fewer complications. Rigorous patient selection and a multidisciplinary team approach are paramount when adopting a day case service to deliver joint replacement surgery. This review outlines the principles of day case total shoulder arthroplasty and highlights key considerations when transitioning to this approach.

Arthroscopic Compaction Bone Grafting for Uncontained Bone Defects of the Greater Tuberosity Associated With a Rotator Cuff Retear.

Revision rotator cuff repair is a technically demanding procedure that can be complicated by the presence of large peri-implant cysts. When multiple suture anchors are encountered, massive bone defects may need to be addressed to ensure that tendon-bone fixation and healing can be optimized. This Technical Note discusses arthroscopic compaction bone grafting for massive uncontained bone defects of the greater tuberosity associated with revision rotator cuff repair.

Protocol for a Retrospective Comparative Study to Determine the Effect of Two Different Biocomposite Suture Anchors on the Occurrence of Bony Ingrowth and Implant Reabsorption Following Arthroscopic Rotator Cuff Repair.

INTRODUCTION: Surgical treatment of rotator cuff tears commonly entails reattachment of the ruptured tendon to its bony insertion using suture anchors. Suture anchor design has evolved from solid metal anchors to vented biocomposite anchors with potentially biologic consequences. Few studies have investigated the differences between different modern anchor design and materials, making it difficult to justify their use or cost. OBJECTIVE: To compare the rate of bony ingrowth and implant resorption between a coil-type open-architecture biocomposite suture anchor and a vented screw-type biocomposite suture anchor, used for arthroscopic double-row rotator cuff repair. METHODS AND ANALYSIS: In this retrospective comparative study, a consecutive series of patients who undergo a double row rotator cuff repair using a coil-type open architecture biocomposite suture anchor in the medial row and a vented screw-type biocomposite suture anchor in the lateral row will be included. A sample size calculation demonstrated that 16 participants are required in each group. Primary outcome measures will be bony ingrowth and reabsorption of the suture anchor as measured on computed tomography (CT). Secondary outcomes will include patient reported outcome measures (The American Shoulder and Elbow Surgeons score and The Western Ontario Rotator Cuff questionnaire), range of motion, postoperative tendon integrity, and cyst formation. HIGHLIGHTS: Open-architecture suture anchors facilitate the release of marrow constituents.The rate of bony ingrowth for coil- and screw-type anchors will be assessed.The difference in functional outcome between the two anchors will be assessed.

Rotator cuff repair techniques: Current concepts.

Arthroscopic rotator cuff repair is being performed by an ever-increasing number of surgeons. With an ageing population and growing patient expectations it is crucial that clinical outcomes are optimised. Anatomical reduction of the tendon back to its footprint with minimal tension contributes to this, but this can only be achieved if key biomechanical factors are taken into consideration. In this review of the technical aspects of a rotator cuff repair, we focus on: (1) patient positioning, (2) biomechanical principles, (3) optimal visualisation, and (4) repair techniques for both anterior and postero-superior tears.

Characterisation of the tensile properties of Demineralised Cortical Bone when used as an anterior cruciate ligament allograft.

BACKGROUND: Graft choice in anterior cruciate ligament (ACL) reconstruction remains controversial and some grafts fail due to inadequate osteointegration. Demineralised cortical bone (DCB) is an osteoinductive collagen-based scaffold. The aim of this study was to measure the tensile properties of DCB from different locations and from different ages, and determine its compatibility with current ACL fixation systems. METHODS: The tensile properties of DCB manufactured from femur and tibia of young (9 month) and old (2-3 years) sheep was measured to determine the most appropriate graft choice. The ultimate load and stiffness of DCB allograft using two fixation systems, interference screws and sutures tied around screw posts, was measured ex vivo in an ovine ACL reconstruction model. Comparison was made with superficial digital flexor tendon (SDFT) and ovine ACL. RESULTS: DCB derived from young tibia had the highest ultimate load and stiffness of 67.7 ± 10.6 N and 130.2 ± 64.3 N/mm respectively. No DCB fixation system reached the published peak in vivo force through the ovine ACL of 150 N. SDFT fixation with interference screws (308.2 ± 87.3 N) did reach the in vivo threshold but was significantly weaker than ovine ACL (871.0 ± 64.2 N). CONCLUSION: The tensile properties of DCB were influenced by the donor age and bone. Owing to inferior tensile properties and incompatibility with suspensory fixation devices, this study indicates DCB is inferior to current tendon grafts options for ACL reconstruction.

The biomechanics of proximal humeral fractures: Injury mechanism and cortical morphology.

BACKGROUND: The aim of this study was to examine the effect of arm position on proximal humerus fracture configuration and to determine whether cortical thinning would predispose to fracture propagation and more complex patterns of injury. METHODS: A drop test rig was designed to simulate falls onto an outstretched arm ('parachute reflex'). Thirty-one cadaveric specimens underwent computer tomography scanning and cortical thicknesses mapping. Humeri were fractured according to one of the two injury mechanisms and filmed using a high-speed camera. Anatomical descriptions of the injuries were made. Areas of thinning were measured and correlated with zones of fracture propagation. RESULTS: Direct impact simulation resulted in undisplaced humeral head split fractures in 53% of cases, with the remainder involving disruption to the articular margin and valgus impaction. Alternatively, the 'parachute reflex' predominantly produced shield-type injuries (38%) and displaced greater tuberosity fractures (19%). A strong correlation was demonstrated between cortical thinning and the occurrence of fracture (odds ratio = 7.766, 95% confidence interval from 4.760 to 12.669, p<0.0001). CONCLUSION: This study has shown that arm position during a fall influences fracture configuration of the proximal humerus. Correlating fracture pattern and mechanism of injury will allow more appropriate fracture reduction techniques to be devised.