Bone block augmentation from the iliac crest for treatment of deep osteochondral defects of the knee resembles biomechanical properties of the subchondral bone.

PURPOSE: Bone block augmentation from the iliac crest can be used for reconstruction of the osteochondral unit to restore the underlying subchondral bone upon restoration of the cartilaginous layer via matrix-induced chondrocyte transplantation. To critically understand the successful restoration of the defect, biomechanical and histological analysis of the implanted bone blocks is required. The aim of the study was to analyse the ability of the bone block technique to restore huge bone defects by mimicking the physiological subchondral zone. METHODS: The experiments were performed using lateral femoral condyles and iliac crest bone grafts from the same cadavers (n = 6) preserved using the Thiel method. CT scans were made to evaluate bone pathology. Bone mineral density of all specimens was evaluated in the femoral head prior to testing. A series of tests were conducted for each pair of specimens. A static compression test was performed using an electro dynamic testing machine with maximal strength and failure behavior analyzed. Biomechanical tests were performed in the medial-lateral direction for iliac crest and for femoral condyles with and without removal of the cartilage layer. Histological analysis was performed on decalcified specimens for comparison of the condyle at lesion site and the graft. RESULTS: No significant difference in failure load could be found for iliac crest (53.3-180.5 N) and femoral condyle samples upon cartilage removal (38.5-175.1 N) (n.s.). The femoral condyles with an intact cartilage layer showed significantly higher loads (118.3-260.4N) compared to the other groups indicating that native or regenerated cartilage can further increase the failure load (p < 0.05). Bone mineral density significantly influenced failure load in all study groups (p < 0.05). Histological similarity of the cancellous bone in the femoral condyle and in the iliac crest was observed. However, within the subchondral zone, there was a higher density of sponge like organized trabeculae in the bone samples from the iliac crest. Tide mark was only detected at the osteochondral interface in femoral condyles. CONCLUSION: This study demonstrated that, bone blocks derived from the iliac crest allow a biomechanical appropriate and stable restoration of huge bony defects by resembling the subchondral zone of the femoral condyle. Therefore, bone augmentation from the iliac crest combined with matrix-induced autologous chondrocyte transplantation seems to be a reasonable method to treat these challenging injuries.

The nerve supply of zygomaticus major: Variability and distinguishing zygomatic from buccal facial nerve branches.

The zygomaticus major (ZM) is important for the human smile. There are conflicting data about whether the zygomatic or buccal branches of the facial nerve are responsible for its motor innervation. The literature provides no precise distinction of the transition zone between these two branch systems. In this study, a definition to distinguish the facial nerve branches at the level of the body of the zygoma is proposed. In the light of this definition, we conducted an anatomical study to determine how the source of innervation of the ZM was distributed. A total of 96 fresh-frozen cadaveric facial halves were dissected under loupe magnification. A hemiparotidectomy was followed by antegrade microsurgical dissection. Any branch topographically lying superficial to the zygoma or touching it was classed as zygomatic, and any neighboring inferior branch was considered buccal. The arborization of the facial nerve was diffuse in all cases. In 64 out of 96 specimens (67%, 95% CI: 56% to 76%), zygomatic branches innervated the ZM. Buccal branches innervated ZM in the other 32 facial halves (33%, 95% CI: 24% to 44%). There were no differences in respect of sex or facial side. All facial halves displayed additional branches, which crossed the muscle on its inner surface without supplying it. In 31 specimens, a nerve branch ran superficial to ZM in its cranial third. According to our classification, the zygomaticus major is innervated by zygomatic branches in 67% of cases and by buccal branches in 33%. Clin. Anat. 31:560-565, 2018. © 2018 Wiley Periodicals, Inc.

Proximal Femoral Fractures and Anticoagulation Therapy - When Is Surgery Safe?

Patients presenting with proximal femur fractures are at high risk of developing DVT and pulmonary embolism. Many of these patients suffer from additional anticoagulant treatment. Patients on anticoagulation treatment are complex to manage, especially regarding timing of surgery due to implemented quality control recommendations. The present review analyses the present data timing of surgery and perioperative surgical considerations on anticoagulation treatment in this patients group.

Standard Approaches to the Acetabulum Part 1: Kocher-Langenbeck Approach.

Historically, standard approaches for surgical treatment of displaced acetabular fractures were the KocherLangenbeck approach, the ilioinguinal approach and the extended iliofemoral approach (12). Presently, several modifications of these approaches are accepted alternatives, especially anterior modifications based on the intrapelvic approach described by Hirvensalo (8). Single access approaches allowing visualization of one acetabular column are the posterior Kocher-Langenbeck approach and the anterior ilioinguinal approach (12) and the use of a single approach is favoured (9, 24). For more complex situations, in the 80s and 90s extended approaches (extended iliofemoral approach according to Letournel (12), its modification to Reinert (19) (Baltimore approach), and the Triradiate approach according to Mears (14)) were introduced. These approaches are presently rarely choosen due to the extensive soft tissue dissection and higher complication rates (28). Alternatively, the combination of an anterior and posterior standard approach was recommended (7, 21, 22) having the disadvantage of longer operating time and blood loss and showed no superior results compared to a single approach. The meta-analysis by Giannoudis et al. stated that 48,7% of patients were treated using the Kocher-Langenbeck approach, followed by 21,9% ilioinguinal approaches and 12,4% extended approaches (6). More recent data from the years 2005-2007, showed that anterior approaches are now predominantly used according to a higher number of acetabular fractures with anterior column involvement. Overall, more than 40% of all patients with acetabular fractures are still approached via the Kocher-Langenbeck approach (18). Therefore, the Kocher-Langenbeck approach is still a "working horse" in approaching displaced acetabular fractures. The Kocher-Langenbeck approach consists of two parts. In 1874 von Langenbeck described a longitudinal incision starting from above the greater sciatic notch to the greater trochanter, dissecting the gluteal muscles for treating hip joint infections (11). Theodor Kocher in 1911 described a curved incision starting from the posterior-inferior corner of the greater trochanter, running across the postero-superior tip of the greater trochanter passing oblique in line with the fibres of the gluteus maximus muscle in direction to the posterior superior iliac spine (10). The aim of the present analysis is the detailed anatomi - cal analysis of this standard approach, focusing on fracture indication, positioning of the patient, exposure, dissection, reduction techniques of special fracture types, approach modifications/extensions, complications and approach-specific results.

Standard Approaches to the Acetabulum Part 2: Ilioinguinal Approach.

The ilioinguinal approach is one of the standard approaches in the treatment of displaced acetabular fractures used during the last decades (9). The meta-analysis of Giannoudis et al. showed that 21.9% of acetabular fractures were historically treated using this approach (3). One of the disadvantages of this study was, that studies focussing especially on posterior wall stabilization and studies dealing with more complex fracture types treated by extended approaches were integrated. Thus, these fracture types were overrepresented. Re-analysis excluding these data lead to an increase of the rate of anterior approaches to 25.9%. More recent data (years 2005-2007) from the German multicenter study showed that presently in almost 45% of the cases the single ilioinguinal approach was used and only 38% of patients were stabilized via the KocherLangenbeck approach (11). Historically, the Smith-Peterson approach (15, 17) and the iliofemoral approach were used to treat acetabular fractures. In the 60ies, based on the work by Letournel and Judet, the ilioinguinal approach was developed for acetabular fracture fixation (9). It is an extrapelvic approach resulting in an indirect reconstruction concept of the acetabulum without direct visualization of the articular acetabulum. The ilioinguinal approach was the standard anterior approach during the last 30-40 years. An important advantage is the reduced soft tissue detachment of periarticular muscles with only a small risk of developing heterotopic bone formation. The aim of the second part of "Standard approaches to the acetabulum" is to report on the special topics indication, positioning, exposure, incision, dissection, the anatomical basis of osteosynthesis and present results using ilioinguinal approach.

Standard Approaches to the Acetabulum Part 3: Intrapelvic Approach.

Introduction The intrapelvic approach was originally described by Hirvensalo et al. from Finland in the early 90ies (8) and a further comparable description was published shortly thereafter by Cole et al. (5). Since then, various modifications have been described. Whereas the ilioinguinal approach was used until then to treat acetabular fractures with relevant anterior column involvement from an extrapelvic view, the intrapelvic approach was developed to address the often accompanied central hip dislocation in these fracture types with relevant fractures of the quadrilateral surface. With this approach a complete different view to the antero-medial acetabular pathology was possible. The view from more medial allows a better direct access to joint structures "below" the pelvic brim in the true pelvis (intrapelvic) in contrast to the extrapelvic access with the ilioinguibnal approach. Meanwhile, the surgical technique has been described in detail and some modifications and tricks have been published (5, 8, 10, 13, 19). The intrapelvic approach offers several advantages compared to the ilioinguinal approach: • lower invasiveness without substantial muscle detachment, • direct view of the superior pubic rami from superior and medial, the inferior anterior column and the quadrilateral surface up to the posterior border of the posterior column at the greater sciatic notch, • reduction and fixation of the anterior column and the quadrilateral surface under direct visualization, • reduction of antero-superior marginal impactions under direct visualization, • low risk of heterotopic ossification, • low risk of lesions to the lateral cutaneous femoral nerve. The aim of the third part of "standard approaches of the acetabulum" is to report on the special topics indication, positioning, exposure, incision, dissection, the anatomical basis of osteosynthesis and present results using the via the intrapelvic approach.

Minimal Invasive Dorsal Plate Osteosynthesis of the Tibia--Are Nerves and Vessels at Risk? An Anatomical Study.

PURPOSE OF THE STUDY: Purpose of this anatomic study was to develop a new and safe technique of minimal invasive dorsal plate osteosynthesis for tibia shaft fractures. MATERIAL AND METHODS: Sixteen paired adult lower limbs of eight different cadaveric specimens were examined. Anatomical prebending for each plate was done. Plates were inserted percutaneously, following plate fixation the neurovascular bundle was dissected out. The distance between the neurovascular bundle (posterior tibial nerve, posterior tibial artery) and the plate was measured at two different positions. The distance to the origin of the flexor digitorum longus muscle and the arch of the soleus muscle was measured. RESULTS: The mean distance between the neurovascular bundle and the plate amounted 1.4 cm (±0,2 cm; 1.0-1.7 cm) at hole number six and 1.1 cm (±0.4 cm; 0.6-2.0 cm) at hole number ten. The nerve was never directly in contact with the plate. The flexor digitorum longus muscle had its origin along the plate and was between the plate and the neurovascular bundle in all cases. CONCLUSIONS: Dorsal percutaneous plate insertion is a safe and easy method for osteosyntesis of tiba shaft fractures. Especially in case of poor skin and soft tissue conditions this technique offers a good alternative.

The risk of neurovascular injury in minimally invasive plate osteosynthesis (MIPO) when using a distal tibia anterolateral plate: a cadaver study.

PURPOSE OF THE STUDY: Percutaneous plating of the distal tibia via a limited incision is an accepted technique of osteosynthesis for extra-articular and simple intra-articular distal tibia fractures. The aim of this study was to analyze structures that are at risk during this approach. MATERIAL AND METHODS: Thirteen unpaired adult lower limbs were used for this study. Thirteen, 15-hole LCP anterolateral distal tibial plates were percutaneously inserted according to the recommended technique. Dissection was performed to examine the relation of the superficial and deep peroneal nerves and anterior tibial artery relative to the plate. RESULTS: The superficial peroneal nerve was found to cross the vertical limb of the LCP plate at a mean distance of 63 mm (screw hole five) but with a wide range of 21 to 105 mm. The neurovascular bundle (deep peroneal nerve and anterior tibial artery) crossed the plate at a mean of 76 mm (screw hole six) but also with a wide range of 38 to 138 mm. The zone of danger of the neurovascular structures ranges from 21 to 138 mm from the tibial plafond. In one specimen, a significant branch of the deep peroneal nerve was found to be entrapped under the plate. CONCLUSION: Caution is advised when using anterolateral minimally invasive technique for plate insertion and screw placement in the distal tibia due to great variability in the neurovascular structures that course distally in the lower leg and cross the ankle.

Minimal invasive plating of distal radius fractures. A safe procedure?

BACKGROUND: Minimal invasive plate osteosynthesis (MIPO) with preservation of the pronator quadratus (PQ) muscle represents a new technique for stabilization of distal radius fractures. However, the complex anatomy of the distal radius metaphysis requires implants with features that address all morphologic specifics of this area to avoid complications, which are still reported with this technique. It was the aim of our anatomic investigation to evaluate the feasibility of plate insertion via a minimal transverse approach as well as the risk of soft- tissues compromise with the use of an implant, which is only partially adapted to the characteristics of distal radius metaphysis. METHODS: Twenty forearm specimens, conservated with Thiels method, have been used for this study. The majority (n = 19/20) of implants (2.4 mm small fragment juxta-articular locking compression/ LCP T-plate -5-hole; Depuy - Synthes®, Solothurn, Switzerland) could be inserted easily and all were seated proximal to the so called "watershed line" (n = 20/20). RESULTS: In a total of 8/20 specimens close contacts or potential compromise to neighboring soft- tissues was seen: perforation of the PQ muscle by the plate occurred in 2/20 specimens and was related to an extreme muscle morphology. In 7/20 specimens close contacts between the T-plate and other soft tissues were observed, which were exclusively located at the radial edge of the distal transverse bar. They affected the brachio-radialis tendon (elevation: 2/20, side-to-side contact: 3/20, overriding: 1/20) and the radial artery (elevation: 4/20, side-to-side contact: 2/20, overriding: 1/20). No significant differences of morphologic types of PQ muscle and the difficulty of plate insertion, adjustment on the bone, PQ muscle damage and contact to neighboring soft-tissues could be evaluated. CONCLUSIONS: Insertion of volar radius plates through a MIPO approach can be easily accomplished without detachment and damage to the PQ muscle even with grossly adapted implants. However, perfectly pre-shaped plates which are adapted to all anatomic aspects of the distal radius metaphysis are required to achieve optimal contact with the metaphyseal bone and to avoid potential complications.

Frequency of successful intra-articular puncture of finger joints: influence of puncture position and physician experience.

OBJECTIVE: Physicians and specialists routinely perform IA punctures and injections on patients with joint injuries, chronic arthritis and arthrosis to release joint effusion or to inject drugs. The purpose of this study was to investigate the frequencies of intra- and peri-articular cannula positioning during this procedure. METHODS: A total of 300 cadaveric finger joints were injected with a methyl blue-containing solution and subsequently dissected to distinguish intra- from peri-articular injections. To assess the influence of puncture position on successful injection, half of the joints were injected dorsally and the other half dorso-radially. To assess the importance of practical experience for a positive outcome, half of the injections were performed by an inexperienced resident and half by a skilled specialist. RESULTS: The overall frequency of occurrence of peri-articular injections was much higher than expected (overall: 23%, specialist: 15%, resident: 32%) The failure rate was significantly higher than the average with the joints of the little finger and the DIP joints of each phalanx. CONCLUSIONS: Even skilled specialists cannot guarantee to insert the cannula into the joint in every case. Unintended peri-articular drug injection moreover may affect the surrounding ligaments or tendons, leading to serious complications. Correct positioning of the needle in the joint may be facilitated by fluoroscopy in doubtful cases.

Biomechanical evaluation of a new gliding screw concept for the fixation of proximal humeral fractures.

AIMS: Plating displaced proximal humeral fractures is associated with a high rate of screw perforation. Dynamization of the proximal screws might prevent these complications. The aim of this study was to develop and evaluate a new gliding screw concept for plating proximal humeral fractures biomechanically. METHODS: Eight pairs of three-part humeral fractures were randomly assigned for pairwise instrumentation using either a prototype gliding plate or a standard PHILOS plate, and four pairs were fixed using the gliding plate with bone cement augmentation of its proximal screws. The specimens were cyclically tested under progressively increasing loading until perforation of a screw. Telescoping of a screw, varus tilting and screw migration were recorded using optical motion tracking. RESULTS: Mean initial stiffness (N/mm) was 581.3 (sd 239.7) for the gliding plate, 631.5 (sd 160.0) for the PHILOS and 440.2 (sd 97.6) for the gliding augmented plate without significant differences between the groups (p = 0.11). Mean varus tilting (°) after 7500 cycles was comparable between the gliding plate (2.6; sd 1.9), PHILOS (1.2; sd 0.6) and gliding augmented plate (1.7; sd 0.9) (p = 0.10). Similarly, mean screw migration(mm) after 7500 cycles was similar between the gliding plate (3.02; sd 2.85), PHILOS (1.30; sd 0.44) and gliding augmented plate (2.83; sd 1.18) (p = 0.13). Mean number of cycles until failure with 5° varus tilting were 12702 (sd 3687) for the gliding plate, 13948 (sd 1295) for PHILOS and 13189 (sd 2647) for the gliding augmented plate without significant differences between the groups (p = 0.66). CONCLUSION: Biomechanically, plate fixation using a new gliding screw technology did not show considerable advantages in comparison with fixation using a standard PHILOS plate. Based on the finding of telescoping of screws, however, it may represent a valid approach for further investigations into how to avoid the cut-out of screws.Cite this article: Y. P. Acklin, I. Zderic, J. A. Inzana, S. Grechenig, R. Schwyn, R. G. Richards, B. Gueorguiev. Biomechanical evaluation of a new gliding screw concept for the fixation of proximal humeral fractures. Bone Joint Res 2018;7:422-429. DOI: 10.1302/2046-3758.76.BJR-2017-0356.R1.

Are two retrograde 3.5 mm screws superior to one 7.3 mm screw for anterior pelvic ring fixation in bones with low bone mineral density?

OBJECTIVES: Osteosynthesis of anterior pubic ramus fractures using one large-diameter screw can be challenging in terms of both surgical procedure and fixation stability. Small-fragment screws have the advantage of following the pelvic cortex and being more flexible.The aim of the present study was to biomechanically compare retrograde intramedullary fixation of the superior pubic ramus using either one large- or two small-diameter screws. MATERIALS AND METHODS: A total of 12 human cadaveric hemipelvises were analysed in a matched pair study design. Bone mineral density of the specimens was 68 mgHA/cm3 (standard deviation (sd) 52). The anterior pelvic ring fracture was fixed with either one 7.3 mm cannulated screw (Group 1) or two 3.5 mm pelvic cortex screws (Group 2). Progressively increasing cyclic axial loading was applied through the acetabulum. Relative movements in terms of interfragmentary displacement and gap angle at the fracture site were evaluated by means of optical movement tracking. The Wilcoxon signed-rank test was applied to identify significant differences between the groups RESULTS: Initial axial construct stiffness was not significantly different between the groups (p = 0.463). Interfragmentary displacement and gap angle at the fracture site were also not statistically significantly different between the groups throughout the evaluated cycles (p ⩾ 0.249). Similarly, cycles to failure were not statistically different between Group 1 (8438, sd 6968) and Group 2 (10 213, sd 10 334), p = 0.379. Failure mode in both groups was characterised by screw cutting through the cancellous bone. CONCLUSION: From a biomechanical point of view, pubic ramus stabilisation with either one large or two small fragment screw osteosynthesis is comparable in osteoporotic bone. However, the two-screw fixation technique is less demanding as the smaller screws deflect at the cortical margins.Cite this article: Y. P. Acklin, I. Zderic, S. Grechenig, R. G. Richards, P. Schmitz, B. Gueorguiev. Are two retrograde 3.5 mm screws superior to one 7.3 mm screw for anterior pelvic ring fixation in bones with low bone mineral density? Bone Joint Res 2017;6:8-13. DOI: 10.1302/2046-3758.61.BJR-2016-0261.

[Complication management for failed bone fracture healing: pseudarthrosis]. / Komplikationsmanagement bei fehlender Knochenbruchheilung: Pseudarthrosen.

Delayed fracture healing for more than 6-8 months is defined as non-union (pseudarthrosis). Non-unions are classifiable as septic, aseptic, hypertrophic and atrophic non-unions. In case of septic non-unions the infection is treated primarily followed by treatment of the delayed fracture healing. Aseptic non-unions may be treated non-operatively (e.g. shock wave therapy and/or ultrasound) or by various surgical strategies to stimulate bone regeneration and healing.

[The distal radius and surrounding soft tissues--ultrasound anatomy and ultrasound pathology in the adult and child]. / Der distale Radius und seine umgebenden Weichteile--Sonoanatomie und Sonopathologie beim Erwachsenen und beim Kind.

BACKGROUND: The aim of the study was to evaluate the ultrasonographic anatomy of the distal forearm (i.e. distal radius and surrounding soft tissue) and the typical changes occurring during growth, in adults and children. MATERIAL AND METHODS: The ultrasonographic anatomy was evaluated in 10 healthy adults aged between 20 and 60 years, and 20 healthy children aged between 2 and 18 years. Particular attention was paid to dynamic examination comparing both limbs, and isolated investigations of functional tendon. RESULTS: An anatomical description of the tissues of the distal forearm was possible at all ages. During growth, secondary ossification centres and the transitional osteochondral region of the growth plate need particular consideration. DISCUSSION AND CONCLUSION: Both in children and adults, ultrasonography can provide valuable information in the evaluation of acute trauma, follow-up of fractures and osteosynthesis, suspected osteomyelitis and chronic disorders. In children, special attention must be paid to the development of the epiphyseal region, as reflected by ossification centre, growth plate and articular cartilage.

Screw fixation of medial malleolar fractures: a cadaveric biomechanical study challenging the current AO philosophy.

The AO Foundation advocates the use of partially threaded lag screws in the fixation of fractures of the medial malleolus. However, their threads often bypass the radiodense physeal scar of the distal tibia, possibly failing to obtain more secure purchase and better compression of the fracture. We therefore hypothesised that the partially threaded screws commonly used to fix a medial malleolar fracture often provide suboptimal compression as a result of bypassing the physeal scar, and proposed that better compression of the fracture may be achieved with shorter partially threaded screws or fully threaded screws whose threads engage the physeal scar. We analysed compression at the fracture site in human cadaver medial malleoli treated with either 30 mm or 45 mm long partially threaded screws or 45 mm fully threaded screws. The median compression at the fracture site achieved with 30 mm partially threaded screws (0.95 kg/cm(2) (interquartile range (IQR) 0.8 to 1.2) and 45 mm fully threaded screws (1.0 kg/cm(2) (IQR 0.7 to 2.8)) was significantly higher than that achieved with 45 mm partially threaded screws (0.6 kg/cm(2) (IQR 0.2 to 0.9)) (p = 0.04 and p < 0.001, respectively). The fully threaded screws and the 30mm partially threaded screws were seen to engage the physeal scar under an image intensifier in each case. The results support the use of 30 mm partially threaded or 45 mm fully threaded screws that engage the physeal scar rather than longer partially threaded screws that do not. A 45 mm fully threaded screw may in practice offer additional benefit over 30 mm partially threaded screws in increasing the thread count in the denser paraphyseal region.

Does the anteromedial or anterolateral approach alter the rate of joint puncture in injection of the ankle?: A cadaver study.

Injection or aspiration of the ankle may be performed through either an anteromedial or an anterolateral approach for diagnostic or therapeutic reasons. We evaluated the success of an intra-articular puncture in relation to its site in 76 ankles from 38 cadavers. Two orthopaedic surgical trainees each injected methylene blue dye into 18 of 38 ankles through an anterolateral approach and into 20 of 38 through an anteromedial. An arthrotomy was then performed to confirm the placement of the dye within the joint. Of the anteromedial injections 31 of 40 (77.5%, 95% confidence interval (CI) 64.6 to 90.4) were successful as were 31 of 36 (86.1%, 95% CI 74.8 to 97.4) anterolateral injections. In total 62 of 76 (81.6%, 95% CI 72.9 to 90.3) of the injections were intra-articular with a trend towards greater accuracy with the anterolateral approach, but this difference was not statistically significant (p = 0.25). In the case of trainee A, 16 of 20 anteromedial injections and 14 of 18 anterolateral punctures were intra-articular. Trainee B made successful intra-articular punctures in 15 of 20 anteromedial and 17 of 18 anterolateral approaches. There was no significant difference between them (p = 0.5 and p = 0.16 for the anteromedial and anterolateral approaches, respectively). These results were similar to those of other reported studies. Unintended peri-articular injection can cause complications and an unsuccessful aspiration can delay diagnosis. Placement of the needle may be aided by the use of ultrasonographic scanning or fluoroscopy which may be required in certain instances.

[The dorsal approach to the radiocarpal joint: an anatomic variant and its clinical implications]. / Der dorsale Zugang zum Handgelenk: Fallbericht über eine anatomische Variante und Diskussion der relevanten Literatur.

The extensor carpi radialis longus tendon and the extensor carpi radialis brevis tendon are important landmarks for the dorsoradial approach to the wrist. This case report presents an anatomic variant: both tendons are divided into two different reins. Knowledge about this anatomic variant is of importance in order to avoid misinterpretations.

Intra-articular injection of the acromioclavicular joint.

Intra-articular punctures and injections are performed routinely on patients with injuries to and chronic diseases of joints, to release an effusion or haemarthrosis, or to inject drugs. The purpose of this study was to investigate the accuracy of placement of the needle during this procedure. A total of 76 cadaver acromioclavicular joints were injected with a solution containing methyl blue and subsequently dissected to distinguish intra- from peri-articular injection. In order to assess the importance of experience in achieving accurate placement, half of the injections were performed by an inexperienced resident and half by a skilled specialist. The specialist injected a further 20 cadaver acromioclavicular joints with the aid of an image intensifier. The overall frequency of peri-articular injection was much higher than expected at 43% (33 of 76) overall, with 42% (16 of 38) by the specialist and 45% (17 of 38) by the resident. The specialist entered the joint in all 20 cases when using the image intensifier. Correct positioning of the needle in the joint should be facilitated by fluoroscopy, thereby guaranteeing an intra-articular injection.