Joint registries report that 25–40% of UKR revisions are performed for pain. Proximal tibial strain and microdamage are possible causes of this “unexplained” pain. The aim of this study was to examine the effect of UKR implant design and material on proximal tibial cortical strain and cancellous microdamage.

Composite Sawbone tibias were implanted with cemented UKR components: 5 fixed bearing all-polyethylene (FB-AP), 5 fixed bearing metal backed (FB-MB), and 5 mobile bearing metal backed implants (MB-MB). Five intact tibias were used as controls. Tibias were loaded in 500N increments to 2500N. Cortical surface strain was measured using digital image correlation (DIC). Cancellous microdamage was measured using acoustic emission (AE), a technique which detects elastic waves produced by the rapid release of energy during microdamage events.

DIC showed significant differences in anteromedial cortical strain between implants at 1500N and 2500N in the proximal 10mm only (p<0.001) with strain shielding in metal backed implants. AE showed significant differences in cancellous microdamage (AE hits), between implants at all loads (p=0.001). FB-AP implants displayed significantly more hits at all loads than both controls and metal backed implants (p<0.001). FB-AP implants also differed significantly by displaying AE hits on unloading (p=0.01), reflecting a lack of implant stiffness. Compared to controls, the FB-AP implant displayed 15x the total AE hits, the FB-MB 6x and the MB-MB 2.7x. All-polyethylene medial UKR implants are associated with greater cancellous bone microdamage than metal backed implants even at low loads.

Summary

Strong mechanical fixation is critical to the success of rotator cuff repairs. In this comparative study in cadaveric shoulders, single-tendon full-thickness supraspinatus tears were repaired using two different types of PEEK knotless suture anchors-ReelX STT (Stryker) and Opus Magnum PI (Arthrocare)-using a single-row technique in both instances. Cyclic testing was performed followed by loading until mechanical failure. No significant difference was observed in gap formation, measured as the distance between the supraspinatus tendon and bone at the repair site, during cyclic loading. However, the maximum load was statistically higher for repairs with the ReelX anchor.

Introduction

The most common treatment options for fixation of osteoporotic distal femur fractures are retrograde nails and locking plates. There are proponents of more elastic titanium plates as well as more rigid steel plates; No clear superiority of one over the other has been established. We aimed to evaluate the mechanical differences between stainless steel and titanium locking plates in the fixation of distal femur fractures in osteoporotic bone. We hypothesized that due to its higher elasticity titanium locking plates can absorb more energy and are therefore less likely to “cut” into the bone compared to stainless steel locking plates resulting in improved metaphyseal osteoporotic fracture fixation.

Introduction

The objective of this study was to determine if a synthetic bone substitute would provide results similar to bone from osteoporotic femoral heads during in vitro testing with orthopaedic implants. If the synthetic material could produce results similar to those of the osteoporotic bone, it could reduce or eliminate the need for testing of implants on bone.

Background

The suicidal jumper's fracture of the pelvis is a special form of sacrum fractures associated with high energy trauma. The typical H-type fracture pattern runs transforaminal on both sides with a connecting transverse component between S1 and S3. Due to the high-grade instability operative treatment is imperative. Aim of this study was to compare iliosacral double screwing (2×7,3mm canulated screw with 16mm thread) with spinopelvic internal fixation.

Due to its popularity of intramedullary nails (IMN) high success rate, newer design (titanium) IMN system have been introduced to replace stainless steel system. However the stability provided by the titanium IMN. may not be adequate, there by influencing the union rate. We aimed to compare the results of both IMN systems via prospective clinical study and biomechanical testing using RSA. Biomechanical study. This study was done in an experimental set-up which consisted of a physically simulated femoral shaft fractures models fixed with a stainless steel (Russell Taylor) or Titanium (Trigen) IM nailing system. Two common fracture configurations with stimulated weight bearing conditions were used and the axis of fragment movements recorded. Clinical study. The data on two groups of patients were collected as part of a prospective cohort study. Details of the implant, such as size of nail, cross screw lengths, screw thickness, etc. was collected. Patients were followed up for a minimum of 4 months and details of clinical complications recorded. Biomechanical study. The degree of translation movement in comminuted fracture, using titanium IMN system, was 6 times more compared to stainless steel IMN system. Clinical study. The results show that there is a 5.7% of non union and 14% hardware problems with titanium based IMN system when compared to 2.2% non union in the stainless steel IMN system. Titanium based IM nailing system have a potential to inherent mechanical instability when used to treat comminuted fractures. This may explain some of the clinically observed delayed or non-union of femoral fractures

Background. The inherently high stiffness of locked plate constructs is increasingly recognized as a potential cause of deficient healing observed in patients with periarticular locked plating systems. The objective of this study is to perform a biomechanical comparison of distal femur locked plating systems. Methods. Biomechanical study using bone substitutes in a distal femur fracture model (OTA/AO 33-A3). Four different locked plate fixation systems were compared (AxSOS, LCP, PERI-LOC, POLYAX). Eight bone implant constructs of each plating system were evaluated in a multiple testing model to examine static failure, stiffness under static and cyclic loading and cyclic fatigue. Results. The implant systems made of titanium alloy (POLYAX & LCP) supported smaller torsional stiffness values under static loads and smaller axial stiffness values under cyclic loads compared with the implant systems made of stainless steel (PERI-LOC & AxSOS). All bone implant constructs reached the cyclic failure criterion of 10 degrees displacement at the fracture area within the third load level (>50000 cycles) except for the LCP which failed earlier. Conclusion. The tested four different locked plating systems differ significantly in terms of stiffness and load to failure. Two of the clinical available systems differed almost 100% in stiffness values. And one system differed almost 100% in fatigue strength. For clinical use, this knowledge is essential for the practicing orthopaedic surgeon

Introduction. Biomechanical studies have shown that a long, centrally placed screw is favourable in scaphoid fracture fixation. A volar percutaneous transtrapezial approach was developed to facilitate central screw placement. The purpose of this study was to evaluate radiographic changes at the ST-joint at long term follow up in patients where this approach was used. Method. Results were graded with use of the visual analogue scale (VAS) and modified Mayo wrist score. Radiographs of both hands, comprising an anteroposterior, lateral and 45 degrees pronated oblique view were obtained. Degenerative changes at the ST-joint were staged according to the modified Eaton & Glickel classification. Results. 34 patients with an average age of 34 years were followed at a mean of 6.1 years (4–9). Union was obtained in all at an average time of 6.4 weeks (6–10). There were no significant differences in VAS score and ROM, between the operated and nonoperated side (p>0.05). The mean Mayo wrist score was 93 (80–100). Three patients showed stage 2 osteoarthritis of the ST-joint. In 2 patients, stage 2 osteoarthritis was found in both the injured and uninjured side. One patient had asymptomatic stage 2 osteoarthritic changes at the injured side. Discussion. The advantages of the volar percutaneous transtrapezial approach include central screw placement, without the need for manipulation of the wrist. From the present study it can be concluded that the volar percutaneous transtrapezial approach to fix scaphoid fractures does not lead to significant radiographic degenerative changes in the ST joint at a follow-up of more than 6 years

Introduction. The degeneration of the adjacent segment in lumbar spine with spondylodesis is well known, though the exact incidence and the mechanism is not clear. Several implants with semi rigid or dynamic behavior are available to reduce the biomechanical loads and to prevent an adjacent segment disease (ASD). Randomized controlled trials are not published. We investigated the biomechanical influence of dynamic and semi rigid implants on the adjacent segment in cadaver lumbar spine with monosegmental fusion (MF). Materials and Methods. 14 fresh cadaver lumbar spines were prepared; capsules and ligaments were kept intact. Pure rotanional moments of ±7.5 Nm were applied with a Zwick 1456 universal testing machine without preload in lateral bending and flexion/extension. The intradiscal pressure (IDP) and the range of motion (ROM) were measured in the segments L2/3 and L3/4 in following situations: in the native spine, monosegmental fusion L4/5 (MF), MF with dynamic rod to L3/4 (Dynabolt), MF with interspinous implant L3/4 (Coflex), and semi rigid fusion with PEEK rod (CD Horizon Legacy) L3-L5. Results. Under flexion load all implants reduced the IDP of segment L2/L3, whereas the IDP in the segment L3/4 was increased using interspinous implants in comparison to the other groups. The IDP was reduced in extension in both segments for all semi rigid or dynamic implants. Compared under extension to the native spine the MF had no influence on the IDP of the adjacent disc. The rod instrumentation (Dynabolt, PEEK rod) lead to a decreased IDP in lateral bending tests. The ROM in L3 was reduced in all groups compared to the native spine. The dynamic and semi rigid stabilization in the segment L3/4 limited the ROM more than the MF. Discussion. The MF reduced the ROM in all directions, whereas the IDP of the adjacent segment remained unaffected. The support of the adjacent segment by semi rigid and dynamic implants decreased the IDP of both segments in extension mainly. This fact is an agreement with other studies. Compared to our data, no significant effect on the adjacent levels was observed. Interestingly, in our study, the IDP of the adjacent segment is unaffected by MF. The biomechanical influence in the view of an ASD could be comprehended, but is not completely clear. The fact of persistent IDP in the adjacent segment suggests that MF has a lower effect on the adjacent segment degeneration as presumed. Biomechanical studies with human cadaver lumbar spines are limited and depend on age and degenerative situation. The effect on supporting implants on adjacent segment disease in lumbar spine surgery has to be investigated in clinical long term studies

Aims

Minimally invasive fixation of pelvic fragility fractures is recommended to reduce pain and allow early mobilization. The purpose of this study was to evaluate the outcome of two different stabilization techniques in bilateral fragility fractures of the sacrum (BFFS).

Although the importance of lateral femoral wall integrity is increasingly being recognised in the treatment of intertrochanteric fracture, little attention has been put on the development of a secondary post-operative fracture of the lateral wall. Patients with post-operative fractures of the lateral wall were reported to have high rates of re-operation and complication. To date, no predictors of post-operative lateral wall fracture have been reported. In this study, we investigated the reliability of lateral wall thickness as a predictor of lateral wall fracture after dynamic hip screw (DHS) implantation.

A total of 208 patients with AO/OTA 31-A1 and -A2 classified intertrochanteric fractures who received internal fixation with a DHS between January 2003 and May 2012 were reviewed. There were 103 men and 150 women with a mean age at operation of 78 years (33 to 94). The mean follow-up was 23 months (6 to 83). The right side was affected in 97 patients and the left side in 111. Clinical information including age, gender, side, fracture classification, tip–apex distance, follow-up time, lateral wall thickness and outcome were recorded and used in the statistical analysis.

Fracture classification and lateral wall thickness significantly contributed to post-operative lateral wall fracture (both p < 0.001). The lateral wall thickness threshold value for risk of developing a secondary lateral wall fracture was found to be 20.5 mm.

To our knowledge, this is the first study to investigate the risk factors of post-operative lateral wall fracture in intertrochanteric fracture. We found that lateral wall thickness was a reliable predictor of post-operative lateral wall fracture and conclude that intertrochanteric fractures with a lateral wall thickness < 20.5 mm should not be treated with DHS alone.

Cite this article: Bone Joint J 2013;95-B:1134–8.

Most fractures of the radial head are stable undisplaced or minimally displaced partial fractures without an associated fracture of the elbow or forearm or ligament injury, where stiffness following non-operative management is the primary concern. Displaced unstable fractures of the radial head are usually associated with other fractures or ligament injuries, and restoration of radiocapitellar contact by reconstruction or prosthetic replacement of the fractured head is necessary to prevent subluxation or dislocation of the elbow and forearm. In fractures with three or fewer fragments (two articular fragments and the neck) and little or no metaphyseal comminution, open reduction and internal fixation may give good results. However, fragmented unstable fractures of the radial head are prone to early failure of fixation and nonunion when fixed. Excision of the radial head is associated with good long-term results, but in patients with instability of the elbow or forearm, prosthetic replacement is preferred.

This review considers the characteristics of stable and unstable fractures of the radial head, as well as discussing the debatable aspects of management, in light of the current best evidence.

Cite this article: Bone Joint J 2013;95-B:151–9.

The aim of this study was to review the number of patients operated on for traumatic disruption of the pubic symphysis who developed radiological signs of movement of the anterior pelvic metalwork during the first post-operative year, and to determine whether this had clinical implications. A consecutive series of 49 patients undergoing internal fixation of a traumatic diastasis of the pubic symphysis were studied. All underwent anterior fixation of the diastasis, which was frequently combined with posterior pelvic fixation. The fractures were divided into groups using the Young and Burgess classification for pelvic ring fractures. The different combinations of anterior and posterior fixation adopted to stabilise the fractures and the type of movement of the metalwork which was observed were analysed and related to functional outcome during the first post-operative year.

In 15 patients the radiographs showed movement of the anterior metalwork, with broken or mobile screws or plates, and in six there were signs of a recurrent diastasis. In this group, four patients required revision surgery; three with anterior fixation and one with removal of anterior pelvic metalwork; the remaining 11 functioned as well as the rest of the study group.

We conclude that radiological signs of movement in the anterior pelvic metalwork, albeit common, are not in themselves an indication for revision surgery.

A series of 103 acute fractures of the coronoid process of the ulna in 101 patients was reviewed to determine their frequency. The Regan-Morrey classification, treatment, associated injuries, course and outcomes were evaluated. Of the 103 fractures, 34 were type IA, 17 type IB, ten type IIA, 19 type IIB, ten type IIIA and 13 type IIIB. A total of 44 type-I fractures (86%) were treated conservatively, while 22 type-II (76%) and all type-III fractures were managed by operation.

At follow-up at a mean of 3.4 years (1 to 8.9) the range of movement differed significantly between the types of fracture (p = 0.002). Patients with associated injuries had a lower Mayo elbow performance score (p = 0.03), less extension (p = 0.03), more pain (p = 0.007) and less pronosupination (p = 0.004), than those without associated injuries. The presence of a fracture of the radial head had the greatest effect on outcome. An improvement in outcome relative to that of a previous series was noted, perhaps because of more aggressive management and early mobilisation. While not providing complete information about the true details of a fracture and its nature, the Regan-Morrey classification is useful as a broad index of severity and prognosis.