Aims. To draw a comparison of the pullout strengths of buttress thread, barb thread, and reverse buttress thread bone screws. Methods. Buttress thread, barb thread, and reverse buttress thread bone screws were inserted into synthetic cancellous bone blocks. Five screw-block constructs per group were tested to failure in an axial pullout test. The pullout strengths were calculated and compared. A finite element analysis (FEA) was performed to explore the underlying failure mechanisms. FEA models of the three different screw-bone constructs were developed. A pullout force of 250 N was applied to the screw head with a fixed bone model. The compressive and tensile strain contours of the midsagittal plane of the three bone models were plotted and compared. Results. The barb thread demonstrated the lowest pullout strength (mean 176.16 N (SD 3.10)) among the three thread types. It formed a considerably larger region with high tensile strains and a slightly smaller region with high compressive strains within the surrounding bone structure. The reverse buttress thread demonstrated the highest pullout strength (mean 254.69 N (SD 4.15)) among the three types of thread. It formed a considerably larger region with high compressive strains and a slightly smaller region with high tensile strains within the surrounding bone structure. Conclusion. Bone screws with a reverse buttress thread design will significantly increase the pullout strength. Cite this article: Bone Joint Res 2021;10(2):105–112

Aims. Posterior column plating through the single anterior approach reduces the morbidity in acetabular fractures that require stabilization of both the columns. The aim of this study is to assess the effectiveness of posterior column plating through the anterior intrapelvic approach (AIP) in the management of acetabular fractures. Methods. We retrospectively reviewed the data from R G Kar Medical College, Kolkata, India, from June 2018 to April 2023. Overall, there were 34 acetabulum fractures involving both columns managed by medial buttress plating of posterior column. The posterior column of the acetabular fracture was fixed through the AIP approach with buttress plate on medial surface of posterior column. Mean follow-up was 25 months (13 to 58). Accuracy of reduction and effectiveness of this technique were measured by assessing the Merle d’Aubigné score and Matta’s radiological grading at one year and at latest follow-up. Results. Immediate postoperative radiological Matta’s reduction accuracy showed anatomical reduction (0 to 1 mm) in 23 cases (67.6%), satisfactory (2 to 3 mm) in nine (26.4%), and unsatisfactory (> 3 mm) in two (6%). Merle d’Aubigné score at the end of one year was calculated to be excellent in 18 cases (52.9%), good in 11 (32.3%), fair in three (8.8%), and poor in two (5.9%). Matta’s radiological grading at the end of one year was calculated to be excellent in 16 cases (47%), good in nine (26.4%), six in fair (17.6%), and three in poor (8.8%). Merle d’Aubigné score at latest follow-up deteriorated by one point in some cases, but the grading remained the same; Matta’s radiological grading at latest follow-up also remained unchanged. Conclusion. Stabilization of posterior column through AIP by medial surface plate along the sciatic notch gives good stability to posterior column, and at the same time can avoid morbidity of the additional lateral window. Cite this article: Bone Jt Open 2024;5(2):147–153

Introduction. Fibula contributes to weight bearing and serves as a lateral buttress to the talus. Fibular shortening leads to ankle valgus, distal tibial epiphyseal wedging and ankle instability. Trauma, infection and skeletal dyplasias are the common causes of fibular shortening in children. Aim was to review this cohort who underwent fibular lengthening and ankle reconstruction. Materials and Methods. Retrospective review from a prospective database of clinical and radiographic data of all children who underwent fibular lengthening for correction of ankle valgus. Distraction osteogenesis with external fixator was performed for all cases. Results. Eight children with 10 fibulae (average age: 10 years) were followed up for an average of 75.6 months. In older children, corrective tibial osteotomy was performed in addition to fibular lengthening. TSF frame mounted with mini-rail fixator was used in seven children who required adjuvant tibial correction and mini-rail was used for bilateral fibular lengthening in one. Remodelling of the wedged distal tibial epiphysis was noted in 75%. Talar tilt and mLDTA improved in 66.7% and fibular station in 85.7% limbs. Seven year old girl required re-lengthening. Two children developed fibular non-union. Proximal fibular migration was observed in one child, in whom the tibial wire did not engage the fibula. Conclusions. Restoration of tibial mechanical axis and lateral talar buttress is necessary to correct ankle valgus. Stabilisation of fibula to the tibia is prudent during distraction. Younger children may require re-lengthening. Remodelling of the triangular tibial epiphysis can be achieved when done early

Introduction: Recombinant human bone morphogenetic protein-2 (rhBMP-2) (Infuse) has been shown to cause osteolysis rather than accelerated fusion in some series. This paper reports two cases of vertebral osteolysis in patients undergoing anterior cervical corpectomy with stabilization using titanium prosthesis where rhBMP-7 (OP1) has been used in high concentration. Methods: Case series and review of literature. Results: OP1 was used in 23 patients undergoing anterior cervical surgery. Each case had at least two CT scans during the first twelve months of follow-up. The two cases of osteolysis were identified amongst a subgroup of 8 patients undergoing anterior cervical corporectomy and reconstruction using a titanium rod and buttress implant. The first case was a 71 year old man who underwent C4-T1 corpectomy for spondylotic cord compression and the second case was a 62 year old man who underwent C3-T1 corpectomy for spondylotic cord compression. In both cases a bottle of OP1 (3.5mg) was mixed with 5mls of carboxy-methyl-cellulose/tri-calcium phosphate (CMC/TCP) putty, approximately half of which was then applied to the ends of the titanium rod and buttress prosthesis and compressed between the buttress end and the vertebral endplate, and some residual OP1-containing putty was placed at the sides of each buttress. CT scans performed at 3 months postoperative in case 1 and 3.5 months postoperatively in case 2 demonstrated osteolysis in the vertebral bodies adjacent to the implant. In both cases however, CT scans performed 12 months post-operatively showed that the osteolytic cysts were beginning to resolve and fusion at the bone-titanium junction may have begun. No other cases of cystic osteolysis were found amongst other anterior cervical cases or 115 posterior lumbar interbody fusion (PLIF) cases similarly followed-up with serial CT scans. The concentration of rhBMP-7 used in a subgroup of 8 corpectomy cases undergoing anterior cervical corporectomy and reconstruction using a titanium rod and buttress implant was at least twice the concentration used in other anterior cervical cases and approximately one quarter to one fifth the concentration used in lumbar interbody PLIF cages. Discussion: These are the first reported cases of osteolysis associated with the use of BMP-7. Osteolysis has been described in association with the use of rhBMP-2. Following these reports, the manufacturers of rhBMP-2 have advised surgeons strongly not to use more than the (recently) recommended dose, despite there being no published evidence that osteolysis is dose-related. Similar recommendations have not been made regarding the use of BMP-7 (OP1). The concentration of BMP-7 (OP1) which led to osteolysis in these cases was much greater than used elsewhere in the spine, where OP1 (3.5mg) is usually mixed with 10–15 mls of finely-milled autograft. This suggests that the concentration achieved by mixing 3.5 mg of OP1 with 5 mls of CMC/TPC putty may increase the risk of osteolysis when inserted into the anterior cervical spine

To evaluate if adequate restoration of the medial cortical buttress reduces the high reported incidence of mechanical complications when using the AO unreamed femoral nail with spiral blade (UFN-SB) in the management of subtrochanteric femoral fractures. The clinical notes and radiographs of sixty-five patients treated with the UFN-SB between November 1996 and February 1999 were retrospectively reviewed. Twenty-eight of these fractures were subtrochanteric. Mean patient age was seventy-five and thirteen patients had metastatic disease. At the time of review the patients or their doctor were contacted by telephone to establish accurately the associated morbidity and mortality. Follow up information was obtained for every patient. Post-operative radiographs were assessed for accuracy of fracture reduction. The medial cortical buttress was adequately restored in every case. This required open fracture reduction in eleven patients and cerclage wires augmented the reduction in eight of these cases. Open reduction did not significantly increase time to fracture union or transfusion requirement. Every surviving patient was fully weight bearing within three months. One patient required a second operation for spiral blade migration but there were no implant breakages or other mechanical complications after a mean follow-up of thirty-seven months. Conclusion: Adequate restoration of the medial cortical buttress allows the UFN-SB to function as a load-sharing device and achieves reliable skeletal stability in these potentially unstable fractures that typically occur in osteoporotic or pathological bone

Background: Moore et al. recently described five radiological signs (absence of radiolucent line, zone 2 osteo-penia, superolateral buttress, inferomedial buttress and radial trabeculae) for predicting osseointegration of porous coated uncemented acetabular components in the long term. The positive predictive value for a stable fixation was 96.9% when three or more signs were present. 83% of the cups with one or no signs were unstable. Aim: To evaluate the prevalence of these signs in clinically well functioning uncemented acetabular components in the short term and to evaluate whether there is a difference acetabular components with different modulus of elasticity. Materials and methods: The preoperative, immediate postoperative and the latest (minimum 2 years) radiographs of 196 hip replacements with 2 different acetabular components: a 2.9 mm, thin, flexible, macro textured titanium component (Allofit, Zimmer) and a 4 mm thick, stiff, titanium plasma sprayed chrome-cobalt component (Durom, Zimmer) were reviewed by two independent observers searching for the five osseointegration signs. The observers also looked for conventional signs of loosening including: continuous radiolucency of more than 2 mm, component migration of more than 3 mm, component rotation, or the presence of broken screws. Results: 95 Allofit components and 101 Durom components were available for evaluation. None of the hips were considered loose according to conventional criteria and were well functioning. Out of the new osseointegration signs, at least one sign was present in 100 % of the cases, two signs or more in 30%, three signs or more in 5% and four signs in 1%. There was no difference between the two types of cups. In addition, superolateral buttress and zone 2 osteopenia were also present in preoperative/immediate postoperative radiographs in 8% and 4% of respectively. Conclusion: Apart from absence of radiolucency, very few of the five osseointegration signs were present at short term follow-up of two very different well functioning uncemented acetabular components designs. We conclude they are not useful in evaluation of unce-mented acetabular components at a follow up of 2–5 years. Further study at mid-term follow-up might reveal whether the bony adaptive changes occur with time

Femoral neck fractures account for half of all hip fractures and are recognized as a major public health problem associated with a high socioeconomic burden. Whilst internal fixation is preferred over arthroplasty for physiologically younger patients, no consensus exists about the optimal fixation device yet. The recently introduced implant Femoral Neck System (FNS) (DePuy Synthes, Zuchwil, Switzerland) was developed for dynamic fixation of femoral neck fractures and provides angular stability in combination with a minimally invasive surgical technique. Alternatively, the Hansson Pin System (HPS) (Swemac, Linköping, Sweden) exploits the advantages of internal buttressing. However, the obligate peripheral placement of the pins, adjacent to either the inferior or posterior cortex, renders the instrumentation more challenging. The aim of this study was to evaluate the biomechanical performance of FNS versus HPS in a Pauwels II femoral neck fracture model with simulated posterior comminution. Forty-degree Pauwels II femoral neck fractures AO 31-B2.1 with 15° posterior wedge were simulated in fourteen paired fresh-frozen human cadaveric femora, followed by instrumentation with either FNS or HPS in pair-matched fashion. Implant positioning was quantified by measuring the shortest distances between implant and inferior cortex (DI) as well as posterior cortex (DP) on anteroposterior and axial X-rays, respectively. Biomechanical testing was performed in 20° adduction and 10° flexion of the specimens in a novel setup with simulated iliopsoas muscle tension. Progressively increasing cyclic loading was applied until construct failure. Interfragmentary femoral head-to-shaft movements, namely varus deformation, dorsal tilting and rotation around the neck axis were measured by means of motion tracking and compared between the two implants. In addition, varus deformation and dorsal tilting were correlated with DI and DP. Cycles to 5/10° varus deformation were significantly higher for FNS (22490±5729/23007±5496) versus HPS (16351±4469/17289±4686), P=0.043. Cycles to 5/10° femoral head dorsal tilting (FNS: 10968±3052/12765±3425; HPS: 12244±5895/13357±6104) and cycles to 5/10° rotation around the femoral neck axis (FNS: 15727±7737/24453±5073; HPS: 15682±10414/20185±11065) were comparable between the implants, P≥0.314. For HPS, the outcomes for varus deformation and dorsal tilting correlated significantly with DI and DP, respectively (P=0.025), whereas these correlations were not significant for FNS (P≥0.148). From a biomechanical perspective, by providing superior resistance against varus deformation and performing in a less sensitive way to variations in implant placement, the angular stable Femoral Neck System can be considered as a valid alternative to the Hansson Pin System for the treatment of Pauwels II femoral neck fractures

Coronoid fractures account for 2 to 15% of the cases with elbow dislocations and usually occur as part of complex injuries. Comminuted fractures and non-unions necessitate coronoid fixation, reconstruction or replacement. The aim of this biomechanical study was to compare the axial stability achieved via an individualized 3D printed prosthesis with curved cemented intramedullary stem to both radial head grafted reconstruction and coronoid fixation with 2 screws. It was hypothesized that the prosthetic replacement will provide superior stability over the grafted reconstruction and screw fixation. Following CT scanning, 18 human cadaveric proximal ulnas were osteotomized at 40% of the coronoid height and randomized to 3 groups (n = 6). The specimens in Group 1 were treated with an individually designed 3D printed stainless steel coronoid prosthesis with curved cemented intramedullary stem, individually designed based on the contralateral coronoid scan. The ulnas in Group 2 were reconstructed with an ipsilateral radial head autograft fixed with two anteroposterior screws, whereas the osteotomized coronoids in Group 3 were fixed in situ with two anteroposterior screws. All specimens were biomechanically tested under ramped quasi-static axial loading to failure at a rate of 10 mm/min. Construct stiffness and failure load were calculated. Statistical analysis was performed at a level of significance set at 0.05. Prosthetic treatment (Group 1) resulted in significantly higher stiffness and failure load compared to both radial head autograft reconstruction (Group 2) and coronoid screw fixation, p ≤ 0.002. Stiffness and failure load did not reveal any significant differences between Group 2 and Group 3, p ≥ 0.846. In cases of coronoid deficiency, replacement of the coronoid process with an anatomically shaped individually designed 3D printed prosthesis with a curved cemented intramedullary stem seems to be an effective method to restore the buttress function of the coronoid under axial loading. This method provides superior stability over both radial head graft reconstruction and coronoid screw fixation, while achieving anatomical articular congruity. Therefore, better load distribution with less stress at the bone-implant interface can be anticipated. In the clinical practice, implementation of this prosthesis type could allow for early patient mobilization with better short- and long-term treatment outcomes and may be beneficial for patients with irreparable comminuted coronoid fractures, severe arthritic changes or non-unions

The use of jig instrumentation has significantly improved the reproducibility of total knee replacement (TKR). The establishment of mechanical axis, femoral rotation and joint line can be considerably enhanced by jig instrumentation. Soft tissue balance is less amenable to the jig solution. Medial compartmental osteoarthritis can be considered extension gap disease; there is no defect in the flexion gap. Although the radiographic studies demonstrate loss of joint space, the biologic defect includes laxity of the ACL and MCL with a lateral tibial thrust in the extension gap with no ligament imbalance in the flexion gap. It is critical to rebalance the ligaments to restore knee function. Statistical studies have demonstrated 8–10 year 90% survivability with unicompartmental arthroplasty; however, statistics beyond 10 years have been disappointing. It can be assumed a significant number of uni patients will come to revision. It is therefore necessary to preserve bone for future TKR. The major difficulty in converting a uni to a TKR is loss of medial tibial buttress. Preserving a rim of medial tibial bone, the medial tibial buttress, by inlay technique simplifies conversion to TKR. It is also necessary to preserve adequate sclerotic bone to support the prosthetic system. The major advantages of jigs when performing TKR, establishing mechanical axis, femoral rotation and joint line do not apply to uni technology, while the major requirements for a successful uni, medial tibial buttress preservation, sclerotic bone preservation and soft tissue balance are not improved by the use of jigs. Whereas jigs may have limitations, the procedure is not without guides. The usual articular surface defect in the extension gap is 6–8 mm while there is no defect in the flexion gap. The prosthetic components are approximately 10 mm thick. The bur utilised is 5.5 mm in diameter, a useful reference point. Various sized femoral and tibial guides are utilised. Ligament tension can be palpated, while a thin shim can be used to check ligament tension in the flexion and extension gap. The various anatomical reference points, guides, their advantages and disadvantages will be discussed. With due regard to the limitations of guide and jig instrumentation, consistent reproducibility requires a reasonable degree of surgeon experience with the procedure

Displaced intraarticular calcaneal fractures are debilitating injuries with significant socioeconomic and psychological effects primarily affecting patients in active age between 30 and 50 years. Recently, minimally and less invasive screw fixation techniques have become popular as alternative to locked plating. The aim of this study was to analyze biomechanically in direct comparison the primary stability of 3 different cannulated screw configurations for fixation of Sanders type II-B intraarticular calcaneal fractures. Fifteen fresh-frozen human cadaveric lower limbs were amputated mid-calf and through the Chopart joint. Following, soft tissues at the lateral foot side were removed, whereas the medial side and Achilles tendon were preserved. Reproducible Sanders type II-B intraarticular fracture patterns were created by means of osteotomies. The proximal tibia end and the anterior-inferior aspect of the calcaneus were then embedded in polymethylmethacrylate. Based on bone mineral density measurements, the specimens were randomized to 3 groups for fixation with 3 different screw configurations using two 6.5 mm and two 4.5 mm cannulated screws. In Group 1, two parallel longitudinal screws entered the tuber calcanei above the Achilles tendon insertion and proceeded to the anterior process, and two transverse screws fixed the posterior facet perpendicular to the fracture line. In Group 2, two parallel screws entered the tuber calcanei below the Achilles tendon insertion, aiming at the anterior process, and two transverse screws fixed the posterior facet. In Group 3, two screws were inserted along the bone axis, entering the tuber calcanei above the Achilles tendon insertion and proceeding to the central-inferior part of the anterior process. In addition, one transverse screw was inserted from lateral to medial for fixation of the posterior facet and one oblique screw – inserted from the posterior-plantar part of the tuber calcanei – supported the posterolateral part of the posterior facet. All specimens were tested in simulated midstance position under progressively increasing cyclic loading at 2 Hz. Starting from 200N, the peak load of each cycle increased at a rate of 0.1 N/cycle. Interfragmentary movements were captured by means of optical motion tracking and triggered mediolateral x-rays. Plantar movement, defined as displacement between the anterior process and the tuber calcanei at the most inferior side was biggest in Group 2 and increased significantly over test cycles in all groups (P = 0.001). Cycles to 2 mm plantar movement were significantly higher in both Group 1 (15847 ± 5250) and Group 3 (13323 ± 4363) compared to Group 2 (4875 ± 3480), P = 0.048. Medial gapping after 2500 cycles was significantly bigger in Group 2 versus Group 3, P = 0.024. No intraarticular displacement was observed in any group during testing. From biomechanical perspective, screw configuration implementing one oblique screw seems to provide sufficient hindfoot stability in Sanders Type II-B intraarticular calcaneal fractures under dynamic loading. Posterior facet support by means of buttress or superiorly inserted longitudinal screws results in less plantar movement between the tuber calcanei and anterior fragments. On the other hand, inferiorly inserted longitudinal screws seem to be associated with bigger interfragmentary movements

Aim. To review the results of patients who underwent fixation of complex proximal femur fractures using the Proximal Femur Locking Plates (PFP) and analyse causes of failure of PFP. Methods. Retrospective review of radiographs and case notes of PFP fixations in two hospitals between February 2008 and June 2011. Primary outcome was union at six months. Secondary outcome included post-operative complications, and need for further surgical intervention. Results. There were a total of 32 patients who underwent 34 operations. Two patient had fracture of both the proximal femur requiring bilateral PFP fixation. Mean age of the patients was 68.4 years (range 17–96 years). There were twelve males and twenty female patients. 26 (81%) of the operations were done as primary surgery for fixation of the complex proximal femur fractures. According to the AO/OTA fracture classification, there were four cases of 31-A2.2, seven cases of 31-A2.3, two cases of 31-A3.1 one case each of 31-A3.2 and 32-B1.1 and ten cases of 31 A3.3 fractures. At least six months of follow up was achieved for 30 cases. Union was achieved in 20 fixations (62%) primarily; two more cases needed bone grafting at three months which went on to union improving the total union rate to 70% at 6 months. There was failure of fixation in eight cases requiring further surgery. Varus fixation, loss of posteromedial buttress and loss of protected weight bearing were associated with fixation failure. Conclusion. Contrary to the reported literature, (1) our results are better. Analysis of the failure cases emphasises the importance of postero medial buttress restoration, avoidance of varus fixation, and protection of weight bearing till fracture unites to achieve good outcome

Introduction. Acetabular revision for cavitary defects in failed total hip replacement remains a challenge for the orthopaedic surgeon. Bone graft with cemented or uncemented revision is the primary solution; however, there are cases where structural defects are too large. Cup cage constructs have been successful in treating these defects but they do have their problems with early loosening and metalwork failure. Recently, highly porous cups that incorporate metal augments have been developed to achieve greater intra-operative stability showing encouraging results. Methods. Retrospective analysis of twenty-six consecutive acetabular revisions with Trabecular Titanium cups. Inclusion criteria included aseptic cases, adult patients, end-stage disease with signs of loosening, no trauma nor peri-prosthetic fractures. Data was obtained for patient demographics, Paprosky classification, use of bone graft, use of acetabular augment, and Moore index of osseointegration. Results. Twenty-six subjects were included in the study. Four patients were lost to follow up due to death. The average age was 73 (range 50–91) with 16 females and 10 males. The Paprosky classification was as follows: type I=7 (26.9%), type IIa=7 (26.9%), type IIb=4 (15.4%), type IIc=2 (7.7%), type IIIa=6 (23%). The Moore index at 6 months was as follows: type I=2 (7.7%), type II=4 (15.4%), type III=8 (30.1%), type IV= 6 (23%), type V=3 (11.5%), no data =3 (11.5). At 12 months: type I=0, type II=2 (7.7%), type III=5 (19.2%), type IV=7 (26.9%), type V=4 (15.4%), no data = 8 (4 no radiographs and 4 deceased). Augments were used in 8 patients. All cups implanted had supplemented screw fixation. Discussion. Revision acetabular surgery for aseptic loosening remains a challenge, particularly with cavitary defects. Success of surgery depends on solid fixation at the time of implantation and good, rapid osseointegration. With cavitary defects, stability of the implant becomes an issue, needing implants capable of filling the defects, with good porosity and enough surface roughness to achieve early stability. We found the Trabecular Titanium cup to have very high porosity and surface roughness allowing very good and stable fixation. The use of augments did not affect the initial stability of the implant. The Moore index of osseointegration reliably detects bony ingrowth of the cup of radiographic analysis by assessing (1) absence of radiolucent lines; (2) presence of a superolateral buttress; (3) medial stress-shielding; (4) radial trabeculae; and (5) an inferomedial buttress. Each sign had a high PPV for the presence of bone ingrowth. Ninety-seven percent of cups with three to five signs were ingrown, whereas 83% of cups with one or no signs were unstable. With three or more signs present, the PPV was 96.9%, the sensitivity was 89.6%, and specificity was 76.9%. In our study, 61.5% of patients had 3 signs or more and 69.2% of patients had 2 signs or more at 12 months. Conclusion. The Trabecular Titanium. TM. cup demonstrates good initial stability at implantation, and at twelve-months excellent osseointegration. These results are comparable to published results for similar trabecular cup designs. Further long-term studies are welcome and we continue to monitor this group of patients

Purpose: Radiographic signs of osseointegration have been well established for cementless femoral components, but not for cementless acetabular components. At our institution using principles similar to those applied to cementless femoral components, we have observed apparent radiographic signs of osseointegration of porous-coated cups. We then hypothesized that these signs could be used to predict bone ingrowth of porous-coated acetabular components. Methods: In a series of 119 total hip arthroplasties with porous-coated cementless cups, we reviewed post-primary and prerevision serial radiographs and proposed five radiographic signs for detecting osseointegration of a porous-coated acetabular component: absence of radiolucent lines, presence of a superolateral buttress, medial stress shielding, radial trabeculae, and an infero-medial buttress. We compared the predictability of each sign to intraoperative findings of cup stability and measured the sensitivity, specificity, and intra-observer agreement of each sign. Results: . In our population, ninety-eight cups had three to five radiographic signs of osseointegration; of these, ninety-five cups (97%) were found to be bone-ingrown at the revision operation. Conversely, twelve cups had only one or no sign; of these, ten (83%) were clinically unstable at the revision operation. Conclusions: We concluded these five, readily detectable signs of acetabular osseointegration are very useful in predicting acetabular component stability found at surgery

The reduction for unstable femoral intertrochanteric fracture should be extramedullary, which means that the proximal fragment protrudes for the distal fragment. However, only few articles have compared extramedullary and intramedullary reductions in a biomechanical study. Thus, we created unstable femoral intertrochanteric fracture models using imitational bone (extramedullary and intramedullary groups, each with 12 cases) and evaluated their biomechanical stabilities. The fracture type was 31-A2 according to the AO-OTA Classification of Fractures and Dislocations and greatly lacked bone on the posterior side. We performed compression examination and evaluated stiffness. The implant used for fixation was TFNA (DePuy Synthes). We applied axial compression with 20 adduction in the standing position. Statistical analysis was performed using the Mann-Whitney U test. No significant difference in initial loading force was found between the two groups. However, the axial stiffness of the extramedullary bone showed a significant increase (p < 0.05) in high loading force (800–1000 N). This means that the stability of the extramedullary reduction was superior to that of the intramedullary reduction in terms of high loading force in the standing position. We suggest that antero-medial bony buttress is important for unstable femoral intertrochanteric fractures. These data indicate that extramedullary reduction and fixation for unstable femoral intertrochanteric fractures increase stability

Aims

The Chopart joint complex is a joint between the midfoot and hindfoot. The static and dynamic support system of the joint is critical for maintaining the medial longitudinal arch of the foot. Any dysfunction leads to progressive collapsing flatfoot deformity (PCFD). Often, the tibialis posterior is the primary cause; however, contrary views have also been expressed. The present investigation intends to explore the comprehensive anatomy of the support system of the Chopart joint complex to gain insight into the cause of PCFD.

Introduction. Trabecular Titanium is a biomaterial characterized by a regular three-dimensional hexagonal cell structure imitating trabecular bone morphology. Components are built via Electron Beam Melting technology in aone- step additive manufacturing process. This biomaterial combines the proven mechanical properties of Titanium with the elastic modulus provided by its cellular solid structure (Regis 2015 MRS Bulletin). Several in vitro studies reported promising outcomes on its osteoinductive and osteoconductive properties: Trabecular Titanium showed to significantly affect osteoblast attachment and proliferation while inhibiting osteoclastogenesis (Gastaldi 2010 J Biomed Mater Res A, Sollazzo 2011 ISRN Mater Sci); human adipose stem cells were able to adhere, proliferate and differentiate into an osteoblast-like phenotype in absence of osteogenic factors (Benazzo 2014 J Biomed Mater Res A). Furthermore, in vivo histological and histomorphometric analysis in a sheep model indicated that it provided bone in-growth in cancellous (+68%) and cortical bone (+87%) (Devine 2012 JBJS). A multicentre prospective study was performed to assess mid-term outcomes of acetabular cups in Trabecular Titanium after Total Hip Arthroplasty (THA). Methods. 89 patients (91 hips) underwent primary cementless THA. There were 46 (52%) men and 43 (48%) women, with a median (IQR) age and BMI of 67 (57–70) years and 26 (24–29) kg/m2, respectively. Diagnosis was mostly primary osteoarthritis in 80 (88%) cases. Radiographic and clinical evaluations (Harris Hip Score [HHS], SF-36) were performed preoperatively and at 7 days, 3, 6, 12, 24 and 60 months. Bone Mineral Density (BMD) was determined by dual-emission X-ray absorptiometry (DEXA) according to DeLee &Charnley 3 Regions of Interest (ROI) postoperatively at the same time-points using as baseline the measureat 1 week. Statistical analysis was carried out using Wilcoxon test. Results. Median (IQR) HHS and SF-36 improved significantly from 48 (39–61) and 49 (37–62) preoperatively to 99 (96–100) and 76 (60–85) at 60 mo. (p≤0.0001). Radiographic analysis showed evident signs of bone remodelling and biological fixation, with presence of superolateral and inferomedial bone buttress, and radial trabeculae in ROI I/II. All cups resulted radiographically stable without any radiolucent lines. The macro-porous structure of this biomaterial generates a high coefficient of friction (Marin 2012 Hip Int), promoting a firm mechanical interlocking at the implant-bone interface which could be already observed in the operating room. BMD initially declined from baseline at 7 days to 6 months. Then, BMD slightly increased or stabilized in all ROIs up to 24 months, while showing evidence of partial decline over time with increasing patient' age at 60 months, although without any clinical significance in terms of patients health status or implant stability. Statistical significant correlations in terms of bone remodeling were observed between groups of patients on the basis of gender and age (p≤0.05). No revision or implant failure was reported. Conclusions. All patients reported significant improvements in quality of life, pain relief and functional recovery. Radiographic evaluation confirmed good implant stability at 60 months. These outcomes corroborate the evidence reported on these cups by orthopaedic registries and literature (Perticarini 2015 BMC Musculoskelet Disord; Bistolfi 2014 Min Ortop)

Revision of total hip arthroplasty (THA) is being performed with increasing frequency. However, outcomes of repeated revisions have been rarely reported in the literature, especially for severe defects. Cup revision can be a highly complex operation depending on the bone defect. In acetabular defects like Paprosky types 1 and 2 porous cementless cups fixed with screws give good results. Modern trabecular metal designs improve these good results. Allografts are useful for filling cavitary defects. In acetabular defects Paprosky types 3A and 3B, especially the use of trabecular metal cups, wedges, buttresses and cup-cage systems can produce good results. Difficult cases in combination with pelvic discontinuity require reconstruction of the acetabulum with acetabular plates or large cup-cages to solve these difficult problems. However, there is still no consensus regarding the best option for reconstructing hips with bone loss. Although the introduction of ultraporous metals has significantly increased the surgeon's ability to reconstruct severely compromised hips, there remain some that cannot be managed readily using cups, augments, or cages. In such situations custom acetabular components may be required. Individual implants represent yet another tool for the reconstructive surgeon. These devices can be helpful in situations of catastrophic bone loss. Ensuring long-term outcome, mechanical stability has a greater impact than restoring an ideal center of rotation. However, despite our consecutive case series there are no mid- to long-term results available so far. Re-revision for failed revision THA acetabular components is a technically very challenging condition

Aims

To report the development of the technique for minimally invasive lumbar decompression using robotic-assisted navigation.

Revision hip arthroplasty requires a comprehensive appreciation of abnormal bony anatomy. Advances in radiology and manufacturing technology have made three-dimensional representation of actual osseous anatomy obtainable. These models provide a visual and tactile reproduction of the bony abnormality in question. Life size three dimensional models were manufactured from CT scans of two patients. The first had multiple previous hip arthroplasties and bilateral hip infections. There was a pelvic discontinuity on the right and a severe postero-superior deficiency on the left. The second patient had a first stage revision for infection and recurrent dislocations. Specific metal reduction protocols were used to reduce artefact. The dicom images were imported into Mimics, medical imaging processing software. The models were manufactured using the rapid prototyping process, Selective Laser Sintering (SLS). The models allowed accurate templating using the actual prosthesis templates prior to surgery. Acetabular cup size, augment and buttress sizes, as well as cage dimensions were selected, adjusted and re-sterilised in advance. This reduced operative time, blood loss and improved surgical decision making. Screw trajectory simulation was also carried out on the models, thus reducing the chance of neurovascular injury. With 3D printing technology, complex pelvic deformities can be better evaluated and can be treated with improved precision. The life size models allow accurate surgical simulation, thus improving anatomical appreciation and pre-operative planning. The accuracy and cost-effectiveness of the technique were impressive and its use should prove invaluable as a tool to aid clinical practice

Introduction. Posterolateral tibial plateau fractures account for 7 % of all proximal tibial fractures. Their fixation often requires posterolateral buttress plating. Approaches for the posterolateral corner are not extensile beyond the perforation of the anterior tibial artery through the interosseous membrane. This study aims to provide accurate data about the inferior limit of dissection by providing measurements of the anterior tibial artery from the lateral joint line as it pierces the interosseous membrane. Materials and Methods. Forty unpaired adult lower limbs cadavers were used. The posterolateral approach to the proximal tibia was performed as described by Frosch et al. Perpendicular measurements were made from the posterior limit of the articular surface of the lateral tibial plateau and fibula head to the perforation of the anterior tibial artery through the interosseous membrane. Results. The anterior tibial artery coursed through the interosseous membrane at 46.3 +/− 9.0 mm (range 27–62 mm) distal to the lateral tibial plateau and 35.7 +/− 9.0 mm (range 17–50 mm) distal to the fibula head. There was no significant difference between right or left sided knees. Discussion. This cadaveric study demonstrates the safe zone (min 27 mm, mean 45mm) up to which distal exposure can be performed for fracture manipulation and safe application of a buttress plate for displaced posterorlateral tibial plateau fractures. Evidence demonstrates quality of reduction correlates with clinical outcome and the surgeon can expect to be able to use a small fragment buttress plate of up to 45mm as this is the mean