Aims. Unicompartmental knee arthroplasty (UKA) is the preferred treatment for anterior medial knee osteoarthritis (OA) owing to the rapid postoperative recovery. However, the risk factors for UKA failure remain controversial. Methods. The clinical data of Oxford mobile-bearing UKAs performed between 2011 and 2017 with a minimum follow-up of five years were retrospectively analyzed. Demographic, surgical, and follow-up data were collected. The Cox proportional hazards model was used to identify the risk factors that contribute to UKA failure. Kaplan-Meier survival was used to compare the effect of the prosthesis position on UKA survival. Results. A total of 407 patients who underwent UKA were included in the study. The mean age of patients was 61.8 years, and the mean follow-up period of the patients was 91.7 months. The mean Knee Society Score (KSS) preoperatively and at the last follow-up were 64.2 and 89.7, respectively (p = 0.001). Overall, 28 patients (6.9%) with UKA underwent revision due to prosthesis loosening (16 patients), dislocation (eight patients), and persistent pain (four patients). Cox proportional hazards model analysis identified malposition of the prostheses as a high-risk factor for UKA failure (p = 0.007). Kaplan-Meier analysis revealed that the five-year survival rate of the group with malposition was 85.1%, which was significantly lower than that of the group with normal position (96.2%; p < 0.001). Conclusion. UKA constitutes an effective method for treating anteromedial knee OA, with an excellent five-year survival rate. Aseptic loosening caused by prosthesis malposition was identified as the main cause of UKA failure. Surgeons should pay close attention to prevent the potential occurrence of this problem. Cite this article: Bone Jt Open 2023;4(12):914–922

Many factors can negatively impact acetabular component positioning including poor visualization, increased patient size, inaccuracies of mechanical guides, and inconsistent precision of conventional instruments and techniques, and changes in patient positioning. Improper orientation contributes to increased dislocation rates, leg length discrepancies, altered hip biomechanics, component impingement, acetabular component migration, bearing surface wear, and pelvic osteolysis thus affecting revision rates and long-term survivorship. Despite the established definitions of acetabular safe zones, recent analysis of U.S. Medicare THA data found dislocation rates during the first six months to be 3.9% for primary surgeries and 14.4% for revision surgeries. Accurate and precise acetabular component orientation during initial THA is an increasingly important factor in decreasing revision THA; a recent report cites instability and dislocation as the primary cause of revision accounting for 22.5% of cases. Larger femoral heads and alternative bearing couples are less tolerant of variation in acetabular orientation and thus are poor substitutes for proper acetabular component placement.

Variability in acetabular orientation has been reported to have both an inter-surgeon and an intra-surgeon component; pre-surgical templating combined with intraop-erative measurements is subject to inconsistencies and errors. Current methods for determining acetabular orientation include preoperative imaging such as CT scans, intraoperative imaging such as plain radiographs and fluoroscopy, and intraoperative anatomical tests. Combining the concepts of patient-specific morphology (PSM) and quantitative technologies (QuanTech) such as computer-assisted navigation (CAN) has the potential to maximise range of motion and to further improve acetabular component orientation through improved accuracy and precision.

PSM refers to the practice of allowing the form and structure of the patient’s hip joint to guide surgical reconstruction and component placement thus creating an individualised and more accurate “target zone”; unlike “safe zones,” PSM does not rely on averages. Although gross anatomic changes may make it difficult to use PSM, certain structures may be used as guide-posts for orientation, alignment, and stability in most patients. At present, there are three options when considering anatomic landmarks as guides for acetabular component placement: bony landmarks, soft tissue landmarks, or a combination.

QuanTech has been shown to increase the precision of component placement by reducing intra-surgeon deviation. Some pitfalls of current CAN techniques result from maintaining camera line of sight during surgery, registration process, and pin placement. Performing THA using smaller incisions can impose additional complications as well as risks for errors in component positioning; QuanTech has the potential to provide greater visualization and precision, thus decreasing the impact of those constraints.

THA has become one of the most common and successful orthopaedic procedures; its efficacy at relieving pain and its ability to help patients have improved quality of life is without dispute yet results continue to vary with inter-surgeon and intra-surgeon differences. As the population needing THA increases, the prevalence of complications and problems will increase, even if the percentage of complications decreases. Coupling PSM with QuanTech such as CAN may allow the surgeon to decrease variability and more consistently implant THA components based on each patient’s individualized requirements. The goal of combining PSM and CAN is to further reduce inter-and intra-surgeon variation, thereby decreasing outliers, complications, and revision rates, and possibly narrowing the gap between specialist and generalist. More accurate and precise acetabular component orientation correlates with better hip biomechanics, translating into better function, fewer dislocations, fewer impingements, maximized safe range of motion, less wear, and therefore less aseptic loosening and improvements in survivorship of primary THA. Decreasing revision rates, combined with the benefits listed above, could translate into increased THA survivorship, improved patient satisfaction, and decreased economic burden on the entire healthcare system.

Aims

The material and design of knee components can have a considerable effect on the contact characteristics of the tibial post. This study aimed to analyze the stress distribution on the tibial post when using different grades of polyethylene for the tibial inserts. In addition, the contact properties of fixed-bearing and mobile-bearing inserts were evaluated.

Ligament reconstruction following multi-ligamentous knee injuries involves graft fixation in bone tunnels using interference screws (IS) or cortical suspensory systems. Risks of IS fixation include graft laceration, cortical fractures, prominent hardware, and inability to adjust tensioning once secured. Closed loop suspensory (CLS) fixation offers an alternative with fewer graft failures and improved graft-to-tunnel incorporation. However, graft tensioning cannot be modified to accommodate errors in tunnel length evaluation. Adjustable loop suspensory (ALS) devices (i.e., Smith & Nephew Ultrabutton) address these concerns and also offer the ability to sequentially tighten each graft, as needed. However, ALS devices may lead to increased graft displacement compared to CLS devices. Therefore, this study aims to report outcomes in a large clinical cohort of patients using both IS and CLS fixation. A retrospective review of radiographic, clinical, and patient-reported outcomes following ligament reconstruction from a Level 1 trauma centre was completed. Eligible patients were identified via electronic medical records using ICD-10 codes. Inclusion criteria were patients 18 years or older undergoing ACL, PCL, MCL, and/or LCL reconstruction between January 2018 and 2020 using IS and/or CLS fixation, with a minimum of six-month post-operative follow-up. Exclusion criteria were follow-up less than six months, incomplete radiographic imaging, and age less than 18 years. Knee dislocations (KD) were classified using the Schenck Classification. The primary outcome measure was implant removal rate. Secondary outcomes were revision surgery rate, deep infection rate, radiographic fixation failure rate, radiographic malposition, Lysholm and Tegner scores, clinical graft failure, and radiographic graft failure. Radiographic malposition was defined as implants over 5 mm off bone or intraosseous deployment of the suspensory fixation device. Clinical graft failure was defined as a grade II or greater Lachman, posterior drawer, varus opening at 20° of knee flexion, and/or valgus opening at 20° of knee flexion. Radiographic failure was defined when over 5 mm, 3.2 mm, and/or 2.7 mm of side-to-side difference occurred using PCL gravity stress views, valgus stress views, and/or varus stress views, respectively. Descriptive statistics were used. Sixty-three consecutive patients (mean age = 41 years, range = 19-58) were included. A total of 266 CLS fixation with Ultrabuttons and 135 IS were used. Mean follow-up duration was 383 days. Most injuries were KD type II and III. Graft revision surgery rate was 1.5%. Intraosseous deployment occurred in 6.2% and 17% had implants secured in soft tissue, rather than on bone. However, the implant removal rate was only 6.2%. Radiographic PCL gravity stress views demonstrated an average of 1.2 mm of side-to-side difference with 6.2% meeting criteria for radiographic failure. A single patient met radiographic failure criteria for collateral grafts. Mean Lysholm and Tegner scores were 87.3 and 4.4, respectively, with follow-up beyond one year. Both IS and CLS fixation demonstrate an extremely low revision surgery rate, a high rate of implant retention, excellent radiographic stability, and satisfactory patient-reported outcome scores. Incorrect implant deployment was seen in a total of 17% of patients, yet none required implant removal. A single patient required graft revision due to implant failure

The periclavicular space is a conduit for the brachial plexus and subclavian-axillary vascular system. Changes in its shape/form generated by alteration in the anatomy of its bounding structures, e.g. clavicle malunion, cause distortion of the containing structures, particularly during arm motion, leading to syndromes of thoracic outlet stenosis etc., or alterations of scapular posture with potential reduction in shoulder function. Aim of this study was developing an in vitro methodology for systematic and repeatable measurements of the clinically poorly characterized periclavicular space during arm motion using CT-imaging and computer-aided 3D-methodologies. A radiolucent frame, mountable to the CT-table, was constructed to fix an upper torso in an upright position with the shoulder joint lying in the isocentre. The centrally osteotomized humerus is fixed to a semi-circular bracket mounted centrally at the end of the frame. All arm movements (ante-/retroversion, abduction/elevation, in-/external rotation) can be set and scanned in a defined and reproducible manner. Clavicle fractures healed in malposition can be simulated by osteotomy and fixation using a titanium/carbon external fixator. During image processing the first rib served as fixed reference in space. Clavicle, scapula and humerus were registered, segmented, and triangulated. The different positions were displayed as superimposed surface meshes and measurements performed automatically. Initial results of an intact shoulder girdle demonstrated that different arm positions including ante-/retroversion and abduction/elevation resulted solely in a transverse movement of the clavicle along/parallel to the first rib maintaining the periclavicular space. A radiolucent frame enabling systematic and reproducible CT scanning of upper torsos in various arm movements was developed and utilized to characterize the effect on the 3D volume of the periclavicular space. Initial results demonstrated exclusively transverse movement of the clavicle along/parallel to the first rib maintaining the periclavicular space during arm positions within a physiological range of motion

Periprosthetic femoral fractures are increasingly seen in recent years, adding considerable burden to the National Health Service. These require complex revision or fixation and prolonged post-operative care, with significant morbidity with associated costs. The purpose of this study was to assess whether the size of femoral cement mantle is associated with periprosthetic femoral fractures (PPF). This retrospective study was carried out on a cohort of 49 patients (Fracture Group - FG) who previously had a revision procedure following a proximal PPF between 2010 and 2021. Inclusion criteria – all primary cemented total hip replacements (THR). Exclusion criteria – complex primary THR, any implant malposition that required early revision surgery or any pre-fracture stem loosening. The antero-posterior (AP) radiographs from this cohort of patients were assessed and compared to an age, sex, time since THR-matched control group of 49 patients without PPF (Control Group - CG). Distal cement mantle area (DCMA) was calculated on an AP radiograph of hip; the position of the femoral stem tip prior to fracture was also recorded: valgus, varus or central. Limitations: AP radiographs only. Statistical analyses were performed using Microsoft® Excel. Chi-square test demonstrated statistically significant difference in DCMA between FG and CG. DCMA of 700 to 900 mm² appeared to be protective when compared to DCMA of 0 to 300 mm². Also, a valgus position observed in 23% in FG Vs 4 % in CG increased the risk, with a smaller area of DCMA. This study demonstrates and recommends that a size of 700 – 900 mm² of the DCMA is protective against periprosthetic fractures, which are further influenced by the positioning of the distal stem tip. This could be due to the gradual decrease in the stiffness gradient from proximal to distal around the stem tip than steep changes, thereby decreasing possibility of a stress riser just distal to the cement mantle or restrictor. Further biomechanical research specific to this finding may be helpful to validate the observation, progressing to suggest a safe standardised surgical technique

The purpose of this study is to evaluate risk factors for distal construct failure (DCF) in posterior spinal instrumented fusion (PSIF) in adolescent idiopathic scoliosis (AIS). We observed an increased rate of DCF when the pedicle screw in the lowest instrumented vertebra (LIV) was not parallel to the superior endplate of the LIV, however this has not been well studied in the literature. We hypothesise a more inferiorly angled LIV screw predisposes to failure and aim to find the critical angle that predisposes to failure. A retrospective cohort study was performed on all patients who underwent PSIF for AIS at the Starship Hospital spine unit from 2010 to 2020. On a lateral radiograph, the angle between the superior endplate of the LIV was measured against its pedicle screw trajectory. Data on demographics, Cobb angle, Lenke classification, instrumentation density, rod protrusion from the most inferior screw, implants and reasons for revision were collected. Of 256 patients, 10.9% (28) required at least one revision. The rate of DCF was 4.6% of all cases (12 of 260) and 25.7% of revisions were due to DCF. The mean trajectory angle of DCF patients compared to all others was 13.3° (95%CI 9.2° to 17.4°) vs 7.6° (7° to 8.2°), p=0.0002. The critical angle established is 11°, p=0.0076. Lenke 5 and C curves, lower preoperative Cobb angle, titanium only rod constructs and one surgeon had higher failure rates than their counterparts. 9.6% of rods protruding less than 3mm from its distal screw disengaged. We conclude excessive inferior trajectory of the LIV screw increases the rate of DCF and a screw trajectory greater than 11° predisposes to failure. This is one factor that can be controlled by the surgeon intraoperatively and by avoiding malposition of the LIV screw, a quarter of revisions can potentially be eliminated

Aims. The Mathys Affinis Short is the most frequently used stemless total shoulder prosthesis in the UK. The purpose of this prospective cohort study is to report the survivorship, clinical, and radiological outcomes of the first independent series of the Affinis Short prosthesis. Methods. From January 2011 to January 2019, a total of 141 Affinis Short prostheses were implanted in 127 patients by a single surgeon. Mean age at time of surgery was 68 (44 to 89). Minimum one year and maximum eight year follow-up (mean 3.7 years) was analyzed using the Oxford Shoulder Score (OSS) at latest follow-up. Kaplan-Meier survivorship analysis was performed with implant revision as the endpoint. Most recently performed radiographs were reviewed for component radiolucent lines (RLLs) and proximal humeral migration. Results. Five shoulders underwent revision surgery (3.5%); three for rotator cuff failure, one for infection, and one for component malposition. Survivorship of the implant was 95.4% (95% confidence interval 90.1% to 97.9%) at five and nine years. Mean OSS improved significantly compared to preoperative values from 19.0 (1 to 35) to 43.3 (7 to 48) (p < 0.001). Radiological analysis was undertaken for 99 shoulders. This revealed humeral RLLs in one case (1%), glenoid RLLs in 15 cases (15.2%), and radiological rotator cuff failure in 22 cases (22.2%). Conclusion. This prospective cohort study shows encouraging short- to mid-term survivorship and clinical and radiological results for the Mathys Affinis Short, Short Stem Total Shoulder Prosthesis. Level of Evidence: IV. Cite this article: Bone Jt Open 2021;2(1):58–65

Introduction. Total knee replacement (TKR) is an established and effective surgical procedure in case of advanced osteoarthritis. However, the rate of satisfied patients amounts only to about 75 %. One common cause for unsatisfied patients is the anterior knee pain, which is partially caused by an increase in patellofemoral contact force and abnormal patellar kinematics. Since the malpositioning of the tibial and the femoral component affects the interplay in the patellofemoral joint and therefore contributes to anterior knee pain, we conducted a computational study on a cruciate-retaining (CR) TKR and analysed the effect of isolated femoral and tibial component malalignments on patellofemoral dynamics during a squat motion. Methods. To analyse different implant configurations, a musculoskeletal multibody model was implemented in the software Simpack V9.7 (Simpack AG, Gilching, Germany) from the SimTK data set (Fregly et al.). The musculoskeletal model comprised relevant ligaments with nonlinear force-strain relation according to Wismans and Hill-type muscles spanning the lower extremity. The experimental data were obtained from one male subject, who received an instrumented CR TKR. Muscle forces were calculated using a variant of the computed muscle control algorithm. To enable roll-glide kinematics, both tibio- and patellofemoral joint compartments were modelled with six degrees of freedom by implementing a polygon-contact-model representing the detailed implant surfaces. Tibiofemoral contact forces were predicted and validated using data from experimental squat trials (SimTK). The validated simulation model has been used as reference configuration corresponding to the optimal surgical technique. In the following, implant configurations, i.e. numerous combinations of relative femoral and tibial component alignment were analysed: malposition of the femoral/tibial component in mediolateral (±3 mm) and anterior-posterior (±3 mm) direction. Results. Mediolateral translation/malposition of the tibial component did not show high influence on the maximal patellofemoral contact force. Regarding the mediolateral translation of the femoral component, similar tendencies were observed. However, lateralisation of the femoral component (3 mm) clearly increased the lateral patella shift and medialisation of the tibial component (3 mm) led to a slightly increased lateral patella shift. Compared to the reference model, pronounced posterior translation of the tibial and femoral component resulted in a lower patellofemoral contact force, further increasing with higher anterior translation of the components. The translation of the tibial component showed smaller influence on the patellofemoral contact force than the translation of the femoral component. Discussion. In our present study, the mediolateral malposition of the femoral and tibial component showed no major impact on patellofemoral contact force and contribution to anterior knee pain in patients with CR TKR. However, the influence of implant component positioning in anterior-posterior direction on patellofemoral contact force is evident, especially for the femoral component. Our generated musculoskeletal model can contribute to computer-assisted preclinical testing of TKR and may support clinical decision-making in preoperative planning

Aims. Appropriate acetabular component placement has been proposed for prevention of postoperative dislocation in total hip arthroplasty (THA). Manual placements often cause outliers in spite of attempts to insert the component within the intended safe zone; therefore, some surgeons routinely evaluate intraoperative pelvic radiographs to exclude excessive acetabular component malposition. However, their evaluation is often ambiguous in case of the tilted or rotated pelvic position. The purpose of this study was to develop the computational analysis to digitalize the acetabular component orientation regardless of the pelvic tilt or rotation. Methods. Intraoperative pelvic radiographs of 50 patients who underwent THA were collected retrospectively. The 3D pelvic bone model and the acetabular component were image-matched to the intraoperative pelvic radiograph. The radiological anteversion (RA) and radiological inclination (RI) of the acetabular component were calculated and those measurement errors from the postoperative CT data were compared relative to those of the 2D measurements. In addition, the intra- and interobserver differences of the image-matching analysis were evaluated. Results. Mean measurement errors of the image-matching analyses were significantly small (2.5° (SD 1.4°) and 0.1° (SD 0.9°) in the RA and RI, respectively) relative to those of the 2D measurements. Intra- and interobserver differences were similarly small from the clinical perspective. Conclusion. We have developed a computational analysis of acetabular component orientation using an image-matching technique with small measurement errors compared to visual evaluations regardless of the pelvic tilt or rotation. Cite this article: Bone Joint Res 2020;9(7):360–367

Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. At our center, we have tried to approach the unstable hip by identifying the primary cause of instability and correcting that at the time of revision surgery. Type 1:. Malposition of the acetabular component treated with revision of the acetabular component and upsizing the femoral head. Type 2:. Malposition of the femoral component treated with revision of the femur and upsizing the femoral head. Type 3:. Abductor deficiency treated with a constrained liner or dual mobility bearing. Type 4:. Soft tissue or bony impingement treated with removal of impingement sources and upsizing the femoral head. Type 5:. Late wear of the bearing treated with bearing surface exchange and upsizing the femoral head. Type 6:. Unclear etiology treated with a constrained liner or dual mobility articulation. These may be patients with abnormal spino-pelvic motion. The most common etiologies of instability in our experience include cup malposition (Type 1) and abductor deficiency (Type 3). We reviewed 75 hips revised for instability and at a mean 35.3 months 11 re-dislocations occurred (14.6%). Acetabular revisions were protective against re-dislocation (p<0.02). The number of previous operations (p=0.04) and previously failed constrained liners (p<0.02) were risk factors for failure. The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%. Although instability can be multifactorial, by identifying the primary cause of instability, a rational approach to treatment can be formulated. In general the poorest results were seen in patients with abductor deficiency. Given the high rate of failure of constrained liners (9 of the 11 failures were constrained), we currently are exploring alternatives such as dual mobility articulations. Our early experience with dual mobility suggests improved results when compared to constrained liners

To assess screw malposition rates and complications associated with pedicle screw insertion using 3D navigation technology. A retrospective study was undertaken for all cases where O-arm® and StealthStation® systems were used over a 2-year period. The primary outcome measure was return to theatre rates for pedicle screw malposition. A total of 938 screws were inserted (934 thoracolumbar and 4 cervical), and 103 patients underwent spinal fixation using O-arm® and StealthStation® navigation. 64 were revision cases and 39 primary cases. Average number of levels was 4.6. There were a total of 10 complications: 3 infections, 1 DVT, 1 PE, 1 fast atrial fibrillation (AF), 1 screw malposition, 1 non-union, 1 undisplaced vertebral body fracture and 1 nerve root compression following osteotomy. The percentage return to theatre for screw malposition using 3D navigation was 1% of patients and 0.1% of pedicle screws. No patients developed permanent neurological compromise. These systems provide accuracy that is comparable to traditional 2D fluoroscopic techniques. We advocate their use in the safe insertion of pedicle screws in complex revision deformity cases where original anatomical landmarks are absent or obscured. We also believe that radiation exposure is considerably less with navigation especially in these complex and revision cases

Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. At our center, we have tried to approach the unstable hip by identifying the primary cause of instability and correcting that at the time of revision surgery. Type 1: Malposition of the acetabular component treated with revision of the acetabular component and upsizing the femoral head. Type 2: Malposition of the femoral component treated with revision of the femur and upsizing the femoral head. Type 3: Abductor deficiency treated with a constrained liner or dual mobility bearing. Type 4: Soft tissue or bony impingement treated with removal of impingement sources and upsizing the femoral head. Type 5: Late wear of the bearing treated with bearing surface exchange and upsizing the femoral head. Type 6: Unclear etiology treated with a constrained liner or dual mobility articulation. The most common etiologies of instability in our experience include cup malposition (Type 1) and abductor deficiency (Type 3). We reviewed 75 hips revised for instability and at a mean 35.3 months, 11 re-dislocations occurred (14.6%). Acetabular revisions were protective against re-dislocation (p<0.02). The number of previous operations (p=0.04) and previously failed constrained liners (p<0.02) were risk factors for failure. The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%. Although instability can be multifactorial, by identifying the primary cause of instability, a rational approach to treatment can be formulated. In general, the poorest results were seen in patients with abductor deficiency. Given the high rate of failure of constrained liners (9 of the 11 failures were constrained), we currently are exploring alternatives such as dual mobility articulations. Our early experience with dual mobility suggests improved results when compared to constrained liners

Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. At our center, we have tried to approach the unstable hip by identifying the primary cause of instability and correcting that at the time of revision surgery. Type 1: Malposition of the acetabular component treated with revision of the acetabular component and upsizing the femoral head. Type 2: Malposition of the femoral component treated with revision of the femur and upsizing the femoral head. Type 3: Abductor deficiency treated with a constrained liner or dual mobility bearing. Type 4: Soft tissue or bony impingement treated with removal of impingement sources and upsizing the femoral head. Type 5: Late wear of the bearing treated with bearing surface exchange and upsizing the femoral head. Type 6: Unclear etiology treated with a constrained liner or dual mobility articulation. The most common etiologies of instability in our experience include cup malposition (Type 1) and abductor deficiency (Type 3). We reviewed 75 hips revised for instability and at a mean 35.3 months 11 re-dislocations occurred (14.6%). Acetabular revisions were protective against re-dislocation (p<0.015). The number of previous operations (p=0.0379) and previously failed constrained liners (p<0.02) were risk factors for failure. The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%. Although instability can be multifactorial, by identifying the primary cause of instability, a rational approach to treatment can be formulated. In general the poorest results were seen in patients with abductor deficiency. Given the high rate of failure of constrained liners (9 of the 11 failures were constrained), we currently are exploring alternatives such as dual mobility articulations

Management of recurrent instability of the hip requires careful assessment to determine any identifiable causative factors. While plain radiographs can give a general impression, CT is the best methodology for objective measurement. Variables that can be measured include: prosthetic femoral anteversion, comparison to contralateral native femoral anteversion, total offset from the medial wall of the pelvis to the lateral side of the greater trochanter, comparison to total offset on the contralateral side, acetabular inclination, & acetabular anteversion. Wera et al describe potential causes of instability. These are typed into I. Acetabular Component Malposition; II. Femoral Component Malposition; III. Abductor Deficiency; IV. Impingement; V. Late Wear; and VI. Unknown. Acetabular component malposition is the most common cause of instability and so measurement of cup orientation is essential. It is well known that excessive or inadequate anteversion can lead to anterior and posterior dislocation respectively but horizontal components are also associated with posterior dislocation due to deficient posterior/inferior acetabular surface. Similarly, excessive or inadequate femoral anteversion can be easily identified on CT as can insufficient total offset of the reconstructed joint compared to the contralateral side. This can be caused by medialization of the acetabular component. Abductor deficiency can be a soft-tissue cause of instability, but it certainly isn't the only one. Knowledge of the prior surgical exposure can be instructive. Anterior exposures can be prone to deficient anterior capsule just as posterior exposures can be prone to deficient posterior capsule and short rotators, while anterolateral and lateral exposures can be associated with gluteus minimus and gluteus medius compromise. Impingement, whether involving implants, bone, or soft tissue are primarily secondary to the above factors, if osteophytes were properly trimmed at the index procedure. Correction of the incorrect variables is the primary goal of revision for instability and greatly preferable to using salvage options such as dual-mobility or constrained articulations which invoke additional concerns. Ultimately though, such salvage options are necessary if the cause of the instability cannot be determined or can be determined but not corrected. Bracing, while highly inconvenient and sometimes impractical for certain patients, still has a role in specific circumstances. Formal analysis of the unstable prosthetic reconstruction is the key to successful treatment

Spezializing in subfields of Orthopaedics is common in anglo-american countries for more than 20 years. IThe aim of this paper is to demonstrate the necessity of fellowship programms in extremity orientated subfileds of orthopaedics. Analyzing the results of ankle arthrodesis performed by general orthopaedic surgeons campared to ankle arthrodesis performed by spezialized foot and ankle surgeons the difference in results will be demonstrated. Patients and methods. In 40 patients an ankle arthrodesis was performed between 1998 and 2012. Group A was formed by 20 consecutive patients treated by spezial trained Foot and Ankle surgeons and group B was formed by 20 patients treted by general orthopaedic surgeons. The average age in group A at the time of surgery was 59,9y (34 to79y) compared to 63,4y (41 to 80y) in group B. The average follow up was 34 months respectively 32 months after surgery. The study included a spezial questionnaire with the AOFAS score and rating of patients dissatisfaction. The successful healing of the arthrodesis was determied by using standardized radiographs, Furthermore a pedobarography, and a videoanalyzis of the walking was incuded. Results. All procedures in group A were performed using an anterior approach. Neither pseudarthroses, equinus or other malositions were detected in this group. In group B wurdenin 16 patients an anterior and in 4 patients a lateral approach was used. Complications included 3 pseudarthroses, 4 equinus malpositions, 4 varus malpositions, 4 valgus malpositions and 8 penetrations of the subtalar joint. The AOFAS score on average was 78 (46–92) points in group A and 75 (34 – 94) in group B. Conclusion. The analyzis of the data revealed that the results in Group A were comparable to the results published in the literature. Results in group B were inferior to those in group A and to the results published in the literature of Foot and Ankle surgery. Foot and Ankle surgery became more demanding over the last decades. As already shown in anglo-american countries spezializing in certain fields of orthopaedics is a necessity. More complex hindfoot surgery should be performed in special centers with an adequate case load

Introduction. Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. The purpose of this study was to classify causes of instability and evaluate outcomes based on an algorithmic approach to treatment. Methods. Two surgeons performed 77 consecutive revisions for instability. Patients had a mean of 2 (range, 0 to 6) prior operative attempts to resolve their instability. Subjects were divided into 6 types based on the etiology of instability: I) malposition of the acetabular component, II) malposition of the femoral component, III) abductor deficiency, IV) impingement, V) late wear, or VI) unclear etiology. Types I /II were treated with revision of the malpositioned component, Type III/VI with a constrained liner, Type IV by removing sources of impingement and Type V with a liner change. Large (>36 mm) femoral heads were used routinely. Results. The causes of instability were Type I: 25 (33%); Type II: 8 (10%); Type III: 28 (37%); Type IV: 7 (9%); Type V: 5 (7%); Type VI: 3 (4%). At a mean of 32.5 months (Range, 24 to 79) 12 patients re-dislocated (15.6%). Among these 12 failures 8 (75%) were in patients with abductor insufficiency (Type III) treated with a constrained liner. Conclusions. The most common causes of instability were cup malposition and abductor insufficiency. Our treatment protocol had an 84.4% success rate. The highest risk of failure was in patients with abductor insufficiency with a revision for other etiologies having a success rate of 92%

There has recently been an increase in the number of hip replacement procedures performed through an anterior approach. Every procedure has a risk profile, and in the case of a new procedure or technique it is important to investigate the incidence of complications. The aim of this study is to identify the complications encountered in the first 100 patients treated with the minimally invasive anterior approach. This is a case series of the first 100 hips treated and were assessed for complications. These were classified according to the severity and outcome [1]. The 100 hip comprised of 98 patients; 46 males and 52 females with an average operation age on 70.1 (±9.38) years. There were 2 bilateral procedures. Specific patient selection criteria were used. All complications occurred within one month of surgery. Complications such as fracture, deep vein thrombosis (DVT), cup malposition, femoral stem malposition, retained screw, excessive acetabular reaming and skin numbness were noted. Complications associated with fracture were characterized as either periprosthetic or trochanteric. Clinical outcome scores of SF36v2, WOMAC, Harris Hip and Tegner activity score were analysed at pre-operative, 6 months, 12 months 24 months and 36 months intervals. A total of 13 early complications occurred. Of these 13 complications the most common complications were trochanteric fracture, 3 instances (3.00%), periprosthetic fracture, 2 (2.00%), DVT, 2 (2.00%), numbness, 2 (2.00%) and loosening. Other complications recorded were cup malposition, 1 (1.00%), femoral stem malpositon, 1 (1.00%), retained screw, 1 (1.00%) and excessive acetabular reaming, 1 (1.00%). All fractures occurred in patients over the age of 60 years. Significant differences (p<0.05) were observed between all clinical outcomes measures pre-operatively and postoperatively (6, 12, 24 and 36 months). The unfamiliarity of the approach, however, increased operating time, and exposure problems, lead to trochanteric fracture

Background:. Varus-valgus constrained (VVC) implants are used in cases of severe valgus deformity, attenuated medial collateral ligament and difficulty in balancing the medial and lateral gaps of the knee. The increased constraint has been postulated to lead to more stress at the bone-implant interface and early loosening. The objective of this study was to compare the wear characteristics of the polyethylene liner in VVC prosthesis with the posterior-stabilized (PS) prosthesis and identify the factors leading to more wear in the VVC tibial inserts. Methods:. This was a retrieval analysis of all VVC liners collected from patients who underwent revision surgery from 1999 to 2011. These patients were matched to another group with posterior-stabilized inserts who underwent revision in the same time period. These two groups of patients were similar in terms of their demographic data and implant dimensions. Inserts were divided into 16 zones and a microscopic analysis of surface damage was carried out. We determined overall damage with a scoring system. Pre-revisions radiographs were reviewed and analyzed for correlation with the wear profile. Results:. There was significantly more damage in the posts of the VVC group (13.0 ± 5.0, compared to 4.7 ± 1.9 in the PS group) (p < 0.001). There was no difference in the backside wear, or wear in the medial and lateral compartments. Within the VVC group, the total damage score and cold flow damage were significantly higher with excessive joint line changes (≥ 5 mm). The excessive joint line elevation was associated with rotational wear pattern of the post (p = 0.004). The total abrasion and pitting scores were also higher in knees without proper restoration of the limb alignment (> 3° varus or valgus). Femoral component malposition correlated with higher total cold flow, pitting, debris damage scores, wear in medial and lateral compartments, and the anterior portion of the insert. The total damage scores for the posts in the VVC group were significantly higher with anterior tibial slope, and tibial component malposition. The most common cold flow deformation was found in the posterior post, followed by the anterior post. The cold flow damage to the post was significantly higher in excessive joint line changes (anterior and posterior post) and in tibial malposition (medial and lateral post). Conclusion:. The increased constraint resulted in more post damage. Joint line elevation, femoral and tibial component malposition, and anterior tibial slope resulted in significantly more wear in the VVC inserts

Introduction:. Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. The purpose of this study was to classify causes of instability and evaluate outcomes based on an algorithmic approach to treatment. Methods:. Two surgeons performed 77 consecutive revisions for instability. Patients had a mean of 2 years (range, 0 to 6) prior operative attempts to resolve their instability. Subjects were divided into 6 types based on the etiology of instability: I) malposition of the acetabular component, II) malposition of the femoral component, III) abductor deficiency, IV) impingement, V) late wear, or VI) unclear etiology. Types I /II were treated with revision of the malpositioned component, Type III/VI with a constrained liner, Type IV by removing sources of impingement and Type V with a liner change. Large (>36mm) femoral heads were used routinely. Results:. The causes of instability were Type I: 25 (33%); Type II: 8 (10%); Type III: 28 (37%); Type IV: 7 (9%); Type V: 5 (7%); Type VI: 3 (4%). At a mean of 32.5 months (Range, 24 to 79) 12 patients re-dislocated (15.6%). Among these 12 failures 8 (75%) were in patients with abductor insufficiency (Type III) treated with a constrained liner. Conclusions:. The most common causes of instability were cup malposition and abductor insufficiency. Our treatment protocol had an 84.4% success rate. The highest risk of failure was in patients with abductor insufficiency with a revision for other etiologies having a success rate of 92%