Preoperative radiographs to predict component malposition in direct anterior approach total hip arthroplasty.

INTRODUCTION: There is conflicting evidence as to whether or not patients undergoing total hip arthroplasty (THA) via the direct anterior approach (DAA) have increased risk of component malposition. The aim of this study was to investigate whether specific preoperative radiographic features were predictive of postoperative component malposition in DAA THA. PATIENTS AND METHODS: We examined 204 THA operations performed for osteoarthritis via the DAA at a single institution. Preoperative radiographs were analysed with numerous pre-specified measurements and classifications being recorded. Postoperative radiographs were analysed to determine if any of these preoperative radiographic factors correlated with component malposition in regard to cup inclination, cup version, femoral stem coronal alignment, leg-length discrepancy (LLD) and femoral offset discrepancy. RESULTS: Numerous preoperative factors were associated with component malposition. Coxa profunda was found to be a significant predictor of cup anteversion being outside of the target range (p = 0.0089) and an increased centre-edge angle was a significant predictor for a postoperative LLD (p = 0.0134). A decreased neck-shaft angle (p = 0.0007) and a lower preoperative LLD (p = 0.0019) were both predictive of femoral stem coronal malalignment. CONCLUSIONS: Preoperative radiographs can be a valuable tool for surgeons in predicting patients at risk of component malposition in DAA THA.

Accuracy of computer navigation in total knee arthroplasty: A prospective computed tomography-based study.

INTRODUCTION: Evidence now exists advocating the use of computer navigation in total knee arthroplasty (TKA). Despite the introduction of new navigation systems into clinical practice no evidence currently exists showing independent verification of their accuracy. The aim of this study was to validate the in vivo accuracy of the Exactech Guided Personalised Surgery (GPS) computer navigation system using a validated computed tomography (CT) measurement of alignment. METHOD: Consecutive patients who underwent TKA using the GPS Navigation System at our institution were prospectively recruited. Intraoperative parameters of 3D alignment as measured by the GPS navigation system were recorded and compared against the postoperative measurements of alignment measured using the Perth CT Protocol to assess the accuracy of the GPS navigation system. RESULTS: 29 consecutive patients (13 male, 16 female) who underwent TKA were prospectively recruited. Overall, for all measures of 3D alignment the mean difference between intraoperatively recorded and postoperative CT-measured alignment was 1.55° ± 0.22° (95% confidence interval). Individual measurement differences in the femoral prosthesis were: coronal alignment 1.64° ± 0.52°; flexion 2.07° ± 0.55°; rotation 1.38° ± 0.33° Differences in the tibial prosthesis were: coronal alignment 2.03° ± 0.53°; slope 1.14° ± 0.39° The whole limb coronal alignment difference was 2.34° ± 0.83° CONCLUSION: The Exactech GPS Navigation system is very accurate with a high concordance between intraoperative and postoperative measures of alignment and prosthesis positioning. We therefore confidently validate the system and support its continued use in clinical practice. Other navigation systems should undergo a similar validation process.

Transfusion rates with intravenous tranexamic acid in total hip arthroplasty performed using the direct anterior approach.

INTRODUCTION: Tranexamic acid (TXA) has been shown to reduce blood loss and transfusion requirements in patients undergoing total hip arthroplasty (THA). Most studies have focused on TXA in THA performed using a posterior approach (PA) or lateral approach. The aim of this study was to analyse the efficacy of TXA in patients undergoing THA using the direct anterior approach (DAA). PATIENTS AND METHODS: Using our institutional database, a retrospective analysis was conducted on consecutive primary THA performed for osteoarthritis to determine transfusion rates in patients undergoing THA with the DAA with and without TXA. RESULTS: 146 consecutive THA were performed using DAA: 83 (56.8%) patients had TXA and 63 (43.2%) did not have TXA. Among patients who had TXA, 1 patient required a blood transfusion compared to 7 patients among those who did not have TXA (1.2% vs. 11.12%, p = 0.02). The relative risk of 0.11 (95% confidence interval 0.01-0.86) indicates an 89% reduction in the risk of requiring blood transfusion with TXA administration compared to no TXA. CONCLUSION: TXA is effective in reducing blood transfusion requirements for patients undergoing DAA THA.

Direct Anterior Approach Total Hip Arthroplasty: An Adjunct to an Enhanced Recovery Pathway: Outcomes and Learning Curve Effects in Surgeons Transitioning From Other Surgical Approaches.

BACKGROUND: The aim of this study was to investigate whether the direct anterior approach (DAA) to total hip arthroplasty (THA) resulted in a shorter length of stay (LOS) in surgeons new to the approach when compared to their previously used approach. Perioperative complications were also assessed. METHODS: We examined 93 DAA THA performed by 3 hip arthroplasty surgeons at a single institution comparing these to their previous 166 operations performed using the lateral or posterior approach. RESULTS: Fixed-effects generalized linear modeling demonstrated that patients who underwent THA by the DAA had 26% shorter LOS than those who were operated on using lateral or posterior approaches (adjusted risk ratio = 0.74; 95% confidence interval = 0.65-0.84; P < .001). A greater proportion of DAA patients were discharged directly home (98% vs 87%, F (1,233) = 8.12, P = .005) and complication rates were comparable between groups. CONCLUSION: The DAA can reduce patient LOS and may be a valuable addition to enhanced recovery pathways. Our findings also suggest that surgeons transitioning to the DAA do not have an increased complication rate when compared to their previous approach.

How should new orthopaedic implants be introduced: an example and recommendations for best practice.

Continued advancements in orthopaedics have led to the development of many new implants; many of these are being utilized in clinical practice with little or no evidence base for their safety or effectiveness. Highly publicized failures in orthopaedic technology have led to an increased awareness of this issue in both medical and non-medical circles. In most cases, the significant harm caused to the public could have been avoided by the appropriately staged implementation of new implants. This review comments on the current literature regarding the optimal practice for the introduction of new orthopaedic technology. The authors' experience with the failed ESKA Adapter Short-stem/Modular Hip is described; the methodology used for its evaluation is used as a basis to discuss what was successful about the process and also give warning on what could be improved upon. The ideal practice requires new orthopaedic implants to be evaluated by high-volume surgeons in specialist orthopaedic hospitals. These studies should include biomechanical studies, radiostereophotometric analysis, implant retrieval and outcome assessment. Results and complications should be reported early to the appropriate joint registry and regulatory body. Once a suitable evidence base has developed, the implant can be distributed into wider clinical practice or withdrawn. These recommendations aim to protect the patient and public from harm while allowing surgical innovation to still continue.

A cadaver study validating CT assessment of acetabular component orientation: the Perth CT hip protocol.

OBJECTIVE: The aim was to develop a CT-based protocol to accurately measure post-operative acetabular cup inclination and anteversion establishing which bony reference points facilitate the most accurate estimation of these variables. MATERIALS AND METHODS: An all-polyethylene acetabular liner was implanted into a cadaveric acetabulum. A conventional pelvic CT scan was performed and reformatted images created in both functional and anterior pelvic planes. CT images were transferred to a Freedom-Plus Graphics software package enabling an identical, virtual 3D model of the cadaveric pelvis to be created and definitive acetabular cup orientation established. Using coronal and axial slices of the CT scans, acetabular cup inclination and anteversion were measured on five occasions by ten radiographers using differing predetermined bony landmarks as reference points. The intra- and inter-observer variation in measurement of acetabular cup orientation using varying bony reference points was assessed in comparison to the elucidated definitive cup position. RESULTS AND CONCLUSION: Virtually derived definitive acetabular cup orientation was measured showing cup inclination and anteversion as 41.0 and 22.5° respectively. Mean CT-based measurement of cup inclination and anteversion by ten radiographers were 43.1 and 20.8° respectively. No statistically significant difference was found in intra- and inter-observer recorded results. No statistically significant differences were found when using different bony landmarks. CT assessment of acetabular component inclination and anteversion is accurate, reliable and reproducible when measured using differing bony landmarks as reference points. We recommend measuring acetabular inclination and anteversion from the inferior acetabular wall/teardrop and posterior ischium respectively.

Stiffness after total knee arthroplasty: does component alignment differ in knees requiring manipulation? A retrospective cohort study of 281 patients.

This study aims to evaluate component alignment in a large cohort of total knee arthroplasties (TKAs) and ascertain whether alignment in TKAs undergoing postoperative manipulation under anesthetic is significantly different from those achieving good function. A retrospective review of 281 consecutive primary TKAs was performed. All TKAs underwent computed tomographic scanning (Perth computed tomography knee protocol). Of 281 TKAs, 21 (7.4%) underwent manipulation, performed at a mean of 8.1 weeks (range, 3-14 weeks) after surgery. No statistically significant difference was seen between groups for any of 12 parameters of alignment. Postoperative stiffness with the need for manipulation under anesthetic is multifactorial in origin. This study found insufficient evidence to support the theory that component alignment contributes significantly to the etiology of this difficult problem.

Metal-on-metal bearings, inflammatory pseudotumours and their neurological manifestations.

Metal-on-metal bearings have become more popular for hip arthroplasty in younger patients in the last 15 years. We present a review of the neurological consequences relating to such bearing surfaces illustrated by an appropriate case report. The mechanisms of increased metal ion production and pseudotumour formation are discussed. If unexplained neurology, hip/groin pain or a localised mass around the hip are present with a metal bearing hip then urgent referral to a specialist orthopaedic surgeon is warranted for consideration of exchange arthroplasty.

Computer navigation vs conventional total knee arthroplasty: five-year functional results of a prospective randomized trial.

Seventy-one patients were randomly allocated to undergo either computer-navigated or conventional arthroplasty. A statistically significant improvement in alignment was seen in the computer-navigated cohort. Five-year functional outcome was assessed using the Knee Society, Short Form-36, Western Ontario and McMaster Universities Osteoarthritis Index, and a patient satisfaction score. At 5 years, 46 patients were available for assessment (24 navigated and 22 conventional knees). No patients had undergone revision. No statistically significant difference was seen in any component of any measure of outcome between navigated and conventional cohorts. Longitudinal data showed function to be well maintained with no difference in functional score between 2 and 5 years in either cohort. Despite achieving better alignment, 5 years postoperatively, the functional outcome with computer-navigated knee arthroplasty appears to be no different to that implanted using a conventional jig-based technique.

Common peroneal nerve palsy associated with pseudotumour after total knee arthroplasty.

Pseudotumours about the hip as a result of metal-on-metal wear debris are now widely reported. Nerve palsies associated with such lesions are less commonly described. To our knowledge no previous reports exist which describe pseudotumours about a total knee arthroplasty. The case of a metal-on-metal debris-induced pseudotumour about a total knee arthroplasty with an associated common peroneal nerve palsy is presented. The use of serum ion levels is discussed, specifically for the early detection and diagnosis of full-thickness polyethylene liner wear and subsequent revision options.

Morbidity of navigated vs conventional total knee arthroplasty: a retrospective review of 327 cases.

A retrospective review of 146 patients undergoing navigated total knee arthroplasty (NTKA) and 181 patients undergoing conventional total knee arthroplasty (CTKA) was undertaken to establish whether NTKA, with its avoidance of intramedullary instrumentation, resulted in less early postoperative morbidity than CTKA. Cohorts were well matched in terms of age, sex, body mass index, and American Society of Anesthesiologists grade. Statistically significantly longer operative and tourniquet times were seen with NTKA. Blood transfusion requirements were significantly higher in CTKA. No statistically significant differences were seen in any other measure of postoperative morbidity (length of stay, hemoglobin drop, transfusion rate, postoperative anemia, time to achieve 70° flexion, and thromboembolic phenomena). In large, well-matched cohorts, NTKA offered no benefit in terms of early postoperative morbidity when compared with conventional jig-based techniques.

Three-dimensional component alignment and functional outcome in computer-navigated total knee arthroplasty: a prospective, randomized study comparing two navigation systems.

Computer navigation in total knee arthroplasty produces better component alignment than conventional techniques. Different navigation systems exist. We undertook a prospective, randomized study comparing 2 navigations systems (Stryker Full Navigation and Stryker Articular Surface Mounted [ASM] navigation systems). Three-dimensional component alignment (Perth computed tomographic knee protocol) and function at 1 year (Knee Society Scores) were assessed. Forty patients participated (20 fully navigated and 20 ASM-navigated total knee arthroplasties). Cohorts were well matched according to sex, age, and body mass index. No statistically significant difference was seen in any parameter of 3-dimensional component alignment or function between cohorts. Operative time for the ASM cohort was significantly less than the fully navigated cohort (P = .001). Both systems performed equally well, and therefore, surgeon preference should determine which system is used.

The imaging spectrum of peri-articular inflammatory masses following metal-on-metal hip resurfacing.

INTRODUCTION: Resurfacing metal-on-metal hip arthroplasty is increasing in popularity, especially in younger patients. To date, studies indicate that the procedure is associated with a good outcome in the medium-term. Formation of a peri-articuar mass is a rarely reported complication. In this study we analyse the imaging findings in patients with resurfacing implants presenting to our institution with peri-articular masses identified on cross sectional imaging. MATERIALS AND METHODS: All patients with documented peri-articular masses following resurfacing arthroplasty were included. The available imaging related to the masses was reviewed and the findings documented along with the patient's demographics. RESULTS: There were 10 patients (13 joints). All patients were female. Patients presented with periprosthetic anterior or posterolateral solid and cystic masses. The anterior masses involved psoas muscle and were predominately solid. The posterolateral masses were predominately cystic. In the three cases with bilateral arthroplasties, masses were detected in both hips. Histology in six cases showed features compatible with a type IV hypersensitivity reaction. CONCLUSIONS: The preponderance of females, the bilateral nature of the masses and the histological features suggest that peri-articular masses following resurfacing arthroplasty is due to the metal hypersensitivity.

Calcific tendinitis: natural history and association with endocrine disorders.

A retrospective, observational cohort study of 102 consecutive patients (125 shoulders) with calcific tendinitis is presented. Of the patients, 73 (71.6%) were women and 29 (28.4%) were men. Compared with population prevalences, significant levels of endocrine disorders were found. We compared 66 patients (62 women [93.9%] and 4 men [6.1%]; mean age, 50.3 years) (81 shoulders) with associated endocrine disease with 36 patients (11 women [30.6%] and 25 men [69.4%]); mean age, 52.4 years) (44 shoulders) without endocrine disease. The endocrine cohort was significantly younger than the non-endocrine cohort when symptoms started (mean, 40.9 years and 46.9 years, respectively), had significantly longer natural histories (mean, 79.7 months compared with 47.1 months), and had a significantly higher proportion who underwent operative treatment (46.9% compared with 22.7%). Disorders of thyroid and estrogen metabolism may contribute to calcific tendinitis etiology. Classifying calcific tendinitis into type I (idiopathic) and type II (secondary or endocrine-related) aids prognosis and management.

Ulnar nerve compression at Guyon's canal by an anomalous abductor digiti minimi muscle: the role of ultrasound in clinical diagnosis.

Anomalous variations of abductor digiti minimi are commonly found at Guyon's canal but rarely cause ulnar nerve compression. We report such a case with particular emphasis on the effectiveness of ultrasound to detect and delineate anatomical structures in this region.