Ambient theatre temperature and cement setting time in total knee arthroplasty.

BACKGROUND: Polymethylmethacrylate cement is used in total knee arthroplasty and plays a significant role in the success of the procedure. Temperature variation is known to influence cement setting time in vitro. Our aim is to evaluate the relationship between ambient theatre temperature and cement setting time in vivo. METHODS: Theatre temperature and cement setting time were prospectively recorded during 683 total knee arthroplasties over 8 years using a single cement and vacuum mixing system (Simplex with tobramycin). Setting time was defined as the time until a scalpel blade could not indent the cement surface. RESULTS: Mean temperature was 18.92°C (SD 1.16) and setting time 13.08 min (SD 1.92). A moderate inverse relationship exists between ambient temperature and setting time (Pearson's R = -0.423); however, potential setting times within a given temperature range varied considerably (<19°C: 8-19.1 min, 19-20°C: 7-18 min and >20°C: 7.5-16 min), suggesting that temperature alone cannot reliably predict setting time. CONCLUSION: Our data support the current understanding of bone cement properties in vivo and suggest that surgeons should be mindful in regards to unpredictable cement setting time and optimal theatre environment.

Accuracy of MRI-based vs. CT-based patient-specific instrumentation in total knee arthroplasty: A meta-analysis.

INTRODUCTION: The technical objective of total knee arthroplasty (TKA) is to restore normal mechanical parameters to the knee. Patient-specific instrumentation (PSI) was developed to streamline the operative process and improve accuracy. PSI produces individualized cutting guides based on three-dimensional models of the patient's anatomy acquired from computed-tomography (CT) or magnetic-resonance imaging (MRI). However, the superiority of one modality over the other remains unclear. Therefore, we aimed to compare the accuracy of patient-specific cutting guides produced from MRI or CT imaging methods in TKA. METHODS: Electronic databases were systematically searched using relevant keywords and MeSH terms for original-data English-language publications comparing the accuracy of CT and MRI-based PSI cutting guides in TKA. Data was extracted from the text, tables and figures of studies and meta-analysed. RESULTS: MRI-based PSI cutting guides produced a lower proportion of coronal plane outliers (>3°) with regard to overall limb mechanical axis (OR 2.75, p = 0.01). There were no significant differences between the two in terms of sagittal femoral and tibial component placement, or coronal femoral and tibial placement, or femoral component axial rotation. Tibial rotation was not analysed in the literature. CONCLUSIONS: MRI-based patient-specific cutting guides produced a lower proportion of outliers in the overall coronal alignment of the limb compared to CT, with no significant difference between the two in terms of femoral or tibial component placement. Future studies should investigate the differences in resource usage and operative time between the two to inform surgeons' decision making when choosing an ideal imaging modality for PSI TKA. STUDY DESIGN: Meta-analysis. LEVEL OF EVIDENCE: III, systematic review of cohort and comparative studies.

The accuracy of bony resection from patient-specific guides during total knee arthroplasty.

PURPOSE: In patient-specifically instrumented (PSI) total knee arthroplasty, the correlation between the pre-operative surgical plan, accuracy of the cutting block, and intra-operative resection size is unclear. The aim of this study was to evaluate the ability to accurately execute the PSI surgical plan and to add to the merging information with respect to this technology with the hypothesis that the PSI blocks would demonstrate good accuracy with regard to the bony thickness of the resections. METHODS: One hundred and thirty TKAs using PSI (MRI/long-leg radiographs) were retrospectively analysed. All surgeries were conducted via similar surgical approach and technique, with resection performed after guide placement and alignment assessment. The bony cut thicknesses of the medial (MTP) and lateral tibial plateau (LTP), distal medial (DM), distal lateral (DL), posterior medial (PM) and posterior lateral (PL) femur were measured with a vernier calliper. The measured resection thickness was subtracted from the planned resection. Errors were defined as ≤1.5 mm (acceptable), 1.5-2.5 mm (borderline), and >2.5 mm (outliers). RESULTS: Overall, 81 (62.3 %) of the knees were free of outliers. The distal femur cut had the highest proportion of acceptable cut error with 209 of 260 total cuts acceptable (80.4 %). The tibial cuts had the lowest proportion of "acceptable" cuts (68.9 %). Tibial cuts had more outliers (33 of 260 cuts, 12.7 %) than the femur (39 of 520 cuts, 7.5 %) (p = 0.01). Pre-operative varus (n = 97) and valgus (n = 33) deformities demonstrated 7.7 % (45/482) and 13.6 % (27/198) of cuts which were outliers, respectively (p = 0.01). CONCLUSION: PSI showed only fair to moderate accuracy with 62.3 % of the knees presenting no outliers. The tibia cutting guide was less accurate than the femur. Specific attention is needed when cutting the tibia and in correction of valgus deformity. Moreover, intra-operative verifying measurements can provide feedback to the accuracy of the surgical plan. LEVEL OF EVIDENCE: IV, case series with no comparison group.

Early clinical and radiological results of total knee arthroplasty using patient-specific guides in obese patients.

PURPOSE: Total knee arthroplasty (TKA) is a challenging procedure in patients with a high body mass index (BMI). The aim of our study was to assess the outcome and accuracy of restoration of mechanical alignment in TKA using patient-specific guides (PSG) involving patients with high BMI. MATERIALS AND METHODS: Patients with BMI of 30 or above were enrolled in the study. The mean age of the patients was 65.15 years. The study comprised of 46 males and 54 females. Total knee arthroplasty was planned after a pre-operative MRI and long leg x-ray films using customized PSG. RESULTS: Of the 105 knees (100 patients) in the study, average BMI was 35.42 kg/m(2) (30-56). Twenty patients (20 %) had class III obesity (≥40 kg/m(2)). The average blood loss and operative time were 236.1 ml (range 50-700 ml) and 92.2 min (65-130 min), respectively. The average post-operative mechanical axis was noted to be 1.85° varus (range 4° valgus to 6° varus). Eighty-eight patients (86.27 %) had mechanical alignment within 3° of neutral. There were no adverse intraoperative events. One patient had deep infection that required a two-stage revision. The average post-operative range of motion at 1-year follow-up was 105.8° (range 80°-130°). CONCLUSION: Patient-specific guides technology restores the coronal mechanical axis reliably in obese patients without adversely affecting outcomes. Our short-term follow-up has shown favorable outcomes. Surgeons should use these customized jigs as a guide and adjust the size of components, alignment and rotation according to normal surgical principles.

Verification of the Australian Orthopaedic Association National Joint Replacement Registry using a surgeon's database.

PURPOSE: To assess the completeness of registration and any discrepancies between the senior author's database and the Australian Orthopaedic Association National Joint Replacement Registry (AOA NJRR). METHODS: From 2002 to 2005, the senior author performed 231 primary total hip arthroplasty (THA) on 217 patients using the Corail femoral stem and one of the 3 types of the acetabular component: Pinnacle, ASR, or Duraloc/Option. The name of each patient was forwarded to the AOA NJRR for matching and verification. RESULTS: The AOA NJRR recorded 230 of the 231 primary THAs; all but one was matched with the senior author's database. Nine (3.9%) of them were revised by the same (n=7) or another (n=2) surgeon. Three (43%) of the 7 revision surgeries were not recorded on the AOA NJRR. One patient revised for a ceramic liner fracture was incorrectly recorded as 'wear acetabulum' in the AOA NJRR. CONCLUSION: Although the AOA NJRR achieved high registration completeness for primary THA, accuracy for revision THA was much lower.

Whip stitch versus grasping suture for tendon autograft.

PURPOSE: During tendon autograft harvest, either a grasping suture or traditional whip stitch can be used to grasp tendon prior to definitive bone fixation. Their grip strength has not, to our knowledge, been compared. This article compares a needle-free suture technique to a standard whip stitch by testing grip strength in vitro. METHODS: Twelve uniform ovine flexor tendons were prepared; six tendons with a standard, non-locking whip stitch and six tendons with a grasping suture. All the samples were tested to failure in uniaxial tension in a materials testing machine. Load/displacement curves were generated, and qualitatively assessed and peak loads were compared. RESULTS: There were no significant differences between the groups in tendon length or diameter. Modes of failure between the groups, as characterised by the load/displacement curves, were quite distinct. Peak load to failure was lower in the utility suture group (mean peak load at failure 121.28 N) than the whip stitch group (mean peak load to failure 188.82 N). All failures in the utility suture group occurred when the suture snapped. CONCLUSIONS: The grasping suture described here is weaker than a standard whip stitch but may be sufficiently strong to harvest and handle tendon autograft. A standard whip stitch remains the choice for definitive graft fixation.

Infection or allergy in the painful metal-on-metal total hip arthroplasty?

Metal-on-metal articulations are increasingly used in total hip arthroplasty. Patients can be sensitive to metal ions produced by the articulation and present with pain or early loosening. Infection must be excluded. Correct diagnosis before revision surgery is crucial to implant selection and operation planning. There is no practical guide in the literature on how to differentiate between allergy and infection in a painful total hip arthroplasty. We present the history, clinical findings and hip scores, radiology, serology, hip arthroscopy and aspirate results, labeled white cell scan, revision-hip findings, histology and clinical results of a typical patient with a hypersensitivity response to a metal-on-metal hip articulation, and how results differ from patients with an infected implant. A practical scheme to investigate patients with a possible hypersensitivity response to an implant is presented.

Primary total hip arthroplasty in severe developmental dysplasia of the hip. Ten-year results using a cementless modular stem.

We report the average 10-year clinical and radiographic results of 28 hips with Crowe III or IV developmental dysplasia of the hip (DDH) and a technically difficult primary hip arthroplasty using the cementless modular S-ROM stem (DePuy Orthopedics, Warsaw, Ind). Twenty-one patients required significant autologous bone grafting, 1 had a large allograft, and 6 patients required femoral shortening at the time of their total hip arthroplasty. Three patients had an intraoperative technical complication. The average preoperative Harris hip score was 37; at 10 years, 81. The Short Form 12 was 41.64 physical/54.03 mental at 10 years, and the WOMAC average score was 23 at 10 years. None of the S-ROM stems had been revised or were loose at latest follow-up. Six hips had osteolysis in Gruen zones 1 or 7 but none around or distal to the sleeve. The 10-year results of the S-ROM stem used in patients with osteoarthritis secondary to severe DDH are excellent.

The accuracy of bone resections made during computer navigated total knee replacement. Do we resect what the computer plans we resect?

Many studies have shown that computer navigation in total knee arthroplasty aids the surgeon to place the prosthesis in a more accurate overall alignment. Bony resection creates the flexion and extension gaps; important in balancing the knee and implant selection in TKR. The computer plans the bone cuts but has variables that it cannot control: the surgeon, the saw blade thickness and oscillation, the accuracy of the jigs, movement of the pins, and the quality of initial mapping data inputted by the surgeon. The accuracy of computer navigated bone resections are validated on cadavers, but this is the first study to compare the predicted bone cuts to that physically resected during TKR. For 89 patients undergoing primary TKR, the bone cut from the distal femur and proximal tibia was measured using Vernier callipers and compared to the computer calculation of the same. Results show that computer measurement of the physical space left by the resected bone is accurate.

Effect of low intensity pulsed ultrasound on healing of an ulna defect filled with a bone graft substitute.

A 1.5 cm unilateral rabbit ulna defect model was performed in 18 adult NZ white rabbits. The defects were filled with a beta-tricalcium phosphate bone graft substitute (JAX TCP). The surgical site in half the animals was treated daily with 20 min of low intensity pulsed ultrasound (LIPUS). Animals were sacrificed at 4 weeks (n = 3 per group) or 12 weeks (n = 6 per group) following surgery for radiographic and histologic endpoints. Radiography revealed some resorption of the JAX TCP by 12 weeks in the control and LIPUS treated groups. LIPUS treatment did not accelerate this resorption. Some new bone formation was noted in the control groups at the defect margins while little bone formed in the center of the defect at 4 and 12 weeks. In contrast, radiographs revealed more new bone at 4 and 12 weeks in the LIPUS treated animals throughout the section. Bone mineral density (DEXA) revealed a statistically significant difference at 4 weeks with LIPUS while no differences were found at 12 weeks. Histology of the LIPUS treated sections demonstrated new woven bone formation on and between the JAX TCP bone graft substitute particles across the defect. VEGF expression was increased with LIPUS treatment at 4 weeks and remained elevated at 12 weeks compared with controls. CBFA-1 expression levels were elevated with LIPUS treatment at both time points. LIPUS treatment increased bone formation in ulna defect healing with a beta-tricalcium phosphate bone graft substitute.

Role of community diagnostic ultrasound examination in the diagnosis of full-thickness rotator cuff tears.

BACKGROUND: Diagnostic ultrasound examination has become the most commonly used investigation in Australia for diagnosing rotator cuff tears. The authors felt that the results of such investigations were often inaccurate in their clinical practices. METHODS: The diagnostic ultrasound findings in 336 cases were compared to arthrography, and in 225 cases findings at surgery. RESULTS: A very poor accuracy rate of 0.38 was found for diagnostic ultrasound examination. The sensitivity was 0.24 and specificity was 0.61. CONCLUSIONS: Extreme caution is recommended in the use of diagnostic ultrasound, as currently practised in a general community setting, in diagnosing full-thickness rotator cuff tears.