Preoperative Templating for Total Hip Arthroplasty: A Method for Calibrating Digital Radiographs Using Patient Demographics and Anthropometric Measurements

Background Preoperative templating aids the surgeon in estimating implant size and placement. Calibration markers are used to set the correct magnification of digital images before templating. Improper marker placement or complete absence can lead to inaccuracy or an inability to calibrate images altogether. Aims This study describes a method for calibrating images using a patient's femoral head size (FHS) predicted using demographics and anthropometric data. Materials and methods A formula predicting the FHS was derived from a cohort of 507 patients who underwent hemiarthroplasty for an intracapsular fractured neck of the femur through multivariate regression analysis. A separate validation cohort (n=50) who had undergone total hip arthroplasty (THA) had postoperative radiographs calibrated using the predicted FHS and the native contralateral hip as a surrogate calibration marker. The THA femoral head implant size was subsequently measured and compared with the actual implant size selected intraoperatively. Measurements were performed by two independent assessors to determine intra- and interobserver reliability. Results Multivariate regression analyses showed four variables significantly correlated with the size of the femoral head: gender (p < 0.001), height (p < 0.001), weight (p < 0.001), and race (Asian) (p = 0.01). Using these, a regression model to predict the FHS was obtained with an R2 value of 0.65 and a standard error of 2.18 mm. The validation cohort showed that THA head implant size could be accurately measured with an average root-mean-squared error (RMSE) of 1.41 mm (SD = 0.97 mm; %RMSE = 4.7%). The implant head size was measured to be within 5%, 10%, and 15% RMSE in 57.5%, 93.0%, and 100.0% of cases, respectively. There was excellent intraobserver (R2 = 0.94 and 0.95) and interobserver (R2 = 0.94) reliability. Conclusions The novel method proposed and validated in this study, using a predicted FHS to calibrate digital images, provides an alternative means of templating THA for fractured neck of the femur patients, in whom external calibration markers are often absent.

How Accurate is the Use of Contralateral Implant Size as a Template in Bilateral Hemiarthroplasty?

PURPOSE

Accurately predicting implant size for hemiarthroplasties offers an important contribution to theatre efficiency and patients' intraoperative care. However, pre-operative sizing using templating of implants in hip fracture patients requiring a hemiarthroplasty is often difficult due to non-standard radiographs, absence of a calibration marker, poor marker placement, variable patient position, and in many institutions a lack of templating facilities. In patients who have previously undergone a hemiarthroplasty on the contralateral side, surgeons can use the contralateral implant size for pre-operative planning purposes. However, the accuracy of doing this has not previously been reported. The aim of this study was to investigate the reliability of using an in situ contralateral implant as a predictor of implant size on the contralateral side.

METHODS

A retrospective review of our local neck of femur fracture (NOF) database was undertaken to identify patients who had bilateral hip hemiarthroplasty. Operative records were reviewed to establish the size of prostheses used at operation. Correlation, agreement, and reliability analysis were performed using the least squares, Bland-Altman plot, and intra-class correlation coefficient (ICC) methods, respectively.

RESULTS

Operative records were identified for 45 patients who had bilateral hemiarthroplasties. There was a difference in implant size used in 58% of cases. Of these 77% required a larger implant on the right. Implant sizes were within 1 mm of the contralateral side in 78% and within 2 mm in 91% of patients. However, in 9% of patients, there was a discrepancy greater than 2 mm with some cases having up to 6 mm discrepancy. Correlation coefficient was 0.83 and the ICC 0.90.

CONCLUSIONS

The findings in this study indicated that using the size of a contralateral implant can be used as a reliable indicator of head size in cases of bilateral hemiarthroplasty. However, the surgeon should remain cautious as there is a one in ten chance of there being a 3 mm or more difference in implant size.

There is no 'weekend effect' in elective orthopaedic surgery

Introduction The 'weekend effect' is said to occur when patient outcomes are adversely affected by the day of the week on which they present to hospital or have surgery. However, it is uncertain whether such a phenomenon exists for elective orthopaedic surgery. We investigated whether there is a 'weekend effect' in elective orthopaedic patients. Methods Retrospectively collected data were obtained from our institution's electronic patient records. We collected demographic and International Statistical Classification of Diseases and Related Health Problems tenth revision coding data for all included patients. Multivariate analyses identified covariate-adjusted risk factors, associated with prolonged stays. Thirty-day mortality data were assessed according to the day on which surgery occurred. Results We analysed data for 892 patients over a one-year period. During the year, 457 patients had a total hip and 435 had a total knee replacement; 814 patients (91.3%) underwent surgery during the week, while 78 (8.7%) had surgery on a Saturday. There was no difference in average length of stay between the groups (5.0, 2.6 vs 5.0, 3.4, P = 0.95). Variables associated with prolonged hospitalisation included increasing age (covariate adjusted relative risk 1.02, 95% confidence interval 1.01-1.03, P < 0.001) and an American Society of Anesthesiologists score of 2, (relative risk 1.6, 95% confidence interval 1.15-2.20, P = 0.005). There was one death in a patient who underwent surgery on a Monday. Conclusions There is no 'weekend effect' for elective orthopaedic surgery.

Case report: Rhodococcus erythropolis osteomyelitis in the toe

The Rhodococcus species rarely cause musculoskeletal infections, with only two cases reported in the literature. We report the case of a 53-year-old woman who had an infection develop after first metatarsophalangeal joint fusion. A year after surgery, she continued to have pain and swelling with nonunion. She underwent revision of the arthrodesis and tissue samples from surgery revealed Rhodococcus erythropolis. The patient's symptoms improved with oral antibiotics. One year after the revision surgery, the fusion had united. We believe this is the first report of a case of a musculoskeletal infection caused by Rhodococcus erythropolis.

A minimally invasive surgical technique for augmented reconstruction of the lateral ankle ligaments with woven polyester tape

Although stabilization of the lateral ankle ligament complex (LALC) with augmented techniques is known to be successful, it is associated with a number of complications. We hypothesize that successful stabilization of LALC can be achieved with a woven polyester tape implant via a minimally invasive procedure, as an alternative to tenodesis. Four men with chronic instability of the ankle underwent a minimally invasive surgical stabilization of LALC with a woven polyester tape. This tape was passed through the distal fibula to the base of the fifth metatarsal and then back to the fibula once more before being tied. The foot was immobilized in a neutral position for 2 weeks. Partial weightbearing with a walking stick began on the same day, and physiotherapy began for 10 weeks. Evaluation was performed at a mean follow-up of 24.5 months postoperatively. Preoperatively, all patients had a chronically unstable index ankle both functionally and clinically. At a mean of 24.5 months postoperatively, functional stability for all patients was normal (Sefton grade 1). Subjective ankle performance grades were normal in all cases, and all patients felt the outcome was excellent. Objective measurement with clinical stress testing showed anterior drawer and inversion tests to be the same as the contralateral ankle in all patients. However, each displayed limited inversion of the ankle. No complications such as wound dehiscence, infection, pain, or nerve injury were observed after the procedure. All were able to return to their preinjury activity level within 3 months. Stabilization of LALC may be simply and successfully achieved with a woven polyester graft as an alternative to tenodesis.

Partial rupture of the distal semitendinosus tendon treated by tenotomy--a previously undescribed entity

Hamstring strains are common. They are usually treated conservatively, with good results. Thus far, the only subset of patients who have been considered for surgery are those with complete avulsions of the attachments. We describe a new clinical entity: partial rupture of the distal semitendinosus tendon; which has failed to settle with conservative treatment; and has been successfully treated by tenotomy.

Systemic effects of bilateral tibial versus bilateral femoral shaft fractures. Is there a difference?

The authors investigated the prevalence and the difference in the severity of systemic complications following intramedullary nailing of bilateral tibial and femoral shaft fractures. A retrospective chart analysis of 12 consecutive patients with bilateral tibial shaft fractures (TF) and 14 patients with bilateral femoral shaft fractures (FF) was performed. The incidences of bilateral tibial fractures and bilateral femoral shaft fractures were 3.8% and 4.6% respectively. The median Injury Severity Score (ISS) in TF group was 13 (9-29) compared to 16 (9-34) in the FF group (p = 0.169). The mean resuscitation requirements were 4.2 (3-11) litres of colloids and crystalloids and 1.7 (0-10) units of blood in the TF group and 10.6 (6-16) litres of colloids and crystalloids and 9.2 (5-25) units of blood in the FF group (p = 0.002). In the TF group there was 1 death compared to 2 in the FF group. In the TF group, there were 2 cases of ARDS, 4 cases of deep sepsis and 3 above knee amputations. In the FF group, there were 6 cases of ARDS (p = 0.04), 1 case of deep sepsis and 1 above knee amputation. Patients with bilateral tibial shaft fractures revealed lower ISS, resuscitation requirements, ARDS, associated injuries, and mortality when compared to bilateral femoral shaft fractures. This is probably due to the anatomical difference in the morphology of the bones, volume of liberated intravascular marrow fat, organisation and layout of the venous capillary network and severity of associated injuries.

Restriction enzymes increase efficiencies of illegitimate DNA integration but decrease homologous integration in mammalian cells

Mammalian cells repair DNA double-strand breaks by illegitimate end-joining or by homologous recombination. We investigated the effects of restriction enzymes on illegitimate and homologous DNA integration in mammalian cells. A plasmid containing the neo(R) expression cassette, which confers G418 resistance, was used to select for illegitimate integration events in CHO wild-type and xrcc5 mutant cells. Co-transfection with the restriction enzymes BamHI, BglII, EcoRI and KpnI increased the efficiency of linearized plasmid integration up to 5-fold in CHO cells. In contrast, the restriction enzymes did not increase the integration efficiency in xrcc5 mutant cells. Effects of restriction enzymes on illegitimate and homologous integration were also studied in mouse embryonic stem (ES) cells using a plasmid containing the neo(R) gene flanked by exon 3 of HPRT: The enzymes BamHI, BglII and EcoRI increased the illegitimate integration efficiency of transforming DNA several-fold, similar to the results for CHO cells. However, all three enzymes decreased the absolute frequency of homologous integration approximately 2-fold, and the percentage of homologous integration decreased >10-fold. This suggests that random DNA breaks attract illegitimate recombination (IR) events that compete with homology search.

Polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin induce intrachromosomal recombination in vitro and in vivo

Polychlorinated aromatic hydrocarbons such as polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are extremely stable and widely distributed environmental pollutants. These chemicals are animal carcinogens and probable human carcinogens, and TCDD is possibly one of the most potent toxins ever evaluated by the United States Environmental Protection Agency. Polychlorinated aromatic hydrocarbons score negatively in most genotoxicity assays, including the Ames (Salmonella) assay. Although their mechanism of toxicity is not well understood, they induce aryl hydrocarbon (AH) hydroxylases and bind to the AH receptor, which is believed to mediate toxicity. Here, we determine effects of polychlorinated aromatic hydrocarbons in genotoxicity assays that score for DNA deletions by intrachromosomal recombination in vivo and in vitro. In this study, TCDD, Aroclor 1221, and Aroclor 1260 induced deletions in vivo in the mouse embryo; Aroclor 1221 and Aroclor 1260 induced deletions in yeast. We also show that the induced deletion events did not correlate with induction of AH hydroxylase. None of the tested compounds induced CYP1A-associated ethoxyresorufin-O-deethylase activity in mouse embryos or in vitro. These results clearly demonstrate a genotoxic activity of polychlorinated aromatic hydrocarbons in vitro and in vivo, which is independent of induction of cytochrome P450 activity. Because genetic instability and deletions may be mechanistically involved in carcinogenesis, these results may encourage further research to determine whether such genotoxic mechanisms may be useful for cancer risk assessment of polychlorinated aromatic hydrocarbons.