Externalised locking compression plate as an alternative to the unilateral external fixator: a biomechanical comparative study of axial and torsional stiffness

Objectives

External fixators are the traditional fixation method of choice for contaminated open fractures. However, patient acceptance is low due to the high profile and therefore physical burden of the constructs. An externalised locking compression plate is a low profile alternative. However, the biomechanical differences have not been assessed. The objective of this study was to evaluate the axial and torsional stiffness of the externalised titanium locking compression plate (ET-LCP), the externalised stainless steel locking compression plate (ESS-LCP) and the unilateral external fixator (UEF).

Methods

A fracture gap model was created to simulate comminuted mid-shaft tibia fractures using synthetic composite bones. Fifteen constructs were stabilised with ET-LCP, ESS-LCP or UEF (five constructs each). The constructs were loaded under both axial and torsional directions to determine construct stiffness.

Results

The mean axial stiffness was very similar for UEF (528 N/mm) and ESS-LCP (525 N/mm), while it was slightly lower for ET-LCP (469 N/mm). One-way analysis of variance (ANOVA) testing in all three groups demonstrated no significant difference (F(2,12) = 2.057, p = 0.171).

There was a significant difference in mean torsional stiffness between the UEF (0.512 Nm/degree), the ESS-LCP (0.686 Nm/degree) and the ET-LCP (0.639 Nm/degree), as determined by one-way ANOVA (F(2,12) = 6.204, p = 0.014). A Tukey post hoc test revealed that the torsional stiffness of the ESS-LCP was statistically higher than that of the UEF by 0.174 Nm/degree (p = 0.013). No catastrophic failures were observed.

Conclusion

Using the LCP as an external fixator may provide a viable and attractive alternative to the traditional UEF as its lower profile makes it more acceptable to patients, while not compromising on axial and torsional stiffness.

Cite this article: B. F. H. Ang, J. Y. Chen, A. K. S. Yew, S. K. Chua, S. M. Chou, S. L. Chia, J. S. B. Koh, T. S. Howe. Externalised locking compression plate as an alternative to the unilateral external fixator: a biomechanical comparative study of axial and torsional stiffness. Bone Joint Res 2017;6:216–223. DOI: 10.1302/2046-3758.64.2000470.

The accuracy of a hand-held navigation system in total knee arthroplasty

INTRODUCTION

This study aims to evaluate the effectiveness of a new hand-held navigation system. The authors of this study hypothesize that this navigation system will improve overall lower limb alignment and implant placement without causing a delay in surgery.

PATIENTS AND METHODS

Two hundred consecutive patients diagnosed with tricompartmental osteoarthritis and underwent total knee arthroplasty by a senior surgeon were included in this study. One hundred patients underwent TKA using the hand-held navigation system, while the other 100 patients underwent TKA using the conventional technique. The primary outcomes of this study were the overall alignment of the lower limb and the position of the components. This was determined radiologically using the: (1) Hip-Knee-Ankle angle (HKA) for lower limb alignment; (2) Coronal Femoral-Component angle (CFA); and (3) Coronal Tibia-Component angle (CTA) for component position. Normal alignment was taken as 180° ± 3° for the HKA and 90° ± 3° for both the CFA and CTA.

RESULTS

For the CFA, the proportion of outliers was 7 and 17% in the hand-held navigation and conventional group, respectively (p = 0.030). For the HKA and CTA, there was no difference in the proportion of outliers between the two groups. The duration of surgery was 73 ± 9 min and 87 ± 15 min in the hand-held navigation and conventional group, respectively (p < 0.001).

CONCLUSION

This hand-held navigation system is an effective intraoperative tool for reducing the proportion of outliers for femoral implant placement as well as the duration of surgery. The authors conclude that it can be considered for use to check femoral implant placement intra-operatively.

LEVEL OF EVIDENCE

III.

The influence of body mass index on functional outcome and quality of life after total knee arthroplasty

AIMS

This study investigated the influence of body mass index (BMI) on the post-operative fall in the level of haemoglobin (Hb), length of hospital stay (LOS), 30-day re-admission rate, functional outcome and quality of life, two years after total knee arthroplasty (TKA).

PATIENTS AND METHODS

A total of 7733 patients who underwent unilateral primary TKA between 2001 and 2010 were included. The mean age was 67 years (30 to 90). There were 1421 males and 6312 females. The patients were categorised into three groups: BMI < 25.0 kg/m(2) (normal); BMI between 25.0 and 39.9 kg/m(2) (obese); and BMI ≥ 40.0 kg/m(2) (morbidly obese).

RESULTS

Compared with the normal and obese groups, the mean LOS was longer by one day (95% confidence interval (CI) 0 to 2) in the morbidly obese group (p = 0.003 and p = 0.001 respectively). The 30-day re-admisison rate was also higher in the morbidly obese group compared to the obese group (OR 2.323, 95% CI 1.101 to 4.900, p = 0.024); and showed a higher trend compared to the normal group (OR 1.850, 95% CI 0.893 to 3.831, p = 0.100). However, the morbidly obese group had a smaller drop in post-operative Hb level by a mean of 0.5 g/dl (0.3 to 0.6) and 0.3 g/dl (0.1 to 0.5), when compared with the normal and obese groups respectively (both p < 0.001). Furthermore, the mean improvement in Oxford Knee Score (OKS) and Knee Society Knee Score (KSKS) at two years follow-up was three points (two to four) and five points (two to seven) more in the morbidly obese group than in the normal group (both p < 0.001). The mean improvement in Knee Society Function Score, and Physical and Mental Component Scores of Short Form-36 were comparable between the three BMI groups (p = 0.736, p = 0.739 and p = 0.731 respectively). The ten-year rate of survival was 98.8% (98.0 to 99.3), 98.9% (98.5 to 99.2) and 98.0% (95.8 to 100), for the normal, obese and morbidly obese groups, respectively (p = 0.703).

CONCLUSION

Although morbidly obese patients have a longer LOS and higher 30-day re-admission rate after TKA, they have a smaller drop in post-operative Hb level and larger improvement in OKS and KSKS at two years follow-up. The ten-year rate of survival of TKA was also comparable with those with a normal BMI.

TAKE HOME MESSAGE

Morbidly obese patients should not be excluded from the benefits of TKA. Cite this article: Bone Joint J 2016;98-B:780-5.

Clinical outcomes of computer-assisted total knee arthroplasty using pinless navigation

This study aims to evaluate the 2-year post-operative clinical outcomes of patients undergoing total knee arthroplasty (TKA) with computer-assisted surgery (CAS) using the pinless BrainLAB^® VectorVision^® Knee 2.5 Navigation System versus standard CAS. A retrospective case-control study of 200 patients who underwent TKA with CAS from 2008 to 2012 was conducted. Patients in the pinless arm underwent a shorter duration of surgery compared to the standard CAS arm with 72 ± 13 min and 83 ± 11 min, respectively ( p < 0.001), with improvement in Oxford Knee Score from 34 ± 8 to 18 ± 5 and 34 ± 9 to 18 ± 5, respectively, without statistically significant differences in clinical outcomes at 2 years.

Does obesity influence early outcome of fixed-bearing unicompartmental knee arthroplasty?

Obesity is a known major contributing risk factor for knee osteoarthritis (OA). It is also believed that obese unicompartmental knee arthroplasty (UKA) patients tend to have poorer outcome and possible early failure. The purpose of this study is to investigate the early outcome of obese UKA patients in a single institution. Patients who underwent fixed bearing medial UKA in between year 2005 and 2010 were included in this study. They were divided into four groups based on Body Mass Index (BMI): 25 kg/m² (Control); 25-29.9 kg/m² (Overweight); 30-34.9 kg/m² (Obese); >35 kg/m² (Severely Obese). Functional outcome was assessed using Knee Society Score (KSS), Oxford Knee Score (OKS) and Short-form 36 (SF-36). One-way ANOVA with Bonferroni post-hoc test was used to compare the four groups for quantitative variables. There were 673 patients in this study, no significant difference between the four BMI groups for gender and side of operated knee ( p > 0.05). The functional outcome of all four groups at 2 years were comparable (all p > 0.05). At a mean follow up of 5.4 (range 2.5, 8.5) years, 9 revision surgeries (1.3%) were identified. The mean duration from initial surgery to revision surgery was 49 months (Range 6, 90). Patients' pre-operative BMI did not influence the early outcome of UKA patients. However, patients with higher BMI had relatively lower functional score prior to the surgery and tended to be younger. This did not translate to early failure and the functional improvement was similar among all four groups.

Protecting microRNAs from RNase degradation with steric DNA nanostructures

A DNA nanostructure bearing a “Shuriken” shape is designed to deliver, protect and activate microRNA-145 functionality in human colorectal cancer cells. This novel DNA nanostructure enabled therapeutic platform greatly suppresses cancer cell proliferation and tumor growth.

Tumor suppressive microRNAs are potent molecules that might cure cancer, one day. Despite the many advanced strategies for delivery of these microRNAs to the cell, there are few therapeutic microRNAs in clinical use. Progress in microRNA bioapplications is hindered by a high vulnerability of exogeneous microRNA molecules to RNase degradation that occurs in extra- and intracellular physiological conditions. In this proof-of-concept study, we use a programmable self-assembled DNA nanostructure bearing a “shuriken” shape to not only deliver but more importantly protect a tumor suppressive microRNA-145 for a sufficiently long time to exert its therapeutic effect in human colorectal cancer cells. Our DNA nanostructure harbored complementary sequences that can hybridize with the microRNA cargo. This brings the microRNA–DNA duplex very close to the core structure such that the microRNA cargo becomes sterically shielded from RNase's degradative activity. Our novel DNA nanostructure based protector concept removes the degradative bottleneck that may plague other nucleic acid delivery strategies and presents a new paradigm towards exploiting these microRNAs for anti-cancer therapy.

Fixed Flexion Deformity After Unicompartmental Knee Arthroplasty: How Much Is Too Much

BACKGROUND

The detrimental impact of postoperative fixed flexion deformity (FFD) after unicompartmental knee arthroplasty (UKA) is manifold. This study aims to define the amount of postoperative FFD that is clinically relevant after UKA.

METHODS

Between 2005 and 2012, 803 patients who underwent a primary UKA at a tertiary hospital were prospectively followed up. They were categorized into 3 groups based on the amount of postoperative FFD: (1) 0° (control); (2) 1°-10° (mild FFD); and (3) >10° (severe FFD).

RESULTS

There were 26 patients (3%) with severe FFD at 2 years after UKA. The Knee Society Function Score and Knee Score in the severe FFD group were 10 ± 4 and 10 ± 2 points lower than in the control group, respectively (P = .017 and P = .001). Similarly, the Oxford Knee Score and Physical Component Score in the severe FFD group was 5 ± 1 and 7 ± 2 points lower than in the control group, respectively (P = .033 and P < .001).

CONCLUSION

This study suggests that postoperative FFD of >10° after UKA is associated with significantly poorer functional outcomes.

Early Outcomes of Unicompartmental Knee Arthroplasty in Patients With Preoperative Genu Recurvatum of Non-neurological Origin

BACKGROUND

This study aims to evaluate outcomes of unicompartmental knee arthroplasty (UKA) in patients with preoperative genu recurvatum.

METHODS

From patients who underwent UKA at a tertiary hospital between 2005 and 2012, the study selected 30 patients with genu recurvatum (group A) compared with a matching cohort of 60 without genu recurvatum (group B). Group A was also compared with a matched cohort of 60 patients with genu recurvatum who underwent total knee arthroplasty (group C). Functional outcomes data were prospectively collected at 6-month and 2-year follow-up.

RESULTS

Two years after UKA, group A had poorer Oxford Knee Score of 22 ± 8 compared with group B at 16 ± 3 (P < .001), and the trend is reflected in the Knee Society Score (71 ± 17 vs 87 ± 17, P < .001) and the 36 Item Short Form Health Survey Physical Component Score (47 ± 10 vs 52 ± 6, P = .014). After 2 years, group C had superior Oxford Knee Score (16 ± 2, P < .001), Knee Society Score (82 ± 14, P = .003), and 36 Item Short Form Health Survey Physical Component Score (53 ± 6, P = .005). The hyperextension angle in group A decreased from 6° ± 2° to 2° ± 4° after 2 years with an improvement of 4° ± 4° (P < .001). The hyperextension angle in group C decreased from 7° ± 2° to 1° ± 3° after 2 years with an improvement of 6° ± 3° (P < .001) with a significant difference (P = .002) in hyperextension angle correction between group A and C.

CONCLUSION

Preoperative recurvatum is a predictor of poorer outcome after UKA, and this patient population benefits from better 2-year functional outcomes after total knee arthroplasty.

Age and Preoperative Knee Society Score Are Significant Predictors of Outcomes Among Asians Following Total Knee Arthroplasty

BACKGROUND

The ability to predict patients' functional outcomes will add value to preoperative counseling. The purpose of this study was to evaluate predictors of good outcomes following total knee arthroplasty (TKA) among Asian patients.

METHODS

Registry data from 2006 to 2010 were extracted. The Oxford Knee Score (OKS) and the Short Form (SF)-36 physical component summary (PCS) were used to evaluate outcomes. A "good outcome" was defined as an improvement in scores of greater than or equal to the minimal clinically important difference (MCID) in the primary analysis. The MCID for the OKS was 5, and the MCID for the PCS was 10. For the sensitivity analyses, a "good outcome" was defined as an OKS of <30 and a PCS score of >50. Clinical variables were used to develop a multiple logistic regression model for a good outcome following total knee arthroplasty at 5 years.

RESULTS

Follow-up data were available for 3,062 patients who underwent primary TKA (mean age of 66.4 years; 79.5% female). Eighty-five percent had a good outcome on the basis of the OKS and 83%, on the basis of the SF-36 PCS. Age and preoperative Knee Society score (KSS) were found to be significant predictors. When outcomes were assessed by the MCID, lesser age and lower (worse) preoperative KSS predicted a good outcome at 5 years. When outcomes were assessed by absolute criteria (postoperative scores measured against OKS and PCS thresholds), a higher (better) preoperative KSS predicted a good outcome at 5 years. Body mass index, preoperative flexion range, SF-36 mental component summary (MCS) score, mechanical alignment, sex, education level, ethnicity, operative side, number of comorbidities, type of anesthesia, and type of implant were found not to be significant predictors.

CONCLUSIONS

The majority of Asian patients with osteoarthritis had good outcomes according to the MCID criterion and benefitted from primary TKA. On the basis of our findings, we believe that older patients with a lower (worse) preoperative KSS can be informed that they have a high likelihood of improvement but a lower likelihood of achieving as good a functional outcome as those with better scores.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Minimally Invasive Computer-Assisted Total Knee Arthroplasty Compared With Conventional Total Knee Arthroplasty: A Prospective 9-Year Follow-Up

BACKGROUND

Studies on minimally invasive computer-assisted total knee arthroplasty (MICA-TKA) have shown promising results, but are limited by short follow-up. The purpose of this study was to compare the midterm radiographic features and functional outcomes between patients who underwent MICA-TKA and conventional TKA.

METHODS

A total of 108 patients who were randomized to undergo MICA-TKA or conventional TKA during 2004 and 2005 were contacted for a prospective follow-up review. Patients who were lost to contact, have passed away, or declined to participate in the study were excluded. Objective functional measurements and radiographs were obtained for assessment.

RESULTS

By the time of this study, 2 patients from the conventional group had undergone revision TKA, one due to infection and one due to aseptic loosening. A total of 67 patients (62.04%) were followed up for an average period of 9.07 years (8.51-9.61 years). At follow-up, functional scores were comparable between the 2 groups. No significant intergroup differences were found in mechanical knee alignment and component placement angle in the coronal views. No statistical or clinical significance were noticed in radiographic signs of component loosening.

CONCLUSIONS

MICA-TKA provided similar clinical, functional, and radiographic outcomes compared with conventional TKA after an average of 9-year follow-up. This technique can be used to exploit its short-term advantages without compromising midterm outcomes.

Obesity and the absence of trochlear dysplasia increase the risk of revision in patellofemoral arthroplasty

PURPOSE

Proper indications and patient selection are of paramount importance in patellofemoral arthroplasty (PFA). Although factors predicting outcomes in total knee arthroplasty (TKA) have been studied, there are no such studies for modern PFA. This retrospective study reports the midterm clinical and radiological outcomes and survivorship of PFA, investigating the risk factors associated with poorer outcomes and higher revision rates.

METHODS

Fifty-one patients (51 knees) with isolated patellofemoral arthritis underwent PFA with a second-generation implant. The mean follow-up duration was 4.1 years (range, 2.2 to 6.1). The cohort was stratified into obese (body mass index (BMI)≥30 kg/m(2), n=16), overweight (BMI 25 to 29.9 kg/m(2), n=20) and control (BMI 18.5 to 24.9 kg/m(2), n=15) groups. The same cohort was stratified based on the presence (n=11) or absence (n=40) of trochlear dysplasia (TD).

RESULTS

The mean Knee Society objective and function scores, the Melbourne Knee score and the Physical Component Score of Short Form 36 improved significantly. Obesity was associated with no significant improvement in the Melbourne Knee score and the Knee Society function score (p>0.05), a higher incidence of radiographic outliers and lower patient satisfaction. There was no significant difference in outcomes between the TD and non-TD groups at two years (p>0.05), with a survivorship of 92.2%. Three revisions for progression of tibiofemoral osteoarthritis were noted in the non-TD and obese or overweight groups.

CONCLUSIONS

Patients with obesity and the absence of TD are at a potentially higher risk of revision surgery to TKA, and they should be counselled that PFA may represent a 'bridging' procedure.

LEVEL OF EVIDENCE

III.

Reducing allograft contamination and disease transmission: intraosseous temperatures of femoral head allografts during autoclaving

INTRODUCTION

The Singapore General Hospital Bone Bank, which exclusively stores femoral head allografts, relies on flash sterilisation to prevent allograft-related disease transmission and wound infection. However, intraosseous temperatures during autoclaving may be lower than required to eliminate human immunodeficiency virus, and hepatitis B and C viruses. The aim of this study is to determine the intraosseous temperatures of femoral head allografts during autoclaving and to assess the adequacy of autoclaving in preventing disease transmission.

METHODS

Six femoral heads were acquired from patients who underwent hip arthroplasty. The specimens were divided into two groups. The first group underwent flash sterilisation with a sterilisation time of 4 min, while a longer sterilisation time of 22 min was used for the second group.

RESULTS

The highest core temperature in the first group was 130°C, while the core temperatures in the second group plateaued at 133°C for all allografts. In the first group, only smaller allografts maintained temperatures sufficient for the inactivation of the clinically relevant viral pathogens. In contrast, all allografts in the second group were terminally sterilised.

CONCLUSION

There is an inverse correlation between the size of allografts and intraosseous temperatures achieved during autoclaving. Therefore, we recommend dividing large allografts into smaller pieces, in order to achieve intraosseous temperatures adequate for the elimination of transmissible pathogens during flash sterilisation. Allografts should not be terminally sterilised, as the resulting allografts will become unusable. Despite modern processing techniques, stringent donor selection remains vital in the effort to prevent allograft-related infections. Autoclaving is an economical and efficacious method of preventing allograft-related disease transmission.

Intravenous versus intra-articular tranexamic acid in total knee arthroplasty: A double-blinded randomised controlled noninferiority trial

BACKGROUND

Despite the proven efficacy of both intravenous (IV) and intra-articular (IA) tranexamic acid (TXA) in reducing blood loss during total knee arthroplasty (TKA), the ideal route of administration remained debatable. This study aimed to compare the effect of IV versus IA TXA on transfusion incidences, perioperative blood loss and postoperative lower limb swelling during TKA.

METHODS

One hundred patients were prospectively randomised into two groups: 1) IV TXA; and 2) IA TXA. In both groups, TXA was administered intraoperatively after cementing the prostheses. The perioperative blood loss was calculated using the haemoglobin balance method. The thigh, suprapatellar, and calf girths were measured preoperatively and on postoperative day (POD) 4.

RESULTS

Two patients in the IV group and one patient in the IA group required blood transfusion (p=0.500). The median and interquartile range (IQR) of perioperative blood loss on POD1 and POD4 was 530 (IQR 386,704) and 730 (IQR 523,925) ml for the IV group, compared with 613 (IQR 506,703) and 799 (IQR 563,1067) ml for the IA group (p=0.090 and p=0.232 respectively). The median increment in thigh, suprapatellar, and calf girths were 1.5 (IQR 0, 3.0), 2.0 (IQR 0.5, 4.0) and 0 (IQR 0, 1.0) cm for the IV group, compared to 2.0 (IQR 1.0, 4.0), 2.0 (IQR 0, 4.5) and 0 (IQR 0, 1.5) cm for the IA group (p=0.246, p=0.562, and p=0.937 respectively).

CONCLUSIONS

Both IV and IA TXA had comparable effect on transfusion incidences, perioperative blood loss, and postoperative lower limb swelling during TKA. IA TXA is an alternative to IV TXA.

LEVEL OF EVIDENCE

I.

Intra-articular tranexamic acid wash during bilateral total knee arthroplasty

PURPOSE

To compare the outcome after simultaneous bilateral total knee arthroplasty (TKA) with or without an intra-articular tranexamic acid (TXA) wash in terms of blood loss, haemoglobin change, and transfusion requirement.

METHODS

35 women and 10 men (mean age, 67.5 years) who underwent primary simultaneous bilateral TKA by a single senior surgeon were compared with 45 matched controls. In the TXA group, 1500 mg of TXA diluted in 100 ml of 0.9% sodium chloride was administered as a wash after cementing of implant and before closure of the retinaculum. At least 5 minutes of contact time was allowed before wound closure and tourniquet deflation. No drain was used.

RESULTS

No patients had thromboembolic complication. Compared with controls, the TXA group had lower perioperative blood loss (920 vs. 657 ml, p=0.001), total blood loss (997 vs. 679 ml, p<0.001), blood transfusion rate (60% vs. 37.8%, p=0.035), percentage of patients requiring more than one blood unit (24.4% vs. 8.9%, p=0.048), and length of hospitalisation (6 vs. 4 days, p<0.001). Nonetheless, the 2 groups were comparable in blood units and volume transfused.

CONCLUSION

An intra-articular TXA wash during simultaneous bilateral TXA reduced total blood loss and resulted in a difference of 22.2% in blood transfusion rate and a 2-day reduction in the length of hospital stay.

Cruciate retaining versus posterior stabilized total knee arthroplasty after previous high tibial osteotomy

PURPOSE

This study aimed to investigate the clinical outcome of total knee arthroplasty (TKA) after previous high tibial osteotomy (HTO) using cruciate retaining (CR) versus posterior stabilized (PS) prostheses.

METHODS

Between 2001 and 2010, 133 patients who underwent TKA after previous HTO were included in this study and prospectively followed up for two years. Two independent assessors recorded the range of motion of the operated knee, anterior-posterior (AP) laxity, medial-lateral (ML) laxity, Oxford Knee Score (OKS), Knee Society Function Score (KSFS) and Knee Society Knee Score (KSKS).

RESULTS

Thirty-three patients received CR prostheses, while 100 patients received PS prostheses. The median (inter-quartile range) knee flexion at 6 months and 2 years post-TKA was 101° (90, 116) and 110° (90, 118), respectively for the CR group, compared to 115° (100, 121) and 118° (108, 125) for the PS group (p = 0.010 and p = 0.009, respectively). AP and ML laxities were comparable in both groups of patients. While both groups of patients showed improvement in OKS, KSFS and KSKS at 6 months and 2 years post-TKA, there was no significant difference in these clinical scores between the two groups at both time points of follow-up. None of the 133 patients required revision surgery.

CONCLUSIONS

Although PS prostheses offer better knee flexion in TKA after previous HTO, the knee stability, clinical scores and revision rate at 6 months and 2 years post-TKA are comparable between CR and PS prostheses. The authors conclude that CR is an alternative to PS prostheses in patients undergoing TKA after previous HTO.

LEVEL OF EVIDENCE

III.

Radiological outcomes of pinless navigation in total knee arthroplasty: a randomized controlled trial

PURPOSE

This study aimed to investigate the accuracy of pinless navigation (BrainLAB(®) VectorVision(®) Knee 2.5 Navigation System) as an intra-operative alignment guide in total knee arthroplasty (TKA). The authors hypothesized that pinless navigation would reduce the proportion of outliers in conventional TKA, without a significant increase in the duration of surgery.

METHODS

Between 2011 and 2012, 100 patients scheduled for a unilateral primary TKA were randomized into two groups: pinless navigation and conventional surgery. All TKAs were performed with the surgical aim of achieving neutral coronal alignment with a 180° mechanical axis. The primary outcomes of this study were post-operative radiographic assessment of lower limb alignment using hip-knee-ankle angle (HKA) and components placement using coronal femoral-component angle (CFA) and coronal tibia-component angle (CTA).

RESULTS

There was a smaller proportion of outliers for HKA, CFA and CTA at 10, 2 and 2 % respectively, in the pinless navigation group, compared to 32, 16 and 16 %, respectively, in the conventional group (p = 0.013, p = 0.032 and p = 0.032, respectively). The mean CFA was also more accurate at 90° in the pinless navigation group compared to 91° in the conventional group (p = 0.002). There was no difference in the duration of surgery between the two groups (n.s.).

CONCLUSIONS

Pinless navigation improves lower limb alignment and components placement without a significant increase in the duration of surgery. The authors recommend the use of pinless navigation to verify the coronal alignments of conventional cutting blocks in TKA before the bone cuts are made.

LEVEL OF EVIDENCE

I.

Drilling the near cortex with elongated figure-of-8 holes to reduce the stiffness of a locking compression plate construct

PURPOSE

To compare the stiffness of locking compression plate (LCP) constructs with or without drilling the near cortex with elongated figure-of-8 holes.

METHODS

24 synthetic bones were sawn to create a 10-mm gap and were fixed with a 9-hole 4.5-mm narrow LCP. In 12 bones, the near cortex of the adjacent holes to the LCP holes was drilled to create elongated figure-of-8 holes before screw insertion. The stiffness of LCP constructs under axial loading or 4-point bending was assessed by (1) dynamic quasi-physiological testing for fatigue strength, (2) quasi-static testing for stiffness, and (3) testing for absolute strength to failure.

RESULTS

None of the 24 constructs had subcatastrophic or catastrophic failure after 10 000 cycles of fatigue loading (p=1.000). The axial stiffness reduced by 16% from 613±62 to 517±44 N/mm (p=0.012) in the case group, whereas the bending stiffness was 16±1 Nm2 in both groups (p=1.000). The maximum axial load to catastrophic failure was 1596±84 N for the control group and 1627±48 N for the case group (p=0.486), whereas the maximum bending moment to catastrophic failure was 79±12 and 80±10 Nm, respectively (p=0.919).

CONCLUSION

Drilling the near cortex with elongated figure-of-8 holes reduces the axial stiffness of the LCP construct, without compromising its bending stiffness or strength.

Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty

Patient-specific instrumentation (PSI) surgery may represent the next advancement in total knee arthroplasty (TKA). In 2011, 60 patients were prospectively recruited and divided into two groups based on the patient's choice: (1) PSI surgery; and (2) conventional TKA. At two years after surgery, the Knee Society Function Score, Oxford Knee Score and SF-36 scores were comparable between the two groups. Although the Knee Society Knee Score (KSKS) was 9 ± 3 points better in the PSI group (P=0.008), the two years improvement in KSKS was comparable between the two groups. None of the patients required revision surgery. These findings cannot justify the additional costs and waiting time incurred by the patients with PSI surgery in the practice of a high volume surgeon.

Gender-specific total knee arthroplasty in Singaporean women

PURPOSE

To compare the outcome of 145 women who underwent conventional total knee arthroplasty (TKA) with 77 women who underwent gender-specific TKA.

METHODS

Records of 222 women who underwent primary TKA using a conventional (n=145) or gender-specific (n=77) size E or F prosthesis for end-stage osteoarthritis were reviewed. The gender-specific prosthesis has a narrower mediolateral dimension. Patients were assessed for flexion, Oxford Knee Score, Knee Society function and knee scores, and Short Form-36 Health Survey preoperatively and postoperatively (at 6 months and 2 years).

RESULTS

The 2 groups were comparable in terms of age (67.8 vs. 68.1 years, p=0.789), body mass index (28.6 vs. 27.8 kg/m(2), p=0.189), and preoperative scores. 12 women with conventional TKA and 4 women with gender-specific TKA were lost to followup. Compared with women with conventional TKA, women with gender-specific TKA had better flexion at 6 months (116° vs. 121.9°, p=0.007) and 2 years (118.7° vs. 124.6°, p=0.006), better bodily pain score at 2 years (65.1 vs. 72.4, p=0.049), and greater improvement in bodily pain score from baseline to 2 years (30 vs. 38.5, p=0.034).

CONCLUSION

Gender-specific TKA enables better knee flexion and less bodily pain in women who have a high propensity to develop mediolateral overhang of the femoral component.

Gender difference in outcome after total knee replacement

PURPOSE

To compare the outcome after primary total knee replacement (TKR) for end-stage knee osteoarthritis (OA) in men versus women.

METHODS

Records of 214 men and 1040 women who underwent primary TKR for end-stage knee OA and were followed up for a minimum of 2 years were reviewed. Knee flexion, Oxford Knee Score, Knee Society Score (KSS), and 8 subscores of Short Form 36 (SF-36) were recorded preoperatively and at postoperative 6 months and 2 years.

RESULTS

Men and women were comparable only in age (67.9 vs. 67.3 years, p=0.244); men had a lower mean body mass index (27.0 vs. 28.3 kg/m(2), p<0.001). Preoperatively, men had better knee flexion (117º vs. 114.8º, p=0.05), Oxford Knee Score (33.5 vs. 36.8, p<0.001), KSS knee score (44.3 vs. 40.3, p=0.001), KSS function score (52.5 vs. 47.1, p<0.001), and all 8 subscores of SF-36 (p=0.005 to p<0.001). Compared with men, women achieved greater improvement at 6 months in Oxford Knee score (13.2 vs. 15.1, p=0.009) and KSS knee score (36.9 vs. 41.6, p=0.016), and at 2 years in Oxford Knee Score (15.0 vs. 17.9, p<0.001), KSS knee score (39.8 vs. 43.9, p=0.009), and SF-36 subscores of social functioning (23.6 vs. 35.1, p<0.001) and mental health (3.9 vs. 8.2, p=0.003).

CONCLUSION

Compared with men, women had poorer preoperative knee flexion, Oxford Knee Score, KSS, and 8 subscores of SF-36, but achieved greater improvement in the Oxford Knee Score and KSS knee score at 6 months and 2 years, as well as in SF-36 subscores of social functioning and mental health at 2 years.

Intra-articular administration of tranexamic acid in total hip arthroplasty

PURPOSE

To evaluate the effectiveness of intraarticular tranexamic acid (TXA) in reducing blood loss and the need for blood transfusion during total hip arthroplasty (THA).

METHODS

Records of 19 men and 31 women aged 46 to 83 (mean, 62) years who underwent primary THA with intra-articular administration of TXA were reviewed. They were compared with a matched cohort of 17 men and 33 women aged 40 to 87 (mean, 62) years who underwent the same procedure by the same surgeon without use of TXA. Postoperatively, a standard thromboembolic prophylaxis protocol was followed. A serum haemoglobin level of <80 g/l was the trigger for blood transfusion.

RESULTS

The 2 groups were comparable in terms of age, gender, body mass index, side involved, and anaesthesia method. No patient developed infection, wound haematoma, symptomatic deep vein thrombosis, or pulmonary embolism within 30 days. Compared with controls, patients in the TXA group had a higher median postoperative serum haemoglobin level (103 vs. 112 g/l, p=0.013), lower median drop in serum haemoglobin level (31 vs. 20 g/l, p<0.001), lower median total blood loss (900 vs. 575 ml, p<0.001), and lower transfusion rate (32% vs. 10%, p=0.007). The TXA treatment cost S$19.50 per patient, whereas one unit of allogenic blood cost S$123 per patient. Respectively in the control and TXA groups, the mean cost per patient was S$39.36 and S$31.80, indicating a 19% difference.

CONCLUSION

Intra-articular administration of TXA is a cost-effective and safe means to reduce blood loss and the need for blood transfusion during THA, without increasing the risk of thromboembolic events.

Recovery in knee range of motion reaches a plateau by 12 months after total knee arthroplasty

PURPOSE

The primary aim of this study was to identify the time point at which improvements in knee range of motion reach a plateau, if any. The secondary aim of this study was to investigate the correlation between the improvements in knee range of motion and patient-reported outcomes [Oxford knee score (OKS) and SF-36]. The hypothesis is that there is a time point at which the recovery in the knee range of motion after total knee arthroplasty (TKA) plateaus.

METHOD

A prospective study of 145 patients who underwent TKA was conducted. All TKAs were performed by the same surgeon. OKS and SF-36 scores were measured preoperatively and at 6, 12, and 24 months. Range of motion was measured preoperatively and at 1, 3, 6, 12, and 24 months postoperatively.

RESULTS

This study shows that for surgeon/therapist reported range of motion, a plateau in recovery was reached at 12 months after TKA. It was also found that range of extension is significantly correlated with OKS, whereas range of flexion was not significantly correlated with OKS.

CONCLUSIONS

Knowledge of when patients fully recover after TKA will allow appropriate counseling of patients during preoperative consultation. Also, this knowledge will enable surgeons/therapists to better monitor the rehabilitation progress of TKA patients, and make adjustments to the rehabilitation protocol. In addition, our study shows that objective surgeon-/therapist-measured outcome (range of motion) has a significant correlation with subjective patient-reported outcomes (OKS). Hence, both outcome measures should be employed in the postoperative monitoring of patient progress.

LEVEL OF EVIDENCE

Prospective case series, Level IV.