Comparison of the in vivo kinematics between robotic-assisted Bi-cruciate retaining and Bi-cruciate stabilised total knee arthroplasty.

BACKGROUND: Up to 20% of patients remain unsatisfied after total knee arthroplasty (TKA), prompting the development of new implants. Bi-Cruciate Retaining (BCR) TKA preserves both the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), with the ACL beneficial for its proprioceptive qualities. The Bi-Cruciate Stabilised (BCS) TKA substitutes the ACL and PCL with a unique dual cam-post mechanism. Robotics improve accuracy and facilitate technically demanding TKA. METHODS: This was a retrospective case-control study recruited from two centres. Measured outcomes included kinematic analysis, proprioception, and functional outcomes. RESULTS: There was a significantly larger maximum flexion angle and range of flexion to extension in sit-to-stand and stairs in BCR when compared to BCS. Further analysis revealed more similarities between BCR and normal native knees. Proprioception and functional scores did not have any statistical difference. CONCLUSION: BCR TKA demonstrated better knee flexion in weight-bearing active range of motion and showed similarities with normal knee kinematics.

Vitamin D as an intervention for improving quadriceps muscle strength in patients after anterior cruciate ligament reconstruction: study protocol for a randomized double-blinded, placebo-controlled clinical trial.

BACKGROUND: The goal of anterior cruciate ligament reconstruction (ACLR) is to restore the preinjury level of knee function to return to play (RTP). However, even after completing the rehabilitation programme, some patients may have persistent quadriceps muscle weakness affecting knee function which ultimately leads to a failure in returning to play. Vitamin D has been long recognized for its musculoskeletal effects. Vitamin D deficiency may impair muscle strength recovery after ACLR. Correcting vitamin D levels may improve muscle strength. METHODS: This is a double-blinded, randomized controlled trial to investigate the effects of vitamin D supplementation during the post-operative period on quadriceps muscle strength in anterior cruciate ligament (ACL)-injured patients. Patients aged 18-50 with serum vitamin D < 20 ng/ml, unilateral ACL injury, > 90% deficit in total quadriceps muscle volume on the involved leg compared with uninvolved leg, Tegner score 7 + , and no previous knee injury/surgery will be recruited. To assess patient improvement, we will perform isokinetic and isometric muscle assessments, ultrasound imaging for quadriceps thickness, self-reported outcomes, KT-1000 for knee laxity, biomechanical analysis, and Xtreme CT for bone mineral density. To investigate the effect of vitamin D status on quadriceps strength, blood serum samples will be taken before and after intervention. DISCUSSION: Patients with low vitamin D levels had greater quadriceps fibre cross-sectional area loss and impaired muscle strength recovery after ACL. The proposed study will provide scientific support for using vitamin D supplementation to improve quadriceps strength recovery after ACLR. TRIAL REGISTRATION: ClinicalTrials.gov NCT05174611. Registered on 28 November 2021.

Reconsidering "Critical" Bone Loss in Shoulder Instability: 17-Year Follow-Up Study following Arthroscopic Bankart Repair.

Background: Glenoid bone loss is a risk factor leading to the failure of arthroscopic Bankart repair. While 20-25% glenoid bone loss has long been considered the level to necessitate bony augmentation, recent studies indicate that 13.5% has a "subcritical" glenoid bone loss level, which is associated with decreased short- and medium-term functional scores. Few researchers worked on the long-term effect of "subcritical" or even less severe degrees of glenoid bone loss on redislocation rates and functional outcomes after arthroscopic Bankart repair. This study aimed to evaluate the effect of subcritical or less severe glenoid bone loss on redislocation rates and function after arthroscopic Bankart repair. Methods: A patient cohort who had undergone computed tomography (CT) of glenoid bone loss and arthroscopic Bankart repair over 15 years ago was reviewed. Western Ontario Shoulder Instability (WOSI) score, Single Assessment Numeric Evaluation (SANE) score, redislocation after operation, mechanism of recurrence, and revision details were reviewed. Results: Seventy-five patients were reassessed 17.6 ± 1.9 years following initial surgery. The age at enrolment was 26.8 ± 8.3 years. Twenty-two (29%) patients of the 75 patients had a redislocation on long-term follow-up, though this was not related to glenoid bone loss severity. The impaired functional score was found in patients with initial glenoid bone loss of 7% or more on long-term follow-up: WOSI (physical symptoms): 0.98 ± 2.00 vs 2.25 ± 4.01, p=0.04 and WOSI (total): 0.79 ± 1.43 vs 1.88 ± 3.56, p=0.04. Conclusions: At a mean of 17.5 years following arthroscopic Bankart repair, redislocation occurs in over a quarter of 75 patients, and they are not related to initial glenoid bone loss severity. Impaired functional outcome is apparent in patients with initial glenoid bone loss of >7%, though this impairment does not seem sufficiently severe to warrant an alternative treatment approach.

Unsupervised domain adaptation for automated knee osteoarthritis phenotype classification.

Background: Osteoarthritis (OA) is a global healthcare problem. The increasing population of OA patients demands a greater bandwidth of imaging and diagnostics. It is important to provide automatic and objective diagnostic techniques to address this challenge. This study demonstrates the utility of unsupervised domain adaptation (UDA) for automated OA phenotype classification. Methods: We collected 318 and 960 three-dimensional double-echo steady-state magnetic resonance images from the Osteoarthritis Initiative (OAI) dataset as the source dataset for phenotype cartilage/meniscus and subchondral bone, respectively. Fifty three-dimensional turbo spin echo (TSE)/fast spin echo (FSE) MR images from our institute were collected as the target datasets. For each patient, the degree of knee OA was initially graded according to the MRI Knee Osteoarthritis Knee Score before being converted to binary OA phenotype labels. The proposed four-step UDA pipeline included (I) pre-processing, which involved automatic segmentation and region-of-interest cropping; (II) source classifier training, which involved pre-training a convolutional neural network (CNN) encoder for phenotype classification using the source dataset; (III) target encoder adaptation, which involved unsupervised adjustment of the source encoder to the target encoder using both the source and target datasets; and (IV) target classifier validation, which involved statistical analysis of the classification performance evaluated by the area under the receiver operating characteristic curve (AUROC), sensitivity, specificity and accuracy. We compared our model on the target data with the source pre-trained model and the model trained with the target data from scratch. Results: For phenotype cartilage/meniscus, our model has the best performance out of the three models, giving 0.90 [95% confidence interval (CI): 0.79-1.02] of the AUROC score, while the other two model show 0.52 (95% CI: 0.13-0.90) and 0.76 (95% CI: 0.53-0.98). For phenotype subchondral bone, our model gave 0.75 (95% CI: 0.56-0.94) at AUROC, which has a close performance of the source pre-trained model (0.76, 95% CI: 0.55-0.98), and better than the model trained from scratch on the target dataset only (0.53, 95% CI: 0.33-0.73). Conclusions: By utilising a large, high-quality source dataset for training, the proposed UDA approach enhances the performance of automated OA phenotype classification for small target datasets. As a result, our technique enables improved downstream analysis of locally collected datasets with a small sample size.

Surgical accuracy of image-free versus image-based robotic-assisted total knee arthroplasty.

BACKGROUND: This study investigated the accuracy in achieving proper lower limb alignment and component positions after total knee replacement (TKR) with image-free and image-based robotic-assisted TKR. METHODS: A total of 129 patients (166 knees) suffering from end-stage knee arthritis who underwent TKA operated by robotic-assisted surgery between the years 2018 and mid-2021 were recruited. Radiological outcomes were compared between image-free and image-based robotic-assisted surgical systems. RESULTS: There were significant differences between the two robotic systems when comparing the mean planned component alignment and the mean measured alignment on radiographs, in which the image-free robotic-assisted system was more varus, whereas the image-based robotic-assisted system was more valgus for both the mean femoral and tibial component coronal alignment (p < 0.001). For tibial component sagittal alignment, the image-based group had a larger deviation from the planned posterior slope (p < 0.001). CONCLUSION: Image-free and image-based robotic assisted TKR had differing accuracy in femoral and tibial alignment.

Effectiveness of a theory-driven mHealth intervention in promoting post-surgery rehabilitation adherence in patients who had anterior cruciate ligament reconstruction: A randomized clinical trial.

RATIONALE: Patients with anterior cruciate ligament (ACL) reconstruction often have poor adherence to post-surgery rehabilitation. OBJECTIVE: This study applied the integrated model of self-determination theory and the theory of planned behavior to examine the effects of a smartphone-delivered intervention on the recovery outcomes of patients with an ACL rupture during post-surgery rehabilitation period. Additionally, we explored the effects of the intervention on participants with different beliefs toward rehabilitation at baseline. METHODS: The randomized control trial recruited 96 eligible participants (M age = 27.82 years, SD = 8.73; female = 39%) who underwent ACL reconstruction surgery. Participants were randomly assigned to an intervention group (n = 41), which received standard post-surgical treatment (usual-care) and smartphone application ("ACL-Well"), or a usual-care control group (n = 55). The primary outcomes were recovery outcomes from ACL surgery measured by knee muscle strength and laxity, and subjective knee evaluation completed 4-month post-intervention. Secondary outcomes were the psychological and behavioral outcomes measured at baseline, at 2- and 4-month post-intervention. RESULTS: ANCOVA indicated no significant between-group differences in primary outcomes: knee muscle strength, knee laxity and subjective knee evaluation, Fs(1, 27 to 55) = 0.01 to 1.36, p = .25 to .99, η2 = 0.01 to 0.03. For the secondary outcomes, growth mixture modelling revealed self-determined treatment motivation declined significantly over the intervention period in the control group (M slope = -0.39 to -0.12, p = .01 to .04), but not in the intervention group (M slope = -0.19 to -0.08, p = .06 to .38). CONCLUSIONS: The smartphone application fell short in promoting orthopedic outpatients' recovery outcomes. Yet, it shows some promises as a mean to maintain patients' motivation and adherence to treatment.

Assessments of early patellofemoral joint osteoarthritis features after anterior cruciate ligament reconstruction: a cross-sectional study.

BACKGROUND: Persistent anterior knee pain and subsequent patellofemoral joint (PFJ) osteoarthritis (OA) are common symptoms after anterior cruciate ligament reconstruction (ACLR). Quadriceps weakness and atrophy is also common after ACLR. This can be contributed by arthrogenic muscle inhibition and disuse, caused by joint swelling, pain, and inflammation after surgery. With quadriceps atrophy and weakness are associated with PFJ pain, this can cause further disuse exacerbating muscle atrophy. Herein, this study aims to identify early changes in musculoskeletal, functional and quality of health parameters for knee OA after 5 years of ACLR. METHODS: Patients treated with arthroscopically assisted single-bundle ACLR using hamstrings graft for more than 5 years were identified and recruited from our clinic registry. Those with persistent anterior knee pain were invited back for our follow-up study. For all participants, basic clinical demography and standard knee X-ray were taken. Likewise, clinical history, symptomatology, and physical examination were performed to confirm isolated PFJ pain. Outcome measures including leg quadriceps quality using ultrasound, functional performance using pressure mat and pain using self-reported questionnaires (KOOS, Kujala and IKDC) were assessed. Interobserver reproducibility was assessed by two reviewers. RESULTS: A total of 19 patients with unilateral injury who had undergone ACLR 5-years ago with persistent anterior knee pain participated in this present study. Toward the muscle quality, thinner vastus medialis and more stiffness in vastus lateralis were found in post-ACLR knees (p < 0.05). Functionally, patients with more anterior knee pain tended to shift more of their body weight towards the non-injured limb with increasing knee flexion. In accordance, rectus femoris muscle stiffness in the ACLR knee was significantly correlated with pain (p < 0.05). CONCLUSION: In this study, it was found that patients having higher degree of anterior knee pain were associated with higher vastus medialis muscle stiffness and thinner vastus lateralis muscle thickness. Similarly, patients with more anterior knee pain tended to shift more of their body weight towards the non-injured limb leading to an abnormal PFJ loading. Taken together, this current study helped to indicate that persistent quadriceps muscle weakness is potential contributing factor to the early development of PFJ pain.

Single use Negative Pressure Wound Therapy (NPWT) system in the management of knee arthroplasty.

BACKGROUND: Wound complication, skin blister formation in particular, causes devastating consequences after total knee arthroplasty (TKA). Negative Pressure Wound Therapy (NPWT) tries to improve wound management leading to decrease length of hospital stay and better clinical outcomes. Low body mass index (BMI) could play a part in wound recovery management although lacking evidence. This study compared length of hospital stay and clinical outcomes between NPWT and Conventional groups, and factors affected and how BMI affected. METHODS: This was a retrospective clinical record review of 255 (160 NPWT and 95 Conventional) patients between 2018 and 2022. Patient demographics including body mass index (BMI), surgical details (unilateral or bilateral), length of hospital stay, clinical outcomes including skin blisters occurrence, and major wound complications were investigated. RESULTS: Mean age of patients at surgery was 69.95 (66.3% were female). Patients treated with NPWT stayed significantly longer in the hospital after joint replacement (5.18 days vs. 4.55 days; p = 0.01). Significantly fewer patients treated with NPWT found to have blisters (No blisters: 95.0% vs. 87.4%; p = 0.05). In patients with BMI < 30, percentage of patients requiring dressing change was significantly lower when treated with NPWT than conventional (0.8% vs. 33.3%). CONCLUSION: Percentage of blisters occurrence in patients who underwent joint replacement surgery is significantly lower using NPWT. Patients using NPWT stayed significantly longer in the hospital after surgery because significant proportion received bilateral surgery. NPWT patients with BMI < 30 were significantly less likely to change wound dressing.

Long-term survivorship and results in lower limb arthroplasty: a registry-based comparison study.

INTRODUCTION: Popularity of joint replacement surgery due to ever aging population surges the demand for a proper national joint registry. Our Chinese University of Hong Kong - Prince of Wales Hospital (CUHK-PWH) joint registry has passed the 30th year. The aims of this study are 1) summarize our territory-wide joint registry which has passed the 30th year since establishment and 2) compare our statistics with other major joint registries. METHODS: Part 1 was to review the CUHK-PWH registry. Demographic characteristics of our patients who underwent knee and hip replacements had been summarized. Part 2 was a series of comparisons with registries from Sweden, UK, Australia and New Zealand. RESULTS: CUHK-PWH registry captured 2889 primary total knee replacements (TKR) (110 (3.81%) revision) and 879 primary total hip replacements (THR) (107 (12.17%) revision). Median Surgery time of TKR was shorter than THR. Clinical outcome scores were much improved after surgery in both. Uncemented of hybrid in TKR were most popular in Australia (33.4%) and 40% in Sweden and UK. More than half of TKR and THR patients showed the highest percentage with ASA grade 2. New Zealand reflected the best cumulative percentage survival 20 years after surgery of 92.2%, 76.0%, 84.2% survivorship 20 years after TKR, unicompartmental knee replacement (UKR) and Hip. CONCLUSION: A worldwide accepted patient-reported outcome measure (PROM) is recommended to develop to make comparisons among registries and studies feasible. Completeness of registry data is important and useful to improve surgical performance through data comparisons from different regions. Funding from government on sustaining registries is reflected. Registries from Asian countries have yet to be grown and reported.

Surgical accuracy and clinical outcomes of image-free robotic-assisted total knee arthroplasty.

BACKGROUND: The development of total knee arthroplasty (TKA) for knee osteoarthritis (OA) has a good reputation for its effectiveness in reducing joint pain and improving range of motion. We aimed to review our early results using the image-free robotic-assisted technology in knee arthroplasty. METHODS: A total of 71 patients suffering from end-stage OA knee receiving TKA operated by robotic-assisted surgery between the years 2018 and mid-2021 were recruited. Clinical and radiological outcomes were compared with age and sex-matched control group (conventional TKA). RESULTS: The radiological outcome showed significantly more postoperative lower limb alignment outliers in conventional side than robotic-assisted sides. Postoperative knee scores were similar among both groups. Robotic-assisted TKA required a longer implantation time but a shorter hospital stay. CONCLUSION: Robotic-assisted TKA achieved a lower rate of mechanical axis Outlier in the coronal and sagittal plane with a shorter hospital stay. Yet both methods achieve a similar functional outcome.

Effect of pulsed electromagnetic field as an intervention for patients with quadriceps weakness after anterior cruciate ligament reconstruction: a double-blinded, randomized-controlled trial.

BACKGROUND: The ultimate goal of anterior cruciate ligament reconstructions (ACLR) is to fulfil the return-to-play (RTP) criteria. Quadriceps muscle strength is one of the key determinants for a patient's successful return-to-play after ACLR. Quadriceps muscle atrophy can persist beyond the completion of the rehabilitation program in almost half the patients and the reason behind this is still unknown. There are emerging evidences showing that pulsed electromagnetic field (PEMF) can modulate mitochondrial activities for muscle gain. PEMF exposure on top of regular exercise training may promote muscle regeneration and tissue healing. METHODS: This is a double-blinded, randomized controlled trial to investigate the effects of PEMF treatment during the postoperative period on quadriceps muscle strength in ACL injured patient. Adult patients (aged 18-30) with a unilateral ACL injury, total quadriceps muscle volume is equal or more than 7% deficit on involved leg compared with uninvolved leg, sporting injury with a Tegner score of 7+, and both knees without a history of injury/prior surgery will be recruited. To estimate the improvement of patients, isokinetic muscle assessment, ultrasound imaging and MRI for quadriceps muscle thickness, self-reported outcomes with questionnaires, KT-1000 for knee laxity and biomechanical analysis, and Xtreme CT for bone mineral density will be performed. To investigate the mechanism of PEMF therapy on increasing quadriceps strength, samples of blood serum will be drawn before and after intervention. DISCUSSION: This is the first trial evaluating the effects of PEMF on quadriceps muscle recovery after ACLR. The proposed study addresses a huge research gap by evaluating practical use of PEMF as part of rehabilitation. The proposed study will provide much needed scientific support in the use of this noninvasive treatment modality to facilitate recovery of quadriceps strength after PEMF. TRIAL REGISTRATION: ClinicalTrials.gov NCT05184023. Registered on 5 January 2022.

Muscle satellite cells are impaired in type 2 diabetic mice by elevated extracellular adenosine.

Muscle regeneration is known to be defective under diabetic conditions. However, the underlying mechanisms remain less clear. Adult quiescent muscle satellite cells (MuSCs) from leptin-receptor-deficient (i.e., db/db) diabetic mice are defective in early activation in vivo, but not in culture, suggesting the involvement of pathogenic niche factors. Elevated extracellular adenosine (eAdo) and AMP (eAMP) are detected under diabetic conditions. eAdo and eAMP potently inhibit cell cycle re-entry of quiescent MuSCs and injury-induced muscle regeneration. Mechanistically, eAdo and eAMP engage the equilibrative Ado transporters (ENTs)-Ado kinase (ADK)-AMPK signaling axis in MuSCs to inhibit the mTORC1-dependent cell growth checkpoint. eAdo and eAMP also inhibit early activation of quiescent fibroadipogenic progenitors and human MuSCs by the same mechanism. Treatment of db/db diabetic mice with an ADK inhibitor partially rescues the activation defects of MuSCs in vivo. Thus, both ADK and ENTs represent potential therapeutic targets for restoring the regenerative functions of tissue stem cells in patients with diabetes.

Avulsion Fracture of Bicruciate Ligament and Patellar Tendon in Bicruciate-Retaining Total Knee Arthroplasty.

Tibial intercondylar fracture with anterior cruciate ligament avulsion is a unique but rare complication of bicruciate-retaining total knee arthroplasty. Here, we describe an even rarer condition that the tibial intercondylar fracture involved bicruciate ligament and partial patellar tendon avulsion fracture resulting in significant clinical instability in a 70-year-old woman, a combination not yet reported in the literature. Dual-energy computed tomography helped characterize the fracture. During revision surgery, the bicruciate retaining total knee arthroplasty was revised to posterior-stabilized total knee arthroplasty and the patellar tendon was repaired with a suture anchor. She recovered well progressively, and at 6 months, she could walk with the use of an assisted walking device.

Traditional Chinese-Hong Kong version of Forgotten Joint Score-12 (FJS-12) for patients with osteoarthritis of the knee underwent joint replacement surgery: cross-cultural and sub-cultural adaptation, and validation.

BACKGROUND: A patient-reported outcome (PRO) tool which reflects the outcomes of patients underwent total knee arthroplasty (TKA) are important to be "ceiling effect free" which commonly used PRO tools face. Forgotten joint score-12 (FJS-12) has been proved to reduce or even free from ceiling effect. FJS-12 has been translated to different languages. The objectives of this study are to validate FJS-12 in Traditional Chinese-Hong Kong language and look for the goodness of FJS-12 still exist in this language adapted FJS-12 version. METHODS: FJS-12 was administered to 75 patients whose majority was obese underwent TKA between September 2019 and March 2020. Patients completed 3 sets of questionnaires (FJS-12, Oxford Knee Score (OKS), and Numeric Rating Scale (NRS)) twice, 2 weeks apart. Reliability, internal consistency, responsiveness, test-retest agreement and discriminant validity were evaluated. RESULTS: Reliability of FJS-12 showed moderate to excellent internal consistency (Cronbach's α = 0.870). Test-retest reliability of FJS-12 was good (ICC = 0.769). Bland-Altman plot showed good test-retest agreement. Construct validity in terms of correlations between FJS-12 and OKS, and FJS-12 and NRS were moderate at baseline (Pearson's coefficient r = 0.598) and good at follow-up (r = 0.879). Smallest detectable change (Responsiveness) was higher than MIC. Floor effect was none observed, and ceiling effect was low. Discriminant validity was found to have no significance. BMI (obesity) did not affect FJS-12 outcomes. CONCLUSIONS: The Traditional Chinese-Hong Kong version of FJS-12 showed good test-retest reliability, validity, responsiveness, BMI non-specific, with no floor and low ceiling effects for patients who underwent TKA. Sub-culture differences in individual PRO tools should be considered in certain ethnicities and languages.

Large lateral tibial slope and lateral-to-medial slope difference are risk factors for poorer clinical outcomes after posterolateral meniscus root tear repair in anterior cruciate ligament reconstruction.

BACKGROUND: Meniscus root tear is an uncommon but detrimental injury of the knee. Hoop stress is lost during meniscus root tear, which can lead to excessive tibiofemoral contact pressure and early development of osteoarthritis. Posterolateral meniscus root tears (PLRT) are more commonly associated with anterior cruciate ligament (ACL) tears. As the lateral compartment is less congruent than the medial compartment, it is more susceptible to a shearing force, which is increased in the ACL-deficient knee. In accordance with the compressive axial load, the increase in the tibial slope would generate a greater shearing force. The additional lateral compartment mobility caused by ACL tear should be reduced after ACL reconstruction (ACLR). However, there is a lack of evidence to conclude that ACLR can sufficiently limit the effect of large tibial slope (LTS) on the healing after PLRT repair. This study aimed to evaluate whether a steep LTS would be a risk factor for poorer clinical outcomes after PLRT repair concomitant with ACLR. METHODS: In this retrospective study, a chart review was conducted to identify patients with concomitant unilateral primary ACLR and PLRT repair. Patients with a partial tear or healed tear were excluded. Postoperative MRI and clinical assessments were performed at a mean follow up of 35 months. MRI data was used to measure the LTS, medial tibial slope (MTS), coronal tibial slope (CTS), the lateral-to-medial slope difference (LTS-MTS) and meniscus healing and extrusion. Functional outcomes were evaluated by patient-reported outcomes (International Knee Documentation Committee [IKDC], Lysholm and Tegner scores) and KT-1000 arthrometer assessment. Interobserver reproducibility was assessed by two reviewers. RESULTS: Twenty-five patients were identified for the analysis. Patients with larger LTS and larger LTS-MTS differences were shown to be correlated with poorer IKDC scores after surgery (R = -0.472, p = 0.017 and R = -0.429, p = 0.032, respectively). Herein, patients with LTS ≥ 6° or LTS-MTS ≥ 3° demonstrated poorer IKDC scores. CONCLUSION: A large LTS (≥ 6°) and a large difference of LTS-MTS (≥ 3°) were shown to be risk factors for poorer functional and radiological outcomes for PLRT repair in patients after ACLR. Clinically, closer monitoring and a more stringent rehabilitation plan for patients with LTS ≥ 6° or LTS-MTS ≥ 3° would be recommended.

Biodegradable magnesium pins enhanced the healing of transverse patellar fracture in rabbits.

Displaced fractures of patella often require open reduction surgery and internal fixation to restore the extensor continuity and articular congruity. Fracture fixation with biodegradable magnesium (Mg) pins enhanced fracture healing. We hypothesized that fixation with Mg pins and their degradation over time would enhance healing of patellar fracture radiologically, mechanically, and histologically. Transverse patellar fracture surgery was performed on thirty-two 18-weeks old female New Zealand White Rabbits. The fracture was fixed with a pin made of stainless steel or pure Mg, and a figure-of-eight stainless steel band wire. Samples were harvested at week 8 or 12, and assessed with microCT, tensile testing, microindentation, and histology. Microarchitectural analysis showed that Mg group showed 12% higher in the ratio of bone volume to tissue volume at week 8, and 38.4% higher of bone volume at week 12. Tensile testing showed that the failure load and stiffness of Mg group were 66.9% and 104% higher than the control group at week 8, respectively. At week 12, Mg group was 60.8% higher in ultimate strength than the control group. Microindentation showed that, compared to the Control group, Mg group showed 49.9% higher Vickers hardness and 31% higher elastic modulus at week 8 and 12, respectively. At week 12, the new bone of Mg group remodelled to laminar bone, but those of the control group remained woven bone-like. Fixation of transverse patellar fracture with Mg pins and its degradation enhanced new bone formation and mechanical properties of the repaired patella compared to the Control group.

Osteonecrosis of the hip: is there a difference in the survivorship of total hip arthroplasty with or without previous vascular iliac bone grafting?

BACKGROUND: Osteonecrosis of the femoral head (ONFH) is a debilitating condition. Vascularized iliac bone graft (VIBG) is a joint-preserving surgery to improve blood supply to the avascular portion of the femoral head which may delay secondary osteoarthritis and total hip arthroplasty (THA). However, whether VIBG will affect the subsequent THA survivorship and outcomes are still uncertain. METHODS: Implant survivorship and clinical outcomes were compared between 27 patients who had undergone prior VIBG and 242 patients who had only undergone THA for ONFH. Baseline characteristics and the postoperative Harris Hip Score (HHS) were also recorded and compared between the two groups. Implant survivorship was determined using Kaplan-Meier survival analysis. RESULTS: The overall implant survival for all patients who had a primary diagnosis of ONFH and eventually underwent THA was 92.9%. There was no significant difference in the implant survivorship between the group who directly received THA (survivorship of 93%) and the group which failed VIBG and was subsequently converted to THA (survivorship of 91.9%) (p = 0.71). In addition, higher THA revision rates were associated with smokers and drinkers. CONCLUSIONS: VIBG may be a reasonable option as a "buy-time" procedure for ONFH. Even if conversion to THA is eventually required, patients may be reassured that the overall survivorship and clinical outcomes may not be compromised. Patients are recommended to give up smoking and binge drinking prior to THA to increase implant survival rate.

Posterior Tibial Loading Results in Significant Increase of Peak Contact Pressure in the Patellofemoral Joint During Anterior Cruciate Ligament Reconstruction: A Cadaveric Study.

BACKGROUND: Inappropriate posterior tibial loading and initial graft tension during anterior cruciate ligament (ACL) reconstruction may cause altered patellofemoral joint (PFJ) contact mechanics, potentially resulting in pain and joint degeneration. HYPOTHESIS: PFJ contact pressure would increase with the increases in posterior tibial loading and graft tension during ACL reconstruction. STUDY DESIGN: Controlled laboratory study. METHODS: Nine fresh-frozen, nonpaired human cadaveric knees were tested in a customized jig from 0° to 120° of knee flexion. First, the knee was tested in the ACL-intact state. Second, reconstruction of the ACLs using different posterior tibial loadings and graft tensions were performed. The posterior tibial loading was evaluated at 2 levels: 33.5 and 67 N. Graft tension was assessed at 3 levels: low tension (20 N), medium tension (60 N), and high tension (80 N). Maximum values of peak contact pressure in the medial and lateral patellar facets were compared between ACL-intact and ACL-reconstructed knees. The PFJ kinematics between ACL-intact knees and ACL-reconstructed knees were compared during knee flexion at 30°, 60°, 90°, and 120°. RESULTS: Reconstruction of ACLs with both low and high posterior tibial loading resulted in significant increases of peak contact pressure in the medial (range of differences, 0.46-0.92 MPa; P < .05) and lateral (range of differences, 0.51-0.83 MPa; P < .05) PFJ compared with the ACL-intact condition. However, no significant differences in PFJ kinematics were identified between ACL-reconstructed knees and ACL-intact knees. In ACL-reconstructed knees, it was found that a high posterior tibial loading resulted in high peak contact pressure on the medial patellar side (range of differences, 0.37-0.46 MPa; P < .05). No significant difference in peak contact pressure was observed among the differing graft tensions. CONCLUSION: In this cadaveric model, ACL reconstruction resulted in significant increases of peak contact pressure in the PFJ facet when compared with the ACL-intact condition. A high posterior tibial loading can lead to high medial PFJ peak contact pressure. Graft tension was found to not significantly affect PFJ contact pressure during ACL reconstruction. CLINICAL RELEVANCE: An excessive posterior tibial loading during ACL reconstruction resulted in increased PFJ contact pressures at time of surgery. These data suggest that a low posterior tibial loading might be preferred during ACL reconstruction surgery to reduce the PFJ contact pressure close to that of the ACL-intact condition.