Imperial College London

ProfessorJustinCobb

Faculty of MedicineDepartment of Surgery & Cancer

Chair in Orthopaedic Surgery
 
 
 
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Contact

 

+44 (0)20 7594 5534j.cobb Website

 
 
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Assistant

 

Miss Colinette Hazel +44 (0)20 7594 2725

 
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Location

 

c/oBuilding E - Sir Michael UrenWhite City Campus

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Summary

 

Publications

Publication Type
Year
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255 results found

Dandridge O, Garner A, Amis A, Cobb J, van Arkel RJet al., 2022, Variation in the patellar tendon moment arm identified with an improved measurement framework, Journal of Orthopaedic Research, Vol: 40, Pages: 799-807, ISSN: 0736-0266

The mechanical advantage of the knee extensor mechanism depends heavily on the patellar tendon moment arm (PTMA). Understanding which factors contribute to its variation may help improve functional outcomes following arthroplasty. This study optimized PTMA measurement, allowing us to quantify the contribution of different variables. The PTMA was calculated about the instantaneous helical axis of tibiofemoral rotation from optical tracked kinematics. A fabricated knee model facilitated calculation optimization, comparing four data smoothing techniques (raw, Butterworth filtering, generalized cross-validated cubic spline-interpolation and combined filtering/interpolation). The PTMA was then measured for 24 fresh-frozen cadaveric knees, under physiologically based loading and extension rates. Combined filtering/interpolation enabled sub-mm PTMA calculation accuracy throughout the range of motion (root-mean-squared error 0.2 mm, max error 0.4 mm), whereas large errors were measured for raw, filtered-only and interpolated-only techniques at terminal flexion/extension. Before scaling, the mean PTMA was 46 mm; PTMA magnitude was consistently larger in males (mean differences: 5 to 10 mm, p < .05) and was strongly related to knee size: larger knees have a larger PTMA. However, while scaling eliminated sex differences in PTMA magnitude, the peak PTMA occurred closer to terminal extension in females (female 15°, male 29°, p = .01). Knee size accounted for two-thirds of the variation in PTMA magnitude, but not the flexion angle where peak PTMA occurred. This substantial variation in angle of peak PTMA has implications for the design of musculoskeletal models and morphotype-specific arthroplasty. The developed calculation framework is applicable both in vivo and vitro for accurate PTMA measurement.

Journal article

Edwards T, Guest B, Garner A, Logishetty K, Liddle A, Cobb Jet al., 2022, The metabolic equivalent of task score: a useful metric for comparing high functioning hip arthroplasty patients, Bone & Joint Research, ISSN: 2046-3758

Aims: This study investigates the use of the Metabolic Equivalent of Task (MET) score in a young hip arthroplasty population and its ability to capture additional benefit beyond the ceiling effect of conventional patient reported outcomes.Patients & Method: Oxford Hip Score (OHS), EuroQol-5D index (EQ-5D), and the MET were recorded in 221 primary hip arthroplasty procedures pre-operatively and at 1-year. The distribution was examined reporting the presence of ceiling & floor effects. Validity was assessed correlating the MET with the other scores using Spearman’s rank and determining responsiveness. A subgroup of 93 patients scoring 48/48 on the OHS were analysed by age, sex, BMI and pre-operative MET using the other metrics to determine if differences could be established despite scoring identically on the OHS.Results: From our electronic database of 751 hip arthroplasty procedures, 117 primary total hip and 104 hip resurfacing arthroplasty operations were included. Mean age was 59.4 ± 11.3. Post-operatively the OHS and EQ-5D demonstrate significant negatively skewed distributions with ceiling effects of 41% and 53%, respectively. The MET was normally distributed post-operatively with no ceiling effect. Weak-moderate significant correlations were found between the MET and the other two metrics. In the 48/48 subgroup, no differences were found comparing groups with the EQ-5D, however significantly higher MET scores were demonstrated for patients aged <60 (12.7 vs 10.6, p=0.008), male patients (12.5 vs 10.8, p=0.024) and those with pre-operative MET scores >6 (12.6 vs 11.0, p=0.040). Conclusion: The MET is normally distributed in patients following hip arthroplasty, recording levels of activity which are undetectable using the OHS.

Journal article

Munford M, Liddle A, Stoddart J, Cobb J, Jeffers Jet al., 2022, Total and partial knee replacement implants that maintain native load transfer in the Tibia, Bone and Joint Research, Vol: 11, Pages: 1-3, ISSN: 2046-3758

Aims:Unicompartmental and total knee arthroplasty (UKA and TKA) are successful treatments for osteoarthritis, but the solid metal implants disrupt the natural distribution of stress and strain which can lead to bone loss over time. This generates problems if the implant needs to be revised. This study investigates whether titanium lattice UKA and TKA implants can maintain natural load transfer in the proximal tibia. Methods:In a cadaveric model, UKA and TKA procedures were performed on 8 fresh-frozen knee specimens, using conventional (solid) and titanium lattice tibial implants. Stress at the bone-implant interfaces were measured and compared to the native knee.Results:Titanium lattice implants were able to restore the mechanical environment of the native tibia for both UKA and TKA designs. Maximum stress at the bone-implant interface ranged from 1.2-3.3 MPa compared to 1.3-2.7 MPa for the native tibia. The conventional solid UKA and TKA implants reduced the maximum stress in the bone by a factor of 10 and caused >70% of bone surface area to be underloaded compared to the native tibia. Conclusions:Titanium lattice implants maintained the natural mechanical loading in the proximal tibia after UKA and TKA, but conventional solid implants did not. This is an exciting first step towards implants that maintain bone health, but such implants also have to meet fatigue and micromotion criteria to be clinically viable.

Journal article

Ng KC, Bankes M, El Daou H, Beaule P, Cobb J, Jeffers Jet al., 2022, Hip dysplasia capsular mechanics after periacetabular osteotomy, The Journal of Bone and Joint Surgery, ISSN: 0021-9355

Background: Hip dysplasia is characterized by an insufficient acetabular coverage around the femoral head which leads to instability, pain, and injury. Periacetabular osteotomy (PAO) aims to restore acetabular coverage and function, but its effects on capsular mechanics and joint stability are still unclear. The purpose was to examine the effects of PAO on capsular mechanics and joint range of motion in dysplastic hips.Methods: Twelve cadaveric dysplastic hips (denuded to bone-and-capsule) were mounted onto a robotic tester and tested in multiple positions: (1) Extension, (2) Neutral 0°, (3) Flexion 30°, (4) Flexion 60°, (5) Flexion 90°; rotating to 5 Nm of torque in internal-external rotation and abduction-adduction. Each hip underwent a PAO to reorient the acetabular fragment, preserving the capsular ligaments, and was retested in the robot.Results: The PAO reduced internal rotation at Flexion 90° (∆IR = –5°; p = 0.003), and increased external rotation in Flexion 60° (∆ER = +7°; p = 0.001) and Flexion 90° (∆ER = +11°; p = 0.001). The PAO also reduced abduction in Extension (∆ABD = –10°; p = 0.002), Neutral 0° (∆ABD = –7°; p = 0.001), and Flexion 30° (∆ABD = –8°; p = 0.001), but increased adduction in Neutral 0° (∆ADD = +9°; p = 0.001), Flexion 30° (∆ADD = +11°; p = 0.002), and Flexion 60° (∆ADD = +11°; p = 0.003).Conclusions: The PAO reduced hip abduction and internal rotation but further increased hip adduction and external rotation. The osseous acetabular structure and capsule both play a role in balancing joint mobility and stability after PAO. Level of Evidence: Basic Science Research, Descriptive Laboratory Study

Journal article

Logishetty K, Edwards T, Ponniah HS, Ahmed M, Liddle AD, Cobb J, Clark Cet al., 2022, How to prioritise patients and redesign care to safely resume planned surgery during the COVID-19 pandemic. A clinical validation study, Bone & Joint Open, Vol: 2, Pages: 134-140, ISSN: 2633-1462

Background and Purpose: Restarting planned surgery during the COVID-19 pandemic is a clinical and societal priority, but it is unknown whether it can be done safely and include high-risk or complex cases. We developed a Surgical Prioritization and Allocation Guide (SPAG). Here, we validate its effectiveness and safety in COVID-free sites. Patients and Methods: A multidisciplinary Surgical Prioritisation Committee developed the SPAG, incorporating procedural urgency, shared decision making, patient safety and biopsychosocial factors; and applied it to 1142 adult patients awaiting orthopaedic surgery. Patients were stratified into four priority groups and underwent surgery at three COVID-free sites – including one with access to a High Dependency Unit (HDU) or Intensive Care Unit (ICU) and specialist resources. Safety was assessed by the number of patients requiring inpatient postoperative HDU/ICU admission, contracting COVID-19 within 14 days postoperatively, and mortality within 30 days postoperatively. Results: 1142 patients were included, 47 declined surgery. 110 were deemed high-risk or requiring specialist resources. In the 10-week study period, 28 high-risk patients underwent surgery, during which 68% of Priority 2 (P2, surgery within 1 month) patients underwent surgery, and 15% of P3 (<3 months) and 16% of P4 (>3 months) groups. Of the 1032 low-risk patients, 322 patients underwent surgery. Twenty-one P3 and P4 patients were expedited to ‘Urgent’ based on biopsychosocial factors identified by the SPAG. During the study period, 91% of the Urgent group, 52% of P2, 36% of P3, and 26% of P4 underwent surgery. No patients died or were admitted to HDU/ICU, or contracted COVID-19. Interpretation: Our widely generalisable model enabled the restart of planned surgery during the CO

Journal article

Musbahi O, Syed L, Le Feuvre P, Cobb J, Jones Get al., 2021, Public patient views of artificial intelligence in healthcare: A nominal group technique study, Digital Health, Vol: 7, Pages: 1-11, ISSN: 2055-2076

Objectives: The beliefs of laypeople and medical professionals often diverge with regards to disease, and technology has had a positive impact on how research is conducted. Surprisingly, given the expanding worldwide funding and research into Artificial Intelligence (AI) applications in healthcare, there is a paucity of research exploring the public patient perspective on this technology. Our study sets out to address this knowledge gap, by applying the Nominal Group Technique (NGT) to explore patient public views on AI. Methods: A Nominal Group Technique (NGT) was used involving four study groups with seven participants in each group. This started with a silent generation of ideas regarding the benefits and concerns of AI in Healthcare. This was followed by a group discussion. Then a round-robin process was conducted until no new ideas were generated. Participants then ranked their top five benefits and top five concerns regarding the use of AI in healthcare. A final group consensus was reached. Results: Twenty-Eight participants were recruited with the mean age of 47 years. The top five benefits were: Faster health services, Greater accuracy in management, AI systems available 24/7, reducing workforce burden, and equality in healthcare decision making. The top five concerns were: Data cybersecurity, bias and quality of AI data, less human interaction, algorithm errors and responsibility, and limitation in technology. Conclusion: This is the first formal qualitative study exploring patient public views on the use of AI in healthcare, and highlights that there is a clear understanding of the potential benefits delivered by this technology. Greater patient public group involvement, and a strong regulatory framework is recommended.

Journal article

Edwards TC, Coombs AW, Szyszka B, Logishetty K, Cobb JPet al., 2021, Cognitive task analysis-based training in surgery: a meta-analysis, BJS OPEN, Vol: 5, ISSN: 2474-9842

Journal article

Dandridge O, Garner A, Jeffers JRT, Amis AA, Cobb JP, van Arkel RJet al., 2021, Validity of repeated-measures analyses of in vitro arthroplasty kinematics and kinetics, Journal of Biomechanics, Vol: 129, Pages: 1-5, ISSN: 0021-9290

In vitro models of arthroplasty enable pre-clinical testing and inform clinical decision making. Repeated-measures comparisons maximise resource efficiency, but their validity without testing order randomisation is not known. This study aimed to identify if there were any large testing order effects for cadaveric models of knee and hip arthroplasty. First, the effect of testing order on total knee arthroplasty (TKA) biomechanics was assessed. Extension moments for TKAs (N=3) implanted into the native knee (TKA-only) were compared to a dataset of TKAs (N=24) tested after different combinations of partial knee arthroplasty (TKA-last). The effect of repeatedly testing the same knee five times over 36 hours on patellofemoral and tibiofemoral kinematics was also quantified. Second, the effect of testing order on capsular ligament function after total hip arthroplasty (THA) was assessed. Randomisation was removed from a previously published dataset to create increasing and decreasing head size groups, which were compared with t-tests.All three TKA-only extension moments fell within the 95% CI of the TKA-last knees across the full range of knee flexion/extension. Repeated testing resulted in root-mean-squared kinematics errors within 1 mm, 1°, or < 5 % of total range of motion. Following THA, smaller head-size resulted in greater laxity in both the increasing (p=0.01) and decreasing (p<0.001) groups. Testing order did not have large effects on either knee or hip arthroplasty biomechanics measured with in vitro cadaveric models.

Journal article

Garner A, Dandridge O, Amis A, Cobb J, van Arkel RJet al., 2021, Bi-unicondylar arthroplasty: a biomechanics and clinical outcomes study, Bone & Joint Research, Vol: 10, Pages: 723-733, ISSN: 2046-3758

Aims Bi-Unicondylar Arthroplasty (Bi-UKA) is a bone and anterior cruciate ligament (ACL) preserving alternative to Total Knee Arthroplasty (TKA) when the patellofemoral joint is preserved. The aim of this study is to investigate the clinical outcomes and biomechanics of Bi-UKA. Methods Bi-UKA subjects (N = 22) were measured on an instrumented treadmill, using standard gait metrics, at top walking speeds. Age, sex and BMI-matched healthy (N = 24) and primary TKA (N = 22) subjects formed control groups. TKA subjects with pre-operative patellofemoral or tricompartmental arthritis or ACL dysfunction were excluded. The Oxford Knee Score (OKS) and EuroQol-5D (EQ-5D) were compared. Bi-UKA then TKA were performed on eight fresh frozen cadaveric knees, to investigate knee extensor efficiency under controlled laboratory conditions, using a repeated measures study design. Results Bi-UKA walked 20% faster than TKA (Bi-UKA 6.70.9km/h, TKA 5.60.7km/h p<0.001), exhibiting nearer-normal vertical Ground Reaction Forces in maximum weight-acceptance and mid-stance, with longer step and stride lengths compared to TKA (p<0.05). Bi-UKAsubjects reported higher OKS (p=0.004) and EQ-5D (p<0.001). In vitro, Bi-UKA generated the same extensor moment as native knees at low flexion angles, whilst reduced extensor moment was measured following TKA (p<0.003). Conversely, at higher flexion angles, the extensor moment of TKA was normal. Over the full range, the extensor mechanism was more efficient following Bi-UKA than TKA (p<0.05). Conclusion Bi-UKA had more normal gait characteristics and improved patient reported outcomes, compared to matched TKA subjects. This can, in part, be explained by differences in extensor efficiency.

Journal article

Garner A, Dandridge O, Amis A, Cobb J, van Arkel Ret al., 2021, Partial and combined partial knee arthroplasty: greater anterior-posterior stability than posterior-cruciate retaining total knee arthroplasty, The Journal of Arthroplasty, Vol: 36, Pages: 3765-3772.e4, ISSN: 0883-5403

BackgroundLittle is known regarding anterior-posterior stability after anterior cruciate ligament–preserving partial (PKA) and combined partial knee arthroplasty (CPKA) compared to standard posterior cruciate–retaining total knee arthroplasty (TKA).MethodsThe anterior-posterior tibial translation of twenty-four cadaveric knees was measured, with optical tracking, while under 90N drawer with the knee flexed 0-90°. Knees were tested before and after PKA, CPKA (medial and lateral bicompartmental and bi-unicondylar), and then posterior cruciate–retaining TKA. The anterior-posterior tibial translations of the arthroplasty states, at each flexion angle, were compared to the native knee and each other with repeated measures analyses of variance and post-hoc t-tests.ResultsUnicompartmental and bicompartmental arthroplasty states had similar laxities to the native knee and to each other, with ≤1-mm differences throughout the flexion range (P ≥ .199). Bi-unicondylar arthroplasty resulted in 6- to 8-mm increase of anterior tibial translation at high flexion angles compared to the native knee (P ≤ .023 at 80-90°). Meanwhile, TKA exhibited increased laxity across all flexion angles, with increased anterior tibial translation of up to 18 ± 6 mm (P < .001) and increased posterior translation of up to 4 ± 2 mm (P < .001).ConclusionsIn a cadaveric study, anterior-posterior tibial translation did not differ from native laxity after PKA and CPKA. Posterior cruciate ligament–preserving TKA demonstrated increased laxity, particularly in anterior tibial translation.

Journal article

Garner AJ, Dandridge OW, van Arkel RJ, Cobb JPet al., 2021, Medial bicompartmental arthroplasty patients display more normal gait and improved satisfaction, compared to matched total knee arthroplasty patients, Knee Surgery, Sports Traumatology, Arthroscopy, ISSN: 0942-2056

PurposeMedial bicompartmental arthroplasty, the combination of ipsilateral medial unicompartmental and patellofemoral arthroplasty, is an alternative to total knee arthroplasty for patients with medial tibiofemoral and severe patellofemoral arthritis, when the lateral tibiofemoral compartment and anterior cruciate ligament are intact. This study reports the gait and subjective outcomes following medial bicompartmental arthroplasty.MethodsFifty-five subjects were measured on the instrumented treadmill at top walking speeds, using standard metrics of gait. Modular, single-stage, medial bicompartmental arthroplasty subjects (n = 16) were compared to age, body mass index, height- and sex-matched healthy (n = 19) and total knee arthroplasty (n = 20) subjects. Total knee arthroplasty subjects with pre-operative evidence of tricompartmental osteoarthritis or anterior cruciate ligament dysfunction were excluded. The vertical component of ground reaction force and temporospatial measurements were compared using Kruskal–Wallis, then Mann–Whitney test with Bonferroni correction (α = 0.05). Oxford Knee and EuroQoL EQ-5D scores were compared.ResultsObjectively, the medial bicompartmental arthroplasty top walking speed of 6.7 ± 0.8 km/h was 0.5 km/h (7%) slower than that of healthy controls (p = 0.2), but 1.3 km/h (24%) faster than that of total knee arthroplasty subjects (5.4 ± 0.6 km/h, p < 0.001). Medial bicompartmental arthroplasty recorded more normal maximum weight acceptance (p < 0.001) and mid-stance forces (p = 0.03) than total knee arthroplasty subjects, with 11 cm (15%) longer steps (p < 0.001) and 21 cm (14%) longer strides (p = 0.006). Subjectively, medial bicompartmental arthroplasty subjects reported Oxford Knee Scores of median 41 (interquartile range 38.8&nd

Journal article

Edwards TC, Patel A, Szyszka B, Coombs AW, Kucheria R, Cobb JP, Logishetty Ket al., 2021, The Impact of Using A Virtual Reality Surgical Curriculum to Train Scrub Practitioners in Complex Orthopaedic Surgery, Publisher: OXFORD UNIV PRESS, ISSN: 0007-1323

Conference paper

Garner AJ, Dandridge OW, van Arkel RJ, Cobb JPet al., 2021, The compartmental approach to revision of partial knee arthroplasty results in nearer-normal gait and improved patient reported outcomes compared to total knee arthroplasty, Knee Surgery Sports Traumatology Arthroscopy, ISSN: 0942-2056

PURPOSE: This study investigated the gait and patient reported outcome measures of subjects converted from a partial knee arthroplasty to combined partial knee arthroplasty, using a compartmental approach. Healthy subjects and primary total knee arthroplasty patients were used as control groups. METHODS: Twenty-three patients converted from partial to combined partial knee arthroplasty were measured on the instrumented treadmill at top walking speeds, using standard gait metrics. Data were compared to healthy controls (n = 22) and primary posterior cruciate-retaining total knee arthroplasty subjects (n = 23) where surgery were performed for one or two-compartment osteoarthritis. Groups were matched for age, sex and body mass index. At the time of gait analysis, combined partial knee arthroplasty subjects were median 17 months post-revision surgery (range 4-81 months) while the total knee arthroplasty group was median 16 months post-surgery (range 6-150 months). Oxford Knee Scores and EuroQol-5D 5L scores were recorded at the time of treadmill assessment, and results analysed by question and domain. RESULTS: Subjects revised from partial to combined partial knee arthroplasty walked 16% faster than total knee arthroplasty (mean top walking speed 6.4 ± 0.8 km/h, vs. 5.5 ± 0.7 km/h p = 0.003), demonstrating nearer-normal weight-acceptance rate (p < 0.001), maximum weight-acceptance force (p < 0.006), mid-stance force (p < 0.03), contact time (p < 0.02), double support time (p < 0.009), step length (p = 0.003) and stride length (p = 0.051) compared to primary total knee arthroplasty. Combined partial knee arthroplasty subjects had a median Oxford Knee Score of 43 (interquartile range 39-47) vs. 38 (interquartile range 32-41, p < 0.

Journal article

Preston B, Harris S, Villet L, Mattathil C, Cobb J, Riviere Cet al., 2021, The medial condylar wall is a reliable landmark to kinematically align the femoral component in medial UKA: an in-silico study, KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, ISSN: 0942-2056

Journal article

Garner AJ, Edwards TC, Liddle AD, Jones GG, Cobb JPet al., 2021, The revision partial knee classification system: understanding the causative pathology and magnitude of further surgery following partial knee arthroplasty., Bone & Joint Open, Vol: 2, Pages: 638-645, ISSN: 2633-1462

AIMS: Joint registries classify all further arthroplasty procedures to a knee with an existing partial arthroplasty as revision surgery, regardless of the actual procedure performed. Relatively minor procedures, including bearing exchanges, are classified in the same way as major operations requiring augments and stems. A new classification system is proposed to acknowledge and describe the detail of these procedures, which has implications for risk, recovery, and health economics. METHODS: Classification categories were proposed by a surgical consensus group, then ranked by patients, according to perceived invasiveness and implications for recovery. In round one, 26 revision cases were classified by the consensus group. Results were tested for inter-rater reliability. In round two, four additional cases were added for clarity. Round three repeated the survey one month later, subject to inter- and intrarater reliability testing. In round four, five additional expert partial knee arthroplasty surgeons were asked to classify the 30 cases according to the proposed revision partial knee classification (RPKC) system. RESULTS: Four classes were proposed: PR1, where no bone-implant interfaces are affected; PR2, where surgery does not include conversion to total knee arthroplasty, for example, a second partial arthroplasty to a native compartment; PR3, when a standard primary total knee prosthesis is used; and PR4 when revision components are necessary. Round one resulted in 92% inter-rater agreement (Kendall's W 0.97; p < 0.005), rising to 93% in round two (Kendall's W 0.98; p < 0.001). Round three demonstrated 97% agreement (Kendall's W 0.98; p < 0.001), with high intra-rater reliability (interclass correlation coefficient (ICC) 0.99; 95% confidence interval 0.98 to 0.99). Round four resulted in 80% agreement (Kendall's W 0.92; p < 0.001). CONCLUSION: The RPKC system accounts for all procedures which may be appropriate following partial knee arthroplasty. It h

Journal article

Edwards TC, Patel A, Szyszka B, Coombs AW, Liddle AD, Kucheria R, Cobb JP, Logishetty Ket al., 2021, Immersive virtual reality enables technical skill acquisition for scrub nurses in complex revision total knee arthroplasty., Archives of Orthopaedic and Trauma Surgery, Vol: 141, ISSN: 0344-8444

INTRODUCTION: Immersive Virtual Reality (iVR) is a novel technology which can enhance surgical training in a virtual environment without supervision. However, it is untested for the training to select, assemble and deliver instrumentation in orthopaedic surgery-typically performed by scrub nurses. This study investigates the impact of an iVR curriculum on this facet of the technically demanding revision total knee arthroplasty. MATERIALS AND METHODS: Ten scrub nurses completed training in four iVR sessions over a 4-week period. Initially, nurses completed a baseline real-world assessment, performing their role with real equipment in a simulated operation assessment. Each subsequent iVR session involved a guided mode, where the software taught participants the procedural choreography and assembly of instrumentation in a simulated operating room. In the latter three sessions, nurses also undertook an assessment in iVR. Outcome measures were related to procedural sequence, duration of surgery and efficiency of movement. Transfer of skills from iVR to the real world was assessed in a post-training simulated operation assessment. A pre- and post-training questionnaire assessed the participants knowledge, confidence and anxiety. RESULTS: Operative time reduced by an average of 47% across the 3 unguided sessions (mean 55.5 ± 17.6 min to 29.3 ± 12.1 min, p > 0.001). Assistive prompts reduced by 75% (34.1 ± 16.8 to 8.6 ± 8.8, p < 0.001), dominant hand motion by 28% (881.3 ± 178.5 m to 643.3 ± 119.8 m, p < 0.001) and head motion by 36% (459.9 ± 99.7 m to 292.6 ± 85.3 m, p < 0.001). Real-world skill improved from 11% prior to iVR training to 84% correct post-training. Participants reported increased confidence and r

Journal article

Ponniah HS, Ahmed M, Edwards T, Cobb J, Dean E, Clark C, Logishetty Ket al., 2021, How to prioritise patients and safely resume elective surgery during the Covid-19 pandemic, Publisher: OXFORD UNIV PRESS, ISSN: 0007-1323

Conference paper

Abel R, Behforootan S, Boughton O, Hansen U, Cobb J, Huthwaite Pet al., 2021, Ultrasound and Bone Disease: A Systematic Review, World Journal of Surgery and Surgical Research

Journal article

Stoddart J, Dandridge O, Garner A, Cobb J, van Arkel RJet al., 2021, The compartmental distribution of knee osteoarthritis – a systematic review and meta-analysis, Osteoarthritis and Cartilage, Vol: 29, Pages: 445-455, ISSN: 1063-4584

ObjectivesFor a population with knee osteoarthritis (OA), determine: 1) the prevalence of single compartmental, bicompartmental and tricompartmental OA, 2) the prevalence of isolated medial tibiofemoral, lateral tibiofemoral, or patellofemoral OA, and combinations thereof.MethodsPubMed and Web of Science databases, and reference lists of identified studies, were searched to find studies which reported on the compartmental distribution and prevalence of knee OA. Two independent reviewers assessed studies against pre-defined inclusion criteria and prevalence data were extracted along with subject characteristics. The methodological quality of each included study was assessed. A random-effects model meta-analysis was performed for each OA category to estimate the relative prevalence of OA in the knee compartments amongst people with knee OA.Results16 studies (3,786 knees) met the inclusion criteria. High heterogeneity was measured. Normalised for knees with OA, estimated prevalence rates (95% CI) were: single compartmental 50% (31.5–58.3%), bicompartmental 33% (23.1–37.2%) and tricompartmental only 17% (8.8–24.8%). Isolated medial tibiofemoral OA, isolated patellofemoral OA, and combined medial tibiofemoral and patellofemoral OA were more common than tricompartmental disease, occurring in 27% (15.2–31.1%), 18% (9.9–22.7%) and 23% (14.1–27.3%) of people respectively. Single/bicompartmental patterns of disease involving the lateral tibiofemoral compartment were less common, summing to 15% (8.5–18.7%).ConclusionThree-quarters of people with knee OA do not have tricompartmental disease. This is not reflected in the frequency with which partial and combined partial knee arthroplasties are currently used.Trial registration numberPROSPERO systematic review protocol (CRD42019140345).KeywordsGonarthrosisUnicompartmentalBicompartmentalPrevalenceEpidemiology

Journal article

Wiik AV, Aqil A, Al-Obaidi B, Brevadt M, Cobb JPet al., 2021, The impact of reducing the femoral stem length in total hip arthroplasty during gait, Archives of Orthopaedic and Trauma Surgery, Vol: 141, Pages: 1993-2000, ISSN: 0344-8444

AimThe length of the femoral stem in total hip arthroplasty (THA) is a practical consideration to prevent gait impairment. The aim of this study was to determine if reducing the femoral stem length in THA would lead to impaired gait biomechanics.MethodsPatients uniformly with the same brand implant of differing lengths (100 mm vs 140–166 mm) were taken retrospectively from a prospective trial introducing a new short stem. Twelve patients without any other disorder to alter gait besides contralateral differing length stem THA were tested at differing gradients and speed on a validated instrumented treadmill measuring ground reaction forces. An anthropometrically similar group of healthy controls were analysed to compare.ResultsWith the same posterior surgical approach, the offset and length of both hips were reconstructed within 5 mm of each other with an identical mean head size of 36 mm. The short stem was the last procedure for all the hips with gait analysis occurring at a mean of 31 and 79 months postoperatively for the short and long stem THA, respectively. Gait analysis between limbs of both stem lengths demonstrated no statistical difference during any walking condition. In the 90 gait assessments with three loading variables, the short stem was the favoured side 51% of the time compared 49% for the long stem.ConclusionBy testing a range of practical walking activities, no lower limb loading differences can be observed by reducing the femoral stem length. A shorter stem demonstrates equivalence in preference during gait when compared to a reputable conventional stem in total hip arthroplasty.

Journal article

Riviere C, Sivaloganathan S, Villet L, Cartier P, Lustig S, Vendittoli P-A, Cobb Jet al., 2021, Kinematic alignment of medial UKA is safe: a systematic review, KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 30, Pages: 1082-1094, ISSN: 0942-2056

Journal article

Logishetty K, Edwards TC, Subbiah Ponniah H, Ahmed M, Liddle AD, Cobb J, Clark Cet al., 2021, How to prioritize patients and redesign care to safely resume planned surgery during the COVID-19 pandemic., Bone & Joint Open, Vol: 2, Pages: 134-140, ISSN: 2633-1462

AIMS: Restarting planned surgery during the COVID-19 pandemic is a clinical and societal priority, but it is unknown whether it can be done safely and include high-risk or complex cases. We developed a Surgical Prioritization and Allocation Guide (SPAG). Here, we validate its effectiveness and safety in COVID-free sites. METHODS: A multidisciplinary surgical prioritization committee developed the SPAG, incorporating procedural urgency, shared decision-making, patient safety, and biopsychosocial factors; and applied it to 1,142 adult patients awaiting orthopaedic surgery. Patients were stratified into four priority groups and underwent surgery at three COVID-free sites, including one with access to a high dependency unit (HDU) or intensive care unit (ICU) and specialist resources. Safety was assessed by the number of patients requiring inpatient postoperative HDU/ICU admission, contracting COVID-19 within 14 days postoperatively, and mortality within 30 days postoperatively. RESULTS: A total of 1,142 patients were included, 47 declined surgery, and 110 were deemed high-risk or requiring specialist resources. In the ten-week study period, 28 high-risk patients underwent surgery, during which 68% (13/19) of Priority 2 (P2, surgery within one month) patients underwent surgery, and 15% (3/20) of P3 (< three months) and 16% (11/71) of P4 (> three months) groups. Of the 1,032 low-risk patients, 322 patients underwent surgery. Overall, 21 P3 and P4 patients were expedited to 'Urgent' based on biopsychosocial factors identified by the SPAG. During the study period, 91% (19/21) of the Urgent group, 52% (49/95) of P2, 36% (70/196) of P3, and 26% (184/720) of P4 underwent surgery. No patients died or were admitted to HDU/ICU, or contracted COVID-19. CONCLUSION: Our widely generalizable model enabled the restart of planned surgery during the COVID-19 pandemic, without compromising patient safety or excluding high-risk or complex cases. Patients classified as Urgent or P2 w

Journal article

Boughton O, Cobb J, owyang D, Bakhsh A, brewer Det al., 2021, Patient and Public Involvement Within Orthopaedic Research: A Systematic Review, Journal of Bone and Joint Surgery: American Volume, ISSN: 0021-9355

Journal article

Garner A, Dandridge O, Amis A, Cobb J, van Arkel Ret al., 2021, The extensor efficiency of unicompartmental, bicompartmental and total knee arthroplasty, Bone and Joint Research, Vol: 10, Pages: 1-9, ISSN: 2046-3758

Aims: Unicompartmental (UKA) and bicompartmental (BCA) knee arthroplasty have been associated with improved functional outcomes compared to Total Knee Arthroplasty (TKA) in suitable patients, although the reason is poorly understood. The aim of this study was to measure how the different arthroplasties affect knee extensor function. Methods: Extensor function was measured for sixteen cadaveric knees and then re-tested following the different arthroplasties. Eight knees underwent medial UKA then BCA, then posterior-cruciate retaining TKA, and eight underwent the lateral equivalents then TKA. Extensorefficiency was calculated for ranges of knee flexion associated with common 46activities of daily living. Data were analyzed with repeated measures analysis of variance (=0.05). Results: Compared to native, there were no reductions in either extension moment or efficiency following UKA. Conversion to BCA resulted in a small decrease in extension moment between 70-90° flexion(p<0.05), but when examined in the context of daily activity ranges of flexion, extensor efficiency was largely unaffected. Following TKA, large decreases in extension moment were measured at low knee flexion angles(p<0.05), resulting in 12-43% reductions in extensor efficiency for the daily activity ranges. Conclusion: This cadaveric study found that TKA resulted in inferior extensor function compared to UKA and BCA. This may, in part, help explain the reported differences in 58function and satisfaction differences between partial and total knee arthroplasty.

Journal article

Ng KCG, Bankes M, El Daou H, Rodriguez y Baena F, Jeffers Jet al., 2021, Cam osteochondroplasty for femoroacetabular impingement increases microinstability in deep flexion: A cadaveric study, Arthroscopy: The Journal of Arthroscopy and Related Surgery, Vol: 37, Pages: 159-170, ISSN: 0749-8063

Purpose: The purpose of this in vitro cadaveric study was to examine the contributions of each surgical stage during cam femoroacetabular impingement (FAI) surgery (i.e., intact cam hip, T8 capsulotomy, cam resection, capsular repair) towards hip range of motion, translations, and microinstability.Methods: Twelve cadaveric cam hips were denuded to the capsule and mounted onto a robotic tester. Hips were positioned in several flexion positions: Full Extension, Neutral 0°, Flexion 30°, and Flexion 90°; and performed internal-external rotations to 5-Nm torque in each position. Hips underwent a series of surgical stages (T-capsulotomy, cam resection, capsular repair) and was retested after each stage. Changes in range of motion, translation, and microinstability (overall translation normalized by femoral head radius) were measured after each stage.Results: For range of motion, cam resection increased internal rotation at Flexion 90° (ΔIR = +6°, P = .001), but did not affect external rotation. Capsular repairs restrained external rotations compared to the cam resection stage (ΔER = –4 to –8°, P ≤ .04). For translations, the hip translated after cam resection at Flexion 90° in the medial-lateral plane (ΔT = +1.9 mm, P = .04), relative to the intact and capsulotomy stages. For microinstability, capsulotomy increased microinstability in Flexion 30° (ΔM = +0.05; P = .003), but did not further increase after cam resection. At Flexion 90°, microinstability did not increase after capsulotomy (ΔM = +0.03; P = .2, d = .24), but substantially increased after cam resection (ΔM = +0.08; P = .03), accounting for a 31% change with respect to the intact stage.Conclusions: Cam resection increased microinstability by 31% during deep hip flexion relative to the intact hip. This suggests that iatrogenic microinstability may be due to separation of the labral seal and resected contour of the femoral head.

Journal article

Wiik AV, Nathwani D, Akhtar A, Al-Obaidi B, Strachan R, Cobb JPet al., 2020, The unicompartmental knee is the preferred side in individuals with both a unicompartmental and total knee arthroplasty, Knee Surgery Sports Traumatology Arthroscopy, Vol: 28, Pages: 3193-3199, ISSN: 0942-2056

PurposeTo determine the preferred knee in patients with both one total and one unicompartmental knee arthroplasty.MethodPatients simply with a unicompartmental (UKA) and total knee arthroplasty (TKA) on contralateral sides were retrospectively screened from three senior knee surgeon’s logs over a 15 year period. Patients safe and free from other diseases to affect gait were approached. A total of 16 patients (mean age 70 ± 8) agreed to ground reaction force testing on an instrumented treadmill at a fair pace and incline. A gender-ratio identical group of 16 healthy control subjects (mean age 67 ± 10) and 16 patients with ipsilateral medial knee OA (mean age 66 ± 7) were analysed to compare.ResultsRadiographically the mode preoperative Kellgren–Lawrence knee grade for each side was 3. Postoperatively, the TKA side had a mean coronal femoral component alignment of 7° and a mean tibial coronal alignment of 89° with a mean posterior slope of 5° in the sagittal plane. The UKA side had a mean coronal femoral component alignment of 7° and a mean tibial coronal alignment of 86° with a mean posterior slope of 4° in the sagittal plane. In 7 patients, the TKA was the first procedure, while 6 for the UKA and 3 done simultaneously. Gait analysis demonstrated in both walking conditions the UKA limb was the preferred side through all phases of loading (p < 0.05) and nearer to normal than the TKA limb when compared to healthy controls and patients with knee OA. The greatest difference was observed between the transition of weight acceptance and midstance (p = 0.008), when 22% more load was taken by the UKA side.ConclusionBy using a dynamic metric of an everyday activity, a distinct gait difference between differing arthroplasty types were established. A more natural loading pattern can be achieved with unicompartmentals as compared to total knees.Level o

Journal article

Clark J, Heyraud A, Tavana S, Al-Jabri T, Tallia F, Clark B, Blunn G, Cobb J, Hansen U, Jones J, Jeffers Jet al., 2020, Exploratory full-field mechanical analysis across the osteochondral tissue– biomaterial interface in an ovine model, Materials, Vol: 13, ISSN: 1996-1944

Osteochondral injuries are increasingly prevalent, yet success in articular cartilage regeneration remains elusive, necessitating the development of new surgical interventions and novel medical devices. As part of device development, animal models are an important milestone in illustrating functionality of novel implants. Inspection of the tissue-biomaterial system is vital to understand and predict load-sharing capacity, fixation mechanics and micromotion, none of which are directly captured by traditional post-mortem techniques. This study aims to characterize the localised mechanics of an ex vivo ovine osteochondral tissue–biomaterial system extracted following six weeks in vivo testing, utilising laboratory micro-computed tomography, in situ loading and digital volume correlation. Herein, the full-field displacement and strain distributions were visualised across the interface of the system components, including newly formed tissue. The results from this exploratory study suggest that implant micromotion in respect to the surrounding tissue could be visualised in 3D across multiple loading steps. The methodology provides a non-destructive means to assess device performance holistically, informing device design to improve osteochondral regeneration strategies.

Journal article

Edwards TC, Logishetty K, Cobb JP, 2020, Letter to the Editor on "Patient-Reported Outcomes Following Total Hip Arthroplasty: A Multicenter Comparison Based on Surgical Approaches", JOURNAL OF ARTHROPLASTY, Vol: 35, Pages: 2686-2687, ISSN: 0883-5403

Journal article

Ma S, Goh EL, Tay T, Wiles C, Boughton O, Churchwell J, Wu Y, Karunaratne A, Bhattacharya R, Terrill N, Cobb J, Hansen U, Abel Ret al., 2020, Nanoscale mechanisms in age-related hip-fractures, Scientific Reports, Vol: 10, Pages: 1-14, ISSN: 2045-2322

Nanoscale mineralized collagen fibrils may be important determinants of whole-bone mechanical properties and contribute to the risk of age-related fractures. In a cross-sectional study nano-and tissue-level mechanics were compared across trabecular sections from the proximal femora of three groups(n=10 each): ageing non-fractured donors (Controls);untreated fracture patients (Fx-Untreated); bisphosphonate-treated fracture patients (Fx-BisTreated).Collagen fibril, mineral and tissue mechanics were measured using synchrotron X-Ray diffraction,of bone sections under load. Mechanical data were compared across groups, and tissue-level data were regressed against nano. Compared to controls fracture patients exhibited significantly lower critical strain, max strain and normalized strength, with lower peak collagen and mineral strain. Bisphosphonate-treated exhibited the lowest properties. In all three groups, peak mineral strain coincided with maximum tissue strength (i.e. ultimate stress), whilst peak fibril strain occurred afterwards(i.e. higher strain). Tissue strain and strength were positively and strongly correlated with peak fibril and mineral strains. Age-related fractures were associated with lower peak fibril and mineral strain irrespective of treatment. Indicating earlier mineral disengagement and the subsequent onset of fibril sliding is one of the key mechanisms leading to fracture. Treatments for fragility should target collagen-mineral interactions to restore nano-scale strain to that of healthy bone.

Journal article

Saracco A, Grassi A, Romagnoli M, Camarda L, Logishetty K, Zaffagnini S, Cobb Jet al., 2020, Reduced -dose computed tomography is the most accurate method to measure ceramic hip resurfacing cup version, EUROPEAN JOURNAL OF RADIOLOGY, Vol: 128, ISSN: 0720-048X

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