Anatole Wiik

Unicompartmental Knee Arthroplasty Enables Near Normal Gait at Higher Speeds, Unlike Total Knee Arthroplasty

Top walking speed (TWS) was used to compare UKA with TKA. Two groups of 23 patients, well matched for age, gender, height and weight and radiological severity were recruited based on high functional scores, more than twelve months post UKA or TKA. These were compared with 14 preop patients and 14 normal controls. Their gait was measured at increasing speeds on a treadmill instrumented with force plates. Both arthroplasty groups were significantly faster than the preop OA group. TKA patients walked substantially faster than any previously reported series of knee arthroplasties. UKA patients walked 10% faster than TKA, although not as fast as the normal controls. Stride length was 5% greater and stance time 7% shorter following UKA — both much closer to normal than TKA. Unlike TKA, UKA enables a near normal gait one year after surgery.

Validation of an ear-worn sensor for gait monitoring using a force-plate instrumented treadmill

A force-plate instrumented treadmill (Hp Cosmos Gaitway) was used to validate the use of a miniaturised lightweight ear-worn sensor (7.4 g) for gait monitoring. Thirty-four healthy subjects were asked to progress up to their maximum walking speed on the treadmill (starting at 5 km/h, with 0.5 km increments). The sensor houses a 3D accelerometer which measures medio-lateral (ML), vertical (VT) and anterior–posterior (AP) acceleration. Maximum signal ranges and zero crossings were derived from accelerometer signals per axis, having corrected for head motion and signal noise. The maximal force, measured by the instrumented treadmill correlated best with a combination of VT and AP acceleration (R-squared = 0.36, p = 0), and combined VT, ML, and AP acceleration (R-squared = 0.36, p = 0). Weight-acceptance peak force and impulse values also correlated well with VT and AP acceleration (Weight acceptance: R-squared = 0.35, p = 0, Impulse: 0.26, p = 0), and combined VT, ML, and AP acceleration (Weight acceptance: R-squared = 0.35, p = 0, Impulse: 0.26, p = 0). Zero crossing features on the ML axis provided an accurate prediction of the gait-cycle, with a mean difference of 0.03 s (−0.01, 0.05 confidence intervals).

Gait comparison of unicompartmental and total knee arthroplasties with healthy controls

Aims To compare the gait of unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) patients with healthy controls, using a machine-learning approach. Patients and Methods 145 participants (121 healthy controls, 12 patients with cruciate-retaining TKA, and 12 with mobile-bearing medial UKA) were recruited. The TKA and UKA patients were a minimum of 12 months post-operative, and matched for pattern and severity of arthrosis, age, and body mass index. Participants walked on an instrumented treadmill until their maximum walking speed was reached. Temporospatial gait parameters, and vertical ground reaction force data, were captured at each speed. Oxford knee scores (OKS) were also collected. An ensemble of trees algorithm was used to analyse the data: 27 gait variables were used to train classification trees for each speed, with a binary output prediction of whether these variables were derived from a UKA or TKA patient. Healthy control gait data was then tested by the decision trees at each speed and a final classification (UKA or TKA) reached for each subject in a majority voting manner over all gait cycles and speeds. Top walking speed was also recorded. Results 92% of the healthy controls were classified by the decision tree as a UKA, 5% as a TKA, and 3% were unclassified. There was no significant difference in OKS between the UKA and TKA patients (p = 0.077). Top walking speed in TKA patients (1.6 m/s; 1.3 to 2.1) was significantly lower than that of both the UKA group (2.2 m/s; 1.8 to 2.7) and healthy controls (2.2 m/s; 1.5 to 2.7; p < 0.001). Conclusion UKA results in a more physiological gait compared with TKA, and a higher top walking speed. This difference in function was not detected by the OKS. Cite this article: Bone Joint J 2016;98-B(10 Suppl B):16–21.

Abnormal ground reaction forces lead to a general decline in gait speed in knee osteoarthritis patients

AIM To analyse ground reaction forces at higher speeds using another method to be more sensitive in assessing significant gait abnormalities. METHODS A total of 44 subjects, consisting of 24 knee osteoarthritis (OA) patients and 20 healthy controls were analysed. The knee OA patients were recruited from an orthopaedic clinic that were awaiting knee replacement. All subjects had their gait patterns during stance phase at top walking speed assessed on a validated treadmill instrumented with tandem force plates. Temporal measurements and ground reaction forces (GRFs) along with a novel impulse technique were collected for both limbs and a symmetry ratio was applied to all variables to assess inter-limb asymmetry. All continuous variables for each group were compared using a student t-test and χ2 analysis for categorical variables with significance set at α = 0.05. Receiver operator characteristics curves were utilised to determine best discriminating ability. RESULTS The knee OA patients were older (66 ± 7 years vs 53 ± 9 years, P = 0.01) and heavier (body mass index: 31 ± 6 vs 23 ± 7, P < 0.001) but had a similar gender ratio when compared to the control group. Knee OA patients were predictably slower at top walking speed (1.37 ± 0.23 m/s vs 2.00 ± 0.20 m/s, P < 0.0001) with shorter mean step length (79 ± 12 cm vs 99 ± 8 cm, P < 0.0001) and broader gait width (14 ± 5 cm vs 11 ± 3 cm, P = 0.015) than controls without any known lower-limb joint disease. At a matched mean speed (1.37 ± 0.23 vs 1.34 ± 0.07), ground reaction results revealed that push-off forces and impulse were significantly (P < 0.0001) worse (18% and 12% respectively) for the knee OA patients when compared to the controls. Receiver operating characteristic curves analysis demonstrated total impulse to be the best discriminator of asymmetry, with an area under the curve of 0.902, with a cut-off of -3% and a specificity of 95% and sensitivity of 88%. CONCLUSION Abnormal GRFs in knee osteoarthritis are clearly evident at higher speeds. Analysing GRFs with another method may explain the general decline in knee OA patient’s gait.

Use of ketamine sedation for the management of displaced paediatric forearm fractures

AIM To determine if ketamine sedation is a safe and cost effective way of treating displaced paediatric radial and ulna fractures in the emergency department. METHODS Following an agreed interdepartmental protocol, fractures of the radius and ulna (moderately to severely displaced) in children between the age of 2 and 16 years old, presenting within a specified 4 mo period, were manipulated in our paediatric emergency department. Verbal and written consent was obtained prior to procedural sedation to ensure parents were informed and satisfied to have ketamine. A single attempt at manipulation was performed. Pre and post manipulation radiographs were requested and assessed to ensure adequacy of reduction. Parental satisfaction surveys were collected after the procedure to assess the perceived quality of treatment. After closed reduction and cast immobilisation, patients were then followed-up in the paediatric outpatient fracture clinic and functional outcomes measured prospectively. A cost analysis compared to more formal manipulation under a general anaesthetic was also undertaken. RESULTS During the 4 mo period of study, 10 closed, moderate to severely displaced fractures were identified and treated in the paediatric emergency department using our ketamine sedation protocol. These included fractures of the growth plate (3), fractures of both radius and ulna (6) and a single isolated proximal radius fracture. The mean time from administration of ketamine until completion of the moulded plaster was 20 min. The mean time interval from sedation to full recovery was 74 min. We had no cases of unacceptable fracture reduction and no patients required any further manipulation, either in fracture clinic or under a more formal general anaesthetic. There were no serious adverse events in relation to the use of ketamine. Parents, patients and clinicians reported extremely favourable outcomes using this technique. Furthermore, compared to using a manipulation under general anaesthesia, each case performed under ketamine sedation was associated with a saving of £1470, the overall study saving being £14700. CONCLUSION Ketamine procedural sedation in the paediatric population is a safe and cost effective method for the treatment of displaced fractures of the radius and ulna, with high parent satisfaction rates.

Patient-specific guides improve hip arthroplasty surgical accuracy

Abstract The role of patient-specific (PS) technology in total hip arthroplasty remains relatively unexplored. We asked whether PS guides: (1) Reduced average surgical errors? (2) Reduced outlier error frequencies? (3) Could predict the size of implants used? A single surgeon implanted femurs using either standard or PS guides and was blinded to the pre-operative plans. There were significant differences in median leg length errors between standard (3.3 mm) and PS groups (1.4 mm), U = 110, z = –2.3, p = 0.02. In contrast to the PS group, the standard group had significantly more outlier errors and frequently undersized implants. PS guides improve hip arthroplasty surgical accuracy.Abbreviations: PS: patient specific; THA: total hip arthroplasty; LLD: leg length discrepancies; HRA: hip resurfacing arthroplasty

Letter to the Editor regarding ‘How symmetric are metal-on-metal hip resurfacing patients during gait? Insights for the rehabilitation’

http://dx.doi.org/10.1016/j.jbiomech.2017.07.037 0021-9290/ 2017 Elsevier Ltd. All rights reserved. We read with great interest the article written by Resende and colleagues (Resende et al., 2017) entitled, ‘How symmetric are metal-on-metal hip resurfacing patients during gait? Insights for the rehabilitation’ Hip resurfacing arthroplasty (HRA) is a contentious subject given the high profile withdrawal of the DePuy Orthopaedic ASR metal-on-metal (MoM) implant (DePuy-ASR) due to high failure rates (de Steiger et al., 2011; Prosser et al., 2010). In their welldesigned kinematic study (Resende et al., 2017), the authors assessed whether a unilateral DePuy ASR HRA can result in symmetric gait. We applaud such a study, which aims to take assessment beyond functional scores, which have many well-documented limitations (Fitzpatrick et al., 1998). Despite analysing a withdrawn implant, the study demonstrates that all 12 ASR HRA patients having reported no pain. This is particularly reassuring as the mean time from surgery to gait assessment was 45 months, which puts this group of patients at the highest risk as most revisions occur in the early mid-term (Curtin et al., 2017; Laaksonen et al., 2017). Sadly, though, there was no mention of serum metal ions. It is well reported that raised serum metal ions are correlated to adverse local tissue reactions (ALTRs) (Laaksonen et al., 2017; Reito et al., 2013), which would negatively alter hip biomechanics. The prevalence of ALTRs in asymptomatic patients is also high (Chang et al., 2012; WynnJones et al., 2011). Moreover, the research looked at lower limb kinematic function and there is no evidence that these patients had any further imaging (ultrasound or MARS MRI) to ensure that there was not any surrounding soft tissue destruction. These omissions, which are now standard recommendations (MHRA, 2017), make it difficult to conclude as to whether these were well functioning or failing hips. Furthermore the authors present what appears to be a retrospective study as no preoperative data was presented. It is important to have baseline data in order to appreciate the effect of the intervention, which could be significantly worse or better. A single snapshot study, particularly with small numbers, could easily draw incorrect conclusions. Given this, the title of this paper would be better changed to ‘How symmetric are ASR hip resurfacing patients during gait’. Instead, the current title of the study would be better addressed by prospectively evaluating a HRA implant with a proven track record to answer the important question of whether HRA results in symmetric gait, and to give insight for rehabilitation. Conflict of interest