Objectives. We performed in vitro validation of a non-invasive skin-mounted system that could allow quantification of anteroposterior (AP) laxity in the outpatient setting. Methods. A total of 12 cadaveric lower limbs were tested with a commercial image-free navigation system using trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° of knee flexion and 100 N of force was applied perpendicular to the tibia. Acceptable coefficient of repeatability (CR) and limits of agreement (LOA) of 3 mm were set based on diagnostic criteria for anterior cruciate ligament (ACL) insufficiency. Results. Reliability and precision within the individual invasive and non-invasive systems was acceptable throughout the range of flexion tested (intra-class correlation coefficient 0.88, CR 1.6 mm). Agreement between the two systems was acceptable measuring AP laxity between full extension and 40° knee flexion (LOA 2.9 mm). Beyond 40° of flexion, agreement between the systems was unacceptable (LOA > 3 mm). Conclusions. These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard validated commercial system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative evaluation of ACL pathology. Cite this article: Bone Joint Res 2013;2:233–7

In skeletally immature patients, resection of bone tumours and reconstruction of the lower limb often results in leg-length discrepancy. The Stanmore non-invasive extendible endoprosthesis, which uses electromagnetic induction, allows post-operative lengthening without anaesthesia. Between 2002 and 2009, 55 children with a mean age of 11.4 years (5 to 16) underwent reconstruction with this prosthesis; ten patients (18.2%) died of disseminated disease and one child underwent amputation due to infection. We reviewed 44 patients after a mean follow-up of 41.2 months (22 to 104). The mean Musculoskeletal Tumor Society score was 24.7 (8 to 30) and the Toronto Extremity Salvage score was 92.3% (55.2% to 99.0%). There was no local recurrence of tumour. Complications developed in 16 patients (29.1%) and ten (18.2%) underwent revision. The mean length gained per patient was 38.6 mm (3.5 to 161.5), requiring a mean of 11.3 extensions (1 to 40), and ten component exchanges were performed in nine patients (16.4%) after attaining the maximum lengthening capacity of the implant. There were 11 patients (20%) who were skeletally mature at follow-up, ten of whom had equal leg lengths and nine had a full range of movement of the hip and knee. This is the largest reported series using non-invasive extendible endoprostheses after excision of primary bone tumours in skeletally immature patients. The technique produces a good functional outcome, with prevention of limb-length discrepancy at skeletal maturity

Aims. The aim of this study was to describe, analyze, and compare the survival, functional outcome, and complications of minimally invasive (MI) and non-invasive (NI) lengthening total femoral prostheses. Patients and Methods. A total of 24 lengthening total femoral prostheses, 11 MI and 13 NI, were implanted between 1991 and 2016. The characteristics, complications, and functional results were recorded. There were ten female patients and ten male patients. Their mean age at the time of surgery was 11 years (2 to 41). The mean follow-up was 13.2 years (seven months to 29.25 years). A survival analysis was performed, and the failures were classified according to the Modified Henderson System. Results. The overall implant survival was 79% at five, ten, and 20 years for MI prostheses, and 84% at five years and 70% at ten years for NI prostheses. At the final follow-up, 13 prostheses did not require further surgery. The overall complication rate was 46%. The mean revision-free implant survival for MI and NI prostheses was 59 months and 49 months, respectively. There were no statistically significant differences in the overall implant survival, revision-free survival, or the distribution of complications between the two types of prosthesis. Infection rates were also comparable in the groups (9% vs 7%; p = 0.902). The rate of leg-length discrepancy was 54% in MI prostheses and 23% in NI prostheses. In those with a MI prosthesis, there was a smaller mean range of movement of the knee (0° to 62° vs 0° to 83°; p = 0.047), the flexion contracture took a longer mean time to resolve after lengthening (3.3 months vs 1.07 months; p < 0.001) and there was a lower mean Musculoskeletal Tumor Society (MSTS) score (24.7 vs 27; p = 0.295). Conclusion. The survival and complications of MI and NI lengthening total femoral prostheses are comparable. However, patients with NI prosthesis have more accurate correction of leg-length discrepancy, a better range of movement of the knee and an improved overall function

Background. Non-invasive hemoglobin measurement was introduced to potentially eliminate blood draws postoperatively. We compared the accuracy and effectiveness of a non-invasive hemoglobin measurement system with a traditional blood draw in patients undergoing total joint arthroplasty. Methods. After IRB approval, 100 consecutive patients undergoing primary total hip or knee arthroplasty had their hemoglobin level tested by both traditional blood draw and a non-invasive hemoglobin monitoring system. Results were analyzed for the entire group, further stratifying patients based on gender, race, surgery (THA versus TKA), and post-operative hemoglobin level. Finally, we compared financial implications and patient satisfaction with the device. Paired t-test with 0.05 conferring significance was used. Stratified analyses of the absolute difference between the two measures were assessed using Mann- Whitney test. To assess the level of agreement between the two measures, the concordance correlation coefficient (CCC) was calculated. Results. Mean blood-draw hemoglobin value on POD1 was 11.063 ± 1.39 g/dL and 11.192 ± 1.333 g/dL with the non-invasive device. For all patients, the mean absolute difference between the two methods was 0.13 g/dL (p = 0.30). The CCC between the two methods was 0.58, conferring a moderate to strongly positive linear relationship (Figure 1). Non-invasive measurement was preferred by 100% of patients with a mean VAS score of 0/10. Additionally, the cost savings with the non-invasive system was $16.50 per patient. Discussion. Overall, there was no significant difference between the hemoglobin level obtained by traditional laboratory methods versus the Masimo Radical-7 system on post-operative day #1 in patients who underwent total joint arthroplasty. In the minority of patients (19%) who had a hemoglobin level of less than 10 g/dL, the difference between the two methods was statistically significant. Additionally, 100% of patients preferred the Masimo device to a traditional blood draw and the Masimo device was substantially cheaper. While further investigation of non-invasive hemoglobin monitoring systems is necessary, particularly in patients with a post-operative hemoglobin of less than 10 g/dL, our study shows that the Masimo Radical-7 device provides an accurate, preferable, and less expensive alternative to a traditional blood draw after total joint replacement. Conclusion. Overall, the non-invasive hemoglobin monitoring system offered a similar hemoglobin reading to the standard lab-draw reading, while improving satisfaction and lowering cost. The system relies on adequate perfusion for measurement, and our study demonstrated that lower hemoglobin values may reduce finger-tip perfusion and affect the hemoglobin reading

INTRODUCTION. Navigation systems have proved allowing performing measurement of the lower limb axis with a good accuracy, but the mandatory use of reference pins or screws limit their use to the operating room. The use of non-invasive navigation systems has been suggested to overcome this limitation. We conducted a prospective study to assess the validity of such a measurement system with non-invasive fixation of the reference arrays. The main goal was to compare this method with a standard, invasive navigation system requiring bony fixation of the arrays. The following hypothesis was tested: there will be a significant difference between the simultaneous measurement of the mechanical femoro-tibial angle by a standard navigation system and by the non-invasive navigation system. MATERIAL AND METHODS. 20 patients scheduled for total or partial knee arthroplasty were included after giving their informed consent. There were 7 men and 13 women with a median age of 65 years (range, 55 to 90). The median coronal deformation measured by X-rays was 8° of varus (range, 5° valgus to 22 ° varus). The same navigation system was used for both invasive and non-invasive measurements, but the basic algorithms were adapted for the non-invasive technique. For the non-invasive technique, metallic plates were strapped on the thigh and the calf to allow arrays fixation (fig. 1). Coronal femoro-tibial mechanical angle (CMFA) in maximal extension without stress was recorded by the non invasive system. This non-invasive analysis was immediately followed by surgery, and the same angle was measured intra-operatively with the invasive system. Comparisons between non-invasive and invasive measurements were performed using a Wilcoxon test, after checking that their distribution followed a normal distribution, and an equivalence testing with limits of ±3°. The correlation between the two sets of measurements was analyzed using a correlation test Spearman rank. The analysis of the concordance of the two sets of measurements was performed using Bland and Altman tests. The significance level p was set at 0.05. RESULTS. There was no significant difference between non invasive and invasive measurements of the CMFA in full extension. There was a good correlation (fig. 2) and a good concordance (fig. 3) between both measurements. DISCUSSION. The non invasive measurement technique system seems to be as accurate as conventional, invasive navigation. CONCLUSION. This technique might be a valuable alternative to long leg x-rays, with a good accuracy but without radiation exposure. For any figures or tables, please contact the authors directly

We describe the application of a non-invasive extendible endoprosthetic replacement in skeletally-mature patients undergoing revision for failed joint replacement with resultant limb-length inequality after malignant or non-malignant disease. This prosthesis was developed for tumour surgery in skeletally-immature patients but has now been adapted for use in revision procedures to reconstruct the joint or facilitate an arthrodesis, replace bony defects and allow limb length to be restored gradually in the post-operative period. We record the short-term results in nine patients who have had this procedure after multiple previous reconstructive operations. In six, the initial reconstruction had been performed with either allograft or endoprosthetic replacement for neoplastic disease and in three for non-neoplastic disease. The essential components of the prosthesis are a magnetic disc, a gearbox and a drive screw which allows painless lengthening of the prosthesis using the principle of electromagnetic induction. The mean age of the patients was 37 years (18 to 68) with a mean follow-up of 34 months (12 to 62). They had previously undergone a mean of six (2 to 14) open procedures on the affected limb before revision with the non-invasive extendible endoprosthesis. The mean length gained was 56 mm (19 to 107) requiring a mean of nine (3 to 20) lengthening episodes performed in the outpatient department. There was one case of recurrent infection after revision of a previously infected implant and one fracture of the prosthesis after a fall. No amputations were performed. Planned exchange of the prosthesis was required in three patients after attainment of the maximum lengthening capacity of the implant. There was no failure of the lengthening mechanism. The Mean Musculoskeletal Tumour Society rating score was 22 of 30 available points (18 to 28). The use of a non-invasive extendible endoprosthesis in this manner provided patients with good functional results and restoration of leg-length equality, without the need for multiple open lengthening procedures

Introduction: The use of extendible endoprosthetic implants in the skeletally immature has been used for just under 30 years. Limb salvage has become a realistic alternative to those children presenting with primary bone sarcomas. We aim to review the use of an implant which uses a non-invasive mechanism of adjusting the length of the prosthesis, during the growth phase. Method: A retrospective review of consecutive patients undergoing primary or revision endoprosthetic replacement with non-invasive extensible implants, was undertaken. Between January 1993 and February 2008, 34 children were treated with non-invasive extensible endoprosthetic replacements, 26 distal femur, 5 total femurs, 3 proximal tibias and 1 proximal femur. Results: The underlying pathology, requiring excision, was Ewings sarcoma in 4 patients and osteosarcoma in the remaining 30 patients. Most underwent pre-operative chemotherapy and 2 patients died of their disease. Four operations were secondary procedures following previous non-grower implant failures (1 infection of previous EPR, 1 IM nail non-union, 1 failed allograft and a revision of a proximal femoral EPR to a total femoral prosthesis). Five patients required revision of the primary prosthesis (2 with motor failures, 3 due to prosthesis infections). Mean time to start lengthening from surgery was 12.2 months. The mean number of lengthenings was 4 with an average total length of 30 mm achieved, mean leg length difference was 0.8 cm. All lengthenings were undertaken with the patient fully alert, no adverse incidents occurred at the time or after lengthening. Discussion: The non-invasive prostheses show promise in handling the difficult problem of limb preservation in a growing child, with similar complication rates to that of an invasive type, but without the need for multiple anaesthetics for lengthening

We reviewed our initial seven-year experience with a non-invasive extendible prosthesis in 34 children with primary bone tumours. The distal femur was replaced in 25 cases, total femur in five, proximal femur in one and proximal tibia in three. The mean follow-up was 44 months (15 to 86) and 27 patients (79%) remain alive. The prostheses were lengthened by an electromagnetic induction mechanism in an outpatient setting and a mean extension of 32 mm (4 to 80) was achieved without anaesthesia. There were lengthening complications in two children: failed lengthening in one and the formation of scar tissue in the other. Deep infection developed in six patients (18%) and local recurrence in three. A total of 11 patients required further surgery to the leg. Amputation was necessary in five patients (20%) and a two-stage revision in another. There were no cases of loosening, but two patients had implant breakage and required revision. The mean Musculoskeletal Tumor Society functional score was 85% (60% to 100%) at last known follow-up. These early results demonstrate that the non-invasive extendible prosthesis allows successful lengthening without surgical intervention, but the high incidence of infection is a cause for concern

Conventional computer navigation systems using bone fixation have been validated in measuring anteroposterior (AP) translation of the tibia. Recent developments in non-invasive skin-mounted systems may allow quantification of AP laxity in the out-patient setting. We tested cadaveric lower limbs (n=12) with a commercial image free navigation system using passive trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° knee flexion and 100N of force applied perpendicular to the tibial tuberosity using a secured dynamometer. Repeatability coefficient was calculated both to reflect precision within each system, and demonstrate agreement between the two systems at each flexion interval. An acceptable repeatability coefficient of ≤3 mm was set based on diagnostic criteria for ACL insufficiency when using other mechanical devices to measure AP tibial translation. Precision within the individual invasive and non-invasive systems measuring AP translation of the tibia was acceptable throughout the range of flexion tested (repeatability coefficient ≤1.6 mm). Agreement between the two systems was acceptable when measuring AP laxity between full extension and 40° knee flexion (repeatability coefficient ≤2.1 mm). Beyond 40° of flexion, agreement between the systems was unacceptable (repeatability coefficient >3 mm). These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard invasive system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative follow-up of ACL pathology

Conventional computer navigation systems using bone fixation have been validated in measuring anteroposterior (AP) translation of the tibia. Recent developments in non-invasive skin-mounted systems may allow quantification of AP laxity in the out-patient setting. We tested cadaveric lower limbs (n=12) with a commercial image free navigation system using passive trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° knee flexion and 100N of force applied perpendicular to the tibial tuberosity using a secured dynamometer. Repeatability coefficient was calculated both to reflect precision within each system, and demonstrate agreement between the two systems at each flexion interval. An acceptable repeatability coefficient of ≤3mm was set based on diagnostic criteria for ACL insufficiency when using other mechanical devices to measure AP tibial translation. Precision within the individual invasive and non-invasive systems measuring AP translation of the tibia was acceptable throughout the range of flexion tested (repeatability coefficient ≤1.6mm). Agreement between the two systems was acceptable when measuring AP laxity between full extension and 40° knee flexion (repeatability coefficient ≤2.1mm). Beyond 40° of flexion, agreement between the systems was unacceptable (repeatability coefficient >3mm). These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard invasive system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative follow-up of ACL pathology

Conventional computer navigation systems using bone fixation have been validated in measuring anteroposterior (AP) translation of the tibia. Recent developments in non-invasive skin-mounted systems may allow quantification of AP laxity in the out-patient setting. We tested cadaveric lower limbs (n=12) with a commercial image free navigation system using passive trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° knee flexion and 100N of force applied perpendicular to the tibial tuberosity using a secured dynamometer. Repeatability coefficient was calculated both to reflect precision within each system, and demonstrate agreement between the two systems at each flexion interval. An acceptable repeatability coefficient of ≤3mm was set based on diagnostic criteria for ACL insufficiency when using other mechanical devices to measure AP tibial translation. Precision within the individual invasive and non-invasive systems measuring AP translation of the tibia was acceptable throughout the range of flexion tested (repeatability coefficient ≤1.6 mm). Agreement between the two systems was acceptable when measuring AP laxity between full extension and 40° knee flexion (repeatability coefficient ≤2.1 mm). Beyond 40° of flexion, agreement between the systems was unacceptable (repeatability coefficient >3 mm). These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard invasive system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative follow-up of ACL pathology

The knee joint displays a wide spectrum of laxity, from inherently tight to excessively lax even within the normal, uninjured population. The assessment of AP knee laxity in the clinical setting is performed by manual passive tests such as the Lachman test. Non-invasive assessment based on image free navigation has been clinically validated and used to quantify mechanical alignment and coronal knee laxity in early flexion. When used on cadavers the system demonstrated good AP laxity results with flexion up to 40°. This study aimed to validate the repeatability of the assessment of antero-posterior (AP) knee joint laxity using a non-invasive image free navigation system in normal, healthy subjects. Twenty-five healthy volunteers were recruited and examined in a single centre. AP translation was measured using a non-invasive navigation system (PhysioPilot) consisting of an infrared camera, externally mounted optical trackers and computer software. Each of the volunteers had both legs examined by a single examiner twice (two registrations). The Lachman test was performed through flexion in increments of 15°. Coefficients of Repeatability (CR) and Interclass Correlation Coefficients (ICC) were used to validate AP translation. The acceptable limits of agreement for this project were set at 3mm for antero-posterior tibial translation. The most reliable and repeatable AP translation assessments were at 30° and 45°, demonstrating good reliability (ICC 0.82, 0.82) and good repeatability (CR 2.5, 2.9). The AP translation assessment at 0°, 15°, 75° and 90° demonstrated moderate reliability (ICC ≤ 0.75), and poor repeatability (CR ≥3.0mm). The non-invasive system was able to reliably and consistently measure AP knee translation between 30° and 45° flexion, the clinically relevant range for this assessment. This system could therefore be used to quantify abnormal knee laxity and improve the assessment of knee instability and ligamentous injuries in a clinic setting

This prospective clinical study investigates the relationship between intra-compartmental pressure and soft tissue oxygenation (StO2) measured non-invasively by near-infrared spectroscopy (NIRS) in patients at risk of acute compartment syndrome. Patients (over 13 years) with fractures of the tibial diaphysis or high-energy fractures of the forearm or distal radius, or patients with soft tissue injury were recruited. Non-invasive and invasive monitoring was carried out pre and post operatively. The ‘Delta P’ value (DP) was calculated as the compartment pressure subtracted from the diastolic blood pressure. The threshold for fasciotomy was a DP < 30mmHg. Non-invasive tissue saturation measurements and pressure measurements were taken from the same compartment (anterior tibial or volar forearm). StO2 values were simultaneously recorded from the contralateral (uninjured) limb at the same anatomical site. All patients had the difference between the StO2 value on the injured and uninjured sides calculated (‘StO2 difference’). 42 patients with tibial diaphyseal fractures, 2 patients with forearm fractures and one case with thigh swelling were recruited to the study. The mean age was 40 years (SD 17 years). 11 patients underwent a four-compartment lower leg fasciotomy determined by a DP < 30mmHg. Patients who required a fasciotomy had an ‘StO2 difference’ that was 20% lower (p = 0. 002) compared to those who did not develop acute compartment syndrome. This suggests that patients who require a fasciotomy have reduced StO2 values on their injured legs compared to the contralateral (uninjured) side. We have observed that non-invasive StO2 measurements for patients over 13 years at risk of acute compartment syndrome, correlates with the requirement for a fasciotomy as defined by P < 30mmHg. We are optimistic that near-infrared spectroscopy (NIRS) will be a reliable new non-invasive technique for detection of an acute compartment syndrome

Computer-assisted technology has provided surgeons with intra-operative quantitative measurement tools that have led to the development of soft-tissue balancing algorithms based on surgeon-applied varus-valgus stress. Unfortunately these forces tend not to be standardised and the resultant algorithms may at best be surgeon-specific. Furthermore, these techniques are only available intra-operatively and rely on the rigid fixation of trackers to bone. The aim of this study was to develop a non-invasive computer-assisted measurement technique and assess the variation in collateral knee laxity measurements between different clinicians. An image-free navigation system was adapted for non-invasive use by developing external mountings for active infrared trackers. A leg model with rigid tracker mountings was designed and manufactured for comparison. Multiple kinematic registrations of alignment were made for both the model and the right leg of a volunteer to quantify the soft tissue artefacts. Repeatability of the system was assessed by performing two registration processes on eight volunteers. Collateral knee laxity was assessed on a single volunteer by 16 participants of varying experience each applying a maximum varus and valgus knee stress. Two surgeons performed repeated examinations to assess intra-observer variation. For repeated registrations of alignment, the SD of the non-invasive mounting (0.8°) was only a third higher than the leg model (0.6°) and the actual range was only 1° larger. The repeated alignment measurements on the volunteers showed a high level of agreement with an intraclass correlation coefficient of 0.93. Varus-valgus stress values showed poor inter-observer variation with a wide range of angles for both varus (1° to 7°) and valgus stress (0.5° to 5°). A Mann-Whitney test between the two sets of repeated tests showed that both varus stress and overall laxity were significantly different (p< 0.0001) but that valgus stress was marginal (p=0.052). Intra-observer measurements overall appeared more consistent. Soft tissue artefacts did not significantly reduce the repeatability of the assessment of coronal knee alignment using a navigation system and this provided a non-invasive technique for assessing coronal knee laxity. The perception of an ‘end-point’ varied significantly between different clinicians and although there may be a role for surgeon-specific algorithms, to use this quantitative data more widely there is a need to standardise the forces and moments applied

Purpose of the study: The issue of patellar kinematics remains a difficult problem for patellar resurfacing during conventional or computer-assisted knee surgery, yet adequate knowledge is required for appropriate orientation of the patellar cut and insert positioning. The purpose of this study was to develop a non-invasive tool for in vivo kinematic analysis of the patellar tract and to compare results with the gold-standard invasive method. Material and methods: A special experimental set-up designed for this study enabled experimental simulation of load-bearing flexion-extension cycles of the knee joint. Range of motion from 0 to 102° was imposed with a computer-controlled motor. The analysis was conduced on 14 complete lower limb cadaver specimens. Patellar kinematics was analyzed for each knee simultaneously with two systems: a non-invasive method using a low-dose stereoradiographic scan linked to a 3D reconstruction software; and the reference system using tripodes implanted on the patella and radio-opaque spherical markers. Six degrees of freedom were considered: three translations and three rotations. Sequential kinematic recordings were made by calculating the position of a patellar landmark in relation to a femoral landmark. Results: The mean difference between the results obtained with the two systems was less than 1 mm for anteroposterior and vertical translations, greater for mediolateral translations. It was less than 2° for patellar flexion-extension, to the order of the motion itself for abduction-adduction, and to the order of 5° for horizontal tilt. Discussion and conclusion: The non-invasive technique proposed here appears to be reliable for patellar translations and flexion, but need further improvement for tilt and adduction-abduction. This is particularly true for the 45° to 90° range of motion because of the difficult problem of determining the contours of the patella. Further developments for this tool are under way

Introduction. Following bone tumour resection, lower limb reconstruction results in leg-length discrepancy in skeletally immature patients. Previously, minimally invasive endoprostheses have been associated with a high risk of complications including joint stiffness, nerve injury, aseptic loosening and infection. The purpose of this study was to examine the outcome of the Stanmore non-invasive extendible endoprostheses used in our institution between 2002 and 2009 and compare them with implants used in the past. Methods. Fifty-five children with a mean age of 11.4 years (5 to 16) underwent limb reconstruction with thirty-three distal femoral, two total femoral, eight proximal femoral and twelve proximal tibial implants. Forty-six endoprostheses were lengthened in clinic without anaesthesia using the principle of electromagnetic induction. Patients were assessed using the Musculoskeletal Tumour Society Score (MSTS) and the Toronto Extremity Salvage Score (TESS). Results. Ten children (18.2%) died of disseminated disease. One child underwent amputation for infected prosthesis. Forty-four patients were reviewed after a mean follow-up of 41 months (16 to 98). The mean MSTS score was 80.7% (26.7-100) and the TESS score was 92.3% (55.2-99). There was no local tumour recurrence. Complications developed in sixteen patients (29.1%). Seven patients (12.7%) underwent ten revision procedures. The mean length gained per patient was 38.6mm (3.5 to 161.5) requiring a mean of 11.3 (1-40) extensions. Ten component exchanges were performed in nine patients (16.4%) after attaining the maximum lengthening capacity of the implant. Eleven patients (20%) were skeletally mature at follow-up, of which ten had equal leg-lengths and nine had full range of hip and knee movement. Overall our outcomes compared favourably with minimal endoprostheses and other non-invasive designs. Discussion. This is the largest reported series of non-invasive extendible endoprostheses, demonstrating good functional outcome with prevention of limb-length discrepancy at skeletal maturity

The detection and treatment of acute compartment syndrome following trauma is critical if contractures, delayed fracture healing and possible amputations are to be avoided. The current standard for monitoring relies on invasive compartment pressure measurements. These require an additional procedure and cause discomfort to the patient. This prospective clinical study investigates the relationship between the intra-compartmental pressure and soft tissue oxygenation (%StO. 2. ) measured non-invasively by near-infrared spectroscopy (NIRS) in patients at risk of acute compartment syndrome. Adults with acute tibial or radial diaphyseal fractures were recruited on admission to the orthopaedic trauma unit. Non-invasive and invasive monitoring over anterior tibial or volar forearm compartments was carried out from admission and continued post-operatively. The differential pressure (ΔDP) was calculated as the compartment pressure subtracted from the diastolic blood pressure. The threshold for fasciotomy was a ΔDP < 30mmHg. StO. 2. values were simultaneously recorded from the contralateral (uninjured) limb at the same site. All patients had the difference between the StO. 2. value on the injured and uninjured sides calculated (‘StO. 2. difference’). Sixty patients with tibial fractures and 5 patients with forearm fractures were recruited. The mean age was 39 years (S.D.18 years). Fourteen patients underwent a four-compartment lower leg fasciotomy determined by a ΔDP < 30mmHg. We have observed that the difference in StO. 2. between limbs (measured non-invasively) was significantly lower in patients undergoing a fasciotomy. This suggests that NIRS is able to detect a change in oxygenation of the soft tissues in trauma patients developing an acute compartment syndrome. We are optimistic that near-infrared spectroscopy (NIRS) will be a reliable new non-invasive technique for detection of an acute compartment syndrome

We undertook a trial on 60 patients with AO 31A2 fractures of the hip who were randomised after stabilisation of the fracture into two equal groups, one of which received post-operative treatment using a non-invasive interactive neurostimulation device and the other with a sham device. All other aspects of their rehabilitation were the same. The treatment was continued for ten days after operation. Outcome measurements included the use of a visual analogue scale for pain, the brief pain inventory and Ketorolac for post-operative control of pain, and an overall assessment of outcome by the surgeon. There were significantly better results for the patients receiving treatment by active electrical stimulation (repeated measures analysis of variance, p < 0.001). The findings of this pilot trial justify a larger study to determine if these results are more generally applicable

We report our early experience with the use of a non-invasive distal femoral expandable endoprosthesis in seven skeletally immature patients with osteosarcoma of the distal femur. The patients had a mean age of 12.1 years (9 to 15) at the time of surgery. The prosthesis was lengthened at appropriate intervals in outpatient clinics, without anaesthesia, using the principle of electromagnetic induction. The patients were functionally evaluated using the Musculoskeletal Tumour Society scoring system. The mean follow-up was 20.2 months (14 to 30). The prostheses were lengthened by a mean of 25 mm (4.25 to 55) and maintained a mean knee flexion of 110° (100° to 120°). The mean Musculoskeletal Tumour Society score was 68% (11 to 29). Complications developed in two patients; one developed a flexion deformity of 25° at the knee joint, which was subsequently overcome and one died of disseminated disease. The early results from patients treated with this device have been encouraging. The implant avoids multiple surgical procedures, general anaesthesia and assists in maintaining leg-length equality

Introduction: Non-invasive expandable prostheses for limb salvage tumour surgery was first used in 2002 and has now been implanted in a series of 40 skeletally immature patients. Method: Our review of these includes 24 distal femoral replacements, 5 proximal femoral replacements, 3 total femoral replacements and 8 proximal tibial replacements. These were used to treat 31 osteosarcomas, 7 Ewing’s sarcomas, 1 chondrosarcoma and 1 aneurysmal bone cyst. Patients had a mean age of 11.7 years (7–16). Follow-up extended to 88 months with a mean of 26.3 months. Results: There has been 1 failure of the prosthesis gearbox which required revision surgery. 4 of the prostheses reached their maximum length and were successfully re-operated to exchange components of the prosthesis and resume lengthening. 3 patients had disseminated meta-static disease (1 being present before primary surgery) and another developed infection of the prosthesis that required an above-knee amputation. There have been 233 lengthenings overall with 1 patient requiring reversal on one occasion due to intractable pain; this pain rescinded 30 minutes after lengthening was reduced by 10mm. Otherwise lengthening was well tolerated despite the significant growth of the limbs: mean 21.2mm (0.5–84mm). At latest follow-up the mean Musculoskeletal Tumour Society score was 75% (26–93%). Discussion: The results achieved are equivalent to our series of minimally invasive growers which require repeated surgery. Our non-invasive growing prostheses remain reliable and negate the need for recurrent operations, thus resulting in low infection rates. Our results remain encouraging up to 7 years after first use, maintaining leg-length equality and function