The December 2013 Oncology Roundup³⁶⁰ looks at: Peri-articular resection fraught with complications; Navigated margins; Skeletal tumours and thromboembolism; Conditional survival in Ewing’s sarcoma; Reverse shoulders and tumour; For how long should we follow up sarcoma patients?; and already metastasised?

Excision of a physeal bar and filling the space with interposition material may allow resumption of normal growth. Both the extent and the location of the bar and the amount of growth remaining from physis must be determined. Computer-assisted surgery is being used increasingly in various fields of orthopaedics. We describe the management of a patient with premature physeal arrest of the right distal tibia in which resection of a physeal bar was achieved under real-time three-dimensional intra-operative monitoring by computer-assisted navigation.

The advantage of this method over other means of imaging is that intra-operative identification can increase the accuracy of resection of the bar.

The use of robotics in arthroplasty surgery is expanding rapidly as improvements in the technology evolve. This article examines current evidence to justify the usage of robotics, as well as the future potential in this emerging field.

The aim of this pilot study was to evaluate the accuracy of two different methods of navigated retrograde drilling of talar lesions. Artificial osteochondral talar lesions were created in 14 cadaver lower limbs. Two methods of navigated drilling were evaluated by one examiner. Navigated Iso-C^3D was used in seven cadavers and 2D fluoroscopy-based navigation in the remaining seven. Of 14 talar lesions, 12 were successfully targeted by navigated drilling. In both cases of inaccurate targeting the 2D fluoroscopy-based navigation was used, missing lesions by 3 mm and 5 mm, respectively. The mean radiation time was increased using Iso-C^3D navigation (23 s; 22 to 24) compared with 2D fluoroscopy-based navigation (14 s, 11 to 17).

We have investigated the benefits of patient specific instrument guides, applied to osteotomies around the knee. Single, dual and triple planar osteotomies were performed on tibias or femurs in 14 subjects. In all patients, a detailed pre-operative plan was prepared based upon full leg standing radiographic and CT scan information. The planned level of the osteotomy and open wedge resection was relayed to the surgery by virtue of a patient specific guide developed from the images. The mean deviation between the planned wedge angle and the executed wedge angle was 0° (-1 to 1, sd 0.71) in the coronal plane and 0.3° (-0.9 to 3, sd 1.14) in the sagittal plane. The mean deviation between the planned hip, knee, ankle angle (HKA) on full leg standing radiograph and the post-operative HKA was 0.3° (-1 to 2, sd 0.75). It is concluded that this is a feasible and valuable concept from the standpoint of pre-operative software based planning, surgical application and geometrical accuracy of outcome.

Cite this article: Bone Joint J 2013;95-B, Supple A:153–8.

The June 2015 Knee Roundup360 looks at: Cruciate substituting versus retaining knee replacement; What’s behind the psychology of anterior cruciate ligament (ACL) reconstruction?; Is there a difference in total knee arthroplasty risk of revision in highly crosslinked versus conventional polyethylene?; Unicompartmental knee arthroplasty: is age the missing variable?; Satisfaction rates following total knee arthroplasty; Is knee alignment dynamic?; Unicompartmental knee arthroplasty: cemented or cementless?; Can revision knee services pay?

We have evaluated in vitro the accuracy of percutaneous and ultrasound registration as measured in terms of errors in rotation and version relative to the bony anterior pelvic plane in computer-assisted total hip replacement, and analysed the intra- and inter-observer reliability of manual or ultrasound registration.

Four clinicians were asked to perform registration of the landmarks of the anterior pelvic plane on two cadavers. Registration was performed under four different conditions of acquisition. Errors in rotation were not significant. Version errors were significant with percutaneous methods (16.2°; p < 0.001 and 19.25° with surgical draping; p < 0.001), but not with the ultrasound acquisition (6.2°, p = 0.13). Intra-observer repeatability was achieved for all the methods. Inter-observer analysis showed acceptable agreement in the sagittal but not in the frontal plane.

Ultrasound acquisition of the anterior pelvic plane was more reliable in vitro than the cutaneous digitisation currently used.

The April 2015 Research Roundup360 looks at: MCID in grip strength and distal radial fracture; Experiencing rehab in a trial setting; Electrical stimulation and nerve recovery; Molecular diagnosis of TB?; Acetabular orientation: component and arthritis; Analgesia after knee arthroplasty; Bisphosphonate-associated femoral fractures

Our aim was to assess the intra- and inter-observer reliability in the establishment of the anterior pelvic plane used in imageless computer-assisted navigation. From this we determined the subsequent effects on version and inclination of the acetabular component.

A cadaver model was developed with a specifically-designed rod which held the component tracker at a fixed orientation to the pelvis, leaving the anterior pelvic plane as the only variable. Eight surgeons determined the anterior pelvic plane by palpating and registering the bony landmarks as reference points. The exact anterior pelvic plane was then established by using anatomically-placed bone screws as reference points.

The difference between the surgeons was found to be highly significant (p < 0.001). The variation was significantly larger for anteversion (sd 9.6°) than for inclination (sd 6.3°). The present method for registering pelvic landmarks shows significant inaccuracy, which highlights the need for improved methods of registration before this technique is considered to be safe.

The February 2013 Oncology Roundup³⁶⁰ looks at: proximal fibular tumours; radiotherapy-induced chondrosarcoma; mega-prosthesis; CRP predictions of sarcoma survival; predicting survival in metastatic disease; MRI for recurrence in osteoid osteoma; and a sarcoma refresher

The restoration of knee alignment is an important goal during total knee arthroplasty (TKA). In the past surgeons aimed to restore neutral limb alignment during surgery. However, previous studies have demonstrated alignment to be dynamic, varying depending on the position of the limb and the degree of weight-bearing, and between patients. We used a validated computer navigation system to measure the femorotibial mechanical angle (FTMA) in 264 knees in 77 male and 55 female healthy volunteers aged 18 to 35 years (mean 26.2). We found the mean supine alignment to be a varus angle of 1.2° (standard deviation (sd) 4), with few patients having neutral alignment. FTMA differs significantly between males and females (with a mean varus of 1.7° (sd 4) and 0.4° (sd 3.9), respectively; p = 0.008). It changes significantly with posture, the knee hyperextending by a mean of 5.6°, and coronal plane alignment becoming more varus by 2.2° (sd 3.6) on standing compared with supine.

Knee alignment is different in different individuals and is dynamic in nature, changing with different postures. This may have implications for the assessment of alignment in TKA, which is achieved in non-weight-bearing conditions and which may not represent the situation observed during weight-bearing.

Cite this article: Bone Joint J 2015; 97-B:498–502

A cadaver study using six pairs of lower limbs was conducted to investigate the accuracy of computer navigation and standard instrumentation for the placement of the Birmingham Hip Resurfacing femoral component. The aim was to place all the femoral components with a stem-shaft angle of 135°.

The mean stem-shaft angle obtained in the standard instrumentation group was 127.7° (120° to 132°), compared with 133.3° (131° to 139°) in the computer navigation group (p = 0.03). The scatter obtained with computer-assisted navigation was approximately half that found using the conventional jig.

Computer navigation was more accurate and more consistent in its placement of the femoral component than standard instrumentation. We suggest that image-free computer-assisted navigation may have an application in aligning the femoral component during hip resurfacing.

We have developed a new tensor for total knee replacements which is designed to assist with soft-tissue balancing throughout the full range of movement with a reduced patellofemoral joint. Using this tensor in 40 patients with osteoarthritis we compared the intra-operative joint gap in cruciate-retaining and posterior-stabilised total knee replacements at 0°, 10°, 45°, 90° and 135° of flexion, with the patella both everted and reduced.

While the measurement of the joint gap with a reduced patella in posterior-stabilised knees increased from extension to flexion, it remained constant for cruciate-retaining joints throughout a full range of movement. The joint gaps at deep knee flexion were significantly smaller for both types of prosthetic knee when the patellofemoral joint was reduced (p < 0.05).

The April 2012 Knee Roundup³⁶⁰ looks at the torn ACL, ACL reconstruction, the risk of ACL rupture, the benefit of warm-ups before exercise, glucosamine and tibiofemoral osteoarthritis, sensitisation and sporting tendinopathy, pain relief after TKR, the long-term results of the Genesis I, the gender specific recovery times after TKR, and the accuracy of the orthopaedic eyeball

After obtaining informed consent, 80 patients were randomised to undergo a navigated or conventional total knee replacement. All received a cemented, unconstrained, cruciate-retaining implant with a rotating platform. Full-length standing and lateral radiographs and CT scans of the hip, knee and ankle joint were carried out five to seven days after operation.

No notable differences were found between computer-assisted navigation and conventional implantation techniques as regards the rotational alignment of the femoral or tibial components. Although the deviation from the transepicondylar axis was relatively low, there was a considerable range of deviation for the tibial rotational alignment. There was no statistically significant difference regarding the occurrence pattern of outliers in mechanical malalignment but the number of outliers was reduced in the navigated group.

The aim of this study was to determine the accuracy of registration and the precision of the resection volume in navigated hip arthroscopy for cam-type femoroacetabular impingement, using imageless and image-based registration. A virtual cam lesion was defined in 12 paired cadaver hips and randomly assigned to either imageless or image-based (three-dimensional (3D) fluoroscopy) navigated arthroscopic head–neck osteochondroplasty. The accuracy of patient–image registration for both protocols was evaluated and post-operative imaging was performed to evaluate the accuracy of the surgical resection. We found that the estimated accuracy of imageless registration in the arthroscopic setting was poor, with a mean error of 5.6 mm (standard deviation (sd) 4.08; 95% confidence interval (CI) 4.14 to 7.19). Because of the significant mismatch between the actual position of the probe during surgery and the position of that probe as displayed on the navigation platform screen, navigated femoral osteochondroplasty was physically impossible. The estimated accuracy of image-based registration by means of 3D fluoroscopy had a mean error of 0.8 mm (sd 0.51; 95% CI 0.56 to 0.94). In terms of the volume of bony resection, a mean of 17% (sd 11; -6% to 28%) more bone was resected than with the virtual plan (p = 0.02). The resection was a mean of 1 mm deeper (sd 0.7; -0.3 to 1.6) larger than on the original virtual plan (p = 0.02).

In conclusion, given the limited femoral surface that can be reached and digitised during arthroscopy of the hip, imageless registration is inaccurate and does not allow for reliable surgical navigation. However, image-based registration does acceptably allow for guided femoral osteochondroplasty in the arthroscopic management of femoroacetabular impingement.

This review examines the future of total hip arthroplasty, aiming to avoid past mistakes

The August 2014 Knee Roundup³⁶⁰ looks at: re-admission following total knee replacement; out with the old and in with the new? computer navigation revisited; approach less important in knee replacement; is obesity driving a rise in knee replacements?; knee replacement isn’t cheap in the obese; cruciate substitution doesn’t increase knee flexion; and sonication useful diagnostic aid in two-stage revision.

With the development of systems of trauma care the management of pelvic disruption has evolved and has become increasingly refined. The goal is to achieve an anatomical reduction and stable fixation of the fracture. This requires adequate visualisation for reduction of the fracture and the placement of fixation. Despite the advances in surgical approach and technique, the functional outcomes do not always produce the desired result. New methods of percutaneous treatment in conjunction with innovative computer-based imaging have evolved in an attempt to overcome the existing difficulties. This paper presents an overview of the technical aspects of percutaneous surgery of the pelvis and acetabulum.

We retrospectively assessed the value of identifying impinging osteophytes using dynamic computer simulation of CT scans of the elbow in assisting their arthroscopic removal in patients with osteoarthritis of the elbow. A total of 20 patients were treated (19 men and one woman, mean age 38 years (19 to 55)) and followed for a mean of 25 months (24 to 29). We located the impinging osteophytes dynamically using computerised three-dimensional models of the elbow based on CT data in three positions of flexion of the elbow. These were then removed arthroscopically and a capsular release was performed.

The mean loss of extension improved from 23° (10° to 45°) pre-operatively to 9° (0° to 25°) post-operatively, and the mean flexion improved from 121° (80° to 140°) pre-operatively to 130° (110° to 145°) post-operatively. The mean Mayo Elbow Performance Score improved from 62 (30 to 85) to 95 (70 to 100) post-operatively. All patients had pain in the elbow pre-operatively which disappeared or decreased post-operatively. According to their Mayo scores, 14 patients had an excellent clinical outcome and six a good outcome; 15 were very satisfied and five were satisfied with their post-operative outcome.

We recommend this technique in the surgical management of patients with osteoarthritis of the elbow.

Cite this article: Bone Joint J 2014;96-B:237–41.