The use of robots in orthopaedic surgery is an emerging field that is gaining momentum. It has the potential for significant improvements in surgical planning, accuracy of component implantation and patient safety. Advocates of robot-assisted systems describe better patient outcomes through improved pre-operative planning and enhanced execution of surgery. However, costs, limited availability, a lack of evidence regarding the efficiency and safety of such systems and an absence of long-term high-impact studies have restricted the widespread implementation of these systems. We have reviewed the literature on the efficacy, safety and current understanding of the use of robotics in orthopaedics.

Cite this article: Bone Joint J 2015; 97-B:292–9.

We compared the medium-term clinical and radiological results of hybrid total hip replacement (THR) with metal-on-metal Birmingham hip resurfacing (BHR) in two groups of 54 young patients matched for age, gender, body mass index and pre-operative levels of activity.

The clinical outcome was assessed by the University of California, Los Angeles (UCLA) activity score, the Oxford Hip Score (OHS) and the EuroQol scores. Radiologically, all hips were assessed for migration and osteolysis, the hybrid THRs for polyethylene wear and the BHRs for a pedestal sign. The mean follow-up of the patients with a hybrid THR was ten years and for those with a BHR, nine years. Four patients with a hybrid THR and one with a BHR had died. In each group five were lost to follow-up. The revision rate of the hybrid THRs was 16.7% (9 of 54) and of the BHRs 9.3% (5 of 54) (p = 0.195). Radiographs of a further eight hybrid THRs demonstrated wear and osteolysis, and they await revision (p = 0.008). Of the unrevised BHRs 90% had radiological changes, of which approximately 50% had progressed over the previous four years. All hybrid THRs demonstrated linear polyethylene wear with a mean of 1.24 mm (0.06 to 3.03). The BHRs recorded superior OHS (p = 0.013), UCLA (p = 0.008), and EuroQol visual analogue scores (p = 0.009).

After nine years, patients with BHRs remained more active and had a lower rate of revision than those with hybrid THRs. Both groups demonstrated progressive radiological changes at medium-term follow-up.

Metal-on-metal resurfacing of the hip (MoMHR) has enjoyed a resurgence in the last decade, but is now again in question as a routine option for osteoarthritis of the hip. Proponents of hip resurfacing suggest that its survival is superior to that of conventional hip replacement (THR), and that hip resurfacing is less invasive, is easier to revise than THR, and provides superior functional outcomes. Our argument serves to illustrate that none of these proposed advantages have been realised and new and unanticipated serious complications, such as pseudotumors, have been associated with the procedure. As such, we feel that the routine use of MoMHR is not justified.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):17–21.

Dysplasia of the hip, hypotonia, osteopenia, ligamentous laxity, and mental retardation increase the complexity of performing and managing patients with Down syndrome who require total hip replacement (THR). We identified 14 patients (six males, eight females, 21 hips) with Down syndrome and degenerative disease of the hip who underwent THR, with a minimum follow-up of two years from 1969 to 2009. In seven patients, bilateral THRs were performed while the rest had unilateral THRs. The mean clinical follow-up was 5.8 years (standard deviation (sd) 4.7; 2 to 17). The mean Harris hip score was 37.9 points (sd 7.8) pre-operatively and increased to 89.2 (sd 12.3) at final follow-up (p = 1x10^-9). No patient suffered a post-operative dislocation. In three patients, four hips had revision THR for aseptic loosening at a mean follow-up of 7.7 years (sd 6.3; 3 to 17). This rate of revision THR was higher than expected. Our patients with Down syndrome benefitted clinically from THR at mid-term follow-up.

Cite this article: Bone Joint J 2014;96-B:1455–8.

Non-modular tapered fluted, titanium stems are available for use in femoral revision. The combination of taper and flutes on the stem provides axial and rotational stability, respectively. The material and surface properties of the stem promotes bone on-growth. If the surgeon is confident and reasonably experienced in the surgical use of this sort of design and the case is relatively straightforward, a non-modular design is effective. It also potentially reduces implant inventory, and circumvents the potential problems of taper junction corrosion and fatigue fracture. There are reports of excellent survival, good clinical and functional results and evidence of subsequent increase in proximal bone stock.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):56–9.

Advances in the treatment of periprosthetic joint infections of the hip have once more pushed prosthesis preserving techniques into the limelight. At the same time, the common infecting organisms are evolving to become more resistant to conventional antimicrobial agents. Whilst the epidemiology of resistant staphylococci is changing, a number of recent reports have advocated the use of irrigation and debridement and one-stage revision for the treatment of periprosthetic joint infections due to resistant organisms. This review presents the available evidence for the treatment of periprosthetic joint infections of the hip, concentrating in particular on methicillin resistant staphylococci.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):60–5.

The June 2013 Wrist & Hand Roundup³⁶⁰ looks at: whether size is a limitation; cancellous bone grafting in scaphoid nonunion; the Kienböck’s dichotomy; late displacement of the distal radius; flexor slide for finger contracture; aesthetic syndactyly; flexor tendon repair; and fixation of trapeziometacarpal cups.

A retrospective review was performed of patients undergoing primary cementless total knee replacement (TKR) using porous tantalum performed by a group of surgical trainees. Clinical and radiological follow-up involved 79 females and 26 males encompassing 115 knees. The mean age was 66.9 years (36 to 85). Mean follow-up was 7 years (2 to 11). Tibial and patellar components were porous tantalum monoblock implants, and femoral components were posterior stabilised (PS) in design with cobalt–chromium fibre mesh. Radiological assessments were made for implant positioning, alignment, radiolucencies, lysis, and loosening. There was 95.7% survival of implants. There was no radiological evidence of loosening and no osteolysis found. No revisions were performed for aseptic loosening. Average tibial component alignment was 1.4° of varus (4°of valgus to 9° varus), and 6.2° (3° anterior to 15° posterior) of posterior slope. Mean femoral component alignment was 6.6° (1° to 11°) of valgus. Mean tibiofemoral alignment was 5.6° of valgus (7° varus to 16° valgus). Patellar tilt was a mean of 2.4° lateral (5° medial to 28° lateral). Patient satisfaction with improvement in pain was 91%. Cementless TKR incorporating porous tantalum yielded good clinical and radiological outcomes at a mean of follow-up of seven-years.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):87–92.

The August 2012 Hip & Pelvis Roundup³⁶⁰ looks at: whether cemented hip replacement might be bad for your health; highly cross-linked polyethylene; iHOT-33 - a new hip outcome measure; hamstring injuries; total hip replacement; stemmed metal-on-metal THR; bipolar hemiarthroplasty, neuromuscular disease and dislocation; the high risk of secondary hemiarthroplasty; and whether we have to repair the labrum after all?

The piriformis muscle is an important landmark in the surgical anatomy of the hip, particularly the posterior approach for total hip replacement (THR). Standard orthopaedic teaching dictates that the tendon must be cut in to allow adequate access to the superior part of the acetabulum and the femoral medullary canal. However, in our experience a routine THR can be performed through a posterior approach without sacrificing this tendon.

We dissected the proximal femora of 15 cadavers in order to clarify the morphological anatomy of the piriformis tendon. We confirmed that the tendon attaches on the crest of the greater trochanter, in a position superior to the trochanteric fossa, away from the entry point for broaching the intramedullary canal during THR. The tendon attachment site encompassed the summit and medial aspect of the greater trochanter as well as a variable attachment to the fibrous capsule of the hip joint. In addition we dissected seven cadavers resecting all posterior attachments except the piriformis muscle and tendon in order to study their relations to the hip joint, as the joint was flexed. At flexion of 90° the piriformis muscle lay directly posterior to the hip joint.

The piriform fossa is a term used by orthopaedic surgeons to refer the trochanteric fossa and normally has no relation to the attachment site of the piriformis tendon. In hip flexion the piriformis lies directly behind the hip joint and might reasonably be considered to contribute to the stability of the joint.

We conclude that the anatomy of the piriformis muscle is often inaccurately described in the current surgical literature and terms are used and interchanged inappropriately.

Cite this article: Bone Joint J 2013;95-B:764–9.

Peri-acetabular tumour resections and their subsequent reconstruction are among the most challenging procedures in orthopaedic oncology. Despite the fact that a number of different pelvic endoprostheses have been introduced, rates of complication remain high and long-term results are mostly lacking.

In this retrospective study, we aimed to evaluate the outcome of reconstructing a peri-acetabular defect with a pedestal cup endoprosthesis after a type 2 or type 2/3 internal hemipelvectomy.

A total of 19 patients (11M:8F) with a mean age of 48 years (14 to 72) were included, most of whom had been treated for a primary bone tumour (n = 16) between 2003 and 2009. After a mean follow-up of 39 months (28 days to 8.7 years) seven patients had died. After a mean follow-up of 7.9 years (4.3 to 10.5), 12 patients were alive, of whom 11 were disease-free. Complications occurred in 15 patients. Three had recurrent dislocations and three experienced aseptic loosening. There were no mechanical failures. Infection occurred in nine patients, six of whom required removal of the prosthesis. Two patients underwent hindquarter amputation for local recurrence.

The implant survival rate at five years was 50% for all reasons, and 61% for non-oncological reasons. The mean Musculoskeletal Tumor Society score at final follow-up was 49% (13 to 87).

Based on these poor results, we advise caution if using the pedestal cup for reconstruction of a peri-acetabular tumour resection.

Cite this article: Bone Joint J 2014;96-B:1706–12.

The December 2014 Knee Roundup³⁶⁰ looks at: national guidance on arthroplasty thromboprophylaxis is effective; unicompartmental knee replacement has the edge in terms of short-term complications; stiff knees, timing and manipulation; neuropathic pain and total knee replacement; synovial fluid α-defensin and CRP: a new gold standard in joint infection diagnosis?; how to assess anterior knee pain?; where is the evidence? Five new implants under the spotlight; and a fresh look at ACL reconstruction

We assessed the orientation of the acetabular component in 1070 primary total hip arthroplasties with hard-on-soft, small diameter bearings, aiming to determine the size and site of the target zone that optimises outcome. Outcome measures included complications, dislocations, revisions and ΔOHS (the difference between the Oxford Hip Scores pre-operatively and five years post-operatively). A wide scatter of orientation was observed (2sd 15°). Placing the component within Lewinnek’s zone was not associated withimproved outcome. Of the different zone sizes tested (± 5°, ± 10° and ± 15°), only ± 15° was associated with a decreased rate of dislocation. The dislocation rate with acetabular components inside an inclination/anteversion zone of 40°/15° ± 15° was four times lower than those outside. The only zone size associated with statistically significant and clinically important improvement in OHS was ± 5°. The best outcomes (ΔOHS > 26) were achieved with a 45°/25° ± 5° zone.

This study demonstrated that with traditional technology surgeons can only reliably achieve a target zone of ±15°. As the optimal zone to diminish the risk of dislocation is also ±15°, surgeons should be able to achieve this. This is the first study to demonstrate that optimal orientation of the acetabular component improves the functional outcome. However, the target zone is small (± 5°) and cannot, with current technology, be consistently achieved.

Cite this article: Bone Joint J 2015;97-B:164–72.

The most common reasons for revision of unicompartmental knee arthroplasty (UKA) are loosening and pain. Cementless components may reduce the revision rate. The aim of this study was to compare the fixation and clinical outcome of cementless and cemented Oxford UKAs.

A total of 43 patients were randomised to receive either a cemented or a cementless Oxford UKA and were followed for two years with radiostereometric analysis (RSA), radiographs aligned with the bone–implant interfaces and clinical scores.

The femoral components migrated significantly during the first year (mean 0.2 mm) but not during the second. There was no significant difference in the extent of migration between cemented and cementless femoral components in either the first or the second year. In the first year the cementless tibial components subsided significantly more than the cemented components (mean 0.28 mm (sd 0.17) vs. 0.09 mm (sd 0.19 mm)). In the second year, although there was a small amount of subsidence (mean 0.05 mm) there was no significant difference (p = 0.92) between cemented and cementless tibial components. There were no femoral radiolucencies. Tibial radiolucencies were narrow (< 1 mm) and were significantly (p = 0.02) less common with cementless (6 of 21) than cemented (13 of 21) components at two years. There were no complete radiolucencies with cementless components, whereas five of 21 (24%) cemented components had complete radiolucencies. The clinical scores at two years were not significantly different (p = 0.20).

As second-year migration is predictive of subsequent loosening, and as radiolucency is suggestive of reduced implant–bone contact, these data suggest that fixation of the cementless components is at least as good as, if not better than, that of cemented devices.

Cite this article: Bone Joint J 2015; 97-B:185–91.

The Unified Classification System (UCS) emphasises the key principles in the assessment and management of peri-prosthetic fractures complicating partial or total joint replacement.

We tested the inter- and intra-observer agreement for the UCS as applied to the pelvis and femur using 20 examples of peri-prosthetic fracture in 17 patients. Each subtype of the UCS was represented by at least one case. Specialist orthopaedic surgeons (experts) and orthopaedic residents (pre-experts) assessed reliability on two separate occasions.

For the pelvis, the UCS showed inter-observer agreement of 0.837 (95% confidence intervals (CI) 0.798 to 0.876) for the experts and 0.728 (95% CI 0.689 to 0.767) for the pre-experts. The intra-observer agreement for the experts was 0.861 (95% CI 0.760 to 0.963) and 0.803 (95% 0.688 to 0.918) for the pre-experts. For the femur, the UCS showed an inter-observer kappa value of 0.805 (95% CI 0.765 to 0.845) for the experts and a value of 0.732 (95% CI 0.690 to 0.773) for the pre-experts. The intra-observer agreement was 0.920 (95% CI 0.867 to 0.973) for the experts, and 0.772 (95% CI 0.652 to 0.892) for the pre-experts. This corresponds to a substantial and ‘almost perfect’ inter- and intra-observer agreement for the UCS for peri-prosthetic fractures of the pelvis and femur.

We hope that unifying the terminology of these injuries will assist in their assessment, treatment and outcome.

Cite this article: Bone Joint J 2014;96-B:1472–7.

Neurological conditions affecting the hip pose a considerable challenge in replacement surgery since poor and imbalanced muscle tone predisposes to dislocation and loosening. Consequently, total hip replacement (THR) is rarely performed in such patients. In a systematic review of the literature concerning THR in neurological conditions, we found only 13 studies which described the outcome. We have reviewed the evidence and discussed the technical challenges of this procedure in patients with cerebral palsy, Parkinson’s disease, poliomyelitis and following a cerebrovascular accident, spinal injury or development of a Charcot joint. Contrary to traditional perceptions, THR can give a good outcome in these often severly disabled patients.

There are many reasons why a total knee replacement (TKR) may fail and qualify for revision. Successful revision surgery depends as much on accurate assessment of the problem TKR as it does on revision implant design and surgical technique. Specific modes of failure require specific surgical solutions. Causes of failure are often presented as a list or catalogue, without a system or process for making a decision. In addition, strict definitions and consensus on modes of failure are lacking in published series and registry data. How we approach the problem TKR is an essential but neglected aspect of understanding knee replacement surgery. It must be carried out systematically, comprehensively and efficiently. Eight modes of failure are described: 1) sepsis; 2) extensor discontinuity; 3) stiffness; 4) tibial- femoral instability; 5) patellar tracking; 6) aseptic loosening and osteolysis; 7) periprosthetic fracture and 8) component breakage. A ninth ‘category’, unexplained pain is an indication for further investigation but not surgery.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):105–11.

We report the outcome at ten to 15 years of two-stage revision for hip infection in 99 patients using the Prostalac articulated hip spacer system.

All the patients were contacted to determine their current functional and infection status using the Oxford-12, Short form-12, and Western Ontario and McMaster University Osteoarthritis Index questionnaires. A total of 11 of the 99 patients had a further infection, of whom seven responded to repeat surgery with no further sequelae. The mean interval between the stages was five months (1 to 36). We were able to review 48 living patients, with a mean age of 72 years (46 to 86), 34 (71%) of whom provided health-related quality-of-life outcome scores.

The mean follow-up was 12 years (10 to 15). The long-term success rate was 89% and with additional surgery this rose to 96%. The mean global Western Ontario and McMaster University Osteoarthritis Index score was 80.6 (sd 18.3). The mean Oxford-12 score was 74.0 (sd 22.3), and the mean Short form-12 score was 53.1 (sd 9.4) (mental) and 33.5 (sd 13.5) (physical). The mean satisfaction score was 90.5 (sd 15.3).

Two-stage revision for hip infection using a Prostalac interim spacer offers a predictable and lasting solution for patients with this difficult problem.

The treatment of substantial proximal femoral bone loss in young patients with developmental dysplasia of the hip (DDH) is challenging. We retrospectively analysed the outcome of 28 patients (30 hips) with DDH who underwent revision total hip replacement (THR) in the presence of a deficient proximal femur, which was reconstructed with an allograft prosthetic composite. The mean follow-up was 15 years (8.5 to 25.5). The mean number of previous THRs was three (1 to 8). The mean age at primary THR and at the index reconstruction was 41 years (18 to 61) and 58.1 years (32 to 72), respectively. The indication for revision included mechanical loosening in 24 hips, infection in three and peri-prosthetic fracture in three.

Six patients required removal and replacement of the allograft prosthetic composite, five for mechanical loosening and one for infection. The survivorship at ten, 15 and 20 years was 93% (95% confidence interval (CI) 91 to 100), 75.5% (95% CI 60 to 95) and 75.5% (95% CI 60 to 95), respectively, with 25, eight, and four patients at risk, respectively. Additionally, two junctional nonunions between the allograft and host femur required bone grafting and plating.

An allograft prosthetic composite affords a good long-term outcome in the management of proximal femoral bone loss in revision THR in patients with DDH, while preserving distal host bone.

Comparison of the safety and efficacy of bilateral simultaneous total hip replacement (THR) and that of staged bilateral THR and unilateral THR was conducted using DerSimonian-Laird heterogeneity meta-analysis. A review of the English-language literature identified 23 citations eligible for inclusion. A total of 2063 bilateral simultaneous THR patients were identified. Meta-analysis of homogeneous data revealed no statistically significant differences in the rates of thromboembolic events (p = 0.268 and p = 0.365) and dislocation (p = 0.877) when comparing staged or unilateral with bilateral simultaneous THR procedures. A systematic analysis of heterogeneous data demonstrated that the mean length of hospital stay was shorter after bilateral simultaneous THR. Higher blood transfusion requirements were expected following bilateral simultaneous THR than staged or unilateral THR, and surgical time was not different between groups. This procedure was also found to be economically and functionally efficacious when performed by experienced surgeons in specialist centres.