In this study we randomised 140 patients who were due to undergo primary total knee arthroplasty (TKA) to have the procedure performed using either patient-specific cutting guides (PSCG) or conventional instrumentation (CI).

The primary outcome measure was the mechanical axis, as measured at three months on a standing long-leg radiograph by the hip–knee–ankle (HKA) angle. This was undertaken by an independent observer who was blinded to the instrumentation. Secondary outcome measures were component positioning, operating time, Knee Society and Oxford knee scores, blood loss and length of hospital stay.

A total of 126 patients (67 in the CI group and 59 in the PSCG group) had complete clinical and radiological data. There were 88 females and 52 males with a mean age of 69.3 years (47 to 84) and a mean BMI of 28.6 kg/m² (20.2 to 40.8). The mean HKA angle was 178.9° (172.5 to 183.4) in the CI group and 178.2° (172.4 to 183.4) in the PSCG group (p = 0.34). Outliers were identified in 22 of 67 knees (32.8%) in the CI group and 19 of 59 knees (32.2%) in the PSCG group (p = 0.99). There was no significant difference in the clinical results (p = 0.95 and 0.59, respectively). Operating time, blood loss and length of hospital stay were not significantly reduced (p = 0.09, 0.58 and 0.50, respectively) when using PSCG.

The use of PSCG in primary TKA did not reduce the proportion of outliers as measured by post-operative coronal alignment.

Cite this article: Bone Joint J 2015;97-B:56–63.

Objective

This study compared the primary stability of two commercially available acetabular components from the same manufacturer, which differ only in geometry; a hemispherical and a peripherally enhanced design (peripheral self-locking (PSL)). The objective was to determine whether altered geometry resulted in better primary stability.

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

The aim of this study was to investigate the possible benefit of large-head metal-on-metal bearing on a stem for primary hip replacement compared with a 28 mm diameter conventional metal-on-polyethylene bearing in a prospective randomised controlled trial. We investigated cemented stem behaviour between these two different bearings using Einzel-Bild-Röntgen-Analyse, clinical and patient reported measures (Harris hip score, Western Ontario and McMaster Universities osteoarthritis index, Short Form-36 and satisfaction) and whole blood metal ion levels at two years. A power study indicated that 50 hips were needed in each group to detect subsidence of > 5 mm at two years with a p-value of < 0.05.

Significant improvement (p < 0.001) was found in the mean clinical and patient reported outcomes at two years for both groups. Comparison of outcomes between the groups at two years showed no statistically significant difference for mean stem migration, clinical and patient reported outcomes; except overall patient satisfaction which was higher for metal-on-metal group (p = 0.05). Metal ion levels were raised above the Medicines and Healthcare products Regulatory Agency advised safety level (7 µg per litre) in 20% of the metal-on-metal group and in one patient in metal-on-polyethylene group (who had a metal-on-metal implant on the contralateral side). Two patients in the metal-on-metal group were revised, one for pseudotumour and one for peri-prosthetic fracture.

Use of large modular heads is associated with a risk of raised whole blood metal ion levels despite using a proven bearing from resurfacing. The head-neck junction or excess stem micromotion are possibly the weak links warranting further research.

The aim of this study was to find anatomical landmarks for rotational alignment of the tibial component in total knee replacement (TKR) in a CT-based study. Pre-operative CT scanning was performed on 94 South Korean patients (nine men, 85 women, 188 knees) with osteoarthritis of the knee joint prior to TKR. The tibial anteroposterior (AP) axis was defined as a line perpendicular to the femoral surgical transepicondylar axis and passing through the centre of the posterior cruciate ligament (PCL). The angles between the defined tibial AP axis and anatomical landmarks at various levels of the tibia were measured. The mean values of the angles between the defined tibial AP axis and the line connecting the anterior border of the proximal third of the tibia to the centre of the PCL was -0.2° (-17 to 14.1, sd 4.1). This was very close to the defined tibial axis, and remained so regardless of lower limb alignment and the degree of tibial bowing. Therefore, AP axis defined as described, is a reliable anatomical landmark for rotational alignment of tibial components.

Cite this article: Bone Joint J 2014; 96-B:1485–90.

Aims

Femoroacetabular Junction Impingement (FAI) describes abnormalities in the shape of the femoral head–neck junction, or abnormalities in the orientation of the acetabulum. In the short term, FAI can give rise to pain and disability, and in the long-term it significantly increases the risk of developing osteoarthritis. The Femoroacetabular Impingement Trial (FAIT) aims to determine whether operative or non-operative intervention is more effective at improving symptoms and preventing the development and progression of osteoarthritis.

Total hip replacement for developmental hip dysplasia is challenging. The anatomical deformities on the acetabular and femoral sides are difficult to predict. The Crowe classification is usually used to describe these cases – however, it is not a very helpful tool for pre-operative planning. Small acetabular components, acetabular augments, and modular femoral components should be available for all cases. Regardless of the Crowe classification, the surgeon must be prepared to perform a femoral osteotomy for shortening, or to correct rotation, and/or angulation.

Cite this article: Bone Joint J 2013;95-B, Supple A:31–6.

It is probable that both genetic and environmental factors play some part in the aetiology of most cases of degenerative hip disease. Geneticists have identified some single gene disorders of the hip, but have had difficulty in identifying the genetics of many of the common causes of degenerative hip disease. The heterogeneity of the phenotypes studied is part of the problem. A detailed classification of phenotypes is proposed. This study is based on careful documentation of 2003 consecutive total hip replacements performed by a single surgeon between 1972 and 2000. The concept that developmental problems may initiate degenerative hip disease is supported. The influences of gender, age and body mass index are outlined. Biomechanical explanations for some of the radiological appearances encountered are suggested. The body weight lever, which is larger than the abductor lever, causes the abductor power to be more important than body weight. The possibility that a deficiency in joint lubrication is a cause of degenerative hip disease is discussed. Identifying the phenotypes may help geneticists to identify genes responsible for degenerative hip disease, and eventually lead to a definitive classification.

Instability is the reason for revision of a primary total knee replacement (TKR) in 20% of patients. To date, the diagnosis of instability has been based on the patient’s symptoms and a subjective clinical assessment. We assessed whether a measured standardised forced leg extension could be used to quantify instability.

A total of 25 patients (11 male/14 female, mean age 70 years; 49 to 85) who were to undergo a revision TKR for instability of a primary implant were assessed with a Nottingham rig pre-operatively and then at six and 26 weeks post-operatively. Output was quantified (in revolutions per minute (rpm)) by accelerating a stationary flywheel. A control group of 183 patients (71 male/112 female, mean age 69 years) who had undergone primary TKR were evaluated for comparison.

Pre-operatively, all 25 patients with instability exhibited a distinctive pattern of reduction in ‘mid-push’ speed. The mean reduction was 55 rpm (sd 33.2). Post-operatively, no patient exhibited this pattern and the reduction in ‘mid-push’ speed was 0 rpm. The change between pre- and post-operative assessment was significant (p < 0.001). No patients in the control group exhibited this pattern at any of the intervals assessed. The between-groups difference was also significant (p < 0.001). This suggests that a quantitative diagnostic test to assess the unstable primary TKR could be developed.

Cite this article: Bone Joint J 2014;96-B:1339–43.

Fracture of a ceramic component in total hip replacement is a rare but potentially catastrophic complication. The incidence is likely to increase as the use of ceramics becomes more widespread. We describe such a case, which illustrates how inadequate initial management will lead to further morbidity and require additional surgery. We present the case as a warning that fracture of a ceramic component should be revised to another ceramic-on-ceramic articulation in order to minimise the risk of further catastrophic wear.

In a decidedly upper limb themed series of reviews this edition of Cochrane Corner summarises four new and updated reviews published by the Cochrane Bone, Joint and Muscle Trauma Group over the last few months. The tenacious reviewers at the Cochrane collaboration have turned their beady eyes to conservative treatments for shoulder dislocations and clavicle fractures along with evaluation of femoral nerve blocks in knee replacement and how to best manage entrapment injuries in children.

The October 2014 Knee Roundup³⁶⁰ looks at: microfracture equivalent to OATS; examination better than MRI in predicting hamstrings re-injury; a second view on return to play with hamstrings injuries; dislocation risks in the Oxford Unicompartmental Knee; what about the tibia?; getting on top of lateral facet pain post TKR; readmission in TKR; patient-specific instrumentation; treating infrapatellar saphenous neuralgia; and arthroscopy in the middle-aged.

The February 2013 Hip & Pelvis Roundup³⁶⁰ looks at: amazing alumina; dual mobility; white cells and periprosthetic infection; cartilage and impingement surgery; acetabulum in combination; cementless ceramic prosthesis; metal-on-metal hips; and whether size matters in failure.

This conversation represents an attempt by several arthroplasty surgeons to critique several abstracts presented over the last year as well as to use them as a jumping off point for trying to figure out where they fit in into our current understanding of multiple issues in modern hip and knee arthroplasty.

The popularity of cementless total hip replacement (THR) has surpassed cemented THR in England and Wales. This retrospective cohort study records survival time to revision following primary cementless THR with the most common combination (accounting for almost a third of all cementless THRs), and explores risk factors independently associated with failure, using data from the National Joint Registry for England and Wales. Patients with osteoarthritis who had a DePuy Corail/Pinnacle THR implanted between the establishment of the registry in 2003 and 31 December 2010 were included within analyses. There were 35 386 procedures. Cox proportional hazard models were used to analyse the extent to which the risk of revision was related to patient, surgeon and implant covariates. The overall rate of revision at five years was 2.4% (99% confidence interval 2.02 to 2.79). In the final adjusted model, we found that the risk of revision was significantly higher in patients receiving metal-on-metal (MoM: hazard ratio (HR) 1.93, p < 0.001) and ceramic-on-ceramic bearings (CoC: HR 1.55, p = 0.003) compared with the best performing bearing (metal-on-polyethylene). The risk of revision was also greater for smaller femoral stems (sizes 8 to 10: HR 1.82, p < 0.001) compared with mid-range sizes. In a secondary analysis of only patients where body mass index (BMI) data were available (n = 17 166), BMI ≥ 30 kg/m² significantly increased the risk of revision (HR 1.55, p = 0.002). The influence of the bearing on the risk of revision remained significant (MoM: HR 2.19, p < 0.001; CoC: HR 2.09, p = 0.001). The risk of revision was independent of age, gender, head size and offset, shell, liner and stem type, and surgeon characteristics.

We found significant differences in failure between bearing surfaces and femoral stem size after adjustment for a range of covariates in a large cohort of single-brand cementless THRs. In this study of procedures performed since 2003, hard bearings had significantly higher rates of revision, but we found no evidence that head size had an effect. Patient characteristics, such as BMI and American Society of Anesthesiologists grade, also influence the survival of cementless components.

Cite this article: Bone Joint J 2013;95-B:747–57.

The aim of this study was to assess a specific protocol for the treatment of patients with a parosteal osteosarcoma of the distal femur with limb salvage involving hemicortical resection and reconstruction using recycled pasteurised autograft and internal fixation. Between January 2000 and January 2010, 13 patients with a mean age of 26.5 years (17 to 39) underwent this procedure. All the tumours were staged according to Enneking’s criteria: there were eight stage IA tumours and five stage IB tumours. The mean follow-up was 101.6 months (58 to 142), and mean post-operative Musculoskeletal Tumour Society functional score was 88.6% (80% to 100%) at the final follow-up. All the patients had achieved bony union; the mean time to union was 11.2 months (6 to 18). Local recurrence occurred in one patient 27 months post-operatively. No patient had a pulmonary metastasis.

A hemicortical procedure for the treatment of a parosteal osteosarcoma is safe and effective. Precise pre-operative planning using MRI is essential in order to define the margins of resection. Although it is a technically demanding procedure, gratifying results make it worthwhile for selected patients.

Cite this article: Bone Joint J 2013;95-B:1275–9.

Metal artefact reduction (MAR) MRI is now widely considered to be the standard for imaging metal-on-metal (MoM) hip implants. The Medicines and Healthcare Products Regulatory Agency (MHRA) has recommended cross-sectional imaging for all patients with symptomatic MoM bearings. This paper describes the natural history of MoM disease in a 28 mm MoM total hip replacement (THR) using MAR MRI. Inclusion criteria were patients with MoM THRs who had not been revised and had at least two serial MAR MRI scans. All examinations were reported by an experienced observer and classified as A (normal), B (infection) or C1–C3 (mild, moderate, severe MoM-related abnormalities). Between 2002 and 2011 a total of 239 MRIs were performed on 80 patients (two to four scans per THR); 63 initial MRIs (61%) were normal. On subsequent MRIs, six initially normal scans (9.5%) showed progression to a disease state; 15 (15%) of 103 THRs with sequential scans demonstrated worsening disease on subsequent imaging.

Most patients with a MoM THR who do not undergo early revision have normal MRI scans. Late progression (from normal to abnormal, or from mild to more severe MoM disease) is not common and takes place over several years.

Cite this article: Bone Joint J 2013;95-B:1035–9.

In a time of limited resources, the debate continues over which types of hip prosthesis are clinically superior and more cost-effective. Orthopaedic surgeons increasingly need robust economic evidence to understand the full value of the operation, and to aid decision making on the ‘package’ of procedures that are available and to justify their practice beyond traditional clinical preference.

In this paper we explore the current economic debate about the merits of cemented and cementless total hip replacement, an issue that continues to divide the orthopaedic community.

Cite this article: Bone Joint J 2013;95-B:874–6.

Stems improve the mechanical stability of tibial components in total knee replacement (TKR), but come at a cost of stress shielding along their length. Their advantages include resistance to shear, reduced tibial lift-off and increased stability by reducing micromotion. Longer stems may have disadvantages including stress shielding along the length of the stem with associated reduction in bone density and a theoretical risk of subsidence and loosening, peri-prosthetic fracture and end-of-stem pain. These features make long stems unattractive in the primary TKR setting, but often desirable in revision surgery with bone loss and instability. In the revision scenario, stems are beneficial in order to convey structural stability to the construct and protect the reconstruction of bony defects. Cemented and uncemented long stemmed implants have different roles depending on the nature of the bone loss involved.

This review discusses the biomechanics of the design of tibial components and stems to inform the selection of the component and the technique of implantation.