Reported rates of dislocation in hip hemiarthroplasty (HA) for the treatment of intra-capsular fractures of the hip, range between 1% and 10%. HA is frequently performed through a direct lateral surgical approach. The aim of this study is to determine the contribution of the anterior capsule to the stability of a cemented HA through a direct lateral approach.

A total of five whole-body cadavers were thawed at room temperature, providing ten hip joints for investigation. A Thompson HA was cemented in place via a direct lateral approach. The cadavers were then positioned supine, both knee joints were disarticulated and a digital torque wrench was attached to the femur using a circular frame with three half pins. The wrench applied an external rotation force with the hip in extension to allow the hip to dislocate anteriorly. Each hip was dislocated twice; once with a capsular repair and once without repairing the capsule. Stratified sampling ensured the order in which this was performed was alternated for the paired hips on each cadaver.

Comparing peak torque force in hips with the capsule repaired and peak torque force in hips without repair of the capsule, revealed a significant difference between the ‘capsule repaired’ (mean 22.96 Nm, standard deviation (sd) 4.61) and the ‘capsule not repaired’ group (mean 5.6 Nm, sd 2.81) (p < 0.001). Capsular repair may help reduce the risk of hip dislocation following HA.

Cite this article: Bone Joint J 2015;97-B:141–4.

Pre-existing hip pathology such as femoroacetabular impingement is believed by some, to have a direct causal relationship with osteoarthritis of the hip. The strength of this relationship remains unknown.

We investigate the prevalence of abnormal bone morphology in the symptomatic hip on the pre-operative anteroposterior pelvic radiograph of consecutive patients undergoing hip resurfacing. Rotated radiographs were excluded. One hundred patients, of mean age 53.5 years were included (range 33.4–71.4 years, 32% female). We examined the films for evidence of a cam-type impingement lesion (alpha angle >50.5°, a pistol grip, Pitt's pits, a medial hook, an os acetabuli and rim ossification), signs of acetabular retroversion or a pincer-type impingement lesion (crossover sign, posterior wall sign, ischial sign, coxa profunda, protrusio, coxa vara, Tonnis angle < 5°), and hip dysplasia (a Tonnis acetabular angle >14° and a lateral centre-edge angle of Wiberg <20°).

Pre-existing radiographic signs of pathology were present in a large proportion of hips with low grade (Tonnis grade 1–2) arthritis. There is a group of patients who presented with more advanced osteoarthritis in which we suspect abnormal bone morphology to be a causative factor but, for example, neck osteophytes obscure the diagnosis of a primary cam lesion.

Our findings corroborate those of Harris and Ganz. Impingement is radiographically detectable in a large proportion of patients who present with early arthritis of the hip, and therefore we agree that it is a likely pre-cursor for osteoarthritis. Treatments directed at reducing hip impingement may stifle the progression of osteoarthritis.

There are a growing number of younger patients with developmental dysplasia of hip, proximal femoral deformity and osteonecrosis seeking surgical intervention to restore quality of life, and the advent of ISTCs has resulted in a greater proportion of such cases being referred to existing NHS departments.

Bone-saving hip athroplasty is often advocated for younger active patients, as they are potential candidates for subsequent revision arthroplasty. If resurfacing is contraindicated, short bone-conserving stems may be an option. The rationale for short stems in cementless total hip arthroplasty is proximal load transfer and absence of distal fixation, resulting in preserved femoral bone stock and avoidance of thigh pain.

We have carried out 17 short stem hip replacements (Mini-hip, Corin Medical, Cirencester, UK) using ceramic bearings in 16 patients since June 2010. There were 14 females and 2 males, with a mean age of 50.1 years (range 35–63 years) at the time of the surgery. The etiology was osteoarthritis in 11, developmental dysplasia in 4, and osteonecrosis of the femoral head in one patient. All operations were performed through a conservative anterolateral (Bauer) approach. These patients are being followed and evaluated clinically with the Harris and Oxford hip scores, with follow-up at 6 weeks, 3 months, and annually thereafter.

Initital results have been encouraging in terms of pain relief, restoration of leg length (one of the objectives in cases of shortening) and rage of movement. Radiological assessment has shown restoration of hip biomechanics. Specific techniques are required to address varus, valgus and femoral deformity with leg length inequality.

There are two main groups of short stems, those that are neck-preserving and those that do not preserve the femoral neck. The latter group requires traditional techniques for revision. Another feature that differentiates them is the availability of modularity. The device we employed is neck-preserving and available with different neck lengths and offsets, which help in restoration of hip biomechanics.

The advantage of such short stems may be preservation of proximal femoral bone stock, decreased stress shielding and the ease of potential revision. Such devices may be a consideration for patients with malformations of the proximal femur. Long-term follow-up will be of value in determining if perceived benefits are realised in practice.

Introduction: Tourniquets are commonly employed in surgical procedures of the knee. The use of the same tourniquet on a repetitive basis without a standard protocol for cleaning has recently been questioned as a potential source of cross-infection. This study examines the contamination of the tourniquets in our institution and results of cleaning the tourniquets with a disinfectant and detergent wipe.

Material and methods: Tryptone soya agar plates were used to take samples from 20 tourniquets employed in knee replacement. Four specified sites on each tourniquet were cultured and incubated at 37° for 48 hrs.

Results: All sampled tourniquets were contaminated with colony counts varying from 9 to > 385.

Coagulase negative Staphylococcus was the most commonly grown organism from the tourniquets (96%).

Some tourniquets had growths of important pathogens including MRSA, Pseudomonas and Staphylococcus aureus (these organisms have not been previously cultured from tourniquets). On cleaning five tourniquets with clinell (detergent and disinfectant) wipes, there was a 99.2% reduction in contamination of the tourniquets five minutes after cleaning.

Conclusion: Contamination is more worrying in relation to pneumatic tourniquets, as they are commonly employed in knee surgery where implants are frequently used with the tourniquet lying within inches of the operative wound.

We have found a 99% reduction in contamination of tourniquets by employing disinfectant wipes. This is a simple, cost-effective and quick method to clean tourniquets and we recommend the use of wipes before every case in addition to the manufactures guidelines for general cleaning of tourniquets.

Introduction: Restoration of hip biomechanics is an important part of successful total hip replacement. Preoperative templating acts as a guide to selection of size and positioning of prostheses to enable this. We aimed to Establish how closely natural femoral offset could be reproduced using the manufacturers templates for 10 femoral stems in common use in the U.K.

Method: The10 most frequently used femoral components from the U.K. national joint registry (cemented and un-cemented) were identified. Sets of templates for these designs were used to template a series of 47 consecutive pre-operative radiographs from patients who had undergone unilateral total hip replacement for unilateral osteoarthritis of the hip. The non-operated on side of the pelvic radiographs were templated using the 10 sets of templates according to the technique of Schmalzreid. This demonstrated how much the offset of the hip would be changed if that prosthesis were selected and implanted in the templated position. 3 different surgeons performed the complete process. The standard deviation of change in offset between the templated centre of rotation and the normal centre of rotation of the set of radiographs for each prosthesis was then calculated allowing us to rank the templates and hence implants according to their ability to reproduce the normal anatomical offset.

Results: The most accurate template was the CPS with a Root Mean Square Error of 2.0mm followed in rank order by: C stem 2.16, CPT 2.40, Exeter 3.23, Stanmore 3.28, Charnley 3.65, Corail 3.72, ABG II 4.30, Furlong HAC 5.08, Furlong modular 7.14.

Discussion: There is fairly wide variation in the ability of the femoral prosthesis templates to reproduce normal femoral offset in a series of standard pre-operative hip radiographs. The more modern polished tapered stems with high modularity were best able to reproduce femoral offset. There is however no correlation between the prostheses ability to restore offset and clinical results. Some of the older less modular stems, which were unable to get close to normal offset, have some of the best longterm clinical results. With the increasing digitalisation of radiographs a change in the method of templating is required. This may allow manufactures to re-examine their templates and improve the accuracy of this process.

Introduction: A reduced range of movement and associated pain due to impingement following hip resurfacing is a side effect leading to significant morbidity in the affected patient. We have found it may possible to identify those patients most at risk of impingement from plain radiograph analysis.

Methods: Using Corin Cormet^TM resurfacing templates angles of impingement of different size femoral heads were measured and compared by using a theoretical head neck ratio of one. Following this a single femoral head size of 56mm was taken and the impingement angle was measured with altering neck sizes.

Femoral head: femoral neck ratios were then measured on a series of 43 plain AP pelvic radiographs using calibrated digital calipers. The range of values was compared to a normal distribution curve. Inter and intra observer variation was calculated.

Results: Varying the template femoral head size with the corresponding acetabular component will give the same impingement angle. With a single femoral head size and altering femoral neck sizes the angle of impingement in the AP view decreases with an increasing head neck ratio.

Analysis of 43 pelvic radiographs revealed a range of head neck ratios from 0.64 to 0.80 with a mean of 0.71 and standard deviation of 0.038. This data compares with a normal distribution.

Conclusion: The risk of impingement in hip resurfacing is not related to femoral head size alone, but also to the head neck ratio. Furthermore it is evident that range of movement is a function of the head neck ratio and not the femoral head size alone. Those ratios which fall within the upper standard deviation may require further consideration as to the suitability of a planned resurfacing procedure. This study also highlights the need for surgeons to become experienced in the technique of osteochondroplasty to minimise the head neck ratio.

Introduction: Hip resurfacing has become re-established in recent years as a viable option in younger, active individuals. The results of a multi-centre evaluation of the Cormet resurfacing device are presented.

Methods: Data has been entered from 1997 onwards from 5 centres, patients being selected as suitable by 8 individual surgeons. Pre and intraoperative details recorded including indications, patient details, implant used, Harris Hip Score (HHS) and surgical approach.

Results: A total of 905 procedures in 782 patients have been recorded (52% posterior approach, 39% anterolateral 9% Ganz approach). The mean follow-up is 2.8 years (0.1–9.5 yrs) and the mean postoperative HHS is 86.1 (range 25–100). The mean age at surgery was 54.4 years. 61% of patients were male. The principal diagnosis was; OA 88.3%, RA 4.3%, AVN 2.1%, posttraumatic OA 1.1%, DDH 2.1%, Perthes 0.7% and the remainder 1.4%. It is thought likely that many cases of OA had many of the above-named pathologies as a precursor. The mean maximum flexion postoperatively was 98.7 degrees. Uncemented heads (a recent innovation) were used in 10%. Kaplan-Meier survivorship is 93% at 9 to 10 years. Survivorship in the OA subgroup was 96.7% with approximately equal numbers for femoral head collapse, dislocation and cup loosening, but the vast majority due to femoral neck fracture, which in turn was generally associated with the posterior approach.

Discussion: The results of this cohort (including all contributors’ learning curves) indicate highly satisfactory outcomes in terms of HHS and implant longevity. Subclassification of cases into those presenting abnormal anatomy and those with ‘ordinary’ OA indicates better survivorship still in the latter group. The surgical challenge varies more with hip resurfacing than with standard hip arthroplasty and this should be considered when results of surgery are reviewed. The revision options are generally much simpler than after standard THR.

Polymethylmethacrylate remains one of the most enduring materials in orthopaedic surgery. It has a central role in the success of total joint replacement and is also used in newer techniques such as percutaneous vertebroplasty and kyphoplasty.

This article describes the current uses and limitations of polymethylmethacrylate in orthopaedic surgery. It focuses on its mechanical and chemical properties and links these to its clinical performance. The behaviour of antibiotic-loaded bone cement are discussed, together with areas of research that are now shedding light upon the behaviour of this unique biomaterial.

We determined the effect of the surgical approach on perfusion of the femoral head during hip resurfacing arthroplasty by measuring the concentration of cefuroxime in bone samples from the femoral head. A total of 20 operations were performed through either a transgluteal or an extended posterolateral approach.

The concentration of cefuroxime in bone was significantly greater when using the transgluteal approach (mean 15.7 mg/kg; 95% confidence interval 12.3 to 19.1) compared with that using the posterolateral approach (mean 5.6 mg/kg; 95% confidence interval 3.5 to 7.8; p < 0.001). In one patient, who had the operation through a posterolateral approach, cefuroxime was undetectable.

Using cefuroxime as an indirect measure of blood flow, the posterolateral approach was found to be associated with a significant reduction in the blood supply to the femoral head during resurfacing arthroplasty compared with the transgluteal approach.

The aim of this study was to re-assess whether the use of a ‘one-knife technique’ can be considered as safe as the alternative practice of using separate skin and inside knives for elective orthopaedic surgery. A total of 609 knife blades from 203 elective orthopaedic operations, with equal numbers of skin, inside and control blades, were cultured using direct and enrichment media. We found 31 skin blades (15.3%), 22 inside blades (10.8%), and 13 control blades (6.4%) gave bacterial growth.

Of the 31 contaminated skin blades only three (9.7%) had growth of the same organism as found on the corresponding inside blade. It is not known whether contamination of deeper layers in the remaining 90% was prevented by changing the knife after the skin incision. The organisms cultured were predominantly coagulase-negative staphylococci and proprionibacterium species; both are known to be the major culprits in peri-prosthetic infection. Our study suggests that the use of separate skin and inside knives should be maintained as good medical practice, since the cost of a single deep infection in human and financial terms can be considerable.

Joint fluids obtained for diagnostic purposes from 25 patients were assayed for the presence of gentamicin. All of the patients had presented with failing or painful joints at periods up to 10 years following primary hip or knee arthroplasty using gentamicin-impregnated cement. Gentamicin was detected in the joint fluids from 9 of 15 patients with knee prostheses and 4 of 10 with hip prostheses. Gentamicin concentrations ranged from 0.06mg/L to 0.85 mg/L with no significant differences in concentration between patients with hip or knee prostheses, or type of prosthesis, and no identifiable relationship was found gentamicin concentration and the time after primary arthroplasty. Although the majority of the gentamicin concentrations were found to be below the levels required to inhibit susceptible pathogens, we conclude that gentamicin release around failing implants may lead to false negative cultures in some patients and provide selective pressure for the emergence of resistance where infection is present in others.

Introduction: The CPS-Plus cemented, collarless, polished stem, is a double-taper design with rectangular cross section. An additional proximal stem centraliser ensures optimal alignment of the stem and an even cement mantle and has been shown to increase cement pressurisation during insertion.

Guidelines from the National Institute of Clinical Excellence (NICE) recommend comparative clinical evaluation for prostheses without long-term follow-up data and set an initial ‘benchmark’ for performance at 3 years.

Data collection for the CPS-Plus stem is on-going as part of a multi-centre prospective clinical trial. 227 patients have been recruited to the trial and 70 of these have reached 3 years follow-up.

Method: Patients were recruited to the study by surgeons working at three centres in the UK and two in Norway. Patients were fully evaluated pre-operatively. Operative details, post-operative course and follow-up visits at 3, 6, 12, 24, and 36 months were recorded. Postoperative clinical progress was monitored using recognised scoring systems and radiographic assessment.

Results: The mean Harris hip score (0 – 100) improved from 42.7 pre-op to 91.6 at 6 months and 95.8 at 3 years. The mean Merle d’Aubigne and Postel score (0 – 18) improved from 8.55 pre-op to 16.09 at 6 months and 17.08 at 3 years. The mean Oxford hip score (60 – 12) improved from 41.6 pre-op to 14.1 at 3 years. Radiological subsidence at 3 years is less that 1.5mm in 97% of patients and less than 3mm in the remainder. From all 227 implants, there has been one revision for deep infection. There have been no cases of aseptic loosening. Other significant complications include one peri-prosthetic fracture and 4 dislocations, but these were not thought to be related to the design of the implant.

Discussion: The early results of the CPS-Plus femoral stem are encouraging and the prosthesis achieves the 3-year benchmark set out in the NICE guidelines, with a zero revision rate in the first 70 patients recruited to the trial. The prosthesis shares many design features with other well-established collarless, polished, tapered stems. The ease of accurate insertion and improved cement pressurisation resulting from its unique design features should ensure excellent medium to long-term outcome. The multi-centre clinical trial will continue to monitor progress.

Bone cement containing gentamicin may release antibiotic when fractured during revision operations. Tissue samples taken during surgery may be contaminated by gentamicin and give inaccurate microbiological assessment.

We studied five patients in whom cement containing gentamicin had been used in the primary procedure. During revision hip replacement, samples of joint fluid, tissues and cement were taken both before and after disruption of the cement.

With the exception of one sample of joint fluid, low concentrations of gentamicin were recorded in the samples taken before the cement was disrupted, but after disruption the specimens contained gentamicin at concentrations high enough to inhibit or prevent growth of sensitive organisms. The cement contained very high levels up to ten years after insertion.

Our findings suggest that no reliance can be placed on the microbiological assessment of specimens taken once cement splitting has started and that specimens should therefore be taken as early as possible.