Definition and validation of a system for classifying the undersized Corail femoral stem in total hip arthroplasty.

INTRODUCTION: The uncemented total hip arthroplasty relies on a secure initial fixation of the femoral stem to achieve osseointegration. Undersizing of the femoral implant compromises this. Surgeons routinely review postoperative radiographs to assess appropriate sizing, but existing methods of assessment lack standardisation. We present a system of accurately and reliably classifying radiological undersizing, which will help us better understand the factors that might have led to undersizing. AIM: To describe and evaluate a classification system for assessing radiological undersizing of the uncemented stem in hip arthroplasty. METHOD: We conducted a retrospective review of 1,337 consecutive hip arthroplasties using the Corail stem. Two independent investigators reviewed post-operative radiographs and classified them as either appropriately sized or undersized. Undersized stems were sub-categorised into four subtypes: uniformly undersized, varus undersized, valgus undersized or 'cocktail-glass' undersized. Inter- and intra-observer agreement was determined. The accuracy of our classification system was validated by comparison with digital re-templating. We further assessed patient demographics and stem size in relation to sizing. RESULTS: 1 in 5 cases (19.75%) were deemed radiologically undersized. The commonest subtypes of undersizing were uniformly (47%) and varus (39%) undersized. When assessing sizing and subtype categorisation, inter-observer agreement was 89-92% and intra-observer agreement 86%. Classification decisions showed 92% and 97% accuracy for uniformly undersizing and varus undersizing respectively when validated against digital re-templating. Age, gender and smaller stem size were significantly associated with radiological undersizing. The Corail KLA model (125° neck) was found to have a higher incidence of stems undersized in varus. CONCLUSIONS: This study describes and validates a classification system for the analysis of radiological undersizing.

A modified technique to extract fractured femoral stem in revision total hip arthroplasty: A report of two cases.

INTRODUCTION: The removal of well-fixed broken femoral component and cement mantle can be extremely demanding, time consuming and potentially damaging to the host bone. Different methods have been described to extract broken femoral stem yet this remains one of the most challenging prospect to the revision hip surgeon. PRESENTATION OF CASE: The authors present two cases underwent a modified sliding cortical window technique utilising a tungsten carbide drill, Charnley pin retractor and an orthopaedic mallet to aid extraction of a fractured cemented femoral stem in revision total hip arthroplasty. DISCUSSION: The modified technique offers a simple and controlled method in extracting a well fixed fractured cemented femoral stem. It has the advantage of retaining the cement mantle with subsequent good seal of the femoral cortical window secured with cable ready system. Furthermore, tungsten carbide drill bit and Charnley pin retractor are relatively readily available to aid the extraction of the broken stem. Finally, it yields the option of implanting a standard femoral stem and obviates the need for bypassing the cortical window with long revision femoral component. CONCLUSION: Fractured femoral stem is a rare yet a complex and very demanding prospect to both patients and hip surgeons. The sliding cortical window technique utilising tungsten carbide drill and Charnley pin retractor is technically easy and most importantly; preserves host bone stock with cement-in-cement revision hip arthroplasty. We believe this technique can be added to the armamentarium of revision hip surgeon when faced with the challenge of extracting a fractured cemented femoral stem.

Absence of the flexor digitorum longus tendon: an MRI study.

Flexor digitorum longus (FDL) is the primary flexor of the lateral four toes. It is a reliable source of tendon for transfer surgery. We present a case whereby a patient who required a reconstruction for adult acquired flatfoot deformity using FDL as a dynamic structure for transfer was found to have an absent FDL tendon at the time of operation, necessitating the use of flexor hallucis longus (FHL) instead. This unusual finding prompted us to investigate the frequency of absence of the FDL tendon. We reviewed our hospital MRI database of foot and ankle images specifically looking for patients with absence of this tendon. After randomization, 756 images were reviewed independently by two surgeons and a consultant musculoskeletal radiologist. No instances of an absent FDL tendon were identified. In conclusion, the frequency of absence of the FDL tendon is less than 1 in 750. Surgeons who require FDL for tendon transfer surgery need not image the foot preoperatively to anticipate the need for the use of FHL as an alternative.

Genetic aspects of tendinopathy.

Tendinopathy is characterised by a disorganised, haphazard healing response with no histological signs of inflammation. Research on tendon injuries is limited to the description of the condition and its management, and the pathogenesis is still ill defined. Together with known intrinsic and extrinsic factors, genetics may play a significant role in the aetiopathogenesis of tendinopathy. ABO and other closely linked genes, COL5A1, and tenascin-C have all been implicated in the aetiopathogenesis of tendinopathy. However, the precise role of these genes in causing or protecting individuals from developing tendinopathy is yet to be defined. An interaction between the various intrinsic and extrinsic factors with the genetic make-up of an individual may increase the likelihood of one individual developing tendinopathy over another. Tendinopathy may well be polygenic, involving complex interactions between multiple genes, and could possibly run in families. Further investigations should determine the exact role played by genetic influences in maintaining tendon homeostasis and pave the way for gene transfer therapy to be developed for the management of tendinopathies.

A review of epidemiology of paediatric elbow injuries in sports.

The elbow is a common site of orthopaedic injury in the paediatric population. The number of these injuries continues to rise following increased levels of participation in paediatric recreational and competitive sport. Injuries to the paediatric elbow can be classified as either overuse or acute. Delineating injury patterns to the elbow in children can be challenging, given the cartilaginous composition of the distal humerus and the multiple secondary ossification centres that appear and unite with the epiphysis at defined ages. Pitching in baseball, serving in tennis, spiking in volleyball, passing in American football and launching in javelin-throwing can all produce elbow pathology by forceful valgus stress, with medial stretching, lateral compression and posterior impingement. In children and adolescents, the epiphyseal plate is weaker than the surrounding ligaments, predisposing them to epiphyseal plate injuries. On the other hand, post-pubescent or skeletally mature athletes are more prone to tendinous or ligamentous injury. Injuries may cause significant impact on the athlete, parents and healthcare system. With the exception of baseball, there are few prospective cohort studies on the epidemiological trends of childhood elbow injuries in other sports. This paper aims to describe the epidemiological trends in paediatric elbow injuries related to sports, suggests prevention strategies and discusses the scope for further research. A web-based search of existing articles pertaining to paediatric elbow injuries in sports was performed. The implications of acute and overuse injuries and the possibility of permanent damage should be understood by parents, coaches and the athletes. Proper understanding of the intrinsic and extrinsic risk factors that could lead to elbow injuries is thus required. Measures to prevent elbow injuries should include proper coaching, warm-up, officiation, legislation, medical expertise and protective gear. There are still many opportunities for prospective studies and other research projects among young athletes in various sports. Current studies will serve as a baseline for future research to assess the success of specific interventions in reducing the incidence of elbow injury in the paediatric athlete. Further epidemiological studies in various sports will help expand our knowledge and prevent potential disability and deformity in the paediatric elbow.

VOCCs and TREK-1 ion channel expression in human tenocytes.

Mechanosensitive and voltage-gated ion channels are known to perform important roles in mechanotransduction in a number of connective tissues, including bone and muscle. It is hypothesized that voltage-gated and mechanosensitive ion channels also may play a key role in some or all initial responses of human tenocytes to mechanical stimulation. However, to date there has been no direct investigation of ion channel expression by human tenocytes. Human tenocytes were cultured from patellar tendon samples harvested from five patients undergoing routine total knee replacement surgery (mean age: 66 yr; range: 63-73 yr). RT-PCR, Western blotting, and whole cell electrophysiological studies were performed to investigate the expression of different classes of ion channels within tenocytes. Human tenocytes expressed mRNA and protein encoding voltage-operated calcium channel (VOCC) subunits (Ca alpha(1A), Ca alpha(1C), Ca alpha(1D), Ca alpha(2)delta(1)) and the mechanosensitive tandem pore domain potassium channel (2PK(+)) TREK-1. They exhibit whole cell currents consistent with the functional expression of these channels. In addition, other ionic currents were detected within tenocytes consistent with the expression of a diverse array of other ion channels. VOCCs and TREK channels have been implicated in mechanotransduction signaling pathways in numerous connective tissue cell types. These mechanisms may be present in human tenocytes. In addition, human tenocytes may express other channel currents. Ion channels may represent potential targets for the pharmacological management of chronic tendinopathies.

Molecular events in tendinopathy: a role for metalloproteases.

Disorganized, haphazard ineffective healing is a constant feature of chronic tendinopathy. Normal tendon is composed mostly of type I collagen. Tendinopathic tendons, conversely, have a greater proportion of type III collagen, which is associated with tendon rupture. Matrix metalloproteinases (MMPs) are involved in remodelling of the extracellular matrix (ECM) of tendons, because they are either up- or down-regulated in tendinopathy. A balance between MMPs and tissue inhibitors of metalloproteinases is required to maintain tendon homeostasis. The mechanism of activation of MMPs is poorly understood, and their precise role in tendinopathy is unclear.