Ankylosing spondylitis (AS) is a progressive multisystem chronic inflammatory disorder. The hallmark of this pathological process is a progressive fusion of the zygapophyseal joints and disc spaces of the axial skeleton, leading to a rigid kyphotic deformity and positive sagittal balance. The ankylosed spine is unable to accommodate normal mechanical forces, rendering it brittle and susceptible to injury. Traumatic hyperextension injury of the cervical spine leading to atlantoaxial subluxation (AAS) in AS patients can often be fatal. We report a non-traumatic mechanism of injury in AS progressing to AAS attributable to persistent hyperextension, which resulted in fatal migration of C2 through the foramen magnum. Cite this article: Bone Joint J 2013;95-B:206–9

Abnormal sagittal kinematics after total knee replacement (TKR) can adversely affect functional outcome. Two important determinants of knee kinematics are component geometry and the presence or absence of a posterior-stabilising mechanism (cam-post). We investigated the influence of these variables by comparing the kinematics of a TKR with a polyradial femur with a single radius design, both with and without a cam-post mechanism. We assessed 55 patients, subdivided into four groups, who had undergone a TKR one year earlier by using an established fluoroscopy protocol in order to examine their kinematics in vivo. The kinematic profile was obtained by measuring the patellar tendon angle through the functional knee flexion range (0° to 90°) and the results compared with 14 normal knees. All designs of TKR had abnormal sagittal kinematics compared with the normal knee. There was a significant (p < 0.05) difference between those of the two TKRs near to full extension. The presence of the cam-post mechanism did not influence the kinematics for either TKR design. These differences suggest that surface geometry is a stronger determinant of kinematics than the presence or absence of a cam-post mechanism for these two designs. This may be because the cam-post mechanism is ineffective

Disruption of the extensor mechanism in total knee arthroplasty may occur by tubercle avulsion, patellar or quadriceps tendon rupture, or patella fracture, and whether occurring intra-operatively or post-operatively can be difficult to manage and is associated with a significant rate of failure and associated complications. This surgery is frequently performed in compromised tissues, and repairs must frequently be protected with cerclage wiring and/or augmentation with local tendon (semi-tendinosis, gracilis) which may also be used to treat soft-tissue loss in the face of chronic disruption. Quadriceps rupture may be treated with conservative therapy if the patient retains active extension. Component loosening or loss of active extension of 20° or greater are clear indications for surgical treatment of patellar fracture. Acute patellar tendon disruption may be treated by primary repair. Chronic extensor failure is often complicated by tissue loss and retraction can be treated with medial gastrocnemius flaps, achilles tendon allografts, and complete extensor mechanism allografts. Attention to fixing the graft in full extension is mandatory to prevent severe extensor lag as the graft stretches out over time

Aims

Paediatric triplane fractures and adult trimalleolar ankle fractures both arise from a supination external rotation injury. By relating the experience of adult to paediatric fractures, clarification has been sought on the sequence of injury, ligament involvement, and fracture pattern of triplane fractures. This study explores the similarities between triplane and trimalleolar fractures for each stage of the Lauge-Hansen classification, with the aim of aiding reduction and fixation techniques.

1. The influence of various methods of preserving bone on the calcifying mechanism of the tibial epiphysial cartilage of rachitic rats was studied. An in vitro calcification technique was employed. 2. Preservation by deep freezing, aqueous merthiolate, boiling, or acetone inactivated the calcifying mechanism. 3. The inactivation was reversed with calcium ions, most readily in the deep-frozen bones, less readily in the merthiolate treated bones, still less readily in the acetone stored bones, and least in boiled bones. 4. Exposure to calcium ions before preservation in the deep-freeze chest prevented inactivation. 5. The inactivation, reactivation and survival of the calcifying mechanism were confirmed by metachromasia studies. 6. The theory of the mode of action of calcium chloride on reactivation and survival of the calcifying mechanism is presented

Anterior knee pain due to dysplasia of the extensor mechanism is common. We have studied 137 knees (103 patients) in order to identify a rapid and reproducible radiological feature which would indicate the need for further analysis. Overall, 67 knees (49%) had at least one radiological abnormality; 70 (51%) were considered normal. There were five cases of Dejour type-3 dysplasia of the femoral trochlea, nine of type-2 and 12 of type-1. There were 49 cases of patella alta and five of patella infera. Four knees had an abnormal lateral patellofemoral angle (patellar tilt), and in 15 knees there was more than one abnormality. Classification of trochlear dysplasia was difficult and showed poor reproducibility. This was also true for the measurement of the lateral patellofemoral angle. Patellar height was more easily measured but took time. The sulcus angle is an easily and rapidly measurable feature which was reproducible and was closely related to other features of dysplasia of the extensor mechanism. The finding of a normal sulcus angle suggested that seeking other radiological evidence of malalignment of the extensor mechanism was unlikely to reveal additional useful information. The severity of other features of dysplasia of the extensor mechanism correlated with increasing sulcus angle

Deficiency of the abductor mechanism is a well-recognised cause of pain and limping after total hip replacement (THR). This can be found incidentally at the time of surgery, or it may arise as a result of damage to the superior gluteal nerve intra-operatively, or after surgery owing to mechanical failure of the abductor muscle repair or its detachment from the greater trochanter. The incidence of abductor failure has been reported as high as 20% in some studies. The management of this condition remains a dilemma for the treating surgeon. We review the current state of knowledge concerning post-THR abductor deficiency, including the aetiology, diagnosis and management, and the outcomes of surgery for this condition. Cite this article: Bone Joint J 2013;95-B:343–7

1. Twenty cases of tarso-metatarsal joint injury have been studied with regard to the mechanism of injury, and experiments have been done on cadavers to confirm clinical impressions. 2. Injuries of the tarso-metatarsal joints occur by direct and indirect mechanisms, the latter being more common. 3. Indirect injuries occur in at least two ways-namely, acute abduction of the forefoot and plantar-flexion of the forefoot. 4. Most of the indirect injuries occur when the ankle joint is in a plantar-flexed position. 5. Whereas this foot injury once gained prominence on the field of battle amongst cavalrymen, it is currently associated with the motor car, the step ladder, the toboggan, the joy-rider, and commonly the simple misguided step

We describe the influence of the angle of immobilisation during partial weight-bearing on the forces across the extensor mechanism of the knee. Gait analysis was performed on eight healthy male subjects with the right knee in an orthotic brace locked at 0°, 10°, 20° and 30°, with the brace unlocked and also without a brace. The ground reaction force, the angle of the knee and the net external flexion movement about the knee were measured and the extensor mechanism force was calculated. The results showed a direct non-linear relationship between the angle of knee flexion and the extensor mechanism force. When a brace was applied, the lowest forces occurred when the brace was locked at 0°. At 30° the forces approached the failure strength of some fixation devices. We recommend that for potentially unstable injuries of the extensor mechanism, when mobilising with partial weight-bearing, the knee should be flexed at no more than 10°

Six mechanisms which may produce fracture-separation of the proximal humeral epiphysis are proposed. Four of them are illustrated by case reports. It is suggested that they may be differentiated by examination of the patient and study of the radiographs. In unstable fractures manipulation is indicated and, if performed with an understanding of the mechanism of injury, will produce a stable reduction

A consecutive series of 150 patients with clavicular fractures is presented. In 81% detailed information regarding the mechanism of the injury was available and, of these, 94% had fractured their clavicle from a direct blow on the shoulder; only 6% had fallen on the outstretched hand. This finding, at variance with commonly held views regarding the mechanism of this injury, was further investigated by biomechanical analysis of the forces involved in clavicular fractures. The biomechanical model supported the clinical findings

1 . The concept of the capsular mechanism of the shoulder joint with regard to recurrent anterior dislocation of the shoulder has been defined and a survey of the literature presented. 2. An anatomical, including an embryological, investigation of shoulder joints with special reference to the structure and function of the glenoid labrum and to the variations in the arrangement of the gleno-humeral ligaments and the synovial recesses of the anterior capsular mechanism is reported. The labrum, which is generally believed to be a consistent, fibrocartilaginous structure, is shown to be a redundant portion of capsular tissue and a continuation of the capsule as it attaches to the osseous glenoid rim. The fibrocartilaginous element is confined to a small transition zone at the capsular attachment in the great majority of cases. The great variability in the arrangement of the gleno-humeral ligaments and synovial recesses is stressed, and it is shown that an anterior pouch of variable size is present when the middle gleno-humeral ligament is attached to the scapular neck and not to the labrum. 3. The basic lesions of the anterior capsular mechanism found at operation for recurrent anterior dislocation of the shoulder in twenty-five consecutive cases using a modified Bankart procedure with a standard anterior approach to the joint are reported, and the findings are correlated with the results of the anatomical investigation. In most cases the lesions were found to be of the Bankart type with or without avulsion of the periosteum of the scapular neck. In four cases, however, the soft-tissue attachment to the anterior glenoid rim was intact; in those cases a large synovial pouch was present and the middle gleno-humeral ligament was either not discernible or it arose from the scapular neck. In all cases a postero-lateral notch on the humeral head was palpable and laxity of the subscapularis could be demonstrated. When measured, the joint capacity was always greatly augmented. 4. The present work shows, from a basic standpoint, that Bankart's original idea that the recurrent state was due to the failure of healing of the fractured fibrocartilaginous glenoid labrum is no longer tenable. 5. Finally, the anomalous attachment or the insufficient development of the middle gleno-humeral ligament in certain cases of recurrent anterior shoulder dislocation is shown to provide the anatomical basis for the recurrent state in these cases; this is the weak area in the antero-inferior part of the capsule which has been described in the literature for the past hundred years. Thus we have returned to the original view of Hippocrates

We present the histological findings of an extensor mechanism allograft which was used in a total knee arthroplasty two years after implantation. Analysis of the graft was undertaken at four distinct anatomical levels and it was found to be incorporated into host tissue at each level. A wedge of fibrinoid necrosis, probably related to impingement of the graft on the tibial polyethylene insert, was seen. Impingement may play a role in the injury and necrosis of an allograft and may be one mode of failure in an extensor mechanism allograft

We measured the contact areas and contact stresses at the post-cam mechanism of a posterior-stabilised total knee arthroplasty when a posterior force of 500 N was applied to the Kirschner Performance, Scorpio Superflex, NexGen LPS Flex Fixed, and NexGen LPS Flex Mobile knee systems. Measurements were made at 90°, 120°, and 150° of flexion both in neutral rotation and 10° of internal rotation of the tibial component. Peak contact stresses at 90°, 120°, and 150° were 24.0, 33.9, and 28.8 MPa, respectively, for the Kirschner; 26.0, 32.4, and 22.1 MPa, respectively, for the Scorpio; and 34.1, 31.5, and 32.5 MPa, respectively, for the NexGen LPS Flex Fixed. With an internally rotated tibia, the contact stress increased significantly with all the fixed-bearing arthroplasties but not with the NexGen LPS Flex Mobile arthroplasty. The post-cam design should be modified in order to provide a larger contact area whilst avoiding any impingement and edge loading

The mechanism of the pivot shift was investigated by analysing movements under valgus torque in 29 fresh cadaveric knees. The movements were measured in three dimensions, using biplanar photography, when all the ligaments were intact, and then after the ligaments were sequentially divided. When only the anterior cruciate ligament was sectioned, the pivot shift occurred in seven out of 20 knees examined. In the other 13, though the pivot shift was not observed, an abnormal internal rotation occurred at between 10 degrees and 50 degrees of flexion. Division of the iliotibial tract in addition to division of the anterior cruciate ligament stopped the pivot shift, as the tibia remained internally rotated throughout the range of flexion. The axis of rotation of the pivot shift was located at the medial collateral ligament, which was kept tight by the applied valgus torque. The sudden movement in the pivot shift was caused by a complex interaction between the geometry of the knee and the valgus torque applied

We developed an in vivo model of the attachment of a patellar tendon to a metal implant to simulate the reconstruction of an extensor mechanism after replacement of the proximal tibia. In 24 ewes, the patellar tendon was attached to a hydroxyapatite (HA)-coated titanium prosthesis. In 12, the interface was augmented with autograft containing cancellous bone and marrow. In the remaining ewes, the interface was not grafted. Kinematic gait analysis showed nearly normal function of the joint by 12 weeks. Force-plate assessment showed a significant increase in functional weight-bearing in the grafted animals (p = 0.043). The tendon-implant interface showed that without graft, encapsulation of fibrous tissue occurred. With autograft, a developing tendon-bone-HA-implant interface was observed at six weeks and by 12 weeks a layered tendon-fibrocartilage-bone interface was seen which was similar to a direct-type enthesis. With stable mechanical fixation, an appropriate bioactive surface and biological augmentation the development of a functional tendon-implant interface can be achieved

This study reports the clinical outcome of reconstruction of deficient abductor muscles following revision total hip arthroplasty (THA), using a fresh–frozen allograft of the extensor mechanism of the knee. A retrospective analysis was conducted of 11 consecutive patients with a severe limp because of abductor deficiency which was confirmed on MRI scans. The mean age of the patients (three men and eight women) was 66.7 years (52 to 84), with a mean follow-up of 33 months (24 to 41). . Following surgery, two patients had no limp, seven had a mild limp, and two had a persistent severe limp (p = 0.004). The mean power of the abductors improved on the Medical Research Council scale from 2.15 to 3.8 (p < 0.001). Pre-operatively, all patients required a stick or walking frame; post-operatively, four patients were able to walk without an aid. Overall, nine patients had severe or moderate pain pre-operatively; ten patients had no or mild pain post-operatively. . At final review, the Harris hip score was good in five patients, fair in two and poor in four. . We conclude that using an extensor mechanism allograft is relatively effective in the treatment of chronic abductor deficiency of the hip after THA when techniques such as local tissue transfer are not possible. . Longer-term follow-up is necessary before the technique can be broadly applied. Cite this article: Bone Joint J 2015;97-B:1050–5

By polarising microscope and x-ray crystallographic techniques the annulus fibrosus has been shown to consist of regularly oriented sheets of collagen fibres. These results have been interpreted in terms of an elastic mechanism whereby thrust from the nucleus causes increased girth in the annulus. It is suggested that this is accomplished by a change in the angle between the axis of the fibres in adjacent uniaxial layers of the annulus. Furthermore, the loss of elasticity of the intervertebral disc associated with age would seem to be mainly due to changes occurring in the nucleus pulposus

1. An experimental study of the healing mechanism in circumscribed defects in femora of albino rats of the Wistar strain is described. 2. Only the outer one-fifth of the defect is repaired by subperiosteal bony callus, the rest of the defect being repaired by endosteal callus. 3. Subperiosteal callus does not bridge the defect until endosteal callus is developed fully. 4. As peripheral callus matures the greater part of the endosteal callus is resorbed, with the exception of trabeculae attached to the margin of the defect. 5. The resorbed area in the medullary part of the defect is gradually obliterated by deposition of inner circumferential lamellae. 6. There appear to be differences between the mechanism responsible for repair of fractures of a long bone and that which heals circumscribed bone defects

Studies derived from analyses of radiographs and dissections of cadaveric wrists have been directed at testing and disproving the commonly held theories that link chip fractures of the os triquetrum with avulsion. The authors found that the mechanism of such injuries involved a chisel action of the ulnar styloid upon the dorsum of the os triquetrum; furthermore, the impact of a fall on the outstretched arm with the hand rigidly held in strong dorsiflexion and ulnar deviation could be forceful enough to fracture the body of the os triquetrum as well. In all cases a striking prolongation of the ulnar styloid, beyond the surface of the ulnar head, was consistently noted

1. The semilunar cartilages are part of the rotator mechanism of the knee joint. 2. Movement of the weight-bearing knee comprises synchronous lateral rotation of the tibia with extension and medial rotation of the tibia with flexion. 3. When this synchrony is disturbed, injuries to the semilunar cartilages result. 4. Damage to the anterior two-thirds of the medial cartilage blocks lateral rotation of the tibia, with consequent physical signs that are pathognomonic of the retracted and the bowstring cartilage, which are the most common types of injury. 5. Each type of cartilage injury produces its own pattern of erosion of articular cartilage and its own sequence of symptoms as so-called arthritis develops. 6. The sequence of symptoms may be halted and often reversed by removal of the torn cartilage. Operation is warranted in most cases however long the history and whatever the age of the patient. 7. The development of medial retropatellar arthritis is explained. The symptoms are often relieved by removal of the medial semilunar cartilage and adequate post-operative rehabilitation

Recent surveys have shown that idiopathic structural scoliosis of mild degree is generally not progressive. We will propose a mechanism which may be responsible for deterioration in the few. It has been observed that the spinal cord, although displaced towards the concavity, does not rotate in company with the vertebrae, thus exposing the emerging nerve roots to the effects of traction and possibly of entrapment. We suggest that progression occurs when the neuraxis is unable to adjust to the change in the anatomy of vertebral column. Our proposition is based upon our findings in a complete spinal column obtained from a baby with structural scoliosis. Support is provided by intercostal angiography, and by observations upon normal anatomy, the pathological anatomy of mature scoliotic spines and the anatomy of contrived scoliosis in normal spines. Although our histological and electrophysiological investigations are incomplete we can demonstrate a significant increase in degenerate cells in the dorsal root ganglia at the apex on the convex side. Lack of suitable necropsy material prevents us from confirming our observations so that our report is inevitably preliminary. We enter a plea that careful examination of the neuraxis be undertaken whenever a specimen of a scoliotic spine becomes available

Experience with thirty-eight Asian children and adolescents who presented with either stiffness of the knee, genu recurvatum, habitual dislocation of the patella or congenital lateral dislocation of the patella showed that all those disorders were manifestations of contracture of the extensor mechanism, which fell into two groups according to the components involved. In Group I the main components affected were in the midline of the limb, namely rectus femoris and vastus intermedius; these patients presented with varying degrees of stiffness of the knee, or worse, with genu recurvatum. In Group II the main components involved were lateral to the midline of the limb, namely vastus lateralis and the ilio-tibial band; these patients presented with habitual dislocation of the patella, or worse, congenital lateral dislocation of the patella. In both groups untreated patients developed secondary adaptive changes such as subluxation of the tibia or marked genu valgum which made operative procedures more formidable and less effective. Release of the contracture should therefore be performed as early as possible

The factors involved in the mechanism leading to traumatic posterior dislocation of the hip are examined. In 47 adult patients who had previously suffered such a dislocation, ultrasound scans were used to measure femoral anteversion on both the affected and the uninjured side. In 36 normal adult volunteers, used as controls, similar measurements were made. Femoral anteversion on both the injured and uninjured side was significantly reduced in the patients compared with the volunteers. These findings are discussed in the light of previous work which indicates that medial rotation is a factor in the mechanism of posterior dislocation of the hip. It is suggested that reduced anteversion acts like medial rotation to make the hip more susceptible to posterior dislocation, and that the less the anteversion the more likely is the injury to be a dislocation rather than a fracture-dislocation. It is concluded that patients who suffer such dislocated hips belong at one extreme of the normal population, having either reduced femoral anteversion or even retroversion, and that this anatomical feature selects towards hip dislocation rather than to injury of the femoral shaft, knee or tibia during the appropriate type of accident

The aim of this study was to analyse the gait pattern, muscle force and functional outcome of patients who had undergone replacement of the proximal tibia for tumour and alloplastic reconstruction of the extensor mechanism using the patellar-loop technique. Between February 1998 and December 2009, we carried out wide local excision of a primary sarcoma of the proximal tibia, proximal tibial replacement and reconstruction of the extensor mechanism using the patellar-loop technique in 18 patients. Of these, nine were available for evaluation after a mean of 11.6 years (0.5 to 21.6). The strength of the knee extensors was measured using an Isobex machine and gait analysis was undertaken in our gait assessment laboratory. Functional outcome was assessed using the American Knee Society (AKS) and Musculoskeletal Tumor Society (MSTS) scores. The gait pattern of the patients differed in ground contact time, flexion heel strike, maximal flexion loading response and total sagittal plane excursion. The mean maximum active flexion was 91° (30° to 110°). The overall mean extensor lag was 1° (0° to 5°). The mean extensor muscle strength was 25.8% (8.3% to 90.3%) of that in the non-operated leg (p < 0.001). The mean functional scores were 68.7% (43.4% to 83.3%) (MSTS) and 71.1 (30 to 90) (AKS functional score). In summary, the results show that reconstruction of the extensor mechanism using this technique gives good biomechanical and functional results. The patients’ gait pattern is close to normal, except for a somewhat stiff knee gait pattern. The strength of the extensor mechanism is reduced, but sufficient for walking. . Cite this article: Bone Joint J 2015;97-B:1063–9

1. The claw position of a finger with intrinsic paralysis is caused by the blocking effect of the transverse lamina on the long extensor. This starts as soon as the metacarpo-phalangeal joint is hyperextended, and increases with further hyperextension. Thus the long extensor loses its pull on the interphalangeal joints and allows them to flex. Therefore, in intrinsic paralysis the claw position can be prevented or cured by keeping the metacarpo-phalangeal joint in flexion, however slight, which can be done by splinting, by tenodesis or by capsulorrhaphy.

2. Replacement of the intrinsics by some active element, although it may improve the action of the fingers, is not necessary for the correction of claw finger. The function of the intrinsics in the prevention of claw finger is not to be found in their extending effect on the interphalangeal joints, but in the flexion effect on the metacarpo-phalangeal joint, or at least in preventing its hyperextension. This is in accordance with the fact that loss of intrinsic function is disastrous only in supple fingers, in which the metacarpo-phalangeal joints tend to assume extreme degrees of hyperextension (Riordan 1953, Brand 1958). In such fingers, the wide range of hyperextension available at the metacarpo-phalangeal joints is, of course, part of a generalised laxity of the soft parts of the fingers. These soft parts generally tend to counteract the tendency to clawing; the less their resistance, the more the human finger as a whole will tend to behave like a musculo-articular model, and such a model without intrinsics will always immediately assume the claw position.

Segmental spinal reflexes (stretch reflexes) were studied in patients with scoliosis. The proprioceptive responses to the phasic stretch of the paraspinal muscles were asymmetric in all patients, and were increased on the convex side. The asymmetry was more pronounced when the patients were standing. The observed asymmetry of the reflex responses was taken to indicate asymmetry in the tone and postural activity of the superficial layer of the paraspinal muscles. A reciprocal relationship was found in the segmental reflex organisation between the superficial and deep layers of the paraspinal muscles. The increase in reflex response of the superficial muscles on the convex side can be due to diminished reciprocal inhibition from weak, deep muscles. Thus a segmental neurogenic disorder involving predominantly the deep paraspinal muscles of the convexity of the curve may be the primary lesion responsible for the development of scoliosis.

Many knee surgeons flex the knee and sometimes also extend the hip before inflating a tourniquet on the thigh. This practice stems from the belief that these manoeuvres prevent excessive strain on the quadriceps during surgery, the assumption being that movement of the muscle is restricted by an inflated tourniquet. We therefore examined, using ultrasound, the movement of the quadriceps muscle above and below the tourniquet before and after inflation.

We applied a tourniquet of standard size to the thigh of five volunteers for approximately five minutes. A bubble of air was injected into the quadriceps muscle above the tourniquet and was the proximal point of reference. The musculotendinous junction was the distal point. The movement of the reference point was measured by ultrasound before and after inflation of the tourniquet. Each measurement was repeated with either the knee flexed and the hip extended, or the hip flexed and the knee extended. The mean and standard deviation were recorded.

Before inflation the mean amount of passive movement was 1.1 ± 0.13 cm proximal and 4.0 ± 0.08 cm distal to the tourniquet, with a range of movement of the knee of 0° to 137° (6.7°). After inflation the mean passive movement was 1.0 ± 0.07 cm proximal and 4.0 ± 0.08 cm distal to the tourniquet with a range of 0° to 132° (± 7.6°).

The ultrasound findings therefore have shown no evidence of restriction of the quadriceps muscle by an inflated tourniquet.

1. A clinical test of diagnostic significance in Morton's metatarsalgia is described.

2. Findings at operation in twelve cases are recorded.

3. The causation of the digital neuroma is discussed.

A case of cervical traumatic paraplegia is described in which there was no evidence of damage to vertebrae, discs or ligaments. Experimental evidence suggests that such injuries may be caused by inward bulging of the ligamentum flavum during hyperextension. The reasons why this inward bulging may occur, despite the elasticity of the ligamentum flavum, are discussed. Treatment of such cases is considered and the importance of avoiding extension emphasised.

We used an in vivo model to assess the use of an autogenous cancellous bone block and marrow graft for augmenting tendon reattachment to metallic implants. We hypothesised that augmentation of the tendon-implant interface with a bone block would enable retention of the graft on the implant surface, enhance biological integration, and result in more consistent functional outcomes compared with previously reported morcellised graft augmentation techniques.

A significant improvement in functional weight-bearing was observed between six and 12 weeks. The significant increase in ground reaction force through the operated limb between six and 12 weeks was greater than that reported previously with morcellised graft augmented reconstructions. Histological appearance and collagen fibre orientation with bone block augmentation more closely resembled that of an intact enthesis compared with the morcellised grafting technique. Bone block augmentation of tendon-implant interfaces results in more reliable functional and histological outcomes, with a return to pre-operative levels of weight-bearing by 24 weeks.

Aims. Isolated acetabular liner exchange with a highly crosslinked polyethylene (HXLPE) component is an option to address polyethylene wear and osteolysis following total hip arthroplasty (THA) in the presence of a well-fixed acetabular shell. The liner can be fixed either with the original locking mechanism or by being cemented within the acetabular component. Whether the method used for fixation of the HXLPE liner has any bearing on the long-term outcomes is still unclear. Methods. Data were retrieved for all patients who underwent isolated acetabular component liner exchange surgery with a HXLPE component in our institute between August 2000 and January 2015. Patients were classified according to the fixation method used (original locking mechanism (n = 36) or cemented (n = 50)). Survival and revision rates were compared. A total of 86 revisions were performed and the mean duration of follow-up was 13 years. Results. A total of 20 patients (23.3%) had complications, with dislocation alone being the most common (8.1%; 7/86). Ten patients (11.6%) required re-revision surgery. Cementing the HXLPE liner (8.0%; 4/50) had a higher incidence of re-revision due to acetabular component liner-related complications than using the original locking mechanism (0%; 0/36; p = 0.082). Fixation using the original locking mechanism was associated with re-revision due to acetabular component loosening (8.3%; 3/36), compared to cementing (0%; 0/50; p = 0.038). Overall estimated mean survival was 19.2 years. There was no significant difference in the re-revision rate between the original locking mechanism (11.1%; 4/36) and cementing (12.0%; 6/50; p = 0.899). Using Kaplan-Meier survival analysis, the revision-free survival of HXLPE fixed with the original locking mechanism and cementing was 94.1% and 93.2%, respectively, at ten years, and 84.7% and 81.3%, respectively, at 20 years (p = 0.840). Conclusion. The re-revision rate and the revision-free survival following acetabular component liner exchange revision surgery using the HXLPE liner were not influenced by the fixation technique used. Both techniques were associated with good survival at a mean follow-up of 13 years. Careful patient selection is necessary for isolated acetabular component liner exchange revision surgery in order to achieve the best outcomes. Cite this article: Bone Joint J 2024;106-B(5 Supple B):59–65

Periprosthetic joint infection (PJI) is a difficult complication requiring a comprehensive eradication protocol. Cure rates have essentially stalled in the last two decades, using methods of antimicrobial cement joint spacers and parenteral antimicrobial agents. Functional spacers with higher-dose antimicrobial-loaded cement and antimicrobial-loaded calcium sulphate beads have emphasized local antimicrobial delivery on the premise that high-dose local antimicrobial delivery will enhance eradication. However, with increasing antimicrobial pressures, microbiota have responded with adaptive mechanisms beyond traditional antimicrobial resistance genes. In this review we describe adaptive resistance mechanisms that are relevant to the treatment of PJI. Some mechanisms are well known, but others are new. The objective of this review is to inform clinicians of the known adaptive resistance mechanisms of microbes relevant to PJI. We also discuss the implications of these adaptive mechanisms in the future treatment of PJI. Cite this article: Bone Joint J 2022;104-B(5):575–580

Aims. Tibial tubercle osteotomy (TTO) facilitates surgical exposure and protects the extensor mechanism during revision total knee arthroplasty (rTKA). The purpose of this study was to determine the rates of bony union, complications, and reoperations following TTO during rTKA, to assess the functional outcomes of rTKA with TTO at two years’ minimum follow-up, and to identify the risk factors of failure. Methods. Between January 2010 and September 2020, 695 rTKAs were performed and data were entered into a prospective database. Inclusion criteria were rTKAs with concomitant TTO, without extensor mechanism allograft, and a minimum of two years’ follow-up. A total of 135 rTKAs were included, with a mean age of 65 years (SD 9.0) and a mean BMI of 29.8 kg/m. 2. (SD 5.7). The most frequent indications for revision were infection (50%; 68/135), aseptic loosening (25%; 34/135), and stiffness (13%; 18/135). Patients had standardized follow-up at six weeks, three months, six months, and annually thereafter. Complications and revisions were evaluated at the last follow-up. Functional outcomes were assessed using the Knee Society Score (KSS) and range of motion. Results. The mean follow-up was 51 months (SD 26; 24 to 121). Bony union was confirmed in 95% of patients (128/135) at a mean of 3.4 months (SD 2.7). The complication rate was 15% (20/135), consisting of nine tibial tubercle fracture displacements (6.7%), seven nonunions (5%), two delayed unions, one tibial fracture, and one wound dehiscence. Seven patients (5%) required eight revision procedures (6%): three bone grafts, three osteosyntheses, one extensor mechanism allograft, and one wound revision. The functional scores and flexion were significantly improved after surgery: mean KSS knee, 48.8 (SD 17) vs 79.6 (SD 20; p < 0.001); mean KSS function, 37.6 (SD 21) vs 70.2 (SD 30; p < 0.001); mean flexion, 81.5° (SD 33°) vs 93° (SD 29°; p = 0.004). Overall, 98% of patients (n = 132) had no extension deficit. The use of hinge implants was a significant risk factor for tibial tubercle fracture (p = 0.011). Conclusion. TTO during rTKA was an efficient procedure to improve knee exposure with a high union rate, but had significant specific complications. Functional outcomes were improved at mid term. Cite this article: Bone Joint J 2023;105-B(10):1078–1085

Periprosthetic joint infection represents a devastating complication after total elbow arthroplasty. Several measures can be implemented before, during, and after surgery to decrease infection rates, which exceed 5%. Debridement with antibiotics and implant retention has been reported to be successful in less than one-third of acute infections, but still plays a role. For elbows with well-fixed implants, staged retention seems to be equally successful as the more commonly performed two-stage reimplantation, both with a success rate of 70% to 80%. Permanent resection or even amputation are occasionally considered. Not uncommonly, a second-stage reimplantation requires complex reconstruction of the skeleton with allografts, and the extensor mechanism may also be deficient. Further developments are needed to improve our management of infection after elbow arthroplasty. Cite this article: Bone Joint J 2024;106-B(11):1321–1326

The critical relationship between airborne microbiological contamination in an operating theatre and surgical site infection (SSI) is well known. The aim of this annotation is to explain the scientific basis of using settle plates to audit the quality of air, and to provide information about the practicalities of using them for the purposes of clinical audit. The microbiological quality of the air in most guidance is defined by volumetric sampling, but this method is difficult for surgical departments to use on a routine basis. Settle plate sampling, which mimics the mechanism of deposition of airborne microbes onto open wounds and sterile instruments, is a good alternative method of assessing the quality of the air. Current practice is not to sample the air in an operating theatre during surgery, but to rely on testing the engineering systems which deliver the clean air. This is, however, not good practice and microbiological testing should be carried out routinely during operations as part of clinical audit. Cite this article: Bone Joint J 2024;106-B(9):887–891

Aims. Frailty greatly increases the risk of adverse outcome of trauma in older people. Frailty detection tools appear to be unsuitable for use in traumatically injured older patients. We therefore aimed to develop a method for detecting frailty in older people sustaining trauma using routinely collected clinical data. Methods. We analyzed prospectively collected registry data from 2,108 patients aged ≥ 65 years who were admitted to a single major trauma centre over five years (1 October 2015 to 31 July 2020). We divided the sample equally into two, creating derivation and validation samples. In the derivation sample, we performed univariate analyses followed by multivariate regression, starting with 27 clinical variables in the registry to predict Clinical Frailty Scale (CFS; range 1 to 9) scores. Bland-Altman analyses were performed in the validation cohort to evaluate any biases between the Nottingham Trauma Frailty Index (NTFI) and the CFS. Results. In the derivation cohort, five of the 27 variables were strongly predictive of the CFS (regression coefficient B = 6.383 (95% confidence interval 5.03 to 7.74), p < 0.001): age, Abbreviated Mental Test score, admission haemoglobin concentration (g/l), pre-admission mobility (needs assistance or not), and mechanism of injury (falls from standing height). In the validation cohort, there was strong agreement between the NTFI and the CFS (mean difference 0.02) with no apparent systematic bias. Conclusion. We have developed a clinically applicable tool using easily and routinely measured physiological and functional parameters, which clinicians and researchers can use to guide patient care and to stratify the analysis of quality improvement and research projects. Cite this article: Bone Joint J 2024;106-B(4):412–418

Aims. The outcomes following nonoperative management of minimally displaced greater tuberosity (GT) fractures, and the factors which influence patient experience, remain poorly defined. We assessed the early patient-derived outcomes following these injuries and examined the effect of a range of demographic- and injury-related variables on these outcomes. Methods. In total, 101 patients (53 female, 48 male) with a mean age of 50.9 years (19 to 76) with minimally displaced GT fractures were recruited to a prospective observational cohort study. During the first year after injury, patients underwent experiential assessment using the Disabilities of the Arm, Shoulder and Hand (DASH) score and assessment of associated injuries using MRI performed within two weeks of injury. The primary outcome was the one-year DASH score. Multivariate analysis was used to assess the effect of patient demographic factors, complications, and associated injuries, on outcome. Results. The mean DASH score improved from 42.3 (SD 9.6) at six weeks post-injury, to 19.5 (SD 14.3) at one-year follow-up (p < 0.001), but outcomes were mixed, with 30 patients having a DASH score > 30 at one year. MRI revealed a range of associated injuries, with a full-thickness rotator cuff tear present in 19 patients (19%). Overall, 11 patients (11%) developed complications requiring further operative intervention; 20 patients (21%) developed post-traumatic secondary shoulder stiffness. Multivariate analysis revealed a high-energy mechanism (p = 0.009), tobacco consumption (p = 0.033), use of mobility aids (p = 0.047), a full-thickness rotator cuff tear (p = 0.002), and the development of post-traumatic secondary shoulder stiffness (p = 0.035) were independent predictors of poorer outcome. Conclusion. The results of nonoperative management of minimally displaced GT fractures are heterogeneous. While many patients have satisfactory early outcomes, a substantial subgroup fare much worse. There is a high prevalence of rotator cuff injuries and post-traumatic shoulder stiffness, and their presence is associated with poorer patient experience. Furthermore, patients who have a high-energy injury, smoke, or use walking aids, have worse outcomes. Cite this article: Bone Joint J 2023;105-B(5):534–542

Aims. The aim of this study was to compare a bicruciate-retaining (BCR) total knee arthroplasty (TKA) with a posterior cruciate-retaining (CR) TKA design in terms of kinematics, measured using fluoroscopy and stability as micromotion using radiostereometric analysis (RSA). Methods. A total of 40 patients with end-stage osteoarthritis were included in this randomized controlled trial. All patients performed a step-up and lunge task in front of a monoplane fluoroscope one year postoperatively. Femorotibial contact point (CP) locations were determined at every flexion angle and compared between the groups. RSA images were taken at baseline, six weeks, three, six, 12, and 24 months postoperatively. Clinical and functional outcomes were compared postoperatively for two years. Results. The BCR-TKA demonstrated a kinematic pattern comparable to the natural knee’s screw-home mechanism in the step-up task. In the lunge task, the medial CP of the BCR-TKA was more anterior in the early flexion phase, while laterally the CP was more posterior during the entire movement cycle. The BCR-TKA group showed higher tibial migration. No differences were found for the clinical and functional outcomes. Conclusion. The BCR-TKA shows a different kinematic pattern in early flexion/late extension compared to the CR-TKA. The difference between both implants is mostly visible in the flexion phase in which the anterior cruciate ligament is effective; however, both designs fail to fully replicate the motion of a natural knee. The higher migration of the BCR-TKA was concerning and highlights the importance of longer follow-up. Cite this article: Bone Joint J 2023;105-B(1):35–46

The anterior cruciate ligament (ACL) is frequently injured in elite athletes, with females up to eight times more likely to suffer an ACL tear than males. Biomechanical and hormonal factors have been thoroughly investigated; however, there remain unknown factors that need investigation. The mechanism of injury differs between males and females, and anatomical differences contribute significantly to the increased risk in females. Hormonal factors, both endogenous and exogenous, play a role in ACL laxity and may modify the risk of injury. However, data are still limited, and research involving oral contraceptives is potentially associated with methodological and ethical problems. Such characteristics can also influence the outcome after ACL reconstruction, with higher failure rates in females linked to a smaller diameter of the graft, especially in athletes aged < 21 years. The addition of a lateral extra-articular tenodesis can improve the outcomes after ACL reconstruction and reduce the risk of failure, and it should be routinely considered in young elite athletes. Sex-specific environmental differences can also contribute to the increased risk of injury, with more limited access to and availablility of advanced training facilities for female athletes. In addition, football kits are designed for male players, and increased attention should be focused on improving the quality of pitches, as female leagues usually play the day after male leagues. The kit, including boots, the length of studs, and the footballs themselves, should be tailored to the needs and body shapes of female athletes. Specific physiotherapy programmes and training protocols have yielded remarkable results in reducing the risk of injury, and these should be extended to school-age athletes. Finally, psychological factors should not be overlooked, with females’ greater fear of re-injury and lack of confidence in their knee compromising their return to sport after ACL injury. Both intrinsic and extrinsic factors should be recognized and addressed to optimize the training programmes which are designed to prevent injury, and improve our understanding of these injuries. Cite this article: Bone Joint J 2023;105-B(10):1033–1037

Aims. The aim of this study was to compare the biomechanical models of two frequently used techniques for reconstructing severe acetabular defects with pelvic discontinuity in revision total hip arthroplasty (THA) – the Trabecular Metal Acetabular Revision System (TMARS) and custom triflange acetabular components (CTACs) – using virtual modelling. Methods. Pre- and postoperative CT scans from ten patients who underwent revision with the TMARS for a Paprosky IIIB acetabular defect with pelvic discontinuity were retrospectively collated. Computer models of a CTAC implant were designed from the preoperative CT scans of these patients. Computer models of the TMARS reconstruction were segmented from postoperative CT scans using a semi-automated method. The amount of bone removed, the implant-bone apposition that was achieved, and the restoration of the centre of rotation of the hip were compared between all the actual TMARS and the virtual CTAC implants. Results. The median amount of bone removed for TMARS reconstructions was significantly greater than for CTAC implants (9.07 cm. 3. (interquartile range (IQR) 5.86 to 21.42) vs 1.16 cm. 3. (IQR 0.42 to 3.53) (p = 0.004). There was no significant difference between the median overall implant-bone apposition between TMARS reconstructions and CTAC implants (54.8 cm. 2. (IQR 28.2 to 82.3) vs 56.6 cm. 2. (IQR 40.6 to 69.7) (p = 0.683). However, there was significantly more implant-bone apposition within the residual acetabulum (45.2 cm. 2. (IQR 28.2 to 72.4) vs 25.5 cm. 2. (IQR 12.8 to 44.1) (p = 0.001) and conversely significantly less apposition with the outer cortex of the pelvis for TMARS implants compared with CTAC reconstructions (0 cm. 2. (IQR 0 to 13.1) vs 23.2 cm. 2. (IQR 16.4 to 30.6) (p = 0.009). The mean centre of rotation of the hip of TMARS reconstructions differed by a mean of 11.1 mm (3 to 28) compared with CTAC implants. Conclusion. In using TMARS, more bone is removed, thus achieving more implant-bone apposition within the residual acetabular bone. In CTAC implants, the amount of bone removed is minimal, while the implant-bone apposition is more evenly distributed between the residual acetabulum and the outer cortex of the pelvis. The differences suggest that these implants used to treat pelvic discontinuity might achieve short- and long-term stability through different biomechanical mechanisms. Cite this article: Bone Joint J 2024;106-B(5 Supple B):74–81

Aims. The aims of this study were to assess quality of life after hip fractures, to characterize respondents to patient-reported outcome measures (PROMs), and to describe the recovery trajectory of hip fracture patients. Methods. Data on 35,206 hip fractures (2014 to 2018; 67.2% female) in the Norwegian Hip Fracture Register were linked to data from the Norwegian Patient Registry and Statistics Norway. PROMs data were collected using the EuroQol five-dimension three-level questionnaire (EQ-5D-3L) scoring instrument and living patients were invited to respond at four, 12, and 36 months post fracture. Multiple imputation procedures were performed as a model to substitute missing PROM data. Differences in response rates between categories of covariates were analyzed using chi-squared test statistics. The association between patient and socioeconomic characteristics and the reported EQ-5D-3L scores was analyzed using linear regression. Results. The median age was 83 years (interquartile range 76 to 90), and 3,561 (10%) lived in a healthcare facility. Observed mean pre-fracture EQ-5D-3L index score was 0.81 (95% confidence interval 0.803 to 0.810), which decreased to 0.66 at four months, to 0.70 at 12 months, and to 0.73 at 36 months. In the imputed datasets, the reduction from pre-fracture was similar (0.15 points) but an improvement up to 36 months was modest (0.01 to 0.03 points). Patients with higher age, male sex, severe comorbidity, cognitive impairment, lower income, lower education, and those in residential care facilities had a lower proportion of respondents, and systematically reported a lower health-related quality of life (HRQoL). The response pattern of patients influenced scores significantly, and the highest scores are found in patients reporting scores at all observation times. Conclusion. Hip fracture leads to a persistent reduction in measured HRQoL, up to 36 months. The patients’ health and socioeconomic status were associated with the proportion of patients returning PROM data for analysis, and affected the results reported. Observed EQ-5D-3L scores are affected by attrition and selection bias mechanisms and motivate the use of statistical modelling for adjustment. Cite this article: Bone Joint J 2024;106-B(4):394–400