Treated conservatively, hyperextension injuries of the cervical spine have a poor outcome, but surgical treatment does not yet provide a realistic alternative. This study was prompted by the lack of classifications of cervical spondylosis and outcome studies of hyperextension in the literature, and the absence of a user-friendly neurological score. The retrospective study included 60 patients admitted over the last 12 years with hyperextension injuries and varying degrees of neurological deficit. The mean age of patients was 52 years and most had radiological evidence of cervical spondylosis. None had any neurological deficit before the accident. Injuries were sustained in falls in 56%, in motor vehicle accidents in 34%, in assaults in 8% and in sports injuries in 2%. The neurological deficits varied: 11% had complete lesions, 33% central cord syndrome, 18% motor complete-sensory incomplete, 33% motor incomplete-sensory incomplete. The nervous system was normal in 2%. The posterior columns were often involved, with loss of pro-prioception. In the majority of cases conservative treatment consisted of six weeks of light traction in gentle flexion, followed by mobilisation in an ABCO brace for six weeks. The results showed that the mean Asia score gain for the group treated conservatively was 23, for the surgically stabilised group 3 and the surgically- decompressed group 55. There was a 16% mortality rate. The mean time for rehabilitation was 5.5 months. Both the final outcome and the time to rehabilitation were extremely variable. We present a classification of cervical spondylosis and ways of measuring congenital and acquired spinal cord narrowing. We combine the Asia and Frankel scoring systems to give a user-friendly guide

Study design: Retrospective, descriptive study. Objectives: To describe the characteristics and outcomes of patients with spinal canal stenosis who suffer significant spinal cord injury (SCI) due to hyperextension injury of the cervical spine. To compare their characteristics and outcomes with all patients suffering traumatic cervical SCI and with the total cohort of patients admitted to a Spinal Injuries Unit for rehabilitation. Setting: Spinal Injuries Unit (SIU), Princess Alexandra Hospital, Brisbane. Methods: Demographic, injury and outcome data were obtained from an existing database and by review of the medical records of 575 patients admitted to and discharged from the SIU between July 1st, 1995 and July 1st 2002. Main outcome measures were: change in American Spinal Injury Association (ASIA) scale category, change in ASIA motor score, discharge Functional Independence Measure (FIM) score and change in FIM score, length of stay (LOS), primary means of mobility at discharge and discharge destination. Standard statistical methods were used to compare groups. Results: A total of 18 (3%) of the 575 patients were found to have cervical canal stenosis and hyperextension injury (the CCS/HI group). This represents 8% of the total group suffering traumatic injury to the cervical spinal cord (the total cervical trauma: TCT group, n = 225). This CCS/HI group was found to have a mean age at injury of 55.1 years compared to 37.1 and 37.8 years respectively for the TCT and total groups. Ninety-four percent of patients were found to have a neurological level at admission at C1–3 or C4–5 compared to 75.6% of the TCT group and only 5.6% of patients had an ASIA Impairment Category A lesion at admission compared to 38.7% of the TCT group. Falls (55.6%) was the most common cause of injury in the CCS/HI group with motor vehicle accidents (33.8%) most common in the TCT group. The mean change in ASIA motor score between admission and discharge was 34.7 compared to 20.4 for the TCT group. Degree of impairment (measured by a change in ASIA Category) improved in 28% of patients and mean change in total FIM score was 41.3. There was no difference seen with the TCT group. LOS was shorter for these patients (111.1 days vs. 161.6 days). The primary means of mobility at discharge was “walking” for 50% of this group (compared to 28.4% for the TCT group) while the next most common means of mobility was “power wheelchair” at 28% (17% of TCT group). Most patients (55.4%) were discharged to their previous home following rehabilitation and 22.3% were discharged to another rehabilitation unit or acute hospital. Conclusions: Patients with cervical spinal canal stenosis who suffer hyperextension injury constitute a distinct subgroup with the total group of traumatic cervical spinal cord injuries. This study suggests that they are older at the time of injury, have more rostral cervical injuries, are more likely to have incomplete injuries and that falls is the most common cause of injury. They have greater improvement in motor function but this does not appear to result in greater function at discharge as measured by the FIM. There appears to be a dichotomy with results for mobility at discharge with patients either being able to walk or requiring a power wheelchair. LOS in the SIU is shorter but a higher percentage are discharged to another hospital or rehabilitation unit

STUDY DESIGN: Retrospective, descriptive study. OBJECTIVES: To describe the characteristics and outcomes of patients with spinal canal stenosis who suffer significant spinal cord injury (SCI) due to hyperextension injury of the cervical spine. To compare their characteristics and outcomes with all patients suffering traumatic cervical SCI and with the total cohort of patients admitted to a Spinal Injuries Unit for rehabilitation. SETTING: Spinal Injuries Unit (SIU), Princess Alexandra Hospital, Brisbane. METHODS: Demographic, injury and outcome data were obtained from an existing database and by review of the medical records of 575 patients admitted to and discharged from the SIU between July 1st, 1995 and July 1st 2002. Main outcome measures were: change in American Spinal Injury Association (ASIA) scale category, change in ASIA motor score, discharge Functional Independence Measure (FIM) score and change in FIM score, length of stay (LOS), primary means of mobility at discharge and discharge destination. Standard statistical methods were used to compare groups. RESULTS: A total of 18 (3%) of the 575 patients were found to have cervical canal stenosis and hyperextension injury (the CCS/HI group). This represents 8% of the total group suffering traumatic injury to the cervical spinal cord (the total cervical trauma: TCT group, n = 225). This CCS/HI group was found to have a mean age at injury of 55.1 years compared to 37.1 and 37.8 years respectively for the TCT and total groups. Ninety-four percent of patients were found to have a neurological level at admission at C1-3 or C4-5 compared to 75.6% of the TCT group and only 5.6% of patients had an ASIA Impairment Category A lesion at admission compared to 38.7% of the TCT group. Falls (55.6%) was the most common cause of injury in the CCS/HI group with motor vehicle accidents (33.8%) most common in the TCT group. The mean change in ASIA motor score between admission and discharge was 34.7 compared to 20.4 for the TCT group. Degree of impairment (measured by a change in ASIA Category) improved in 28% of patients and mean change in total FIM score was 41.3. There was no difference seen with the TCT group. LOS was shorter for these patients (111.1 days vs. 161.6 days). The primary means of mobility at discharge was “walking” for 50% of this group (compared to 28.4% for the TCT group) while the next most common means of mobility was “power wheelchair” at 28% (17% of TCT group). Most patients (55.4%) were discharged to their previous home following rehabilitation and 22.3% were discharged to another rehabilitation unit or acute hospital. CONCLUSIONS: Patients with cervical spinal canal stenosis who suffer hyperextension injury constitute a distinct subgroup with the total group of traumatic cervical spinal cord injuries. This study suggests that they are older at the time of injury, have more rostral cervical injuries, are more likely to have incomplete injuries and that falls is the most common cause of injury. They have greater improvement in motor function but this does not appear to result in greater function at discharge as measured by the FIM. There appears to be a dichotomy with results for mobility at discharge with patients either being able to walk or requiring a power wheelchair. LOS in the SIU is shorter but a higher percentage are discharged to another hospital or rehabilitation unit

Introduction: Neck hyperextension (NH) is defined as a progressive increase of lordosis associated with a limitation in flexion of the cervical spine, which ultimately results in an inability to approximate the chin to the sternum. NH may occur in relation to several myopathies. It is characterized by a general weakness and contractures of the axial muscles which produces a progressive increase of lordosis associated with a limitation in flexion of the cervical spine, that forces the patient to assume awkward compensatory postures to maintain balance and level vision. This study reports on operative complications, the degree of correction, the achievement of a solid arthrodesis, the maintenance of the correction and the clinical assessment of 7 patients. Material and methods: Seven patients affected by various myophaties and NH were included. The mean age was 16.5 years (10–28 years). All underwent surgery, in which the paravertebral muscles were detached from the spinous processes and then transversally sectioned in order to bilaterally expose the laminas of vertebrae C2 to C7. The space between C1–C2 appeared mobile, while the spinous processes from C2 to C7 were close together and thus allowed only a very limited motion in between them. Ligamenti interspinosus and nuchae were detached and the facet joints from C2 to C7 were enlarged by capsulotomy. With a spreader rongeur, the interspinous spaces at each level were gently opened. Cortical cancellous autologue graft were shaped into wedges. After careful opening of each interspinous space, the bone wedges were driven between the spinous processes to maintain the achieved correction. The average follow-up time was 10.4 years (2.4–16.5 years). Results: No major surgical complications occurred. At follow-up, the average angle between C2–C7 in neutral position had decreased (p = 0.016) from 50.7 (40–70) to 21.4 (2–50). The range of motion in the C1–C2 joint remained unaffected, while it decreased in C2–C7 (p = 0.016) from 33.5 (15–64) to 1.8 (0–8). In all cases, a solid arthrodesis was achieved. Discussion and conclusion: The follow-up showed significant clinical improvement of posture in all patients. Our study has shown surgical treatment of NH to be an effective method within the whole series of seven patients, achieving both good immediate and good long-term results

Proximal tibial epiphyseal injuries are rare. Reported incidence varies from 0.5 – 3% of epiphyseal injuries. Proximal tibial epiphysis is well protected unlike distal femoral epiphysis. Thus, the distal femoral injuries are 7 times more frequent than proximal tibial epiphyseal injuries.

Case Report: 12-year old boy, hit a pole at the bottom of a dry ski slope and presented to A& E within 20 minutes. He had a swollen, deformed knee and leg that was immobilised in a temporary splint. He had absent posterior tibial and dorsalis pedis pulses. Emergency manipulation under GA and further stabilised with K-wires, A/K Back Slab in 450 flexion. Distal pulses returned on table. K-wires were removed after 4 weeks and physiotherapy started. At 3 months, he was back to normal activities except sports. At 2 years, he was longer by 1 cm in left tibia, valgus of 120 at the knee, full ROM, no ligament laxity and reports occasional anterior knee pain.

Discussion: Posteriorly displaced proximal tibial Salter Harris II injuries are very rare. Emergency reduction and stabilisation, absence of popliteal artery tear had prevented the immediate complications. The late complications did not warrant a surgical intervention.

Aims. The paediatric trigger thumb is a distinct clinical entity with unique anatomical abnormalities. The aim of this study was to present the long-term outcomes of A1 pulley release in idiopathic paediatric trigger thumbs based on established patient-reported outcome measures. Methods. This study was a cross-sectional, questionnaire-based study conducted at a tertiary care orthopaedic centre. All cases of idiopathic paediatric trigger thumbs which underwent A1 pulley release between 2004 and 2011 and had a minimum follow-up period of ten years were included in the study. The abbreviated version of the Disabilities of Arm, Shoulder and Hand questionnaire (QuickDASH) was administered as an online survey, and ipsi- and contralateral thumb motion was assessed. Results. A total of 67 patients completed the survey, of whom 63 (94%) had full interphalangeal joint extension or hyperextension. Severe metacarpophalangeal joint hyperextension (> 40°) was documented in 15 cases (22%). The median QuickDASH score was 0 (0 to 61), indicating excellent function at a median follow-up of 15 years (10 to 19). Overall satisfaction was high, with 56 patients (84%) reporting the maximal satisfaction score of 5. Among 37 patients who underwent surgery at age ≤ two years, 34 (92%) reported the largest satisfaction, whereas this was the case for 22 of 30 patients (73%) with surgery at aged > two years (p = 0.053). Notta’s nodule resolved in 49 patients (73%) at final follow-up. No residual triggering or revision surgery was observed. Conclusion. Surgical release of A1 pulley in paediatric trigger thumb is an acceptable procedure with excellent functional long-term outcomes. There was a trend towards higher satisfaction with earlier surgery among the patients. Cite this article: Bone Jt Open 2024;5(9):736–741

Aims. Avascular femoral head necrosis in the context of gymnastics is a rare but serious complication, appearing similar to Perthes’ disease but occurring later during adolescence. Based on 3D CT animations, we propose repetitive impact between the main supplying vessels on the posterolateral femoral neck and the posterior acetabular wall in hyperextension and external rotation as a possible cause of direct vascular damage, and subsequent femoral head necrosis in three adolescent female gymnasts we are reporting on. Methods. Outcome of hip-preserving head reduction osteotomy combined with periacetabular osteotomy was good in one and moderate in the other up to three years after surgery; based on the pronounced hip destruction, the third received initially a total hip arthroplasty. Results. The described pathology is quite devastating, and extensive joint preserving surgery (which has been shown successful in Perthes’ cases) was less successful in this patient cohort. Conclusion. Supraselective angiography may be helpful to improve pathomechanical understanding and surgical decision making. Cite this article: Bone Jt Open 2022;3(9):666–673

Introduction. Instability continues to be the number one reason for revision in primary total hip arthroplasty (THA). Commonly, impingement precedes dislocation, inducing a levering out the prosthetic head from the liner. Impingement can be prosthetic, bony or soft tissue, depending on component positioning and anatomy. The aim of this virtual study was to investigate whether bony or prosthetic impingement occurred first in well positioned THAs, with the hip placed in deep flexion and hyperextension. Methods. Twenty-three patients requiring THA were planned for a TriFit/Trinity ceramic-on-poly cementless construct using the OPS. TM. dynamic planning software (Corin, UK). The cups were sized to best fit the anatomy, medialised to sit on the acetabular fossa and orientated at 45° inclination and 25° anteversion when standing. Femoral components and head lengths were then positioned to reproduce the native anteversion and match the contralateral leg length and offset. The planned constructs were flexed and internally rotated until anterior impingement occurred in deep flexion [Fig. 1]. The type (bony or prosthetic), and location, of impingement was then recorded. Similarly, the hips were extended and externally rotated until posterior impingement occurred, and the type and location of impingement recorded [Fig. 2]. Patients with minimal pre-operative osteophyte were selected as a best-case scenario for bony impingement. Results. 6/23 (26%) patients were planned with only a 32mm articulation (<50mm cup size), with the remaining 17 patients all planned with both 32mm and 36mm articulations (≥50mm cup size). Anterior impingement was 26% prosthetic and 74% bony with the 32mm articulations, and 100% bony with the 36mm articulations. Bony impingement in deep flexion was exclusively anterior neck on anterior inferior iliac spine. Posterior impingement was 57% prosthetic and 43% bony with the 32mm articulations, and 41% prosthetic and 59% bony with the 36mm articulations. Bony impingement in hyperextension was exclusively lesser trochanter (LT) on ischium. Of the patients planned with both 32mm and 36mm articulations, there was a 14% increase in prosthetic impingement when a 32mm head was planned (35% and 21% respectively). Discussion. Impingement in THA usually precedes dislocation and should be avoided with appropriate component positioning. We found that in hyperextension, prosthetic and bony impingement were equally common. In deep flexion, impingement was almost exclusively bony. Further studies should investigate the effects of stem version, cup orientation, liner design, cup depth, native offset and retained osteophytes on the type of impingement in THA. For any figures or tables, please contact the authors directly

Aims. Traumatic central cord syndrome (CCS) typically follows a hyperextension injury and results in a motor impairment affecting the upper limbs more than the lower limbs, with occasional sensory impairment and urinary retention seen. Current evidence on mortality and long-term outcomes is limited. The primary aim of this study is to assess the five-year mortality of CCS, and to determine any difference in mortality between management groups or age. Patients and Methods. Patients ≥18 years with traumatic CCS between January 2012 and December 2017 in Wales were identified. Patient demographics and injury, management and outcome data was collected. Statistical analysis was performed to assess mortality and between group differences. Results. 65 patients were identified (66.2% male, mean age 63.9 years). At five-years follow-up, 32.3% (n=21) of CCS patients were dead. 6 (9.2%) patients had died within 31 days of their injury. 69.2% (n=45) of patients were managed conservatively and there was no significant difference (p=0.062) in age between conservatively and surgically managed patients. Kaplan-Meier analysis revealed no significant difference in mortality between patients managed conservatively compared to those managed surgically (log rank test, p=0.819). However, there was a significant difference (p=0.001) in mortality between the different age groups (<50 years vs 50–70 years vs >70 years). At five-years follow up, 55.6% of the patient group aged >70 years at time of injury were dead. Respiratory failure was the most common cause of death (n=9, 42.9%). Conclusion. Almost one third of patients with traumatic CCS in Wales were dead at five years following their injury. Management type did not significantly affect mortality, however age at time of injury did. Further work assessing the long-term functional outcomes of surviving patients is needed, to allow more reliable prognostic information and functional recovery predictions to be given

Femoral head necrosis in the context of high impact gymnastics of young adolescents is rare but seems a more serious complication compared to a Perthes like necrosis. Between 2017 and 2019, three young females aged from12 to 14 years were referred due incapacitating hip pain and severe collapsing femoral head necrosis. The indication of hip preserving surgery was based on the extent of the necrosis, presence of a vital lateral pillar and joint subluxation. In one of our 3 cases total head involvement made THR necessary, which was performed elsewhere. In the remaining 2 cases, head reduction osteotomy plus periacetabular osteotomy led to a good and a fair result. Repetitive impact between the main supplying vessels on the posterolateral femoral neck and the posterior acetabular wall in hyperextension/ external rotation could be the cause of severe femoral head necrosis in three adolescent female gymnasts we are reporting on. Supra-selective angiography or sonography may be helpful to improve indication. Targeted adaptation of training methods should be discussed. Due to the severe vascular insult, results have to be considered moderate

Retrospectively to analyse factors contributing to the development of hyperextension deformity after distal surgical lengthening of hamstrings in cerebral palsy. In the cohort of 51 diparetic patients (98 operated knees ) surgically treated for fixed flexion deformity at least five yers before this study was contemplated, the range of of hyperextension of the knee was measured. According to surgical technique two subgroups were differentiated:. A./ Simple cutting of gracilis and semitendinosus, followed by fractional lengthening of semimembranosus and biceps femoris. B./ Proximal stumps of gracilis and semitendinosus after its transverse division were anchored to fractionally lengthened semimembranosus. Assessment involved: Measurement of hyperextension of the knee in lying and standing position and by walking using video-documentation. Values of Bleck popliteal angle before and after operation were estimated. This cohort did not involve any case with residual fixed plantar flexion of the foot. Both surgical subgroups were compared for occurence of hyperextension deformity > 5° in lying, standing positions and by walking. Testing by Fisher exact test did not show any statistical difference in all three compared situations (p > 0,05). The occurence of hyperextension > 5°in lying position was found in 5 knees ( 5,1 %), in standing position in 8 knees ( 8,2 %) and by walking during stance phase in 12 knees (12,3 %). In no case hyperextension of the knee exceeded 15°. Statistical testing between the postoperative Bleck popliteal angle ( stratified into classes below 20° and over 20°) and the occurence of hyperextension deformity did not show in Fisher exact test any statistical significance. On the other side the testing between postoperative Bleck popliteal angle ( stratified as above) and the type of surgery showed statistical significancy in Fisher exact test. Simple cutting of gracilis and semitendinosus brought about oftener the lower values of Bleck popliteal angle below 20°. It seems that the role of type of treating superficial flexors in the ways used in this study was not so much decisive for development of hyperextension deformity

Introduction. Genu recurvatum deformities are unusual before total knee arthroplasty (TKA), occurring in less than 1% of patients. The purpose of this study is to evaluate the clinical and radiographic results of primary TKA in patients that had recurvatum deformities before surgery. Patients and Methods. The inclusion criteria was to have recurvatum deformity over 10 degrees on lateral standing X-ray view. We retrospectively reviewed 22 knees with pre-operative recurvatum deformities, and the incident was 1.0% of all TKAs at our hospital. The etiology of the arthritis was osteoarthritis in 21 knees, of which 3 knees were neuropathic disease, and rheumatoid arthritis in 1 knee. There were 6 men and 16 women, and the average age was 73.3 years (range, 53 to 83 years) at the time of operation. The average follow-up period was 15 months (range, 3 to 81 months). We performed to use medial parapatellar approach and bone cutting was done by measured resection technique. The surgical knacks were resection of less distal femur and proximal tibia bone to make extension gap tightly, additionally decrease the tibial posterior slope. Posterior-stabilizer (PS) implants (NexGen LPS: Zimmer, Bisurface KU4+: JMM) were used in 20 knees and constrained implants (NexGen RH knee: Zimmer, Endo-Model Hinge Knee: Link) were in 2 knees with neuropathic joints. Results. The averaged Knee Society Knee and Function score improved from 33.1 points to 94.1 points, and 28.0 points to 60.5 points at the time of the last follow-up. The femorotibial angle changed from averaged 183.4 degrees (range, 162 to 195 degrees) preoperatively to averaged 173.3 degrees (range, 170 to 177 degrees). Preoperative hyperextension was averaged 18.2 degrees (range, 10 to 40 degrees). Intraoperatively, the hyperextension deformity was corrected in all cases. The tibial posterior slope was averaged 1.7 degrees (range, −2.7 to 6 degrees). The final hyperextension improved averaged 6.9 degrees (range, −1.7 to 26.6 degrees), all but one knee were corrected. One case treated with a standard PS type, who was associated with neuropathic disease, had a recurrence of recurvatum deformity and required revision surgery. Discussion. Recurvatum may be associated with a severe osseous deformity, capsular or ligamentous laxity, and neuromuscular disease. Surgical solutions may be to use a standard PS prosthesis with a slight underresection of the bone edge, and decrease tibial posterior slope. An alternative solution is to use a rotating-hinge prosthesis with less than antigravity quadriceps strength for neuromuscular disease

Purpose. This study was to investigate the effect of posterior tibial slope (PTS) on the kinematics in the cruciate-retaining total knee arthroplasty (CR-TKA) using 2- to 3- dimensional registration technique. Material & Methods. A total of 75 knees in 58 patients were recruited and categorized into the following two groups according to PTS. Group A was categorized PTS under 7degrees (n = 33) and group B was categorized PTS over 7 degrees (n = 42). The average age of group A and group B at the time of fluoroscopic surveillance date was 73.5 ± 7.4 years and 74.3 ± 4.5 years, respectively and the average follow-up period from operation date to fluoroscopic surveillance date was 13.8 ± 9.3 months and 16.7 ± 8.6 months, respectively. In vivo kinematics during sequential deep knee bending under weight-bearing condition were evaluated using fluoroscopic image analysis and 2- to 3- dimensional registration technique. Range of motion (ROM), axial rotation, anteroposterior (AP) translations of medial and lateral nearest points of the femoral component relative to the tibial component were measured and compared between the two groups. The nearest points were determined by calculating the closest distance between the surfaces of femoral component model and the axial plane of coordinate system of the tibial component. We defined external rotation and anterior translation as positive. P values under 0.05 was defined as statistically significant. Results. The mean PTS in group A and B were 5.5 ± 1.4°and 9.9 ± 1.9°, respectively. There was no statistically significant difference in the degrees of axial rotation from 0° to 110° of flexion between the two groups (4.9 ± 4.2° vs 5.2 ± 4.2°, p > 0.05), respectively. The hyperextension of group B were significantly larger than group A (−2.3 ± 6.6°vs −9.8 ± 8.7°, p <0.05). The ROM of group B were significantly larger than group A (118.7 ± 10.8°vs 128.7 ± 17.7°, p <0.05). However, there was no significant difference in the maximum flexion between the two groups (116.4 ±10.8°vs 118.9±14.5°, p >0.05), respectively. In terms of AP translation, medial nearest points were located significantly more posterior at 0°, 10°, 30°, 40° of flexion in group B compared to group A. There was no significant difference in the location of lateral nearest points between the two groups during all knee range of motion. Discussion/Conclusion. The results shown in this study demonstrated that the PTS influenced the kinematics and ROM under weight-bearing condition in CR-TKA. The large PTS induced great posterior displacement of medial nearest points during early flexion phase and increased hyperextension between the femoral and tibial components

Introduction. Genu recurvatum is a deformity rarely seen in patients receiving total knee arthroplasty. This deformity is defined as hyperextension of the knee greater than 5°. The incidence of recurvatum has been cited in the literature as less than 1%. Purpose. The purpose of this study was to report data on 1510 consecutive total knee replacements (TKR) with navigation to demonstrate that the incidence of genu recurvatum is higher than what is cited in the literature. Methods. This is a retrospective review that was approved by our health science institutional review board. We reviewed resting, intra-operative alignment of 206 navigated total knee arthroplasty cases with recurvatum. This is data from 4 surgeons who are lower extremity joint replacement physicians. The range of motion (ROM) is measured and recorded by the attending physician during routine physical examination of the lower extremity. Demographic data was used to describe the patient group. The data will include pre-operative, intra-operative and post-operative ROM. The intra-operative data will be captured by the navigation system, this sytem is accurate to 1° and 1mm. The post-operative ROM will be obtained from an office visit. We are interested in the post-operative ROM to demonstrate correction of the recurvatum. Results. One thousand five hundred and ten primary TKR were reviewed for this study. Two hundred and six patients (13.6%) had genu recurvatum as measured by the navigation computer. The range of recurvatum was 0.5–30°; mean 5 degrees (STD 4.3°). Sixty six patients had >5 degrees of recurvatum (4.4%). Only 2 patients had recurvatum recorded on their pre-operative office visit. These 2 patients did not have extreme recurvatum, 3° and a few degrees on walking respectively. No patient had recurvatum at the 4 year visit (visit range 3 months – to 4 years). The primary diagnosis for the group was osteoarthritis, 92 %. All cases of recurvatum were treated with under resection of the femur and correction of the coronal plane. All cases were corrected intraoperatively. Conclusion. Etiology of recurvatum can be due to bony insufficiency at the anterior tibia, insufficiency at both femoral condyles or laxity of the posterior capsule and ligaments. During surgery this can be addressed by under resection of the femur and undersizing the femoral component to increase the flex space, or soft tissue tightening can be implemented. Our surgical technique aimed to balance hyperextension with reduction of the distal femoral cut. Coronal balance is also important in the management of hyperextension. Current total knee designs lack the extension cam effect and make sagital balancing critical. Recurvatum is difficult to correct after total knee arthroplasty and this issue is important to address at the time of primary surgery. The use of a navigation system helped us appreciate a deformity that is not easily detected during routine examination. This study found that genu recurvatum in patients receiving TKR is significantly higher than what is reported in the literature. This finding has important implications for the management of a small percentage but nonetheless significant number of patients. This deformity is not appreciated in the clinical setting during routine examination

Introduction. Severe angular deformities in total knee arthroplasty require specific attention to bone resections and soft tissue balancing. This can add technical complexity and time, with some authors reporting an increase of approximately 20 minutes in mean surgery time when managing large deformities with conventional instrumentation [1]. We evaluate the utility of computer-navigation with imageless BoneMorphing® and Apex Robotic Technology, or A.R.T.® for managing large deformities in TKA. BoneMorphing® allows for real-time visualization of virtual bone resection contours, limb alignment and soft-tissue balance during TKA. A.R.T. permits accurate cutting and recutting of the distal femur in 1 mm increments. We asked what effects do severe pre-operative deformities have on post-operative alignment and surgery time in comparison to knees with only mild deformities when using this system. Methods. This was a retrospective cohort study of 128 consecutive A.R.T. TKA's performed by a single surgeon (mean age: 71 y/o [range 53–93], BMI: 31.1 [20–44.3], 48 males). Patients were stratified into three groups according to their pre-operative coronal plane deformity: Neutral or mild deformity <10° (baseline group); Severe varus ≥10°; and Severe valgus ≥10°; and according to the degree of flexion contracture: Neutral or mild flexion from −5° hyperextension to 10° flexion (baseline group); Hyperextension ≤−5°, and Severe flexion ≥10°. The degree of deformity and final postoperative alignment achieved was measured using computer navigation in all patients and analyzed using multivariate regression. The APEX CR/Ultra Knee System (OMNIlife Science, Inc.) was used in all cases. Results. Pre-operative coronal alignment ranged from 27° varus to 22° valgus (figure 1). Postoperative alignment across all patients ranged from 2° valgus to 3.5° varus (figure 2), and from 4° flexion to −4° hyperextension. Effect of deformity on alignment accuracy. Mean post-operative alignment was 1.4° varus in the control group, 0.4° varus in the severe valgus group (p=0.004), and 1.8° varus in the severe varus group (p=0.111). Preoperative flexion, obesity, and gender had no significant effect on alignment accuracy or final extension. Tourniquet time. Mean tourniquet time for the control group was 48.8 minutes [95% CI: 45.3–52.4] (figure 3). Severe varus knees took 4.8 min longer (p=0.006), while valgus knees took 2.9 min longer (p=0.260). Flexion contractures ≥10° and ≥15° increased tourniquet time by 3.8 min (p=0.152) and 10 min (p=0.033), respectively. Tourniquet time was slightly longer in obese patients by 3.2 min (p = 0.048) and was 6.3 min shorter for females than males (p<0.001). Conclusions. We have shown that in one surgeon's hands severe coronal deformities and flexion contractures can be consistently corrected to within 3–4° of neutral when using A.R.T. This is achieved by assessing the pre-resection kinematics, formulating a virtual plan, and executing and validating in real time that plan's execution. The additional time required for managing these more difficult cases using this technology was typically less than 5 minutes, which demonstrates the effectiveness of real-time navigation and robotics for TKA

MIS techniques in hip arthroplasty above all have the objective to shorten the rehabilitation period by suitable preparation. A modified Watson-Jones approach through the muscle interval between the middle gluteus and the tensor muscle of fascia latae via a 6 – 8 cm anterolateral skin incision provides a good overview to the preparation. The risk of damaging the lateral femoral cutaneous muscle is relatively low when a suitable incision technique is employed. The use of special instruments decisively decreases the risk of preparation errors, extension damage of the skin nerve and misimplantation of prosthesis components. Back-positioning of the patient on the operating table has clear advantages compared to lateral positioning. When the stem is prepared the proximal femur can be brought into the surgery area by re-positioning the leg under the contralateral leg without overstretching the leg which in turn might lead to extension damage of the femoral nerve. When the implant is chosen, short stems provide minimum bone loss and the advantage of a varic access to the bone, which makes the preparation substantially easier and additionally spares the soft parts. Straight stem prostheses may also be implanted using this method, however, here the danger of an extension damage of the femoral nerve is given by the hyperextension of the leg during preparation. A further common minimal invasive approach is ventral access between the tensor muscle of fascia latae and the sartorious muscle. Here in particular with muscular patients the danger of damaging the rectus femoris by post-operative bleeding is given. The skin is incised in alignment with the lateral femoral cutaneous muscle, which is to be displayed imperatively to be spared. For stem preparation an even more disadvantageous hyperextension of the leg is required. The two-incision-technique where the straight stem is implanted by a gluteussnip – comparable with femur nailing – only provides a very bad view at the proximal femur. Here there is a greater risk of an unnoticed bone fissure when cement-free pressfit stems are used. The advantage of this technique lies in minor hyperextension of the leg for preparation. Minimal invasive hip arthroplasty provides advantages for the patients above all in the early rehabilitation stage. However, the total concept is to be “minimal invasive” and skin incision, sparing of soft parts, choice of prosthesis and duration of surgery are to be considered

Introduction. The large diameter mobile polyethylene liner of the dual mobility implant provides increased resistance to hip dislocation. However, a problem specific to the dual mobility system is intra-prosthetic dislocation (IPD), secondary to loss of the retentive rim, causing the inner head to dissociate from the polyethylene liner. We hypothesized that impingement of the polyethylene liner with the surrounding soft-tissue inhibits liner motion, thereby facilitating load transfer from the femoral neck to the liner and leading to loss of retentive rim over time. This mechanism of soft-tissue impingement with the liner was evaluated via cadaver experiments, and retrievals were used to assess polyethylene rim damage. Methods. Total hip arthroplasty was performed on 10 cadaver hips using 3D printed dual mobility components. A metal wire was sutured to the posterior surface (underside) of the iliopsoas, and metal wires were embedded into grooves on the outer surface of the liner and inner head to identify these structures under fluoroscopy. Tension was applied to the iliopsoas to move the femur from maximum hyperextension to 90° of flexion for the purpose of visualizing the iliopsoas and capsule interaction with the mobile liner. The interaction of the mobile liner with the iliopsoas was studied using fluoroscopy and direct visual observation. Fifteen retrieved dual mobility liners were assessed for rim edge and rim chamfer damage. Rim edge damage was defined as any evidence of contact, and rim chamfer damage was classified into six categories: impact ribs on the chamfer surface, loss of machining marks, scratching or pitting, rim deformation causing a raised lip, a rounded rim edge, or embedded metal debris. Results. Manipulation of the cadaver specimens through full range of motion showed liner impingement with the iliopsoas tendon in low flexion angles, which impeded liner motion. At high flexion angles (beyond 30°), the iliopsoas tendon moved away from the liner and impingement was not observed. The fluoroscopy tests using the embedded metal wires confirmed what was observed during manual manipulation of the specimen. When observing the hip during maximum hyperextension, 0°, 15°, and 30° of flexion, there was obvious tenting of the iliopsoas. All retrieved components showed damage on the rim and the chamfer surface. The most common damage seen was scratching/ pitting. There was no association between presence of damage and time in vivo controlling for age and Body Mass Index (p≥0.255). Discussion. The cadaver studies showed that the mobile liner motion could be impeded by impingement with the iliopsoas tendon and hip capsule. Visual and fluoroscopic observation showed impingement of iliopsoas and hip capsule with the distal portion of the mobile liner, particularly during low flexion angles. All retrieved liners showed damage despite their limited time in vivo and despite being retrieved for reasons other than IPD. This suggests that soft-tissue impingement may inhibit liner motion routinely in vivo, resulting in load transfer from the femoral neck on to the rim of the liner. This may be an important mechanism for IPD

Introduction. Post cam is useful to realize the intrinsic stability of a posterior-stabilized (PS) knee prosthesis replaced for a case with the severe degeneration. Some retrieval studies reveal the ultrahigh molecular weight polyethylene (UHMWPE) deformation or severe failure of the tibial post of PS knee. Strength of the tibial post of available design is obviously insufficient to prevent the severe deformation. The large size post might, however, shorten the range of knee motion. Therefore, minimally required size of the post should be clarified for polyethylene inserts. In the present study, we performed finite element (FE) analysis assumed the mechanical conditions of a tibial post in a PS knee and aimed to design criterion of a post of polyethylene insert of a knee prosthesis. Method. The shape of three commercially available knee prostheses, product A, B, and C was referred as PS knee prosthesis. The contour of the metallic femoral component and the UHMWPE insert were digitized by a computed tomography apparatus. Three dimensional finite elements were generated by modeling software (Simpleware, Ltd. UK) as four-node tetrahedral elements. In FE analysis, we used LS-DYNA ver.971 (Livemore Software Technology Corp. USA) as the software and Endeaver Pro-4500 (EPSON Corp. Japan) as the hardware. These bottoms of the tibial insert were fully constrained. The value of 30MPa was defined as yield stress of UHMWPE. 500N posterior load was applied to each femoral component at 10 degree hyperextension. Then, 1000N anterior load at 120 degree flexion, after tibial insert was located 10 degree internal rotation (Fig. 1). These loads were assumed to realize the two types of tibial post impingement under several kinds of knee motions. The distributed values of von Mises stress and plastic strain on the tibial post were shown as the results of the analysis. Results. At the 10 degree hyperextension, these maximum values of von Mises stress were 24.5, 3.23, 27.09MPa on anterior aspect of tibial post of the product A, B, and C, respectively (Fig. 2). These plastic strains were 0.045, 0.001, 0.064. At the 120 degree flexion, these maximum values of von Mises stress were 33.67, 4.53, 27.03MPa on posterior aspect of the product A, B, and C, respectively (Fig. 3). These plastic strains were 0.28, 0.004, 0.061. The stress of product A was higher than yield stress of UHMWPE. The strain was obviously higher than that of product B and C. Discussion. Our results showed that plastic deformation may occur in the posterior aspect of a tibial post by impingement during common exercises like climbing up, or squatting. In the femoro-tibial articulation, the true-stress decreases with increase in load because the compressive deformation can widen the contact area on the UHMWPE. The true-stress in the tibial post, however, increases with increase in load because bending and tensile deformation reduces the section area. Therefore, the design criterion including the post size must be revised the safety coefficient which realizes that the generated stress in the tibial post is sufficiently lower than the yield stress of UHMWPE

Purpose of the study. Two patients with very severe thoracolumbar Scheuermann's kyphosis who developed spontaneous bony fusion across the apex of the deformity are presented and their treatment, as well as surgical outcome is discussed. Summary of Background Data. Considerable debate exists regarding the pathogenesis, natural history and treatment of Scheuermann's kyphosis. Surgical correction is indicated in the presence of severe kyphosis which carries the risk of neurological complications, persistent back pain and significant cosmetic deformity. Methods. We reviewed the medical notes and radiographs of 2 adolescent patients with severe thoracolumbar Scheuermann's kyphosis who developed spontaneous posterior and anteroposterior fusion across the apex of the deformity. Results. Patient 1. A male patient aged 17 years and 11 months underwent kyphosis correction when the deformity measured 115o and only corrected to 100o on supine hyperextension radiograph against the bolster; he had a small associated scoliosis. The surgery involved a combined single-stage anterior and posterior spinal arthrodesis T4-L3 with the use of posterior pedicle hook/screw/rod instrumentation and autologous rib graft. The anterior longitudinal ligament was ossified from T10 to L1 with bridging osteophytes extending circumferentially from T11 to T12 at the apex of kyphosis and displacing the major vessels anteriorly. The intervertebral discs from T9 to T12 were very stenotic and immobile. The osteophytes were excised both on the convexity and concavity of the associated thoracolumbar scoliosis. The anterior longitudinal ligament was released and complete discectomies back to the posterior longitudinal ligament were performed from T7 to L1. During the posterior exposure, the spine was found to be spontaneously fused across the apex of the kyphosis from T9 to L1. There were no congenital vertebral anomalies. Extensive posterior apical closing wedge osteotomies were performed from T7 to T12. The fused facets and ossified ligamentum flavum were excised and the spine was mobilised at completion of the anterior and posterior osteotomies. The kyphosis was corrected using a cantilever maneuver from proximal to distal under spinal cord monitoring. Excellent correction to 58o was achieved and maintained at follow-up. Autologous rib graft was used to enhance a solid bony fusion. Patient 2. A female patient aged 18 years and one month underwent kyphosis correction when the deformity measured 115o and only corrected to 86o on supine hyperextension radiograph against the bolster; she had a small thoracolumbar scoliosis. The surgery involved a single-stage posterior spinal arthrodesis T2-L4 with the use of posterior pedicle hook/screw/rod instrumentation and autologous iliac crest bone. The spine was spontaneously fused across the apex of kyphosis from T9 to L1. There were no congenital vertebral anomalies. Extensive posterior apical closing wedge osteotomies were performed from T6 to T12. The fused facets and ossified ligamentum flavum were excised and the spine was mobilised at completion of the osteotomies. The kyphosis was corrected using a cantilever maneuver from proximal to distal under spinal cord monitoring. Excellent correction to 60o was achieved and maintained at follow-up. Autologous iliac crest graft was used to achieve a solid bony fusion. In both patients the preoperative MRI assessed the intraspinal structures but failed to diagnose the solid fusion across the posterior bony elements at the apex of kyphosis. A CT scan with 3D reconstruction would have illustrated the bony anatomy across the kyphosis giving valuable information to assist surgical planning. This is recommended in the presence of rigid thoracolumbar Scheuermann's kyphosis which does not correct in hyperextension, especially if the plain radiograph shows anterior bridging osteophytes. Conclusion. Spontaneous posterior or anteroposterior fusion can occur across the apex of severe thoracolumbar Scheuermann's kyphosis; this should be taken into account when surgical correction is anticipated. The bony ankylosis may represent the natural history of an extreme deformity as an attempt of the spine to auto-stabilise. A combination of factors including a rigid deformity, which limits significantly active movement of the spine, as well as anterior vertebral body wedging with severe adjacent disc stenosis which induces bridging osteophyte formation may result in the development of spontaneous fusion across the apex of the kyphosis either posteriorly or anteroposteriorly. In the presence of an isolated posterior fusion, segmental posterior closing wedge osteotomies with complete excision of the ossified ligamentum flavum and fused facets should mobilise the thoracolumbar spine and allow for kyphosis correction. An additional anterior spinal release including complete discectomies, resection of the anterior longitudinal ligament and osteophytes is required if the bony fusion extends anteroposteriorly. Patients with Scheuermann's kyphosis should be ideally treated at an earlier stage and with a lesser degree of deformity so that this ossification process is prevented

Introduction. Post cam structure, which is the main structure of posterior-stabilized design (PS), is useful to realize the intrinsic stability of a knee prosthesis replaced for a case with the severe degeneration. A large size post might, however, shorten the range of knee motion. On the other hand, retrieval studies sometimes reveal the ultrahigh molecular weight polyethylene (UHMWPE) deformation or severe failure of the tibial post of PS knee. Strength of a tibial post of available design is obviously insufficient to prevent the severe deformation. Therefore, minimally required size of the post should be clarified for polyethylene inserts. In the present study, we performed finite element (FE) analysis assumed the mechanical conditions of a tibial post in a PS knee and aimed to design criterion of a post of polyethylene insert of a knee prosthesis. Method. The shape of one commercially available knee prosthesis was referred as a posterior-stabilized knee prosthesis. The contour of the metallic femoral component was traced and digitized by hand. The contour of the UHMWPE insert was digitized by a micro computed tomography apparatus. Three dimensional finite elements were generated by a modeling software (Simpleware, Ltd. UK) as total 83000 four-noded tetrahedral elements. The bottom of the tibial insert was fully constrained. Load on femoral component was assumed to realize the tibial post impingement under several kinds of knee motions. Posterior load 100 N or 500N at the 10 degree hyperextension, anterior load 500N or 1000N during 120 degree flexion were applied (Fig. 1). The software of FE analysis was LS-DYNA ver.971 (Livemore Software Technology Corp. USA). The hardware was Endeaver Pro-4500 (EPSON Corp. Japan). The distributed values of von Mises stress and plastic strain of the tibial post were shown as the results of the analysis. Results. At the 10 degree hyperextension, the maximum values of von Mises stress and plastic strain of anterior aspect of tibial post were 26.0 MPa, 0.054 at posterior load 100 N., 35.3 MPa, 0.383 at posterior load 500N, respectively (Fig. 2). At 120 degree flexion, these values of posterior aspect of tibial post were 27.6 MPa, 0.086 at anterior load 500 N, 32.1 MPa, 0.208 at anterior load 1000N, respectively (Fig. 3). Plastic deformation has occurred on the contact area, as shown in Fig. 2, 3. Discussion. Our results showed that large plastic deformation may occur in the anterior or the posterior aspect of a tibial post by impingement during common exercises like running, climbing up, or squatting. In the femoro-tibial articulation, the true-stress decreases with increase in load because the compressive deformation can widen the contact area on the UHMWPE. The true-stress in the tibial post, however, increases with increase in load because bending and tensile deformation reduces the section area. Therefore, the design criterion of tibial post of PS knee prosthesis including the size of the post must be revised the safety coefficient that realize the sufficiently lower stress generated in the tibial post than the yield stress of UHMWPE