We evaluated the efficacy of Escherichia coli-derived recombinant human bone morphogenetic protein-2 (E-BMP-2) in a mini-pig model of spinal anterior interbody fusion. A total of 14 male mini-pigs underwent three-level anterior lumbar interbody fusion using polyether etherketone (PEEK) cages containing porous hydroxyapatite (HA). Four groups of cages were prepared: 1) control (n = 10 segments); 2) 50 μg E-BMP-2 (n = 9); 3) 200 μg E-BMP-2 (n = 10); and 4) 800 μg E-BMP-2 (n = 9). At eight weeks after surgery the mini-pigs were killed and the specimens were evaluated by gross inspection and manual palpation, radiological evaluation including plain radiographs and micro-CT scans, and histological analysis. Rates of fusion within PEEK cages and overall union rates were calculated, and bone formation outside vertebrae was evaluated. One animal died post-operatively and was excluded, and one section was lost and also excluded, leaving 38 sites for assessment. This rate of fusion within cages was 30.0% (three of ten) in the control group, 44.4% (four of nine) in the 50 μg E-BMP-2 group, 60.0% (six of ten) in the 200 μg E-BMP-2 group, and 77.8% (seven of nine) in the 800 μg E-BMP-2 group. Fusion rate was significantly increased by the addition of E-BMP-2 and with increasing E-BMP-2 dose (p = 0.046). In a mini-pig spinal anterior interbody fusion model using porous HA as a carrier, the implantation of E-BMP-2-loaded PEEK cages improved the fusion rate compared with PEEK cages alone, an effect that was significantly increased with increasing E-BMP-2 dosage.

Cite this article: Bone Joint J 2013;95-B:217–23.

Introduction

Many literatures regarding more specific tests to diagnose the supraspinatus tendon injuries and the best rehabilitation methods to strengthen the supraspinatus have been published. However, conflicting results have been reported. 2-deoxy-2-[18F] fluoro-D-glucose (FDG) positron emission tomography (PET) has been recently used to assess skeletal muscle activities in various fields.

We hypothesised whether MIS techniques confer any benefit when treating thoracolumbar burst fractures.

This was a prospective, non-randomised study over the past seven years comparing conservative (bracing:n=27), conventional surgery (open techniques:n=23) and MIS techniques (n=21) for stabilisation and correction of all thoracolumbar spinal fractures with kyphosis of >20⁰, using Camlok S-RAD 90 system (Stryker Spine). All patients previously had normal spines, sustained only a single level burst fracture (T12, L1 or L2) as their only injury. Age range 18–65 years.

All patients in both operatively treated groups were corrected to under 10⁰ of kyphosis, posteriorly only. All pedicle screws/rods were removed between 6 months and 1 year post surgery to remobilise the stabilised segments once the spinal fracture had healed, using the original incisions and muscle splitting/sparing techniques. Patients were assessed via Oswestry Disability Index (ODI) and work/leisure activity status 1 year post fracture.

The conservatively treated group fared worst overall, with highest length of stay, poorest return to work/activity, and with a proportion (5/27) requiring later intervention to deal with post-traumatic deformity. 19/27 returned to original occupation, at average 9 months. ODI 32%.

Conventional open techniques fared better, with length of stay 5 days, most (19/23) returning to original work/activity, and none requiring later intervention. Average return to work was at 4 months. ODI 14%.

MIS group fared best, with shorter length of stay (48 hours), all returning to original work/activity at average 2 months, and none requiring later intervention. ODI negligible.

There was no loss of correction in either operatively treated groups.

The Camlok S-RAD 90 system is a powerful tool for correction of thoracolumbar burst fractures, and maintains an excellent correction.

MIS techniques provide the best outcomes in treating this group of spinal fractures, and offer patients the best chance of restoration to pre-fracture levels of activity.

The zona conoidea comprises the area of the lateral trochlear ridge of the humerus. The purpose of this study is to reintroduce this term ‘zona conoidea’ to the discussion of the human elbow and to investigate its significance in the development of osteoarthritis of the elbow.

The upper extremities of 12 cadavers were prepared. With the forearm in neutral, pronation and supination, the distance between the bevel of the radial head and zona conoidea was inspected. A total of 12 healthy volunteers had a CT scan. The distance between the zona conoidea and the bevelled rim of the radial head was measured in these positions.

In the anatomical specimens, early osteo-arthritic changes were identified in the posteromedial bevelled rim of the radial head, and the corresponding zona conoidea in supination. Measurement in the CT study showed that in full supination, the distance between the bevel of the radial head and the zona conoidea was at a minimum.

This study suggests that the significant contact between the bevel of the radial head and the zona conoidea in supination is associated with the initiation of osteoarthritis of the elbow in this area.

Haemophilia care has steadily improved over the years and especially so during the last decade. The routine use of prophylactic treatment has undoubtedly resulted in a significant improvement in the life-style, quality of life and life expectancy of these patients. However despite our best efforts there is still a group of young adults who have a severe degree of knee joint destruction as a result of repeated articular bleeding episodes during their early years.

The knee is the most common joint affected in haemophilia (50%). The repeated articular bleeding episodes during the patients' early years leads to the onset of pain and significant functional disability at a time when they require the best possible quality of life. The major objective of total joint replacement is to reduce the level of pain in the affected joint and, in addition, a significant reduction in the frequency and number of joint bleeds, which improves both function and mobility.

The results of 60 primary total knee replacements performed in 42 patients with severe haemophilia between 1983 and 2003 were reviewed retrospectively. Functional results were assessed using the Hospital for Special Surgery (HSS) knee score both pre- and post-operatively. Kaplan-Meier survivorship analysis was used to calculate prosthetic survival.

The mean age of patients was 43.35 (range 25-70yrs). The overall prevalence of infection was less than 2%. The HSS clinical score was excellent or good for 95% of the knees.

We believe that total joint replacement is a safe and effective procedure in the management of haemophilic joint arthropathy. The latest techniques using continuous infusion and recombinant factor replacement have gone a long way to reducing the complications rate and to achieving results that match those of the general population.

We conducted a prospective, randomized study comparing the outcomes of total knee arthroplasty (TKA) respectively through a quadriceps-sparing (QS) approach and a MIS medial parapatellar (MP) approach at 2-year follow-up. Sixty patients (80 knees) with primary osteoarthritis were enrolled in this study. Patients were blinded to be treated with and randomized to be grouped by either MP group (40 knees) or QS group (40 knees). Thirty-seven MIS MP TKAs and thirty-eight QS TKAs completed the 2-year follow-up.

According to the isokinetic study, the recovery of muscle strength (peak muscle torque) and normalization of muscle balance (H/Q peak-torque ratio) were comparable in both groups at either 2-month or 2-year follow-up. Tourniquet and surgical time in the QS group was significantly longer (approximately 20 minutes) than that in the MP group. The hip-knee-ankle axis measured after surgery was significantly more varus in the QS group than that in the MP group. The axis in both groups did not significantly progress at 2-year follow-up. There were no infections and no revisions at 2-year follow-up in both groups. More outlier cases (4 knees) were noted in the QS group when compared with the MP group (no outlier).

However, no differences regarding the clinic outcomes (including VAS, HSS knee score, ROM and satisfaction) were observed between these two groups after either two months or two years upon operation. In both groups, there was a significant improvement of these parameters at 2-year follow-up in contrast with 2-month follow-up and pre-operative status.

In this study, we conclude that MIS medial parapatellar TKAs could achieve comparable recovery of muscle strength, normalization of hamstring-quadriceps muscle balance and clinical outcomes when compared with QS TKAs; moreover it provides more reliable alignment and fewer complications than quadriceps-sparing TKAs.

We examined the differences in post-operative functional disability and patient satisfaction between 56 patients who underwent a lumbar fusion at three or more levels for degenerative disease (group I) and 69 patients, matched by age and gender, who had undergone a one or two level fusion (group II). Their mean age was 66 years (49 to 84) and the mean follow-up was 43 months (24 to 65).

The mean pre-operative Oswestry Disability Index (ODI) and visual analogue scale (VAS) for back and leg pain, and the mean post-operative VAS were similar in both groups (p >  0.05), but post-operatively the improvement in ODI was significantly less in group I (40.6%) than in group II (49.5%) (p < 0.001). Of the ten ODI items, patients in group I showed significant problems with lifting, sitting, standing, and travelling (p < 0.05). The most significant differences in the post-operative ODI were observed between patients who had undergone fusion at four or more levels and those who had undergone fusion at less than four levels (p = 0.005). The proportion of patients who were satisfied with their operations was similar in groups I and II (72.7% and 77.0%, respectively) (p = 0.668). The mean number of fused levels was associated with the post-operative ODI (r = 0.266, p = 0.003), but not with the post-operative VAS or satisfaction grade (p > 0.05). Post-operative functional disability was more severe in those with a long-level lumbar fusion, particularly at four or more levels, but patient satisfaction remained similar for those with both long- and short-level fusions.

Osteoarthritis (OA) is a common degenerative disease associated with aging thatas yet has no cure. Glucosamine (Gln) is a naturally produced amino sugar that forms part of the cartilage matrix and is taken by millions of OA sufferers in the hope of alleviating their symptoms. Apart from alleviating pain, there is evidence in the literature that Gln may also be a chondroprotective drug in OA and some clinical trials have shown reduced joint space narrowing in patients taking 1mg Gln per day. However, the mechanisms by which Gln might have its beneficial effects are still uncertain.

We wanted to determine whether Gln has any influence on the aberrant gene expression that takes place in OA chondrocytes. To this end, we cultured healthy articular chondrocytes and induced aberrant gene expression with TNF-α /OSM. Healthy human chondrocytes were isolated from the cartilage of the femoral head obtained after hemiarthroplasty from four patients who had fractured the neck of their femur. Each sample was divided in to 4 groups prior the monolayer culture:

Control culture,

At confluency (~ 2 weeks) RNA was extracted for analysis of mRNA expression by RT-PCR. The impact of Gln on the expression if the inflammatory cytokine IL-1b and the protease MMP-13 was determined by conventional RT-PCR.

No expression of IL-1b was found in control cultures and Gln on its own did not induce expression. As expected, TNF-a/OSM induced the expression of IL-1b in all four patients. When Gln was present together with TNF-a/OSM, IL-1b expression was prevented in two patients and considerably reduced in the other two patients. With respect to MMP-13, expression was present in 3/4 cultured controls and Gln did not influence this expression. TNF-α /OSM increased expression of IL-1b, and the cytokine-induced expression was slightly reduced by Gln in 2/4 patients.

These results suggest that Gln prevents the TNF-α /OSM-induced expression of IL-1b, but has limited direct influence on MMP-13 expression, at least in vitro. If the data are applicable to the in vivo situations, the results support the proposed chondroprotective effect of glucosamine at the cellular level.

The prosthesis anchored to the vertebral body by a large central keel has inherent risk of angular mismatching between vertebral endplate and prosthesis endplate at large lordotic segment such as L5-S1. Theoretically, these angular mismatching can be considered to cause several problems such as segmental hyperlordosis, anterior positioning of upper prosthesis, posterior prosthetic edge subsidence, decreased ROM and poor clinical outcome. The purpose of this study is to assess whether angular mismatching between vertebral endplate and prosthesis endplate in lumbar total disc replacement (L-TDR) with ProDisc-L influence on radiological and clinical outcomes.

We evaluated 64 levels of 56 patients who were implanted with ProDisc-L from 2002 to 2006. Prosthetic levels were 38 levels of L4–5, and 26 levels of L5-S1 (8 patients had 2 level-operations of L4–5 and L5-S1). Mean follow-up was 25.6 (12–49) months. Angle of mismatching between lower endplate of upper vertebral body and upper prosthetic plate, segmental flexion/extension ROM, segmental lordosis angle at extension, distance from the posterior wall of vertebral body to posterior prosthetic edge were measured in the radiographs. Clinically VAS and ODI were evaluated. Angular mismatching between upper vertebra and prosthesis of L4–5 and L5-S1 was 1.6° (range, 0–6°) and 5.6° (0–13°) (p< 0.001) respectively, at final follow-up. Angular mismatching at immediate postoperative radiographs (2.3° in L4–5 and 4.9° in L5-S1) and at final follow-up was not significantly different (p=0.324 in L4–5, 0.620 in L5-S1). Mean segmental ROM of operated levels was 10.6° (4–22°) in L4–5 and 6.1° (2–13°) in L5-S1(p< 0.001). Mean segmental ROM, mean segmental lordosis angle, and mean distance from posterior margin of vertebral body to posterior end of prosthesis in L5-S1 were 6.8° (4–13°), 12.8° (8–17°), 3.8mm (1–6mm) in cases with angular mismatching less than 10°, and 4.6° (2–7°), 21.3° (19–25°), 6.0 mm (2–8mm) in that of 10° or more (p=0.024, < 0.001, 0.039), respectively. In L4–5 angular mismatching of more than 5° were only 2 cases without statistical significance. Clinical outcomes, VAS and ODI, of L4–5 compared with that of L5-S1 and of angular mismatching less than 10° with that of 10° or more in L5-S1 did not have difference between them (p> 0.05). Angular mismatching between lower endplate of upper vertebra with upper prosthesis endplate is more common in L5-S1 than in L4–5. L-TDR at the most lordotic level, L5-S1, implantation of upper prosthesis with mismatched angle seems to be the causes of lessened segmental ROM, increased segmental lordosis, and anterior positioning of prosthesis.

Anterior decompression and fusion has been standard treatment for cervical disc herniation and myelopathy with disc degeneration. Since cervical total disc replacement (TDR) has been introduced with early favorable results and ideal mechanism, it has gained its popularity recently. But varying degrees of heterotopic ossification (HO) around the operated segment have been noted in the literatures. The theoretical advantages of TDR are the maintenance of intervertebral motion and prevention of adjacent segment degeneration. It is questionable that if HO occurs after TDR, mobility of operated segments would be restricted then clinical outcome worse. Purpose of this study is to determine prevalence of HO and to investigate that the presence of HO would limit motion and subsequently negatively affect clinical outcome following cervical TDR.

We analyzed 29 patients (30 levels) who were treated with cervical TDR by 2 spine specialists using 4 types of prostheses (Mobi-C: 13 levels, ProDisc: 10, Bryan: 5, Prestige LP: 2) consecutively from July 2004 to June 2007. Postoperative mean follow-up period was 21.4 (12–36) months. We assessed presence of HO and segmental ROM radiographically and clinical outcome by VAS, ODI after 1.5, 3, 6 months, and every year postoperatively in principle. All subjects were divided by 3, which were group A (no HO, McAfee class 0), group B (class I and II), and group C (class III and IV), then compared with each other.

HO was detected on 14 levels (46.7%) in the 30 levels after at mean of 8.2 (4–18) months after operation. There were 15 levels(53.3%) of group A (no HO, class 0), 7 levels of group B (class I HO:3, II: 4), and 7 levels of group C (class III: 3, IV: 4). Segmental flexion-extension ROM of group A was 10.1 (5.6–16.2)°, group B is 8.3 (3.5–14.4)°, and group C is 3.1 (0.0–6.6)° (p< 0.001, multiple comparison test with post hoc Bonferroni correction). And no difference in the clinical outcomes, VAS and ODI, was found compared with each other among group A, B, and C (p> 0.05).

Nonetheless, longer term follow-up should be performed to investigate whether clinical outcomes would be changed and occur adjacent level degeneration as time goes on. In addition, further study for prevention of HO may be needed as in HO of other joint replacement surgery not to lose superior mechanism to fusion treatment.

Vast amount of literature is available on mechanical properties of PMMA, but not about the composite specimens of old and new cement. This is important, as in cement revision has become established technique with good clinical results. Originally Greenwald and later Li described properties of such specimens. However in these studies the old samples were only few days old, unlike clinical situation, where the old cement is a few years old.

We therefore decided to test short-term mechanical properties of composite specimens and compare these with new uniform specimens. We choose specimens of cement 3–17 years old (median 11.8) for the manufacturing of the composite specimens.

Material and Methods: Uniform and composite specimens were fabricated and were tested for bending, tensile and shear strength. Beam shaped specimens were fabricated for bending and tensile tests, cylindrical for shear. Seventeen beams and eight cylindrical specimens fabricated earlier (1988–2002) using the same moulds were available to form composite specimens. Old specimens were placed into the moulds and new cement was injected next to these. Specimens were allowed to polymerize at room temperature for 30 minutes and stored in saline at 37 °C for 6 weeks before testing. Specimens were tested in Lloyds EZ 20 machine with customized jig so that the junction was subjected to bending, tensile or shear force.

Results: Bending tests: The load and bending stress for new specimen was 80N and 47MPa as compared with 72N and 38MPa for composite specimens. 4 composite specimens failed though old cement, 3 through the junction and 1 through the new cement. There was no statistical difference in maximum load between uniform and composite specimens (p=.29). However there was a difference in the stress between uniform and composite specimens.

Tensile tests: The load and tensile stress for new specimen was 916N and 29MPa as compared with 795N and 24MPa for composite specimens. 7 composites failed through old cement, 1 through new cement and 1 at junction. There was difference in the load and stress of uniform specimens as compared with composite specimens.

Shear tests: The load and shear stress for new specimen was 2718N and 35MPa as compared with 2055N and 26MPa for composite specimens. There was significant difference in load as well as stress in uniform specimens as compared with composite specimens.

Discussion: This study demonstrates that composite specimens fail at 89.6% of bending load, 77.2% of tensile and 74.6% of shear load as compared with uniform new cement specimens. They have 81.4% of bending stress, 74.9% of tensile stress and 73.3% of shear stress at failure as compared with uniform specimens. Of more importance is the fact that only four of these composite specimens (23.5%) failed at the junction and the rest thirteen failed either through old cement (64.7%) or through new cement (11.8%).

Introduction: Bone cements produced by different manufacturers vary in their mechanical properties and antibiotic elution characteristics. Small changes in the formulation of a bone cement, which may not be apparent to surgeons, may also affect these properties. The manufacturing method of Palacos bone cement with added gentamicin has recently changed. We have carried out a study to examine the mechanical characteristics and antibiotic elution of Schering-Plough Palacos (‘old’ version), Heraeus Palacos (‘new’ version) and Depuy CMW Smartset bone cements.

Methods: Schering-Plough Palacos R40G (contains 0.5g gentamicin per 40g mix), Heraeus Palacos R+G (contains 0.5g gentamicin per 40g mix) and Depuy-CMW Smartset GHV (contains 1g gentamicin per 40g mix) were used. 40g samples of the three cements with no additional vancomycin, 1g and 2g vancomycin were prepared by a standard method using vacuum mixing in a syringe. Antibiotic elution over a five week period was measured using an immunoassay method. Standard mechanical testing was carried out according to methods defined in ISO 5833.

Results: Both Heraeus Palacos and Smartset bone cements performed significantly better than Schering-Plough Palacos in terms of mechanical characteristics both with and without additional antibiotics. All cements show a deterioration in flexural strength with increasing addition of vancomycin although staying above ISO minimum levels. Both Heraeus Palacos and Smartset elute significantly more gentamicin cumulatively than Schering-Plough Palacos. Smartset elutes significantly more vancomycin cumulatively compared with Heraeus Palacos.

Discussion: Both Heraeus Palacos and Smartset Bone cements elute significantly more gentamicin than Schering-Plough Palacos with no deterioration in mechanical characteristics. Smartset also elutes significantly more vancomycin than Heraeus Palacos without adverse affect on mechanical characteristics. Although marketed as the ‘original’ Palacos, Heraeus Palacos has significantly altered mechanical and antibiotic elution characteristics compared with previous versions.

Background: The Oxford unicompartmental knee replacement (UKR) use in the lateral compartment has been associated with a reduced flexion range and diminished femoral rollback. It is postulated that this may be due to a flat tibial tray replacing the domed anatomy of the lateral tibia, tightening the posterolateral flex-ion gap. A new design incorporating a domed tibial component and a biconcave meniscal bearing has been developed to increase; (i) the posterolateral flexion gap in deep knee flexion (ii) meniscal bearing movement and (iii) lateral femoral condyle (LFC) rollback. A cadaveric study was designed to test these three outcomes.

Methods: The sagittal plane kinematics of seven thawed fresh frozen cadaver specimens within an upright Oxford testing rig were assessed under three different conditions; (i) intact normal cadaver knee (ii) flat lateral Oxford UKR (iii) domed lateral Oxford UKR. Each condition was tested during three ranges of motion (ROM) and data recorded during a flexion or extension half cycle. Knee flexion angle (KFA) and displacement measures of the lateral collateral ligament (LCL), LFC rollback and anteroposterior meniscal bearing movement were performed throughout knee ROM using four [3 linear, 1 rotary] potentiometer devices. Potentiometer data was recorded as a voltage reading and subsequently converted to either a millimetre displacement or degree measure using a calibration formula. All data points were compared at 10 degree interpolations of KFA.

Results: The flexion half cycles demonstrated the flat Oxford lateral UKR achieved 80.7% of normal cadaveric LFC rollback. The domed Oxford lateral UKR achieved 108.8% of normal cadaveric LFC rollback. The ratio of LFC rollback in the domed to flat UKR’s was 1.35 times (134.9%). Meniscal bearing movement in flexion demonstrated a domed to flat UKR ratio of 1.3 times (129.7%). Similar values were obtained for extension half cycles in favour of the domed Oxford lateral UKR. No significant differences were identified in LCL measures.

Conclusions: The domed Oxford lateral UKR implant allows for improved bearing movement and femoral rollback when compared to the flat Oxford lateral UKR. The sagittal plane kinematics of the domed Oxford lateral UKR as represented by femoral rollback values approximate those of the normal cadaver knee.

Haemophilia care has steadily improved over the years and especially so during the last decade. The routine use of prophylactic treatment has undoubtedly resulted in a significant improvement in the life-style, quality of life and life expectancy of these patients, and bodes well for the future.

The knee is the most common joint affected in patients with severe haemophilia (approx 50%) and despite best efforts there is still a group of young adults who have a severe degree of knee joint destruction as a result of repeated articular bleeding episodes during their early years.

The indications for operation are primarily disabling pain that is unresponsive to medical treatment. Deformity and poor functional range of motion, particularly a severe flexion contracture of the knee, are relative indications and may in themselves justify joint replacement. Equally joint contractures and flexion deformity pose various surgical challenges for the surgeon. The introduction of continuous replacement clotting factor has facilitated the operation and in our experience has reduced the complications of TKR. We have found that it permits earlier rehabilitation and in our present series the outcome in this group of patients almost comparable to TKR performed in the general population.

Nutritional osteomalacia is a metabolic bone disorder common among the Asian female immigrant population in the United Kingdom. We describe the case of a female of Asian origin, who was found to have a unilateral undisplaced pseudofracture of the neck of the femur during pregnancy. Although not operated on the fracture was treated successfully with calcium and vitamin D supplement therapy. Within one month of treatment, the bone pain subsided and she was able to bear full weight. Subsequent radiological follow-up showed the pseudofracture to have healed sufficiently with no evidence of avascular necrosis.

There should be a high index of suspicion of this disease, particularly among Asian patients presenting with persistent and non-specific musculoskeletal pain.

Purpose: The purpose of this study was to use the thromboelastogram to determine whether autologous blood transfusion following primary total knee replacement surgery results in an alteration to systemic coagulation.

Methods: 44 patients were randomised to receive either Hartmann’s solution alone postoperatively (control group), or Hartmann’s solution and autologous blood at six hours (ABT group). Thromboelastogram measurements of systemic blood clotting were performed pre-operatively, and post operatively at 6h just prior to the commencement of the ABT, 6h 30mins, and 8h.

Results: At 8h post operation (2h post ABT), the ABT group when compared with the control group showed an earlier onset of coagulation (3.83 minutes versus 4.49 minutes, p=0.003) and the formation of a stronger clot as assessed by the TEG maximum amplitude (maximum clot strength 83.9mm versus 75.9mm, p< 0.001).

Conclusion: The transfusion of drained autologous blood following total knee replacement may lead to an exaggerated hypercoagulable postoperative state. Further investigation of this potentially serious consequence of autologous blood transfusion is required.

Introduction: Aim of the study was to investigate the fixation patterns of cementless short-stem designs compared to the fixation patterns of well-known conventional stems artificially shortened in several steps.

Method: Primary rotational stability and tilting were measured in a standardized and validated simulator set-up. The tested short-stem designs included the Mayo (Zimmer), the CFP (Link), and the CUT (Eska). The “conventional” group consisted of the ABG (Stryker), the S-Rom (DePuy), and the G2 (DePuy). Additionally, these systems were tested when gradually shortened in several steps.

Results: The Mayo stem showed a 2/3 fixation pattern with 11.5 mdeg/Nm relative movement at the level of the lesser trochanter. The CFP showed a more distal fixation with 6.8 mdeg/Nm, and the CUT a proximal fixation with 7.6 mdeg/Nm. The Mayo and the CFP adapted to the femoral canal during ventro-dorsal tilting. The CUT tilted like a rigid body. This pattern of tilting was also shown by the ABG after it was shortened from 12.5 cm to 8.5 cm, by the G2 after a reduction from 15 to 6 cm, and the S-Rom after shortening from 18 to 6.9 cm.

Discussion: The shortened conventional stems showed a similar fixation pattern compared to the short-stem designs, the rotational stability was even better than with the Mayo and CFP stem. The CUT design acts like an extensively shortened conventional stem and seems to tilt in the femoral canal like a rigid body with a pressure increase at the lateral cortex of the femur.

To report on previously unreported behaviour of a rare condition and to recommend suitable management.

Fibrous periosteal tethers are a rare but recognised cause of angular growth deformity, usually of the femur. The periosteum is thought to act as a brake to growth, and unilateral tethering has been shown to cause angular growth deformity experimentally, although the aetiology of periosteal tethers is obscure.

Nine cases have previously been reported, all of which were progressive and none of which were present at birth. All required release of the tether and all but one required osteotomy to correct deformity. It has been thought that periosteal tethering might remodel if allowed to and that, if periosteal release were carried out, the deformity might correct without the need for osteotomy. However, this has never been reported.

We report two cases of periosteal tethering, well demonstrated on MRI which were remarkable in that they were present at birth. Neither child had any history of an intrauterine event or any other pathology. One involved the tibia, which remodelled without intervention. This is the first ever report of a tibial periosteal tether, and the tether could clearly be seen to be reabsorbed as the tibia remodelled. The other involved the ulna, which corrected after release of the tether alone.

Periosteal tethering can affect children of any age and has the potential to remodel without intervention. We therefore recommend a period of observation first if the deformity is not progressive. If the deformity is progressive, then early release of the tether is recommended. If this path is followed then it is likely that osteotomy would not be required. M.R.I. demonstrates the tether well and is the investigation of choice for this condition.

Patients with severe haemophilia have a tendency towards recurrent haemarthroses resulting in chronic synovitis and leading to end stage haemophilic arthropathy. From 1997 to 2001 five patients underwent sequential bilateral total knee replacement. We compared these patients with 13 haemophilic patients undergoing primary unilateral total knee replacement. One senior surgeon performed all surgery using an identical prosthesis under similar surgical and haematological conditions.

We reviewed information regarding pre-operative medical condition, antibiotic prophylaxis, blood replacement requirement and tourniquet time were all recorded. The rate of post-operative complications and economic evaluation between the two cohorts was calculated. Functional results were assessed using the Hospital for Special Surgery knee scoring system both pre and postoperatively.

We have shown that complication rates following bilateral and unilateral total knee replacements are comparable and that there are no differences in the functional outcomes or complication rates between the two groups. Furthermore, we found that bilateral procedures were advantageous with respect to total rehabilitation times, length of in-patient stay clotting factor usage and cost efficiency.

Fourteen patients with neurofibromatosis presented with symptoms or radiological evidence of cervical spine involvement over a period of 27 years. The symptoms included neurological deficit in five, neck mass in two, deformity in eight, decrease in neck movement in two and two with neck pain. Patients’ age ranged from five to forty-two years. Twelve patients have had surgical procedures. Two patients have been followed up and treated non-operatively despite osteolysis of vertebral bodies with kyphosis of more than 100°.

Current literature presents few cases of neurofibromatosis of the cervical spine. The largest World Series is of eight cases (Craig and Govender et al 1992). At present there is no coherent strategy of management for these conditions. The authors of this series recommend that correcting spinal deformity or to stabilise an unstable spine requires combined anterior and posterior fusion. Posterior fusion alone has a higher failure rate. Surgery for severe kyphotic deformity is questionable especially with no neurological deficit.