Anders Björkman

Cemented tibial component fixation performs better than cementless fixation: a randomized radiostereometric study comparing porous-coated, hydroxyapatite-coated and cemented tibial components over 5 years.

Background The question whether the tibial component of a total knee arthroplasty should be fixed to bone with or without bone cement has not yet been definitely answered. We studied movements between the tibial component and bone by radiostereometry (RSA) in total knee replacement (TKR) for 3 different types of fixation: cemented fixation (C-F), uncemented porous fixation (UC-F) and uncemented porous hydroxyapatite fixation (UCHA-F). Patients 116 patients with osteoarthrosis, who had 146 TKRs, were included in 2 randomized series. The first series included 86 unilateral TKRs stratified into 1 of the 3 types of fixation. The second series included 30 patients who had simultaneous bilateral TKR surgery, and who were stratified into 3 subgroups of pairwise comparisons of the 3 types of fixation. Results After 5 years 2 knees had been revised, neither of which were due to loosening. 1 UCHA-F knee in the unilateral series showed a large and continuous migration and a poor clinical result, and is a pending failure. The C-F knees rotated and migrated less than UC-F and UCHA-F knees over 5 years. UCHA-F migrated less than UC-F after 1 year. Interpretation Cementing of the tibial component offers more stable bone-implant contact for 5 years compared to uncemented fixation. When using uncemented components, however, there is evidence that augmenting a porous surface with hydroxyapatite may mean less motion between implant and bone after the initial postoperative year.

Acute improvement of hand sensibility after selective ipsilateral cutaneous forearm anaesthesia.

The cortical representation of body parts is constantly modulated in response to the afferent input, and acute deafferentation of a body part results in bilateral cortical reorganization. To study the effects on hand function of right forearm anaesthesia, we investigated ten human subjects (group 1) for perception of touch, tactile discrimination and grip strength in the right (ipsilateral) and left (contralateral) hand before, during and 24 h after forearm skin anaesthesia with a local anaesthetic cream (EMLA®). Ten age‐matched controls (group 2) were investigated in the same way but received placebo. In group 1 a significant improvement was seen in tactile discrimination in the ipsilateral hand compared to base line (P = 0.009) and compared to group 2 (P = 0.006). The improvement in tactile discrimination remained for at least 24 h after anaesthesia. Perception of touch, was improved during anaesthesia compared to baseline values in group 1 (P = 0.046) and remained for at least 24 h. Grip strength did not change. These findings suggest that transient selective deafferentation of an extremity results in enhanced sensory functions of the functionally preserved parts of the same extremity, presumably as a result of expansion of adjacent cortical territories. Such rapid functional changes suggest unmasking of pre‐existing synaptic connections as the mechanism underlying the acute modulation of sensory functions in the hand. Our findings open new perspectives for sensory re‐education and rehabilitation following injury to the peripheral and central nervous system.

Rupture of the extensor pollicis longus tendon: a study of aetiological factors

Although rupture of the extensor pollicis longus (EPL) tendon is a wellknown complication of distal radial fractures, a number of patients rupture the EPL because of other conditions. We have retrospectively studied the aetiology of 27 ruptures of the EPL in 26 consecutive patients. Of 19 patients with injured wrists 12 had distal radial fractures, five had blunt trauma, and two had stab wounds that resulted in rupture. In the radial fractures operated on, the EPL rupture was caused by chafing against a dorsal plate (n = 2) or wear against the pins of an external fixator (n = 2). Six patients were taking steroids for systemic diseases and in two cases a local steroid injection was given just before the rupture. We conclude that previous injury is the most common cause of rupture of the EPL, but that rheumatoid arthritis or local or systemic steroids, or both, are also important aetiological factors. Seven patients had an iatrogenic cause for their rupture.

Rapid cortical reorganisation and improved sensitivity of the hand following cutaneous anaesthesia of the forearm.

The cortical representation of various body parts constantly changes based on the pattern of afferent nerve impulses. As peripheral nerve injury results in a cortical and subcortical reorganisation this has been suggested as one explanation for the poor clinical outcome seen after peripheral nerve repair in humans. Cutaneous anaesthesia of the forearm in healthy subjects and in patients with nerve injuries results in rapid improvement of hand sensitivity. The mechanism behind the improvement is probably based on a rapid cortical and subcortical reorganisation. The aim of this work was to study cortical changes following temporary cutaneous forearm anaesthesia. Ten healthy volunteers participated in the study. Twenty grams of a local anaesthetic cream (EMLA®) was applied to the volar aspect of the right forearm. Functional magnetic resonance imaging was performed during sensory stimulation of all fingers of the right hand before and during cutaneous forearm anaesthesia. Sensitivity was also clinically assessed before and during forearm anaesthesia. A group analysis of functional magnetic resonance image data showed that, during anaesthesia, the hand area in the contralateral primary somatosensory cortex expanded cranially over the anaesthetised forearm area. Clinically right hand sensitivity in the volunteers improved during forearm anaesthesia. No significant changes were seen in the left hand. The clinically improved hand sensitivity following forearm anaesthesia is probably based on a rapid expansion of the hand area in the primary somatosensory cortex which presumably results in more nerve cells being made available for the hand in the primary somatosensory cortex.

Factor V Leiden and the prothrombin 20210A gene mutation and osteonecrosis of the knee.

IntroductionThe pathogenesis behind osteonecrosis of the knee is still unknown. Circulatory impairment of the bone secondary to thrombosis in the microcirculation has been suggested as a mechanism. The purpose of this study was to examine the association between osteonecrosis of the knee and abnormalities in the thrombotic pathway in the form of factor V Leiden and the prothrombin 20210A gene mutation.Materials and methodsThirty-eight consecutive patients (13 men and 25 women) with osteonecrosis of the knee without a history of knee trauma or surgery to the knee were enrolled in this study. Assays for the detection of factor V Leiden and the prothrombin 20210A gene mutation were performed, and the results were compared with those from 282 healthy volunteers.ResultsSix patients were diagnosed with secondary osteonecrosis, four corticosteroid-induced and two alcohol-induced. In 32 patients, no aetiological factor was found, and these patients were diagnosed with primary osteonecrosis of the knee. Twelve patients had 14 gene mutations, 11 factor V Leiden and 3 prothrombin 20210A gene mutations. Factor V Leiden and the prothrombin 20210A gene mutation occurred significantly (p=0.006) more frequently in patients with osteonecrosis than in a population of 282 healthy volunteers (odds ratio 3.1, 95%CI 1.4–6.6).ConclusionThe results of this study suggest that coagulation abnormalities in the form of factor V Leiden and the prothrombin 20210A gene mutation might play a role in osteonecrosis of the knee.

Acute improvement of contralateral hand function after deafferentation

To study cortical reorganisation after acute hand deafferentation, we investigated 10 experimental subjects and 10 controls for function in the left hand, before, during and after tourniquet induced anaesthesia of the right hand. fMRI was performed in three experimental subjects. Right hand anaesthesia resulted in rapid significant improvement in grip strength, tactile discrimination and sensibility in the left hand. Tactile discrimination and grip strength improvements lasted at least 15 mins after anaesthesia. fMRI showed increased activation in the right primary motor cortex after anaesthesia. We conclude that tourniquet induced anaesthesia is an easy way to induce rapid and significant improvement in contralateral hand function. This finding may have a potential clinical application for evolving sensory relearning strategies after nerve repair.

Optimizing the mapping of finger areas in primary somatosensory cortex using functional MRI.

Functional magnetic resonance imaging mapping of the finger somatotopy in the primary somatosensory cortex requires a reproducible and precise stimulation. The highly detailed functional architecture in this region of the brain also requires careful consideration in choice of spatial resolution and postprocessing parameters. The purpose of this study is therefore to investigate the impact of spatial resolution and level of smoothing during tactile stimulation using a precise stimuli system. Twenty-one volunteers were scanned using 2(3) mm(3) and 3(3) mm(3) voxel volume and subsequently evaluated using three different smoothing kernel widths. The overall activation reproducibility was also evaluated. Using a high spatial resolution proved advantageous for all fingers. At 2(3) mm(3) voxel volume, activation of the thumb, middle finger and little finger areas was seen in 89%, 67% and 50% of the volunteers, compared to 78%, 61% and 33% at 3(3) mm(3), respectively. The sensitivity was comparable for nonsmoothed and slightly smoothed (4 mm kernel width) data; however, increasing the smoothing kernel width from 4 to 8 mm resulted in a critical decrease ( approximately 50%) in sensitivity. In repeated measurements of the same subject at six different days, the localization reproducibility of all fingers was within 4 mm (1 S.D. of the mean). The precise computer-controlled stimulus, together with data acquisition at high spatial resolution and with only minor smoothing during evaluation, could be a very useful strategy in studies of brain plasticity and rehabilitation strategies in hand and finger disorders and injuries.

Functional outcome thirty years after median and ulnar nerve repair in childhood and adolescence.

BACKGROUND Age at injury is believed to be a factor that strongly influences functional outcome after nerve injury. However, there have been few long-term evaluations of the results of nerve repair and reconstruction in children. Our aim was to evaluate the long-term functional outcome of nerve repair or reconstruction at the forearm level in patients with a complete median and/or ulnar nerve injury at a young age. METHODS Forty-five patients were assessed at a median of thirty-one years after a complete median and/or ulnar nerve injury in the forearm. The outcome was classified with a total score (the Rosén score), a standardized outcome instrument consisting of three separate domains for sensory and motor function as well as pain/discomfort. In addition, the DASH (Disabilities of the Arm, Shoulder and Hand) score, sensitivity to cold, and locognosia were assessed specifically, together with the patients estimation of the overall outcome and impact on his or her education, work, and leisure activities. Comparisons were made between injuries that occurred in childhood (less than twelve years of age) and those that were sustained in adolescence (twelve to twenty years of age), and according to the nerve(s) that was injured (median nerve, ulnar nerve, or both). RESULTS Functional recovery, expressed as the total outcome score, the sensory domain of that score, and the patients subjective estimation of outcome, was significantly better after injuries sustained in childhood than after those that occurred in adolescence (87% and 67% of complete recovery, respectively; p < 0.001). No significant differences in recovery were seen between median and ulnar nerve injuries, or even when both nerves were injured. Motor function was close to normal, and cold sensitivity was not a problem in either age group. The median DASH scores were within normal limits and did not differ between the groups. Patients who sustained the injury in adolescence indicated that the nerve injury had a significantly higher effect on their profession, education, and leisure activities. CONCLUSIONS At a median of thirty-one years after a median or ulnar nerve repair at the level of the forearm, nerve function is significantly better in those injured in childhood than in those injured in adolescence, with almost full sensory and motor recovery in individuals injured in childhood.

The incidence of intrinsic and extrinsic ligament injuries in scaphoid waist fractures.

PURPOSE To determine the incidence of associated intrinsic and extrinsic ligament injuries in patients with a nondisplaced or displaced scaphoid waist fracture. METHODS During a 3-year period, a study of all scaphoid fractures was performed at our institution. Diagnosis was confirmed by plain radiographs, computed tomography, and magnetic resonance imaging. A 3-part anatomic classification was used to categorize the scaphoid fractures. The study population comprised 40 patients with 41 scaphoid waist fractures who had wrist arthroscopy for treatment and evaluation of the scaphoid fracture and associated carpal injuries. RESULTS We observed fresh intrinsic ligament injuries in 34 of 41 wrists. In 29 cases, the scapholunate ligament was injured, with complete rupture occurring in 10 wrists. The lunotriquetral ligament was injured in 8 wrists, and the triangular fibrocartilage complex was injured in 11 wrists. Statistically, the number of intrinsic ligament injuries did not differ between nondisplaced and displaced scaphoid fractures (p> .30). CONCLUSIONS In this study of acute scaphoid waist fractures, the overall incidence of associated ligament injuries was surprisingly high, at 34 of 41 wrists. Complete scapholunate ligament rupture was found in 10 of 41 wrists. This incidence is higher than previously reported and emphasizes the need for careful assessment of the intrinsic and extrinsic ligaments, particularly the scapholunate ligament, before deciding on treatment.

Enhanced function in nerve-injured hands after contralateral deafferentation.

To explore whether contralateral deafferentation by tourniquet-induced anaesthesia can improve function in a nerve-injured hand, we investigated 14 patients with median or ulnar nerve injuries at wrist level. Deafferentation of the contralateral forearm and hand resulted in significantly improved tactile discrimination, threshold for perception of touch in the injured nerve area and in the area corresponding to the intact nerve in the injured hand, and significantly increased grip strength. Improvements lasted at least 15 min. The results show that hand function after peripheral nerve injury can be temporarily enhanced by manipulation of the process of brain plasticity. Our results may have practical applications in the rehabilitation of peripheral nerve-injured patients.