A computer-based model of the knee was used to study forces in the cruciate ligaments induced by co-contraction of the extensor and flexor muscles, in the absence of external loads. Ligament forces are required whenever the components of the muscle forces parallel to the tibial plateau do not balance. When the extending effect of quadriceps exactly balances the flexing effect of hamstrings, the horizontal components of the two muscle forces also balance only at the critical flexion angle of 22 degrees. The calculations show that co-contraction of the quadriceps and hamstring muscles loads the anterior cruciate ligament from full extension to 22 degrees of flexion and loads the posterior cruciate at higher flexion angles. In these two regions of flexion, the forward pull of the patellar tendon on the tibia is, respectively, greater than or less than the backward pull of hamstrings. Simultaneous quadriceps and gastrocnemius contraction loads the anterior cruciate over the entire flexion range. Simultaneous contraction of all three muscle groups can unload the cruciate ligaments entirely at flexion angles above 22 degrees. These results may help the design of rational regimes of rehabilitation after ligament injury or repair

The aim of this study was to examine the loading of the other joints of the lower limb in patients with unilateral osteoarthritis (OA) of the knee. We recruited 20 patients with no other symptoms or deformity in the lower limbs from a consecutive cohort of patients awaiting knee replacement. Gait analysis and electromyographic recordings were performed to determine moments at both knees and hips, and contraction patterns in the medial and lateral quadriceps and hamstrings bilaterally. The speed of gait was reduced in the group with OA compared with the controls, but there were only minor differences in stance times between the limbs. Patients with OA of the knee had significant increases in adduction moment impulse at both knees and the contralateral hip (adjusted p-values: affected knee: p < 0.01, unaffected knee p = 0.048, contralateral hip p = 0.03), and significantly increased muscular co-contraction bilaterally compared with controls (all comparisons for co-contraction, p < 0.01). The other major weight-bearing joints are at risk from abnormal biomechanics in patients with unilateral OA of the knee. Cite this article: Bone Joint J 2013;95-B:348–53

Aims

Improvements in the evaluation of outcomes following peripheral nerve injury are needed. Recent studies have identified muscle fatigue as an inevitable consequence of muscle reinnervation. This study aimed to quantify and characterize muscle fatigue within a standardized surgical model of muscle reinnervation.

Aims

To fully quantify the effect of posterior tibial slope (PTS) angles on joint kinematics and contact mechanics of intact and anterior cruciate ligament-deficient (ACLD) knees during the gait cycle.

Objectives

Unicompartmental knee arthroplasty (UKA) is one surgical option for treating symptomatic medial osteoarthritis. Clinical studies have shown the functional benefits of UKA; however, the optimal alignment of the tibial component is still debated. The purpose of this study was to evaluate the effects of tibial coronal and sagittal plane alignment in UKA on knee kinematics and cruciate ligament tension, using a musculoskeletal computer simulation.

Aims

In patients with a rotator cuff tear, tear pattern and tendon involvement are known risk factors for the development of pseudoparalysis of the shoulder. It remains unclear, however, why similar tears often have very different functional consequences. The present study hypothesizes that individual shoulder anatomy, specifically the moment arms (MAs) of the rotator cuff (RC) and the deltoid muscle, as well as their relative recruitment during shoulder abduction, plays a central role in pseudoparalysis.

The transfer of part of the ulnar nerve to the musculocutaneous nerve, first described by Oberlin, can restore flexion of the elbow following brachial plexus injury. In this study we evaluated the additional benefits and effectiveness of quantitative electrodiagnosis to select a donor fascicle. Eight patients who had undergone transfer of a simple fascicle of the ulnar nerve to the motor branch of the musculocutaneous nerve were evaluated. In two early patients electrodiagnosis had not been used. In the remaining six patients, however, all fascicles of the ulnar nerve were separated and electrodiagnosis was performed after stimulation with a commercially available electromyographic system. In these procedures, recording electrodes were placed in flexor carpi ulnaris and the first dorsal interosseous. A single fascicle in the flexor carpi ulnaris in which a high amplitude had been recorded was selected as a donor and transferred to the musculocutaneous nerve. In the two patients who had not undergone electrodiagnosis, the recovery of biceps proved insufficient for normal use. Conversely, in the six patients in whom quantitative electrodiagnosis was used, elbow flexion recovered to an M4 level.

Quantitative intra-operative electrodiagnosis is an effective method of selecting a favourable donor fascicle during the Oberlin procedure. Moreover, fascicles showing a high-amplitude in reading flexor carpi ulnaris are donor nerves that can restore normal elbow flexion without intrinsic loss.

Whereas a general trend in the management of obstetric brachial plexus injuries has been nerve reconstruction in patients without spontaneous recovery of biceps function by three to six months of age, many recent studies suggest this may be unnecessary. In this study, the severity of glenohumeral dysplasia and shoulder function and strength in two groups of matched patients with a C5-6 lesion at a mean age of seven years (2.7 to 13.3) were investigated. One group (23 patients) underwent nerve reconstruction and secondary operations, and the other (52 patients) underwent only secondary operations for similar initial clinical presentations. In the patients with nerve reconstruction shoulder function did not improve and they developed more severe shoulder deformities (posterior subluxation, glenoid version and scapular elevation) and required a mean of 2.4 times as many operations as patients without nerve reconstruction.

This study suggests that less invasive management, addressing the muscle and bone complications, is a more effective approach. Nerve reconstruction should be reserved for those less common cases where the C5 and C6 nerve roots will not recover.

Aims

Tibiofemoral alignment is important to determine the rate of progression of osteoarthritis and implant survival after total knee arthroplasty (TKA). Normally, surgeons aim for neutral tibiofemoral alignment following TKA, but this has been questioned in recent years. The aim of this study was to evaluate whether varus or valgus alignment indeed leads to increased medial or lateral tibiofemoral forces during static and dynamic weight-bearing activities.

Aims

Improvements in the evaluation of outcome after nerve transfers are required. The assessment of force using the Medical Research Council (MRC) grades (0 to 5) is not suitable for this purpose. A ceiling effect is encountered within MRC grade 4/5 rendering this tool insensitive. Our aim was to show how the strength of flexion of the elbow could be assessed in patients who have undergone a re-innervation procedure using a continuous measurement scale.

The June 2013 Oncology Roundup³⁶⁰ looks at: whether allograft composite is superior to megaprosthesis in massive reconstruction; pain from glomus tumours; thromboembolism and orthopaedic malignancy; bone marrow aspirate and cavity lesions; metastasectomy in osteosarcoma; spinal giant cell tumour; post-atomic strike sarcoma; and superficial sarcomas and post-operative infection rates.

Residual muscle weakness in obstetric brachial plexus palsy results in soft-tissue contractures which limit the functional range of movement and lead to progressive glenoid dysplasia and joint instability. We describe the results of surgical treatment in 98 patients (mean age 2.5 years, 0.5 to 9.0) for the correction of active abduction of the shoulder. The patients underwent transfer of the latissimus dorsi and teres major muscles, release of contractures of subscapularis pectoralis major and minor, and axillary nerve decompression and neurolysis (the modified Quad procedure). The transferred muscles were sutured to the teres minor muscle, not to a point of bony insertion. The mean pre-operative active abduction was 45° (20° to 90°). At a mean follow-up of 4.8 years (2.0 to 8.7), the mean active abduction was 162° (100° to 180°) while 77 (78.6%) of the patients had active abduction of 160° or more. No decline in abduction was noted among the 29 patients (29.6%) followed up for six years or more. This procedure involving release of the contracted internal rotators of the shoulder combined with decompression and neurolysis of the axillary nerve greatly improves active abduction in young patients with muscle imbalance secondary to obstetric brachial plexus palsy.

We describe the results of surgical treatment in a prospective study of 183 consecutive cases of subluxation (101) and dislocation (82) of the shoulder secondary to obstetric brachial plexus palsy between 1995 and 2000. Neurological recovery was rated ‘good’ or ‘useful’ in all children, whose lesions fell into groups 1, 2 or 3 of the Narakas classification. The mean age at operation was 47 months (3 to 204). The mean follow-up was 40 months (24 to 124).

The mean gain in function was 3.6 levels (9.4 to 13) using the Mallet score and 2 (2.1 to 4.1) on the Gilbert score. The mean active global range of shoulder movement was increased by 73°; the mean range of active lateral rotation by 58° and that of supination of the forearm by 51°. Active medial rotation was decreased by a mean of 10°. There were 20 failures. The functional outcome is related to the severity of the neurological lesion, the duration of the dislocation and onset of deformity.