Enhancing biology and providing structural support for acetabular reconstruction in single-stage revision for infection.

BACKGROUND: Reconstruction of combined segmental and cavitary defects of the acetabulum is a challenge to the hip surgeon. One question regards the efficacy of reconstruction of acetabular defects using a combination of tantalum metal augments (TMAs) and impaction graft in single-stage revision for periprosthetic infection. MATERIALS AND METHODS: In the period between July 2009 and August 2014, 24 patients with combined segmental and cavitary acetabular defects and Paprosky classification grade IIB, IIC, and IIIA had hips reconstructed using the combination of TMAs and antibiotic-loaded impaction grafting. A similar group of 30 patients who received single-stage revision without metal augments were identified and taken as control. All patients received a polyethylene cemented cup and long cementless (Wagner SL) stem. Patients were prospectively evaluated using the modified Harris Hip Score (HHS) in addition to radiological evaluation at 3, 6, and 12 months then annually thereafter. RESULTS: At an average follow-up period of 4 years (range 2-7 years), all but one patient in the study group were free of infection, indicating a 96% success rate. This rate of eradicating infection was comparable to the 97% success rate in the control group. All metal augments were stable, and good incorporation of the impacted bone graft was observed. The HHS improved significantly from 27 preoperatively to 83 postoperatively (P < 0.001). CONCLUSION: Metal augments can convert massive acetabular defects to a more contained defect suitable for grafting. The combination of tantalum augments that provide strong structural support and antibiotic-loaded allograft is successful in the mid-term in single-stage revisions for infection. LEVEL OF EVIDENCE: Level IV (prospective case series).

A protocol for staged arthroplasty to salvage infected nonunion of hip fractures.

BACKGROUND: Nonunion of hip fractures is not uncommon. Total hip arthroplasty is used to salvage cases of non union or secondary arthritis in these fractures. However, this option may not be available or may be difficult to achieve when infection has superseded the site of nonunion. The objective of this prospective study was to assess if a staged protocol of treatment yields good results in these difficult cases. MATERIALS AND METHODS: Twenty-seven consecutive patients who had deep hip infection with failed treatment of hip fractures (intracapsular in 16 cases and extracapsular in 11) were treated between June 2007 and September 2011. Twenty-six completed the planned two-stage hip arthroplasty and one case was lost after the first stage. The average age of the patients was 48.9 years (range 26-74 years) with an average follow up period of 44 months (30-72 months). Analysis was done using the paired t test where P < 0.05 was considered significant. RESULTS: Infection was controlled in all cases that completed the treatment protocol with no recurrence in all cases at the latest follow up. The Harris hip score of the patients improved significantly from 29 preoperatively to 85 at the latest follow up (P < 0.0001). Two patients had hip dislocation with displacement of the trochanteric fragment while three other patients had fibrous union of the trochanter. CONCLUSIONS: Staged Arthroplasty procedure to salvage infected non-union of hip fractures is successful in eradicating infection and regaining hip function. Level of evidence IV.

Single-stage revision for periprosthetic hip infection using antibiotic loaded impaction graft.

BACKGROUND: Staged revision for periprosthetic infection of the hip is an accepted and widely used technique by many surgeons. However, single-stage exchange of the hip prosthesis remains an attractive option to others because of the advantages of reduced morbidity, shorter treatment time and hospital stay in addition to the reduced cost of treatment. HYPOTHESIS: Single-stage revision for periprosthetic hip infection can achieve excellent results if a specific protocol for patients' selection and management is followed. METHODS: 52 patients with evidence of periprosthetic infection had preoperative aspiration of the affected hip. The infecting organisms were identified in 33/52 and single-stage revision was performed. The remaining 19 patients had a 2-stage exchange arthroplasty. Patients in the single-stage revision protocol had antibiotic loaded morsellized bone graft, a cemented cup and a long cementless stem. RESULTS: At an average follow up of 6 (range 4-8) years postoperatively, only 1 case of persistent infection was found in the single-stage group - a 97% rate of eradicating infection was achieved. DISCUSSION: Single-stage exchange achieves excellent success rate in patients with periprosthetic infection when a specific protocol for patient selection and management is followed.

Reconstruction of the medial patello-femoral and patello-tibial ligaments for treatment of patellar instability.

PURPOSE: The importance of the medial patello-femoral (MPFL) and medial patello-tibial ligaments (MPTL) to the stability of the patella is undoubted. The purpose of this work was to present a technique for the reconstruction of both ligaments and prospectively record its outcome. METHODS: Cadaveric part: the MPFL and MPTL were identified in five knee specimens. Sequential cutting and reattaching of these ligaments were performed to study their effect on patellar stability. CLINICAL PART: In the years between 2005 and 2008, twenty-five knees in twenty-one patients had reconstruction of their MPFL and MPTL using the semitendinosus tendon. In eight of these knees, ligament reconstruction was combined with tibial tubercle osteotomy. The IKDC and Insall's classification of outcome were used for the evaluation of all knees. RESULTS: Cadaveric study revealed that resecting the MPTL increased the lateral translation of the patella up to subluxation at full extension. Intact MPFL avoids full dislocation. Regarding the clinical study, at a minimum 24-months follow-up, all patients reported to have stable patello-femoral joints. There was a significant improvement of the IKDC score 54 ± 2 pre-operatively to 81 ± 2 (Mean ± SD) at 24 months post-operative (P < 0.0003). Nineteen knees scored excellent, five were good and one had fair result. CONCLUSION: A technique for the reconstruction of the MPFL and MPTL that can be performed through minimally invasive approach has been presented and shown to be successful in restoring knee function in cases of traumatic and recurrent patellar dislocation. LEVEL OF EVIDENCE: III.

Measuring myoelectric fatigue of the serratus anterior in healthy subjects and patients with long thoracic nerve palsy.

Proper function of serratus anterior plays a vital role in the movement and stability of the scapula, and thus of the glenohumeral joint and the upper limb. The unique anatomy of this muscle makes direct measurements of its fatigue properties impossible. Here we describe for the first time indirect measurements of the myoelectric manifestations of fatigue in the serratus anterior. Eight healthy volunteers (29-35 years) were tested, four of them on two different occasions, using two exercise protocols (60 s isometric maximum upward force in 120 degrees arm flexion, and 60 s maximum forward force at 90 degrees arm flexion) with simultaneous recording by surface and wire electrodes applied according to established methods. Signals were analysed to obtain the rate of fall of median EMG frequency and the rate of rise of amplitude. Both exercise protocols gave similar results. Frequency-slope measurements (mean rate of fall 0.6+/-0.1% initial value per second (% s(-1)) with both surface and wire electrodes) were more precise than those of amplitude (mean rate of rise 2.6+/-0.3% s(-1) with surface electrodes, only 1.3+/-0.2% s(-1) with wire electrodes). Surface electrodes gave much lower variation than fine wires, the coefficient of variation of slopes for surface electrodes being approximately 20-40% both between studies in a single subject and between subjects. In 5 patients (aged 22-59 years) recovering from long thoracic nerve palsy studied using surface electrodes the frequency slopes was normal (0.6+/-0.1% s(-1)), while the amplitude slope was reduced (0.9+/-0.4% s(-1), P = 0.01). This shows abnormal fatigue properties of the reinnervated muscle and a dissociation between the frequency and amplitude manifestations of fatigue.

The role of cutaneous sensation in the motor function of the hand.

We studied the effect of abolishing cutaneous sensation (by infiltrating local anaesthetic around the median nerve at the wrist) on the ability of 10 healthy volunteers (a) to maintain a submaximal isometric pinch-grip force for 30 s without visual feedback, and (b) to perform a fine finger-manipulation 'handwriting' task. Blocking cutaneous sensation had no effect on ability to maintain pinch force, suggesting that muscle afferents have the major role in force-control feedback. However, a near-linear fall in force, present with or without block (mean slope=-1.3+/-0.2% s(-1)), which cannot be attributed to motor fatigue, reveals a shortcoming of the afferent feedback system. Blocking cutaneous sensation did impair ability to perform the more demanding writing task, as judged by an 18+/-6% increase in the length of the path between target points, a 22+/-9% increase in the duration of the movement and a 63+/-24% in 'normalised averaged rectified jerk', an averaged time-derivative of acceleration (all significantly nonzero, P < 0.04). These experiments demonstrate the relative importance of muscular and cutaneous afferent feedback on two aspects of hand performance, and provide a way to quantify the deficit resulting from the lack of cutaneous sensation.